In 120 ml of dimethylacetamide, 6.0 g of arabinofuranosylcytosine is dissolved and to the resultant solution are added 4.15 g of sodium hydrogen carbonate and 7.66 g of nonyloxycarbonyl chloride. The mixture is then allowed to react under stirring at 20 to 25° C. for 2 hours. After the reaction, the solvent is removed under reduced pressure and the residue is dissolved in a small amount of ethanol. Water is then added to the resultant solution and the precipitated solids are collected by filtration, followed by drying. The white powders obtained are washed thoroughly with ethyl ether to obtain 3.8 g of N4 -nonyloxycarbonyl-1-β-D-arabinofuranosylcytosine (Yield:37%).
