Anti-protozoal and anti-fungal evaluation of 3,5-disubstituted 1,2-dioxolanes

Article abstract of DOI:10.1016/j.bmcl.2021.128196

Endoperoxides are a class of compounds, which is well-known for their antimalarial properties, but few reports exist about 3,5-disubstituted 1,2-dioxolanes. After having designed a new synthetic route for the preparation of these substances, they were evaluated against 4 different agents of infectious diseases, protozoa (Plasmodium and Leishmania) and Fungi (Candida and Aspergillus). Whereas moderate antifungal activity was found for our products, potent antimalarial and antileishmanial activities were observed for a few compounds. The nature of the substituents linked to the endoperoxide ring seems to play an important role in the bioactivities.

Full text of DOI:10.1016/j.bmcl.2021.128196

Bioorg. Med. Chem. Lett. 47 (2021) 128196
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Anti-protozoal and anti-fungal evaluation of 3,5-disubstituted
1,2-dioxolanes
,
,
b
a
Alexis Pineta, Sandrine Cojeana d, Linh Thuy Nguyena , Pedro Vasquez-Ocmín ,
´
a
a
c
a
a,*
´
`
Alexandre Maciuk , Philippe M. Loiseau , Patrice Le Pape , Bruno Figadere , Laurent Ferrie
a
´
ˆ
BioCIS, CNRS, Universite Paris-Saclay, Chatenay-Malabry 92290, France
b Institute of Marine Biochemistry (IMBC), Vietnam Academy of Science and Technology (VAST), Cau Giay, Hanoi, Viet Nam
c Department of Parasitology and Medical Mycology University of Nantes, EA1155 IICiMed, Nantes Atlantique Universities, Faculty of Pharmacy, Nantes, France
d
´ ´
ˆ
National de Reference du Paludisme, Hopital Bichat-Claude Bernard, APHP, 75018 Paris, France
A R T I C L E I N F O
A B S T R A C T
Keywords:
Endoperoxides are a class of compounds, which is well-known for their antimalarial properties, but few reports
exist about 3,5-disubstituted 1,2-dioxolanes. After having designed a new synthetic route for the preparation of
these substances, they were evaluated against 4 different agents of infectious diseases, protozoa (Plasmodium and
Leishmania) and Fungi (Candida and Aspergillus). Whereas moderate antifungal activity was found for our
products, potent antimalarial and antileishmanial activities were observed for a few compounds. The nature of
the substituents linked to the endoperoxide ring seems to play an important role in the bioactivities.
Endoperoxide
Antifungal
Antileishmanial
Antimalarial
1,2-Dioxolane
Endoperoxides are a source of potent bioactive compounds, such as
important anti-malarial drugs artemisinin, artemether and
arterolane.1–4 1,2-Dioxane is the predominant endoperoxide structure
among all peroxy natural products, however plakinic acids A-P illustrate
a major family of endoperoxides exhibiting a 1,2-dioxolane scaffold with
antiprotozoal, anti-HIV, antibacterial or cytotoxic activities.5,6 These
products are in particular 3,3,5,5-tetrasubstituted on the 1,2-dioxolane
ring and the interest of chemists for these compounds culminated in
studies towards their total synthesis.7–9 Because plakinic acids, and
endoperoxides in general, exhibit potent bioactivities, medicinal
chemistry studies carried out by Woerpel & Clardy reported moderate
antimalarial activity of many synthetic 3,3,5,5-tetrasubstituted 1,2-
dioxolanes obtained from formal [3 + 2] cycloadditions.10 Nevertheless,
Woerpel & Stockwell found also that one of the described endoperoxide,
called FlNO2, initiates ferroptosis through GPX4 inactivation.11,12
Vennerstrom et al. also prepared a 1,2-dioxolane analogue of arterolan
using the same technique, but they found that it was about 100-fold less
active than the original compound (Fig. 1).13–15
against Plasmodium falciparum., MIC = 0.61 µM against C. albicans WT].
The nature of the substitution is relatively uncommon among natural
products containing a 1,2-dioxolane, and by consequence we wanted to
know how we could access to such a structure.18 For this purpose, we
developed new methodologies to synthesize specifically 3,5-disubsti-
tuted 1,2-dioxolane rings.19–21 Having in hand a small chemical li-
brary resulting from our synthetic methodology studies, we decided to
assess their anti-fungal, antimalarial and anti-leishmanial properties
(Table 1).
Chemical synthesis
The preparation of 3,5 disubstituted 1,2-dioxolanes was achieved by
using two different approaches, both of them employing an oxidative
ring expansion of cyclopropanols as a key step. In the first method,
cyclopropanols 3b-e were obtained by applying a Kulinkovich reaction
with ethyl formate from bromides 1b-e. Alternatively, 3a was prepared
by methylenation of aldehyde 2a, followed by a reductive cyclization
with CrCl2 and water, because of the hindrance of tert-butyl group which
did not permit the use of the original pathway. Cyclopropanols 3a-e in
hand, oxidative ring expansion was achieved with Mn(acac)2, providing
1,2-dioxolanols 4a-e in good yields. Then, Lewis acid catalyzed acety-
lation furnished the corresponding acetate derivatives 5a-e. Acetate
At the same time, mycangimycin, a new polyene endoperoxide, was
identified in 2009 from some Streptomyces strains living in symbiosis
with the southern pine beetle Dendroctonus frontalis.16,17 This compound
bears a 3,5-disubstituted 1,2-dioxolane ring and was reported to possess
excellent antimalarial and antifungal activities [EC50 = 0.052 µM
* Corresponding author.
´
E-mail address: laurent.ferrie@universite-paris-saclay.fr (L. Ferrie).
https://doi.org/10.1016/j.bmcl.2021.128196
Received 18 March 2021; Received in revised form 28 May 2021; Accepted 6 June 2021
Available online 8 June 2021
0960-894X/© 2021 Elsevier Ltd. All rights reserved.

