DBU induced formation of 8-bromoguanosine dimer with three hydrogen bonds between the GG- base pairs
In: Tetrahedron; (2011-12-06)
Online
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Zugriff:
Upon hemideprotonation of 8-bromoguanosine (8-BrG) at the N1 position, induced by DBU, the adduct [8-BrG][8-BrG]−[DBU–H]+ was formed. Slow evaporation of the 8-BrG methanol solution, in the presence of 0.5 equiv of DBU, yielded two polymorphic structures (1 and 2), where a neutral [8-BrG] (A) and N1 deprotonated, anionic 8-bromoguanosine [8-BrG]− (B) were joined together through three intermolecular hydrogen bonds involving O6, N1 and C2–NH2 sites. Such pairing gave planar GG− dimers as the basic motif of crystal packing in both polymorphs. Both neutral and deprotonated guanosine molecules in the structure of 1 had the ribose units in a syn conformation. In the structure of polymorph 2, the N1 deprotonated guanosine molecule (B) retained the syn glycosidic conformation, while the non-deprotonated guanosine molecule (A) adopted the natural anti conformation of the ribose unit with respect to the nucleobase. Ribose rings revealed different puckering; only those of deprotonated molecules 1B and 2B possessed the usual C2′-endo envelope conformation. Crystal packing in both structures was guided by the highly complex H-bonded pattern. The CSD was searched for related structures, which are discussed with reference to polymorphs 1 and 2. 1H and 13C NMR spectroscopic evidence is provided showing that the three H-bonded adduct [8-BrG][8-BrG]−[DBU–H]+ was also formed in the highly H-bond competitive DMSO solution.
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DBU induced formation of 8-bromoguanosine dimer with three hydrogen bonds between the GG- base pairs
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Autor/in / Beteiligte Person: | Žinić, Biserka ; Saftić, Dijana ; Višnjevac, Aleksandar |
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Quelle: | Tetrahedron; (2011-12-06) |
Veröffentlichung: | Elsevier, 2011 |
Medientyp: | unknown |
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