Dithioles reduction

This scheme does not link the oxidation of As(III) with methylation and posits that the obligatory substrate for methylation is an As(III)-GSH complex. In a related analysis of AS3 ATT-catalyzed methylation, it has been suggested that As(III) bound to cellular proteins are the substrates for methylation (Naran-mandura, Suzuki and Suzuki, 2006). Because AS3MT can catalyze the methylation of inorganic As(III) in reaction mixtures that do not contain GSH, but do contain dithiol reductants, it is unclear how the presence of GSH can be considered a requirement for AS3 ATT-catal yzed methylation. In cellular environments that contain the dithiol reductants, GSH, and a plethora of proteins that could bind As(III), it is quite possible that multiple reaction pathways may be involved in the production of methylated arsenicals. Further experimental work will be required to identify each of the molecular components of these pathways. 

Tagaya, Y., Maeda, Y., Mitsui, A., Kondo, N., Matsui, H., Hamuro, J., Brown, N., Arai, K., Yokota, T., Wakasugi, H., and et al. (1989). ATL-derived factor (ADF), an IL-2 receptor/Tac inducer homologous to thioredoxin possible involvement of dithiol-reduction in the IL-2 receptor induction. EMBO J 8,757-64. 

The sulphate reductase factor which has already been mentioned was the first of these polypeptide dithiol-disulphide cofactors to be recognized . In this case the reduction of PAPS to PAP and sulphite was shown possible with a dithiol reductant such as dihydrolipoate or with NADPH and two protein components. One of the protein factors was not inactivated by heating. Incubation of the two protein fractions with NADPH generated... 

Dithiols, like diols, have been protected as 5,5 -methylene, 5,5 -isopropylidene, and 5,5 -benzylidene derivatives, formed by reaction of the dithiol with formaldehyde, acetone, or benzaldehyde, respectively. The methylene and benzylidene derivatives are cleaved by reduction with sodium/ammonia. The isopropylidene and benzylidene derivatives are cleaved by mercury(II) chloride with sodium/ ammonia the isopropylidene derivative is converted to a monothio ether, HSCHR-CHRSCHMe2- ... 

Quite a number of mixed sulfur-nitrogen macrocycles have been prepared, but these have largely been by the methods outlined in Chaps. 4 and 5 for the respective heteroatoms. An alternative method, involves the formation of a Schiff base, followed by reduction to the fully saturated system, if desired. An interesting example of the Schiff base formation is found in the reaction formulated in (6.12). Dialdehyde 14 is added to ethylenediamine in a solution containing ferrous ions. Although fully characterized, the yield for the reaction is not recorded. To avoid confusion with the original literature, we note the claim that the dialdehyde [14] was readily prepared in good yield by reaction of the disodium salt of 3-thiapentane-l, 5-diol . The latter must be the dithiol rather than the diol. 

There has been recent interest in naphtho-fused dithiepines as chiral acyl anion equivalents, particularly since the starting dithiol 128 can be obtained in enan-tiomerically pure form (89TL2575). This is transformed using standard methods into the dithiepine 129, but showed only moderate diastereoselectivity in its addition to carbonyl compounds. On the other hand, as we have seen previously for other systems, formation of the 2-acyl compound 130 and reduction or addition of a Grignard reagent gave the products 131 with much better stereoselectivity (91JOC4467). 

Rennie (49), working in my laboratory, succeeded in converting d-glucose into 4-deoxy-D-Jct/Zo-hexose, albeit with considerable difficulty, by the following sequence of reactions which incorporate mercaptalation of the carbonyl group and reductive desulfurization of the dithiol 1 2 D-glucose methyl 2,3-di-0-benzyl-6-0-trityl-a-D-glucopyranoside - ... 

In another procedure, 2-aminobenzophenone is acylated with an sc-azido acid in the presence of l-[3-(dimethylamino)propyl]-3-ethylcarbodiimide and the product 23 is converted into a benzodiazepinone by reductive cyclization with propane-1,3-dithiol (Method F).200... 

