Design, synthesis, and pharmacological effects of structurally simple ligands for MT1 and MT2 melatonin receptors

Article abstract of DOI:10.1016/j.bmc.2010.06.100

A series of phenoxyalkyl and phenylthioalkyl amides were prepared as melatoninergic ligands. Modulation of affinity of the newly synthesized compound by applying SARs around the terminal amide moiety, the alkyl chain, and the methoxy group on the aromatic ring provides compounds with nanomolar affinity for both melatonin receptor subtypes. Affinity towards MT₁ and MT₂ receptors were modulated also exploiting chirality. The investigation of intrinsic activity revealed that all the tested compounds behave as full or partial agonists.

Full text of DOI:10.1016/j.bmc.2010.06.100

Bioorganic & Medicinal Chemistry 18 (2010) 6496–6511
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Design, synthesis, and pharmacological effects of structurally simple ligands
for MT1 and MT2 melatonin receptors
a
a
a
b
c
Alessia Carocci a, , Alessia Catalano , Angelo Lovece , Giovanni Lentini , Andrea Duranti , Valeria Lucini ,
*
Marilou Pannacci c, Francesco Scaglione c, Carlo Franchini a
a Dipartimento Farmaco-Chimico, Università degli Studi di Bari, Via E. Orabona 4, 70126 Bari, Italy
b Dipartimento di Scienze del Farmaco e della Salute, Università degli Studi di Urbino ‘Carlo Bo’, Piazza del Rinascimento 6, 61029 Urbino, Italy
c Dipartimento di Farmacologia, Chemioterapia e Tossicologia Medica, Università degli Studi di Milano, Via Vanvitelli 32, 20129 Milano, Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of phenoxyalkyl and phenylthioalkyl amides were prepared as melatoninergic ligands. Modula-
tion of affinity of the newly synthesized compound by applying SARs around the terminal amide moiety,
the alkyl chain, and the methoxy group on the aromatic ring provides compounds with nanomolar affin-
ity for both melatonin receptor subtypes. Affinity towards MT1 and MT2 receptors were modulated also
exploiting chirality. The investigation of intrinsic activity revealed that all the tested compounds behave
as full or partial agonists.
Received 17 February 2010
Revised 22 June 2010
Accepted 29 June 2010
Available online 3 July 2010
Keywords:
Melatonin
Ó 2010 Elsevier Ltd. All rights reserved.
MT1 and MT2 receptors
Bioisosteres
Phenoxyalkyl amides
NHCOMe
MeO
1. Introduction
O
NHCOMe
Melatonin (N-acetyl-5-methoxytryptamine, MLT, Fig. 1) is a
neurohormone secreted primarily by the pineal gland, the highest
levels occurring during the period of darkness.1 It plays a major
role in the regulation of circadian rhythms and the control of sea-
sonal cycles.2 Extensive studies have demonstrated that adminis-
tration of MLT alleviates jet-lag and regulates delayed sleep
phase syndrome.3 Furthermore, exogenous MLT acts as sleep pro-
moter, chronohypnotic and/or chronobiotic.4,5 Neuroprotective,6
free radical scavenging, antioxidant,7–9 and immunomodulatory10
properties of MLT have also been reported. Recently, MLT has been
investigated for its potential use as anticancer,11–13 antinflamma-
tory,14 antihypertensive,15 radioprotector in radiotherapy,16 and
it has been even postulated the existence of a possible link
between it and type 2 diabetes.17 The obvious impact of MLT is actu-
ally underlined by more than 14,000 articles. Many of its physio-
logical actions are mediated through G-protein coupled
receptors18 expressed in a wide variety of tissues. Cloning studies
have revealed at least three MLT receptor subtypes, two of which
have been found in mammals, MT1 (Mel1a) and MT2 (Mel1b),19
localized in the central nervous system and in peripheral tis-
sues.20,21 Recently, another MLT binding site (MT3) has been
N
H
Melatonin (MLT)
Ramelteon
Figure 1. Chemical structures of MLT and Ramelteon.
described in hamster as homologue of the cytoplasmic quinone
reductase 2.22 The way in which MLT binds at these receptors
and the possible therapeutic potential of MLT in a wide variety of
clinical conditions has led to a rising interest in the development
of compounds capable of mimicking the effects of MLT, also con-
sidering that the use of MLT as a drug is limited by its short biolog-
ical half-life, poor oral bioavailability, and ubiquitous action.23
Thus, during the past decade, a great number of structurally dif-
ferent MLT receptor ligands, which range from simple indole deriv-
atives and their bioisosteres to phenylalkyl amides and constrained
melatoninergic agents, have been reported in the literature.24 It is
noteworthy that nearly all these compounds present an amido
group and an alkoxyaryl moiety that seem to be critical in deter-
mining the binding affinity and biological activity of these melaton-
inergic ligands.25 Some MT1/MT2 agonists are currently under
clinical evaluation or have been approved for their hypnotic
properties; ramelteon (Fig. 1) is at the present the only non selec-
tive MLT receptors agonist marketed in the US for the treatment
* Corresponding author. Tel.: +39 0805442746; fax: +39 0805442724.
E-mail address: carocci@farmchim.uniba.it (A. Carocci).
0968-0896/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2010.06.100

A. Carocci et al. / Bioorg. Med. Chem. 18 (2010) 6496–6511
6497
of insomnia.26,27 Other MT1/MT2 agonists, such as LY-15673528 or
tasimelteon (VEC-162),29 are undergoing clinical trials for the treat-
ment of sleep disorders. Agomelatine, an MT1/MT2 agonist and 5-
HT2c antagonist, is under evaluation for the treatment of unipolar
depression.30
Optically active propyl N-alkanamides (7d,e, 15d,e, and 16d,e)
were prepared according to the same route followed for the syn-
thesis of racemic propyl N-alkanamides except for the first step
where the alcohols 13d,e were obtained by condensation of the
appropriate phenol or thiophenol (1d,e) with enantiomerically
pure methyl 2-hydroxypropanoates [(R)- and (S)-17] under Mits-
unobu conditions (Scheme 4).
1-Methylethylacetamides (23c,d) in their racemic and optically
active forms were prepared according to the synthetic route re-
ported in Scheme 5, which involved the Mitsunobu reaction of
2-aminopropanols (19), efficiently protected with phthalic anhy-
dride, with the appropriate phenol (1c,d). Hydrazinolysis of the
resultant phthalimido derivatives (21c,d) and N-acylation of the
obtained amines (22c,d) with acetic anhydride gave the desired
acetamides.
Several years ago, basing on results obtained on a series of
phenylalkyl amides by Garratt et al.31 we examined several substi-
tuted phenoxyalkyl amides by exploiting the well known isosteric
relationship between the methylene group and the oxygen atom.32
From structure–activity relationships (SARs) on these compounds,
it appeared that the phenoxy moiety is a sufficient core to provide
compounds with significant potency as MLT agonists. In this paper,
we report the synthesis, the binding data, and activity results for
human MT1 and MT2 receptors of N-(phenoxyalkyl)amides and
their thioisologues, novel non-indolic MLT-like compounds, that
could be considered simplified models of MLT (Fig. 2). Starting
from N-(2-phenoxyethyl)acetamide as a scaffold we investigated
in detail: (i) the role and the optimal position of the methoxy group
on the aromatic moiety in structures that do not show the indole
nucleus; (ii) the effect of isosteric substitution of the side chain;
(iii) the effect of formal introduction of a methyl group on the alkyl
chain; and (iv) the effect of a slight modulation of the acyl group.
Starting from the observation that both indole33,34 and non-in-
dole35,36 chiral MT1 and MT2 ligands can show stereoselectivity
in terms of affinity and efficacy, we speculated that affinity to-
wards MLT receptors might be modulated exploiting chirality;
thus, we decided to synthesize and test our chiral compounds in
their optically active form.
Phenylthio methylethylacetamides (23e,f), in their racemic and
optically active forms, were prepared as reported in Scheme 6, by
modifying a one-pot literature procedure,41 which involved the
reaction of the appropriate thiol (1e,f) with 2-aminopropanol and
acetic acid.
Enantiomeric excess (ee) values for all the homochiral com-
pounds were determined either by chiral HPLC or GC analyses.
2.2. Structure–affinity and structure–intrinsic activity
relationships
The binding affinities of N-(phenoxyalkyl)amides and N-(phen-
ylthioalkyl)amides for human MT1 and MT2 receptors measured by
competition binding analysis using the radioligand 2-[125I]-iodom-
elatonin are shown in Table 1.
2. Results and discussion
2.1. Chemistry
Comparison of phenoxyethyl acetamides 12a–d reveals clearly
that the isomer with the methoxy group in the meta-position of
the aromatic moiety (12d) has the highest binding affinity; these
results agree with the data obtained by Garratt et al.31 in the cor-
responding series of phenylpropyl acetamides, which demon-
strated the superiority of compounds with methoxy groups in
the meta-position over their isomers. It is noteworthy that the
unsubstituted phenoxy derivative 12c shows a slightly higher
affinity than the corresponding ortho- and para-methoxy deriva-
tives 12a,b. Furthermore, 12d behaves as full agonist, whereas
compounds 12a–c are partial agonists.
Compound 2037 in its racemic and enantiomeric forms and (R)-
and (S)-23c38 were prepared as previously described.37,38 Racemic
propylacetamides 7a,b were prepared via the synthetic route
shown in Scheme 1. Alkylation of the suitable phenol (1a,b) with
racemic ethyl 2-bromopropanoate 2 gave 3a,b which were hydro-
lyzed and then converted into the corresponding amides (5a,b).
Reduction of the amides and successive N-acetylation with acetic
anhydride afforded the target compounds.
Results for compounds 7a–d, in which a methyl group has been
formally introduced into the position adjacent to the oxygen atom
of the alkyl chain, reveal an interesting increase of binding affinity
at both receptor subtypes for all derivatives of this series when
compared to the related compounds 12a–d. Also in this case, the
highest binding affinity occurs for the meta-methoxy derivative
7d, followed by the unsubstituted derivative 7c.
Ethylacetamides (12a–h) were prepared either by condensation
of the phthalimido alcohol 8 with the appropriate phenol (1a–d)
under Mitsunobu conditions39 or by a Williamson reaction of N-
(2-bromoethyl)phthalimide (9) with the suitable thiophenol (1e–
h), followed by hydrazinolysis40 of the corresponding phthalimido
derivatives (10a–h) and N-acylation of amines 11a–h with acetic
anhydride (Scheme 2).
On the other hand, the formal introduction of a methyl group
into the position adjacent to the nitrogen atom, as in 23c,d, leads
to a decrease in MT1 and MT2 binding affinity (23d vs 12d) or
has no effect (23c vs 12c). In order to optimize the biological profile
of the highest-affinity ligand 7d, we modulated the acyl chain by
replacing the methyl group with substituents that are often pres-
ent in other MLT ligands, such as cyclopropyl or n-propyl, obtain-
ing 15d and 16d, respectively. The replacement of the methyl
group in 7d with a cyclopropyl gave the most interesting com-
pound of the series, 15d, which showed an excellent binding affin-
ity for MT1 receptors (pKi = 9.03) close to that of MLT (pKi = 9.48)
with a MT2/MT1 selectivity ratio of 13. On the other hand, MT1
and MT2 binding affinities were substantially unaffected by substi-
tution of the methyl group with a n-propyl as in 16d. The most po-
tent compounds (7d, 15d, and 16d) act as full agonists.
Racemic propyl N-alkanamides (7c–e, 15d–e, and 16d–e) were
prepared according to Scheme 3. Alkylation of the suitable phenol
or thiophenol (1c–e) with racemic 2 gave the esters (3c–e) which
were submitted to reduction. The alcohols obtained (13c–e) were
condensed with phthalimide following a typical Mitsunobu proce-
dure. Hydrazinolysis run on the resulting phthalimido derivatives
(14c–e) gave the corresponding amines 6c–e. N-Acylation of the
crude amines with acetic or n-butyric anhydride or with cyclopro-
panecarbonyl chloride provides the desired MLT ligands.
X = O, S
R1 = H, OMe
R2, R3 = H, Me
R3
X
NHCOR4
R1
R2
In order to probe the lipophilic and electronic requirements of
the receptors binding pocket accommodating the aromatic moiety,
we replaced the oxygen atom of the alkyl chain by a sulphur.
R4 = Me, c-Pr, n-Pr
Figure 2. General structures of the newly synthesized compounds.

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A. Carocci et al. / Bioorg. Med. Chem. 18 (2010) 6496–6511
OH
O
COOEt
O
COOH
i
ii
R1
R1
R1
+
Br
COOEt
1a,b
3a,b
4a,b
2
a: R1 = p-OMe
b: R1 = o-OMe
iii, iv
O
O
O
CONH2
vi
v
NHCOCH3
NH2
R1
R1
R1
7a,b
6a,b
5a,b
Scheme 1. Reagents and conditions: (i) Na, EtOH, 70 °C; (ii) KOH, EtOH/H2O, reflux; (iii) SOCl2, Py, THF, rt; (iv) conc NH4OH, reflux then rt; (v) LiAlH4, THF, reflux then rt; (vi)
Ac2O, Et3N, THF, 0 °C.
O
HO
OH
N
R1
+
O
i
1a-d
8
O
X
N
R1
O
O
ii
Br
SH
N
10a-h
R1
+
O
iii
1e-h
9
X
X
NHCOCH3
NH2
iv
R1
R1
12a-h
11a-h
a: X = O; R1 = p-OMe
b: X = O; R1 = o-OMe
c: X = O; R1 = H
d: X = O; R1 = m-OMe
e: X = S; R1 = m-OMe
f: X = S; R1 = H
g: X = S; R1 = p-OMe
h: X = S; R1 = o-OMe
Scheme 2. Reagents and conditions: (i) DEAD, PPh3, THF, rt; (ii) K2CO3, DMF, reflux; (iii) aq N2H4, AcOH, MeOH, reflux; (iv) Ac2O, Et3N, THF, 0 °C.
Despite a slight increase or no significant difference in affinity
showed by phenylthioethyl acetamides 12e–h with respect to
the corresponding phenoxyethyl acetamides 12a–d, the same
modifications to the alkyl chain as were carried out for the phen-
oxyethyl derivatives generally reduces the affinity for both MT1
and MT2 receptors (see 7e, 15e, 16e, and 23e vs 7d, 15d, 16d,
and 23d, respectively). Functional analysis on MT1 and MT2 recep-
tors of the most potent sulphurated isologues (12e and 16e)
showed them to be full agonists except for compound 15e which
behaves as partial agonist.
Furthermore, in order to investigate the stereochemical require-
ments for the binding site, the enantiomers of the chiral com-
pounds were prepared in their highly optically enriched
enantiomeric forms and examined for their binding affinity. As
expected, a significant difference between the enantiomers was
observed; in particular, among the most potent compounds, the

A. Carocci et al. / Bioorg. Med. Chem. 18 (2010) 6496–6511
6499
R1
R1
R1
XH
X
COOEt
X
OH
i
ii
+
Br
COOEt
1c-e
2
3c-e
13c-e
iii
O
R1
R1
R1
X
X
X
NHCOCH3
NH2
N
v
iv
O
7c-e
6c-e
14c-e
vi
O
vii
R1
X
N
H
c: X = O; R1 = H
R1
X
d: X = O; R1 = OMe
e: X = S; R1 = OMe
NHCOC3H7
15d,e
16d,e
Scheme 3. Reagents and conditions: (i) Na, EtOH, 70 °C; (ii) LiAlH4, THF, reflux then rt; (iii) phthalimide, DEAD, PPh3, THF, rt; (iv) aq N2H4, AcOH, MeOH, reflux; (v) Ac2O, Et3N,
THF, 0 °C; (vi) cyclopropanecarbonyl chloride, Et3N, toluene, reflux; (vii) butyric anhydride, Et3N, THF, reflux.
XH
X
COOMe
X
H3CO
H3CO
H3CO
OH
OCH3
i
ii
HO
+
O
1d,e
(
R)-17, (S)-17
(R)-18d,e, (S)-18d,e
(R)-13d,e, (S)-13d,e
iii
O
X
H3CO
X
H3CO
X
H3CO
NH2
NHCOCH3
N
v
iv
O
(R)-7d,e, (S)-7d,e
(R)-6d,e, (S)-6d,e
(R)-14d,e, (S)-14d,e
vi
O
vii
X
H3CO
N
H
X
H3CO
d: X = O
e: X = S
NHCOC3H7
(R)-15d,e, (S)-15d,e
(R)-16d,e, (S)-16d,e
Scheme 4. Reagents and conditions: (i) DEAD, PPh3, THF, rt; (ii) LiAlH4, THF, reflux; (iii) phthalimide, DEAD, PPh3, THF, rt; (iv) aq N2H4, AcOH, MeOH, reflux; (v) Ac2O, Et3N,
THF, 0 °C; (vi) cyclopropanecarbonyl chloride, Et3N, toluene, reflux; (vii) butyric anhydride, Et3N, THF, reflux.
S-enantiomers behave as eutomers. The highest stereoselectivity was
observed for the thioderivative 7e, being Ki distomer/Ki eutomer
ratio of 460 and 94 for MT1 and MT2 receptors, respectively. It is
noteworthy that the most potent compound of the series (S)-15d
shows a certain degree of selectivity in favour of MT1 with a
MT2/MT1 selectivity ratio of 6. As regards the intrinsic activity, all
the most potent homochiral compounds behave as agonists, with
the exception of compounds 15e and 16e for which the eutomers
(S-enantiomers) are full agonists, whereas the distomers are partial
agonists.
In summary, a novel series of N-(phenoxyalkyl)amides and their
thioisologues were prepared in order to investigate structure–
affinity and structure–intrinsic activity relationships for MT1
and MT2 receptors. Within this series, the effect of bioisosteric

