Synthesis of β-substituted Naphth-1-yl ethylamido derivatives as new melatoninergic agonists

Article abstract of DOI:10.1016/S0968-0896(99)00236-9

Naphthalene melatoninergic ligands with alkyl groups (Me, Et, Pr, Bz) in the β position of the ethylamido chain were synthesised. The affinity of the compounds for chicken brain melatonin receptors was evaluated using 2-[¹²⁵I]-iodomelatonin as the radioligand. An increase in the affinity was observed with the β-methyl derivatives and the greatest increase was seen with the (-) enantiomers. The introduction of a 2- or 7-MeO group on the naphthalene ring and the lengthening (Et, Pr) of the alkylamido chain gave potent compounds such as (-)1h (K(i)=24pM). The functional activity of these compounds was evaluated by the aggregation of melanophores in Xenopus laevis tadpoles. The potency to produce lightening of the skin of Xenopus laevis was related to the affinities values of the molecules at melatonin chicken brain receptors. The most potent ligands were found to be full agonists and compound 1h was 25 fold more potent than melatonin in this bioassay. Copyright (C) 1999 Elsevier Science Ltd.

Full text of DOI:10.1016/S0968-0896(99)00236-9

Bioorganic & Medicinal Chemistry 7 (1999) 2945±2952
Synthesis of ꢀ-Substituted Naphth-1-yl Ethylamido
Derivatives as New Melatoninergic Agonists
Monique Mathe-Allainmat, Marie Le Gall, Carole Jellimann,
Jean Andrieux and Michel Langlois*
Â
Â
CNRS-BIOCIS (UPRES A 8076), Universite de Paris-Sud, Faculte de Pharmacie, 5 rue J. B.
Â
Clement, 92296, Chatenay-Malabry, France
Ã
Received 15 September 1998; accepted 2 August 1999
AbstractÐNaphthalene melatoninergic ligands with alkyl groups (Me, Et, Pr, Bz) in the b position of the ethylamido chain were
synthesised. The anity of the compounds for chicken brain melatonin receptors was evaluated using 2-[125I]-iodomelatonin as the
radioligand. An increase in the anity was observed with the b-methyl derivatives and the greatest increase was seen with the ( )
enantiomers. The introduction of a 2- or 7-MeO group on the naphthalene ring and the lengthening (Et, Pr) of the alkylamido chain
gave potent compounds such as ( )1h (Ki=24 pM). The functional activity of these compounds was evaluated by the aggregation
of melanophores in Xenopus laevis tadpoles. The potency to produce lightening of the skin of Xenopus laevis was related to the
anities values of the molecules at melatonin chicken brain receptors. The most potent ligands were found to be full agonists and
compound 1h was 25 fold more potent than melatonin in this bioassay. # 1999 Elsevier Science Ltd. All rights reserved.
Introduction
mimicking or antagonising the response to melato-
nin.12,13 In particular, naphthalene derivatives were
designed as bioisosteric melatonin compounds14 and
several of these, such as agomelatine (S 20098), were
claimed to control circadian rhythm disorders.15 Naph-
thalene melatoninergic ligands were structurally char-
acterised by the position of the methoxy group which
can occupy the melatonin-like position 7 or be located
in the ortho position of the ethylamido chain.16
Melatonin (N-acetyl-5-methoxytryptamine) is the verte-
brate pineal gland hormone secreted during darkness.1
It is now well recognised that it regulates the circadian
rhythm2 in a large number of animals and in man. It can
be used to control diseases associated with circadian
rhythm disorders.3 Melatonin alleviates jet-lag, reg-
ulates delayed sleep phase syndrome4 and induces
sleep.5 Conversely, it has been implicated in seasonal
and winter depression.6 Melatonin controls the breeding
cycle in photoperiodic species and can be used to induce
reproduction outside of the breeding season.7 Melato-
nin has also been reported to have antiproliferative
e€ects on mammary cell lines.8
To date, few data on the in¯uence of substitution of the
ethylamido ¯exible chain have been reported: the unfa-
vourable e€ect of the a-methyl group was noted in the
naphthalene16 and indole17 derivatives, while an
increase in anti-ovulatory activity with regard to mela-
tonin was demonstrated with b-methyl 6-chloro-
melatonin and a marked anity for melatonin receptors
was demonstrated with the b-methyl 2-phenyl-
tryptamine derivatives.18 We report herein the results of
preliminary structure±activity relationship studies on
the in¯uence of b-alkyl substitution and the corre-
sponding chirality on the ethyl chain of the naphthalene
melatonergic derivatives 1, 10 and 11 which were eval-
uated by their anity for chicken brain melatonin
receptors and compared to the reference compounds,
melatonin and agomelatine (S 20098). Their functional
activity on melatonin receptors was evaluated by exam-
ining the potency of the compounds to lighten the skin
It has been demonstrated that a number of the e€ects of
melatonin are mediated through G protein-coupled
receptors9 which have been cloned10 and coupling to
one of the Gi family of G-proteins appears to be the
common signalling pathway for the receptors char-
acterised to date.11 Recently, considerable interest has
evolved in the search for new molecules capable of
Key words: Melatonin; receptors; N-(2-methyl-2-(7-methoxy-naphth-
1-yl)ethyl) butyramide; melanophore; agonist.
* Corresponding author. Tel.: +33-1-4-683-5738; fax: +33-1-4683-
5740; e-mail: michel.langois@cep.u.psud.fr
0968-0896/99/$ - see front matter # 1999 Elsevier Science Ltd. All rights reserved.
PII: S0968-0896(99)00236-9

Â
M. Mathe-Allainmat et al. / Bioorg. Med. Chem. 7 (1999) 2945±2952
2946
of Xenopus laevis tadpoles as it has been clearly demon-
strated that melatonin mediates the aggregation of
melanophores.19,20 The degree of the dispersion of mela-
nophores on the head and dorsal surface of the tadpoles
observed under a microscope can be assessed using the
melanophore index scale (1±5) of Hogben and Slome21
and a concentration±e€ect curve (5 concentrations) can be
plotted. The potency of each compound was expressed as
the EC50 melatonin/EC50 compound ratio evaluated in
the same experiment.
