Highly Stereoselective β-Mannopyranosylation via the 1-α-Glycosyloxy-isochromenylium-4-gold(I) Intermediates
作者:Yugen Zhu、Biao Yu
DOI:10.1002/chem.201500648
日期:2015.6.8
ortho‐alkynylbenzoate β‐donors, an anomerization and glycosylation sequence can also ensure the highly β‐selective mannosylation. The 1‐α‐mannosyloxy‐isochromenylium‐4‐gold(I) complex (Cα), readily generated upon activation of the α‐mannosyl ortho‐alkynylbenzoate (1 α) with Ph3PAuBAr4F at −35 °C, was well characterized by NMR spectroscopy; the occurrence of this species accounts for the high β‐selectivity
虽然金(I) -催化的与糖基化反应4,6- ø -亚苄基甘露糖基栓系邻-alkynylbenzoates作为供体完全属于入克里奇型β选择性甘露糖基化的类别当PH 3 PAuOTf被用作催化剂时,在该甘露糖基α-三氟甲磺酸酯被调用,替换了的-在金光学传递函数(I)配合物与亲核性降低的抗衡阴离子(即,- NTF 2,-的SbF 6,- BF 4,和-巴4 ˚F)导致完全甘露糖基邻位蛋白的β-选择性丧失炔基苯甲酸β-供体。然而,对于α-给体,在Ph 3 PAuBAr 4 F(BAr 4 F =四[3,5-双(三氟甲基)苯基]硼酸酯)催化下的甘露糖基化反应具有很高的β-选择性,适用范围很广。基板;这些包括与甘露糖基供体在O3上安装了庞大的TBS基团的糖基化,带有4,6-二-O-苯甲酰基的供体以及在空间上不匹配或受阻的受体。对于邻炔基苯甲酸酯的β-供体,其异构化和糖基化序列也可以确保高度β-选择性甘