Synthesis and biological activities of novel furo[2,3,4-jk][2]benzazepin- 4(3H)-one derivatives

Article abstract of DOI:10.1039/b614510h

A novel seven-membered lactam formation method has been established by intramolecular ring closure reaction of 4-bromo-(E)-3-[(2-alkylvinyl) carbonylamino]benzo[b]furans (17) under Heck coupling conditions. A number of furo[2,3,4-jk][2]benzazepin-4(3H)-on

Full text of DOI:10.1039/b614510h

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PAPER
www.rsc.org/obc | Organic & Biomolecular Chemistry
Synthesis and biological activities of novel
furo[2,3,4-jk][2]benzazepin-4(3H)-one derivatives†
Kumiko Ando,a Yukiko Akai,a Jun-ichi Kunitomo,a Takehiko Yokomizo,b Hidemitsu Nakajima,c Tadayoshi
Takeuchi,c Masayuki Yamashita,d Shunsaku Ohta,d Takahiro Ohishie and Yoshitaka Ohishi*a
Received 5th October 2006, Accepted 11th December 2006
First published as an Advance Article on the web 18th January 2007
DOI: 10.1039/b614510h
A novel seven-membered lactam formation method has been established by intramolecular ring closure
reaction of 4-bromo-(E)-3-[(2-alkylvinyl)carbonylamino]benzo[b]furans (17) under Heck coupling
conditions. A number of furo[2,3,4-jk][2]benzazepin-4(3H)-ones (20), tricyclicbenzo[b]furans, have been
prepared by this method and evaluated for their leukotriene B4 (LTB4) receptor and
poly(ADP-ribose)polymerase-1 (PARP-1) inhibitory activities.
Introduction
We previously reported the preparation of various 2- and 4-[(E)-2-
alkylcarbamoyl-1-methylvinyl]benzo[b]furan derivatives and their
selective LTB4 receptor (BLT1, BLT2) inhibitory activities. This
study revealed a significant relation between the conformation of
the (E)-2-alkylcarbamoyl-1-methylvinyl group and BLT1 and/or
BLT2 inhibitory activity.1,2 The (E)-2-(2-alkylcarbamoyl-1-methyl-
vinyl) group of (E)-2-(2-alkylcarbamoyl-1-methylvinyl)benzo-
[b]furans (A) showing selective BLT2 inhibition lay on nearly the
same plane as the benzo[b]furan ring. On the other hand, (E)-4-(2-
alkylcarbamoyl-1-methylvinyl)benzo[b]furans (C) inhibited both
BLT1 and BLT2, and the (E)-4-(2-alkylcarbamoyl-1-methylvinyl)
group had a substantial torsion angle from the benzo[b]furan ring
plane. These results suggested that conformational restriction of
the (E)-2-alkylcarbamoyl-1-methylvinyl group by conversion of a
ring-type functional group might affect the inhibitory potency and
the selectivity for BLT1 and/or BLT2 (Fig. 1).
The ring formation originating from the (E)-2-alkylcarbamoyl-
Fig. 1 Cyclization of the alkylcarbamoylvinyl group.
1-methylvinyl group of A affords 2,3-fused benzo[b]furan deriva-
tives (B).3–8 There have been many reports of the preparation
and bioactivity of these derivatives (B).9–11 On the other hand,
fused tricyclicbenzo[b]furan derivatives.12 We were interested in
both the synthesis and bioactivities of the tricyclicbenzo[b]-
furans (D).
ring formation of the (E)-2-alkylcarbamoyl-1-methylvinyl group
of C affords tricyclicbenzo[b]furans (D) having a seven-membered
lactam fused to the 3,4-position of the benzo[b]furan (Fig. 1).
There have been few reports concerning the synthesis of 3,4-
Recently, the PARP-1 inhibitory activity of some tricyclic
lactam compounds has been reported (Fig. 2).13–16 PARP-1 is
a nuclear enzyme that is activated by DNA strand breaks. It
plays an important role in the reaction that transfers the ADP-
ribose moiety from nicotinamide adenine dinucleotide (NAD+)
to various proteins.17–20 PARP-1 inhibitors are thought to be
implicated in a wide spectrum of diseases, including ischemic
diseases, inflammatory diseases, multiple sclerosis, arthritis and
Parkinson’s disease. Therefore, much work has been done toward
preparing PARP-1 inhibitors.21–30 These reports suggested that
the tricyclicbenzo[b]furans (D) might possess PARP-1 inhibitory
activity.
