Studies of cyclodextrin effect for glycosylation by galactosyltransferase

Cyclodextrins (CDs) do not disturb HPLC purification and do not form lather, which makes them superior to commonly used surfactants. In this paper, the authors describe the utility of CDs, specifically α-CD, β-CD, and γ-CD, for the synthesis of neoglycolipids from insoluble peptide-linked substrates. γ-CD was found to be well matched to the bulky benzyl group and accelerated the reaction for the substrate having Phe (F), while β-CD was well matched to the methyl group and accelerated the reaction for the substrate having Ala (A). Galactosylation to water-insoluble peptide-linked glucosaminide substrate by galactosyltransferase proceeded 63% at the most, but using either β-CD or γ-CD gave quantitative yield within 10 h.     

Direct glycosylation with anomeric hydroxy sugars by activation with 3-fluorophthalic anhydride and trifluoromethanesulfonic anhydride

An efficient and direct one-pot glycosylation method using anomeric hydroxy sugars as glycosyl donors, employing 3-fluorophthalic anhydride and triflic anhydride as activating agents, has been developed. The present glycosylation utilizing 3-fluorophthalic anhydride resulted in few to no undesired self-condensed esters than the glycosylation using phthalic anhydride. Intermediates in the present glycosylation were identified by an NMR study.     

Rh(III)-catalyzed C8 arylation of quinoline N-oxides with arylboronic acids

Herein, we report the first Rh^III-catalyzed regioselective C8 arylation of quinoline N-oxides with commercially available arylboronic acids as coupling partners. This procedure is simple, and the reaction shows perfect regioselectivity, a broad substrate scope, and isolated yields of up to 92%. We demonstrate the utility of the reaction by using it for late-stage functionalization of a fungicide.     

ipso-Nitrosation of arylboronic acids with chlorotrimethylsilane and sodium nitrite

Nitroso compounds are versatile reagents in synthetic organic chemistry. Herein, we disclose a feasible protocol for the ipso-nitrosation of aryl boronic acids using chlorotrimethylsilane–sodium nitrite unison as nitrosation reagent system.     

Efficient synthesis of core 2 class glycosyl amino acids by one-pot glycosylation approach

We describe the one-pot synthesis of core 2 class branched oligosaccharides initiated by chemo-selective glycosylation of silyl ether. Glycosylation of 6-O-silyl-4-benzyl-2-azido-thiogalactoside with glycosyl fluoride provided selectively 6-glycosylated thioglycoside without both O-glycosylation at the 3 position and S-glycosylation. Subsequent coupling of galactosyl fluoride and amino acids afforded the protected branched oligosaccharides in good yields.     

Regioselective arylation of 2′-deoxyribonucleosides on amido or imino sites by copper(II)-mediated direct coupling with arylboronic acids

N¹-Aryl derivatives of 2′-deoxyguanosine (dG) were synthesized by copper(II)-mediated coupling of dG with arylboronic acids. Analogous aryl derivatives of 2′-deoxyinosine (dIn), 2′-deoxyuridine (dU), thymidine (T), 2′-deoxyadenosine (dA), and 2′-deoxycytidine (dC) were also conveniently synthesized by this method. Arylation took place preferentially on the amido functions in dG and dIn and the imino functions in dU or T. Remarkably, the nucleosides themselves served as internal ligands as well as reactants.     

Regioselective synthesis of 2,5-dihydro-4H-pyrazolo[4,3-c]quinolin-4-ones by the cyclization of 3-acyl-4-methoxy-1-methylquinolinones with hydrazines

Reaction of 3-acyl-4-methoxy-1-methylquinolinones 2 and 5 with hydrazines has been investigated under different experimental conditions. Compound 2 always gave rise selectively and exclusively to the regioisomeric 1,3-disubstituted- or 2,3-disubstituted-pyrazolo[4,3-c]quinolin-4(5H)one (compounds 3a,b or 4a,b, respectively), while reaction of 5 with N-methylhydrazine led to a mixture of pyrazoles 7a and 8a. With N-phenylhydrazine, compounds 7b or 8b were regioselectively obtained. Compound 8a could be selectively synthesized working in solventless conditions. Structural elucidation of all products was independently achieved by NMR spectroscopy.     

Facile synthesis of substituted alkynes by nano-palladium catalyzed oxidative cross-coupling reaction of arylboronic acids with terminal alkynes

The oxidative cross-coupling of terminal alkynes with arylboronic acids catalyzed by the porous palladium nanospheres was developed. In the presence of silver oxide, triphenylphosphine and cesium carbonate, the reaction provided the corresponding arylalkynes with good to excellent yields. There were also other obvious advantages such as broad applicability, high selectivity, simple experimental operation as well as the convenient preparation, high efficiency and reusability of catalyst. The possible mechanism of this transition-metal nanoparticles catalyzed oxidative cross-coupling reaction of two nucleophiles was proposed.     

Regioselective synthesis of functionalized 2-(phenylthio)benzoates by ‘[3+3] cyclization/homo-Michael’ reactions of 1-methoxy-1-trimethylsilyloxy-3-phenylthio-1,3-butadienes with 1,1-diacylcyclopropanes

2-(Phenylthio)benzoates containing a remote halide function are regioselectively prepared by ‘[3+3] cyclization/homo-Michael’ reactions of 1-methoxy-1-trimethylsilyloxy-3-phenylthio-1,3-butadienes with 1,1-diacylcyclopropanes.     

