Synthesis of some new cytidine derivatives

The bromination of 2',3'-O-isopropylidenecytidine (2) in the presence of 1,4-dioxane and carbon tetrachloride afforded 5-bromocytidine analogue 3 from which some 5-substituted 2',3'-O-isopropylidenecytidine 5-8 were obtained by nucleophilic substitution. While, the treatment of compound 4 with maleic anhydride afforded pyridocytidines 9. On the other hand, the oxidation of the 5'- CH2OH group of compound 2 using DCC afforded 5'-formylcytidine 10, which on condensation with methylamine afforded the Schiff base analogue 11, followed by reduction afforded the 5'- methylaminocytidines 12. Mesylation of 5'-hydroxycytidines (3) followed by the reaction with sodium iodide afforded T-iodocytidine derivatives.