Efficient synthesis of pyruvate ketals of carbohydrates

An efficient method for the preparation of pyruvate ketals of carbohydrates has been developed using N-iodosuccinimide or 1,3-dibromo-5,5-dimethylhydantoin as activator and methyl 2,2-di(ethylthio)propionate. The method has been applied for the preparation of a pyruvate ketal-containing trisaccharide present in the bacterial cell-wall of Mycobacterium smegmatis.