Shicong Hou

Highly Enantioselective Zinc/Amino Alcohol-Catalyzed Alkynylation of Aldehydes

Meeting the challenge: The zinc/amino alcohol catalyzed enantioselective addition of terminal alkynes to aldehydes is effective with both phenylacetylene and methyl propiolate, leading to chiral secondary propargyl alcohols with very high enantioselectivity (see scheme).

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.

Cobalt‐Catalyzed Enantioselective Negishi Cross‐Coupling of Racemic α‐Bromo Esters with Arylzincs

The first cobalt-catalyzed enantioselective Negishi cross-coupling reaction, and the first arylation of α-halo esters with arylzinc halides, are disclosed. Employing a cobalt-bisoxazoline catalyst, various α-arylalkanoic esters were synthesized in excellent enantioselectivities and yields (up to 97 % ee and 98 % yield). A diverse range of functional groups, including ether, halide, thioether, silyl, amine, ester, acetal, amide, olefin and heteroaromatics is tolerated by this method. This method was suitable for gram-scale reactions, enabling the synthesis of (R)-xanthorrhizol with high enantiopurity. Radical clock experiments support the intermediacy of radicals.

Highly Enantioselective Addition of Phenylethynylzinc to Aldehydes Catalyzed by Chiral Cyclopropane-Based Amino Alcohols

The enantioselective addition of phenylethynylzinc to aldehydes catalyzed by a series of cyclopropane-based amino alcohol ligands 7 was investigated. The reactions afforded chiral propargylic alcohols in high yields (up to 96%) and with excellent enantioselectivities (up to 98% ee) under mild conditions. Furthermore, studies on the structural relationship show that the matching of the chiral center configuration is crucial to obtain the high enantioselectivity.

(1R,3S)-Methyl 3-[(S)-2-(hydroxy­diphenyl­meth­yl)pyrrolidin-1-ylmeth­yl]-2,2-dimethyl­cyclo­propane­carboxyl­ate

The asymmetric unit of the title compound, C25H31NO3, prepared from (−)-1R-cis-caronaldehyde, contains three independent molecules with similar conformations. The hydroxy groups are involved in intramolecular O—H⋯N hydrogen bonds. The crystal packing exhibits weak intermolecular O—H⋯O and C—H⋯O hydrogen bonds.

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.

(1R,3S)-3-Hydroxy-meth-yl-N-isopropyl-2,2-dimethyl-cyclo-propane-carboxamide.

The asymmetric unit of the title compound, C10H19NO2, prepared from (−)-1R-cis-caronaldehyde, contains two independent molecules. In the crystal structure, intermolecular O—H⋯O and O—H⋯N hydrogen bonds form an extensive three-dimensional hydrogen-bonding network.