Formation of yohimbanones via a novel rearrangement

An investigation of the reaction of tryptophan and its methyl ester with ninhydrin has been conducted. In the reaction of tryptophan with ninhydrin only one product, yohimbanone (), is isolated. In contrast, an intermediate, Pictet–Spengler product , is isolated from the reaction of tryptophan methyl ester with ninhydrin. The isolation of this intermediate provides support for a proposed mechanism of this novel rearrangement, which is presented herein.