4,5,6-三取代-2H-吡喃-2-酮的简便合成法

2H-吡喃-2-酮及其衍生物是有机合成的蓬要中间体。对于它们的合成已有许多报道,例如利用烯醇醚或烯醇砖醚与丁酰氯反应;羰基化合物与甲氧亚甲螭丙二酸二甲酯反应;α-苯基丙醛酸酯与丙酮的成环缩合2,6-二氯-3-三氯甲基吡啶与亚甲基丁二酸酯的反应,邻氰基苯乙炔、二苯乙二酮和丙酮的反应。但上述方法往往原料较难得到,产率较低或操作麻烦。     

Comparison of the Hartree-Fock,Møller-Plesset,and Hartree-Fock-Slater method with respect to electrostatic properties of small molecules

Summary The results of various quantum chemical calculations, the Hartree-Fock (HF) method, the Møller-Plesset perturbation theory (MP2), and the Hartree-Fock-Slater (HFS) method are compared. Atomic charges, dipole moments, topological properties of the electron density distribution and polarizabilities, and first hyperpolarizabilities are calculated. Atomic charges obtained with the HFS method are found to be very close to those calculated with the MP2 method, from which we conclude that the HFS method describes to some extent electron correlation effects. Performing an MP2 calculation after an HF calculation improves the molecular dipole moments considerably, yielding values close to the experimental ones. HFS calculations are computationally less demanding than MP2 and yield comparable results for the electron density distributions, dipole moments and polarizabilities.     

Selective Electroanalytical Assay for Cysteine at a Boron Doped Diamond Electrode

The electrochemical oxidation of the cysteine‐quinone adduct has been examined as a means of providing an electroanalytical cysteine specific detection protocol. The appliance of square‐wave voltammetry allowed 0.5 μM as a limit of detection. The effects of various biologically relevant interferences including other thiols were studied and found to present no change in the voltammetric profile. The practical applicability and efficiency of the methodology was probed through the determination of cysteine concentration in growth tissue medium.     

Heisenberg’s Relations in Discrete N-Dimensional Parameterized Metric Vector Spaces

This paper shows that Heisenbergp84450/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">s relations are deducible from the structure of parameterized metric vector spaces of arbitrary dimension, by means of some new ideas, not entirely found in the current and vast literature about this subject. In order to allow this task to be done, some new concepts are put forward, as the real inward product of two vectors, described within vector spaces defined over the complex field, which permit further construction of real scalar products and Euclidian norms. Also, the definition of triads in parameterized metric vector spaces, which are constructs formed by three linearly independent vectors: a parameterized vector, the triad generator, and a pair of vectors orthogonal to the generator, the triad companions, one is simply made of the generator multiplied by the parameter and the other by using the first derivative with respect the parameter over the generator. Triads appear as forming a crucial building block for deduction of Heisenbergp84450/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">s relations. Building Heisenbergp84450/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">s relations is based on setting up the Gram matrix of a vector pair, which provides a new definition of the cosine of the angle subtended by two vectors in complex metric spaces, as well as an ancillary redefinition of the Schwarz inequality. It must be noted the fact that covariance of conjugated pairs of quantum mechanical variables appears to be a constant in the present scheme and others, a property which seems to become equivalent to the Heisenbergp84450/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">s relations, where in the current descriptions only variances or uncertainties are involved.     

A structural analysis of the complexes of (S,S)-dimethylpyridino-18-crown-6 with (R) and (S)-[α-(1-naphthyl)ethyl]ammonium perchlorate by NMR techniques and molecular modeling

Significant p3313011123g5123/xxlarge960.gif" alt="pgr" align="BASELINE" BORDER="0">-p3313011123g5123/xxlarge960.gif" alt="pgr" align="BASELINE" BORDER="0"> interaction is found in the complexes of (S, S)-dimethylpyridino-18-crown-6 with (R)- and (S)-[p3313011123g5123/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-(1-naphthyl)ethyl]ammonium perchlorate. This finding is supported by thep>1p>H NOESY NMR spectral technique, greater chemical shift changes of aromatic protons in both host and guest molecules upon complexation, and by molecular mechanics calculations. Because of the flexibility of the ligand, the tripod hydrogen bonding causesp>13p>C relaxation times of all periphery carbons to decrease without significant selectivity. Rotational energy barrier calculations of the methyl groups of the complexed ligand also show that the (S, S)-host-(R)-guest is the more stable complex.     

