DMFDMA catalyzed synthesis of 2-((Dimethylamino)methylene)-3,4-dihydro-9-arylacridin-1(2H)-ones and their derivatives: In-vitro antifungal, antibacterial and antioxidant evaluations

Article abstract of DOI:10.1515/chem-2018-0110

A series of 3,4-dihydro-9-arylacridin-1(2H)-ones was synthesized and enaminone function was introduced at the C-2 position using DMFDMA catalyst which in turn successfully converted into pyrazole, isoxazol, 1-phenyl-1H-pyrazole by treating it with reagent

Full text of DOI:10.1515/chem-2018-0110

Open Chem., 2018; 16: 1077–1088
Research Article
Open Access
L. Jyothish Kumar, S. Sarveswari, V. Vijayakumar*
DMFDMA catalyzed synthesis of
2-((Dimethylamino)methylene)-3,4-dihydro-9-
arylacridin-1(2H)-ones and their derivatives: in-
vitro antifungal, antibacterial and antioxidant
evaluations
https://doi.org/10.1515/chem-2018-0110
received December 11, 2017; accepted June 6, 2018.
1 Introduction
Abstract: A series of 3,4-dihydro-9-arylacridin-1(2H)-ones N, N-Dimethylformamide dimethyl acetal (DMFDMA)
was synthesized and enaminone function was introduced also known as 1, 1-dimethoxy-N, N-dimethylmethylamine
at the C-2 position using DMFDMA catalyst which in or 1, 1-dimethoxytrimethylamine, as its name indicates,
turn successfully converted into pyrazole, isoxazol, is a derivative of formamide [1] acts as methylating and
1-phenyl-1H-pyrazole by treating it with reagents such as formylating agent. Formylated products obtained by
hydrazine, hydroxylamine and phenylhydrazine. These treating compounds with active methylene group and
newly synthesized compounds were evaluated for their DMFDMA have proved to be very useful intermediates in
antibacterial activity against a series of Gram-Positive the synthesis of heterocycles [1-4]. Enaminone derivatives
bacteria including Staphylococcus aureus, Bacillus have been proven to be valuable synthon for the synthesis
cereus, Staphylococcus aureus MLS16 and Gram-Negative of a wide variety of biologically active heterocycles [4].
bacteria including Klebsiella planticol, Escherichia coli On the other hand, the functionalized acridines are
and Pseudomonas aeruginosa and also against fungal often used to design and synthesize the compounds with
strains including Candida albicans, Candida parapsilosis, various pharmacological activities such as antibacterial
Candida glabrata, Candida aaseri, Aspergillus niger [5], antifungal [5], anti-inflammatory [6], anticancer [7],
and Issatchenkia hanoiensis. The compounds 3a and 6a anti-cytotoxic [8] and anti-malarial activities [9]. Though
exhibited considerable antifungal activity (MIC value the synthesis of enaminone and its derivatives from simple
0.007 and 0.006 μM) against Candida albicans and ketones using DMFDMA are available in the literature,
Aspergillus niger respectively. The compound 4a showed only a very few reports are available on the enaminones
excellent antibacterial activity towards Escherichia Coli from active methylene of the various heterocycles [1-4
(MIC = 0.003 μM) and the compound 5a found to show and 10-14]. This prompted us to attempt the present
prominent DPPH radical scavenging activity with EC50 work in which we have used the active methylene group
value 16.85 1.5μg mL−1.
of 3,4-dihydro-9-arylacridin-1(2H)-ones to synthesize
the corresponding enaminone which in turn used as a
synthon to obtain the corresponding pyrazole, isoxazole
and 1-aryl-1H-pyrazole using hydrazine, hydroxylamine,
phenylhydrazine respectively.
Keywords: DMFDMA; Enaminones; antifungal;
antibacterial; antioxidant evaluations.
Ethical approval: The conducted research is not
related to either human or animal use.
*Corresponding author: V. Vijayakumar, Centre for Organic and
Medicinal Chemistry, School of Advanced Sciences, VIT University,
Vellore-632014, Tamil Nadu, India, E-mail: kvpsvijayakumar@gmail.com
L. Jyothish Kumar, S. Sarveswari: Centre for Organic and
Medicinal Chemistry, School of Advanced Sciences, VIT University,
Vellore-632014, Tamil Nadu, India
Open Access. © 2018 L. Jyothish Kumar et al., published by De Gruyter.
Attribution-NonCommercial-NoDerivatives 4.0 License.
This work is licensed under the Creative Commons
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2 Materials and Methods
Melting points (mp) reported in this work are recorded
2.1.2 7-chloro-3,4-dihydro-9-phenylacridin-1(2H)-one
(2b)
1
in Elchem microprocessor based DT apparatus in open Yellow solid, (yield 80%), m.p: 185-187 ºC; H NMR (400
1
capillary tubes and are uncorrected. H NMR and 13C MHz, CDCl3): δ ppm 7.97 (d, J = 8.80 Hz, 1H), 7.68 (dd, J =
NMR are recorded in Bruker 400 MHz NMR spectrometer 8.80 Hz, 2.40 Hz, 1H), 7.53-7.47 (m, 3H), 7.41 (d, J = 2.40 Hz,
with TMS as an internal reference. The chemical shift 1H), 7.15 (dd, J = 7.20 Hz, 2.40 Hz, 2H), 3.35 (t, J = 6.20 Hz,
values are reported in parts per million (δ, ppm) from 2H), 2.70 (t, J = 6.20 Hz, 2H), 2.27-2.21 (m, 2H); 13C NMR (100
internal standard TMS. High-Resolution Mass spectra MHz, CDCl3): δ ppm 197.7, 162.5, 150.5, 147.0, 136.8, 132.6,
were recorded using Bruker MaXis HR-MS (ESI-Q-TOF-MS) 132.4, 130.2, 128.3, 128.3, 127.9, 126.7, 124.4, 40.6, 34.5, 21.2.
instrument. All the reagents were purchased from Aldrich
and used as received. Excess solvents were removed under
vacuum. Organic extracts were dried with anhydrous 2.1.3 7-chloro-9-(2-chlorophenyl)-3,4-dihydroacridin-
Na2SO4. Silica gel 60F254aluminum sheets were used in 1(2H)-one (2c)
analytical thin-layer chromatography. Visualization of
1
spots on TLC plates was effected by UV illumination, Yellow solid, (yield 78%), m.p: 180-181ºC ; H NMR (400
exposure to iodine vapour and heating the plates dipped MHz, CDCl3): δ ppm 8.02 (d, J = 9.00 Hz, 1H), 7.71 (dd, J
in a KMnO4 stain. In column chromatography, the silica = 9.00 Hz, 1.40 Hz, 1H), 7.55 (d, J = 7.60 Hz, 1H), 7.46-7.42
gel with 230-400 mesh size was used for the purification.
(m,2H), 7.30 (s, 1H), 7.10 (d, J = 6.80 Hz, 1H), 3.37 (t, J =
6.00 Hz, 2H), 2.80-2.65 (m, 2H), 2.24 (t, J = 6.00 Hz, 2H);
13C NMR (100 MHz, CDCl3): δ ppm 197.4, 162.5, 147.4, 147.0,
135.9, 133.1, 132.8, 132.1, 130.7, 130.7, 130.4, 125.9, 125.5, 40.1,
34.4, 21.2.
2.1 General procedure for the synthesis of
3,4-dihydro-9-arylacridin-1(2H)-ones.
