Since no one else has responded to this query, it comfirms what I
suspected: there is little information about oxidative desulfurization.
The last (and maybe only) study I know of was done by Ilse and Edman
[Austalian J. Chem. 16, 411 (1963)], who bubbled air through solutions of
PTC amino acids (they were trying to determine the cause of low repetitive
yields in the Edman degradation). I don't think there has ever been a real
mechanistic study of this reaction. In fact, the term "oxidative
desulfuration" may be a misnomer, because the sulfur in a
phenylthiocarbamyl group can be replaced by oxygen by simple nucleophilic
attack of the C=S bond by hydroxide (desulfurization takes place under
alkaline conditions), followed by loss of H2S. No oxidation is involved,
but the PTC group is transformed to a phenylcarbamyl group.
A historical note:
About 25 years ago I submitted a grant application entitled, "Chemistry of
the Edman Degradation." It was turned down, and one reviewer commented
that, "the Edman degradation is now essentially quantitative and all the
chemical problems have been solved." Well, Edman, in his classic paper
[Begg and Edman, Eur. J. Biochem. 1, 80-91 (1967)], was able to sequence
the first 60 residues of myoglobin, and people today can't do much better,
if as well. During the past 30 years there have been enormous improvements
in the sensitivity of PTH detection, but not much in repetitive
yields......But I'm too old to worry about these things any more.
By the way, if you are interested in a real (and only) physical organic
study of the Edman degradation, see the papers of Drobnica and Augustin
[Coll. Czech. Chem. Comm 30, 99-104 and 1221-1228 (1965). They don't
discuss desulfurization, however.
Richard Laursen
Richard A. Laursen
Department of Chemistry
Boston University
590 Commonwealth Ave.
Boston, MA 02215
Tel (617) 353-2491; FAX (617) 353-6466
email: <laursen@bu.edu>