Alditols, methylene acetals, acetolysis

Much work was conducted by Hudson and his school on the acetolysis of methylene acetals of alditols. Their principal finding was that a methylene acetal that links primary and secondary positions is cleaved readily, and preferentially, at the primary position to give the primary acetate and the acetoxymethyl ether of the secondary hydroxyl group (Scheme 1). The reagent... 

Prolonged treatment of 1,3-erythro methylene acetals of alditols does, however, cause their acetolysis. ... 

Trifluoroacetic anhydride-acetic acid, when used for the acetolysis of methylene acetals of alditols, shows the same specificity as acetic anhydride-sulfuric acid. - However, the products formed can be converted, by very mild hydrolysis, into the acetate-hydroxy derivative (6), because of facile cleavage of the (trifluoroacetoxy) methyl ether linkage (5). 

The structures of many methylene sugar derivatives have not been determined, but those of many of the alditol derivatives are known. The greater ease of acetolysis of methylene groups attached to primary hydroxyls over those attached to secondary hydroxyls, has been of considerable value in the elucidation of the structures of these compounds by Hudson and co-workers (96), Thus the linkages at carbons 1 and 6 of 1,3 2,4 5,6-tri-O-methylene-D-glucitol are cleaved with sulfuric acid in acetic anhydride and acetic acid as shown in the formulas. The structure of the mono-0-methylene-D-glucitol is demonstrated by its oxidation with periodic acid... 

---

See also in sourсe #XX -- [ ]

---