Fullerene derivatives as dual inhibitors of HIV-1 reverse transcriptase and protease

Article abstract of DOI:10.1016/j.bmcl.2020.127675

In the present study, we newly synthesized three types of novel fullerene derivatives: pyridinium-type derivatives trans-3a and 4a-5b, piperidinium-type derivative 9, and proline-type derivatives 10a-12. Among the assessed compounds, 5a, 10e, 10f, 10i, 11

Full text of DOI:10.1016/j.bmcl.2020.127675

Bioorg. Med. Chem. Lett. 31 (2021) 127675
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Fullerene derivatives as dual inhibitors of HIV-1 reverse transcriptase
and protease
,
Takumi Yasunoa, Tomoyuki Ohea *, Hiroki Kataokaa, Kosho Hashimotoa, Yumiko Ishikawaa,
Keigo Furukawaa, Yasuhiro Tateishia, Toi Kobayashia, Kyoko Takahashia, Shigeo Nakamurab,
,
*
Tadahiko Mashinoa
a Department of Pharmaceutical Sciences, Faculty of Pharmacy, Keio University, 1-5-30 Shibakoen, Minato-ku, Tokyo, Japan
b Department of Chemistry, Nippon Medical School, 1-7-1 Kyonan-cho, Musashino-shi, Tokyo, Japan
A R T I C L E I N F O
A B S T R A C T
Keywords:
In the present study, we newly synthesized three types of novel fullerene derivatives: pyridinium-type derivatives
trans-3a and 4a-5b, piperidinium-type derivative 9, and proline-type derivatives 10a-12. Among the assessed
compounds, 5a, 10e, 10f, 10i, 11a-d, and 12 were found to inhibit both HIV reverse transcriptase and HIV
protease (HIV-PR), with IC50 values in the low micromolar range being observed. Regarding HIV-PR inhibition
activity, proline-type derivatives 11a-11d and 12, bearing an alkyl chain between the hydroxylmethylcarbonyl
(HMC) moiety and pyrrolidine ring, were more potent than other derivatives. This result might indicate that
connecting HMC moieties with proline-type fullerene derivatives through properly sized alkyl chain leads to
improved HIV-PR inhibitory activity.
Fullerene
HIV reverse transcriptase
HIV protease
The human immunodeficiency virus (HIV), which is a retrovirus with
a positive-sense single-stranded RNA genome, causes acquired immu-
nodeficiency syndrome (AIDS). Globally, more than 37 million people
infected HIV, and approximately 35 million people died due to HIV to
date.1 HIV infection leads to the destruction of immune cells, including
CD4-positive T-cells and macrophages.
improvement of medication adherence and simplification of the
regimen.
In addition to STRs, multitarget drugs have also been a focus over the
past few years. It was reported that multitarget drugs, interacting with
multiple disease-relevant targets, are able to improve therapeutic effi-
cacy, prevent drug resistance and reduce unwanted side effects.3 For
instance, several multikinase inhibitors, e.g., sorafenib, ponatinib and
lenvatinib, have been approved to date. With regard to anti-HIV agents,
KNI-10394 was reported to inhibit both HIV reverse transcriptase (HIV-
RT) and HIV protease (HIV-PR). The HIV-RT/PR dual inhibitor KNI-
1039, a conjugant of the peptide mimic HIV-PR inhibitor and 3′-azido-
3′-deoxythymidine, improved HIV-RT/PR inhibition activity compared
with parental compounds. Despite the high therapeutic potential of
multitarget drugs, their rational drug discovery remains a challenge, and
it is particularly difficult to create compounds exhibiting well-balanced
potency against each target.
Antiretroviral therapy (ART), the standard regimen for people living
with HIV, provides maintained suppression of viral replication and the
maintenance of an acceptable level of immune reconstitution. The ART
regimen is recommended to include two nucleoside reverse transcrip-
tase inhibitors (NRTI) in combination with a nonnucleoside reverse-
transcriptase inhibitor (NNRTI), one protease inhibitor or an integrase
inhibitor.2 In spite of the spread of ART, the emergence of multidrug-
resistant HIV is still a serious problem in anti-HIV therapy. For this
reason, it is an urgent challenge to develop a novel anti-HIV drug that is
structurally distinct from the pharmaceutical agents currently used.
