D. Cabaret et M. Wakselman, A LOW-EPIMERIZING PEPTIDE COUPLING REAGENT BASED ON THE REARRANGEMENTOF A CARBOXYLIC-SULFONIC MIXED ANHYDRIDE, Tetrahedron letters, 35(51), 1994, pp. 9561-9564
A series of peptides has been prepared using an o-hydroxybenzenesulfon
yl chloride as the condensation reagent. Experimentally, the coupling
is a one pot two-steps reaction: formation and aminolysis of a substit
uted aryl ester. The first step occurs by an elimination-addition reac
tion involving a sulfoquinone intermediate, followed by an efficient s
ix-membered acyl transfer reaction in the phenolic carboxylic-sulfonic
mixed anhydride intermediate. The Young and Anteunis tests show that
the degree of epimerization is very low in methylene chloride and acet
onitrile.