methyl ethylacetamido chain was introduced into the 2-
pyrrolidone ring, were synthesised. Compound 10 was
prepared by the double alkylation of 2 (Ar=naphth-1-yl)
with methyl iodide. Compound 11a±b were synthesised
Table 1. Biological data of compounds 1,10 and 11 for chicken brain
melatonin receptors and Xenopus laevis melanophores
Compound
R1
R2 R3
aKi (nM)
bXenopus
melanophores,c
potency with
regard to
melatonin (=1)
1a
(‹)1b
(‹)1b
H
H
H
H
H
H
H
H
Me
321[290-370]
73[30-175]
>1000
dNT
einactive
dNT
einactive
einactive
0.005(100%)
dNT
Me Me
Me Me
Me Me
Et Me
n-Pr Me
Bz Me
(
)1b
32[18-55]
1c
1d
1e
1f
1g
130[82-206]
96[64-147]
>1000
0.16[0.12-0.22]
0.25 [0.16-0.38]
7-MeO Me Me
7-MeO Me Et
7-MeO Me n-Pr 0.032 [0.021-0.047]
7-MeO Me n-Pr 0.13 [0.055-0.31]
7-MeO Me n-Pr 0.024 [0.011-0.042]
7-MeO
2-MeO
2-MeO Me Me
8 (100%)
25 (100%)
26 (100%)
dNT
(‹)1h
(+)1h
(
)1h
dNT
dNT
1i
1j
1k
10
11a
11b
H
H
n-Pr 0.146[0.10-0.211]
Me
2.68 [2-4.2]
1.23 [0.95-1.6]
29[24-34]
0.4 (100%)
0.4 (100%)
einactive
dNT
Chemistry
>1000
>1000
dNT
Agomelatine
Melatonin
0.53 [0.41-0.67]
0.67 [0.41-0.67]
0.8 (100%)
1 (100%)
The compounds were synthesised according to the che-
mical pathway described in Scheme 1. Cyano derivatives
4a±c were prepared (method A) by the reaction of Tos-
MIC with the ketones 3a±c in DME in the presence of t-
BuOK while compounds 4d, 5a and 6a were prepared
by the alkylation of the corresponding cyano derivative
2 with methyl iodide or benzyl bromide in the presence
of NaH in DMF at room temperature (method B). The
monosubstituted cyano derivatives were isolated with
moderate to good yields. Compounds 4a±d, 5a and 6a
were reduced to the amines 7a±d, 8a, 9a by hydrogen at
atmospheric pressure in the presence of Raney nickel in
EtOH. The amines were acylated by the anhydride
method (method C) or by the reaction of acyl chloride
(method D) in the presence of Et3N according to the
processes already reported16 to provide the compounds 1
(Table 1). For the purpose of comparison, the b,b0-dime-
thyl derivative 10 and compounds 11a±b where the b-
a
2-[125I]-iodomelatonin was used as the radioligand and the binding
assays were carried out using membranes prepared from chicken
brain. Non-speci®c binding was de®ned with 10 mM 2-iodomelatonin
in melatonin and represented about 10% of the total binding. Ki
values are expressed in nM and were calculated using the Cheng-
Prussof equation from the IC50 values (PRISM software package),
95% limits are in brackets.
b
Xenopus laevis tadpoles were placed in groups of 5 in 100 mL bea-
kers. The compounds under test (5 concentrations) were dissolved in a
®nal volume of 5 mL and added to the beaker. The degree of the mel-
anophore response was determined by examination of the head and
body surface using the melanophore index scale (1±5) of Hogben and
Slome (reference 20). EC50 values were determined using PRISM and
are the result of 2 separate experiments.
c
The potency of the molecules was calculated as the EC50 melatonin/
EC50 compound ratio determined in the same experiment. % repre-
sents the percentage of the maximum e€ect observed with regard to
that of melatonin (100%).
d
Not tested.
Scheme 1. (a) MeI or BzBr, HNa, DMF, r.t., 1 h; (b) TosMIC, t-BuOK, DME, r.t.; (c) H2, r.t., Raney Ni; (d) Ac2O, AcONa, H2O or R3COCl,
Et3N, CH2Cl2, r.t.

Â
M. Mathe-Allainmat et al. / Bioorg. Med. Chem. 7 (1999) 2945±2952
2947
according to the process already described for the 2-
pyrrolidones.19,20 Nitriles 2 (Ar=naphth-1-yl or 7-
methoxy-naphth-1-yl) were alkylated with ethyl bro-
moacetate and then reduced with hydrogen in the pre-
sence of Raney nickel and aqueous ammoniac to give
compounds 11a and 11b respectively. The di€erent inter-
mediates were characterised by their NMR spectra and
thin layer chromatography. The new compounds 1, 10
and 11 were characterised by NMR spectra and micro-
analysis. The (+) and ( ) enantiomers of compounds 1b
and 1h were isolated by semi-preparative enantiomeric
HPLC separation using the CHIROS-BOND22,23 col-
umn, containing a chiral stationary phase made with b-
cyclodextrin linked to functionalised silica. Enantiomeric
separation was achieved using a hexane/AcOEt/EtOH
mobile phase. The enantiomers, obtained with a high
enantiomeric purity (>99%), were characterised by their
optical rotations: 1b (aD=+45ꢀ and aD= 45ꢀ, c=0.2 in
MeOH) and 1h (aD=+60ꢀ and aD= 50ꢀ, c=0.3 in
MeOH).
ethyl and propyl groups, respectively. They were potent
melatonin receptor ligands. In particular, ( ) 1h was
one of the most potent compounds (Ki ˆ 24 pM with
regard to a Ki ˆ 146 pM for the corresponding unsub-
stituted compound 1i) synthesised by us.
The results obtained with the enantiomers of 1b and 1h
indicated that they could not be correlated with the clas-
sical eudismic-anity analysis rules because the enantio-
selectivity of melatonin receptors was more marked for 1b
than for the very potent compound, 1h. This point was
supported by the high enantiomeric purity of (+) 1h
which was not contaminated with the ( ) enantiomer
(<0.1%). However, these results con®rmed the enantio-
selectivity of the melatonin receptor already observed for
the partially constrained tricyclic indoles with a b chiral
center.25,26 On the other hand, the anity of the b,b0-
dimethyl derivative 10 (Ki ˆ 29 nM), which was equipo-
tent to ( ) 1b was unexpected. It was important to evalu-
ate the selectivity of the molecules for the cloned human
receptors mt1 and MT2. Preliminary results indicated that
the compounds were not selective for the receptors
expressed in HEK 293 cells27 (1f, IC50=0.053 and
0.23nM; 1b, IC50=7.4 and 4.1 nM for mt1 and MT2
receptors, respectively).
Results and Discussion
The anity (Ki) of compounds 1, 10 and 11 for chicken
brain melatonin receptors was evaluated in binding
assays using 2-[125I]-iodomelatonin according to the
method already described.16 This assay was not pre-
dictive for the selectivity of the compounds as all mela-
The compounds 1f, 1g, (‹) 1h, ( )1h, 1k with high a-
nity for chicken brain melatonin receptors were char-
acterised as potent full agonists (Table 1) in the X. laevis
melanophore assay and the potency of the compounds as
agonists was correlated to their anity for melatonin
receptors. It is worth noting that 1g and 1h were 25-fold
more potent than melatonin. These data indicate that the
introduction of the b-methyl substitution on the ethyl
amido chain does not in¯uence the activation process of
the receptor by the agonists, thus 1f and 1k were practi-
cally equipotent to agomelatine and to the 2-methoxy
analogue 1j. As has been shown previously, the lack of the
7-methoxy group brought about an important decrease in
the ecacy, EC50 values could not be determined for (‹)
1b, ( )1b, 1c and 10, at 1 mM concentration, no activity on
the lightening of the skin of X. laevis can be observed. In
summary, the data reported here have shown that, in
contrast to a substitution, introduction of b-methyl sub-
stitution on the ethylamido chain is a favourable steric
parameter for recognition by melatonin receptors. In
addition, the pharmacological pro®le of the compounds
was not modi®ed as several melatonin receptor full ago-
nists, equipotent to the unsubstituted compounds were
obtained.
