A STEREOSPECIFIC ROUTE TO 2-DEOXY-BETA-GLYCOSIDES
A STEREOSPECIFIC ROUTE TO 2-DEOXY-BETA-GLYCOSIDES
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DOI：
10.1021/jo00018a047
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发表时间：
1991-08-30
影响因子：
3.6
通讯作者：
DANISHEFSKY, S
中科院分区：
文献类型：
--
作者：
GERVAY, J;DANISHEFSKY, S
从各种2-脱氧糖基供体立体特异性合成这种键在几个水平上是复杂的。首先，在C2缺乏直接影响的系统中，具有立体控制的异头活化基团的立体特异性安装困难重重。Nicolaou提供了一个巧妙的解决方案，他从C2-苯硫基，C2 d-氟排列（反过来由-* C2的苯硫基迁移产生）指导。[4]另一种策略涉及用亲电试剂活化糖基，亲电试剂倾向于在α意义上攻击双键。如此产生的α“鎓”物质将糖基受体引导至供体的β-面。Franck最近公开了一种特别有前途的方法，利用硫锍活化，具有良好的立体选择性。在Nicolaou和Franck序列中，C2苯硫基取代基被还原裂解生成2-脱氧-d-糖苷系统。采用Franck法合成了苯基d-糖苷。最近报道了由D-葡萄糖醛和D-半乳糖醛衍生物与3，3-二甲基二环氧乙烷直接表氧化合成1a，2a环氧乙烷。6 7在适当的情况下，这些环氧化物作为立体特异性糖基供体，有利于亲核试剂通过在异头碳上的反转进行d-面攻击。6，7糖基化反应产生的C2羟基需要脱氧才能得到标题系列。在本文中，我们描述这样的脱氧。应用
The stereospecific synthesis of such a linkage from various 2-deoxyglycosyl donors is complicated at several levels. First, the stereospecific installation of an anomeric activating group, with stereo-control, in a system that lacks a directing influence at C2 is beset with difficulties. Furthermore, lack of guidance from C2 may erode the selectivity in the glycosylation reaction, if even a single anomer is available.An ingenious solution to the problem was provided by Nicolaou, whoused guidance from a C2-phenylthio, C2 d-fluoro arrangement (in turn generated by migration of a phenylthio group from-* C2). 4 An alternative strategy involves activation of a glycal with an electrophile disposed to attack the double bond in an a sense. The a “onium” species, so generated, directs the glycosyl acceptor to the/3-face of the of the donor. A particularly promising version of this method, utilizing thiosulfonium ac-tivation, was recently disclosed by Franck5 with favorable stereoselectivity. In boththe Nicolaou and Franck se-quences, a C2 phenylthio substituent is reductively cleaved to generate the 2-deoxy-d-glycoside system. TheFranck method was applied to the synthesis of phenyl d-glycosides. Recently the synthesis ofla, 2a oxiranes by direct ep-oxidation of D-glucal and D-galactal derivatives with 3, 3-dimethyldioxirane was reported. 6 7Under appropriate circumstances these epoxides function as stereospecific glycosyl donors, favoring d-face attack by the nucleophile by inversion at the anomeric carbon. 6, 7 The deoxygenation of the C2 hydroxyl group, generated from the glycosylation reaction, would be required to reach the title series. In this paper, we describe such deoxygenations. Applications