Synthesis of new tetracyclic 7-oxo-pyrido[3,2,1-de]acridine derivatives

Article abstract of DOI:10.1016/j.tet.2011.06.062

A series of (±)3-hydroxyl- and 2,3-dihydroxy-2,3-dihydro-7- oxopyrido[3,2,1-de]acridines were synthesized for antitumor evaluation. These agents can be considered as analogues of glyfoline or (±)1,2- dihydroxyacronycine derivatives. The key intermediates,

Full text of DOI:10.1016/j.tet.2011.06.062

Tetrahedron 67 (2011) 5883e5893
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Synthesis of new tetracyclic 7-oxo-pyrido[3,2,1-de]acridine derivatives
Ching-Huang Chen a, Yi-Wen Lin a, Rajesh Kakadiya a, Amit Kumar a, Yu-Ting Chen a, Te-Chang Lee a,
,b,
Tsann-Long Su a
*
a Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan
b Graduate Institute of Pharmaceutical Chemistry, China Medical University, Taichung, Taiwan
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 29 April 2011
Received in revised form 9 June 2011
Accepted 21 June 2011
Available online 25 June 2011
A series of (ꢀ)3-hydroxyl- and 2,3-dihydroxy-2,3-dihydro-7-oxopyrido[3,2,1-de]acridines were synthe-
sized for antitumor evaluation. These agents can be considered as analogues of glyfoline or (ꢀ)1,2-
dihydroxyacronycine derivatives. The key intermediates, 3,7-dioxopyrido[3,2,1-de]acridines (15a,b or
24a,b), for constructing the target compounds were synthesized either from 3-(N,N-diphenylamino)
propionic acid (14a,b) by treating with Eaton’s reagent (P2O5/MsOH) (Method 1) or from (9-oxo-9H-
acridin-10-yl)propionic acid (23aec) via ring cyclization under the same reaction conditions (Method 2).
Compounds 15a,b and 24a,b were converted into (ꢀ)3-hydroxy derivatives (25aed), which were then
further transformed into pyrido[3,2,1-de]acridin-7-one (28aed) by treating with methanesulfonic an-
hydride in pyridine via dehydration. 1,2-Dihydroxylation of 28aed afforded (ꢀ)cis-2,3-dihydroxy-7-
oxopyrido[3,2,1-de]acridine (29aed). Derivatives of (ꢀ)3-hydroxy (25a,b) and (ꢀ)cis-2,3-dihydroxy
(29aed) were further converted into their O-acetyl congeners 26a,b and 30aed, respectively. We also
synthesized 2,3-cyclic carbonate (31, 32, and 33) from 29aec. The anti-proliferative study revealed that
these agents exhibited low cytotoxicity in inhibiting human lymphoblastic leukemia CCRF-CEM cell
growth in culture.
Keywords:
Acridine
Acronycine
Eaton’s reagent
Ullmann condensation
Cyclization
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction
found that this agent induced the appearance of spindle abnor-
malities, chromosome mis-segregation, multipolar cell division,
One of our ongoing research programs is searching for the an-
titumor agents that have a novel mechanism of action. We have
previously studied the antitumor effect of naturally occurring
acridone alkaloids, glyfoline (1, Fig. 1) and acronycine (2) de-
rivatives. Acridone alkaloids were also known as potential antitu-
mor agents since acronycine (2) was found to have potent
antitumor activity in the middle of the 1960s.1e4 Previously, we
have evaluated the anti-proliferative activity of a series of acridone
alkaloids and found that glyfoline (1) was the most cytotoxic
against human leukemia HL-60 cell growth in vitro.5 The alkaloid
was first isolated from Glyfoline citrifolia (Willd.) Lindl. (Rutaceae),
an indigenous plant from Taiwan. Glyfoline was about 10-fold more
potent than acronycine and exhibited moderate in vivo antitumor
activity in mice bearing murine and human tumors xenograft.6
Remarkably, we have recently found that the alkaloid exhibits
a novel mechanism of action by targeting the mitochondria and
releasing cytochrome c to induce tumor cell death.7 More recently,
we studied on the detailed mechanism of action of glyfoline, and
and multiple nuclei, traits indicative of mitotic catastrophe.8
2
1
O
OH
O
OMe
O
OMe
O
11
14
3
OMe
OMe
12
13
9
8
16
15
4
10
5
7
N
HO
N
O 20
6
21
N
Me
O
19
OMe Me OMe
1
Me
17
23
18
2
3
22
O
N
Me
ROCO
OMe
O
OMe
O
N
Me
ROCO
O
OCOR
4
OCOR
5
Fig. 1. Structures of glyfoline (1) and acronycine derivatives (2e5).
Acronycine (2, Fig. 1), isolated from the Australian scribe ash
Acronychia baueri Schott (Rutaceae), possessed moderate in vitro
potency and a broad spectrum of antitumor activity.2,3,9,10 This al-
kaloid was in clinical trials.1 However, limited efficacy was
* Corresponding author. Tel.: þ886 2 2789 9045; fax: þ886 2 2782 5573; e-mail
address: tlsu@ibms.sinica.edu.tw (T.-L. Su).
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.06.062

5884
C.-H. Chen et al. / Tetrahedron 67 (2011) 5883e5893
observed, probably due to its poor physiochemical properties. Dorr
and Liddil have demonstrated that this alkaloid may interact with
DNA, either by intercalation or by some other noncovalent pro-
cess.11 Recently, several acronycine derivatives, such as unstable
natural epoxides (3, Fig. 1) and synthetic diesters of (ꢀ)-cis-1,2-
dihydroxy-1,2-dihydroacronycine (4)12 and its benzo[b]acronycine
derivatives (5)13 or their acetates,14e16 were reported to have
markedly improved antitumor activity. Particular interest is that
the latter compound was able to covalently bind with DNA.17,18 It
was reported that (ꢀ)1,2-dihydroxy-1,2-dihydroacronycine diesters
(6, Fig. 2) exhibited potent in vivo antitumor activity against murine
P388 leukemia and colon 38 adenocarcinoma when compared with
acronycine. Costes et al. synthesized a series of (ꢀ)-cis-1,2-
dihydroxy-1,2-dihydrobenzo[b]acronycine derivatives.13 The diac-
etates (7, S23906-1) and the cyclic carbonate 8 displayed potent
antitumor effects in mice bearing P388 leukemia and colon 38
adenocarcinoma. More than 80% of tumors were suppressed in
mice at doses 16-fold lower than the effective dose of acronycine
itself. Compound 7 was the most active, with all the treated mice
being tumor-free on day 23 at the dose of 12.5 mg/kg (drug was
administrated by intraperitoneous injection on day 2 and 9).14
Compound 7 is currently undergoing phase I clinical trials.17 It
was found to be as efficient as a variety of clinically used drugs in
human orthotopic models of carcinomas.19,20
2,3-dihydro-1H,7H-pyrido[3,2,1-de]-acridin-3-yl derivatives (A,
Scheme 2) for antitumor evaluation. These compounds can be
considered as analogues of glyfoline with an additional fused
cyclohexanyl ring on the C4-N10 position of the acridin-9-one
chromophore. One can anticipate that the O-acetyl function at C2
of these derivatives might be more acceptable for nucleophilic at-
tack by DNA than the corresponding O-acetyl function in 1,2-
dihydroxyacronycine derivatives (6 or 7), since they lack the ster-
ical hindrance of the N-Me function. We herein describe the
chemical synthesis and antitumor activity of 2,3-dihydroxy-7-oxo-
pyridoacridines.
2. Results and discussion
Scheme 2 shows the retro-synthesis of the newly synthesized
compounds. The target compound A could be easily prepared by
1,2-dihydroxylation of the olefin function of B. To prepare the in-
termediate B, it is necessary to construct the key intermediate 3,7-
dioxopyrido[3,2,1-de]acridines C, which can be reduced to alcohols,
followed with dehydration to yield B. The 3,7-di-oxo compound C
can be synthesized from 3-(N,N-diphenylamino)propionic acid D
by ring cyclization via FriedeleCraft acylation (Method 1). The in-
termediate can be prepared by Ullmann condensation of 2-
iodobenzoic acid E and m-anisidines F, followed with N-alkyl-
ation with ethyl acrylate. Alternatively, one can prepare the in-
termediate C from 9-acridones by reacting with propionate,
followed by intramolecular cyclization (Method 2). The synthesis of
the desired compound A was then carried out and is described as
follows.
In Method 1, attempts to prepare ethyl 3-(N,N-diphenylamino)
propionate (12a,b) either by Ullmann condensation of 2-
iodobenzoic acid with m-anisidine derivatives, followed by N-al-
kylation with ethyl acrylate or reaction of 2-iodobenzoic acid with
3-(m-anisidinyl)propionate failed. We finally found that dipheny-
liodonium-2-carboxylate (DPIC, 11) is an appropriate reactant for
the Ullmann condensation with m-anisidine. Thus, the known ethyl
3-anisidinypropionates (10a,b)24,25 was synthesized in good yield
(85%) by reacting m-anisidine (9a) with a large excess of ethyl ac-
rylate in the presence of acetic acid under refluxing for one day
(Scheme 3). However, under the same reaction conditions, the re-
action of 3,4,5-trimethoxyaniline with ethyl acrylate required
a longer reaction time (about 2 weeks) to yield 10b in moderate
yield (55%). Condensation of 10a,b with diphenyliodonium-2-
carboxylat (DPIC, 11) afforded ethyl 3-(N,N-diphenylamino)pro-
pionates (12a,b), which were then saponified (NaOH/MeOH) to give
propionic acid derivatives 13a,b. We attempted to prepare pyr-
idoacridines 15a,b by treating 13a,b with various Lewis acids.
Among these agents, we found the reaction of 13a with trifluoro-
acetic anhydride gave tetrahydroquinolin-4-one 14 in good yield at
low temperature (ꢁ5 to ꢁ10 ꢂC). It indicated that the cyclization
preferably occurred on the para-position to the MeO function of the
O
OH
O
OH
O
OH
N
O
N
O
N
O
Me
Me
Me
AcO
O
AcO
OAc
OAc
O
O
8
6
7
Fig. 2. Structures of acronycine derivatives (6e8).
At the cellular level, compound 7 induced an irreversible S-phase
blockadeof the cellcycle andefficientlytriggeredapoptosis inseveral
cancer cell types.13,21,22 At the molecular level, diacetates 7 were
found to bind covalently both with purified DNA fragments and with
genomic DNA extracted from treated tumor cells.17,23 The studies
have demonstrated that compound 7 readilyalkylated G$C base pairs
and specifically bonded to the exocyclic NH2 group of the guanine
residue.22 The study showed that there was a strong correlation be-
tween DNA alkylation by the various 1,2-dihydroxy-1,2-dihydro-
benzo[b]acronycine diesters and their respective cytotoxic poten-
tial.23 Studies on the mechanism of action of 1,2-dihydroxy-1,2-
dihydro-benzo[b]acronycine diesters revealed that the ester at C-1
acts as a leaving group, which generates a cation at C-1 andallowsthe
nucleophilic attack by DNA (Scheme 1). Since (ꢀ)cis-1,2-diesters and
(ꢀ)2-monoester were equally potent, it suggests that the monoester
at C-2 could spontaneously lead to the corresponding more reactive
monoester at C-1 by a transesterification process.23
O
N
O
O
N
OMe
O
N
OMe
O
N
OMe
OCOR
OCOR
dG
OCOR
dG
OCOR
OCOR
Scheme 1. The proposed mechanism of DNA alkylation by new acridine derivatives.
On the basis of the super antitumor activity and mechanism of
action of (ꢀ)-cis-1,2-dihydroxy-1,2-dihydroacronycine derivatives
(6 and 7), we have design and synthesize new glyfoline analogues,
namely (ꢀ)6-methoxy-7-oxo-3-hydroxy- (or cis-2,3-dihydroxy)-
m-anisidine, leading to the formation of 14 instead of the tri-cyclic
acridin-9-one.26 Compound 14 was then converted into tetra-cyclic
3,7-dioxopyridoacridine 15a in moderate yield by treating with
Eaton’s reagent (10% P2O5/MsOH) at room temperature.26

C.-H. Chen et al. / Tetrahedron 67 (2011) 5883e5893
5885
O
N
OMe
R1
O
OMe
R1
O
OMe
O
OMe
R1
R2
R2
R2
Method-2
R2
R1
N
N
N
H
C
C
COOEt
OH
O
G
C
B
OH
A
Method-1
OMe
OMe
COOH
N
COOH
R2
R2
R1
R1
I
H2N
C
C
COOEt
COOH
E
F
D
Scheme 2. Retrosynthetic analysis.
COO
I
OMe
R1
OMe
OMe
11
R1
R1
COOH
R1
R1
a
b
R1
COOEt
EtOOC
H2N
HN
N
COOR2
9a,b
a: R1 = H
b: R1 = OMe
2
10a
(89%)
(55%)
12a
12b
13b
(34%),
(63%),
(53%) R = Et
10b
c
2
13a
(90%) R = H
d
e
O
OMe
OMe
O
OH
8
COOH
N
6
R1
R1
7
R1
R1
9
d
5
10
4
N
N
H
11
1
3
O
2
O
16a,b
(83%)
14
15a (57%)
15b
(36%)
Scheme 3. Reagents and conditions: (a) AcOH/EtOH, reflux; (b) Cu(OAc)2/DMF, 90 ꢂC; (c) NaOH/MeOH, rt; (d) 10% P2O5/MsOH (Eton’s reagent), rt; (e) trifluoroacetic anhydride, rt.
