QSAR study for?a?novel series of?ortho disubstituted phenoxy analogues of?α1-adrenoceptor antagonist WB4101

Article abstract of DOI:10.1016/j.ejmech.2006.04.004

On the basis of the affinities at the α_1a-, α_1b- and α_1d-adrenoceptors and the 5-HT_1A receptor of a previous series of sixteen 2-[(2-phenoxyethyl)aminomethyl]-1,4-benzodioxanes ortho monosubstituted at the pheno

Full text of DOI:10.1016/j.ejmech.2006.04.004

European Journal of Medicinal Chemistry 41 (2006) 1025–1040
http://france.elsevier.com/direct/ejmech
Original article
QSAR study for a novel series of ortho disubstituted
phenoxy analogues of α1-adrenoceptor antagonist WB4101
M. Pallavicini a, L. Fumagalli a, M. Gobbi b, C. Bolchi a, S. Colleoni b, B. Moroni a
A. Pedretti a, C. Rusconi a, G. Vistoli a, E. Valoti a,*
a Istituto di Chimica Farmaceutica e Tossicologica, Università di Milano, viale Abruzzi 42, I-20131 Milan, Italy
b Istituto di Ricerche Farmacologiche ‘Mario Negri’, via Eritrea 62, I-20157 Milan, Italy
Received in revised form 6 April 2006; accepted 14 April 2006
Available online 05 June 2006
Abstract
On the basis of the affinities at the α1a-, α1b- and α1d-adrenoceptors and the 5-HT1A receptor of a previous series of sixteen 2-[(2-phenox-
yethyl)aminomethyl]-1,4-benzodioxanes ortho monosubstituted at the phenoxy moiety, a number of ortho disubstituted analogues were designed,
synthesized in both the enantiomeric forms and tested in binding assays on the same receptors. The affinity values of the new compounds 1–11
were compared with those of the enantiomers of the 2,6-dimethoxyphenoxy analogue, the well-known α1 antagonist WB4101, and of the ortho
monosubstituted derivatives, suggesting some distinctive aspects of the interaction of the phenoxy moiety, in particular with the α1a-AR and the
5-HT1A receptor, of the monosubstituted and the disubstituted compounds. A classical quantitative structure-activity relationship (Hansch) ana-
lysis was applied to the whole set of the S enantiomers of the ortho mono- and disubstituted WB4101 analogues (26 compounds), finding a very
good correlation for the α1a affinity. For this latter, a significant parabolic relationship was also found with the volume of the two ortho sub-
stituents. Diametrically opposite, the same relationships for the 5-HT1A exhibit low or insignificant correlation coefficients.
© 2006 Elsevier SAS. All rights reserved.
Keywords: WB4101 analogues; α1-Adrenoreceptor; 5-HT1A receptor; Binding affinity; QSAR
1. Introduction
Current evidences, based on the acknowledged existence of
multiple α1-adrenoceptor (α1-AR) subtypes and on their distri-
bution and function [1], indicate that subtype selective α1
antagonists can represent therapeutic options for lower urinary
tract (LUT) syndromes such as bladder overactivity and urinary
Fig. 1.
incontinence [2]. In particular, compounds with selective
blocking properties for the α1A and α1D subtypes, the predomi-
nating ARs, together with the β3 subtype, in human LUT, and
for the 5-HT1A serotoninergic receptor [3] might be efficacious
we have recently proved to exhibit about nanomolar affinity
in relieving symptoms associated with such disorders. In this
context, a renewed interest has been taken in investigations
devoted to clarifying the pharmacophoric features and to
improving both affinity and selectivity of the α1 antagonist
WB4101 (Fig. 1) [4–19], a 2-aminomethyl-1,4-benzodioxane
derivative first described in 1965 [20], whose S enantiomer
toward the three different α1-ARs (α1a, α1b and α1d) and the 5-
HT1A receptor with a slight selectivity for α1a- and, to a minor
degree, for α1d-ARs [4]. The attractive challenge to modulate
the interaction capabilities of this potent α1 antagonist further
differentiating its selectivity profile has prompted us to develop
series of novel WB4101 analogues. Among these, the S
naphtho- and tetrahydronaphthodioxane derivatives are signifi-
* Corresponding author.
E-mail address: ermanno.valoti@unimi.it (E. Valoti).
cantly more selective for the α1a-AR than (S)-WB4101 [4],
0223-5234/$ - see front matter © 2006 Elsevier SAS. All rights reserved.
doi:10.1016/j.ejmech.2006.04.004

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M. Pallavicini et al. / European Journal of Medicinal Chemistry 41 (2006) 1025–1040
while the S forms of ortho monosubstituted phenoxy analogues
lose most of the affinity of (S)-WB4101 for the α1-ARs, espe-
cially for the α1a and α1b subtypes, but preserve, in some cases,
its nanomolar affinity for the 5-HT1A receptor thus acquiring a
moderate 5-HT1A selectivity [5]. A classical QSAR analysis,
applied to (S)-WB4101, its unsubstituted phenoxy analogue
and a relatively wide number of ortho monosubstituted phe-
noxyethylaminomethyl derivatives of benzodioxane, has
allowed a better insight into some determinants for the affinity
spectrum of this class of compounds to be got [5]. Electron rich
and/or hydrogen bond accepting atoms or groups are recog-
nized as advantageous ortho substituents for the affinities
toward the three α1-ARs and the 5-HT1A receptor by the
respective QSARs. Furthermore, the ortho dimethoxy substitu-
tion has been found important for the interaction with the α1-
ARs, in particular with the α1a and α1b subtypes, but not for the
5-HT1A affinity. In QSAR terms, this is expressed by the rela-
tively low negative incidence of the volume of the two ortho
substituents or by the largely positive effect of their length in
the three α1 subtype equations. In fact, such a situation inevi-
tably handicaps the α1 affinities of the derivatives bearing one
or two hydrogens as ortho substituents in comparison with (S)-
WB4101. Otherwise, the absence of the volumetric term, com-
bined with the most beneficial effect of the electron-richness,
in the 5-HT1A QSAR makes the same derivatives competitive
with (S)-WB4101 in 5-HT1A affinity.
On the basis of these results, we recently extended our
investigations to the novel ortho disubstituted phenoxy analo-
gues of WB4101 1–11 (Fig. 2). To design such compounds,
among the previously reported ortho monosubstitutions at the
phenoxy moiety, we selected some of those producing high
and/or specific affinity for the 5-HT1A and α1d receptors,
namely fluoro, chloro, methyl and t-butyl. Intermediate alkyl
and alkenyl groups (ethyl, propyl, allyl and isopropyl) were
also considered. The same substituent was then introduced
into both ortho positions to give the o-difluoro, o-dichloro
and o-di-tert-butyl derivatives 1–3 or, alternatively, the two
ortho positions were occupied by a methoxyl and one of the
above substituents yielding the unsymmetrically ortho disubsti-
tuted compounds 4–11. The interest in these compounds has a
duplex nature. Firstly, no 2,6-disubstitution at the phenoxy
moiety of WB4101, alternative to that with two methoxyls or
methyls [21,22], has been ever considered; secondly, such an
investigation naturally tails after that on the ortho monosubsti-
tuted analogues of WB4101 [5] with the aim of gaining further
information on the relationship between the ortho disubstitu-
tion pattern and the affinity profile of the N-phenoxyethyl deri-
vatives of aminomethylbenzodioxane. Herein we report the
synthesis and the binding affinities for the α1a-AR, α1b-AR,
α1d-AR and the 5-HT1A receptor of both the enantiomers of
compounds 1–11 discussing their SAR data, in particular of
the S isomers, and finally trying a compendious analysis of
the results obtained for all the ortho mono- and disubstituted
phenoxy analogues of WB4101 we have so far characterized.
2. Chemistry
The enantiomeric pairs of compounds 1–11 were prepared
by alkylation of ortho disubstituted 2-phenoxyethylamines
with the enantiomers of 2-iodomethyl- or 2- mesyloxymethyl-
1,4-benzodioxane, in turn obtained according to previously
reported procedures [4,18,23,24]. As outlined in Scheme 1,
the various 2-phenoxyethylamines were synthesized by differ-
ent strategies. Those with the same substituent (F, Cl or t-Bu)
at the ortho positions, namely the amines 18, 25 and 26, were
obtained from the corresponding 2,6-substituted phenols by 2-
hydroxyethylation with ethylene carbonate. The resultant ethy-
lene glycols mono-phenyl ethers 12–14 were converted into the
tosylate 16 and the mesyl esters 19 and 20. These latter were
reacted with potassium phthalimide and submitted to hydrazi-
nolysis to give the dichloro- and di-t-butylphenoxyethylamines
25 and 26 respectively, while the tosylate was transformed into
azide and reduced to the difluorophenoxyethylamine 18. For
the synthesis of the fenoxyethylamines bearing two different
ortho substituents, namely the amines 27 and 28 and the
amines 71–76, we exploited the Claisen and the Fries rearran-
gement, respectively. As reported in literature, 2-methoxyphe-
nyl allyl ether underwent, upon heating, allyl migration to give
2-methoxy-6-allylphenol, which was converted into amine 27
by the same pathway as 2,6-dichlorophenol into amine 25. The
allylphenoxyethylamine 27 was then hydrogenated to the pro-
pylphenoxyethylamine 28. Otherwise, in the case of the amines
71–76, the ortho methoxy substituent was introduced into the
properly 2-substituted phenyl acetates, readily available from
the corresponding 2-substituted phenols, by AlCl3 catalyzed
conversion into o-hydroxyacetophenones followed by: (a) ben-
zylation of the unmasked phenolic moiety; (b) Baeyer–Villiger
oxidation of the resultant o-benzyloxyacetophenones 29–34 to
the respective o-benzyloxyphenyl acetates 35–40; (c) methano-
lysis of the ester function; (d) methylation of the resulting o-
benzyloxyphenols 41–46; (e) hydrogenolytic debenzylation
(53–58); (f) 2-bromoethylation with 1,2-dibromoethane (59–
64). The 6-substituted 2-methoxyphenyl bromoethyl ethers 60
and 62 were converted into phthalimido derivatives yielding,
after hydrazinolysis, the 2,6-susbstituted phenoxyethylamines
72 and 74, respectively. The same two-step transformation
Fig. 2.

M. Pallavicini et al. / European Journal of Medicinal Chemistry 41 (2006) 1025–1040
1027
Scheme 1. Reagents: (a) ethylene carbonate, K2CO3, DMF or toluene. (b) TsCl, Py. (c) NaN3, DMF, H2O. (d) Hydrazine, PdO, MeOH. (e) MsCl, Et3N, DCM. (f)
Potassium phthalimide, DMF. (g) Hydrazine, 2-methoxyethanol or methanol. (h) H2-Pd/C, MeOH. (i) Benzyl bromide, tetrabutylammonium bromide, 10% NaOH,
DCM. (j) m-CPBA, DCM. (k) TsOH or NaOH, MeOH. (l) CH3I, NaOH, MeOH or EtOH or tetrabutylammonium bromide and DCM. (m) Dibromoethane, KOH,
DMSO or tetrabutylammonium bromide and DCM.
from bromo to amino group was accomplished, in the case of
the phenoxyethylamines 71, 73, 75 and 76, by reaction with
sodium azide and successive reduction of the azido moiety.
The final nucleophilic substitutions leading to the S isomers
of 1–11 are illustrated in Scheme 2. The R isomers of 1–11
were synthesized by the same reactions as their antipodes, but
using the 2-substituted 1,4-benzodioxane intermediates with
inverted configuration. In particular, compounds 1, 2 and 4
were prepared by N-alkylation of the corresponding primary
ortho disubstituted 2-phenoxyethylamines 18, 25 and 71 with
enantiopure 2-iodomethyl-1,4-benzodioxane, whereas com-
pounds 3 and 5–11 of the respective primary ortho disubsti-
tuted 2-phenoxyethylamines 26, 72–74, 28, 75, 27 and 76
with enantiopure 2-mesyloxymethyl-1,4-benzodioxane.

