Synthesis of novel carbohydrate mimetics via 1,2-oxazines*

The combination of lithiated alkoxyallenes with carbohydrate-derived nitrones constitutes a flexible entry to highly functionalized enantiopure 1,2-oxazine derivatives. They can be used as precursors for acyclic and cyclic carbohydrate-like products such as amino sugar alcohols, azetidine and pyrrolidine derivatives. The Lewis acid-promoted rearrangement of 1,3-dioxolanyl-substituted 1,2-oxazines to bicyclic compounds allows an efficient route to novel amino pyran and oxepane derivatives. After subsequent transformations, new carbohydrate mimetics or “real” carbohydrates were obtained in good yield and often in a stereodivergent fashion. These compounds have already been employed for the preparation of unusual diand trisaccharide derivatives. Several of the products prepared showed interesting biological activities, e.g., as Land P-selectin inhibitors with IC50 values in the subnanomolar range.