The simple carbohydrates and the glucosides / by E. Frankland Armstrong.

  • Armstrong, E. Frankland (Edward Frankland), 1878-1945.
Date:
1912
Catalogue details

Licence: In copyright

Credit: The simple carbohydrates and the glucosides / by E. Frankland Armstrong. Source: Wellcome Collection.

    24/188 (page 12)
    Acetochloro and acetobromo glucose have been rendered easily accessible by a more convenient method of preparation: /3-glucose pentacetate, dissolved in acetic acid, is treated with a saturated solution of the hydrogen halide in glacial acetic acid. Acetoiodo glucose has also been prepared. In all cases, by this method only the /3-deriva- tives are obtained. Apparently rearrangement takes place very readily during the preparation of a-acetochloro glucose by means of anhydrous hydrogen chloride and the a-derivatives are not always obtainable; indeed Fischer’s most recent investigation has cast some doubt on their existence. When the action of anhydrous hydrogen bromide on glucose pentacetate is prolonged dibromo-triacetyl glucose is obtained. One of the bromine atoms can be replaced by methoxyl with the formation of triacetyl methyl glucoside bromohydrin. This compound has served as the starting-point for the preparation of a new isomeride of glucosamine (p. 43). When it is heated with barium hydroxide hydrogen bromide is eliminated, and anhydromethyl glucoside, CTH]205, is formed ; this when hydrolysed by dilute acids yields anhydroglucose, a well-characterised crystalline substance. It forms a phenylhydrazone and phenylosazone, both containing one molecule of water less than the corresponding glucose compounds. On the assumption of a 7-oxide ring structure for the new anhydride, anhydro glucose will have the attached formula. This is fully in harmony with the deductions HCOH possible from the solid model of glucose. The e-carbon being free to rotate can take up the position indicated, which is favourable for the formation of a 7-oxide ring, linking it with the /3-carbon atom through oxygen. The second bromine atom in triacetyl-dibromo glucose is presumably in the /3-position, the only possible alternative being the e-position. Anhydromenthol glucoside has been obtained in a similar manner to anhydromethyl glucoside ; it is of interest that emulsin is without