关键词： HIGHER-ORDER CYCLOADDITION   ENOL ETHER   ORGANIC-SYNTHESIS   AUXILIARY   CYCLOPROPANATION   OXIDATION  

摘要： Optically active tropilidenes were prepared by cycloaddition of a diazo ester to an aromatic ring using 2,4-pentanediol as a chiral linking bridge under complete regio- and stereo-differentiations.

关键词： asymmetric synthesis   heterocycles   pyrrolidines   samarium   sulfoximines  

摘要： Thanks to a productive interaction between reagent and substrate control, 2-alkenylsulfoximides 1 react to provide highly substituted pyrrolidine derivatives 2 enantiomerically pure and with defined absolute configuration at the newly formed stereogenic centers. Tol=tolyl, BOC=tert-butoxycarbonyl.◆ (© 1998 WILEY-VCH Verlag GmbH, Weinheim, Fed. Rep. of Germany.)

关键词： .building blocks   keto   salen   asymmetric synthesis   Chem Commun   benzyl   synthetic applications   Med Chem   Zinc Borohydride   amino indanol   Applications of cis  

摘要： By examining the examples discussed in this review, it becomes clear that the cis-1- amino-2-indanolnucleushasplayedapower- ful role in asymmetric synthesis and the bio- logical manifold.

关键词： 酮咯酸   非甾体镇痛消炎药   合成   熊去氧胆酸   脱氢   环氧化   催化氢化   还原  

关键词： SIDE-CHAIN ANALOGS   ESTERIFICATION   EFFICIENT   TAXOTERE(R)   REAGENT  

摘要： Total asymmetric synthesis of Taxol was completed by dehydration condensation between a protected N-benzoylphenylisoserine 4 or 9 and 7-TES baccatin III which was prepared from 8-membered ring enone. Taxol side chains 4, 7, 9 and 11, optically active protected N-benzoylphenylisoserines, were successfully synthesized by enantioselective aldol reaction from two achiral starting materials, benzaldehyde and an enol silyl ether derived from S-ethyl benzyloxyethanethioate.

摘要： (S)-5,5,5,5',5',5'-Hexafluoroleucine ((S)-13) of 81% ee is prepared from hexafluoroacetone (1) and ethyl bromopyruvate (= ethyl 2-oxopropanoate) in 7 steps with an overall yield of 18% (Schemes 1 and 2). Key step in this sequence is the highly enantioselective reduction of the carbonyl group in alpha-keto ester 4 either by bakers' yeast (91% ee) or by 'catecholborane' 6 utilizing an oxazaborolidine catalyst, yielding hydroxy ester (R)-5 with 99% ee. The absolute configuration was determined by X-ray analysis of the HCl adduct (S,R)-9b of (2S)-N-[(R)-1-phenylethyl]-5,5,5,5',5',5'-hexafluoroleucine ethyl ester.

关键词： asymmetric amplification   asymmetric catalysis   asymmetric synthesis   autocatalysis   chiral auxiliaries  

摘要： Who would have thought before 1986 that an enantiomerically impure catalyst could give a product in an asymmetric synthesis with an enantiomeric excess higher than that of the catalyst? Until then it was assumed that the ee value of the product (ee prod ) from an asymmetric synthesis was linearly correlated to the ee value of the chiral auxiliary (ee aux )-in fact a large deviation is possible (see diagram). These nonlinear effects are not only of academic interest since they have a variety of practical uses, which are highlighted in this review.◆ (© 1998 WILEY-VCH Verlag GmbH, Weinheim, Fed. Rep. of Germany.)

关键词： ABSOLUTE-CONFIGURATION   ACETALS   KETONES  

摘要： The asymmetric synthesis of 1-substituted 2,2,2-trifluoroethylamines from chiral 1,3-oxazolidines having trifluoromethyl group derived from trifluoromethyl ketones and (R)-phenylglycinol is described. The stereospecific reduction of chiral 1,3-oxazolidines with LiAlH4 proceeds in retention fashion.

关键词： 固定化酶   固定化酵母   布洛芬   (S)-(+)-布洛芬  

摘要： 能够不对称水解布洛芬乙酯的酵母菌Ｔ１５８（ＴｒｉｃｈｏｓｐｏｒｏｎｃｕｔａｎｅｕｍＴ１５８）固定化在壳聚糖珠中，固定化酵母菌的活力回收达６０％，最适温度为４５℃（游离酵母为３５℃），半衰期为７５ｄ以上．脂肪酶（Ｃａｎｄｉｄａｃｙｌｉｎｄｒａｃｅａ）也固定化在中空纤维反应器中，利用该反应器水解外消旋布洛芬乙酯得到的（Ｓ）－（＋）－布洛芬，其ｅ．ｅ．值为８０％．

关键词： 分子   对称性   手性   不对称合成   旋光化合物  

摘要： 本文以对称性的观点阐述对称性、手性和旋光性化合物合成的相关性．文中分成三个部分：手性与对称性；手性分子的形成；旋光性化合物的合成途径．