Synthesis, calcium channel antagonist activity, and anticonvulsant activity of 3-ethyl 5-methyl 1,4-dihydro-2-[(2-hydroxyethoxy)methyl]6-methyl- 4-(2,3-dichlorophenyl)-3,5-pyridinedicarboxylate coupled to a 1-methyl-1,4- dihydropyridyl-3-carbonyl chemical

Article abstract of DOI:10.1002/(SICI)1521-4184(199910)332:10<363::AID-ARDP363>3.0.CO;2-T

3-Ethyl 5-methyl 1,4-dihydro-2-[(2-hydroxyethoxy)methyl]-6-methyl-4- (2,3-dichlorophenyl)-3,5-pyridinedicarboxylate (13), a bioisostere of amlodipine, was prepared by the reaction of ethyl 4-(2- hydroxyethoxy)acetoacetate (11) with methyl 2-(2,3- dichloro

Full text of DOI:10.1002/(SICI)1521-4184(199910)332:10<363::AID-ARDP363>3.0.CO;2-T

1,4-Dihydropyridine Derivatives
363
Synthesis, Calcium Channel Antagonist Activity, and Anticonvulsant
Activity of 3-Ethyl 5-Methyl 1,4-Dihydro-2-[(2-hydroxyethoxy)methyl]-
6
-methyl-4-(2,3-dichlorophenyl)-3,5-pyridinedicarboxylate Coupled to a
-Methyl-1,4-dihydropyridyl-3-carbonyl Chemical Delivery System
1
Sai-hay Yiu and Edward E. Knaus*
Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2N8
Key Words: 1,4-Dihydropyridines; calcium channel antagonist and anticonvulsant activities
Summary
The Bodor 1-methyl-1,4-dihydropyridyl-3-carbonyloxy-
amino) dihydropyridine–pyridinium salt redox chemical de-
livery system (CDS) was designed as a method to facilitate
(
[7]
3
-Ethyl 5-methyl 1,4-dihydro-2-[(2-hydroxyethoxy)methyl]-6-
enhanced delivery of drugs to the brain . This CDS moiety,
after uptake of the parent drug-CDS into brain, undergoes
oxidation to a polar pyridinium species that is trapped in
brain. Subsequent ester (esterase), or amide (amidase), cleav-
age releases the active drug and 1-methylpyridinium-3-car-
boxylate (trigonelline). Accordingly, coupling this CDS to a
methyl-4-(2,3-dichlorophenyl)-3,5-pyridinedicarboxylate (13), a
bioisostere of amlodipine, was prepared by the reaction of ethyl
4
-(2-hydroxyethoxy)acetoacetate (11) with methyl 2-(2,3-dichlo-
robenzylidene)acetoacetate (12) and NH4OAc. Compound 13 was
elaborated to the target product 3-ethyl 5-methyl 1,4-dihydro-2-[2-
[
6
(1-methyl-1,4-dihydropyridyl-3-carbonyloxy)ethoxy]methyl]-
-methyl-4-(2,3-dichlorophenyl)-3,5-pyridinedicarboxylate (16).
[8]
–
9
γ-aminobutyric acid derivative (GABA-CDS, 3) , or
The C-2 CH2OCH2CH2OH compound (13, IC50 = 6.56 × 10 M)
was about 44-fold more active as a calcium channelantagonist than
the reference drug nimodipine (IC50 = 1.49 × 10 M), but 4-fold
less potent than felodipine (IC50 = 1.45 × 10–9 M). Compound 16,
possessing the 1-methyl-3-pyridylcarbonyloxy chemical delivery
system moiety is a slightly less potent calcium channel antagonist
[9]
diphenylhydantoin (DPH-CDS, 4) , resulted in superior
anticonvulsant protection in animal seizure models compared
to the parent compounds GABA or DPH. In an earlier study,
it was shown that the C-3 2-hydroxyethyl analog of felodipine
–8
–8
(5) and the felodipine-CDS (6) provided protection against
(IC50 = 2.99 × 10 M) than the parent compound 13. Compounds
1
3
3, 16, felodipine and nimodipine are highly lipophilic (Kp = 227,
44, 442 and 187, respectively). The C-2 CH2OCH2CH2OH com-
maximal electroshock (MES) induced seizures in mice but
were inactive in the subcutaneous metrazol (scMet) anticon-
pound (13) exhibited equipotent anticonvulsant activity to nimo-
dipine in the maximal electroshock (MES) anticonvulsant screen.
Unlike nimodipine, 13 provided modest protection in the subcuta-
neous metrazol (scMet) anticonvulsant screen. In contrast, com-
pound 16 was inactive in both the MES and scMet screens.
[10]
vulsant screen
. The felodipine-CDS (6) enters the brain
readily, and it undergoes facile oxidation to a pyridinium
species that is retained in brain tissues up to four days after
drug administration. However, the slow hydrolysis rate of the
pyridinium ester to the 3-(2-hydroxyethyl) compound 5 and
the rapid egression of felodipine-CDS (6) from brain likely
contributed to the modest anticonvulsant activity exhibited
Introduction
[
10]
The discovery of non-toxic drugs that provide effective by the felodpine-CDS (6) . The long acting second-genera-
seizure control, particularly for refractory epileptics, and tion CCA amlodipine (7), having a novel C-2 –
exert their anticonvulsant effect by a new mechanism of CH2OCH2CH2NH2 substituent, is a potent antihypertensive
[
11]
action constitutes a challenge in medicinal chemistry drug drug that is amenable to once-a-day dosing
. It was antici-
design. It has been reported that a pathological influx of
calcium into neurons is likely associated with neuronal dam-
pated that the sterically less hindered C-2 substituted felodip-
ine-CDS (16), or a pyridinium species (15), may undergo
more rapid ester cleavage than the C-3 substituted-CDS (6).
Furthermore, retention of the 3-ethoxycarbonyl substituent
present in felodipine [3-ethyl 5-methyl 1,4-dihydro-2,6-di-
methyl-4-(2,3-dichlorophenyl)-3,5-pyridinedicarboxylate]
may result in enhanced anticonvulsant activity relative to the
[
1]
age in status epilepticus , that calcium deposits are elevated
in brain tissue after seizure activity [ , and that the calcium
channel agonist Bay K 8644 (1) increases the influx of
2,3]
calcium into cells to induce seizures in a dose-dependent
manner [4]. These results stimulated studies to evaluate the
potential utility of calcium channel antagonists (CCAs) as a
novel class of anticonvulsant drugs. In this regard, it was
found that the central nervous system (CNS) selective 1,4-di-
hydropyridine CCA nimodipine (2) provided protection
3
-(2-hydroxyethoxycarbonyl) moiety (5). As part of our on-
going program to design calcium channel modulators, we
now describe the synthesis, and CCA and anticonvulsant
activities, for the C-2 oxygen isostere (CH2OCH2CH2OH)
(13) of amlodipine and its CDS derivative (16).
against electroshock- [ and pentylenetetrazole-induced
5]
[6]
seizures.
Arch. Pharm. Pharm. Med. Chem.
© WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999
0365-6233/99/1010/0363 $17.50 +.50/0

364
Yiu and Knaus
Figure 1. Structures of Bay K 8644 (1), Nimodipine (2), γ-aminobutyric acid derivative-CDS (3), Diphenylhydantoin-CDS (4), 3-(2-Hydroxyethyl) 5-methyl
,4-dihydro-2,6-dimethyl-4-(2,3-dichlorophenyl)-3,5-pyridinedicarboxylate (5), Felodipine-CDS (6) and Amlodipine (7).
