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Updated: Feb 27, 2026
13:02
Production, Crystallization, and Structure Determination of the IKK-binding Domain of NEMO
Published on: December 28, 2019
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Synthesis and crystal structures of two structurally related kryptoracemates
Philipp Kramer1, Michael Bolte2
1Institut für Organische Chemie, J. W. Goethe-Universität Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt/Main, Germany.
Summary
This study investigates kryptoracemates, which are chiral compounds crystallizing in specific space groups. Researchers found both enantiomers present in the asymmetric unit, an uncommon occurrence, with one compound even containing two pairs of enantiomers.
Area of Science:
- Crystallography
- Stereochemistry
- Organic Chemistry
Background:
- Kryptoracemates are racemic compounds that crystallize in Sohnke space groups, lacking common symmetry elements.
- The two independent molecules (enantiomers) in the asymmetric unit cannot be interconverted by crystal symmetry.
- Pseudosymmetry, often a pseudocenter of inversion, can relate enantiomers and is favored for crystal packing.
Purpose of the Study:
- To investigate the crystal structures of two novel kryptoracemates.
- To analyze the presence and arrangement of enantiomers within the asymmetric unit of these kryptoracemates.
- To understand the packing motifs and intermolecular interactions in the crystal structures.
Main Methods:
- Single-crystal X-ray diffraction was used to determine the crystal structures of the two compounds.
- Analysis of space groups and asymmetric units to identify the presence and number of enantiomers.
- Examination of intermolecular interactions, such as hydrogen bonds, within the crystal lattices.
Main Results:
- Crystals of two kryptoracemates, C27H32N2O3 (I) and C25H28N2O3·0.5CH2Cl2 (II), were obtained and their structures solved.
- Both compounds crystallized in Sohnke space groups (P212121 for I, P1 for II), confirming their kryptoracemate nature.
- Uncommon finding: Both enantiomers were present in the asymmetric unit for both compounds. Compound (II) uniquely contained two pairs of enantiomers in its asymmetric unit.
- Intermolecular N-H...O hydrogen bonds were observed, leading to chain and layered structures.
Conclusions:
- The study demonstrates the formation of kryptoracemates with both enantiomers in the asymmetric unit, a rare crystallographic phenomenon.
- The specific crystal packing is influenced by intermolecular hydrogen bonding, leading to distinct structural motifs.
- The findings contribute to the understanding of chiral crystal engineering and the behavior of enantiomers in the solid state.
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