Synthesis and bioactivity of 4,10-dimethyl-pyridino[2,3-h]quinolin-2(1H)-one-9-carboxylic acid and its esters

Article abstract of DOI:10.1016/S0968-0896(02)00526-6

4,10-Dimethyl-pyridino[2,3-h]quinolin-2(1H)-one-9-carboxylic acid (1) was synthesized by a new approach via the key intermediate 7-[1-aza-2-(dimethylamino)vinyl]-4-methylquinolin-2(1H)-one (4). Compound 1 and its esters were evaluated in cytotoxicity and anti_HIV assays. The 9-carboxyl (1s)-endo-(-)-borneol ester (9) showed marginal cytotoxic activity in CAK1-1, HOS, KB, and HCT-8 cells.

Full text of DOI:10.1016/S0968-0896(02)00526-6

Bioorganic & Medicinal Chemistry 11 (2003) 1031–1034
Synthesis and Bioactivity of 4,10-Dimethyl-pyridino[2,3-h]quinolin-
2
(1H)-one-9-carboxylic Acid and Its Esters
a
a
a
a,
b
b
Qian Zhang, Ying Chen, Yun Qing Zheng, Peng Xia, * Yi Xia, Zheng Yu Yang,
b
b
b,
Kenneth F. Bastow, Susan L. Morris-Natschke and Kuo-Hsiung Lee *
aDepartment of Medicinal Chemistry, School of Pharmacy, Fudan University, Shanghai 200032, China
bNatural Products Laboratory, School of Pharmacy, University of North Carolina, Chapel Hill, NC 27599, USA
Received 13 March 2002; accepted 25 September 2002
Abstract—4,10-Dimethyl-pyridino[2,3-h]quinolin-2(1H)-one-9-carboxylic acid (1) was synthesized by a new approach via the key
intermediate 7-[1-aza-2-(dimethylamino)vinyl]-4-methylquinolin-2(1H)-one (4). Compound 1 and its esters were evaluated in cyto-
Kt o Bx i, c ai t ny da Hn dC aT n- t8 i- cHe lI l Vs . assays. The 9-carboxyl (1s)-endo-(ꢀ)-borneol ester (9) showed marginal cytotoxic activity in CAK1-1, HOS,
#
2003 Elsevier Science Ltd. All rights reserved.
5
Introduction
and subsequently constructs the C ring. The key point
is regioselective formation of the C ring (Scheme 4).
As recently reported, 4-methylhydro-2H-pyrano[6,5-h]-
chromen-2-ones and 4-methylhydro-2H-pyrano[6,5-h]-
quinolin-2-ones show interesting bioactivities with di-O-
(S)-camphanoyl(+)-cis-khellactone (DCK) derivatives
displaying potent anti-HIV activity and 4,8,8-trimethyl-
Chemistry
1
We have now developed a different synthetic approach
starting from 7-amino-4-methylquinolin-2(1H)-one (3),
which is readily available by heating 1,3-phenylenedi-
amine with ethyl acetoacetate. Highly regioselective C
ring closure via the intermediate 7-[1-aza-2-(dimethyl-
amino)vinyl]-4-methylquinolin-2(1H)-one (4) led to the
target hydropyridino[2,3-h]quinolin-2-ones (Scheme 5).
hydro-2H-pyrano[6,5-h]quinolin-2-one displaying sig-
2
nificant cytotoxic activity. These findings prompted us
to synthesize two series of diaza three-ring heterocyclic
analogues, trihydropyridino[2,3-h]quinolin-2-ones and
hydropyridino[2,3-h]quinolin-2-ones (Scheme 1).
