A new approach to asymmetric synthesis of (−)-epiquinamide from d-glucose

The asymmetric total synthesis of (?)-epiquinamide has been achieved starting from a 5-iodofuranoside synthon derived from d-glucose. The methods featured Bernet-Vasella reaction followed by Horner-Wadsworth-Emmons (HWE) reaction to provide a new chiral building block diene as the key steps. The bicyclic framework of this quinolizidine was constructed by selective reduction of α,β-unsaturated ester, intramolecular nucleophilic substitution and ring-closing metathesis.     

A facile approach towards synthesis of verbalactone and biologically active δ-lactones using d-glucose

A general synthetic approach has been developed for the asymmetric synthesis of chiral δ-lactones and verbalactone using d-glucose. The key intermediate used in this approach was α-diazoketone.     

A novel amperometric biosensor based on a co-crosslinked l-lysine-α-oxidase/overoxidized polypyrrole bilayer for the highly selective determination of l-lysine

An amperometric biosensor for the determination of l-lysine based on l-lysine-α-oxidase immobilized by co-crosslinking on a platinum electrode previously modified by an overoxidized polypyrrole film is described. The optimization of experimental parameters, such as pH and flow rate, permitted to minimize significantly substrate interferences even using a low specific, commercial enzyme. The relevant biases introduced in the measurement of lysine were just about 1% for l-arginine, l-histidine and l-ornithine, roughly 4% for l-phenylalanine and l-tyrosine. The developed approach allowed linear lysine responses from 0.02 mM up to 2 mM with a sensitivity of 41 nA/(mM × mm²) and a detection limit of 4 μM (S/N = 3). No appreciable loss in lysine sensitivity was observed up to about 40 days. Allowing polypyrrole layer to remove interference from electroactive compounds, the present method revealed suitable to detect l-lysine in a pharmaceutical and cheese sample, showing a good agreement with the expected values.     

Nitrone in l-lyxose series: cycloaddition way for the synthesis of new C-α-fucosides

Nitrone 3 analogue of 5-deoxy-l-lyxose was derived from d-ribose. Its reduction with aqueous SO₂ gave the corresponding 4-amino-sugar 2, a potent α-l-fucosidase inhibitor. 1,3-Dipolar cycloaddition of 3 with alkenes allowed the synthesis of acetohydroxamic acid and ethane-phosphonate derivatives. Hydroxy-ethane derivative 15 is a nanomolar α-l-fucosidase inhibitor.     

First synthesis of an α-d-Fucp3NAc containing oligosaccharide: a study on d-Fucp3NAc glycosylation

3-Acetamido-3,6-dideoxy-d-galactopyranose (d-Fucp3NAc) is an aminosugar almost exclusively found in phytopathogenic O-antigens. The glycosylation reaction involving d-Fucp3NAc donors was studied with several rhamnosyl acceptors, revealing that the best yields and highest α-stereoselectivity were obtainable by coupling a N-phenyl trifluoroacetimidate glycosyl donor in a ternary mixture (dioxane/DME/toluene 4:1:1) as solvent. For the first time a synthetic access to α-d-Fucp3NAc containing oligorhamnans, that are interesting molecules for studying the effects of O-antigen model oligosaccharides on the modulation of plant response to bacteria, was reported. An example is the pentasaccharide repeating unit of the major O-antigen component from Pseudomonas syringae pv. holci IMV 8300, which was synthesized as its methyl glycoside.     

Synthesis of threo-β-aminoalcohols from aminoaldehydes via chelation-controlled additions. Total synthesis of l-threo sphingosine and safingol

Chelation-controlled addition of organocuprates to N-carbamoyl aminoaldehydes, prepared from functionalized amino acids, generated predominately the threo-β-amino alcohol derivatives through chelation with the carbamoyl moiety. The carbamate group is a stronger chelating group than other potentially good chelators, for example ethers, esters, thioethers, and gives good diastereoselectivity with cuprates. Thus addition of lithium divinylcuprate to the aldehyde generated from the serine derivative 25 in the presence of extra copper for chelation afforded the threo compound 26 in 83% yield. Cross-metathesis and cleavage of the protecting groups furnished l-threo sphingosine 21. In addition the lyso-sphingolipid protein kinase C inhibitor, safingol, 22, was prepared from commercially available O-benzyl N-BOC serine 28 in six steps and 56% overall yield by this method.     

Stille cross-coupling reaction of polyfluorovinylstannanes: Stereospecific synthesis of polyfluoro-alkenes and -α,β-unsaturated ketones

The palladium/copper (I) iodide cocatalyzed coupling reaction of (Z)-α-fluoro-β-trifluoromethylvinylstannanes 1 with aryl iodides 2 and acid chloride 4 has been explored affording substituted (E)-α-fluoro-β-trifluoromethylalkenes 3 and (E)-α-fluoro-β-trifluoromethyl-α,β-unsaturated ketones 5, respectively. The effect of cocatalyst, solvent as well as reaction temperature has been investigated in more detail. The geometric isomers were easily ascertained on the basis of their coupling constant () across the double bond and the retention of the configuration of the products for this conversion was found.     

