Synthesis of a Pentasaccharide Corresponding to the Antithrombin III Binding Fragment of Heparin

The synthesis of a protected pentasaccharide 27b corresponding to the antithrombin III binding region of heparin is presented. This pentasaccharide was prepared from two disaccharides (12c and 23) and a monosaccharide (1). The glucuronic acid containing disaccharide 12c was prepared from easily available monomers 6 and 7. Oxidation to the uronic acid was performed in the disaccharide stage. L-Idose derivative 16, prepared via a new route, was coupled with 1,6-anhydro derivative 17, oxidized and transformed into disaccharide 23. Coupling of 12c and 23 to tetrasaccharide 24a has been investigated. Better yields were obtained without collidine, the reason for which is explained. Coupling of 24b and 1 afforded the pentasaccharide 27b, protected with acetyl at the positions to be sulphated, benzyl at the other hydroxyl functions and azide at the 2-position of the glucosamine residues. Conversion of 27b into the sulphated pentasaccharide Ib can be performed according to published procedures.     

Enzymatic Synthesis of a CCK-8 Tripeptide Fragment

A process for the synthesis of CCK-8 tripeptide H-Gly-Trp-Met-OH catalyzed by immobilized enzyme was reported. Enzymes were used for the formation of peptide bonds and the removal of protecting group. Starting with phenylacetyl (PhAc) glycin, N-protected dipeptide PhAc-Gly-Trp-OMe was obtained by coupling PhAc-protected glycine carboxamidomethyl ester (OCam) with Trp-OMe catalyzed by immobilized papain in buffered ethyl acetate. Then the condensation between PhAc-Gly-Trp-OMe and Met-OEtoHC1 was carried out by immobilized α-chymotrypsin catalysis in solvent free system. Basic hydrolysis was followed getting PhAc-Gly-Trp-Met-OH. The PhAc-group was removed with penicillin G amidase and H-Gly-Trp-Met-OH was obtained in an overall yield of 43.9%. The reaction conversion of tripeptide in solvent free system was strongly affected by the system of basic salts added. The influence of the support materials used to deposit enzymes and structures of acyl donor and nucleophile on the reaction was also investigated.     

Enzymatic Synthesis of a CCK-8 Tetrapeptide Fragment

The enzymatic synthesis of a tetrapeptide Phac-Met-Gly-Trp-Met-OEt is reported. It was synthesized by coupling Phac-Met-OEt with Gly-OMe. HCI, Trp-OMe and Met-OEt successively, catalyzed by α-chymotrypsin, papain and α-chymotrypsin respectively. The results of FAB-MS showed that the products had the correct molecular mass.     

Synthesis of Triterpenoid with an Ethylidene Fragment in the E Ring from Allobetulin

Russian Journal of Organic Chemistry - Allobetulin was converted to 3β-acetoxy-21β-acetyl-20β,28-epoxy-18α,19β-ursane, followed by reduction of the acetyl fragment and...     

Synthesis of an Octacyclic C60 Fragment

Fragments of buckminsterfullerene (C₆₀) include the monumental three compounds corannulene, sumanene, and truxene. These three have served as leading molecules in ongoing research for curved, fused, and π-extended polyaromatic materials. Achieving more structural variations that join the ranks of these three archetypes remains challenging. Herein we report synthesis of an octacyclic hydrocarbon that is an unexplored C₆₀-fragment, namely, a 4,11-dihydrodiindeno[7,1,2-ghi:7′,1′,2′-pqr]chrysene (C₂₈H₁₆, which we named Metelykene). The key to success was solution-compatible synthesis in which double pentagonal rings flank hexagonal ones. This solution-phase approach, coupled with the resulting non-planar π-conjugation, is so straightforward that it offers an entry to a derivative such as a cardo aromatic monomer.     

The Synthesis of the Trnas Anticodon Loop Fragment (“U-Turn”) with Modified Uridines as the Components

Abstract

To continue studies on dynamics of tRNAs anticodon loop fragments conformation (1) the series of oligomers 1-5 has been synthes ized.     