1
Chemistry
which could be biotransformed by esterase(s) to 13, and the
reference drugs felodipine and nimodipine, were determined
3
-Ethyl 5-methyl 1,4-dihydro-2-[(2-hydroxyethoxy)-
2+
using the muscarinic receptor-mediated (carbachol) Ca -de-
methyl]-6-methyl-4-(2,3-dichlorophenyl)-3,5-pyridinedicar-
boxylate (13), an analog of amlodipine (7), was prepared
using the synthetic methodologies shown in Scheme 1. Thus,
the 4-Me-C H -SO H catalyzed reaction of 3,4-dihydro-2H-
pyran (8) with HOCH CH OH afforded the mono-protected
pendent contraction of guinea pig ileum longitudinal smooth
muscle (GPILSM) assay. These results and their n-octanol-
aqueous phosphate buffer (pH = 7.4) partition coefficients
–9
6
4
3
(Kp) are listed in Table 1. Felodipine (IC50 = 1.45 × 10 M)
2
2
was about 4-fold more potent as a CCA than its C-2
2
-(2-hydroxyethoxy)tetrahydropyran (9, 55%), together with
the bis(tetrahydropyranyl) ether derivative and unreacted
HOCH CH OH, which were separated by silica gel column
–9
CH OCH CH OH derivative (13, IC = 6.56 × 10 M), but
2
2
2
50
1
3 was about 44-fold more active than the reference drug
–8
2
2
nimodipine (IC50 = 1.49 × 10 M). These results indicate that
the C-2 CH OCH CH OH substituent in 13 is a suitable
chromatography. Deprotonation of 9 using NaH followed by
reaction with ClCH COCH CO Et gave the ethyl ace-
toacetate derivative (10), which without isolation was con-
verted to 4-(2-hydroxyethoxy)acetoacetate (11, 65%) by
treatment with HCl-EtOH at reflux for 10 minutes. Conden-
sation of 11 with (Z/E)-methyl 2-(2,3-dichlorobenzylid-
2
2
2
2
2
2
replacement for the C-2 Me substituent of felodipine. Elabo-
–8
ration of 13 to 16 (IC50 = 2.99 × 10 M) possessing a
1
-methyl-1,4-dihydropyridyl-3-carbonyloxy CDS moiety re-
duced CCA. All four compounds 13, 16, felodipine, and
ine)acetoacetate and NH OAc afforded 3-ethyl 5-methyl
Table 1. Calcium channel antagonist activity and partition coefficient (Kp)
data.
——————————————————————————————
4
1
,4-dihydro-2-[(2-hydroxyethoxy)methyl]-6-methyl-4-(2,3-
dichlorophenyl)-3,5-pyridinedicarboxylate (13, 32%). The
subsequent condensation of 13 with nicotinoyl chloride hy-
Compd
Calcium channel
antagonist activity
IC50, M
Partition
coefficient (Kp)[
b]
drochloride in the presence of Et N afforded the nicotinoyl
3
[a]
derivative 14 (90%) that was then quaternized with MeI to
yield the 1-methylpyridinium iodide salt (15, 85%). Reduc-
—
—————————————————————————————
13
6.56 ± 0.48 × 10–9
2.99 ± 0.96 × 10–8
227
344
442
187
tion of 15 with sodium dithionite (Na S O ) in the presence
2
2 6
of NaHCO using a two-phase degassed H O-Et O solvent
16
3
2
2
Felodipine
Nimodipine
1.45 ± 0.05 × 10–9
system afforded the target product 3-ethyl 5-methyl 1,4-dihy-
dro-2-[2-[1-methyl-1,4-dihydropyridyl-3-carbonyloxy)eth-
oxy]methyl]-6-methyl-4-(2,3-dichlorophenyl)-3,5-pyridine-
dicarboxylate (16, 95%).
1.49 ± 0.08 × 10–8
—
—————————————————————————————
[a]
The molar concentration of the test antagonist compound causing a 50%
decrease in the slow component, or tonic contractile response (IC50 ± SEM,
n = 3) in guinea pig ileum longitudinal smooth muscle by the muscarinic
Results and Discussion
–7
agonist carbachol (1.67 × 10 M) was determined graphically from the
The in vitro calcium channel antagonist (CCA) activities of
the 2-[2-(hydroxyethoxy)methyl] compound (13), its 1-
methyl-1,4-dihydropyridyl-3-carbonyloxy derivative (16)
dose-response curves.
[
b]Kp = concentration of the test compound in n-octanol/concentration of the
test compound in phosphate buffer (pH = 7.4).
Arch. Pharm. Pharm. Med. Chem. 332, 363–367 (1999)

1,4-Dihydropyridine Derivatives
365
Scheme 1. Reagents and conditions: (a) HOCH2CH2OH, 4-Me-C6H4-SO3H, THF, 25 °C, 16 h; (b) NaH, THF, ClCH2COCH2CO2Et, 25 °C, 16 h; (c)
HCl-EtOH, reflux, 10 min; (d) NH4OAc, EtOH, reflux, 16 h; (e) nicotinoyl chloride hydrochloride, Et3N, CH2Cl2, 25 °C, 16 h; (f) MeI, dry acetone, reflux,
16 h; (g) sodium dithionite (Na2S2O6), NaHCO3, Et2O-H2O, 25 °C, 1 h.
Table 2. Anticonvulsant activities in the maximal electroshock (MES) and
subcutaneous metrazol (scMet) screens.
nimodipine (Kp = 227, 344, 442, and 187) are highly lipo-
philic which should allow their facile passage across the
[12]
——————————————————————————————
blood-brain-barrier (BBB)
.
MES[a]
00 mg/kg 300 mg/kg 100 mg/kg 300 mg/kg
0.5 h[b] 4 h 0.5 h 4 h 0.5 h 4 h 0.5 h 4 h
——————————————————————————————
ScMet[a]
The anticonvulsant activities of 13, the CDS compound
16), felodipine and nimodipine were determined by the U.S.
(
1
National Institutes of Health, Antiepileptic Drug Develop-
ment Program [13,14]
Compd
. Phase 1 identification of anticonvulsant
activity in mice, following intraperitoneal (ip) injection of the
test compound, was determined against maximal electro-
shock (MES) and subcutaneous metrazol (scMet) induced
seizures which are models for generalized tonic clonic or
grand mal epilepsy, and absence or petit mal epilepsy, respec-
tively (see Table 2). In the MES screen, the C-2
1
3
6
0/3
0/3
1/3 0/1
0/3 0/1
2/3 1/1 NT[c] 0/1
1/1 0/1
0/1 0/1
0/1 0/1
0/1 0/1
0/1 0/1
0/1 0/1
1/5
0/1
NT
0/1
1
Felodipine 2/3
Nimodipine 0/3
1/3 0/1 1/1 0/1
CH OCH CH OH compound 13, like nimodipine, protected
2
2
2
—
—————————————————————————————
1
4
3
/3 (100 mg/kg ip dose) and 1/1 mice (300 mg/kg ip dose) at
h. The reference drug felodipine protected 2/3 mice at both
0 min and 4 h for a 100 mg/kg ip dose. In addition 13, unlike
[a]
Phase 1 identification of anticonvulsant data are expressed as the num-
ber of mice protected/the number of mice tested.
[b]
felodipine, provided modest protection in the scMet screen
1/5 mice protected at 4 h for a 300 mg/kg ip dose). In
contrast, 16 was inactive in both the MES and scMet screens
300 mg/kg ip dose). The lack of activity for 16 could be due
Time after test compound administration.
NT = not tested.
(
[c]
(
to a number of potential factors resulting in a subtherapeutic
brain concentration that include rapid egress of 16 from brain
due to a slow rate of oxidation of the CDS moiety to a
pyridinium species that would be locked in brain (see struc-
ture 15) and/or a slow rate of hydrolysis of the parent com-
pound 16 or the pyridinium species in brain to release the
Acknowledgments
We are grateful to the Medical Research Council of Canada (Grant No.
MT-8892) for financial support of this research and to the Anticonvulsant
Drug Development Program, Epilepsy Branch, NINCDS, Bethesda, for the
anticonvulsant test data.
active C-2 CH OCH CH OH compound (13).
2
2
2
Arch. Pharm. Pharm. Med. Chem. 332, 363–367 (1999)

366
Yiu and Knaus
1
Experimental
(OH), 3453 (NH), 1690, 1644 (C=O).– H NMR (CHCl3-d1): δ 7.45 (s, 1H,
NH), 7.31 (dd, J = 7.7, J = 1.6 Hz, 1H, aryl H-4), 7.24-7.27 (m, 1H, aryl H-6),
7.08 (t, J = 7.7 Hz, 1H, aryl H-5), 5.48 (s, 1H, H-4), 4.82 (d, Jgem = 16.7 Hz,
Melting points were determined using a Thomas-Hoover capillary appa-
ratus and are uncorrected. H NMR spectra were recorded on a Bruker
1
1
H, C-2 CHH′O), 4.73 (d, Jgem = 16.7 Hz, 1H, C-2 CHH′O), 4.05 (q, J = 7.1
Hz, 2H, COOCH2CH3), 3.88 (t, J = 4.3 Hz, 2H, OCH2CH2OH), 3.60-3.75
m, 2H, CH2OH), 3.62 (s, 3H, COOCH3), 2.35 (s, 3H, C-6 CH3), 1.84 (br s,
H, OH), 1.18 (t, J = 7.1 Hz, 3H, CH2CH3). Anal. Calcd. for C20H23Cl2NO6:
AM-300 spectrometer with Me4Si as internal standard. The assignment of
exchangeable protons (OH, NH) was confirmed by the addition of [D2]H2O.
IR spectra were acquired using a Nicolet 5DX-FT spectrometer. Quantitative
UV analyses, to determine partition coefficients, were performed using a
Philips PU 8700 Series UV/visible spectrometer. Microanalyses were within
(
1
C, H, N.
±0.4% of theoretical values for all elements listed, unless otherwise stated.
Column chromatography was performed using Merck 7734 (100–200 mesh)
silica gel. Tetrahydrofuran (THF) was dried over sodium-benzophenone and
3-Ethyl 5-Methyl 1,4-Dihydro-2-[2-[(3-pyridylcarbonyloxy)ethoxy]-
methyl]-6-methyl-4-(2,3-dichlorophenyl)-3,5-pyridinedicarboxylate 14
distilled just prior to use. Methyl 2-(2,3-dichlorobenzylidene)actoacetate
15]
(
12) was prepared according to the literature procedure [ . All other re-
Nicotinoyl chloride hydrochloride (0.89 g, 5 mmol) was added to a solu-
agents were purchased from the Aldrich Chemical Co.
tion of 13 (2.2 g, 5.0 mmol) and Et3N (1.4 ml, 10 mmol) in dry CH2Cl2
(30 ml) at 0 °C with stirring and the reaction was allowed to proceed at 25 °C
for 16 h. The reaction mixture was washed with water (3 × 15 ml), the solvent
from the organic layer was removed after drying (Na2SO4), and the residue
was recrystallized from EtOAc-hexane to yield 14 as a yellow crystalline
2
-(2-Hydroxyethoxy)tetrahydropyran 9
A solution of 8 (16.8 g, 200 mmol) in dry THF (50 ml) was added to a
solution of dry ethylene glycol (31.0 g, 500 mmol) in dry THF (50 ml)
containing p-toluenesulphonic acid (1.0 g, 5.3 mmol) and the reaction was
allowed to proceed at 25 °C for 16 hours with stirring. The reaction mixture
was treated with a saturated ammonia solution in MeOH until the pH was
–1
solid (5.1 g, 90%); mp 146–148 °C; IR (KBr): ν = 3386 cm (NH), 1726,
1
1
691 (C=O), 743 (pyridine CH).– H NMR (CDCl3-d1): δ 9.27 (d, J = 1.2
Hz, 1H, pyridyl H-2), 8.81 (dd, J = 4.8, J = 1.2 Hz, 1H, pyridyl H-6), 8.34
ddd, J = 7.8, J = 1.2, J = 1.2 Hz, 1H, pyridyl H-4), 7.43 (dd, J = 7.8, J = 4.8
Hz, 2H, pyridyl H-5), 7.22–7.29 (m, 2H, aryl H-4 and H-6), 7.15 (s, 1H, NH),
(
10. After removal of the solvent in vacuo, the residue was dissolved in
CH2Cl2 (50 ml), washed with saturated brine solution (3 × 15 ml) and the
organic phase was dried (Na2SO4). Removal of the solvent in vacuo, and
purification of the product obtained by elution from a silica gel column using
EtOAc-hexane (1:1, v/v) as eluent, afforded a bis-(2-tetrahydropyranyl)ethyl
7
1
2
4
1
.05 (t, J = 7.8 Hz, 1H, aryl H-5), 5.45 (s, 1H, H-4), 4.83 (d, Jgem = 15.9 Hz,
H, C-2 CHH′O), 4.74 (d, Jgem = 15.9 Hz, 1H, C-2 CHH′O), 4.58–4.69 (m,
H, OCH2CH2OCO), 4.04 (q, J = 7.1 Hz, 2H, COOCH2CH3), 3.93 (t, J =
.5 Hz, 2H, OCH2CH2OCO), 3.60 (s, 3H, CO2CH3), 2.30 (s, 3H, C-6 CH3),
.16 (t, J = 7.1 Hz, 3H, CO2CH2CH3). Product 14 was used for the synthesis
ether (1.3 g, 2.8%) that was discarded and then 9 as a light yellow liquid
1
(
16.0 g, 55%); IR (film) ν = 3080–3720 cm–1 (OH).– H NMR (CHCl3-d1):
of 15.
δ 4.40–4.50 (m, 1H, pyranyl H-2), 3.8–4.0 and 3.4–3.5 (two m, 1H each,
pyranyl H-6), 3.5-3.8 (m, 4H, HOCH2CH2O), 3.05–3.24 (br s, 1H, OH),
1
.6–2.0 (m, 2H, pyranyl H-3), 1.34–1.60 (m, 4H, pyranyl H-4 and H-5).
3-Ethyl 5-Methyl 1,4-Dihydro-2-[2-[(1-methylpyridinium-3-carbonyl-
oxy)ethoxy]methyl]-6-methyl-4-(2,3-dichlorophenyl)-3,5-pyridinedicarbox-
ylate iodide 15
Product 9 was used in the subsequent reaction for the synthesis of 11.
Ethyl 4-(2-Hydroxyethoxy)acetoacetate 11
A solution of 14 (4.2 g, 7.7 mmol) and iodomethane (2.4 ml, 38 mmol) in
dry acetone (15 ml) was heated at reflux for 16 h. The solvent was removed
in vacuo, the residue was washed with dry ether (3 × 15 ml), and dried in
A solution of 9 (16.0 g, 109 mmol) in dry THF (10 ml) was added to a
stirred suspension of NaH (8.4 g, 80% dispersion in oil, 275 mmol) in dry
THF (20 ml) under an argon atmosphere. After stirring at 25 °C for 1 h, this
mixture was cooled to 5 °C, a solution of ethyl 4-chloroacetoacetate (18.9 g,
–1
vacuo to afford 15 as a yellow foam (4.5 g, 85%); IR (KBr): ν = 3400 cm
1
(
NH), 1734, 1690 (C=O).– H NMR (CDCl3-d1): δ 9.70 (d, J = 6.1 Hz, 1H,
110 mmol) in dry THF (10 ml) was added slowly, and the reaction was
pyridinium H-6), 9.63 (s, 1H, pyridinium H-2), 9.00 (d, J = 8.1 Hz, 1H,
pyridinium H-4), 8.29 (dd, J = 8.1, J = 6.1 Hz, pyridinium H-5), 7.31 (dd, J
allowed to proceed at 25 °C for 16 h. Ethanol (5 ml) was added to the reaction
mixture and the pH was adjusted to 6–7 using 0.5 N HCl. The precipitate of
NaCl, that was formed upon acidification, was dissolved by the addition of
a minimal amount of water. After separating the aqueous layer, the solvent
from the organic phase was removed in vacuo and the residue obtained was
treated with a solution of EtOH:0.1N HCl (100:1, v/v; 20 ml). This mixture
was then refluxed for 10 min before adding water (10 ml) at 25 °C. The
solvent was removed in vacuo to the extent possible. The residue was then
dissolved in ethyl acetate (50 ml) and dried (Na2SO4). Purification of the
product by elution from a silica gel column using EtOAc-hexane (1:1, v/v)
as eluent afforded 11 as a yellow liquid (13.5 g, 65%); IR (film): ν =
=
7.9, J = 1.6 Hz, 1H, aryl H-4), 7.25 (dd, J = 7.9, J = 1.6 Hz, 1H, aryl H-6),
7
1
2
3
.08 (t, J = 7.9 Hz, 1H, aryl H-5), 5.45 (s, 1H, H-4), 4.93 (d, Jgem = 15.5 Hz,
H, C-2 CHH′O), 4.79–4.84 (m, 4H, N CH3, C-2 CHH′O), 4.70–4.72 (m,
H, OCH2CH2OCO), 3.98–4.07 (m, 4H, OCH2CH2OCO, COOCH2CH3),
.61 (s, 3H, CO2CH3), 2.37 (s, 3H, C-6 CH3), 1.18 (t, J = 7.1 Hz, 3H,
+
CH2CH3). Product 15 was used for the synthesis of 16.
