Inducing apoptosis through upregulation of p53: structure–activity exploration of anthraquinone analogs

Article abstract of DOI:10.1007/s00044-020-02563-y

We previously reported a series of p53-elevating anthraquinone compounds with considerable cytotoxicity for acute lymphoblastic leukemia (ALL) cells. To further develop this class of compounds, we examined the effect of a few key structural features on the anticancer structure–activity relationship (SAR) in ALL cells. The active analogs showed comparable cytotoxicity and upregulation of p53 but did not induce significant downregulation of MDM2 as seen with the lead compound AQ-101, indicating the importance of the anthraquinone core scaffold for MDM2 regulation. The result from the current study not only contributes to the SAR framework of these anthraquinone derivatives but also opens up new chemical space for further optimization work.

Full text of DOI:10.1007/s00044-020-02563-y

MEDICINAL
CHEMISTRY
RESEARCH
Medicinal Chemistry Research
https://doi.org/10.1007/s00044-020-02563-y
REVIEW ARTICLE
Inducing apoptosis through upregulation of p53: structure–activity
exploration of anthraquinone analogs
Abiodun Anifowose1 Ayodeji A. Agbowuro1 Ravi Tripathi1 Wen Lu1 Chalet Tan2 Xiaoxiao Yang1
Binghe Wang
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Received: 25 April 2020 / Accepted: 15 May 2020
© Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract
We previously reported a series of p53-elevating anthraquinone compounds with considerable cytotoxicity for acute
lymphoblastic leukemia (ALL) cells. To further develop this class of compounds, we examined the effect of a few key
structural features on the anticancer structure–activity relationship (SAR) in ALL cells. The active analogs showed
comparable cytotoxicity and upregulation of p53 but did not induce significant downregulation of MDM2 as seen with the
lead compound AQ-101, indicating the importance of the anthraquinone core scaffold for MDM2 regulation. The result from
the current study not only contributes to the SAR framework of these anthraquinone derivatives but also opens up new
chemical space for further optimization work.
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Keywords Leukemia Anthraquinone Structure–activity relationships p53 Covalent inhibitor
Introduction
et al. 1976; Slats et al. 2005). Based on the origin and
duration of occurrence, four broad types of leukemia are
presently identified, namely acute lymphoblastic leukemia
(ALL), acute myeloid leukemia, chronic lymphocytic leu-
kemia, and chronic myeloid leukemia (Zhao et al. 2018). In
2018, it was estimated that over 400,000 new cases of
leukemia were reported, with about 300,000 deaths. It is the
most diagnosed cancer in children, about 75% of which are
of the ALL type (Bray et al. 2018; Hunger et al. 2020).
Despite the availability of a wide range of therapeutic
options, the prognosis for leukemia is still poor and treat-
ment is often marred by unbearable side effects (Terwilliger
and Abdul-Hay 2017; Watts and Nimer 2018). Therefore,
there is a need for new treatments with improved efficacy
and a better safety profile. While the exact cause of leuke-
mia is largely unknown, genetic factors are believed to play
a part in the etiology of the disease (Hutter 2010; Etzel
2016). The dysregulation of the tumor suppressor p53
protein through mutations, deletions, and inactivation is
strongly implicated (Gaidano et al. 1991; Prokocimer et al.
2017). p53 dysregulation is also reported to be responsible
for patients’ poor response to conventional therapy
(Lozanski et al. 2004). A major pathway for p53 inactiva-
tion involves the murine double minute 2 (MDM2) protein,
an E3 ligase that mediates the ubiquitination of the p53
protein leading to its proteasomal degradation (Haupt et al.
1997; Momand et al. 1992). Almost half of the ALL cell
Leukemia is a group of blood cancers characterized by
uncontrolled production of ill-functioning blood cells, par-
ticularly the leukocytes (Zou 2007). Due to the central roles
played by these cells in the body’s immune system, a
common complication of this often fatal disease is recurrent
infections, mostly of bacterial and/or fungal origin (Chang
These authors contributed equally: A. Anifowose, A. A. Agbowuro
Dedicated to Professor Robert P. Hanzlik on the occasion of his
retirement after 49 years of service on the faculty of the Department of
Medicinal Chemistry, University of Kansas.
Supplementary information The online version of this article (https://
doi.org/10.1007/s00044-020-02563-y) contains supplementary
material, which is available to authorized users.
* Xiaoxiao Yang
xyang20@gsu.edu
* Binghe Wang
wang@gsu.edu
1
Department of Chemistry and Center for Diagnostics and
Therapeutics, Petit Science Center, Georgia State University,
100 Piedmont Ave, Atlanta, GA 30303, USA
2
Department of Pharmaceutical Sciences, College of Pharmacy,
University of Mississippi, Oxford, MS, USA

Medicinal Chemistry Research
lines with wild-type p53 (wt-p53) harbors overexpression of
MDM2, which leads to inhibition of p53’s tumor-
suppressing functions. Downregulation of the MDM2 pro-
tein would in turn elevate the levels of the p53 protein and
consequently restore its functions.
Results and discussion
Chemistry
Modification to the anthraquinone scaffold (A)
We had previously reported novel anthraquinone com-
pounds with considerable cytotoxic activity (Anifowose
et al. 2020; Draganov et al. 2019; Yang et al. 2011). The
prototype is AQ-101 (1, Fig. 1), with an IC50 of 0.83
0.18 µM against EU-1 ALL cells (Draganov et al. 2019).
AQ-101 was shown to induce MDM2 protein degradation
and subsequently an increase in p53 levels in a dose-
dependent manner. Further investigations revealed that AQ-
101 induced MDM2 self-ubiquitination and reduced p53
polyubiquitination by binding to the MDM2 protein,
blocking its dimerization with MDM4 (Gu et al. 2018),
which is a crucial step in the proteasomal degradation of
p53 (Wade et al. 2013). Many of the tested analogs
including AQ-101 showed good selectivity for leukemia
cells with wt-p53 among a panel of cancer cell lines (Dra-
ganov et al. 2019). AQ-101 in particular produced complete
disease remission in animal models of ALL at a dose of
20 mg/kg (Gu et al. 2018; Draganov et al. 2019). With the
aim of further developing these anthraquinone compounds,
we sought to achieve further understanding of the
structure–activity relationships (SAR) for this class of
compounds. We herein report our effort in examining three
key structural features of this class of compounds for their
in vitro antileukemic activity (Fig. 1).
For further medicinal chemistry work, we first worked on
the modification of the anthraquinone core structure
(Region A) to determine whether the planar anthraquinone
structure and the carbonyl groups are critical to the activity.
Secondly, we explored whether the acetamide group (B)
poses a hydrolytic liability. If so, whether there are ways to
ameliorate this liability. Further, we explored whether the
NH group is essential for activity, possibly as a hydrogen
bond donor. Therefore, we were interested in replacing the
NH group with a methylene group. Thirdly, based on our
previous results of modifications to the alpha-
chloroacetamide moiety (C) (Draganov et al. 2019), we
explored several other structural variations of this
alkylating group.
