Table 2.

PDE5 inhibitory activity of tetrahydro-β-carboline-hydantoins (5–20).

Compd	R	Chirality	PDE5 % inhibition at 10 μma)	PDE5 inhibition IC50 (μm)b)
5	–C2H5	5S, 11aR	99	0.2
6	–C2H5	5R, 11aR	66	4.8
7	–C2H5	5R, 11aS	78	2
8	–C2H5	5S, 11aS	99	0.16
9	–(CH2)3CH3	5S, 11aR	99	0.17
10	–(CH2)3CH3	5R, 11aR	<60	ND
11	–(CH2)3CH3	5R, 11aS	<60	ND
12	–(CH2)3CH3	5S, 11aS	92	0.47
13	–C–(CH3)3	5S, 11aR	97	0.39
14	–C–(CH3)3	5R, 11aR	<60	ND
15	–C–(CH3)3	5R, 11aS	<60	ND
16	–C–(CH3)3	5S, 11aS	90	1
17	–CH2–CH=CH2	5S, 11aR	96	0.29
18	–CH2–CH=CH2	5R, 11aR	67	5.4
19	–CH2–CH=CH2	5R, 11aS	<60	ND
20	–CH2–CH=CH2	5S, 11aS	97	0.32

^a)Calculated from triplicate values.

^b)Calculated from 10 concentrations, each with double replicates.