Tribromoisocyanuric Acid (TBCA) and Oxone®‐MX Systems as Oxidizing Agents: Oxidative Coupling of Thiols to Their Corresponding Disulfides under Mild and Heterogeneous Conditions

Tribromoisocyanuric acid (TBCA) and Oxone^®‐MX systems were used as effective oxidizing agents for the oxidation of thiols to their corresponding disulfides under mild conditions at room temperature with good to excellent yields.     

Synthesis and Dynamic NMR Study of Functionalized 1-(3-Furyl)-1H-indole-2,3-diones

Protonation of the highly reactive 1:1 intermediates produced in the reaction between alkyl(aryl) isocyanides and dibenzoylacetylene by isatin, leads to vinylnitrilium cations, which undergo carbon-centered Michael-type addition with the conjugate base of the NH-acid to produce highly functionalized 1-(3-furyl)-1H-indole-2,3-diones. A dynamic NMR effect is observed in the ¹H NMR spectra of these compounds as a result of restricted rotation around the single bond linking the indole moiety and the furan system. The free-energy of activation (ΔG ^#) for this process is 69–71 ± 2 kJ mol⁻¹.     

A mild conversion of arylboronic acids and their pinacolyl boronate esters into phenols using hydroxylamine

Hydroxylamine was found to be a mild reagent for conversion of arylboronic acids and their pinacolyl boronate esters into phenols. This procedure works on most arylboronic acids at room temperature, yielding phenols in moderate to good yields, and efficiently on arylboronates also yielding phenols in good yields.     

Characterization and determination of fatty acids in fish oil using gas chromatography-mass spectrometry coupled with chemometric resolution techniques

Characterization and determination of a complex mixture of fatty acid methyl esters was performed for commercial fish oil using two-dimensional GC-MS data coupled with resolution techniques. Various principle component analysis methods such as significant factor analysis and fixed size moving window evolving factor analysis were used for the number of factors, zero concentration and selective regions. Then, the convoluted chromatograms were resolved into pure chromatograms and mass spectra using heuristic evolving latent projections (HELP) method. Fatty acids of C16:1omega7, C18:4omega3, C18:1omega11, C18:1omega9, C18:0, C20:2omega6, C20:1omega9, C22:1omega11, C22:1omega9 and C24:1omega9 were resolved an fied by using similarity searches between deconvoluted mass spectra and MS database, in different parts of total ion current chromatogram. Window target testing factor analysis is also applied for confirming the presence or absence of target analytes. The results of the present work show that combination of hyphenated chromatographic methods and resolution techniques provide a complementary method for accurate analysis of real multi-component systems such as fish oil.     

A synthesis of pyrrolo[2,1-a]isoquinolines through the reaction of activated acetylenes and isoquinoline in the presence of ethyl bromopyruvate

Isoquinoline reacts with ethyl bromopyruvate in the presence of dialkyl acetylenedicarboxylates or diaryloylacetylenes to produce dialkyl 1-(2-ethoxy-2-oxoacetyl)pyrrolo[2,1-a]isoquinoline-2,3-dicarboxylates or ethyl 2-[2,3-diaryloylpyrrolo[2,1-a]isoquinoline-1-yl]-2-oxoacetates in good yields.     

Partial-filling affinity capillary electrophoresis

Partial-filling affinity capillary electrophoresis (PFACE) is used to examine the binding interactions between two model biological systems: D-Ala-D-Ala terminus peptides to the glycopeptide antibiotic vancomycin (Van) from Streptomyces orientalis, and arylsulfonamides to carbonic anhydrase B (CAB, EC 4.2.1.1, bovine erythrocytes). Using these two systems, modifications in the PFACE technique are demonstrated including flow-through PFACE (FTPFACE), competitive flow-through PFACE (CFTPFACE), on-column ligand synthesis PFACE (OCLSPFACE), and multiple-step ligand injection PFACE (MSLIPFACE). In PFACE small plugs of sample are injected into the capillary column and an equilibrium is established between receptor and ligand during electrophoresis. Binding constants are then obtained by Scatchard analysis using changes in the migration time of the receptor/ligand on changing the concentration of the ligand/receptor. Data demonstrating the quantitative potential of these methods are presented. This review focuses on the unique capabilities of the different PFACE techniques as applied to two model biological systems.     

Ru-catalyzed synthesis of substituted phthalides through C–H bond activation and functionalization

Synthesis of substituted phthalides through a ruthenium-catalyzed reaction of phthalic anhydrides with acrylates is described. The reaction proceeds via CH bond activation and leads to the formation of vinylated phthalides through a successive double vinylation accompanied by decarboxylation and annulation reactions.     

Calculation of the viscosity of binary liquids at various temperatures using Jouyban-Acree model

Applicability of the Jouyban-Acree model for calculating absolute viscosity of binary liquid mixtures with respect to temperature and mixture composition is proposed. The correlation ability of the model is evaluated by employing viscosity data of 143 various aqueous and non-aqueous liquid mixtures at various temperatures collected from the literature. The results show that the model is able to correlate the data with an overall percentage deviation (PD) of 1.9+/-2.5%. In order to test the prediction capability of the model, three experimental viscosities from the highest and lowest temperatures along with the viscosities of neat liquids at all temperatures have been employed to train the model, then the viscosity values at other mixture compositions and temperatures were predicted and the overall PD obtained is 2.6+/-4.0%.     

Photocycloaddition of Six‐Membered Cyclic Enones to Propen‐2‐yl Isocyanate

On irradiation in the presence of propen‐2‐yl isocyanate ( 4 ), six‐membered cyclic enones 3 are converted into regio‐ and stereoisomeric mixtures of [2+2] cycloadducts 5 – 10 ; the preferentially formed HT products, 5 – 8 , can be converted into the corresponding bicyclic amines by acid hydrolysis, whereas, under these conditions, the regioisomeric HH‐isocyanato derivatives undergo a retro‐Mannich reaction.     

Estimation of binding constants between ristocetin and teicoplanin and peptides using on-column ligand derivatization coupled to affinity capillary electrophoresis

This work utilizes on-column ligand synthesis and affinity capillary electrophoresis (ACE) to determine binding constants (K_b) of 9-flourenylmethyloxy carbonyl (Fmoc)-amino acid derivatives to the glycopeptide antibiotics ristocetin (Rist) and teicoplanin (Teic). In this technique, two separate plugs of sample are injected on to the capillary column and electrophoresed. The initial sample plug contains a d-Ala-d-Ala terminus peptide and either one or two non-interacting standard(s). The second plug contains a Fmoc-amino acid-N-hydroxysuccinimide (NHS) ester. The electrophoresis is then carried out with an increasing concentration of Rist or Teic in the running buffer. Upon electrophoresis the initial d-Ala-d-Ala peptide reacts with the Fmoc-amino acid yielding a new Fmoc-amino acid-d-Ala-d-Ala peptide derivative. Continued electrophoresis results in the binding of Rist or Teic to the Fmoc-amino acid-d-Ala-d-Ala peptide derivatives. Analysis of the change in the relative migration time ratio (RMTR) or electrophoretic mobility () of the Fmoc-amino acid-d-Ala-d-Ala peptide derivatives relative to the non-interacting standards, as a function of the concentration of Rist and Teic, yields a value for K_b. These findings demonstrate the advantage of coupling on-column ligand synthesis to ACE for estimating binding parameters between antibiotics and ligands.Abbreviations Rist Ristocetin - Teic Teicoplanin - ACE Affinity capillary electrophoresis - RMTR Relative migration time ratio