Structure-activity relationships in the acronycine and benzo[b]acronycine series: Role of the pyran ring

Article abstract of DOI:10.1016/j.ejmech.2008.01.033

In order to explore the structure-activity relationships in the acronycine series, simplified analogues of cis-1,2-diacetoxy-1,2-dihydroacronycine and cis-1,2-diacetoxy-1,2-dihydrobenzo[b]acronycine (S23906-1, under clinical trials) lacking the fused pyran ring, but possessing an acetoxymethyl leaving group at position 4 were prepared. These new analogues only displayed marginal antiproliferative activity compared to the parent compounds. The presence of the angularly fused dimethylpyran ring appears as an indispensable structural requirement to observe significant cytotoxic activity in this series.

Full text of DOI:10.1016/j.ejmech.2008.01.033

Available online at www.sciencedirect.com
European Journal of Medicinal Chemistry 43 (2008) 2677e2687
http://www.elsevier.com/locate/ejmech
Original article
Structureeactivity relationships in the acronycine and
benzo[b]acronycine series: Role of the pyran ring
a
Quyen Do , Huong Doan Thi Mai , Thomas Gaslonde , Bruno Pfeiffer , Stephane Leonce ,
a
a
b
b
ˆ
´
Alain Pierre , Sylvie Michel , Franc¸ois Tillequin , Hanh Dufat
´
b
a
a,
a
*
´
a Laboratoire de Pharmacognosie de l’Universite´ Paris Descartes, U.M.R./C.N.R.S. nꢀ 8638, Faculte´ de Pharmacie,
4 Avenue de l’Observatoire, 75006 Paris, France
b Institut de Recherches Servier, Division Recherche Cance´rologie, 125 Chemin de Ronde, 78290 Croissy sur Seine, France
Received 20 July 2007; received in revised form 18 January 2008; accepted 24 January 2008
Available online 3 February 2008
Abstract
In order to explore the structureeactivity relationships in the acronycine series, simplified analogues of cis-1,2-diacetoxy-1,2-dihydroacro-
nycine and cis-1,2-diacetoxy-1,2-dihydrobenzo[b]acronycine (S23906-1, under clinical trials) lacking the fused pyran ring, but possessing an
acetoxymethyl leaving group at position 4 were prepared. These new analogues only displayed marginal antiproliferative activity compared
to the parent compounds. The presence of the angularly fused dimethylpyran ring appears as an indispensable structural requirement to observe
significant cytotoxic activity in this series.
Ó 2008 Elsevier Masson SAS. All rights reserved.
Keywords: Acridone; Benzo[b]acridone; Acronycine; Cytotoxicity
1. Introduction
and potency were obtained with derivatives modified in the py-
ran ring, which had a similar reactivity toward nucleophilic
agents as acronycine epoxide, but an improved chemical
stability. Such compounds are exemplified by diesters of
cis-1,2-dihydroxy-1,2-dihydroacronycine (i.e., diacetate 2)
[8] and cis-1,2-dihydroxy-1,2-dihydrobenzo[b]acronycine
((ꢁ)-cis-1,2-dihydroxy-6-methoxy-3,3,14-trimethyl-1,2,3,14-
tetrahydro-7H-benzo[b]pyrano[3,2-h]acridin-7-one) [9]. Rep-
resentatives of the latter series are considered as valuable
drug candidates [10]. For instance, diacetate 3, developed
under the code S23906-1, is currently under phase I clinical
trials. Their mechanism of action implies alkylation of the
2-amino group of DNA guanine residues by the carbocation
resulting from the elimination of the ester leaving group at
position 1 of the drug [11e14], inducing a marked destabiliza-
tion of the double helix, with the formation of single-stranded
DNA [15], which finally leads to cell apoptosis [16].
The pyranoacridone alkaloid acronycine (1), originally iso-
lated from Acronychia baueri Schott (Rutaceae) [1e3], has
shown antitumor properties against a large panel of murine
solid tumor models [4,5]. However, its moderate potency
and poor solubility in water severely hampered the subsequent
clinical trials, which were rapidly discontinued due to modest
therapeutic effects and dose-limiting gastrointestinal toxicity
after oral administration [6]. Consequently, the development
of structural analogues with increased potency and/or better
solubility in biocompatible solvents was highly desirable
(Chart 1).
Our efforts toward the obtainment of more potent deriva-
tives were guided by a hypothesis of bioactivation of the
1,2-double bond of acronycine into the corresponding epoxide
in vivo [7]. Significant improvements in terms of solubility
In the course of the exploration of the structureeactivity re-
lationships [17,18], the presence of a methoxy electron-donat-
ing group at C-6, which facilitates the formation and
stabilization of a carbocation at the benzylic position 1, was
* Corresponding author. Tel.: þ33 1 53 73 98 10; fax: þ33 1 40 46 96 58.
E-mail address: francois.tillequin@univ-paris5.fr (F. Tillequin).
0223-5234/$ - see front matter Ó 2008 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2008.01.033

2678
Q. Do et al. / European Journal of Medicinal Chemistry 43 (2008) 2677e2687
O
O
O
O
N
O
O
N
O
N
O
O
AcO
AcO
3
OAc
OAc
1
2
Chart 1.
shown to have a marked influence on the activity and appeared
as an important structural feature to observe potent cytotoxic
effects in both acronycine and benzo[b]acronycine series
[8,12]. The surprising activity of cis-1,2-dihydroxy-1,2-dihy-
drobenzo[b]acronycine monoesters at position 2 could be ra-
tionalized on the basis of spontaneous transesterification into
the isomeric cis-monoesters at position 1 [12,14]. In contrast,
Michael acceptors in the benzo[b]acronycine series, possess-
ing a 1,2-pyran double bond substituted at position 2 by an
acyl group, were devoid of significant cytotoxic activity,
most probably in correlation with the high delocalization of
the electrons in the large polyaromatic chromophore [19].
The purpose of this work is to determine whether the pres-
ence of the angularly fused pyran ring present in acronycine
and S23906 is important or not to observe biological activity.
We describe here the synthesis and antiproliferative activities
of simplified compounds in the acridone and benzo[b]acridone
series, lacking the fused pyran ring, but possessing an acylox-
ymethyl leaving group at position 4, hence potentially able to
undergo additions onto intracellular nucleophilic targets. Es-
ters of 4-hydroxymethyl-acridones and -benzo[b]acridones
bearing alkoxy substituents at position 3 or positions 1 and
3, which mimic the methoxy group and the pyran ring oxygen
of acronycine derivatives, respectively, have been envisaged.
dihydroacronycine diacetate (2), was envisioned from the
readily available 1,3-dimethoxy-10-methylacridone-4-carbal-
dehyde (5). Indeed, this latter compound can be conveniently
prepared through Ullmann condensation of 2-chlorobenzoic
acid and 3,5-dimethoxyaniline, followed by simultaneous
cyclization and formylation of the intermediate carboxylic
diarylamine under VilsmeiereHaack conditions, and final N-
methylation [20]. Sodium borohydride reduction of
5
smoothly afforded 4-hydromethyl-1,3-dimethoxy-10-methyla-
cridone (6) in almost quantitative yield. Acetylation of 6 with
acetic anhydride in pyridine gave 4, which was purified by col-
umn chromatography over neutral alumina, using a mixture of
cyclohexane and acetone as solvent. In contrast, all attempts to
purify 4 over silica gel column, using dichloromethaneemeth-
anol mixture as solvent, only resulted in the isolation of 1,3-
dimethoxy-4-methoxymethyl-10-methylacridone (7), giving
evidence for the high reactivity of 4 toward nucleophilic
agents under mild acidic conditions (Chart 2).
