C-Branched pyrrolidines from 2-C-acetylmethyl-glycosylazides. Reduction of imines formed by monosaccharide ring opening

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• 作者：Huawu Shao ; Dean T. Williams ; Shih-Hsiung Wu and Wei Zou
• 关键词：C-Branched pyrrolidines ; Glycosylamine ; Glycosylimine ; Reductive amination ; Epimerization
• 刊名：Carbohydrate Research
• 出版年：2006
• 出版时间：16 October 2006
• 年：2006
• 卷：341
• 期：14
• 页码：2434-2438
• 全文大小：126 K

文摘

Reduction of the protected 2-C-acetylmethyl-β-glucopyranosyl azide derivative 1 produced the corresponding β-glucosylamine 3. Rather than forming a conformationally strained 1,2-trans-fused bicyclic imine, we propose that the β-glycosylamine underwent anomerization to an acyclic imine (4) followed by an intramolecular ring closure by the 5-hydroxy group. The resultant 2-C-acetylmethyl-α-glucopyranosylamine 5, which possesses the 1,2-cis-configuration was immediately converted to a bicyclic imine (2) in excellent yield. Attempts to selectively reduce the CN double bond of 2 using sodium borohydride and cyanoborohydride failed to produce bicyclic amine 6. Instead, compound 6 underwent another ring-opening elimination and further reduction to produce a C-branched pyrrolidine (8) in good yield. Catalytic hydrogenation of 1 and 2 also provided the C-branched pyrrolidine (10).