Synthesis and preliminary biological evaluation of 4,6-disubstituted 3-cyanopyridin-2(1H)-ones, a new class of calcium entry blockers

Article abstract of DOI:10.1016/S0960-894X(00)00361-9

The preparation of 3-cyano-4,6-diaryl-pyridin-2(1H)-ones 4a-h, calcium entry blockers related to diltiazem, is described starting from 1,3-diaryl-2-propen-1-ones 5. On preliminary pharmacological tests all compounds are active and some of them show calcium antagonistic activity superior or comparable to diltiazem. (C) 2000 Elsevier Science Ltd. All rights reserved.

Full text of DOI:10.1016/S0960-894X(00)00361-9

Bioorganic & Medicinal Chemistry Letters 10 (2000) 1883±1885
Synthesis and Preliminary Biological Evaluation of
4,6-Disubstituted 3-Cyanopyridin-2(1H)-ones, a New Class
of Calcium Entry Blockers
Fedele Manna,a,* Franco Chimenti,a Adriana Bolasco,a Bruna Bizzarri,a
Maurizio Botta,b Andrea Ta®,b Amelia Filippellic and Settimio Rossic
aDipartimento di Studi di Chimica e Tecnologia delle Sostanze Biologicamente Attive,
Á
Universita di Roma `La Sapienza', P. le Aldo Moro 5, 00185 Rome, Italy
b
Á
Dipartimento Farmaco Chimico Tecnologico, Universita di Siena, Via Aldo Moro, 53100 Siena, Italy
Istituto di Farmacologia e Tossicologia, Facolta di Medicina e Chirurgia, II Universita di Napoli,
c
Á
Á
Via Costantinopoli 16, 80138 Naples, Italy
Received 23 March 2000; accepted 22 June 2000
AbstractÐThe preparation of 3-cyano-4,6-diaryl-pyridin-2(1H)-ones 4a±h, calcium entry blockers related to diltiazem, is described
starting from 1,3-diaryl-2-propen-1-ones 5. On preliminary pharmacological tests all compounds are active and some of them show
calcium antagonistic activity superior or comparable to diltiazem. # 2000 Elsevier Science Ltd. All rights reserved.
After the introduction of calcium channel blockers
(CCBs) into clinical practice,1 many compounds with
calcium antagonistic activity have been described, most
of them being structurally related to dihydropyridines
(DHPs) nifedipine 1,2 5 while very few e€ective calcium
antagonists related to benzothiazepines (BTZs) diltia-
zem 2 (Fig. 1) have been reported until today. More
recently, several novel classes of CCBs have emerged:
diphenylbutylpiperidines (¯uspirilene),6,7 1,3-diphos-
phonates (belfosdil),8 and, in addition, benzothiazinone
(HOE 166),9,10 1,5-benzothiazepines11 and benzothia-
zines 3,12,13 the chemical structure of which bears some
resemblance to diltiazem. In the present paper, we wish
to report the synthesis and pharmacological properties
of 3-cyano-4,6-diaryl-pyridin-2(1H)-ones 4, a new class
of CCBs related to diltiazem.
conformation of diltiazem.13 The moieties to be super-
imposed were selected taking into account the ®ndings
of a previous 3D-QSAR study, in which a hypothesis of
the receptor-binding site of diltiazem-like calcium entry
blockers was developed.11 The phenyl ring of diltiazem,
which occupies the hydrophobic region 1 of that theor-
etical model, was superimposed onto the phenolic moi-
ety of 4g while matching the hydroxyl oxygen with the
sulphur atom of diltiazem. Furthermore, the p-
methoxyphenyl ring of diltiazem was superimposed into
the 2,5-dimethoxyphenyl ring of 4g so that the 5-meth-
oxy group of 4g could occupy the same position in 3D
space occupied by the corresponding functionality of the
template. This group was recognised, in fact, to have
pharmacophoric relevance, possibly through the inter-
action with one hydrogen-bonding site of the receptor.11
The same superimposition procedure could not be
applied to nifedipine, due to the lack in this compound
of the aromatic ring corresponding to the condensed
phenyl of diltiazem.
diltiazem was chosen as the reference compound (tem-
plate) for a 3D-comparative study in which the structural
similarity between this compound and products 4 was
investigated. Superimpositions were performed14 between
all the conformers obtained by an extensive conforma-
tional analysis executed in a 3.0 kcal/mol energetic window
on 4g (Search/Compare module) and the lowest energy
A very good structural similarity was observed between
4g and diltiazem. This result is depicted in Figure 1,
where the conformer of 4g, giving the best match, is
superimposed onto the template molecule. The distance
between the hydrogen at C-5 of the phenolic ring of 4g
and the oxygen at C-4 of the 2,5-dimethoxyphenyl ring
of 4g (both depicted as a ball in Figure 1) was found to
*Corresponding author. Tel.: +39-06-49913735; fax: +39-49913976; e-
mail: fmanna@uniromal.it
0960-894X/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved.
PII: S0960-894X(00)00361-9

