Phosphorus thioesters

The oxidation of thioesters of phospho-rus(III) acids (S -ethyldiphenylphosphi-nite, S, S -diethylphenylphosphonite and triethylthiophosphite) in AN/NaCl04 occurs at potentials characteristic for thioethers with substituents other than for phosphorus(III) groups, which suggests the contribution of the lone pair of sulfur to the HOMO to be predominant. The process is thought to proceed via an intermediate cation radical with the number of electrons n varying from 0.65 to 0.85, which suggests a catalytic mechanism [12-15]. 

Thioamide formation benzodiazepinone, 505 heteiodiazepinone, 621 phosphorus pentasulf ide, 323, 600 Thioazole formation, nitrile addition, 301 Thiocarbamate formation, 588 phenol, 95 rearrangement, 517 Thioenol ether formation, 185, 517 addition-elimination, 554 Thioester formation, mixed anhydride, 184 Thioether formation, 241, 300, 413, 416 alkylation, 586, 588 aromatic displacement, 416 Thiohydantoin formation, 293 Thiol interchange, benzothiazole formation, 422... 

Figure 13.19 Examples of other phosphorus-containing hydrolyzable functionalities. In these compounds, carbons are directly bonded to phosphorus. Note that if-0-R3 is replaced by -S-Rj one obtains the corresponding thioesters.

For purposes of classifying the reactions of metabolism, in this book the nucleophilic displacements are grouped into four subtypes (Table 10-1). These are displacements on (A) a saturated carbon atom, often from a methyl group or a glycosyl group (B) a carbonyl group of an ester, thioester, or amide (C) a phospho group or (D) a sulfur atom. In addition, many enzymes employ in sequence a displacement on a carbon atom followed by a second displacement on a phosphorus atom (or vice versa). 

The Preparation of Phosphorus Esters and Thioesters from White Phosphorus... 

In many examples, it is not necessary to prepare the phosphorane. Instead, the dicarbonyl compound is heated with a trialkyl or triaryl ester of phosphorus acid or, less commonly, with a diester of a phosphonous acid (RP(OH)2, where R is an organic group). For example, when the thioester 301 is heated with dipropyl ethylphosphonite the 2-substituted carbapenem 302 is produced in 80% yield (Equation 32) <1997CPB1439>. This general method has been used to prepare 2-sulfide-substituted 1/3-methylcarbapenems <2000CPB126, 2001SC587> and O-protected 2-hydroxymethyl derivatives < 1999JA11261 >. 

The reaction of N-arylsulfonylsuinmides with a range of trivalent phosphorus compounds gave near quantitative yields of the phosphinimides and the sulfide. I Addition of protic solvents led to reduction products, which contain, besides the original sulfides, an alkyl-exchanged sulfide in which the alkyl group derived from the alcohol. 126.127 other derivatives, (acid anhydride, amide, ester or thioester) were formed in the presence of carboxylic acid derivatives. 128,129 xhese reactions were favoured by the dipolar nature of the intermediately formed sulfurane. 127... 

If the carboxylate ion attacks the y-phosphorus of ATP, an acyl phosphate is formed. The acyl phosphate then reacts with the thiol in a nucleophilic acyl substitution reaction (Section 17.5) to form the thioester. 

Other inorganic esters are generally prepared by the reaction of an acid chloride with a hydroxy cmppound or its sodium salt. Phosphates are prepared by the reaction of phosphorus pentachloride or phosphorus oxji chloride with the appropriate alcohol or phenol. If the sulfur analogue of phosphorus oxychloride, PSCls, is baused to react with an alcohol, or its sulfur analogue, a mercaptan, the corresponding thioester is obtmned. 

Walling C, Basedow OH, Savas ES (1960) Some extensions of the reaction of trivalent phosphorus derivatives with alkoxy and thiyl radicals a new synthesis of thioesters. J Am Chem Soc 82 2181-2184... 

Secondary antioxidants are used in conjunction with primary antioxidants to provide added stability to the polymer. Typical compounds contain sulfur or phosphorus. The more popular secondary antioxidants are thioesters (thiodipropionic acid derivatives and polythiodipropionates) and organophosphites. 

A general approach to both saturated and unsaturated thioesters consists of reaction between phosphorus ylides and carbon oxysulphide (Scheme 46). °... 

Unlike some of the other common test methods, the XRF technique does not provide any structural information about the antioxidants detected. In addition to the total concentration, chromatographic and infrared based methods can also provide information on the degree of antioxidant degradation products (such as the phosphate content, which is the oxidized form of phosphite antioxidants, normally created during polymer processing). The XRF technique also has limited utility when more than one phosphite or thioester antioxidant is present in the sample, because the total phosphorus or sulfur concentration does not provide the degree of distribution from each antioxidant. 

Acyl CoAs, such as acetyl CoA, are the most common thioesters in nature. Coenzyme A, abbreviated CoA, is a thiol formed by a phosphoric anhydride linkage (0=P-0-P=0) between phosphopantetheine and adenosine 3, 5 -bisphosphate. (The prefix bis- means two and indicates that adenosine 3, 5 -bisphosphate has two phosphate groups, one on C3 and one on C5. ) Reaction of coenzyme A with an acyl phosphate or acyl adenylate gives the acyl CoA (Figure 16.10). As we saw in Section 16.5 (Figure 16.6), formation of the acyl adenylate occurs by reaction of a carboxylic acid with ATP and is itself a nucleophilic acyl substitution reaction that takes place on phosphorus. 

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