A novel "turn-on" fluorescent probe based on thiocarbamoyl-DHP for Hg2+ detection in water samples and living cells

In this study, two fluorescent sensing probes, dihydropyridine (DHP) derivatives (DHP-CT1 and DHP-CT2) bearing phenoxy thiocarbonyl group, have been developed for Hg2+ detection. The tandem trimerization-cyclization of methylpropiolate with ammonium acetate gave 1.4-DHP and 1,2-DHP derivatives, which were reacted with O-phenylcarbonochloridothioate to produce DHP-CT1 and DHP-CT2, respectively. DHP-CT1 exhibits superior sensitivity and selectivity of fluorescence enhancement towards Hg2+ in aqueous media. The fluorescence intensity shows a good linear relationship with the concentration of Hg2+ in the range of 0-10 µM providing the extremely low LOD of 346 nM (69.4 ppb). The fluorescence enhancement is caused by the Hg2+ promoted hydrolysis of the thioamide bond releasing the fluorescent 1,4-DHP that was confirmed by NMR and HRMS. The quantitative analysis of Hg2+ in water samples using DHP-CT1 probe was demonstrated in aqueous solution and paper-based sensing strips. Furthermore, DHP-CT1 was also applied for monitoring intracellular Hg2+ in living RAW264.7 macrophages through fluorescence cell imaging.

Formation of seven-membered rings by RCM of vinyl bromides

Grubbs II catalyst mediated ring-closing metathesis (RCM) of mono-brominated dienes is reported to proceed in moderate to good yields (40–80%) where the linking chain contains five atoms, leading to carbocyclic and heterocyclic 7-membered bromo-olefins. Notably, RCM to form 5-, 6- or 8-membered bromo-olefins was unsuccessful, with the exception of one example where RCM afforded diethyl 3-bromocyclohex-3-ene-1,1-dicarboxylate. In this case a bromomethyl-substituted cyclohexene was obtained as a byproduct. The utility of selected bromo-olefin RCM products was demonstrated through their participation in Suzuki-Miyaura reactions. Vinyl halide exchange (BrCl) was noted as a side reaction under RCM conditions.

Transition-Metal-Mediated Chemo- and Stereoselective Total Synthesis of (-)-Galanthamine

An asymmetric synthetic route to (-)-galanthamine (1), a pharmacologically active Amaryllidaceae alkaloid used for the symptomatic treatment of early onset Alzheimer's disease, was successfully established with very high levels of stereocontrol. The key to achieving high chemo- and stereo-selectivity in this approach was the use of transition-metal-mediated reactions, namely, enyne ring-closing metathesis, Heck coupling, and titanium-based asymmetric allylation.

An Efficient One-Step Synthesis of Dihydroquinoline and Its Application as a Fluorescence Sensor for Selective Detection of Copper (II)

An efficient one-step synthetic pathway to dihydroquinoline (DHQ) and benzodihydroquinoline (BDHQ) derivatives involving 1,2-Michael addition reaction between amino phenol/naphthol and two molecules of methyl propiolate followed by intramolecular cyclization and aromatization using cuprous iodide as a catalyst was successfully developed. The synthesized DHQ derivatives displayed highly selective fluorescence quenching in the presence of copper(II) with a very low detection limit (LOD for DHQ is 0.20 μM). Moreover, the mechanisms of both formation of the corresponding DHQ and the fluorescence quenching by copper(II) are proposed along with the evidence of X-ray diffraction data.

Novel racemic tetrahydrocurcuminoid dihydropyrimidinone analogues as potent acetylcholinesterase inhibitors

The synthesis of racemic tetrahydrocurcumin- (THC-), tetrahydrodemethoxycurcumin- (THDC-) and tetrahydrobisdemethoxycurcumin- (THBDC-) dihydropyrimidinone (DHPM) analogues was achieved by utilizing the multi-component Biginelli reaction in the presence of copper sulphate as a catalyst. The evaluation of acetylcholinesterase inhibitors for Alzheimer's disease of these compounds showed that they exhibited higher inhibitory activity than their parent analogues. THBDC-DHPM demonstrated the most potent inhibitory activity with an IC50 value of 1.34±0.03μM which was more active than the approved drug galanthamine (IC50=1.45±0.04μM).