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M. Pallavicini et al. / European Journal of Medicinal Chemistry 41 (2006) 1025–1040
For all the S and R isomers of 1–11, the maximum affinity
diminution was invariably observed at the α1d-AR; at the
other three receptors (α1a, α1b and 5-HT1A), the decreases
were significantly less pronounced and inter se comparable.
Furthermore, a clear-cut boundary distinguishes the group of
the methoxy derivatives 4–11 from that of the ortho symmetri-
cally disubstituted compounds 1–3. In fact, excepting (S)-11 at
the α1-ARs and (R)-6 at the 5-HT1A receptor, it can be stated
that all the S and R methoxy derivatives are more potent,
almost always in a significant degree, than the homochiral
WB4101 analogues without methoxy substituents. In these
two groups, the t-butyl derivatives invariably display the low-
est affinities, with < 6 pKi values in the case of the di-t-butyl
substitution.
Scheme 2. Synthesis of the S isomers of compounds 1–11.
3. Results and discussion
Considering the S isomers, such trends result in a number of
compounds, namely all the methoxy analogues excepting that
with an ortho-t-butyl, which exhibit α1a and α1b affinities very
close to those of (S)-WB4101 (subnanomolar at the α1a-AR
and nearly 10 nanomolar at the α1b-AR). Among the non-meth-
oxy compounds, only the dichloro derivative (S)-2 approxi-
mates similar α1a and α1b affinity values. Otherwise, in the
case of the α1d-AR, the affinities are from 10-fold to 50-fold
lower than that of (S)-WB4101 (pKi 9.29) for the methoxy
compounds (S)-4 to (S)-10 and the ratio is largely over 2 orders
of magnitude for (S)-11 and all the non-methoxy S isomers.
Finally, the methoxy derivatives, (S)-11 included, show seroto-
ninergic affinities about 10 nanomolar with the maximum for
(S)-7, whose almost nanomolar 5-HT1A affinity (pKi 8.86) is
similar to that of (S)-WB4101 (pKi 8.61). For the non-methoxy
compounds, 29 and 44 nanomolar 5-HT1A affinity values were
Table 1 reports the affinities, expressed as pKi values (–log
Ki, M) , at the three cloned human α1-AR subtypes and 5-HT1A
serotoninergic receptor of the enantiomeric pairs of compounds
1–11 and, as comparison terms, of (S)- and (R)-WB4101.
The affinities of the S enantiomers are always higher than
those of their antipodes, the eudismic indexes ranging between
a maximum of 1.42 and a minimum of 0.52, in the case of the
affinities displayed by the enantiomers of 4 for the α1d-AR and
the 5-HT1A receptor respectively. Compared to the respective
homochiral enantiomers of WB4101, all the ortho disubstituted
phenoxy derivatives 1–11 are less potent, excepting both the
enantiomers of 7 at the 5-HT1A receptor. A more detailed ana-
lysis of the binding data reveals quite different affinity
decreases with respect to the S and R enantiomers of the 2,6-
dimethoxy substituted lead compound depending on the recep-
tor subtype and on the presence of an ortho methoxy group.
Table 1
Experimental affinity constants, expressed as pKi (–logKi, M) S.E., of the enantiomers of compounds 1–11 and of WB4101 for cloned human α1-adrenoceptor
subtypes and 5-HT1A receptor
Phenoxy
o-substituents
F,F
Compound
pKi
α1d
6.88 ( 0.04)
< 6
7.15 ( 0.04)
< 6 ( 0.08)
< 6
α1a
α1b
5-HT1A
(S)-1
(R)-1
(S)-2
(R)-2
(S)-3
(R)-3
(S)-4
(R)-4
(S)-5
(R)-5
(S)-6
(R)-6
(S)-7
(R)-7
(S)-8
(R)-8
7.56 ( 0.05)
6.43 ( 0.07)
8.22 ( 0.03)
7.21 ( 0.04)
< 6
7.04 ( 0.04)
6.04 ( 0.10)
7.28 ( 0.04)
6.03 ( 0.10)
< 6
7.53 ( 0.09)
6.94 ( 0.29)
7.36 ( 0.78)
6.55 ( 0.11)
< 6
Cl,Cl
t-Bu,t-Bu
OMe,F
< 6
< 6
< 6
< 6
8.68 ( 0.10)
7.33 ( 0.06)
8.94 ( 0.13)
7.73 ( 0.06)
8.71 ( 0.08)
7.61 ( 0.03)
8.70 ( 0.09)
7.76 ( 0.04)
8.44 ( 0.11)
7.58 ( 0.04)
8.55 ( 0.13)
7.72 ( 0.05)
8.63 ( 0.10)
7.66 ( 0.05)
7.08 ( 0.03)
n.d.
7.75 ( 0.04)
6.35 ( 0.06)
7.74 ( 0.08)
6.38 ( 0.05)
7.98 ( 0.05)
6.73 ( 0.03)
8.04 ( 0.04)
6.79 ( 0.04)
7.72 ( 0.06)
6.87 ( 0.09)
8.12 ( 0.05)
6.99 ( 0.08)
7.96 ( 0.06)
6.91 ( 0.05)
7.09 ( 0.04)
n.d.
7.69 ( 0.04)
6.27 ( 0.08)
8.39 ( 0.11)
7.08 ( 0.07)
7.73 ( 0.05)
6.46 ( 0.09)
8.01 ( 0.03)
6.72 ( 0.04)
7.60 ( 0.07)
6.56 ( 0.07)
8.01 ( 0.06)
6.80 ( 0.06)
7.80 ( 0.04)
6.66 ( 0.05)
6.95 ( 0.04)
n.d.
7.69 ( 0.11)
7.17 ( 0.12)
8.26 ( 0.03)
6.99 ( 0.02)
7.73 ( 0.09)
6.86 ( 0.09)
8.86 ( 0.05)
7.55 ( 0.08)
7.89 ( 0.10)
7.06 ( 0.06)
7.80 ( 0.11)
6.93 ( 0.07)
8.00 ( 0.10)
7.04 ( 0.08)
7.73 ( 0.06)
n.d.
OMe,Cl
OMe,Me
OMe,Et
OMe,Pr
OMe,i-Pr
OMe,Allyl
OMe,t-Bu
OMe,OMe
a
(S)-9
(R)-9
(S)-10
(R)-10
(S)-11
(R)-11
(S)-WB4101
(R)-WB4101
a
9.39 ( 0.06)
7.95 ( 0.04)
8.24 ( 0.04)
7.14 ( 0.06)
9.29 ( 0.11)
7.98 ( 0.08)
8.61 ( 0.04)
7.39 ( 0.03)
a
Data taken from Ref. [4].

M. Pallavicini et al. / European Journal of Medicinal Chemistry 41 (2006) 1025–1040
1029
respectively determined in the case of the dihalo derivatives
(S)-1 and (S)-2.
equation is given in Table 3. The level of significance was
judged by the squared correlation coefficient (r2), the squared
cross-validated correlation coefficient (q2), the standard error
of the estimates (SE) and the Fisher significance ratio (F).
Interestingly, r2 drops from high values for the α1a and α1b
equations, 0.86 and 0.74, respectively, to low ones for the α1d
(0.54) and, especially, for the 5-HT1A (0.35) equations and
similar trends are also shown by the other statistical para-
meters. This is consistent with the previously reported
QSARs of monosubstituted compounds (S)-I-(S)-XVI, which
indicate different steric effects of the ortho substituents
depending on the considered receptor: (i) a simply negative
incidence of the volume on the α1a and, to a minor extent, on
the α1b affinity, (ii) a negative incidence of the volume, but
counteracted by a largely positive effect of the length, on the
α1d affinity and, finally, (iii) no influence of the volume, but
only a negative effect of the length in the case of the 5-HT1A
receptor.
The affinity profiles of the S isomers of compounds 1–11,
compared to that of (S)-WB4101, are characterized by a reduced
α1a versus α1b selectivity, with the exception of (S)-5, and by a
moderate α1a/α1d selectivity, of which (S)-WB4101 is virtually
devoid. Otherwise, the degree of α1a/5-HT1A selectivity of the
lead compound is generally maintained and, in the only cases
of (S)-7 and (S)-11, annihilated and reversed respectively.
As stated introducing the paper, compounds 1–11 were
designed not selecting a number of substituents with maximum
variance and minimum covariance in physico-chemical proper-
ties, but on the basis of indications provided by the previous
SAR analysis of a set of sixteen ortho monosubstituted phe-
noxy analogues of WB4101 (compounds (S)-I-(S)-XVI in
Table 2) [5]. Such indications restricted the choice to three
types of substituent, namely alkyl, alkoxyl and halogen, thus
limiting the sampling of the property space. This discouraged a
classical Hansch multivariate regression analysis, like that pre-
viously performed for compounds (S)-I-(S)-XVI. Otherwise, it
seemed worthwhile to verify whether parabolic relationships
could describe the dependence of the affinities of (S)-
WB4101 and of compounds (S)-1, (S)-2 and (S)-4-(S)-11 at the
α1-AR subtypes and the 5-HT1A receptor on the volume of the
two ortho substituents, the only parameter, among those
selected, which shows a relatively large variation in this series
of compounds ((S)-3 was excluded due to its indefinite < 6 pKi
values). For each of the four receptors, the resultant parabolic
A
classical quantitative structure-activity relationship
(Hansch) study was applied to (S)-WB4101 and to its 26 ana-
logs, that is the present o-disubstituted derivatives (S)-1, (S)-2,
(S)-4-(S)-11 and the previously reported unsubstituted or o-
monosubstituted derivatives (S)-I-(S)-XVI, considering, for
these latter, also the contribution of the one or two ortho
hydrogen atoms. In this case, a variety of substituents was
represented and the mass of data was undoubtedly suitable
material for a QSAR investigation. First, we maintained the
same physicochemical parameters used for the QSAR of (S)-
Table 2
Experimental affinity constants, expressed as pKi (–logKi, M) S.E., of the enantiomers of compounds I–XVI for cloned human α1-adrenoceptor subtypes and 5-
a
HT1A receptor
Phenoxy
Compound
pKi
α1d
o-substituent
H
Me
Et
t-Bu
CN
CF3
COMe
F
α1a
α1b
5-HT1A
(S)-I
(S)-II
7.34 ( 0.05)
7.51 ( 0.04)
7.58 ( 0.14)
6.22 ( 0.04)
7.06 ( 0.09)
7.16 ( 0.04)
7.26 ( 0.04)
7.47 ( 0.10)
7.62 ( 0.07)
7.72 ( 0.10)
7.17 ( 0.07)
6.98 ( 0.15)
7.31 ( 0.27)
7.46 ( 0.19)
7.26 ( 0.11)
7.90 ( 0.09)
7.02 ( 0.03)
7.13 ( 0.05)
7.06 ( 0.07)
6.29 ( 0.08)
6.05 ( 0.08)
6.99 ( 0.08)
6.73 ( 0.05)
7.27 ( 0.04)
7.24 ( 0.29)
7.46 ( 0.26)
6.90 ( 0.04)
7.00 ( 0.04)
7.24 ( 0.12)
6.81 ( 0.14)
6.88 ( 0.10)
7.37 ( 0.14)
7.57 ( 0.08)
7.10 ( 0.05)
8.01 ( 0.17)
6.12 ( 0.04)
8.17 ( 0.22)
7.77 ( 0.18)
7.54 ( 0.19)
7.16 ( )
8.08 ( 0.32)
8.34 ( 0.17)
7.11 ( 0.11)
6.69 ( 0.06)
7.96 ( 0.13)
7.73 ( 0.03)
7.88 ( 0.17)
7.52 ( )
8.57 ( 0.07)
8.55 ( 0.04)
7.26 ( 0.04)
7.59 ( 0.03)
7.15 ( 0.06)
6.75 ( 0.05)
7.17 ( 0.08)
8.52 ( 0.02)
7.96 ( 0.04)
7.62 ( 0.08)
7.33 ( 0.04)
6.96 ( 0.04)
7.44 ( 0.06)
8.16 ( 0.43)
8.06 ( 0.08)
8.67 ( 0.02)
(S)-III
(S)-IV
(S)-V
(S)-VI
(S)-VII
(S)-VIII
(S)-IX
(S)-X
(S)-XI
(S)-XII
(S)-XIII
(S)-XIV
(S)-XV
(S)-XVI
Cl
SMe
SOMe
SO2Me
NO2
NHCOMe
NH2
OMe
a
Data taken from Ref. [5].
Table 3
Parabolic relationships between the volume (V) of the ortho phenoxy substituents of (S)-WB4101, (S)-1, (S)-2 and (S)-4 -(S)-11 and the affinity for the α1-ARs and
the 5-HT1A receptor. V is the sum of the fragmental volume of the two aromatic substituents (data taken from Ref. [25])
Receptor
α1a
α1b
α1d
5-HT1A
Equations
n
r2
q2
S.E.
F
(1) pKi = 5.92–0.0014V2 + 0.13V
(2) pKi = 5.89–0.0008V2 + 0.084V
(3) pKi = 5.29–0.0012V2 + 0.118V
(4) pKi = 6.54–0.0006V2 + 0.062V
11
11
11
11
0.858
0.739
0.542
0.346
0.822
0.673
0.427
0.183
0.269
0.236
0.519
0.411
24.16
11.31
4.730
2.123

