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1

Optimization of Azimuthal Scan Procedure for Absolute Structure Determination

100%

Grochowski J., Serda P.

Acta Physica Polonica A

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1997

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vol. 91

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issue 5

961-968

EN

The paper describes the application of the azimuthal scan technique for absolute structure determination using X-ray anomalous dispersion. A diffraction pattern with rotation around the scattering vector provides information about various anisotropic effects: absorption, extinction and multi-beam interaction. Recording of azimuthal scans for Friedel pairs is proposed as an alternative to single reflection measurement. Several factors affecting the smoothness of the azimuthal scan curves are discussed and a procedure for eliminating various sources of errors, involving a Fourier filtering, is proposed in order to increase feasibility of chiral discrimination.

2

Resonant Scattering of Light Atoms - Measuring Methods and Applications

100%

Grochowski J., Serda P.

Acta Physica Polonica A

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1992

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vol. 82

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issue 1

147-156

EN

The paper describes measuring methods of weak resonant scattering signals occurring in X-ray diffraction pattern of a crystal containing light atoms (C, N, O, F) in its unit cell. Difficulties resulting from the large distance on the energy scale between the K-absorption edges of light atoms and contemporary available energy range of X-ray sources for diffraction experiments may be overcome using mixed synchrotron radiation and sealed tube measurements. Techniques such as high resolution synchrotron radiation diffraction experiment, low resolution azimuthal scan, top reflection azimuthal scan are discussed and their applications are presented. Several enantiomer correctness indicators, evaluating the confidence level of absolute structure determination, are applied for crystals containing oxygen or nitrogen as anomalous scatterers. Resonant scattering of light atoms, which are fundamental constituents of organic molecules and polymers, carries the information about the absolute structure. Growing importance of stereospecific drugs which follows recent recognition of drug-receptor interaction mechanism increases the demand for determination of drug molecule handedness. Investigation of absolute structure for molecules in their original shape (without the introduction of heavy anomalous scatterers) is potentially a vast application field of the described methodology.

3

Structural Characterization of Carane Derivative Stereoisomers - Potent Local Anesthetics

61%

Grochowski J., Serda P., Pasenkiewicz-Gierula M., Czarnecki R., Librowski T., Lochyński S., Frąckowiak B.

Acta Physica Polonica A

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2002

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vol. 101

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issue 5

665-674

EN

The paper reports on structural investigation and phase analysis of a newly synthesized potent local anesthetic with chiral molecular structure. Absolute structure and absolute configuration on four chiral centres was determined using microcrystalline single-crystal diffraction with anomalous scattering of X-ray radiation azimuthal scan technique. Phase analysis for new compound (KP23SS) and its epimer (KP23RS) was carried out using classical and synchrotron radiation powder diffraction. Enantiopurity of the bulk material was verified for both isomers by comparison of experimental and simulated high-resolution powder diffraction diagrams. The presence of two new polymorphic phases of KP23RS was documented. Comparative conformational analysis was carried out using differential Fourier synthesis and least-squares molecule overlap technique. A model of epimeric disorder was discussed for the homochiral phase.

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3 Acta Physica Polonica A

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3 Grochowski J.

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1 Librowski T.

1 Lochyński S.

1 Pasenkiewicz-Gierula M.

Optimization of Azimuthal Scan Procedure for Absolute Structure Determination

Resonant Scattering of Light Atoms - Measuring Methods and Applications

Structural Characterization of Carane Derivative Stereoisomers - Potent Local Anesthetics