1: hydrazine hydrate / methanol / 4 h / 20 °C 2: jack-bean β-hexosaminidase; water / 25 °C / pH 5.5 / aq. buffer; Enzymatic reaction 3: sodium hydride; sodium iodide / N,N-dimethyl-formamide 4: thionyl chloride / dichloromethane View Scheme