A compound, or a pharmaceutically acceptable salt or ester thereof, according to formula I:

R20—(Z)b—(Y)c—(R21)a—(X)d—R22—R23

wherein R20 is aryl, substituted aryl, heteroaryl, substituted heteroaryl, cycloalkyl, substituted cycloalkyl, heterocycloalkyl, substituted heterocycloalkyl, alkoxy, aryloxy, a thio-containing group, or a seleno-containing group; Z is alkanediyl, substituted alkanediyl, cycloalkanediyl, or substituted cycloalkanediyl; Y is S, O, S(═O), —S(═O)(═O)—, or NR10, wherein R10 is H or alkyl; R21 is alkanediyl, substituted alkanediyl, cycloalkanediyl, substituted cycloalkanediyl, alkadienyl, substituted alkadienyl, cycloalkenediyl, substituted cycloalkenediyl, alkatrienyl, substituted alkatrienyl; X is —C(═O)—, —S(═O)(═O)—, or —N(H)C(═O)—; R22 includes at least one divalent amino radical; R23 is aryl, substituted aryl, heteroaryl, substituted heteroaryl, cycloalkyl, substituted cycloalkyl, heterocycloalkyl, substituted heterocycloalkyl, alkoxy, aryloxy, a thio-containing group, or a seleno-containing group; a, b, c, and d independently are 0 or 1.