As aforementioned, the dihydroxyanthraquinone scaffold
was changed in our previously reported studies (Anifowose
et al. 2020; Draganov et al. 2019; Yang et al. 2011). To
determine if the anthraquinone structure is essential to the
activity, we made three modifications to the dihydroxyan-
thraquinone core while maintaining the alkylating moiety as
the chloroacetamide used in AQ-101: (1) elimination of one
keto group to open the anthraquinone central ring to form a
diphenyl ketone scaffold, leading to a molecule that is no
longer flat; (2) reduction of the anthraquinone leading to
anthracene as the core; and (3) elimination of the phenolic
hydroxyl groups leading to an anthraquinone core structure.
The diphenyl ketone analogs 3a–c with different sub-
stitution patterns were synthesized by direct acylation of the
commercially available amines (2a–c) with chloroacetyl
chloride (Scheme 1a). To probe the effect of increasing the
electron density of the phenyl ring (ring activation) on
activity, diphenyl ketone analogs with a methoxyl or a
hydroxyl substituent were also made. To synthesize com-
pound 6, Friedel–Crafts acylation of anisole under neat
condition led to intermediate 4. The nitro group was
reduced through hydrogenation to give amine 5, which was
acylated with chloroacetyl chloride to afford 6 as a pink
solid (Scheme 1b). The hydroxyl substituted compound 9
was synthesized similarly by first demethylating compound
4 to give compound 7 (Scheme 1c).
The two phenolic hydroxyl groups in compound 1 could
serve as sites for intermolecular and/or intramolecular
hydrogen bond formation, contributing to the observed
activity (Malik and Muller 2016). To understand how much
these phenolic hydroxy groups and the quinone scaffold
contribute anticancer activity, the corresponding
anthracene-based analogs 12a, b and 13 were synthesized
(Scheme 2). Generally, anthraquinone amine with or with-
out the methoxy group was reduced to form anthracene
amine, followed by acylation to form the anthracene ana-
logs 12a and 12b. Alkylation of the 3-amino anthraquinone
10a gave the target anthraquinone analog 13 without the
phenolic hydroxyl groups.
Modification of the alkylating group (B and C)
Analogs of AQ-101 with the NH replaced by a CH2 moiety
were synthesized from the anthraquinone amine 10b
(Scheme 3a). By a diazonium-iodination reaction, the key
intermediate 14 was formed. Sonogashira coupling with
2-propynol followed by thionylation and hydrolysis
Fig. 1 Chemical structure of AQ-101(1) and its three regions (A–C)
for modifications

Medicinal Chemistry Research
Scheme 1 Synthesis of diphenyl ketone analogs. Reagents and conditions: a chloroacetyl chloride, dioxane, RT, 30 min, 39–96%; b ZnCl2, neat,
150 °C, 30 min, 89%; c hydrogen, Pd/C, RT, overnight, 68–72%; d BBr3, DCM, 40 °C, overnight, 45%
lead compound AQ-101, selected analogs were subjected to
Western blot analysis to probe if they can time-dependently
induce MDM2 degradation.
Modifying the anthraquinone scaffold resulted in diverse
changes in activity. Eliminating the phenolic hydroxyl
groups and one ketone group to open the anthraquinone
reduced the activity by about twofold (3a); however, it did
not lead to the abolishment of the activity. The latter part is
important because the flat structure of the anthraquinone
moiety is a major issue that affects water solubility. Being
Scheme 2 Synthesis of anthracene and anthraquinone analogs.
able to pursue the ring-opened scaffolds suggests ways to
further optimize this class of compounds for improved
potency and solubility. Changing the substitution position
from the para- to the meta- (3b) or ortho- (3c) position
completely abolished activity, suggesting the critical nature
of the relative positions of these functional groups. Intro-
ducing a methoxy or a hydroxy group (6 and 9, respec-
tively) did not enhance activity. It should be noted that a
study by Nomura’s group has already revealed that com-
pound 3a was a covalent inhibitor of ubiquitin-like modifier
activating enzyme 5 (UBA5), which is a potential target for
pancreatic cancer (Roberts et al. 2017). As an analog of 3a,
compound 9 was chosen to verify its effect on MDM2
degradation. However, compound 9 at its IC50 concentra-
tion did not induce significant changes in MDM2 levels,
albeit an increase in p53 level was detected (Fig. 3a), sug-
gesting a different mechanism of action for the diphenyl
ketone derivatives when compared with the lead compound
AQ-101.
Reagents and conditions: a Zn/NaOH, reflux, overnight, 64–75%;
b chloroacetyl chloride, dioxane, RT, 30 min, 87–91%; c chloroacetyl
chloride, dioxane, RT, 30 min, 46%
afforded 17 with an alpha-hydroxy group. Further chlor-
ination with N-chloro-succinimide (NCS) and triphenyl-
phosphine yielded target compound 18. Compounds 19
and 20 were synthesized by acylating 10b with 2-
chloropropionyl chloride and chloromethyl chloroformate,
respectively, (Scheme 3b). To synthesize compound 22,
amine 10b was converted to N-sulfinyl amine 21 followed
by reacting with glycolic acid (Scheme 3c). Compound 25
with the benzylic chloride group as the alkylating moiety
was synthesized by chlorination of aloe emodin 24,
obtained from reducing the methyl ester of rhein with
LiAlH4 (Scheme 3d).
Biological activity
With the structurally modified compounds in hand, the
in vitro activity against the wt-p53-expressing EU-1 ALL
cells was tested using the WST-8 assay (Table 1, see Fig. 2
for dose–response curves). In order to assess whether these
compounds are able to induce MDM2 degradation as the
Reducing the anthraquinone core to anthracene (12a and
12b) abolished activity, although the methoxy group in 12b
was known to help retain activity in the anthraquinone
series as described previously (Draganov et al. 2019). It
suggested that the alkylating group alone without attaching

Medicinal Chemistry Research
Scheme 3 Synthesis of AQ-101
analogs with different alkylating
groups. Reagents and
conditions: a HNO3/H2SO4, KI,
H2O/THF, −5 °C at RT, 30 min,
71%; b propargyl alcohol, Pd
(PPh3)Cl2, CuI, TEA, dioxane,
80 °C, 6 h, 86%; c propanethiol,
KOH, ACN, 60 °C, 30 min;
d H2SO4, methanol, 70 °C, 2 h,
90%; e NCS/TPP, DCM, RT,
5 min, 94%; f α-methyl
chloroacetyl chloride for 19 or
chloromethyl chloroformate for
20, dioxane, RT, 30 min,
68–90%; g SOCl2, toluene,
reflux, 3 h; h glycolic acid,
ACN, RT, overnight, 45%;
i LiAlH4, THF, 0 °C at RT, then
reflux, 2 h, 65%; j SOCl2, DMF,
RT, overnight, 83%
to a proper targeting scaffold would not induce significant
cytotoxicity, which is an essential premise in designing
covalent binding inhibitor (Wang et al. 2017). Our own
work using α-chloroacetamide suggests the same. Elim-
ination of the phenolic hydroxyl group in the anthraquinone
scaffold (13) allowed for retention of cytotoxicity at a
potency level similar with the lead compound. However,
western blot studies did not show downregulation of
MDM2. Interestingly, an increase of MDM2 level was
observed along with increased p53 expression (Fig. 3b).
