Microchip extraction of catecholamines using a boronic acid functional affinity monolith

A novel solid phase extraction microchip with a boronic acid functional affinity monolithic disc was developed in this work. Vinyl phenylboronic acid–ethylene glycol dimethacrylate co-polymer monoliths, which have pore sizes up to 20 μm, were investigated for extraction of catecholamines using adsorption and desorption studies in a batch system. Desorption yields of greater than 90% were achieved for catecholamines at pH 3 and below. Monolithic discs were then formed in chambers in borofloat glass microfluidic chips using in situ UV polymerization. Adsorption on the monolithic discs was performed via electrokinetic flow, with catecholamines determined via laser-induced native fluorescence (LINF) detection following electrokinetic elution. Microchips containing the boronic acid functional polymer discs worked well for extraction of catecholamines, providing greater than 100 fold concentration enrichment. This study demonstrated that a solid phase extraction microchip, containing an easily prepared monolith disc, will be useful for boronate affinity extraction of cis-diol containing compounds.     

Synthesis of a new ionic spin probe for investigation of polar and non-polar solvents

A synthesis is described for the new ionic spin probe potassium-(18-crown-6)-4-sulfonatooxy-2,2,6,6-tetramethyl-piperidine-1-yloxyl. This new spin probe shows an improved solubility in both polar and non-polar solvents in comparison with the potassium-4-sulfonatooxy-2,2,6,6-tetramethylpiperidine-1-yloxyl. Furthermore, the solubility of potassium-(18-crown-6)-4-sulfonatooxy-2,2,6,6-tetramethyl-piperidine-1-yloxyl is also improved in ionic liquids relative to the potassium salt comprising no crown ether moiety. The spin probe potassium-(18-crown-6)-4-sulfonatooxy-2,2,6,6-tetramethyl-piperidine-1-yloxyl is highly suitable for investigation of both less polar and highly polar environments.     

A mild and efficient new synthesis of aryl sulfones from boronic acids and sulfinic acid salts

A new efficient and mild preparation of sulfones from boronic acids and sulfinic acid salts is reported. The cross-coupling reaction mediated by cupric acetate gives access to a variety of sulfones in excellent yield.     

Iminophosphine-palladium(0) complexes as highly active catalysts in the Suzuki reaction. Synthesis of undecaaryl substituted corroles

The iminophosphine-palladium(0) complex [Pd(dmfu)(P-N)] [dmfu=dimethyl fumarate; P-N=2-(PPh₂)C₆H₄-1-CHNC₆H₄-4-OMe] is a very efficient catalyst for the Suzuki coupling. In the reaction of aryl bromides with phenylboronic acid, turnover numbers up to ca. 200,000 are obtained at 110 °C in 2 h. Good rates are obtained also with the sterically hindered and electronically deactivated 2-bromo-1,3,5-trimethylbenzene. The complex is able to catalyze the exhaustive arylation of 2,3,7,8,12,13,17,18-octabromo-5,10,15-triphenylcorroleCu(III) to yield the corresponding undecaaryl substituted derivative.     

DFT calculations as a powerful tool for ESR spin trapping experiments

A combined electron spin resonance (ESR) and density functional theory study has been carried out to obtain deeper insight in the reaction mechanism of the photorearrangement of 3‐hydroxyindolic nitrones. Also, in this case, the combination of these techniques constitutes a powerful tool when discriminating between different reaction pathways. In particular, density functional theory calculations played an important role for unraveling the overlapping of signals coming from different species in the ESR spin trapping experiments. In the present study, the computed energies and the corresponding ESR parameters of each possible isomer hypothesized have been considered, taking also into account their different possibilities of intramolecular H‐bond formation. However, the results obtained indicate that the possibility of intramolecular H‐bonding did not play a determinant role in this case. Copyright © 2016 John Wiley & Sons, Ltd.     

Recognition of phospho sugars and nucleotides with an array of boronic acid appended bipyridinium salts

The solution-phase sensor array of three cationic bis-boronic acid appended benzyl viologens (BBV) and the anionic fluorescent dye, 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS), is able to discriminate among five phospho sugars, four nucleotides and three neutral saccharides in aqueous buffered solution at low mM concentrations. Linear discriminant analysis, principal component analysis, and hierachical cluster analysis studies showed the “discrimination limit” (lowest analyte concentration where the discrimination is still 100%) to be 4 mM. Calculated K_b and F_max/F₀ values from binding curves of the three BBVs with 1-12 were also used to perform multi-variate analyses with very good discrimination results.     

