Table 3.

SAR of substituents on middle phenyl ring

Compd	R3	R4	Kd (µM)[a]	LE[b]
20	Me	H	7 ± 3	0.23
20m	H	H	17 ± 1	0.22
20n	Et	H	4 ± 0.25[c]	0.23
20o	iPr	H	5 ± 0.19[c]	0.22
20p	Me	Me	14 ± 1.5	0.21

^[a]Average K_d values (n=2) calculated using Cheng-Prusoff equation from IC₅₀ values measured in FPA competition assay.

^[b]LE values calculated using LE = 1.4*pK_d/HAC, using the FPA data.

^[c]Some evidence of precipitation noted at highest concentrations.