Formation of 4,4-dialkoxycyclohexa-2,5-dienone N-(thiol-S-yl)imine during reaction of 4-alkoxynitrosobenzenes with thiols in alcoholic solvents.
During the interaction of nitrosoarenes with glutathione in aqueous media, intermediate generation of a highly resonance-stabilized sulfenamide cation has been repeatedly suggested. Most intermediates and end products could be explained by reactions of this sulfenamide cation with different nucleophiles such as excess thiol, solvent water, and metabolically produced arylamine. The present paper presents evidence for adduct formation of the sulfenamide cation with solvent alcohol at neutral pH. Sulfenamide cations generated from 4-nitrosophenetole and 4-nitrosoanisole, respectively, are strongly suggested to form the metastable ketals 4-ethoxy-4-methoxycyclohexa-2,5-dienone N-(glutathion-S-yl)imine and 4,4-dimethoxycyclohexa-2,5-dienone N-(glutathion-S-yl)imine, respectively, during reaction with solvent methanol. Reaction of the two sulfenamide cations in ethanol yielded 4,4-diethoxycyclohexa-2, 5-dienone N-(glutathion-S-yl)imine and 4-ethoxy-4-methoxycyclohexa-2, 5-dienone N-(glutathion-S-yl)imine, respectively. Although the metastability of the ketals did not allow isolation of pure solid material, chromatographic and chemical behavior as well as tandem MS fragmentation substantiate a ketal structure of these intermediates. To confirm the proposed structure, new compounds, 2, 6-dimethyl-4-nitrosophenetole, 2,6-dimethyl-4-nitrophenetole, 2, 6-dimethyl-4-phenetidine, and N-(glutathion-S-yl)-N-hydroxy-4-aminoacetophenone, were synthesized and included in supportive experiments. In summary, the detection of ketals corroborates once more the occurrence of a sulfenamide cation which obviously not only reacts with soft nucleophiles such as GSH but, to a limited extent, also reacts with hard nucleophiles. The toxicological significance of this result is discussed.
Gallemann
D
D
Walther-Straub-Institut, Ludwig-Maximilians-Universität München, Nussbaumstrasse 26, D-80336 München, Germany.gallemann@lrz-muenchen.d e
Greif
A
A
Eyer
P
P
Dasenbrock
J
J
Wimmer
E
E
Sonnenbichler
J
J
Sonnenbichler
I
I
Schäfer
W
W
Buhrow
I
I
D000438:Alcohols / Q000737:chemistry*; D000473:Alkanes / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D004355:Drug Stability; D009682:Magnetic Resonance Spectroscopy; D009603:Nitroso Compounds / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry*; D016339:Spectrometry, Mass, Fast Atom Bombardment; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet; D013438:Sulfhydryl Compounds / Q000737:chemistry*
D000438:Alcohols; D000473:Alkanes; D009603:Nitroso Compounds; D012997:Solvents; D013438:Sulfhydryl Compounds