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1.
Kimio Takahashi Bernhard Witkop Arnold Brossi Mohammed A. Maleque Edson X. Albuquerque 《Helvetica chimica acta》1982,65(1):252-261
Natural (?)-perhydrohistrionicotoxin ( 6a ), its unnatural (+)-antipode 6b , (?)-2-depentylperhydrohistrionicotoxin ( 7a ) and its (+)-antipode 7b have been prepared and characterized. Kishi's lactam 8 reacted with optically active iso-cyanates, and the mixture of diastereomeric carbamates so obtained was separated and hydrolyzed yielding the optical antipodes of Kishi's lactam in optically pure form. Reduction with LiAlH4 yielded the optically active 2-depentyl analogs, while another sequence already developed in the racemic series afforded the natural toxin and its (+)-antipode. Some electrophysiological properties of these compounds are presented. 相似文献
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Previ0uslyitwasf0undthatphosph0amin0acidscouldstimulatemanyinterestingbioorganicreacti0nsI-3.In0rderfurthert0confirmthesignificanceofph0sphorusinbiochemistry,tw0m0delcomp0unds,anal0gue0fphosphorylaminoacidsc0ntainingP-Cbondandphosphorylglucoaminoacids,weresynthesized.Theirreacti0nswithalcoholandamin0acidwerealsoinvestigatedbyNMRandMSmeth0ds.Theresultsindicatedthatthereactioncharacteristicsofphosphorylbio1ogicalsmallmoleculesweredependentonthe'configuration,functiongroupsandpositions.(O,O-b… 相似文献
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Ricci M Madariaga L Skrydstrup T 《Angewandte Chemie (International ed. in English)》2000,39(1):242-246
Considering that the amide NH groups are neither protected nor deprotonated, reductive samariation in the presence of a carbonyl substrate is a remarkably efficient method for the formation of a C-C bond. This was shown for a series of dipeptides and a tripeptide [Eq. (a)]. For the latter the product was obtained in a good yield of 50 %, despite the presence of three amide protons. 相似文献
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K. P. R. Kartha Akihiko Kameyama Makoto Kiso Akira Hasegawa 《Journal of carbohydrate chemistry》2013,32(1):145-158
Abstract 2-(Trimethylsilyl)ethyl 2, 3, 6, 2′-tetra-O-acetyl-3′-O-benzyl-6′-O-benzyloxymethyl-β-d-lactoside (9) was synthesized starting from acetobromolactose (1) via 2-(trimethylsilyl)ethyl β-d-lactoside (3). Compound 9 was converted to the trisaccharide derivative 17 after coupling with 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-α-d-galacto-pyranosyl bromide (11). Coupling of 17 with acetobromogalactose (19) gave the tetrasaccharide 20. 相似文献
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Daniel K. Baeschlin Andr R. Chaperon Virginie Charbonneau Luke G. Green Steven V. Ley Ulrich Lücking Eric Walther 《Angewandte Chemie (International ed. in English)》1998,37(24):3423-3428
Six building blocks, six reaction steps : The recently developed innovative methodology facilitated the convergent synthesis of the complex oligosaccharide core 1 (shown here with protecting groups) for the total synthesis of a glycosylphosphatidylinositol (GPI) anchor. The key factors are the tuning of the reactivity of the building blocks by using 1,2-diacetal protecting groups and the desymmetrization of glycerol and myo-inositol with a chiral bis(dihydropyran). 相似文献
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《国际化学动力学杂志》2018,50(5):325-334
We extend our former kinetic and experimental study of hydrogenolysis of di‐ and trisaccharides using Ru/C in combination with a molecular acid as a catalyst system, to longer oligosaccharides up to heptasaccharide. The extended kinetics, despite the considerably more complex reaction network, reconfirms our previous hypothesis that reactions of oligosaccharides proceed through two competing reaction pathways, namely hydrolysis of oligosaccharides and their hydrogenation to a reduced form. This challenges the widely accepted supposition that conversion of polysaccharides to sorbitol passes consecutively through hydrolysis to monosaccharides followed by hydrogenation to sorbitol. This works also sets forth the hypothesis that hydrogenation of long‐chain oligosaccharides increases the rate of hydrolysis to a considerable extent and presents a significant alternative pathway in sorbitol formation. 相似文献
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肝素类寡糖合成研究进展 总被引:1,自引:0,他引:1
肝素(heparin,HP)和硫酸乙酰肝素(heparan sulfate,HS)是糖胺聚糖(glycosaminoglycans,GAGs)家族中的一类线性硫酸化多糖,其结构复杂、牛物活性多样.为了深入研究其结构序列与小同生物活性之间的关系,近年来针对肝素类寡糖的合成与功能研究成为糖化学和糖牛物学研究的一个热点领域,涌现出一些新的合成方法与合成策略.选取了2001年以来国际上一些在肝素类寡糖的化学合成和酶法合成方面的代表性工作予以综述. 相似文献
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The Use of Microwave Irradiation for the Rapid Organic Synthesis 总被引:1,自引:0,他引:1
Introduction With the development of scientific technology, people continuously search for new methods which can accelerate reactions. Nowadays as a new technology, microwave irradiation has gained much practical importance in chemical reactions. Microwave irradiation has been applied successfully to the areas, such as inorganic synthesis, the prepara- 相似文献
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乙酰肝素酶(Heparanase,Hpa)是哺乳动物体内的内切葡萄糖醛酸苷水解酶,通过水解葡萄糖醛酸(GlcA)与己胺糖(GlcN)之间的β-糖苷键,选择性地降解肝素和硫酸肝素糖胺聚糖,从而释放多功能的肝素寡糖.本文报道一条高效的肝素酶底物寡糖的合成路线:采用苯甲酰基保护待硫酸化的羟基,苄基保护羧基和裸露的羟基,叠氮基保护氨基,应用脱水糖苷化方法高效地构建关键的a-GlcN-(1→4)-GlcA糖苷键.然后通过标准化的保护基脱除和硫酸化操作,获得肝素酶底物三糖和四糖1-4.最后五步反应的总收率超过52%.肝素酶底物寡糖的合成为研究肝素酶的底物选择性和活性检测打下了基础. 相似文献
10.
