Asymmetric Synthesis of Trisubstituted Vicinal Diols through Copper(I)-Catalyzed Diastereoselective and Enantioselective Allylation of Ketones with Siloxypropadienes.

Chiral trisubstituted vicinal diols are a type of important organic compounds, serving as both common structure units in bioactive natural products and chiral auxiliaries in asymmetric synthesis. Herein, by using siloxypropadienes as the precursors of allyl copper(I) species, a copper(I)-catalyzed diastereoselective and enantioselective reductive allylation of ketones was achieved, providing both syn-diols and anti-diols in good to excellent enantioselectivity. DFT calculations show that cis-γ-siloxy-allyl copper species are generated favorably with either 1-TBSO-propadiene or 1-TIPSO-propadiene. Moreover, the steric difference of TBS group and TIPS group distinguishes the face selectivity of acetophenone, leading to syn-selectivity for 1-TBSO-propadiene and anti-selectivity for 1-TIPSO-propadiene. Easy transformations of the products were performed, demonstrating the synthetic utility of the present method. Moreover, one chiral diol prepared in the above transformations was used as a suitable organocatalyst for the catalytic asymmetric reductive self-coupling of aldimines generated in situ with B2(neo)2.

Study on Bulk Texture and Mechanical Properties of As-Extruded Wide Mg-Al-Zn Alloy Sheets with Different Al Addition.

The wide Mg alloy sheets produced by hot extrusion usually can easily form an inhomogeneous texture, resulting in anisotropic mechanical properties and poor formability. However, few studies have been carried out on the bulk texture investigation at different areas of as-extruded Mg alloy sheets, especially the Mg alloys with different alloying elements. In this work, the effect of Al on the bulk texture and mechanical properties at different areas for three wide Mg-Al-Zn alloy sheets with different Al contents (Mg-3Al-0.5Zn, Mg-8Al-0.5Zn and Mg-9Al-0.5Zn) are mainly investigated by neutron diffraction. The results showed that a strong and uneven basal texture was formed in the Mg-3Al-0.5Zn sheet. Meanwhile, the intensity of the basal texture was significantly weakened due to the numerous fine precipitates of Mg17Al12 particles, with the Al content increasing, which hinder the grain growth during extrusion, while fine recrystallized grains have a more random orientation. The enhanced tensile properties in Mg-8Al-0.5Zn and Mg-9Al-0.5Zn alloy sheets are ascribed to the cooperation effect of a refined microstructure, precipitates and weakened basal texture. Among the three Mg alloy sheets, the Mg-8Al-0.5Zn alloy sheet has a yield strength of about 270 MPa, an ultimate tensile strength of about 330 MPa and ultimate elongation of about 16% in the extrusion direction, which possesses the most excellent comprehensive mechanical properties.

Simple transabdominal minimally invasive direct coronary artery bypass surgery with right gastroepiploic artery.

For three patients with isolated right coronary artery disease who had drug resistance and were intolerant to interventional therapy, simple transabdominal small incision bypass grafting of the right gastroepiploic artery and the posterior descending branch of the right coronary artery was conducted without cardiopulmonary. All three patients were discharged smoothly without complications, and were followed up for three months, during which time the myocardial bridges were unobstructed and the cardiac functions were good. The surgery needs no thoracotomy and the injury is small, and avoids influences of sternum and pericardium adhesion on other cardiac surgery in the future. The risk of median sternotomy can be avoided for patients undergoing reoperation for coronary artery bypass surgery.

Copper(I)-Catalyzed Asymmetric Vinylogous Aldol-Type Reaction of Allylazaarenes.

A vinylogous aldol-type reaction of allylazaarenes and aldehydes is disclosed that affords a series of chiral γ-hydroxyl-α,ß-unsaturated azaarenes in moderate to excellent yields with high to excellent regio- and enantioselectivities. With (R,RP )-TANIAPHOS and (R,R)-QUINOXP* as the ligand, the carbon-carbon double bond in the products is generated in (E)-form. With (R)-DTBM-SEGPHOS as the ligand, (Z)-form carbon-carbon double bond is formed in the major product. In this vinylogous reaction, aromatic, α,ß-unsaturated, and aliphatic aldehydes are competent substrates. Moreover, a variety of azaarenes, such as pyrimidine, pyridine, pyrazine, quinoline, quinoxaline, quinazoline, and benzo[d]imidazole are well-tolerated. At last, the chiral vinylogous product is demonstrated as a suitable Michael acceptor towards CuI-catalyzed nucleophilic addition with organomagnesium reagents.

A novel amphiphilic oligopeptide induced the intrafibrillar mineralisation via interacting with collagen and minerals.

Mineralised collagen fibrils constitute the basic building blocks of bone, dentin and cementum. Noncollagenous proteins (NCPs) that are indispensable for collagen biomineralisation are not commercially available, and the mechanism of intrafibrillar mineralisation remains debatable. Herein, synthetic biomimetic molecules are regarded as alternative candidates for NCPs, and more convenient in revealing the mechanism of intrafibrillar mineralisation in vitro. Here, we fabricated a novel amphiphilic oligopeptide imitating a natural NCP. We aimed to investigate the effectiveness of the oligopeptide in intrafibrillar mineralisation and partially reveal the corresponding mechanism in vitro. The effectiveness of the oligopeptide in intrafibrillar mineralisation was characterised from the following aspects: (1) mineral interaction, (2) collagen binding and (3) induction of intrafibrillar mineralisation. Results indicated that the self-assembled oligopeptide could attract calcium ions inducing the formation of amorphous precursors; and bind onto the surface of collagen fibrils. These processes were mainly driven by the electrostatic attraction and hydrogen bonds. The self-assembled oligopeptide induced the intrafibrillar mineralisation of reconstituted collagen fibrils, in which the c-axis of apatite crystallites was roughly parallel to the long axis of the fibrils. The collagen mineralisation was achieved by binding with the self-assembled oligopeptide to increase the pool of mineralization precursors available for intrafibrillar mineralisation. In addition, the self-assembled oligopeptide induced dentin collagen remineralisation and formed a 30 µm-thick remineralised layer within 96 h. Our work sheds light on the fabrication of a novel biomimetic molecule for collagen mineralisation. The results should serve as a reference for understanding the mechanism of intrafibrillar mineralisation.

