Xanthen-9-ylidene and 2,7-dimethylxanthen-9-ylidene protecting groups

The preparation of the 2′,3′-O-[di-(p-anisyl)methylene]uridine 10, 2′,3′-O-(xanthen-9-ylidene)uridine 12a and 2′,3′-O-(2,7-dimethylxanthen-9-ylidene)uridine 12b is described. The rates of hydrolysis of these three compounds are compared with that of 2′,3′-O-isopropylideneuridine 6a in trifluoroacetic acid–water–methanol (1:2:7 v/v) at 30°C.