Regiochemical control of the ring-opening of aziridines by means of chelating processes. Part 4: Regioselectivity of the opening reactions with MeOH of 1-(benzyloxy)-2,3- and -3,4-N-(methoxycarbonyl)aziridoalkanes under condensed and gas-phase operating conditions

The regioselectivity of the addition reaction of MeOH both in the condensed phase (MeOH/H₂SO₄) and in the gas-phase (MeOH/D₃⁺) was examined in a series of activated aziridines. The results indicate that gas-phase operating conditions are particularly favorable for the occurrence of D⁺-mediated chelated bidentate species, which influence the regioselectivity of the opening process. In the condensed phase, the chelating MeOH/LiClO₄ protocol turned out to be decidedly less effective for regioselectivity and also in determining the composition of the reaction mixture.     

Synthesis of orthogonally protected 1,2-diaminopropanoic acids by ring-opening of 3-unsubstituted N-activated aziridine 2-carboxylates with para-methoxybenzylamine: a study of the regioselectivity of the reaction

Orthogonally protected 1,2-diaminopropanoic acids (DAPs) have been synthesised in good yields by the ring-opening of 3-unsubstituted N-activated aziridine 2-carboxylates with para-methoxybenzylamine. The choice of both the N-activating group and ester alkyl group had a significant influence on the ratio of attack at the α or β positions of the aziridine. However, the regiochemical outcome is not predictable.     

Regiochemical control of the ring opening of 1,2-epoxides by means of chelating processes. Part 18: Regioselectivity of the opening reactions with MeOH of 1-(benzyloxy)-2,3- and -3,4-epoxyalkanes under condensed and gas phase operating conditions

The regiochemical behavior of a series of aliphatic open chain epoxides bearing a heterofunctionality in an allylic or homoallylic relationship has been examined in the opening reaction with MeOH under both condensed and gas phase operating conditions. The results indicate that the proton (actually D⁺) possesses in the gas phase intrinsic chelating properties which are even superior than those of Li⁺ in the condensed phase.     

Generally applicable and efficient oxidative Heck reaction of arylboronic acids with olefins catalyzed by cyclopalladated ferrocenylimine under base- and ligand-free conditions

A mild and efficient method for oxidative Heck-type reaction of arylboronic acids with olefins catalyzed by cyclopalladated ferrocenylimine was developed. The results represent the first examples involving the palladacycle as the catalyst for such couplings. Moreover, the catalytic system could tolerate various functional groups, such as F, Cl, Br, NO₂ and CH₃O, and the substrates could be extended to a wide range of olefins from acrylic esters, α,β-unsaturated ketones to alkenes. Furthermore, the olefination could proceed well under base- and ligand-free conditions and employ oxygen as the environmentally benign oxidant.     

Adsorption behavior of urokinase by polypropylene film modified with amino acids as affinity groups

In order to prepare a new-type adsorbent with an affinity ligand, polypropylene films modified with amino acid groups such as -phenylalanine (Phe), , -Phe, -cysteine (Cys), and , -tryptophane (Try), were prepared by radiation-induced grafting of glycidyl methacrylate (GMA) onto polypropylene (PP) films and subsequent amination of poly-GMA graft chains. The physical and chemical properties of the GMA-grafted PP film and the PP film modified with amino acid groups were investigated by IR and XPS. The adsorption of urokinase for the PP films modified with four kinds of amino acid groups were examined under various conditions, such as the contents of the amino acid group and pH value. The adsorption of urokinase increased with the increasing content of the amino acid group. The adsorption of the PP film modified with four kinds of amino acid groups was in the following order: -Phe> , -Phe> , -Try> -Cys. The adsorption amounts of urokinase by the PP film modified with four kinds of amino acid groups at pH 7.4 was higher than that at pH 9.0.     

Efficient construction of C–C bonds from aryl halides/aryl esters with arylboronic acids catalysed by palladium(II) thiourea complexes

A new set of palladium(II) complexes comprising phenyl(thiazolyl)thiourea ligands have been successfully synthesized and characterized with the aid of analytical as well as spectral (IR, UV–visible and NMR) methods. A distorted square‐planar geometry with N^S coordination mode of thiourea ligands in the new palladium complexes was corroborated by single‐crystal X‐ray diffraction methods. Interestingly, the palladium(II) thiourea complexes showed the highest catalytic activity with 0.1 mol% catalyst loading in Suzuki–Miyaura cross‐coupling reactions utilizing a range of aryl bromides/unactivated aryl chlorides with arylboronic acids as coupling partners in aqueous–organic media. Syntheses of diaryl ketones using aryl esters and arylboronic acids as coupling partners were also achieved with low catalyst loading within 20 h. The potential of our catalyst was demonstrated by its wide substrate scope, low catalyst loadings and high isolated yield. Moreover, the influences of key parameters like solvent, base, temperature and catalyst loading were also investigated.     

Analysis of the compounds in the synthesis mixtures of hydroxy acids by a gradient programmed RP-HPLC with UV/vis and RI detectors

Summary A gradient programmed reversed phase high-performance liquid chromatographic (RP-HPLC) method is described for the quantitative determination of some aldehydes, hydroxy aldehydes, unsaturated aldehydes, hydroxy carboxylic acids, carboxylic acids, alcohols and polyols using an ultraviolet and a refractive index detector in series. The sample matrices are synthesis mixtures of hydroxy carboxylic acids. The structures of the hydroxy aldehyde intermediates are determined by¹³C NMR and the influence of sample preparation on analysis results is discussed. The limits of detection and the precision of the method are evaluated.