HIV-1 replication inhibitors of the styrylquinoline class: Incorporation of a masked diketo acid pharmacophore

Article abstract of DOI:10.1016/S0040-4039(01)01767-1

A novel variant of HIV-1 replication inhibitors of the styrylquinoline class, bearing an α-keto acid appendage at C-7, has been synthesized. Though completely inactive in in vitro experiments against HIV-1 integrase, this compound exhibited a significant antiviral activity (IC₅₀ = 10 μM).

Full text of DOI:10.1016/S0040-4039(01)01767-1

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 42 (2001) 8189–8192
HIV-1 replication inhibitors of the styrylquinoline class:
incorporation of a masked diketo acid pharmacophore
Fatima Zouhiri,a,c Didier Desmae¨le,a,* Jean d’Angelo,a,* Miche`le Ourevitch,a
Jean-Franc¸ois Mouscadet,b Herve´ Lehb,c and Marc Le Bretd
aUnite´ Associe´e au CNRS, Faculte´ de Pharmacie, 5, rue J.-B. Cle´ment, 92290 Chaˆtenay-Malabry, France
bUnite´ Associe´e au CNRS, Institut Gustave Roussy, PR II, 39 rue Camille Desmoulins, 94805 Villejuif, France
cBioAlliance Pharma SA, 59 bd du Ge´ne´ral Martial Valin, 75015 Paris, France
dUnite´ Associe´e au CNRS, Ecole Normale Supe´rieure, 61 av. du Pre´sident Wilson, 94235 Cachan, France
Received 24 July 2001; revised 18 September 2001; accepted 19 September 2001
Abstract—A novel variant of HIV-1 replication inhibitors of the styrylquinoline class, bearing an a-keto acid appendage at C-7,
has been synthesized. Though completely inactive in in vitro experiments against HIV-1 integrase, this compound exhibited a
significant antiviral activity (IC50=10 mM). © 2001 Elsevier Science Ltd. All rights reserved.
AIDS is essentially a viral disease and should be treated
with antiretroviral agents. Although the advent of com-
bination therapy with reverse transcriptase and
protease inhibitors has made it possible to suppress the
replication of HIV-1 in infected individuals, the virus
persists in reservoirs such as peripheral blood mononu-
clear cells or resting T-lymphocytes. Moreover, the
capability of HIV to evolve drug resistance and the
cytotoxicity of present regimens make the third enzyme,
the integrase (IN), a legitimate new drug target.1
We have recently reported that polyhydroxylated
styrylquinolines, exemplified by 1, are potent HIV-1 IN
inhibitors in in vitro experiments, block the replication
of HIV-1 in cell culture, and are devoid of cytotoxicity.2
Although the exact mechanism by which drug 1 and
analogs exert their inhibitory potency remains
unknown, their salicylic acid part has been identified as
a possible pharmacophore which binds Mg2+, a cation
which is essential to the catalytic activity of HIV-1 IN.3
In addition to styrylquinolines, two other families of
COOH
O
O
HOOC
O
7
OH
O
HOOC
N
8
OH
OH
1
OH
HO
HO
OH
2
HOOC
N
7
HOOC
OH
OH
O
O
N
H
8
O
O
H
F
3
Figure 1.
Keywords: antivirals; enzyme inhibitors; keto acids and derivatives; quinolines; thioacetals.
* Corresponding authors. Fax: +33(0)146835752; e-mail: jean.dangelo@cep.u-psud.fr
0040-4039/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(01)01767-1

