N^a-(tert-butoxycarbonyl)-N^t-(diphenyl(pyridin-4-yl)methyl)-L-histidyl-L-leucine

methylN^a-(tert-butoxycarbonyl)-N^t-(diphenyl(pyridin-4-yl)methyl)-L-histidyl-L-leucinate

benzyl (S)-(1-azido-3-(1H-imidazol-4-yl)-1-oxopropan-2-yl)carbamate

optically inactive N-(Nα-benzyloxycarbonyl-histidyl)-leucine-methyl ester

N-(1,Nα-bis-benzyloxycarbonyl-histidyl)-leucine methyl ester