Microbiologically Modified Chiral Synthon. I. 3, 8-Dioxo-4-methoxycarbonyl-9-methyl-Δ⁴⁽¹⁰⁾-octalin for Formal Total Syntheses of Certain Sesquiterpenoids and Diterpenoids

Abstract

Microbiological reduction of prochiral 3, 8-dioxo-4-methoxycarbonyl-9-methyl-Δ⁴⁽¹⁰⁾-octalin (1ab) with various yeasts was carried out. (+)-(8S)-Hydroxy-4-methoxycarbonyl-(9S)-methyl-3-oxo-Δ⁴⁽¹⁰⁾-octalin (2a) was desired as a chiral synthon for the formal total syntheses of certain sesquiterpenoids, e.g. α-costal. This ketol was obtained with high optical purity (>99% ee) when propely selected microorganisms such as Hansenula anomala were used. Another chiral synthon produced in high optical purity, that is, 3, 8-dioxo-4-methoxycarbonyl-(9R)-methyl-Δ⁴⁽¹⁰⁾-octalin (1b), was also available for the formal total syntheses of ent-type diterpenoids e.g. zonarol.