Novel pyrrolo[3,2-f]quinolines: Synthesis and antiproliferative activity

Article abstract of DOI:10.1016/S0968-0896(01)00071-2

Novel pyrrolo[3,2,f]quinoline derivatives have been synthesized and tested as antiproliferative agents. They are characterized by an angular aromatic tricyclic system, to which a methyl group can be bound at position 7, and by a methanesulfonanisidide sid

Full text of DOI:10.1016/S0968-0896(01)00071-2

Bioorganic & Medicinal Chemistry 9 (2001) 1843–1848
Novel Pyrrolo[3,2-f]quinolines: Synthesis and
Antiproliferative Activity
M. G. Ferlin, B. Gatto, G. Chiarelotto and M. Palumbo*
Department of Pharmaceutical Sciences, University of Padova,
via Marzolo 5, 35131 Padova, Italy
Received 31 January 2001;accepted 16 March 2001
Abstract—Novel pyrrolo[3,2,f]quinoline derivatives have been synthesized and tested as antiproliferative agents. They are char-
acterized by an angular aromatic tricyclic system, to which a methyl group can be bound at position 7, and by a methanesulfon-
anisidide side chain as such, or lacking the m-methoxy substituent at position 1. The novel compounds were shown to exhibit cell
growth inhibitory properties when tested against the NCI panel of cell lines, in particular those obtained from leukemias. Although
the compounds are able to stimulate topoisomerase II poisoning at high concentration, the cell growth inhibition properties do not
appear to rest principally on this mechanism of action. Overall, the most active proved to be compound 9, having the m-methoxy
substituent typical of amsacrine, followed by the 7-methyl derivative 10 and by the unsubstituted compound 8. Comparison with
previously investigated regioisomers shows modulation of activity dictated by the position and conformational freedom of side-
chain groups. # 2001 Elsevier Science Ltd. All rights reserved.
Introduction
assess the pharmacological effects connected to side-
chain location.
Although many effective anticancer agents are available
at present, they generally exhibit important side-effects
including severe toxicity and resistance.1 Therefore,
new compounds are still needed to better understand
the drugs’ mechanism of cytotoxic action so that more
selective therapies can be rationally devised. We recently
,2
Results and Discussion
Chemistry
3
synthesized and investigated new derivatives, char-
The preparation of the desired compounds was accom-
plished according to Scheme 1. Compounds 1a,b, pre-
acterized by an angular 9-anilino-3H-pyrrolo[3,2-
f]quinoline planar nucleus connected to the methane-
sulfon-anisidide residue characteristic of the known
pared from 5-nitroindole as the starting material by two
were
previously described multistep procedures,5
dechlorinated to pyrrole[3,2-f]quinolines 2a,b by catal-
,6
4
anticancer drug m-AMSA. They were rather interest-
ing, since their profile of antiproliferative activity was
substantially different from that of the parent m-
AMSA. In particular they were remarkably active
against cell lines deriving from solid tumors like CNS-,
melanoma- and prostate-derived cells. To further inves-
tigate the antiproliferative potential of the pyrrolo-
quinoline family, in this paper we describe the synthesis
and cell growth inhibitory activity of pyrrolo[3,2-
f]quinoline derivatives to which the m-AMSA side chain
is linked through position 1 (Fig. 1). These congeners of
the previously investigated compounds will allow us to
ytic hydrogenation and then transformed into 1-formyl-
derivatives 3a,b with POCl in DMF by classical Vils-
3
meier–Haach reactions. In order to obtain 1-anilino-
methyl-substituted compounds, two-step reductive
7
alkylation reactions were performed without separating
the anilinium-methyl Schiff base intermediates formed
by condensation of 3a,b with p-methanesulfonamido-
anilines. NaBH CN was used as the selective reductive
3
agent. Hence, compounds 4–7 were obtained in good
yields, and easily transformed into the water-soluble
dihydrochlorides 8–11. Yields, melting points, recrys-
1
tallization solvents, IR and H NMR spectral data of
derivatives 2–7 are reported in Table 1;yields, analytical
data and MS spectra of compounds 8–11 are reported in
Table 2.
*
5
Corresponding author. Tel.: +39-49-827-5711;fax: +39-49-827-
366;e-mail: mpalumbo@purple.dsfarm.unipd.it
0
968-0896/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved.
