Synthesis, spectral analysis and in vitro microbiological evaluation of novel ethyl 4-(naphthalen-2-yl)-2-oxo-6-arylcyclohex-3-enecarboxylates and 4,5-dihydro-6-(napthalen-2-yl)-4-aryl-2H-indazol-3-ols

Article abstract of DOI:10.3109/14756361003689856

A series of ethyl 4-(naphthalen-2-yl)-2-oxo-6-arylcyclohex-3- enecarboxylates 8-14 and 4,5-dihydro-6-(naphthalen-2-yl)-4-aryl-2H-indazol-3-ols 15-21 were synthesised and characterised by their spectroscopic data. In vitro microbiological evaluations were carried out for all the newly synthesised compounds 8-21 against clinically isolated bacterial and fungal strains. Compounds 9, 12 and 20 against Staphylococcus aureus, 10, 12, 20 against β-haemolytic streptococcus, 11, 17 against Bacillus subtilis, 12, 16 and 20 against Vibreo cholerae, 13, 16 against Escherichia coli, 13, 16, 18, 19 against Salmonella typhii, 12, 18 against Shigella flexneri, 10 against Salmonella typhii, 10, 13, 17, 18 against Aspergillus flavus, 12, 17, 21 against Aspergillus niger, 12, 15, 17, 18, 20 against Mucor, Rhizopus and Microsporeum gypsuem exhibit potent antimicrobial activity.

Full text of DOI:10.3109/14756361003689856

Journal of Enzyme Inhibition and Medicinal Chemistry, 2011; 26(1): 56–66
Copyright © 2011 Informa UK, Ltd.
ISSN 1475-6366 print/ISSN 1475-6374 online
DOI: 10.3109/14756361003689856
RESEARCH ARTICLE
Synthesis, spectral analysis and in vitro microbiological
evaluation of novel ethyl 4-(naphthalen-2-yl)-2-oxo-6-
arylcyclohex-3-enecarboxylates and 4,5-dihydro-6-
(napthalen-2-yl)-4-aryl-2H-indazol-3-ols
V. Kanagarajan, J. anusu, and M. Gopalakrishnan
Synthetic Organic Chemistry Laboratory, Department of Chemistry, Annamalai University, Annamalainagar, Tamil
Nadu, India
Abstract
A series of ethyl 4-(naphthalen-2-yl)-2-oxo-6-arylcyclohex-3-enecarboxylates 8–14 and 4,5-dihydro-6-(naphthalen-
2-yl)-4-aryl-2H-indazol-3-ols 15–21 were synthesised and characterised by their spectroscopic data. In vitro
microbiological evaluations were carried out for all the newly synthesised compounds 8–21 against clinically isolated
bacterial and fungal strains. Compounds 9, 12 and 20 against Staphylococcus aureus, 10, 12, 20 against β-haemolytic
streptococcus, 11, 17 against Bacillus subtilis, 12, 16 and 20 against Vibreo cholerae, 13, 16 against Escherichia coli, 13,
16, 18, 19 against Salmonella typhii, 12, 18 against Shigella flexneri, 10 against Salmonella typhii, 10, 13, 17, 18 against
Aspergillus flavus, 12, 17, 21 against Aspergillus niger, 12, 15, 17, 18, 20 against Mucor, Rhizopus and Microsporeum
gypsuem exhibit potent antimicrobial activity.
Keywords: Ethyl 4-(naphthalen-2-yl)-2-oxo-6-arylcyclohex-3-enecarboxylates, 4,5-dihydro-6-(naphthalen-2-yl)-4-
aryl-2H-indazol-3-ols, hydrazine hydrate, antibacterial activity, antifungal activity
Introduction
Figure 1 shows that the indazole nucleus is a widely
studied pharmacophoric scaffold that has emerged as
a core structural unit of various bioactive molecules
[6–10]. Adjudin (A) is currently under phase II human
trials as a potential non-hormonal male contracep-
tive drug containing an indazole nucleus, which acts
by blocking the production of sperm in the testes, but
without affecting testosterone production [6]. It is an
analogue of the chemotherapy drug lonidamine, (B)
an indazole-carboxylic acid, which for a long time, has
been known to inhibit aerobic glycolysis in cancer cells
[7]. 7-Nitroindazole (C) acts as a selective inhibitor for
neuronal nitric oxide synthase, a haemoprotein enzyme
which converts arginine to citrulline and nitric oxide
(NO) in neuronal tissue [8]. YM-348, (S)-1-(7-ethyl-
1H-furo[2,3-g]indazol-1-yl)propan-2-amine (D) is an
e dramatic increase in antibacterial and antifungal
resistance has limited the effectiveness of currently used
drugs and represents a health threat. Amongst the five
memberedheterocycles,fusedindazolesareanimportant
class of compounds and are of increased importance due
to their therapeutic and pharmacological properties. A
variety of structurally diverse indazole nuclei have arisen
due to their wide variety of biological properties such
as antimicrobial activity [1], inhibitors of protein kinase
B/Akt [2], antiprotozoal agents [3], antichagasic activ-
ity [3], leishmanocidal activity [3], trypanocidal activity
[3], inhibitors of S-adenosyl homocysteine/methylthio
adenosine (SAH/MTA) nucleosides [4], potent activator
of the nitric oxide receptor [5] and inhibition of platelet
aggregation [5].
Address for Correspondence: M. Gopalakrishnan, Synthetic Organic Chemistry Laboratory, Department of Chemistry, Annamalai
University, Annamalainagar, 608 002, Tamil Nadu, India. Tel: + 91 4144 228 233; E-mail address: profmgk@yahoo.co.in
(Received 01 November 2009; revised 06 January 2010; accepted 09 February 2010)
56

In vitro antimicrobial activity of naphthyl substituted azoles
57
Cl
Cl
Cl
Cl
N
N
N
N
NH2
OH
O
N
H
O
O
Adjudin
Lonidamine
A
B
NH2
O−
N+
N
H
O
N
N
N
7-nitro-1H-indazole
YM-348
C
D
NH2
N
NH
OH
O
N
N
X
AL-38022A
Target molecule
E
Figure 1. Novel bioactive compounds with a core indazole nucleus of pharmacological importance.
indazole derivative drug which acts as a potent and
selective 5-HT2C receptor agonist. It shows thermogenic
and anorectic effects in animal studies [9]. AL-38022A,
(S)-1-(8,9-dihydropyrano[2,3-g]indazol-1(7H)-yl)-pro-
pan-2-amine (E) is an indazole derivative drug that acts
as a potent and selective agonist for the 5-HT2 family of
serotonin receptors.
6-(naphthalen-2-yl)-4-aryl-2H-indazol-3-ols (15–21), a
novel fused indazole derivative and to study their bio-
potential against clinically isolated bacterial and fungal
strains.
Experimental
A literature survey revealed the value of chalcones as
potent biologically active compounds. In recent years
there has been a great deal of interest in exploiting more
than one proximal functional group for designing novel
structures capable of performing a variety of functions.
