Synthesis, cytotoxicity evaluation, and molecular modeling studies of 2,N10-substituted acridones as DNA-intercalating agents

Article abstract of DOI:10.1177/1747519820902674

Acridine-based compounds possess anticancer activities by intercalating to DNA. Although they have chemotherapeutic potential, acridine-based compounds are not used to treat cancer. In this study, 2,N¹⁰-acridone derivatives are designed and synthesized based on acridone, a ketone derivative of acridine. Herein, acridone is functionalized with alkyl side chains containing terminal nitrogen-based moieties at the N¹⁰-position and substituted at the C2-position. The products are evaluated for in vitro cytotoxicity against four cancer cell lines: Molt-3, HepG2, A549, and HuCCA-1. The derivative bearing two butyl piperidine side chains at the C2- and N¹⁰-positions is the most active, with IC₅₀ values ranging from 2.96 to 9.46 μM. Molecular modeling studies supported the binding of the derivatives to DNA by intercalation, thereby confirming the observed cytotoxic effects.

Full text of DOI:10.1177/1747519820902674

9
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0cle2020 2674CHL0010.1177/1747519820902674Journal of Chemical ResearchKhunnawutmanotham et al.
Research Paper
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Synthesis, cytotoxicity evaluation, and molecular
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1
0
modeling studies of 2,N -substituted acridones
as DNA-intercalating agents
1
2
Nisachon Khunnawutmanotham , Watthanachai Jumpathong ,
2
3
Chatchakorn Eurtivong , Nitirat Chimnoi
1
and Supanna Techasakul
Abstract
Acridine-based compounds possess anticancer activities by intercalating to DNA. Although they have chemotherapeutic
1
0
potential, acridine-based compounds are not used to treat cancer. In this study, 2,N -acridone derivatives are designed
and synthesized based on acridone, a ketone derivative of acridine. Herein, acridone is functionalized with alkyl side
1
0
chains containing terminal nitrogen-based moieties at the N -position and substituted at the C2-position. The products
are evaluated for in vitro cytotoxicity against four cancer cell lines: Molt-3, HepG2, A549, and HuCCA-1. The derivative
1
0
bearing two butyl piperidine side chains at the C2- and N -positions is the most active, with IC values ranging from
5
0
2
.96 to 9.46µM. Molecular modeling studies supported the binding of the derivatives to DNA by intercalation, thereby
confirming the observed cytotoxic effects.
Keywords
acridone, cytotoxicity, intercalating agent, synthesis
Date received: 3 September 2019; accepted: 7 January 2020
Introduction
Cancer is a class of disease characterized by an abnormal
growth of tissues that can metastasize. In 2018, the World
Health Organization (WHO) reported approximately 9.6
1Laboratory of Organic Synthesis, Chulabhorn Research Institute,
Bangkok, Thailand
Program in Chemical Biology, Chulabhorn Graduate Institute, Bangkok,
1
2
million deaths from cancers worldwide. Undeniably, can-
cer is a serious health concern globally. The development
of chemotherapeutics faces challenging obstacles including
the development of potent small molecule drugs against
mutant forms of protein targets with high selectivity and
tolerable adverse effects. Thus, research to develop new
anticancer drugs with the above-mentioned properties is
Thailand
3
Laboratory of Natural Products, Chulabhorn Research Institute,
Bangkok, Thailand
Corresponding author:
Supanna Techasakul, Laboratory of Organic Synthesis, Chulabhorn
Research Institute, 54 Kamphaeng Phet 6, Talat Bang Khen, Lak Si,
Bangkok 10210, Thailand.
highly desirable. Existing anticancer chemotherapeutic Email: supanna@cri.or.th

2
Journal of Chemical Research 00(0)
Figure 1. Structures of some DNA-targeting anticancer drugs.
Figure 2. Chemical structures of known DNA-intercalating agents: ethidium bromide, daunomycin, and quinacrine.
agents exert different mechanisms of action, for example, bromide, daunomycin, and quinacrine, interact with DNA
kinase inhibition, inhibition of DNA transcription activity, through intercalation (Figure 2).
manipulation of tubulin dynamics, and DNA-targeting
Acridone (1) is a flat planar heterocyclic scaffold consisting
compounds. DNA is one of the most viable and successful of three ortho-fused aromatic rings with a keto group and a
targets for anticancer chemotherapy as seen by the approval nitrogen atom at the 9- and 10-positions, respectively. The flat
2
of many DNA-targeting anticancer drugs, for example, planar shape allows acridone to intercalate between DNA bases
bleomycin, doxorubicin, mephalan, and cyclophosphamide disrupting the intermolecular bonding networks of the DNA
(
Figure 1).
Herein, we have developed DNA-targeting anticancer have chemotherapeutic potential. Numerous naturally occurring
agents that can interfere with the DNA base-pairing system acridone alkaloids have been isolated and studied for their bio-
molecule. Hence, acridone-based compounds are regarded to
5–7
8,9
through intermolecular interactions. This mechanism logical activities, including antiproliferative, antiviral, and
10
causes conformational changes in the DNA structure and antiparasitic activities. Some well-recognized naturally occur-
often disrupts the recognition of DNA-binding proteins ring cytotoxic acridone-based compounds include acronycine
such as DNA polymerases, transcription factors, and topoi- and glyfoline (Figure 3). These compounds have been studied
somerases. Furthermore, intercalation is one of the most and structurally modified to improve their potency and solubil-
important mechanisms of action exhibited by DNA- ity for clinical applications as anticancer drug candidates.
targeting drugs, which are classified as DNA-intercalating Recognizing the potential of acridone-based compounds
3
11–13
agents. The mechanism of action relies on the flat planar as DNA-intercalating chemotherapeutic agents, we focused
structure of the drug, which can be inserted between DNA our investigations on developing qualitative structure-
base pairs. The stability of the complex is considerably activity relationships (SARs) by means of synthetic struc-
influenced by van der Waal’s forces, hydrophobic interac- tural modifications and experimentally testing for the
4
tions, π–π stacking interactions, and electrostatic forces.
cytotoxic activities of the derivatives in vitro against four
Various well-known compounds, such as ethidium cancer cell lines: acute lymphoblastic leukemia (Molt-3),

Khunnawutmanotham et al.
3
Figure 3. Chemical structures of acridone (1) and the naturally occurring acridone-based cytotoxic compounds acronycine and
glyfoline.
Scheme 1. (a) NaH, DMF, dibromoalkane, 80°C, 0.5h; (b) amine, CH CN, rt, 24h; (c) MeI, CH Cl , rt, 18h; (d) NaOH, DMSO,
3
2
2
pyrrole, rt, 2h; (e) NaN (0.5M) in DMSO, rt, 1h; (f) NaH, DMF, PrI (for 2i), or BuBr (for 3i), 80°C, 0.5h.
3
hepatocarcinoma (HepG2), lung carcinoma (A549), and (data from our preliminary cytotoxicity screening). This
cholangiocarcinoma (HuCCA-1). Inspired by the structure finding may partly be due to its structural simplicity and
of quinacrine, we introduced various basic side chains to lack of functionalities that can allow extensive interactions
the core structure to enhance the electrostatic binding of with DNA. We modified the SARs between acridone and
acridone to the DNA target. The structures of the deriva- the target molecules by adding alkyl amines with varying
tives comprise an acridone core scaffold, which can form chain lengths and different terminal nitrogen-based moie-
1
0
π–π interactions with the DNA base pair and the basic side ties to the N -position of the acridone tricyclic core via a
chain at the C2-terminus, creating an electrostatic interac- two-step reaction, as shown in Scheme 1.
tion with the negative phosphate backbone of DNA.
Commercially available acridone (1) was used as the
Furthermore, molecular modeling was employed to under- starting material for the N-alkylations (Scheme 1). A
stand the basic binding conformations of the compounds strong base was required for deprotonation to achieve
and interactions with the DNA target.
N-alkylation due to the weak basic nature of the nitrogen
in acridone. Using sodium hydride as the base, acridone
could be alkylated with different dibromoalkanes in
dimethylformamide at 80°C to afford the corresponding
N -bromoalkyl acridones (2–5) in acceptable yields. An
O-alkylated compound was formed as a by-product
accompanied with the N-alkylated product but was unsta-
Results and discussion
1
0
Synthesis and cytotoxicity of
10
N -substituted acridones
Acridone (1) was shown to be almost inactive against all ble and readily transformed into acridone (1) under mild
the four tested cell lines, despite its planar structure acidic conditions. The number of methylenes in the alkyl

4
Journal of Chemical Research 00(0)
chain affected the alkylation reaction. Under the same chain lengths and terminal nitrogen-based moieties as side
conditions, alkylation reactions with butyl to hexyl chain chains (Scheme 1). The synthesized compounds were
spacers were accomplished with acceptable yields. Other evaluated for their cytotoxic activities and the results are
undesired side products were obtained from the alkylation summarized in Table 1.
of acridone with dibromopropane, whereas alkylation
with dibromoethane did not occur. The resulting bro-
moalkyl acridones 2–5 underwent nucleophilic substitu-
tion with various nitrogen-containing moieties to yield
1
0
N -substituted acridones bearing an alkyl side chain with
a nitrogen atom at the terminal position. The first set of
acridone derivatives was synthesized with varying alkyl
1
0
Table 1. Cytotoxic activities and the Moriguchi octanol-water partition coefficient (MlogP) values of N -substituted acridone
derivatives.
Compound
R
n
IC50 (µM)a
Molt-3
ΔG
kcalmol )
MlogP
−
1
(
HepG2
A549
HuCCA-1
Acridone
0
3
4
5
6
Inactiveb
15.5±6.7
17.2±4.6
14.2±3.3
12.0±3.6
14.9±5.7
Inactive
Inactive
−6.6
−7.3
−7.4
−7.5
−7.0
2.44
3.14
3.36
3.58
3.79
2a
3a
4a
5a
11.1±3.9
14.8±2.5
14.6±2.5
19.9±1.2
43.3±3.9
38.9±5.1
41.1±10.6
44.2±7.0
61.6±12.2
56.9±2.8
58.5±0.6
64.0±1.4
2b
3b
4b
5b
3
4
5
6
43.9±4.7
22.8±0.2
16.6±2.6
18.1±0.6
Inactive
Inactive
Inactive
−7.3
−7.5
−7.2
−7.2
2.11
2.34
2.55
2.77
38.7±5.2
42.9±0.0
27.5±5.9
67.0±6.3
77.1±8.1
57.0±0.6
103.1±2.7
97.1±1.4
93.1±3.1
2c
3c
4c
5c
3
4
5
6
14.9±3.6
16.9±3.0
14.8±3.6
16.9±3.1
16.3±3.5
16.7±3.6
19.8±4.5
18.2±4.4
40.9±5.3
38.1±6.6
52.1±6.8
49.3±1.8
63.1±5.5
55.9±6.6
68.3±5.7
60.1±7.7
−7.0
−6.9
−6.8
−6.8
2.92
3.14
3.36
3.58
2d
3d
4d
5d
3
4
5
6
19.2±2.4
26.5±5.2
25.7±5.1
23.8±0.3
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
−7.0
−6.7
−6.8
−6.9
2.77
2.99
3.21
3.42
69.6±0.0
53.0±6.4
65.9±11.7
2e
3e
4e
5e
3
4
5
6
17.2±6.3
21.0±0.9
21.8±0.6
23.5±3.7
11.6±1.3
14.0±2.7
17.5±5.2
17.5±7.0
33.1±3.4
42.7±5.1
49.9±3.0
54.0±1.2
69.5±2.1
74.2±16.2
68.4 ± 8.4
80.0±1.8
−6.3
−6.3
−6.5
−6.1
3.31
3.54
3.75
3.97
2f
3f
4f
5f
3
4
5
6
14.1±0.2
15.6±3.7
13.6±1.2
12.2±3.1
15.6±2.7
21.0±5.2
20.6±5.0
18.6±6.2
35.7±4.7
64.0±1.9
61.7±1.2
51.7±2.8
50.0±6.8
87.8±13.2
73.7±7.8
62.9±3.3
−6.2
−6.8
−6.6
−6.4
2.85
3.09
3.31
3.54
2g
3g
4g
5g
3
4
5
6
100.8±6.6
38.7±9.6
80.2±29.9
inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
−6.7
−6.8
−6.7
−6.7
−0.60
−0.37
−0.15
0.07
2h
3h
4h
5h
N3
3
4
5
6
27.2±4.5
34.1±11.1
33.5±11.8
24.9±5.4
98.9±10.4
79.6±9.4
83.9±13.2
63.3±12.6
Inactive
Inactive
Inactive
150.3±18.5
Inactive
−6.9
−6.6
−6.8
−6.7
2.25
2.49
2.73
2.96
157.5±9.7
150.3±9.2
135.9±11.0
2
3
i
i
H
−
3
4
31.8±0.5
44.2±2.6
80.2±14.2
95.6±6.9
192.8±5.4
Inactive
173.0±1.5
Inactive
−6.2
−6.1
3.21
3.45
Doxorubicin
−
NDc
0.4±0.2
0.2±0.0
0.9±0.7
−9.2
−0.82
a
Results are expressed as mean±standard error; average of three independent experiments.
b
−1
IC50 ⩾50µgmL .
c
Not determined.

