Structure-activity relationships in platelet-activating factor. Part 14: Synthesis and biological evaluation of piperazine derivatives with dual anti-PAF and anti-HIV-1 activity

Article abstract of DOI:10.1016/j.bmc.2006.07.043

As HIV-associated dementia prevalence has risen with the lifespan of HIV-infected individuals, there is an important need for antiretroviral and anti-inflammatory drugs targeting the central nervous system. Platelet-activating factor, a mediator of inflam

Full text of DOI:10.1016/j.bmc.2006.07.043

Bioorganic & Medicinal Chemistry 14 (2006) 7999–8013
Structure–activity relationships in platelet-activating factor.
Part 14: Synthesis and biological evaluation of piperazine
derivatives with dual anti-PAF and anti-HIV-1 activity
Wafa Sallem,a Nawal Serradji,a,* Nathalie Dereuddre-Bosquet,b Georges Dive,c
Pascal Clayetteb and Franc¸oise Heymansa
a
`
Unite´ de Recherche Pharmacochimie Mole´culaire et Systemes Membranaires (EA 2381),
Laboratoire de Pharmacochimie Mole´culaire, Universite´ Paris 7 – Denis Diderot, case 7066,
2 Place Jussieu, 75251 Paris Cedex 05, France
bSPI-BIO, CEA, DSV/DRM, 18 route du Panorama, BP 6, 92265 Fontenay aux Roses Cedex, France
c
` ˆ ˆ
Centre d’Inge´nierie des Prote´ines, Institut de Chimie, Universite´ de Liege, Batiment B6, Allee du 6 Aout,
13 Sart Tilman, 4000 Liege, Belgium
´
`
Received 26 June 2006; revised 20 July 2006; accepted 24 July 2006
Abstract—As HIV-associated dementia prevalence has risen with the lifespan of HIV-infected individuals, there is an important
need for antiretroviral and anti-inflammatory drugs targeting the central nervous system. Platelet-activating factor, a mediator
of inflammation, is an HIV-induced neurotoxin secreted in the infected brain. In this work, we developed piperazine derivatives
bearing a heterocyclic moiety as PAF-antagonists and HIV-1 replication inhibitors with micromolar potency.
Ó 2006 Elsevier Ltd. All rights reserved.
1. Introduction
less severe form of CNS dysfunction which does not al-
ways progress to HAD, becomes more frequent10,11 and
probably results from a weak penetration of the antiret-
roviral drugs into the CNS12 allowing a low-level viral
replication and a progressive neurodegeneration. The
pathogenesis of HAD may result from the secretion of
neurotoxins by mononuclear phagocytes (MPs) (peri-
vascular and brain macrophages and microglia) after
HIV-1 infection, stimulation by viral proteins and
immune activation.11,13 Platelet-activating factor
(PAF), a phospholipid inflammatory mediator, is pro-
duced in response to the viral infection and activation
of MPs and has been identified as an HIV-1-induced
neurotoxin.14,15 Indeed, HIV-1 production is up-regulat-
ed by TNF-a in infected macrophages, and PAF, in
turn, appears to increase TNF-a synthesis in HIV-in-
fected cells of monocytic lineage.16,17 High levels of
PAF are detected in cerebrospinal fluids (CSF) of pa-
tients with neurologic dysfunctions and correlated with
the degree of neurological impairments. Moreover,
when added at concentrations close to those found in
CSF of HIV-infected patients, PAF produces a dose-de-
pendent neurotoxicity, inhibited by NMDA antagonists
MK-801 and memantine.14 The neurotoxicity induced
by HIV-1-infected macrophages can be prevented by
The infection of central nervous system (CNS) by hu-
man immunodeficiency virus-1 (HIV-1) occurs early
after the systemic infection.1,2 Mild to severe neurologi-
cal complications as a consequence of this infection are
known as HIV-associated dementia (HAD) or acquired
immunodeficiency syndrome (AIDS) dementia complex
(ADC) and were observed in about 30% of adults and
half of children with AIDS before the use of highly ac-
tive antiretroviral therapy (HAART) in the developed
world.3,4 HAART has played an important role in
declining the incidence of neurological complications
in AIDS patients (approximately 10% now)5,6 but these
neurological impairments still occur not only in untreat-
ed but in treated individuals as well and HAD preva-
lence has risen with HIV-infected individual’s lifespan
as they live longer.7–9 Moreover, with the use of
HAART, minor cognitive motor disorder (MCMD), a
Keywords: Piperazine; Anti-PAF; Anti-HIV-1; AIDS dementia
complex.
*
Corresponding author. Tel.: +33 1 4427 5594; fax: +33 1 4427
5641; e-mail: serradji@paris7.jussieu.fr
0968-0896/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2006.07.043

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W. Sallem et al. / Bioorg. Med. Chem. 14 (2006) 7999–8013
CH3O
CH3O
OCH3 CH3O
OCH3
OCH3
SO2CH3
oxyphenyl groups of PMS 601 by an indole moiety
HN
found in Delavirdine and to evaluate the influence of
this modification on both biological activities. We
described here the structure–activity relationship trig-
gered around this heterocyclic moiety by (i) varying
the nature of the linker between this ring and the
piperazine and its position on the indole group; (ii)
introducing an electron-donating or -withdrawing group
on C5-indole; (iii) incorporating other heterocyclic units;
(iv) methylating the indole nitrogen. Moreover, the
second trimethoxybenzoyl substituent of PMS 601 was
replaced by a benzyl or a 3,4,5-trimethoxybenzyl group
since a previous study showed that compounds with a
benzylic moiety exhibit higher antiviral activities than
our reference compound.20 All compounds were tested
in vitro to evaluate their anti-PAF and anti-HIV-1
activities. The 3D electrostatic potential maps of certain
compounds were also calculated to understand their
anti-PAF activity.
HN
N
N
O
O
N
H
O
N
N
CH2OCNEt2
N
O
I
II
Figure 1. PMS 601 (I) and Delavirdine (II) structures.
PAF–acetylhydrolase (PAF–AH), the main enzyme
responsible for PAF catabolism, or WEB 2086, a PAF
receptor antagonist.15 Taking together, these results sug-
gest that PAF plays an important role in the HIV-1-in-
duced neurologic dysfunctions. These findings prompted
us to evaluate, in a previous work, the antiviral activity
of several PAF-antagonists and led us to the discovery
of a lead compound, PMS 601 (Fig. 1), a trisubstituted
piperazine with both a PAF-antagonism (IC50 = 8 lM)
and anti-HIV-1 effects (IC50 = 11 lM).18 All the modifi-
cations undertaken in order to improve its dual activity
have been realized by either replacing the carbamate
group of PMS 601 by other functions19 or introducing
an aromatic group on one or both nitrogens of the
piperazine ring.20 Those studies showed that more po-
tent compounds than PMS 601 can be obtained and de-
note the absence of correlation between both anti-PAF
and anti-HIV activities. Moreover, PMS 601 and Dela-
virdine (RescriptorÒ, Fig. 1), a nonnucleoside reverse
transcriptase inhibitor, are both piperazine derivatives
carrying aryl groups as nitrogen substituents. This
observation prompted us to replace one of both trimeth-
2. Results and discussion
2.1. Chemistry
In Scheme 1, the monoacylated piperazines 1 and 2 were
prepared according to the previously published proce-
dures.20 Coupling 1 and 2 with commercial heterocyclic
acid (HetCOOH), in the presence of DCC or DIC, led to
the heteroarylamide piperazine derivatives 3a–j and
4a–f. The N-methylation of 3a and 4a using iodome-
thane and K2CO3 in acetonitrile gave 3k and 4k, respec-
tively. The compounds 6a,b were obtained, as outlined
a
OCH3
OCH3
OCH3
O
C
X N N Y
CH2OCN(Et)2
X N N Y
TMB :
CH2OCN(Et)2
O
O
Het: heterocycle
3a-j: X=TMB ; Y=Het
4a-f: X=Het ; Y=TMB
1: X=TMB ; Y=H
2: X=H ; Y=TMB
b
3k, 4k
O
Cl
c:
a:
b:
g:
d:
e:
N
N
H
N
H
S
N
H
O
O
O
H
O
O
CH3O
Het =
f:
j:
i:
h:
O
N
H
N
N
N
H
O
O
O
H
O
O
k:
N
CH3
Scheme 1. Reagents and conditions: (a) HetCOOH, DCC or DIC, HOBT, CH2Cl2, reflux; (b) CH3I, K2CO3, CH3CN, reflux.
O2N
O2N
6a, X= TMB, Y =
a
C
O
N
X N N Y
CH2OCN(Et)2
H
COOH
O2N
N
H
6b, X=
,
Y= TMB
5
6a-b
O
C
O
N
H
Scheme 2. Reagents: (a) i—SOCl2, CH2Cl2; ii—1 or 2, Et3N, CH2Cl2.

