456 Notes salt of cytidine and uridine 2', 3'-phosphates were synthesized by modified procedure of K horana et al.(8). Ethyl cytidine and ethyl uridine 3'-phosphates were prepared by enzymatic ethanolysis of the corresponding cyclic phosphates with RNase-I according to the method of H eppe 1 (9). The yield for each compounds was ca. 30 per cent. Yeast RNA was purchased from Schwartz Biore search. Inc. Mount Vernon, NY and used as sodium salt after dialysis in Visking cellulose tube and subsequent lyophilization. Heparin was purchased from Mochida Pharmaceutical Co. Ltd.. Enzymatic activity was estimated from the amount of the reaction products separated by paper chromatography.