Palladium-catalyzed asymmetric allylic alkylation using iminophosphine ligands derived from chiral primary 1-ferrocenylalkylamines

The palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propen-1-yl acetate 4 with dimethyl malonate in the presence of chiral iminophosphine ligands 3a–3d derived from chiral primary 1-ferrocenylalkylamines 1 and 2-(diphenylphosphino)benzaldehyde 2 was investigated. Excellent enantioselectivity (up to 97%) was achieved when ligand 3d was used. A mechanism for asymmetric induction in this reaction was proposed by theoretical modeling of the intermediate π-allylpalladium complexes.     

Two New Lignans from Phryma leptostachya L.

Haedoxancoside A ( 1 ), a new sesquilignan glycoside, and phrymarolin V ( 2 ), a new lignan, together with two known compounds, were isolated from Phryma leptostachya L. Their structures were determined on the basis of comprehensive spectroscopic analysis, mainly 1D‐ and 2D‐NMR spectroscopy as well as mass spectrometry. This is the first report of a sesquilignan glycoside isolated from a species of the Phrymaceae family.     

Fast profiling ecotoxicity and skin permeability of benzophenone ultraviolet filters using biopartitioning micellar chromatography based on penetrable silica spheres

Penetrable silica possesses hierarchical pores, mesopores and penetrable macropores, offering fast mass transfer, satisfactory mechanical strength as well as low column pressure. In the present study, penetrable octadecyl-bonded silica (ODS) was for the first time used as biopartitioning micellar chromatography (BMC) stationary phase to profile ecotoxicity and skin permeability of benzophenone UV-filters. Mobile phase (MP) pH and concentration of polyoxyethylene(23)lauryl ether in the MP were systematically studied. Quantitative retention–activity relationships (QRARs) model was established to correlate retention factors (k) on BMC with bioconcentration factor (BCF) and transdermal rate (TR) of UV-filters. Coefficient of determination (r²) of the QRARs model between log BCF and log k were 0.9398–0.9753, while r² between TR and log k were 0.7569–0.8434, which demonstrated satisfactory predictive ability of the methodology. It was a powerful tool for fast screening by combining penetrable ODS with BMC, and avoiding column blockage often occurring in BMC.     

N,N′,N″-1,4,7-Triazacyclononane with pendant alkyne arms: Crystal structures of [CuL2′][PF6]2, [NiL2′][ClO4]2 and CuL″Cl2 (L′=N-(4-but-2-yne)-1,4,7-triazacyclononane,L″=N-(5-pent-2-yne)-1,4,7-triazacyclononane)

We report the synthesis of a series of macrocyclic ligands based on N,N′,N″-1,4,7-triazacyclononane with pendant alkyne arms. N,N′,N″-tris-(3-prop-1-yne)-1,4,7-triazacyclononane (L) has three pendant alkyne arms while N-(4-but-2-yne)1,4,7-triazacyclononane (L′) and N-(5-pent-2-yne)-1,4,7-triazacyclononane (L″) each have a single pendant arm. The ligands form coordination complexes with Cu(II), Ni(II), Co(II) and Mo(0). The crystal structures of [CuL₂′][PF₆]₂, [NiL₂′][ClO₄]₂ and CuL″Cl₂ are presented and discussed.     

Electrochemical sensing chemical oxygen demand based on the catalytic activity of cobalt oxide film

Cobalt oxide sensing film was in situ prepared on glassy carbon electrode surface via constant potential oxidation. Controlling at 0.8 V in NaOH solution, the high-valence cobalt catalytically oxidized the reduced compounds, decreasing its surface amount and current signal. The current decline was used as the response signal of chemical oxygen demand (COD) because COD represents the summation of reduced compounds in water. The surface morphology and electrocatalytic activity of cobalt oxide were readily tuned by variation of deposition potential, time, medium and Co²⁺ concentration. As confirmed from the atomic force microscopy measurements, the cobalt oxide film, that prepared at 1.3 V for 40 s in pH 4.6 acetate buffer containing 10 mM Co(NO₃)₂, possesses large surface roughness and numerous three-dimensional structures. Electrochemical tests indicated that the prepared cobalt oxide exhibited high electrocatalytic activity to the reduced compounds, accompanied with strong COD signal enhancement. As a result, a novel electrochemical sensor with high sensitivity, rapid response and operational simplicity was developed for COD. The detection limit was as low as 1.1 mg L⁻¹. The analytical application was studied using a large number of lake water samples, and the accuracy was tested by standard method.     

Two new diterpenoids from the buds of Wikstroemia chamaedaphne

Two new diterpenoids, wikstroelide Q (1) and prostratin Q (5), together with three known diterpenoids, pimelea factors P? (2), P? (3), and prostratin (4), and five known lignans, (+)-epipioresinol (6), (+)-isolariciresinol (7), (?)-lariciresinol (8), (+)-epi-sesaminone (9), and prestegane B (10), were isolated from the buds of Wikstroemia chamaedaphne Meissn. Their structures were elucidated by a combination of spectroscopic analyses. Compounds 1–10 were evaluated for their cytotoxicities against HL-60, SMMC-7721, A549, MCF-7, SW480, and BEAS-2B cell lines in vitro.     

Exposure to persistent organic pollutants as potential risk factors for developing diabetes

Persistent organic pollutants(POPs),such as dioxins,polychlorinated biphenyls(PCBs) ,and organochlorine pesticides(OCPs),which are synthetic chemicals or by-products with an intrinsic resistance to natural degradation processes,are released into the environment,resulting in the widespread dispersal and accumulation in the environment,as well as in human and ecological food chains.Due to their ubiquity in the environment and lipophilic properties,there is emerging concern over the potential risks of human ex...     

Three New E‐Secoursane Triterpenoid Saponins from the Leaves of Ilex dunniana

Three new triterpenoid saponins with an 18,19‐secours‐13(18)‐ene skeleton, dunnianaolactones A–C ( 1 – 3 , resp.), together with nine known compounds i.e., the ursane‐type triterpene saponin 4 , the two benzofuran lignans 5 and 6 , five flavonoid glycosides, and 4‐hydroxybenzoic acid, were isolated from the leaves of Ilex dunniana Levl . (Aquifoliaceae). Their structures were elucidated by means of spectroscopic and chemical methods. The configuration of dunnianaolactone A ( 1 ) was further confirmed by X‐ray crystal‐structure analysis.     

Two New Flavonoids from the Rhizomes of Abacopteris penangiana

A new flavan‐4‐ol glycoside, abacopterin K ( 1 ), and a new dihydrochalcone glycoside, abacopterin L ( 2 ), were isolated from the rhizomes of Abacopteris penangiana. Their structures were elucidated on the basis of various spectroscopic analyses and chemical evidences. The novel glucosylation pattern of abacopterin K consisting of two ‘glucose‐fused’ dioxepine ring moieties is found for the first time within natural flavonoids.     

一类随机微分方程的稳定性

本文用Rn中一类半线性椭圆方程正解结果讨论了随机微分方程的随机稳定性.