肟的无气味硫缩醛/酮化反应

探讨了以无气味且稳定的α-羰基二硫缩烯酮(1)作为代硫醇试剂的肟(2)的硫缩醛/酮化反应. 在乙酰氯-乙醇(体积分数95%)或4-十二烷基苯磺酸(DBSA)-水体系中及回流条件下, 化合物1与肟2能有效地进行硫缩醛/酮化反应. 反应过程中未闻到硫醇的恶臭气味.     

Glycosylation reactions with ‘disarmed’ thioglycoside donors promoted by N-iodosuccinimide and HClO4-silica

Glycosylation of ‘disarmed’ thioglycosides promoted by NIS in the presence of HClO₄ immobilized on silica compares very favourably with the accepted NIS-TfOH procedure.     

Improved Synthesis of 1‐Benzenesulfinyl Piperidine and Analogs for the Activation of Thioglycosides in Conjunction with Trifluoromethanesulfonic Anhydride*

An improved protocol for the large‐scale production of 1‐benzenesulfinyl piperidine and other sulfinamides is described. It is demonstrated that 1‐benzenesulfinyl pyrrolidine and N,N‐diethyl benzenesulfinamide function analogously to 1‐benzenesulfinyl piperidine in the trifluoromethanesulfonic anhydride‐mediated activation of thioglycosides, and that their less crystalline nature enables them to be used at ?78°C as opposed to the ?60°C required to keep 1‐benzenesulfinyl piperidine in solution. N,N-Dicyclohexyl benzenesulfinamide does not activate thioglycosides in combination with trifluoromethanesulfonic anhydride, which is attributed to its greater steric bulk.     

Electrochemical O-glycosylation using thioglycosides as glycosyl donors in the presence of a catalytic amount of sodium trifluoromethanesulfonate as a supporting electrolyte

Electrochemical O-glycosylation of primary alcohols with O-protected thioglycosides was performed in the presence of a small amount of sodium trifluoromethansulfonate (12.5 mol % to glycosyl acceptor) as a supporting electrolyte. The reaction was successfully carried out in an undivided cell to give O-glycosides in good yields with a high electro-efficiency (ca. 1 F/mol) at 15 °C in acetonitrile.     

4,4-二乙硫／苄硫基-3-烯-2-丁酮的合成及其作为无气味硫醇替代试剂的缩硫醛/酮化反应

经由3-(二乙硫／苄硫基)亚甲基-2,4-戊二酮(1)的酸催化脱乙酰基反应高产率地合成了4,4-二乙硫／苄硫基-3-烯-2-丁酮(2). 化合物2作为无气味的乙硫醇及苄硫醇替代试剂能与各种醛／酮在温和的反应条件下生成相应的缩硫醛／酮.     

Synthesis of Novel Thioglycoside Derivatives Containing Quinazolinone

A series of novel thioglycoside derivatives containing 4(3H)‐quinazolinone was designed and synthesized from 2‐chloromethyl‐quinazolin‐4(3H)‐ones and 1‐thioglycose. Several 2‐chloromethyl‐quinazolin‐4(3H)‐ones were synthesized on refluxing with 2‐(chloroacetylamino)‐benzoic acid and arylamines in acetonitrile. All of the novel compounds were characterized by IR, ¹H NMR spectra and elemental analysis. The structures of compounds 7b, 8b and 8c have been determined by X‐ray diffraction analysis.     

Glycosylation of vanillin by amyloglucosidase in organic media

Glycosylation of vanillin using amyloglucosidase from a Rhizopus mold with d-glucose, d-galactose, d-mannose, maltose, sucrose and d-sorbitol in di-isopropyl ether yielded glycosides in the range 13-53%. NMR spectral data confirmed linking between the phenolic OH of vanillin and C1 and/or C6 of the carbohydrate moieties.     

