99768-12-4Relevant articles and documents
Boronic acid fluorophore/β-cyclodextrin complex sensors for selective sugar recognition in water
Tong,Yamauchi,Hayashita,Zhang,Smith,Teramae
, p. 1530 - 1536 (2001)
A novel boronic acid fluorophore 1/β-cyclodextrin (β-CyD) complex sensor for sugar recognition in water has been designed. The probe 1 bearing pyrene moiety as a fluorescent signal transducer exhibits no fluorescence emission, due to its aggregation in water containing 2% DMSO; however, the addition of β-CyD to this solution largely changes UV-vis and fluorescence spectra of 1 by forming an inclusion complex with β-CyD, and an efficient fluorescence emission response of 1/β-CyD complex upon sugar binding is found to be obtained at pH 7.5. The pH-fluorescence profile of the 1/β-CyD complex reveals that the boronate ester formation with fructose induces the apparent pKa shift from 7.95 ± 0.03 in the absence of fructose to 6.06 ± 0.03 in the presence of 30 mM fructose, resulting in the fluorescence emission response under the neutral condition. The spectral properties of 1 in 95% methanol:5% water (v/v), as well as the fluorescence quenching study of 1-methylpyrene with 4-methoxycarbonylphenyl-boronic acid 2, demonstrate that the response mechanism is based on the photoinduced electron transfer (PET) from the pyrene donor to the acid form of phenylboronic acid acceptor in 1, and thus, the proton dissociation of phenylboronic acid induced by sugar binding inhibits the PET system while increasing the fluorescence intensity of the pyrene moiety. To evaluate the binding ability and selectivity of the 1/β-CyD complex for monosaccharides in water, the response equilibria have been derived. The 1:1 binding constants of the 1/β-CyD complex obtained from the equilibrium analysis are in the order: D-fructose (2515 ± 134 M-1) ? L-arabinose (269 ± 28 M-1) > D-galactose (197 ± 28 M-1) > D-glucose (79 ± 33 M-1), which is consistent with the binding selectivity of phenylboronic acid.
Hydroxyl radical-mediated oxidative cleavage of CC bonds and further esterification reaction by heterogeneous semiconductor photocatalysis
Hong, Mei,Jia, Rui,Miao, Hongyan,Ni, Bangqing,Niu, Tengfei,Wang, Hui
, p. 6591 - 6597 (2021/09/10)
A hydroxyl radical-mediated aerobic cleavage of alkenes and further sequence esterification reaction for the preparation of carbonyl compounds have been developed by using tubular carbon nitride (TCN) as a general heterogeneous photocatalyst under an oxygen atmosphere with visible light irradiation. This protocol has an excellent substrate scope and gives the desired aldehydes, ketones and esters in moderate to high yields. Importantly, this metal-free procedure employed photogenerated hydroxyl radicals in situ as green oxidation active species, avoiding the present additional initiators. The reaction could be carried out under solar light irradiation and was applicable to large-scale reactions. Furthermore, the recyclable TCN catalyst could be used several times without a significant loss of activities.
Synthesis of 3,5-Disubstituted Isoxazoles through a 1,3-Dipolar Cycloaddition Reaction between Alkynes and Nitrile Oxides Generated from O-Silylated Hydroxamic Acids
Carloni, Laure-Elie,Mohnani, Stefan,Bonifazi, Davide
supporting information, p. 7322 - 7334 (2019/11/05)
In this paper, we report the regioselective synthesis of 3,5-disubstituted isoxazoles by 1,3-dipolar cycloaddition between alkynyl dipolarophiles and nitrile oxide dipoles generated in-situ from O-silylated hydroxamic acids in the presence of trifluoromethanesulfonic anhydride and NEt3. Thanks to the mild, metal-free and oxidant-free conditions that this strategy offers, the reaction was successfully applied to a wide variety of alkynyl dipolarophiles, demonstrating the tolerance of this approach to diverse functional groups. In particular, we have shown that the method was compatible with biological molecules such as peptides and peptide nucleic acids (PNA). This protocol constitutes another example of metal-free 1,3-dipolar cycloaddition leading to the regioselective formation of isoxazoles.