To our knowledge, the following three synthetic approa-
ches to the above diaza three-ring heterocyclic analo-
gues have been reported. (1) The first route uses
7-Amino-4-methylquinolin-2(1H)-one (3) was obtained
by reacting 1,3-phenylenediamine with ethyl aceto-
acetate using a reported method. We then tried to
6
1
,3-phenylenediamine as the starting material and
3
simultaneously constructs the A and C rings. Although
this route is short, the structures of the A and C rings
must be identical (Scheme 2). (2) The second route uses
construct the C ring by intermolecular electrophilic
substitution of 3 with b-substituted acid chloride, anhy-
dride or methylketone reagents at position-8 followed
by ring closure through formation of the N–C bond or
alternatively by first establishing the N–C bond fol-
lowed by ring closure through an intramolecular elec-
trophic substitution. However, numerous reactions failed,
most likely because of low nucleophilic reactivity of the
B ring. However, when 3 was reacted with the strongly
5
-aminoquinoline as starting material and then con-
4
structs the A ring. However, although the C ring is
already established in the starting material and the A
ring formation is highly regioselective, preparation of
the 5-aminoquinoline is tedious (Scheme 3). (3) The
third route uses 7-aminoquinoline as starting material
electrophilic Vilsmeier Reagent (DMF and POCl ), an
3
unexpected product was identified as: 7-[1-aza-2-(di-
methylamino)vinyl]-4-methylquinolin-2(1H)-one (4). This
compound exhibited different H NMR behavior in
*
Corresponding authors. Tel.: +86-21-6404-1900x2563; e-mail:
pxia@shmu.edu.cn (P. Xia); tel.: +1-919-962-0066; e-mail: khlee@
unc.edu (K.-H. Lee).
1
0
968-0896/03/$ - see front matter # 2003 Elsevier Science Ltd. All rights reserved.
PII: S0968-0896(02)00526-6

1032
Q. Zhang et al. / Bioorg. Med. Chem. 11 (2003) 1031–1034
various solvents, which suggested a partial double-bond
nature of the C–N single-bond in the –N¼CH–N(CH )
Because the –N¼CH–N(CH ) group could enhance the
3
2
nucleophilic reactivity of the B-ring via an electron
donating effect and also act as a nucleophile acceptor at
the –N¼C– carbon atom, we turned our attention to
using 4 as an intermediate to form the C ring. Initially,
we tried reacting 4 with ethyl acetoacetate and obtained
3
2
group, presumably due to hindered rotation around the
C–N s-bond. Accordingly, a rotation energy barrier of
7
1
ÁG=66.5 KJ/mol was calculated via
(
H NMR
DMSO-d ) at different temperatures.
6
0 0
-[N-(2 -acetyl-2 -ethoxycarbonyl-vinyl)]amino-4-methyl-
7
quinolin-2(1H)-one (5), which was conveniently con-
verted to 2-chloro-4,10-dimethylpyridino[2,3-h]quinoline-
9-carboxyl ethyl ester (6) by heating with POCl . The C
3
ring closure was highly regioselective at position-8 and
no linear tri-ring product was isolated; however, the
amide group in 5 was also converted to a chloro imine
moiety in 6. Hydrolysis of 6 with concd HCl gave the
2-chloro-9-carboxylic acid (7), which was further
hydrolyzed with aq NaOH (13%, g/mL) to yield 1.
Additionally, treating 6 with aq NaOH (13%, g/mL)
resulted in complete hydrolysis of both the 9-ester and
chloro imine to directly produce 4,10-dimethyl-pyr-
idino[2,3-h]quinolin-2(1H)-one-9-carboxylic acid (1).
Scheme 1.
Biological Results
Two esters of 1, 9-carboxyl ethyl ester (8) and 9-car-
boxyl (1s)-endo-(ꢀ)-borneol ester (9), were also synthe-
sized for bioactivity screening. Cytotoxic evaluation of
Scheme 4.
Scheme 2.
Scheme 5. (a) CH
CH COCH COOEt/Et
NaOH, reflux; (g) SOCl
3
COCH
N; (d) POCl
, alcohol.
2
COOEt, reflux; (b) DMF/POCl
3
; (c)
3
2
3
3
, reflux; (e) HCl, reflux; (f)
Scheme 3.
2

Q. Zhang et al. / Bioorg. Med. Chem. 11 (2003) 1031–1034
1033
8
Table 1. ED50 values in cytotoxicity assay (mg/mL)
6- and 8-H), 6.27 (s, 1H, 3-H), 4.07 (q, 2H, –OCH CH ),
2 3
2
–
.37 (s, 1H, CH CO–), 2.30 (s, 3H, 4-Me), 1.18 (t, 3H,
3
Compd
Cell linesa
OCH CH ).