The reason for the observed phenomenon is not clear. It is
possible that this was the result of transactivation of MDM2
by p53 induced by other stress signals. As a feedback loop,
p53 can bind to the MDM2 promoter to increase MDM2
expression (Vousden and Prives 2009). However, more
work needs to be done in the future to firmly establish the
mechanism of action.
In previous studies (Draganov et al. 2019), we have
demonstrated that the chloroacetamide was an optimal
alkylating moiety among those tested. Preliminary phar-
macokinetic studies indicated that AQ-101 “disappeared”
very quickly (within minutes) from the blood after i.v.
injection in mice (unpublished results). Many reasons could
contribute to the short half-life including hydrolytic liability
of the acetamide group, covalent binding to albumin
cysteine (Turell et al. 2013), and/or fast alkylation of the
intended target, thus trapping AQ-101 in the target protein.
To address the possible hydrolytic liability issue, we made
further modifications to this part by replacing the NH–
group in the chloroacetamide group by a methylene moiety.
Though the resulting analog 18 showed decreased cyto-
toxicity (IC50 = 1.75 μM), it is more important to note that
this modification did not abolish the activity, suggesting
new directions for future optimization work. Preliminary
western blot studies showed that compound 18 induced p53
expression but did not induce appreciable time-dependent
downregulation of the MDM2 in EU-1 cells (Fig. 4).
Similar to the results with compound 13, more work is
needed to affirm the results of the study and to fully elu-
cidate the mechanism of action.
Modification of the alkylating moiety by increasing steric
hindrance to the alkylating moiety through alpha-
methylation (19) led to decreased activity. Changing
chloroacetamide to chloromethyl carbamate (20) or hydro-
xyacetamide (22) abolished activity, demonstrating the
essential nature of the chloroacetyl group as the electro-
philic moiety. However, a more chemically reactive chlor-
omethyl analog 25 was much less active than the lead
compound, presumably because of the mispositioned alky-
lating moiety as a result of the shortened chain.

Medicinal Chemistry Research
Table 1 Average IC50 values of analogs
Compound NO.
1
AQ ID
Structure
IC50 (µM)
1.37 (0.96–1.96)
AQ-101
2.06 (1.81–2.36)
> 50
3a
3b
AQ-270
AQ-271
> 50
3c
6
AQ-272
AQ-285
2.27 (2.14–2.40)
3.12 (2.32–4.18)
9
AQ-273
AQ-332
AQ-333
>50
12a
12b
>50
0.74 (0.62–0.89)
13
17
AQ-131
AQ-283
>50
1.75 (1.27–2.41)
18
19
AQ-284
AQ-317
17.6 (16.7–18.6)
>50
20
22
25
AQ-340
AQ-282
AQ-300
≈50
25.9 (25.2–26.6)
Experiment triplicates with 95% confidence intervals of IC50 showing in parentheses
Conclusion
development of such anthraquinone compounds into
potential therapy for treating ALL. The results showed that
drastic changes such as opening the tricyclic ring or elim-
inating the phenolic hydroxyl group of anthraquinone core
In conclusion, structural modifications conducted in this
study provide valuable SAR information toward the

Medicinal Chemistry Research
Fig. 2 Dose–response curves of the active compounds by the WST-8 assay
Fig. 3 Western blot studies of
protein levels in EU-1 ALL cell
line showed that a compound 9
(AQ-273) and b compound 13
(AQ-131) upregulated p53
expression in a time-dependent
manner but did not significantly
downregulate MDM2
Experimental
Biology experiments
Cytotoxicity assay
All WST-8 cytotoxicity experiments were conducted in
triplicates using Cell Counting Kit-8 (CCK-8, Dojindo,
Japan). EU-1 cells were cultured in RPMI-1640 medium.
The medium was supplemented with 10% fetal bovine
serum and 1% penicillin/streptomycin. Cells were seeded
into 96-well plates (3 × 105 in 100 μL volume per well).
Compounds to be tested were dissolved in DMSO to make
10 mM stock solutions, and then diluted with culture
medium to various concentrations; final DMSO concentra-
tion was kept at 0.5%. The dissolved compounds were
added immediately after seeding. Following incubation for
24 h at 37 °C in humidified atmosphere with 5% CO2; 10 μL
of CCK-8 solution was added to each well, and the plate
was incubated for an additional 2–4 h at 37 °C before
measuring the optical density at 450 nm with a microplate
reader (PerkinElmer Victor2, USA). The cell viability of
each well was calculated as the percentage of the untreated
control according to the manufacturer’s manual. Average
Fig. 4 Western blot in EU-1 ALL cell line showed that compound 18
(AQ-284) upregulated p53 expression in a time-dependent manner but
did not induce significant downregulation of MDM2
allowed the retention of activity. However, the resulting
compounds may function through different mechanism(s)
other than downregulating MDM2 in upregulating p53.
This aspect needs more work to achieve a better under-
standing. The α-chloroacetamide remains the most prefer-
able electrophilic moiety, and the NH group of the
acetamide group can be replaced, but with the possibility of
modifying the detailed mechanism of action. These findings
provide a more detailed picture with regard to the SAR of
this class of compounds and will further guide the design of
new compounds with improved potency and pharmaceutical
property.

Medicinal Chemistry Research
IC50 values were computed based on various concentrations
by nonlinear regression using GraphPad Prism 5.
(0.15 mmol) in dry dioxane (2 ml). Then, chloroacetyl
chloride (0.02 ml, 0.23 mmol) was injected slowly into the
mixture and the mixture was stirred at RT for 30 min. About
10 ml of water was added to quench the reaction. The
precipitate formed was filtered to afford 3a (0.035 g), 3b
(0.036 g), or 3c (0.037 g) as a white solid, which was further
purified by flash chromatography using ethyl acetate/hexane
as the eluent.