A similar approach was first considered for the synthesis of
a 1,3-dialkoxy-4-hydroxymethylbenzo[b]acridone ester ana-
logue of S23906-1 (3). Condensation of 3-bromo-2-naphthoic
acid (8) with 3,5-dimethoxyaniline (9) under Ullmann condi-
tions gave 3-(3,5-dimethoxyphenyl)-amino-2-naphthoic acid
(10). However, VilsmeiereHaack formylation of 10, by treat-
ment with phosphoryl chloride in N,N-dimethylformamide, led
to
1,3-dimethoxybenzo[b]acridone-6-carbaldehyde
(11),
2. Synthesis and biological activity of 1,3-dialkoxy-4-
hydroxymethylacridone and benzo[b]acridone esters
accompanied by smaller amounts of 1,3-dimethoxybenzo[b]a-
cridone (12), which could not be further formylated at position
4. Consequently, obtainment of a conveniently substituted
benzoacridone basic core bearing a carbaldehyde group at po-
sition 4 was envisaged through periodate oxidation of cis-1,2-
dihydroxy-1,2-dihydrobenzo[b]acronycine (13), since this
2.1. Chemistry
The access to 4-acetoxymethyl-1,3-dimethoxy-10-methyla-
cridone (4), a simplified analogue of cis-1,2-dihydroxy-1,2-
O
O
O
O
O
O
Ac2O, 4-DMAP
Pyridine
NaBH4
MeOH
N
O
N
O
N
O
CH2OAc
CH2OH
CHO
5
6
4
O
O
silica, CH2Cl2, MeOH
N
O
CH2OMe
7
Chart 2.

Q. Do et al. / European Journal of Medicinal Chemistry 43 (2008) 2677e2687
2679
method had previously given satisfactory results for pyran ring
opening in the acronycine series [21,22]. Thus, treatment of 13
with sodium periodate in acetone afforded the dialdehyde 14
in almost quantitative yield. Reduction of the carbaldehyde
groups of 14 with sodium borohydride gave the diol 15 in
68% yield. Finally, 15 was acetylated to the desired ester 16
upon treatment with excess acetic anhydride in pyridine.
Due to reactivity similar to that of 4 in the presence of silica,
purification of 16 was conducted by column chromatography
over neutral alumina, using dichloromethane as eluent
(Charts 3 and 4).
or cytoplasm before it can reach its nuclear target. This latter
assumption prompted us to synthesize and evaluate 3-alkoxy-
4-hydroxymethyl-acridone and -benzo[b]acridone esters,
lacking the methoxy electron-donating group at C-1, known
to facilitate the formation and stabilization of a carbocation
at the benzylic position [12].
3. Synthesis and biological activity of 3-alkoxy-4-
hydroxymethylacridone and benzo[b]acridone esters
3.1. Chemistry
2.2. Pharmacology
In a first attempt, access to 4-hydroxymethyl-3-methoxy-
10-methylacridone (17) was envisioned through reduction of
a carbaldehyde obtained by formylation of 3-methoxyacridone
(18) [23]. Condensation of 2-chlorobenzoic acid (19) with 3-
methoxyaniline (20) gave 2-(3-methoxyphenyl)-aminobenzoic
acid (21) [23]. Treatment of 21 under VilsmeiereHaack con-
ditions only resulted in cyclization into 3-methoxyacridone
(18) in a moderate 10% yield, without simultaneous formyla-
tion reaction, and all further attempts to formylate 18 at posi-
tion 4 remained unsuccessful. Therefore, a second approach,
whose key step was the oxidation of the methyl group of
a 4-methylacridone, was considered. The starting material,
3-methoxy-2-methylaniline (22), was prepared from commer-
cially available 2-methyl-3-nitrophenol, which was converted
to 2-methoxy-6-nitrotoluene (23) in 94% yield by treatment
with methyl iodide in N,N-dimethylformamide in the presence
of sodium hydride. Reduction of 23 by zinc wool in acetic acid
afforded 22 in 92% yield. Ullmann condensation of 22 with 2-
chlorobenzoic acid (19) gave 2-(3-methoxy-2-methylphenyl)-
aminobenzoic acid (24) [24,25] in an acceptable 52% yield.
Cyclization of 24 by trifluoroacetic anhydride in dichlorome-
thane [26,27] gave 3-methoxy-4-methylacridone (25) in 85%
yield, which was methylated to 3-methoxy-4,10-dimethylacri-
done (26) in 72% yield by the use of methyl iodide and sodium
hydride in tetrahydrofuran. Conversion of 26 into the desired
4-hydroxymethyl-3-methoxy-10-methylacridone (17) was en-
sured in a one-pot process involving benzylic bromination
by N-bromosuccinimide followed by hydrolysis of the bro-
mine atom. Under those conditions, compound 17 was isolated
Compounds 6, 4, 7, 15, and 16 were evaluated in vitro for
their cytotoxicity against two tumor cell lines, a murine leuke-
mia cell line (L1210) and a human epidermoid carcinoma cell
line (KB-3-1), in comparison with cis-1,2-diacetoxy-1,2-dihy-
droacronycine (2) and cis-1,2-diacetoxy-1,2-dihydrobenzo[-
b]acronycine (3). The results (IC50) are reported in Table 1.
2.3. Results and discussion
As expected, diacetate 16, with an acyloxymethyl leaving
group at position 4, displayed significant cytotoxic activity
against both cell lines, even if 10- to 50-fold less potent
than its pentacyclic pyran counterpart 3. Similarly, the fact
that compounds 6, 7, and 15, whose structures do not include
an ester leaving group at the benzylic position, were found
almost inactive appears to be in full agreement with the
mechanism of action previously established for cis-1,2-dihy-
droxy-1,2-dihydroacronycine and cis-1,2-dihydroxy-1,2-dihy-
drobenzo[b]acronycine esters and diesters [12e14]. In
contrast, the lack of activity of 4-acetoxymethyl-1,3-dime-
thoxy-10-methylacridin-9(10H )-one (4) is more surprising,
but can be most probably rationalized on the basis of high
chemical instability of this compound which readily reacts
with nucleophiles, as shown by its facile total conversion
into 7 in the presence of methanol in slightly acidic medium.
In this context, it seems reasonable to hypothesize that 4
should be destroyed in the culture medium, cell membrane
O
O
COOH
COOH
Br
K2CO3 Cu(OAc)2.H2O
+
H2N
Et3N i-PrOH
N
H
O
O
8
9
10
O
O
O
O
DMF POCl3
+
N
H
N
H
O
O
CHO
11
12
Chart 3.

2680
Q. Do et al. / European Journal of Medicinal Chemistry 43 (2008) 2677e2687
O
O
O
N
O
NaIO4, H2O
acetone
N
O
O
CHO
CHO
HO
OH
13
14
O
O
O
N
O
NaBH4
EtOH
Ac2O, 4-DMAP
Pyridine
CH2OH
N
O
O
CH2OAc
CH2OH
CH2OAc
15
16
Chart 4.
in 25% yield after column chromatography over silica gel, ac-
companied by 2-bromo-3-methoxy-4,10-dimethylacridone
(27) obtained in 3% yield. Finally, acetylation of 17 with
acetic anhydride in anhydrous pyridine gave 4-acetoxy-
methyl-3-methoxy-10-methylacridone (28) in 65% yield
(Charts 5 and 6).
3.2. Pharmacology
When evaluated in vitro against L1210 and KB-3-1 cell
lines under conditions similar to those previously described
for their 1-methoxy counterparts, compounds 17, 28, 33, and
29 were found almost devoid of significant cytotoxic activity,
as shown in Table 1.
A similar approach was used for the preparation of 4-ace-
toxymethyl-3-methoxy-5-methylbenzo[b]acridin-12(5H )-one
(29). Ullmann condensation of 3-methoxy-2-methylaniline
(22) with 3-bromo-2-naphthoic acid (8) gave 3-(3methoxy-2-
methylphenyl)-amino-2-naphthoic acid (30) in 40% yield.
