When methyl \(\alpha-\mathrm{D}-\) glucoside was treated with \(\mathrm{HIO}_{4}\), it yielded 1 mole of formic acid, plus a product (A). Write the structure of \(\mathrm{A}\). When a methyl glycoside of unknown structure (B) was similarly treated with \(\mathrm{HIO}_{4}\), only 1 mole of \(\mathrm{HIO}_{4}\), was consumed, and no formic acid was produced, but the same product (A) was obtained. Draw the configurational structure of \(\mathrm{B}\).

In Reaction 1, methyl \(\alpha-\mathrm{D}\)-glucoside is treated with \(\mathrm{HIO}_{4}\), yielding 1 mole of formic acid and product A. Given that \(\mathrm{HIO}_4\) is a strong oxidizing agent and breaks C-C bonds, we can infer that the bond adjacent to the anomeric carbon in methyl \(\alpha-\mathrm{D}\)-glucoside is broken, resulting in the formation of formic acid and the remaining part of the molecule, which is product (A). Methyl \(\alpha-\mathrm{D}\)-glucoside is a glucose molecule with a methyl group at the anomeric carbon. The oxidation process breaks the C1-C2 bond, and so the structure of product A is glucose without C1 and C2 attached, forming an aldehyde at C3: Product A: \(\mathrm{CH_3-CH(OH)-CH(OH)-CH(OH)-CH_2OH}\), which represents a methyl-glyceraldehyde molecule.

In Reaction 2, an unknown methyl glycoside (B) is treated with \(\mathrm{HIO}_{4}\), consuming 1 mole of \(\mathrm{HIO}_{4}\) without forming any formic acid, but yielding the same product A. This information suggests that the glycoside (B) only has one bond susceptible to oxidation, but that this bond is not connected directly to the anomeric carbon (as no formic acid is produced). Since product A is formed in both reactions, we can infer that compound B also has the same methyl-glyceraldehyde structure as product A. The only difference is that in compound B, there is a glycosidic bond with the anomeric carbon of another sugar moiety. This bond does not break because it is not directly connected to the anomeric carbon. Thus, the structure for the unknown glycoside compound (B) is a disaccharide that has product A as one of its units, with a glycosidic bond with the anomeric carbon of another sugar moiety. Hence, the configurational structure of compound B is: \(\mathrm{CH_3-CH(OH)-CH(OH)-CH(OH)-CH_2OH} - \mathrm{(--) - O - Sugar}\), with the glycosidic bond attached to the anomeric carbon of the sugar moiety. Further identification of the attached sugar moiety would require additional information not provided in this exercise.