Stereoselective total synthesis of bengamide E from glyceraldehyde acetonide and a nonracemic .gamma.-alkoxy allylic stannane

Abstract

The synthesis of bengamide E (30) was achieved starting from the furan adduct 1 of (R)-glyceraldehyde acetonide. The key step entailed MgBr 2 -promoted addition of the (S)-γ-alkoxy allylic stannane (S)-25 to the aldehyde 8 obtained from the oxidation product of furan 1 after protection as the methyl ether. The adduct of stannane (S)-25 and aldehyde 8, a 1:1 mixture of hydroxy ester 27 and lactone 28 was converted to bengamide E by aminolysis with (S)-2-aminocaprolacm and subsequent debenzylation with Li in NH 3