Patent ID: 7109191

Claim:
A compound of the structural formula I: wherein X is selected from the group consisting of or a pharmaceutically acceptable salt thereof; wherein the aromatic ring carbon atoms are unsubstituted or substituted with one R 2 substituent and the non-aromatic ring carbon atoms are unsubstituted or substituted with one or two R 2 substituents; R 2 is selected from the group consisting of hydrogen, C 1-4 alkyl, and C 3-6 cycloalkyl; or two R 2 substituents, when on the same non-aromatic carbon atom, are taken together with the carbon atom to which they are attached to form a cyclopropyl group; R 1 is hydrogen or C 1-4 alkyl; and R 3 and R 4 are each independently hydrogen or C 1-4 alkyl.