Synthesis and antiproliferative activity of benzyl and phenethyl analogs of makaluvamines

Article abstract of DOI:10.1016/j.bmc.2007.11.051

Analogs of marine alkaloid, makaluvamine, bearing substituted benzyl and substituted phenethyl side chains have been synthesized and their antiproliferative activities have been evaluated. 4-Methyl, 4-chloro, and 4-fluoro substituted benzyl analogs possessed pronounced antiproliferative effects on the breast cancer cell line, MCF-7 at IC₅₀ values of 2.3 μM, 1.8 μM, and 2.8 μM, respectively. 4-Methyl, 4-chloro, and 3,4-methylenedioxy derivatives showed the best activity against MCF-7 among the phenethyl analogs with IC₅₀ values of 2.3 μM, 2.8 μM, and 2.4 μM, respectively. In general, methoxy substitutions resulted in slight loss in activity in both benzyl and phenethyl series. Benzyl, 4-fluorobenzyl, 3,4-dimethoxyphenethyl, and 3,4-methylenedioxyphenethyl analogs were tested by NCI in their 60 cell lines in vitro human cancer cell screen. All four compounds showed excellent inhibition against several tested cancer cell lines. Benzyl and 4-fluorobenzyl analogs were relatively more active than 3,4-dimethoxy phenethyl and 3,4-methylenedioxy phenethyl analogs. In NCI assays, the best Log GI₅₀ values were shown by the fluorobenzyl analog against the renal cancer cell line RXF-393 (<-8.0 M) and dimethoxy phenethyl analog against the CNS cancer cell line, SF-268 (<-8.0 M). The best Log LC₅₀ value was shown by the fluorobenzyl analog against the breast cancer cell line MCF-7 (-6.01 M).

Full text of DOI:10.1016/j.bmc.2007.11.051

Available online at www.sciencedirect.com
Bioorganic & Medicinal Chemistry 16 (2008) 2541–2549
Synthesis and antiproliferative activity of benzyl
and phenethyl analogs of makaluvamines
Bidhan A. Shinkre,a Kevin P. Raisch,b Liming Fanb and Sadanandan E. Velua,*
aDepartment of Chemistry, University of Alabama at Birmingham, 901 14th Street South, Birmingham, AL 35294, USA
bDepartment of Radiation Oncology, University of Alabama at Birmingham, 1824 6th Avenue South, Birmingham, AL 35294, USA
Received 22 September 2007; revised 18 November 2007; accepted 20 November 2007
Available online 28 November 2007
Abstract—Analogs of marine alkaloid, makaluvamine, bearing substituted benzyl and substituted phenethyl side chains have been
synthesized and their antiproliferative activities have been evaluated. 4-Methyl, 4-chloro, and 4-fluoro substituted benzyl analogs
possessed pronounced antiproliferative effects on the breast cancer cell line, MCF-7 at IC50 values of 2.3 lM, 1.8 lM, and
2.8 lM, respectively. 4-Methyl, 4-chloro, and 3,4-methylenedioxy derivatives showed the best activity against MCF-7 among the
phenethyl analogs with IC50 values of 2.3 lM, 2.8 lM, and 2.4 lM, respectively. In general, methoxy substitutions resulted in slight
loss in activity in both benzyl and phenethyl series. Benzyl, 4-fluorobenzyl, 3,4-dimethoxyphenethyl, and 3,4-methylenedioxyphen-
ethyl analogs were tested by NCI in their 60 cell lines in vitro human cancer cell screen. All four compounds showed excellent inhi-
bition against several tested cancer cell lines. Benzyl and 4-fluorobenzyl analogs were relatively more active than 3,4-dimethoxy
phenethyl and 3,4-methylenedioxy phenethyl analogs. In NCI assays, the best LogGI50 values were shown by the fluorobenzyl ana-
log against the renal cancer cell line RXF-393 (<ꢀ8.0 M) and dimethoxy phenethyl analog against the CNS cancer cell line, SF-268
(<ꢀ8.0 M). The best LogLC50 value was shown by the fluorobenzyl analog against the breast cancer cell line MCF-7 (ꢀ6.01 M).
ꢀ 2007 Elsevier Ltd. All rights reserved.
1. Introduction
antiviral, antimalarial, and antibiotic activities.3 While
a number of these alkaloids have been isolated in quan-
tities sufficient to ascertain their biological profile, many
with unique structures are available only in minute
quantities, precluding their thorough biological evalua-
tions. Laboratory synthesis of these alkaloids and their
analogs is the only practical solution to this problem.
For the past quarter of a century, global marine sources
have proven to be a rich source of a vast array of new
medicinally valuable compounds.1 These natural prod-
ucts exist as secondary metabolites in marine inverte-
brates such as sponges, bryazoa, tunicates, and
ascidians. As a result of the potential for drug discovery,
marine natural products have attracted scientists from
different disciplines, such as organic chemistry, bioor-
ganic chemistry, pharmacology, and biology. About a
dozen of marine alkaloids are currently in various
phases of human clinical trials for treatment of different
types of cancers.2 The largest number of bioactive mar-
ine alkaloids with novel structures have been isolated
from marine sponges.3 Sponges produce a plethora of
chemical compounds with widely varying carbon skele-
tons. Most bioactive compounds from sponges have
exhibited a variety of activities such as anti-inflamma-
tory, antitumor, immunosuppressive, neurosuppressive,
Marine sponges of the genera Latrunculia, Batzella, Pri-
anos, and Zyzzya are a rich source of alkaloids bearing a
pyrrolo[4,3,2-de]quinoline skeleton.4,5 This series of
alkaloids comprise of about 60 metabolites’ including
discorhabdins,6 epinardins,7 batzellines’8 isobatzellines,8
makaluvamines9–14, and veiutamine.15 Pyrrolo[4, 3, 2-
de]quinoline alkaloids have shown a variety of biological
activities such as inhibition of topoisomerase I9 and II,14
cytotoxicity against different tumor cell lines,14,16 anti-
fungal9 and antimicrobial activities.17 Pyrrolo[4, 3, 2-
de]quinoline alkaloids have recently received increasing
attention as a source of new anticancer drugs.18–23 Their
unique fused ring skeletons’ carrying interesting biolog-
ical properties’ have made them targets for several syn-
thetic and biological studies. There has been a rapid
growth of interest in the synthesis and biological evalu-
ation of this class of compounds and their analogs. Sev-
eral reviews have been published on the chemistry and
Keywords: Marine; Alkaloid; Makaluvamine; Analogs; Benzyl; Phen-
ethyl; Cytotoxicity; Antiproliferative; Antitumor.
*
Corresponding author. Tel.: +1 205 975 2478; e-mail: svelu@uab.
edu
0968-0896/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2007.11.051

2542
B. A. Shinkre et al. / Bioorg. Med. Chem. 16 (2008) 2541–2549
bioactivity of this class of compounds.4,24,25. Our inter-
est is focused on makaluvamines which belong to this
family of alkaloids. Makaluvamines A–P are a group
of 16 marine alkaloids isolated mainly from four species
of marine sponges, namely the Fijian sponge Zyzzya cf.
marsailis,14 Indonesian sponge Histodermella sp.,9
Pohnpeian sponge Zyzzya fuliginosa,13, and Jamaican
sponge Smenospongia aurea.12 A few examples of mak-
aluvamine alkaloids are given in Figure 1.
