Patent ID: 8513425

Claim:
A compound of formula I: or a pharmaceutically acceptable salt thereof, wherein: m is 1; n is 2; Ar is: optionally substituted phenyl; R 1 is: hetero-C 1-6 alkyl; halo-C 1-6 alkyl; C 3-7 cycloalkyl-C 1-6 alkyl; C 1-6 alkyl-C 3-6 cycloalkyl-C 1-6 alkyl; or aryl-C 1-3 alkyl; R 2 is: hydrogen; or C 1-6 alkyl; and R a and R b each independently is: hydrogen; C 1-6 alkyl; or or R a and R b together form a C 1-2 alkylene; provided that when m is 1, n is 2 and Ar is optionally substituted phenyl, then R 1 is not methyl or ethyl.