Dedicated to Prof. Erick M. Carreira on the occasion of his 60th birthday
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.
Key words
alkaloids - enantioselectivity - gold catalysis - desymmetrization - quaternary centers