Synthesis of (1,4)-naphthoquinono-[3,2-c]-1H-pyrazoles and their (1,4)-naphthohydroquinone derivatives as antifungal, antibacterial, and anticancer agents

Article abstract of DOI:10.1016/j.bmcl.2005.04.066

A series of (1,4)-naphthoquinono [3,2-c]-1H-pyrazoles and their (1,4)-naphthohydroquinone derivatives 2-7 were synthesized and evaluated for antifungal, antibacterial, and anticancer activities. The structure-activity relationship of these compounds was s

Full text of DOI:10.1016/j.bmcl.2005.04.066

Bioorganic & Medicinal Chemistry Letters 15 (2005) 3288–3291
Synthesis of (1,4)-naphthoquinono-[3,2-c]-1H-pyrazoles
and their (1,4)-naphthohydroquinone derivatives
as antifungal, antibacterial, and anticancer agents
Vishnu K. Tandon,a,* Dharmendra B. Yadav,a Ashok K. Chaturvedib and
Praveen K. Shuklab
aDepartment of Chemistry, Lucknow University, Lucknow 226007, India
bDivision of Fermentation Technology, Central Drug Research Institute, Lucknow 226001, India
Received 1 March 2005; accepted 21 April 2005
Available online 23 May 2005
Abstract—A series of (1,4)-naphthoquinono [3,2-c]-1H-pyrazoles and their (1,4)-naphthohydroquinone derivatives 2–7 were synthe-
sized and evaluated for antifungal, antibacterial, and anticancer activities. The structure–activity relationship of these compounds
was studied and the results show that the compound 2b exhibited in vitro antifungal activity against Candida albicans and Crypto-
coccus neoformans, and also possessed antibacterial profile against Klebsiella pneumoniae and Escherichia coli whereas 1c showed
anticancer activity against Walker 256 Carcinosarcoma in rats.
ꢀ 2005 Elsevier Ltd. All rights reserved.
Heterocyclic 1,4-benzo- and 1,4-naphthoquinones con-
taining nitrogen atom have been reported to possess
cytotoxic,1–5 antibacterial, antiproliferative,6 antiplate-
let, anti-inflammatory, antiallergic,7,8 and antifungal9
activities. The structure–activity relationship of hetero-
cyclic quinones has revealed that the cytotoxic activity
relies upon the number and position of nitrogen atom
in the heterocyclic quinone.2
by NCCLS.10,11 The minimum inhibitory concentration
(MIC) of each compound was determined against test
isolates using this technique.
The antifungal activity was compared with standard
drugs like miconazole, nystatin, fluconazole, and
amphotericin B. MIC of standard drugs is referred to
in Table 1 and the compounds were determined in 96-
well tissue culture plates using RPMI 1640 media buf-
fered with MOPS (3-[N-morpholino]-propane sulfonic
acid) (Sigma Chemical Co.).
The interesting biological profile of heterocyclic 1,4-ben-
zo- and 1,4-naphthoquinones containing one or more
nitrogen atoms and the presence of carboxamido group7,8
prompted us to synthesize (1,4)-naphthoquinono-[3,2-c]-
1H-pyrazoles and their (1,4)-naphthohydroquinone
derivatives 2–7 possessing two nitrogen atoms inside the
ring and the carboxamido group in the side chain.
Comparison of the activity of compounds 2–7 referred to
in Table 1 with that of the antifungal drug miconazole
showed that compound 2b had better activity against fun-
gi C. albicans and C. neoformans. Compound 2b also
exhibited enhanced activity against fungi C. albicans
when compared with the antifungal drug nystatin. Com-
pounds 4a and 4c had some activity against C. albicans
when compared with miconazole. Compound 2b also
exhibited moderate activity against fungi T. mentagra-
phytes, A. fumigatus, and C. parapsilosis. Other com-
pounds whose MIC was >75lg/mL are not reported in
Table 1 as these were considered to be inactive
compounds.
The evaluation of antifungal activities of 2–7 against var-
ious strains of pathogenic fungi, for example, Candida
albicans, Cryptococcus neoformans, Sporothrix schenckii,
Trichophyton mentagraphytes, Aspergillus fumigatus,
and Candida parapsilosis (ATCC 22019) was carried out
according to the broth microdilution technique described
*
Antibacterial activities of compounds 2–7 against vari-
ous strains of the bacteria, for example, Staphylococcus
Corresponding author. Fax: +91 522 2684388; e-mail: vishnutandon@
yahoo.co.in
0960-894X/$ - see front matter ꢀ 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2005.04.066