Dibenzo[c,g][l,2]dithiocin (4) can be readily prepared by reductive cyclization of the dithiol 3. On the basis of the electronic spectrum analysis it can be concluded that there is no conjugation in the 8-membered ring system of dibenzo[c,g][l,2]dithiocin (4).1... 

Complexes of manganese with the 1,1-dithiolates have been restricted to the (PrSN)3[Mn(i-mnt)3] complex (112) and nitrosyl or carbonyl derivatives, e.g., [7i--CpMn(NO)(S2C==X)] (X = C(CN)C02Et, C(CN)C0NH2, NCN, C(CN)2, or (HNO2) (110, 204, 205). These complexes undergo electrochemical, one-electron oxidations and reductions to afford the neutral or dianionic species. 

The reduction of ribonucleoside triphosphates by various dithiols which are capable of intramolecular cyclization on oxidation (dihydrolipoate, dithioerythritol, dithiothreitol) yields 2 -deoxyribonucleoside triphosphates. These reactions also require 5-deoxyadenosylcorrinoids. 

The coordination of redox-active ligands such as 1,2-bis-dithiolates, to the M03Q7 cluster unit, results in oxidation-active complexes in sharp contrast with the electrochemical behavior found for the [Mo3S7Br6] di-anion for which no oxidation process is observed by cyclic voltammetry in acetonitrile within the allowed solvent window [38]. The oxidation potentials are easily accessible and this property can be used to obtain a new family of single-component molecular conductors as will be presented in the next section. Upon reduction, [M03S7 (dithiolate)3] type-11 complexes transform into [Mo3S4(dithiolate)3] type-I dianions, as represented in Eq. (7). 

Attempts to follow a published procedure for the preparation of 1,3 -dithiole-2-thione-4,5-dithiolate salts [1], involving reductive coupling of carbon disulfide with alkali metals, have led to violent explosions with potassium metal, but not with sodium [2], However, mixtures of carbon disulfide with potassium-sodium alloy, potassium, sodium, or lithium are capable of detonation by shock, though not by heating. The explosive power decreases in the order given above, and the first mixture is more shock-sensitive than mercury fulminate [3],... 

In the former case, the dibromo- or dichloro-substituted arene is reacted with cuprous or sodium thiolates to give vicinal thioethers, which can be reductively dealkylated, for example with Na/NH3, to give the dithiols.63 Alternatively, benzenethiol is reacted with ra-BuLi, and the resulting lithiated product is made to react with elemental sulfur to give the 1,2-dithiolate salt. 

Several studies suggest that LA and DHLA form complexes with metals (Mn2+, Cu2+, Zn2+, Cd2+, and Fe2+/Fe3+) [215-218]. However, in detailed study of the interaction of LA and DHLA with iron ions no formation of iron LA complexes was found [217]. As vicinal dithiol, DHLA must undoubtedly form metal complexes. However, the high prooxidant activity of DHLA makes these complexes, especially with transition metals, highly unstable. Indeed, it was found that the Fe2+-DHLA complex is formed only under anerobic conditions and it is rapidly converted into Fe3+ DHLA complex, which in turn decomposed into Fe2+ and LA [217]. Because of this, the Fe3+/DHLA system may initiate the formation of hydroxyl radicals in the presence of hydrogen peroxide through the Fenton reaction. Lodge et al. [218] proposed that the formation of Cu2+ DHLA complex suppressed LDL oxidation. However, these authors also found that this complex is unstable and may be prooxidative due to the intracomplex reduction of Cu2+ ion. 

Mammalian thioredoxin reductases are a family of selenium-containing pyridine nucleotide-disulfide oxidoreductases. These enzymes catalyze NADPH-dependent reduction of the redox protein thioredoxin (Trx), which contains a redox-active disulfide and dithiol group and by itself may function as an efficient cytosolic antioxidant [77]. One of the functions of Trx/ thioredoxin reductase system is the NADPH-catalyzed reduction of protein disulfide [78] ... 

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