N-(N-cyclohexyl-O-t-butyl-(S)-α-aspartyl)-2(S)-{2-[N-(N,N'-di-t-butoxycarbonylamidino)-4-piperidyloxy]ethyl}piperidine

N-(N-cyclohexyl-O-t-butyl-(S)-α-glutamyl)-2(S)-{2-[N-(N,N'-di-t-butoxycarbonylamidino)-4-piperidyloxy]ethyl}piperidine

N-(N-cycloheptyl-O-t-butyl-(S)-α-aspartyl)-2(S)-{2-[N-(N,N'-di-t-butoxycarbonylamidino)-4-piperidyloxy]ethyl}piperidine

N-[N-(α-fluorenylmethoxycarbonyl)-O-t-butyl-(S)-α-glutamyl]-2(S)-{2-[N-(N,N'-di-t-butoxycarbonylamidino)-4-piperidyloxy]ethyl}piperidine

N-benzyloxycarbonyl-2(S)-{2-[N-(N,N'-di-t-butoxycarbonylamidino)-4-piperidyloxy]ethyl}piperidine