Total synthesis of infectopyrone,aplysiopsenes A–C,ent-aplysiopsene D,phomapyrones A and D, 8,9-dehydroxylarone,and nectriapyrone

The total synthesis of the 2-pyrone natural products nectriapyrone, aplysiopsenes A–C, ent-aplysiopsene D, phomapyrones A and D, and of 8,9-dehydroxylarone were achieved by Wittig olefination starting with vermopyrone. Infectopyrone was synthesized by Horner–Wadsworth–Emmons reaction starting with phomapyrone D. Racemic phomapyrone C methyl ether was obtained by hydrogenation of nectriapyrone. The total syntheses were achieved starting from commercially available 3,5-heptanedione and led to the desired natural products in 18–46% over 5–6 steps, whereupon all five-step syntheses were carried out with a single chromatographic workup. The total synthesis of infectopyrone, aplysiopsenes A–D, of phomapyrones A and D, and of 8,9-dehydroxylarone were achieved for the first time, giving unambiguous proof for the proposed structures of these natural products.     

A Novel, Simple and Efficient Synthesis of Ferrocenyl Enones and Alkynols

Propargylic alcohols are versatile precursors to many organic molecules including natural products and pharmaceutical compounds.[1] In our continuing interest in the development of practical methods for synthesis of ferrocene derivatives, we decided to investigate the efficiencies of ferrocenylacetylene addition to aromatic aldehydes under t-BuOKcatalyzed condition.[2] Interestingly, we found that the usually reliable coupling reaction between terminal alkyne of type 1 and aromatic aldehydes of type 2 does not furnish the expected propargylic alcohols, but that the isomeric aryl enones 3are found in high yield and very short reaction time (10～20 min). This provided a promising protocol for preparation of ferrocenyl chalcones in a practical, economical and mild sense compared with the traditional method. To the best of our knowledge, this unusual reaction was first observed for the addition of ferrocenylacetylene to aldehyde in a base-catalyzed manner (Eq. 1).     

Measurement of bisphenol A, bisphenol A ß-D-glucuronide, genistein, and genistein 4'-ß-D-glucuronide via SPE and HPLC-MS/MS

Bisphenol A (BPA) is a synthetic industrial reactant used in the production of polycarbonate plastics, and genistein is a natural phytoestrogen abundant in the soybean. Current studies investigating the endocrine-disrupting effects of concomitant exposures to BPA and genistein have warranted the development of an analytical method for the simultaneous measurement of BPA and genistein, as well as their primary metabolites, bisphenol A ?-d-glucuronide (BPA gluc) and genistein 4′-?-d-glucuronide (genistein gluc), respectively. All four analytes were extracted from rat plasma via solid phase extraction (SPE). Three SPE cartridges and four elution schemes were tested. Plasma extraction using Bond Elut Plexa cartridges with sequential addition of ethyl acetate, methanol, and acetonitrile yielded optimal average recoveries of 98.1 ± 1.8% BPA, 94.9 ± 8.0% genistein, 91.4 ± 6.1% BPA gluc, and 103 ± 6.1% genistein gluc. Identification and quantification of the four analytes were performed by a validated HPLC-MS/MS method using electrospray ionization and selective reaction monitoring. This novel analytical method should be applicable to the measurement of BPA, genistein, BPA gluc, and genistein gluc in urine, cultures, and tissue following in vivo exposures. While reports of the determination of BPA and genistein independently exist, the simultaneous optimized extraction and detection of BPA, genistein, BPA gluc, and genistein gluc have not previously been reported.     

Total Syntheses of Kopsaporine,Kopsinol and Kopsiloscine A

Kopsia alkaloids represent a complex class of natural products bearing a polycyclic ring system with two or three consecutive quaternary carbon centers. In this article, we report the first total synthesis of Kopsaporine related alkaloids. Features of our structure-unit-based strategy are an intramolecular Pummerer rearrangement induced nucleophilic cyclization/aza-Prins cyclization to construct the highly functional hexahydrocarbazole skeleton, an olefin migration vinylogous alkylation to establish the C20 all-carbon quaternary center, an iridium complex mediated radical addition to fuse the aspidofractine framework, an unprecedented IBX oxidation to introduce the α-hydroxyketone moiety, and a bioinspired retro-Aldol/Aldol reaction to convert kopsaporine to kopsiloscine A.     

TiCl4, Dioxane—A Facile and Efficient System for De-O-Benzylation,De-O-Allylation,and De-O-Xylylation of Phenolic Ethers

Abstract

Simultaneous de-O-xylylation and reductive coupling was observed when 1 equiv. of the dialdehyde 2a/2b was treated with 5 equiv. of each TiCl₄ and Zinc which lead to the development of TiCl₄ in dioxane as a new system for the facile deprotection of phenolic ethers 4a–4d, 5a–5d, and 6a–6c.     

