Synthesis and crystal structures of 3-hydroxy-2,4-dimethyl-2H-thiophen-5-one and 3-hydroxy-4-methyl-2H-thiophen-5-one

The structures of two hydroxy-thiophenone derivatives related to the antibiotic thiolactomycin are presented. These are the racemic 3-hydroxy-2,4-dimethyl-2H-thiophen-5-one, C6H8O2S, and 3-hydroxy-4-methyl-2H-thiophen-5-one, C5H6O2S. The main structural feature of both compounds is C(6) hydrogen-bonded chains formed between the OH and C=O groups. In achiral C5H6O2S, these chains propagate only by translation, corresponding to x + 1, y, z + 1. However, in contrast, for racemic C6H8O2S the hydrogen-bonded chains propagate through a −x + {3\over 2}, y + {1\over 2}, z operation, giving chains lying parallel to the crystallographic b-axis direction that are composed of alternate R and S enantiomers. The crystals of 3-hydroxy-4-methyl-2H-thiophen-5-one were found to be twinned by a 180° rotation about the reciprocal 001 direction. In the final refinement the twin ratio refined to 0.568 (2):0.432 (2).

Crystal structure of tetrakis[μ2-2-(dimethylamino)ethanolato-κ3N,O:O]di-μ3-hydroxido-dithiocyanato-κ2N-dichromium(III)dilead(II) dithiocyanate acetonitrile monosolvate

The tetranuclear complex cation of the title compound, [Cr2Pb2(NCS)2(OH)2(C4H10NO)4](SCN)2·CH3CN, lies on an inversion centre. The main structural feature of the cation is a distorted seco-norcubane Pb2Cr2O6cage with a central four-membered Cr2O2ring. The CrIIIion is coordinated in a distorted octahedron, which involves two N atoms of one bidentate ligand and one thiocyanate anion, two μ2-O atoms of 2-(dimethylamino)ethanolate ligands and two μ3-O atoms of hydroxide ions. The coordination geometry of the PbIIion is a distorted disphenoid, which involves one N atom, two μ2-O atoms and one μ3-O atom. In addition, weak Pb...S interactions involving the coordinating and non-coordinating thiocyanate anions are observed. In the crystal, the complex cations are linked through the thiocyanate anionsviathe Pb...S interactions and O—H...N hydrogen bonds into chains along thecaxis. The chains are further linked togetherviaS...S contacts. The contribution of the disordered solvent acetonitrile molecule was removed with the SQUEEZE [Spek (2015).Acta Cryst.C71, 9–18] procedure inPLATON. The solvent is included in the reported molecular formula, weight and density.

Crystal structure of alluaudite-type Na4Co(MoO4)3

The title compound, tetrasodium cobalt(II) tris[molybdate(IV)], was prepared by solid-state reactions. The structure is isotypic with Na3In2(AsO4)3and Na3In2(PO4)3. The main structural feature is the presence of infinite chains of edge-sharingX2O10(X= Co/Na) dimers, which are linked by MoO4tetrahedra, forming a three-dimensional framework enclosing two types of hexagonal tunnels in which Na+cations reside. In this alluaudite structure, Co and Na atoms are located at the same general site with occupancies of 0.503 (5) and 0.497 (6), respectively. The other three Na and one of the two Mo atoms lie on special positions (site symmetries 2, -1, 2 and 2, respectively). The structure is compared with similar structures and other members of alluaudite family.

A Prophase Study on the Concise Synthesis of Aculeatin A

The 1,7-dioxadispiro [5.1.5.-pentadecane spirocyclic architecture is the main structural feature in the aculeatins which attracted scientists interesting for the remarkably high cytotoxicity, anti-bacterial and anti-protozoal activities. A prophase study on concise synthesis of the core 1,7-dioxadispiro [5.1.5.-pentadecane spirocyclic architecture of aculeatins was accomplished by using Mukaiyama aldol reaction.

