Oxidized l-glutathione was esterified to the tetra methyl ester using thionyl chloride in methanol solvent. Other alcohols were tested and the reaction progress was monitored via ESI-MS. This procedure proved to be compatible with other small peptides not containing serine and cysteine residues. In contrast to previously reported methods this procedure provided convenient access to esterified peptides requiring no purification, extended reaction times, or complicated reaction setups.
