Synthesis of the Cellulose Model Compound Methyl 4″-O-Methyl-β-D-Cellotrioside

A high-yield synthetic route towards methyl 4″-O-methyl-β-D -cellotrioside ( 17 ) via cellobioside acceptor 8 and glucosyl fluoride donor 15 was established. The former was synthesized from cellobiose peracetate in 7 steps and 21% overall yield, while the latter was obtained from methyl β-D -glucopyranoside in a 6-step-synthesis with 19% yield. Glycosidation afforded 13% of α-compound besides the desired β-isomer (31%). The target compound, being the higher homologue of the recently prepared 4′-O-methyl-β-D -cellobioside ( 1 ), is required to study by solid-state techniques the hydrogen bond network in cellodextrins and cellulose, and its changes upon swelling and dissolution.     

Effect of Support of СоМоS Catalysts on Hydrodeoxygenation of Guaiacol as a Model Compound of Biopetroleum

СоМоS/Sup catalysts were prepared from 12-molybdophosphoric heteropoly acid and cobalt citrate, with Al₂O₃, SiO₂, TiO₂, and ZrO₂ used as supports (Sup). The synthesized catalysts were studied by low-temperature nitrogen adsorption, X-ray diffraction, temperature-programmed ammonia desorption, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. The catalytic properties of the catalysts were studied in a flow-through installation at 260 and 340°С, pressure of 3.0 MPa, feed space velocity of 80 h^–1, and Н2/feed ratio of 500 L_n.c. L^–1. The guaiacol hydrodeoxygenation rate increases with a decrease in the mean length of the active phase particles, irrespective of the kind of the oxide support. As for the support effect, the catalyst activity decreases in the order SiO₂ > Al₂O₃ > ZrO₂ ~ TiO₂. On the other hand, the catalysts supported on ZrO₂ and Al₂O₃ exhibit the highest stability. The causes of the observed trends and the possible relationships between the characteristics of the catalysts and active phase nanoparticles are discussed.     

Improved Synthesis of Methyl 4,6-O-Benzylidene-3-cyano-2,3-dideoxy-α-D-erythro-hex-2-enopyranoside and Methyl 4,6-O-Benzylidene-2,3-dideoxy-3-C-formyl-α-D-erythro-hex-2-enopyranoside

Simple and efficient route to the title compounds by using diethyl aluminium cyanide in benzene for the epoxide ring opening and the electrophilic assistance of LiCIO₄ during the isomerization-elimination process.     

Silica Chromate as a Novel Oxidizing Agent for the Oxidation of 1,4‐Dihydropyridines

Silica chromate easily converts 1,4‐dihydropyridines to their corresponding pyridines in the presence of NaHSO₄ · H₂O and wet SiO₂ in dichloromethane at room temperature in good to excellent yields.     

α-Synuclein as a Target for Metallo-Anti-Neurodegenerative Agents

The unique thermodynamic and kinetic coordination chemistry of ruthenium allows it to modulate key adverse aggregation and membrane interactions of α-synuclein (α-syn) associated with Parkinson's disease. We show that the low-toxic Ru^III complex trans-[ImH][RuCl₄(Me₂SO)(Im)] (NAMI-A) has dual inhibitory effects on both aggregation and membrane interactions of α-syn with submicromolar affinity, and disassembles pre-formed fibrils. NAMI-A abolishes the cytotoxicity of α-syn towards neuronal cells and mitigates neurodegeneration and motor impairments in a rat model of Parkinson's. Multinuclear NMR and MS analyses show that NAMI-A binds to residues involved in protein aggregation and membrane binding. NMR studies reveal the key steps in pro-drug activation and the effect of activated NAMI-A species on protein folding. Our findings provide a new basis for designing ruthenium complexes which could mitigate α-syn-induced Parkinson's pathology differently from organic agents.     

Stereochemistry of the Addition of Organometallic Reagents to Methyl 2,3-O-Isopropylidene-β-D-ribo-pentodialdo-1,4-furanose

Methyl 2, 3-O- isopropylidene-β-D-ribo-pen tod ialdo-1,4-furanoside, upon reaction with either methyl lithium or methyImagnesium iodide/ gave a ca. 2-3:1 mixture of β-D-allo to α-L-talo adducts. Reaction with 2-lithio-l,3-d ithiane gave much improved stereoselectivity, in line with either the Cram or Felkin model, to give the dithianyl adducts in a ratio of 97:3 of β-D-allo to α-talo isomers.     

Selective Oxidation of Propane over CsFePVAsMo Heteropoly Compound Catalyst

Both the partially reduced and non-reduced multi-component heteropoly compound catalysts with Keggin structure were prepared and used for the selective oxidation of propane. The catalysts were characterized by IR, H2-TPR, NH3-TPD, SEM and XRD. The addition of Cs increased the selectivity of acrylic acid and acetic acid. The selective oxidation performance was greatly improved with the addition of As. Among all of the tested catalysts, the catalytic performance of the Cs1.8Fe0.16HxPVAs0.4Mo11O40 (non-reduced) was the best and the maximum yield of acrylic acid reached 16.42%.     