Cyclization of 30 with trifluoroacetic anhydride in dichloro-
methane gave 3-methoxy-4-methylbenzo[b]acridin-12(5H )-
one (31) in 47% yield. Methylation of 31 upon treatment
with methyl iodide and sodium hydride in tetrahydrofuran
afforded 3-methoxy-4,5-dimethylbenzo[b]acridin-12(5H )-one
(32) in 94% yield. Benzylic bromination with N-bromosucci-
nimide followed by hydrolysis gave 4-hydroxymethyl-3-
methoxy-5-methylbenzo[b]acridin-12(5H )-one (33) in 13%
overall yield. Acetylation of 33 afforded the desired acetate
29 in 65% yield (Chart 7).
4. Conclusion
In conclusion, the simplified compounds lacking the fused
pyran ring, prepared on the models of cis-1,2-dihydroxy-
1,2-dihydroacronycine and cis-1,2-dihydroxy-1,2-dihydroben-
zo[b]acronycine esters and diesters only displayed marginal
antiproliferative activity compared to the parent compounds
2 and 3. In terms of structureeactivity relationships, the pres-
ence of the angularly fused dimethylpyran ring appears as an
indispensable structural requirement to observe significant
cytotoxic activity. This 2,2-dimethylpyran motif fused onto
an aromatic or heteroaromatic basic core is frequently encoun-
tered in natural products, in which it arises from the conden-
sation of a phenol with an active isoprene unit. It appears as
a ‘‘privileged structure’’ present in numerous bioactive com-
pounds [28,29], including several cytotoxic, antitumor, or
antineoplastic agents exemplified by the isoflavonoids amor-
phispironone and tephrosin [30], the quinolone 4,8,8-
trimethyl-1,8-dihydro-2H-pyrano[2,3-h]quinolin-2-one [31],
the phloroglucinol derived calanone [32], and the quinone b-
lapachone [33].
Table 1
Cytotoxic Activity of Compounds 6, 4, 7, 15, 16, 17, 28, 33, and 29 in com-
parison with cis-1,2-diacetoxy-1,2-dihydroacronycine (2) and cis-1,2-diace-
toxy-1,2-dihydrobenzo[b]acronycine (S23906-1) (3)
Compound
Cytotoxicity IC50 (mM)
L1210
KB-3-1
6
23.9
39.9
51.7
1.3
34.1
17.7
36.2
26.2
4.9
4
5. Experimental section
7
15
16
17
28
33
29
2
3
5.1. Chemistry
13.9
24
n.d.
n.d.
22.5
7.9
Melting points were determined on a hot stage Reichert mi-
croscope and are not corrected. IR spectra (nmax in cmꢂ1) were
obtained from potassium bromide pellets or sodium chloride
films on a Nicolet 510 FT-IR instrument. UV spectra (lmax
in nm) were recorded in spectroscopic grade MeOH on
34.6
18.5
3.4
n.d.
0.095
3
0.79
n.d., Not determined.

Q. Do et al. / European Journal of Medicinal Chemistry 43 (2008) 2677e2687
2681
COOH
COOH
K2CO3 Cu(OAc)2.H2O
+
Et3N i-PrOH
Cl
H2N
O
O
N
H
19
20
21
O
DMF POCl3
N
H
O
18
Chart 5.
1
a Beckman DU 640 spectrophotometer. H NMR (d [ppm], J
[Hz]) were recorded at 400 MHz, using a Bruker Avance
400 spectrometer. 13C NMR spectra were recorded at
75 MHz or 100 MHz, using Bruker AC-300 or Avance 400
spectrometers. When necessary, the signals were unambigu-
ously assigned by 2D NMR techniques: 1He1H COSY,
1He1H NOESY, 13Ce1H HMQC, and 13Ce1H HMBC. These
experiments were performed using standard Bruker micropro-
grams. Mass spectra were recorded with ZQ 2000 Waters and
Q-Tof1 Micromass spectrometers using electrospray ioniza-
tion (ES-MS; Vc ¼ 30 V), or with a Nermag R-10-10C spec-
trometer using desorption-chemical ionization (DCI-MS;
reagent gas: NH3). Flash column chromatographies were per-
formed using silica gel SDS (Chromatogel 60, 35e70 mm)
with an overpressure of 300 mbar.
addition of water (15 mL), the mixture was extracted with
CH2Cl2 (5 ꢃ 50 mL). The combined organic phase was dried
over anhydrous Na2SO4, filtered, and evaporated under re-
duced pressure. Silica gel column chromatography (solvent:
CH2Cl2, then CH2Cl2/MeOH, 99.5:0.5 to 95:5) gave 6
(122 mg, 93%) as a pale yellow amorphous solid. UV l nm
(MeOH) (log 3) 215 (3.88), 251 (4.12), 274 (4.83), 297
(4.44), 387 (4.26); IR (KBr) n, cmꢂ1 3370, 3047, 2934,
1649, 1620, 1594, 1578, 1555, 1507, 1459, 1391, 1320,
1239, 1207, 1133, 1097, 1055, 1029, 942, 805, 754; 1H
NMR (400 MHz, CDCl3) d 8.36 (1H, dd, J ¼ 8, 1.5 Hz, H8),
7.65 (1H, td, J ¼ 8, 1,5 Hz, H6), 7.38 (1H, dd, J ¼ 8, 1,5 Hz,
H5), 7.23 (1H, td, J ¼ 8, 1,5 Hz, H7), 6.36 (1H, s, H2), 4.76
(2H, s, CH2eOH), 4.04 (3H, s, C1eOCH3), 4.02 (6H, s,
C3eOCH3 et NCH3); 13C NMR (75 MHz, CDCl3) d 177,2
(C9), 164.0 (C3), 162.9 (C1), 149.6 (C4a), 145.0 (C10a), 132.8
(C6), 127.0 (C8), 125.0 (C8a), 121.6 (C7), 116.1 (C5), 111.0
(C9a), 108.2 (C4), 89.2 (C2), 58.4 (C4eCH2OH), 56.4 (C1e
OCH3), 56.0 (C3eOCH3), 44.8 (NCH3); ES-MS m/z 300
[MH]þ, 322 [MNa]þ. Anal. Calcd. for C17H17NO4: C 68.21;
H 5.72; N 4.68%. Found: C 68.14; H 5.78; N 4.72%.
5.1.1. 4-Hydroxymethyl-1,3-dimethoxy-10-
methylacridin-9(10H )-one (6)
Sodium borohydride (80 mg, 2.2 mmol) was added at 0 ꢀC
to a solution of 5 (130 mg, 0.44 mmol) in MeOH (5 mL) and
the reaction mixture was stirred at 25 ꢀC for 30 min. After
CH3I NaH
DMF
AcOH
Zn
OH
O2N
O
O
H2N
O2N
23
22
COOH
Cl
O
19
COOH
(CF3CO)2O
CH2Cl2
N
H
N
H
O
K2CO3 Cu(OAc)2.H2O
O
Et3Ni -PrOH
24
25
O
N
Br
O
O
27
CH3I NaH
1) NBS hv CCl4
2) H2O
+
THF
N
O
O
O
Ac2O 4-DMAP
Pyridine
26
17
N
O
N
O
CH2OAc
CH2OH
28
Chart 6.

2682
Q. Do et al. / European Journal of Medicinal Chemistry 43 (2008) 2677e2687
COOH
COOH
Br
K2CO3 Cu(OAc)2.H2O
+
H2N
O
O
Et3N i-PrOH
N
H
8
30
22
O
O
N
(CF3CO)2O
CH2Cl2
CH3I NaH
THF
N
H
O
O
31
32
O
N
O
N
1) NBS hν CCl4
Ac2O 4-DMAP
Pyridine
2) H2O
O
O
CH2OH
CH2OAc
33
29
Chart 7.
