Nucleosides. 125. Synthesis of 5'-deoxy-5'-substituted-1,3-dimethyl-psi-uridines from 3',5'-O-(1,1,3,3-tetraisopropyldisiloxanyl)-1,3-dimethyl-psi-uridine. A novel isomerization reaction.

Treatment of 3'-5'-O-(1,1,3,3-tetraisopropyldisiloxanyl)-1,3-dimethyl-psi-uridine (7) . with one equivalent of base and a slight excess of trifluoromethanesulfonic anhydride afforded 5'-O-trifluoromethanesulfonyl-2',3'-O-(1, 1,3,3-tetraisopropyldisiloxanyl)-1,3-dimethyl-psi-uridine (8). Nucleophilic displacement of the 5'-trifluoromethanesulfonyloxy group by treatment with various alkali metal salts of halide, azide, or acetate followed by deprotection by fluoride ion treatment afforded the corresponding 5'-substituted-1, 3-dimethyl-psi-uridine derivatives (10) in good yields in crystalline form.