Western blot
5 × 106 EU-1 cells in 3 ml RPMI-1640 culture media
(supplemented with 10% fetal bovine serum and 1% peni-
cillin/streptomycin) were seeded in a six-well plate and
incubated for 12 h, then 1 ml of the drug-loaded medium
was added. The cells were harvested at a designated time
point, washed with cold PBS then centrifuged at 1500 rpm
(three times). The cells were lysed by adding 200 μL of cold
NP-40 buffer (supplied with cOmplete™ protease Inhibitor
tablet (Roche) and 1 mM PMSF). The cell lysates were
centrifuged at 12,500 rpm at 4 °C for 10 min and total
protein concentration in the supernatant was measured with
the BCA assay (Thermo Fisher). Overall, 30 μL of the cell
lysate was mixed with 10 μL 4× laemmli sample buffer and
denatured at 95 °C for 5 min. The total protein concentration
was adjusted with 1× laemmli sample buffer. Equal amount
of protein sample was loaded onto 4–15% gradient SDS
PAGE gel (Bio-rad). After electrophoresis, the protein was
transfer to PTFE membrane (Bio-rad) and probed with the
corresponding antibody. MDM2 ((SMP14), 1:500 Santa
Cruz); p53 ((DO-1), 1:800, Santa Cruz); GAPDH ((0411),
1:2000, Santa Cruz) and HRP conjugated goat anti-mouse
secondary antibody (Bio-rad, 1:2000). The chemilumines-
cent result was detected with Pierce ECL Plus Substrate
(Thermo Scientific) and imaged with LSA4000 (GE
Healthcare, Fairfield, USA).
N-(4-Benzoylphenyl)-2-chloroacetamide (3a) Yield: 90%.
1H NMR (Chloroform-d) δ 8.56 (s, 1H), 7.90–7.82 (m, 2H),
7.79 (dt, J = 8.4, 1.4 Hz, 2H), 7.76–7.68 (m, 2H), 7.61 (td,
J = 7.4, 1.4 Hz, 1H), 7.50 (td, J = 7.5, 7.1, 1.4 Hz, 2H),
4.23 (d, J = 1.2 Hz, 2H). 13C NMR (Chloroform-d) δ 195.6,
164.2, 140.5, 137.6, 133.9, 132.4, 131.5, 129.91, 128.3,
119.2, 42.9. HRMS (ESI) m/z: Calculated for C15H13O2NCl
[M + H]+ 274.0630; Found 274.0629.
N-(3-Benzoylphenyl)-2-chloroacetamide (3b) Yield: 92%.
1H NMR (Chloroform-d) δ 8.44 (s, 1H), 7.96 (ddd, J = 8.1,
2.3, 1.1 Hz, 1H), 7.89 (t, J = 1.9 Hz, 1H), 7.87–7.80 (m,
2H), 7.67–7.59 (m, 1H), 7.63–7.56 (m, 1H), 7.56–7.46 (m,
3H), 4.22 (s, 2H). 13C NMR (Chloroform-d) δ 196.0, 164.1,
138.4, 137.1, 136.9, 132.7, 130.1, 129.2, 128.4, 126.8,
124.0, 121.4, 42.8. HRMS (ESI) m/z: Calculated for
C15H13O2NCl [M + H]+ 274.0630; Found 274.0629.
N-(2-Benzoylphenyl)-2-chloroacetamide (3c) Yield: 96%.
1H NMR (Chloroform-d) δ 11.64 (s, 1H), 8.63 (dd, J = 8.9,
1.2 Hz, 1H), 7.77–7.70 (m, 2H), 7.61 (tt, J = 7.6, 1.2 Hz,
3H), 7.54–7.45 (m, 2H), 7.17 (td, J = 7.6, 1.2 Hz, 1H), 4.21
(s, 2H). 13C NMR (Chloroform-d) δ 199.1, 165.4, 139.2,
138.3, 134.1, 133.5, 132.6, 130.0, 128.3, 124.2, 123.1,
121.5, 43.1. HRMS (ESI) m/z: Calculated for C15H13O2NCl
[M + H]+ 274.0631; Found 274.0629.
Synthesis experiments
Chemicals were purchased from Sigma-Aldrich, VWR, or
Acros. Analytical-grade solvents were used for all reactions
except for moisture-sensitive reactions, in which case anhy-
drous solvents were used. TLC analyses were conducted on
silica-gel plates (Silica GF254); and column chromatography
was carried out on flash silica-gel (230 − 400 mesh). NMR
Synthesis of (4-methoxyphenyl)(4-nitrophenyl)methanone
(4)
1
spectra were recorded at 400 MHz for H and 100 MHz for
Into a 50-ml round-bottom flask, para-nitrobenzoyl chloride
(0.50 g 2.72 mmol) was added successively together with
ZnCl2 (0.073 g, 0.54 mmol) and methoxybenzene (0.87 ml,
8 mmol). The neat mixture was heated to about 150 °C for
about 30 min. At the consumption of the starting material,
the mixture was diluted with ethyl acetate and washed
successively with HCl (100 ml, 1 M), NaHCO3 (100 ml,
saturated). The organic layer was dried over anhydrous
sodium sulfate and concentrated under reduced pressure.
The pure product (0.12 g) was crystallized from DCM/
13C on a Bruker Avance NMR spectrometer with TMS (δ =
0.00 ppm) or residual solvent as the internal reference. Data
are reported as follows: chemical shift, multiplicity (s =
singlet, d = doublet, t = triplet, m = multiplet), coupling
constant, and integration. High-resolution mass spectrometry
(HRMS) was performed using electrospray ionization (ESI)
by the GSU Mass Spectrometry Facilities.
General experimental procedure for the synthesis of
compounds 3a–c
1
hexane. Yield: 89%. H NMR (Chloroform-d) δ 8.35–8.29
(m, 2H), 7.92–7.85 (m, 2H), 7.85–7.77 (m, 2H), 7.03–6.95
(m, 2H), 3.91 (s, 3H). 13C NMR (Chloroform-d) δ 193.4,
164.0, 149.4, 143.7, 132.6, 130.3, 128.9, 123.4, 113.9,
Triethylamine (0.03 ml, 0.23 mmol) was added into a
solution of commercially available starting material 2a-c

Medicinal Chemistry Research
55.6. HRMS (ESI) m/z: Calculated for C14H11O4NNa [M +
d6) δ 193.3, 163.2, 149.4, 144.3, 133.2, 130.7, 130.6, 127.4,
124.1, 124.0, 116.0. HRMS (ESI) m/z: Calculated for
C13H9O4NNa [M + Na]+ 266.0428; Found 266.0429.
Na]+ 280.0583; Found 280.0586.
Synthesis of compound (4-Aminophenyl)(4-
methoxyphenyl)methanone (5)
Synthesis of (4-Aminophenyl)(4-hydroxyphenyl)methanone
(8)
Into a 100-ml round-bottomed flask, compound 4 (1.00 g,
3.89 mmol) was added and dissolved in 10 ml of methanol
followed by addition of 50 mg of Pd/C. Hydrogen gas was
introduced via a balloon and the reaction was left to stir
overnight at room temperature. At the consumption of the
starting material, the reaction mixture was filtered with a
0.45 μm syringe filter to obtain the filtrate. Methanol was
removed by vacuo to give the product as a white solid
(0.64 g).