Makaluvamines exhibited in vitro cytotoxicity against
human colon tumor cell line, HCT-116. The cytotoxici-
ties of makaluvamines against Xrs-6, a Chinese hamster
ovary (CHO) cell line sensitive to agents that cause dou-
ble stranded breaks,14 paralleled the data obtained with
HCT-116. Makaluvamines are topoisomerase II inhibi-
tors.14 According to a recent literature report, makaluv-
amines produce their anticancer activity by direct DNA
damage under reductive activation conditions as well.26
Figure 2. Benzyl and phenethyl analogs of makaluvamine and their
IC50 values against breast cancer cell lines MCF-7 and MDA-MB-468
and human colon tumor cell line HCT-116.
2. Results and discussion
As a part of our work on analogs of marine natural
products with potential pharmacological value, we have
been interested in studying the anticancer activity of
makaluvamine analogs. Many pyrroloiminoquinone
alkaloids with proven anticancer activities were found
to have substitutions at the 7-position of the pyrroloimi-
noquinone ring. We have explored some simple substitu-
tions with increased steric bulk, hydrophobicity, and
hydrophilicity at the 7- position of the pyrroloiminoqui-
none ring and examined their anticancer activity.27
These derivatives were tested against two human breast
cancer cell lines, MCF-7 and MDA-MB-468, and one
human colon tumor cell line, HCT-116. All of the mak-
aluvamine analogs showed cytotoxicity against the
tested cell lines with IC50 values ranging from 0.56 lM
to 11 lM. Two analogs (benzyl analog, 4, and phenethyl
analog, 5) showed excellent activity against MCF-7,
MDA-MB-468, and HCT-116 (Fig. 2).27 Compounds 4
and 5 exhibited topoisomerase II inhibition comparable
to two clinically used topoisomerase II targeting drugs,
m-AMSA and etoposide.27
We have explored structure–activity relationship studies
on these two lead compounds 4 and 5 with the objective
of optimizing their activity. As a first step, we decided to
examine the effect of electron releasing and electron
withdrawing polar substituents on the phenyl rings pres-
ent in these two compounds. Proposed target structures
are given in Figure 3. The choice of substituents was lim-
ited by the commercial availability of benzyl and phen-
ethyl amines required for the synthesis of these target
compounds.
2.1. Chemistry
Synthesis of proposed target compounds is outlined in
Scheme 1. All target compounds were synthesized in
two steps starting from the known tricyclic pyrroloimi-
noquinone compound, 8. Synthesis of compound 8 has
been reported in the literature by several groups.28 We
prepared this compound following the 4,6,7-trim-
ethoxyindole approach described previously.29 Treat-
ment of compound 8 with different amine derivatives
(9) in anhydrous methanol at room temperature pro-
vided the aminated compounds 10. Intermediate prod-
Figure 1. A few examples of naturally occurring makaluvamines.
Figure 3. Proposed target structures.

B. A. Shinkre et al. / Bioorg. Med. Chem. 16 (2008) 2541–2549
2543
Table 2. Activity of phenethyl analogs of makaluvamines against
MCF-7
Compound
R00=
IC50 (lM)
7a
7b
7c
7d
7e
7f
4-CH3
2.3 0.6
3.4 1.1
13.7 1.8
4.6 0.2
2.4 0.4
2.8 0.2
5.1 0.3
4-OCH3
3,4-Di-OCH3
3,4-Di-Cl
3,4-OCH2O
4-Cl
Scheme 1. Synthesis of makaluvamine analogs.
7g
4-F
ucts 10 were subjected to detosylation reaction without
further purification and characterization. Removal of
tosyl protecting group from the compound 10 was
accomplished by treatment with NaOMe in MeOH to
obtain the final products 6a–g or 7a–g in 48–62 % yield.
All final products were completely characterized.
were not more active than the lead compounds 4 or 5. In
the case of benzyl analogs several of the derivatives
(compounds 6a, 6f, and 6g) showed comparable activity
to the parent compound 4. Substitution of monometh-
oxy, dimethoxy, trimethoxy or methylene dioxy groups
resulted in decrease in activity as compared to com-
pound 4. As the number of methoxy groups increased
from 1 to 3 a regular decrease in activity was observed
(6b, 3.6 lM, 6c, 6.6 lM, and 6d, 34.7 lM). 3,4-Methyl-
enedioxy substitution exhibited a similar decrease in
activity (6e, 5.2 lM) as compared to compound 4. The
trimethoxy substituted benzyl derivative was the least
active of all benzyl analogs (6d, 34.7 lM). Substitution
of halogens (4-Cl and 4-F) on the ring did not have a
major impact on the activity of benzyl analog 4 (6f,
1.8 lM and 6g, 2.8 lM).
2.2. Biology
Compounds 6a–g and 7a–g were evaluated for their
cytotoxicities against breast cancer cell line MCF-7 at
UAB. The dose of the compound that inhibits 50% cell
proliferation (IC50) was calculated using the data gener-
ated from 2 to 4 independent tetrazolium-based (XTT)
cytotoxicity assays (R&D Systems Inc., Minneapolis,
MN) performed in triplicate and were combined for
an average standard deviation. Two known topoiso-
merase II targeting drugs, m-AMSA and etoposide,
were included in our experiment for comparison.
Similar trends in activity as observed in the case of ben-
zyl analogs were observed in the case of phenethyl ana-
logs as well (Table 2). Methyl substitution did not
change the activity much (7a, 2.3 lM) as compared to
the parent compound 5. Methoxy and dimethoxy substi-
tution did show a decrease in activity (7b, 3.4 lM, 7c,
13.7 lM). However, methylene dioxy substitution did
not have a major influence on the activity (7e,
2.4 lM). 4-Chloro substitution did not change the activ-
ity much (7f, 2.8 lM). But, a 3,4-dichloro substitution
(7d, 4.6 lM) and 4-fluoro substitution (7e, 5.1 lM)
showed a slight reduction in activity.
Cytotoxic activities of benzyl analogs against MCF-7
are given in Table 1 and cytotoxic activities of phenethyl
analogs against MCF-7 are given in Table 2. All of the
synthesized benzyl analogs were found to be more active
than the control drug, etoposide. All benzyl analogs ex-
cept one compound (6d) were more active than m-
AMSA. All of the phenethyl analogs were found to be
more active than both of the control drugs, etoposide
and m-AMSA. However, the newly synthesized analogs
Table 1. Activity of benzyl analogs of makaluvamines against MCF-7
Two benzyl analogs (4,6g) and two phenethyl analogs
(7c,7e) were selected by the Developmental Therapeutic
Program of NCI (National Cancer Institute, Bethesda,
MD, USA) to undergo in vitro testing against a panel
of approximately 60 human tumor cell lines. These com-
pounds were tested against cell lines derived from nine
tumor types: leukemia, lung, colon, CNS, melanoma,
ovarian, renal, prostate, and breast. The compounds
were tested at five concentrations at 10-fold dilution.30,31
The antitumor activity of the tested compounds is ex-
pressed as Log GI50 values which is log of molar concen-
tration of the compound that inhibits 50% net cell
growth and LogLC50 values which is log of molar con-
centration leading to 50% net cell death. The LogGI50
and LogLC50 values of compounds 4, 6g, 7c, and 7e
are summarized in Table 3.
Compound
R=
IC50 (lM)
6a
6b
4-CH3
2.3 0.8
3.6 1.2
6.6 0.8
34.7 5.9
5.2 0.9
1.8 0.7
2.8 0.3
35.6 3.4
21.7 2.5
4-OCH3
3,4-Di-OCH3
3,4,5-Tri-OCH3
3,4-OCH2O
4-Cl
6c
6d
6e
6f
6g
4-F
Etoposide
m-AMSA

2544
B. A. Shinkre et al. / Bioorg. Med. Chem. 16 (2008) 2541–2549
Table 3. In vitro inhibitiona of cancer cell lines by compounds 4, 6g, 7c, and 7e
Compound no.
