Solid phase synthesis of α-amino squaric acid-containing peptides

Abstract

A new method has been developed for the synthesis of 3-(1-aminoalkyl)-4-hydroxycyclobut-3-ene-1,2-dione [α-amino squaric acid (α-Asq)]-containing peptides using solid phase peptide synthesis according to an Fmoc protecting group strategy. FmocHN-Gly-[α-Asq]-Oi-Pr was successfully used as a coupling unit in this method, which allowed for the construction of α-Asq-containing hexapeptide libraries including Sq-Gly and Sq-Phe units using the Wang-resin. Peptides containing the α-Asq moiety exhibited inhibitory activity towards a digestive enzyme.