Thiyl radicals acids

The addition of aromatic and aUphatic thiols, RSH and ArSH, and a thioacetic acid to isoprene yields mainly the trans-l,4-adduct (56). The aromatic thiyl radicals, ArS , add almost entirely to the first carbon atom however, aUphatic thiyl radicals, RS, also add to the fourth C atom in significant amounts. 

The degradation of tetrachloromethane by a strain of Pseudomonas sp. presents a number of exceptional features. Although was a major product from the metabolism of CCI4, a substantial part of the label was retained in nonvolatile water-soluble residues (Lewis and Crawford 1995). The nature of these was revealed by the isolation of adducts with cysteine and A,A -dimethylethylenediamine, when the intermediates that are formally equivalent to COClj and CSClj were trapped—presumably formed by reaction of the substrate with water and a thiol, respectively. Further examination of this strain classified as Pseudomonas stutzeri strain KC has illuminated novel details of the mechanism. The metabolite pyridine-2,6-dithiocarboxylic acid (Lee et al. 1999) plays a key role in the degradation. Its copper complex produces trichloromethyl and thiyl radicals, and thence the formation of CO2, CS2, and COS (Figure 7.64) (Lewis et al. 2001). 

The attack by the thiolate anion on the N-oxide oxygen of 62 produces the intermediate sulfenic acid derivative 65, which, in the presence of thiols, further reacts with the thiolate anion, to give the oxime 66, which has been isolated among the reaction products. By contrast, spontaneous loss of the halide anion from 65 affords the ni-troso intermediate 67 that, by losing NO and the thiyl radical directly, or through 68, produces the a-nitrosoolefm 69. By a Michael type reaction with water this last product immediately yields the final oxime 70, which has been isolated among the reaction products. 

In a similar manner, many additions of heteroatom radicals to unsaturated positions have been studied. In many cases, addition reactions of heteroatom radicals to alkenes are reversible and thermodynamically disfavored, but their occurrence is apparent. For example, the rapid addition and elimination of thiyl radicals to unsaturated fatty acid methyl esters results in isomerization reactions from which kinetic parameters can be obtained. Additions of group 14 (IV A) metal-centered... 

Thiepane (35) has been synthesized by an intramolecular radical addition of the thiyl radical (equation 59) which was generated by photolysis of a thiol (71TL2025). Similarly, C—S bond formation has been achieved (equation 60) by an intramolecular condensation of 6-mercaptohexanoic acid to give the thiolactone, thiepan-2-one (135) (64MI51700). A Dieckmann-type base-catalyzed cyclization of a diester precursor followed by acid-catalyzed hydrolysis and decarboxylation has been used in the synthesis of thiepan-3-one (41) as indicated in equation (61) (52JA917). 

Thiyl radicals from irradiated bis(2,2 -carboxyphenyl) disulfide failed to abstract hydrogen from acetic acid or an electron from acetate ion,... 

Schmittel M, Ghorai MK (2001) Reactivity patterns of radical ions - a unifying picture of radical-anion and radical-cation transformations. In Balzani V (ed) Electron transfer in chemistry, vol 2. Organic molecules. Wiley-VCH, Weinheim, pp 5-54 Schoneich C, Bonifacic M, Dillinger U, Asmus K-D (1990) Hydrogen abstraction by thiyl radicals from activated C-H-bond of alcohols, ethers and polyunsaturated fatty acids. In Chatgilialoglu C, Asmus K-D (eds) Sulfur-centered reactive intermediates in chemistry and biology. Plenum, New York, pp 367-376... 

Adhikari S, Sprinz H, Brede 0 (2001) Thiyl radical induced isomerization of unsaturated fatty acids determination of equilibrium constants. Res Chem Intermed 27 549-559 Adhikary A, Bothe E, Jain V, von Sonntag C (2000) Pulse radiolysis of the DNA-binding bisbenzimid-azole derivatives Hoechst 33258 and 33342 in aqueous solution. Int J Radiat Biol 76 1157-1166 Akhlaq MS, von Sonntag C (1986) Free-radical-induced elimination of H2S from dithiothreitol. A chain reaction. J Am Chem Soc 108 3542-3544... 

Fang X, Jin F, Jin H, von Sonntag C (1998) Reaction of the superoxide radical with the A/-centered radical derived from N-acetyltryptophan methyl ester. J Chem Soc Perkin Trans 2 259-263 Ferreri C, Costantino C, Landi L, Mulazzani QG, Chatgilialoglu C (1999) The thiyl radical-mediated isomerisation of c/s-monounsaturated fatty acid residues in phospholipids a novel path of membrane damage Chem Commun 407-408... 

Schoneich C, Asmus K-D (1990) Reaction of thiyl radicals with alcohols, ethers and polyunsaturated fatty acids a possible role of thiyl free radicals in thiol mutagenesis Radiat Environ Biophys 29 263-271... 

Sprinz H, Schwinn J, Naumov S, Brede O (2000) Mechanism of thiyl radical-catalyzed isomerization of unsaturated fatty acids in homogeneous solution and in liposomes. Biochim Biophys Acta 1483 91-100... 

Sprinz H, Adhikari S, Brede O (2001) Transformation of phospholipid membranes by thiyl radicals via ds-tmns isomerization in fatty acid residues. Adv Colloid Interface Sci 89/90 313-325 Stefanic I, Bonifacic M, Asmus K-D, Armstrong DA (2001) Absolute rate constants and yields of transients from hydroxyl radical and H atom attack on glycine and methyl-substituted glycine anions. J Phys Chem A 105 8681-8690... 

For the first two peptides, CysS radicals abstract hydrogen atoms from the or-carbon of glycine with 7 = (1.0 to 1.1) x 10 s , while the reverse reaction proceeds with = (8.0 to 8.9) x 10 s . For the latter peptide, CysS radicals abstract hydrogen atoms from the ce-carbon of alanine with = (0.9 to 1.0) x 10 s while the reverse reaction proceeds with k -j = 1.0 x 10 s" The order of reactivity, Gly > Ala, is in accordance with previous studies on intermolecular reactions of thiyl radicals with these amino acids. The fact that < k y suggests that some secondary structure prevents the adoption of extended conformations for which calculations of homolytic bond dissociation energies would have predicted k j > k y. 

Arachidonic acid residue (5c,8c,llc,14c-20 4) was studied in order to assess whether the cis-tmns isomerization induced by RS radicals depends on location of a cis double bond. Thiyl radicals... 

Nauser T, Schoneich C. (2003) Thiyl radicals abstract hydrogen atoms from the aC-H bonds in model peptides Absolute rate constants and effect of amino acid structure. / Am Chem Soc 125 2042-2043. 

Nauser T, Felling J, Schoneich C. (2004) Thiyl radical reaction with amino acid side chains Rate constants for hydrogen transfer and relevance for posttransla-tional protein modification. Chem Res Toxicol 17 1323-1328. 

ChatgiKaloglu C, AUtieri A, Fisher H. (2002) The kinetics of thiyl radical-induced reactions of monounsaturated fatty acid esters. / Am Chem Soc 124 12816-12823. 

Schwinn J, Sprinz H, Drossier K, Leistner S, Brede O. (1998) Thiyl radical-induced cis/tr r-isomerization of methyl linoleate in methanol and of linoleic acid residues in liposomes. Int JRadiat Biol 74 359-365. 

Ferreri C, Costantino C, Perrotta L, Landi L, Mulazzani QG, ChatgiKaloglu C. (2001) Cis-trans isomerization of polyunsaturated fatty acid residues in phospholipids catalyzed by thiyl radicals. J Am Chem Soc 123 4459 468. 

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