Synthesis of D-Fructofuranosides Using Phenyl Thioglycosides as Glycosyl Donors

: Benzoylated phenyl α - and β - 2-thio-D-fructofuranosides were synthesthed and firstly used as donors in coupling with sucrose acceptor. a-Fructohanoside was stereospecifically synthesized by employing NIS(N - iodosuccinimide)/AgOTf as catalysts. The structure of all products was confirmed by 13C-NMR or 1H-NMR spectrum

Synthesis of 2-Amino-2-deoxy-1,3-dithioidoglycosides via Organocatalytic Relay Glycosylation of 3-O-Acetyl-2-nitrogalactals

Idose-type glycosides have numerous biological activities and have been widely used as anticoagulant drugs and anti-infection drugs.Thioglycosides have enhanced stability for acid-mediated or enzymatic hydrolysis,and have a wide range of applications in glycobiology and drug development.Herein,we describe an efficient method for site-selective and stereoselective synthesis of potential bioactive 2-amino-2-deoxy-1,3-dithioidoglycosides via organocatalysis sequential C3-Ferrier rearrangement and Michael addition of 3-O-acetyl-2-nitrogalactals.Both stepwise and one-pot protocols were carried out and work well.This unique thio-glycosylation protocol highlighted the various advantages,including(i)mild reaction conditions;(ii)excellent site-selectivity and stereoselectivity,good to excellent yields;(iii)broad substrate scopes;(iv)being atom-economic and environmentally friendly;(v)the reactions can be scaled up.

Stereoselective synthesis of the 3,6-branched Fuziα-glucans up to 15-mer via a one-pot and convergent glycosylation strategy

A family of the 3,6-branched Fuziα-glucans including the pentasaccharide repeating unit as well as its di-and trimers were efficiently achieved via a one-pot and convergent glycosylation strategy.All the protectedα-glucans up to 15-mer were assembled with high yields and excellentα-stereoselectivity,which was secured by the synergisticα-directing effects of the Tol SCl/Ag OTf promotion system and the stericβ-facial shielding of bulky saccharide residues linked at the 6-O-position of glucosyl donors.Moreover,the 3,6-branched architecture of glycosyl donor was revealed to be more favorable for theα-selective glucosidation of primary hydroxyl group,especially in the case of large oligosaccharide acceptor.The structurally well-defined syntheticα-glucans would be useful for various biological studies.

Stereodirecting Effects of 4-O-ortho-cyanobenzyl Ether on Chemical Glycosylation with Glucopyranosyl Donor

Here we report a systematic investigation on the stereodirecting effects of a 4-O-ortho-cyanobenzyl ether(oBCN)group with a glucopyranosyi donor.Experimental studies revealed that the glycosylation reactions using this donor generally show dual-stereoselectivities depending on the acceptor nucleophilicity,that is,glycosylation of weak nucleophile acceptors generally affordsα-glycosides specifically while glycosylation of strong nucleophile acceptors affords β-glycosides preferentially.

低聚异麦芽糖糖化转苷工艺的优化及成分分析

以玉米面挤压液化后的液化液为原料,使用真菌α-淀粉酶和α-葡萄糖转苷酶完成共同糖化转苷过程。在单因素试验基础上,采用Box-Behnken设计,运用响应面分析法,研究探讨真菌α-淀粉酶加量、α-葡萄糖转苷酶加量、酶解温度、酶解时间与低聚异麦芽糖(IMO)含量的关系。试验结果表明:低聚异麦糖共同糖化转苷的最佳工艺是:真菌α-淀粉酶加量35 U/g,α-葡萄糖转苷酶加量128 U/g,酶解温度55℃,酶解时间18 h,在此条件下进行共同糖化转苷,玉米面的糖化转苷糖液IMO含量可达57.94%。研究为以玉米面为原料高效生产低聚异麦糖提供了参考。

N-乙酰氨基葡萄糖苷内切酶的功能与机制

N-乙酰氨基葡萄糖苷内切酶(endo-beta-N-acetylglucosaminidase,ENGase)广泛分布于各种生物中,主要通过降解错误折叠的糖蛋白,参与细胞和生命的调控。ENGase也是糖链编辑的有效工具酶,可专一性水解游离寡糖链及糖肽或糖蛋白上核心五糖的N-乙酰氨基葡萄糖(GlcNAc)之间的β-14糖苷键。其水解产物是寡糖链和一个GlcNAc,或带有一个GlcNAc的糖肽或糖蛋白。本文对ENGase的发现、分布、蛋白质结构、酶学反应及生物学功能进行阐述,为ENGase的生物学研究提供思路,为糖生物学与糖组学的应用研究奠定基础。

