The 4,6-<i>O</i>-[α-(2-(2- Iodophenyl)ethylthiocarbonyl)benzylidene] Protecting Group: Stereoselective Glycosylation, Reductive Radical Fragmentation, and Synthesis of β-<scp>d</scp>-Rhamnopyranosides and Other Deoxy Sugars
作者:David Crich、Qingjia Yao
DOI:10.1021/ol034741r
日期:2003.6.1
[reaction: see text] In the thioglycoside/BSP/Tf(2)O glycosylation method, the 4,6-O-[alpha-(2-(2-iodophenyl)ethylthiocarbonyl)benzylidene] group enforces beta-selectivity in mannopyranosylations. Following glycosylation, treatment with Bu(3)SnH in toluene at reflux affords regioselective, reductive fragmentation to the 6-deoxy-beta-mannosides (beta-rhamnosides). Applied to glucosides, the radical fragmentation
[反应:见正文]在硫代糖苷/ BSP / Tf(2)O糖基化方法中,4,6-O- [α-(2-(2-碘苯基)乙基硫代羰基)亚苄基]基团在甘露吡喃糖基化反应中增强了β选择性。糖基化后,在甲苯中用Bu(3)SnH在甲苯中回流处理,得到区域选择性的还原片段化成6-脱氧-β-甘露糖苷(β-鼠李糖苷)。应用于葡糖苷时,自由基断裂提供6-脱氧葡糖苷,而4-脱氧半乳糖苷是半乳糖系列中的优选产物。自由基断裂与苄基和对甲氧基苄基醚的存在以及与乙酸酯完全相容