A review, with 17 refs. Methods for the regioselective introduction of alkoxymethyl-groups into the 2'-O-position of 5'-O-dimethoxytritylated, nucleobase-protected ribonucleosides and for the N-alkyloxycarbonylation of adenine and guanine nucleosides were developed. These methods were used for the prepn. of RNA-phosphoramidites carrying novel fluoride- and photolabile sugar and nucleobase protecting groups. [on SciFinder (R)]