The 2-amino benzophenone 1a (0.1 g, 0.0005 M) was
treated with 1,3-cyclohexanedione (0.06 g, 0.0005 M) in 2.2 General procedure for synthesis of (E)-
presence of ortho-phosphoric acid (catalyst) in ethanol
2-((dimethylamino)methylene)-3,4-dihydro-
and refluxed for 12 hrs. After the completion of the
9-arylacridin-1(2H)-ones (3a-c)
reaction the crude was poured into ice cold water and
the formed precipitate was filtered and dried to afford A mixture of 3,4-dihydro-9-phenylacridin-1(2H)-one (0.1g,
the product 2a. The obtained product was used without 0.0005M)2a-cwithDMFDMA(0.1mL, 0.0005M)intoluene
further purification. And the procedure was repeated with (5 mL) and refluxed for 8-10 hrs to afford the product 3a.
1b-c to get 2b-c.
The mixture was then evaporated under reduced pressure
to afford the solid, which was filtered, washed with hexane
and then dried. The similar procedure was repeated with
2b-c to get 3b-c. The obtained product used for further
analysis without any purification process.
2.1.1 3,4-dihydro-9-phenylacridin-1(2H)-one (2a)
1
Yellow solid, (yield 86%), m.p: 156-157ºC; H NMR (400
MHz, CDCl3): δ ppm 8.00 (d, J = 9.00 Hz, 1H), 7.69 (dd, J =
9.00 Hz, 2.20 Hz, 1H), 7.53-7.49 (m, 4H), 7.41 (d, J = 2.20 Hz, 2.2.1 (E)-2-((dimethylamino)methylene)-3,4-dihydro-9-
1H), 7.15 (dd, J = 7.00 Hz, 2.20 Hz, 2H), 3.36 (t, J = 6.40 Hz, phenylacridin-1(2H)-one (3a)
2H), 2.70 (t, J = 6.40 Hz, 2H), 2.28-2.20 (m, 2H); 13C NMR
(100 MHz, CDCl3): δ ppm 197.7, 162.5, 150.5, 147.0, 136.8, Colourless solid (yield 86%), m.p: 162-163ºC; 1H NMR (400
132.6, 132.4, 130.1, 128.3, 128.3, 128.0, 127.9, 126.7, 124.4, MHz, CDCl3): δ ppm 7.98 (d, J = 8.80 Hz, 1H), 7.62 (dd, J =
40.6, 34.5, 21.2.
8.80 Hz, 2.10 Hz, 2H), 7.50-7.45 (m, 4H), 7.42 (d, J = 2.10 Hz,
1H), 7.22 (d, J = 7.60 Hz, 2H), 3.22 (t, J = 6.40 Hz, 2H), 3.10 (s,
6H), 3.02 (t, J = 6.40 Hz, 2H); 13C NMR (100 MHz, CDCl3): δ
ppm 185.2, 162.0, 151.1, 148.3, 146.1, 137.9, 131.7, 131.2, 130.0,
129.0, 128.5, 128.3, 128.1, 127.9, 127.4, 126.9, 126.4, 104.7, 43.5,
34.6, 23.2. HRMS-ESI (m/z) calcd for C22H20N2O [M+H]+ =
329.1654, found = 329.1660.
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DMFDMA catalyzed synthesis of 2-((Dimethylamino)methylene)-3,4-dihydro-9-arylacridin-1(2H)-ones...
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2.2.2 (E)-7-chloro-2-((dimethylamino)methylene)-3,4-
dihydro-9-phenylacridin-1(2H)-one (3b)
3.00 Hz, 1H), 7.37 (d, J = 5.40 Hz, 2H), 7.33 (d, J = 8.00 Hz,
1H), 3.40 (t, J = 6.80 Hz, 2H), 2.98 (t, J = 6.80 Hz, 2H), 1.90
13
(s, 1H). C NMR (100 MHz, CDCl3): δ ppm 158.1, 148.60,
Colourless solid, (yield 85%), m.p: 172-174ºC; 1H NMR (400 147.1, 142.7, 135.9, 130.2, 129.3, 128.7, 128.5, 127.3, 127.0, 126.7,
MHz, CDCl3): δ ppm 7.98 (d, J = 9.20 Hz, 1H), 7.62 (dd, J = 117.4, 115.1, 33.7, 17.6; HRMS- ESI (m/z) calcd for C20H15N3
9.20 Hz, 2.40 Hz, 2H), 7.50-7.46 (m, 3H), 7.44 (dd, J = 12.80 [M+H] + = 298.1344, found = 298.1338.
Hz, 2.40 Hz, 1H), 7.22 (dd, J = 7.80 Hz, 1.80 Hz, 2H), 3.22
(t, J = 6.40 Hz, 2H), 3.10 (s, 6H), 3.02 (t, J = 6.40 Hz, 2H);
13C NMR (100 MHz, CDCl3): δ ppm 185.2, 162.0, 151.1, 148.3, 2.3.2 9-chloro-4,5-dihydro-11-phenyl-1H-pyrazolo[3,4-a]
146.1, 137.9, 131.7, 131.2, 130.0, 129.0, 128.5, 128.3, 128.1, 127.9, acridine(4b)
127.4, 126.9, 126.4, 104.7, 43.5, 34.6, 23.2. HRMS- ESI (m/z)
calcd for C22H19ClN2O [M+H]+ = 362.1654, found = 362.1654. Colourless solid, (yield 79%), m.p: 155-157ºC; 1H NMR (400
MHz, CDCl3): δ ppm 8.00 (d, J = 8.40 Hz, 1H), 7.69 (dd, J =
8.40 Hz, 1.20 Hz, 1H), 7.62-7.59 (m, 2H), 7.58 (t, J = 2.20 Hz,
2.2.3 (E)-7-chloro-2-((dimethylamino)methylene)-9-(2-
chlorophenyl)-3,4 dihydroacridin-1(2H)-one (3c)
1H), 7.54 (dt, J = 1.20 Hz, 7.50 Hz, 1H), 7.39 (s, 1H), 7.35 (dd,
J = 7.50 Hz, 1.60 Hz, 1H), 7.18 (d, J = 2.20 Hz, 1H), 3.38 (t, J =
3.00 Hz, 2H), 3.00 (t, J = 3.00 Hz, 2H), 2.16 (s, 1H). 13C NMR
1
Light brown solid, (yield 84%), m.p.: 158-159ºC; H NMR (100 MHz, CDCl3): δ ppm 159.0, 144.7, 138.9, 137.0, 136.7,
(400 MHz, CDCl3): δ ppm 8.00 (d, J = 9.00 Hz, 1H), 7.64 (dd, 135.9, 132.4, 130.3, 130.1, 130.0, 129.7, 129.6, 129.1, 128.0,
J = 9.00 Hz, 2.40 Hz, 2H), 7.53 (dd, J = 7.10 Hz, 1.80 Hz, 1H), 127.9, 124.7, 119.3, 118.9, 34.4, 29.7. HRMS- ESI (m/z) calcd
7.42-7.36 (m, 2H), 7.27 (d, J = 2.40 Hz, 1H), 7.15 (dd, J = 7.10 for C20H14ClN3 [M+H]+ = 332.0955, found = 332.1001.
Hz, 1.80 Hz, 1H), 3.24 (t, J = 6.40 Hz, 2H), 3.10 (s, 6H), 3.03
(t, J = 6.40 Hz, 2H); 13C NMR (100 MHz, CDCl3): δ ppm 184.7,
161.9, 151.3, 146.4, 145.0, 137.1, 132.4, 132.1, 131.4, 130.2, 2.3.3 9-chloro-11-(2-chlorophenyl)-4,5-dihydro-1H-
129.6, 129.2, 128.9, 127.0, 126.5, 125.6, 104.2, 43.6, 34.5, 23.1. pyrazolo[3,4-a]acridine (4c)
HRMS- ESI (m/z) calcd for C22H18Cl2N2O [M+H]+ = 397.0874,
1
found = 397.0871.
