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  • 1
    Language: English
    In: The journal of physical chemistry. B, 11 March 2010, Vol.114(9), pp.3398-403
    Description: Cavities in proteins can be studied experimentally by using some detectable atoms, such as xenon, or molecules which act as reporter, such as a spy. The interest of sulfur hexafluoride (SF(6)) for probing hydrophobic cavities by solution-state NMR is investigated. The wheat nonspecific lipid transfer protein (LTP) was selected as a model system for this purpose. The binding of SF(6) is straightforwardly detected by the (19)F chemical shift, line width, or longitudinal relaxation time measurements, which can be carried out at low SF(6) concentration without interference from resonances of the protein. Most interestingly, the binding of SF(6) gives rise to selective intermolecular (1)H{(19)F} heteronuclear Overhauser effects (HOEs). Molecular dynamics simulation and NMR spectrum modeling show that the experimental HOESY spectra are consistent with (1)H{(19)F} HOEs arising from SF(6) in the cavity of LTP. SF(6) is found to be an advantageous alternative to hyperpolarized (129)Xe and small organic compounds for probing cavities in proteins by solution-state NMR.
    Keywords: Proteins -- Chemistry ; Sulfur Hexafluoride -- Chemistry
    ISSN: 15206106
    E-ISSN: 1520-5207
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  • 2
    Language: English
    In: Inorganic Chemistry, August 18, 2014, Vol.53(16), p.8717-8722
    Keywords: Aqueous Solution Reactions -- Analysis ; Nuclear Magnetic Resonance -- Analysis ; Rare Earth Metals -- Magnetic Properties
    ISSN: 0020-1669
    Source: Cengage Learning, Inc.
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  • 3
    Language: English
    In: Inorganic chemistry, 18 August 2014, Vol.53(16), pp.8717-22
    Description: The complexes between the polyaminocarboxylate DOTA ligand and the whole series of stable lanthanide(III) metal ions, except Gd(3+), were studied in aqueous solution by (17)O NMR. For all of the paramagnetic systems, the (17)O NMR signals of both the nonchelating (O1) and chelating (O2) oxygen atoms could be detected, and for some of them, the signals of both the SAP and TSAP (TSAP') conformational isomers were also observed. Line width data analysis reveals that signal broadening is not dominated by paramagnetic relaxation enhancement, as it was believed to be. The data indicate that quadrupole relaxation and, for some complexes, chemical exchange between the SAP and TSAP isomers are the major contributions to the (17)O NMR line width at 25 °C. Besides, the Fermi contact and pseudocontact contributions to the observed lanthanide-induced shifts could be extracted. The (17)O hyperfine coupling constants determined for O2 in the SAP and TSAP isomers are similar to each other and to the values reported for several Gd(III) complexes comprising fast-exchanging ligands. Interestingly, the results suggest that (17)O NMR should prove to be useful for the study of highly paramagnetic Gd(III) complexes of nonlabile ligands.
    ISSN: 00201669
    E-ISSN: 1520-510X
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  • 4
    Language: English
    In: Tetrahedron, 22 November 2018, Vol.74(47), pp.6727-6736
    Description: Copper acetylides are readily available and especially convenient reagents for the alkynylation of a broad range of heteronucleophiles. Upon simple activation with molecular oxygen in the presence of suitable ligands and solvents, they readily transfer their alkyne moiety at room temperature, notably yielding a variety of nitrogen- and phosphorus-substituted alkynes. We report in this manuscript an extensive study of the chemoselectivity of this alkynylation based on quantitative C NMR analyses. With suitable ligand/solvent combinations, various phosphorus-based nucleophiles can be alkynylated with excellent levels of selectivity, even in the presence of a large excess of a nitrogen-nucleophile. This chemoselective alkynylation could be further extended to an even more challenging selective alkynylation of a nitrogen-nucleophile over another one, further highlighting the synthetic potential of copper acetylides as alkynylating agents that can selectively “fish” a nucleophile without affecting others.
    Keywords: Alkynylation ; Copper Acetylides ; Chemoselectivity ; Ynamides ; Alkynylphosphonates ; Ynimines ; Quantitative 13c NMR ; Chemistry
    ISSN: 0040-4020
    E-ISSN: 1464-5416
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  • 5
    Language: English
    In: The Journal of organic chemistry, 18 July 2014, Vol.79(14), pp.6563-70
    Description: General and efficient methods for selective modification of macrocyclic oligomers are rare, mostly because restricting a reaction to a defined number of identical functional groups is difficult to achieve. This work describes a unique, general, and rational methodology for the iteroselective functionalization of polyphenolic platforms by N-tert-butylaminocarbonyl (Bac) groups. The methodology consists of reacting the oligomeric platform with t-BuNCO and an inorganic base in an apolar solvent. This very simple one-step procedure has been applied to various calix[4, 5, 6, and 8]arenes, and in all cases, calixarenes with a single leftover phenolic moiety were isolated in high yields (〉90%). Interestingly, this so-called "all-but-one" methodology gives a straightforward access to calixarenes displaying inherent chirality. It is also shown that the Bac group can be used as a protective group. Thus, the all-but-one methodology has been used for the efficient monofunctionalization of a key precursor platform, illustrating its huge potential for the tailored synthesis of sophisticated macrocyclic oligomers.
