Subtype SelectiVe R-Adrenoreceptor Antagonists
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 24 7147
(70 mL). The organic phase was separated, washed with water (70
mL), dried, and concentrated to give 4.32 g (98.2%) of 13 as an
orange oil.
mg, 1.3 mmol) in 2-methylpropanol (5 mL) was submitted to
microwave irradiation for 60 min (120 °C, 100 W). The solvent
was evaporated and the resultant residue purified by chromatog-
raphy on silica gel (eluent cyclohexane/ethyl acetate/triethylamine,
50/50/0.1), yielding 240 mg of (S)-2-[((2-(2-methoxy-4-phenylphe-
noxy)ethyl)amino)methyl]-1,4-benzodioxane as a colorless oil:
[R]25D ) -26.4 (c 1, CHCl3). The secondary amine was dissolved
in ethanol (2 mL) and 1.4 N HCl/EtOH (0.2 mL) was added. The
resulting precipitate was isolated and dried, yielding 130 mg (25.3%,
based on the starting amount of mesylate) of (S)-7 as a white
solid: mp 140.9 °C; [R]25D ) -41.6 (c 1, ethanol). Anal. (C24H26-
ClNO4) C, H, Cl, N.
(R)-2-[((2-(2-Methoxy-4-phenylphenoxy)ethyl)amino)methyl]-
1,4-benzodioxane hydrochloride [(R)-7] was obtained from (S)-
2-mesyloxymethyl-1,4-benzodioxane and 12 as described for (S)-
7: mp 140.6; [R]25D ) +35.8 (c 1, ethanol); 1H NMR identical to
that of (S)-7. Anal. (C24H26ClNO4) C, H, Cl, N.
(S)-2-[((2-(2-Methoxy-5,6,7,8-tetrahydronaphthoxy)ethyl)ami-
no)methyl]-1,4-benzodioxane Hydrochloride [(S)-4]. A mixture
of (S)-2-aminomethyl-1,4-benzodioxane (1.5 g, 7.8 mmol) and 9
(1.15 g, 3.8 mmol) in 2-methylpropanol (5 mL) was submitted to
microwave irradiation for 60 min (120 °C, 100 W). The solvent
was evaporated and the residue purified by chromatography on silica
gel (eluent cyclohexane/ethyl acetate/triethylamine, 50/50/0.1),
yielding 491 mg of (S)-2-[((2-(2-methoxy-5,6,7,8-tetrhydronaph-
thoxy)ethyl)amino)methyl]-1,4-benzodioxane as a colorless oil:
[R]25D ) -30.2 (c 1, CHCl3). The secondary amine was dissolved
in ethanol (1.2 mL), and 1.4 N HCl/EtOH (0.7 mL) was added.
The resulting precipitate was isolated and dried, yielding 280 mg
(17%, based on the starting amount of 9) of (S)-4 as a white solid:
mp 122.6 °C; [R]25D ) -43.5 (c 1, ethanol). Anal. (C22H28ClNO4)
C, H, Cl, N.
(S)-2-[((2-(2-Methoxy-1-naphthoxy)ethyl)amino)methyl]-
2,3,6,7,8,9-hexahydronaphtho[2,3-b][1,4]dioxine Hydrochloride
[(S)-8]. A mixture of (R)-2-mesyloxymethyl-2,3,6,7,8,9-hexahy-
dronaphtho[2,3-b][1,4]dioxine (520 mg, 1.7 mmol) and 13 (410
mg, 1.9 mmol) in 2-methylpropanol (5 mL) was submitted to
microwave irradiation for 60 min (120 °C, 100 W). The solvent
was evaporated and the resultant residue purified by chromatog-
raphy on silica gel (eluent cyclohexane/ethyl acetate/triethylamine,
50/50/0.1), yielding 335 mg of (S)-2-[((2-(2-methoxy-1-naphthoxy)-
ethyl)amino)methyl]-2,3,6,7,8,9-hexahydronaphtho[2,3-b][1,4]-
(R)-2-[((2-(2-Methoxy-5,6,7,8-tetrahydronaphthoxy)ethyl)ami-
no)methyl]-1,4-benzodioxane hydrochloride [(R)-4] was obtained
from (R)-2-aminomethyl-1,4-benzodioxane and 9 as described for
(S)-4: mp 121.8; [R]25D ) +36.2 (c 1, ethanol); 1H NMR identical
to that of (S)-4. Anal. (C22H28ClNO4) C, H, Cl, N.
