An efficient synthesis tetrazole and oxadiazole analogues of novel 2'-deoxy-C-nucleosides and their antitumor activity.

Various tetrazole and oxadiazole C-nucleoside analogues were synthesized starting from pure α- or β-glycosyl-cyanide. The synthesis of glycosyl-cyanide as key precursor was optimized on gram-scale to furnish crystalline starting material for the assembly of C-nucleosides. Oxadizole C-nucleosides were synthesized via two independent routes. First,  the glycosyl-cyanide was converted into an amidoxime which upon ring closure offered an alternative pathway for the assembly of 1,2,4-oxadizoles in an efficient manner. Second, both anomers of glycosyl-cyanide were transformed into tetrazole nucleosides followed by acylative rearrangement to furnish 1,3,4-oxadiazoles in high yields. These protocols offer an easy access to otherwise difficult to synthesize C-nucleosides in good yield and protecting group compatibility. These C-nucleosides were evaluated for their antitumor activity. This work paves a path for facile assembly of library of new chemical entities useful for drug discovery.