Diethyl 5-Amino-3-methylthiophene-2,4-dicarboxylate is used as a reagent in the synthesis of novel pyrazolo-pyrimidinones as dipeptidyl peptidase IV (DPP-IV) inhibitors in diabetes. It is also used in the synthesis of N-phenylthieno[2,3-d]pyrimidin-4-amines which act as inhibitors of fibroblast grow factor receptor 1 and therefore may be further used as anticancer agents.