Synthesis of Methyl α-D-Kijanoside

Abstract

In 1981, Mallams and coworkers reported¹ the discovery of - D-kijanose 1, a branched-chain nitro sugar, isolated from the antitumor antibiotic kijanimicin by acid hydrolysis. The structure of this unusual carbohydrate was established ^1,2 as 2,3,4,6-tetadeo xy-4 - (methoxy carbony1 amino 1-3-c-methyl - 3 -nitro - D-xylo-hexopyranose by spectroscopic and crystallographic analysis, and comparison with D-rubranitrose 2, a carbohydrate found in the antibiotic rubradirin .³Two other nitro sugars, L-evernitrose 3 and - L-decilonitrose 4⁵, have been discoveredas components of antibiotics.     

Synthesis of Methyl α-d-Allopyranoside and Methyl α-d-Ribo-hexopyranoside: A Convenient Chemoenzymatic Approach

Abstract

An efficient chemoenzymatic synthesis of methyl α-d-allopyranoside and methyl 3-deoxy-α-d-ribo-hexopyranoside starting from methyl 4,6-O-benzylidene-α-d-glucopyranoside is described.     

Gamma radiolysis of Methyl Red solution and reaction induced by γ-irradiated NaCl in Methyl Red

The -radiolysis of Methyl Red solution in HCl medium at pH=2 has been studied along with energy transfer reaction brought about byF and hole centers of -irradiated NaCl. The G-values for degradation of the azo dye indicator by radiolysis and -irradiated salt were determined as 9·10^–1 and 4.8·10^–3, respectively. The kinetic rate constants (k) of degradation are evaluated as 2·10^–5 rad^–1 in the case of direct radiolysis, while for the irradiated salt it is 2·10^–7 rad^–1. The extent of degradation by direct -radiolysis is 100–200 times greater as compared to that by the -irradiated salt. The same mechanism is proposed for radiolysis as well as the reaction induced by -irradiated sodium chloride.     

Oil Imports Raise Security Concern

Economic researchers have raised fresh concernsover China's energy security with crude-oil importsexpected to hit a record 80 million metric tons thisyear. Alarmed by the growing dependence on oil im-ports, they are urging for multi-pronged measures todevelop new energy sources to prevent potential short-ages hurting the country's robust economic growth.     

Lucidone和Methyl Lucidone的简洁合成

报道了lucidone和methyl lucidone的简洁合成,其关键步骤为方酸二甲酯的还原/重排"一锅"反应和单甲氧基环丁烯二酮的达森/扩环反应.Lucidone的合成经过两步反应以46%的总收率实现.Methyl lucidone的合成经过三步反应以43%的总收率完成.     

?thylacetat und Methyl?thylketon nebeneinander

Ohne Zusammenfassung     

Crystal Structures of Methyl (Methyl 3-azido-2,3-dideoxy-β-L-lyxo- and -β-D-arabino-hexopyranosid)uronates

Single-crystal x-ray diffraction data for methyl (methyl 3-azido-2,3-dideoxy-β-L-lyxo- and β-D-arabino-hexopyranosid)uronates are presented. Three independent molecules in the asymmetric part of the unit cell of the β-D-arabino stereoisomer were found. These differ slightly in the geometry of the groups bound to the pyranose rings. Conformations and the geometry parameters of all the molecules as well as the planarity of the carbomethoxy group, the linearity of the azido group, and the orientation of the aglycone in the crystal lattice are discussed. Influence of the hybridization, resonance, and crystal packing on the geometry parameters is shown.     

Studies on the Mechanism of Methyl Methacrylate Polymerization Initiated by Volatile and Nonvolatile Products of Methyl Methacrylate Plasma

ＳｔｕｄｉｅｓｏｎｔｈｅＭｅｃｈａｎｉｓｍｏｆＭｅｔｈｙｌＭｅｔｈａｃｒｙｌａｔｅＰｏｌｙｍｅｒｉｚａｔｉｏｎｉｎｉｔｉａｔｅｄｂｙＶｏｌａｔｉｌｅａｎｄＮｏｎｖｏｌａｔｉｌｅＰｒｏｄｕｃｔｓｏｆＭｅｔｈｙｌＭｅｔｈａｃｒｙｌａｔｅＰｌａｓｍａＬＩＵ...     

Profits Gush for Offshore Oil Firm

China National Offshore Oil Corp’s profits surgedby 85.6 per cent year-on-year in the first five monthsof 2003 despite the outbreak of SARS that loweredoil demand since April.Profits jumped to 6.4 bil-lion yuan(US＄773.8 million)during the period onthe back of strong oil prices.Oil production reached     

Phase Transfer Catalysed Synthesis of Methyl α-Bromomethylacrylate

Methyl α-bromomethylacrylate 1 is an important intermediate both as a starting material for specifically functionalized polymers and for use in general organic synthesis. As an example of the former it has been used to prepare polymeric anthraquinoid dyes¹. Synthetically, its bifunctional reactivity towards nucleophilic attack has made it useful in the preparation of both spiro² and bicyclic^3,4 ring systems. Several reports of synthetic methods leading to α-methylenelactones, having potential antitumor activity, have also been reported which use α-bromomethylacrylate as a starting point⁵.     

