Glucofuranose 1,2-0-isopropylidene-6-0-tosyl

If the disposition of hydroxyl groups is such that either an ethylene oxide or a hydrofuranol ring could be formed, then it is the three-membered anhydro ring that is preferentially established. Thus, if 6-tosyl-isopropylidene-D-glucofuranose (XII), in which there are present free hydroxyls at C3 and C5, is submitted to alkaline hydrolysis, it is the 5,6-anhydride VI alone that is formed7 the 3,6-anhydride appears only if the hydroxyl at C5 is protected by substitution as in X. 

Another example is provided by the observation of Ohle and Wilcke16 that whereas 3-tosyl-l,2-isopropylidene-D-glucofuranose (XXXV) is saponified without anhydro ring formation and without Walden inversion, the triacetate of methyl 3-tosyl-/3-D-glucofuranoside (XXXVI) is... 

The C-3 tosylate ester of I,2 5,6-di-0-isopropylidene-QL-D-glucofuranose is particularly resistant to displacement with charged nucleophiles [96]. The -elimination product is usually observed because of the trans relation between the leaving group and H-4. The C-3 imidazylate ester is displaced by several nucleophiles under mild conditions and in good yields [68] (Scheme 14). The facile displacement with benzoate ion [97] is note-... 

Fig. 55—Tosylation of 3-0-benzyl-l,2-0-isopropylidene-< -D-glucofuranose with reversed regioselectivity.20...

Pyridazine 3-(2,2-Dimethyl-l,3-dioxolan-4-yl)- E9a, 577 (1,2 5,6-Di-O-isopropyliden-3-O-tosyl-a-D-glucofuranose + N2H4) Pyridin... 

The exception noted for hydroxyl ions in rule (2) is well established for other sulfonic esters of carbohydrates, which therefore differ from simple alkyl sulfonates. An example of hydrolysis of an exo sulfonyloxy group is provided by the compound described as methanesulfonyl-monochloro-l,4 3,6-dianhydrosorbitol which must now be designated 1,4 3,6-dianhydro-5-chloro-5-deoxy-2-0-mesyl-L-iditol reaction with sodium hydroxide affords the free, hydroxy compound of the same configuration. Examples of the hydrolysis of endo sulfonyloxy groups are not available in the dianhydrohexitols, but the endo tosyloxy group in the stereochemically equivalent 3,6-anhydro-l, 2-0-isopropylidene-5-0-tosyl-D-glucofuranose (LXVII) is hydrolyzed by sodium hydroxide to the corresponding hydroxyl... 

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