Synthesis of Lakshminine and antiproliferative testing of related oxoisoaporphines

Article abstract of DOI:10.1021/np100370g

Lakshminine (6-amino-1-aza-5-methoxy-7H-dibenzo[de,h]quinolin-7-one, 1) is a recent addition to the small family of oxoisoaporphine alkaloids and a member of an even smaller set bearing an amino group at C-6. This rare natural product has now been synthesized in order to have sufficient amounts for biological testing. Lakshminine, its 4-amino isomer (2), their 6- and 4-nitro precursors (8 and 10, respectively), the intermediate 5-methoxy-7H-dibenzo[de,h]quinolin-7- one (6), and the unsubstituted skeleton (11) were tested against normal human fibroblasts and three human solid tumor cell lines. Only compound 10 showed marginal antiproliferative activity.

Full text of DOI:10.1021/np100370g

J. Nat. Prod. 2010, 73, 1951–1953
1951
Synthesis of Lakshminine and Antiproliferative Testing of Related Oxoisoaporphines
,
†,‡
‡
3
‡,§
Vicente Castro-Castillo,* Marco Rebolledo-Fuentes, Cristina Theoduloz, and Bruce K. Cassels
˜
Faculty of Basic Sciences, Metropolitan Educational Sciences UniVersity, AVenida J.P. Alessandri 774, Nu n˜ oa, Santiago, Chile, Department of
Chemistry, Faculty of Sciences, UniVersity of Chile, Santiago, Chile, Faculty of Health Sciences, UniVersity of Talca, Talca, Chile, and
Millennium Institute for Cell Dynamics and Biotechnology, Santiago, Chile
ReceiVed June 2, 2010
Lakshminine (6-amino-1-aza-5-methoxy-7H-dibenzo[de,h]quinolin-7-one, 1) is a recent addition to the small family of
oxoisoaporphine alkaloids and a member of an even smaller set bearing an amino group at C-6. This rare natural product
has now been synthesized in order to have sufficient amounts for biological testing. Lakshminine, its 4-amino isomer
(
2), their 6- and 4-nitro precursors (8 and 10, respectively), the intermediate 5-methoxy-7H-dibenzo[de,h]quinolin-7-
one (6), and the unsubstituted skeleton (11) were tested against normal human fibroblasts and three human solid tumor
cell lines. Only compound 10 showed marginal antiproliferative activity.
a
The oxoisoaporphines constitute a small family of alkaloids that
are only known to occur in two species of Menispermaceae,
Scheme 1. Synthesis of Lakshminine (1)
1
-8
plants characterized by the accumulation of “regular” isoquinoline
alkaloids. Their planar 7H-dibenzo[de,h]quinolin-7-one skeleton
(
commonly known as 1-azabenzanthrone, particularly in the dye
and pigment industries) could be assumed to intercalate between
DNA base pairs. Their redox-active iminoquinone structure could
also be expected to interfere with mitochondrial electron transport.
Therefore, these compounds might inhibit cell replication and
possibly exhibit anticancer properties. In fact, two of these alkaloids
isolated from Menispermum dauricum DC, bearing a nitrogen
substituent at C-6 of the polycyclic scaffold, have demonstrated
cytotoxicity and are claimed to be more potent against human
7
mammary cancer cells than the widely used etoposide or VP-16.
The cognate daurioxoisoaporphine C does not seem to have been
tested, nor is there any report on the antiproliferative or related
activity of tyraminoporphine, the first 6-aminooxoisoaporphine
6
reported, or lakshminine (1), the most recently described member
of this group, isolated from Sciadotenia toxifera Krukoff & A.C.
8
Smith. While the literature records no data on the antiproliferative
a
Reagents and conditions: (a) H /HNO
2
SO
4
3
, TFA, rt, 2 h; (b) air, Pd/C,
activity of alkaloids of this family lacking a nitrogen substituent at
C-6, a number of synthetic 1-aza-9-(substituted amino)benzan-
thrones have been screened and have been found to be weakly to
toluene, reflux, 24 h; (c) Na
2
S, NaOH, H O, reflux, 5 h.
