Chemoenzymatic synthesis of the branched oligosaccharides which correspond to the core structures of N-linked sugar chains
摘要:
Synthetic routes are described to a partial structure common to all high mannose-type sugar chains and complex-type sugar chains based on a chemoenzymatic strategy which incorporates, (a) enzymatic synthesis of oligosaccharide blocks using glycosidases, and (b) chemical synthesis of the branching oligosaccharides via regioselective coupling. All reaction products correspond to key intermediates necessary for the construction of N-linked oligosaccharides and we have synthesized the branched tetra-manno-oligosaccharide high mannose-type sugar chain and the branched hexa-oligosaccharide complex-type sugar chain using this simple and direct method. (C) 1998 Elsevier Science Ltd.
Sonochemistry: A Powerful Way of Enhancing the Efficiency of Carbohydrate Synthesis
作者:Shenglou Deng、Umesh Gangadharmath、Cheng-Wei Tom Chang
DOI:10.1021/jo060374w
日期:2006.7.1
[GRAPHICS]Using sonication as a means of facilitating organic reactions in carbohydrate chemistry was explored under the conditions used for traditional organic synthesis. An array of representative reactions, including hydroxy group manipulation ( acylation, protection/deprotection, acyl group migration), thioglycoside synthesis, azidoglycoside synthesis, 1,3-dipolar cycloaddition and reductive cleavage of benzylidene, commonly used in the synthesis of carbohydrate derivatives was examined. A series of glycosylation reactions that employ thioglycosides, glycosyl trichloroacetimidate, glycosyl bromide and glycosyl acetate as the glycosyl donors was also examined. Our results demonstrate that sonication can significantly shorten the reaction time, enhance the reactivity of reactant and lead to superior yield and excellent stereoselectivity. More importantly, a general protocol of glycosylation may finally be developed. Sonication is compatible to the conditions used for traditional organic synthesis. We believe that sonication can also be applied to other areas of synthetic processes.