Acylimidazoles have been alkylated with trialkyloxonium tetrafluoroborates to form acylimidazolium salts. These salts, particularly (benzyloxycarbony1) imidazolium salts, are shown to be effective agents for the direct, mono-N-protection of deoxynucleosides as their acyl derivatives. These acyl nucleosides are also available via thiocarbamate intermediates. Thus 3', 5'-bis (tert-butyldimethylsilyl)-2'-deoxyguanosine (4b), on treatment with phenyl ...
