Lewis acid promoted anomerisation of alkyl O- and S-xylo-, arabino- and fucopyranosides
作者:Lisa M. Doyle、Fiach B. Meany、Paul V. Murphy
DOI:10.1016/j.carres.2018.11.010
日期:2019.1
and 6-deoxyhexopyranosides, such as those from d-xylose, l-arabinose and l-fucose are components of natural products, oligosaccharides or polysaccharides. Lewis acid promoted anomerisation of some of their alkyl O- and S-glycopyranosides is reported here. SnCl4 was more successful than TiCl4, with the latter giving the glycosyl chloride by-product in some cases, and both were superior to BF3OEt2. Kinetics
戊吡喃糖苷和6-脱氧己吡喃糖苷,例如来自d-木糖,l-阿拉伯糖和l-岩藻糖的那些,是天然产物,寡糖或多糖的组分。这里报道了路易斯酸促进了它们的一些烷基O-和S-糖吡喃糖苷的异构化。SnCl4比TiCl4更成功,在某些情况下后者提供糖基氯的副产物,两者均优于BF3OEt2。使用1H NMR光谱进行的动力学研究显示出反应顺序:O-吡喃吡喃糖苷> O-阿拉伯吡喃吡喃糖苷> O-褐藻糖苷。苯甲酰化的糖苷比乙酰化的糖苷具有更高的反应性。S-糖苷对阿拉伯糖和岩藻糖衍生物的反应性均大于O-糖苷。O-和S-吡喃吡喃糖苷的反应性相似。烟曲喃糖苷的立体选择性最高。