aSchool of Pharmaceutical Sciences, Mukogawa Women’s University, 11–68
Koshien Kyuban-cho, Nishinomiya 663-8179, Japan. E-mail: yohishi@
mukogawa-u.ac.jp; Fax: +798 45 9953; Tel: +798 45 9953
bDepartment of Medical Biochemistry, Graduate School of Medical Sciences,
Kyushu University, Maidashi 3-1-1, Higashi-ku, Fukuoka, 812-8582, Japan
cDepartment of Veterinary Pharmacology, Graduate School of Life and
Environmental Science, Osaka Prefecture University, 1-1 Gakuen-cho,
Sakai, 599-8531, Japan
dKyoto Pharmaceutical University, Misasagi-Nakauchicho 5, Yamashinaku,
Kyoto 607-8414, Japan
eScience of Environment and Mathematical Modeling, Graduate School of
Engineering, Doshisha University, Kyotanabe, Kyoto 610-0394, Japan
We report here the synthesis of novel tricyclicbenzo[b]furans
(D) and their evaluation for LTB4 receptor and PARP-1 inhibitory
activities.
† Electronic supplementary information (ESI) available: Physical data
and yields of compounds 7, 10–14, 17–21, 23 and 25. See DOI:
10.1039/b614510h
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with chloroacetone and 2-bromo-4ꢀ-chloroacetophenone afforded
2-acetyl-3-amino-4-bromo-7-methoxybenzo[b]furan (12a) and
3-amino-4-bromo-2-(4-chlorobenzoyl)-7-methoxybenzo[b]furan
(12b), respectively. On the other hand, treatment of 10 with ethyl
bromoacetate under similar conditions afforded only the alkyloxy
compound (11), which was converted to 3-amino-4-bromo-2-
ethoxycarbonyl-7-methoxybenzo[b]furan (12c) by treatment with
NaH (Scheme 1).
The key intermediates (12a, 12c) were treated with cinnamoyl
chloride (16a) to give 4-bromo-3-(E)-cinnamoylaminobenzo-
[b]furans (17a, 17b, respectively). A mixture of 17a and 17b, pal-
ladium acetate, tri-o-tolylphosphine and triethylamine in acetoni-
trile was heated at 82 ◦C for 4–12 h under Heck coupling conditions
to afford yellow needles of 20a (34.4%) and 20b (62.2%) as the main
product, respectively. MS, 1H-NMR and elemental analysis data of
20a and 20b suggested them to be tricyclicbenzo[b]furans, 2-acetyl-
9-methoxy-6-phenylfuro[2,3,4-jk][2]benzazepin-4(3H)-one (20a)
Fig. 2 Tricyclic lactams with PARP-1 inhibition activity.
1
[MS; m/z (EI) 333 (M+, 100.00). H-NMR; d 5.99 (1H, d, J 2.3,
Results and discussion
5-H), 9.71 (1H, br s, NH)] and 2-ethoxycarbonyl-9-methoxy-6-
phenylfuro[2,3,4-jk][2]benzazepin-4(3H)-one (20b) [MS; m/z (EI)
363 (M+, 100.00). 1H-NMR; d 5.94 (1H, d, J 2.2, 5-H), 9.00
(1H, br s, NH)]. The intramolecular cyclization forming seven-
membered lactams under Heck coupling conditions proceeded
successfully (Scheme 2, path A).
Chemistry
Tricyclic lactam compounds have been prepared using intramolec-
ular cyclization, for example Friedel–Crafts reaction,31 Bischler–
Napieralski reaction32,33 and lactam cyclization reaction.34 We
hypothesized that 4-bromobenzo[b]furans having the vinylcar-
Syntheses of furo[2,3,4-jk][2]benzazepin-4(3H)-one derivatives
having an aromatic substituent group at the 6-position were carried
=
bonylamino group (–NHCOCH CH–R) at the 3-position would
out.
3-Amino-4-bromo-2-ethoxycarbonyl-7-methoxybenzo[b]-
be subject to intramolecular cyclization between the two groups
to form seven-membered lactam fused benzo[b]furan rings under
Heck coupling conditions.35
furan (12c) was treated with chloroacetyl chloride to give 4-bromo-
3-chloroacetylamino-2-ethoxycarbonyl-7-methoxybenzo[b]furan
(13). Diethyl[2-(4-bromo-2-ethoxycarbonyl-7-methoxybenzo[b]-
furan-3-ylamino)-2-oxoethyl]phosphonate (14) was obtained from
13 by treatment with triethyl phosphite. Treatment of 14 with
several benzaldehydes (15a–15d) in the presence of NaH under
the Horner–Wadsworth–Emmons (HWE) reaction conditions39
afforded the corresponding 4-bromo-(E)-3-cinnamoylamino-
benzo[b]furans (17f–17i). Ring closure reaction of 17f–17i under
3-Amino-4-bromobenzo[b]furans (12), key intermediates to
synthesize the tricyclicbenzo[b]furan (D), were prepared. Regio-
selective bromination of 2-acetoxy-3-methoxybenzaldehyde (6)
with bromine in the presence of KBr gave 2-acetoxy-6-bromo-3-
methoxybenzaldehyde (7) according to the procedure reported by
Smil et al.36 Compound (7) was converted to 6-bromo-2-hydroxy-
3-methoxybenzonitrile (10) in three steps.37,38 Reaction of 10
Scheme 1
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Scheme 2
Heck coupling conditions as mentioned above afforded 6-(3,4,5-
trimethoxyphenyl)-(20f), 6-(2-methoxyphenyl)-(20g), 6-(2-,6-
dichlorophenyl)-(20h) and 6-(3-pyridyl)-2-ethoxycarbonyl-9-
methoxyfuro[2,3,4-jk][2]benzazepin-4(3H)-one (20i), respectively
(Scheme 2, path B).