PII: S0968-0896(01)00071-2

1844
M.G.Ferlin et al./ Bioorg.Med.Chem.9 (2001) 1843–1848
Topoisomerase II poisoning
and produced the expected cleavage of the nucleic acid
in a concentration dependent manner. Compounds 10
and 11 failed to show appreciable DNA-cleavage sti-
mulation in the concentration range 1–100 mM. The
same is true for compounds 8 and 9 up to 10 mM when
the appropriate lanes are compared to that showing
background cleavage (topo II). However, at 100 mM,
both congeners exhibited a remarkable level of clea-
vage stimulation, comparable to m-AMSA at the
same conditions. However, the cleavage intensity pat-
terns exhibited by the new derivatives are considerably
different from the patterns observed with m-AMSA.
This suggests changes in sequence preference exhibited
by pyrrolo-quinolines.
The extent of DNA damage induced by the test drugs in
the presence of human topoisomerase II a was eval-
uated by gel electrophoresis techniques. The results are
summarized in Figure 2. Etoposide (VP-16) and m-
AMSA were used as reference topoisomerase II poisons
8
From the above data, we can conclude that the topoi-
somerase-dependent mechanism of DNA damage is
appreciably operating only for compounds 8 and 9 at
high concentration.
Cell cytotoxicity
Derivatives 8–11 were tested as cytotoxic agents in the
9
Figure 1. Chemical structure of the test pyrrolo-quinoline derivatives
and m-AMSA.
in vitro primary NCI antitumor screen.
Figure 2. Topoisomerase II-stimulated DNA cleavage. The compounds tested were examined for their ability to stimulate human topoisomerase II-
mediated DNA cleavage in the concentration range 1–100 mM. A representative gel showing the activity of the test compounds at three concentra-
tions alongside with the reference compounds m-AMSA and etoposide (VP-16, 10 mM) is reported in the figure. The lane labelled DNA contains
DNA alone, the lane labeled Topo II contains a mixture of DNA and topoisomerase II at the concentration used in the presence of drugs (1%
DMSO in all tubes).

M.G.Ferlin et al./ Bioorg.Med.Chem.9 (2001) 1843–1848
1845
The results are reported in Table 3 as the average of the
data obtained with cell lines corresponding to specific
types of cancer and as the global average. The measured
potency is in the range 0.8–50 mM for the tested com-
pounds. In the case of leukemia cells compound 9
appears to be remarkably effective. In particular, it is
found to inhibit tumor cell growth in the nanomolar
range using CCRF-CEM or HL-60 (GI =34 nM)
Potency against solid tumor cell lines is less prominent.
Nonetheless, all compounds were active in the micro-
molar range and did not show particular selectivity for a
specific type of tumor (Table 3). The order of effective-
ness was in general 9 > 10 > 8 > 11. In terms of
0
structure–activity relationships, the double 7-methyl-2 -
methoxy substitution is clearly decreasing the drug’s
performance, as well as lack of substitution (see com-
pound 8). Compounds bearing either the methoxy
group or the methyl substituent are more potent, 9 per-
forming somewhat better than 10.
5
0
lines. Derivatives 11, 8, and 10 are on average 6, 20, and
7 times less potent than 9 against the same leukemia
lines.
2
Scheme 1.

1846
M.G.Ferlin et al./ Bioorg.Med.Chem.9 (2001) 1843–1848
As far as the mechanism of action is concerned, topoi-
somerase II-mediated DNA damage does not seem to
be the major cause of cell death. In fact, considering the
potency exhibited by the novel compounds, enzyme-
mediated DNA cleavage could hardly be detected in the
range of drug concentrations at which remarkable
cytotoxic effects are observed. In addition the order of
potency does not follow that of cleavage stimulation. In
fact, compound 10, not showing any evidence of topoi-
somerase-mediated effects, is more effective than com-
pound 8, the latter behaving as a topoisomerase II
poison at high concentration (100 mM). On the other
hand, compound 9 is active against leukemia cells at
sub-micromolar concentration, while it causes no
enzyme poisoning up to 10 mM. Hence, despite the
structural similarity with m-AMSA shown by the test
compounds, they have lost their ability to interfere effi-
ciently with topoisomerase II at cytotoxic concentra-
tions. Moreover, in analogy to our previous findings on
important biological pathways.
