Microbial hydroxylation of (±)- and (-)-(2Z,4E)-5-(1′,2′-Epoxy-2′,6′,6′- trimethylcyclohexyl)-3-methyl-2,4-pentadienoic acid into (±)- and (-)-Xanthoxin acid by Cunninghamella echinulata

Abstract

Microbial hydroxylation of (±)-(2Z,4E)-5-(1′,2′-epoxy-2′,6′,6′- trimethylcyclohexyl)-3-methyl-2,4-pentadienoic acid (3a) with Cercospora cruenta, a fungus producing (+)-abscisic acid, gave a four-stereoisomeric mixture consisting of (+)- and (-)-xanthoxin acid (4a), and (+)- and (-)-epi-xanthoxin acid (5a) by an HPLC analysis with a chiral column. Screening of the microorganisms capable of oxidizing (±)-3a showed that Cunninghamella echinulata stereoselectively oxidized (±)-3a to xanthoxin acid (4a) with the some degree of enantioselectivity as (-)-3a to (-)-4a.