SELECTIVE PRODUCTION OF C_2 AND C_3ALCOHOLS FROM SYNTHESIS GAS

IntroductionTheaimofprcscllt\t-orbisthedot'clopmcntofcatal}-stsu'hicharchighl}'sclccti\'ctothes"nthcsisofCZandC3alcoholsfronls}'llgas.Cocatal}'stscanenhancetheproductionofCZalcohol.butthe}'arcalsoacti\'cfortheF-Ts}.nthcsisint'hichtheproductdistributionfol…     

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.     

Über die Phasenbreite von V2O5 im Temperaturbereich von 450°C bis 620°C

About the Homogeneity Range of V₂O₅ in the Temperature Range of 450°C to 620°C The influence of the deposition temperature T₁ on the homogeneity range of V₂O₅-crystalls was investigated by using a solid electrolyte cell. The deviation x in V₂O_5–x from the stoichiometric composition was obtained with: x = 0.0066 at T₁ = 450°C up to x = 0.0326 at T₁ = 620°C.     

海洋放线菌Streptomyces sp. V5产生的一个新的八元环内酯

海洋放线菌Streptomyces sp. V5分离自南中国海红树根部土壤, 从其培养液分离获得一个新的八元环内酯octalactin C (A), 以及四个已知化合物2-甲基-3-呋喃甲酸(B)、环(脯-亮)二肽(C)、环(丙-缬)二肽(D)和尿嘧啶(E). 通过完整的波谱数据解析了它们的结构.     

ICP-AES法测定菜头肾中多种微量元素

为探讨测定菜头肾中多种微量元素的方法,采用HNO3-HC lO4体系湿法消化,运用ICP-AES法测定了菜头肾中的多种微量元素。结果表明,菜头肾中K、Ca、Mg、P、S、A l、Na、Fe、Mn等元素含量相对较高,变异系数范围在0.23%~8.92%之间,元素的回收率在82.9%~106.1%之间。该法简便快速,可同时测定菜头肾中多种微量元素。     

The molecular structure of gaseous methyl vinyl ether at room temperature, studied by molecular orbital constrained electron diffraction and microwave spectroscopy

The gas phase molecular structure of methyl vinyl ether at room temperature has been studied by joint analysis of electron diffraction and microwave data. Constraints on geometrical and thermal parameters were derived from the geometry and force field of the s-cis form, obtained by ab-initio calculations (4–21 G basis set) after complete geometry relaxation. A range of models was investigated that fits all available data (infrared, microwave and electron diffraction). The following r_g/r-parameters were obtained: C=C: 1.337 Å, C(sp²)---O: 1.359 Å, C(sp³)---O: 1.427 Å, : 1.102 Å C=C---O : 127.3° and COC: 116.8°. Experimental r_g---r_e (ab initio) corrections are given for C=C, C(sp²)---O and Csp³)---O.

This investigation demonstrates that molecular orbital constrained electron diffraction is sufficiently reliable and in such a manner that it can be applied to more complicated problems.     

PRODUCTION OF LIGHTOLEFINS FROM CO_2 HYDROGENATION OVER Fe/SILICALITE-2 CATALYST Ⅱ. PROMOTION EFFECT OF MnO PROMOTER

IntroductionItilasbeenshot'-nthattileadditionofMnOpromotertoFocatal}stcanresultinaremarkableimprovementinthesclectivit}'to11ghtalkenesforCOh}!drogenationll'l.Ho-c'cvcr.thecadetofMnOonCH4formationandCOconversionisvery'ambigUouslltolMoreover.MnOpromotergrca…     

Prepatellamide A, a new cyclic peptide from the ascidian Lissoclinum patella

A new cyclic peptide, prepatellamide A (1), along with three known cyclic peptides (2)-(4), was isolated from the ascidian Lissodinum patella. The structure of prepatellamide A was determined from one- and two-dimensional H and 13C NMR spectra. The known cyclic peptides were identified as patellamides A (2), B (3) and C (4).     

