关键词： 手性磷化合物   配体催化剂   不对称硼烷还原反应   不对称烷基化反应   不对称硅腈化反应  

摘要： 从L-氨基酸、D-樟脑、(-)-假麻黄碱、(-)-α-苯乙胺、(S)-(-)-联萘二酚等旋光源出发,合成了26个三配位及四配位手性磷化合物.作为配体催化剂,试验了它们在潜手性酮及亚胺的不对称硼烷还原反应、醛与二乙基锌的不对称烷基化反应以及醛的不对称硅腈化反应中的催化活性.发现其中有些催化剂有很好的立体选择性.

摘要： The title salt crystallises as a conglomerate (space group P2(1)2(1)2(1), Z = 4) With one solvate CHCl3 molecule forming strong shortened contact with I-[Cl . . .I- 3.599(2) Angstrom]. Therefore, it undergoes spontaneous resolution by simple crystallisation with a deficiency of the conglomerator CHCl3 or by an internal entrainment procedure. It exhibits the (S)-(+) absolute configuration and racemises in solution (DeltaG(rac)(#): = 26.5 kcal mol(-1)). The salt was almost completely converted into one enantiomer by stirred crystallisation from solution (with full evaporation) or from a melt under conditions of enantiomerisation. The contribution of autocatalysis to this process is discussed.

关键词： inclusion compounds   molecular recognition   NMR spectroscopy   palladium   supramolecular chemistry  

摘要： Chiral aluminum complexes 3 have been employed as catalysts of the stereoselctive synthesis of cis-5-substituted 2-oxazoline-4-carboxylates from the aldol reaction of oxazole 1 and aldehydes. Cis-Product diastereoselction ranges from 3:1-50:1, while enantioselectivities vary from 92-99% for reaction with the 25 aromatic aldehydes investigated.

摘要： A systematic investigation of the stereoselectivity in Lewis acid-promoted (Mukaiyama) aldol reactions of achiral unsubstituted enolsilanes and chiral β-hydroxy aldehydes proceeding under conditions favoring chelation control is presented. Good stereocontrol can be realized for enolsilane aldol reactions of β-alkoxy and β-silyloxy aldehydes bearing only an α- or a β-stereogenic center. Examination of the chelated intermediates for α,β-disubstituted aldehydes concludes that the syn aldehyde diastereomer possesses the arrangement of stereocenters wherein the α- and β-substituents impart a reinforcing facial bias upon the aldehyde carbonyl. Aldol reactions of syn aldehydes were thus observed to proceed with uniformly excellent diastereofacial selectivity. Aldol reactions of the corresponding anti aldehydes containing opposing stereocontrol elements at the α- and β-positions exhibit variable and unpredictable selectivity. Chelation of silyl-bearing substituents was observed with Me2AlCl and MeAlCl2 as Lewis acids.* A study of the optimization and large-scale development of catalytic asymmetric aldol reactions catalyzed by the chelating copper Lewis acid, Cu[( S,S)-phenyl-pyridine(bis-oxazoline)](SbF6)2·2 H2O is presented. The bis-aquo complex of the catalyst has been isolated as an amorphous blue powder. The solid catalyst has been shown to be a stable, viable form of the catalyst which can endure prolonged storage without significant loss of catalytic activity. A selection of particularly useful silylketene acetal nucleophiles was examined in order to determine if a generally applicable process for scale-up of the aldol reactions could be outlined. It was found that each reacting nucleophile requires varying optimum reaction conditions as a result of differences in catalyst turnover properties. The reactions studied have been scaled up from less than 200 mg quantities to 2–20 g quantities of aldol adducts, and catalyst loadings have been reduced in the process to 0.5 m

关键词： Carbon  

摘要： We have devised an expeditious. efficient, asymmetric synthesis of the C(33)-C(37) fragment of amphotericin B that proceeds in 14 steps and 16% overall yield from tiglic aldehyde ((E)-2-methylbut-2-enal) with complete stereocontrol. The route described herein relies on the application of recently developed methods in catalytic asymmetric synthesis for stereocontrol through enantio- and diastereoselective functionalization of a substituted sorbate derivative.

摘要： This dissertation concerns the design and synthesis of a range of C 2 -symmetric sulfur compounds, and their use in asymmetric reactions. Chapter 1 presents the concepts of asymmetric synthesis and the use of sulfur compounds in organic synthesis, before going on to discuss the published literature concerning experimental and computational investigations in the area of enantioselective sulfur-ylide epoxidation reactions. Chapter 2 discusses the sulfur compounds that were prepared, including some background as to why they were chosen, a description of the synthetic route towards each compound, the results of each epoxidation reaction, and finally a discussion of how each sulfide performed and improvements that could be made. Molecular modelling was carried out in conjunction with the experimental epoxidation studies; a force field capable of dealing with sulfonium-ylides was used to investigate the shape and relative energies of the sulfides, their corresponding sulfonium salts, and their ylides. Thus, it was possible to gain some insight into the conformation of the sulfides and to rationalise the enantioselectivities achieved experimentally. Chapter 3 introduces the Baylis-Hillman reaction. It begins with an overview of amine and phosphine catalysed reactions, including investigations that resulted in Baylis-Hillman products with a certain degree of enantioselectivity. It goes on to discuss in more detail the literature concerning Lewis acid catalysed Baylis-Hillman reactions, in particular those which were thought to be catalysed by chalcogenides. This leads into a report on the work that was carried out in this area which used chiral sulfides in an attempt to render the reaction asymmetric. The chapter closes with suggestions of future work to be carried out in this area.