24
tonin receptors subtypes, mt1, MT2 and Mel1C are
present in the chicken brain. The compounds were
evaluated as agonists by the aggregation of the melano-
phores of X. laevis and the potency was expressed with
regard to that of melatonin (=1).
The results (Table 1) demonstrated, ®rst, that the intro-
duction of marked steric constraints in the ethylaceta-
mido chain, as in compounds 11a and 11b, was not
favourable because these compounds were inactive.
These data also indicate that the cis orientation of the
amide group was probably unfavourable for the ®t with
the binding site of the melatonin receptor. On the other
hand, the presence of a methyl group (compound 1b) in
the b position of the ethylacetamido chain of 1a
(Ki ˆ 321 nM) produced a clear increase in the anity
for melatonin receptors. The ( ) enantiomer of 1b was
one order of magnitude more potent (Ki ˆ 32 nM),
while the e€ect of the ethyl and propyl substituents
(compounds 1c and 1d) seemed to be less marked
(Ki ˆ 130 and Ki ˆ 96 nM for the racemic mixtures,
respectively). However, the introduction of a benzyl
group at this position (compound 1e) greatly reduced
the anity, indicating the limits of the favourable in¯u-
ence of steric factors in this domain of the receptor. b-
Methyl substitution of the potent melatoninergic naph-
thalene compound, agomelatine (S 20098) and the cor-
responding 2-methoxy derivative 1j gave compounds 1f
and 1k (Ki ˆ 0:16 nM and Ki ˆ 1:23 nM, respectively).
Their anities were similar to those of the parent com-
pounds, but with a small improvement for the b-methyl
substituted compounds. This point was con®rmed with
the derivatives 1g (R3=Et) and 1h (R3=n-Pr) which
resulted from the lengthening of the amido chain by
Experimental
Melting points were determined on a KOFLER 7841
1
apparatus and are uncorrected. H and 13C NMR spec-
tra were recorded on a BRUCKER AC 200 or an AM
400 spectrometer with tetramethylsilane as the internal
standard. Chemical shifts are reported in parts per mil-
1
lion (ppm) in d units. H NMR multiplicity data are
denoted by s (singlet), d (doublet), dd (doublet of
doublets), t (triplet), q (quadruplet), m (multiplet) and
br (broad). Coupling constants are in Hertz. TLC was

Â
M. Mathe-Allainmat et al. / Bioorg. Med. Chem. 7 (1999) 2945±2952
2948
1
performed on Silica Gel 60 F254 (Merck) with detection
by UV light. Preparative chromatography was performed
at atmospheric pressure with SDS Chromagel Silica 60,
70±200 mesh. All solvents and reagents were reagent grade
unless otherwise noted. Elemental analyses were per-
formed at the CNRS microanalysis service in Chatenay-
Malabry (France). Starting materials and reactants were
purchased from Aldrich-Chimie (Strasbourg). (Naphth-1-
yl) ethylketone (3b) and (naphth-1-yl) propylketone (3c)
were synthesised in methylene chloride according to the
Friedel±Craft reaction.28 The following cyano compounds
2: 2-(naphth-1-yl) acetonitrile, 2-(2-methoxy-naphth-1-
yl) acetonitrile and 2-(7-methoxy-naphth-1-yl) acetoni-
trile were synthesised according to the process reported
elsewhere.14,16 N-(2-(naphth-1-yl)ethyl) acetamide 1a, N-
(2-(7-methoxy-naphth-1-yl)ethyl) butyramide 1i, N-(2-
(2-methoxy-naphth-1-yl) ethyl) acetamide 1j were syn-
thesised according to the methods already reported.14,16
obtained as an oil (yield: 35%). H NMR (200MHz,
CDCl3): d 7.91 (d, 1H, Har), 7.89 (d, 1H, Har), 7.83 (d, 1H,
Har), 7.69 (d, 1H, Har), 7.6±7.56 (m, 2H, Har), 7.48 (t, 1H,
Har), 4.55 (t, 1H, CH), 1.99 (m, 2H, CH2CH), 1.69 (m, 2H,
CH2CH3), 1.03 (t, 3H, CH3); 13C NMR (200MHz,
CDCl3): d 133.83 (C10), 132.12 (C1), 129.81 (C9), 129.15
(C4), 128.69 (C5), 126.68 (C2), 125.91 (C7), 125.63 (C6),
125.30 (C3), 121.95 (C8), 121.91 (CN), 36.59 (CH), 34.0
(CH2CH), 20.57 (CH2CH3), 13.30 (CH3).
Method B
2-(Naphth-1-yl)-3-phenyl propionitrile (4d). A solution of
2-(naphth-1-yl)acetonitrile (3 g, 18mmol) in 25mL of
DMF was added dropwise to a 60% suspension of NaH
in oil (0.65 g, 21.6 mmol). The mixture was stirred for
30min at room temperature, benzyl bromide (2.4 mL,
18mmol) in DMF was slowly added and the mixture was
stirred for 1 h. The organic solution was poured into
200 mL cold water and the mixture was extracted with
methylene chloride. The organic solution was dried over
MgSO4 and the solvent was evaporated under reduced
pressure. The compound was puri®ed by column chro-
matography (silica gel) and eluted with ether, 4 g of 4d
were obtained as an oil (yield: 86%). 1H NMR (200MHz,
CDCl3): d 7.9±7 (m, 12H, Har), 4.65 (q, 1H, CH), 3.2 (m,
2H, CH2); 13C NMR (200MHz, CDCl3): d 136.78, 134.21,
130.57, 130.39, 130.03, 129.63, 128.89, 127.67, 127.23,
126.33, 126.13, 125.62, 122.09 (16 Car), 120.80 (CN), 41.02
(CH2), 37.04 (CH).
Synthesis of 2-(naphth-1-yl) alkylnitriles 4a±d, 5, 6.
Method A
2-(Naphth-1-yl) propionitrile (4a). A solution of ace-
naphtone (1g, 5.58 mmol) and TosMIC (2.29 g,
11.75 mmol) in 25 mL of 1,2-dimethoxy ethane (DME)
was stirred at 0ꢀC under nitrogen and a t-BuOK (1.65 g,
14.7 mmol) suspension in t-BuOH (14 mL) was added
dropwise. The mixture was stirred for 15min at 0ꢀC and
then for 20h at room temperature under nitrogen. The
solution was ®ltered and the organic solution was washed
successively with a AcOH:H2O mixture (4:100), water and
a saturated NaHCO3 solution. The organic solution was
dried over MgSO4 and the solvent was removed under
2-(7-Methoxy-naphth-1-yl) propionitrile (5a). It was syn-
thesised according to the previous process from (7-meth-
oxy-naphth-1-yl) acetonitrile (2g, 10.15 mmol), methyl
iodide (1.44 mL, 10.15 mmol) and a 60% suspension of
NaH (0.49 g, 12.18 mmol) in oil. It was puri®ed by column
chromatography (silica gel) and eluted with Et2O. The
compound was isolated as a colorless oil (1.8g, yield:
84%) which crystallised slowly, mp: 70±72 C. H NMR
(200MHz, CDCl3): d 7.78 (t+d, 2H, Har), 7.63 (d, 1H,
Har), 7.37 (d, 1H, Har), 7.25±7.18 (t+s, 2H, Har), 4.54 (q,
1H, CH), 3.95 (s, 3H, OCH3), 1.79 (d, 3H, CH3).
