Some steric aspects of synthesis of oligoribonucleotides by phosphoroamidite approach on solid support.

The influence of 2'-O-substituents (i.e. methyl, tetrahydropyranyl, t-butyldimethylsilyl) on the chemical synthesis of oligoribonucleotides by the phosphoroamidite approach on solid support is studied and compared with 2'-deoxynucleosides. Strong dependence on the steric hindrance of 2'-substituents both for the 3'-phosphitylation and condensation steps is described.