Synthesis of Some Novel Piperazine Side Chain Modified 4- Aminoquinoline Mannich Bases and Evaluation for Their in Vitro Antimalarial Activity

Synthesis of Some Novel Piperazine Side Chain Modified 4- Aminoquinoline Mannich Bases and Evaluation for Their in Vitro Antimalarial Activity | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Synthesis of Some Novel Piperazine Side Chain Modified 4- Aminoquinoline Mannich Bases and Evaluation for Their in Vitro Antimalarial Activity Bhupendra Singh, Dipak Chetia This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4428579/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 3 You are reading this latest preprint version Abstract Twelve new compounds (Piperazine side chains modified 4-Aminoquinoline Mannich Bases) were synthesized and characterized utilizing a variety of analytical and spectroscopic techniques. All the synthesized compounds were screened for in vitro antimalarial activity aganist 3D7 strain of Plasmodium falciparum . In vitro antimalarial screening revealed that the all synthesized compounds exhibited minimum inhibitory concentrations (MIC) ranging from 3.9 to 31.25 μg/ml. One compound 9l (MIC=3.9 μg/ml or1.953±0.10μM) was found most potent against chloroquine sensitive 3D7 strain of Plasmodium falciparum which is comparable to standard drug chloroquine (MIC=0.4 μg/ml or 0.106±0.01 μM). malaria 4-aminoquinoline piperazine side chain modification Mannich base Plasmodium falciparum Introduction Human malaria is caused by five species of Plasmodium, e.g., P. falciparum , P. vivax , P. ovale , P. malariae , and P. knowlesi . The vast majority of deaths are caused by P. falciparum. P. vivax , P. ovale , and P. malariae are responsible for a generally milder form of malaria that is rarely fatal. The zoonotic species P. knowlesi , prevalent in Southeast Asia, causes malaria in macaques but can also cause severe infections in humans. [ 1 , 2 ] The structure-activity relationship studies on 4-aminoquinoline antimalarial compounds suggest that the 7-chloro-4-aminoquinoline nucleus is quint essential for antimalarial activity, particularly inhibition of β-hematin formation and accumulation of the drug at the target site [ 3 – 6 ]. The importance of the 4-aminopyridine substructure for hematin binding and antimalarial activity was also supported by experimental and molecular modeling studies by Cheruku and co-workers [ 7 ]. A series of short-chain chloroquine derivatives was reported by Stocks and co-workers [8], in which replacement of the diethylamino function with the more metabolically stable side chain ( tert -butyl) as well as heterocyclic ring (piperidyl, pyrrolidinyl, and morpholinyl) modifications led to a substantial increase in the antimalarial activity. These findings have given impetus to the idea that side chain modification is an attractive strategy for the development of antimalarial drugs with a desirable activity profile. On the basis of this evidence, we presumed that selectively modifying the side chain with a heterocyclic nucleus as well as a pendent amino group with 4-aminoquinoline Mannich bases could modulate the antimalarial activity. In the present study, we have proposed to synthesize compounds by modifications at the side chain of chloroquine with piperazine and the pendent amino group with Mannich bases of substituted acetophenone without altering the 7-chloro-4-aminoquinoline nucleus. Materials and Methods Chemistry Structural investigation The entire chemicals used in the present study were obtained from Sigma-Aldrich Corporation (USA), Rankem Pvt. Ltd. (India), and Merck Specialties Pvt. Ltd. (India). They were used without further purification unless otherwise stated. 4, 7-Dichloroquinoline (DCQ) was obtained as a gift sample from Ipca Laboratories Ltd., Ratlam, India. The melting point was determined using the MP-M560 Bucchi melting point apparatus. We checked that the reaction was complete using silica gel-G TLC plates and different solvent ratios. Iodine vapors or UV light (254 nm and 365 nm) were used to see what was going on. The Shimadzu UV-1700 Pharamspec UV-visible spectrophotometer was used for recording UV-visible spectra [ 9 , 10 ]. A FT-IR-IRlpha Bruker) spectrometer without a KBr disc was used for recording the IR spectrum [ 10 – 12 ]. The 1 H and 13 C NMR spectra were recorded on a Bruker Avance II 400 NMR spectrometer at 400 MHz and 100 MHz, respectively, using either DMSO-d 6 or CDCl 3 as solvent with tetramethylsilane (TMS) as an internal standard [ 10 – 12 ]. The mass spectrum was obtained on a TOF micromass spectrometer using electrospray ionization (ESI) [ 10 – 12 ]. Elemental microanalyses (CHN) were performed on a Perkin Elmer 2400 Series II CHNS/O analyzer (Jean PD 1963). General Procedure The targeted compounds were synthesized in five steps (Step-I to Step-V) according to the method originally utilized by Wenzel and co-workers [ 13 ], Furniss and co-workers [ 10 ], Antinarelli and co-workers [ 14 ], Kumar A and co-workers [ 15 ], and Singh B and co-workers [ 16 ]. Step-I Secondary amine (33 mmol), powdered paraformaldehyde (33 mmol), and acetophenone or substituted acetophenone (25 mmol) were placed in a 250-ml round-bottomed flask attached to a reflux condenser. Introduce 10 ml of 95% ethanol, to which 0.1 ml of concentrated hydrochloric acid was added, and reflux the mixture on a water bath for 2–3 hours. After the reflux period, the solvent was removed under reduced pressure and the crude product was purified. Step-II Sodium borohydrate (500 mg) was dissolved in 10 ml of ethanol and product of step-I was added by maintaining temperature 30–50 30–50°C.The reaction mixture was allowed to stand at room temperature for 15 minutes with stirring. Hydrochloric acid (3 ml, 3 M) was added to the reaction mixture, and this mixture was heated to boiling on a hot plate until the mixture separated into two layers. It was cooled in an ice bath and transferred to a separating funnel with dichloromethane (DCM), and water was added to dissolve inorganic salt precipitate, if any, and then the aqueous layer was extracted with DCM. The organic layer was dried with anhydrous. Sodium sulfate and the solvent were evaporated to get the crude product. Step-III The product of step-II (4.5 mmol) and thionyl chloride (4.5 mmol) in chloroform was heated for one hour (with occasional gentle shaking) in a round bottom flask attached with a reflux condenser and calcium chloride tube. After heating, unchanged thionyl chloride was removed by distillation to get the product. Step-IV A stirred mixture of 4, 7-dichloroquinoline (50 mmol), piperazine (150 mmol), and potassium iodide (12 mmol) in isopropyl alcohol (70 ml) was heated to reflux for 10 hours, cooling the reaction mass to room temperature. Isopropyl alcohol was distilled completely under vacuum. Water and methylene chloride were added to the residue and stirred for about 10 minutes at room temperature. The pH of the reaction mass was adjusted to 3-3.5 with dilutions of HCl, separated into an aqueous layer, and washed with methylene chloride. The pH of the aqueous layer was adjusted to 10–11 with ammonia solution. The reaction mass was filtered and the precipitate was washed with water till the pH of the mother liquor became neutral. The solids obtained were dried. Step-V The product of step IV (1.80 mmol) was dissolved in anhydrous ethanol (25 ml) under heating. After cooling to room temperature, triethylamine (9.02 mmol) was added. Then the product of step III was added as a solid in three portions: first 1.89 mmol, then a further 0.39 mmol after 16 hours, and then 0.22 mmol after another 7 hours. After 12 hours of stirring at room temperature, the solvent was evaporated and the residue was purified by flash chromatography to obtain the final desired product as piperazine side chain modified 4-Aminoquinoline Mannich bases. 7-chloro-4-(piperazin-1-yl)quinoline ( An intermediate ) : Creamy white solid with characteristic odour; soluble in Methanol, Ethanol, and Dichloromethane; Melting Point range 114-117 o C; %Yield 70%; R f value 0.34 (Dichloromethane: Methanol:: 1:4); UV-Visible Spectrum (Methanol), λ max (nm): 223.20, 320.60; IR Spectrum (υ, cm − 1 ): 3252 (N-H str., >NH); 1604 (N-H def., >NH); 1291(C-N str., >NH); 1322 (C-N str., >N-); 1566, 1493, 1453, 1421 (C = C str., Ar. ring); 1374, 1261 (C-N str.); 1071 (Ar. C-Cl str.); 819, 802, 770 (Ar. C-H bend.); 1 H NMR (400 MHz, DMSO), δ (ppm) : 3.06–3.09 (m,8H, piperazine); 3.14–3.16 (m, 1H, >NH), 6.91–6.92 (d, 1H, J = 4 Hz, quinoline-H 3 ); 7.45–7.48 (dd, 1H, J = 8Hz, 4Hz, quinoline-H 6 ); 7.94–7.95 (d, 1H, J = 4Hz, quinoline-H 5 ); 7.99–8.01 (d, 1H, J = 8Hz, quinoline-H 8 ); 8.67–8.68 (d, 1H, J = 4Hz, quinoline-H 2 ); 13 C NMR (100 MHz, DMSO), δ (ppm) 45.24 (CH 2 ); 52.67 (CH 2 ); 108.95 (C-2, quinoline), 121.38 (C-4a, quinoline); 125.42 (C-5, quinoline); 125.65 (C-6, quinoline); 128.00 (C-8, quinoline); 133.63 (C-7, quinoline, C-Cl); 149.61 (C-8a, quinoline); 151.80 (C-2, quinoline); 156.69 (C-4, quinoline); Mass Spectrum (m/z): 248.11 [M + H] + . N,N-dibenzyl-3-(4-(7-chloroquinolin-4-yl)piperazin-1-yl)-3-phenylpropan-1-amine ; 9a : Light brown Gummy Solid with characteristic odour; soluble in Methanol, Ethanol; %Yield 69%; R f value 0.44 (Dichloromethane: methanol::1:4); UV-Visible Spectrum (Methanol), λ max (nm) 224, 320.5; IR Spectrum (υ, cm − 1 ): 2923 (C-H str., >CH 2 ); 1571, 1493, 1451 (C = C str., Ar. ring); 1374 (C-N str., >N-); 1114 (Ar. C-Cl str).; 916, 824, 778 (Ar. C-H bend); 1 H NMR (400 MHz, DMSO), δ (ppm) 1.22–1.25 (m, 2H, -CH 2 -); 2.15 (s, 4H, CH 2 -Ar); 2.50–2.53 (t, 2H, J = 12Hz, CH 2 -N); 3.04–3.11 (m, 1H, Ar-CHNH); 3.40–3.58 (m,8H, piperazine); 6.50–6.54 (d, 1H, J = 16Hz, quinoline-H 3 ); 7.07–7.09 (d, 1H, J = 8Hz, quinoline-H 5 );7.55–7.58 (dd, 1H, J = 4Hz, 4Hz, quinoline-H 6 ); 8.06 (s, 5H, Ar-H); 8.08–8.09 (d, 1H, J = 4Hz, quinoline-H 8 ); 8.25 (s, 10H, Ar-H); 8.71–8.73 (d, 1H, J = 8Hz, quinoline-H 2 ); 13 C NMR (100 MHz, DMSO), δ (ppm) 38.90 (-CH 2 -); 45.93 (-CH 2 -N); 49.83 (CH 2 -Piperazine); 60.52 (Ar-CH 2 -N); 78.55 (> CH-Ar.); 109.65 (C-3, quinoline); 121.17 (C-4a, quinoline); 125.53 (C-5, quinoline); 125.76 (C-6, quinoline); 126.03 (C-8, quinoline); 128.05, 129.97 (Ar.-C); 139.04 (C-7, quinoline, C-Cl); 149.52 (C-8a, quinoline); 151.98 (C-2, quionline); 155.37 (C-4, quinoline); Mass Spectrum (m/z) 562.01 [M + H] + ; Elemental Analysis: Cal. (%) for C 36 H 37 ClN 4 : C, 77.05; H, 6.65; N, 9.98; Obs. (%): C, 77.09; H, 6.61; N, 9.95. N,N-dibenzyl-3-(4-(7-chloroquinolin-4-yl)piperazin-1-yl)-3-p-tolylpropan-1-amine ; 9b : Light brownish gummy solid with characteristic odour; soluble in Methanol, Ethanol; %Yield 71%; R f value 0.54 (Dichloromethane: methanol:: 1:4); UV-Visible Spectrum (Methanol), λ max (nm) 224, 318; IR Spectrum (υ, cm − 1 ) 2921 (C-H str., >CH 2 ); 1573, 1492, 1452 (C = C str., Ar. ring); 1372 (C-N str., >N-); 1112 (Ar. C-Cl str).; 922, 822, 776 (Ar. C-H bend); 1 H NMR (400 MHz, DMSO), δ (ppm) 1.21–1.26 (m, 2H, -CH 2 -); 2.07 (s, 3H, Ar-CH 3 ); 2.18 (s, 4H, CH 2 -Ar); 2.49–2.52 (t, 2H, J = 12Hz, CH 2 -N); 3.09–3.15 (m, 1H, Ar-CHNH); 3.46–3.55 (m,8H, piperazine); 6.49–6.52 (d, 1H, J = 12Hz, quinoline-H 3 ); 7.02–7.04 (d, 1H, J = 8Hz, quinoline-H 5 ); 7.15–7.17 (d, 2H, J = 8Hz, Ar-H); 7.26–7.29 (d, 2H, J = 12Hz, Ar-H); 7.50–7.53 (dd, 1H, J = 4Hz, 4Hz, quinoline-H 6 ); 8.11–8.13 (d, 1H, J = 8Hz, quinoline-H 8 ); 8.20 (s, 10H, Ar-H); 8.77–8.79 (d, 1H, J = 8Hz, quinoline-H 2 ); Mass Spectrum (m/z): 576.07 [M + H] + . N,N-dibenzyl-3-(4-(7-chloroquinolin-4-yl)piperazin-1-yl)-3-(4-methoxyphenyl)propan-1-amine ; 9c : Dark brown gummy solid with characteristic odour; soluble in Methanol, Ethanol; %Yield 75%; R f value 0.63 (Dichloromethane:methanol::1:4); UV-Visible Spectrum (Methanol), λ max (nm) 225, 324; IR Spectrum (υ, cm − 1 ) 2930 (C-H str., >CH 2 ); 1572, 1508, 1451 (C = C str., Ar. ring); 1370 (C-N str., >N-); 1245 (Ar.