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唾液酸是一类重要的具有多种生物学功能的糖酸化合物. 唾液酸糖苷化反应条件较一般糖苷化反应苛刻, 立体选择性通常较差, 端基碳的立体构型较难控制. 在唾液酸糖苷化反应中能否高效地得到α糖苷键是评价该反应优劣的重要标志之一. 唾液酸苷化方法的研究一般涉及以下几个方面: C-2上的离去基团的运用, C-1, C-3上辅助基团的参与作用, C-5上氨基保护基团的修饰, 以及一些新的糖苷化反应催化剂的发展. 近些年来, 这些研究领域, 尤其是C-5上氨基保护基团的研究, 取得了重要进展. 将着重对唾液酸糖苷化方法的新进展做一总结和评述. 相似文献
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本文系统总结了糖苷化亚氨基糖的分离、合成方法与生物活性。天然存在的糖苷化的亚氨基糖根据其亚氨基糖部分的结构可以分为五类,大部分均具有重要的生物活性,尤其是糖苷酶抑制活性。此类化合物潜在的药理活性促进了相关合成方法的研究,根据糖苷键的构建方式大致可以分为酶催化的转糖基化反应和化学合成法,两者主要区别在于反应条件。酶催化的转糖基化反应条件温和,且能够减少保护基的使用,但在反应效率和选择性上仍需改进。化学合成法普适性高,有大量普通糖苷的合成经验可供借鉴,但存在反复上保护-脱保护的问题。通过以上两种合成方法,大量衍生物和类似物被设计和合成出来,大大丰富了糖苷化亚氨基糖的种类和生物活性。糖苷化亚氨基糖的生物活性往往与糖基结构和亚氨基糖环均有密切关系。作为传统糖化学与亚氨基糖的交叉领域,糖苷化亚氨基糖的结构多样性为发展高活性和选择性的先导化合物提供了优良的修饰骨架。因此,此类化合物有望在相关新药创制领域得到重要应用。 相似文献
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首次将穿心莲内酯与2,3,4,6-四- O -乙酰基- β -D-溴化吡喃葡萄糖通过Koenigs-Knorr反应及二丁基氧化锡脱保护方法合成穿心莲内酯糖苷衍生物,所得糖苷结构经IR,NMR及高分辨质谱分析证实。实验结果表明:用二丁基氧化锡脱乙酰保护基的方法,反应条件比较温和,可以选择脱除糖元上的乙酰基,保留苷元乙酰基,且不影响分子中的酸碱敏感基团。 相似文献
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Merritt J. Winchester 《Journal of heterocyclic chemistry》1979,16(7):1455-1458
The synthesis and reactions of 2-amino-4-hydroxypyrimido[4,5-b][1,4]oxazines with functionalities in the six position are described (1). The use of functionalities in the six position for coupling side chains to the pyrimido-oxazine system is discussed and a successful coupling described. 相似文献
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J. Grosser 《Chemical physics》1978,30(2):187-199
Charge transfer and elastic scattering differential cross sections in Li+ + Na are described in a two state model by a consequent application of semiclassical methods. The coupling model used is Demkov coupling; coupling parameters and potential curves are taken from calculations of other authors. The theoretical results, which contain no adjustable parameters, are in good agreement with experiment. 相似文献
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S. Hger 《Macromolecular Symposia》1999,142(1):185-191
The synthesis of shape-persistent macrocycles via oxidative dimerization or trimerization of rigid bisacetylenes (via Glaser coupling) is described. To enhance the yield of the desired target structures, the precursors are temporarily covalently bound to a template resulting in an intramolecular coupling instead of an intermolecular coupling. As a result, product yields up to over 90 % are observed. 相似文献
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K Itami T Nokami Y Ishimura K Mitsudo T Kamei J Yoshida 《Journal of the American Chemical Society》2001,123(47):11577-11585
A novel strategy for the diversity-oriented synthesis of multisubstituted olefins, where 2-pyridyldimethyl(vinyl)silane functions as a versatile platform for olefin synthesis, is described. The palladium-catalyzed Heck-type coupling of 2-pyridyldimethyl(vinyl)silanes with organic iodides took place in the presence of Pd2(dba)3/tri-2-furylphosphine catalyst to give beta-substituted vinylsilanes in excellent yields. The Heck-type coupling occurred even with alpha- and beta-substituted 2-pyridyldimethyl(vinyl)silanes. The one-pot double Heck coupling of 2-pyridyldimethyl(vinyl)silane took place with two different aryl iodides to afford beta,beta-diarylated vinylsilanes in good yields. The palladium-catalyzed Hiyama-type coupling of 2-pyridyldimethyl(vinyl)silane with organic halides took place in the presence of tetrabutylammonium fluoride to give di- and trisubstituted olefins in high yields. The sequential integration of Heck-type (or double Heck) coupling and Hiyama-type coupling produced the multisubstituted olefins in regioselective, stereoselective, and diversity-oriented fashions. Especially, the one-pot sequential Heck/Hiyama coupling reaction provides an extremely facile entry into a diverse range of stereodefined multisubstituted olefins. Mechanistic considerations of both Heck-type and Hiyama-type coupling reactions are also described. 相似文献