5.1.2. 4-Acetoxymethyl-1,3-dimethoxy-10-
methylacridin-9(10H )-one (4)
(log 3) 215 (3.47), 251 (3.76), 273 (4.49), 296 (4.07), 385
(3.89); IR (KBr) n, cmꢂ1 3014, 2922, 1632, 1596, 1579,
1498, 1460, 1392, 1312, 1214, 1137, 1128, 1092, 1051, 941,
762; 1H NMR (400 MHz, CDCl3) d 8.34 (1H, dd, J ¼ 8,
1.5 Hz, H8), 7.60 (1H, td, J ¼ 8, 1.5 Hz, H6), 7.38 (1H, dd,
J ¼ 8, 1.5 Hz, H5), 7.22 (1H, td, J ¼ 8, 1.5 Hz, H7), 6.36
(1H, s, H2), 4.46 (2H, s, CH2OCH3), 4.03 (3H, s, C1e
OCH3), 4.01 (3H, s, NCH3), 4.00 (3H, s, C3eOCH3), 3.53
(3H, s, CH2OCH3); 13C NMR (75 MHz, CDCl3) d 177.0
(C9), 164.6 (C3), 163.0 (C1), 150.6 (C4a), 145.2 (C10a), 132.8
(C6), 127.1 (C8), 125.2 (C8a), 121.6 (C7), 116.2 (C5), 110.9
(C9a), 105.7 (C4), 89.4 (C2), 67.2 (CH2OCH3), 58.8
(CH2OCH3), 56.4 (C1eOCH3), 56.2 (C3eOCH3), 43.6
(NCH3); ES-MS m/z 314 [MH]þ, 336 [MNa]þ. Anal. Calcd.
for C18H19NO4: C 68.99; H 6.11; N 4.47%. Found: C 69.06;
H 6.08; N 4.41%.
Acetic anhydride (92 mL, 0.1 mmol) was added to an ice-
cooled solution of 6 (30 mg, 0.1 mmol) and 4-dimethylamino-
pyridine (2 mg) in dry pyridine (1.5 mL). After stirring at
25 ꢀC for 3 h, the reaction mixture was poured on cold water
(10 mL). The precipitate was filtered, washed with water
(2 ꢃ 5 mL), and dried in vacuum over P2O5. Column chroma-
tography over neutral alumina (solvent: cyclohexane, then cy-
clohexane/Me2CO, 99:1 to 95:5) gave 4 (21 mg, 61%) as
a whitish amorphous solid. UV l nm (MeOH) (log 3) 215
(3.79), 251 (4.11), 274 (4.82), 297 (4.42), 386 (4.00); IR
(KBr) n, cmꢂ1 2997, 2925, 2845, 1727, 1638, 1630, 1602,
1587, 1578, 1496, 1468, 1440, 1392, 1313, 1237, 1210,
1143, 1091, 1058, 1013, 958, 767; 1H NMR (400 MHz,
CDCl3) d 8.34 (1H, dd, J ¼ 8, 1.5 Hz, H8), 7.62 (1H, td,
J ¼ 8, 1.5 Hz, H6), 7.32 (1H, dd, J ¼ 8, 1.5 Hz, H5), 7.22
(1H, td, J ¼ 8, 1.5 Hz, H7), 6.38 (1H, s, H2), 5.22 (2H, s,
CH2OAc), 4.05 (3H, s, OCH3), 3.99 (3H, s, NCH3), 3.86
(3H, s, OCH3), 2.17 (3H, s, OCOCH3); 13C NMR (75 MHz,
CDCl3) d 177.7 (C9), 171.3 (OCOCH3), 164.8 (C3), 163.6
(C1), 150.8 (C4a), 145.2 (C10a), 132.8 (C6), 127.0 (C8), 125.3
(C8a), 121.8 (C7), 116.2 (C5), 111.0 (C9a), 102.9 (C4), 89.4
(C2), 60.2 (CH2OAc), 56.4 (C1eOCH3), 56.1 (C3eOCH3),
44.3 (NCH3), 21.2 (OCOCH3); ES-MS m/z 364 [MNa]þ.
Anal. Calcd. for C19H19NO5: C 66.85; H 5.61; N 4.10%.
Found: C 68.84; H 5.66; N 4.07%.
5.1.4. 3-(3,5-Dimethoxyphenyl)-amino-2-
naphthoic acid (10)
A mixture of 8 (3.2 g, 13.1 mmol), 9 (2.0 g, 13.1 mmol),
potassium acetate (2.65 g), cupric acetate monohydrate
(0.08 g), and triethylamine (1.5 mL) in 2-propanol (50 mL)
was heated under reflux for 48 h. The reaction mixture was
evaporated under reduced pressure and the residue was parti-
tioned between CH2Cl2 and 1 N aqueous HCl. The aqueous
phase was extracted with CH2Cl2 (4 ꢃ 50 mL). The combined
organic phase was dried over anhydrous Na2SO4, filtered, and
evaporated under reduced pressure. Flash chromatography
(solvent: CH2Cl2, then CH2Cl2/MeOH, 99:1 to 90:10) gave
5.1.3. 1,3-Dimethoxy-4-methoxymethyl-10-
methylacridin-9(10H )-one (7)
1
10 (2.5 g, 58%) as a pale yellow amorphous solid. H NMR
Preparation of 7 followed the procedure described for the
preparation of 4 from 6, but the final column chromatography
was conducted over silica gel (solvent: CH2Cl2, then CH2Cl2/
MeOH, 99.8:0.2 to 98:2). Compound 7 (18 mg, 56%) was ob-
tained as a pale yellow amorphous solid. UV l nm (MeOH)
(400 MHz, CDCl3) d 8.99 (1H, br s, NH), 8.73 (1H, s, H1),
7.79 (1H, d, J ¼ 8 Hz, H8), 7.67 (1H, s, H4), 7.58 (1H, d, J ¼
8 Hz, H5), 7.47 (1H, t, J ¼ 8 Hz, H6), 7.28 (1H, t, J ¼ 8 Hz,
0
0
H7), 6.55 (2H, d, J ¼ 2.5 Hz, H2 , H6 ), 6.27 (1H, t,
J ¼ 2.5 Hz, H4 ), 3.84 (6H, s, 2 ꢃ OCH3); 13C NMR
0

Q. Do et al. / European Journal of Medicinal Chemistry 43 (2008) 2677e2687
2683
(75 MHz, CDCl3) d 172.8 (COOH), 143.2 (C3), 142.9 (2C,
2845, 1730, 1644, 1621, 1596, 1555, 1486, 1460, 1387, 1321,
1291, 1235, 1251, 1139, 1117, 1088, 1043, 1007, 877, 815;
1H NMR (400 MHz, CDCl3) d 10.43 (1H, s, C4eCHO), 9.86
(1H, s, C3eOeC(CH3)2CHO), 8.92 (1H, s, H11), 8.03 (1H, d,
J ¼ 8 Hz, H10), 7.91 (1H, d, J ¼ 8 Hz, H7), 7.81 (1H, s, H6),
7.57 (1H, t, J ¼ 8 Hz, H8), 7.45 (1H, t, J ¼ 8 Hz, H9), 5.97
(1H, s, H2), 3.98 (3H, s, OCH3), 3.73 (3H, s, NCH3), 1.66
(6H, s, C(CH3)2); 13C NMR (75 MHz, CDCl3) d 201.1 (C3e
OeC(CH3)2CHO), 185.7 (C4eCHO), 177.3 (C12), 167.6 (C3),
165.6 (C1), 149.8 (C4a), 140.4 (C5a), 135.9 (C6a), 129.6 (C10),
129.2 (C10a), 128.6 (C8), 128.2 (C11), 127.2 (C7), 125.2 (C9),
124.9 (C11a), 113.7 (C6), 109.5 (C12a), 91.8 (C2), 85.3 (C4),
77.1 (C(CH3)2), 55.7 (OCH3), 45.3 (NCH3), 21.9 (C(CH3)2);
DCI-MS m/z 404 [MH]þ. Anal. Calcd. for C24H21NO5: C
71.45; H 5.25; N 3.47%. Found: C 71.51; H 5.29; N 3.43%.