2
3
KB A549 HCT-8 CAKI-1 MCF-7 HOS 1A9 U-87-MG
2
-Chloro-4,10-dimethylpyridino[2,3-h]quinoline-9-carboxyl
b
1
12 20
Salt of 1 16 20
24
NA
NA
6
8
11
11
25
25
25
28
11
9
9
NA
NA
NA
18
18
13
31
b
b
b
b
ethyl ester (6). Compound 5 was poorly soluble and
crude 5 was used directly in the preparation of 6. Crude
5 (4.50 g) was added to POCl (30 mL) and refluxed for
8
9
15 30
41
5
4.3
4.8 35
3
2
pH was adjusted to 8 with NaOH (10%) and the solu-
h. The mixture was poured into 200 mL ice water. The
aHuman tumor cell lines include KB, nasopharyngeal; A549 lung;
HCT-8, ileocecal; CAKI, kidney; MCF-7, breast; HOS, bone; 1A9,
ovarian; U87-MG, gliobastoma.
tion extracted with CHCl (100 mL ꢂ 3). The extract
3
b
NA, not active.
was passed through a silica H column and concentrated
to give a brown solid (6). Crude 6 was recrystallized
from EtOAc to give colorless floccular crystals (1.50 g).
ꢁ
The yield from 4 to 6 was 16.80%. Mp 190–192 C; MS
+
+
37
1
, 8, 9 and the sodium salt of 1 (Table 1) showed that 9
m/z (%): 314 (M , 36.96), 316 ( Cl, 9.92), 313 (M ꢀ1,
3
7
+
was marginally active against CAK1-1, HOS, KB,
and HCT-8 cells with EC50 values of 4.3, 4.8, 5.0, and
6.0 mg/mL, respectively. None of the compounds showed
significant anti-HIV activity.
100), 315 ( Cl, 38.09), 269 (M ꢀOCH CH , 79.29),
2 3
+
1
241 (M ꢀCOOEt, 59.39); H NMR (CDCl ) d 9.90 (s,
3
1H, 8-H), 8.19 (d, J=9.34 Hz, 1H, 6-H), 8.05 (d,
J=9.34 Hz, 1H, 5-H), 7.45 (s, 1H, 3-H), 4.50 (q, 2H,
–OCH CH ), 3.05 (s, 3H, 10-Me), 2.77 (s, 3H, 4-Me),
2 3
1
.50 (t, 3H, –OCH CH ). Anal. for C H ClN O :
3
2
17 15
2
2
calcd C 64.87, H 4.80, N 8.90, Cl 11.26; found C 64.88,
H 4.72, N 8.85, Cl 11.44.
Experimental
-Amino-4-methylquinolin-2(1H)-one (3). 1,3-Phenylene-
diamine (2) (2.00 g, 18.49 mmol) and ethyl acetoacetate
2.36 mL, 18.51 mmol) were refluxed for 48 h. The
7
2-Chloro-4,10-dimethylpyridino[2,3-h]quinoline-9-carboxylic
acid (7). HCl (concd 5 mL) was added to a solution of 6
(0.25 g, 0.79 mmol) and dioxane (5 mL) and refluxed for
7 h. The mixture gradually produced a white solid. The
mixture then was poured into 20 mL ice water, filtered
and washed with water until pH=7 to give crude 7
(0.16 g, 70.28%). The product was precipitated from an
alkaline (NaOH) solution by addition of HCl to give
(
mixture solidified gradually. MeOH (5 mL) was added
to loosen the solid and filtration gave crude 3 (3.00 g).
Crystallization using MeOH gave colorless needle
ꢁ
crystals (1.60 g, 49.69%). Mp 268–271 C (ref.
ꢁ
2
71–272 C).
