Nucleophilicity of halide ions in the micellar pseudophase
作者:Hamad A. Al-Lohedan
DOI:10.1016/s0040-4020(01)80038-7
日期:1989.1
The reaction of Br− or Cl− with both n-butyl-4-nitrobenzenesulfonate and n-butyl-4-bromobenzenesulfonate 1a and 1b respectively is catalyzed by cationicmicelles of cetyltrimethylammonium chloride or bromide (CTACl or CTABr respectively). The increase of rate constant with [surfactant] can be analyzed in terms of the concentration of substrate (1a - b) and halide ion in the micellar pseudophase, and
Nucleophilicity of azide ion in the micellar pseudophase
作者:Hamad A.Al-Lohedan
DOI:10.1016/s0040-4020(01)81527-1
日期:1990.1
The reaction of azideion with 2-chloro-3,5-dinitropyrldine, n-butyl-4-nitrobenzenesulfonate and n-butyl-4-bromobenzenesulfonate is catalyzed by cationic micelles of cetyltrimethylammonium salt (CTAX, X=Cl-, Br-, 0.5 SO=4, OMes, N-3) The second-order rate constants in the micellar pseudophase is smaller than that in water.
叠氮化物离子与2-氯-3,5-二dinitropyrldine,正丁基-4-硝基苯磺酸酯和正丁基-4-溴苯磺酸是由十六烷基三甲基盐的阳离子胶束催化(CTAX,将反应X =氯- ,溴- ,0.5 SO = 4,OMes,N - 3)胶束假相中的二级速率常数小于水中的二级速率常数。
ZnO and ZnO-nanoparticles: Efficient and reusable heterogeneous catalysts for one-pot synthesis of N-acylsulfonamides and sulfonate esters
作者:Fatemeh Tamaddon、Mohammad Reza Sabeti、Abbas Ali Jafari、Farhang Tirgir、Elham Keshavarz
DOI:10.1016/j.molcata.2011.09.010
日期:2011.12
Commercially available and preparative ZnO nanoparticles are reported as efficient and reusable catalysts for the chemoselective synthesis of N-acylsulfonamides and sulfonate esters. A one-pot sequential sulfonylation and acylation of amines took place to afford the N-acylsulfonamides in excellent yields under solvent-free conditions. The ZnO catalyst can be reused for without significant loss of catalytic activity. (C) 2011 Elsevier B.V. All rights reserved.
Al-Lohedan, Hamad A., Journal of the Chemical Society. Perkin transactions II, 1995, # 8, p. 1707 - 1714
作者:Al-Lohedan, Hamad A.
DOI:——
日期:——
Inscribing the Perimeter of the PagP Hydrocarbon Ruler by Site-Specific Chemical Alkylation
作者:M. Adil Khan、Joel Moktar、Patrick J. Mott、Mary Vu、Aaron H. McKie、Thomas Pinter、Fraser Hof、Russell E. Bishop
DOI:10.1021/bi1011496
日期:2010.10.26
The Escherichia coli outer membrane phospholipid:lipid A palmitoyltransferase PagP selects palmitate chains using its beta-barrel-interior hydrocarbon ruler and interrogates phospholipid donors by gating them laterally through an aperture known as the crenel. Lipid A palmitoylation provides antimicrobial peptide resistance and modulates inflammation signaled through the host TLR4/MD2 pathway. Gly88 substitutions can raise the PagP hydrocarbon ruler floor to correspondingly shorten the selected acyl chain. To explore the limits of hydrocarbon ruler acyl chain selectivity, we have modified the single Gly88Cys sulfhydryl group with linear alkyl units and identified C10 as the shortest acyl chain to be efficiently utilized. Gly88Cys-S-ethyl, S-n-propyl, and S-n-butyl PagP were all highly specific for C12, C11, and C10 acyl chains, respectively, and longer aliphatic or aminoalkyl substitutions could not extend acyl chain selectivity any further. The donor chain length limit of C10 coincides with the phosphatidylcholine transition from displaying bilayer to micellar properties in water, but the detergent inhibitor lauryldimethylamine At-oxide also gradually became ineffective in a micellar assay as the selected acyl chains were shortened to C10. The Gly88Cys-S-ethyl and norleucine substitutions exhibited superior C12 acyl chain specificity compared to that of Gly88Met PagP, thus revealing detection by the hydrocarbon ruler of the Met side chain tolerance for terminal methyl group gauche conformers. Although norleucine substitution was benign, selenomethionine substitution at Met72 was highly destabilizing to PagP. Within the hydrophobic and van der Waals-contacted environment of the PagP hydrocarbon ruler, side chain flexibility, combined with localized thioether-aromatic dispersion attraction, likely influences the specificity of acyl chain selection.