Synthetic ferrocenic mefloquine and quinine analogues as potential antimalarial agents

Article abstract of DOI:10.1016/S0223-5234(00)00178-1

A few years ago we proposed a strategy for the synthesis of new ferrocene-chloroquine analogues replacing the carbon chain of chloroquine by hydrophobic ferrocenyl moieties. Now, this strategy has been applied to the antimalarial amino-alcohols class to afford new potentially active analogues of mefloquine and quinine bearing a substituted ferrocenic group. The pathway used for the synthesis of the mefloquine analogues includes the coupling of an aminomethyl substituted ferrocene carboxaldehyde with a lithio quinoline compound. On the other hand, the synthesis of quinine analogues was ensured by the 'inverse' reaction of a lithio aminomethyl ferrocene with a quinoline carboxaldehyde. The configurations of each diastereoisomer were unambiguously determined by spectroscopic data. The mechanistic interpretations were fully discussed. Ferrocenyl analogues of mefloquine and quinine exhibited a lower antimalarial activity than mefloquine and quinine themselves. Comparing optical isomers, those isomers dissimilar to ferrocenyl derivatives presented better antimalarial activities than those similar to ferrocenyl. (C) 2000 Editions scientifiques et medicales Elsevier SAS.

Full text of DOI:10.1016/S0223-5234(00)00178-1

Eur. J. Med. Chem. 35 (2000) 707−714
2000 Éditions scientifiques et médicales Elsevier SAS. All rights reserved
S0223523400001781/FLA
©
Preliminary communication
Synthetic ferrocenic mefloquine and quinine analogues
as potential antimalarial agents
a*
b,c
a
b
Christophe Biot , Laurence Delhaes , Lucien A. Maciejewski , Marlène Mortuaire , Daniel
b,c
b
a
Camus , Daniel Dive , Jacques S. Brocard
a
Laboratoire de catalyse de Lille, groupe de synthèse organométallique, UPRESA 8010, école nationale supérieure de chimie de Lille,
bâtiment C7 université des sciences et technologies BP 108, F-59652 Villeneuve d’Ascq cedex, France
b
INSERM U.42, 369, rue Jules Guesde BP 39, 59651 Villeneuve d’Ascq cedex, France
c
Laboratoire de parasitologie-mycologie, faculté de médecine, 1, place de Verdun, 59045 Lille cedex 2, France
Received 14 September 1999; revised 28 January 2000; accepted 10 February 2000
Abstract – Afew years ago we proposed a strategy for the synthesis of new ferrocene-chloroquine analogues replacing the carbon chain of
chloroquine by hydrophobic ferrocenyl moieties. Now, this strategy has been applied to the antimalarial amino-alcohols class to afford new
potentially active analogues of mefloquine and quinine bearing a substituted ferrocenic group. The pathway used for the synthesis of the
mefloquine analogues includes the coupling of an aminomethyl substituted ferrocene carboxaldehyde with a lithio quinoline compound. On
the other hand, the synthesis of quinine analogues was ensured by the ‘inverse’ reaction of a lithio aminomethyl ferrocene with a quinoline
carboxaldehyde. The configurations of each diastereoisomer were unambiguously determined by spectroscopic data. The mechanistic
interpretations were fully discussed. Ferrocenyl analogues of mefloquine and quinine exhibited a lower antimalarial activity than mefloquine
and quinine themselves. Comparing optical isomers, those isomers dissimilar to ferrocenyl derivatives presented better antimalarial activities
than those similar to ferrocenyl. © 2000 Éditions scientifiques et médicales Elsevier SAS
malaria / ferrocene / mefloquine / quinine / diastereomers
1. Introduction
to deal with the development of resistance to the drugs in
current use.
The incidence of malaria in the world is estimated to be
00–500 million clinical cases annually. An estimated
.5–2.7 million people die of malaria each year [1–4].
