A compound, or a pharmaceutically acceptable salt thereof, having a structure of wherein Z is aryl or substituted aryl, heteroaryl, or substituted heteroaryl; X is —S—, —S(O)—, or S(O)2—; R20 and R21 are each independently H, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, aryl, substituted aryl, or halogenated alkyl; one of R22, R23, and R24 is —O— and the others of R22, R23 and R24 are independently —CH2—, or —C(R13)— wherein R13 is alkyl, alkenyl, alkynyl, trialkylsilyl group, or —(CH2)mOR15, wherein R15 is alkyl or an aryl and m is an integer in the range of 1 to 10; and R25 is H, alkyl, substituted alkyl, halogen, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl, C1-C3 alkoxy, aryloxy, or —(CH2)qOR17, wherein R17 is alkyl an aryl and q is an integer in the range of 1 to 10.