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
Organic Chemistry
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Conclusions
- 1.
Catalytic reductive aminolysis of the azalactones of N-acyl-p-difluoromethoxy-α-aminocinnamic acid in dimethoxyethane, isopropanol, and tert-butanol proceeds stereoselectively, leading to the α-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-(+)-α-phenylethylamide of N-acyl-p-difluoromethoxy-α-aminocinnamic acid proceeds stereoselectively, and leads to production of the α-phenylethylamide of N-acyl-p-difluoromethoxyphenylalanine with a 9–18% excess of the R,S-diastereomer.
Keywords
Hydrogenation Isopropanol Asymmetric Synthesis Dimethoxyethane Acid Proceeds
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© Plenum Publishing Corporation 1989