W. Sallem et al. / Bioorg. Med. Chem. 14 (2006) 7999–8013
8001
in Scheme 2, from the acyl chloride of 5-nitro-1H-in-
dole-2-carboxylic acid 5,21 prepared in situ using thionyl
chloride, and the piperazine derivatives 1 and 2, respec-
tively. The compound 8 was synthesized, as shown in
Scheme 3, by reaction of the amine 1 with 7.22 Treat-
ment of 923 with DIC led to indole-1-carboxylic anhy-
dride which was coupled directly to the amine 1 to
provide 10 (Scheme 4). The synthetic route to obtain
the derivatives 16a,b, 17a,b and 18 is detailed in Scheme
5. The condensation of 1120 with 1H-indole-2-carboxylic
acid led to 12 which was deprotected into 13 using triflu-
oroacetic acid (TFA) in MeOH. The monosubstitution
of 1424 using 1H-indole-2-carboxylic acid and DCC
led to 15. The compounds 16a,b, 17a,b and 18 were
obtained using a reductive amination process from the
piperazines 13, 15 and 2, respectively, and the corre-
sponding aldehyde in dichloromethane or dichloroeth-
ane (DCE).
one hand and to inhibit the viral replication in MDM
in vitro infected with the reference macrophage-tropic
HIV-1/Ba-L strain on the other hand.18–20 All the results
obtained are listed in Tables 1–3. Our initial synthetic ef-
forts focused on determining the influence of the hetero-
cyclic substitution position on the dual activity.
2.2.1. Anti-HIV activity (Tables 1–3). The anti-HIV tar-
get of this piperazinic series of compounds remains
undefined.18 In this new set of experiments, PMS 601
and all the new compounds were tested according to
the previously published procedures.18 The replacement
of a 3,4,5-trimethoxylphenyl moiety of PMS 601 by an
indole as in 3a (Table 1) leads to an activity close to
the reference compound one. As a general trend for
the results listed in Table 1, no real improvement of
the antiviral activity is obtained when either the position
of the carbonyl function on the indole group (3a,b, and
10) or the nature of the linker between this heterocycle
and the piperazine ring (3i,j, 8) is modified. The nature
of the introduced heterocycle (3c,d,g,h) or the electron
donating or -withdrawing effects of the group on the
C5-indole (3e,f, 6a) do not increase this activity as well.
Nevertheless, a loss of activity is observed when the in-
dole is replaced by another heterocyclic ring as benzofu-
rane (3g), benzothiophene (3c), pyrrole (3d) and
quinoleine (3h) or when it is N-methylated (3k) suggest-
ing that this heterocycle found in Delavirdine induces
this activity. The comparison of Tables 1 and 2, where
are listed the results obtained with the position analogs
of the compounds listed in Table 1, shows that whatever
2.2. Anti-PAF and anti-HIV effects
All final compounds were tested for their ability to
antagonize PAF-induced platelet aggregation on the
O
CH3O
CH3O
CH3O
O
Cl
O
C N
a
O
N
N
O
N
H
H
7
8
CH2OCN(Et)2
O
Scheme 3. Reagents: (a) 1, Et3N, CH2Cl2.
CH3O
O
O
O
O
a
b
CH3O
CH3O
C N N C N
N C O C N
N
COOH
9
CH2OCN(Et)2
10
O
Scheme 4. Reagents: (a) DIC, CH2Cl2; (b) 1, CH2Cl2.
O
O
a
b
(Ph)3C N N C
HN N C
(Ph)3C N NH
N
H
N
H
CH2OCN(Et)2
O
CH2OCN(Et)2
13
CH2OCN(Et)2
O
12
11
O
O
a
, 2HCl
C N NH
HN NH
N
H
CH2OCN(Et)2
15
O
CH2OCN(Et)2
O
14
c
2, 13 or 15
X N N Y
CH2OCN(Et)2
O
16a : X= PhCH2-
16b : X= 3,4,5-(MeO)3C6H2CH2-
Y=
X=
N
O
O
H
17a : Y= PhCH2-
17b : Y= 3,4,5-(MeO)3C6H2CH2-
N
H
Y= TMB
18: X=
N
H
Scheme 5. Reagents and condition: (a) 1H-indole-2-carboxylic acid, DCC, CH2Cl2, reflux; (b) TFA, MeOH; (c) PhCHO, 3,4,5-(MeO)3C6H2CHO or
indole-3-carboxaldehyde, NaBH(OAc)3, CH2Cl2 or DCE.

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W. Sallem et al. / Bioorg. Med. Chem. 14 (2006) 7999–8013
Table 1. In vitro anti-PAF and anti-HIV-1 activities of heterocyclic derivatives at the N1-position of the piperazine
CH3O
O
O
CH3O
CH3O
C N N C Ar
CH2OCN(Et)2
O
Compound
Ar
Anti-PAF IC50 (lM)
Anti-HIV (lM)
Toxicity (lM)
ED50
32
ED70
ED90
480
CH3O
CH3O
CH3O
PMS 601
8
90
>500
500
3a
3b
3c
3d
3e
3f
3g
3h
3i
1
18.8
4.5
58
54
>100
140
82
N
H
24
17
>500
500
N
H
0.13
2.97
0.28
0.57
0.5
67
S
ꢀ15 33%a
>50
100
N
H
Cl
7.3
6
13
>20
100
210
N
H
CH3O
20
500
N
H
97
130
36 9%a
42
>500
>50
>500
500
O
0.92
0.27
0.95
25.50
0.34
0.11
0.56
N
28
25
58
78
72
N
H
3j
38
N
H
3k
6a
8
100
—
>100
500
N
CH3
O2N
50b
N
H
O
17
>100
19
>100
>20
500
N
H
N
10
5.9
100
a % of inhibition of viral replication at 50 lM.
b 53 7% of toxicity at 50 lM.
be the position (1 or 4) of the heterocyclic moiety on the
piperazine ring, the same range of activity is obtained
(3a–f, 6a and 3k vs 4a–f, 6b and 4k, respectively). A pre-
vious work underlined the positive effects of the intro-
duction of a benzyl or a 3,4,5-trimethoxybenzyl group
instead of a 3,4,5-trimethoxybenzoyl moiety on the
antiviral activity (Table 3, compounds A and B).20 To
see whether this observation was available in the hetero-
cyclic series, we synthesized the compounds listed in
Table 3. All bear an indole and a benzyl or a 3,4,

W. Sallem et al. / Bioorg. Med. Chem. 14 (2006) 7999–8013
8003
Table 2. In vitro anti-PAF and anti-HIV-1 activities of heterocyclic derivatives at the N4-position of the piperazine
OCH3
O
Ar N N C
OCH3
OCH3
CH2OCN(Et)2
O
Compound
Ar
Anti-PAF IC50 (lM)
Anti-HIV (lM)
Toxicity (lM)
ED50
ED70
ED90
49
4a
4b
4c
4d
4e
4f
0.47
5
13
23.5
500
500
0
N
H
O
O
O
6.5
16.1
75
N
H
0.13
1.32
0.11
0.017
1
15 17a
S
4
8.3
56
64
—
—
23a
0
N
H
O
Cl
2.3
>20
100
100
500
500
50b
50c
N
O
H
CH3O
37
N
O
H
4k
6b
18
19
>100
N
O
CH3
O2N
0.10
306
N
O
H
N
H
a % of inhibition of viral replication at 50 lM.
b 55 6% of toxicity at 50 lM.
c 89 2% of toxicity at 50 lM.
5-trimethoxybenzyl group on the piperazine. All the
compounds are either inactive (3d, 4c–d), weakly active
(3h) or cytotoxic (6a,b, 16a,b, 17a,b, 18) at the first dose
tested, that is, 50 lM, suggesting that the introduction
of a benzyl moiety in this heterocyclic series is not
favourable to the antiviral activity.
with the positive zones of the PAF-R are generated
by, on the one hand, the methoxyl groups and form
˚
the large ‘cache-oreilles’ system (11–14 A) and by the
carbonyl groups of the amide functions on the other
hand and form the short ‘cache-oreilles’ system (6–
24
˚
7 A). Those potentials are determinant to the anti-
PAF activity. In this paper, we determined the 3D elec-
trostatic potential maps (isocontoured at ꢀ20 kcal/mol)
of PMS 601 and some heterocyclic derivatives in order
to explain the anti-PAF activity obtained for those com-
pounds. The PMS 601 3D electrostatic map (Fig. 2) pre-
sents two major ‘cache-oreilles’ systems generated by
both the methoxyl groups, located at a distance of
2.2.2. Anti-PAF activity (Tables 1–3) and molecular
modelling (Fig. 2). In this study, the geometry of the
studied compounds has been fully optimized using the
double basis set 6–31 g.25
In 1991, Batt et al. proposed a model for the PAF-recep-
tor (PAF-R) structure from 3D electrostatic maps of
several structurally unrelated synthetic and natural
PAF-antagonists.26 It would be a multipolarized cylin-
˚
11.34 A, and the carbonyl groups of amides at a distance
˚
of 6.3 A. This result is in harmony with what was previ-
ously established. The results presented in Table 1 show
that the replacement of a 3,4,5-trimethoxyphenyl moiety
of PMS 601 by an indole leads to the same anti-PAF
activity. We can notice that whatever the nature of the sub-
stituent on the C5-indole (3e–f, 6a), the linker between
this heterocycle and the piperazine ring (3i–j, 8), the con-
nection position of the carbonyl to the indole ring and
˚
der with a diameter of 14 A with three couples of posi-
˚
tive areas detected at 14, 10–12 and 6.5–7 A and
would contain two hydrophobic subsites. In 1993,
the calculations of 3D electrostatic maps of 3,4,5-
di(trimethoxybenzoyl)piperazine derivatives revealed
that negative electrostatic potentials able to interact

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W. Sallem et al. / Bioorg. Med. Chem. 14 (2006) 7999–8013
Table 3. In vitro anti-PAF and anti-HIV-1 activities of indole derivatives
Ar1
N
N Ar2
CH2OCN(Et)2
O
Compound
Ar1
Ar2
Anti-PAF IC50 (lM)
Inhibition of viral
replication % at 50 lM
Toxicity %
at 50 lM
CH3O
CH3O
CH3O
CH3O
CH3O
CH3O
Aa
Ba
Ca
Da
3a
2.5
>100
13
75 at 10 lMb
0
0d
0
, HCl
, HCl
2c
, HCl
, HCl
CH3O
CH3O
CH3O
40c
13c
, HCl
O
CH3O
CH3O
CH3O
>100
1
0
, HCl
O
CH3O
CH3O
70
9
0
N
O
O
H
CH3O
CH3O
CH3O
46 28 at 20 lM
93 3 at 100 lMb
4a
0.47
0
N
H
O
O
CH3O
16a
16b
17a
17b
4.54
0.12
157
—
—
—
—
60 16
N
H
O
O
CH3O
CH3O
82
85
67
4
3
1
N
H
CH3O
N
H
O
O
CH3O
CH3O
CH3O
11
N
H
a Serradji et al. (Bioorg. Med. Chem., 2006).
b Not performed at 50 lM not provided.
c ED50
d Toxic at 100 lM.
.
the heterocyclic cycle introduced to replace the indole
moiety (3c–d, g–h), anti-PAF activity remains close to
the micromolar range (except for 3b and 3k).
recovery of the indole ring orientation allowed by this
methylene. Nevertheless, increasing this flexibility with
one more methylene as in 3j (map not provided) does
not improve the anti-PAF potency. The introduction
of a second carbonyl in 8 pronounces the electronegative
well around both carbonyls and then ameliorates the
anti-PAF activity compared to 3b. The introduction of
an electron-donating (chloro in 3e, map not provided,
or methoxy in 3f) or -withdrawing (nitro in 6a, map
not provided) substituent at the C5-position of the
indole enables the formation of a supplementary nega-
tive electrostatic potential around this group, as shown
in 3f map. Coupled to the well formed by the 3,4,5-
trimethoxyphenyl, it could be considered as the large
‘cache-oreilles’ system and would increase the activity
of these compounds. Surprisingly, the compounds 3e,f
and 6a are not more potent than 3a suggesting that
either the potential created is insufficient or is not
The study of 3a electrostatic map shows that only the
short ‘cache-oreilles’ system, generated by both carbonyl
functions carried by the piperazine, is present in this
molecule and seems to be responsible for the activity.
This short system is also found in the compounds 10
(map not provided) and 3b although the latter is less ac-
tive than 3a. Its 3D map reveals that the indole adopts a
different spatial orientation from that observed in 3a,
suggesting an influence of the position of the carbonyl
function on the molecule conformation which can be
considered as a less active conformation in this case.
Interestingly, the insertion of one methylene between
the carbonyl and the indole in 3i confers a micromolar
activity to the compound likely due to the freedom

