Dolbier HW Solutions 629

Dolbier HW Solutions 629 - 723 CARBOHYDRATES To find out...

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Unformatted text preview: 723 CARBOHYDRATES To find out which one of these is identical with the degradation product of compound A, carry compound A through the required transformations. O O OH O Ag2O HO OCH3 O CH3I CH3O OH OCH3 Compound A Tri-O-methyl ether of compound A H3 O (acetal hydrolysis) H CHO OCH3 CH3O H HO H H H HO O CH HO CH3O OCH3 OCH3 OCH3 CH2OH 2,3,5-Tri-O-methylD-galactose 25.33 C21H24O10 The fact that phlorizin is hydrolyzed to D-glucose and compound A by emulsin indicates that it is a -glucoside in which D-glucose is attached to one of the phenolic hydroxyls of compound B. H2O emulsin HO HOCH2 HO OH O OH HO O CCH2CH2 HO OH OH d-Glucose (C6H12O6) Compound A (C15H14O5) The methylation experiment reveals to which hydroxyl glucose is attached. Excess methyl iodide reacts with all the available phenolic hydroxyl groups, but the glycosidic oxygen is not affected. Thus when the methylated phlorizin undergoes acid-catalyzed hydrolysis of its glycosidic bond, the oxygen in that bond is exposed as a phenolic hydroxyl group. CH3O O CH3O CCH2CH2 OCH3 OH Compound B This compound must arise by hydrolysis of CH3O CH3O CCH2CH2 O Back Forward Main Menu TOC O OCH3 -d-glucose Study Guide TOC Student OLC MHHE Website ...
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