1,3-Dioxolane-based ligands as a novel class of α1-adrenoceptor antagonists

Article abstract of DOI:10.1021/jm021078o

1,3-Dioxolane-based compounds (2-14) were synthesized, and the pharmacological profiles at α₁-adrenoceptor subtypes were assessed by functional experiments in isolated rat vas deferens (α_1A), spleen (α_1B), and aorta (α_1D). Compound 9, with a pA₂ of 7.53, 7.36, and 8.65 at α_1A, α_1B, and α_1D, respectively, is the most potent antagonist of the series, while compound 10 with a pA₂ of 8.37 at α_1D subtype and selectivity ratios of 162 (α_1D/α_1A) and 324 (α_1D/α_1B) is the most selective. Binding assays in CHO cell membranes expressing human cloned α₁-adrenoceptor subtypes confirm the pharmacological profiles derived from functional experiments, although the selectivity values are somewhat lower. Therefore, it is concluded that 1,3-dioxolane-based ligands are a new class of α₁-adrenoceptor antagonists.

Full text of DOI:10.1021/jm021078o

1504
J . Med. Chem. 2003, 46, 1504-1511
1,3-Dioxola n e-Ba sed Liga n d s a s a Novel Cla ss of r1-Ad r en ocep tor An ta gon ists
Livio Brasili,*,† Claudia Sorbi,† Silvia Franchini,† Massimo Manicardi,†,| Piero Angeli,‡ Gabriella Marucci,‡
Amedeo Leonardi,§ and Elena Poggesi§
Dipartimento di Scienze Farmaceutiche, Universita` degli Studi di Modena e Reggio Emilia, Via Campi 183,
41100 Modena, Italy, Dipartimento di Scienze Chimiche, Universita` degli Studi di Camerino, Via S. Agostino 1,
62032 Camerino, Italy, and Divisione Ricerca e Sviluppo, Recordati S.p.A., Via Civitali 1, 20148 Milano, Italy
Received October 23, 2002
1,3-Dioxolane-based compounds (2-14) were synthesized, and the pharmacological profiles at
R1-adrenoceptor subtypes were assessed by functional experiments in isolated rat vas deferens
(R1A), spleen (R1B), and aorta (R1D). Compound 9, with a pA2 of 7.53, 7.36, and 8.65 at R1A, R1B,
and R1D, respectively, is the most potent antagonist of the series, while compound 10 with a
pA2 of 8.37 at R1D subtype and selectivity ratios of 162 (R1D/R1A) and 324 (R1D/R1B) is the most
selective. Binding assays in CHO cell membranes expressing human cloned R1-adrenoceptor
subtypes confirm the pharmacological profiles derived from functional experiments, although
the selectivity values are somewhat lower. Therefore, it is concluded that 1,3-dioxolane-based
ligands are a new class of R1-adrenoceptor antagonists.
Ch a r t 1. Strategy for the Design of 1,3-Dioxolanes as
R1-Adrenoceptor Antagonists
In tr od u ction
The receptors for adrenaline and noradrenaline,
designed as the adrenoceptors, have been studied for
almost a century and have provided many targets for
drug action. Before the advent of molecular biology,
functional and binding assays were used initially to
divide adrenoceptors into the major classes R and â1 and
then into R1 and R22,3 and â1 and â2.4 Adrenoceptors were
one of the first targets for the cloning technique
developed in the 1980s. At present, nine human ones
falling into three groups (R1, R2, and â) have been cloned.
After some initial confusion,5 there now appears to be
a correlation between the recombinant adrenoceptors
and those previously characterized in native tissues.
Amino acid sequence analyses show 50% identity among
the three members of each group and 30-40% identity
between receptors in different groups. This is consistent
with functional adrenoceptor pharmacology, which sug-
gests much greater divergence among R1-, R2-, and
â-adrenoceptors than among subtypes of either class.
As far as R1-adrenoceptors are concerned, they can
be divided into at least three subtypes, namely, R1A (R1a),
R1B (R1b), and R1D (R1d), with upper and lower case
subscripts being used to designate the native and
recombinant receptors, respectively.5-7
This situation, although not definitive because emerg-
ing data seem to predict further subtyping, has given
new impulse to medicinal chemists in their search of
new and more selective ligands. As a result, several
relatively selective ligands for R1-adrenoceptor subtypes
are now available.8,9 The R1A subtype, being the most
prevalent subtype present in the prostate,10,11 has
received much attention as a potential target for symp-
tomatic treatment of benign prostatic hyperplasia (BPH),
and several uroselective agents have been revealed.12
In contrast, a potential therapeutic use for R1B and R1D
subtype selective ligands has not been found yet.
However, there is some evidence of a prominent role of
the R1B subtype in the regulation of blood pressure
because R1B knockout mice displayed a significantly
reduced responsiveness to phenylephrine-induced in-
crease in blood pressure.13 There is also much interest
in better understanding the role of the R1D subtype. It
has been shown that in the human bladder detrusor,
R
1d mRNA is the predominant subtype,14 and it has been
postulated that the R1D receptor blockade may amelio-
rate the irritative symptoms of BHP that result from
involuntary contraction of the bladder smooth muscle.15
Therefore, the discovery of selective agents is of para-
mount importance in order to define better their physi-
ological role(s) and to discover new drug candidates.
Our group has recently undertaken a research project
aimed at developing new and selective R1-subtype
antagonists using as a starting point WB 4101 {N-[2-
(2,6-dimethoxyphenoxy)ethyl]-2,3-dihydro-1,4-benzodiox-
in-2-methanamine, 1}, a prototype of the well-known
class of R1-adrenoceptor antagonists (benzodioxanes)
whose chemical structure incorporates a 2,3-dihydro-
1,4-benzodioxin-2-yl moiety as its main feature.16
Our first aim was to verify whether the 2,3-dihydro-
1,4-benzodioxin-2-yl moiety could be replaced by the
2-phenyl-1,3-dioxolanyl structure, as in 2 (Chart 1).
Structure modification of compound 2 has led to the
* To whom correspondence should be addressed. Phone: ++39 59
205 5139. Fax: ++39 59 205 5131. E-mail: brasili.livio@ unimore.it.
† Universita` degli Studi di Modena e Reggio Emilia.
| Current address: Department of Medicinal Chemistry, Glaxo-
SmithKline, Stevenge, England.
‡ Universita` degli Studi di Camerino.
§ Recordati S.p.A., Milano.
10.1021/jm021078o CCC: $25.00 © 2003 American Chemical Society
Published on Web 03/13/2003

1,3-Dioxane-Based Ligands as Antagonists
J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 8 1505
Ta ble 1. Antagonist Potency, Expressed as pKb (or pA2) Values, and Selectivities of Compounds 1, 2-4c/t, 5, 6-8c/t at
R1-Adrenoceptors in Isolated Rat Prostatic Vas Deferens (R1A), Spleen (R1B), and Thoracic Aorta (R1D
)
discovery of a new class of R1-adrenoceptor ligands.
