M. Upendar Reddy1,4*, M.C. Somasekhara Reddy2, Venu Chakravartula3
1Department of Chemistry, Rayalaseema University, Kurnool-518007, AP India
2Department of Basic Sciences, G.P.R Engineering College (Autonomous), Kurnool-518007, AP India
3Department of chemistry, Osmania University, Hyderabad-500007, Telangana, India
4Dr. J.C.R Bio, Plot No. 79/80, Survey No-12, Chengicherla Village, Cherlapalli Phase III Industrial Park, Hyderabad-500039, Telangana State, India
*Corresponding Author E-mail: upendram2509@gmail.com
ABSTRACT:
1,4-dihydropyridines (1,4-DHPs) represent a class of compounds possessing various structural modified derivatives, particularly amongst natural products and bioactive agents. The clinically important drugs such as Nicardipine, Nifedipine, Nimodipine, Felodipine, Isradipine and Amlodipine appeared on the market with new active functional group in their main skeleton. Due to their importance in medicinal chemistry, the present paper describes the synthesis of eight new 1,4-dihydropyridine derivatives based on the coupling of 2-amino-4H-chromen-4-one, benzaldehyde and 5-substituted dimedones. These derivatives were evaluated for antibacterial activity (at concentration of 30 μg/mL) with reference to the antibiotic drug streptomycin. The screening results revealed that compounds with R = -CH3, (-CH3)2 and –CH2-CH3 (7b, 7c and 7d) showed antibacterial good activity.
KEYWORDS:Anti-bacterial activity, 1,4-dihydropyridine, Dimedone, Hantzsch, Synthesis.
1,4-dihydropyridines (1,4-DHPs) represent a class of compounds possessing various structural modified derivatives, particularly amongst natural products and bioactive agents1. Together with calcium channel blocker and neuroprotective activity, a number of dihydropyridine derivatives have been found to be vasodilatory, antihypertensive, bronchodilatory, antiatherosclerotic, hepatoprotective, antitumor, antimutagenic, geroprotective, antidiabetic, and antiplatelet aggregation agents2–6. The clinically important drugs such as Nicardipine, Nifedipine, Nimodipine, Felodipine, Isradipine and Amlodipine appeared on the market with new active functional group in their main skeleton7–10. Numerous methods have been reported for the synthesis of 1,4-DHP derivatives, the classical Hantzsch reaction method involves the three-component coupling of an aldehyde with β-ketoester and ammonia in acetic acid or in refluxing alcohol11,12.
In recent years, the clinical use of the existing antimicrobials has been limited due to the following parameter (i) relatively high risk of toxicity (ii) pharmacokinetic problems and (iii) development of bacterial and fungal resistance resulting from the widespread use and misuse of classical antimicrobial agents13. Hence, the need of hour, demands the necessity to identify novel antimicrobial agents effective against pathogenic microorganisms resistant to currently available treatments14.
Encouraged by the various medicinal importance of 1,4-dihydropyridine derivatives, herein we report the synthesis and anti-bacterial activity of some new 1,4-Dihydropyridine derivatives (7a-h) (embedded with chromone and dimedone based hybrids). These derivatives have been synthesized, introducing a one pot three-component coupling of 2-aminochromone, benazldehyde and 5-substituted cyclohexane-1,3-dione derivatives. 2-aminochromone was prepared from commercial available 2-Hydroxyacetophenone as the staring material.
MATERIAL AND METHODS:
The uncorrected melting points of compounds were taken in an open capillary in a paraffin bath. All reagents used were commercial and laboratory grade, melting points were determined in open capillaries and are uncorrected. IR spectra were recorded on potassium bromide disks on a Perkin-Elmer 383 spectrophotometer. 1H NMR spectra were obtained on Varian 400 MHz instrument and Varian 500 MHz, with TMS as internal Standard and chemical shifts are expressed in d ppm solvent used in CDCl3 (in case of intermediate compounds) and DMSO-d6 (in case of final compounds) and mass spectrum on a Hewelett Packard mass spectrometer operating at 70 ev, purity of the compounds were checked by TLC, which is performed with E. Merck pre coated silica gel plates (60 F-254) with iodine as a developing agent. Acme, India silica gel, 60-120 mesh for column chromatography is used. All final compounds were purified by titurating washings with diethyl ether.
