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Biomedical subjects

Allen D Hunter

Publications and source records attributed to Allen D Hunter.

7 recordsLinked to original sources
PubMed2006

Synthesis of isostructural cage complexes of copper with cobalt and nickel for deposition of mixed ceramic oxide materials.

Heterobimetallic molecular precursors [Co2(acac)2mu-OH)2Cu4(dmae)4Cl4] (2) and [Ni2(acac)2(mu-OH)2Cu4(dmae)4Cl4] (3) [dmaeH = N,N-dimethylaminoethanol and acac = 2,4-pentanedionate] for the deposition of mixed oxide thin films were prepared by the interaction of tetrameric N,N-dimethylaminoethanolato copper(II) chloride, [Cu(dmae)Cl]4 (1) with M(acac)2.xH2O, [M = Co, Ni] in toluene. Both heterobimetallic cage complexes were characterized by melting point, elemental analysis, FT-IR spectroscopy, mass spectrometry, magnetometery, and single-crystal X-ray diffraction. Complexes 2 and 3 are isostructural and crystallize in the monoclinic space group P21/n. A TGA study shows that both complexes undergo controlled thermal decomposition at 450 degrees C to give mixed metal oxides. Solid-state infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and X-ray powder diffraction (XRD) analysis were performed to analyze the chemical composition and surface morphology of the deposited oxide thin films. The results obtained indicate the formation of impurity-free crystalline mixed oxide films with particle sizes ranging from 0.55 to 2.0 microm.

Journal Article↗
PubMed2005

Semiconductive coordination networks from bismuth(III) bromide and 1,2-bis(methylthio)phenylacetylene-based ligands.

This paper reports our initial efforts to integrate phenylacetylene-based conjugate pi-electron systems into hybrid semiconductive coordination networks, as part of the larger scheme to fully synergize organic functionalities and electronic properties in crystalline solid-state materials. On the basis of a well-established Pd-catalyzed procedure, ligands of 3,3',4,4'-tetrakis(methylthio)tolan (L1) and 1,3,5-tris[[3,4-bis(methylthio)phenyl]ethynyl]benzene (L2) were efficiently synthesized in relatively simple procedures. Molecule L1 reacts with BiBr3 to form a 2D semiconductive coordination network (L1.2BiBr3), which consists of infinite chains of the BiBr3 component cross-linked by L1 through the chelation between the 1,2-bis(methylthio) groups and the Bi(III) centers. Molecule L2 reacts with BiBr3 to from a 1D semiconductive coordination network (L2.2BiBr3), which features discrete tetrameric Bi4Br12 units linked by the thioether groups from L2 [only two of the three 1,2-bis(methylthio) groups from each L2 molecule are bonded to the Bi(III) centers]. Diffuse reflectance spectra of both L1.2BiBr3 and L2.2BiBr3 feature strong optical absorptions at energy levels significantly lower than those of the corresponding molecular solids (L1 and L2) and BiBr3, indicating significant electronic interaction between the organic pi-electron systems and the BiBr3 components. Both L1.2BiBr3 and L2.2BiBr3 readily form in high yields and are stable to air, providing advantages for further studies as potentially applicable semiconductive materials.

Acetylene↗
PubMed2005

Inhibition of carboxylesterases by benzil (diphenylethane-1,2-dione) and heterocyclic analogues is dependent upon the aromaticity of the ring and the flexibility of the dione moiety.

Benzil has been identified as a potent selective inhibitor of carboxylesterases (CEs). Essential components of the molecule required for inhibitory activity include the dione moiety and the benzene rings, and substitution within the rings affords increased selectivity toward CEs from different species. Replacement of the benzene rings with heterocyclic substituents increased the K(i) values for the compounds toward three mammalian CEs when using o-nitrophenyl acetate as a substrate. Logarithmic plots of the K(i) values versus the empirical resonance energy, the heat of union of formation energy, or the aromatic stabilization energy determined from molecular orbital calculations for the ring structures yielded linear relationships that allowed prediction of the efficacy of the diones toward CE inhibition. Using these data, we predicted that 2,2'-naphthil would be an excellent inhibitor of mammalian CEs. This was demonstrated to be correct with a K(i) value of 1 nM being observed for a rabbit liver CE. In addition, molecular simulations of the movement of the ring structures around the dione dihedral indicated that the ability of the compounds to inhibit CEs was due, in part, to rotational constraints enforced by the dione moiety. Overall, these studies identify subdomains within the aromatic ethane-1,2-diones, that are responsible for CE inhibition.

Animals↗
PubMed2005

beta-Acyloxysulfonyl tethers for intramolecular Diels-Alder cycloaddition reactions.

[reaction: see text]. beta-Hydroxy sulfone-based tethers were employed for the first time to achieve thermally mediated intramolecular Diels-Alder cycloaddition. The reactions proceeded with complete regioselectivity and high (10/1) to complete endo/exo-selectivity and resulted in the preferential formation of one of the two possible endo-cycloadducts. The yields and stereoselectivities were proportional to the bulk of the R(1) substituent on the beta-acyloxysulfonyl tether.

Journal Article↗
PubMed2004

p-Nitrophenyl isocyanide.

Achiral p-nitrophenyl isocyanide, C(7)H(4)N(2)O(2), crystallizes in the orthorhombic chiral space group P2(1)2(1)2(1). Attractive intermolecular interactions between the nitro O atoms and both aromatic H and nitro N atoms of neighbouring molecules are observed. The O.N interaction is surprisingly strong [N.O = 2.869 (2) A] compared with other aromatic nitro compounds.

Journal Article↗
PubMed2003

C-H-deprotonation mediated by a remote syn-axial acetoxy group--an unprecedented double bond formation upon cyanation of the dimer from L-fucal.

Replacement of the anomeric acetate by a cyanide group in the dimer of di-O-acetyl-L-fucal by the action of mild Lewis acid [Hg(CN)(2)-HgBr(2)-Me(3)SiCN], resulted not only in the desired transformation but also in the introduction of an additional double bond between C-2A and C-3A. Due to its configuration, the remote C-4A acetoxy group may facilitate the deprotonation by functioning as an internal base. 1H NMR spectroscopy and X-ray crystallography indicate that the conformations of both rings A and B and their relative orientation in the resulting C-linked disaccharidic glycosyl cyanide, 4-O-acetyl-2-C-(4-O-acetyl-2,3-dideoxy-alpha-L-threo-hex-2-enopyranosyl)-2,3-dideoxy-2-eno-alpha-L-fucopyranosyl cyanide, in solution are virtually identical to the crystal structure.

Carbohydrate Conformation↗