Here, we report on the syntheses and initial qualitative
structure-activity relationship studies.
P h a r m a cology
Receptor subtype selectivity of compounds 2-14 was
determined at R1-adrenoceptors on different isolated
tissues using 1 and BMY-7378 as standard compounds.
Blocking activity was assessed by antagonism of (-)-
noradrenaline-induced contraction of rat prostatic vas
Ch em istr y
Compounds 2-14 were synthesized (Schemes 1-3)
by standard procedures and characterized by 1H nuclear
magnetic resonance (NMR) and elemental analysis. The
chloro derivatives 21-28, the key intermediates ob-
tained by reacting the appropriate aldehyde or ketone
with 3-chloro-1,2-propanediol, were aminated with
amines 18-20. The diastereomeric mixtures were sepa-
rated by flash chromatography at this stage, and the
cis and trans stereochemistry was assigned by measure-
ments of the nuclear Overhauser effect (NOE) between
the hydrogen atom (or methyl group) at C2 and the
hydrogen atom at C4. Methylation of the nitrogen atom,
as in 41, was achieved through the acylation reaction
to give 40, followed by reduction with LiAlH4. Amines
18-20 were prepared by reacting chloroacetamide and
the appropriate phenol followed by reduction with
diborane.
17
19
deferens (R1A
)
or thoracic aorta (R1D
)
and by antago-
nism of (-)-phenylephrine-induced contraction of rat
spleen (R1B).18
The pharmacological profile was further evaluated
by radioligand binding assay using [3H]prazosin to
label cloned human R1-adrenoceptors expressed in CHO
cells.20
Resu lts a n d Discu ssion
The pharmacological results expressed as pKb or pA2,
obtained on functional preparations such as prostatic
vas deferens (R1A), spleen (R1B), and thoracic aorta (R1D
of rat, are reported in Tables 1 and 2. All the compounds
behave as R1-adrenoceptor antagonists with varying
degrees of potency and selectivity. Compounds 2c/t (c,
)

1506 J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 8
Brasili et al.
Ta ble 2. Antagonist Potency, Expressed as pKb (or pA2) Values, and Selectivities of Compounds 5, 9-12, 13c/t, 14, and BMY-7378 at
R1-Adrenoceptors in Isolated Rat Prostatic Vas Deferens (R1A), Spleen (R1B), and Thoracic Aorta (R1D
)
cis; t, trans), regardless of the stereochemistry at
positions 2 and 4 of the 1,3-dioxolane ring, are less
active than the lead compound 1, indicating that the
2-phenyl-1,3-dioxolanyl moiety as such is not a good
replacement for the 2,3-dihydro-1,4-benzodioxin-2-yl
structure. However, the affinity values found encour-
aged us to carry out further structure modification in
an attempt to improve both affinity and selectivity.
Introduction of bulkier substituents at position 2 has
a divergent effects on R1A and R1D subtypes. At R1A, a
decrease of affinity is observed (the exceptions being 3t
and 6t), while at R1D the affinity is increased (with the
exception of 3c/t). As a consequence, a significant
selectivity for the latter subtype is observed. Particu-
larly interesting are the results obtained by replacing
the phenyl ring with an R-naphthyl to give compounds
7c/t. In this case when the stereochemistry is cis
(compound 7c), although the affinity is not striking (pKb
) 7.32), the R1D selectivity is relevant and higher by 2
subtypes, while at the R1D subtype a small, not signifi-
cant, variation was observed. As a result, the R1D
selectivity was therefore increased by up to more than
2 orders of magnitude (R1D/R1A ) 162; R1D/R1B ) 324).
It appears that only one methoxy group, in the ortho
position, is allowed for optimal interaction at the three
receptor subtypes (9 vs 5), a second one being detri-
mental, most probably because of steric hindrance, to
affinity. Furthermore, one methoxy group seems to
contribute positively to the binding at R1A and R1B
subtypes, while at the R1D subtype it does not play any
significant role.
Compound 10 has a basic center represented by the
secondary amine that, once protonated at physiological
pH, should constitute the first recognition step through
a long-range electrostatic interaction. We synthesized
compounds 11 and 12 in order to verify the importance
of a secondary amine as the basic center. The results
show that the secondary amine is important for affinity,
since the tertiary amine and its quaternary derivative
are less active than the secondary one.
orders of magnitude over the R1A-subtype (R1D/R1A
209).
g
Another important finding of this investigation is the
role played by the diphenyl substitution. The results
obtained with monophenyl derivatives 13c/t and with
the spiro derivative 14 show that both aromatic rings
are important for affinity at R1A and R1D subtypes and
selectivity, since the three derivatives are less active
at the two receptor subtypes and slightly more active
than compound 10 at the R1B subtype.
Compounds 9 and 10 were also tested on cloned
human R1-adrenoceptor subtypes. The results, shown
in Table 3, confirm that this new class of compounds
potently binds to the R1-adrenoceptors, although the
Owing to the presence of only one chiral center, which
would avoid the time-consuming diastereomer separa-
tion, we chose compound 5 as a new starting point at
which to modify the structure of the lateral chain
carrying the basic moiety. Removing one of the two
methoxy groups of the (2,6-dimethoxyphenoxy)ethyl
portion of the molecule, affording compound 9, caused
30- to 60-fold increase of affinity at the three receptor
subtypes, while the selectivity for the R1D subtype was
virtually unchanged. When the second methoxy group
was also removed, as in 10, the affinity decreased by
23-fold and 32-fold, respectively, at the R1A and R1B

1,3-Dioxane-Based Ligands as Antagonists
J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 8 1507
a
Ta ble 3. Affinity Constants, Expressed as pKi Values, and
Selectivities of Compounds 1, 9-12, and BMY-7378 for Human
Recombinant R1-Adrenoceptor Subtypes
Sch em e 1
compd
pKi(R1a
)
pKi(R1b
)
pKi(R1d
)
R
1d/R1a R1d/R1b R1a/R1b
1
9
10
11
12
9.37
7.61
7.43
6.08
7.47
6.42
8.0
9.29
8.03
7.94
<6
0.8
3
3
20
7
6
23
2
2
0.3
0.6
2
7.34
7.20
6.59
7.69
6.15
<0.9
<0.03 <0.02
<0.3
<6
BMY-7378
8.89 295
550
a
pKi values agreed to (20%.
selectivity is not as large as that found in functional
studies. Binding studies also confirm the detrimental
effect of nitrogen methylation, since compound 11 shows
affinity values lower than those of parent compound 10.
Surprisingly, the methyl iodide derivative of 11, com-
pound 12, behaves differently with respect to functional
studies. In fact, 12 either maintains affinity at the R1A
subtype or slightly increases it at the R1B one, while at
the R1D subtype the affinity is practically lost. These
discrepancies are not unusual and may be ascribed to
several factors such as species variations and/or differ-
ent bioavailability of compounds at the receptor level.
