The syntheses of 5-substituted uridines and their 5'-phosphates were described. 5-Bromo-2', 3'-isopropylideneuridine was phosphorylated with phosphoryl chloride and from the mixture of 5-Bromo-UMP, -UDP, and -UTP obtained, 5-Bromo-UMP was isolated by ion exchange chromatography. Phosphorylation of 5-bromo-2', 3'-isopropylideneuridine with polyphosphoric acid afforded 5-Bromo-UMP in a good yield. 5-Hydroxyuridine and its 5'-phosphate were synthesized by the addition of bromine to uridine or UMP and successive treatment with pyridine. 5-Morpholinouridine and its isopropylidene derivative were obtained from corresponding 5-bromo derivatives and morpholine, and 5-Morpholino-UMP was obtained by phosphorylation of 5-morpholino-2', 3'-isopropylideneuridine with polyphos phoric acid.