3-{[(tert-butoxy)carbonyl](2,2-dimethoxyethyl)amino}propanoic acid

3-{[(tert-butoxy)carbonyl](3-ethoxypropyl)amino}propanoic acid

3-((tert-butoxycarbonyl)(4-phenylbutan-2-yl)amino)propanoic acid

3-{[(tert-butoxy)carbonyl][2-(1H-indol-3-yl)ethyl]amino}propanoic acid

tert-butyl 3-[(pentan-3-yl)amino]propanoate

tert-butyl 3-{[2-(3,4-dimethoxyphenyl)ethyl]amino}propanoate

tert-butyl 3-{[2-(pyrrolidin-1-yl)ethyl]amino}propanoate

tert-butyl 3-{[2-(piperidin-1-yl)ethyl]amino}propanoate

tert-butyl 3-{[2-(dimethylamino)ethyl]amino}propanoate

tert-butyl 3-{[2-(diethylamino)ethyl]amino}propanoate

tert-butyl 3-{[(2-chlorophenyl)methyl]amino}propanoate

tert-butyl 3-{[(4-methoxyphenyl)methyl]amino}propanoate

tert-butyl 3-(cyclopentylamino)propanoate

ethyl 3-[(2-ethoxyethyl)amino]propanoate

ethyl 3-[(2-phenylethyl)amino]propanoate