-O-CH 3 ); 1113 (Ar. C-Cl str).; 916, 824, 778 (Ar. C-H bend); 1 H NMR (400 MHz, DMSO), δ (ppm) 1.19–1.24 (m, 2H, -CH 2 -); 2.23 (s, 4H, CH 2 -Ar); 2.42–2.45 (t, 2H, J = 12Hz, CH 2 -N); 3.12–3.17 (m, 1H, Ar-CHNH); 3.44–3.51 (m,8H, piperazine); 4.32 (s, 3H, Ar-OCH 3 ); 6.45–6.47 (d, 1H, J = 8Hz, quinoline-H 3 ); 7.11–7.13 (d, 1H, J = 8Hz, quinoline-H 5 ); 7.19–7.21 (d, 2H, J = 8Hz, Ar-H); 7.31–7.33 (d, 2H, J = 8Hz, Ar-H); 7.58–7.61 (dd, 1H, J = 4Hz, 4Hz, quinoline-H 6 ); 8.19–8.21 (d, 1H, J = 8Hz, quinoline-H 8 ); 8.27 (s, 10H, Ar-H); 8.69–8.71 (d, 1H, J = 8Hz, quinoline-H 2 ); Mass Spectrum (m/z) 592.02 [M + H] + . 3-(4-(7-chloroquinolin-4-yl)piperazin-1-yl)-N,N-diethyl-3-phenylpropan-1-amine; 9d : Creamy white solid with characteristic odour; soluble in Methanol, Ethanol; Melting range: 166-169 o C; %Yield 67%; R f value 0.53 (Dichloromethane:methanol::1:4); UV-Visible Spectrum (Methanol), λ max (nm) 221.5, 343.5; IR Spectrum (υ, cm − 1 ) 2934 (C-H str., >CH 2 ); 1568, 1495, 1458 (C = C str., Ar. ring); 1377 (C-N str., >N-); 1118 (Ar. C-Cl str).; 927, 837, 768 (Ar. C-H bend); 1 H NMR (400 MHz, DMSO), δ (ppm) 1.14–1.17 (t, 6H, J = 12Hz, NCH 2 CH 3 ); 1.19–1.24 (m, 2H, -CH 2 -); 2.47–2.50 (t, 2H, J = 12Hz, CH 2 -N); 2.65–2.71 (m, 4H, NCH 2 CH 3 ); 3.12–3.17 (m, 1H, Ar-CHNH); 3.39–3.45 (m,8H, piperazine); 6.57–6.59 (d, 1H, J = 8Hz, quinoline-H 3 ); 7.13–7.15 (d, 1H, J = 8Hz, quinoline-H 5 );7.45–7.48 (dd, 1H, J = 4Hz, 4Hz, quinoline-H 6 ); 8.11 (s, 5H, Ar-H); 8.19–8.21 (d, 1H, J = 8Hz, quinoline-H 8 ); 8.52–8.54 (d, 1H, J = 8Hz, quinoline-H 2 ); 13 C NMR (100 MHz, DMSO), δ (ppm) 9.08 (CH 3 -CH 2 ), 36.46 (-CH 2 -); 46.25 (-CH 2 -N); 47.51 (CH 2 -Piperazine); 78.55 (> CH-Ar.); 111.36 (C-3, quinoline); 120.11 (C-4a, quinoline); 124.05 (C-5, quinoline); 125.67 (C-6, quinoline); 126.32 (C-8, quinoline); 127.05, 128.57 (Ar.-C); 139.64 (C-7, quinoline, C-Cl); 150.72 (C-8a, quinoline); 154.08 (C-2, quionline); 156.43 (C-4, quinoline); Mass Spectrum (m/z): 437.16 [M + H] + ; Elemental Analysis Cal. (%) for C 26 H 33 ClN 4 : C, 71.46; H, 7.61; N, 12.82; Obs. (%): C, 71.55; H, 7.64; N, 12.79. 3-(4-(7-chloroquinolin-4-yl)piperazin-1-yl)-N,N-diethyl-3-p-tolylpropan-1-amine; 9e : Light brown gummy solid with characteristic odour; soluble in Methanol, Ethanol; %Yield 71%; R f value 0.58 (Dichloromethane:methanol::1:4); UV-Visible Spectrum (Methanol), λ max (nm) 222, 341; IR Spectrum (υ, cm − 1 ) 2922 (C-H str., >CH 2 ); 1574, 1510, 1452 (C = C str., Ar. ring); 1375 (C-N str., >N-); 1114 (Ar. C-Cl str).; 926, 823, 769 (Ar. C-H bend); 1 H NMR (400 MHz, DMSO), δ (ppm) 1.11–1.14 (t, 6H, J = 12Hz, NCH 2 CH 3 ); 1.23–1.28 (m, 2H, -CH 2 -); 2.19 (s, 3H, Ar-CH 3 ); 2.35–2.38 (t, 2H, J = 12Hz, CH 2 -N); 2.71–2.76 (m, 4H, NCH 2 CH 3 ); 3.22–3.27 (m, 1H, Ar-CHNH); 3.45–3.49 (m,8H, piperazine); 6.67–6.69 (d, 1H, J = 8Hz, quinoline-H 3 ); 6.95–6.97 (d, 2H, J = 8Hz, Ar-H); 7.18–7.20 (d, 2H, J = 8Hz, Ar-H); 7.28–7.30 (d, 1H, J = 8Hz, quinoline-H 5 ); 7.55–7.58 (dd, 1H, J = 4Hz, 4Hz, quinoline-H 6 ); 8.11–8.13 (d, 1H, J = 8Hz, quinoline-H 8 ); 8.42–8.44 (d, 1H, J = 8Hz, quinoline-H 2 ); Mass Spectrum (m/z): 452.01 [M + H] + . 3-(4-(7-chloroquinolin-4-yl)piperazin-1-yl)-N,N-diethyl-3-(4-methoxyphenyl)propan-1-amine; 9f : Chocolate brownish gummy solid with characteristic odour; soluble in Methanol, Ethanol; %Yield 73%; R f value 0.55 (Dichloromethane:methanol::1:4); UV-Visible Spectrum (Methanol), λ max (nm) 224, 343; IR Spectrum (υ, cm − 1 ) 2932 (C-H str., >CH 2 ); 1574, 1508, 1453 (C = C str., Ar. ring); 1376 (C-N str., >N-); 1245 (Ar.-O-CH 3 ); 1113 (Ar. C-Cl str).; 924, 824, 711 (Ar. C-H bend); 1 H NMR (400 MHz, DMSO), δ (ppm) 1.13–1.16 (t, 6H, J = 12Hz, NCH 2 CH 3 ); 1.29–1.34 (m, 2H, -CH 2 -); 2.41–2.44 (t, 2H, J = 12Hz, CH 2 -N); 2.68–2.77 (m, 4H, NCH 2 CH 3 ); 3.19–3.25 (m, 1H, Ar-CHNH); 3.51–3.57 (m,8H, piperazine); 3.71 (s, 3H, Ar-OCH 3 ); 6.77–6.79 (d, 1H, J = 8Hz, quinoline-H 3 ); 6.91–6.93 (d, 2H, J = 8Hz, Ar-H); 7.14–7.16 (d, 2H, J = 8Hz, Ar-H); 7.31–7.32 (d, 1H, J = 8Hz, quinoline-H 5 ); 7.61–7.64 (dd, 1H, J = 4Hz, 4Hz, quinoline-H 6 ); 8.31–8.34 (d, 1H, J = 8Hz, quinoline-H 8 ); 8.47–8.49 (d, 1H, J = 8Hz, quinoline-H 2 ); Mass Spectrum (m/z): 468.7 [M + H] + . 3-(4-(7-chloroquinolin-4-yl)piperazin-1-yl)-N,N-dimethyl-3-phenylpropan-1-amine; 9g : Dark brownish gummy solid with characteristic odour; soluble in Methanol, Ethanol; %Yield 71%; R f value 0.48 (Dichloromethane:methanol::1:4); UV-Visible Spectrum (Methanol), λ max (nm) 224.5, 321; IR Spectrum (υ, cm − 1 ) 2932 (C-H str., >CH 2 ); 1574, 1492, 1450 (C = C str., Ar. ring); 1296 (C-N str., >N-); 1115 (Ar. C-Cl str).; 923, 824, 778 (Ar. C-H bend).; 1 H NMR (400 MHz, DMSO), δ (ppm) 1.17–1.23 (m, 2H, -CH 2 -); 2.31 (s, 6H, N-CH 3 ); 2.43–2.47 (t, 2H, J = 12Hz, CH 2 -N); 3.17–3.23 (m, 1H, Ar-CHNH); 3.51–3.57 (m,8H, piperazine); 6.63–6.65 (d, 1H, J = 8Hz, quinoline-H 3 ); 7.03–7.05 (d, 1H, J = 8Hz, quinoline-H 5 );7.41–7.44 (dd, 1H, J = 4Hz, 4Hz, quinoline-H 6 ); 8.22 (s, 5H, Ar-H); 8.34–8.36 (d, 1H, J = 8Hz, quinoline-H 8 ); 8.61–8.63 (d, 1H, J = 8Hz, quinoline-H 2 ); 13 C NMR (100 MHz, DMSO), δ (ppm) 36.46 (-CH 2 -); 45.6 (CH 3 -N); ); 49.51 (CH 2 -Piperazine); 53.50 (CH 2 -N); 71.55 (> CH-Ar.); 115.36 (C-3, quinoline); 123.21 (C-4a, quinoline); 125.05 (C-5, quinoline); 126.07 (C-6, quinoline); 126.09, 127.88 (Ar.-C); 129.31 (C-8, quinoline); 134.66 (C-7, quinoline, C-Cl); 150.02 (C-8a, quinoline); 151.18 (C-2, quionline); 158.73 (C-4, quinoline); Mass Spectrum (m/z) 409.56 [M + H] + ; Elemental Analysis Cal. (%) for C 24 H 29 ClN 4 : C, 70.48; H, 7.15; N, 13.70; Obs. (%): C, 70.51; H, 7.12; N, 13.73. 3-(4-(7-chloroquinolin-4-yl)piperazin-1-yl)-N,N-dimethyl-3-p-tolylpropan-1-amine; 9h : Chocolate brown gummy solid with characteristic odour; soluble in Methanol, Ethanol; %Yield 66%; R f value 0.53 (Dichloromethane:methanol::1:4); UV-Visible Spectrum (Methanol), λ max (nm) 224, 319; IR Spectrum (υ, cm − 1 ) 2920 (C-H str., >CH 2 ); 1566, 1512, 1453 (C = C str., Ar. ring); 1375 (C-N str., >N-); 1114 (Ar. C-Cl str).; 925, 822, 794 (Ar. C-H bend); 1 H NMR (400 MHz, DMSO), δ (ppm) 1.13–1.19 (m, 2H, -CH 2 -); 2.11 (s, 3H, Ar-CH 3 ); 2.33 (s, 6H, N-CH 3 ); 2.39–2.42 (t, 2H, J = 12Hz, CH 2 -N); 3.07–3.12 (m, 1H, Ar-CHNH); 3.42–3.48 (m,8H, piperazine); 6.66–6.68 (d, 1H, J = 8Hz, quinoline-H 3 ); 6.81–6.83 (d, 2H, J = 8Hz, Ar-H); 7.01–7.03 (d, 1H, J = 8Hz, quinoline-H 5 ); 7.14–7.16(d, 2H, J = 8Hz, Ar-H); 7.31–7.34 (dd, 1H, J = 4Hz, 4Hz, quinoline-H 6 ); 8.27–8.29 (d, 1H, J = 8Hz, quinoline-H 8 ); 8.51–8.53 (d, 1H, J = 8Hz, quinoline-H 2 ); Mass Spectrum (m/z) 423.69 [M + H] + . 3-(4-(7-chloroquinolin-4-yl)piperazin-1-yl)-3-(4-methoxyphenyl)-N,N-dimethylpropan-1-amine; 9i : Light brown gummy solid with characteristic odour; soluble in Methanol, Ethanol; %Yield 69%; R f value 0.57 (Dichloromethane:methanol::1:4); UV-Visible Spectrum (Methanol), λ max (nm) 226, 324; IR Spectrum (υ, cm − 1 ) 2938 (C-H str., >CH 2 ); 1569, 1506, 1457 (C = C str., Ar. ring); 1377 (C-N str., >N-); 1245 (Ar.-O-CH 3 ); 1114 (Ar. C-Cl str).; 928, 824, 768 (Ar. C-H bend); 1 H NMR (400 MHz, DMSO), δ (ppm) 1.12–1.18 (m, 2H, -CH 2 -); 2.31 (s, 6H, N-CH 3 ); 2.41–2.43 (t, 2H, J = 8Hz, CH 2 -N); 3.14–3.20 (m, 1H, Ar-CHNH); 3.32–3.38 (m,8H, piperazine); 3.85(s, 3H, Ar-OCH 3 ); 6.61–6.62 (d, 1H, J = 4Hz, quinoline-H 3 ); 6.71–6.73 (d, 2H, J = 8Hz, Ar-H); 7.05–7.07 (d, 1H, J = 8Hz, quinoline-H 5 ); 7.22–7.23(d, 2H, J = 4Hz, Ar-H); 7.43–7.47 (dd, 1H, J = 8Hz, 4Hz, quinoline-H 6 ); 8.32–8.35 (d, 1H, J = 8Hz, quinoline-H 8 ); 8.47–8.49 (d, 1H, J = 8Hz, quinoline-H 2 ); Mass Spectrum (m/z) 439.74 [M + H] + . 7-chloro-4-(4-(3-morpholino-1-phenylpropyl) piperazin-1-yl) quinoline ; 9j : Light Brownish gummy solid with characteristic odour; soluble in Methanol, Ethanol; %Yield 65%; R f value 0.63 (Dichloromethane:methanol::1:4); UV-Visible Spectrum (Methanol), λ max (nm) 224.5, 321; IR Spectrum (υ, cm − 1 ) 2930 (C-H str., >CH 2 ); 1569, 1492, 1450 (C = C str., Ar. ring); 1375 (C-N str., >N-); 1113 (Ar. C-Cl str).; 922, 823, 745 (Ar. C-H bend).; 1 H NMR (400 MHz, DMSO), δ (ppm) 1.24–1.31 (m, 2H, -CH 2 -); 1.79–1.81 (t, 4H, J = 8Hz, morpholinyl-H); 2.39–2.42 (t, 2H, J = 8Hz, CH 2 -N); 3.17–3.26 (m, 1H, Ar-CHNH); 3.41–3.49 (m,8H, piperazine); 3.81–3.83 (t, 4H, J = 8Hz, morpholinyl-H); 6.84–6.86 (d, 1H, J = 4Hz, quinoline-H 3 ); 7.05–7.06 (d, 1H, J = 4Hz, quinoline-H 5 ); 7.42–7.45 (dd, 1H, J = 4Hz, 4Hz, quinoline-H 6 ); 7.82–7.84 (d, 1H, J = 4Hz, quinoline-H 8 ); 8.13 (s, 5H, Ar-H); 8.75–8.77 (d, 1H, J = 4Hz, quinoline-H 2 ).; 13 C NMR (100 MHz, DMSO), δ (ppm) 35.97 (-CH 2 -); 49.07 (CH 2 -N); 50.07 (CH 2 -Piperazine); 53.89, 66.68 (CH 2 -Morpholine); 70.78 (> CH-Ar.); 117.86 (C-3, quinoline); 124.91 (C-4a, quinoline); 125.95 (C-5, quinoline); 126.01, 127.91 (Ar.-C); 128.03 (C-6, quinoline); 129.87 (C-8, quinoline); 134.95 (C-7, quinoline, C-Cl); 149.03 (C-8a, quinoline); 150.98 (C-2, quionline); 158.93 (C-4, quinoline); Mass Spectrum (m/z) 451.03 [M + H] + ; Elemental Analysis Cal. (%) for C 26 H 31 ClN 4 O: C, 69.24; H, 6.93; N, 12.42; Obs. (%): C, 69.27; H, 6.90; N, 12.45. 7-chloro-4-(4-(3-morpholino-1-p-tolylpropyl)piperazin-1-yl)quinoline ; 9k : Dark Brownish gummy solid with characteristic odour; soluble in Methanol, Ethanol; %Yield 62%; R f value 0.58 (Dichloromethane:methanol::1:4); UV-Visible Spectrum (Methanol), λ max (nm) 224, 320; IR Spectrum (υ, cm − 1 ) 2926 (C-H str., >CH 2 ); 1571, 1492, 1450 (C = C str., Ar. ring); 1376 (C-N str., >N-); 1112 (Ar. C-Cl str).; 925, 824, 801 (Ar. C-H bend); 1 H NMR (400 MHz, DMSO), δ (ppm) 1.27–1.33 (m, 2H, -CH 2 -); 1.77–1.80 (t, 4H, J = 12Hz, morpholinyl-H); 2.11 (s,3H, Ar-CH 3 ); 2.43–2.45 (t, 2H, J = 8Hz, CH 2 -N); 3.12–3.17 (m, 1H, Ar-CHNH); 3.45–3.50 (m,8H, piperazine); 3.77–3.80 (t, 4H, J = 12Hz, morpholinyl-H); 6.72–6.74 (d, 2H, J = 8Hz, Ar-H); 6.89–6.91 (d, 1H, J = 8Hz, quinoline-H 3 ); 7.09–7.10 (d, 1H, J = 4Hz, quinoline-H 5 ); 7.23–7.25 (d,2H, J = 8Hz, Ar-H); 7.39–7.42 (dd, 1H, J = 4Hz, 4Hz, quinoline-H 6 ); 7.77–7.78 (d, 1H, J = 4Hz, quinoline-H 8 ); 8.65–8.67 (d, 1H, J = 8Hz, quinoline-H 2 ); Mass Spectrum (m/z) 466.11 [M + H] + . 7-chloro-4-(4-(1-(4-methoxyphenyl)-3-morpholinopropyl)piperazin-1-yl)quinoline ; 9l : Light Brownish gummy solid with characteristic odour; soluble in Methanol, Ethanol; %Yield 65%; R f value 0.63 (Dichloromethane:methanol::1:4); UV-Visible Spectrum (Methanol), λ max (nm) 224.5, 321; IR Spectrum (υ, cm − 1 ): 2930 (C-H str., >CH 2 ); 1569, 1492, 1450 (C = C str., Ar. ring); 1375 (C-N str., >N-); 1113 (Ar. C-Cl str).; 922, 823, 745 (Ar. C-H bend); 1 H NMR (400 MHz, DMSO), δ (ppm): 1.24–1.31 (m, 2H, -CH 2 -); 1.79–1.81 (t, 4H, J = 8Hz, morpholinyl-H); 2.39–2.42 (t, 2H, J = 8Hz, CH 2 -N); 3.17–3.26 (m, 1H, Ar-CHNH); 3.41–3.49 (m,8H, piperazine); 3.81–3.83 (t, 4H, J = 8Hz, morpholinyl-H); 6.84–6.86 (d, 1H, J = 4Hz, quinoline-H 3 ); 7.05–7.06 (d, 1H, J = 4Hz, quinoline-H 5 ); 7.42–7.45 (dd, 1H, J = 4Hz, 4Hz, quinoline-H 6 ); 7.82–7.84 (d, 1H, J = 4Hz, quinoline-H 8 ); 8.13 (s, 5H, Ar-H); 8.75–8.77 (d, 1H, J = 4Hz, quinoline-H 2 ); 13 C NMR (100 MHz, DMSO), δ (ppm) 35.97 (-CH 2 -); 49.07 (CH 2 -N); 50.07 (CH 2 -Piperazine); 53.89, 66.68 (CH 2 -Morpholine); 70.78 (> CH-Ar.); 117.86 (C-3, quinoline); 124.91 (C-4a, quinoline); 125.95 (C-5, quinoline); 126.01, 127.91 (Ar.