2
2
0 g of dried, powdered ketoconazole-supplemented M. dauricum
6
9
moderately active.
root culture. Starting from 20 kg of M. dauricum roots, Yu et al.
were only able to obtain 20, 9, and 10 mg of dauriosoisoaporphines
7
A, B, and C, respectively. Finally, Killmer et al. reported the
8
isolation of 2 mg of 1 from 4.2 kg of S. toxifera vines. As we
already had experience in the synthesis of 2,3-dihydro-5-methoxy-
7H-dibenzo[de,h]quinolin-7-one (1-aza-2,3-dihydro-5-methoxyben-
zanthrone), we decided to use this substance as starting material
for a straightforward preparation of 1 in sufficient amount to
determine its antiproliferative activity against a panel of normal
and cancer cell lines.
1-Aza-2,3-dihydro-5-methoxybenzanthrone (3) and its 6-methoxy
(4) and 6-hydroxy (5) derivatives were obtained by polyphosphoric
acid (PPA)-catalyzed cyclization of homoveratrylaminophthalide,
which, in spite of its low yield, still appears to be the best available
1
0
approach to the desired intermediate.
The scanty biological data on these alkaloids may, at least in
part, be a consequence of the small quantities in which they have
been isolated. Thus, Sugimoto et al. isolated 20 mg of crude 5 from
Nitration of 1-aza-2,3-dihydro-5-methoxybenzanthrone in tri-
fluoroacetic acid (TFA) produced a mixture of isomers (7 and 9).
Subsequent oxidation of 3, 7, and 9 with air, over Pd/C in toluene,
afforded 6, 8, and 10 in approximately 90% yields, and selective
reduction of the nitro groups of the latter products with sodium
sulfide in alkaline solution gave lakshminine (1, Scheme 1) and
the isomeric 4-amino-1-aza-5-methoxybenzanthrone (2).
*
To whom correspondence should be addressed. Tel: +56 2 241 2494.
Fax: +56 2 239 3932. E-mail: vicente.castro@umce.cl.
†
Metropolitan Educational Sciences University.
University of Chile.
University of Talca.
‡
3
Aromatic electrophilic substitution reactions of the 1-azaben-
zanthrone system and its 2,3-dihydro analogue have been described
§
Millennium Institute.
1
0.1021/np100370g  2010 American Chemical Society and American Society of Pharmacognosy
Published on Web 10/20/2010

1
952 Journal of Natural Products, 2010, Vol. 73, No. 11
Notes
a
Scheme 2. Synthesis of 2
CH
2
Cl
2
layer was washed with H
2
O and dried over Na
2
SO
4
, and the
solvent was evaporated to a dark brown residue that was chromato-
graphed on silica gel. Elution of the column with EtOAc afforded: 2,3-
dihydro-5-methoxy-7H-dibenzo[de,h]quinolin-7-one (1-aza-2,3-
dihydro-5-methoxybenzanthrone, 3): yellow needles, 2.3 g (15%);
1
0
1
mp 165 °C (lit. 168-170 °C); H NMR (CDCl
.6 Hz, CH ), 3.92 (3H, s, OCH ), 4.13 (2H, t, J ) 7.6 Hz, CH
1H, d, J ) 2.5 Hz, ArH), 7.59-7.63 (2H, m, ArH), 7.68 (1H, t, J )
.3 Hz, ArH), 8.27 (1H, d, J ) 7.6 Hz, ArH), 8.38 (1H, d, J ) 7.8 Hz,
ArH). 2,3-Dihydro-5,6-dimethoxy-7H-dibenzo[de,h]quinolin-7-one
1-aza-2,3-dihydro-5,6-dimethoxybenzanthrone, 4): yellow needles,
3
) δ 2.89 (2H, t, J )
7
(
7
2
3
2
), 6.98
(
a
11
1
Reagents and conditions: (a) H
2
SO
4
/HNO
3
, TFA, rt, 2 h; (b) Na
2
S, NaOH,
0.086 g (0.5%); mp 156 °C (lit. 154-155 °C); H NMR (CDCl
3
) δ
), 3.33-348 (1H, m,
), 4.13-4.23 (1H, m,
), 6.57 (1H, s, ArH), 7.49 (1H, d, J ) 7.6 Hz, ArH), 7.66 (2H, m,
H
2
O, reflux, 5 h.
