New methods in peptide synthesis. Part IV. N → S transfer of N-o-nitrophenylsulphenyl groups in cysteine peptides

Abstract

When the N-o-nitrophenylsulphenyl group is removed from cysteine peptides by means of hydrogen chloride in methanol or non-polar solvents, or by means of acids in aqueous methanol or acetone, an N → S transfer of the o-nitrophenylsulphenyl-group takes place, to give the corresponding S-o-nitrophenylsulphenyl derivative. Even in alkaline solution transfer of the o-nitrophenylsulphenyl group from the α-amino-group to the thiol can occur to some extent.