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用不保护或少保护的糖基受体合成寡糖* 总被引:3,自引:0,他引:3
用不保护或少保护的葡萄糖、甘露糖、鼠李糖作为糖基受体,经由糖原酸酯的中间体,能高区选和立体选地合成寡糖. α-(1→6)-连接的甘露寡糖、β-(1→6)-连接的葡萄寡糖、3,6-支化的甘露寡糖及葡萄寡糖用此方法能用很简单步骤合成,如具有重要生物活性的寡糖植保素激活剂葡萄六糖、具有抗肿瘤活性的香菇多糖的活性片段,以及一些具有重要生理功能的多糖的重复单元等.本文同时简述了用少保护的半乳糖和氨基葡萄糖为糖基受体合成寡糖的进展. 相似文献
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天然木葡聚糖类寡糖是一类对植物生长具有调节作用的寡糖, 本文以3个单糖组分为原料, 经5步合成了一种木葡聚糖三糖(1)(总产率15%), 以及该三糖的糖苷缀合物1a及其异构体1b. 利用糖基化立体选择性原则, 一步偶联反应同时得到所需的α,β连接产物, 整个合成路线高效简捷. 活性测试结果表明, 3种目标寡糖在1 mg/L浓度下, 对烟草的生长均显示出一定的促进作用, 表明所合成的3种寡糖有望发展成为植物生长促进剂. 相似文献
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利用三氯乙酰氧基、三氯乙酰氧基和三氯乙酰亚胺基作为糖端基离去基团, 在Lewis酸催化下合成了粘质沙雷氏菌O4抗原寡糖片段.反应条件温和, 收率良好.三氟乙酸酯和三氯乙酸酯法具有很好的立体选择性, 运用波谱方法确定了所有化合物的结构. 相似文献
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用不保护和少保护的糖为原料,用酰基为保护基,通过糖原酸酯的生成与重排,能高区选,高立体选地合成寡糖,合成步骤大为简化,此方法对甘露糖,葡萄糖非常有效,区选主要在3,6位,立体选对甘露糖只得到α-连接,对葡萄糖只是得到β-连接。一些有重要生理活性的寡糖,如植保素激活剂六糖-香菇多糖核心片段都能用此方法方便地合成。 相似文献
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E.coli O86 O-Antigen全保护五糖重复单元的化学简易合成 总被引:1,自引:1,他引:0
以5个单糖组分为原料, 经过7步, 以21%的总产率得到E.coli O86抗原全保护的五糖重复单元.在合成路线中, 充分利用糖基化反应的立体选择性原则, 结合HClO4-SiO2固体催化剂和“IP”策略, 大大提高了合成的效率. 整个合成路线设计操作简单, 选择性高, 消耗低, 产率高, 可以用于快速高效地合成其它一些具有生物活性的寡糖分子. 相似文献
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αGal抗原决定簇二糖具有重要的生物学功能。以α-半乳糖甲苷为原料,经多步反应立体选择性地合成了Gal(α1→3)Gal(α—OCH3),并以^1H NMR、^13C NMR及MALDI—TOF—MS等对关键中间体及终产物进行了表征。比较了硫苷法、溴代糖法和三氯乙酸酯法构建糖苷键反应的结果,表明采用三氯乙酸酯法合成寡糖,具有反应条件温和、收率高和立体选择性好的特点。 相似文献
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合成了两个结构新颖的几丁寡糖结构类似物: β-1,3连接的乙酰氨基葡聚二糖和β-1,3连接的乙酰氨基葡聚三糖, 并通过核磁共振和质谱分析确证了其化学结构. 与天然的几丁寡糖不同, 本文所合成的葡聚二糖和葡聚三糖均采取了1→3糖苷键的连接方式, 为研究几丁寡糖诱导植物抗病活性与寡糖区域异构体之间的关系提供有用材料. 相似文献
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Michelangelo Gruttadauria Renato Noto Serena Riela 《Journal of heterocyclic chemistry》1998,35(4):865-869
The stereoselective synthesis of a 2-substituted tetrahydropyran with adjacent alkoxy-bearing stereogenic centre is described. The key steps of this synthesis were the stereoselective epoxidation of an allylic alcohol and the regioselective epoxide ring opening by lithium aluminum hydride. The regio and stereoselective synthesis of a trihydroxyselenide and a trihydroxysulfide is also described. The latter compounds are not suitable for cyclization to tetrahydrofuran ring. 相似文献
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Hoffmann RW 《Angewandte Chemie (International ed. in English)》2003,42(10):1096-1109
After more than a quarter of a century of development, the methodology of stereoselective synthesis appears to be fully matured. In line with this, the potential that meso compounds offer in stereoselective synthesis is clearly recognized. The use of meso compounds in synthesis is, however, in no way commensurate with this potential, because, ironically, the synthesis of meso compounds in the first place is a problem of stereoselective synthesis. Present-day methodology does not provide many useful solutions to this problem. This Review therefore addresses the strategies available for the synthesis of more elaborate meso compounds whose stereogenic centers have a distance >1,4 between them. meso Compounds with more than four stereogenic centers are also considered. The criteria used in choosing from several strategies in the synthesis of such compounds are discussed. 相似文献