Taking these considerations into account and as part of
our research programme aimed at the synthesis of bio-
active novel structurally diverse heterocycles [11–15], we
report the molecular conjugation of the naphthyl substi-
tuted chalcone moiety with two or more active counter-
parts that has been designed and synthesised with the
hope of producing novel ethyl 4-(naphthalen-2-yl)-2-
oxo-6-arylcyclohex-3-enecarboxylates (8–14) an inter-
mediate with three versatile functional groups i.e.
ketone, olefin and ester for the synthesis of 4,5-dihydro-
Chemistry
e progress of the reaction was monitored by TLC
analysis. All the reported melting points are taken in
open capillaries and are uncorrected. IR spectra were
recorded in KBr (pellet forms) on a ermo Nicolet-
Avatar–330 (ermo Fisher Scientific Inc., Waltham, US)
FT-IR spectrophotometer and important absorption
values (cm−1) alone are listed. H and 13C NMR spectra
1
were recorded at 400 MHz and 100 MHz respectively on a
Bruker Avance II 400 NMR spectrometer using DMSO-d6
as solvent. Two dimensional homonuclear correalation
(HOMOCOR) and heteronuclear single quantum cor-
relation (HSQC) spectra were recorded at Bruker DRX
500 (Bruker Biospin International, Ag, Aegeristrasse,
Switzerland) NMR spectrometer. e ESI +ve MS spectra
© 2011 Informa UK, Ltd.

58
V. Kanagarajan et al.
were recorded on a Bruker Daltonics LC-MS spectrom-
eter. Satisfactory microanalyses are obtained on Carlo
Erba 1106 (ermo Fisher Scientific Inc, Waltham, US)
CHN analyser. (E)-1-naphthalen-2-yl)-3-arylprop-2-
en-1-ones 1-7 were prepared according to the literature
precedent [16].
Ethyl 6-(4-methoxyphenyl)-4-(naphthalen-2-yl)-2-
oxocyclohex-3-enecarboxylate 11
IR (KBr) ν (cm−1): 3056, 2987, 2932, 2838, 1738, 1657,
1
1606, 1252, 888, 831, 815, 749; H NMR (δ ppm), (J Hz):
0.96 (3H, t, CH2CH3 at C-1, J= 7), 3.16–3.29 (2H, H5, m),
3.59–3.67 (1H, H6, m), 3.73 (3H, s, OCH3 at phenyl ring),
3.92 (2H, q, CH2CH3 at C-1, J= 7), 4.10 (1H, H1, d, J= 14.3),
6.71 (1H, s, H3), 6.89–8.32 (11H, m, Harom.); 13C NMR (δ
ppm): 14.2 CH2CH3 at C-1, 35.7 C-5, 43.5 C-6, 55.4 OCH3
at phenyl ring, 59.5 CH2CH3 at C-1, 60.2 C-1, 123.5 C-3,
169.7 C=O at C-1, 194.7 C-2, 114.1–129 -Carom., C-4 carbon
may be merged with -Carom, 129.2, 133.1, 134, 134.7, 159.1
ipso-Cs.
General procedure for the synthesis of ethyl 4-(naphthalen-2-
yl)-2-oxo-6-arylcyclohex-3-enecarboxylates 8–14
To a solution of sodium ethoxide (0.001mol) in 30 mL
of absolute ethanol, freshly distilled ethyl acetoacetate
(0.01 mol) and respective (E)-1-naphthalen-2-yl)-3-
arylprop-2-en-1-ones (0.01 mol) in absolute ethanol
(40mL) was mixed. is mixture was refluxed in a water
bath for 1–3 h by maintaining the temperature around
70 to 80°C. e reaction mixture was allowed to cool and
filtered. en the crude product was recrystallised from
absolute ethanol to afford ethyl 4-(naphthalen-2-yl)-2-
oxo-6-arylcyclohex-3-enecarboxylates 8–14.
Ethyl 6-(4-chlorophenyl)-4-(naphthalen-2-yl)-2-oxocyclohex-
3-enecarboxylate 12
IR (KBr) ν (cm−1): 3056, 3022, 2978, 2928, 1738, 1658, 1257,
1147,890,850,818,749;1HNMR(δppm),(JHz):0.95(3H,t,
CH2CH3 at C-1, J= 7), 3.19-3.29 (2H, H5, m), 3.68-3.75 (1H,
H6, m), 3.93 (2H, q, CH2CH3 at C-1, J= 7.1), 4.18 (1H, H1, d,
J= 13.4), 6.73 (1H, s, H3), 7.4–8.32 (11H, m, Harom.); 13C NMR
(δ ppm): 13.8 CH2CH3 at C-1, 34.8 C-5, 43.1 C-6, 58.5
CH2CH3 at C-1, 60 C-1, 123 C-3, 169.1 C=O at C-1, 193.9
C-2, 123.3-129.5 -Carom., C-4 carbon may be merged with
-Carom, 132.7, 133.6, 134.2, 134.9, 140.5 ipso-Cs.
Ethyl 4-(naphthalen-2-yl)-2-oxo-6-phenylcyclohex-3-
enecarboxylate 8
IR (KBr) ν (cm−1): 3057, 2987, 2929, 1738, 1659, 1606, 1292,
1155, 847, 816, 766, 704; 1H NMR (δ ppm), (J Hz): 0.92 (3H,
t, CH2CH3 at C-1, J= 7.1), 3.22-3.28 (2H, H5, m), 3.65–3.73
(1H, H6, m), 3.91 (2H, q, CH2CH3 at C-1, J= 7), 4.17 (1H,
H1, d, J= 13.4), 6.73 (1H, s, H3), 7.24–8.33 (12H, m, Harom.);
13C NMR (δ ppm): 13.7 CH2CH3 at C-1, 35.1 C-5, 43.8 C-6,
58.7 CH2CH3 at C-1, 59.9 C-1, 123.1 C-3, 169.2 C=O at C-1,
194.2 C-2, 123.4-128.8 -Carom., C-4 carbon may be merged
with -Carom, 132.7, 133.6, 134.3, 141.5 ipso-C’s.
Ethyl 6-(4-bromophenyl)-4-(naphthalen-2-yl)-2-oxocyclohex-
3-enecarboxylate 13
IR (KBr) ν (cm−1): 3058, 3027, 2977, 2929, 2907, 2863,
1732, 1657, 1598, 1170, 1145, 892, 817, 748, 711; 1H NMR
(δ ppm), (J Hz): 0.96 (3H, t, CH2CH3 at C-1, J= 7), 3.19-3.21
(2H, H5, m), 3.67–3.74 (1H, H6, m), 3.94 (2H, q, CH2CH3 at
C-1, J= 7), 4.18 (1H, H1, d, J= 13.4), 6.73 (1H, s, H3), 7.42–
8.32 (11H, m, Harom.); 13C NMR (δ ppm): 13.8 CH2CH3 at
C-1, 34.8 C-5, 43.2 C-6, 58.5 CH2CH3 at C-1, 60 C-1, 123.1
C-3, 169.1 C=O at C-1, 194 C-2, 120.1-129.9 -Carom., C-4
carbon may be merged with -Carom, 131.3, 132.7, 133.6,
134.2, 141 ipso-Cs.