Panel/cell line
4
7c
7e
6g
A
B
A
B
A
B
A
B
Leukemia
CCRF-CEM
HL-60(TB)
K-562
ꢀ6.05
ꢀ6.49
ꢀ5.63
ꢀ6.50
ꢀ5.87
ꢀ5.76
>ꢀ4.00
ꢀ5.14
ꢀ4.97
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
N.T.d
ꢀ5.53
ꢀ5.72
ꢀ5.46
ꢀ5.70
N.T.d
ꢀ5.60
>ꢀ4.00
ꢀ5.00
ꢀ5.85
ꢀ4.12
ꢀ5.07
ꢀ5.50
ꢀ4.77
ꢀ5.31
ꢀ5.81
ꢀ5.97
ꢀ6.10
ꢀ6.25
ꢀ5.92
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
N.T.d
>ꢀ4.00
N.T.d
ꢀ4.28
ꢀ5.04
MOLT-4
RPMI-8226
SR
N.T.d
ꢀ4.21
N.T.d
>ꢀ4.00
ꢀ5.24
>ꢀ4.00
>ꢀ4.00
Non-small cell lung cancer
A549/ATCC
EKVX
HOP-62
ꢀ5.67
ꢀ4.60
ꢀ5.05
ꢀ4.28
ꢀ4.47
ꢀ4.37
>ꢀ4.00
ꢀ4.54
ꢀ4.36
ꢀ5.01
ꢀ5.57
ꢀ5.51
ꢀ5.29
ꢀ4.99
ꢀ4.98
ꢀ5.70
ꢀ5.55
ꢀ5.85
ꢀ5.65
ꢀ4.22
ꢀ4.43
ꢀ4.32
>ꢀ4.00
ꢀ4.26
ꢀ4.70
ꢀ4.31
ꢀ4.40
ꢀ4.38
N.T.d
ꢀ5.71
ꢀ5.60
ꢀ5.26
ꢀ5.36
ꢀ5.77
ꢀ5.55
ꢀ6.00
ꢀ5.58
N.T.d
ꢀ4.56
ꢀ4.38
>ꢀ4.00
ꢀ4.20
ꢀ5.00
ꢀ4.44
ꢀ4.92
ꢀ4.43
ꢀ5.84
ꢀ6.34
ꢀ5.42
ꢀ5.77
ꢀ5.63
ꢀ6.28
ꢀ5.93
ꢀ6.09
ꢀ5.70
ꢀ5.25
ꢀ5.23
ꢀ4.38
ꢀ4.72
ꢀ4.89
>ꢀ4.00
ꢀ5.02
ꢀ4.71
ꢀ5.03
ꢀ6.57
ꢀ5.43
ꢀ6.51
ꢀ5.26
ꢀ5.83
ꢀ6.20
ꢀ5.82
ꢀ5.77
HOP-92
NCI-H226
NCI-H23
NCI-H322M
NCI-H460
NCI-H522
Colon cancer
COLO 205
HCC-2998
HCT-116
HCT-15
HT29
ꢀ6.42
ꢀ5.58
ꢀ6.51
ꢀ5.86
ꢀ6.31
ꢀ5.69
ꢀ5.97
ꢀ5.24
ꢀ4.32
ꢀ5.86
ꢀ5.63
ꢀ5.62
ꢀ5.58
ꢀ5.60
ꢀ5.65
ꢀ5.51
ꢀ5.13
ꢀ4.61
ꢀ4.32
ꢀ4.40
ꢀ4.42
ꢀ4.00
ꢀ4.55
ꢀ5.99
ꢀ5.81
ꢀ5.62
ꢀ5.73
ꢀ5.68
ꢀ5.64
ꢀ5.46
ꢀ5.03
ꢀ4.87
ꢀ4.50
ꢀ4.46
ꢀ4.76
ꢀ4.09
ꢀ4.48
ꢀ6.44
ꢀ5.57
ꢀ6.15
ꢀ5.83
ꢀ6.22
ꢀ5.69
ꢀ5.74
ꢀ5.36
ꢀ4.39
ꢀ4.24
ꢀ5.23
ꢀ4.71
>ꢀ4.00
ꢀ4.61
>ꢀ4.00
ꢀ5.16
ꢀ4.48
KM12
SW-620
>ꢀ4.00
ꢀ4.59
CNS cancer
SF-268
SF-295
SF-539
SNB-19
SNB-75
U251
ꢀ5.55
ꢀ5.95
ꢀ5.72
ꢀ5.71
ꢀ4.78
ꢀ5.57
ꢀ4.25
ꢀ4.64
ꢀ5.01
ꢀ5.10
ꢀ4.15
ꢀ4.62
<ꢀ8.00
ꢀ5.73
ꢀ5.48
ꢀ5.49
ꢀ5.28
ꢀ5.46
>ꢀ4.00
ꢀ4.65
ꢀ4.45
ꢀ4.44
ꢀ4.29
ꢀ4.44
ꢀ5.44
ꢀ5.73
ꢀ5.66
ꢀ5.48
ꢀ5.46
ꢀ5.52
>ꢀ4.00
ꢀ5.01
ꢀ4.63
ꢀ4.41
ꢀ4.37
ꢀ4.42
ꢀ5.78
ꢀ5.97
ꢀ5.76
ꢀ5.75
ꢀ5.28
ꢀ5.70
ꢀ4.36
ꢀ5.14
ꢀ5.14
ꢀ5.12
ꢀ4.21
ꢀ5.01
Melanoma
LOX IMVI
MALME-3M
M14
ꢀ5.74
ꢀ6.52
ꢀ5.89
ꢀ5.28
ꢀ5.13
ꢀ6.34
ꢀ6.50
ꢀ5.74
ꢀ4.84
ꢀ5.41
ꢀ5.17
ꢀ4.26
ꢀ4.27
ꢀ5.38
ꢀ5.29
ꢀ5.11
ꢀ5.63
ꢀ6.60
ꢀ5.65
ꢀ5.14
ꢀ4.99
ꢀ5.87
ꢀ5.51
5.66
ꢀ4.58
ꢀ5.44
ꢀ4.58
>ꢀ4.00
ꢀ4.07
ꢀ5.29
>ꢀ4.00
ꢀ4.88
ꢀ5.78
ꢀ6.47
ꢀ5.85
ꢀ5.23
ꢀ5.31
ꢀ6.02
ꢀ5.53
ꢀ5.64
ꢀ4.64
ꢀ5.40
ꢀ5.12
ꢀ4.26
ꢀ4.32
ꢀ5.33
>ꢀ4.00
ꢀ5.00
ꢀ5.80
ꢀ6.68
ꢀ5.84
ꢀ5.34
ꢀ5.24
ꢀ6.49
ꢀ6.72
ꢀ5.81
ꢀ5.02
ꢀ5.65
ꢀ5.21
ꢀ4.31
ꢀ4.35
ꢀ5.44
ꢀ5.45
ꢀ5.20
SK-MEL-2
SK-MEL-28
SK-MEL-5
UACC-257
UACC-62
Ovarian cancer
IGROV1
ꢀ6.10
ꢀ5.59
ꢀ6.21
ꢀ5.57
ꢀ5.68
ꢀ5.15
ꢀ5.02
ꢀ4.25
ꢀ5.31
ꢀ4.59
ꢀ4.08
ꢀ4.28
ꢀ5.37
ꢀ5.79
ꢀ5.93
ꢀ5.29
ꢀ5.75
ꢀ4.84
ꢀ4.13
ꢀ4.59
ꢀ5.21
ꢀ4.27
ꢀ5.12
>ꢀ4.00
ꢀ5.60
ꢀ5.70
ꢀ6.01
ꢀ5.57
ꢀ5.79
ꢀ5.01
ꢀ4.32
ꢀ4.57
ꢀ5.85
ꢀ5.65
ꢀ5.96
ꢀ5.63
ꢀ5.70
ꢀ5.50
ꢀ5.00
ꢀ4.23
ꢀ5.30
ꢀ4.93
ꢀ4.74
ꢀ4.41
OVCAR-3
OVCAR-4
OVCAR-5
OVCAR-8
SK-OV-3
ꢀ5.25
>ꢀ4.00
ꢀ5.17
>ꢀ4.00
Renal cancer
786-0
A498
ꢀ5.49
ꢀ4.78
ꢀ5.55
ꢀ6.53
ꢀ5.68
ꢀ5.72
ꢀ5.33
ꢀ5.58
>ꢀ4.00
ꢀ4.26
ꢀ4.42
ꢀ4.49
ꢀ4.38
ꢀ5.02
ꢀ4.24
>ꢀ4.00
ꢀ5.26
ꢀ5.14
ꢀ5.38
ꢀ5.57
N.T.d
ꢀ5.51
ꢀ5.29
ꢀ5.15
ꢀ4.09
ꢀ4.33
ꢀ4.35
ꢀ4.50
N.T.d
ꢀ5.40
ꢀ5.22
ꢀ5.49
ꢀ5.75
N.T.d
ꢀ5.57
ꢀ5.35
ꢀ5.23
ꢀ4.27
ꢀ4.32
ꢀ4.06
ꢀ4.93
N.T.d
ꢀ5.46
ꢀ5.51
ꢀ5.69
ꢀ6.48
<ꢀ8.00
ꢀ5.71
ꢀ5.50
ꢀ5.59
ꢀ4.27
ꢀ4.55
ꢀ4.77
ꢀ4.45
ꢀ5.29
ꢀ5.05
ꢀ4.34
ꢀ4.27
ACHN
CAKI-1
RXF 393
SN12C
TK-10
ꢀ4.47
>ꢀ4.00
>ꢀ4.00
ꢀ4.60
>ꢀ4.00
ꢀ4.09
UO-31
Prostate cancer
PC-3
DU-145
ꢀ5.81
ꢀ5.75
>ꢀ4.00
ꢀ4.60
ꢀ5.12
ꢀ5.55
>ꢀ4.00
ꢀ4.45
ꢀ5.23
ꢀ5.87
>ꢀ4.00
ꢀ5.29
ꢀ5.80
ꢀ5.97
ꢀ4.27
ꢀ5.32

B. A. Shinkre et al. / Bioorg. Med. Chem. 16 (2008) 2541–2549
2545
Table 3 (continued)
Compound no.
Panel/cell line
4
7c
7e
6g
A
B
A
B
A
B
A
B
Breast cancer
MCF7
ꢀ7.22
ꢀ5.46
ꢀ6.36
ꢀ5.28
ꢀ5.69
ꢀ5.34
ꢀ6.28
