methyl (2S,3R)-2-azido-3-(benzyloxycarbonyl-N-methylamino)butyrate

(2R,3R)-3-Methylamino-2-(4-methyl-benzyloxycarbonylamino)-butyric acid methyl ester

(2R,3R)-3-(Benzyloxycarbonyl-methyl-amino)-2-tert-butoxycarbonylamino-butyric acid methyl ester

(2R,3R)-2-tert-Butoxycarbonylamino-3-methylamino-butyric acid methyl ester

(2R,3R)-2-tert-Butoxycarbonylamino-3-[(9H-fluoren-9-ylmethoxycarbonyl)-methyl-amino]-butyric acid methyl ester