Nitrosothiols RSNO

S -nitrosothiols may adopt either cis (64a) or trans (64b) conformations with respect to the S-N bond. S-nitrosocaptopril189 assumes a cis arrangement, while the trans isomer pertains in the solid state for S-nitroso-TV-acetylpenic-illamine and Ph3CSN0.190 The S-N bond lengths are typical for a single bond. Nevertheless, there is a significant barrier to rotation about the S-N bond.189 192 In solution the cis and trans isomers may co-exist. 

Stable S-nitrosothiols and S-nitrososelenols have also been generated by attaching bowl-shaped aryl substituents to the nitrogen centre.193,194 The alkyl derivative (Me3Si)3CSeNO is prepared by nitrosation of (Me3Si)3CSeH with tert-butylnitrite.195 

The ability of S -nitrosothiols to mimic many of the biological properties of NO itself may emanate from in vivo decomposition to generate NO. This decomposition is catalysed by Cu2+,n and may be important in the development of thrombo-resistant devices used in kidney dialysis or coronary by-pass surgery.196 It is also possible that direct transfer of NO from RSNO occurs in biological systems.197 

Tribenzenesulfenamide (PhS)3N is obtained as a pale yellow solid by the treatment of the sodium salt of dibenzenesulfenamide, generated in situ, with acetic anhydride. The perfluorinated analogue (C6F5S)3N is prepared by the reaction of (C6F5S)2NH and C6F5SC1 in diethyl ether.198 

The solid-state structures of (PhS)3N and (CgF5S)3N and the gas-phase structure of (CF3S)3N all show nearly planar S3N units with the S-N bond lengths longer than typical single-bond values. Tribenzenesulfenamide 

5-nitrosothiols, several of which occur naturally, e.g., iS-nitrosocysteine and S-nitrosoglutathione, have an important role in NO transport and regulation in biological systems. Potential appKcations of RSNO compounds include their use as vasodilators in the treatment of angina and in the search for a cure for male impotence. The most convenient route to 5-nitrosothiol formation is the nitrosation of thiols. 

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Some acyclic sulfur-nitrogen compounds also exhibit intense colours. For example, S-nitrosothiols RSNO are either green, red or pink (Section 9.7). Their UV-visible spectra show an intense band in the 330-350 nm region (no it ) and a weaker band in the visible region at 550-600 nm... 

S-nitrosothiols (RSNO) have emerged as important species in the storage and transport of nitric oxide. As NO donors these S-N compounds have potential medical applications in the treatment of blood circulation problems. 

Recently, it has been found that NO donors inhibit HIV-1 replication in acutely infected human peripheral blood mononuclear cells (PBMCs), and have an additive inhibitory effect on HIV-1 replication in combination with 3 -azido-3 -deoxythymisylate (AZT) [139, 140]. S-nitrosothiols (RSNOs) inhibit HIV-1 replication at a step in the viral replicative cycle after reverse transcription, but before or during viral protein expression through a cGMP-independent mechanism. In the latently infected U1 cell line, NO donors and intracellular NO production stimulate HIV-1 reactivation. These studies suggest that NO both inhibits HIV-1 replication in acutely infected cells and stimulates HIV-1 reactivation in chronically infected cells. Thus, NO donors may be useful in the treatment of HIV-1 disease by inhibiting acute infection, or reactivating a latent virus. 

Baciu, C., Gauld, J. W., An assessment of theoretical methods for the calculation of accurate stmctures and S-N bond dissociation energies of S-nitrosothiols (RSNOs),/. Phys. 

DNICs are relatively stable and can be stored at —80°C for weeks without much loss of NO [155], however, their stabilities decrease dramatically at room temperature to render unbound NO. NO bound to thiols may account for the low yield of free NO sometimes detected in solutions involving DNICs in the presence of high concentrations of thiols [126]. The decomposition is acid catalyzed to free NO and S-nitrosothiol (RSNO). Of course, protein-bound DNICs are more stable and serve as potential sinks for low molecular weight DNICs. 

S-Nitrosothiols undergo a reversible transnitrosation reaction at zinc tris(pyrazolyl)boratozinc thiolates, " TpZn-SR. These zinc thiolates are rmreactive toward anaerobic NO but rapidly react with NO in the presence of O2 or anaerobically with NO2 to release the S-nitrosothiol RSNO with formation of the corresponding zinc nitrate 125). 

Finally, there is at least one nonenzymatic proposed route for endogenous HNO production, which follows the decomposition of nitrosothiols (RSNOs) by other thiols (such as glutathione) according to the reaction shown below (Eq. (3)) ... 

Tsou CC, Liaw WF (2011) Transformation of the Fe (NO)2 9 dinitrosyl iron cranplexes (DNICs) into S-nitrosothiols (RSNOs) triggered by add-base pairs. Chemistry 17 13358-13366... 

Dicks, A., Swift, H., Williams, D., Butler, A., Alsadoni, H., Cox, B., 1996. Identification of Cu as the effective reagent in nitric oxide formation from S-nitrosothiols (RSNO). Journal of the Chemical Society, Perkin Transactions 2, 481-487. 

Thionitrites (or S -nitrosothiols), RSNO, are currently believed to be involved in the storage and transport of nitric oxide in the body. The reactivity of this class of compound is clearly of importance and now the reactions of a number of nitrogen nucleophiles with a model compound, 5-nitrosopenicillamine (168), have been investigated. In addition to primary, secondary, and tertiary aliphatic amines, hydrazine. 

In biological systems, 5-nitrosothiols (RSNO) play key roles as reagents for the storage and transport of nitric oxide However, they are usually unstable due... 

Fig. 16.6 Types of NO-releasing/generating polymers, where the NO that is released/gener-ated can prevent activation of platelets that approach the polymer surface. Mazeniumdiolate-based materials undergo proton and thermal driven mechanisms to release NO. 5-nitrosothiol (RSNO)-based polymers can release NO in the presence of heat, light, or metal ions (e.g., Cu+). NO-generating materials consist of immobdized catalysts (e.g., Cu or Se compounds) that generate NO from endogenous RSNOs...

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