A COMPARE10 analysis was performed using the toxi-
city data obtained with all new derivatives. This could
unravel mechanism(s) of action in common with other
previously identified anticancer drugs. The rank of
similarity showed that the test drugs can be related to
compounds belonging to different chemical classes (see,
for example, NSC 71633 and NSC 134120 having a high
correlation with compound 9). In general, they are
mono- or bicyclic compounds, with amide, sulfonamide
or ester side chains. Amsacrine or related analogues
were never found in the list of the 20 most probable hits,
which confirms lack of similarity in the mechanism of
cytotoxic action.
Finally, it is interesting to compare the newly reported
1-substituted drugs with the previously tested con-
geners, either substituted at position 9 or having posi-
tions 1 and 9 linked through an extra cycle. Indeed, it
appears that the position and rigidity of the side-chain
modulates drug activity to a significant extent. In fact,
3
3
the parent 9-substituted derivatives, we tend to rule out
a topoisomerase I-related mechanism. As a result, the
observed tumor cell growth inhibition by pyrrolo-qui-
nolines should primarily rest on the impairment of other
0
the rank of potency in the present series is in favor of 2
Table 1. Analytical data for compounds 2–7
ꢀ
ꢁ1
1
a
Compound
Yield %
81
Mp ( C)
IR (cm
)
H NMR d (ppm)
2
ab
b
181–
c
Ref 12
Ref 12
1
82
268
2
78
3357, 3185,
1640, 1373
12.26 (1H, bs, NH), 9.36 (1H, d, J9,8=8.69 Hz, HC-9), 8.20 (1H, d,
4,5=8.94 Hz, HC-4), 7.98 (1H, d, J5,4=8.94 Hz, HC-5), 7.92 (1H, d,
d
(
dec)
J
J
8,9=8.69 Hz, HC-8), 7.73 (1H, t, J2,1ꢁ2,3=2.61 Hz, HC-2), 7.36 (1H,
3
bt, J1,2=2.42 Hz, J1,3=2.16 Hz HC-1), 2.94 (3H, s, CH )
3a
52
280–
c
3106, 825,
2734, 1659
9.99 (1H, s, ald.), 9.75 (1H, dd, J9,7=1.7 Hz, J9,8=8.5 Hz, HC-9), 8.86 (1H, dd,
2
83
J7,9=1.7 Hz, J7,8=4.2 Hz, HC-7), 8.54 (1H, s, HC-2), 7.96 (1H, d, J4,5=9.1 Hz,
HC-4), 7.89 (1H, d, J5,4=9.1 Hz, HC-5), 7.61 (1H, dd, J8,7=4.2 Hz,
J8,9=8.5 Hz, HC-8)
3
4
b
62
60
246–
c
3096,2895–
2815, 2714,
10.31 (1H, d, J9,8=8.5 Hz, HC-9), 10.04 (1H, s, H ald.), 8.70 (1H, d,
2,3=2.2 Hz, HC-2), 8.23 (1H, d, J4,5=9 Hz, HC-4), 8.13 (1H, d, J5,4=9 Hz,
2
48
J
1
669
3475, 3015,
309
HC-5), 7.91 (1H, d, J8,9=8.5 Hz, HC-8), 2.89 (3H, s, CH
3
)
184d
11.60 (1H, bs, NH ind.), 8.99 (1H, s, amide NH), 8.72 (1H, d, J7,8=4.31 Hz,
HC-7), 8.59 (1H, d, J9,8=7.9 Hz, HC-9), 7.84 (1H, d, J4,5=8.95 Hz, HC-4), 7.69
1H, d, J5,4=8.95 Hz, HC-5), 7.46 (1H, dd, J8,7=4.1 Hz, J8,9=7.9 Hz, HC-8), 7.50
1
(
0 0
3 ,5
1H, s, HC-2), 7.01 (2H, d, J =8.51 Hz, HC-3 and HC-5 ), 6.73 (2H, d,
0 0
(
0
0
J
2
0
,6
0
=8.59 Hz, HC-2 and HC-6 ), 5.97 (1H, bt, JNH,CH2=4.76 Hz, amine NH),
