Formal Synthesis of Vallesamidine

Abstract

Abstract A novel route to the racemic selenide (1 RS ,12b RS )‐1‐ethyl‐2,3,6,7,12,12b‐hexahydro‐1‐[2‐(phenylseleno)ethyl]indolo[2,3‐ a ]quinolizin‐4(1 H )‐one ( 13b ), a key intermediate in the total synthesis of vallesamidine ( 1 ), was elaborated. Compound 3a , obtained by Pictet–Spengler reaction of tryptamine and cyclohept‐4‐enyl‐1‐carbaldehyde ( 2c ), was oxidized with KMnO 4 to the diacid 4 , which was subsequently converted into the isomeric tetracyclic lactams 5a,b . After proper protection maneuvers, Barton decarboxylation of 10a,b , trapping with PhSe 2 Ph, and Boc removal afforded 13b .