Synthetic studies towards compounds related to sterpurene and protoilludene

Abstract

As part of synthetic strategies towards the sesquiterpenes 6-protoilludene and sterpurene the intramolecular aldol condensation of 1-(2-oxopropyl)-2-acetyl-4,4-dimethylcyclopentane was studied in detail. Mixtures of 5,8,8-trimethylbicyclo[4.3.0]-4-nonen-3-one and 4,8,8-trimethylbicyclo[4.3.0]-3-nonen-2-one were formed. The reaction was carried out under different acidic and basic conditions, giving the two compounds in ratios varying from 1:1 to 12:1. The best conditons were found to be methanesulfonic acid in methanol. The preparation of trans-5,8,8-trimethylbicyclo[4.3.0]-4-nonen-3-one by our route in about 70% overall yield constitutes formally a new synthesis of sterpurene. © Acta Chemica Scandinavica 1998.