Asymmetric Michael-type alkylation of chiral imines. Enantioselective syntheses of (−)-geosmin and two other related natural terpenes, as well as enant-(+)-geosmin

Abstract

Natural (−)-geosmin 11, (+)-octalone 14 (from Vetiveria zizanioides), and (+)-octalin 15 (from Bazzania fauriana and B. angustifolia) have been prepared in high chemical and enantiomeric yields via the asymmetric process involving Michael-type alkylation of chiral imines 6 and 12. Enant-(+)-geosmin has been also synthesized by the same procedure.