Investigations on Solid‐Phase Peptide Synthesis in N‐to‐C Direction (Inverse Synthesis)

Abstract The possibility of peptide assembly in the N‐C direction by using HOBt salts of the amino acid 9‐fluorenylmethyl esters has been investigated. The first amino acid derivative has to be coupled with the N‐terminus to the polymer‐bound trityl linker. Determination of the loading with the first amino acid derivative could be carried out according to the same method as for Fmoc‐amino acids on the resin. Kinetic measurements were made of both the coupling of the amino acid derivatives during chain elongation, and the cleavage of the peptide from the resin. Several C‐terminally modified peptides were synthesized with chain elongation being monitored by UV as it is standard practice in peptide synthesis in the usual direction. Particular attention was paid to racemization that may possibly occur.