Into a 25 ml vial, 7 (0.05 g, 0.20 mmol) was added and
dissolved in 5 ml of methanol followed by addition of 5 mg
of Pd/C. Hydrogen gas was introduced via a balloon and the
reaction was left to stir overnight at room temperature. At
the consumption of the starting material, the reaction mix-
ture was filtered with a 0.45 μm syringe filter to obtain the
filtrate. Then, methanol was removed by vacuo to give the
1
product as a white solid (0.027 g). Yield: 68%. H NMR
1
Yield: 72%. H NMR (Chloroform-d) δ 7.80–7.73 (m,
(DMSO-d6) δ 10.15 (s, 1H), 7.54 (dd, J = 8.6, 1.7 Hz, 4H),
6.86 (dd, J = 8.6, 1.7 Hz, 2H), 6.63–6.55 (m, 2H), 6.02 (s,
2H). 13C NMR (DMSO-d6) δ 192.8, 161.0, 153.5, 132.6,
132.0, 130.1, 125.0, 115.2, 112.9. HRMS (ESI) m/z: Cal-
culated for C13H11O2NNa [M + Na]+ 236.0676; Found
236.0687.
2H), 7.73–7.64 (m, 2H), 6.99–6.91 (m, 2H), 6.71–6.62 (m,
2H), 4.32 (s, 2H), 3.86 (s, 3H). 13C NMR (Chloroform-d) δ
194.4, 162.4, 151.0, 132.6, 132.0, 131.3, 127.6, 113.6,
113.3, 55.4. HRMS (ESI) m/z: Calculated for C14H13O2NNa
[M + Na]+ 250.0832; Found 250.0832.
Synthesis of 2-Chloro-N-(4-(4-methoxybenzoyl)phenyl)
Synthesis of 2-Chloro-N-(4-(4-hydroxybenzoyl)phenyl)
acetamide (6)
acetamide (9)
Triethylamine (0.66 mmol) was added into a solution of 5
(0.10 g, 0.44 mmol) in dry dioxane (2 ml). Then, chlor-
oacetyl chloride (0.05 ml, 0.66 mmol) was slowly injected
into the mixture, and the mixture was stirred at RT for
30 min. Then, about 10 ml of water was added. The pre-
cipitate formed was filtered to afford the desired products as
Triethylamine (0.02 ml, 0.10 mmol) was added into a
solution of 8 (0.015 g, 0.07 mmol) in dry dioxane (2 ml).
Then, chloroacetyl chloride (0.01 ml, 0.10 mmol) was
injected slowly into the mixture, and the mixture was stirred
at RT for 30 min. After completion of the reaction mon-
itored by TLC, about 10 ml of water was added. The pre-
cipitate formed was filtered to afford the desired product as
a white solid (0.008 g). Yield: 39%. 1H NMR (DMSO-d6) δ
10.63 (s, 1H), 10.38 (s, 1H), 7.79–7.62 (m, 6H), 6.94–6.86
(m, 2H), 4.32 (s, 2H). 13C NMR (DMSO-d6) δ 193.6, 165.6,
162.1, 142.2, 133.4, 132.7, 131.1, 128.6, 119.0, 115.6.
HRMS (ESI) m/z: Calculated for C15H12O3NClNa [M +
Na]+ 312.0417; Found 312.0403.
1
a pink solid (0.12 g). Yield: 93%. H NMR (Chloroform-d)
δ 8.53 (s, 1H), 7.86–7.78 (m, 4H), 7.74–7.67 (m, 2H),
7.02–6.94 (m, 2H), 4.24 (s, 2H), 3.91 (s, 3H). 13C NMR
(Chloroform-d) δ 194.4, 164.1, 163.2, 140.1, 134.6, 132.4,
131.2, 130.1, 119.1, 113.6, 55.5, 42.9. HRMS (ESI) m/z:
Calculated for C16H14O3NClNa [M + Na]+ 326.0573;
Found 326.0560.
Synthesis of (4-Hydroxyphenyl)(4-nitrophenyl)methanone (7)
Synthesis of Anthracen-2-amine compound (11a)
Into a 20 ml sealed tube, compound 4 (0.25 g, 0.97 mmol)
was added and dissolved in 5 ml of dry DCM followed by
slowly injection of BBr3 (1 M in DCM, 3.9 ml, 3.9 mmol).
The reaction was then stirred at 40 °C in a sealed tube
overnight. At the consumption of the starting material,
water (10 ml) was added, and the mixture stirred for another
1 h. At the consumption of the starting material, the mixture
was extracted with ethyl acetate, washed with brine, and
purified by silica-gel column chromatography (Hex/EA: 9/1)
Into a 100-ml round-bottom flask, 10a (0.5 g, 2.24 mmol)
was added followed by addition of 20 ml of NaOH (8%,
aqueous solution). Then, zinc dust (2.00 g, 30.00 mmol)
was added, and the mixture was stirred at reflux overnight.
At the consumption of the starting material, the mixture was
neutralized with 30 ml of HCl (10%). The mixture was
extracted with dichloromethane (30 ml), and the organic
layer was washed with water (200 ml) and brine (200 ml).
The resultant organic portion was dried over anhydrous
sodium sulfate and purified by silica-gel column chroma-
tography to obtain 11a (0.33 g). Yield: 75%. 1H NMR
(DMSO-d6) δ 8.28 (s, 1H), 8.03 (s, 1H), 7.85–7.93 (m, 2H),
1
to yield 0.11 g of 7. Yield: 45%. H NMR (DMSO-d6) δ
10.63 (s, 1H), 8.40–8.31 (m, 2H), 7.95–7.84 (m, 2H),
7.76–7.62 (m, 2H), 6.96–6.88 (m, 2H). 13C NMR (DMSO-

Medicinal Chemistry Research
7.81 (d, J = 9.0 Hz, 1H), 7.41–7.33 (m, 1H), 7.29 (dd, J =
8.4, 6.5 Hz, 1H), 7.05 (dd, J = 9.0, 2.2 Hz, 1H), 6.89 (d,
J = 2.1 Hz, 1H), 5.56 (s, 2H). 13C NMR (DMSO-d6) δ
146.5, 134.1, 132.4, 129.4, 128.9, 128.5, 127.5, 127.0,
126.2, 125.6, 123.5, 121.4, 121.3, 103.2. HRMS (ESI) m/z:
Calculated for C14H12N [M + H]+ 194.0960; Found
194.0964.
