Synthesis and antibacterial activity of 1,3,4-thia(oxa)diazino[6,5,4-i,j]quinoline derivatives

Full text of DOI:10.1023/A:1015189626030

Pharmaceutical Chemistry Journal
Vol. 35, No. 11, 2001
SYNTHESIS AND ANTIBACTERIAL ACTIVITY
OF 1,3,4-THIA(OXA)DIAZINO[6,5,4-i,j]QUINOLINE
DERIVATIVES
É. V. Nosova,1 G. N. Lipunova,1 and V. N. Charushin1
Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 35, No. 11, pp. 15 – 17, November, 2001.
Original article submitted May 11, 2001.
O
Synthetic compounds of the fluoroquinolone group, rep-
F
COOH
resenting derivatives of 4-oxo-1,4-dihydro-3-quinolinecar-
boxylic acid, are widely used as antibacterial drugs
(pefloxacin, norfloxacin, ciprofloxacin, etc.) [1 – 3]. Besides
the therapeutic breadth and high level of activity, an impor-
tant advantage of fluoroquinolones in comparison to b-lac-
tams (penicillins, cephalosporins), aminoglycosides, and
some other antibiotics is their high chemical stability. Exper-
iments on the chimeric modification of fluoroquinolones
have been conducted for more than a decade [3 – 5]. In re-
cent years, considerable attention of researchers has been de-
voted to the condensed fluoroquinolones, the most widely
known representatives of which are ofloxacin and
marbofloxacin [6, 7].
N
N
X
N
O
H3C
CH CH3
X =
X =
(ofloxacin)
N
CH3 (marbofloxacin)
Y
O
O
8
7
F
COOH
F
COOH
9
6
5
1
R
1
R
10
N4
N3
N
N
1S
O
We have developed new approaches to the synthesis of
annelated fluoroquinolones [8, 9] based on the intramolecu-
lar cyclization of ethyl esters of 3-[R-carbonyl(thiocarbo-
R
R
Ia – Ik
IIà – IIf
(for R, R1, and Y see Table 1 )
nyl)hydrazino]-2-tetra(penta)fluorobenzoylacrylic
acid.
Using this method, we obtained ethyl esters of
1,3,4-thia(oxa)diazino[6,5,4-i,j]quinoline-6-carboxylic acids
and determined the conditions for hydrolysis of the ester
groups and for replacement of the fluorine atoms in positions
8 and 10. This allowed us to synthesize a series of modified
fluoroquinolones Ia – Ik and IIa – IIe.
The synthesis of ethyl esters of 1,3,4-thia(oxa)- diazino-
[6,5,4-i,j]quinoline-6-carboxylic acid was described in detail
in [9, 10] and the synthesis of compounds Ia – Ik was re-
ported in [11]. For this reason, below we describe only the
synthesis of previously unreported 1,3,4-oxadiazino-
[6,5,4-i,j]quinolines (IIa – IIe).
Since compounds Ia – Ik are representatives of a new
heterocyclic system containing fluoroquinolone fragments
and compounds IIa – IIe are the analogs of marbofloxacin, it
was interesting to evaluate the antimicrobial activity of these
substances.
EXPERIMENTAL CHEMICAL PART
2-Phenyl-7-oxo-7-H-9,10-difluoro[1,3,4]oxadiazino[6,
5,4-i,j]quinoline-6-carboxylic acid (IIa). To 2.85 g
(7.7 mmole) of 2-phenyl-7-oxo-7-H-9,10-difluoro[1,3,4]-
oxadiazino[6,5,4-i,j]quinoline-6-carboxylic acid ethyl ester
was added 70 ml of an HCl – AcOH (1 : 4) acid mixture. The
reaction mixture was boiled for 3.5 h and cooled. The precip-
itate of compound IIa was separated by filtration and
recrystallized from DMSO; yield, 1.9 g (73%); m.p.,
232 – 234°C; C17H8F2N2O4; 1H NMR spectrum in DMSO-d6
(d, ppm): 7.85 (dd, 1H, 3J 10.4, 4J 7.6 Hz, 8-H), 7.96 (m, 3H,
3¢-H, 4¢-H, 5¢-H), 8.06 (m, 2H, 2¢-H, 6¢-H), 8.80 (s, 1H,
CH=), 14.3 (bs, 1H, COOH).
