Design, synthesis, and structure-activity relationships of 3,4-dihydropyridopyrimidin-2(1H)-one derivatives as a novel class of sodium/calcium exchanger inhibitor

Article abstract of DOI:10.1248/cpb.53.1236

Design, synthesis, and structure-activity relationships for 3,4-dihydropyridopyrimidin-2(1H)-one derivatives, which are aza-3,4-dihydro- 2(1H)-quinazolinone derivatives, as the sodium/calcium (Na⁺/Ca ²⁺) exchanger inhibitors are disc

Full text of DOI:10.1248/cpb.53.1236

1236
Chem. Pharm. Bull. 53(10) 1236—1239 (2005)
Vol. 53, No. 10
Design, Synthesis, and Structure–Activity Relationships of
3,4-Dihydropyridopyrimidin-2(1H)-one Derivatives as a
Novel Class of Sodium/Calcium Exchanger Inhibitor
b
Hirohiko HASEGAWA, ,a Masami MURAOKA,a Mikiko OHMORI,a Kazuki MATSUI,a and Atsuyuki KOJIMA
*
a Research Division, Sumitomo Pharmaceuticals Co., Ltd.; 3–1–98 Kasugadenaka, Konohana-ku, Osaka 554–0022, Japan:
and b Takarazuka Organic Synthesis Department, Sumika Technoservice Co., Ltd.: 4–2–1 Takatsukasa, Takarazuka, Hyogo
665–0051, Japan. Received March 29, 2005; accepted July 22, 2005
Design, synthesis, and structure–activity relationships for 3,4-dihydropyridopyrimidin-2(1H)-one deriva-
tives, which are aza-3,4-dihydro-2(1H)-quinazolinone derivatives, as the sodium/calcium (Naꢀ/Ca2ꢀ) exchanger
inhibitors are discussed. These studies based on 3,4-dihydro-2(1H)-quinazolinone derivatives led to the discovery
of a structurally novel and potent Naꢀ/Ca2ꢀ exchanger inhibitor, 3,4-dihydropyridopyrimidin-2(1H)-one deriva-
tive (26), with an IC30 value of 0.02 mM. Compound 26 directly inhibited the Naꢀ-dependent Ca2ꢀ influx via the
Naꢀ/Ca2ꢀ exchanger after Naꢀ-free treatment in cardiomyocytes.
Key words sodium/calcium exchanger; Naꢀ/Ca2ꢀ exchanger; 3,4-dihydropyridopyimidin-2(1H)-one
The sodium/calcium (Naꢀ/Ca2ꢀ) exchanger is involved in more, KB-R7943 (4),13,14) SEA0400 (5),15,16) benzyloxy-
myocardial Ca2ꢀ regulation.1) Clinically, coronary reperfu- phenyl derivative (6)17) and SN-6 (7)18) have been reported.
sion by thrombolytic therapy or percutaneous transluminal
We have already reported design, synthesis and structure–
angioplasty has emerged as a fundamental strategy in the activity relationships for 3,4-dihydro-2(1H)-quinazolinone
management of ischemic heart disease. Nonetheless, it has derivatives with the inhibitory activities of the Naꢀ/Ca2ꢀ ex-
been suggested that sometimes early restitution of blood flow changer.19,20) In the previous article, we disclosed that these
after a period of hypoxia results in the deteriorous effects studies based on lead compound 8 with a moderate potent in-
called reperfusion injury.2,3)
hibitory activity led to the identification of a structurally
Intracellular Ca2ꢀ overload via activation of the Naꢀ/Ca2ꢀ novel and highly potent inhibitor against the Naꢀ/Ca2ꢀ ex-
exchanger after ischemic reperfusion has been indicated as a changer 9 (SM-15811), which directly inhibited the Naꢀ-de-
potential cause of this, which induces post-ischemic cardiac pendent Ca2ꢀ influx via the Naꢀ/Ca2ꢀ exchanger in car-
injury.1,3—9) Thus, inhibition of the Naꢀ/Ca2ꢀ exchanger, diomyocytes with high potency and exerted the protective ef-
which would lead to prevention of Ca2ꢀ overload, could be- fect against myocardial ischemic reperfusion injury (Fig. 2).
come a new approach for the treatment of ischemic reperfu- In order to explore a novel class of inhibitors with new skele-
sion injury. Our research therefore focused upon the discov- ton, we designed, synthesized and evaluated 3,4-dihydropyri-
ery of an inhibitor of the Naꢀ/Ca2ꢀ exchanger with high po- dopyrimidin-2(1H)-one derivatives, which is an aza-3,4-di-
tency and selectivity. A number of compounds, including hydro-2(1H)-quinazolinone derivatives (Fig. 3). Herein, we
peptidic and non-peptidic compounds have been reported as wish to report the results.
