2',3'-Isopropylideneuridine 2',3'-O-Isopropylideneuridine 362-43-6 Ip-U NSC520038 Uridine 2',3'-acetonide Uridine, 2',3'-O-(1-methylethylidene)- Uridine, 2',3'-O-isopropylidene-