ꢀ5.98
ꢀ6.58
ꢀ4.91
ꢀ5.49
ꢀ5.30
ꢀ5.69
ꢀ5.34
ꢀ5.60
ꢀ5.34
ꢀ5.92
ꢀ4.75
ꢀ5.63
ꢀ5.54
ꢀ5.72
ꢀ5.51
ꢀ5.53
ꢀ5.25
ꢀ6.80
ꢀ5.51
ꢀ6.14
ꢀ4.36
ꢀ5.76
ꢀ5.50
ꢀ6.20
ꢀ6.01
NCI/ADR-RES
MDA-MB-231/ATCC
HS 578T
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
ꢀ5.07
>ꢀ4.00
ꢀ4.03
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
ꢀ5.21
>ꢀ4.00
ꢀ4.32
>ꢀ4.00
ꢀ5.09
ꢀ4.57
N.T.d
>ꢀ4.00
ꢀ5.20
MDA-MB-435
BT-549
T-47D
ꢀ4.40
ꢀ4.38
ꢀ4.43
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
b
c
Response parameters, A = LogGI50 in Molar units and B = LogLC50 in Molar units.
a Data obtained from the NCI’s in vitro disease-oriented human tumor cell screen.
b LogGI50 is the log of molar concentration causing 50% growth inhibition of tumor cells.
c LogLC50 is the log of the molar concentration leading to 50% net cell death.
d Not tested.
All four compounds tested by the Developmental Ther-
apeutic Program of NCI exhibited high potency against
several tested cancer cell lines with LogGI50 values rang-
ing from <ꢀ8.00 M to ꢀ4.36 M and LogLC50 values
ranging from ꢀ6.01 M to >ꢀ4.0 M. The best LogGI50
values were shown by the fluorobenzyl analog, 6g,
against the renal cancer cell line RXF-393 (<ꢀ8.0 M)
and the dimethoxy phenethyl analog, 7c, against CNS
cancer cell line SF-268 (<ꢀ8.00 M). The best LogLC50
value was shown by 6g against the breast cancer cell line,
MCF-7 (ꢀ6.01 M).
kemia cell lines HL-60 (TB) and SR; non-small lung
cancer cell lines A549/ATCC, EKVX, NCI-H322M,
and NCI-H522; colon cancer cell lines COLO205 and
HCT-15; CNS cancer cell lines SF-295, SF-539, SNB-
19, and U251; melanoma cell lines LOX IMVI,
MALME-3M, M14, SK-MEL-5, UACC-257, and
UACC-62; ovarian cancer cell lines IGROV1 and
OVCAR-4; renal cancer cell lines RXF-393 and SN12C;
prostate cancer cell line DU-145; and breast cancer cell
lines MCF-7, MDA-MB-435.
The best LogGI50 value of the dimethoxy phenethyl ana-
log, 7c, was against the CNS cancer cell line SF-268
(<ꢀ8.0 M). It also exhibited LogGI50 values of
6ꢀ6.0 M against the melanoma cell line MALME-3M
and breast cancer cell line MCF-7. It showed LogLC50
values of 6ꢀ5.0 M against colon cancer cell line
COLO205, melanoma cell lines MALME-3M
and SK-MEL-5, ovarian cancer cell lines OVCAR-4
and OVCAR-8, and breast cancer cell lines, MCF-7 and
MDA-MB-435.
Overall, LogGI50 and LogLC50 values indicate that the
two benzyl analogs, 4 and 6g, are more active than the
two phenethyl analogs, 7c and 7e. The benzyl analog,
4, exhibited LogGI50 values of 6ꢀ6.0 against leukemia
cell lines CCRF-CEM, HL-60 (TB), and MOLT-4; non-
small cell lung cancer cell lines, EKVX, HOP-92, and
NCI-H332M; colon cancer cell lines COLO205, HCT-
116, and HT-29; melanoma cell lines, MALME-3M,
SK-MEL-5, and UACC-257; ovarian cancer cell lines,
IGROV1 and OVCAR-4; renal cancer cell line CAKI-
1, and breast cancer cell lines MCF-7, MDA-MB-231/
ATCC, and T47-D. The benzyl analog, 4, exhibited
LogLC50 values of 6ꢀ5.0 M against several cell lines.
This includes leukemia cell line HL-60 (TB); non-small
cell lung cancer cell lines EKVX and NCI-H522; colon
cancer cell lines COLO205 and HCT-15; CNS cancer
cell lines SF-539 and SNB-19; melanoma cell lines
MALME-3M, M-14, SK-MEL-5, UACC-257, and
UACC-62; ovarian cancer cell lines IGROV1 and OV-
CAR-4; renal cancer cell line SN12C, and breast cancer
cell lines MCF-7 and MDA-MB-435.
The best LogGI50 of methylene dioxy phenethyl analog, 7e
was against melanoma cell line MALME-3M (ꢀ6.47 M).
It also exhibited LogGI50 values of 6ꢀ6.0 M against
non-small lung cancer cell line NCI-H460, melanoma cell
line SK-MEL-5, and ovarian cancer cell line OVCAR-4.
It had LogLC50 values of 6ꢀ5.0 M against leukemia cell
line HL-60(TB), non-small lung cancer cell line
NCI-H23, colon cancer cell line COLO205, CNS cancer
SF-295, melanoma cell lines MALME-3M, M14,
SK-MEL-5, and UACC-62; ovarian cancer cell lines OV-
CAR-4 and OVCAR-8; prostate cancer cell line DU-145,
and breast cancer cell lines MCF-7 and MDA-MB-435.
Fluorobenzyl analog, 6g, was also equally potent exhib-
iting LogGI50 values of 6ꢀ6.0 against several cancer
cell lines. This includes leukemia cell lines MOLT-4
and RPMI-8226; non-small lung cancer cell lines
EKVX, NCI-H23, and NCI-H460; colon cancer cell
lines COLO205, HCT-116, and HT-29; melanoma cell
lines MALME-3M, SK-MEL-5, and UACC-257; renal
cancer CAKI-1 and RXF-393 and breast cancer cell
lines MCF-7, MDA-MB-231/ATCC, and T-47D. The
fluorobenzyl analog, 6g, exhibited LogLC50 values of
6ꢀ5.0 M against several cell lines. This includes the leu-
Interestingly, all four analogs 4, 6g, 7c, and 7e also
exhibited activity against adriamycin-resistant breast
cancer cell line NCI/ADR-RES with LogGI50 values
ꢀ5.46, ꢀ5.51, ꢀ4.91, and ꢀ4.75, respectively.
3. Conclusions
Analogs of marine alkaloid, makaluvamine, bearing
substituted benzyl and phenethyl side chains have been

2546
B. A. Shinkre et al. / Bioorg. Med. Chem. 16 (2008) 2541–2549
synthesized and their antiproliferative activities have
been evaluated at UAB against breast cancer cell line
MCF-7. 4-Methyl, 4-chloro, and 4-fluoro substituted
benzyl analogs possessed a pronounced antiproliferative
effect on the breast cancer cell line MCF-7, at IC50 val-
ues of 2.3, 1.8, and 2.8 lM, respectively, as compared to
35.6 lM for etoposide and 21.7 lM for m-AMSA. 4-
Methyl, 4-chloro, and 3,4-methylenedioxy derivatives
were the best among the phenethyl analogs exhibiting
IC50 values of 2.3 lM, 2.8 lM, and 2.4 lM, respectively.
In general methoxy substitution resulted in a slight loss
in activity in both benzyl and phenethyl series. Benzyl,
4-fluorobenzyl, 3,4-dimethoxyphenethyl, and 3,4-methy-
lenedioxyphenethyl analogs were tested by NCI in their
60 cell lines in vitro human cancer cell screen. All four
compounds showed excellent inhibition against several
tested cell lines. Benzyl and 4-fluorobenzyl analogs were
more active than 3,4-dimethoxy and 3,4-methylenedioxy
phenethyl analogs. In NCI assays, the best LogGI50 val-
ues were shown by the fluorobenzyl analog against the
renal cancer cell line RXF-393 (<ꢀ8.0 M) and 3,4-
dimethoxyphenethyl analog against CNS cancer cell line
SF-268 (<ꢀ8.0 M). The best LogLC50 value was shown
by the fluorobenzyl analog against the breast cancer cell
line MCF-7 (ꢀ6.01 M). All four analogs also exhibited
activity against adriamycin-resistant breast cancer cell
line NCI/ADR-RES.
1/9) revealed that the reaction was complete. The reaction
mixture was cooled to 0 ꢁC and quenched by adding tri-
fluoroacetic acid (2.2 equiv). The reaction mixture was al-
lowed to attain room temperature at which it was stirred
for 30–45 min. The solvent was removed under reduced
pressure and the residue was passed through a pad of sil-
ica gel with MeOH/CHCl3 (1/15) as eluent to furnish the
crude product 10. The crude product 10 as such was sub-
jected to detosylation without further purification.
4.3. General procedure for detosylation
To a solution of N-tosyl makaluvamine derivatives 10
(1 equiv) in anhydrous MeOH, sodium methoxide
(20 equiv) was added and stirred at room temperature
for 4–6 h. TLC analysis (MeOH/CHCl3, 1/9) revealed
that the deprotection was complete. The resulting solu-
tion was quenched at 0 ꢁC with trifluoroacetic acid
(30 equiv) and stirred further at RT for 30 min. The sol-
vent was completely removed under reduced pressure
and the residue obtained was co-evaporated three times
with CHCl3 to remove the traces of TFA. The crude
compound thus obtained was purified by chromatogra-
phy over a column of Si gel (20 · 2 cm) using MeOH/
CHCl3 (1/10) as eluent to afford the pure detosylated
makaluvamine analogs 4, 5, 6a–g or 7a–g (30–51% over-
all yield for two steps starting from the compound 8).
4.3.1. 7-(Benzylamino)-1,3,4,8-tetrahydropyrrolo[4,3,2-
de]quinolin-8(1H)-one (4). Following the typical proce-
dure, pyrroloiminoquinone 8 (80 mg, 0.17 mmol) and
benzyl amine (6c) (22.0 mg, 0.20 mmol) in anhydrous
MeOH (15 mL) were stirred at room temperature for
20 h to furnish 48 mg (0.09 mmol) of tosyl compound
which was detosylated using NaOMe (97 mg, 1.80 mmol)
in MeOH (8 mL) to furnish compound 4 (28 mg, 42%). 1H
NMR (CD3OD) d 2.92 (t, 2H, J = 7.8 Hz), 3.80 (t, 2H,
J = 7.8 Hz), 4.58 (s, 2H), 5.38 (s, 1H), 7.13 (s, 1H), and
7.20–7.45 (m, 5H); 13C NMR (CD3OD) d 19.4, 44.2,
48.0, 86.3, 120.2, 123.7, 125.7, 127.1, 128.3 (2C), 128.9,
130.0 (2C), 137.2, 155.2, 159.9, and 168.8; MS (ES+) m/z
278 (M+); HRMS (EI at 70 eV) m/z. Found: 277.1218;
calcd for C17H15N3O: 277.1215 (M+ꢀH).
4. Experimental
4.1. General methods for synthesis
Solvent evaporations were carried out in vacuo with ro-
tary evaporator. Thin layer chromatography (TLC) was
performed on silica gel plates with fluorescent indicator
(Whatmann, silica gel, UV254, 25 lm plates). Spots
were visualized by UV light (254 and 365 nm). Purifica-
tion by column and flash chromatography was carried
out using ‘BAKER’ silica gel (40 lm) in the solvent sys-
tems indicated. The amount (weight) of silica gel for col-
umn chromatography was in the range of 50–100 times
the amount (weight) of the crude compounds being sep-
arated. Proton nuclear magnetic resonance (1H NMR)
and carbon nuclear magnetic resonance (13C NMR)
spectra were recorded on a Brucker DPX-300 spectrom-
eter using TMS as internal standard. The values of
chemical shifts (d) are given in ppm and coupling con-
stants (J) in Hz. Mass spectra were recorded on Micro-
mass Platform LCC instrument. Anhydrous solvents
used for reactions were purchased in Sure-SealTM bottles
from Aldrich Chemical Company. Other reagents were
purchased from Aldrich, Lancaster or Fisher chemical
companies and used as received.