Recently, single tablet regimens (STRs), e.g., Biktarvy® and Genvoya®,
were approved by the FDA. These STRs contain an HIV integrase in-
hibitor, two NRTIs and a CYP3A-specific inhibitor, contributing to the
Fullerene (C60), discovered by Kroto et al.,5 is a carbon allotrope and
is expected to be pharmaceutically useful6 on account of its three-
dimensional structure and physical properties. However, evaluation of
Abbreviations: AIDS, acquired immunodeficiency syndrome; ART, antiretroviral therapy; HIV, human immunodeficiency virus; HIV-PR, HIV protease; HIV-RT,
HIV reverse transcriptase; HMC, hydroxylmethylcarbonyl; NNRTI, nonnucleoside reverse-transcriptase inhibitor; NRTI, nucleoside reverse transcriptase inhibitors;
SAR, structure-activity relationship; STRs, single tablet regimens.
* Corresponding authors.
E-mail addresses: ohe-tm@pha.keio.ac.jp (T. Ohe), mashino-td@pha.keio.ac.jp (T. Mashino).
https://doi.org/10.1016/j.bmcl.2020.127675
Received 13 August 2020; Received in revised form 27 October 2020; Accepted 1 November 2020
Available online 5 November 2020
0960-894X/© 2020 Elsevier Ltd. All rights reserved.

T. Yasuno et al.
Bioorganic & Medicinal Chemistry Letters 31 (2021) 127675
the bioactivity of fullerene has been restricted due to its insolubility in
water. To overcome this issue, a variety of fullerene derivatives with
hydrophilic substituents have been studied. Water-soluble fullerene
derivatives have been reported to possess a range of pharmacological
properties, including antitumor,7 antiproliferative8,9 and antibacterial
9–11 activities, as well as inhibitory effects against various enzymes, such
as protein tyrosine phosphatase,12 cysteine/serine protease,13 HCV
NS3/4A protease,14 HCV NS5B polymerase,14,15 HIV-RT 15–17 and HIV-
PR.18
prevent catalytic cleavage of large polyprotein precursors. Ibrahim and
Saleh et al. reported that fullerene derivatives bearing a hydrox-
ymethylcarbonyl (HMC) moiety, the transition-state mimic isostere of
substrate processing, might have high HIV-PR inhibitory activity due to
the effective interaction between the HMC moiety and aspartic acid
residues of HIV-PR on the docking simulation.21,22
On the basis of these reports, we hypothesized that it is possible to
create fullerene-based HIV-RT/PR dual inhibitors. Thus, we strategically
designed three types of fullerene derivatives: pyridinium-type de-
rivatives trans-3a and 4a-5b, piperidinium-type derivative 9, and
proline-type derivatives 10a-12 (Fig. 1). Then, we evaluated HIV-RT
and HIV-PR inhibition activities of these novel fullerene derivatives as
well as the derivatives which were already reported as HIV-RT inhibitors
(1, 2a, 2b, cis-3a, 3b) or antitumor agents (3c, 6a, 6b, 7a-c, 8) in our
previous work,7,15–17 and we examined their structure–activity rela-
tionship (SAR).
We previously reported that several types of fullerene derivatives
exhibit HIV-RT inhibitory activity: pyrrolidinium-type derivative 1,
proline-type derivatives 2a and 2b, and pyridinium-type cis-3a and 3b
(Fig. 1).15–17 The HIV-RT inhibitory activities of pyridinium-type cis-3a
and 3b were comparable to, or slightly less potent than, proline-type
derivatives 2a and 2b, while they were found to be stronger than that
of pyrrolidinium-type derivative 1.17 Furthermore, we also reported that
proline-type derivative 2a showed HCV NS3/4A protease/NS5B poly-
merase dual inhibition activity,14 suggesting that 2a has potency as a
multitarget agent.
