Glucopyranoside oxidation products

The oxidation product from methyl 6-0-trityl-a-D-glucopyranoside has been used in the preparation of 1-0-methyl-L-glyceritol. The oxidation product from methyl 5,6-di-O-methyl-a-D-glucoside has been used in the preparation of 1,2-di-O-methylerythritol. ... 

The most studied compound in this group is the oxidation product from methyl a-D-glucopyranoside, which, of course, can be prepared from other glycosides. At least six structures are theoretically possible for this dial-dehyde the free dialdehyde (48) or its hydrated form, a dioxane derivative formed by hemiacetal formation (49) or its hydrate, a fused tricyclic form (50) by further hemiacetal formation in (49), and a hemialdal form (51). Equilibria between the various forms should be possible, and, in different reactions detailed below, derivatives of the different forms are produced. Some workers have sought one structure for the dialdehyde, ... 

An alternative, or supplementary, approach is provided by oxidation with lead tetraacetate or, preferably, periodate, and possibly by identification of the products. Caution must, however, be observed in using this method, as Buchanan has shown that the compound previously designated as methyl 3-chloro-3-deoxy-a-D-gulopyranoside consumes periodic acid extremely slowly (seven days) and is, in fact, methyl 4-chloro-4-deoxy-a-D-glucopyranoside. The products of epoxide cleavage are usually completely defined by these procedures, because irans addition can be assumed, although considerable care must be exercised when there is a possibility of epoxide migration. ... 

FIGURE 22.42 Formation of methyl D-glucopyranoside and further oxidation with periodic acid gives the observed dialdehyde product, which is evidence that the cyclic form of glucose is (mainly) a pyranose. A furanose would give a different oxidation product. 

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