SOME REMARKABLE REACTIONS OF THE DITERPENE ERIOCEPHALIN - NEOCLERODANE DERIVATIVES WITH INSECT ANTIFEEDANT ACTIVITY

Base-catalyzed reaction of the neo-clerodane diterpenoid eriocephalin (1) gave the derivatives 3 and 4. The formation of these compounds imp lies an elimination of the C-19 carbon atom of 1 as formaldehyde by a retroaldol reaction and, in the case of 4, subsequent reaction of this formaldehyde with the 18-alkoxide intermediate followed by an intramo lecular and stereoselective 1,4-addition of the resulting C-18-oxa-met hylene alkoxide. Treatment of the derivative of eriocephalin 9 with ba se yielded transacetylation and hydrolysis products (10-14), with inve rsion of the configuration at the C-20 asymmetric centre. Mechanistic aspects of these transformations and the results achieved in the biolo gical assay as insect antifeedants of these neo-clerodane derivatives are also reported.