.57 (2H, d, JCH2,NH=4.76 Hz, CH ), 2.84 (3H, s, CH
4
2
3
)
5
6
65
50
223d
3418-3367,
11.62 (1H, bs, indolic NH), 9.09 (1H, bs, amide NH), 8.73 (1H, d, J7,8=4.3 Hz,
HC-7), 8.60 (1H, d, J9,8=7.61 Hz, HC-9), 7.84 (1H, d, J4,5=8.96 Hz, HC-4), 7.7
(1H, d, J5,4=8.96 Hz, HC-5), 7.48 (2H, m, HC-2 and HC-8), 6.76 (3H, m,
aromatic), 4.77 (1H, t, JNH,CH2=4.77 Hz, amine NH), 4.65 (2H, d,
3
2
287, 3126,
905, 1604,
1
147
J
CH2,NH=4.77 Hz, CH
11.53 (1H, bs, indolic NH), 8.99 (1H, bs, amide NH), 8.48 (1H, d,
9,8=8.46 Hz, HC-9), 7.78 (1H, d, J4,5=8.9 Hz, HC-4), 7.60 (1H, d, J5,4=8.9 Hz,
HC-5), 7.47 (1H, d, J2,3=2.28 Hz, HC-2), 7.35 (1H, d, J8,9=8.46 Hz, HC-8), 7.00
2 3 3 2
), 3.70 (3H, s,-OCH ), 2.87 (3H, s, CH SO )
220–
d
3367-3307,
3066, 1604-
2
21
J
1
510, 1307
0
0
0
(
2H, d, J
3
0
,5
0
=8.71 Hz, HC-3 and HC-5 ), 6.72 (2H, d, J
0
2
0
,6
0
=8.79 Hz, HC-2
and HC-6 ), 5.95 (1H, t, JNH,CH2=4.68 Hz, amine NH), 4.55 (2H, d,
2 3 2 3
JCH2,NH=4.68 Hz, CH ), 2.84 (3H, s, CH -SO ), 2.62 (3H, s, CH )
7
52
221–
d
3548, 3377,
1313, 1257-
11.53 (1H, bs, indolic NH), 9.09 (1H, bs, amide NH), 8.48 (1H, d, J9,8=8.6 Hz,
HC-9), 7.78 (1H, d, J4,5=8.9 Hz, HC-4), 7.60 (1H, d, J5,4=8.9 Hz, HC-5), 7.46
(1H, d, J2,3=2.48 Hz, HC-2), 7.35 (1H, d, J8,9=8.6 Hz, HC-8), 6.81–6.71 (3H,
m, aromatic), 4.72 (1H, bt, JNH,CH2=4.4 Hz, amine NH), 4.63 (2H, bd,
2
24
1
031, 1142
J
CH2,NH=4.4 Hz, CH
2
3 2 3
), 3.70 (3H, s,–OCH ), 2.87 (3H, s, SO CH ), 2. 62 (3H, s,
CH
3
)
a
6
Solvent: DMSO-d .
b
Ref 12.
Recrystallized from CH
c
3
OH.
Recrystallized from C H OH.
d
2 5

M.G.Ferlin et al./ Bioorg.Med.Chem.9 (2001) 1843–1848
Table 2. Analytical data for compounds 8–11
1847
Compound
Yield (%)
70
+13C NMR d (ppm)a
Elemental analysisb
Ms (70 eV) m/z (%)
8c
39.9 (S–CH
15.1 (2CH, C-2 and C-6 ), 121 (C-1 ), 122.1
), 50.0 (CH ), 110.5 (q, C-1),
2
C 49.90 (49.88)
H 4.85 (4.52)
N 12.25 (12.57)
S 7.01 (7.04)
Cl 15.50 (15.73)
367 [M+, 8], 288
(32), 271 (9), 180
(28), 166 (100),
79 (13), 64 (32)
3
0
0
0
0
1
(
0
CH, C-8), 122.6 (2CH, C-3 and C-5 ), 124.7
(CH, C-2), 126.0 (CH, C-5), 126.1 (2q, C-3a
0
and C-3b), 132.57 (CH, C-4), 135.6 (q, C-4 ),
1
37.7 (q, C-9a), 141.1 (CH, C-9), 143.2 (CH,
C-7), 145.7 (q, C-5a)
40.0 (S–CH ), 50 (CH ), 57.3 (OCH ), 105.16
9c
53
45
40
C 49.29 (49.25)
H 4.96 (4.68)
N 11.50 (11.27)
S 6.58 (7.06)
Cl 14.55 (14.38)
396 [M+, 10], 305
(32), 290 (9),
199 (27), 185
(100), 79 (12), 64
(33)
3
2
3
0
0
(
CH, C-3 ), 110.48 (q, C-1), 112.9 (CH, C-5 ),
0
0
115.15 (CH, C-6 ), 121.3 (q, C-1 ), 122.11
CH, C-8), 124.72 (CH, C-2), 126.05 (q, C-
(
3a), 126.12 (q, C-3b), 126.28 (CH, C-5),
0
32.72 (CH, C-4), 135.91 (q, C-4 ), 137.3 (q,
1
C-9a), 141.28 (CH, C-9), 143.17 (CH, C-7),
0
1
30.38 (CH
45.7 (q, C-5a), 154.64 (q, C-2 ).
