Synthesis of activity-based carbocyclic probes for the specific inhibition and detection of glucuronidases

Abstract

Glucuronidases are part of the glycosidase enzyme family that cleaves polysaccharide chains in organisms. In humans, exo-acting β-glucuronidase and endo-acting heparanase were identified as the main glucuronidases, though, despite their important function in the body, their disfunction plays a significant role in various diseases, including Sly syndrome, Crohn’s disease and cancer. To design novel drugs to treat these diseases, understanding the role of these enzymes in pathology is crucial. Though structures have been identified that can act as irreversible inhibitors and activity-based probes, the current generation lacks the enzyme specificity required to be utilized as diagnostic tools.

A cyclophellitol derivative with an aziridine warhead, which was previously synthesized and evaluated by Wu et al., showed a higher specificity as a glucuronidase inactivator than its predecessors. A crucial step in its synthesis, the installation of the aziridine ring, is, however, met with poor yields and side-product formation, and requires four individual reaction steps. The goal of this project was to explore an alternative one-step method to install the aziridine warhead utilizing Du Bois’ catalyst and O-(2,4-dinitrophenyl)hydroxylamine (DPH).

Although the final structure could not be synthesized due to time constraints, the work in this thesis shows that the ester located at the C6 position may not need to be reduced whilst generating the cyclophellitol aziridine scaffold. This could potentially allow for a milder, more convenient implementation of the COO- functionality at a later stage. Furthermore, it was shown that BCl3 could be used for an effective debenzylation of the carbocycle intermediate with good yields under mild conditions.