[Physiological responses of five plants in northwest China arid area under drought stress]. / 五种西北旱区植物对干旱胁迫的生理响应.

Effects of drought stress on photosynthetic characteristics, water status, physiological and biochemical indexes were studied in five arid area plants in northwest China, including Potentilla fruticosa, Lycium ruthenicum, Caryopteris mongholica, Caragana korshinskii and Hedysarum scoparium, using pot experiments. The results showed that with the prolongation of drought stress, the water conservation capacity of leaves totally increased in above five plants, the leaf relative water content rose first and then fell, and the relative chlorophyll content and chlorophyll fluorescence parameters decreased to some extent. Overall, the photosynthetic system of H. scoparium and L. ruthenicum least affected by the stress, and P. fruticosa suffered with the most serious damage. The electric conductivity and malondialdehyde (MDA) content of P. fruticosa firstly decreased and then sharply increased, while superoxide dismutase (SOD) and peroxidase (POD) activities firstly increased and then dramatically decreased. With the decrease of soil water content, the electric conductivity rose firstly and then fell in the other four plants,the change of MDA content rose first and then fell, or fell first and then rose, and the activities of SOD and POD almost displayed upward trend. Especially, SOD activity of C. mongholica and POD activity of H. scoparium had the biggest increment among the five plants after 28 days of drought stress, increasing by 1.1 and 13.1 times respectively, compared with before processing. Additionally, there was significant variance in the accumulation of organic solutes among the five plants during the drought stress treatment. The accumulation of soluble sugar and free proline was the most in P. fruticosa, increasing by 1.1 and 22.4 times respectively, after 28 days of drought treatment. H. sco-parium accumulated the most soluble protein, increasing by 1.0 times after 28 days of drought treatment. The result of membership function method showed that the drought tolerance decreased in order of H. scoparium ＞ L. ruthenicum ＞ C. korshinskii ＞ C. mongholica ＞ P. fruticosa. The research revealed that all five plants could make positive response to drought stress through improving the activity of antioxidant enzymes and accumulating organic solutes, which could help to reduce cell damage. P. fruticos was most sensitive to water deficit in the five plants, and the degree of drought had exceeded its own regulated capacity threshold during the experiment.

Synthesis of oxazolines from amides via palladium-catalyzed functionalization of unactivated C(sp(3))-H bond.

A complementary method that enables the expeditious synthesis of oxazolines from amides via Pd-catalyzed C(sp(3))-H functionalization has been described. Preliminary studies indicate that the reaction might go through a chlorination/nucleophilic cyclization sequence, and the high efficiency of this sequence is enhanced by the in situ cyclative capture of the chlorinated intermediate. The resulting oxazolines can be further converted into the corresponding ß-amino alcohols without chromatography.

4,5-Diaza-9H-fluoren-9-imine.

In the title compound, C(11)H(7)N(3), the diaza-fluorene rings are almost coplanar with an r.m.s. deviation of 0.0160 Å. In the crystal structure, C-H⋯N hydrogen bonds link mol-ecules into sheets parallel to the ab plane. Mol-ecules are also stacked regularly along the c axis by a variety of π-π inter-actions with centroid-centroid distances in the range 3.527 (2)-3.908 (2) Å.

N-(4,5-Diaza-9H-fluoren-9-yl-idene)-4-meth-oxy-aniline.

In the title compound, C(18)H(13)N(3)O, the diaza-fluorene ring system is almost coplanar (r.m.s. deviation = 0.0640 Å) and subtends an angle of 61.5 (4)° with the plane of the meth-oxy-substituted benzene ring. In the crystal structure, pairs of C-H⋯O hydrogen bonds link mol-ecules into centrosymmetric dimers parallel to the ab plane. Mol-ecules are also stacked in an obverse fashion along the c axis by a variety of π-π inter-actions with centroid-centroid distances in the range 3.557 (2)-3.921 (2) Å.

N-(4,5-Diaza-fluoren-9-yl-idene)aniline.

In the mol-ecule of the title compound, C(17)H(11)N(3), the 4,5-diaza-fluorenyl-idene unit is nearly planar and is oriented with respect to the phenyl ring at a dihedral angle of 75.75 (3)°. In the crystal structure, the mol-ecules are aligned in the [100] direction in such a way that neighbouring 4,5-diaza-fluorenyl-idene planes face each other in an anti-parallel fashion.

N-(4,5-Diaza-fluoren-9-yl-idene)-4-methyl-aniline.

In the mol-ecule of the title compound, C(18)H(13)N(3), the 4,5-diaza-fluorenyl-idene unit is nearly planar and is oriented at a dihedral angle of 66.31 (1)° with respect to the benzene ring. In the crystal structure, mol-ecules are stacked regularly along the c axis.