Catalytic oxidation of γ-dehydro-arylhimachalene: synthesis and antibacterial study of novel oxygenated derivatives of himachalanes

Abstract

Functionalized sesquiterpenes are a highly sought-after compounds for their olfactive as well as therapeutic properties. Herein, we report the oxidation of γ-dehydro-arylhimachalene, an olefin obtained via the aromatization of himachalene mixture, the major components of cadar oil, using ruthenium- and vanadium-based catalysts. While ruthenium catalyzed oxidation leads to the formation of a ketone and an aldehyde with poor selectivity, vanadium-catalyzed oxidation of the same substrate using hydrogen peroxide as an oxidant leads to the selective formation of the ketone. Finally, γ-dehydro-arylhimachalene, the ketone and the aldehyde were explored as antibacterial agents against two gram positive (Staphylococcus Aureus and Enterococcus faecalis) and two gram negative (Escherechia Coli and Pseudomonas aeruginosa) bacteria. The ketone showed the best activity against E.coli and P. aeruginosa with MIC equal to 0.78 mg/mL and 0.1 mg/mL respectively, while γ-dehydro-arylhimachalene displayed the best activity, with MIC equal to 1.56 and 0.2 mg/mL against S.aureus and E. faecalis respectively.