Pseudopolymorphs of 2,6-diaminopyrimidin-4-one and 2-amino-6-methylpyrimidin-4-one: one or two tautomers present in the same crystal

Gerhardt, Valeska; Tutughamiarso, Maya; Bolte, Michael

doi:10.1107/s0108270111013072

Cited by 11 publications

(11 citation statements)

References 22 publications

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“…Interestingly enough, the 1,2-I tautomer of the derivatives substituted in position 6 is destabilised by both electron-accepting and electron-donating groups, except alkyl groups. These calculations agree with the previous observation that the 2,3-I tautomer of compound 9 is strongly preferred in cocrystallisation with compounds containing complementary functional groups, whereas both 1,2-I and 2,3-I tautomers of compound 7 are formed in cocrystals with suitable partners [34].…”

Section: Methodssupporting

confidence: 92%

Tautomerism of Guanine Analogues

Štoček

Dračínský

2020

Biomolecules

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Tautomerism of nucleic acid (NA) bases is a crucial factor for the maintenance and translation of genetic information in organisms. Only canonical tautomers of NA bases can form hydrogen-bonded complexes with their natural counterparts. On the other hand, rare tautomers of nucleobases have been proposed to be involved in processes catalysed by NA enzymes. Isocytosine, which can be considered as a structural fragment of guanine, is known to have two stable tautomers both in solution and solid states. The tautomer equilibrium of isocytosine contrasts with the remarkable stability of the canonical tautomer of guanine. This paper investigates the factors contributing to the stability of the canonical tautomer of guanine by a combination of NMR experiments and theoretical calculations. The electronic effects of substituents on the stability of the rare tautomers of isocytosine and guanine derivatives are studied by density functional theory (DFT) calculations. Selected derivatives are studied by variable-temperature NMR spectroscopy. Rare tautomers can be stabilised in solution by intermolecular hydrogen-bonding interactions with suitable partners. These intermolecular interactions give rise to characteristic signals in proton NMR spectra, which make it possible to undoubtedly confirm the presence of a rare tautomer.

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Section: Methodssupporting

confidence: 92%

Tautomerism of Guanine Analogues

Štoček

Dračínský

2020

Biomolecules

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“…In this case, they are present as the keto tautomer 2,6dimethylpyrimidin-4-(1H)-one, as confirmed by the C1-O1 and C7-O2 bond distances whose values, 1.245 (2) and 1.241 (2) Å respectively, are typical of a C=O double bond. This finding is in agreement with what is observed for all other compounds involving the 2-amino-6methylpyrimidin-4-(1H)-one entity described so far[24][25][26].…”

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confidence: 93%

Hirshfeld surface analysis, crystal structure and physicochemical studies of a new Zn(II) complex with the 2,6-dimethylpyrimidin-4-(1H)-one ligand

Klai

Jelsch²,

Lefèbvre

et al. 2020

Solid State Sciences

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A new Zn(II) complex with the monodentate ligand 2,6-dimethylpyrimidin-4-(1H)-one, [ZnCl(C6H8N2O)2H2O]NO3.H2O, has been prepared and characterized by single crystal X-ray diffraction, elemental analysis, CP-MAS NMR and IR spectroscopy. The Zn(II) cation is tetracoordinated, in a distorted tetrahedral fashion, by two nitrogen atoms of two organic ligands, one water oxygen atom and one chlorine atom. In the atomic arrangement, the [ZnCl(C6H8N2O)2H2O] + neighbor complexes are connected to each other via O-H….O, O-H…Cl and N-H…O hydrogen bonds to form a ribbon running along the b-axis direction. The ribbons are interconnected by the nitrate anions via O-H…O and N4-H…O hydrogen bonds to form layers parallel to (102) plane. Intermolecular interactions were investigated by Hirshfeld surfaces. Globally, the structure is maintained primarily by the metal atom coordination as well as strong and weak (O,N,C)-H…O hydrogen bonds and C-H… interactions. Besides a few strong electrostatic interactions (coordination and H-bonds), the nitrate and chloride anions are surrounded by many electropositive CH3 groups. The 13 C and 15 N CP-MAS NMR spectra are discussed and the vibrational absorption bands were identified by infrared spectroscopy. Electronic properties such as HOMO and LUMO energies were derived.

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“…Only the H atoms involved in hydrogen bonding are shown. Symmetry codes: (i) Àx þ 1; y À 1 2 ; Àz þ 3 aminoisocytosine, see below) 6-methylisocytosine can crystallize as the 1H or 3H tautomer, or as a 1:1 mixture of both tautomers (Gerhardt et al, 2011). Therefore, in order to crystallize one tautomeric form selectively, a complementary coformer allowing for AAD/DDA heterodimer formation could be very useful; 5-FC (AAD) and 6-aminoisocytosine (DDA) meet this condition.…”

Section: Influence Of Specific Binding On the Tautomeric Equilibriummentioning

confidence: 99%

Cocrystals of 5-fluorocytosine. II. Coformers with variable hydrogen-bonding sites

Tutughamiarso¹,

Egert²

2012

Acta Crystallogr Sect B

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Two flexible molecules, biuret and 6-acetamidouracil, were cocrystallized with 5-fluorocytosine to study their conformational preferences. In the cocrystal with 5-fluorocytosine (I), biuret exhibits the same conformation as in its hydrate. In contrast, 6-acetamidouracil can adopt two main conformations depending on its crystal environment: in crystal (II) the trans form characterized by an intramolecular hydrogen bond is observed, while in the cocrystal with 5-fluorocytosine (III), the complementary binding induces the cis form. Three cocrystals of 6-methylisocytosine demonstrate that complementary binding enables the crystallization of a specific tautomer. In the cocrystals with 5-fluorocytosine, (IVa) and (IVb), only the 3H tautomer of 6-methylisocytosine is present, whereas in the cocrystal with 6-aminoisocytosine, (V), the 1H tautomeric form is adopted. The complexes observed in the cocrystals are stabilized by three hydrogen bonds similar to those constituting the Watson-Crick C·G base pair.

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Pseudopolymorphs of 2,6-diaminopyrimidin-4-one and 2-amino-6-methylpyrimidin-4-one: one or two tautomers present in the same crystal

Cited by 11 publications

References 22 publications

Tautomerism of Guanine Analogues

Tautomerism of Guanine Analogues

Hirshfeld surface analysis, crystal structure and physicochemical studies of a new Zn(II) complex with the 2,6-dimethylpyrimidin-4-(1H)-one ligand

Cocrystals of 5-fluorocytosine. II. Coformers with variable hydrogen-bonding sites

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