A,D-Oligomethylenic capping of α- and β-cyclodextrins

α- and β-cyclodextrins have easily been converted into basket molecules, the handle being an oligomethylenic chain bridging A and D positions on the primary rim. The size of the handle influences the complexing properties of these cyclodextrins. To cite this article: T. Lecourt et al., C. R. Chimie 6 (2003) 000–000.     

A facile synthesis of (+)/(−)-pentenomycin I and analogs,and their antimicrobial evaluation

This study reported a stereoselective synthesis of (+)/(+)-pentenomycin I in 4–5 steps through regioselective silylation, optical resolution and dihydroxylation, followed by an olefin formation, from a known racemic cyclopentenone prepared from 2-deoxy-d-glucose. We also accomplished the transformation of a common intermediate into a variety of analogs. In addition, the antimicrobial activities of the pentenomycin analogs were evaluated, which revealed important structural factors of pentenomycins for the antimicrobial activities.     

A comparative study of CE-SDS,SDS-PAGE,and Simple Western—Precision,repeatability, and apparent molecular mass shifts by glycosylation

SDS gel electrophoresis is a commonly used approach for monitoring purity and apparent molecular mass (Mr) of proteins, especially in the field of quality control of biopharmaceutical proteins. The technological installation of CE-SDS as the replacement of the slab gel technique (SDS-PAGE) is still in progress, leading to a continuous improvement of CE-SDS instruments. Various CE-SDS instruments, namely Maurice (CE-SDS/CE-SDS PLUS) and Wes by ProteinSimple as well as the microchip gel electrophoresis system LabChip® GXII Touch™ HT by PerkinElmer were tested for precision and repeatability compared to SDS-PAGE (Bio-Rad). For assessing these quality control parameters, standard model proteins with minor post-translational modifications were used. Overall, it can be concluded that the CE-SDS-based methods are similar to SDS-PAGE with respect to these parameters. Quality characteristics of test systems gain more significance by testing proteins that do not behave like model proteins. Therefore, glycosylated proteins were analyzed to comparatively investigate the influence of glycosylation on Mr determination in the different instruments. In some cases, high deviations were found both among the methods and with regard to reference values. This article provides possible explanations for these findings.     

What Factors Determine Hierarchical Structure of Microbial Cellulose – Interplay among Physics,Chemistry and Biology –

A microbial cellulose film (pellicle), prepared by Acetorbactor xylinum, is a supramolecule system, absorbing a huge amount of water (99% by weight). To elucidate the affinity to water, we investigated the hierarchical structure in a pellicle by using ultra-small-angle and small-angle neutron scattering, observing a wide range of length scales from nm to µm. We successfully determined mass fractal dimensions for the amorphous structure, which hierarchically varies local concentration fluctuations, bundle and network, appeared as the length scale increases. On a basis of these findings, we discuss to address a question what factors determine the hierarchy in the microbial cellulose. This is a new topic of soft matter science, regarded as reaction-induced self-assembly in a non-equilibrium open system, therein soft matter physics, biochemistry and cell biology crucially interplay.     

Isolation, Purification, and Properties of α-Amylase from Bacillus subtilis-7A

Cultivation ofBacillus subtilis-7A on waste from alcohol production yielded an active extracellular enzyme -amylase with MW 75 kDa. The enzyme was isolated from the culture medium by 60% saturated ammonium sulfate and purified until homogeneous by gel filtration on Sephadex G-100 and ion-exchange chromatography on DEAE-cellulose. The optimum temperatures for the complex and purified enzyme are 30 and 50°C, respectively. The optimum activity for both preparations occurred at pH 6.5. The substrate specificity of the isolated preparations was studied.     

Density Functional Study on the Mechanism of Collision Reaction among Protons, N2 and Water Vapor

The mechanism of collision reaction among protons, N2 and water vapor was theoretically studied using Density Functional Theory. The geometries of reactants, transition states, intermediates and products were optimized at the B3LYP/6-311 G^** level by the BERNY gradient analysis method. Transition states and intermediates have been identified by vibrational frequency analysis. The relationship among reactants, intermediates, transition states and products was affirmed by IRC calculation. The variations of energy and geometry along the IRC-determined reaction paths were described. The possible reaction pathways were represented and the optimal one was decided from the viewpoint of energy.     

