Table 4.

Examples of representative 4-oxo-1,4-dihydropyridine derivatives developed by Boehringer Ingelheim GmbH.

Compound	R1	R3	R5	X	IC50 (nM)a	Reference
20	CH2CH3		CF3	C	< 1b	[146]
21	CH(CH3)2		CHF2	C	< 1b	[146]
22			CHF2	C	< 1b	[146]
23			CF3	C	< 1c	[147]
24		CH3	CF3	C	< 1c	[147]
25		CH3	CF3	N	3.7c	[147]
26			CF3	N	2.8c	[147]
27			CF3	N	2.3c	[147]
28			CHF2	C	< 1c	[147]
29	CH(CH3)2		CHF2	C	3	[148]

^aThe results are means of two independent experiments, each performed in duplicate (HNE enzyme assay).

^bIC₅₀ values are related to the racemate.

^cIC₅₀ values are related to eutomer [(R)-enantiomer].