Hydrolysis of 5-methylfuran-2-yl to 2,5-dioxopentanyl allows for stable bio-orthogonal proximity-induced ligation.

Ligation methodologies featuring bio-orthogonal units and leading to the formation of a stable adduct are the ideal candidates for being applied in a biological context. However, most of the available strategies rely on highly reactive species that require careful handling, or on the activation of pro-reactive functional groups. We here report on a proximity-induced ligation reaction that relies on a stable 2,5-dione, that can be conveniently generated under acidic conditions from a 2,5-dialkylfuran building block, and hydrazine nucleophiles. This bio-orthogonal ligation, which proceeds under physiological conditions, does not require any stimulus or trigger and leads to the formation of a pyridazinium adduct that demonstrates excellent stability under harsh conditions (24 h at 90 °C). The reaction was applied to the formation of PNA-PNA adducts, DNA- and RNA-templated ligations, and for the formation of peptide-peptide adducts in solution. This convenient methodology was further implemented on plastic and glass surfaces to realize self-addressable covalent constructs.