Ethyl 4-(naphthalen-2-yl)-2-oxo-6-p-tolylcyclohex-3-
enecarboxylate 9
IR (KBr) ν (cm−1): 3065, 3027, 2979, 2923, 2863, 1740,
1660, 1604, 1148, 897, 849, 816, 753; 1H NMR (δ ppm), (J
Hz): 0.96 (3H, t, CH2CH3 at C-1, J= 7.1), 2.28 (3H, s, CH3
at phenyl ring), 3.15–3.17 (2H, H5, m), 3.62-3.66 (1H, H6,
m), 3.92 (2H, q, CH2CH3 at C-1, J= 6.9), 4.11 (1H, H1, d,
J= 13.3), 6.71 (1H, s, H3), 7.13–8.30 (11H, m, Harom.); 13C
NMR (δ ppm): 14.2 CH2CH3 at C-1, 21 CH3 at phenyl ring,
35.7 C-5, 43.8 C-6, 59.2 CH2CH3 at C-1, 60.3 C-1, 123.5 C-3,
169.6 C=O at C-1, 194.7 C-2, 123.7-129.2 -Carom., C-4 car-
bon may be merged with -Carom, 133.1, 134, 134.7, 136.5,
138.9 ipso-Cs.
Ethyl 4-(naphthalen-2-yl)-6-(4-nitrophenyl)-2-oxo-cyclohex-
3-enecarboxylate 14
IR (KBr) ν (cm−1): 3057, 2978, 2925, 2852, 1734, 1658,
1
1599, 1278, 1149, 893, 856, 815, 743; H NMR (δ ppm),
(J Hz): 0.94 (3H, t, CH2CH3 at C-1, J= 6.9), 3.17–3.26 (2H,
H5, m), 3.68–3.73 (1H, H6, m), 3.92 (2H, q, CH2CH3 at C-1,
J= 6.8), 4.17 (1H, H1, d, J= 13.7), 6.73 (1H, s, H3), 6.98–8.22
(11H, m, Harom.); 13C NMR (δ ppm): 13.5 CH2CH3 at C-1,
34.8 C-5, 43.3 C-6, 58.7 CH2CH3 at C-1, 60.3 C-1, 123.2
C-3, 169.8 C=O at C-1, 193.2 C-2, 123.8-129.1 -Carom., C-4
carbon may be merged with -Carom, 132.6, 133.6, 134.3,
134.8, 140.1 ipso-Cs.
Ethyl 6-(4-fluorophenyl)-4-(naphthalen-2-yl)-2-oxocyclohex-
3-enecarboxylate 10
IR (KBr) ν (cm−1): 3054, 2989, 2925, 1739, 1656, 1603, 1225,
1153, 888, 841, 815, 752; 1H NMR (δ ppm), (J Hz): 0.94 (3H,
t, CH2CH3 at C-1, J= 7), 3.19–3.21 (2H, H5, m), 3.68–3.75
(1H, H6, m), 3.93 (2H, q, CH2CH3 at C-1, J= 7), 4.16 (1H,
H1, d, J= 13.4), 6.73 (1H, s, H3), 7.16–8.33 (11H, m, Harom.);
13C NMR (δ ppm): 13.8 CH2CH3 at C-1, 35 C-5, 43 C-6, 58.8
CH2CH3 at C-1, 59.9 C-1, 123 C-3, 169.1 C=O at C-1, 194.1
C-2, 114.9-129.6 -Carom., C-4 carbon may be merged with
-Carom, 132.7, 1333.6, 134.2, 137.7, 160 ipso-Cs.
General method for the synthesis of 4,5-dihydro-6-
(naphthalen-2-yl)-4-aryl-2H-indazol-3-ols 15-21
A solution of ethyl 4-(naphthalen-6-yl)-2-oxo-6-arylcy-
clohex-3-enecarboxylates 8-14 (0.001 mol) in ethanol
(40 mL) was treated with hydrazine hydrate (0.001 mol)
Journal of Enzyme Inhibition and Medicinal Chemistry

In vitro antimicrobial activity of naphthyl substituted azoles
59
and anhydrous sodium acetate (0.001 mol) and refluxed
for 6–8 h. e reaction mixture was cooled and then
poured over crushed ice. After filtration, the crude prod-
ucts were recrystallised twice using ethanol as solvent to
afford the product.
OH proton disappeared; 13C NMR (δ ppm): 33.5 C-4, 36.2
C-5, 55 OCH3 at phenyl ring, 98.8 C-9, 113.8 C-7, 141, C-8,
157.5 C-3, 113.4-129.2 Carom., C-6 carbon may be merged
with Carom., 132.2, 133, 135.8, 137.2, 160.1 ipso-Cs.
4-(4-chlorophenyl)-4,5-dihydro-6-(naphthalen-2-yl)-2H-
indazol-3-ol 19
4,5-dihydro-6-naphthalen-2-yl-4-phenyl-2H-indazol-3-ol 15
IR (KBr) (cm−1): 3399, 3213, 3055, 3016, 2929, 2863, 2728,
IR (KBr) (cm−1): 3415, 3180, 3053, 2967, 2925, 2874, 2716,
1
1
1598, 1500, 848, 815, 747, 699; H NMR (δ ppm) (J Hz) :
2574, 1597, 1489, 815, 848, 744, 670; H NMR (δ ppm)
3.01–3.09 (1H, m, H5a), 3.25–3.29 (1H, m, H5e), 4.22–4.24
(1H, dd, J4a,5a=8.1 Hz, J4a,5e=3.2Hz), 6.94 (1H, s), 7.08–8.26
(12H, m, Harom.), 9.59 (1H, bs, H2), 11.61 (1H, bs, H3); In the
(J Hz) : 3.01–3.06 (1H, m, H5a), 3.23–3.28 (1H, m, H5e), 4.22-
4.26 (1H, dd, J4a,5a=8.3 Hz, J4a,5e=3.9Hz), 6.94 (1H, s), 7.18-
7.9 (11H, m, Harom.), 9.9 (1H, bs, H2), 11.49 (1H, bs, H3);
In the D2O exchanged 1H NMR spectrum, two broad sin-
glets, one at 9.9 ppm due to labile NH proton and another
at 11.49 ppm due to OH proton disappeared; 13C NMR (δ
ppm): 33.8 C-4, 35.8 C-5, 97.9 C-9, 113.8 C-7, 144.2, C-8,
156.3 C-3, 123.3-129.1 Carom., C-6 carbon may be merged
with Carom., 130.4, 132.3, 133, 135.7, 137 ipso-Cs.
1
D2O exchanged H NMR spectrum, two broad singlets,
one at 9.59 ppm due to labile NH proton and another at
11.61 ppm due to OH proton disappeared; 13C NMR (δ
ppm): 33.9 C-4, 36.1 C-5, 98.6 C-9, 113.8 C-7, 142.2 C-8,
158.2 C-3, 123.3-128.5 Carom., C-6 carbon may be merged
with Carom., 132.2, 133, 134.7, 135.8, 137.2, 141.2 ipso-Cs.
