Optically active alcohols: Resolution and synthesis from asymmetric reduction of prochiral ketones

The recent methods of resolution, enantiomeric excess determination and synthesis of optically active alcohols from asymmetric reduction of prochiral ketones are reviewed in the article with references. Important functions and applications of optically active alcohols in biological and chemical research area are described in an introduction part. The following part deals with resolution and enaniiomeric excess determination of racemic alcohols. The next part discusses asymmetric reduction of prochiral ketone and related compounds, which including: (a) Reduction by chirally modified aluminum and boron hydrides: (b) Catalytic reduction with chiral transition metal, complexes: (c) Enantioselective reduction by hydride transfer from carbon: (d) Biocatalytic reduction: (e) Asymmetric synthesis of chiral nonracemic alcohols with help of physical methods. A conclusion about optically active, alcohols from asymmetric reduction of ketones followes in the final part of article. Foundation item: Supported by the Fundation of High Education Ministry for the Scholars Back from Abroad Biography: HU Xian-ming (1950-), male, Associate Professor, Ph. D. (Univ of Groningen), email: xmhu@wh.edu.cn.     

Cayley树上非对称马氏链的局部收敛性质

通过构造鞅,研究了Cayley树上非对称马氏链的局部收敛性质.     

Oribatid mite (Acari) community structure in steppic habitats of Burgos Province,central northern Spain

This work is a study of the communities of oribatid mites in steppic areas of Burgos Province, central northern Spain, in relation to different habitat types belonging to natural or disturbed ecosystems. The primary objective was to find the relationship between anthropogenic use of land and several diversity indices. Parameters such as abundance, species richness, real diversity (H′) and equitability (J′) of the mite communities were calculated in 20 soil plots, sampled in spring and autumn 2000, belonging to the predominant habitat types of this area: (1) cultivated lands, (2) abandoned crop lands, (3) grasslands/pastures, and (4) natural oak forests or a pine plantation. The most widespread species in the area as well as the most abundant taxa overall are documented, together with the faunistic checklist of oribatid mites identified in the study. The results show a general decline in the composition of the oribatid community, in terms of species diversity and abundance, from non‐disturbed soils to cultivated lands. The number of species (richness) was usually higher in forest soils than in disturbed ecosystems, in which the most degraded soils showed the lowest number of species. The community analysis shows the differences due to habitat type and ubiquitous bioindicator species.     

两段不对称非线性系统的自适应控制新算法

针对两段不对称非线性系统，分别就非线性部分已知和未知两种情形提出了基于极点配置控制策略的自适应控制新算法，非线性部分已知时，该算法不仅能保证全局稳定性，而且能渐近跟踪一大类参考输出，非线性部分未知时，提出了一种新的辨识方法，使原耦合在一起的线性动态部分和非线性静态部分的参数分开进行辨识，新算法可用于非最小相位系统，并且可辨识的参数少，因此减小了计算量，仿真表明新算法的良好性能。     

有限平面非对称载荷裂纹问题的边界积分方程方法

本文使用边界积分方程方法，将非对称载荷作用下的平面裂纹问题，归结为求解一组混和型奇异积分方程，并构造了高精度的数值方法。为说明本文的可靠性。文中对几个实例作了数据计算，得到了它们的应力强度因子。     

不同公司规模下现金流量对投资决策影响的实证研究

根据现代公司金融理论，在公司投资模型中引进融资因素，研究了不同规模公司投资与现金流量的关系，并探讨了不同公司规模投资决策行为的差异．实证研究发现，大规模公司投资对现金流量的敏感性要高于小规模公司．动因检验的结果表明，大规模公司投资依赖于现金流量源于信息不对称理论，小规模公司投资依赖于现金流量源于自由现金流量的代理成本理论．     

N-烃基化和N-磺酰化的手性氨基醇和硼烷对前手性酮的不对称还原

为研究不对称催化合成反应,以L 亮氨酸为原料,由酯化、格式反应、还原N 烃基化反应合成3个新手性胺醇(6a,6b,6c),6b和6c经磺酰化得7a和7b.将手性配体6a,6b,6c,7a,7b分别与BH3·Me2S络合,由2种方法对芳香酮进行不对称还原,得芳香醇,不对称还原收率(ee)为3.9%～60.5%,其中手性磺胺醇的不对称催化收率较胺醇高.     

Syntheses of oxysterol receptors‘(LXRs)ligands

The LXRs‘ and agonist,24S,25-epoxycholesterol 1,was synthesized stereoselectively(100%d.e.)in 56% overall yield from methyl hyodeoxycholanate 4 in 9 steps with des mosterol acetate 11 as the key intermediate and the modified Sharpless asymmetric dihydroxylation as the key step.The LXRα subtype selective agonist 5α,6α,24S,25-diepoxycholesterol 2 and the novel LXRs‘ ligand 5β,6β:24S,25-diepoxycholesterol 3 were also synthesized from 1.