2.63-2.73 (1H, m, CH
2
), 2.84-3.01 (1H, m, CH
2
CH
CH
2
), 3.84 (3H, s, OCH ), 3.96 (3H, s, OCH
3
3
2
1
1
extensively. With regard to nitration of the 5-methoxy-substituted
compounds, it is worth pointing out that, although 1-aza-2,3-
dihydro-5-methoxybenzanthrone undergoes reaction with similar
ArH), 8.00 (1H, d, J ) 7.6 Hz, ArH). 2,3-Dihydro-6-hydroxy-5-
methoxy-7H-dibenzo[de,h]quinolin-7-one (1-aza-2,3-dihydro-6-hy-
droxy-5-methoxybenzanthrone, 5): red needles, 0.935 g (6%); mp
1
0
1
efficiency at both positions neighboring the OCH
3
group, its
158 °C (lit. 173.5-174.5 °C); H NMR (CDCl
.3 Hz, CH ), 3.97 (3H, s, OCH ), 4.10 (2H, t, J ) 8.3 Hz, CH
1H, s, ArH), 7.6 (1H, t, J ) 7.6 Hz, ArH), 7.71 (1H, t, J ) 7.3 Hz,
ArH), 8.27 (1H, d, J ) 7.8 Hz, ArH), 8.38 (1H, d, J ) 8.1 Hz, ArH),
2.93 (1H, s, OH).
,3-Dihydro-5-methoxy-6-nitro-7H-dibenzo[de,h]quinolin-7-
3
) δ 2.80 (2H, t, J )
8
2
3
2
), 6.9
aromatized analogue gives the 4-nitro compound (10) as the major
product. In our hands, the latter reaction occurred in 68% yield.
Considering that 10 was reduced to 2, the regioisomer of 1, in 70%
yield, this alternative route is clearly preferable for the synthesis
of 2 (Scheme 2).
The effects of these compounds on cell proliferation were
determined in four different human cell lines (MRC-5: normal lung
fibroblasts (CCL-171); AGS: gastric adenocarcinoma cells (CRL-
(
1
2
one (1-aza-5-methoxy-6-nitrobenzanthrone, 7) and 2,3-dihydro-5-
methoxy-4-nitro-7H-dibenzo[de,h]quinolin-7-one (1-aza-5-methoxy-
4
-nitrobenzanthrone, 9). To a solution of 5 (0.5 g, 3.8 mmol) in TFA
(
10 mL) was added carefully H SO /HNO , 1:1 (10 mL), stirring at
2
4
3
1
739); SK-MES-1: lung cancer cells (HTB-58); and J82: bladder
room temperature for 2 h. The reaction mixture was poured into water
carcinoma (HTB-1)), using the MTT reduction assay. The concen-
trations of the compounds inhibiting cell growth by 50% (IC50
values) were obtained adjusting the dose-response curves to a
sigmoidal model. Only compound 10 was moderately active and
slightly more toxic (IC50 ) 4.5 µM) toward gastric adenocarcinoma
cells than toward normal fibroblasts.