4-(4-bromophenyl)-4,5-dihydro-6-(naphthalen-2-yl)-
2H-indazol-3-ol 20
4,5-dihydro-6-naphthalen-2-yl-4-p-tolyl-2H-indazol-3-
ol 16
IR (KBr) (cm−1): 3355, 3180, 3052, 2924, 2869, 2732, 1596,
IR (KBr) (cm−1): 3388, 3196, 3050, 3022, 2919, 2858, 2721,
1
1
1536, 849, 815, 745, 667; H NMR (δ ppm) (J Hz): 3–3.05
1596, 1509, 848, 813, 772, 745, 670; H NMR (δ ppm) (J
(1H, m, H5a), 3.23–3.27 (1H, m, H5e), 4.21–4.24 (1H, dd,
Hz) : 2.18 (3H, s, CH3 at phenyl ring, 3.01-3.06 (1H, m,
H5a), 3.21–3.28 (1H, m, H5e), 4.17-4.2 (1H, dd, J4a,5a = 8.3
Hz, J4a,5e = 3.6Hz), 6.98 (1H, s), 7–7.96 (11H, m, Harom.),
9.65 (1H, bs, H2), 11.7 (1H, bs, H3); In the D2O exchanged
1H NMR spectrum, two broad singlets, one at 9.65 ppm
due to labile NH proton and another at 11.70ppm due to
OH proton disappeared; 13C NMR (δ ppm): 33.9 C-4, 36.1
C-5, 98.6 C-9, 113.8 C-7, 142.2, C-8, 158.3 C-3, 123.3-128.5
Carom., C-6 carbon may be merged with Carom., 132.2, 133.0,
134.7, 135.8, 137.2, 141.2 ipso-Cs.
J4a,5a = 8.2, J4a,5e = 4), 6.94 (1H, s), 7.12–7.96 (11H, m, Harom.),
9.84 (1H, bs, H2), 11.57 (1H, bs, H3); In the D2O exchanged
1H NMR spectrum, two broad singlets, one at 9.84 ppm
due to labile NH proton and another at 11.57ppm due to
OH proton disappeared; 13C NMR (δ ppm): 33.9 C-4, 35.8
C-5, 97.8 C-9, 113.9 C-7, 144.6, C-8, 158.1 C-3, 118.9-129.5
Carom., C-6 carbon may be merged with Carom., 130.3, 130.9,
131.1, 132.3, 133, 135.7, 137 ipso-Cs.
4,5-dihydro-6-naphthalen-2-yl-4-(4-nitrophenyl)-2H-indazol-
3-ol 21
4-(4-fluorophenyl)-4,5-dihydro-6-(naphthalen-2-yl)-2H-
indazol-3-ol 17
IR (KBr) (cm−1): 3371, 3191, 3054, 2922, 2847, 1598, 1522,
851, 813, 740, 684; 1H NMR (δ ppm) (J Hz): 3.01–3.06 (1H,
m,H5a),3.23–3.28(1H,m,H5e),4.21–4.24(1H,dd,J4a,5a = 8.1,
IR (KBr) (cm−1): 3382, 3213, 3051, 3022, 2919, 2858, 2721,
1596, 1510, 848, 814, 773, 745, 671; 1H NMR (δ ppm) (J Hz)
: 3.01–3.09 (1H, m, H5a), 3.21–3.28 (1H, m, H5e), 4.17–4.2
(1H, dd, J4a,5a = 8.3 Hz, J4a,5e = 3.6Hz), 6.98 (1H, s), 7–7.96
(11H, m, Harom.), 9.85 (1H, bs, H2), 11.48 (1H, bs, H3); In the
J4a,5e = 3.8), 6.93 (1H, s), 6.96–7.88 (11H, m, Harom.), 9.72
(1H, bs, H2), 11.52 (1H, bs, H3); In the D2O exchanged
1H NMR spectrum, two broad singlets, one at 9.72 ppm
due to labile NH proton and another at 11.52ppm due to
OH proton disappeared; 13C NMR (δ ppm): 33.7 C-4, 35.6
C-5, 97.6 C-9, 113.8 C-7, 144.5, C-8, 158.4 C-3, 124.9-128.9
Carom., C-6 carbon may be merged with Carom., 130.6, 130.9,
131.1, 132.6, 133.2, 135.6, 137.2 ipso-Cs.
1
D2O exchanged H NMR spectrum, two broad singlets,
one at 9.85 ppm due to labile NH proton and another at
11.48 ppm due to OH proton disappeared; 13C NMR (δ
ppm): 33.9 C-4, 36.1 C-5, 98.6 C-9, 113.8 C-7, 142.2, C-8,
158.3 C-3, 123.3-128.5 Carom., C-6 carbon may be merged
with Carom., 133, 135, 135.8, 137.2, 141, 156.4 ipso-Cs.
Microbiology
Materials
4,5-dihydro-4-(4-methoxyphenyl)-6-(naphthalene-2-yl)-2H-
indazol-3-ol 18
All the clinically isolated bacterial strains namely
Staphylococcus aureus, β-haemolytic streptococ-
cus, Bacillus subtilis, Vibreo cholerae, Escherichia
coli, Salmonella typhii, Shigella flexneri and the fun-
gal strains namely Aspergillus flavus, Aspergillus
niger, Mucor, Rhizopus and Microsporeum gyp-
suem were obtained from the Faculty of Medicine,
IR (KBr) (cm−1): 3380, 3172, 3053, 2994, 2931, 2891, 2832,
1
1604, 1508, 817, 746, 774, 705, 673; H NMR (δ ppm) (J
Hz) : 3.01–3.06 (1H, m, H5a), 3.2–3.27 (1H, m, H5e), 3.64
(3H, s, OCH3 at phenyl ring, 4.16–4.19 (1H, dd, J4a,5a = 8.2
Hz, J4a,5e = 3.6Hz), 6.74 (1H, s), 6.76–7.97 (11H, m, Harom.),
9.86 (1H, bs, H2), 11.34 (1H, bs, H3); In the D2O exchanged
1H NMR spectrum, two broad singlets, one at 9.86 ppm
due to labile NH proton and another at 11.34ppm due to
Annamalai
Tamil Nadu, India.
University,
Annamalainagar,
© 2011 Informa UK, Ltd.

60
V. Kanagarajan et al.
e reaction mechanism for the formation of ethyl
4-(naphthalen-2-yl)-2-oxo-6-arylcyclohex-3-enecarbox-
ylates 8–14 and 4,5-dihydro-6-(naphthalen-2-yl)-4-aryl-
2H-indazol-3-ols 15–21 is shown in Scheme 2.
In order to discuss the spectral data of Ethyl
4-(naphthalen-2-yl)-2-oxo-6-arylcyclohex-3-enecarbox-
ylates 8–14, ethyl 4-(naphthalen-2-yl)-2-oxo-6-phenyl
cyclohex-3-enecarboxylate 8 has been chosen as a repre-
sentative compound.
In vitro antibacterial and antifungal activity
Minimum inhibitory concentration (MIC) in μg/mL val-
ues was carried out by the two-fold serial dilution method
[17]. e respective test compounds (8–21) were dissolved
in dimethyl sulphoxide (DMSO) to obtain a 1mg mL−1
stock solution. Seeded broth (broth containing microbial
spores) was prepared in nutrient broth (NB) from 24h old
bacterial cultures on nutrient agar (Hi-media, Mumbai) at
37 1°C while fungal spores from 1 to 7 day old Sabourauds
agar (Hi-media, Mumbai) slant cultures were suspended
in Sabouraud’s dextrose broth (SDB). e colony forming
units (CFU) of the seeded broth were determined by a plat-
ingtechniqueandadjustedintherangeof104-105 CFU/mL.
e size of the final inoculums were 105CFU/mL for the
antibacterial assay and 1.1–1.5×102 CFU/mL for the anti-
fungal assay. Testing was performed at pH 7.4 0.2 for the
bacteria (NB) and at a pH 5.6 for the fungi (SDB). Exactly
0.4mL of the solution of test compound was added to
1.6mL of seeded broth to form the first dilution. One milli-
liter of this was diluted with a further 1mL of seeded broth
to give the second dilution and so on till six such dilutions
were obtained. A set of assay tubes containing only seeded
broth were kept as controls. e tubes were incubated
in biological oxygen demand (BOD) incubators (Sigma
Instruments, Chennai, India) at 37 1°C for bacteria and
28 1°C for the fungi. e minimum inhibitory concentra-
tions (MICs) were recorded by visual observations after
24h (for bacteria) and 72–96h (for fungi) of incubation.
