Methods for the synthesis of nucleotides and nucleoside analogs

Synthetic methods were developed for the synthesis of N-acyl sulfonamide-containing nucleosides. The condensation of sulfonamides with nucleoside-5' -carboxylic acids in the presence of DCC and DMAP gives N-acyl sulfonamide-containing nucleosides in good yield. In the presence of CeCl3, N-benzyl-sulfonamide dianions add diastereoselectively to 3'-keto-nucleosides in high yield. The utility of this reaction has been extended by development of a new protecting group strategy for the sulfonamide functionality. Use of these methods led to the synthesis of nucleoside-3″-sulfonamides. Condensation of nucleoside-3'-sulfonamides with nucleoside-5 '-acids led to the first synthesis of N-acyl sulfonamide-linked dinucleosides. Deoxyribonucleic acid form (Ki = 460 muM) and ribonucleic acid form (Ki = 370 muM) of N-acyl sulfonamide-linked uridylyl adenosine bind tighter to RNase than a phosphate diester d(TpA) (K i = 1.2 mM). Thus, the N-acyl sulfonamide moiety is an effective phosphate analog with the potential to be a useful tool for probing biochemical function.; Progress on methodology toward a modular synthesis of polyphosphorylated nucleosides is described. Experimental evidence for the reduction of pyrimidine nucleobase functionality during the hydrogenolysis of O-benzyl moieties is given. However, reduction of pyrimidine nucleobases does not occur when O-carbobenzyloxy protecting groups are used in lieu of O-benzyl protecting groups and removed by transfer hydrogenolysis. Further, experimental evidence shows that the sluggish deprotection of O-benzyl-protected nucleosides is most likely a result of the nucleobase functioning as an inhibitor of the reaction. Based upon these results, a modular approach has been designed for the synthesis of nucleoside polyphosphates utilizing phosphoramidite chemistry. The synthesis of dibenzyl-nucleoside-phosphites of O-Cbz protected cytidine, thymidine, adenosine and uridine are described. Oxidation of the nucleoside phosphites with molecular bromine leads to a 'universal' phosphoryl electrophile that can accept a variety of nucleophilic phosphate species. Three nucleoside polyphosphates (TDP, ADP and ATP) have been synthesized as proof of principle.