Syntheses of 4′-deoxy-α-maltosyl fluoride and 4″-deoxy-α-maltotriosyl fluoride as probes of α-glucanotransferase mechanisms

4′-Deoxy-α-maltosyl fluoride and 4″-deoxy-α-maltotriosyl fluoride were synthesized to serve as mechanistic probes for α-glucanotransferases such as the glycogen debranching enzyme. The deoxy derivatives were prepared starting from maltose and maltotriose, respectively. Deoxygenation of the terminal 4-hydroxyl group was accomplished by radical reduction of the iodo sugar formed after iodide displacement of the corresponding protected triflate. The anomeric fluoride was introduced by treatment of the protected hemiacetal with diethylaminosulfur trifluoride, predominantly giving the β-anomeric product. Conversion to the α anomer was achieved using HF · pyridine.