Approximately 1 million deaths among children under
five years of age are attributed to malaria alone or in
combination with other diseases. Countries in tropical
Africa are estimated to account for more than 90% of the
total malaria incidence and the great majority of malaria
deaths [1–4]. So there is a great need for new antimalari-
als, with different structures and modes of action, in order
Organometallic compounds offer exciting new possi-
bilities in drug development due to their unique structure
[5–8]. In our laboratory, we have previously synthesized
a ferrocene-chloroquine analogue, i.e. ferrochloroquine
(7-chloro-4-[(2-N,N-dimethylaminomethyl)ferrocenylme-
thylamino]quinoline) which proved to be active against
chloroquine-resistant parasites [9–12]. In this new drug,
the carbon chain of chloroquine was replaced by a
ferrocenyl group [9–11]. A similar strategy may be
achieved through application of new antimalarials with
the structure of amino-alcohols (such as mefloquine or
quinine) covalently linked to a substituted ferrocenyl unit
3
1
[
9–10]. It is expected that this modification should
enhance the antimalarial activity. We report here the
synthesis, determination structures and the in vitro anti-
malarial activity of synthetic ferrocenic mefloquine and
quinine analogues.
*
Correspondence and reprints: ch_biot@club-internet.fr
Present address: UMR 8525 CNRS, université de Lille II, institute
de biologie et institute Pasteur de Lille, 1, rue du Professeur
Calmette, BP 447, 59021 Lille, France

7
08
C. Biot et al. / Eur. J. Med. Chem. 35 (2000) 707–714
Figure 1. [2-(N,N-substituted aminomethylferrocenyl)]-{4[(2,8-
bistrifluoromethyl)quinolyl]}-methanol derivatives. The rela-
tive proportion of each diastereomer was determined by H-
Figure 2. Synthesis of [2-(N,N-substituted aminomethyl-
ferrocenyl)]-{4[(2,8-bistrifluoro-methyl)quinolyl]}-methanol
derivatives.
1
NMR of the crude mixture.
2
. Chemistry
Fc–CH–OH proton [17]. In A, this resonance appears at
δ ∼ 6.5 ppm (singlet, 1H) and corresponds to a seven-
membered ring. In B, the resonance appears at δ ∼ 6.2 ppm
due to a different anisotropic zone of the ferrocenic
skeleton. A is a solid, whereas B is an oil (figure 4).
The pathway used for the synthesis of the mefloquine
analogues includes the addition of a prochiral carboxal-
dehyde function of a racemic metallocene to a lithio
quinoline compound. On the other hand, the synthesis of
quinine analogues was ensured by the addition of a
prochiral carboxaldehyde quinoline derivative into race-
mic chelated metallocycle (figure 1).
2.2. Ferrocenic quinine analogues
The ferrocenic analogues were prepared by replace-
ment of the quinuclidinyl group by a substituted ferroce-
nyl moiety. 4-Carboxaldehyde-6-methoxyquinoline was
obtained by selenium dioxide oxidation of 6-methoxy-4-
methylquinoline in dioxane in 77% yield and 63%
conversion, as described by Kwartler and Lindwall [18]
and modified [19]. Then, the lithio ferrocenic derivative
was condensed with the crude product (described above)
2
.1. Ferrocenic mefloquine analogues
The piperidinyl group of mefloquine was replaced by
the hydrophobic ferrocenyl unit. 2,8-Bis(trifluoromethyl)-
-lithioquinoline was obtained by metalation with
4
n-butyllithium in anhydrous diethylether of 4-bromo-2,8-
bis(trifluoromethyl)quinoline at –65 °C under nitrogen
atmosphere [13]. Subsequent addition of the 2-(N,N-
substituted aminomethyl)ferrocenecarboxaldehyde to the
lithiation mixture afforded the ferrocenic mefloquine
analogues in 51–90% yields (figure 2).
Three products were isolated from the sequence shown
in figure 3 by chromatography over silica gel of the crude
reaction mixture.
in anhydrous THF/Et O giving, after work up, the ferro-
2
cenic quinine analogues (figure 5).
The amount of each diastereomer was deduced from
1
the intensity of the H-NMR resonance for the Fc-
–
CH–OH proton (singlet) in the spectra of the crude
product. The reaction mixture was purified by chroma-
tography over silica gel. Compound A (minor, the less
polar) was found to exhibit a singlet at δ ∼ 6.1 ppm. For
compound B (major, the more polar), the signal is shifted
by c.a. ∼ 0.4 ppm downfield (figure 6).