Naꢀ/Ca2ꢀ exchanger inhibitors (Fig. 1). As a peptidic in-
hibitor, Val-Met-Arg-Phe-NH2 (1) with IC50 value of 1.5 mM Chemistry
has been reported, which is a non-selective inhibitor.10) As a
Synthesis of 4-phenyl-3,4-dihydropyrido[2,3-d]pyrimidin-
non-peptidic inhibitor, aroylguanidine derivative (2)11) with 2(1H)-one (19), 4-phenyl-3,4-dihydropyrido[3,4-d]pyrim-
IC50 value of 3.4 mM has been reported which is a modified idin-2(1H)-one (20), and 4-phenyl-3,4-dihydropyrido[4,3-
amiloride derivative as is dimethylamiloride (3).12) Further- d]pyrimidin-2(1H)-one (21) having a N,N-diethylaminoethyl
as a chain aminoalkyl group at the 3-position is illustrated in
Chart 1. Trichloroacetylation of aminobenzoylpyridine 10,21)
11,21) and 1221) with trichloroacetyl chloride, followed by
Fig. 2. Chemical Structure of 3,4-Dihydro-2(1H)-quinazolinone Deriva-
tive 8 and 9 (SM-15811)
Fig. 1. Chemical Structures of Non-Peptidic Inhibitor of the Naꢀ/Ca2ꢀ
Exchanger: (2) Aroylguanidine Derivative; (3) Dimethylamiloride; (4) KB- Fig. 3. Conversion of 3,4-Dihydro-2(1H)-quinazolinone Skeleton into 3,4-
R7943; (5) SEA0400; (6) Benzyloxyphenyl Derivative; (7) SN-6
Dihydropyridopyrimidin-2(1H)-one Skeleton
∗ To whom correspondence should be addressed. e-mail: hhasegaw@sumitomopharm.co.jp
© 2005 Pharmaceutical Society of Japan

October 2005
1237
Reagents: (a) CCl3COCl, Et3N, THF; (b) Et2N(CH2)2NH2, DMSO; (c) (i) NaBH4,
DMF; (ii) EtOH, reflux.
Chart 1
treatment with N,N-diethylethylenediamine in dimethylsul-
foxide (DMSO) gave directly cyclized products 16—18, with
accompanying rearrangement of trichloromethyl group. Re-
moval of the trichloromethyl group leading to the 3,4-di-
hydropyridopyrimidin-2(1H)-one 19—21 was effected by
NaBH4. A new signal at 5.75 ppm for 19, 5.76 ppm for 20,
and 5.80 ppm for 21 indicated that trichloromethyl group
at the 4-position of 3,4-dihydropyridopyrimidin-2(1H)-one
(16—18) was replaced with hydrogen atom. These data sup-
ported the formation of 3,4-dihydropyridopyrimidin-2(1H)-
one (16—18) by the treatment of tricloroamide (13—15)
with N,N-diethylethylenediamine, respectively.
Reagents: (a) 4-aminobenzylpiperidine, DMSO; (b) NaBH4, EtOH; (c) LiAlH4, THF;
(d) 1,1ꢁ-caronyldiimidazole, THF; (e) HCl/diethyl ether.
Chart 2
Synthesis of 4-phenyl-3,4-dihydropyrido[4,3-d]pyrimidin-
2(1H)-one 26 having 1-benzylpiperidin-4-yl at the 3-position
is illustrated in Chart 2. Treatment of trichloroacetylamide
15 with 4-amino-1-benzylpiperidine in DMSO gave imine
22. Removal of the trichloroacetyl moiety with NaBH4 gave
a mixture of imine 23 and diamine 24. After separation of
imine 23 and diamine 24, imine 23 was converted into di-
amine 24 by treating with LiAlH4 in tetrahydrofuran (THF).
Treatment of diamine 24 with 1,1ꢁ-carbonyldiimidazole led
to cyclization to afford 25, which was then converted into
HCl salt of 26 by treating 25 with HCl/diethyl ether.