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A. Carocci et al. / Bioorg. Med. Chem. 18 (2010) 6496–6511
O
O
R1
HO
O
i
ii
HO
N
N
NH2
O
O
19, (R)-19, (S)-19
20, (R)-20, (S)-20
21c,d, (R)-21d, (S)-21d
iii
c: R1 = H
d: R1 = OMe
R1
O
R1
O
NHCOCH3
NH2
iv
23c,d, (R)-23d, (S)-23d
22c,d, (R)-22d, (S)-22d
Scheme 5. Reagents and conditions: (i) phthalic anhydride, Et3N, toluene, reflux; (ii) phenol (1c or 1d), DIAD, PPh3, THF, rt; (iii) aq N2H4, AcOH, MeOH, reflux; (iv) Ac2O, Et3N,
THF, 0 °C.
R1
SH
R1
S
NH2
HO
NHCOCH3
i
e: R1 = OMe
f: R1 = H
+
19, (R)-19, (S)-19
23e,f, (R)-23e,f, (S)-23e,f
1e,f
Scheme 6. Reagents and conditions: (i) AcOH, HCl, Zn, benzene, reflux.
substitution of the indole nucleus, the role of the methoxy group
and changes in the N-acyl side chain were considered. Furthermore,
in order to gain more insight into the receptor stereochemistry,
we have examined the affinities of the single enantiomers of the
chiral compounds. Our experience establishes the substituted
phenoxy and phenylthio moieties as novel bioisosteres for the in-
dole nucleus of the endogenous ligand and its close analogues.
The data highlight that derivatives with a methoxy group (12d vs
12a–c, 12e vs 12f–h, and 7d vs 7a–c) placed in a position that
can be easily superposed to position 5 of the indole ring of MLT
usually have the highest binding affinity, a behaviour consistent
with what was observed for other series of MLT receptor li-
gands.31,42 Shift of the methoxy group from the meta- to the para-
or ortho-positions, in fact, greatly reduces binding affinity and
intrinsic activity at both receptor subtypes; the pKi values obtained
for these compounds are even lower than those of the unsubstitut-
ed analogues. These data are in agreement with the results ob-
tained on MLT derivatives in which the shift of the methoxy
group from position 5 to position 6 led to a drastic reduction in
binding affinity and to partial agonist behaviour.43 Reduction of
binding affinity and intrinsic activity because of the shifting of
the methoxy group has also been observed in other series of MLT
receptor ligands.44 The effect of acyl chain modulation has been
evaluated on the basis of compounds 15d,e and 16d,e. The N-propyl
substituent is tolerated at both receptor subtypes. Interestingly,
pursuing a similar substitution pattern with the cyclopropyl
derivatives 15d resulted in the achievement of subnanomolar
MT1 affinity. The positive effect of cyclopropyl group had already
been observed for other MLT ligands.45 Our experience evidenced
a stereoselective behaviour of the most potent compounds both
in phenoxyalkyl and phenylthioalkyl series; in all cases the S-enan-
tiomers were found to be more potent agonists than the R-ones.
In general, replacement of the ether function with a thioether
one slightly influences receptor binding affinity, but provides com-
pound 7e which shows the highest stereodifferentiation especially
for MT1 subtype. A reasonable interpretation of this result could be
related to the different lipophilic and electronic properties of
oxygen and sulphur atoms.
3. Conclusions
SARs have been defined around the terminal amide moiety, the
alkyl chain, and the methoxy group on the aromatic ring of a new
series of phenoxyalkyl and phenylthioalkyl amides as novel mel-
atoninergic ligands. A methoxy group in the meta-position is cru-
cial for receptor binding affinity. Intrinsic activity and affinity
towards MT1 and MT2 receptors can be modulated by replacing
the methyl group of the acyl function with a propyl one. On the
other hand, receptor binding affinity strongly depends on the pres-
ence and the location of a methyl group on the alkyl chain. Affinity
towards MT1 and MT2 receptors can be modulated also exploiting
chirality. These chemical modifications have afforded potent nano-
molar compounds for both receptor subtypes. The highest level of
stereoselectivity was found in the series of the thioisologues for
compound 7e (Ki distomer/Ki eutomer ratio: 457 for MT1 subtype).
Of particular interest, compound (S)-15d shows a binding affinity
for the MT1 receptors (pKi = 9.14) close to that of MLT
(pKi = 9.48). These findings establish the meta-methoxyphenoxy
or meta-methoxyphenylthio ring as a novel bioisostere for the alk-
oxyaryl moiety of the endogenous ligand. The synthetic procedures
used are facile and versatile and allow insertion on the alkyl chain
of groups of different size and shape and, in general, modification
of the scaffold according to classical medicinal chemistry proce-
dures, thus envisaging further development of the present study.

A. Carocci et al. / Bioorg. Med. Chem. 18 (2010) 6496–6511
6501
Table 1
Experimental binding affinity and relative intrinsic activity (IAr) of newly synthesized compounds for human MT1 and MT2 melatonin receptors stably expressed in NIH3T3 cells
R3
X
NHCOR4
R1
R2
Compd
X
R1
R2
R3
R4
MT1
MT2
pKia
IAr SEMb
pKia
IAr SEMb
MLT
7a
7b
7c
9.48 0.06
4.37 0.27
4.98 0.04
5.86 0.14
8.44 0.41
7.31 0.37
8.77 0.43
6.96 0.05
5.56 0.23
8.24 0.08
4.21 0.18
4.43 0.32
4.94 0.07
7.39 0.22
7.26 0.16
5.42 0.30
5.55 0.46
5.44 0.38
9.03 0.01
8.11 0.16
9.14 0.05
8.07 0.02
6.92 0.02
8.27 0.02
8.38 0.01
7.09 0.03
8.51 0.07
8.04 0.01
7.15 0.03
8.41 0.06
4.92 0.17
4.20 0.18
4.68 0.31
6.45 0.20
4.44 0.26
6.46 0.22
4.92 0.10
4.94 0.07
6.32 0.12
4.50 0.46
4.13 0.13
5.43 0.24
1.00 0.18
0.15 0.01
0.19 0.01
0.48 0.02
1.01 0.03
0.79 0.04
1.01 0.06
ndc
9.21 0.09
4.90 0.10
5.29 0.17
5.94 0.06
8.02 0.71
6.96 0.38
8.33 0.49
6.58 0.22
6.18 0.09
8.15 0.13
4.34 0.13
5.18 0.15
5.26 0.18
7.17 0.01
7.40 0.17
6.47 0.23
5.62 0.38
6.30 0.25
7.89 0.49
7.68 0.18
8.36 0.15
8.01 0.23
7.31 0.01
8.17 0.01
8.43 0.01
7.17 0.06
8.56 0.12
8.30 0.05
7.58 0.08
8.22 0.12
5.42 0.19
4.27 0.13
5.34 0.14
6.46 0.08
5.31 0.14
6.52 0.21
5.88 0.13
4.91 0.12
6.58 0.16
5.17 0.13
4.19 0.11
5.36 0.25
1.00 0.07
0.13 0.01
0.45 0.02
0.69 0.03
1.01 0.07
0.93 0.20
1.09 0.07
ndc
O
O
O
O
O
O
S
p-OMe
o-OMe
H
Me
Me
Me
Me
Me
Me
Me
Me
Me
H
H
H
H
H
H
H
H
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
c-Pr
c-Pr
c-Pr
c-Pr
c-Pr
c-Pr
n-Pr
n-Pr
n-Pr
n-Pr
n-Pr
n-Pr
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
7d
m-OMe
m-OMe
m-OMe
m-OMe
m-OMe
m-OMe
p-OMe
o-OMe
H
(R)-7d
(S)-7d
7e
(R)-7e
(S)-7e
12a
12b
12c
12d
12e
S
S
ndc
ndc
ndc
ndc
O
O
O
O
S
S
S
S
O
O
O
S
S
S
O
O
O
S
S
S
O
O
O
O
O
O
S
S
S
S
S
0.26 0.02
0.23 0.01
0.31 0.03
0.81 0.06
0.85 0.03
0.22 0.02
0.48 0.02
0.27 0.01
0.91 0.04
0.90 0.03
1.01 0.06
0.77 0.01
0.49 0.09
0.80 0.05
1.04 0.03
1.06 0.13
1.01 0.05
1.02 0.08
0.59 0.05
0.99 0.07
0.04 0.01
0.17 0.02
0.05 0.01
0.63 0.03
0.35 0.02
0.75 0.05
ndc
0.44 0.03
0.22 0.01
0.50 0.03
0.80 0.05
0.81 0.04
0.50 0.05
0.56 0.02
0.56 0.03
1.02 0.02
0.77 0.01
1.26 0.06
0.63 0.09
0.59 0.05
0.80 0.05
1.12 0.12
0.86 0.06
1.07 0.18
0.99 0.03
0.64 0.07
0.96 0.10
0.15 0.01
0.11 0.01
0.26 0.03
0.71 0.05
0.43 0.02
0.80 0.06
ndc
m-OMe
m-OMe
H
12f
12g
12h
15d
p-OMe
o-OMe
m-OMe
m-OMe
m-OMe
m-OMe
m-OMe
m-OMe
m-OMe
m-OMe
m-OMe
m-OMe
m-OMe
m-OMe
H
(R)-15d
(S)-15d
15e
(R)-15e
(S)-15e
16d
(R)-16d
(S)-16d
16e
(R)-16e
(S)-16e
23c
(R)-23c
(S)-23c
23d
(R)-23d
(S)-23d
23e
(R)-23e
(S)-23e
23f
(R)-23f
(S)-23f
H
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
H
H
m-OMe
m-OMe
m-OMe
m-OMe
m-OMe
m-OMe
H
0.29 0.01
0.30 0.02
0
0.32 0.02
0.50 0.02
0.20 0.03
ꢀ0.04 0.01
0.25 0.03
H
H
H
H
H
ꢀ0.05 0.01
S
ꢀ0.07 0.01
a
pKi values were calculated from IC50 values obtained from competition curves by the method of Cheng and Prusoff,52 and are the mean of at least three determinations
performed in duplicate.
b
The relative intrinsic activity values were obtained dividing the maximum analogue-induced G-protein activation by that of MLT.
nd: not determined.
c
and 13C, respectively, using CDCl3 as solvent. Chemical shifts are
4. Experimental
4.1. Chemistry
reported in parts per million (ppm) relative to solvent resonance:
CDCl3, d 7.26 (1H NMR) and d 77.3 (13C NMR). J values are given
in Hertz. EIMS spectra were recorded on a Hewlett–Packard
6890–5973 MSD gas chromatograph/mass spectrometer at low
resolution. Elemental analyses were performed with a Eurovector
Euro EA 3000 analyzer. Optical rotations were measured on a Per-
kin-Elmer (Norwalk, CT) model 341 spectropolarimeter; concen-
trations are expressed in g/100 mL, and the cell length was 1 dm,
General experimental methods. All chemicals, including chiral
starting materials of known absolute stereochemistry, were pur-
chased from Sigma-Aldrich or Lancaster. Yields refer to purified
products and were not optimized. The structures of the compounds
were confirmed by routine spectrometric analyses. Only spectra for
compounds not previously described are given. Melting points
were determined on a Gallenkamp melting point apparatus in open
glass capillary tubes and are uncorrected. Infrared spectra were re-
corded on a Perkin-Elmer (Norwalk, CT) Spectrum One FT spectro-
photometer and band positions are given in reciprocal centimeters
(cmꢀ1). 1H NMR and 13C NMR spectra were recorded on a Varian
VX Mercury spectrometer operating at 300 and 75 MHz for 1H
thus ½a 2D0
ꢁ
values are given in units of 10ꢀ1 deg cm2 gꢀ1. HPLC anal-
yses were performed with an Agilent chromatograph (model 1100)
equipped with a diode array detector. Ee values were determined
either by direct HPLC analysis on a Daicel Chiralpak IA column,
or by GC analysis with Varian GC-3800 gas-chromatograph on
CP-Chirasil DEX CB (25 ꢂ 0.25 mm, 0.25
lM thickness). Chromato-
graphic separations were performed on silica gel columns by flash