(50 mL), made alkaline with 10% NH3(aq) (pH 8-9), and extracted
with CH
2 2 2 2
Cl . The CH Cl layer was washed with water and dried over
Na SO . The solvent was evaporated to a yellow residue, which was
2
4
chromatographed on silica gel (AcOEt) to afford 2,3-dihydro-5-
methoxy-6-nitro-7H-dibenzo[de,h]quinolin-7-one (1-aza-2,3-dihy-
dro-5-methoxy-6-nitrobenzanthrone, 7): 0.205 g (35%); mp 209-210
1
°
C; H NMR (CDCl
3
) δ 2.99 (2H, t, J ) 7.9 Hz, CH
2
), 4.00 (3H, s,
), 7.19 (1H, s, ArH), 7.64 (1H, t,
J ) 7.6 Hz, ArH), 7.74 (1H, t, J ) 7.4 Hz, ArH), 8.23 (1H, d, J ) 7.8
For comparison, the IC50 values obtained for daurioxoisoapor-
phines A and B, using similar methodology in four different tumor
OCH
3
), 4.20 (2H, t, J ) 7.8 Hz, CH
2
cell lines, were reported to be in the range 3.0 µM to greater than
13
Hz, ArH), 8.38 (1H, d, J ) 7.8 Hz, ArH); C NMR (DMSO-d
5.2, 47.6, 57.9 (CH ), 109.8, 118.9, 120.6, 121.2, 122.8, 124.9, 126.9,
6
) δ
7
5
0 µM. Another similar study, in which 12 synthetic 1-azaben-
2
3
zanthrones were tested against three different tumor cell lines, gave
131.3, 131.7, 134.9, 135.4, 141.3, 152.6, 180.0 (CO); HREIMS m/z
308.0570 (calcd for C H N O , 308.0797) and 2,3-dihydro-5-meth-
9
IC50 values between 2.09 and >100 µM. Our results, added to the
1
7
12
2
4
previously published data, suggest that further modification of the
oxy-4-nitro-7H-dibenzo[de,h]quinolin-7-one (1-aza-2,3-dihydro-5-
1
-azabenzanthrone scaffold might lead to the development of
methoxy-4-nitrobenzanthrone, 9): 0.178 g (30%); mp 190-191 °C;
1
H NMR (CDCl
.21 (2H, t, J ) 7.8 Hz, CH
1H, t, J ) 7.4 Hz, ArH), 7.82 (1H, s, ArH), 8.32 (1H, d, J ) 7.6 Hz,
3
2 3
) δ 2.88 (2H, t, J ) 7.8 Hz, CH ), 4.07 (3H, s, OCH ),
cytotoxic anticancer drugs. Nevertheless, a rational series of
compounds with a broader range of substitution patterns would have
to be synthesized and tested before any reasonable structure-activity
relationships could be discerned.
4
(
2
), 7.68 (1H, t, J ) 7.4 Hz, ArH), 7.77
1
3
ArH), 8.44 (1H, d, J ) 7.9 Hz, ArH); C NMR (DMSO-d
4
1
6
) δ 20.5,
), 108.5, 114.0, 124.9, 126.9, 127.8, 130.6, 131.3, 131.7,
31.8, 134.7, 135.6, 149.7, 152.6, 182.2 (CO); HREIMS m/z 308.1463
7.0, 57.7 (CH
3
Experimental Section
17 12 2 4
(calcd for C H N O , 308.0797).
5
-Methoxy-6-nitro-7H-dibenzo[de,h]quinolin-7-one (1-aza-5-
General Experimental Procedures. All reagents and solvents were
commercially available from Sigma-Aldrich (St. Louis, MO, USA) or
Merck (Darmstadt, Germany) and were used without further purifica-
tion. Melting points are uncorrected and were determined with a
Reichert Galen III hot plate microscope equipped with a DUAL JTEK
methoxy-6-nitrobenzanthrone, 8). To a solution of 7 (1.0 g, 3.2 mmol)
in toluene (30 mL) was added Pd/C (0.1 g), and the suspension was
refluxed with stirring under air for 24 h. The hot mixture was filtered
through Celite and washed several times with hot toluene, and the
1
13
solvent was evaporated to dryness to leave 8: brownish-yellow needles
Dig-Sense thermocouple thermometer. H and C NMR spectra were
recorded at 300 or 400 MHz and 75 or 100 MHz, respectively, on
1
(MeOH), 870 mg (87%); mp 277-279 °C; H NMR (CDCl
3
) δ 4.10
Bruker Avance 300 or AMX 400 spectrometers, using CDCl
DMSO-d as solvent. The chemical shifts are reported as δ (ppm)
downfield from TMS for H NMR and relative to the central DMSO-
3
or
3
(3H, s, OCH ), 7.59 (1H, s, ArH), 7.66 (1H, t, J ) 7.8 Hz, ArH), 7.68
(1H, d, J ) 5.5 Hz, ArH), 7.84 (1H, t, J ) 7.6 Hz, ArH), 8.34 (1H, d,
6
1
J ) 7.8 Hz, ArH), 8.79 (1H, d, J ) 5.6 Hz, ArH), 8.88 (1H, d, J ) 7.9
13
13
d
6
resonance (39.5 ppm) for C NMR. Coupling constants (J) are given
Hz, ArH); C NMR (DMSO-d
6
) δ 58.5 (CH
3
), 115.5, 116.5, 117.3,
in Hz. EIMS were run on a Thermo Finnigan MAT 95XP instrument,
with electron impact ionization at 70 eV and with perfluorokerosene
as reference. Purities of the compounds subjected to biological testing
were >95% in every case (HPLC).
