H. Beaton et al. / Bioorg. Med. Chem. Lett. 11 (2001) 1023–1026
1025
Table 2. Inhibition of NOS isoforms by alkyl and heteroaryl substituted isoquinolinamines
R
R0
n
iNOS IC50 (mM)
nNOS IC50 (mM)
eNOS IC50 (mM)
6a
6b
6c
6d
6e
6f
6g
6h
6i
H
CH3
H
H
H
H
CH3
H
H
H
H
H
1
1
1
1
1
1
1
1
1
2
32
18
2.7
1.3
0.4
3
0.4
1.5
10
2
0.9
8
2
4
0.9
CꢃCH
c-Pr
CH3
3.6
n.s.@100a
n.s@100a
2.7
1.2
4.2
47%@100a
n.s.@100a
2-Thienyl
2-Furanyl
2-Thiazolyl
2-Imidazolyl
H
8
5
19
n.s.@100a
2
n.s.@100a
12
6j
aSee footnote to Table 1.
selectivity against eNOS. The suspicion that compound
5a represented a close to maximum size fit for the active
site of NOS led us to examine the preparation of smaller
analogues (Table 2).
cells) the compounds show a similar rank order of
potency. Several show potency in the cell comparable
or superior to that of the standard inhibitors such as
l-NMMA 1, l-NAME 2b or aminoguanidine 4.
The 3-unsubstituted compound 6a has a reversed selec-
tivity compared to that of 5 resulting from a reduction
in iNOS potency combined with an increase in activity
against nNOS and eNOS. Small alkyl substituents or
five-membered heterocycles at position 3 give com-
pounds with little selectivity. Disubstitution at the 3-
position as in 6e and increase in amidine ring size to
seven (6j) reduces potency.
In conclusion, we have described a series of dihydro-
isoquinolines which led to the discovery of a highly
selective iNOS inhibitor. The levels of selectivity
achieved demonstrate that good isoform selectivity is
indeed an achievable goal and points the way to com-
pounds which could not only more closely define the
role of inducible nitric oxide synthase, but also offer a
novel therapy for inflammatory diseases.
Some of the more potent and selective compounds were
examined for their ability to inhibit nitric oxide synth-
esis in intact DLD-1 cells (Table 3). Although the
absolute value of the IC50 in these experiments is much
higher than in the enzyme assays (largely due to the
much higher arginine concentration of ꢂ1 mM in the
References and Notes
1. (a) For reviews see: Kerwin, J. F., Jr.; Lancaster, J. R.;
Feldman, P. L., Jr. J. Med. Chem. 1995, 38, 4343. (b)
Boughton-Smith, N. K.; Tinker, A. C. IDrugs 1998, 1, 321.
2. (a) Connor, J. R.; Manning, P. T.; Settle, S. L.; Moore,
W. M.; Jerome, G. M.; Webber, R. K.; Tjoeng, F. S.; Currie,
M. G. Eur. J. Pharmacol. 1995, 273, 15. (b) Salvemini, D.;
Wang, Z.-Q.; Wyatt, P. S.; Bourdon, D. M.; Marino, M. H.;
Manning, P. T.; Currie, M. G. Br. J. Pharmacol. 1996, 118,
829.
Table 3. Inhibitory activity of selected compounds in intact DLD-1
cells
Compound
IC50 (mM)
Compound
IC50 (mM)
1 (l-NMMA)
2b (l-NAME)
4 (AG)
170
ꢂ300
1100
470
5j
5l
6d
6h
83
350
300
880
3. Eliasson, M. J. L.; Huang, Z.; Ferrante, R. J.; Sasamata,
M.; Molliver, M. E.; Snyder, S. H.; Moskowitz, M. A. J.
Neurosci. 1999, 19, 5910.
5
5f
130
4. Moore, W. M.; Webber, R. K.; Jerome, G. M.; Tjoeng,
F. S.; Misko, T. P.; Currie, M. G. J. Med. Chem. 1994, 37,
3886.
5. (a) Wolff, D. J.; Lubeskie, A. Arch. Biochem. Biophys. 1995,
316, 290. (b) Misko, T. P.; Moore, W. M.; Kasten, T. P.;
Nickols, G. A.; Corbett, J. A.; Tilton, R. G.; McDaniel, M. L.;
Williamson, J. R.; Currie, M. G. Eur. J. Pharmacol. 1993, 233,
119.
6. (a) Hamley, P.; Tinker, A. C. Bioorg. Med. Chem. Lett.
1995, 5, 1573. (b) Lee, Y.; Marletta, M. A.; Martasek, P.;
Roman, L. J.; Masters, B. S. S.; Silverman, R. B. Bioorg. Med.
Chem. 1999, 7, 1097.
Scheme 2. (i) EtSCN, SnCl4; (ii) R3NH2.