4-Benzylamino-1-chloro-6-substituted Phthalazines
J ournal of Medicinal Chemistry, 1998, Vol. 41, No. 18 3371
washed with brine, dried over anhydrous MgSO4, and concen-
trated under reduced pressure to give 10b (30 g, 96%) as a
white solid: 1H NMR (CDCl3) δ 1.45 (3H, t, J ) 7.2 Hz), 4.12
(2H, q, J ) 7.2 Hz), 6.97-7.02 (2H, m), 7.81-7.86 (2H, m),
9.88 (1H, s).
3-Ch lor o-4-m eth oxyben za ld eh yd e (12a ). Gen er a l P r o-
ced u r e. A mixture of 10a (420 g, 3.09 mol) and pyridine (6
mL) was treated dropwise with SO2Cl2 (510 g, 3.78 mol) with
stirring, while the temperature was held below 30 °C. The
mixture was stirred at room temperature for 0.5 h and at 70
°C for 4 h. Excess SO2Cl2 was evaporated off, and IPE (500
mL) and hexane (5 L) were added to the residue to afford a
precipitate. The precipitate was collected by filtration, washed
with hexane, and dried to give 12a (379 g, 72%) as a pinkish
solid: 1H NMR (CDCl3) δ 3.99 (3H, s), 7.05 (1H, d, J ) 8.6
Hz), 7.78 (1H, dd, J ) 8.6, 2.0 Hz), 7.91 (1H, d, J ) 2.0 Hz),
9.86 (1H, s).
3-Ch lor o-4-m eth oxya cetop h en on e (12c). To a suspen-
sion of 11 (10.0 g, 70.1 mmol) and AlCl3 (28.0 g, 210 mmol) in
CH2Cl2 (150 mL) was added AcCl (16.5 g, 210 mmol) at 0 °C.
The mixture was stirred for 2 h at 0 °C, then poured into ice
water, and extracted with CH2Cl2. The organic layer was
washed with saturated aqueous NaHCO3 and brine, then dried
over anhydrous MgSO4, and concentrated under reduced
pressure to give 12c (12.9 g, quant.) as a white solid: 1H NMR
(CDCl3) δ 2.55 (2H, s), 3.97 (3H, s), 6.96 (1H, d, J ) 8.6 Hz),
7.86 (1H, dd, J ) 8.6, 2.2 Hz), 7.99 (1H, d, J ) 2.2 Hz).
N-(3-Ch lor o-4-m eth oxyben zyl)for m a m id e (13a ). Gen -
er a l P r oced u r e. A mixture of 12a (551 g, 3.23 mol), forma-
mide (1.5 L), and formic acid (1 L) was heated at 130 °C for 6
h, then poured into ice water, and extracted with EtOAc. The
organic layer was washed with H2O, saturated aqueous
NaHCO3, H2O, and brine. After having been dried over
anhydrous MgSO4, the solution was filtered through a silica
gel pad, and the filtrate was concentrated under reduced
pressure to about 1 L. Hexane (500 mL) was added to the
residue to afford a precipitate. The precipitate was collected
by filtration and washed with a mixture of EtOAc and hexane
(1:1) to give 13a (410 g, 64%) as a white solid: 1H NMR (CDCl3)
δ 3.89 (3H, s), 4.41 (2H, d, J ) 5.6 Hz), 5.85 (1H, br s), 6.88
(1H, d, J ) 8.4 Hz), 7.16 (1H, dd, J ) 8.4, 2.4 Hz), 7.30 (1H,
d, J ) 2.4 Hz), 8.26 (1H, s).
(1H, d, J ) 7.6 Hz), 6.91 (1H, dd, J ) 7.6, 1.2 Hz), 6.94 (1H,
d, J ) 1.2 Hz), 7.86 (1H, dd, J ) 8.4, 0.4 Hz), 8.01 (1H, dd, J
) 8.4, 1.6 Hz), 8.54 (1H, dd, J ) 1.6, 0.4 Hz).
En zym e Sou r ce a n d P h osp h od iester a se Activity As-
sa y. PDE5 was separated from the supernatant of a homo-
genate of porcine platelets by DEAE-Toyopearl 650S chroma-
tography.8
PDE5 activity was determined by a modification of a
previously described two-step radioisotopic procedure.11 [3H]-
cGMP at a concentration of 1 µM was used as a substrate.
