Synthesis of a new class of conformationally rigid phosphino-oxazolines: highly enantioselective ligands for Ir-catalyzed asymmetric hydrogenation

[reaction: see text] A new class of conformationally rigid phosphino-oxazoline ligands were synthesized from readily available enantiopure phenyl glycinol. Ir complexes with these ligands are air-stable and highly enantioselective catalysts for asymmetric hydrogenation of aryl alkenes and alpha,beta-unsaturated esters in up to 99% ee.     

Simultaneous Modulation of Magnetic and Dielectric Transition via Spin‐Crossover‐Tuned Spin Arrangement and Charge Distribution

Magnetic and dielectric properties have been tuned simultaneously by external stimuli with rapid and sensitive response, which is crucial to monitor the magnetic state via capacitive measurement. Herein, positive charged Fe^II ions were linked via negative charged [(Tp)Fe^III(CN)₃]^? (Tp=hydrotris(pyrazolyl)borate) units to form a neutral chain. The spin‐crossover (SCO) on Fe^II sites could be sensitively triggered via thermal treatment, light irradiation, and pressure. SCO switched the spin state of the Fe^II ions and antiferromagnetic interactions between Fe^III and Fe^II ions, resulting in significant change in magnetization. Moreover, SCO induced rotation of negative charged [(Tp)Fe^III(CN)₃]^? units, generating dielectric anomaly due to geometric change of charges distribution. This work provides a rational way to manipulate simultaneous variations in magnetic and dielectric properties utilizing SCO as an actuator to tune spin arrangement, magnetic coupling, and charge distribution.     

Pd-Catalyzed asymmetric hydrogenation of 3-(toluenesulfonamidoalkyl)indoles

A series of 2-substituted 3-(toluenesulfonamidoalkyl)indoles was synthesized by application of (EtO)(2)POH or iodine as the catalyst, and was hydrogenated using chiral Pd catalyst, giving the 2,3-disubstituted indolines with up to 97% ee.     

Theoretical investigation on the chiral diamine-catalyzed epoxidation of cyclic enones: mechanism and effects of cocatalyst

The asymmetric epoxidation of 2-cyclohexen-1-one with aqueous H(2)O(2) as oxidant, 1,2-diaminocyclohexane as catalyst, and a Br?nsted acid trifluoroacetic acid (TFA) as cocatalyst has been studied by performing density functional theory calculations. It is confirmed that the catalyzed epoxidation proceeds via sequential nucleophilic addition and ring-closure processes involving a ketiminium intermediate. Four possible pathways associated with two Z isomers and two E isomers of ketiminium have been explored in detail. Our calculation indicates that these four pathways have high barriers and a small energy gap between two more favorable R and S pathways. We have analyzed the effects of the TFA anion and H(2)O on the activity and enantioselectivity of catalytic epoxidation. It is found that the TFA anion acts as a counterion to stabilize the transition states of the catalytic epoxidation by hydrogen-bond acceptance, leading to decreases in the barriers of the nucleophilic addition and ring-closure processes. The most significant decrease occurred in the ring-closure step of the Z-R-pathway, resulting in H-bond-induced enantioselectivity. Our calculations also show that water cooperates with TFA to further increase the reaction rate significantly.     

MH－Ni电池低温性能的研究

从合金组成及电解液组份研究了ＭＨ－Ｎｉ电池的低温性能,确定了适宜的合金组成和电解液组成。     

Advances in the chemical analysis and biological activities of chuanxiong

Chuanxiong Rhizoma (Chuan-Xiong, CX), the dried rhizome of Ligusticum chuanxiong Hort. (Umbelliferae), is one of the most popular plant medicines in the World. Modern research indicates that organic acids, phthalides, alkaloids, polysaccharides, ceramides and cerebrosides are main components responsible for the bioactivities and properties of CX. Because of its complex constituents, multidisciplinary techniques are needed to validate the analytical methods that support CX's use worldwide. In the past two decades, rapid development of technology has advanced many aspects of CX research. The aim of this review is to illustrate the recent advances in the chemical analysis and biological activities of CX, and to highlight new applications and challenges. Emphasis is placed on recent trends and emerging techniques.     

Blockade of inflammatory responses by a small-molecule inhibitor of the Rac activator DOCK2

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Highlights? CPYPP binds to DOCK2 DHR-2 domain and inhibits its catalytic activity ? CPYPP inhibits DOCK2-mediated Rac activation in cells ? The structural features of CPYPP required for its inhibitory effect were revealed ? CPYPP inhibits lymphocyte migration and activation in vitro and in vivo     

Morphology effects on the biofunctionalization of nanostructured ZnO

A stepwise surface functionalization methodology was applied to nanostructured ZnO films grown by metal organic chemical vapor deposition (MOCVD) having three different surface morphologies (i.e., nanorod layers (ZnO films-N), rough surface films (ZnO films-R), and planar surface films (ZnO films-P). The films were grown on glass substrates and on the sensing area of a quartz crystal microbalance (nano-QCM). 16-(2-Pyridyldithiol)-hexadecanoic acid (PDHA) was bound to ZnO films-N, -R, and -P through the carboxylic acid unit, followed by a nucleophilic displacement of the 2-pyridyldithiol moiety by single-stranded DNA capped with a thiol group (SH-ssDNA). The resulting ssDNA-functionalized films were hybridized with complementary ssDNA tagged with fluorescein (ssDNA-Fl). In a selectivity control experiment, no hybridization occurred upon treatment with non complementary DNA. The ZnO films' surface functionalization, characterized by FT-IR-ATR and fluorescence spectroscopy and detected on the nano-QCM, was successful on films-N and -R but was barely detectable on the planar surface of films-P.