Reaction of 3-amino-4-bromobenzo[b]furans (12a–12c) with
crotonyl chloride (16b) afforded 4-bromo-3-crotonoylamino-
benzo[b]furans (17c–17e) containing a very small portion of 4-
bromo-3-(3-chlorobutyrylamino)benzo[b]furans. The compounds
(17c–17e) were subject to ring closure reaction under Heck cou-
pling conditions to afford 6-methylfuro[2,3,4-jk][2]benzazepin-
4(3H)-ones (20c–20e) accompanying formation of a small por-
tion of 5,6-dihydro-6-methylfuro[2,3,4-jk][2]benzazepin-4(3H)-
ones (21a, 21b) (Scheme 2, path A).
stituent at the 6-position via paths A and B. We thus devised path C
to synthesize 20j–20l. 3-Amino-4-bromobenzo[b]furans (12a–12c)
were treated with chloropropionyl chloride to give 4-bromo-3-(3-
chloropropionylamino)benzo[b]furans (18a–18c). The alkylchlo-
rides (18a–18c) were treated with palladium acetate, tri-o-tolyl-
phosphine and triethylamine under Heck coupling conditions to
also afford the corresponding furo[2,3,4-jk][2]benzazepin-4(3H)-
ones (20j–20l) (Scheme 2, path C). In these reactions, 4-bromo-
3-(3-chloropropionylamino)benzo[b]furans (18) were converted to
afford 3-acryloylamino-4-bromobenzo[b]furans (19) with accom-
panying loss of HCl. Subsequently, 19 was subjected to ring
closure reaction to afford furo[2,3,4-jk][2]benzazepin-4(3H)-ones
(20j–20l). Indeed, 3-acryloylamino-4-bromo-2-ethoxycarbonyl-7-
methoxybenzo[b]furan (19a) was isolated from the reaction mix-
ture in an early stage of the reaction process. These results suggest
Unfortunately, the reaction of 12a with acryloyl chlo-
ride (16c) did not afford 2-acetyl-3-acryloylamino-4-bromo-7-
methoxybenzo[b]furan. Therefore, it was difficult to synthesize
furo[2,3,4-jk][2]benzazepin-4(3H)-ones (20j–20l) without any sub-
=
that not only acryloylamino (–NHCOCH CH2) compounds but
also 3-chloropropionylamino (–NHCOCH2CH2Cl) compounds
can be subjected to the Heck coupling reaction.
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The representative tricyclicbenzo[b]furan (20j) showed charac-
teristic 5-H signals (d 5.92, dd, J 12.5 and 2.2) with coupling
with the 3-NH in its 1H-NMR spectrum. On the seven-membered
lactam ring, the 5-H signals showed coupling with NH like
meta-coupling. NOE correlations among 5-H, 6-H and 7-H were
also observed (Fig. 3). These 1H-NMR, 13C NMR, MS and
elemental analysis observations suggested 20j to be 2-acetyl-9-
methoxyfuro[2,3,4-jk][2]benzazepin-4(3H)-one.
Next, the Heck coupling reaction using alkylchlorides was exa-
mined. 3-Chloro-N-[2-(3,4-dimethoxyphenyl)ethyl]propionamide
(23a), 3-chloro-N-(3-methoxyphenyl)propionamide (23b) and
3-chloro-N,N-diethylpropionamide (23c) were prepared from
2-(3,4-dimethoxyphenyl)ethylamine (22a), m-anisidine (22b) and
diethylamine (22c), respectively, by treatment with chloropro-
pionyl chloride. 2-Acetyl-4-bromo-7-methoxybenzo[b]furan (24)2
treated with N-alkyl-3-chloropropionamides (23a–23c) under
Heck coupling conditions afforded 4-[2-[2-(3,4-dimethoxy-
phenyl)ethylcarbamoyl]vinyl]-(25a), 4-[2-(3-methoxyphenylcar-
bamoyl)vinyl]-(25b) and 4-[2-(diethylcarbamoyl)vinyl]-2-acetyl-7-
methoxybenzo[b]furan (25c), respectively, as expected (Scheme 3).
