A-AcETAMINOCINNAMIC ACID

Source (L(-))-Phenylalanine is isolated commercially from proteins (ovalbumin, lactalbumin, zein, and fibrin). DL-Phenylalanine is synthesized from a-acetaminocinnamic acid. 

The azlactone of a-acetaminocinnamic acid may also be prepared by substituting the equivalent amount of glycine for acetylglycine and increasing the amount of atetic anhydride to three molecular proportions, but the yield is only about 45-50 per cent of the theoretical amount. 

Phenylpyruvic acid has been prepared by the hydrolysis of a-benzoylaminocinnamic add with alkalies or acids by the acid hydrolysis of ethyl phenyloxalacetate by the acid hydrolysis of ethyl phenylcyanopyruvate by dehydration of -phenyl-glyceric acid with sulfuric acid by the alkaline hydrolysis of phenylethoxalylacetamide and by the alkaline hydrolysis of a-acetaminocinnamic acid. ... 

The solubility of a-acetaminocinnamic acid in water decreases very rapidly on cooling below the boiling point of the solution. Since the solution is very nearly saturated with the product, a large share of the acid will crystallize in the funnel during filtration if the solution is allowed to cool too much. This property of the product makes it inadvisable to work with larger quantities. 

The azlactone of a-acetaminocinnamic acid has been prepared by heating a mixture of glycine, benzaldehyde, acetic anhydride, and anhydrous sodium acetate and from iV-chloroacetylphe-nylalanine by treatment with acetic anhydride. ... 

A SOLUTION of 20.5 g. (o.i mole) of a-acetaminocinnamic acid (p. i) in 150 cc, of glacial acetic acid (Note i) is placed in the bottle of a Burgess-Parr reduction apparatus, 0.5 g. of platinum oxide catalyst (Org. Syn. Coll. Vol. I, 452 17, 98) is added, and the mixture shaken in an atmosphere of hydrogen under an initial pressure of 40 lb. per sq. in. until the calculated amount of gas is taken up usually about two hours is required (Notes 2 and 3). When the reduction is complete, the catalyst is removed by suction filtration and washed with a little water. The combined filtrate and washings are evaporated to dryness under diminished pressure on a water bath. 

To the methods of preparation cited by Gillespie and Snyder the following may be added the reduction of phenylpyruvic acid in alcoholic-ammoniacal solution with hydrogen in the presence of platinum catalyst and the reduction of a-acetaminocinnamic acid with hydrogen in the presence of platinum followed by hydrolysis of the resulting acetylphenylalanine. ... 

Pyruvic acid yields mainly a,a-diacetaminopropionic acid, which can be converted into a-acetaminoacrylic acid by hot acetic acid. > Under the optimum conditions " a 23% yield of a-acetaminoacrylic acid is obtained. Phenylpyruvic acid gives mainly a-acetaminocinnamic acid, as would be expected in view of the activating effect of the benzene ring. Benzoylformic acid and a-ketoglutaric acid have been employed as the acid components in this reaction, and benzamide, benzylcarbar mate," and chloroacetamide " as the amide components. The preparation of a-acetaminocinnamic acid by this method is described in the next section. 

Procedures. The preparation of df- phenylalanine by the reduction and cleavage of a-benzoylaminocinnamic azlactone with phosphorus, hydriodic acid, and acetic anhydride, and the preparation of the same amino add from a-acetaminocinnamic acid by catalytic reduction and hydrolysis, are described in Organic Syntheses. ... 

Atropic acid hydrogenated with an optically active diphosphine-rhodium(I) catalyst and triethylamine in 1 2 benzene-ethanol (S)-hydratropic acid. Y ca. 100% optical purity 63%. - Similarly a-Acetaminocinnamic acid (R)-N-... 

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