Brown solid, (yield 59%), m.p: 164-166ºC; H NMR (400
MHz, CDCl3): δ ppm 8.01 (d, J = 6.90 Hz, 1H), 7.71 (d, J =
6.90 Hz, 1H), 7.61-7.57 (m, 2H), 7.53 (t, J = 6.90 Hz, 1H), 7.39
(s, 1H), 7.36 (dd, J = 6.00 Hz, 1.80 Hz, 1H), 7.19 (d, J = 1.80
Hz, 1H), 3.38 (t, J = 3.40 Hz, 2H), 3.00 (t, J = 3.40 Hz, 2H),
2.00 (s, 1H).13C NMR (100 MHz, CDCl3): δ ppm 159.3, 144.8,
136.2, 135.1, 133.8, 132.6, 131.0, 130.7, 130.5, 130.1, 128.0,
2.3 General procedure for the synthesis
of 4,5-dihydro-11-aryl-2H-pyrazolo[3,4-a]
acridines (4a-c)
A mixture of compound 3a (0.1 g, 0.0003 M), hydrazine 127.4, 124.2, 120.2, 34.4, 18.6. HRMS- ESI (m/z) calcd for
hydrate (0.05 mL, 0.0101 M) and 1-2 drops of acetic acid C20H13Cl2N3 [M+H]+ = 366.0565, found = 366.0565.
(catalyst) in ethanol (10 mL) was refluxed at 80 °C for 6-8
h. The mixture was then extracted with ethyl acetate,
dried over sodium sulphate and concentrated under 2.4 General procedure for the synthesis
reduced pressure to afford the crude product 4a. The
of 4,5-dihydro-11-phenylisoxazolo[5,4-a]
obtained crude product was purified by silica gel column
acridines (5a-c)
chromatography using ethylacetate/hexane (4:6) eluent.
To check there reproducibility the reaction and to get 4b- A mixture of compound 3a (0.1 g, 0.0003 M) in ethanol
c, the procedure was repeated with 3b-c.
(10 mL), hydroxyl amine hydrochloride (0.02 g, 0.0003 M)
was refluxed at 80°C for 6-8 h. After the completion of the
reaction, the reaction mixture was poured into ice water;
the obtained crude was filtered, dried to afford the product
5a. The obtained product was purified by silica gel column
chromatography using ethylacetate/hexane (4:6) eluent.
2.3.1 4,5-dihydro-11-phenyl-2H-pyrazolo[3,4-a]acridine
(4a)
1
Colourless solid, (yield 76%), m.p: 166-168ºC; H NMR (400 Similar procedure was adopted with 3b-c to get 5b-c.
MHz, CDCl3): δ ppm 8.40 (d, J = 8.00 Hz, 1H), 7.65 (dd, J =
5.40 Hz, 1.80 Hz, 4H), 7.41 (d, J = 3.00 Hz, 1H), 7.39 (d, J =
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L. Jyothish Kumar et al.
2.4.1 4,5-dihydro-11-phenylisoxazolo[5,4-a]ccridine (5a)
then extracted with DCM, dried over sodium sulphate and
concentrated under reduced pressure to afford the crude
1
Colourless solid, (yield 86%), m.p: 160-161ºC; H NMR product 6a. The obtained crude product was purified by
(400 MHz, CDCl3): δ ppm 8.11 (s, 1H), 8.05 (d, J = 8.20 Hz, silica gel column chromatography using ethylacetate/
1H), 7.64 (t, J = 8.20 Hz, 1H), 7.54 (t, J = 2.40 Hz, 3H), 7.48 hexane (4:6) eluent. To check the reproducibility similar
(d, J = 7.90 Hz, 1H), 7.41 (t, J = 7.90 Hz, 1H), 7.34 (dd, J = 6.60 procedure was adopted with 3b-c to get 6b-c.
Hz, 2.40 Hz, 2H), 3.44 (t, J = 7.20 Hz, 2H), 2.95 (t, J = 7.60 Hz,
13
2H). C NMR (100 MHz, CDCl3): δ ppm 158.1, 148.6, 147.1,
142.7, 135.9, 130.2, 129.3, 128.7, 128.5, 127.3, 127.0, 126.7, 117.4, 2.5.1 4,5-dihydro-1,11-diphenyl-1H-pyrazolo[3,4-a]
115.1, 33.7, 17.6. HRMS- ESI (m/z) calcd for C20H14N2O [M+H]+ ccridine (6a)
= 299.1184, found = 299.1191.
1
Yellow solid, (yield 66%), m.p: 182-183ºC; H NMR (400
MHz, CDCl3): δ ppm 8.09 (d, J = 7.00 Hz, 1H), 7.71 (t, J =
2.4.2 9-chloro-4,5-dihydro-11-phenylisoxazolo[3,4-a]
Acridine (5b)
7.00 Hz, 2H), 7.54 (d, J = 7.60 Hz, 2H), 7.46 (d, J = 7.00 Hz,
2H), 7.42 (dd, J = 6.00 Hz, 2.00 Hz, 2H), 7.36 (d, J = 2.00 Hz,
1H), 7.34 (t, J = 2.40 Hz, 2H), 7.31 (d, J = 7.60 Hz, 1H), 7.28-
1
Yellow solid, (yield 69%), m.p: 152-154ºC; H NMR (400 7.27 (m, 1H), 7.25 (d, J = 2.40 Hz, 1H), 3.28 (t, J = 6.60 Hz,
MHz, CDCl3): δ ppm 8.12 (s, 1H), 7.98 (d, J = 8.80 Hz, 1H), 2H), 2.98 (t, J = 6.60 Hz, 2H). 13C NMR (100 MHz, CDCl3): δ
7.66 (dd, J = 5.20 Hz, 2.20 Hz, 1H), 7.63 (d, J = 2.00 Hz, 1H), ppm 152.2, 147.9, 147.4, 146.3, 144.6, 136.6, 129.9, 129.6, 129.6,
7.62 (dd, J = 8.80 Hz, 2.00 Hz, 1H), 7.56 (dd, J = 4.90 Hz, 2.50 129.5, 128.5, 128.4, 128.2, 127.7, 127.7, 126.7, 126.4, 126.1, 126.0,
Hz, 2H), 7.32 (dd, J = 4.90 Hz, 2.50 Hz, 2H), 3.43 (t, J = 7.20 125.7, 33.9, 29.7. HRMS- ESI (m/z) calcd for C26H19N3 [M+H]+
Hz, 2H), 2.96 (t, J = 7.20 Hz, 2H). 13C NMR (100 MHz, CDCl3): = 374.1675, found = 374.1655.
δ ppm 163.8, 158.4, 148.6, 146.2, 145.5, 141.7, 135.2, 132.6,
132.2, 131.3, 130.9, 130.3, 129.4, 129.2, 129.2, 128.9, 128.7,
128.5, 128.2, 127.6, 125.7, 125.3, 122.5, 117.9, 115.9, 33.7, 17.5. 2.5.2 9-chloro-4,5-dihydro-1,11-diphenyl-1H-
HRMS- ESI (m/z) calcd for C20H13ClN2O [M+H]+ = 332.0950, pyrazolo[3,4-a]acridine (6b)
found = 332.0950.
