Glucose benzoylation

Benzoates. Benzoyl chloride has a very limited application as a reagent in the sugar series, but it is useful for the preparation of a crystal line derivative of glucose and of fructose. 

In a 50-100 ml. conical flask place a solution of 0 -5 g. of glucose in 5 ml. of water, 12-15 ml. of 10 per cent, sodium hydroxide solution and 1 ml. of benzoyl chloride, cork tightly, and shake until the odour of benzoyl chloride has disappeared and a crystalline (frequently sticky) soUd has separated. Filter oflF the solid, wash it with a Uttle water, and recrystaUise it from ethyl or n-butyl alcohol. (If the product is sticky, it should be removed, and spread on a porous tile before recrystaUisation.) Glucose pentabenzoate has m.p. 179°. Fructose pentabenzoate, m.p. 78-79°, may be similarly prepared. 

In extending this direct method of synthesis, we next investigated the possibility of preparing similarly constituted halides from 2-deoxy-D-arabino-hexose (2-deoxy-D-glucose) (21). The hexose was subjected to a partial anomerization procedure described by Bergmann and co-workers (1). The solid material obtained by this procedure is a mixture of the anomeric forms of 2-deoxy-D-arabino-hexose low temperature p-nitro-benzoylation of the latter in pyridine resulted in a mixture of crystalline, anomeric tetrakis-p-nitrobenzoates in a ratio of approximately 1 1. They were readily separable by fractional recrystallization, and treatment of either with an excess of hydrogen bromide in dichloromethane, or with... 

Anhydro-D-glucose resulted, as mentioned, from the hydrolytic removal of a halogen atom at C6. Similar hydrolytic scission of sugar esters of carboxylic acids takes place without dehydration and with the liberation of the normal sugar. Thus, saponification of 6-benzoyl- or... 

J. M. Williams and A. C. Richardson, Selective acylation of pyranosides I. Benzoylation of methyl a-D-glycopyranosides of mannose, glucose and galactose, Tetrahedron, 23 (1967) 1369-1378. 

The first benzoylated nitrile of an aldonic acid was prepared by Brigl, Muhlschlegel and Schinle by benzoylation of the n-manno-n- oZa-heptononitrile the hexabenzoyl derivative was obtained. A series of benzoylated nitriles has recently been prepared by Restelli de Labriola and Deulofeu by treatment of the oximes of L-rhamnose, D-glucose, D-galactose and D-mannose with benzoyl chloride and pyridine. They were the sole products and were obtained in high yields. 

Evidence that the aldose diacetamides are derived from the union of preformed amides with the aldehydo form of the aldose was obtained many years later. Brigl, Miihlschlegel and Schinle, obtained n-glucose dibenzamide (XXXVIII) by the action of methanolic ammonia on penta-benzoyl-oWe%do-D-glucose (XXXVII). They studied the same reaction... 

In the case of the above mentioned benzoyl-D-glucose derivatives a correlation was found between the formation of D-glucose dibenzamide and the permanent or transitory existence of a free aldehyde group. The same behavior was noted for triacetyl-oZdehydc-L-erythrose (XLI), which by the action of ammonia produces L-erjrthrose diacetamide (XLII). Isbell and Frush have obtained a similar result in the case of tetraacetyl-oWe/it/do-L-arabinose which, when treated with methanolic ammonia, gave L-arabinose diacetamide in 53 % yield. 

Brigl, Muhlschleger and Schinle also obtained a monobenzamide by the action of ammonia on 2-thioethyl-3,4,5,6-tetrabenzoyl-aZde/iydo-D-glucose (LI). Without further evidence of its ring structure, they assumed this compound to be W-benzoyl-(2-thioethyI-D-glucopyranosyl)-... 

The method proposed by Zempl4n has given in some cases, as in the degradation of n-glucose to n-arabinose, higher yields than Wohl s method, but the difficulty of isolation of the new sugars has hindered its application to preparative work. It has been extended to the propiony-lated nitriles by Gim4nez and to benzoylated ones by Restelli de Labriola and Deulofeu. Usually yields lower than with the acetyl derivatives have been obtained. 

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