Rhamnosylation: Diastereoselectivity of Conformationally Armed Donors

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• 作者：Mads Heuckendorff ; Christian Marcus Pedersen ; Mikael Bols
• 刊名：The Journal of Organic Chemistry
• 出版年：2012
• 出版时间：July 6, 2012
• 年：2012
• 卷：77
• 期：13
• 页码：5559-5568
• 全文大小：399K
• 年卷期：v.77,no.13(July 6, 2012)
• ISSN：1520-6904

文摘

The 伪/尾-selectivity of super-armed rhamnosyl donors have been investigated in glycosylation reactions. The solvent was found to have a minor influence, whereas temperature was crucial for the diastereoselectivity. At very low temperature, a modest 尾-selectivity could be obtained, and increasing temperature gave excellent 伪-selectivity. The donors were highly reactive, and activation was observed at temperatures as low as 鈭?07 掳C. Different promoter systems and leaving groups were investigated, and only activation with a heterogeneous catalyst increased the amount of the 尾-anomer significantly. By introducing an electron-withdrawing nonparticipating group, benzyl sulfonyl, on 2-O, an increase in 尾-product was observed.