119.4, 121.0, 125.5, 127.7, 128.8, 130.1, 131.5, 135.7, 136.1, 146.1,
151.5, 153.5, 183.7 (CO); HREIMS m/z 306.0655 (calcd for
C
17
H
10
N
2
O
4
, 306.0641).
5-Methoxy-7H-dibenzo[de,h]quinolin-7-one (1-aza-5-methoxy-
Synthesis of 2,3-dihydro-7H-dibenzo[de,h]quinolin-7-one Deriva-
tives (3, 4, and 5). A solution of phthalaldehydic acid (10 g, 66.6 mmol)
in toluene (50 mL) was treated with 3,4-dimethoxyphenethylamine (11.0
mL, 66.6 mmol). The solution was refluxed with stirring under a
Dean-Stark trap for 2 h. The solvent was removed in vacuo, and the
crude product was heated with polyphosphoric acid (40 g) at 100 °C
for 20 min with stirring. The mixture was poured into ice water, made
benzanthrone, 6). A solution of 5 (2.0 g, 7.5 mmol) in benzene (10
mL) was treated with Pd/C (400 mg) and refluxed under air for 48 h.
The hot mixture was filtered through Celite and washed several times
with hot benzene. The solvent was removed to afford 6: yellow crystals
1
0
1
(MeOH), 1.4 g (73%); mp 178-179 °C (lit. 180-181 °C); H NMR
(CDCl ) δ 4.05 (3H, s, OCH
(1H, t, J ) 8.1 Hz, ArH), 7.66 (1H, d, J ) 5.6 Hz, ArH), 7.81 (1H, t,
J ) 7.8 Hz, ArH), 8.29 (1H, d, J ) 2.5 Hz, ArH), 8.41 (1H, d, J ) 7.8
3
3
), 7.43 (1H, d, J ) 2.4 Hz, ArH), 7.65
2 2
alkaline (pH 8-9) with 10% NH3(aq), and extracted with CH Cl . The

Notes
Journal of Natural Products, 2010, Vol. 73, No. 11 1953
Hz, ArH), 8.70 (1H, d, J ) 5.6 Hz, ArH), 8.90 (1H, d, J ) 7.9 Hz,
medium (for AGS cells) supplemented with 2 mM L-glutamine and
1.5 g/L NaHCO . Both media were additionally supplemented with
3
1
3
ArH); C NMR (CDCl
3
) δ 55.9 (CH
3
), 112.0, 118.6, 120.2, 120.8,
1
1
2
25.3, 127.1, 129.9, 130.7, 132.2, 134.1, 136.8, 137.3, 143.9, 148.1,
61.0, 183.1 (CO); HREIMS m/z 261.0813 (calcd for C17H11NO ,
2
61.0790).
10% heat-inactivated fetal bovine serum, 100 IU/mL penicillin G, and
10 µg/mL streptomycin. Cells were subcultured once a week, and the
medium was changed every two days. The cells were stored in liquid
nitrogen in media with 10% glycerol added, and their viability after
thawing was higher than 90%, as assessed by the trypan blue exclusion
test. For the assay, cells were plated in 96-well plates (100 µL/well) at
5
-Methoxy-4-nitro-7H-dibenzo[de,h]quinolin-7-one (1-aza-5-
methoxy-4-nitrobenzanthrone, 10). To a solution of 6 (1.0 g, 3.8
mmol) in TFA (50 mL) was added carefully H SO /HNO . 1:1 (10
mL), and the resulting mixture was stirred at room temperature for
h. The reaction mixture was poured into water (150 mL), made
alkaline with 10% NH3(aq) (pH 8-9), and extracted with CH Cl . The
CH Cl layer was washed with H O and dried over Na SO , and the
2
4
3
4
a density of 5 × 10 cells/mL. One day after seeding, the cells were
6
treated with the medium containing the compounds at concentrations
ranging from 0 to 100 µM, first dissolved in DMSO (final concentration
of 1%), diluted with complete medium, and incubated for 72 h in a
2
2
2
2
2
2
4
solvent was removed to leave a yellow residue, which was chromato-
graphed on silica gel (AcOEt), giving compound 10: 0.802 g (68%);
humidified incubator with 5% CO
MTT reduction assay was performed as described previously.