-C); 128.03 (C-6, quinoline); 129.87 (C-8, quinoline); 134.95 (C-7, quinoline, C-Cl); 149.03 (C-8a, quinoline); 150.98 (C-2, quionline); 158.93 (C-4, quinoline); Mass Spectrum (m/z): 451.03 [M + H] + ; Elemental Analysis: Cal. (%) for C 26 H 31 ClN 4 O: C, 69.24; H, 6.93; N, 12.42; Obs. (%): C, 69.27; H, 6.90; N, 12.45. Antimalarial Activity Evaluation The in-vitro antimalarial assay of the synthesized compounds was carried out on 96 well-microtitre plates [ 17 ]. The cultures of chloroquine-sensitive stains of P. falciparum 3D7 were routinely maintained in medium RPMI 1640 supplemented with 25 mM HEPES, 1% D-glucose, 0.23% sodium bicarbonate, and 10% heat-inactivated human serum. The culture was synchronized using a 5% aqueous solution of sorbitol. All other stages except rings were degenerated. Thus, parasites of the ring stage remain in the culture. Centrifuging at 1500 rpm for 5 minutes removed the degenerated stages. The supernatant was discarded, and the pellet was washed twice with incomplete media. Parasitaemia was adjusted to about 1% for the assay by diluting with freshly washed RBCs. The material to be tested was dissolved in 100 µl of DMSO. The stock solution was diluted with RPMI-1640 to obtain different concentrations. The tests were performed on 96-well microtitre plates using chloroquine-sensitive and resistant isolates. Solutions of different concentrations of compounds were dispensed in 96-well microtitre plates in triplicate. The first well in all the rows was without any drugs and considered to be under control. The synchronized parasites were inoculated in all the wells, including the control wells, to get a final concentration of 5% haematocrit. The plates were incubated at 37 ºC for 24–30 h, depending on the maturation of the schizont. After confirmation of schizont maturation, smears were prepared from all the wells. The smear was stained with Geimsa stain or JSB stain, and the numbers of dead rings and schizonts were counted per 200 asexual stage parasites. The values were compared between the control and test wells. The inhibition percentage of schizont for each concentration of test sample was calculated as: $$\text{I}\text{n}\text{h}\text{i}\text{b}\text{i}\text{t}\text{i}\text{o}\text{n}=100-\text{A}$$ Here A is the percentage growth of schizont in the test wells. This was determined by the following formula: $$\text{A}=\text{N}\text{o}. \text{o}\text{f} \text{s}\text{c}\text{h}\text{i}\text{z}\text{o}\text{n}\text{t} \text{i}\text{n} \text{t}\text{h}\text{e} \text{t}\text{e}\text{s}\text{t} \text{w}\text{e}\text{l}\text{l}÷\text{N}\text{o}. \text{o}\text{f} \text{s}\text{c}\text{h}\text{i}\text{z}\text{o}\text{n}\text{t} \text{i}\text{n} \text{t}\text{h}\text{e} \text{c}\text{o}\text{n}\text{t}\text{r}\text{o}\text{l}\times 100$$ Chloroquine was used as the standard reference drug. Results and Discussion Chemistry The targeted compounds were synthesized in five steps as outlined in the scheme. In step-I, a mixture of substituted acetophenone (1), paraformaldehyde (2), and substituted amine (3) was heated under reflux for varying lengths of time in 95% ethanol to form substituted Mannich bases (4). In Step II, the keto group of the substituted Mannich bases (4) was reduced to the alcohols (5) using sodium borohydrate in an acidic environment. Step III involved the nucleophilic substitution of the hydroxyl group of substituted Mannich bases (5) for chloride upon thionyl chloride treatment, which led to substituted Mannich bases (6). Step IV involved the preparation of 7-chloro-4-(piperazin-1-yl)quinoline (8) by aromatic nucleophilic substitution on 4,7-dichloroquinoline (7) with an excess of piperazine. The final step-V involved again nucleophilic substitution of the chloride of substituted Mannich bases (6) by 7-chloro-4-(piperazin-1-yl)quinoline, yielding the targeted compounds. All the compounds (in methanol) exhibited three characteristic absorption maxima (λ max ) in the range between 215 and 340 nm. The shift of λ max towards longer wavelengths (320–340 nm) indicated the presence of strong chromophoric groups, such as a quinoline structure, in the molecule. The maxima in the lower wavelength range between 215–260 nm were due to the presence of a substituted phenyl ring and a hetero-aromatic ring system. The FT-IR-IRectra showed the C = C stretching bands for aromatic rings appeared between 1600 and 1450 cm1. The in-plane C-H bending vibrations occurred in the range of 1300 − 1000 cm1. The out-of-plane C-H bending vibrations appeared in the range of 900–690 cm1. These extremely intense absorptions, resulting from strong coupling with adjacent hydrogen atoms, are used to assign the positions of substituents on the aromatic ring. The N-H stretching vibrations occurred in the range of 3500–3300 cm1. The C-Cl stretching absorption occurred in the range between 1100 and 1035 cm1 for aryl chlorides. The C-H stretching absorptions occurred around 3000 cm1. In alkanes, sp 3 C-H absorption occurred at frequencies less than 3000 cm1 (3000–2840 cm1). 1H NMR spectra of the compounds showed that in alkanes (aliphatic or saturated hydrocarbons), all of the CH hydrogen absorption was found in the range of 0.7 to 1.7 ppm. Hydrogens in methyl groups are highly shielded and found in chemical shift values of 0.7–1.3 ppm, while hydrogens in the methylene group are found in the region of 1.2–1.4 ppm. The analytical and spectral data of the synthesized compounds showed good compliance with their structure. Antimalarial activity evaluation The in vitro antimalarial activity results displayed in Table-1 indicate that all of the synthesized compounds (9a to 9l) demonstrated moderate antimalarial activity against the chloroquine-sensitive 3D7 strain of Plasmodium falciparum at the tested dose. Table-1 In vitro antimalarial activity data of the compounds (9a-9l) Compound Code MIC a (µg/mL) IC 50 b (µM) (n = 3, \(\pm\) SD) 9a 31.25 2.5860.05 9b 15.6 2.6460.03 9c 15.6 2.3210.01 9d 31.25 2.4460.04 9e 31.25 3.3320.12 9f 15.6 2.0300.06 9g 31.25 2.3490.15 9h 15.6 4.2040.06 9i 15.6 2.3860.01 9j 15.6 2.5090.02 9k 15.6 2.8480.11 9l 3.9 1.9530.10 CQ 0.4 0.1060.01 a MIC = minimum inhibiting concentration for the development of the ring stage parasite into the schizont stage during 40 h of incubation against the 3D7 strain of P. falciparum . b IC50 = 50% inhibitory concentration values (µM) against the 3D7 strain of P. falciparum (data are expressed as mean SD from at least three different experiments in triplicate). The MIC values for all the compounds (9a–9l) ranged from 3.9 to 31.25µg/ml. Compound 9l (MIC = 3.9 µg/ml or 1.953 0.10 µM) was shown to be moderately active against the 3D7 strain of Plasmodium falciparum , as compared to Chloroquine (MIC = 0.4 µg/ml or 0.106 0.01 µM) among all the synthesized compounds. It was evident from a comparison of the antimalarial effects of the series that morpholine side chain alteration was advantageous for antimalarial activity. However, a comparison of the antimalarial impact across the series revealed that the antimalarial activity of 4-methoxyphenyl substituted Mannich bases was favorable. Compounds 9b, 9c, 9f, 9h to 9k were found to have the modestest levels of antimalarial activity, while compounds 9a, 9d, 9e, and 9g had the lowest levels. Compound 9l was found to have the greatest levels of antimalarial activity. In piperazine side chain modified 4-aminoquinoline Mannich bases, the MIC results of Compounds 9a-9l explained the SAR that p-methoxyphenyl & p-tolyl substitution enhanced antimalarial potency compared to unsubstituted phenyl along with dibenzylamino, diethylamino, dimethylamino, and morpholine side chain modification. Conclusion We have demonstrated the potential of 4-Aminoquinoline Mannich Bases modified by Piperazine side chains as antimalarial agents in vitro . Designed molecules show the possibility of developing chemical diversity around the core skeleton of Mannich bases to generate newer and more potent molecules with heterocyclic amine substitution. Declarations Acknowledgement The authors are thankful to Dr. C. R. Pillai, Emeritus Scientist, and Dr . Anup Anvikar , Director, National Institute of Malaria Research (Indian Council of Medical Research), New Delhi, for providing antimalarial screening facilities and training. The authors are also thankful to S.A.I.F., Punjab University, Chandigarh, India, for providing spectroscopic data. Conflict of interest: The authors have no conflicts of interest. Funding: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Data availability: All data generated or analyzed during this study are included in this published article. References Burger’s medicinal chemistry and drug discovery, A John Wiley & Sons, Inc., Publication, New York, 5, pp. 920-931(2003). N. White. Plasmodium knowlesi: the fifth human malaria parasite, The University of Chicago Press, (2008). A. C. Chou, R. Chevli and C. D. Fitch, Biochemistry , 19 (8), 1543-1549 (1980). T. J. Egan and H. M. Marques, Coord. Chem. Rev. , 190 , 493-517 (1999). A. Dorn, R. Stoffel, H. Matile, A. Bubendorf andR. G. Ridley, Nature , 374 (6519), 269-271 (1995). D. J. Sullivan, I. Y. Gluzman, D. G. Russell and D.E. Goldberg, Proceedings of the National Academy of Sciences, 93(21) pp.11865-11870 (1996). S. R. Cheruku, S. Maiti, A. Dorn, B. Scorneaux, A.K. Bhattacharjee, W.Y. Ellis and J.L. Vennerstrom, J Med. Chem. , 46 (14), 3166-3169 (2003). P. A. Stocks, K. J. Raynes, P. G. Bray, B.K. Park, P.M. O'Neill and S.A. Ward, J. Med. Chem. , 45 (23), 4975-4983 (2002). D. J. Pasto, C. R. Johnson and M. J. Miller. Experiments and techniques in organic chemistry, Prentice Hall Englewood Cliffs, NJ, (1992). B. Furniss, A. Hannaford, P. Smith and A.R. Tatchell, Vogel’s textbook of practical organic chemistry, ELBS, Longman: London, (1989). R. M. Silverstein and G. C. Bassler, J. Chem. Educ. , 39 (11), 546 (1962). D. W. Mathieson. Interpretation of organic spectra, Academic Press, New York, (1965). N. I. Wenzel, N. Chavain, Y. Wang, W. Friebolin, L.Maes, B.Pradines, M.Lanzer, V.Yardley, R.Brun, C.Herold-Mende, C.Biot, K. Toth and E. Davioud-Charvet, J Med. Chem. , 53 (8), 3214-3226 (2010). L. M. Antinarelli, A. M. Carmo, F. R. Pavan, C. Q. F. Leite, A. D. Da Silva, E. S. Coimbra and D. B. Salunke, Bioorg. Med. Chem. Lett. , 2 (1), 16 (2012). A. Kumar, K. Srivastava, S. R. Kumar, M.I. Siddiqi, S. K. Puri, J. K. Sexana and P.M.S. Chauhan , Eur. J. Med. Chem. , 46 (2), 676-690 (2011). B. Singh, D. Chetia and M. K. Kumawat, Pharm. Chem. J. , 55(7), 681-688 (2021). W. Trager and J. B. Jensen, Science , 193 (4254), 673-675 (1976). Scheme Scheme 1 is available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files Scheme1.docx Cite Share Download PDF Status: Under Review Version 1 posted Editor assigned by journal 06 Jun, 2024 Submission checks completed at journal 06 Jun, 2024 First submitted to journal 16 May, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4428579","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":311583095,"identity":"fa697301-9513-478c-a3f5-1bad00a22138","order_by":0,"name":"Bhupendra Singh","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA6ElEQVRIiWNgGAWjYBACAwkwxQxmM3wAkmzspGhhnAHSwkyKFmYeOBsPMJfuMXvwcYd1Pn8D8zZpm1/b5PmYGRg/fMzBrcVyzhlzw5ln0i1nHGArk87tu23YxszALDlzGx6H3cgxk+ZtO2zAcIDHTDq35zYjUAsbMy8hLX+BWuRBWix7btsTp4URqMUApIXhx+1EglosZ6SVG/a2pRsYHmYrtuxtuJ3cxszYjNcv5hLJ2x78bLM2kDvevPHGjz+3bee3Nx/88BGPFiBgg1Cg6GBsA7EYG/CqR2gBgz+EFI+CUTAKRsFIBAC8VkqzmO5yEQAAAABJRU5ErkJggg==","orcid":"","institution":"Graphik Era Hill University","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Bhupendra","middleName":"","lastName":"Singh","suffix":""},{"id":311583096,"identity":"6b336b0b-3c52-46dd-80d3-2661d2ac9815","order_by":1,"name":"Dipak Chetia","email":"","orcid":"","institution":"Dibrugarh University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Dipak","middleName":"","lastName":"Chetia","suffix":""}],"badges":[],"createdAt":"2024-05-16 05:33:49","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4428579/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4428579/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":58733081,"identity":"f9fcca48-2a1c-4cce-a0d7-e52ef5b5ad7b","added_by":"auto","created_at":"2024-06-20 11:48:45","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":727341,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4428579/v1/a0041d08-9cd6-441e-9056-44891d154ae9.pdf"},{"id":58732737,"identity":"8b5caf82-b323-451e-a6e7-a94f5663c685","added_by":"auto","created_at":"2024-06-20 11:40:45","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":90611,"visible":true,"origin":"","legend":"","description":"","filename":"Scheme1.docx","url":"https://assets-eu.researchsquare.com/files/rs-4428579/v1/8ca3d0deb6f076e3c833cc22.