Dynamic resolution of α-halo chiral esters for the synthesis of 3-substituted piperazin-2-ones

Dynamic resolution of α-halo esters derived from five chiral alcohols has been investigated in nucleophilic substitution with ethylenediamine nucleophiles. Stereoselective substitution of α-halo esters and following spontaneous cyclization provide a practical protocol for asymmetric syntheses of 3-substituted piperazin-2-ones up to 94:6 er.     

Colorimetric detection of glucose using a boronic acid derivative receptor attached to unmodifed AuNPs简

A simple, cheap and non-enzymatic colorimetric strategy for glucose detection has been designed based on the interactions between a phenylboronic acid （PBA） derivative, which is coupled with gold nanoparticles （AuNPs） as the colorimetric reporters, and glucose. The PBA-AuNPs hybrid system proposed here exhibits ordered photochemistry behaviors upon the addition of glucose at different pH values. There are two linear regions of glucose concentration for the glucose sensor at different pH values, i.e., between 0.1 mmol/L and 9.8 mmol/L at pH 6 with the detection limit of 64μmol/L and between 0 and 6.5 mmol/L with the detection limit of 48 μmol/L at pH 9, respectively. To test the practicality of the sensor system, we also applied this assay to detect a glucose sample in the artificial saliva.     

One-pot synthesis of novel pyrrolo-1,4-benzoxazines via a three- component reaction of 2-amino phenols,acetylenic esters and nitrostyrene derivatives简

A simple and efficient synthetic protocol has been developed using a one-pot, three-component reaction involving 2-amino phenols, dialkyl acetylene dicarboxylates and nitrostyrene derivatives. Utilizing this protocol, a variety of novel pyrrolo-1,4-benzoxazine derivatives were synthesized in excellent yields.     

Deoxygenation of 5-O-benzoyl-1,2-isopropylidene-3-O-imidazolylthiocarbonyl-α-d-xylofuranose using dimethyl phosphite: an efficient alternate method towards a 3′-deoxynucleoside glycosyl donor

An efficient radical deoxygenation reaction of thiocarbonylimidazolyl activated glycoside analogue using dimethyl phosphite as hydrogen source and radical chain carrier was performed as a key step in a multi step synthesis towards a common 3-deoxy glycosyl donor for 3′-deoxynucleosides. This method has safety and cost advantages compared to the generally used radical reduction reagents.     

Determination of the local electron number density in laser-induced plasmas by Stark-broadened profiles of spectral lines: Comparative results from Hα, Fe I and Si II lines

Measurements of the local electron density in laser-induced plasma have been carried out from the Stark-broadened profiles of three reference lines (H_α, Fe I and Si II). The plasma has been generated from a Fe–Si sample in air using a Nd:YAG laser. Compatible values of the local electron density have been obtained from the three lines. The experiment is based on the use of an imaging spectrometer, the capability for spatial resolution of a charge-coupled device and the application of a spatial deconvolution procedure to the spectra. Distributions of the emission coefficient have been obtained, showing that the three lines are emitted from different regions of the plasma. The implications in the apparent electron density values obtained in spatially-integrated measurements are discussed: similar values are obtained for the H_α and Si II lines, while the Fe I line leads to a 25% lower value.     

Efficient synthesis of α-substituted-α-arylmethyl phosphonates using trichloroacetimidate CC coupling method

A simple convenient protocol for the synthesis of diethyl α,α-diaryl methylphosphonate derivatives 5a-f, 6b-f, 7a-f and 8a-f, diethyl α-alkenyl α-aryl methylphosphonates 9a-d and 10a-d and α-(oxoalkyl) α-aryl methylphosphonate 11a-d and 12a-d is described. Trichloroacetimidates 3a-d were treated with activated arenes, styrene, allyltrimethylsilane or silylenol ethers C-nucleophiles in the presence TMSOTf to afford the desired products in good yields and short reaction time.     

[Cu2(μ-(3,4,5-meo-ba)2bn)(μ-I)2]n, a new 1D polymeric copper(I) chain Synthesis, crystal structure, spectral and thermal studies

New 1D-chain copper(I) complex [Cu₂(μ-(3,4,5-MeO-ba)₂bn)(μ-I)₂] _n (1), where (3,4,5-MeO-ba)₂bn = N,N′-bis(3,4-dimethoxybenzylidene)-butane-1,4-diamine, involving a new bidentate Schiff-base containing a flexible spacer (=N–C–C–C–C–N=) has been synthesized and characterized by elemental analyses (CHN) and FT-IR spectroscopy. The crystal structure of 1 was determined from single-crystal X-ray diffraction analyses and shows the (3,4,5-MeO-ba)₂en acts as a bridging ligand with the nitrogen atoms of the two imine functions and leading to the dinuclear [Cu₂((μ-(3,4,5-MeO-ba)₂en)] groups. Such dinuclear [Cu₂((μ-(3,4,5-MeO-ba)₂en)] groups are bridged by two iodine anions [(μ-I)₂] to form a neutral 1D-chain copper(I) iodide coordination polymer. The coordination polyhedron about the copper(I) center in 1 is best described as a distorted trigonal planar. Thermogravimetric analyses reveal the thermal stability and decomposition pattern of 1.