α-Cyclodextrin and 3,3′-benzophenonedisulfonylimidazole in a unimolecular ratio were stirred at 40 °C for 1 h in the presence of a catalytic amount of Cs₂CO₃ in DMF, and then treated with sodium hydroxide to give 2^A,3^A-mannoepoxy-2^B-sulfonyl-α-cyclodextrin in 14% isolated yield. The isomer with the reversed saccharide sequence was not detected.