V. K. Tandon et al. / Bioorg. Med. Chem. Lett. 15 (2005) 3288–3291
Table 1. In vitro antifungal activity for compounds 2–7
3289
Compds
MIC (lg/mL)
T. mentagraphytes
C. albicans
C. neoformans
S. schenckii
A. fumigatus
C. parapsilosis
12.5
>50
2b
3b
6.25
>50
25
6.25
>50
25
50
>50
>50
>50
>50
>50
>50
>50
>50
25
>50
>50
>50
>50
>50
>50
>50
>50
>50
25
>50
>50
>50
>50
>50
>50
>50
>50
>50
4a
4c
50
>50
>50
>50
50
25
>50
>50
>50
>50
>50
>50
>50
12.5
3.5
6a
6b
>50
>50
>50
>50
>50
>50
25
7d
7f
7g
>50
>50
7h
>50
a
>50
a
Miconazole
Nystatin
Fluconazole
Amphotericin B
<0.78
12.5
a
a
a
7.8
1.0
13.2
2.0
1.0
0.78
0.5
1.56
2.0
2.0
a
a
a
0.39
a Activity not reported.
Table 2. In vitro antibacterial activity for compounds 2–7
Compds
MIC (lg/mL)
S. faecalis
K. pneumoniae
6.25
12.5
>50
E. coli
P. aeruginosa
S. aureus
2b
3b
25
12.5
>50
>50
>50
25
6.25
25
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
0.78
>128
25
25
4a
4c
>50
>50
>50
>50
>50
12.5
25
>50
>50
>50
>50
>50
>50
>50
>50
0.78
2.0
>50
>50
6a
6b
12.5
25
7d
>50
>50
>50
7f
7g
12.5
25
7h
Gentamycin
Kanamycinb
>50
a
>50
0.39
32
>50
a
a
16
a Activity not reported.
b MIC90 (lg/mL).
Table 3. Anticancer activity against Walker 256 Carcinosarcoma in
rats
aureus, Streptococcus faecalis, Klebsiella pneumoniae,
Escherichia coli, and Pseudomonas aeruginosa were car-
ried out according to the broth microdilution technique
described by NCCLS. The results are reported in Table
2. The MIC of each compound was determined against
test isolates using this technique. Gentamycin the stan-
dard antibacterial drug was used as a positive control
in all the tests and its MIC value is expressed in micro-
grams per milliliter. The antibacterial activity was also
compared with kanamycin12 (MIC90 75lg/mL).
Compds
Dose (mg/kg)
Survivors
T/C (%)
Remark
1c
3a
10
50
3/4
3/3
37
115
Active
Inactive
the compounds tested showed better activity than the
marked activity exhibited by naphthazarin (1c).13
The synthesis of (1,4)-naphthoquinono-[3,2-c]-1H-pyr-
azoles and their (1,4)-naphthohydroquinone derivatives
2 and 3 is shown in Scheme 1. Compounds 2 and 3 were
synthesized as a mixture of compounds by condensation
of 1,4-naphthoquinones 1 with diazomethane and its
ethyl ester using benzene as solvent.
Compound 2b showed marked activity against K. pneu-
moniae and E. coli which in vitro showed better results
than kanamycin against these two bacteria. Compounds
3b, 6b, 7f, and 7g exhibited moderate activity against K.
pneumoniae and E. coli. Compounds 2b, 3b, and 6b
exhibited moderate activity against S. faecalis whereas
2b and 3b showed activity against S. aureus. However,
the compound referred to in Table 2 and discussed
above did not exhibit better activity than the standard
drug gentamycin.
Compound 3 was exclusively obtained as a single prod-
uct by reaction of 1,4-naphthoquinones 1 with diazome-
thane and its ethyl ester by carrying out reaction in
diethyl ether at 0ꢁC.14
The anticancer activity was carried out against Walker
256 Carcinosarcoma in rats. The anticancer activities
of 1c and 3a are shown in Table 3. However, none of
Reaction of pyrazoles 2b and 3b with substituted hydra-
zines and primary amines results in the formation
of (1,4)-naphthohydroquinono-[3,2-c]-1H-pyrazole-3-car-

