SYNTHETIC STUDIES OF SESQUITERPENES WITH A CIS-FUSED DECALIN SYSTEM .4. SYNTHESIS OF (+)-5-BETA-H-EUDESMA-3,11-DIENE, (-)-5-BETA-H-EUDESMANE-4-BETA,11-DIOL AND (+)-5-BETA-H-EUDESMANE-4-ALPHA,11-DIOL, AND STRUCTURE REVISION OF A NATURAL EUDESMANE-4,11-DIOL ISOLATED FROM PLUCHEA-ARGUTA

The syntheses of (+)-5 beta H-eudesma-3,11-diene [1], (-)-5 beta H-eudesman- 4 beta,11-diol [2], and (+)-5 beta H-eudesmane-4 alpha,11-diol [15] were carried out by an unambiguous procedure starting from cr-santonin. The diene 1 was identical with a natural product which was isolated previously as a termite defense substance. Although structure 2 was recently proposed for a new eudesmane-1,4-diol [A] isolated from Pluchea arguta, synthetic 2 and its C-4 epimer, 15, were not identical with this natural eudesmane-4,11-diol when their physical and spectroscopic parameters were compared. The structure of this natural eudesmane-4,11-diol has been revised from 2 to 3 (7 beta H-eudesmane-4 alpha,11-diol) as a result of the analysis of the H-1- and C-13-nmr spectra of related natural and unnatural eudesmane derivatives.