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M. Pallavicini et al. / European Journal of Medicinal Chemistry 41 (2006) 1025–1040
I-(S)-XVI, namely the resonance constant of Swain and Lup-
ton (R) [26], the fragmental volume of aromatic substituents
(V) [25], the length parameter of Verloop (L) [27] and the abil-
ity of accepting H bonds (HBβ) [28]. The resultant four equa-
tions, corresponding to the α1a-, α1b- and α1d-AR and to the 5-
HT1A receptor, exhibited r2 values of 0.65, 0.58, 0.41 and 0.36.
Compared to the previous corresponding values (0.78, 0.53,
0.71 and 0.85) obtained for (S)-I-(S)-XVI, these new correla-
tion coefficients were generally lower and only in the case of
the α1a and α1b QSARs they maintained some statistical signif-
icance, which was instead completely lost by the equations for
the other two receptors. Furthermore, the new α1a QSAR had
nearly unchanged coefficients indicating the robustness and the
good predictive power of the previous quantitative relationship,
constructed on the basis of the α1a affinities of (S)-I-(S)-XVI.
Consistently with what we had already observed for these latter
compounds, a sort of solidarity between α1a and α1b affinity
trends in contrast with diverging SAR data for the α1d and 5-
HT1A receptors resulted as a consequence of the o-disubstitu-
tion pattern at the phenoxy moiety. Such a behavior should
have been better enlightened by new more significant equa-
tions, de novo constructed reselecting physicochemical para-
meters. For each of the four receptors, the new equation
adopted as the final model is given in Table 4. The exclusion
of the o-monoamino substituted analogue (S)-XV from the cal-
culation resulted in a remarkable enhancement of the correla-
tion coefficients, probably due to the unique nature of the
amino group, among these substituents, of strong hydrogen
bond donor, not parametrized by the physicochemical proper-
ties represented in the final equations. Therefore, these corre-
late the affinities of 26 compounds: (S)-WB4101, (S)-I-(S)-
XIV, (S)-XVI, (S)-1, (S)-2 and (S)-4-(S)-11. The physicochem-
ical parameters, suitably chosen out of 27, and the respective
values for each pair of ortho substituents are shown in Table 5.
As electronic parameters, the resonance and field constants of
Swain and Lupton R and F [26], the Taft σR [29] and the Esaki
flow intensity IF [30], indicative of the inductive-field effect,
were used, while the fragmental volume of aromatic substitu-
ents (V) and the length parameter of Verloop (L) were
employed as steric descriptors. In comparison with the pre-
vious equations, constructed for (S)-I-(S)-XVI and recalculated
including the present disubstituted derivatives without chan-
ging the parameters, the QSARs reported in Table 4 exhibit a
much better statistic significance, as demonstrated by the r2
values (0.90, 0.66, 0.59 and 0.67 vs. 0.65, 0.58, 0.41 and
0.36). Partly, this can be ascribed to the presence of squared
parameters (V2 in the three α1 equations and L2 in that for the
α1a subtype) and of the indicator variable IOMe. This notwith-
standing, it is to be underlined the 0.90 value of the α1a squared
correlation coefficient, which allows a good prediction of the
α1a affinities (Fig. 3). Furthermore, some trends, previously
observed for (S)-I-(S)-XVI, are confirmed and some new
ones are recognized: (i) the α1a and α1b QSARs are similar,
but the correlation coefficient is much better for the α1a-AR;
(ii) the volumetric term, squared in the three α1 equations,
has a modestly negative incidence on the α1 affinities, which
becomes remarkable for the highest values of V only in the α1a
and α1d relationships, where it is however counteracted by L;
in the 5-HT1A equation, V, which is the only steric parameter,
is not squared and has a low negative coefficient; (iii) the ben-
eficial effect of the methoxy substituent is parametrized by the
new entered indicator variable IOMe, which appears in the three
α1 equations, but not in the 5-HT1A QSAR; (iv) conversely,
disappears the HBβ parameter, probably due to the absence
of hydrogen bond acceptor substituents, methoxyl excepted,
in the new disubstituted WB4101 analogues; (v) electron
donor substituents by resonance favor the α1a, α1b and 5-
HT1A affinities (see the negative coefficient of R), while
depress the affinity for the α1d-AR, already modestly advan-
taged by such substituents in the monosubstituted WB4101
analogues (Table 4).
4. Conclusion
The extension of QSAR analysis from the heterogeneously
o-monosubstituted WB4101 analogues (S)-I-(S)-XVI, to the
less representative selection of o-disubstituted derivatives (S)-
1-(S)-11 makes the correlation between biological and struc-
tural data more difficult. The affinity profiles at the four recep-
tors (α1a, α1b, α1d and 5-HT1A) are less differentiated and the
affinity ratios generally less marked than for the monosubsti-
tuted analogues. In this context, however, quantitative structure
affinity relationships are still able to give relevant information
to understanding some determinants of the interaction of these
WB4101 related compounds with each of the four receptors,
drawing, in particular, interesting distinctions between the α1a
-AR and the 5-HT1A receptor. For instance, parallel ortho sub-
stitutions on (S)-I and on (S)-XVI result in parallel shifts in α1a
affinity. This is well represented by a plot of the α1a pKi values
for (S)-I and its ortho methyl, ethyl, t-butyl, fluoro, chloro and
methoxy analogues versus the corresponding o-methoxy
homologues, that is (S)-XVI, (S)-6, (S)-7, (S)-11, (S)-4, (S)-5
and (S)-WB4101. Such a plot reveals the existence of a signif-
icant linear correlation (r = 0.944), suggesting that the o-mono-
Table 4
Equations for QSAR of (S)-WB4101, (S)-1, (S)-2, (S)-4 -(S)-11, (S)-I-(S)-XIV and (S)-XVI at the α1-ARs and the 5-HT1A receptor
Receptor
α1a
Equation
n
r2
0.896
q2
0.876
S.E.
0.267
F
45.19
(1) pKi = 6.60–3.46 10–4V2–0.54R + 0.53IOMe 26
+ 0.032L2
α1b
α1d
(2) pKi = 7.01–5.09 10–5V2–0.50R + 0.53IOMe 26
0.655
0.592
0.608
0.515
0.340
0.444
13.91
7.634
(3) pKi = 5.89–3.51 10–4V2 + 0.87IOMe
+ 0.76σR + 0.35L
26
26
5-HT1A
(4) pKi = 8.66–1.31 F–0.87R–0.12IF–0.020V
0.670
0.608
0.360
10.68

M. Pallavicini et al. / European Journal of Medicinal Chemistry 41 (2006) 1025–1040
1031
Table 5
a
Values of the physicochemical parameters used in the QSAR study of ortho mono- and disubstituted phenoxy analogues of (S)-WB4101
b
c
d
e
b
f
Compound
(S)-I
(S)-II
o-Substituent
H, H
H, Me
H, Et
H, t-Bu
H, CN
H, CF3
H, Ac
H, F
H, Cl
H, SMe
H, SOMe
H, SO2Me
H, NO2
H, NHAc
H, NH2
H, OMe
F, F
R
0
V
L
IF
0
F
0
σR
0
IOMe
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
1
1
1
1
1
1
1
1
2
9.24
4.12
4.93
6.17
6.17
6.29
5.36
6.12
4.71
5.58
6.36
6.17
6.17
5.50
7.15
4.84
6.04
5.30
7.04
8.22
6.63
7.50
6.85
8.09
8.09
8.12
8.90
8.09
7.96
–0.13
–0.10
–0.13
0.19
0.19
0.20
–0.34
–0.15
–0.18
0.22
0.10
0.16
–0.26
–0.18
–0.51
–0.68
–0.30
–0.26
–0.85
–0.66
–0.64
–0.61
–0.61
–0.70
–0.59
–0.64
–1.02
22.70
36.16
63.08
22.00
31.12
37.16
11.41
20.32
37.70
42.50
47.04
25.08
46.03
19.53
27.76
13.58
31.40
116.92
38.84
29.93
41.22
54.68
68.14
58.90
68.14
81.60
46.28
1.64
0.72
0.35
–0.41
2.94
–0.04
–0.05
–0.07
0.51
0.38
0.32
0.43
0.41
0.20
0.59
0.54
0.67
0.28
0.02
0.26
0.86
0.82
-0.14
0.69
0.65
0.22
0.21
0.21
0.23
0.20
0.19
0.52
–0.14
–0.09
–0.13
0.19
0.19
0.19
–0.45
–0.24
–0.20
0.18
0.18
0.15
-0.26
–0.76
–0.55
–0.90
–0.48
–0.26
–1.00
–0.79
–0.69
–0.60
–0.65
–0.74
–0.63
–0.68
–1.10
(S)-III
(S)-IV
(S)-V
(S)-VI
(S)-VII
(S)-VIII
(S)-IX
(S)-X
(S)-XI
(S)-XII
(S)-XIII
(S)-XIV
(S)-XV
(S)-XVI
(S)-1
(S)-2
(S)-3
(S)-4
(S)-5
(S)-6
(S)-7
(S)-8
(S)-9
–0.04
1.32
–1.46
–0.65
–1.80
–1.74
1.40
–1.88
0.19
–3.00
2.64
Cl, Cl
–2.92
0.70
t-Bu, t-Bu
F, MeO
Cl, MeO
Me, MeO
Et, MeO
Pr, MeO
i-Pr, MeO
Allyl, MeO
t-Bu, MeO
MeO, MeO
–1.68
–4.46
–1.36
–2.28
–2.58
–2.48
–2.43
–2.65
–6.00
(S)-10
(S)-11
(S)-WB4101
a
For each parameter, the reported value is the sum of the contributions of the two substituents in 2 and in 6.
b
c
d
e
f
Data taken from Ref. [26].
Data taken from Ref. [25].
Data taken from Ref. [27].
Data taken from Ref. [30].
Data taken from Ref. [29].
substituted WB4101 analogues and the respective o-methoxy
α1a interaction, would account for the unequalized potency of
WB4101, which has two o-methoxy groups. Contrariwise, our
analysis suggests that the ortho monosubstituted WB4101 ana-
logues and their ortho methoxy homologues interact with the
5-HT1A receptor in a different fashion, considering the null
correlation between the respective affinities. This would
explain why, in the case of this receptor, the contributions of
the two ortho substituents are not additive, as also indicated by
the low correlation coefficient of the respective QSAR here
reported, and why properly o-monosubstituted WB4101 analo-
gues can compete with this latter and other o-disubstituted
WB4101 related compounds in 5-HT1A affinity.
homologues bind at α1a-AR in a similar fashion with an addi-
tive average contribution of o-methoxyl to α1a pKi of about one
unit. The additivity of the ortho substituent contributions to the
α1a affinity is also indicated by the plots of the α1a pKi values
of the difluoro, dichloro and dimethoxy derivatives versus the
corresponding monosubstituted analogues and versus the fluor-
omethoxy, chloromethoxy and dimethoxy derivatives. In these
two graphs, the points are only three, but perfectly lying on a
straight line (r = 1).
In the case of the 5-HT1A receptor, attempts at correlation
between the same sets of affinity data were completely unsuc-
cessful giving insignificant or nearly null values of r.
5. Experimental protocols
On the basis of these results and of previous evidences, we
can conclude that the interaction of the phenoxy moiety of
WB4101 related compounds with the α1a-AR is greatly advan-
taged by the ortho disubstitution. Likely, it stabilizes an
extended conformation of the molecule and a proper orienta-
tion of the phenyl ring. We don’t know if both the ortho sub-
stituents are involved in the interaction. At any event, if they
both have suitable properties, conforming to the present QSAR
indications, this should increase the population of bioactive
conformers and result in higher affinities. This fact, together
with the optimal properties of the methoxy substituent for the
5.1. Chemistry
Melting points were measured on Buchi melting point appa-
ratus and are uncorrected. 1H NMR spectra were recorded
operating at 200 or 300 MHz. Chemical shifts are reported in
ppm relative to residual solvent (CHCl3 or DMSO) as internal
standard. Signal multiplicity is designed according to the fol-
lowing abbreviations: s = singlet, d = doublet , dd = doublet of
doublets, t = triplet, m = multiplet, br s = broad singlet, br

