(2S)-3-{[(tert-butoxy)carbonyl]amino}-2-hydroxypropanoic acid

(2S)-3-{[(tert-butoxy)carbonyl]amino}-2-methoxypropanoic acid

(2S)-3-{[(tert-butoxy)carbonyl]amino}-2-methylpropanoic acid

(2S)-3-{[1,1'-biphenyl]-4-yl}-2-[(2S)-3-methyl-2-sulfanylbutanamido]propanoic acid

(2S)-4,10-diacetyl-3,11,13-trihydroxy-2,12-dimethyl-8-oxatricyclo[7.4.0.0,2,7]trideca-1(13),3,6,9,11-pentaen-5-one

(2S)-4,4,4-trifluoro-2-methylbutanoic acid

(2S)-4,4,4-trifluorobutan-2-amine hydrochloride

(2S)-4,4-difluoro-1-nitrosopyrrolidine-2-carboxylic acid

(2S)-4,4-difluoro-2-(trifluoromethyl)pyrrolidine hydrochloride

(2S)-4,4-difluoro-2-methylpyrrolidine hydrochloride

(2S)-4,4-difluoro-5-oxopyrrolidine-2-carboxylic acid

(2S)-4,4-difluoro-N-methylpyrrolidine-2-carboxamide hydrochloride

(2S)-4,4-difluorobutane-1,2-diol

(2S)-4,4-difluorooxolane-2-carboxylic acid

(2S)-4,4-difluoropyrrolidine-2-carbonitrile hydrochloride

(2S)-4,4-difluoropyrrolidine-2-carboxamide hydrochloride

(2S)-4,4-difluoropyrrolidine-2-carboxylic acid hydrochloride

(2S)-4,4-dimethylpentan-2-amine hydrochloride

(2S)-4,6-dioxopiperidine-2-carboxylic acid

(2S)-4-(acetyloxy)-2-aminobutanoic acid

(2S)-4-(benzyloxy)-2-({[(9H-fluoren-9-yl)methoxy]carbonyl}amino)-4-oxobutanoic acid

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

(2S)-4-(benzyloxy)butan-2-amine hydrochloride

(2S)-4-(benzyloxy)butan-2-ol

(2S)-4-(dimethylamino)-2-hydroxybutanoic acid

(2S)-4-(dimethylamino)butan-2-ol

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

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

(2S)-4-(methylamino)butan-2-ol

(2S)-4-(methylsulfanyl)butane-1,2-diamine

(2S)-4-(piperidin-4-yl)butan-2-ol

(2S)-4-(piperidin-4-yl)butan-2-ol hydrochloride

(2S)-4-(pyridin-4-yl)but-3-yn-2-ol

(2S)-4-(pyridin-4-yl)butan-2-ol

(2S)-4-(tert-butoxy)-2-(dimethylamino)-4-oxobutanoic acid

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

(2S)-4-(tert-butoxy)-2-hydroxy-4-oxobutanoic acid

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

(2S)-4-(tert-butoxy)butan-2-amine hydrochloride

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

(2S)-4-amino-1-(benzyloxy)butan-2-ol hydrochloride

(2S)-4-amino-2-(tert-butoxy)butanoic acid

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

(2S)-4-amino-2-hydroxybutanoic acid

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