Effective and chemoselective glycosylations using 2,3-unsaturated sugarsElectronic Supplementary Information (ESI) available: Effective and chemoselective glycosylations using 2,3-unsaturated sugars. See DOI: 10.1039/c004204h

Glycosyl donors containing a double bond between C2 and C3 were designed by mimicking the reaction mechanism of lysozyme-initiated hydrolysis of mucopolysaccharides. It was found that, under various glycosylation conditions, the reactivities of 2,3-unsaturated glycosyl acetates were significantly higher, while those of the corresponding 2,3-unsaturated-4-keto glycosyl acetates were much lower than those of the corresponding 2,3-dideoxy (2,3-saturated) glycosyl acetates. Based on these results, chemoselective glycosylations were effectively realized via combinatorial techniques in short-steps using three types of glycosyl donors to construct several types of deoxyoligosaccharides. Furthermore, the highly reactive 2,3-unsaturated glycosyl acetates were found to be useful in the synthesis of the O -glycosides of low reactive tertiary alcohols. The 2,3-unsaturated glycosyl donors were found to exhibit high reactivity, while the corresponding 2,3-unsaturated-4-keto glycosyl donors showed low reactivity, under several conditions. These findings make it possible to realize chemoselective glycosylations via combinatorial uses of 2,3-unsaturated, 2,3-unsaturated-4-keto, and 2,3-dideoxy glcosyl donors providing various types of deoxyoligosaccharides in short-steps.