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F. Zouhiri et al. / Tetrahedron Letters 42 (2001) 8189–8192
HIV-1 IN inhibitors have shown anti-HIV-1 activity in
cell culture, namely
-chicoric acid (2) and analogs,4
critical moiety. The keto group could be present at the
outset of the synthesis on a quinoline ring, or incorpo-
rated at an advanced stage, via the displacement of the
ester function of a styrylquinoline (e.g. 10) with an
appropriate nucleophile. The second approach, which
has been more successful thus far, has taken advantage
of the one-carbon elongation of esters developed by
Degani and Fochi, using the anion of tris-
(methylthio)methane (11).7
L
and various a,g-diketo acids (exemplified by L 731,988,
3).5
In the course of our ongoing research on HIV-1 replica-
tion inhibitors of the styrylquinoline class, we recently
envisioned to elaborate the new structural variant 4,
bearing an a-keto acid appendage at C-7. The factor
that has stimulated our interest in synthesizing
styrylquinoline 4 has been the structural analogy
between its HOOC-CO-CꢀC(OH)- system and the enol
form of the a,g-diketo acid pharmacophore found in
inhibitor 3 (Fig. 1). On the other hand, a docking
protocol using the program MORCAD has recently
been designed to study the interaction between the
catalytic core of HIV-1 IN and molecules 1 and 4.6 This
computer simulation revealed that the two styrylquino-
lines bind in a similar fashion to the protein. Since drug
1 was proved to be a strong inhibitor of HIV-1 IN,2 a
significant in vitro HIV-1 IN inhibitory activity was
therefore expected for compound 4.
The first stage of the synthesis was the methylation of
known hydroxy acid 58 to produce the dimethylated
derivative 69 (MeI–K2CO3, DMF–acetone, 12 h at
50°C, 81% yield). Perkin-type condensation of quinal-
dine
6
with 3,4-dihydroxybenzaldehyde (7) then
afforded styrylquinoline 8 (Ac2O, 12 h at 140°C, 79%
yield).2 Replacement of the two labile acetoxy groups of
compound 8 by more robust tert-butyldimethylsilyl
ethers (OTBDMS) was next accomplished, employing
the following two-step procedure. Hydrolysis of 8 (pyr-
idine–H2O, 3 h at 100°C) gave with a 74% yield cate-
chol 9,10 which was converted into bis-silylated
derivative 10 (TBDMSCl, imidazole, DMF, 12 h at
20°C, 84% yield). At this juncture, we stood ready to
introduce the crucial keto group at C-7. In the event,
Here, we report the synthesis and the evaluation of the
biological activity of styrylquinoline 4. Structurally,
compound 4 only differs from lead inhibitor 1 in the
presence of an additional keto group at C-7. Two
strategies have evolved for the introduction of this
condensation
of
ester
10
with
tris(methyl-
thio)methyllithium7 (i: 11, n-BuLi, THF, 2 h at −95°C;
ii: 10, 30 min at −95°C; iii: H2O/CH2Cl2 at −95°C)
CHO
OH
OH
K2CO3
7
OAc
OAc
MeO2C
N
MeO2C
N
HO2C
N
MeI
OMe
OMe
OH
Ac2O
8
5
6
H2O, Py
TBDMSCl/
Imidazole
OTBDMS
OTBDMS
MeO2C
N
OH
OH
MeO2C
N
OMe
OMe
10
9
(MeS)3CH/n-BuLi
11
SMe
O
NBS/H2O
MeS
MeS
OTBDMS
OTBDMS
OTBDMS
OTBDMS
N
N
MeS
O
O
OMe
OMe
12
13
4
HBr/H2O, ∆
Scheme 1.