Interestingly, we were able to convert 13a directly to the desired
tetra-cyclic 15a by reacting with Eaton’s reagent. It should be noted
that when the reaction was carried out in concentrated sulfuric
acid, polyphosphoric acid, or phosphoryl chloride,27 a mixture of
acridin-9-ones 15a,b together with 1-hydroxyacridin-9-ones
(16a,b) was obtained. It suggested that the propionic acid side-
to give acridin-9-ones 20a,b. It is noted that one should work up the
reaction with caution, since the methoxy function at the C1 posi-
tion is labile and can be hydrolyzed into C1eOH (nor acridin-9-one)
under acidic conditions. Reaction of 20a,b with ethyl propiolate
afforded mainly the trans-isomer. The pure trans-21a,b (major
products) can be obtained by recrystallization or chromatography,
while the cis-21a,b isomer (>2%) was rather difficult to be sepa-
rated from the mixture. The 1H NMR spectrum analyses for 21b
reveal the protons on the double bond: for trans-isomer, appeared
chain is unstable under acidic conditions and may undergo
b-
elimination to form acrdin-9-one. Method 1, however, can not be
applied for synthesizing 24aec derivatives, which bear sub-
stituent(s) on the A-ring of the acridin-2-one, since we could not
prepare the substituted DPIC derivative.
at
d
5.45 and 8.11 with a coupling constant of J¼14.0 Hz; for cis-
isomer, located at
d
6.18 and 7.94 having coupling constant of
Method 2 was then developed to construct the key intermediate
C, 3,7-dioxopyrido[3,2,1-de]acridines having substituent(s) on the
A-ring (i.e., compounds 24aec Scheme 4). We first synthesized
substituted 2-iodobenzoic acids 18a,b in high yield from anthranilic
acid 17a,b by treating with NaNO2/HCl/KI following the known
procedure.6,28 Ullmann condensation of anthranilic acid 18a,b with
3,4,5-trimethoxyaniline (9b) gave N-phenylanthranilic acids 19a,b,
which were then ring cyclized by treating with phosphoryl chloride
J¼8.4 Hz. Since compounds 21a,b were not suitable for ring
cyclizing to give the tetra-cyclic derivatives, these derivatives were
directly converted into N-propionic acid derivatives 22a,b via sa-
ponification (NaOH/MeOH), followed by hydrogenation (10% Pd/C,
H2, EtOH). Under the reaction conditions, the O-benzyl protecting
function of 22b (R¼OBn) was removed during the hydrogenation to
form 23b, which was reprotected by treating with acetic anhydride/
pyridine to afford O-acetyl 23c. Similarly, compound 23a was then

5886
C.-H. Chen et al. / Tetrahedron 67 (2011) 5883e5893
OMe
OMe
O
OMe
OMe
H2N
OMe
R1
COOH
OMe
OMe
COOH
NH2
COOH
I
OMe
OMe
c
9b
a
R1
N
H
R1
R1
b
N
H
OMe
OMe
OMe
OMe
20a (67%) R1 = H
20b
(90%) R1 = H
19a (57%) R1 = H
19b
R
R
1 = H
18a
17a
(82%) R1 = OBn
18b (94%) R1 = OBn
(69%) R1 = OBn
1 = OBn
17b
d
O
N
OMe
O
O
N
OMe
O
N
OMe
OMe
OMe
OMe
OMe
OMe
OMe
h
f
R1
R1
R1
OMe
COOR2
OMe
OMe
21a
COOH
(43%) R1 = H
(45%) R1 = H
R
1 = H, R2 = Et
23a
24a
24b
24c
21b R1 = OBn, R2 = Et
23b (37%) R1 = OH
(31%) R1 = OH
(21%) R1 = OAc
g
e
(55%) R1 = OAc
(51%) R1 = H, R2 = H
23c
22a
(98%) R1 = OBn, R2 = H
22b
Scheme 4. Reagents and conditions: (a) NaNO2/HCl, KI, 5 ꢂC; (b) CuI, Cu, K2CO3/DMF, 40e80 ꢂC; (c) POCl3, 40 ꢂC, and then 5% HCl 40 ꢂC; (d) ethyl propionate/K2CO3/DMF, rt; (e)
NaOH/Ac2O; (f) 10% Pd/C, H2/EtOH, 40 psi; (g) Ac2O/pyridine; (h) 10% P2O5/MsOH (Eton’s reagent), rt.
treated with Eaton’s reagent (P2O5/MsOH) to give the tetra-cyclic
24a. In the case of 23c, the O-acetyl function was partially hydro-
lyzed to form 24b and 24c upon treatment of Eaton’s reagent.
Using 3,7-dioxopyrido[3,2,1-de]acridines (15a,b and 24a,b) as
the starting materials, we successfully converted them into the
corresponding 2,3-dihydroxy derivatives (Scheme 5). Thus, com-
pounds 15a,b and 24a,b were reduced with NaBH4 in THF to 3-
hydroxy derivatives (ꢀ)25aed, which were then treated with
methanesulfonyl chloride in the presence of triethylamine in
chloroform to give the desired 7-oxo-1H,7H-pyrido-[3,2,1-de]acri-
din-3-yl derivatives 28aed in high yield (Scheme 5). The reaction
proceeded smoothly without observing the formation of O-meth-
anesulfonyl intermediate. Dihydroxylation of the 2,3-olefin in
28aed using OsO4 in the presence of 4-methylmorpholin N-oxide
in THF gave (ꢀ) 2,3-dihydroxy derivatives (29aed).
derivatives to realize whether the C3-O-acetyl or 3-O-methyl-
carbamoyl can act as a leaving group to generate a cation for nu-
cleophilic attack by DNA as that of (ꢀ)1,2-di-O-acetylacronycine
analogues. Thus, compounds (ꢀ)25a,b or (ꢀ)29aed were reacted
with acetic anhydride in pyridine, affording O-acetate derivatives
(ꢀ)26a,b and (ꢀ)30aed, respectively (Scheme 5). Compound (ꢀ)27
was prepared in good yield from 25a by treating with methyl-
isocyanate in CHCl3 solution in the presence of triethylamine.
Similarly, we also prepared cyclic carbonate derivatives, (ꢀ)31, (ꢀ)
32, (ꢀ)33, from (ꢀ)29a, (ꢀ)29b, and (ꢀ)29c, respectively, by
reacting with N,N-carbonyldiimidazole in 2-butanone.
Our earlier studies revealed that glyfoline and related acridin-9-
ones exhibited cytotoxic effects in inhibiting human leukemia HL-
60 cell growth in culture.5 In the present study, we have synthe-
sized a series of (ꢀ)3-hydroxy-7-oxo-1H,7H-pyrido[3,2,1-de]acri-
din-3-yl (25aed) and (ꢀ)2,3-dihydroxy derivatives (29aed) and
their O-acetyl derivatives (26a,b and 30aed). These agents can be
also considered as analogues of glyfoline or (ꢀ)1,2-dihydroxy-1,2-
To design and synthesize pyrido[3,2,1-de]acridines with DNA
alkylating potential, we prepare (ꢀ)3-O-acetyl (26a,b), (ꢀ)3-O-
methylcarbamoyl (27), and (ꢀ)2,3-di-O-acetate (30aed)
O
OMe
O
OMe
O
OMe
R1
R2
R1
R2
R1
R2
b
c
a
15a,b, 24a,b
50-70%
R4
N
R4
N
R4
N
R3
25a
R3
R3
OH
OR
OR
29b
25b
(73%),
(84%),
28a,b,c,d
29a
25c (89%), 25d (83%)
(88%),
(82%),
R = H
29c (56%), 29d (30%)
d
30a 30b
(84%),
30c (94%), 30d (83%)
(90%),
d
R = Ac
f
25 28 29 30
,
Substitution in
,
,
: R1 = R2 = R3 = R4 = H
a
e
: R1 = R2 = OMe, R3 = R4 = H
O
N
OMe
b
O
OMe
c: R1 = R2 = R3 = OMe, R4 = H
d
R
OMe
OMe
O
N
OMe
: R1 = R2 = R3 = OMe, R4 = OH
R1
R2
for 30d R4 = OAc
R
N
OAc
OCONHMe
(85%)
R3
26a (73%) R = H
27
O
O
26b
(95%) R = OMe
O
31 (29%) R1 = R2 = R3 = H
32
(46%) R1 = R2 = OMe, R3 = H
(67%) R1 = R2 = R3 = OMe
33
Scheme 5. Reagents and conditions: (a) NaBH4/THF/H2O; (b) (MeSO2)2O/Et3N, pyridine or DMAP/CHCl3, rt; (c) OsO4/4-methylmorpholine-N-oxide/THF, rt; (d) Ac2O/pyridine, rt; (e)
N,N-carbonyldiimidazole/butanone; (f) MeN]C]O/Et3N.

C.-H. Chen et al. / Tetrahedron 67 (2011) 5883e5893
5887
dihydroacronycine. The newly synthesized compounds were sub-
jected to antitumor evaluation against human lymphoblastic leu-
kemia cell (CCRF/CEM) growth in vitro. However, it was shown that
these agents exhibited low cytotoxicity against the tested tumor
cell line. Comparing the chemical structure of 2,3-dihydroxy-2,3-
J¼7.1 Hz, Me). Anal. Calcd for C14H21NO5: C, 59.35; H, 7.47; N, 4.94,
found: C, 59.15; H, 7.44; N, 4.77.
4.3. 2-((3-Ethoxy-3-oxopropyl)(3-methoxyphenyl)amino)
benzoic acid (12a)
dihydro-1H,7H-pyrido-[3,2,1-de]acridin-3-yl
dihydroxyacronycines, the later derivatives bearing
and
1,2-
1,2-
a
A mixture of DPIC (78 g, 240 mmol), 10a (44.66 g, 200 mmol),
CuOAc2 (3.63 g, 20 mmol) in dry DMF (400 mL) was stirred at room
temperature for 1h, and then heated at 80e90 ꢂC for 4 h. The
mixture was evaporated in vacuo to remove DMF. The residue was
dissolved in CHCl3 (250 mL) and extracted with 0.2 N aqueous so-
lution of K2CO3 (200 mLꢃ6) until no more product in the organic
layer. The water layer was acidified with acetic acid, extracted with
CHCl3 (100 mLꢃ2), dried over Na2SO4, and evaporated to dryness.
The product was purified by silica gel column chromatography
(4ꢃ29 cm, hexane/EtOAc, 3:2 v/v) to give 12a as yellow syrup
(23.54 g, 34%); 1H NMR (500 MHz, DMSO-d6): 12.74 (1H, br s,
COOH), 7.81 (1H, m, ArH), 7.61 (1H, m, ArH), 7.39 (1H, m, ArH), 7.27
(1H, m, ArH), 6.99 (1H, m, ArH), 6.24 (1H, m, ArH), 6.03(1H, m, ArH),
5.98 (1H, br s, ArH), 3.99 (2H, q, J¼7.2 Hz, CH2), 3.86 (2H, t, J¼7.1 Hz,
CH2), 3.62 (3H, s, OCH3), 2.64 (2H, t, J¼7.1 Hz, CH2), 1.12 (3H, t,
dihydroxy-3,3-dimethylpyrano ring angularly fused in the posi-
tion of [2,3-d] on the acridin-9-one basic skeleton, which may be
essential for anti-proliferative activity. While our newly synthe-
sized derivatives were inactive probably due to have a 2,3-
dihydroxy-2,3-dihydropyrido ring fused in position [3,2,1-de] on
the acridin-9-one chromophore.
3. Conclusion
We have designed and synthesized a new series of (ꢀ)3-
hydroxyl- and 2,3-dihydroxy-2,3-dihydro-7-oxopyrido[3,2,1-de]
acridines for antitumor evaluation. These agents can be considered
as analogues of glyfoline and (ꢀ)1,2-dihydroxyacronycine de-
rivatives and anticipate to have antitumor activity. However, these
congeners were found to have low biological activity due to their
compact structure and lacking of1,2-dihydroxy-3,3-dimethylpyrano
ring.
J¼7.2 Hz, CH3); 13C NMR (500 MHz, DMSO-d6) (
d, ppm): 172.3,169.7,
159.4, 151.3, 148.3, 136.9, 134.8, 131.2, 122.5, 120.4, 119.4, 117.4, 115.5,
92.5, 56.5, 55.9, 55.6, 32.5, 14.0. Anal. Calcd for C19H21NO5: C, 66.46;
H, 6.18; N, 4.08, found: C, 66.37; H, 6.05; N, 4.11.
4. Experimental section
4.3.1. 2-((3-Ethoxy-3-oxopropyl)(3,4,5-trimethoxyphenyl)amino)
benzoic acid (12b). By following the same procedure as that for the
preparation of 12a, compound 12b was prepared from 10b (17.0 g,
60 mmol) and DPIC (19.5 g, 60 mmol). Yield, 13 g (53%) as syrup; 1H
NMR (500 MHz, CDCl3): 8.34 (1H, d, J¼7.8 Hz, ArH), 7.62 (1H, t,
J¼7.6 Hz, ArH), 7.46 (2H, t, J¼7.5 Hz, ArH), 7.28 (1H, d, J¼7.9 Hz,
ArH), 6.21 (2H, s, 2ꢃ ArH), 4.12 (2H, q, J¼7.1 Hz, CH2), 3.91 (2H, t,
J¼7.2 Hz, CH2), 3.79 (3H, s, OMe), 3.76 (6H, s, 2ꢃ OMe), 2.61 (2H, t,
J¼7.2 Hz, CH2), 1.24 (3H, t, J¼7.1 Hz, Me); 13C NMR (500 MHz,
4.1. General methods and materials
All commercial chemicals and solvents were reagent grade and
were used without further purification unless otherwise specified.
