Table 4.

Synthesized prodrugs, metabolic stability (based on LC–UV analysis), and effect on PC3 proliferation.^[a]

Compd	R	Residual microsomal substrate [%] (t=60 min)	Mouse plasma t 1/2 [min]	Cell proliferation
64	Me	20	13.3	active
65	Bn	53	<1	active
66	iPr	16	15.1	active
67	Et	24	4.5	active
68	Bu	53	<1	active
69	tBu	79	N.C.	inactive
70	CH2‐pyridin‐4‐yl	0	<1	active
71	(CH2)2‐morpholinyl	18	2.5	active
72	piperonyl	83	<1	active
73	isopentyl	39	<1	active
74	1‐methylbutanyl	60	4.2	inactive
75	(CH2)10Me	80	4.4	inactive
76	(CH2)17Me	100	N.C.	inactive

[a] N.C.: not calculable as hydrolytically stable. Active: able to reduce proliferation to an extent greater than 50 %; inactive: able to reduce proliferation to an extent less than 50 %.