Photocyclization of enamides. XXVI Photochemical synthesis of yohimban, epiyohimban, and alloyohimban, basic skeletal structures of yohimbine- and reserpine-type alkaloids.
Photocyclization of enamides. XXVI Photochemical synthesis of yohimban, epiyohimban, and alloyohimban, basic skeletal structures of yohimbine- and reserpine-type alkaloids.
One new yohimbane and five new sarpagine-type indole alkaloids were isolated from the radix of Gelsemiumsempervirens 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.