Recently, other explanations have been taken into
consideration.16,21 Receptor dimerization or heterodimer-
ization, which may occur in both natural and artificial
systems, is one of these. In this case, the new entities
formed do not always give a signal as a monomer or as
dimers. Alternatively, the antagonist may not adhere
perfectly to the concept of neutral antagonism but
behaves as an inverse agonist that is system-dependent.
In conclusion, starting from WB 4101, we have
discovered a new class of R1-adrenoreceptor ligands
bearing a 1,3-dioxolane structure. Adequate substitu-
ents may address the selectivity toward one subtype or
the other. Compounds 9 and 10 are outstanding for their
affinity and selectivity, with the latter being one of the
most selective antagonists, at least in functional studies,
for the R1D subtype.
solvent was evaporated under vacuum, and the residue was
treated with a solution of 5% NaOH. Then it was extracted
with CHCl3 (3×). The organic layer was dried over Na2SO4
and the solvent was evaporated under vacuum to give the
desired compound.
2-(2-Meth oxyph en oxy)acetam ide (16): 18.13 g (100 mmol);
1
yield 83%; mp 131-132 °C; H NMR (CDCl3) δ 3.92 (s, 3H),
4.57 (s, 2H), 5.95 (brs, 2H), 7.00 (m, 4H).
2-P h en oxya ceta m id e (17): 4.45 g (29 mmol); yield 56%;
mp 90-92 °C; 1H NMR (CDCl3) δ 4.48 (s, 2H), 5.80 (brs, 1H),
6.55 (brs, 1H), 6.94 (m, 3H), 7.28 (m, 2H).
Gen er a l P r oced u r e for th e Syn th esis of Com p ou n d s
19 a n d 20 (Sch em e 1). These compounds were prepared
following the procedure already described for 18.22 To a
solution of 16 or 17 in dry diglyme was added dropwise a
solution of 2 M BH3S(CH3)2 in dry THF while stirring at room
temperature and under nitrogen atmosphere. The mixture was
heated at 90 °C for 18 h. After the mixture was cooled, the
excess reducing agent was destroyed by cautious addition of
MeOH. After 2 h, the solution was acidified with concentrated
HCl (pH 2) and then refluxed for an additional 2 h. The solvent
was evaporated under vacuum, water was added, and the
residue was washed with CHCl3 (3×). The aqueous phase was
basified with NaOH pellets and then extracted with CHCl3
(3×). The organic layer was dried over Na2SO4, and the solvent
was evaporated under vacuum to give the desired compound
as oils.
More extensive structure-activity relationship stud-
ies are in progress and will be reported in due course.
2-(2-Meth oxyph en oxy)eth ylam in e (19): 4.47 g (27 mmol);
1
yield 55%; H NMR (CDCl3) δ 1.59 (s, 2H), 3.14 (t, 2H), 3.90
Exp er im en ta l Section
(s, 3H), 4.08 (t, 2H), 6.95 (m, 4H).
2-P h en oxyeth yla m in e (20): 2.35 g (17 mmol); yield 59%;
1H NMR (CDCl3) δ 1.59 (s, 2H), 3.03 (t, 2H), 3.94 (t, 2H), 6.90
(m, 3H), 7.25 (m, 2H).
Ch em istr y. The structural characterization was done with
NMR and elemental analyses techniques (C, H, N elemental
analyzer model 1106, Carlo Erba Instruments). Analyses
indicated by the symbols were within (0.4 of the theoretical
values. Melting points were determined on a Bu¨chi 510
capillary melting point apparatus and are uncorrected. 1H
NMR spectra were recorded on a Bruker DPX 200 Avance
working at 200.13 MHz and at a temperature of 300 K.
Chemical shifts are reported as δ (ppm) relative to tetra-
methylsilane (s ) singlet, brs ) broad singlet, d ) doublet, dd
) double doublet, ddd ) double double-doublet, t ) triplet,
m ) multiplet, pseudot ) pseudotriplet). Silica gel TLC plates
(Merck, Kieselgel 60, F254) were used to monitor the progres-
sion of the reactions. Chromatographic separations were
performed on silica gel columns (Kieselgel 60, 0.040-0.063
mm, Merck) by flash chromatography. The names of com-
pounds were generated by applying the PC software AU-
TONOM, version 2.1.
Gen er a l P r oced u r e for th e Syn th esis of Com p ou n d s
21-28 (Sch em e 2). To a solution of aldehyde or ketone in
toluene was added an excess (1.5-3 equiv) of 3-chloro-1,2-
propanediol and a catalytic amount of p-toluenesulfonic acid
(pTsOH). The reaction mixture was then refluxed, using a
Dean-Stark apparatus, for 4-5 h in the case of reactions with
aldehydes and for 2-4 days in the case of those with ketones.
The mixture was washed with 10% NaHSO3 solution (3×) (in
the case of aldehydes) or with H2O (2×) (in the case of ketones)
and then with a saturated solution of NaHCO3 (3×) and brine
(2×). The organic layer was dried over Na2SO4, and the solvent
was evaporated under vacuum to give the desired compounds
21-28 as oils. Compounds 22 and 23 were purified by flash
chromatography, eluting with cyclohexane/ethyl acetate, 95:
5. With the exception of 24, all the compounds were cis and
trans mixtures and no attempts at diastereomeric separation
were made at this stage.
Gen er a l P r oced u r e for th e Syn th esis of Com p ou n d s
16 a n d 17 (Sch em e 1). These compounds were prepared
following the procedure already described for 15.22 To a
solution of Na in ethanol was added, under mechanical
stirring, guaiacol or phenol. The mixture was refluxed for 30
min. Then 2-chloroacetamide and a catalytic amount of KI
were added and heating was maintained for 20-22 h. The
4-Ch lor om eth yl-2-p h en yl[1,3]d ioxola n e (21): 9.70 g (49
1
mmol); yield 75%; H NMR (CDCl3) δ 3.57 (dd, 1H), 3.64 (dd,
1H), 3.70 (dd, 1H), 3.76 (dd, 1H), 3.96 (dd, 1H), 4.17 (d, 2H),
4.33 (dd, 1H), 4.49, 4.51 (m, m, 1H, 1H), 5.87, 6.03 (s, s, 1H,
1H), 7.46 (m, m, 5H, 5H).

1508 J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 8
Brasili et al.
Sch em e 2a
Sch em e 3
a
c: cis. t: trans. The cis and trans compounds were separated
when indicated by c/t.
2-Ben zyl-4-ch lor om eth yl[1,3]d ioxola n e (22): 1.57 g (7.4
mmol); yield 89%; 1H NMR (CDCl3) δ 3.03 (m, 4H), 3.24, 3.46
(dd, dd, 1H, 1H), 3.52, 3.66 (dd, dd, 1H, 1H), 3.77, 4.18 (dd,
dd, 1H, 1H), 3.94, 3.99 (ddd, dd, 1H, 1H), 4.32 (m, 2H), 5.19,
5.31 (t, t, 1H, 1H), 7.33 (m, 10H).
