Synthetic Procedure for <i>N</i>-Fmoc Amino Acyl-<i>N</i>-Sulfanylethylaniline Linker as Crypto-Peptide Thioester Precursor with Application to Native Chemical Ligation
acyl aniline linkers 4 of practical use in NCL chemistry, except in the case of the proline- or aspartic acid-containing linker, were successfully synthesized by coupling of POCl3- or SOCl2-activated Fmoc amino acid derivatives with sodium anilide species 6, without accompanying racemization and loss of side-chain protection. Furthermore, SEAlide peptides 7 possessing various C-terminal amino acids (Gly