1,1-Diphenyl-2-methylsulfinyl ethanol: a model compound to study the reactivity towards CNBr of a photoadduct of methionine on CγH2

The photoadduct formed by photolysis of the [Bapa0, (pBzl)Phe5, Met(O2)11]SP/NK-1 complex localised within the T173MP175 domain of the NK-1 receptor cannot be cleaved by CNBr on the C-side of methionine; an unusual rearrangement of the intermediate sulfonium instead occurred. The reactivity of 1,1-diphenyl-2-methylsulfinyl ethanol 10 towards CNBr treatment and the stability of the 1,1-diphenyl oxirane 14 were analysed by NMR and mass spectrometry. 1,1-Diphenyl ethylene 13 can be formed from epoxide 14 even in slightly acidic conditions and during positive DCI/NH3 mass spectrometry analysis. Altogether, these results suggest that if a covalent linkage between the [Bapa0, (pBzl)Phe5, Met(O2)11] and the NK-1 receptor occurred on the CγH2 of methionine-174, CNBr treatment will lead to an epoxide/ketone and an ethylenic compound.