Therapeutic agents

A compound of formula I:

• or a pharmaceutically acceptable salt thereof, wherein in formulae I:
• X is O;
• R1 is selected from substituted or unsubstituted aralkyl, substituted alkyl, propyl, substituted or unsubstituted hydroxyalkyl, substituted or unsubstituted alkylamine, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, and substituted or unsubstituted heteroaralkyl;
• R2 is selected from substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted branched hydroxyalkyl, substituted or unsubstituted cycloalkyl having 6 ring carbon atoms or greater, substituted or unsubstituted cycloalkenyl, hydroxyalkylaralkyl, hydroxyalkylheteroaralkyl, and a carboxylic acid-containing group;
• R3 is selected from substituted or unsubstituted alkyl, substituted or unsubstituted hydroxyalkyl, substituted or unsubstituted alkylamine, substituted or unsubstituted alkoxy, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted aralkyl, and substituted or unsubstituted heteroaralkyl;
• and
• R4-R7 represents groups R4, R5, R6 and R7 which are independently selected from hydrogen, halo, hydroxy, substituted or unsubstituted alkyl, substituted or unsubstituted hydroxyalkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted heteroaryl, substituted or unsubstituted heteroaralkyl, substituted or unsubstituted alkylamine, substituted or unsubstituted alkoxy, trifluoromethyl, amino, nitro, carboxyl, carbonyl, methylsulfone, trifluoromethylsulfone, cyano and substituted or unsubstituted sulfonamide.