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eSynthesis of Some Novel Piperazine Side Chain Modified 4- Aminoquinoline Mannich Bases and Evaluation for Their in Vitro Antimalarial Activity\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003eHuman malaria is caused by five species of Plasmodium, e.g., \u003cspan type=\"ItalicUnderline\" class=\"ItalicUnderline\" name=\"Emphasis\"\u003eP. falciparum\u003c/span\u003e, \u003cspan type=\"ItalicUnderline\" class=\"ItalicUnderline\" name=\"Emphasis\"\u003eP. vivax\u003c/span\u003e, \u003cspan type=\"ItalicUnderline\" class=\"ItalicUnderline\" name=\"Emphasis\"\u003eP. ovale\u003c/span\u003e, \u003cem\u003eP. malariae\u003c/em\u003e, and \u003cspan type=\"ItalicUnderline\" class=\"ItalicUnderline\" name=\"Emphasis\"\u003eP. knowlesi\u003c/span\u003e. The vast majority of deaths are caused by \u003cspan type=\"ItalicUnderline\" class=\"ItalicUnderline\" name=\"Emphasis\"\u003eP.\u003c/span\u003e falciparum. \u003cspan type=\"ItalicUnderline\" class=\"ItalicUnderline\" name=\"Emphasis\"\u003eP. vivax\u003c/span\u003e, \u003cspan type=\"ItalicUnderline\" class=\"ItalicUnderline\" name=\"Emphasis\"\u003eP. ovale\u003c/span\u003e, and \u003cem\u003eP. malariae\u003c/em\u003e are responsible for a generally milder form of malaria that is rarely fatal. The zoonotic species \u003cspan type=\"ItalicUnderline\" class=\"ItalicUnderline\" name=\"Emphasis\"\u003eP. knowlesi\u003c/span\u003e, prevalent in Southeast Asia, causes malaria in macaques but can also cause severe infections in humans. [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/p\u003e \u003cp\u003eThe structure-activity relationship studies on 4-aminoquinoline antimalarial compounds suggest that the 7-chloro-4-aminoquinoline nucleus is quint essential for antimalarial activity, particularly inhibition of β-hematin formation and accumulation of the drug at the target site [\u003cspan additionalcitationids=\"CR4 CR5\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. The importance of the 4-aminopyridine substructure for hematin binding and antimalarial activity was also supported by experimental and molecular modeling studies by Cheruku and co-workers [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eA series of short-chain chloroquine derivatives was reported by Stocks and co-workers \u003csup\u003e[8],\u003c/sup\u003e in which replacement of the diethylamino function with the more metabolically stable side chain (\u003cem\u003etert\u003c/em\u003e-butyl) as well as heterocyclic ring (piperidyl, pyrrolidinyl, and morpholinyl) modifications led to a substantial increase in the antimalarial activity.\u003c/p\u003e \u003cp\u003eThese findings have given impetus to the idea that side chain modification is an attractive strategy for the development of antimalarial drugs with a desirable activity profile. On the basis of this evidence, we presumed that selectively modifying the side chain with a heterocyclic nucleus as well as a pendent amino group with 4-aminoquinoline Mannich bases could modulate the antimalarial activity. In the present study, we have proposed to synthesize compounds by modifications at the side chain of chloroquine with piperazine and the pendent amino group with Mannich bases of substituted acetophenone without altering the 7-chloro-4-aminoquinoline nucleus.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eChemistry\u003c/h2\u003e \u003cdiv id=\"Sec4\" class=\"Section3\"\u003e \u003ch2\u003eStructural investigation\u003c/h2\u003e \u003cp\u003eThe entire chemicals used in the present study were obtained from Sigma-Aldrich Corporation (USA), Rankem Pvt. Ltd. (India), and Merck Specialties Pvt. Ltd. (India). They were used without further purification unless otherwise stated. 4, 7-Dichloroquinoline (DCQ) was obtained as a gift sample from Ipca Laboratories Ltd., Ratlam, India. The melting point was determined using the \u003cem\u003eMP-M560\u003c/em\u003e Bucchi melting point apparatus. We checked that the reaction was complete using silica gel-G TLC plates and different solvent ratios. Iodine vapors or UV light (254 nm and 365 nm) were used to see what was going on. The \u003cem\u003eShimadzu UV-1700 Pharamspec\u003c/em\u003e UV-visible spectrophotometer was used for recording UV-visible spectra [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. A FT-IR-IRlpha Bruker) spectrometer without a KBr disc was used for recording the IR spectrum [\u003cspan additionalcitationids=\"CR11\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. The \u003csup\u003e1\u003c/sup\u003eH and \u003csup\u003e13\u003c/sup\u003eC NMR spectra were recorded on a \u003cem\u003eBruker Avance II 400\u003c/em\u003e NMR spectrometer at 400 MHz and 100 MHz, respectively, using either DMSO-d\u003csub\u003e6\u003c/sub\u003e or CDCl\u003csub\u003e3\u003c/sub\u003e as solvent with tetramethylsilane (TMS) as an internal standard [\u003cspan additionalcitationids=\"CR11\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. The mass spectrum was obtained on a TOF micromass spectrometer using electrospray ionization (ESI) [\u003cspan additionalcitationids=\"CR11\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Elemental microanalyses (CHN) were performed on a \u003cem\u003ePerkin Elmer 2400 Series II\u003c/em\u003e CHNS/O analyzer (Jean PD 1963).\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eGeneral Procedure\u003c/h2\u003e \u003cp\u003eThe targeted compounds were synthesized in five steps (Step-I to Step-V) according to the method originally utilized by Wenzel and co-workers [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], Furniss and co-workers [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e], Antinarelli and co-workers [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], Kumar A and co-workers [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e], and Singh B and co-workers [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eStep-I\u003c/h2\u003e \u003cp\u003eSecondary amine (33 mmol), powdered paraformaldehyde (33 mmol), and acetophenone or substituted acetophenone (25 mmol) were placed in a 250-ml round-bottomed flask attached to a reflux condenser. Introduce 10 ml of 95% ethanol, to which 0.1 ml of concentrated hydrochloric acid was added, and reflux the mixture on a water bath for 2\u0026ndash;3 hours. After the reflux period, the solvent was removed under reduced pressure and the crude product was purified.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eStep-II\u003c/h2\u003e \u003cp\u003eSodium borohydrate (500 mg) was dissolved in 10 ml of ethanol and product of step-I was added by maintaining temperature 30\u0026ndash;50 30\u0026ndash;50\u0026deg;C.The reaction mixture was allowed to stand at room temperature for 15 minutes with stirring. Hydrochloric acid (3 ml, 3 M) was added to the reaction mixture, and this mixture was heated to boiling on a hot plate until the mixture separated into two layers. It was cooled in an ice bath and transferred to a separating funnel with dichloromethane (DCM), and water was added to dissolve inorganic salt precipitate, if any, and then the aqueous layer was extracted with DCM. The organic layer was dried with anhydrous. Sodium sulfate and the solvent were evaporated to get the crude product.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eStep-III\u003c/h2\u003e \u003cp\u003eThe product of step-II (4.5 mmol) and thionyl chloride (4.5 mmol) in chloroform was heated for one hour (with occasional gentle shaking) in a round bottom flask attached with a reflux condenser and calcium chloride tube. After heating, unchanged thionyl chloride was removed by distillation to get the product.\u003c/p\u003e \u003cdiv id=\"Sec9\" class=\"Section3\"\u003e \u003ch2\u003eStep-IV\u003c/h2\u003e \u003cp\u003eA stirred mixture of 4, 7-dichloroquinoline (50 mmol), piperazine (150 mmol), and potassium iodide (12 mmol) in isopropyl alcohol (70 ml) was heated to reflux for 10 hours, cooling the reaction mass to room temperature. Isopropyl alcohol was distilled completely under vacuum. Water and methylene chloride were added to the residue and stirred for about 10 minutes at room temperature. The pH of the reaction mass was adjusted to 3-3.5 with dilutions of HCl, separated into an aqueous layer, and washed with methylene chloride. The pH of the aqueous layer was adjusted to 10\u0026ndash;11 with ammonia solution. The reaction mass was filtered and the precipitate was washed with water till the pH of the mother liquor became neutral. The solids obtained were dried.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section3\"\u003e \u003ch2\u003eStep-V\u003c/h2\u003e \u003cp\u003eThe product of step IV (1.80 mmol) was dissolved in anhydrous ethanol (25 ml) under heating. After cooling to room temperature, triethylamine (9.02 mmol) was added. Then the product of step III was added as a solid in three portions: first 1.89 mmol, then a further 0.39 mmol after 16 hours, and then 0.22 mmol after another 7 hours. After 12 hours of stirring at room temperature, the solvent was evaporated and the residue was purified by flash chromatography to obtain the final desired product as piperazine side chain modified 4-Aminoquinoline Mannich bases.