W. Sallem et al. / Bioorg. Med. Chem. 14 (2006) 7999–8013
8005
PMS 601
3a
3b
3c
3f
3i
4a
3k
8
16a
16b
17b
Figure 2. 3D Electrostatic maps calculated of selected compounds.
˚
located at the proper position, that is, at 10–14 A from
of the carbonyl electrostatic potential through a H-bond
as shown in Fig. 2. In Table 2 are summarized the activ-
ities obtained with the position isomers of several com-
pounds in Table 1 and no significant influence of
isomerization on the PAF-antagonism is observed (ex-
cept for 4b, 4f and 4k). The compound 18, where the
carbonyl of 4b was replaced by a methylene, is inactive
as expected. Indeed, this modification deletes the poten-
tial induced by the carbonyl function and underlines the
necessity of its presence for anti-PAF activity (map not
provided). In Table 3, the replacement of the second tri-
the negative potential of the trimethoxyl groups. The
replacement of the indole moiety by another heterocy-
clic ring (benzofuran in 3g, benzothiophene in 3c, pyr-
role in 3d, and quinoline in 3h) has no or little
influence on the negative electrostatic potential generat-
ed by the carbonyl function as illustrated in the map of
the compound 3c and thus does not greatly improve the
anti-PAF activity of 3a. The weak activity of 3k (IC50 of
25.5 lM) is due neither to an influence of the methyl on
the conformation of the molecule nor to a modification

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W. Sallem et al. / Bioorg. Med. Chem. 14 (2006) 7999–8013
methoxybenzoyl moiety of 3a by a benzyl group as in
17a leads to a loss of activity because of the absence
of a carbonyl function and its associated electrostatic
potential. Surprisingly, its position analogue 16a is
much more active. This difference of behaviour has al-
ready been observed in a previous work with the com-
pounds C and D where a benzyl group is present as
well and should be clarified. The introduction of a
3,4,5-trimethoxybenzyl moiety in 16b and 17b confers
an anti-PAF potency to the molecules. In these com-
pounds, both potentials are generated on the one hand
by the trimethoxyl groups and by the carbonyl on the in-
Curie, Paris, France) and were within 0.4% of theoret-
ical values.
3.1.1. General procedure for the synthesis of 3a–j and
4a–f. To a solution of the amine 1 or 2 in CH2Cl2 were
added the carboxylic acid (1 or 1.2 equiv), the N,N0-dic-
yclohexylcarbodiimide, DCC (1 or 1.2 equiv) or N,N0-
diisopropylcarbodiimide, DIC (1 or 1.2 equiv) and,
with or without 1-hydroxybenzotriazole, HOBT (1 or
1.2 equiv). The mixture was refluxed until the reaction
was complete (TLC monitored). After cooling at room
temperature and filtration, the mixture was washed with
HCl 1 N and water, then with saturated NaHCO3 and
twice with water. The organic layer was dried (MgSO4)
and concentrated in vacuo. The residue was chromato-
graphed on a silica gel column as indicated.
˚
dole on the other hand and are located at 10 and 8 A
from each other in 16b and 17b, respectively. We can
thus assume that a hybrid ‘cache-oreilles’ system can
be identified here as responsible for the anti-PAF
˚
activity. Nevertheless, the distance of 8 A observed in
17b is insufficient to enable a proper interaction of the
molecule with the PAF-R but the activity of this mole-
cule (IC50 of 11 lM) suggests that a distance of
10–12 A must be reached in other conformation than
the one used to realize its 3D electrostatic map.
3.1.2. 2-(N,N-Diethylaminocarbonyloxymethyl)-1-(1H-
indole-2-ylcarbonyl)-4-(3,4,5-trimethoxybenzoyl)pipera-
zine (3a). Compound 3a was prepared using 1H-indole-
2-carboxylic acid (234 mg), DCC (301 mg), HOBT
(197 mg) and 1 (500 mg, 1.22 mmol), and obtained as
a white solid (600 mg, 89%) after a silica gel column
chromatography using MeOH/CH2Cl2 (1:99, v/v) as elu-
ent: Rf 0.36 (MeOH/CH2Cl2, 5:95, v/v); mp 148 °C; IR
(m cmꢀ1) 3380 (NH), 1697 (C@O carbamate), 1636
˚
In conclusion, the 3,4,5-trimethoxyphenyl moiety
found in PMS 601, our reference compound, can be
replaced by an indole without modifying either its
anti-PAF or antiviral activity. The structure–activity
relationships studied around this heterocycle led to
compounds presenting a dual activity at the micromo-
lar potency. The variations of the anti-PAF activity
are in concordance with the PAF-receptor model pre-
viously proposed by our laboratory. The antiviral
mechanism of this series of compounds is still un-
known and the identification of their biological target
is now a priority to greatly improve the antiviral
activity of this piperazine series.
1
(C@O amide), 1585 (ArC@C); H NMR (CDCl3, d):
10.02 (br s, 1H, NH), 7.55 (d, 1H, J = 8 Hz, ArH),
7.35 (d, 1H, J = 8 Hz, ArH), 7.22 (m, 1H, ArH), 7.08
(m, 1H, ArH), 6.80 (s, 1H, ArH), 6.60 (s, 2H, ArH),
5.30–4.90 (m, 1H, CH2OC@O), 4.80–4.30 (m, 3H,
CH2OC@O and piperazine), 4.20–4.00 (m, 2H, pipera-
zine), 3.79 (s, 9H, OCH3), 3.75–2.60 (m, 7H, NCH2CH3
and piperazine), 1.01, 0.98 (2m, 6H, NCH2CH3); 13C
NMR (CDCl3, d): 170.76, 163.34 (C@O amide), 154.97
(C@O carbamate), 153.30, 139.33, 135.95, 130.03,
128.45, 127.13, 124.45, 121.79, 120.46, 111.74, 105.82,
104.23 (ArC@C), 60.84 (CH2O), 60.72, 56.16 (CH3O),
41.74, 41.00 (NCH2CH3), 13.64, 13.14 (NCH2CH3).
Anal. (C29H36O7N4Æ0.33H2O) C, H, N.
3. Experimental
3.1. Materials and methods
3.1.3. 2-(N,N-Diethylaminocarbonyloxymethyl)-1-(1H-
indole-3-ylcarbonyl)-4-(3,4,5-trimethoxybenzoyl)pipera-
zine (3b). Compound 3b was prepared using 1H-indole-
3-carboxylic acid (197 mg), DCC (251 mg), HOBT
(197 mg), 1 (500 mg, 1.22 mmol) and obtained as a white
solid (560 mg, 83%) after a silica gel column chromatog-
raphy using MeOH/CH2Cl2 (1:99, v/v) as eluent: Rf 0.38
All materials were obtained from commercial suppliers
and used without further purification. Thin-layer chro-
matography was performed on TLC plastic sheets of
silica gel 60F254 (layer thickness 0.2 mm) from
Merck. Column chromatography purification was car-
ried out with silica gel 60 (70–230 mesh ASTM,
Merck). All melting points were determined on a dig-
ital melting point apparatus (Electrothermal) and are
uncorrected. The structures of all compounds were
confirmed by IR and NMR spectra. IR spectra were
obtained with a ATI Mattson Genesis Series FTIR
spectrometer, and 1H NMR and 13C NMR spectra
were recorded in CDCl3 or in DMSO-d6 on a BRUC-
KER AC 200 spectrometer using hexamethyldisilox-
ane (HMDS) as an internal standard. Chemical
shifts are given in ppm and peak multiplicities are des-
ignated as follows: s, singlet; d, doublet; dd, doublet
doublet; t, triplet; br s, broad singlet; m, multiplet;
q, quadruplet; sex, sextuplet and sep, septuplet. Ele-
mental analyses were obtained from the ‘Service
(MeOH/CH2Cl2, 5:95, v/v); mp 174 °C; IR (m cmꢀ1
)
3192 (NH), 1698 (C@O carbamate), 1618, 1604 (C@O
1
amide), 1582 (ArC@C); H NMR (CDCl3, d): 9.32 (br
s, 1H, NH), 7.60 (m, 1H, ArH), 7.45 (s, 1H, ArH),
7.32 (m, 1H, ArH), 7.10 (m, 2H, ArH), 6.58 (s, 2H,
ArH), 4.94 (m, 1H, CH2OC@O), 4.44 (m, 2H,
CH2OC@O and piperazine), 4.25–4.00 (m, 2H, pipera-
zine), 3.78 (s, 9H, OCH3), 3.71–2.90 (m, 10H,
NCH2CH3 and piperazine), 1.02–0.81 (m, 6H,
NCH2CH3); 13C NMR (CDCl3, d): 170.97, 167.84
(C@O amide), 155.20 (C@O carbamate), 153.25,
139.24, 135.78, 130.05, 127.77, 125.28, 122.57, 120.96,
119.87, 111.82, 109.68, 104.20 (ArC@C), 60.93
(CH2O), 60.72, 56.13 (CH3O), 41.74, 41.08 (NCH2CH3),
13.65, 13.11 (NCH2CH3). Anal. (C29H36O7N4) C, H, N.
´ ´
Regional de Microanalyse’ (Universite Pierre et Marie