O‐Glycosylation/Alkylation and Antimicrobial Activity of 4,6‐Diaryl‐2‐Oxonicotinonitrile Derivatives

A series of glycosylation and alkylation reactions of 6‐phenanthernyl‐2‐pyridone derivatives 1a , 1b containing electron withdrawing and electron donating substituents at 4‐position is reported. Regioselective 2‐O‐ alkylated/glycosylated products were obtained exclusively, irrespective of the electronic nature of alkylating or the glycosyling agent. Glycosylation of 1a , 1b with glucosyl/galactosyl and lactosyl bromides afforded 2a , 2b ; 4a , 4b ; and 6a , respectively. Alkylation of 1a , 1b with epichlorohydrin, propargyl, allyl bromides, and 3‐chloropropanol resulted in compounds 8 , 9 , 10 and 13 , respectively. Deprotection of O‐glycosylated products under conventional conditions provided the free glycosides 3a , 3b ; 5a , 5b ; 7a , 12 ; and 13 , respectively. The minimal inhibitory concentration for some of the newly synthesized compounds showed high significant activity against Gram (+ve) and Gram (−ve) and antifungal activities. Among the screened compounds, the 4‐trifluromethyl phenyl derivatives 2a , 3a , 4a , 8a , and 11a exhibited strong antimicrobial activity.     

Color‐Transformable Silicone Elastomers Prepared by Thiol‐Ene Reaction with Potential Application in UV‐LEDs

A series of high‐efficiency, full‐color fluorescent elastomers based on polysiloxane matrix prepared by an easy thiol‐ene “click” reaction is reported here. It is found for the first time that the same elastomer can emit transformable colors by conveniently altering the excitation wavelength because of the effect of energy transfer and the “fluorescence switch” of lanthanide ions. A fluent change in emission colors can also be feasible and conveniently reproducible by varying the stoichiometric ratio of lanthanide ions and rhodamine‐B in solution and in polymer elastomers. The obtained elastomers are further coated onto commercially available UV‐LED cells from the solution medium followed by an in situ cross‐linking step.

     

Novel Chiral Aminophosphine Ligand:Synthesis and Application in Saymmetric Catalytic Hydrogenation Reaction

A new chiral aminophosphine ligand 6,6′-dimethoxy-2,2′-bis(diphenylphosphinoamino)biphenyl(DMBDPPABP) was prepared and its rhodium complex was found to be an effective catalyst for the asymmetric hydrogenation of amidoacrylic acid and its dervatives.The effects of solvent and reaction temperature on enantioselectivity were also studied.     

Application of Odorless Thiols for the Cleavage of 2‐ and 4‐Nitrobenzenesulfonamides

Several odorless or faint‐smelling thiols were tested to cleave 2‐ and 4‐nitrobenzenesulfonyl groups, which are widely utilized for selective protection and activation of amines. p‐Mercaptobenzoic acid (7) was found to be the most useful thiol for cleaving the o‐ and p‐nosyl groups in terms of ease of separation of the product from the workup residue, reaction temperature, and reaction time.     

Phosphite-based sialic acid donors in the synthesis of α(2→9) oligosialic acids

The combination of a phosphite donor and an anomeric thiocresol-protected acceptor, both with a TFA protecting group at C-5 of the sialic acid, provides good α-selectivity and yield in sialylation. Although the convergent synthetic strategy of using a phosphite disialo-donor and a disialo-acceptor assembles tetra-sialic acid efficiently, overcoming the low α-selectivity of α-anomer and purifying it remain to be achieved. Furthermore, mono- and di-sialic acids were, respectively, conjugated on carrier protein, keyhole limpet hemocyanin. The enzymatic hydrolysis method is recommended for estimating the amount of sialic acid on a protein conjugate.     

Enzymatic Synthesis of Novel Bavachinin Glucoside by UDP‐glycosyltransferase

Bavachinin, a member of the flavanone subclass of flavonoids, has long been considered to have various biological activities. Here, the synthesis of novel bavachinin glucoside by the in vitro glycosylation reaction was successfully achieved using a UDP‐glucosyltransferase YjiC, from Bacillus licheniformis DSM‐13. The chemical structure of bavachinin glucoside was characterized based on spectroscopic techniques as bavachinin‐4′‐O‐ß‐D‐glucopyranoside ( 1 ). The water‐solubility of bavachinin‐4′‐O‐ß‐D‐glucopyranoside was found to be 9.96 μM, about 10 times higher than bavachinin. In addition, compound 1 showed moderate anti‐proliferative activity against four human tumor cell lines, with IC₅₀ values ranging from 48.5 to 61.4 μM.     

