Allyl tetrahydropyranyl ether: a versatile alcohol/thiol protecting reagent

Allyl tetrahydropyranyl ether (ATHPE) can be used as a versatile protecting reagent. In combination with NBS/I₂, O-allyl group can easily be replaced by hydroxyls (including tertiary-OH) or thiols, in the molecules comprising other reactive functional groups such as halogen, nitro, acetonide and alkene under mild reaction conditions (near neutral pH and ambient temperature).     

Quantum to classical transition in the ground state of a spin-S quantum antiferromagnet

We study a frustrated spin-S staggered-dimer Heisenberg model on square lattice by using the bond-operator representation for quantum spins, and investigate the emergence of classical magnetic order from the quantum mechanical (staggered-dimer singlet) ground state for increasing S. Using triplon analysis, we find the critical couplings for this quantum phase transition to scale as 1 /S(S + 1). We extend the triplon analysis to include the effect of quintet dimer-states, which proves to be essential for establishing the classical order (Néel or collinear in the present study) for large S, both in the purely Heisenberg case and also in the model with single-ion anisotropy.     

Biorecognizable polymers: Structure-properties relationship

The biocompatibility of polymers depends on their chemical composition, as well as physical and physico-chemical structure. However, biocompatibility is not an intrinsic polymer property since it relates to a particular localization of the polymer in the living organism. Any foreign macromolecule may be recognized by the living organism as “non-self”. The degree of recognition can be altered by modification of the structure of macromolecules or biomaterial surfaces. Modification of biomacromolecules (e.g., enzymes¹) or biomaterial surfaces with hydrophilic polymers, e.g., poly(ethylene oxide²) or other semitelechelic hydrophilic macromolecules³ has been shown to minimize biorecognition. On the other hand, to achieve specific recognition by cell receptors and/or antigens, complementary structures have to be incorporated as a part of the polymer structure^{4, 5}. The biorecognition of fluorescently labeled N-(2-hydroxypropyl)-methacrylamide copolymers containing side-chains terminated in acylated galactosamine by Hep G2 cells on the cellular and subcellular levels can be visualized by confocal fluorescence microscopy. The recognition of modified water soluble macromolecules strongly depends on their solution properties⁶. Incorporation of stimuli sensitive moieties into copolymer side-chains permits to control recognition by external stimuli, e.g., irradiation^{7, 8}, resulting in the change of the copolymer conformation. On the other hand, the biorecognition of unsoluble (crosslinked) copolymers depends mainly on their surface structure. The rationale for the structure modification of synthetic copolymers to regulate biorecognition will be reviewed. The principles will be described for the interaction of synthetic polymers with enzymes⁹, cell surface receptors and/or antigens^{10, 11}, lectins of the gastrointestinal tract^{12, 13}, and immobilized lectins¹⁴.     

Searching Anti-Zika Virus Activity in 1H-1,2,3-Triazole Based Compounds

Zika virus (ZIKV) is a mosquito-borne virus belonging to the Flaviviridae family and is responsible for an exanthematous disease and severe neurological manifestations, such as microcephaly and Guillain-Barré syndrome. ZIKV has a single strand positive-sense RNA genome that is translated into structural and non-structural (NS) proteins. Although it has become endemic in most parts of the tropical world, Zika still does not have a specific treatment. Thus, in this work we evaluate the cytotoxicity and antiviral activities of 14 hybrid compounds formed by 1H-1,2,3-triazole, naphthoquinone and phthalimide groups. Most compounds showed low cytotoxicity to epithelial cells, specially the 3b compound. After screening with all compounds, 4b was the most active against ZIKV in the post-infection test, obtaining a 50% inhibition concentration (IC₅₀) of 146.0 µM and SI of 2.3. There were no significant results for the pre-treatment test. According to the molecular docking compound, 4b was suggested with significant binding affinity for the NS5 RdRp protein target, which was further corroborated by molecular dynamic simulation studies.     

