CHEMICAL-TRANSFORMATIONS OF THE NEOCLERODANE DITERPENES ERIOCEPHALIN AND CAPITATIN - AN ACCESS TO 4,5-SECO-NEOCLEROD-5(19)-ENE DERIVATIVES

Treatment of the 7-O-acetyl derivative (2) of eriocephalin (1) with HC l yielded minor quantities of the 4,5-seco-neoclerod-5(19)-ene derivat ives 3 and 4. Under the same treatment, capitatin (6) underwent an ide ntical fragmentation reaction giving 9 in good yield, via the unstable chlorohydrin intermediate 8. Sodium cyanoborohydride reduction of 9 y ielded compounds 10 and 11 by a stereoselective 1,4-reduction process. The mechanistic aspects of these transformations are discussed. The 4 ,5-seco derivatives 9, 10, and 11 can be useful intermediates for the synthesis of natural and synthetic neoclerodane diterpenoids, which ar e of interest on account of their activity as insect antifeedants and other important biological properties.