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DBU induced formation of 8-bromoguanosine dimer with three hydrogen bonds between the GG- base pairs

Saftić, Dijana; Žinić, Biserka; Višnjevac, Aleksandar (2011) DBU induced formation of 8-bromoguanosine dimer with three hydrogen bonds between the GG- base pairs. Tetrahedron, 68 . pp. 1062-1070. ISSN 0040-4020

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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 nondeprotonated 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 Hbond competitive DMSO solution.

Item Type: Article
Additional Information: This work was supported by the Ministry of Science, Education and Sports of the Republic of Croatia through Grants nos. 098-0982914-2935 and 098-1191344-2943.
Uncontrolled Keywords: 8-Bromoguanosine; Hemideprotonation; DBU; X-ray analysis; Hydrogen bonding
NATURAL SCIENCES > Chemistry > Organic Chemistry
Divisions: Division of Organic Chemistry and Biochemistry
Division of Physical Chemistry
Project titleProject leaderProject codeProject type
Sinteza novih biološki aktivnih derivata nukleobaza i nukleotida-Biserka Žinić098-0982914-2935MZOS
Protein-ligand međudjelovanja na atomnoj razini-Marija Luić098-1191344-2943MZOS
Depositing User: Dijana Pavlović Saftić
Date Deposited: 02 May 2018 13:19
DOI: 10.1016/j.tet.2011.11.086

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