Carbohydrates sulfonic esters

SCHEME 42. The physical basis of Richardson s rules for nucleophilic displacement of carbohydrate sulfonic esters (1969). 

Lithium aluminum hydride, effect of solvents on reduction of carbohydrate sulfonic esters, 269 Lutease, 380 Luteic acid, fungal, 378 Lyxitol, 1-acetamido-l-deoxy-L-, 170 Lyxofuranose, 5 - acetamido - 5 - deoxy-D-, 171... 

Platinum catalyst (Adams), in oxidation of carbohydrate sulfonic esters, 258 Poisson distribution, 304 Polarimetric measurement, of mutarota-tion, 47,52... 

Rotation, hindered, of acetyl group in monosaccharides, 193,197 Ruthenium tetraoxide, for oxidation of carbohydrate sulfonic esters, 258... 

Tipson, R. Stuart, The Chemistry of the Nucleic Acids, I, 193-245 Tipson, R. Stuart, Sulfonic Esters of Carbohydrates, VIII, 107-215... 

The common methods of esterification utilize an acid chloride or an acid anhydride as the reagent, but other acid derivatives often show different selectivities, and these are also considered here. In view of the extensive articles on sulfonic esters of carbohydrates,2 4... 

The importance of reactions with complex, metal hydrides in carbohydrate chemistry is well documented by a vast number of publications that deal mainly with reduction of carbonyl groups, N- and O-acyl functions, lactones, azides, and epoxides, as well as with reactions of sulfonic esters. With rare exceptions, lithium aluminum hydride and lithium, sodium, or potassium borohydride are the... 

An alternative procedure for the introduction of the fluorine substituent in secondary positions of carbohydrates consists in nucleophilic displacement of sulfonic esters. Walden inversion always accompanies such displacements, and the success of this method may be attributed to two factors. 

Some 40 research articles resulted from Tipson s 18 years at the Mellon Institute, and they demonstrate that he was able to sustain some of his interest in carbohydrate chemistry, and he continued to study the reactions of sulfonic esters with sodium iodide. In 1945 he compiled his published work into a senior thesis for the D.Sc. degree that was awarded by the University of Birmingham. However, a considerable proportion of the research at the Mellon Institute was never published because of patent restrictions. This was particularly true for his work on carbohydrates and other organic compounds conducted after July 1952, when he was assigned to the Parke, Davis and Company Fellowship in Medicinal Chemistry to synthesize potential antiviral and anticancer agents. 

Tipson s long-standing interest in sulfonic esters led him to contribute a landmark article on carbohydrate sulfonates for Volume 8 of Advances in Carbohydrate Chemistry, which marked the start of his editorial involvement with the series he joined as assistant editor to M. L. Wolfrom starting with Volume 9. This was the beginning of a long and fruitful association between Wolfrom and Tipson that assured researchers in the carbohydrate field of a regular series of authoritative articles on a wide range of topics, both fundamental and applied, related to carbohydrates. 

In addition to these physical studies at the Bureau, Tipson was able to return to his synthetic interests, both alone and in collaboration with other staff members. He was especially pleased to prepare D-talose in crystalline form, an accomplishment that had eluded Emil Fischer. Pursuing his longstanding interest in the reaction of sulfonic esters with iodide and following an earlier observation that the tetratosyl ester of erythritol is converted into butadiene by the action of sodium iodide and zinc, he demonstrated (with A. Cohen) that nonterminal unsaturation may be conveniently introduced into alditol derivatives by reaction of contiguous secondary sulfonates with sodium iodide and zinc dust in boiling A.A-dimethylformamide. This Tipson-Cohen reaction subsequently proved of great utility in other hands for the conversion of more complex carbohydrate structures into vicinal dideoxy derivatives. 

Hydrolysis can detoxify a wide range of aliphatic and aromatic organics such as esters, ethers, carbohydrates, sulfonic acids, halogen compounds, phosphates, and nitriles. It can be conducted in simple equipment (in batches in open tanks) or in more complicated equipment (continuous flow in large towers). However, a potential disadvantage is the possibility of forming undesirable reaction products. This possibility must be evaluated in bench- and pilot-scale tests before hydrolysis is implemented. 

It is often possible to predict the reactivity of a chlorosulfonyloxy group by a consideration of the steric and polar factors affecting the formation of the transition state,27-28 as indicated in Section 11,1 (see p. 227) for nucleophilic-replacement reactions of sulfonic esters of carbohydrate derivatives. Thus, it has been found that the presence of a vicinal, axial substituent or of a (3-trans-axial substituent on a pyranoid ring inhibits replacement of a chlorosulfonyloxy group also, a chlorosulfate group at C-2 has been observed to be deactivated to nucleophilic substitution by chloride ion. 

Bimolecular, nucleophilic-displacement reactions of sulfonic esters of carbohydrates have been reviewed.77,78... 

Until the introduction of triflate or imidazylate esters in carbohydrates, SN2-displacements of carbohydrate sulfonates with charged nucleophiles in certain positions of hexopyranose orfuranose derivatives were not possible, or gave low yields of substituted products owing to the predominance of elimination or rearrangement reactions [6,22,32,33]. 

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