The
first
eluted
product
was
2,8-bis(tri-
fluoromethyl)quinoline, resulting from an uncompleted
addition. The second and third band to elute were the
isomeric amino alcohols A and B. In solution (CHCl3),
compound A was found to exhibit an infrared absorption
for the hydroxyl group (∼ 3 000 cm ), indicating that the
hydroxyl group participates in a strong hydrogen bond
with the nitrogen lone pair [14]. Compound B was found
3
. Results and discussion
–
1
3.1. Ferrocenic mefloquine analogues
to exhibit
a
broad, strong hydroxyl absorption
The electronic and steric interactions between the
aldehydic O atom and the N,N-substituted aminomethyl
side chain are not prominent. This repulsion is compen-
sated by the possibility for a chelation on the lithium
atom [20]. The condensation step of the lithio derivative
–
1
(
∼ 3 000 cm ) characteristic of a hydroxyl group coordi-
nated to an iron atom [15, 16].
1
The H-NMR and MS spectra of the two amino-
alcohols are similar, except for the resonance of the

C. Biot et al. / Eur. J. Med. Chem. 35 (2000) 707–714
709
Figure 3. Diastereoselective synthesis of the ferrocenic mefloquine analogues.
with induction by the N,N-substituted aminomethyl side
chain allows for the formation of a stable cyclic complex
(figure 1). The observed diastereomeric excess for the
formation of 4 seems to be caused by the second nitrogen
atom in the side chain which contributes to the decrease
of the steric interactions.
(figure 7). During this stereoselective reaction, the u
diastereomer, i.e. compound A: (R, S) and (S, R), is
obtained.
3
.2. Ferrocenic quinine analogues
The transition state relative to the other diastereomer
(
figure 7) does not present this stabilization and leads to
The condensation step which produces the ferrocenic
quinine analogues involves steric interaction [21]. The
selectivity depends on the difference in the bulkiness of
the l form, i.e. compound B: (R, R) and (S, S), as an oil.
The relative proportion of the u and l diastereomers
depends on the bulky group borne by the nitrogen atom
Figure 4. [2-(N,N-substituted aminomethylferrocenyl)]-(6-
methoxyquinolyl)methanol derivatives. The relative proportion
of each diastereomer was determined by H-NMR of the crude
1
Figure 5. Synthesis of [2-(N,N-substituted aminomethyl-
mixture.
ferrocenyl)]-(6-methoxyquinolyl)-methanol derivatives.

7
10
C. Biot et al. / Eur. J. Med. Chem. 35 (2000) 707–714
Figure 8. Mechanistic interpretation for the formation of the
diastereoisomers of the quinine analogues. is
-methoxyquinoline.
Q
6
Figure 6. Diastereomers of the ferrocenic quinine analogues.
analogue solutions seemed to be unstable. Comparing
isomers, the isomers dissimilar to ferrocenyl derivatives,
the groups on 6-methoxyquinoline and the hydrogen
atom, and not on the substituents on the nitrogen atom.
The re-face of the aldehyde is attacked in the proposed
most stable transition state with an exo-orientation of the
quinoline group of the aldehyde, leading to the l amino-
alcohols (figure 7 and 8). The alternative transition state
with an endo-quinoline group has severe interaction
between the quinoline and the ferrocenic nucleus (figure
(R, S) and (S, R), presented better antimalarial activities
than corresponding similar isomers (figures 9 and 10). In
spite of debated results [22–24], the structure of the
aromatic ring system seems to be important to the
differential activity exhibited by antimalarial agents con-
taining a piperidine ring such as mefloquine and quinine.
Moreover, stereoselective differences between the two
mefloquine enantiomers have been reported in pharma-
cokinetic studies in human subjects [25].
8
). This addition leads to the minor u amino-alcohols
figure 7).
(
The relative proportion of the u and l diastereomers is
not influenced by the nature of the substituents on the
nitrogen atom (figure 4).
4
. Conclusion
To summarize, we have shown that it is possible to
3
.3. Biological activities
synthesize ferrocenic mefloquine and quinine analogues.
The configurations of each diastereomer were determined
by spectroscopic data. So, these compounds are close
structural and stereochemical mimics of the parent drugs.
We compared the biological activity of the new ferro-
cenyl analogues to those of the parent compounds:
mefloquine or quinine. The in vitro screening assays are
briefly described in the experimental protocols section.