Table 1. Inhibitory Activities against the Naꢀ/Ca2ꢀ Exchanger
Compounda)
Structure
IC30 (mM)
1
Val-Met-Arg-Phe-NH2
10
3
9b)
19
20
21
26c)
30
0.017
4.4
Pharmacological Results and Discussion
The inhibitory activity of test compounds on Naꢀ/Ca2ꢀ ex-
change was measured by the inhibition of Naꢀ- and Kꢀ-free
contracture in isolated guinea pig left atria, performed as de-
scribed previously.22) The inhibitory activities were calcu-
lated as IC30 values. In this system, Val-Met-Arg-Phe-NH2
(1) and dimethylamiloride (3), which are known inhibitors of
the Naꢀ/Ca2ꢀ exchanger, showed inhibitory activities with
IC30 values of 10 mM and 30 mM, respectively.
6.2
2.7
At first, in order to investigate the possibility of replacing
the 2,3-dihydro-2(1H)-quinazolinone skeleton with aza-2,3-
dihydro-2(1H)-quinazolinone, we designed and synthesized
4-phenyl-3,4-dihydropyrido[2,3-d]pyrimidin-2(1H)-one (19),
4-phenyl-3,4-dihydropyrido[3,4-d]pyrimidin-2(1H)-one (20)
and 4-phenyl-3,4-dihydropyrido[4,3-d]pyrimidin-2(1H)-one
(21) having a N,N-diethylaminoethyl as a chain aminoalkyl
group at the 3-position. Their inhibitory activities were
0.02
a) All the compounds tested were racemic. b) Compound tested as citrate.
c) Compound tested as HCl salt.

1238
Vol. 53, No. 10
concentration-dependently attenuated the increase in Naꢀ-
free induced fura 2 fluorescence ratio, indicating 26 directly
inhibited the Naꢀ-dependent Ca2ꢀ influx via the Naꢀ/Ca2ꢀ
exchanger after Naꢀ-free treatment in cardiomyocytes. Com-
pound 26 would be a useful tool as a novel class of the
Naꢀ/Ca2ꢀ exchanger inhibitor as well as indicate a potential
for generating a novel class of highly potent Naꢀ/Ca2ꢀ ex-
changer inhibitors.
Experimental
Melting points were measured on a Thomas-Hoover melting point appara-
1
tus and uncorrected. H-NMR spectra were recorded on a JEOL GX270 or
JEOL JNM-LA300 spectrometers in the stated solvents using tetramethylsi-
lane as an internal standard. Elemental analyses were obtained from Sumi-
tomo Analytical Center Inc. and results obtained were withinꢂ0.4% of theo-
retical values. Thin layer chromatography and flash column chromatography
were performed on silica gel glass-backed plates (5719, Merck & Co.) and
silica gel 60 (230—400 or 70—230 mesh, Merck & Co.), respectively. Un-
less otherwise noted, all the materials were obtained from commercial sup-
pliers and used without further purification. All solvents were commercially
available grade. All reactions were carried out under a nitrogen atmosphere
unless otherwise mentioned.
The Representative Example of Synthesis of 13—15. N-(3-Ben-
zoylpyridin-2-yl)-2,2,2-trichloroacetamide (13) To a stirred THF solu-
tion (20 ml) of 2-amino-3-benzoylpyridine (10) (1.10 g, 5.54 mmol) and tri-
ethylamine (610 mg, 6.03 mmol) was added trichloroacetyl chloride (1.00 g,
5.50 mmol) dropwise at 5—15 °C. The mixture was stirred at ambient tem-
perature for 3 h. The mixture was poured into ice/water and the resultant
mixture was extracted with EtOAc. The organic layer was washed with
brine, dried over anhydrous Na2SO4, filtered, and evaporated to dryness. The
residue was crystallized from EtOH to give 13 (1.40 g, yield 74%) as a white
powder. 1H-NMR (CDCl3) d: 8.73—8.75 (1H, m), 7.99—8.02 (1H, m),
7.71—7.77 (2H, m), 7.62—7.68 (1H, m), 7.42—7.56 (2H, m), 7.23—7.28
(1H, m).
Fig. 4. Effect of 26 on the Naꢀ/Ca2ꢀ Exchange Activity in Rat Cardiomy-
ocytes
The Naꢀ/Ca2ꢀ exchange activity was estimated as the increase in fura 2 fluorescence
ratio induced by exposing to the Naꢀ-free HEPES-based buffer using a Ca2ꢀ sensitive
fluorescent indicator fura 2. Each point represents the meanꢂS.E.M. of 5 experiments.
