To provide a method for efficiently and safely producing (2S, 3S)-3- amino-2-hydroxy-4-phenylbutyric acid with improved erythroselectivity via a silyl derivative as a new compound, and to provide a method for efficiently and safely producing its intermediate.

The (2S, 3S)-(3-protected amino)-2-hydroxy-4-phenylbutyric acid is produced by the following procedure: the new compound (2S, 3S)-3-(N- protected amino)-1-(alkoxydialkylsilanyl)-4-phenylbutan-2-ol making the erythroselectivity determinant is used, and the terminal hydroxy group thereof is converted to a carboxy group without changing the configuration of the hydroxy group formed, using 2,2,6,6-tetramethylpiperidine-1-oxyl, a chlorite and a hypochlorite.