Alkynes From Furans: A General Fragmentation Method Applied to the Synthesis of the Proposed Structure of Aglatomin B

Abstract

Furans are versatile synthons in organic chemistry. Described is ag eneral method for transforming furans into alkynes by dual CÀCd ouble-bond cleavage.T he reaction is proposed to proceed by sequential [4+ +2] cycloaddition between furan and singlet oxygen and af ormal retro-(3+ +2) fragmentation of the endoperoxide intermediate.Awide array of furans,i ncluding those derived from sapogenins,a re amenable to this reaction, thus providing the corresponding alkynoic acids in up to 88 %y ields.T he synthetic utility was demonstrated by as even-step synthesis of the proposed structure of ap regnane natural product, aglatomin B, from aknownintermediate.