Sugar benzoates

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. 

The presence of hydroxyl groups in the benzylidene sugars does not interfere with the reaction and by-products are usually minor. Suitable solvents other than carbon tetrachloride, include benzene and tetra-chloroethane. Epoxide, amide, and other commonly encountered functionalities in sugar derivatives are unaffected under the reaction conditions. The corresponding 6-bromo-4-benzoates are valuable intermediates... 

For quite sparingly soluble substances, formic acid, pyridine, bromobenzene, nitrobenzene, and occasionally also phenol, ethyl benzoate, aniline, and dioxan are used. A distinct relation exists between the constitution of solute and solvent, and is expressed by the old rule similia similibus solvuntur. Thus, as is well known, substances containing hydroxyl (e.g. sugars, carboxylic acids) are soluble in water, whereas hydrocarbons are more soluble in benzene and petrol ether than, for example, in alcohols. 

Binkley, R. W., Inversion of Configuration in 2,6-Dideoxy Sugars - Triflate Displacement by Benzoate and Nitrite Anions. J. Org. Chem. 1991, 56, 3892-3896. 

Food preservatives prevent spoilage of food due to microbial growth. The most commonly used preservatives include table salt, sugar, vegetable oils and sodium benzoate, CeHgCOONa. Sodium benzoate is used in limited quantities and is metabolised in the body. Salts of sorbic acid and propanoic acid are also used as preservatives. 

Differential triflate reactivities as just described similarly gave access to the regioisomeric tricunines 6 and from a single precursor, the unsymmetrical diazido sugar 89 (Figure 14). Action of sodium azide upon the diepoxide (readily prepared from had been known known to give mainly the symmetrical counterpart 88 (35), but was now found (53) to yield additionally the (partial) anti-FUrst — Plattner product, on a practical scale. Sequential displacements in its ditriflate, with azide followed by benzoate and in reverse order, furnished 2,3,3 - and 2,3,2 -triazido D-manno.D-manno derivatives, respectively, which were used to prepare 65 and by standard manipulations. The tetraamine was synthesized via double displacement, with azide, from the ditriflate of 88 (53). 

If the benzylidene acetal ring spans the oxygen atoms of two erstwhile secondary hydroxyl groups, the reaction with N-bromosuc-cinimide usually affords isomeric, bromodeoxy sugar benzoates. Thus, for example, the reaction with methyl 2,3-0-benzylidene-5-0-methyl-/3-D-ribofuranoside (106) afforded145 an approximately 1 1 mixture of the bromides 109 and 108, presumably by way of attack on C-2 and C-3 of the benzoxonium intermediate 107 by bromide ion. 

The isostere in which sulfur replaces the methylene group at the 4 position in the furan ring of customary sugars also shows good activity as an inhibitor of HIV reverse transcriptase. The initial step consists of formation of the thioacetal (53-3) from glyoxal benzoate (53-1) and the methyl acetal of thioglyoxal (53-2). Reaction of... 

In summary, it may be stated that the reaction of acyl esters of aldoses and aldobioses (see Section III, p. 92) with ammonia consists of a set of competitive pathways, including intramolecular O —> N migrations of acyl groups, deacylations, and transesterifications, with formation of aldose amides and variable proportions of the free sugar as the principal products. Significant proportions of basic or insoluble polymeric substances were not observed with aldose acetates or benzoates, although occurrence of extensive browning indicates the probable formation of soluble melanoidins. 

On the other hand, formation of methyl benzoate was also found to occur in methanol, indicating that, together with a general base-catalysis to produce benzamide and with the intramolecular, orthoester mechanism (see p. 110) to give the nitrogenated sugars, a transesterification reaction takes place in which the alkoxide ions play an important role. This can be exemplified by the following sequence. 

As previously indicated (see pp. 88-91), formation of heterocyclic compounds, mainly pyrazines, was found only in the ammonolysis of some aldose nicotinates33 35 and acetates and benzoates of ketoses.39 37 For ketose esters, whose behavior differed from that of the aldose esters, the formation of imidazole derivatives was also observed these heterocyclic compounds also result from the direct action of ammonia upon the corresponding free sugars, but the presence of the esterifying acyl groups evidently increases their ease of formation and raises their yields. 

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