Melting points were determined on a Fargo melting point appara-
tus and are uncorrected. Column chromatography was carried out
on silica gel G60 (70e230 mesh, ASTM; Merck and 230e400 mesh,
Silicycle Inc.). Thin-layer chromatography was performed on silica
gel G60 F254 (Merck) with short-wavelength UV light for visuali-
zation. All reported yields are isolated yields after chromatography
or crystallization. Elemental analyses were done on a Heraeus CHN-
O Rapid instrument. 1H NMR spectra were recorded on a 500 MHz,
Brucker AVANCE 500 DRX and 400 MHz, Brucker Top-Spin spec-
trometers in the indicated solvent. The chemical shifts were
DMSO-d6) (d, ppm): 171.6, 167.8, 153.2, 145.2, 144.6, 132.8, 131.2,
130.9, 130.1, 129.7, 125.9, 92.5, 60.1, 55.9, 55.6, 48.2, 32.5, 14.0. Anal.
Calcd for C21H25NO7$0.5H2O: C, 61.15; H, 6.35; N, 3.39, found: C,
61.33; H, 6.17; N, 3.07.
4.4. 2-((2-Carboxyethyl)(3-methoxyphenyl)amino)benzoic
acid (13a)
reported in parts per million (d) relative to TMS.
4.2. Ethyl 3-(3-methoxyphenylamino)propionate (10a)24
To a stirred solution of 12a (10.3 g, 30 mmol) in methanol
(50 mL) was slowly added 1 N NaOH aqueous solution (60 mL) at
room temperature until TLC indicated absence of the ester. After
stirring an additional 1 h, the methanol was removed and aqueous
layer was neutralized with saturated NH4Cl solution to pH 7 and
then extracted with CHCl3 (100 mLꢃ5). The combined organic ex-
tract was washed with water (100 mLꢃ2), dried over Na2SO4, and
evaporated under reduced pressure. The residue was crystallized
from CHCl3. Addition product was obtained from mother liquid by
column chromatography (SiO2, CHCl3/MeOH, 30:1) to give 13a,
total 5.1 g (63%); mp 85e87 ꢂC; 1H NMR (500 MHz, DMSO-d6):
12.54 (2H, br s, 2ꢃ COOH), 7.81 (1H, m, ArH), 7.62 (1H, m, ArH), 7.40
(1H, m, ArH), 7.30 (1H, m, ArH), 6.99 (1H, m, ArH), 6.24 (1H, m,
ArH), 6.02 (1H, m, ArH), 5.98 (1H, m, ArH), 3.83 (2H, t, J¼7.4 Hz,
CH2), 3.62 (3H, s, OMe), 2.58 (2H, t, J¼7.4 Hz, CH2); 13C NMR
A mixture of m-anisidine (9a, 172 mL, 1.5 mol) and ethyl acrylate
(184 mL, 1.7 mol) containing acetic acid (6 mL) was heated under
reflux for 24 h. The mixture was evaporated to remove excess ethyl
acrylate and acetic acid and the residue was chromatographed on
a silica gel column (10ꢃ33 cm) using hexane/EtOAc (20:1 v/v) as
the eluant. Compound 9a was eluated by hexane/EtOAc (5:1 v/v) as
orange syrup (298 g, 89%); 1H NMR (500 MHz, DMSO-d6): 7.08 (1H,
t, J¼8.80 Hz, ArH), 6.28 (1H, m, ArH), 6.24 (1H, m, ArH), 6.17 (1H, m,
ArH), 4.15 (2H, q, J¼7.3 Hz, OCH2), 4.05 (1H, br s, NH), 3.77 (3H, s,
OMe), 3.43 (2H, t, J¼6.6 Hz, CH2), 2.60 (2H, t, J¼6.6 Hz, CH2), 1.27
(3H, t, J¼7.3 Hz, Me).
4.2.1. Ethyl 3-(3,4,5-trimethoxyphenylamino)propionate (10b)25. By
following the same procedure as that for the synthesis of 10a,
compound 10b was prepared from 3,4,5-trimethoxyaniline (9b,
55 g, 300 mmol), ethyl acrylate (33 g, 330 mmol), and acetic acid
(2 mL) in EtOH (1 L) by refluxing for 2 weeks. The product was
crystallized from ethyl acetate/hexane, 47 g (55%); mp 51e52 ꢂC
(EtOAc/hexane); 1H NMR (500 MHz, CDCl3): 5.87 (2H, s, 2ꢃ ArH);
4.16 (2H, q, J¼7.1 Hz, CH2), 3.81 (6H, s, 2ꢃ OMe), 3.76 (3H, s, OMe),
3.41 (2H, t, J¼6.4 Hz, CH2), 2.61 (2H, t, J¼6.4 Hz, CH2), 1.26 (3H, t,
(500 MHz, DMSO-d6) (d, ppm): 173.0, 167.5, 160.2, 149.3, 145.2,
133.1, 131.4, 131.2, 130.7, 129.6, 126.5, 106.4, 102.1, 99.6, 54.7, 48.1,
32.3. Anal. Calcd for C17H17NO5: C, 64.75; H, 5.43; N, 4.44, found: C,
64.45; H, 5.65; N, 4.18.
4.4.1. 2-((2-Carboxyethyl)(3,4,5-trimethoxyphenyl)amino)benzoic
acid (13b). By following the same procedure as that for the syn-
thesis of 13a, compound 13b was prepared from 12b (12 g,

5888
C.-H. Chen et al. / Tetrahedron 67 (2011) 5883e5893
30 mmol). Yield, 10 g (90%) as syrup. The crude product was used
directly for the next reaction without further purification. A small
amount of sample was purified by column chromatography for 1H
NMR spectrophotometric analysis; 1H NMR (500 MHz, CDCl3): 8.26
(1H, m, ArH), 7.61 (1H, m, ArH), 7.43 (1H, m, ArH), 7.28 (1H, m, ArH),
7.25 (2H, s, ArH), 3.92 (2H, t, J¼6.8 Hz, CH2), 3.78 (3H, s, OMe), 3.74
(6H, s, 2ꢃ OMe), 2.65 (2H, t, J¼6.8 Hz, CH2); 13C NMR (500 MHz,
MeOH (300 mL), filtered with a pad of Celite, and washed with
MeOH. The combined filtrate and washings was diluted with water
(1 L) and then acidified with CH3COOH to pH 4e5. The precipitate
was collected by filtration. It was dissolved in NaOH aqueous so-
lution and then acidified with acetic acid to pH 4e5 and then
extracted with CHCl3 (200 mLꢃ5). The organic layer was washed
with water, dried over Ns2SO4, and evaporated to dryness. The
residue was crystallized from EtOH to give 19a (15.05 g, 57%); mp:
185e189 ꢂC (EtOH); 1H NMR (500 MHz, DMSO-d6): 7.80 (1H, m,
ArH), 7.21 (1H, m, ArH), 7.14 (1H, m, ArH), 6.04 (2H, s, 2ꢃ ArH), 3.79
(6H, s, 2ꢃ OMe), 3.76 (6H, s, 2ꢃ OMe). Anal. Calcd for C17H19NO6: C,
61.25; H, 5.74; N, 4.20; found: C, 61.06; H, 5.59; N, 4.11.
DMSO-d6) (d, ppm): 174.5, 171.1, 149.2, 144.2, 134.1, 131.3, 131.2,
130.8, 123.9, 118.1, 115.2, 106.2, 102.9, 99.6, 58.9, 56.2, 55.6, 49.8,
33.4.
4.5. 2-(7-Methoxy-4-oxo-3,4-dihydroquinolin-1(2H)-yl)
benzoic acid (14)
4.7.1. 4-Benzyloxy-3-methoxy-2-(3,4,5-trimethoxy-phenyl-amino)
benzoic acid (19b). By following the same procedure as that for the
synthesis of 19a, compound 19b was prepared from 18b (20.45 g,
60 mmol) and 3,4,5-trimethoxyaniline 9b (12 g, 66 mmol). Yield,
18.2 g (69%), mp 159e160 ꢂC; 1H NMR (DMSO-d6): 12.85 (1H, br,
COOH), 8.85 (1H, br, NH), 7.64 (1H, m, ArH), 7.47e7.48 (2H, m, ArH),
7.39e7.42 (2H, m, ArH), 7.34e7.36 (1H, m, ArH), 6.84 (1H, d,
J¼9.0 Hz, ArH), 6.15 (1H, s, ArH), 5.22 (2H, s, CH2), 3.67 (6H, s, 2ꢃ
OMe), 3.59 (3H, s, OMe), 3.47 (3H, s, OMe). Anal. Calcd for
C24H25NO7$0.5H2O: C, 64.27; H, 5.84; N, 3.12; found: C, 64.90; H,
5.90; N, 3.12.
A
solution of freshly distillated trifluoroacetic anhydride
(2.8 mL, 20 mmol) in dry CH2Cl2 (650 mL) was added dropwise to
a solution of 13a (3.15 g, 10 mmol) in dry CH2Cl2 (150 mL) at ꢁ5 to
ꢁ10 ꢂC during 2.5 h under argon. After stirring for additional 4 h,
the precipitate appeared in the reaction mixture was separated by
filtration. Additional product was obtained after the concentration
of the filtrate. The combined solid was recrystallized from CHCl3 to
give 14 (2.46 g, 83%); mp 227e229 ꢂC; 1H NMR (500 MHz, DMSO-
d6): 8.32 (1H, m, ArH), 8.27 (1H, m, ArH), 7.80 (2H, m, 2ꢃ ArH), 7.33
(1H, m, ArH), 7.16 (1H, s, ArH), 6.92 (1H, m, ArH), 4.72 (2H, t,
J¼7.5 Hz, CH2), 3.97 (3H, s, OMe), 2.83 (2H, t, J¼7.5 Hz, CH2). Anal.
Calcd for C17H15NO4$H2O: C, 64.75; H, 5.43; N, 4.44; found: C, 64.51;
H, 5.32; N, 4.41.
4.8. 1,2,3,5-Tetramethoxy-10H-acridin-9-one (20a)
A mixture of 19a (10 g, 30 mmol) and POCl3 (30 mL) containing 4
drop of DMF was heated at 40 ꢂC for 1 h. The reaction mixture was
evaporated in vacuo to dryness and the residue was dissolved in
CHCl3 (50 mL). 5% aqueous solution of HCl (40 mL) was added
slowly in the CHCl3 solution with stirring and then diluted with
EtOH (400 mL). After being stirred at room temperature for over-
night, the mixture was concentrated and the solid was collected by
filtration. The solid product was purified by column chromatogra-
phy (SiO2, CHCl3/MeOH 10:1) to give 20a, 6.35 g (67%); mp
93e94 ꢂC; 1H NMR (500 MHz, DMSO-d6): 10.08 (1H, br s, NH), 7.73
(1H, m, ArH), 7.35 (1H, s, ArH), 7.24 (1H, m, ArH), 7.12 (1H, m, ArH),
4.02, 3.82, 3.90, and 3.75 (each 3H, s, 4ꢃ OCH3). Anal. Calcd for
C17H17NO5$HCl$1.5H2O: C, 53.90; H, 5.59; N, 3.70; found: C, 53.45;
H, 5.61; N, 3.73.
4.6. 2-Iodo-3-methoxybenzoic acid (18a)29
To a suspension of 3-methoxy-2-amino-benzoic acid (17a,
20.06 g, 120 mmol) in a mixture of ice-water (300 mL), acetone
(100 mL), and HCl (57.6 mL, 720 mmol) was added dropwise a so-
lution of NaNO2 (16.6 g, 240 mmol) in water (120 mL) over 1 h at
7e10 ꢂC (interior temperature). After being stirred for 2 h, the solid
KI (39.84 g, 240 mmol) was added directly during 5 min and kept
the temperature at 7e10 ꢂC for additional 30 min. The reaction
mixture was heated at 80e90 ꢂC until purple gas disappear and
then cooled to room temperature. The inorganic solid was removed
by filtration and the filtrate was concentrated under reduced
pressure to remove acetone. The aqueous solution was extracted
with CHCl3 (200 mLꢃ5), and the organic layer was combined and
washed with water (100 mLꢃ2), dried over Na2SO4, and evaporated
to dryness. The residue was crystallized from MeOH to give 18a,
29.9 g (90%), mp 148e149 ꢂC (MeOH) (lit.30 146.5e149.5 ꢂC); 1H
NMR (500 MHz, DMSO-d6): 13.26 (1H, br s, COOH), 7.48 (1H, m,
ArH), 7.11 (2H, t, J¼8.5 Hz, 2ꢃ ArH), 3.86 (3H, s, OMe).
4.8.1. 6-Benzyloxy-1,2,3,5-tetramethoxy-10H-acridin-9-one (20b). A
mixture of 19b (13.18 g, 30 mmol) in POCl3 (30 mL) containing 3-
drops of DMF was heated at 60 ꢂC for 1 h. After cooling, the mix-
ture was evaporated in vacuo to dryness and the residue was dis-
solved in MeOH (500 mL) containing 5% HCl (40 mL) and then
stirred at 40 ꢂC for overnight. The reaction mixture was concen-
trated to 100 mL and the solid appeared was collected by filtration.