Donor Preactivation-Based Glycosylation:An Efficient Strategy for Glycan Synthesis

Carbohydrates have gained a lot of appreciation in the past few decades due to their important roles in numerous biological events.Acquiring a structurally well-defined carbohydrate compound is essential for the understanding of its functions.Although some innovative methods have been developed for the synthesis of complex oligosaccharides,glycan synthesis is in general still a time-consuming and difficult work.Herein,we will introduce the preactivation-based glycosylation strategy,which is an efficient protocol independent of the reactivity of glycosyl donor.This review will focus on summarizing the versatile applications of preactivation strategy in stereoselective glycosylation and one-pot assembly of biologically important oligosaccharides and even polysaccharides。

Capture-Release Strategy Facilitates Rapid Enzymatic Assembly of Oligosaccharides

A convenient and highly efficient strategy was developed for the simplification of enzymatic synthesis and purification of oligosaccharides.Glycosyl acceptors terminated with a thiol tag were extended by enzymatic modular assembly(EMA)in the aqueous phase,and the desired products were captured during solid-phase workup(SPW)using commercially available thiopropyl Sepharose 6B resin through a reversible disulfide linkage.Finally,the products were released from solid-phase resin in the presence of dithio-threitol(DTT)as reducing agent and the resin could be recovered and reused.This strategy overcomes the uncertain influence of polymer-or ionic-supports commonly used in enzymatic glycosylation,and showed perfect compatibility with all 10 enzyme modules for the rapid assembly of a series of complex oligosaccharides.

低聚糖改性对蛋清蛋白凝胶性影响研究进展

蛋清蛋白是一种营养价值丰富,具有多种功能特性的优质蛋白。低聚糖可通过糖基化反应与蛋清蛋白共价结合,其偶联物的功能特性较天然蛋清蛋白有所改善。文章综述了低聚糖-蛋清蛋白偶联物的凝胶机理,探讨了低聚糖改性蛋清蛋白凝胶的影响因素,梳理了低聚糖对蛋清蛋白功能特性产生的影响,并对低聚糖改性蛋清蛋白的加工应用进行了展望。

壳寡糖酶法糖基化大豆蛋白提高乳液冻融稳定性及机制研究

目的 通过谷氨酰胺转氨(transglutaminase glycosylation,TG)酶催化技术制备壳寡糖(chitosan oligosaccharide,COS)糖基化大豆分离蛋白(soy protein isolate,SPI),并研究改性产物结构变化及其功能性改进机制。方法 以COS与SPI为原料,采用TG酶催化技术制备大豆分离蛋白-壳寡糖共价改性产物(SPI-COS)。采用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(sodium dodecyl sulfate-polyacrylamide gel electrophoresis,SDS-PAGE)、傅里叶变换红外光谱(Fourier transform-infrared spectroscopy,FT-IR)、荧光光谱研究SPI-COS的结构特征变化,采用乳析指数(creaming index,CI)、出油率、絮凝程度(flocculation degree,FD)、聚结程度(coalescence degree,CD)、电子显微镜观察等方法表征不同SPI产物乳液的冻融稳定性。结果 蛋白乳液在经历1、2、3次冻融循环处理后,与对照SPI相比,SPI-COS乳析指数分别降低了58.66%、25.51%和13.63%,出油率分别降低了49%、69%和48%,冻融稳定性显著提高。SDS-PAGE和FT-IR分析表明,SPI与COS形成共价键,SPI-COS二级结构中α-螺旋和β-转角的含量显著减少(P<0.05),而β-折叠和无规则卷曲的含量显著增加(P<0.05)。微观状态分析表明,与对照SPI冻融乳液相比,SPI-COS乳液不规则,聚集体更小,状态更稳定。结论 酶法糖基化蛋白可以通过改变大豆蛋白理化结构特性,进而提高其乳液的冻融稳定性,本研究为制备高冻融稳定性SPI提供理论指导及技术支持,可以扩大大豆蛋白乳液在冷冻食品中的应用。

硫代糖苷在糖化学合成中的应用

介绍了近几年来有关硫代糖苷在一些复杂寡糖及其缀合物合成中的应用。

免疫球蛋白糖链结构异常和自身免疫性疾病

免疫球蛋白在人体体液免疫中发挥巨大作用 ,而其均为糖蛋白 .免疫球蛋白中与蛋白质相连的寡糖链结构及组成对其功能有很大影响 ,当寡糖链糖基化异常时 ,可导致一些自身免疫性疾病 .从IgA肾病和类风湿性关节炎的结构基础、分子机制、酶学基础、临床意义等方面对这两类自身免疫性疾病的发病机制与糖基化异常之间的密切相关性予以详细论述 ,为这两类疾病在临床上建立一种特异、灵敏的血清学检测方法提供了理论基础 ,开辟了一条新途径 .