These results revealed that alkylchlorides could be used for
the Heck coupling reaction instead of the usually used olefinic
reagents.
Scheme 3
measurement of the inhibition of calcium mobilization in both
CHO cells overexpressing human BLT1 (CHO–hBLT1) and human
BLT2 (CHO–hBLT2) at the concentration of 10 lM.41,42
The tricyclicbenzo[b]furan series (20) was less active than the
original compounds (26 and 27) having a diethyl group on
the nitrogen atom of the carbamoylvinyl group (26 and 27, as
representative compounds of A and B in Fig. 1). The substituent
on the nitrogen of the carbamoyl group might play an important
role in the appearance of inhibitory activities of hBLT1 and/or
hBLT2.1,2 Tricyclicbenzo[b]furans (20) don’t have an appropriate
substituent on the nitrogen atom of the carbamoylvinyl group for
inhibitory activities of hBLT1 and/or hBLT2.
Finally, X-ray analysis of 20h, as a representative compound,
was examined to confirm the structure of the tricyclicbenzo-
[b]furans. The seven-membered lactam formed between the 3- and
4-positions of the original benzo[b]furan skeleton was confirmed
by this work. The lactam ring lay on the same plane as the
benzo[b]furan ring (Fig. 4).40
Tricyclicbenzo[b]furan (20c), having a methyl group at the 6-
position, showed moderate inhibitory activity, but was less potent
than 26 and 27. These compounds (26, 27) having a methyl
group substituted on the vinyl group were most potent in our
Biological activity
The representative tricyclicbenzo[b]furans (20a–20c, 20j–20l) pre-
pared were evaluated for LTB4 receptor inhibitory activity by
Fig. 3 Structure, 1H-NMR and 13C-NMR of 20j.
Fig. 4 Structure of 6-(2,6-dichlorophenyl)-2-ethoxycarbonyl-9-methoxyfuro[2,3,4-jk][2]benzazepin-4(3H)-one (20h) and its X-ray analysis
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current LTB4 study.1,2 On the other hand, 20a and 20b, having
a phenyl group at the 6-position, were inactive. These results
suggested that the substituent on the olefinic carbon of both
tricyclicbenzo[b]furans (20) and the original 2-alkylcarbamoyl-1-
methylvinyl compounds (26, 27) might also be an important factor
in the appearance of inhibitory activities for hBLT1 and/or hBLT2.
The moderately active compound (20c) showed an approx-
imately two-fold potency for hBLT1 than for hBLT2. In our
previous study, the (E)-2-diethylcarbamoyl-1-methylvinyl group
the benzo[b]furan ring on the basis of the X-ray analysis of
20h. These data showed good correlations between selectivity for
hBLT2 and stereostructure of the carbamoylvinyl group for both
tricyclicbenzo[b]furans (20) and original compound (27) (Table 1).
Most of the tricyclicbenzo[b]furans (20a–20h, 20j–20l) were
evaluated for their PARP-1 inhibitory activity at a concen-
tration of 10 lM (Table 1).29,43 Compound (20g) having a 2-
methoxyphenyl group at the 6-position among the evaluated
compounds showed 17.2% inhibitory activity. It has been reported
that the benzamide structure is effective for leading to inhibitory
activity against PARP-1.44 Compounds (20) were introduced a
=
(–C(CH3) CHCON(C2H5)2) of 27, showing selective inhibition of
hBLT2, lay on nearly the same plane as the benzo[b]furan ring.1,2
=
=
Similarly, the carbamoylvinyl moiety (–C(R) CH–CONH–) in
the seven-membered lactam of 20 lay on the same plane as
C C bond as a spacer between the amide functional group
(–CONH–) and the phenyl group of the benzamide structure. The
Table 1 Evaluations of 20 for LTB4 receptor (BLT1, BLT2) and PARP-1 inhibitory activitiesa
LTB4 receptor inhibition (%)
Inhibition (10 lM)
PARP-1 inhibition (%)
Inhibition (10 lM)
Compound
Path
R1
R2
Yield (%)
CHO–hBLT1
CHO–hBLT2
20a
20b
20c
20d
20e
20f
A
A
A
A
A
B
CH3
OC2H5
CH3
C6H4(4-Cl)
OC2H5
OC2H5
C6H5
C6H5
CH3
CH3
CH3
34.4
62.2
34.3
42.7
60.9
44.9
N. I.
N. I.
26.1
—
—
—
9.1
2.7
60.1
—
—
—
N. I.b
N. I.b
N. I.b
N. I.b
N. I.
N. I.b
20g
20h
B
B
OC2H5
OC2H5
51.8
41.0
—
—
—
—
17.2
4.2
20i
B
OC2H5
12.5
—
—
—
20j
20k
20l
26
C
C
C
—
—
—
CH3
C6H4(4-Cl)
OC2H5
—
—
H
H
H
—
—
—
30.2
24.1
28.0
—
—
—
N. I.
N. I.
N. I.
92.6
69.9
—
N. I.
3.6
N. I.
92.8
> 100
—
6.1
N. I.b
N. I.
N. I.
N. I.
58.9
27
3-AB
—
a 3-AB: 3-aminobenzamide, N. I.: not inhibited, —: not tested. b At 1 l M concentration.