0
C3 , C5 ), 137.6 (C4a), 135.3 (2C, C1, C4a), 129.5 (C8), 129.3
0
0
(C6), 126.4 (C1 ), 126.0 (C5), 124.2 (C8a), 123.5 (C7), 109.8
0
0
0
(C4), 99.9 (2C, C2 , C6 ), 95.6 (C4 ), 55.4 (2C, 2 ꢃ OCH3);
ES-MS m/z 324 [MH]þ, 346 [MNa]þ. Anal. Calcd. for
C19H17NO4: C 70.58; H 5.30; N 4.33%. Found: C 70.54; H
5.28; N 4.32%.
5.1.5. 1,3-Dimethoxybenzo[b]acridin-12(5H )-one-
6-carbaldehyde (11) and 1,3-
dimethoxybenzo[b]acridin-12(5H )-one (12)
The diarylamine 10 (650 mg, 20 mmol) was slowly added
(40 min at 25 ꢀC) to a well-stirred mixture of dry DMF
(2 mL) and POCl3 (1 mL), and stirring was continued for
2 h. The dark viscous liquid was diluted with water (10 mL),
and 2 M NaOH aqueous solution (20 mL) was added. The so-
lution was boiled for 0.5 h and filtered. The precipitate was
washed with water (2 ꢃ 10 mL), and dried in vacuum over
P2O5. Silica gel column chromatography (solvent: CH2Cl2,
then CH2Cl2/MeOH, 99:1 to 95:5) successively gave 11
(393 mg, 59%) and 12 (85 mg, 14%) as yellow amorphous
solids.
5.1.7. 4-Hydroxymethyl-5-methyl-3-(1,1-dimethyl-
2-hydroxyethoxy)-1-methoxybenzo[b]acridin-
12(5H )-one (15)
Sodium borohydride (43 mg, 1.14 mmol) was added to a so-
lution of 14 (80 mg, 0.19 mmol) in EtOH (5 mL) and the reac-
tion mixture was stirred at 25 ꢀC for 24 h. After addition of
water (20 mL), the mixture was extracted with CH2Cl2
(5 ꢃ 50 mL). The combined organic phase was dried over an-
hydrous MgSO4, filtered, and evaporated under reduced pres-
sure. Silica gel column chromatography (solvent: CH2Cl2,
then CH2Cl2/EtOH, 99:1 to 70:30) gave 15 (55 mg, 68%) as
a pale yellow amorphous solid. UV l nm (MeOH) (log 3)
251 (3.95), 280 (4.82), 289 (4.77), 342 (4.13), 440 (3.74);
IR (KBr) n, cmꢂ1 3342, 2962, 2848, 2356, 1638, 1611,
1581, 1463, 1436, 1358, 1327, 1243, 1201, 1131, 1089,
5.1.5.1. 1,3-Dimethoxybenzo[b]acridin-12(5H )-one-6-carbal-
dehyde (11). 1H NMR (400 MHz, CDCl3) d 9.87 (1H, s,
CHO), 9.20 (1H, s, H11), 8.77 (1H, d, J ¼ 8 Hz, H7), 8.10
(1H, d, J ¼ 8 Hz, H10), 7.90 (1H, t, J ¼ 8 Hz, H8), 7.74 (1H,
t, J ¼ 8 Hz, H9), 7.07 (1H, d, J ¼ 1.5 Hz, H4), 6.61 (1H, d,
J ¼ 1.5 Hz, H2), 4.12 (3H, s, OCH3), 4.05 (3H, s, OCH3);
ES-MS m/z 334 [MH]þ. Anal. Calcd. for C20H15NO4: C
72.06; H 4.54; N 4.20%. Found: C 72.14; H 4.58; N 4.12%.
1
1023, 920, 869, 803; H NMR (400 MHz, DMSO-d6) d 8.64
5.1.5.2. . 1,3-Dimethoxybenzo[b]acridin-12(5H )-one (12)
1H NMR (400 MHz, CDCl3) d 8.89 (1H, s, H11), 7.94 (1H,
d, J ¼ 8 Hz, H10), 7.70 (1H, d, J ¼ 8 Hz, H7), 7.45 (1H, s, H6),
7.43 (1H, t, J ¼ 8 Hz, H8), 7.30 (1H, t, J ¼ 8 Hz, H9), 6.15
(1H, d, J ¼ 1.5 Hz, H4), 6.02 (1H, d, J ¼ 1.5 Hz, H2), 3.93
(3H, s, OCH3), 3.81 (3H, s, OCH3); ES-MS m/z 306 [MH]þ,
328 [MNa]þ. Anal. Calcd. for C19H15NO3: C 74.74; H 4.95;
N 4.59%. Found: C 74.83; H 5.01; N 4.52%.
(1H, s, H11), 8.08 (1H, d, J ¼ 8 Hz, H10), 7.98 (1H, d,
J ¼ 8 Hz, H7), 7.93 (1H, s, H6), 7.58 (1H, t, J ¼ 8 Hz, H8),
7.42 (1H, t, J ¼ 8 Hz, H9), 6.51 (1H, s, H2), 5.00 (1H, t,
J ¼ 5 Hz, D2O exch., C4eCH2eOH ), 4.86 (1H, s, D2O
exch., C(CH3)2eCH2OH ), 4.67 (2H, d, J ¼ 5 Hz, C4eCH2e
OH), 4.06 (3H, s, OCH3), 3.96 (2H, s, C(CH3)2eCH2eOH),
3.92 (3H, s, NCH3), 1.28 (6H, s, C(CH3)2); 13C NMR
(75 MHz, DMSO-d6) d 177.7 (C12), 165.1 (C3), 163.1 (C1),
150.6 (C4a), 143.0 (C5a), 136.5 (C6a), 130.2 (C10), 129.1
(C8), 128.7 (C10a), 127.9 (C11), 127.4 (C7), 125.9 (C11a),
125.4 (C9), 113.5 (C6), 110.2 (C12a), 92.1 (C2), 78.1 (2C,
C4, C(CH3)2), 70.0 (C(CH3)2CH2eOH), 57.1 (C4eCH2OH),
56.9 (OCH3), 45.4 (NCH3), 27,6 (C(CH3)2); ES-MS m/z 407
[M]þ. Anal. Calcd. for C24H25NO5: C 70.74; H 6.18; N
3.44%. Found: C 70.81; H 6.21; N 3.42%.