Whichever Plasmodium falciparum strain used: sensitive
(HB3) or chloroquine, mefloquine-resistant (Dd2), the
ferrocenyl compounds exhibited a lower antimalarial
activity than mefloquine or quinine themselves (figures 9
and 10). Though no precipitate was observed making
pre-dilutions and dilutions in extemporane, all ferrocenyl
Figure 9. Mean of IC50 of mefloquine and ferrocenyl ana-
logues for each P. falciparum strain: the chloroquine-sensitive
strain HB3 and the mefloquine and chloroquine-resistant strain
Dd2. Results are means of at least three independent experi-
ments. Bars denote ± standard deviations.
Figure 7. Mechanistic interpretation for the formation of the
diastereomers of the mefloquine analogues. Q is 2,8-
bis(trifluoromethyl)quinoline.

C. Biot et al. / Eur. J. Med. Chem. 35 (2000) 707–714
711
5
5
.1.1. Synthesis of ferrocenic mefloquine analogues
.1.1.1. [2-(N,N-Diethylaminomethylferrocenyl)]-
{
4-[(2,8-bistrifluoromethyl)quinolyl]}methanol 1
Under nitrogen, a stirred solution of 2,8-bis-
trifluoromethyl)-4-bromoquinoline (172 mg; 0.5 mmol)
(
in 5 mL of anhydrous diethylether was treated with
n-butyllithium in hexane (200 µL; 0.5 mmol) at –65 °C.
Metalation was completed in 20 min at –65 °C. The crude
solution was reacted with 2-(N,N-diethylamino-
methyl)ferrrocenecarboxaldehyde (140 mg; 0.5 mmol) in
5
mL of anhydrous diethylether. After 1 h at –65 °C, the
solution was progressively warmed up to room tempera-
ture. The compound was hydrolysed by addition of water
(
10 mL). The organic layer was separated and the remain-
ing aqueous phase was washed with small portions of
diethylether (2 × 30 mL). The Et O extracts were com-
Figure 10. Mean of IC50 of quinine and ferrocenyl analogues
for each P. falciparum strain: the chloroquine-sensitive strain
HB3 and the mefloquine and chloroquine-resistant strain Dd2.
Results are means of at least three independent experiments.
Bars denote ± standard deviations.
2
bined, dried over Na SO and evaporated to dryness. The
resulting oil was purified by chromatography over silica
2
4
gel (eluent: Et O/hexane/triethylamine, 30:60:10). Com-
2
pound 1 was isolated as an oil (254 mg; 90%). The
diastereomers were separated by TLC (silica gel: acetone/
hexane, 40:60).
These modifications were expected to result in our new
potential antimalarial compounds with properties mark-
edly different from mefloquine and quinine. But which-
ever Plasmodium falciparum strain used: sensitive (HB3)
or chloroquine, mefloquine-resistant (Dd2) and which-
ever isomer (similar or dissimilar) tested, the ferrocenyl
compounds exhibited a lower antimalarial activity than
mefloquine or quinine themselves.
u diastereomer 56%. Yellow solid. Decomposed over
5 °C. H-NMR: δ 8.87 (d, J = 8.50 Hz, 1H, H-5), 8.16
1
4
(
d, J = 7.30 Hz, 1H, H-7), 7.97 (s, 1H, H-3), 7.66 (dd,
J = 7.50, 8.10 Hz, 1H, H-6), 6.53 (s, 1H, CHOD), 4.23
(
(
m, 1H, 1H Cp), 4.16 (d, J = 13.20 Hz, 1H, 1CHN), 4.02
s, 5H, Cp′), 3.94 (m, 1H, 1H Cp), 3.22 (m, 2H, 1H Cp
and 1CHN), 2.79 (q, J = 7.10 Hz, 2H, CH –CH ), 2.46
2
3
5
. Experimental protocols
(
q, J = 7.10 Hz, 2H, CH –CH ), 1.10 (t, J = 7.10 Hz, 6H,
2 3
+ +
CH ). MS (dhb): 564 M , 548 (M.– O) , 492 (M –
3
5
.1. Chemistry
+
+
(NEt )) , 476 (M – (ONEt )) , 388, 300.
