Compounds of formula (Ia) are found to be active in inhibiting replication of flaviviridae viruses (Ia), wherein R
1
and R
2
are the same or different and represent hydrogen, halogen, -L-O—R
3
, -L-O-L-A or -L-O-L′-A′, wherein each L is the same or different and represents a direct bond or a C
1
-C
4
alkylene group; L′ represents a direct bond or a C
2
-C
4
alkylene group; R
3
represents hydrogen, C
1
-C
4
alkyl or C
1
-C
4
haloalkyl; A represents a 5- to 10-membered heterocyclyl group; and A′ represents a C
6
-C
1
aryl group; wherein at least one of R
1
and R
2
is -L-O—R
3
, -L-O-L-A or -L-O-L′-A′.
The invention includes a compound of formula I:
wherein R
1
, Y, A, n, R
4
and Z have any of the values described herein, as well as salts of such compounds, compositions comprising such compounds, and therapeutic methods that comprise the administration of such compounds. The compounds are inhibitors of PDE4 function and are useful for improving cognitive function and/or treating cognitive disorders or impairment, traumatic and/or ischemic injuries of the central and peripheral nervous system and/or psychiatric disorders in animals, especially humans.