4-oxo-2, 2, 6, 6-tetramethylpiperidinyl-1-oxy radical (TEMPO), a nitroxide, oxidized 4-substituted Hantzsch 1,4-dihydropyridines (DHP) under UV irradiation in CH3CN to give aromatic products in good yields. A possible mechanism for the oxidation was suggested.

Nitric oxide (NO) is an endogenous compound of the body involved in a variety of biological processes,1 including immunity-regulating functions, physiological control of blood pressure, and neurotransmission. Authentic NO in vivo has only a 0.1 s half-life.2 Nitrosothiols (RSNO), which are formed in vivo from the reaction of NO with protein or nonprotein thiols, can increase the effective tissue half-life of NO.3 RSNO is commonly referred to as a NO-donor and is found in various biological systems, such as in human plasma, airways, white blood cells, and rat cerebellum.4 Nitrosoglutathione (GSNO) has been shown to be one of the most aboundant RSNOs,4c,5,6 e.g., 0.3μM in bronchial lavage fluid and 0.7μM in brain, and to exhibit depressor action.7

Using laser photolysis of basic anaerobic aqueous solutions of a-glycine, L-a-alanine and a-aminoisobutyric acid containing anthraquinone-2,6-disulfonic acid the two spin-polarized (CIDEP) C

Thermal or photolytic reactions of bioactive S-nitrosothiols and related thiols in the presence of radical generators in deaerated DMSO or aqueous solutions under argon or saturated with nitric oxide (NO) produced nitroxides and an oxyaminyl radical, which were well characterized by EPR spectra. Nitroxides containing a thiyl substituent were obtained. Possible mechanisms are proposed. Bioactive S-nitrosothiols such as S-nitrosoglutathione, S-nitroso-N-acetylpenicillamine and related thiols such as glutathione and N-acetylpenicillamine were used for the investigation. Radical generators utilized as transient radical sources were 2,2'-azobisisobutyronitrile, 2,2'-azobis (2-methylpropionamidine) dihydrochloride, tert-butyl peroxide and benzoyl peroxide.

Photochemical or thermal decomposition of azo-compounds (such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylpropionamidine) dihydrochloride, dialkyl peroxides (such as tert-butyl peroxide and diacyl peroxides (such as benzoyl peroxide) in anaerobic nitric oxide (NO)-saturated dimethylsulfoxide (DMSO) or aqueous solutions yielded nitroxides. Well-characterized electron paramagnetic resonance spectra of nitroxides revealed that NO was favorable for reacting with carbon-centered and less stereoinhibited transient alkyl radicals, giving kinds of nitrosoalkane, typically nitrosomethane, which act sequentially as C-nitroso compounds to trap transient radicals present in solution, yielding spin-trapping adducts, i.e. nitroxides. Radicals, including sulfinyl radicals from UV-irradiated DMSO, were trapped by the in situ formed CH3NO. O-centered radicals could not add to the freshly formed C-nitroso compounds. Possible mechanisms are suggested.