Benzenoid-quinoid tautomerism of azomethines and their structural analogs 56. Azomethine imines,derivatives of salicylic and 2-hydroxynaphthoic aldehydes

A study by IR, electronic and NMR (¹Н and ¹³С) spectroscopy together with X-ray structure analysis and quantum chemical calculations using DFT B3LYP/6-31G(d,p) determined N,N´-cyclic azomethine imines — 1-(2-hydroxyphenylmethylidene)-3-oxo-5-phenylpyrazolydin-1-ium-2-yde (1) и 1-[(2-hydroxynaphthalene-1-yl)methylidene]-3-oxo-5-phenylpyrazolydin-1-ium-2-yde (2) — to exist in solutions as isomers with an intramolecular hydrogen bond between the hydroxyl group and the nitrogen of the pyrazolidone ring. Compound 1 undergoes photoexcitation in the wavelength range 363—320 nm followed by luminescence with an anomalous Stokes shift that is caused by the intramolecular excited state proton transfer mechanism (ESIPT effect).     

Coordination silver polymer with the bridging anion of oxadiazolylacrylic acid: Synthesis,crystal structure,and luminescence properties

Metal complex [AgL] (I) is synthesized by the reaction of AgNO₃ with 3-(5-furyl-1,3,4-oxadiazol-2-yl)acrylic acid (HL, C₉H₆N₂O₄), and its crystal structure is determined (CIF file CCDC no. 1426528). The crystals are monoclinic, space group P2₁/n, a = 4.946(1), b = 20.084(1), c = 9.015(1) Å, β = 92.32(1)°, V = 894.482 ų, ρ_calcd = 2.442 g/cm3, Z = 4. In structure I, pairs of centrosymmetric silver atoms are bound by bidentate-bridging oxygen atoms of two anions L into dimeric blocks. The Ag–Ag distance in the dimer is 2.854(1) Å. The coordination sphere of Ag⁺ contains two oxygen atoms, one silver atom, and one nitrogen atom of the diazolyl fragment of the adjacent anion. The coordination polyhedron of Ag⁺ is a strongly distorted tetrahedron. The molecular packing of crystal I is built of infinite ribbons (AgL)n extended along the direction [001]. The photoluminescence spectrum of compound I contains intense bands about 550 nm corresponding to the green spectral range and less intense bands at 425 and 485 nm.     

Unexpected synthesis of a novel heterocyclic system – (7E,10aE)-2,7-Dimethylfuro[3′,4′:6,7]cycloocta[1,2,3-cd]indole-8,10(2H,6H)-dione

The first derivative of a novel heterocyclic system, (7E,10aE)-2,7-dimethylfuro[3′,4′:6,7]-cycloocta[1,2,3-cd]indole-8,10(2H,6H)-dione, was synthesized based on the Stobbe condensation of 3-chloro-1-methylindole-2-carbaldehyde with diethyl isopropylidenesuccinate. Cyclization of the 2-indolyl-containing diacid, formed by subsequent hydrolysis of the condensation product, did not lead to the expected fulgide, but rather to an unprecedented tetracyclic compound, the structure of which was established by ¹H, ¹³C NMR, IR spectroscopy, mass-spectrometry and single crystal X-ray diffraction.     

Synthesis,characterization and antimicrobial activity of β-aminovinylphosphonium salts derived from aromatic amino acids

This study presents the synthesis, characterization and antimicrobial activity evaluation of β-aminovinyl-phosphonium salts derived from aromatic amino acids. The compounds were prepared in the reaction of (formylmethyl)triphenylphosphonium chloride with various aromatic amino acids and their structures were determined by elemental analysis, IR and NMR spectroscopy. All synthesized compounds were tested for their antibacterial and antifungal activity.     

Nitration of 3-methyl-1<Emphasis Type="Italic">H</Emphasis>-1,2-diazaphenalene and its n-substituted derivatives

1-Substituted 1H-1,2-diazaphenalenes (1H-benzo[de]cinnolines) undergo nitration with nitric acid leading to the formation of di- and trinitro derivatives. The yield of nitration products depends on nitric acid concentration.     

Synergy of peptide and sugar in O-GlcNAcase substrate recognition

Protein O-GlcNAcylation is an essential reversible posttranslational modification in higher eukaryotes. O-GlcNAc addition and removal is catalyzed by O-GlcNAc transferase and O-GlcNAcase, respectively. We report the molecular details of the interaction of a bacterial O-GlcNAcase homolog with three different synthetic glycopeptides derived from characterized O-GlcNAc sites in the human proteome. Strikingly, the peptides bind a conserved O-GlcNAcase substrate binding groove with similar orientation and conformation. In addition to extensive contacts with the sugar, O-GlcNAcase recognizes the peptide backbone through hydrophobic interactions and intramolecular hydrogen bonds, while avoiding interactions with the glycopeptide side chains. These findings elucidate the molecular basis of O-GlcNAcase substrate specificity, explaining how a single enzyme achieves cycling of the complete O-GlcNAc proteome. In addition, this work will aid development of O-GlcNAcase inhibitors that target the peptide binding site.     

Synthesis,Structure, and Spectral Properties of 3,5-Di-tert-butyl-1,2-benzoquinone 3-Hydroxynaphthoyl Hydrazone and Its Complexes with Zn(II), Cd(II), Ni(II), and Co(II)

Russian Journal of General Chemistry - Novel complexes of Zn(II), Cd(II), Ni(II), and Co(II) with 3,5-di-tert-butyl-1,2-benzoquinone 3-hyd-roxynaphthoyl hydrazone have been synthesized....     

Synthesis of macrolide antibiotics. 13. synthesis of certain derivatives of the seco-acid of erythronolide B

Conclusions The synthesis of 9-R-8-hydroxymethyl epi derivative of the seco acid 9-dihydroerythronolide B was carried out and its macrolactonization was studied.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 165–171, January, 1989.     

Effect of the medium on the rate of the degenerate rearrangement of 1,2,3,4,5-pentamethyl-1,3-cyclopentadiene

Conclusions The rate of the 1,2 hydrogen atom shift in the degenerate rearrangement of 1,2,3,4,5-pentamethyl-1,3-cyclopentadiene is only slightly sensitive to variation in the medium.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimlcheskaya, No. 11, pp. 2622–2624, November, 1985.     

Molecular and Crystal Structure of 1,10-Phenanthroline Complex with Nitrosonium Cation

1,10-Nitroso-1,10-phenanthrolinium tetrafluoroborate was subjected to X-ray diffraction analysis. A distinctive feature of the complex is the NO group position between two nitrogen atoms of the phenanthroline skeleton, and so the complex may be regarded as belonging to bidentate type. The distance from the N atom of the group to the nitrogens of the skeleton are approximately equal (2.3 Å) and are considerably shorter that the average intermolecular contacts of the pair of nitrogen atoms N...N (3.0 Å). In the crystal two types of cations are present where the NO groups are oriented at angles 54 and 61° with respect to phenanthroline skeleton, and the length of N-O bonds is close to that in NO⁺ cation. The geometrical parameters of cation obtained by ab initio calculations are close to experimental data.