Solvent Polarity-controlled Selective Synthesis Of Methyl Pyranosides And Furanosides

Firstly, a selective synthesis for methylD-glucopyranosides or furanosides inexcellent yields via tuning the ratio of MeOH/DMSO/TCT has been reported in thisdissertation. When the concentration of DMSO in MeOH is17or8.5equiv/mL,pyranosides are synthesized in close to quantitative yields. When the concentration ofDMSO in MeOH is0.1equiv/mL, furanosides are synthesized in close to quantitativeyields. Methyl furanosides are a kinetic product and not commercially available. Theirpreparative methods include the reduction of sugar lactones, cyclization with mercuricsalts, synthesis using ethyl dimethoxyborane, iodine-promoted glycosylation andFeCl3-promoted glycosylation. In these reactions, a multistep synthesis is required orelse the formation of the side product methyl pyranoside is unavoidable.Secondly, an efficient glycosylation of alcohols higher than MeOH withD-glucose has been reported in this dissertation. All these higher alcohols are lesspolar than methanol, resulting a decrease in the proportion of furanosides. Theseresults also indicate that the solvent polarity is critical to the ratio of furanosides andpyranosides.Finally, the synthesis of a series of glycosides other than glucoside has beenreported in this dissertation. In addition, the reaction mechanism is supported by13CNMR spectra analysis. At higher concentrations of DMSO, only pyranosides wereformed and at lower concentrations of DMSO, only furanosides were formed.In conclusion, solvent polarity-controlled selective synthesis of methylpyranosides and furanosides reported herein are operationally simple, more selective,commercially available reagents and high yielding, which represent new useful toolsin carbohydrate chemistry.