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An enantioselective total synthesis of the naturally occurring antitubercular agent pseudopteroxazole is described. The synthesis is organized around the use of a stereoselective, intramolecular addition of a sulfoximine carbanion to an alpha,beta-unsaturated ester to form an enantiomerically pure benzothiazine. Other important processes include a completely stereoselective intramolecular Friedel-Crafts alkylation and a stereoselective and regioselective hydrogenation. [structure: see text] 相似文献
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A general strategy is developed for the stereoselective synthesis of C-substituted morpholine derivatives using intramolecular reductive etherification reaction. The method is extended to the first stereoselective total synthesis of (±)-chelonin C. 相似文献
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[reaction: see text] The stereoselective synthesis of the tetracyclic intermediate 21 for (+)-naphthyridinomycin (1) has been accomplished. The convergent synthesis used the Ugi 4CC reaction with the amine derivative 10. The key features of the stereoselective synthesis of 21 were the intramolecular Mizoroki-Heck reaction, an aromatic-aldehyde cyclization, and a stereoselective hydroboration. 相似文献
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The highly stereoselective total synthesis of nemorosone via a new approach to the bicyclo[3.3.1]nonane-2,4,9-trione core which features intramolecular cyclopropanation of an α-diazo ketone, stereoselective alkylation at the C8 position, and regioselective ring-opening of cyclopropane is described. The total synthesis of nemorosone includes chemo- and stereoselective hydrogenation directed by the internal alkene. 相似文献
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A practical and efficient stereoselective synthesis of the side chain of neomarinone is reported. The synthesis was achieved in six steps (41% overall yield) from 2-methyl-2-cyclohexenone. The key step is a novel stereoselective 1,4-conjugate addition/enolate alkylation by an epoxide-opening reaction. 相似文献
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A stereoselective synthesis of (+)-herboxidiene is described. The convergent synthesis utilized a Suzuki cross-coupling reaction to assemble the key segments. The synthesis of the functionalized tetrahydropyran ring utilized an Achmatowicz reaction as the key step. The synthesis of the C10-C19 segment was accomplished using Brown's crotylboration, asymmetric alkylation, and a stereoselective allylic chlorination reactions. 相似文献
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Deiniol R. Pritchard 《Tetrahedron letters》2010,51(14):1819-8406
A concise stereoselective synthesis of the N-benzylated bicyclic core of the marine natural product awajanomycin is described starting with naturally occurring l-alanine. Key steps in the synthesis include a ring-closing metathesis to establish a δ-lactam ring followed by a stereoselective hydroxylation to instal the quaternary centre. 相似文献
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In Su Kim 《Tetrahedron letters》2007,48(36):6258-6261
An efficient stereoselective synthesis of (+)-deoxoprosophylline from readily available p-anisaldehyde is described. Key steps in the synthesis include the stereoselective amination of anti-1,2-dibenzyl ether using chlorosulfonyl isocyanate, intermolecular olefination, and Pd-catalyzed intramolecular cyclization. 相似文献