Towards the synthesis of 2′-fluorinated pyrimidine-based nucleosides

The progress towards the development of a model system for late-stage fluorination of pyrimidine-based nucleosides is described in this paper. The synthesis involved the introduction of a cyclic protecting group on the 3'- and 5'-hydroxyls of a ribose sugar that locks its conformation and reorients the nucleobase away from blocking an incoming nucleophile. Subsequent use of electron withdrawing protecting groups in the pyrimidine nucleobase modulated the nucleophilicity of C-2 carbonyl group oxygen to prevent its neighboring group participation. Specifically, the use of triazole protecting group in the pyrimidine nucleobase afforded greater versatility by allowing easy access to either the uridine and cytidine analogs depending on the deprotection condition that will be used