Thermostability of landscape phage probes

Immunoassays have traditionally relied on antibodies as diagnostic probes. Their use outside of a laboratory, however, may be problematic because antibodies are often unstable in severe environmental conditions. Environmental monitoring requires thermostable probes, such as landscape phage, that carry thousands of foreign peptides on their surfaces, are superior to antibodies, and can operate in non-controlled conditions. While parent wild-type phage are known to be extremely stable in various media at high temperatures, no work has been done to demonstrate the stability of landscape phage probes. We examined the thermostability of a landscape phage probe and a monoclonal antibody specific for p2w93882l7520834/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-galactosidase in parallel in an enzyme-linked immunosorbent assay (ELISA) format. They were both stable for greater than six months at room temperature, but at higher temperatures the antibody degraded more rapidly than the phage probe. Phage retained detectable binding ability for more than six weeks at 63 °C, and three days at 76 °C. The activation energy of phage degradation was determined to be 1.34×10p>5p> J/mol. These results confirm that phage probes are highly thermostable and can function even after exposure to high temperatures during shipping, storage and operation.     

A new approach to 6-deoxy-D-allofuranose- and 6-deoxy-L-talofuranose derivatives from 1,2:5,6-di-O-isopropylidene α-D-glucofuranose

3-O-Acetyl-1,2-O-isopropylidene-p202x5k268606h31/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-D-allofuranose (2 b) was prepared from 1,2:5,6-di-O-isopropylidene-p202x5k268606h31/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-D-allofuranose (1 b). Treatment of2 b with triphenylphosphine-diethyl azodicarboxylate afforded regio- and stereospecifically the 5,6-epoxy-p202x5k268606h31/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-D-allo derivative (3). The other diastereomeric compound, 5,6-epoxy-1,2-O-isopropylidene-p202x5k268606h31/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-L-talofuranose (6) was also prepared stereoselectively from2 b via the intermediates5 a and5 b. The epoxy sugars3 and6 were converted with lithium aluminum hydride to the corresponding 6-deoxy-1,2-O-isopropylidene-p202x5k268606h31/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-D-allofuranose (4 a) and -p202x5k268606h31/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-L-talofuranose (7 a) derivatives. Hydrolysis of4 a and7 a afforded 6-deoxy-D-allose and 6-deoxy-L-talose, respectively. The corresponding 3,5-di-O-acetyl- (4 b and7 b) and the 3,5-O-(tetraisopropyldisiloxane-1,3-diyl) derivatives (4 c and7 c) are also described. Selective removal of the isopropylidene group and subsequent acetylation offers a convenient route to prepare sugar derivatives containing furanose ring, like8 b, as a suitable precursor for nucleoside analogs.Herrn Prof. Dr.K. Komarek mit den besten Wünschen zum 60. Geburtstag gewidmet.     

高折光指数光学树脂的合成——相转移法合成不饱和硫醇酯单体的条件控制

采用正常的低温相转移催化（ＰＴＣ）和反滴碱溶液ＰＴＣ法分别合成了含硫双烯ＭＥＳＤＭＡ和单烯ＭＥＰＳＭＡ．１Ｈ ＮＭＲ分析证明ＭＥＳ中的杂质主要是由原料ＴＤＧ引入的．对含单个巯基的ＭＥＰＳ的正常ＰＴＣ酯化接枝双键，因存在巯基和不饱和双键的加成反应而导致失败．作者最终得到了折光指数在１６２５以上的ＭＥＳＤＭＡ／ＭＥＰＳＭＡ共聚物．     

Phytoecdysteroids of Plants of the Silene Genus. 2-Deoxyecdysterone-25-Acetate from Silene wallichiana

The new ecdysteroid 2-deoxyecdysterone-25-acetate was isolated from roots of Silene wallichiana Klotzsch.     

Synthesis and fluorination of nitro-substituted thionocarbonates

Thiocarbonylchloride reacts with p220367862547/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-nitroalcohols yielding symmetrical thionocarbonates. Transesterification of bis(2-fluoro-2,2-dinitroethyl)thioncarbonate affords alkyl 2-fluoro-2,2-dinitroethylthionocarbonates. Fluorination of these thionocarbonates yields the corresponding difluoroformals.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 375–376, February, 1993.