\u003c/p\u003e \u003cp\u003e \u003cb\u003e7-chloro-4-(piperazin-1-yl)quinoline\u003c/b\u003e \u003cb\u003e(\u003c/b\u003e\u003cb\u003eAn intermediate\u003c/b\u003e\u003cb\u003e)\u003c/b\u003e: Creamy white solid with characteristic odour; soluble in Methanol, Ethanol, and Dichloromethane; Melting Point range 114-117\u003csup\u003eo\u003c/sup\u003eC; %Yield 70%; R\u003csub\u003ef\u003c/sub\u003e value 0.34 (Dichloromethane: Methanol:: 1:4); UV-Visible Spectrum (Methanol), λ\u003csub\u003emax\u003c/sub\u003e (nm): 223.20, 320.60; IR Spectrum (υ, cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e): 3252 (N-H str., \u0026gt;NH); 1604 (N-H def., \u0026gt;NH); 1291(C-N str., \u0026gt;NH); 1322 (C-N str., \u0026gt;N-); 1566, 1493, 1453, 1421 (C\u0026thinsp;=\u0026thinsp;C str., Ar. ring); 1374, 1261 (C-N str.); 1071 (Ar. C-Cl str.); 819, 802, 770 (Ar. C-H bend.); \u003csup\u003e1\u003c/sup\u003eH NMR (400 MHz, DMSO), δ (ppm) : 3.06\u0026ndash;3.09 (m,8H, piperazine); 3.14\u0026ndash;3.16 (m, 1H, \u0026gt;NH), 6.91\u0026ndash;6.92 (d, 1H, J\u0026thinsp;=\u0026thinsp;4 Hz, quinoline-H\u003csub\u003e3\u003c/sub\u003e); 7.45\u0026ndash;7.48 (dd, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, 4Hz, quinoline-H\u003csub\u003e6\u003c/sub\u003e); 7.94\u0026ndash;7.95 (d, 1H, J\u0026thinsp;=\u0026thinsp;4Hz, quinoline-H\u003csub\u003e5\u003c/sub\u003e); 7.99\u0026ndash;8.01 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e8\u003c/sub\u003e); 8.67\u0026ndash;8.68 (d, 1H, J\u0026thinsp;=\u0026thinsp;4Hz, quinoline-H\u003csub\u003e2\u003c/sub\u003e); \u003csup\u003e13\u003c/sup\u003eC NMR (100 MHz, DMSO), δ (ppm) 45.24 (CH\u003csub\u003e2\u003c/sub\u003e); 52.67 (CH\u003csub\u003e2\u003c/sub\u003e); 108.95 (C-2, quinoline), 121.38 (C-4a, quinoline); 125.42 (C-5, quinoline); 125.65 (C-6, quinoline); 128.00 (C-8, quinoline); 133.63 (C-7, quinoline, C-Cl); 149.61 (C-8a, quinoline); 151.80 (C-2, quinoline); 156.69 (C-4, quinoline); Mass Spectrum (m/z): 248.11 [M\u0026thinsp;+\u0026thinsp;H]\u003csup\u003e+\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003cb\u003eN,N-dibenzyl-3-(4-(7-chloroquinolin-4-yl)piperazin-1-yl)-3-phenylpropan-1-amine\u003c/b\u003e; \u003cb\u003e9a\u003c/b\u003e: Light brown Gummy Solid with characteristic odour; soluble in Methanol, Ethanol; %Yield 69%; R\u003csub\u003ef\u003c/sub\u003e value 0.44 (Dichloromethane: methanol::1:4); UV-Visible Spectrum (Methanol), λ\u003csub\u003emax\u003c/sub\u003e (nm) 224, 320.5; IR Spectrum (υ, cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e): 2923 (C-H str., \u0026gt;CH\u003csub\u003e2\u003c/sub\u003e); 1571, 1493, 1451 (C\u0026thinsp;=\u0026thinsp;C str., Ar. ring); 1374 (C-N str., \u0026gt;N-); 1114 (Ar. C-Cl str).; 916, 824, 778 (Ar. C-H bend); \u003csup\u003e1\u003c/sup\u003eH NMR (400 MHz, DMSO), δ (ppm) 1.22\u0026ndash;1.25 (m, 2H, -CH\u003csub\u003e2\u003c/sub\u003e-); 2.15 (s, 4H, CH\u003csub\u003e2\u003c/sub\u003e-Ar); 2.50\u0026ndash;2.53 (t, 2H, J\u0026thinsp;=\u0026thinsp;12Hz, CH\u003csub\u003e2\u003c/sub\u003e-N); 3.04\u0026ndash;3.11 (m, 1H, Ar-CHNH); 3.40\u0026ndash;3.58 (m,8H, piperazine); 6.50\u0026ndash;6.54 (d, 1H, J\u0026thinsp;=\u0026thinsp;16Hz, quinoline-H\u003csub\u003e3\u003c/sub\u003e); 7.07\u0026ndash;7.09 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e5\u003c/sub\u003e);7.55\u0026ndash;7.58 (dd, 1H, J\u0026thinsp;=\u0026thinsp;4Hz, 4Hz, quinoline-H\u003csub\u003e6\u003c/sub\u003e); 8.06 (s, 5H, Ar-H); 8.08\u0026ndash;8.09 (d, 1H, J\u0026thinsp;=\u0026thinsp;4Hz, quinoline-H\u003csub\u003e8\u003c/sub\u003e); 8.25 (s, 10H, Ar-H); 8.71\u0026ndash;8.73 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e2\u003c/sub\u003e); \u003csup\u003e13\u003c/sup\u003eC NMR (100 MHz, DMSO), δ (ppm) 38.90 (-CH\u003csub\u003e2\u003c/sub\u003e-); 45.93 (-CH\u003csub\u003e2\u003c/sub\u003e-N); 49.83 (CH\u003csub\u003e2\u003c/sub\u003e-Piperazine); 60.52 (Ar-CH\u003csub\u003e2\u003c/sub\u003e-N); 78.55 (\u0026gt;\u0026thinsp;CH-Ar.); 109.65 (C-3, quinoline); 121.17 (C-4a, quinoline); 125.53 (C-5, quinoline); 125.76 (C-6, quinoline); 126.03 (C-8, quinoline); 128.05, 129.97 (Ar.-C); 139.04 (C-7, quinoline, C-Cl); 149.52 (C-8a, quinoline); 151.98 (C-2, quionline); 155.37 (C-4, quinoline); Mass Spectrum (m/z) 562.01 [M\u0026thinsp;+\u0026thinsp;H]\u003csup\u003e+\u003c/sup\u003e; Elemental Analysis: Cal. (%) for C\u003csub\u003e36\u003c/sub\u003eH\u003csub\u003e37\u003c/sub\u003eClN\u003csub\u003e4\u003c/sub\u003e: C, 77.05; H, 6.65; N, 9.98; Obs. (%): C, 77.09; H, 6.61; N, 9.95.\u003c/p\u003e \u003cp\u003e \u003cb\u003eN,N-dibenzyl-3-(4-(7-chloroquinolin-4-yl)piperazin-1-yl)-3-p-tolylpropan-1-amine\u003c/b\u003e; \u003cb\u003e9b\u003c/b\u003e:\u003c/p\u003e \u003cp\u003eLight brownish gummy solid with characteristic odour; soluble in Methanol, Ethanol; %Yield 71%; R\u003csub\u003ef\u003c/sub\u003e value 0.54 (Dichloromethane: methanol:: 1:4); UV-Visible Spectrum (Methanol), λ\u003csub\u003emax\u003c/sub\u003e (nm) 224, 318; IR Spectrum (υ, cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) 2921 (C-H str., \u0026gt;CH\u003csub\u003e2\u003c/sub\u003e); 1573, 1492, 1452 (C\u0026thinsp;=\u0026thinsp;C str., Ar. ring); 1372 (C-N str., \u0026gt;N-); 1112 (Ar. C-Cl str).; 922, 822, 776 (Ar. C-H bend); \u003csup\u003e1\u003c/sup\u003eH NMR (400 MHz, DMSO), δ (ppm) 1.21\u0026ndash;1.26 (m, 2H, -CH\u003csub\u003e2\u003c/sub\u003e-); 2.07 (s, 3H, Ar-CH\u003csub\u003e3\u003c/sub\u003e); 2.18 (s, 4H, CH\u003csub\u003e2\u003c/sub\u003e-Ar); 2.49\u0026ndash;2.52 (t, 2H, J\u0026thinsp;=\u0026thinsp;12Hz, CH\u003csub\u003e2\u003c/sub\u003e-N); 3.09\u0026ndash;3.15 (m, 1H, Ar-CHNH); 3.46\u0026ndash;3.55 (m,8H, piperazine); 6.49\u0026ndash;6.52 (d, 1H, J\u0026thinsp;=\u0026thinsp;12Hz, quinoline-H\u003csub\u003e3\u003c/sub\u003e); 7.02\u0026ndash;7.04 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e5\u003c/sub\u003e); 7.15\u0026ndash;7.17 (d, 2H, J\u0026thinsp;=\u0026thinsp;8Hz, Ar-H); 7.26\u0026ndash;7.29 (d, 2H, J\u0026thinsp;=\u0026thinsp;12Hz, Ar-H); 7.50\u0026ndash;7.53 (dd, 1H, J\u0026thinsp;=\u0026thinsp;4Hz, 4Hz, quinoline-H\u003csub\u003e6\u003c/sub\u003e); 8.11\u0026ndash;8.13 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e8\u003c/sub\u003e); 8.20 (s, 10H, Ar-H); 8.77\u0026ndash;8.79 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e2\u003c/sub\u003e); Mass Spectrum (m/z): 576.07 [M\u0026thinsp;+\u0026thinsp;H]\u003csup\u003e+\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003cb\u003eN,N-dibenzyl-3-(4-(7-chloroquinolin-4-yl)piperazin-1-yl)-3-(4-methoxyphenyl)propan-1-amine\u003c/b\u003e; \u003cb\u003e9c\u003c/b\u003e: Dark brown gummy solid with characteristic odour; soluble in Methanol, Ethanol; %Yield 75%; R\u003csub\u003ef\u003c/sub\u003e value 0.63 (Dichloromethane:methanol::1:4); UV-Visible Spectrum (Methanol), λ\u003csub\u003emax\u003c/sub\u003e (nm) 225, 324; IR Spectrum (υ, cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) 2930 (C-H str., \u0026gt;CH\u003csub\u003e2\u003c/sub\u003e); 1572, 1508, 1451 (C\u0026thinsp;=\u0026thinsp;C str., Ar. ring); 1370 (C-N str., \u0026gt;N-); 1245 (Ar.-O-CH\u003csub\u003e3\u003c/sub\u003e); 1113 (Ar. C-Cl str).; 916, 824, 778 (Ar. C-H bend); \u003csup\u003e1\u003c/sup\u003eH NMR (400 MHz, DMSO), δ (ppm) 1.19\u0026ndash;1.24 (m, 2H, -CH\u003csub\u003e2\u003c/sub\u003e-); 2.23 (s, 4H, CH\u003csub\u003e2\u003c/sub\u003e-Ar); 2.42\u0026ndash;2.45 (t, 2H, J\u0026thinsp;=\u0026thinsp;12Hz, CH\u003csub\u003e2\u003c/sub\u003e-N); 3.12\u0026ndash;3.17 (m, 1H, Ar-CHNH); 3.44\u0026ndash;3.51 (m,8H, piperazine); 4.32 (s, 3H, Ar-OCH\u003csub\u003e3\u003c/sub\u003e); 6.45\u0026ndash;6.47 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e3\u003c/sub\u003e); 7.11\u0026ndash;7.13 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e5\u003c/sub\u003e); 7.19\u0026ndash;7.21 (d, 2H, J\u0026thinsp;=\u0026thinsp;8Hz, Ar-H); 7.31\u0026ndash;7.33 (d, 2H, J\u0026thinsp;=\u0026thinsp;8Hz, Ar-H); 7.58\u0026ndash;7.61 (dd, 1H, J\u0026thinsp;=\u0026thinsp;4Hz, 4Hz, quinoline-H\u003csub\u003e6\u003c/sub\u003e); 8.19\u0026ndash;8.21 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e8\u003c/sub\u003e); 8.27 (s, 10H, Ar-H); 8.69\u0026ndash;8.71 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e2\u003c/sub\u003e); Mass Spectrum (m/z) 592.02 [M\u0026thinsp;+\u0026thinsp;H]\u003csup\u003e+\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003cb\u003e3-(4-(7-chloroquinolin-4-yl)piperazin-1-yl)-N,N-diethyl-3-phenylpropan-1-amine; 9d\u003c/b\u003e: Creamy white solid with characteristic odour; soluble in Methanol, Ethanol; Melting range: 166-169\u003csup\u003eo\u003c/sup\u003eC; %Yield 67%; R\u003csub\u003ef\u003c/sub\u003e value 0.53 (Dichloromethane:methanol::1:4); UV-Visible Spectrum (Methanol), λ\u003csub\u003emax\u003c/sub\u003e (nm) 221.5, 343.5; IR Spectrum (υ, cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) 2934 (C-H str., \u0026gt;CH\u003csub\u003e2\u003c/sub\u003e); 1568, 1495, 1458 (C\u0026thinsp;=\u0026thinsp;C str., Ar. ring); 1377 (C-N str., \u0026gt;N-); 1118 (Ar. C-Cl str).; 927, 837, 768 (Ar. C-H bend); \u003csup\u003e1\u003c/sup\u003eH NMR (400 MHz, DMSO), δ (ppm) 1.14\u0026ndash;1.17 (t, 6H, J\u0026thinsp;=\u0026thinsp;12Hz, NCH\u003csub\u003e2\u003c/sub\u003eCH\u003csub\u003e3\u003c/sub\u003e); 1.19\u0026ndash;1.24 (m, 2H, -CH\u003csub\u003e2\u003c/sub\u003e-); 2.47\u0026ndash;2.50 (t, 2H, J\u0026thinsp;=\u0026thinsp;12Hz, CH\u003csub\u003e2\u003c/sub\u003e-N); 2.65\u0026ndash;2.71 (m, 4H, NCH\u003csub\u003e2\u003c/sub\u003eCH\u003csub\u003e3\u003c/sub\u003e); 3.12\u0026ndash;3.17 (m, 1H, Ar-CHNH); 3.39\u0026ndash;3.45 (m,8H, piperazine); 6.57\u0026ndash;6.59 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e3\u003c/sub\u003e); 7.13\u0026ndash;7.15 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e5\u003c/sub\u003e);7.45\u0026ndash;7.48 (dd, 1H, J\u0026thinsp;=\u0026thinsp;4Hz, 4Hz, quinoline-H\u003csub\u003e6\u003c/sub\u003e); 8.11 (s, 5H, Ar-H); 8.19\u0026ndash;8.21 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e8\u003c/sub\u003e); 8.52\u0026ndash;8.54 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e2\u003c/sub\u003e); \u003csup\u003e13\u003c/sup\u003eC NMR (100 MHz, DMSO), δ (ppm) 9.08 (CH\u003csub\u003e3\u003c/sub\u003e-CH\u003csub\u003e2\u003c/sub\u003e), 36.46 (-CH\u003csub\u003e2\u003c/sub\u003e-); 46.25 (-CH\u003csub\u003e2\u003c/sub\u003e-N); 47.51 (CH\u003csub\u003e2\u003c/sub\u003e-Piperazine); 78.55 (\u0026gt;\u0026thinsp;CH-Ar.); 111.36 (C-3, quinoline); 120.11 (C-4a, quinoline); 124.05 (C-5, quinoline); 125.67 (C-6, quinoline); 126.32 (C-8, quinoline); 127.05, 128.57 (Ar.-C); 139.64 (C-7, quinoline, C-Cl); 150.72 (C-8a, quinoline); 154.08 (C-2, quionline); 156.43 (C-4, quinoline); Mass Spectrum (m/z): 437.16 [M\u0026thinsp;+\u0026thinsp;H]\u003csup\u003e+\u003c/sup\u003e; Elemental Analysis Cal. (%) for C\u003csub\u003e26\u003c/sub\u003eH\u003csub\u003e33\u003c/sub\u003eClN\u003csub\u003e4\u003c/sub\u003e: C, 71.46; H, 7.61; N, 12.82; Obs. (%): C, 71.55; H, 7.64; N, 12.79.\u003c/p\u003e \u003cp\u003e \u003cb\u003e3-(4-(7-chloroquinolin-4-yl)piperazin-1-yl)-N,N-diethyl-3-p-tolylpropan-1-amine; 9e\u003c/b\u003e: Light brown gummy solid with characteristic odour; soluble in Methanol, Ethanol; %Yield 71%; R\u003csub\u003ef\u003c/sub\u003e value 0.58 (Dichloromethane:methanol::1:4); UV-Visible Spectrum (Methanol), λ\u003csub\u003emax\u003c/sub\u003e (nm) 222, 341; IR Spectrum (υ, cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) 2922 (C-H str., \u0026gt;CH\u003csub\u003e2\u003c/sub\u003e); 1574, 1510, 1452 (C\u0026thinsp;=\u0026thinsp;C str., Ar. ring); 1375 (C-N str., \u0026gt;N-); 1114 (Ar. C-Cl str).; 926, 823, 769 (Ar. C-H bend); \u003csup\u003e1\u003c/sup\u003eH NMR (400 MHz, DMSO), δ (ppm) 1.11\u0026ndash;1.14 (t, 6H, J\u0026thinsp;=\u0026thinsp;12Hz, NCH\u003csub\u003e2\u003c/sub\u003eCH\u003csub\u003e3\u003c/sub\u003e); 1.23\u0026ndash;1.28 (m, 2H, -CH\u003csub\u003e2\u003c/sub\u003e-); 2.19 (s, 3H, Ar-CH\u003csub\u003e3\u003c/sub\u003e); 2.35\u0026ndash;2.38 (t, 2H, J\u0026thinsp;=\u0026thinsp;12Hz, CH\u003csub\u003e2\u003c/sub\u003e-N); 2.71\u0026ndash;2.76 (m, 4H, NCH\u003csub\u003e2\u003c/sub\u003eCH\u003csub\u003e3\u003c/sub\u003e); 3.22\u0026ndash;3.27 (m, 1H, Ar-CHNH); 3.45\u0026ndash;3.49 (m,8H, piperazine); 6.67\u0026ndash;6.69 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e3\u003c/sub\u003e); 6.95\u0026ndash;6.97 (d, 2H, J\u0026thinsp;=\u0026thinsp;8Hz, Ar-H); 7.18\u0026ndash;7.20 (d, 2H, J\u0026thinsp;=\u0026thinsp;8Hz, Ar-H); 7.28\u0026ndash;7.30 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e5\u003c/sub\u003e); 7.55\u0026ndash;7.58 (dd, 1H, J\u0026thinsp;=\u0026thinsp;4Hz, 4Hz, quinoline-H\u003csub\u003e6\u003c/sub\u003e); 8.11\u0026ndash;8.13 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e8\u003c/sub\u003e); 8.42\u0026ndash;8.44 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e2\u003c/sub\u003e); Mass Spectrum (m/z): 452.01 [M\u0026thinsp;+\u0026thinsp;H]\u003csup\u003e+\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003cb\u003e3-(4-(7-chloroquinolin-4-yl)piperazin-1-yl)-N,N-diethyl-3-(4-methoxyphenyl)propan-1-amine; 9f\u003c/b\u003e: Chocolate brownish gummy solid with characteristic odour; soluble in Methanol, Ethanol; %Yield 73%; R\u003csub\u003ef\u003c/sub\u003e value 0.55 (Dichloromethane:methanol::1:4); UV-Visible Spectrum (Methanol), λ\u003csub\u003emax\u003c/sub\u003e (nm) 224, 343; IR Spectrum (υ, cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) 2932 (C-H str., \u0026gt;CH\u003csub\u003e2\u003c/sub\u003e); 1574, 1508, 1453 (C\u0026thinsp;=\u0026thinsp;C str., Ar. ring); 1376 (C-N str., \u0026gt;N-); 1245 (Ar.