To produce the subject new compound useful for producing a β-amino alcohol.

This α-hydroxy-β-amino acid ester is represented by formula I (R2 is a lower alkyl) or its salt, e.g. ethyl (2S,3S)-3-amino-2-hydroxy-4- phenylbutyrate. The compound represented by formula I is produced by converting a compound represented by formula II into a compound represented by formula III (R3 is H, a lower alkanoyl or the like), cleaving a tri(lower alkyl)silyl group present in the nitrile represented by formula III, converting the resultant nitrile represented by formula III into a salt of an iminoether in the presence of a lower alkanol represented by the formula R2-OH using a strong acid, as necessary, isolating the salt of the iminoether, then hydrolyzing the isolated salt, providing a compound represented by formula IV and converting the resultant compound into the compound represented by formula I by initially using a base and then a strong acid. The compound represented by formula I is a new intermediate useful for producing a compound represented by formula V.