Uridine selective benzylation

Five-membered stannylene derivatives of furanosides exhibit almost no regio-selectivity. A 1 1 mixture of 2 - and 3 -0-benzyl derivatives has been obtained from uridine [128]. Similarly, methyl 5-0-benzoyl-P-D-ribofuranoside gave a 2 3 mixture of 2-benzyl and 3-benzyl ethers in 70 % yield [147], a slightly better result (ratio of 1 3) was obtained-for the parent methyl P-D-ribofuranoside [147a], The reversed ratio (4 1) was found for the a-anomer, methyl 2-0-benzyl-oc-D-ribofuranoside being the major product [147a]. 

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