reduced pressure. The crude material was distilled (Eb0.01
:
110ꢀC) to give 0.87g (yield: 82%) of nitrile 4a as an oil. 1H
NMR (200MHz, CDCl3): d 7.96±7.83 (m, 3H, Har), 7.71
(d, 1H, Har), 7.64±7.46 (m, 3H, Har), 4.63 (q, 1H, CH),
1.79 (d, 3H, CH3); 13C NMR (200MHz, CDCl3): d
134.98, 133.64, 130.77 (C10, C9, C1), 130.28, 129.91 (C5,
C4), 127.90, 127.09, 126.53, 125.66 (C8, C7, C6, C3), 123.05
(C2), 122.78 (CN), 29.21 (CH), 21.54 (CH3).
ꢀ
1
2-(Naphth-1-yl) butyronitrile (4b). It was synthesised
according to the previous method from (naphth-1-yl)
ethylketone 3b (1.84g, 10mmol), TosMIC (3.9 g,
20mmol) and t-BuOK (3 g, 26mmol). The compound was
puri®ed by column chromatography (silica gel) and eluted
with Et2O:petroleum ether (10:90). 0.66g of 4b was
2-(2-Methoxy-naphth-1-yl) propionitrile (6a). It was syn-
thesised according to the previous process from (2-meth-
oxy-naphth-1-yl) acetonitrile (1 g, 5.07mmol), methyl
iodide (0.875 g, 6.08mmol) and a 60% suspension of NaH
(0.245 g, 6.08mmol) in oil. It was puri®ed by column chro-
matography (silica gel) and eluted with an Et2O:petroleum
ether mixture (20:80) and was isolated as a white amor-
1
obtained as an oil (yield: 35%). H NMR (200MHz,
CDCl3): d 7.91 (d, 1H, Har), 7.89 (d, 1H, Har), 7.84 (d, 1H,
Har), 7.68 (d, 1H, Har), 7.6±7.57 (m, 2H, Har), 7.48 (t, 1H,
Har), 4.51 (dd, 1H, CH), 2.08 (m, 2H, CH2), 1.17 (t, 3H,
CH3); 13C NMR (200MHz, CDCl3): d 133.80 (C10),
132.15 (C1), 129.85 (C9), 129.17 (C4), 128.75 (C5), 126.69
(C2), 125.92 (C7), 125.44 (C6), 125.27 (C3), 121.95 (C8),
120.83 (CN), 35.79 (CH), 27.92 (CH2), 11.69 (CH3).
1
phous product (0.65g, yield: 61%). H NMR (200 MHz,
CDCl3): d 8.09 (d, 1H, Har), 7.84 (2d, 2H, Har), 7.58 (t, 1H,
Har), 7.40 (t, 1H, Har), 7.28 (d, 1H, Har), 4.95 (q, 1H, CH),
3.97 (s, 3H, OCH3), 1.73 (d, 3H, CH3); 13C NMR
(200 MHz, CDCl3): d 154.29, 134.19, 130.46, 129.53,
129.22, 127.39, 123.86, 122.28 (8C, Car), 117.52 (CN),
113.46, 103.39 (2C, Car), 56.70 (OCH3), 21.80 (CH), 18.62
(CH3).
2-(Naphth-1-yl) valeronitrile (4c). It was synthesised
according to the previous method from (naphth-1-yl)
propylketone 3c (1.98 g, 10 mmol), TosMIC (3.9 g,
20mmol) and t-BuOK (3g, 26mmol). The compound was
puri®ed by column chromatography (silica gel) eluting
with Et2O:petroleum ether (10:90). 0.76g of 4c was
Synthesis of the arylalkylamines 7a±d, 8a, 9a, 2-(naphth-
1-yl) propanamine, HCl (7a). 2-(naphth-1-yl) propioni-
trile 4a (0.5 g, 2.76 mmol) was dissolved in 10 mL of
EtOH with 0.1 mL of aqueous ammoniac (20%) in the

Â
M. Mathe-Allainmat et al. / Bioorg. Med. Chem. 7 (1999) 2945±2952
2949
presence of Raney nickel (100 mg). The suspension was
Synthesis of the alkylamido derivatives 1b±h, 1k, 10.
Method C
stirred under hydrogen at atmospheric pressure for 20 h at
40ꢀC. The solution was ®ltered on Celite and the solvent
was evaporated under reduced pressure. The crude mate-
rial was dissolved in diethyl ether and an anhydrous HCl
diethyl ether solution was added. The hydrochloride salt
formed was collected by ®ltration and dried in vacuo,
0.37 g of 7a was obtained as a white powder (yield: 72%).
1H NMR (200MHz, CD3OD): d 8.12 (d, 1H, Har), 7.85±
7.72 (m, 2H, Har), 7.55±7.40 (m, 4H, Har) 4.03±3.93 (m, 1H,
CH), 3.37±3.13 (m, 2H, NCH2), 1.42 (d, 3H, CH3); 13C
NMR (200 MHz, CD3OD): d 139.26, 135.81, 132.77 (3Car,
C10-C9-C1), 130.30, 129.02, 127.68, 126.98, 126.84, 124.21,
123.60 (7Car, C2-C3-C4-C5-C6-C7-C8), 46.45 (CH2), 33.61
(CH), 19.76 (CH3).
N-(2-methyl-2-(naphth-1-yl)ethyl) acetamide (1b). To a
stirred solution of the hydrochloride salt of the corre-
sponding amine 7a (0.26 g, 1.17 mmol) in water (15 mL)
were added successively AcONa (1.4g, 17.03mmol) and
acetic anhydride (2.7mL, 28.62mmol). After these addi-
tions, the reaction mixture was stirred at room temperature
for 30 min. The amide was extracted from water with
CH2Cl2 (3Â20mL) The organic solution was successively
washed with a saturated NaHCO3 solution and water. The
organic extract was dried over MgSO4 and evaporated in
vacuo. The crude product was puri®ed by column chro-
matography (silica gel) and eluted with a CH2Cl2:MeOH
(98:2) mixture to give 0.25 g of a solid, mp: 105ꢀC (yield:
1
2-(Naphth-1-yl) butanamine (7b). The compound (0.2 g,
yield: 67%) was synthesised according to the previous
process from 2-(naphth-1-yl)-butyronitrile 4b (0.29 g,
1.5 mmol), it was puri®ed by column chromatography
(neutral aluminum oxyde) and eluted with a CH2Cl2:
MeOH mixture (98:2) and isolated as the amine.1H NMR
(200MHz, CDCl3): d 8.05 (dd, 1H, Har), 7.75 (dd, 1H,
Har), 7.6 (d, 1H, Har), 7.45±7.30 (m, 3H, Har), 7.22 (dd, 1H,
Har), 3.55±3.4 (m, 1H, CH), 2.92±2.85 (dd, 2H, CH2), 2.2
(brs, 2H, NH2), 1.88±1.49 (m, 2H, CH2), 0.72 (t, 3H, CH3).
