Concise synthesis of anti-HIV-1 active (+)-inophyllum B and (+)-calanolide A by application of (-)-quinine-catalyzed intramolecular oxo-Michael addition

(-)-Quinine-catalyzed intramolecular oxo-Michael addition (IMA) of 7-hydroxy-5-methoxy-8-tigloylcoumarins was developed for the enantioselective construction of 2,3-dimethyl-4-chromanone systems in the context of the asymmetric synthesis of anti-HIV-1 active Calophyllum coumarins. Combination of the IMA and MgI(2)-assisted demethylation of the 5-methoxy group along with isomerization of the formed chromanone systems as key steps successfully led to the concise synthesis of (+)-inophyllum B and (+)-calanolide A, possible candidates for AIDS drugs. Further examination of the asymmetric IMA with cinchona alkaloids lacking a methoxy group on the quinoline skeleton suggested the influence of the methoxy substituent on stereoselectivity at the stereogenic centers of the chromanone systems.     

Characterization and decomposition mechanism of an unusual nickel, thiocyanate and 4-methylpyridine polymeric complex

The synthesis, characterization, and thermal decomposition of the [Ni(SCN)₂(H⁺SCN)₂(4-mepy)₂] compound with an octahedral structure in polymeric chain were reported, in which SCN groups form bridges among Ni(II) ions. The compound decomposes in water resulting in a pH<4 solution. The FT-IR spectrum presented doublet bands at 2117; 2128 cm⁻¹, 788; 773 cm⁻¹ assigned to ν(C---N) and ν(C---S) stretching modes, respectively, and δ(SCN) deformation modes at 468; 476 cm⁻¹. The Raman spectrum of the compound presented the ν(C---N) stretching as a strong doublet at 2122; 2128 cm⁻¹, ν(C---S) at 783; 770 cm⁻¹, and δ(SCN) at 468; 477 cm⁻¹. No significant changes were observed in the 4-mepy ligand bands compared with the vibrational frequencies of the pure compound or the compound in aqueous solution 0.2 mol l⁻¹. The crystal UV–vis reflectance spectrum presented two bands centered in 626 and 424 nm tentatively assigned to the d→d type transitions, ³A_2g→³T_1g and ³A_2g→³T_1g, for a symmetry close to O_h. The TG curve showed a mass loss between 120 and 200 °C assigned to the loss of the two 4-mepy molecules; from 200 to 265 °C, the loss of the two H⁺SCN groups; and from 265 to 450 °C, the loss of the two SCN groups that formed the bridges among the nickel atoms. Based on these mass loss data, a mechanism of thermal decomposition for the compound was proposed.     

Approaches to dioxin analysis by HRGC-HRMS and hybrid HRGC-MS-MS

A hybrid mass spectrometer with an EBQQ configuration was used to investigate two approaches to trace dioxin analysis: high resolution gas chromatography – high resolution mass spectrometry (HRGC-HRMS) and high resolution gas chromatography – mass spectrometry – mass spectrometry (HRGC-MS-MS). It is shown that selected ion monitoring (SIM) HRGC-HRMS exhibits better selectivity for dioxins separated on a cyanopropyl column than is otherwise obtained under medium resolution mass spectrometry (3,000 resolution), while optimization of conditions for HRGC-MS-MS allowed the observation of 350 femtograms of the highly toxic 2,3,7,8-TCDF at a S/N ratio of 5:1. Both methods were applied to environmental samples with good results.     

Concise total synthesis of flavone C-glycoside having potent anti-inflammatory activity

The total synthesis of anti-inflammatory active flavone C-glycoside isolated from oolong tea extract is achieved. Introducing a C-glucosyl moiety to an aryl system and constructing a fused tetracyclic ring characteristic to this natural product were conducted based on the O-to-C rearrangement of sugar moiety and the successive intramolecular Mitsunobu reaction, respectively. This concise and efficient synthetic pathway is applicable to the large-scale synthesis of target flavone and for constructing a large library of related compounds.     

Effect of an electric field on defects in a nematic liquid crystal with variable surface anchoring

We report experimental studies on defects in a nematic liquid crystal with negative dielectric anisotropy mounted in a cell with perfluoropolymer-coated surfaces. The sample exhibits a discontinuous anchoring transition from planar to homeotropic on cooling at zero or a small electric field, and above a cross-over voltage a continuous ‘inverse Freedericksz transition’, at which the director starts tilting in opposite directions at the two surfaces. Defects of strength ±1/2 are either annihilated or expelled when the director tilts. On the other hand, disclination lines of ±1 which end in partial point defects (boojums) at the surfaces in the planar alignment regime acquire point defects of strength ±1 at the midplane of the cell when the director tilts. At a low enough temperature, the homeotropic anchoring becomes strong, and an electric field above the Freedericksz threshold generates the usual umbilic defects, which follow the dynamic scaling laws found in earlier studies.     

Non‐contact evaluation of the electrical conductivity of thin metallic films by eddy current microscopy

An eddy current microscopy technique to evaluate the electrical conductivity of thin metallic films in a non‐contact manner is reported. A narrow track formed in an approximately 100 nm thick Au film was prepared, and a Co–Cr coated magnetic tip was driven to oscillate above the track both with and without current passing through the track. Despite the absence of current, the electromagnetic interaction between the tip and the stray magnetic field from the track gave rise to a phase delay in the probe. This was due to an eddy current being induced within part of the track. Moreover, measurements of the phase change in the probe oscillation for different metallic films with thicknesses of about 100 nm found this to be proportional to the electrical conductivity of the film. Finally, the electrical conductivity of an Al film was evaluated using the eddy current microscopy technique. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis and crosslinking reaction of a novel polymer containing benzoxazine and phenyleneethynylene moieties in the main chain

A novel polymer, poly( 1 ) containing benzoxazine and phenyleneethynylene moieties in the main chain with number‐average molecular weights ranging from 1400 to 9800 was obtained quantitatively by the Sonogashira–Hagihara coupling polymerization of the corresponding iodophenyl‐ and ethynylphenyl‐substituted monomer 1 . Poly( 1 ) was heated at 200 °C under N₂ for 2 h to obtain the cured polymer, poly( 1 )′ via the ring‐opening polymerization of the benzoxazine moieties. The structures of the polymer before and after curing were confirmed by ¹H‐NMR, IR, and UV–vis absorption and reflectance spectroscopies. Poly( 1 )′ was thermally more stable than monomer 1 and poly( 1 ). A specimen was prepared from a mixture of poly( 1 ) and phenol‐diaminodiphenylmethane type benzoxazine 2 by heating at 200 °C for 2 h under N₂. The poly( 1 )/ 2 resin was thermally stable than bisphenol‐A type benzoxazine resin 3 . Poly( 1 ) exhibited XRD peaks corresponding to the d‐spacings of 1.26–0.98 and 0.40 nm, assignable to the repeating monomer unit and alignment of polymer molecules, respectively. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2581–2589