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cinnamamide lactam of 20 might not be appropriate as a PARP-1
recrystallized from ethyl acetate to give 12c (3.2 g, 77.2%) as pale
inhibitor.
yellow needles.
4-Bromo-3-(2-chloroacetylamino)-2-ethoxycarbonyl-7-
methoxybenzo[b]furan (13)
Conclusion
In this study, we established a synthetic method for 6-substituted
furo[2,3,4-jk][2]benzazepin-4(3H)-ones (tricyclicbenzo[b]furan,
20a–20i) from 3-[(E)-(2-alkylvinyl)carbonylamino]-4-bromo-
benzo[b]furans (17) by intramolecular cyclization under Heck
coupling conditions. 4-Bromo-3-chloropropionylaminobenzo-
[b]furans (18) could also be used to obtain furo[2,3,4-jk][2]-
benzazepin-4(3H)-ones (20j–20l) via 3-acryloylamino-4-bromo-
benzo[b]furans under the same reaction conditions. The furo[2,3,4-
jk][2]benzazepin-4(3H)-ones (20) having a characteristic seven-
membered lactam showed moderate hBLT2 receptor and weak
PARP-1 inhibitory activities. Further work is in progress to
synthesize a new series of tricyclicbenzo[b]furans (20) to find
more active PARP-1 inhibitors.
To a solution of 12c (1.1 g, 3.4 mmol) in THF (40 ml) was added
dropwise chloroacetyl chloride (0.42 ml, 5.3 mmol) with vigorous
stirring at 25 ◦C. The reaction mixture was stirred at the same
temperature for 17 h and poured into ice water. The resulting
precipitate was collected by filtration and washed with water, then
recrystallized from acetonitrile to give 13 (1.6 g, 93.0%) as colorless
needles.
Diethyl [2-(4-bromo-2-ethoxycarbonyl-7-methoxybenzo[b]furan-3-
ylamino)-2-oxoethyl]phosphonate (14)
A mixture of 13 (12.3 g, 31.5 mmol) and triethyl phosphite (100 ml,
0.58 mol) was stirred at 140 ◦C for 21 h. The reaction mixture
was cooled to room temperature, and the resulting precipitate was
collected by filtration. The precipitate was recrystallized from ethyl
acetate to give 14 (13.1 g, 86.1%) as colorless needles.
Experimental
All melting points were determined using a Yanako microscopic
1
hot-stage apparatus and are uncorrected. H-NMR, 13C-NMR,
4-Bromo-3-(E)-cinnamoylamino-2-ethoxycarbonyl-7-
methoxybenzo[b]furan (17b)
HMBC and HMQC spectra were obtained with a JEOL JNM-
ECP400, JEOL JNM-ECP500 and a JEOL PMX60FT spectrom-
eter with tetramethylsilane as an internal standard. MS spectra
(MS, HRMS) were obtained using a JEOL JMS-700 EIMS
spectrometer. Elemental analyses (EA) were performed using a
CHN CORDER MT-3 (Yanako). All organic extracts were dried
over anhydrous MgSO4. Column chromatography was carried out
on Wakogel C-200. Thin layer chromatography was performed on
a Merck silica gel plate (0.5 mm, 60F-254).
A mixture of 12c (1.1 g, 3.4 mmol) and cinnamoyl chl◦oride (16a)
(0.57 g, 3.7 mmol) in THF (50 ml) was heated at 60 C for 9 h.
The reaction mixture was poured into ice water, and the resulting
precipitate was collected by filtration, then recrystallized from
acetonitrile to give 17c (1.1 g, 74.3%) as colorless needles.
Compound (17a) was prepared according to the procedure
described for 17b.
3-Amino-4-bromo-2-(4-chlorobenzoyl)-7-methoxybenzo[b]furan
(12b)
4-Bromo-3-(E)-crotonoylamino-2-ethoxycarbonyl-7-
methoxybenzo[b]furan (17e)
A mixture of 10 (2.0 g, 8.8 mmol), K2CO3 (3.0 g, 21.7 mmol) and 2-
bromo-4ꢀ-chloroacetophenone (2.2 ml, 9.7 mmol) in DMF (80 ml)
was stirred at 92 ◦C for 2 h. The reaction mixture was poured into
ice water, and the resulting precipitate was collected by filtration,
then recrystallized from ethyl acetate to give 12b (2.7 g, 81.6%) as
yellow needles.
