Synthesis of deoxy sugar esters: a chemoenzymatic stereoselective approach affording deoxy sugar derivatives also in the form of aldehyde

A chemoenzymatic synthesis of deoxy sugar esters is described. The synthesis is based on the O-alkylation of carboxylic acid with 2-bromo-5-acetoxypentanal. The method allows treatment of hydroxy carboxylic acids without protection of alcoholic hydroxyl groups. Several stereoisomeric deoxy sugar esters were resolved (up to ee or de > 98%) using a lipase-catalyzed acetylation of hemiacetals that in certain cases afforded deoxy sugar derivatives in the form of aldehydes. The stereochemistry of the reactions was determined by the NMR spectra of mandelic acid derivatives.     

Microstructure,texture and oral processing: New ways to reduce sugar and salt in foods

Food oral processing as the bridge between food texture, microstructure and sensory perception has gained enormous interest in the last decade. This review provides an overview of the role of the microstructure of soft- and semi-solid foods in food oral processing and sensory perception. Phase separated mixed protein–polysaccharide gels and emulsion-filled gels are described as suitable model foods to investigate food oral processing systematically. Special attention is given to the sensory perception of texture, taste and interactions thereof. Several approaches to reduce the salt and sugar content of semi- and soft-solid foods without compromising taste are reviewed. These reduction approaches are based on an understanding of food oral processing in relation to the microstructure of the foods and its breakdown.     

Cobalt analogues of Roussin's red salt esters: a density functional study

Density functional theory calculations on the Co(2)(NO)(4)(SR)(2) compounds (R = CH(3), CF(3) and C(4)H(9)) predict butterfly and open isomeric structures with and without a direct Co-Co bond. The open Co(2)(NO)(4)(SR)(2) structures are favored over the butterfly isomers, in terms of relative energy. Furthermore the open structures are predicted to have approximately twice as large HOMO-LUMO gaps than the butterfly Co(2)(NO)(4)(SR)(2) isomers. For the related Co(2)(CO)(6)(SR)(2) species, competing open and butterfly structures with similar HOMO-LUMO gaps were predicted. This could explain why the Co(2)(NO)(4)(μ-SR)(2) compounds have already been synthesized and why no genuine Co(2)(CO)(6)(SR)(2) derivatives have yet been reported.     

Synthesis of 1,4-dihydropyridine esters using low-melting sugar mixtures as green solvents

Several low-melting sugar mixtures (LMMs) were synthesized and used for preparation of 1,4-dihydropyridines with aldehydes, 1,3-dicarbonyl compounds, and a nitrogen source as starting materials. Good yields, low reaction times, recyclability of LMMs, and catalyst-free methodology are some of the highlights of this new protocol.     

Reactions of benzamidoxime and its sodium salt with methyl esters of fluorinated acids

The reactions of benzamidoxime and its sodium salt with methyl esters of fluorinated acids at 20–100°C give 1, 2, 4-oxadiazoles or O-addition products.Translated fromIzvestiya Akademli Nauk. Seriya Khimicheskaya, No. 3, pp. 530–532, March, 1993.     

Production of water-soluble sugar from cellulose and corn stover via molten salt hydrate impregnation and separation

Cellulose - Saccharification of cellulose into glucose is a key step for the utilization of lignocellulose. Molten salt hydrate (MSH) is unique in selective hydrolysis of cellulose into glucose but...     

Adsorption and aggregation properties of heterogemini surfactants containing a quaternary ammonium salt and a sugar moiety

A novel heterogemini surfactant comprising two hydrocarbon chains and two different hydrophilic groups such as a quaternary ammonium cation and gluconamide nonion N,N-dimethyl-N-[2-(N'-alkyl-N'-gluconamide)ethyl]-1-alkylammonium bromides (2CnAmGlu, where n represents hydrocarbon chain lengths of 8, 10, 12, and 14) was synthesized by reacting N,N-dimethylethylenediamine with alkyl bromide, followed by a reaction with 1,5-D(+)-gluconolactone. The adsorption properties of 2CnAmGlu were characterized by surface tension measurements made using the Wilhelmy plate method, and their aggregation properties were investigated by dynamic light scattering and cryogenic transmission electron microscopy techniques. The relationship between the hydrocarbon chain length and the logarithm of the critical micelle concentration (cmc) for 2CnAmGlu exhibited a linear decrease when the chain length was increased up to 12 and then a departure from linearity at n=14. The surface tension reached 24-26 mN m-1 at each cmc, indicating high efficiency in lowering the surface tension of water. Furthermore, it was found that the structure of the aggregate formed for 2CnAmGlu in solution was influenced by the hydrocarbon chain length; that is, for n=10 and 12, micelles with a hydrodynamic radius of 2-5 nm were formed, whereas vesicles were also observed for n=14.     

