22,135 results for Journal article

  • (4-(Ferrocene-1-carboxamido)pyridine)(tetraphenylporphyrinato)zinc(II). Toluene sesquisolvate

    Boyd, Peter; Hosseini, A (2006)

    Journal article
    The University of Auckland Library

    The title compound is a five-coordinate square-pyramidal zinc-porphyrin complex, [(C44H28N4)Zn(C10H9N2O)Fe(C5H5)]·1.5C7H8, with a 4-(ferrocene-1-carboxamido)pyridine apical ligand. The complexes assemble in the crystal structure by head-to-tail stacking of the 4-(ferrocene-1-carboxamido)pyridine groups, which interact through - stacking of the pyridine and cyclopentadienyl rings.

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  • Asymmetric Azo-ene Reactions Using the Chiral Azo-enophile Di-(-)-(1R,2S)-2-phenyl-1-cyclohexyl Diazenedicarboxylate

    Brimble, Margaret; Lee, CY (1998)

    Journal article
    The University of Auckland Library

    The preparation of di-(−)-(1R,2S)-2-phenyl-1-cyclohexyl diazenedicarboxylate 4 is described. Reaction of (1R,2S)-2-phenyl-1-cyclohexanol 1 with excess phosgene in the presence of quinoline afforded chloroformate 2 which was treated directly with hydrazine monohydrate (0.5 equiv.) to afford di-(−)-(1R,2S)-2-phenyl-1-cyclohexyl diazanedicarboxylate 3. Oxidization of 3 to the azo-enophile 4 was then readily effected in high yield using N-bromosuccinimide and pyridine. The azo-ene reactions of 4 with the alkenes cyclohexene 5, cyclopentene 6, trans-3-hexene 7 and trans-4-octene 8 were carried out using the Lewis acid tin(IV) chloride. Use of cyclohexene 5 afforded the ene adduct 9 in 80% yield with a diastereomeric excess of >97:3 whilst the use of cyclopentene 6, trans-3-hexene 7 and trans-4-octene 8 afforded the ene adducts 10 (77%), 11 (71%) and 12 (92%) with a diastereomeric excess of 86:14 in each case. Use of the conjugated aromatic acyclic alkene 13 afforded the product of an ionic addition, namely, chloride 14 in 57% yield. Cleavage of the N–N bond of the ene adduct 9 was effected using lithium in liquid ammonia affording the carbamate 16 in moderate yield.

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  • A supramolecular porphyrin-ferrocene-fullerene triad

    Lyons, DM; Mohanraj, J; Accorsi, G; Armaroli, N; Boyd, Peter (2011)

    Journal article
    The University of Auckland Library

    A ferrocene (Fc) functionalized bis-porphyrin molecule has been synthesized as a host for fullerenes. The porphyrin used in these studies was prepared using a mixed boronic acid Suzuki reaction, which gives A(2)BC type porphyrins in high yield. The bis-porphyrin was characterized through H-1 NMR spectroscopy, high-resolution mass spectroscopy and analyzed via molecular modeling studies. Complexation experiments with fullerenes utilizing both UV-visible and fluorescence spectroscopy demonstrated formation of strong complexes for the bis-porphyrin. A short-lived charge transfer luminescent state is detected for the fullerene adducts. Owing to the tight coupling of the fullerene and porphyrin partners, the host-appended Fc moiety does not show a direct role in the pattern of photoinduced processes upon excitation of either chromophores, but causes blue-shift of the NIR CT luminescence compared to previously investigated systems without appended fragments. Instead, the active role of Fc in photoinduced processes is observed for the guest molecules alone, where photoinduced energy transfer from the porphyrin to the ferrocene occurs.

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  • A double Mannich approach to the synthesis of substituted piperidones-application to the synthesis of substituted E-ring analogues of methyllycaconitine

    Chan, YM; Balle, J; Sparrow, JK; Boyd, Peter; Brimble, Margaret; Barker, David (2010-08-28)

    Journal article
    The University of Auckland Library

    The double Mannich reaction of acyclic alpha,gamma-substituted beta-keto esters and bis(aminol) ethers gives substituted 3,5-substituted-4-piperidones with high levels of diastereoselectivity. These piperdiones can be easily transformed into substituted E-ring analogues of the delphinium alkaloid methyllycacotine. (C) 2010 Elsevier Ltd. All rights reserved.