Khunnawutmanotham et al.
5
Scheme 2. (a) Cu, K CO , DMF, reflux, 4h; (b) Conc. H SO , 100°C, 4h; (c) NaH, DMF, dibromobutane, 80°C, 1h; (d)
2
3
2
4
piperidine, CH CN, rt, 24h; (e) 5% NaOH, EtOH, reflux, 1h; (f) SOCl , reflux, 3h then cold MeOH; (g) amino acid or amine,
3
2
HOBt, EDCI, DIPEA, DMF, rt, 24h; (h) H , 10% Pd/C, MeOH, rt, 24h.
2
Table 1 shows that the introduction of the side chains, acridone significantly improved its cytotoxicity compared
1
0
particularly tertiary amine, to the N -position of the par- with alkyl morpholine. Alkyl piperidines (pK =11.22)
a
ent acridone (1) led to cytotoxicity against the tested cell had a higher level of positive-charged forms at physiolog-
lines. Acridones with alkyl piperidine 2a–5a, alkyl mor- ical pH compared to alkyl morpholines (pK =8.36)
a
pholine 2b–5b, alkyl pyrrolidine 2c–5c, alkyl diethyl- because of the higher basicity of the former. The high
amine 2e–5e, and alkyl dimethylamine 2f–5f demonstrated extent of electrostatic interactions imposed by alkyl piper-
improved cytotoxicity, whereas acridones with alkyl pyr- idine derivatives contributed to the lower IC50 values
role 2d–5d, alkyl azide 2h–5h, and alkyl ammonium salts compared with those of alkyl morpholines. The slightly
2
g–5g were inactive or displayed modest activity. These higher pK values of alkyl pyrrolidines (e.g. pK 11.27)
a
a
results are presumably due to their poor ability to interact compared with those of alkyl piperidines (e.g. pK 11.22)
a
with DNA. Varying the chain length from three to six car- resulted in slightly lower cytotoxicities. This phenomenon
bons resulted in slight differences in the cytotoxicities. could be due to the higher level of positive-charged forms
Among the tested cell lines, Molt-3 was the most sensitive of alkyl pyrrolidine acridones, as reflected in the lower
against alkyl piperidines 2a–5a, alkyl pyrrolidines 2c–5c, Moriguchi partition coefficients (MlogP), thereby pre-
alkyl diethylamines 2e–5e, and alkyl dimethylamines 2f– venting them from entering into the cell. It is noted that
5
f, with comparable IC values ranging from 11 to 23µM. MlogP was calculated with nitrogen atoms negatively
50
1
4
For the HepG2 cell line, acridones bearing alkyl piperi- contributing to the parameter. Despite the low value of
dine 2a–5a, alkyl pyrrolidine 2c–5c, and alkyl diethyl- MlogP calculated from doxorubicin caused by the nega-
amine 2e–5e units displayed cytotoxicities within tive contribution of the nitrogen and an oxygen atoms, this
1
2−20µM, which were comparable with that of unsubsti- drug is actually carried into cells by organic anion trans-
1
5
tuted acridone (1). For the A549 cell line, acridones con- porting peptide 1A/1B (OATP1A/1B). Among alkyl
taining alkyl piperidine 2a–5a exhibited the highest piperidine derivatives 2a–5a, butyl and pentyl piperidines
improvement in cytotoxicity, with IC50 values ranging (3a and 4a, respectively) were equally effective against
from 39 to 44µM. For the HuCCA-1 cell line, acridones the tested cell lines. However, the cytotoxicity was sig-
with alkyl piperidine 2a–5a and alkyl pyrrolidine 2c–5c nificantly compromised after lengthening the alkyl chain
substituents showed the highest improvement in cytotox- by adding six carbons. This finding could be due to the
icity, with comparable IC50 values ranging from 56 to higher degree of freedom of the acridone moiety to escape
6
8µM. Hence, introducing an alkyl piperidine at N10 of from base-pair stacking.

6
Journal of Chemical Research 00(0)
with a free carboxylic acid. Simple methyl ester 13 was pre-
pared to investigate the cytotoxicity. The conjugation of 12
with an amino acid was aimed toward enhancing the cyto-
toxicity. The amino acid, L-valine benzyl ester, was conju-
gated to acridone 12 by using 1-hydroxybenzotriazole
(HOBt) and 1-ethyl-3-(3-dimethylaminopropyl) carbodiim-
ide (EDCI) to obtain acridone 14 in good yield. The benzyl
ester group of 14 was removed by hydrogenation to form
acridone 15. A benzyl amide protecting group was incorpo-
rated to yield acridone 16. The simple benzyl amide of 12
(compound 17) was also prepared to investigate its cytotox-
icity. Compounds 11a and 12–16 were subjected to cyto-
1
0
Figure 4. Binding conformation of N -substituted acridone
toxic testing. The corresponding molecules of these
1
0
10
derivative 3a (a) and C2,N -substituted acridone derivative
1a (b). The DNA fragment is represented as sticks, and ligands
are represented as balls and sticks. The DNA surface has been
rendered. Blue, red, and gray surfaces represent partial positive,
negative, and neutral charges, respectively. Green solid lines are
π–π stacking interactions and red dotted lines depict hydrogen
bonding.
compounds without the N -butyl piperidine side chain were
1
also prepared by following similar procedures and were also
subjected to cytotoxic testing (compounds 18, 19, 20, and
2
1). The IC values of the substituted acridone derivatives
50
and those of 3a are summarized in Table 2.
Considering C2-derivatized 3a, the presence of a polar
carboxyl moiety at C2 in compound 12 led to it being inac-
tive in cytotoxicity studies. The inactivity of 12 could be
due to the high hydrophilicity, as shown by the low parti-
tion coefficient (MlogP), thereby prohibiting cellular
uptake. Decreasing the polarity of the compounds might
increase their cytotoxicity. Hence, the carboxyl group of 12
was converted into a butyl piperidine ester (compound
1
0
Introducing a butyl piperidine to the N of acridone led
to the highest cytotoxicity for compound 3a. This finding
encouraged us to improve the cytotoxicity of 3a. The addi-
tion of a butyl piperidine side chain to the aromatic ring of
3
a was aimed toward enhancing the cytotoxicity by
increasing the binding interaction to the negative groove of
DNA. Evidence suggests that conjugating an amino acid to
compounds of interest can improve their bioavailability in
tissues. Therefore, acridone 3a was conjugated to an
amino acid in an effort to enhance the cytotoxicity. A car-
boxyl group was used to connect the butyl piperidine side
chain or amino acid to the aromatic ring of acridone 3a.
Hence, acridone-2-carboxylic acid was prepared and used
11a), a methyl ester (compound 13), and a benzyl amide
(compound 17), which greatly improved their activities.
The conjugation of 12 with L-valine amino acid led to com-
pound 15, in which the presence of the carboxyl group
resulted in inactivity. Therefore, the uptake of acridone
derivatives was not facilitated by amino acid transporting
proteins but by passive diffusion. To confirm the above
argument, the free acid was protected as a benzyl ester
1
6
1
0
as a precursor for the synthesis of 2,N -substituted
(compound 14) and a benzyl amide (compound 17), result-
acridones.
ing in the recovery of the activity. When the R group was
1
0
the same, for example, compound 11a, with the N -butyl
10
Synthesis and cytotoxicity of 2,N -
piperidine side chain, exhibited higher cytotoxic activity
substituted acridones
10
compared to 11b without the N -attached group. This find-
1
0
ing indicates the crucial role of the N -butyl piperidine side
chain in the cytotoxicity of acridone. Introducing a butyl
piperidine ester, a methyl ester, a benzyl amide, a L-valine
benzyl ester, and a L-valine benzyl amide at the C2-position
of 3a increased the cytotoxicity. Compound 11a, which was
obtained from the addition of butyl piperidine ester at the
C2-position of 3a, exhibited the highest improvement in
cytotoxicity against the tested cell lines. The cytotoxicity of
The precursor, acridone-2-carboxylic acid (9), was prepared
via two steps (Scheme 2) to obtain key intermediates for
10
synthesis of 2,N -substituted compounds. The Ullmann
condensation of 2-bromobenzoic acid (6) with 4-aminoben-
zoic acid (7) in the presence of copper and potassium car-
bonate in refluxing N,N-dimethylformamide yielded
17
diphenylamine-2,4′-dicarboxylic acid (8). Treatment of 8
with concentrated sulfuric acid formed the desired acridone-
11a was improved by 4.5-, 4.8-, 7.5- and 6-fold against
2-carboxylic acid (9). A butyl piperidine side chain was
Molt-3, HepG2, A549, and HuCCA-1, respectively, com-
pared with 3a.
incorporated into 9 through the previously described
method. The use of NaH and 1,4-dibromobutane led to the
generation of N,O- and O-alkylated products (10a and 10b,
respectively). Stirring the resulting bromobutyl acridone
10a with piperidine in acetonitrile at room temperature
yielded acridone 11a containing two butyl piperidine side
chains. Reaction under the same conditions with 10b pro-
vided 11b. The basic hydrolysis of 11a afforded acridone 12

Khunnawutmanotham et al.
7
1
0
Table 2. Cytotoxic activities and MlogP values of the acridone derivatives substituted at C-2 and/or the N -position.
Compound
R
R′
IC50 (µM)a
Molt-3
ΔG
kcalmol )
MlogP
−
1
(
HepG2
A549
HuCCA-1
3
1
a
H
14.8±2.5
14.2±3.3
38.9±5.1
56.9±2.8 −7.4
9.5±0.3 −7.8
3.36
4.00
1a
3.3±0.5
3.0±0.5
5.2±0.5
1
2
COOH
Inactiveb
Inactive
Inactive
Inactive
−7.7
2.98
1
3
4
COOMe
3.6±0.4
6.1±0.2
4.3±1.5
7.0±0.5
10.8±1.9
8.9±0.9
25.6±2.5 −7.8
9.4±0.3 −7.9
3.20
3.99
1
15
16
17
Inactive
9.6±1.9
8.2±0.6
Inactive
Inactive
Inactive
−6.7
2.81
3.59
3.84
35.3±3.5
2.0±0.2
19.3±3.2
7.5±1.1
20.9±3.3 −7.8
9.9±3.3 −8.7
9
1
H
H
COOH
Inactive
Inactive
Inactive
Inactive
−7.0
2.06
2.98
1b
8
12.4±0.7
18.9±7.5
20.2±2.0
25.9±1.8 −7.5
1
1
H
H
COOMe
43.9±12.2
6.9±1.0
5.9±3.4
11.1±0.4
16.7±3.1
12.1±2.8 −6.9
2.32
3.40
9
13.8±3.5
22.5±1.3 −8.3
2
0
1
H
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
−7.6
−8.3
2.05
3.15
2
H
−
105.7±11.5 Inactive
Doxorubicin
−
NDc
ND
0.7±0.1
ND
0.1±0.0
ND
0.5±0.4 −9.2
ND −9.4
−0.82
ND
3
′-desamino-3′-(2-methoxy-4-morpholinyl)-
doxorubicin
a
Results are expressed as mean±standard error; average of three independent experiments.
b
−1
IC50 ⩾50µgmL .
c
Not determined.
1
0
Molecular modeling of 2,N -substituted
3′-desamino-3′-(2-methoxy-4-morpholinyl)-doxorubicin,
was removed and then docked again to the DNAcrystal struc-
ture. The docked conformation and the co-crystallized con-
formationweresuperimposed(FigureS1intheSupplementary
Information) and showed similar orientations, which means
acridones
Molecular modeling was conducted using theAutoDock Vina
.1.2 software suite to elucidate the binding modes and
18
1
binding energies of the acridone derivatives. A double-
stranded DNAcrystal structure was obtained from the Protein
that our method can be used further for all the derivatives.
All the derivatives were docked to the DNA crystal struc-
19,20
Data Bank (PDB code: 2DES)
and was used as the dock- ture and the binding energies measured as ΔG values are
ing scaffold. The native co-crystallized ligand, shown in Tables 1 and 2. The docking results revealed that the

