An efficient rhodium(III)-catalyzed synthesis of 2H-chromene from N-phenoxyacetamides and cyclopropenes has been developed. The reaction represents the first example of using cyclopropenes as a three-carbon unit in rhodium(III)-catalyzed C(sp(2))-H activations.

Fast, sensitive, and simple methods for quantitative analysis of disparities in glycan expression between different biological samples are essential for studies of protein glycosylation patterns (glycomics) and the search for disease glycan biomarkers. Relative quantitation of glycans based on stable isotope labeling combined with mass spectrometric detection represents an emerging and promising technique. However, this technique is undermined by the complexity of mass spectra of isotope-labeled glycans caused by the presence of multiple metal ion adduct signals, which result in a decrease of detection sensitivity and an increase of difficulties in data interpretation. Herein we report a simplified quantitative glycomics strategy, which features nonreductive isotopic labeling of reducing glycans with either nondeuterated (d0-) or deuterated (d5-) Girard's reagent P (GP) without salts introduced and simplified mass spectrometric profiles of d0- and d5-GP derivatives of neutral glycans as molecular ions without complex metal ion adducts, allowing rapid and sensitive quantitative comparison between different glycan samples. We have obtained optimized GP-labeling conditions and good quantitation linearity, reproducibility, and accuracy of data by the method. Its excellent applicability was validated by comparatively quantitative analysis of the neutral N-glycans released from bovine and porcine immunoglobulin G as well as of those from mouse and rat sera. Additionally, we have revealed the potential of this strategy for the high-sensitivity analysis of sialylated glycans as GP derivatives, which involves neutralization of the carboxyl group of sialic acid by chemical derivatization.

The phase behavior of CO 2 -water-1-n-butyl-3-methyl-imidazolium tetrafluoroborate ([bmim][BF 4 ]) system at different conditions has been studied by the static method in the temperature range of 5 to 25 1C and pressures up to 16 MPa. At a fixed temperature or pressure there can exist four phases. However, this work focuses on the compositions of the phases in three-phase region (ionic liquid-rich phase, water-rich phase, CO 2 -rich phase). The phase diagrams at 20.0 1C and 5.0 MPa have been discussed in detail. At 20.0 1C the concentration difference of the ionic liquid (IL) in IL-rich phase and water-rich phase becomes larger and larger with increasing pressure. At 5.0 MPa, IL concentration in the IL-rich phase decreases with increasing temperature, while that in the waterrich phase increases as temperature rises, and the difference of IL concentration in the IL-rich phase and waterrich phase is sensitive to temperature. On the basis of phase equilibrium data the distribution coefficients of [bmim][BF 4 ] between IL-rich phase and water-rich phase are calculated, and separation of IL and water is discussed.

Developing electrolytes compatible with efficient and reversible cycling of electrodes is critical to the success of rechargeable Li metal batteries (LMBs). The Coulombic efficiencies and cycle lives of LMBs with ethylene carbonate (EC), dimethyl carbonate, ethylene sulfite (ES), and their combinations as electrolyte solvents show that in a binarysolvent electrolyte the extent of electrolyte decomposition on the electrode surface is dependent on the solvent component that dominates the solvation sheath of Li + . This knowledge led to the development of an EC-ES electrolyte exhibiting high performance for Li jj LiFePO 4 batteries. Carbonate molecules occupy the solvation sheath and improve the Coulombic efficiencies of both the anode and cathode. Sulfite molecules lead to desirable morphology and composition of the solid electrolyte interphase and extend the cycle life of the Li metal anode. The cooperation between these components provides a new example of electrolyte optimization for improved LMBs.Lithium ion batteries (LIBs) have boosted the development of portable electronics, electric vehicles, and smart grids in the past decades. [1] Nevertheless, their energy density is approaching the ceiling, which plagues their wider application in the future. The demand for more powerful batteries has motivated researchers to explore new chemistries beyond Li ion intercalation. Li metal electrodes operating upon the interconversion between Li 0 and Li + are a popular candidate for the anode. [2][3][4][5] Despite its ultrahigh specific capacity of 3860 mAh g À1 , the deposition/dissolution process often exhibits relatively low Coulombic efficiency (CE) owing to the high reactivity of Li metal with common electrolytes, which would corrode the Li anode and shorten its cycle life. [6][7][8][9] In our prior research, we found that the efficiency of a thick Li metal electrode is limited by the reactivity of the electrolyte and the cycle life is determined by the properties of the interphase layer. [10] Yet how the electrolyte species interact with the Li metal electrode under electrochemical conditions and affect the performance of Li metal batteries (LMBs) are not well understood. Solvation of the Li + ion is considered to be important to the chemistry at the electrode/ electrolyte interface. [11] Various techniques, including vibrational spectroscopy (FTIR or Raman), [12][13][14][15] electrospray ionization mass spectrometry, [16] and nuclear magnetic resonance spectroscopy [17,18] have been employed to study the structure of the solvation sheath and to understand the interfacial chemistry on the molecular level. It has been shown that the solvation structure is related to important phenomena in LIBs, including formation of the solid electrolyte interphase (SEI), [19] co-intercalation of solvent, [20] and effects of concentrated electrolyte. [14,15,21] As new electrolytes remain to be developed for efficient and stable LMBs, it is necessary to study the correlation of the Li + ion solvation with the performance of Li metal ...

