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Bohle DS, Perepichka I. A new synthetic route to 3-oxo-4-amino-1,2,3-oxadiazole from the diazeniumdiolation of benzyl cyanide: stable sydnone iminium N-oxides. J Org Chem 2009; 74:1621-6. [PMID: 19199666 DOI: 10.1021/jo802343k] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Treating benzylcyanide with nitric oxide in basic methanol returns 3-oxo-4-phenyl-5-amino-1,2,3-oxadiazole (a 5-iminium-sydnone N-oxide), 5, in addition to the known 2-(hydroxyimino)-2-phenylacetonitrile, 6, and the bisdiazeniumdiolate imidate salt, 7. Conditions for the separation and purification of the new 1,2,3-oxadiazole 5 are described along with its theory, structure, spectroscopy, and reactivity which demonstrate the predominance of the amino tautomer over the N-hydroxide tautomer. New derivatives of 5 include a Schiff base, from the condensation with salicylaldehyde, 8, and a dimethylamino analogue of 5, from its reaction with methyliodide and NaH. As with other related 3-oxo-1,2,3-oxadiazoles 5 has pronounced acid/base stability. Theoretical calculations demonstrate that the only other prior sydnone N-oxides prepared were misformulated as the N-hydroxide imines and are better described as 3-oxo-5-amino-derivatives of 1,2,3-oxadiazoles.
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Bohle DS, Spina CJ. Cationic and Anionic Surface Binding Sites on Nanocrystalline Zinc Oxide: Surface Influence on Photoluminescence and Photocatalysis. J Am Chem Soc 2009; 131:4397-404. [PMID: 19265384 DOI: 10.1021/ja808663b] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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78
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Arulsamy N, Bohle DS, Chuang CH, Moore RC. Base controlled polydiazeniumdiolation of 4-heptanone and a new water layer structure. J Org Chem 2008; 73:8077-80. [PMID: 18803420 DOI: 10.1021/jo801583f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In a stoichiometry-controlled reaction, nitric oxide adds to the enolate of 4-heptanone at ca. -23 degrees C to give mono-, bis-, or tris-diazeniumdiolate (-N2O2(-)) products: potassium 4-heptanone-3,3,5-tris(diazeniumdiolate) (1), potassium butanoate 2,2-bis(diazeniumdiolate) (2), and potassium butanoate 2-diazeniumdiolate (3). The diazeniumdiolate products are stable crystalline solids under ambient conditions and as solids exothermally decompose at high temperatures. Single-crystal X-ray data measured for the dihydrate 3 reveal a new layer aggregation, L4(4)8(8), as octameric water aggregates in a stair conformation which interacts minimally with the cation of the salt.
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Bohle DS, Ishihara Y, Perepichka I, Zhang L. Decarboxylation and ring fragmentation reactions of sydnone N-oxides. Tetrahedron Lett 2008. [DOI: 10.1016/j.tetlet.2008.05.025] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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80
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Bohle DS, Smith KN. Kinetics and Mechanism of Nucleophilic Addition to Nitric Oxide: Secondary Amine Diazeniumdiolation. Inorg Chem 2008; 47:3925-7. [DOI: 10.1021/ic800027m] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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81
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Junnila A, Bohle DS, Prichard R, Perepichka I, Spina C. Fluorescent Diethylcarbamazine Analogues: Sites of Accumulation in Brugia malayi. Bioconjug Chem 2007; 18:1818-23. [PMID: 17927226 DOI: 10.1021/bc0701040] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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82
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Sienkiewicz A, Krzystek J, Vileno B, Chatain G, Kosar AJ, Bohle DS, Forró L. Multi-frequency high-field EPR study of iron centers in malarial pigments. J Am Chem Soc 2007; 128:4534-5. [PMID: 16594665 DOI: 10.1021/ja058420h] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The multi-frequency high-field electron paramagnetic resonance (HFEPR) was used to study the magnetic properties of malarial pigment hemozoin and its synthetic analogue, beta-hematin. (FeIII-protoporphyrin-IX)2 dimers containing five-coordinate high-spin FeIII, S = 5/2, are the building blocks of these pigments. The fit of EPR spectra that were acquired in an unprecedented wide range of microwave frequencies of 34 and 94 GHz for hemozoin and 27-500 GHz for beta-hematin yielded a complete set of intrinsic spin Hamiltonian parameters: D = +5.85(1) cm-1, E = 0, g perpendicular = 1.95(1), g parallel = 2.00(1). These results point to the existence of largely axial symmetry of the iron environment in the bulk phase of hemozoin and beta-hematin.