We previously reported that the formation of the trans isomer may be
explained by a mechanistic hypothesis in which the (E, Z) or (Z, E)
azomethine ylide intermediate (which leads to the trans product)
generated from the corresponding secondary amine and ketone or
aldehyde is more dominant than the other configurations due to its steric
stability.14 On the basis of this finding, derivative trans-3a” was syn-
thesized by the 1,3-dipolar cycloaddition reaction of 3-pyridinecarbox-
aldehyde and N-(4-methoxybenzyl)-glycine ethyl ester (15), as
illustrated in Scheme 1. In fact, the methine proton on the C-5 of the
pyrrolidine ring in the trans isomer was clearly downfield-shifted
Regarding the HIV-PR inhibition activity of fullerene derivatives,
there are few precedents for synthesis, while a number of groups have
reported on 3D QSAR, molecular docking and molecular dynamics of
fullerene-based HIV-PR inhibitors.19–22 HIV-PR is one of the significant
enzymes that leads to HIV proliferation. The active site of HIV-PR con-
sists of hydrophobic amino acid residues, except the two hydrophilic
aspartic acids. HIV-PR inhibitors occupy the substrate binding site and
Fig. 1. Structures of fullerene derivatives.
2

T. Yasuno et al.
Bioorganic & Medicinal Chemistry Letters 31 (2021) 127675
Scheme 1. Synthesis of trans-3a. (a) ethyl chloroacetate, triethylamine, CH2Cl2, 0 ◦C to r.t, 44%; (b) 15, 3-pyridinecarboxaldehyde, toluene, reflux, 11%; (c) Tri-
fluoroacetic acid, CHCl3, r.t, 61%; (d) CH3I, r.t, 65%.
compared to the cis isomer, which was consistent with the NMR-analysis
reported by Filippone et al.23 Derivative trans-3a was subsequently
synthesized through PMB deprotection of trans-3a” and methylation of
trans-3a’ with methyl iodide. In the case of 4a-5b, the precursor 13 was
synthesized in the same manner as our previous report.17Amidation with
corresponding amine followed by methylation with methyl iodide pro-
duced 4a-5b (Scheme 2). The introduction of methyl groups onto the
pyridine nitrogen was confirmed by the downfield shift of the 1H NMR
Scheme 3. Synthesis of 9. (a) sarcosine, 1-methyl-4-pyrrolidone, toluene,
reflux, 27%; (b) CH3I, DMF, r.t. to 60 ◦C, 76%.
signals for the aromatic protons and the observation of a signal on the 1-
position of the pyrrolidine ring. For the synthesis of piperidinium de-
rivative 9, precursor 9′ were synthesized by 1,3-dipolar cycloaddition
reaction of the corresponding ketone and glycine derivatives. Subse-
quent methylation with methyl iodide produced compound 9 (Scheme
3). In the case of 9, the introduction of methyl group onto the piperidine
nitrogen was confirmed by the downfield shift of the 1H NMR signals for
the piperidine-ring protons and the observation of an unchanged signal
on the 1-position of the pyrrolidine ring.
Compound 23, the exo-substituent of 10b, was synthesized by depro-
tection of 18b with trifluoromethanesulfonic acid (Scheme 6). The
identification and the purity of the compounds synthesized in the pre-
sent study were confirmed by NMR as well as by mass spectrometry and
in some cases by high-resolution mass spectrometry.
We first investigated the HIV-RT inhibition activities of fullerene
derivatives using recombinant RT derived from HIV-1. The HIV-RT in-
hibition activities were examined in a similar manner as O’Meara et al.24
The HIV-RT inhibition activities of all of the novel fullerene derivatives
synthesized in the present study were more potent than nevirapine
(Table 1). Regarding the HIV-RT inhibition activities of C60-based
compounds, pyrrolidinium-type derivative 1, proline-type derivatives
2a and 2b, and pyridinium-type cis-3a and 3b were comparable to
The preparation of proline derivatives 10a-f, 11a-d is illustrated in
Scheme 4. Compound 14 was synthesized by 1,3-dipolar cycloaddition
reaction of C60
, paraformaldehyde and glycine tert-butyl ester.
Regarding the benzoic acid analogues 18a, 18b and 18e-h, ethyl gly-
colate was used as the starting material. Protection of the hydroxyl
group with TBDPS-Cl produced 16a, which was hydrolyzed with NaOH
to yield 17a. After the treatment of 17a with oxalyl chloride, amidation
using the corresponding carboxylic acids produced 18a, 18b and 18e-h.