4.3.2. 1,3,4,8-tetrahydro-7-(phenethylamino)pyrrolo[4,3,2-de]-
quinolin-8(1H)-one (5). Following the typical procedure,
pyrroloiminoquinone 8 (80 mg, 0.17 mmol) and phen-
ethyl amine (24.5 mg, 0.20 mmol) in anhydrous MeOH
(15 mL) were stirred at room temperature for 20 h to fur-
nish 47 mg (0.08 mmol) of tosyl compound which was
detosylated using NaOMe (91 mg, 1.68 mmol) in MeOH
1
(8 mL) to furnish compound 5 (27 mg, 39%). H NMR
(CD3OD) d 2.89–3.05 (m, 4H), 3.60 (t, 2H, J = 7.2 Hz),
3.83 (t, 2H, J = 7.5 Hz), 5.41 (s, 1H), 7.14 (s, 1H), and
7.20–7.40 (m, 5H); 13C NMR (CD3OD) d 19.5, 35.1,
44.1, 46.2, 85.2, 120.2, 123.9, 125.5, 127.2, 127.9, 129.8
(2C), 129.9 (2C), 139.4, 155.0, 159.7, and 168.5; MS
(ES+) m/z 292 (M+). HRMS (EI at 70 eV) m/z. Found:
291.1371; calcd for C18H17N3O: 291.1371 (M+ꢀH).
4.2. General procedure for amination of the pyrroloimi-
noquinone derivative 8
To a solution of pyrroloiminoquinone derivative 8
(1 equiv) in anhydrous MeOH, a solution of amine 9
(1.2 equiv) in anhydrous MeOH was added dropwise
over a period of 10–15 min. The resulting solution was
stirred at RT for 16–36 h. TLC analysis (MeOH/CHCl3,
4.3.3. 7-(4-Methylbenzylamino)-1,3,4,8-tetrahydropyrrol-
o[4,3,2-de]quinolin-8(1H)-one (6a). Following the typical
procedure, pyrroloiminoquinone 8 (80 mg, 0.17 mmol)

B. A. Shinkre et al. / Bioorg. Med. Chem. 16 (2008) 2541–2549
2547
and 4-methylbenzyl amine (25 mg, 0.20 mmol) in anhy-
drous MeOH (15 mL) were stirred at room temperature
for 15 h to furnish 53 mg (0.095 mmol) of tosyl com-
pound which was detosylated using NaOMe (103 mg,
1.9 mmol) in MeOH (8 mL) to furnish compound 6a
(ES+) m/z 368 (M+); HRMS (EI at 70 eV) m/z. Found:
367.1534; calcd for C20H21N3O4: 367.1532 (M+ꢀH).
4.3.7. 7-(3,4-Methylenedioxybenzylamino)-1,3,4,8-tetra-
hydropyrrolo[4,3,2-de]quinolin-8(1H)-one (6e). Following
the typical procedure, pyrroloiminoquinone 8 (80 mg,
0.17 mmol) and piperonyl amine (31 mg, 0.20 mmol) in
anhydrous MeOH (15 mL) were stirred at room tempera-
ture for 16 h to furnish 46 mg (0.08 mmol) of tosyl com-
pound which was detosylated using NaOMe (84 mg,
1.56 mmol) in MeOH (8 mL) to furnish compound 6e
(31 mg (42%). 1H NMR (CD3OD) d 2.93 (t, 2H,
J = 7.5 Hz), 3.82 (t, 2H, J = 7.5 Hz), 4.48 (s, 2H), 5.42
(s, 2H), 5.92 (s, 2H), 6.75–6.83 (m, 3H), 7.14 (s, 1H); 13C
NMR (CD3OD) d 19.4, 44.2, 47.8, 86.3, 102.6, 108.8,
109.4, 120.2, 122.0, 123.7, 125.7, 127.1, 130.9, 148.8,
149.7, 155.0, 159.9, and 168.8; MS (ES+) m/z 322 (M+);
HRMS (EI at 70 eV) m/z. Found: 321.1122; calcd for
C18H15N3O3: 321.1113 (M+ꢀH).
1
(32 mg, 46%). H NMR (CD3OD) d 2.29 (s, 3H), 2.91
(t, 2H, J = 7.6 Hz), 3.79 (t, 2H, J = 7.6 Hz), 4.51 (s,
2H), 5.37 (s, 1H), 7.12 (s, 1H), 7.13–7.24 (m, 4H); 13C
NMR (CD3OD) d 19.4, 21.1, 44.2, 47.8, 86.3, 120.2,
123.7, 125.6, 127.1, 128.4 (2C), 130.6 (2C), 134.1,
138.9, 155.1, 159.8, and 168.8; MS (ES+) m/z 292
(M+); HRMS (EI at 70 eV) m/z. Found: 291.1379; calcd
for C18H17N3O: 291.1372 (M+ꢀH).
4.3.4. 7-(4-Methoxybenzylamino)-1,3,4,8-tetrahydropyr-
rolo[4,3,2-de]quinolin-8(1H)-one (6b). Following the typi-
cal procedure, pyrroloiminoquinone
8
(80 mg,
0.17 mmol) and 4-methoxybenzyl amine (28 mg,
0.20 mmol) in anhydrous MeOH (15 mL) were stirred at
room temperature for 16 h to furnish 48 mg (0.083 mmol)
of tosyl compound which was detosylated using NaOMe
(90 mg, 1.67 mmol) in MeOH (8 mL) to furnish the com-
pound 6b ( 31 mg, 43%). 1H NMR (CD3OD) d 2.92 (t, 2H,
J = 7.6 Hz), 3.75 (s, 3H), 3.80 (t, 2H, J = 8.0 Hz), 4.49 (s,
2H), 5.40 (s, 1H), 6.89 (d, 2H, J = 6.8 Hz), 7.12 (s, 1H),
7.23 (d, 2H, J = 6.8 Hz); 13C NMR (CD3OD) d 19.4,
44.1, 47.5, 55.7, 86.2, 115.3 (2C), 120.2, 123.7, 125.6,
127.1, 129.0, 129.8 (2C), 155.0, 159.8, 160.9, and 168.8;
MS (ES+) m/z 308 (M+); HRMS (EI at 70 eV) m/z. Found:
307.1317; calcd for C18H17N3O2: 307.1321 (M+ꢀH).
4.3.8. 7-(4-Chlorobenzylamino)-1,3,4,8-tetrahydropyrrol-
o[4,3,2-de]quinolin-8(1H)-one (6f). Following the typical
procedure, pyrroloiminoquinone 8 (80 mg, 0.17 mmol)
and 4-chlorobenzyl amine (29 mg, 0.20 mmol) in anhy-
drous MeOH (15 mL) were stirred at room temperature
for 36 h to furnish 42 mg (0.072 mmol) of tosyl com-
pound which was detosylated using NaOMe (78 mg,
1.45 mmol) in MeOH (8 mL) to furnish compound 6f
(23 mg, 32%). 1H NMR (CD3OD) d 2.93 (t, 2H,
J = 7.5 Hz), 3.82 (t, 2H, J = 7.5 Hz), 4.57 (s, 2H), 5.35
(s, 1H), 7.14 (s, 1H), and 7.21–7.42 (m, 4H); 13C
NMR (CD3OD) d 19.4, 44.2, 47.2, 86.5, 120.2, 123.6,
125.5, 127.1, 129.9 (2C), 130.0 (2C), 134.7, 136.1,
155.1, 160.0, and 168.8; MS (ES+) m/z 312 (M+); HRMS
(EI at 70 eV) m/z. Found: 311.0826; calcd for
C17H14ClN3O: 311.0825 (M+ꢀH).