6502
A. Carocci et al. / Bioorg. Med. Chem. 18 (2010) 6496–6511
chromatography (Kieselgel 60, 0.040–0.063 mm, Merck, Darms-
tadt, Germany) as described by Still et al.46 TLC analyses were per-
formed on precoated silica gel on aluminum sheets (Kieselgel 60
was acidified with 2 N HCl and extracted with Et2O. The combined
organic layers were dried (Na2SO4) and concentrated under re-
duced pressure to give 4.40 g (92%) of 4a as a white solid: mp
92–94 °C. Spectroscopic data were in agreement with the
literature.48
F254, Merck).
4.2. General procedure for the preparation of esters 3a–e
4.3.1. 2-(2-Methoxyphenoxy)propanoic acid (4b)
Prepared as reported above for 4a starting from 3b. Yield: 85%;
white solid: mp 76–77 °C. Spectroscopic data were in agreement
with the literature.48
The method adopted for the synthesis of ethyl 2-(4-methoxy-
phenoxy)propanoate (3a) is described. Sodium (0.93 g, 40.4 mmol)
was added in small pieces to absolute EtOH (62 mL) and the mix-
ture was heated at 70 °C. After completion of sodium dissolution,
a solution of 4-methoxyphenol (1a) (5.0 g, 40.4 mmol) in absolute
EtOH (20 mL) was added dropwise. After 30 min, a solution of ethyl
2-bromopropanoate (2) (7.3 g, 40.4 mmol) in absolute EtOH
(32 mL) was added dropwise and the mixture was heated at reflux
for 5 h. The solid residue was filtered off, the solvent was evapo-
rated in vacuo and the residue was taken up with Et2O, washed
with 2 N NaOH and dried (Na2SO4). Removal of the solvent under
vacuo gave 5.70 g (63%) of 3a as a slightly yellowish oil. Spectro-
scopic data were in agreement with those reported in the literature
for the (+)-isomer.47
4.4. General procedure for the preparation of amides 5a,b
The method adopted for the synthesis of 2-(4-methoxyphen-
oxy)propanamide (5a) is described. Compound 4a (2.50 g, 12.7 mmol)
was dissolved in SOCl2 (6 mL) at the temperature of 90 °C. After
stirring for 1.5 h, excess SOCl2 was evaporated in vacuo. The resi-
due was taken up with THF (50 mL) and concentrated NH4OH
(50 mL) was added dropwise while cooling at 0 °C. The mixture
was refluxed for 1 h and stirred at room temperature overnight.
After evaporation of the solvent the residue was taken up with
EtOAc, washed with a saturated NaHCO3 solution and dried
(Na2SO4). Evaporation of the solvent gave 1.50 g (61%) of a white
solid: mp 108–110 °C; IR (KBr): 3390, 3184 (NH2), 1661 (C@O)
4.2.1. Ethyl 2-(2-methoxyphenoxy)propanoate (3b)
Prepared as reported above for (3a) starting from 1b. Yield:
81%; slightly yellowish oil. Spectroscopic data were in agreement
with those reported in the literature for the (+)-isomer.47
cmꢀ1 1H NMR d 1.54 (d, 3H, J = 6.9 Hz, CH3CH), 3.75 (s, 3H,
;
CH3O), 4.54 (q, 1H, J = 6.7 Hz, CH), 6.09 (br s, 1H, NHH), 6.47 (br
s, 1H, NHH), 6.75–6.90 (m, 4H, Ar); 13C NMR d 18.8 (1C), 55.9
(1C), 75.9 (1C), 115.1 (2C), 117.0 (2C), 151.2 (1C), 155.0 (1C),
175.7 (1C); MS (70 eV) m/z (%) 195 (M+, 88), 124 (100).
4.2.2. Ethyl 2-phenoxypropanoate (3c)
Prepared as reported above for 3a starting from 1c. Yield: 52%;
slightly yellowish oil; IR (neat): 1753 (C@O) cmꢀ1; 1H NMR d 1.25 (t,
3H, J = 7.1 Hz, CH3CH2), 1.62 (d, 3H, J = 6.9 Hz, CH3CH), 4.22 (q, 2H,
J = 7.1 Hz, CH2), 4.74 (q, 1H, J = 6.9 Hz, CH), 6.83–6.92 (m, 2H, Ar),
6.92–7.02 (m, 1H, Ar), 7.22–7.32 (m, 2H, Ar); 13C NMR d 14.3 (1C),
18.8 (1C), 61.5 (1C), 72.9 (1C), 115.3 (2C), 121.8 (1C), 129.7 (2C),
157.8 (1C), 172.5 (1C); MS (70 eV) m/z (%) 194 (M+, 42), 121 (100).
4.4.1. 2-(2-Methoxyphenoxy)propanamide (5b)
Prepared as reported above for 5a starting from 4b. Yield: 50%;
white solid: mp 112–113 °C; IR (KBr): 3398, 3220 (NH2), 1634
(C@O) cmꢀ1 1H NMR d 1.63 (d, 3H, J = 6.9 Hz, CH3CH), 3.86 (s, 3H,
;
CH3O), 4.63 (q, 1H, J = 6.8 Hz, CH), 5.99 (br s, 1H, NHH), 6.80–7.05
(m partially overlapped to br s at 7.09 ppm, 4H, Ar), 7.09 (br s, 1H,
NHH); 13C NMR d 19.0 (1C), 56.0 (1C), 77.6 (1C), 112.4 (1C), 117.4
(1C), 121.4 (1C), 123.6 (1C), 147.0 (1C), 150.3 (1C), 175.7 (1C); MS
(70 eV) m/z (%) 195 (M+, 96), 151 (100). Anal. Calcd for C10H13NO3:
C, 61.53; H, 6.71; N, 7.18. Found: C, 61.85; H, 6.72; N, 7.23.
4.2.3. Ethyl 2-(3-methoxyphenoxy)propanoate (3d)
Prepared as reported above for 3a starting from 1d. Yield: 69%;
slightly yellowish oil; IR (neat): 1754 (C@O) cmꢀ1 1H NMR d 1.25
;
(t, 3H, J = 7.0 Hz, CH3CH2), 1.60 (d, 3H, J = 6.9, CH3CH), 3.77 (s, 3H,
CH3O), 4.21 (q, 2H, J = 7.1 Hz, CH2), 4.73 (q, 1H, J = 6.8 Hz, CH),
6.40–6.55 (m, 3H, Ar), 7.15 (apparent t, 1H, Ar); 13C NMR d 14.4
(1C), 18.8 (1C), 55.5 (1C), 61.5 (1C), 72.8 (1C), 101.9 (1C), 107.0
(1C), 107.6 (1C), 130.2 (1C), 159.0 (1C), 161.1 (1C), 172.4 (1C);
MS (70 eV) m/z (%) 224 (M+, 48), 151 (100).
4.5. General procedure for the preparation of amines 6a,b and
alcohols 13c–e, (R)- and (S)-13d,e
The method adopted for the synthesis of 2-(4-methoxyphen-
oxy)propan-1-amine (6a) is described. To a stirred suspension of
LiAlH4 (0.06 g, 1.58 mmol) in dry THF (20 mL) under N2 atmo-
sphere and in an ice-bath, a solution of 5a (0.15 g, 0.77 mmol) in
dry THF (20 mL) was added dropwise. After the addition, the mix-
ture was stirred at reflux for 2 h. After cooling at 0 °C, cold H2O was
added dropwise to destroy the excess hydride. The mixture was fil-
tered and the filtrate was concentrated in vacuo. The residue was
taken up with Et2O and the product was extracted with 2 N HCl.
The aqueous extracts were combined, brought to pH alkaline with
2 N NaOH and extracted with Et2O. The combined organic layers
were dried (Na2SO4). The filtrate was concentrated to yield 0.08 g
4.2.4. Ethyl 2-[(3-methoxyphenyl)thio]propanoate (3e)
Prepared as reported above for 3a starting from 1e. Yield: 95%;
slightly yellowish oil; IR (neat): 1732 (C@O) cmꢀ1 1H NMR d 1.19
;
(t, 3H, J = 7.1 Hz, CH3CH2), 1.49 (d, 3H, J = 7.1 Hz, CH3CH), 3.75–3.83
(m overlapping s at 3.79, 1H, CH), 3.79 (s overlapping m at 3.75–
3.83, 3H, CH3O), 4.13 (q, 2H, J = 7.1 Hz, CH2), 6.77–6.86 (m, 1H,
Ar), 6.96–7.08 (m, 2H, Ar), 7.21 (apparent t, 1H, Ar); 13C NMR d
14.3 (1C), 17.7 (1C), 45.4 (1C), 55.5 (1C), 61.5 (1C), 114.0 (1C),
117.9 (1C), 124.9 (1C), 129.9 (1C), 134.9 (1C), 159.9 (1C), 172.9
(1C); MS (70 eV) m/z (%) 240 (M+, 75), 167 (100).
(57%) of 6a as a yellow oil: IR (neat): 3372 (NH2) cmꢀ1 1H NMR
;
4.3. General procedure for the preparation of carboxylic acids
4a,b
d 1.23 (d, 3H, J = 6.0 Hz, CH3CH), 2.02 (br s, exch D2O, 2H, NH2),
2.86 (d, 2H, J = 5.5 Hz, CH2), 3.76 (s, 3H, CH3O), 4.22 (apparent sex-
tet, 1H, CH), 6.75–6.90 (m, 4H, Ar); 13C NMR d 17.5 (1C), 47.7 (1C),
55.9 (1C), 76.9 (1C), 114.9 (2C), 117.8 (2C), 152.2 (1C), 154.3 (1C);
MS (70 eV) m/z (%) 181 (M+, 21), 124 (100).
The method adopted for the synthesis of 2-(4-methoxyphen-
oxy)propanoic acid (4a) is described. Compound 3a (5.45 g,
24.3 mmol) was dissolved in a solution of KOH (2.73 g, 48.6 mmol)
in H2O/EtOH (15 mL/15 mL) and the reaction mixture was refluxed
for 45 min. After evaporation of the solvent, the residue was dis-
solved in H2O and extracted with Et2O, then the aqueous phase
4.5.1. 2-(2-Methoxyphenoxy)propan-1-amine (6b)
Prepared as reported above for 6a starting from 5b. Yield: 20%;
slightly yellowish oil; IR (neat): 3375 (NH2) cmꢀ1 1H NMR d 1.29
;

A. Carocci et al. / Bioorg. Med. Chem. 18 (2010) 6496–6511
6503
(d, 3H, J = 6.3 Hz, CH3CH), 2.19 (br s, 2H, NH2), 2.84–2.88 (m, 2H,
CH2), 3.84 (s, 3H, CH3O), 4.22–4.36 (m, 1H, CH), 6.82–7.0 (m, 4H,
Ar); 13C NMR d 17.8 (1C), 47.6 (1C), 56.0 (1C), 78.1 (1C), 112.3
(1C), 117.4 (1C), 121.1 (1C), 122.3 (1C), 147.6 (1C), 150.9 (1C);
MS (70 eV) m/z (%) 181 (M+, 12), 58 (100).
4.6. General procedure for the preparation of amines 6c–e, 11a–h
and 22c,d
The method adopted for the synthesis of 2-(3-methoxyphen-
oxy)propan-1-amine (6d) is described. To a stirred solution of
14d (1.80 g, 5.8 mmol) in MeOH (67 mL), glacial AcOH (11.6 mmol)
and N2H4ꢃH2O (23.2 mmol) were added and the mixture was kept
under reflux for 4 h. The solid residue was filtered off. After evap-
oration of the filtrate, the residue was taken up with EtOAc and ex-
tracted with 2 N HCl; then the aqueous phase was made alkaline
and extracted twice with EtOAc. The combined organic layers were
dried (Na2SO4) and concentrated under vacuum. The final product
was a slightly yellowish oil (0.90 g, 86%): IR (neat): 3375 (NH2)
4.5.2. 2-Phenoxypropan-1-ol (13c)
Prepared as reported above for 6a starting from 3c. Yield: 29%;
transparent oil; IR (neat): 3392 (OH) cmꢀ1 1H NMR d 1.27 (d, 3H,
;
J = 6.0 Hz, CH3), 2.04 (br s, exch D2O, 1H, OH), 3.65–3.82 (m, 2H,
CH2), 4.45–4.56 (m, 1H, CH), 6.90–7.05 (m, 3H, Ar), 7.25–7.35 (m,
2H, Ar); 13C NMR d 16.0 (1C), 66.6 (1C), 75.0 (1C), 116.4 (2C),
121.5 (1C), 129.8 (2C), 157.9 (1C); MS (70 eV) m/z (%) 152 (M+,
19), 94 (100).
cmꢀ1 1H NMR d 1.26 (d, 3H, J = 5.8 Hz, CH3CH), 2.11 (br s, 2H,
;
NH2), 2.88 (d, 2H, J = 5.8 Hz, CH2), 3.77 (s, 3H, CH3O), 4.35 (apparent
sextet, 1H, CH), 6.40–6.55 (m, 3H, Ar), 7.10–7.20 (m, 1H, Ar); 13C
NMR d 17.4 (1C), 47.6 (1C), 55.5 (1C), 75.6 (1C), 102.6 (1C), 106.6
(1C), 108.2 (1C), 130.2 (1C), 159.4 (1C), 161.1 (1C); MS (70 eV)
m/z (%) 181 (M+, 17), 58 (100).
4.5.3. 2-(3-Methoxyphenoxy)propan-1-ol (13d)
Prepared as reported above for 6a starting from 3d. Yield: 57%;
slightly yellowish oil; IR (neat): 3414 (OH) cmꢀ1; 1H NMR d 1.27 (d,
3H, J = 6.0 Hz, CH3CH), 2.08 (br s, 1H, OH), 3.68–3.76 (m, 2H, CH2),
3.78 (s, 3H, CH3O), 4.42–4.54 (m, 1H, CH), 6.46–6.56 (m, 3H, Ar),
7.18 (apparent t, 1H, Ar); 13C NMR d 16.0 (1C), 55.5 (1C), 66.5
(1C), 75.0 (1C), 102.8 (1C), 106.9 (1C), 108.4 (1C), 130.2 (1C),
159.2 (1C), 161.1 (1C); MS (70 eV) m/z (%) 182 (M+, 41), 124 (100).
4.6.1. (ꢀ)-(R)-2-(3-Methoxyphenoxy)propan-1-amine [(ꢀ)-(R)-
6d]
Prepared as reported above for 6d starting from (R)-14d. Yield:
95%; slightly yellowish oil; ½a D20
= ꢀ44 (c 1, CHCl3); IR (neat): 3376
ꢁ
4.5.4. (ꢀ)-(R)-2-(3-Methoxyphenoxy)propan-1-ol [(ꢀ)-(R)-13d]
Prepared as reported above for 6a starting from (R)-18d. Yield:
(NH2) cmꢀ1 1H NMR d 1.26 (d, 3H, J = 6.0 Hz, CH3CH), 1.73 (br s,
;
2H, exch D2O, NH2), 2.88 (br s, 2H, CH2), 3.77 (s, 3H, CH3O), 4.35
(apparent sextet, 1H, CH), 6.44–6.55 (m, 3H, Ar), 7.16 (apparent t,
1H, Ar); 13C NMR d 17.4 (1C), 47.7 (1C), 55.5 (1C), 75.8 (1C),
102.6 (1C), 106.6 (1C), 108.2 (1C), 130.2 (1C), 159.5 (1C), 161.1
(1C); MS (70 eV) m/z (%) 181 (M+, 26), 58 (100).
90%; slightly yellowish oil; ½a D20
= ꢀ48 (c 2, CHCl3). Spectroscopic
ꢁ
and spectrometric data were in agreement with those reported
for the (S)-isomer.
4.5.5. (+)-(S)-2-(3-Methoxyphenoxy)propan-1-ol [(+)-(S)-13d]
Prepared as reported above for 6a starting from (S)-18d. Yield:
4.6.2. (+)-(S)-2-(3-Methoxyphenoxy)propan-1-amine [(+)-(S)-6d]
Prepared as reported above for (RS)-6d starting from (+)-(S)-
90%; slightly yellowish oil; ½a D20
ꢁ
= +41 (c 2, CHCl3); IR (NaCl): 3408
(OH) cmꢀ1
;
1H NMR d 1.26 (d, 3H, J = 6.3 Hz, CH3CH), 2.07 (s, 1H,
14d. Yield: 73%; slightly yellowish oil; ½a D20
ꢁ
= +45 (c 1, CHCl3). Spec-
troscopic and spectrometric data were in agreement with those re-
OH), 3.68–3.74 (m, 2H, CH2), 3.78 (s, 3H, CH3O), 4.42–4.53 (m,
1H, CH), 6.45–6.56 (m, 3H, Ar), 7.17 (apparent t, 1H, Ar); 13C
NMR d 16.0 (1C), 55.5 (1C), 66.4 (1C), 74.9 (1C), 102.7 (1C), 106.9
(1C), 108.3 (1C), 130.2 (1C), 159.1 (1C), 161.1 (1C); MS (70 eV)
m/z (%) 182 (M+, 47), 124 (100).
ported for the (R)-isomer.
4.6.3. 2-Phenoxypropan-1-amine (6c)
Prepared as reported above for 6d starting from 14c. Yield: 82%;
IR (neat): 3375 (NH2) cmꢀ1; 1H NMR d 1.27 (d, 3H, J = 6.0 Hz, CH3),
1.69 (br s, 2H, NH2), 2.90 (br s, 2H, CH2), 4.36 (apparent sextet, 1H,
CH), 6.88–6.99 (m, 3H, Ar), 7.23ꢀ7.34 (m, 2H, Ar); 13C NMR d 17.4
(1C), 47.7 (1C), 75.5 (1C), 116.3 (2C), 121.1 (1C), 129.8 (2C), 158.2
(1C); MS (70 eV) m/z (%) 151 (M+, 10), 58 (100).
4.5.6. 2-[(3-Methoxyphenyl)thio]propan-1-ol (13e)
Prepared as reported above for 6a starting from 3e. Yield: 88%;
transparent oil; IR (neat): 3391 (OH) cmꢀ1 1H NMR d 1.31 (d, 3H,
;
J = 6.9 Hz, CH3CH), 2.12 (apparent br t, 1H, exch D2O, OH), 3.33
(apparent sextet, 1H, CH), 3.46–3.66 (m, 2H, CH2), 3.79 (s, 3H,
CH3O), 6.75–6.85 (m, 1H, Ar), 6.95–7.05 (m, 2H, Ar), 7.21 (apparent
t, 1H, Ar); 13C NMR d 17.8 (1C), 46.7 (1C), 55.5 (1C), 65.7 (1C), 113.4
(1C), 118.1 (1C), 125.0 (1C), 130.0 (1C), 134.8 (1C), 160.0 (1C); MS
(70 eV) m/z (%) 198 (M+, 82), 167 (100), 140 (99).
4.6.4. 2-[(3-Methoxyphenyl)thio]propan-1-amine (6e)
Prepared as reported above for 6d starting from 14e. Yield: 29%;
slightly yellowish oil; IR (neat): 3299 (NH2) cmꢀ1 1H NMR d 1.29
;
(d, 3H, J = 6.9 Hz, CH3CH), 1.95 (br s, 2H, NH2), 2.70–2.85 (m, 2H,
CH2), 3.79 (s, 3H, CH3O), 4.88–5.05 (m, 1H, CH), 6.72–6.84 (m,
1H, Ar), 6.86–7.05 (m, 2H, Ar), 7.13–7.25 (m, 1H, Ar); 13C NMR d
19.0 (1C), 47.3 (1C), 55.5 (2C), 112.9 (1C), 117.7 (1C), 124.5 (1C),
129.9 (1C), 135.9 (1C), 159.9 (1C); MS (70 eV) m/z (%) 197 (M+,
43), 168 (100).
4.5.7. (ꢀ)-(R)-2-[(3-Methoxyphenyl)thio]propan-1-ol [(ꢀ)-(R)-
13e]
Prepared as reported above for 6a starting from (R)-18e. Yield:
63%; transparent oil; ½a D20
= ꢀ9.6 (c 1, CHCl3); IR (neat): 3391 (OH)
ꢁ
cmꢀ1; 1H NMR d 1.31 (d, 3H, J = 6.9 Hz, CH3CH), 1.84 (br s, 1H, OH),
3.27–3.41 (m, 1H, CH), 3.52 (dd, 1H, J = 11.4, 6.2 Hz, CHH), 3.61 (dd,
1H, J = 11.3, 5.2 Hz, CHH), 3.80 (s, 1H, CH3O), 6.76–6.84 (m, 3H, Ar),
6.95–7.05 (m, 2H, Ar), 7.22 (apparent t, 1H, Ar); MS (70 eV) m/z (%)
198 (M+, 82), 167 (100), 140 (88). 13C NMR was identical to the one
of the racemate.
4.6.5. (ꢀ)-(R)-2-[(3-Methoxyphenyl)thio]propan-1-amine [(ꢀ)-
(R)-6e]
Prepared as reported above for 6d starting from (R)-14e. Yield:
68%; slightly yellowish oil; ½a D20
= ꢀ2.0 (c 1, CHCl3); IR (neat): 3376
ꢁ
(NH2) cmꢀ1 1H NMR d 1.30 (d, 3H, J = 6.9 Hz, CH3CH), 1.98 (br t,
;
2H, J = 3.4 Hz, NH2), 2.72–2.85 (m, 2H, CH2), 3.79 (s, 3H, CH3O),
4.97 (tq, seven lines, 1H, J = 6.3 Hz, CH), 6.74–6.84 (m, 1H, Ar),
6.90–7.05 (m, 2H, Ar), 7.15–7.25 (m, 1H, Ar); 13C NMR d 19.0
(1C), 47.1 (1C), 55.5 (2C), 113.0 (1C), 117.8 (1C), 124.6 (1C),
129.9 (1C), 135.8 (1C), 160.0 (1C); MS (70 eV) m/z (%) 197 (M+,
36), 168 (100).
4.5.8. (+)-(S)-2-[(3-Methoxyphenyl)thio]propan-1-ol [(+)-(S)-13e]
Prepared as reported above for 6a starting from (ꢀ)-(S)-18e. Yield:
90%; transparent oil; ½a D20
ꢁ
= +10.8 (c 1, CHCl3); MS (70 eV) m/z (%)
198 (M+, 82), 167 (86), 140 (100). Spectroscopic and spectrometric
data were in agreement with those reported for the (R)-isomer.

