Table 1. Inhibition Assay of Influenza A Endonuclease by Phenyl Substituted 3-Hydroxypyrazin-2(1H)-ones, 5-Hydroxypyrimidin-4(3H)-ones, and 4-Hydroxypyridazin-3(2H)-ones.

compd	IC50 (μM)	R1	R2
1	59.0	4-FC6H5
2	>193	4-FC6H5	H
3	0.58	H	4-FC6H4
4	1.56	H	3-FC6H4
5	1.67	H	2-FC6H4
6	2.24	H	4-[1,1′]-biphenyl
7	0.40	H	3-[1,1′]-biphenyl
8	1.10	H	2-[1,1′]-biphenyl
9	0.52	H	4-CNC6H4
10	0.25	H	3-CNC6H4
11	0.15	H	4-(CN4H)phenyl
12	0.48	H	3-(CN4H)phenyl
13	177	4-FC6H4	H
14	6.0	H	4-FC6H4
15	9.3	H	4-CNC6H4
16	3.0	H	4-(CN4H)phenyl
5-FPhP	0.73
6-FPhP	0.43