2
in air at 37 °C, after which the
12
1
1
1
mp 232-233 °C (lit. 231-233 °C); H NMR (400 MHz, CDCl
3
) δ
), 7.52 (1H, d, J ) 5.9 Hz, ArH), 7.68 (1H, t, J )
.8 Hz, 1H, ArH), 7.84 (1H, t, J ) 7.0 Hz, ArH), 8.38 (1H, d, J ) 7.8
Etoposide (98% purity, Sigma-Aldrich, St. Louis, MO, USA) was used
as a positive control. Each experiment was carried out three times in
quadruplicate. The IC50 value was obtained adjusting the dose-response
4
.22 (3H, s, OCH
3
7
(x-c)
Hz, ArH), 8.44 (1H, s, ArH), 8.77 (1H, d, J ) 5.9 Hz, ArH), 8.87 (1H,
curve to a sigmoidal model (a + (b - a)/1 + 10
IC50.
), where c ) log
13
d, J ) 7.9 Hz, ArH); C NMR (DMSO-d
6
) δ 58.0 (CH
17.5, 126.3, 128.3, 129.2, 129.5, 131.7, 132.2, 132.6, 135.4, 135.9,
48.1, 150.1, 152.5, 181.9 (CO); HREIMS m/z 306.0781 (calcd for
, 306.0641).
-Amino-5-methoxy-7H-dibenzo[de,h]quinolin-7-one (lakshmi-
nine, 1). To a stirred suspension of 8 (1.5 g, 4.8 mmol) in EtOH (50
mL) was added a solution of Na S.9H O (2.7 g, 11.2 mmol) and NaOH
1.0 g, 25 mmol) in water (50 mL). The mixture was refluxed for 5 h
3
), 114.4, 115.9,
1
1
Acknowledgment. V.C.-C. is the recipient of a MeceSup (UMCE-
0204) fellowship. This work was supported by grants from CONICYT
(AT-23070040), FIBE 27/10, ICM (P05-001-F), and MeceSup (UCH-
0601).
17 10 2 4
C H N O
6
2
2
Supporting Information Available: T1: Antiproliferative activity
(
1
13
and left to stand overnight. The EtOH was removed in vacuo, and the
precipitate formed was collected by filtration, washed with water, and
dried to yield compound 1: red needles (MeOH), 1.18 g (87%); mp
of compounds 1, 2, 6, 8, 10, and 11. Figures S1-S10: H and
C
NMR spectra of compounds 1, 2, 7, 8, and 9. These materials are
available free of charge via the Internet at http://pubs.acs.org.
1
2
06-207 °C; H NMR (CDCl
3
) δ 3.97 (3H, s, OCH
3
), 6.34 (1H, s,
NH ), 6.97 (1H, s, ArH), 7.44 (1H, d, J ) 2.1 Hz, ArH), 7.66 (1H, t,
2
References and Notes
J ) 7.1 Hz, ArH), 7.80 (1H, t, J ) 7.1 Hz, ArH), 8.53 (1H, d, J ) 7.7
Hz, ArH), 8.60 (1H, d, J ) 2.2 Hz, ArH), 9.00 (1H, d, J ) 7.9 Hz,
(
(
(
1) Kunitomo, J.; Satoh, M.; Shingu, T. Tetrahedron 1983, 79, 3261–
3265.