5.1.6. 1-Methoxy-5-methyl-3-(2-oxo-1,
1-dimethylethoxy)benzo[b]acridin-12-oxo-5,
12-dihyro-4-carbaldehyde (14)
A solution of sodium periodate (526 mg, 3.14 mmol) in wa-
ter (40 mL) was added dropwise to a solution of (ꢁ)-cis-1,2-di-
hydroxy-6-methoxy-3,3,14-trimethyl-1,2,3,14-tetrahydro-7H-
benzo[b]pyrano[3,2-h]acridin-7-one (13) (500 mg, 1.23 mmol)
in acetone (40 mL). The reaction mixture was stirred at 25 ꢀC
for 4 days, filtered, and evaporated under reduced pressure. Af-
ter addition of water (100 mL), the residue was extracted with
EtOAc (4 ꢃ 100 mL). The combined organic phase was dried
over anhydrous MgSO4, filtered, and evaporated. Silica gel col-
umn chromatography (solvent: CH2Cl2, then CH2Cl2/Me2CO,
99:1 to 80:20) gave 14 (470 mg, 94%) as a pale yellow amor-
phous solid. UV l nm (MeOH) (log 3) 251 (4.44), 275 (4.73),
313 (4.82), 430 (4.01); IR (KBr) n, cmꢂ1 3055, 2975, 2912,
5.1.8. 2-(4-acetoxymethyl-5-methyl-1-methoxy-12-oxo-5,12-
dihydrobenzo[b]acridin-3-oxy)-2-methylpropyl acetate (16)
An ice-cooled mixture of acetic anhydride (0.2 mL,
2.2 mmol) and dry pyridine (1.5 mL) was added to 15 (30 mg,
0.074 mmol) and 4-dimethylaminopyridine (2 mg). After
stirring at room temperature for 24 h, the mixture was poured
on cold water (20 mL). The precipitate was filtered, washed
with water (2 ꢃ 5 mL), and dried in vacuum over P2O5. Column
chromatography over neutral alumina (solvent: CH2Cl2, then

2684
Q. Do et al. / European Journal of Medicinal Chemistry 43 (2008) 2677e2687
CH2Cl2/Me2CO, 99:1 to 98:2) gave 16 (30 mg, 84%) as a yellow
amorphous solid. UV l nm (MeOH) (log 3) 251 (4.37), 280
(4.91), 289 (4.91), 339 (4.25), 435 (3.81); IR (KBr) n, cmꢂ1
3054, 2913, 2846, 1738, 1649, 1620, 1584, 1495, 1463, 1440,
1402, 1325, 1327, 1248, 1204, 1146, 1088, 1066, 1018, 957;
1H NMR (400 MHz, CDCl3) d 8.91 (1H, s, H11), 8.01 (1H, d,
J ¼ 8 Hz, H10), 7.85 (1H, d, J ¼ 8 Hz, H7), 7.63 (1H, s, H6),
7.54 (1H, t, J ¼ 8 Hz, H8), 7.41 (1H, t, J ¼ 8 Hz, H9), 6.30
(1H, s, H2), 5.25 (2H, s, C4eCH2eOAc), 4.30 (2H, s,
C(CH3)2eCH2OAc), 4.06 (3H, s, OCH3), 3.95 (3H, s, NCH3),
2.18 (3H, s, C4eCH2OCOCH3), 2.04 (3H, s, OC(CH3)2e
CH2OCOCH3), 1.60 (6H, s, C(CH3)2); 13C NMR (75 MHz,
CDCl3) d 178.7 (C12), 171.3 (C(CH3)2CH2OCOCH3), 170.7
(C4eCH2eOCOCH3), 164.3 (C3), 163.9 (C1), 151.6 (C4a),
142.4 (C5a), 136.0 (C6a), 129.7 (C10), 128.7 (C10a), 128.4 (C8),
128.1 (C11), 126.9 (C7), 125.5 (C11a), 124.6 (C9), 112.3 (C6),
110.4 (C12a), 103.0 (C4), 89.8 (C2), 80.2 (C3eOeC(CH3)2),
73.1 (C(CH3)2CH2eOCOCH3), 57.1 (C4eCH2OCOCH3),
56.5 (OCH3), 4.,9 (NCH3), 23.8 (C(CH3)2), 22.4
(C(CH3)2CH2eOCOCH3), 21.2 (C4eCH2OCOCH3); ES-MS
m/z 492 [MH]þ, 514 [MNa]þ, 530 [MK]þ. Anal. Calcd. for
C28H29NO7: C 68.42; H 5.95; N 2.85%. Found: C 68.37; H
5.98; N 2.89%.
aqueous NaHCO3 (100 mL). The aqueous phase was extracted
with CH2Cl2 (3 ꢃ 50 mL). The combined organic phase was
shaken for 15 min with 1 N NaOH (50 mL), dried over anhy-
drous MgSO4, filtered, and evaporated under reduced pressure.
Flash chromatography (solvent: CH2Cl2, then CH2Cl2/MeOH,
99:1) gave 25 (0.75 g, 85%) as a pale yellow amorphous solid.
IR (KBr) n, cmꢂ1 2921, 2849, 1722, 1597, 1463, 1262, 1159;
1H NMR (400 MHz, CDCl3) d 8.45 (1H, br s, NH), 8.39 (1H,
dd, J ¼ 8, 1.5 Hz, H8), 8,34 (1H, d, J ¼ 9 Hz, H1), 7.61 (1H, td,
J ¼ 8, 1.5 Hz, H6), 7.40 (1H, dd, J ¼ 8, 1.5 Hz, H5), 7,23 (1H,
td, J ¼ 8, 1.5 Hz, H7), 6.93 (1H, d, J ¼ 9 Hz, H2), 3.96 (3H, s,
OCH3), 2.36 (3H, s, AreCH3); 13C NMR (75 MHz, CDCl3)
d 178.6 (C9), 160.8 (C3), 147.0 (2C, C4a, C10a), 133.3 (C6),
126.8 (C8), 126.5 (C1), 122.3 (C8a), 121.5 (C7), 120.7 (C9a),
116.6 (C5), 115.9 (C4), 106.5 (C2), 56.0 (OCH3), 8,4 (Are
CH3); ES-MS m/z 240 [MH]þ; 262 [MNa]þ; 278 [MK]þ.
Anal. Calcd. for C15H13NO2: C 75.30; H 5.48; N 5.85%.
Found: C 75.36; H 5.48; N 5.83%.
5.1.11. 3-Methoxy-4,10-dimethylacridin-9(10H )-one (26)
Sodium hydride (0.3 g of 50% oil dispersion, 12 mmol) was
added to a solution of 25 (0.73 g, 3 mmol) in dry THF
(20 mL). Methyl iodide (0.78 mL, 12.5 mmol) was added
dropwise. The reaction mixture was stirred for 24 h at room
temperature, diluted with water (20 mL), and extracted with
CH2Cl2 (3 ꢃ 50 mL). The combined organic layer was dried
over MgSO4, filtered, and evaporated under reduced pressure.
Flash chromatography (solvent: CH2Cl2/hexane 9:1) afforded
26 (0.56 g, 72%) as a yellow amorphous solid. IR (KBr) n,
cmꢂ1 2921, 1632, 1592, 1557, 1462, 1445, 1408, 1283,
1263, 1237, 1101, 769, 687; 1H NMR (400 MHz, CDCl3)
d 8.41 (1H, dd, J ¼ 8, 1.5 Hz, H8), 8.37 (1H, d, J ¼ 9 Hz,
H1), 7.68 (1H, td, J ¼ 8, 1.5 Hz, H6), 7.44 (1H, dd, J ¼ 8,
1.5 Hz, H5), 7.25 (1H, td, J ¼ 8, 1.5 Hz, H7), 6.95 (1H, d,
J ¼ 9 Hz, H2), 3.98 (3H, s, OCH3), 3.85 (3H, s, NCH3), 2.44
(3H, s, AreCH3); 13C NMR (75 MHz, CDCl3) d 178.6 (C9),
162.8 (C3), 147.6 (C4a), 147.1 (C10a), 133.4 (C6), 127.1 (C8),
126.7 (C1), 123.2 (C8a), 121.4 (C7), 119.8 (C9a), 116.7 (C5),
113.0 (C4), 106.4 (C2), 56.1 (OCH3), 43.7 (NCH3), 15.5
(AreCH3); ES-MS m/z 254 [MH]þ; 276 [MNa]þ; 292
[MK]þ. Anal. Calcd. for C16H15NO2: C 75.87; H 5.97; N
5.53%. Found: C 75.91; H 5.98; N 5.51%.