Crystal and molecular structure of the tetrachloropalladate of the dication meso-3,7-diazonia tricyclo[4.2.2.22,5]dodeca-3,7,9,11-tetraen-4,8 diamine obtained by coupling reaction of 2-aminopyridines

A solution of trans-bis(2-aminopyridine)dichloropalladium(II) in DMF and HCl 2 N was left for several weeks. The compound isolated from this solution was identified by X-ray structural analysis as the tetrachloropalladate of meso-3,7-diazonia tricyclo[4.2.2.2^2,5] dodeca-3,7,9,11-tetraen-4,8 diamine, which contains a dication not previously described in literature. The organic dication is formed by two aminopyridine rings linked by CC bonds whose length is greater (1.61 Å) than a normal single CC bond.     

The time-resolved spectra of a crowned indolinospiroben-zopyran

The photochromic process of an indolinospiropyran with a crown ether fragment (BN-BIPS) was studied by nanosecond laser photolysis technique. The results show that quinonic merocyanine B was formed via an excited singlet state from BN-BIPS; in acetonitrile solution, the transient absorption of merocyanine B showed an obvious decay while a new transient absorption at 440nm (from isomer C) was observed simultaneously. The decay of merocyanine B and the formation of isomer C (at 440nm) were accelerated in the presence of alkali metal cation. In contrast, the formation of isomer C was not observed in spiropyran without a crown ether fragment: BIPS.     

Synthesis of the tricyclic indole alkaloids,dilemmaones A and B

Dilemmaones A-C are naturally occurring tricyclic indole alkaloids possessing a unique hydroxymethylene or methoxymethylene substituent at the C2 position of the indole core and a C6–C7 fused cyclopentanone. Dilemmaone B has been prepared in 5 steps from 5-methylindan-1-one, and dilemmaone A has been prepared in 3 steps from a common precursor, 6-bromo-5-methyl-7-nitroindan-1-one. In both syntheses, key steps include a Kosugi-Migita-Stille cross coupling and a reductive cyclization using hydrogen gas and a transition metal catalyst.     

A New Cyclic Peptide from Schnabelia tetradonta

A new cyclic octapeptide (schnabepeptide B) was isolated from the aerial part of Schnabelia tetradonta (Sun) C. Y. Wu et C. Chert (Lamiaceae). Its structure was elucidated as cyclo-(NH-Trp-Gly1-Leu1-Gly2-Pro1-Pro2-Leu2-Pr03-CO) on the basis of extensive 2D NMR and MS spectra.     

A Stereostructural Study of 17-Hydroxylupanine and its Perchlorate

Summary.  The bisquinolizidine carbinolamine 17-hydroxylupanine was synthesized de novo from lupanine using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone; its structure was established by NMR techniques. The equatorial position of the hydroxy group as well as the prevailing boat form of ring C were determined. As expected, the carbinolamine converted into the C17=N16 anhydronium perchlorate upon treatment with HClO₄. NMR analysis of the salt revealed a conformational equilibrium within rings A and D, whereas rings B and C remain rigid. Received March 13, 2000. Accepted March 21, 2000     

Preparation and Characterization of Fullerene C_(60) and Phthalocyanine Co-grafted Poly(epoxy propyl carbazole)

Fullerenes and its derivatives have attracted great interest from the viewpoints of both fundamental science and potential application. Fullerene-doping polymeric photoconductors have been extensively investigated due to their potential technological application. The enhancement of the photoconductivity of the poly (N-vinylcarbazole) (PVK) films by dopong with fullerenes (a mixture of C60 and C70) was for the first time reported by Wang1. He proposed that enhanced photoconductivity was attr…     

A new stereoisomer of stemmadenine alkaloid from Tabernaemontana heyneana

A new alkaloid, 15‐β‐stemmadenine, was isolated from the fruits of Tabernaemontana heyneana Wall. from the ethanolic extract. The complete ¹H and ¹³C NMR assignments of the compound were carried out using COSY, HMQC and HMBC. Stereochemistry at C‐15 and C‐16 was established using ROESY and temperature‐dependent ¹H NMR studies. Copyright © 2002 John Wiley & Sons, Ltd.     