A. Pinet et al.
Bioorganic & Medicinal Chemistry Letters 47 (2021) 128196
dioxanyl derivatives are much more resistant to acid hydrolysis than
their tetrahydrofuranyl analogues (Fig. 2).
A second approach is based on our pioneering work towards syn-
thesis of analogues of mycangimycin.18 Kulinkovich reaction between
olefin 20 and methyl palmitate 21 using Cha’s protocol22 afforded
cyclopropanol 22 and subsquent oxidative ring expansion with molec-
ular oxygen gave dioxolanol 23. Reduction of the ketal with Et3SiH and
triflic acid at –78 ◦C, followed by the silyl ether cleavage provided
alcohol 18f with the cis configuration predominating. Oxidation of the
hydroxy group with periodic acid and RuCl3 furnished 19f, which cor-
responds to the saturated side chain analogue of mycangimycin (Fig. 3).
Antifungal evaluation
All twenty-three 1,2-dioxolanes were evaluated for antifungal ac-
tivity against Candida albicans (CAAL93) and Aspergillus fumigatus
ASFU76 clinical isolates; for antimalarial activity against Plasmodium
falciparum 3D7 strain; for antileishmanial activity against Leishmania
donovani LV9 axenic amastigote stage. Some selected 1,2-dioxolanes
were also tested against Leishmania donovani LV9 intramacrophage
form and a cytotoxicity test was performed with those compounds on
HUVEC cells to calculate the selectivity index for treatment against
malaria and leishmaniasis. Results are reported in Table 1.
Fig. 1. Selected examples of reported bioactive 1,2-dioxolanes.
derivatives 5a-e were then substituted with various neutral nucleophiles
by using conditions reported by us; namely a stoichiometric protocol
with a strong Lewis acid such as TiCl4 at low temperature (–40 ◦C)
corresponding to “Conditions A”;19 and a catalytic procedure using mild
Lewis acid such as Sc(OTf)3 at room temperature, corresponding to
“Conditions B”.20 Sakurai reaction with different allylsilanes was per-
formed to build 1,2-dioxolanes 6c-e and 7c-9c; reaction with TMSCN or
TMSN3 afforded compounds 10c and 11c, while Et3SiH gave 12c;
Mukaiyama aldol reactions furnished ketones 13c&14c from the cor-
responding silylenol ethers and thioesters 15c&16c were obtained from
the corresponding silyl ketene(thio)acetals. It is noteworthy that hy-
droxyl compounds 4a-e exist in equilibrium with the open hydroperoxy
aldehyde form, while the structure of 5a-e, 10c and 11c is blocked.
Their hydrolysis in a biological medium might be possible, however 1,2-
Antifungal evaluation
The results reported in Table 1 showed that most of compounds were
inactive towards the tested fungi clinical isolates. Only compounds 6c,