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  • Density Functional Theory Study on the Mechanism of the Reductive Cleavage of CO2 by a Bis-beta-Diketoiminatediiron Dinitrogen Complex

    Ariafard, A; Brookes, NJ; Stranger, R; Boyd, Peter; Yates, BF (2010-09-06)

    Journal article
    The University of Auckland Library

    Density functional theory has been used to analyze the detailed reaction mechanism for the reductive cleavage of CO2 by a dinitrogen bridged bis-beta-diketoiminatediiron complex, (LFe)-Fe-tBu-N-2-FeLtBu (I), recently reported by Holland and co-workers. A number of pathways have been investigated and the most likely mechanism correlates well with experimental evidence. A rationale has been provided for the binding of CO2, the release of CO, and the ready formation of CO32-. Our results show that the insertion of CO2 into the diiron complex is the rate determining step of the reductive cleavage reaction. An intramolecular reduction step from the reduced dinitrogen bridge is proposed which serves to increase the activation of CO2. This is followed by an intersystem crossing from the septet to the nonet state which acts as a driving force for the subsequent release of CO. The overall reductive cleavage reaction is exergonic by 120 kJ/mol, and further reaction of the released CO with the starting diiron complex is also predicted to be strongly exergonic.

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  • Frame-based 3D interactive modeling of heart motion.'

    Young, Alistair; Cowan, Brett (1997)

    Journal article
    The University of Auckland Library

    IEEE Nonrigid and Articulated Motion Workshop: June 16, 1997, San Juan, Puerto Rico. pp 128-135

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  • GPU accelerated non-rigid registration for the evaluation of cardiac function

    Li, Bo; Young, Alistair; Cowan, Brett (2008)

    Journal article
    The University of Auckland Library

    We present a method for the fast and efficient tracking of motion in cardiac magnetic resonance (CMR) cines. A GPU accelerated Levenberg-Marquardt non-linear least squares optimization procedure for finite element non-rigid registration was implemented on an NVIDIA graphics card using the OpenGL environment. Points were tracked from frame to frame using forward and backward incremental registration. The inner (endocardial) and outer (epicardial) boarders of the heart were tracked in six short axis cines with ~25 frames through the cardiac cycle in 36 patients with vascular disease. Contours placed by two independent expert observers using a semi-automatic ventricular analysis program (CIM version 4.6) were used as the gold standard. The method took 0.5 seconds per frame, and the maximum Hausdorff errors were less than 2 mm on average which was of the same order as the expert inter-observer error. In conclusion, GPU accelerated Levenberg-Marquardt non-linear optimization enables fast and accurate tracking of cardiac motion in CMR images.

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  • Impact of coronary revascularization and transmural extent of scar on regional left ventricular remodelling

    Chan, J; Khafagi, F; Young, Alistair; Cowan, Brett; Thompson, C; Marwick, Thomas (2008)

    Journal article
    The University of Auckland Library

    Aims Transmural extent (TME) of myocardial scar, contractile reserve, and perfusion all predict improvement in regional myocardial function after coronary revascularization. We sought their association with regional remodelling after infarction. Methods and results We studied 89 patients (age 62 ± 10 years) with left ventricular (LV) dysfunction, at least 1 month post infarction. Viability was identified by TME < 75% on contrast-enhanced magnetic resonance imaging (ce-MRI), augmentation at low-dose dobutamine echocardiography (DbE), or >60% uptake on delayed redistribution on TI-201 SPECT (single photon emission computed tomography). Coronary revascularization was performed in 36 patients. Regional LV end-diastolic volume (EDV) and end-systolic volume, and ejection fraction were measured with MRI at baseline and after a median follow-up of 18 months. Of 357 segments identified with subendocardial infarction (TME 0–25%) on ce-MRI, 176 were revascularized. Subendocardial scar segments were associated with reverse regional remodeling during follow-up. Revascularization was an independent correlate of change in EDV, but TME and revascularization showed no interaction with respect to their influence on regional volumes. Contractile reserve was present on DbE in 228 segments, of which 129 were TME 0–25%; remodelling was associated with intervention in non-transmural infarcts showing viability by DbE. Viability was identified by TI-201 SPECT in 381 segments (233 with TME 0–25%), but viability by SPECT was not associated with reverse remodelling. No significant reverse remodelling occurred in segments with intermediate scar thickness (TME 26–75%) or transmural scar, independent of revascularization or viability by DbE or TI-SPECT. Conclusion Reverse regional remodelling is associated with subendocardial infarction, especially in the setting of contractile reserve and revascularization.

