[2] Rapid in situ neutralization protocols for Boc and Fmoc solid-phase chemistries

This chapter discusses rapid in situ neutralization protocols for Boc and Fmoc solid-phase chemistries. The protocols for Boc chemistry are characterized by the use of a single and inexpensive solvent dimethylformamide (DMF), to maintain maximum solvation of the peptide-resin. This ensures swelling of the peptide-resin while potentially aiding the disaggregation of intermolecularly H-bonded aggregates, a major contributor to “difficult sequences.” Rapid flow washes of the swollen peptide-resin, combined with high concentrations (0.3–0.5 M) of activated amino acids and in situ neutralization, provide improved coupling efficiencies. Together with modern analytical techniques for peptide analysis such as mass spectrometry (MS) and MS combined with liquid chromatography (LC–MS), it is now feasible to observe and determine the nature of the various side products in solid-phase peptide synthesis (SPPS). Such analyses are critical for future improvements in peptide synthesis.