13C nuclear magnetic resonance spectra and microbiological hydroxylation of 7α- and 7β-hydroxykaurenolide

Abstract
The 13C n.m.r. spectra of some kaurenolides have been assigned. Changes in the spectra are used to show that microbiological hydroxylation of 7α-hydroxykaurenolide by Rhizopus arrhizus affords 7α,11α-, 7α,12ζ-, and 7α,13-dihydroxy- and 7α,16α,17-trihydroxykaurenolide. 7β-Hydroxykaurenolide affords 7β,11α- and 7β,13-dihydroxykaurenolide.