W. Sallem et al. / Bioorg. Med. Chem. 14 (2006) 7999–8013
8007
3.1.4. 1-(Benzothiophene-2-ylcarbonyl)-2-(N,N-diethyla-
minocarbonyloxymethyl)-4-(3,4,5-trimethoxybenzoyl)pi-
perazine (3c). Compound 3c was prepared using
benzothiophene-2-carboxylic acid (261 mg), DCC
(301 mg), HOBT (197 mg), 1 (500 mg, 1.22 mmol)
and obtained as a white solid (400 mg, 57%) after a
silica gel column chromatography using MeOH/
CH2Cl2 (1:99, v/v) as eluent: Rf 0.43 (CH2Cl2/MeOH,
95:5, v/v); mp 105 °C; IR (m cmꢀ1) 3379 (NH), 1698
(C@O carbamate), 1634 (C@O amide), 1585
56.18 (CH3O), 41.77, 40.99 (NCH2CH3), 13.63, 13.14
(NCH2CH3). Anal. (C29H35O7N4Cl) C, H, N.
3.1.7.
2-(N,N-Diethylaminocarbonyloxymethyl)-1-(5-
methoxy-1H-indole-2-ylcarbonyl)-4-(3,4,5-trimethoxy-
benzoyl)piperazine (3f). Compound 3f was prepared
using 5-methoxy-1H-indole-2-carboxylic acid (514 mg),
DCC (510 mg), 1 (850 mg, 2.07 mmol) and obtained as
a white solid (840 mg, 70%) after a silica gel column
chromatography using MeOH/CH2Cl2 (1:99, v/v) as elu-
ent: Rf 0.26 (CH2Cl2/MeOH, 95:5, v/v); mp 174 °C; IR
(m cmꢀ1) 3268 (NH), 1700 (C@O carbamate), 1635
1
(ArC@C); H NMR (CDCl3, d): 7.75 (m, 2H, ArH),
7.46 (s, 1H, ArH), 7.35 (m, 2H, ArH), 6.58 (s, 2H,
ArH), 4.50 (m, 1H, CH2OC@O), 4.60–4.10 (m, 5H,
CH2OC@O and piperazine), 3.81 (s, 9H, OCH3),
3.70-2.60 (m, 7H, NCH2CH3 and piperazine), 0.97
(m, 6H, NCH2CH3); 13C NMR (CDCl3, d): 170.78,
164.57 (C@O amide), 154.99 (C@O carbamate),
153.34, 140.17, 139.39, 138.41, 135.9, 130.03, 125.99,
125.67, 124.86, 124.65, 122.27, 104.23 (ArC@C),
60.76 (CH2OC@O), 60.69, 56.21 (CH3O), 41.81,
41.13 (NCH2CH3), 13.83, 13.25 (NCH2CH3). Anal.
(C29H35O7N3S) C, H, N.
1
(C@O amide), 1596 (ArC@C); H NMR (CDCl3, d):
8.72 (s, 1H, NH), 7.32 (d, 1H, J = 8.8 Hz, ArH), 7.01
(s, 1H, ArH), 6.95 (d, 1H, J = 8.8 Hz, ArH), 6.78 (s,
1H, ArH), 6.65 (s, 2H, ArH), 5.20–3.96 (m, 6H,
CH2OC@O and piperazine), 3.86, 3.81 (2 s, 12H,
OCH3), 3.70–3.01 (m, 7H, NCH2CH3 and piperazine),
1.00, 0.85 (2m, 6H, NCH2CH3); 13C NMR (CDCl3, d):
170.80, 163.26 (C@O amide), 155.00 (C@O carbamate),
154.52, 153.35, 139.40, 131.30, 130.07, 128.90, 127.55,
115.95, 112.64, 105.57, 104.29, 102.09 (ArC@C), 60.88
(CH2OC@O), 60.77, 56.22 (CH3O), 55.58 (CH3O),
41.80, 41.07 (NCH2CH3), 13.70, 13.21 (NCH2CH3).
Anal. (C30H38O8N4) C, H, N.
3.1.5. 1-(Pyrrole-2-ylcarbonyl)-2-(N,N-diethylaminocar-
bonyloxymethyl)-4-(3,4,5-trimethoxybenzoyl)piperazine
(3d). Compound 3d was prepared using pyrrole-2-car-
boxylic acid (325 mg), DCC (482 mg), 1 (800 mg,
1.95 mmol) and obtained as a white solid (450 mg,
52%) after a silica gel column chromatography using
MeOH/CH2Cl2 (1:99, v/v) as eluent: Rf 0.2 (CH2Cl2/
MeOH, 95:5, v/v); mp 86 °C; IR (m cmꢀ1) 3293 (NH),
1694 (C@O carbamate), 1633 (C@O amide), 1585
3.1.8. 1-(Benzofurane-2-ylcarbonyl)-2-(N,N-diethylami-
nocarbonyloxymethyl)-4-(3,4,5-trimethoxybenzoyl)piper-
azine (3g). Compound 3g was prepared using
benzofuran-2-carboxylic acid (197 mg), DCC (251 mg),
HOBT (197 mg), 1 (500 mg, 1.22 mmol) and obtained
as a white solid (450 mg, 67%) after a silica gel column
chromatography using MeOH/CH2Cl2 (1:99, v/v) as elu-
ent: Rf 0.27 (CH2Cl2/MeOH, 95:5, v/v); mp 102 °C; IR
(m cmꢀ1) 2999 (ArCH), 1702 (C@O carbamate), 1618
1
(ArC@C); H NMR (CDCl3, d): 10.07 (br s, 1H, NH),
6.87 (s, 1H, ArH), 6.87–6.55 (m, 3H, ArH), 6.21 (s,
1H, ArH), 5.20–3.98 (m, 6H, CH2OC@O and pipera-
zine), 3.83 (s, 9H, OCH3), 3.83–2.50 (m, 7H, NCH2CH3
and piperazine), 1.00, 0.83 (2m, 6H, NCH2CH3); 13C
NMR (CDCl3, d): 170.75, 162.44 (C@O amide), 154.93
(C@O carbamate), 153.28, 139.29, 130.15 123.73,
121.61, 112.69, 109.54, 104.24 (ArC@C), 60.80
(CH2OC@O), 60.72, 56.17 (CH3O), 41.70, 40.93
(NCH2CH3), 13.59, 13.18 (NCH2CH3). Anal.
(C25H34O7N4Æ0.5H2O) C, H, N.
1
(C@O amide), 1583 (ArC@C); H NMR (CDCl3, d):
7.58 (d, 1H, J = 8 Hz, ArH), 7.44 (d, 1H, J = 8 Hz,
ArH), 7.43, 7.19 (m, 3H, ArH), 6.60 (s, 2H, ArH),
5.06 (m, 1H, CH2OC@O), 4.80, 4.00 (2m, 4H,
CH2OC@O and piperazine), 3.82 (s, 9H, OCH3), 3.59–
2.80 (m, 8H, NCH2CH3 and piperazine), 1.10, 0.91
(2m, 6H, NCH2CH3); 13C NMR (CDCl3, d): 170.74,
160.42 (C@O amide), 154.85 (C@O carbamate),
154.54, 153.33, 148.29, 139.36, 130.06, 126.60, 125.99,
125.67, 124.86, 124.65, 122.27, 104.23 (ArC@C), 60.82
(CH2OC@O), 60.75, 56.20 (CH3O), 41.70, 41.00
(NCH2CH3), 13.69, 13.18 (NCH2CH3). Anal.
(C29H35O8N3) C, H, N.
3.1.6. 1-(5-Chloro-1H-indole-2-ylcarbonyl)-2-(N,N-dieth-
ylaminocarbonyloxymethyl)-4-(3,4,5-trimethoxybenzo-
yl)piperazine (3e). Compound 3e was prepared using
5-chloro-1H-indole-2-carboxylic acid (555 mg), DCC
(602 mg), 1 (1 g, 2.44 mmol) and obtained as a white sol-
id (1 g, 66%) after a silica gel column chromatography
using MeOH/CH2Cl2 (1:99, v/v) as eluent: Rf 0.30
3.1.9. 2-(N,N-Diethylaminocarbonyloxymethyl)-1-(quino-
line-2-ylcarbonyl)-4-(3,4,5- trimethoxybenzoyl)piperazine
(3h). Compound 3h was prepared using quinoline-2-car-
boxylic acid (463 mg), DCC (431 mg), 1 (730 mg,
1.78 mmol) and obtained as a white solid (760 mg,
76%) after a silica gel column chromatography using
MeOH/CH2Cl2 (1:99, v/v) as eluent: Rf 0.32 (CH2Cl2/
MeOH, 95:5, v/v); mp 72 °C; IR (m cmꢀ1) 3270 (NH),
1705 (C@O carbamate), 1635 (C@O amide), 1597
(ArC@C); 1H NMR (CDCl3, d): 8.27 (d, 1H,
J = 8.49 Hz, ArH), 8.06 (d, 1H, J = 8.42 Hz, ArH),
7.86 (d, 1H, J = 8.2 Hz, ArH), 7.78–7.56 (m, 3H,
ArH), 6.63 (s, 2H, ArH), 5.40–4.00 (m, 6H, CH2OC@O
and piperazine), 3.86 (s, 9H, OCH3), 3.71–2.70 (m, 7H,
(CH2Cl2/MeOH, 95:5, v/v); mp 168 °C; IR (m cmꢀ1
)
3263 (NH), 1704 (C@O carbamate), 1634 (C@O amide),
1
1595 (ArC@C); H NMR (CDCl3, d): 9.83 (br s, 1H,
NH), 7.58 (s, 1H, ArH), 7.36 (d, 1H, J = 8.7 Hz,
ArH), 7.22 (d, 1H, J = 8.7 Hz, ArH), 6.80 (s, 1H,
ArH), 6.65 (s, 2H, ArH), 5.10–4.00 (m, 6H, CH2OC@O
and piperazine), 3.86 (s, 9H, OCH3), 3.50–2.80 (m, 7H,
NCH2CH3 and piperazine), 1.07, 0.86 (2m, 6H,
NCH2CH3); 13C NMR (CDCl3, d): 170.77, 162.80 (C@O
amide), 155.00 (C@O carbamate), 153.32, 139.43, 134.13,
129.90, 129.76, 128.09, 126.09, 125.01, 120.98, 112.78,
105.31, 104.26 (ArC@C), 60.84 (CH2OC@O), 60.73,

