Fe3O4@chitosan-bound boric acid composite as pH-responsive reusable adsorbent for selective recognition and capture of cis-diol-containing shikimic acid

Recently, shikimic acid (SA) has aroused great concern as the starting raw material for the synthesis of antiviral drug (Tamiflu) against the spread of influenza virus in the body. In this work, magnetic chitosan composite modified with boric acid and its application in SA recognition and separation was described. Chitosan (CT) with plenty of hydroxyl and amino groups was first coated on the surface of magnetic core Fe₃O₄, then carboxylic groups were grafted to the surface of Fe₃O₄@CT via anhydride modification, followed by the introduction of 3-aminophenylboronic acid (APBA). The uniform morphology and composition analysis of the adsorbent (Fe₃O₄@CT-COOH-BA) were characterized by FT-IR, XRD, XPS, SEM, TEM and UV–visible spectroscopy. The adsorption capacity of as-prepared material was explored in detail by batch mode experiments. The adsorption kinetics fitted well with a pseudo-second order model, and the adsorption isotherms was well described by the Langmuir model with a maximum adsorption capacity of 23.8 mg g⁻¹ at 25 °C. Solution pH plays a crucial role in adsorption process and the optimized pH was 8.0. In addition, Fe₃O₄@CT-COOH-BA could be easily reused through an external magnet and the adsorption capacity reduced by only 4% after five adsorption–desorption cycles. These results prove that boric acid modified magnetic chitosan composite is an effective and practical adsorbent for specific recognition and selective adsorption of cis-diol-containing compounds.     

Synthesis of phthalocyanine dimers,trimers, and oligomers bridged via phenyl groups

Several phthalocyanine dimers, trimers, and oligomers bridged via aryl (phenyl) groups were prepared using the Suzuki–Miyaura cross coupling reaction of phthalocyanine-boronate ester and various halide derivatives under palladium catalyst reaction conditions. Photophysical data reveal energy transfer between the Pc moieties resulting in the appearance of new red-shifted Q-bands. The shift and the nature of Q-band depend on the number of phenyl groups, the number of Pc, and the position of attachment on the phenyl ring.     

Investigating a Boronate-Affinity-Guided Acylation Reaction for Labelling Native Antibodies

The excellent molecular recognition capabilities of monoclonal antibodies (mAbs) have opened up exciting opportunities for biotherapeutic discovery. Taking advantage of the full potential of this tool necessitates affinity ligands capable of conjugating directly with small molecules to a defined degree of biorthogonality, especially when modifying natural Abs. Herein, a bioorthogonal boronate-affinity-based Ab ligand featuring a 4-(dimethylamino)pyridine and an S-aryl thioester to label full-length Abs is reported. The photoactivatable linker in the acyl donor facilitated purification of azide-labelled Ab (N₃-Ab) was quantitatively cleaved upon brief exposure to UV light while retaining the original Ab activity. Click reactions enabled the precise addition of biotin, a fluorophore, and a pharmacological agent to the purified N₃-Abs. The resulting immunoconjugate showed selectivity against targeted cells. Bioorthogonal traceless design and reagentless purification allow this strategy to be a powerful tool to engineer native antibodies amenable to therapeutic intervention.     

Solid‐state 11B and 13C NMR,IR, and X‐ray crystallographic characterization of selected arylboronic acids and their catechol cyclic esters

