Replacement of acyloxy groups by halogen halo sugars

Replacement of acyloxy groups by halogen (halo sugars) 

Acetohalo- -D-glucose Pentaacetyl-/ -D-glucose Acetohalo-a-D-glucose ac = CH3CO or C6H5CO. 

A particularly simple process, giving the /9-product, is treatment of a solution or suspension of a sugar acetate with dry HC1. 

Acetochloro- -D-glucose 1012 HC1 (50 g) is led during 40 min into a stirred mixture of penta-0-acetyl-/ -D-glucose (20 g) and dry ether (250 ml) at 5°, whereupon most of the pentaacetylglucose dissolves. The mixture is kept for 2 days in a closed flask at 0°, whereafter the resulting clear solution is concentrated in a vacuum. A total of 65 % of crude product is thus obtained and after recrystallization from dry ether has m.p. 98-99°, [oc]D20 —12°. 

Acetochloro-/ -D-glucose can also be obtained by passing dry HC1 into a mixture of PC13 (100 ml) and penta-0-acetyl-/9-D-glucose (10 g) at 90-100° for 5 h, and an analogous process gives /9-acetochlorogalactose.1013 

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