Diastereo- and enantio-selective crotylation of α-ketoesters using crotyl boronic acid ester complexes

A diastereo- and enantio-selective crotylation of ethyl pyruvate has been achieved using a chiral boronic acid auxiliary-based approach. This reaction creates two contiguous stereogenic centers, one of which is a quaternary carbon with complete diastereoselectivity and with enantioselectivities up to 7:1 (73% ee).     

LIC-KOR promoted formation of conjugated dienes as useful building blocks for palladium-catalyzed syntheses

It is demonstrated that α,β-unsaturated acetals can be considered a synthetic tool for transforming carbonyl derivatives into cheap and easily accessible starting materials for the construction of various and more complex structures. The lithium-potassium mixed superbase LIC-KOR induces a conjugate elimination reaction that converts α,β-unsaturated acetals into 1E-1-alkoxybuta-1,3-dienes. These derivatives can be readily metalated in situ and functionalized by reaction with electrophiles. The results can be grouped in two sections: (1) the palladium-catalyzed cross-coupling reaction between alkoxydienylboronates and tetralone- or isochromanone-derived vinyl triflates; (2) the regio- and stereoselective cross coupling reaction with aryl derivatives in the presence of a palladium catalyst (Heck conditions).     

Petasis reaction of activated quinoline and isoquinoline with various boronic acids

Petasis reactions of activated forms of quinolines and isoquinolines with electron sufficient boronic acids such as 2-benzofuranboronic acid, trans-2-phenylvinylboronic acid etc in DCM proceeded smoothly at room temperature to provide the corresponding dihydroquinolines and dihydroisoquinolines in good to high yields.     

Synthesis of a boronated amino acid as a potential neutron therapy agent: 1-amino-3-[(dihydroxyboryl)ethyl]cyclobutanecarboxylic acid

A novel boronated aminocyclobutanecarboxylic acid was synthesized in 10 steps for potential use in neutron capture therapy. The molecule was modeled after the unnatural amino acid 1-aminocyclobutanecarboxylic acid, which has shown high uptake in brain tumors.     

Synthesis of novel triazolopyridylboronic acids and esters. Study of potential application to Suzuki-type reactions

This paper describes a general method for the synthesis of novel [1,2,3]triazolo[1,5-a]pyridylboronic acids and esters, and the first results on Suzuki cross-coupling reactions with these new compounds and [1,2,3]triazolo[5,1-a]isoquinolylboronic acid, reacting with a variety of aryl halides as a route to 7-aryltriazolopyridines and 5-aryltriazoloisoquinolines.     

Sensitive determination of four camptothecins by solid-phase microextraction-HPLC based on a boronic acid contained polymer monolithic layer

Camptothecin (CPT) and its derivative have been revealed to possess special anti-cancer activity, extraction methods are necessary for trace determination of CPTs in complex samples. In this work, we prepared a high efficient boronic acid-based polymer monolithic layer for microextraction of CPTs. A disposable membrane filter-based extraction device was developed, and boronic acid groups were co-polymerized into a polyporous polymer skeleton and served as the monolithic sorbent. The prepared poly(4-VB-MA-TRIM) showed good stability and great extraction efficiency toward four CPTs. After optimization of extraction conditions, poly(4-VB-MA-TRIM)-based solid-phase microextraction was coupled HPLC for determination of CPTs in biological samples. The method exhibited low limits of detection of 0.05–0.2 ng mL⁻¹, which is significantly more sensitive than reported HPLC methods. The method also showed wide linear range (0.1–100 and 0.5–200 ng mL⁻¹), good linearity (R² ≥ 0.9981) and good reproducibility (RSD ≤3.76%). The method has been applied in plasma samples, with good selectivity and good recoveries ranging from 85.1 to 104.7%.     

Synthesis of new, BODIPY-based sensors and labels

New, 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) dye based thiol-reactive fluorescent label, fluorescent amino acid, and fluoroionophore compounds with 540-560 nm emission are described. Combination of a BODIPY dye with a nitronyl nitroxide or an imino nitroxide or a bifunctional pyrroline nitroxide furnished a nitric oxide, a redox sensitive molecule and a double (spin and fluorescence) label, respectively.     

