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.