SYNTHETIC STUDIES TOWARDS COMPOUNDS RELATED TO STERPURENE AND PROTOILLUDENE

As part of synthetic strategies towards the sesquiterpenes 6-protoillu dene and sterpurene the intramolecular aldol condensation of 1-(2-oxop ropyl)-2-acetyl-4,4-dimethylcyclopentane was studied in detail. Mixtur es of 5,8,8-trimethylbicyclo[4.3.0]-4-nonen-3-one and 4,8,8-trimethylb icyclo[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 b e methanesulfonic acid in methanol. The preparation of trans-5,8,8-tri methylbicyclo[4.3.0]-4-nonen-3-one by our route in about 70% overall y ield constitutes formally a new synthesis of sterpurene.