C-[L-Ser-L-Ser]催化的不对称Reformatsky反应

利用液相法合成了侧链带双羟基且具有C2 对称性的环二肽C_[L_Ser_L_Ser]并将其作手性配体催化不对称的Reformatsky反应。考察了反应底物结构以及反应条件等因素对反应产物e.e.值的影响。产物的e.e.值最高达 64%。提出了可能的反应机理     

6’-醛基螺吡喃的合成及提纯方法改进

通过氯甲基化等一系列反应合成了含有醛基的螺吡喃,一种方法是在原合成方法基础上对最后一步提纯过程进行了改进,较简便地得到了纯净的化合物;另一种方法是在合成过程中加入抗氧化剂和阻聚剂直接得到纯度较高的化合物。简化了提纯步骤．两种方法中得到的化合物熔点都与文献值吻合较好．测试了化合物的光致变色性及荧光性．     

新型树枝状化合物的合成与应用研究进展

树枝状化合物具有精致、对称的结构,是一类可以从分子水平上控制、设计合成的新型化合物.树枝状化合物独特的结构伴随着独特的性能,这些独特的性能使得它在实际生产的各个领域有广泛的用途.树枝状化合物发展至今其合成方法不断进步、完善,不断朝向多样化、功能化的方向发展.其合成的基本思想方法可以归结为收敛法和发散法.树枝状化合物今后将在许多方面与现有聚合物或小分子材料竞争,并可能取而代之,因而对于新型树枝状化合物的合成研究具有重要的意义.     

嘧啶酮类化合物的合成方法研究进展

综述了嘧啶酮类化合物的合成,介绍了几种主要的研究方法的合成路线.     

3,4—二甲基—2—苯基—1,4—氧氮杂—5,7—二酮的合成

通过对—二甲基—2—苯基—1,4—氧氮杂—5,7—二酮的研究,表明这一化合物及其衍生物是手性源化合物,利用它合成许多手性化合物同时找到了合成1,4—氧氮杂的方法,产率较高．     

不含菊酸类拟除虫菊酯化合物的合成

讨论不含菊酸类拟除虫菊酯化合物中的两类化合物的合成 .一类为不含菊酸结构的拟除虫菊酯化合物 ,另一类为不含酯键类的拟除虫菊酯化合物的合成方法及其进展     

异黄酮合成的研究及进展

阐述了异黄酮类化合物的化学结构、生理活性及其应用,介绍异黄酮的天然来源及提取、分离方法。分类报道了我国在合成异黄酮化合物方面的研究进展及合成方法,尤其详尽地介绍了合成方法,并合成了依普异黄酮,最后分析异黄酮合成的发展趋势,并提出一些建议。     

有机化学复习纲要(二)

复习有机化学时必须搞清基本概念,将所学内容规律化。要求以化合物的结构与性质的关系为主线,掌握各类化合物的基本反应和条件以及合成方法。能鉴别各类化合物,并能设计一些化合物的合成路线和根据反应判断化合物的结构。同时,还要掌握各类化合物的命名。对反应历程只要求一般了解。     

不含菊酸类拟除虫菊酯化合物的合成

讨论不含菊酸类拟除虫菊酯化合物中的两类化合物的合成。一类不含菊酸结构的拟除虫菊酯化合物，另一类为不含酯键类的拟除虫菊酯化合物的合成方法及其进展。     

基于取代水杨醛与取代邻氨基酚Schiff碱的合成、表征及光谱性质研究

通过合成的取代水杨醛与取代邻氨基酚反应,合成了系列的取代水杨醛缩取代邻氨基酚Schiff碱化合物(B1-B12),通过元素分析、FT-IR、1H NMR、UV-Visible和ESI-MS对Schiff碱化合物进行了表征。测定了合成Schiff碱化合物的荧光光谱,结果表明:合成Schiff碱化合物苯环上连接卤素原子越多,其荧光越强,且溴原子的作用强于氯原子。     

卡思卡特城堡

It is worthy of noting that, whilst Crookston Castle witnessed the earlier and happier portion of Mary's variegated life,     

Western and Eastern culture differences in commercial field

The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity.     

不同的吃喝玩乐

一、吃和喝吃苹果 eat an apple, 吃药 take medicine,吃糖 have some sweets,吃饭 have one's meals,吃馆子 dine out,吃惊 be surprised/     

漏洞百出的教育

Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help?     

只要努力,不要后悔

There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love.     

浅谈移民问题

Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject.     

Sister Carrie, an Adherent of Desires

Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities.     

Improvement of one-cycle controller by use of proportional integral differential controller

1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec…     

风的曲线

Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose.