Brief Articles
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 7 1697
br, 1H), 4.45 (m, 2H), 3.53 (m, 2H), 2.72 (s, 3H), 2.33 (m, 2H),
1.82 (m, 2H), 1.27 (m, 2H).
counteract bronchoconstriction produced by i.v. injection of Ach,
20 µg kg-1. Bronchoconstriction, quantified as a reduction of tidal
volume, was evaluated according to the method of Konzett and
Roessler.9 Ach challenge was applied at 5, 15, and 30 min and
then every 30 min up to 180 min from the intratracheal administra-
tion of test compounds. The effect of test compounds was expressed
as percentage of inhibition of Ach-evoked bronchoconstriction, as
compared to basal response obtained in control animals. Ethical
approval of the experimental protocols with animals (in vitro and
in vivo) was obtained from the local Ethics Committee.
General Procedure 2. Reduction with Red-Al and Alkylation.
Synthesis of 1-Benzyl-1-methyl-4-(2-oxo-4,4-diphenyl-imidazo-
lidin-1-yl)-piperidinium (4). (1) 3-(1-Methyl-piperidin-4-yl)-5,5-
diphenyl-imidazolidin-2-one. A 3.5 M solution of sodium bis-(2-
methoxyethoxy)aluminum hydride (Red-Al) in toluene (5.37 mL,
18.4 mmoles) is dissolved in dry THF (15 mL) under nitrogen
atmosphere and cooled to 0 °C. A solution of compound 3a (0.803
g, 2.3 mmoles) in dry THF (20 mL) is added dropwise. The mixture
is then heated to 85 °C for 4 h. The reaction is cooled again to 0
°C and quenched with water (5 mL); then 2 M sodium hydroxide
is added (10 mL) and the mixture is extracted with ethyl acetate;
and the organic phase is washed with water, then with brine, and
finally dried and concentrated under vacuum to give a yellowish
solid that is crystallized from acetone to give the desired product
Acknowledgment. This study was supported by Chiesi
Farmaceutici, Parma, Italy. The authors thank Dr. Samuele
Pedraglio and Dr. Chiara Bigogno (NiKem Research) for the
analytical support.
1
as a white solid (0.65 g). LC-MS (ESI POS): 336.20 (MH+). H
Supporting Information Available: Spectroscopic data and
elemental analyses for compounds 3a-i and 4-34. This material
NMR (DMSO; 343 K): 7.80 (s br, 1H), 7.40-7.21 (m, 10H), 3.91
(s, 2H), 3.80 (m, 1H), 3.41 (m, 2H), 3.09 (m, 2H), 2.72 (s, 3H),
2.01 (m, 2H), 1.80 (m, 2H).
References
(2) 1-Benzyl-1-methyl-4-(2-oxo-4,4-diphenyl-imidazolidin-1-
yl)-piperidinium (4). 3-(1-Methyl-piperidin-4-yl)-5,5-diphenyl-
imidazolidin-2-one (0.08 g, 0.24 mmoles) is dissolved in CH3CN
(4 mL) in a microwave tube. Benzyl bromide (0.164 g, 0.96 mmol)
is added, the tube is sealed, and the solution is heated at 120 °C in
a microwave oven for 2 h. The solvent is evaporated and the crude
compound is triturated with i-Pr2O/DCM. The desired product 4 is
obtained as a pale yellow solid (0.08 g). LC-MS (ESI pos): 426.18
(1) Peretto, I.; Forlani, F.; Fossati, C.; Giardina, G. A. M.; Giardini, A.;
Guala, M.; La Porta, E.; Petrillo, P.; Radaelli, S.; Radice, L.; Raveglia,
L. F.; Santoro, E.; Scudellaro, R.; Scarpitta, F.; Bigogno, C.; Misiano,
P.; Dondio, G. M.; Rizzi, A.; Armani, E.; Amari, G.; Civelli, M.;
Villetti, G.; Patacchini. R.; Bergamaschi, M.; Delcanale, M.; Salcedo,
C.; Ferna´ndez, A. G.; Imbimbo, B. P. Discovery of diaryl imidazo-
lidin-2-one derivatives, a novel class of muscarinic M3 selective
antagonists (Part 1) J. Med. Chem. 2007, 50, 1571-1583 and
references therein.
(2) Minette, P. A.; Barnes, P. J. Muscarinic receptor subtypes in lung.
Clinical implications. Am. ReV. Respir. Dis. 1990, 141, S162-S165.
(3) Coulson, F. R.; Fryer, A. D. Muscarinic acetylcholine receptors and
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1
(MH+). H NMR (CDCl3): 7.66-7.21 (m, 15H), 5.00 (s br, 1H),
4.13 (m, 2H), 4.09 (s, 2H), 3.92 (m, 2H), 3.56 (m, 2H), 3.23 (s,
3H), 2.59 (m, 2H), 2.00 (m, 2H).
All the quaternary ammonium salts reported in Tables 1-3 were
synthesized following the same procedure starting from the corre-
sponding tertiary amine and the appropriate alkylating agent.
Biology. Cell lines and membrane preparations and radioligand
binding conditions are as described previously.1
Isolated Guinea-Pig Trachea. Tracheal zigzag preparations were
obtained from tracheal segments excised from male albino Dunkin-
Hartley guinea pigs (450-550 g, Charles River Laboratories Italia,
Calco, Italy) and set up as described previously.8 Test compounds
were assayed for their ability to relax a smooth muscle tone raised
by a submaximally effective concentration (0.3 µM) of carbachol.
The antagonist concentration producing a 50% reversal of carba-
chol-induced tonic contraction (IC50) was taken as a measure of
antagonist potency. Isoprenaline-induced relaxation was used as
the maximal inhibitory reference effect.
Isolated Guinea-Pig Left Atrium. The hearts were rapidly
removed from male albino Dunkin-Hartley guinea pigs (325 (
25 g), and the left and right atria were separately excised. The left
atria were mounted with a preload of 0.5 g in McEwens, pH 7.4.
The solution was maintained at 32 °C, and tissues were stimulated
by the application of methacholine 1 µM. Negative ionotropic
responses to the addition of methacholine were recorded as changes
in isometric tension, as previously reported.9 Dose-response curves
were obtained for selected test compounds.
In Vivo Bronchoconstriction in Guinea Pig. All in vivo
experiments were performed on male albino Dunkin-Hartley
guinea pigs (450-550 g, Charles River Laboratories Italia, Calco,
Italy), as described previously.8 Test compounds (given intratra-
cheally to anesthetized animals) were assayed for their ability to
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