Nine arylboronic acids, seven arylboronic catechol cyclic esters, and two trimeric arylboronic anhydrides (boroxines) are investigated using ¹¹B solid‐state NMR spectroscopy at three different magnetic field strengths (9.4, 11.7, and 21.1 T). Through the analysis of spectra of static and magic‐angle spinning samples, the ¹¹B electric field gradient and chemical shift tensors are determined. The effects of relaxation anisotropy and nutation field strength on the ¹¹B NMR line shapes are investigated. Infrared spectroscopy was also used to help identify peaks in the NMR spectra as being due to the anhydride form in some of the arylboronic acid samples. Seven new X‐ray crystallographic structures are reported. Calculations of the ¹¹B NMR parameters are performed using cluster model and periodic gauge‐including projector‐augmented wave (GIPAW) density functional theory (DFT) approaches, and the results are compared with the experimental values. Carbon‐13 solid‐state NMR experiments and spectral simulations are applied to determine the chemical shifts of the ipso carbons of the samples. One bond indirect ¹³C‐¹¹B spin‐spin (J) coupling constants are also measured experimentally and compared with calculated values. The ¹¹B/¹⁰B isotope effect on the ¹³C chemical shift of the ipso carbons of arylboronic acids and their catechol esters, as well as residual dipolar coupling, is discussed. Overall, this combined X‐ray, NMR, IR, and computational study provides valuable new insights into the relationship between NMR parameters and the structure of boronic acids and esters. Copyright © 2012 John Wiley & Sons, Ltd.     

Boronate affinity adsorption of cis‐diol‐containing biomolecules in nonaqueous solvent

Boronate affinity has attracted much attention in recent years. It has been broadly used for selective isolation and enrichment of cis‐diol‐containing molecules. Conventionally, the cis‐diols are adsorbed in mild alkaline aqueous solutions. In this work, for the first time, we found that boronate affinity adsorption could also be performed in nonaqueous solvent at nonbasic pH. Cis‐diol‐containing compounds present in herbal medicines were used for the adsorption test. The results indicated that all compounds obtained higher recoveries in the organic solvents (methanol, acetonitrile, ethyl acetate) compared with alkaline buffer. The adsorption of vicinal cis‐diol‐containing molecules in organic solvents could be accomplished rapidly, with high selectivity and high recoveries (>80%). These results shed light on the possibility of boronate affinity adsorption in nonaqueous solvents. The results are very important for the isolation and enrichment of cis‐diols, which have poor solubility in water, especially for those in herbal medicines. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis of Boronate‐Based Benzo[fg]tetracene and Benzo[hi]hexacene via Demethylative Direct Borylation

A demethylative direct borylation is reported, which was applied to the synthesis of benzo[fg]tetracenes containing boronate ester, amide, and thioester substructures. Depending on the heteroatom adjacent to boron, the molecules showed characteristic photophysical properties, molecular arrangements, and chemical stabilities. The key to the successful synthesis is the appropriate choice of the boron source and Brønsted base. The versatility of the direct borylation was demonstrated by the synthesis of a boronate‐based benzo[hi]hexacene.     

Borated Titania,a New Option for the Selective Enrichment of cis‐Diol Biomolecules

As low abundance cis‐diol biomolecules are of great significance in biological organisms, preparation of materials for the selective enrichment of such compounds is highly favorable for the development of the related proteomics and metabolomics. To this end, we have prepared monolithic borated titania by a non‐aqueous sol‐gel strategy as a new inorganic affinity material for the specific capture of nucleosides, glycopeptides and glycoproteins. Benefiting from the inorganic framework, this material prevented the hydrophobic interference, which was somewhat inevitable for the mainstream organic‐based boronate affinity materials. The prepared material was carefully characterized by scanning electron microscope (SEM), X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS) and nitrogen‐sorption experiments to investigate the morphology and elemental composition. The excellent performance of borated titania on enrichment of cis‐diol biomolecules was demonstrated by extracting the glycopeptides from horseradish peroxidase (HRP) digestion, standard glycoproteins, and nucleosides from a human‐urine matrix. This kind of inorganic affinity material offers a new option for selective enrichment or separation of cis‐diol biomolecules.     

Metal-free halogenation of arylboronate with N-halosuccinimide

Efficient bromination and chlorination of aryl pinacol boronates were accomplished without the addition of metal reagent. The reaction proceeded efficiently with electron-rich arylboronates or heteroarylboronates in DMF or acetonitrile, to afford mono-, di-, or trihalogenated aryl pinacol boronates.