Asymmetrically decorated POM framework formed by a chiral polyanion

<p>Reactions of NaH₂AsO₄ with C-type polyanion precursor lead to a new compound, (NH₄)₁₅[As₂Fe₆Mo₂₂O₈₅AsO₂(OH)₂]·31.5H₂O (<b>1</b>). Compound <b>1</b> was characterized by elemental analysis, infrared spectra, thermogravimetric analysis, and single-crystal X-ray diffraction. Structural analysis reveals that AsO₂(OH)²⁻ asymmetrically decorated the POM framework, constituting the first inorganic anion asymmetrically decorating a POM. AC measurements of the frequency-dependent <i>χ</i>′′ below 5 K indicated a slow magnetization relaxation in <b>1</b>, resembling typical single-molecule-magnet behavior. Photocatalytic experiments indicated that introduction of AsO₂(OH)²⁻ may offer new active sites and enhanced the overall photocatalytic activity compared with the C-type precursor.</p

Silver-Catalyzed Radical Arylphosphorylation of Unactivated Alkenes: Synthesis of 3‑Phosphonoalkyl Indolines

A silver-catalyzed phosphorylation/cyclization cascade of <i>N</i>-allyl anilines was developed, allowing direct access to 3-phosphonoalkyl indolines, which were previously obtainable only via tedious procedures under harsh/toxic conditions. The unactivated double bond serves as the radical acceptor, whereas H-phosphonates or -phosphine oxides act as the radical precursor. This protocol features simple operation, broad substrate scope, and great <i>exo</i> selectivity, and a gram-scale synthesis could be readily carried out

Novel and potent Lewis acid catalyst: Br₂-catalyzed Friedel–Crafts reactions of naphthols with aldehydes

<p>A discovery that the inexpensive Br₂ can serve as a potent Lewis acid catalyst for bis(2-hydroxy-1-naphthyl)methanes synthesis is presented. Under the catalysis of Br₂ at room temperature, naphthols reacted smoothly with various aldehydes with high efficiency and broad substrate scope. This reaction used to require highly acidic conditions and/or high temperature and/or pressure, and sometimes featured poor yields. Moreover, theoretical calculations suggested that Br₂ is a potent Lewis acid to activate the carbonyl group, yet it was not the primary cause for the remarkable activity of Br₂ in the current communication.</p

Experimental and theoretical study of I₂-catalyzed dialkenyl oxindoles synthesis from isatins and α-cyano ketene ethylene dithioacetal

<p>An I₂-catalyzed synthesis of dialkenyl oxindoles from isatins and α-cyano ketene ethylene dithioacetal is described. Both electron-withdrawing groups (EWGs) and alkylthio groups exert effects on the reactivities of ketene dithioacetals. Density functional theory (DFT) calculations suggested that the highest negative charge density on the α-carbon of α-cyano ketene ethylene dithioacetal and the largest positive charge on C(3) of the related key intermediate are both responsible for the superior activity of α-cyano ketene ethylene dithioacetal. The cationic intermediate derived from 2-(1,3-dithian-2-ylidene)acetonitrile is the most stable but the least positive, thus the corresponding alkenylhydroxyoxindole is the thermally stable and separable product. Other ketene dithioacetals are less nucleophilic, and their corresponding cationic intermediates are probably not positive enough to enable further transformation.</p

Molecular Modeling Application on Hapten Epitope Prediction: An Enantioselective Immunoassay for Ofloxacin Optical Isomers

To deepen our understanding of the physiochemical principles that govern hapten–antibody recognition, ofloxacin enantiomers were chosen as a model for epitope prediction of small molecules. In this study, two monoclonal antibodies (mAbs) mAb-WR1 and mAb-MS1 were raised against <i>R</i>-ofloxacin and <i>S</i>-ofloxacin, respectively. The enantioselective mAbs have a high sensitivity and specificity, and the enantioselectivity is not affected by heterologous coating format reactions. The epitopes of the ofloxacin isomers were predicted using the hologram quantitative structure–activity relationship (HQSAR) and comparative molecular field analysis (CoMFA) approaches. The results consistently show that the epitope of the chiral hapten should be primarily composed of the oxazine ring and the piperazinyl ring and mAbs recognize the hapten from the side of this moiety. The enantioselectivity of mAbs is most likely due to the steric hindrance caused by the stereogenic center of the epitope. Modeling of chiral hapten–protein mimics reveals that ofloxacin isomers remain upright on the surface of the carrier protein. Suggestions to improve the enantioselectivity of antibodies against ofloxacin isomers were also proposed. This study provided a simple, efficient, and general method for predicting the epitopes of small molecules via molecular modeling. The epitope predictions for small molecules may create a theoretical guide for hapten design