关键词： sultones   asymmetric synthesis   chiral auxiliaries   sulfonates   one-pot reaction   cyclization  

摘要： The first auxiliary controlled asymmetric synthesis of enantiopure alpha,gamma-substituted (gamma-sultones via alpha-allylation of lithiated sulfonates by using 1,2:5,6-di-O-isopropylidene-alpha-D-allofuranose as chiral auxiliary is described. The high asymmetric inductions of the alpha-allylations were reached in good to excellent yields. Successive epimerization-free cleavage of the auxiliary and diastereoselective ring closure of the sulfonic acid intermediates in a one-pot procedure led to the title compounds in good to excellent yields and diastereo- and enantiomeric excesses (de, ee greater than or equal to 98%). ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).

关键词： Functionalization   Redox reactions   Organic compounds   Anions   Piperidines  

摘要： [GRAPHICS] The hydroxy-directed reduction of 1,2-dehydropiperidines with the "ate" complex of DIBAL-H and n-BuLi affords functionalized trans-2,6-disubstituted piperidines. This methodology was employed in the asymmetric synthesis of the quinolizidine alkaloid (-)-lasubine I.

关键词： asymmetric synthesis   chiral resolution   chirality   Grignard reaction  

摘要： Two new six-coordinate Grignard reagents, cis-[(p-CH3C6H4)-MgBr(dme)(2)] (1) and cis-[MgCH3(thf)-(dme)(2)]I (2), have been synthesized and their crystal structures have been determined. Both reagents are cis-octahedral and therefore chiral. They crystallize as conglomerates and racemize rapidly in solution. By utilizing these properties, the absolute asymmetric synthesis of specifically the Delta or the Lambda enantiomer was achieved for both Grignard reagents. Enantiopure 1 and 2 were then reacted with butyraldehyde or benzaldehyde to give the corresponding alcohol in up to 22% enantiomeric excess. At -60degreesC, the Grignard reagents crystallize as racemic phases instead of conglomerates. Consequently, the crystal structures of rac-cis-[(p-CH3C6H4)MgBr(dme)(2)] (.) DME (3) and rac-cis-[MgCH3(thf)(dme)(2)]I (4) could be determined.

关键词： Diastereoisomers   Asymmetric synthesis   Organic acids  

摘要： Four unique diastereomers of 3-hydroxy-2,4,6-trimethylheptanoic acid-(2R,3R,4R), (2S,3R,4R), (2S,3R,4S), and (2R,3R,4S)-the fatty acid component of callipeltin A and D, have been synthesized from commercially available (+)- and (-)-pseudoephedrine propionamide in 6 steps and 59% average overall yield. Comparison of the H-1 and C-13 NMR and optical rotation data of the resulting isomers with the natural fragment unambiguously verifies the configurational assignment of the natural isomer as (2R,3R,4R).

关键词： ASYMMETRIC synthesis   STEREOISOMERS  

摘要： A diastereoselective and modular approach to the synthesis of the 3-hydroxymethyl-2,3,5,6,7,7a-hexahydro-1H-pyrrolizine-1,2,7-triol structure, characteristic of several natural pyrrolizidine natural products, has been developed. This approach culminated in the synthesis of (-)-7-epiaustraline and (+)-1,7-diepiaustraline. The oxazolidinone group has been found to be a useful protecting group in the RCM reaction and, as part of a pyrrolo[1,2-c]oxazol-3-one ring system, has functioned as a stereo- and regio-directing group in a key diastereoselective cis-dihydroxylation reaction and a regioselective nucleophilic ring-opening of a S,S-dioxo-dioxathiole.

关键词： glycine derivative   tryptophan derivative   propargyl bromide   Tryptophan   Central   Residue   Key Transformation   Alkylation   Asymmetric synthesis   Residues  

摘要： Chiral phase-transfer catalyst 5 containing an electron-deficient trifluorobenzyl moiety promoted the alkylation of glycine derivative 6 with propargyl bromide 7a in good yield and excellent ee. The resulting propargyl glycine 8 was converted to 14, the central tryptophan residue of Celogentin C, in two steps, with the Pd-catalyzed heteroannulation as the key transformation. This method promises to be an efficient route for the preparation of tryptophan derivatives possessing substitution on the indole ring.

关键词： 医药中间体   市场动向   反倾销   贸易壁垒   手性化合物   不对称合成  

摘要： 发展中国家在国际市场竞争中的地位日益提升 ,这也使得国外对我国化学品提出的反倾销案件增多 ,设置的贸易壁垒增加。而为保证国内企业的健康发展 ,近几年我国也对一些国外化工产品进行了反倾销调查。在医药中间体的生产过程中 ,应结合市场充分利用一些能够创造更大价值的副产物。当前 ,采用不对称合成获得手性化合物成为新药开发中的热点。随着医药中间体生产向发展中国家的转移 ,我国企业应注重从技术实力、客户关系和营销技巧

关键词： 手性助剂   6,6’-二羟基-5,5’-双喹啉   不对称合成  

摘要： 以手性诱导体(+)＿α＿甲基苄胺和CuCl2形成的络合物为催化剂,不对称氧化偶联6＿羟基喹啉生成R＿(+)＿6,6'＿二羟基＿5,5'＿双喹啉.粗产品与稀HCl形成盐酸盐晶体,再用Na2CO3水解得到光学纯的R＿(+)＿6,6'＿二羟基＿5,5'＿双喹啉.

关键词： Diels-Alder反应   不对称合成   研究进展   催化   Lewis酸   手性助剂   手性双烯  

摘要： 狄尔斯 -阿尔德 (DA)反应自被发现以来 ,在有机化学中占有重要地位 .对近年来DA反应中不对称合成催化剂 (尤其是手性Lewis酸化合物 )、手性助剂和手性双烯三个主要方面的研究进展进行了讨论 .

关键词： 8-O-4′新木脂素   不对称合成   木脂素   立体选择性   合成路线   结构表征  

摘要： 报道了一种手性合成 8-O-4′新木脂素的新方法 ,其中的关键步骤是以 Sharpless不对称双羟化反应来构筑手性中心并以 Mitsunobu反应立体选择性地构建 8-O-4′新木脂素的骨架 ,最终以 8步反应得到了天然降碳 8-O-4′新木脂素的苏赤混合物 ,苏赤比为 2∶ 1 .