Phthalate Esters in Benzene Solvent

Abstract

High-boiling constituents included in commercial first grade benzene solvent were investigated by thin layer and gas chromatography, UV, IR, NMR and mass spectrometry, and the presence of di-n-butyl phthalate and di-2-ethylhexyl phthalate was confirmed.     

Palladium-catalyzed coupling of allenylphosphonates, phenylallenes, and allenyl esters: remarkable salt effect and routes to novel benzofurans and isocoumarins

Coupling reactions of allenylphosphonates (OCH(2)CMe(2)CH(2)O)P(O)CH=C=CRR' [R, R' = H (1a), R = H, R' = Me (1b), R = R' = Me (1c)] with aryl iodides, iodophenol, and iodobenzoic acid in the presence of palladium(II) acetate are investigated and compared with those of phenylallenes PhCH=C=CR2 [R = H (2a), Me (2b)] and allenyl esters EtO(2)CCH=C=CR(2) [R = H (2c), Me (2d)]. While 1b and 1c couple with different stereochemical outcomes using PhI in the presence of Pd(OAc)(2)/PPh(3)/K(2)CO(3) to give phenyl-substituted 1,3-butadienes, 1a does not undergo coupling but isomerizes to the acetylene (OCH(2)CMe(2)CH(2)O)P(O)CCMe (7). In the reaction of 1c with PhI, use of K(2)CO(3) affords the butadiene (Z)-(OCH(2)CMe(2)CH(2)O)P(O)CH=C(Ph)-C(Me)=CH(2) (12); in contrast, the use of Ag(2)CO(3) leads to the allene (OCH(2)CMe(2)CH(2)O)P(O)C(Ph)=C=CMe(2) (20), showing that these bases differ very significantly in their roles. The reaction of 1a with PhI or PhB(OH)2 in (t)he presence of Pd(OAc)2/CsF/DMF leads mainly to (E)-(OCH(2)CMe(2)CH(2)O)P(O)CH=C(Me)Ph (21) and (OCH(2)CMe(2)CH(2)O)P(O)CH2-C(Ph)=CH(2) (22) and is thus a net 1,2-addition of Ph-H. Compound 1b reacts with iodophenol in the presence of Pd(OAc)(2)/PPh(3)/K(2)CO(3) to give a benzofuran that has a structure different from that obtained by using 1c under similar conditions. Treatment of 1a with iodophenol/Pd(OAc)(2)/CsF/DMF also gives a benzofuran whose structure is different from that obtained by using 2a under similar conditions. In the reaction with 2-iodobenzoic acid, 1a and 2c afford one type of isocoumarin, while 1b,c and 2a,b give a second type of isocoumarin. The structures of key compounds are established by X-ray crystallography. Utility of the phosphonate products in the Horner-Wadsworth-Emmons reaction is demonstrated.     

A highly stereoselective construction of beta-glycosyl linkages by reductive cleavage of cyclic sugar ortho esters

The preparation of beta-glycosides by the reductive cleavage of spiro sugar ortho esters is described in this report. This procedure is based on a concept completely different from those of other methods for glycosylation. Twelve sugar ortho esters that commonly possess perhydrospiro[2H-pyran-2,2'-pyrano[3,2-d][1,3]dioxin] ring systems in their molecules were reduced by LiAlH(4)/AlCl(3) or NaCNBH(3)/AlCl(3). Among these ortho esters, those (9a-12a) prepared from the D-sugar lactones (1-4) and 2, 3-di-O-benzyl-alpha-D-glucopyranoside (7) or those (19a, 20a) prepared from the L-sugar lactones (5, 6) and 2, 3-di-O-benzyl-alpha-D-galactopyranoside (8) were selectively converted into beta-(1 --> 4)-glycosides (9b-12b or 19b, 20b) in excellent yields by the treatment of LiAlH(4)/AlCl(3). In contrast, the ortho esters (13a-16a or 17a, 18a) that were prepared from combinations of the D-sugar lactones and 8 or those of the L-sugar lactones and 7 were efficiently reduced with NaBH(3)CN/AlCl(3) to afford beta-(1 --> 6)-glycosides (13b-16b or 17b, 18b) selectively. It was remarkable that the resulting disaccharides were obtained with extremely high beta-selectivity even in the cases with mannosyl or rhamnosyl glycosides. Moreover, these products would be useful units for the construction of branched saccharides, because the newly formed hydroxy groups could be again glycosylated without further deprotection procedures. The high regio- and stereoselectivity was totally explained by considering the structures and the conformations of these ortho ester molecules and the stereoelectoronic effects of their spiro ring systems. In addition, the preparation of the sugar ortho esters with glucosamine derivatives and the reactivity of these ortho esters are described in this report. N-Phthaloyl glucosamine derivatives (21, 22) were efficiently reacted with the benzyl-protected gluconolactone (1) in the presence of TMSOMe and TMSOTf to afford ortho esters (23a-c). After the conversion of the phthalimido functionality to the dibenzyl amino group, glucosylideneglucosamine (25) was reduced with LiAlH(4)/AlCl(3) to afford beta-(1 --> 4)-glycoside (26) selectively.     

