1′,5′-Anhydro-L-ribo-hexitol Adenine Nucleic Acids (α-L-HNA-A): Synthesis and Chiral Selection Properties in the Mirror Image World

The synthesis and a preliminary investigation of the base pairing properties of (6′ → 4′)-linked 1′,5′-anhydro-l-ribo-hexitol nucleic acids (α-l-HNA) have herein been reported through the study of a model oligoadenylate system in the mirror image world. Despite its considerable preorganization due to the rigidity of the “all equatorial” pyranyl sugar backbone, α-l-HNA represents a versatile informational biopolymer, in view of its capability to cross-communicate with natural and unnatural complements in both enantiomeric forms. This seems the result of an inherent flexibility of the oligonucleotide system, as witnessed by the singular formation of iso- and heterochiral associations composed of regular, enantiomorphic helical structures. The peculiar properties of α-l-HNA (and most generally of the α-HNA system) provide new elements in our understanding of the structural prerequisites ruling the stereoselectivity of the hybridization processes of nucleic acids.