1,3-bis-(tert-butoxycarbonyl)-1-(trimethylsilylethyl-6-hexanoate)-2-methyl-2-thiopseudourea

N-(allyl)-N,N'-bis-(tert-butoxycarbonyl)-N''-(4-aminobutyl)-guanidine

Bis(1,1-dimethylethyl) 3-[[(1,1-dimethylethoxy)carbonyl]amino]-20-[(1,1-dimethylethoxy)carbonyl]-13-hydroxy-12,14-dioxo-2,4,11,15,20,24-hexaazapentacos-2-enedioate

Bis(1,1-dimethylethyl) 3-[[(1,1-dimethylethoxy)carbonyl]amino]-20-[(1,1-dimethylethoxy)carbonyl]-12,14-dioxo-13-fluoro-2,4,11,15,20,24-hexaazapentacos-2-enedioate