A-D-Glucopyranose pentaacetate

Fig. 2.—Relative Rates of Mercaptolysis of the Pentaacetates of D-Glucopyranose and D-Mannopyranose in Ethyl Mercaptan at 0° in the Presence of Zinc Chloride 105 1, /3-D-Glucopyranose Pentaacetate 2, S-D-Mannopyranose Pentaacetate 3, a-D-Mannopyranose Pentaacetate 4, a-D-Glucopyranose Pentaacetate.

Mercaptolysis of /3-D-glucopyranose pentaacetate in ethyl mercaptan at 0°, with zinc chloride as catalyst, gives ethyl tetra-O-acetyl-l-deoxy-1-thio-/S-D-glucopyranoside in 71% yield. Under the same conditions, a-D-glucopyranose pentaacetate reacted only very slowly, but it could be shown that the deoxy-thio-/3-D-glucoside is formed in much greater amount than is the a anomer. Mercaptolysis of the D-mannopyranose pentaacetates under the same conditions for 48 hours resulted in a 70% yield of ethyl tetra-O-acetyl-l-deoxy-l-thio-a-D-mannopyranoside from the /3-D-pentaacetate, and in a 60% yield from the a anomer.103 Inspection, by preparative paper chromatography, of the residual sirups, after deacetylation, led in each case to the isolation of the anomeric ethyl-1-... 

See Cetearyl glucoside Glucopyranose pentaacetate a-D-Glucopyranose, pentaacetate. See a-D-Glucose pentaacetate... 

Draw a synthesis of a-d-glucose-(l->l)-a-d-idosopyranose from a-d-glucopyranose pentaacetate using the Koenigs-Knorr method. 

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