Highly active potential antituberculotics: 3-(4-Alkylphenyl)-4-thioxo-2H-1, 3-benzoxazine-2(3H)-ones and 3-(4-Alkylphenyl)-2H-1,3-benzoxazine-2,4(3H)- dihiones substituted in ring-B by halogen

Article abstract of DOI:10.1002/ardp.200800004

A series of 6-chloro-3-(4-alkylphenyl)-4-thioxo-2H-1,3-benzoxazine-2(3H)- ones, 7-chloro-3-(4-alkylphenyl)-4-thioxo-2H-1,3-benzoxazine-2(3H)-ones, 6-bromo-3-(4-alkylphenyl)-4-thioxo-2H-1,3-benzoxazine-2(3H)-ones, 6,8-dibromo-3-(4-alkylphenyl)-4-thioxo-2H-

Full text of DOI:10.1002/ardp.200800004

800
Arch. Pharm. Chem. Life Sci. 2008, 341, 800–803
Full Paper
Highly Active Potential Antituberculotics: 3-(4-Alkylphenyl)-4-
thioxo-2H-1,3-benzoxazine-2(3H)-ones and 3-(4-Alkylphenyl)-
2H-1,3-benzoxazine-2,4(3H)-dihiones Substituted in Ring-B by
Halogen*
1
1
1
1
2
ˇ
Karel Waisser , Josef Matyk , Jirꢀ KuneÐ , Rafael Dolezal , Jarmila Kaustovꢁ ,
and Hans-Martin Dahse3
1 Department of Inorganic and Organic Chemistry, Charles University in Prague, Faculty of Pharmacy in
Hradec Krꢀlovꢁ, Hradec Krꢀlovꢁ, Czech Republic
2 Regional Institute of Public Health, Department for Diagnostics of Mycobacteria, Ostrava, Czech Republic
3 Leibniz Institute for Natural Product Research and Infection Biology – Hans Knoell Institute, Jena, Germany
A series of 6-chloro-3-(4-alkylphenyl)-4-thioxo-2H-1,3-benzoxazine-2(3H)-ones, 7-chloro-3-(4-alkyl-
phenyl)-4-thioxo-2H-1,3-benzoxazine-2(3H)-ones, 6-bromo-3-(4-alkylphenyl)-4-thioxo-2H-1,3-benz-
oxazine-2(3H)-ones,
chloro-3-(4-alkylphenyl)-2H-1,3-benzoxazine-2,4(3H)-dithiones, 7-chloro-3-(4-alkylphenyl)-2H-1,3-
benzoxazine-2,4(3H)-dithiones, 6-bromo-3-(4-alkylphenyl)-2H-1,3-benzoxazine-2,4(3H)-dithiones
6,8-dibromo-3-(4-alkylphenyl)-4-thioxo-2H-1,3-benzoxazine-2(3H)-ones,
6-
and 6,8-dibromo-3-(4-alkylphenyl)-2H-1,3-benzoxazine-2,4(3H)-dithiones was synthesized. The
compounds exhibited in-vitro activity against Mycobacterium tuberculosis, M. kansasii (two strains),
and M. avium. 6-bromo-3-(4-propylphenyl)-4-thioxo-2H-1,3-benzoxazin-2(3H)-one and 6-bromo-3-(4-
propylphenyl)-2H-1,3-benzoxazin-2,4(3H)-dithione are the most active compounds against M.
tuberculosis. The activity is similar to isoniazid (INH). The compounds under study have a broad
spectrum of activity against potential pathogenic strains. The replacement of the oxo group by
thioxo group of 3-(4-alkylphenyl)-2H-1,3-benzoxazine-2,4(3H)-diones often led to an improvement
in the antimycobacterial activity against M. tuberculosis.
Keywords: Antimycobacteroal activity / Antituberculotics / Benzoxazine / Thioxo group / Tuberculostatics /
Received: December 12, 2007; accepted: May 15, 2008
DOI 10.1002/ardp.200800004
Supporting Information for this article is available from the author or on the WWW under
http://www.wiley-vch.de/contents/jc_2019/2008/200800004_s.pdf
considered to be non-transferable to human beings have
Introduction
occurred (mycobacterioses produced by potentially
pathogenic strains). The development of new antituber-
culotic agents is the principal goal of our group. We have
recently studied a number of structurally different com-
pounds, such as of pyridine [1], alkoxyphenylcarbamic
acids [2], and dihydroindolethiones [3]. The replacement
of the oxo group by a thioxo group usually increases the
antimycobacterial activity [3]. The thioxo group is con-
tained in several antitubercular drugs. (e.g. Ethioamide,
The return of tuberculosis to Europe and North America
is among others a features of the period dating back to
1985. New mycobacterial diseases which are currently
Correspondence: Karel Waisser, Charles University in Prague, Faculty
of Pharmacy in Hradec Krꢀlovꢁ, Heyrovskꢁho 1203, CZ 500 05 Hradec
Krꢀlovꢁ, Czech Republic.
