The synthesis of new pyrimidine bases and their derivatives are of particular im- portaFlce in the search for antiviral and anticancer compounds. Some of synthetic nucleosides containing a substituent in position 5 of pyrimidine base are potential1 •2 or actually used antiviral drugs3 • It is assumed that the antiviral activity of the major- ity of these compounds is mainly due to their inhibiting effect on important enzymatic reactions4 • It has been observed that ...