Monoesters sulfate

Sulfate monoesters can react by dissociative paths, and this is the favored path. Whether such reactions are concerted or involve a very short-lived sulfur trioxide intermediate has been the subject of debate. ° Benkovic and Benkovic reported evidence suggesting that the nucleophile is present (though there is little bond formation) in the transition state for the reaction of amines with p-nitrophenyl sulfate. Alkyl esters of sulfuric or sulfonic acids normally react with C-0 cleavage only when this is disfavored, as in aryl esters, does one see S-0 cleavage. Sulfate diester... 

The hydrolysis of sulfate monoesters has been studied increasingly in relation to sulfate group transfer in vivo. In general, the rate-enhancing effect on the sulfate cleavage is small even with hydroxamate- or imidazole-functionalized cationic micelles which are extremely effective for the hydrolysis of phenyl esters. Recently, Kunitake and Sakamoto (1979a) found that zwitterionic hydroxamate [47] cleaved 2,4-dinitrophenyl sulfate effectively in cationic and... 

The available studies imply that general catalysis will be operative in systems involving sulfate monoesters and potential six-membered ring transition states. Salicyl sulfate hydrolyzes at pH 4 via intramolecular carboxyl group participation involving pre-equilibrium proton transfer leading to sulfur trioxide expulsion (Fig. 9)2HH, viz. 

A different approach to the synthesis of sulfate esters was discussed by Buncel and co-workers (97 ). The sulfate monoester was obtained after neutral or alkaline methanolysis of methyl 4-nltro-phenyl sulfate. The methoxide Ion attacks only at the alkyl carbon with the formation of dimethyl ether and 4-nltrophenyl sulfate Ion as the leaving group. Other substituted methyl phenyl sulfates have been converted to phenyl sulfates In the same manner (98). Correspondingly l,2 5,6-dl-0-lsopropylldlne-a-D-glucofuranose was reacted with phenyl chlorosulfate to give the carbohydrate... 

Phosphoric and sulfuric acid derivatives possess crucial properties that allow them to uniquely fill their many roles in biochemistry. Phosphoric acid may be esterified to form a monoester, diester, or triester (Figure 1). Sulfuric acid may be esterified at one or two positions, to form a monoester or a diester. Sulfate diesters are highly reactive, and have not been found in nature nor do phosphate triesters occur naturally. The hydrolysis of both phosphate and sulfate esters are thermodynamically favorable, but nucleophiles are repelled by the negative charge of the ionized forms. The resulting kinetic stability of phosphate monoesters and diesters, and of sulfate monoesters, is a major factor in their suitability for biological roles. For example, the half-life for hydrolysis of alkyl phosphate dianions by water is approximately 1.1 X 10 years k=2 x 10 s ) at 25°C. Such species... 

Figure 1 On the left are the structures of a phosphate monoester, diester, and triester. The first pK of an alkyl phosphate monoester, and the pKa of a dialkyl diester, are typically between 1 and 2. The second pKa of an alkyl monoester is approximately 6.8, and from one to two units lower for aryl esters. At the right are the structures of a sulfate monoester and diester. Sulfate monoesters have a very low pKa values and as a result are always ionized at physiological pH.

Sulphur was found through spark source mass spectrometry to be abundant in SRS-A [93], Also, incorporation of S into SRS has been reported [64,94-96], The observation that several thiols enhance SRS formation in different systems [97-100] and that arylsulfatase (an enzyme that cleaves sulfate monoesters of phenolic and other unsaturated hydroxylated systems) inactivates SRS-A [101,102] opened the view that a thiol is a constituent of the active compound. However, it has recently been shown that the SRS-inactivating action of commercially available arylsulfatase is not due to sulfate ester cleavage, but to a dipeptidase contaminant [103,104]. The destruction of different SRS compounds by hpoxygenase [67,105,106] shows that SRS contains a cij,c/s-1,4-pentadiene structure, since this is a prerequisite for a lipoxygenase substrate [107], For a review of the earlier structural work on SRS, see ref. 108. 

Chem. Descrip. Sodium salt of a sulfated monoester of fatty acid Uses Wetting agent in textile industry dispersion aid in paint industry ... 

L-Ascorbic acid, sulfate monoester, disodium salt. See Disodium ascorbyl sulfate Ascorbo-120, Ascorbo-C Tablets. See L-Ascorbic acid... 

Synonyms L-Ascorbic acid, sulfate monoester, disodium salt... 

Concentrated 70-98% snlfuric acid was used as the catalyst at a low pressure and temperature. The reaction mechanism involved the sulfate monoester intermediate, which was then hydrolyzed to isopropanol. The proeess is similar to the production of ethanol from ethylene, although the hydration step beeomes easier as the carbon number of the olefin inereases. The acid strength reqnired for effective operation deereases from more than 90% for ethylene hydration to abont 70% for propylene hydration. 

This efficient procedure for deoxygenation of ally lie alcohols involving the reduction of an intermediate sulfate monoester was developed earlier by E. J. Corey and K. Achiwa, J. Org. Chem., 34, 3667 (1969). 

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