Direct Synthesis of DI-and Trimethoxybenzyl Thiols from the Corresponding Alcohol

An efficient and reliable procedure for the one-pot synthesis of di-and trimethoxybenzyl thiols from the corresponding benzyl alcohol is described.     

Synthetic Approach to the Synthesis of Physiologically Active Compounds: II. Synthesis of Disubstituted Adamantanes Containing an N-Benzoylphenylisoserine Fragment

A preparation is reported of some previously unknown 1,4-disubstituted adamantane derivatives containing a phenylisoserine fragment.     

Synthesis and Antibacterial Activity of New Acridone Derivatives Containing an Isoxazoline Fragment

A method was developed for the preparation of N-(4-R-4,5-dihydroisoxazol-5-yl)methylacridones by the reaction of aromatic aldehyde oximes with allyl acridones. For the obtained compounds, a high inhibitory activity in relation to test strains of pathogenic microorganisms was revealed, exceeding furacilin.

     

Enzymatic Determination of Methylmercury Traces using Alcohol Dehydrogenase from Baker’s Yeast

 Methylmercury as well as mercury (II) were found to be effective inhibitors of the catalytic activity of alcohol dehydrogenase from baker’s yeast in the reaction of ethanol oxidation by nicotinamide adenine dinucleotide. It was stated that the methylmercury inhibitory action belonged to the non-competitive type, whereas Hg(II) inhibited the enzyme according to the mixed type. The inversely proportional dependence of the indicator reaction rate on the concentration of methylmercury allowed to develop an enzymatic procedure for its determination with a detection limit of 3 nM. The possibility of methylmercury determination in presence of mercury (II) and mercury (II) determination in presence of methylmercury (concentration ratios CH₃Hg⁺:Hg(II) were 1:1 and 1:10, respectively) was shown. In the first case masking reagents, DEDTC or thiourea, were used to form stable complexes with Hg(II). Received February 9, 2001; accepted August 10, 2001; published online June 24, 2002     

非离子型表面活性剂对木质纤维素酶催化水解的影响及机理

木质纤维素的酶解糖化过程是纤维素生物质转化中的关键步骤,也是限制纤维素生物转化生产燃料和化学品的主要瓶颈。大量的研究表明,非离子型表面活性剂能够强化木质纤维素酶解过程,显著提高纤维素的酶催化水解效率。本文综述了非离子型表面活性剂对纯纤维素和木质纤维素底物酶解的影响,分析了底物结构特性、水解条件、纤维素酶组成等诸多因素与表面活性剂作用效果之间的关联,并从纤维素酶的吸附特性、纤维素酶组分间的协同作用等方面对非离子表面活性剂的作用机理进行了总结。结合已有的研究进展和存在的问题,提出了今后表面活性剂对于木质纤维素酶催化水解影响的研究重点方向,即系统分析底物结构、水解条件等因素对表面活性剂作用的宏观影响,以及分析这种作用的热力学和动力学特性,而微观上需要从原子和分子层面上解析表面活性剂与底物和纤维素酶之间的相互作用特性。     

Synthesis of Enantioenriched Sulfoxides by an Oxidation-Reduction Enzymatic Cascade

Chiral sulfoxides are versatile synthons and have gained a particular interest in asymmetric synthesis of active pharmaceutical and agrochemical ingredients. Herein, a linear oxidation–reduction bienzymatic cascade to synthesize chiral sulfoxides is reported. The extraordinarily stable and active vanadium-dependent chloroperoxidase from Curvularia inaequalis (CiVCPO) was used to oxidize sulfides into racemic sulfoxides, which were then converted to chiral sulfoxides by highly enantioselective methionine sulfoxide reductase A (MsrA) and B (MsrB) by kinetic resolution, respectively. The combinatorial cascade gave a broad range of structurally diverse sulfoxides with excellent optical purity (>99 % ee) with complementary chirality. The enzymatic cascade requires no NAD(P)H recycling, representing a facile method for chiral sulfoxide synthesis. Particularly, the envisioned enzymatic cascade not only allows CiVCPO to gain relevance in chiral sulfoxide synthesis, but also provides a powerful approach for (S)-sulfoxide synthesis; the latter case is significantly unexplored for heme-dependent peroxidases and peroxygenases.     

