2001 Fiscal Year Final Research Report Summary
Studies on generalization of a new enantiomeric resolution phenomenon (Preferential Enrichment)
| Project/Area Number |
10440187
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Organic chemistry
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
TAMURA Rui Kyoto University, Graduate School of Human and Environmental Studies, Professor, 大学院・人間・環境学研究科, 教授 (60207256)
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| Co-Investigator(Kenkyū-buntansha) |
HAYASHI Naoto Kyoto University, Graduate School of Human and Environmental Studies, Assistant Professor, 大学院・人間・環境学研究科, 助手 (90281104)
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| Project Period (FY) |
1998 – 2001
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| Keywords | Enantiomeric Resolution / Preferential Enrichment / Racemic Mixed Crystal / Polymorphic Transition / Phase Transition / Crystal Structure / X-ray Crystallagraphy / Enantiomer |
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| Research Abstract |
In order to elucidate the mechanism of Preferential Enrichment, the following four points must be fully understood; (i) the supramolecular association structure in solution, (ii) the crystal structure of the metastable crystalline phase formed kinetically from the supersaturated solution, (iii) the mechanism of polymorphic transition of the metastable crystalline phase into the stable form in the supersaturated solution. For the understanding of (i), the solubility and supersolubility measurement of the solid material, the number-averaged molecular weight measurement in solution, and the molecular dynamics simulation of the stable supramolecular association structure were carried out. For the isolation of the metastable crystals in (ii), the epitaxial crystallization by using seed crystals, or the selective crystallization of the desired polymorph by inhibition of the nucleation or crystal growth process of an undesired stable polymorph were used. In addition, when the single crystal f
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or X-ray crystallographic analysis was not available, the crystal structure was able to be solved from the powder X-ray diffraction data by the Monte Carlo method and the subsequent Rietveld refinement. For the aim of (iii), the in situ and real time AIR-IR measurement of the supersaturated solution or the DSC measurement of the deposited crystals was effective. It was also shown that the mechanism of polymorphic transition could be rationalized by comparison of the metastable and stable crystal structures. By using these methods, the following four results concerning the mechanism of Preferential Enrichment were obtained.
(1) In a solution of the racemate showing Preferential Enrichment, the homochiral molecular association is preferred to the heterochial one.
(2) The nature of the racemic crystal of the compound showing Preferential Enrichment has been classified as a fairly ordered racemic mixed crystal composed of the two enantiomers.
(3) The mechanism of Preferential Enrichment is closely associated with the polymorphic transition occurring during crystallization from the supersaturated solution.
(4) By comparison of the crystal structures before and after the phase transition, the mechanism of the solid-to-solid type of polymorphic transition can be understood. On the basis of this mechanism, the unique mechanism of Preferential Enrichment has been proposed. Less
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