不对称

Wherein X is an oxygen atom or a sulfur atom; C*, C** and C*** are asymmetric carbons; R 1 , R 2 , R 4 , R 5 , R 8 , R 9 and R 10 are each a lower alkyl group optionally having substituent and the like, or R 4 and R 5 and the like in combination optionally form a homocyclic ring optionally having substituent and the like; R 3 is an aryl group optionally having substituent and the like; R 6 and R 7 are each a hydrogen atom and the like; Nu is -CR 16 (COR 17 )(COR 18 ) wherein R 16 , R 17 and R 18 are each a lower alkyl group optionally having substituent and the like, and the like; and EWG is an electron withdrawing group.

通式中，X代表氧或硫；C *、C **和C ***分别表示不对称碳；R 1 、R 2 、R 4 、R 5 、R 8 、R 9 和R 10 分别代表任选取代的低级烷基等，条件是例如R 4 和R 5 可以相互结合形成任选取代的同素环等；R 3 代表任选取代的芳基等；R 6 和R 7 分别代表氢原子等；Nu表示-CR 16 (COR 17 )(COR 18 )(其中R 16 、R 17 和R 18 分别代表任选取代的低级烷基等)等；并且EWG表示吸电子基团。

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。

ABSTRACT This thesis focused on the studies of setereoselectively total synthesis of naturally occurring bisabolane sesquiterpenes and hydroxamic acid derivatives; it contains the following five parts: Part Ⅰ: Hydroformylation reaction have been taken an overview for past 40 years.

本论文主要对防风根烯类倍半萜天然产物和羟肟酸类化合物的全合成进行了研究，内容概要如下：一、对近年来氢甲酰化反应——特别是不对称氢甲酰化反应作了详尽的综述。

The developing trends of biocatalytic asymmetric synthesis of β-hydroxy acids are also discussed.

最后，展望了生物催化不对称合成β-羟基酸的发展方向。

The developing trends of biocatalytic asymmetric synthesis of β-hydroxy acids is also discussed.

最后，对今后生物催化不对称合成β-羟基酸的发展方向做一展望。

Results Preparation of ss probes by asymmetric PCR and single-pr imer PCR gets success.

结果 不对称PCR及单引物PCR技术制备单链探针均获得成功；目的基因单链探针杂交条带清晰且几乎无背景值。

The addition reactions with phosphine anion andthe CsF promoted Strecker reactions were chose to evaluate the relationship of thesetwo chiral groups in the diastereoselective additions of the imino group.

通过亚磷酸负离子的加成反应和CsF促进下的Strecker反应研究了这两个手性基团的不对称诱导的匹配情况。

In the forth part, in the presence of chiral phosphoric acid, highly enantio-enriched (up to 98% ee)α-aryl glycine derivatives could be synthesized via asymmetric transfer hydrogenation of the α-aryl imino esters using Hantzsch ester as the hydrogen source.

第四部分工作中，利用Hantzsch酯作为氢源，高对映选择性地实现了手性磷酸催化芳基酮酸酯亚胺的不对称仿生氢化反应，以最高98％的对映选择性得到苯甘氨酸衍生物。

The author consider that the market of hygienic food has the severest problem, customers are deluged with all kind of inveracious advertising and their benefit is damaged by those distorted information.

表现在广告无信息量和无信息质上，并阐述由此带来的后果。笔者结合实际分析得出，信息不对称现象最严重，问题最为突出的就是中国的保健品市场。

Ab initio and density functional theory (B3LYP) in G98 were employed to study the following four direct aldol reactions between acetone and isobutyraldehyde or 3,3-dimethylbutyric aldehyde or benzaldehyde or 4-bromo-phenyl aldehyde catalyzed by-proline .

中文摘要：本文采用G98程序包中的从头计算方法和密度泛函方法计算研究了-脯氨酸催化丙酮与异丁醛、3，3-二甲基丁醛、苯甲醛及对溴苯甲醛的不对称直接羟醛缩合反应，共计四个反应体系。

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％。