Betulenols from Betula species.

The essential oils from buds of five Betula species growing in Turkey were investigated by GC-MS. A major component in the essential oils was shown to be 14-hydroxy-beta-caryophyllene (6). The structure of beta-betulenal (12) which was isolated from Betula essential oils was also confirmed by synthesis. Chemical reactions yielded 14-acetoxy-beta-caryophyllene (15), 14-hydroxy-isocaryophyllene (10) and its acetate (14), giving evidence to the natural occurrence in Betula species of the formerly known alpha-betulenol acetate (3), beta-betulenol (2) and beta-betulenol acetate (4), respectively. Compounds 6, 9, 10, 12, and 15 were evaluated for antimicrobial activity.