Protecting groups for the synthesis of ribonucleic acids

Methods for the regioselective introduction of alkoxymethyl-groups into the 2'-O-position of 5'-O-dimethoxytritylated, nucleobase-protected ribonucleo sides and for the N-alkyloxycarbonylation of adenine and guanine nucleoside s were developed. These methods were used for the preparation of RNA-phosph oramidites carrying novel fluoride- and photolabile sugar and nucleobase pr otecting groups.