HIV-1 replication inhibitors of the styrylquinoline class: Introduction of an additional carboxyl group at the C-5 position of the quinoline

Article abstract of DOI:10.1016/j.tetlet.2005.02.033

Novel variants of HIV-1 replication inhibitors of the styrylquinoline class, bearing an additional acid group or a propenoic acid moiety at the C-5 position of the quinoline have been synthesized. Key steps included Heck reaction and palladium catalyzed carbonylation reaction of 5-haloquinaldine derivatives. These compounds exhibited reinforced anti-integrase potency and significant antiviral activities.

Full text of DOI:10.1016/j.tetlet.2005.02.033

Tetrahedron
Letters
Tetrahedron Letters 46 (2005) 2201–2205
HIV-1 replication inhibitors of the styrylquinoline
class: introduction of an additional carboxyl group at
the C-5 position of the quinoline
a
a
a
Fatima Zouhiri,a,b Michele Danet, Christophe Benard, Marie Normand-Bayle,
`
Jean-Franc¸ois Mouscadet, Herve Leh, Claire Marie Thomas, Gladys Mbemba,
´
c
b
b
c
´
Jean dꢀAngeloa and Didier Desmae¨lea,*
a
´ ´ ´ ´ ˆ
Unite Associee au CNRS, UMR 8076, Faculte de Pharmacie, 5, rue J.-B. Clement, 92290 Chatenay-Malabry, France
b
´ ´
Bioalliance Pharma SA, 59 bd du General Martial Valin, 75015 Paris, France
´
c
´ ´
Unite Associee au CNRS, UMR 8113, Ecole Normale Superieure de Cachan, 94235 Cachan, France
Received 3 January 2005; revised 3 February 2005; accepted 7 February 2005
Abstract—Novel variants of HIV-1 replication inhibitors of the styrylquinoline class, bearing an additional acid group or a pro-
penoic acid moiety at the C-5 position of the quinoline have been synthesized. Key steps included Heck reaction and palladium
catalyzed carbonylation reaction of 5-haloquinaldine derivatives. These compounds exhibited reinforced anti-integrase potency
and significant antiviral activities.
Ó 2005 Elsevier Ltd. All rights reserved.
The substantial incidence of resistance observed in ther-
apy-experienced patients and newly acquired HIV-1
infections underscores the need for new antiretroviral
agents. All oral agents licensed to treat HIV-1 diseases
target two of the three essential, virally-encoded enz-
ymes, reverse transcriptase and protease.1 The third enz-
yme, integrase inserts the viral DNA into the cellular
genome through a multi-step process that includes two
catalytic reactions, 30 endonucleolytic processing of the
viral DNA ends, and joining of the viral and cellular
DNAs (strand transfer).2 The availability of in vitro as-
says using recombinant integrase has allowed the dis-
covery of numerous classes of compounds with
inhibitory activity.3
drug 1 and analogs exert their inhibitory potency re-
mains unknown, it has been recently proposed that such
drugs might act prior to integration by preventing viral
DNA–integrase-binding.5 Thus, SQLs constitute unique
class of integrase inhibitors, distinct from the diketoacid
group (illustrated by L 731,988, 2), which affect viral
DNA integration.3a Within the carbon framework of
SQLs, we have identified the salicylic acid moiety at
C-7, C-8 of the quinoline ring, and the 40-OH on the
ancillary aromatic nucleus as critical pharmacophores
for antiviral activity.
Since it was recognized that carboxylic acid groups are
beneficial to both integrase inhibition potency and cyto-
toxicity, we envisioned to elaborate new structural vari-
ants possessing an additional carboxyl group at C-5
while keeping the salicylic acid system at C-7/C-8. Here-
in, we report the synthesis and the evaluation of the bio-
logical activity of new styrylquinoline derivatives 3a,b
bearing a carboxyl group either directly bound to the
quinoline ring or through an ethylenic spacer.
We have reported that polyhydroxylated styrylquino-
lines (SQLs), exemplified by 1, are potent HIV-1 integr-
ase inhibitors in in vitro experiments, block the
replication of HIV-1 in cell culture, and are devoid of
cytotoxicity.4 Although the exact mechanism by which
From the outset of the work we planned to incorporate
the requisite function at an early stage of the synthesis,
via a palladium-catalyzed coupling reaction of the 5-
bromoquinaldine 6, before to elaborate the arylethenyl
Keywords: Antivirals; Enzyme inhibitors; Heck reactions; Carbonyl-
ation; Quinolines.
*
Corresponding author. Tel.: +33
146835752; e-mail: didier.desmaele@cep.u-psud.fr
0 146835753; fax: +33 0
0040-4039/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2005.02.033

