Effect of Crystalline Form on the Air‐Oxidation of Steroidal 11β‐ols to 11‐ones

Brenner, Gerald S.; Roberts, F. E.; Hoinowski, A. M.; Budavari, J.; Powell, B.; Hinkley, D. F.; Schoenewaldt, Erwin F.

doi:10.1002/anie.196909751

Cited by 18 publications

(6 citation statements)

References 3 publications

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“…The desolvation of solvated organic crystals, caffeine, theophylline and cycloserine has been studied by Lin and Byrn (1979). The dehydration of crystalline hydrates of ergosterol, dialuric acid and hydrocortisone have been related to their crystal packings (Callow, 1931;Brener, 1969;Clay, 1982). Ampicillin hydrate polymorphs have been investigated by Shefter (1973).…”

Section: Determination Of Dissolution Ratementioning

confidence: 99%

The kinetics of solvent-mediated phase transformations

1985

Proc. R. Soc. Lond. A

336

210

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A number of mineralogical and synthetic precipitates undergo solid to solid phase changes via a solution phase. A review of the literature reveals a lack of both experimental data and a framework for its interpretation. A model is developed, for the case of a polymorphic phase transformation, which involves the dissolution of the metastable phase and growth of nuclei of the stable phase. The concepts of dissolution and growth time scales have been introduced and it is shown that their sum is the time required for the disappearance of the metastable phase. Mechanistic insight is best obtained by measurement of the supersaturation profile rather than conversion data. It is shown that such profiles are dominated by the plateau supersaturation, which is the point at which dissolution and growth are balanced. Its value is determined by the relative surface areas of the phases and their kinetic constants. The model has been successfully used to simulate available kinetic data for the α → β polymorphic transformation in copper phthalocyanine.

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Section: Determination Of Dissolution Ratementioning

confidence: 99%

The kinetics of solvent-mediated phase transformations

1985

Proc. R. Soc. Lond. A

336

210

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“…In crystals of the drug itself, removal of water from the lattice can lead to three possible scenarios: (1) the lattice structure is unaltered by water removal, (2) the lattice collapses, or (3) the lattice packing is altered upon dehydration 6. When the lattice structure is retained after dehydration (case 1 above), the product phase is often more reactive and less stable due to voids within the lattice 7. Similarly, when dehydration leads to a collapsed lattice (case 2), the noncrystalline product phase is metastable 8.…”

Section: Introductionmentioning

confidence: 99%

Insights into the dehydration behavior of thiamine hydrochloride (Vitamin B1) hydrates: Part I

Chakravarty

Berendt

Munson

et al. 2010

Journal of Pharmaceutical Sciences

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“…Hydrates can be problematic to the pharmaceutical industry, with compounds exposed to multiple sources of water during product development and manufacture. Understanding the polymorph, solvate, and hydrate landscape of the active pharmaceutical ingredient (API) is particularly important, as changes in the crystal structure can affect the physicochemical properties of a material, thus potentially influencing the manufacturability, compaction properties, and chemical stability , of the API or drug product. , The formation of a hydrate, in general, lowers solubility; therefore, the conversion of the anhydrate to the hydrate, in the formulation or GI tract, could affect bioavailability . For nitrofurantoin this behavior has been harnessed to provide an extended-release formulation (MacroBID) for this important antibiotic, reducing the dosing regimen.…”

Section: Introductionmentioning

confidence: 99%

Conformational Change Initiates Dehydration in Fluconazole Monohydrate

Basford

Cameron

Cruz‐Cabeza

2020

Crystal Growth & Design

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Experimental and computational techniques have been used in combination, to monitor the dehydration process of fluconazole monohydrate (MH), this unveiling the dehydration mechanism at the molecular level. Experimentally, dehydration was observed to start at around 55 °C and complete around 100 °C, with metastable Pbca, Z'=1 polymorph (AH-C) as the sole product of dehydration (as determined by in-situ hot stage PXRD). Conformational and structural changes were identified as key in the initiation and progression of the dehydration process. Thermal expansion is most significant along the c-axis, with molecular dynamic (MD) simulations and experimental observations identifying that water migrates through the MH crystal lattice within the plane perpendicular to that direction. Water was found to migrate within the (001) plane along both the a and b-axis directions. The MD simulations revealed that water was not able to migrate within the lattice at room temperature. Migration at 70°C (342K) was plausible, but only after the hydroxyl group undergoes conformational change. The conformational change, around the hydroxyl group, is key to both the weakening of the fluconazole-water hydrogen bonding, found in the MH structure, and the promotion of the fluconazole-fluconazole hydrogen bonding, required for the formation of polymorph AH-C.

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Effect of Crystalline Form on the Air‐Oxidation of Steroidal 11β‐ols to 11‐ones

Cited by 18 publications

References 3 publications

The kinetics of solvent-mediated phase transformations

The kinetics of solvent-mediated phase transformations

Insights into the dehydration behavior of thiamine hydrochloride (Vitamin B1) hydrates: Part I

Conformational Change Initiates Dehydration in Fluconazole Monohydrate

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