8
Journal of Chemical Research 00(0)
positive control, doxorubicin, had the lowest General procedure for the preparation
−
1
ΔG=–9.2kcalmol , suggesting that this compound binds
very tightly, as reflected in the very low value of IC (<1µM).
of bromoalkyl acridones 2−5
50
10
Asolution of acridone (1mmol) in N,N-dimethylformamide
The ΔG values of the N -substituted acridone derivatives
tended to be more positive with ΔG values ranging between
6.1 and −7.5kcalmol compared to the more cytotoxic
(10mL) was added to a stirred solution of sodium hydride
−1
(3mmol) in N,N-dimethylformamide (10mL). The mixture
was heated at 80°C for 15min, treated with the appropriate
dibromoalkane (6mmol) and heated at 80°C for an addi-
tional 0.5h. The reaction mixture was cooled, water was
added, and the mixture was extracted with ethyl acetate.
The combined organic layer was washed with brine and
water, dried over anhydrous Na SO , and concentrated
−
10
C2,N -substituted acridone derivatives with ΔG values rang-
−1
ing between −6.7 and −9.1kcalmol , in congruence with the
cytotoxicity results. Depicted in Figure 4(a), the tricyclic acri-
done core is inserted and stabilized by π–π stacking with the
base pairs in DNA, thereby perturbing DNA base-pairing
1
0
interactions. The N -alkyl side chains (Figures 4(a) and (b))
interact with the DNA minor groove, most probably through
van der Waal’s interactions, and the nitrogen-based moieties
could potentially form electrostatic attractions with the phos-
2
4
under reduced pressure. The residue was purified by silica
gel column chromatography.
2
1
10-(3′-N-Bromopropyl)acridone (2): (32%) yellow
−1
10
solid, m.p. 113.5°C−114.5°C; FTIR, ν
(cm ): 1631,
phate backbones. For the C2,N -substituted acridone deriva-
tives (Figure 4(b)), the C2-substituted ester is predicted to
interact with the DNA major groove.
max
1
1596, 1489, 1461, 1377, 1177, 752, 673; H NMR (400MHz,
CDCl ): δ 8.49 (dd, J=8.0, 1.6Hz, 2H), 7.68−7.63 (m, 2H),
3
7.48 (d, J=8.7Hz, 2H), 7.22 (t, J=7.5Hz, 2H), 4.48 (t,
J=7.7Hz, 2H), 3.56 (t, J=6.0Hz, 2H), 2.35−2.43 (m, 2H);
1
3
Conclusion
C NMR (100MHz, CDCl ): δ 177.9, 141.6 (2C), 134.1
3
(
3
2
2C), 128.1 (2C), 122.5 (2C), 121.4 (2C), 114.2 (2C), 44.5,
0.2, 29.4; MS (EI): m/z (relative intensity): 315 (M , 20),
08 (100), 180 (26), 152 (13); HRMS (APCI): m/z calcd for
The introduction of two butyl piperidine side chains at the
+
10
C2- and N -positions of acridone (compound 11a) could
enhance the cytotoxicity of acridine-based compounds. The
+
C H NOBr [M+H] : 316.0332; found: 316.0339.
16
15
optimal pK (piperidinyl moiety) improved the ability of the
a
22
1
0-(4′-N-Bromobutyl)acridone (3): (57%) yellow solid,
derivative to bind to the DNAphosphate backbone and enter
the cell compared with the other derivatives, that is, mor-
pholine-, pyrrolidine-, pyrrole-, 3° and 4° amines and azide-
substituted compounds. The substitution of the butyl
piperidine side chain at the C2-position could provide tight
binding of the compound to DNA, as supported by the
increased binding energy from the computational calcula-
tions. The incorporation of two butyl piperidines at the C2-
−1
m.p. 145.5°C−146.5°C; FTIR, νmax (cm ): 1631, 1601,
1
CDCl ): δ 8.56 (dd, J=8.0, 1.2Hz, 2H), 7.75−7.68 (m, 2H),
7
1
492, 1461, 1264, 1176, 732, 704; H NMR (300MHz,
3
.47 (d, J=8.7Hz, 2H), 7.28 (t, J=7.7Hz, 2H), 4.34 (t,
J=7.7Hz, 2H), 3.52 (t, J=6.5Hz, 2H), 2.05−2.15 (m, 4H);
13
C NMR (75MHz, CDCl ): δ 177.9, 141.6 (2C), 134.0 (2C),
28.0 (2C), 122.4 (2C), 121.3 (2C), 114.4 (2C), 45.1, 32.7,
9.7, 25.7; MS (EI): m/z (relative intensity): 329 (M , 23),
08 (100), 180 (21); HRMS (APCI): m/z calcd for
3
1
2
2
+
10
and N -positions of acridone did not affect the cellular
uptake of the compound. In addition, the positive-charged
piperidinium moieties could electrostatically bind to the
DNA phosphate backbone, facilitating the tight binding
DNA. As a result, compound 11a showed the greatest
enhanced DNA intercalation.
+
C H NOBr [M+H] : 330.0488; found: 330.0491.
17
17
1
0-(5′-N-Bromopentyl)acridone (4): (75%) yellow solid,
−1
m.p. 114.5°C−115.0°C; FTIR, νmax (cm ): 1632, 1597,
1
(
1
490, 1460, 1377, 1290, 1264, 1176, 753, 673; H NMR
300MHz, CDCl ): δ 8.58 (dd, J=8.0, 1.4Hz, 2H),
3
7
.78−7.68 (m, 2H), 7.47 (d, J=8.7Hz, 2H), 7.29 (t,
Experimental
J=7.6Hz, 2H), 4.35 (t, J= 8.2Hz, 2H), 3.47 (t, J=6.5Hz,
1
3
2
H), 2.05−1.91 (m, 4H), 1.78−1.68 (m, 2H); C NMR
Chemistry
(
75MHz, CDCl ): δ 177.9, 141.6 (2C), 133.9 (2C), 128.0
3
1H NMR and 13C NMR spectra were recorded on Bruker (2C), 122.5 (2C), 121.3 (2C), 114.4 (2C), 45.8, 33.3, 32.2,
1
13
+
AVANCE 400 (400MHz for H and 100MHz for C) and 26.3, 25.4; MS (EI): m/z (relative intensity): 343 (M , 27),
1
Bruker AVANCE 300 (300MHz for H and 75MHz for 208 (100), 180 (17); HRMS (APCI): m/z calcd for
1
3
+
C) spectrometers. Chemical shifts are reported as δ values C H NOBr [M+H] : 344.0644; found: 344.0647.
1
8
19
in ppm relative to tetramethylsilane. Mass spectra were
2.2.4 10-(6′-N-Bromohexyl)acridone (5): (70%) yellow
obtained on a Finnigan Polaris GCQ mass spectrometer, solid, m.p. 103.0°C−104.0°C; FTIR, νmax (cm ): 1632,
while accurate masses (HRMS) were obtained using a 1597, 1490, 1460, 1377, 1290, 1264, 1176, 753, 673; H
−1
1
Bruker Micro TOF in APCI or ESI positive mode. Infrared NMR (300MHz, CDCl ): δ 8.59 (dd, J=8.0, 1.7Hz, 2H),
3
−
1
(
IR) spectra were recorded in terms of cm on a Perkin 7.74−7.67 (m, 2H), 7.50 (d, J=8.7Hz, 2H), 7.31 (t, J=7.6Hz,
Elmer Spectrum One FTIR spectrometer. Melting points 2H), 4.36 (t, J=8.3Hz, 2H), 3.46 (t, J=6.6Hz, 2H),
were determined on an SMP3 melting point apparatus. 2.05−1.90 (m, 4H), 1.75−1.55 (m, 4H); C NMR (75MHz,
13
Column chromatography analysis was performed on Merck CDCl ): δ 177.9, 141.7 (2C), 133.9 (2C), 128.0 (2C), 122.4
3
silica gel 60 (70–230 mesh).
(2C), 121.2 (2C), 114.4 (2C), 45.9, 33.5, 32.5, 27.8, 27.0,

Khunnawutmanotham et al.
9
+
2
6.1; MS (EI): m/z (relative intensity): 357 (M , 33), 208 concentrated under reduced pressure. The residue was puri-
(
100), 195 (19), 180 (13); HRMS (APCI): m/z calcd for fied by silica gel column chromatography.
+
23
C H NOBr [M+H] : 358.0801; found: 358.0795.
10-(3′-N-Piperidinopropyl)acridone (2a): (67%) yel-
19
21
−
1
low solid, m.p. 135.0°C−136.0°C; FTIR, νmax (cm ):
1
1
634, 1598, 1489, 1462, 1377, 1262, 1177, 753, 674; H
General procedure for the preparation
of N -substituted acridones
10
NMR (300MHz, CDCl ): δ 8.58 (dd, J=8.0, 1.5Hz, 2H),
3
7
.80−7.60 (m, 4H), 7.29 (t, J=7.6Hz, 2H), 4.47 (t,
Preparation of compounds 2a–5a, 2b–5b, 2c–5c, 2e–5e,
and 2f–5f. Amine (5mmol) was added to a stirred solution
of bromoalkyl acridone (1mmol) in acetonitrile (25mL).
The reaction mixture was stirred at room temperature for
J=8.4Hz, 2H), 2.55−2.40 (m, 6H), 2.10−2.00 (m, 2H),
13
1
.75−1.60 (m, 4H), 1.60−1.45 (m, 2H); C NMR (75MHz,
CDCl ): δ 178.0, 141.9 (2C), 133.8 (2C), 127.9 (2C), 122.4
3
(
(
2C), 121.1 (2C), 114.8 (2C), 55.7, 54.8 (2C), 44.1, 26.1
2C), 24.8, 24.4; MS (EI): m/z (relative intensity): 320 (M ,
2
4h and concentrated under reduced pressure. The residue
+
was treated with water and extracted with dichloromethane.
The combined organic layer was washed with saturated
aqueous sodium hydrogen carbonate and water, dried over
anhydrous Na SO and concentrated under reduced pres-
sure. The residue was purified by silica gel column
chromatography.
8
), 208 (4), 180 (4), 124 (10), 98 (100); HRMS (APCI): m/z
+
calcd for C H N O [M+H] : 321.1961; found: 321.1954.
2
1
25
2
23
1
0-(4′-N-Piperidinobutyl)acridone (3a): (96%) yellow
−1
2
4
solid, m.p. 115.5°C−116.0°C; FTIR, νmax (cm ): 1633,
1
1
598, 1490, 1461, 1377, 1264, 1177, 752, 732, 673; H
NMR (400MHz, CDCl ): δ 8.58 (dd, J=8.0, 1.2Hz, 2H),
3
7
2
2
.74−7.60 (m, 4H), 7.31−7.25 (m, 2H), 4.37 (t, J=7.6Hz,
Preparation of compounds 2d–5d. Pyrrole (3mmol) was
added to a mixture of sodium hydroxide (9mmol) in
dimethyl sulfoxide (5mL) and the mixture was stirred at
room temperature for 30min. After cooling in an ice bath,
the mixture was treated with a solution of bromoalkyl acri-
done (1mmol) in dimethyl sulfoxide (15mL) and then
stirred at room temperature for 2h. Water was added and
the mixture was extracted with ethyl acetate. The com-
bined organic layer was washed with water, dried over
anhydrous Na SO , and concentrated under reduced pres-
H), 2.50−2.40 (m, 6H), 2.00−1.91 (m, 2H), 1.80−1.70 (m,
13
H), 1.70−1.60 (m, 4H), 1.60−1.55 (m, 2H); C NMR
(
(
100MHz, CDCl ): δ 178.0, 141.7 (2C), 133.8 (2C), 127.8
2C), 122.4 (2C), 121.1 (2C), 114.8 (2C), 57.9, 54.6 (2C),
3
4
5.9, 26.1 (2C), 24.6, 24.5, 23.6; MS (EI): m/z (relative
+
intensity): 334 (M , 44), 208 (10), 138 (21), 98 (100);
HRMS (APCI): m/z calcd for C H N O [M+H] :
3
+
2
2
27
2
35.2118; found: 335.2125.
1
0-(5′-N-Piperidinopentyl)acridone (4a): (77%) yellow
−1
2
4
solid, m.p. 121.5°C−122.5°C; FTIR, νmax (cm ): 1632,
sure. The residue was purified by silica gel column
chromatography.
1
1
597, 1490, 1460, 1376, 1290, 1262, 1176, 753, 673; H
NMR (300MHz, CDCl ): δ 8.57 (dd, J=8.1, 1.5Hz, 2H),
3
7
.74−7.68 (m, 2H), 7.47 (d, J=8.7Hz, 2H), 7.28 (t, J = 7.5
Preparation of compounds 2g–5g. A solution of 2f–5f
Hz, 2H), 4.32 (t, J = 8.4 Hz, 2H), 2.38−2.31 (m, 6H),
2
(
1mmol) in dichloromethane (10mL) was treated with
13
.00−1.89 (m, 2H), 1.70−1.44 (m, 10H); C NMR
iodomethane (5mmol) and the mixture was stirred under
argon at room temperature for 12h. The precipitate was
collected, washed with dichloromethane, and dried to yield
trimethylammonium salts 2g–5g.
(
(
4
75MHz, CDCl ): δ 177.9, 141.7 (2C), 133.8 (2C), 127.9
2C), 122.4 (2C), 121.1 (2C), 114.5 (2C), 59.2, 54.7 (2C),
3
6.1, 27.0, 26.7, 26.0 (2C), 25.0, 24.4; MS (EI): m/z (rela-
+
tive intensity): 348 (M , 30), 208 (13), 154 (14), 98 (100);
HRMS (APCI): m/z calcd for C H N O [M+H] :
3
+
2
3
29
2
Preparation of compounds 2h–5h. A solution of bromoal-
kyl acridone (1mmol) in dimethyl sulfoxide (3mL) was
treated with sodium azide (0.5M) in dimethyl sulfoxide
49.2274; found: 349.2281.
1
0-(6′-N-Piperidinohexyl)acridone (5a): (77.5%) yel-
−1
low solid, m.p. 81.0°C−82.0°C; FTIR, νmax (cm ): 1631,
1
NMR (400MHz, CDCl ): δ 8.59 (dd, J=8.0, 1.6Hz, 2H),
7
J=7.2Hz, 2H), 4.36 (t, J = 8.0 Hz, 2H), 3.00−2.77 (m, 6H),
2
CDCl ): δ 177.9, 141.7 (2C), 134.0 (2C), 128.0 (2C), 122.5
(
3mL, 1.5mmol) and the mixture was stirred at room tem-
1
598, 1492, 1460, 1377, 1289, 1263, 1178, 756, 674; H
perature for 3h. Water was added and the mixture was
extracted with ethyl acetate. The combined organic layer
was washed with water, dried over anhydrous Na SO , and
3
.78−7.73 (m, 2H), 7.50 (d, J=8.8Hz, 2H), 7.30 (t,
2
4
concentrated under reduced pressure. The residue was puri-
fied by silica gel column chromatography.
13
.00−1.75 (m, 8H), 1.66−1.40 (m, 6H); C NMR (100MHz,
3
(
2
2C), 121.2 (2C), 114.5 (2C), 57.9, 53.7 (2C), 45.8, 27.1,
Preparation of compounds 2i and 3i. A solution of acri-
done (1mmol) in N,N-dimethylformamide (10mL) was
added to a stirred suspension of sodium hydride (3mmol)
in N,N-dimethylformamide (10mL). The mixture was
heated at 80°C for 15 min, treated with propyl iodide (for
6.8, 26.4, 24.5, 23.5 (2C), 22.7; MS (EI): m/z (relative
+
intensity): 362 (M , 5), 208 (12), 149 (25), 98 (98), 86
(
3
+
100); HRMS (APCI): m/z calcd for C H N O [M+H] :
2
4
31
2
63.2431; found: 363.2438.
0-(3′-N-Morpholinopropyl)acridone (2b):23 (78.5%)
1
2
i) or 1-bromobutane (for 3i) (5mmol), and heated at 80°C
−1
yellow solid, m.p. 114.0°C−114.5°C; FTIR, νmax (cm ):
for an additional 0.5h. The reaction mixture was cooled
and then water was added and the mixture was extracted
with ethyl acetate. The combined organic layer was washed
1
6
2
633, 1598, 1491, 1462, 1378, 1290, 1263, 1178, 1115, 754,
1
74; H NMR (300MHz, CDCl ): δ 8.59 (dd, J=8.0, 1.2Hz,
3
H), 7.75−7.62 (m, 4H), 7.29 (t, J=7.4Hz, 2H), 4.49 (t,
with brine and water, dried over anhydrous Na SO , and
2
4
J=7.5Hz, 2H), 3.80 (t, J= 4.5Hz, 4H), 2.55−2.47 (m, 6H),