4.3.5. 7-(3,4-Dimethoxybenzylamino)-1,3,4,8-tetrahydro-
pyrrolo[4,3,2-de]quinolin-8(1H)-one (6c). Following the
typical procedure, pyrroloiminoquinone
8 (80 mg,
0.17 mmol) and veratryl amine (34 mg, 0.20 mmol) in
anhydrous MeOH (15 mL) were stirred at room temper-
ature for 20 h to furnish 46 mg (0.076 mmol) of tosyl
compound which was detosylated using NaOMe
(82 mg, 1.52 mmol) in MeOH (8 mL) to furnish com-
4.3.9. 7-(4-Fluorobenzylamino)-1,3,4,8-tetrahydropyrrol-
o[4,3,2-de]quinolin-8(1H)-one (6g). Following the typical
procedure, pyrroloiminoquinone 8 (80 mg, 0.17 mmol)
and 4-fluorobenzyl amine (26 mg, 0.20 mmol) in anhy-
drous MeOH (15 mL) were stirred at room temperature
for 36 h to furnish 44 mg (0.078 mmol) of tosyl compound
which was detosylated using NaOMe (84 mg, 1.56 mmol)
in MeOH (8 mL) to furnish compound 6g (22 mg, (31%).
1H NMR (CD3OD) d 2.94 (t, 2H, J = 7.7 Hz), 3.82 (t, 2H,
J = 7.7 Hz), 4.57 (s, 2H), 5.38 (s, 1H), 7.01–7.19 (m, 3H),
and 7.29–7.40 (m, 2H); 13C NMR (CD3OD) d 19.4, 44.2,
47.2, 86.3, 116.5 and 116.8 (C–F coupling), 120.2, 123.6,
125.7, 127.1, 130.3, and 130.4 (C–F coupling), 133.3,
155.1, and 160.0 (C–F coupling), 165.4, 168.8, 173.2;
MS (ES+) m/z 296 (M+); HRMS (EI at 70 eV) m/z.
Found: 295.1114; calcd for C17H14FN3O: 295.1121
(M+ꢀH).
1
pound 6c (31 mg, 40%). H NMR (CD3OD) d 2.93 (t,
2H, J = 7.8 Hz), 3.80 (s, 3H), 3.81 (s, 3H), 3.75–3.85
(m, 2H), 4.51 (s, 2H), 5.42 (s, 1H), 6.75–6.95 (m, 3H),
7.14 (s, 1H); 13C NMR (CD3OD) d 19.5, 44.2, 47.9,
56.5 (2C), 86.3, 112.3, 113.1, 120.2, 121.0, 123.7, 125.6,
127.1, 129.8, 150.3, 150.9, 155.1, 159.9, and 168.8; MS
(ES+) m/z 338 (M+); HRMS (EI at 70 eV) m/z.
Found: 337.1437; calcd for C19H19N3O3: 337.1426
(M+ꢀH).
4.3.6. 7-(3,4,5-Trimethoxybenzylamino)-1,3,4,8-tetrahy-
dropyrrolo[4,3,2-de]quinolin-8(1H)-one (6d). Following
the typical procedure, pyrroloiminoquinone 8 (80 mg,
0.17 mmol) and 3,4,5-trimethoxybenzyl amine (40 mg,
0.20 mmol) in anhydrous MeOH (15 mL) were stirred at
room temperature for 16 h to furnish 41 mg (0.064 mmol)
of tosyl compound which was detosylated using NaOMe
(70 mg, 1.29 mmol) in MeOH (8 mL) to furnish com-
4.3.10. 7-(4-Methylphenethylamino)-1,3,4,8-tetrahydro-
pyrrolo[4,3,2-de]quinolin-8(1H)-one (7a). Following the
typical procedure, pyrroloiminoquinone 8 (80 mg,
1
pound 6d (28 mg, 34%). H NMR (CD3OD) d 2.93 (t,
2H, J = 7.5 Hz), 3.72 (s, 3H), 3.81 (s, 6H), 3.82 (t, 2H,
J = 7.5 Hz), 4.51 (s, 2H), 5.41 (s, 1H), 6.64 (s, 2H), 7.14
(s, 1H); 13C NMR (CD3OD) d 19.4, 44.2, 48.6, 56.6
(2C), 61.0, 86.4, 105.6 (2C), 120.2, 123.7, 125.7, 127.1,
133.3, 138.6, 155.0 (2C), 155.1, 159.9, and 168.8; MS
0.17 mmol) and 4-methylphenethyl amine (27.6 mg,
0.20 mmol) in anhydrous MeOH (15 mL) were stirred
at room temperature for 15 h to furnish 49 mg
(0.10 mmol) of tosyl compound which was detosylated
using NaOMe (112 mg, 2.07 mmol) in MeOH (8 mL)

2548
B. A. Shinkre et al. / Bioorg. Med. Chem. 16 (2008) 2541–2549
to furnish compound 7a ( 29 mg, 41%). 1H NMR
(CD3OD) d 2.28 (s, 3H), 2.85–3.00 (m, 4H), 3.56
(t, 2H, J = 7.2 Hz), 3.83 (t, 2H, J = 7.2 Hz), 5.39 (s,
1H), 7.05–7.15 (m, 4H), 7.13 (s, 1H); 13C NMR
(CD3OD) d 19.5 and 21.0, 34.7, 44.1, 46.3, 85.2, 120.2,
123.9, 125.5, 127.2, 129.7 (2C), 130.3 (2C), 136.2,
137.5, 155.0, 159.7, 168.5; MS (ES+) m/z 306 (M+);
HRMS (EI at 70 eV) m/z. Found: 305.1518; calcd for
C19H19N3O: 305.1528 (M+ꢀH).
4.3.14. 7-(3,4-Methylenedioxyphenethylamino)-1,3,4,8-
tetrahydropyrrolo[4,3,2-de]quinolin-8(1H)-one (7e). Fol-
lowing the typical procedure, pyrroloiminoquinone 8
(80 mg, 0.17 mmol) was stirred in anhydrous MeOH
(8 mL) and a solution of 3,4-methylenedioxyphenethyl-
amine hydrochloride (41 mg, 0.20 mmol) and triethyl-
amine (0.03 mL, 0.25 mmol) in anhydrous MeOH
(7 mL) were added to it dropwise. The resulting reaction
mixture was stirred at room temperature for 24 h to fur-
nish 57 mg (0.094 mmol) of tosyl compound which was
detosylated using NaOMe (102 mg, 1.89 mmol) in MeOH
(8 mL) to furnish compound 7e (34 mg, 45%).1H NMR
(CD3OD) d 2.88 (t, 2H, J = 7.8 Hz), 2.94 (t, 2H,
J = 7.5 Hz), 3.55 (t, 2H, J = 7.2 Hz), 3.84 (t, 2H,
J = 7.8 Hz), 5.40 (s, 1H), 5.89 (s, 2H), 6.60–6.80 (m,
3H), 7.14 (s, 1H); 13C NMR (CD3OD) d 19.5, 34.8,
44.1, 46.3, 85.2, 102.3, 109.3, 110.0, 120.2, 123.0, 123.9,
125.4, 127.2, 133.0, 147.9, 149.3, 155.0, 159.7, and 168.5;
MS (ES+) m/z 336 (M+); HRMS (EI at 70 eV) m/z. Found:
335.1276; calcd for C19H17N3O3: 335.1270 (M+ꢀH).
