School of Chemistry - Research Publications
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ItemPhotophysics and spectroscopy of 1,2-Benzazulene(Elsevier, 2021-12)The electronic spectroscopy and photophysics of 1,2-benzazulene (BzAz) have been examined in solution and in thin solid films, with the objective of comparing its intramolecular and intermolecular excited state decay processes with those of azulene. Unlike azulene, the S2 – S0 absorption and fluorescence spectra exhibit a clear mirror image relationship dominated by a single strong Franck-Condon active progression. Picosecond transient absorption spectra and non-linear S2 fluorescence upconversion experiments reveal lifetimes that follow a well-established energy gap law correlation, indicative of a dominant S2 – S1 decay route. Mechanistic interpretations, including the possibility of S2 singlet fission in aggregates, are discussed.
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ItemNo Preview AvailableSynthesis of acyloin natural products by Mukaiyama hydration(ROYAL SOC CHEMISTRY, 2022-05-18)The acyloin natural products are a family of bioactive compounds isolated from fungi and myxobacteria. The total synthesis of 7 members of the acyloin family was achieved via a HWE reaction followed by Mukaiyama-Isayama hydration, using novel Co(II) and Co(III) Schiff base SALPN complexes as catalysts for the key enone hydration step. Furthermore, we have shown that a mild acyloin rearrangement is possible under Mukaiyama hydration conditions, which was crucial in the success of this approach.
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ItemNo Preview AvailableIdentification of Anthelmintic Bishomoscalarane Sesterterpenes from the Australian Marine Sponge Phyllospongia bergquistae and Structure Revision of Phyllolactones A-D(AMER CHEMICAL SOC, 2022-07-22)High-throughput screening of the NatureBank marine extract library (7616 samples) identified an extract derived from the Australian marine sponge Phyllospongia bergquistae with activity against Hemonchus contortus (barber's pole worm), an economically important parasitic nematode. Bioassay-guided fractionation of the CH2Cl2/MeOH extract from P. bergquistae led to the purification of four known bishomoscalarane sesterterpenes, phyllolactones A-D (1-4). The absolute configurations of phyllolactones B (2) and C (3) were determined by single-crystal X-ray diffraction analysis; literature and data analyses revealed the need for these chemical structures to be revised. Compounds 2-4 induced a lethal, skinny (Ski) phenotype in larvae of H. contortus at concentrations between 5.3 and 10.1 μM. These data indicate that the bishomoscalarane sesterterpene structure class warrants further investigation for nematocidal or nematostatic activity.
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ItemNo Preview AvailableSynthesis of the Alkylsulfonate Metabolites Cysteinolic Acid, 3-Amino-2-hydroxypropanesulfonate, and 2,3-Dihydroxypropanesulfonate(AMER CHEMICAL SOC, 2022-03-18)Chiral hydroxy- and aminohydroxysulfonic acids are widespread in the marine and terrestrial environment. Here we report simple methods for the synthesis of d- and l-cysteinolic acid (from (Boc-d-Cys-OH)2 and (Boc-l-Cys-OH)2, respectively), R- and S-3-amino-2-hydroxypropanesulfonate (from S- and R-epichlorohydrin, respectively), and R- and S-2,3-dihydroxypropanesulfonate (from S- and R-epichlorohydrin, respectively). d-Cysteinolate bile salts were generated by coupling with cholic and chenodeoxycholic acids. A series of single-crystal 3D X-ray structures confirmed the absolute configurations of the aminosulfonates. By comparison of optical rotation, we assign naturally occurring 3-amino-2-hydroxypropanesulfonate from Gateloupia livida as possessing the R-configuration. This simple synthetic approach will support future studies of the occurrence, chemotaxonomic distribution, and metabolism of these alkylsulfonates.
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ItemNo Preview AvailableSome new antimicrobial/antioxidant nanostructure zinc complexes: Synthesis, crystal structure, Hirshfeld surface analyses and thermal behavior(Elsevier BV, 2022-01-01)In this study, the synthesis and characterization of a new bidentate ligand and some its zinc halide/pseudohalide complexes and nano-structures are described. The crystal structures of the ligand and its zinc nitrate complex as typical examples were determined by single crystal X-ray diffraction. Hirshfeld surface analysis of these structures provided insight into the various intra and inter-molecular interactions and therefore a description of the supramolecular structure for the ligand and its zinc nitrate complex in solid state. Furthermore, the thermal behavior of the complexes was established by TG/DTG/DTA curves analysis. Moreover an antibacterial bioassay of the zinc complexes was been performed in vitro against two gram-positive (Staphylococcus aureus and Bacillus subtilis) and two gram negative (Escherichia coli and Pseudomonas aeruginosa)] bacterial strains. The antifungal activities of the compounds against two fungal strains of Aspergilus niger and Candida albicans were also investigated. The antioxidant capabilities of the Schiff base ligand and its zinc complexes were determined by the in vitro methods of ABTS and DPPH as compared with the standard Trolox. Finally, ZnO nanoparticles were synthesized by direct calcination of the zinc iodide complex at 550 °C under air atmosphere confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) and energy dispersive X-ray analyses (EDX).
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ItemCellular Up-regulation of Nedd4 Family Interacting Protein 1 (Ndfip1) using Low Levels of Bioactive Cobalt Complexes(AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC, 2011-03-11)The delivery of metal ions using cell membrane-permeable metal complexes represents a method for activating cellular pathways. Here, we report the synthesis and characterization of new [Co(III)(salen)(acac)] complexes capable of up-regulating the ubiquitin ligase adaptor protein Ndfip1. Ndfip1 is a neuroprotective protein that is up-regulated in the brain after injury and functions in combination with Nedd4 ligases to ubiquitinate harmful proteins for removal. We previously showed that Ndfip1 can be increased in human neurons using CoCl(2) that is toxic at high concentration. Here we demonstrate a similar effect can be achieved by low concentrations of synthetic Co(III) complexes that are non-toxic and designed to be activated following cellular entry. Activation is achieved by intracellular reduction of Co(III) to Co(II) leading to release of Co(II) ions for Ndfip1 up-regulation. The cellular benefit of Ndfip1 up-regulation by Co(III) complexes includes demonstrable protection against cell death in SH-SY5Y cells during stress. In vivo, focal delivery of Co(III) complexes into the adult mouse brain was observed to up-regulate Ndfip1 in neurons. These results demonstrate that a cellular response pathway can be advantageously manipulated by chemical modification of metal complexes, and represents a significant step of harnessing low concentration metal complexes for therapeutic benefit.