ꢁ
7-[1-Aza-2-(dimethylamino)vinyl]-4-methylquinolin-2(1H)-
one (4). POCl (0.45 mL, 4.60 mmol) was added drop-
pure 7 as a white solid. Mp 264–266 C (carbonization);
+
37
MS m/z (%): 285 (M ꢀ1, 100), 287 ( Cl, 38.60), 241
3
+
1
wise to a mixture of 0.80 g (4.59 mmol) of 3 and 8 mL
DMF at ꢀ5 to 0 C. After stirring for 30 min at 0 C,
(M ꢀCOOH, 58.95); H NMR (DMSO-d ) d 9.79 (s,
6
ꢁ
0% Na CO was added until the pH=8. The pre-
ꢁ
1H, 8-H), 8.49 (d, J=9.07 Hz, 1H, 6-H), 8.20 (d,
J=9.07 Hz, 1H, 5-H), 7.79 (s, 1H, 3-H), 4.0–4.4 (br,
COOH), 3.07 (s, 3H, 10-Me), 2.81 (s, 3H, 4-Me); IR
2
cipitate was filtered and washed with ice water to give
2
3
ꢀ
1
crude 4 in quantitative yield. Crystallization from
ꢁ
(KBr) n cm : 1715 (C¼O), 1640, 1610, 1590, 1560
CHCl gave colorless needle crystals. Mp 221–222 C;
3
(C¼C, C¼N), 610 (C–Cl), 3000–2600 (CH, OH).
+
+
MS (m/z, %): 229 (M , 100), 214 (M ꢀMe, 20.18), 44
+
2
1
(
NMe , 16.49); H NMR (CDCl ) d 10.45 (s, 1H, N–H),
4,10-Dimethylpyridino[2,3-h]quinolin-2(1H)-one-9-car-
boxylic acid (1). Compound 6 (0.08 g, 0.25 mmol) and
NaOH (13%, 15 mL) were mixed and refluxed for 19 h
with gradual dissolution of the solid. The mixture was
3
7
.62 (s, 1H, N¼C–H), 7.54 (d, J=8.60 Hz, 1H, 5-H),
6
J=2.04 Hz, 1H, 8-H), 6.39 (s, 1H, 3-H), 3.06 (s, 6H,
NMe ), 2.45 (s, 3H, 4-Me). H NMR (DMSO-d ) d
.89 (dd, J=8.60 Hz, J=2.04 Hz, 1H, 6-H), 6.76 (d,
1
filtered and extracted with CHCl . Then HCl (concd)
3
2
6
1
1.30 (s, 1H, N–H), 7.80 (s, 1H, N¼C–H), 7.50 (d,
was added until pH=2 and a white solid (1) was
ꢁ
J=8.67 Hz, 1H, 5-H), 6.82 (dd, J=8.67 Hz, J=1.90
Hz, 1H, 6-H), 6.75 (d, J=1.90 Hz, 1H, 8-H), 6.18 (s,
1
obtained in quantitative yield. Mp >310 C; MS m/z
1
+
+
-
(%): 268 (M , 100), 224 (M ꢀCOO , 23.36); H NMR
H, 3-H), 3.04 and 2.94 (2s, 6H, NMe ), 2.53 (s, 3H,
2
(DMSO-d ) d 9.95 (s, 1H, 8-H), 8.18 (d, J=7.83 Hz, 1H,
6
4
-Me).
5-H), 7.79 (d, J=7.83 Hz, 1H, 6-H), 6.62 (s, 1H, 3-H),
3
.30 (s, 3H, 10-Me), 2.50 (s, 3H, 4-Me); IR (KBr) n
0
quinolin-2(1H)-one (5). Compound 4 (8.20 g, 35.76
0
ꢀ1
7
-[N-(2 -Acetyl-2 -ethoxycarbonyl)vinyl]amino-4-methyl-
cm 1640–1690 (C¼O), 1625, 1590, 1545, 1470 (C¼C,
1
3
C¼N), 3500–2800 (NH, OH); C NMR (D O) d 177.2
2
mmol), triethylamine (9 mL) and ethyl acetoacetate
(
(COOH), 165.9 (2-C), 160.4 (4-C), 153.5 (8-CH), 148.0
(6a-C), 135.4 (4b-C), 135.3 (10-C), 131.5 (5-CH), 127.8
(9-C), 123.7 (6-CH), 121.0 (4a-C), 118.0 (10a-C), 116.6
(3-CH), 25.6 (4-CH ), 21.2 (10-CH ).
