A modified backbone amide linker (BAL) solid-phase peptide synthesis strategy accommodating prolyl, N-alkylamino acyl, or histidyl derivatives at the C-terminus

A new variation of the Backbone Amide Linker (BAL) approach has been developed for Nα-Fmoc solid-phase synthesis (SPS) of C-terminal modified peptides; this provides a convenient route to peptides containing prolyl, N-alkylamino acyl, or histidyl derivatives at the C-terminus. To illustrate the principles, several model peptides were prepared in high yields and excellent purities; diketopiperazines and racemized byproducts which otherwise form when alternative procedures are used were absent from the syntheses reported herein.