Catalytic Enantioselective Synthesis of (20S)-Camptothecin Intermediates Using Cyanosilylation of Ketones Promoted by D-Glucose-derived Lanthanide Catalyst

Abstract

An efficient catalytic enantioselective synthetic route was developed for Curran's versatile camptothecin intermediate (5).The key step is the catalytic enantioselective cyanosilylation of ketone (7) using a chiral samarium (Sm) complex.The target ketone cyanohydrin (6) was obtained with 90% ee using 2 mol % of the catalyst.A gadolinium (Gd) complex derived from the same chiral ligand could also be used as an enantioselective catalyst to synthesize Corey's intermediate (11).