1032
M. Pallavicini et al. / European Journal of Medicinal Chemistry 41 (2006) 1025–1040
5.1.3. 2-(2,6-Di-t-butylphenoxy)ethanol (14)
Prepared from 2,6-di-t-butylphenol as described for 12 but
replacing toluene with DMF. After chromatography on silica
gel (cyclohexane/ethyl acetate 90:10), the product was isolated
1
as a yellow oil (56.9%): H NMR (CDCl3) δ 1.44 (s, 18H),
1.97 (br s, 1H), 3.93 (t, 2H), 4.02 (t, 2H), 6.99 (t, 1H), 7.26
(d, 2H). Anal. Calcd for C16H26O2 (250.38).
5.1.4. 2-(2-Allyl-6-methoxyphenoxy)ethanol (15)
Prepared from 2-allyl-6-methoxyphenol as described for 12
but replacing toluene with DMF. After chromatography on
silica gel (cyclohexane/ethyl acetate 80:20), the product was
1
isolated (62.5%) as a yellow oil: H NMR (CDCl3) δ 3.06 (br
s, 1H), 3.45 (d, 2H), 3.86 (m, 5H), 4.07 (t, 2H), 5.00–5.09 (m,
2H), 5.88–6.08 (m, 1H), 6.80 (d, 2H), 7.03 (t, 1H). Anal. Calcd
for C12H16O3 (208.25).
5.1.5. 1-Tosyloxy-2-(2,6-difluorophenoxy)ethane (16)
Tosyl chloride (19.3 g, 101.3 mmol) was added drop-wise
to a stirred solution of 12 (16.8 g, 97.5 mmol) in pyridine (20
ml) at 0 °C. The resulting mixture was stirred at room tempera-
ture for 20 h, diluted with diethyl ether (120 ml) and washed
with 10% HCl (120 ml). The aqueous layer was separated and
extracted with diethyl ether twice. The organic phases were
combined, dried and concentrated to give 21.5 g (67%) of 16
as an oil which was used for the subsequent step without
Fig. 3. Relationship between calculated and experimental α1a affinities of (S)-I-
(S)-XIV and (S)-XVI (triangles) and of (S)-1, (S)-2, (S)-4-(S)-11 and (S)-
WB4101 (circles) (r2 = 0.90; n = 26).
1
further purification: H NMR (CDCl3) δ 2.40 (s, 3H), 4.60–
t = broad triplet. Optical rotations were determined by a Per-
kin-Elmer 241 Polarimeter at 25 °C. Elemental analyses
(CHN) of the new substances are within 0.40% of theoretical
values. Purifications were performed by flash chromatography
using silica gel (particle size 40–63 μm, Merck).
4.80 (m, 4H), 6.80–8.00 (m, 7H). Anal. Calcd for
C15H14F2O4S (328.34).
5.1.6. 1-Azido-2-(2,6-difluorophenoxy)ethane (17)
Sodium azide (60 g, 0.92 mol) was added to a stirred solu-
tion of 16 in DMF (300 ml) and water (100 ml). The resulting
mixture was heated at 90 °C for 5 h. After cooling at room
temperature, water (100 ml) was added and the resulting mix-
ture was extracted with hexane (4 × 100 ml). The organic
phases were combined, washed with water (30 ml), dried and
concentrated to give 14 g of crude product which was purified
by chromatography on silica gel. Elution with hexane/ethyl
5.1.1. 2-(2,6-Difluorophenoxy)ethanol (12)
A mixture of 2,6-difluorophenol (15 g, 115.3 mmol), ethy-
lene carbonate (20.3 g, 230.6 mmol) and potassium carbonate
(26.5 g, 185 mmol) in toluene (75 ml) was refluxed for 2 h.
After cooling at room temperature, water (40 ml) was added.
The aqueous layer was separated and extracted with toluene
(3 × 35 ml). The organic phase was treated with 10% NaOH
(40 ml), washed with water twice (2 × 30 ml), dried and con-
centrated to give the crude product which was purified by chro-
matography on silica gel. Elution with cyclohexane/ethyl acet-
1
acetate (85:15) yielded 11 g (90%) of 17 as a yellow oil: H
NMR (CDCl3) δ 3.60 (t, 2H), 4.30 (t, 2H), 6.80–7.05 (m, 3H).
Anal. Calcd C8H7F2N3O (199.16).
1
ate (90:10) yielded 20.08 g (83.9%) of 12 as a yellow oil: H
5.1.7. 2-(2,6-Difluorophenoxy)ethylamine (18)
NMR (CDCl3) δ 2.45 (br s, 1H), 4.05 (m, 2H), 4.25 (m, 2H),
6.80–7.00 (m, 3H). Anal. Calcd for C8H8F2O2 (174.15).
Hydrazine hydrate (20 ml) was added drop-wise to a stirred
mixture of 17 (11 g, 63.5 mmol) and PdO (50 mg) in methanol
(100 ml) at 65 °C. The reaction mixture was refluxed for 4 h.
After cooling at room temperature, PdO was removed by filtra-
tion and the resulting solution concentrated to give the crude
product, which was purified by chromatography on silica gel.
Elution with dichloromethane/methanol (97:3) yielded 4.8 g
5.1.2. 2-(2,6-Dichlorophenoxy)ethanol (13)
Prepared from 2,6-dichlorophenol as described for 12 but
replacing toluene with DMF. The crude product was isolated
(100%) as a yellow oil which was used for the subsequent step
1
1
without further purification: H NMR (CDCl3) δ 2.73 (br s,
(50%) of 18 as a yellow oil: H NMR (CDCl3) δ 1.50 (s,
1H), 3.94 (m, 2H), 4.18 (m, 2H), 6.95 (t, 1H), 7.25 (m, 2H).
Anal. Calcd for C8H8Cl2O2 (207.05).
2H), 3.05 (s, 2H), 4.15 (t, 2H), 6.80–7.05 (m, 3H). Anal.
Calcd for C8H9OF2N (173.16).

M. Pallavicini et al. / European Journal of Medicinal Chemistry 41 (2006) 1025–1040
1033
5.1.8. 1-Mesyloxy-2-(2,6-dichlorophenoxy)ethane (19)
5.1.14. 2-(2,6-Dichlorophenoxy)ethylamine (25)
Hydrazine hydrate (2.95 ml) was added drop-wise to a stir-
red mixture of 22 (15.6 g, 46.4 mmol) in 2-methoxyethanol (95
ml) at 125 °C. After refluxing for 2 h, 10% HCl was added
until pH 3. After cooling at room temperature, the reaction
mixture was concentrated, the residue treated with 10%
NaOH (70 ml) and washed with dichloromethane. The organic
phases were combined, dried and concentrated. Distillation
under vacuum (b.p. 110 °C at 1 mbar) of the residue gave
Mesyl chloride (11.13 ml, 143 mmol) was added drop-wise
to a stirred solution of 13 (28 g, 136.9 mmol) and TEA (20 ml)
in dichloromethane (375 ml) at 0 °C. After 1 h at room tem-
perature, the reaction mixture was washed with a saturated
solution of NaHCO3. The aqueous layer was separated and
extracted with dichloromethane twice. The organic phases
were combined, dried and concentrated to give 34.26 g
(87.8%) of 19 as a yellow oil, which was used for the subse-
1
1
8.5 g (89%) of 25 as a yellow oil: H NMR (CDCl3) δ 1.56
(br s, 2H), 3.07 (t, 2H), 4.03 (t, 2H), 6.95 (t, 1H), 7.25 (d, 2H).
Anal. Calcd for C8H9Cl2NO (206.07).
quent step without further purification: H NMR (CDCl3) δ
3.09 (s, 3H), 4.26 (m, 2H), 4.56 (m, 2H), 6.96 (t, 1H), 7.36
(m, 2H). Anal. Calcd for C9H10Cl2O4S for (285.15).
5.1.15. 2-(2,6-Di-t-butylphenoxy)ethylamine (26)
5.1.9. 1-Mesyloxy-2-(2,6-di-t-butylphenoxy)ethane (20)
Prepared from 14 as described for 19. Crystallization from
hexane yielded 20 as a light yellow solid (77.1%): m.p. 54.9–
55.7 °C; H NMR (CDCl3) δ 1.43 (s, 18H), 3.11 (s, 3H), 4.05
(t, 2H), 4.60 (t, 2H), 7.01 (t, 1H), 7.26 (d, 2H). Anal. Calcd for
C17H28O4S (328.47).
Prepared from 23 as described for 25. After distillation
under vacuum (b.p. 110 °C at 0.2 mbar), the product was iso-
1
lated (100%) as a colorless oil: H NMR (CDCl3) δ 1.44 (s,
1
20H), 3.16 (t, 2H), 3.81 (t, 2H), 6.98 (t, 1H), 7.25 (d, 2H).
Anal. Calcd for C16H27NO (249.39).
5.1.16. 2-(2-Allyl-6-methoxyphenoxy)ethylamine (27)
5.1.10. 1-Mesyloxy-2-(2-allyl-6-methoxyphenoxy)ethane (21)
Prepared from 15 as described for 19. The resulting crude
product (91%) was used for the subsequent step without further
purification:1H NMR (CDCl3) δ 3.09 (s, 3H), 3.44 (d, 2H),
3.84 (s, 3H), 4.23 (dd, 2H), 4.53 (dd, 2H), 4.99–5.08 (m,
2H), 5.86–6.06 (m, 1H), 6.77–6.81 (dd, 2H), 7.03 (t, 1H).
Anal. Calcd for C13H18O5S (286.35).
Prepared from 24 as described for 25 but replacing 2-meth-
oxyethanol with methanol. The crude product was isolated
(100%) and used for the subsequent step without further
1
purification: H NMR (CDCl3) δ 1.57 (s, 2H), 3.03 (t, 2H),
3.45 (d, 2H), 3.84 (s, 3H), 3.97 (t, 2H), 5.08 (m, 2H), 5.87–
6.07 (m, 1H), 6.80 (d, 2H), 7.00 (t, 1H). Anal. Calcd for
C12H17NO2 (207.27).
5.1.17. 2-(2-Methoxy-6-propylphenoxy)ethylamine (28)
5.1.11. N-[2-(2,6-dichlorophenoxy)ethyl]phthalimide (22)
A solution of 19 (34.26 g, 120 mmol) in DMF (180 ml) was
added to a stirred solution of potassium phthalimide (30.5 g,
164.75 mmol) in DMF (400 ml). The resulting mixture was
heated at 100 °C for 1.5 h and, after cooling at room tempera-
ture, quenched into ice and water (800 ml). The resulting pre-
cipitate was isolated, washed with EtOH (50 ml), dried and
crystallized from EtOH (100 ml) to give 15.6 g (39%) of 22
A solution of 27 (4.92 g, 23.7 mmol) in methanol (50 ml)
was added with 10% Pd/C (500 mg) and vigorously shaken
under hydrogen at room temperature. After removing the cata-
lyst by filtration, the filtrate was concentrated and distilled
under vacuum (110 °C at 0.2 mbar) to give 4.91 g (98.8%)
1
of 28 as a colorless oil: H NMR (CDCl3) δ 0.95 (t, 3H),
1.63 (m, 4H), 2.62 (t, 2H), 3.04 (t, 2H), 3.83 (s, 3H), 3.96 (t,
2H), 6.79 (dd, 2H), 6.98 (t, 1H). Anal. Calcd for C12H19NO2
(209.28).
1
as a white solid: m.p. 127 °C; H NMR (CDCl3) δ 4.17 (m,
2H), 4.27 (m, 2H), 6.95 (m, 1H), 7.27 (m, 2H), 7.73 (m, 2H),
7.87 (m, 2H). Anal. Calcd for C16H11Cl2NO3 (336.17).
5.1.18. 2-Benzyloxy-3-fluoroacetophenone (29)
Prepared from 2-hydroxy-3-fluoroacetophenone according
to the procedure reported in Ref. [19].
5.1.12. N-[2-(2,6-di-t-butylphenoxy)ethyl]phthalimide (23)
Prepared from 20 as described for 22 and isolated after crys-
tallization from EtOH as a white solid (63.9%): m.p. 107.5–
5.1.19. 2-Benzyloxy-3-chloroacetophenone (30)
1
108.3 °C; H NMR (CDCl3) δ 1.39 (s, 18H), 3.95 (t, 2H),
Prepared
from
2-hydroxy-3-chloroacetophenone
as
4.16 (t, 2H), 6.96 (t, 1H), 7.22 (d, 2H), 7.73 (m, 2H), 7.87
(m, 2H). Anal. Calcd for C24H29NO3 (379.49).
described for 29. After chromatography on silica gel (cyclo-
hexane/ethyl acetate 95:5), the product was isolated (67.1%)
1
as a yellow oil: H NMR (CDCl3) δ 2.55 (s, 3H), 5.02 (s,
5.1.13. N-[2-(2-allyl-6-methoxyphenoxy)ethyl]phthalimide (24)
Prepared from 21 as described for 22 and isolated after crys-
tallization from EtOH as a white solid (50%): m.p. 76.8–77 °C;
1H NMR (CDCl3) δ 3.32 (d, 2H), 3.63 (s, 3H), 4.09 (t, 2H),
4.20 (t, 2H), 4.86–4.95 (m, 2H), 5.74–5.94 (m, 1H), 6.71 (d,
2H), 6.93 (t, 1H), 7.74 (m, 2H), 7.86 (m, 2H). Anal. Calcd for
C20H19NO4 (337.37).
2H), 7.15 (t, 1H), 7.38 (m, 3H), 7.48 (m, 3H), 7.56 (dd, 1H).
Anal. Calcd for C15H13ClO2 (260.72).
5.1.20. 2-Benzyloxy-3-methylacetophenone (31)
Prepared from 2-hydroxy-3-methylacetophenone as
described for 29. After chromatography on silica gel (cyclo-
hexane/ethyl acetate 75:25), the product was isolated (77%)

