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Five dimeric Erythrina alkaloids, named erythrivarines J-N, were isolated from the barks of Erythrina variegata L. (Fabaceae). The erythrivarines J-L featured a 6/6/5/6/6/5/6/6/6 ring system and super conjugated double bond systems, causing intense color from blue to wine red, while erythrivarines M-N looked orange. The structures of the isolated compounds were elucidated by 1D and 2D NMR experiments combined with MS and confirmed by the X-ray crystal diffraction technique. The performed bioassay using HEI-OC-1 cells revealed neuroprotective properties of erythrivarine N against the hearing loss causing antibiotics, neomycin.

Biphenylcarboxylic acid with two competing C(sp2)-H sites was designed for site selective C(sp2)-H functionalization by developing carboxylic acids assisted remote and selective olefination via 7-membered palladacycle. Mechanism investigation and DFT calculations reveal a kinetics-determined process, which could be utilized to explore a variety of remote site selectivity. The practicability of this method was highlighted by the precise construction of phenathrene under sequential site selectivity.

Ru(II)-catalyzed direct alkylation of tertiary phosphines via hydroarylation of activated olefins promoted by mono-N-protected amino acid (MPAA) was achieved. This protocol provides a straightforward access to a large library of Buchwald-type bulky alkylated monophosphines from commercially available biaryl phosphine. Moreover, two ruthenacycle intermediates of tertiary phosphines via C–H bond cleavage were isolated to illustrate the mechanism of P(III)-directed C–H activation.

The Escherichia coli-derived tyrosyl-tRNA synthetase was the first enzyme engineered for genetic code expansion in a eukaryotic system but can charge only a limited set of structurally simple noncanonical amino acids. In contrast, the thermophilic Methanocaldococcus jannaschii-derived tyrosyl-tRNA synthetase mutants, used in only a prokaryotic system, can charge a surprisingly large set of structurally diverse ncAAs, due to their remarkable structural ability to tolerate mutations. Inspired by this, we characterized a new class of tyrosyl-tRNA synthetase/tRNATyr pairs from thermophilic bacterium Geobacillus stearothermophilus, which is homologous to the E. coli tyrosyl-tRNA synthetase but with better thermostability. This new pair is both orthogonal in mammalian cells and in Saccharomyces cerevisiae for genetic code expansion and can charge a diverse set of ncAAs with a comparable cellular efficiency, better specificity, and lower background, as compared to those of its E. coli homologue. This thermostable enzyme provides an alternative scaffold for synthetase library screening or evolution to genetically encode more structurally complex ncAAs in eukaryotic cells.

Eleven new meroterpenoids, bipolahydroquinones A-C (1-3), cochlioquinones I-N (4-8 and 11), and isocochlioquinones F and G (9 and 10), together with six known ones, were obtained from an endophytic fungus Bipolaris sp. L1-2 from Lycium barbarum. Compound 2 is the first example of cochlioquinone derivatives possessing a benzofuran moiety. The structures and absolute configurations of the new compounds were elucidated by spectroscopic data interpretation, single-crystal X-ray diffraction analysis, chemical transformations, and biosynthetic considerations. Compounds 3, 4, and 6-8 showed cytotoxicity against NCI-H226 and/or MDA-MB-231 with IC50 values ranging from 5.5 to 9.5 μM.

Magnetic resonance contrast agent employs the use of gadolinium chelates, which has many limitations for clinical use including a low contrast effect, a short diagnostic window, and a brief blood circulation time. On this basis, we designed a gadolinium-labeled dendrimer nanocluster (GdDN) loaded graphene oxide nanosheet (GO-GdDN) to boost T1 contrast ability for imaging in vivo and improve blood circulation time. GO-GdDN presented an ultrahigh r1 relaxivity up to 19.07 mM–1 s–1 in a 9.4 T MR scanner, and a bright contrast image in vitro experiment. In addition, GO-GdDN could be internalized by HepG2 cells and presented strong cell contrast enhancement and reduction of the T1 value in HepG2 cells. In vivo, the retention time of GO-GdDN was significantly improved, so that the accumulation of GO-GdDN in liver was enhanced. Moreover, compared to Gd-DTPA, systemic delivery of GO-GdDN dramatically enhanced the signal-to-noise ratio of liver images, which was helpful for accurate imaging of liver and detection ...

Existing stereoselective routes to 2,5-cyclohexadienones involve either desymmetrization of an achiral substrate or have attempted to perform an asymmetric dearomatization of a phenol. Herein, we report proof-of-principle experiments aimed at developing a kinetic resolution as an alternative method for accessing enantioenriched 2,5-cyclohexadienones. More specifically, chiral bifunctional thiourea catalysts were used to promote the addition of 2-thionapthalene into unsymmetric para-quinols. The selectivity of the kinetic resolution was found to be quite sensitive to substitution around the substrate.

Mesoporous zeolite ZSM-5 (ZSM-5-M) was synthesized and used as support for the preparation of highly efficient nickel phosphide catalyst (Ni2P/ZSM-5-M) in the deep hydrogenation of phenanthrene and in the hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DM-DBT). Compared with Ni2P catalysts supported silica and high surface area hexagonal mesoporous silica (HMS) (Ni2P/SiO2 and Ni2P/HMS), Ni2P/ZSM-5-M exhibits higher hydrogenation and HDS activity. The phenanthrene conversion and deep hydrogenation products selectivity over Ni2P/ZSM-5-M (95% and 83%) are much higher than those over Ni2P/SiO2 (61% and 73%) and Ni2P/HMS (69% and 45%) under mild conditions. The 4,6-DM-DBT conversion over Ni2P/ZSM-5-M (93%) was higher than that over Ni2P/SiO2 (62%). This feature is attributed to the difference in surface properties of support. A large amount of acidic hydroxyl groups on the zeolites can interact strongly with catalyst precursor, resulting in the formation of highly dispersed Ni2P particles with ...

A novel palladium-catalyzed three-component reaction for the synthesis of quinazolin-4(3H)-ones from readily available 2-aminobenzamides and aryl halides via a palladium-catalyzed isocyanide insertion/cyclization sequence has been developed. This methodology efficiently constructs quinazolin-4(3H)-ones in moderate to excellent yields with the advantages of operational simplicity.

Hexamethyldisiloxane (HMDO) has been developed to efficiently promote the metal-free direct coupling of an amino function of one cysteine-free peptide or protein and a C-terminal thioester of the second peptide in ionic liquids. The amide-coupling reaction proceeds smoothly under mild conditions to afford the corresponding products in good to excellent yields (63-94%). Peptide couplings were also achieved using in-situ-generated thioesters by the thioesterification of oxo esters.

A facile and efficient copper-catalyzed method for the synthesis of 4H-3,1-benzoxazin-4-one derivatives has been developed. This procedure is based on a tandem intramolecular C-N coupling/rearrangement process. This method would provide a new and useful strategy for construction of N-heterocycles.