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Details of the evolution of strategies toward convergent assembly of the histone deacetylase inhibiting natural product largazole exploiting γ,δ-unsaturated-α,β-epoxy-aldehydes and a thiazole-thiazoline containing ω-amino-acid are described. The initial N-heterocyclic carbene mediated redox amidation exploying these two types of building blocks representing largazole’s structural domains of distinct biosynthetic origin directly afforded the seco-acid of largazole. This was accomplished without any protecting groups resident upon either thioester bearing epoxy-aldehyde or the tetrapeptide. However, the ineffective production of largazole via the final macrolactonization led to an alternative intramolecular esterification/macrolactamization strategy employing the established two building blocks. This provided largazole along with its C2-epimer via an unexpected inversion of the α-stereocenter at the valine residue. The biological evaluation demonstrated that both largazole and 2-epi-largazole led to dose-dependent increases of acetylation of histone H3, indicating their potencies as class I histone deacetylase selective inhibitiors. Enhanced p21 expression was also induced by largazole and its C2 epimer. In addition, 2-epi-largazole displayed more potent activity than largazole in cell viability assays against PC-3 and LNCaP prostate cancer cell lines.

The double 1,3-dipolar cycloaddition of allenoates with nitrilimines has been achieved under mild reaction conditions, affording a variety of spirobidihydropyrazoles in moderate to excellent yields with excellent diastereoselectivities. The reaction diastereoselectively constructs double dihydropyrazole moieties and two chiral centers including a spiro carbon center.

Wellbore instability and formation collapse are crucial issues in the process of well excavation in the oil industry under extreme salinity and high-temperature conditions. This study demonstrates that a salt-responsive zwitterionic polymer brush (NS-DAD) based on modified nanosilica as a fluid-loss additive utilizing the anti-polyelectrolyte effect in water-based drilling fluids (WDFs) to overcome the wellbore instability caused by the failure of polyelectrolytes at extreme salinity and high temperature. Additionally, a nonionic polymer brush (NS-D), an anionic polymer brush (NS-DA), and a cationic brush (NS-DD) were also prepared for comparison. Compared with NS-D, NS-DA, and NS-DD, NS-DAD exhibited the anti-polyelectrolyte phenomenon, in which the sodium chloride electrolyte shields the electrostatic interaction in the molecular chain of the polyzwitterion and the molecular structure changes from a collapsed sphere to a more open helix. Macroscopically, NS-DAD exhibited a higher viscosity than NS-D, NS-DA, and NS-DD in saturated salt-based mud (SSBM). A typical “star-net” structure was observed between NS-DAD and the bentonite layer. Energy-dispersive spectroscopy (EDS) analysis of filter cakes showed that NS-DAD could significantly reduce the content of chloride and sodium ions in the bentonite layer. Therefore, compared with NS-D/SSBM, NS-DA/SSBM, and NS-DD/SSBM, NS-DAD/SSBM had excellent rheological properties, thermal stability, less fluid-loss volume, and thinner filter cake under extreme salinity and high-temperature conditions. The fluid-loss additive can be used to reduce the fluid-loss volume of WDFs in harsh reservoir conditions of high temperature and high salinity.