A Diketone Linchpin Strategy for On-DNA Macrocyclization and Late-Stage Diversification.

We report a DNA-compatible linchpin strategy for the construction and late-stage diversification of macrocyclic peptide DNA-encoded libraries (MPDELs). Treatment of DNA-conjugated linear peptides with 1,5-dichloropentane-2,4-dione (DPD) enabled highly efficient macrocyclization while introducing a versatile 1,3-diketone linchpin. Subsequent DNA-compatible late-stage diversification afforded four classes of heterocycle-embedded DNA-conjugated macrocycles, including pyrazoles, azolopyrimidines, 2-aminonicotinamides, and 2-hydroxynicotinonitriles, with a broad substrate scope and high conversion. A scale-up test, cross-substrate scope study, and enzymatic ligation demonstrated excellent compatibility with DNA-encoded library synthesis, providing a versatile platform for expanding the chemical space of macrocyclic peptide DNA-encoded libraries.