Selective deoxygenation and modification at C2' of nucleosides.

Treatment of nucleosides with 1,1,3,3-tetraisopropyl-1,3-dichlorodisiloxane in pyridine gives the 3',5'-O-(1,1,3,3-tetraisopropyldisilox-1,3-diyl) derivatives in high yields. These selectively protected 3',5'-O-TPDS-nucleosides can be functionalized readily at 02'. Deoxygenation of beta-ribonucleosides affords the 2'-deoxy-beta-D-erythro-pentofuranosyl compounds. Analogous treatment of alpha-arabinonucleosides provides a stereoselective route to the 2'-deoxy-alpha-D-erythro-pentofuranosyl products. Sequential oxidation and reduction of 3',5'-O-TPDS-beta-ribonucleosides gives the beta-arabinonucleosides. Triflation followed by nucleophilic displacements converts 3',5'-O-TPDS-ribo and arabinonucleosides to their corresponding 2'-deoxy-2'-substituted arabino and ribo analogues, respectively.