Microbial transformations of sesquiterpenoids: conversion of deoxyvulgarin by Rhizopus nigricans and Aspergillus ochraceous

Abstract

Microbial transformation of the sesquiterpene lactone deoxyvulgarin (2) has been carried out with Aspergillus ochraceous and Rhizopus nigricans cultures. A. ochraceous converted deoxyvulgarin (2) into vulgarin (3) and 11,13-dihydrodouglanin (4). R. nigricans transformed deoxyvulgarin (2) into vulgarin (3), erivanin (6), and 1β-hydroxy-2-oxoeudesm-3-en-6,13-olide (7). Vulgarin (3) was obtained chemically by epoxidation of deoxyvulgarin (2) in a one-step process in virtually quantitative yield. A pathway proposed for the conversion of deoxyvulgarin (2) into the more functionalized metabolites is discussed.