1884
F. Manna et al. / Bioorg. Med. Chem. Lett. 10 (2000) 1883±1885
be 11.7 A. This value is shorter than the maximum value
of 11.8 A reported as the maximum dimension that
CCBs should not exceed to be accepted by their recep-
tor-binding site.11 A very good match was found
between the superimposed aromatic rings as well as an
unexpected correspondence in the 3D space between the
hydroxyl oxygen of 4g and the sulphur atom of diltiazem
(annotation B in Fig. 1).15 Finally, proximity in 3D space
was observed between the endocyclic nitrogen of diltia-
zem and the nitrogen atom of 4g16a (annotation A in
Fig. 1) and between the ester oxygen of diltiazem and
the 2-methoxy oxygen of the dimethoxyphenyl ring of
4g.16b
Therefore, we synthesised the family of compounds 4a±
h in order to assess their antagonistic properties. The 3-
cyano-4-(R,R0-aryl)-6-(2-hydroxyphenyl)-2(1H)-pyridones
were prepared as previously reported,17 by reaction of
substituted 1,3-diaryl-2-propen-1-ones 5 with ethyl cya-
noacetate in the presence of ammonium acetate. Sub-
stituted 1,3-diaryl-2-propen-1-ones were obtained by
condensation of o-hydroxyacetophenone 6 with sub-
stituted benzaldehydes 7 (Scheme 1) (Table 1).
Pharmacology
Compounds 4a±h were tested in vitro on K+-depo-
larised rat aorta strips18 to evaluate their ability to relax
the initial contraction induced by K+ (IC50 values) and
activity in maximum smooth muscle relaxation (max-
imum relaxation %). Pharmacological data are reported
in Table 2. All compounds examined displayed a good
vasorelaxing activity and, while 4c,f,h were less active,
4a,b,d,e,g were from 2- to 10-fold more potent than dil-
tiazem in IC50 assay and showed also a good maximum
smooth muscle relaxing ability. These results con®rmed
the molecular modelling predictions regarding the
interaction of 2(1H)-pyridone derivatives with the active
site of L-type calcium channels20 and showed that there
are possible other modi®cations of the structure of
diltiazem with retention of the inhibitory activity.
In conclusion, we synthesised some 3-cyano-4-(R,R0a-
aryl)-6-(2-hydroxyphenyl)-2(1H)-pyridones 4a±h which
could be considered a novel class of CCBs related to
diltiazem, characterised by the contraction of the seven-
membered ring together with elimination of the con-
densed benzene nucleus. Some of them showed potent
calcium blocking properties in pharmacological tests.
Table 1. Chemical and physical data (4a±h)
Compound
R
R0
Yield (%) Mp (ꢀC)
Formulaa
4a
4b
4c
4d
4e
4f
H
H
H
H
H
H
2-Cl
2-Br
2-CH3
2-OCH3
40
30
30
20
27
25
20
55
280±281 C18H12N2O2
210±212 C18H11N2O2Cl
309±310 C18H11N2O2Br
265±266 C19H14N2O2
318±320 C19H14N2O3
2-OCH3 4-OCH3
2-OCH3 5-OCH3
Oil
C20H16N2O4
Figure 1. Stereo view of the superimposition between 4g (black) and
diltiazem (grey). The sole hydrogen at C-5 of the phenolic ring of 4g is
displayed (smaller ball). Annotation A highlights the proximity
4g
4h
255±258 C20H16N2O4
332±333 C18H11N3O4
H
3-NO2
between the endocyclic nitrogen of diltiazem and the nitrogen atom of
4g. Annotation B highlights the correspondence in 3D space between
the hydroxyl oxygen of 4g and the sulphur atom of diltiazem.
aResults of elemental analysis were Æ0.4% of theoretical values; NMR
and IR spectra con®rmed the assigned structures.
Scheme 1.

