Heterocyclic compounds possess a cyclic structure with two or more different kinds of atoms in the ring. These type of compounds are widely distributed in nature and are essential for life, playing a vital role in the metabolism of all living cells e.g. the pyrimidine and purine bases of the genetic material DNA, the essential amino acids proline, hisitidine, the vitamins and coenzymes etc. There are number of pharmacologically active heterocyclic compounds, many of which are in regular clinical use. A wide range of synthetic and naturally occurring heterocyclic compounds are useful in considerable amount of research leading to new heterocyclic molecules having an array of biological activities.