[14618-10-1] · C7H5NO5S · 5-Nitro-3H-1,2-benzoxathiole S,S-Dioxide · (MW 215.20)
(peptide coupling reagent)
Physical Data: very pale yellow crystals; mp 148.5-149.5 °C.
Analysis of Reagent Purity: satisfactory microanalytical data have been reported.1
Preparative Method: by nitration of the corresponding sultone.1
5-Nitro-3H-1,2-benzoxathiole S,S-dioxide is a peptide coupling reagent.2,3 Its reactivity derives from the inherent strain present in cyclic five-membered sulfonate esters. These species react with nucleophiles such as carboxylates to form mixed carboxylic sulfonic anhydrides (1) (eq 1), which rearrange via an intramolecular acyl transfer to phenyl esters (2) (eq 2). When the carboxylate nucleophile in eq 1 is that of an N-protected a-amino acid, (2) reacts with a-amino esters to give peptides (eq 3 and Table 1). The process offers the advantage that the byproduct of the coupling reaction (sulfonate (3)) is water-soluble and, therefore, easily removed from the reaction mixture.
University of Bristol, UK