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83
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Fotie J, Bohle DS, Olivier M, Adelaida Gomez M, Nzimiro S. Trypanocidal and antileishmanial dihydrochelerythrine derivatives from Garcinia lucida. JOURNAL OF NATURAL PRODUCTS 2007; 70:1650-3. [PMID: 17880175 DOI: 10.1021/np0702281] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Three benzo[ c]phenanthridine alkaloids have been isolated from the stem bark of Garcinia lucida: dihydrochelerythrine ( 1), 6-acetonyldihydrochelerythrine ( 2), and its new derivative, ( S)1''-(9,10-dihydro-2',3'-dihydroxy-7,8-dimethoxy-10-methyl-1,2-benzophenanthridin-9-yl)propan-2''-one (lucidamine A) ( 3). The new diisoprenylated derivative of lucidamine B ( 4) was obtained by semisynthesis. These dihydrochelerythrine derivatives as well as the crude extract displayed attractive antiprotozoal activity against Trypanosoma brucei brucei and Leishmania donovani, with little toxicity to Vero cells and the host cells. This is the first trypanocidal and antileishmanial bioguided study of G. lucida, and the activity of the crude extract as well as of the dihydrochelerythrine derivatives are reported for the first time.
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84
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Arulsamy N, Bohle DS, Imonigie JA, Moore RC. Group 8 and 10 hyponitrite and dinitrosyl complexes. Polyhedron 2007. [DOI: 10.1016/j.poly.2007.05.009] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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85
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Bohle DS, Spina CJ. The Relationship of Oxygen Binding and Peroxide Sites and the Fluorescent Properties of Zinc Oxide Semiconductor Nanocrystals. J Am Chem Soc 2007; 129:12380-1. [PMID: 17887759 DOI: 10.1021/ja0747223] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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86
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Bohle DS, McQuade LE, Perepichka I, Zhang L. Methylation of Sydnone N-Oxides: Kinetic and Thermodynamic Control in the Alkylation Site of an Electron-Rich Heterocycle. J Org Chem 2007; 72:3625-31. [PMID: 17439281 DOI: 10.1021/jo062235k] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Methylation of the anionic 4-methylcarboxy 1,2,3-oxadiazolate 3-oxide occurs at either the disubstituted ring nitrogen or the oxygen of the N-oxide depending upon the conditions and reagents employed. Alkylation with methyl iodide leads to N-alkylation, while dimethyl sulfate gives O-alkylation and trifluoromethanemethylsulfonate gives a mixture of the two products. The regioselectivity of these methylations has been confirmed by X-ray diffraction of the two products, and these are in turn correlated with their theoretically predicted (B3LYP//6-311++G**) relative energies and vibrational spectra. Theoretically, N-alkylation is expected to give an isomer that is over 10 kcal mol-1 more stable than the O-alkylated product. As a neat melt the kinetic O-alkylation product cleanly isomerizes in 2 h when heated to 140 degrees C to give the thermodynamic N-methylated isomer. Taken together the results illustrate the remarkable new sydnone N-oxide derivatives which are readily accessed in this chemistry, with the N-alkylation of the sydnone N-oxide, corresponding to the first case of such an N-alkylation for a diazenium diolate.
