Biotransformation of two ent-Pimara-9(11),15-diene derivatives by Gibberella fujikuroi

Abstract

The incubation of 19-hydroxy-13-epi-ent-pimara-9(11),15-diene (4) with Gibberella fujikuroi gave 8α,19-dihydroxy-9α,11α-epoxy-13-epi-ent-pimara-15-ene (6), 7-oxo-11α,19-dihydroxy-13-epi-ent-pimara-8(9),15-diene (7), 7-oxo-11β,19-dihydroxy-13-epi-ent-pimara-8(9),15-diene (9), and 8α,19-dihydroxy-9α,11α:15,16-diepoxy-13-epi-ent-pimarane (11), while the feeding of 13-epi-ent-pimara-9(11),15-diene-19-oic acid (5) with this fungus afforded 1-oxo-2α,9α-dihydroxy-13-epi-ent-pimara-11,15-dien-19-oic acid (13), 1-oxo-2β,9α-dihydroxy-13-epi-ent-pimara-11,15-dien-19-oic acid (14), 13-epi-ent-pimara-9(11),15-dien-1,19-dioic acid 1,2-lactone (15), and 1-oxo-12β-hydroxy-13-epi-ent-pimara-9(11),15-dien-19-oic acid (16). In both biotransformations, the main reaction was the epoxidation of the 9(11)-double bond, followed by rearrangement to afford allylic alcohols. The formation of lactone 15 represents the first time that a Baeyer−Villiger oxidation has been observed in a microbiological transformation with this fungus.