New approaches towards automated oligoribonucleotide synthesis.

Several protecting group combinations have been investigated to achieve an automated oligoribonucleotide synthesis on a solid support. The use of 2'-O-tert-butyldimethylsilyl-5'-O-monomethoxytrityl-ribonucleoside -3'-(p-nitrophenylethyl, N,N-diethyl)-phosphoramidites in conjunction with beta-eliminating blocking groups at the aglycone gave satisfactory results. An inverse protecting group strategy based upon analogously substituted 5'-O-2-dansylethoxycarbonyl-2'-O-4- methoxytetrahydropyran-4-yl-phosphoramidites can be regarded as another promising approach.