Anthracene array-type porous coordination polymer with host-guest charge transfer interactions in excited states

Confinement of electron donor guests affords an efficient, photo-induced charge transfer (CT) with the anthracene moieties of a porous coordination polymer.     

Stereoselective vinylogous Mukaiyama aldol reaction of α-haloenals

We have developed a high-yielding and stereoselective vinylogous Mukaiyama aldol reaction (VMAR) of α-haloenals. Contrary to the simple α,β-unsaturated aldehyde, α-haloenals were found to be reactive affording the corresponding VMAR adducts in excellent yields. Some transformations of VMAR adducts by Pd-mediated cross-coupling were also examined in order to demonstrate the synthetic utility of VMAR of α-haloenals.     

Kinetic study of proton-transfer reactions of phenylnitromethanes. Implication for the origin of nitroalkane anomaly

Measurements of rate constants and substituent effects for three important elementary steps of proton-transfer reactions of phenylnitromethane were reported. The Hammett ρ values for the deprotonation of ArCH(2)NO(2) with OH(-), protonation of ArCH═NO(2)(-) with H(2)O, and protonation of ArCH═NO(2)(-) with HCl were determined in aqueous MeOH at 25 °C. Comparison of these experimentally observed ρ values with those calculated at B3LYP/6-31G* revealed that aci-nitro species (ArCH═NO(2)H), which is formed on the O-protonation of ArCH═NO(2)(-), does not lie on the main route of the proton-transfer reaction. Analysis of the Br?nsted plot implies that the proton-transfer reaction of most XC(6)H(4)CH(2)NO(2) exhibits nitroalkane anomaly, but not for p-NO(2)C(6)H(4)CH(2)NO(2), and that the transition state charge imbalance is an origin of anomaly.     

Hydration structure in dilute hydrofluoric acid

We have performed the multistate empirical valence bond (MS-EVB) molecular dynamics simulations of a dilute hydrofluoric acid solution at ambient temperature to study the hydration structure associated with its weak acidity. The developed MS-EVB model showed reasonable agreement with experimental and previous ab initio molecular dynamics and reference interaction site model self-consistent field simulations for the free energy and structural properties. The local tetrahedral and translational order parameters around the fluorine atom significantly increase in the transition and product states of the HF dissociation reaction. This indicates that the angular and translational rearrangements of the hydrogen-bond topology are necessary especially around the fluorine atom. At the transition state of the proton transfer, the tetrahedral order parameters are very large, whereas the translational order parameters are not. This suggests that for the proton transfer to occur the large angular rearrangements of the hydrogen-bond topology are more necessary than the translational ones.     

Specific isolation of N-terminal fragments from proteins and their high-fidelity de novo sequencing

A new method to determine N-terminal amino acid sequences of multiple proteins at low pmol level by a parallel processing has been developed. The method contains the following five steps: (1) reduction, S-alkylation and guanidination for targeted proteins; (2) coupling with sulfosucccimidyl-2-(biotinamido)ethyl-1,3-dithiopropionate(sulfo-NHS-SS-biotin) to N(alpha)-amino groups of proteins; (3) digestion of the modified proteins by an appropriate protease; (4) specific isolation of N-terminal fragments of proteins by affinity capture using the biotin-avidin system; (5) de novo sequence analysis of peptides by MALDI-TOF-/MALDI-TOF-PSD mass spectrometry with effective utilization of the CAF (chemically assisted fragmentation) method.1 This method is also effective for N-terminal sequencing of each protein in a mixture of several proteins, and for sequencing components of a multiprotein complex. It is expected to become an essential proteomics tool for identifying proteins, especially when used in combination with a C-terminal sequencing method.     