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87
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Arulsamy N, Bohle DS, Perepichka I. Chemistry of the potassium, silver, and tetra(n-butyl)ammonium salts of sydnone N-oxide (Traube's anion). CAN J CHEM 2007. [DOI: 10.1139/v07-001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Traube's dianion, 4-methylcarboxysydnone-3-hydroxylate (2), and its monomethyl ester (1) are readily isolated as their di- and mono-potassium salts from the reaction of nitric oxide with dimethylmalonate and potassium methoxide in methanol. Metathesis reactions of 1 with silver nitrate and tetra(n-butyl)ammonium bromide yield the silver and tetra(n-butyl)ammonium salts of 4-methylcarboxysydnone-3-hydroxylate. In contrast to other known sydnone derivatives, the present sydnones are stable in both acidic and basic solutions. Single crystal X-ray diffraction data obtained for 2 and the silver salt (3) reveal planarity and delocalization of double bonds in the sydnone ring, indicating aromatic behavior. The tetra(n-butyl)ammonium salt (4) is soluble in a range of organic compounds. Cyclic voltammetric data measured for 4 in acetonitrile reveal an irreversible oxidation peak at +1.09 V vs. Fc–Fc+ couple suggesting that the sydnone derivatives can be oxidized with an appropriate oxidizing agent. Differential scanning calorimetry data reveal thermal stability at ambient conditions and exothermic decomposition at high temperatures (>229 °C). The sydnone derivatives are characterized by two strong electronic absorptions in the UV region and rich vibrational (IR and Raman) spectra in the 1800–1500 cm–1 region. Density functional theory (B3LYP/6-311+++G**) is applied to estimate the aromaticity of the sydnone ring and to assign the vibrational spectral data.Key words: sydnone, trans-diazeniumdiolate, N-oxide.
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Bohle DS. The evolution and refinement of a chemical biology training program: A Canadian perspective. ACS Chem Biol 2006; 1:485-6. [PMID: 17168531 DOI: 10.1021/cb600316j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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89
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Abstract
Five new cyclic dialkoxy disulfides have been synthesized and fully characterized. An X-ray structure was obtained for the 2,3-furandimethylene dialkoxy disulfide.
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90
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Li Z, Bohle DS, Li CJ. Cu-catalyzed cross-dehydrogenative coupling: a versatile strategy for C-C bond formations via the oxidative activation of sp(3) C-H bonds. Proc Natl Acad Sci U S A 2006; 103:8928-33. [PMID: 16754869 PMCID: PMC1482542 DOI: 10.1073/pnas.0601687103] [Citation(s) in RCA: 500] [Impact Index Per Article: 27.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2006] [Indexed: 11/18/2022] Open
Abstract
Cu-catalyzed cross-dehydrogenative coupling (CDC) methodologies were developed based on the oxidative activation of sp(3) C-H bonds adjacent to a nitrogen atom. Various sp, sp(2), and sp(3) C-H bonds of pronucleophiles were used in the Cu-catalyzed CDC reactions. Based on these results, the mechanisms of the CDC reactions also are discussed.
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91
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Prémont-Schwarz M, Bohle DS, Gilson DF. High-pressure infrared spectroscopic study of the nitric oxide complex of iron(II)-meso-tetraphenyl porphyrinate. Inorganica Chim Acta 2006. [DOI: 10.1016/j.ica.2005.09.055] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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92
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Scott Bohle D, Breidt VF, Powell AK, Vahrenkamp H. Oxidative Addition von Aldehyden und Schiffbasen an Ru
3
(CO)
12. ACTA ACUST UNITED AC 2006. [DOI: 10.1002/cber.19921250521] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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93
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Fotie J, Bohle DS, Leimanis ML, Georges E, Rukunga G, Nkengfack AE. Lupeol long-chain fatty acid esters with antimalarial activity from Holarrhena floribunda. JOURNAL OF NATURAL PRODUCTS 2006; 69:62-7. [PMID: 16441070 DOI: 10.1021/np050315y] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
An ethnopharmacological investigation was conducted among the Baka pygmies of Dja biosphere reserve (Cameroon) to collect information on the antimalarial plants used in their daily life. Holarrhena floribunda is one of those plants. Extracts of the stem barks of H. floribunda showed remarkable inhibitory activity against drug-resistant strains of Plasmodium falciparum at doses of 1.02-18.53 microg/mL when tested in vitro against two parasite clones designated as Indochina (W-2) and Sierra Leone (D-6). The aqueous extract was the most active against Indochina (W-2), with IC50 values of 1.02 microg/mL, while the ethanolic extract appeared to be the most active against Sierra Leone (D-6), with an IC50 of 4.33 microg/mL. The bioassay-guided fractionation of the neutral fraction of the crude extract led to the isolation of lupeol (1) and its three new long-chain fatty acid ester derivatives, namely, 3-O-(3'-hydroxyeicosanoyl)lupeol (2), 3-O-[(2'-(tetracosyloxy)acetyl]lupeol (3), and 3-O-[(1' '-hydroxyoctadecyloxy)-2'-hydroxypropanoyl]lupeol (4). These new compounds displayed some in vitro inhibition activity against the chloroquine-resistant strain FCR-3 isolated from Gambia and the chloroquine-sensitive standard strain 3D7. The hydroxy group of the fatty acid side chain appears to decrease the observed activity.
