Reactions of 2-(trifluoromethyl)chromones with cyanoacetamides, ethyl cyanoacetate and diethyl malonate. Unexpected synthesis of benzo[c]coumarin derivatives

While 2-(trifluoromethyl)chromones react with cyanoacetamides in the presence of sodium ethoxide to produce 6-(2-hydroxyaryl)-4-(trifluoromethyl)-2-oxo-1,2-dihydropyridine-3-carbonitriles, their reactions with ethyl cyanoacetate and diethyl malonate under the same conditions took an entirely different course and gave novel functionalized derivatives of 6H-benzo[c]chromen-6-one.     

Enantioseparation of organic acids of pharmaceutical interest using eremomycin as a chiral selector

Strong adsorption of eremomycin on the fused-silica capillary wall was used for separation of enantiomers by CE. The capillary with adsorbed chiral selector was shown to be easily prepared and has reproducible properties. The effect of the chiral selector concentration, pH and composition of the BGE, and applied voltage on enantioseparation of acidic compounds, such as profens and aromatic carboxylic acids, was investigated. Two native α-amino acids, aspartic acid and glutamic acid, were enantioseparated. Fourteen tested compounds (including amino acids) were baseline resolved. Good selectivity of separation (α>1.09) was achieved. The migration order of ibuprofen and ketoprofen enantiomers was determined. The procedures were proposed for the analysis of flurbiprofen and warfarin in pharmaceuticals. Linearity was achieved in the concentration range of 4.0×10(-5)-2.0×10(-3) M for flurbiprofen and 3.2×10(-6)-4.9×10(-6) M for warfarin. The detection limits were found to be about 1×10(-5) M for flurbiprofen and 1×10(-6) M for warfarin.     

Historical development of theories of the electrochemical double layer

This review describes the evolution of important concepts related to potential drops at interfaces in electrochemical systems. The role of the thermodynamic theory of electrocapillarity of perfectly polarizable electrodes in the development of interfacial electrochemistry is emphasized. A critical analysis of the phenomenological models of the electrical double layer on ideally polarizable electrodes is given. Certain trends in studying solid electrodes with well-defined surfaces brought into contact with electrolyte solutions are summarized. Attention is drawn to several unsolved problems crucial for the future development of electrochemical surface science. Finally, some recent experimental data are analyzed for selected models.     

Synthesis and biological activity of optimized belactosin C congeners

Successful biochemical studies of the natural products belactosin A and C as well as their more stable acylated derivatives have proved them to be powerful proteasome inhibitors and thereby potential candidates as pharmacologically relevant active compounds. In order to understand their structure-biological activity relations in detail and to find ways of improving their biological activity, four new modified belactosin congeners have been synthesized and tested. One of them (compound 6) turned out to be a more potent inhibitor against HeLa cells than the known proteasome inhibitor MG132.     

N-aryl pyrazoles: DFT calculations of CH acidity and deprotonative metallation using a combination of lithium and zinc amides

A series of N-aryl and N-heteroaryl pyrazoles have been deproto-metallated using a 2,2,6,6-tetramethylpiperidino-based mixed lithium-zinc combination. Mono-, di-, and tri-iodides have been obtained after subsequent trapping with iodine, depending on the substrate and on the quantity of base used. The results have been discussed in the light of the CH acidities of the substrates, determined both in the gas phase and in THF solution using the DFT B3LYP method.     

Early-late heterobimetallic Rh-Ti and Rh-Zr complexes via addition of early metal chlorides to mono- and divalent rhodium

Addition of TiCl(4) or ZrCl(4) to (PNP)Rh(CH(2)==CH(t)Bu) (1) rapidly gives complexes (PNP)Rh(MCl(3))(Cl) (M = Ti, 2; Zr, 3) in 75-77% yield (PNP = (4-Me-2-((i)Pr(2)P)-C(6)H(3))(2)N). Compound 2 can also be synthesized via a reaction of (PNP)RhCl with TiCl(3) or of (PNP)TiCl(3) with 1/2 [(cod)RhCl](2).     

Chiral ionic liquid/ESI-MS methodology as an efficient tool for the study of transformations of supported organocatalysts: deactivation pathways of Jørgensen-Hayashi-type catalysts in asymmetric Michael reactions

The deactivation pathways of Jørgensen–Hayashi‐type organocatalysts modified with an ionic liquid fragment in asymmetric Michael reactions of α,β‐enals with C‐ (nitromethane, dimethylmalonate) or N‐nucleophiles (N‐carbobenzyloxyhydroxylamine) that involved an iminium‐ion formation step were studied for the first time by the electrospray ionization mass spectrometry (ESI‐MS). “Parasitic” side reactions and undesirable cation intermediates that poisoned the catalysts were identified in accordance with their m/z values as well as their relation to the reported mechanisms of Michael reactions in the presence of O‐TMS‐α,α‐diarylprolinol (TMS=trimethylsilyl) derivatives. The proposed approach may be useful for the study of transformations of other types of organocatalysts modified with ionic groups in various organocatalytic reactions and for the development of novel robust catalysts and processes that would be suitable for large‐scale industrial applications.     

Compressibility study of quaternary phospholipid blend monolayers

The mechanical properties of liposome membranes are strongly dependent on type and ratio of lipid compounds, which can have important role in drug targeting and release processes when liposome is used as drug carrier. In this work we have used Brewster's angle microscopy to monitor the lateral compression process of lipid monolayers containing as helper lipids either distearoyl phosphatidylethanolamine (DSPE) or dioleoyl phophatidylethanolamine (DOPE) molecules on the Langmuir trough. The compressibility coefficient was determined for lipid blend monolayers containing the helper lipids above, cholesterol, distearoyl phosphatidylcholine (DSPC) and pegylated-DSPE at room temperature. Two variables, the cholesterol fraction and the ratio ρ between the helper lipid (either DSPE or DOPE) and the reference lipid DSPC, were studied by multivariate analysis to evaluate their impact on the compressibility coefficient of the monolayers. The cholesterol level was found to be the most significant variable for DSPE blends while the ratio ρ was the most significant one for DOPE blend monolayers. It was also found that these two variables can exhibit positive interaction and the same compressibility value can be obtained with different blend compositions.     

Nonequilibrium phases of nanoparticle Langmuir films

We report on an in-situ observation of the colloidal silver nanoparticle self-assembly into a close-packed monolayer at the air/water interface followed by a 2D to 3D transition. Using the fast tracking GISAXS technique, we were able to observe the immediate response to the compression of the self-assembled nanoparticle layer at the air/water interface and to identify all relevant intermediate stages including those far from the equilibrium. In particular, a new nonequilibrium phase before the monolayer collapse via the 2D to 3D transition was found that is inaccessible by the competing direct space imaging techniques such as the scanning and transmission electron microscopies due to the high water vapor pressure and surface tension.