1
0c
3
), 39.78 (S–CH
3
), 50 (CH ), 110.16
2
C 50.96 (51.30)
H 5.13 (4.89)
N 11.89 (11.98)
S 6.80 (7.01)
Cl 15.04 (14.84)
380 [M+, 7], 299
(31), 196 (18),
183 (100), 108
(22), 79 (9), 64
(30)
0
0
(
q, C-1), 114.65 (2CH, C-2 and C-6 ), 121.2
0
0
0
(q, C-1 ), 122.64 (2CH, C-3 and C-5 ),
23.53 (CH, C-8), 124.54 (CH, C-2), 125.5
1
(CH, C-5), 125.79 (2q, C-3a, C-3b), 132.70
0
CH, C-4), 135.23 (q, C-4 ), 137.09 (q, C-9a),
(
1
42.25 (CH, C-9), 145.8 (q, C-5a), 160 (q,
C-7).
30.38 (CH ), 39.98 (S–CH ), 50 (CH ), 57.4
1
1d
3
3
0
2
C 52.18 (51.93)
H 5.00 (4.87)
N 11.59 (11.40)
S 6.63 (6.82)
Cl 14.67 (14.45)
411 [M+, 20], 332
(35), 196 (20),
215 (100), 138
(25), 79 (9), 64
(30)
(
1
(
2
OCH ), 105.16 (CH, C-3 ), 110.1 (q, C-1),
3
0
0
12.93 (CH, C-5 ), 115.3 (CH, C-6 ), 121.2
0
q, C-1 ), 123.53 (CH, C-8), 124.54 (CH, C-
), 125.4 (CH, C-5), 126.1 (2q, C-3a and C-
0
3
b), 132.72 (CH, C-4), 135.91 (q, C-4 ),
37.11 (q, C-9a), 142.28 (CH, C-9), 145.7 (q,
C-5a), 154.64 (q, C-2 ), 161.2 (q, C-7)..
1
0
a
Solvent CD
3
OD.
Calculated values in parentheses.
b
c
As the dihydrochloride monohydrate.
As the dihydrochloride.
d
or 7-monosubstituted drugs, while in the 9-substituted
family, lack of substituents at those positions was pre-
ferred. Moreover, 2 ,7 disubstitution and/or ring closure
renders the novel compound an interesting lead for
anticancer drug development.
0
between position 1 and 9 is confirmed to generate less
potent drugs. Hence, the side chain groups need to be
more flexible to increase activity. Finally, the pre-
ferential and potent action against leukemia cell lines
exhibited by compound 9 was not observed before in
the pyrrolo-quinoline family. This information, along
with the unconventional mechanism of cytotoxicity,
Experimental
Chemistry
Melting points were determined with a Gallenkamp
MFB-595-010M Melting Point Apparatus, and are
uncorrected.
Table 3. Cell growth inhibition properties of the test pyrrolo-quino-
lines
1H NMR spectra were obtained with a Varian Gemini
2
00 MHz spectrometer using the indicated solvents and
1
Type of cancer cell linea
b
TMS as internal reference. The H NMR signals are
reported in parts per million (d, ppm), and are char-
acterized as singlet (s), doublet (d), triplet (t), quartet
GI50 (mM)
8
910
11
(
q), or multiplet (m). In the case of multiplets, the quo-
Leukemia (6)
Non-small cell lung (8)
Colon (6)
15.7ꢂ4.6 0.80ꢂ0.76 21.2ꢂ1.7 5.1ꢂ4.5
32.8ꢂ15 21.8ꢂ3.1 23.4ꢂ12 53.7ꢂ14
24.0ꢂ6.7 20.9ꢂ3.3 26.3ꢂ12 43.3ꢂ11
ted chemical shift corresponds to the multiplet centre.