F. Zouhiri et al. / Tetrahedron Letters 42 (2001) 8189–8192
8191
4. (a) King, P. J.; Ma, G.; Miao, W.; Jia, Q.; McDougall,
B. R.; Reinecke, M. G.; Cornell, C.; Kuan, J.; Kim, T.
R.; Robinson, Jr., W. E. J. Med. Chem. 1999, 42, 497–
509; (b) King, P. J.; Robinson, Jr., W. E. J. Virol. 1998,
72, 8420–8424.
Table 1. Biological data of compounds 1, 3 and 4
Compound
HIV-1 integrase inhibitory
potency (strand transfer
process) IC50 (mM)
Anti-HIV-1 activity
IC50 (mM)
5. Hazuda, D. J.; Felock, P.; Witmer, M.; Wolfe, A.; Still-
mock, K.; Grobler, J. A.; Espeseth, A.; Gabryelski, L.;
Schleif, W.; Blau, C.; Miller, M. D. Science 2000, 287,
646–650.
1
3
4
1
0.1
100
1
1
10
6. Le Bret, M. et al., manuscript in preparation (see also
Ref. 3).
7. Barbero, M.; Cadamuro, S.; Degani, I.; Dughera, S.;
Fochi, R. J. Org. Chem. 1995, 60, 6017–6024.
8. Meek, W. H.; Fuschman, C. H. J. J. Chem. Eng. Data
1969, 14, 388–391.
9. Compound 6: Colorless crystals; mp 33–34°C; IR (neat,
cm−1) w: 1709, 1610, 1556, 1505; 1H NMR (DMSO-d6,
200 MHz) l: 7.90 (d, J=8.4 Hz, 1H), 7.66 (d, J=8.5
Hz, 1H), 7.39 (d, J=8.5 Hz, 1H), 7.21 (d, J=8.4 Hz,
1H), 4.18 (s, 3H), 3.90 (s, 3H), 2.65 (s, 3H); 13C NMR
(CDCl3, 50 MHz), l: 166.6 (C), 158.6 (C), 156.2 (C),
142.3 (C), 135.7 (CH), 129.5 (C), 125.4 (CH), 123.2 (C),
123.1 (CH), 122.2 (CH), 63.1 (CH3), 51.8 (CH3), 25.1
(CH3).
delivered with a 57% yield the a-oxo trithioorthoester
12,11 which, upon treatment with N-bromosuccinimide
(NBS, THF–H2O, 2 h at 20°C),12 gave the a-oxo thiol
ester 1313 (52% yield). The next issue of the synthesis
was the conversion of the thiol ester group of 13 into
a carboxylic acid. A variety of operating conditions
were considered (1N NaOH, MeOH, 20°C; or 0.1N
NaOH, t-BuOOH, 20°C; or AgNO3, CH3CN, H2O,
20°C), but they all proved to be inappropriate for the
purpose. Finally, after extensive experiments, it was
discovered that subjection of 13 to harsh hydrolytic
conditions (40% aqueous HBr, AcOH, 12 h at 80°C),
not only achieved the task, but also resulted in the
removal of the aromatic OMe and OTBDMS protect-
ing groups, providing our goal 414 in 47% yield
(Scheme 1).
10. Compound 9: Yellow solid; mp 180–185°C (dec.); IR
(neat, cm−1) w: 3340, 2946, 1722, 1631, 1600, 1508; 1H
NMR (DMSO-d6, 200 MHz) l: 9.20 (broad s, 2H), 8.30
(d, J=9.1 Hz, 1H), 7.86 (d, J=9.1 Hz, 1H), 7.75–7.55
(m, 3H), 7.16 (d, J=16.8 Hz, 1H), 7.10 (s, 1H), 7.00 (d,
J=7.9 Hz, 1H), 6.78 (d, J=7.9 Hz, 1H), 4.20 (s, 3H),
3.98 (s, 3H); 13C NMR (DMSO-d6, 50 MHz) l: 166.6
(C), 156.0 (C), 155.5 (C), 147.0 (C), 145.7 (C), 142.3 (C),
136.6 (CH), 135.4 (CH), 130.1 (C), 127.8 (C), 125.2
(2CH), 124.0 (C), 122.9 (CH), 121.3 (CH), 120.1 (CH),
116.0 (CH), 114.1 (CH), 63.0 (CH3), 52.3 (CH3).
11. Compound 12: Orange solid; mp 158–160°C; IR (neat,
cm−1) w: 2930, 2857, 1688, 1505, 1286, 1250; 1H NMR
(CDCl3, 200 MHz) l: 8.09 (d, J=8.4 Hz, 1H), 7.93 (d,
J=8.2 Hz, 1H), 7.65 (d, J=8.4 Hz, 1H), 7.60 (d, J=
16.2 Hz, 1H), 7.46 (d, J=8.2 Hz, 1H), 7.21 (d, J=16.2
Hz, 1H), 7.15–7.05 (m, 2H), 6.84 (d, J=8.6 Hz, 1H),
4.20 (s, 3H), 2.12 (s, 9H), 0.95 (s, 9H), 0.92 (s, 9H), 0.19
(s, 6H), 0.18 (s, 6H); 13C NMR (CDCl3, 50 MHz) l:
193.5 (C), 155.7 (C), 154.2 (C), 147.9 (C), 147.0 (C),
142.3 (C), 136.2 (CH), 134.6 (CH), 132.0 (C), 130.1 (C),
129.3 (C), 126.9 (CH), 125.3 (CH), 121.8 (CH), 121.1
(2CH), 120.2 (CH), 119.7 (CH), 76.8 (C), 64.0 (CH3),
25.8 (6CH3), 18.4 (2C) 14.0 (3CH3), −4.1 (4CH3).
12. Degani, I.; Dughera, S.; Fochi, R.; Gatti, A. Synthesis
1996, 467–469.
13. Compound 13: Yellow solid; mp 129–130°C; IR (neat,
cm−1) w: 2930, 2856, 1672, 1662, 1594, 1506, 1303, 1249;
1H NMR (CDCl3, 200 MHz) l: 8.10 (d, J=8.7 Hz,
1H), 7.72 (d, J=8.4 Hz, 1H), 7.69 (d, J=8.7 Hz, 1H),
7.63 (d, J=16.2 Hz, 1H), 7.53 (d, J=8.4 Hz, 1H), 7.16
(d, J=16.2 Hz, 1H), 7.12–7.02 (m, 2H), 6.85 (d, J=8.8
Hz, 1H), 4.35 (s, 3H), 2.54 (s, 3H), 1.03 (s, 9H), 1.00 (s,
9H), 0.25 (s, 6H) 0.24 (s, 6H); 13C NMR (CDCl3, 50
MHz) l: 193.3, 190.2, 158.7, 155.7, 148.8, 147.1, 142.1,
136.5, 135.1, 132.3, 130.0, 126.4, 125.5, 124.9, 123.1,
121.9, 121.2 (2C), 119.9, 63.9, 26.0 (6C), 18.4, 11.0 (2C),
−4.0 (4C).
Keto acid 4 was evaluated in vitro for its inhibitory
activity against HIV-1 IN, and ex vivo for its antiviral
activity against HIV-1 replication in CEM cells.2 The
results, together with those obtained with lead
inhibitors 1 and 3, are listed in Table 1. A moderate
antiviral activity was gained with styrylquinoline 4
(IC50=10 mM). However, in contrast with parent com-
pound 1, this keto acid exhibited a complete lack of in
vitro inhibitory potency (IC50>100 mM). Therefore, in
contradiction with the aforementioned docking stud-
ies,6 the ultimate target of drug 4 in the ex vivo
experiments is not HIV-1 IN. Work directed toward
the identification of this viral target is in progress.
References
1. For recent reviews, see: (a) Pommier, Y.; Marchand, C.;
Neamati, N. Antivir. Res. 2000, 47, 139–148; (b) d’An-
gelo, J.; Mouscadet, J.-F.; Desmae¨le, D.; Zouhiri, F.;
Leh, H. Pathol. Biol. 2001, 49, 237–246.
2. (a) Mekouar, K.; Mouscadet, J.-F.; Desmae¨le, D.;
Subra, F.; Savoure´, D.; Auclair, C.; d’Angelo, J. J. Med.
Chem. 1998, 41, 2846–2857; (b) Zouhiri, F.; Mouscadet,
J.-F.; Mekouar, K.; Desmae¨le, D.; Savoure´, D.; Leh, H.;
Subra, F.; Le Bret, M.; Auclair, C.; d’Angelo, J. J. Med.
Chem. 2000, 43, 1533–1540.
3. (a) Ouali, M.; Laboulais, C.; Leh, H.; Gill, D.; Des-
mae¨le, D.; Mekouar, K.; Zouhiri, F.; d’Angelo, J.;
Auclair, C.; Mouscadet, J.-F.; Le Bret, M. J. Med.
Chem. 2000, 43, 1949–1957; (b) Ouali, M.; Laboulais,
C.; Leh, H.; Gill, D.; Xhuvani, E.; Zouhiri, F.; Des-
mae¨le, D.; d’Angelo, J.; Auclair, C.; Mouscadet, J.-F.;
Le Bret, M. Acta Biochim. Polonica 2000, 47, 11–22.

