Absolute structure of panaxytriol.

Diastereomeric mixture at C-3 of (9R,10R)-panaxytriol acetonide (3) and (9S,10S)-panaxytriol acetonide (4) were enantioselectively acetylated to give (3R)-acetates (3a-Ac, 4a-Ac) and (3S)-alcohols (3b, 4b) by enzyme mediated-acetylation using CHIRAZYME and vinyl acetate, respectively. Hydrolysis of (3R)-acetate (3a-Ac, 4a-Ac) with CHIRAZYME and phosphate buffer afforded (3R)-alcohols (3a, 4a), respectively. Deprotection of panaxytriol acetonides (3a, 3b, 4a, 4b) gave panaxatriol and its isomers, respectively. Comparison of optical rotation values of the synthetic panaxatriols with that of the natural one confirmed that the absolute configuration of panaxytriol sould be 3R,9R,10R.