FMMT-N2-iBu-dG CEP bears a fluorous-tagged monomethoxytrityl (FMMT) group rather than a fluorous-tagged dimethoxytrityl (FDMT) group, and is for applications where a more robust 5-terminal purification tag is needed. FDMT groups such as FDMT-N2-iBu-dG CEP (F160020) can be used as reactant/reagent in synthetic preparation and and solid-phase fluorous affinity purification of oligodeoxyribonucleotides using pH-stable fluorinated adsorbent.