Abstract: .alpha.-(S)-amino acid..alpha.-phenylethanesulfonate compounds and methods of optical resolution of .alpha.-amino acids and .alpha.-phenylethanesulfonic acids are described.

Abstract: The present invention relates to the optical resolution of a p-hydroxyphenylglycine salt with simultaneous racemization of the undesired enantiomer thereof. The invention is carried out by preferential crystallizing out the desired enantiomer from a supersaturated solution of the racemic modification thereof in a lower aliphatic acid in the presence of an aliphatic or aromatic aldehyde.

Abstract: p-Hydroxyphenylglycine..alpha.-phenylethanesulfonate which is useful for the production of optically active p-hydroxyphenylglycine and optically active .alpha.-phenylethanesulfonic acid is disclosed. p-Hydroxyphenylglycine..alpha.-phenylethanesulfonate is produced by either reacting DL-p-hydroxyphenylglycine with optically active .alpha.-phenylethanesulfonic acid or reacting (.+-.)-.alpha.-phentylethanesulfonic acid with optically active p-hydroxyphenylglycine to form two diastereomers of DL-p-hydroxyphenylglycine optically active .alpha.-phenylethanesulfonate or optically active p-hydroxyphenylglycine (.+-.)-.alpha.-phenylethanesulfonate, and isolating one diastereomer according to the difference between solubilities of the diastereomers, optionally, combining selective crystallization of one diastereomer and epimerization of another diastereomer in the case of reaction of DL-p-hydroxyphenylglycine and optically active .alpha.-phenylethanesulfonic acid.

Abstract: DL-.alpha.-amino acids or a salt thereof can be obtained by racemizing an optically active .alpha.-amino acid or a salt thereof in the presence of an aliphatic acid and an aldehyde.

Abstract: Seed crystals of an optically active enantiomer of any one of p-hydroxyphenylglycine benzenesulfonate, p-hydroxyphenylglycine p-ethylbenzenesulfonate, p-hydroxyphenylglycine o-toluenesulfonate or p-hydroxyphenylglycine sulfosalicylate are added to a supersaturated solution of the racemic modification of the corresponding p-hydroxyphenylglycine salt. Crystallization of the optically active enantiomer results. Then, the crystals are recovered. Alternatively, crystals of the optically active enantiomer may be added to a hot solution of the racemic modification of the corresponding p-hydroxyphenylglycine salt to produce a supersaturated solution thereof. The solution is then cooled to crystallize out the optically active enantiomer. Optically active p-hydroxyphenylglycine benzenesulfonate, optically active p-hydroxyphenylglycine p-ethylbenzenesulfonate, optically active p-hydroxyphenylglycine o-toluenesulfonate or optically active p-hydroxyphenylglycine sulfosalicylate is thereby obtained.