The solid was recrystallized from EtOH to give 20b (10.4 g, 82%); mp
227e228 ꢂC; 1H NMR (500 MHz, DMSO-d6): 10.71 (1H, s, NH), 7.86
(1H, d, J¼9.0 Hz, ArH), 7.51e7.52 (2H, m, ArH), 7.41e7.44 (2H, m,
ArH), 7.36e7.37 (1H, m, ArH), 7.28 (1H, s, ArH), 7.10 (1H, d, J¼9.0 Hz,
ArH), 5.29 (2H, s, CH2), 3.89, 3.72, 3.79, and 3.70 (each 3H, s, OMe).
Anal. Calcd for C24H23NO6: C, 68.40; H, 5.50; N, 3.32; found: C,
68.43; H, 5.48; N, 3.31.
4.6.1. 4-Benzyloxy-2-iodo-3-methoxybenzoic acid (18b). By follow-
ing the same procedure as that for the synthesis of 18a, compound
18b was prepared from 4-benzyloxy-3-methoxyanthranilic acid
18b (41 g, 150 mmol),6 sodium nitrite (300 mL, 300 mmol), and KI
(49.7 g, 300 mmol). Yield, 49 g (94%), mp 191e192 ꢂC; 1H NMR
(500 MHz, CDCl3): 7.48e7.51 (3H, m, 3ꢃ ArH), 7.41e7.44 (2H, m, 2ꢃ
ArH), 7.34e7.36 (1H, m, ArH), 7.21 (1H, m, ArH), 5.23 (2H, s, CH2),
3.72 (3H, s, OMe). Anal. Calcd for C15H13O4I: C, 46.90; H, 3.41, found:
C, 46.76; H, 3.49.
4.9.. 3-(1,2,3,5-Tetramethoxy-9-oxo-9H-acridin-10-yl)acrylic
4.7. 3-Methoxy-2-(3,4,5-trimethoxyphenylamino)benzoic
acid (19a)
acid (22a)
To a mixture of 20a (3.15 g, 10 mmol) and K2CO3 (2.76 g,
20 mmol) in DMF (30 mL) was added dropwise ethyl propiolate
(2.04 mL, 20 mmol) in an ice bath under argon atmosphere over
30 min. A reaction mixture was stirred at room temperature for
overnight. The reaction was not complete. Additional K2CO3 (2.76 g,
20 mmol) and ethyl propiolate (2.04 mL, 20 mmol) were added into
A mixture of 18a (22.25 g, 80 mmol), 3,4,5-trimethoxyaniline
(9b, 21.98 g, 120 mmol), Cu (0.51 g, 8 mmol), CuI (1.52 g,
8 mmol), and potassium carbonate (33.17 g, 240 mmol) in DMF
(500 mL) was stirred and heated at 40e50 ꢂC for overnight. The
solvent was removed in vacuo and the residue was dissolved in

C.-H. Chen et al. / Tetrahedron 67 (2011) 5883e5893
5889
the reaction mixture per day (total 6 days). The solvent was re-
moved under reduced pressure and the residue was dissolved in
EtOH (250 mL), followed with addition of 2 N NaOH aqueous so-
lution (10 mL) and stirred at room temperature for 1.5 h. The re-
action mixture was acidified with acetic acid to pH 5e6. The solvent
was removed under reduced pressure and the residue was crys-
tallized from EtOH to give trans-22a (1.82 g). The mother liquid was
concentrated and the residue [containing two product with Rf
values of 0.41 and 0.21 by monitoring with thin-layer chromatog-
raphy, TLC: SiO2, CHCl3/MeOH (5:1 v/v)] was chromatographed on
a silica gel column (2ꢃ30 cm) using CHCl3/MeOH (5:1 v/v) as the
eluant. Additional trans-22a, 0.18 g (total 2.0 g, 51%) was eluted first,
followed with a mixture of trans- and cis-22a, 95 mg (2.4%).
Compound trans-22a: mp 194e196 ꢂC (EtOH); 1H NMR
(500 MHz DMSO-d6): 11.90 (1H, br s, COOH), 8.12 (1H, d, J¼14.0 Hz,
]CH), 7.62 (1H, s, ArH), 7.47 (1H, s, ArH), 7.46 (1H, m, ArH), 7.34
(1H, s, ArH), 5.23 (1H, d, J¼14.0 Hz, ]CH), 3.98 (6H, s, 2ꢃ OMe),
3.87 (3H, s, OMe), 3.78 (3H, s, OMe); 13C NMR (500 MHz, DMSO-d6)
m, ArH), 7.32e7.33 (1H, m, ArH), 7.20e7.23 (1H, m, ArH), 7.09 (1H, s,
ArH), 4.56 (2H, t; J¼8.3 Hz, CH2), 3.96 (3H, s, OMe), 3.93 (3H, s, OMe),
3.80 (3H, s, OMe), 3.74 (3H, s, OMe), 2.64 (2H, t, J¼8.3 Hz, CH2); 13
C
NMR (500 MHz, DMSO-d6) (d, ppm): 175.4, 172.8, 157.6, 152.8, 149.5,
143.5,137.5,133.4,127.0,122.3,117.8,115.1,112.1, 95.1, 61.4, 60.9, 56.5,
56.1, 48.5, 34.3; HRMS (ESI) m/z: calcd for MþHþ C20H21NO7:
388.1391; found: 388.1378. Anal. Calcd for C20H21NO7$H2O: C, 59.40;
H, 5.48; N, 3.46; found: C, 59.62; H, 5.55; N, 3.56.
4.10.1. 3-(6-Hydroxy-1,2,3,5-tetramethoxy-9-oxo-9H-acridin-10-yl)
propionic acid (23b). By following the same procedure as that for
the synthesis of 23a, compound 23b was prepared from 22b (4.90 g,
10 mmol) and Pd/C (0.49 g). Yield, 1.5 g (37%), mp 234e235 ꢂC; 1H
NMR (500 MHz, CDCl3): 7.75 (1H, d, J¼8.0 Hz, ArH), 7.23 (1H, s,
ArH), 6.85 (1H, d, J¼8.0 Hz, ArH), 4.56 (1H, br s, CH2), 3.95 (3H, s,
OMe), 3.79 (3H, s, OMe), 3.76 (3H, s, OMe), 3.73 (3H, s, OMe), 2.41
(3H, br s, CH2); 13C NMR (500 MHz, DMSO-d6) (
d, ppm): 175.0,172.6,
157.2, 154.7, 153.0, 143.2, 137.6, 137.4, 135.7, 122.3, 120.2, 112.5, 112.2,
95.6, 61.4, 60.9, 60.2, 56.1, 47.2 33.3; HRMS (ESI) m/z: calcd for
MþHþ C20H21NO8: 404.1340; found: 404.1320. Anal. Calcd for
C20H21NO8$0.5H2O: C, 58.25; H, 5.38; N, 3.40; found: C, 58.32; H,
5.35; N, 3.46.
(d, ppm): 175.4, 164.6, 157.0, 152.8, 148.6, 142.0, 141.8, 137.5, 133.0,
125.6, 121.9, 118.0, 116.0, 110.9, 95.0, 61.4, 60.9, 56.7, 56.0; HRMS
(ESI) m/z: calcd for MþHþ C20H19NO7: 386.1234; found: 386.1224.
Anal. Calcd for C20H19NO7$0.5H2O: C, 60.91; H, 5.11; N, 3.55; found:
C, 60.52; H, 5.00; N, 3.21.
Compound cis-22a: 1H NMR (500 MHz, DMSO-d6): 11.90 (1H, br
s, COOH), 8.12 (1H, d, J¼8.4 Hz, ]CH), 7.62 (1H, s, ArH), 7.47 (1H, s,
ArH), 7.46 (1H, m, ArH), 7.34 (1H, s, ArH), 6.03 (1H, d, J¼8.4 Hz, ]
CH), 3.97 and 3.98 (each 3H, 2ꢃ OMe), 3.78 (3H, s, OMe), 3.87 (3H, s,
OMe). Anal. Calcd for C20H19NO7$0.5H2O: C, 60.91; H, 5.11; N, 3.55;
found: C, 60.52; H, 5.00; N, 3.21.
4.10.2. 3-(6-Acetoxy-1,2,3,5-tetramethoxy-9-oxo-9H-acridin-10-yl)-
propionic acid (23c). To a solution of 23b (6.05 g, 15 mmol) in 1 N
NaOH (45 mL) was added dropwise Ac2O (2.3 g, 22.5 mmol) at room
temperature. The reaction mixture was stirred at room tempera-
ture for overnight. The reaction mixture was acidified with acetic
acid to pH 5e6 and extracted with CHCl3 (30 mLꢃ3). The combined
extract was concentrated under reduced pressure and the residue
was chromatographed on a silica gel column (6ꢃ40 cm) using
CHCl3/MeOH (20:1 v/v) as the eluant. The fractions containing main
product were combined and concentrated in vacuo. The product
was crystallized from EtOH to give 23c (3.47 g, 55%); mp
210e211 ꢂC; 1H NMR (500 MHz, CDCl3): 12.29 (1H, br s, COOH), 7.91
(1H, d, J¼9.0 Hz, ArH), 7.11 (1H, d, J¼9.0 Hz, ArH), 7.03 (1H, s, ArH),
4.71 (1H, t, J¼6.5 Hz, CH2), 3.99 (3H, s, OMe), 3.80 (3H, s, OMe), 3.77
(3H, s, OMe), 3.75 (3H, s, OMe), 2.59 (2H, t, J¼6.5 Hz, CH2), 2.38 (3H,
4.9.1. 3-(6-Benzyloxy-1,2,3,5-tetramethoxy-9-oxo-9H-acridin-10-yl)
acrylic acid (22b). By following the same procedure as that for the
synthesis of 22a, compound 22b was prepared from 20b (16.85 g,
40 mmol) and ethyl propiolate (7.8 g, 80 mmol). The reaction was
complete in 3 days. The solid residue contained a mixture of trans-
and cis-isomer (total yield, 19.2 g, 98%), which were difficult to be
separated by column chromatography. However, a small amount of
trans- and cis-isomer were isolated for structural determination.
Compound trans-22b: mp 175e176; 1H NMR (500 MHz, CDCl3):
12.32 (1H, br s, COOH), 8.11 (1H, d, J¼14.0 Hz, CH), 7.78 (1H, d,
J¼9.0 Hz, ArH), 7.52e7.56 (2H, m, ArH), 7.42e7.45 (2H, m, ArH),
7.34e7.38 (1H, m, ArH), 7.33 (1H, d, J¼9.0 Hz, ArH), 7.31 (1H, s, ArH),
5.45 (1H, d, J¼14.0 Hz, ]CH), 5.31 (2H, s, CH2), 3.97 (3H, s, OMe), 3.85
(3H, s, OMe), 3.80 (3H, s, OMe), 3.77 (3H, s, OMe). Anal. Calcd for
C27H25NO8: C, 65.98; H, 5.13; N, 2.85; found: C, 65.79; H, 5.15; N, 2.75.
Compound cis-22b: 1H NMR (500 MHz, CDCl3): 12.32 (1H, br s,
COOH), 7.94 (1H, d, J¼8.0 Hz, CH), 7.69 (1H, d, J¼9.0 Hz, ArH),
7.51e7.53 (2H, m, ArH), 7.41e7.44 (2H, m, ArH), 7.36e7.37 (1H, m,
ArH), 7.18 (1H, d, J¼9.0 Hz, ArH), 6.82 (1H, s, ArH), 6.18 (1H, d,
J¼8.0 Hz, ]CH), 5.27 (2H, s, CH2), 3.88 (3H, s, OMe), 3.82 (3H, s,
OMe), 3.74 (3H, s, OMe), 3.69 (3H, s, OMe); 13C NMR (500 MHz,
s, OAc); 13C NMR (500 MHz, DMSO-d6) (
d, ppm): 175.0, 172.4, 168.6,
157.7, 152.9, 147.2, 143.3, 141.4, 137.8, 137.1, 125.4, 121.7, 117.6, 112.5,
95.9, 61.4, 61.0, 60.9, 56.2, 46.8, 33.0, 20.6; HRMS (ESI) m/z: calcd for
MþHþ C22H23NO9: 446.1446; found: 446.1416. Anal. Calcd for
C22H23NO9$0.5H2O: C, 58.15; H, 5.32; N, 3.08; found: C, 58.36; H,
5.43; N, 2.98.
4.11. 6-Methoxy-1,2-dihydropyrido[3,2,1-de]acridine-3,7-
dione (15a)
To a solution of Eaton’s reagent [freshly prepared from P2O5
(5.5 g, 39 mmol) and methanesulfonic acid (55 g)] was added
dropwise a solution of 13a (3.89 g,13 mmol) in dry CH2Cl2 (100 mL).