75 mL) were refluxed for 72 h and the mixture solidified
gradually. The solid was filtered and washed with water
and diethyl ether successively. Column chromatography
3
3
(
mp 272 C (carbonization); MS m/z (%): 314 (M ,
Silica H, EtOAc/MeOH=15:1) gave a white solid (5),
ꢁ
+
4,10-Dimethylpyridino[2,3-h]quinolin-2(1H)-one-9-car-
boxyl ethyl ester (8). SOCl (10 mL) was added to 1
1
5
9.77); H NMR (CDCl –CD OD, 5:1) d 8.38 (s, 1H,
3
3
2
HC¼C), 7.55 (d, J=8.79 Hz, 1H, 5-H), 6.96–6.91 (m, 2H,
(0.10 g, 0.37 mmol). After refluxing 12 h, the SOCl was
2

1034
Q. Zhang et al. / Bioorg. Med. Chem. 11 (2003) 1031–1034
removed by vacuum distillation. Then 15 mL EtOH was
added to the residue and reflux continued for 5 h. A
yellow solid was obtained after removing solvent. Pure 8
25 mM HEPES, 0.25% sodium bicarbonate, 10% fetal
bovine serum, and 100 mg/mL kanamycin). Freshly
trypsinized cell suspensions were seeded in 96-well
microtitre plates at densities of 1500–7500 cells per well
with test compounds from DMSO-diluted stock. After 3
days in culture, cells attached to the plastic substractum
were fixed with cold 50% trichloroacetic acid and then
stained with 0.4% sulforhodamine B (SRB). The absor-
bancy at 562 nm was measured using a microplate
reader after solubilizing the bound dye. The ED50 is the
concentration of test compound that reduced cell
growth by 50% over a 3-day assay period.
was obtained by column chromatography (silica H,
ꢁ
CHCl /MeOH=30:1). Mp 264–266 C; MS m/z (%): 296
3
+
+
+
(
2
M , 100), 251 (M ꢀOEt, 38.11), 223 (M ꢀCOOEt,
+
1
7.69), 268 (M ꢀCO, 18.22); H NMR (CDCl ) d 9.72
3
(
J=9.31 Hz, 1H, 6-H), 6.67 (s, 1H, 3-H), 4.53 (q, 2H,
s, 1H, 8-H), 8.00 (d, J=9.31 Hz, 1H, 5-H), 7.85 (d,
–
1
OCH CH ), 3.05 (s, 3H, 10-Me), 2.62 (s, 3H, 4-Me),
2 3
1
3
.50 (t, 3H, –OCH CH ); C NMR (CDCl ) d 165.9
2
3
3
(
(
(
(
COO–), 163.9 (2-C), 160.2 (4-C), 149.8 (8-CH), 135.6
6a-C), 134.4 (4b-C), 127.4 (10-C), 124.3 (5-CH), 123.3
9-C), 123.2 (6-CH), 120.9 (4a-C), 116.7 (10a-C), 115.4
3-CH), 61.7 (–OCH CH ), 25.5 (4-CH ), 19.8 (10-CH ),
Anti-HIV assay. The anti-HIV assay was carried out
according to the procedures described in our previous
2
3
3
3
1
1
4.4 (–OCH CH ).
2
papers.
3
4
,10-Dimethylpyridino[2,3-h]quinolin-2(1H)-one-9-car-
boxyl (1s)-endo-(ꢀ)-borneol ester (9). SOCl (10 mL)
Acknowledgements
2
was added to 1 (0.10 g, 0.37 mmol). After refluxing 12 h,
the SOCl was removed by vacuum distillation. Then a
This research was supported by a grant from National
Science Foundation of China awarded to P. Xia and in
part by a grant from the National Cancer Institute (CA
17625) awarded to K. H. Lee.
