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201.
Frank D. Popp Miland Rajopadhye David S. Brown David Waddington Barrie C. Uff 《Journal of heterocyclic chemistry》1987,24(1):261-265
The title compounds have been prepared by the cyclocondensation of mercaptosuccinic acid with isatin-3-imines. The 1-benzyl derivatives have been synthesized by simultaneously reacting 1-benzylisatin, substituted anilines and mercaptosuccinic acid. The structure of the products has been confirmed by X-ray diffraction measurements. 相似文献
202.
Neverov AA Liu CT Bunn SE Edwards D White CJ Melnychuk SA Brown RS 《Journal of the American Chemical Society》2008,130(20):6639-6649
The di-Zn(II) complex of 1,3-bis[ N1, N1'-(1,5,9-triazacyclododecyl)]propane with an associated methoxide ( 3:Zn(II) 2: (-)OCH 3) was prepared and its catalysis of the methanolysis of a series of fourteen methyl aryl phosphate diesters ( 6) was studied at s (s)pH 9.8 in methanol at 25.0 +/- 0.1 degrees C. Plots of k obs vs [ 3:Zn(II) 2: (-)OCH 3] free for all members of 6 show saturation behavior from which K(M) and kcat (max) were determined. The second order rate constants for the catalyzed reactions (kcat (max)/K(M)) for each substrate are larger than the corresponding methoxide catalyzed reaction (k 2 (-OMe)) by 1.4 x 10(8) to 3 x 10 (9)-fold. The values of k cat (max) for all members of 6 are between 4 x 10(11) and 3 x 10(13) times larger than the solution reaction at s (s)pH 9.8, with the largest accelerations being given for substrates where the departing aryloxy unit contains ortho-NO 2 or C(O)OCH 3 groups. Based on the linear Br?nsted plots of k cat (max) vs s (s)pKa of the phenol, beta lg values of -0.57 and -0.34 are determined respectively for the catalyzed methanolysis of "regular" substrates that do not contain the ortho-NO 2 or C(O)OCH 3 groups, and those substrates that do. The data are consistent with a two step mechanism for the catalyzed reaction with rate limiting formation of a catalyst-coordinated phosphorane intermediate, followed by fast loss of the aryloxy leaving group. A detailed energetics calculation indicates that the catalyst binds the transition state comprising [CH 3O (-): 6], giving a hypothetical [ 3:Zn(II) 2:CH 3O (-): 6] complex, by -21.4 to -24.5 kcal/mol, with the strongest binding being for those substrates having the ortho-NO 2 or C(O)OCH 3 groups. 相似文献
203.
Wang ZJ Brown CJ Bergman RG Raymond KN Toste FD 《Journal of the American Chemical Society》2011,133(19):7358-7360
Gold(I)-phosphine complexes are readily encapsulated by a tetrahedral supramolecular host (Ga(4)L(6)). We have investigated the catalytic activity of the resulting complexes for the intramolecular hydroalkoxylation of allenes. The catalytic activity of Me(3)PAuBr was increased 8-fold by encapsulation, as determined by initial rate kinetics, and we observed up to 67 catalytic turnovers by Me(3)PAu(+) encapsulated in Ga(4)L(6). 相似文献
204.
Rosado A Hicks GR Norambuena L Rogachev I Meir S Pourcel L Zouhar J Brown MQ Boirsdore MP Puckrin RS Cutler SR Rojo E Aharoni A Raikhel NV 《Chemistry & biology》2011,18(2):187-197
Sortin1 is a chemical genetic-hit molecule that causes specific mislocalization of plant and yeast-soluble and membrane vacuolar markers. To better understand its mode of action, we designed a Sortin1-hypersensitive screen and identified several Sortin1-hypersensitive and flavonoid-defective mutants. Mechanistically, Sortin1 mimics the effect of the glutathione inhibitor buthionine sulfoximine and alters the vacuolar accumulation of flavonoids, likely blocking their transport through vacuole-localized ABC transporters. Structure-activity relationship studies conducted in Arabidopsis revealed the structural requirements for Sortin1 bioactivity and demonstrated that overlapping Sortin1 substructures can be used to discriminate between vacuolar-flavonoid accumulations and vacuolar-biogenesis defects. We conclude that Sortin1 is a valuable probe for dissecting novel links among flavonoid transport, vacuolar integrity, and the trafficking of vacuolar targeted cargoes in Arabidopsis. 相似文献
205.
Ashraf A. Aly Alaa A. Hassan Alan B. Brown Kamal M. El‐Shaieb Tarek M. I. Bedair 《Journal of heterocyclic chemistry》2011,48(4):787-791
New imidazoles were easily prepared from 2,3‐diamino‐1,4‐naphthoquinone and stoichiometric quantities of the appropriate aldehydes in dimethyl sulfoxide as a solvent. The reaction proceeded for few hours. The procedure can be generalized to different classes of aldehydes. 2‐Methyl‐1H‐naphtho[2,3‐d]imidazole‐4,9‐dione was also obtained in good yield during refluxing of 2,3‐diaminonaphthoquinone in acetic acid. The structure of the newly synthesized imidazoles was extensively investigated using NMR experiments. J. Heterocyclic Chem., (2011). 相似文献
206.