The reaction mixture was stirred for overnight at room tempera-
ture. The mixture was poured onto ice and then basified with sat-
urated NaHCO3 aqueous solution followed with NH4OH. The
organic layer was separated and the aqueous layer was extracted
with CHCl3 (100 mLꢃ5). The combined organic extract was washed
with water (100 mLꢃ2), dried over Na2SO4, and evaporated to
dryness. The product was purified by column chromatography
(SiO2, CHCl3/MeOH, 80:1 v/v) and was crystallized from EtOH to
give 15a, 2.07 g (57%); mp 235e236 ꢂC; 1H NMR (500 MHz, DMSO-
d6): 8.49 (1H, d, J¼9.1 Hz, ArH), 8.31 (1H, m, ArH), 7.80e7.82 (2H, m,
ArH), 7.39 (1H, m, ArH), 7.16 (1H, d, J¼9.1 Hz, ArH), 4.59 (2H, t,
J¼7.1 Hz, CH2), 3.97 (3H, s, OMe), 2.94 (2H, t, J¼7.1 Hz, CH2); 13C
DMSO-d6) (d, ppm): 174.8, 164.5, 156.8, 155.1, 153.1, 142.4, 141.8,
137.4, 136.7, 136.6, 135.8, 128.6, 128.1, 127.8, 122.2, 119.9, 119.2, 110.4,
108.9þ, 94.8, 70.3, 61.5, 60.9, 59.8, 56.0; HRMS (ESI) m/z: calcd for
MþH C27H25NO8: 492.1653; found: 492.1614.
4.10. 3-(1,2,3,5-Tetramethoxy-9-oxo-9H-acridin-10-yl)
propionic acid (23a)
A suspension of 22a (1.93 g, 5 mmol) and Pd/C 10% (0.58 g) in
MeOH (300 mL) containing aceticacid (3 drops) was hydrogenated at
30e35 psi for 2 days. The reaction mixture was filtered through a pad
of Celite, and washed with MeOH. The combined filtrate and wash-
ings were concentrated and the product was purified by column
chromatography (SiO2, CHCl3/MeOH 100:1 v/v) to give 23a (840 mg,
43%); mp 210e211 ꢂC; 1H NMR (500 MHz, DMSO-d6): 7.75e7.77 (1H,
NMR (500 MHz, DMSO-d6) (d, ppm): 190.2, 175.3, 163.7, 144.5, 141.7,
134.2, 134.0, 126.3, 122.1, 121.6, 115.7, 115.2, 109.2, 107.1, 56.5, 43.4,
37.6; HRMS (ESI) m/z: calcd for MþHþ C17H13NO3: 280.0968; found:

5890
C.-H. Chen et al. / Tetrahedron 67 (2011) 5883e5893
280.0962. Anal. Calcd for C17H13NO3: C, 70.82; H, 4.89; N, 4.86;
found: C, 71.03; H, 4.86; N, 4.82.
By following the same procedure as that for the synthesis of 15a,
the following compounds were prepared:
washed with water (200 mLꢃ2), dried with Na2SO4, and evapo-
rated to dryness. The residue was crystallized from ethanol/hexane
to give 25a (1.24 g, 73%) as a mixture of enantiomeric isomers (1:1);
mp 224e225 ꢂC; 1H NMR (500 MHz, CDCl3): 8.29e8.33 (2H, m, 2ꢃ
ArH), 7.84 (1H, m, ArH), 7.78e7.80 (1H, m, ArH), 7.30e7.33 (1H, m,
ArH), 7.11 (1H, d, J¼8.9 Hz, ArH), 5.19 (1H, d, J¼3.8 Hz, CH), 5.11 (1H,
d, J¼3.8 Hz, OH, exchangeable), 4.46e4.48 (1H, m, 1/2ꢃ CH2),
4.04e4.09 (1H, m, 1/2ꢃ CH2), 3.96 (3H, s, OMe), 2.24e2.26 (1H, m,
1/2ꢃ CH2), 1.92e1.96 (1H, m, 1/2ꢃ CH2); 13C NMR (500 MHz,
4.11.1. 4,5,6-Trimethoxy-1,2-dihydropyrido[3,2,1-de]acridin-3,7-
dione (15b). Compound 15b was prepared from 13b (15 g, 40 mmol)
and Eaton’s reagent [freshly prepared from P2O5 (34 g, 240 mmol) in
340 mL of TsOH]. Yield, 4.86 g (36%); mp 156e157 ꢂC (EtOH); 1H NMR
(500 MHz, CDCl3): 8.46 (1H, m, ArH), 7.71 (1H, m, ArH), 7.48 (1H, m,
ArH), 7.33 (1H, m, ArH), 4.46 (2H, t, J¼6.9 Hz, CH2), 4.13 (3H, s, OMe),
DMSO-d6) (d, ppm): 176.1, 156.9, 151.3, 141.1, 139.8, 137.5, 131.2,
122.2, 121.9, 120.1, 116.7, 112.8, 107.9, 65.1, 57.6, 42.7, 29.5; HRMS
(ESI) m/z: calcd for MþHþ C22H21NO8: 282.1125; found: 282.1118.
Anal. Calcd for C17H15NO3$0.5H2O: C, 70.33; H, 5.55; N, 4.82; found:
C, 70.51; H, 5.47; N, 4.68.
By following the same procedure as that for the synthesis of 25a,
the following compounds were prepared:
4.10 (3H, s, OMe), 3.89 (3H, s, OMe), 2.98 (2H, t, J¼6.9 Hz, CH2); 13
C
NMR (500 MHz, DMSO-d6) (d, ppm): 190.1, 175.0, 159.4, 159.0, 142.4,
140.7, 140.6, 133.6, 126.3, 122.8, 122.0, 115.3, 112.5, 111.5, 62.3, 61.7,
61.4, 43.4, 37.4; HRMS (ESI) m/z: calcd for MþHþ C19H17NO5:
340.1179; found: 340.1176. Anal. Calcd for C19H17NO5: C, 67.25; H,
5.05; N, 4.13; found: C, 67.10; H, 5.11; N, 4.09.
4.12.1. (ꢀ)3-Hydroxy-4,5,6-trimethoxy-2,3-dihydro-1H-pyrido[3,2,1-
de]acridin-7-one (25b). Compound 25b was prepared from 15b
(2.04 g, 6 mmol) and NaBH4 (227 mg, 6 mmol). Yield, 1.74 g (84%);
mp 160e161 ꢂC (EtOH/hexane); 1H NMR (500 MHz, CDCl3): 8.48
(1H, m, ArH), 7.66 (1H, m, ArH), 7.50 (1H, m, ArH), 7.25e7.28 (1H, m,
ArH), 5.30 (1H, s, CH), 4.37e4.39 (1H, m, 1/2ꢃ CH2), 4.09e4.14 (1H,
m,1/2ꢃ CH2), 4.15 (3H, s, OMe), 4.04 (3H, s, OMe), 3.93 (3H, s, OMe),
2.47 (1H, s, OH, exchangeable), 2.43 (1H, J¼2.7 and 14.0 Hz, 1/2ꢃ
CH2), 2.00e2.06 (1H, m, 1/2ꢃ CH2); 13C NMR (500 MHz, DMSO-d6)
4.11.2. 4,5,6,11-Tetramethoxy-1,2-dihydropyrido[3,2,1-de]acridine-
3,7-dione (24a). Compound 24a was prepared from 23a (1.94 g,
5 mmol) and Eaton’s reagent (P2O5, 2.1 g and TsOH 20 mL). Yield,
0.83 g (45%), mp 144e145 ꢂC; 1H NMR (500 MHz, CDCl3): 7.97 (1H,
m, ArH), 7.28 (1H, m, ArH), 7.19 (1H, m, ArH), 4.47 (2H, t, J¼6.0 Hz,
CH2), 4.13 (3H, s, OMe), 4.10 (3H, s, OMe), 4.01(3H, s, OMe), 3.90 (3H,
s, OMe), 3.04 (2H, t, J¼6.0 Hz, CH2); 13C NMR (500 MHz, DMSO-d6)
(d, ppm): 191.1, 175.6, 160.4, 158.4, 149.5, 145.7, 141.0, 132.4, 126.6,
123.2, 117.4, 115.5, 112.8, 112.2, 62.0, 61.6, 61.4, 56.8, 56.6, 48.5, 40.1;
HRMS (ESI) m/z: calcd for MþHþ C20H19NO6: 370.1285; found:
370.1276. Anal. Calcd for C20H19NO6: C, 65.03; H, 5.18; N, 3.79;
found: C, 64.82; H, 5.16; N, 3.70.
(d, ppm): 175.3, 155.5, 153.7, 141.1, 140.3, 136.6, 133.3, 126.2, 122.4,
121.2, 116.2, 114.8, 113.2, 61.7, 61.5, 61.2, 56.7, 40.1, 28.2; HRMS (ESI)
m/z: calcd for MþHþ C19H19NO5: 342.1336; found: 342.1328. Anal.
Calcd for C19H19NO5: C, 66.85; H, 5.61; N, 4.10; found: C, 66.68; H,
5.68; N, 4.06.
4.11.3. 10-O-Acetyl-4,5,6,11-tetramethoxy-1,2-dihydropyrido[3,2,1-
de]acridine-3,7-dione (24b) and 10-hydroxy-4,5,6,11-tetramethoxy-
1,2-dihydropyrido[3,2,1-de]acridine-3,7-dione (24c). Compound 24b
was prepared from 23c (0.64 g, 1.5 mmol) and Eaton’s reagent
[freshly prepared from P2O5 (638 mg, 4.5 mmol) in TsOH (6.3 mL)].
Two products, 24b and 24c, were separated by column chroma-
tography (SiO2, CHCl3/MeOH, 100:2 v/v):
4.12.2. (ꢀ)3-Hydroxy-4,5,6,11-tetramethoxy-2,3-dihydro-1H-pyrido
[3,2,1-de]acridin-7-one (25c). Compound 25c was prepared from
24a (554 mg, 1.5 mmol) and NaBH4 (55 mg, 1.5 mmol). Yield, 0.5 g
(89%), mp 159e160 ꢂC; 1H NMR (500 MHz, CDCl3): 8.03e8.05 (1H,
m, ArH), 7.19e7.21 (1H, m, ArH), 7.15e7.16 (1H, m, ArH), 5.17 (1H, s,
CH), 4.83e4.86 (1H, m, 1/2ꢃ CH2), 4.15 (3H, s, OMe), 4.04 (3H, s,
OMe), 3.99e4.04 (1H, m, 1/2ꢃ CH2), 3.95 (3H, s, OMe), 3.93 (3H, s,
OMe), 2.80 (1H, s, OH), 2.31e2.37 (1H, m, 1/2ꢃ CH2), 2.15e2.20 (1H,
Compound 24b: yield, 181 mg (31%), mp 208e209 ꢂC; 1H NMR
(500 MHz, CDCl3): 8.14 (1H, d, J¼9.0 Hz, ArH), 7.01 (1H, d, J¼9.0 Hz,
ArH), 6.37 (1H, br s, OH), 4.62 (2H, t, J¼6.5 Hz, CH2), 4.12 (3H, s,
OMe), 4.10 (3H, s, OMe), 3.90 (3H, s, OMe), 3.89 (3H, s, OMe), 3.08
m, 1/2ꢃ CH2); 13C NMR (500 MHz, DMSO-d6) (
d, ppm): 175.5, 155.8,
153.1, 149.7, 140.3, 137.9, 133.3, 126.1, 122.2, 117.8, 116.7, 116.1, 113.0,
61.7, 61.4, 61.1, 57.5, 56.9, 44.0, 30.2; HRMS (ESI) m/z: calcd for
MþHþ C20H21NO6: 372.1442; found: 372.1425. Anal. Calcd for
C20H21NO6$0.5H2O: C, 63.15; H, 5.82; N, 3.68; found: C, 63.68; H,
5.74; N, 3.67.
(2H, t, J¼6.5 Hz, CH2); 13C NMR (500 MHz, DMSO-d6) (
d, ppm):
191.1, 174.8, 160.0, 158.6, 155.5, 145.6, 141.1, 136.9, 135.6, 122.5, 119.4,
113.3, 112.7, 112.3, 62.0, 61.7, 61.4, 60.6, 48.2; HRMS (ESI) m/z: calcd
for MþHþ C20H19NO7: 386.1234; found: 386.1223. Anal. Calcd for
C20H19NO7: C, 62.33; H, 4.97; N, 3.63; found: C, 62.10; H, 5.03; N,
3.67.
4.12.3. (ꢀ)3,10-Dihydroxy-4,5,6,11-tetramethoxy-2,3-dihydro-1H-
pyrido[3,2,1-de]acridin-7-one (25d). Compound (ꢀ)25d was pre-
pared from 24b (0.19 g, 0.5 mmol) and NaBH4 (18.9 mg, 0.5 mmol).
Yield, 0.16 g (83%), mp 220e221 ꢂC; 1H NMR (500 MHz, CDCl3): 8.19
(1H, d, J¼9.0 Hz, ArH), 6.95 (1H, d, J¼9.0 Hz, ArH), 6.31 (1H, s, OH),
5.20 (1H, s, CH), 4.90e4.93 (1H, m, 1/2ꢃ CH2), 4.17 (3H, s, OMe),
4.09e4.16 (1H, m, 1/2ꢃ CH2), 4.04 (3H, s, OMe), 3.93 (3H, s, OMe),
3.77 (3H, s, OMe), 2.74 (1H, s, OH), 2.37e2.40 (1H, m, 1/2ꢃ CH2),
Compound 24c: yield, 132 mg (21%), mp 190e191 ꢂC (EtOH); 1H
NMR (500 MHz, CDCl3): 8.18 (1H, d, J¼9.0 Hz, ArH), 7.07 (1H, d,
J¼9.0 Hz, ArH), 4.60 (2H, t, J¼6.5 Hz, CH2), 4.13 (3H, s, OMe), 4.11
(3H, s, OMe), 3.90 (3H, s, OMe), 3.87 (3H, s, OMe), 3.04 (2H, t,
J¼6.5 Hz, CH2), 2.41 (3H, s, OAc); 13C NMR (500 MHz, DMSO-d6) (
d,
ppm): 190.8, 175.0, 168.5, 160.5, 158.5, 148.0, 145.6, 141.4, 141.3,
136.5,124.6,122.0,118.4,112.8,112.4, 63.0, 61.8, 61.7, 61.4, 48.1, 20.5;
HRMS (ESI) m/z: calcd for MþHþ C22H21NO8: 428.1340; found:
428.1326. Anal. Calcd for C22H21NO8: C, 61.82; H, 4.95; N, 3.28;
found: C, 61.63; H, 4.89; N, 3.30.
