Visible-light-promoted organic-dye-catalyzed sulfonylation/cyclization to access indolo[2,1-a]isoquinoline derivatives.

An efficient visible-light-promoted organic-dye-catalyzed radical cascade cyclization was developed for the rapid synthesis of sulfonyl-substituted indolo[2,1-a]isoquinolines and benzimidazo[2,1-a]isoquinolin-6(5H)-ones. Using the economical and environmentally benign Eosin B as the photocatalyst, a wide range of indolo[2,1-a]isoquinoline derivatives were obtained in moderate to good yields. Mechanistic studies indicate that a sulfonyl radical pathway is involved in this reaction. Compared with previous works, this protocol has the advantages of being metal- and base-free, using visible light as a traceless energy source, simple operation and mild reaction conditions, all of which make this methodology more attractive.

Metal- and additive-free radical-triggered nitration/cyclization to construct indolo[2,1-α]isoquinoline and benzimidazo[2,1-a]isoquinolin-6(5H)-one derivatives using t-BuONO as nitro reagents.

An efficient metal- and additive-free nitro radical-triggered addition/cyclization of 2-aryl-N-acryloyl indoles/2-arylbenzimidazoles for the synthesis of nitro-substituted indolo[2,1-α]isoquinoline and benzimidazo[2,1-a]isoquinolin-6(5H)-one derivatives has been developed. The commercially available and low-cost t-BuONO was used as a nitro reagent. Due to mild reaction conditions, a variety of functional groups could be tolerated to give the corresponding products in moderate to good yields. Moreover, this nitration process could be scaled-up and the nitro group could be readily converted into the amino group, which may find applications in synthetic and medicinal chemistry.

An ESIPT-based reversible ratiometric fluorescent sensor for detecting HClO/H2S redox cycle in living cells.

HClO and H2S, as two kinds of crucial small biomolecules, are endowed various roles in biological organisms. The redox balance between HClO and H2S is closely related to the physiological and pathological processes. Thus, it is significant to monitor the redox process between HClO and H2S. Inspired by the advantages of ratiometric fluorescent probes, we firstly developed a reversible ratiometric fluorescent probe (BT-Se) for HClO and H2S via combination of phenyl selenide as the response group and 2-(2'-hydroxyphenyl)benzothiazole dye as the fluorophore. The proposed probe BT-Se could detect HClO with well-separated dual emission (110 nm), fast response, good selectivity and sensitivity owing to the oxidation reaction of the Se atom induced by HClO. Moreover, only H2S could effectively recover the fluorescence of the detection system to the original state via H2S induced-reduction of selenoxide. Cell imaging studies demonstrated that the probe BT-Se was capable of ratiometric monitoring the changes of intracellular HClO/H2S, which suggested that it has great potential for researching the biological functions of HClO and H2S.

Synthesis of ester-functionalized indolo[2,1-a]isoquinolines via iron-catalyzed radical cascade cyclization of 2-aryl-N-acryloyl indoles with carbazates.

An FeCl2·4H2O-catalyzed oxidative alkoxycarbonylation/cyclization reaction of 2-aryl-N-acryloyl indoles with carbazates leading to ester-functionalized indolo[2,1-a]isoquinoline derivatives has been developed. The reaction features mild reaction conditions and broad functional group tolerance. Moreover, the ester group could be easily converted to the corresponding free acid and alcohol, and has high potential applications in organic and pharmaceutical synthesis. A radical pathway was proposed to explain this experiment.

Anticancer activity, topoisomerase I inhibition, DNA 'light switch' behavior and molecular docking of two ruthenium complexes containing phenazine ring.

Ruthenium(II) complexes containing phenazine ring have attracted attention to design as 'molecular light switches'. In this study, we synthesized two ruthenium complexes containing phenazine ring and studied their abilities to function as DNA intercalators, DNA 'light switches', DNA topo I inhibitors, DNA photocleavers and potential antitumor reagents. [Ru(bpy)2(mbipz)](PF6)2 (1) (bpy = 2,2'-bipyridine, mbipz = 2-(4'-methyl-bipyridine-4-yl)-1H-imidazo[4,5-b]phenazine) exhibited off-on type DNA 'light swtich' behavior. DNA binding modes of the two complexes were determined as intercalation by using UV-vis spectra, emission spectra, viscosity and molecular docking experiments. DNA photocleavage experimental results showed that the two ruthenium complexes effectively cleave plasmid DNA by producing singlet oxygen. Furthermore, they displayed good topo I inhibition activities. We further found that the two complexes displayed good antitumor activities against Eca-109 cells and A549 cells. The results demonstrated that introduction of phenazine ring will be helpful to design DNA 'light switch' based on ruthenium complex.Communicated by Ramaswamy H. Sarma.

Gene expression profile of lipopolysaccharide­induced apoptosis of nucleus pulposus cells reversed by syringic acid.