1
Yellow solid, (yield 58%), m.p: 175-177ºC; H NMR (400
MHz, CDCl3): δ ppm 8.10 (d, J = 8.60 Hz, 1H), 7.71 (t, J = 8.60
2.4.3 9-chloro-11-(2-chlorophenyl)-4,5-
dihydroisoxazolo[5,4-a]Acridine (5c)
Hz, 2H), 7.54 (d, J = 7.60 Hz, 2H), 7.47 (d, J = 7.10 Hz, 2H),
7.36 (dd, J = 7.60 Hz, 2.40 Hz, 2H), 7.35 (d, J = 1.80 Hz, 1H),
7.31 (d, J = 7.10 Hz, 2H), 7.28 (t, J = 1.80 Hz, 1H), 7.27 (d, J =
1
Yellow solid, (yield 49%), m.p: 168-170ºC; H NMR (400 5.60 Hz, 1H), 3.29 (t, J = 6.20 Hz, 2H), 2.99 (t, J = 6.20 Hz,
MHz, CDCl3): δ ppm 8.12 (s, 1H), 7.98 (d, J = 8.80 Hz, 1H), 2H). 13C NMR (100 MHz, CDCl3): δ ppm 160.9, 152.9, 147.9,
7.62 (d, J = 8.80 Hz, 2.40 Hz, 1H), 7.56 (dd, J = 9.00 Hz, 2.00 147.4, 146.3, 144.6, 136.6, 129.9, 129.8, 129.6, 129.6, 128.6,
Hz, 2H), 7.43 (d, J = 2.40 Hz, 1H), 7.30 (dd, J = 9.00 Hz, 2.40 128..5, 128.4, 128.2, 128.0, 127.6, 126.6, 126.4, 126.2, 126.1,
Hz, 2H), 3.41 (t, J = 7.30 Hz, 2H), 2.97 (t, J = 7.30 Hz, 2H). 126.0, 125.7, 33.9, 29.7. HRMS- ESI (m/z) calcd for C26H18ClN3
13C NMR (100 MHz, CDCl3): δ ppm 160.8, 152.2, 147.9, 147.4, [M+H]+ = 408.1268, found = 408.1267.
146.3, 144.6, 136.6, 129.9, 129.8, 129.6, 129.6, 129.5, 128.6,
128.5, 128.4, 128.2, 128.0, 127.7, 127.5, 126.7, 126.4, 126.2,
126.1, 125.9, 125.7, 33.9, 29.7. HRMS- ESI (m/z) calcd for 2.5.3 9-chloro-11-(2-chlorophenyl)-4,5-dihydro-1-
C20H12Cl2N2O [M+H]+ = 367.0405, found = 367.0403.
phenyl-1H-pyrazolo[3,4-a]acridine (6c)
1
Brown solid, (yield 59%), m.p: 187-189ºC; H NMR (400
MHz, CDCl3): δ ppm 8.10 (d, J = 8.60 Hz, 1H), 7.71 (t, J = 8.60
Hz, 2H), 7.54 (d, J = 7.60 Hz, 2H), 7.47 (d, J = 7.00 Hz, 2H), 7.42
(d, J = 1.40 Hz, 2H), 7.36 (dd, J = 7.60 Hz, 2.40 Hz, 2H), 7.31
(d, J = 7.00 Hz, 1H), 7.28 (t, J = 1.40 Hz, 1H), 3.29 (t, J = 6.20
2.5 General procedure for the synthesis of
4,5-dihydro-1,11-diaryl-1H-pyrazolo[3,4-a]
acridine (6a-c)
A mixture of compound 3a (0.1 g, 0.0003 M), phenyl Hz, 2H), 2.99 (t, J = 6.20 Hz, 2H).13C NMR (100 MHz, CDCl3):
hydrazine (0.03 g, 0.0003 M) in glacial acetic acid (5 mL), δ ppm 160.9, 152.2, 147.9, 147.4, 146.3, 144.6, 136.6, 129.9,
was refluxed at 110°C for 12 h. The reaction mixture was 129.8, 129.6, 129.6, 129.5, 128.6, 129.5, 128.4, 128.2, 128.0,
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DMFDMA catalyzed synthesis of 2-((Dimethylamino)methylene)-3,4-dihydro-9-arylacridin-1(2H)-ones...
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.
-
7 42 736
127.7, 127.6, 126.7, 126.4, 126.2, 126.1, 126.0, 125.7, 33.9, 29.7.
HRMS- ESI (m/z) calcd for C26H17Cl2N3 [M+H]+ = 442.0881,
found = 442.0881.
.
7 27
-
.
736
2
7 4
16
15
.
7 15
17
18
14
a
19
.
7 53
Cl
O
.
7 64
.
12 3 10
11
8
9
2
Cl
9
a
a
2.6 Spectral Characterization
8
N
13
7
1
.
3 10
3
6
4
a
All these newly synthesized compounds 3a-c to 6a-c
1
0
5
N
10
.
3 24
.
7 64
5
1
13
were characterized using H-NMR, C-NMR, DEPT-135, H,
H-COSY, C, H-COSY, HR-MS (ESI) and the data included
in the experimental section. Consequently, all the newly
derived target molecules 3a-c to 6a-c subjected to the
in-vitro anti-fungal, anti-bacterial and antioxidant
evaluations and their results were discussed under
biological evaluations.
.
3 03
.
8 00
Figure 1: Summary of Proton d Values of 3c.
5
1
.
2
6
5
.
9
2
.
6
6
1
2
1
3
0
.
5
2
1
1
3
2
9
.
4
1
.
7
2.6.1 Spectral Characterization of Compound 3c
1
3
2
1
8
3
.
.
9
Cl
O
2
0
1
.
43 6
.
.
2
2
1
.
5
.
5
4
4
8
3
1
1
Cl
1
2
0
The compound 3c has been characterized by H-NMR,
1
N
1
1
.
184 7
.
127 0
13C-NMR, DEPT-135, H, H-COSY, C, H-COSY, HR-MS (ESI)
.
43 6
1
6
1
1
N
4
spectral data. The H-NMR spectrum of compound 3c
1
6
.
130 2
.
9
.
34 5
.
4
exhibited the following chemical shifts, d 8.00 d [J =
9.00 Hz, one proton], 7.64 dd [J = 9.00 Hz, 2.40 Hz, two
proton], 7.53 dd [J = 7.10 Hz, 1.80 Hz, one proton], 7.42-
7.36 m [two protons], 7.27 d [J = 2.10 Hz, one proton], 7.15
dd [J = 7.10 Hz, 2.10 Hz, one proton], 3.24 t [J = 6.40 Hz,
.
23 1
.
131 4
Figure 2: Summary of Carbon d Values of 3c.
two protons], 3.10 s [six protons], 3.03 t [J = 6.40 Hz, two due to symmetry. The extreme downfield signal at d 84.7
protons]. The examination of H, H-COSY spectrum of the ppm is indicates the carbonyl group at C-22. The signal at
molecule shows that the singlet at d 3.10 ppm which is d 151.3 ppm has been assigned to the carbon at C-17 due
integrating for six protons due to the two methyl groups of to the deshielding effect of adjacent functional groups.
the molecule at C-18 and C-19 and it is appeared as a single The C-7 and C-8 carbons were identified as d 130.2 and
peak due to symmetry. The remaining two methylene 132.4 ppm respectively. The aliphatic CH2 carbons at (C-14
protons have appeared at d 3.24 and 3.03 ppm which are and C-15) carbons were distinguished using the DEPT-135
integrating for two protons of each at C-14 and C-15. The spectrum of the compound. Remaining aromatic carbon
signals at d 8.00 d [J = 9.00 Hz, one proton], 7.64 dd [J attached hydrogen appears from the aromatic region from
= 9.00 Hz, 2.40 Hz, two protons] and 7.27 d [J = 2.40 Hz, d 151.4 to 125.6 ppm. Similarly, the ortho, meta and para
one proton] are appearing as coupling partners, which is carbons of phenyl group at C-4 were identified as d 129.2,
assigned to C-8, C-7 and C12 respectively. The signals at d 126.5 and 125.6 ppm respectively. The signals at d 104.2,
7.53 dd [J = 7.10 Hz, 1.80 Hz, one proton] and 7.16 dd [J = 7.20 127.0, 132.1, 137.2, 145.0, 146.4, 161.9 and 184.7 ppm were
Hz, 1.60 Hz, one proton] ppm are assigned to C-10 and C-13 due to the non-proton bearing carbons at C-20, C-6, C-3,
respectively and are found to couple with the multiplet C-23, C-16, C-2, C-22 and ipso positions. The formation of
in the range of 7.42-7.36 ppm and hence the multiplet compound 3c also been supported by the observation of
assigned to the protons at C-11 and C-12. The 13C-NMR (ESI-HRMS) m/z value at 397.0871 in the mass spectrum.
