N-(N-(3-tetrahydropyranyl)-O-t-butyl-(S)-α-aspartyl)-2(S)-{2-[N-(N,N'-di-t-butoxycarbonylamidino)-4-piperidyloxy]ethyl}piperidine

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

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

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

N-(N-methyl-N-(3-tetrahydropyranyl)-O-t-butyl-(S)-α-aspartyl)-2(S)-{2-[N-(N,N'-di-t-butoxycarbonylamidino)-4-piperidyloxy]ethyl}piperidine