2.16e2.19 (1H, m, 1/2ꢃ CH2); 13C NMR (500 MHz, DMSO-d6) (
d,
ppm): 174.8, 155.4, 155.3, 153.3, 140.2, 137.6, 137.2, 135.4, 122.5,
119.1, 116.7, 113.0, 112.4, 61.6, 61.4, 61.0, 60.8, 57.3, 43.0, 30.0; HRMS
(ESI) m/z: calcd for MþHþ C20H21NO7: 388.1391; found: 388.1373.
Anal. Calcd for C20H21NO7$0.5H2O: C, 60.60; H, 5.59; N, 3.53, found:
C, 60.93; H, 5.50; N, 3.46.
4.12. ( )3-Hydroxy-6-methoxy-2,3-dihydro-1H-pyrido[3,2,1-
de]acridin-7-one (25a)
To a solution of 15a (1.68 g, 6 mmol) in THF (100 mL) containing
H2O (5 mL) was added portionwise NaBH4 (0.23 g, 6 mmol) at 10 ꢂC
over 30 min. After being stirred at 10 ꢂC for 5 h, the solvent was
removed in vacuo and the residue was dissolved in EtOAc (200 mL),
4.12.4. (ꢀ)3-Acetyl-6-methoxy-2,3-dihydro-1H-pyrido[3,2,1-de]acri-
din-7-one (26a). A solution of (ꢀ)25a (100 mg, 0.35 mmol) in
a mixture of pyridine (2 mL) and acetic anhydride (2 mL) was
stirred at room temperature for overnight. MeOH (10 mL) was

C.-H. Chen et al. / Tetrahedron 67 (2011) 5883e5893
5891
added into the reaction mixture in an ice bath, and then evaporated
in vacuo to dryness. The residue was crystallized from ethanol to
give (ꢀ)26a, 84 mg (73%); mp 178e179 ꢂC; 1H NMR (500 MHz,
CDCl3): 8.59 (1H, d, J¼9.0 Hz, ArH), 8.56e8.58 (1H, m, ArH),
7.71e7.74 (1H, m, ArH), 7.55e7.57 (1H, m, ArH), 7.30e7.33 (1H, m,
ArH), 6.94 (1H, d, J¼8.9 Hz, ArH), 6.50 (1H, s, CH), 4.46e4.48 (1H, m,
1/2ꢃ CH2), 4.02e4.08 (1H, m, 1/2ꢃ CH2), 4.00 (3H, s, OMe),
2.57e2.60 (1H, m, 1/2ꢃ CH2), 2.16e2.19 (1H, m, 1ꢃ CH2), 2.12 (3H, s,
ppm): 175.3, 157.4, 141.2, 138.6, 133.8, 127.6, 126.4, 121.8, 115.0,
108.5, 107.3, 56.2, 47.6; HRMS (ESI) m/z: calcd for MþHþ C17H13NO2:
264.1019; found: 264.1013. Anal. Calcd for: C, 77.55; H, 4.98; N, 5.32;
found: C, 77.40; H, 4.81; N, 5.12.
By following the same procedure as that for the synthesis of 28a,
the following compounds were prepared:
4.13.1. 4,5,6-Trimethoxy-1H-pyrido[3,2,1-de]acridin-7-one
(28b). Compound 28b was prepared from 25b (1.7 g, 5 mmol),
methanesulfonic anhydride (1.74 g, 10 mmol), and triethylamine
(1.65 ml, 12 mmol). Yield, 1.1 g (70%); mp 184e185 ꢂC (EtOAc/
hexane); 1H NMR (500 MHz, CDCl3): 8.57 (1H, m, ArH), 7.71 (1H, m,
ArH), 7.33 (2H, m, 2ꢃ ArH), 6.89 (1H, m, ]CH), 5.59 (1H, m, ]CH),
5.04 (2H, m, CH2), 4.02 (3H, s, OMe), 4.00 (3H, s, OMe), 3.93 (3H, s,
COOMe); 13C NMR (500 MHz, DMSO-d6) (
d, ppm): 175.6, 169.7,
161.0, 141.9, 139.8, 133.9, 129.7, 126.4, 121.5, 121.3, 115.7, 115.0, 108.3,
106.4, 60.8, 56.5, 25.3, 21.0; HRMS (ESI) m/z: calcd for MþHþ
C19H17NO4: 324.1230; found: 324.1223. Anal. Calcd for
C19H17NO4$0.5H2O: C, 68.66; H, 5.46; N, 4.21, found: C, 68.70; H,
5.46; N, 4.15.
OMe); 13C NMR (500 MHz, DMSO-d6) (
d, ppm): 174.6, 153.0, 152.5,
4.12.5. (ꢀ)3-Acetyl-4,5,6-trimethoxy-2,3-dihydro-1H-pyrido[3,2,1-
de]acridin-7-one (26b). By following the same procedure, com-
pound 26b was prepared from (ꢀ)25b (1.37 g, 4 mmol) and Ac2O/
pyridine (each 6 mL). Yield, 1.4 g (95%); mp 157e158 ꢂC (EtOH); 1H
NMR (500 MHz, CDCl3): 8.53e8.55 (1H, m, ArH), 7.70e7.73 (1H, m,
ArH), 7.52e7.54 (1H, m, ArH), 7.31e7.34 (1H, m, ArH), 6.48 (1H, s,
CH), 4.43e4.45 (1H, m, 1/2ꢃ CH2), 4.09 (6H, s, 2ꢃ OMe), 4.00e4.04
(1H, m, 1/2ꢃ CH2), 3.97 (3H, s, OMe), 2.57e2.60 (1H, m, 1/2ꢃ CH2),
2.17e2.20 (1H, m, 1/2ꢃ CH2), 2.14 (3H, s, COOMe); 13C NMR
140.6, 140.2, 136.2, 133.4, 126.4, 122.9, 121.7, 121.6, 117.1, 114.7, 112.8,
111.0, 61.5, 61.4, 61.1, 47.9; HRMS (ESI) m/z: calcd for MþHþ
C19H17NO4: 324.1230; found: 324.1223. Anal. Calcd for C19H17NO4:
C, 70.58; H, 5.30; N, 4.33; found: C, 70.33; H, 5.31; N, 4.25.
4.13.2. 4,5,6,11-Tetramethoxy-1H-pyrido[3,2,1-de]acridin-7-one
(28c). Compound 28c was prepared from 25c (0.45 g, 1.2 mmol),
pyridine (20 mL), methanesulfonic anhydride (0.42 g, 2.4 mmol),
and DMAP (catalytic amount). The crude product was not stable
during purification by column chromatography and was used di-
rectly for the next reaction. However, a small amount of pure 28c
was isolated for NMR analysis; 1H NMR (500 MHz, CDCl3):
8.04e8.05 (1H, m, ArH), 7.23e7.27 (1H, m, ArH), 7.17e7.18 (1H, m,
ArH), 6.97 (1H, d, J¼9.5 Hz, m, ]CH), 6.19 (1H, t, J¼4.5 and 9.5 Hz, ]
CH), 4.87 (2H, dd, J¼1.0 and 4.5 Hz, CH2), 4.04 (3H, s, OMe), 4.02
(3H, s, OMe), 4.01 (3H, s, OMe), 3.94 (3H, s, OMe).
(500 MHz, DMSO-d6) (d, ppm): 175.1, 169.5, 155.9, 155.2, 140.9,
140.1, 137.2, 133.4, 126.3, 122.5, 121.4, 114.6, 113.0, 110.6, 61.5, 61.4,
61.3, 61.2, 39.9, 25.3, 21.0; HRMS (ESI) m/z: calcd for MþHþ
C21H21NO6: 384.1442; found: 384.1431. Anal. Calcd for
C21H21NO6$1.5H2O: C, 65.79; H, 5.52; N, 3.65, found: C, 65.88; H,
5.50; N, 3.58.
4.12.6. 4,5,6-Trimethoxy-7-oxo-1,2,3,7-tetrahydropyrido[3,2,1-de]ac-
ridin-3-yl methylcarbamate (27). To a solution of (ꢀ)25b (683 mg,
2 mmol) and triethylamine (1.4 mL, 10 mmol) in CHCl3 (10 mL) was
slowly added methylisocyanate (570 mg, 10 mmol). The mixture
was stirred for overnight at room temperature and then evaporated
in vacuo to dryness. The solid residue was recrystallized from
EtOAc/hexane to give 27, 672 mg (85%); mp 184e185 ꢂC. 1H NMR
(500 MHz, CDCl3): 8.49e8.50 (1H, m, ArH), 7.65e7.68 (1H, m, ArH),
7.47e7.48 (1H, m, ArH), 7.26e7.29 (1H, m, ArH), 6.32 (1H, s, CH),
4.72 and 4.73 (each 1H, s, NH, exchangeable), 4.36e4.38 (1H, m, 1/
2ꢃ CH2), 4.05 (6H, s, 2ꢃ OMe), 3.94e3.99 (1H, m, 1/2ꢃ CH2), 3.93
(3H, s, OMe), 2.86e2.87 (3H, m, NMe), 2.63e2.66 (1H, m,1/2ꢃ CH2),
4.13.3. 10-Hydroxy-4,5,6,11-tetramethoxy-1H-pyrido[3,2,1-de]acri-
din-7-one (28d). Compound 28d was prepared from 25d (129 mg,
0.33 mmol), pyridine (0.97 mL, 12 mL), methanesulfonic anhydride
(418 mg, 2.4 mmol), and DMAP (catalytic amount). The crude
product 28d was not stable during the purification and was used
directly for the next reaction. A small amount of pure compound
was used for NMR analysis; 1H NMR (500 MHz, CDCl3): 8.14 (1H, d,
J¼9.0 Hz, ArH), 6.98 (1H, dd, J¼1.5 and 9.5 Hz, ]CH), 6.95 (1H, d,
J¼9.0 Hz, ArH), 6.36 (1H, br, OH), 6.20 (1H, dd, J¼4.5 and 9.5 Hz, ]
CH), 4.84 (2H, dd, J¼1.5 and 4.5 Hz, CH2), 4.03 (6H, s, 2ꢃ OMe), 3.93
(3H, s, OMe), 3.88 (3H, s, OMe).
2.06e2.10 (1H, m, 1/2ꢃ CH2); 13C NMR (500 MHz, DMSO-d6) (
d,
ppm): 175.2, 155.9, 155.8, 154.9, 141.0, 140.2, 137.1, 133.5, 126.3,
122.5, 121.5, 114.7, 113.1, 111.5, 61.6, 61.5, 61.2, 61.1, 40.2, 26.9, 25.7;
HRMS (ESI) m/z: calcd for MþHþ C21H22N2O6: 399.1551; found:
399.1541. Anal. Calcd for C21H22N2O6: C, 63.31; H, 5.57; N, 7.03,
found: C, 63.10; H, 5.56; N, 6.99.
4.14. 2,3-Dihydroxy-6-methoxy-2,3-dihydro-1H-pyrido[3,2,1-
de]acridin-7-one (29a)
A mixture of 28a (395 mg, 1.5 mmol), OsO4 (catalytic amount),
and 4-methylmorpholine-N-oxide (4.8 N, 0.33 mL, 1.6 mmol) in
a mixture of THF (40 mL) and H2O (8 mL) was stirred at room
temperature for overnight. HCl (2% aqueous solution) was added
dropwise into the reaction mixture and then quenched with 15%
NaHSO3. The solvent was evaporated under reduced pressure to
dryness and the solid residue was recrystallized from EtOH to give
29a, 0.39 g (88%); mp 235e236 ꢂC; 1H NMR (500 MHz, CDCl3):
8.30e8.31 (1H, m, ArH), 8.30 (1H, J¼8.9 Hz, ArH), 7.77e7.82 (2H, m,
2ꢃ ArH), 7.23e7.34 (1H, m, ArH), 7.13 (1H, J¼8.9 Hz, ArH), 5.38 (1H,
d, J¼5.6 Hz, OH, exchangeable), 5.19 (1H, d, J¼4.6 Hz, OH, ex-
changeable), 5.08 (1H, s, CH), 4.21 (1H, dd, J¼5.2 and 10.5 Hz, CH),
3.97 (3H, s, OMe), 3.93e4.15 (2H, m, CH2); 13C NMR (500 MHz,
4.13. 6-Methoxy-1H-pyrido[3,2,1-de]acridin-7-one (28a)
A mixture of (ꢀ)25a (1.1 g, 4 mmol) and methanesulfonic an-
hydride (418 mg, 2.4 mmol) in pyridine (0.97 mL, 12 mL) containing
a catalytic amount of dimethylaminopyridine (DMAP) was heated
at 110 ꢂC under argon. After being stirred for 5 h, the reaction
mixture was cooled down to room temperature and then poured
into ice water (150 mL). The crude solid product was collected by
filtration, washed with water, and dried. The crude product was
purified by column chromatography (SiO2, hexane/CHCl3 1:9 v/v)
and recrystallized from EtOH to give 28a (525 mg, 50%); mp
199e200 ꢂC; 1H NMR (500 MHz, CDCl3): 8.59e8.60 (1H, m, ArH),
8.33 (1H, d, J¼9.1 Hz, ArH), 7.72e7.75 (1H, m, ArH), 7.33e7.35 (2H,
m, 2ꢃ ArH), 6.96 (1H, dt, J¼10.0 and 2.6 Hz, ]CH), 6.83 (1H, d,
J¼9.1 Hz, ArH), 5.92 (1H, dd, J¼10.0 and 3.6 Hz, ]CH), 5.06 (2H, t,
DMSO-d6) (d, ppm): 175.7, 160.7, 142.0, 139.0, 133.8, 128.4, 126.3,
121.3, 121.2, 115.8, 115.0, 113.2, 106.6, 65.8, 60.6, 56.2, 44.5; HRMS
(ESI) m/z: calcd for MþHþ C17H15NO4: 298.1074; found: 298.1067.