In the case of 18c and 18d, amidation of the corresponding amino
benzoic acids with 17b, prepared stepwise from methyl 3-hydroxypro-
panoate, gave 18c and 18d. For the synthesis of compounds 21a and
21b, 2-aminoethan-1-ol was used as the starting material. Protection of
the hydroxyl group in a similar manner to 17a/17b followed by ami-
dation with 3-/4-formylbenzoic acid and Pinnick oxidation of carbonyl
group produced 21a/21b. After the treatment of 18a-h, 21a and 21b
with oxalyl chloride, amidation of the corresponding acid chlorides with
14. Subsequent deprotection with trifluoromethanesulfonic acid pro-
duced the proline derivatives 10a-f and 11a-d. With respect to 12,
condensation of 17b with 5-aminovaleric acid gave 22. After the
treatment of 22 with oxalyl chloride, amidation with 14 and the
following deprotection produced proline derivative 12 (Scheme 5).
previous data (IC50 = 1.4–1.7 μM (1), 0.032 μM (2a), 0.029 μM (2b),
0.094
μM (cis-3a), 0.25
μ
M (3b), respectively).15–17 In the case of
pyridinium-type and piperidinium-type derivatives, there was no
remarkable difference in the inhibitory activities of trans-3a, 4a-5b, 7a-
c, 8 and 9, whereas 3c, 6a and 6b inhibited HIV-RT with slightly lower
potency than cis-3a. These results suggest that it is favorable to bear an
ester or amide moiety on the pyrrolidine ring in terms of the HIV-RT
inhibition of pyridinium-type derivatives. Among the proline-type de-
rivatives 10a-12, 10c was equally potent relative to 2a and 2b, while the
HIV-RT inhibition activities of the others were slightly weaker than
those of 2a and 2b.
We next examined HIV-PR inhibitory activity using recombinant PR
derived from HIV-1 in a similar manner to Friedman et al.18 Pyridinium-
type and piperidinium-type derivatives trans-3a, 4a, 4b, 5a, 5b and 9
exhibited potency of HIV-PR inhibition, whereas most cationic
Scheme 2. Synthesis of 4a-b and 5a-b. (a) glycine tert-butyl ester hydrochloride, 3-pyridinecarboxaldehyde, toluene, reflux, 29%; (b) trifluoromethanesulfonic acid,
CS2, r.t, 91%; (c) corresponding amine hydrochloride, HOBt, EDC hydrochloride, N-methylmorpholine, CH2Cl2, r.t, 10–54%; (d) CH3I, r.t, 45–92%.
3

T. Yasuno et al.
Bioorganic & Medicinal Chemistry Letters 31 (2021) 127675
Scheme 4. Synthesis of 10a-f and 11a-d. (a) TBDPS-Cl, imidazole, DMF, 0 ◦C to r.t, quant; (b) NaOHaq, EtOH, 0 ◦C to r.t, 72%; (c) (COCl)2, DMF, Et2O, 0 ◦C to r.t; (d)
pyridine, Et2O or THF or CH2Cl2, 0 ◦C to r.t, 12–67%; (e) TBDPS-Cl, imidazole, CH2Cl2, 0 ◦C to r.t, 77%; (f) NaOHaq, MeOH, 0 ◦C to r.t, 78%; (g) (COCl)2, DMF, Et2O,
0 ◦C to r.t; (h) pyridine, Et2O, 0 ◦C to r.t, 80%-quant; (i) TBDPS-Cl, imidazole, CH2Cl2, 0 ◦C to r.t, 94%; (j) (COCl)2, DMF, acetonitrile, 0 ◦C to r.t; (k) pyridine, THF,
0 ◦C to r.t, 18–63%; (l) 2-methyl-2-butene, NaClO2, NaH2PO4, tBuOH/water, r.t, 12%-quant; (m) glycine tert-butyl ester hydrochloride, paraformaldehyde, LiClO4,
triethylamine, toluene, reflux, 42%; (n) (COCl)2, DMF, toluene or CH2Cl2, 0 ◦C to r.t; (o) pyridine, toluene or CH2Cl2, 0 ◦C to r.t, 15–70%; (p) tri-
fluoromethanesulfonic acid, toluene or CH2Cl2, 0 ◦C or 0 ◦C to r.t, 21–96%.