Methanol solutions containing Cd(II), Mn(II), and a palladacycle, (dimethanol bis(N,N-dimethylbenzylamine-2C,N)palladium(II) (3), are shown to promote the methanolytic transesterification of O-methyl O-4-nitrophenyl phosphorothioate (2b) at 25 °C with impressive rate accelerations of 10(6)-10(11) over the background methoxide promoted reaction. A detailed mechanistic investigation of the methanolytic cleavage of 2a-d having various leaving group aryl substitutions, and particularly the 4-nitrophenyl derivative (2b), catalyzed by Pd-complex 3 is presented. Plots of k(obs) versus palladacycle [3] demonstrate strong saturation binding to form 2b:3. Numerical fits of the kinetic data to a universal binding equation provide binding constants, K(b), and first order catalytic rate constants for the methanolysis reaction of the 2b:3 complex (k(cat)) which, when corrected for buffer effects, give corrected (k(cat)(corr)) rate constants. A sigmoidal shaped plot of log(k(cat)(corr)) versus (s)(s)pH (in methanol) for the cleavage of 2b displays a broad (s)(s)pH independent region from 5.6 ≤ (s)(s)pH ≤ 10 with a k(minimum) = (1.45 ± 0.24) × 10(-2) s(-1) and a [lyoxide] dependent wing plateauing above a kinetically determined (s)(s)pK(a) of 12.71 ± 0.17 to give a k(maximum) = 7.1 ± 1.7 s(-1). Br?nsted plots were constructed for reaction of 2a-d at (s)(s)pH 8.7 and 14.1, corresponding to reaction in the midpoints of the low and high (s)(s)pH plateaus. The Br?nsted coefficients (β(LG)) are computed as -0.01 ± 0.03 and -0.86 ± 0.004 at low and high (s)(s)pH, respectively. In the low (s)(s)pH plateau, and under conditions of saturating 3, a solvent deuterium kinetic isotope effect of k(H)/k(D) = 1.17 ± 0.08 is observed; activation parameters (ΔH(Pd)(++) = 14.0 ± 0.6 kcal/mol and ΔS(Pd)(++)= -20 ± 2 cal/mol·K) were obtained for the 3-catalyzed cleavage reaction of 2b. Possible mechanisms are discussed for the reactions catalyzed by 3 at low and high sspH. This catalytic system is shown to promote the methanolytic cleavage of O,O-dimethyl phosphorothioate in CD3OD, producing (CD3O)2P═O(S(-)) with a half time for reaction of 34 min. 相似文献
207.
208.
209.
Brown SP Pérez-Torralba M Sanz D Claramunt RM Emsley L 《Journal of the American Chemical Society》2002,124(7):1152-1153
A new method for detecting hydrogen bonds in the solid state is presented. Using two-dimensional NMR correlation experiments, it is shown that a hydrogen-bond mediated J coupling can be observed in a powder under magic-angle spinning conditions, even though the J coupling is 2 orders of magnitude smaller than the dominant anisotropic interactions encountered in solid-state NMR. Specifically, the observation of a pair of peaks in a two-dimensional 15N-15N solid-state INADEQUATE experiment due to two nitrogens that have no covalent connectivity is attributed to the presence of a J coupling across a linking hydrogen bond. 相似文献
210.
Essmat M. El-Sheref Mohammed A. I. Elbastawesy Alan B. Brown Ahmed M. Shawky Hesham A. M. Gomaa Stefan Brse Bahaa G. M. Youssif 《Molecules (Basel, Switzerland)》2021,26(22)
A mild and versatile method based on Cu-catalyzed [2+3] cycloaddition (Huisgen-Meldal-Sharpless reaction) was developed to tether 3,3’-((4-(prop-2-yn-1-yloxy)phenyl)methylene)bis(4-hydroxyquinolin-2(1H)-ones) with 4-azido-2-quinolones in good yields. This methodology allowed attaching three quinolone molecules via a triazole linker with the proposed mechanism. The products are interesting precursors for their anti-proliferative activity. Compound 8g was the most active one, achieving IC50 = 1.2 ± 0.2 µM and 1.4 ± 0.2 µM against MCF-7 and Panc-1 cell lines, respectively. Moreover, cell cycle analysis of cells MCF-7 treated with 8g showed cell cycle arrest at the G2/M phase (supported by Caspase-3,8,9, Cytochrome C, BAX, and Bcl-2 studies). Additionally, significant pro-apoptotic activity is indicated by annexin V-FITC staining. 相似文献