4-Ch lor om eth yl-2-m eth yl-2-p h en yl[1,3]d ioxola n e (23):
1.21 g (5.7 mmol); yield 14%; 1H NMR (CDCl3) δ 1.68, 1.72 (s,
s, 6H), 3.18, 4.30 (dd, dd, 1H, 1H), 3.64 (m, 4H), 3.85, 3.98
(dd, dd, 1H, 1H), 4.27 (m, 1H), 4.48 (m, 1H), 7.37 (m, 6H), 7.50
(m, 4H).
SO4 and the solvent was evaporated under vacuum to give the
desired amines as oils. Diastereomeric separations were ac-
complished by flash chromatography, eluting with cyclohexane/
ethyl acetate, 20:80 f ethyl acetate, 100% f ethyl acetate/
methanol, 80:20. In the case of amines 32, 36, 37, and 39, the
residues were purified by flash chromatography, eluting with
ethyl acetate, 100%.
cis-[2-(2,6-Dim e t h oxyp h e n oxy)e t h yl](2-p h e n yl[1,3]-
d ioxola n -4-ylm eth yl)a m in e (29c): 0.17 g (0.47 mmol); yield
4-Ch lor om eth yl-2,2-d ip h en yl[1,3] d ioxola n e (24): 15.00
1
1
g (55 mmol); quantitative yield; H NMR (CDCl3) δ 3.50 (dd,
11%; H NMR (CDCl3) δ 2.35 (brs, 1H), 2.96 (m, 4H), 3.80 (s,
1H), 3.71 (dd, 1H), 4.04 (dd, 1H), 4.16 (dd, 1H), 4.46 (m, 1H),
7.34 (m, 6H), 7.53 (m, 4H).
6H), 3.91 (dd, 1H), 4.15 (m, 3H), 4.41 (m, 1H), 5.85 (s, 1H),
6.57 (d, 2H), 6.99 (dd, 1H), 7.38 (m, 3H), 7.53 (m, 2H).
The free amine was transformed into the corresponding
oxalate salt, which is crystallized from methanol to give
2-Ben zyd r yl-4-ch lor om eth yl[1,3] d ioxola n e (25): 7.20 g
(25 mmol); quantitative yield; 1H NMR (CDCl3) δ 2.80 (dd, 1H),
3.22 (dd, 1H), 3.60 (ddd, 2H), 3.80 (dd, 1H), 3.94 (ddd, 2H),
3.99 (dd, 1H), 4.17 (m, 1H), 4.27 (d, 1H), 4.29 (m, 1H), 4.32 (d,
1H), 5.62 (d, 1H), 5.78 (d, 1H), 7.33 (m, 20H).
4-Ch lor om eth yl-2-n a p h th a len -1-yl[1,3]d ioxola n e (26):
1.04 g (4.2 mmol); yield 65%; 1H NMR (CDCl3) δ 3.60 (dd, 1H),
3.79 (m, 3H), 4.12 (dd, 1H), 4.30 (m, 2H), 4.41 (dd, 1H), 4.62
(m, 2H), 6.57 (s, 1H), 6.71 (s, 1H), 7.57, 7.90 (m, m, 12H), 8.20
(m, 2H).
4-Ch lor om eth yl-2-n a p h th a len -2-yl[1,3]d ioxola n e (27):
3.20 g (12.9 mmol); quantitative yield; 1H NMR (CDCl3) δ 3.71
(m, 4H), 4.04 (dd, 1H), 4.24 (d, 2H), 4.40 (dd, 1H), 4.56 (m,
2H), 6.05 (s, 1H), 6.22 (s, 1H), 7.58 (m, 6H), 7.95 (m, 8H).
(1,4-Dioxa sp ir o[4.5]d ec-2-ylm eth yl)(2-p h en oxyeth yl)-
a m in e (28): 5.80 g (30 mmol); quantitative yield; 1H NMR
(CDCl3) δ 1.40, 1.58 (m, m, 10H), 3.44 (dd, 1H), 3.58 (dd, 1H),
3.87 (dd, 1H), 4.10 (dd, 1H), 4.30 (m, 1H).
1
compound 2c: mp 156 °C; H NMR (DMSO) δ 3.30 (m, 4H),
3.78 (s, 6H), 3.98 (dd, 1H), 4.16 (m, 3H), 4.59 (m, 1H), 5.83 (s,
1H), 6.71 (d, 2H), 7.06 (dd, 1H), 7.47, 7.60 (m, m, 5H). Anal.
(C22H27NO9) C, H, N.
tr a n s-[2-(2,6-Dim eth oxyp h en oxy)eth yl](2-p h en yl[1,3]-
d ioxola n -4-ylm eth yl)a m in e (29t): 0.26 g (0.72 mmol); yield
17%; 1H NMR (CDCl3) δ 2.29 (brs, 1H), 2.86 (dd, 1H), 2.97 (m,
2H), 3.01 (dd, 1H), 3.81 (dd, 1H), 3.84 (s, 6H), 4.22 (m, 3H),
4.45 (m, 1H), 5.98 (s, 1H), 6.58 (d, 2H), 7.00 (dd, 1H), 7.39,
7.50 (m, m, 5H).
The free amine was transformed into the corresponding
oxalate salt, which is crystallized from methanol to give
compound 2t: mp 165-168°C; 1H NMR (DMSO) δ 3.30 (m,
4H), 3.78 (dd, 1H), 3.80 (s, 6H), 4.13 (t, 2H), 4.32 (dd, 1H),
4.64 (m, 1H), 5.98 (s, 1H), 6.72 (d, 2H), 7.07 (dd, 1H), 7.47 (m,
5H). Anal. (C22H27NO9) C, H, N.
Gen er a l P r oced u r e for th e Syn th esis of Am in es 29-
31c/t, 32, 33-35c/t, 36, 37, 38c/t, a n d 39 a n d Th eir Oxa la te
Sa lts 2-4c/t, 5, 6-8c/t, 9, 10, 13c/t, 14 (Sch em es 2 a n d 3).
A solution of chloromethyl derivative (21-28) in 2-methoxy-
ethanol with a large excess (5-10 equiv) of amine (18-20) and
with a catalytic amount of KI was refluxed for 18-24 h. The
solvent was evaporated under vacuum, CHCl3 was added, and
the residue was washed with a solution of 5% NaOH (3×) and
then with brine (2×). The organic layer was dried over Na2-
cis-(2-Ben zyl[1,3]d ioxola n -4-ylm et h yl)[2-(2,6-d im et h -
oxyp h en oxy)eth yl]a m in e (30c): 0.44 g (1.18 mmol); yield
26%; 1H NMR (CDCl3) δ 2.57 (brs, 1H), 2.72 (dd, 2H), 2.88 (m,
2H), 2.99 (ddd, 2H), 3.67 (dd, 1H), 3.82 (s, 6H), 3.92 (dd, 1H),
4.14 (m, 3H), 5.12 (t, 1H), 6.58 (d, 2H), 7.00 (dd, 1H), 7.24 (m,
5H).
