Development of Efficient Synthetic Method for N-Amino Acyl N-Sulfanylethyl Anilide Linkers as Peptide Thioester Equivalent

摘要

Native chemical ligation (NCL) which features the use of peptide thioesters is the most practical fragment condensation method for the synthesis of proteins [1]. However, preparation of peptide thioesters using Fmoc SPPS has encountered some problems including decomposition of thioesters during peptide chain elongation. Previously, we reported that N-sulfanylethylanilide (SEAlide) peptides 1 as a peptide thioester equivalent could be synthesized using N-Fmoc amino acyl N-sulfanylethyl anilide linkers 2 by Fmoc SPPS [2]. Although requisite amino acyl linkers 2 have been prepared using Fmoc amino acyl chlorides resulting from treatment of Fmoc amino acids with SOC12, such treatment induces the loss of acid-labile protections such as fert-butyl group. In this paper, we report an efficient introduction method of Fmoc amino acid derivatives to the N-sulfanylethyl aniline linker 3. In addition, the synthesis of a human GM2 activator protein (GM2AP) analog, which is an essential glycoprotein co-factor for degradation of ganglioside GM2 by P-hexosaminidase A (HexA) [3], using the SEAlide peptides 1 is also described.