Microgram detection of nitriles using resin beads

Summary Some nitriles (benzonitrile, acetonitrile, propionitrile, butyronitrile, and cyanoacetic acid) can be detected by means of ion exchange resin beads after hydrolysis with dil. H₂SO₄ to produce ammonium ions. The ammonium ions are retained by the resin and then detected by the indophenol blue color using sodium hypochlorite and phenol. The new method is more sensitive and selective than the existing methods.

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Zusammenfassung Einige Nitrile (Benzo-, Aceto-, Propio-, Butyronitril und Cyanessig-säure) lassen sich mit Hilfe von Austauscherharz-Perlen nach Hydrolyse mit verd. Schwefelsäure zur Freisetzung von Ammoniumionen nachweisen. Diese werden an dem Harz festgehalten und dann durch Bildung von Indophenolblau mit Hilfe von Hypochlorit und Phenol nachgewiesen. Diese Methode ist empfindlicher und selektiver als bisher existierende Verfahren.

     

Proton-ligand and metal ligand stability constants ofN-o-chlorophenylbenzohydroxamic acids with manganese(II), nickel(II), copper(II), zinc(II), cadmium(II) and mercury(II)

Summary The thermodynamic proton-ligand and metal ligand stability constants of the newN-o-chlorophenylbenzohydroxamic acids with manganese, nickel, copper, zinc, cadmium and mercury have been determined in 1 : 1 dioxan : water at 25°.The stability of the complexes mostly follow the ligand basicity order and also the metal ion electron affinities as measured by their ionization potential. The stability constants of the metal complexes follow the order: Cu^(II) > Zn^(II) > Ni^(II) > Mn^(II) > Hg^(II) > Cd^(II).     

Effect of stereochemistry on the electrospray ionization tandem mass spectra of transition metal chloride complexes of monosaccharides

The effect of stereochemistry on the complexation of aldohexoses (glucose, mannose, galactose, allose and talose) and ketohexoses (fructose, tagitose and sorbose) with transition metal chlorides (CoCl(2), NiCl(2), MnCl(2) and ZnCl(2)) has been investigated by electrospray ionization tandem mass spectrometry. Electrospray ionization of methanolic solutions of hexoses containing metal chlorides gave abundant ions corresponding to [M + MetCl](+) and [2M + MetCl](+) which on collision-induced dissociation gave characteristic fragment ions. The fragmentation pathways have been confirmed by examining methyl glucoside and several isotopically labeled glucoses. Eliminations of H(2)O and HCl, C-C cleavages and elimination of metalhydroxychloride are the competing fragmentation pathways observed. All these pathways seem to be influenced by the stereochemistry of the molecule. The fragmentation of the dimeric complexes, [2M + MetCl](+), is also controlled by the stereochemistry of the molecule. The abundance of the product ions corresponding to elimination of HCl is found to increase with increasing number of axial hydroxyl groups in aldohexoses. [2M + MetCl](+) dissociates by elimination of HCl followed by C(2)H(4)O(2) in aldohexose complexes and by elimination of HCl followed by C(3)H(6)O(3) in ketohexose complexes.     

Regioselective synthesis of 2-amino-isophthalonitriles through a ring transformation strategy

An expeditious synthesis of several 2-amino-isophthalonitriles and their biaryl compounds is described and illustrated by carbanion-induced ring transformation of functionalized 2H-pyran-2-ones with malononitrile in excellent yields. The strength of the reaction lies in the creation of an aromatic ring at room temperature from six-membered lactones under mild reaction conditions. This approach is an alternative to Diels-Alder reactions of 2H-pyran-2-ones with dienophiles, which require forcing thermal conditions to obtain benzene derivatives.     

A facile approach to chiral 1,4-benzodioxane toward the syntheses of doxazosin,prosympal, piperoxan,and dibozane

The process describes the concise synthesis of (R/S)-enantiomers of doxazosin, an antidepressant drug and α-adrenergic receptor antagonists like prosympal, piperoxan, and dibozane in practical yields from easily available (R)-2,3-O-cyclohexylidene-d-glyceraldehyde and (S)-3-(benzyloxy)propane-1,2-diol.