(S)-2-[((2-(2-Methoxy-6-phenylphenoxy)ethyl)amino)methyl]-
1,4-benzodioxane Hydrochloride [(S)-5]. A mixture of (S)-2-
aminomethyl-1,4-benzodioxane (590 mg, 3.6 mmol) and 10 (1 g,
3.25 mmol) in 2-methylpropanol (2.7 mL) was submitted to
microwave irradiation for 60 min (120 °C, 100 W). The solvent
was evaporated and the resultant residue treated with dichlo-
romethane and saturated aqueous solution of NaHCO3. The organic
phase was separated, dried, and concentrated and the residue
purified by chromatography on silica gel (eluent cyclohexane/ethyl
acetate/triethylamine, 50/50/0.1), yielding 400 mg of (S)-2-[((2-
(2-methoxy-6-phenylphenoxy)ethyl)amino)methyl]-1,4-benzodiox-
ane as a colorless oil: [R]25D ) -15.4 (c 1, CHCl3). The secondary
amine was dissolved in ethyl acetate (10 mL), and 2.3 N HCl/
EtOH (0.5 mL) was added. The resulting precipitate was isolated
and dried, yielding 347 mg (27%, based on the starting amount of
dioxine as a colorless oil: [R]25 ) -26.3 (c 1, CHCl3). The
D
secondary amine was dissolved in ethyl ether (2 mL) and 1.8 N
HCl/Et2O (0.23 mL) was added. The resulting precipitate was
isolated and dried, yielding 190 mg (24.5%, based on the starting
amount of mesylate) of (S)-8 as a white solid: mp 255.5 °C; [R]25
D
) -63.7 (c 1, ethanol). Anal. (C26H30ClNO4) C, H, Cl, N.
(R)-2-[((2-(2-Methoxy-1-naphthoxy)ethyl)amino)methyl]-
2,3,6,7,8,9-hexahydronaphtho[2,3-b][1,4]dioxine hydrochloride
[(R)-8] was obtained from (S)-2-mesyloxymethyl-2,3,6,7,8,9-
hexahydronaphtho[2,3-b][1,4] dioxine and 13 as described for (S)-
8: mp 255.0 °C; [R]25D ) +61.8 (c 1, ethanol); 1H NMR identical
to that of (S)-8. Anal. (C26H30ClNO4) C, H, Cl, N.
10) of (S)-5 as a white solid: mp 144.8 °C; [R]25 ) -45.1 (c 1,
D
ethanol). Anal. (C24H26ClNO4) C, H, Cl, N.
Biology. Radioligand Binding Assays. Affinities for R1a, R1b,
1d AR-subtypes and 5-HT1A serotoninergic receptor were measured
(R)-2-[((2-(2-Methoxy-6-phenylphenoxy)ethyl)amino)methyl]-
1,4-benzodioxane hydrochloride [(R)-5] was obtained from (R)-
2-aminomethyl-1,4-benzodioxane and 10 as described for (S)-5: mp
144.6; [R]25D ) +47.3 (c 1, ethanol); 1H NMR identical to that of
(S)-5. Anal. (C24H26ClNO4) C, H, Cl, N.
