Six new indole alkaloids from Gelsemium sempervirens Ait. f.

One new yohimbane and five new sarpagine-type indole alkaloids were isolated from the radix of Gelsemium sempervirens Ait. f., and their structures were determined by spectroscopic analysis, chemical conversion or total synthesis. It was found that 2-acyl sarpagine-type alkaloids possessing an Nb-methyl group take a keto–amino structure or a transannular form in solution depending on the solvent.