1034
M. Pallavicini et al. / European Journal of Medicinal Chemistry 41 (2006) 1025–1040
as a yellow oil: 1H NMR (CDCl3) δ 2.33 (s, 3H), 2.59 (s, 3H),
4.85 (s, 2H), 7.10 (t, 1H), 7.34–7.45 (m, 7H). Anal. Calcd for
C16H16O2 (240.30).
(d, 6H), 2.18 (s, 3H), 3.36 (m, 1H), 4.93 (s, 2H), 6.92–6.96
(dd, 1H), 7.07–7.18 (m, 2H), 7.36–7.41 (m, 5H). Anal. Calcd
for C13H20O3 (226.31).
5.1.21. 2-Benzyloxy-3-ethylacetophenone (32)
5.1.29. 2-Benzyloxy-3-t-butylphenyl acetate (40)
Prepared from 2-hydroxy-3-ethylacetophenone as described
for 29. After chromatography on silica gel (toluene), the pro-
duct was isolated (54%) as a yellow oil: H NMR (CDCl3) δ
Prepared from 34 as described for 35. Crystallization from
methanol gave 40 as a yellow solid (88.3%): m.p. 68.8 °C; H
NMR (CDCl3) δ 1.29 (s, 9H), 2.29 (s, 3H), 5.07 (s, 2H), 6.90–
1
1
1.28 (t, 3H), 2.62 (s, 3H), 2.75 (q, 2H), 4.87 (s, 2H), 7.16 (t,
7.38 (m, 8H). Anal. Calcd C19H22O3 (298.38).
1H), 7.30–7.50 (m, 7H). Anal. Calcd for C17H18O2 (254.32).
5.1.30. 2-Benzyloxy-3-fluorophenol (41)
Prepared from 35 according to the procedure reported in
Ref. [19].
5.1.22. 2-Benzyloxy-3-i-propylacetophenone (33)
Prepared from 2-hydroxy-3-i-propylacetophenone as
described for 29. After chromatography on silica gel (cyclo-
hexane/ethyl acetate 95:5), the product was isolated (87%) as
5.1.31. 2-Benzyloxy-3-chlorophenol (42)
1
a yellow oil: H NMR (CDCl3) δ 1.22 (d, 6H), 2.61 (s, 3H),
A solution of 36 (51.50 g, 186 mmol) and 2.5 N NaOH
(83.2 ml) in methanol (520 ml) was stirred for 2 h at room
temperature. The solvent was evaporated and the resulting resi-
due added with dichloromethane (400 ml) and washed with
water (350 ml). The aqueous layer was treated with 10% HCl
(pH 1) and extracted with dichloromethane (4 × 200 ml). The
organic phases were combined, dried and concentrated to give
35.69 g (81.7%) of 42 as a dark oil, which was used for the
subsequent step without further purification: 1H NMR (CDCl3)
δ 5.10 (s, 2H), 5.62 (br s, 1H), 6.85 (m, 1H), 6.97 (m, 2H),
7.41 (m, 5H). Anal. Calcd for C13H11ClO2 (234.68).
3.42 (m, 1H), 4.83 (s, 2H), 7.18 (t, 1H), 7.37–7.46 (m, 7H).
Anal. Calcd for C18H20O2 (268.35).
5.1.23. 2-Benzyloxy-3-t-butylacetophenone (34)
Prepared from 3-t-butyl-2-hydroxyacetophenone as
described for 29. After chromatography on silica gel (toluene)
1
the product was isolated (47.5%) as a solid: m.p. 97.5 °C; H
NMR (CDCl3) δ 1.32 (s, 9H), 2.62 (s, 3H), 5.16 (s, 2H), 6.97
(d, 1H), 7.35–7.50 (m, 6H), 7.79 (d, 1H). Anal. Calcd for
C19H22O2 (282.38).
5.1.24. 2-Benzyloxy-3-fluorophenyl acetate (35)
Prepared from 29 according to the procedure reported in
Ref. [19].
5.1.32. 2-Benzyloxy-3-methylphenol (43)
Prepared from 37 as described for 41. After chromatography
on silica gel (cyclohexane/ethyl acetate 80:20), the crude pro-
1
duct was isolated (49%) as a yellow oil: H NMR (CDCl3) δ
5.1.25. 2-Benzyloxy-3-chlorophenyl acetate (36)
2.23 (s, 3H), 4.99 (s, 2H), 5.51 (s, 1H), 6.76–6.82 (m, 2H),
6.98 (t, 1H), 7.35–7.52 (m, 5H). Anal. Calcd for C14H14O2
(214.26).
Prepared from 30 as described for 35. The crude product
was isolated (100%) as dark oil which was used for the subse-
1
quent step without further purification: H NMR (CDCl3) δ
2.55 (s, 3H), 5.03 (s, 2H), 7.00 (dd, 1H), 7.07 (t, 1H), 7.29
(dd, 1H), 7.40 (m, 5H). Anal. Calcd for C15H13ClO (276.71).
5.1.33. 2-Benzyloxy-3-ethylphenol (44)
Prepared from 38 as described for 41. After chromatography
on silica gel (toluene), 44 was isolated (86%) as a yellow oil:
1H NMR (CDCl3) δ 1.34 (t, 3H), 2.79 (q, 2H), 4.96 (s, 2H),
5.74 (s, 1H), 6.80–7.10 (m, 3H), 7.35–7.50 (m, 5H). Anal.
Calcd for C15H16O2 (228.29).
5.1.26. 2-Benzyloxy-3-methylphenyl acetate (37)
Prepared from 31 as described for 35. The product was iso-
lated (83.5%) as a yellow oil which was used for the subse-
1
quent step without further purification: H NMR (CDCl3) δ
2.20 (s, 3H), 2.28 (s, 3H), 4.92 (s, 2H), 6.91–7.09 (m, 3H),
7.36–7.51 (m, 5H). Anal. Calcd for C16H16O3 (256.30).
5.1.34. 2-Benzyloxy-3-i-propylphenol (45)
Prepared from 39 as described for 41. After chromatography
on silica gel (cyclohexane/ethyl acetate 90:10), the product was
1
5.1.27. 2-Benzyloxy-3-ethylphenyl acetate (38)
isolated (51.6%) as a yellow oil: H NMR (CDCl3) δ 1.27 (d,
6H), 3.37 (m, 1H), 4.90 (s, 2H), 5.49 (s, 1H), 6.83 (t, 2H), 7.04
(t, 1H), 7.35–7.48 (m, 5H). Anal. Calcd for C16H18O2
(242.31).
Prepared from 32 as described for 35. The product was iso-
lated (96.3%) as a yellow oil which was used for the subse-
quent step without further purification: H NMR (CDCl3) δ
1
1.25 (t, 3H), 2.20 (s, 3H), 2.70 (q, 2H), 4.95 (s, 2H), 6.90–
7.00 (m, 1H), 7.10–7.20 (m, 2H), 7.30–7.50 (m, 5H). Anal.
Calcd for C17H18O3 (270.32).
5.1.35. 2-Benzyloxy-3-t-butylphenol (46)
Prepared from 40 as described for 41. After chromatography
on silica gel (toluene), the product was isolated (73.4%) as a
yellow oil: 1H NMR (CDCl3) δ 1.33 (s, 9H), 5.11 (s, 2H), 5.68
(s, 1H), 6.89 (s, 2H), 7.06 (s, 1H), 7.44 (m, 5H). Anal. Calcd
for C17H20O2 (254.34).
5.1.28. 2-Benzyloxy-3-i-propylphenyl acetate (39)
Prepared from 33 as described for 35. The crude product
1
was isolated (98%) as a yellow oil: H NMR (CDCl3) δ 1.19

M. Pallavicini et al. / European Journal of Medicinal Chemistry 41 (2006) 1025–1040
1035
5.1.36. 2-Benzyloxy-3-fluoroanisole (47)
2H), 6.97 (br s, 1H), 7.30–7.55 (m, 5H). Anal. Calcd for
C18H22O2 (270.37).
Iodomethane (6.1 g, 41.3 mmol) was added drop-wise to a
solution of 41 (6 g, 27.5 mmol) and NaOH (1.1 g, 27.5 mmol)
in ethanol (60 ml) at room temperature. After 24 h, ethanol was
evaporated and the residue treated with 10% HCl (200 ml) and
extracted with ethyl acetate (3 × 100 ml). The organic phases
were combined, washed with water (10 ml), dried and concen-
trated to give the crude product, which was purified by chro-
matography on silica gel. Elution with cyclohexane/ethyl acet-
ate (90:10) afforded 6 g (94%) of 47 as an oil: 1H NMR
(CDCl3) δ 3.86 (s, 3H), 5.10 (s, 2H), 6.67–6.72 (m, 2H),
6.92–6.99 (m, 1H), 7.26–7.52 (m, 5H). Anal. Calcd for
C14H13FO2 (232.11).
5.1.42. 2-Fluoro-6-methoxyphenol (53)
A solution of 47 (6 g, 25.8 mmol) in methanol (60 ml) was
added with 10% Pd/C (250 mg) and vigorously shaken under
hydrogen at room temperature. The catalyst was removed by
filtration and the filtrate concentrated to give 53, which was
purified by chromatography on silica gel. Elution with cyclo-
hexane/ethyl acetate (95:5) yielded 3 g (82%) of 53 as a color-
1
less oil: H NMR (CDCl3) δ 3.90 (s, 3H), 5.40 (s, 1H), 6.64–
6.78 (m, 3H). Anal. Calcd for C7H7FO2 (142.04).
5.1.43. 2-Chloro-6-methoxyphenol (54)
5.1.37. 2-Benzyloxy-3-chloroanisole (48)
Prepared from 48 as described for 53. After chromatography
on silica gel (cyclohexane/ethyl acetate 80:20), 54 was isolated
(87.2%) as a solid: m.p. 52.9 °C; H NMR (CDCl3) δ 3.89 (s,
3H), 5.85 (br s, 1H), 6.78 (m, 2H), 6.93 (m, 1H). Anal. Calcd
for C7H7ClO2 (158.58).
Iodomethane (1.75 ml, 28.1 mmol) was added drop-wise to
a solution of 42 (6 g, 25.6 mmol) and tetrabutylammonium
bromide (0.84 g, 2.6 mmol) in dichloromethane (60 ml) and
2.5 N NaOH (20.5 ml, 51.1 mmol). The resulting mixture
was stirred at room temperature for 7 h. The organic layer
was separated, washed with 10% HCl (80 ml) and then with
water (80 ml), dried and concentrated to give 6.77 g of the
crude product, which was purified by chromatography on silica
gel. Elution with cyclohexane/ethyl acetate (90:10) afforded
1
5.1.44. 2-Methyl-6-methoxyphenol (55)
Prepared from 49 as described for 53. The crude product
was isolated (77%) as yellow oil and used without further
1
purification: H NMR (CDCl3) δ 2.27 (s, 3H), 3.88 (s, 3H),
1
4.3 g (67.6%) of 48 as a yellow oil: H NMR (CDCl3) δ 3.85
5.68 (br s, 1H), 6.72–6.75 (m, 3H). Anal. Calcd. for C8H10O2
(s, 3H), 5.07 (s, 2H), 6.82 (m, 1H), 7.01 (m, 2H), 7.40 (m, 3H),
7.60 (m, 2H).Anal. Calcd for C14H13ClO2 (248.70).
(138.16).
5.1.45. 2-Ethyl-6-methoxyphenol (56)
5.1.38. 2-Benzyloxy-3-methylanisole (49)
Prepared from 50 as described for 53. The crude product
was isolated (92%) as a yellow oil and used for the subsequent
Prepared from 43 as described for 47. After chromatography
on silica gel (hexane/ethyl acetate 80:20), the product was iso-
lated (72%) as an oil: 1H NMR (CDCl3) δ 2.23 (s, 3H), 3.88 (s,
3H), 4.99 (s, 2H), 6.76–6.82 (m, 2H), 6.98 (t, 1H), 7.32–7.51
(m, 5H). Anal. Calcd for C15H16O2 (228.29).
1
step without further purification: H NMR (CDCl3) δ 1.32 (t,
3H), 2.80 (q, 2H), 3.92 (s, 3H), 5.84 (s, 1H), 6.75–6.90 (m,
3H). Anal. Calcd for C9H12O2 (152.19).
5.1.46. 2-i-Propyl-6-methoxyphenol (57)
5.1.39. 2-Benzyloxy-3-ethylanisole (50)
Prepared from 51 as described for 53. After chromatography
on silica gel (cyclohexane/ethyl acetate 80:20), 57 was isolated
(79%) as a colorless oil: 1H NMR (CDCl3) δ 1.24 (d, 6H), 3.32
(m, 1H), 3.88 (s, 3H), 5.74 (s, 1H), 6.70–6.77 (m, 1H), 6.82–
7.26 (m, 2H). Anal. Calcd for C10H14O2 (166.22).
Prepared from 44 as described for 47, but replacing ethanol
with methanol. After chromatography on silica gel (toluene),
1
50 was isolated (48%) as an oil: H NMR (CDCl3) δ 1.32 (t,
3H), 2.79 (q, 2H), 3.97 (s, 3H), 5.14 (s, 2H), 6.80–7.00 (m,
2H), 7.10–7.20 (m, 1H), 7.25–7.65 (m, 5H). Anal. Calcd for
C16H18O2 (242.31).
5.1.47. 2-t-Butyl-6-methoxyphenol (58)
Prepared from 52 as described for 53. The crude product
was isolated (95.4%) as a red oil and used for the subsequent
step without further purification: H NMR (CDCl3) δ 1.36 (s,
9H), 3.93 (s, 3H), 5.40–5.80 (s, 1H), 6.91–6.97 (m, 3H). Anal.
Calcd for C11H16O2 (180.24).
5.1.40. 2-Benzyloxy-3-i-propylanisole (51)
1
Prepared from 45 as described for 47. After chromatography
on silica gel (cyclohexane/ethyl acetate 90:10), the product was
1
isolated (78.4%) as a yellow oil: H NMR (CDCl3) δ 1.18 (d,
6H), 3.39 (m, ,1H), 3.89 (s, 3H), 5.02 (s, 2H), 6.79–6.89 (m,
2H), 7.08 (t, 1H), 7.33–7.52 (m, 5H). Anal. Calcd for
C17H20O2 (256.34).
5.1.48. 2-(2-Fluoro-6-methoxyphenoxy)-1-bromoethane (59)
Dibromoethane (15.8 g, 84 mmol) was added drop-wise to a
solution of 53 (3 g, 21 mmol) and KOH (4.8 g, 84 mmol) in
DMSO (30 ml). The resulting mixture was stirred for 24 h and
then treated with 10% HCl (100 ml) and extracted with diethyl
ether (3 × 50 ml). The organic phases were combined, washed
with water, dried and concentrated to give the crude product
which was purified by chromatography on silica gel. Elution
5.1.41. 2-Benzyloxy-3-t-butylanisole (52)
Prepared from 46 as described for 47, but replacing ethanol
with methanol. The crude product was isolated (88.8%) and
1
used for the subsequent step without further purification: H
NMR (CDCl3) δ (s, 9H), 3.93 (s, 3H), 5.16 (s, 2H), 6.86 (dd,

