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121.
[structure: see text] Two novel hybrid polyketide-terpenoid metabolites were isolated from a Penicillium sp. growing in the Berkeley Pit Lake of Butte, Montana. Their structures were deduced by spectroscopic analysis and confirmed by single-crystal X-ray analysis on berkeleydione (1). Both compounds inhibited matrix metalloproteinase-3 and caspase-1, and berkeleydione showed activity toward non-small-cell lung cancer in NCI's human cell line antitumor screen. 相似文献
122.
Busacca CA Grossbach D Campbell SJ Dong Y Eriksson MC Harris RE Jones PJ Kim JY Lorenz JC McKellop KB O'Brien EM Qiu F Simpson RD Smith L So RC Spinelli EM Vitous J Zavattaro C 《The Journal of organic chemistry》2004,69(16):5187-5195
The Boehringer-Ingelheim phosphinoimidazoline (BIPI) ligands were applied to the formation of chiral quaternary centers in the asymmetric Heck reaction. Several different substrates were examined in detail, using more than 70 members of this new ligand class. Hammett relationships were determined through systematic variation of the ligand electronics. All substrates showed essentially the same Hammett behavior, where enantioselectivity increased as the ligands were made more electron-deficient. Ligand optimization has led to catalysts which give the highest enantioselectivities reported to date for these difficult systems. 相似文献
123.
The mechanism of decomposition of dialkylamino diazeniumdiolate salts, R(2)N[NONO](-)M(+), to form nitric oxide, NO, was explored using theoretical methods. B3LYP/6-311+G(d) density functional theory calculations gave the optimized geometries, and energetics were further evaluated with the high accuracy CBS-QB3 method, when feasible. Relative pK(a) values were estimated using the PCM model for aqueous solvation. The terminal oxygen is the most basic site, followed closely by the internal oxygen. Protonation of these sites does not lead to decomposition. However, protonation of the weakly basic amino nitrogen leads to very rapid decomposition and NO generation. 相似文献
124.
Selenium-catalyzed halolactonization: nucleophilic activation of electrophilic halogenating reagents
Diphenyl diselenide catalyzes the halolactonization of unsaturated acids with N-halosuccinimides under mild conditions. The diselenide not only accelerates the reactions, but in some cases affords regiocontrol in favor of gamma-lactone products. Experiments show that the regioselectivity in favor of gamma-lactones is a result of kinetic rather than thermodynamic control. 相似文献
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126.
Nagarajan K Joshi HK Chaudhury PK Pal K Cooney JJ Enemark JH Sarkar S 《Inorganic chemistry》2004,43(15):4532-4533
Synthesis of [PPh4]2[Mo(SPh)2(S2C2(CN)2)2] (2) from [PPh4]2[MoO(S2C2(CN)2)2] (1) has been achieved to mimic the postulated [Mo(S)6] core of polysulfide reductase with two thiolates and two bis(ene-dithiolate) ligands. Compound 2 reacts with polysulfide to yield H2S, modeling the function of polysulfide reductase. The facile conversion of 2 back to 1 in moist solvent suggests that the interconversion of the [MoIV = O] and [MoIV - X] (X = O-Ser, S-Cys, Se-Cys) moieties might occur in the DMSO reductase class of enzymes under appropriate hydrophobic/hydrophilic conditions. 相似文献
127.
We show that the position of a fluorescent nanoparticle can be measured in three dimensions with subnanometer precision and 100-ms temporal resolution by use of standard epifluorescence video imaging in off-focus mode. The particle can be tracked without feedback in a volume of at least 40 microm x 60 microm x 3 microm. With the technique presented, the structure-mobility relationship of 216-nm latex particle in a porous polymer network was studied in three dimensions. 相似文献
128.
The coupling of rhodium carbenoids from vinyl diazoacetates with 2-thio-3-alkyl indoles was found to generate C(3) quaternary substituted indolines via a thionium ylide-initiated [3,3]-sigmatropic rearrangement. 相似文献
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130.