Expeditious synthesis of C-glycosyl conjugated dienes and aldehydes from sugar lactones

Several C-glycosyl conjugated dienes were prepared in two steps from protected sugar lactones via addition of allylmagnesium chloride and the subsequent dehydration. A sequence of allylic addition, ozonolysis and dehydration led to the corresponding glycosyl conjugated aldehydes. These conjugated functionalities can be used as diagnostic chromophores for sugar synthesis and purification. The synthetic studies of glycosyl dienes were also pursued. Hydroboration of a sugar diene led to either homoallylic alcohol or spiroacetal depending on the workup conditions.