5.1.9. 2-(3-Methoxy-2-methylphenyl)-
aminobenzoic acid (24)
A solution of 19 (1.33 g, 8.5 mmol), 22 (1.11 g, 8.1 mmol),
potassium acetate (1.74 g), and cupric acetate monohydrate
(0.05 g), and triethylamine (1 mL) in anhydrous 2-propanol
(50 mL) was heated under reflux for 48 h. The reaction mix-
ture was evaporated under reduced pressure and the residue
was partitionned between CH2Cl2 (100 mL) and 1 N aqueous
HCl (100 mL). The aqueous phase was extracted with CH2Cl2
(3 ꢃ 50 mL). The combined organic phase was dried over an-
hydrous MgSO4, filtered, and evaporated under reduced pres-
sure. Flash chromatography (solvent: CH2Cl2, then CH2Cl2/
MeOH, 99:1 to 95:15) gave 24 (1.1 g, 52%) as whitish nee-
dles: m.p. 197e199 ꢀC (recrystallized from CH2Cl2). IR
(KBr) n, cmꢂ1 2919, 1658, 1594, 1575, 1500, 1441, 1272,
1164, 776, 749, 730; 1H NMR (400 MHz, CDCl3) d 9.15
(1H, s, NH), 8.02 (1H, d, J ¼ 8 Hz, H6), 7.30 (1H, t,
0
J ¼ 8 Hz, H4), 7.19 (1H, t, J ¼ 8 Hz, H5 ), 6.96 (1H, d, J ¼
0
8 Hz, H4 ), 6.81 (1H, d, J ¼ 8 Hz, H3), 6.75 (1H, d,
0
J ¼ 8 Hz, H2 ), 6.71 (1H, t, J ¼ 8 Hz, H5), 3.89 (3H, s,
5.1.12. 4-Hydroxymethyl-3-methoxy-10-
methylacridin-9(10H )-one (17) and 2-bromo-3-
OCH3), 2.15 (3H, s, AreCH3); 13C NMR (75 MHz, CDCl3)
0
0
d 172.2 (COOH), 158.8 (C3 ), 150.0 (C2), 139.6 (C1 ), 135.3
methoxy-4,10-dimethylacridin-9(10H )-one (27)
0
(C4), 132.5 (C6), 126.6 (C5 ), 122.6 (C2 ), 117.9 (C4 ), 116.5
0
0
N-Bromosuccinimide (197 mg, 1.11 mmol) was added to
a solution of 26 (281 mg, 1.11 mmol) in CCl4 (15 mL) the re-
action mixture was irradiated (1000 W) for 15 min. After cool-
ing, water (5 mL) was added and the resulting mixture was
evaporated under reduced pressure. Column chromatography
over silica gel (solvent: C6H6/EtOAc 7:3) gave 17 (75 mg,
25%) and 27 (10 mg, 3%) as bright yellow amorphous solids.
0
(C5), 114.1 (C3), 109.5 (C1), 107.3 (C6 ), 55.8 (OCH3), 10,6
(AreCH3).; ES-MS m/z 258 [MH]þ, 280 [MNa]þ, 296
[MK]þ. Anal. Calcd. for C15H15NO3: C 70.02; H 5.88; N
5.44%. Found: C 69.97; H 5.85; N 5.47%.
5.1.10. 3-Methoxy-4-methylacridin-9(10H )-one (25)
Trifluoroacetic anhydride (5.2 mL) was added to a solution
of 24 (0.95 g, 3.7 mmol) in CH2Cl2 (50 mL). The mixture was
stirred at room temperature for 48 h, evaporated under reduced
pressure, and taken up by CH2Cl2 (75 mL) and saturated
5.1.12.1. 4-Hydroxymethyl-3-methoxy-10-methylacridin-
9(10H )-one (17). IR (KBr) n, cmꢂ1 2191, 2846, 2356, 1593,
1
1460, 1402, 1272, 1236, 1084, 817, 752; H NMR (400 MHz,

Q. Do et al. / European Journal of Medicinal Chemistry 43 (2008) 2677e2687
2685
CDCl3) d 8.49 (1H, d, J ¼ 9 Hz, H1), 8.43 (1H, dd, J ¼ 8,
1.5 Hz, H8), 7.72 (1H, td, J ¼ 8, 1.5 Hz, H6), 7.48 (1H, dd,
J ¼ 8, 1.5 Hz, H5), 7.29 (1H, td, J ¼ 8, 1.5 Hz, H7), 6.95 (1H,
d, J ¼ 9 Hz, H2), 4,57 (2H, s, CH2OH), 4.13 (3H, s, NCH3),
4.03 (3H, s, OCH3), 2.61 (1H, br s, OH); 13C NMR (75 MHz,
CDCl3) d 178.0 (C9), 164.0 (C3), 147.0 (C4a), 146.0 (C10a),
133.6 (C6), 129.5 (C1), 127.1 (C8), 122.8 (C8a), 121.6 (C7),
119.6 (C9a), 116.6 (C5), 115.1 (C4), 106.0 (C2), 58.3
(CH2OH), 56.3 (OCH3), 43.7 (NCH3); ES-MS m/z 270
[MH]þ. Anal. Calcd. for C16H15NO3: C 71.36; H 5.61; N
5.20%. Found: C 71.42; H 5.67; N 5.13%.
1524, 1433, 1292, 1216, 1148, 1112, 882, 758; 1H NMR
(400 MHz, CDCl3) d 8.84 (1H, br s, NH), 8.70 (1H, s, H1),
7.76 (1H, d, J ¼ 8 Hz, H8), 7.50 (1H, d, J ¼ 8 Hz, H5), 7.40
0
(1H, t, J ¼ 8 Hz, H6), 7.23 (1H, t, J ¼ 8 Hz, H5 ), 7.21 (1H,
t, J ¼ 8 Hz, H7), 7.10 (1H, s, H4), 7.09 (1H, d, J ¼ 8 Hz,
0
0
H4 ), 6.77 (1H, d, J ¼ 8 Hz, H6 ), 3.91 (3H, s, OCH3), 2.20
(3H, s, AreCH3); 13C NMR (75 MHz, CDCl3) d 172.0
0
(COOH), 158.9 (C3 ), 144.8 (C3), 140.3 (C1 ), 137.9 (C4a),
0
0
135.2 (2C, C1, C8a), 129.4 (2C, C8, C6), 126.6 (C5 ), 125.9
0
(C5), 122.9 (C7), 121.9 (C2 ), 117.8 (C4 ), 113.5 (C2), 108.1
0
0
(C4), 106.8 (C6 ), 55.8 (OCH3), 10.6 (AreCH3); ES-MS m/z
308 [MH]þ, 330 [MNa]þ, 346 [MK]þ. Anal. Calcd. for
C19H17NO3: C 74.25; H 5.58; N 4.56%. Found: C 74.18; H
5.53; N 4.61%.
5.1.12.2. 2-Bromo-3-methoxy-4,10-dimethylacridin-9(10H )-
one (27). IR (KBr) n, cmꢂ1 2950, 2927, 2852, 2356, 1732,
1629, 1609, 1436, 1398, 1265, 1090, 1051, 1009, 739, 704;
1H NMR (400 MHz, CDCl3) d 8.56 (1H, s, H1), 8,40 (1H, d,
J ¼ 8 Hz, H8), 7.72 (1H, t, J ¼ 8 Hz, H6), 7.47 (1H, d,
J ¼ 8 Hz, H5), 7.29 (1H, t, J ¼ 8 Hz, H7), 3.96 (3H, s,
NCH3), 3.87 (3H, s, OCH3), 2.60 (3H, AreCH3); 13C NMR
(75 MHz, CDCl3) d 177.5 (C9), 160.4 (C3), 146.8 (C4a),
146.7 (C10a), 133.9 (C6), 129.5 (C1), 127.2 (C8), 123.1 (C8a),
122.7 (C9a), 121.9 (C7), 121.4 (C2), 116.7 (C5), 111.7 (C4),
56.5 (OCH3), 42.4 (NCH3), 15.4 (AreCH3); ES-MS m/z
354/356 [MNa]þ, 370/372 [MK]þ. Anal. Calcd. for
C16H14BrNO2: C 57.85; H 4.25; N 4.22%. Found: C 57.91;
H 4.19; N 4.26%.
