Fmoc-removal of a heptapeptide in solution and on solid support using 20% piperidine in different solvents as reported by Jad et al.^36a.

^aColour code for Fmoc-removal performance: green: good; orange: moderate; red: poor.

^bFmoc-Phe-OH (0.1 mmol) was dissolved in the solvent to be studied and toluene was added as an internal standard. Piperidine was added, and the reaction was monitored by RP-HPLC.

^cTime required to achieve complete Fmoc-removal.

^dThe resin was swelled in the solvent to be studied followed by addition of 20% piperidine in the same solvent for 45 s or 7 min. The resin was washed and coupled with Boc-Gly-OH, COMU® and DIPEA in DMF. Fmoc-removal of any remaining Fmoc-protected peptide was performed by treatment with 20% piperidine in DMF, followed by coupling with Boc-Leu-OH, COMU®, and DIPEA in DMF. The yield was calculated by the ratio of H-Gly-Ile-Asp-Tyr-Ile-Asn-Gly-NH₂vs. H-Leu-Ile-Asp-Tyr-Ile-Asn-Gly-NH₂.

^e16.6% of starting materials after stirring for 30 min.