4.4, 6.2 and 2.7 mM, respectively. Among them, 4-phenyl-
3,4-dihydropyrido[4,3-d]pyrimidin-2(1H)-one skeleton (21)
showed strongest activity. Since we have investigated the ef-
fects of substituents at the 3-position of the 3,4-dihydro-
2(1H)-quinazolinone on the activities,19,20) we introduced a 1-
benzylpiperidin-4-yl at the 3-position of 4-phenyl-3,4-dihy-
dropyrido[4,3-d]pyrimidin-2(1H)-one. As we anticipated,
compound 26 increased the activity dramatically, showing
the strong activity with an IC30 value of 0.02 mM. Its activity
was almost same as previously reported compound 911) hav-
ing the 3,4-dihydro-2(1H)-quinazolinone skeleton.
We found that 26 having 3,4-dihydropyrido[4,3-d]pyrim-
idin-2(1H)-one skeleton had strong inhibitory activity against
Naꢀ- and Kꢀ-free contracture after 30 min of Kꢀ free incuba-
tion in isolated left atria from guinea pigs. Moreover, we
evaluated 26 by fura 2 fluorescence ratio (an index of
[Ca2ꢀ]i) increased by Naꢀ-dependent Ca2ꢀ influx via the
Naꢀ/Ca2ꢀ exchanger after Naꢀ-free treatment in cardiomy-
ocytes.23) Figure 4 shows the results. 26 concentration-depen-
dently attenuated the increase in Naꢀ-free induced fura 2 flu-
orescence ratio, indicating 26 directly inhibited the Naꢀ-de-
pendent Ca2ꢀ influx via Naꢀ/Ca2ꢀ exchanger after Naꢀ-free
treatment in cardiomyocytes.
The following compounds (14, 15) were prepared by a similar method de-
scribed above for the synthesis of 13 using the appropriate starting mater-
ial(s).
N-(4-Benzoylpyridin-3-yl)-2,2,2-trichloroacetamide (14) The title
compound was prepared from 3-amino-4-benzoylpyridine (11) to give 14 in
1
96% yield. H-NMR (CDCl3) d: 11.52 (1H, br s), 9.88 (1H, s), 8.62 (1H, d,
Jꢃ5.0 Hz), 7.77—7.81 (2H, m), 7.67—7.73 (1H, m), 7.53—7.59 (2H, m),
7.49 (1H, dd, Jꢃ5.0, 0.7 Hz).
N-(3-Benzoylpyridin-4-yl)-2,2,2-trichloroacetamide (15) The title
compound was prepared from 4-amino-5-benzoylpyridine (12) to give 15 in
1
92% yield. H-NMR (CDCl3) d: 12.59 (1H, br s), 8.90 (1H, s), 8.79 (1H, d,
Jꢃ6.3 Hz), 8.60 (1H, d, Jꢃ5.6 Hz), 7.65—7.79 (3H, m), 7.52—7.59 (2H, m).
The Representative Example of Synthesis of 16—18. 3-[2-(Diethyl-
amino)ethyl]-4-phenyl-4-(trichloromethyl)-3,4-dihydropyrido[2,3-
d]pyrimidin-2(1H)-one (16) To a stirred DMSO solution (50 ml) of 13
(1.40 g, 4.07 mmol) at room temperature was added N,N-diethylethylenedi-
amine (520 mg, 4.48 mmol), and the mixture was stirred at room tempera-
ture for 24 h. The reaction mixture was poured into ice/water, then the mix-
ture was extracted with EtOAc. The organic layer was washed with brine,
dried over anhydrous Na2SO4, filtered, and evaporated to dryness. The
residue was purified by silica gel column chromatography (MeOH/CHCl3
1 : 9) to give 16 (240 mg, yield 23%). mp 252—254 °C; 1H-NMR (CDCl3) d:
9.42 (1H, br s), 8.33—8.38 (2H, m), 7.31—7.46 (3H, m), 7.13—7.19 (2H,
m), 6.83 (1H, dd, Jꢃ7.9, 4.9 Hz), 3.89—4.00 (1H, m), 3.15—3.26 (1H, m),
2.75—2.85 (1H, m), 2.20—2.34 (4H, m), 1.92—2.02 (1H, m), 0.79 (6H, m).
