(2S)-4-[(acetamidomethyl)sulfanyl]-2-({[(9H-fluoren-9-yl)methoxy]carbonyl}amino)butanoic acid

(2S)-4-[(piperidin-4-yl)amino]butan-2-ol dihydrochloride

(2S)-4-[(tert-butoxy)carbonyl]-5,5-dimethylmorpholine-2-carboxylic acid

(2S)-4-[(tert-butoxy)carbonyl]-6,6-dimethylmorpholine-2-carboxylic acid

(2S)-4-[(tert-butoxy)carbonyl]morpholine-2-carboxylic acid

(2S)-4-[(tert-butoxy)carbonyl]piperazine-2-carboxylic acid

(2S)-4-[3-(but-3-yn-1-yl)-3H-diazirin-3-yl]-2-({[(9H-fluoren-9-yl)methoxy]carbonyl}amino)butanoic acid

(2S)-4-[3-(but-3-yn-1-yl)-3H-diazirin-3-yl]-2-{[(tert-butoxy)carbonyl]amino}butanoic acid

(2S)-4-{bicyclo[1.1.1]pentan-1-yl}-1-[(tert-butoxy)carbonyl]pyrrolidine-2-carboxylic acid

(2S)-4-{bicyclo[1.1.1]pentan-1-yl}pyrrolidine-2-carboxylic acid hydrochloride

(2S)-4-{[(9H-fluoren-9-yl)methoxy]carbonyl}-5,5-dimethylmorpholine-2-carboxylic acid

(2S)-4-{[(9H-fluoren-9-yl)methoxy]carbonyl}morpholine-2-carboxylic acid

(2S)-4-{[(benzyloxy)carbonyl]amino}-2-hydroxybutanoic acid

(2S)-4-{[(tert-butoxy)carbonyl]amino}-2-(difluoromethoxy)butanoic acid

(2S)-4-{[(tert-butoxy)carbonyl]amino}-2-({[(9H-fluoren-9-yl)methoxy]carbonyl}amino)butanoic acid

(2S)-4-{[(tert-butoxy)carbonyl]amino}-2-hydroxybutanoic acid

(2S)-4-{[(tert-butoxy)carbonyl]amino}-2-methoxybutanoic acid

(2S)-4-{[3-(tert-butoxy)-3-oxopropyl]sulfanyl}-2-({[(9H-fluoren-9-yl)methoxy]carbonyl}amino)butanoic acid

(2S)-5,5-difluorohexan-2-amine hydrochloride

(2S)-5,5-dimethylmorpholine-2-carboxylic acid hydrochloride

(2S)-5-(benzyloxy)-2-({[(9H-fluoren-9-yl)methoxy]carbonyl}amino)-5-oxopentanoic acid

(2S)-5-(carbamoylamino)-2-({[(9H-fluoren-9-yl)methoxy]carbonyl}amino)pentanoic acid

(2S)-5-(carbamoylamino)-2-acetamidopentanoic acid

(2S)-5-(dimethylamino)-2-({[(9H-fluoren-9-yl)methoxy]carbonyl}amino)pentanoic acid hydrochloride

(2S)-5-(tert-butoxy)-2-(dimethylamino)-5-oxopentanoic acid

(2S)-5-(tert-butoxy)-2-({[(9H-fluoren-9-yl)methoxy]carbonyl}amino)-5-oxopentanoic acid

(2S)-5-(tert-butoxy)-2-{[(tert-butoxy)carbonyl]amino}-5-oxopentanoic acid

(2S)-5-({1-[(tert-butoxy)carbonyl]-4,5-dihydro-1H-imidazol-2-yl}amino)-2-({[(9H-fluoren-9-yl)methoxy]carbonyl}amino)pentanoic acid

(2S)-5-amino-2-(4-nitrobenzenesulfonamido)pentanoic acid hydrochloride

(2S)-5-amino-2-(dimethylamino)pentanoic acid hydrochloride

(2S)-5-amino-2-({[(9H-fluoren-9-yl)methoxy]carbonyl}amino)pentanoic acid

(2S)-5-amino-2-({[(9H-fluoren-9-yl)methoxy]carbonyl}amino)pentanoic acid hydrochloride

(2S)-5-amino-2-{[(tert-butoxy)carbonyl]amino}pentanoic acid

(2S)-5-azido-2-({[(9H-fluoren-9-yl)methoxy]carbonyl}amino)pentanoic acid

(2S)-5-azido-2-hydroxypentanoic acid

(2S)-5-bromo-2,3-dihydro-1H-indole-2-carboxylic acid

(2S)-5-bromo-2-methyl-2,3-dihydro-1H-indole

(2S)-5-bromo-2-methylpentanoic acid

(2S)-5-carbamimidamido-2-(4-methylbenzenesulfonamido)pentanoic acid

(2S)-5-carbamimidamido-2-(carbamoylamino)pentanoic acid

(2S)-5-carbamimidamido-2-(phenylformamido)pentanoic acid

(2S)-5-carbamimidamido-2-({[(9H-fluoren-9-yl)methoxy]carbonyl}amino)pentanoic acid

(2S)-5-carbamimidamido-2-acetamidopentanoic acid

(2S)-5-chloro-2,3-dihydro-1H-indole-2-carboxylic acid hydrochloride

(2S)-5-methyl-3,4-dihydro-2H-pyrrole-2-carboxylic acid hydrochloride