Our group is working on the development of reliable access to biol. relevant, long, and modified RNA sequences. Here, we briefly present the chem. synthesis of such sequences with 2'-O-triisopropylsilyloxymethyl (= 2'-O-tom) protected ribonucleoside phosphoramidites, their template-directed enzymic ligation, and some examples of modified nucleotides, designed to promote structural and biol. studies. [on SciFinder (R)]