Pharmaceutical Research, Vol. 18, No. 2, 2001
Research Paper
ide-like vasodilator activities. These compounds, which are
structurally related to Nifedipine 1 and to its meta-analogue 2
(Fig. 1), are characterized by having furoxan substructures
endowed with different NO-donor properties at the ortho and
meta position of the 4-phenyl ring (Fig. 1, derivatives 3a–8a
and 3b–8b). A number of these compounds behaved as well-
balanced hybrids, because they were able to display NO-
dependent and Ca2+-antagonist dependent vasodilating prop-
erties in the same range of concentration. In particular, 1,4-
DHPs bearing appropriately substituted furoxans at ortho
position were as potent as the references 1 and 2 (5).
In this paper, we report the preparation and the phar-
macological characterization of a series of 4-(3-nitrophenyl)-
1,4-dihydropyridines analogues of 1, having furoxan moieties
on the 3-positioned lateral ester chain (Fig. 2, derivatives 15a,
15b; 16a, 16b; 17a, 17b; and 21). Furoxan substituents were
appropriately chosen, in order to modulate NO-release of the
final products. These compounds should display differences
over other known NO-donor 1,4-DHPs bearing nitrate
groups in their ester side chain (7,8). In fact the presence of
suitable substituted furoxan moieties gives rise to a series of
compounds widely modulated in their NO-release properties.
In addition, these products could lack significant tolerance
development (9,10). In this paper, related furazan derivatives
(Fig. 2, derivatives 15, 16, 17, and 22) were also considered for
control purposes, because they are unable to release NO.
Nifedipine 1 and its meta-nitro analogue 2 were used as ref-
erences.
Studies on Agents with Mixed
NO-Dependent and Calcium Channel
Antagonistic Vasodilating Activities
Clara Cena,1 Sonja Visentin,1 Antonella Di Stilo,1
Donatella Boschi,2 Roberta Fruttero,1 and
Alberto Gasco1,3
Received September 30, 2000; accepted November 8, 2000
Purpose. To obtain new cardiovascular agents with mixed Ca2+
-
channel antagonistic and NO-donor properties, a series of “hybrid”
1,4-dihydropyridines (1,4-DHPs), bearing NO-donating furoxan moi-
eties on the 3-positioned lateral ester chain were synthesized and
pharmacologically characterized. Furazan analogues were also pre-
pared and investigated for control purposes, because they are unable
to release NO.4
Methods. Synthesis of the models was achieved by a modified Hantz-
sch approach. All of the final furoxan 1,4-DHPs were assessed for
their ability to produce nitrite in the presence of a large excess of
cysteine by the Griess reaction. Vasodilating activity was evaluated
MB
on rat aorta and expressed as EC50 and EC50
values, obtained in
the absence and in the presence of methylene blue (MB) respectively,
a well-known guanylate cyclase inhibitor. Affinities to 1,4-DHP re-
ceptor on Ca2+-channels, expressed as IC50 values, were determined
through displacement experiments of [3H]-nitrendipine on rat cortex
homogenates.
Results. Some hybrid compounds (derivatives 15a, 15b, 16a, and 16b)
displayed vasodilating activity depending predominantly on their
Ca2+-channel blocker properties. By contrast, some others (deriva-
tives 17a, 17b, and 21) behaved as well-balanced hybrids with mixed
Ca2+-channel blocking and NO-dependent vasodilating activities.
Conclusion. This work demonstrates the possibility of obtaining well-
balanced hybrids endowed with mixed NO-donor and Ca2+-channel
blocker properties using appropriate 1,4-DHP and furoxan moieties.
A procedure for the individual evaluation of the NO-dependent va-
sodilator component and that due to Ca2+-channel blocking is pro-
posed.
MATERIALS AND METHODS
Chemistry
Synthesis
Melting points were measured on a Bu¨chi 530 capillary
apparatus and are uncorrected. Melting points with decom-
position were determined after introducing the sample into
the bath at a temperature 10°C lower than the melting point.
A heating rate of 3°C min−1 was used. The compounds were
routinely checked by infrared spectroscopy (Shimadzu FT-IR
8101M, Shimadzu Italia, Milan, Italy) and mass spectroscopy
(Finnigan-Mat TSQ-700 spectrometer, Finnigan, Milan,
Italy), and 1H and 13C nuclear magnetic resonance at 200 and
50 MHz, respectively (Bruker AC-200 spectrometer, Bruker,
Milan, Italy). All of the spectra were in keeping with the
proposed structures. Column chromatography was performed
on silica gel (Merck Kieselgel 60, 230–400 mesh ASTM,
Merck, Milan, Italy) with the indicated solvent system. An-
hydrous magnesium sulfate was used as the drying agent of
the organic extracts. Petroleum ether (PE) 40–60°C was used.
Solvent removal was achieved under reduced pressure at
room temperature. Elemental analyses of the new com-
pounds were performed by REDOX (Cologno Monzese,
Italy) and the results are within 0.4% of theoretical values.
Intermediates 9a (11), 9b (5), and 18 (12) were synthesized
according to procedures described in the literature. Deriva-
tives 10a and 10b were a gift from Dr. K. Scho¨nafinger,
Aventis Pharma (Frankfurt am Main, Germany). Compounds
11, 13, and 14 are commercial reagents (Aldrich Chemical
Co., Milwaukee, WI, USA).
KEY WORDS: NO donors; 1,4-dihydropyridines; Ca2+-channel
blockers; hybrid drugs; furoxans; vasodilation.
INTRODUCTION
Medicinal chemical hybridization is a well-known ap-
proach to drug design. It involves the combination of two
complementary biological activities by joining appropriate
pharmacophoric groups directly or via spacers (1,2). We have
designed a number of drugs by combining suitable pharma-
cophoric groups with different NO-donor moieties (3–6).
Among these, we also realized new 1,4-dihydropyridines
(DHPs) with mixed calcium channel antagonist and nitric ox-
1 Dipartimento di Scienza e Tecnologia del Farmaco, via P. Giuria 9,
I-10125, Torino, Italy.
2 Dipartimento di Scienze Chimiche, Alimentari, Farmaceutiche, Far-
macologiche, V.le Ferrucci 33, I-28100, Novara, Italy.
3 To whom correspondence should be addressed. (e-mail: gasco@
pharm.unito.it)
4 In this paper, the term nitric oxide (NO) is used as a family name.
When necessary in the discussion, we specify the particular redox
form to which we refer.
3-(3-(Benzenesulfonyl)furoxan-4-yloxy)propanol,
19. A 50% w/w NaOH aqueous solution (2.19 g, 27.3 mmol),
157
0724-8741/01/0200-0157$19.50/0 © 2001 Plenum Publishing Corporation