The following compounds (17, 18) were prepared by a similar method de-
scribed above for the synthesis of 16 using the appropriate starting material(s).
3-[2-(Diethylamino)ethyl]-4-phenyl-4-(trichloromethyl)-3,4-dihy-
dropyrido[3,4-d]pyrimidin-2(1H)-one (17) The title compound was pre-
Conclusion
We designed, synthesized and evaluated 3,4-dihydropyri-
dopyrimidin-2(1H)-one derivatives, in which 2,3-dihydro-
2(1H)-quinazolinone skeleton is replaced with aza-2,3-dihy-
dro-2(1H)-quinazolinone skeleton, in order to investigate a
novel class of Naꢀ/Ca2ꢀ exchanger inhibitors. At first, we in-
vestigated the possibility of replacing the 3,4-dihydro-2(1H)-
quinazolinone skeleton with 3,4-dihydropyridopyrimidin-
2(1H)-one. Although their inhibitory activities were not
so strong, they showed activity. Then, based on the results
we have already reported, we introduced the 4-benzyl-
aminopiperidin-4-yl at the 3-position to enhance the activity.
These simple and effective studies led to the identification of
3,4-dihydropyridopyrimidin-2(1H)-one derivative 26 having
a new type of skeleton with an IC30 value of 0.02 mM, which
1
pared from 14 to give 17 in 64% yield. H-NMR (CDCl3) d: 9.97 (1H, s),
8.33 (1H, d, Jꢃ5.3 Hz), 7.50—7.54 (3H, m), 7.17—7.20 (2H, m), 6.81 (1H,
dd, Jꢃ5.3, 0.7 Hz), 3.52—3.57 (2H, m), 2.77—2.80 (2H, m), 2.44 (4H, q,
Jꢃ7.3 Hz), 0.94 (6H, t, Jꢃ7.3 Hz).
3-[2-(Diethylamino)ethyl]-4-phenyl-4-(trichloromethyl)-3,4-dihy-
dropyrido[4,3-d]pyrimidin-2(1H)-one (18) The title compound was pre-
pared from 15 to give 18 in 32% yield. 1H-NMR (CDCl3) d: 10.45 (1H,
br s), 8.30 (1H, d, Jꢃ5.6 Hz), 7.95 (1H, s), 7.52 (2H, m), 7.31—7.40 (3H,
m), 6.79 (1H, d, Jꢃ5.6 Hz), 3.30—3.46 (2H, m), 2.70—2.81 (1H, m), 2.44

October 2005
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3.48 (2H, s), 2.82 (1H, m), 2.45 (1H, m), 1.86—2.00 (4H, m), 1.36—1.54
(2H, m).
(4H, d, Jꢃ7.3 Hz), 1.97—2.08 (1H, m), 0.93 (6H, t, Jꢃ7.3 Hz).
The Representative Example of Synthesis of 19—21. 3-[2-(Diethyl-
amino)ethyl]-4-phenyl-3,4-dihydropyrido[2,3-d]pyrimidin-2(1H)-one
(19) To a stirred N,N-dimethylfomamide (DMF) solution (10 ml) of 16
(240 mg, 0.543 mmol) at 0 °C was added sodium borohydride (82 mg,
2.17 mmol), and the mixture was stirred at ambient temperature for 3 h. The
reaction mixture was poured into ice/water, then the mixture was extracted
with EtOAc. The organic layer was washed with brine, dried over anhydrous
Na2SO4, filtered, and evaporated to dryness. The residue was dissolved in
EtOH, then the mixture was heated under reflux for 5 h. The mixture was
evaporated to dryness. The residue was purified by silica gel column chro-
matography (MeOH/CHCl3 1 : 9) to give 19 (110 mg, yield 63%). mp 160—
163 °C (from EtOAc); 1H-NMR (CDCl3) d: 8.14 (1H, dd, Jꢃ5.0, 1.7 Hz),
7.78 (1H, br s), 7.31—7.39 (5H, m), 7.25—7.28 (1H, m), 6.82 (1H, dd,
Jꢃ7.4, 5.0 Hz), 5.75 (1H, s), 3.77—3.87 (1H, m), 2.99—3.03 (1H, m),
2.69—2.79 (1H, m), 2.42—2.60 (5H, m), 0.99 (6H, t, Jꢃ7.4 Hz); Anal.
