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Chapter 31: Problem 716

Show how the structure of maltose can be deduced from the following evidence: (a) The sugar is hydrolyzed by yeast \(\alpha\) -D-glucosidase to \(\mathrm{D}\) glucose. (b) Maltose mutarotates and forms a phenylosazone. Methylation with dimethyl sulfate in basic solution followed by acid hydrolysis gives \(2,3,4,6\) -tetra- \(\mathrm{O}\) -methyl-Dglucopyranose and \(2,3,6-\) tri-O-methyl- D-glucose. (c) Bromine oxidation of maltose followed by methylation and hydrolysis gives \(2,3,4,6\) -tetra-O-methyl-D- glucopyranose and a tetramethyl-D-gluconic acid which readily forms a \(\gamma\) -lactone.

Short Answer

Expert verified
The structure of maltose can be deduced based on the provided evidence as follows: maltose contains α-D-glucose residues linked together via an α-1,4-glycosidic bond, as evidenced by its hydrolysis by yeast α-D-glucosidase to D-glucose (Step 1), the formation of phenylosazone and products of methylation (Step 2), and the products of bromine oxidation (Step 3). The structure of maltose is α-D-Glucopyranosyl-(1→4)-D-glucopyranose.

Step by step solution

01

Analyzing the hydrolysis of maltose

Maltose is hydrolyzed by yeast α-D-glucosidase to D-glucose. This indicates that maltose contains α-D-glucose residues in its structure, and the linkage is likely an α-glycosidic bond.
02

Analyzing the formation of phenylosazone and products of methylation

Maltose mutarotates and forms a phenylosazone, which indicates that maltose contains a reducing sugar. Methylation with dimethyl sulfate in basic solution followed by acid hydrolysis gives 2,3,4,6-tetra-O-methyl-D-glucopyranose and 2,3,6-tri-O-methyl-D-glucose. This result shows that one of the glucose residues has hydroxyl groups at C2, C3, and C6 methylated, while the other has hydroxyl groups at C2, C4, and C6 methylated, suggesting that the linkage is between C1 of one glucose residue and C4 of the other glucose residue.
03

Analyzing the products of bromine oxidation

Bromine oxidation of maltose followed by methylation and hydrolysis gives 2,3,4,6-tetra-O-methyl-D-glucopyranose and a tetramethyl-D-gluconic acid which readily forms a γ-lactone. Since the bromine oxidation occurs on the nonreducing sugar, we can correlate this observation to step 2, which showed the glucose with C1 linked at C4 as the nonreducing residue of maltose. The reducing sugar part is then readily converted to a lactone.
04

Deduce the structure of maltose

Based on the evidence provided, we can deduce that maltose is composed of two α-D-glucose residues linked together via an α-1,4-glycosidic bond. The structure of maltose can be written as α-D-Glucopyranosyl-(1→4)-D-glucopyranose.

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Most popular questions from this chapter

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 \(\mathrm{B}\).

D-Arabinose and D-ribose give the same phenylosazone. D-Ribose is reduced to the optically inactive penta- hydric alcohol, ribitol. D-Arabinose can be degraded by the Ruff method, which involves the following reactions: The tetrose, D-erythrose, so obtained can be oxidized with nitric acid to mesotartaric acid. What are the configurations of D-arabinose, D-ribose, ribitol, and D-erythrose?

Identify each of the following glucose derivatives: (a) \(\mathrm{A}+4 \mathrm{HIO}_{4} \rightarrow 3 \mathrm{HCOOH}+\mathrm{HCHO}+\mathrm{OHC}-\mathrm{COOH}\) (b) \(\mathrm{B}+5 \mathrm{HIO}_{4} \rightarrow 4 \mathrm{HCOOH}+2 \mathrm{HCHO}\) (c) \(\mathrm{C}+3 \mathrm{HIO}_{4} \rightarrow 2 \mathrm{HCOOH}+2 \mathrm{OHC}-\mathrm{COOH}\) (d) \(\mathrm{D}+4 \mathrm{HIO}_{4} \rightarrow 4 \mathrm{HCOOH}+\mathrm{OHC}-\mathrm{COOH}\)

D-Raffinose is a trisaccharide that does not react with Fehling's solution. Upon hydrolysis it produces \(\mathrm{D}\) - glucose, D-galactose, and D-fructose. Completely methylated raffinose is hydrolyzed to \(2,3,4-\) tri- O -methylglucose, \(1,3,4,6-\) tetra-O-methylfrueto se, and \(2,3,4,6-\) tetra- \(\mathrm{O}-\) methylgalactose. What structures for raffinose are consistent with these data? What further information, if any, is required to identify completely the structure of raffinose?

Will 2-deoxyribose form an osazone? Why?
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