Then, chloroacetyl chloride (0.01 ml, 0.18 mmol) was
injected slowly into the mixture and the mixture was stirred
at RT for 30 min. At the consumption of the starting
material, about 10 ml of water was added. The precipitate
formed was filtered to afford the desired product as a white
1
solid (0.034 g). Yield: 87%. H NMR (DMSO-d6) δ 10.52
(s, 1H), 8.97 (s, 1H), 8.36 (s, 1H), 8.06 (s, 1H), 7.58 (d, J =
8.5 Hz, 1H), 7.42 (t, J = 8.0 Hz, 1H), 7.01 (d, J = 1.7 Hz,
1H), 6.86 (d, J = 7.4 Hz, 1H), 4.34 (s, 2H), 4.04 (d, J =
3.7 Hz, 6H). 13C NMR (Chloroform-d) δ 157.1, 156.1,
144.0, 134.2, 133.7, 125.6, 122.3, 121.7, 120.7, 119.9,
119.7, 115.7, 100.3, 99.0, 96.7, 55.5, 55.4. HRMS (ESI) m/
z: Calculated for C18H17NClO3 [M + H]+ 330.0889; Found
330.0891.
Synthesis of compound N-(Anthracen-2-yl)-2-
chloroacetamide (12a)
Triethylamine (0.03 ml, 0.23 mmol) was added into a
solution of 11a (0.03 g, 0.16 mmol) in dry dioxane (2 ml).
Then, chloroacetyl chloride (0.02 ml, 0.23 mmol) was
injected slowly into the mixture and the mixture was stirred
at RT for 30 min. Then, about 10 ml of water was added.
The precipitate formed was filtered to afford the desired
Synthesis of 2-Chloro-N-(9,10-dioxo-9,10-dihydroanthracen-
2-yl)acetamide (13)
1
product as a white solid (0.04 g). Yield: 91%. H NMR
(DMSO-d6) δ 10.58 (s, 1H), 8.47–8.55 (m, 3H), 8.16–7.94
(m, 3H), 7.64–7.38 (m, 3H), 4.35 (s, 2H). 13C NMR
(DMSO-d6) δ 165.5, 135.8, 132.2, 131.8, 131.0, 129.5,
129.1, 128.5, 128.2, 126.4, 126.2, 125.7, 125.6, 121.1,
115.0, 44.1. HRMS (ESI) m/z: Calculated for C16H12ClNO
[M + H]+ 270.0678; Found 270.0680.
Triethylamine (0.03 ml, 0.20 mmol) was added into a
solution of 10a (0.03 g, 0.13 mmol) in dry dioxane
(2 ml). Then, chloroacetyl chloride (0.02 ml, 0.20 mmol)
was injected slowly into the mixture and the mixture was
stirred at RT for 30 min. Then, about 10 ml of water was
added. The precipitate formed was filtered to afford the
desired products as a white solid. Isolated yield: 46%. 1H
NMR (Chloroform-d) δ 8.62 (s, 1H), 8.41–8.27 (m, 4H),
8.25 (d, J = 2.3 Hz, 1H), 7.89–7.78 (m, 2H), 4.29 (s, 2H).
13C NMR (DMSO-d6) δ 182.8, 181.8, 166.0, 144.3, 135.0,
134.7, 134.6, 133.5, 133.5, 129.0, 128.8, 127.2, 127.1,
124.5, 116.5, 44.0. HRMS (ESI) m/z: Calculated for
C16H11NClO3 [M + H]+ 300.0423; Found 300.0422.
Synthesis of compound 4,5-Dimethoxyanthracen-2-amine
(11b)
In a 100-ml round-bottom flask was added compound 10b
(0.07 g, 0.25 mmol) followed by the addition of 10 ml of
NaOH (8%, aqueous solution). Then, zinc dust (229 mg,
3.52 mmol) was added, and the mixture was stirred at reflux
overnight. At the consumption of the starting material, the
mixture was neutralized with 12 ml of HCl (10%). The
mixture was then extracted with dichloromethane (10 ml) and
the organic layer was washed with water (100 ml) and brine
(100 ml). The resultant organic portion was dried over
anhydrous sodium sulfate and purified by silica-gel column
chromatography to obtain a gray solid (0.04 g). Yield: 64%.
1H NMR (Chloroform-d) δ 9.08 (s, 1H), 8.00 (s, 1H), 7.46 (d,
J = 8.5 Hz, 1H), 7.32 (dd, J = 8.5, 7.4 Hz, 1H), 6.70 (t, J =
1.3 Hz, 1H), 6.64 (d, J = 7.3 Hz, 1H), 6.28 (d, J = 2.0 Hz,
1H), 4.07 (d, J = 6.0 Hz, 6H). 13C NMR (DMSO-d6) δ 156.2,
155.8, 135.0, 133.6, 126.1, 121.0, 120.7, 119.7, 119.6, 115.0,
100.7, 98.2, 55.8, 55.7. HRMS (ESI) m/z: Calculated for
C16H16NO2 [M + H]+ 254.1172; Found 254.1176.
Synthesis of 3-Iodo-1,8-dimethoxyanthracene-9,10-dione
(14)
Compounds 10b (0.55 mmol) was dissolved in 5 ml of THF
and 5 ml of water. Then, 2 M H2SO4 (1 ml) was added and
the reaction mixtures; the mixture was stirred at −5 °C for
about 10 min. Sodium nitrite (0.045 g, 0.66 mmol) in 0.5 ml
of water was then added and the mixture was stirred at
−5 °C for 5 min. KI (0.18 g, 1.10 mmol) was then added
gradually while gas evolution was observed. When the
reaction was completed, the mixture was diluted with water
and the resulting black precipitate was filtered. The crude
product was purified by silica-gel column chromatography
to obtain compounds as a bright yellow solid. Yield: 0.13 g
1
(71%). H NMR (Chloroform-d) δ 8.13 (s, 1H), 7.79 (d,
Synthesis of 2-Chloro-N-(4,5-dimethoxyanthracen-2-yl)
acetamide (12b)
J = 7.7 Hz, 1H), 7.67–7.57 (m, 2H), 7.31 (s, 1H), 3.99 (d,
J = 2.9 Hz, 6H). 13C NMR (Chloroform-d) δ 182.7, 182.1,
159.5, 159.4, 134.8, 134.1, 128.0, 127.0, 123.6, 123.1,
119.0, 118.3, 100.5, 56.8, 56.5. HRMS (ESI) m/z: Calcu-
lated for C16H12O4I [M + H]+ 394.9773; Found 394.9775.
Triethylamine (0.02 ml, 0.18 mmol) was added into a
solution of 11b (0.03 g, 0.12 mmol) in dry dioxane (2 ml).

Medicinal Chemistry Research
Synthesis of 3-(3-hydroxyprop-1-yn-1-yl)-1,8-
dimethoxyanthracene-9,10-dione (15)
Synthesis of 3-(3-Chloro-2-oxopropyl)-1,8-
dimethoxyanthracene-9,10-dione (18)
Compounds 14 (0.50 mmol) was dissolved in 10 ml of
dioxane. Propargyl alcohol (0.04 ml, 0.61 mmol) was then
added, followed by addition of 5 ml of TEA as a co-solvent.