Ciprofloxacin was used as the standard for bacterial stud-
ies and Fluconazole was the standard for fungal studies.
Analysis of FT-IR spectrum of ethyl 4-(naphthalen-2-yl)-2-oxo-
6-phenylcyclohex-3-enecarboxylate 8:
FT-IR spectrum of ethyl 4-(naphthalen-2-yl)-2-oxo-6-
phenylcyclohex-3-enecarboxylate 8 shows two strong
characteristic absorptions at 1738 and 1659 cm−1 due to
the ester carbonyl and ketone functional groups respec-
tively. e band at 1606 cm−1 is due to the presence of
C=C stretching frequency. e absorption frequency
at 3057 cm−1 is assigned to aromatic C-H stretching
vibration and the absorption frequencies at 2987 and
2929 cm−1 is assigned to aliphatic C-H stretching vibra-
tion. e observed ester carbonyl, ketone and C=C
stretching vibrational bands are supporting evidence
for the formation of synthesised compound 8.
Analysis of 1H NMR spectrum of ethyl 4-(naphthalen-2-yl)-2-
oxo-6-phenylcyclohex-3-enecarboxylate 8:
1
In the H NMR spectrum of 8, a triplet was observed at
0.92 ppm (J= 7.1 Hz) corresponding to three protons and
this signal is due to the ester methyl protons at C-1. A
quartet was observed at 3.91 ppm (J= 7 Hz) correspond-
ing to two protons and this signal was due to the ester
methylene protons at C-1. Two multiplets are obtained in
the range 3.22–3.28 and 3.65–3.73 and they are due to H-5
and H-6 protons. e doublet at 4.17ppm (J= 13.4 Hz) has
been assigned to the H-1 proton. e singlet observed in
downfield region at 6.73 ppm is due to the H-3 proton.
e aromatic protons appeared as a multiplet in the
range 7.24–8.33ppm.
Results and Discussion
Chemistry
e conventional approach for the synthesis of 4,5-
dihydro-6-(naphthalen-2-yl)-4-aryl-2H-indazol-3-ols
15-21 is as follows: (E)-1-(naphthalen-2-yl)-3-arylprop-
2-ene-1-ones 1-7 are synthesised by the Claisen-
Schmidt condensation of 2-acetyl naphthalene and
substituted benzaldehydes in the presence of alcoholic
sodium hydroxide. Treatment of (E)-1-(naphthalen-2-
yl)-3-arylprop-2-ene-1-ones 1–7 with ethyl acetoacetate
in the presence of sodium ethoxide in refluxing ethanol
(Scheme 1 and Table 1) afford ethyl 4-(naphthalen-
Analysis of 13C NMR spectrum of ethyl 4-(naphthalen-2-yl)-2-
oxo-6-phenylcyclohex-3-enecarboxylate 8
Two 13C resonances at 194.2 and 169.26 ppm are assigned
to the C-2 carbonyl carbon and ester carbonyl carbon
respectively. e 13C resonances at 35.1 and 43.8 ppm
are due to the C-5 and C-6 carbons respectively. e 13C
resonance observed at 58.7 and 13.7 ppm were assigned
to the ester methylene and methyl carbons at C-1 respec-
tively. e signal observed at 59.9 ppm is assigned to the
C-1 carbon, whereas the signal at 123.1 ppm is assigned
to the C-3 carbon. e aromatic carbons are observed in
the range of 123.4–128.8 ppm. C-4 carbon may be merged
with the aromatic carbons. e remaining 13C signals at
132.7, 133.6, 134.3, 141.5 ppm were due to ipso carbons.
In order to discuss the spectral data of 4,5-dihydro-6-
(naphthalen-2-yl)-4-aryl-2H-indazol-3-ols 15–21, 4,5-
dihydro-6-naphthalen-2-yl-4-phenyl-2H-indazol-3-ol
15 was chosen as the representative compound.
2-yl)-2-oxo-6-arylcyclohex-3-enecarboxylates
8–14.
Compounds 8–14 on reaction with hydrazine hydrate
in the presence of anhydrous sodium acetate in reflux-
ing ethanol yield the respective indazole derivatives,
4,5-dihydro-6-(naphthalen-2-yl)-4-aryl-2H-indazol-3
-ols 15–21. e structures of all the newly synthesised
ethyl
4-(naphthalen-2-yl)-2-oxo-6-arylcyclohex-3-
enecarboxylates 8–14 were confirmed by FT-IR, MS,
1H NMR and 13C NMR spectral studies and elemental
analysis. Moreover, 4,5-dihydro-6-(naphthalen-2-yl)-4-
aryl-2H-indazol-3-ols 15–21 were confirmed by mps,
1
1
FT-IR, MS, H NMR, D2O exchanged H NMR, 13C NMR,
two dimensional H-1H HOMOCOR and H-13C HSQC
1
1
spectral studies and elemental analysis.
Journal of Enzyme Inhibition and Medicinal Chemistry

In vitro antimicrobial activity of naphthyl substituted azoles
61
H
O
O
X
NaOH
stirring
20°C, 1 h
CH3
+
X
O
(1–7)
O
O
NaOEt
EtOH
reflux
H3C
CH3
O
O
1–3 h
O
CH3
O
(8–14)
X
EtOH
Anhyd. sodium acetate
NH2-NH2.H2O
reflux
6–8 h
NH
N1
2
Compounds
X
3
OH
H
1,8,15
8
5
CH3
F
2,9,16
7
9
4
3,10,17
4,11,18
5,12,19
6,13,20
7,14,21
6
OCH3
Cl
Br
NO2
(15–21)
X
Scheme 1. Synthetic route for the formation of new ethyl 4-(naphthalen-2-yl)-2-oxo-6-arylcyclohex-3-enecarboxylates 8–14 and 4,5-dihydro-6-
(naphthalen-2-yl)-4-aryl-2H-indazol-3-ols 15–21.
bands are supporting evidence for the formation of the
synthesised compound 15.