80%). H NMR (200MHz, CDCl3): d 8.09 (d, 1H, Har),
7.79 (dd, 1H, Har), 7.67 (d, 1H, Har), 7.5±7.3 (m, 4H, Har),
4.30 (brs, 1H, NH), 3.89±3.75 (m, 1H, CH), 3.67±3.37 (m,
2H, CH2), 1.76 (s, 3H, COCH3), 1.33 (d, 3H, CH3CH); 13
C
NMR (200MHz, CDCl3): d 170.24 (CO), 140.18, 134.06,
132.06, 129, 127.19, 126.22, 125.70, 125.64, 123.14, 122.68
(10C, Car), 45.98 (NCH2), 33.67 (CH), 23.32 (COCH3),
19.33 (CH3CH). Anal. (C15H17NO+1/3 H2O); calc.
C.77.22, H 7.63, N 6.00; F. C 77.59, H 7.63, N 6.00.
Method D
2-(Naphth-1-yl) pentanamine, HCl (7c). The compound
(0.459g, yield: 60%) was synthesised according to the
previous process described for 7a (0.76 g, 3.4 mmol).1H
NMR (200MHz, CD3OD): d 8.2 (d, 1H, Har), 7.90 (d, 1H,
Har), 7.88 (d, 1H, Har), 7.57±7.45 (m, 4H, Har) 3.83 (m,
1H, CH), 3.31 (d, 2H, NCH2), 1.84 (m, 2H, CHCH2), 1.16
(m, 2H, CH3CH2), 0.84 (t, 3H, CH3).
N-(2-ethyl-2-(naphth-1-yl)ethyl) acetamide (1c). To a stirred
solution of the amine 7b (0.26 g, 1.3 mmol) in anhydrous
CH2Cl2 (10 mL) under an Ar atmosphere and at 0ꢀC were
added dropwise Et3N (0.27 mL, 1.95 mmol) and then acetyl
chloride (0.11 mL, 1.56 mmol). After these additions, the
reaction mixture was stirred for 30 min. The mixture was
poured into water (20 mL) and extracted with CH2Cl2
(3Â20 mL). The combined organic extracts were dried over
MgSO4 and the solvent was evaporated under reduced
pressure. The compound was puri®ed by column chroma-
tography (silica gel) and eluted with a CH2Cl2: MeOH
(98:2) mixture to give a white solid, mp: 88±89ꢀC (yield:
3-Phenyl-2-(naphth-1-yl) propanamine, HCl (7d). The
compound (1.32g, yield: 82%) was synthesised according
to the previous process described for 7a (1.65 g,
6.05mmol).1H NMR (200MHz, CD3OD): d 8.11 (d, 1H,
Har), 7.99±7.79 (2d, 2H, 2Har), 7.64±7.48 (m, 4H, Har),
1.22 (brs, 5H, Har), 4.42±4.24 (m, 1H, CH), 3.52±3.29 (m,
2H, CH2), 3.12 (d, 2H, CH2).
1
64%). H NMR (200 MHz, CDCl3): d 8.06 (m, 1H, Har),
7.80 (m, 1H, Har), 7.67 (d, 1H, Har), 7.45±7.31 (m, 4H, Har),
5.15 (brs, 1H, NH), 3.84±3.75 (m, 1H, NCH2), 3.71±3.58
(m, 1H, CH), 3.38±3.25 (m, 1H, NCH2), 1.84±1.49 (m, 2H,
CH2CH3), 1.69 (s, 3H, COCH3), 0.78 (t, 3H, CH3CH2).
Anal. (C16H19NO); calc. C.79.63, H 7.93, N 5.80; F. C
79.45, H 7.96, N 5.78.
2-(7-Methoxy-naphth-1-yl) propanamine (8a). The amine
(0.3 g, yield: 33%) was synthesised according to the pre-
vious process described for 7a from 2-(7-methoxy-naphth-
1-yl) propionitrile 5a (0.9 g, 4.26mmol). 1H NMR
(200MHz, CDCl3): d 7.7 (d, 1H, Har), 7.65 (m, 1H, Har),
7.45 (s, 1H, Har), 7.32 (d+t, 2H, Har), 7.15 (dd, 1H, Har),
3.95 (s, 3H, OCH3), 3.6 (q, 1H, CH), 3.05 (m, 2H, NCH2),
1.4 (d+s, 5H, CH3 et NH2); 13C NMR (200MHz,
CDCl3): d 157.88, 139.64, 133.21, 130.6, 126.59, 123.43,
123.31, 117.88, 102.2, (10Car), 55.44 (OCH3), 48.57 (CH2),
37.47 (CH), 19.23 (CH3).
N-(2-propyl-2-(naphth-1-yl)ethyl) acetamide (1d). It was
synthesised according to the previous process from the amine
7c (0.14 g, 0.65 mmol), Et3N (0.1 mL, 0.65 mmol) and acetyl
chloride (0.065 mL, 0.65 mmol). The compound was isolated
as an amorphous compound (0.14 g, yield: 84%). 1H NMR
(200 MHz, CDCl3): d 8.13 (m, 1H, Har), 7.86 (m, 1H, Har),
7.75 (d, 1H, Har), 7.56±7.25 (m, 4H, Har), 5.21 (brs, 1H, NH),
3.92±3.75 (m, 2H, CH et NCH2), 3.41±3.32 (m, 1H, NCH2),
1.81±1.63 (m, 2H, CH2), 1.71 (s, 3H, COCH3), 1.33±1.16 (m,
2H, CH2), 0.85 (t, 3H, CH3CH2). Anal. (C17H21NO); calc.
C.79.96, H 8.29, N 5.48; F. C 79.74, H 8.32, N 5.41.
2-(2-Methoxy-naphth-1-yl) propanamine, HCl (9a). The
compound (0.37 g, yield: 55%) was synthesised accord-
ing to the process described for 7a from 2-(2-methoxy-
naphth-1-yl) propionitrile 6a (0.78 g, 3.69 mmol). 1H
NMR (200 MHz, CD3OD): d 7.99 (d, 1H, Har), 7.76
(2d, 2H, 2Har), 7.46±7.22 (m, 3H, 3Har), 4.10±3.85 (m,
1H, CH), 3.85 (s, 3H, CH3), 3.55±3.33 (m, 2H, CH2N),
1.39 (d, 3H, CH3).
N-(3-phenyl-2-(naphth-1-yl)propyl) acetamide (1e). It
was synthesised according to the process described for
compound 1c from the amine 7d (0.22 g, 0.85 mmol),

Â
M. Mathe-Allainmat et al. / Bioorg. Med. Chem. 7 (1999) 2945±2952
2950
Et3N (0.118mL, 0.85mmol) and acetyl chloride
(0.060mL, 0.85mmol). The compound was isolated as an
amorphous compound (0.19 g, yield: 75%). 1H NMR
(200MHz, CDCl3): d 8.13 (m, 1H, Har), 7.86 (m, 1H, Har),
7.75 (d, 1H, Har), 7.56±7.39 (m, 4H, Har), 7.25±7.09 (m,
5H, Har), 5.15 (brs, 1H, NH), 4.14±4.03 (m, 1H, CH),
3.85±3.72 (m, 1H, NCH2), 3.63±3.42 (m, 1H, NCH2),
3.19±2.98 (m, 2H, PhCH2), 1.71 (s, 3H, COCH3). Anal.