Calcd for C19H24N4O·1/3H2O: C, 69.06; H, 7.52; N, 16.96. Found: C, 68.87;
H, 7.40; N, 16.83.
The following compounds (20, 21) were prepared by a similar method de-
scribed above for the synthesis of 19 using the appropriate starting material(s).
3-[2-(Diethylamino)ethyl]-4-phenyl-3,4-dihydropyrido[3,4-d]pyrim-
idin-2(1H)-one (20) The title compound was prepared from 17 to give 20
in 54% yield. mp 138—141 °C (from EtOAc); 1H-NMR (CDCl3) d: 8.11
(1H, s), 8.11 (1H, d, Jꢃ5.0 Hz), 7.68 (1H, br s), 7.30—7.36 (5H, m), 6.86
(1H, d, Jꢃ5.0 Hz), 5.76 (1H, s), 3.77—3.87 (1H, m), 2.97—3.08 (1H, m),
2.66—2.78 (1H, m), 2.41—2.59 (5H, m), 0.99 (6H, t, Jꢃ7.3 Hz); Anal.
Calcd for C19H24N4O: C, 70.34; H, 7.46; N, 17.27. Found: C, 69.95; H, 7.35;
N, 16.98.
3-(1-Benzylpiperidin-4-yl)-4-phenyl-3,4-dihydropyrido[4,3-d]pyrim-
idin-2(1H)-one (25) To a stirred THF solution (100 ml) of 24 (8.00 g,
21.5 mmol) at room temperature was added 1,1ꢁ-carbonyldiimidazole
(5.00 g, 30.8 mmol), and the mixture was heated under reflux for 8 h. After
the mixture was cooled to room temperature, the mixture was evaporated to
dryness. The residue was purified by silica gel column chromatography
(MeOH/CHCl3 1 : 9) to give the crude crystal. This crude crystal was crys-
tallized from EtOH/diethyl ether to give 25 (4.20 g, yield 49%). mp 209—
1
210 °C (from EtOH/diethyl ether); H-NMR (CDCl3) d: 8.35 (1H, s), 8.26
(1H, d, Jꢃ5.6 Hz), 8.09 (1H, br s), 7.23—7.38 (10H, m), 6.65 (1H, d,
Jꢃ5.6 Hz), 5.64 (1H, s), 4.36 (1H, m), 3.46 (2H, s), 2.96 (1H, m), 2.80 (1H,
m), 2.00—2.10 (3H, m), 1.50—1.65 (3H, m); Anal. Calcd for C25H26N4O:
C, 75.35; H, 6.58; N, 14.05. Found: C, 74.97; H, 6.41; N, 14.02.
HCl Salt of 3-(1-Benzylpiperidin-4-yl)-4-phenyl-3,4-dihydropyrido-
[4,3-d]pyrimidin-2(1H)-one (26) To a stirred EtOH solution of 25 at
room temperature was added 1 M HCl/diethyl ether, and the mixture was
stirred at ambient temperature for 30 min. The mixture was evaporated to
dryness. The residue was recrystallized from EtOH/diethyl ether to give 26.
mp ꢄ230 °C; 1H-NMR (CDCl3) d: 11.27 (1H, s), 10.66 (1H, br s), 8.81 (1H,
s), 8.45 (1H, d, Jꢃ6.8 Hz), 7.56 (2H, m), 7.43—7.48 (5H, m), 7.39 (2H, m),
7.31 (1H, m), 7.24 (1H, d, Jꢃ6.8 Hz), 6.04 (1H, s), 4.27 (1H, m), 4.21 (2H,
s), 3.21—3.42 (3H, m), 2.95—3.04 (2H, m), 1.88 (1H, m), 1.65 (2H, m);
Anal. Calcd for C25H26N4O·2HCl·3/2H2O: C, 60.24; H, 6.27; N, 11.24.
Found: C, 60.04; H, 6.22; N, 11.04.
Acknowledgement We wish to thank Ms. Hitomi Sakanaka for evaluat-
ing the inhibitory activities of the compounds against the Naꢀ/Ca2ꢀ ex-
changer.
