Recent advances in the chemistry of Gelsemium alkaloids

Abstract

This chapter reviews the recent intensive research that led to significant progress in the field of Gelsemium alkaloid chemistry. It presents alkaloids isolated from the Gelsemium species. The structure elucidation of the representative alkaloids using mainly spectroscopic methods is described. The chapter discusses the biogenetic speculation of the structurally unique Gelsemium alkaloids and the biomimetic transformation of the known indole alkaloids leading to the various skeletal types of Gelsemium alkaloids. A genuine indole nucleus is present only in the sarpagine group and sempervirine among the many skeletal classes of the Gelsemium alkaloids. The sarpagine group found in the Gelsemium species consists of six indole alkaloids, 19( Z )-akuammidine (koumicine), koumicine N -oxide, koumidine, 16 -epi- voacarpine, 19(Z)-anhydrovobasine-diol, and N a -methoxy-19( Z )-anhydrovobasinediol. The structure elucidation of the indole alkaloid, the so-called akuammidine isolated from Gelsemium elegans is discussed in the chapter. The configuration of the ethylidene side chain was considered the 19( E ) form as generally found in the monoterpenoid indole alkaloids. The so-called akuammidine from G. elegans showed the same mass spectral fragment pattern as authentic akuammidine obtained from other plant sources.