7c and 8c showed moderate antifungal activity, 7c being only active
against Aspergillus, but with IC50 values approximately one hundred
times higher than references. It is also disappointing to see that the
saturated analog of mycangimycin 19f showed absolutely no inhibitory
Table 1
Inhibitory concentration (IC50), expressed in µM, of 3,5-disubtituted 1,2-dioxolanes against Candida albicans CAAL93 & Aspergillus fumigatus ASFU76 strains (controls:
fluconazole & amphotericin B); against Plasmodium falciparum 3D7 (control: chloroquine); against Leishmania donovani LV9 under axenic amastigote form and
intramacrophage form (control: miltefosine). Evaluation of toxicity (CC50, µM) towards HUVEC cells line (control: chloroquine and miltefosine) and selectivity indexes
(SI) to evaluate beneficial effect of antimalarial and antileishmanial activities (on axenic amastigote form) versus human cell death.
Compounds
Candida albicans
Aspergillus
fumigatus
(ASFU76) (IC50
µM)
Plasmodium
L. donovani LV9
axenic amastigote
(IC50, µM)
L. donovani LV9
Intramacrophage (IC50
µM)
Toxicity
HUVEC
SI
SI
(CAAL93) (IC50
,
falciparum (3D7)
(IC50, µM)
,
P. falciparum
L. donovani
µM)
,
(CC50, µM)
4a
>100
>100
>100
>100
>100
>100
>100
>100
35.73 ± 5.12
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
–
0.34 ± 0.03
>100
>100
12.23 ± 1.63
12.56 ± 1.16
28.19 ± 4.03
59.32 ± 6.07
71.68 ± 6.08
57.83 ± 1.49
0.7 ± 0.16
11.69 ± 1.72
6.13 ± 0.55
2.29 ± 0.14
12.17 ± 1.48
10.94 ± 3.92
10.64 ± 2.35
6.09 ± 0.93
9.02 ± 0.43
1.89 ± 0.55
1.82 ± 0.44
ND
35
<0.12
<0.13
<0.28
<0.59
<0.72
0.82
<0.01
1.71
4.09
1.48
0.64
0.26
0.2
5a
>100
0.02 ± 0.009
>100
44.26 ± 16.09
628
234
293
<71
<57
7
4b
>100
0.12 ± 0.02
>100
>100
5b
>100
0.1 ± 0.02
>100
32.86 ± 13.38
4c
>100
>1
>100
>100
5c
>100
>1
70.65 ± 10.52
>100
>100
6c
25.24 ± 3.40
35.73 ± 2.00
33.39 ± 2.63
>100
0.1 ± 0.03
ND
7c
0.17 ± 0.05
6.82 ± 1.04
1.50 ± 0.09
1.55 ± 0.21
19.15 ± 1.77
42.87 ± 6.16
49.77 ± 1.16
4.42 ± 1.34
> 100
>100
68
8c
0.15 ± 0.02
28.35 ± 15.44
40
9c
>1
33.56 ± 8.76
<2
405
<10
<10.6
<6
24
10c
>100
0.03 ± 0.01
37.61 ± 11.08
11c
>100
>1
>100
12c
>100
>1
ND
13c
>100
>1
>100
1.38
<0.09
1.01
0.83
ND
14c
>100
0.37 ± 0.10
ND
15c
>100
0.25 ± 0.05
1.88 ± 0.31
2.20 ± 0.49
>100
38.93 ± 13.59
7
16c
>100
>1
>100
<1.8
ND
ND
ND
ND
ND
ND
–
5d
>100
>1
ND
6d
>100
>1
>100
ND
ND
ND
5e
>100
>1
56.60 ± 3.32
6.78 ± 1.23
5.57 ± 0.18
6.16 ± 0.21
–
ND
ND
ND
6e
>100
>1
ND
ND
ND
18f
>100
>1
ND
ND
ND
19f
>100
>1
ND
ND
ND
Fluconazole
Ampho. B
Chloroquine
Miltefosine
0.30 ± 0.04
–
–
–
–
–
0.33 ± 0.00
–
–
–
–
–
–
–
–
–
–
0.0166 ± 0.0055
–
31.50 ± 1.40
1897
ND
ND
–
–
1.7 ± 0.573
0.61 ± 0.14
54.3 ± 2.14
32
ND: not determined.
2

