This invention provides, among other things, novel compounds useful for treating protozoal infections, pharmaceutical compositions containing such compounds, as well as combinations of these compounds with at least one additional therapeutically effective agent. The exemplary compounds have the following formula: wherein X is selected from the group consisting of substituted phenyl, substituted or unsubstituted heteroaryl and unsubstituted cycloalkyl; R3a is selected from the group consisting of H, unsubstituted C1 or C2 or C3 or C4 or C5 or C6 alkyl and unsubstituted C3 or C4 or C5 or C6 cycloalkyl; R3b is selected from the group consisting of H, unsubstituted C1 or C2 or C3 or C4 or C5 or C6 alkyl and unsubstituted C3 or C4 or C5 or C6 cycloalkyl; with the proviso that R3a and R3b, along with the atom to which they are attached, are optionally joined to form a 3 or 4 or 5 or 6 membered ring, with the proviso that R3a and R3b cannot both be H, or a salt thereof.