8008
W. Sallem et al. / Bioorg. Med. Chem. 14 (2006) 7999–8013
NCH2CH3 and piperazine), 1.10, 1.00 (2 m, 6H,
NCH2CH3); 13C NMR (CDCl3, d): 170.90, 168.17
(C@O amide), 153.36 (C@O carbamate), 146.14,
137.00, 130.32, 128.04, 137.24, 130.17, 129.74, 127.88,
127.59, 121.22, 120.65, 104.21 (ArC@C) 61.38
(CH2OC@O), 60.80, 56.24 (CH3O), 41.81, 41.15
(NCH2CH3), 13.88, 13.36 (NCH2CH3). Anal.
(C30H36O7N4) C, H, N.
(C@O carbamate), 1644 (C@O amide), 1585 (ArC@C);
1H NMR (CDCl3, d): 9.46 (br s, 1H, NH), 7.55 (d,
1H, J = 8 Hz, ArH), 7.35 (d, 1H, J = 8 Hz, ArH), 7.21
(m, 1H, ArH), 7.06 (m, 1H, ArH), 6.71 (s, 1H, ArH),
6.60 (s, 2H, ArH), 5.20–4.30 (m, 5H, CH2OC@O and
piperazine), 4.25–40 (m, 1H, piperazine), 3.80 (s, 9H,
OCH3), 3.70, 2.80 (2m, 7H, NCH2CH3 and piperazine),
0.95 (m, 6H, NCH2CH3); 13C NMR (CDCl3, d): 170.72,
163.44 (C@O amide), 155.16 (C@O carbamate), 153.37,
139.53, 135.84, 130.32, 128.37, 127.25, 124.59, 121.81,
120.66, 111.81, 105.33, 104.40 (ArC@C), 61.12
(CH2OC@O), 60.85, 56.23 (CH3O), 41.82, 41.11
(NCH2CH3), 13.89, 13.32 (NCH2CH3). Anal.
(C29H36O7N4) C, H, N.
3.1.10. 2-(N,N-Diethylaminocarbonyloxymethyl)-1-(1H-
indole-3-ylacetyl)-4-(3,4,5-trimethoxybenzoyl)piperazine
(3i). Compound 3i was prepared using 1H-indole-3-
acetic acid (257 mg), DCC (301 mg), HOBT (197 mg),
1 (500 mg, 1.22 mmol) and obtained as a white solid
(520 mg, 75%) after a silica gel column chromatography
using MeOH/CH2Cl2 (2:98, v/v) as eluent: Rf 0.16
3.1.13. 2-(N,N-Diethylaminocarbonyloxymethyl)-4-(1H-
indole-3-ylcarbonyl)-1-(3,4,5-trimethoxybenzoyl)pipera-
zine (4b). Compound 4b was prepared using 1H-indole-
3-carboxylic acid (197 mg), DCC (251 mg), HOBT
(197 mg), 2 (500 mg, 1.22 mmol) and obtained as a white
solid (580 mg, 86%) after a silica gel column chromatog-
raphy using MeOH/CH2Cl2 (1:99, v/v) as eluent: Rf 0.42
(CH2Cl2/MeOH, 95:5, v/v); mp 97 °C; IR (m cmꢀ1
)
3192 (NH), 1685 (C@O carbamate), 1645 (C@O amide),
1
1583 (ArC@C); H NMR (CDCl3, d): 8.48 (br s, 1H,
NH), 7.55 (d, 1H, J = 8 Hz, ArH), 7.29–7.00 (m, 4H,
ArH), 6.49 (s, 2H, ArH), 5.10, 4.10 (2m, 3H, CH2OC@O
and piperazine), 4.05–3.86 (m, 5H, CH2CO and pipera-
zine), 3.76 (s, 9H, OCH3), 3.60–2.50 (m, 7H, NCH2CH3
and piperazine), 1.01 (m, 6H, NCH2CH3); 13C NMR
(CDCl3, d): 171.25, 170.79 (C@O amide), 155.02
(C@O carbamate), 153.27, 139.27, 136.18, 130.11,
126.67, 122.15, 119.55, 118.54, 111.28, 108.61, 104.18
(ArC@C), 61.03 (CH2C@O), 60.74 (CH2OC@O),
60.51, 56.16 (CH3O), 41.88, 41.23 (NCH2CH3), 13.88,
13.32 (NCH2CH3). Anal. (C30H38O7N4) C, H, N.
(MeOH/CH2Cl2, 5:95, v/v); mp 201 °C; IR (m cmꢀ1
)
3171 (NH), 1699 (C@O carbamate), 1629 (C@O amide),
1
1599 (ArC@C); H NMR (CDCl3, d): 9.35 (br s, 1H,
NH), 7.58 (m, 1H, ArH), 7.32 (m, 2H, ArH), 7.20 (m,
2H, ArH), 6.58 (s, 2H, ArH), 5.10–3.90 (m, 5H,
CH2OC@O and piperazine), 3.78 (s, 9H, OCH3), 3.69–
2.87 (m, 8H, NCH2CH3 and piperazine), 0.97 (m, 6H,
NCH2CH3); 13C NMR (CDCl3, d): 170.71, 167.55
(C@O amide), 155.30 (C@O carbamate), 153.20,
139.44, 135.69, 130.50, 127.58, 125.12, 122.92, 121.33,
120.11, 111.85, 110.52, 104.42 (ArC@C), 61.29
(CH2O), 60.87, 56.24 (CH3O), 41.87, 41.23 (NCH2CH3),
13.92, 13.46 (NCH2CH3). Anal. (C29H36O7N4) C, H, N.
3.1.11. 2-(N,N-Diethylaminocarbonyloxymethyl)-1-(1H-
indole-3-ylpropionyl)-4-(3,4,5-trimethoxybenzoyl)pipera-
zine (3j). Compound 3j was prepared using (1H-indole-
3-propionic acid (231 mg), DCC (251 mg), HOBT
(197 mg), 1 (500 mg, 1.22 mmol) and obtained as a white
solid (600 mg, 85%) after a silica gel column chromatog-
raphy using MeOH/CH2Cl2 (2:98, v/v) as eluent: Rf 0.2
3.1.14.
4-(Benzothiophene-2-ylcarbonyl)-2-(N,N-dieth-
ylaminocarbonyloxymethyl)-1-(3,4,5-trimethoxybenzo-
yl)piperazine (4c). Compound 4c was prepared using
benzothiophene-2-carboxylic acid (430.2 mg), DIC
(375.7 lL), 2 (830 mg, 2.19 mmol) and obtained as a
white solid (980 mg, 83%) after a silica gel column
chromatography using MeOH/CH2Cl2 (1:99, v/v) as
eluent: Rf 0.38 (CH2Cl2/MeOH, 95:5, v/v); mp 75 °C;
IR (m cmꢀ1) 3379 (NH), 1698 (C@O carbamate),
(CH2Cl2/MeOH, 95:5, v/v); mp 100 °C; IR (m cmꢀ1
)
3310 (NH), 1696 (C@O carbamate), 1633 (C@O amide),
1582 (ArC@C); 1H NMR (CDCl3, d): 8.08 (s, 1H, NH),
7.53 (s, 1H, ArH), 7.29 (d, 1H, J = 7.8 Hz, ArH), 7.25,
6.90 (m, 3H, ArH), 6.49 (s, 2H, ArH), 5.20–4.30 (m,
1H, CH2OC@O), 4.25–3.80 (m, 4H, CH2OC@O and
piperazine), 3.69 (s, 9H, OCH3), 3.59–3.40 (m, 1H,
CH2CO), 3.30, 2.30 (2m, 11H, CH2CH2CO, NCH2CH3
and piperazine), 1.02, 0.81 (2m, 6H, NCH2CH3); 13C
NMR (CDCl3, d): 172.45, 170.75 (C@O amide), 154.89
(C@O carbamate), 153.30, 139.36, 136.23, 130.17,
127.18, 121.99, 121.77, 119.32, 118.66, 1180.49, 114.73,
111.24 (ArC@C), 60.80 (CH2OC@O), 60.55, 56.21
(CH3O), 41.83, 41.10 (NCH2CH3), 34.13 (CH2CO),
21.43 (CH2CH2CO), 13.83, 13.31 (NCH2CH3). Anal.
(C31H40O7N4) C, H, N.
1
1634 (C@O amide), 1585 (ArC@C); H NMR (CDCl3,
d): 7.82 (m, 2H, ArH), 7.49 (s, 1H, ArH), 7.38 (m,
2H, ArH), 6.62 (s, 2H, ArH), 5.52 (m, 1H,
CH2OC@O), 4.55–4.20 (m, 3H, CH2OC@O and piper-
azine), 4.00–3.40 (m, 2H, piperazine), 3.84 (s, 9H,
OCH3), 3.70–2.80 (m, 7H, NCH2CH3 and piperazine),
1.07, 0.88 (2m, 6H, NCH2CH3); 13C NMR (CDCl3,
d): 170.67, 164.79 (C@O amide), 155.10 (C@O carba-
mate), 153.31, 140.14, 138.40, 135.34, 130.20, 126.00,
125.76, 124.90, 124.65, 122.32, 104.29 (ArC@C),
60.96 (CH2OC@O), 60.82, 56.18 (CH3O), 41.82,
41.06 (NCH2CH3), 13.78, 13.37 (NCH2CH3). Anal.
(C29H35O7N3S) C, H, N.
´
3.1.12. 2-(N,N-Diethylaminocarbonyloxymethyl)-4-(1H-
indole-2-ylcarbonyl)-1-(3,4,5-trimethoxybenzoyl)pipera-
zine (4a). Compound 4a was prepared using 1H-indole-
2-carboxylic acid (234 mg), DCC (301 mg), HOBT
(197 mg), 2 (500 mg, 1.22 mmol) and obtained as a white
solid (500 mg, 74%) after a silica gel column chromatog-
raphy using CH2Cl2 as eluent: Rf 0.43 (CH2Cl2/MeOH,
95:5, v/v); mp 159.6 °C; IR (m cmꢀ1) 3370 (NH), 1698
3.1.15. 2-(N,N-Diethylaminocarbonyloxymethyl)-4-(1H-
pyrrole-2-ylcarbonyl)-1-(3,4,5-trimethoxybenzoyl)pipera-
zine (4d). Compound 4d was prepared using pyrrole-2-
carboxylic acid (202 mg), DIC (335 lL), 2 (670 mg,