R
by in vitro binding studies. Briefly, membranes derived from
Chinese hamster ovary (CHO) cells expressing R1-AR subtypes
(prepared as described by Testa et al.30) were resuspended in 50
mM Tris HCl, pH 7.7, containing 10 µM pargyline and 0.1%
ascorbic acid and incubated for 30 min at 25 °C with 0.5 nM [3H]-
prazosin (NEN, 80.5 Ci/mmol) in the absence or presence of
different concentrations of the tested compounds. Prazosin (1 µM)
was routinely used to determine nonspecific binding, although our
data indicate that identical levels of nonspecific binding could be
obtained by using R1-AR ligands chemically distinct from [3H]-
prazosin, such as WB-4101 or the other compounds tested in the
present study (data not shown). Binding studies at 5-HT1A receptors
were carried out using crude membrane preparations from rat
hippocampus, which were resuspended in 50 mM Tris HCl, pH
7.7, with 10 µM pargyline and 4 mM CaCl2 and incubated for 30
min at 25 °C with 1 nM [3H]-8-OH-DPAT in the absence or
presence of different concentrations of the tested compounds. 5-HT
(1 µM) was used to determine nonspecific binding. Incubations
were stopped by rapid filtration, through GF/B filters, which were
then washed, dried, and counted in a Wallac 1409 rack â-liquid
scintillation spectrometer. At least three different experiments, in
triplicate, were carried out for each compound, and usually each
compound was tested simultaneously on the different R1-AR
subtypes. Prazosin or 5-HT were always tested in parallel, as
reference drugs. The percentage inhibitory effects obtained in the
different experiments were pooled together and the inhibition curves
were analyzed using the “one-site competition” equation built into
GraphPad Prism 4.0 (GraphPAD Softwaree, San Diego, CA). This
analysis gives the IC50 (i.e., the drug concentration inhibiting
specific binding by 50%), calculated with the relative standard error.
(S)-2-[((2-(2-Methoxy-5-phenylphenoxy)ethyl)amino)methyl]-
1,4-benzodioxane Hydrochloride [(S)-6]. A mixture of (R)-2-
mesyloxymethyl-1,4-benzodioxane (630 mg, 2.5 mmol) and 11 (700
mg, 2.9 mmol) in 2-methylpropanol (5 mL) was refluxed for 24 h.
The solvent was evaporated and the resultant residue treated with
dichloromethane (30 mL) and a saturated aqueous solution of
NaHCO3 (15 mL). The organic phase was separated, washed with
a saturated aqueous solution of NaHCO3 again (2 × 15 mL) and
then with water, dried, and concentrated. The residue was purified
by chromatography on silica gel (eluent cyclohexane/ethyl acetate/
2-methylpropanol, 50/50/0.3), yielding 470 mg of (S)-2-[((2-(2-
methoxy-5-phenylphenoxy)ethyl)amino)methyl]-1,4-benzodiox-
ane as a colorless oil: [R]25D ) -19.8 (c 1, CHCl3). The secondary
amine was dissolved in ethanol (5 mL), and 1.4 N HCl/EtOH (3
mL) was added. The resulting precipitate was isolated and dried,
yielding 250 mg (23.4%, based on the starting amount of mesylate)
of (S)-6 as a white solid: mp 159.6 °C; [R]25 ) -38.6 (c 1,
D
ethanol). Anal. (C24H26ClNO4) C, H, Cl, N.
(R)-2-[((2-(2-Methoxy-5-phenylphenoxy)ethyl)amino)methyl]-
1,4-benzodioxane hydrochloride [(R)-6] was obtained from (S)-
2-mesyloxymethyl-1,4-benzodioxane and 11 as described for (S)-
6: mp 159.6; [R]25D ) +34.3 (c 1, ethanol); 1H NMR identical to
that of (S)-6. Anal. (C24H26ClNO4) C, H, Cl, N.
(S)-2-[((2-(2-Methoxy-4-phenylphenoxy)ethyl)amino)methyl]-
1,4-benzodioxane Hydrochloride [(S)-7]. A mixture of (R)-2-
mesyloxymethyl-1,4-benzodioxane (300 mg, 1.2 mmol) and 12 (374