Total synthesis of hydrocinchonidine and hydrocinchonine via photo-oxygenation of an indole derivative

Abstract

3-Ethylpiperidin-4-one (9) has been stereoselectively converted into (±)-2-{2-[(3RS,4SR)-N-benzyloxycarbonyl-3-ethyl-4-piperidyl]ethyl}-3-formylmethylindole (20), whose ring transformation via photo-oxygenation produced the 4-acylquinoline (23). Optical resolution of (±)-hydrocinchotoxine (24), derived from (23), led to a formal total synthesis of (+)-hydrocinchonine (25) and (–)-hydrocinchonidine (26).