diphenyl 1-[(N-p-cyanobenzenesulfonyl-O-tert-butyl-D-seryl)-L-alanyl]amino-2-[4-(N,N'-bis(tert-butyloxycarbonyl)guanidino)phenyl]ethanephosphonate

diphenyl 1-[(N-1-naphthalenesulfonyl-O-tert-butyl-D-seryl)-L-alanyl]amino-2-[4-(N,N'-bis(tert-butyloxycarbonyl)guanidino)phenyl]ethanephosphonate

diphenyl 1-((N-benzyloxycarbonyl-L-alanyl)amino)-2-(4-(N,N'-bis(tert-butyloxycarbonyl)guanyl)phenyl)ethanephosphonate