低聚木糖修饰对牛乳β-乳球蛋白功能性质的影响

以低聚木糖(XOS)为修饰剂,采用不同的质量比对β-乳球蛋白进行糖基化修饰,研究了糖基化前后的β-乳球蛋白功能性质的变化。结果表明,质量比为6∶1的糖蛋白配比时低聚木糖和β-乳球蛋白的糖基化反应的接枝度最高,达28.1%;与未被糖基化的β-乳球蛋白相比,10∶1的低聚木糖修饰β-乳球蛋白后,溶解性最高增加了71.4%;6∶1的低聚木糖修饰后显著提高β-乳球蛋白的乳化性及其稳定性,乳化性最高增加了40.2%;而不同的糖蛋白配比对β-乳球蛋白起泡性没有显著影响。

转谷氨酰胺酶催化的糖基化修饰对黑豆蛋白抗氧化活性的影响

以DPPH自由基清除能力、ABTS自由基清除能力、总还原能力、总抗氧化能力、清除亚硝酸盐能力作为评价指标,比较了酶法糖基化黑豆蛋白、湿热法糖基化黑豆蛋白、黑豆分离蛋白、自交联黑豆蛋白和Trolox的抗氧化能力,结果表明:酶法糖基化黑豆蛋白、湿热法糖基化黑豆蛋白以及Trolox抗氧化能力均高于自交联黑豆蛋白以及黑豆分离蛋白,其中酶法糖基化黑豆蛋白以及Trolox的抗氧化能力强于湿热法糖基化黑豆蛋白。

乙酰化呋喃型糖基三唑羧酸酯及硫苷的立体选择性合成

自从发现糖酯及硫苷类化合物具有抗菌、抗肿瘤等广泛的生理活性以来,有关这两类化合物的合成及其性质研究已成为人们极为关注的课题。但具有某些生理活性的三唑羧酸类和巯基嘧啶类化合物与糖基形成糖酯和硫苷的有关合成尚未见文献报道。为了寻找高效低毒的化合物,本文通过相转移催化法,在温和的反应条件下。

糖苷合成酶合成低聚糖的研究及应用

由于低聚糖的潜在疗效 ,合成低聚糖变得越来越重要。糖苷水解酶的突变体———糖苷合成酶合成低聚糖 ,具有成本低 ,得率高的特性 ,成为低聚糖合成的新发展方向。本文介绍了糖苷合成酶合成低聚糖的作用机理及其应用。

用不保护或少保护的糖基受体合成寡糖

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。

Anti-Inflammatory Glycosaminoglycan Oligosaccharides from Colwellia psychrerythraea 34H Capsule:Synthesis and Biological Evaluation

Capsular polysaccharides(CPS)of Colwellia psychrerythraea 34H consist of linear tetrasaccharides repeating units in a glycosaminoglycan-like fashion.Their biological function is likely involved in the cold adaptation of microbial organisms.The low availability of these glycosaminoglycan structures greatly limits the study of their functions and biological activities.Here,an efficient semisynthetic strategy for CPS tetrasaccharide derivatives is achieved by using disaccharide units degraded from hyaluronic acids.This new synthetic process is suitable for largescale preparation,and several rare tetrasaccharide derivatives containing GalA-GalNAc were readily obtained in high yields.Biological evaluation of their anti-inflammatory effects demonstrated that these CPS tetrasaccharides effectively attenuated the lipopolysaccharide-induced sepsis and acute lung injury by decreasing macrophage infiltration and secretion of microphage-related cytokines in mice.All these results suggest that this new type of CPS tetrasaccharide can be developed as an anti-inflammation agent.

Assembly of a Library of Trisaccharides as Mimics of Sialyl Lewis Xvia Random Combination Strategy

A small library containing six positional isomers of fucosyl on the modified lactoside backbone as mimics of the Sialyl Lewis X was synthesized via random combinatorial glycosylation, which was charactered by ESI-MS and HPLC.