(2S)-2-(((2-cyano-1-phenylethoxy)carbonyl)amino)-6-((2,4-dinitrophenyl)amino)hexanoic acid

(S)-2-(((2-cyanoethoxy)carbonyl)amino)-6-((2,4-dinitrophenyl)amino)hexanoic acid

(S)-6-((2,4-dinitrophenyl)amino)-2-(((2-(phenylsulfonyl)ethoxy)carbonyl)amino)hexanoic acid

(2S)-2-((((1-cyanopropan-2-yl)oxy)carbonyl)amino)-6-((2,4-dinitrophenyl)amino)hexanoic acid

(2S)-6-((2,4-dinitrophenyl)amino)-2-((((1-(phenylsulfonyl)propan-2-yl)oxy)carbonyl)amino)hexanoic acid