The invention provides processes for producing efficiently optically
active 2-halogenocarboxylic acids useful in the preparation of drugs or
the like and salts thereof with amines. Specifically, an optically active
2-halogenocarboxylic acid is produced by halogenating an optically active
amino acid in water in the presence of a hydrophobic organic solvent and
nitrous acid with the configuration retained and with the racemization
inhibited through the removal of 2-hydroxy-bromocarboxylic acid formed as
a by-product; the obtained optically active 2-halogenocarboxylic acid is
transferred to an aqueous phase by converting it into a salt thereof with
a base, followed by the removal of the organic phase; and the optically
active 2-halogenocarboxylic acid is transferred again to an organic
solvent phase, followed by the removal of the aqueous phase, whereby an
optically active 2-halogenocarboxylic acid is obtained through the
removal of a halogen component. Further, a high-quality salt of an
optically active 2-halogenocarboxylic acid with an amine can be obtained
by a crystallization method wherein the amine is added over the period of
1/2 hour or longer either continuously or in portions and/or wherein the
crystallization solvent consists of a hydrophobic organic solvent and a
hydrophilic organic solvent.