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首页> 外文期刊>Chemistry: A European journal >An Efficient Approach towards the Convergent Synthesis of 'Fully-Carbohydrate' Mannodendrimers
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An Efficient Approach towards the Convergent Synthesis of 'Fully-Carbohydrate' Mannodendrimers

机译：一种高效合成“全碳水化合物”曼诺地木的方法

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摘要

Glycosylation of sugar trityl ethers with sugar 1,2-O-(1-cyano)ethylidene derivatives (the trityl-cyanoethylidene condensation) has been applied to the synthesis of highly branched (dendritic) mannooligosaccharides incorporating a Manalpha1->3(Manalpha1->6)Man structural motif. The convergent synthetic strategy used to assemble these oligosaccharides was based on the use of glycosyl acceptors and/or a glycosyl donor already bearing this structural motif. The former were represented by mono-and ditrityl ethers of ManalphaOMe, Manalpha1->3ManalphaOMe and Manalpha1->3(Manalpha1->6)ManalphaX, where X = OMe or SEt. The pivotal glycosyl donor was the peracetylated 1,2-O-(1-cyano)ethyliden-3,6-di-O-(alpha-D-mannopyranosyl)-beta-D-mannopyranose (1), prepared by orthogonal Helferich glycosylation of the known 1,2-O-(1-cyano)ethyidene-beta-D-mannopyranosyl bromide followed by O-acetylation. Glycosylation of acetates of methyl 6-O-trityl-alpha-D-mannopyranoside and methyl 3,6-di-O-trityl-alpha-D-mannopyranoside with one equivalent of the donor 1 gave rise to the isomeric tetrasaccharide derivatives, Manalpha1->3(Manalpah1->6)Manalpha1->6Man-alphaOMe and Manalpha1->3(Manalpha1->6)Manalpha1->3ManalphaOMe, respectively. The latter derivative was further mannosylated at the remaining 6-O-trityl acceptor site to give the protected pentasaccharide Manalpah1->3(Manalpha1->6)Manalpha1->3(Manalpha1->6)ManalphaOMe. The isomeric pentasaccharide. Manalpha1->3)Manalpha1->6)Manalpha1->6(Manalpha1->3)ManalphaOMe, was prepared by reaction of 1 with the 6-O-trityl derivative of (Manalpha1->3)ManalphaOMe. In a similar fashion, 6'- and 6"-O-trityl derivatives of the branched trisaccharide Manalpha1->3(Manalpha1->6)ManalphaOMe served as precursors for two isomeric mannohexaosides. The 3,6-di-O-trityl ether of ManalphaOMe and the 6,6"-di-O-trityl ether of Manalpha1->3(Manalpha1->6)ManalphaX (X = OMe or SEt) were efficiently bis-glycosylated with the donor 1 to give the corresponding protected mannoheptaoside and mannononaoside. The yields of these glycosylations with the donor 1 ranged from 50 to 66%. Final deprotection of all the oligosaccharides was straightforward and afforded the target products in high yields. Both the acylated and deprotected products were characterized, and the intersaccharide connectivities were elucidated by extensive one-and two-dimensional NMR spectroscopy. The described blockwise convergent approach allows assembly of a variety of 3,6-branched mannoligosaccharides.
机译：糖三苯甲基醚与糖1,2-O-（1-氰基）亚乙基衍生物的糖基化作用（三苯甲基-氰基亚乙基缩合）已用于合成结合Manalpha1-> 3（Manalpha1->的高支化（树状）甘露寡糖的合成。 6）人的结构图案。用于组装这些寡糖的收敛合成策略是基于使用已经带有该结构基序的糖基受体和/或糖基供体。前者由ManalphaOMe，Manalpha1→3ManalphaOMe和Manalpha1→3（Manalpha1→6）ManalphaX的单和二三苯醚表示，其中X = OMe或SEt。关键的糖基供体是通过正交Helferich糖基化制备的过乙酰化1,2-O-（1-氰基）亚乙基-3,6-二-O-（α-D-甘露吡喃糖基）-β-D-甘露吡喃糖（1）。已知的1,2-O-（1-氰基）乙叉基-β-D-甘露吡喃糖基溴化物，然后进行O-乙酰化。甲基6-O-三苯甲基-α-D-甘露糖吡喃糖苷和甲基3,6-二-O-三苯甲基-α-D-甘露糖吡喃糖苷与一当量的供体1的乙酸酯基糖基化产生同分异构的四糖衍生物Manalpha1- > 3（Manalpah1-> 6）Manalpha1-> 6Man-alphaOMe和Manalpha1-> 3（Manalpha1-> 6）Manalpha1-> 3ManalphaOMe。后者的衍生物在剩余的6-O-三苯甲基受体位点进一步被甘露糖基化，得到被保护的五糖Manalpah1-> 3（Manalpha1-> 6）Manalpha1-> 3（Manalpha1-> 6）ManalphaOMe。五糖异构体。 Manalpha1-> 3）Manalpha1-> 6）Manalpha1-> 6（Manalpha1-> 3）ManalphaOMe是通过1与（Manalpha1-> 3）ManalphaOMe的6-O-三苯甲基衍生物反应制备的。以类似的方式，支链三糖Manalpha1-> 3（Manalpha1-> 6）ManalphaOMe的6'-和6“ -O-三苯甲基衍生物用作两个异构甘露糖苷的前体。3,6-二-O-三苯甲基醚ManalphaOMe和Manalpha1-> 3（Manalpha1-> 6）ManalphaX（X = OMe或SEt）的6,6“ -di-O-三苯甲基醚（X = OMe或SEt）被供体1有效地双糖基化，得到相应的保护的甘露庚糖苷和甘露糖苷。用供体1的这些糖基化的产率为50％至66％。所有寡糖的最终脱保护是直接的，并以高收率提供了目标产物。对酰化和脱保护的产物都进行了表征，并通过广泛的一维和二维NMR光谱阐明了糖间的连接性。所描述的逐块收敛方法允许组装各种3，6-支化甘露寡糖。

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