spectrum exhibited the following chemical shift values: d
23.1, 34.5, 43.6, 104.2, 125.6, 126.5, 127.0, 128.9, 129.2, 130.2,
131.4, 132.1, 132.4, 137.1, 145.6, 146.4, 151.3, 161.9, 184.7 ppm. 2.6.2 Spectral Characterization of Compound 4a
The up-field signal at d 23.1 ppm has been assigned as a
1
methylene carbon at C-15 and one more signal at d 34.5 The compound 4a has been characterized by H-NMR,
ppm represents at C-14. And the remaining two methyl 13C-NMR, DEPT-135, H, H- COSY, C, H-COSY, HR-MS (ESI)
1
groups at C-18 and C-19 appear as a singlet at d 43.6 ppm is spectral data. The H-NMR spectrum of compound 4a
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1082ꢀ
L. Jyothish Kumar et al.
exhibited the following chemical shifts, d 8.40 d [J = 8.00
Hz, one proton], 7.64 dd [J = 5.40 Hz, 1.80 Hz, four protons],
7.41 d [J = 3.00 Hz, one proton], 7.39 d [J = 3.00 Hz, one
proton], 7.37 d [J = 5.40 Hz, two protons], 7.33 d [J = 8.00 Hz,
one proton], 3.40 t [J = 6.80 Hz, two protons], 2.98 t [J = 6.80
Hz, two protons], 1.90 s [one proton]. The examination of
H, H-COSY spectrum of the molecule shows that the two
triplets at d 3.40 and 2.98 ppm which is integrating for two
protons of each are assigned to C-14 and C-15. The signal at
d 8.40 ppm which integrates for one proton is assigned to
C-8. The signal at d 7.64 [J = 5.40 Hz, 1.80 Hz, four protons]
is assigned to C-7, C-6, C-5 and C-9 respectively. The signal
at d 7.41 d [J = 3.00 Hz, one proton], 7.39 d [J = 3.00 Hz,
one proton] are appearing as a coupling partner, which
is assigned to C-10 and C-11 respectively. And a signal
at d 7.33 d [J = 8.00 Hz, one proton] is assigned to C-13.
.
7 37
.
7 39
.
7 37
14
15
.
7 33
1
N
13
12
.
7 64
.
1 90
2
17 16
NH
.
7 64
.
7 41
11
.
7 64
10
a
3
11
a
10
18
5
9
8
19
4
.
7 64
N
6
a
6
a
7
.
2 98
7
.
8 40
.
3 40
Figure 3: Summary of Proton d Values 4a.
.
127 0
.
126 7
.
127 3
7
.
.
128 3
NH
N
2
4
13
.
128 3
1
The C-NMR spectrum exhibited the following chemical
2
1
.
.
9
.
7
7
.
4
5
128 5
shift values: d 17.6, 33.7, 115.4, 117.2, 126.7, 127.0, 127.3, 128.7,
128.0, 128.8, 130.2, 135.9, 142.7, 147.1, 148.6, 158.1 ppm.
The up-field signal at d 17.6 ppm has been assigned as
methylene carbon at C-15 and one more signal at d 34.5
ppm represents at C-14. The extreme downfield signal at d
158.1 ppm is assigned to C-18. The proton bearing carbons
are identified using HSQC spectrum. The signal at d 126.0
ppm has been assigned to the carbon at C-16 due to the
shielding effect of adjacent functional groups. The C-7
and C-8 carbons were identified as d 129.8 and 128.7 ppm
respectively. The aliphatic CH2 carbons at (C-14 and C-15)
carbons were distinguished using the DEPT-135 spectrum
of the compound. Remaining aromatic carbon attached
hydrogen appears from the aromatic region from d 129.8
to 18.7 ppm. Similarly, the ortho, meta and para carbons
of phenyl group at C-4 were identified as d 129.3, 129.1 and
126.5 ppm respectively. The signals at d 117.9, 127.0, 127.3,
130.2, 135.9, 142.7, 147.1, 158.1 ppm were due to the non-
proton bearing carbons at C-21, C-17, C-20, C-3, C-19, C-18,
C-2 and ipso positions. The formation of compound 4a
also been supported by the observation of (ESI-HRMS)
m/z value at 298.1338 in the mass spectrum.
1
.
130 2
1
3
1
1
.
128 5
.
5
11 4
.
128 7
1
1
5
4
N
.
17 6
8
8
.
128 8
.
.
6
1
.
33 7
.
129 3
Figure 4: Summary of Carbon d Values 4a.
.
7 54
14
.
7 48
.
7 54
13
15
.
1
7 34
2
N
.
7 54
17
16
12
O
.
7 41
3
10
a
11
a
10
.
7 34
18
.
8 11
11
19
4
9
8
a
7
N
6
a
6
7
5
.
.
2 95
7 64
.
8 05
.
3 44
Figure 5: Summary of Proton d Values 5a.
.
128 3
.
128 5
.
128 5
2.6.3 Spectral Characterization of Compound 5a
9
.
.
127 0
.
128 3
6
3
1
1
2
2
.
7 .
N
.
128 7
7 O
.
1
The compound 5a has been characterized by H-NMR,
2
4
7
4
1
1
1
.
148 6
1
13C-NMR, DEPT-135, H, H- COSY, C, H-COSY, HR-MS (ESI)
.
128 8
1
4
1
2
7
.
115 4
7
1
.
.
3
1
spectral data. The H-NMR spectrum of compound 5a
8
1
1
N
.
17 6
2
5
exhibited the following chemical shifts, d 8.11 s [one
proton], 8.05 d [J = 8.20 Hz, one proton], 7.64 t [J = 8.20 Hz,
one proton], 7.54 t [J = 2.40 Hz, three protons], 7.48 d [J =
7.90 Hz, one proton], 7.41 d [J = 7.90 Hz, one proton], 7.34 dd
[J = 6.60 Hz, 2.40 Hz, two protons], 3.44 t [J = 7.20 Hz, two
6
8
.
7
.
.
129 3
1
.
33 7
.
130 2
Figure 6: Summary of Carbon d Values 5a.
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DMFDMA catalyzed synthesis of 2-((Dimethylamino)methylene)-3,4-dihydro-9-arylacridin-1(2H)-ones...
ꢀ1083
.
7 34
protons], 2.95 t [J = 7.60 Hz, two protons]. The examination
of H, H-COSY spectrum of the molecule shows that the
two triplets at d 3.44 and d 2.95 ppm which is integrating
for two protons of each are indicated at C-14 and C-15. The
signal at d 8.05d [J = 8.20 Hz, one proton] and 7.64 t [J =
8.20 Hz, one proton] are appearing as a coupling partner,
which is assigned to C-8 and C-7 respectively. The signal
at d 8.11 ppm is assigned to C-16. The signals at d 7.54 t
[J = 2.40 Hz, three protons] and 7.34 dd [J = 6.60 Hz, 2.40
Hz, two protons] with a coupling constant of [J = 6.00
Hz, 2.40 Hz, two protons]. And the signals at d 7.48 d [J
= 7.90 Hz, one proton] and 7.41 d [J = 7.90 Hz, one proton]
are appearing as a coupling partners is assigned for C-10
and C-9 respectively. The 13C-NMR spectrum exhibited the
following chemical shift values: d 17.6, 33.7, 115.1, 117.1,
126.7, 127.0, 127.3, 128.5, 128.7, 129.3, 130.2, 135.9, 142.7,
147.1, 148.6, 158.1 ppm. The up-field signal at d 33.7 ppm
has been assigned as a methylene carbon at C-14 and one
more signal at d 17.6 ppm represents at C-15. The extreme
downfield signal at d 158.1 ppm is assigned to C-2. The
signal at d 148.6 ppm has been assigned to the carbon at
C-16 due to shielding effect of adjacent functional groups.