3-Ethyl 5-Methyl 1,4-Dihydro-2-[2-[(1-methyl-1,4-dihydropyridyl-
3-carbonyloxy)ethoxy]methyl]-6-methyl-4-(2,6-dichlorophenyl)-
3,5-pyridinedicarboxylate 16
–
1
1
3
072–3747 cm (OH), 1737 (C=O).– H NMR (CHCl3-d1): δ 4.95 (s, 1H,
OH), 4.14–4.23 (m, 3H, CH2CH3 and HOCH2CHH′O), 3.49–3.73 (m, 4H,
HOCH2CHH′O and OCHH′CO), 3.43 (d, Jgem = 11.3 Hz, 1H, OCHH′CO),
Sodium dithionite (3.0 g, 17 mmol) was added to a mixture of 15 (2.4 g,
2
.63 (d, Jgem = 15.3 Hz, 1H, COCHH′CO), 2.47 (d, Jgem = 15.3 Hz, 1H,
3.4 mmol) and NaHCO3 (1.43 g, 17 mmol) in degassed water (50 ml) and
diethyl ether (50 ml) under an argon atmosphere with stirring and the reaction
was allowed to proceed at 25 °C for 1 h with stirring. The organic layer was
separated and washed with degassed water (3 × 10 ml). The organic layer
was dried (Na2SO4) and the solvent was removed in vacuo to yield 16 as a
COCHH′CO), 1.26 (t, J = 7.2 Hz, 3H, CH2CH3). Product 11 was used in the
subsequent reaction for the preparation of 13.
3-Ethyl 5-Methyl 1,4-Dihydro-2-[(2-hydroxyethoxy)methyl]-6-methyl-
–1
yellow foam (1.83 g, 95%); IR (KBr): ν = 3507 cm (NH), 1696 (C=O).–
4-(2,3-dichlorophenyl)-3,5-pyridinedicarboxylate 13
1
H NMR (MeSOMe-d6): δ 8.60 (s, 1H, NH), 7.40 (dd, J = 7.7, J = 1.7 Hz,
A solution of 11 (4.25 g, 22.3 mmol), (E/Z)-12 (5.3 g, 22.3 mmol) and
1
H, aryl H-4), 7.30 (dd, J = 7.7, J = 1.7 Hz, 1H, aryl H-6), 7.24 (t, J = 7.7
Hz, 1H, aryl H-5), 7.06 (d, J = 1.4 Hz, 1H, dihydropyridyl H-2), 5.84 (dd, J
7.9, J = 1.4 Hz, 1H, dihydropyridyl H-6), 5.36 (s, 1H, H-4), 4.57-4.73 (m,
3H, dihydropyridyl H-5 and C-2 CH OCH CH ), 4.10–4.24 (m, 2H,
NH4OAc (1.9 g, 25 mmol) in EtOH (100 ml) was heated at reflux for 16 h.
After removing the solvent in vacuo, the residue was dissolved in CH2Cl2
=
(
50 ml) and washed with water (3 × 25 ml). Removal of the solvent from the
2
2
2
organic phase in vacuo and purification of the residue by silica gel column
chromatography with EtOAc-hexane (1:1, v/v) as eluent afforded a yellow
solid which on recrystallization from CH2Cl2-hexane yielded 13 as a light
yellow solid (2.5 g, 32%); mp 129–131 °C. IR (KBr): ν = 3309–3557 cm–1
2 2 2 3
OCH CH OCO), 3.97 (q, J = 7.1 Hz, 2H, COOCH CH ), 3.67 (br t, J = 4.5
Hz, 2H, OCH CH OCO), 3.50 (s, 3H, COOCH ), 2.86–2.99 (m, 2H, dihy-
2
2
3
dropyridyl H-4), 2.92 (s, 3H, NCH ), 2.28 (s, 3H, C-6 CH ), 1.08 (t, J = 7.1
3
3
Hz, 3H, COOCH2CH3). Anal. Calcd. for C27H30Cl2N2O7.1/2H2O: C, H, N.
Arch. Pharm. Pharm. Med. Chem. 332, 363–367 (1999)

1,4-Dihydropyridine Derivatives
367
Determination of Partition Coefficients (Kp)
[5] G. J. Sills, A. Carswell, M. J. Brodie, Epilepsia 1994, 35, 437–442.
n-Octanol-phosphate buffer Kp values were determined using a modified
[6] P. Popoli, A. Pezzola, S. Decarolia, Arch. Int. Pharmacodyn. Ther.
