3-Amino-1H-pyrazole-4-carboxylic Acid, is a heterocyclic building block used for the synthesis of more complex pharmaceutical and biologically active compounds, including inhibitors. It can be used for the preparation of some impurities and/or degradation products of Zaleplon (Z145000), and also for Arylsulfonamidopiperidone derivatives as a novel class of factor Xa inhibitors.