Scheme 5. Synthesis of 12. (a) EDC hydrochloride, CH2Cl2, r.t; (b) 5-aminovaleric acid, CH2Cl2, r.t, 30%; (c) EDC hydrochloride, CH2Cl2, r.t, 14%; (d) tri-
fluoromethanesulfonic acid, toluene, 0 ◦C to r.t, 52%.
derivatives lack HIV-PR inhibitory activity. Among the pyridinium-type
derivatives cis-3a, trans-3a and 3c, only trans-3a showed HIV-PR
inhibitory activity, indicating that the stereochemistry of ethyl ester
might contribute to the inhibition of HIV-PR. In addition, 4a-5b showed
HIV-PR inhibition activity. This result suggests that an amide moiety of
the pyrrolidine ring significantly contributes to the enhancement of HIV-
PR inhibition. Furthermore, the comparison between HIV-PR inhibition
activities of 10a-12 with those of 2a and 2b indicated that fullerene
derivatives bearing hydroxylmethylcarbonyl (HMC) moieties are more
likely to have higher inhibition activity. In the case of 10a-f, there was
4

T. Yasuno et al.
Bioorganic & Medicinal Chemistry Letters 31 (2021) 127675
The membrane permeability and cytotoxicity of fullerene derivatives
11c and 11d were evaluated (Table 2). The Papp values of the fullerene
derivatives in parallel artificial membrane permeability assay (PAMPA)
were higher than saquinavir, a clinically used HIV-PR inhibitor. It
should be noted that the permeability of 11c and 11d was comparable to
propranolol, a highly membrane permeable drug. In addition, the
cytotoxicity of 11c and 11d on normal cells (mouse fibroblast NIH3T3)
and human cells (human hepatoma HepG2) were assessed using a con-
ventional trypan blue dye exclusion test. The CC50 values on both cell
Scheme 6. Synthesis of 23. (a) trifluoromethanesulfonic acid, toluene,
0 ◦C, 88%.
Table 1
lines were over 30 μM. These results indicate that 11c and 11d are able
HIV-RT/PR inhibition activities of fullerene derivatives.
to passively permeate across the cell membrane and inhibit HIV-RT and
HIV-PR without serious toxicity.
Compound
HIV-RT Inhibitory Activity IC50
M)
HIV-PR Inhibitory Activity IC50
(μM)
(μ
In summary, this is the first report to indicate that cationic-type and
proline-type fullerene derivatives show potent HIV-RT and HIV-PR dual
inhibition. The inhibition activities against HIV-PR were weaker than a
clinically used HIV-PR inhibitor, ritonavir. However, the newly syn-
thesized fullerene derivatives 5a, 10a, 10b, 10e, 11a-d and 12 showed
HIV-PR as well as HIV-RT inhibition activities. Of these, proline-type
derivatives 11c and 11d showed the best-balanced activity in the cur-
rent work, namely, a similar level of inhibitory activities against HIV-RT
and HIV-PR with submicromolar IC50 values, suggesting that 11c and
11d may strongly inhibit HIV replication by the synergistic effect as an
HIV-RT/PR dual inhibitor. The effects of these derivatives in HIV-
infected cells are under investigation.
1
1.0
0.06
0.05
0.4
0.4
0.4
1.0
0.6
0.3
0.6
0.3
1.5
1.6
0.3
0.2
0.1
0.5
0.5
0.4
0.2
0.05
0.7
0.1
0.6
1.0
0.5
0.6
0.2
0.8
N. T.
2.1
N. T.
>10
6.4
2a
2b
4.3
cis-3a
trans-3a
3b
>10
7.7
>10
>10
6.2
3c
4a
4b
6.4
5a
1.9
5b
8.7
6a
>10
>10
>10
>10
>10
>10
5.7
6b
7a
7b
7c
Declaration of Competing Interest
8
9
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.
10a
10b
10c
10d
10e
10f
11a
11b
11c
11d
12
1.4
2.0
2.1
4.9
1.9
Acknowledgements
3.0
1.3
This research was supported by the Platform Project for Supporting
Drug Discovery and Life Science Research (Basis for Supporting Inno-
vative Drug Discovery and Life Science Research) from AMED under
Grant Number JP20am0101089.
1.3
0.6
0.7
1.0
23
>10
N. T.
1.7 nM
Nevirapine
Ritonavir
Appendix A. Supplementary data
N.T.: Not Tested.