Experimental section:
3-(dimethylamino)-1-(2-hydroxyphenyl)prop-2-en-1-one (2)
A mixture of 2-Hydroxyacetophenone (2g, 14.68 mmol) and dimethylformamide dimethylacetal (2.61g, 22.02 mmol) was taken in a sealed tube apparatus and heated to 110oC for 1h. The reaction mixture is cooled to room temperature and poured into the ice-cold water and stirred for 15 min. The precipitated solids was filtered at the pump and dried to obtain brown solid, which was re-crystallised from isopropyl alcohol to obtain the pure compound 2. Yield: 2.66g (95%); M.p 129-130oC (Lit., 128-131oC)15.
2-(isoxazol-5-yl)phenol (3):
In an sealed tube apparatus is added 3-(dimethylamino)-1-(2-hydroxyphenyl)prop-2-en-1-one (2) (2g, 10.45 mmol) was added ethanol (25 mL) followed by hydroxylamine hydrochloride (1.08g, 15.67 mmol) and heated to 100oC for 10h. After completion of the reaction, ethanol was evaporated under reduced pressure and the residue was poured into ice-cold water (20 mL). The precipitated white solid was filtered and dried at the pump. The crude compound (3) was utilized in the next step without further purification.
2-amino-4H-chromen-4-one (4):
To a stirred solution of 2-(isoxazol-5-yl)phenol (3) (1g, 6.20 mmol) in DMF (12 mL) was added (s)-prolinol (0.750g, 7.40 mmol) and heated to 80oC for 8h. The reaction mixture was cooled to room temperature and diluted with ice-cold water and stirred for 30 min. The pale yellow precipitated solids was filtered and re-crystallized from ethanol to afford pure 2-amino-4H-chromen-4-one (4). Yield: 0.82 g, 82%; M.p 272–274 °C (Lit.5 275 °C)16. IR: 3303, 3098, 1644, 1609, 1546, 1276, 755 cm–1. 1H NMR (CDCl3, 400 MHz): 5.19 (s, 1H, 3-H), 7.32–7.38 (m, 2H, 6-H, 8-H), 7.53 (s, exchangeable, 2H, NH2), 7.57–7.63 (m, 1H, 7-H), 7.90 (dd, J = 7.7, 1.4 Hz, 1H, 5-H).
General procedure for the synthesis of 8-substituted-11-phenyl-7,8,9,11-tetrahydro-10H-chromeno[2,3-b]quinoline-10,12 (6H)-dione derivatives (7a-7h):
To a stirred mixture of 2-amino-4H-chromen-4-one (100mg, 0.62 mmol), benzaldehyde (65mg, 0.62 mmol), 5-methylcyclohexane-1,3-dione (78mg, 1.0 mmol) in ethyl-L-lactate (5 mL) and (±) lactic acid (2 mmol). The reaction mixture was stirred at 100oC for 2-3h. After completion of the reaction, the reaction contents were poured into ice cold water and stirred for 10 min. The precipitated solid was filtered at the pump and washed with diethyl ether to obtain pure compounds. The yields of the products differed between 89-92%.
11-phenyl-7,8,9,11-tetrahydro-10H-chromeno[2,3-b]quinoline-10,12 (6H)-dione (7a):
Off white coloured solid; M.p.: 185oC; IR (KBr): γmax 3410, 3080, 2896, 1653, 1607, 1492 cm-1cm-1; 1H NMR (500 MHz, dmso-d6): δ 10.75 (br,s, 1H, D2O exchangeable), 7.91 (d, J = 7.5 Hz, 1H), 7.71-7.68 (m, 1H), 7.50 (d, J = 9.0 Hz, 1H), 7.40 (t, J = 8.0 Hz, 1H), 7.27 (d, J = 7.5 Hz, 2H), 7.17 (t, J = 7.5 Hz, 2H), 7.06 (t, J = 7.0 Hz, 1H), 5.20 (s, 1H), 2.63-2.61 (m, 2H), 2.28-2.25 (m, 2H), 1.98-1.94 (m, 1H), 1.87-1.84 (m, 1H); ESI MS: m/z, 344.2 (M+1);
