Conversion of Thiosulfinate Derivatives of Cystine to Unsymmetrical Cystines and Lanthionines by Reaction with Tris(dialkylamino)phosphines

Article abstract of DOI:10.1021/jo00222a026

Synthetic routes to the unsymmetrical lanthionines 2 and 3 have been developed.Reaction of a thiosulfinate, derived by oxidation of the corresponding symmetrical cystine with m-chloroperbenzoic acid, with a protected cysteine in the presence of a tris(dialkylamino)phosphine, hexaethylphosphorus triamide, yielded an unsymmetrical or mixed cystine.Contraction of the disulfide linkage in the appropriate mixed cystine by reaction with hexaethylphosphorus triamide provided the unsymmetrical lanthionines 2 and 3.A second route to unsymmetrical lanthionines was investigated that involved the attempted displacement of sulfonate leaving groups from di- or tripeptides containing a serylvaline residue.The sulfonate ester function was observed to be very unreactive toward displacement by mercaptide anion in these peptides, a fact that may be due to steric or conformational effects originating from the adjacent valine residue.