Glycosyl N-Tosyl Benzimidate as a New Building Block for Chemical Glycosylation
作者:Ming Li、Shaojing Liu、Yannan Peng、Peng Wang
DOI:10.1055/s-0031-1290920
日期:2012.6
Seven novel glycosyl N -tosyl benzimidates were prepared by the reactions of the corresponding hemiacetals with imidoyl chloride in 55–88% yields, which were smoothly converted to glycosides, upon treatment with alcohols and catalytic TMSOTf, in 57–99% yields.
A catalytic glycosylation protocol was established using Tf2O or TfOH as catalyst and o-(p-methoxyphenylethynyl)benzyl (MPEB) glycosides as donors. The MPEB donors are stable and readily prepared from inexpensive starting material. The donors were activated by 10 mol% Tf2O or TfOH and coupled with various acceptors to provide desired glycosides in modest to good yield. This glycosylation protocol was
使用 Tf 2 O 或 TfOH 作为催化剂并使用o -(对甲氧基苯基乙炔基) 苄基 (MPEB) 糖苷作为供体建立催化糖基化方案。MPEB 供体稳定且易于从廉价的起始材料制备。供体被 10 mol% Tf 2 O 或 TfOH 激活,并与各种受体偶联,以适度到良好的产率提供所需的糖苷。该糖基化方案通过“潜在活性”策略进一步应用于线性六甘露糖的合成。
A Cu(OTf)<sub>2</sub>-Catalyzed Glycosylation with Glycosyl <i>ortho</i>-<i>N</i>-Phthalimidoylpropynyl Benzoates as Donors
A Cu(OTf)2-catalyzed glycosylation protocol using glycosyl ortho-N-phthalimidoylpropynyl benzoates (NPPBs) as donors was disclosed, which features an inexpensive copper catalyst, operationally convenient conditions, high to excellent yields, and a broad substrate scope. Mechanistic studies indicated an isochromen-4-yl copper(II) intermediate arising from the departure of the leaving group.