Ethyl (3S)-2-(1-benzylpyrrolidin-3-yl)acetate

diethyl (S)-2-(1-benzylpyrrolidin-3-yl)malonate

6-tert-butyl 1-ethyl 5-((tert-butoxycarbonyl)amino)hex-2-enedioate

(S)-3-((S)-2-Amino-2-carboxy-ethyl)-pyrrolidine-1-carboxylic acid benzyl ester

(S)-2-tert-Butoxycarbonylamino-3-(5-oxo-pyrrolidin-3-yl)-propionic acid tert-butyl ester