Synthesis of triazole nucleoside derivatives

5'-O-Mesyl-2',3'-O-isopropylidene ribonucleosides (4 and 12) were converted to their 5'-substituted nucleosides in good yields by reacted with NaN3 or KI. 2',3'-O-Isopropylidene ribonucleosides (3 and 11) were prepared in good yields from ribonucleosides 1 and 2 with a reaction mixture of acetone and triethyl orthoformate instead of using acetone diethyl acetal. Compound 1 or 2 was treated with 2-acetoxyisobutyryl halide (Cl or Br) to give 1-[2-O-acetyl-3-halo-3-deoxy-5-O-(2,5,5-trimethyl-1,3-dioxolan-4-on-2-yl)-beta-D-xylofuranosyl]-1,2,4-triazole-3-carboxamide (19, 22, and 23) in high yields. Instead of using 2-acetoxyisobutyryl bromide, the mixture of 2-acetoxyisobutyryl chloride and NaBr was employed in the synthesis of 22 and 23. Treatment of 19 with an activated Zn/Cu couple and deprotection gave 2',3'-anhydro nucleoside (21), and treatment of 22 and 23 with an activated Zn/Cu couple and a little of HOAc and deprotection gave corresponding 2',3'-unsaturated triazole nucleosides (24 and 25), respectively. The biological activity of the compounds (7-10, 15-18, and 24) was examined in human liver cancer cells (A-549), lung cancer cells (BEL-7402), and Flu-A cells.