Photochemistry of N-nitroso-N-alkyl amino acids: a facile oxidative decarboxylation

Abstract

Thispaper is dedicated to Prof. Raymond U . Lemieux on the occasion of his 60th birthday YUAN L. CHOW, DOUGLAS P. HORNING, and JOEL POLO. Can. J. Chem. 58,2477Chem. 58, (1980. Several N-alkyl or N-phenyl-N-nitroso a-amino acids were synthesized and were shown to photolytically rearrange to amidoximes with concurrent decarboxylation in solution or solid states without the presence of externally added acids. In contrast, N-nitrosonipecotinic acid, a N-nitroso p-amino acid, as well as N-nitrosopiperidine in the presence of acetic acid were not photolabile. The photolability of N-nitroso a-amino acids was ascribed to the presence of an intramolecular association between the nitrosamino and carboxyl groups through hydrogen bonding. The species having the hydrogen bonding through the nitroso oxygen in the 2-configuration was believed to be photolabile and decomposed to alkylideneimines as the primary product. The mechanism of the oxidative photorearrangement was discussed.

Mutagenicity and NO Formation from UVA Irradiated N-Nitrosoproline, and Characterization of Photoproduct Formed in UVA-irradiated Mixture of N-Nitrosoproline with 2^|^prime;-Deoxyguanosine in Neutral Solution

“…5, Reaction 3) (17). Our present work suggests that the photoreaction of NPRO might trigger multiple reactions, namely, 1) NPRO may react with phosphate to create a mutagenic substance and 2) NPRO can facilitate UVA-induced release of NO to create an aminium ion and subsequent production of an alkyl-radical as well as active oxygen species that could generate 8-oxodG from dG (Fig.…”

“…Chow et al (17) observed that UVC-photolysis of NPRO produced piperidonoxime with the release of NO (Fig. 5, Reaction 2).…”

“…UVA-photolysis of NPRO and NO production was observed in both aqueous and nonaqueous NPRO solutions. Although photo-elimination of NO radical from N-nitrosodimethylamine was stimulated by hydrogen bonding under acidic aqueous conditions (25), N-nitroso-a-amino acids may participate in intramolecular hydrogen bonding (17). The photo-induced elimination of nitric oxide from NPRO dissolved in methanol and acetonitrile may progress via intramolecular hydrogen bonding between the N-nitroso and carboxy moieties.…”

“…Earlier studies in our laboratory showed that UVA-irradiated NPRO could be converted to a direct mutagenic compound that can produce strand breaks in treated DNA on the release of nitric oxide (NO) and active oxygen species (16). Chow et al (17) showed that nitroso-a-amino acids including NPRO can be UVCphotolyzed to release NO. Suzuki et al have shown that treatment of dG with NO in acetate buŠer (pH 3.7) produces 2?-deoxyoxanosine (dO), 2?-deoxyxanthosine (dX), 2-nitro-deoxyinosine, and 8-oxo-7,8-dihydro-2?-deoxyguanosine (8-oxodG) (18).…”