2-(3-Nitrophenyl)-7-oxo-7-H-9,10-difluoro[1,3,4]oxad
iazino[6,5,4-i,j]quinoline-6-carboxylic acid (IIf). Com-
pound IIe was obtained using a procedure analogous to that
described above; yield, 78%; m.p., 252 – 254°C;
1
Ural State Technical University, Yekaterinburg, Russia.
599
0091-150X/01/3511-0599$25.00 © 2001 Plenum Publishing Corporation

600
E. V. Nosova et al.
1
C17H7F2N3O6; H NMR spectrum in DMSO-d6 (d, ppm):
8-H), 7.4 – 7.7 (m, 2H, 2¢-H, 5¢-H), 8.15 (m, 1H, 4¢-H, 6¢–H),
8.32 (m, 1H, 4¢-H, 6¢-H), 8.52 (s, 1H, CH=), 14.5 (bs, 1H,
COOH).
2-(Pyridin-4-yl)-7-oxo-7-H-9-fluoro-10-(pyrrolidin-1-
yl)-[1,3,4]oxadiazino[6,5,4-i,j]quinoline-6-carboxylic acid
3
4
7.76 (m, 1H, 2¢-H), 7.78 (dd, 1H, J 10.4, J 7.6 Hz, 8-H),
7.93 (dd, 1H, 3J 7.9 Hz, 5¢-H), 8.43 (m, 1H, 4¢-H, 6¢–H), 8.53
(m, 1H, 4¢-H, 6¢-H), 8.84 (s, 1H, CH=), 14.1 (bs, 1H,
COOH).
(IIe). To
a
solution of 0.75 g (2.0 mmole) of
2-Aryl-7-oxo-7-H-9-fluoro-10-cycloalkylimino[1,3,4]-
oxadiazino[6,5,4-i,j]quinoline-6-carboxylic acids (IIb – IId).
To a suspension of 0.6 g (1.9 mmole) of acid IIa 15 ml of an-
hydrous acetonitrile was added 0.8 g (8 mmole) of
morpholine and 6 drops of diazabicycloundecene (DBU).
The reaction mixture was boiled for 4 h and cooled. The pre-
cipitate of compound IIc was separated by filtration and
recrystallized from DMSO; yield, 0.48 g (62%); m.p.,
212 – 214°C; C21H16FN3O5; 1H NMR spectrum in DMSO-d6
(d, ppm): 3.38 [m, 4H, N(CH2)2], 3.79 [m, 4H, O(CH2)2],
7.54 (d, 1H, 3J 12.5 Hz, 8-H), 7.67 (m, 3H, 3¢-H, 4¢-H, 5¢-H),
2-(pyridin-4-yl)-7-oxo-7-H-9,10-difluoro[1,3,4]oxadiazino-
[6,5,4-i,j]quinoline-6-carboxylic acid ethyl ester in 12 ml of
acetonitrile was added 0.57 ml (8.0 mmole) of pyrrolidine
and 0.2 ml (1.5 mmole) of triethylamine. The reaction mix-
ture was boiled for 3.5 h and cooled and the precipitate was
separated by filtration. To this product were added 5 ml of
ethanol and 3 ml of 2 N hydrochloric acid and the mixture
was allowed to stand for 15 min. The precipitate of com-
pound IIe was separated by filtration and recrystallized from
DMSO; yield 0.6 g (73%); m.p., > 300°C; C20H15FN4O4; 1H
NMR spectrum in DMSO-d6 (d, ppm): 1.92 [m, 4H, (CH2)2],
2
8.00 (m, H, 2¢-H, 6¢-H), 8.60 (s, 1H, CH=), 14.6 (bs, 1H,
COOH).
3
3.67 [m, 4H, N(CH2)2], 7.28 (d, 1H, J 12.2 Hz, 8-H), 8.03
Compound IIb was obtained by an analogous procedure
using acid IIa and pyrrolidine; yield 57%; m.p., 261 – 263°C;
(d, 2H, 3J 6.0 Hz, 2¢-H, 6¢-H), 8.62 (s, 1H, CH=), 8.86 (d, 2H,
3J 6.0 Hz, 3¢-H, 5¢-H), 14.3 (bs, 1H, COOH).