2 2
1
1
The H-NMR spectra were recorded on a Bruker AC
l diastereomer 44%. Brown oil. H-NMR: δ 8.42 (s,
3
00 spectrometer using tetramethylsilane (TMS) as the
internal standard. δ are given in ppm, solvent: CDCl +
D O (95:5), s: singlet; d: doublet; t: triplet; q: quadruplet
3
2
and m: multiplet. MS MALDI TOF spectra were obtained
using a Vision 2000 time-of-flight instrument (Finnigan
MAT, Bremen, Germany) equipped with a nitrogen laser
operating at a wavelength of 337 nm. Between 20 and 30
single-shot spectra in the reflector mode were accumu-
lated to obtain a good signal-to-noise ratio. The matrix
used was 2,4,6-trihydroxyacetophenone (thap) or dihy-
droxybenzoic acid (dhb). EI mass spectra were acquired
with a quadrupole instrument Nermag R 10-10 H. Melt-
ing points are uncorrected. Merck’s Kieselgel 60 PF254
was used for the chromatography. Elemental analyses
were performed at the ‘Service Central d’Analyse’,
Vernaison and were within ± 0.4% of the theoretical
values. The preparation of the ferrocenic aldehydes is
analogous to that previously described [11].

7
12
C. Biot et al. / Eur. J. Med. Chem. 35 (2000) 707–714
Cp), 2.97 (d, J = 12.70 Hz, 1H, 1CHN), 2.30 (s, 6H,
1CHN), 4.05 (m, 2H, 2H Cp), 4.02 (s, 5H, Cp′), 3.15 (d,
+
2
CH ). MS (EI, m/e (%)): 536 M (77), 492 (M –
J = 12.79 Hz, 1H, 1CHN), 2.8–2.3 (m, 8H, CH ), 2.28 (s,
3
2
+
+
N(CH ) ) (26), 491 (M – HN(CH ) ) (100), 354 (27),
3H, CH3).
3
2
3 2
1
3
5
34 (16), 285 (15), 242 (16); (MALDI TOF (dhb)): 536,
20, 492.
l diastereomer 19% (NMR estimation). H-NMR: δ
8.38 (d, J = 7.89 Hz, 1H, H-5), 8.26 (s, 1H, H-3), 8.18 (d,
J = 7.09 Hz, 1H, H-7), 7.72 (m, 1H, H-6), 6.23 (s, 1H,
CHOD), 3.97–3,89 (m, 3H, 2H Cp and 1CHN), 3.84 (s,
1
l diastereomer 41%. Brown oil. H-NMR: δ 8.39 (d,
J = 8.90 Hz, 1H, H-5), 8.35 (s, 1H, H-3), 8.18 (d, J =
.30 Hz, 1H, H-7), 7.71 (m, 1H, H-6), 6.25 (s, 1H,
CHOD), 4.14 (m, 1H, 1H Cp), 4.03 (m, 1H, 1H Cp), 3.93
d, J = 13.03 Hz, 1H, 1CHN), 3.76 (s, 5H, Cp′), 2.93 (d,
J = 13.03 Hz, 1H, 1CHN), 2.35 (s, 6H, 2CH ). MS (EI,
5
2
H, Cp′), 3.72 (m, 1H, 1H Cp), 3.62 (m, 1H, 1CHN),
.8–2.3 (m, 8H, CH ), 2.18 (s, 3H, CH ).
7
2
3
(
5
.1.2. Synthesis of ferrocenic quinine analogues
3
+
+
+
m/e (%)): 536 M (42), 491 (M –HN(CH ) ) (100), 353
3
2
5.1.2.1. 4-Carboxaldehyde-6-methoxyquinoline
(13), 334 (13), 199 (11); (MALDI TOF (dhb)): 536, 492.
A solution of selenium dioxide (130 mg; 1.16 mmol) in
a mixture of 2 mL of dioxane and 500 µL of water was
added for 1 h to a well-stirred solution of 6-methoxy-4-
methylquinoline (200 mg; 1.16 mmol) in 1 mL of diox-
ane kept at 65 °C. The mixture was stirred at 85 °C for
5
.1.1.3. [2-(Piperidinomethylferrocenyl)]-
{
4-[(2,8-bistrifluoromethyl)quinolyl]}methanol 3
The preparation is analogous to the preparation of 1
85% yield).
5
h and then filtered over celite. The dioxane was
(
evaporated from the filtrate and the crude mixture was
u diastereomer 68%. Yellow solid. M.p. 157–159 °C.