The free amine was transformed into the corresponding
oxalate salt, which is crystallized from methanol to give
1
compound 3c; mp 197°-200 °C; H NMR (DMSO) δ 2.98 (m,

1,3-Dioxane-Based Ligands as Antagonists
J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 8 1509
2H), 3.05 (m, 1H), 3.20 (m, 3H), 3.80 (s, 6H), 3.82 (dd, 1H),
3.95 (dd, 1H), 4.09 (m, 2H), 4.39 (m, 1H), 5.09 (t, 1H), 6.73 (d,
2H), 7.08 (dd, 1H), 7.26 (m, 5H). Anal. (C23H29NO9) C, H, N.
tr a n s-(2-Ben zyl[1,3]dioxolan -4-ylm eth yl)[2-(2,6-dim eth -
oxyp h en oxy)eth yl]a m in e (30t): 0.42 g (1.13 mmol); yield
25%; 1H NMR (CDCl3) δ 2.03 (brs, 1H), 2.70 (dd, 1H), 2.92 (m,
5H), 3.58 (dd, 1H), 3.80 (s, 6H), 4.11 (m, 3H), 4.24 (m, 1H),
5.22 (t, 1H), 6.56 (d, 2H), 6.99 (dd, 1H), 7.26 (m, 5H).
1H), 5.82 (d, 1H), 6.71 (d, 2H), 7.07 (dd, 1H), 7.30 (m, 10H).
Anal. (C29H33NO9) C, H, N.
cis-[2-(2,6-Dim eth oxyp h en oxy)eth yl](2-n a p h th a len -1-
yl[1,3]d ioxola n -4-ylm eth yl)a m in e (34c): 0.24 g (0.59 mmol);
yield 21%; 1H NMR (CDCl3) δ 2.05 (brs, 1H), 3.01 (m, 4H),
3.78 (s, 6H), 4.00 (dd, 1H), 4.16 (m, 2H), 4.30 (dd, 1H), 4.58
(m, 1H), 6.52 (s, 1H), 6.56 (d, 2H), 7.00 (dd, 1H), 7.52 (m, 3H),
7.88 (m, 3H), 8.26 (m, 1H).
The free amine was transformed into the corresponding
oxalate salt, which is crystallized from ethanol to give com-
pound 3t; mp 164°-165 °C; H NMR (DMSO) δ 2.93 (dd, 2H),
3.20 (m, 4H), 3.61 (dd, 1H), 3.78 (s, 6H), 4.08 (m, 2H), 4.15
(dd, 1H), 4.47 (m, 1H), 5.25 (t, 1H), 6.72 (d, 2H), 7.07 (dd, 1H),
7.27 (m, 5H). Anal. (C23H29NO9) C, H, N.
The free amine was transformed into the corresponding
oxalate salt, which is crystallized from ethanol to give com-
pound 7c: mp 154-157 °C; 1H NMR (DMSO) δ 3.32 (m, 4H),
3.75 (s, 6H), 4.09 (m, 3H), 4.31 (m, 1H), 4.71 (m, 1H), 6.51 (s,
1H), 6.70 (d, 2H), 7.06 (dd, 1H), 7.55 (m, 3H), 7.86 (m, 1H),
8.00 (m, 2H), 8.22 (m, 1H). Anal. (C26H29NO9) C, H, N.
1
ci s-[2-(2,6-D im e t h o x y p h e n o x y )e t h y l](2-m e t h y l-2-
p h en yl[1,3]d ioxola n -4-ylm eth yl)a m in e (31c): 0.16 g (0.44
mmol); yield 9%; 1H NMR (CDCl3) δ 1.62 (s, 3H), 2.63 (m, 2H),
2.83 (pseudot, 2H), 3.48 (dd, 1H), 3.80 (s, 6H), 4.10 (m, 2H),
4.18 (dd, 1H), 4.39 (m, 1H), 6.55 (d, 2H), 6.97 (dd, 1H), 7.28
(m, 3H), 7.50 (m, 2H).
tr a n s-[2-(2,6-Dim eth oxyp h en oxy)eth yl](2-n a p h th a len -
1-yl[1,3]dioxolan -4-ylm eth yl)am in e (34t): 0.30 g (0.74 mmol);
yield 26%; 1H NMR (CDCl3) δ 2.31 (brs, 1H), 3.03 (m, 4H),
3.84 (s, 6H), 3.96 (dd, 1H), 4.19 (m, 2H), 4.38 (dd, 1H), 4.57
(m, 1H), 6.59 (d, 2H), 6.66 (s, 1H), 7.02 (dd, 1H), 7.51 (m, 3H),
7.86 (m, 3H), 8.28 (m, 1H).
The free amine was transformed into the corresponding
oxalate salt, which is crystallized from methanol to give
compound 4c: mp 157°-158 °C; 1H NMR (DMSO) δ 1.61 (s,
3H), 2.99 (dd, 1H), 3.25 (m, 3H), 3.54 (dd, 1H), 3.76 (s, 6H),
4.09 (m, 2H), 4.32 (dd, 1H), 4.59 (m, 1H), 6.71 (d, 2H), 7.07
(dd, 1H), 7.34 (m, 3H), 7.53 (m, 2H). Anal. (C23H29NO9‚1H2O)
C, H, N.
The free amine was transformed into the corresponding
oxalate salt, which is crystallized from ethanol to give com-
pound that is crystallized from methanol to give compound
7t: mp 146-150°C; 1H NMR (DMSO) δ 3.38 (m, 4H), 3.80 (s,
6H), 3.92 (dd, 1H), 4.15 (m, 2H), 4.39 (dd, 1H), 4.75 (m, 1H),
6.64 (s, 1H), 6.72 (d, 2H), 7.07 (dd, 1H), 7.57 (m, 3H), 7.75 (m,
1H), 8.00 (m, 2H), 8.27 (m, 1H). Anal. (C26H29NO9) C, H, N.
t r a n s-[2-(2,6-Dim e t h oxyp h e n oxy)e t h yl](2-m e t h yl-2-
p h en yl[1,3]d ioxola n -4-ylm et h yl)a m in e (31t ): 0.71 g (1.9
mmol); yield 38%; H NMR (CDCl3) δ 1.70 (s, 3H), 2.44 (brs,
1H), 2.81 (dd, 1H), 2.94 (m, 3H), 3.75 (dd, 1H), 3.82 (m, 1H),
3.86 (s, 6H), 4.16 (m, 3H), 6.58 (d, 2H), 7.00 (dd, 1H), 7.32 (m,
3H), 7.51 (m, 2H).
cis-[2-(2,6-Dim eth oxyp h en oxy)eth yl](2-n a p h th a len -2-
yl[1,3]d ioxola n -4-ylm eth yl)a m in e (35c): 0.13 g (0.32 mmol);
yield 12%; 1H NMR (CDCl3) δ 2.16 (brs, 1H), 3.01 (m, 4H),
3.80 (s, 6H), 3.98 (dd, 1H), 4.19 (m, 3H), 4.49 (m, 1H), 6.04 (s,
1H), 6.57 (d, 2H), 7.00 (dd, 1H), 7.52 (m, 2H), 7.65 (dd, 1H),
7.93 (m, 4H).
