关键词： QD431.2A6L2  

摘要： 3-Methylaspartate ammonia-lyase is a bacterial enzyme that catalyses the reversible elimination of ammonia, in the presence of monovalent and divalent metal ions, from (2S,3S)-3-methylaspartic acid to yield mesaconic acid. The catalytic mechanism of the wild type enzyme obtained from Clostridium tetanomorphum involves a concerted elimination of ammonia and is thought to operate via the intermediacy of a dehydroalanine residue at the active site. No direct evidence has been established so far concerning the existence of this dehydroalanine residue, except that 3-methylaspartate ammonia-lyase was found to be irreversibly inactivated by phenylhydrazine. Inactivation of the enzyme with labelled ¹⁵Nβ-phenylhydrazine and subsequent ¹⁵N-edited NMR spectra of the digested enzyme resulted in a proposal for the inhibition mechanism by phenylhydrazine. This mechanism involved the conjugate addition of phenylhydrazine onto the dehydroalanine moiety and the subsequent cyclisation to give a cyclic adduct. A synthetic model containing a ¹⁵N atom of this adduct was synthesised and the NMR data obtained were compared with the spectra obtained earlier from the enzyme experiment. In order to carry out mapping studies of the active site it was highly desirable to prepare molecules capable of reacting specifically and irreversibly at the active site. To this end, the synthesis of aminofumaric acid and (2S,3S)-3-methyl N-amino aziridine dicarboxylic acid were attempted. (2S,3R) and (2R,3R)-3-Methylsuccinic acids were prepared in 5 steps from (2S,3S)-3-methyl aspartic acid. These compounds were found to behave as noncompetitive inhibitors of β-methylaspartase. (2S)-3,3-Dimethylaspartic acid was also synthesised and found to be a competitive inhibitor having the same binding affinity as the natural substrate. In order to prepare a β-electrophilic amino acid analogue of the physiological substrate, an asymmetric synthesis was designed that involved the stereoselective alkylation and acylati

关键词： 杀虫   溴氟菊酯   异黄烷   老年痴呆   药物  

摘要： 该论文的目的在于希望找到一条合成药效最好的光学异构体、并且适合工业化生产的途径,并进一步探索了与之有关的苯基氰醇不对称合成的方法.

摘要： The cyclopropanation reactions of (1a) with ethyl and t-butyl (dimethylsulfuranylidene) acetate proceeded with good diastereoselectivity and resulted in the formation of three diastereoisomeric products. The major diastereoisomeric product ((2a) and (2b), respectively) could be isolated in pure form by simple recrystallization. The stereochemistry of the major cyclopropane product (2b) has been determined by single-crystal X-ray structural analysis. These cyclopropanation products were susceptible to ring opening of the cyclopropane ring upon reduction with sodium borohydride or acid hydrolysis. The reaction of (1b) with ethyl (dimethylsulfuranylidene) acetate gave a mixture of four diastereoisomeric cyclopropanation products. The reactions of (1a) and (1b) with the sulfur ylide derived from 3-methoxycarbonylallyldimethylsulfonium bromide were less successful in terms of product diastereoselectivities.

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： 喜树碱   不对称合成   合成   抗癌药物  

摘要： 本文对喜树碱合成研究的新进展作了综述，包括外消旋喜树碱的合成，及不对称合成。

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．

关键词： L-(-)-肉碱   不对称合成   化学法   酶法   肉碱   合成  

摘要： 综述了β－羟基卤代丙烷Ｋｏｌｂｅ，反应合成法，ｒ－氯－乙酰乙酸酯不对称还原６合成法和ｒ－丁基甜菜碱β－羟化合成法生产Ｌ－肉碱的新近研究进展。

关键词： 双乙烯基甲醇   不对称环氧化反应   不对称合成  

关键词： 1-substituted-2,2,2-trifluoroethylamines   asymmetric addition reaction   chiral fluoral hemiacetal   Grignard reagents   fluoral   (R)-phenylglycinol  

摘要： Asymmetric synthesis of 1-substituted-2,2,2-trifluoroethylamines is described starting from chiral fluoral hemiacetals derived from fluoral and (R)-phenylglycinol. The asymmetric addition reactions of Grignard reagents to the resultant imine are used in the key reaction step.

关键词： Alcohols   Organic compounds   Molecular structure   Peptides and proteins   Alkyls  

摘要： An efficient, stereodivergent, and enantioselective synthesis of the syn and anti diastereomers of N-Boc-beta-methylphenylalanine has been developed. Starting from enantiomerically pure (2S,3S)-2,3-epoxy-3-phenyl-1-propanol, a three-step sequence, consisting of the oxidation of the primary alcohol up to the carboxyl stage, ring opening of the epoxy acid with Me2CuCNLi2, and esterification of the resulting hydroxy acid with methyl iodide, leads to the hydroxy ester anti-10, which has been converted in a stereodivergent manner into both the (2S,3R) and the (2R,3R) diastereomers of N-Boc-beta-methylphenylalanine, syn-1 and anti-1, respectively. Activation of the secondary hydroxy group in anti-10 as a mesylate, followed by nucleophilic displacement with sodium azide, hydrogenolysis with simultaneous protection of the amino group, and saponification with LiOH, affords syn-1. The same reaction sequence applied to syn-10, obtained in turn by Mitsunobu reaction of anti-10 with p-nitrobenzoic acid followed by the hydrolysis of the resulting p-nitrobenzoate, leads tb anti-1. Both products have been obtained with greater than or equal to 99% enantiomeric excess.