Simple and Advantageneous Stereoselective Synthesis of (Z)-Allyl Phosphonates Starting from Baylis–Hillman Adducts

Baylis–Hillman adducts 3-hydroxyl-2-methylene alkanoates have been converted in one pot into the corresponding (Z)-allyl phosphonates by treatment with FeCl₃ and trialkyl phosphites in toluene under reflux. The products are formed in excellent yields (88–98%) within 1–1.5 h. The process is highly convenient and efficient, cost-effective, and remarkably stereoselective.     

Lipase-catalyzed kinetic resolution approach toward enantiomerically enriched 1-(β-hydroxypropyl)indoles

In a route towards enantiomerically enriched 1-(β-hydroxypropyl)indoles, which are potentially useful building blocks for high value-added chemicals synthesis, a kinetic resolution approach by means of lipase-catalyzed enantioselective acylation as well as hydrolysis/methanolysis has been elaborated for the first time. The enzymatic resolution of chiral N-substituted indole-based sec-alcohols was successfully accomplished, yielding both enantiomeric forms of the employed derivatives with up to >99% enantiomeric purity via an enantioselective transesterification under mild reaction conditions. The most selective resolutions were obtained using fungal (CAL-B and TLL) and bacterial (PFL and BCL) lipases and vinyl acetate as the acyl?group donor. The synthetic protocol described herein is very simple, user-friendly and efficient, thus paving the way for future access towards more complex compounds of this type. The absolute configurations of novel enantiomeric derivatives, and thus stereoselectivity of the described enzymatic reactions were confirmed by application of CDA-based NMR methodology and single-crystal X-ray diffraction analysis.     

Structural characterisation of a water-soluble polysaccharide from tissue-cultured Dendrobium huoshanense C.Z. Tang et S.J. Cheng

A water-soluble polysaccharide TC-DHPA4 with a molecular weight of 8.0 × 10⁵ Da was isolated from tissue-cultured Dendrobium huoshanense by anion exchange and gel permeation chromatography. Monosaccharide analysis revealed that the homogeneous polysaccharide was made up of rhamnose, arabinose, mannose, glucose, galactose and glucuronic acid with a molar ratio of 1.28:1:1.67:4.71:10.43:1.42. The sugar residue sequence analysis based on the GC-MS files and NMR spectra indicated that the backbone of TC-DHPA4 consisted of the repeated units:→6)-β-Galp-(1→6)-β-Galp-(1→4)-β-GlcpA-(1→6)-β-Glcp-(1→6)-β-Glcp-(→. The sugar residue sequences β-Glcp-(1→)-α-Rhap-(1→3)-β-Galp-(1→, β-Glcp-(1→4)-α-Rhap-(1→3)-β-Galp-(1→, β-Galp-(1→6)-β-Manp-(1→3)-β-Galp-(1→, and α-l-Araf-(1→2)-β-Manp-(1→3)-β-Galp-(1→ were identified as the branches attached to the C-3 position of (1→6)-linked galactose in the backbone.     

层状配位聚合物犤Pb(NCS)_2(bpea)_n的合成,结构和非线性光学性质(bpea=1,2-双(4-吡啶基)乙烷)(英文)

室温下Pb(OAC)2·3H2O,KNCS,和1,2-双(4-吡啶基)乙烷在甲醇中反应生成了八员环支撑的层状配位聚合物犤Pb(NCS)2(bpea)犦n。三阶非线性Z-扫描研究表明该化合物具有非线性折射行为:其非线性吸收系数α2=1.1×10-11m·W-1,非线性折射系数n2=6.055×10-18m2·W-1。     

Synthesis and structure of O-(arylcarbamoyl)butyrhydroximoyl chlorides

The O-(arylcarbamoyl)butyrhydroximoyl chlorides were synthesized, and the x-ray structural analysis (XSA) of one of them — O-(o-tolylcarbamoyl)butyrhydroximoyl chloride — was performed. It was established from the data of the XSA and the PMR spectra that all synthesized compounds are the Z isomers.Institute of Physiologically Active Substances, Russian Academy of Sciences, 142432 Chernogolovka. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 315–319, February, 1992.     

${\mathbb{Z}}/3{\mathbb{Z}}$-量子群的Gr\"{o}bner-Shirshov 基

通过计算合成, 我们证明了Yamane 给出的关系是 ${\mathbb{Z}}/3{\mathbb{Z}}$-量子群的一个Gr\"{o}bner-Shirshov 基.     

CRITERION FOR SL（2,Z）－MATRIX TO BE CONJUGATE TO ITS INVERSE

This paper gives a necessary and sufficient condition for a matrix in SL(2, Z) to be conjugate to its inverse. This condition reduces the determination of the conjugation to solving some indeterminate equation of second degree. It yields an algorithm to determine this conjugation in finite steps based on the elementary number theory.     

区间规划问题的最优性条件

区间规划是带有区间参数的规划问题,是一种更易于求解实际问题的柔性规划。它是确定性优化问题的延伸,有区间线性规划和区间非线性规划两种形式。本文讨论了目标函数是区间函数的区间非线性问题。给出了区间规划问题最优性必要条件的较简单证明方法,并利用LU最优解的概念,在一类广义凸函数－(p,r)－ρ－(η,θ)－不变凸函数定义下讨论了最优性充分条件。     

一类二阶常微分方程奇异边值问题多重解的至少个数

本文利用变分原理和Z2不变群指标研究了二阶常微分方程边值问题的多重解．得出了这类解个数的下界估计     

Clifton-pohl torus and geodesic completeness by a ‘complex’ point of view

We show that a natural complexification and a mild generalization of the idea of completeness guarantee geodesic completeness of Clifton-Pohl torus; we explicitely compute all of its geodesics.