Supplementary data to this article can be found online at https://doi.
org/10.1016/j.bmcl.2020.127675.
no remarkable difference in HIV-PR inhibitory activity, suggesting that
it is not effective to replace an HMC moiety (10a and 10b) into a
hydroxyethylcarbonyl unit (10c and 10d) or reversed amide (10e and
10f). In contrast, it should be noted that proline-type derivatives 11a-
d and 12, bearing an alkyl spacer between the HMC moiety and pyrro-
lidine ring, tended to show more potency than 10a and 10b. Further-
more, HMC analogue 23, the exo-substituent of 10b, indicated a loss of
HIV-PR inhibition activity. These results might imply that connecting
the HMC moiety with proline-type fullerene derivatives through prop-
erly sized alkyl chain leads to improved HIV-PR inhibitory activity.
Among the proline-type derivatives, compound 11c and 11d showed the
best HIV-PR inhibition activity.
References
1 Beccari MV, Mogle BT, Sidman EF, Mastro KA, Asiago-Reddy E, Kufel WD.
Ibalizumab, a novel monoclonal antibody for the management of multidrug-resistant
HIV-1 infection. Antimicrob Agents Chemother. 2019;63:e00110–19. https://doi.org/
10.1128/AAC.00110-19.
´
2 Menendez-Arias L. Molecular basis of human immunodeficiency virus type 1 drug
resistance: overview and recent developments. Antivir Res. 2013;98:93–120. https://
doi.org/10.1016/j.antiviral.2013.01.007.
3 Peters JU. Polypharmacology – foe or friend? J Med Chem. 2013;56:8955–8971.
https://doi.org/10.1021/jm400856t.
4 Matsumoto H, Hamawaki T, Ota H, et al. ‘Double-drugs’ – a new class of prodrug
form of an HIV protease inhibitor conjugated with a reverse transcriptase inhibitor
by a spontaneously cleavable linker. Bioorg Med Chem Lett. 2000;10:1227–1231.
https://doi.org/10.1016/S0960-894X(00)00202-X.
5 Kroto HW, Health JR, O’Brien SC, Curl RF, Smalley RE. C60: buckminsterfullerene.
Nature. 1985;318:162–163. https://doi.org/10.1038/318162a0.
Table 2
Membrane permeability and cytotoxicity of 11c and 11d.
6 Bosi S, Da Ros T, Spalluto G, Prato M. Fullerene derivatives: an attractive tool for
biological applications. Eur J Med Chem. 2003;38:913–923. https://doi.org/
10.1016/j.ejmech.2003.09.005.
Compound
PAMPA Papp (10ꢀ 6 cm/s)
Cell growth Inhibition CC50 (μM)
7 Yasuno T, Ohe T, Ikeda H, Takahashi K, Nakamura S, Mashino T. Synthesis and
antitumor activity of novel pyridinium fullerene derivatives. Int J Nanomed. 2019;14:
6325–6337. https://doi.org/10.2147/IJN.S212045.
NIH3T3
HepG2
11c
16
>30
>30
N.T.
N.T.
N.T.
>30
>30
N.T.
N.T.
N.T.
11d
9.7
8.1
0.52
1.2
8 Nishizawa C, Hashimoto N, Yokoo S, et al. Pyrrolidinium-type fullerene derivatives-
induced apoptosis by the generation of reactive oxygen species in HL-60 cells. Free
Radic Res. 2009;43:1240–1247. https://doi.org/10.3109/13814780903260764.
9 Mashino T, Nishikawa D, Takahashi K, et al. Antibacterial and antiproliferative
activity of cationic fullerene derivatives. Bioorg Med Chem Lett. 2003;13:4395–4397.
https://doi.org/10.1016/j.bmcl.2003.09.040.
Propranolol
Furosemide
Saquinavir
N.T.: Not Tested.
5

T. Yasuno et al.
Bioorganic & Medicinal Chemistry Letters 31 (2021) 127675
10 Bosi S, Da Ros T, Castellano S, Banfi E, Prato M. Antimycobacterial activity of ionic
fullerene derivatives. Bioorg Med Chem Lett. 2000;10:1043–1045. https://doi.org/
10.1016/S0960-894X(00)00159-1.
hydrophobic desolvation. J Med Chem. 1998;41:2424–2429. https://doi.org/
10.1021/jm970689r.
