Regioselective and asymmetric allylic alkylation of vinyl epoxides for the construction of allylic alcohols via synergistic catalysis

A highly efficient asymmetric allylic alkylation of cyclic and acyclic carbon nucleophiles with vinyl epoxides has been developed,which exhibits good functional group compatibility,high atomic and step economy.This protocol utilizes a strategy of synergistic catalysis with a chiral N,N'-dioxide/Ni~Ⅱ complex and an achiral Pd~0 catalyst,generating a series of multisubstituted allylic alcohols with a quaternary carbon stereocenter in high yield and excellent regio-,Z/E-and enantioselectivity under mild conditions.Further transformations of the product demonstrate the potential utility of this protocol in the synthesis of allyl alcohol derivatives and natural product analogues.Experimental studies revealed that the N,N′-dioxide/metal complexes play an important role in controlling the Z/E-and enantioselectivity.The density functional theory(DFT) calculations further demonstrated that multiple C–H···π interactions between the aromatic rings of the two substrates and the amide moiety in the ligand stabilized the dominant transition state.

Toll-like receptors 2 polymorphism is associated with psoriasis: A case-control study in the northern Chinese population

Background:Psoriasis is a disease caused by genetics and immune system dysfunction,affecting the skin and joints.Toll-like receptors(TLRs)play an important role in triggering the innate immune response and controlling adaptive immunity.The role of TLR2 in the progression of psoriasis is not well understood.Methods:A case-control study was conducted on a northern Chinese Han population,consisting of psoriasis patients and healthy control subjects.Genotyping was performed using the tetra-primer amplification refractory mutation system-polymerase chain reaction(ARMS-PCR),and allele and genotype frequencies of four SNPs in TLR2 were analyzed in 270 psoriasis patients and 246 healthy controls.Results:Four TLR2 SNPs(rs11938228,rs4696480,rs3804099,rs5743699)were genotyped and found to be in linkage disequilibrium.The genotype distributions of rs11938228 and rs4696480 in two groups were in Hardy-Weinberg equilibrium and statistically significant except for the overdominance model.The haplotypes ATTC and ATCC were found to be protective against psoriasis.Conclusion:Our study found a correlation between TLR2 genetic variations and the likelihood of psoriasis in northern China.

Preparation and Characterization of Ag_2S/PMMA Nanocomposites by Microemulsion

Ag2S nanoparticles in polymethyl methacrylate （PMMA） are prepared in n-heptane/sodium bis（2-ethyl- hexyl）sulfosuccinate/water microemulsions. The Ag2S nanoparticles dispersed in the polymer are characterized by FT-IR spectrum, UV-Vis absorption spectroscopy, transmission electron microscopy （TEM）, and X-ray powder diffraction （XRD）. The FT-IR spectrum shows that the composite has the characteristic bands of nano-Ag2S and pure PMMA. The TEM photograph of the sample shows that the Ag2S nanoparticles are elliptical. The phase structure of the composite is characterized by XRD, which reveals that Ag2S particles are formed. The UV-Vis absorption recorded at various times indicates an initial rapid formation of the nanoparticles and the quantum confinement effect of Ag2S nanoparticles.

Isolating the direct and indirect impacts of urbanization on vegetation carbon sequestration capacity in a large oasis city:evidence from Urumqi,China

Oasis cities are deeply affected by human activities in arid and semi-arid regions.Vegetation is an important repository in the carbon cycle of oasis urban ecosystems.The continuous expansion of urban has a disproportionate impact on the carbon sequestration capacity of vegetation.Till now,studies have been conducted to quantify the impact of urbanization on vegetation carbon sequestration capacity,the mechanism of such impact remains unclear and lacks systematic investigations,especially in oasis urban.Understanding the impact mechanism greatly benefits the sustainable development of oasis urban and regional carbon neutrality.To fill this knowledge gap,we design a theoretical framework to analyze the impact of urbanization on vegetation carbon sequestration capacity by isolating the direct and indirect impacts in Urumqi,China.Some results based on Landsat images indicated that the Impervious Surface Areas(ISAs)expanded by 436.98 km2 during 2000-2019.The Net Primary Productivity(NPP)calculated using the Vegetation Photosynthesis Model(VPM)was directly caused by the loss of 51.45 Gg C(1 Gg=109 g).Another important finding proved that the direct carbon loss caused by urbanization did not change the upward trend of the total carbon sequestration capacity of vegetation,but only slowed down this upward trend by 20.86%.Our results provide new insights into urban vegetation carbon sinks and contribute to a better understanding of the uncertainty of urbanization toward carbon neutrality.This study will provide scientific data support and suggestions for the sustainable development of oasis cities and the regional carbon budget.