NEW NUCLEOSIDE PHOSPHORAMIDITES AND COUPLING PROTOCOLS FOR SOLID-PHASE RNA-SYNTHESIS

The 5'-O-(4,4'-dimethoxytrityl)-2'-O-(trialkylsilyl)ribonucleoside 3'-O-(2-cyanoethyl N,N-diethylphosphoramidites) 3, 5, 7, and 9, modified monomers for RNA synthesis, were prepared from 2-cyanoethyl N,N-diethylchloro-phosphoramidite (1). In conjunction with newly developed coupling protocols for automated solid-phase synthesis, they afforded synthetic oligoribonucleotides up to 74 base units in length. The performance of the new compounds was compared to the analogous 5'-O-(4,4'-dimethoxytrityl)-2'-O-(trialkylsilyl)ribonucleoside 3'-O-(2-cyanoethyl N,N-diisopropylphosphoramidites) 4, 6, 8, and 10. Complete removal of benzoyl groups from N2-benzoylguanosine, which was incorporated into some of the synthetic oligoribonucleotides, was demonstrated. Purification procedures by reverse phase HPLC and PAGE methods are also presented.