Oligoribonucleotide Synthesis. VIII. Insertion of Terminal 5-Phosphate Groupings

General oligoribonucleotide synthesis using phosphotriester protection has been extended to allow insertion of terminal 5′-phosphates. Selective removal of 5′-triphenylmethoxyacetyl groups allow phosphorylation by TPS-activated mono-2,2,2-trichloroethylphosphate on protected oligomers.