Highly selective valorisation of D-xylose from corncobs hydrolysates catalysed by C-scorpionate gold(III) complexes

Highly selective valorisation of D-xylose from corncobs hydrolysates catalysed by C-scorpionate gold(III) complexes | 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 Highly selective valorisation of D-xylose from corncobs hydrolysates catalysed by C-scorpionate gold(III) complexes Vanmira Van-Dúnem, Luís C. Duarte, Pedro L. Martins, Hugo M. Lapa, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9149017/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract D-xylonic acid is a multifunctional, environmentally friendly, and versatile platform chemical, and one of the most promising conversion products of D-xylose for replacing several petrochemicals that is still not produced commercially. Although microbial conversion is the most widely studied process, the low efficiency and cost of these methods create opportunities for the development of chemical routes. In this work, we report for the first time the direct chemical conversion of real hemicellulose-derived pentose-rich hydrolysates into D-xylonic acid using a novel chemical oxidation route based on C-scorpionate gold(III) complexes which can be readily obtained, for example, as the cationic [AuCl₂(κ 2 -Tpm)]Cl ( 1 , Tpm = hydrotris(pyrazol-1-yl)methane, HC(C₃N₂H₃)₃) or the neutral [AuCl₂(κ 2 -Tpms)] complex ( 2 , Tpms = tris(1 H -pyrazol-1-yl)methane sulfonate, [SO₃C(C₃H₃N₂)₃]⁻). The catalytic operational conditions ( i.e ., reaction time, temperature, type and concentration of alkali and oxidant agent) were initially optimised for D-xylose solutions using cationic complex 1 . Under the best conditions (100 ºC, 2 mmol NaOH and 20 mmol H 2 O 2 ) nearly 100% conversion of D-xylose and a 94% D-xylonic acid yield were achieved, with minimal formation of secondary products. Under the same conditions, the direct catalytic conversion of real hemicellulosic hydrolysate, without purification, enabled 59% D-xylose conversion and a similar stoichiometric yield. These results were further improved by using the neutral gold(III) C-scorpionate complex 2 , which increased the D-xylose conversion to 65%, with high selectivity. Both C-scorpionate gold(III) complexes demonstrated exceptional selectivity in oxidising D-xylose to D-xylonic acid in corncobs hydrolysate, with high tolerance for the presence of other sugars, furans and phenolic compounds. Corncobs C-scorpionate Gold(III) complex D-xylonic acid D-xylose Catalytic oxidation Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted 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-9149017","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":635205792,"identity":"db87cbbe-6c72-4892-96dc-defe0fecc641","order_by":0,"name":"Vanmira Van-Dúnem","email":"","orcid":"","institution":"LNEG – Laboratório Nacional de Energia e Geologia","correspondingAuthor":false,"prefix":"","firstName":"Vanmira","middleName":"","lastName":"Van-Dúnem","suffix":""},{"id":635205793,"identity":"e88c1240-a40c-477b-b3d7-c78b71079ac6","order_by":1,"name":"Luís C. 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Although microbial conversion is the most widely studied process, the low efficiency and cost of these methods create opportunities for the development of chemical routes. In this work, we report for the first time the direct chemical conversion of real hemicellulose-derived pentose-rich hydrolysates into D-xylonic acid using a novel chemical oxidation route based on C-scorpionate gold(III) complexes which can be readily obtained, for example, as the cationic [AuCl₂(κ\u003csup\u003e2\u003c/sup\u003e-Tpm)]Cl (\u003cem\u003e1\u003c/em\u003e, Tpm\u0026thinsp;=\u0026thinsp;hydrotris(pyrazol-1-yl)methane, HC(C₃N₂H₃)₃) or the neutral [AuCl₂(κ\u003csup\u003e2\u003c/sup\u003e-Tpms)] complex (\u003cem\u003e2\u003c/em\u003e, Tpms\u0026thinsp;=\u0026thinsp;tris(1\u003cem\u003eH\u003c/em\u003e-pyrazol-1-yl)methane sulfonate, [SO₃C(C₃H₃N₂)₃]⁻).\u003c/p\u003e \u003cp\u003eThe catalytic operational conditions (\u003cem\u003ei.e\u003c/em\u003e., reaction time, temperature, type and concentration of alkali and oxidant agent) were initially optimised for D-xylose solutions using cationic complex \u003cem\u003e1\u003c/em\u003e. Under the best conditions (100 \u0026ordm;C, 2 mmol NaOH and 20 mmol H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e) nearly 100% conversion of D-xylose and a 94% D-xylonic acid yield were achieved, with minimal formation of secondary products. Under the same conditions, the direct catalytic conversion of real hemicellulosic hydrolysate, without purification, enabled 59% D-xylose conversion and a similar stoichiometric yield. These results were further improved by using the neutral gold(III) C-scorpionate complex \u003cem\u003e2\u003c/em\u003e, which increased the D-xylose conversion to 65%, with high selectivity. Both C-scorpionate gold(III) complexes demonstrated exceptional selectivity in oxidising D-xylose to D-xylonic acid in corncobs hydrolysate, with high tolerance for the presence of other sugars, furans and phenolic compounds.\u003c/p\u003e","manuscriptTitle":"Highly selective valorisation of D-xylose from corncobs hydrolysates catalysed by C-scorpionate gold(III) complexes","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-05-11 04:45:47","doi":"10.21203/rs.3.rs-9149017/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"f2f25e88-e256-4fb5-9186-0308f011cb24","owner":[],"postedDate":"May 11th, 2026","published":true,"recentEditorialEvents":[{"type":"reviewerAgreed","content":"89596361932302529298774582748345313632","date":"2026-05-16T08:09:20+00:00","index":18,"fulltext":""},{"type":"reviewerAgreed","content":"109009264836222893152949274871298694605","date":"2026-05-06T05:37:00+00:00","index":13,"fulltext":""},{"type":"reviewerAgreed","content":"8170006769869577682613702319362670086","date":"2026-05-05T18:01:19+00:00","index":12,"fulltext":""},{"type":"reviewersInvited","content":"8","date":"2026-05-04T04:25:32+00:00","index":"","fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-05-11T04:45:48+00:00","versionOfRecord":[],"versionCreatedAt":"2026-05-11 04:45:47","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9149017","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9149017","identity":"rs-9149017","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}