1
0
Journal of Chemical Research 00(0)
2
1
.12−2.02 (m, 2H); 13C NMR (75MHz, CDCl ): δ 178.0,
41.8 (2C), 133.8 (2C), 128.0 (2C), 122.4 (2C), 121.2 (2C), solid, m.p. 108.5°C−109.5°C; FTIR, νmax (cm ): 1633,
10-(4′-N-Pyrrolidinobutyl)acridone (3c): (93%) yellow
3
−1
1
114.6 (2C), 67.0 (2C), 55.4, 53.8 (2C), 43.7, 24.3; MS (EI): 1597, 1490, 1461, 1378, 1264, 1177, 752, 673; H NMR
+
m/z (relative intensity): 322 (M , 6), 279 (8), 222 (12), 208 (400MHz, CDCl ): δ 8.57 (dd, J=8.0, 1.6Hz, 2H),
3
(
10), 180 (9), 100 (100); HRMS (APCI): m/z calcd for 7.73−7.68 (m, 2H), 7.59 (d, J=8.7Hz, 2H), 7.30−7.25 (m,
+
C H N O [M+H] : 323.1754; found: 323.1750.
2H), 4.37 (t, J=8.3Hz, 2H), 2.62−2.53 (m, 6H), 2.03−1.94
2
0
1
23
2
2
23
13
0-(4′-N-Morpholinobutyl)acridone (3b): (73%) yel- (m, 2H), 1.86−1.73 (m, 6H); C NMR (100MHz, CDCl ):
3
−1
low solid, m.p. 143.5°C−144.5°C; FTIR, νmax (cm ): 1632, δ 177.9, 141.7 (2C), 133.8 (2C), 127.9 (2C), 122.4 (2C),
1
1
600, 1493, 1462, 1378, 1265, 1116, 731, 703; H NMR 121.1 (2C), 114.7 (2C), 55.3, 54.1 (2C), 45.9, 25.7, 24.9,
+
(400MHz, CDCl ): δ 8.57 (dd, J=8.0, 1.6Hz, 2H), 23.5 (2C) ppm; MS (EI): m/z (relative intensity): 320 (M ,
3
7
2
2
.74−7.69 (m, 2H), 7.58 (d, J=8.4Hz, 2H), 7.30−7.26 (m, 25), 208 (9), 180 (11), 124 (21), 84 (100); HRMS (APCI):
+
H), 4.37 (t, J=8.3Hz, 2H), 3.78 (t, J=4.8Hz, 4H), m/z calcd for C H N O [M+H] : 321.1961; found:
2
1
25
2
.55−2.47 (m, 6H), 2.02−1.93 (m, 2H), 1.82−1.73 (m, 2H); 321.1962.
1
3
C NMR (100MHz, CDCl ): δ 177.9, 141.7 (2C), 133.8
10-(5′-N-Pyrrolidinopentyl)acridone (4c): (73%) yel-
3
−
1
(
(
2C), 127.9 (2C), 122.4 (2C), 121.2 (2C), 114.6 (2C), 67.0 low solid, m.p. 113.0°C−114.0°C; FTIR, νmax (cm ):
2C), 57.6, 53.7 (2C), 45.8, 24.4, 23.2; MS (EI): m/z (rela- 1633, 1597, 1490, 1460, 1377, 1290, 1263, 1176, 753, 673;
+
1
tive intensity): 336 (M , 10), 293 (14), 222 (9), 208 (23),
H NMR (400MHz, CDCl ): δ 8.58 (dd, J=8.0, 1.4Hz,
3
1
80 (15), 142 (14), 100 (100); HRMS (APCI): m/z calcd for 2H), 7.75−7.70 (m, 2H), 7.49 (d, J=8.7Hz, 2H), 7.29 (t,
+
C H N O [M+H] : 337.1911; found: 337.1908.
J=7.4Hz, 2H), 4.34 (t, J= 8.2Hz, 2H), 2.58−2.50 (m, 6H),
21
25
2
2
1
0-(5′-N-Morpholinopentyl)acridone (4b): (75%) yel- 2.01−1.91 (m, 2H), 1.85−1.78 (m, 4H), 1.74−1.56 (m, 4H);
−1
13
low solid, m.p. 116.5°C−117.0°C; FTIR, νmax (cm ):
C NMR (100MHz, CDCl ): δ 177.9, 141.8 (2C), 133.8
3
1
7
1
7
633, 1597, 1490, 1460, 1376, 1290, 1261, 1176, 1116, (2C), 128.0 (2C), 122.5 (2C), 121.2 (2C), 114.5 (2C), 56.3,
1
53, 673; H NMR (400MHz, CDCl ): δ 8.58 (dd, J=8.0, 54.3 (2C), 46.1, 28.6, 27.1, 25.0, 23.4 (2C); MS (EI): m/z
3
+
.6Hz, 2H), 7.75−7.70 (m, 2H), 7.48 (d, J=8.7Hz, 2H), (relative intensity): 334 (M , 13), 208 (11), 180 (8), 140
.29 (t, J=7.6Hz, 2H), 4.34 (t, J=8.2Hz, 2H), 3.74 (t, (17), 84 (100); HRMS (APCI): m/z calcd for C H N O
2
2
27
2
+
J=4.6Hz, 4H), 2.50−2.37 (m, 6H), 2.02−1.91 (m, 2H), [M+H] : 335.2118; found: 335.2106.
1
3
1
1
.70−1.54 (m, 4H); C NMR (100MHz, CDCl ): δ 177.9,
41.7 (2C), 133.8 (2C), 128.0 (2C), 122.5 (2C), 121.2 (2C), solid, m.p. 76.0°C−77.0°C; FTIR, νmax (cm ): 1630, 1596,
10-(6′-N-Pyrrolidinohexyl)acridone (5c): (71%) yellow
3
−1
1
114.4 (2C), 66.9 (2C), 58.7, 53.8 (2C), 46.0, 27.0, 26.2, 1491, 1460, 1377, 1263, 1177, 755, 674; H NMR
+
2
4.7; MS (EI): m/z (relative intensity): 350 (M , 4), 332 (300MHz, CDCl ): δ 8.58 (dd, J=8.0, 1.5Hz, 2H),
3
(
(
[
9), 319 (15), 307 (19), 264 (20), 222 (18), 208 (41), 180 7.77−7.72 (m, 2H), 7.50 (d, J=8.7Hz, 2H), 7.30 (t,
20), 100 (100); HRMS (APCI): m/z calcd for C H N O
J=7.5Hz, 2H), 4.34 (t, J=8.0Hz, 2H), 3.08 (br s, 4H), 2.88
(t, J=7.9Hz, 2H), 2.10−1.81 (m, 8H) 1.63−1.45 (m, 4H);
2
2
27
2
2
+
M+H] : 351.2067; found: 351.2065.
0-(6′-N-Morpholinohexyl)acridone (5b): (77%) yellow
1
3
1
C NMR (75MHz, CDCl ): δ 177.9, 141.7 (2C), 134.0
3
−1
solid, m.p. 95.5°C−96.0°C; FTIR, νmax (cm ): 1634, 1598, (2C), 127.9 (2C), 122.4 (2C), 121.2 (2C), 114.5 (2C), 55.6,
1
NMR (400MHz, CDCl ): δ 8.58 (dd, J=8.0, 1.5Hz, 2H), m/z (relative intensity): 348 (M , 13), 208 (8), 180 (9), 110
1
490, 1460, 1376, 1290, 1262, 1176, 1116, 753, 673; H 53.7 (2C), 45.8, 27.0, 26.8, 26.5, 26.4, 23.3 (2C); MS (EI):
+
3
7
2
2
1
.74−7.69 (m, 2H), 7.48 (d, J=8.7Hz, 2H), 7.31−7.26 (m, (11), 84 (100); HRMS (APCI): m/z calcd for C H N O
23 29 2
+
H), 4.32 (t, J=8.2Hz, 2H), 3.73 (t, J=4.6Hz, 4H), 2.47– [M+H] : 394.2274; found: 349.2283.
.42 (m, 4H), 2.36 (t, J=7.3Hz, 2H), 1.98−1.89 (m, 2H), 10-(3′-(N-Pyrrole)propyl)acridone (2d): (78%) yellow
13
−1
.62−1.52 (m, 4H), 1.50−1.43 (m, 2H); C NMR (100MHz, solid, m.p. 154.5°C−155.5°C; FTIR, νmax (cm ): 1632,
1
CDCl3): δ 177.9, 141.7 (2C), 133.8 (2C), 127.9 (2C), 122.4 1598, 1491, 1461, 1291, 1264, 1177, 732, 673; H NMR
2C), 121.1 (2C), 114.5 (2C), 66.9 (2C), 58.9, 53.8 (2C), 46.0, (300MHz, CDCl ): δ 8.54 (dd, J=8.0, 1.6Hz, 2H),
(
3
2
7.2, 27.1, 26.8, 26.5; MS (EI): m/z (relative intensity): 364 7.68−7.60 (m, 2H), 7.26 (t, J=7.0Hz, 2H), 7.13 (d,
+
(
(
[
M , 4) 346 (23), 333 (37), 321 (32), 277 (16), 222 (18), 208 J=8.8Hz, 2H), 6.78 (t, J=2.0Hz, 2H), 6.30 (t, J=2.1Hz,
43), 100 (100); HRMS (APCI): m/z calcd for C H N O
M+H] : 365.2224; found: 365.2225.
2H), 4.25 (t, J=8.1Hz, 2H), 4.15 (t, J=6.2Hz, 2H),
23
29
2
2
+
13
2.40−2.26 (m, 2H); C NMR (75MHz, CDCl ): δ 177.9,
3
1
0-(3′-N-Pyrrolidinopropyl)acridone (2c): (69%) yel- 141.4 (2C), 134.0 (2C), 128.0 (2C), 122.4 (2C), 121.3 (2C),
−
1
low solid, m.p. 70.5°C−71.5°C; FTIR, νmax (cm ): 1633, 120.8 (2C), 114.0 (2C), 109.1 (2C), 46.8, 43.1, 28.9; MS
1
1
+
598, 1490, 1461, 1377, 1290, 1263, 1177, 753, 674; H (EI): m/z (relative intensity): 302 (M , 41), 222 (62), 208
NMR (300MHz, CDCl ): δ 8.58 (dd, J=8.0, 1.2Hz, 2H), (35), 180 (20), 152 (13), 81 (100); HRMS (APCI): m/z
3
+
7
.77−7.68 (m, 2H), 7.64 (d, J=8.7Hz, 2H), 7.29 (t, calcd for C H N O [M+H] : 303.1492; found: 303.1494.
J=7.5Hz, 2H), 4.50 (t, J=7.7Hz, 2H), 2.75−2.62 (m, 6H),
.22−2.11 (m, 2H), 1.92−1.85 (m, 4H); C NMR (75MHz, solid, m.p. 145.0°C−146.0°C; FTIR, νmax (cm ): 1633,
CDCl ): δ 178.0, 141.8 (2C), 133.9 (2C), 127.9 (2C), 122.4 1603, 1594, 1491, 1458, 1377, 1172, 752, 726, 673; H
2
0
19
2
10-(4′-(N-Pyrrole)butyl)acridone (3d): (66%) yellow
1
3
−1
2
1
3
(
2
2
2C), 121.2 (2C), 114.7 (2C), 54.2 (2C), 52.9, 43.9, 26.4, NMR (300MHz, CDCl ): δ 8.56 (d, J=8.0, 1.6Hz, 2H),
3.5 (2C); MS (EI): m/z (relative intensity): 306 (M , 13), 7.72−7.65 (m, 2H), 7.35 (d, J=8.7Hz, 2H), 7.30−7.22 (m,
3
+
08 (6), 180 (6), 110 (7), 84 (100); HRMS (APCI): m/z 2H), 6.69 (t, J=2.1Hz, 2H), 6.19 (t, J= 2.1Hz, 2H), 4.25 (t,
+
calcd for C H N O [M+H] : 307.1805; found: J= 8.2Hz, 2H), 4.00 (t, J=6.8Hz, 2H), 2.08−1.84 (m, 4H);
3
2
0
23
2
1
3
07.1819.
C NMR (75MHz, CDCl ): δ 177.9, 141.6 (2C), 133.9
3