Analysis of FT-IR spectrum of 4,5-dihydro-6-naphthalen-2-yl-
4-phenyl-2H-indazol-3-ol 15
e FT-IR spectrum of 4,5-dihydro-6-naphthalen-2-yl-
4-phenyl-2H-indazol-3-ol 15 shows two characteristic
absorption frequencies at 3399 and 3213cm−1 suggests
the presence of -OH and -NH functional groups. e
absorption frequency at 1598 cm−1 is assigned to C=N
stretching vibration. e band at 1500 cm−1 is due to the
presence of C=C stretching frequency. Besides these,
aromatic CH stretching frequencies were observed at
3055 and 3016 cm−1 and the aliphatic CH stretching fre-
quencies were observed at 2929, 2863, and 2728cm−1.
e observed –OH, -NH, C=N, C=C stretching vibrational
Analysis of 1H NMR spectrum of 4,5-dihydro-6-naphthalen-2-
yl-4-phenyl-2H-indazol-3-ol 15
1
In the H NMR spectrum of compound 15, a doublet of
doubletwasobservedfortheH-4protonandtwocoupling
constants were extracted from it, namely J4a,5a = 8.1 Hz and
J
4a,5e = 3.2 Hz. Two multiplets in the region 3.01–3.09 and
3.25–3.29 ppm were assigned to H5a and H5e respectively.
A singlet at 6.94 ppm was conveniently assigned to the
H-7 proton. e aromatic protons appeared as a multip-
let around 7.08–8.26 ppm. e labile OH and NH protons
© 2011 Informa UK, Ltd.

62
V. Kanagarajan et al.
Table 1. Physical and analytical data of ethyl 4-(naphthalen-2-yl)-2-oxo-6-arylcyclohex-3-enecarboxylates 8–14 and 4,5-dihydro-6-
(naphthalen-2-yl)-4-aryl-2H-indazol-3-ols 15–21.
Elemental analysis
m/z (M+1)+•
Molecular
formula
Entry
8
9
X
Reaction time(h) Yield(%) m.p.(°C) CFound(Calculated) HFound(Calculated) NFound(Calculated)
H
2
3
1
3
1
1
2
8
6
8
6
8
8
6
80
78
82
80
75
78
65
60
55
62
50
45
60
45
146
110
126
122
114
126
132
187
173
165
176
180
190
172
81.01(81.06)
81.17(81.22)
77.24(77.3)
77.91(77.98)
74.12(74.16)
66.76(66.82)
72.22(72.28)
81.57(81.63)
81.71(81.79)
77.44(77.51)
78.18(78.24)
74.01(74.09)
66.13(66.2)
72(72.05)
5.92(5.99)
6.25(6.29)
5.4(5.45)
6(6.04)
-
371C25H22O3
CH3
F
-
385C26H24O3
10
11
12
13
14
15
16
17
18
19
20
21
-
389C25H21FO3
401C26H24O4
OCH3
Cl
-
5.2(5.23)
4.67(4.71)
5.07(5.1)
5.29(5.36)
5.64(5.72)
4.75(4.81)
5.41(5.47)
4.54(4.6)
4.07(4.11)
4.41(4.47)
-
405C25H21ClO3
449C25H21BrO3
416C25H21NO5
339C23H18N2O
353C24H20N2O
357C23H17FN2O
369C24H20N2O2
373C23H17ClN2O
417C23H17BrN2O
384C23H17N3O3
Br
-
NO2
H
3.33(3.37)
8.21(8.28)
7.9(7.95)
7.79(7.86)
7.54(7.6)
7.46(7.51)
6.66(6.71)
10.89(10.96)
CH3
F
OCH3
Cl
Br
NO2
(exchangeable with D2O) appeared as a broad singlet at
11.61 and 9.59 ppm respectively.
e 13C resonance at 113.8 ppm has correlations with
singlet at 6.94 ppm. So the signal at 6.94 ppm was conve-
niently assigned to the H-7 proton and the carbon signal
at 113.8 ppm was assigned to C-7.In the HSQC, the 13C
resonances at 98.4, 145.3 and 158.2 ppm has no correla-
tions with protons and hence is due to quaternary car-
bons. e 13C resonances at 98.4, 145.3 and 158.2 ppm
were due to the C-9, C-8 and C-3 carbons respectively.
e C-6 carbon may be merged with the aromatic car-
bons. Among the quaternary carbons, the 13C resonances
at 132.2, 133.0, 135.8, 137.2, and 138.1 are due to ipso
carbons.
Analysis of 1H-1H COSY spectrum of 4,5-dihydro-6-naphthalen-
2-yl-4-phenyl-2H-indazol-3-ol 15
In the homonuclear correlation spectroscopy
(HOMOCOSY)spectrumof15,thesignalat4.22–4.24 ppm
showed cross peaks with the signals at 3.01–3.09 and
3.25–3.29 ppm. e signal at 3.25–3.29 ppm showed cross
peaks with 3.01–3.09 ppm and 4.22–4.24 ppm. Similarly
the signals at 3.01–3.09 showed cross peaks with 3.25–3.29
and 4.22-4.24 ppm. e signal at 4.22-4.24 ppm must be
due to the H-4 proton, since this can have coupling with
the H5a and H5e protons. Consequently, two signals at
3.01–3.09 ppm and 3.25–3.29 ppm must be due to the H5a
and H5e protons. e signal at 6.94 ppm showed a cross
peak with 3.25–3.29 ppm and vice versa. Hence the signal
at 6.94 ppm was conveniently assigned to the H-7 proton
and the signal at 3.25–3.29 ppm was assigned to H5e.
Antibacterial activity
Novelethyl4-(naphthalen-2-yl)-2-oxo-6-arylcyclohex-3-
enecarboxylates 8–14 and 4,5-dihydro-6-(naphthalen-2-
yl)-4-aryl-2H-indazol-3-ols
15–21
were
tested
for their antibacterial activity in vitro against
S. aureus, β.H. streptococcus, B. subtilis, V.
cholerae, E. coli, S. typhii and S. flexneri. cip-
rofloxacinwasusedasthestandarddrug.Minimuminhib-
itory concentration (MIC) in μg/mL values is shown in
Analysis of 13C NMR spectrum of 4,5-dihydro-6-naphthalen-2-
yl-4-phenyl-2H-indazol-3-ol 15
In the 13C NMR spectrum of 15, the two resonances in the
aliphatic region at 34.3 and 35.9 ppm were due to the C-4
and C-5 carbons respectively. e remaining 13C reso-
nances in the quaternary carbon signals at 158.2, 113.8,
145.3 and 98.4 were due to C-3, C-7, C-8 and C-9 carbons.
e aromatic carbons were observed in the range of
123.3–129.6 ppm. e 13C resonances at 132.2, 133, 135.8,
137.2 and 138.1 were due to ipso carbons.
Table 2.
ues indicates that all the compounds (8–21)
exhibit varied range (6.25–200 μg/mL)
A
close survey of the MIC val-
a
of antibacterial activity against all the tested bacte-
rial strains except compounds 8, 15 and 16 against
E. coli, S. aureus and β.H. streptococcus respectively,
which didn’t have activity even at a maximum con-
centration of 200 μg/mL. Compound 8 which with no
substitution at the para position of the phenyl rings
attached to C-4 of the cyclohexenone moiety exerted
moderate activity against all the tested bacterial strains.
Compounds 9 and 11, which have an electron donating
methyl/methoxy substituent at the para position of the
phenyl rings attached to the C-4 of cyclohexenone moi-
ety, exerted excellent antibacterial activity against the
all the gram positive bacterial strains that were tested,
Analysis of 1H-13C HSQC spectrum of 4,5-dihydro-6-
naphthalen-2-yl-4-phenyl-2H-indazol-3-ol 15
In the HSQC spectrum of 15, one bond correlation
(34.3/4.22–4.24 ppm) was observed between C-4 and
H-4. e 13C resonance at 35.9 has correlations with
the methylene protons H5a and H5e (35.9/3.01–3.09;
35.9/3.25–3.29) and hence C-5 resonates at 35.9 ppm.
