Direct Glycosylation of Unprotected and Unactivated Sugars Using Bismuth Nitrate Pentahydrate
摘要:
Bi(NO3)(3), a low-cost, mild, and environmentally green catalyst, has been successfully utilized for Fischer glycosylation for the synthesis of alkyl/aryl glycopyranosides by reacting unprotected sugars, namely, D-glucose, L-rhamnose, D-galactose, D-arabinose, and N-acetyl-D-glucosamine with various alcohols in good to excellent yields. The glycosides were formed with high alpha-selectivity. Further, an expedient separation of alpha- and beta-glycosides using silver nitrate-impregnated silica gel flash liquid chromatography has been developed.
Glycosyl trichloroacetimidates react smoothly in the presence of trimethylsilyl trifluoromethanesulfonate as a catalyst with a variety of alcohols and monosaccharides in [bmim]PF6 (1-butyl-3-methylimidazolium hexafluorophosphate) as a solvent to afford the corresponding glycosides or disaccharides.
Supercritical carbon dioxide (scCO2) is a suitable medium to perform transition metal-free glycosylations in the absence of volatile organic solvents (VOCs) using glycosyl halides as glycosyl donors. The methodology here described can be applied for obtaining O-glycosides in a totally green reaction, as well as orthoesters, depending on the reaction conditions. The process is much more sensitive to
超临界二氧化碳(sc CO 2)是一种合适的介质,可在无挥发性有机溶剂(VOC)的情况下使用糖基卤化物作为糖基供体来进行无过渡金属的糖基化反应。根据反应条件,此处描述的方法可用于在完全绿色反应以及原酸酯中获得O-糖苷。该方法对温度的变化比对压力的改变更为敏感,与糖基溴相比,糖基氯化物需要更高的温度才能被活化。新戊酰基作为良好的CO 2-亲和单元,并被证明是获得良好立体选择性的最佳选择。流体性质和超临界条件的相关性也得到了证明
A new strategy for diversity-oriented direct glycosylation of bioactive small molecules was developed. This reaction features (-)-beta-pinene as acid scavenger and work with glycosyl iodides under mild conditions. With the aid of RP-HPLC and chiral SFC separation techniques, the new direct glycosylation proved effective at gram scale on bioactive small molecules including AZD6244, podophyllotoxin, paclitaxel, and docetaxel. Interesting glycoside derivatives were efficiently created with good yields and 1,2-cis selectivity.