Reactions of Bunte salts with carbocations of isobenzofuranone and isoindolone

Reduction with tris(2-carboxyethyl)phosphine (TCEP) enables the use of an S-sulphonate protecting group for thiol-mediated bioconjugation

“…For example, S-sulphocysteine derivatives have been used during peptide synthesis, 3 the preparation of carbapenem antibiotics, 4 RAFT polymerisation reactions, 5 the preparation of self-assembled monolayers on gold surfaces, 6 or reactions with isobenzofuranone and isoindolone carbocations. 7 S-Sulphonates, also known as Bunte salts or S-alkyl thiosulphates, can be efficiently prepared either by oxidation of thiols in presence of sulphites, 8 or by nucleophilic substitution of alkyl halides with thiosulphate (Scheme 1). 9 However, deprotection reactions from the Bunte salts in aqueous solutions reported so far occur under strong acidic conditions, 10 by exchange reactions in the presence of high concentrations of other thiols, 9 or by reduction with NaBH 4 .…”