Stereoselective Additions of Chiral α-Sulfinyl Ketimine Anions to Ene Esters. Asymmetric Syntheses of Indoloquinolizidine and Yohimban Alkaloids

Article abstract of DOI:10.1021/jo00025a011

The in-situ 1,4-addition/ring-closure reactions of chiral α-sulfinyl ketimine anions with acyclic and cyclic ene esters offer a simple, convenient route for the construction of chiral cyclic alkaloids having a nitrogen-atom ring juncture.Asymmetric induction in the conjugate-addition reaction of the carbanions derived from α-sulfinyl ketimines possessing chiral sulfur with various cyclic and acyclic ene esters, subsequent ring-closure reaction, and reduction of the resulting β-sulfinyl enamides were utilized in the syntheses of (-)-1,2,3,4,6,7,12,12b-octahydroindolo<2,3-a>quinolizine <(-)-1>, (-)-alloyohimban <(-)-2>, (+)-3-epi-alloyohimban <(+)-3>, and (-)-yohimban <(-)-4>.