INDO Investigation of the halogen N.Q.R. frequencies and 14N nuclear quadrupole coupling constants of halothiophenes and halopyridines

The ³⁵Cl, ⁷⁹Br, and ¹²⁷I N.Q.R. frequencies of a number of halothiophenes and halopyridines and the ¹⁴N nuclear quadrupole coupling constants of halopyridines have been determined in terms of the Kaplansky-Whitehead theory with the INDO MO approximations using a consistent set of atomic parameters derived from SCF Hartree-Fock calculations. The theoretical spectral properties are in satisfactory overall agreement with experiment. This result supports the validity of using the above method to provide reliable predictions of N.Q.R. parameters for heteroaromatic systems.This work was carried out with the support of the Consiglio Nazionale delle Ricerche (C.N.R.) of Italy.     

Ginsenoside-Rg6, a Novel Triterpenoid Saponin from the Stem-Leaves of Panax ginseng C. A. Mey.

A novel dammarane-type triterpene oligoglycoside, named ginsenoside-Rg6 3, was isolated from the stem-leaves of Panax ginseng C.A.Mey., together with two known ones, 20(S)-ginsenoside-Rg2 1 and 20(R)-ginsenoside-Rg2 2.On the basis of chemical and physicochemical evidence , the structure of ginsenoside-Rg6 have been elucidated as 6-O-α-L-rhamnosyl-(1→2)-β-D-glucopyranosyl-dammarane-(E)-20(22), 24-diene-3β, 6α, 12β-triol.     

广防己挥发油的GC-MS指纹图谱研究

防己药材主要分粉防己和木防己两类,木防己包括广防己和汉中防己。广防己为马兜铃科植物广防己AristolochiafangchiY.C.WuexL.D.Chou.etS.M.Hwang的干燥根,习称"木防己"、"水防己",主产于广东、广西,具有祛风止痛、清热利水之功效。广防己主要成分为为生物碱及挥发油,己有报道的生物碱主要有:木防己碱、异木防己碱、木兰花碱、木防己胺、大防己宾碱、甲门尼萨任碱。挥发油成分未见报道,本文采用气相色谱-质谱(GC-MS)测定广防已挥发油成分,建立能够反映出定性、定量信息的GC-MS指纹谱图。结果表明:挥发油中主要含有β-古芸烯     

A New Flavonoid Ketohexofuranoside from Leaves of Crataegus pinnatifida Bge.var. major N.E.Br.

Crataegus pinnatifida Bge.var.major N.E.Br. is widely distributed in the northeast part of China. It is used as a medicinal plant to improve digestion, remove retention of food, promote blood circulation and resolve blood stasis both in traditional and folk medicine 1. Preparations of Crataegus leaves improve the heart function, the coronary blood supply and arrhythmia2. Up to now, fifty flavonoids have been isolated from Crataegus3,4. In our previous paper, some new flavonoid glycosides we…     

Norditerpenoid Alkaloids from the Roots of Aconitum hemsleyanum Pritz.var.Pengzhouense

In continuation of our studies on Aconitum hemsleyanum Pritz.var. pengzhouense, two new norditerpenoid alkaloids, pengshenines A(1) and B(2),have isolated from the roots of the plants and their strucures were elucidated by 1D-and 2D-NMR.     

Kalman滤波分辩交流示波极谱图中重叠切口

交流示波极谱过去仅用于简单体系的测定,当溶液中含有大量干挠离子时,dE/dt～E曲线上将产生许多切口,它们互相重叠干扰,无法进行定量测定,本文首次将Kalman滤波算法引入交流示波极谱,用于解析多组分共存时的示波图,将重叠切口进行分离,使干扰共存时定量测定成为可能。     

M. S. Tswett and the 1918 Nobel Prize in Chemistry

Summary The general recognition of M. S. Tswett and his achievements are discussed, with special emphasis to his nomination for the 1918 Nobel Prize in Chemistry.     

Two New C—glucoside Flavonoids from Leaves of Crataegus pinnatifida Bge. var. major N.E.Br.

Two new C-glucoside flavonoids,namely 8-C-β-D-（2″-O-acetyl) glucofuranosyl apigenin and 3″-O-acetylvitexin, were isolated from beaves of Crataegus pinnatifida Bge. var. major N.E.Br.Their structures were elucidated by the spectroscopic means and chemical evidence.     

Effect of frequency on the deposition of microcrystalline silicon from tetrachlorosilane in low-pressure r.f. plasmas

The efficiency of reduction of silicon tetrachloride and the rate of deposition of Si in a low-pressure r.f. plasma was investigated at two frequencies (0.4 and 27 MHz) as a function of position with regard to the rf coil, pressure, and time of deposition. At 27 MHz the decomposition efficiency of silicon tetrachloride and the deposition rate of Si are about three times higher than at 0.4 MHz.     