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F. Zouhiri et al. / Tetrahedron Letters 42 (2001) 8189–8192
14. Compound 4: Brick red solid; mp 250°C (dec.); IR (neat,
cm−1) w: 3600–2500, 1740, 1580, 1522, 1442, 1290, 1240;
1H NMR (DMSO-d6, 400 MHz) l: 9.50–8.50 (broad s,
4H), 8.36 (d, J=8.8 Hz, 1H), 8.12 (d, J=15.8 Hz, 1H),
7.89 (d, J=8.8 Hz, 1H), 7.70 (d, J=8.8 Hz, 1H), 7.42 (d,
J=8.8 Hz, 1H), 7.23 (d, J=15.8 Hz, 1H), 7.10 (d, J=1.2
Hz, 1H), 7.00 (dd, J=8.2, 1.2 Hz, 1H), 6.80 (d, J=8.2
Hz, 1H); 13C NMR (DMSO-d6, 100 MHz) l: 186.6 (C),
167.2 (C), 157.2 (C), 155.0 (C), 147.1 (C), 145.6 (C), 138.2
(C), 137.8 (CH), 137.2 (CH), 135.6 (CH), 130.6 (C), 127.8
(C), 124.0 (CH), 123.3 (CH), 120.3 (CH), 118.1 (CH),
116.1 (CH), 115.8 (C), 114.5 (CH); MS (ESI, −70.0 V)
m/z (rel. intensity): 352 (M+1, 2), 351 (M, 20), 350 (M−1,
100), 322 (2), 306 (M−1−CO2, 2), 278 (1).