3-[2-(Diethylamino)ethyl]-4-phenyl-3,4-dihydropyrido[4,3-d]pyrim-
idin-2(1H)-one (21) The title compound was prepared from 18 to give 21
in 66% yield. mp 133—134 °C (from EtOH/diethyl ether); 1H-NMR
(CDCl3) d: 8.26 (1H, d, Jꢃ5.3 Hz), 8.16 (1H, s), 7.30—7.36 (5H, m), 6.63
(1H, d, Jꢃ5.3 Hz), 5.80 (1H, s), 3.81—3.89 (1H, m), 2.97—3.09 (1H, m),
2.73—2.76 (1H, m), 2.44—2.60 (5H, m), 0.99 (6H, t, Jꢃ7.3 Hz); Anal.
Calcd for C19H24N4O·0.28H2O: C, 69.26; H, 7.51; N, 17.01. Found: C,
68.93; H, 7.11; N, 16.84.
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N-{3-[(E)-[(1-Benzylpiperidin-4-yl)imino](phenyl)methyl]pyridin-4-
yl}-2,2,2-trichloroacetamide (22) To a stirred DMSO solution (100 ml) of
15 (19.6 g, 57.0 mmol) at room temperature was added 4-amino-1-ben-
zylpiperidine (13.0 g, 68.3 mmol), and the mixture was stirred at ambient
temperature for 48 h. The mixture was poured into ice/water, then the mix-
ture was extracted with EtOAc. The organic layer was washed with brine,
dried over anhydrous Na2SO4, filtered, and evaporated to dryness. The
residue was purified by silica gel column chromatography (hexane/EtOAc
1 : 1) to give the crude product. This crude product was crystallized from
1
EtOAc to give 22 (18.5 g, yield 63%). mp 151—152 °C; H-NMR (CDCl3)
d: 8.60 (1H, d, Jꢃ5.9 Hz), 8.52 (1H, d, Jꢃ5.9 Hz), 8.07 (1H, s), 7.51—7.53
(3H, m), 7.27—7.32 (5H, m), 7.14—7.18 (2H, m), 3.44 (2H, s), 3.14—3.22
(1H, m), 2.87 (2H, m), 1.96—2.08 (2H, m), 1.52—1.83 (4H, m).
3-[(E)-[(1-Benzylpiperidin-4-yl)imino](phenyl)methyl]pyridin-4-
amine (23) and 3-[[(1-Benzylpiperidin-4-yl)amino](phenyl)methyl]-
pyridin-4-amine (24) To a stirred EtOH solution (150 ml) of 22 (18.0 g,
34.9 mmol) at 0 °C was added NaBH4 (2.65 g, 70.1 mmol), and the mixture
was stirred at ambient temperature for 5 h. The reaction mixture was poured
into ice/water, then EtOH was evaporated. The mixture was extracted with
EtOAc. The organic layer was washed with brine, dried over anhydrous
Na2SO4, filtered, and evaporated to dryness. The residue was purified by sil-
ica gel column chromatography (MeOH/CHCl3 1 : 9) to give 23 (4.82 g,
yield 37%) and 24 (6.65 g, yield 51%).
To a stirred suspension of LiAlH4 (680 mg, 17.9 mmol) in THF (100 ml)
at room temperature was added a THF solution (30 ml) of 23 (6.65 g,
17.9 mmol), and the mixture was heated under reflux for 1 h. After the mix-
ture was cooled to room temperature, a mixture of THF and H2O (1 : 1) was
added dropwisely. Then, the resultant mixture was filtered through celite.
The filtrate was concentrated and the residue was extracted with EtOAc. The
organic layer was washed with brine, dried over anhydrous Na2SO4, filtered,
and evaporated to dryness. The residue was purified by silica gel column
chromatography (MeOH/CHCl3 1 : 9) to give 24 (4.20 g, yield 63%).
Compound 23: 1H-NMR (CDCl3) d: 7.80 (1H, d, Jꢃ5.6 Hz), 7.74 (1H, s),
7.43—7.46 (3H, m), 7.22—7.33 (5H, m), 7.11—7.14 (2H, m), 6.49 (1H, d,
Jꢃ5.6 Hz), 3.47 (2H, s), 3.15—3.22 (1H, m), 2.77—2.81 (2H, m), 1.95—
2.02 (2H, m), 1.73—1.87 (2H, m), 1.63—1.67 (2H, m).
Compound 24: 1H-NMR (CDCl3) d: 8.06 (1H, d, Jꢃ5.6 Hz), 7.98 (1H, s),
7.24—7.35 (10H, m), 6.42 (1H, d, Jꢃ5.6 Hz), 5.59 (2H, br s), 5.08 (1H, s),