Syntheses of Carnosic Acid and Carnosol, Anti-oxidants in Rosemary, from Pisiferic Acid, the Major Constituent of Sawara

Carnosic acid (2), a major anti-oxidant in rosemary (Rosmarinus officinalis), was synthesized from pisiferic acid (1), the major constituent of Sawara (Chamaecyparis pisifera), via ortho-oxidation of the phenol using meta-chlorobenzoyl peroxide (mCBPO), chloroacetyl meta-chlorobenzoyl peroxide (CAMCBPO) or 2-iodoxybenzoic acid (IBX). Carnosol (3), another anti-oxidant in rosemary, was synthesized from carnosic acid by oxidation with silver oxide. Potent antibacterial activities against Propionibacterium acnes (ATCC 6919) (minimum inhibitory concentration (MIC) μg/ml) and Staphylococcus aureus ME/GM/TC Resistant (ATCC 33592) (MIC μg/ml) of carnosic acid and carnosol were reported.