The C-7 and C-8 carbons were identified as d 130.3 and
130.9 ppm respectively. The aliphatic CH2 carbons at
(C-14 and C-15) carbons were distinguished using DEPT-
135 spectrum of the compound. Remaining aromatic
carbon attached hydrogen appears from aromatic region
from d 148.6 to 125.7 ppm. Similarly, the ortho, meta and
.
- .
7 28 7 27
.
7 31
.
.
7 4 7 71
6
.
7 54
22
25
14
24
.
7 46
.
7 25
13
20
15
.
7 54
23
2
1
N
17
16
N
12
21
.
7 34
.
7 42
10
11
3
.
a
11
7 42
10
a
.
7 36
9
18
19
.
7 71
8
N
6
4
a
7
a
6
.
2 98
7
5
.
8 09
.
3 28
Figure7: Summary of Proton d Values of 6a.
1
7
2 .
6
0
1
2 .
8
1
2 .
8
4
0
1
2 .
5
1
2 .
8
2
1
2 .
6
7
1
2 .
8
0
.
136 6
1
2 .
6
2
1
2 .
7
6
7
.
4
4
1
N
N
1
2 .
7
1
2 .
9
7
5
2
4
.
.
5
.
9
7
8
4
2
1
1
.
128 6
2
1
2
1
2 .
6
1
4
9
1
2 .
6
1
.
6
1
1
N
5
4
2
2 .
9
7
7
.
129 6
.
2
.
9
3 .
3
9
.
129 8
Figure 8: Summary of Carbon d Values of 6a.
para carbons of phenyl group at C-4 were identified as d 7.00 Hz, two protons] are appearing as a coupling partners
129.7, 129.2 and 128.5 ppm respectively. The formation of is assigned to C-8, C-7, C-9, C-5 and C10 respectively. The
compound 5a also been supported by the observation of signals at d 7.54 d [J = 7.60 Hz, two protons] and 7.31 d [J =
(ESI-HRMS) m/z value at 299.1191 in the mass spectrum.
7.60 Hz, one proton] are appearing as a coupling partners
is assigned to C-12, C-13 and C-11 respectively. Similarly, the
signals at d 7.34 t [J = 2.40 Hz, two protons] and 7.25 d [J
= 2.40 Hz, one proton] is assigned for phenyl substituent
at C-17. The 13C-NMR spectrum exhibited the following
2.6.4 Spectral Characterization of Compound 6a
1
The compound 6a has been characterized by H-NMR, chemical shift values: d 29.7, 33.9, 125.7, 126.0, 126.1, 126.2,
13C-NMR, DEPT-135, H, H-COSY, C, H-COSY, HR-MS (ESI) 126.4, 126.7, 127.6, 127.7, 128.0, 128.2, 128.4, 128.5, 128.6,
1
spectral data. The H-NMR spectrum of compound 6a 129.5, 129.6, 129.8, 129.9, 136.6, 144.6, 146.3, 147.4, 147.9, 152.2
exhibited the following chemical shifts, d 8.09 d [J = 7.00 ppm. The up-field signal at d 33.9 ppm has been assigned
Hz, one proton], 7.71 t [J = 7.00 Hz, two protons], 7.54 d [J = as a methylene carbon at C-14 and one more signal at
7.60 Hz, two protons], 7.46 d [J = 7.00 Hz, two protons], 7.42 d 29.7 ppm represents at C-15. The extreme downfield
dd [J = 6.00 Hz, 2.00 Hz, two protons], 7.36 d [J = 2.00 Hz, signal at d 152.2 ppm is assigned to C-2. The signal at d
one proton], 7.34 t [J = 2.40 Hz, two protons], 7.31 d [J = 7.60 129.8 ppm has been assigned to the carbon at C-16 due
Hz, one proton], 7.28-7.27 m [one proton], 7.25 d [J = 2.40 Hz, to shielding effect of adjacent functional groups. The C-7
one proton], 3.28 t [J = 6.60 Hz, two protons], 2.98 t [J = 6.60 and C-8 carbons were identified as d 129.6 and 128.6 ppm
Hz, two protons]. The examination of H, H-COSY spectrum respectively. The aliphatic CH2 carbons at (C-14 and C-15)
of the molecule shows that the two triplets at d 3.28 and carbons were distinguished using the DEPT-135 spectrum
2.98 ppm which is integrating for two protons of each are of the compound. Remaining aromatic carbon attached
due to C-14 and C-15. The signals at d 8.09 d [J = 7.00 Hz, hydrogen appears from the aromatic region from d 152.2
one proton], 7.71 t [J = 7.00 Hz, two protons] and 7.46 d [J = to 146.6 ppm. Similarly, the ortho, meta and para carbons
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1084ꢀ
L. Jyothish Kumar et al.
of phenyl group at C-4 were identified as d 127.7, 126.7 and results were given as Table-3 along with the minimum
125.9 ppm respectively. The signals at d 126.1, 129.9, 136.6, inhibitory concentrations. The compounds exhibited a
144.6, 146.3, 147.4, 147.9, 152.2 ppm were due to the non- broad spectrum of antibacterial activity against the tested
proton bearing carbons at C-18, C-3, C-4, C-17, C-19, C-20,C-2 Gram-positive bacterial pathogens.
and ipso positions. The formation of compound 6a also
been supported by the observation of (ESI-HRMS) m/z
value at 374.1655 in mass the spectrum.
2.8 In-vitro antioxidant activity by DPPH free
radical scavenging method
2.7 In-vitro antibacterial studies by micro
The antioxidant activity of the compounds was assayed
by measuring scavenging of 1,1-diphenyl-2-picrylhydrazyl
(DPPH) free radicals. In this experiment, different
dilution method
The indicator strains used were Staphylococcus aureus concentrations (10, 20, 40, 80, and 200 μg mL−1) of each
MTCC 737, Bacillus Cereus MTCC 430, Staphylococcus compound were prepared in methanol. Then, working
aureusMLS16, KlebsiellaplanticolaMTCC2277, Escherichia solutionsweremixedwith100μL160μMmethanolsolution
Coli MTCC 1687 and Pseudomonas aeruginosa MTCC 424. of DPPH. The reaction mixture was thoroughly mixed for
The test bacterial strains were grown in nutrient broth 2 min. The samples were then incubated for 30 min in the
medium and inoculums prepared were stored at 4°C for dark at 35°C. After incubating for 30 min, the absorbance
further use. The dilutions of the bacterial inoculums of the samples was measured spectroscopically at 517 nm
were cultured on a nutrient agar medium to check for using a TRIAD multimode reader. In this experiment,
the presence of contamination. The bacterial suspension ascorbic acid was used as positive control and methanol
was adjusted with sterile saline to a final concentration solution as a negative control. The radical scavenging
of approximately 107 CFU/mL in a final volume of 100 μL potential is expressed as an EC50 value, representing the
per well in 96 well plate. The bacterial pathogens were compound concentration at which 50% of the DPPH
inoculated in Muller-Hinton broth along with different radicals was scavenged. All tests were performed in
concentrations of compounds including 0.488, 0.244, triplicate, and values are presented as means. The ability
0.122, 0.061, 0.030, 0.015, 0.007, 0.003, 0.001 and 0.001 of the compound to scavenge the formation of DPPH free
μM. Neomycin (Sigma) was used as positive control and radicals was measured in a concentration-dependent
Muller-Hinton culture media alone was used as negative manner and the DPPH scavenging activity calculated in
control. The bacterial pathogens were incubated along terms of the effective concentration.
with compounds for 24 h. After incubating for 24 h, 40 μL
of INT dye solution was added to each well. The INT dye
solution was prepared by dissolving 0.02% of 20 mg INT in 2.9 In-vitro antifungal studies by broth
100 mL of 40% DMF. Further the samples were incubated
for 2 h. Then the samples were spectrometrically read at
dilution method
450 nm using TRIAD multi-mode reader which measures The antifungal activity of the compounds was determined
the reduction of INT dye by bacterial pathogens. The by broth dilution method using p-iodonitrotetrazolium
percentage of bacterial growth inhibition was calculated (INT) dye reduction method in 96 well plates. Different
using the formula:
test fungal pathogens used in the study include Candida
albicans MTCC 227 (MTCC-Microbial Type Culture
Collection), Candida parapsilosis MTCC 6510, Candida
glabrata MTCC 3984, Candida aaseri MTCC 1907,
% of bacterial growth inhibition = (1−Ac/Ao) × 100.
