Antibacterial and antifungal nucleosides

5'-O-Acyl-5-fluorouridines and 5'-O-acyl-5-sluorocytidines are prepared by the direct acylation of the 5'-hydroxyl group with amino acids under Mitsunobu conditions and the amino acyl derivatives are coupled with other amino acids or peptides to provide antibacterial and antifungal derivatives of the nucleosides. For example, 5-fluorouridine is acylated at the 5'-hydroxyl group with an amino protected L-valine and the acylation product is deprotected to provide 5'-O-(L-valinyl)-5-fluorouridine having activity against Gram-positive bacteria including resistant staphylococcus. Preferred peptide derivatives comprise the tripeptides of ornithine and lysine wherein the terminal amino group is substituted by both hydroxy and acetyl. The latter peptides inhibit the growth of C. albicans.