On the relation between the solvent parameters and the physical properties of methyl-4,6-O-benzylidene-α-d-glucopyranoside organogels

This paper reports the mechanisms of gel formation, the thermal properties and the microstructures of the networks of the gels composed of methyl-4,6-O-benzylidene-α-d-glucopyranoside and selected organic solvents: p-xylene, benzene, toluene, diphenyl ether and tetraethoxysilane. The Fourier transform infrared measurements together with simulation spectra, the air bath method and Polarized Optical Microscopy were employed in our studies. The experimental data show that the solvent has an influence on the microstructure of the gel network but there is no predictable influence of the solvent polarity on the shape of the formed gelator aggregates and correspondingly on the fibrous assemblies as revealed by the different microstructure of the gel network. Independently of the solvent polarity, the studied gelator, like other methyl-4,6-O-benzylidene derivatives of monosaccharides, formed gels through the formation of a hydrogen-bond network. The solvent parameters, such as the dielectric constant, Hildebrand solubility parameter, the polarity scale E_T and the Kamlet–Taft parameters were considered to quantify solvent effects on the gelation. The conclusions about the correlations are of interest but only to this particular sugar based gels.     

Aerobic Oxidation of Methyl Vinyl Ketone in Supercritical Carbon Dioxide

Ｔｈｅａｅｒｏｂｉｃｏｘｉｄａｔｉｏｎｏｆｅｔｈｙｌｅｎｅｔｏａｃｅｔａｌｄｅｈｙｄｅａｎｄｔｅｒｍｉｎａｌｏｌｅｆｉｎｓｔｏｃｏｒｒｅｓｐｏｎｄｉｎｇａｌｋａｎ 2 ｏｎｅｓｃａｔ ａｌｙｚｅｄｂｙｐａｌｌａｄｉｕｍ(ＩＩ)ａｎｄｃｏｐｐｅｒ(ＩＩｏｒＩ)ｓａｌｔｓａｒｅｃｏｌ ｌｅｃｔｉｖｅｌｙｋｎｏｗｎａｓＷａｃｋｅｒｏｘｉｄａｔｉｏｎｓ (Ｓｃｈｅｍｅ 1) .1Ｔｈｅｙａｒｅｖｅｒｙｉｍｐｏｒｔａｎｔｉｎｂｏｔｈｓｙｎｔｈｅｔｉｃａｎｄｉｎｄｕｓｔｒｉａｌｃｈｅｍ ｉｓｔｒｙ .Ｔｒｅａｔｍｅｎｔｏｆｔ…     

Dimerization by Hetero Diels-Alder Reaction of Methyl 4,6-O-Benzylidene-3-Deoxy-3-C-Methylene-α-D-Erythro-Hexopyranosid-2-Ulose

Abstract

The dimerization by hetero Diels-Alder reaction of methyl 4,6-O-benzylidene-3-deoxy-3-C-methylene-α-D-erythro-hexopyranosid-2-ulose was found to be regio and stereospecific. The structure of the cycloadduct was assigned from NMR spectrographic and X-ray crystallographic results. These results indicated that this cycloaddition occurred by a concerted hetero Diels-Alder reaction with inverse electron demand.     

Oxidation of L-sorbose and 2,3;4,6-di-O-isopropylidene-α-L-sorbose over supported platinum and palladium catalysts

Oxidation of L-sorbose and 2,3;4,6-di-O-isopropylidene--L-sorbose by oxygen (air) has been studied over supported Pt and Pd catalysts. The results indicate that the activity and stability of these catalysts are greatly dependent on their composition and preparation conditions.

---

L- 2,3;4,6--O---L- () . , .

     

Some Aspects of the Reaction of Methyl 4,6-O-benzylidene-α-D-glucopyranoside 2,3-Carbonate with 1-Dodecanol: Novel Non-Ionic Surfactants

Abstract

The reaction of methyl 4, 6-0-benzylidene-α-D-glucopyranoside 2, 3-cyclic carbonate (2) with 1-dodecanol in the presence of a catalytic amount of triethylamine to yield the 2-O-and the 3-O-alkoxycarbonyl esters 5 and 6 is described. Catalytic hydrogenation of 5 and 6 gave the deprotected mono-esters 3 and 4 which are of interest as potential non-ionic surfactants. The corresponding ethoxycarbonyl esters 7 and 8 were also prepared and their possible role as intermediates in the formation of 2 is discussed.     

