关键词： 醛   酮   醇   胺   不对称合成  

摘要： 根据对866个有代表性的旋光物质的研究,***和***指出,半数以上的旋光物质是手性的,至少具有一个或一个以上手性中心。其中22％光活性物质来自天然产物或从天然产物通过部分合成得到。78％光活性物质是全合成的,但是纯的对映体仅占5％。众所周知。

关键词： 不对称合成   硼氢化锌   α-羟基酮   β-羟基酮α,   β-环氧酮   β-酮酸酯   β-酮酰胺   立体选择还原  

摘要： 综述了硼氢化锌对α-羟基酮、β-羟基酮、α,β-环氧酮、β-酮酸酯和β-酮酰胺的高立体选择性还原和硼氢化锌在不对称合成中的应用。

关键词： 丙酮缩合   油酰胺   肉桂酸钠   不对称合成  

摘要： 本文探索了原黄皮酰胺和去甲原黄皮酰胺及其衍生物的合成。 (一)通过以下四条不对称合成路线，探索并合成了光活去甲原黄皮酰胺(N—β—苯乙基—3—苯塞甘油酰胺)的四个立体异构体。

摘要： This thesis is concerned with the asymmetric synthesis of cyclopropyl derivatives via the use of chiral iron acyl complexes of the type (<IMG WIDTH=6 HEIGHT=14 ALIGN=MIDDLE SRC="/maths/***">5-C 5 H 5 )Fe(CO)(PPh 3 )(COCH = CR'R). Chapter 1 reviews previous routes to optically active yclopropyl derivatives and reviews the use of the chiral auxiliary (<IMG WIDTH=6 HEIGHT=14 ALIGN=MIDDLE SRC="/maths/***">5-C 5 H 5 )Fe(CO)(PPh 3 ) for asymmetric synthesis. Chapter 2 describes the synthesis of the complexes (<IMG WIDTH=6 HEIGHT=14 ALIGN=MIDDLE SRC="/maths/***">5-C 5 H 5 )Fe(CO)(PPh 3 )(COCH = CRR') and presents a conformational analysis of the <IMG WIDTH=7 HEIGHT=7 ALIGN=BOTTOM SRC="/maths/***">,<IMG WIDTH=9 HEIGHT=24 ALIGN=MIDDLE SRC="/maths/***">-unsaturated acyl ligand. Chapter 3 describes the diastereoselective synthesis of cis -substituted cyclopropyl complexes via the reaction of Z-<IMG WIDTH=7 HEIGHT=7 ALIGN=BOTTOM SRC="/maths/***">,<IMG WIDTH=9 HEIGHT=24 ALIGN=MIDDLE SRC="/maths/***">-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-<IMG WIDTH=7 HEIGHT=7 ALIGN=BOTTOM SRC="/maths/***">,<IMG WIDTH=9 HEIGHT=24 ALIGN=

关键词： .having   chiral   dimethyl   opening   Lipase   glutaric   diisopropyl   monoesters   Organic Solvents   asymmetric ring   AmanoP   Acid Anhydrides  

摘要： Under heterogeneous conditions, a lipase (Amano P) catalyzed the asymmetric ring opening of 3-substituted glutaric anhydrides with 1-butanol in diisopropyl ether to afford the R mono esters, which were converted to the 3-substituted .delta.-lactones having ***.93%e.e. This process offered a practical means for preparing optically active 3-methyl-.delta.-valerolactone (93%e.e) which is a useful chiral building block. The enzyme hydrolyzed the corresponding dimethyl esters to give the S mono esters in an aqueous medium. In both reactions, the pro R carbonyl group was preferentially attacked to yield pairs of enantiomers.

关键词： .allyl   asymmetric synthesis   aldol   stereochemical   mismatched   stereogenic   synthesis of bryostatin   crotylboration   Bryostatins  

摘要： After a brief introduction that outlines our general strategy for the stereoselective synthesis of complex natural products, based on the rule of multiple asymmetric synthesis, this article will present a critical evaluation of reagents recently developed to effect asymmetric aldol and allyl- and crotylboration, perhaps the two most important carbon, carbon bond forming reactions in the synthesis of polyketide-type natural products. Some emphasis will be placed on the mechanistic and synthetic aspects of newly discovered (R-) and (S)-2-trimethylsilylborolane mediated reactions. The latter half of the article will deal with the application of these reactions as illustrated by our work directed towards the synthesis of bryostatin 1, C47H68O17, a marine natural product isolated in minute quantities from Bulgula neritina. Bryostatins are potential anti-leukemic agents.

关键词： .olefinic   adducts   conjugate   stereoselectivity   protected   asymmetric synthesis   chiral auxiliary   aldehyde   preference   nor-ephedrine   alkenyloxazolidines  

摘要： The stereochemistry of ti,e acid catalysed cyclization between N-protected norephedrine and w,P-unsaturated dimethyl acetals to give 2-alkenyloxazolidines is described. Such heterocycles, on the basis of their different formation and reactivity behaviour, are classified as electron rich or electron poor olefinic appendages. The mechanism and the factors determining the kinetic preference for the cis C-2/C-5 isomer is discussed. Experimental evidence together with theoretical considerations provide a reasonable rationalization for the observed selectivity of the conjugate addition. The addition of cuprates, KC10, NaOCHzC6H,, and (CH3)zC=P(C6H~)3 to a$-unsaturated esters, ketones and aldehydes with a chiral oxazolidine in 7 position, occur with high stereoselectivity and yield. The corresponding adducts provide a useful tool for manipulation to more complex structures.

关键词： .asymmetric synthesis   DIBAL   using chiral   Ketosulfoxides   Solladig   hydroxysulfoxide  

摘要： Chiral sulfoxides are very useful groups i n asymmetric synthesis. We have recently concentrated our e f f o r t s towards the asymmetric synthesis o f o p t i c a l l y a c t i v e poly-hydroxylated chains which are present i n many important n a t u r a l products, Our method i s based on the combination o f reduction o f 6-ketosulfoxides and hydroxylation o f the double bond, reactions which have been shown t o be extremely stereoselective. This method was improved i n order t o obtain d i f f e r e n t stereochemistry i n the r e s u l t i n g polyol. Several applications w i l l be described t o i l l u s t r a t e t h i s methodology.