For studying the structure-activity relationship of cytostatically active hexitol derivatives, 1,2:5,6-dianhydro-3,4-di-O-methyl- (I), -ethyl-, -allyl-, and -pentyl-D-mannitol, as well as 1,2:5,6-dianhydro-3,4-di-O-methyl-L-iditol, -galactitol, and -D-glucitol were prepared; in the preparation of I, 2,5-di- O acetyl-1,6-di-O-mesyl-3,4-di-O-methyl-D-mannitol was used as an intermediate that could be deacetylated to give 1,6-di-O-mesyl-3,4-di-O-methyl-D-mannitol, a compound that proved to be about 10 times as active as 1,6-di-O-mesyl-D-mannitol (Mannitol-Myleran), a known cytostatic compound