Asymmetric synthesis of amino acids by catalytic reduction of the azlactones of substituted acylaminoacrylic acids. 4. production of (S)-tyrosine and (S)-O-methyltyrosine

Conclusions

• 1. The reaction of the azlactones of 4-acetoxy- and 4-methoxy-a-acetamidocinnamic acids with S-(-)-α-phenylethylamine and hydrogen in the presence of a palladium catalyst in aprotic solvents gives the α-phenylethylamides of 4-acetoxy- and 4-methoxyacetylphenylalanine with the preferred SS configuration.

• 2. Conditions were found for the production of the pure SS-diastereomers, which give the optically pure S-tyrosine and S-O-methyltyrosine on hydrolysis.

• 3. During the reduction of the azlactone of 4-methoxyacetamidocinnamic acid in methanol in the presence of S-(-)-α-phenylethylamine and a palladium catalyst R-(-)-N-acetyl-O-methyltyrosine methyl ester was obtained with an optical yield of 35%.

• 4. Aminolysis of the saturated azlactones of N,O-diacetyltyrosine and N-acetyl-O-methyltyrosine by optically active S-phenylethylamine leads to a-phenylethylamides of N, O-diacetyltyrosine and N-acetyl-O-methyltyrosine with the preferred SS configuration.

• 5. Aminolysis of the optically active azlactone of S-(-)-N,O-dxacetyltyrosine by the racemic α-phenylethylamine is accompanied by racemization, the rate of which is higher than the rate of aminolysis.

• 6. The reductive aminolysis of the azlactones occurs mainly as reaction of the azlactone with the amine and hydrogen at the surface of the catalyst.