1036
M. Pallavicini et al. / European Journal of Medicinal Chemistry 41 (2006) 1025–1040
with cyclohexane/ethyl acetate (90:10) afforded 4 g (76%) of
59 as a yellow oil: H NMR (CDCl3) δ 3.60 (t, 2H), 3.85 (s,
3H), 4.36 (t, 2H), 6.65–6.80 (m, 2H), 6.84–7.08 (m, 1H). Anal.
Calcd for C9H10BrFO2 (248.96).
5.1.55. 2-(2-Methyl-6-methoxyphenoxy)ethylazide (66)
Prepared from 61 as described for 65. The crude product
was isolated (80%) as a yellow oil and used without further
1
1
purification: H NMR (CDCl3) δ 2.31 (s, 3H), 3.57 (t, 2H),
3.85 (s, 3H), 4.11 (t, 2H), 6.77 (d, 2H), 6.97 (t, 1H). Anal.
Calcd for C10H13N3O2 (207.23).
5.1.49. 2-(2-Chloro-6-methoxyphenoxy)-1-bromoethane (60)
Prepared from 54 as described for 59. After chromatography
on silica gel (toluene), 60 was isolated (85.2%) as a colorless
oil: 1H NMR (CDCl3) δ 3.70 (t, 2H), 3.81 (s, 3H), 4.22 (t, 2H),
7.05 (m, 3H). Anal. Calcd for C9H10BrClO2 (265.53).
5.1.56. 2-(2-i-Propyl-6-methoxyphenoxy)ethylazide (67)
Prepared from 63 as described for 65. The crude product
was isolated (91.5%) as a yellow oil and used without further
1
purification: H NMR (CDCl3) δ 1.23 (q, 6H), 3.42 (m, 1H),
3.59 (t, 2H), 3.86 (s, 3H), 4.13 (t, 2H), 6.75–6.89 (m, 2H), 7.05
(t, 1H). Anal. Calcd for C12H17N3O2 (235.28).
5.1.50. 2-(2-Methyl-6-methoxyphenoxy)-1-bromoethane (61)
Prepared from 55 as described for 59. The crude product
was isolated (98.6%) by distillation under vacuum (100 °C at
0.2 mbar) as a yellow oil: H NMR (CDCl3) δ 2.31 (s, 3H),
3.64 (t, 2H), 3.84 (s, 3H), 4.27 (t, 2H), 6.77 (d, 2H), 6.93 (t,
1H). Anal. Calcd for C10H13BrO2 (245.11).
1
5.1.57. 2-(2-t-Butyl-6-methoxyphenoxy)ethylazide (68)
Prepared from 64 as described for 65. The crude product
was isolated (94.2%) as a yellow oil and used without further
1
purification: H NMR (CDCl3) δ 1.33 (s, 9H), 3.61 (m, 2H),
3.89 (s, 3H), 4.17 (m, 2H), 6.90–7.0 (m, 3H). Anal. Calcd for
C13H19N3O2 (249.31).
5.1.51. 2-(2-Ethyl-6-methoxyphenoxy)-1-bromoethane (62)
Dibromoethane (18.80 ml, 0.218 mol) was added drop-wise
to a solution of 56 (8.3 g, 0.054 mol), KOH (12.24 g, 0.218
mol) and tetrabutylammonium bromide (3.33 g, 10.3 mmol) in
dichloromethane (110 ml) and water (90 ml). The resulting
mixture was stirred for 24 h and then treated with 10% HCl
(60 ml). The aqueous layer was extracted with dichloro-
methane (3 × 70 ml). The organic phases were combined,
washed with water, dried and concentrated to give 13.5 g
(96.4%) of 62, which was used for the subsequent step without
5.1.58. N-[2-(2-ethyl-6-methoxyphenoxy)ethyl]phthalimide
(69)
A solution of phthalimide (12.55 g, 67.7 mmol) in DMF
was added drop-wise to 62 (13.5 g, 52.1 mmol) in DMF (48
ml). The mixture was refluxed for 3 h and, after cooling at
room temperature, quenched into ice and water (300 ml). The
resulting precipitate was isolated yielding 12.98 g (76.7%) of
69 as a white solid: m.p. 81–82.4 °C; 1H NMR (CDCl3) δ 1.05
(t, 3H), 2.52 (q, 2H), 3.65 (s, 3H), 4.10–4.30 (m, 4H), 6.60–
6.80 (m, 2H), 6.90–7.00 (m, 1H), 7.70–7.80 (m, 2H), 7.80–
7.90 (m, 2H). Anal. Calcd for C19H19NO4 (325.36).
1
further purification: H NMR (CDCl3) δ 1.22 (t, 3H), 2.72 (q,
2H), 3.67 (t, 2H), 3.85 (s, 3H), 4.28 (t, 2H), 6.70–6.90 (m, 2H),
6.95–7.10 (m, 1H). Anal. Calcd for C11H15BrO2 (259.14).
5.1.52. 2-(2-i-Propyl-6-methoxyphenoxy)-1-bromoethane (63)
Prepared from 57 as described for 59. Distillation under
vacuum (110 °C at 0.3 mbar) gave 63 (51.3%) as a yellow oil:
1H NMR (CDCl3) δ 1.22 (d, 6H), 3.46 (m, 1H), 3.62 (t, 2H),
3.85 (s, 3H), 4.27 (t, 2H), 6.76 (d, 1H), 6.87 (d, 1H), 7.05 (t,
1H). Anal. Calcd for C12H17BrO2 (273.17).
5.1.59. N-[2-(2-chloro-6-methoxyphenoxy)ethyl]phthalimide
(70)
Prepared from 60 as described for 69 and isolated (100%) as
1
a white solid: m.p. 94.4 °C; H NMR (CDCl3) δ 3.60 (s, 3H),
4.15 (t, 2H), 4.25 (t, 2H), 6.70 (dd, 1H), 6.93 (m, 2H), 7.70 (m,
2H), 7.90 (m, 2H). Anal. Calcd. for C17H14ClNO4 (331.75).
5.1.53. 2-(2-t-Butyl-6-methoxyphenoxy)-1-bromoethane (64)
Prepared from 58 as described for 62. After chromatography
on silica gel (toluene), 64 was isolated (73.3%) as a yellow oil:
1H NMR (CDCl3) δ 1.33 (s, 9H), 3.65 (t, 2H), 3.90 (s, 3H),
4.32 (t, 2H), 6.80–7.00 (m, 3H). Anal. Calcd for C13H19BrO2
(287.19).
5.1.60. 2-(2-Fluoro-6-methoxyphenoxy)ethylamine (71)
Hydrazine hydrate (7 ml) was added to a stirred mixture of
65 (3.35 g, 15.8 mmol) and PdO (60 mg) in methanol at 65 °C.
After refluxing for 5 h, PdO was removed by filtration and the
filtrate was concentrated. The residue was treated with a satu-
rated solution of NaCl and dichloromethane (30 ml). The aqu-
eous layer was separated and extracted with dichloromethane
again. The organic phases were combined, washed with water,
dried and concentrated. Distillation under vacuum (110 °C at
0.2 mbar) of the residue gave 2.5 g (85%) of 71 as a colorless
oil: 1H NMR (CDCl3) δ 1.60 (s, 2H), 2.95 (t, 2H), 3.83 (s, 3H),
4.10 (t, 2H), 6.71–6.78 (m, 2H), 6.82–6.99 (m, 1H). Anal.
Calcd for C9H12FNO2 (185.06).
5.1.54. 2-(2-Fluoro-6-methoxyphenoxy)ethylazide (65)
A mixture of 59 (4 g, 16 mmol) and sodium azide (10.5 g,
16 mmol) in DMF (60 ml) and water (30 ml) was heated at
90 °C for 5 h. After cooling at room temperature, water (30
ml) was added and the resulting mixture extracted with n-hex-
ane (7 × 20 ml). The organic phases were combined, washed
with water, dried and concentrated to give 3.35 g (98%) of 65
as an oil, which was used without further purification: 1H
NMR (CDCl3) δ 3.50 (t, 2H), 3.90 (s, 3H), 4.20 (t, 2H),
6.65–6.79 (m, 2H), 6.90–7.06 (m, 1H). Anal. Calcd for
C9H10FN3O2 (211.06).
5.1.61. 2-(2-Chloro-6-methoxyphenoxy)ethylamine (72)
Hydrazine hydrate (1.88 ml) was added drop-wise to a stir-
red solution of 70 (4.26 g, 12.8 mmol) in 2-methoxyethanol