W. Sallem et al. / Bioorg. Med. Chem. 14 (2006) 7999–8013
8009
1.65 mmol) and obtained as a white solid (550 mg,
67%) after a silica gel column chromatography using
MeOH/CH2Cl2 (1:99, v/v) as eluent: Rf 0.2 (CH2Cl2/
MeOH, 95:5, v/v); mp 133 °C; IR (m cmꢀ1) 3299
(NH), 1695 (C@O carbamate), 1630 (C@O amide),
1583 (ArC@C); 1H NMR (CDCl3, d): 9.50 (br s,
1H, NH), 6.92 (m, 1H, ArH), 6.64 (s, 2H, ArH),
6.51 (m, 1H, ArH), 6.23 (m, 1H, ArH), 5.00–4.27
(m, 3H, CH2OC@O and piperazine), 4.23–3.90 (m,
2H, piperazine), 3.86 (m, 9H, OCH3), 3.80, 2.98
(2m, 8H, NCH2CH3 and piperazine), 1.06 (t, 6H,
J = 7 Hz, NCH2CH3); 13C NMR (CDCl3, d): 170.64,
162.62 (C@O amide), 155.00 (C@O carbamate),
153.30, 139.44, 130.43 123.65, 123.67, 112.30, 109.54,
104.39 (ArC@C), 61.39 (CH2OC@O), 60.81, 56.18
(CH3O), 41.75, 41.10 (NCH2CH3), 13.85, 13.30
(NCH2CH3). Anal. (C25H34O7N4) C, H, N.
3.1.18.
methyl-1H-indole-2-ylcarbonyl)-4-(3,4,5-trimethoxyben-
zoyl)piperazine (3k). mixture of 3a (590 mg,
2-(N,N-Diethylaminocarbonyloxymethyl)-1-(1-
A
1.06 mmol), iodomethane (520 lL, 10.6 mmol) and
K2CO3 (1.46 g, 10.6 mmol) in acetonitrile (25 mL) was
refluxed for 24 h. After evaporation, the residue was
taken in CH2Cl2 (25 mL) and then washed with water,
dried (MgSO4) and filtered, and the solvent was re-
moved in vacuo. The product was isolated as a solid
(380 mg, 63%) after a silica gel column chromatography
using CH2Cl2 as eluent: Rf 0.47 (MeOH/CH2Cl2, 5:95,
v/v); mp 120 °C; IR (m cmꢀ1) 1691 (C@O carbamate),
1
1628 (C@O amide), 1585 (ArC@C); H NMR (CDCl3,
d): 7.55 (d, 1H, J = 7.9 Hz, ArH), 7.24 (m, 2H, ArH),
7.11 (m, 1H, ArH), 6.58 (s, 3H, ArH), 5.1 (m, 1H,
CH2OC@O), 4.80–3.95 (m, 4H, CH2OC@O and pipera-
zine), 3.79 (m, 12H, OCH3, NCH3), 3.70–2.70 (m, 8H,
NCH2CH3 and piperazine), 1.02, 0.99 (2m, 6H,
NCH2CH3); 13C NMR (CDCl3, d): 170.86, 163.81
(C@O amide), 155.05 (C@O carbamate), 153.39,
139.37, 138.08, 130.62, 130.12, 126.09, 123.72, 121.64,
120.41, 109.85, 104.28, 104.20 (ArC@C), 60.83
(CH2OC@O), 60.78, 56.25 (CH3O), 41.84, 41.12
(NCH2CH3), 13.84, 13.33 (NCH2CH3). Anal.
(C30H38O7N4) C, H, N.
3.1.16.
4-(5-Chloro-1H-indole-2-ylcarbonyl)-2-(N,N-
diethylaminocarbonyloxymethyl)-1-(3,4,5-trimethoxyben-
zoyl)piperazine (4e). Compound 4e was prepared using
5-chloro-1H-indole-2-carboxylic acid (300 mg), DIC
(239 lL), 2 (570 mg, 2.44 mmol) and obtained as a
white solid (450 g, 55%) after a silica gel column chro-
matography using MeOH/CH2Cl2 (1:99, v/v) as eluent:
Rf 0.32 (CH2Cl2/MeOH, 95:5, v/v); mp 160 °C; IR (m
cmꢀ1) 3198 (NH), 1694 (C@O carbamate), 1611
3.1.19.
2-(N,N-Diethylaminocarbonyloxymethyl)-4-(1-
1
(C@O amide), 1585 (ArC@C); H NMR (CDCl3, d):
methyl-1H-indole-2-ylcarbonyl)-1-(3,4,5-trimethoxyben-
zoyl)piperazine (4k). Compound 4k was prepared using
the same procedure as for 3k but from 4a (130 mg,
0.235 mmol), iodomethane (117 lL), K2CO3 (63 mg)
and obtained as a white solid (130 mg, 98%) after a silica
gel column chromatography using CH2Cl2 as eluent: Rf
9.95 (br s, 1H, NH), 7.54 (s, 1H, ArH), 7.36 (d, 1H,
J = 8.75 Hz, ArH), 7.22 (d, 1H, J = 8.75 Hz, ArH),
6.64 (s, 3H, ArH), 5.20–4.00 (m, 5H, CH2OC@O
and piperazine), 3.85 (s, 9H, OCH3), 3.70–2.90 (m,
8H, NCH2CH3 and piperazine), 1.07, 0.99 (m, 6H,
N(CH2CH3)2); 13C NMR (CDCl3, d): 170.71, 163.14
(C@O amide), 155.07 (C@O carbamate), 153.36,
139.55, 134.25, 130.21, 129.69, 128.07, 126.12,
124.92, 120.87, 113.01, 104.54, 104.40 (ArC@C),
61.02 (CH2OC@O), 60.83, 56.21 (CH3O), 41.80,
40.09 (NCH2CH3), 13.86, 13.29 (NCH2CH3). Anal.
(C29H35O7N4Cl) C, H, N.
0.5 (MeOH/CH2Cl2, 5:95, v/v); mp 86 °C; IR (m cmꢀ1
)
1696 (C@O carbamate), 1626 (C@O amide), 1582
(ArC@C); 1H NMR (CDCl3, d): 7.53 (d, 1H,
J = 7.9 Hz, ArH), 7.27 (m, 2H, ArH), 7.07 (m, 1H,
ArH), 6.58 (m, 3H, ArH), 5.10–3.95 (m, 5H, CH2OC@O
and piperazine), 3.79 (m, 12H, OCH3 and NCH3), 3.60–
2.50 (m, 8H, NCH2CH3 and piperazine), 0.98, 0.81 (2m,
6H, NCH2CH3); 13C NMR (CDCl3, d): 170.70, 163.93
(C@O amide), 155.04 (C@O carbamate), 153.35,
139.08, 130.37, 130.23, 126.38, 123.64, 121.59, 120.38,
109.86, 104.37, 104.16 (ArC@C), 60.58 (CH2OC@O),
60.83, 56.21 (CH3O), 41.83, 41.02 (NCH2CH3), 13.74,
13.39 (NCH2CH3). Anal. (C30H38O7N4) C, H, N.
3.1.17.
2-(N,N-Diethylaminocarbonyloxymethyl)-4-(5-
methoxy-1H-indole-2-ylcarbonyl)-1-(3,4,5-trimethoxy-
benzoyl)piperazine (4f). Compound 4f was prepared
using 5-methoxy-1H-indole-2-carboxylic acid (308 mg),
DIC (251 lL), 2 (610 mg, 1.61 mmol) and obtained as
a white solid (700 mg, 75%) after a silica gel column
chromatography using CH2Cl2 as eluent: Rf 0.4
3.1.20. 2-(N,N-Diethylaminocarbonyloxymethyl)-1-(5-ni-
tro-1H-indole-2-ylcarbonyl)-1-(3,4,5-trimethoxybenzo-
yl)piperazine (6a). A solution of 5-nitro-1H-indole-2-
carboxylic acid 521 (181 mg, 0.88 mmol) in thionyl chlo-
ride (147 lL, 2 mmol) was stirred in dichloromethane
(20 mL) under reflux for one night. The solvent was then
evaporated under reduced pressure and a solution of the
amine 1 (300 mg, 0.73 mmol) and triethylamine (205 lL,
1.42 mmol) in dichloromethane (40 mL) was added. The
mixture was stirred at room temperature for 12 h. The
reaction mixture was then washed with saturated
NaHCO3 and water, dried (MgSO4), filtered and the sol-
vent removed in vacuo. The compound 6a was obtained
after a silica gel column chromatography using MeOH/
CH2Cl2 (1:99, v/v) as eluent, as a yellow powder
(222 mg, 51%): Rf 0.30 (CH2Cl2/MeOH, 95:5, v/v); mp
(CH2Cl2/MeOH, 95:5, v/v); mp 192 °C; IR (m cmꢀ1
)
3283 (NH), 1694 (C@O carbamate), 1626 (C@O amide),
1
1585 (ArC@C); H NMR (CDCl3, d): 9.22 (br s, 1H,
NH), 7.28 (d, 1H, J = 8.8 Hz, ArH), 7.01–6.92 (m, 2H,
ArH), 6.68 (s, 1H, ArH), 6.65 (s, 2H, ArH), 4.70–4.19
(m, 3H, CH2OC@O and piperazine), 4.05 (m, 1H, piper-
azine), 3.86, 2.80 (2s, 12H, OCH3), 3.77–3.30 (m, 3H,
piperazine), 3.17–2.77 (m, 6H, NCH2CH3 and pipera-
zine), 1.02 (m, 6H, NCH2CH3); 13C NMR (CDCl3, d):
171.11, 163.60 (C@O amide), 154.68 (C@O carbamate),
153.39, 139.67, 131.35, 129.85, 128.39, 127.54 (ArC@C),
116.16, 112.80, 105.36, 104.44, 102.17 (ArC@C), 61.22
(CH2OC@O), 60.86, 56.24, 55.65 (CH3O) 41.89, 41.19
(NCH2CH3), 13.85, 13.28 (NCH2CH3). Anal.
(C30H38O8N4) C, H, N.