A review of: “ELECTRICAL PHENOMENA AT INTERFACES (Fundamentals,Measurements and Applications) A. Kitahara and A. Watanabe,Eds., Marcel Dekker,New York, 1984; hardbound, 463 pages, $79.50”

Electrokinetic analysis is a family of techniques for estimating the charge on solid surfaces, macroscopic particles, colloidal species, and macromolecular aggregates. Charges on surfaces are critical to the behavior of colloids, coatings, films, fibers, and many other materials in a variety of application areas. In addition to estimating the charge, electrokinetic analysis provides the means for measuring how the surrounding medium and imposed electric fields interact with extended flat surfaces, channels, pores, particles, and molecular aggregates to produce motion. Such motion has found wide use as a means for separating complex mixtures into their components. This section will present how measurements are made, some theoretical underpinnings, and examples of the instrumentation used for making measurements.     

o-Cresol,thiourea and formaldehyde terpolymer – A cation exchange resin

o-Cresol–thiourea–formaldehyde terpolymer resin was synthesized through the condensation of o-cresol and thiourea with formaldehyde in the mole ratio 1:3:5 in the presence of 2 M hydrochloric acid as a catalyst. The resulting copolymer was characterized with IR and ¹H NMR spectral data. The average molecular weight of the resin was determined by Gel permeation chromatography. Thermal study of the resin was carried out to calculate the activation energy (Ea), enthalpy of activation (H³), entropy of activation (S³), free energy of activation (G³), and pre-exponential factor (A) of various steps of thermal decomposition of the terpolymer. The Dharwadkar and Kharkhanavala method has been used to calculate thermal activation energy and thermal stability. The chelation ion-exchange properties were also studied with the batch equilibrium method. The chelation ion-exchange properties of the copolymer was studied for Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Pb²⁺ and Cd²⁺ ions. The resin was proved to be selective chelating ion-exchange copolymer for certain metals. The study was carried out over a wide pH range and in media of various ionic strengths.     

A Study of Synthesis, Immobilization and Catalytic Capability of Metalloporphyrin

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The open-close mechanism of M2 channel protein in influenza A virus:A computational study on the hydrogen bonds and cation-π interactions among His37 and Trp41

The M2 protein from influenza A virus is a tetrameric ion channel. It was reported that the permeation of the ion channel is correlated with the hydrogen bond network among His37 residues and the cation-π interactions between His37 and Trp41. In the present study,the hydrogen bonding network of 4-methyl-imidazoles was built to mimic the hydrogen bonds between His37 residues,and the cation-π interactions between 4-methyl-imidazolium and indole systems were selected to represent the interac-tions between His37 and Trp41. Then,quantum chemistry calculations at the MP2/6-311G level were carried out to explore the properties of the hydrogen bonds and the cation-π interactions. The calcula-tion results indicate that the binding strength of the N-H···N hydrogen bond between imidazole rings is up to -6.22 kcal·mol-1,and the binding strength of the strongest cation-π interaction is up to -18.8 kcal·mol-1(T-shaped interaction) or -12.3 kcal·mol-1(parallel stacking interaction). Thus,the calcu-lated binding energies indicate that it is possible to control the permeation of the M2 ion channel through the hydrogen bond network and the cation-π interactions by altering the pH values.     

Magnetic and thermoelectric properties of REMoN3 (RE = La,Ce, Pr,Nd, and Sm): A first-principles study

We investigated the magnetic and thermoelectric properties of REMoN₃ (RE = La, Ce, Pr, Nd, Sm) perovskites using the full potential linearized augmented plane wave (FP-LAPW) method. To overcome the problem of underestimation of electronic interaction, we employed the DFT + U approach to accurately map the electronic structure of these compounds. Our study shows an increasing trend in the magnetic moments with the increasing number of unpaired electrons in RE. Among these compounds, SmMoN₃ possesses a large magnetic moment, which is suitable for applications such as memory devices and sensors. Interestingly, all these perovskites display ferromagnetic behavior except CeMoN₃, which exhibits an antiferromagnetic nature. Furthermore, our analysis indicates n-type thermoelectric behavior in all these materials. The compound, namely PrMoN₃, exhibits a high figure of merit among REMoN₃, which can be improved by modifying the lattice sites.     

A general,Brønsted acid-catalyzed hetero-Michael addition of nitrogen,oxygen, and sulfur nucleophiles

[reaction: see text] Strong Br?nsted acids such as bis(trifluoromethanesulfon)imide catalyze the hetero-Michael addition of carbamates, alcohols, and thiols to alpha,beta-unsaturated ketones, alkylidene malonates, and acrylimides. Scope, reaction rates, and yields are superior to comparable Lewis acid-catalyzed processes.     

A calorimetric study of N,N-diethyl-N′-furoylthiourea and N,N-diisobutyl-N′-furoylthiourea

The standard ( p^o =  0.1 MPa) molar enthalpies of combustion in oxygen, at T =  298.15 K, were measured by rotative bomb calorimetry for crystalline N, N -diethyl- N^′-furoylthiourea, (2-C₄H₃O)CONHCSN(C₂H₅)₂, HFET, and N, N -diisobutyl- N^′-furoylthiourea, (2-C₄H₃O)CONHCSN(iso-C₄H₉)₂, HFIB. The standard molar enthalpies of sublimation of both HFET and HFIB were measured by high-temperature Calvet microcalorimetry. These values were used to derive the standard molar enthalpies of formation of the compounds, in their crystalline and gaseous phases.