Oxazolo[3,2-a]pyridine. A new structural scaffold for the reversal of multi-drug resistance in Leishmania.

Compounds belonging to three different classes of fused heterocyclic systems, structurally related to Calcium-channel blockers of the 1,4-dihydropyridine family, were evaluated in their ability to overcome leishmanial resistance to common drugs in a MDR Leishmania tropica strain. Compounds with the skeletal basis of oxazolo[3,2-a]pyridine displayed significant reversion of resistance to daunomycin and miltefosine, with reversion indexes up to 6.7-fold and 8.7-fold, respectively. Most interestingly, the enantiopure compound 20S attained to revert the resistance to both drugs and fairly more significantly than its enantiomer 20R.