Watson–Crick base pairing in 9-methyladenine and ethylene-9,9′-diadenine structures with close to 70% solvent content

Abstract

In small organic molecules with adenine (A) moieties the nucleobases usually form hydrogen-bonded AAA tapes with trans Watson-Crick/Hoogsteen base pairs. In the crystal structure of ethylene-9,9′diadenine tetra-1,1,1,3,3,3-hexafluoro-2-propanol solvate presented here, the hydroxyl group of the cocrystallized solvent molecules replaces the adenine -NH 2 group as donor for the attractive N7 acceptor, leading instead to a highly solvated structure with less common trans Watson-Crick/Watson-Crick base pairs. The properties of hexafluoro-2-propanol as a hydrogen bond pattern modifier was subsequently demonstrated by using it as a crystallization solvent for 9-methyladenine, yielding a structure with the same hydrogen bonds and solvent content as the diadenine analogue.

9-Ethyladenine: Mechanochemical Synthesis, Characterization, and DFT Calculations of Novel Cocrystals and Salts

“…They are formed by trans Watson−Crick/Hoogsteen base pairs, which compared to trans Watson−Crick/Watson−Crick are somewhat higher in energy but occur more frequently. 53,54 9-Ethyladenine−Glutaric Acid (1:1) Cocrystal (4) and 9-Ethyladenine−Adipic Acid (1:1) Cocrystal (7). Both cocrystals present very similar structures, crystallizing in the monoclinic P2 1 /c space group, where the cell for compound 4 is half the one for compound 7.…”

“…These zigzag tapes have been previously described. They are formed by trans Watson–Crick/Hoogsteen base pairs, which compared to trans Watson–Crick/Watson–Crick are somewhat higher in energy but occur more frequently. , …”

A new guaninate hydrate K+·C5H4N5O−·H2O: crystal structure from 100 to 300 K in a comparison with 2Na+·C5H3N5O2−·7H2O

“…Rare tautomers of nucleobases have been proposed to be involved in the ISSN 2052-5206 processes catalysed by NA enzymes (Š toček & Dračínský, 2020;Singh et al, 2015). Also, various types of noncanonical base pairs in crystal structures of different DNA play an important role in the maintenance of the nucleic acid spatial structure (Kitayner et al, 2010;Giovannangé li et al, 1992;Liu et al, 1993;Povsic & Dervan, 1989;Nikolova et al, 2011;Hoogsteen, 1963;Han, 2019;Park & Han, 2019;Zhou, Sathyamoorthy et al, 2019;Geng et al, 2019;Brovarets et al, 2018;Brovarets & Hovorun, 2018;Abu El Asrar et al, 2017;Bande et al, 2016;Chakraborty & Wales, 2018;Qi et al, 2016;Mondal et al, 2015;Hintze et al, 2017;Copp et al, 2017;Cruz-Ortiz et al, 2017;Ding et al, 2018;Xu et al, 2018).…”