Stereocontrolled Total Synthesis of Alkaloid G via the Oxy-anion Cope Rearrangement and Improved Total Synthesis of (+)-Ajmaline

Abstract

[figure: see text] The oxy-anion Cope rearrangement followed by protonation of the enolate which resulted under conditions of kinetic control has been employed to generate the key asymmetric centers at C(15), C(16), and C(20) in alkaloid G (1) and (+)-ajmaline (2) in a highly stereocontrolled fashion. The aldehyde 7b from this process has been converted into alkaloid G (1) and (+)-ajmaline (2) in 36% and 13% overall yields (11 reaction vessels from 3), respectively.