8-methyl-11-phenyl-7,8,9,11-tetrahydro-10H-chromeno[2,3-b]quinoline-10,12 (6H)-dione (7b):
Off white coloured solid; M.p.: 198oC; IR (KBr): γmax 3431, 3076, 2896, 1653, 1608, 1492 cm-1cm-1; 1H NMR (500 MHz, dmso-d6): δ 10.69 (br,s, 1H, D2O exchangeable), 7.90 (d, J = 8.0 Hz, 1H), 7.70-7.67 (m, 1H), 7.50 (d, J = 8.0 Hz, 1H), 7.40-7.37 (m, 1H), 7.26 (d, J = 7.5 Hz, 2H), 7.17-7.14 (m, 1H), 7.06-7.03 (m, 1H), 5.15 (s, 1H), 2.67-2.60 (m, 2H), 2.49-2.40 (m, 1H), 2.34-2.28 (m, 2H), 2.04-1.99 (m, 1H), 0.97 (d, J = 6.0 Hz, 3H);13C NMR (100 MHz, DMSO-d6): δ 194.20, 173.68, 154.73, 152.86, 150.12, 146.05, 133.15, 127.72 (2C), 127.64 (2C), 125.84, 125.06, 124.86, 123.10, 117.12, 111.94, 99.85, 44.47, 34.06, 33.58, 28.35, 20.28; ESI MS: m/z, 358.3 (M+1);
8,8-dimethyl-11-phenyl-7,8,9,11-tetrahydro-10H-chromeno[2,3-b]quinoline-10,12(6H)-dione (7c):
Off white coloured solid;M.p.: 325oC; IR (KBr): γmax 3434, 3022, 2931,1650,1634, 1458 cm-1; 1H NMR (500 MHz, dmso-d6): δ 10.70 (br,s, 1H, D2O exchangeable), 7.91 (dd, J = 10.0, 1.6 Hz, 1H), 7.70 (td, J = 2.0, 2.0, 1.6 Hz, 1H), 7.50 (d, J = 8.0 Hz, 1H), 7.42-7.38 (m, 1H), 7.29-7.26 (m, 2H), 7.23 (t, J = 7.2 Hz, 2H), 7.06 (t, J = 7.2 Hz, 1H), 5.15 (s, 1H), 2.55 (d, J = 17.2 Hz, 2H), 2.45 (d, J = 17.2 Hz, 1H), 2.23 (d, J = 16.0 Hz, H), 2.06 (d, J = 16.0 Hz, 1H), 1.04 (s, 1H), 0.93 (s, 3H); ESI MS: m/z, 372.3 (M+1);
8-ethyl-11-phenyl-7,8,9,11-tetrahydro-10H-chromeno[2,3-b]quinoline-10, 12 (6H)-dione (7d):
Off white coloured solid;M.p.: 205oC; IR (KBr): γmax 3433, 3082, 2896, 1652, 1602, 1489 cm-1cm-1; 1H NMR (500 MHz, dmso-d6): δ 10.67 (br,s, 1H, D2O exchangeable), 7.89 (d, J = 7.5 Hz, 1H), 7.68 (t, J = 8.0 Hz, 1H), 7.50-7.48 (m, 1H), 7.38 (t, J = 7.0 Hz, 1H), 7.25 (d, J = 7.5 Hz, 2H), 7.16 (t, J = 7.5 Hz, 2H), 7.04 (t, J = 6.5 Hz, 1H), 5.14 (s, 1H), 2.66 (d, J = 16.5 Hz, 1H), 2.49-2.41 (m, 1H), 2.36-2.31 (m, 1H), 2.06-2.00 (m, 2H), 1.36-1.29 (m, 2H), 0.87 (t, J = 11.0 Hz, 3H); 13C NMR (100 MHz, DMSO-d6): δ 194.22, 173.67, 154.74, 152.85, 150.32, 146.03, 133.14, 127.81, 127.71, 127.64, 127.56, 125.84, 125.04, 124.85, 123.09, 117.12, 112.13, 99.84, 42.55, 35.07, 34.10, 31.55, 27.11, 11.04; ESI MS: m/z, 372.3 (M+1);
11-phenyl-7,11-dihydrospiro[chromeno[2,3-b]quinoline-8,1'-cyclopropane]-10,12(6H,9H)-dione (7e):
