Herein a friendly method for the preparation of 1-hydroxypyridine-2-one (1,2-HOPO)-containing peptides is described. The elongation of the peptide is carried out on a solid support, using a protecting group for the ε-amino of the Lys that is removable in very mild conditions and that does not provoke cleavage of the peptide from the resin. Once the ε-amino of the Lys is released, HOPO can be incorporated using a commercially available derivative (1,2-HOPO-4-COOH), which has a carboxylic acid at position 4 of the aromatic ring. 1,2-HOPO-4-COOH can be introduced with the free N-hydroxyl or protected with the benzyl group. The former is recommended in many cases. If the protected derivative is to be used, the benzyl group can be removed during global deprotection and cleavage from the resin by adding trifluoromethanesulfonic acid to the cleavage cocktail.

The work was funded in part by the following: the National Research Foundation, South Africa (NRF) (# 105892 and Blue Sky’s Research Programme # 120386) and the University of KwaZulu-Natal (South Africa); and the Spanish Ministry of Science, Innovation, and Universities (RTI2018-093831-B-100), the Generalitat de Catalunya (2017 SGR 1439) (Spain), and Marató TV3 foundation 2018 (#20183530). We thank Professor Miquel Viñas (University of Barcelona) for fruitful discussions.