4.3.11. 7-(4-Methoxyphenethylamino)-1,3,4,8-tetrahydro-
pyrrolo[4,3,2-de]quinolin-8(1H)-one (7b). Following the
typical procedure, pyrroloiminoquinone 8 (80 mg, 0.17
mmol) and 4-methoxyphenethyl amine (31 mg, 0.20
mmol) in anhydrous MeOH (15 mL) were stirred at room
temperature for 16 h to furnish 59 mg (0.10 mmol) of tosyl
compound which was detosylated using NaOMe (108 mg,
2.0 mmol) in MeOH (8 mL) to furnish compound 7b
1
(38 mg, 51%). H NMR (CD3OD) d 2.81–3.00 (m, 4H),
3.54 (t, 2H, J = 7.5 Hz), 3.73 (s, 3H), 3.82 (t, 2H,
J = 7.2 Hz), 5.37 (s, 1H), 6.83 (d, 2H, J = 8.1 Hz), 7.13 (s,
1H), 7.15 (d, 2H, J = 8.1 Hz); 13C NMR (CD3OD) d 19.5,
34.3, 44.1, 46.4, 55.6, 85.2, 115.1 (2C), 120.2, 123.9, 125.4,
127.2, 130.8 (2C), 131.2, 155.0, 159.6, 160.1, and 168.5;
MS (ES+) m/z 322 (M+); HRMS (EI at 70 eV) m/z.
Found: 321.1465; calcd for C19H19N3O2: 321.1477
(M+ꢀH).
4.3.15. 7-(4-Chlorophenethylamino)-1,3,4,8-tetrahydro-
pyrrolo[4,3,2-de]quinolin-8(1H)-one (7f). Following the
typical procedure, pyrroloiminoquinone
8 (80 mg,
0.17 mmol) and p-chlorophenethyl amine (32 mg,
0.20 mmol) in anhydrous MeOH (15 mL) were stirred at
room temperature for 24 h to furnish 48 mg (0.081 mmol)
of tosyl compound which was detosylated using NaOMe
(88 mg, 1.62 mmol) in MeOH (8 mL) to furnish com-
pound 7f (28 mg, 37%). 1H NMR (CD3OD) d 2.82–3.00
(m, 4H), 3.50–3.69 (m, 2H), 3.85 (t, 2H, J = 7.5 Hz),
5.38 (s, 1H), 7.15 (s, 1H), 7.16–7.33 (m, 4H); 13C NMR
(CD3OD) d 19.5, 34.4, 44.2, 45.9, 85.3, 120.2, 123.8,
125.5, 127.2, 129.8 (2C), 131.5 (2C), 133.8, 138.2, 155.1,
159.8, and 168.5; MS (ES+) m/z 326 (M+); HRMS (EI at
70 eV) m/z. Found: 325.0974; calcd for C18H16ClN3O:
325.0982 (M+ꢀH).
4.3.12. 7-(3,4-Dimethoxyphenethylamino)-1,3,4,8-tetra-
hydropyrrolo[4,3,2-de]quinolin-8(1H)-one (7c). Following
the typical procedure, pyrroloiminoquinone 8 (80 mg,
0.17 mmol) and 3,4-dimethoxyphenethyl amine (37 mg,
0.20 mmol) in anhydrous MeOH (15 mL) were stirred
at room temperature for 16 h to furnish 51 mg
(0.082 mmol) of tosyl compound which was detosylated
using NaOMe (89 mg, 1.65 mmol) in MeOH (8 mL) to
furnish compound 7c (41 mg, 52%). 1H NMR (CD3OD)
d 2.85–3.00 (m, 4H), 3.57 (t, 2H, J = 7.2 Hz), 3.77 (s,
3H), 3.78 (s, 3H), 3.82 (t, 2H, J = 7.5 Hz), 5.36 (s,
1H), 6.72–6.91 (m, 3H), 7.14 (s, 1H); 13C NMR
(CD3OD) d 19.5, 34.7, 44.1, 46.3, 56.3, 56.4, 85.2,
113.2, 113.7, 120.2, 122.2, 123.9, 125.4, 127.2, 132.1,
149.4, 150.6, 155.0, 159.6, and 168.5; MS (ES+) m/z
352 (M+); HRMS (EI at 70 eV) m/z. Found: 351.1571;
calcd for C20H21N3O3: 351.1583 (M+ꢀH).
4.3.16. 7-(4-Fluorophenethylamino)-1,3,4,8-tetrahydro-
pyrrolo[4,3,2-de]quinolin-8(1H)-one (7g). Following the
typical procedure, pyrroloiminoquinone 8 (80 mg, 0.17
mmol) and 4-fluorophenethyl amine (28 mg, 0.20 mmol)
in anhydrous MeOH (15 mL) were stirred at room tem-
perature for 36 h to furnish 53 mg (0.092 mmol) of tosyl
compound which was detosylated using NaOMe
(99 mg, 1.84 mmol) in MeOH (8 mL) to furnish com-
1
4.3.13. 7-(3,4-Dichlorophenethylamino)-1,3,4,8-tetrahy-
dropyrrolo[4,3,2-de]quinolin-8(1H)-one (7d). Following
the typical procedure, pyrroloiminoquinone 8 (80 mg,
0.17 mmol) and 3,4-dichlorophenethyl amine (39 mg,
0.20 mmol) in anhydrous MeOH (15 mL) were stirred
at room temperature for 36 h to furnish 46 mg
(0.073 mmol) of tosyl compound, which was detosylated
using NaOMe (79 mg, 1.46 mmol) in MeOH (8 mL) to
furnish compound 7d (24 mg, 30%). 1H NMR (CD3OD)
d 2.89–3.02 (m, 4H), 3.60 (t, 2H, J = 7.0 Hz), 3.85 (t, 2H,
J = 7.5 Hz), 5.40 (s, 1H), 7.15 (s, 1H), 7.19 (dd, 1H,
J1 = 2.2 Hz, J2 = 7.9 Hz), and 7.41–7.48 (m, 2H). 13C
NMR (CD3OD) d 19.5, 34.1, 44.2, 45.5, 85.4, 120.2,
123.8, 125.5, 127.2, 130.0, 131.8 (2C), 132.0, 133.4,
140.4, 155.1, 159.8, and 168.5. MS (ES+) m/z 360
(M+). HRMS (EI at 70 eV) m/z. Found: 359.0583; calcd
for C18H15Cl2N3O: 359.0592 (M+ꢀH).
pound 7g (26 mg, (36%). H NMR (CD3OD) d 2.89–
3.01 (m, 4H), 3.58 (t, 2H, J = 6.9 Hz), 3.84 (t, 2H,
J = 7.5 Hz), 5.39 (s, 1H), 6.95–7.06 (m, 2H), 7.15 (s,
1H), and 7.20–7.34 (m, 2H); 13C NMR (CD3OD) d 19.5,
34.2, 44.2, 46.1, 85.2, 116.2, and 116.5 (C–F coupling),
120.2, 123.9, 125.5, 127.2, 131.6 and 131.7 (C–F cou-
pling), 135.4, 155.1, and 159.8 (C–F coupling), 161.7,
164.9, and 168.5; MS (ES+) m/z 310 (M+); HRMS (EI at
70 eV) m/z. Found: 309.1270; calcd for C18H16FN3O:
309.1277 (M+ꢀH).
Acknowledgments
Authors wish to acknowledge the financial support by
Breast Spore pilot grant from the University of
Alabama at Birmingham (UAB). S.E.V. also wishes to

B. A. Shinkre et al. / Bioorg. Med. Chem. 16 (2008) 2541–2549
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