1
The free amine was transformed into the corresponding
oxalate salt, which is crystallized from ethanol to give com-
pound 4t: mp 166°-168 °C; H NMR (DMSO) δ 1.66 (s, 3H),
3.30 (m, 4H), 3.80, 3.82 (m, s, 8H), 4.13 (m, 2H), 4.31 (m, 1H),
6.73 (d, 2H), 7.08 (dd, 1H), 7.41 (m, 5H). Anal. (C23H29NO9) C,
H, N.
The free amine was transformed into the corresponding
oxalate salt, which is crystallized from ethanol to give com-
pound 8c: mp 160-163°C; H NMR (DMSO) δ 3.36 (m, 4H),
3.76 (s, 6H), 4.14 (m, 4H), 4.66 (m, 1H), 6.01 (s, 1H), 6.70 (d,
1
1
2H), 7.06 (dd, 1H), 7.62 (m, 3H), 8.00 (m, 4H). Anal. (C26H29
NO9) C, H, N.
-
[2-(2,6-Dim e t h oxyp h e n oxy)e t h yl](2,2-d ip h e n yl[1,3]-
d ioxola n -4-ylm eth yl)a m in e (32): 1.24 g (2.85 mmol); yield
70%; 1H NMR (CDCl3) δ 2.22 (brs, 1H), 2.85 (dd, 1H), 2.96 (m,
2H), 3.01 (dd, 1H), 3.83 (s, 6H), 3.89 (dd, 1H), 4.16 (m, 3H),
4.40 (m, 1H), 6.59 (d, 2H), 7.02 (dd, 1H), 7.34 (m, 6H), 7.55
(m, 4H).
tr a n s-[2-(2,6-Dim eth oxyp h en oxy)eth yl](2-n a p h th a len -
2-yl[1,3]dioxolan -4-ylm eth yl)am in e (35t): 0.24 g (0.59 mmol);
yield 21%; 1H NMR (CDCl3) δ 2.17 (brs, 1H), 2.91 (dd, 1H),
2.99 (m, 2H), 3.07 (dd, 1H), 3.86 (m, 6H), 3.90 (dd, 1H), 4.19
(m, 2H), 4.35 (dd, 1H), 4.54 (m, 1H), 6.17 (s, 1H), 6.60 (d, 2H),
7.02 (dd, 1H), 7.50 (m, 2H), 7.63 (dd, 1H), 7.92 (m, 4H).
The free amine was transformed into the corresponding
oxalate salt, which is crystallized from methanol to give
compound 5: mp 187-189 °C; 1H NMR (DMSO) δ 3.26 (m,
4H), 3.76 (s, 6H), 3.88 (dd, 1H), 4.13 (m, 3H), 4.49 (m, 1H),
6.71 (d, 2H), 7.07 (dd, 1H), 7.42 (m, 10H). Anal. (C28H31NO9)
C, H, N.
The free amine was transformed into the corresponding
oxalate salt, which is crystallized from ethanol to give com-
pound 8t: mp 176-178 °C; H NMR (DMSO) δ 3.35 (m, 4H),
3.80 (s, 6H), 3.81 (dd, 1H), 4.16 (m, 2H), 4.38 (dd, 1H), 4.74
(m, 1H), 6.16 (s, 1H), 6.72 (d, 2H), 7.07 (dd, 1H), 7.60 (m, 3H),
7.99 (m, 4H). Anal. (C26H29NO9) C, H, N.
1
ci s-(2-B e n zy d r y l[1,3]d io x o la n -4-y lm e t h y l)[2-(2,6-
d im eth oxyp h en oxy)eth yl]a m in e (33c): 0.13 g (0.29 mmol);
yield 12%; 1H NMR (CDCl3) δ 2.21 (brs, 1H), 2.56 (d, 2H), 2.84
(m, 2H), 3.56 (dd, 1H), 3.83 (s, 6H), 3.98 (dd, 1H), 4.12 (m,
3H), 4.30 (d, 1H), 5.63 (d, 1H), 6.60 (d, 2H), 7.03 (dd, 1H), 7.32
(m, 10H).
The free amine was transformed into the corresponding
oxalate salt, which is crystallized from ethanol to give com-
pound 6c: mp 191-193°C; 1H NMR (DMSO) δ 2.83 (dd, 1H),
3.11 (m, 3H), 3.73 (m, 1H), 3.76 (s, 6H), 4.01 (m, 3H), 4.26 (d,
1H), 4.42 (m, 1H), 5.66 (d, 1H), 6.72 (d, 2H), 7.08 (dd, 1H),
7.29 (m, 10H). Anal. (C29H33NO9) C, H, N.
tr a n s-(2-Be n zyd r yl[1,3]d ioxola n -4-ylm e t h yl)[2-(2,6-
d im eth oxyp h en oxy)eth yl]a m in e (33t): 0.20 g (0.45 mmol);
yield 18%; 1H NMR (CDCl3) δ 2.28 (brs, 1H), 2.74 (dd, 1H),
2.90 (m, 3H), 3.67 (dd, 1H), 3.80 (s, 6H), 3.97 (dd, 1H), 4.13
(m, 3H), 4.24 (d, 1H), 5.74 (d, 1H), 6.59 (d, 2H), 7.02 (dd, 1H),
7.32 (m, 10H).
(2,2-Dip h en yl[1,3]d ioxola n -4-ylm eth yl)[2-(2-m eth oxy-
p h en oxy)eth yl]a m in e (36): 0.44 g (1.09 mmol); yield 30%;
1H NMR (CDCl3) δ 2.99 (d, 2H), 3.15 (m, 2H), 3.85 (s, 3H),
3.93 (dd, 1H), 4.15 (dd, 1H), 4.19 (t, 2H), 4.53 (m, 1H), 6.96
(m, 4H), 7.32 (m, 6H), 7.54 (m, 4H).
The free amine was transformed into the corresponding
oxalate salt, which is crystallized from methanol to give
compound 9: mp 189 °C; 1H NMR (DMSO) δ 3.31 (m, 4H),
3.76 (s, 3H), 3.86 (dd, 1H), 4.12 (dd, 1H), 4.24 (pseudot, 2H),
4.48 (m, 1H), 7.00 (m, 4H), 7.41 (m, 10H). Anal. (C27H29NO8)
C, H, N.
(2,2-Diph en yl[1,3]dioxolan -4-ylm eth yl)(2-ph en oxyeth yl)-
1
a m in e (37): 1.45 g (3.87 mmol); yield 35%; H NMR (CDCl3)
δ 1.67 (brs, 1H), 2.86 (ddd, 2H), 3.01 (t, 2H), 3.84 (dd, 1H),
4.04 (t, 2H), 4.09 (dd, 1H), 4.33 (m, 1H), 6.91 (m, 3H), 7.29 (m,
8H), 7.48 (m, 4H).
