4-aminophenylboronic acid

Boronic acid-containing polyaniline has also been utilized in diabetes-related research. One such polymer (23) (Fig. 17) has been observed to exhibit a linear near-infrared optical response to saccharides.43 The polymer was prepared by the copolymerization of aniline with 3-aminophenylboronic acid using lOmM (NH4)S208 in 1M HC1. The films were observed to undergo changes in the absorption spectra on addition of saccharides at pH 7.2. 

TOP Tobacco peroxidase, HRP Horseradish peroxidase, APB A 3-Aminophenylboronic acid monohydrate, TBA 3-Thiopheneboronic acid, VYP 4-vinylpyridine, TRIM Trimethylolpropane trimethacrylate... 

MAA Methacrylic acid, EGDMA Ethylenglycoldimethacrylate, DAM Diethylaminoethylaminoethylmethacrylate, VPY4-Vinylpiridine DVB Divinylbenzene, CMMC 7-Carboxymethoxy-4-methylcoumarin, AA Allylamine, 4MU 4-Methylumbelliferone, OP A o-Phthalic dialdehyde + beta-mercaptoethanol, APBA 3-Aminophenylboronic acid, TBA 3-Thiopheneboronic acid, DTAF 5-[(4,6-Dichlorotriazin-2-yl)amino]fluorescein, FITC Fluorescein isothiocyanate... 

Arylidene thioxanthenes, for example, 580, prepared by the Pd(0) coupling of 9-bromomethylenethioxanthene and 3-aminophenylboronic acid, are useful for treating congestive heart disease, hypertension, and inflammatory diseases (Equation 203) <2005W02005/066153>. 

Although the most widely used ligand is 3-aminophenylboronic acid, a variety of other boronate ligands have been described to identify modulation in their specificity for glycoproteins and to favor the esterification with c/s-diols at a neutral pH. 

Scheme 20.4 Coupling of 3-aminophenylboronic acid (12) to poly (acrylic acid) (11) attached to a magnetic surface.

For MIP deposition at relatively low monomer conversion, other polymerization mechanisms had also been used. For example, a functional polyaniline layer with about 100 nm thickness, coating the bottom of polystyrene microplates, was obtained from 3-aminophenylboronic acid in aqueous buffer solution, initiated by chemical... 

Thin layers on microtiter plate wells The microtiter plate format is universally employed in biological immunoassays such as ELISA and enables a very high assay throughput, in particular when combined with automation. Thus, thin layers ofMIPs in microtiter plate wells are of immense interest for MIAs involving colorimetric or fluorescence detection. Two approaches have been described the entrapment of 2,4-D-imprinted vinylpyridine/TRIM microspheres in films of polyvinylalcohol hydrogel [53] and the preparation of imprinted poly-3-aminophenylboronic acid and related conjugated polymers which precipitate as films on the microwell surface [19,54]. The polyvinyl alcohol composite films have been used in combination with... 

The enhanced reactivity of 3-aminophenylboronic acid in the presence of fluoride was reportedly due to interaction between fluoride and boron. The complexation of fluoride with the boronic acid moiety substantially reduced the oxidation potential required for polymerization, thereby avoiding deleterious side reactions that occur at more positive potentials. The binding of fluoride was confirmed by Fabre et al. [31] with NMR spectroscopy of monomer solution before and after addition of fluoride, since the chemical shift is sensitive to the hybridization of the boron. In monomer solution without fluoride, a NMR signal was observed at 27.7 ppm with reference to borontrifluoride etherate. However, after addition of fluoride, a new signal was observed at 3.4 ppm. The B chemical shift of a tetrahedral boronate formed in the presence... 

Figure 3.4 Cyclic voltammogram of 40mM 3-aminophenylboronic acid plus (a)40mM NaF and (b) 300mM NaF in pH 5.0 10 X PBS (pH was adjusted with 0.5 M HCl) and (c) 300mM NaF in pH 7.4 10 X PBS at GC electrode. Scan rate lOOmV/s (Analyst, 2003, 128, 803, B. A. Deore, M. S. Freund. Reproduced with permission of Tbe Royal Society of Chemistry.)...

Similarly, self-doped PABA can be prepared using excess of saccharide and one equivalent of fluoride to monomer. Complexation between saccharides and aromatic boronic acids is highly pH dependent, presumably due to the tetrahedral intermediate involved in complexation [25]. Because the pKa of 3-aminophenylboronic acid is 8.75, complexation requires pH values above 8.6. This pH range is not compatible with the electrochemical synthesis of polyaniline, which is typically carried out near a pH value of 0. However, Smith et al. have shown that the addition of fluoride can stabilize the complexation of molecules containing vicinal diols with aromatic boronic acids [23]. Based on this work, it was postulated that the electrochemical polymerization of a saccharide complex with 3-aminophenylboronic acid in the presence of one molar equivalent of fluoride at pH values lower than 8 is possible if a self-doped polymer is produced in the process. 

Cyclic voltammograms of 3-aminophenylboronic acid in 10 M D-fructose in 10 X PBS without and with fluoride is shown in Figure 3.5. No oxidation of monomer is observed without fluoride in pH 5.0 10 X PBS even in the presence of relatively high D-fructose concentrations (Figure 3.5, a). This is in contrast to the clear oxidation of 3-aminophenylboronic acid under identical conditions in the absence of fluoride and D-fructose (Figure 3.6, a). Similar behavior was observed at pH 7.4, in the absence of fluoride (Figure 3.6, b). However, after... 

Table 3.2 B and NMR chemical shifts of 3-aminophenylboronic acid (3-APBA) adducts. (Reprinted with permission from Chemistry of Materials, 16,1427. Copyright (2004) American Chemical Society.)...

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