N-Protected amino acid bromides: efficient reagents for the incorporation into peptides of extremely hindered α,α-dialkyl- and α-fluoroalkyl-amino acids

N-Protected amino acid bromides were found to be exceptionally well suited for the coupling of extremely hindered amino acids. Bromides were generated in situ under neutral conditions and used for coupling with a number of α,α-dialkyl- and N-Me-amino acids, affording configurationally pure peptides in very high yields. For the first time, peptide bond formation on the amino group of α-fluoroalkyl-amino acids is described with satisfactory yields.