Short syntheses of (−)-clavaminol A and deacetyl (+)-clavaminol H

Concise stereoselective syntheses of (?)-clavaminol A and deacetyl (+)-clavaminol H have been achieved from simple starting materials. Highlights of the synthesis for (?)-clavaminol A include a highly diastereoselective chelation-controlled hydride reduction of an amino ketone to give the anti amino alcohol directly, and NaBH₄-mediated dehalogenation. The main synthetic approach for deacetyl (+)-clavaminol H features a highly diastereoselective chelation-controlled hydride reduction of the amino ketone to construct the anti amino alcohol and a palladium catalyzed hydrogenation reaction at the final step.     

Liquid crystal biosensor for detecting ischemia modified albumin

Research on Chemical Intermediates - Ischemia modified albumin detection has great significance in early diagnosis and treatment of myocardial ischemia. In this study, anti-IMA was immobilized on...     

A “Mitsubishi emblem” tetrauclear aluminum complex containing two unsymmetric N2O2‐ligands and a symmetric NO3‐ligand as initiator for polymerization of rac‐lactide

A novel hydroxy‐, methoxy‐, and phenoxy‐bridge “Mitsubishi emblem” tetranuclear aluminum complex ( 1 ) is synthesized from an unsymmetric amine‐pyridine‐bis(phenol) N₂O₂‐ligand (H₂L¹) and a symmetric amine‐tris(phenol) NO₃‐ligand (H₂L²). Two same configuration chiral nitrogen atoms are formed in the tetranuclear Al complex upon coordination of the unsymmetric tertiary amine ligand to central Al. Complex 1 initiates controlled ring‐opening polymerization (ROP) of rac‐lactide and afford polylactide (PLA) with narrow molecular weight distributions (M_w/M_n = 1.05–1.19). The analysis of ¹H NMR spectra of the oligomer indicates that the methoxy group is the initiating group and the ring‐opening polymerization of lactide follows a coordination‐insertion mechanism. The Homonuclear decoupled ¹H NMR spectroscopy suggests the isotactic‐rich chains is preferentially formed in PLA. The study on kinetics of the ROP of lactide reveals the homopropagation rate is higher than the cross‐propagation rate, which is in agreement with the observed isotactic selectivity in the ROP of rac‐lactide. The stereochemistry of the polymerization was also supported by activation parameters. The introduction of unsymmetric ligand H₂L¹ has an effect on stereoslectivity of polymerization. This result may be of interest for the design of multinuclear metal complex catalysts containing functionalized ligands. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2084–2091     

Existence results for second-order system with impulse effects via variational methods

In this paper, we investigate the positive solutions of a second-order system with impulse effects. By using critical point theory the existence result of positive solutions is obtained.     

Side-lobeless far-field spectrum of a short pulse from a circular aperture with Gaussian form of transmittance

The spectrum change of a Gaussian pulse in the far field is studied with the Fresnel diffraction integral when it is incident on an aperture with Gaussian form transmittance. It is found that the side-lobes of the diffracted spectral intensity, which exist in a normal circular aperture with unit transmittance, can be eliminated completely under such a condition. Also, the red shift and blue shift of the spectral intensity maximum of the incident pulse are presented.     

MR microscopy of micron scale structures

Magnetic resonance (MR) microscopy of up to 1–5-μm resolutions have been reported previously. The tested phantom structures, however, had widths one order of magnitude bigger than the reported resolutions, e.g., spherical beads or capillary tubes of tens-of-micron diameters or wall thicknesses have been imaged. In this study, we fabricated structures having a few micron widths on a silicon wafer and imaged them using our 1-μm-resolution MR microscopy at 14.1 T. Micron scale width structures were, for the first time, resolved by MR microscopy.