Table 1.

HNE inhibitory activity of compounds 2a-t, 4, 6, 7, and 9.

Compound	N	R3	X	R1	IC50 (μM)a
2a	7	CF3	CO	m-CH3-Ph	0.42 ± 0.12
2b	7	CF3	CO	cC3H5	0.050 ± 0.01
2c	7	CN	CH2	Ph	N.A.b
2d	7	CN	CO	Ph	0.16 ± 0.05
2e	7	CN	CO	m-CH3-Ph	0.33 ± 0.03
2f	7	CN	CO	p-CH3-Ph	1.5 ± 0.051
2g	7	CN	CO	cC3H5	0.034 ± 0.012
2h	7	CN	CO	cC5H9	0.14 ± 0.04
2i	7	CN	CO	cC6H11	1.1 ± 0.22
2l	7	COOEt	CO	m-CH3-Ph	2.0 ± 0.44
2m	7	COOiPr	CO	m-CH3-Ph	0.98 ± 0.31
2n	5	CF3	CO	m-CH3-Ph	0.033 ± 0.011
2o	5	CF3	CO	cC3H5	0.087 ± 0.021
2p	5	CN	CO	m-CH3-Ph	0.010 ± 0.003
2q	5	CN	CO	cC3H5	0.079 ± 0.023
2r	5	COOEt	CO	m-CH3-Ph	0.016 ± 0.005
2s	5	COOEt	CO	cC3H5	0.069 ± 0.026
2t	5	CH3	CO	m-CH3-Ph	0.760 ± 0.14
4	7	NO2	CO	cC3H5	0.021 ± 0.002
6	7	NH2	CO	cC3H5	9.9 ± 1.3
7	7	NHCO-cC3H5	CO	cC3H5	1.5 ± 0.14
9	7	NHCO-m-CH3-Ph	CO	CH3	25.2 ± 1.3
Sivelestat					0.050 ± 0.020
A 20	–	CN	CO	m-CH3-Ph	0.007 ± 0.0015

^aIC₅₀ values are presented as the mean ± SD of three independent experiments.

^bN.A.: no inhibitory activity was found at the highest concentration of compound tested (50 μM).