关键词： 不对称   化合物   缩酮   手性助剂   芳基   取代基   光学活性   烷酸   酒石酸   羟基羧酸  

摘要： 2-芳基烷酸类化合物在解热、镇痛药中占有重要地位,它的分子中有一不对称中心,因此存在一对对映体。对于某些化合物,其对映体之一具有较高的生物活性,往往需要得到光学纯产物。通常以光学活性的胺进行拆分。其缺点在于非活性对映体的消旋、拆分剂的回收及操作条件的控制等较为繁复,因此该类化合物的不对称合成即成为研究的目标之一,有不少精采的报道。新近发展的几种以α-易离去基团取代的烷基芳基缩酮经芳基1,2-迁移合成2-芳基烷酸的方法,由于经济、简便、选择性高,已

关键词： D-苯丙氨酸   不对称合成   手性相转移催化剂  

摘要： 目前,氨基酸不对称合成方法甚多,但是使用手性相转移催化剂未见有报道。本文报道在同位素标记氨基酸不对称合成研究中,用非标记甘氨酸进行模型试验的初步结果:使用(-)-氯化-N-苄基辛可尼丁鎓作催化剂,可获得近90%光学纯度的 D-苯丙氨酸,化学产率61.6%。

摘要： This thesis is concerned with the asymmetric synthesis of cyclopropyl derivatives via the use of chiral iron acyl complexes of the type ($\eta\sp5$-C$\sb5$H$\sb5$)Fe(CO)(PPh$\sb3$)(COCH=CR$\sp\prime$R). Chapter 1 reviews previous routes to optically active cyclopropyl derivatives and reviews the use of the chiral auxiliary ($\eta\sp5$-C$\sb5$H$\sb5$)Fe(CO)(PPh$\sb3$) for asymmetric synthesis. Chapter 2 describes the synthesis of the complexes ($\eta\sp5$-C$\sb5$H$\sb5$)Fe(CO)(PPh$\sb3$)(COCH=CRR$\sp\prime$) and presents a conformational analysis of the $\alpha$,$\beta$-unsaturated acyl ligand. Chapter 3 describes the diastereoselective synthesis of cis-substituted cyclopropyl complexes via the reaction of Z-$\alpha$,$\beta$-unsaturated iron acyl complexes with electrophilic alkylidene species. Decomplexation, to give the corresponding cyclopropyl esters, occurred without epimerisation of the cyclopropane ring. By the use of homochiral iron acyl complexes the enantioselective synthesis of cyclopropyl derivatives was achieved. Section A describes methylene addition and Section B isopropylidene addition reactions. Section C describes attempts to synthesise pyrethroid insecticide precursors which occurred with good diastereoselectivity but poor regioselectivity. Section D describes electrophilic ethylidene addition reactions in which the chiral auxiliary exerts good stereochemical control over three new chiral centres. Chapter 4 describes the diastereoselective synthesis of trans-substituted cyclopropyl complexes via the reaction of E-$\alpha$,$\beta$-unsaturated iron acyl complexes with nucleophilic alkylidene transfer reagents. Section A describes methylene transfer reagents. Whilst $\alpha$-lithiosulphides and $\alpha$-lithiosulphoxides were of limited use, iodomethyllithium (generated in situ) resulted in highly diastereoselective syntheses of the cyclopropyl complexes. Decomplexation, to give the corresponding cyclopropyl esters, occurred without epimerisation of t

摘要： A study of alkylation, conjugation addition and cyclisation reactions of sulphoxides was carried out. Lithiation of 4-alkoxybutyl p-tolyl sulphoxides with lithium diisopropylamide and alkylation with methyl iodide and benzyl bromide gave very poor stereoselectivity, but use of the corresponding t-butyl derivatives led to a large increase in selectivity. Addition of lithiated phenethyl t-butyl sulphoxides to methyl acrylate and methyl crotonate at low temperature, gave the conjugation addition products in good yields. Moreover, the stereoselectivity was high and an x-ray crystal structure determination was used to determine the relative configuration of the adduct derived from methyl crotonate. Attempted cyclisation of the methyl acrylate conjugation addition product, and the alcohol obtained by reduction with lithium aluminium hydride, by reduction of the sulphoxides, S-methylation of the resulting sulphides and intramolecular displacements of the sulphonium salts could not be achieved since S-alkylations using reagents such as methyl triflate and trimethyloxonium tetrafluoroborate were not successful under various conditions. However, reaction of the methyl acrylate adducts with iodotrimethylsilane resulted in the reduction of the sulphoxides, cleavage of the t-butyl sulphides and cyclisation leading to a cyclic thioester. The corresponding alcohol yielded a tetrahydrothiophene and this is a new method for the formation of this ring system.

关键词： Aspartame   天冬   二肽   盐酸水解   分离制   Fischer   丙二酸   糖质   不对称合成   乙酞胺  

摘要： 苯丙氨酸是1879年Scholze和Barbieri发现的。并且首先从羽扁豆中分离出来。接着1901年Fischer用盐酸水解酪元(Casein)分离制得苯丙氨酸。以后苯丙氨酸的提取、合成和发酵等制备方法陆续出现,并且不断改进和创新。苯丙氨酸纯品白色粉末结晶。呈苦味,

关键词： 不对称   手性助剂   合成方法   烯丙醇   环丙烷衍生物   天然产物   药物  

摘要： 四、(S)-(-)-和(R)-(+)-2-(甲氧基甲基)四氢吡咯(SMP,5;RMP,6)被化学家称为“魔术般的手性助剂”的SMP和RMP已广泛用于合成手性β烷基醛。

关键词： 邻苯二甲酰亚胺   相转移催化剂   手性季铵盐   光学活性   相转移催化反应   催化不对称合成   羧酸酯   光学纯度  

摘要： 在固液两相条件下用手性季铵盐为相转移催化剂,邻苯二甲酰亚胺钾与α-溴代羧酸酯反应,合成了十二个具有光学活性的α-(邻苯二甲酰亚胺基)羧酸酯,经肼解和水解,得到相应的光学活性α-氨基酸,光学纯度百分率为3.6-17.8%。

关键词： 不对称   手性助剂   仲醇   天然产物   药物  

摘要： 不同立体构型的物质常呈现不同的生理活性,因此,在药物、食品添加剂、昆虫信息素、抗生素等的合成中如何获得特定立体构型化合物的问题具有特别重要的意义。

关键词： 生物碱   反应性  

摘要： 近廿年来,人们利用△~2-哌啶的反应性已发展了若干合成外消旋生物碱的方法,然而其反应性仅局限于C-3位的亲电取代和C-2位的亲核取代,在合成一些具有重要生物活性的哌啶类生物碱工作中,我们注

关键词： 不对称   脂肪酮   II,Iv   烯丙基醇   立体选择性合成   化合物   Sn  

摘要： 在有机化学中,长期认为Sn(Ⅱ)化合物如氯化锡(Ⅱ)是芳香硝基化合物还原为芳香胺的还原剂。最近几只相继报道了Sn(Ⅱ,Ⅳ)化合物应用于碳——碳键形成的合成,特别是可应用于不对称合成。本文现就Sn(Ⅱ,Ⅳ)在不对称合成的应用作一综述。简介Sn(Ⅱ,Ⅳ)化合物的合成,着重叙述它们在不对称合成上的应用。