A Prophase Study on Applying Conia-Ene Reation in Constructing bicyclo [3, 3, 1] Nonane Ring

The bicyclo [3, 3, 1] nonane ring system is the main structural feature in the lycopodium alkaloids. There are many methods to build the [3, 3, 1] bridged ring system, Herein, we designed to use indium Lewis acid which can activate the triple bond to construct [3, 3, 1] bridged ring system via Conia-ene reaction, and described a prophase study of applying Conia-ene reaction to construct such bicycle [3, 3, 1] nonane ring.

MTERF factors: a multifunction protein family

The MTERF family is a large protein family, identified in metazoans and plants, which consists of four subfamilies, MTERF1, 2, 3 and 4. Mitochondrial localisation was predicted for the vast majority of MTERF family members and demonstrated for the characterised MTERF proteins. The main structural feature of MTERF proteins is the presence of a modular architecture, based on repetitions of a 30-residue module, the mTERF motif, containing leucine zipper-like heptads. The MTERF family includes transcription termination factors: human mTERF, sea urchin mtDBP and Drosophila DmTTF. In addition to terminating transcription, they are involved in transcription initiation and in the control of mtDNA replication. This multiplicity of functions seems to flank differences in the gene organisation of mitochondrial genomes. MTERF2 and MTERF3 play antithetical roles in controlling mitochondrial transcription: that is, mammalian and Drosophila MTERF3 act as negative regulators, whereas mammalian MTERF2 functions as a positive regulator. Both proteins contact mtDNA in the promoter region, perhaps establishing interactions, either mutual or with other factors. Regulation of MTERF gene expression in human and Drosophila depends on nuclear transcription factors NRF-2 and DREF, respectively, and proceeds through pathways which appear to discriminate between factors positively or negatively acting in mitochondrial transcription. In this emerging scenario, it appears that MTERF proteins act to coordinate mitochondrial transcription.

Structure and Properties of Murine and Human Dentin

Mice are commonly considered the model mammal for many biomedical studies. In this work, mouse and human dentin were compared to specify structural and mechanical differences to establish a baseline for comparison of dental tissues between these species. Atomic force microscopy revealed tubules of about 1.0 to 1.6 μm in diameter as the main structural feature in dentin of both species. Nanoindentation yielded the elastic modulus about 15% lower in murine intertubular dentin while the hardness was almost equal. Dynamic stiffness mapping confirmed the lower elastic properties and also revealed that the peritubular region of increased mineralization around tubules is drastically reduced or maybe absent in murine dentin of this age. This study suggests that structural and mechanical differences need to be considered when murine dentin is used as a model system.

A glucan from active dry baker’s yeast (Saccharomyces cerevisiae): A chemical and enzymatic investigation of the structure

The structure of a polysaccharide consisting of D-glucose isolated from the cell-wall of active dry baker?s yeast (Saccharomyces cerevisiae) was investigated by using methylation analysis, periodate oxidation, mass spectrometry, NMR spectroscopy, and enzymic hydrolysis, as a new approach in determination of structures. The main structural feature of the polysaccharide deduced on the basis of the obtained results is a linear chain of (1?3)-linked ?-D-glucopyranoses, a part of which is substituted through the positions O-6. The side units or groups are either a single D-glucopyranose or (1?3)-?-oligoglucosides, linked to the main chaing through (1?6)-glucosidic linkages. The low optical rotation as well as the 13C-NMR and FTIR spectra suggest that the glycosidic linkages are in the ?-D-configuration.

Chemical applications of the Laplacian spectrum. VI On the largest Laplacian eigenvalue of alkanes

The largest Lapacian eigenvalue ?1 of the molecular graph is a quantity important in the theory of the photoelectron spectra of saturated hydrocarbons. It is shown that in the case of alkanes, the presence or absence of quaternary carbon atoms is the main structural feature on which ?1 depends. Within sets of all alkanes with a given number of carbon atoms the species (with and without quaternary carbons atoms) whose ?1-values are minimal and maximal are determined.