The present invention provides a compound having the structure: wherein R1 is halogen, —NR5R6, —NR5—C(═O)—R6, —NH—C(═O)—OR7, —OR7, —NO2, —CN, —SR7, —SO2R7, —CO2R7, CF3, —SOR7, —POR7, —C(═S)R7, —C(═O)—NR5R6, —CH2—C(═O)—NR5R6, —C(═NR5) R6, —P(═O)(OR5)(OR6), —P(OR5)(OR6), —C(═S)R7, C1-5 alkyl, C2-5 alkenyl, C2-5 alkynyl, aryl, heteroaryl, or heterocyclyl, wherein R5, R6, and R7 and are each, independently, H, C1-5 alkyl, C2-5 alkenyl, C2-5 alkynyl, heteroalkyl, hydroxyalkyl, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, C1-5 alkyl-aryl, or C1-5 alkyl-NH-aryl; Ar1 is phenyl or thiophene; wherein when Ar1 is phenyl, then R1 is other than —C(═O)—NR5R6, where one of R5 or R6 is phenyl or quinoline and the other of R5 or R6 is hydroxyalkyl, or where one of R5 or R6 is quinoline and the other of R5 or R6 is H; and wherein when Ar1 is phenyl, then R1 is other than —NR5—C(═O)—R6, where one of R5 is H and R6 is quinoline, or a pharmaceutically acceptable salt thereof.