3290
V. K. Tandon et al. / Bioorg. Med. Chem. Lett. 15 (2005) 3288–3291
Scheme 1.
Scheme 2.
boxylic acid hydrazides 4a–c, (1,4)-naphthoquinono-[3,2-
c]-1H-pyrazole-3-carboxylic acid hydrazides 6a–c, (1,4)-
naphthohydroquinono-[3,2-c]-1H-pyrazole-3-carboxylic
acid amides 5d–h, and (1,4)-naphthoquinono-[3,2-c]-
1H-pyrazole-3-carboxylic acid amides 7d–h as shown
in Scheme 2.15,16
Acknowledgments
We thank Regional Scientific Instrumentation Centre
(RSIC) for spectral data and Pharmacology Division
of Central Drug Research Institute, Lucknow, India,
for biological screening reported in the manuscript.
In conclusion, we have synthesized a series of (1,4)-naph-
thoquinono-[3,2-c]-1H-pyrazoles and their (1,4)-naph-
thohydroquinono derivatives and carried out their
biological activities. Among the promising compounds,
2b has shown in vitro significant antifungal activity
against C. albicans and C. neoformans. Compound 2b also
exhibited marked antibacterial activity against K. pneu-
moniae and E. coli. Compounds 3b, 6b, 7f, and 7g also
showed some antibacterial activity. Compound 2b is the
lead compound for both antifungal and antibacterial
activities. Among the promising compounds, only 1c
has shown significant activity against Walker 256 Carci-
nosarcoma in rats. Further work on compound 2b is in
progress.
References and notes
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tion with benzene, 48% yield; mp 145ꢁC; IR (KBr): 3200–
3406 (NH), 1725 (>C@O of COOEt)cmÀ1 1H NMR
;
(CDCl3): d 1.54 (t, 3H, CH3), 4.54 (q, 2H, CH2), 6.68 (s,
1H, OH), 7.01 (s, 1H, OH), 7.42–7.82 (m, 2H, C6–H and
C7–H), 8.04–8.14 (m, 2H, C5–H and C8–H), 8.87 (s, 1H,
NH); MS: M+ (m/e) 272. Compound 3b: Mother liquor on
crystallization yielded 3b as yellow crystals; 47% yield; mp
184–185ꢁC; IR (KBr): 3181 (NH), 1591 and 1682 (>C@O
of quinone), 1747 (>C@O of COOEt)cmÀ1 1H NMR
;
(CDCl3): d 1.50 (t, 3H, CH3), 1.79 (br h, 1H, NH), 4.56 (q,
2H, CH2), 7.84 (m, 2H, C6–H and C7–H), 8.29 (m, 2H,
C5–H and C8–H); MS: M+ (m/e) 270. Compound 3b
obtained by carrying out reaction in diethyl ether as a
solvent had similar spectroscopic data.
15. General procedure for the preparation of (1,4)-naphtho-
quinono-[3,2-c]-1H-pyrazole-3-carboxylic acid hydrazides
6a–c. Hydrazine derivatives (20mmol) were added to a
stirred solution of 1,4-naphthoquinone derivative 3b
(2.70g, 10mmol) in abs. EtOH (50mL) at room temper-
ature. The reaction mixture was allowed to stir at rt for
2–5h. The reddish brown solid thus obtained was filtered
and crystallized from CH3OH. Compound 6b: 94% yield;
mp >280ꢁC; IR (KBr): 3416 (NH), 1599 and 1686
12. Chambers, H. F.; Sande, M. A. In The Pharmacological
Basis of Therapeutics; Goodman, G., Ed., 9th ed.;
McGraw-Hill: USA, 1996, p 1108.
(>C@O of quinone), 1638 (>C@O of amide)cmÀ1 1H
;
13. Tandon, V. K.; Chhor, R. B.; Singh, R. V.; Rai, S.;
Yadav, D. B. Bioorg. Med. Chem. Lett. 2004, 14, 1079.
14. General procedure for the preparation of (1,4)-naphtho-
hydroquinono-[3,2-c]-1H-pyrazoles 2a–d and (1,4)-naph-
thoquinono-[3,2-c]-1H-pyrazoles 3a–d. Ethyldiazoacetate/
diazomethane (10mmol) in benzene (5mL) was added to a
stirred solution of 1,4-naphthoquinone derivatives 1a–d
(10mmol) in benzene (20mL). The reaction mixture was
refluxed with stirring for 1.5h and allowed to stand
overnight at room temperature. To the dark red semi-solid
solution was added CHCl3 (20mL). The solid thus
obtained was filtered. The residue consisted of 2a–d
whereas filtrate on concentration in vacuo yielded 3a–d.
The reaction of ethyldiazoacetate/diazomethane (10mmol)
in diethyl ether (30mL) with 1,4-naphthoquinones 1a–d
(10mmol) in diethyl ether (50mL) at 0–4ꢁC for 48h
resulted in the formation of only 3a–d as the isolated
product. Compound 2b: colorless solid after crystalliza-
NMR (DMSO-d6): d 2.55 (s, 1H, NH), 3.48 (br h, 2H,
NH · 2), 7.26 (s, 5H, C6H5), 7.83 (m, 2H, C6–H and
C7–H), 8.20 (m, 2H, C5–H and C8–H); MS: M+ (m/e)
332. Analogous procedure was followed for the synthesis
of 4a–c.
16. General procedure for the preparation of (1,4)-naphtho-
quinono-[3,2-c]-1H-pyrazole-3-carboxylic acid amides
7d–h. Primary aliphatic amines (100mmol) were added
to a stirred solution of 1,4-naphthoquinone derivative 3b
(2.70g, 10mmol) in abs EtOH (50mL). The reaction
mixture was refluxed for 1–5h. The yellow solid thus
obtained was filtered and crystallized from CH3OH.
Compound 7d: 75% yield; mp >260ꢁC; IR (KBr): 3433
(NH), 1588 and 1658 (>C@O of quinone), 1634 (>C@O of
amide)cmÀ1; 1H NMR (CDCl3): d 2.58 (s, 3H, CH3), 7.66
(s, 1H, NH), 7.81 (m, 2H, C6–H and C7–H), 8.24 (m, 2H,
C5–H and C8–H); MS: M+ (m/e) 245. Analogous proce-
dure was followed for the synthesis of 5a–c.