Gui Gao

Palladium-Catalyzed α-Arylation of Methyl Sulfonamides with Aryl Chlorides

A Palladium-catalyzed α-arylation of sulfonamides with aryl chlorides is presented. A Buchwald type precatalyst formed with Kwongs indole-based ligand enabled this transformation to be compatible with a large variety of methyl sulfonamides and aryl chlorides in good to excellent yields. Importantly, under the optimized reaction conditions, only mono-arylated products were observed. This method has been applied to the efficient synthesis of sumatriptan, which is used to treat migraines.

Arylation of Azaarylmethylamines with Aryl Chlorides and a NiBr2/NIXANTPHOS-based Catalyst

A nickel-catalyzed coupling of azaarylmethylamines with aryl chlorides has been achieved. NIXANTPHOS together with low cost NiBr2 was successfully developed and optimized to exhibit high reactivity at 2.5 mol % loading. Under optimized reaction conditions, aryl(azaaryl)methylamine products were afforded in good to excellent yields (22 examples, up to 98% yield).

A coumarin-based colorimetric and fluorescent dual probe for palladium(II) ions that can be used in live cells

A new coumarin-based fluorescent probe (P) has been developed for visual detection of Pd(II) ions, based on a striking color change from green to yellow and significant fluorescence quenching in the presence of Pd(II) ions. The probe shows high sensitivity and selectivity and a rapid response time to Pd(II) ions in aqueous medium, with a detection limit as low as 4.0 × 10−8 M. Fluorescence microscopy imaging of HeLa cells showed that this fluorescent probe is effective for detecting intracellular Pd(II) ions.

Novel fluorescent probe for rapid and ratiometric detection of β-galactosidase and live cell imaging

β-Galactosidase (β-gal) is an important biomarker for primary ovarian cancers and cell senescence; however, a fast response fluorescent probe for ratiometric monitoring is still rare. A novel, ratiometric water-soluble fluorescent probe (FLM) for β-gal was developed. The emission ratio F550/F450 reached the maxima at about 5 min and can be used for real-time detection of β-gal; the ratio gained an ultimate enhancement of about 260-fold. The ratio (F550/F450) displayed brilliant β-gal-dependent performance and responded linearly with β-gal activity. The probe showed wonderful biocompatibility and was successfully used for the bioimaging of endogenous β-gal in the human ovarian cancer cell line OVCAR-3.

A novel 3-hydroxychromone fluorescent probe for hydrogen sulfide based on an excited-state intramolecular proton transfer mechanism

Hydrogen sulfide (H2S) is a signaling gasotransmitter that plays important roles in modulating the functions of different systems. We have designed and synthesized a 3-hydroxychromone-based fluorescent probe A for H2S detection. Probe A is based on a H2S-induced thiolysis reaction and an excited-state intramolecular proton transfer (ESIPT) process. The probe shows high selectivity and sensitivity for the detection of H2S over glutathione, cysteine and homocysteine. Moreover, this probe was successfully applied for imaging exogenous and endogenous H2S in living cells.

Ratiometric fluorescent probes with a self-immolative spacer for real-time detection of β-galactosidase and imaging in living cells

Ratiometric fluorescent probes with a self-immolative spacer for β-galactosidase (β-gal) were developed. They function by β-gal-cleaving the β-galactoside bond of fluorescent substrates, followed by self-immolation to liberate the amino group of fluorophore. Thus, a remarkable variation in the photophysical properties was observed and the corresponding ratiometric detection of β-gal was realized. Our studies demonstrated that the GNPN exhibited high sensitivity for recognition of β-gal, with a detection limit as low as 0.17 U L-1. GNPN can rapidly quantify β-gal enzyme activity; the emission ratio F545/F475 for the GNPN reached maxima after approximately 4 min, which was one of the shortest response time ever reported. Furthermore, we demonstrated that these probes possess excellent biocompatibility and can be used to visualize the endogenous β-gal in ovarian cancer cells.