2
solution of (1s)-endo-(ꢀ)-borneol (0.10 g, 0.65 mmol)
and DMAP (0.05 g, 0.37 mmol) in CHCl (15 mL) was
3
added. After refluxing for 30 min, the solvent was removed
by distillation and the residue was washed with water
and diethyl ether. The crude 9 was purified via column
chromatography (Silica H, CHCl /MeOH=40:1) to
3
References and Notes
ꢁ
give pure 9. Mp. >360 C (dec.); MS m/z (%): 209
+
(
(
100.00), 296 (84.73), 267 (M ꢀC H O, 46.69), 294
1. (a) Huang, L.; Kashiwada, Y.; Cosentino, L. M.; Fan, S.;
Chen, C. H.; McPhail, A. T.; Fujioka, T.; Mihashi, K.; Lee,
K. H. J. Med. Chem. 1994, 37, 3947. (b) Xie, L.; Takeuchi, Y.;
Cosentino, L. M.; Lee, K. H. Bioorg. Med. Chem. Lett. 1998,
, 2151.
. Yang, Z. Y.; Xia, Y.; Xia, P.; Tachibana, Y.; Bastow, K. F.;
Lee, K. H. Bioorg. Med. Chem. Lett. 1999, 9, 713.
. (a) Lukes, T.; Pliml, J. Chem. Listy 1955, 1836. (b) Alex-
andar, R. S.; Royal, A. C. J. Am. Chem. Soc. 1954, 76, 1109.
4. (a) Chakravorti, S. S.; Bhattacharya, B.; Basu, U. P. Indian
J. Chem. 1967, 5, 24. (b) Otsuka Pharmaceutical Co. Ltd., Jpn.
Kokai Tokyo Koho 1980, 69, 582.
5. Hamann, L. G.; Higuchi, R. I.; Zhi, L.; Edwards, J. P.;
Wang, X. N.; Marschke, K. B.; Kong, J. W.; Farmer, L. J.;
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Org. Chem. 1991, 56, 980.
1
0
17
46.69), 341 (44.35), 208 (37.50), 295 (36.31), 153 (8.77,
+
1
C H O ), 223 (MꢀC H OOC–, 15.10); H NMR
1
0
17
10 17
(
(
CDCl ) d 13.52 (s, 1H, N–H), 10.02 (s, 1H, 8-H), 8.01
3
8
2
d, J=9.12 Hz, 1H, 5-H), 7.91 (d, J=9.12 Hz, 1H, 6-H),
6
4
3
.77 (s, 1H, 3-H), 4,09 (m, 1H, borneol CHOH), 4.43,
.03, 3.65 (sꢂ3, 3Hꢂ3, CH in borneol), 2.60, 2.57 (sꢂ2,
3
3
Hꢂ2, 4- and 10-Me), 2.18–0.88 (m, 7H, the other H in
1
3
borneol); C NMR (DMSO-d ) d 162.5 (COO–), 162.1
6
(
C), 131.4 (10-C), 130.2 (5-CH), 129.6 (9-C), 125.9 (6-CH),
2-C), 161.0 (4-C), 150.8 (8-CH), 148.5 (6a-C), 131.6 (4b-
0
3.1 (1 -C), 63.0 (7 -C), 54.3 (4 -CH), 31.2 (4-CH ), 30.6
1
6
(
22.4 (4a-C), 122.2 (10a-C), 120.5 (3-CH), 79.1 (2 -CH),
0
3 ,6 -CH ), 28.9 (5 -CH ), 18.9 (9 or 10 -CH ), 18.6 (9
0
0
3
0
or 10 -CH ), 15.9 (10-CH ), 15.9 (8 -CH ).
0
0
0
0
0
2
2
3
0
0
3
3
3
7
. Zhang, Q.; Chen, L. Y.; Zheng, Y. H.; Sheng, W. Y.; Xia, P.;
Xia, Y.; Yang, Z. Y.; Lee, K. H. Chin. Chem. Lett. 2001, 12, 11.
. Note: the cytotoxicity evaluation was performed according
Bioactivity evaluation
8
Cytotoxicity assay. In vitro cytotoxicity assay was car-
ried out according to the procedures described in
Rubinstein et al. All stockcultures were grown in T-25
flasks (5 mL of RPMI-1640 medium supplemented with
to the standard method referenced in: Rubinstein, L. V.;
Shoemaker, R. H.; Paull, K. D.; Simon, R. M.; Tosini, S.;
Skehan, P.; Scudiero, D. A.; Monks, A.; Boyd, M. R. J. Natl.
Cancer. Inst. 1990, 82, 1113.
8