The present invention relates to a novel compound represented by formula (1), or salt thereof,wherein R is hydroxy group or hydrogen atom； R1 and R2 are the same or different, and are each independently benzyl group which may have a substituent. The present invention provides therapeutically agents, which have remarkable stability against cytidine deaminase, a metabolic enzyme, can be absorbed in vivo by oral administration and inhibit protein synthesis by being incorporated easily into nucleic acid bio-synthesis in vivo for replacing injection agent (5-azacytidine or 2′-deoxy-5-azacytidine) used in clinic for treating myeloma.