2202
F.Zouhiri et al./ Tetrahedron Letters 46 (2005) 2201–2205
system through a Perkin-type condensation with aro-
matic aldehydes 4. Our starting point for the synthesis
of compound 3a was the 8-hydroxy-2-methyl-quino-
line-7-carboxylic acid 7 available, although in moderate
yield, by Kolbe–Schmidt carboxylation of 8-hydroxy-
quinaldine (Scheme 1).6
Bromination of acid 7 using bromine or NBS provided
the desired bromo acid 6 in 30–40% yield, along a sub-
stantial amount of dibromoquinoline 8.7 Since these
procedures turned out to be quite erratic, we turned to
a more reliable method. Thus methylation of 7 produced
the corresponding dimethylated derivative, which
uneventfully gave bromoester 9 in 72% yield upon treat-
ment with bromine. To our delight, Heck reaction of 9
with ethyl acrylate delivered the desired unsaturated es-
ter 10 in 66% yield. Finally, Perkin-type condensation of
quinaldine 9 with 3,4-dihydroxybenzaldehyde (4, R=H),
followed by deprotection afforded the desired diacid 3a
in 49% overall yield from 10 (Scheme 2).8
Scheme 2. Reagents and conditions: (a) NBS, DMF, 20 °C, 1 h, 6:
40%; (b) 20 equivMeI, 20 equivK 2CO3, DMF–acetone, 12 h at 50 °C,
95%; (c) Br2, DMF, CH2Cl2, 20 °C, 72%; (d) 5 mol % Pd(OAc)2,
20 mol % PPh3, 5 equivH C@CHCO2Et, 5 equivEt N, 110 °C, 2.5 h,
We next turned our attention to the synthesis of diacid
3b, bearing the carboxyl group directly bound to the
quinoline nucleus. Introduction of a nitrile function as
carboxyl group surrogate was first investigated. Thus,
when the n-butyl ester 11, easily available from acid
7,4f was reacted with sodium iodide in the presence of
chloramine-T,9 the desired 5-iodoquinaldine derivative
12 was obtained in 80% yield. Protection of the phenol
group as a pivalate, followed by palladium(0) and cop-
per(I) co-catalyzed cyanation reaction10 delivered the
carbonitrile 13 in 62% overall yield. However the final
hydrolysis was disappointing. For example, hydrolysis
of 13 with concentrated hydrochloric acid in refluxing
acetic acid gave mainly the hydroxy-acid 14 in which
the nitrile group was unaffected. On the other hand,
2
3
66%; (e) (i) 3,4-dihydroxybenzaldehyde (4, R = H) 4 equiv, Ac2O,
140 °C, 12 h; (f) HBr 48%, AcOH, 100 °C, 30 h, 49%.
the use of more drastic conditions (e.g., 50% H2SO4,
100 °C) led to complete decomposition (Scheme 3).
This problem combined with the modest yield encoun-
tered in the Kolbe–Schmidt carboxylation to access
the acid 7, prompted us to explore an alternative strat-
egy based on the regioisomeric quinaldine 16.11 Since
this material was originally prepared according to a
lengthy sequence, we decided to explore the Doebner
and Miller condensation of commercially available 3-
amino-4-hydroxybenzoic acid 15. In the event treatment
15 with crotonaldehyde in refluxing 6 N hydrochloric
acid provides quinoline 16 in 52% yield. Iodination of
16 with the KI/I2 system as reported12 provided iodo
phenol 17. Benzylation of 17 afforded ester 18, which,
Scheme 3. Reagents and conditions: (a) 1.5 equivNaI, 1.5 equiv p-
TolN(Na)Cl, DMF, 20 °C, 1 h, 80%; (b) t-BuCOCl, py, DMF, 18 h,
20 °C, 82%; (c) 5 mol % Pd(PPh3)4, 10 mol % CuI, 2 equivKCN,
refluxing THF, 2 h, 76% (d) HCl concd, AcOH, 110 °C, 16 h, 54%.
Scheme 1.

