关键词： Crystals   Crystallization   Nuclear radiation   Molecules   Sodium  

摘要： The readily available sodium chlorate is an interesting ionic compound because, although achiral, it forms optically active crystals. When unperturbed, an aqueous solution of sodium chlorate yields a random distribution of + and - crystals on evaporation. Some chiral perturbations profoundly alter this distribution, however. These include seeding, the addition of the optically active cosolutes D-mannitol and D-sorbitol, and the energetic and chiral beta particles and positrons. The chiral weak interaction inherent in all atomic nuclei and thus atoms and molecules does not alter the distribution of + and - crystals. Stirring during evaporation, an achiral perturbation, affects the distribution of crystals in a given crystallization;when crystals from a large number of experiments are considered, however, the distribution of + and - crystals is random.

关键词： Ethers   Organic compounds   Molecular structure   Alkyls   Cyclization  

摘要： [GRAPHICS] We report a method for the synthesis of chiral cyclopentanes using tin-lithium exchange and cycloalkylation reactions. The sec-butyllithium/(-)-sparteine-mediated deprotonation of an alkyl carbamate and subsequent substitution furnishes a highly enantioenriched stannane as a stable carbanion equivalent. It was transformed into suitable cyclization precursors, which underwent tin-lithium exchange and stereoselective cycloalkylation when reacted with n-butyllithium, giving highly enantioenriched cyclopentanes in very good yields. A kinetic resolution was observed with a higher substituted stannane.

关键词： PALLADIUM   AMINATION   ACETATES  

摘要： 4'-Substituted nucleoside analogues have been synthesized using palladium-catalyzed asymmetric allylic amination conditions. A kinetic discrimination between the diastereomeric lactol acetates (3) produced the desired aminated products (6a-d) and recovered acetate (alpha-3) in high yields and <97:3 diastereoselectivity. Epimerization of the recovered lactol acetate (alpha-3) produced a 60:40 alpha/beta mixture of (3), which could be resubjected, in principle, to the palladium-catalyzed asymmetric allylic amination conditions.

关键词： AMINO acids   HYDRIDES  

摘要： Esters of three types of silylated alpha-amino acids have been prepared from appropriate zirconaaziridines. Slow addition (syringe pump) of the (R,R) carbonate of transstilbene gave metallacycles with the maximum possible diastereomeric excess (as determined by the diastereomeric excess produced by the Hoffmann test-the same reaction but with racemic carbonate). Methanolysis gave esters (RO2C)CH(R')(NHPh) (R' = Me3Si, Me3SiCH2, and p-Me-3-SiC6H4) with the same optical purity at the alpha carbon.

关键词： Anti-Bacterial Agents   Catalysis   Ethylenes   Imines   Ketones   Lactams   Models   Molecular   Support   Non-U.S. Gov't   Support   U.S. Gov't   Non-P.H.S.   Support   U.S. Gov't   P.H.S.  

摘要： We report practical methodology for the catalytic, asymmetric synthesis of beta-lactams resulting from the development of a catalyzed reaction of ketenes (or their derived zwitterionic enolates) and mines. The products of these asymmetric reactions can serve as precursors to a number of enzyme inhibitors and drug candidates as well as valuable synthetic intermediates. We present a detailed study of the mechanism of the beta-lactam forming reaction with proton sponge as the stoichiometric base, including kinetics and isotopic labeling studies. Stereochemical models based on molecular mechanics (MM) calculations are also presented to account for the observed stereoregular sense of induction in our reactions and to provide a guidepost for the design of other catalyst systems.

关键词： Amino Alcohols   Stereoisomerism   Support   Non-U.S. Gov't   Support   U.S. Gov't   Non-P.H.S.  

摘要： The first application of metalloenamines derived from N-sulfinyl imines is reported for the highly diastereoselective addition to aldehydes. Reduction of the beta-hydroxy-N-sulfinyl imine products with catecholborane and LiBHEt3 provides syn- and anti-1,3-amino alcohol derivatives, respectively, with very high diastereomeric ratios.

关键词： 手性二茂铁氨基醇   不对称合成   结构表征   核磁共振谱   红外光谱   元素分析  

摘要： 从二茂铁和天然光学活性氨基酸出发,合成了两个新型的手性二茂铁氨基醇,它们的结构通过了核磁共振谱,红外光谱,元素分析表征.

关键词： 固相合成   不对称合成   碳青霉烯   固载化催化剂   酯化反应   酯交换反应   Friedel-Crafts反应   Lewis酸   催化   烷基化   酰基化  

摘要： 该论文主要对碳青霉烯类抗生素的固相全合成方法和有机催化剂二苯胺三氟甲磺酸盐及其固载催化剂进行了研究,取得了以下成果:(1)首次建立了1-β-甲基碳青霉烯的固相不对称合成方法学.以交联聚合物PS-DES-SiH树脂为支载物,采用\"茶叶袋\"合成技术,由乙酰氧基氮杂环丁酮手性合成砌块出发,通过固载化反应、辅助基团诱导的不对称Reformatsky反应、Dieckmann反应等7步反应,固相合成了3种1-β-甲基碳青霉烯的衍生物,其中2个为新化合物.这一研究为利用组合化学构建碳青霉烯类化合物库、发展新药物提供了重要方法.(2)通过酰胺化反应、钯催化的偶联反应等,制备了两种新的有机催化剂:即4-苄氨基甲酰基二苯胺的三氟甲磺酸盐(BDPAT)和用交联聚合物固载化的4-氨基甲酰基二苯胺三氟甲磺酸盐(PS-AFDPAT)催化剂,并发现PS-AFDPAT和BDPAT均能有效的催化等当量羧酸和醇的酯化,以及酯和醇的酯交换反应,而且可以回收和循环使用.(3)意外发现4-苄氨基甲酰基二苯胺的三氟甲磺酸盐(BDPAT)是一种新型的Friedel-Crafts反应催化剂,它能够有效地催化芳烃化合物的苄基化、环己基化和酰基化;此外,它还可以有效地催化醇和胺类化合物的酰化等反应.与传统的Lewis酸(如三氯化铝)和新近发展的稀土金属Lewis酸类催化剂相比,这种有机催化剂具有对水稳定、只需催化量、无重金属污染、可循环使用以及价格便宜等优点,因而是一种高效的绿色催化剂,具有良好的实际应用前景.

关键词： 胍类化合物   制备   有机合成   应用   有机碱   不对称合成  

摘要： 综述了胍类化合物的制备及其在有机合成中的应用 .特别着重合成方法研究的近期进展及在不对称合成中的应用 .

关键词： 手性   2,4-二羟甲基吡咯   衍生物   不对称合成   1,3-偶极环加成  

摘要： 在碱Na2 CO3或CH3ONa存在下 ,芳香醛或脂肪醛与芳香取代的甘氨酸甲酯反应 ,生成Schiff碱 ;Schiff碱在有机强碱DBU和金属离子作用下 ,生成 1,3 偶极试剂 ,并与手性丙烯酸薄荷醇酯原位发生不对称 1,3 偶极环加成反应 ,得手性 2 ,4 二酯基四氢吡咯衍生物 ;然后 ,在无水THF中用氢化铝锂还原 ,得纯的手性 2 ,4 二羟甲基四氢吡咯衍生物 .所有二酯基、二羟甲基四氢吡咯衍生物的结构都经过红外光谱、核磁共振、质谱鉴定 .