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94
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Arulsamy N, Bohle DS. Synthesis of Diazeniumdiolates from the Reactions of Nitric Oxide with Enolates. J Org Chem 2005; 71:572-81. [PMID: 16408967 DOI: 10.1021/jo051998p] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
[reaction: see text] Reactions of nitric oxide with enolates derived from aliphatic methyl ketones containing alpha-methylene or alpha-methine groups and with enolates derived from alpha,alpha'-dimethylene or alpha,alpha'-dimethine ketones yield mono- or bis(diazeniumdiolate) products. Diazeniumdiolation occurs in the following order: alpha-methine > alpha-methylene > alpha-methyl. The amount of the base used alters the extent of diazeniumdiolation and the course of the reaction. Mono- and bis(diazeniumdiolate)-substituted methyl ketones are cleaved in the presence of excess base before and after the subsequent diazeniumdiolation of the alpha-methyl group. Similar to the trihalogenated methyl groups in the base-assisted halogenation reactions of methyl ketones, the bis(diazeniumdiolate)-substituted alpha-methylene and alpha-methyl groups act as leaving groups in the presence of excess base. The reaction of nitric oxide with a (approximately 20:80, cis/trans) mixture of 2,6-cyclohexananone yields the cis and trans isomers of 2,6-dimethylcyclohexanone-2,6-bis(diazeniumdiolate) in 12.9% and 57.6% yield. Single-crystal X-ray diffraction data determined for potassium cis-2,6-dimethylcyclohexanone-2,6-bis(diazeniumdiolate), cis-14b, reveal that the N(2)O(2-) substituent is planar with considerable delocalization of a double bond over the anionic four-atom group. Except for one of the diazeniumdiolate products, namely, potassium propanoate 2,2-bis(diazeniumdiolate), 8b, all are stable in neutral and basic aqueous media. Compound 8b slowly decomposes in neutral aqueous solution releasing nitrous oxide and nitric oxide gases but is stable in basic aqueous media. Differential scanning calorimetry data measured for the diazeniumdiolate products indicate that they decompose exothermally with most of them undergoing explosive decomposition at moderately high temperatures (181-274 degrees C).
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Bohle DS, Ivanic J, Saavedra JE, Smith KN, Wang YN. E/Z conformation and the vibrational spectroscopy of Me2NN(O)=NOMe. J Phys Chem A 2005; 109:11317-21. [PMID: 16331917 DOI: 10.1021/jp054730a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The simple neutral diazenium diolate, O2-methyl-1-(N, N-dimethylamino)diazen-1-ium-1,2-diolate, [Me2NN(O)=NOMe], was experimentally examined by vibrational spectroscopy and the results compared to the theoretically calculated values in an effort to detect both Z and E conformers which result from the stereochemistry of the N=N multiple bond. Room-temperature Raman and infrared spectra were measured and the results compared with the values calculated theoretically with MP2 and density functional techniques (B3LYP). An analysis of the observed frequencies suggests that, down to a detection limit of about 1/1000, only a small quantity of trans (E) diazeniumdiolate, <0.05%, may be present at room temperature.
