We describe the synthesis of novel C4-linked imidazole ribonucleoside phosphoramidite (PA) 1a by which the imidazole moiety is incorporated into VS ribozyme to study its role in general acid and base catalysis. Investigation of protecting groups for the imidazole-N first indicated that pivaloyloxymethyl (POM) was adequate as an N-protecting group for the imidazole nucleoside, which could be readily
The synthesis of C4-linked imidazole C-0- and C-2-2'-deoxyribonucleoside phosphoramidites (dPAs), in which the final phosphitylations are greatly improved by 4,5-dicyanoimidazole-promoted conversion, is described. The respective dPAs are successfully incorporated into the sequence of a 15-nt DNA, and the abilities of one or two imidazoles to pair with different bases are investigated through thermal melting (T-m) experiments on the resulting DNA duplexes. Furthermore, computational models of the imidazole-modified DNAs are found to be in good agreement with the results of the thermal melting experiments.