Tuberculosis is an ancient, contagious and possibly deadly disease caused by the infection with bacterium Mycobacterium tuberculosis. The bacterial cell wall has an unusual structure and is composed of mycolic acids. The immunity of M. tuberculosis to antituberculosis drugs used in standard therapy poses a serious problem. Isoniazid, first-line agents, is a prodrug and needs to be activated in vivo by KatG enzyme. The formed adduct is a strong inhibitor of the enzyme InhA, present in biosynthesis of mycolic acids. Due to common mutations on KatG enzyme, the inhibitors directly targeting the InhA enzyme become auspicious candidates for the development of active substances against the growing threat of M. tuberculosis strains that are immune to medications.
In the first part of our research we synthesised four potential direct inhibitors of enzyme InhA (7, 8, 15 and 16). We used the compound ? in which we replaced the tetrahydropyran part with 1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine with different substituents in positions 1 and 6. This way we could explore chemical space in the active site of InhA enzyme where lipophilic interactions between the substance and the binding site take place. At the Faculty of Pharmacy, they defined the synthesised compounds as IC50. The compound 15 exhibited the highest activity with IC50 totalling 830 nM. According to our predictions that only one enantiomer is responsible for the activity, we concluded that a chiral separation would be more reasonable for the molecule with a chiral centre. Furthermore, we found out that in 1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine the replacement of the substituent in position 6 is essential due to the instability of pyrrole.
In the second part of our research we performed chiral separation of the racemic mixture of thiadiazole inhibitor InhA M1155 and of immunoproteasome inhibitor LR114P. We carried out the direct chiral separation by HPLC. We did not manage to separate the enantiomers of the first compound on baseline. Nevertheless, we obtained adequate results for future research. The optimisation of the conditions for the separation of the second compound enabled the baseline separation of enantiomers. Gathered individual fractions of enantiomers will be used at the Faculty of Pharmacy for further testing.