A novel, simple and rapid stability-indicating high-performance liquid chromatographic (HPLC) method for pravastatin sodium (PRA) was successfully developed and validated for the assay of in tablets. Chromatographic separation was achieved isocratically on a C18 column (150 mm × 4.6 mm) utilizing a mobile phase of methanol-phosphate buffer (pH 7; 0.02 M) (57:43, v/v) at a flow rate of 1.0 mL min−1 with UV detection at 238 nm. A linear response (r = 0.9999) was observed in the range of 1–5 μg mL−1. The method showed good recoveries (100.50%) and the relative standard deviation of intra and inter-day were 1.40%. The method can be used for both quality control assay of pravastatin in tablets and for stability studies as the method separates pravastatin from its degradation products and tablet excipients.An erratum to this article can be found at 相似文献
11.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(8):2124-2128
The unique α‐(1→7)‐bradyrhizoside linkages are constructed for the first time via judicious choice of the glycosylation partners and conditions, thus tetra‐ and penta‐bradyrhizosides relevant to the peculiar O‐antigen of Bradyrhizobium are synthesized, which are shown to adopt the defined right‐handed helical conformations and to be unable to induce innate immune responses in plants. 相似文献
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糖苷和寡糖的立体选择性合成研究进展 总被引:1,自引:1,他引:0
精苷、寡糖的立体选择性合成是一个十分重要的课题. 本文结合作者的研究工作介绍了糖苷、寡糖的立体选择合成的方法学进展,主要涉及近年来合成寡糖的新方法,并对这些方法的优势及不足进行了评述. 相似文献
16.
Vijayalaxmi Amareshwar 《合成通讯》2013,43(2):342-346
Various nucleobases, 5-heteroaryl substituted 2,4-alkoxy, and/or aryloxy pyrimidines were prepared in an easy method. 相似文献
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Abstract A series of three oligosaccharides, α-d-Glc-(1→4)-β-d-GlcA-1ωe, β-d-GlcA-(1→4)-α-d-Glc-(1→4)-β-d-GlcA-lωe and α-d-Glc-(1→4)-β-d-GlcA-(1→4)-α-d-Glc-(1→4)-β-d-GlcA-1ωe was prepared by a short synthetic route, using maltose and glucuronic acid derivatives as starting materials. The oligosaccharides contain glucose residues instead of glucosamines, and have a less complicated structure than the corresponding unsulphated structures found in native heparin and heparan sulphate. This simplification in structure has diminished the number of synthetic steps and raised the total yield compared to the preparation of the corresponding heparin/heparan sulphate structures which have been found to bind acidic and basic FGF. 相似文献
18.
Prof. Pedro Laborda Yong-Mei Lyu Dr. Fabio Parmeggiani Dr. Ai-Min Lu Wen-Jiao Wang Ying-Ying Huang Dr. Kun Huang Juan Guo Prof. Li Liu Prof. Sabine L. Flitsch Prof. Josef Voglmeir 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(13):5346-5349
Chitin is one of the most abundant and cheaply available biopolymers in Nature. Chitin has become a valuable starting material for many biotechnological products through manipulation of its N-acetyl functionality, which can be cleaved under mild conditions using the enzyme family of de-N-acetylases. However, the chemoselective enzymatic re-acylation of glucosamine derivatives, which can introduce new stable functionalities into chitin derivatives, is much less explored. Herein we describe an acylase (CmCDA from Cyclobacterium marinum) that catalyzes the N-acylation of glycosamine with a range of carboxylic acids under physiological reaction conditions. This biocatalyst closes an important gap in allowing the conversion of chitin into complex glycosides, such as C5-modified sialosides, through the use of highly selective enzyme cascades. 相似文献
19.
Statine及其类似物是一类特殊的β-羟基-γ-氨基酸,是许多活性化合物的核心结构单元.综述了其不对称合成研究的进展. 相似文献
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