Spectroscopic analyses and chemical transformation for structure elucidation of two novel indole alkaloids from Gelsemium elegans

Two new monoterpenoid oxindole alkaloids, gelsevanillidine (1) having an additional vanillin residue on gelsenicine-type alkaloid and gelseoxazolidinine (2) possessing an unusual oxazolidine ring, were isolated from Gelsemium elegans. To confirm their structures, the chemical transformation of a humantenine-type alkaloid into gelsevanillidine (1) and the deacetoxy derivative of gelseoxazolidinine was performed.