Catalyst-free Petasis-type reaction: Three-component decarboxylative coupling of boronic acids with proline and salicylaldehyde for the synthesis of alkylaminophenols

A simple method is reported for the synthesis of alkylaminophenols in moderate to good yields via a three-component, catalyst-free decarboxylative coupling of proline with salicylaldehyde and boronic acids.     

Synthesis of novel fluorescent 3-aryl- and 3-methyl-7-aryl-[1,2,3]triazolo[1,5-a]pyridines by Suzuki cross-coupling reactions

Two series of compounds, 3-aryl- (series A, compounds 2a-j) and 3-methyl-7-aryl-[1,2,3]triazolo[1,5-a]pyridines (series B, compounds 3a-j) have been synthesized by Suzuki cross-coupling reactions, with a triazolopyridine halide and an aryl or heteroaryl boronic acid in moderate to good yields. All compounds obtained are fluorescents, the quantum yields, particularly those of compounds 3f-j, are very high.     

Phenylboronic acid as a mild and efficient catalyst for Biginelli reaction

The synthesis of 3,4-dihydropyrimidinone derivatives was achieved in good to excellent yields using phenylboronic acid as catalyst to promote the Biginelli three-component condensation of a diversity of aromatic aldehydes, ethyl acetoacetate and urea or thiourea.     

Fluorogenic derivatization of aryl halides based on the formation of biphenyl by Suzuki coupling reaction with phenylboronic acid

The fluorogenic derivatization method for aryl halide was developed for the first time. This method was based on the formation of fluorescent biphenyl structure by Suzuki coupling reaction between aryl halides and non-fluorescent phenylboronic acid (PBA). We measured the fluorescence spectra of the products obtained by the reaction of p-substituted aryl bromides (i.e., 4-bromobenzonitrile, 4-bromoanisole, 4-bromobenzoic acid ethyl ester and 4-bromotoluene) with PBA in the presence of palladium (II) acetate as a catalyst. The significant fluorescence at excitation maximum wavelength of 275–290 nm and emission maximum wavelength of 315–350 nm was detected in all the tested aryl bromides. This result demonstrated that non-fluorescent aryl bromides could be converted to the fluorescent biphenyl derivatives by the coupling reaction with non-fluorescent PBA. We tried to determine these aryl bromides by HPLC-fluorescence detection with pre-column derivatization. The aryl bromide derivatives were detected on the chromatogram within 30 min without any interfering peak derived from the reagent blank. The detection limits (S/N = 3) for aryl bromides were 13–157 fmol/injection.     

Combining ferrocene,thiophene and a boronic acid: a hybrid ligand for reagentless electrochemical sensing of cis-diols

A redox-active affinity ligand suitable for reagentless sensing of cis-diols was synthesised and characterised. 4-[(Ferrocenylamino)methyl]thiophene-3-boronic acid (FcTBA) was allowed to interact with the model cis-diol, sorbitol. A discrete, cathodic shift of the redox potential was observed upon interaction of FcTBA with sorbitol thus providing simultaneous differentiation between the free and bound forms of this sensor molecule. Similar behaviour was observed also for FcTBA co-immobilised with thiophene in a mixed self-assembled monolayer on a gold electrode.     

Preparation and application of functionalized nanoparticles of CdSe capped with 11-mercaptoundecanoic acid as a fluorescence probe

A new fluorescence probe, CdSe nanocrystal has been prepared and modified with 11-mercaptoundecanoic acid [HS-(CH₂)₁₀-COOH]. The functionalized nanoparticles were characterized using transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) spectroscopy and photoluminescence (PL) spectroscopy. The results demonstrate that CdSe is dispersed homogeneously in aqueous solution and well protected from the environmental oxygen. They can be used as a new fluorescence probe for lysozyme, which was simple, rapid and specific. Under the optimum condition, the response is linearly proportional to the amount of lysozyme from 0.20 to 26.0 μg ml⁻¹, and the limit of detection is 0.115 μg ml⁻¹. The proposed method has been applied to the determination of lysozyme in egg white, with the recovery of 96-105%.