Anionic Sublattices in Halide Solid Electrolytes: A Case Study with the High-Pressure Phase of Li3ScCl6

The Li₃MX₆ compounds (M=Sc, Y, In; X=Cl, Br) are known as promising ionic conductors due to their compatibility with typical metal oxide cathode materials. In this study, we have successfully synthesized γ-Li₃ScCl₆ using high pressure for the first time in this family. Structural analysis revealed that the high-pressure polymorph crystallizes in the polar and chiral space group P6₃mc with hexagonal close-packing (hcp) of anions, unlike the ambient-pressure α-Li₃ScCl₆ and its spinel analog with cubic closed packing (ccp) of anions. Investigation of the known Li₃MX₆ family further revealed that the cation/anion radius ratio, r_M/r_X, is the factor that determines which anion sublattice is formed and that in γ-Li₃ScCl₆, the difference in compressibility between Sc and Cl exceeds the ccp r_M/r_X threshold under pressure, enabling the ccp-to-hcp conversion. Electrochemical tests of γ-Li₃ScCl₆ demonstrate improved electrochemical reduction stability. These findings open up new avenues and design principles for lithium solid electrolytes, enabling routes for materials exploration and tuning electrochemical stability without compositional changes or the use of coatings.     

Stereoselective one-pot three-component coupling approach towards the synthesis of the AC ring system of taxanes

The stereoselective one-pot three-component coupling reaction was accomplished by 1,4-addition of the protected cyanohydrin ether 9f to cyclohexenone 10g and subsequent addition of the resulting enolate to formaldehyde in high yield for the formation of the AC ring system of taxanes. We found that the bulky substituents at the 10-position in the A ring prevent the desired 1,4-addition. Similarly, the bulky trialkylsiloxy groups at the 4-position in the C ring prevent the 1,4-addition and electron-donating alkoxy groups at the same position induce the undesired retro-Michael reaction.     

H NMR aided elucidation of products derived from photodegradation of ethyl 3-azido-4,6-difluorobenzoate in 2,2,2-trifluoroethanol

The major products formed upon photolysis of ethyl 3-azido-4,6-difluorobenzoate in 2,2,2-trifluoroethanol-d₃ has been elucidated by ¹H NMR analysis of the product mixture. Among the products formed and structurally elucidated was a hitherto unreported product formed during photolysis of aryl azides, namely azoxybenzene 19. The structural assignments of the major components of the reaction mixture were aided by comparison with ¹H NMR data from synthetic reference materials and compound isolation. MS, MS/MS, and HPLC analysis as well as UV spectroscopy was also employed in order to confirm and aid the structural analysis.     

Molecular weight characterization of poly[(R)-3-hydroxybutyrate] synthesized by genetically engineered strains of Escherichia coli

This study investigated the relationship of growth conditions, host strains and molecular weights of poly[(R)-3-hydroxybutyrate] [P(3HB)] synthesized by genetically engineered Escherichia coli. Various PHA synthases belonging to types I-IV enzymes were expressed in E. coli JM109 under the same experimental conditions, and the molecular weights of the polymers were characterized by gel permeation chromatography. The results demonstrate that P(3HB) polymers have varied molecular weights and polydispersities dependent on the characteristics of the individual PHA synthase employed. P(3HB) with high number-average molecular weights (M_n) [(1.5-4.0) × 10⁶] and narrow polydispersities (1.6-1.8) were synthesized by PHA synthases from Ralstonia eutropha (type I), Delftia acidovorans (type I) and Allochromatium vinosum (type III). Contrary to these, P(3HB) with relatively low M_n [(0.17-0.79) × 10⁶] and broad polydispersities (2.2-9.0) were synthesized by PHA synthases from Aeromonas caviae (type I), Pseudomonas sp. 61-3 (type II) and Bacillus sp. INT005 (type IV). Furthermore, the molecular weights of P(3HB) synthesized under various culture conditions, in various hosts of E. coli and by mutants of PHA synthase were characterized. It was found that, in addition to culture pH [Kusaka et al. Appl Microbiol Biotechnol 1997;47:140], other variances such as culture temperature, host strain and use of mutants are effective in changing polymer molecular weight.     

Modeling on debonding dynamics of pressure-sensitive adhesives

We propose a simple mechanical model describing viscoelasticity and cavitation during the debonding process in pressure-sensitive adhesives (PSA). Our calculation qualitatively reproduces typical stress-strain curves in the probe-tack test, such as the steep stress maxima and the following plateau region. It is shown that in the thin-film geometry the stress-strain curve is essentially determined by the cavities created by the large negative pressure. Effects of pre-existent air bubbles due to surface roughness are also discussed.     