General procedure for 17c and 17d from 12. A mixture of 12c
(1.3 g, 4.1 mmol) and crotonyl chloride (16b) (0.51 ml, 5.4 mmol) in
THF (25 ml) was heated at 66 ◦C for 18 h. The reaction mixture was
poured into ice water, and the resulting precipitate was collected by
filtration, then recrystallized from acetonitrile to give 17e (1.21 g,
76.6%) containing a small portion of 4-bromo-2-ethoxycarbonyl-
3-(3-chlorobutyrylamino)-7-methoxybenzo[b]furan.
Compound (12a) was prepared according to the procedure
described for 12b.
3-Amino-4-bromo-2-ethoxycarbonyl-7-methoxybenzo[b]furan
4-Bromo-2-ethoxycarbonyl-7-methoxy-3-[[(E)-3-(2-
(12c)
methoxyphenyl)-1-oxo-2-propenyl]amino]benzo[b]furan (17g)
A mixture of 10 (3.0 g, 13.2 mmol), K2CO3 (5.4 g, 39.1 mmol) and
bromoethylacetate (1.7 ml, 15.5 mmol) in acetonitrile (50 ml) was
stirred at 82 ◦C for 4.5 h. After the insoluble portion was filtered
off, the filtrate was evaporated under reduced pressure to give 11
(3.8 g) as a pale yellow solid. This solid was used for the next step
without further purification.
General procedure for 17f, 17h, and 17i from 14. To a suspen-
sion of NaH (60% in oil, 0.33 g, 8.2 mmol) in THF (20 ml) was
added dropwise a solution of 14 (2.0 g, 4.1 mmol) in THF (40 ml)
under a N2 atmosphere at 0 ◦C with stirring. The solution was
stirred at the same temperature until it became clear. A solution
of o-anisaldehyde (15b) (0.59 ml, 4.9 mmol) in THF (20 ml) was
added dropwise to the clear solution at 0 ◦C, and the mixture was
stirred at the same temperature for 1 h. The mixture was then
quenched with H2O and added to saturated NH4Cl solution. The
resulting precipitate was collected by filtration and washed with
water, then recrystallized from ethyl acetate to give 17h (1.6 g,
82.5%) as colorless needles.
To a suspension of NaH (60% in oil, 0.57 g, 14.3 mmol) in
DMF (20 ml) was added dropwise a solution of crude 11 in DMF
(10 ml) under a N2 atmosphere at −5 ◦C with stirring. The mixture
◦
was stirred at 0 C for 15 min. The mixture was then quenched
with H2O, and added to saturated NH4Cl solution. The resulting
precipitate was collected by filtration and washed with water, then
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4-Bromo-3-(3-chloropropionylamino)-2-ethoxycarbonyl-7-
methoxybenzo[b]furan (18c)
(500 MHz; CDCl3; Me4Si) 1.38 (3H, d, J 6.9, CH(CH3)), 2.60
(3H, s, COCH3), 2.97–3.02 (2H, m, CH2), 3.32–3.38 (1H, m,
CH(CH3)), 4.02 (3H, s, OCH3), 6.93 (1H, d, J 7.8, 8-H), 7.00 (1H,
d, J 8.3, 7-H), 9.55 (1H, br s, NH); m/z (EI) 273 (M+, 85.79%),
258 (100.00).
General procedure for 18a and 18b from 12. To a solution
of 12c (1.5 g, 3.7 mmol) in THF (40 ml) was added dropwise
3-chloropropionyl chloride (0.46 ml, 4.8 mmol) with vigorous
stirring at 25 ◦C. The solution was heated at 60 ◦C for 11 h, and
poured into ice water. The resulting precipitate was collected by
filtration, then recrystallized from acetonitrile to give 18c (1.5 g,
79.0%) as colorless needles.
Compound (21b) was prepared according to the procedure
described for 21a.
2-Acetyl-7-methoxyfuro[2,3,4-jk][2]benzazepin-4(3H)-one (20j)
General procedure for 20k, 20l from 18. A mixture of 18a
(1.5 g, 4.0 mmol), palladium acetate (49.0 mg, 0.20 mmol), tri-o-
tolylphosphine (0.15 g, 0.40 mmol) and Et3N (6.0 ml, 42.0 mmol)
in acetonitrile (40 ml) was heated at 82 ◦C for 3 h. The mixture was
treated with chloroform, and the insoluble portion was removed
by filtration. The filtrate was evaporated to dryness. The residue
was poured into water, made acidic with 10% HCl solution and
extracted with chloroform. The organic layer was washed with
brine and dried. The solvent was evaporated off. The residue was
recrystallized from ethyl acetate to give 20j (0.31 g, 30.2%) as
yellow needles (Found: C, 65.36; H, 4.22; N, 5.42. C14H11NO4
requires C, 65.37; H, 4.31; N, 5.44); mp 247.1–249.7 ◦C; dH
(400 MHz; CDCl3; Me4Si) 2.55 (3H, s, COCH3), 4.04 (3H, s,
OCH3), 5.92 (1H, dd, J 12.5 and 2.2, 5-H), 6.79 (1H, d, J 12.8,
6-H), 6.89 (1H, d, J 8.0, 8-H), 7.02 (1H, d, J 8.1, 7-H), 9.55 (1H,
br s, NH); dC (500 MHz; CDCl3; Me4Si) 26.20, 56.36, 110.84,
123.04, 123.36, 123.76, 125.68, 130.92, 135.05, 138.30, 142.94,
147.55, 164.69, 190.57; m/z (EI) 257 (M+, 100.00%).