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96
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Bohle DS, Hung CH, Smith BD. Theoretical, thermal, and coordination chemistry of the amphoteric thiazate (NSO)1 ion. CAN J CHEM 2005. [DOI: 10.1139/v05-191] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The isomers of thiazate (NSO) have a rich chemistry that is examined theoretically and experimentally for their thermal and coordination characteristics. The intramolecular isomerization of NSO to monothionitrite (ONS) is predicted (B3LYP/6-311+G*) to have a substantial barrier, greater than 418 kJ mol1. Thus, thiazates are expected to be relatively thermally stable towards isomerization, and DSC indicates that KNSO undergoes a two stage irreversible thermolytic decomposition only beginning at 132 °C with ΔH = 116.3 kJ mol1. As a ligand, the thiazate can adopt a range of geometries in response to the metal's oxidation state and ligand sphere. For example, in Ru(TTP)(NO)(NSO) the ligand has a markedly bent Ru-N-S geometry, and when contrasted with other structurally characterized thiazate coordination compounds, it is concluded that in addition to σ donation the thiazate binds to metals in an amphoteric manner because of either a forward or reverse OSN → M π donation similar to transition metal nitrosyl, amido, and imido complexes.Key words: thiazate, isomerization, thermolysis, amphoteric ligand, coordination chemistry.
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97
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Oliveira MF, Kycia SW, Gomez A, Kosar AJ, Bohle DS, Hempelmann E, Menezes D, Vannier-Santos MA, Oliveira PL, Ferreira ST. Structural and morphological characterization of hemozoin produced by Schistosoma mansoni and Rhodnius prolixus. FEBS Lett 2005; 579:6010-6. [PMID: 16229843 DOI: 10.1016/j.febslet.2005.09.035] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2005] [Revised: 07/22/2005] [Accepted: 09/05/2005] [Indexed: 11/30/2022]
Abstract
Hemozoin (Hz) is a heme crystal produced upon the digestion of hemoglobin (Hb) by blood-feeding organisms as a main mechanism of heme disposal. The structure of Hz consists of heme dimers bound by reciprocal iron-carboxylate interactions and stabilized by hydrogen bonds. We have recently described heme crystals in the blood fluke, Schistosoma mansoni, and in the kissing bug, Rhodnius prolixus. Here, we characterized the structures and morphologies of the heme crystals from those two organisms and compared them to synthetic beta-hematin (betaH). Synchrotron radiation X-ray powder diffraction showed that all heme crystals share the same unit cell and structure. The heme crystals isolated from S. mansoni and R. prolixus consisted of very regular units assembled in multicrystalline spherical structures exhibiting remarkably distinct surface morphologies compared to betaH. In both organisms, Hz formation occurs inside lipid droplet-like particles or in close association to phospholipid membranes. These results show, for the first time, the structural and morphological characterization of natural Hz samples obtained from these two blood-feeding organisms. Moreover, Hz formation occurring in close association to a hydrophobic environment seems to be a common trend for these organisms and may be crucial to produce very regular shaped phases, allowing the formation of multicrystalline assemblies in the guts of S. mansoni and R. prolixus.
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98
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Saavedra JE, Bohle DS, Smith KN, George C, Deschamps JR, Parrish D, Ivanic J, Wang YN, Citro ML, Keefer LK. Chemistry of the diazeniumdiolates. O- versus N-alkylation of the RNH[N(O)NO](-) ion. J Am Chem Soc 2005; 126:12880-7. [PMID: 15469285 DOI: 10.1021/ja031538i] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Monomethylation of the potentially ambident RNH[N(O)NO](-) ion (R = isopropyl or cyclohexyl) has been shown to occur at the terminal oxygen to yield the novel diazeniumdiolate structural unit, RNHN(O)=NOMe. The NH bond of the product proved acidic, with a pK(a) of 12.3 in aqueous solution. The ultraviolet spectrum showed a large bathochromic shift on ionization (lambda(max) 244 --> 284 nm, epsilon(max) 6.9 --> 9.8 mM(-1) cm(-1)). Deprotonation led to a pH-dependent line broadening in the (1)H NMR spectrum of iPrNHN(O)=NOMe, suggesting a complex fluxionality possibly involving isomerizations around the N-N bonds. Consistent with this interpretation, evidence for extensive delocalization and associated changes in bond order on ionizing RNHN(O)=NOR' were found in density functional theory calculations using Gaussian 03 with B3LYP/6-311++G basis sets. With MeNHN(O)=NOMe as a model, all N-N and N-O bonds lengthened by 0.04-0.07 A as a result of ionization except for the MeN-N linkage, which shortened by 7%. These anions can be N-alkylated to generate R(1)R(2)NN(O)=NOR(3) derivatives that would otherwise be difficult to access synthetically. Additionally, some RNHN(O)=NOR' species may display unique and beneficial pharmacological properties. As one example, an agent with R = isopropyl and R' = beta-D-glucosyl was prepared and shown to generate nitric oxide in the presence of glucosidase at pH 5.