1
3
2 3 3
ArH), 10.59 (1H, s, NH ); C NMR (CDCl ) δ 56.0 (CH ), 104.2,
2) Takani, M.; Takasu, Y.; Takahashi, K. Chem. Pharm. Bull. 1983, 31,
1
1
08.3, 119.4, 120.2, 124.8, 126.4, 128.9, 129.5, 132.3, 132.8, 136.4,
41.9, 143.2, 148.0, 150.5, 183.8 (CO); HREIMS m/z 276.08917 (calcd
, 276.0899).
-Amino-5-methoxy-7H-dibenzo[de,h]quinolin-7-one (2). Reduc-
tion of 10, following the same procedure used to obtain lakshminine
3
091–3093.
3) Kunitomo, J.-I.; Kaede, S.; Satoh, M. Chem. Pharm. Bull. 1985, 33,
778–2782.
12 2 2
for C17H N O
2
4
(4) Hou, C.; Xue, H. Acta Pharm. Sin. 1985, 20, 112–117.
(5) Zhao, S.; Ye, W.; Tan, N.; Zhao, H.; Xia, Z. J. China Pharm. UniV.
1989, 20, 312.
(6) Sugimoto, Y.; Babiker, H. A. A.; Inanaga, S.; Kato, M.; Isogai, A.
Phytochemistry 1999, 52, 1431–1435.
(
1), yielded 2: red needles (MeOH), 0.95 g (70%); mp 232-233 °C;
1
H NMR (DMSO-d
6 3 2
) δ 4.05 (3H, s, OCH ), 7.40 (2H, s, NH ), 7.69
(
1H, t, J ) 7.5 Hz, ArH), 7.80 (1H, t, J ) 7.3 Hz, ArH), 8.11 (1H, s,
(
7) Yu, B.-W.; Meng, L.-H.; Chen, J.-Y.; Zhou, T.-X.; Cheng, K.-F.; Ding,
ArH), 8.26 (1H, d, J ) 7.7 Hz, ArH), 8.29 (1H, d, J ) 5.8 Hz, ArH),
J.; Qin, G.-W. J. Nat. Prod. 2001, 64, 968–970.
8) Killmer, L.; Vogt, F. G.; Freyer, A. J.; Menachery, M. D.; Adelman,
C. M. J. Nat. Prod. 2003, 66, 115–118.
9) Tang, H.; Wang, X. D.; Wei, Y.-B.; Huang, S.-L.; Huang, Z.-S.; Tan,
J.-H.; An, L.-K.; Wu, J.-Y.; Chan, A. S.-C.; Gu, L.-Q. Eur. J. Med.
Chem. 2008, 43, 973–980.
1
3
8
.62 (1H, d, J ) 5.7 Hz, ArH), 8.83 (d, J ) 1H, 7.9 Hz, ArH);
NMR (DMSO-d ) δ 56.09 (CH ), 114.4, 115.4, 116.5, 119.3, 122.4,
24.7, 126.2, 130.0, 132.3, 132.7, 135.6, 141.0, 141.4, 143.5, 146.5,
79.1 (CO); HREIMS m/z 276.0890 (calcd for C17 , 276.0899).
Cell Viability Assay. The MTT reduction assay was used to
determine the viability of MRC-5 normal human lung fibroblasts (CCL-
71), AGS human gastric adenocarcinoma cells (CRL-1739), SK-
C
(
6
3
1
1
(
12 2 2
H N O
(10) Walker, G. N.; Kempton, R. J. J. Org. Chem. 1971, 36, 1413–1416.
11) Sobarzo-S a´ nchez, E. Syntheses and reactivity in the 7H-dibenzo-
de,h]quinoline field. Ph.D. Thesis, Faculty of Sciences, University
(
1
[
MES-1 human lung cancer cells (HTB-58), and J82 human bladder
carcinoma cells (HTB-1) from the American Type Culture Collection
of Chile, Santiago, Chile, 2003, p 236.
12) Rodr ´ı guez, J. A.; Haun, M. Planta Med. 1999, 65, 522–526.
(
(
ATCC, Manassas, VA, USA), grown in Eagle’s minimum essential
medium (for MRC-5, AGS, and SK-MES-1 cells) or Ham’s F-12
NP100370G