Synthesis of Oligonucleotides Containing Site-specific Carcinogen Adducts. Preparation of the 2-Cyanoethyl N,N-Diisopropylphosphoramidite of N-(2'-Deoxyguanosin-8-yl)-2-(acetylamino)fluorene with Fmoc as the Base-Protecting Group

Abstract

A 9-fluorenylmethoxycarbonyl (Fmoc) group was used to protect the exocyclic amine on the modified guanine of N-(2'-deoxyguanosin-8-yl)-2-(acetylamino)fluorene (dG-Cs-AAF) so that oligonucleotides containing a site-specific AAF adduct could be prepared. Reaction of Fmoc-Cl with dG-Cg-AAF gave N-[N-(9-fluorenylmethoxycarbonyl)-2'-deoryguanosin-8-yl]-2-(acetylamino)fluorene (N 2 -Fmoc-dG-C 8 -AAF) and N-[O 6 -(9-fluorenylmethoxycarbonyl)-2'-deoxyguanosin-8-yl]-2-(acetylamino)fluorene (O 6 -Fmoc-dG-Cg-AAF). The 5'-OH of N 2 -Fmoc-dG-C 8 -AAF was protected using 4,4'-dimethoxytrityl chloride to yield 5'-DMT-N 2 -Fmoc-dG-C 8 -AAF which was then reacted with 2-cyanoethyl N,N,N',N'-tetraisopropylphosphorodiamidite to obtain the corresponding phosphoramidite. The phosphoramidites of Fmoc-protected dA, dC and dG were also prepared similary. The stability of Fmoc-protected C 8 -AAF-modified deoxyguanosine was studied under different conditions to establish the utility of the prepared phosphoramidite of the prepared phosphoramidite in solid-phase DNA synthesis