On the E.S.R. spectra of intermediates generated during the electrochemical oxidation of triphenylacetic acid in acetonitrile

The acidity level and the fluoride ion activity are evaluated in anhydrous HF and in water+HF mixtures of HF content higher than 70% by means of R(H) and R(F) functions. For both functions, the potentials of the ferrocene/ferricinium or perylene⁺/perylene²⁺ systems are used as reference potentials. A hydrogen electrode is used for acidity level evaluation and it is shown that the R(H) function decreases (acidity increases) when HF content increases in the mixture; the value of R(H) is ?15.5 for anhydrous hydrogen fluoride (+KF 0.1 M). A lanthanum trifluoride monocrystal electrode is built and used for F^? activity evaluations and it is shown that the R(F) function increases (activity of fluoride ion decreases) when HF content increases, up to R(F)=13.6 for basic anhydrous HF (KF 0.1 M solution).     

C.P.M.G.脉冲序列法用于抑制和消除水信号

大约0.3M的NH_4Al(SO_4)_2的重水溶液用作溶剂而令其活泼氢交换,结果水的横向弛豫时间T_2缩短,可用C.P.M.G.脉冲序列法消除水峰。以此为溶剂测定了葡萄糖的图谱,结果满意。     

聚合物电解质界面性质交流阻抗研究

合成了一种新型聚合物基质材料聚(甲基丙烯酸甲酯-丙烯腈-甲基丙烯酸锂)(简记为PMAML),并以PMAML/PVDF-HFP(偏氟乙烯-六氟丙烯共聚合物)复合物为基质制备了聚合物电解质.利用FTIR对合成的PMAML进行结构表征,并用扫描电镜观察聚合物基质膜的表面形貌.聚合物电解质由聚合物基质膜浸渍电解质溶液得到,其室温电导率可达到2.6×10－3 S• cm－1.利用交流阻抗技术研究了聚合物电解质与锂电极间的界面性质,并考察了开路放置时间、循环伏安及恒流充电对界面阻抗的影响.结果表明,聚合物电解质与锂电极界面阻抗随放置时间的延长而增加,更新锂电极表面可降低界面阻抗,PMAML能提高界面稳定性.     

一株曲霉属印楝植物内生真菌的代谢产物研究

内生真菌(Endophytic fungi)是指其在生活史的某一段时期生活在植物组织内,对植物组织没有引起明显病害症状的真菌[1]。内生真菌具有丰富的多样性,是一大类尚未被开发的资源。近年来的研究表明,它们能产生结构多样的活性代谢产物,已成为国内外的研究热点之一[2]。印楝(Azadirac     

Fragment interaction analysis in the framework of ab initio UHF MO computations. I. Conformational preference in the ethyl radical

In this paper we describe a procedure which allows to obtain estimates of the energy effects associated with the orbital interactions occurring between the component fragments of a radical species in the framework of ab initio Unrestricted Hartree-Fock computations. This procedure is used here to analyze the factors which control the conformational isomerism of the ethyl radical.On leave from C.N.R.S., GR 12, Thiais, France     

HPLC测定河套大黄中的土大黄苷含量

从河套大黄中分离纯化出活性成分土大黄苷,作为自制的标准品,利用KromasilTM C(18)(250 mm×4.6 mm I.d.,5μm)反相色谱柱,以V(甲醇):V(乙腈):V(水)=35:5:60为流动相,以320mm为检测波长,对河套大黄中土大黄苷进行测定.土大黄苷在0.427～4.190μg范围内与峰面积呈良好线性关系(r=0.9994),平均回收率为99.12%.该方法为河套大黄的质量控制奠定了基础.     

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.     

Determination of Methylmercury by Phase-Sensitive A. C. Polarography

Abstract

The polarographic reduction of methylmercury in aqueous medium takes place in two steps, each of which involves the transfer of a single electron. The first reduction step proceeds reversibly both in direct current and in sinusoidal alternating current. Since the polarograms corresponding to this step are well defined, they can be successfully used to determine methylmercuric compounds by phase-sensitive sinusoidal a.c. polarography, in the concentration range 1 × 10^?7 ?1 × 10^?4 mole.dm.^?3     

Regioselective Isomerisation of Highly Substituted 1-Methylenecyclohexenepoxides to the Corresponding Allylic Alcohols. Influence of the Base and of the Protecting Groups

Summary. Highly substituted 1-methylenecyclohexenepoxides 3, useful building blocks for a projected synthesis of wailupemycin A (1), were synthesized from (R)-carvone in eight synthetic steps in 23–40% overall yield. The regioselectivity of the subsequent isomerisation to the corresponding allylic alcohols was shown to depend on the basicity of the reagent and on the bulkiness of the protecting groups existing in 3. With diethylaluminum 2,2,6,6-tetramethylpiperidid (DATMP), secondary allylic alcohols 5 were formed exclusively. With strong bases such as a mixture of lithium di-iso-propylamide and potassium tert-butoxide (LIDAKOR), the tertiary allylic alcohol 6 was obtained as predominant product.To whom inquiries about the X-ray analysis should be addressed     

Lipophilic pigments and fatty acids from the aerial parts of certain plant species of the genus Limonium. VII

Pigments and lipids from the aerial parts of six plant species from the genus Limonium (Plumbaginaceae, Limoniacea) were studied. Xanthophylls dominated among the carotinoids; chlorophyll, the chlorophylls, according to spectrophotometry. Unsaturated fatty acids, the content of which reached 80%, dominated in all samples according to GC. The principal fatty acids were 18:1 and 18:2. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 412–414, September–October, 2006.