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99
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Wang YN, Bohle DS, Bonifant CL, Chmurny GN, Collins JR, Davies KM, Deschamps J, Flippen-Anderson JL, Keefer LK, Klose JR, Saavedra JE, Waterhouse DJ, Ivanic J. Chemistry of the Diazeniumdiolates: Z ⇌ E Isomerism. J Am Chem Soc 2005; 127:5388-95. [PMID: 15826177 DOI: 10.1021/ja042258l] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Here, we explore the chemistry of the previously undocumented E form of diazeniumdiolates having the structure R(1)R(2)NN(O)=NOR(3). Reported crystallographic studies have uniformly revealed the Z configuration, and our attempts to observe a Z --> E conversion through thermal equilibration or photochemical means have, until now, consistently failed to reveal a significant amount of a second conformer. As a typical example, the NMR spectrum of trimethyl derivative Me(2)NN(O)=NOMe revealed no evidence for a second configuration. Electronic structure calculations attribute this finding to a prohibitively high interconversion barrier of approximately 40 kcal/mol. A similar result was obtained when we considered the case of R(1) = Me = R(3) and R(2) = H at the same levels of theory. However, when MeHNN(O)=NOMe was ionized by dissociating the N-H bond, the barrier was calculated to be lower by approximately 20 kcal/mol, with the E form of the anion being favored over Z. This circumstance suggested that an E isomer might be isolable if a Z anion were formed and given sufficient time to assume the E configuration, then quenched by reaction with an electrophile to trap and neutralize the E form and restore the putatively high interconversion barrier. Consistent with this prediction, basifying iPrHNN(O)=NOCH(2)CH(2)Br rapidly led to a six-membered heterocycle that was crystallographically characterized as containing the -N(O)=NO- functional group in the E configuration. The results suggest an approach for generating pairs of Z and E diazeniumdiolates for systematic comparison of the rates at which the individual isomers release bioactive NO and of other physicochemical determinants of their biomedical utility.
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100
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Diaz Z, Colombo M, Mann KK, Su H, Smith KN, Bohle DS, Schipper HM, Miller WH. Trolox selectively enhances arsenic-mediated oxidative stress and apoptosis in APL and other malignant cell lines. Blood 2005; 105:1237-45. [PMID: 15466933 DOI: 10.1182/blood-2004-05-1772] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractAlthough arsenic trioxide (As2O3) is an effective therapy in acute promyelocytic leukemia (APL), its use in other malignancies is limited by the toxicity of concentrations required to induce apoptosis in non-APL tumor cells. We looked for agents that would synergize with As2O3 to induce apoptosis in malignant cells, but not in normal cells. We found that trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid), a widely known antioxidant, enhances As2O3-mediated apoptosis in APL, myeloma, and breast cancer cells. Treatment with As2O3 and trolox increased intracellular oxidative stress, as evidenced by heme oxygenase-1 (HO-1) protein levels, c-Jun terminal kinase (JNK) activation, and protein and lipid oxidation. The synergistic effects of trolox may be specific to As2O3, as trolox does not add to toxicity induced by other chemotherapeutic drugs. We explored the mechanism of this synergy using electron paramagnetic resonance and observed the formation of trolox radicals when trolox was combined with As2O3, but not with doxorubicin. Importantly, trolox protected nonmalignant cells from As2O3-mediated cytotoxicity. Our data provide the first evidence that trolox may extend the therapeutic spectrum of As2O3. Furthermore, the combination of As2O3 and trolox shows potential specificity for tumor cells, suggesting it may not increase the toxicity associated with As2O3 monotherapy in vivo.
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