Conformational restriction of nucleic acid fragments has attracted a lot of attention due to important potential applications in therapeutics and diagnostics. 1,2 Thus, oligonucleotides containing nucleoside monomers with bi- and tricyclic carbohydrate moieties have demonstrated high affinity for complementary nucleic acids. 2–4 Furthermore, conformationally restricted dinucleotides mimicking tertiary structure elements 5–7 eg the anticodon loop in bacterial tRNA 7 have ...