The methyl ether of cyclitols with vicinal hydroxyl group was cleaved chemoselectively in preference to both cis- and trans-cyclohexylidene moieties by AlCl3-n-Bu4NI to afford parent alcohols in good yields. (-)-Conduritol F was prepared from L-quebrachitol, an optically active cyclitol from the serum of rubber trees, in five steps by use of the demethylation reaction. The first chiral synthesis of (+)-conduritol B and the total synthesis of cyclophellitol, a novel beta-glucosidase inhibitor, are described.