A novel process for producing derivatives of the anti-tumor agent N.sup.4 -acyl-5'-deoxy-5-fluorocytidine using the novel 5'-deoxy-5-fluoro-N.sup.4, 2'-0,3'-0-triacylcytidine derivatives as intermediates is provided.5-Deoxy-1,2,3-tri-0-acyl-.beta.-D-ribofuranoside is reacted with 5-fluorocytosine to produce 5'-deoxy-2',3'-di-0-acyl-5-fluorocytidine, followed by acylation, to produce the novel intermediate 5'-deoxy-5-flouro-N.sup.4,2'-0,3'-0-triacylcytidine. The acyl radicals of this intermediate are selectively de-0-acylated to obtain N.sup.4 -acyl-5'-deoxy-5-fluorocytidine derivatives. From fluorocytosine, N.sup.4 -acyl-5'-deoxy-5-fluorocytidine derivatives can be obtained through few steps in high yield, an in satisfactory purity.