Convenient Intermediates for the Preparation ofC-4 Modified Derivatives of Pyrimidine Nucleosides

4-(4-Nitrophenoxy)-1-(βD-ribofuranosyl) pyrimidin-2(1H)-one 15, 5-methyl-4-(1, 2, 4-triazol-1-yl)-1-(βD-2-deoxyribofu-nosyl) pyrimidin-2(1H)-one 7a and 4-(4-nitro-phenoxy)-1-(β-D-2-deoxyribofurnosyl) pyrimidin-2(1H)-one 17a, respectively, have been prepared and are recommended as reactive intermediates for the preparation of derivatives of uridine, thymidine and 2′-deoxyuridine which are modified at C-4.