H-NMR: δ 8.87 (d, J = 8.80 Hz, 1H, H-5), 8.17 (d, J =
treated as described below (77% yield, 63% conversion).
1
1
H-NMR: δ 10.42 (s, 1H, CHO), 9.04 (d, J = 4.30 Hz,
7
8
.30 Hz, 1H, H-7), 7.97 (s, 1H, H-3), 7.67 (dd, J = 7.60,
.10 Hz, 1H, H-6), 6.53 (s, 1H, CHOD), 4.21 (m, 1H, 1H
1
9
H, H-2), 8.47 (d, J = 2.80 Hz, 1H, H-5), 8.10 (d, J =
.28 Hz, 1H, H-7), 7.76 (d, J = 4.30 Hz, 1H, H-3), 7.47
Cp), 4.07 (d, J = 13.00 Hz, 1H, 1CHN), 4.01 (s, 5H, Cp′),
(
dd, J = 2.83, 9.27 Hz, 1H, H-8), 4.00 (s, 3H, CH O).
3
3
1
6
4
.94 (m, 1H, 1H Cp), 3.23 (m, 1H, 1H Cp), 3.08 (d, J =
3.00 Hz, 1H, 1CHN), 2.54 (m, 4H, NCH CH ), 1.57 (m,
2
2
5.1.2.2. [2-(N,N-Dimethylaminomethyl-
ferrocenyl)]-(6-methoxyquinolyl)methanol 5
+
H, CH (CH ) CH ). MS (EI, m/e (%)): 576 M (46),
2
2 3
2
92 (37), 491 (100), 311 (14), 121 (36), 56 (21).
The mixture described above was dissolved in anhy-
drous tetrahydrofuran (25 mL) and reacted with the
2-lithio-(N,N-dimethylaminomethyl)ferrocene (2 eq.) in
anhydrous diethylether (20 mL) under nitrogen at room
temperature. The resulting solution was stirred 4 h at
room temperature, quenched by addition of water (50 mL)
and extracted with portions of diethylether (2 × 30 mL).
1
l diastereomer 32%. Brown oil. H-NMR: δ 8.36 (d,
J = 7.30 Hz, 1H, H-5), 8.35 (s, 1H, H-3), 8.18 (d, J =
7
6
1
.10 Hz, 1H, H-7), 7.73 (dd, J = 7.80, 8.10 Hz, 1H, H-6),
.23 (s, 1H, CHOD), 4.12 (m, 1H, 1H Cp), 4.01 ppm: (m,
H, 1H Cp), 3.87 (d, J = 13.00 Hz, 1CHN), 3.75 (s, 1H,
Cp′), 3.65 (m, 1H, 1H Cp), 3.00 (d, J = 13.00 Hz, 1H,
CHN), 2.56 (m, 4H, NCH CH ), 1.66 (m, 4H,
1
The combined extracts were dried over Na SO and
2 4
2
2
2
2
2
2
2
+

C. Biot et al. / Eur. J. Med. Chem. 35 (2000) 707–714
713
9
.15 Hz, 1H, H-7), 7.29 (d, J = 2.47 Hz, 1H, H-5), 6.12
concentration ranged from 1.4–90.4 nM for HB3 strain
and from 2.8–180.7 nM for Dd2 strain. Concerning each
mefloquine ferrocenyl derivative, they ranged from
16.9–1 084.2 nM for the two P. falciparum strains. The
final concentration of quinine and ferrocenyl analogues
ranged from 52.08–3 333.3 nM for both strains. All these
concentrations contained less than 0.01% dimethyl sul-
phoxide which had no detectable effect on parasite
multiplication [29]. After addition of a suspension of
parasitized erythrocytes in complete culture medium
(
s, 1H, CHOD), 4.11 (m, 1H, 1H Cp), 4.03 (m, 1H, 1H
Cp), 3.94 (d, J = 12.17 Hz, 1H, 1CHN), 3.93 (s, 3H,
CH O), 3.88 (m, 1H, 1H Cp), 3.70 (s, 5H, Cp′), 2.91 (d,
J = 12.85 Hz, 1H, 1CHN), 2.33 (s, 6H, 2CH N). MS
3
3
+
+
+
(
thap): 453 (M+ Na) , 430 M , 386 (M – NMe ) , 385
2
+ +
(M – HNMe ) , 367 (M – (H O + HNMe )) .