A. Pinet et al.
Bioorganic & Medicinal Chemistry Letters 47 (2021) 128196
Fig. 2. Synthesis of dioxolanes 4a-e, 5a-e, 6c-e, 8c-17c. “dr” represents trans:cis diastereomeric ratios. (A) or (B) refers to the conditions A or B used for the
nucleophilic substitution.
Fig. 3. Synthesis of dioxolanes 18f and 19f.
properties against tested fungi. By consequence, the role of the unsatu-
ration on the side chain of mycangimycin is probably crucial for the
antifungal activity.
contrast, saturated analogue of mycangimycin 19f showed no activity
below the micromolar range, which means that the potent antimalarial
property of the natural product is probably not only associated with the
endoperoxide scaffold, but also with the unsaturated side chain. Some
complementary studies were also performed by using a mass spec-
trometry technique, which can detect hemin-binding of chemicals with
potential antimalarial molecules such as artemisin.23–25 Although a
certain number of our 1,2-dioxolanes showed covalent hemin-binding,
no correlation with the observed antimalarial activity could be
deduced (e.g. the most active compounds 5a and 10c did not show any
hemin-binding). This suggests that the mechanism might not be the
same as other known antimalarial endoperoxides,14,26,27 with possibly
off target interactions. Moreover, azide 10c might undergo reduction
with glutathionehemin and hemin,28 to provide an unstable amino-
dioxolane,29 which might interferes directly on the biomineralisation of
hemin by the parasite.
Antimalarial evaluation
Evaluation of the antimalarial activity concluded that eleven com-
pounds out of twenty-three exhibited a potential antimalarial activity
below micromolar range (4a, 4b, 5a, 5b, 6c-8c, 10c, 14c, 15c). Among
them, 5a and 10c displayed powerful properties in this area with ac-
tivities in the same range as chloroquine. Their strong antimalarial ac-
tivity seems associated with the nature of the alkyl substituent, because
α
-branched substituents showed good antimalarial properties overall
(4a-b, 5a-b). The substituent put at position 3 in the last nucleophilic
substitution (See Fig. 2) plays also an important role, and azide obvi-
ously enhances significantly antiplasmodial properties of compound
10c. Antimalarial activity is significantly higher for these compounds,
with selectivity indexes of 628 and 405 for 5a and 10c, respectively. In
3

A. Pinet et al.
Bioorganic & Medicinal Chemistry Letters 47 (2021) 128196
Antileishmanial evaluation
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Declaration of Competing Interest
`
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The authors declare that they have no known competing financial
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`
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4

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