Methylxanthines. I. Anhydrous Theophylline

Ebisuzaki, Y.; Boyle, P. D.; Smith, Jason A.

doi:10.1107/s0108270197001960

Cited by 107 publications

(115 citation statements)

References 5 publications

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“…The crystal structures of both TPa and TPh have been published, [39][40][41] being evident that the major structural differences between the two polymorphs occur in the hydrogen-bonding network. These structural differences have a direct effect on the vibrational spectra (both in the position and in the relative intensities of the bands) as was reported previously by some of us.…”

Section: Introductionmentioning

confidence: 99%

Probing Pseudopolymorphic Transitions in Pharmaceutical Solids using Raman Spectroscopy: Hydration and Dehydration of Theophylline

Amado

Nolasco

Ribeiro‐Claro

2007

Journal of Pharmaceutical Sciences

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Theophylline is known to undergo vapor phase induced hydrate-anhydrate pseudopolymorphic transformations, which can affect its bioavailability. In this work, the kinetics of the pseudopolymorphic transitions of theophylline crystals in different storage conditions is studied using a vibrational spectroscopic technique. While the hydration is a single-step process with a half-life time of ca. 5 h, the dehydration occurs through a two-step mechanism. In addition, the phase stability of hydrate-anhydrate systems in different relative humidity (RH) conditions was probed. The critical RH for anhydrous teophylline was found to be at ca. 79%, while the critical RH for dehydration is ca. 30%. ß

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Section: Introductionmentioning

confidence: 99%

Probing Pseudopolymorphic Transitions in Pharmaceutical Solids using Raman Spectroscopy: Hydration and Dehydration of Theophylline

Amado

Nolasco

Ribeiro‐Claro

2007

Journal of Pharmaceutical Sciences

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“…[13][14][15][29][30][31][32][33] The application of the previously described methodology requires ab initio calculations on molecular pairs that simulate the molecular associations found in the solid structures. In the case of TP and CA, the crystal structures of both hydrate forms (hereafter named TPh and CAh, respectively) and anhydrate forms (hereafter named TPa and CAa, respectively) must be considered, while for TB only the anhy-drous form (hereafter named TBa) is known to exist.…”

Section: Selection Of Relevant Molecular Pairs From the Crystal Strucmentioning

confidence: 99%

Computationally‐Assisted Approach to the Vibrational Spectra of Molecular Crystals: Study of Hydrogen‐Bonding and Pseudo‐Polymorphism

2006

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Zwei Stufen, ein Katalysator: Ein Vanadium(V)‐Oxo‐Komplex mit einer dreizähnigen Schiff‐Base als weiterem Ligand katalysiert die Titelreaktion, die racemische (Bis)homoallyl‐α‐hydroxyester in trans‐Tetrahydropyrane (THPs) oder cis‐Tetrahydrofurane (THFs) überführt. Auf diese Art lassen sich cyclische Ether effizient asymmetrisch synthetisieren, wie mit der ersten enantioselektiven Synthese von (−)‐Pantofuranoid E belegt wird.

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“…In this example, electron diffraction did again identify the Table 6. Unit cell parameters for the 12 lowest energy computationally derived crystal structures of theophylline and the experimentally derived crystal structure of Form II of theophylline (BAPLOT01) [30] .…”

Section: Crystal Structure Determination With Form II Of Theophyllinementioning

confidence: 99%

Determination of the Crystal Structure of a New Polymorph of Theophylline

Eddleston

Hejczyk

Bithell

et al. 2013

Chemistry A European J

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Electron diffraction offers advantages over X-ray based methods for crystal structure determination as it can be applied to sub-micron sized crystallites, and picogram quantities of material. With molecular organic species, however, crystal structure determination with electron diffraction is hindered by rapid crystal deterioration in the electron beam, limiting the amount of diffraction data that can be collected, and by the effect of dynamical scattering on reflection intensities. While automated electron diffraction tomography provides one possible solution, in this paper we demonstrate an alternative approach where a set of putative crystal structures of the compound of interest is generated using crystal structure prediction methods, and electron diffraction is used to determine which of these putative structures is in agreement with the available electron diffraction data. This approach enables the advantages of electron diffraction to be exploited, while avoiding the need to obtain large amounts of diffraction data or accurate reflection intensities. We demonstrate the methodology using the pharmaceutical compounds paracetamol, scyllo-inositol and theophylline.

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Methylxanthines. I. Anhydrous Theophylline

Cited by 107 publications

References 5 publications

Probing Pseudopolymorphic Transitions in Pharmaceutical Solids using Raman Spectroscopy: Hydration and Dehydration of Theophylline

Probing Pseudopolymorphic Transitions in Pharmaceutical Solids using Raman Spectroscopy: Hydration and Dehydration of Theophylline

Computationally‐Assisted Approach to the Vibrational Spectra of Molecular Crystals: Study of Hydrogen‐Bonding and Pseudo‐Polymorphism

Determination of the Crystal Structure of a New Polymorph of Theophylline

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