Under argon, Pd(PPh3)2Cl2 (0.018 g, 0.03 mmol) and CuI
(0.01 g, 0.05 mmol) was quickly added. The mixture was
then stirred at 80 °C for about 5 h. At the consumption of
the starting material, the solvent was removed in vacuo; the
residue was dissolved with DCM and washed with water
(150 ml) and brine (150 ml) successively and dried over
anhydrous sodium sulfate. The solvent was removed, and
the crude product was purified by silica-gel column chro-
matography (DCM/MeOH, 200/1). The product was iso-
lated as a yellow solid. Yield: 0.14 g (86%). 1H NMR
(DMSO-d6) δ 7.72 (t, J = 8.0 Hz, 1H), 7.63 (dd, J = 7.7,
1.1 Hz, 1H), 7.56 (d, J = 1.5 Hz, 1H), 7.51 (dd, J = 8.5,
1.2 Hz, 1H), 7.45 (d, J = 1.5 Hz, 1H), 5.48 (t, J = 6.0 Hz,
Into a 20-ml vial, NCS (0.023 g, 0.17 mmol) and triphe-
nylphosphine (0.046 g, 0.17 mmol) were dissolved in 2 ml
of DCM, and the mixture stirred under argon for about
2 min. Then, 17 (0.15 mmol) in 1 ml of DCM was gradually
added and the mixture stirred at room temperature for about
5 min. TLC showed consumption of the starting material
and the formation of the product. The mixture was washed
with water (50 ml) and brine (50 ml) successively and dried
over anhydrous sodium sulfate. The crude product was
purified by silica-gel column chromatography (DCM only)
1
to obtain a yellow solid. Yield: 94%. H NMR (Chloro-
form-d) δ 7.83 (dd, J = 7.7, 1.1 Hz, 1H), 7.67 (d, J =
1.6 Hz, 1H), 7.64 (t, J = 8.0 Hz, 1H), 7.31 (dd, J = 8.4,
1.1 Hz, 1H), 7.16 (d, J = 1.6 Hz, 1H), 4.18 (s, 2H), 4.04 (s,
2H), 4.01 (d, J = 1.7 Hz, 6H). 13C NMR (Chloroform-d) δ
198.8, 183.8, 182.4, 159.8, 159.5, 139.2, 135.0, 134.6,
133.9, 123.8, 123.1, 119.8, 119.0, 118.2, 56.6, 56.5, 47.8,
46.5, 29.7. HRMS (ESI) m/z: Calculated for C19H15O5ClNa
[M + Na]+ 381.0514; Found 381.0506.
1H), 4.37 (d, J = 6.0 Hz, 2H), 3.91 (d, J = 6.2 Hz, 6H). 13
C
NMR (DMSO-d6) δ 183.0, 180.9, 159.2, 159.2, 134.7,
134.7, 134.2, 128.3, 123.7, 123.4, 120.8, 120.8, 119.5,
118.6, 94.2, 82.8, 56.7, 56.7, 49.9. HRMS (ESI) m/z: Cal-
culated for C19H14O5Na [M + Na]+ 345.0727; Found
345.0739.
Synthesis of 2-Chloro-N-(4,5-dimethoxy-9,10-dioxo-9,10-
dihydroanthracen-2-yl)propenamide (19)
Synthesis of 3-(3-Hydroxy-2-oxopropyl)-1,8-
dimethoxyanthracene-9,10-dione (17)
Triethylamine (0.01 ml, 0.08 mmol) was added into a
solution of 10b (0.020 g, 0.08 mmol) in dry dioxane (2 ml).
Then, 2-chloropropionyl chloride (0.01 ml, 0.08 mmol) was
injected slowly into the mixture and the mixture was stirred
at room temperature for 10 min. Next, about 10 ml of water
was added and the mixture was extracted with DCM,
washed with brine, and dried over anhydrous sodium sul-
fate. The solvent was removed, and the crude product was
purified by silica-gel column chromatography (DCM/
MeOH, 150/1). Compound 19 was isolated as a yellow
Into a 20-ml vial, compound 15 (0.16 mmol) was dis-
solved in acetonitrile (4 ml). Then, propanethiol (0.02 ml,
0.18 mmol) was slowly added at room temperature and
catalytic amount of potassium hydroxide (0.03 g, 0.0
5 mmol) in 0.5 ml of water was added and the mixture
stirred to 80 °C. The starting material was consumed after
about 30 min. Then the solvent was removed, and the
crude product 16 was used without purification for the
next hydrolysis step. Into 25-ml vial, 16 (0.15 mmol) was
dissolved in 5 ml of methanol and 2 M H2SO4 (5 ml) and
the mixture was allowed to stir at 80 °C for about 4 h. At
the consumption of the starting material, the mixture was
extracted with DCM (5 ml) and dried over anhydrous
sodium sulfate. The crude product was purified by silica-
gel column chromatography (DCM/MeOH, 200/2) to
obtain a yellow solid. Yield: 0.046 g (90%). 1H NMR
(Chloroform-d) δ 7.86 (dd, J = 7.7, 1.1 Hz, 1H), 7.72–7.63
(m, 2H), 7.34 (s, 1H), 7.34 (d, J = 8.4 Hz, 1H), 7.19 (d,
J = 1.6 Hz, 1H), 4.41 (s, 2H), 4.03 (s, 6H), 3.88 (s, 2H).
13C NMR (Chloroform-d) δ 205.7, 183.8, 182.1, 159.9,
159.5, 139.0, 135.0, 134.6, 134.0, 123.8, 123.2, 119.6,
119.0, 118.8, 118.2, 68.1, 56.6, 56.5, 45.5. HRMS (ESI)
m/z: Calculated for C19H16O6Na [M + Na]+ 363.0830;
Found 363.0845.
1
solid (0.027 g). Yield: 90%. H NMR (DMSO-d6) δ 10.89
(s, 1H), 7.94 (d, J = 1.9 Hz, 1H), 7.84 (d, J = 2.0 Hz, 1H),
7.75 (t, J = 7.9 Hz, 1H), 7.69 (dd, J = 7.7, 1.2 Hz, 1H), 7.54
(d, J = 8.1 Hz, 1H), 4.71 (q, J = 6.6 Hz, 1H), 3.90 (d, J =
5.3 Hz, 6H), 1.65 (d, J = 6.6 Hz, 3H). 13C NMR (DMSO-
d6) δ 183.6, 181.7, 168.0, 161.2, 159.7, 142.1, 135.4, 134.6,
133.8, 123.9, 120.3, 119.0, 118.4, 108.9, 108.4, 56.6, 56.5,
55.9, 53.4, 22.4. HRMS (ESI) m/z: Calculated for
C19H17NClO5 [M + H]+ 374.0788; Found 374.0790.