One‐Handed Helical Screw Direction of Homopeptide Foldamer Exclusively Induced by Cyclic α‐Amino Acid Side‐Chain Chiral Centers

Chiral cyclic α,α‐disubstituted amino acids, (3S,4S)‐ and (3R,4R)‐1‐amino‐3,4‐(dialkoxy)cyclopentanecarboxylic acids ((S,S)‐ and (R,R)‐Ac₅c^dOR; R: methyl, methoxymethyl), were synthesized from dimethyl L ‐(+)‐ or D ‐(?)‐tartrate, and their homochiral homoligomers were prepared by solution‐phase methods. The preferred secondary structure of the (S,S)‐Ac₅c^dOMe hexapeptide was a left‐handed (M) 3₁₀ helix, whereas those of the (S,S)‐Ac₅c^dOMe octa‐ and decapeptides were left‐handed (M) α helices, both in solution and in the crystal state. The octa‐ and decapeptides can be well dissolved in pure water and are more α helical in water than in 2,2,2‐trifluoroethanol solution. The left‐handed (M) helices of the (S,S)‐Ac₅c^dOMe homochiral homopeptides were exclusively controlled by the side‐chain chiral centers, because the cyclic amino acid (S,S)‐Ac₅c^dOMe does not have an α‐carbon chiral center but has side‐chain γ‐carbon chiral centers.     

Elucidation of the Active Conformation of Vancomycin Dimers with Antibacterial Activity against Vancomycin‐Resistant Bacteria

Covalently linked vancomycin dimers have attracted a great deal of attention among researchers because of their enhanced antibacterial activity against vancomycin‐resistant strains. However, the lack of a clear insight into the mechanisms of action of these dimers hampers rational optimization of their antibacterial potency. Here, we describe the synthesis and antibacterial activity of novel vancomycin dimers with a constrained molecular conformation achieved by two tethers between vancomycin units. Conformational restriction is a useful strategy for studying the relationship between the molecular topology and biological activity of compounds. In this study, two vancomycin units were linked at three distinct positions of the glycopeptide (vancosamine residue (V), C terminus (C), and N terminus (N)) to form two types of novel vancomycin cyclic dimers. Active NC‐VV‐linked dimers with a stable conformation as indicated by molecular mechanics calculations selectively suppressed the peptidoglycan polymerization reaction of vancomycin‐resistant Staphylococcus aureus in vitro. In addition, double‐disk diffusion tests indicated that the antibacterial activity of these dimers against vancomycin‐resistant enterococci might arise from the inhibition of enzymes responsible for peptidoglycan polymerization. These findings provide a new insight into the biological targets of vancomycin dimers and the conformational requirements for efficient antibacterial activity against vancomycin‐resistant strains.     

Fundamental investigation on interaction between hexafluoroisopropylalcohol‐containing styrene and photochemical acid generator for rationale design of photoresist system

This article presents the effect of some ionic photochemical acid generators (PAGs) to inhibit the dissolution of hexafluoroisopropylalcohol (HFA)‐containing polystyrene to an aqueous alkaline developer, which is a highly important effect in photoresist application to enhance resolution of patterning. The dissolution inhibiting factors and mechanisms were investigated by evaluating the solubility and the ¹H‐NMR analysis of OH proton in HFA moiety. The dissolution inhibition effect was enhanced when the structures of PAGs fulfill some requirements: (a) their anions should have higher basicity and smaller van der Waals volume; (b) their cations should be stabilized by conjugation with electron‐rich aromatics. In the dissolution inhibition, the HFA moiety interacts with the anionic part of PAGs liberated from the electrostatic interaction with the counter cation. These interactions were predicted and quantified by DFT calculations using Gaussian 09, leading to the rational designs of PAGs with higher dissolution inhibiting effect in photoresist systems. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 531–538     

Neutron spin rotation and P-violation

A new apparatus to measure the neutron spin rotation due to interaction with matter has been developed at KEK. The present apparatus enables us to measure the parity violating neutron spin rotation in the p-wave resonance in the energy region of eV.On leave from Tohoku University.     

A note on stochastic phase lockings in a relaxation oscillator forced by a sine input with additive noise

Summary Noise effects on phase lockings in a system consisting of a piecewise-linear van der Pol relaxation oscillator driven by a periodic input are studied. The problem of finding the period of the oscillator is reduced to the first-passage-time problem of the Ornstein-Uhlenbeck process with time-varying boundary. Using the probability density functions of the first-passage time, the operator which governs a transition of an input phase density after one cycle of the oscillator is defined. Phase lockings in a stochastic sense are investigated on the basis of the density evolution by the operator. Paper presented at the International Workshop ?Fluctuations in Physics and Biology: Stochastic Resonance, Signal Processing and Related Phenomena?, Elba, 5–10 June 1994.