Khunnawutmanotham et al.
11
(
(
2C), 128.0 (2C), 122.4 (2C), 121.3 (2C), 120.4 (2C), 114.4
10-(5′-(N-Diethylamino)pentyl)acridone (4e):24 (85%)
−
1
2C), 108.5 (2C), 49.0, 45.6, 28.6, 24.4; MS (EI): m/z (rela- yellow solid, m.p. 61.5°C−62.5°C; FTIR, νmax (cm ):
+
tive intensity): 316 (M , 40), 222 (23), 208 (100), 180 (31), 1630, 1597, 1492, 1459, 1378, 1290, 1263, 1178, 751,
1
C H N O [M+H] : 317.1648; found: 317.1640.
1
52 (16), 122 (49), 80 (46); HRMS (APCI): m/z calcd for 671; H NMR (300MHz, CDCl ): δ 8.55 (d, J=8.1Hz,
3
+
2H), 7.70 (t, J=7.0Hz, 2H), 7.46 (d, J=8.7Hz, 2H), 7.26
2
1
21
2
1
0-(5′-(N-Pyrrole)pentyl)acridone (4d): (63%) yellow (t, J=7.5Hz, 2H), 4.29 (t, J=8.1Hz, 2H), 2.60−2.45 (m,
−1
solid, m.p. 109.0°C−110.0°C; FTIR, νmax (cm ): 1630, 6H), 2.00−1.85 (m, 2H), 1.70−1.50 (m, 4H), 1.05 (t,
1
1
13
597, 1492, 1458, 1375, 1279, 1174, 749, 720, 699; H J=7.2Hz, 6H); C NMR (75MHz, CDCl ): δ 177.9,
3
NMR (300MHz, CDCl ): δ 8.58 (dd, J=8.0, 1.6Hz, 2H), 141.7 (2C), 133.9 (2C), 127.9 (2C), 122.4 (2C), 121.1
3
7
.74−7.68 (m, 2H), 7.43 (d, J=8.7Hz, 2H), 7.29 (t, (2C), 114.6 (2C), 52.6, 47.0, 46.1 (2C), 27.0, 26.9, 24.9,
+
J=7.2Hz, 2H), 6.67 (t, J= 2.0Hz, 2H), 6.18 (t, J= 2.0Hz, 11.6 (2C); MS (EI): m/z (relative intensity): 336 (M , 3),
2
1
H), 4.29 (t, J=8.2Hz, 2H), 3.94 (t, J=7.0Hz, 2H), 208 (5), 180 (4), 126 (6), 86 (100); HRMS (APCI): m/z
1
3
+
.96−1.87 (m, 4H), 1.57−1.47 (m, 2H); C NMR (75MHz, calcd for C H N O [M+H] : 337.2274; found:
2
2
29
2
CDCl ): δ 177.9, 141.7 (2C), 133.8 (2C), 128.0 (2C), 122.5 337.2278.
3
(2C), 121.2 (2C), 120.4 (2C), 114.4 (2C), 108.1 (2C), 49.2,
10-(6′-(N-Diethylamino)hexyl)acridone (5e):24 (79%)
−
1
45.8, 31.2, 26.8, 24.1; MS (EI): m/z (relative intensity); 330 yellow solid, m.p. 150.0°C−151.0°C; FTIR, νmax (cm ):
+
(M , 35), 236 (26), 222 (46), 208 (100), 195 (17), 180 (40), 1632, 1597, 1490, 1460, 1376, 1289, 1262, 1176, 754, 674;
1
1
49 (27), 80 (43); HRMS (APCI): m/z calcd for C H N O
H NMR (400MHz, CDCl ): δ 8.56 (dd, J=8.0, 1.6Hz,
2
2
23
2
3
+
[
M+H] : 331.1805; found: 331.1804.
2H), 7.75−7.69 (m, 2H), 7.48 (d, J=8.7Hz, 2H), 7.28 (t,
1
0-(6′-(N-Pyrrole)hexyl)acridone (5d): (70%) yellow J=7.7Hz, 2H), 4.32 (t, J=8.1Hz, 2H), 2.81 (q, J=7.2Hz,
−
1
solid, m.p. 82.0°C−83.0°C; FTIR, νmax (cm ): 1632, 4H), 2.71−2.66 (m, 2H), 1.96−1.87 (m, 2H), 1.75−1.65 (m,
597, 1490, 1460, 1376, 1289, 1262, 1176, 753, 723, 673; 2H), 1.63−1.54 (m, 2H), 1.50−1.42 (m, 2H), 1.20 (t,
1
1
13
H NMR (300MHz, CDCl ): δ 8.56 (dd, J=8.0, 1.5Hz, J=7.2Hz, 6H); C NMR (100MHz, CDCl ): δ 177.8,
3
3
2
H), 7.73−7.76 (m, 2H), 7.42 (d, J=8.7Hz, 2H), 7.27 (t, 141.6 (2C), 133.9 (2C), 127.8 (2C), 122.3 (2C), 121.1 (2C),
J=7.7Hz, 2H), 6.65 (t, J=2.1Hz, 2H), 6.15 (t, J=2.1Hz, 114.5 (2C), 52.0, 46.6 (2C), 45.9, 27.0 (2C), 26.5, 25.4,
+
2
1
H), 4.27 (t, J=8.1Hz, 2H), 3.90 (t, J=7.0Hz, 2H), 10.1 (2C); MS (EI): m/z (relative intensity): 350 (M , 23),
1
3
.94−1.77 (m, 4H), 1.58−1.36 (m, 4H); C NMR 335 (9), 321 (9), 208 (23), 180 (13), 86 (100); HRMS
75MHz, CDCl ): δ 177.9, 141.6 (2C), 133.9 (2C), 128.0 (APCI): m/z calcd for C H N O [M+H] : 351.2431;
+
(
(
3
23 31
2
2C), 122.4 (2C), 121.2 (2C), 120.4 (2C), 114.4 (2C), found: 351.2430.
2
5
1
08.0 (2C), 49.4, 45.9, 31.5, 27.1, 26.6, 26.5; MS (EI):
10-(3′-(N-Dimethylamino)propyl)acridone (2f): (78%)
m/z (relative intensity): 344 (M , 80), 264 (36), 222 (50), yellow solid, m.p. 86.0°C−86.5°C; FTIR, νmax (cm ):
+
−1
2
08 (100), 196 (36), 180 (40), 80 (38); HRMS (APCI): 1634, 1597, 1490, 1461, 1377, 1291, 1261, 1178, 753, 674;
+
1
m/z calcd for C H N O [M+H] : 345.1961; found:
3
H NMR (400MHz, CDCl ): δ 8.58 (dd, J=8.0, 1.6Hz,
2
3
25
2
3
45.1952.
1
2H), 7.75−7.69 (m, 2H), 7.62 (d, J=8.7Hz, 2H), 7.29 (t,
0-(3′-(N-Diethylamino)propyl)acridone (2e):24 (69%) J=7.6Hz, 2H), 4.46 (t, J=7.7Hz, 2H), 2.48 (t, J=6.6Hz,
−
1
13
yellow solid, m.p. 100.5°C−101.0°C; FTIR, νmax (cm ): 2H), 2.33 (s, 6H), 2.11−2.03 (m, 2H); C NMR (100MHz,
633, 1598, 1490, 1461, 1376, 1291, 1265, 1178, 752, 673; CDCl ): δ 178.0, 141.8 (2C), 133.9 (2C), 127.9 (2C), 122.4
1
3
1
H NMR (300MHz, CDCl ): δ 8.58 (dd, J=8.0, 1.5Hz, (2C), 121.2 (2C), 114.7 (2C), 56.4, 45.5 (2C), 43.9, 25.4;
3
+
2
H), 7.75−7.62 (m, 4H), 7.28 (t, J=7.8Hz, 2H), 4.45 (t, MS (EI): m/z (relative intensity): 280 (M , 100), 236 (46),
J=8.0Hz, 2H), 2.70−2.60 (m, 6H), 2.10−2.00 (m, 2H), 222 (51), 209 (43), 180 (31) 166 (40), 152 (28), 58 (74);
1
3
+
1
1
1
(
(
.13 (t, J=7.1Hz, 6H); C NMR (75MHz, CDCl ): δ HRMS (APCI): m/z calcd for C H N O [M+H] :
3
18 21
2
78.0, 141.8 (2C), 133.8 (2C), 127.9 (2C), 122.4 (2C), 281.1648; found: 281.1642.
21.1 (2C), 114.7 (2C), 50.2, 46.9 (2C), 44.3, 25.4, 11.7
2C); MS (EI): m/z (relative intensity): 308 (M , 9), 208 yellow solid, m.p. 96.5 °C−97.5 °C; FTIR, νmax (cm ):
7), 180 (6), 166 (9), 86 (100); HRMS (APCI): m/z calcd 1632, 1596, 1490, 1460, 1378, 1290, 1264, 1177, 1043,
10-(4′-(N-Dimethylamino)butyl)acridone (3f): (95%)
+
−1
+
1
for C H N O [M+H] : 309.1961; found: 309.1966.
753, 674; H NMR (400 MHz, CDCl ): δ 8.57 (dd, J = 8.0,
2
0
25
2
3
2
4
1
0-(4′-(N-Diethylamino)butyl)acridone (3e): (94%) 1.5 Hz, 2H) 7.72 (m, 2H), 7.55 (d, J = 8.7 Hz, 2H), 7.28 (t,
−1
yellow solid, m.p. 63.0°C−64.0°C; FTIR, νmax (cm ): J = 7.2 Hz, 2H), 4.37 (t, J = 8.3 Hz, 2H), 2.44 (t, J = 7.2 Hz,
633, 1598, 1490, 1461, 1378, 1290, 1264, 1177, 752, 674; 2H), 2.31 (s, 6H), 2.01−1.91 (m, 2H), 1.80−1.71 (m, 2H);
H NMR (400MHz, CDCl ): δ 8.57 (dd, J=8.0, 1.5Hz,
1
1
13
C NMR (100 MHz, CDCl ): δ 177.9, 141.7 (2C), 133.8
3
3
2
H), 7.74−7.69 (m, 2H), 7.58 (d, J=8.7Hz, 2H), 7.28 (t, (2C), 127.9 (2C), 122.4 (2C), 121.1 (2C), 114.6 (2C),
J=7.5Hz, 2H), 4.36 (t, J=8.3Hz, 2H), 2.67−2.57 (m, 6H), 58.8, 45.9, 45.3 (2C), 24.9, 24.6; MS (EI): m/z (relative
+
2
6
1
5
.00−1.90 (m, 2H), 1.82−1.72 (m, 2H), 1.10 (t, J=7.2Hz, intensity): 294 (M , 5), 222 (3), 208 (3), 180 (3), 100 (4),
1
3
H); C NMR (100MHz, CDCl ): δ 178.0, 141.7 (2C), 71 (4), 58 (100); HRMS (APCI): m/z calcd for C H N O
3
19 23
2
+
33.8 (2C), 127.9 (2C), 122.4 (2C), 121.1 (2C), 114.7 (2C), [M + H] : 295.1805; found: 295.1797.
2.1, 46.6, 46.0 (2C), 24.8, 24.1, 11.3 (2C); MS (EI): m/z
10-(5′-(N-Dimethylamino)pentyl)acridone (4f): (71%)
+
−1
(
(
[
relative intensity): 322 (M , 19), 208 (14), 180 (9), 112 yellow solid, m.p. 65.0°C−65.5°C; FTIR, νmax (cm ):
13), 86 (100); HRMS (APCI): m/z calcd for C H N O 1632, 1591, 1492, 1459, 1376, 1261, 1181, 1037, 754, 673;
2
1
27
2
+
1
M+H] : 323.2118; found: 323.2107.
H NMR (400MHz, CDCl ): δ 8.58 (dd, J=8.0, 1.4Hz,
3

