A new route for the synthesis of indolizidine (−)-209D: excellent diastereoselectivity in the intramolecular hydroamination of alkynes

A highly efficient synthesis of indolizidine (−)-209D I has been accomplished. The key reaction in the synthesis is the palladium(0)/benzoic acid catalyzed intramolecular hydroamination of the ε-amino alkyne 6. The excellent diastereoselectivity in the intramolecular hydroamination is discussed on the basis of the proposed transition state.