One-pot full peptide deprotection in Fmoc-based solid-phase peptide synthesis: methionine sulfoxide reduction with Bu4NBr

The reduction of methionine sulfoxide with Bu4NBr in TFA is reported. The use of this reagent in conjunction with Fmoc chemistry-based acidolytic cocktails and the short reaction times that are needed for sulfoxide reduction (5 min) are the main advantages of this method, which is compatible with peptides containing aromatic amino acids. Cysteine is also stable under these conditions although, if desired, simultaneous disulfide formation can be achieved in the absence of thiols.