Where Ac represents intensity of the wells with compound Aspergillus niger MTCC 1344 and Issatchenkia hanoiensis
concentration C; Ao represents intensity of the negative MTCC 4755. The test fungal strains (107 CFU/mL) were
control without compound concentrations. Further, inoculated in 100 μL of potato dextrose broth and the
minimum inhibitory concentration, MIC (μM) values test cultures were stored at 4°C for further experiments.
representing the lowest concentration of the compound The purity of the test cultures was verified by culturing
which exhibited significant decrease in bacterial viability on nutrient agar medium. In a 96-well plate, fungal test
(>95%) was determined. All the experiments were cultures were inoculated with the final concentration of
performed in triplicate and the results were expressed approximately 107 CFU/mL in the final volume of 100 μL
as the average of three independent experiments. The per well. To each fungal suspension, compound was
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DMFDMA catalyzed synthesis of 2-((Dimethylamino)methylene)-3,4-dihydro-9-arylacridin-1(2H)-ones...
ꢀ1085
Table 1: Optimization for the synthesis of 3,4-dihydro-9-arylacridin-
1(2H)-ones based enaminones.
added at different concentrations of 0.720, 0.360, 0.180,
0.090, 0.045, 0.011, 0.005, 0.002 and 0.001 μM. In positive
control experiments, miconazole (Sigma) was added to
each fungal test culture, while potato dextrose broth
medium alone was used as negative control. The fungal
pathogens were incubated along with test compound
for 24 h at 30°C. Aspergillus strain was incubated at
25°C for 72 h. After incubation periods, 40 mL INT test
reagent containing 0.02% 20 mg INT in 100 mL 40%
dimethylformamide (DMF) was added to each well. The
samples were further incubated for 2 h at 37°C. Reduction
of INT dye was monitored spectrometrically by measuring
samples at 450 nm using a TRIAD multimode reader. The
S. No
1
Solvents
DMF
T (°C)
90
Time (h)
Yield (%)
14
12
8
18
38
51
2
3
4
5
6
7
DMF
100
>110
120
110
DMF
Xylene
Toluene
6
66
85
12
11
6
Acetonitrile 90
Dioxane 100
48
36
percentage of fungal pathogen growth inhibition was 1H-NMR, 13C-NMR, DEPT-135, H, H-COSY, HSQC, HR-MS
calculated using the formula:
(ESI) and the detailed data included in the experimental
part.
The above enaminone derivatives (3a-c) afford
various cyclized derivatives of 3,4-dihydro-9-arylacridin-
% of fungal pathogen growth inhibition = (1−Ac/Ao) × 100.
Where AC is the INT absorbance of wells with compound 1(2H)-ones such as 4a-c, 5a-c, and 6a-c (Scheme) while it
at concentration C and A0 represents the INT absorbance is treated with reagents such as hydrazine, hydroxylamine
of the negative control without compound. The minimum hydrochloride and phenylhydrazine. All these newly
inhibitory concentration (MIC, μM) of the samples synthesized compounds were characterized using
represents the lowest concentration of the compound 1H-NMR, 13C-NMR, DEPT-135, H, H-COSY, HSQC, HR-MS
with >95% decrease in fungal growth. All experiments were (ESI) and the data included in the experimental section.
performed in triplicates, and the results are expressed as Consequently, all the newly derived compounds 3a-c,
the average of three independent experiments.
4a-c, 5a-c and 6a-c were subjected to the antifungal, anti-
Ethical approval: The conducted research is not bacterial and anti-oxidant evaluations and their results
related to either human or animal use.
are discussed under biological evaluation.
3.2 Biological evaluations
3 Results and discussion
3.2.1 In-vitro antifungal activity
3.1 Chemistry
The antifungal activity of the compounds is presented
In the present work, a series of 3,4-dihydro-9-arylacridin- in terms of MIC in Table-2. These minimum inhibitory
1(2H)-one based enaminones and their derivatives were concentration values demonstrate that the compounds
synthesized. In the first step different benzophenone exhibited good to moderate antifungal activity
derivatives (1a-c) were converted into their corresponding against the tested fungal pathogens. Among the
3,4-dihydro-9-arylacridin-1(2H)-ones (2a-c) by treating compounds, 3a and 6a showed the highest antifungal
them with 1, 3-cyclohexanedione (Scheme) in ethanol in activitywithMICvalue0.007and0.006μMagainstCandida
the presence of ortho-phosphoric acid as a catalyst. The albicans and Aspergillus niger respectively. In the case
obtained products 2a-c were further treated with DMFDMA of Candida parapsilosis, promising antifungal activity
catalyst to form corresponding enaminones (3a-c) under was observed for compounds 3a, 5a and 6a with MIC
the conventional heating method, in which different values such as 0.028, 0.031 and 0.023 μM respectively.
solvents such as DMF, xylene, toluene, acetonitrile and In the case of Aspergillus niger, compound 6a showed
dioxane were examined for the effective conversion of good antifungal activity as compared with positive
2a-c to 3a-c (Scheme). The yield was observed to be control miconazole with MIC value of 0.006 μM. In the
better with toluene and hence, toluene was considered case of Candida glabrata, compound 4a exhibited good
as a suitable solvent for this reaction (Table-1). All the antifungal activity with MIC value 0.031 μM. The other
newly formed enaminones 3a-c were characterized using compounds such as 4b, 5b-c and 6b-c failed to exhibit
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1086ꢀ
L. Jyothish Kumar et al.
NH
Y
N
X
N
a-c
4
NH2NH2
ano
a
Eth
l
c
N
O
Y
Y
O
ano
Eth
ce c ac
l
id
N
Y
N
X
X
A
ti
N
.
NH H H l
2O
C
X
ano
Eth
l
N
N
b
N
a-c
3
a-c
NH2
5
N
H
a-c
6
n
o uene
DMFDMA i T l
e ux
R fl
ea en s an con ons:
R
t
d
diti
g
O
a
,
=
e ux n
ano
th
rs
6
h
b
R fl
i
E
l
,
.
o
Y
H
H
N
X
S
Y
O
Y
c = e ux n ace c ac
rs
R fl id 5 h
i
ti
,
O
H
a- a
1
6
X
X
l
C
O
ano
Eth
l
-
1b 6b
N
o- os or c ac
id
-
c c
1
6
h
h
i
l
C
p
p
NH2
l
C
a-c
2
a-c
1
Scheme 1: Synthesis of enaminone of 3,4-dihydro-9-arylacridin-1(2H)-ones and their derivatives.
the activity against the all the fungal pathogens tested and Gram-negative bacteria pathogens. The antibacterial
and hence not included in Table-2. The compound which activity of the compounds is presented in terms of
showed lower antifungal activity is due to substitution on minimum inhibitory concentration in Table-3. In case
benzene ring, whereas compound 3a, 4a and 6a has no of S. aureus strain, the compounds 5a and 6a exhibited
such substitution and hence exhibiting better activity.
the highest antibacterial activity with minimum
The results demonstrate that the compounds possess MIC value (0.015 and 0.012 μM) compared with the
good antifungal activity against the fungal pathogens. positive control. In the case of K. planticola strain,
Among all the compounds, the compounds 3a and 6a compounds 4a exhibited the highest antibacterial
exhibited considerable fungal activity (MIC value as 0.89 activity with minimum MIC value (0.007 μM) compared
μM) against Candida albicans MTCC 227 and Aspergillus with the positive control. The compounds 4a and 5a
niger MTCC 1344 respectively. Whereas other compounds, showed promising antibacterial activity in the case of test
the anti-fungal activity is lower than 3a and 6a due to strain Bacillus cereus with MIC value 0.007 μM. Similarly,
substitution on the aryl ring but in 3a and 6a there is no in the case of Staphylococcus aureus compounds 3b and
substitution on it.
