Silicon-directed stereocontrolled cyclization. Possible route to functionalized tetrahydrofurans
Cyclization of 3,4,6-tri-O-benzyl-1-deoxy-1-phenyldimethylsilyl-L-glucitol using a slight excess of BF3Et2O or a catalytic amount of H2SO4 gives access to the 2,5-anhydro-L-glucitol or 2,5-anhydro-L-mannitol der