E-mail: waisser@faf.cuni.cz
Fax: +420 495514330
Abbreviations:. gHMBC (Gradient-assisted Heteronuclear Multiple-Bond
Correlation); isoniazid (INH); quantitative structure-activity relationship
(QSAR)
* Dedicated to Prof. Hans-Dietrich Stachel (Munich) on the occasion of
his 80th birthday.
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Arch. Pharm. Chem. Life Sci. 2008, 341, 800–803
Highly Active Potential Antituberculotics
801
Protionamide, derivatives of diarylthiourea). The new zine-2,4(3H)-diones with phosphorus pentasulfide. The
antimycobacterial compounds, derivatives of the ring-B- products were separated by chromatography. The fre-
halogenated
3-(4-alkylphenyl)-2H-1,3-benzoxazine- quencies in the infrared spectra within the region
2,4(3H)-diones, have been recently found by QSAR (Quan- (1758–1781 cm1) are characteristic for the 3-(4-alkyl-
titative Structure-Activity Relationship) [4]. The goal of phenyl)-4-thioxo-2H-1,3-benzoxazine-2(3H)-ones. The loca-
this paper is the study of the antimycobacterial activity tion of sulfur for 3-(4-alkylphenyl)-4-thioxo-2H-1,3-ben-
of
3-(4-alkylphenyl)-4-thioxo-2H-1,3-benzoxazine-2(3H)- zoxazine-2(3H)-ones was elaborated by gHMBC (Gradient-
ones 1a–10a and 3-(4-alkylphenyl)-2H-1,3-benzoxazine- assisted Heteronuclear Multiple-Bond Correlation)
2,4(3H)-dihiones 1b–10b.
experiments. The correlation of the chemical shifts of
carbon in the thiocarbonyl moiety with the chemical
shifts of H-5 was observed. The structure of 3-(4-alkyl-
phenyl)-2H-1,3-benzoxazine-2,4(3H)-dihiones was con-
firmed by NMR as well. The structure is summarized in
Table 1, yield, melting point, and carbonyl frequency in
Results and discussion
Chemistry
The synthetic pathway is illustrated in Scheme 1. The IR in Table 2.
first two steps have already been published [4, 5]. The
mixture of 3-(4-alkyphenyl)-4-thioxo-2H-1,3-benzoxazine- Cytotoxicity
2(3H)-ones 1a–10a and 3-(4-alkylphenyl)-2H-1,3-benzoxa- The most active compounds, 6-bromo-3-(4-propylphenyl)-
zine-2,4(3H)-dihiones 1b–10b was prepared by the reac- 4-thioxo-2H-1,3-benzoxazin-2(3H)-one 4a and 6-bromo-3-
tion of the halogenated 3-(4-alkylphenyl)-2H-1,3-benzoxa- (4-propylphenyl)-2H-1,3-benzoxazin-2,4(3H)-dithione 4b,
Table 1. Minimum inhibitory concentrations (MIC) of halogenated 3-(4-alkylphenyl)-4-thioxo-2H-1,3-benzoxazine-2(3H)-ones 1 to 10
and 3-(4-alkylphenyl)-2H-1,3-benzoxazine-2,4(3H)-dihiones 1b to 10b.
Compounds
R2
MIC (lmol/L) at an incubation time of 14 d/21 d
R1
M. tuberculosis My M. kansasii My
M. avium My
M. kansasii
331/88
235/80
330/88
6509/96
1a
2a
3a
4a
5a
6a
7a
8a
9a
10a
1b
2b
3b
4b
5b
6b
7b
8b
9b
10b
6-Cl
7-Cl
7-Cl
6-Br
6-Br
6-Br
6-Br
6-Br
6,8 Br2
6,8 Br2
6-Cl
7-Cl
7-Cl
6-Br
6-Br
6-Br
6-Br
octyl
4 / 4
16 / 16
2 / 2
4 / 4
16 / 16
8 / 8
4 / 4
8 / 8
2 / 2
4 / 8
8 / 8
8 / 8
butyl
hexyl
propyl
butyl
pentyl
heptyl
octyl
butyl
hexyl
octyl
butyl
hexyl
propyl
butyl
pentyl
heptyl
octyl
1 / 1
8 / 16
16 / 16
32 / 32
4 / 8
8 / 16
32 / 62.5
32 / 32
4 / 8
8 / 8
8 / 8
8 / 16
32 / 32
32 / 32
4 / 8
32 / 32
16 / 32
62.5 / 62.5
8 / 16
8 / 16
– / –a)
– / –a)
4 / 8
8 / 8
16 / 16
32 / 32
2 / 2
16 / 16
32 / 32
4 / 8
8 / 16
– / –a)
32 / 32
4 / 8
8 / 8
8 / 8
8 / 8
8 / 16
a)
– / –
16 / 32
2 / 4
8 / 8
2 / 2
1 / 1
32 / 32
32 / 32
2 / 4
4 / 8
2 / 4
32 / 32
16 / 32
16 / 32
8 / 8
8 / 16
– / –a)
62.5
16 / 16
32 / 32
4 / 8
6-Br
6,8 Br2
6,8 Br2
8 / 8
8 / 8
4 / 8
butyl
hexyl
– / –a)
32 / 32
1 / 1
– / –a)
16 / 32
>250 / >250
62.5 / 62.5
32 / 32
8 / 8
Isoniazid (isonicotinehydrazide)
>250 / >250
a)
MIC values could not be determined due to the low solubility.
