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The secondary metabolites (or natural products),such as flavonoids,steroids,triterpenes,and antibiotics,are frequently post-modified with saccharides.These ubiquitous glycosides are extremely diverse in structures and functions.Purification of a homogeneous glycoside from natural sources,especially in an appreciable amount,is always difficult.Chemical synthesis provides a feasible access to the homogenous glycosides and their congeners.