6504
A. Carocci et al. / Bioorg. Med. Chem. 18 (2010) 6496–6511
4.6.6. (+)-(S)-2-[(3-Methoxyphenyl)thio]propan-1-amine [(+)-
(S)-6e]
2H, CH2O), 3.88 (s, 3H, CH3), 6.85 (d, J = 8.3 Hz, 1H, Ar), 6.91 (appar-
ent dt, 1H, Ar), 7.21 (apparent dt, 1H, Ar), 7.32 (dd, 1H, J = 7.4,
1.5 Hz, Ar); 13C NMR 37.2 (1C), 41.2 (1C), 56.0 (1C), 111.0 (1C)
121.3 (1C), 123.7 (1C), 128.0 (1C), 131.2 (1C), 158.3 (1C); MS
(70 eV) m/z (%) 183 (M+, 32), 154 (100).
Prepared as reported above for 6d starting from (S)-14e. Yield:
63%; slightly yellowish oil; ½a D20
ꢁ
= +4.4 (c 0.5, CHCl3). Spectroscopic
and spectrometric data were in agreement with those reported for
the (R)-isomer.
4.6.15. 1-Phenoxypropan-2-amine (22c)
4.6.7. 2-(4-Methoxyphenoxy)ethanamine (11a)
Prepared as reported above for 6d starting from 10a. Yield: 89%;
slightly yellowish oil. Spectroscopic data were in agreement with
the literature.49
Prepared as reported above for 6d starting from 21c. Yield: 56%;
slightly yellowish oil. Spectroscopic and spectrometric data were
in agreement with those reported in the literature for (R)- and
(S)-isomers.38
4.6.8. 2-(2-Methoxyphenoxy)ethanamine (11b)
Prepared as reported above for 6d starting from 10b. Yield: 86%;
slightly yellowish oil. Spectroscopic data were in agreement with
the literature.50
4.6.16. 1-(3-Methoxyphenoxy)propan-2-amine (22d)
Prepared as reported above for 6d starting from 21d. Yield: 94%;
slightly yellowish oil: IR (neat): 3361 (NH) cmꢀ1; 1H NMR d 1.16 (d,
3H, J = 6.3 Hz, CH3CH), 1.96 (br s, 2H, NH2), 3.26–3.40 (br s, 1H, CH),
3.60–3.70 (m, 1H, CHH), 3.78 (s, 3H, CH3O), 3.85 (dd, 1H, J = 8.8,
4.1 Hz, CHH), 6.43–6.56 (m, 3H, Ar), 7.17 (apparent t, 1H, Ar); 13C
NMR d 20.0 (1C), 46.5 (1C), 55.5 (1C), 74.7 (1C), 101.2 (1C), 106.6
(1C), 106.9 (1C), 130.1 (1C), 160.4 (1C), 161.1 (1C); MS (70 eV)
m/z (%) 181 (M+, 3), 44 (100).
4.6.9. 2-Phenoxyethanamine (11c)
Prepared as reported above for 6d starting from 10c. Yield: 60%;
slightly yellowish oil; IR (neat): 3373 (NH2) cmꢀ1 1H NMR d 1.77
;
(s, 2H, NH2), 3.07 (t, 2H, J = 5.0 Hz, CH2N), 3.98 (t, 2H, J = 5.1 Hz,
CH2O), 6.84–7.0 (m, 3H, Ar), 7.22–7.34 (m, 2H, Ar); 13C NMR d
41.7 (1C), 70.2 (1C), 114.7 (2C), 121.1 (1C) 129.7 (2C), 159.1 (1C);
MS (70 eV) m/z (%) 137 (M+, 54), 44 (100).
4.6.17. (ꢀ)-(R)-1-(3-Methoxyphenoxy)propan-2-amine [(ꢀ)-(R)-
22d]
Prepared as reported above for 6d starting from (R)-21d. Yield:
4.6.10. 2-(3-Methoxyphenoxy)ethanamine (11d)
93%; slightly yellowish oil: ½a D20
= ꢀ14.9 (c 2, CHCl3); IR (neat):
ꢁ
Prepared as reported above for 6d starting from 10d. Yield: 69%;
3364 (NH) cmꢀ1 1H NMR d 1.16 (d, 3H, J = 6.6 Hz, CH3CH), 1.95
;
slightly yellowish oil; IR (neat): 3370 (NH2) cmꢀ1
;
1H NMR d 1.68
(br s, 2H, NH2), 3.33 (br s, 1H, CH), 3.60–3.70 (m, 1H, CHH), 3.78
(s, 3H, CH3O), 3.85 (dd, 1H, J = 9.1, 4.1 Hz, CHH), 6.44–6.56 (m,
3H, Ar), 7.16 (apparent t, 1H, Ar); 13C NMR d 20.0 (1C), 46.5 (1C),
55.5 (1C), 74.7 (1C), 101.2 (1C), 106.7 (1C), 106.9 (1C), 130.1
(1C), 160.4 (1C), 161.1 (1C); MS (70 eV) m/z (%) 181 (M+, 4), 44
(100).
(br s, 2H, NH2), 3.08 (t, 2H, J = 5.1 Hz, CH2N), 3.79 (s, 3H, CH3O),
3.97 (t, 2H, J = 5.1 Hz, CH2O), 6.48 (apparent t, 1H, Ar), 6.50 (d,
1H, J = 2.5 Hz, Ar), 6.52 (d, 1H, J = 2.5 Hz, Ar), 7.18 (apparent t,
1H, Ar); 13C NMR d 41.8 (1C), 55.5 (1C), 70.4 (1C), 101.3 (1C)
106.7 (1C), 107.0 (1C), 130.1 (1), 160.4 (1), 161.1 (1); MS (70 eV)
m/z (%) 167 (M+, 16), 124 (100).
4.6.18. (+)-(S)-1-(3-Methoxyphenoxy)propan-2-amine [(+)-(S)-
22d]
4.6.11. 2-[(3-Methoxyphenyl)thio]ethanamine (11e)
Prepared as reported above for 6d starting from 10e. Yield: 51%;
Prepared as reported above for 6d starting from (ꢀ)-(S)-21d.
slightly yellowish oil; IR (neat): 3359 (NH2) cmꢀ1
;
1H NMR d 2.05
Yield: 91%; slightly yellowish oil; ½a D20
ꢁ
= +16.2 (c 5, CHCl3). Spectro-
(br s, 2H, NH2), 2.88–2.96 (m, 2H, CH2N), 2.98–3.06 (m, 2H,
CH2O), 3.79 (s, 3H, CH3), 6.72 (ddd, 1H, J = 8.3, 2.5, 0.8 Hz, Ar),
6.90 (apparent t, 1H, Ar) 6.93 (dt, 1H, J = 8.1, 1.2 Hz, Ar), 7.19
(apparent t, 1H, Ar); 13C NMR d 38.1 (1C), 41.2 (1C), 55.5 (1C),
112.1 (1C), 115.4 (1C), 122.0 (1C), 130.0 (1C), 137.3 (1C), 160.1
(1C); MS (70 eV) m/z (%) 183 (M+, 33), 154 (100).
scopic and spectrometric data were in agreement with those found
for the (R)-isomer.
4.7. General procedure for the preparation of acetamides 7a–e,
12a–h and 23c–d
The method adopted for the synthesis of N-[2-(4-methoxyphen-
oxy)propyl]acetamide (7a) is described. To a stirring solution of 6a
(0.43 g, 2.37 mmol) and Et3N (0.66 mL, 4.75 mmol) in dry THF
(16 mL) under N2 atmosphere, acetic anhydride (0.48 g, 4.75 mmol)
was added dropwise in an ice-water bath and the stirring was
continued for 5 h. The reaction mixture was concentrated under
vacuum. The residue was taken up with EtOAc and washed with
2 N HCl, a saturated solution of NaHCO3 and then brine. The
combined organic layers were dried (Na2SO4) and concentrated.
The residue was purified by column chromatography on silica gel
(EtOAc) to give 0.16 g (30%) of 7a as a yellow solid: mp 44–
46 °C; IR (KBr): 3266 (NH), 1639 (C@O); 1H NMR d 1.23 (d, 3H,
J = 6.0 Hz, CH3CH), 1.98 (s, 3H, CH3CO), 3.24 (ddd, 1H, J = 14.0,
7.4, 4.8 Hz, CHH), 3.68 (ddd, 1H, J = 14.0, 6.9, 3.3 Hz, CHH), 3.76
(s, 3H, CH3O), 4.30–4.42 (m, 1H, CH), 5.94 (br s, 1H, NH), 6.76–
6.90 (m, 4H, Ar); 13C NMR d 17.4 (1C), 23.5 (1C), 44.7 (1C), 55.9
(1C), 74.1 (1C), 115.0 (2C), 117.7 (2C), 151.6 (1C), 154.5 (1C),
170.5 (1C); MS (70 eV) m/z (%) 223 (M+, 7), 100 (100).
4.6.12. 2-(Phenylthio)ethanamine (11f)
Prepared as reported above 6d starting from 10f. Yield: 85%:
slightly yellowish oil; IR (neat): 3357, 3285 (NH2) cmꢀ1 1H NMR
;
d 1.67 (br s, 2H, NH2), 2.86–2.96 (m, 2H, CH2N), 2.98–3.05 (m,
2H, CH2O), 7.19 (tt, 1H, J = 7.3, 1.7 Hz, Ar), 7.24–7.32 (m, 2H, Ar),
7.32–7.40 (m, 2H, Ar); 13C NMR d 38.3 (1C), 41.1 (1C), 126.5 (1C),
129.2 (2C) 130.0 (2C), 135.9 (1C); MS (70 eV) m/z (%) 153 (M+,
23), 124 (100).
4.6.13. 2-[(4-Methoxyphenyl)thio]ethanamine (11g)
Prepared as reported above for 6d starting from 10g. Yield: 79%:
slightly yellowish oil; IR (neat): 3362, 3294 (NH2) cmꢀ1; 1H NMR d
1.58 (br s, exch D2O, 2H, NH2), 2.74–2.94 (m, 4H, CH2CH2), 3.78 (s,
3H, CH3), 6.80–6.88 (m, 2H, Ar), 7.32–7.40 (m, 2H, Ar); 13C NMR d
40.4 (1C), 41.1 (1C), 55.5 (1C), 114.9 (2C), 125.9 (1C) 133.9 (2C),
159.3 (1C); MS (70 eV) m/z (%) 183 (M+, 40), 154 (100).
4.6.14. 2-[(2-Methoxyphenyl)thio]ethanamine (11h)
Prepared as reported above for 6d starting from 10h. Yield: 76%:
4.7.1. N-[2-(2-Methoxyphenoxy)propyl]acetamide (7b)
slightly yellowish oil; IR (neat): 3358 (NH2) cmꢀ1
;
1H NMR d 1.76
Prepared as reported above for 7a starting from 6b. Yield: 82%;
(br s, exch D2O, 2H, NH2), 2.80–2.90 (m, 2H, CH2N), 2.92–3.02 (m,
slightly yellowish oil; IR (neat): 3303 (NH), 1658 (C@O) cmꢀ1 1H
;