Integrals corresponded satisfactorily to those expected
on the basis of compound structure. Coupling constants
are expressed in Hertz (Hz).
Central nervous system (5) 30.9ꢂ13 24.9ꢂ6.9 24.1ꢂ12 50.1ꢂ18
Melanoma (8)
Ovarian (6)
Renal (8)
20.1ꢂ5.1 17.7ꢂ2.1 18.5ꢂ2.3 53.0ꢂ18
36.7ꢂ13 21.7ꢂ11.4 23.9ꢂ3.4 51.2ꢂ21
24.5ꢂ5.0 16.6ꢂ11.0 21.0ꢂ12 29.5ꢂ9.1
22.2ꢂ4.1 19.4ꢂ1.8 21.8ꢂ2.8 37.1ꢂ5.2
27.0ꢂ9.9 16.1ꢂ7.6 24.1ꢂ10 51.2ꢂ9.8
Prostate (2)
Breast (8)
Average
Mass spectra were obtained with a Mass spectrometer
Mat 112 Varian Mat Bremen.
26.3
14.4
22.9
37.1
a
Elemental analyses were performed at the microanalysis
laboratory, Department of Pharmaceutical Sciences,
Number of tested lines in brackets.
Drug concentration inhibiting tumor cell growth by 50%.
b

1848
M.G.Ferlin et al./ Bioorg.Med.Chem.9 (2001) 1843–1848
University of Padova, Italy, using a Perkin-Elmer ele-
mental analysis apparatus model 240B. The results for
compounds 2–7 were within ꢂ0.4% of the theoretical
values. Data for compounds 8–11 are given in Table 3.
Upon bubbling dry HCl through a solution of com-
pounds 4–7 in absolute ethanol, crystalline precipitates
formed. They were collected and recristallyzed from
methanol–ethanol mixtures to yield the water-soluble
pure dihydrochlorides 8–11 (Table 2).
ꢁ
1
IR spectra were recorded in cm with a Perkin-Elmer
760FTIR spectrophotometer using potassium bromide
pressed disks.
1
Topoisomerase II cleavage assay
The plasmid pBR322 was cut at the EcoR1 site, pre-
cipitated and labelled by fill-in with the Large (Klenow)
Fragment of DNA Polymerase I and [a- P]dATP.
DNA was resuspended and treated with Hind III to
obtain uniquely end-labeled pBR322. DNA (60 ng) was
finally reacted with the indicated concentrations of
Thin layer chromatography (TLC) was performed with
Merck silica gel F254 polystyrene-backed plates. Elu-
ents used in TLC analysis: a, (ethyl acetate/n-hexane 7:3
v/v), b, (methanol/n-hexane 9:1 v/v). Column flash
chromatography was performed with Merck silica gel
3
2
(
250–400 mesh ASTM).
drugs and 1.2 units of human topoisomerase II-a
ꢀ
mM Tris–HCl (pH 8.0), 10 mM MgCl , 120 mM KCl,
(TopoGEN, Inc., Columbus, OH, USA) at 37 C in 50
Chemicals were purchased from Fluka or Aldrich. p-
Methansolfonamido-anilines were synthesized in our
laboratory according to previous procedures.
2
0.5 mM DTT, 30 mg/mL BSA and 0.5 mM ATP. Fol-
lowing 30 min of incubation at 37 C, samples were
3
,11
ꢀ
stopped by incubation with 0.5 mg/mL proteinase K
and 1% SDS at 60 C for 3 h, and then loaded on 1%
ꢀ
General procedure for the synthesis of dechlorinated
compounds 2a,b. A solution of 9-chloro-pyrrolo[3,2-
agarose gel (0.089 M Tris-borate pH 8.3, 2.5 mM
EDTA) and run for 16 h at 35 volts. The gel was then
dried and autoradiographed. The effects of drugs were
examined up to 100 mM concentration.
3
f]quinolines 1a,b (2–3 mmol) in methanol was slowly
added to a 5% palladium on charcoal/methanol suspen-
sion saturated with hydrogen and the mixture was hydro-
ꢀ
material disappeared according to a TLC analysis. After
genated at atmospheric pressure at 40 C until the starting
Antitumor screen
3–6 h, the mixture was filtered and the filtrate evapo-
rated to dryness to give almost pure crude solids.
