“…25 Many different types of hexopyranosyl nucleosides have been so far synthesized by the groups of Herdewijn 9 and Eschenmoser. 25 These hexopyranosyl nucleosides have also been incorporated in to oligonucleotides, and their affinity toward complementary RNA or DNA, as well as their biochemical features have been studied: oligonucleotides composed of dideoxyglycopyranosyl-4',6'-nucleoside (homo-DNA, Figure 1) is almost linear, and not able to form duplexes with either RNA or DNA, 25,26 while oligonucleotides with 1',5'-anhydrohexitol nucleoside (HNA, Figure 1), 27,28 cyclohexanyl nucleoside (CNA, Figure 1) 29 or cyclohexenyl nucleoside (CeNA, Figure 1) [30][31][32] modification have improved affinity toward RNA and show improved nuclease resistance compared to the native counterpart. Amongst these, CeNA modified oligonucleotides have attracted more attention because they are able to activate RNase H, resulting in cleavage of the RNA strand in the DNA-RNA heteroduplexes.…”