N , N -Diisopropylethylamine (DIPEA) PEPTIPURE ® ≥99,5 %, for peptide synthesis Diisopropylethylamine (DIPEA) is a tertiary amine, which makes it a strong organic base with a pKa value of about 11. It is often used as a nucleophilic catalyst to promote the formation of peptide bonds in solid phase peptide synthesis (SPPS). DIPEA is often used in peptide synthesis because of its high basicity and low nucleophilicity. It can promote the reaction between the carboxyl group of the activated amino acid and the amine group of the growing peptide chain without affecting the formation of the peptide bond. In addition, DIPEA can improve the deprotection of amino acid residues during peptide synthesis by scavenging acidic impurities.