Synthesis of some 4,5-cyclo cytosine nucleosides

Synthesis of some 4,5-cyclo cytosine nucleosides derivatives was performed by the individual reactions of 5-hydroxy, 5-mercapto and 5-amino cytidines with chloroethyl formate, thionyl chloride and thiophosgene, successively. On the other hand, reactions of cytidine with chloroacetone or chloropropionaldehyde produced 3,4-cyclized cytidine products.