One embodiment of the present invention is a compound represented by the Structural Formula (I): ##STR00001## Y is a covalent bond of a substituted or unsubstituted straight chained hydrocarbyl group. In addition, Y, taken together with both >C.dbd.Z groups to which it is bonded, is a substituted or unsubstituted aromatic group. Preferably, Y is a covalent bond or --C(R.sub.7R.sub.8)--.R.sub.1 is an aliphatic group, a substituted aliphatic group, a non-aromatic heterocyclic group, or a substituted non-aromatic heterocyclic group, R.sub.2-R.sub.4 are independently --H, an aliphatic group, a substituted aliphatic group, a non-aromatic heterocyclic group, a substituted non-aromatic heterocyclic group, an aryl group or a substituted aryl group, or R.sub.1 and R.sub.3 taken together with the carbon and nitrogen atoms to which they are bonded, and/or R.sub.2 and R.sub.4 taken together with the carbon and nitrogen atoms to which they are bonded, form a non-aromatic heterocyclic ring optionally fused to an aromatic ring.R.sub.5-R.sub.6 are independently --H, an aliphatic group, a substituted aliphatic group, an aryl group or a substituted aryl group.R.sub.7 and R.sub.8 are each independently --H, an aliphatic or substituted aliphatic group, or R.sub.7 is --H and R.sub.8 is a substituted or unsubstituted aryl group, or, R.sub.7 and R.sub.8, taken together, are a C2-C6 substituted or unsubstituted alkylene group.Z is .dbd.O or .dbd.S.Also disclosed are pharmaceutical compositions comprising the compound of the present invention and a pharmaceutically acceptable carrier or diluent.