2
2
2
5
.1.2.3. [2-(Piperidinomethyl-
ferrocenyl)]-(6-methoxyquinolyl)methanol 6
The preparation is analogous to the preparation of 5
(
200 µL/well, 0.5% initial parasitaemia with a majority of
3
(
58% yield). We were unable to separate the diastereo-
ring stages, 2% haematocrit) and [H ]Hypoxanthine
Amersham, Little Chalfont, Buckinghamshire, UK,
.5 µCu/well), the test plates were incubated at 37 °C in
an atmosphere of 5% O , 5% CO and 90% N for 48 h.
isomers by chromatography column or by HPLC. MS
(
0
+
+
+
(thap): 493 (M+ Na) , 471 MH , 470: M , 386 (M –
+ +
N(CH ) ) , 367: (M – (H O + H N(CH ) )) .
2
5
2
2 5
2
2
2
1
u diastereomer 31% (NMR estimation). H-NMR: δ
.80 (d, J = 4.40 Hz, 1H, H-2), 8.05 (d, J = 9.25 Hz, 1H,
Growth of the parasites was estimated by the incorpora-
3
8
tion of radiolabelled [H ]Hypoxanthine into the parasites
H-8), 7.80 (d, J = 2.82 Hz, 1H, H-5), 7.48 (d, J = 4.45 Hz,
nucleic acids, measured in a liquid scintillation spectrom-
eter (Beckman). Fifty percent inhibitory concentrations
1
1
H, H-3), 7.36 (dd, J = 2.88, 9.25 Hz, 1H, H-7), 6.44 (s,
H, CHOD), 4.15–3.85 (m, 4H, 3H Cp and 1CHN), 4.01
(
IC ) refer to molar concentrations of drug causing 50%
50
3
(
1
1
s, 5H, Cp′), 3.79 (s, 3H, CH O), 3.05 (d, J = 12.80 Hz,
H, 1CHN), 2.53 2 (m, 4H, CH ), 1.63 2 (m, 4H, CH )
2 2
.45 (m, 2H, CH2).
3
reduction in [H ]Hypoxanthine incorporation compared
to drug-free control wells. They were estimated by linear
regression analysis of log dose–response curves.
1
l diastereomer 69% (NMR estimation). H-NMR: δ
,91 (d, J = 4.35 Hz, 1H, H-2), 8.09 (d, J = 9.20 Hz, 1H,
8
Acknowledgements
H-8), 7.78 (d, J = 4.54 Hz, 1H, H-3), 7.40 (dd, J = 2.73,
.22 Hz, 1H, H-7), 7.32 (d, J = 2.71 Hz, 1H, H-5), 6.12
s, 1H, CHOD), 4.15–3.85 (m, 4H, 3H Cp and 1CHN),
9
This research was supported by the ‘Ministère de
l’Enseignement Supérieur et de la Recherche’, the ‘Cen-
tre national de la Recherche Scientifique’, the World
Heath Organisation (contract: ID 980-140) and ‘Pierre
Fabre Medicament’. We thank Sophie Picart-Goetgheluck
for his assistance with the NMR spectra experiments.
(
3
.96 (s, 3H, CH O), 3.63 (s, 5H, Cp′), 2.96 (d, J =
3
1
2.98 Hz, 1H, 1CHN), 2.53 (m, 4H, CH ), 1.63 (m, 4H,
2
CH ), 1.45 CH (m, 2H, CH ).
2
2
2
5
5
.2. Biology protocols
.2.1. Parasite cultures
References
Two culture-adapted strains of P. falciparum were
[1] WHO (1997) Weekly Epidemiol. Rep. 36, 269–276.
[2] WHO (1997) Weekly Epidemiol. Rep. 37, 277–284.
[3] WHO (1997) Weekly Epidemiol. Rep. 38, 285–292.
using Trager and Jensen’s method [26, 27].
[4] Snow R.W., Craig M., Deichmann U., Marsh K., Bull. World Health
Org. 77 (1999) 624–640.
5
.2.2. In vitro activity
[5] Dombrowski K.E., Baldwin W., Sheats J.E., J. Organomet. Chem.
3
02 (1986) 281–306.