Photochemical investigation of Roussin's red salt esters: Fe2(mu-SR)2(NO)4

The photochemistry of various Roussin's red ester compounds of the general formula Fe(2)(SR)(2)(NO)(4), where R = CH(3), CH(2)CH(3), CH(2)C(6)H(5), CH(2)CH(2)OH, and CH(2)CH(2)SO(3)(-), were investigated. Continuous photolyses of these ester compounds in aerated solutions led to the release of NO with moderate quantum yields for the photodecomposition of the ester (Phi(RSE) = 0.02-0.13). Electrochemical studies using an NO electrode demonstrated that 4 mol of NO are generated for each mole of ester undergoing photodecomposition. Nanosecond flash photolysis studies of Fe(2)(SR)(2)(NO)(4) (where R = CH(2)CH(2)OH and CH(2)CH(2)SO(3)(-)) indicate that the initial photoreaction is the reversible dissociation of NO. In the absence of oxygen, the presumed intermediate, Fe(2)(SR)(2)(NO)(3), undergoes second-order reaction with NO to regenerate the parent cluster with a rate constant of k(NO) = 1.1 x 10(9) M(-1) s(-1) for R = CH(2)CH(2)OH. Under aerated conditions the intermediate reacts with oxygen to give permanent photochemistry.     

Iodomethaneboronic esters and aminomethaneboronic esters

An efficient preparation of pinacol iodomethaneboronate and dibutyl iodomethaneboronate from the respective (phenylthio)methaneboronic esters has been devised, using the reaction with methyl iodide. Pinacol iodomethaneboronate reacts efficiently wit tertiary amines to form the crystalline quaternary ammonium salts. Dibutyl iodomethaneboronate reacts with excess piperidine or morpholine in ether to precipitate piperidine or morpholine hydriodide and yield the distillable piperidino- or morpholinomethaneboronic ester. Benzylamine failed to yield a stable product.     

Effects of added nonionic surfactant and inorganic salt on the rheology of sugar surfactant and CTAB aqueous solutions

The effect of adding tri(oxyethylene) dodecyl ether (C₁₂EO₃) on the phase and rheological behavior of sucrose hexadecanoate and CTAB aqueous solutions in the presence of added salt (NaBr) was investigated. Viscoelastic solutions are formed in CTAB and C₁₆SE systems upon addition of lipophilic nonionic surfactant C₁₂EO₃. The zero-shear viscosity shows a maximum at a certain mixing fraction of C₁₂EO₃, except in the case of the aqueous CTAB/C₁₂EO₃ system in the absence of salt. The rheological properties are strongly affected by the addition of salt to the CTAB systems but they remain unaltered in the case of C₁₆SE systems. In ionic systems, the mixing fraction of C₁₂EO₃ for the maximum viscosity depends on salt concentration.     

Stereoselective synthesis of functionalized gamma-amino esters: azetidinium salts and epoxy esters

Addition of several lithium ester enolates to chiral 1-aminoalkyl chloromethyl ketones 1 affords enantiomerically pure 3-hydroxyazetidinium salts 3 or 3-(1'-aminoalkyl)-3,4-epoxy esters 4, depending on the reaction conditions. [reaction: see text]     

土壤中痕量酞酸酯的提取与分析方法研究

采用ＣＨ_２Ｃｌ_２超声提取、氧化铝、硅胶双柱净化、高效液相色谱（ＨＰＬＣ）测定土壤中的酞酸酯（ＰＥｓ）、标准添加回收率达９３％～１０６％，对超声提取与索氏提取进行了比较，并对实际土壤样品中的ＰＥｓ进行了初步分析。     

Copper-catalyzed enantioselective Henry reactions of alpha-keto esters: an easy entry to optically active beta-nitro-alpha-hydroxy esters and beta-amino-alpha-hydroxy esters

The catalytic enantioselective Henry reaction of alpha-keto esters with nitromethane has been developed. The reaction conditions have been optimized by the screening of different chiral Lewis acids, solvents, and bases, and it was found that the copper(II)-tert-butyl bisoxazoline complex in combination with triethylamine catalyzed a highly enantioselective reaction giving optically active beta-nitro-alpha-hydroxy esters in high yields and with excellent enantiomeric excesses. The scope of the reaction is demonstrated by the reaction of a variety of different alpha-keto esters. The catalytic enantioselective Henry reaction of beta,gamma-unsaturated-alpha-keto esters proceeds as a 1,2-addition reaction exclusively, in contrast to the uncatalyzed reaction where both the 1,2- and 1,4-addition products are formed. It is demonstrated that the beta-nitro-alpha-hydroxy esters can be converted into, e.g., Boc-protected beta-amino-alpha-hydroxy esters in high yields and without loss of optical purity. The mechanism for the reaction is discussed, and it is postulated that both the alpha-keto ester and nitromethane/nitronate is coordinated to the metal center during the reaction course.