N-[(R)-cyclohexylalanyl]-2(RS)-{2-[N-(N,N'-di-t-butoxycarbonylamidino)-4-piperidyloxy]ethyl}piperidine

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

N-[N-(t-butoxycarbonylmethyl)-(R)-phenylalanyl]-2(RS)-{2-[N-(N,N'-di-t-butoxycarbonylamidino)-4-piperidyloxy]ethyl}piperidine

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

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