Immunotherapeutic agents

A substantially pure (E)-compound, a substantially pure (Z)-compound, or a mixture of (E)- and (Z)-compounds having the formula (I):

• wherein:
• X is —O—, and R1 is any alkyl of up to 10 carbon atoms, any monocycloalkyl of up to 10 carbon atoms, any polycycloalkyl of up to 10 carbon atoms, or any benzocyclic alkyl of up to 10 carbon atoms;
• R2 is nitro, cyano, trifluoromethyl, carbethoxy, carbomethoxy, carbopropoxy, acetyl, carbamoyl, acetoxy, carboxy, hydroxy, amino, lower alkyl, lower alkoxy, or halo;
• and
• R3 is (i) phenyl unsubstituted or substituted with 1 or more substituents wherein each substituent is independently a nitro, a cyano, a halo, a trifluoromethyl, a carbethoxy, a carbomethoxy, a carbopropoxy, an acetyl, a carbamoyl, a carbamoyl substituted with an alkyl of 1 to 3 carbon atoms, an acetoxy, a carboxy, a hydroxy, an amino, an amino substituted with an alkyl of 1 to 5 carbon atoms, an alkyl or cycloalkyl of 1 to 10 carbon atoms, or an alkoxy or cycloalkoxy of 1 to 10 carbon atoms;
• or (ii) phenyl substituted with 1 or more substituents wherein each substituent is independently an alkylidenemethyl of up to 10 carbon atoms, a cycloalkylidenemethyl of up to 10 carbon atoms, a phenyl, or a methylenedioxy.