M. Pallavicini et al. / European Journal of Medicinal Chemistry 41 (2006) 1025–1040
1037
(26 ml) at 125 °C. After refluxing for 3 h, 10% HCl was added
(pH 3). After cooling, the precipitate was removed and the fil-
trate was concentrated. The resulting residue was dissolved in
dichloromethane (100 ml) and treated with 10% HCl. The aqu-
eous layer was separated, treated with 2.5 N NaOH and
extracted with dichloromethane (4 × 50 ml). The organic
phases were combined, washed with a saturated solution of
NaCl, dried and concentrated to give 2.04 g (78.7%) of 72 as
isolated and dried yielding 180 mg (21.3% based on the start-
ing amount of (2R)-2-iodomethyl-1,4-benzodioxane) of (S)-1
as a white solid: m.p. 178–182 °C; [α]D25 = –56.3 (c 1, metha-
nol); 1H NMR (DMSO-d6) δ 3.20–3.50 (m, 5H), 4.05–4.20 (m,
1H), 4.30–4.55 (m, 3H), 4.70 (m, 1H), 6.80–6.95 (m, 4H),
7.05–7.15 (m, 3H), 9.60 (br s, 1H). Anal. Calcd for
C17H18ClF2NO3 (357.78).
1
5.1.67. (R)-2-[((2-(2,6-difluorophenoxy)ethyl)amino)methyl]-
1,4-benzodioxane hydrochloride [(R)-1]
a yellow oil: H NMR (CDCl3) δ 1.73 (br s, 2H), 3.02 (t, 2H),
3.85 (s, 3H), 4.05 (t, 2H), 6.80 (m, 1H), 6.97 (m, 2H). Anal.
Calcd for C9H12ClNO2 (201.65).
Prepared from (S)-2-iodomethyl-1,4-benzodioxane and 18
as described for (S)-1: m.p. 178–182 °C; [α]D25 = +58.2 (c 1,
1
5.1.62. 2-(2-Methyl-6-methoxyphenoxy)ethylamine (73)
Prepared from 66 as described for 71. Distillation under
vacuum (90 °C at 0.3 mbar) gave 73 (69.3%) as a colorless oil:
1H NMR (CDCl3) δ 1.76 (br s, 2H), 2.25 (s, 3H), 2.98 (t, 2H),
3.78 (s, 3H), 3.91 (t, 2H), 6.72 (d, 2H), 6.91 (t, 1H). Anal.
Calcd for C10H15NO2 (181.23).
methanol); H NMR identical to that of (S)-1.
5.1.68. (S)-2-[((2-(2,6-dichlorophenoxy)ethyl)amino)methyl]-
1,4-benzodioxane hydrochloride [(S)-2]
Prepared from (R)-2-iodomethyl-1,4-benzodioxane (1 g,
3.62 mmol) and 25 (2.98 g, 14.48 mmol) as described for
(S)-1 but replacing 2-propanol with 2-methyl-1-propanol and
refluxing for 48 h. After chromatography on silica gel (dichlor-
omethane/methanol 98:2), the secondary amine was isolated as
a yellow oil: [α]D25 = –26.77 (c 1, chloroform); 1H NMR
(CDCl3) δ 2.00 (br s, 1H), 2.98–3.13 (m, 4H), 4.14 (m, 1H),
4.19 (m, 2H), 4.32–4.40 (m, 2H), 6.86 (m, 4H), 7.00 (t, 1H),
7.29 (d, 2H). Subsequent treatment with HCl/EtOH yielded
(S)-2 (31.4% based on the starting amount of (R)-2-iodo-
methyl-1,4-benzodioxane) as a white solid: m.p. 174.5 °C; [α]
5.1.63. 2-(2-Ethyl-6-methoxyphenoxy)ethylamine (74)
Prepared from 69 as described for 72. Distillation under
vacuum (105 °C at 0.5 mbar) gave 74 (72%) as a colorless oil:
1H NMR (CDCl3) δ 1.23 (t, 3H), 1.63 (br s, 2H), 2.67 (q, 2H),
3.04 (t, 2H), 3.83 (s, 3H), 3.96 (t, 3H), 6.78 (m, 1H), 6.99 (m,
1H). Anal. Calcd for C11H17NO2 (195.26).
5.1.64. 2-(2-i-Propyl-6-methoxyphenoxy)ethylamine (75)
Prepared from 67 as described for 71. Distillation under
vacuum (100 °C at 0.2 mbar) gave 75 (79.2%) as a colorless
25 = –52.6 (c 1, methanol); 1H NMR (DMSO-d6) δ 3.54–3.43
D
(m, 4H), 4.16 (dd, 1H), 4.35–4.47 (m, 3H), 4.80 (m, 1H), 6.95
(m, 4H), 7.27 (t, 1H), 7.57 (d, 2H), 9.76 (m, 2H). Anal. Calcd
for C17H18Cl3NO3 (390.23).
1
oil: H NMR (CDCl3) δ 1.22 (d, 6H), 1.74 (br s, 2H), 3.05 (t,
2H), 3.37 (m, 1H), 3.83 (s, 3H), 3.95 (t, 2H), 6.75 (d, 1H), 6.84
(d, 1H), 7.03 (t, 1H). Anal. Calcd for C12H19NO2 (209.28).
5.1.69. (R)-2-[((2-(2,6-dichlorophenoxy)ethyl)amino)methyl]-
1,4-benzodioxane hydrochloride [(R)-2]
5.1.65. 2-(2-t-Butyl-6-methoxyphenoxy)ethylamine (76)
Prepared from 68 as described for 71. Distillation under
vacuum (120 °C at 0.3 mbar) gave 76 (74.3%) as a colorless
Prepared from (S)-2-iodomethyl-1,4-benzodioxane and 25
as described for (S)-2: m.p. 173.5 °C; [α]D25 = +53.0 (c 1,
1
1
oil: H NMR (CDCl3) δ 1.30 (s, 9H), 1.87 (br s, 2H), 3.07 (t,
methanol); H NMR identical to that of (S)-2.
2H), 3.86 (s, 3H), 4.01 (t, 2H), 6.75–7.00 (m, 3H). Anal. Calcd
5.1.70. (S)-2-[((2-(2,6-di-t-butylphenoxy)ethyl)amino)methyl]-
for C13H21NO2 (223.31).
1,4-benzodioxane hydrochloride [(S)-3]
5.1.66. (S)-2-[((2-(2,6-difluorophenoxy)ethyl)amino)methyl]-
1,4-benzodioxane hydrochloride [(S)-1]
A
mixture of (R)-2-mesyloxymethyl-1,4-benzodioxane
(0.98 g, 4.01 mmol) and 26 (2 g, 8.02 mmol) in 2-methyl-1-
propanol (5 ml) was refluxed for 24 h. After cooling at room
temperature, dichloromethane and a saturated aqueous solution
of NaHCO3 were added. The aqueous layer was separated and
extracted with dichloromethane again. The organic phases
were combined, dried and concentrated to give the crude pro-
duct, which was purified by chromatography on silica gel. Elu-
tion with cyclohexane/ethyl acetate (70:30) afforded 1.38 g
(86.8%) of (S)-2-[((2-(2,6-Di-t-butylphenoxy)ethyl)amino)
methyl]-1,4-benzodioxane as a yellow oil: [α]D25 = –25.6
A solution of (R)-2-iodomethyl-1,4-benzodioxane (650 mg,
2.36 mmol) and 18 (800 mg, 4.62 mmol) in 2-propanol was
refluxed for 18 h. After cooling at room temperature, the sol-
vent was removed and dichloromethane and a saturated aqu-
eous solution of NaHCO3 were added. The aqueous layer
was separated and extracted with dichloromethane again. The
organic phases were combined, dried and concentrated to give
the crude product which was purified by chromatography on
silica gel. Elution with cyclohexane/ethyl acetate (80:20)
afforded 320 mg (42%) of (S)-2-[((2-(2,6-difluorophenoxy)
1
(c 1, chloroform); H NMR (CDCl3) δ 1.44 (s, 18H), 1.68 (s,
ethyl)amino)methyl]-1,4-benzodioxane as
a
yellow oil:
1H), 2.99 (m, 2H), 3.13 (t, 2H), 3.89 (t, 2H), 4.01–4.11 (dd,
1H), 4.29–4.34 (m, 2H), 6.87 (m, 4H), 4.98 (t, 1H), 7.25 (d,
2H). The secondary amine was dissolved in ethanol (5 ml) and
2.2 N HCl/EtOH (2.5 ml) was slowly added. The solvent was
evaporated and the residue crystallized from ethyl acetate
1H NMR (CDCl3) δ 2.05 (s, 1H), 2.95–3.10 (m, 4H), 3.95–
4.10 (dd, 1H), 4.20–4.40 (m, 4H), 6.75–7.05 (m, 7H). The sec-
ondary amine was dissolved in ethanol (3 ml) and 5 N HCl/
EtOH (1 ml) was slowly added. The resulting precipitate was

1038
M. Pallavicini et al. / European Journal of Medicinal Chemistry 41 (2006) 1025–1040
(20 ml). The resulting precipitate was dried yielding 910 mg of
(S)-3 (52% based on the starting amount of (R)-2-mesyloxy-
methyl-1,4-benzodioxane) as a white solid: m.p. 176.5 °C; [α]
5.1.75. (R)-2-[((2-(2-chloro-6-methoxyphenoxy)ethyl)amino)
methyl]-1,4-benzodioxane hydrochloride [(R)-5)]
Prepared from (S)-2-mesyloxymethyl-1,4-benzodioxane and
72 as described for (S)-5: m.p. 136.5 °C; [α]D25 = +46.8 (c 1,
25 = –50.1 (c 1, methanol); H NMR (DMSO-d6) δ 1.44 (s,
1
D
1
methanol); H NMR identical to that of (S)-5.
18H), 3.25–3.65 (m, 4H), 4.01–4.16 (m, 3H), 4.40–4.45 (dd,
1H), 4.76 (br s, 1H), 6.87 (m, 4H), 6.98 (t, 1H), 7.25 (d, 2H),
9.6 (br s, 1H), 10.06 (br s, 1H). Anal. Calcd for C25H36NO3Cl
(434.02).
5.1.76. (S)-2-[((2-(2-methyl-6-methoxyphenoxy)ethyl)amino)
methyl]-1,4-benzodioxane hydrochloride [(S)-6)]
Prepared from (R)-2-mesyloxymethyl-1,4-benzodioxane
(1.28 g, 5.25 mmol) and 73 (1.90 g, 10.5 mmol) as described
for (S)-3. After chromatography on silica gel (cyclohexane/
ethyl acetate 1:1), the free amine was isolated as an oil: [α]
5.1.71. (R)-2-[((2-(2,6-di-t-butylphenoxy)ethyl)amino)methyl]-
1,4-benzodioxane hydrochloride [(R)-3]
Prepared from (S)-2-mesyloxymethyl-1,4-benzodioxane and
25 = –30.3 (c 1, chloroform); H NMR (CDCl3) δ 1.94 (br s,
1
26 as described for (S)-3: m.p. 172.9 °C; [α]D25 = +49.8 (c 1,
D
1
1H), 2.29 (s, 3H), 2.90–3.09 (m, 4H), 3.83 (s, 3H), 4.01–4.11
methanol); H NMR identical to that of (S)-3.
(m, 3H), 4.30–4.35 (m, 2H), 6.74–7.00 (m, 7H). Subsequent
treatment with HCl/EtOH afforded (S)-6 (51% based on the
starting amount of (R)-2-mesyloxymethyl-1,4-benzodioxane)
as a white solid: m.p. 142.7 °C; [α]D25 = –58.2 (c 1, methanol);
1H NMR (DMSO-d6) δ 2.27 (s, 3H), 3.43–3.46 (m, 4H), 3.82
(s, 3H), 4.11–4.21 (m, 3H), 4.46 (dd, 1H), 4.81 (m, 1H), 6.80–
7.07 (m, 7H), 9.63 (br s, 2H). Anal. Calcd for C19H24ClNO4
(765.39).
5.1.72. (S)-2-[((2-(2-fluoro-6-methoxyphenoxy)ethyl)amino)
methyl]-1,4-benzodioxane hydrochloride [(S)-4)]
Prepared from (R)-2-iodomethyl-1,4-benzodioxane (1.2 g,
4.34 mmol) and 71 (1.18 g, 6.37 mmol) as described for (S)-
1 but replacing 2-propanol with 2-methyl-1-propanol and
refluxing for 24 h. After chromatography on silica gel (dichlor-
omethane/methanol 98:2), the secondary amine was isolated as
a yellow oil: [α]D25 = +26.6 (c 1, chloroform); 1H NMR
(CDCl3) δ 2.05 (br s, 1H), 2.80–3.12 (m, 4H), 3.85 (s, 3H),
4.05–4.12 (m, 1H), 4.15–4.23 (m, 2H), 4.26–4.39 (m, 2H),
6.80–6.52 (m, 5H), 6.65–7.00 (m, 7H). Subsequent treatment
with HCl/EtOH yielded (S)-4 (23.4% based on the starting
amount of (R)-2-iodomethyl-1,4-benzodioxane) as a white
5.1.77. (R)-2-[((2-(2-methyl-6-methoxyphenoxy)ethyl)amino)
methyl]-1,4-benzodioxane hydrochloride [(R)-6)]
Prepared from (S)-2-mesyloxymethyl-1,4-benzodioxane and
73 as described for (S)-6: m.p. 142.7 °C; [α]D25 = +58.6 (c 1,
1
methanol); H NMR identical to that of (S)-6.
1
solid: m.p. 111 °C; [α]D25 = +53.90 (c 1, methanol); H NMR
5.1.78. (S)-2-[((2-(2-ethyl-6-methoxyphenoxy)ethyl)amino)
methyl]-1,4-benzodioxane hydrochloride [(S)-7]
(DMSO-d6) δ 3.38–3.58 (m, 4H), 3.80 (s, 3H), 4.12–4.29 (m,
1H), 4.32–4.40 (m, 2H), 4.42–4.58 (m, 1H), 4.75–4.82 (m,
1H), 6.85–7.00 (m, 6H), 7.10–7.20 (m, 1H), 9.60 (br s, 2H).
Anal. Calcd for C18H21ClFNO4 (369.58).
Prepared from (R)-2-mesyloxymethyl-1,4-benzodioxane
(1 g, 4.09 mmol) and 74 (1.59 g, 8.19 mmol) as described
for (S)-3. After chromatography on silica gel (dichloro-
methane/methanol 9:/5), the free amine was isolated as an oil:
5.1.73. (R)-2-[((2-(2-fluoro-6-methoxyphenoxy)ethyl)amino)
methyl]-1,4-benzodioxane hydrochloride [(R)-4)]
1
[α]D25 = –30.3 (c 1, chloroform); H NMR (CDCl3) δ 1.22 (t,
3H), 2.67 (q, 2H), 3.05–3.11 (m, 4H), 3.20–3.35 (br s, 1H),
3.84 (s, 3H), 4.03–4.12 (m, 3H), 4.31–4.44 (m, 2H), 6.75–
7.02 (m, 7H). Subsequent treatment with HCl/EtOH yielded
(S)-7 (37.4% based on the starting amount of (R)-2-mesyloxy-
Prepared from (S)-2-iodomethyl-1,4-benzodioxane and 71
as described for (S)-4: m.p. 111 °C; [α]D25 = –48.3 (c 1, metha-
1
nol); H NMR identical to that of (S)-4.
25
methyl-1,4-benzodioxane) as a white solid: m.p. 225 °C; [α]D
1
5.1.74. (S)-2-[((2-(2-chloro-6-methoxyphenoxy)ethyl)amino)
methyl]-1,4-benzodioxane hydrochloride [(S)-5)]
= –57.2 (c 1, methanol); H NMR (DMSO-d6) δ 1.18 (t, 3H),
2.65 (q, 2H), 3.30–3.60 (m, 4H), 3.82 (s, 3H), 4.10–4.35 (m,
3H), 4.45 (d, 1H), 4.81 (m, 1H), 6.83–7.10 (m, 7H), 9.50 (m,
2H). Anal. Calcd for C20H26ClNO4 (379.42).
Prepared from (R)-2-mesyloxymethyl-1,4-benzodioxane
(0.637 g, 2.61 mmol) and 72 (1.05 g, 5.21 mmol) as described
for (S)-3. After chromatography on silica gel (cyclohexane/
ethyl acetate 60:40), the secondary amine was isolated as a
5.1.79. (R)-2-[((2-(2-ethyl-6-methoxyphenoxy)ethyl)amino)
methyl]-1,4-benzodioxane hydrochloride [(R)-7]
1
dark oil: [α]D25 = –27.2 (c 1, chloroform); H NMR (CDCl3)
δ 1.90 (br s, 1H), 2.99 (m, 4H), 3.85 (s, 3H), 4.06 (dd, 1H),
4.15 (m, 2H), 4.30 (m, 2H), 6.85 (m, 5H), 6.97 (m, 2H). Sub-
sequent treatment with HCl/EtOH yielded (S)-5 (32% based on
the starting amount of (R)-2-mesyloxymethyl-1,4-benzodiox-
ane) as a white solid: 136.5 °C; [α]D25 = –54.2 (c 1, methanol);
1H NMR (DMSO-d6) δ 3.40 (m, 4H), 3.81 (s, 3H), 4.08 (dd,
1H), 4.20 (m, 2H), 4.36 (dd, 1H), 4.69 (m, 1H), 6.88 (m, 4H),
7.08 (m, 3H), 9.40 (br s, 2H). Anal. Calcd for C18H21Cl2NO4
(386.27).
Prepared from (S)-2-mesyloxymethyl-1,4-benzodioxane and
74 as described for (S)-7: m.p. 225 °C; [α]D25 = +56.5 (c 1,
1
methanol); H NMR identical to that of (S)-7.
5.1.80. (S)-2-[((2-propyl-6-methoxyphenoxy)ethyl)amino)
methyl]-1,4-benzodioxane hydrochloride [(S)-8]
Prepared from (R)-2-mesyloxymethyl-1,4-benzodioxane
(1.17 g, 4.78 mmol) and 28 (2 g, 9.56 mmol) as described
for (S)-3. After chromatography on silica gel (cyclohexane/