A. Carocci et al. / Bioorg. Med. Chem. 18 (2010) 6496–6511
6505
NMR d 1.32 (d, 3H, J = 6.3 Hz, CH3CH), 2.01 (s, 3H, CH3CO), 3.23–
3.35 (m, 1H, CHH), 3.64 (ddd, 1H, J = 14.0, 6.5, 2.9 Hz, CHH), 3.88
(s, 3H, CH3O), 4.44–4.72 (m, 1H, CH), 6.57 (br s, 1H, NH), 6.82–
7.06 (m, 4H, Ar); 13C NMR d 18.0 (1C), 23.5 (1C), 44.8 (1C), 56.1
(1C), 74.2 (1C), 112.4 (1C), 119.3 (1C), 121.5 (1C), 123.4 (1C),
147.1 (1C), 151.0 (1C), 170.7 (1C); MS (70 eV) m/z (%) 223 (M+,
1), 100 (100).
(chiral HPLC, Chiralpak IB, tR 50.3, flow 0.6 mL/min, k 210 nm, elu-
ent 95:5 hexane/i-PrOH); IR (neat): 3297 (NH), 1657 (C@O) cmꢀ1
;
1H NMR d 1.29 (d, 3H, J = 6.9 Hz, CH3CH), 1.94 (s, 3H, CH3CO), 3.22–
3.33 (m, 1H, CHH), 3.35–3.52 (m, 2H, CHH + CH), 3.80 (s, 3H, CH3O),
5.85 (br s, 1H, NH), 6.75–6.82 (m, 1H, Ar), 6.95–7.02 (m, 1H, Ar),
7.22 (apparent t, 1H, Ar); 13C NMR d 19.0 (1C), 22.2 (1C), 43.4
(1C), 44.7 (1C), 55.5 (1C), 113.3 (1C), 117.5 (1C), 124.3 (1C),
130.1 (1C), 135.3 (1C), 160.1 (1C), 170.4 (1C); MS (70 eV) m/z (%)
239 (M+, 2), 180 (100).
4.7.2. N-(2-Phenoxypropyl)acetamide (7c)
Prepared as reported above for 7a starting from 6c. Yield: 92%;
slightly yellowish oil; IR (neat): 3296 (NH), 1657 (C@O) cmꢀ1
;
1H
4.7.8. (ꢀ)-(S)-N-{2-[(3-Methoxyphenyl)thio]propyl}acetamide
[(ꢀ)-(S)-7e]
NMR d 1.27 (d, 3H, J = 6.0 Hz, CH3CH), 1.98 (s, 3H, CH3CO), 3.22–
3.34 (m, 1H, CHH), 3.65–3.77 (m, 1H, CHH), 4.44–4.56 (m, 1H,
CH), 5.92 (br s, 1H, NH), 6.87–7.00 (m, 3H, Ar), 7.24–7.34 (m, 2H,
Ar); 13C NMR d 17.4 (1C), 23.5 (1C), 44.7 (1C), 72.9 (1C), 116.1
(2C), 121.4 (1C), 129.9 (2C), 157.7 (1C), 170.5 (1C); MS (70 eV)
m/z (%) 193 (M+, 2), 100 (100).
Prepared as reported above for 7a starting from (ꢀ)-(S)-6e.
Yield: 98%; slightly yellowish oil; ½a D20
= ꢀ19.0 (c 0.5, CHCl3); 96%
ꢁ
ee (chiral HPLC, Chiralpak IA, tR 23.1, flow 1.0 mL/min, k 210 nm,
eluent 95:5 hexane/i-PrOH). Spectroscopic and spectrometric data
were in agreement with those reported for the (R)-isomer.
4.7.3. N-[2-(3-Methoxyphenoxy)propyl]acetamide (7d)
4.7.9. N-[2-(4-Methoxyphenoxy)ethyl]acetamide (12a)
Prepared as reported above for 7a starting from 6d. Yield: 92%;
Prepared as reported above for 7a starting from 11a. Yield: 85%;
white crystals: mp 100–101 °C (EtOAc/hexane); IR (KBr): 3291
(NH), 1646 (C@O) cmꢀ1; 1H NMR d 2.0 (s, 3H, CH3C), 3.63 (apparent
q, 2H, CH2N), 3.76 (s, 3H, CH3O), 3.98 (t, 2H, J = 4.9 Hz, CH2O), 5.98
(br s, 1H, NH), 6.83 (s, 4H, Ar); 13C NMR d 23.5 (1C), 39.4 (1C), 56.0
(1C), 67.6 (1C), 115.0 (2C), 115.6 (2C), 152.8 (1C), 154.4 (1C), 170.4
(1C); MS (70 eV) m/z (%) 209 (M+, 2), 86 (100). Anal. Calcd for
slightly yellowish oil; IR (neat): 3296 (NH), 1655 (C@O) cmꢀ1 1H
;
NMR d 1.27 (d, 3H, J = 6.0 Hz, CH3CH), 1.97 (s, 3H, CH3CO), 3.22–
3.33 (m, 1H, CHH), 3.64–3.74 (m, 1H, CHH), 3.78 (s, 3H, CH3O),
4.42–4.54 (m, 1H, CH), 5.90 (br s, 1H, NH), 6.42–6.55 (m, 3H, Ar),
7.17 (apparent t, 1H, Ar); 13C NMR d 17.4 (1C), 23.5 (1C), 44.7
(1C), 55.5 (1C), 73.0 (1C), 102.6 (1C), 106.9 (1C), 108.1 (1C), 130.3
(1C), 159.0 (1C), 161.2 (1C), 170.5 (1C); MS (70 eV) m/z (%) 223
(M+, 9), 100 (100).
C11H15NO3: C, 63.14; H, 7.23; N, 6.69. Found: C, 62.80; H, 7.24;
N, 6.32.
4.7.4. (ꢀ)-(R)-N-[2-(3-Methoxyphenoxy)propyl]acetamide [(ꢀ)-
(R)-7d]
4.7.10. N-[2-(2-Methoxyphenoxy)ethyl]acetamide (12b)
Prepared as reported above for 7a starting from 11b. Yield: 40%;
white crystals: mp 62–63 °C (EtOAc/hexane); IR (KBr): 3541 (NH),
Prepared as reported above for 7a starting from (R)-6d. Yield:
49%; slightly yellowish oil; ½a D20
ꢁ
= ꢀ84 (c 2, CHCl3), 96% ee (chiral
1660 (C@O) cmꢀ1 1H NMR d 2.00 (s, 3H, CH3C), 3.65 (apparent q,
;
HPLC, Chiralpak IA, tR 31.5 min, flow 1 mL/min, k 280 nm, eluent
2H, CH2N), 3.87 (s, 3H, CH3O), 4.09 (t, 2H, J = 5.1 Hz, CH2O), 6.29
(br s, 1H, NH), 6.88–7.02 (m, 4H, Ar); 13C NMR d 23.5 (1C), 39.2
(1C), 56.0 (1C), 69.0 (1C), 112.1 (1C), 115.0 (1C), 121.4 (1C),
122.3 (1C), 148.0 (1C), 149.8 (1C), 170.5 (1C); MS (70 eV) m/z (%)
150 (M+ꢀ59, 1), 86 (100). Anal. Calcd for C11H15NO3ꢃ0.25H2O: C,
61.81; H, 7.31; N, 6.55. Found: C, 61.88; H, 7.02; N, 6.37.
87:13:0.1 hexane/THF/TFA); IR (neat): 3295 (NH), 1652, 1602
(C@O) cmꢀ1 1H NMR d 1.27 (d, 3H, J = 6.0 Hz, CH3CH), 1.98 (s,
;
3H, CH3CO), 3.22–3.34 (m, 1H, CHH), 3.69 (ddd, 1H, J = 13.8, 6.9,
3.3 Hz, CHH), 3.78 (s, 3H, CH3O), 4.42–4.54 (m, 1H, CH), 6.00 (br
s, 1H, NH), 6.42–6.55 (m, 3H, Ar), 7.17 (apparent t, 1H, Ar); 13C
NMR d 17.4 (1C), 23.5 (1C), 44.7 (1C), 55.5 (1C), 73.0 (1C), 102.6
(1C), 106.9 (1C), 108.1 (1C), 130.3 (1C), 158.9 (1C), 161.2 (1C),
170.7 (1C); MS (70 eV) m/z (%) 223 (M+, 8), 100 (100).
4.7.11. N-(2-Phenoxyethyl)acetamide (12c)
Prepared as reported above for 7a starting from 11c. Yield: 62%;
slightly yellowish crystals: mp 89–90 °C (EtOAc/hexane); IR (KBr):
4.7.5. (+)-(S)-N-[2-(3-Methoxyphenoxy)propyl]acetamide [(+)-
(S)-7d]
3316 (NH), 1654 (C@O) cmꢀ1 1H NMR d 2.01 (s, 3H, CH3), 3.65
;
(apparent q, 2H, CH2N), 4.02 (t, J = 5.1 Hz, 2H, CH2O), 6.24 (br s,
1H, NH), 6.88 (d, 2H, J = 8.5 Hz, Ar), 6.96 (apparent t, 1H, Ar), 7.28
(apparent t, 2H, Ar); 13C NMR d 23.4 (1C), 39.3 (1C), 66.8 (1C),
114.6 (2C), 121.4 (1C), 129.8 (2C), 158.6 (1C), 170.7 (1C); MS
(70 eV) m/z (%) 179 (M+, 1), 86 (100). Anal. Calcd for C10H13NO2:
C, 67.02; H, 7.31; N, 7.82. Found: C, 67.16; H, 7.33; N, 7.79.
Prepared as reported above for 7a starting from (S)-6d. Yield:
89%; slightly yellowish oil; ½a D20
ꢁ
= +83 (c 1, CHCl3), 96% ee (chiral
HPLC, Chiralpak IA, tR 35.5 min, flow 1 mL/min, k 280 nm, eluent
87:13:0.1 hexane/THF/TFA). Spectroscopic and spectrometric data
were in agreement with those reported for the (R)-isomer.
4.7.6. N-{2-[(3-Methoxyphenyl)thio]propyl}acetamide (7e)
Prepared as reported above for 7a starting from 6e. Yield: 90%;
4.7.12. N-[2-(3-Methoxyphenoxy)ethyl]acetamide (12d)
Prepared as reported above for 7a starting from 11d. Yield: 85%;
slightly yellowish oil; 13C NMR d 23.5 (1C), 39.3 (1C), 55.5 (1C),
67.0 (1C), 101.2 (1C), 106.8 (1C), 106.9 (1C), 130.3 (1C), 159.9
(1C), 161.1 (1C), 170.5 (1C). Other spectroscopic data were in
agreement with the literature.51
slightly yellowish oil; IR (neat): 3293 (NH), 1657 (C@O) cmꢀ1 1H
;
NMR d 1.29 (d, 3H, J = 6.6 Hz, CH3CH), 1.94 (s, 3H, CH3CO), 3.20–
3.33 (m, 1H, CHH), 3.34–3.52 (m, 2H, CHH + CH), 3.80 (s, 3H,
CH3O), 5.86 (br s, 1H, NH), 6.79 (dd, 1H, J = 8.3 Hz, 2.5 Hz, Ar),
6.94–7.04 (m, 2H, Ar), 7.21 (apparent t, 1H, Ar); 13C NMR d 19.0
(1C), 23.4 (1C), 43.4 (1C), 44.7 (1C), 55.5 (1C), 113.2 (1C), 117.5
(1C), 124.3 (1C), 130.1 (1C), 135.3 (1C), 160.1 (1C), 170.4 (1C);
MS (70 eV) m/z (%) 239 (M+, 15), 180 (100).
4.7.13. N-{2-[(3-Methoxyphenyl)thio]ethyl}acetamide (12e)
Prepared as reported above for 7a starting from 11e. Yield: 56%;
slightly yellowish solid: mp 35–36 °C (toluene/i-Pr2O); IR (KBr):
3255 (NH), 1639 (C@O) cmꢀ1 1H NMR d 1.93 (s, 3H, CH3C), 3.05
;
4.7.7. (+)-(R)-N-{2-[(3-Methoxyphenyl)thio]propyl}acetamide
[(+)-(R)-7e]
(t, 2H, J = 6.3 Hz, CH2S), 3.45 (apparent q, 2H, CH2N), 3.79 (s, 3H,
CH3O), 6.0 (br s, 1H, NH), 6.68–6.78 (m, 1H, Ar), 6.87–6.98 (m,
2H, Ar) 7.20 (apparent t, 1H, Ar); 13C NMR d 23.4 (1C), 33.5 (1C),
39.0 (1C), 55.5 (1C), 112.4 (1C), 115.1 (1C), 121.8 (1C), 130.2
Prepared as reported above for 7a starting from (ꢀ)-(R)-6e.
Yield: 57%; slightly yellowish oil; ½a D20
ꢁ
= +8.2 (c 2, CHCl3); 80% ee

6506
A. Carocci et al. / Bioorg. Med. Chem. 18 (2010) 6496–6511
(1C), 136.6 (1C), 160.2 (1C), 170.5 (1C); MS (70 eV) m/z (%) 225 (M+,
20), 166 (100). Anal. Calcd for C11H15NO2S: C, 58.64; H, 6.71; N,
6.22. Found: C, 58.42; H, 6.80; N, 6.08.
metric data were in agreement with those found for the (R)-isomer.
Anal. Calcd for C12H17NO3ꢃ0.17C6H8: C, 65.99; H, 7.81; N, 5.92.
Found: C, 66.07; H, 8.22; N, 6.20.
4.7.14. N-[2-(Phenylthio)ethyl]acetamide (12f)
4.8. General procedure for the synthesis of acetamides (23e,f)
Prepared as reported above for 7a starting from 11f. Yield: 84%.
Spectroscopic data were in agreement with the literature.52
The method adopted for the synthesis of (ꢀ)-(S)-N-[1-methyl-2-
(phenylthio)ethyl]acetamide [(ꢀ)-(S)-23f] is described. A solution of
1f (1.02 mL, 1.09 g, 9.93 mmol), (+)-(S)-19 (0.77 mL, 0.746 g,
9.93 mmol), AcOH (0.57 mL, 9.93 mmol) and 2 N HCl (0.36 mL,
9.93 mmol) and two little pieces of zinc in benzene (1.6 mL) was
heated under reflux in a flask fitted with a Dean–Stark apparatus for
6 h. All volatile matter were then evaporated under vacuum and the
solid residue (1.70 g) was purified by flash column chromatography
4.7.15. N-{2-[(4-Methoxyphenyl)thio]ethyl}acetamide (12g)
Prepared as reported above for 7a starting from 11g. Yield: 81%;
slightly yellowish crystals: mp 106–107 °C (EtOAc); IR (KBr): 3260
(NH), 1640 (C@O) cmꢀ1 1H NMR d 1.94 (s, 3H, CH3C), 2.93 (t, 2H,
;
J = 6.3 Hz, CH2S), 3.38 (apparent q, 2H, CH2N), 3.78 (s, 3H, CH3O),
5.97 (br s, 1H, NH), 6.80–6.90 (m, 2H, Ar), 7.32–7.42 (m, 2H, Ar);
13C NMR d 23.4 (1C), 35.8 (1C), 38.8 (1C), 55.6 (1C), 115.0 (2C),
125.1 (1C), 133.9 (2C), 159.6 (1C), 170.4 (1C); MS (70 eV) m/z (%)
225 (M+, 33), 166 (100). Anal. Calcd for C11H15NO2S: C, 58.65; H,
6.71; N, 6.22. Found: C, 58.65; H, 6.87; N, 5.87.
(EtOAc) to give 1.64 g (79%) of a slightly yellowish oil: ½a D20
= ꢀ17.4
ꢁ
(c 1.3, CHCl3): 99% ee (chiral GC, tR 9.51 min, flow 1.3 mL/min, T
180 °C); IR (neat): 3279 (NH), 1647 (C@O) cmꢀ1 1H NMR d 1.23 (d,
;
3H, J = 6.9 Hz, CH3CH), 1.85 (s, 3H, CH3CO), 3.04 (dd, 1H, J = 13.5,
6.1 Hz, CHH), 3.12 (dd, 1H, J = 13.6, 5.1 Hz, CHH), 4.23 (dtq, seven lines,
1H, J = 6.9 Hz, CH), 5.51 (br s, 1H, NH), 7.13–7.22 (m, 1H, Ar), 7.24–7.33
(m, 2H, Ar), 7.37–7.43 (m, 2H, Ar); 13C NMR d 19.8 (1C), 23.5 (1C), 40.1
(1C), 45.2 (1C), 126.5 (1C), 129.3 (1C), 129.6 (1C), 136.4 (1C), 169.7
(1C); MS (70 eV) m/z (%) 209 (M+, 8), 150 (100).
4.7.16. N-{2-[(2-Methoxyphenyl)thio]ethyl}acetamide (12h)
Prepared as reported above for 7a starting from 11h. Yield: 80%;
slightly yellowish oil; IR (neat): 3288 (NH), 1651 (C@O) cmꢀ1 1H
;
NMR d 1.94 (s, 3H, CH3C), 3.01 (t, 2H, J = 6.2 Hz, CH2S), 3.42 (appar-
ent q, 2H, CH2N), 3.90 (s, 3H, CH3O), 6.01 (br s, 1H, NH), 6.88 (dd,
1H, J = 8.3, 0.8 Hz, Ar), 6.93 (apparent dt, 1H, Ar), 7.24 (apparent
dt, 1H, Ar), 7.37 (dd, 1H, J = 7.7, 1.7 Hz, Ar); 13C NMR d 23.4 (1C),
33.1 (1C), 38.7 (1C), 56.1 (1C), 111.2 (1C), 121.5 (1C), 122.8 (1C),
128.6 (1C), 131.9 (1C), 158.4 (1C), 170.2 (1C); MS (70 eV) m/z (%)
225 (M+, 24), 166 (100).
4.8.1. N-[1-Methyl-2-(phenylthio)ethyl]acetamide (23f)
Prepared as reported above for (S)-23f starting from 19. Yield:
68%; white crystals: mp 91–92 °C (CH2Cl2/petroleum ether); IR
(neat): 3258 (NH), 1634 (C@O) cmꢀ1 1H NMR d 1.23 (d, 3H,
;
J = 6.6 Hz, CH3CH), 1.85 (s, 3H, CH3CO), 3.04 (dd, 1H, J = 13.5,
6.1 Hz, CHH), 3.12 (dd, 1H, J = 13.5, 5.0 Hz, CHH), 4.23 (dtq, seven
lines, 1H, J = 6.5 Hz, CH), 5.58 (br s, 1H, NH), 7.13–7.22 (m, 1H,
Ar), 7.24–7.33 (m, 2H, Ar), 7.35–7.44 (m, 2H, Ar); 13C NMR d 19.8
(1C), 23.5 (1C), 40.0 (1C), 45.2 (1C), 126.5 (1C), 129.3 (1C), 129.6
(1C), 136.4 (1C), 169.7 (1C); MS (70 eV) m/z (%) 209 (M+, 8), 150
(100). Anal. Calcd for C11H15NOS: C, 63.12; H, 7.22; N, 6.69. Found:
C, 62.73; H, 7.13; N, 6.73.
4.7.17. N-(1-Methyl-2-phenoxyethyl)acetamide (23c)
Prepared as reported above for 7a starting from 22c. Yield: 93%.
Spectroscopic and spectrometric data were in agreement with
those reported in the literature for (R)- and (S)-isomers.38
4.7.18. N-[2-(3-Methoxyphenoxy)-1-methylethyl]acetamide (23d)
Prepared as reported above for 7a starting from 22d. Yield: 28%;
slightly yellowish oil; IR (neat): 3283 (NH), 1652, 1603 (C@O)
cmꢀ1; 1H NMR d 1.29 (d, 3H, J = 6.9 Hz, CH3CH), 1.98 (s, 3H, CH3CO),
3.78 (s, 3H, CH3O), 3.89 (dd, 1H, J = 9.1, 3.6 Hz, CHH), 3.94 (dd, 1H,
J = 9.4, 4.1 Hz, CHH), 4.28–4.43 (m, 1H, CH), 5.85 (br d, 1H, NH),
6.40–6.58 (m, 3H, Ar), 7.17 (apparent t, 1H, Ar); 13C NMR d 17.8
(1C), 23.7 (1C), 44.8 (1C), 55.5 (1C), 70.8 (1C), 101.2 (1C), 106.8
(1C), 106.9 (1C), 130.2 (1C), 160.1 (1C), 161.1 (1C), 169.8 (1C);
MS (70 eV) m/z (%) 223 (M+, 3), 100 (100).
4.8.2. (+)-(R)-N-[1-Methyl-2-(phenylthio)ethyl]acetamide [(+)-
(R)-23f]
Prepared as reported above for (S)-23f starting from (R)-19.
Yield: 66%; slightly yellowish oil; ½a D20
ꢁ
= +12.1 (c 1.2, CHCl3); 99%
(chiral GC, tR 9.82 min, flow 1.3 mL/min, T 180 °C). Spectroscopic
and spectrometric data were in agreement with those found for
the (S)-isomer.
4.8.3. N-{2-[(3-Methoxyphenyl)thio]-1-methylethyl}acetamide
(23e)
4.7.19. (+)-(R)-N-[2-(3-Methoxyphenoxy)-1-methylethyl]acet-
amide [(+)-(R)-23d]
Prepared as reported above for (S)-23f starting from 1e and 19.
Yield: 11%; slightly yellowish oil; IR (neat): 3281 (NH), 1645 (C@O)
cmꢀ1; 1H NMR d 1.24 (d, 3H, J = 6.6 Hz, CH3CH), 1.87 (s, 3H, CH3CO),
3.03 (dd, 1H, J = 13.6, 6.2 Hz, CHH), 3.14 (dd, 1H, J = 13.7, 5.0 Hz,
CHH), 4.23 (tq, seven lines, 1H, J = 6.5 Hz, CH), 5.50 (br d, 1H,
J = 4.1 Hz, NH), 6.65–6.78 (m, 1H, Ar), 6.92–7.02 (m, 2H, Ar), 7.19
(apparent t, 1H, Ar); 13C NMR d 19.8 (1C), 23.5 (1C), 39.7 (1C), 45.2
(1C), 55.5 (1C), 112.3 (1C), 114.6 (1C), 121.5 (1C), 130.1 (1C), 137.7
(1C), 160.2(1C), 169.8 (1C); MS (70 eV) m/z(%) 239 (M+, 12), 180 (100).
Prepared as reported above for 7a starting from (R)-22d. Yield:
83%; white crystals: mp 62–63 °C (EtOAc/hexane); ½a D20
ꢁ
= +88 (c 2,
CHCl3); 98% ee (chiral HPLC, Chiralpak IA, tR 16.3, flow 1.0 mL/min,
k 210 nm, eluent 95:5 hexane/iPrOH); IR (neat): 3274 (NH), 1645
(C@O) cmꢀ1 1H NMR d 1.29 (d, 3H, J = 6.9 Hz, CH3CH), 1.99 (s, 3H,
;
CH3CO), 3.79 (s, 3H, CH3O), 3.89 (dd, 1H, J = 9.0, 3.6 Hz, CHH), 3.95
(dd, 1H, J = 9.3, 4.2 Hz, CHH), 4.30–4.40 (m, 1H, CH), 5.78 (br d, 1H,
J = 6.9 Hz, NH), 6.43–6.57 (m, 3H, Ar), 7.18 (apparent t, 1H, Ar); MS
(70 eV) m/z (%) 223 (M+, 4), 100 (100). 13C NMR spectrum was iden-
tical to the one reported for the racemate. Anal. Calcd for C12H17NO3:
C, 64.55; H, 7.67; N, 6.27. Found: C, 64.19; H, 7.85; N, 6.33.
4.8.4. (+)-(R)-N-{2-[(3-Methoxyphenyl)thio]-1-methylethyl}acet-
amide [(+)-(R)-23e]
Prepared as reported above for (S)-23f starting from 1e and (R)-
4.7.20. (ꢀ)-(S)-N-[2-(3-Methoxyphenoxy)-1-methylethyl]acet-
amide [(ꢀ)-(S)-23d]
19. Yield: 7%; slightly yellowish oil; ½a D20
ꢁ
= +3.9 (c 1.4, CHCl3); >99%
(chiral GC, tR 33.8 min, flow 1.4 mL/min, T 170 °C); IR (neat): 3281
Prepared as reported above for 7a starting from (S)-22d. Yield:
(NH), 1650 (C@O) cmꢀ1 1H NMR d 1.23 (d, 3H, J = 6.6 Hz, CH3CH),
;
1.87 (s, 3H, CH3CO), 3.01 (dd, 1H, J = 13.6, 6.2 Hz, CHH), 3.13 (dd,
1H, J = 13.6, 5.1 Hz, CHH), 3.79 (s, 3H, CH3O), 4.23 (tq, seven lines,
1H, J = 6.5 Hz, CH), 5.66 (br d, 1H, J = 6.0 Hz, NH), 6.64–6.74 (m, 1H,
89%; white crystals: mp 62–63 °C (EtOAc/hexane); ½a D20
ꢁ
= ꢀ72 (c 2,
CHCl3); 98% ee (chiral HPLC, Chiralpak IA, tR 51.6, flow 0.5 mL/min,
k 230 nm, eluent 95:5 hexane/iPrOH). Spectroscopic and spectro-

