Abstract: In K₂CO₃-CH₃COCH₃-H₂O system, N-acyl-a-amino acids (Ⅰ_a-j) were prepared by the reaction of amino acids with N-acyl thiazolidines-2-thiones and the yields were 76%～95%. The synthesis of saturated 5(4H)-oxazolones(Ⅱ_a-h) from Iunder mild reaction conditions in yields of 43%～84% by the use of cyanuric chloride as a condensing reagent in the presence of triethylamine was reported. Unsaturated 5(4H)-oxazolones (Ⅲ_a-j) were obtained from Iin the yields of 43%～93% by the aldol reaction in which Fe₂SO₄)₃ was used as a catalyst.

Key words: N-acyl-a-amino acid, Cyanuric chloride, Saturated 5(4H)-oxazolone, Unsaturated 5(4H)-oxazolone