Palladium-Catalyzed para-Selective C-H Olefination and Acetoxylation of Benzylamines Enabled by an Unmasked Benzoyl Template.

Benzylamines belong to an important class of building blocks in the synthesis of biologically active natural products and drugs. Encumbered by amide-directed ortho-C-H activation, remote para-selective C-H functionalization of benzylamines has hitherto not been realized to date. Here, we report a palladium-catalyzed para-selective C-H olefination and acetoxylation of benzylamines using a functionalized benzoyl template. Enhancing the coordination strength of the directing group in the template significantly improved the site selectivity of C-H functionalization.

Regiodivergent Remote C-H Functionalization by Tuning Template Geometry.

For transition-metal-catalyzed C-H functionalization, precise differentiation between remote adjacent C(sp2)-H bonds remains a long-standing challenge. Here, the template structure-directivity relationship on remote C-H functionalization of arenes was experimentally and computationally studied. By using geometry-tunable templates, Pd-catalyzed remote meta- and para-C-H activation of benzoic acids was achieved with high site selectivity.

Macrocyclization via remote meta-selective C-H olefination using a practical indolyl template.

The synthesis of macrocyclic compounds with different sizes and linkages remains a great challenge via transition metal-catalysed intramolecular C-H activation. Herein, we disclose an efficient macrocyclization strategy via Pd-catalysed remote meta-C-H olefination using a practical indolyl template. This approach was successfully employed to access macrolides and coumarins. In addition, the intermolecular meta-C-H olefination also worked well and was exemplified by the synthesis of antitumor drug belinostat from inexpensive and readily available benzenesulfonyl chloride. Notably, catalytic copper acetate and molecular oxygen were used in place of silver salts as oxidants. Furthermore, for the first time, the formation of a macrocyclophane cyclopalladated intermediate was detected through in situ Fourier-transform infrared monitoring experiments and ESI-MS.

Molecular characterization of thioredoxin reductase in waterflea Daphnia magna and its expression regulation by polystyrene microplastics.

Global scale concerns regarding rise in microplastics pollution in the environment have recently aroused. Ingestion of microplastics by biota, including freshwater zooplankton has been well studied, however, despite keystone species in freshwater food webs, the molecular response (e.g. oxidative defense) of zooplankton in response to microplastics is still in its infancy. The thioredoxin (TRx) system has a vital function in cellular antioxidative defense via eliminating the excessive generation of reactive oxygen species (ROS). Therefore, it is necessary to investigate the effects of thioredoxin reductase (TRxR), due to its triggering the TRx catalysis cascade. The present study identified TRxR in Daphnia magna (Dm-TRxR) for the first time, and found that the full-length cDNA was 1862 bp long, containing an 1821-bp open reading frame. Homologous alignments showed the presence of conserved catalytic domain CVNVGC and the seleocysteine (SeCys) residue (U) located in the N- and C- terminal portions. Subsequently, the expression of Dm-TRxR, together with permease, arginine kinase (AK), was investigated by approach of quantitative real-time PCR after exposure to four (1.25-µm) polystyrene (PS) microbeads concentrations: 0 (control), 2, 4 and 8 mg L-1 for 10 days. Dm-TRxR, permease and AK mRNA were significantly upregulated after exposure to 2, 4 mg L-1 of PS, but then declined in the presence of 8 mg L-1 PS. The gene expression results suggested that oxidative defense, energy production and substance extra cellular transportation were significantly regulated by microplastic exposure. Collectively, the present study will advance our knowledge regarding the biological effects of microplastic pollution on zooplankton, and builds a foundation for freshwater environmental studies on mechanistic and biochemical responses to microplastics.

Allelopathic inhibition of juglone (5-hydroxy-1,4-naphthoquinone) on the growth and physiological performance in Microcystis aeruginosa.

The elimination of cyanobacteria blooms has become an urgent concern in aquatic environmental protection. Allelopathic control is considered a potential approach because of its exclusive and ecological safety properties. The present study evaluated the allelopathic effect of juglone, a derivative from the genus Juglans, on the toxic Microcystis aeruginosa. Juglone at 3.0-9.0 mg L-1 notably depressed the cell proliferation of M. aeruginosa. The cell abundance treated by 9.0 mg L-1 juglone decreased by 75% after an 11-day exposure. The antioxidant enzyme activity (SOD and CAT) in juglone groups increased remarkably, suggesting juglone-induced oxidant stress in the M. aeruginosa cells. Juglone exposure enhanced the intracellular and extracellular microcystin contents per cell. Nonetheless, the total amount of microcystins in the juglone-treated cyanobacterial system did not increase because of the decreased cell abundance. These results indicated the application potential of juglone for M. aeruginosa extermination.