Enantioselective access to (−)-indolizidines 167B, 209D, 239AB, 195B and (−)-monomorine from a common chiral synthon

An enantioselective access to (−)-indolizidine alkaloids 167B, 209D, 239AB, 195B and (−)-monomorine from a new chiral synthon is described. The use of (S)-3-(Cbz-amino)-4-(tert-butyldimethylsilyloxy)butanal, obtained from l-aspartic acid, has provided efficient access of the indolizidine frame work through a Horner-Wadsworth-Emmons reaction and reductive cyclization as the key steps.