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    • Several versions

    Unusual Nucleophilic Addition of Grignard Reagents in the Synthesis of 4‑Amino-pyrimidines

    Tinson, Ryan A. J, Hughes, David L, Ward, Leanne, Stephenson, G. Richard
    ACS omega, 31 August 2018, Vol.3(8), pp.8937-8944

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    Spectroscopic, structural and DFT study of the responses of carbonylmetal crown ether complexes to alkali metal cations

    Stephenson, G. Richard
    Anson, Christopher E, Creaser, Colin S, Daul, Claude A
    European Journal of Inorganic Chemistry. - 2011///2086–2097
    2011-04-20
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    Title: Spectroscopic, structural and DFT study of the responses of carbonylmetal crown ether complexes to alkali metal cations
    Author: Stephenson, G. Richard
    Contributor: Anson, Christopher E; Creaser, Colin S; Daul, Claude A
    Date: 2011-04-20
    Description: FTIR spectra of tricarbonyl(η⁶-benzo-15-crown-5)chromium(0) (1) in the presence of lithium, sodium and potassium perchlorate salts in methanol show different responses in the Cr–CO vibrational region of the spectrum. Data from the symmetric (νsym) and antisymmetric (νasym) Cr–CO vibrational stretching modes have been analysed by principal component analysis (PCA) to generate a factor score plot that provides a visual representation of these differential responses. X-ray crystallographic data for the sodium perchlorate complex 1·Na⁺ and dimensions from DFT-derived structures of 1·Li⁺, 1·Na⁺ and 1·K⁺ indicate that binding M⁺ in the crown causes electron density and structural changes in the [O(4)–C(9)–C(4)–O(8)]Cr–C(1)=O(1) sections of 1, which vary depending on the nature of the cation. This suggests a mode of action in which Li⁺ associates with a more compact O(4)–C(9)–C(4)–O(8), while Na⁺ and K⁺ differ crucially in the extent of σ and π contributions to their effect on νsym and νasym. A comparison of the FTIR data from 1, tricarbonyl(η⁶-1-phenyl-1-aza-15-crown-5)chromium(0) (2) and tricarbonyl(η⁶-2-phenyl-15-crown-5)chromium(0) (3) with a wider range of cations (NH₄⁺, Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Mg²⁺, Ba²⁺) and anions (AcO⁻, BPh₄⁻, Br⁻, C1O₄⁻, I⁻, SCN⁻), showed that 1 and 3 both responded significantly to the different metal cations, but 2 did not. The relative cation differentiation of 1, 2 and 3 was measured using the parameter ΔR(cation), and ratios of ΔN(cation) values [calculated from ΔR(cation)] distinguished different effects in the FTIR spectra of 1 and 3 for different pairs of cations.
    Linked entry: European Journal of Inorganic Chemistry. - 2011///2086–2097
    Host document: European Journal of Inorganic Chemistry
    Identifier: 10.1002/ejic.201001274 (DOI)

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    (2E)-N-(2-iodo-4,6-dimethylphenyl)-2-methylbut-2-enamide

    Hughes, David L, Mcdermott, Michael C, Stephenson, G Richard, Walkington, Andrew J
    Acta crystallographica. Section C, Crystal structure communications, January 2008, Vol.64(Pt 1), pp.o7-9 [Peer Reviewed Journal]
    MEDLINE/PubMed (U.S. National Library of Medicine)
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    Title: (2E)-N-(2-iodo-4,6-dimethylphenyl)-2-methylbut-2-enamide
    Author: Hughes, David L; Mcdermott, Michael C; Stephenson, G Richard; Walkington, Andrew J
    Subject: Anilides -- Chemistry ; Hydrocarbons, Iodinated -- Chemistry
    Description: The title compound, C14H18INO, crystallizes as +sc/+sp/+sc 2-iodoanilide molecules (and racemic opposites) and shows significant intermolecular I...O interactions in the solid state, forming dimeric pairs about centres of symmetry. Under asymmetric Heck conditions, the S enantiomer of the dihydroindol-2-one was obtained using (R)-(+)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl [(R)-BINAP], suggesting a mechanism that proceeds by oxidative addition to give the title (P) enantiomer of the compound and pro-S coordination of the Re face of the alkene in a conformation similar to that defined crystallographically, except that rotation about the C-C bond of the butenyl group is required.
    Is part of: Acta crystallographica. Section C, Crystal structure communications, January 2008, Vol.64(Pt 1), pp.o7-9
    Identifier: 1600-5759 (E-ISSN); 18216456 Version (PMID); 10.1107/S0108270107056016 (DOI)

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    Synthesis of Novel Stilbene-Coumarin Derivatives and Antifungal Screening of -Specialized Metabolites Against

    Fotso, Ghislain Wabo, Ngameni, Bathelemy, Storr, Thomas E, Ngadjui, Bonaventure Tchaleu, Mafu, Sibongile, Stephenson, G Richard
    Antibiotics (Basel, Switzerland), 25 August 2020, Vol.9(9) [Peer Reviewed Journal]

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    Trypanocidal and leishmanicidal activity of six limonoids

    Steverding, Dietmar, Sidjui, Lazare S, Ferreira, Éden Ramalho, Ngameni, Bathelemy, Folefoc, Gabriel N, Mahiou-Leddet, Valérie, Ollivier, Evelyne, Stephenson, G Richard, Storr, Thomas E, Tyler, Kevin M
    Journal of natural medicines, June 2020, Vol.74(3), pp.606-611 [Peer Reviewed Journal]
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    Title: Trypanocidal and leishmanicidal activity of six limonoids
    Author: Steverding, Dietmar; Sidjui, Lazare S; Ferreira, Éden Ramalho; Ngameni, Bathelemy; Folefoc, Gabriel N; Mahiou-Leddet, Valérie; Ollivier, Evelyne; Stephenson, G Richard; Storr, Thomas E; Tyler, Kevin M
    Subject: African Trypanosomiasis ; Leishmania Major ; Leishmaniasis ; Limonoids ; Trypanosoma Brucei ; Leishmania Major -- Drug Effects ; Leishmaniasis -- Drug Therapy ; Limonins -- Pharmacology ; Trypanocidal Agents -- Pharmacology ; Trypanosoma Brucei Brucei -- Drug Effects ; Trypanosomiasis -- Drug Therapy
    Description: Six limonoids [kotschyienone A and B (1, 2), 7-deacetylgedunin (3), 7-deacetyl-7-oxogedunin (4), andirobin (5) and methyl angolensate (6)] were investigated for their trypanocidal and leishmanicidal activities using bloodstream forms of Trypanosoma brucei and promastigotes of Leishmania major. Whereas all compounds showed anti-trypanosomal activity, only compounds 1-4 displayed anti-leishmanial activity. The 50% growth inhibition (GI) values for the trypanocidal and leishmanicidal activity of the compounds ranged between 2.5 and 14.9 μM. Kotschyienone A (1) was found to be the most active compound with a minimal inhibition concentration (MIC) value of 10 μM and GI values between 2.5 and 2.9 μM. Only compounds 1 and 3 showed moderate cytotoxicity against HL-60 cells with MIC and GI values of 100 μM and 31.5-46.2 μM, respectively. Compound 1 was also found to show activity against intracellular amastigotes of L. major with a GI value of 1.5 μM. The results suggest that limonoids have potential...
    Is part of: Journal of natural medicines, June 2020, Vol.74(3), pp.606-611
    Identifier: 1861-0293 (E-ISSN); 32277328 Version (PMID); 10.1007/s11418-020-01408-7 (DOI)