6a exhibited good antibacterial activity with minimum
MIC values (0.006 and 0.012 μM) in comparison with
neomycin standard. Furthermore, it was observed that
compound 4a showed excellent antibacterial activity
compared with neomycin standard against Escherichia
3.2.2 In-vitro antibacterial activity
The compounds exhibited promising broad-spectrum coli bacterial pathogen with MIC value (0.003 μM). In
antibacterial activity against the tested Gram-positive the case of Pseudomonas aeruginosa, compared with
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DMFDMA catalyzed synthesis of 2-((Dimethylamino)methylene)-3,4-dihydro-9-arylacridin-1(2H)-ones...
ꢀ1087
Table 2: Antifungal activity of compounds by broth dilution method.
Compounds Minimum Inhibitory Concentration, MIC (μM )
Candida
albicans
MTCC 227
Candida
parapsilosis
MTCC 6510
Candida
aaseri
MTCC 1907
Candida
glabrata
MTCC 3984
Issatchenkia
hanoiensis
MTCC 4755
Aspergillus
niger
MTCC 1344
3a
3b
3c
4a
4c
5a
6a
0.007
0.028
0.051
0.094
0.063
-
0.228
0.057
-
0.057
0.057
-
-
-
-
-
-
-
-
0.051
0.378
0.094
0.031
0.113
0.062
0.050
0.094
0.047
0.252
-
-
-
0.113
0.251
-
-
0.031
0.023
0.251
-
-
0.006
- : No Activity; Miconazole 0.022 † Standard.
Table 3: Antibacterial activity of compounds by micro dilution method.
Compounds
Minimum Inhibitory Concentration, MIC (μM)
Gram Positive Bacteria
Gram Negative Bacteria
Staphylococcus
Bacillus
Staphylococcus
aureus
MLS16
-
Klebsiella
Escherichia
Pseudomonas
aeruginosa
MTCC 424
0.007
aureus
cereus
planticola
coli
MTCC 737
MTCC 430
MTCC 2277
MTCC 1687
0.007
-
3a
3b
4a
-
-
-
-
-
-
0.006
-
0.031
0.007
0.252
0.007
0.003
0.007
4c
5a
-
-
0.056
0.125
0.056
-
-
-
0.015
0.007
0.015
0.031
6a
6c
0.012
0.021
-
-
0.012
0.042
0.050
-
0.025
-
0.100
-
– : No Activity; Nm-Neomycin (0.030) † Standard.
standard neomycin (MIC 0.030 μM), compound 3a and Escherichia Coli MTCC 1687 (MIC value 0.003 μM). Whereas
4a exhibited the highest antibacterial activity with other compounds, the anti-bacterial activity is low due to
MIC of 0.007 and 0.007 μM. This data clearly suggests substitution on benzene ring but in compound 4a there is
that the compounds exhibit promising broad-spectrum no substitution on it.
antibacterial activity against test bacterial pathogens.
The compound 4a showed excellent antibacterial activity
towards Escherichia coli MTCC 1687 (MIC value 0.003 3.2.3 In-vitro antioxidant activity
μM). The other compounds such as 3c, 4b, 5b-c and
6b failed to exhibit the activity against the all the bacterial The results of free radical-scavenging capacity of the
pathogens tested and hence are not included in Table-3. compounds by DPPH methods are shown in Table-4. All
The compound which showed lower antibacterial of the compounds except 3c, 4b and 5b-c demonstrated
activity is due to substitution on the aryl ring, whereas in inhibitoryactivityagainsttheDPPHfreeradicals.Theorder
compounds 3a, 4a and 6a has no such substitution and of free radical-scavenging capacity of the compounds was
hence exhibiting better activity.
The data clearly suggested that the compounds showed the highest free radical-scavenging capacity as
exhibit promising broad-spectrum of antibacterial compared to standard ascorbic acid with EC50 values 18.9
activity against test bacterial pathogens. The compound
4a showed excellent antibacterial activity towards
5a>4a>3a>6b>6a>4c = 3b>6c. The compounds 4a and 5a
1.9 and 16.85 1.5μgmL–1 respectively.
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1088ꢀ
L. Jyothish Kumar et al.
[2] Kumar, D., Kommi, D.N., Chopra, P., Ansari, M.I, Chakraborti,
A.K., L‐Proline‐Catalyzed Activation of Methyl Ketones or Active
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induced synthesis and anti-microbial activities of
Table 4: In-vitro antioxidant activity by DPPH free radical scavenging
method.
Compounds
EC50 (concentration of 50% scavenging of
DPPH free radicals) [μgmL–1]
19.58 1.1
3a
3b
4a
4c
5a
6a
6b
6c
33.5 1.7
18.9 1.9
33.5 1.7
16.85 1.5
24.8 1.3
20.74 1.6
41.7 2.1
18.22 1.25
7,10,11,12-tetrahydrobenzo[c]acridin-8(9H)-one derivatives,
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action of 9-anilinoacridines against chloroquine-resistant
Plasmodium falciparum in vitro, Antimicrob Agents and
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[10] Jyothish Kumar, L., Vijayakumar, V., An efficient solvent-free
synthesis of 3-acetyl-4-arylquinoline-based enaminones and
its derivatives using DMFDMA reagent, Chemical Papers, 2018,
72, 2001-2012. Chemical Papers, 2018, 72, 2001-2012.
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of Fully Substituted Pyridines via Ring Construction Based
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Ascorbic acid†
4 Conclusion
The
3,4-dihydro-9-arylacridin-1(2H)-one
based
enaminones was successfully synthesized by exploring
the synthetic potential of DMFDMA which in turn
converted into number of biologically potent heterocycles.
In addition all the newly synthesized compounds were
subjected to the in-vitro antifungal, antibacterial and
antioxidant evaluations to find their efficacy and the
potent lead molecules were found.
Acknowledgements: Authors are thankful to the
administration, VIT University, Vellore, India for providing
facilities to carry the research work and also thankful
to SIF-Chemistry for providing NMR facility. Authors
are thankful to the University of Hyderabad (Network
resource centre (UGC-NRC) for HRMS facility and also
NMR facilities. The authors thankful to the department
of Life Sciences, University of Hyderabad, for extending
their facilities to perform the biological activities. Author
L. Jyothish Kumar is thankful to the VIT University for
providing Research Associateship.
[12] Liu, Y, Zhou, R, Wan, J. P., Water-Promoted Synthesis of
Enaminones: Mechanism Investigation and Application in
Multicomponent Reactions, Synth. Commun., 2013, 43, 2475-
2483. Synth. Commun., 2013, 43, 2475-2483.
[13] Wan, J. P, Gao, Y., Domino Reactions Based on Combinatorial
Bond Transformations in Electron‐Deficient Tertiary Enamines,
The Chemical Record, 2016, 16, 1164–1177.
Conflict of interest: Authors declare no conflict of
interest.
[14] Wan, J. P, Zhong, S, Xie, L, Cao, X, Liu, Y, Wei, L., KIO3-Catalyzed
Aerobic Cross-Coupling Reactions of Enaminones and
Thiophenols: Synthesis of Polyfunctionalized Alkenes by Metal-
Free C–H Sulfenylation, Org. Lett., 2016, 18, 584−587.
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Supplemental Material: The online version of this article offers
supplementary material (https://doi.org/10.1515/chem-2018-0110).
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