Anal. Calcd for C17H15NO4$H2O: C, 64.75; H, 5.43; N, 4.44; found: C,
64.56; H, 5.40; N, 4.28.
J¼2.6 Hz, CH2), 3.96 (3H, s, OMe); 13C NMR (500 MHz, DMSO-d6) (
d,

5892
C.-H. Chen et al. / Tetrahedron 67 (2011) 5883e5893
By following the same procedure as that for the synthesis of 29a,
the following compounds were prepared:
4.05 (1H, t, J¼11.0 Hz, 1/2ꢃ CH2), 3.94 (3H, s, OMe), 2.11 (3H, s, OAc),
2.07 (3H, s, OAc); 13C NMR (500 MHz, DMSO-d6) (
, ppm): 175.5,
d
169.7, 169.3, 161.4, 141.7, 139.6, 134.0, 130.4, 126.4, 121.8, 121.5, 115.6,
115.3, 106.7, 106.3, 66.4, 60.6, 56.6, 20.6; HRMS (ESI) m/z: calcd for
MþHþ C21H19NO6: 382.1285; found: 382.1277. Anal. Calcd for
C21H19NO6$0.5H2O: C, 64.61; H, 5.16; N, 3.59; found: C, 64.78; H,
5.23; N, 3.21.
4.14.1. (ꢀ)2,3-Dihydroxy-3,4,5-trimethoxy-2,3-dihydro-1H-pyrido
[3,2,1-de]acridin-7-one (29b). Compound (ꢀ)29b was prepared
from 28b (607 mg, 2 mmol), 4-methylmorpholine-N-oxide (4.8 N,
0.46 mL, 2.2 mmol), and OsO4 (catalytic amount). Yield, 0.59 g
(82%); mp 183e184 ꢂC (EtOAc/hexane); 1H NMR (500 MHz, CDCl3):
8.39e8.42 (1H, m, ArH), 7.60e7.63 (1H, m, ArH), 7.41e7.42 (1H, m,
ArH), 7.23e7.26 (1H, m, ArH), 5.27 (1H, m, CH), 4.30 (1H, dd, J¼11.1
and 5.3 Hz, 1/2ꢃ CH2), 4.14e4.19 (1H, m, 1/2ꢃ CH2), 4.15 (3H, s,
OMe), 4.00 (3H, s, OMe), 3.95 (1H, t, J¼11.1 Hz, 1/2ꢃ CH2), 3.91 (3H,
s, OMe), 3.31 (1H, d, J¼3.5 Hz, OH, exchangeable), 3.21 (1H, d,
By following the same procedure as that for the synthesis of (ꢀ)
30a, the following compounds were prepared:
4.15.1. (ꢀ)2,3-Diacetyl-4,5,6-trimethoxy-2,3-dihydro-1H-pyrido
[3,2,1-de]acridin-7-one (30b). Compound (ꢀ) 30b was prepared
from (ꢀ)29b (355 mg, 1.0 mmol), pyridine (3 mL), and acetic an-
hydride (3 mL). Yield, 0.39 g (90%); mp 177e178 ꢂC (EtOH); 1H NMR
(500 MHz, CDCl3): 8.49e8.50 (1H, m, ArH), 7.68e7.71 (1H, m, ArH),
7.43e7.46 (1H, m, ArH), 7.30e7.33 (1H, m, ArH), 6.75 (1H, d,
J¼1.2 Hz, CH), 5.35 (1H, m, CH), 4.34 (1H, dd, J¼5.7 and 11.0 Hz,1/2ꢃ
CH2), 4.04e4.08 (1H, dt, J¼6.5 and 11.0 Hz, 1/2ꢃ CH2), 4.06 (6H, s,
2ꢃ OMe), 3.92 (3H, s, OMe), 2.15 (3H, s, OAc), 2.13 (3H, s, OAc); 13C
J¼8.6 Hz, OH, exchangeable); 13C NMR (500 MHz, DMSO-d6) (
d,
ppm): 175.9, 155.7, 153.9, 141.0, 140.5, 136.4, 133.4, 126.3, 122.4,
121.2, 115.8, 114.7, 113.0, 65.4, 61.8, 61.5, 61.3, 61.1, 45.1; HRMS (ESI)
m/z: calcd for MþHþ C19H19NO6: 358.1285; found: 358.1274. Anal.
Calcd for C19H19NO6: C, 63.86; H, 5.36; N, 3.92; found: C, 63.61; H,
5.48; N, 3.85.
NMR (500 MHz, DMSO-d6) (d, ppm): 175.0, 169.5, 169.3, 156.1, 155.8,
4.14.2. (ꢀ)2,3,-Dihydroxy-4,5,6,11-tetramethoxy-2,3-dihydro-1H-
pyrido[3,2,1-de]acridin-7-one (29c). Compound (ꢀ)29c was pre-
pared from crude 28c (424 mg, 1.2 mmol), 4-methylmorpholine-N-
oxide (4.8 N, 0.5 mL, 2.4 mmol), and OsO4 (catalytic amount). Yield,
0.26 g (56%, calculated from 25c), mp 118e119 ꢂC; 1H NMR
(500 MHz, CDCl3): 8.01 (1H, dd, J¼1.6 and 8.0 Hz, ArH), 7.21 (1H, t,
J¼8.0 Hz, ArH), 7.15 (1H, dd, J¼1.6 and 8.0 Hz, ArH), 5.15 (1H, d,
J¼3.8 Hz, CH), 4.82 (1H, dd, J¼3.8 and 12.0 Hz, CH), 4.21 (1H, br, 1/
2ꢃ CH2), 4.15 (3H, s, OMe), 4.02 (3H, s, OMe), 3.95e4.00 (1H, m, 1/
2ꢃ CH2), 3.97 (3H, s, OMe), 3.91 (3H, s, OMe), 3.12 (2H, br s, OH,
140.8, 140.3, 136.9, 133.6, 126.3, 122.5, 121.8, 114.9, 112.9, 108.6, 66.2,
61.6, 61.5, 61.2, 61.1, 42.2, 20.7, 20.6; HRMS (ESI) m/z: calcd for
MþHþ C23H23NO8: 442.1496; found: 442.1471. Anal. Calcd for
C23H23NO8$0.5H2O: C, 61.33; H, 5.37; N, 3.11; found: C, 61.39; H,
5.39; N, 3.14.
4.15.2. (ꢀ)2,3,-Diiacetyl-4,5,6,11-tetramethoxy-2,3-dihydro-1H-pyr-
ido[3,2,1-de]acridin-7-one (30c). Compound (ꢀ)30c was prepared
form (ꢀ)29c (78 mg, 0.2 mmol), pyridine (0.5 mL), and acetic an-
hydride (0.25 mL). Yield, 79 mg (94%), mp 167e168 ꢂC; 1H NMR
(500 MHz, CDCl3): 8.03e8.05 (1H, m, ArH), 7.22e7.25 (1H, m, ArH),
7.16e7.18 (1H, m, ArH), 6.61 (1H, s, CH), 5.34 (1H, dd, J¼4.2 and
12.0 Hz, CH), 4.81 (1H, dd, J¼3.0 and 12.0 Hz, 1/2ꢃ CH2), 4.20 (1H, t,
J¼12.0 Hz, 1/2ꢃ CH2), 4.05 (3H, s, OMe), 4.04 (3H, s, OMe), 3.96 (3H,
s, OMe), 3.90 (3H, s, OMe), 2.16 (3H, s, OAc), 2.13 (3H, s, OAc); 13C
exchangeable); 13C NMR (500 MHz, DMSO-d6) (
d, ppm): 175.3,
155.8, 153.3, 149.7, 140.4, 137.5, 133.3, 126.0, 122.3, 118.0, 116.4,
115.8, 112.8, 66.3, 61.9, 61.7, 61.4, 61.1, 56.9, 48.8; HRMS (ESI) m/z:
calcd for MþHþ C20H21NO7: 388.1391; found: 388.1379. Anal. Calcd
for C20H21NO7: C, 62.00; H, 5.46; N, 3.62; found: C, 62.18; H, 5.35;
N, 3.51.
NMR (500 MHz, DMSO-d6) (d, ppm): 175.2, 169.4, 169.3, 156.4,
155.0, 149.3, 140.3, 139.0, 132.6, 126.3, 122.8, 117.9, 116.2, 112.8,
109.3, 66.7, 61.9, 61.5, 61.3, 61.1, 56.8, 46.0, 20.7, 20.6; HRMS (ESI) m/
z: calcd for MþHþ C24H25NO9: 472.1602; found: 472.1574. Anal.
Calcd for C24H25NO9: C, 61.14; H, 5.34; N, 2.97; found: C, 61.05; H,
5.65; N, 2.92.
4.14.3. (ꢀ)2,3,10-Trihydroxy-4,5,6,11-tetramethoxy-2,3-dihydro-1H-
pyrido[3,2,1-de]acridin-7-one (29d). Compound (ꢀ)29d was pre-
pared from crude 28d (122 mg, 0.33 mmol), 4-methylmorpholine-
N-oxide (4.8 N, 0.14 mL, 0.66 mmol), and OsO4 (catalytic amount).
Yield, 40.7 mg (30%, calculated from 25d), mp 217e218 ꢂC; 1H NMR
(500 MHz, CDCl3): 8.17 (1H, d, J¼8.8 Hz, ArH), 6.95 (1H, d, J¼8.8 Hz,
ArH), 6.27 (1H, s, OH), 5.18 (1H, t, J¼4.0 Hz, CHeOH), 4.78 (1H, dd,
J¼3.0 and 11.5 Hz, CH), 4.13e4.26 (1H, m, CH2), 4.16 (3H, s, OMe),
4.03 (3H, s, OMe), 3.92 (3H, s, OMe), 3.81 (3H, s, OMe), 3.13 (1H, d,
J¼2.5 Hz, OH, exchangeable), 3.02 (1H, d, J¼8.0 Hz, OH, exchange-
4.15.3. (ꢀ)2,3,10-Triacetyl-4,5,6,11-tetramethoxy-2,3-dihydro-1H-
pyrido[3,2,1-de]acridin-7-one (30d). Compound (ꢀ)30d was pre-
pared from (ꢀ)29d (48 mg, 0.12 mmol), pyridine (0.5 mL), and
acetic anhydride (0.5 mL). Yield, 52 mg (83%), mp 152e153 ꢂC; 1H
NMR (500 MHz, CDCl3): 8.23 (1H, d, J¼8.8 Hz, ArH) 7.03 (1H, d,
J¼8.8 Hz, ArH), 6.62 (1H, d, J¼2.0 Hz, CH), 5.36 (1H, dd, J¼4.0 and
12.0 Hz, CH), 4.91e4.93 (1H, dd, J¼3.2 and 2.0 Hz, 1/2ꢃ CH2), 4.10
(1H, t, J¼12.0 Hz, 1/2ꢃ CH2), 4.05 (6H, s, 2ꢃ OMe), 3.91 (3H, s, OMe),
3.80 (3H, s, OMe), 2.39 (3H, s, OAc), 2.15 (3H, s, OAc), 2.12 (3H, s,
able); 13C NMR (500 MHz, DMSO-d6) (
d, ppm): 174.6, 156.4, 155.3,
153.4, 140.4, 137.4, 137.3, 135.3, 122.5, 115.8, 112.8, 112.6, 66.2, 61.8,
61.6, 61.4, 61.1, 60.8, 48.0; HRMS (ESI) m/z: calcd for MþHþ
C20H21NO8: 404.1340; found: 404.1326. Anal. Calcd for C20H21NO8:
C, 59.55; H, 5.25; N, 3.47; found: C, 59.47; H, 5.20; N, 3.42.
OAc); 13C NMR (500 MHz, DMSO-d6) (
d, ppm): 174.8, 169.5, 169.4,
168.5, 156.5, 155.3, 148.3, 141.0, 140.7, 138.5, 136.5, 124.2, 122.2,
118.0, 113.0, 109.5, 66.6, 62.0, 61.7, 61.6, 61.4, 61.2, 45.1, 20.7, 20.6,
20.5; HRMS (ESI) m/z: calcd for MþHþ C26H27NO11: 530.1657;
found: 530.1629. Anal. Calcd for C26H27NO11: C, 58.97; H, 5.14; N,
2.65; found: C, 58.92; H, 5.10; N, 2.60.
4.15. ( )2,3-Diacetyl-6-methoxy-2,3-dihydro-1H-pyrido[3,2,1-
de]acridin-7-one (30a)
A solution of (ꢀ)29a (99 mg, 0.33 mmol) in a mixture of pyridine
(1 mL) and Ac2O (1 mL) was stirred at room temperature overnight.
