Synthesis of Antibacterial Norlabdane Compounds with Rearranged Cycle B and Molecular Docking Studies

The synthesis of tetra- and pentanorlabdane compounds with rearranged cycle B based on commercially available (+)-sclareolide is reported. Desired compounds were prepared from intermediate ketones via Baeyer-Villiger oxidation. The structures of synthesized compounds were confirmed by spectral IR, 1D (1H, 13C and 15N, DEPT) and 2D (H-COSY, H,C-HSQC, H,C-HMBC, H,N-HMBC, NOESY) NMR analyses, mass-spectrometry and single crystal X-rays diffraction. Two of the four obtained compounds showed high antifungal and antimicrobial activity, comparable and exceeding that of standards Caspofungin and Kanamycin. DFT calculations revealed the stability of compounds in gas, DCM, water and methanol. Molecular docking to four targets (1KZN, 1U1Z, 3QLS, 2Q85) showed good agreement with the results of in vitro evaluation and confirmed the biological activity of compounds 3 and 4, with binding affinities comparable and for some targets exceeding that of Caspofungin and Kanamycin.