不对称

Chiral auxiliary controlled asymmetric reaction is one of the main methods in asymmetric synthesis.

手性助剂控制的不对称反应是不对称合成的主要方法之一。

The third part of this thesis is reactive simulating calculation In this section, some well-known auxiliaries are selected to compute in density functional theory B3LYP on Gaussian 03, from which the relationship between reaction active energies of transition states and enantiomeric excess of chiral products homoallylic alcohols isobtained based on relative reactive ratio theory. Using this relationship, calculations on the reaction of more than eight auxiliaries with four other aldehydes are carried out in AMI and MNDO, proving that N,N\'-dibenzyl tartamide has higher enantioselectivity than others in this reaction.

第三部分为计算化学部分，运用密度泛函理论B3LYP方法在Gaussian03软件上对已经报道的几种手性配体参与的醛不对称烯丙基化反应过程进行模拟计算，基于相对反应速率理论找出两种构型过渡态间活化能的差异与产物光学收率之间的关系；并以此为基础，用AM1和MNDO方法对上述合成的几种配体控制的反应过程进行量化计算，从而在理论上证实了N-苄基酒石酸二酰胺配体在醛的不对称烯丙基化反应中具有较高的立体选择性。

The first asymmetric synthesis of trans-β-hydroxy-γ-butyrolactones:-(3R, 4R, 5S)-4-(1-acetoxy-isopropyl)-3-hydroxy-butyrolactone 65a was achieved starting from isobutylaldehyde through nine steps. The key steps involve the construction of three chiral carbon centers by the Sharpless's asymmetric epoxidation and Substrate directable chemical reaction.

以异丁醛为起始原料，经过九步反应首次设计合成了具有三个手性中心的trans-β-羟基-γ-丁内酯：-（3R，4〓，5S）-4-（1-乙酰氧基-异丙基）-3-羟基-丁内酯65a，关键步骤是Sharpless不对称环氧化和底物定向不对称合成反应。

The principle of harmonic wave detection which is based on wavelet transform was expatiated. It introduced a new approach of harmonic measurement based on period-interleaving of arithmetic for dissymmetrical system.

首先论述了基于小波变换的谐波检测的原理，根据目前小波变换在三相不对称系统谐波检测中存在的无法分离基波信号之不足，介绍了一种用于三相不对称系统的基于周期交错的测量方法。

Based on different structure types, the slide shoes are designed in symmetrical and dissymmetrical, continuous and discontinuous types, therefore, the loading technique is characterized by diffcult operation, high technical requirements and complex process.

由于结构物类型不同，滑靴的设计有对称与不对称、连续与不连续之分，因此滑移装船作业难度大，技术要求高，工艺复杂。

The first part of this dissertation described a new effective method for asymmetric synthesis of,α,α-disubstituted amino acids from the asymmetric Strecker reaction products of aldehydes.

在本论文的第一部分，我们开发了一条以醛为原料，以不对称Strecker反应和不对称烷基化为关键步骤的合成α，α双取代氨基酸的有效方法，并对其立体选择性结果进行了机理探讨。

The synthesis of chiral pharmaceuticals is a hot issue of the development in pharmaceutical in the world,asymmetric hydrogenization of which is the successful technology in the chiral synthesis .

手性药物的合成是目前全球药物开发研究的热点，而不对称氢化是手性合成中最成熟的技术。讨论了不对称氢化技术在镇痛类、抗生素类、抗菌类、抗忧郁类以及维生素类等9类手性药物合成中的实际应用

Based on analysis of the asymmetrical hysteretic nonlinearity of materials, a piecewise linear asymmetrical hysteretic model was built.

摘要分析了振动压实过程中被压实材料的不对称迟滞特性，建立了一种分段线性的不对称迟滞模型。

The inconsistence of information is the major factor of financial crisis, and will create more affects to the insurance industry.

信息不对称是金融业运行中产生金融风险的主要原因，不对称信息对保险市场的影响尤为突出。

In Me〓N·H〓O/solvent system,-menthyl acrylate and N-α-phenylethyl acrylamide were found to be highly effective to the diastereoselective Baylis-Hillman reaction.

在Me〓N·H〓O/溶剂体系中，研究了它们的不对称Baylis-Hillman反应，取得了较好的不对称诱导效果。

Breath, muscle contraction of the buttocks; arch body, as far as possible to hold his head, right leg straight towards the ceiling (peg-leg knee in order to avoid muscle tension).

呼气，收缩臀部肌肉；拱起身体，尽量抬起头来，右腿伸直朝向天花板（膝微屈，以避免肌肉紧张）。

The cost of moving grain food products was unchanged from May, but year over year are up 8%.

粮食产品的运输费用与5月份相比没有变化，但却比去年同期高8％。