(S)-3-Methyl-2-(toluene-4-sulfonylamino)-butyric acid (S)-2-tert-butoxycarbonylamino-3-(4-nitro-6,7,8,9-tetrahydro-1H-benzo[g]indol-3-yl)-propyl ester
(S)-3-Methyl-2-(toluene-4-sulfonylamino)-butyric acid (R)-2-tert-butoxycarbonylamino-3-(4-nitro-6,7,8,9-tetrahydro-1H-benzo[g]indol-3-yl)-propyl ester