Vibrational studies of biomolecules—III. 6-Thioguanine

Singh, Kamalendra; Yadav, R.A.; Yadav, Janardan

doi:10.1016/0584-8539(91)80154-b

Cited by 13 publications

(5 citation statements)

References 5 publications

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“…The DFT calculations revealed that in the gas phase 6-TG exists predominantly as the N1,9(H) amino−thiol form, which is in good agreement with the results of previous experimental and theoretical ab initio and semiempirical studies, − whereas the N1,7(H) amino−thione form is the favored tautomeric form in solids, which is in agreement with results of the X-ray and IR and Raman studies. ,, 6-MP differing only in the presence of −NH 2 group, exists in the gas phase predominantly as the N9(H) amino−thiol form, whereas the N1,9(H) amino−thione form is the favored tautomeric form in anhydrous solids…”

Section: Resultssupporting

confidence: 89%

“…The DFT calculations revealed that in the gas phase 6-TG exists predominantly as the N1,9(H) amino-thiol form, which is in good agreement with the results of previous experimental and theoretical ab initio and semiempirical studies, 28-30 whereas the N1,7(H) amino-thione form is the favored tautomeric form in solids, which is in agreement with results of the X-ray and IR and Raman studies. 13,31,32 6-MP differing only in the presence of -NH 2 group, exists in the gas phase predominantly as the N9(H) amino-thiol form, whereas the N1,9(H) amino-thione form is the favored tautomeric form in anhydrous solids. 14 The correlation between the 14 N NQR frequencies obtained in experiment and those calculated by DFT, assuming the monomer of the most stable amino-thione N1,7(H) form of 6-TG, is only fairly good (the correlation coefficient is 0.889 and the standard deviation is 0.494 MHz) with proton optimization in a single molecule but improves significantly under assumption of pentamers, Figure 4a.…”

Section: Resultsmentioning

confidence: 99%

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Hydrogen Bonding and Stacking π−π Interactions in Solid 6-Thioguanine and 6-Mercaptopurine (Antileukemia and Antineoplastic Drugs) Studied by NMR-NQR Double Resonance Spectroscopy and Density Functional Theory

et al. 2009

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A chemotherapeutic drug 6-thioguanine (2-amino-1,7-dihydro-6H-purine-6-thione, 6-TG) has been studied experimentally in the solid state by NMR-NQR double resonance and theoretically by the density functional theory. Fourteen resonance frequencies on (14)N have been detected and assigned to particular nitrogen sites in the 6-TG molecule. A valid assignment of NQR frequencies for 6-mercaptopurine (6-MP) has been proposed. The effects of molecular aggregations, related to intermolecular hydrogen bonding and stacking pi-pi interactions on the NQR parameters have been analyzed within the DFT and AIM (atoms in molecules) formalism for 6-TG and 6-mercaptopurine (6-MP). The so-called global reactivity descriptors have been calculated to compare the properties of molecules of 6-TG and 6-MP, to check the effect of -NH(2) group as well as to identify the differences in crystal packing.

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Section: Resultssupporting

confidence: 89%

Section: Resultsmentioning

confidence: 99%

Hydrogen Bonding and Stacking π−π Interactions in Solid 6-Thioguanine and 6-Mercaptopurine (Antileukemia and Antineoplastic Drugs) Studied by NMR-NQR Double Resonance Spectroscopy and Density Functional Theory

et al. 2009

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“…Tautomerism of SG investigated by IR spectra in an argon matrix shows that it occurs mainly in the SGH form with a pendant SH group, in agreement with ab initio calculations . With regard to the position of the other NH proton, X‐ray analysis and other IR and Raman solid state studies demonstrate that SG exists as the N 7 H amino‐thione tautomer in the crystal structure; this is in sharp contrast with G in the crystal and in solution . Such differences between theoretical predictions of relative stabilities and the structure experimentally observed in the crystal may be a result of the intermolecular interactions, particularly H‐bonding in the crystal which are not considered in the calculations.…”

Section: Methodssupporting

confidence: 64%

Interactions between temozolomide and guanine and its S and Se-substituted analogues

Kasende

Matondo

Muya

et al. 2016

Int. J. Quantum Chem.

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Temozolomide was paired with guanine, 6‐selenoguanine, and 6‐thioguanine, as well as the SH tautomer of the latter. The potential energy surface of each heterodimer was searched for all minima, using Dispersion‐Corrected Density Functional Theory and MP2 methods. Among the dozens of minima, three categories were observed. Stacked geometries place the aromatic systems of the two molecules parallel to one another, while the two systems are roughly perpendicular to one another in a second category. Also found are coplanar structures held together by H‐bonds. Dispersion proves to be a dominating attractive force for the stacked structures, less so for perpendicular, and smallest for the coplanar dimers. Geometries and energetics are relatively insensitive to S and Se substitution, but tautomerization reverses relative stabilities of different geometries.

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“…Uracil derivatives are used in anti-carcinogenic drug synthesis against cancer and anti-HIV viruses. The earlier works of the paper are a continuation of works [1][2][3][4] on substituted biomolecules. These molecules do not occur freely in natural biological metabolism.…”

Section: Introductionmentioning

confidence: 99%

Laser Raman and infra-red spectra of biomolecule: 5-aminouracil

Singh

2008

Pramana - J Phys

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Laser Raman (200-4000 cm −1 ) and IR (200-4000 cm −1 ) spectra of 5-aminouracil were recorded in the region 200-4000 cm −1 . Assuming a planar geometry and Cs point group symmetry, it has been possible to assign all the 36 (25a + 11a ) normal modes of vibration for the first time. The two NH bonds of the NH2 group appear to be equivalent as the NH2 stretching frequencies satisfy the empirical relation proposed for the two equivalent NH bonds of the NH2 group. The two NH2 stretching frequencies are distinctly separated from the CH/NH ring stretching frequencies. A strong and sharp IR band at 3360 cm −1 could be identified as the anti-symmetric NH2 mode whereas the band at 3290 cm −1 with smaller density could be identified as the symmetric NH2 stretching mode. All other bands have also been assigned different fundamentals/overtones/combinations.

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Vibrational studies of biomolecules—III. 6-Thioguanine

Cited by 13 publications

References 5 publications

Hydrogen Bonding and Stacking π−π Interactions in Solid 6-Thioguanine and 6-Mercaptopurine (Antileukemia and Antineoplastic Drugs) Studied by NMR-NQR Double Resonance Spectroscopy and Density Functional Theory

Hydrogen Bonding and Stacking π−π Interactions in Solid 6-Thioguanine and 6-Mercaptopurine (Antileukemia and Antineoplastic Drugs) Studied by NMR-NQR Double Resonance Spectroscopy and Density Functional Theory

Interactions between temozolomide and guanine and its S and Se-substituted analogues

Laser Raman and infra-red spectra of biomolecule: 5-aminouracil

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