Abstract A 7-deazaadenosine (= tubercidin; c 7 A; 1) building block for solid-phase oligoribonucleotide synthesis was prepared. The amino group of 1 was protected with the (dimethylamino) methylidene residue ([RIGHTWARDS ARROW] 3), and the monomethoxytrityl group was introduced at OH [BOND] C (5′)([RIGHTWARDS ARROW] 4). Protection of OH [BOND] C (2′) was carried out by silylation, showing that use of the (i-Pr ...