The microbiological transformations of three 19-oxygenated ent-kauranes with Rhizopusnigricans, Aspergillus ochraceous and Calonectria decora have been investigated. The most common transformation observed is hydroxylation at the C-1 and C-7 positions. For ent-kaur-16-en-19-oic acid allylic hydroxylation and hydration of the double bond also occur.
A minor glucoside, corymbosin, has been isolated fromTurbinacorymbosa and the structure and partial stereochemistry of its aglucone, corymbositin, established.