Synthesis of Chloromethyl-N-(4,5-dimethoxy-9,10-dioxo-
9,10-dihydroanthracen-2-yl)carbamate (20)
Triethylamine (0.01 ml, 0.08 mmol) was added into a
solution of 10b (0.020 g, 0.08 mmol) in dry dioxane (2 ml).
Then, chloromethyl chloroformate (0.01 ml, 0.10 mmol)
was injected slowly into the mixture and the mixture was

Medicinal Chemistry Research
stirred at room temperature for 10 min. At the complete
consumption of the starting material, the solvent was
removed in vacuo, and the crude product was purified by
silica-gel column chromatography (hexane: Ethyl acetate, 1/
1). Compound 27 was isolated as a yellow solid (0.018 g).
solvent was removed, and the crude product was purified by
silica-gel column chromatography (DCM /MeOH, 150/1).
The desired product was isolated as a yellow solid
1
(0.066 g). Yield: 65%. H NMR (DMSO-d6) δ 11.93 (s,
1H), 11.87 (s, 1H), 7.78 (t, J = 7.9 Hz, 1H), 7.72–7.62 (m,
2H), 7.55 (s, 1H), 7.35 (dd, J = 8.4, 1.2 Hz, 1H), 7.25 (d,
J = 1.5 Hz, 1H), 5.60 (s, 1H), 4.62 (s, 2H). 13C NMR
(DMSO-d6) δ 192.0, 181.8, 162.0, 161.7, 154.1, 137.7,
133.7, 133.4, 124.8, 121.1, 119.7, 117.5, 116.2, 114.8,
62.5. HRMS (ESI) m/z: Calculated for C15H11O5 [M + H]+
271.0599; Found 271.0601.
1
Yield: 68%. H NMR (CD3CN) δ 8.52 (s, 1H), 7.78–7.61
(m, 4H), 7.44 (d, J = 7.8 Hz, 1H), 5.89 (s, 2H), 3.94 (s, 6H).
13C NMR (DMSO-d6) δ 183.7, 181.1, 160.4, 159.2, 151.4,
143.8, 135.4, 134.8, 134.3, 123.4, 119.6, 119.1, 118.7,
107.8, 82.2, 71.4, 56.7, 56.5. HRMS (ESI) m/z: Calculated
for C18H14ClNO6 [M + Na]+ 398.0407; Found 398.2289.
Synthesis of N-(4,5-Dimethoxy-9,10-dioxo-9,10-
dihydroanthracen-2-yl)-2-hydroxyacetamide (22)
Synthesis of 3-(Chloromethyl)-1,8-dihydroxyanthracene-
9,10-dione (25)
Compound 10b (0.50 g, 1.76 mmol) was added into a 50 ml
round-bottom flask followed by 10 ml of toluene. Then,
5 ml of thionyl chloride was added and the mixture was
stirred at reflux for about 3 h. At the consumption of the
starting material, the solvent was removed in vacuo to get a
the intermediate 21 which was used directly next step
without purification. Compound 21 was then transferred
into a 20-ml vial containing 5 ml of acetonitrile. Glycolic
acid (3.52 mmol) was added and the mixture was stirred at
room temperature overnight. At the consumption of 21,
acetonitrile was removed by vacuo, and the residue was
diluted with water and extracted with DCM (5 ml, ×3). The
combined organic layer was washed with water (50 ml) and
brine (50 ml) successively and dried over anhydrous sodium
sulfate. The solvent was removed, and the crude product
was purified by silica-gel column chromatography (DCM/
MeOH, 200/1). The product was isolated as a yellow solid
Compound 24 (0.5 g, 1.9 mmol) was added into a 20 ml vial
followed by anhydrous DMF (20 ml). Then, 2 ml of thionyl
chloride was slowly added under stirring at room tem-
perature and the reaction was stirred overnight. At the
consumption of the starting material, the solvent was
removed in vacuo and the mixture was diluted with water
and extracted with DCM (5 ml, ×3). The combined organic
layer was washed with water (50 ml) and brine (50 ml)
successively and dried over anhydrous sodium sulfate. The
solvent was removed, and the crude product was purified by
silica-gel column chromatography (DCM only). The desired
product was isolated as a yellow solid (0.44 g). Yield: 83%.
1H NMR (Chloroform-d) δ 12.10 (s, 1H), 12.04 (s, 1H),
7.90–7.84 (m, 1H), 7.86 (s, 1H), 7.73 (t, J = 8.0 Hz, 1H),
7.40–7.31 (m, 2H), 4.64 (s, 2H). 13C NMR (Chloroform-d)
δ 192.6, 181.3, 162.8, 162.6, 147.1, 137.4, 134.0, 133.4,
124.8, 123.7, 120.2, 119.8, 115.7, 115.4, 44.6. HRMS (ESI)
m/z: Calculated for C15H10O4Cl [M + H]+ 289.0262; Found
289.0262.
1
(0.26 g). Yield: 45%. H NMR (Chloroform-d) δ 8.74 (s,
1H), 8.23 (s, 1H), 7.85 (d, J = 7.6 Hz, 1H), 7.66 (t, J =
8.0 Hz, 1H), 7.49 (d, J = 2.0 Hz, 1H), 7.34 (d, J = 8.4 Hz,
1H), 5.32 (s, 2H), 4.34 (d, J = 5.2 Hz, 2H), 4.03 (d, J =
2.2 Hz, 6H), 2.92 (s, 1H). 13C NMR (DMSO-d6) δ 183.7,
180.7, 172.4, 160.2, 159.2, 144.1, 135.3, 134.5, 134.4,
123.8, 119.5, 119.4, 118.6, 109.0, 109.0, 62.4, 56.7, 56.6.
HRMS (ESI) m/z: Calculated for C18H16O6N [M + H]+
342.0972; Found 342.0972.
Acknowledgements Financial support from the National Institutes of
Health (CA180519) is gratefully acknowledged. We also thank the
Center for Diagnostics and Therapeutics for a University fellowship to
AA, the Georgia Research Alliance for an Eminent Scholar endow-
ment, and GSU internal support.
Compliance with ethical standards
Synthesis of 1,8-Dihydroxy-3-(hydroxymethyl)anthracene-
9,10-dione (24)
Conflict of interest The authors declare that they have no conflict of
interest.
Publisher’s note Springer Nature remains neutral with regard to
jurisdictional claims in published maps and institutional affiliations.
Into a 100 ml round-bottom flask, 0.1 g of 23 (0.34 mmol)
was dissolved in 5 ml of THF. Then, 0.026 g of LiAlH4 was
added at 0 °C and the mixture was stirred at reflux and
stirring continued for about 2 h. At the consumption of the
starting material, the mixture was cooled to 0 °C and acid-
ified with dilute H2SO4 (1 ml). Then, the reaction mixture
was extracted with DCM (50 ml) and washed with brine
(100 ml) and dried over anhydrous sodium sulfate. The
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