Coumarin derivatives as protease-sensitive prodrugs

To overcome the lack of selectivity of anticancer drugs toward malignant cells, the development of prodrugs, which could be activated selectively by tumour-specific proteases is the goal of these studies. In this work tripartate prodrugs have been evaluated consisting of a carrier unit and a spacer group, which allows for intramolecular cyclisation while releasing the third component, the compound attached to the carboxylic acid moiety of the spacer group. As carrier units amino acids or peptides have been used, which are required for recognition by the protease. As the spacer unit the "trimethyl-lock"-spacer has been applied; as a model leaving group p-anisidine was attached to the carboxylic acid moiety. It was intended to test the compounds for their releasing rate of p-anisidine. Two of the evaluated compounds, 9b and 9h, were degraded with half-lives of 46 min at room temperature. However, the poor solubility in aqueous solutions proved the major disadvantage of the TML-based prodrugs.