The dissertation will give an introduction, background and current research progress in the areas of antifolates and chemotherapy of anticancer. The design and synthesis of classical 6- substituted pyrrolo[2,3-d]pyrimidines and 5-substituted pyrrolo[2,3-d]pyrimidines as potential antifolates have been described. The design variations include: methylated thiophene regioisomers, fluorinated phenyl regioisomers, thionyl regioisomers on the side chain of pyrrolo[2,3-d]pyrimidines. As a part of this study, a series of new compounds have been synthesized and characterized. Of these, ten final compounds were submitted for biological evaluation