1
2
Journal of Chemical Research 00(0)
2
H), 7.73 (m, 2H), 7.49 (d, J=8.7Hz, 2H), 7.29 (t, (63), 55 (100); HRMS (APCI): m/z calcd for C H N O
2
1
27
2
+
J=7.8Hz, 2H), 4.34 (t, J=8.1Hz, 2H), 2.36 (t, J=6.6Hz, [M] : 323.2118; found: 323.2109.
2
H), 2.28 (s, 6H), 2.01−1.91 (m, 2H), 1.68−1.55 (m, 4H);
10-(6′-(N-Trimethylammonium)hexyl)acridone
(5g):
1
3
C NMR (100MHz, CDCl ): δ 177.9, 141.7 (2C), 133.8 (99% from 5f) yellow solid, m.p. 103.0°C−104.0°C; FTIR,
3
−1
(
2C), 128.0 (2C), 122.5 (2C), 121.1 (2C), 114.4 (2C), 59.4, νmax (cm ): 1627, 1607, 1596, 1494, 1459, 1378, 1265,
1
4
6.0, 45.4 (2C), 27.3, 27.0, 24.7; MS (EI): m/z (relative 1178, 756, 674; H NMR (400MHz, DMSO-d ): δ 8.35 (d,
6
+
intensity): 308 (M , 4), 208 (3), 180 (3), 149 (4), 114 (11), J=7.8Hz, 2H), 7.85−7.81 (m, 4H), 7.36−7.30 (m, 2H),
5
8 (100); HRMS (APCI): m/z calcd for C H N O 4.48 (t, J=7.8Hz, 2H), 3.36−3.34 (m, 11H), 1.85−1.46 (m,
20 25 2
+
[
M+H] : 309.1961; found: 309.1958.
2H), 1.72−1.63 (m, 2H), 1.60−1.51 (m, 2H), 1.41−1.32 (m,
1
3
1
0-(6′-(N-Dimethylamino)hexyl)acridone (5f): (95%) 2H); C NMR (100MHz, DMSO-d ): δ 176.9, 141.9 (2C),
6
−
1
yellow solid, m.p. 102.5 °C−103.0 °C; FTIR, νmax (cm ): 134.7 (2C), 127.2 (2C), 122.1 (2C), 121.7 (2C), 116.3 (2C),
1
6
1
629, 1594, 1494, 1461, 1380, 1291, 1265, 1179, 748, 65.8, 52.7 (3C), 45.5, 27.1, 26.1, 25.9, 22.4; MS (EI): m/z
1
+
70; H NMR (400 MHz, CDCl ): δ 8.58 (dd, J = 8.0, (relative intensity): 322 ([M–CH ] , 4), 208 (9), 180 (4),
3
3
.6 Hz, 2H), 7.72 (m, 2H), 7.48 (d, J = 8.7 Hz, 2H), 7.29 142 (13), 58 (100); HRMS (APCI): m/z calcd for C H N O
2
2
29
2
+
(
t, J = 7.4 Hz, 2H), 4.33 (t, J = 8.0 Hz, 2H), 2.35−2.30 (m, [M] : 337.2274; found: 337.2265.
2
6
1
H), 2.26 (s, 6H), 2.00−1.90 (m, 2H), 1.63−1.44 (m,
10-(3′-N-Azidopropyl)acridone (2h): (89%) yellow
1
3
−1
H); C NMR (100 MHz, CDCl ): δ 177.9, 141.7 (2C), solid, m.p. 78.5°C−79.5°C; FTIR, νmax (cm ): 2094, 1632,
3
1
33.8 (2C), 128.0 (2C), 122.5 (2C), 121.1 (2C), 114.5 1595, 1490, 1461, 1377, 1290, 1261, 1177, 751, 673; H
(
(
(
2C), 59.5, 46.1, 45.3 (2C), 27.5, 27.1 (2C), 26.8; MS NMR (300MHz, CDCl ): δ 8.55 (d, J=7.8, 2H), 7.75−7.69
EI): m/z (relative intensity): 322 (M , 5), 208 (4), 180 (m, 2H), 7.50 (d, J=8.7Hz, 2H), 7.31−7.24 (m, 2H), 4.44
3
+
4), 167 (6), 149 (19), 58 (100); HRMS (APCI): m/z (t, J=7.8Hz, 2H), 3.58 (t, J=6.0Hz, 2H), 2.19−2.10 (m,
+
13
calcd for C H N O [M + H] : 323.2118; found: 2H); C NMR (75MHz, CDCl ): δ 177.8, 141.6 (2C),
3
2
1
27
2
3
23.2113.
134.0 (2C), 128.1 (2C), 122.5 (2C), 121.4 (2C), 114.2 (2C),
1
0-(3′-(N-Trimethylammonium)propyl)acridone (2g): 48.9, 43.0, 26.6; MS (EI): m/z (relative intensity): 278
+
(
99% from 2f) yellow solid, m.p. 266.0°C−267.0°C; FTIR, ([M] , 59), 250 (13), 208 (100), 195 (34), 180 (53), 166
νmax (cm ): 1608, 1590, 1497, 1460, 1267, 1179, 1020, (28); HRMS (APCI): m/z calcd for C H N O [M+H] :
59, 673; H NMR (300MHz, DMSO-d ): δ 8.37 (d, 279.1240; found: 279.1238.
−
1
+
16
15
4
1
7
6
J=7.9Hz, 2H), 8.00−7.80 (m, 4H), 7.38 (t, J=7.4Hz, 2H),
10-(4′-N-Azidobutyl)acridone (3h): (95%) yellow solid,
−1
4
2
1
1
.51 (t, J=7.7Hz, 2H), 3.70 (t, J=7.8Hz, 2H), 3.12 (s, 9H), m.p. 112.5°C−113.5°C; FTIR, νmax (cm ): 2094, 1632,
1
3
1
.30−2.15 (m, 2H); C NMR (75MHz, DMSO-d ): δ 1596, 1491, 1460, 1379, 1290, 1263, 1175, 753, 673; H
6
76.5, 141.3 (2C), 134.4 (2C), 126.9 (2C), 122.6 (2C), NMR (400MHz, CDCl ): δ 8.58 (dd, J=8.0, 1.6Hz, 2H),
3
21.5 (2C), 115.9 (2C), 62.3, 52.5 (3C), 42.2, 20.7; MS 7.76−7.71 (m, 2H), 7.48 (d, J=8.7Hz, 2H), 7.32−7.27 (m,
+
(
EI): m/z (relative intensity): 280 ([M–CH ] , 7), 208 (7), 2H), 4.38 (t, J=8.1Hz, 2H), 3.45 (t, J=6.6Hz, 2H),
3
1
3
1
42 (17), 127 (7), 58 (100); HRMS (ESI): m/z calcd for 2.08−1.90 (m, 2H), 1.88−1.80 (m, 2H); C NMR (100MHz,
+
C H N O [M] :295.1805; found: 295.1796.
CDCl ): δ 177.9, 141.6 (2C), 134.0 (2C) 128.0 (2C), 122.4
1
9
23
2
3
1
0-(4′-(N-Trimethylammonium)butyl)acridone
(3g): (2C), 121.3 (2C), 114.3 (2C), 51.0, 45.4, 26.2, 24.5; MS
+
(
87% from 3f) yellow solid, m.p. 260.0°C−261.0°C; FTIR, (EI): m/z (relative intensity): 292 ([M] , 66), 220 (59), 208
νmax (cm ): 1627, 1607, 1594, 1492, 1457, 1261, 1174, (100), 195 (20), 180 (43), 152 (23); HRMS (APCI): m/z
54, 676; H NMR (400MHz, DMSO-d ): δ 8.35 (dd, calcd for C H N O [M+H] : 293.1397; found: 293.1387.
J=8.1, 1.3Hz, 2H), 7.89−7.81 (m, 4H), 7.35 (t, J=6.6Hz,
H), 4.51 (t, J=8.2Hz, 2H), 3.48−3.38 (m, 2H), 3.43 (s, solid, m.p. 79.0°C−80.0°C; FTIR, νmax (cm ): 2085, 1634,
H), 2.07−1.97 (m, 2H), 1.84−1.75 (m, 2H); C NMR 1594, 1489, 1458, 1377, 1263, 1171, 755, 672; H NMR
−
1
1
+
7
6 17 17 4
10-(5′-N-Azidopentyl)acridone (4h): (72%) yellow
−1
2
9
1
3
1
(
100MHz, DMSO-d ): δ 176.9, 141.8 (2C), 134.7 (2C), (400MHz, CDCl ): δ 8.58 (t, J=7.9Hz, 2H), 7.73 (t,
6
3
1
27.3 (2C), 122.1 (2C), 121.8 (2C), 116.2 (2C), 65.5, 52.9 J=8.2Hz, 2H), 7.47 (d, J=8.7Hz, 2H), 7.29 (t, J=7.4Hz,
(
(
3C), 45.2, 24.1, 19.9; MS (EI): m/z (relative intensity): 294 2H), 4.34 (t, J=7.6Hz, 2H), 3.36 (t, J=6.3Hz, 2H),
+
13
[M–CH ] , 4), 208 (6), 142 (13), 69 (36), 58 (100); 2.00−1.90 (m, 2H), 1.78−1.60 (m, 4H); C NMR (100MHz,
3
+
HRMS (APCI): m/z calcd for C H N O [M] : 309.1961; CDCl ): δ 177.8, 141.7 (2C), 133.9 (2C), 128.0 (2C), 122.5
2
0
25
2
3
found: 309.1951.
(2C), 121.2 (2C), 114.3 (2C), 51.2, 45.8, 28.7, 26.8, 24.1;
+
1
0-(5′-(N-Trimethylammonium)pentyl)acridone (4g): MS (EI): m/z (relative intensity): 306 ([M] , 27), 208 (100),
(
61% from 4f) yellow solid, m.p. 263.0°C−263.5°C; FTIR, 196 (44), 180 (44), 166 (19), 152 (22); HRMS (APCI): m/z
−
1
+
νmax (cm ): 1627, 1607, 1596, 1494, 1459, 1378, 1265, calcd for C H N O [M+H] : 307.1553; found: 307.1545.
1
J=7.8Hz, 2H), 7.85−7.81 (m, 4H), 7.36−7.30 (m, 2H), m.p. 77.0°C−78.0°C; FTIR, νmax (cm ): 2093, 1634, 1598,
4
2
2
1
6
18
19
4
1
178, 756, 674; H NMR (400MHz, DMSO-d ): δ 8.35 (d,
10-(6′-N-Azidohexyl)acridone (5h): (96%) yellow solid,
6
−1
1
.50 (f, J=7.8Hz, 2H), 3.36−3.34 (m, 11H), 1.85−1.46 (m, 1491, 1460, 1376, 1290, 1262, 1176, 754, 673; H NMR
H), 1.72−1.63 (m, 2H), 1.60−1.51 (m, 2H), 1.41−1.32 (m, (300MHz, CDCl ): δ 8.58 (dd, J=8.0, 1.5Hz, 2H),
3
1
3
H); C NMR (100MHz, DMSO-d ): δ 176.9, 141.9 (2C), 7.75−7.70 (m, 2H), 7.47 (d, J=8.7Hz, 2H), 7.29 (t,
6
34.7 (2C), 127.2 (2C), 122.1 (2C), 121.7 (2C), 116.4 (2C), J=7.8Hz, 2H), 4.33 (t, J=8.1Hz, 2H), 3.32 (t, J=6.5Hz,
1
3
5.6, 52.7 (3C), 45.3, 26.9, 23.2, 22.5; MS (EI): m/z (rela- 2H), 2.00−1.90 (m, 2H), 1.70−1.50 (m, 6H); C NMR
+
tive intensity): 296 ([M–27] , 12), 268 (9), 185 (9), 69 (75MHz, CDCl ): δ 177.9, 141.7 (2C), 133.9 (2C), 128.0
3

Khunnawutmanotham et al.
13
(
2C), 122.4 (2C), 121.2 (2C), 114.4 (2C), 51.3, 45.9, 28.8, N,N-dimethylformamide (25mL) was added to a stirred
2
7.1, 26.5, 26.4; MS (EI): m/z (relative intensity): 320 suspension of sodium hydride (250mg, 6.25mmol) in
+
(
(
[
[M] , 78), 292 (15), 208 (98), 180 (100), 166 (54), 152 N,N-dimethylformamide (10mL). The mixture was heated
60), 140 (47); HRMS (APCI): m/z calcd for C H N O at 80°C for 15 min, treated with 1,4-dibromobutane
M+H] : 321.1710; found: 321.1699.
1
9
21
4
+
(1.5mL, 12.71mmol) and heated at 80°C for an additional
0-(N-propyl)acridone (2i): (74%) yellow solid, m.p. 1h. The reaction mixture was cooled and water was added
30.0°C−131.0°C; FTIR, νmax (cm ): 1634, 1597, 1490, and the mixture was extracted with ethyl acetate. The com-
458, 1377, 1290, 1263, 1174, 747, 670; H NMR bined organic layer was washed with brine and water,
2
6
1
−
1
1
1
1
(
400MHz, CDCl ): δ 8.59 (dd, J=8.0, 1.6Hz, 2H), dried over anhydrous Na SO , and concentrated under
3
2
4
7
2
.75−7.70 (m, 2H), 7.50 (d, J=8.7Hz, 2H), 7.31−7.26 (m, reduced pressure. The residue was purified by silica gel
H), 4.31 (t, J=8.3Hz, 2H), 2.03−1.93 (m, 2H), 1.17 (t, column chromatography to provide 10a (245mg, 23%)
1
3
J=7.5Hz, 3H); C NMR (100MHz, CDCl ): δ 178.0, and 10b (226mg, 29%).
3
1
41.8 (2C), 133.8 (2C), 127.9 (2C), 122.4 (2C), 121.2 (2C),
10a: Yellow solid, m.p. 107.5°C−108.0°C; FTIR, ν
max
−1
114.5 (2C), 47.7, 20.5, 11.1; MS (EI): m/z (relative inten- (cm ): 1716, 1639, 1610, 1596, 1482, 1297, 1246, 1139,
+
1
sity): 237 ([M] , 54), 208 (100), 180 (13), 166 (8), 152 (8), 754; H NMR (300MHz, CDCl ): δ 9.16 (s, 1H), 8.84 (d,
3
+
1
2
40 (5); HRMS (APCI): m/z calcd for C H NO [M+H] : J=7.9Hz, 1H), 8.31 (d, J=8.9Hz, 1H), 7.76 (t, J=8.0Hz,
1
6
16
38.1226; found: 238.1231.
1H), 7.51 (d, J=9.0Hz, 2H), 7.34 (t, J=7.6Hz, 1H),
26
1
0-(N-butyl)acridone (3i): (70%) yellow solid, m.p. 4.45−4.35 (m, 4H), 3.60−3.50 (m, 4H), 2.20−1.90 (m, 8H);
−1
13
98.5°C−99.0°C; FTIR, νmax (cm ): 1633, 1596, 1489,
C NMR (75MHz, CDCl ): δ 177.5, 165.8, 144.2, 141.5,
3
1
1459, 1375, 1290, 1259, 1175, 751, 671; H NMR (400MHz, 134.4, 134.3, 130.5, 128.1, 122.9, 122.8, 122.3, 121.6,
CDCl ): δ 8.59 (dd, J=8.0, 1.7Hz, 2H), 7.75−7.70 (m, 2H), 114.7, 114.6, 64.1, 45.5, 33.2, 32.5, 29.5, 29.3, 27.4, 25.6;
3
+
7
.50 (d, J=8.7Hz, 2H), 7.31−7.26 (m, 2H), 4.34 (t, MS (EI): m/z (relative intensity): 507 ([M] , 36), 386 (98),
J=8.3Hz, 2H), 1.97−1.88 (m, 2H), 1.65−1.55 (m, 2H), 1.09 356 (12), 306 (11), 252 (100), 224 (15), 165 (16); HRMS
1
3
+
(
1
t, J=7.4Hz, 3H); C NMR (100MHz, CDCl ): δ 178.0, (ESI): m/z calcd for C H Br NO (M+H) : 508.0117;
3
22 24
2
3
41.7 (2C), 133.8 (2C), 128.0 (2C), 122.4 (2C), 121.1 (2C), found: 508.0125.
1
14.5 (2C), 45.9, 29.2, 20.2, 13.8; MS (EI): m/z (relative
10b: Yellow solid, m.p. 257.5°C−258.5°C; FTIR, ν
max
+
−1
intensity): 251 ([M] , 41), 208 (100), 180 (21), 166 (9), 152 (cm ): 1713, 1634, 1593, 1562, 1526, 1478, 1293, 1243,
1
(8), 140 (6); HRMS (APCI): m/z calcd for C H NO 1130, 756, 676; H NMR (400MHz, DMSO-d ): δ 12.08 (s,
17
18
6
+
[M+H] : 252.1383; found: 252.1377.
1H), 8.84 (d, J=2.0Hz, 1H), 8.25−8.20 (m, 2H), 7.81−7.76
2
7
Diphenylamine-2,4′-dicarboxylic acid (8): A mixture (m, 1H), 7.63−7.56 (m, 2H), 7.31 (t, J=7.4Hz, 1H), 4.35 (t,
of 2-bromobenzoic acid (6) (2.0g, 9.95mmol), 4-amin- J=6.4Hz, 2H), 3.63 (t, J=6.4Hz, 2H), 2.00−1.86 (m, 4H);
1
3
obenzoic acid (7) (1.37g, 9.95mmol), potassium carbonate
C NMR (100MHz, DMSO-d ): δ 176.7, 165.3, 143.7,
6
(
1.38g, 9.95mmol) and copper powder (60mg, 3% w/w) in 140.8, 134.1, 133.1, 128.6, 126.1, 122.1, 122.0, 120.9,
N,N-dimethylformamide (10mL) was refluxed for 4h. The 119.7, 117.9, 117.7, 63.9, 34.7, 29.1, 27.1; MS (EI): m/z
+
mixture was cooled and slowly added to aqueous HCl (1:1) (relative intensity): 373 ([M] , 44), 239 (96), 222 (100),
(
50mL). The precipitate was collected, washed with hot 194 (42), 166 (23), 139 (29); HRMS (ESI): m/z calcd for
+
water, and dried to provide the title compound.
C H BrNO [M+H] : 374.0386; found: 374.0389.
1
8
17
3
27
9
(10H)-Acridone-2-carboxylicacid(9): Diphenylamine-
,4′-dicarboxylic acid (8) (2.57g, 10.0mmol) in concen- butyl]carboxylate (11a): A solution of 10a (1mmol) and
trated H SO (5mL) was heated at 100°C for 4h. The piperidine (5mmol) in acetonitrile was stirred at room tem-
10-(4′-N-Piperidinobutyl)acridone-20[(N-piperidino)
2
2
4
reaction mixture was cooled and poured into ice water. The perature for 24h. The reaction mixture was then concen-
precipitate was filtered and washed with hot water. The solid trated under reduced pressure, the residue was treated with
was redissolved in 5% aqueous sodium hydroxide and fil- water and then extracted with dichloromethane. The com-
tered. The filtrate was diluted with an equal volume of etha- bined organic layer was washed with saturated aqueous
nol and acidified with acetic acid. The precipitate was filtered sodium hydrogen carbonate and water, dried over anhy-
off, washed with water, and dried to yield 9 (1.70g, 71% drous Na SO , and concentrated under reduced pressure.
2
4
from 2-bromobenzoic acid). m.p.>300°C; FTIR, ν
The residue was purified by silica gel column chromatogra-
max
−1
1
(
(
cm ): 3387, 1634, 1595, 1576, 1399, 1136; H NMR phy to yield 11a in 97% yield as a yellow solid: m.p.
−1
300MHz, DMSO-d ): δ 12.16 (s, 1H), 8.85 (s, 1H), 8.22 (t, 104.5°C−105.5°C; FTIR, ν (cm ): 1703, 1639, 1602,
6
max
1
J=8.3Hz, 2H), 7.76 (t, J=7.5Hz, 1H), 7.59 (d, J=8.5Hz, 1479, 1251, 1137, 758; H NMR (300MHz, acetone-d ): δ
6
13
2
H), 7.30 (t, J=7.5Hz, 1H); C NMR (75MHz, DMSO-d ): 9.04 (s, 1H), 8.41 (d, J=7.8Hz, 1H), 8.26 (d, J=8.7Hz,
6
δ 176.9, 167.2, 143.3, 140.9, 133.9, 133.4, 128.6, 126.1, 1H), 7.96 (d, J = 8.1Hz, 1H), 7.94 (d, J=7.2Hz, 1H), 7.80
1
24.0, 121.8, 120.9, 119.7, 117.7, 117.6; MS (EI): m/z (rela- (t, J=7.6Hz, 2H), 7.34 (t, J=7.3Hz, 1H), 4.52 (t, J=8.2Hz,
+
tive intensity): 239 ([M] , 100), 222 (32), 195 (24), 139 (28), 2H), 4.37 (t, J=6.6Hz, 2H), 2.50−2.30 (m, 12H), 2.10−1.35
1
3
97 (45), 83 (44); HRMS (ESI): m/z calcd for C H NO
(m, 20H); C NMR (75MHz, acetone-d ): δ 177.5, 166.2,
14
10
3
6
+
[M+H] : 240.0655; found: 240.0652.
145.4, 142.7, 135.1, 134.4, 130.2, 128.0, 123.6 (2C), 122.8,
1
0-(4′-N-Bromobutyl)acridone-2-(4-bromobutyl)car- 122.4, 117.0 (2C), 65.6, 59.4, 58.1, 55.3 (2C), 55.2 (2C),
boxylate (10a) and 9(10H)-Acridone-2-(4-bromobutyl) 46.8, 27.6, 27.0 (2C), 26.9 (2C), 25.4, 25.3, 24.8, 24.2,
carboxylate (10b): A solution of 9 (500mg, 2.09mmol) in 23.6; MS (EI): m/z (relative intensity): 368 (6), 284 (6), 185

