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An NMR spectroscopic investigation of the oxidation reactions of DL ‐selenomethionine
Author(s) -
Zainal H. A.,
Wolf W. R.,
Waters R. M.
Publication year - 1998
Publication title -
journal of chemical technology and biotechnology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.64
H-Index - 117
eISSN - 1097-4660
pISSN - 0268-2575
DOI - 10.1002/(sici)1097-4660(199805)72:1<38::aid-jctb863>3.0.co;2-r
Subject(s) - chemistry , hydrogen peroxide , singlet state , selenium , singlet oxygen , chemical shift , nuclear magnetic resonance spectroscopy , medicinal chemistry , photochemistry , organic chemistry , oxygen , physics , nuclear physics , excited state
Oxidation reactions of DL ‐selenomethionine ( DL ‐SeMet) with hydrogen peroxide and ozone were investigated by 1 H and 13 C NMR spectroscopy. Chemical shifts of the reaction products were measured at different pD values in D 2 O solutions. In the moderate (4–8) pD range, a pair of singlets of equal intensity appeared at 2·71 and 2·80 ppm, with the disappearance of the DL ‐SeMet methyl peak at 2·04 ppm. As the pD of the solution decreased, the chemical shifts of both peaks increased relative to 3‐trimethylsilylpropionic acid‐d 4 sodium salt. In strongly acidic solutions (pD<3), the pair collapsed to one singlet at 3·18 ppm. As pD values increased the chemical shifts decreased in numerical value with only a singlet at 2·69 ppm observed in strongly basic solutions (pD>10). These data were assigned to Met selenoxide in basic solution, stabilized by intermolecular hydrogen bonding, and to the hydration of Met selenoxide to Met dihydroxyselenide in acidic solutions. In moderate pD solutions (pD = 4–8), both forms of the selenoxide can exist. For the reaction of DL ‐SeMet with CNBr, two parallel reactions occur, i.e. oxidation and bond cleavage with cyanization: the bond cleavage giving the expected products, i.e. 2‐amino‐4‐butyrolactone and methyl selenocyanate, with an additional singlet observed at 2·54 ppm. © 1988 SCI