F.Zouhiri et al./ Tetrahedron Letters 46 (2005) 2201–2205
2203
upon Stille reaction with tributyl-(1-ethoxy-vinyl)-stann-
ane 1913 gave the enol ether 20 (82% yield). The later
product was ozonolyzed to give rise to diester 21, but
with a disappointing low yield.14 Notwithstanding this
drawback we continued our synthesis. Thus saponifi-
cation of the ethyl ester followed by conventional hydro-
genolysis of the two benzyl groups furnished the
expected diacid 22 in 38% overall yield from 21 (Scheme
4).
compound produced the targeted diacid 3b in 73% over-
all yield from 22 (Scheme 5).16
Diacids 3a,b were assayed in vitro for inhibitory activity
against HIV-1 integrase, and for antiviral activity
against HIV-1 replication in cells. In vitro IC50 was
determined as the drug concentration that inhibits 50%
of the recombinant integrase activity in a standard 30-
processing and strand transfer assays. Cellular antiviral
IC50 was determined as the drug concentration that
inhibits 50% of viral particles production in de novo
infection assay of HeLa P4 cells.5b,17 TC50 was the drug
concentration that corresponds to 50% of cells survival
as determined by a standard MTT assay.18,19 Results
are listed in comparison with reference compound 1 in
Table 1.4b Diacids 3a,b were found to be highly potent
inhibitors of integrase on both 30-processing and strand
transfer assays (Fig. 1). This result clearly established
that carboxyl groups on the quinoline ring are beneficial
to the inhibitor/integrase interaction as initially sus-
pected. When compared to 1, a marked decline in anti-
viral activity was observed for 3b, on the other hand 3a
kept a good activity on cell culture, but with a slightly
increased cytotoxicity.
Although this route was successful, it suffered from the
tedious procedure for the introduction of the C-7 carb-
oxylic group. Clearly a direct hydroxycarbonylation
reaction would be a more suitable method. In the event,
treatment iodoquinaldine 18 with palladium acetate and
dppp in wet DMSO under 1 atm of CO directly afforded
the expected acid 23 in 41% yield.15
To our surprise, the debenzylation of 23 turned out to be
ineffective probably due to the presence in this polar
material of phosphine traces poisoning the palladium
catalyst. We thus have recourse to a variant of the car-
bonylation reaction using benzyl alcohol as nucleophilic
partner.
Heating a DMSO solution of 18 in the presence of benzyl
alcohol and palladium acetate under CO pressure led
to diester 24 with a 55% yield after chromatographic
purification. By contrast with the reaction of 23, depro-
tection of this material now proceeded smoothly to give
diacid 22 in 70% yield. With an efficient route to this
material, we next proceeded to the implementation of
the arylethenyl appendage. Thus condensation of 22
with 3,4-dihydroxy-5-methoxybenzaldehyde 25, fol-
lowed by hydrolysis of the intermediate acetylated
In short we have devised efficient syntheses of two new
styrylquinoline derivatives with additional carboxylic
residues on the quinoline ring. Although improved
anti-integrase activities were observed, no decisive
Scheme 5. Reagents and conditions: (a) 15 mol % Pd(OAc)2, 20 mol %
dppp, 10 equivEt 3N, DMSO, H2O, 2 atm CO, 70 °C, 20 °C 1 h then
70 °C 2 h, 41%; (b) 15 mol % Pd(OAc)2, 20 mol % dppp, 10 equiv
Et3N, DMSO, 10 equivBnOH, 2 atm CO, 70 °C, 20 °C 1 h then 70 °C
2 h, 55%; (c) Pd(OH)2, 1 atm H2, AcOEt, EtOH, AcOH, 20 °C, 24 h,
70%; (d) (i) 2.5 equiv 25, Ac2O, 4 d, (ii) py, H2O, 110 °C, 3 h, 73%.
Table 1. Biological activities of 3a,b
Compound
1
3
a
3
30 Processinga
Integrationa
1.0
1.7
0.3
0.2
0.07
1.6
60
Scheme 4. Reagents and conditions: (a) HCl 6 N, CH3CH@CHCHO,
100 °C, 1 h, 52%; (b) I2/KI, aq NaOH, 0.5 h, 15 °C, 70% (c) 3 equiv
BnBr, 3 equivK 2CO3, DMF, 24 h, 50 °C, 80%; (d) 1.8 equiv 19,
5 mol % Pd2dba3ÆCHCl3, DMF, 100 °C, 3 h, 82%; (e) (i) O3, CH2Cl2,
ꢀ78 °C, (ii) Me2S, 20 °C, 8 h 20%; (f) 2 N NaOH, MeOH, THF, 18 h;
(g) Pd(OH)2, DMF, AcOH, 1 atm H2, 20 °C, 8 h, 38% from 21.
0.06
35
Antiviral activitya
Cytotoxicityb
0.3
>100
>100
a IC50, lM.
b TC50, lM.

