3(R)-(6-methoxypyridin-3-yl)-3-{2-oxo-3-[3-(5,6,7,8-tetrahydro-[1,8]naphthyridin-2-yl)-propyl]-imidazolidin-1-yl}-propionic acid
(S)-3-(6-methoxypyridin-3-yl)-3-(2-oxo-3-(3-(5,6,7,8-tetrahydro-1,8-naphthyridin-2-yl)propyl)imidazolidin-1-yl)propanoic acid
tert-butyl (3S)-3-{benzyl[(1R)-1-phenylethyl]amino}-3-(6-methoxypyridin-3-yl)propanoate