(2R,5R,11bS,1'S)-2-(tert-butoxycarbonyl)amino-5-(1'-methoxycarbonyl-2'-phenylethyl)carbamoyl-3-oxo-2,3,5,6,11,11b-hexahydro-1H-indolizino[8,7-b]indole

(1S,3R,2'R)-1-[2'-(tert-butoxycarbonyl)amino-2'-carboxyethyl]-3-methoxycarbonyl-1,2,3,4-tetrahydro-β-carboline

(2R,,5R,11bS)-2-(tert-butoxycarbonyl)amino-5-carboxy-3-oxo-2,3,5,6,11,11b-hexahydro-1H-indolizino[8,7-b]indole

(2R,5R,11bS)-2-(tert-butoxycarbonyl)amino-5-methoxycarbonyl-3-oxo-2,3,5,6,11,11b-hexahydro-1H-indolizino[8,7-b]indole

(2R,5R,11bS)-2-(benzyloxycarbonyl)amino-5-methoxycarbonyl-3-oxo-2,3,5,6,11,11b-hexahydro-1H-indolizino[8,7-b]indole