Asymmetric synthesis of amino acids via the catalytic reduction of substituted acylaminoacrylic acid azlactone derivatives

We have studied the reaction of ²-oxazolin-5-ones with R-phenylglycine methyl ester in the presence of PdCl₂; the reaction gives phenylalanine or valine dipeptide derivatives with the RS-configuration. The presence of triethylamine during the reductive aminolysis of oxazolinones in dimethoxyethane solvent significantly increases the stereoselectivity of the reaction process. The stepwise mechanism of the reaction has also been explored.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 818–822, April, 1990.     

Asymmetric synthesis of amino acids via the catalytic reduction of acylaminoacrylic acid azlactone derivatives

Reductive aminolysis of 2-methyl-4-benzylidene-²-oxazolin-5-one upon treatment with a PdCl₂-S-phenylalanine ester (dimethylamide) catalytic system leads to the formation of the corresponding acylated dipeptide derivatives, with the R,S-configuration (diastereomer) predominating (DE 9–27%). The reaction stereoselectivity in dimethoxyethane increases sharply in the presence of triethylamine additive, and in the case of S-phenylalanine methyl ester reaches 47%. The stepwise mechanism for this process has been studied.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 811–818, April, 1990.     

Asymmetric synthesis of aminoacids by catalytic reduction of azlactones by substituted acylaminoacrylic acids. 19. Reaction of catalyst with substrate

Conclusions Reaction of 2-methyl-4-benzylideneoxazol-5-one with a zerovalent palladium complex containing S-(-)--phenylethylamine as ligand, in chloroform or dichloromethane as solvent, gives a heteroligand complex which is a reactive intermediate in reductive aminolysis,Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2283–2286, October, 1987.The authors thank E. S. Shpiro for obtaining and discussing the PES-spectra.