1
C21H15FN3O4; H NMR spectrum in DMSO-d6 (d, ppm):
1.98 [m, 4H, (CH2)2], 3.78 [m, 4H, N(CH2)2], 7.39 (d, 1H, 3J
14.3 Hz, 8-H), 7.58 (m, 3H, 3¢-H, 4¢-H, 5¢-H), 8.39 (s, 1H,
CH=), 8.89 (m, 2H, 2¢-H, 6¢-H), 14.5 (bs, 1H, COOH).
Compound IId was obtained by an analogous procedure
using acid IIf: yield, 81%; m.p., 168 – 170°C; C21H15FN4O6;
1H NMR spectrum in DMSO-d6 (d, ppm): 2.00 [m, 4H,
EXPERIMENTAL BIOLOGICAL PART
The antibacterial activity of compounds Ia – Ik and
IIa – IIe in vitro was determined by the conventional method
of double serial dilutions in liquid nutrient medium. The ex-
periments were performed with respect to the following mi-
crobes: Bacillus subtilis ATCC 6633, Bacillus pumilus
3
(CH2)2], 3.47 [m, 4H, N(CH2)2], 7.61 (d, 1H, J 12.8 Hz,
TABLE 1. Antibacterial Activity in vitro of the Synthesized 1,3,4-Thia(oxa)diazino[6,5,4-i,j]quinoline-6-Carboxylic Acid Derivatives
MIC, mg/ml
Com-
pound
Y
R
R1
Bacillus subtilis Bacillus pumilus
Staphylococcus
Escherichia coli
ATCC 6633
NCTC 8241
aureus 209 P
157
Ia
H
F
Pyrrolidin-1-yl
F
-“-
2 – 4
2 – 4
8
8
8
32
64
Ib
Ic
Id
-“-
-“-
-“-
4
–
8
H
H
Pyrrolidin-1-yl
2 – 4
8
> 128
8
> 128
16
4-Methylpiperazin-
1-yl
Ie
If
H
H
-“-
-“-
Morpholin-1-yl
1
2
4
> 128
> 32
4-Ethoxycarbonylpi-
perazin-1-yl
> 32
> 32
> 32
Ig
Ih
Ii
H
Cyclohexylamino
Pyrrolidin-1-yl
-“-
Pyrrolidin-1-yl
-“-
> 128
32
–
> 128
16
> 128
16
Pyrrolidin-1-yl
32
4-Ethoxycarbonylpi-
perazin-1-yl
4-Ethoxycarbonylpi-
perazin-1-yl
> 32
> 32
> 32
> 32
Ij
NH(CH2)3N(CH3)2
-“-
Cyclohexylamino
Phenyl
NH(CH2)3N(CH3)2
Pyrrolidin-1-yl
F
16
> 128
4
32
64
64
4
32 – 64
> 128
> 128
> 32
Ik
Pyrrolidin-1-yl
64 – 128
IIa
IIb
IIc
IId
IIe
–
–
–
–
–
–
2
-“-
Pyrrolidin-1-yl
Morpholin-1-yl
Pyrrolidin-1-yl
-“-
1
1
-“-
4
–
4
> 128
> 32
3-Nitrophenyl
Pyridin-4-yl
Pefloxacin
> 32
> 32
2
> 32
> 32
–
> 32
> 32
1
> 128
0.5

Synthesis and Antibacterial Activity of 1,3,4-Thia(oxa)diazino[6,5,4-i,j]quinoline Derivatives
601
NCTC 8241, Staphylococcus aureus 209P, and Escherichia
coli 157. The tests with St. aureus 209P, B. pumilus NCTC
8241, and E. coli 157 were conducted in Hottinger broth
(110 – 130 mg% amine nitrogen, pH 7.2 – 7.4), and with B.
subtilis ATCC 6633, in a glucose-free meat-infusion broth
(pH 7.0 – 7.2).
conditionally active with respect to Gram-positive species
(MIC = 4 mg/ml).
It should be noted that the synthesized compounds (ex-
cept for Id and Ih with MIC = 16 mg/ml) exhibited a rather
low activity with respect to E. coli 157.