A. Carocci et al. / Bioorg. Med. Chem. 18 (2010) 6496–6511
6507
Ar), 6.93–7.0 (m, 2H, Ar), 7.18 (apparent t, 1H, Ar); 13C NMR d 19.7
(1C), 23.5 (1C), 39.7 (1C), 45.2 (1C), 55.6 (1C), 112.2 (1C), 114.6
(1C), 121.4 (1C), 130.1 (1C), 137.7 (1C), 160.2 (1C), 169.8 (1C);
MS (70 eV) m/z (%) 239 (M+, 14), 180 (100).
4.9.4. 2-[2-Phenoxypropyl]-1H-isoindole-1,3(2H)-dione (14c)
Prepared as reported above for 10c starting from phthalimide
and 13c. Yield: 22%; white crystals: mp 91–92 °C (EtOAc/hexane);
IR (KBr): 1774, 1721 (C@O) cmꢀ1; 1H NMR d 1.37 (d, 3H, J = 6.0 Hz,
CH3), 3.77 (dd, 1H, J = 13.8, 5.2 Hz, CHH), 4.04 (dd, 1H, J = 13.8,
7.4 Hz, CHH), 4.72–4.86 (m, 1H, CH), 6.82–6.96 (m, 3H, ArO),
7.16ꢀ7.25 (m, 2H, ArO), 7.66–7.74 (m, 2H, Ar), 7.78–7.86 (m, 2H,
Ar); 13C NMR d 18.2 (1C), 43.0 (1C), 71.1 (1C), 116.0 (2C), 121.2
(1C), 123.5 (2C), 129.7 (2C), 132.2 (2C), 134.2 (2C), 157.8 (1C),
168.5 (2C); MS (70 eV) m/z (%) 281 (M+, 9), 188 (100).
4.8.5. (ꢀ)-(S)-N-{2-[(3-Methoxyphenyl)thio]-1-methylethyl}acet-
amide [(ꢀ)-(S)-23e]
Prepared as reported above for (S)-23f starting from 1e and (S)-
19. Yield: 22%; slightly yellowish oil; ½a D20
= ꢀ8.1 (c 4.1, CHCl3);
ꢁ
>99% ee (chiral GC, tR 32.7 min, flow 1.4 mL/min, T 170 °C). Spec-
troscopic and spectrometric data were in agreement with those
found for the (R)-isomer.
4.9.5. 2-[2-(3-Methoxyphenoxy)propyl]-1H-isoindole-1,3(2H)-
dione (14d)
4.9. General procedure for the preparation of phthalimidoalkyl
aryl ethers (10a–d, 14c–e and 21c,d)
Prepared as reported above for 10c starting from phthalimide
and 13d. Yield: 91%; white solid: mp 96–97 °C; IR (KBr): 1774,
1713 (C@O) cmꢀ1 1H NMR d 1.37 (d, J = 6.0 Hz, 3H, CH3CH),
;
The method adopted for the synthesis of 2-(2-phenoxyethyl)-
3.70–3.80 (m overlapping s at 3.74, 1H, CHH), 3.74 (s overlapping
m at 3.70–3.80, 3H, CH3O), 4.03 (dd, 1H, J = 13.8, 7.4 Hz, CHH),
4.70–4.83 (m, 1H, CH), 6.38–6.45 (m, 1H, ArO), 6.46–6.56 (m, 2H,
ArO), 7.09 (apparent t, 1H, ArO), 7.64–7.74 (m, 2H, Ar), 7.78–7.86
(m, 2H, Ar); 13C NMR d 18.2 (1C), 43.0 (1C), 55.5 (1C), 71.1 (1C),
102.2 (1C), 107.1 (1C), 108.0 (1C), 123.5 (2C), 130.1 (1C), 132.1
(2C), 134.2 (2C), 160.0 (1C), 161.0 (1C), 168.5 (2C); MS (70 eV)
m/z (%) 311 (M+, 28), 188 (100).
1H-isoindole-1,3(2H)-dione (10c) is described.
A solution of
diethyl azodicarboxylate (DEAD, 2.73 g, 15.7 mmol) in dry THF
(60 mL) was added dropwise to a solution of 8 (2.0 g, 10.5 mmol),
1c (1.48 g, 15.7 mmol) and triphenylphosphine (4.12 g, 15.7 mmol)
in dry THF (40 mL) under N2 atmosphere at room temperature. The
reaction mixture was stirred overnight and then was concentrated
in vacuo. Et2O was added to the residue and the solid filtered off.
The filtrate was evaporated and the residue was purified by flash
chromatography (petroleum ether/EtOAc 8:2) to give 1.66 g of
10c as a white solid (59%): mp 130–132 °C; IR (KBr): 1771, 1716
4.9.6. (ꢀ)-(R)-2-[2-(3-Methoxyphenoxy)propyl]-1H-isoindole-
1,3(2H)-dione [(ꢀ)-(R)-14d]
(C@O) cmꢀ1
;
1H NMR d 4.11 (t, 2H, J = 5.8 Hz, CH2N), 4.22 (t, 2H,
Prepared as reported above for 10c starting from phthalimide
J = 5.6 Hz, CH2O), 6.85–6.97 (m, 3H, ArO), 7.18–7.30 (m, 2H, ArO),
7.67–7.78 (m, 2H, Ar), 7.82–7.90 (m, 2H, Ar); 13C NMR d 37.6
(1C), 64.8 (1C), 114.8 (2C), 121.3 (1C), 123.6 (2C), 129.7 (2C),
132.3 (2C), 134.3 (2C), 158.5 (1C), 168.4 (2C); MS (70 eV) m/z (%)
267 (M+, 17), 174 (100). Anal. Calcd for C16H13NO3ꢃ0.33H2O: C,
70.32; H, 5.04; N, 5.13. Found: C, 70.18; H, 4.85; N, 5.22.
and (R)-13d. Yield: 52%; white solid: mp 98–99 °C; ½a D20
= ꢀ57 (c
ꢁ
2, CHCl3); IR (KBr): 1774, 1705 (C@O) cmꢀ1 1H NMR d 1.42 (d,
;
3H, J = 6.0 Hz, CH3CH), 3.76–3.85 (m overlapping s at 3.79, 1H,
CHH), 3.79 (s overlapping m at 3.76–3.85, 3H, CH3O), 4.08 (dd,
1H, J = 14.0, 7.4 Hz, CHH), 4.81 (apparent sextet, 1H, CH), 6.42–
6.50 (m, 1H, ArO), 6.52–6.60 (m, 2H, ArO), 7.14 (apparent t, 1H,
ArO), 7.70–7.78 (m, 2H, Ar), 7.82–7.92 (m, 2H, Ar); 13C NMR d
18.2 (1C), 42.9 (1C), 55.5 (1C), 71.1 (1C), 102.2 (1C), 107.1 (1C),
108.0 (1C), 123.5 (2C), 130.1 (1C), 132.1 (2C), 134.2 (2C), 159.0
(1C), 161.0 (1C), 168.5 (2C); MS (70 eV) m/z (%) 311 (M+, 25), 188
(100).
4.9.1. 2-[2-(4-Methoxyphenoxy)ethyl)-1H-isoindole-1,3(2H)-
dione (10a)
Prepared as reported above for 10c starting from 1a. Yield: 44%;
white solid: mp 135–136 °C; IR (KBr): 1770, 1716 (C@O) cmꢀ1 1H
;
NMR d 3.73 (s, 3H, CH3O), 4.05–4.12 (m, 2H, CH2N), 4.14–4.22 (m,
2H, CH2O), 6.74–6.86 (m, 4H, ArO), 7.67–7.76 (m, 2H, Ar), 7.82–
7.90 (m, 2H, Ar); 13C NMR d 37.7 (1C), 55.9 (1C), 65.7 (1C), 114.9
(2C), 116.0 (2C), 123.5 (2C), 132.3 (2C), 134.2 (2C), 152.7 (1C),
154.4 (1C), 168.4 (2C); MS (70 eV) m/z (%) 297 (M+, 12), 174 (100).
4.9.7. (+)-(S)-2-[2-(3-Methoxyphenoxy)propyl]-1H-isoindole-
1,3(2H)-dione [(+)-(S)-14d]
Prepared as reported above for 10c starting from phthalimide
and (S)-13d. Yield: 61%; white solid: mp 84–86 °C; ½a D20
ꢁ
= +52 (c
2, CHCl3). Spectroscopic and spectrometric data were in agreement
4.9.2. 2-[2-(2-Methoxyphenoxy)ethyl)-1H-isoindole-1,3(2H)-
dione (10b)
with those reported for the (R)-isomer.
Prepared as reported above for 10c starting from 1b. Yield: 40%;
4.9.8. 2-{2-[(3-Methoxyphenyl)thio]propyl}-1H-isoindole-
1,3(2H)-dione (14e)
white solid: mp 107–109 °C; IR (KBr): 1772, 1713 (C@O) cmꢀ1 1H
;
NMR d 3.74 (s, 3H, CH3O), 4.08–4.18 (m, 2H, CH2N), 4.24–4.32 (m,
2H, CH2O), 6.81–6.98 (m, 4H, ArO), 7.68–7.76 (m, 2H, Ar), 7.83–
7.90 (m, 2H, Ar); 13C NMR d 37.5 (1C), 56.1 (1C), 66.4 (1C), 112.5
(1C), 115.2 (1C), 121.1 (1C), 122.3 (1C), 123.5 (2C), 132.4 (2C),
134.2 (2C), 148.1 (1C), 150.2 (1C), 168.4 (2C); MS (70 eV) m/z (%)
297 (M+, 9), 174 (100).
Prepared as reported above for 10c starting from phthalimide
and 13e. Yield: 62%; white solid: mp 56–58 °C; IR (KBr): 1772,
1713 (C@O) cmꢀ1 1H NMR d 1.33 (d, 3H, J = 6.6 Hz, CH3CH),
;
3.70–3.96 (m overlapping s at 3.76, 2H, CH2), 3.76 (s overlapping
m at 3.70–3.80, 3H, CH3O), 4.90–5.05 (m, 1H, CH), 6.52–6.60 (m,
1H, ArO), 6.92–7.00 (m, 2H, ArO), 7.02–7.10 (m, 1H, ArO), 7.63–
7.71 (m, 2H, Ar), 7.74–7.82 (m, 2H, Ar); 13C NMR d 22.2 (1C),
40.7 (1C), 44.3 (1C), 55.5 (1C), 113.0 (1C), 116.2 (1C), 123.4 (1C),
123.6 (1C), 123.8 (1C), 129.9 (1C), 132.0 (2C), 134.1 (2C), 135.5
(1C), 159.8 (1C), 168.5 (2C); MS (70 eV) m/z (%) 327 (M+, 100).
4.9.3. 2-[2-(3-Methoxyphenoxy)ethyl)-1H-isoindole-1,3(2H)-
dione (10d)
Prepared as reported above for 10c starting from 1d. Yield: 42%;
white solid: mp 113–114 °C; IR (KBr): 1765, 1708 (C@O) cmꢀ1 1H
;
NMR d 3.75 (s, 3H, CH3O), 4.05–4.14 (m, 2H, CH2N), 4.18–4.25 (m,
2H, CH2O), 6.40–6.52 (m, 3H, ArO), 7.13 (apparent t, 1H, ArO),
7.68–7.76 (m, 2H, Ar), 7.82–7.90 (m, 2H, Ar); 13C NMR d 37.5
(1C), 55.5 (1C), 65.0 (1C), 101.4 (1C), 106.9 (1C), 107.2 (1C),
123.6 (2C), 130.1 (1C), 132.3 (2C), 134.2 (2C), 159.8 (1C), 161.1
(1C), 168.3 (2C); MS (70 eV) m/z (%) 297 (M+, 15), 174 (100).
4.9.9. (+)-(R)-2-{2-[(3-Methoxyphenyl)thio]propyl}-1H-
isoindole-1,3(2H)-dione [(+)-(R)-14e]
Prepared as reported above for 10c starting from phthalimide
and (R)-13e. Yield: 85%; slightly yellowish solid: mp 66–68 °C
(EtOAc/petroleum ether); ½a D20
ꢁ
= +62 (c 2, CHCl3); MS (70 eV) m/z
(%) 327 (M+, 100).

