Palladium‐Catalyzed ortho‐Selective CH Deuteration of Arenes: Evidence for Superior Reactivity of Weakly Coordinated Palladacycles

We disclose a protocol for the palladium‐catalyzed ortho‐selective C? H deuteration of arenes. Phenylacetic acids and benzoic acids are suitable substrates for this reaction. This reaction offers a catalytic route to ortho‐deuterated phenylacetic acids and benzoic acids and demonstrates the sharp difference in reactivity of palladacycle intermediates held together by weak and strong coordination.     

Selectfluor and NFSI exo‐Glycal Fluorination Strategies Applied to the Enhancement of the Binding Affinity of Galactofuranosyltransferase GlfT2 Inhibitors

Two complementary methods for the synthesis of fluorinated exo‐glycals have been developed, for which previously no general reaction had been available. First, a Selectfluor‐mediated fluorination was optimized after detailed analysis of all the reaction parameters. A dramatic effect of molecular sieves on the course of the reaction was observed. The reaction was generalized with a set of biologically relevant furanosides and pyranosides. A second direct approach involving carbanionic chemistry and the use of N‐fluorobenzenesulfonimide (NFSI) was performed and this method gave better diastereoselectivities. Assignment of the Z/E configuration of all the fluorinated exo‐glycals was achieved based on the results of HOESY experiments. Furthermore, fluorinated exo‐glycal analogues of UDP‐galactofuranose were prepared and assayed against GlfT2, which is a key enzyme involved in the cell‐wall biosynthesis of major pathogens. The fluorinated exo‐glycals proved to be potent inhibitors as compared with a series of C‐glycosidic analogues of UDP‐Galf, thus demonstrating the double beneficial effect of the exocyclic enol ether functionality and the fluorine atom.     

Three elementary proofs of the goldberg-straus theorem on numerical radii

Three elementary proofs of the positive definiteness of the A-numerical radius, as defined by Goldberg and Straus, are given and a stronger result concerning exterior powers is conjectured     

Vinyl quinones as Diels-Alder dienes: concise synthesis of (-)-halenaquinone

A concise asymmetric synthesis of (-)-halenaquinone is described. The synthesis features a diastereoselective Heck cyclization to set a quaternary center as well as a novel intramolecular inverse-electron-demand Diels-Alder reaction involving a vinyl quinone. The synthesis is highly convergent and features a minimal amount of protecting group manipulations.     

Enzymatic Oxy- and Amino-Functionalization in Biocatalytic Cascade Synthesis: Recent Advances and Future Perspectives

Biocatalytic cascades are a powerful tool for building complex molecules containing oxygen and nitrogen functionalities. Moreover, the combination of multiple enzymes in one pot offers the possibility to minimize downstream processing and waste production. In this review, we illustrate various recent efforts in the development of multi-step syntheses involving C−O and C−N bond-forming enzymes to produce high value-added compounds, such as pharmaceuticals and polymer precursors. Both in vitro and in vivo examples are discussed, revealing the respective advantages and drawbacks. The use of engineered enzymes to boost the cascades outcome is also addressed and current co-substrate and cofactor recycling strategies are presented, highlighting the importance of atom economy. Finally, tools to overcome current challenges for multi-enzymatic oxy- and amino-functionalization reactions are discussed, including flow systems with immobilized biocatalysts and cascades in confined nanomaterials.     

A simple purification protocol for the detection of peptide hormones in the hemolymph of individual insects by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

The endocrine system of insects is largely based on peptide hormones. Nevertheless, an unequivocal chemical demonstration of the occurence in the hemolymph (the 'insect blood') is still lacking for most if not all insect peptide hormones, although this is the only way to prove their hormonal status. Focusing on peptides released during ecdysis behavior of the tobacco hornworm Manduca sexta, we developed a purification protocol based on ultrafiltration and a single reversed-phase high-performance liquid chromatography (RP-HPLC) step that for the first time allowed the mass spectrometric and chemical identification of a peptide hormone in the hemolymph of single specimens. Since this method is simple, relatively cheap and fast, it should be useful for routine endocrinological analyses and for monitoring peptide release during different physiological conditions and behaviors in insects.     

Vanadium bromoperoxidase from Delisea pulchra: enzyme-catalyzed formation of bromofuranone and attendant disruption of quorum sensing

Vanadium bromoperoxidase was isolated and cloned from the marine red alga Delisea pulchra. This enzyme catalyzes the bromolactonization of 4-pentynoic acid forming 5E-bromo-methylidenetetrahydro-2-furanone, a compound which is shown herein to inhibit quorum sensing in the engineered reporter strain, Agrobacterium tumefaciens NTL4.     

Spectroscopic analysis of packaging concepts for high-power diode laser bars

Double-side cooled high-power diode laser bars packaged by different techniques on different types of passive heat sinks are analyzed in terms of packaging-induced strain. Reference data from standard devices being single-side cooled only and packaged by conventional soft and hard soldering are also presented. Thermal profiling across the devices complements the results. The most suitable packaging architecture and technique for double-side cooled bars is identified. Measurements of the laser emission near field and electroluminescence pattern provide direct reference to the functionality of the devices. Furthermore, a type of cross calibration of the methods used for strain analysis is made, since all techniques are applied to the same set of bars. This involves micro photoluminescence, micro Raman, and degree-of-polarization electroluminescence spectroscopy.     

Sub‐microsecond‐resolved multi‐speckle X‐ray photon correlation spectroscopy with a pixel array detector

Small‐angle X‐ray photon correlation spectroscopy (XPCS) measurements spanning delay times from 826 ns to 52.8 s were performed using a photon‐counting pixel array detector with a dynamic range of 0–3 (2 bits). Fine resolution and a wide dynamic range of time scales was achieved by combining two modes of operation of the detector: (i) continuous mode, where data acquisition and data readout are performed in parallel with a frame acquisition time of 19.36 µs, and (ii) burst mode, where 12 frames are acquired with frame integration times of either 2.56 µs frame^?1 or 826 ns frame^?1 followed by 3.49 ms or 1.16 ms, respectively, for readout. The applicability of the detector for performing multi‐speckle XPCS was demonstrated by measuring the Brownian dynamics of 10 nm‐radius gold and 57 nm‐radius silica colloids in water at room temperature. In addition, the capability of the detector to faithfully record one‐ and two‐photon counts was examined by comparing the statistical distribution of photon counts with expected probabilities from the negative binomial distribution. It was found that in burst mode the ratio of 2 s to 1 s is markedly smaller than predicted and that this is attributable to pixel‐response dead‐time.