-O-CH\u003csub\u003e3\u003c/sub\u003e); 1113 (Ar. C-Cl str).; 924, 824, 711 (Ar. C-H bend); \u003csup\u003e1\u003c/sup\u003eH NMR (400 MHz, DMSO), δ (ppm) 1.13\u0026ndash;1.16 (t, 6H, J\u0026thinsp;=\u0026thinsp;12Hz, NCH\u003csub\u003e2\u003c/sub\u003eCH\u003csub\u003e3\u003c/sub\u003e); 1.29\u0026ndash;1.34 (m, 2H, -CH\u003csub\u003e2\u003c/sub\u003e-); 2.41\u0026ndash;2.44 (t, 2H, J\u0026thinsp;=\u0026thinsp;12Hz, CH\u003csub\u003e2\u003c/sub\u003e-N); 2.68\u0026ndash;2.77 (m, 4H, NCH\u003csub\u003e2\u003c/sub\u003eCH\u003csub\u003e3\u003c/sub\u003e); 3.19\u0026ndash;3.25 (m, 1H, Ar-CHNH); 3.51\u0026ndash;3.57 (m,8H, piperazine); 3.71 (s, 3H, Ar-OCH\u003csub\u003e3\u003c/sub\u003e); 6.77\u0026ndash;6.79 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e3\u003c/sub\u003e); 6.91\u0026ndash;6.93 (d, 2H, J\u0026thinsp;=\u0026thinsp;8Hz, Ar-H); 7.14\u0026ndash;7.16 (d, 2H, J\u0026thinsp;=\u0026thinsp;8Hz, Ar-H); 7.31\u0026ndash;7.32 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e5\u003c/sub\u003e); 7.61\u0026ndash;7.64 (dd, 1H, J\u0026thinsp;=\u0026thinsp;4Hz, 4Hz, quinoline-H\u003csub\u003e6\u003c/sub\u003e); 8.31\u0026ndash;8.34 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e8\u003c/sub\u003e); 8.47\u0026ndash;8.49 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e2\u003c/sub\u003e); Mass Spectrum (m/z): 468.7 [M\u0026thinsp;+\u0026thinsp;H]\u003csup\u003e+\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003cb\u003e3-(4-(7-chloroquinolin-4-yl)piperazin-1-yl)-N,N-dimethyl-3-phenylpropan-1-amine; 9g\u003c/b\u003e: Dark brownish gummy solid with characteristic odour; soluble in Methanol, Ethanol; %Yield 71%; R\u003csub\u003ef\u003c/sub\u003e value 0.48 (Dichloromethane:methanol::1:4); UV-Visible Spectrum (Methanol), λ\u003csub\u003emax\u003c/sub\u003e (nm) 224.5, 321; IR Spectrum (υ, cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) 2932 (C-H str., \u0026gt;CH\u003csub\u003e2\u003c/sub\u003e); 1574, 1492, 1450 (C\u0026thinsp;=\u0026thinsp;C str., Ar. ring); 1296 (C-N str., \u0026gt;N-); 1115 (Ar. C-Cl str).; 923, 824, 778 (Ar. C-H bend).; \u003csup\u003e1\u003c/sup\u003eH NMR (400 MHz, DMSO), δ (ppm) 1.17\u0026ndash;1.23 (m, 2H, -CH\u003csub\u003e2\u003c/sub\u003e-); 2.31 (s, 6H, N-CH\u003csub\u003e3\u003c/sub\u003e); 2.43\u0026ndash;2.47 (t, 2H, J\u0026thinsp;=\u0026thinsp;12Hz, CH\u003csub\u003e2\u003c/sub\u003e-N); 3.17\u0026ndash;3.23 (m, 1H, Ar-CHNH); 3.51\u0026ndash;3.57 (m,8H, piperazine); 6.63\u0026ndash;6.65 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e3\u003c/sub\u003e); 7.03\u0026ndash;7.05 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e5\u003c/sub\u003e);7.41\u0026ndash;7.44 (dd, 1H, J\u0026thinsp;=\u0026thinsp;4Hz, 4Hz, quinoline-H\u003csub\u003e6\u003c/sub\u003e); 8.22 (s, 5H, Ar-H); 8.34\u0026ndash;8.36 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e8\u003c/sub\u003e); 8.61\u0026ndash;8.63 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e2\u003c/sub\u003e); \u003csup\u003e13\u003c/sup\u003eC NMR (100 MHz, DMSO), δ (ppm) 36.46 (-CH\u003csub\u003e2\u003c/sub\u003e-); 45.6 (CH\u003csub\u003e3\u003c/sub\u003e-N); ); 49.51 (CH\u003csub\u003e2\u003c/sub\u003e-Piperazine); 53.50 (CH\u003csub\u003e2\u003c/sub\u003e-N); 71.55 (\u0026gt;\u0026thinsp;CH-Ar.); 115.36 (C-3, quinoline); 123.21 (C-4a, quinoline); 125.05 (C-5, quinoline); 126.07 (C-6, quinoline); 126.09, 127.88 (Ar.-C); 129.31 (C-8, quinoline); 134.66 (C-7, quinoline, C-Cl); 150.02 (C-8a, quinoline); 151.18 (C-2, quionline); 158.73 (C-4, quinoline); Mass Spectrum (m/z) 409.56 [M\u0026thinsp;+\u0026thinsp;H]\u003csup\u003e+\u003c/sup\u003e; Elemental Analysis Cal. (%) for C\u003csub\u003e24\u003c/sub\u003eH\u003csub\u003e29\u003c/sub\u003eClN\u003csub\u003e4\u003c/sub\u003e: C, 70.48; H, 7.15; N, 13.70; Obs. (%): C, 70.51; H, 7.12; N, 13.73.\u003c/p\u003e \u003cp\u003e \u003cb\u003e3-(4-(7-chloroquinolin-4-yl)piperazin-1-yl)-N,N-dimethyl-3-p-tolylpropan-1-amine; 9h\u003c/b\u003e: Chocolate brown gummy solid with characteristic odour; soluble in Methanol, Ethanol; %Yield 66%; R\u003csub\u003ef\u003c/sub\u003e value 0.53 (Dichloromethane:methanol::1:4); UV-Visible Spectrum (Methanol), λ\u003csub\u003emax\u003c/sub\u003e (nm) 224, 319; IR Spectrum (υ, cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) 2920 (C-H str., \u0026gt;CH\u003csub\u003e2\u003c/sub\u003e); 1566, 1512, 1453 (C\u0026thinsp;=\u0026thinsp;C str., Ar. ring); 1375 (C-N str., \u0026gt;N-); 1114 (Ar. C-Cl str).; 925, 822, 794 (Ar. C-H bend); \u003csup\u003e1\u003c/sup\u003eH NMR (400 MHz, DMSO), δ (ppm) 1.13\u0026ndash;1.19 (m, 2H, -CH\u003csub\u003e2\u003c/sub\u003e-); 2.11 (s, 3H, Ar-CH\u003csub\u003e3\u003c/sub\u003e); 2.33 (s, 6H, N-CH\u003csub\u003e3\u003c/sub\u003e); 2.39\u0026ndash;2.42 (t, 2H, J\u0026thinsp;=\u0026thinsp;12Hz, CH\u003csub\u003e2\u003c/sub\u003e-N); 3.07\u0026ndash;3.12 (m, 1H, Ar-CHNH); 3.42\u0026ndash;3.48 (m,8H, piperazine); 6.66\u0026ndash;6.68 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e3\u003c/sub\u003e); 6.81\u0026ndash;6.83 (d, 2H, J\u0026thinsp;=\u0026thinsp;8Hz, Ar-H); 7.01\u0026ndash;7.03 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e5\u003c/sub\u003e); 7.14\u0026ndash;7.16(d, 2H, J\u0026thinsp;=\u0026thinsp;8Hz, Ar-H); 7.31\u0026ndash;7.34 (dd, 1H, J\u0026thinsp;=\u0026thinsp;4Hz, 4Hz, quinoline-H\u003csub\u003e6\u003c/sub\u003e); 8.27\u0026ndash;8.29 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e8\u003c/sub\u003e); 8.51\u0026ndash;8.53 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e2\u003c/sub\u003e); Mass Spectrum (m/z) 423.69 [M\u0026thinsp;+\u0026thinsp;H]\u003csup\u003e+\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003cb\u003e3-(4-(7-chloroquinolin-4-yl)piperazin-1-yl)-3-(4-methoxyphenyl)-N,N-dimethylpropan-1-amine; 9i\u003c/b\u003e: Light brown gummy solid with characteristic odour; soluble in Methanol, Ethanol; %Yield 69%; R\u003csub\u003ef\u003c/sub\u003e value 0.57 (Dichloromethane:methanol::1:4); UV-Visible Spectrum (Methanol), λ\u003csub\u003emax\u003c/sub\u003e (nm) 226, 324; IR Spectrum (υ, cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) 2938 (C-H str., \u0026gt;CH\u003csub\u003e2\u003c/sub\u003e); 1569, 1506, 1457 (C\u0026thinsp;=\u0026thinsp;C str., Ar. ring); 1377 (C-N str., \u0026gt;N-); 1245 (Ar.-O-CH\u003csub\u003e3\u003c/sub\u003e); 1114 (Ar. C-Cl str).; 928, 824, 768 (Ar. C-H bend); \u003csup\u003e1\u003c/sup\u003eH NMR (400 MHz, DMSO), δ (ppm) 1.12\u0026ndash;1.18 (m, 2H, -CH\u003csub\u003e2\u003c/sub\u003e-); 2.31 (s, 6H, N-CH\u003csub\u003e3\u003c/sub\u003e); 2.41\u0026ndash;2.43 (t, 2H, J\u0026thinsp;=\u0026thinsp;8Hz, CH\u003csub\u003e2\u003c/sub\u003e-N); 3.14\u0026ndash;3.20 (m, 1H, Ar-CHNH); 3.32\u0026ndash;3.38 (m,8H, piperazine); 3.85(s, 3H, Ar-OCH\u003csub\u003e3\u003c/sub\u003e); 6.61\u0026ndash;6.62 (d, 1H, J\u0026thinsp;=\u0026thinsp;4Hz, quinoline-H\u003csub\u003e3\u003c/sub\u003e); 6.71\u0026ndash;6.73 (d, 2H, J\u0026thinsp;=\u0026thinsp;8Hz, Ar-H); 7.05\u0026ndash;7.07 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e5\u003c/sub\u003e); 7.22\u0026ndash;7.23(d, 2H, J\u0026thinsp;=\u0026thinsp;4Hz, Ar-H); 7.43\u0026ndash;7.47 (dd, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, 4Hz, quinoline-H\u003csub\u003e6\u003c/sub\u003e); 8.32\u0026ndash;8.35 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e8\u003c/sub\u003e); 8.47\u0026ndash;8.49 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e2\u003c/sub\u003e); Mass Spectrum (m/z) 439.74 [M\u0026thinsp;+\u0026thinsp;H]\u003csup\u003e+\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003cb\u003e7-chloro-4-(4-(3-morpholino-1-phenylpropyl) piperazin-1-yl) quinoline\u003c/b\u003e; \u003cb\u003e9j\u003c/b\u003e: Light Brownish gummy solid with characteristic odour; soluble in Methanol, Ethanol; %Yield 65%; R\u003csub\u003ef\u003c/sub\u003e value 0.63 (Dichloromethane:methanol::1:4); UV-Visible Spectrum (Methanol), λ\u003csub\u003emax\u003c/sub\u003e (nm) 224.5, 321; IR Spectrum (υ, cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) 2930 (C-H str., \u0026gt;CH\u003csub\u003e2\u003c/sub\u003e); 1569, 1492, 1450 (C\u0026thinsp;=\u0026thinsp;C str., Ar. ring); 1375 (C-N str., \u0026gt;N-); 1113 (Ar. C-Cl str).; 922, 823, 745 (Ar. C-H bend).; \u003csup\u003e1\u003c/sup\u003eH NMR (400 MHz, DMSO), δ (ppm) 1.24\u0026ndash;1.31 (m, 2H, -CH\u003csub\u003e2\u003c/sub\u003e-); 1.79\u0026ndash;1.81 (t, 4H, J\u0026thinsp;=\u0026thinsp;8Hz, morpholinyl-H); 2.39\u0026ndash;2.42 (t, 2H, J\u0026thinsp;=\u0026thinsp;8Hz, CH\u003csub\u003e2\u003c/sub\u003e-N); 3.17\u0026ndash;3.26 (m, 1H, Ar-CHNH); 3.41\u0026ndash;3.49 (m,8H, piperazine); 3.81\u0026ndash;3.83 (t, 4H, J\u0026thinsp;=\u0026thinsp;8Hz, morpholinyl-H); 6.84\u0026ndash;6.86 (d, 1H, J\u0026thinsp;=\u0026thinsp;4Hz, quinoline-H\u003csub\u003e3\u003c/sub\u003e); 7.05\u0026ndash;7.06 (d, 1H, J\u0026thinsp;=\u0026thinsp;4Hz, quinoline-H\u003csub\u003e5\u003c/sub\u003e); 7.42\u0026ndash;7.45 (dd, 1H, J\u0026thinsp;=\u0026thinsp;4Hz, 4Hz, quinoline-H\u003csub\u003e6\u003c/sub\u003e); 7.82\u0026ndash;7.84 (d, 1H, J\u0026thinsp;=\u0026thinsp;4Hz, quinoline-H\u003csub\u003e8\u003c/sub\u003e); 8.13 (s, 5H, Ar-H); 8.75\u0026ndash;8.77 (d, 1H, J\u0026thinsp;=\u0026thinsp;4Hz, quinoline-H\u003csub\u003e2\u003c/sub\u003e).; \u003csup\u003e13\u003c/sup\u003eC NMR (100 MHz, DMSO), δ (ppm) 35.97 (-CH\u003csub\u003e2\u003c/sub\u003e-); 49.07 (CH\u003csub\u003e2\u003c/sub\u003e-N); 50.07 (CH\u003csub\u003e2\u003c/sub\u003e-Piperazine); 53.89, 66.68 (CH\u003csub\u003e2\u003c/sub\u003e-Morpholine); 70.78 (\u0026gt;\u0026thinsp;CH-Ar.); 117.86 (C-3, quinoline); 124.91 (C-4a, quinoline); 125.95 (C-5, quinoline); 126.01, 127.91 (Ar.-C); 128.03 (C-6, quinoline); 129.87 (C-8, quinoline); 134.95 (C-7, quinoline, C-Cl); 149.03 (C-8a, quinoline); 150.98 (C-2, quionline); 158.93 (C-4, quinoline); Mass Spectrum (m/z) 451.03 [M\u0026thinsp;+\u0026thinsp;H]\u003csup\u003e+\u003c/sup\u003e; Elemental Analysis Cal. (%) for C\u003csub\u003e26\u003c/sub\u003eH\u003csub\u003e31\u003c/sub\u003eClN\u003csub\u003e4\u003c/sub\u003eO: C, 69.24; H, 6.93; N, 12.42; Obs. (%): C, 69.27; H, 6.90; N, 12.45.