Configuration of echinulin. II. Optical rotatory dispersion of echinulin, hydroechinulin, and the stereoisomeric 3-methyl-6(indolyl-3-methyl)-piperazine-2,5-diones

The optical rotatory dispersion spectra of echinulin and hydroechinulin have been compared with the spectra of the 4 stereoisomers of cyclo-alanyltryptophan. The results indicate appreciable differences in the spectra of the cis- and trans-piperazinediones and that echinulin has the cyclo-L-alanyl-L-tryptophan configuration.