The test derivatives were submitted to an in vitro antic-
9
ancer testing at NCI. The cell panel consisted of 60
General procedure for the synthesis of 1-formyl deriva-
tives 3a,b. A 6:1 mixture of anhydrous DMF and
POCl (0.5 mL) was cooled to 10–15 C by means of an
3
lines against which compounds were tested at five con-
centrations at tenfold dilutions. A 48 h continuous drug
exposure protocol was used, and a sulforhodamine
protein assay was employed to estimate cell viability or
growth. Plot studies were performed for the detection of
patterns of interest.
ꢀ
ice/water bath and then a solution of pyrroloquinoline 2
(
ring for 3–4 h at 35–40 C, one further mL of POCl was
3–3.5 mmol) was added dropwise in DMF. After stir-
ꢀ
3
added and the stirring continued until the starting com-
pound completely disappeared in the TLC assay. After
cooling, the mixture was diluted with iced water, made
alkaline with NaOH 2N, extracted exhaustively with
References and Notes
ethyl acetate, the organic phase was dried over Na SO
2
4
1. Canal, P.;Gamelin, E.;Vassal, G.;Robert, J.
Oncol.Res. 1998, 4, 171.
2. Hortobagyi, G. N. Drugs 1997, 54, 1.
3. Ferlin, M. G.;Gatto, B.;Chiarelotto, G.;Palumbo, M.
Bioorg.Med.Chem. 2000, 8, 1415.
Pathol.
and evaporated under reduced pressure. The crude yel-
low solids obtained by this procedure were finally
recrystallized.
4
5
2
6
2
7
8
. Malonne, H.;Atassi, G. Anticancer-Drugs 1997, 8, 811.
. Conrad, M.., Limpach, L. Ber. 1887, 20, 944; Ber. 1891, 24,
990.
. Gould, R. G.;Jacobs, W. A. J.Am.Chem.Soc. 1939, 61,
890.
General procedure for the synthesis of 1-(p-methanesulfo-
namido-aniline) pyrroloquinolines 4–7. A methanol solu-
tion
of
equimolar
amounts
of
1-formyl-
pyrroloquinoline (1–1.5 mmol) and p-methanesulfona-
mido aniline or o-methoxy-p-methanesulfonamido-ani-
line was made acidic with acetic acid (pH 6) and stirred
at room temperature for a few hours until the starting
products disappeared in the TLC test (ethyl acetate/n-
. Borch, R. F.;Hassid, A. I. J.Org.Chem. 1972, 37, 1673.
. Cornarotti, M.;Tinelli, S.;Willmore, E.;Zunino, F.;
Fisher, L. M.;Austin, C. A.;Capranico, G. Mol.Pharmacol.
1996, 50, 1463.
hexane 7:3 v/v). Subsequently, an excess of NaBH CN
3
9. Christian, M. C.;Pluda, J. M.;Ho, P. T.;Arbuck, S. G.;
Murgo, A. J.;Sausville, E. A. Semin.Oncol. 1997, 24, 219.
(
2.2 mmol) dissolved in 3 mL of methanol was added
10. Boyd, M. R. In Cancer: Principles and Practice of Oncol-
ogy;DeVita, V. T., Jr., Hellman, S., Rosenberg, S. A., Eds.,
and the mixture was stirred for two days at room tem-
perature. A precipitate formed during the reduction, the
yield of which was increased by concentrating the solu-
Lippincott: Philadelphia, PA, 1989;Vol. 3, pp 1–12.
11. Brennan, S. R.;Colbry, M. L.;Leeds, R. L.;Leja, B.;Priele,
S. R.;Reily, M. D.;Showalter, H. D. H.;Uhlendorf, S. E.;
ꢀ
tion to small volume and keeping at 4 C overnight. The
solid was collected, washed with water and dried. Crys-
talline products were obtained by flash chromatography
on silica gel, followed by crystallization with suitable
solvent systems (Table 1).
Atwell, G. J.;Denny, W. A. J.Heter.Chem. 1989, 26, 1469.
2. Gryovznov, A. P.;Akhvlediani, R. N.;Volodina, T. A.;
Vasil’ev, A. M.;Babushkina, T. A.;Suvorov, N. N. Khim.
Geterotsikl.Soedin 1977, 3, 369.
1