Selective efflux inhibitors and related pharmaceutical compositions and methods of treatment

A compound of formula (I), or an enantiomer, diastereomer, tautomer, or pharmaceutically-acceptable salt or hydrate thereof:

• wherein
• R1 is selected from the group consisting of substituted or unsubstituted alkyl, substituted or unsubstituted alkylene, substituted or unsubstituted alkynyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted arylalkyl, and substituted or unsubstituted heteroarylalkyl;
• R2 and R4 are independently selected from the group consisting of hydrogen, halogen, hydroxy, carboxyl, acyl, amino, amide, substituted or unsubstituted alkyl, substituted or unsubstituted alkylene, substituted or unsubstituted alkynyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted arylalkyl, and substituted or unsubstituted heteroarylalkyl;
• R3 is selected from the group consisting of hydrogen, halogen, hydroxy, carboxyl, acyl, amino, amide, substituted or unsubstituted alkyl, substituted or unsubstituted alkylene, or substituted or unsubstituted alkynyl;
• and wherein
• Ra, Rb, Rc, and Rd are independently selected from the group consisting of hydrogen, halogen, hydroxy, carboxyl, oxo, acyl, amino, amide, substituted or unsubstituted alkyl, substituted or unsubstituted alkylene, or substituted or unsubstituted alkynyl, or one or more of Ra, Rb, Rc, and Rd, together with the carbon ring atom to which it is bound, forms carbonyl.