SYNTHESIS OF ALL STEREOISOMERS OF EUDESM-11-EN-4-OL .1. STEREOSPECIFIC SYNTHESIS OF THE TRANS-FUSED AND CIS-FUSED OCTAHYDRO-8-HYDROXY-4A,8-DIMETHYL-2(1H)-NAPHTHALENONES - CONFORMATIONAL-ANALYSIS OF THE CIS-FUSED COMPOUNDS

An efficient method has been developed for the synthesis of the octahydro-8-hydroxy-4a,8-dimethyl-2-(1H)-naphthalenones 9a-d, which are suitable intermediates in the total synthesis of trans- and cis-fused 1-hydroxyeudesmane sesquiterpenes. Starting from the trans-fused dione 7 the corresponding hydroxy ketones 9a and b could be easily prepared. The cis-fused hydroxy ketones 9c and d were synthesized starting from the dione 8. Protection of the C(7) carbonyl function of 8 as its dimethyl acetal followed by treatment with CH3Li gave the hydroxy ketone 9c. On the other hand, protection of the C(7) carbonyl function of 8 as its ethylene acetal and subsequent treatment with CH3MgI afforded the hydroxy ketone 9d as the main product. NMR studies revealed that 9c exists predominantly in the steroid conformation and that 9d exists exclusively in the nonsteroid conformation.