(C21H21NO); calc. C.83.13, H 6.97, N 4.61; F. C 81.19, H
7.27, N 4.30.
2.3 mmol). The compound was recrystallised in a CH2Cl2:
diisopropyl ether mixture to give a solid, mp: 136±138ꢀC
(0.27 g, yield: 40%). 1H NMR (200MHz, CDCl3): d 8.07
(d, 1H, Har), 7.80±7.36 (2d, 2H, 2Har), 7.46 (td, 1H, Har),
7.32 (td, 1H, Har), 7.26 (d, 1H, Har), 5.54 (brs, 1H, NH),
4.03±3.82 (m, 2H, CH et CH2), 3.93 (s, 3H, OCH3), 3.69±
3.56 (m, 1H, CH2), 1.75 (s, 3H, COCH3), 1.44 (d, 3H,
CH3). Anal. (C16H19NO2); calc. C.74.68, H 7.44, N 5.44;
F. C 74.74, H 7.61, N 5.34.
N-(2,2-Dimethyl-2-(naphth-1-yl)ethyl) acetamide (10). 2-
(Naphth-1-yl)-2-methyl-propionitrile was synthesised
according to method B from (naphth-1-yl) acetonitrile
(3 g, 18mmol), methyl iodide (2.24 mL, 36mmol) and a
60% suspension of NaH (1.43 g, 36mmol) in oil. It was
puri®ed by column chromatography (silica gel) and eluted
with an Et2O:petroleum ether mixture (20:80). The com-
N-(2-methyl-2-(7-methoxy-naphth-1-yl)ethyl) acetamide (1f).
It was synthesised according to the process described for
compound 1c from the amine 8a (0.230g, 1.06mmol),
Et3N (0.166mL, 1.2 mmol) and acetyl chloride (0.085 mL,
1.2 mmol). The compound was puri®ed by column chro-
matography (silica gel) and eluted with CH2Cl2:MeOH
(98:2) and crystallised in a CH2Cl2:diisopropyl ether mix-
ture to give a solid, mp: 83±85ꢀC (0.11 g, yield: 40%). 1H
NMR (200MHz, CDCl3): d 7.76 (d, 1H, Har), 7.68 (dd,
1H, Har), 7.53 (sd, 1H, Har), 7.38±7.26 (m, 2H, Har), 7.17
(dd, 1H, Har), 5.49 (brs, 1H, NH), 3.98 (s, 3H, OCH3),
3.94±3.77 (m, 1H, CHCH2), 3.66±3.43 (m, 2H, CHCH2),
1.87 (s, 3H, COCH3), 1.41 (d, 3H, CH3). Anal.
(C16H19NO2); calc. C.74.68, H 7.44, N 5.44; F. C 74.54, H
7.49, N 5.46.
1
pound was isolated as a clear oil (yield: 78%). H NMR
(200MHz, CDCl3): d 8.55 (d, 1H, Har), 7.92 (d, 1H, Har),
7.84 (dd, 1H, Har), 7.64±7.40 (m, 4H, Har), 3.2 (s, 6H,
2CH3). The previous compound (1.5 g) was reduced to 2-
(naphth-1-yl)-2-methyl propanamine, HCl (1.4g, yield:
77%) according to the process used for the preparation of
7a.1H NMR (200MHz, CD3OD): d 8.28 (d, 1H, Har), 7.85
(dd, 1H, Har), 7.65 (d, 1H, Har), 7.5±7.35 (m, 4H, Har),
3.58 (s, 2H, NCH2), 1.60 (s, 6H, 2ÂCH3); 13C NMR
(200MHz, CD3OD): d 139.26, 135.81, 132.77 (3C, Car),
130.30, 129.02, 127.68, 126.98, 126.84, 124.21, 123.60 (7C,
Car), 46.45 (CH2), 33.61 (CH), 19.76 (CH3). 10 was syn-
thesised according to the method D from the previous free
amine (0.3 g, 1.5 mmol), Et3N (0.25 mL, 1.8 mmol) and
acetyl chloride (0.128mL, 1.8 mmol). The compound was
puri®ed by column chromatography (silica gel) and eluted
with CH2Cl2:MeOH (98:2) and crystallised in a CH2Cl2:
diisopropyl ether mixture to give a solid, mp: 138±140ꢀC
(0.12 g, yield: 33%). 1H NMR (200MHz, CDCl3): d 8.44
(m, 1H, Har), 7.89 (m, 1H, Har), 7.76 (d, 1H, Har), 7.55±
7.38 (m, 4H, Har), 5.06 (brs, 1H, NH), 3.92 (d, 2H,
NCH2), 1.83 (s, 3H, COCH3), 1.62 (s, 6H, 2ÂCH3). Anal.
(C16H19NO); calc. C.79.63, H 7.9, N 5.8; F. C 79.47, H
7.92, N 5.74.
N-(2-methyl-2-(7-methoxy-naphth-1-yl)ethyl) propionamide
(1g). It was synthesised according to the process descri-
bed for compound 1c from the amine 8a (0.435g,
2.4 mmol), Et3N (0.33 mL, 2.4 mmol) and propionyl
chloride (0.206mL, 2.4 mmol). The compound was pur-
i®ed by column chromatography (silica gel) and eluted
with a CH2Cl2:MeOH mixture (98:2) and crystallised in
diisopropyl ether to give a solid, mp: 98±100ꢀC (0.3 g,
yield: 55%). 1H NMR (200 MHz, CDCl3): d 7.76 (d, 1H,
Har), 7.67 (dd, 1H, Har), 7.51 (sd, 1H, Har), 7.35±7.25 (m,
2H, Har), 7.15 (dd, 1H, Har), 5.38 (brs, 1H, NH), 3.97 (s,
3H, OCH3), 3.87±3.84 (m, 1H, CHCH2), 3.56 (t, 2H,
NCH2), 2.06 (q, 2H, COCH2), 1.40 (d, 3H, CH3); 1.03 (t,
3H, CH3CH2). Anal. (C17H21NO2); calc. C.75.24, H 7.80,
N 5.16; F. C 74.54, H 7.97, N 5.11.
4-(Naphth-1-yl) 2-pyrrolidone (11a). 2 g of a 60% sus-
pension of NaH (50 mmol) in oil was dissolved in 75 mL of
THF and the mixture was stirred at room temperature
under an argon atmosphere. 1-Naphthylacetonitrile (7.5 g,
45mmol) were added and the mixture was heated at 50ꢀC
for 1 h under an argon atmosphere. 9 g of methyl bro-
moacetate was added dropwise at 0ꢀC and the mixture
was re¯uxed for 1 h. The solution was poured onto ice and
extracted twice with ether. The organic layers were washed
with water and dried over Na2SO4. The organic solvent
was evaporated under reduced pressure to give an oil
which was puri®ed by column chromatography (silica gel,
cyclohexane:Et2O, 40:60) to give 7.8 g (yield: 72%) of
methyl 3-cyano-3-(naphth-1-yl) propionate. 1H NMR
(200MHz, CDCl3): d 7.95±7.40 (7H, Har), 5.03 (m, 1H,
CH), 3.75 (s, 3H, OCH3), 3.04 (m, 2H, CH2). 4.8 g
(20 mmol) of the previous compound were dissolved in a
mixture of EtOH (100 mL) and a concentrated solution of
NH4OH (6mL), then 0.5 g of Raney nickel was added.