Preparation and properties of metallacyclobutanes of nickel and palladium

Bis(phosphine)-3,3-dimethylnickela- and palladacyclobutanes have been prepared by intramolecular C-H insertion reaction of the corresponding dineopentyl metal complexes. Nickelacyclobutane complexes decompose when heated thereby undergoing competitive carbon-carbon bond cleavage to give isobutene and ethylene, with reductive elimination affording 1,1-dimethylcyclopropane and skeletal isomeri-zation of the metallacyclic ring yielding 3-methyl-1-butene, whereas the palladium analog gave no significant amounts of CC bond cleavage products.Added phos-phine was seen to have an effect on CC bond scission of nickelacyclobutane complexes. Nickelacyclobutane complexes in solution are thought to be in equilibrium with olefin-coordinated nickel-carbene complex on the basis of available experimental evidence from hydrogenolysis, carbene-trap reactions with olefins and reaction with carbon monoxide     

A New Compound from the Root of Salvia przewalskii Maxim

Neo-przewaquinone A was isolated from the root of Salvia przewalskii Maxim. The structure elucidation and ^1H, ^13C NMR assignments were achieved by spectroscopic method.     

Thickness-dependent Orientation Structure in Poly（ethylene oxide） Multi-layer Crystals

Poly(ethylene oxide) multi-layer crystals were obtained and the re-crystallization behavior was studied to give insight into how melt thickness and temperature affect the lamellar orientation. For a special re-crystallization temperature, there exists a critical transition thickness range for the occurrence of edge-on lamellar orientation. Below the critical thickness, only flat-on lamellae were observed. While above the critical thickness, both flat-on and edge-on lamellae were found and the proportion of the edge-on lamellae increases with thickness. At low re-crystallization temperatures(below 30 °C), the critical transition thickness gradually increases from about 15 nm to 35 nm when the re-crystallization temperature was increased from 20 °C to 30 °C. However, when the re-crystallization temperature is above 30 °C, the critical transition thickness becomes constant. Our results demonstrated that the lamellar orientation could be specially modified by changing the melt thickness and re-crystallization temperature.     

Extraction of Acetogenins Using Thermosonication-Assisted Extraction from Annona muricata Seeds and Their Antifungal Activity

The objective of this work was to find the optimal conditions by thermosonication-assisted extraction (TSAE) of the total acetogenin content (TAC) and yield from A. muricata seeds, assessing the effect of the temperature (40, 50, and 60 °C), sonication amplitude (80, 90, and 100%), and pulse-cycle (0.5, 0.7, and 1 s). In addition, optimal TSAE conditions of acetogenins (ACGs) were compared with extraction by ultrasound at 25 °C and the soxhlet method measuring TAC and antioxidant capacity. Moreover, solubility and identification of isolated ACGs were performed. Furthermore, the antifungal activity of ACGs crude extract and isolated ACGs was evaluated. Optimal TSAE conditions to extract the highest TAC (35.89 mg/g) and yield (3.6%) were 50 °C, 100% amplitude, and 0.5 s pulse-cycle. TSAE was 2.17-fold and 15.60-fold more effective than ultrasound at 25 °C and the Soxhlet method to extract ACGs with antioxidant capacity. Isolated ACGs were mostly soluble in acetone and methanol. Seven ACGs were identified, and pseudoannonacin was the most abundant. The inhibition of Candida albicans, Candida krusei, and Candida tropicalis was higher from isolated ACGs than crude extract. TSAE was effective to increase the yield in the ACGs extraction from A. muricata seeds and these ACGs have important antifungal activity.     

The effect of the chromophoric group modification on the optical properties of retinal proteins

The effects of chromophoric group structures on the functional properties of bacteriorhodopsin (BR) and proteorhodopsin from E. sibiricum (ESRh) were compared. ESRh retinal binding site was found as preserving the similar stereo- and spatial restrictions on the chromophore structure during the retinal protein reconstitution process (except for C25-analog AR8). It was revealed that the structure peculiarities of the chromophore analog molecules affect the optical parameters of ESRh and BR pigment families in similar ways.