M. Pallavicini et al. / European Journal of Medicinal Chemistry 41 (2006) 1025–1040
1039
ethyl acetate 1:1), the secondary amine was isolated as a yel-
5.1.85. (R)-2-[((2-allyl-6-methoxyphenoxy)ethyl)amino)
methyl]-1,4-benzodioxane hydrochloride [(R)-10]
1
low oil: [α]D25 = –33.3 (c 1, chloroform); H NMR (CDCl3) δ
0.99 (t, 3H), 1.61 (m, 2H), 1.94 (br s, 1H), 2.62 (t, 2H), 3.03
(m, 4H), 3.84 (s, 3H), 4.07 (m, 3H), 4.35 (m, 2H), 6.70–7.05
(m, 7H). Subsequent treatment with HCl/EtOH afforded (S)-8
(41.5% based on the starting amount of (R)-2-mesyloxymethyl-
1,4-benzodioxane) as a white solid: m.p. 120.8 °C; [α]D25 = –
56.4 (c 1, methanol); 1H NMR (DMSO-d6) δ 0.94 (t, 3H), 1.57
(m, 2H), 2.61 (t, 2H), 3.40–3.46 (m, 4H), 3.82 (s, 3H), 4.21
(m, 3H), 4.44 (dd, 1H), 4.82 (m, 1H), 6.94 (m, 7H), 9.57–9.88
(br s, 2H). Anal. Calcd for C21H28ClNO4 (393.44).
Prepared from (S)-2-mesyloxymethyl-1,4-benzodioxane and
27 as described for (S)-10: m.p. 102.5 °C; [α]D25 = +55.2 (c 1,
1
methanol); H NMR identical to that of (S)-10.
5.1.86. (S)-2-[((2-t-butyl-6-methoxyphenoxy)ethyl)amino)
methyl]-1,4-benzodioxane hydrochloride [(S)-11]
Prepared from (R)-2-mesyloxymethyl-1,4-benzodioxane
(1 g, 4.1 mmol) and 76 (1.82 g, 8.15 mmol) as described for
(S)-3. After chromatography on silica gel (cyclohexane/ethyl
acetate 1:1), the secondary amine was isolated as an oil: [α]
25 = –23.3 (c 1, chloroform); H NMR (CDCl3) δ 1.32 (s,
1
5.1.81. (R)-2-[((2-propyl-6-methoxyphenoxy)ethyl)amino)
methyl]-1,4-benzodioxane hydrochloride [(R)-8]
D
9H), 2.03 (br s, 1H), 2.97 (m, 2H), 3.08 (t, 2H), 3.88 (s, 3H),
Prepared from (S)-2-mesyloxymethyl-1,4-benzodioxane and
4.05 (dd, 1H), 4.13 (t, 2H), 4.28–4.35 (m, 2H), 6.80–6.94 (m,
7H). Subsequent treatment with HCl/EtOH gave (S)-11 (35%
based on the starting amount of (R)-2-mesyloxymethyl-1,4-
benzodioxane) as a white solid: m.p. 137 °C; [α]D25 = –49.2
28 as described for (S)-8: m.p. 120.6 °C; [α]D25 = +56.0 (c 1,
1
methanol); H NMR identical to that of (S)-8.
1
5.1.82. (S)-2-[((2-i-propyl-6-methoxyphenoxy)ethyl)amino)
methyl]-1,4-benzodioxane hydrochloride [(S)-9]
(c 1, methanol); H NMR (DMSO-d6) δ 1.31 (s, 9H), 3.35–
3.50 (m, 4H), 3.82 (s, 3H), 4.05–4.20 (m, 1H), 4.35–4.50 (m,
3H), 4.70–4.85 (m, 1H), 6.85–7.00 (m, 7H), 9.70 (br s, 2H).
Anal. Calcd for C22H30ClNO4 (407.47).
Prepared from (R)-2-mesyloxymethyl-1,4-benzodioxane
(0.87 g, 3.58 mmol) and 75 (0.87 g, 3.58 mmol) as described
for (S)-3. After chromatography on silica gel (cyclohexane/
ethyl acetate 1:1), the secondary amine was isolated as an oil:
5.1.87. (R)-2-[((2-t-butyl-6-methoxyphenoxy)ethyl)amino)
methyl]-1,4-benzodioxane hydrochloride [(R)-11]
[α]D25 = –26.8 (c 1, chloroform); H NMR (CDCl3) δ 1.22 (d,
1
6H), 1.85 (br s, 1H), 2.93–3.09 (m, 4H), 3.37 (m, 1H), 3.83 (s,
3H), 4.02–4.11 (m, 3H), 4.29–4.35 (m, 2H), 6.73–6.87 (m,
6H), 7.04 (t, 1H). Subsequent treatment with HCl/EtOH
yielded (S)-9 (46% based on the starting amount of (R)-2-
mesyloxymethyl-1,4-benzodioxane) as a white solid: m.p. 138.
Prepared from (S)-2-mesyloxymethyl-1,4-benzodioxane and
76 as described for (S)-11: m.p. 137 °C; [α]D25 = +45.8 (c 1,
1
methanol); H NMR identical to that of (S)-11.
5.2. Biology
1
9 °C; [α]D25 = –54.4 (c 1, methanol); H NMR (DMSO-d6) δ
5.2.1. Binding assays
1.18 (d, 6H), 3.30–3.60 (m, 5H), 3.81 (s, 3H), 4.10–4.25 (m,
3H), 4.43 (dd, 1H), 4.78 (m, 1H), 6.88–6.99 (m, 6H), 7.11 (t,
1H), 9.73 (br s, 2H). Anal. Calcd for C21H28ClNO4 (393.44).
The pharmacological profile of both the S and R enantio-
mers of compounds 1–11 was assessed by measuring their affi-
nities for α1a, α1b, α1d AR-subtypes and 5-HT1A serotoninergic
receptor with in vitro binding studies.
Briefly, membranes derived from Chinese Hamster Ovary
(CHO) cells expressing α1-AR subtypes (prepared as described
by Testa et al. [31]1) were resuspended in Tris–HCl, 50 mM,
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 (from 0.3 to 1000 nM
depending on the affinity). Prazosin 1 μM was used to deter-
mine non-specific binding.
Binding studies at 5-HT1A receptor were carried out using
crude membrane preparations from rat hippocampus, which
were resuspended in Tris–HCl 50 mM (pH 7.7, 10 μM pargy-
line 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 non-specific binding.
Incubations were stopped by rapid filtration, through GF/B
fiber filters, which were then washed, dried and counted in a
LK1214 rack β Liquid scintillation Spectrometer.
5.1.83. (R)-2-[((2-i-propyl-6-methoxyphenoxy)ethyl)amino)
methyl]-1,4-benzodioxane hydrochloride [(R)-9]
Prepared from (S)-2-mesyloxymethyl-1,4-benzodioxane and
75 as described for (S)-9: m.p. 139.4 °C; [α]D25 = +53.3 (c 1,
1
methanol); H NMR identical to that of (S)-9.
5.1.84. (S)-2-[((2-allyl-6-methoxyphenoxy)ethyl)amino)
methyl]-1,4-benzodioxane hydrochloride [(S)-10]
Prepared from (R)-2-mesyloxymethyl-1,4-benzodioxane
(1.10 g, 4.52 mmol) and 27 (1.34 g, 6.46 mmol) as described
for (S)-3. After chromatography on silica gel (cyclohexane/
ethyl acetate 1:1), the secondary amine was isolated as an oil:
1
[α]D25 = –28.2 (c 1, chloroform); H NMR (CDCl3) δ 1.97 (s,
1H), 3.02 (m, 4H), 3.45 (d, 2H), 3.84 (s, 3H), 4.10 (m, 3H),
4.35 (m, 2H), 5.08 (dd, 2H), 5.88–6.08 (m, 1H), 6.77–7.05 (m,
7H). Subsequent treatment with HCl/EtOH yielded (S)-10
(25% based on the starting amount of (R)-2-mesyloxymethyl-
1,4-benzodioxane) as a white solid: m.p. 102.3 °C; [α]D25 = –
1
55.6 (c 1, methanol); H NMR (DMSO-d6) δ 3.42 (m, 6H),
3.83 (s, 3H), 4.20 (m, 3H), 4.42 (dd, 1H), 4.79 (m, 1H), 5.05
(m, 2H), 6.00 (m, 1H), 6.94 (m, 7H), 9.48–9.80 (br s, 2H).
Anal. Calcd for C21H26ClNO4 (391.43).
At least three different experiments, in triplicate, were car-
ried out for each compound and usually each compound was

1040
M. Pallavicini et al. / European Journal of Medicinal Chemistry 41 (2006) 1025–1040
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(2005) 2547.
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[8] E. Castagnino, G. Strappaghetti, S. Corsano, P. Gallucci, L. Brasili, D.
Giardinà, Farmaco 39 (1984) 569 (Ed. Sci.).
[9] D. Giardinà, P. Angeli, L. Brasili, U. Gulini, C. Melchiorre, G. Strappa-
ghetti, Eur. J. Med. Chem. 19 (1984) 411.
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C. Melchiorre, J. Med. Chem. 31 (1988) 2300.
tested simultaneously on the different α1-AR subtypes. Prazo-
sin or 5-HT was always tested in parallel, as reference drugs.
The % 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 Software, San Diego, CA). This analysis
gives the IC50 (i.e. the drug concentration inhibiting specific
binding by 50%), calculated with the relative standard error. Ki
values were then calculated by IC50 using the Cheng and Prus-
off equation in which the Kd of [3H]-Prazosin for α1a, α1b, α1d
AR-subtypes were 0.4, 0.4 and 0.7 nM, respectively, whereas
the Kd of [3H]-8-OH-DPAT for 5-HT1A receptors was 1.2 nM.
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5.3. Statistics
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The descriptors were selected out of 27 molecular para-
meters, mainly taken from [32]. They were chosen to parame-
terize both electronic and steric properties of substituents. In
order to account for the effect of methoxyl group, a de novo
constant was added indicating its presence. The models were
manually obtained using a step-wise regression method by
which further parameters were progressively included in
QSARs in addition to the best single parameter correlating
with affinity so as to maximize r2 without exceeding the num-
ber of 4 parameters in each model. The statistical analyses
were carried out using Analyse-It 1.68 (Analyse-It software,
Ltd).
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Acknowledgements
Financial support provided by the Italian Ministero dell’Is-
truzione, dell’Università e della Ricerca Scientifica is gratefully
acknowledged.
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