6] Houlton A., Roberts R.M.G., Silver J., J. Organomet. Chem. 418
1991) 107–112.
of mefloquine and quinine analogues
The assays were conducted in vitro using a modifica-
tion of the semi-automated microdilution technique of
[
[
(
7] Ong C., Jeng J., Juang S., Chen C., Bioorg. Med. Chem. Lett. 2
3
Desjardins et al. based on radiolabelled [ H]hypoxanthine
(1992) 929–932.
incorporation [28]. Drug testing was carried out in
[8] Top S., Tang J., Vessières A., Carrez D., Provot C., Jaouen G.,
J. Chem. Soc. Chem. Comm. (1996) 955–956.
9
6-well microtitre plates. All the compounds were tested
as free bases and dissolved in dimethyl sulphoxide
5 mg/mL). They were then pre-diluted in complete
[9] Brocard J., Lebibi J., Maciejewski L., Brevet France (1995) 9505532.
[
10] Brocard J., Lebibi J., Maciejewski L., Brevet international (1996)
(
PCT/FR 96/00721; (1997) Chem. Ab. 126, 60137e.
culture medium (RPMI 1640 supplemented with 10%
pooled human AB+ serum), and titrated immediately in
duplicate in serial 2-fold dilutions. The final mefloquine
[
11] Biot C., Glorian G., Maciejewski L., Brocard J., Domarle O.,
Blampain G., Millet P., Georges A.J., Abessolo H., Dive D.,
Lebibi J., J. Med. Chem. 40 (1997) 3715–3718.

7
14
C. Biot et al. / Eur. J. Med. Chem. 35 (2000) 707–714
[
12] Domarle O., Blampain G., Agnanet H., Nzadiyabi T., Lebibi J.,
Brocard J., Maciejewski L.A., Biot C., Georges A.J., Millet P.,
Antimicrob. Agents Chemother. 42 (1998) 540–544.
[21] Slocum D.W., Engelmann T.R., Ernst C., Jennings C.A., Koons-
vitsky B., Lewis J., Sheenkin P., J. Chem. Soc. 46 (1969) 144–150.
[22] Karle M., Olmeda R., Gerena L., Milhous W.K., Exp. Parasitol. 76
[13] Gilman H., Soddy T.S., J. Org. Chem. 23 (1958) 1584–1585.
(1993) 345–351.
[14] Bellamy L.J., The Infrared Spectra of Complex Molecules, 2nd
Edition, Methnen, London, 1958.
[23] Basco L.B., Gillotin C., Gimenez F., Farinotti R., Le Bras J., Br.
J. Clin. Pharm. 33 (1992) 517–520.
[
[
[
15] Epstein L.M., Shubina E.S., Metalloorg. Khim. 5 (1992) 61–74.
[24] Peters W., Robinson B.L., Mittelholzer M.L., Crevoisier C.,
Stürchler D., Ann. Trop. Med. Parasitol. 5 (1995) 465–468.
16] Triflan D.S., Bacskai R., J. Am. Chem. Soc. 82 (1960) 5010–5011.
[
25] Gimenez F., Pennie R.A., Koren G., Crevoisier C., Wainer I.W.,
17] Battelle L.F., Bau R., Gokel G.W., Oyakawa R.T., Ugi I.K., J. Am.
Farinotti R., J. Pharm. Sci. 83 (1994) 824–827.
Chem. Soc. 95 (1973) 482–486.
[
26] Trager W., Jensen B., Science 193 (1976) 673–675.
[
[
[
18] Kwartler C.E., Lindwall H.G., J. Am. Chem. Soc. 59 (1937)
524–526.
[27] Trager W., Jensen B., Methods Cell. Biol. 45 (1994) 7–26.
19] Campbell K.N., Sommers A.H., Kerwin J.F., Campbell B.K., J. Am.
[28] Desjardins R.E., Canfield C.J., Haynes J.D., Chulay J.D., Antimi-
crob. Agents Chemother. 16 (1979) 710–718.
Chem. Soc. 68 (1946) 1851–1852.
20] Moïse C., Sautrey D., Tirouflet J., Bull. Soc. Chim. France 12 (1971)
[29] Elfort B.C., Roberts M.F., Phillipson J.D., Wilson R.J.M., Trans. R.
4562–4576.
Soc. Trop. Hyg. 81 (1987) 434–436.