The Readout of Base-Pair Information in Adenine-Thymine α-D-Arabinonucleosides

Structurally modified nucleosides are central players in the field of nucleic acid chemistry. Adenine-thymine (AT) pyrimido[4,5-d]pyrimidine furanosyl and pyranosyl arabi-nonucleosides have been synthesized for the first time. Single-crystal X-ray diffraction analysis reveals novel base pairs that, in synergy with the sugar residues, direct the emergence of distinct networks containing channels and cavities. The microscopic noncovalent connections can be translated into macroscopic levels in which robust organogels are formed by the furanoside but not the pyranoside. The influences of the sugars are also displayed by the different shaped superstructures of the free nucleosides in solution. The readout of the information in the base moiety is therefore tailored by the sugar configuration, and the interplays exert subtle effects on the structures, from solid to gel and to the solution state. The potential for forming these appealing base pairs and higher structures enables these intriguing nucleosides to serve as unique building blocks in various areas or to construct innovative nucleic acid structures.