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T. P. Forrest 《Magnetic resonance in chemistry : MRC》1974,6(6):355-357
The calculation of gauche coupling constants from substituent electronegativities by a method which takes into account the orientation of the substituents is described. This correlation has been derived from the coupling constants of disubstituted ethanes and has been applied to the calculation of coupling constants in cyclohexanes and 6-membered heterocycles. The detection of angular distortion in 6-membered rings from the difference between calculated and observed coupling constants is also described. 相似文献
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Antibodies and antigens can be covalently coupled to a variety of carriers, both organic and inorganic. The methods for coupling these proteins may be found scattered throughout the technical literature. This report, although it concentrates on inorganic supports, describes several of the more successful methods used in laboratories today. Each of these methods is described in enough detail for the reader to carry out the coupling method of interest in his or her own laboratory. The coupling methods have been divided into two groups, direct and silane. Under each of these general headings are described the specific methodologies. 相似文献
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Literature reports have described the covalent coupling of the primary amine-containing anticancer drug, adriamycin, to polymeric supports through the amine group on the drug. These reports also have described drug mechanism studies with the immobilized adriamycin, where the release of the drug would undermine the validity of the conclusions. In the present paper, detailed experimental conditions are given for preparation of nonwater-soluble particles of polyvinyl alcohol by crosslinking water-soluble polyvinyl alcohol with 1,4-benzenedicarboxaldehyde, and for activation with cyanuric chloride and covalent attachment of adriamycin. The expected stability of this drug-support linkage against hydrolytic cleavage is compared mechanistically to that expected for less stable coupling through a carbamate linkage or for less stable coupling via an azomethine link. 相似文献
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The synthesis, structure, and spectroscopic features of a bimetallic cyanogen complex obtained from the reductive coupling of cyanide by a niobium(IV) precursor are described, and a mechanism for the coupling reaction is proposed based on DFT calculations. 相似文献
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Pouilhès A Amado AF Vidal A Langlois Y Kouklovsky C 《Organic & biomolecular chemistry》2008,6(8):1502-1510
Pyrinodemin A 1, a cytotoxic marine alkaloid, was synthesized in a convergent and enantioselective fashion. The key steps are an asymmetric intramolecular dipolar cycloaddition of an oxazoline N-oxide to introduce the bicyclic ring system of the molecule, a cuprate coupling for the extension of the saturated chain and a B-alkyl Suzuki coupling for the introduction of a 3-pyridyl moiety. Reductive amination allowed the coupling of the second side-chain onto the nitrogen atom to give 1. Additionally, attempts to prepare 1 from a trienic precursor by a double B-alkyl Suzuki reaction are described. 相似文献