Protease-triggered self-immolative acyl phosphates for controlled phosphate release

The intracellular delivery of phosphate esters remains a challenge, which often requires the use of a prodrug strategy. We report a protease-responsive scaffold that links an enzyme-catalyzed peptide cleavage to a spontaneous intramolecular lactamization onto a sterically encumbered acyl phosphate, resulting in phosphate release. This design represents a distinct mechanistic class of phosphate unmasking, differing fundamentally from phosphoramidate-based ProTides and other esterase-triggered systems. Using a phenylalanine based monoalkyl acyl phosphate as a model substrate, we demonstrate that the scaffold undergoes, chymotrypsin-dependent decomposition to liberate phosphate bearing substrates under mild conditions. The modular synthesis via a modified Staudinger ligation suggests that other protease-recognition sequences could be generated. This proof-of-concept establishes a general platform for enzyme-triggered phosphate release via acyl phosphates with potential applications in prodrug development and intracellular probe delivery.