to covalently bind Lewis basic fluoride ions in a relatively stable fluorosulfite anion (FSO2−). Herein we report the application of liquid SO2 as a promoting solvent for glycosylation with glycosyl fluorides without any external additive. By using various temperature regimes, the method is applied for both armed and disarmed glucose and mannose-derived glycosyl fluorides in moderate to excellent yields
液态SO 2是一种极性溶剂,可溶解共价和离子化合物。二氧化硫也具有路易斯酸性质,包括在一个相对稳定的fluorosulfite阴离子的能力共价结合路易斯碱性氟化物离子(FSO 2 - )。在本文中,我们报道了液态SO 2作为促进剂用于糖基氟化物的糖基化而没有任何外部添加剂的应用。通过使用各种温度方案,该方法可用于中等和极高产率的武装和解除武装的葡萄糖和甘露糖衍生的糖基氟化物。一系列新戊酰基保护的O-和S-甘露糖苷,以及C的一个实例合成甘露糖苷以证明糖基受体的范围。通过19 F NMR光谱证实了在液体SO 2中与糖基氟糖基化的过程中,亚硫酸氢盐物质的形成。提出了通过溶剂分离的离子对进行的二氧化硫辅助的糖基化机制,而观察到的α,β-选择性是受底物控制的,并且取决于热力学平衡。
Reversal of Anomeric Selectivity with O-Glycosyl Trichloroacetimidates as Glycosyl Donors and Thiols as Acceptors Under Acid/Base Catalysis
作者:Amit Kumar、Richard R. Schmidt
DOI:10.1002/ejoc.201200138
日期:2012.5
Borontrifluoride or trimethylsilyl trifluoromethanesulfonate catalysed the generation of thioglycosides from O-glucopyranosyl or O-galactopyranosyl trichloroacetimidates and thiols giving mainly or exclusively α-thioglycosides. However, the same reactions with phenylboron difluoride as catalyst are highly β-selective. An SN2-type reaction course under acid/base catalysis is invoked by these and previous
the endocyclic bond cleavage of the thioglycosides. Herein, we report dehydrative glycosylation in water mediated by a Brønsted acid–surfactant combined catalyst (BASC). Glycosylations between 1-hydroxy furanosyl/pyranosyl sugars and primary, secondary, and tertiary aliphatic/aromatic thiols in the presence of dodecyl benzenesulfonic acid (DBSA) provided the thioglycoside products in moderate to good
Lauryl and stearyl thioglycosides were prepared by the Lewis acid catalyzed reaction of 1-O-acetylated sugars with non-volatile and almost odorless 1-dodecanethiol and 1-octadecanethiol, respectively. These thioglycosides were activated by N-iodosuccinimide-TfOH to glycosyl donors producing disaccharides in good yields.