An NMR spectroscopic investigation of the oxidation reactions of DL-selenomethionine

✍ Scribed by H. A. Zainal; W. R. Wolf; R. M. Waters

• Publisher: Wiley (John Wiley & Sons)
• Year: 1998
• Tongue: English
• Weight: 252 KB
• Volume: 72
• Category: Article
• ISSN: 0268-2575
• DOI: 10.1002/(sici)1097-4660(199805)72:1<38::aid-jctb863>3.0.co;2-r

✦ Synopsis

Oxidation reactions of DL-selenomethionine (DL-SeMet) with hydrogen peroxide and ozone were investigated by 1H and 13C NMR spectroscopy. Chemical shifts of the reaction products were measured at di †erent pD values in solutions. In the moderate (4È8) pD range, a pair of singlets of equal inten-D 2 O sity appeared at 2É71 and 2É80 ppm, with the disappearance of the DL-SeMet methyl peak at 2É04 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 3É18 ppm. As pD values increased the chemical shifts decreased in numerical value with only a singlet at 2É69 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 \ 4È8), 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 2É54 ppm.

1988 SCI