Chlorodeoxy sugars formation

For 49, the reaction was highly successful in that a 3-O-formate ester (127) was indeed formed in a reaction period of 1 to 2 hours at room temperature with 121 followed by usual processing. Refluxing the solution for 3 to 4 hours afforded a chlorodeoxy sugar in 69-71% yield which proved to be 120 rather than the expected 3-chloro derivative (d-alio). 

Deoxyhalogeno sugars are susceptible to nucleophilic attack, leading either to displacement, elimination, or anhydro-ring formation. The ease of displacement decreases in the order I > Br> Cl > F the iodo and bromo derivatives have, therefore, been especially utilized in such reactions, although several reactions with chlorodeoxy sugars have now been reported as a result of the increased availability of these compounds. The approach delineated in Section 11,1 (see p. 227) for predicting the reactivity of sulfonic esters can be expected also to be applicable, in an approximate and qualitative way,... 

An attractive feature in this reaction is the possibility of direct substitution and formation of unblocked sugar derivatives containing one or more chlorodeoxy function in essentially two steps. Another facet is the formation of methyl 4,6-dichloro-4,6-dideoxy-hexosides from certain methyl glycosides in one step. Such compounds could be valuable intermediates in the synthesis of dideoxy and diamino sugars of biological importance. 

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