(4S)-3-aza-4-(tert-butoxycarbonyl)-2-isobutyl-6-phenylhexanamide of (2S,3R,4S)-2-amino-1-cyclohexyl-3,4-dihydroxy-6-methylheptane
2-((S)-1-tert-Butoxycarbonyl-3-phenyl-propylamino)-4-methyl-pentanoic acid
(4S)-benzyl 3-aza-4-(tert-butoxycarbonyl)-2-isobutyl-6-phenylhexanoate