8010
W. Sallem et al. / Bioorg. Med. Chem. 14 (2006) 7999–8013
120 °C; IR (m cmꢀ1) 3262 (NH), 2943 (ArCH), 1697
(C@O carbamate), 1632, 1619 (C@O amide), 1583
104.27 (ArC@C), 60.81 (CH2OC@O), 60.56, 56.22
(CH3O), 41.94, 41.27 (NCH2CH3), 13.88, 13.31
(NCH2CH3). Anal. (C30H36O8N4) C, H, N.
1
(ArC@C); H NMR (CDCl3, d): 10.41 (br s, 1H, NH),
8.6 (s, 1H, ArH), 8.14 (d, 1H, J = 9 Hz, ArH), 7.47 (d,
1H, J = 9 Hz, ArH), 6.87 (s, 1H, ArH), 6.64 (s, 2H,
ArH), 5.40, 4.10 (m, 6H, CH2OC@O and piperazine),
3.87 (s, 9H, OCH3), 3.60, 2.70 (2m, 7H, NCH2CH3
and piperazine), 0.88, 1.01 (2m, 6H, NCH2CH3); 13C
NMR (CDCl3, d): 170.75, 162.43 (C@O amide), 154.87
(C@O carbamate), 153.21, 141.98, 139.31, 138.75,
131.70, 129.74, 126.09, 119.30, 119.06, 112.06, 107.52,
104.20 (ArC@C), 60.73 (CH2OC@O), 60.62, 56.07
(CH3O), 41.72, 40.92 (NCH2CH3), 13.56, 13.05
(NCH2CH3). Anal. (C29H38O8N4) C, H, N.
3.1.23. 2-(N,N-Diethylaminocarbonyloxymethyl)-1-(1H-
indole-1-ylcarbonyl)-4-(3,4,5-trimethoxybenzoyl)pipera-
zine (10). To a mixture of indole-1-carboxylic acid 923
(1.25 g, 7.75 mmol) dissolved in dichloromethane
(20 mL) was added DIC (720 lL, 4.65 mmol). The reac-
tion mixture was stirred for 20 min at room tempera-
ture. A solution of 1 (1.58 g, 3.87 mmol) dissolved in
dichloromethane (15 mL) was then added to the mixture
and stirred at room temperature for 12 h. The solution
was then washed with water, dried (MgSO4), filtered
and the solvent removed in vacuo. The product was iso-
lated as a white solid (2.11 g, 99%) after a silica gel col-
umn chromatography using MeOH/CH2Cl2 (1:99, v/v)
as eluent: Rf 0.3 (MeOH/CH2Cl2, 5:95, v/v); mp 62 °C;
IR (m cmꢀ1) 1700 (C@O carbamate), 1635 (C@O amide),
1596 (ArC@C); 1H NMR (CDCl3, d): 7.64 (d, 1H,
J = 7.9 Hz, ArH), 7.49 (d, 1H, J = 8 Hz, ArH), 7.25–
7.05 (m, 3H, ArH), 6.56 (s, 2H, ArH), 6.49 (m, 1H,
ArH), 4.70–3.90 (m, 5H, CH2OC@O and piperazine),
3.76, 3.75 (2s, 9H, OCH3), 3.70–3.00 (m, 8H, NCH2CH3
and piperazine), 1.00, 0.95 (2m, 6H, NCH2CH3); 13C
NMR (CDCl3, d): 170.38 (C@O amide), 156.96 (C@O
carbamate), 154.70 (C@O ureate), 153.99, 153.04,
139.08, 135.08, 129.68, 129.24, 125.56, 123.43, 212.86,
120.71, 113.04, 106.15, 103.95 (ArC@C), 60.62
(CH2OC@O), 60.41, 55.88 (CH3O), 41.19, 40.81
(NCH2CH3), 13.46, 12.94 (NCH2CH3). Anal.
(C29H36O7N4Æ0.05H2O) C, H, N.
3.1.21. 2-(N,N-Diethylaminocarbonyloxymethyl)-4-(5-ni-
tro-1H-indole-2-ylcarbonyl)-1-(3,4,5-trimethoxybenzo-
yl)piperazine (6b). Compound 6b was prepared using the
same procedure as for 6a from 5-nitro-indole-2-carbox-
ylic acid 521 (258 mg, 1.46 mmol), thionyl chloride
(220 lL, 3 mmol) and the amine 2 (500 mg, 1.22 mmol)
in the presence of triethylamine (300 lL, 2.16 mmol).
The compound 6b was obtained after a silica gel column
chromatography using MeOH/CH2Cl2 (1:99, v/v) as elu-
ent, as a yellow solid (473 mg, 65%): Rf 0.32 (CH2Cl2/
MeOH, 95:5, v/v); mp 111.2 °C; IR (m cmꢀ1) 3438
(NH), 3054 (ArCH), 1694 (C@O carbamate), 1633
1
(C@O amide), 1584 (ArC@C); H NMR (CDCl3, d):
10.93 (br s, 1H, NH), 8.50 (s, 1H, ArH), 8.04 (d, 1H,
J = 9 Hz, ArH), 7.14 (d, 1H, J = 9 Hz, ArH), 6.87 (s,
1H, ArH), 6.64 (s, 2H, ArH), 4.00–5.40 (m, 5H,
CH2OC@O and piperazine), 3.81 (s, 9H, OCH3), 3.70,
2.00 (2m, 8H, NCH2CH3 and piperazine), 0.60–1.10
(m, 6H, NCH2CH3); 13C NMR (CDCl3, d): 170.71,
162.68 (C@O amide), 155.00 (C@O carbamate),
153.29, 142.12, 139.55, 138.78, 131.70, 130.00, 126.00,
119.32, 118.96, 112.15, 106.81, 104.39 (ArC@C), 60.91
(CH2OC@O), 60.74, 56.14 (CH3O), 41.74, 41.03
(NCH2CH3), 13.79, 13.19 (NCH2CH3). Anal.
(C29H38O8N4) C, H, N.
3.1.24. 2-(N,N-Diethylaminocarbonyloxymethyl)-1-(1H-
indole-2-ylcarbonyl)-4-(triphenylmethyl)piperazine (12).
Compound 12 was prepared using the same procedure
as for 3 from 1120 (2.05 g, 3.14 mmol), 1H-indole-2-car-
boxylic acid (854.5 mg), DIC (826 lL) and isolated as a
white solid (2.12 g, 85%) after a silica gel column chro-
matography using MeOH/CH2Cl2 (1:99, v/v) as eluent:
Rf 0.3 (MeOH/CH2Cl2, 2:98, v/v); mp 134 °C; IR (m
cmꢀ1) 3275 (NH), 2974 (ArCH), 1690 (C@O carba-
3.1.22. 2-(N,N-Diethylaminocarbonyloxymethyl)-1-[(1H-
indole-3-yl)oxoacetyl]-1-(3,4,5-trimethoxybenzoyl)pipera-
zine (8). To a mixture of 1 (500 mg, 1.22 mmol) and
triethylamine (200 lL, 1.46 mmol) in dichloromethane
(70 mL) was gradually added a-oxo-1H-indole-3-ylace-
tyl chloride 722 (303 mg, 1.46 mmol). The reaction mix-
ture was stirred for 48 h and then washed with water,
dried (MgSO4), filtered, and the solvent removed in vac-
uo. The product was isolated as a white solid (380 mg,
51%) after a silica gel column chromatography using
MeOH/CH2Cl2 (1:99, v/v) as eluent: Rf 0.24 (MeOH/
CH2Cl2, 5:95, v/v); mp 154 °C; IR (m cmꢀ1) 3259
(NH), 1692 (C@O carbamate), 1629 (C@O amide),
1
mate), 1599 (C@O amide), 1523 (ArC@C); H NMR
(CDCl3, d): 10.10 (br s, 1H, NH), 7.00–8.00 (m, 19H,
ArH), 6.77 (s, 1H, ArH), 5.22 (br s, 1H, CH2OC@O),
5.02 (br s, 1H, CH2OC@O), 3.80–4.70 (m, 3H, pipera-
zine), 2.80–3.50 (m, 6H, NCH2CH3 and piperazine),
1.51–1.47 (m, 2H, piperazine), 0.80–1.15 (m, 6H,
NCH2CH3); 13C NMR (CDCl3, d): 162.84 (C@O
amide), 155.54 (C@O carbamate), 136.36, 135.84,
128.90, 127.05, 127.80, 127.53, 126.20, 123.91, 121.50,
120.00, 111.76, 105.44 (ArC@C), 76.81 (C(Ph)3), 62.83
(CH2OC@O), 48.90, 48.72, 47.85 (CH2 of piperazine),
41.72, 41.05 (NCH2CH3), 13.67, 13.25 (NCH2CH3).
1
1581 (ArC@C); H NMR (CDCl3, d): 10.52 (br s, 1H,
NH), 8.26 (m, 1H, ArH), 7.86 (m, 1H, ArH), 7.39 (s,
1H, ArH), 7.28 (m, 2H, ArH), 6.60 (s, 2H, ArH),
5.20–3.98 (m, 5H, CH2OC@O and piperazine), 3.83 (s,
9H, OCH3), 3.70, 2.80 (2 m, 8H, NCH2CH3 and piper-
azine), 0.99, 0.80 (2m, 6H, NCH2CH3); 13C NMR
(CDCl3, d): 184.75, 170.00, 167.16 (C@O), 155.17
(C@O carbamate), 153.37, 139.46, 136.78, 129.87,
125.27, 114.37, 136.69, 124.28, 123.28, 121.77, 112.07,
3.1.25. 2-(N,N-Diethylaminocarbonyloxymethyl)-1-(1H-
indole-2-ylcarbonyl)piperazine (13). To a solution of 12
(1.64 g, 2.7 mmol) in MeOH (30 mL) was added drop-
wise trifluoroacetic acid (TFA, 3 mL). This solution
was stirred for 20 min at room temperature and the sol-
vent removed in vacuo. The residue was then taken up
with CH2Cl2, washed with saturated NaHCO3 solution
and water, dried (MgSO4), filtered and evaporated.

W. Sallem et al. / Bioorg. Med. Chem. 14 (2006) 7999–8013
8011
The compound 13 was obtained as a wax (900 mg, 93%)
after a silica gel column chromatography using CH2Cl2
as eluent: Rf 0.6 (CH2Cl2/MeOH, 90:10, v/v); IR (m
cmꢀ1) 3276 (NH), 3054 (ArCH), 1692 (C@O carba-
ArH), 7.13 (d, 1H, J = 7,9 Hz, ArH), 6.86 (s, 1H, ArH),
4.10–5.20 (m, 4H, CH2OC@O and piperazine), 3.57
(d, 1H, J = 13.13 Hz, CHPh), 3.47 (d, 1H, J = 13.13 Hz,
CHPh), 3.40, 2.50 (2m, 6H, NCH2CH3 and piperazine),
2.00, 2.40 (m, 2H, piperazine), 0.60–1.20 (m, 6H,
NCH2CH3); 13C NMR (CDCl3, d): 163.45 (C@O amide),
154.94 (C@O carbamate), 136.30, 136.15, 127.54, 126.97,
131.54, 130.13, 129.14, 124.60, 121.81, 120.52, 111.95,
106.29 (ArC@C), 61.20 (CH2OC@O), 60.94 (PhCH2N),
51.57, 49.00 (CH2 piperazine), 41.74, 41.05 (NCH2CH3),
13.58, 13.00 (NCH2CH3). Anal. (C26H32O3N4Æ0.1H2O)
C, H, N.
1
mate), 1604 (C@O amide), 1525 (ArC@C); H NMR
(CDCl3, d): 9.76 (br s, 1H, NH), 7.62 (d, 1H, J = 8 Hz,
ArH), 7.43 (d, 1H, J = 8 Hz, ArH), 7.25 (m, 1H,
ArH), 7.10 (m, 1H, ArH), 6.85 (s, 1H, ArH), 4.20,
5.20 (2m, 5H, CH2OC@O and piperazine), 2.60, 3.85
(2m, 9H, NCH2CH3 and piperazine), 1.16 (m, 6H,
NCH2CH3); 13C NMR (CDCl3, d): 163.30 (C@O
amide), 155.52 (C@O carbamate), 135.84, 129.21,
127.29, 124.11, 121.72, 120.27, 111.75, 105.36 (ArC@C),
61.69 (CH2OC@O), 45.99 (CH2 of piperazine), 41.78,
41.14 (NCH2CH3), 13.79, 13.28 (NCH2CH3).
3.1.29. 2-(N,N-Diethylaminocarbonyloxymethyl)-1-(1H-
indole-2-ylcarbonyl)-4-(3,4,5-trimethoxybenzyl)pipera-
zine (16b). Compound 16b was prepared using 13
(330 mg, 0.92 mmol), 3,4,5-trimethoxybenzaldehyde
(216 mg), NaBH(OAc)3 (292.5 mg) in dichloroethane
(50 mL) and obtained as a white solid (440 mg, 95%)
3.1.26. 3-(N,N-Diethylaminocarbonyloxymethyl)-1-(1H-
indole-2-ylcarbonyl)piperazine (15). Compound 15 was
prepared using the same procedure as described for
3, from 1424 (200 mg, 0.69 mmol), 2-indole carboxylic
acid (134 mg, 0.69 mmol) and DCC (175 lL,
0.69 mmol) in the presence of triethylamine (194 lL,
1.38 mmol) and isolated as a wax (230 g, 90%) after
a silica gel column chromatography using MeOH/
CH2Cl2 (2:98, v/v) as eluent: Rf 0.63 (MeOH/CH2Cl2,
10:90, v/v); IR (m cmꢀ1) 3280 (NH), 3054 (ArCH),
1694 (C@O carbamate), 1607 (C@O amide), 1530
(ArC@C); 1H NMR (CDCl3, d): 9.73 (br s,
1H, NH), 7.61 (d, 1H, J = 7.9 Hz, ArH), 7.42 (d,
1H, J = 7.9 Hz, ArH), 7.22 (m, 1H, ArH), 7.14 (m,
1H, ArH), 6.76 (s, 1H, ArH), 4.70, 4.00 (2m, 4H,
CH2OC@O and piperazine), 3.50, 2.60 (2m, 9H,
NCH2CH3 and piperazine), 2.27 (br s, 1H, NH),
1.16 (m, 6H, NCH2CH3); 13C NMR (CDCl3, d):
165.00 (C@O amide), 155.67 (C@O carbamate),
135.81, 129.25, 127.00, 124.00, 121.80, 120.36,
111.78, 106.00 (ArC@C), 61.59 (CH2OC@O), 45.63
(CH2 piperazine), 41.70, 41.21 (NCH2CH3), 13.86,
13.18 (NCH2CH3).
after
a silica gel column chromatography using
MeOH/CH2Cl2 (1:99, v/v) as eluent: Rf 0.27 (CH2Cl2/
MeOH, 95:5, v/v); mp 75 °C; IR (m cmꢀ1) 3296 (NH),
2967 (ArCH), 1689 (C@O carbamate), 1594 (C@O
1
amide), 1523 (ArC@C); H NMR (CDCl3, d): 9.90 (br
s, 1H, NH), 7.61 (d, 1H, J = 8 Hz, ArH), 7.14 (d, 1H,
J = 8 Hz, ArH), 7.25 (m, 1H, ArH), 7.13 (m, 1H,
ArH), 6.85 (s, 1H, ArH), 6.57 (s, 2H, ArH), 4.10–5.20
(m, 4H, CH2OC@O and piperazine), 3.83 (s, 9H,
OCH3), 3.57 (d, 1H, J = 13.13 Hz, CH2Ar), 3.28 (d,
1H, J = 13.13 Hz, CH2Ar), 2.80–3.20 (m, 7H,
NCH2CH3 and piperazine), 2.00–2.50 (m, 2H, pipera-
zine), 0.98, 0.83 (2m, 6H, NCH2CH3); 13C NMR
(CDCl3, d): 163.06 (C@O amide), 155.47 (C@O carba-
mate), 153.16, 138.00, 135.79, 133.50, 129.20, 127.33,
124.20, 121.78, 120.32, 111.72, 105.60, 105.22 (ArC@C),
62.77 (CH2OC@O), 62.52 (ArCH2N), 60.75, 56.03
(CH3O), 53.40 (CH2 piperazine), 41.03, 39.00
(NCH2CH3), 13.40, 13.19 (NCH2CH3). Anal.
(C29H38O6N4) C, H, N.
3.1.27. General procedure for the synthesis of 16a,b, 17a,b
and 18. A solution of 2, 13 or 15 in dichloroethane
(DCE) or dichloromethane, the aldehyde (1.1 or
1.2 equiv) and NaBH(OAc)3 (1.1 or 1.2 equiv) was stir-
red at room temperature until the reaction was complete
(TLC monitored). The solvent was removed under re-
duced pressure and the residue dissolved in dichloro-
methane and washed with saturated NaHCO3 and
water, dried (MgSO4), filtered and the solvent removed
in vacuum. The residue was chromatographed on a sili-
ca gel column as indicated.
3.1.30. 1-Benzyl-2-(N,N-diethylaminocarbonyloxymeth-
yl)-4-(1H-indole-2-ylcarbonyl)piperazine (17a). Com-
pound 17a was prepared using 15 (200 mg, 0.55 mmol),
benzaldehyde (78 lL), NaBH(OAc)3 (208 mg) in dichlo-
romethane (40 mL) and obtained as a white solid
(150 mg, 65%) after a silica gel column chromatography
using CH2Cl2 as eluent: Rf 0.43 (CH2Cl2/MeOH, 95:5, v/
v); mp 145 °C; IR (m cmꢀ1) 3277 (NH), 3058 (ArCH),
1696 (C@O carbamate), 1603 (C@O amide), 1526
1
(ArC@C); H NMR (CDCl3, d): 9.09 (br s, 1H, NH),
7.60 (d, 1H, J = 7.7 Hz, ArH), 7.43–7.20 (m, 7H,
ArH), 7.14 (d, 1H, J = 7.7 Hz, ArH), 6.78 (s, 1H,
ArH), 4.70–4.10 (m, 4H, CH2OC@O and piperazine),
4.08 (d, 1H, J = 13.43 Hz, CHPh), 3.66–3.51 (m, 2H,
NCH2CH3), 3.46 (d, 1H, J = 13.43 Hz, CHPh), 3.24,
2.32 (2m, 7H, NCH2CH3 and piperazine), 0.60, 1.20
(m, 6H, NCH2CH3); 13C NMR (CDCl3, d): 162.65
(C@O amide), 155.37 (C@O carbamate), 138.26,
135.74, 129.11, 127.35, 128.71, 128.33, 127.16, 124.21,
121.67, 120.40, 111.78, 105.09 (ArC@C), 62.67
(CH2OC@O), 58.40 (PhCH2N), 49.43, 48.10 (CH2
piperazine), 41.64, 41.16 (NCH2CH3), 13.88, 13.44
(NCH2CH3). Anal. (C26H32O3N4) C, H, N.
3.1.28. 4-Benzyl-2-(N,N-diethylaminocarbonyloxymeth-
yl)-1-(1H-indole-2-ylcarbonyl)piperazine (16a). Com-
pound 16a was prepared using 13 (300 mg, 0.838 mmol),
benzaldehyde (101.6 lL), NaBH(OAc)3 (263 mg) in
dichloroethane (50 mL) and obtained as a white solid
(380 mg, 93%) after a silica gel column chromatography
using CH2Cl2 as eluent: Rf 0.43 (CH2Cl2/MeOH, 95:5,
v/v); mp 74 °C; IR (m cmꢀ1) 3270 (NH), 3067 (ArCH),
1694 (C@O carbamate), 1603 (C@O amide), 1526
1
(ArC@C); H NMR (CDCl3, d): 9.37 (br s, 1H, NH),
7.25 (d, 1H, J = 7.9 Hz, ArH), 7.51–7.20 (m, 7H, ArH,