2-Acetyl-7-methoxy-6-phenylfuro[2,3,4-jk][2]benzazepin-4(3H)-
one (20a)
General procedure for 20b, 20f–20i from 17. A mixture of
17a (0.2 g, 0.48 mmol), palladium acetate (6.0 mg, 0.024 mmol),
tri-o-tolylphosphine (17.0 mg, 0.048 mmol) and Et3N (2.0 ml,
◦
14.0 mmol) in acetonitrile (50 ml) was heated at 82 C for 12 h.
The mixture was treated with chloroform, and the insoluble
portion was removed by filtration. The filtrate was evaporated
to dryness. The residue was poured into water, made acidic
with 10% HCl solution and extracted with chloroform. The
organic layer was washed with brine and dried. The solvent was
evaporated off. The residue was recrystallized from ethyl acetate
to give 20a (0.06 g, 34.4%) as yellow needles (Found: C, 71.78;
H, 4.44; N, 4.15. C20H15NO4 requires C, 72.06; H, 4.54; N, 4.20);
mp 246.5–248.3 ◦C; dH (500 MHz; CDCl3; Me4Si) 2.58 (3H, s,
COCH3), 4.01 (3H, s, OCH3), 5.99 (1H, d, J 2.3, 5-H), 6.76 (1H,
d, J 8.2, 7- or 8-H), 6.78 (1H, d, J 8.7, 7- or 8-H), 7.32–7.34 (2H,
m, phenyl H), 7.42–7.45 (3H, m, phenyl H), 9.71 (1H, br s, NH);
m/z (EI) 333 (M+, 100.00%).
2-Acetyl-4-[(E)-2-[2-(3,4-dimethoxyphenyl)ethylcarbamoyl]vinyl]-
7-methoxybenzo[b]furan (25a)
General procedure for 25b, 25c from 24. A mixture of 24 (0.5 g,
1.9 mmol), 23a (0.61 g, 2.2 mmol), palladium acetate (23.0 mg,
0.09 mmol), tri-o-tolylphosphine (68.0 mg, 0.19 mmol) and Et3N
(4.0 ml, 28.0 mmol) in acetonitrile (80 ml) was heated at 82 ◦C for
7 h. The mixture was treated with chloroform, and the insoluble
portion was removed by filtration. The filtrate was evaporated to
dryness. The residue was poured into water, made acidic with 10%
HCl solution and extracted with chloroform. The organic layer
was washed with brine and dried. The solvent was evaporated
off. The residue was recrystallized from ethyl acetate to give 25a
(0.36 g, 45.6%) as pale yellow needles (Found: C, 67.47; H, 6.02;
N, 3.31. C24H25NO6·1/3H2O requires C, 67.12; H, 6.02; N, 3.26);
dH (400 MHz; CDCl3; Me4Si) 2.64 (3H, s, COCH3), 2.86 (2H,
t, J 6.9, NHCH2CH2), 3.67 (2H, m, NHCH2CH2), 3.87 (3H, s,
2-Acetyl-7-methoxy-6-methylfuro[2,3,4-jk][2]benzazepin-4(3H)-
one (20c)
General procedure for 20d and 20e from 17. A mixture of 17c
(0.6 g, 1.7 mmol), palladium acetate (21.0 mg, 0.085 mmol), tri-o-
tolylphosphine (62.0 g, 0.17 mmol) and Et3N (2.0 ml, 14.0 mmol)
in acetonitrile (30 ml) was heated at 82 ◦C for 16 h. The mixture was
treated with chloroform, and the insoluble portion was removed
by filtration. The filtrate was evaporated to dryness. The residue
was poured into water, made acidic with 10% HCl solution and
extracted with chloroform. The organic layer was washed with
brine and dried. The solvent was evaporated off. The residue was
recrystallized from ethyl acetate to give 20c (0.16 g, 34.3%) as
yellow needles (Found: C, 66.19; H, 4.77; N, 5.16. C15H13NO4
requires C, 66.41; H, 4.83; N, 5.16); mp 278.8–280.2 ◦C; dH
(500 MHz; CDCl3; Me4Si) 2.27 (3H, d, J 0.9, 6-CH3), 2.56 (3H, s,
COCH3), 4.05 (3H, s, OCH3), 6.04 (1H, q, J 0.9, 5-H), 6.92 (1H,
d, J 8.3, 8-H), 7.20 (1H, d, J 8.3, 7-H), 9.63 (1H, br s, NH); m/z
(EI) 271 (M+, 100.00%).