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K. Waisser et al.
Arch. Pharm. Chem. Life Sci. 2008, 341, 800–803
Table 2. Yield, melting point and carbonyl frequency in IR.
Compound
Yield (%)
M.p. (8C)
mC=O (cm– 1
)
Compound
Yield (%)
M.p. (8C
1a
2a
3a
4a
5a
6a
7a
8a
9a
10a
35
30
32
39
36
44
37
42
32
35
151–152
148–150
133–134
192–194
148–151
147–148
136–137
144–145
218–220
187–188
1773
1766.
1781
1760
1758
1772
1774
1773
1770
1758
1b
2b
3b
4b
5b
6b
7b
8b
9b
10b
30
32
29
37
40
39
36
31
40
33
94–95
147–148
117–118
181–182
138–140
136–138
114–115
96–96
212–215
145–146
Figure 1. The demonstration of an increase of the antimycobac-
terial activity against M. tuberculosis (incubation 14 d) by
replacement of the carbonyl oxygen for sulfur. (a) Benzosazine-
diones, (b) Benzoxazinedithiones, (c) Thioxobenzoxazinones.
(a) Ref. 5; (b) Ref.4; Substituents are described in Table 1.
pentyl derivatives 6a and 6b). For the graphical expres-
sion see Fig. 1. The activity of the new compounds against
potentially pathogenic strains was stronger than that of
Scheme 1. Synthesis of the compounds
were chosen for cytotoxicity testing. Both compounds
showed cytotoxic properties (compound 4a CC50 10.7 lg/ INH. The activity of the starting compounds is described
mL, compound 4b CC50 5.7 lg/mL).
in the previous paper [4]. The increase of the activity
against M. tuberculosis improves with the replacement of
the first oxo group; the replacement of the second oxo
group for the thioxo group has only a small effect on the
increase of the activity. It is worthy to note that the
monohalogenated compounds are more active than the
Discussion
The structures of the products were confirmed by ele-
mental analyses and by IR,1H and 13C-NMR spectral meth- dihalogenated. The alkyl in the position-4 on N-phenyl
ods. In general, the synthesized compounds possess in- has an effect on the antimycobacterial activity as well. 6-
Bromo-3-(4-propylphenyl)-4-thioxo-2H-1,3-benzoxazin-
2(3H)-one 4a and 6-bromo-3-(4-propylphenyl)-2H-1,3-ben-
vitro activities against all tested mycobacterial strains.
The values of MICs are generally within the range 1–
62.5 lmol/L, most often they range from 2–8 lmol/L. The zoxazin-2,4(3H)-dithione 4b are the most active com-
compounds were predominantly less active than INH pounds against M. tuberculosis. The activity is similar to
INH. On the other hand, 6-chloro-3-(4-propylphenyl)-4-thi-
oxo-2H-1,3-benzoxazin-2(3H)-one 1a has the strongest
against M. tuberculosis 331/88, on the other hand, against
M. kansasii 235/80 and M. avium 330/88, the compounds
were more effective than INH. The replacement of the effect against potential pathogenic strains. The newly
oxo group for the thioxo group in the starting 3-(4-alkyl- synthesized compounds form a new, promising group of
antimycobacterials with a broad spectrum of antimyco-
bacterial activity against the potentially pathogenic
phenyl)-2H-1,3-benzoxazine-2,4(3H)-diones increases the
antimycobacterial activity against M. tuberculosis (with
exception of the butyl derivatives 2a, 5a, and 5b and the strains. Substances, 6-bromo-3-(4-propylphenyl)-4-thioxo-
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Arch. Pharm. Chem. Life Sci. 2008, 341, 800–803
Highly Active Potential Antituberculotics
803
ing to the room temperature, a 10% potassium carbonate solu-
tion (60 mL) was poured into the reaction mixture; the crude
product was filtered off and dissolved in toluene (p.a., at the
most 40 mL). Column chromatography on silica gel gave halo-
genated 3-(4-alkylphenyl)-4-thioxo-2H-1,3-benzoxazine-2(3H)-one
1a–10a and halogenated 3-(4-alkylphenyl)-2H-1,3-benzoxazine-
2,4(3H)-dithione 1b–10b as orange-yellow and red solids, respec-
tively. Recrystallization from ethanol was necessary.
