DISPLACEMENT-REACTIONS ON 3,4,6-TETRA-O-BENZYL-1,5-DI-O-SULFONYL-D-GLUCITOLS - SYNTHESIS OF BENZYLOXY-2-(2-BENZYLOXYETHYLIDENE)TETRAHYDROFURAN

Treatment of the 1,5-dimesylate and 1,5-ditosylate of 2,3,4,6-tetra-O- benzyl-D-glucitol 1 with tetrabutylammonium acetate in acetonitrile le ads, through nucleophilic attack by O-2 at C-5 and normal displacement at C-1, to -O-acetyl-2,5-anhydro-3,4,6-tri-O-benzyl-L-iditol. In cont rast, the corresponding 1,5-ditriflate on similar treatment undergoes displacement at C-1 by attack of O-4 and elimination of triflic acid b etween C-4 and C-5 to afford enzyloxy-2-(2-benzyloxyethylidene)tetrahy drofuran.