3-({[(9H-fluoren-9-yl)methoxy]carbonyl}amino)-4-[(3R)-3-methoxypyrrolidin-1-yl]-4-oxobutanoic acid

4-{[4-({[(9H-fluoren-9-yl)methoxy]carbonyl}amino)-3-iodophenyl]formamido}-3-hydroxybutanoic acid

4-(2-{[2-({[(9H-fluoren-9-yl)methoxy]carbonyl}amino)ethyl]sulfanyl}acetamido)-2-methoxybutanoic acid

4-{[5-({[(9H-fluoren-9-yl)methoxy]carbonyl}amino)-1H-1,2,4-triazol-3-yl]formamido}-2-methoxybutanoic acid

4-[5-({[(9H-fluoren-9-yl)methoxy]carbonyl}amino)-4-methylpentanamido]-2-methoxybutanoic acid

4-{2-[1-({[(9H-fluoren-9-yl)methoxy]carbonyl}amino)cyclopentyl]acetamido}-2-methoxybutanoic acid

1-[3-({[(9H-fluoren-9-yl)methoxy]carbonyl}amino)hexanoyl]-1,2,3,6-tetrahydropyridine-4-carboxylic acid

1-[2-({[(9H-fluoren-9-yl)methoxy]carbonyl}amino)-1,3-thiazole-4-carbonyl]-1,2,3,6-tetrahydropyridine-4-carboxylic acid

2-(2-{[1-benzyl-3-({[(9H-fluoren-9-yl)methoxy]carbonyl}amino)pyrrolidin-3-yl]formamido}acetamido)acetic acid

(2S)-4-{[1-benzyl-3-({[(9H-fluoren-9-yl)methoxy]carbonyl}amino)pyrrolidin-3-yl]formamido}-2-hydroxybutanoic acid

2-{N-benzyl-1-[4-({[(9H-fluoren-9-yl)methoxy]carbonyl}amino)-2-fluorophenyl]formamido}acetic acid