Off white coloured solid;M.p.: 320oC; IR (KBr): γmax 3408, 3079, 2898, 1654, 1606, 1490 cm-1; 1H NMR (500 MHz, dmso-d6): δ 10.73 (br,s, 1H, D2O exchangeable), 7.92 (d, J = 8.5 Hz, 1H), 7.71 (t, J = 7.0 Hz, 1H), 7.48 (d, J = 8.5 Hz, 1H), 7.39 (t, J = 7.5 Hz, 1H), 7.29 (d, J = 5.0 Hz, 2H), 7.17 (t, J = 8.0 Hz, 2H), 7.06 (t, J = 5.8 Hz, 1H), 5.23 (s, 1H), 2.74 (d, J = 17.5 Hz, 1H), 2.42 (d, J = 16.5 Hz, 1H), 2.30 (d, J = 17.5 Hz, 1H), 1.93(d, J = 16.5 Hz, 1H), 0.46-0.30 (t, J = 11.0 Hz, 4H); 13C NMR (100 MHz, DMSO-d6): δ 194.23, 173.83, 154.59, 152.85, 151.01, 146.04, 133.16, 127.82 (2C), 127.55 (2C), 125.90, 125.06, 124.89, 123.10, 117.13, 112.34, 99.97, 45.51, 35.45, 33.83,15.10, 11.27, 10.08; ESI MS: m/z, 370.3 (M+1);
11-phenyl-7,11-dihydrospiro[chromeno[2,3-b]quinoline-8,1'-cyclobutane]-10,12 (6H,9H)-dione (7f):
Off white coloured solid;M.p.: 305oC; IR (KBr): γmax 3197, 3079, 2850, 1653, 1607, 1492 cm-1; 1H NMR (500 MHz, dmso-d6): δ 10.75 (br,s, 1H, D2O exchangeable), 7.90 (d, J = 7.5 Hz, 1H), 7.69 (t, J = 7.5 Hz, 1H), 7.49 (d, J = 8.5 Hz, 1H), 7.39 (t, J = 7.5 Hz, 1H), 7.24 (d, J = 7.0 Hz, 2H), 7.15 (t, J = 7.5 Hz, 2H), 7.04 (t, J = 7.5 Hz, 1H), 5.15 (s, 1H), 2.78 (q, J = 17.0 Hz, 2H), 2.39 (s, 2H), 1.86-1.80 (m, 5H), 1.62-1.61 (m, 1H); ESI MS: m/z, 384.4 (M+1);
11-phenyl-7,11-dihydrospiro[chromeno[2,3-b]quinoline-8,1'-cyclopentane]-10,12(6H,9H)-dione (7g):
Off white coloured solid;M.p.: 172oC; IR (KBr): γmax 3198, 3088, 2894, 1651, 1602, 1492 cm-1cm-1; 1H NMR (500 MHz, dmso-d6): δ 10.70 (br,s, 1H, D2O exchangeable), 7.90 (dd, J = 8.5, 1.5 Hz, 1H), 7.70-7.67 (m, 1H), 7.49 (d, J = 8.5 Hz, 1H), 7.39 (t, J = 8.0 Hz, 1H), 7.26 (d, J = 7.5 Hz, 2H), 7.17 (t, J = 7.5 Hz, 2H), 7.05 (t, J = 7.5 Hz, 1H), 5.14 (s, 1H), 2.66 (d, J = 17.0 Hz, 1H), 2.53 (d, J = 18.0 Hz, 1H), 2.31 (d, J = 16.5 Hz, 1H), 2.17 (d, J = 15.5 Hz, 1H), 1.59-1.41 (m, 7H), 1.27-1.23 (m, 1H); 13C NMR (100 MHz, DMSO-d6): δ 194.30, 173.77, 154.66, 152.87, 150.09, 146.00, 133.17, 127.73, 127.59, 125.87, 125.07, 124.85, 123.09, 117.15, 111.77, 100.02, 48.65, 43.03, 38.32, 38.25, 36.63, 33.99, 23.84, 23.44, ESI MS: m/z, 398.3 (M+1);
11-phenyl-2,3,4,11-tetrahydrochromeno[2,3-b]cyclopenta[e]pyridine-1,10-dione (7h):
Light brown coloured solid; M.p.: 154oC; IR (KBr): γmax 3082, 2894, 1652, 1608, 1492 cm-1 cm-1; 1H NMR (400 MHz, dmso-d6): δ 11.30 (br,s, 1H, D2O exchangeable), 7.89 (dd, J = 8.0, 1.6 Hz, 1H), 7.72 (td, J = 1.6, 1.6, 1.6 Hz, 1H), 7.55 (d, J = 8.4 Hz, 1H), 7.43-7.39 (m, 1H), 7.28-7.26 (m, 2H), 7.19 (t, J = 7.5 Hz, 2H), 7.11-7.09 (m, 1H), 4.95 (s, 1H), 2.76-2.63 (m, 2H), 2.32 (t, J = 4.0 Hz, 2H); 13C NMR (100 MHz, DMSO-d6): δ 200.67, 174.09, 163.77, 155.97, 152.94, 144.88, 133.27, 127.79 (2C), 127.70 (2C), 125.98, 125.17, 124.83, 122.85, 117.20, 117.09, 99.87, 34.52, 33.60, 23.83; ESI MS: m/z, 330.3 (M+1);
Antibacterial Bioassay:
The synthesized 1,4-dihydropyridine derivatives 7a-h were tested against (a) Staphylococcus aureus (MTCC 902), (b) Bacillus subtilus(MTCC 441) a Gram positive strains and (c) Escherichia coli (MTCC 2692), (d) Pseudomonas aeruginosa (MTCC 2453) a Gram negative strains (at concentration of 30 μg/mL) using agar well diffusion method17-19.