Journal of Enzyme Inhibition and Medicinal Chemistry

In vitro antimicrobial activity of naphthyl substituted azoles
63
O
O
NH
N
H3C
CH
H
O
CH3
OH
X
Na+
−O
(15–21)
EtOH
reflux
1–3 h
CH3
X
HC
CH
O
(1–7)
NH
N
OH
O
CH3
H
O
O
X
H3C
CH3
CH
CH
O
O
C
C
H
X
NH2
N
O
CH3
O
Na+
−O
O
O
CH3
H
C
CH
O
CH3
H2
X
O
C
CH
C
H2
EtOH
X
Anhyd. sodium acetate
H2N—NH2.H2O
reflux
6–8 h
Na+
−O
O
O
CH3
O
O
H
H
O
CH3
O
CH3
HO
(8–14)
X
X
Scheme 2. Reaction mechanism for the formation of title compounds ethyl 4-(naphthalen-2-yl)-2-oxo-6-arylcyclohex-3-enecarboxylates and 4,5-
dihydro-6-(napthalen-2-yl)-4-aryl-2H-indazol-3-ols.
© 2011 Informa UK, Ltd.

64
V. Kanagarajan et al.
Table 2. In vitro antibacterial activity (MIC) values for ethyl 4-(naphthalen-2-yl)-2-oxo-6-arylcyclohex-3-enecarboxylates 8–14 and 4,5-
dihydro-6-(naphthalen-2-yl)-4-aryl-2H-indazol-3-ols 15–21.
Minimum Inhibitory Concentration (MIC) in μg/mL
Compound
S. aureus
100
β-H.streptococcus
B. subtilis
50
V. cholerae
200
100
25
E. coli
S. typhii
100
100
6.25
100
25
S. flexneri
50
a
8
9
10
11
12
13
14
15
16
17
18
19
20
21
200
12.5
6.25
12.5
6.25
25
-
6.25
12.5
12.5
6.25
25
12.5
12.5
6.25
12.5
12.5
50
200
25
100
12.5
50
200
6.25
25
100
25
6.25
12.5
50
6.25
100
100
6.25
25
25
50
100
50
100
100
6.25
100
25
50
a
-
50
100
25
200
12.5
25
a
100
12.5
200
25
-
50
12.5
50
6.25
50
12.5
12.5
25
6.25
6.25
50
6.25
12.5
25
25
50
12.5
6.25
25
6.25
100
25
6.25
50
12.5
50
25
25
25
50
Ciprofloxacin
50
25
50
25
25
25
a - No inhibition even at higher concentration i.e. at 200 μg/mL
antifungal activity against Rhizopus, A. niger, Mucor and A.
flavusrespectivelyevenatahighconcentrationof200μg/mL.
Compound 8, having no substitution at the phenyl rings
attached to the C-4 carbon of cyclohexenone moiety
exerted moderate activity against all the tested fungal
strains, whereas their indazole derivative compound
15 exerted good antifungal activity against all the tested
fungal strains at a MIC value range of 50–6.25 μg/mL.
Similar results were observed for the electron donating
methyl and methoxy substituent compounds 9 and 11
when compared to their indazole derivative compounds
16 and 18. Cyclohexenone compounds 10, 12, 13 and
14 as well as the indazole compounds 17, 19, 20 and 21
which all have electron withdrawing fluoro, chloro, bromo
or nitro substituents at the para position of the phenyl
rings attached to C-4 of the cyclohexenone moiety exerted
excellent activity against all the fungal strains tested and
most of them had MIC values in the range of 25–6.25 μg/
mL. All the indazole derivatives 15–21 were more potent
than their counterpart cyclohexenone ester derivatives
8–14 and exerted good antifungal activity when compared
to the standard drug fluconazole. Among the cyclohex-
enone ester derivatives 8–14, compounds having electron
withdrawing fluoro, chloro, bromo or nitro substituent at
the para position of phenyl rings attached to the C–4 of the
cyclohexenone moiety exerted excellent activity against all
the tested fungal strains.
namely S. aureus, β.H. streptococcus and B. subtilis at
MIC values of 6.25–12.5 μg/mL whereas they exerted
only moderate activity against the gram negative bac-
terial strains. Compounds which contain an electron
withdrawing fluoro, chloro or bromo substituent at the
para position of phenyl rings attached to the C-4 of the
cyclohexenone moiety exerted excellent activity against
all the tested bacterial strains, except the nitro substitu-
ent which possess moderate activity. e novel indazole
derivative 15 exerted moderate activity against both gram
positive and gram negative bacterial strains, whereas
the introduction of a methyl/methoxy substitutent at
the para position of the phenyl rings attached to the
C-4 of the cyclohexenone moiety in compounds 16 and
18 respectively possessed excellent antibacterial activ-
ity against al the gram negative bacterial strains tested.
Compounds 16 and 18 showed only moderate activity
against gram positive bacterial strains and had MIC val-
ues in the range of 50–200 μg/mL. With the exception
of the nitro substitutent of compound 21, all the elec-
tron withdrawing substituents namely fluoro, chloro or
bromo compounds such as 17, 19 and 20 exerted strong
antibacterial activity against all the tested strains when
compared to the standard drug ciprofloxacin.
Antifungal activity
e in vitro antifungal activity of ethyl 4-(naphthalen-2-yl)-
2-oxo-6-arylcyclohex-3-enecarboxylates 8–14 and 4,5-di-
hydro-6-(naphthalen-2-yl)-4-aryl-2H-indazol-3-ols15–21
was studied against the following fungal strains: A. flavus,
A. niger, Mucor, Rhizopus and Microsporeum gypsuem.
Fluconazole was used as the standard drug. Minimum
inhibitory concentration (MIC) in μg/mL values are shown
in Table 3. A close survey of the MIC values indicates that
compounds8–14exhibitedavariedrange(6.25–200μg/mL)
of antifungal activity against all the tested fungal strains
except compounds 9, 11, 16 and 21 which didn’t show
Conclusion
In brief, a series of ethyl 4-(naphthalen-2-yl)-2-oxo-6-
arylcyclohex-3-enecarboxylates 8–14 and 4,5-dihydro-6-
(naphthalen-2-yl)-4-aryl-2H-indazol-3-ols
15–21
were synthesised and characterised by their physi-
cal and analytical data. is reaction may have wide
applicability in building a variety of heterocycles by
choosing
4-(naphthalen-2-yl)-2-oxo-6-arylcyclohex-
Journal of Enzyme Inhibition and Medicinal Chemistry

In vitro antimicrobial activity of naphthyl substituted azoles
65
Table 3. In vitro antifungal activity (MIC) values for ethyl 4-(naphthalen-2-yl)-2-oxo-6-arylcyclohex-3-enecarboxylates 8–14 and 4,5-
dihydro-6-(naphthalen-2-yl)-4-aryl-2H-indazol-3-ols 15–21.