关键词： asymmetric catalysis   desymmetrization   epoxidation   natural products   zirconium  

摘要： Zirconium to the rescue! Eight contiguous chiral centers can be established with >95 % ee in the key step of an asymmetric synthetic approach to the cores of certain Celastraceae sesquiterpenes (see scheme). The route required the development of a new zirconium-modified Sharpless asymmetric epoxidation instead of the traditional titanium version. DIPT=diisopropyl tartrate.

关键词： 4-Demethoxydaunmycinone   蒽醌类化合物   抗癌活性   不对称合成  

摘要： 4-Demethoxydaunmycinone为蒽醌类化合物,有很强的抗癌活性.是如盐酸吡柔比星、伊达比星、阿霉素等已上市的抗癌药的甙元部分.药理实验证明,7、9位羟基4的手性对化合物的抗癌活性极为重要,如9位的羟基OH必须与其天然产物的构型一致才有活性.该文对其手性前体A的不对称合成做了一定的探索工作.该论文采用了使用手性联萘酚诱导,与LiAlH<,4>形成手性配合物还原酮的方法获得7位的手性羟基.再在7位手性基因的诱导下,制备9位羟基.主要完成了如下工作:1、手性联萘酚的拆分.2、不对称合成A及其光学异构体.

关键词： （S）－苹果酰亚胺   格氏加成还原   γ－内酯   trans－whisky lactone   （＋）－Blastmycinolactol   （－）－Blastmycinone   （＋）－NFX－2  

摘要： 含手性γ-内酯骨架的天然产物是一类重要的天然产物，它们不但包括了一 系列具有生理活性的化合物，诸如生物碱、大环抗生素、木分酚素内酯、信息 素、抗白血病药、抗真菌药和具有芳香味道的化合物，而且还可用来进一步合 成其它重要的天然产物和药物，这些化合物有着生理、药理、生化和临床上的 应用意义和潜在的应用价值。此外，由于γ-内酯骨架可产生多个手性中心，所 以对于它们的合成研究也侧重于不对称合成，近年来已引起人们的广泛兴趣。 本论文的研究目的在于：继续我们实验室以前的工作，发展一种方便、灵 活的多取代γ-内酯不对称合成方法，完成一些具有γ-内酯骨架重要化合物的不 对称合成。此外，本论文也对苹果酰亚胺I和格氏试剂加成反应的区域选择性 成因作一些理论研究。 本论文取得的主要结果如下： 首先，研究了苹果酰亚胺I的格氏加成产物Ⅱ开环还原为Ⅲ的反应性，发 现只有在NaBH4/MeOH or EtOH条件下，反应才能够得以进行，收率为 80～85％，遗憾的是硼氢化钠还原几乎没有立体选择性(对于不同的烷基， anti：syn为50：50～41：59) 。 其次，从苹果酰亚胺I出发，通过与含有不同烷基的格氏试剂加成、还原， 得到一对差向异构体混合物Ⅲ，后者在盐酸存在下环化得到的容易分离内酯Ⅳ 和V。然后Ⅳ和V分别在10％Pd／C和H2作用下去保护，完成了一系列关键的 中间体(3S．4S)-3-羟基-4-烷基-γ-内酯Ⅵ和(3S．4R)-3-羟基-4-烷基-γ-内酯 Ⅶ的合成。从这些关键中间体出发，我们合成了Ⅷ，从而完成了天然产物 trans-whisky，lactone Ⅸ 形式上的全合成和化合物(+)-Blastmycinolactol X、 (+)-NFX-2 Ⅺ 和(-)-Blastmycinone Ⅻ 的全合成。 最后，我们对格氏试剂与苹果酰亚胺加成反应的区域选择性成因作了一些 理论研究，在PM3计算的基础上对实验现象提出初步的解释。 ＼＼一。n；，。nBnO Ort、HO．。；＼ HO R、xx x－rl＼ ”·、f／＊o＼M／”／——、NH8rH（／二O IRx W。H An Bn OH Ill Ill IV 。一HO urt 八二n、＼／＝口l aanLAs口 ＿Mtw＿N Rx”OnMN＿／＿／”x～e ’””a’”“K”n un’”V VVIVllth ．Hq 尸u－n no D””－”FBuCOOt 3u－n 人H oL＞二OIL二n．（／二O BUx W。’”～W－ ’／ twwffe’”W IXXXIXll

关键词： asymmetric catalysis   diazo compounds   epoxidation   ylides  

摘要： A practical, general, and convergent route to epoxides with control of the relative and absolute stereochemistry has been achieved by generating the reactive intermediate (the diazo compound) in situ from tosylhydrazone salts (see scheme, PTC=phase-transfer catalyst, Ts=toluene-4-sulfonyl). High yields (58-82 %), high d.r. (88:12-98:2), and high ee values (87-94 %) have been obtained using a new class of stable chiral sulfides at low catalyst loading (5 mol %) and [Rh 2 (OAc) 4 ] (0.5 mol %).◆ (© 2001 WILEY-VCH Verlag GmbH, Weinheim, Fed. Rep. of Germany.)