In an autoclave, soyabean casein digest agar Media (50g, Hi-Media) mixed with 1000 mL Milli Q water and then sterilized at 20 lb pressure for 30 minutes and then allowed to cool at 45°C. To the above agar-media, 1 mL of specified bacterial test organism is added. These preparations are then poured into Petri dishes of 90 mm diameter and allowed to solidify medium. The inoculation was done under aseptic conditions and when the medium was in molten state, the solidified plate was bored with 8mm diameter cork borer and was used for the antimicrobial studies.
The test solutions of 1,4-dihydropyridine derivatives 7a-h was prepared by dissolving these compounds in DMSO at concentration of 30 μg/mL. 150 μL each concentration of these compounds was added in the bored place. These compounds were tested with reference to the antibiotic drug streptomycin as a standard reference and DMSO was used as a control solvent (added by using a micropipette) which did not possess any inhibition zone. The plates were incubated at 30-35ºC for 24 hours. The zone of inhibition was calculated by measuring the diameter of the inhibition zone around the well (in mm) including the well diameter. The readings were taken in three different fixed directions in all 3 replicates and the average values were tabulated.
RESULTS AND DISCUSSION:
The synthesis of 1,4-dihydrpyridine derivatives 7a-h was prepared in four synthetic steps from commercial available 2-hydroxy acetophenone (scheme 1). Reaction of 2-hydroxyacetophenone 1 with DMF-DMA in sealed tube at 110oC for 1h produced 3-(dimethylamino)-1-(2-hydroxyphenyl)prop-2-en-1-one (2). Reaction of dialkylaminovinyl ketone 2 with hydroxylamine HCl in ethanol at 100oC for 10h produced 2-(isoxazol-5-yl)phenol (3). Base catalysed rearrangement followed by thermal cyclisation of 2-(isoxazol-5-yl)phenol (3) in presence of (s)-prolinol in DMF at 80oC for 8h resulted in the desired 2-amino-4H-chromen-4-one (4). In the final stage of the synthesis, 1,4-dihydropridine derivatives 7a-h was prepared by one pot three component coupling of 2-amino-4H-chromen-4-one (4), benzaldehyde and 5-substituted dimedones (6a-h) utilizing the protocol reported by Das et al20. The intermediate compound 2, 3 and 4 was prepared by slightly modifying the previous reported literature methods15,16. In addition to the above, we have prepared one more derivative of 1,4-dihydropyridine derivative utilizing cyclopentane-1,3-dione 6h and keeping the remaining components same to afford the 1,4-dihydropyridine 7h. The newly synthesized 1,4-dihydropyridine derivatives 7a-h and 9 were characterized by 1H NMR, 13C NMR, IR and mass spectroscopic techniques.