2204
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8189–8192; (e) Polanski, J.; Zouhiri, F.; Jeanson, L.;
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R.; Gasteiger, J.; Le Bret, M. J.Med.Chem. 2002, 45,
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4647–4654; (f) Benard, C.; Zouhiri, F.; Normand-Bayle,
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F.; Auclair, C.; Brochon, J.-C.; Le Bret, M.; Mouscadet,
J.-F. Mol.Pharmacol. 2004, 65, 85–98; (b) Bonnenfant, S.;
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6. Meek, W. H.; Fuschman, C. H. J. J.Chem.Eng.Data
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7. The halodecarboxylation of salicylic acids has been
previously reported: Grovenstein, E., Jr.; Henderson, U.
V., Jr. J.Am.Chem.Soc. 1956, 78, 569–578.
8. Compound 3a: Brick red solid; mp > 300 °C (dec); IR
(neat, cmꢀ1) m 3400–2300 (broad) d 1677, 1626, 1587, 1518;
1H NMR (DMSO-d6, 400 MHz) d 9.04 (d, J = 9.1 Hz,
1H), 8.42 (d, J = 9.1 Hz, 1H), 8.41 (s, 1H), 8.27 (d,
J = 15.7 Hz, 1H), 8.08 (d, J = 16.4 Hz, 1H), 7.73 (d,
J = 16.4 Hz, 1H), 7.22 (broad s, 1H), 7.14 (d, J = 8.1 Hz,
1H), 6.90 (d, J = 8.1 Hz, 1H), 6.49 (d, J = 15.7 Hz, 1H);
13C NMR (DMSO-d6, 100 MHz) d 169.5 (C), 167.9 (C),
163.1 (C), 152.3 (C), 149.1 (C), 146.2 (C), 142.1 (CH),
139.0 (CH), 138.2 (CH), 134.3 (C), 128.8 (C), 127.9 (CH),
127.5 (C), 121.9 (CH), 121.4 (CH), 118.7 (CH), 118.3
(CH), 116.5 (CH), 115.8 (C), 114.9 (CH), 114.0 (C).
9. Kometani, T.; Watt, D. S.; Ji, T. Tetrahedron Lett. 1985,
26, 2043–2046. A better yield was obtained by adding
quinaldine 11 to a preformed mixture of sodium iodide
and chloramine-T.
Figure 1. Phosphorimager picture of HIV IN integration activity in
presence of increasing concentration of compounds 3a,b. Integration
assays were performed at 100 nM of IN, 12.5 nM of U5-2, and 7.5 mM
of MgCl2.
breakthrough resulted from this substitution pattern on
the antiviral potency. Further studies aimed at exploring
modulations of the ancillary rings of compounds 3a,b
are ongoing.
Acknowledgements
We thank Dr. M. Ourevitch for NMR spectral analysis
and Mrs S. Mairesse-Lebrun for performing elemental
analyses.
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16. Compound 3b: Brick red solid; mp > 260 °C (dec); IR
(neat, cmꢀ1) m 3500–2500 (broad), 1693, 1690, 1584; 1H
NMR (DMSO-d6, 200 MHz) d 9.77 (d, J = 9.4 Hz, 1H),
8.73 (s, 1H), 8.47 (d, J = 9.4 Hz, 1H), 7.99 (d, J = 16.1 Hz,
1H), 7.78 (d, J = 16.1 Hz, 1H), 6.92 (s, 1H), 6.89 (s, 1H),
3.90 (s, 3H); 13C NMR (DMSO-d6, 50 MHz) d 169.4 (C),
168.3 (C), 167.4 (C), 151.5 (C), 149.5 (C), 146.9 (C), 143.1
(CH), 141.6 (CH), 138.6 (C), 136.0 (CH), 135.0 (C), 130.4
(C), 126.7 (C), 122.2 (CH), 118.5 (CH), 113.4 (C), 110.7
(CH), 109.0 (C), 104.5 (CH), 56.8 (CH3); Anal. Calcd for
C20H15NO8Æ2/3H2O: C, 58.68; H, 4.02; N, 3.42. Found: C,
58.53; H, 4.21; N, 3.36.
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17. HeLa P4 cells were infected with viruses and grown in the
presence of increasing concentrations of drugs. After 72 h,
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Desmae¨le, D.; dꢀAngelo, J.; Ourevitch, M.; Mouscadet,

F.Zouhiri et al./ Tetrahedron Letters 46 (2005) 2201–2205
2205
inhibitory concentration (IC50) is the drug concentration
at which 50% of b-Gal production was inhibited compared
to that by untreated infected cells. Cell survival was also
estimated by the use of a standard MTT (3-[4,5-dimeth-
ylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) assay.19
18. Eustice, D. C.; Feldman, P. A.; Colberg-Poley, A. M.;
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