The mixture was stirred with H2 under atmospheric pres-
sure at 45ꢀC for 48 h. The catalyst was ®ltered and the
N-(2-methyl-2-(7-methoxy-naphth-1-yl)ethyl) butyramide
(1h). It was synthesised according to the process descri-
bed for compound 1c from the amine 8a (0.347g,
1.6 mmol), Et3N (0.127 mL, 1.92 mmol) and butyryl chlo-
ride (1.92mmol). The compound was puri®ed by column
chromatography (silica gel) and eluted with a CH2Cl2:
MeOH mixture (98:2) and crystallised in diisopropyl ether
to give a solid, mp: 68±70ꢀC (0.23 g, yield: 50%). 1H NMR
(200MHz, CDCl3): d 7.75 (d, 1H, Har), 7.67 (dd, 1H, Har),
7.52 (sd, 1H, Har), 7.35±7.25 (m, 2H, Har), 7.16 (dd, 1H,
Har), 5.45 (brs, 1H, NH), 3.97 (s, 3H, OCH3), 3.90±3.79
(m, 1H, CHCH2), 3.61±3.51 (m, 2H, NCH2), 2.02 (t, 2H,
COCH2), 1.60±1.39 (m, 2H, CH2CH3); 1.40 (d, 3H,
CH3CH), 0.85 (t, 3H, CH3CH2). Anal. (C18H23NO2);
calc. C.75.75, H 8.12, N 4.90; F. C 75.91, H 8.29, N 4.91.
N-(2-methyl-2-(2-methoxy-naphth-1-yl)ethyl) acetamide (1j).
It was synthesised according to the process described for
compound 1c from the amine 9a (0.420g, 1.93mmol),
Et3N (0.32 mL, 2.3 mmol) and acetyl chloride (0.16 mL,

Â
M. Mathe-Allainmat et al. / Bioorg. Med. Chem. 7 (1999) 2945±2952
2951
solvent was evaporated. The crude product was puri®ed
by column chromatography (silica gel, CH2Cl2) and was
crystallised with a CH2Cl2:Et2O mixture to give a white
solid, mp: 134±135ꢀC (3.3 g, yield: 78%). 1H NMR
(200 MHz, CDCl3): d: 8.20±7.40 (m, 7H, Har), 6.80 (s,
1H, NH), 5.50 (m, 1H, CH), 3.60±3.95 (m, 2H, CH2),
2.80 (m, 2H, COCH2). Anal. (C14H13NO); calc. C.79.58,
H 6.22, N 6.63; F. C 79.42, H 6.41, N 6.51.
centrifugation (44 000 g, 25 min, 4ꢀC). The resulting
pellet was resuspended in 10 volumes of the same bu€er
to a ®nal concentration of 5 or 6 mg protein/mL. The
membrane aliquots (30 mL) were incubated in a total
volume of 0.25 ml Tris±HCl bu€er (50 mM, pH 7.4)
with 0.05 nM 2-[125I]iodomelatonin and seven con-
centrations of the compound under test. Each binding
assay was performed in triplicate. The incubation (25ꢀC,
60 min) was stopped by the addition of 3 mL of ice-cold
bu€er and immediate vacuum ®ltration through glass
®bre ®lters (GF/B Whatman strips) presoaked in 0.1%
poly(ethyleneimine) using a Brandel cell harvester. The
®lters were washed (3Â4 mL) with bu€er, dried, and
counted on a g-counter (Crystal±Packard). Non-speci®c
binding was de®ned with 10 mM melatonin and repre-
sented 10% of the total binding. Ki values are expressed
and were calculated using the Cheng-Prussof equation
from the corresponding IC50 values using PRISM pro-
gram.
4-(7-Methoxy-naphth-1-yl) 2-pyrrolidone (11b). The com-
pound was prepared according to the process described
for 11a: 2-(7-methoxy-naphth-1-yl) acetonitrile gave
methyl 3-cyano-3-(7-methoxy-naphth-1-yl) propionate
which was crystallised as a white solid, mp: 116ꢀC (yield:
67%). 1H NMR (200MHz, CDCl3): d 7.90±7.10 (m, 6H,
Har), 4.90 (m, 1H, CH), 3.90 (s, 3H, OCH3), 3.70 (s, 3H,
OCH3), 3.05 (m, 2H, CH2). Anal. (C16H15NO3); calc.
C.71.36, H 5.62, N 5.20, F. C 71.35, H 5.68, N 5.15. This
compound was reduced with hydrogen and Raney nickel
according to the previous process used for the preparation
of compound 11a. Compound 11b was obtained as a
white solid, mp: 146±147ꢀC (yield: 82%). 1H NMR
(200MHz, CDCl3): d 7.85±7.15 (m, 6H, Har), 6.85 (s, 1H,
NH), 4.30 (m, 1H, CH), 3.95 (s, 3H, OCH3), 3.58±3.97 (m,
2H, CH2), 2.80 (m, 2H, COCH2). Anal. (C15H15NO2);
calc. C.74.66, H 6.27, N 5.81; F. C 74.44, H 6.42, N 5.83.
Melanophore contraction in X. laevis tadpoles
The X. laevis tadpoles (stage 41) used in this study were
obtained from the Laboratoire de Biologie Cellulaire et
Reproduction CNRS (Rennes, France). They were
maintained in an aquarium in the laboratory at 22ꢀC
under natural illumination for 8 days and fed daily with
powdered ®sh food. Prior to the bioassay, tadpoles of
uniform stage, size, and colour, were selected, removed
from the aquarium, and placed in groups of 5 in 100 mL
beakers placed on a dark background and ®lled with
45 mL of pool water, 18 h before the experiments. They
were lit with arti®cial light (60 W) for 3 h before the
experiments which were performed at midday. The
compound under test was dissolved in a DMF and
water mixture in a ®nal volume of 5 mL and added to
the liquid in the beaker (45 mL) to achieve the ®nal
selected concentration. After 15 min, the experiment
was terminated by the addition of a 37% formaldehyde
solution. The degree of the melanophore response in
each tadpole was determined by examination of the
melanophore con®guration under a microscope (Leitz,
magni®cation Â4) and evaluated according to the mel-
anophore index scale (1±5) of Hogben and Slome.21 The
data are the results of the sum of the determinations of
the melanophore index on the body and the dorsal sur-
face of the tadpole. EC50 values for the compounds
were determined from the concentration-e€ect curve
obtained with 5 concentrations in the range of 0.1 to
100ÂKi values for chicken brain receptors. The mean of
the control data (animals with vehicle) represented
100%. Variations in the EC50 values of melatonin (1±
10 nM, n=10) and the reference compounds were
observed between batches of tadpoles at di€erent times
of the year. Consequently the potency of the molecule
was calculated as the ratio between the EC50 melatonin/
EC50 compound ratio determined in the same experi-
ment.
