Table 3. Third-Round SAR Study of the C-5 Position of 4b.

compound	R3	FPA Inh %a
3b	H	0.9
8	Cl	–12
9	Br	–5
11	CN	1.1
12	SCH3	–21
13	S(O)CH3	0.4
16	S(O)2CH3	–10

^aFPA Inh %: Fluorescence polarization inhibition rate was tested with the targeted compound at a concentration of 50 μM and the reported values were represented as the mean (n = 2).