1
4
Journal of Chemical Research 00(0)
(
14), 129 (47), 98 (93), 83 (91), 55 (100); HRMS (APCI): 115.1, 115.0, 57.7, 54.5 (2C), 52.1, 46.2, 25.7 (2C), 24.6,
+
+
m/z calcd for C H N O [M+H] : 518.3377; found: 24.2, 23.2; MS (EI): m/z (relative intensity): 392 ([M] , 21),
5
3
2
44
3
3
18.3379.
167 (3), 149 (9), 138 (19), 98 (100); HRMS (ESI): m/z calcd
+
9
(10H)-Acridone-2-[(N-piperidino)butyl]carboxylate for C H N O [M+H] : 393.2173; found: 393.2177.
24
29
2
3
(
11b): A solution of 10b (1mmol) and piperidine (5mmol)
N-(10-(4′-N-Piperidinobutyl)acridone-2-carbonyl)-L-
in N,N-dimethylformamide was stirred at room temperature valine benzyl ester (14): A solution of 12 (100mg,
for 24h. Water was added to the mixture and the solvent 0.26mmol), L-valine benzyl ester hydrochloride (64.5mg,
was removed under reduced pressure. The precipitate was 0.26mmol), HOBt (53.6mg, 0.40mmol), and EDCI (76mg,
collected, washed with water, and then dichloromethane to 0.40mmol) in N,N-dimethylformamide (10mL) was stirred
give 11b in 92% yield as a yellow solid: m.p. at −10°C for 10 min. The solution was then treated with
−
1
1
1
43.5°C−144.5°C; FTIR, νmax (cm ): 1711, 1627, 1594, DIPEA (0.14mL, 0.78mmol) and stirred at −10°C to room
1
575, 1525, 1475, 1275, 1241, 763; H NMR (300MHz, temperature for 24h. Water was added and the mixture was
DMSO-d ): δ 12.17 (s, 1H), 8.84 (d, J=2.1Hz, 1H), extracted with ethyl acetate. The combined organic layer
6
8
7
6
.25−8.19 (m, 2H), 7.81−7.75 (m, 1H), 7.65−7.58 (m, 2H), was washed with saturated aqueous ammonium chloride,
.33 (t, J=7.2Hz, 1H), 4.35−4.31 (m, 2H), 2.65−2.55 (m, brine, saturated aqueous sodium hydrogen carbonate, and
1
3
H), 1.80−1.42 (m, 10H); C NMR (75MHz, DMSO-d6): water. The organic layer was dried over anhydrous Na SO
2
4
δ 176.7, 165.3, 143.7, 140.8, 134.1, 133.0, 128.6, 126.1, and concentrated under reduced pressure. The residue was
22.1, 121.9, 120.9, 119.6, 117.9, 117.7, 64.4, 57.1, 53.3 purified by silica gel column chromatography to yield 14
2C), 26.1 (2C), 24.4, 23.1, 21.9; MS (EI): m/z (relative (70%) as a yellow solid: m.p. 89.0°C−90.0°C; FTIR, ν
1
(
max
+
−1
intensity): 378 ([M] , 23), 284 (2), 252 (10), 138 (24), 98 (cm ): 2934, 1739, 1637, 1608, 1482, 1466, 1264, 1181,
1
(
100); HRMS (APCI): m/z calcd for C H N O
1155, 757; H NMR (400MHz, CDCl ): δ 8.92 (d,
J=2.4Hz, 1H), 8.60 (dd, J=8.0, 1.2Hz, 1H), 8.34 (dd,
acid J=9.0, 2.0Hz, 1H), 7.81−7.70 (m, 3H), 7.40−7.32 (m, 5H),
2
3
27
2
3
3
+
[
M+H] :379.2016; found: 379.2024.
0-(4′-N-Piperidinobutyl)acridone-2-carboxylic
12): A stirred solution of 11a (248mg, 0.48mmol) in etha- 6.93 (d, J=8.4Hz, 1H), 5.26−5.18 (m, 2H), 4.86 (t,
1
(
nol (5mL) was treated with 2% aqueous NaOH (5mL) and J=5.2Hz, 1H), 4.48−4.43 (m, 2H), 2.50−2.45 (m, 4H),
refluxed for 1h. The reaction mixture was cooled and con- 2.35−2.30 (m, 1H), 2.02−1.96 (m, 2H), 1.82−1.75 (m, 2H),
centrated under reduced pressure to remove the solvent. 1.70−1.63 (m, 6H), 1.55−1.45 (m, 2H), 1.02 (t, J=7.2Hz,
1
3
Water was added to the residue and the mixture was neutral- 6H); C NMR (100MHz, CDCl ): δ 177.7, 171.9, 166.3,
3
ized with 5 M HCl. The yellow precipitate was filtered and 143.6, 141.6, 135.3, 134.3, 133.4, 128.6(2C), 128.4 (3C),
washed with water to give 12 (180mg, 99%) as a yellow 127.9, 126.3, 125.8, 122.6, 122.0, 121.2, 115.5, 115.1, 67.0,
−1
solid: m.p. 136.0°C−137.0°C; FTIR, νmax (cm ): 3369, 57.7, 57.6, 54.4 (2C), 46.1, 31.6, 25.5 (2C), 24.6, 24.0,
1
1
(
1
614, 1593, 1557, 1484, 1376, 1268, 781, 756; H NMR 23.0, 19.1, 18.0; MS (EI): m/z (relative intensity): 567
+
300MHz, DMSO-d ): δ 8.89 (s, 1H), 8.34 (d, J=7.6Hz, ([M] , 13), 415 (3), 376 (3), 207 (9), 138 (41), 98 (100);
H), 8.24 (d, J=8.6Hz, 1H), 8.00–7.80 (m, 3H), 7.40 (t, HRMS (ESI): m/z calcd for C H N O [M+H] :
J=6.0Hz, 1H), 4.55–4.45 (m, 2H), 3.20−2.90 (m, 6H), 568.3170; found: 568.3161.
6
+
3
5
42
3
4
2
.10−1.90 (m, 2H), 1.90−1.70 (m, 6H), 1.60−1.45 (m, 2H);
N-(10-(4′-N-Piperidinobutyl)acridone-2-carbonyl)-L-
1
3
C NMR (75MHz, DMSO-d ): δ 176.4, 166.7, 143.9, valine (15): To a solution of 14 (30mg, 0.05mmol) in meth-
6
1
1
2
2
41.3, 134.7, 134.0, 129.0, 126.8, 123.3, 122.2, 122.0, anol (3mL) was added 10% Pd/C (4mg, 10% w/w) and the
20.8, 116.4, 116.3, 55.5, 52.0 (2C), 45.2, 24.2, 22.4 (2C), suspension was stirred under a H atmosphere at room tem-
2
+
1.6, 20.4; MS (EI): m/z (relative intensity): 378 ([M] , 23), perature for 24h. The reaction was filtered through Celite
52 (10), 138 (24), 98 (100); HRMS (APCI): m/z calcd for and eluting with methanol. The filtrate was concentrated
+
C H N O [M+H] : 379.2016; found: 379.2015.
under reduced pressure to yield 15 (80%); FTIR, ν
2
3
1
27
2
3
max
−1
1
0-(4′-N-Piperidinobutyl)acridone-2-methylcarboxylate (cm ): 1632, 1603, 1593, 1481, 1463, 1369, 1260, 761; H
(
13): Compound 12 (74mg, 0.20mmol) in thionyl chloride NMR (300MHz, DMSO-d ): δ 8.88 (s, 1H), 8.65−8.55 (m,
6
(1mL) was refluxed for 3h. The reaction mixture was 1H), 8.33 (d, J=7.2Hz, 1H), 8.24 (d, J=8.3Hz, 1H), 7.92
cooled and added dropwise to cold methanol. The solution (d, J=8.7Hz, 2H), 7.90−7.70 (m, 1H), 7.40−7.30 (m, 1H),
was then treated with water and extracted with ethyl acetate. 4.55−4.40 (m, 2H), 4.28 (t, J=7.1Hz, 1H), 2.55−2.35 (m,
The combined organic layer was washed with saturated 6H), 2.30−2.15 (m, 1H), 1.85−1.40 (m, 10H), 1.00−0.90 (m,
13
aqueous sodium hydrogen carbonate and water, dried over 6H); C NMR (75MHz, DMSO-d ): δ 176.5, 173.4, 165.6,
6
anhydrous Na SO , and concentrated under reduced pres- 143.0, 141.4, 134.4, 132.9, 126.8, 126.7, 126.5, 121.8 (2C),
2
4
sure. The residue was purified by silica gel column chroma- 120.7, 116.2, 116.0, 58.9, 56.8, 53.6 (2C), 45.2, 29.8, 25.2
tography to yield 13 (63mg, 82%) as a yellow solid: m.p. (2C), 24.0, 23.8, 22.2, 19.5, 18.9; MS (EI): m/z (relative
−
1
+
1
1
(
7
26.5°C−127.5°C; FTIR, ν
(cm ): 1717, 1643, 1608, intensity): 477 ([M] , 1), 415 (16), 373 (61), 282 (39), 250
max
1
481, 1297, 1250, 766; H NMR (300MHz, CDCl ): δ 9.18 (28), 138 (27), 98 (100), 91 (76); HRMS (ESI): m/z calcd for
s, 1H), 8.54 (d, J=8.1Hz, 1H), 8.29 (d, J=8.7Hz, 1H), C H N O [M+H] : 478.2700; found: 478.2693.
.74 (t, J=7.2Hz, 1H), 7.64 (d, J=8.7Hz, 2H), 7.32 (t,
3
+
28
36
3
4
N-(10-(4′-N-Piperidinobutyl)acridone-2-carbonyl)-L-
J=7.2Hz, 1H), 4.41 (t, J=8.0Hz, 2H), 3.96 (s, 3H), valine benzyl amide (16): A procedure analogous to the
2
.60−2.40 (m, 6H), 2.05−1.60 (m, 8H), 1.60−1.45 (m, 2H); preparation of 14 and starting from 15 and benzyl amine
13
C NMR (75MHz, CDCl ): δ 177.7, 166.5, 144.4, 141.7, was conducted to obtain compound 16 in 60% yield as a
3
−1
134.3, 134.1, 130.5, 128.0, 122.8, 122.7, 122.1, 121.6, yellow solid: FTIR, νmax (cm ): 3284, 2931, 1633, 1607,