1988, 292, 62–67.
procedure based on the Fujita method[ as described previously
16]
[17]
.
[
[
7] N. Bodor, Ann. N. Y. Acad. Sci. 1987, 507, 289–305.
In Vitro Calcium Channel Antagonist Assay
8] P. A. Woodard, D. Winwood, M. E. Brewster, K. S. Estes, N. Bodor,
Calcium channel antagonist activity was determined as the molar concen-
tration of the test compound required to produce 50% inhibition of the
muscarinic receptor-mediated (carbachol, 1.67 × 10 M) Ca -dependent
Drug Des. Del. 1990, 6, 15–28.
–
7
2+
[9] E. Shek, T. Murakami, C. Nath, E. Pop, N. S. Bodor, J. Pharm. Sci.
1989, 78, 837–843.
contraction (tonic response) of guinea pig ileum longitudinal smooth muscle
GPILSM) using the procedure previously reported[
.
18]
(
[
10] S.-H. Yiu, E. E. Knaus, J. Med. Chem. 1996, 39, 4576–4582.
Subcutaneous Metrazol and Maximal Electroshock Anticonvulsant Screens
[11] J. E. Arrowsmith, S. F. Campbell, P. E. Cross, J. K. Stubbs, Pharma-
cologist 1985, 270, 290.
The subcutaneous metrazol (scMet) and maximal electroshock (MES)
induced seizure screens were performed by the Anticonvulsant Development
Program, Epilepsy Branch, NINCDS, Bethesda using the procedures pre-
[12] C. Hansch, J. P. Bjorkroth, A. Leo, J. Pharm. Sci. 1987, 76, 663–687.
[19]
[13] R. L. Krall, J. K. Penry, B. G. White, H. J. Kuperberg, E. Swinyard,
viously reported . Briefly, the scMet seizure threshold test was performed
by administering 85 mg/kg of metrazol as a 0.5% solution in the posterior
midline. Protection in this screen was defined as a failure to observe a single
episode of clonic spasms of at least 5 s duration during a 30 min period
following administration of the test compound. MES seizures were elicited
with a 60 cycle ac of 50 mA intensity delivered for 0.2 s via corneal electodes.
A drop of 0.9% saline was instilled in the eye prior to application of
electrodes. Abolition of the hind limb tonic extension component of the
seizure was defined as protection in the MES screen.
Epilepsia 1978, 19, 409–428.
[
14] E. Swinyard, J. H. Woodhead in Antiepileptic Drugs (Ed.: D. M.
Woodbury, J. K. Penry, C. E. Pippenger), Raven Press, New York,
1982, pp. 111–126.
[15] S. Muller in Enantioselektive Hantzschsche Dihydropyridin-Synthese
via Metallierte Chirale β-Ketoester-Hydrazone (Ed.: J. Mainz),
Aachen, 1988, p. 75.
[
16] T. Fujita, J. Iwasa, C. Hansch, J. Am. Chem. Soc. 1964, 86, 5175–5180.
17] S.-H. Yiu, E. E. Knaus, Arch. Pharm. Pharm. Med. Chem. 1997, 330,
References
[
35–43.
[1] K. Inamura, E. Martius, K. Themner, S. Tapper, J. Pallon, G. Lovestam,
K. G. Malmqvist, B. K. Siesjo, Brain Res. 1990, 514, 49–54.
[
18] L. Dagnini, M. C. Li-Kwong-Ken, M. W. Wolowyk, H. Wynn, C. R.
Triggle, E. E. Knaus, J. Med. Chem. 1987, 30, 640–646.
[2] T. Griffiths, M. C. Evans, B. S. Meldrum, Neurosci. 1983, 10, 385–395.
[3] T. Griffiths, M. C. Evans, B. S. Meldrum, Neurosci. 1984, 12, 557–567.
[4] G. B. D. Sarro, B. S. Meldrum, G. Nistico, Br. J. Pharmacol. 1988, 93,
[19] C. Y. Fiakpui, M. N. Namchuk, E. E. Knaus, Drug Des. Del. 1990, 6,
11–121.
1
247–256.
Received: May 25, 1999 [FP399]
Arch. Pharm. Pharm. Med. Chem. 332, 363–367 (1999)