The free amine was transformed into the corresponding
oxalate salt, which is crystallized from methanol to give
compound 10: mp 189-191 °C; 1H NMR (DMSO) δ 3.29 (ddd,
2H), 3.49 (m, 2H), 3.95 (dd, 1H), 4.20 (dd, 1H), 4.34 (t, 2H),
4.58 (m, 1H), 7.09 (m, 3H), 7.49 (m, 12H). Anal. (C26H27NO7)
C, H, N.
The free amine was transformed into the corresponding
oxalate salt, which is crystallized from ethanol to give com-
1
pound 6t: mp 184-188°C; H NMR (DMSO) δ 3.22 (m, 4H),
3.66 (dd, 1H), 3.75 (s, 6H), 4.05 (m, 3H), 4.24 (d, 1H), 4.39 (m,

1510 J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 8
Brasili et al.
cis-(2-P h en oxyeth yl)(2-p h en yl[1,3]d ioxola n -4-ylm eth -
yl)a m in e (38c): 0.52 g (1.7 mmol); yield 35%; 1H NMR (CDCl3)
δ 1.95 (brs, 1H), 2.98 (m, 2H), 3.10 (t, 2H), 3.93 (dd, 1H), 4.08
(t, 2H), 4.16 (dd, 1H), 4.44 (m, 1H), 5.86 (s, 1H), 6.95 (m, 3H),
7.36 (m, 5H), 7.53 (m, 2H).
3.74 (m, 3H), 3.92 (m, 2H), 4.18 (dd, 1H), 4.44 (m, 2H), 4.76
(m, 1H), 6.97 (m, 3H), 7.40 (m, 12H). Anal. (C26H30NO3I) C,
H, N.
P h a r m a cology. F u n ct ion a l An t a gon ism in Isola t ed
Tissu es. Male Wistar rats (275-300 g) were killed by cervical
dislocation, and the organs required were isolated, freed from
adhering connective tissues, and set up rapidly under a
suitable resting tension in 20 mL of organ baths containing
physiological salt solution kept at 37 °C and aerated with 5%
CO2-95% O2 at pH 7.4. Concentration-response curves were
constructed by cumulative addition of agonist. The concentra-
tion of agonist in the organ bath was increased approximately
3-fold at each step, with each addition being made only after
the response to the previous addition had attained a maximal
level and remained steady. Contractions were recorded by
means of a force displacement transducer connected to the Mac
Lab system PowerLab/800 and to a polygraph channel recorder
(Gemini). In addition, parallel experiments in which tissues
did not receive any antagonist were run in order to check any
variation in sensitivity.
Va s Defer en s P r osta tic P or tion . This tissue was used
to assess the antagonism toward R1A adrenoceptors.17 Prostatic
portions of 2 cm length were mounted under 0.5 g of tension
at 37 °C in tyrode solution of the following composition (mM):
NaCl, 130; KCl, 1; CaCl2, 1.8; MgCl2, 0.89; NaH2PO4, 0.42;
NaHCO3, 25; glucose, 5.6. Cocaine hydrochloride (0.1 µM) was
added to the tyrode to prevent the neuronal uptake of (-)-
noradrenaline. The preparations were equilibrated for 60 min
with washing every 15 min. After the equilibration period,
tissues were primed twice by addition of 10 µM noradrenaline.
After another washing and equilibration period of 60 min, a
noradrenaline concentration-response curve was constructed
(basal response). The antagonist was equilibrated for 30 min
before construction of a new concentration-response curve to
the agonist. (-)-Noradrenaline solutions contained 0.05%
Na2S2O5 to prevent oxidation.
Sp leen . This tissue was used to assess the antagonism
toward R1B adrenoceptors.18 The spleen was removed and
bisected longitudinally into two strips, which were suspended
in tissue baths containing Krebs solution of the following
composition (mM): NaCl, 120; KCl, 4.7; CaCl2, 2.5; MgSO4,
1.5; KH2PO4, 1.2; NaHCO3, 20; glucose, 11; K2EDTA, 0.01.
Propranolol hydrochloride (4 µM) was added to block â-adreno-
ceptors. The spleen strips were placed under 1 g of resting
tension and equilibrated for 2 h. The cumulative concentra-
tion-response curves to phenylephrine were measured iso-
metrically and obtained at 30 min intervals, the first one being
discarded and the second taken as a control. The antagonist
was allowed to equilibrate for 30 min before constructing a
new concentration-response curve to the agonist.
Aor ta . This tissue was used to assess the antagonism
toward R1D adrenoceptors.19 Thoracic aorta was cleaned from
extraneous connective tissues and placed in Krebs solution of
the following composition (mM): NaCl, 118.4; KCl, 4.7; CaCl2,
1.9; MgSO4, 1.2; NaH2PO4, 1.2; NaHCO3, 25; glucose, 11.7; K2-
EDTA, 0.01. Cocaine hydrochloride (0.1 µM) and propranolol
hydrochloride (4 µM) were added to prevent the neuronal
uptake of (-)-noradrenaline and to block â-adrenoceptors,
respectively. Two helicoidal strips (15 mm × 3 mm) were cut
from each aorta, beginning from the end that is most proximal
to the heart. The endothelium was removed by rubbing with
filter paper. The absence of acetylcholine (100 µM) induced
relaxation in preparations contracted with (-)-noradrenaline
(1 µM) was taken as an indicator that the vessels were
denuded successfully. Vascular strips were then tied with
surgical thread and suspended in a jacketed tissue bath
containing tyrode solution. Strip contractions were measured
isometrically. After at least a 2 h equilibration period under
an optimal tension of 1 g, cumulative (-)-noradrenaline
concentration-response curves were recorded at 1 h intervals,
the first two being discarded and the third one taken as
control. The antagonist was equilibrated with the tissue for
30 min before the generation of the fourth cumulative con-
centration-response curve to (-)-noradrenaline. (-)-Norad-
The free amine was transformed into the corresponding
oxalate salt, which is crystallized from methanol to give
compound 13c: mp 189-190 °C; 1H NMR (DMSO) δ 3.24, 3.36
(m, m, 4H), 3.97 (dd, 1H), 4.13 (dd, 1H), 4.24 (m, 2H), 4.55 (m,
1H), 5.81 (s, 1H), 6.99 (m, 3H), 7.34, 7.47 (m, m, 7H). Anal.
(C20H23NO7) C, H, N.
tr a n s-(2-P h en oxyeth yl)(2-ph en yl[1,3]dioxolan -4-ylm eth -
yl)a m in e (38t): 0.23 g (0.77 mmol); yield 15%; 1H NMR
(CDCl3) δ 1.74 (brs, 1H), 2.96 (ddd, 2H), 3.12 (t, 2H), 3.81 (dd,
1H), 4.13 (t, 2H), 4.29 (dd, 1H), 4.45 (m, 1H), 5.99 (s, 1H), 6.96
(m, 3H), 7.35 (m, 5H), 7.50 (m, 2H).
