| In recent years, solid acids have participated in many reactions of carbohydrates. In this thesis, we used H2SO4-SiO2as a catalyst on per-O-acetylation of carbohydrates and Ferrier rearrangement of3,4,6-tri-O-benzyl glucal.Per-O-acetylation of carbohydrates has great importance in carbohydrate world. It is one of the most common transformations in glycochemistry, primarily for initial protection of sugar alcohols in organic synthesis and also to aid spectral characterization and identification of natural products containing carbohydrates. In recent years, chemists have exploited many methods to obtain per-O-acetylation of carbohydrates. The catalysts which they used have many disadvantages, such as carbonization and of carbohydrates, noxious, expensive. When H2SO4-SiO2was used in the per-O-acetylation of carbohydrates, it has some advantages, like moderate condition, react quickly, high yield, easy workup, environmentally friendly and so on. Also we find per-O-acetylation of carbohydrates in large scale (10g) proceeds well. The catalyst can be recovered five times without any significant loss in reactivity. H2SO4-SiO2is an efficient catalyst for per-O-acetylation of carbohydrates.3,4,6-tri-O-benzylglycal was transform to2,3-unsaturated glucosides via Ferrier rearrangement,2,3-unsaturated glucosides are very useful chiral building blocks in the synthesis of a great deal of compounds:glycopeptides, nucleosides and so on. Up to now, a variety of catalysts have been reported to use for Ferrier rearrangement. However, these catalysts suffer from many limits such as high cost, unpleasant odors, and toxicity. We used H2SO4-SiO2as the catalyst in Ferrier rearrangement of3,4,6-tri-O-benzylglycal, and we can obtain the2,3-unsaturated glucosides in very good to excellent yields (81%-94%), in short reaction times (0.5h-4h) and with free workup. |
