| abstract |
The present invention provides a compound of formula (I) or a pharmaceutically acceptable salt thereof wherein R1 and R2 are independently H, F, OH, C1-2alkyl, CF3, OC1-2alkyl, optionally substituted with OCH3 or OH, or R1 and R2 taken together form =O, =N-OH, =N-OC1-2alkyl, =CH-CN; R3 is C1-2alkyl, or OC1-2alkyl; and X is H or F. |