Scheme 1: Synthesis of 8-substituted-11-phenyl-7,8,9,11-tetrahydro-10H-chromeno[2,3-b]quinoline-10,12 (6H)-dione derivatives
Reaction conditions:
(a) DMF-DMA, sealed tube, 110oC, 1h; (b) Hydroxy amine HCl, ethanol, 100oC, 10h; (c) (s)-prolinol, DMF, 80oC, 8h; (d) (±) lactic acid, ethyl-L-lactate, 100oC, 2-3h;
As a representative example, structural determination of 11-phenyl-7,11-dihydrospiro[chromeno[2,3-b]quinoline-8,1'-cyclopropane]-10,12(6H,9H)-dione (7e) is discussed here, 1H NMR interpretation: a broad singlet at 10.73 ppm is assigned to –NH group and the characteristic signal at 5.23 ppm as singlet corresponds to –CH(Ph) group of the dihydropryridine group. The protons resonating in the aromatic region 7.92 ppm (doublet), 7.71 ppm (triplet), 7.48 ppm (doublet), 7.39 ppm (triplet) is assigned to the phenyl ring fused to chromeno[2,3-b] ring system while the protons of the phenyl ring flanked to dihydropyridine ring resonated in the region 7.29 ppm (doublet, 2H), 7.17 ppm (triplet, 2H) and 7.06 ppm (triplet, 1H). In the aliphatic region, the protons resonating at 0.46-0.30 as multiplet is assigned to the cyclopropane ring and the protons resonating at 2.74 ppm (doublet, 1H), 2.42 ppm (doublet, 1H), 2.30 ppm (doublet, 1H) and 1.93 ppm (doublet, 1H) is assigned to the cyclohexanone ring system. The above description of spectral data is in agreement with the desired number of protons. 13C NMR interpretation: the characteristic carbon signals in the region 194 ppm, 173 ppm is assigned to –CO-C=C- group of the chromeno[2,3-b] ring system and –C=O- of the fused cyclohexanone ring system respectively, while the aromatic and aliphatic carbon signals appeared in the expected region. IR interpretation: A strong characteristic band in the region 3408 cm-1, 1654 cm-1 corresponds to –NH strt and –C=O strt respectively. Mass interpretation: the mass spectra of compound 6e showed a molecular ion peak at m/z 370.3, corresponding to the desired structure. On the basis of above spectral data, the compound has been characterized as compound 6e. Similarly, the remaining compounds 6a-h has been fully characterized as per the above description.
Antibacterial evaluation:
The results of the antibacterial activity of 1,4-dihydropyridine derivative 7a-h is presented in Table 1. Compounds 7b, 7c and 7d exhibited good activities (ZI in the range 22-37 mm) while compound 7a displayed moderate activity (ZI in the range 18-30 mm) and the compounds 7e, 7f, 7g and 7h showed weak activity (ZI in the range 11-29 mm). Based on the above varying ZI values, in general it is observed that compounds with R = -CH3, (-CH3)2 and –CH2-CH3 (7b, 7c and 7d) showed good activity and compound 7a with R = H showed moderate activity and the remaining compounds in the series R = cyclopropyl, cyclobutane and cyclopentane showed weak activity.
Table 1 Results of antibacterial activity of 1,4-dihydropyridine derivatives 7a-h
|
Compd No |
Gram positive bacteria |
Gram negative bacteria |
||
|
Sa |
Bs |
Pa |
Ec |
|
|
Zone of inhibition (ZI) |
||||
|
7a |
26 |
30 |
18 |
25 |
|
7b |
33 |
35 |
24 |
30 |
|
7c |
35 |
37 |
24 |
28 |
|
7d |
37 |
38 |
22 |
28 |
|
7e |
23 |
29 |
15 |
21 |
|
7f |
22 |
26 |
13 |
19 |
|
7g |
20 |
25 |
13 |
18 |
|
7h |
24 |
24 |
11 |
16 |
|
* SD |
38 |
40 |
25 |
31 |
Sa: Staphylococcusaureus; Bs: Bacillussubtilus; Pa:Pseudomonasaeruginosa; Ec: Escherichia coli; *SD: Streptomycin
CONCLUSION:
In conclusion we have synthesized and characterized some new 1,4-dihydropyridine derivatives 7a-h were screened for their anti-bacterial activity at the concentration of 30 μg/mL with reference antibiotic drug streptomycin. The interpretation of the results revealed that 1,4-dihydropyridine derivatives viz.,compounds with R = -CH3, (-CH3)2 and –CH2-CH3 (7b, 7c and 7d) showed good activity and compound 7a with R = H showed moderate activity.
ACKNOWLEDGEMENT:
The authors are grateful to the authorities of Lalitha College of Pharmacy, Ghatkesar, Hyderabad, for supporting for anti-bacterial studies.
CONFLICT OF INTEREST:
The authors declare no conflict of interest.
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Received on 25.09.2017 Modified on 10.11.2017
Accepted on 14.12.2017 © AJRC All right reserved
Asian J. Research Chem. 2018; 11(1):55-60.
DOI:10.5958/0974-4150.2018.00012.3