Minimum Inhibitory Concentration (MIC) in μg/mL
Compound
A. flavus
50
A. niger
100
Mucor
50
Rhizopus
M. gypsuem
100
8
9
50
a
25
50
25
-
100
10
11
12
13
14
15
16
17
18
19
20
21
6.25
100
25
12.5
12.5
100
12.5
12.5
50
50
200
6.25
25
50
a
-
100
6.25
12.5
100
25
6.25
12.5
25
6.25
50
25
50
12.5
25
6.25
12.5
12.5
6.25
25
a
25
25
-
25
6.25
6.25
25
6.25
12.5
25
12.5
25
6.25
12.5
6.25
6.25
100
25
12.5
25
100
50
12.5
50
a
-
6.25
25
Fluconazole
50
50
25
25
a - No inhibition even at higher concentration i.e. at 200 μg/mL
3-enecarboxylates as synthon, which has three versatile
functional groups i.e., ketone, olefin and ester for the
synthesis of structurally diverse organic compounds.
Hence it may be an attractive compound for organic syn-
thesis. e microbiological screening studies carried out
to evaluate the antibacterial and antifungal potencies of
the newly synthesised ethyl 4-(naphthalen-2-yl)-2-oxo-6
-arylcyclohex-3-enecarboxylates 8–14 and 4,5-dihydro-
6-(naphthalen-2-yl)-4-aryl-2H-indazol-3-ols 15–21 are
shown in Table 2 and Table 3. A close inspection of the
in vitro antibacterial and antifungal activity profile in
differently electron donating (CH3 and OCH3) and elec-
tron withdrawing (-F, -Cl, Br and –NO2) functional group
substituted phenyl rings of novel ethyl 4-(naphthalen-
ciprofloxacin. Compounds 12 and 18 exerted good
antibacterial activity against S. flexneri at a MIC value
of 6.25 μg/mL. Results of the anti-fungal activity study
showed that the nature of substituents on the phe-
nyl ring namely, the methyl, fluoro, methoxy, chloro,
bromo and nitro functions at the para positions of the
aryl moieties are determinant for the nature and extent
of the anti-fungal activity of all the synthesised com-
pounds 8–21 for the fungal strains namely: A. flavus,
A. niger, Mucor, Rhizopus and M. gypsuem. Compounds
10, 13 and 17, which all have electron withdrawing
substitutents and electron donating methoxy substi-
tutent compound 18 against A. flavus exerted eight fold
increases in activity when compared to the standard
drug fluconazole. Similarly compounds 12, 17 and 21
exerted eight fold increases in activity against A. niger
when compared to the standard drug. Moreover, all
the electron withdrawing substituent derivatives such
as compounds 12, 15, 17 and 20 and electron donat-
ing methoxy substitutent compound 18 exerted four
fold increases in activity against Mucor, Rhizopus and
M. gypsuem when compared to the standard drug flu-
conazole. Results of the antimicrobial activity showed
that electron withdrawing substitutents like fluoro,
chloro, bromo and nitro substituted derivatives exerted
excellent antibacterial and antifungal activities, since
electron withdrawing substitutents increase the lipo-
philicity due to the strong electron withdrawing capabil-
ity [18]. Moreover, electron withdrawing substitutents
namely fluorine substitution was commonly used in
contemporary medicinal chemistry to improve meta-
bolic stability, bioavailability and protein ligand interac-
tions [19]. Replacement of the phenyl ring at position 4 in
4,6-diaryl-4,5-dihydro-3-hydroxy-2[H]-indazoles [14] by
a more liphophilic naphthalene core [20] enhanced the
microbiological activity against the tested bacterial and
fungal strains. ese observations may promote a further
2-yl)-2-oxo-6-arylcyclohex-3-enecarboxylates
8–14
and 4,5-dihydro-6-(naphthalen-2-yl)-4-aryl-2H-in-
dazol-3-ols 15–21 exerted strong antibacterial activ-
ity against all the tested bacterial strains. Compounds
9, 12 and 20 exerted a four fold increase in activity
against S. aureus when compared to the standard
drug, and showed excellent antibacterial activity at a
MIC value of 6.25 μg/mL. e compounds 10, 12 and
20, which all have electron withdrawing substituents,
exerted eight fold increases in activity when compared
to the standard drug, and good antibacterial activity
against β.H. streptococcus at a MIC value of 6.25μg/mL.
Four fold increases in activity was observed for
the chloro substituted compound 11 and the
fluoro
pound
substituted
17 exerted
Compounds
potent
indazole
derivative
activities
com-
against
20
good
B.
showed
V. cholerae at
subtilis.
12,
16
and
antibacterial
MIC value of 6.25 μg/mL.,
activity
against
a
Compounds 13, 16, 18 and 19 had good activity against
E.coli, and compound 10 had good activity against
S. typhii at a MIC value of 6.25 μg/mL, these are four
fold increases in activity when compared to the drug,
© 2011 Informa UK, Ltd.

66
V. Kanagarajan et al.
7. Pelicano H, Martin DS, Xu RH, Huang P. Glycolysis inhibition for
anticancer treatment. Oncogene 2006;25:4633–4646.
8. Southan GJ, Szabo C. Selective pharmacological inhibition of
distinct nitric oxide synthase isoforms. Biochem Pharmacol
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A, Wanibuchi F, Yamaguchi T. Pharmacological profile of YM348,
a novel, potent and orally active 5-HT2C receptor agonist. Eur J
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development of our research in this field. Furthermore,
the observed marked antibacterial and antifungal activi-
ties of this group of naphthyl cyclohexenones and their
indazole derivatives may be considered as key steps for
the building of novel chemical entities with comparable
pharmacological profiles to that of the standard drugs.
10. May JA, Sharif NA, Chen HH, Liao JC, Kelly CR, Glennon
RA, Young R, Li JX, Rice KC, France CP. Pharmacological
Acknowledgements
Authors are thankful to NMR Research Centre, Indian
Institute of Science, Bangalore for recording spectra.
properties and discriminative stimulus effects of
a
novel and selective 5-HT(2) receptor agonist AL-38022A
[(S)-2-(8,9-dihydro-7H-pyrano[2,3-g]indazol-1-yl)-1-
methylethylamine. Pharmacol Biochem Behaviour 2009;
91:307–314.
Declaration of Interest
11. Gopalakrishnan M, anusu J, Kanagarajan V, Govindaraju R.
Design, synthesis and in vitro microbiological evaluation of 6,6-
dimethyl-7,9-diaryl-1,2,4,8-tetraazaspiro[4.5]decan-3-thiones - A
new series of ‘tailor-made’ compounds. J Enz Inhib Med Chem
2009;24:406–412.
V. Kanagarajan is grateful to Council of Scientific and
Industrial Research (CSIR), New Delhi, Republic of India
for providing financial support in the form of CSIR-Senior
Research Fellowship (SRF) in Organic Chemistry.
12. Gopalakrishnan M, anusu J, Kanagarajan V. Synthesis and
biological
evaluation
of
5,7-diaryl-4,4-dimethyl-4,5,6,7-
tetrahydropyridino[3,4-d]-1,2,3-thiadiazoles. Med Chem Res
2007;16:392–401.
13. Gopalakrishnan M, Sureshkumar P, anusu J, Kanagarajan V,
Govindaraju R, Jayasri G. A convenient ‘one-pot’ synthesis and in
vitromicrobiologicalevaluationofnovel2,7-diaryl-[1,4]-diazepan-
5-ones. J Enz Inhib Med Chem 2007;22:709–715.
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