Stereoselective Synthesis of the Bis-tetrahydrofuran Fragment (C-1-C-9) of Asteltoxin

Article abstract of DOI:10.1021/jo00084a039

An 18-step synthesis of the chiral bis-tetrahydrofuran fragment 2 of asteltoxin 1 is described.This synthesis proceeds under practically complete substrate stereocontrol, starting with compound 5a.From there the chirality centers of 2 are generated with > 95percent ds each by using a sequence of Claisen rearrangement, chelate Cram Grignard addition, and osmylation reactions.The currant synthesis affords 2 in racemic form.The key intermediate 8 was also synthesized with ee> 96percent, which should provide access to 2 in both enatiomeric forms.