    Keywords: Chemical Synthesis -- Analysis ; Chirality -- Analysis ; Polyphenols -- Structure ; Polyphenols -- Chemical Properties ; Surface Energy -- Measurement;
    ISSN: 00223263
    E-ISSN: 1520-6904
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  • 6
    Language: English
    In: Tetrahedron Letters, Feb 6, 2013, Vol.54(6), p.545(4)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.tetlet.2012.11.079 Byline: Gilles Berger (a), Michel Gelbcke (a), Emilie Cauet (b), Michel Luhmer (c), Jean Neve (a), Francois Dufrasne (a) Keywords: Chiral diamines; Aziridines;.sup.15N NMR; Platinum-based anticancer compounds Abstract: Author Affiliation: (a) Laboratoire de Chimie Pharmaceutique Organique, Faculte de Pharmacie, Universite Libre de Bruxelles, Bd du Triomphe, 1050 Brussels, Belgium (b) Service de Chimie Quantique et Photophysique, Faculte des Sciences, Universite Libre de Bruxelles, 1050 Brussels, Belgium (c) Laboratoire de Resonance Magnetique Nucleaire Haute Resolution, Faculte des Sciences, Universite Libre de Bruxelles, 1050 Brussels, Belgium Article History: Received 11 October 2012; Revised 15 November 2012; Accepted 20 November 2012
    Keywords: Nuclear Magnetic Resonance ; Diamines ; Cancer Treatment
    ISSN: 0040-4039
    Source: Cengage Learning, Inc.
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  • 7
    Language: English
    In: Inorganic Chemistry, August 6, 2012, Vol.51(15), p.8455-8461
    Keywords: Activation Energy -- Measurement ; Aqueous Solution Reactions -- Analysis ; Chelates -- Chemical Properties ; Ion Exchange -- Analysis ; Rare Earth Metal Compounds -- Chemical Properties
    ISSN: 0020-1669
    Source: Cengage Learning, Inc.
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  • 8
    Language: English
    In: Journal of the American Chemical Society, 25 October 2017, Vol.139(42), pp.14909-14912
    Description: The excited-state quenching of [Ru(TAP)(HAT)] (TAP = 1,4,5,8-tetraazaphenanthrene, HAT= 1,4,5,8,9,12-hexaazatriphenylene) by hydroquinone (HQ), N-acetyl-tyrosine (N-Ac-Tyr) or guanosine-5'-monophosphate (GMP) was investigated at various pH values. The quenching occurs via electron/proton transfer, as evidenced by transient absorption spectroscopy and confirmed by H photochemically induced dynamic nuclear polarization (photo-CIDNP). Reductive quenching also occurs in strongly acidic solution despite a much shorter lifetime of the protonated excited-state complex. Photo-CIDNP revealed a different mechanism at low pH, involving protonation before electron transfer and yielding a distinct protonated monoreduced complex. The experimental photo-CIDNP patterns are consistent with density functional theory calculations. This work highlights the power of H photo-CIDNP for characterizing, at the atomic level, transient species involved in electron-transfer processes.
    Keywords: Azo Compounds – Chemical Properties ; Quinones – Chemical Properties ; Absorption Spectroscopy – Usage ; Nuclear Polarization – Research;
    ISSN: 00027863
    E-ISSN: 1520-5126
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  • 9
    Language: English
    In: Tetrahedron Letters, 08 January 2015, Vol.56(2), pp.485-485
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.tetlet.2014.11.086 Byline: Gilles Berger, Michel Gelbcke, Emilie Cauet, Michel Luhmer, Jean Neve, Francois Dufrasne
    Keywords: Chemistry
    ISSN: 0040-4039
    E-ISSN: 1873-3581
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  • 10
    Language: English
    In: Tetrahedron Letters, 06 February 2013, Vol.54(6), pp.545-548
    Description: A new method for the synthesis of N-labeled chiral β-diamines from a common precursor, either optically pure amino acids or -β-amino alcohols, is reported. The two diastereomeric series of vicinal diamines are produced through the nucleophilic ring opening of activated chiral aziridines. N was introduced by means of [ N]-benzylamine, prepared from NH Cl. The final compounds are highly valuable because [ H– N] NMR is considered a powerful tool for studying the chemical properties of platinum-based complexes.
    Keywords: Chiral Diamines ; Aziridines ; 15n NMR ; Platinum-Based Anticancer Compounds ; Chemistry
    ISSN: 0040-4039
    E-ISSN: 1873-3581
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