立体异构

The efficient first asymmetric syntheses of-6β-hydroxy-7αH-eudesm-4-en-3-one, and its C-6 epimer were achieved starting from-dihydrocarvone, whichprovide a novel and efficient synthetic method to 6-oxgenated eudesmanes.

以-二氢香芹酮为原料，经五步反应，首次完成了6β-羟基-4(5)-烯-3-羰基桉烷及其6位差向异构体的立体选择合成，并为C-6位含氧官能团取代桉烷类化合物的合成提供了一种简便有效的方法。

Keywords: solid phase organic synthesis; stereoselective reaction; heterogeneous photosensitization

中文关键词：固相有机合成；立体选择性反应；非均相光敏异构化

This intermediate is responsible for the stereoselective nucleophilic substitution and the subsequent racemization of 3-EtO-NDZ enantiomers in acidic ethanol.

该中间体导致了3-EtO-NDZ对映异构体在酸性乙醇中所发生的立体选择性亲核取代反应及随后的消旋过程。

In stereoisomerism, substances with the same atoms are bonded in the same ways but differ in their three-dimensional configurations.

第二种类型是立体同分异构体，具有相同原子的物质以相同的键合方式结合，但它们的三维构型不同。

In stereoisomerism, substances with the same atoms are bonded in the same ways but differ in their three-dimensional configuration s.

第二种类型是立体同分异构体，具有相同原子的物质以相同的键合方式结合，但它们的三维构型不同。

In stereoisomerism, substances with the same atom s are bonded in the same ways but differ in their three-dimensional configurations.

第二种类型是立体同分异构体，具有相同原子的物质以相同的键合方式结合，但它们的三维构型不同。

Treatment of dials with N-tert-butanesulfinamide, all biaryl dials were successfully converted into the corresponding bis-imines which were then treated with samarium diiodide to afford diamine products. The absolute configurations of all the intramolecular coupling products were determined by X-ray crystallography.

轴手性二醛与N-叔丁基亚磺酰胺缩合得到相应的亚胺，其为一对非对映异构体。N-叔丁基亚磺酰亚胺在二碘化钐条件下得到的偶联产物，经X-衍射也确定了其立体构型。

The yields and ees obtained in the AD reaction of eight olefins utilizing 10 in PEG/NMO system were 72～90% and 79～96%(except for trans-5-decene and ally naphthyl ether).

3配体10和配体8是一对假对映异构体，在AD反应中立体选择面相反，可得到相反构型的产物。

Nevertheless, the yield of pinacol was also strongly affected by the steric environment surrounding the carbonyl group. The pinacol coupling of aromatic aldehydes has been achieved with high yields under such a condition. However, the diastereose-lectivities of pinacols were not satisfying. Unfortunately, the ketones and most aliphatic aldehydes appeared inert under the same reaction conditions.

然而， 呐偶合反应的产率受到羰基周围环境的立体位阻影响较大，在此条件下，锌粉能有效地促进芳香族醛类化合物进行水相呐偶合反应，得到的呐醇产率高，但非对映异构体选择性差，而脂肪族醛类化合物得到的呐醇产率较低，在同样的条件下，酮类化合物不能顺利进行呐偶合反应。

The effect of silicon atom in substrate on the reaction rate and the stereoselectivity of enzymatic reactions was revealed by comparison of horse liver alcohol dehydrogenase-catalyzed stereoselective dehydrogenation of the three isomers of acetyltrimethyl propanone and their carbon analogues in aqueous/organic biphasic systems.

本项目通过对比在水－有机溶剂两相系统中，马肝醇脱氢酶催化三甲基硅烷丙酮的三个异构体及其碳类似物的光学选择性脱氢反应，揭示了底物中的硅原子对酶反应速度、立体选择性的影响规律，成功地合成了高对映体纯度的手性有机硅醇，并实现了辅酶的再生。

According to the clear water experiment, aeration performance of the new equipment is good with high total oxygen transfer coefficient and oxygen utilization ratio.

曝气设备的动力效率在叶轮转速为120rpm～150rpm时取得最大值，此时氧利用率和充氧能力也具有较高值。

The environmental stability of that world - including its crushing pressures and icy darkness - means that some of its most famous inhabitants have survived for eons as evolutionary throwbacks, their bodies undergoing little change.

稳定的海底环境─包括能把人压扁的压力和冰冷的黑暗─意谓海底某些最知名的栖居生物已以演化返祖的样态活了万世，形体几无变化。