Preparation of amino acids from unsaturated hydantoins
申请人:STAUFFER CHEMICAL COMPANY
公开号:EP0177072A2
公开(公告)日:1986-04-09
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.
A process for the preparation of (S)- or L-3-(3,4-dihydroxyphenyl)alanine (L-dopa) is described. The process utilizes water as reaction process solvent and proceeds via formation of an intermediate which can be kinetically resolved in a polar solvent to a precursor of the desired isomer and in which the undesired isomer can be efficiently racemized for reuse.