Asymmetric synthesis of amino acids via catalytic reduction of azalactone-substituted acylaminoacrylic acids. 21. Catalytic asymmetric synthesis of the phenylethylamide of N-acyl-p-difluoromethoxyphenylalanine

1.	Catalytic reductive aminolysis of the azalactones of N-acyl-p-difluoromethoxy--aminocinnamic acid in dimethoxyethane, isopropanol, and tert-butanol proceeds stereoselectively, leading to the -phenylethylamides of N-acyl-p-difluoromethoxyphenylalanine with a 3–55% excess of the S,S-diastereomer.
2.	Replacement of dimethoxyethane by isopropanol or tert-butanol leads to an increase in the stereoselectivity of the process.
3.	Hydrogenation of the S-(+)--phenylethylamide of N-acyl-p-difluoromethoxy--aminocinnamic acid proceeds stereoselectively, and leads to production of the -phenylethylamide of N-acyl-p-difluoromethoxyphenylalanine with a 9–18% excess of the R,S-diastereomer.

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 404–408, February, 1989.