Synthesis of Homodrimane Sesquiterpenoids Bearing 1,3-Benzothiazole Unit and Their Antimicrobial Activity Evaluation.

Based on some homodrimane carboxylic acids and their acyl chlorides, a series of fourteen 2-homodrimenyl-1,3-benzothiazoles, N -homodrimenoyl-2-amino-1,3-benzothiazoles, 4'-methyl-homodrimenoyl anilides and 4'-methyl-homodrimenthioyl anilides were synthesized and their biological activities were evaluated on five species of fungi ( Aspergillus niger , Fusarium solani , Penicillium chrysogenum , P. frequentans , and Alternaria alternata ) and two strains of bacteria ( Bacillus sp. and Pseudomonas aeruginosa ). The synthesis involved the decarboxylative cyclization, condensation and thionation of the said acids, anhydrides or their derivatives with 2-aminothiophenol, 2-aminobenzothiazole, p -toluidine and Lawesson's reagent. As a result, together with the desired compounds, some unexpected products 8 , 25 , and 27 were obtained, and the structures and mechanisms for their formation have been proposed. Compounds 4 , 9 , and 25 showed higher antifungal and antibacterial activity compared to the standards caspofungin (MIC = 1.5 μg/mL) and kanamycin (MIC = 3.0 μg/mL), while compound 8 had comparable activities. In addition, compounds 6 , 17 , and 27 showed selective antifungal activity at MIC = 2.0, 0.25, and 1.0 μg/mL, respectively.