A process for producing an
optically active aminophosphinylbutanoic acid represented by the general formula (2), comprising the step for conducting the
asymmetric hydrogenation of a compound represented by the general formula (1) in the presence of a
ruthenium-(
optically active phosphine) complex. In the general formula (2), R1 represents an
alkyl group having 1 to 4 carbon atoms; R2 represents a
hydrogen atom or an
alkyl group having 1 to 4 carbon atoms; R3 represents an
alkyl group having 1 to 4 carbon atoms, an
alkoxy group having 1 to 4 carbon atoms, an
aryl group, an aryloxy group or a benzyloxy group; R4 represents a
hydrogen atom or an alkyl group having 1 to 4 carbon atoms; and symbol '*' means that a carbon having this symbol is an
asymmetric carbon atom. In the general formula (1), R1 represents an alkyl group having 1 to 4 carbon atoms; R2 represents a
hydrogen atom or an alkyl group having 1 to 4 carbon atoms; R3 represents an alkyl group having 1 to 4 carbonatoms, an
alkoxy group having 1 to 4 carbon atoms, an
aryl group, an aryloxy group or a benzyloxy group; R4 represents a
hydrogen atom or an alkyl group having 1 to 4 carbon atoms; The process enables to produce a compound useful as a herbicide such as L-AHPB, at good efficiency and at high asymmetric yield.