碳糖苷合成的新进展

本文介绍了近几年来有关碳糖苷合成的最新进展, 包括亲电取代、亲核糖取代、过渡金属催化、异头碳自由基反应、重排和环加成反应以及糖环形成反应等。     

食品中维生素D与25-羟基维生素D检测技术及含量分布研究进展

维生素D是一种对于维持人体健康具有重要作用的脂溶性维生素,25-羟基维生素D是其在人体内循环和存储的主要形式。食品中维生素D和25-羟基维生素D前处理的通常采用碱皂化、有机溶剂提取、固相萃取或者半制备色谱净化;其测定方法多为放射免疫法和液相色谱法。液相色谱串联质谱凭借高灵敏度和高准确度,目前在食品中维生素D和25-羟基维生素D测定中发挥重要作用。近年来二维液相色谱和超高效超临界流体色谱由于其强大的分离能力,在食品中维生素D和25-羟基维生素D的分析中表现出强大的潜力。该文综述了近年来食品中维生素D和25-羟基维生素D的检测方法及二者在动物食品和植物食品中的含量分布研究,以期为建立适合不同食物样品的测定方法,指导居民合理膳食,进行膳食摄入量评估等研究工作提供参考。     

A first-principles study of (R)- and (S)-PPA Molecules on Cu(111)

The adsorption of (R)- and (S)-2-phenylpropionamide (PPA, C(9)H(11)ON) molecules on a Cu(111) surface has been investigated using the density functional method with supercell models. The adsorption orientations of both (R)- and (S)-PPA molecules on the surface are the same: the phenyl rings are approximately parallel to the Cu(111) surface and positioned in the hollow sites, the amino and methyl groups occupy two-bridge sites, and the carbonyl occupies the top site. After the adsorption, the bond lengths in the two enantiomers are almost unchanged, but the changes for two dihedral angles show differences, especially for (R)-PPA molecule. The first angles between the (N,C9,C7) plane and the (C9,C7,C6) plane are 19.4 and 0.7 degrees for (R)- and (S)-PPA molecules, respectively, and the second angles between the (C8,C7,C6) plane and the (C7,C6,C5) plane are 74.8 and 0.4 degrees for (R)- and (S)-PPA molecules, respectively. The adsorption energies of (R)- and (S)-PPA molecules are calculated to be -34 and -26 kJ mol(-1), respectively. The simulated scanning tunneling microscopy (STM) images of (R)- and (S)-PPA molecules on the Cu(111) surface display different features and are coincident with the experimental ones. The interaction between the adsorption molecule and the metal surface is found to be responsible for the discrimination of (R)- and (S)-PPA molecules on the surface.     

Clean Aerobic Liquid Oxidation of Aldehydes with Solid Catalyst

Clean liquid oxidation of aldehydes can be accomplished using solid catalyst in the presence of molecular oxygen at room temperature, which is a valuable alternative to traditional counterparts.     

Syntheses of Some New Group 4 non-Cp Complexes Bearing Schiff-base, Thiophene Diamide Ligands Respectively and Their Catalytic Activities for α-Olefin Polymerization

Introduction Tremendous advances have been witnessed during the last decade in the syntheses and application of Group 4 metal complexes because of the motivity which comes from both academic and industrial field. Among them, studies have been dominated by the complexes supported by bis or mono cyclopentadienyl ligands, such as Cp2MX2 or half sandwich amide (CGC) com-plexes.1-6 At that time chemists paid a little attention to the non-cyclopentadienyl complexes, but in recent years, many chem…     

Optically active sum frequency generation from molecules with a chiral center: amino acids as model systems

With amino acids as model systems, optically active sum frequency generation (OA-SFG) was used to probe the chirality of molecules with a chiral center and an intrinsically achiral chromophore in isotropic solution for the first time. Like that of circular dichroism (CD), the OA-SFG's near electronic resonance originates from the extrachromophoric chiral perturbation on the carboxyl chromophore. The difference in the relative strengths of OA-SFG and CD among different amino acids can be explained by the difference in the details of perturbations.     

Synthesis of a Novel Core-shell Type Acrylic-polyurethane Hybrid Emulsion Containing Siloxane and Fluorine as well as Water and the Oil Resistances of Cured Film

Aqueous acrylic-polyurethane dispersions have become one of the major types of materials used in coating, paint and adhesive industries, because of excellent properties and environmental advantages1-5. However, some properties for cured film such as water…     

An Interesting Approach to Bis-calix[5]arene Analogue from Calix[6]arene

Calix [n] arenas {n = 4, 6 or 8} are easily prepared from formaldehyde and para-substituted phenols via cyclic condensation under alkaline conditions in one step. It is not surprising that the calyx [n] arene (n = 4, 6, 8) chemistry has been developing very rapidly during the latest 20 years1. However, it is not the case for calixarenes with odd benzene rings (for example, n = 5). The yield of p-tert-butylcalix [5] arene synthesized in one-step from p-tert-butylphenol and formaldehyde was a…     

Synthesis of Molecularly Imprinted Polymer Particles by Suspension Polymerization in Silicon Oil

Molecular imprinting is a method to prepare polymers with recognition site of desired and predetermined selectivity1. Molecularly imprinted polymers (MIP) are prepared by copolymerizing functional and cross-linking monomers in the presence of a molecular …     

Stereoisomerism and complexation behaviour of functionalized p-tert-calix[6]-1,4-2,5-biscrown-4

p-tert-Calix[6]-1,4-2,5-biscrown-4 was subjected to functionalization by benzyl bromide or ethyl bromoacetate. Two pairs of disubstituted calix[6]biscrown stereoisomers were obtained. Their structures had been deduced from ¹H NMR and ESI-MS (electrospray ionization mass spectroscopy). One of the bisethyloxycarbonylmethylated derivatives 3a was further investigated by X-ray crystallographic analysis. Two-phase extraction experiments indicated that bisethyloxycarbonylmethylated derivatives exhibited high Cs⁺/Na⁺ selectivity. By ESI-MS and ¹H NMR experiments it was confirmed that 3a formed 1:1 complex with Cs⁺.