Apoptosis of nucleus pulposus (NP) cells has an important role in the process of intervertebral disc degeneration (IDD), and the search for novel compounds to prevent apoptosis from occurring is urgently required. In the present study, syringic acid (SyrA) was found to exhibit no cytotoxicity on NP cells, and was able to reverse the cytotoxicity, as well as the abnormal expression of Bcl­2 and caspase­3, that were induced by lipopolysaccharide (LPS). The transcriptomes of each group were then analyzed using RNA­Seq. A total of 65 differentially expressed genes (DEGs) were identified in LPS­stimulated groups (LPS group vs. control group), 819 DEGs were identified in the SyrA­reversed groups (SyrA plus LPS group vs. LPS group), and a further 25 DEGs were identified in the SyrA plus LPS group compared with the control group. Reverse transcription­quantitative PCR validation indicated that the alterations in expression of uroplakin 3B­like 1 (UPK3BL1), voltage­dependent calcium channel subunit α­2/δ­1 (CACNA2D1) and polo­like kinase 4 (PLK4) were consistent with the corresponding results of RNA­Seq, and that these genes were involved in both LPS­stimulation and SyrA­reversion processes. Kyoto Encyclopedia of Genes and Genomes analyses indicated that the DEGs in SyrA­reversed groups were involved in, amongst other pathways, 'Autophagy­other' and 'Apoptosis­multiple species'. In conclusion, the addition of SyrA to the NP cells co­incubated with LPS appeared to help prevent the abnormal expression of mRNAs and apoptosis that had been identified in NP cells incubated with LPS alone. The potential mechanism underlying the reversion of SyrA might be attributed to the regulation of CACNA2D1 and PLK4.

A ratiometric fluorescent probe for visualization of thiophenol and its applications.

Thiophenol has a broad application in agriculture and industry. However, thiophenol can harm to the environment and health for its high toxicity. Developing an effective method for detection of thiophenol in the field of environmental and biology is valuable. In this work, we construct a reaction-based ratiometric fluorescent probe (E)-4-(2-(7-(diethylamino)-2-oxo-2H-chromen-3-yl)vinyl)-1-(4-(2,4-dinitrophenoxy)benzyl)pyridin-1-ium bromide (DCVP-DNP) for probing thiophenol in environment and cells by employing (E)-7-(diethylamino)-3-(2-(pyridin-4-yl)vinyl)-2H-chromen-2-one (DCVP) as the fluorophore and 2,4-dinitrophenyl (DNP) ether as the recognition group for the first time. The probe has high selectivity for thiophenol though thiophenol-triggered nucleophilic substitution reaction. In addition, the ratio of emission intensities of the probe has linearly with thiophenol concentration in the range of 0-65 µM and the detection limit of thiophenol is as low as 4.8 × 10-8 M. Moreover, the probe can not only be applied for detection of thiophenol in water samples, but also image thiophenol in living cells, suggesting its potential application in environment and biological system.

Nitro-Substituted Ruthenium(II) Complex: A New Strategy for a G-Quadruplex DNA Fluorescent Probe.

A new strategy for a G-quadruplex fluorescent probe based on a nitro-substituted ruthenium complex is described. G-quadruplex DNA can be distinguished from double- or single-strand DNA by the naked eye. This ability originates from variation of the degree of protection of the nitro group on the complex from water by G-quadruplex and other structure DNAs.

Tetrabutylammonium iodide-catalyzed oxidative coupling of enamides with sulfonylhydrazides: synthesis of ß-keto-sulfones.

A facile synthetic route towards pharmaceutically interesting ß-keto-sulfone derivatives by tetrabutylammonium iodide (TBAI)/tert-butyl hydroperoxide (TBHP) mediated oxidative coupling of readily prepared enamides with economical sulfonylhydrazides is described. The corresponding ß-keto-sulfone compounds were obtained in moderate to good yields. The present method is metal-free and base-free and shows tolerance to a variety of functional groups.

Iron-catalyzed arylalkoxycarbonylation of N-aryl acrylamides with carbazates.

A novel arylalkoxycarbonylation of N-aryl acrylamides with carbazates leading to alkoxycarbonylated oxindoles has been developed. The reported reactions employ economical and environmentally benign FeCl2·4H2O as a catalyst and easily accessible and safe carbazates as alkoxycarbonyl radical precursors.

Tetrabutylammonium iodide catalyzed allylic sulfonylation of Baylis-Hillman acetates with sulfonylhydrazides in water.

A tetrabutylammonium iodide catalyzed method for the synthesis of allyl aryl sulfone derivatives with Baylis-Hillman acetates and sulfonylhydrazides using tert-butyl hydroperoxide as an oxidation agent in water has been developed. In this process, the group eliminated from the sulfonyl precursor is molecular nitrogen.