[摘要]：Compds. (I-III) isolated from Elysia diomedea are described. Compd. I is an endoperoxide deriv. of elysiapyrone A. The biomimetic-type transformation of compd. I to elysiapyrone A catalyzed by neutral base transformed the endoperoxide to a vicinal diepoxide, thus suggesting the endoperoxide as a key intermediate in the biosynthesis of elysiapyrone A. A biogenetic pathway for their formation involving a cycloaddn. of singlet oxygen to a polypropionate alkenyl open chain is proposed.