OCH3), 3.87 (3H, s, OCH3), 4.05 (3H, s, OCH3), 5.68 (1H, br t,
ꢀ
=
J 5.5, NH), 6.37 (1H, d, J 15.7, CH CH), 6.76–6.79 (2H, m, 2 -,
6ꢀ-H), 6.83 (1H, d, J 7.7, 5ꢀ-H), 6.92 (1H, d, J 8.1, 6-H), 7.39 (1H,
=
d, J 8.4, 5-H), 7.72 (1H, s, 3-H), 7.82 (1H, d, J 15.8, CH CH);
m/z (EI) 423 (M+, 8.64%), 164 (100.00).
2-Acetyl-5,6-dihydro-7-methoxy-6-methylfuro[2,3,4-
PARP inhibition assay
jk][2]benzazepin-4(3H)-one (21a)
The catalytic activity of PARP-1 was measured as described
previously43 with some modifications. Human recombinant
PARP-1 (800 ng ml−1, Trevigen, Gaithersburg, MD) in buffer-A
containing 50 mM Tris-HCl (pH 8.0), 20 lM ZnCl2, 4 mM MgCl2,
1 mM dithiothreitol was immobilized on an ELISA microplate
for 16–18 h at 4 ◦C. After three washings with PBS plus 0.05%
Isolation of 20c gave a residue which was purified by silica gel
column chromatography (CHCl3) to give a yellow solid. The solid
was recrystallized from ethyl acetate to give 21a (10 mg, 2.2%) as
yellow needles (Found: C, 65.71; H, 5.49; N, 5.10. C15H15NO4
requires C, 65.92; H, 5.53; N, 5.13); mp 203.2–204.5 ◦C; dH
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Tween20 (PBST), 1.25 mg ml−1 activated DNA29 diluted in the
buffer-A plus 50 lM NAD+ was added to each well and the
reaction mixture was incubated for 15 min at 4 ◦C. After three
washings with PBST, the synthesis of poly(ADP-ribose) by PARP-
1 was detected by adding the anti-poly(ADP-ribose) pAb (1 :
2500, LP98-10, Alexis Biochemicals, Lausanne, Switzerland) in
1% BSA-PBST. After 1 h incubation at 37 ◦C and three washings
with PBST, peroxidase-conjugated goat anti-rabbit IgG (1 : 5000,
Zymed, South San Francisco, CA) in 1% BSA–PBST was added
and incubated for 30 min at 37 ◦C. After a final series of washings
(twice with PBST and once with H2O), a positive signal was
visualized by 3,3ꢀ,5,5ꢀ-tetramethyl-benzidine in the presence of
H2O2 for 15 min at 37 ◦C. The reaction was terminated by adding
1 N H2SO4 and the absorbance was measured at 450 nm. The
compounds or 3-aminobenzamide (as a positive control) were
dissolved in 1% dimethyl sulfoxide, and then 10 ll (final conc.
0.1%) was added to each assay.
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reported previously.1,2
Acknowledgements
This work was supported in part by a grant from the Ministry
of Education, Culture, Sports, Science and Technology for a
“University–Industry Joint Research” Project (2004–2008). The
authors thank the staff of the Instrument Analysis Center
of Mukogawa Women’s University for the 1H-NMR and MS
measurements and element analyses.
28 G. J. Wells, R. Bihovsky, R. L. Hudkins, M. A. Ator and J. Husten,
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40 Compound 20h formula: C21H15O5NCl2, formula weight: 432.26,
crystal color, habit: yellow, chunk, crystal dimensions: 0.20 × 0.15 ×
0.05 mm, crystal system: monoclinic, lattice type: primitive, indexing
images: 3 oscillations @ 180.0 seconds, detector position: 127.40 mm,
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1997, 387, 620–624.
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Res., 1999, 5, 1169–1172.
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Acad. Sci. U. S. A., 1996, 93, 7481–7485.
˚
pixel size: 0.100 mm, lattice parameters: a = 8.6316(2) A, b = 14.8772(3)
0
3
˚
˚
˚
A, c = 14.4589(3) A, b = 95.3308(11) , V = 1848.70(7) A , space group:
P21/n (#14), Z value: 4, Dcalc: 1.553 g cm−3, F000: 888.00, l(CuKa):
34.790 cm−1‡.
‡ CCDC reference number 623049. For crystallographic data in CIF or
other electronic format see DOI: 10.1039/b614510h
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