\u003c/p\u003e \u003cp\u003e \u003cb\u003e7-chloro-4-(4-(3-morpholino-1-p-tolylpropyl)piperazin-1-yl)quinoline\u003c/b\u003e; \u003cb\u003e9k\u003c/b\u003e: Dark Brownish gummy solid with characteristic odour; soluble in Methanol, Ethanol; %Yield 62%; R\u003csub\u003ef\u003c/sub\u003e value 0.58 (Dichloromethane:methanol::1:4); UV-Visible Spectrum (Methanol), λ\u003csub\u003emax\u003c/sub\u003e (nm) 224, 320; IR Spectrum (υ, cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) 2926 (C-H str., \u0026gt;CH\u003csub\u003e2\u003c/sub\u003e); 1571, 1492, 1450 (C\u0026thinsp;=\u0026thinsp;C str., Ar. ring); 1376 (C-N str., \u0026gt;N-); 1112 (Ar. C-Cl str).; 925, 824, 801 (Ar. C-H bend); \u003csup\u003e1\u003c/sup\u003eH NMR (400 MHz, DMSO), δ (ppm) 1.27\u0026ndash;1.33 (m, 2H, -CH\u003csub\u003e2\u003c/sub\u003e-); 1.77\u0026ndash;1.80 (t, 4H, J\u0026thinsp;=\u0026thinsp;12Hz, morpholinyl-H); 2.11 (s,3H, Ar-CH\u003csub\u003e3\u003c/sub\u003e); 2.43\u0026ndash;2.45 (t, 2H, J\u0026thinsp;=\u0026thinsp;8Hz, CH\u003csub\u003e2\u003c/sub\u003e-N); 3.12\u0026ndash;3.17 (m, 1H, Ar-CHNH); 3.45\u0026ndash;3.50 (m,8H, piperazine); 3.77\u0026ndash;3.80 (t, 4H, J\u0026thinsp;=\u0026thinsp;12Hz, morpholinyl-H); 6.72\u0026ndash;6.74 (d, 2H, J\u0026thinsp;=\u0026thinsp;8Hz, Ar-H); 6.89\u0026ndash;6.91 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e3\u003c/sub\u003e); 7.09\u0026ndash;7.10 (d, 1H, J\u0026thinsp;=\u0026thinsp;4Hz, quinoline-H\u003csub\u003e5\u003c/sub\u003e); 7.23\u0026ndash;7.25 (d,2H, J\u0026thinsp;=\u0026thinsp;8Hz, Ar-H); 7.39\u0026ndash;7.42 (dd, 1H, J\u0026thinsp;=\u0026thinsp;4Hz, 4Hz, quinoline-H\u003csub\u003e6\u003c/sub\u003e); 7.77\u0026ndash;7.78 (d, 1H, J\u0026thinsp;=\u0026thinsp;4Hz, quinoline-H\u003csub\u003e8\u003c/sub\u003e); 8.65\u0026ndash;8.67 (d, 1H, J\u0026thinsp;=\u0026thinsp;8Hz, quinoline-H\u003csub\u003e2\u003c/sub\u003e); Mass Spectrum (m/z) 466.11 [M\u0026thinsp;+\u0026thinsp;H]\u003csup\u003e+\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003cb\u003e7-chloro-4-(4-(1-(4-methoxyphenyl)-3-morpholinopropyl)piperazin-1-yl)quinoline\u003c/b\u003e; \u003cb\u003e9l\u003c/b\u003e: Light Brownish gummy solid with characteristic odour; soluble in Methanol, Ethanol; %Yield 65%; R\u003csub\u003ef\u003c/sub\u003e value 0.63 (Dichloromethane:methanol::1:4); UV-Visible Spectrum (Methanol), λ\u003csub\u003emax\u003c/sub\u003e (nm) 224.5, 321; IR Spectrum (υ, cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e): 2930 (C-H str., \u0026gt;CH\u003csub\u003e2\u003c/sub\u003e); 1569, 1492, 1450 (C\u0026thinsp;=\u0026thinsp;C str., Ar. ring); 1375 (C-N str., \u0026gt;N-); 1113 (Ar. C-Cl str).; 922, 823, 745 (Ar. C-H bend); \u003csup\u003e1\u003c/sup\u003eH NMR (400 MHz, DMSO), δ (ppm): 1.24\u0026ndash;1.31 (m, 2H, -CH\u003csub\u003e2\u003c/sub\u003e-); 1.79\u0026ndash;1.81 (t, 4H, J\u0026thinsp;=\u0026thinsp;8Hz, morpholinyl-H); 2.39\u0026ndash;2.42 (t, 2H, J\u0026thinsp;=\u0026thinsp;8Hz, CH\u003csub\u003e2\u003c/sub\u003e-N); 3.17\u0026ndash;3.26 (m, 1H, Ar-CHNH); 3.41\u0026ndash;3.49 (m,8H, piperazine); 3.81\u0026ndash;3.83 (t, 4H, J\u0026thinsp;=\u0026thinsp;8Hz, morpholinyl-H); 6.84\u0026ndash;6.86 (d, 1H, J\u0026thinsp;=\u0026thinsp;4Hz, quinoline-H\u003csub\u003e3\u003c/sub\u003e); 7.05\u0026ndash;7.06 (d, 1H, J\u0026thinsp;=\u0026thinsp;4Hz, quinoline-H\u003csub\u003e5\u003c/sub\u003e); 7.42\u0026ndash;7.45 (dd, 1H, J\u0026thinsp;=\u0026thinsp;4Hz, 4Hz, quinoline-H\u003csub\u003e6\u003c/sub\u003e); 7.82\u0026ndash;7.84 (d, 1H, J\u0026thinsp;=\u0026thinsp;4Hz, quinoline-H\u003csub\u003e8\u003c/sub\u003e); 8.13 (s, 5H, Ar-H); 8.75\u0026ndash;8.77 (d, 1H, J\u0026thinsp;=\u0026thinsp;4Hz, quinoline-H\u003csub\u003e2\u003c/sub\u003e); \u003csup\u003e13\u003c/sup\u003eC NMR (100 MHz, DMSO), δ (ppm) 35.97 (-CH\u003csub\u003e2\u003c/sub\u003e-); 49.07 (CH\u003csub\u003e2\u003c/sub\u003e-N); 50.07 (CH\u003csub\u003e2\u003c/sub\u003e-Piperazine); 53.89, 66.68 (CH\u003csub\u003e2\u003c/sub\u003e-Morpholine); 70.78 (\u0026gt;\u0026thinsp;CH-Ar.); 117.86 (C-3, quinoline); 124.91 (C-4a, quinoline); 125.95 (C-5, quinoline); 126.01, 127.91 (Ar.-C); 128.03 (C-6, quinoline); 129.87 (C-8, quinoline); 134.95 (C-7, quinoline, C-Cl); 149.03 (C-8a, quinoline); 150.98 (C-2, quionline); 158.93 (C-4, quinoline); Mass Spectrum (m/z): 451.03 [M\u0026thinsp;+\u0026thinsp;H]\u003csup\u003e+\u003c/sup\u003e; Elemental Analysis: Cal. (%) for C\u003csub\u003e26\u003c/sub\u003eH\u003csub\u003e31\u003c/sub\u003eClN\u003csub\u003e4\u003c/sub\u003eO: C, 69.24; H, 6.93; N, 12.42; Obs. (%): C, 69.27; H, 6.90; N, 12.45.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eAntimalarial Activity Evaluation\u003c/h2\u003e \u003cp\u003eThe \u003cem\u003ein-vitro\u003c/em\u003e antimalarial assay of the synthesized compounds was carried out on 96 well-microtitre plates [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. The cultures of chloroquine-sensitive stains of \u003cem\u003eP. falciparum\u003c/em\u003e 3D7 were routinely maintained in medium RPMI 1640 supplemented with 25 mM HEPES, 1% D-glucose, 0.23% sodium bicarbonate, and 10% heat-inactivated human serum. The culture was synchronized using a 5% aqueous solution of sorbitol. All other stages except rings were degenerated. Thus, parasites of the ring stage remain in the culture. Centrifuging at 1500 rpm for 5 minutes removed the degenerated stages. The supernatant was discarded, and the pellet was washed twice with incomplete media.\u003c/p\u003e \u003cp\u003eParasitaemia was adjusted to about 1% for the assay by diluting with freshly washed RBCs. The material to be tested was dissolved in 100 \u0026micro;l of DMSO. The stock solution was diluted with RPMI-1640 to obtain different concentrations. The tests were performed on 96-well microtitre plates using chloroquine-sensitive and resistant isolates. Solutions of different concentrations of compounds were dispensed in 96-well microtitre plates in triplicate. The first well in all the rows was without any drugs and considered to be under control. The synchronized parasites were inoculated in all the wells, including the control wells, to get a final concentration of 5% haematocrit. The plates were incubated at 37 \u0026ordm;C for 24\u0026ndash;30 h, depending on the maturation of the schizont. After confirmation of schizont maturation, smears were prepared from all the wells. The smear was stained with Geimsa stain or JSB stain, and the numbers of dead rings and schizonts were counted per 200 asexual stage parasites. The values were compared between the control and test wells. The inhibition percentage of schizont for each concentration of test sample was calculated as:\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\text{I}\\text{n}\\text{h}\\text{i}\\text{b}\\text{i}\\text{t}\\text{i}\\text{o}\\text{n}=100-\\text{A}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eHere A is the percentage growth of schizont in the test wells. This was determined by the following formula:\u003cdiv id=\"Equb\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equb\" name=\"EquationSource\"\u003e\n$$\\text{A}=\\text{N}\\text{o}. \\text{o}\\text{f} \\text{s}\\text{c}\\text{h}\\text{i}\\text{z}\\text{o}\\text{n}\\text{t} \\text{i}\\text{n} \\text{t}\\text{h}\\text{e} \\text{t}\\text{e}\\text{s}\\text{t} \\text{w}\\text{e}\\text{l}\\text{l}\u0026divide;\\text{N}\\text{o}. \\text{o}\\text{f} \\text{s}\\text{c}\\text{h}\\text{i}\\text{z}\\text{o}\\text{n}\\text{t} \\text{i}\\text{n} \\text{t}\\text{h}\\text{e} \\text{c}\\text{o}\\text{n}\\text{t}\\text{r}\\text{o}\\text{l}\\times 100$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eChloroquine was used as the standard reference drug.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results and Discussion","content":"\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eChemistry\u003c/h2\u003e \u003cp\u003eThe targeted compounds were synthesized in five steps as outlined in \u003cb\u003ethe scheme.\u003c/b\u003e In step-I, a mixture of substituted acetophenone (1), paraformaldehyde (2), and substituted amine (3) was heated under reflux for varying lengths of time in 95% ethanol to form substituted Mannich bases (4). In Step II, the keto group of the substituted Mannich bases (4) was reduced to the alcohols (5) using sodium borohydrate in an acidic environment. Step III involved the nucleophilic substitution of the hydroxyl group of substituted Mannich bases (5) for chloride upon thionyl chloride treatment, which led to substituted Mannich bases (6). Step IV involved the preparation of 7-chloro-4-(piperazin-1-yl)quinoline (8) by aromatic nucleophilic substitution on 4,7-dichloroquinoline (7) with an excess of piperazine. The final step-V involved again nucleophilic substitution of the chloride of substituted Mannich bases (6) by 7-chloro-4-(piperazin-1-yl)quinoline, yielding the targeted compounds.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAll the compounds (in methanol) exhibited three characteristic absorption maxima (λ\u003csub\u003emax\u003c/sub\u003e) in the range between 215 and 340 nm. The shift of λ\u003csub\u003emax\u003c/sub\u003e towards longer wavelengths (320\u0026ndash;340 nm) indicated the presence of strong chromophoric groups, such as a quinoline structure, in the molecule. The maxima in the lower wavelength range between 215\u0026ndash;260 nm were due to the presence of a substituted phenyl ring and a hetero-aromatic ring system. The FT-IR-IRectra showed the C\u0026thinsp;=\u0026thinsp;C stretching bands for aromatic rings appeared between 1600 and 1450 cm1. The in-plane C-H bending vibrations occurred in the range of 1300\u0026thinsp;\u0026minus;\u0026thinsp;1000 cm1. The out-of-plane C-H bending vibrations appeared in the range of 900\u0026ndash;690 cm1. These extremely intense absorptions, resulting from strong coupling with adjacent hydrogen atoms, are used to assign the positions of substituents on the aromatic ring. The N-H stretching vibrations occurred in the range of 3500\u0026ndash;3300 cm1. The C-Cl stretching absorption occurred in the range between 1100 and 1035 cm1 for aryl chlorides. The C-H stretching absorptions occurred around 3000 cm1. In alkanes, \u003cem\u003esp\u003c/em\u003e\u003csup\u003e3\u003c/sup\u003e C-H absorption occurred at frequencies less than 3000 cm1 (3000\u0026ndash;2840 cm1). 1H NMR spectra of the compounds showed that in alkanes (aliphatic or saturated hydrocarbons), all of the CH hydrogen absorption was found in the range of 0.7 to 1.7 ppm. Hydrogens in methyl groups are highly shielded and found in chemical shift values of 0.7\u0026ndash;1.3 ppm, while hydrogens in the methylene group are found in the region of 1.2\u0026ndash;1.4 ppm. The analytical and spectral data of the synthesized compounds showed good compliance with their structure.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eAntimalarial activity evaluation\u003c/h2\u003e \u003cp\u003eThe \u003cem\u003ein vitro\u003c/em\u003e antimalarial activity results displayed in Table-1 indicate that all of the synthesized compounds (9a to 9l) demonstrated moderate antimalarial activity against the chloroquine-sensitive 3D7 strain of \u003cem\u003ePlasmodium falciparum\u003c/em\u003e at the tested dose.\u003c/p\u003e \u003cp\u003e \u003cstrong\u003eTable-1\u003c/strong\u003e \u003cp\u003e \u003cem\u003eIn vitro\u003c/em\u003e antimalarial activity data of the compounds (9a-9l)\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Taba\" border=\"1\"\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCompound Code\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMIC\u003csup\u003ea\u003c/sup\u003e (\u0026micro;g/mL)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eIC\u003csub\u003e50\u003c/sub\u003e\u003csup\u003eb\u003c/sup\u003e (\u0026micro;M) (n\u0026thinsp;=\u0026thinsp;3, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\pm\\)\u003c/span\u003e\u003c/span\u003eSD)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e9a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e31.