Exactly weighed amounts of the synthesized compounds
were dissolved in DMSO and then diluted in Hottinger or
meat-infusion broth. The antibacterial activity was evaluated
in the concentration range from 0.015 to 128.0 mg/ml at a mi-
crobial load of 2 ´ 105 CFU/ml. The activity was expressed
in terms of the minimum inhibiting concentration (MIC,
mg/ml) representing the minimum concentration suppressing
the growth of test microbes. The reference drug was
pefloxacin.
ACKNOWLEDGMENTS
This study was supported by the Russian Foundation for
Basic Research (project No. 00 – 03 – 32785a), by the Urals
Foundation
for
Basic
Research
(project
No.
01 – 03 – 96427), by a joint grant from the Ministry of De-
fense of the Russian Federation and the United States Civil-
ian
Research
and
Development
Foundation
(SKVR-KES-005), and by the Federal Targeted Scien-
tific-Technical Program “Research and Development in Ci-
vilian Basic Science and Technology” (Modern Basic Chem-
istry Problems, project No. 9.1.06).
RESULTS AND DISCUSSION
Among the series of 1,3,4-thiadiazino[6,5,4-i,j]- quinoli-
ne-6-carboxylic acid derivatives (I), the maximum antibacte-
rial activity with respect to Gram-positive species was com-
pound Ie characterized by MIC = 1 – 4 mg/ml. It is interest-
ing to note that substituting of only a morpholine residue for
F 10 in quinolone Ia leads to an increase in the activity with
respect to Gram-positive microbes. On the contrary, intro-
duction of pyrrolidine, 4-methylpiperazine, and 4-ethoxycar-
bonylpiperazine in position 10 (compounds Ic, Id, and If) re-
duces the activity. The presence of fluorine in position 8 de-
creases the antibacterial activity in comparison to that of
8-unsubstituted derivatives. For example, compound Ib is
conditionally active with respect to Gram-positive microor-
ganisms (MIC = 4 – 8 mg/ml). The substitution of pyrrolidi-
ne, 4-ethoxycarbonylpiperazine, and N,N¢-dimethyl-1,3-pro-
panediamine (derivatives Ih – Ij) for F 8 leads to a further de-
crease in the antibacterial activity. Compounds Ig and Ik
containing cyclohexylamine in position 2 are less active than
the analogs with pyrrolidine in this position.
REFERENCES
1. N. I. Fadeeva,
M. V. Shul’gina,
and
R. G. Glushkov,
Khim.-Farm. Zh., 27(5), 4 – 19 (1993).
2. L.l. Shen, L. A. Mitscher, P. N. Sharma, et al., Biochem., 28(9),
3886 – 3894 (1989).
3. U. Petersen, S. Bartel, K.-D. Bremm, et al., Bull. Soc. Chim.
Belg., 105(10), 683 – 699 (1996).
4. G. A. Mokrushina, V. N. Charushin, and O. N. Chupakhin,
Khim.-Farm. Zh., 29(5), 5 – 19 (1995).
5. G. A. Mokrushina, S. G. Alekseev, V. N. Charushin, and
O. N. Chupakhin, Zh. Vses. Khim. O-va im. D. I. Mendeleeva,
36(4), 447 – 455 (1991).
6. I. Hayakawa, T. Hiramitsu, and Y. Tanaka, Chem. Pharm. Bull.,
32(12), 4907 – 4913 (1984).
7. EC Patent No. 9727201 (1977); Chem. Abstr., 127, 176444c
(1997).
8. V. N. Charushin, G. N. Lipunova, E. V. Nosova, et al.,
Mendeleev Commun., No. 4, 131 – 133 (1998).
9. G. N. Lipunova, L. P. Sidorova, E. V. Nosova, et al., Zh. Org.
Khim., 35(11), 1729 – 1735 (1999).
In the series of 1,3,4-oxadiazino[6,5,4-i,j]quinoline-6-
carboxylic acid derivatives (II), the most active was com-
pound IIb containing a phenyl substituent in position II. This
substance suppressed the growth of Gram-positive microbes
with MIC = 1 – 2 mg/ml). Compounds IIa and IIc were also
10. G. N. Lipunova, É. V. Nosova, V. N. Charushin, et al., Khim.
Geterotsikl. Soedin., No. 10 (412), 1396 – 1406 (2001).
11. É. V. Nosova, G. N. Lipunova, L. P. Sidorova, et al., Zh. Org.
Khim., 37(8), 1228 – 1235 (2001).