A series of novel amino acid derivatives has been synthesized by the reaction of 4-[4-methoxy-3-methylphenyl]-4-oxobutenoic acid with primary and secondary amines. The treatment of amino acids with hydrazine afforded pyridazine. Phenylhydrazone was obtained from the reaction of the acid with phenyl hydrazine in ethanol. On the other hand, the acid underwent heterocyclization upon the treatment with 2-aminopyridine, o-phenylenediamine, aryldithiocarbamates and thiourea derivatives to give the corresponding pyridopyrimidine, quinoxalone, 2-thioxo-1,3-thiazole and 4-hydroxy-1,3-thiazole, respectively. The thiazolopyridazine derivatives were obtained from the reaction of 4-hydroxy-1,3-thiazole with hydrazine and phenylhydrazine, respectively. The behaviour of the 4-hydroxy-1,3-thiazole toward acetic anhydride and bromine was also studied. The proposed structures of the products were based on microanalytical and spectroscopic data. Some of the synthesized compounds also exhibited anti-microbial activities.