Stauffer Chemical Company

Mark W Empie

Stanley B Mirviss

Racemates of optically active amino acid substituted at the carbonyl position wherein the alpha amino acid nitrogen is underivatized and can be resolved using a two phase solvent system. The racemate is dissolved in a substantially water immiscible organic material which is a solvent for said amino acid racemate but not for the corresponding amino acids. The racemate is also dissolved in water (aqueous phase) and is in equilibrium with the racemate in the organic phase. One of the optical isomers of the amino acid racemate in the aqueous phase is enzymatically hydrolyzed to the corresponding amino acid and is recovered. The preferred product is L-phenylalanine.

Resolution of racemates of amino acids

Amino acids can be easily prepared by reducing unsaturated hydantoins to the corresponding saturated hydantoins by hydrogenating the unsaturated hydantoin using either Raney Nickel catalyst in the presence of more than a stoichiometric amount of caustic or by using zinc and hydrochloric acid followed by hydrolyzing the resultant composition with at least 3 molar equivalents of an alkali metal hydroxide to produce a racemate of an alpha amino acid. The amino acid in suitable derivative form can then be resolved particularly using a two-phase solvent system. The residual isomer of the amino acid remaining after the resolution process can then be racemized using either pyridoxal-5-phosphate or an aliphatic acid in combination with an aldehyde or a ketone. By these procedures, it is possible to obtain high yields of amino acids.

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Ashland, MA, United States of America

Mark W Empie