A Comprehensive Approach to C3a-Aryl-Substituted Hydroindole Alkaloids by Utilizing Enantioselective Gold Catalysis

Abstract

A diversity-oriented total synthesis for Amaryllidaceae alkaloids incorporating the frequently found C3a-arylated hydroindole moiety was developed. Chiral-anion-induced gold(I) catalysis was employed for the cyclization of 1,4-diynes to the pyrrolidine and the installation of the all-carbon quaternary stereocenter. Both enantiomeric series of crinine-type alkaloids in high enantiopurity were accessible by this methodology. The formal synthesis of a wide range of Amaryllidaceae alkaloids is described, such as (+)-vitattine, (–)-epi-vitattine, (–)-elwesein, (–)-epi-elwesein, (–)-crinine, (–)-epi-crinine, (–)-buphanisine, (–)-flexinine, and (+)-gracilamine.