F. Manna et al. / Bioorg. Med. Chem. Lett. 10 (2000) 1883±1885
1885
Table 2. Inhibiting and vasorelaxing activity (4a±h)
11. Corelli, F.; Manetti, F.; Ta®, A.; Campiani, G.; Nacci, V.;
Botta, M. J. Med. Chem. 1997, 40, 125.
12. Campiani, G.; Nacci, V.; Garofalo, A.; Botta, M.; Fiorini,
I.; Ta®, A.; Bruni, G.; Romeo, M. R.; Peres, A.; Bertollini, L.
Bioorg. Med. Chem. Lett. 1992, 12, 1193.
13. Campiani, G.; Garofalo, A.; Fiorini, I.; Botta, M.; Nacci,
V.; Ta®, A.; Chiarini, A.; Budriesi, R.; Bruni, G.; Romeo, M.
R. J. Med. Chem. 1995, 38, 4393.
14. Calculations and graphics manipulations were performed
on Iris 4D/35 and Indigo R4000 Silicon Graphics work-
stations, using the software packages InsightII and Discover
of MSI (Molecular Simulation Inc., 9685 Scranton Road, San
Diego, CA 92121, USA).
Compound
IC50 (M)
Maximum
relaxation concn (M)
Maximum
relaxation (%)
8
4
diltiazem
4.8Â10
10
10
10
10
10
10
10
10
97.86
23.86
79.78
35.29
89.17
99.54
40.00
95.51
64.00
10
4
4a
4b
4c
4d
4e
4f
9.5Â10
3.0Â10
1.7Â10
1.0Â10
1.2Â10
3.8Â10
1.1Â10
5.0Â10
8
5
6
8
7
9
7
4
4
4
4
4
5
4g
4h
4
10
15. The two atoms were 0.70 A from each other.
16. The two atoms were 1.36 A from each other. (b) The two
atoms were 1.19 A from each other.
Acknowledgements
17. Manna, F.; Chimenti, F.; Bolasco, A.; Filippelli, W.;
Filippelli, A.; Palla, A.; Lampa, E.; Mercantini, R. Eur. J.
Med. Chem. 1992, 27, 627.
We thank Dr. Fabio Fusi and Dr. Simona Saponara for
electrophysiological evaluation. This work was sup-
ported by a grant from MURST, Roma.
18. Method: experiments were carried out according to God-
fraind and Polster.19 Albino Sprague±Dawley rats of both
sexes weighing 200±250 g were killed by a blow to the head
followed by exsanguination and the thoracic aortas removed
and placed in Krebs-bicarbonate bu€er. Excess fat and tissue
were removed and the aorta was cut into helicoidal strips.
Strips were mounted in organ baths in Krebs solution, at 37 ꢀC
and bubbled with 95% O2+5% CO2. Isometric contractions
were recorded by means of NARCO mod F60 coupled to
LINSEIS mod 2046 pen recorder. Tissues were allowed to
equilibrate for 1 h. Maximum responses were obtained under
an applied tension of 2 g. The aorta was washed every 10 min
to avoid interference of metabolites. Afterwards a depolarisa-
tion was induced by adding 80 mM KCl. Subsequent to the
contraction reaching a plateau, the compounds or diltiazem
References and Notes
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10
4
were added at concentrations of 10
to 10 M. The IC50
values were calculated from contractile force changes and
expressed with respect to the control, initial contractile values.
Stock solutions of compounds and diltiazem (10 2) were pre-
pared in DMSO and then diluted in Krebs±Henseleit bu€er.
The ®nal concentration of DMSO in the organ bath was
always 0.1%. Results of these experiments were expressed also
as percent- induced relaxation of the initial contraction, which
were used for calculation of IC50 values.
Â
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electrophysiological techniques.21 This compound showed a
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luations are in progress and will be presented elsewhere.
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