The synthesis of 3-spirooxindole derivatives. VII. Total synthesis of alkaloids (.+-.)-rhynchophylline and (.+-.)-isorhynchophylline.

Abstract

The total synthesis of (±)-rhynchophylline (Ia) and (±)-isorhynchophylline (Ib) which are oxindole alkaloids of Uncaria rhynchophylla MIQ (Ourouparia rhynchophylla MATSUM), has been completed through eight stages starting from the condensation of 2-hydroxytryptamine hydrochloride (III) with ethyl sodium formyl acetate (IV). The success in the first-stage condensation is significant since ethyl sodium formyl acetate (IV) is rather unstable and has not been existent as the liberated ester. The sterostructures of the intermediates are discussed and mostly assigned.