The Reaction of Methyl 2,4,6-Tri-0-benzoyl-3-0-benzyl-β-D-galactopyranoside with 1,1-Dichloromethyl Methyl Ether

When methyl 2,4,6-tri-0-benzoyl-3-0-benzyl-β-D-galacto-pyranoside (JO is treated in purified chloroform at 55-60′ with excess of dichloromethyl methyl ether in the presence of a catalytic amount of freshly fused zinc chloride for 1 h the corresponding α-glycosyl chloride 2 can be isolated by column chromatography in 75-80% yield. Compound 2 is an important intermediate in the synthesis of oligosaccharides containing a glycosyl-3-0-galactosyl sequence. Under the described reaction conditions the conversion 1 - 2 is accompanied by a slow anomerisation of 1 to give methyl 2,4,6-tri-0-benzoyl-3-0-benzyl-α-D-galactopyranoside. Prolonged treatment of 2 with the used excess of the reagent results in complete debenzylation of the substrate and the conversion of the putative 2,4,6-tri-O-benzoyl-α-D-galactopyranosyl chloride into the corresponding 3-0-formyl and 3-0-dichloromethyl derivatives.     

Comparative study on γ-radiolysis and energy transfer reaction induced by γ-irradiated NaCl in Methyl Orange and Methyl Red

A comparative study on -radiolysis and energy transfer reaction induced by -irradiated sodium chloride in azo-dye indicators, viz. Methyl Orange and Methyl Red are undertaken. These indicators undergo degradation following first order kinetics, the determined rate constants being 1.05·10^–8 rad^–1 for Methyl Orange and 5.00·10^–7 rad^–1 for Methyl Red, respectively. TheG-values are also determined and are found to be lower for Methyl Orange (8.60·10^–6) and higher for Methyl Red (4.05·10^–3), suggesting that the former is more resistent to radiation degradation as compared to the latter.     

Influence of Interaction Between Heavy Oil Components and Petroleum Sulfonate on the Oil–Water Interfacial Tension

The purpose of this study is to obtain the interaction between heavy oil components and petroleum sulfonate (NPS). In this article, the effects of pH, NaCl concentration, and NPS on the oil–water interfacial tension (IFT) of Gudao crude oil and its polar components were investigated. The results show that the NPS concentration corresponding to turning point of IFT is 0.001 g·mL^?1. This is lower than the CMC of NPS (0.0015 g·mL^?1) as there is a positive synergetic effect between NPS and the active substances of crude and its components, and the strength of their interaction depends on the interfacial activity of crude components. In simulated system of crude and polar components with 0.1 wt% NPS, at basic condition, the acidic substances in the polar components create naphthenates (the component whose acid number is higher creates more naphthenates), leading to lower IFT, so the interaction between heavy oil components and NPS is stronger in the basic condition. Proper concentration of NaCl in the stimulated systems improved the hydrophile-lipophile balance of emulsifier (NPS), accelerated the well-regulated adsorption of NPS in oil–water interface, and increased the interfacial activity of NPS, the interaction between heavy oil components and NPS was also enhanced.     

Synthesis Characterization and Viscosity Studies of Homopolymer of Methyl Methacrylate and Copolymer of Methyl Methacrylate and Styrene

A homopolymer of methyl methacrylate (MMA) and its copolymer with styrene at different compositions were synthesized and characterized. Viscosity measurements of the synthesized homopolymer and the copolymers in toluene solutions were performed at 313 K. Different equations were used to calculate the intrinsic viscosity, viscometric constants values, and molecular weight of the synthesized polymers. The values of intrinsic viscosity and viscosity average molecular weight obtained by the two methods (single point determination and graphical extrapolation) were compared in order to verify the validity of the single point determination for the polymers. Viscometric properties derived included the specific viscosity (it determines the contribution of the solute to the viscosity of the solution), the reduced viscosity (that provides a measure of the polymer capacity for increasing the solution viscosity), and the intrinsic viscosity.     

Large Oil Reserves Found in Bohai Bay

Exploration teams have found the Bohai Bay Basin of North China may contain 20.5 billion tons of offshore oil reserves, with 9 billion tons already proven, experts said.     

Sinopec Steps up Oil and Gas Exploration

China Petrochemical Corporation (Sinopec Group) will spend more on oil and gas exploration, both at home and abroad. The increased investment aims to alleviate the company's heavy reliance on oil imports. Between 2001 and 2005, the company intends to invest 10 billion yuan (US$1.2 billion) to explore for overseas oil and gas and purchase assets. The investment focuses on West Asia, North Africa, Central Asia, West Africa and Southeast Asia. It is expected that the company will get 2-3 million tons of oil through its overseas initiatives by the year 2005.Seeking overseas oil resources is an important method for Sinopec Group to expand its oil reserves, and the shortage of upstream oil resources has be-     

Die spektrophotometrische Bestimmung von Methyl?thylteton in Aceton

Ohne Zusammenfassung     

Stereocontrolled Conversion of Allylic Alcohols Into Vicinal Cis-Diols: New Syntheses of Methyl α-L-Digitoxoslde and Methyl 2-Deoxy-α-L-Fucoside

A synthetic process is outlined in which an allylic alcohol is converted into its primary urethane derivative, which is then subjected to iodonium ion induced cyclization to give a single iodo-carbonate. The carbonate is then deiodinated reductively and hydrolyzed to afford the vicinal diol. By use of this process the two title sugars have been prepared from methyl 2.3.6-trideoxv-α-L-ervthro-hex-2-enopvranoside and its α-L-threo counterpart.