The invention provides compounds of formula VI
1
and the pharmaceutically acceptable salts thereof, wherein R1, R2, R3, and R4 are as defined, to pharmaceutical compositions containing such compounds and to the use of such compounds in the treatment and prevention of central nervous system and other disorders. The invention also provides methods for inhibiting neurological damage caused by impairment of glucose and/or oxygen to the brain in a mammal, which method comprises administering to the mammal a NOS inhibitor. In one embodiment, the NOS inhibitor is administered to the mammal prior to surgery, for example prior to cardiac surgery, angioplasty, or angiography.