2H-1,3-benzoxazin-2(3H)-one 4a and 6-bromo-3-(4-propyl-
phenyl)-2H-1,3-benzoxazin-2,4(3H)-dithione 4b, were
chosen for preclinical testing but, unluckily, both com-
pounds were found to be cytotoxic. (Compound 4a CC50
10.7 lg/mL, compound 4b CC50 5.7 lg/mL).
This work is a part of the research project No. MSM0021620822
of the Ministry of Education of the Czech Republic.
Microbiology
The antimycobacterial activity of compounds and isoniazid was
tested in vitro against Mycobacterium tuberculosis My 331/88, Myco-
bacterium avium My 330/88, Mycobacterium kansasii My 235/80,
obtained from the Czech National Collection of Type Cultures
(CNCTC), National Institute of Public Health, Prague, and a clini-
cal isolate of Mycobacterium kansasii 6509/96 using the micro-
method for the determination of the minimum inhibitory con-
centration (MIC). The method is described in our previous paper
[2, 6]. The values of MIC are summarized in Table 1.
The authors have declared no conflict of interest.
Experimental
The melting points were determined on a Kofler apparatus (C.
Reichert, Vienna, Austria). The samples for the analyses and anti-
mycobacterial tests were dried over P2O5 at 618C and 66 Pa for
24 h. Elemental analyses (C, H, N) were performed on a CHNS-O
CE elemental analyzer (Fisions EA 1110, Milan, Italy) and were
within l 0.4% of the theoretical values. The IR spectra were meas-
ured in KBr pellets on a Nicolet Impact 400 apparatus (Nicolet,
Madison, WI, USA); the wavenumbers are given in cm1. TLC was
performed on silica gel plates precoated with a fluorescent indi-
cator Silufol UV 254 + 366 (Kavalier Votice, Czech Republic),
cyclohexane-acetone (3 : 1) was used as the mobile phase. The 1H-
NMR and 13C-NMR spectra of new compounds were recorded in
CDCl3 or DMSOd6 solutions at ambient temperature on a Varian
Mercury-Vx BB 300 spectrometer (Varian Inc., Palo Alto, CA, USA)
operating at 300 MHz for 1H-NMR and 75 MHz for 13C-NMR.
Chemical shifts were recorded as d values in parts per million
(ppm) and were indirectly referenced to tetramethylsilane via
Cytotoxicity
The experimental methods were described in our previous paper
[7, 8].
References
[1] J. Adamec, R. Beckert, D. Weiss, V. KlimeÐovꢀ, et al., Bioorg.
Med. Chem. 2007, 15, 2898–2906.
[2] K. Waisser, R. Doleˇzal, J. Ciˇzmꢀrik, J. Kaustovꢀ, Folia Micro-
biol. 2006, 51, 21–24.
1
the solvent signal (2.49 for H or 39.7 for 13C). The starting 3-(4-
[3] K. Waisser, L. Heinisch, M. ꢁlosꢀrek, J. Janota, Folia Micro-
biol. 2006, 51, 25–26.
alkylphenyl)-2H-1,3-benzoxazine-2,4(3H)-diones were prepared
in our previous papers [4, 5] (see Scheme 1).
[4] K. Waisser, J. Matyk., H. DiviÐovꢀ, P. Husꢀkovꢀ, et al., Arch.
Pharm. 2007, 340, 264–267.
Chemistry
[5] K. Waisser, J. Matyk, H. DiviÐovꢀ, P. Husꢀkovꢀ, et al., Arch.
Pharm. 2006, 33, 616–620.
General procedure for the preparation of halogenated 3-
(4-alkylphenyl)-4-thioxo-2H-1,3-benzoxazine-2(3H)-ones
1a–10a and 3-(4-alkylphenyl)-2H-1,3-benzoxazine-
[6] J. Adamec, K. Waisser, J. KuneÐ, J. Kaustovꢀ, Arch. Pharm.
2005, 338, 385–389.
[7] H. M. Dahse, B. Schlegel, U. Grꢂfe, Pharmazie 2000, 56,
2,4(3H)-dithiones 1b–20b
489–491.
Halogenated derivatives 3-(4-alkylphenyl)-2H-1,3-benzoxazine-
2,4(3H)-diones prepared in previous paper [4] (3.8 mmol) were
melted with P4S10 (7.6 mmol) for 20 min (175–2008C). After cool-
[8] H. M. Dahse, U. Mꢃllmann, K. Waisser, K. Palꢀt, et al., Folia
Pharm. Univ. Carol. 2002, 27– 28, 26–33.
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