A synthesis of ψ-cytidine

A practical, seven-step synthesis of 5-(β- d -ribofuranosyl)cytosine ( 1 , ψ-cytidine) was achieved. ψ-Uridine was converted into the 2′,3′-isopropylidene acetal 2 in 85% yield. Tosylation of 2 to the 5′-sulfonate 3 , followed by deacetonation, afforded 5′- O -tosyl-ψ-uridine ( 6 ) in good yield. Treatment of 6 with 1,1′-carbonyldiimidazole afforded the 2′,3′-cyclic carbonate 10 , which was converted into 4,5′-anhydro-2′,3′- O -carbonyl-ψ-uridine ( 11 ) by treatment with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in N , N -dimethylformamide. 4,5′-Anhydro-ψ-uridine ( 7 ) was obtained in quantitative yield from 11 by decarbonylation in aqueous pyridine. Ammonolysis of 7 afforded ψ-cytidine ( 1 ) in good yield.