Sulfinic and Sulfonic Acids

The l3C chemical shifts of methyl derivatives with sulfur substituents [e.g., SH, -S, -SCH3, -SSCH3, -SSSCHj, -S(0)CH3, -S02CH3, -S(CH3)2+, -SC(0)CH3, -SC(S)CH3, and -SC(S)SCH3] (130,131) and of vicinal and gem-inal bis-sulfides (290) have been reported. Freeman and co-workers have published similar studies on thiols, sulfides, disulfides, and sulfinic and sulfonic acid derivatives (131,132,433) and Tseng and Bowler (434), on thiocarbamates, their S-oxides and S,5-dioxides [R-X-C(0)-NR 2 with X = S, SO, S02]. 

The group name is intended to cover esters derived from sulfenic, sulfinic and sulfonic acids, some of which are thermally unstable. This is especially so for esters of unsaturated alcohols, which are also liable to polymerise, catalysed by the liberated acids. Individually indexed compounds are ... 

An important drug in the present context is the mineralocorticoid receptor antagonist spironolactone (7.74, Fig. 7.12). Among its many metabolic reactions, spironolactone is readily hydrolyzed at the thioester bond (Fig. 7.12, Reaction a) to form deacetyl-spironolactone (7.75, Fig. 7.12), a metabolite found in a variety of tissues [155 -157]. This thiol compound, which is also a potent mineralocorticoid antagonist, promotes the mechanism-based inactivation of hepatic, adrenal, and testicular cytochrome P450 isozymes. There is now good evidence to indicate that this behavior is the result of microsomal 5-oxidation (see Chapt. 7 in [7]). When spironolactone was incubated with liver microsomes from rats pretreated with dexamethasone (an inducer of CYP3A), the sulfinic and sulfonic acid derivatives were characterized [158]. Perhaps the importance of the 5-deacetylation of spironolactone... 

Types of compounds are arranged according to the following system hydrocarbons and basic heterocycles hydroxy compounds and their ethers mercapto compounds, sulfides, disulfides, sulfoxides and sulfones, sulfenic, sulfinic and sulfonic acids and their derivatives amines, hydroxylamines, hydrazines, hydrazo and azo compounds carbonyl compounds and their functional derivatives carboxylic acids and their functional derivatives and organometallics. In each chapter, halogen, nitroso, nitro, diazo and azido compounds follow the parent compounds as their substitution derivatives. More detail is indicated in the table of contents. In polyfunctional derivatives reduction of a particular function is mentioned in the place of the highest functionality. Reduction of acrylic acid, for example, is described in the chapter on acids rather than functionalized ethylene, and reduction of ethyl acetoacetate is discussed in the chapter on esters rather than in the chapter on ketones. 

Substituents attached to a heterocyclic ring through a sulfur atom exist in wider variety than those through oxygen. Besides the simple thio analogues—the thiols (mercaptans), thioethers, thioesters and the like—they include compounds of various higher oxidation states of sulfur, including sulfoxides, sulfones, sulfinic and sulfonic acids and their derivatives. 

Looking down the first column we see that a sulfene may be regarded as the most highly oxidized form of the thiocarbonyl group, or, alternatively, as the most highly oxidized member of the series of inner anhydrides of the oxy-acids, i.e. the sulfenic, sulfinic and sulfonic acids. From this viewpoint it is not surprising that sulfene is the member of the series most likely to undergo nucleophilic attack at the sulfur atom. 

Fig. 1 Posttranslational redox modificatitnis to amino acids in proteins. Many amino acids can undergo various posttranslatiraial redox modifications in the presence of NAPQI, oxidative stress, and nitrosative stress. Thiols in cysteine can undergo covalent binding, mixed disulfide formation, nitrosylation, and become oxidized to sulfenic, sulfinic, and sulfonic acids. Tyrosine can become nitrated by peroxynitrate, and methionine can be oxidized by ROS to methionine sulfoxide. Not shown are many other oxidatirais that can occur to other amino acids such as proline, histidine, etc.

The oxidation of tetrametliylthiourea (TTTU) by bromine and acidic bromate ion in aqueous media has been studied. The bromate reaction, which has an induction period followed by formation of bromine, involves formation of tetramethythiourea sulfenic acid, which is oxidized to tetramethylurea and sulfate ion as final products. There was no evidence for formation of the sulfinic and sulfonic acids, which implicated the sulfoxylate anion as a precursor to formation of sulfate ion. ... 

Coenzyme A. cysteamine, firefly luciferin, sulfinic and sulfonic acids. S-alkylated derivatives... 

D 11.2 S-Substituted Cysteine Derivatives and Sulfoxides D 11.1 Sulfinic and Sulfonic Acids... 

Organic sulfur compounds, for example, disulfides, thiosulfinates, thiosul-fonates, thiols, sodium thilates, and sodium sulfinates, were found to be readily oxidized to both sulfinic and sulfonic acid using the poatassium superoxide/18C6 system [234]. 

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