Khunnawutmanotham et al.
15
1
1
481, 1257, 757; H NMR (400MHz, CDCl ): δ 8.89 (d, 166 (8), 139 (7); HRMS (APCI): m/z calcd for C H N O
3
26 25
2
4
+
J=2.4Hz, 1H), 8.55 (d, J=8.0Hz, 1H), 8.23 (dd, J=9.0, [M+H] : 429.1809; found: 429.1803.
.4Hz, 1H), 7.78−7.67 (m, 3H), 7.35−7.23 (m, 5H), 7.11 N-(9(10H)-Acridone-2-carbonyl)-L-valine (20): A pro-
d, J=8.4Hz, 1H), 6.59 (br s, 1H), 4.52−4.39 (m, 5H), cedure analogous to the preparation of 15 and starting from
2
(
2
1
1
1
1
.49−2.40 (m, 6H), 2.37−2.30 (m, 1H), 2.00−1.92 (m, 2H), 19 was used to obtain compound 20 in 82% yield as a yel-
−1
.85−1.75 (m, 2H), 1.70−1.64 (m, 4H), 1.55−1.47 (m, 2H), low solid: m.p. 200.0°C (dec.); FTIR, ν (cm ): 3273,
max
1
3
1
.10−1.05 (m, 6H); C NMR (100MHz, CDCl ): δ 177.7, 1628, 1517, 1474, 1311, 1154, 757; H NMR (300MHz,
3
71.1, 166.6, 143.7, 141.7, 137.9, 134.3, 133.2, 128.7 (2C), DMSO-d ): δ 12.11 (s, 1H), 8.82 (s, 1H), 8.57 (d, J=7.5Hz,
6
28.0, 127.8 (2C), 127.5, 126.2, 126.1, 122.7, 122.0, 121.3, 1H), 8.25 (d, J=8.1Hz, 1H), 8.20 (d, J=8.7Hz, 1H), 7.76 (t,
115.6, 115.2, 59.5, 57.8, 54.6 (2C), 46.2, 43.6, 31.0, 26.0 J=7.2Hz, 1H), 7.60 (d, J=7.2Hz, 2H), 7.29 (t, J=7.2Hz,
(
2C), 24.6, 24.4, 23.3, 19.5, 18.5; MS (EI): m/z (relative 1H), 4.30 (t, J=6.6Hz, 1H), 2.30−2.20 (m, 1H), 1.05−0.90
+
13
intensity): 566 ([M] , 12), 368 (10), 207 (17), 138 (40), 98 (m, 6H); C NMR (75MHz, DMSO-d ): δ 176.9, 173.4,
(
5
6
+
100); HRMS (ESI): m/z calcd for C H N O [M+H] : 166.0, 142.6, 140.8, 133.8, 132.4, 126.7, 126.2, 126.1,
3
5
43
4
3
67.3330; found: 567.3333.
0-(4′-N-Piperidinobutyl)acridone-2-carboxylic
121.6, 120.8, 119.5, 117.6, 117.3, 58.8, 29.7, 19.4, 18.9; MS
+
1
acid (EI): m/z (relative intensity): 293 ([M–45] , 7), 279 (12),
benzylamide (17): A procedure analogous to the preparation 227 (5), 167 (30), 149 (100), 71 (26); HRMS (APCI): m/z
+
of 14 and starting from 12 and benzyl amine was used to calcd for C H N O [M+H] : 339.1339; found: 339.1345.
19
19
2
4
29
obtain compound 17 in 72% yield as a yellow solid: m.p.
9(10H)-Acridone-2-carboxylic acid benzylamide (21):
7.0°C−78.0°C; FTIR, ν (cm ): 1632, 1607, 1480, 1299, A procedure analogous to the preparation of 14 and starting
260, 756; H NMR (300MHz, CDCl ): δ 8.92 (s, 1H), 8.47 from 9 and benzyl amine was used to obtain compound 21
−1
7
1
max
1
3
(
3
d, J=7.8Hz, 1H), 8.36 (d, J=9.0Hz, 1H), 7.80−7.60 (m, in 67% yield as a yellow solid: m.p.>300°C; FTIR, ν
max
−1
1
H), 7.40−7.20 (m, 5H), 4.66 (d, J=5.7Hz, 2H), 4.38 (t, (cm ): 1622, 1579, 1549, 1523, 1308, 756, 736; H NMR
J=7.2Hz, 2H), 2.60−2.40 (m, 6H), 2.00−1.60 (m, 8H), (300MHz, DMSO-d ): δ 12.08 (s, 1H), 9.28 (br t, J=5.2Hz,
6
13
1
.55−1.45 (m, 2H); C NMR (75MHz, CDCl ): δ 177.8, 1H), 8.85 (s, 1H), 8.26 (d, J=8.0Hz, 1H), 8.23 (d, J=8.8Hz,
3
166.2, 143.4, 141.6, 138.2, 133.3, 133.6, 128.6 (2C), 127.8 1H), 7.76 (t, J=7.6Hz, 1H), 7.61 (d, J=8.0Hz, 1H), 7.59 (d,
(
1
2C), 127.4 (2C), 126.7, 125.5, 122.4, 121.9, 121.1, 115.6, J=7.5Hz, 1H), 7.40−7.20 (m, 5H), 4.52 (d, J=5.4Hz, 2H);
13
15.1, 57.7, 54.5 (2C), 46.1, 44.1, 25.8 (2C), 24.5, 24.2, 23.2;
C NMR (75MHz, DMSO-d ): δ 176.9, 165.6, 142.6,
6
+
MS (EI): m/z (relative intensity): 467 ([M] , 20), 376 (3), 140.8, 139.9, 133.8, 132.2, 128.3 (2C), 127.3 (2C), 126.7
41 (3), 207 (9), 138 (39), 98 (100); HRMS (ESI): m/z calcd (2C), 126.1, 125.8, 121.7, 120.8, 119.6, 117.6, 117.4, 42.7;
3
+
+
for C H N O [M+H] : 468.2645; found: 468.2640.
MS (EI): m/z (relative intensity): 328 ([M] , 47), 222 (100),
30
34
3
2
2
8
9
(10H)-Acridone-2-methylcarboxylate (18): A proce- 195 (64), 166 (19), 139 (19), 106 (12); HRMS (ESI): m/z
+
dure analogous to the preparation of 13 and starting from 9 calcd for C H N O [M+H] : 329.1284; found: 329.1287.
was used to obtain compound 18 in 87% yield as a yellow
solid: m.p. >300°C; FTIR, ν (cm ): 1717, 1633, 1595,
1
21
17
2
2
−
1
max
In vitro cytotoxicity
1
575, 1293, 764; H NMR (300MHz, DMSO-d ): δ 12.16
6
(
1
(
1
1
1
s, 1H), 8.82 (d, J=2.1Hz, 1H), 8.23 (dd, J=8.1, 1.5Hz, The cytotoxic activities of compounds 1, 5, 8, and 11–15
H), 8.18 (dd, J=8.7, 2.1Hz, 1H), 7.80-7.74 (m, 1H), 7.61 were evaluated against several cancer cell lines, namely,
d, J=8.4Hz, 1H), 7.58 (d, J=7.5Hz, 1H), 7.34-7.28 (m, Molt-3, HepG2, HuCCA-1, and A549. Cells in the logarith-
1
3
H), 3.89 (s, 3H); C NMR (75MHz, DMSO-d ): δ 176.7, mic growth phase were seeded in 96-well plates (Costar,
6
65.7, 143.6, 140.7, 134.0, 132.9, 128.6, 126.0, 122.0, 3599, USA) at a density of 10,000–15,000cells/well. The
21.7, 120.9, 119.6, 117.9, 117.7, 52.1; MS (EI): m/z (rela- plates were incubated at 37°C in a humidified atmosphere
+
tive intensity): 253 ([M] , 100), 222 (84), 195 (20), 167 with 95% air and 5% CO for 24h. The culture was then
2
(
29), 149 (76), 97 (37), 57 (50); HRMS (ESI): m/z calcd for treated with a medium containing either the test compound
+
C H NO [M+H] : 254.0812; found: 254.0807.
or the vehicle to the desired final concentration and incu-
1
5
12
3
N-(9(10H)-Acridone-2-carbonyl)-L-valine benzyl ester bated for another 48h. The cell monolayer was washed
19): A procedure analogous to the preparation of 14 and with phosphate-buffered saline (pH 7.2), fixed with 95%
starting from 9 was used to obtain 19 in 73% yield as a yel- ethanol, stained with crystal violet solution, and lysed with
(
−
1
low solid: m.p. 211.0°C−212.0°C; FTIR, ν (cm ): 1716, 0.1 N HCl in methanol. The absorbance of the lysate was
1
max
1
642, 1556, 1521, 1479, 1267, 751, 737; H NMR (300MHz, recorded at 540nm on an automatic microtiter plate reader
DMSO-d ): δ 11.98 (s, 1H), 8.93 (d, J=7.5Hz, 1H), 8.87 (s, (Multiskan Ascent, Labsystem). All tests were carried out
6
1
H), 8.27 (d, J=8.1Hz, 1H), 8.20 (d, J=8.7Hz, 1H), 7.77 (t, in triplicate, and the mean value was calculated. Activity is
J=7.5Hz, 1H), 7.58 (d, J=6.6Hz, 2H), 7.39−7.28 (m, 5H), expressed as IC50 (concentration of substance that inhibits
.10 (d, J=4.2Hz, 2H), 4.37 (t, J=7.5Hz, 1H), 2.29−2.22 50% of cell growth) by using doxorubicin (Sigma Aldrich)
5
(
m, 1H), 1.00 (d, J=6.0Hz, 3H), 0.95 (d, J=6.9Hz, 3H); as a standard drug.
1
3
C NMR (75MHz, DMSO-d ): δ 176.9, 171.7, 166.5,
6
1
42.7, 140.8, 136.0, 133.9, 132.6, 128.4 (2C), 128.1, 128.0
Molecular modeling
(2C), 126.5, 126.3, 126.1, 121.7, 120.8, 119.5, 117.6, 117.3,
6
5.8, 59.0, 29.5, 19.3, 19.2; MS (EI): m/z (relative inten- The chemical structures of the selected compounds were built
+
sity): 428 ([M] , 2), 293 (5), 238 (30), 222 (100), 194 (18), using the Scigress software suite 2.8.1 and optimized using

1
6
Journal of Chemical Research 00(0)
the MM2 force field. The X-ray crystal structure of DNA was
obtained from the Protein Data Bank database, code 2DES.
AutoDockTools version 1.5.6 graphic user interface was used
to prepare the crystal structure. Hydrogen atoms were added,
and crystallographic water and co-crystallized 3′-desamino-
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1
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3
′-(2-methoxy-4-morpholinyl)-doxorubicin ligand were
7
8
deleted.AutoDock Vina 1.1.2 was used as the docking engine.
The grid box was set to 40, 40, and 15Å for each of the x, y,
and z dimensions. The center search space coordinates were
set at x, y, z=–0.093, 0.946, and −8.586, respectively. The
exhaustiveness that influences the thoroughness of the search
2
1
9. Queener SF, Fujioka H, Nishiyama Y, et al. Antimicrob
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free for pose search. The number of docking runs was set to
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
0 for each ligand, and the docked conformers were ranked
−1
according to the ΔG values (kcal mol ).
2
002; 13: 445.
3. Su TL, Köhler B, Chou TC, et al. J Med Chem 1992; 35:
703.
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4.
MlogP calculation
2
The Dragon 7.0 software suite was used to calculate the
Moriguchi log P (MlogP) values to determine the lipophi-
licity of the compounds. Cheminformatics software was
used to calculate for molecular descriptors.
4
1
6. Giacomini KM, Huang SM, Tweedie DJ, et al. Nat Rev Drug
Discov 2010; 9: 215.
7. Pellón RF, Carrasco R, Mfirquez T, et al. Tetrahedron Lett
Acknowledgements
The authors acknowledge the assistance of P Intachote, S Sengsai,
and B Saimanee (Biological activity test and screening unit, the
Chulabhorn Research Institute) in the cytotoxicity testing.
1
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9
Declaration of conflicting interests
2
The author(s) declared no potential conflicts of interest with respect
to the research, authorship, and/or publication of this article.
8
Funding
2
The author(s) received no financial support for the research,
authorship, and/or publication of this article.
1
2
ORCID iD
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Agents Chemother 2007; 51: 4133.
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Supanna Techasakul
https://orcid.org/0000-0002-6540-5362
Supplemental material
Figure S1 and 1H NMR and 13C NMR spectra are provided in the
Supplementary Information.
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51.
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