The synthesis of β‐heteroarylamino‐α,β‐dehydro‐α‐amino acid derivatives via thiazolones

2‐Alkoxy‐4‐heteroarylaminomethylene‐5(4 H )‐thiazolones 4 were converted with various nucleophiles into β‐heteroarylamino‐α,β‐dehydro‐α‐amino acid derivatives 11, 14, 15, 16, 17, 18 , and 19 . Reduction of 4 with sodium borohydride in ethanol saturated with gaseous ammonia afforded the corresponding β‐heteroaryl‐amino substituted alanyl amides 20 . Thiazoledione derivative 7a was transformed with sodium methoxide in methanol into 1‐(4,6‐dimethylpyrimidinyl‐2)‐4‐mercaptocarbonylimidazol‐2(3 H )‐one ( 8a ).