Reexamination of the Aqueous Chemistry of N-Nitroso-3-hydroxymorpholine, a Metabolite of the Carcinogen N-Nitrosomorpholine

Abstract

N-Nitroso-3-hydroperoxymorpholine was synthesized in 12 steps starting from a commercially available serine derivative and was subsequently characterized by elemental analysis, one-dimensional (1)H and (13)C NMR spectroscopy, and homonuclear and heteronuclear two-dimensional methods. Treatment of the hydroperoxide with triarylphosphine or trialkylphosphine in CD(2)Cl(2) or CD(3)CN yields N-nitroso-3-hydroxymorpholine, a putative metabolite of the carcinogen N-nitrosomorpholine, as indicated by (1)H and (13)C NMR spectroscopy. A study of the decomposition of N-nitroso-3-hydroxymorpholine in aqueous buffer solution, ionic strength 1 M (KCl), at 25 degrees C is reported. The kinetics of decay obey a three term rate law, with terms for a hydrogen ion-dependent, pH-independent, and hydroxide ion-dependent reactions, similar to what has been reported for other alpha-hydroxynitrosamines. The stability of this compound is similar to that of alpha-hydroxynitrosopiperidine reported previously. The reaction of 3-hydroxymorpholine in aqueous solution, 25 degrees C, pH 6.6, yields (2-hydroxy-ethoxy)acetaldehyde (62%), acetaldehyde (26%), and glycolaldehyde (26%), based on analysis of the dintrophenylhydrazine derivatives. Both the stability and the products of decay of N-nitroso-3-hydroxymorpholine that are reported here contrast strongly with a previous description.

Comparative theoretical investigation of the formation of DNA interstrand crosslinks induced by two kinds of N‐nitroso compounds: nitrosoureas and nitrosamines

“…This indicates that the α‐hydrolyzed nitrosamines are more facile to break down to aldehydes and alkydiazohydroxide than CENUs. The experimental results of Fishbein and colleagues lend strong support to this conclusion, which demonstrated that almost all α‐hydroxynitrosamines were unstable in aqueous environments and decomposed spontaneously with a half life of less than 1 min at 37 °C.…”

The Reaction of Peroxynitrite with Morpholine (Secondary Amines) Revisited: The Overlooked Hydroxylamine Formation

“…The several observed carbonyl 13 C-NMR resonances strongly indicate that oxidative opening of the morpholine ring proceeds at other positions, too. Additional, ring-opened products may also be expected from oxidative attack on the early products, e.g., MorNO [52]. Noteworthy, no monosubstituted morpholinederived products were detected in the 13 C-NMR spectra, indicating that such compounds are rapidly further oxidized and/or easily decomposed by hydrolysis [52].…”

Trapping of a Cross-Link Formed by a Major Purine Adduct of a Metabolite of the CarcinogenN-Nitrosomorpholine by Inorganic and Biological Reductants

“…16 Introduction of cross-link reducing reagent was typically followed by a 30 minute incubation prior to acidification and depurination.…”

“…A solution of 3-hydroperoxy-N-nitrosomorpholine (HOONOMO – 11 , Scheme 1) 16 in acetonitrile was added to a buffered aqueous solution (0.05 M 70% anion cacodylic acid buffer, pH 6.9) containing tris(2-carboxyethyl)phosphine hydrochloride (TCEP) from a freshly neutralized stock and calf thymus DNA. The final concentrations were 10 mM in α-HOONOMO, 10 mM TCEP, and ∼0.5 mg/mL calf thymus DNA.…”