The tested compounds were dissolved in DMSO and diluted
with the assay buffer to give concentrations ranging from 10-10
to 10-6 M. The final concentration of DMSO was 5% (v/v).
Va sor ela xa n t Effect in Isola ted P or cin e Cor on a r y
Ar ter ies P r econ tr a cted w ith P GF 2r. Porcine coronary
arteries were removed, freed from adjacent tissues, and cut
into rings with great care to avoid damage to the endothelium.
The rings were longitudinally opened and mounted in organ
baths containing 10 mL of Krebs-Henseleit solution (37 °C,
pH 7.4, bubbled with 95% O2-5% CO2). The aorta strips were
allowed to equilibrate under a resting tension of 1 g. The
presence of intact endothelial cells was confirmed by brady-
kinin (final concentration, 7 × 10-9 M)-induced relaxation in
preparations precontracted with KCl (final concentration, 50
mM). The strips were contracted with PGF2R (final concentra-
tion, 10-5 M), and after the attainment of a plateau contrac-
tion, cumulative concentration-relaxation curves for a test
compound were constructed. Relaxation was calculated as a
percentage of the contractile response to PGF2R
.
Ack n ow led gm en t. We thank Drs. I. Saito, S. Sou-
da, K. Miyake, S. Abe, H. Ozaki, and K. Ishibashi for
helpful discussions and assistance during the course of
this work and the staff of Eisai Analytical Chemistry
Section for mass spectra and elemental analysis.
Refer en ces
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S. J .; Konishi, Y.; Yu, D. T.; Miskowski, T. A.; Riviello, C. M.;
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phodiesterase inhibitors. 2-Pyridyl- and -imidazoylquinazolines
3-Ch lor o-4-m eth oxyben zyla m in e Hyd r och lor id e (14a ).
Gen er a l P r oced u r e. A mixture of 13a (410 g, 2.06 mol),
EtOH (2.6 L), and concentrated HCl (260 mL) was heated at
reflux for 3 h, during which time a precipitate was formed.
The mixture was cooled, and Et2O (4 L) was added to it. The
resultant precipitate was collected by filtration and washed
with Et2O to give 14a (406 g, 95%) as a white solid. 1H NMR
(DMSO-d6) δ 3.85 (3H, s), 3.94 (2H, s), 7.18 (1H, d, J ) 8.4
Hz), 7.44 (1H, dd, J ) 8.4, 2.0 Hz), 7.61 (1H, d, J ) 2.0 Hz),
8.39 (3H, br s).
1-Ch lor o-4-[[3,4-(m e t h yle n e d ioxy)b e n zyl]a m in o]-6-
p h th a la zin eca r bon itr ile (15b) a n d 1-Ch lor o-7-[[3,4-(m eth -
ylen ed ioxy)b en zyl]a m in o]-7-p h t h a la zin eca r b on it r ile
(16b). Gen er a l P r oced u r e. To a solution of 5d (1.0 g, 4.5
mmol) and piperonylamine (810 mg, 5.4 mmol) in NMP (10
mL) was added DBU (1.7 g, 11.2 mmol). The mixture was
stirred at room temperature for 2 h, then poured into H2O,
and extracted with EtOAc. The organic layer was washed with
H2O and brine, dried over anhydrous MgSO4, and concentrated
under reduced pressure. The residue was purified by silica
gel column chromatography (eluted with toluene-THF) to give
15b, pale yellow crystals, 670 mg (44%), as the less polar
product and 16b, pale yellow crystals, 230 mg (15%), as the
more polar product.
15b: mp 163.0-164.0 °C (EtOAc); 1H NMR (CDCl3) δ 4.78
(2H, d, J ) 5.2 Hz), 5.37 (1H, t, J ) 5.2 Hz), 5.96 (2H, s), 6.81
(1H, d, J ) 8.0 Hz), 6.92 (1H, dd, J ) 8.0, 1.8 Hz), 6.94 (1H,
d, J ) 1.8 Hz), 8.05 (1H, dd, J ) 8.4, 1.4 Hz), 8.11-8.12 (1H,
m), 8.30 (1H, dd, J ) 8.4, 0.6 Hz); MS m/e (FAB) 339 (MH+).
Anal. (C17H11ClN4O2) C, H, N.
16b: mp 165.0-167.0 °C (EtOAc); 1H NMR (CDCl3) δ 4.78
(2H, d, J ) 5.2 Hz), 5.34 (1H, t, J ) 5.2 Hz), 5.96 (2H, s), 6.80