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A. Carocci et al. / Bioorg. Med. Chem. 18 (2010) 6496–6511
4.9.10. (ꢀ)-(S)-2-{2-[(3-Methoxyphenyl)thio]propyl}-1H-isoin-
dole-1,3(2H)-dione [(ꢀ)-(S)-14e]
(80 mL) under N2 atmosphere. The reaction mixture was heated
at 100 °C and then solution of benzenethiol (1f) (0.48 g,
a
Prepared as reported above for 10c starting from phthalimide
and (S)-13e. Yield: 52%; white solid: mp 62–64 °C (EtOAc/hexane);
4.3 mmol) in 40 mL of dry DMF was added dropwise during a per-
iod of 3 h. The mixture was stirred at this temperature for 17 h.
After evaporation of the solvent, the residue was taken up with
EtOAc, washed with 0.5 N NaOH, then with a saturated solution
of NaCl. The organic phase was dried (Na2SO4) and concentrated
under vacuum. The residue was purified by crystallization
(EtOAc/hexane) to give 0.97 g (87%) of 10f as a slightly yellowish
½
a 2D0
ꢁ
= ꢀ65 (c 2.4, CHCl3); IR (KBr): 1773, 1714 (C@O) cmꢀ1
;
1H
NMR d 1.34 (d, J = 6.6 Hz, 3H, CH3CH), 3.72–3.95 (m overlapping
s at 3.77, 3H, CH + CH2), 3.77 (s overlapping m at 3.72–3.95, 3H,
CH3O), 6.54–6.60 (m, 1H, ArO), 6.95–7.01 (m, 2H, ArO), 7.02–7.11
(m, 1H, ArO), 7.65–7.72 (m, 2H, Ar), 7.73–7.80 (m, 2H, Ar); 13C
NMR d 18.7 (1C), 40.7 (1C), 44.3 (1C), 55.4 (1C), 113.0 (1C), 116.2
(1C), 123.4 (2C), 123.6 (1C), 129.9 (1C), 132.0 (2C), 134.1 (2C),
135.5 (1C), 159.8 (1C), 168.5 (2C).
solid: mp 55–56 °C; IR (KBr): 1769, 1713 (C@O) cmꢀ1 1H NMR d
;
3.18–3.28 (m, 2H, CH2N), 3.88–3.98 (t, 2H, J = 7.0 Hz, CH2O), 7.12
(tt, J = 7.4, 1.6 Hz, 1H, ArO), 7.20–7.28 (m, 2H, ArO), 7.38–7.44
(m, 2H, ArO), 7.66–7.74 (m, 2H, Ar), 7.76–7.84 (m, 2H, Ar); 13C
NMR d 31.9 (1C), 37.8 (1C), 123.5 (2C), 126.6 (1C), 129.2 (2C),
130.0 (2C), 132.2 (2C), 134.2 (2C), 135.1 (1C), 168.3 (2C); MS
(70 eV) m/z (%) 283 (M+, 42), 136 (100).
4.9.11. 2-(1-Methyl-2-phenoxyethyl)-1H-isoindole-1,3(2H)-dione
(21c)
Prepared as reported above for 10c starting from 1c and (RS)-20
using diisopropyl azodicarboxylate (DIAD) instead of DEAD. Yield:
44%; slightly yellowish oil; IR (neat): 1775, 1705 (C@O) cmꢀ1
;
1H
4.10.1. 2-{2-[(3-Methoxyphenyl)thio]ethyl}-1H-isoindole-1,3(2H)-
dione (10e)
NMR d 1.56 (d, 3H, J = 7.1 Hz, CH3CH), 4.16 (dd, 1H, J = 9.5, 5.6 Hz,
CHH), 4.53 (apparent t, 1H, CHH), 4.73–4.88 (m, 1H, CH), 6.80–
6.94 (m, 3H, ArO), 7.16–7.28 (m, 2H, ArO), 7.65–7.74 (m, 2H, Ar),
7.76–7.87 (m, 2H, Ar); 13C NMR d 15.4 (1C), 46.7 (1C), 68.4 (1C),
115.0 (2C), 121.3 (1C), 123.4 (2C), 129.7 (2C), 129.8 (2C), 134.2
(2C), 158.6 (1C), 168.6 (2C); MS (70 eV) m/z (%) 281 (M+, 13), 188
(100).
Prepared as reported above for 10f starting from 1e. Yield: 76%;
slightly yellowish solid: mp 95–96 °C; IR (KBr): 1763, 1710 (C@O)
cmꢀ1; 1H NMR d 3.23 (t, 2H, J = 7.0 Hz, CH2S), 3.80 (s, 3H, CH3), 3.95
(t, 2H, J = 7.0 Hz, CH2N), 6.59–6.67 (m, 1H, ArO), 6.93–7.01 (m, 2H,
ArO), 7.13 (apparent t, 1H, ArO), 7.66–7.74 (m, 2H, Ar), 7.76–7.85
(m, 2H, Ar); 13C NMR d 31.6 (1C), 37.9 (1C), 55.5 (1C), 112.7 (1C),
114.7 (1C), 121.9 (1C), 123.5 (2C), 130.1 (1C), 132.2 (2C), 134.2
(2C), 136.4 (1C), 160.1 (1C), 168.3 (2C); MS (70 eV) m/z (%) 313
(M+, 94), 166 (100).
4.9.12. 2-[2-(3-Methoxyphenoxy)-1-methylethyl]-1H-isoindole-
1,3(2H)-dione (21d)
Prepared as reported above for 10c starting from 1d and 20.
Yield: 47%; slightly yellowish oil; IR (neat): 1774, 1709 (C@O)
4.10.2. 2-{2-[(4-Methoxyphenyl)thio]ethyl}-1H-isoindole-1,3(2H)-
dione (10g)
cmꢀ1 1H NMR d 1.55 (d, 3H, J = 7.1 Hz, CH3CH), 3.73 (s, 3H,
;
CH3O), 4.07–4.19 (m, 1H, CHH), 4.51 (apparent t, 1H, CHH), 4.73–
4.86 (m, 1H, CH), 6.36–6.51 (m, 3H, ArO), 7.12 (apparent t, 1H,
ArO), 7.66–7.75 (m, 2H, Ar), 7.78–7.86 (m, 2H, Ar); 13C NMR d
15.4 (1C), 46.7 (1C), 55.5 (1C), 68.5 (1C), 101.4 (1C), 107.0 (1C),
107.1 (1C), 123.4 (2C), 130.0 (1C), 132.2 (2C), 134.2 (2C), 159.8
(1C), 161.0 (1C), 168.6 (2C); MS (70 eV) m/z (%) 311 (M+, 25), 188
(100).
Prepared as reported above for 10f starting from 1g. Yield: 63%;
slightly yellowish solid: mp 98–100 °C; IR (KBr): 1768, 1716 (C@O)
cmꢀ1; 1H NMR d 3.13 (t, 2H, J = 6.7 Hz, CH2S), 3.74 (s, 3H, CH3), 3.88
(t, 2H, J = 6.9 Hz, CH2N), 6.74–6.82 (m, 2H, ArO), 7.36–7.44 (m, 2H,
Ar), 7.65–7.74 (m, 2H, Ar), 7.75–7.85 (m, 2H, Ar); 13C NMR d 33.8
(1C), 38.0 (1C), 55.5 (1C), 114.9 (2C), 123.4 (2C), 125.5 (1C),
132.3 (2C), 133.7 (2C), 134.1 (2C), 159.4 (1C), 168.3 (2C); MS
(70 eV) m/z (%) 313 (M+, 97), 166 (100).
4.9.13. (+)-(R)-2-[2-(3-Methoxyphenoxy)-1-methylethyl]-1H-
isoindole-1,3(2H)-dione [(+)-(R)-21d]
4.10.3. 2-{2-[(2-Methoxyphenyl)thio]ethyl}-1H-isoindole-1,3(2H)-
dione (10h)
Prepared as reported above for 21c starting from 1d and (R)-20.
Yield: 64%; slightly yellowish oil; ½a D20
ꢁ
= +14.9 (c 2, CHCl3); IR
Prepared as reported above for 10f starting from 1h. Yield: 47%;
slightly yellowish solid: mp 91–92 °C; IR (KBr): 1771, 1705 (C@O)
cmꢀ1; 1H NMR d 3.17–3.25 (m, 2H, CH2S), 3.85–3.95 (m overlapping
s at 3.87, 2H, CH2N), 3.87 (s, overlapping m at 3.85–3.95, 3H, CH3),
6.80 (dd, 1H, J = 8.2, 1.1 Hz, Ar), 6.87 (dt, 1H, J = 7.7, 1.3 Hz, Ar), 7.14
(ddd, 1H, J = 8.2, 7.4, 1.6 Hz, Ar), 7.43 (dd, 1H, J = 7.7, 1.6 Hz, Ar),
7.65–7.73 (m, 2H, Ar), 7.75–7.84 (m, 2H, Ar); 13C NMR d 30.2 (1C),
37.9 (1C), 55.9 (1C), 111.0 (1C), 121.3 (1C), 122.7 (1C), 123.4 (2C),
128.2 (1C), 131.4 (1C), 132.3 (2C), 134.1 (2C), 158.2 (1C), 168.2
(2C); MS (70 eV) m/z (%) 313 (M+, 66), 166 (100).
(neat): 1774, 1713 (C@O) cmꢀ1 1H NMR d 1.55 (d, 3H, J = 6.9 Hz,
;
CH3CH), 3.74 (s, 3H, CH3O), 4.07–4.20 (m, 1H, CHH), 4.51 (apparent
t, 1H, CHH), 4.72–4.86 (m, 1H, CH), 6.37–6.50 (m, 3H, ArO), 7.11
(apparent t, 1H, ArO), 7.66–7.75 (m, 2H, Ar), 7.78–7.87 (m, 2H,
Ar); 13C NMR d 15.4 (1C), 46.7 (1C), 55.5 (1C), 68.5 (1C), 101.4
(1C), 107.0 (1C), 107.1 (1C), 123.4 (1C), 123.6 (1C), 130.0 (1C),
132.2 (2C), 134.2 (1C), 134.3 (1C), 159.8 (1C), 161.0 (1C), 168.6
(2C); MS (70 eV) m/z (%) 311 (M+, 18), 188 (100).
4.9.14. (ꢀ)-(S)-2-[2-(3-Methoxyphenoxy)-1-methylethyl]-1H-
isoindole-1,3(2H)-dione [(ꢀ)-(S)-21d]
4.11. General procedure for the preparation of cyclopropane-
carboxamides (15d,e)
Prepared as reported above for 21c starting from 1d and (S)-20.
Yield: 90%; slightly yellowish oil; ½a D20
= ꢀ16.7 (c 4, CHCl3). Spec-
ꢁ
troscopic and spectrometric data were in agreement with those re-
The method adopted for the synthesis of N-[2-(3-methoxyphen-
oxy)propyl]cyclopropane carboxamide (15d) is described. To a stir-
ring solution of 6d (0.50 g, 2.76 mmol) and Et3N (0.11 mL,
0.83 mmol) in dry toluene (5 mL) under N2 atmosphere, a solution
of cyclopropanecarbonyl chloride (0.29 g, 2.76 mmol) was added
dropwise. The reaction mixture was refluxed for 3 h, then the res-
idue was taken up with EtOAc and washed twice with 2 N NaOH,
twice with 2 N HCl and twice with a saturated aqueous NaCl solu-
tion. The combined organic layers were dried (Na2SO4) and con-
centrated to give a yellow oil (78%) which was purified by
ported for the (R)-isomer.
4.10. General procedure for the preparation of phthalimidoalkyl
aryl thioethers (10e–h)
The method adopted for the synthesis of 2-[2-(phenyl-
thio)ethyl]-1H-isoindole-1,3(2H)-dione (10f) is described. K2CO3
(0.54 g, 3.9 mmol) was added to a solution of 2-(2-bromoethyl)-
1H-isoindole-1,3(2H)-dione (9) (1.0 g, 3.9 mmol) in dry DMF

