31 NAPエーテルを利用した分子内アグリコン転移反応の開発と複合糖質糖鎖合成への応用(口頭発表の部)

概要

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1,2-Cis glycosidic linkages are prevalent in natural glycans. Although key factors that control stereoselectivity of glycosylation have been largely understood, stereoselective synthesis of 1,2-cis glycosides is potentially problematic [1]. To achieve exclusive formation of desired isomer, approaches based on intramolecular aglycon delivery (IAD) are of special promise [2,3]. The methodology toward the strereoselective 1,2-cis-glycoside using naphthyl-methyl (NAP) ether-mediated IAD has been developed [4]. Namely, 2-O-NAP protected donor was cleanly converted to the mixed acetal upon oxidative activation with DDQ [5]. Subsequent activation of thioglycosidic linkage initiated the rearrangement of an aglycon from mixed acetal moiety to give a desired 1,2-cis-glycoside. Stereospecific constructions of various 1,2-cis linkages, such as β-mannopyrano-, β-arabinofurano-, and α-glucopyranosides were achieved through NAP-IAD. This methodology was successfully applied to the synthesis of various fragments of natural glycans. In particular the β-L-rhamnopyranosylation, which is one of the most challenging problems in the carbohydrate chemistry, has been successfully achieved through NAP-IAD [7]. It clearly suggests that this novel stereospecific IAD methodology is highly efficient, general and practical.
天然有機化合物討論会の論文
2008-09-01