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  • Characterization of dicarboxylic salts of protonated triethylenetetramine useful for the treatment of copper-related Pathologies

    Soehnel, Kathrin; Boyd, Peter; Sohnel, T; Allen, GR; Phillips, Anthony; Cooper, Garth (2007-09)

    Journal article
    The University of Auckland Library

    X-ray crystal structures of three salts of protonated triethylenetetramine, (H(4)TETA)(4+), with succinate, maleate, and fumarate anions are reported. Structures of the complexes (H-4-triethylenetetramine)(hydrogenmaleate)(4)center dot 2H(2)O [(H(4)TETA)(Hmal)(4)center dot 2H(2)O] (1), (H4-triethylenetetramine)(hydrogenfumarate)(4)center dot 3.3H(2)O [(H(4)TETA)(HfuM)(4)center dot 3.3H(2)O] (2), and (H-4-triethylenetetramine)(succinate)(2) [(H(4)TETA)(suc)(2)] (3) all form assemblies of alternating two-dimensional layers of (H(4)TETA)(4+) and the anionic species via hydrogen-bond networks. Both classical and nonclassical hydrogen bonds between the protonated amine groups, anions, and water molecules were observed. X-ray powder diffraction measurements, differential thermal analysis/thermogravimetry, density vapor sorption, and Karl Fischer titration measurements were performed to obtain confirmatory information about the water content in the structures 1 and 2 and to examine polymorphism within the salts. The nonhydrated salt 3 was determined to be the most favorable salt formulation for use in medicinal applications.

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  • Left ventricular mass and volume: Fast calculation with guide-point modeling on MR images

    Young, Alistair; Cowan, Brett; Thrupp, Steven; Hedley, WJ; DellItalia, LJ (2000)

    Journal article
    The University of Auckland Library

    The authors describe a fast method for calculating left ventricle (LV) mass and volumes from multiplanar magnetic resonance (MR) images. Mathematic models were fitted to a small number of user-selected guide points in 15 healthy volunteers, 13 patien

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  • 2,8,12,18-Tetrabutyl-3,7,13,17-tetramethyl-5,15-bis(3-nitrophenyl)porphyrinogen methanol disolvate

    Boyd, Peter; Hosseini, A; Rickard, CEF (2006-07)

    Journal article
    The University of Auckland Library

    The title compound, C52H66N6O4·2CH3OH, is a 5,15-diaryloctaalkylporphyrinogen. The molecule is centrosymmetric, with the pyrrole rings adopting a 1,2-alternate arrangement. The methanol molecules are included in the tetrapyrrole cavity through hydrogen bonding and O-H interactions. The molecules form chains in the crystal structure via phenyl C-H-pyrrole stacking.

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  • Bis(N,N-diethyl-dithio-carbamato)(1,10-phenanthroline)cobalt(III) tetra-fluorido-borate

    Boyd, Peter; Rickard, CEF (2008)

    Journal article
    The University of Auckland Library

    The cationic complex in the structure of the title compound, [Co(Et2NCS2)(2)(C12H8N2)] BF4, has a Co-III atom with a distorted octahedral coordination formed by four S atoms of two diethyldithiocarbamate and two N atoms of 1,10-phenanthroline ligands. The crystal structure features head-to-tail stacking of the phenanthroline ligands. The tetra-fluoridoborate anions are positioned in the channels between the cation stacks running along the a axis, and form weak C-H center dot center dot center dot F interactions.

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  • (+/-)-N-(3-hydroxy-1,2-diphenylpropyl)-4-methylbenzenesulfonamide

    Tong, Sok; Barker, David; Choi, Ka; Boyd, Peter; Brimble, Margaret (2008)

    Journal article
    The University of Auckland Library

    In the title compound, C22H23NO3S, the relative stereochemistry of the two stereogenic centres is anti with respect to the H atoms. The molecular packing of the crystal shows a doublestrand arrangement, consisting of one strand of (S*,S*)enantiomers and one strand of (R*,R*) enantiomers. Both strands lie parallel to each other along the a axis. Each strand is made up of dimers in which the molecules are connected to each other via an intermolecular O-H...O hydrogen bond between the hydroxyl groups and an O-H..pie interaction with the aromatic ring. These units are then connected to neighbouring dimers via N-H...O hydrogen bonds and C-H...O interactions. Intramolecular C-H...O interactions are also observed.

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  • In-line automated tracking for ventricular function with magnetic resonance imaging

    Li, Bo; Liu, Y; Occleshaw, CJ; Cowan, Brett; Young, Alistair (2010-08)

    Journal article
    The University of Auckland Library

    An efficient nonrigid registration algorithm was implemented on the image reconstruction computer to enable in-line automatic tracking of features in steady-state free precession cine images. Four-dimensional left ventricle function analysis was performed with and without use of the in-line automatic tracking result. The method was tested in 30 patients referred for cardiac magnetic resonance imaging for a variety of clinical assessments. The time required for in-line tracking was 10 +/- 2 s per slice using an image reconstructor with dual Advanced Micro Devices single-core Opteron 248 CPUs (2.2 GHz) and 8GB random access memory. The precision of clinical estimates of left ventricular volumes was significantly improved relative to the ground truth research estimates with automatic tracking versus without (6 ml vs. 9 ml in end-diastolic volume; 5 ml vs. 10 ml in end-systolic volume; both p < 0.05). In-line automatic tracking of image features shows promise for facilitating clinical analysis of ventricular function.