8012
W. Sallem et al. / Bioorg. Med. Chem. 14 (2006) 7999–8013
3.1.31. 2-(N,N-Diethylaminocarbonyloxymethyl)-4-(1H-
indole-2-ylcarbonyl)-1-(3,4,5-trimethoxybenzyl)pipera-
zine (17b). Compound 17b was prepared using 15
(180 mg, 0.50 mmol), 3,4,3-trimethoxybenzaldehyde
(117.8 mg), NaBH(OAc)3 (139 mg) in dichloroethane
(40 mL) and obtained as a white solid (200 mg, 86%)
ubilized in DMSO and added to the incubated
mixture and stirred PRP for 2 min before PAF
(2.5 nM) challenge. Platelet aggregation induced by
PAF in the presence of the antagonists was monitored
by continuous recording of light transmission in a
dual-channel recorder (Cronolog Coultronics Appara-
tus) and was compared to a control aggregation in-
duced by PAF alone. The drug concentration
required to produce 50% inhibition (IC50) was calcu-
lated from one dose–response curve.
after
a silica gel column chromatography using
MeOH/CH2Cl2 (1:99, v/v) as eluent: Rf 0.38 (CH2Cl2/
MeOH, 95:5, v/v); mp 148 °C; IR (m cmꢀ1) 3310 (NH),
2986 (ArCH), 1679 (C@O carbamate), 1595 (C@O
1
amide), 1526 (ArC@C); H NMR (CDCl3, d): 9.72 (br
s, 1H, NH), 7.59 (d, 1H, J = 8 Hz, ArH), 7.40 (d, 1H,
J = 8 Hz, ArH), 7.24 (m, 1H, ArH), 7.10 (m, 1H,
ArH), 6.78 (s, 1H, ArH), 6.58 (s, 2H, ArH), 4.54–4.10
(m, 4H, CH2OC@O and piperazine), 3.99 (d, 1H,
J = 13 Hz, NCH2Ar), 3.86 (m, 9H, OCH3), 3.84–3.70
(m, 3H, piperazine), 3.43 (d, 1H, J = 13 Hz, NCH2Ar),
3.30, 3.36 (m, 5H, NCH2CH3 and piperazine), 2.86,
2.38 (2m, 3H, piperazine), 1.06 (m, 6H, NCH2CH3);
13C NMR (CDCl3, d): 162.73 (C@O amide), 155.35
(C@O carbamate), 153.17, 137.00, 135.74, 133.88,
129.00, 127.33, 124.23, 121.65, 120.40, 111.78, 105.46,
105.10 (ArC@C), 62.46 (CH2OC@O), 60.79, 56.06
(CH3O), 58.73 (CH piperazine), 58.67 (NCH2Ar),
49.37 (CH2 piperazine), 41.84, 41.17 (NCH2CH3),
13.97, 13.34 (NCH2CH3). Anal. (C29H38O6N4) C, H, N.
3.2.2. Antiviral assay and cytotoxicity. All experiments
were performed in triplicate in cells isolated from one
blood donor. Antiviral assays and data analysis were
conducted according to the published procedures.18,19
HIV-1 replication was assessed in cell culture superna-
tants by quantifying reverse transcriptase (RT), using
the RetroSysÒ kit (Innovagen).
The cytotoxicity of different molecules was tested using
a MTT (methyltetrazolium salt) assay (Invitrogen).
3.3. Computational tools
All the calculations were performed with the Gaussian
9825 program on a SGI Origin 3800. All the selected
conformations were fully optimized within RHF molec-
ular orbital formalism, using the 6-31G27 basis set. The
3D electrostatic potential has also been computed at
that level with the same basis set.
3.1.32. 2-(N,N-Diethylaminocarbonyloxymethyl)-4-(1H-
indole-3-ylmethyl)-1-(3,4,5-trimethoxybenzoyl)piperazine
(18). Compound 18 was prepared using 2 (540 mg,
1.32 mmol),
indole-3-carboxaldehyde
(211 mg),
NaBH(OAc)3 (392 mg) in dichloroethane (60 mL)
and obtained as a white powder (510 mg, 76%)
after a silica gel column chromatography using
MeOH/CH2Cl2 (1:99, v/v) as eluent: Rf 0.39
(MeOH/CH2Cl2, 5:95, v/v); mp 75 °C; IR (m
cmꢀ1) 3320 (NH), 3054 (ArCH), 1691 (C@O carba-
mate), 1626 (C@O amide), 1584 (ArC@C); 1H
NMR (CDCl3, d): 8.30 (br s, 1H, NH), 7.73 (d,
1H, J = 7 Hz, ArH), 7.40 (d, 1H, J = 7 Hz, ArH),
7.06–7.30 (m, 3H, ArH), 6.50 (s, 2H, ArH), 5.30–
4.00 (m, 2H, CH2OC@O), 3.83 (s, 9H, OCH3),
3.74–3.46 (m, 3H, NCH2CH3 and piperazine),
3.40, 2.00 (2m, 9H, NCH2CH3, CH2 indole and
piperazine), 1.04 (m, 6H, NCH2CH3); 13C NMR
(CDCl3, d): 170.43 (C@O amide), 155.57 (C@O
carbamate), 139.00, 136.44, 131.17, 127.39,
111.79, 123.50, 122.58, 121.93, 119.46, 119.37,
111.04, 104.36 (ArC@C), 62.66 (CH2OC@O),
60.77, 56.10 (CH3O), 53.84 (CH2 indole), 53.11
(CH2 piperazine), 41.75, 41.13 (NCH2CH3), 13.84,
13.48 (NCH2CH3). Anal. (C29H38O6N4) C, H, N.
Acknowledgments
We thank Karen Naissant-Storck for her technical assis-
tance. This work was supported by the Scientific Coun-
´
cil of the Universite Paris 7 – Denis Diderot (Paris,
France). Georges Dive is chercheur qualifie of the Fond
National de la Recherche Scientifique (FNRS), Brussels.
This work was supported by the Belgian program on
Interuniversity Poles of Attraction initiated by the
Belgian State, Prime Minister’s Office, Service federaux
des affaires scientifiques, techniques et culturelles (PAI
No. P5/33).
´
´ ´
Supplementary data
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.bmc.
2006.07.043.
3.2. Biological methods
References and notes
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(3.8%, pH 7.4), and PRP was obtained by centrifuga-
tion for 15 min at 1200 rpm. The antagonists were sol-
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