MeOH (2 mL) was added dropwise to the reaction mixture and then
evaporated under reduced pressure the residue was co-evaporated
several times with EtOH and the solid residue was recrystallized
from EtOH to give (ꢀ)30a, 0.11 g (84%); mp 231e232 ꢂC. 1H NMR
(500 MHz, CDCl3): 8.56 (1H, d, J¼9.0 Hz, ArH), 8.52e8.54 (1H, m,
ArH), 7.69e7.72 (1H, m, ArH), 7.46e7.48 (1H, m, ArH), 7.29e7.32
(1H, m, ArH), 6.91 (1H, d, J¼9.0 Hz, ArH), 6.80 (1H, m, CH),
5.36e5.39 (1H, m, CH), 4.38 (1H, dd, J¼5.9 and 11.0 Hz, 1/2ꢃ CH2),
4.16. ( )4-Methoxy-13,13a-dihydro-3aH,7H-[1,3]dioxolo
[40,50:4,5]pyrido[3,2,1-de]acridine-2,7-dione (31)
A mixture of (ꢀ)29a (99 mg, 0.33 mmol) and N,N0-carbon-
yldiimidazole (0.27 mg, 1.65 mmol) in butanone (15 mL) was
heated at reflux temperature for 5 h under argon. The solvent was
removed in vacuo to dryness and the residue was chromatographed
on a silica gel column (2ꢃ30 cm) using CHCl3 as the eluant. The

C.-H. Chen et al. / Tetrahedron 67 (2011) 5883e5893
5893
fractions containing product were combined and concentrated in
vacuo. The residue was crystallized from EtOH to give (ꢀ)31, 30 mg
(29%). Mp 205e206 ꢂC; 1H NMR (500 MHz, CDCl3): 8.62 (1H, d,
J¼9.0 Hz, ArH), 8.54e8.55 (1H, m, ArH), 7.72e7.76 (1H, m, ArH),
7.53e7.54 (1H, m, ArH), 7.33e7.36 (1H, m, ArH), 6.99 (1H, d,
J¼9.0 Hz, ArH), 6.14 (1H, d, J¼7.6 Hz, CH), 5.33e5.34 (1H, m, CH),
4.51 (1H, dd, J¼5.7 and 14.0 Hz, 1/2ꢃ CH2), 4.27 (1H, dd, J¼3.0 and
14.0 Hz,1/2ꢃ CH2) 4.06 (3H, s, OMe); 13C NMR (500 MHz, DMSO-d6)
synthesized compounds were obtained at High-Field Biomolecular
NMR Core Facility supported by the National Research Program for
Genomic Medicine (Taiwan). We would like to thank Dr. Shu-Chuan
Jao in the Institute of Biological Chemistry (Academia Sinica) for
providing the NMR service and the National Center for High-
performance computing for computer time and facilities.
References and notes
(d, ppm): 175.4, 163.1, 154.1, 142.2, 140.6, 134.1, 130.6, 126.7, 121.9,
121.8, 115.7, 115.6, 107.0, 106.0, 72.5, 68.7, 56.7, 43.0; HRMS (ESI) m/
z: calcd for MþHþ C18H13NO5: 324.0866; found: 324.0858. Anal.
Calcd for C18H13NO5$0.5H2O: C, 65.06; H, 4.25; N, 4.22, found: C,
65.27; H, 4.30; N, 4.19.
1. Scarffe, J. H.; Beaumont, A. R.; Crowther, D. Cancer Treat. Rep. 1983, 67, 93.
2. Svoboda, G. H.; Poore, G. A.; Simpson, P. J.; Boder, G. B. J. Pharm. Sci. 1966, 55,
758.
3. Dorr, R. T.; Liddil, J. D.; Von Hoff, D. D.; Soble, M.; Osborne, C. K. Cancer Res. 1989,
49, 340.
4. Gout, P. W.; Dunn, B. P.; Beer, C. T. J. Cell. Physiol. 1971, 78, 127.
5. Chou, T.-C.; Tzeng, C. C.; Wu, T.-S.; Watanabe, K. A.; Su, T.-L. Phytother. Res. 1989,
3, 237.
By following the same procedure as that for the synthesis of (ꢀ)
31, the following compounds were prepared:
€
6. Su, T.-L.; Kohler, B.; Chou, T.-C.; Chun, M. W.; Watanabe, K. A. J. Med. Chem. 1992,
35, 2703.
4.16.1. (ꢀ)4,5,6-Trimethoxy-13,13a-dihydro-3aH,7H-[1,3]dioxolo
[40,50:4,5]pyrido[3,2,1-de] acridine-2,7-dione (32). Compound (ꢀ)32
was prepared from (ꢀ)29b (178 mg, 0.5 mmol) and N,N0-carbon-
yldiimidazole (405 mg, 2.5 mmol) in butanone (30 mL). Yield,
88 mg (46%); mp 233e234 ꢂC (EtOH); 1H NMR (500 MHz, CDCl3):
8.45e8.48 (1H, m, ArH), 7.67e7.69 (1H, m, ArH), 7.45e7.47 (1H, m,
ArH), 7.29e7.33 (1H, m, ArH), 6.19 (1H, d, J¼8.1 Hz, CH), 5.32e5.37
(1H, m, CH), 4.60 (1H, dd, J¼4.9 and 14.0 Hz, 1/2ꢃ CH2), 4.18 (3H, s,
OMe), 4.08 (3H, s, OMe), 4.05 (1H, dd, J¼3.1 and 14.0 Hz, 1/2ꢃ CH2),
7. Su, T.-L.; Huang, H.-M.; Wang, C.-K.; Wu, H.-C.; Lin, C.-T. Planta Med. 2005, 71,
28.
8. Wu, Y.-C.; Yen, W.-Y.; Ho, H.-Y.; Su, T.-L.; Yih, L.-H. Int. J. Cancer 2010, 126, 1017.
9. Tillequin, F.; Michel, S.; Skaltsounis, A.-L. In Alkaloids: Chemical and Biological
Perspectives; Pelletier, S. W., Ed.; Elsevier: Amsterdam, 1999; Vol. 12, pp 1e102.
10. Svoboda, G. H. Lloydia 1966, 29, 206.
11. Dorr, R. T.; Liddil, J. D. J. Drug Dev. 1988, 1, 31.
12. Brum-Bousquet, M.; Mitaku, S.; Skaltsounis, A.-L.; Tillequin, F.; Koch, M. Planta
Med. 1988, 54, 470.
13. Costes, N.; Le Deit, H.; Michel, S.; Tillequin, F.; Koch, M.; Pfeiffer, B.; Renard, P.;
ꢀ
ꢀ
Leonce, S.; Guilbaud, N.; Kraus-Berthier, L.; Pierre, A.; Atassi, G. J. Med. Chem.
2000, 43, 2395.
3.93 (3H, s, OMe); 13C NMR (500 MHz, DMSO-d6) (
d, ppm): 174.9,
14. Elomri, A.; Mitaku, S.; Michel, S.; Skaltsounis, A.-L.; Tillequin, F.; Koch, M.;
157.7, 156.0, 154.0, 141.4, 140.7, 138.4, 133.7, 126.6, 123.1, 121.8, 115.4,
113.2, 108.5, 72.8, 69.1, 61.7, 61.6, 61.3, 44.2; HRMS (ESI) m/z: calcd
for MþHþ C20H17NO7: 384.1078; found: 384.1067. Anal. Calcd
C20H17NO7: C, 62.66; H, 4.47; N, 3.65; found: C, 62.22; H, 4.48;
N, 3.59.
ꢀ
ꢀ
Pierre, A.; Guilbaud, N.; Leonce, S.; Kraus-Berthier, L.; Rolland, Y.; Atassi, G. J.
Med. Chem. 1996, 39, 4762.
ꢀ
15. Magiatis, P.; Mitaku, S.; Skaltsounis, A.-L.; Tillequin, F.; Koch, M.; Pierre,
A.;
Atassi, G. J. Nat. Prod. 1998, 61, 198.
16. Costes, N.; Michel, S.; Tillequin, F.; Koch, M.; Pierre, A.; Atassi, G. J. Nat. Prod.
1999, 62, 490.
ꢀ
ꢀ
17. David-Cordonnier, M.-H.; Laine, W.; Lansiaux, A.; Kouach, M.; Briand, G.; Pierre,
A.; Hickman, J. A.; Bailly, C. Biochemistry 2002, 41, 9911.
4.16.2. (ꢀ)4,5,6,11-Tetramethoxy-13,13a-dihydro-3aH,7H-[1,3]diox-
olo[40,50:4,5] pyrido[3,2,1-de]acridine-2,7-dione (33). Compound 33
was prepared from 29c (129 mg, 0.33 mmol) and N,N0-carbon-
yldiimidazole (267 mg, 1.65 mmol) in butanone (10 mL). Yield,
93 mg (67%), mp 229e230 ꢂC; 1H NMR (500 MHz, CDCl3): 7.96e7.98
(1H, m, ArH), 7.25e7.29 (1H, m, ArH), 7.17e7.20 (1H, m, ArH), 6.20
(1H, d, J¼8.8 Hz, CH), 5.32e5.36 (1H, m, CH), 4.93 (1H, dd, J¼4.2 and
13.0 Hz, 1/2ꢃ CH2), 4.15 (3H, s, OMe), 4.05 (3H, s, OMe), 4.00 (3H, s,
OMe), 3.93 (3H, s, OMe), 3.78 (1H, dd, J¼2.8 and 13.0 Hz, 1/2ꢃ CH2);
18. David-Cordonnier, M.-H.; Laine, W.; Kouach, M.; Briand, G.; Vezin, H.; Gaslonde,
ꢀ
ꢀ
T.; Michel, S.; Mai, H. D. T.; Tillequin, F.; Koch, M.; Leonce, S.; Pierre, A.; Bailly, C.
A. Bioorg. Med. Chem. 2004, 12, 23.
19. Guilbaud, N.; Kraus-Berthier, L.; Meyer-Losic, F.; Malivet, V.; Chacun, C.; Jan, M.;
ꢀ
Tillequin, F.; Michel, S.; Koch, M.; Pfeiffer, B.; Atassi, G.; Hickman, J. A.; Pierre, A.
Clin. Cancer Res. 2001, 7, 2573.
ꢀ
ꢀ
20. Guilbaud, N.; Leonce, S.; Tillequin, F.; Koch, M.; Hickman, J. A.; Pierre, A. Anti-
cancer Drugs 2002, 13, 445.
ꢀ
21. Leonce, S.; Perez, V.; Lambel, S.; Peyroulan, D.; Tillequin, F.; Michel, S.; Koch, M.;
ꢀ
Pfeiffer, B.; Atassi, G.; Hickman, J. A.; Pierre, A. Mol. Pharmacol. 2001, 60, 1383.
ꢀ
ꢀ
22. Kluza, J.; Lansiaux, A.; Wattez, N.; Hildebrand, M.-P.; Leonce, S.; Pierre, A.;
Hickman, J. A.; Bailly, C. Biochem. Pharmacol. 2002, 63, 1443.
13C NMR (500 MHz, DMSO-d6) (
d, ppm): 175.7, 157.7, 155.4, 154.3,
23. ThiMai, H. D.; Gaslonde, T.; Michel, S.; Tillequin, F.; Koch, M.; Bongui, J.-B.;
Elomri, A.; Seguin, E.; Pfeiffer, B.; Renard, P.; David-Cordonnier, M.-H.; Laine,
149.8, 142.6, 141.1, 132.9, 127.0, 123.3, 117.8, 115.9, 114.2, 110.2, 75.1,
68.4, 61.8, 61.5, 61.3, 56.7, 50.0; HRMS (ESI) m/z: calcd for MþHþ
C21H19NO8: 414.1183; found: 414.1174. Anal. Calcd for C21H19NO8: C,
61.02; H, 4.63; N, 3.39, found: C, 61.22; H, 4.58; N, 3.49.S.
ꢀ
ꢀ
W.; Bailly, C.; Kraus-Berthier, L.; Leonce, S.; Hickman, J. A.; Pierre, A. J. Med.
Chem. 2003, 46, 3072.
24. Kano, S.; Ebata, T.; Shibuya, S. J. Chem. Soc., Perkin Trans. 1 1980, 2105.
25. Southwick, P. L.; Madhav, R.; Fitzgerald, J. A. J. Heterocycl. Chem. 1969, 6, 507.
26. Eaton, P. E.; Carlson, G. R.; Lee, J. T. J. Org. Chem. 1973, 38, 4071.
27. Field, J. E.; Hill, T. J.; Venkataraman, D. J. Org. Chem. 2003, 68, 6071.
28. Bourne, E. J.; Stacey, M.; Tatlow, J. C.; Tedder, J. M. J. Chem. Soc. 1951, 718.
29. Nguyen, T.-H.; Chau, N. T.; Castanet, A.-S.; Nguyen, K. P.; Mortier, J. J. Org. Chem.
2007, 72, 3419.
Acknowledgements
We are grateful to the National Science council (Grant No.
NSC-95-2320-B-001-025-MY3) and Academia Sinica (Grant No.
AS-96-TP-B06) for financial support. The NMR spectra of the
30. Pollard, M. M.; ter Wiel, M. K. J.; van Delden, R. A.; Vicario, J.; Koumura, N.; van
den Brom, C. R.; Meetsma, A.; Feringa, B. L. Chem.dEur. J. 2008, 36, 11610.