Chlorodeoxy sugars cyclic sulfates

In 1921 Helferich [34J found that treatment of methyl a-D-glucopyranoside 18 with sulfuryl chloride in a mixture of pyridine and chloroform at 5°C afforded a compound, the structure of which was established several years later [37,38] to be that of methyl 4,6-dichloro-4,6-dideoxy-a-D-galactopyranoside 2,3-cyclic sulfate (19 Scheme 3). The cyclic sulfates are readily cleaved by dilute alkalis, or by methanolic ammonia, to give the salt of a monosulfate the hemi-ester is then desulfated by acid to yield the chlorodeoxy sugar [35,36]. Both of these reactions occur with retention of configuration [37]. 

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