Ottilia Andersson, Christodoulos Mitrogiannis, Oscar Verho, Johan Wannberg

Tetrahedron Chem

DOI: 10.1016/j.tchem.2026.100174

Abstract

DNA-encoded library (DEL) synthesis currently relies on a limited repertoire of DNA-compatible protecting group strategies, highlighting the need for orthogonal methods to expand accessible chemical space. Herein, we report a synthetic strategy for the conjugation of phthalimide-protected amino acids to DNA and their subsequent deprotection on-DNA. Optimization studies established mild coupling and deprotection conditions that minimized competing phthalimide hydrolysis, with ethylene-1,2-diamine in aqueous MOPS buffer/acetonitrile affording moderate to good deprotection yields across a range of DNA-conjugated phthalimide-protected amino acids. More sterically demanding substrates required elevated temperatures but remained amenable to deprotection. The utility of the developed protocol was further demonstrated through a subsequent on-DNA amide coupling following phthalimide deprotection. Collectively, these findings establish phthalimide as a removable amine-protecting group for on-DNA synthesis and provide a foundation for its use in sequential functionalization workflows for DEL synthesis.