A. Carocci et al. / Bioorg. Med. Chem. 18 (2010) 6496–6511
6509
column chromatography on silica gel (EtOAc) to give 0.60 g (87%)
of 15d as a slightly yellowish oil: IR (neat): 3299 (NH), 1646,
1602 (C@O) cmꢀ1 1H NMR d 0.65–0.78 (m, 2H, CHHCHH), 0.90–
4.11.5. (+)-(S)-N-{2-[(3-Methoxyphenyl)thio]propyl}cyclopro-
panecarboxamide [(+)-(S)-15e]
;
Prepared as reported above for 14d starting from (S)-6e. Yield:
1.02 (m, 2H, CHHCHH), 1.22–1.38 (m overlapping d at 1.28, 1H,
CHCO), 1.28 (d overlapping m at 1.22–1.38, 3H, J = 6.3 Hz, CH3CH),
3.24–3.36 (m, 1H, CHHN), 3.68–3.82 (m overlapping s at 3.79, 1H,
CHHN), 3.79 (s overlapping m at 3.68–3.82, 3H, CH3O), 4.43–4.55
(m, 1H, CHCH3), 6.03 (br s, 1H, NH), 6.46–6.56 (m, 3H, Ar), 7.18
(apparent t, 1H, Ar); 13C NMR d 7.4 (2C), 15.0 (1C), 17.4 (1C),
44.8 (1C), 55.5 (1C), 73.3 (1C), 102.7 (1C), 107.0 (1C), 108.2 (1C),
130.3 (1C), 159.1 (1C), 161.2 (1C), 173.9 (1C); MS (70 eV) m/z (%)
249 (M+, 6), 126 (100).
95%; slightly yellowish oil; ½a D20
ꢁ
= +16.0 (c 0.5, CHCl3), 96% ee (chi-
ral HPLC, Chiralpak IA, tR 20.1, flow 0.4 mL/min, k 210 nm, eluent
50:50 CH3CN/H2O). Spectroscopic and spectrometric data were in
agreement with those reported for the (R)-isomer.
4.11.6. N-[2-(3-Methoxyphenoxy)propyl]butanamide (16d)
Prepared as reported above for 7a starting from butyric anhy-
dride and 6d. There was a little difference in the procedure. In fact,
butyric acid in excess was taken away by extracting with 2 N NaOH
aqueous solution. Yield: 83%; slightly yellowish oil; IR (neat): 3301
(NH), 1649 (C@O) cmꢀ1; 1H NMR d 0.91 (t, 3H, J = 7.4 Hz, CH3CH2),
1.27 (d, 3H, J = 6.3 Hz, CH3CH), 1.63 (sextet, 2H, J = 7.4 Hz, CH2CH3),
2.14 (t, 2H, J = 7.4 Hz, CH2CO), 3.21–3.35 (m, 1H, CHHNH), 3.63–
3.75 (m overlapping s at 3.78, 1H, CHHNH), 3.78 (s overlapping m
at 3.63–3.75, 3H, CH3O), 4.42–4.54 (m, 1H, CH), 5.85 (br s, 1H,
NH), 6.45–6.58 (m, 3H, Ar), 7.17 (apparent t, 1H, Ar); 13C NMR d
13.9 (1C), 17.4 (1C), 19.3 (1C), 38.9 (1C), 44.5 (1C), 55.5 (1C), 73.2
(1C), 102.6 (1C), 106.9 (1C), 108.2 (1C), 130.3 (1C), 159.0 (1C),
161.2 (1C), 173.4 (1C); MS (70 eV) m/z (%) 251 (M+, 5), 128 (100).
4.11.1. (ꢀ)-(R)-N-[2-(3-Methoxyphenoxy)propyl]cyclopropan-
ecarboxamide [(ꢀ)-(R)-15d]
Prepared as reported above for 15d starting from (R)-6d. Yield:
82%; slightly yellowish oil; ½a D20
= ꢀ80 (c 2, CHCl3), 95% ee (chiral
ꢁ
HPLC, Chiralpak IA, tR 31.3, flow 0.5 mL/min, k 230 nm, eluent
95:5 hexane/EtOH); IR (neat): 3301 (NH), 1646, 1602 (C@O)
cmꢀ1 1H NMR d 0.65–0.77 (m, 2H, CHHCHH), 0.90–1.02 (m, 2H,
;
CHHCHH), 1.25–1.40 (m overlapping d at 1.27, 1H, CHCO), 1.27 (d
overlapping m at 1.25–1.40, 3H, J = 6.3 Hz, CH3CH), 3.30 (ddd, 1H,
J = 14.0, 7.5, 4.8 Hz, CHHN), 3.72 (ddd, 1H, J = 13.9, 7.1, 3.5 Hz,
CHHN), 3.78 (s, 3H, CH3O), 4.43–4.53 (m, 1H, CHCH3), 6.06 (br s,
1H, NH), 6.46–6.55 (m, 3H, Ar), 7.18 (apparent t, 1H, Ar); 13C NMR
d 7.5 (2C), 15.0 (1C), 17.4 (1C), 44.7 (1C), 55.5 (1C), 73.2 (1C),
102.6 (1C), 106.9 (1C), 108.2 (1C), 130.3 (1C), 159.0 (1C), 161.2
(1C), 174.0 (1C); MS (70 eV) m/z (%) 249 (M+, 6), 126 (100).
4.11.7. (ꢀ)-(R)-N-[2-(3-Methoxyphenoxy)propyl]butanamide
[(ꢀ)-(R)-16d]
Prepared as reported above for 16d starting from butyric anhy-
dride and (R)-6d. Yield: 80%; slightly yellowish oil; ½a D20
= ꢀ71 (c 1,
ꢁ
CHCl3); 96% ee (chiral HPLC, Chiralpak IA, tR 59.9, flow 0.4 mL/min,
k 210 nm, eluent 30:70 CH3CN/H2O); IR (neat): 3318 (NH), 1602
4.11.2. (+)-(S)-N-[2-(3-Methoxyphenoxy)propyl]cyclopro-
panecarboxamide [(+)-(S)-15d]
(C@O) cmꢀ1 1H NMR d 0.92 (t, 3H, J = 7.3 Hz, CH3CH2), 1.27 (d,
;
3H, J = 6.0 Hz, CH3CH), 1.64 (sextet, 2H, J = 7.4 Hz, CH2CH3), 2.15
(t, 2H, J = 7.5 Hz, CH2CO), 3.29 (ddd, 1H, J = 13.9, 7.4, 5.1 Hz,
CHHNH), 3.69 (ddd, 1H, J = 14.0, 7.1, 3.5 Hz, CHHNH), 3.78 (s, 3H,
CH3O), 4.42–4.55 (m, 1H, CH), 5.85 (br s, 1H, NH), 6.43–6.60 (m,
3H, Ar), 7.17 (apparent t, 1H, Ar); 13C NMR d 14.0 (1C), 17.4 (1C),
19.3 (1C), 38.9 (1C), 44.5 (1C), 55.5 (1C), 73.1 (1C), 102.6 (1C),
106.9 (1C), 108.1 (1C), 130.3 (1C), 159.0 (1C), 161.2 (1C), 173.4
(1C); MS (70 eV) m/z (%) 251 (M+, 5), 128 (100).
Prepared as reported above for 15d starting from (S)-6d. Yield:
58%; slightly yellowish oil; ½a D20
ꢁ
= +88 (c 2, CHCl3), 95% ee (chiral
HPLC, Chiralpak IA, tR 28.0, flow 0.5 mL/min, k 230 nm, eluent
95:5 hexane/EtOH). Spectroscopic and spectrometric data were in
agreement with those reported for the (R)-isomer.
4.11.3. N-{2-[(3-Methoxyphenyl)thio]propyl}cyclopropane-
carboxamide (15e)
Prepared as reported above for 15d starting from 6e. Yield: 80%;
4.11.8. (+)-(S)-N-[2-(3-Methoxyphenoxy)propyl]butanamide
[(+)-(S)-16d]
slightly yellowish oil; IR (neat): 3298 (NH), 1646 (C@O) cmꢀ1 1H
;
NMR d 0.65–0.80 (m, 2H, CHHCHH), 0.90–1.10 (m, 2H, CHHCHH),
1.22–1.35 (m overlapping d at 1.29, 1H, CHCO), 1.29 (d overlapping
m at 1.22–1.35, 3H, J = 6.9 Hz, CH3CH), 3.25–3.56 (m, 3H, CH2CH),
3.80 (s, 3H, CH3O), 6.00 (br s, 1H, NH), 6.75–6.85 (m, 1H, Ar),
6.95–7.05 (m, 2H, Ar), 7.22 (apparent t, 1H, Ar); 13C NMR d 7.4
(2C), 15.0 (1C), 19.0 (1C), 43.7 (1C), 44.8 (1C), 55.5 (1C), 113.3
(1C), 117.6 (1C), 124.4 (1C), 130.1 (1C), 135.3 (1C), 160.1 (1C),
173.8 (1C); MS (70 eV) m/z (%) 265 (M+, 17), 180 (100).
Prepared as reported above for 16d starting from butyric anhy-
dride and (S)-6d. Yield: 69%; slightly yellowish oil; ½a D20
ꢁ
= +54 (c 2,
CHCl3); 94% ee (chiral HPLC, Chiralpak IA, tR 57.86, flow 0.4 mL/
min, k 210 nm, eluent 30:70 CH3CN/H2O). Spectroscopic and spec-
trometric data were in agreement with those reported for the (R)-
isomer.
4.11.9. N-{2-[(3-Methoxyphenyl)thio]propyl}butanamide (16e)
Prepared as reported above for 16d starting from butyric anhy-
dride and 6e. Yield: 75%; slightly yellowish oil; IR (neat): 3294
(NH), 1646 (C@O) cmꢀ1; 1H NMR d 0.93 (t, 3H, J = 7.4 Hz, CH3CH2),
1.29 (d, 3H, J = 6.6 Hz, CH3CH), 1.63 (sextet, 2H, J = 7.4 Hz, CH2CH3),
2.12 (t, 2H, J = 7.4 Hz, CH2CO), 3.24–3.52 (m, 3H, CH2CH), 3.80 (s,
3H, CH3O), 5.83 (br s, 1H, NH), 6.76–6.84 (m, 1H, Ar), 6.93–7.04
(m, 2H, Ar), 7.22 (apparent t, 1H, Ar); 13C NMR d 14.0 (1C), 19.0
(1C), 19.3 (1C), 38.9 (1C), 43.5 (1C), 44.4 (1C), 55.5 (1C), 113.2
(1C), 117.6 (1C), 124.3 (1C), 130.1 (1C), 135.2 (1C), 160.1 (1C),
173.3 (1C); MS (70 eV) m/z (%) 267 (M+, 11), 180 (100).
4.11.4. (ꢀ)-(R)-N-{2-[(3-Methoxyphenyl)thio]propyl}cycloprop-
anecarboxamide [(ꢀ)-(R)-15e]
Prepared as reported above for 15d starting from (R)-6e. Yield:
90%; slightly yellowish oil; ½a D20
= ꢀ11.2 (c 0.5, CHCl3); 97% ee (chi-
ꢁ
ral HPLC, Chiralpak IA, tR 21.5, flow 0.4 mL/min, k 210 nm, eluent
50:50 CH3CN/H2O); IR (neat): 3299 (NH), 1645 (C@O) cmꢀ1 1H
;
NMR d 0.63–0.80 (m, 2H, CHHCHH), 0.85–1.05 (m, 2H, CHHCHH),
1.20–1.35 (m overlapping d at 1.29, 1H, CHCO), 1.29 (d overlapping
m at 1.22–1.35, 3H, J = 6.9 Hz, CH3CH), 3.20–3.58 (m, 3H, CH2CH),
3.80 (s, 3H, CH3O), 5.99 (br s, 1H, NH), 6.79 (dd, 1H, J = 8.3,
2.2 Hz, Ar), 6.97 (d, 1H, J = 2.2 Hz, Ar), 7.00 (d, 1H, J = 8.0 Hz, Ar),
7.22 (apparent t, 1H, Ar); 13C NMR d 7.4 (2C), 14.9 (1C), 19.0
(1C), 43.7 (1C), 44.8 (1C), 55.5 (1C), 113.3 (1C), 117.6 (1C), 124.4
(1C), 130.1 (1C), 135.3 (1C), 160.1 (1C), 173.8 (1C); MS (70 eV)
m/z (%) 265 (M+, 17), 180 (100).
4.11.10. (ꢀ)-(R)-N-{2-[(3-Methoxyphenyl)thio]propyl}butanamide
[(ꢀ)-(R)-16e]
Prepared as reported above for 16d starting from butyric anhy-
dride and (R)-6e. Yield: 98%; slightly yellowish oil; ½a D20
= ꢀ16.2 (c
ꢁ
0.5, CHCl3); 97% ee (chiral HPLC, Chiralpak IA, tR 133.6, flow 0.4 mL/

6510
A. Carocci et al. / Bioorg. Med. Chem. 18 (2010) 6496–6511
min, k 210 nm, eluent 30:70 CH3CN/H2O); IR (neat): 3296 (NH),
1646 (C@O) cmꢀ1 1H NMR d 0.93 (t, 3H, J = 7.4 Hz, CH3CH2), 1.29
of protein per tube. The membrane protein level was determined
in accordance with a previously reported method.55 2-[125I]Iodom-
elatonin (100 pM) and different concentrations of MLT and/or the
new compounds were incubated with the receptor preparation
for 90 min at 37 °C. IC50 values were determined by nonlinear fit-
ting strategies with the program PRISM (GraphPad SoftWare Inc.,
San Diego, CA). The pKi values were calculated from the IC50 values
in accordance with the Cheng–Prusoff equation.56 The pKi values
are the mean of at least three independent determinations per-
formed in duplicate. To define the functional activity of the new
;
(d, 3H, J = 6.6 Hz, CH3CH), 1.63 (sextet, 2H, J = 7.4 Hz, CH2CH3),
2.12 (t, 2H, J = 7.4 Hz, CH2CO), 3.22–3.52 (m, 3H, CH2CH), 3.80 (s,
3H, CH3O), 5.83 (br s, 1H, NH), 6.75–6.84 (m, 1H, Ar), 6.92–7.04
(m, 2H, Ar), 7.22 (apparent t, 1H, Ar); 13C NMR d 14.0 (1C), 19.0
(1C), 19.3 (1C), 38.9 (1C), 43.6 (1C), 44.5 (1C), 55.5 (1C), 113.3
(1C), 117.6 (1C), 124.4 (1C), 130.1 (1C), 135.3 (1C), 160.1 (1C),
173.3 (1C); MS (70 eV) m/z (%) 267 (M+, 13), 180 (100).
4.11.11. (+)-(S)-N-{2-[(3-Methoxyphenyl)thio]propyl}butanamide
[(+)-(S)-16e]
compounds at MT1 and MT2 receptor subtypes, [35S]GTP
assays in NIH3T3 cells expressing human-cloned MT1 or MT2
receptors were performed. The amount of bound [35S]GTP
S is pro-
cS binding
Prepared as reported above for 16d starting from butyric anhy-
c
dride and (S)-6e. Yield: 98%; slightly yellowish oil; ½a D20
ꢁ
= +16.9 (c
portional to the level of the analogue-induced G-protein activation
and is related to the intrinsic activity of the compound under
study. The detailed description and validation of this method were
0.5, CHCl3); 96% ee (chiral HPLC, Chiralpak IA, tR 120.8, flow
0.4 mL/min, k 210 nm, eluent 30:70 CH3CN/H2O). Spectroscopic
and spectrometric data were in agreement with those reported
for the (R)-isomer.
reported elsewhere,53,57 membranes (15–25
l
g of protein, final
L) were incubated at 30 °C for 30 min in
the presence and in the absence of MLT analogues in an assay buf-
fer consisting of [35S]GTP
S (0.3–0.5 nM), GDP (50 M), NaCl
(100 mM), and MgCl2 (3 mM). Nonspecific binding was defined
using [35S]GTP
S (10 M). In cell lines expressing human MT1 or
MT2 receptors, MLT produced a concentration-dependent stimula-
tion of basal [35S]GTP
S binding with a maximal stimulation,
above basal levels, of 370% and 250% in MT1 and MT2 receptors,
respectively. Basal stimulation is the amount of [35S]GTP
S specif-
incubation volume 100
l
4.11.12. (+)-(R)-Methyl 2-(3-methoxyphenoxy)propanoate [(+)-
(R)-18d]
c
l
Prepared as reported above for 10c starting from 1d and (S)-17.
c
l
Yield: 80%; slightly yellowish oil; ½a D20
ꢁ
= +22.3 (c 2, CHCl3); IR
(neat): 1759, 1738 (C@O) cmꢀ1
;
1H NMR d 1.60 (d, 3H, J = 6.9 Hz,
c
CH3CH), 3.74 (s, 3H, CH3OCO), 3.76 (s, 3H, CH3O), 4.75 (q, 1H,
J = 6.8 Hz, CH), 6.39–6.48 (m, 2H, Ar), 6.49–6.56 (m, 1H, Ar), 7.15
(apparent t, 1H, Ar); 13C NMR d 18.8 (1C), 52.5 (1C), 55.5 (1C),
72.7 (1C), 101.9 (1C), 107.0 (1C), 107.6 (1C), 130.2 (1C), 159.0
(1C), 161.1 (1C), 172.9 (1C); MS (70 eV) m/z (%) 210 (M+, 58), 151
(100).
c
ically bound in the absence of compounds, and it was taken as
100%. The maximal G-protein activation was measured in each
experiment by using MLT (100 nM). Compounds were added at
three different concentrations (one concentration was equivalent
to 100 nM MLT, a second one was 10 times smaller, and a third
one was 10 times larger), and the percent stimulation above basal
was determined. The equivalent concentration was estimated on
the basis of the ratio of the affinity of the test compound over that
of MLT. It was assumed that at the equivalent concentration the
test compound occupies the same number of receptors as
100 nM MLT. All of the measurements were performed in tripli-
cate. The relative intrinsic activity (IAr) values were obtained by
4.11.13. (ꢀ)-(S)-Methyl 2-(3-methoxyphenoxy)propanoate [(ꢀ)-
(S)-18d]
Prepared as reported above for 10c starting from 1d and (R)-17.
Yield: 86%; slightly yellowish oil; ½a D20
= ꢀ19.9 (c 2, CHCl3). Spec-
ꢁ
troscopic and spectrometric data were in agreement with those re-
ported for the (R)-isomer.
4.11.14. (+)-(R)-Methyl 2-[(3-methoxyphenyl)thio]propanoate
[(+)-(R)-18e]
dividing the maximum ligand-induced stimulation of [35S]GTP
cS
binding by that of MLT, as measured in the same experiment. By
Prepared as reported above for 10c starting from 1e and (S)-17.
convention, the natural ligand MLT has an efficacy (Emax) of
Yield: 42%; slightly yellowish oil; ½a D20
ꢁ
= +132 (c 1, CHCl3); IR
100%. Full agonists stimulate [35S]GTP
cS binding with a maximum
(neat): 1737 (C@O) cmꢀ1; 1H NMR d 1.49 (d, 3H, J = 7.1 Hz, CH3CH),
3.69 (s, 3H, CH3OCO), 3.80 (s overlapping m at 3.75–3.85, 3H,
CH3O), 3.75–3.85 (m overlapping s at 3.80, 1H, CH), 6.78–6.86
(m, 1H, Ar), 6.95–7.05 (m, 2H, Ar), 7.22 (apparent t, 1H, Ar); 13C
NMR d 17.8 (1C), 45.3 (1C), 52.6 (1C), 55.5 (1C), 114.1 (1C), 117.9
(1C), 125.0 (1C), 130.0 (1C), 134.7 (1C), 159.9 (1C), 173.4 (1C);
MS (70 eV) m/z (%) 226 (M+, 80), 167 (100).
efficacy close to that of MLT itself. If Emax is between 30% and 70%
that of MLT (0.3 < IAr < 0.7), the compound is considered a partial
agonist, whereas if Emax is lower than 30% (IAr <0.3), the compound
is considered an antagonist.58
Acknowledgements
This work was accomplished thanks to the financial support of
the Ministero dell’Istruzione, dell’Università e della Ricerca (MIUR).
The authors thank Professors Franco Fraschini, Nicola Tangari, and
Vincenzo Tortorella for their valuable suggestions and helpful in-
puts in the early stages of the project.
4.11.15. (ꢀ)-(S)-Methyl 2-[(3-methoxyphenyl)thio]propanoate
[(ꢀ)-(S)-18e]
Prepared as reported above for 10c starting from 1e and (R)-17.
Yield: 30%; slightly yellowish oil; ½a D20
= ꢀ104 (c 1, CHCl3). Spectro-
ꢁ
scopic and spectrometric data were in agreement with those re-
ported for the (R)-isomer.
Supplementary data
4.12. MLT receptor binding assay
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.bmc.2010.06.100. These data
include MOL files and InChiKeys of the most important compounds
described in this article.
Binding affinities of compounds were determined using 2-
[
125I]iodomelatonin as the labelled ligand in competition experi-
ments on cloned human MT1 and MT2 receptors expressed in
NIH3T3 rat fibroblast cells. The characterization of NIH3T3-MT1
and -MT2 cells was already described in detail.53,54 Membranes
were incubated for 90 min at 37 °C in binding buffer (Tris/HCl
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