Synthesis and Structure of an Enantiopure Dirhodium Loop with Unusual Axial Coordination

The crystals of enantiopure SS-[cis-Rh2(Ph2C6H4)2(O2CC2F4CO2)]2((CH3)2CHCH2NH2)3(1) were obtained from the reaction of S-[cis-Rh2(Ph2C6H4)2(CH3CN)6]BF4(S-2) and(Et4N)2(O2CC2F4CO2) in CH2Cl2/CH3OH under the presence of sec-butyl amine.Compound 1 crystallizes in orthorhombic,space group P212121 with a = 16.880(5),b = 28.728(9),c = 20.475(6) ,V = 9929(5) 3,Z = 4,C95H96Cl5F8N3O8.50P4Rh4,Mr = 2280.52,Dc = 1.526 g/cm3,F(000) = 4608 and μ(MoKα) = 0.922 mm-1.The final R = 0.0488 and wR = 0.1164 for 17204 observed reflections with I > 2σ(I) and R = 0.0814 and wR = 0.1374 for all data with absolute structure parameter =-0.04(3).Compound 1 contains two inherently chiral S-[cis-Rh2(Ph2C6H4)2] moieties which are connected by two(O2CC2F4CO2) dicarboxylate ligands in the equatorial positions.One of the dirhodium units with Rh-Rh distance of 2.5445(8)  is further coordinated by a sec-butyl amine in each axial position.Another dirohdium unit has only one axial sec-butyl amine ligand,and its Rh-Rh distance is 2.5079(9) .     

Synthesis of New (2-Acetamido)phenylglyoxylamides Containing an Acetal Fragment

Russian Journal of Organic Chemistry - Mild opening of the five-membered ring in 1-acetylisatins by the action of an equimolar amount of 4,4-diethoxybutan-1-amine afforded...     

Synthesis of New Amides of Isoxazole- and Isothiazole-Substituted Carboxylic Acids Containing an Arylaminopyrimidine Fragment

By acylation of substituted 2-aminoarylpyrimidines with 5-phenyl(p-tolyl)isoxazole- and 4,5-dichloroisothiazole-3-carbonyl chlorides new amides of pyrimidine series were obtained.     

Enzymatic Apporoach to the Synthesis of Non-Racemic,P-Chiral Hydroxymethylphosphonates and Phosphinates

Abstract

α-Hydroxyalkanephosphonates and phosphinates exhibit interesting biologd achvlty whch IS highly dependent on theu absolute configumon Therefore, a search for efficient and general methods of the synthesis of enantlopure htle compounds continues As part of our studies on the use of enzymes in preparahon of non-racemic heteroorganic compounds,2 we have developed a hpasemediated lunebc resoluhon of racemic hydroxy- methylphosphonates and phosphinates, which is based on ather acetylatlon of the substrates 1, or hydrolysis of thar O-acetyl denvatlves 2 The absolute configurahon of the products has been determined by means of CD and chemical conelatlon     

Solid-Phase Enzymatic Synthesis of a Lewis a Trisaccharide Using an Acceptor Reversibly Bound to Sepharose

Abstract

The disaccharide 2-aminoethyl O-β-D-galactopyranosyl-(1→3)-2-acetamido-2-deoxy-β-D-glucopyranoside was reacted with thiobutyrolactone to give a disaccharide with a thiol group on the aglycone. This disaccharide was reacted with activated Thiopropyl Sepharose, which gave a disaccharide bound to Sepharose via a disulphide bond. Enzymatic fucosylation, using GDP-fucose and partially purified human milk fucosyltransferase, gave a trisaccharide in good yield, which was cleaved from Sepharose by treatment with mercaptoethanol or dithiothreitol.