Separation of the enantiomers of N-(2-methyl-2-(naphth-
1-yl)ethyl) acetamide (1b) and N-(2-methyl-2-(7-meth-
oxy-naphth-1-yl)ethyl) butyramide (1h). A direct chro-
matographic method using a semipreparative chiral
HPLC column (CHIROS-BOND C1) 10mm 250Â
10mm (Chiralsep; Parc d'activites de la Boissiere-La Fre-
naye-76170 France) gave the pure enantiomers of 1b and
1h. The conditions for the semi-preparative separations
were estimated by analytical runs on an analytical chiral
HPLC CHIROSE BOND C1 column (5mm 250Â
4.5 mm). A 150 mL loop was used to introduce samples.
The concentrations chosen varied between 10 and 20mg/
mL in a mixture depending on the resolution of the com-
pound. The mobile phase consisted of a hexane:AcOEt:
EtOH mixture (90:9:2) which was degassed by sonica-
tion. The solvent delivery system was a Varian 5000
HPLC pump set at a ¯ow rate of 4 mL/min. Detection
at 254 nm was carried out using a Varian 2050 tuneable
absorbance detector. The chromatograms were regis-
tered with a Varian 4270 integrator. The enantiomers of
1b and 1h were separated on a milligram scale and their
purity was controlled by analytical HPLC (>99%).
Optical rotations ad were measured on a Polartronic
C-Schimdt-Haensch for each enantiomer at 589 nm.
They were uncorrected. (+) 1b: aD=+45ꢀ (c=0.2,
MeOH); ( ) 1b: aD= 45ꢀ (c=0.2, MeOH); (+) 1h:
aD=+60ꢀ (c=0.3, MeOH); ( ) 1h: aD= 50ꢀ (c=0.3,
MeOH).
Melatonin receptor binding assay
Chickens (Red Brook, male or female, 4 months (3±
4 Kg); Cellubio, France) were decapitated at 12 p.m.
The brains were quickly removed and stored at 80ꢀC.
They were homogenised (Polytron) in 10 vol of ice-cold
Tris±HCl bu€er (50 mM, pH 7.4) and washed twice by
Acknowledgements
We are grateful to ADIR for ®nancial support.

Â
M. Mathe-Allainmat et al. / Bioorg. Med. Chem. 7 (1999) 2945±2952
2952
References
15. Mason, R.; Delagrange, P.; Guardiola, B. Br. J. Pharma-
col. 1993, 108, 32P.
1. Reiter, R. J. Endocrinol. Rev. 1991, 12, 151.
2. Klein, D. C.; Roseboom, P. H.; Coon, S. L. TEM 1996, 7,
106.
16. Langlois, M.; Bremont, B.; Shen, S.; Poncet, A.; Andrieux,
J.; Sicsic, S.; Serraz, I.; Mathe-Allainmat, M.; Renard, P.;
Delagrange, P. J. Med. Chem. 1995, 38, 2050.
3. Arendt, J.; Deacon, S. Chronobiol. Int. 1997, 14, 185.
4. Arendt, J.; Deacon, S.; English, J.; Hampton, S.; Morgan,
L. J. Sleep Res. 1995, 4, 74.
5. Wirz-Justice, A.; Amstrong, S. M. J. Sleep Res. 1996, 5, 137.
6. Blehar, M. C.; Lewy, A. J. Psychopharmacol. Bull. 1990, 4,
465.
7. Reiter, R. J. Endocrinol. Rev. 1980, 1, 109.
8. Ying, S-W.; Niles, L. P.; Crocker, C. Eur. J. Pharmacol.-
Mol. Pharmacol. Section, 1993, 246, 89.
9. Stankov, B.; Fraschini, F.; Reiter, R. J. Brain. Res. Rev.
1991, 16, 245.
10. Reppert, S. M.; Weaver, D. R.; Godson, C. TIPS 1996, 17,
100.
11. Morgan, P. J.; Barrett, P.; Hazlerigg, D.; Milligan, G.;
Lawson, W.; MacLean, A.; Davidson, G. J. Neuroendocrinol.
1995, 7, 361.
12. Mahle, C. D.; Takaki, K. S.; Watson, A. J. In: Annual
Reports in Medicinal Chemistry; Bristol J.A., Ed.; Academic
Press: London, 1997; vol. 32, pp. 31.
13. Mathe-Allainmat, M.; Andrieux, J.; Langlois, M. Exp.
Opin. Ther. Patents 1997, 7, 1447.
17. Frohn, M. A.; Seaborn, C. J.; Johnson, D. W. Life Sci.
1980, 27, 2043.
18. Eli Lilly and Co, EP-655243-A (1995); Garratt, P. J.; Jones,
R.; Tocher, D. A.; Sugden, D. J. Med. Chem. 1995, 38, 1132.
19. Rollag, M. D. Pineal Res. Rev. 1988, 6, 67.
20. Sudgen, D.Br. J. Pharmacol. 1991, 104, 922.
21. Hogben, L.; Slome, D. Proc. R. Soc. (London), Ser B
1931, 108, 10.
22. Langlois, M.; Maillard, J. Bull. Soc. Chim. 1971, 2976.
23. CHIRALSEP (76170, La Fresnaye, France).
24. Dubocovich, M. L.; Cardinali, D. P.; Guardiola-Lemaitre,
B.; Hagan, R. M.; Krause, D. N.; Yocca, F. D.; Vanhoutte, P.
M. In The IUPHAR Compendium of Receptor Characteriza-
tion and Classi®cation, Girdlestone, D., Ed; IUPHAR Media:
London, 1998, 187.
25. Sugden, D.; Davies, D. J.; Garratt, P. J.; Jones, R.;
Vonho€, S. Eur. J. Pharmacol. 1995, 287, 239.
26. Davies, D. J.; Garratt, P. J.; Tocher, D. A.; Vonho€, S.;
Davies, J.; Teh, M-T.; Sudgen, D. J. Med. Chem. 1998, 41, 451.
27. Conway, S.; Drew, E. J.; Canning, S. J.; Barett, P.;
Jockers, R.; Strosberg, A. D.; Guardiola-Lemaitre, B.;
Delagrange, Ph.; Morgan, P. J. FEB Lett. 1997, 407, 121.
28. Vogel's Textbook of Practical Organic Chemistry, 5th ed.,
Furniss, B.S.; Hannaford, A.J.; Smith, P.W.G.; Tatchell, A.R.,
Eds.; Langman Scienti®c and Technical: Harlow, UK, p. 1006.
14. Depreux, P.; Lesieur, D.; Mansour, H. A.; Morgan, P.;
Howell, H. E.; Renard, P.; Caignard, D. H.; Pfei€er, B.;
Delagrange, P.; Guardiola, B.; Yous, S.; Demarque, A.;
Adam, G.; Andrieux, J. J. Med. Chem. 1994, 37, 3231.