Crystal structures of racemic and homochiral forms of 2-phenylbutyramide () and 3-methyl-3-phenylpyrrolidine-2,5-dione () were investigated in detail by a single crystal X-ray diffraction study. Absolute configurations of the homochiral forms of and , obtained by chromatographic separation of racemates, were determined. It was revealed that racemate and homochiral forms of are very similar in terms of supramolecular organization (H-bonded ribbons) in crystal, infrared (IR) spectral characteristics, and melting points. The presence of two different molecular conformations in homochiral forms of allowed mimicking of crystal packing of the H-bonded ribbons in racemate . Two polymorph modifications (monoclinic and orthorhombic) comprising very similar H-bonded -like chains were found for the homochiral forms of compound that were significantly different in terms of crystal structure, IR spectra, and melting points from the racemic form of . Unlike compound , homochiral forms of compound have a higher density than the corresponding racemate which contradicts the Wallach rule and indicates that, in this case, homochiral forms are more stable than racemate forms.
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http://dx.doi.org/10.1021/cg500284q | DOI Listing |
Astrobiology
January 2025
Dipartimento di Chimica, Università degli Studi di Bari Aldo Moro, Bari, Italy.
Agent-based simulations are set to describe the early biotic selection of oligomers made of monomers of different chirality. The simulations consider the spatial distribution of agents and resources, the balance of biomass of different chirality, and the balance of chemical energy. Following the well-known Wald's hypothesis, a disadvantage is attributed to the change in chirality along the biochemical sequence.
View Article and Find Full Text PDFMass Spectrom (Tokyo)
November 2024
Department of Chemistry, Graduate School of Science, Osaka Metropolitan University, Osaka 558-8585, Japan.
Intermolecular interactions between aromatic amino acids were investigated by ultraviolet photodissociation spectroscopy of hydrogen-bonded protonated clusters of histidine (His) and tryptophan (Trp) enantiomers in the gas phase. Product ion spectra and photodissociation spectra in the wavelength range of the S-S transition of Trp at several temperatures (8-100 K) were obtained using a tandem mass spectrometer equipped with an electrospray ionization source and a cold ion trap. l-Trp detachment forming protonated His was the main pathway.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
November 2024
Department of Chemistry, King's College London, London, SE1 1DB, United Kingdom.
An atomic-level knowledge of the aggregation of archetypal molecular systems is essential to accurately model supramolecular structures and the transition from gas to liquid phase. The structures and forces involved in ethanol aggregation have been investigated using microwave spectroscopy and extensive quantum chemical calculations. Four isomers of the ethanol trimer have been observed and identified based on comparisons between experimental and predicted spectroscopic parameters, and considering collisional relaxation in the supersonic expansion.
View Article and Find Full Text PDFJ Am Chem Soc
November 2024
Department of Chemistry and Chemical Biology, TU Dortmund University, Otto Hahn Str. 6, 44227 Dortmund, Germany.
A family of Pd cages prepared from ligands based on an axially chiral diamino-[1,1'-biazulene] motif (serving as a unique azulene-based surrogate of the ubiquitous BINOL moiety) is reported. We show that preparing a cage starting from the racemate of a shorter bis-monodentate ligand derivative, equipped with pyridine donor groups, leads to integrative ("social") chiral self-sorting, exclusively yielding the product, but only in a selection of solvents. This phenomenon is driven by individual solvent molecules acting as hydrogen bonding tethers between the amino groups of neighboring ligands, thereby locking the final coordination cage in a single isomeric form.
View Article and Find Full Text PDFJ Am Chem Soc
November 2024
WPI Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
Supramolecular polymerization using two-dimensional π-conjugated chiral monomers has been mainly demonstrated because the supramolecular polymerization can be controlled by stereocommunication through π-π stacking between the two-dimensional chiral monomers. We herein report supramolecular copolymerization utilizing three-dimensional pentahedrons with twisted helical chirality through different combinations of helical-chiral acidic and basic pillar[5]arenes as comonomers. In this case, helical-sense matching is key to facilitating the supramolecular copolymerization.
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