Lactosamine from lactulose via the Heyns rearrangement: a practical protocol

The Heyns rearrangement is possibly one of the oldest, easiest and most economic ways to synthesise 2-deoxy-2-amino sugars. Initially reported yields were disappointingly low, but in the late 90s Wrodnigg and Stütz discovered modified reaction conditions that gave substantially increased yields, making the reaction viable on preparative scale. Requiring larger amounts of N-acetyl lactosamine, we utilised the reported reaction conditions and found that additional modifications, especially in the work-up procedure—for example employing rapid filtration of crude diethyl ether precipitates, were necessary to make this approach robust in the research laboratory environment.