19 Lee VS, Nimmanpipug P, Aruksakunwong O, Promsri S, Sompornpisut P,
Hannongbua S. Structural analysis of lead fullerene-based inhibitor bound to human
immunodeficiency virus type 1 protease in solution from molecular dynamics
simulations. J Mol Graph Model. 2007;26:558–570. https://doi.org/10.1016/j.
jmgm.2007.03.013.
11 Tsao N, Luh T, Chou C, et al. In vitro action of carboxyfullerene. J Antimicrob
Chemother. 2002;49:641–649. https://doi.org/10.1093/jac/49.4.641.
12 Kobzar OL, Trush VV, Tanchuk VY, Zhilenkov AV, Troshin PA, Vovk AI. Fullerene
derivatives as a new class of inhibitors of protein tyrosine phosphatases. Bioorg Med
Chem Lett. 2014;24:3175–3179. https://doi.org/10.1016/j.bmcl.2014.04.110.
13 Tokuyama H, Yamago S, Nakamura E, Shiraki T, Sugiura Y. Photoinduced
biochemical activity of fullerene carboxylic acid. J Am Chem Soc. 1993;115:
7918–7919. https://doi.org/10.1021/ja00070a064.
20 Durdagi S, Mavromoustakos T, Chronakis N, Papadopoulos MG. Computational
design of novel fullerene analogues as potential HIV-1 PR inhibitors: analysis of the
biding interactions between fullerene inhibitors and HIV-1 PR residues using 3D
QSAR, molecular docking and molecular dynamics simulations. Bioorg Med Chem.
2008;16:9957–9974. https://doi.org/10.1016/j.bmc.2008.10.039.
21 Ibrahim M, Saleh NA, Hameed AJ, Elshemey WM, Elsayed AA. Structural and
electronic properties of new fullerene derivatives and their possible application as
HIV-1protease inhibitors. Spectroc Acta Pt A Molec Biomolec Spectr. 2010;75:702–709.
https://doi.org/10.1016/j.saa.2009.11.042.
14 Kataoka H, Ohe T, Takahashi K, Nakamura S, Mashino T. Novel fullerene derivatives
as dual inhibitors of Hepatitis C virus NS5Bpolymerase ans NS3/4A protease. Bioorg
Med Chem Lett. 2016;26:4565–4567. https://doi.org/10.1016/j.bmcl.2016.08.086.
15 Mashino T, Shimotohno K, Ikegami N, et al. Human immunodeficiency virus-reverse
transcriptase inhibition and hepatitis C virus RNA-dependent RNA polymerase
inhibition activities of fullerene derivatives. Bioorg Med Chem Lett. 2005;15:
1107–1109. https://doi.org/10.1016/j.bmcl.2004.12.030.
22 Saleh NA. The QSAR and docking calculations of fullerene derivatives as HIV-1
protease inhibitors. Spectroc Acta Pt A Molec Biomolec Spectr. 2015;136:1523–1529.
https://doi.org/10.1016/j.saa.2014.10.045.
16 Nakamura S, Mashino T. Water-soluble fullerene derivatives for drug discovery.
J Nippon Med Sch. 2012;79:248–254. https://doi.org/10.1272/jnms.79.248.
17 Yasuno T, Ohe T, Takahashi K, Nakamura S, Mashino T. The human
immunodeficiency virus-reverse transcriptase inhibition activity of novel pyridine/
pyridinium-type fullerene derivatives. Bioorg Med Chem Lett. 2015;25:3226–3229.
https://doi.org/10.1016/j.bmcl.2015.05.086.
´
23 Filippone S, Maroto EE, Martín-Domenech A, Suarez M, Martín N. An efficient
approach to chiral fullerene derivatives by catalytic enantioselective 1,3-dipolar
cycloadditions. Nat Chem. 2009;1:578–582. https://doi.org/10.1038/nchem.361.
24 O’Meara JA, Yoakim C, Bonneau PR, et al. Novel 8-substituted dipyridodiazepinone
inhibitors with a broad-spectrum of activity against HIV-1 strains resistant to non-
nucleoside reverse transcriptase inhibitors. J Med Chem. 2005;48:5580–5588.
https://doi.org/10.1021/jm050255t.
18 Friedman SH, Ganapathi PS, Rubin Y, Kenyon GL. Optimizing the binding of
fullerene inhibitors of the HIV-1 protease through predicted increases in
6