5.1.15. 3-Methoxy-4-methylbenzo[b]acridin-
12(5H )-one (31)
Trifluoroacetic anhydride (5.6 mL) was added to a solution
of 30 (1.24 g, 4.04 mmol) in CH2Cl2 (50 mL) and cyclization
was further conducted as described for the preparation of 25
from 24. Flash chromatography (solvent: CH2Cl2, then
CH2Cl2/MeOH, 99:1) gave 31 (0.55 g, 47%) a yellow amor-
phous solid. IR (KBr) n, cmꢂ1 2957, 2918, 2844, 2355,
1729, 1627, 1584, 1454, 1377, 1335, 1261, 1120, 1021, 796;
1H NMR (400 MHz, CDCl3) d 9.06 (1H, s, H11), 8.41 (1H,
d, J ¼ 9 Hz, H1), 8.06 (1H, d, J ¼ 8 Hz, H10), 7.84 (1H, d,
J ¼ 8 Hz, H7), 7.79 (1H, br s, NH), 7.73 (1H, s, H6), 7.56
(1H, t, J ¼ 8 Hz, H8), 7.42 (1H, t, J ¼ 8 Hz, H9), 6.90 (1H,
d, J ¼ 9 Hz, H2), 4.00 (3H, s, OCH3), 2.40 (3H, s, AreCH3);
13C NMR (75 MHz, CDCl3) d 179.6 (C12), 161.4 (C3), 141.2
5.1.13. 4-Acetoxymethyl-3-methoxy-10-
methylacridin-9(10H )-one (28)
Acetylation of 17 (25 mg, 0.08 mmol) under conditions es-
sentially similar to those described for the conversion of 6 to 4,
afforded 28 (18 mg, 65%) as a pale yellow amorphous solid.
IR (KBr) n, cmꢂ1 2919, 2846, 2356, 2333, 1727, 1608,
1581, 1452, 1405, 1270, 1097, 763; 1H NMR (400 MHz,
CDCl3) d 8.55 (1H, d, J ¼ 9 Hz, H1), 8.42 (1H, dd, J ¼ 8,
1.5 Hz, H8), 7.72 (1H, td, J ¼ 8, 1.5 Hz, H6), 7.44 (1H, dd,
J ¼ 8, 1.5 Hz, H5), 7.30 (1H, td, J ¼ 8, 1.5 Hz, H7), 6.97
(1H, d, J ¼ 9 Hz, H2), 4.56 (2H, s, CH2OAc), 4.02 (3H, s,
OCH3), 3.95 (3H, s, NCH3), 2.19 (3H, s, OCOCH3); 13C
NMR (75 MHz, CDCl3) d 178.0 (C9), 170,9 (OCOCH3),
157.9 (C3), 146,1 (2C, C4a, C10a), 133.9 (C6), 1307 (C1),
127.2 (C8), 123.3 (C8a), 122.2 (C9a), 121.7 (C7), 116.9 (C5),
110.7 (C4), 105.9 (C2), 59.5 (CH2eOAc), 56.7 (OCH3), 43.2
(NCH3), 21.3 (OCOCH3); ES-MS m/z 334 [MNa]þ; 350
[MK]þ. Anal. Calcd. for C18H17NO4: C 69.44; H 5.50; N
4.50%. Found: C 69.51; H 5.48; N 4.52%.
(C4a), 137.7 (C5a), 136.2 (C6a), 129.9 (C10), 128.6 (2C, C11a
,
C8), 128.5 (C11), 127.2 (C1), 126.2 (C7), 124.2 (C9), 121.5
(C10a), 120.0 (C4), 114.9 (C12a), 111.2 (C6), 105.4 (C2), 56.0
(OCH3), 14.1 (AreCH3); ES-MS m/z 312 [MNa]þ, 328
[MK]þ. Anal. Calcd. for C19H15NO2: C 78.87; H 5.23; N
4.84%. Found: C 78.79; H 5.28; N 4.77%.
5.1.16. 3-Methoxy-4,5-dimethylbenzo[b]acridin-
12(5H )-one (32)
Methylation of 31 (0.55 g, 1.9 mmol) with excess methyl
iodide (0.78 mL, 12.5 mmol) following the procedure de-
scribed for the preparation of 26 from 25 afforded 32
(0.52 g, 94%) as yellow needles: m.p. 179e180 ꢀC (recrystal-
lized from CH2Cl2). IR (KBr) n, cmꢂ1 2953, 2919, 2842,
1464, 1618, 1592, 1458, 1404, 1294, 1245, 1095, 1055, 776,
1
739; H NMR (400 MHz, CDCl3) d 9.19 (1H, s, H11), 8.37
5.1.14. 3-(3Methoxy-2-methylphenyl)-amino-2-
naphthoic acid (30)
(1H, d, J ¼ 9 Hz, H1), 8.01 (1H, d, J ¼ 8 Hz, H10), 7.86 (1H,
d, J ¼ 8 Hz, H7), 7.72 (1H, s, H6), 7.54 (1H, t, J ¼ 8 Hz,
H8), 7.27 (1H, t, J ¼ 8 Hz, H9), 6.88 (1H, d, J ¼ 9 Hz, H2),
3.89 (3H, s, OCH3), 3.79 (3H, s, NCH3), 2,44 (3H, s, Are
CH3); 13C NMR (75 MHz, CDCl3) d 179.6 (C12), 163.4
(C3), 148.3 (C4a), 144.1 (C5a), 136.3 (C6a), 129.7 (C10),
128.2 (2C, C8, C11a), 128.1 (C11), 127.0 (C1), 126.9 (C7),
124.5 (C9), 123.5 (C10a), 119.0 (C4), 113.0 (C12a), 112.6
(C6), 105.7 (C2), 56.1 (OCH3), 44,3 (NCH3), 15.5 (Are
CH3); ES-MS m/z 304 [MH]þ, 326 [MNa]þ, 342 [MK]þ.
Compound 30 was synthesized from 8 (5.56 g, 22.2 mmol)
and 22 (3.04 g, 22.2 mmol) according to the procedure de-
scribed for the preparation of 24 from 19 and 22, using potas-
sium acetate (4.7 g), cupric acetate monohydrate (0.14 g), and
triethylamine (2.7 mL) in anhydrous 2-propanol (100 mL).
Flash chromatography (solvent: CH2Cl2, then CH2Cl2/
MeOH, 99:1) gave 30 (2.72 g, 40%) as a whitish amorphous
solid. IR (KBr) n, cmꢂ1 2918, 2844, 2560, 1660, 1578,

2686
Q. Do et al. / European Journal of Medicinal Chemistry 43 (2008) 2677e2687
Anal. Calcd. for C20H17NO2: C 79.19; H 5.65; N 4.62%.
Found: C 79.26; H 5.68; N 4.61%.
the concentration that reduced by 50% the optical density of
treated cells with respect to the optical density of untreated
controls.
5.1.17. 4-Hydroxymethyl-3-methoxy-
5-methylbenzo[b]acridin-12(5H )-one (33)
Acknowledgment
N-Bromosuccinimide (0.17 g, 1.0 mmol) was added to a so-
lution of 26 (0.30 g, 1.0 mmol) in CCl4 (15 mL) the reaction
mixture was irradiated (1000 W) for 15 min. After cooling,
water (5 mL) was added and the resulting mixture was evapo-
rated under reduced pressure. Column chromatography over
silica gel (solvent: C6H6/EtOAc 7:3) gave 33 (0.08 g, 25%)
as a bright yellow amorphous solid. IR (KBr) n, cmꢂ1 2960,
2929, 2851, 2544, 1614, 1590, 1450, 1404, 1299, 1186,
1104, 820, 750, 641; 1H NMR (400 MHz, CDCl3) d 8.89
(1H, s, H11), 8.48 (1H, d, J ¼ 9 Hz, H1), 8.00 (1H, d,
J ¼ 8 Hz, H10), 7.90 (1H, d, J ¼ 8 Hz, H7), 7.78 (1H, s, H6),
7.54 (1H, t, J ¼ 8 Hz, H8), 7.42 (1H, t, J ¼ 8 Hz, H9), 6.93
(1H, d, J ¼ 9 Hz, H2), 4.51 (2H, s, CH2OH), 4.20 (3H, s,
OCH3), 4.00 (3H, s, NCH3), 2,15 (1H, br s large, D2O
exch., OH); ES-MS m/z 320 [MH]þ. Anal. Calcd. for
C20H17NO3: C 75.22; H 5.37; N 4.39%. Found: C 75.15; H
5.41; N 4.42%.
´
The authors thank Pr. M. Koch (Universite Paris 5, France)
for his stimulating interest in this work.
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