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  • Paul Dunlop: 14 May 1943 - 24 February 2011. Tragic death of a dedicated New Zealand optometrist.

    Jacobs, Robert (2011-05)

    Journal article
    The University of Auckland Library

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  • Fullerene-porphyrin constructs

    Boyd, Peter; Reed, CA (2005)

    Journal article
    The University of Auckland Library

    Porphyrins and fullerenes are spontaneously attracted to each other. This new supramolecular recognition element can be used to construct discrete host−guest complexes, as well as ordered arrays of interleaved porphyrins and fullerenes. The fullerene−porphyrin interaction underlies successful chromatographic separations of fullerenes, and there are promising applications in the areas of porous framework solids and photovoltaic devices.

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  • Regeneration of the heart in diabetes by selective copper chelation

    Cooper, GJS; Phillips, Anthony; Choong, SY; Leonard, BL; Crossman, DJ; Brunton, DH; Saafi, EL; Dissanayake, AM; Cowan, Brett; Young, AA; Occleshaw, CJ; Chan, YK; Leahy, FE; Keogh, GF; Gamble, GD; Allen, GR; Pope, AJ; Boyd, PDW; Poppitt, SD; Borg, TK; Doughty, Robert; Baker, JR (2004-09)

    Journal article
    The University of Auckland Library

    Heart disease is the major cause of death in diabetes, a disorder characterized by chronic hyperglycemia and cardiovascular complications. Although altered systemic regulation of transition metals in diabetes has been the subject of previous investigation, it is not known whether changed transition metal metabolism results in heart disease in common forms of diabetes and whether metal chelation can reverse the condition. We found that administration of the Cu-selective transition metal chelator trientine to rats with streptozotocin-induced diabetes caused increased urinary Cu excretion compared with matched controls. A Cu-II-trientine complex was demonstrated in the urine of treated rats. In diabetic animals with established heart failure, we show here for the first time that 7 weeks of oral trientine therapy significantly alleviated heart failure without lowering blood glucose, substantially improved cardiomyocyte structure, and reversed elevations in left ventricular collagen and beta(1) integrin. Oral trientine treatment also caused elevated Cu excretion in humans with type 2 diabetes, in whom 6 months of treatment caused elevated left ventricular mass to decline significantly toward normal. These data implicate accumulation of elevated loosely bound Cu in the mechanism of cardiac damage in diabetes and support the use of selective Cu chelation in the treatment of this condition.

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  • Magnetic resonance imaging and ventricle mechanics

    Augenstein, Kevin; McVeigh, ER; Young, Alistair (2001)

    Journal article
    The University of Auckland Library

    Methods for cardiac geometry and motion reconstruction from multi-planar tagged magnetic resonance images (MRI) have been developed and refined over the last decade. This paper firstly provides an overview of a finite-element reconstruction method, i

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  • EVIDENCE FOR HIGH OXIDATION-STATE CHARACTER IN TUNGSTEN ALKYNE COMPLEXES

    NIELSON, AJ; Boyd, Peter; Clark, George; HUNT, TA; Metson, James; RICKARD, CEF; SCHWERDTFEGER, P (1992-06-01)

    Journal article
    The University of Auckland Library

    Synthetic, spectroscopic and structural analogies to organoimido complexes and theoretical calculations indicate the alkyne complexes [WCl4(PhC2Ph)]2, [WCl3(PhC2Ph)(P)2] and [WCl2(PhC2Ph)(P)3] (P= phosphine) have properties similar to d0, d1 and d2 tungsten complexes.

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  • A facile enantioselective synthesis of the dimeric pyranonaphthoquinone core of the cardinalins

    Brimble, Margaret; Gibson, JS; Sejberg, JJP; Sperry, Jonathan (2008)

    Journal article
    The University of Auckland Library

    The enantioselective synthesis of a dimeric pyranonaphthoquinone closely related to cardinalin 3 is described. Key steps include the Hauser-Kraus annulation between a cyanophthalide and a chiral enone to create the naphthalene skeleton, a Suzuki-Miyaura homocoupling of an aryl triflate to construct the biaryl bond and a double stereoselective lactol reduction to install the 1,3-cis stereo-chemistry of the pyran rings.

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