Solvent-Dependent Mechanism and Stereochemistry of Mitsunobu Glycosylation with Unprotected Pyranoses
Solvent-Dependent Mechanism and Stereochemistry of Mitsunobu Glycosylation with Unprotected Pyranoses
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无保护吡喃糖 Mitsunobu 糖基化的溶剂依赖性机制和立体化学
DOI：
10.1021/acs.orglett.0c01549
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发表时间：
2020
期刊：
影响因子：
5.2
通讯作者：
Kawabata Takeo
中科院分区：
文献类型：
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作者：
Takeuchi Hironori;Fujimori Yusuke;Ueda Yoshihiro;Shibayama Hiromitsu;Nagaishi Masaru;Yoshimura Tomoyuki;Sasamori Takahiro;Tokitoh Norihiro;Furuta Takumi;Kawabata Takeo
在光信条件下，苯甲酸与无保护的α-d-葡萄糖在二恶烷中进行高立体选择性糖基化反应的机制为SN2，而在DMF中进行非立体选择性糖基化反应的机制为SN1。sn2型立体选择性Mitsunobu糖基化通常适用于各种无保护的吡喃糖作为糖基供体，与羧酸、酚类、亚胺等多种酸性糖基受体结合，保持其高立体选择性（33个例子）。羧酸与无保护α-d-甘露糖的糖基化也以SN2方式进行，直接产生通常不易获得的1,2-顺式甘露糖苷。采用无保护α-d-葡萄糖的糖基化策略进行了五种简单天然糖苷的一步或两步全合成。
An SN2 mechanism was proposed for highly stereoselective glycosylation of benzoic acid with unprotected α-d-glucose under Mitsunobu conditions in dioxane, while an SN1 mechanism was indicated for nonstereoselective glycosylation in DMF. The SN2-type stereoselective Mitsunobu glycosylation is generally applicable to various unprotected pyranoses as glycosyl donors in combination with a wide range of acidic glycosyl acceptors such as carboxylic acids, phenols, and imides, retaining its high stereoselectivity (33 examples). Glycosylation of a carboxylic acid with unprotected α-d-mannose proceeded also in an SN2 manner to directly afford a usually less accessible 1,2-cis-mannoside. One- or two-step total syntheses of five simple natural glycosides were performed using the glycosylation strategy presented here using unprotected α-d-glucose.