Nanopolyaniline Coupled with an Anticorrosive Graphene as a 3D Film Electrocatalyst for Efficient Oxidation of Toluene Methyl C−H Bonds and Hydrogen Production at Low Voltage

A graphene-wrapped polyaniline nanoparticles film embedded in carbon cloth (CC/PANI/G) was fabricated and used as a 3D anodic electrocatalyst for oxidation of toluene methyl C−H groups. The methyl C−H bonds can be oxidized effectively at the CC/PANI/G anode with 99.9 % toluene conversion at a low applied voltage of only 1.0 V, which implies low energy input. Importantly, 86.6 % of toluene methyl C−H groups were converted to benzoyl groups (C=O), and hydrogen was produced efficiently at the cathode. The electrocatalytic efficiency at the CC/PANI/G anode was higher at lower voltage (1.0 V) than at higher voltage (1.5 V), and more hydrogen was produced at the corresponding cathode. The synergistic effect between the dynamic redox chemistry of nanoPANI and the excellent conductivity and anticorrosive action of graphene determined the high electrocatalytic efficiency of the oxidation of toluene methyl C−H groups at the CC/PANI/G anode. Owing to the chemical bonding between graphene and PANI, the anticorrosive CC/PANI/G anodic electrocatalyst was durable and effective for oxidation of toluene methyl C−H groups in acidic environment. This approach provides advanced electrode materials for transforming stable chemical bonds (C−H) into useful functional groups (C=O), which will be beneficial for the synthesis of organic intermediates with coupled hydrogen production.     

Syntheses of Methyl 2,3-di-O-Glycyl-α-D-glucopyranoside and 4,6-di-O-Glycyl-2,3-di-O-methyl-α-D-glucopyranoside,and Removal of Aminoacyl Groups from Sugar Moieties

Abstract

To confirm the potential usefulness of amino acid residues as protecting groups for sugar hydroxyls, methyl 2,3-di-O-glycyl-α-D-glucopyranoside (5) and methyl 4,6-di-O-glycyl-2,3-di-O-methyl-α-D-gluco-pyranoside (7) were synthesized as reference compounds. Conditions were then established for the removal of these aminoacyl groups from the sugar molecules. The reference compounds were easily prepared by condensation of methyl α-D-glucopyranoside derivatives with N-protected glycine in the presence of dicyclohexyl-carbodiimide (DCC). The aminoacyl groups were removed by alkaline treatment, as were conventional acyl groups and also with ease by enzymatic hydrolysis using Pronase E. Conventional ester and ether protecting groups are not removed by such enzymatic treatment. Removal of aminoacyl group from sugar moieties on a practical scale is also described.     

Microorganisms as reagents for transformations of 5α-steroids

Microbial activation of rings A, B, and C of 5-steroids is reviewed in connection with the prospects for the use of 5-steroids as a new starting material for the manufacturing of steroidal medicinal preparations. The combination of chemical synthesis and microbial methods of steroid transformation allows the successful solution of the problem of selective functionalization of steroid molecules, provided the suitable microorganisms are chosen and the conditions of their cultivation are optimized.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 567–588, April, 1994.     

Heteropolymolybdate as a New Reaction-controlled Phase-transfer Catalyst for Efficient Alcohol Oxidation with Hydrogen Peroxide

Aldehydes are very important raw materials or intermediates, which have widespread applications in the perfumery, pharmaceutical, dyestuff and agrochemical industries1. Oxidation of alcohol is one of the most frequently used synthetic reactions in the lab…     

Shed plane leaves as a source ofα-tocopherol

A natural source of -tocopherol — shed plane leaves — has been found. The dynamics of the accumulation of a-tocopherol over the vegetation period of the plant has been studied, and a method has been developed for its isolation and quantitative determination.Deceased.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 89 14 75. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 372–374, May–June, 1995. Original article     

Studies on the Graft Copolymerization of Methyl Acrylate and Ethyl Acrylate onto Corn Starch Using Potassium Persulfate-Sodium Thiosulphatc as Initiation System

Grafting copolymerizations of methyl acrylate(MA) and ethyl acrylate(EA) onto corn starch, respectively, initiated by potassium persulfate-sodium thiosulphate (KPS-STS) redox system, were studied. The structures of poly(MA)-g-starch and poly(EA)-g-starch were characterized by IR, SEM and X-ray diffraction. Experimental results show that KPS-STS is an efficient initiation system for grafting of MA and EA onto corn starch. The maximum percent grafting was obtained at [KPS] of 6.0× 10~3 mol/L, [STS] of 1.8× 10 5 mol/L, [M] of 6. 0× 101 mol/L, S:L=4:100 at 40℃ for 6 h. The reactivity order is MA>EA.     

Separation of the α-Tocopherol Model Compound 2,2,5,7,8-Pentamethyl-6-Chromanol from its Oxidation Products by High Performance Liquid Chromatography

Abstract

A rapid method is described for the separation of the α-tocopherol model compound, 2,2,5,7,8-pentamethyl-6-chromanol (6), from 9 of its oxidation products in a single 35 minute run. Separated derivatives of 6, in order of elution, included the 5-cholesteroxymethyl (1), spirotrimer (2), spirodimer (3), 5-formyl (4), 5-ethoxymethyl (5), dihydroxydimer (7), chroman dione (8), quinone (9) and pyrano xanthene (10). A normal phase system, using gradient elution is employed, the eluent being monitored at 290 nm. The minimum detection limit for compounds 1–8 was 0.1 μg per injection and for compounds 9 and 10 it was 0.3 μg per injection.