Eoin R. Gould

Catalyst selective and regiodivergent O- to C- or N-carboxyl transfer of pyrazolyl carbonates: synthetic and computational studies

The regiodivergent O- to C- or N-carboxyl transfer of pyrazolyl carbonates is described, with DMAP giving preferential N-carboxylation and triazolinylidenes promoting selective C-carboxylation (both with up to >99 : 1 regioselectivity). An enantioselective O- to C-carboxyl variant using NHC catalysis is demonstrated (up to 92% ee), while mechanistic and DFT studies outline the pathways operative in this system and provide insight into the reasons for the observed selectivity.

Photo-affinity labelling and biochemical analyses identify the target of trypanocidal simplified natural product analogues

Current drugs to treat African sleeping sickness are inadequate and new therapies are urgently required. As part of a medicinal chemistry programme based upon the simplification of acetogenin-type ether scaffolds, we previously reported the promising trypanocidal activity of compound 1, a bis-tetrahydropyran 1,4-triazole (B-THP-T) inhibitor. This study aims to identify the protein target(s) of this class of compound in Trypanosoma brucei to understand its mode of action and aid further structural optimisation. We used compound 3, a diazirine- and alkyne-containing bi-functional photo-affinity probe analogue of our lead B-THP-T, compound 1, to identify potential targets of our lead compound in the procyclic form T. brucei. Bi-functional compound 3 was UV cross-linked to its target(s) in vivo and biotin affinity or Cy5.5 reporter tags were subsequently appended by Cu(II)-catalysed azide-alkyne cycloaddition. The biotinylated protein adducts were isolated with streptavidin affinity beads and subsequent LC-MSMS identified the FoF1-ATP synthase (mitochondrial complex V) as a potential target. This target identification was confirmed using various different approaches. We show that (i) compound 1 decreases cellular ATP levels (ii) by inhibiting oxidative phosphorylation (iii) at the FoF1-ATP synthase. Furthermore, the use of GFP-PTP-tagged subunits of the FoF1-ATP synthase, shows that our compounds bind specifically to both the α- and β-subunits of the ATP synthase. The FoF1-ATP synthase is a target of our simplified acetogenin-type analogues. This mitochondrial complex is essential in both procyclic and bloodstream forms of T. brucei and its identification as our target will enable further inhibitor optimisation towards future drug discovery. Furthermore, the photo-affinity labeling technique described here can be readily applied to other drugs of unknown targets to identify their modes of action and facilitate more broadly therapeutic drug design in any pathogen or disease model.

Development of Simplified Heterocyclic Acetogenin Analogues as Potent and Selective Trypanosoma brucei Inhibitors

Neglected tropical diseases caused by parasitic infections are an ongoing and increasing concern. They are a burden to human and animal health, having the most devastating effect on the world′s poorest countries. Building upon our previously reported triazole analogues, in this study we describe the synthesis and biological testing of other novel heterocyclic acetogenin‐inspired derivatives, namely 3,5‐isoxazoles, furoxans, and furazans. Several of these compounds maintain low‐micromolar levels of inhibition against Trypanosoma brucei, whilst having no observable inhibitory effect on mammalian cells, leading to the possibility of novel lead compounds for selective treatment.

Non-natural Acetogenin Analogues as Potent Trypanosoma brucei Inhibitors

Neglected tropical diseases remain a serious global health concern. Here, a series of novel bis‐tetrahydropyran 1,4‐triazole analogues based on the framework of chamuvarinin, a polyketide natural product isolated from the annonaceae plant species are detailed. The analogues synthesized display low micromolar trypanocidal activities towards both bloodstream and insect forms of Trypanosoma brucei, the causative agent of African sleeping sickness, also known as Human African Trypanosomiasis (HAT). A divergent synthetic strategy was adopted for the synthesis of the key tetrahydropyran intermediates to enable rapid access to diastereochemical variation either side of the 1,4‐triazole core. The resulting diastereomeric analogues displayed varying degrees of trypanocidal activity and selectivity in structure–activity relationship studies. Together, the biological potency and calculated lipophilicity values indicate that while there is room for improvement, these derivatives may represent a promising novel class of anti‐HAT agents.

Design and Synthesis of Broad Spectrum Trypanosomatid Selective Inhibitors

Neglected tropical diseases caused by parasitic infections are an ongoing and increasing concern that have a devastating effect on the developing world due to their burden on human and animal health. In this work, we detail the preparation of a focused library of substituted-tetrahydropyran derivatives and their evaluation as selective chemical tools for trypanosomatid inhibition and the follow-on development of photoaffinity probes capable of labeling target protein(s) in vitro. Several of these functionalized compounds maintain low micromolar activity against Trypanosoma brucei, Trypanosoma cruzi, Leishmania major, and Leishmania donovani. In addition, we demonstrate the utility of the photoaffinity probes for target identification through preliminary cellular localization studies.

Simplifying nature: Towards the design of broad spectrum kinetoplastid inhibitors, inspired by acetogenins.

The need for new treatments for the neglected tropical diseases African sleeping sickness, Chagas disease and Leishmaniasis remains urgent with the diseases widespread in tropical regions, affecting the worlds very poorest. We have previously reported bis-tetrahydropyran 1,4-triazole analogues designed as mimics of the annonaceous acetogenin natural product chamuvarinin, which maintained trypanocidal activity. Building upon these studies, we here report related triazole compounds with pendant heterocycles, mimicking the original butenolide of the natural product. Analogues were active against T. brucei, with a nitrofuran compound displaying nanomolar trypanocidal activity. Several analogues also showed strong activity against T. cruzi and L. major. Importantly, select compounds gave excellent selectivity over mammalian cells with a furan-based analogue highly selective while remaining active against all three cell lines, thus representing a potential lead for a new broad spectrum kinetoplastid inhibitor.