Glycolamidic ester group as labile linkage in solid phase peptide synthesis: use with FMOC‐protected amino acids

The glycolamidic ester (‐O‐CH2‐CO‐NH‐) was tested as labile linkage group in solid phase peptide synthesis using a polyacrylic resin and base‐cleavable fluor‐enylmethoxycarbonyl (FMOC) protecting group for α NH2. Although the glycolamidic ester group was known to be highly labile in basic conditions, the 32–36 thymopoietin segment, Arg‐Lys‐Asp‐Val‐Tyr (TP5), was obtained with high yield using a FMOC‐tBU strategy. The peptide was first deprotected on the carrier and then removed by saponification. The TP5 thus isolated was shown to be pure by high pressure liquid chromatography and amino acid analysis.