Application of Interrupted Pummerer Reaction Mediated (IPRm) Glycosylation in Natural Product Synthesis

Although numerous glycosylation methods have been developed for the construction of glycosidic bonds, the pace of discovering rapid assembly strategies to access complex glycosidic linkages never stops. Over the last several years, we have introduced interrupted Pummerer reaction into carbohydrate chemistry and developed two pairs of latent/active glycosyl donors, OPTB/OPSB and SPTB/SPSB glycosides. After thorough investigation of the reaction mechanism and establishment of the substrate scopes, the extension of these novel glycosylation methods to synthesize naturally occurring biological active glycoconjugates was further illustrated. In this account, the development and especially the application of IPRm glycosylation in the synthesis of phenylethanoids and resin glycosides were introduced.     

Novel Reaction for Rapid,Simple, and Sensitive Determination of Molybdenum in Various Samples

Abstract

A new sensitive, selective, rapid, and reproducible method is presented for the analysis of trace amounts of molybdenum (VI) (Mo(VI)). The method is based on the reaction of molybdenum (VI) with a new analytical reagent, 6‐(5‐Chloro‐2‐hydroxy‐4‐sulfophenylazo)‐5‐hydroxy‐1‐naphthalenesulfonic acid, disodium salt. Under optimum reaction conditions, molybdenum (VI) forms a red complex with a maximum absorption peak at 589 nm. The color reaction is rapidly completed at room temperature. The apparent molar absorption coefficient and Sandell sensitivity were 1.13×10⁴ L · mol^?1 · cm^?1 and 0.0084 µg · cm^?2, respectively. Beer's law was obeyed up to 8.5 µg · mL^?1. Methods for the determination of Mo(VI) by first‐derivative spectrophtometry have also been proposed at 547 and 625 nm. The proposed methods offer the advantages of sensitivity, rapidity, selectivity, and simplicity without any prior separation or extraction. The methods have been applied to the determination of Mo(VI) in various environmental samples and some alloys; satisfactory results have been obtained.     

Oxocentered Units in Three Novel Rb‐Containing Copper Compounds Prepared by CVT Reaction Method

Three novel copper compounds, Rb₄Cu₄OCl₁₀ ( I ), Rb[Cu₃O](SeO₃)₂Cl ( II ), and RbCu₃(OH)(SeO₃)Cl₄(H₂O)₃ ( III ) were prepared by chemical vapor transport (CVT) reactions method from mixtures of CuO, SeO₂, RbCl, and CuCl₂. The crystal structures of the three compounds were determined by direct methods. Compound I is a Rb analogue of ponomarevite, K₄Cu₄OCl₁₀. Its crystal structure contains {[OCu₄]Cl₁₀}^4– clusters with oxocentered [OCu₄]⁶⁺ tetrahedra as cores. The clusters are linked by the Rb⁺ cations. The crystal structure of II contains complex {[O₂Cu₆](SeO₃)₄Cl₂}^2– layers formed by dimers of edge‐sharing [OCu₄]⁶⁺ tetrahedra interlinked via selenite groups and Cl^– anions. The crystal structure of III is based upon {[(OH)Cu₃](SeO₃)}³⁺ layers formed by the [(OH)Cu₃]⁵⁺ tetrahedra attached to (SeO₃)^2– groups. The layers are linked via Cl^– anions and via hydrogen bonds to H₂O molecules.     

Novel Reaction of Nitroxide with Hantzsch Dihydropyridines

Nitroxides have been found to be the intermediate in the in vivo metabolism of hydroxamic acid, a well-known biological molecule1. Structural modification of some antitumor drugs by introducing nitroxides can lower toxicity remarkably with retention or even increase of the antitumor activity2. Furthermore, the use of nitroxides as spin probes makes it possible to get information regarding the microenvironment of the reaction. 4-Substituted Hantzsch 1,4-dihydropyridines (DHP) are analogs …     

Electrochemical Determination of Sulfide at High Temperatures via Its Electrochemically Initiated Reaction with Diethyl‐p‐phenylenediamine in Dimethylformamide

The electrochemical oxidation of DEPD proceeds via an EC_revECE mechanism in dimethylformamide. It has been investigated at elevated temperatures up to 130 °C at both micro and macro platinum and glassy carbon electrodes. Kinetic and thermodynamic parameters for the reaction process have been calculated for each temperature. Further, the voltammetric response of DEPD shows enhanced limiting currents in the presence of sulfide. The analytical utility of the approach has been investigated with linear range from 50 to 850 μM sulfide concentration observed and a corresponding limit of detection of 20 μM achievable at temperatures of 70 °C.