The free amine was transformed into the corresponding
oxalate salt, which is crystallized from methanol to give
compound 13t: mp 206-207 °C; 1H NMR (DMSO) δ 3.27, 3.41
(m, m, 4H), 3.76 (dd, 1H), 4.30 (m, 3H), 4.63 (m, 1H), 5.97 (s,
1H), 7.00 (m, 3H), 7.34, 7.44 (m, m, 7H). Anal. (C20H23NO7) C,
H, N.
(1,4-Dioxa sp ir o[4.5]d ec-2-ylm eth yl)(2-p h en oxyeth yl)-
1
a m in e (39): 0.12 g (0.41 mmol); yield 15%; H NMR (CDCl3)
δ 1.44, 1.64 (m, m, 10H), 2.85 (ddd, 2H), 3.08 (t, 2H), 3.72 (dd,
1H), 4.08 (dd, 1H), 4.11 (t, 2H), 4.29 (m, 1H), 6.97 (m, 3H),
7.31 (m, 2H).
The free amine was transformed into the corresponding
oxalate salt, which is crystallized from methanol to give
compound 14: mp 222-223 °C; 1H NMR (DMSO) δ 1.37, 1.57
(m, m, 10H), 3.10 (m, 2H), 3.37 (m, 2H), 3.72 (dd, 1H), 4.07
(dd, 1H), 4.25 (m, 2H), 4.39 (m, 1H), 7.00 (m, 3H), 7.34 (m,
2H). Anal. (C19H27NO7) C, H, N.
(2,2-Dip h en yl[1,3]d ioxola n -4-ylm eth yl)(2-p h en oxyeth -
yl)ca r ba m ic Acid Eth yl Ester (40). To a solution of 37 (3.6
mmol) in dry CHCl3 (75 mL) and dry pyridine (3.6 mmol) was
added dropwise at 0°C and under nitrogen a solution of ethyl
chloroformate (4.3 mmol) in dry CHCl3 (20 mL). The mixture
was maintained at room temperature for 17 h and then washed
with a solution of 2 N NaOH (75 mL) and then with water
(100 mL). The organic layer was dried over Na2SO4, and the
solvent was evaporated under vacuum. The residue was
purified by flash chromatography, eluting with cyclohexane/
ethyl acetate, 90:10, to give the desired compound 40: 1.18 g
(2.64 mmol); yield 73%; 1H NMR (CDCl3) δ 1.25 (m, 3H), 3.50
(m, 1H), 3.74, 3.85 (m, dd, 4H), 4.13 (m, 5H), 4.41 (m, 1H),
6.84 (m, 2H), 6.94 (m, 1H), 7.29 (m, 8H), 7.49 (m, 4H).
(2,2-Dip h en yl[1,3]d ioxola n -4-ylm eth yl)m eth yl(2-p h en -
oxyeth yl)a m in e (41). To a suspension of LiAlH4 (19.2 mmol)
in dry THF (33 mL) was added dropwise a solution of
compound 40 (2.4 mmol) in dry THF (50 mL). The mixture
was refluxed for 24 h. After the mixture was cooled, water was
added (0.22 mL), then a solution of 5 N NaOH (0.22 mL), and
again water (1.1 mL). The solid was filtered off, and the liquid
phase was dried over Na2SO4. The solvent was evaporated
under vacuum to give the desired compound 41: 0.75 g (1.93
1
mmol); yield 80%; H NMR (CDCl3) δ 2.45 (s, 3H), 2.75 (ddd,
2H), 2.91 (m, 2H), 3.81 (dd, 1H), 4.06 (t, 2H), 4.14 (dd, 1H),
4.38 (m, 1H), 6.92 (m, 3H), 7.27 (m, 8H), 7.52 (m, 4H).
The amine was then transformed into the corresponding
oxalate salt 11: mp 104-106 °C; 1H NMR (DMSO) δ 2.62 (brs,
3H), 3.00, 3.16 (m, m, 4H), 3.73 (m, 1H), 4.08, 4.15 (m, m, 3H),
4.41 (m, 1H), 6.93 (m, 3H), 7.35 (m, 12H). Anal. (C27H29NO7)
C, H, N.
(2,2-Diph en yl[1,3]dioxolan -4-ylm eth yl)dim eth yl(2-ph en -
oxyeth yl)a m m on iu m Iod id e (12). To a solution of compound
41 (0.5 mmol) in dry diethyl ether (10 mL) was added CH3I (5
mmol), and the mixture stood at room temperature for 24 h.
Then it was stored for an additional 24 h at 5 °C. The obtained
precipitate was washed with diethyl ether and the solid was
dried to give the methyl iodide salt 12: 0.069 g (0.13 mmol);
1
yield 26%, mp 133-135 °C; H NMR (DMSO) δ 3.27 (t, 6H),

1,3-Dioxane-Based Ligands as Antagonists
J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 8 1511
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renaline solutions contained 0.05% K2EDTA in 0.9% NaCl to
prevent oxidation.
Ra d iolin ga n d Bin d in g Assa y. Binding to cloned human
R1-adrenoceptor subtype was performed in membranes from
CHO (Chinese hamster ovary) cells transfected by electro-
phoration with DNA expressing the gene encoding each R1-
adrenoceptor subtype.20 Cloning and stable expression of the
human R1-adrenoceptor gene was performed as previously
described. CHO cell membranes (30 µg of protein) were
incubated in 50 mM Tris-HCl, pH 7.4, with 0.1-0.4 nM [3H]-
prazosin, in a final volume of 1.02 mL for 30 min at 25 °C, in
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Tris-HCl buffer and rapid filtration through 0.2% poly(ethyl-
enimine)-pretreated Whatman GF/B or Schleicher & Schuell
GF52 filters.
Da ta An a lysis. In functional studies, responses were
expressed as a percentage of the maximal contraction observed
in the agonist concentration-response curves, taken as a
control, which were analyzed by pharmacological computer
programs. pA2 values were calculated according to Arunlak-
shana and Schild23 from the dose ratios at EC50 values of the
agonists calculated at three different antagonist concentra-
tions. Each concentration was tested at least four times, and
Schild plots were constrained to a slope of -1 as required by
theory.24 pKb values were calculated according to van Rossum25
at one or two concentrations. Binding data were analyzed
using the nonlinear curve-fitting program Allfit.26 Scatchard
plots were linear for all preparations. The pseudo-Hill coef-
ficients (nH) were not significantly different from unity (p >
0.05). Equilibrium dissociation constants (Ki) were derived
from the Cheng-Prusoff equation27 Ki ) IC50/(1 + L/Kd), where
L and Kd are the concentration and the equilibrium dissocia-
tion constant of the radioligand. pKi values are the mean of
two to three separate experiments performed in triplicate,
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Ack n ow led gm en t. This work was supported by a
grant from the University of Modena and Reggio Emilia,
the University of Camerino, and Miur.
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