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.5860.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e9b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e15.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.6460.03\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e9c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e15.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.3210.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e9d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e31.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.4460.04\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e9e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e31.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3.3320.12\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e9f\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e15.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.0300.06\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e9g\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e31.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.3490.15\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e9h\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e15.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e4.2040.06\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e9i\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e15.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.3860.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e9j\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e15.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.5090.02\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e9k\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e15.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.8480.11\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e9l\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.9530.10\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCQ\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.1060.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003csup\u003ea\u003c/sup\u003eMIC = minimum inhibiting concentration for the development of the ring stage parasite into the schizont stage during 40 h of incubation against the 3D7 strain of \u003cem\u003eP. falciparum\u003c/em\u003e.\u003c/p\u003e \u003cp\u003e \u003csup\u003eb\u003c/sup\u003eIC50\u0026thinsp;=\u0026thinsp;50% inhibitory concentration values (\u0026micro;M) against the 3D7 strain of \u003cem\u003eP. falciparum\u003c/em\u003e (data are expressed as mean SD from at least three different experiments in triplicate).\u003c/p\u003e \u003cp\u003eThe MIC values for all the compounds (9a\u0026ndash;9l) ranged from 3.9 to 31.25\u0026micro;g/ml. Compound 9l (MIC\u0026thinsp;=\u0026thinsp;3.9 \u0026micro;g/ml or 1.953 0.10 \u0026micro;M) was shown to be moderately active against the 3D7 strain of \u003cem\u003ePlasmodium falciparum\u003c/em\u003e, as compared to Chloroquine (MIC\u0026thinsp;=\u0026thinsp;0.4 \u0026micro;g/ml or 0.106 0.01 \u0026micro;M) among all the synthesized compounds. It was evident from a comparison of the antimalarial effects of the series that morpholine side chain alteration was advantageous for antimalarial activity. However, a comparison of the antimalarial impact across the series revealed that the antimalarial activity of 4-methoxyphenyl substituted Mannich bases was favorable. Compounds 9b, 9c, 9f, 9h to 9k were found to have the modestest levels of antimalarial activity, while compounds 9a, 9d, 9e, and 9g had the lowest levels. Compound 9l was found to have the greatest levels of antimalarial activity. In piperazine side chain modified 4-aminoquinoline Mannich bases, the MIC results of Compounds 9a-9l explained the SAR that p-methoxyphenyl \u0026amp; p-tolyl substitution enhanced antimalarial potency compared to unsubstituted phenyl along with dibenzylamino, diethylamino, dimethylamino, and morpholine side chain modification.\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eWe have demonstrated the potential of 4-Aminoquinoline Mannich Bases modified by Piperazine side chains as antimalarial agents \u003cem\u003ein vitro\u003c/em\u003e. Designed molecules show the possibility of developing chemical diversity around the core skeleton of Mannich bases to generate newer and more potent molecules with heterocyclic amine substitution.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors are thankful to Dr. C. R. Pillai, Emeritus Scientist, and \u003cem\u003eDr\u003c/em\u003e. Anup \u003cem\u003eAnvikar\u003c/em\u003e, Director, National Institute of Malaria Research (Indian Council of Medical Research), New Delhi, for providing antimalarial screening facilities and training. The authors are also thankful to S.A.I.F., Punjab University, Chandigarh, India, for providing spectroscopic data.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of interest:\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eThe authors\u003c/strong\u003e have no conflicts of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u0026nbsp;\u003c/strong\u003eThis research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability:\u003c/strong\u003e All data generated or analyzed during this study are included in this published article.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eBurger\u0026rsquo;s medicinal chemistry and drug discovery, A John Wiley \u0026amp; Sons, Inc., Publication, New York, 5, pp. 920-931(2003).\u003c/li\u003e\n \u003cli\u003eN. White. Plasmodium knowlesi: the fifth human malaria parasite, The University of Chicago Press, (2008).\u003c/li\u003e\n \u003cli\u003eA. C. Chou, R. Chevli and C. D. Fitch, \u003cem\u003eBiochemistry\u003c/em\u003e, \u003cstrong\u003e19\u003c/strong\u003e(8), 1543-1549 (1980).\u003c/li\u003e\n \u003cli\u003eT. J. Egan and H. M. Marques, \u003cem\u003eCoord. Chem. Rev.\u003c/em\u003e, \u003cstrong\u003e190\u003c/strong\u003e, 493-517 (1999).\u003c/li\u003e\n \u003cli\u003eA. Dorn, R. Stoffel, H. Matile, A. Bubendorf andR. G. Ridley, \u003cem\u003eNature\u003c/em\u003e, \u003cstrong\u003e374\u003c/strong\u003e(6519), 269-271 (1995).\u003c/li\u003e\n \u003cli\u003eD. J. Sullivan, I. Y. Gluzman, D. G. Russell and D.E. Goldberg, Proceedings of the National Academy of Sciences, 93(21) pp.11865-11870 (1996).\u003c/li\u003e\n \u003cli\u003eS. R. Cheruku, S. Maiti, A. Dorn, B. Scorneaux, A.K. Bhattacharjee, W.Y. Ellis and J.L. Vennerstrom, \u003cem\u003eJ Med. Chem.\u003c/em\u003e, \u003cstrong\u003e46\u003c/strong\u003e(14), 3166-3169 (2003).\u003c/li\u003e\n \u003cli\u003eP. A. Stocks, K. J. Raynes, P. G. Bray, B.K. Park, P.M. O\u0026apos;Neill and S.A. Ward, \u003cem\u003eJ. Med. Chem.\u003c/em\u003e, \u003cstrong\u003e45\u003c/strong\u003e(23), 4975-4983 (2002).\u003c/li\u003e\n \u003cli\u003eD. J. Pasto, C. R. Johnson and M. J. Miller. Experiments and techniques in organic chemistry, Prentice Hall Englewood Cliffs, NJ, (1992).\u003c/li\u003e\n \u003cli\u003eB. Furniss, A. Hannaford, P. Smith and A.R. Tatchell, Vogel\u0026rsquo;s textbook of practical organic chemistry, ELBS, Longman: London, (1989).\u003c/li\u003e\n \u003cli\u003eR. M. Silverstein and G. C. Bassler, \u003cem\u003eJ. Chem. Educ.\u003c/em\u003e, \u003cstrong\u003e39\u003c/strong\u003e(11), 546 (1962).\u003c/li\u003e\n \u003cli\u003eD. W. Mathieson. Interpretation of organic spectra, Academic Press, New York, (1965).\u003c/li\u003e\n \u003cli\u003eN. I. Wenzel, N. Chavain, Y. Wang, W. Friebolin, L.Maes, B.Pradines, M.Lanzer, V.Yardley, R.Brun, C.Herold-Mende, C.Biot, K. Toth and E. Davioud-Charvet, \u003cem\u003eJ Med. Chem.\u003c/em\u003e, \u003cstrong\u003e53\u003c/strong\u003e(8), 3214-3226 (2010).\u003c/li\u003e\n \u003cli\u003eL. M. Antinarelli, A. M. Carmo, F. R. Pavan, C. Q. F. Leite, A. D. Da Silva, E. S. Coimbra and D. B. Salunke, \u003cem\u003eBioorg. Med. Chem. Lett.\u003c/em\u003e, \u003cstrong\u003e2\u003c/strong\u003e(1), 16 (2012).\u003c/li\u003e\n \u003cli\u003eA. Kumar, K. Srivastava, S. R. Kumar, M.I. Siddiqi, S. K. Puri, J. K. Sexana and P.M.S. Chauhan , \u003cem\u003eEur. J. Med. Chem.\u003c/em\u003e, \u003cstrong\u003e46\u003c/strong\u003e(2), 676-690 (2011).\u003c/li\u003e\n \u003cli\u003eB. Singh, D. Chetia and M. K. Kumawat, \u003cem\u003ePharm. Chem. J.\u003c/em\u003e, 55(7), 681-688 (2021).\u003c/li\u003e\n \u003cli\u003eW. Trager and J. B. Jensen, \u003cem\u003eScience\u003c/em\u003e, \u003cstrong\u003e193\u003c/strong\u003e(4254), 673-675 (1976).\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Scheme","content":"\u003cp\u003eScheme 1 is available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"structural-chemistry","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"stuc","sideBox":"Learn more about [Structural Chemistry](https://www.springer.com/journal/11224)","snPcode":"11224","submissionUrl":"https://submission.nature.com/new-submission/11224/3","title":"Structural Chemistry","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"malaria, 4-aminoquinoline, piperazine side chain modification, Mannich base, Plasmodium falciparum","lastPublishedDoi":"10.21203/rs.3.rs-4428579/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4428579/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eTwelve new compounds (Piperazine side chains modified 4-Aminoquinoline Mannich Bases) were synthesized and characterized utilizing a variety of analytical and spectroscopic techniques. All the synthesized compounds were screened for \u003cem\u003ein vitro\u003c/em\u003e antimalarial activity aganist 3D7 strain of \u003cem\u003ePlasmodium falciparum\u003c/em\u003e. \u003cem\u003eIn vitro\u003c/em\u003e antimalarial screening revealed that the all synthesized compounds exhibited minimum inhibitory concentrations (MIC) ranging from 3.9 to 31.25 μg/ml. One compound 9l (MIC=3.9 μg/ml or1.953±0.10μM) was found most potent against\u003cstrong\u003e \u003c/strong\u003echloroquine sensitive 3D7 strain of \u003cem\u003ePlasmodium falciparum\u003c/em\u003e which is comparable to standard drug chloroquine (MIC=0.4 μg/ml or 0.106±0.01 μM).\u003c/p\u003e","manuscriptTitle":"Synthesis of Some Novel Piperazine Side Chain Modified 4- Aminoquinoline Mannich Bases and Evaluation for Their in Vitro Antimalarial Activity","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-06-20 11:40:40","doi":"10.21203/rs.3.rs-4428579/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorAssigned","content":"","date":"2024-06-07T03:38:56+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-06-06T10:30:14+00:00","index":"","fulltext":""},{"type":"submitted","content":"Structural Chemistry","date":"2024-05-16T05:32:24+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"structural-chemistry","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"stuc","sideBox":"Learn more about [Structural Chemistry](https://www.springer.com/journal/11224)","snPcode":"11224","submissionUrl":"https://submission.nature.com/new-submission/11224/3","title":"Structural Chemistry","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"c1edb97d-1982-4443-bc79-83b19c090eab","owner":[],"postedDate":"June 20th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2024-06-22T06:21:06+00:00","versionOfRecord":[],"versionCreatedAt":"2024-06-20 11:40:40","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4428579","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4428579","identity":"rs-4428579","version":["v1"]},"buildId":"cBFmMYwuxLRRLfASyISRj","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}