2(RS)-[2-(N-t-butoxycarbonyl-4-piperidyloxy)ethyl]piperidine

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

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

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

N-[N-(2,2,2-trichloroethoxycarbonyl)-(R)-cyclohexylalanyl]-2(RS)-[2-(N-t-butoxycarbonyl-4-piperidinyloxy)ethyl]piperidine