镧系四元混合配体配合物[Ce(CH2ClCOO)2(NO3)(phen)(H2O)]2的晶体结构、芳环堆积效应和2D氢键网络

The quaternary complex, ［Ce(CH2ClCOO)2(NO3)(phen)(H2O)］2, was synthesized. Interestedly, the title compound is a dimer comparing with the 1D polymer ［La(CH2ClCOO)2(NO3)(phen)*(H2O)］n and powder compound ［Nd(CH2ClCOO)2(NO3)(phen)］. In the title compound there is a monodentate NO-3, which is a first example in the all synthesized quaternary mixed anion complexes, and the NO-3 extended the complex into a 2D network with water from other molecules by inter-molecular hydrogen bonds. The intermolecular hydrogen bonds lead to the weaker Ce—O(COO), Ce—O(NO3) and Ce—N bonds comparing with other quaternary mixed anion complexes of cerium. Also the stacking effect, which makes the compound more stable in the situation of weaker Ce—O and Ce—N bonds, was first found in the series compounds.     

Studies on the constituents of Catalpa species. VI. Monoterpene glycosides from the fallen leaves of Catalpa ovata G. Don.

Five new monoterpene glycosides, ovatolactone 7-O-(6'-O-p-hydroxybenzoyl)-beta-D-glucopyranoside, ovatic acid methyl ester 7-O-(6'-O-p-hydroxybenzoyl)-beta-D-glucopyranoside, 7-O-p-hydroxybenzoylovatol 1-O-(6'-O-p-hydroxybenzoyl)-beta-D-glucopyranoside, 6'-O-p-hydroxybenzoylcatalposide and (2E,6R)-2,6-dimethyl-8-hydroxy-2-octenoic acid 8-O-[6'-O-(E)-p-coumaroyl]-beta-D-glucopyranoside were isolated from the fallen leaves of Catalpa ovata G. Don. Their structures were determined by extensive spectroscopic studies and syntheses.     

Preparation of thermo- and redox-responsive branched polymers composed of three-armed oligo(ethylene glycol)

We herein report the preparation of thermo- and redox-responsive branched polymers by the condensation reaction of three-armed oligo(ethylene glycol) (trisOEG) and cystamine (CA). The prepared branched polymers exhibited a soluble–insoluble transition at a lower critical solution temperature (LCST) and formed coacervate droplets through a liquid–liquid phase separation process. We then demonstrated control of the LCSTs of the branched polymers by varying the feed ratio of CA and the surrounding salt concentration close to body temperature. In addition, the trisOEG-cys _x polymer formed coacervate droplets above the LCST, in which hydrophobic molecules were condensed. The redox response of the branched polymers was also investigated. Interestingly, the branched polymers degraded to low-molecular-weight materials (i.e., trisOEG) in the presence of dithiothereitol as a reducing agent through cleavage of the disulfide bond of CA. This facile preparation of branched polymers is expected to be valuable in the context of functional biomedical materials and modifiers for materials surfaces, such as the bases for drug delivery carriers and separation materials. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2623–2629     

Efficient CO2 Removal for Ultra‐Pure CO Production by Two Hybrid Ultramicroporous Materials

Removal of CO₂ from CO gas mixtures is a necessary but challenging step during production of ultra‐pure CO as processed from either steam reforming of hydrocarbons or CO₂ reduction. Herein, two hybrid ultramicroporous materials (HUMs), SIFSIX‐3‐Ni and TIFSIX‐2‐Cu‐i , which are known to exhibit strong affinity for CO₂, were examined with respect to their performance for this separation. The single‐gas CO sorption isotherms of these HUMs were measured for the first time and are indicative of weak affinity for CO and benchmark CO₂/CO selectivity (>4000 for SIFSIX‐3‐Ni ). This prompted us to conduct dynamic breakthrough experiments and compare performance with other porous materials. Ultra‐pure CO (99.99 %) was thereby obtained from CO gas mixtures containing both trace (1 %) and bulk (50 %) levels of CO₂ in a one‐step physisorption‐based separation process.     

A practical synthesis of archaeosine and its base

A practical synthetic route to 7-formamidino-7-deazaguanosine (archaeosine), a hypermodified nucleoside observed in archaeal tRNA, has been developed, which involves the addition of hydroxylamine to the cyano group of 7-cyano-7-deazaguanosine (preQ₀-nucleoside) and a subsequent Pd-catalyzed hydrogenation. PreQ₀-nucleoside was obtained from an optimized β-selective glycosylation developed by Hocek et al. The corresponding archaeosine base was subsequently synthesized in high yield from its precursor 7-cyano-7-deazaguanine (preQ₀).