Microbial Transformation of Sesquiterpenes, (−)‐Ambrox® and (+)‐Sclareolide

Abstract

AbstractThe microbial transformation of (−)‐Ambrox® (1), a perfumery sesquiterpene, by a number of fungi, by means of standard two‐stage‐fermentation technique, afforded ambrox‐1α‐ol (2), ambrox‐1α,11α‐diol (3), ambrox‐1α,6α‐diol (4), ambrox‐1α,6α,11α‐triol (5), ambrox‐3‐one (6), ambrox‐3β‐ol (7), ambrox‐3β,6β‐diol (8), 13,14,15,16‐tetranorlabdane‐3,8,12‐triol (9), and sclareolide (10) (Schemes 1 and 2). Further incubation of compound 10 with Cunninghamella elegans afforded 3‐oxosclareolide (11), 3β‐hydroxysclareolide (12), 2α‐hydroxysclareolide (13), 2α,3β‐dihydroxysclareolide (14), 1α,3β‐dihydroxysclareolide (15), and 3β‐hydroxy‐8‐episclareolide (16) (Scheme 3). Metabolites 2–5, 12, 13, and 16 were found to be new compounds. The major transformations include a reaction path involving hydroxylation, ether‐bond cleavage and inversion of configuration. Metabolites 11–16 of sclareolide showed significant phytotoxicity (Table 1). The structures of the metabolites were characterized on the basis of spectroscopic techniques.