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Vol-3, Issue-4, Suppl-2, Nov 2012 ISSN: 0976-7908 Anand et al
www.pharmasm.com IC Value – 4.01 2763
PHARMA SCIENCE MONITOR
AN INTERNATIONAL JOURNAL OF PHARMACEUTICAL SCIENCES
SYNTHESIS OF SOME NOVEL MANNICH BASES OF 1,4-
DIHYDROPYRIDINE NUCLEUS OF BIOLOGICAL INTEREST
Kinjal Anand*, Hardi Bhavsar, Bhavika Patel, Prof. Vijayalakshmi Gudaparthi and Prof.
Hansa Parikh
Department of Pharmaceutical Chemistry, L.J.Institute of Pharmacy, S.G.Highway, Ahmedabad-382210
ABSTRACT Heterocyclic compounds are widely distributed in nature and are essential for life. Many heterocyclic compounds due to their specific activity are employed in the treatment of many diseases. Heterocyclic 1,4-dihydropyridines are important class of compounds. They may become promising candidates for exploiting more useful therapeutically active molecules. The compounds having 1,4-dihydropyridines moiety are associated with interesting wide spectrum biological activities, such as antibacterial, antihypertensive, antianginal, vasodilator, cardiac depressant activities, adenosine receptor antagonism, tumor growth inhibition and etc. Based on the above studies, an attempt was made to synthesize heterocyclic Mannich bases (Ia-If)) from parent molecule of 1,4-dihydropyridine and its derivatives. The synthesized compounds were then characterized by TLC, melting point determination, IR, 1H-NMR and Mass spectral studies and tested for their antibacterial and antifungal activity against both Gram+ ve and Gram- ve bacteria B.cereus, S. aureus and E.coli, B.subtillus and C.albicans respectively and compared with the standard drug and all the synthesized compounds showed significant antibacterial and antifungal activity. Keywords: 1,4-dihydropyridine, Mannich bases, antibacterial activity, antifungal activity. INTRODUCTION
1,4-Dihydropyridine (1) is the most feasible nitrogen containing heterocyclic ring with
various substitutions at several positions. This molecule binds to the L-type calcium
channel and acts as a multifunctional lead molecule for the various cardiovascular
activities which include antihypertensive, antianginal, vasodilator and cardiac depressant
activities. Apart from the CVS activities it also exhibit antitubercular, anticonvulsant,
antitumor, analgesic, anti-inflammatory, and stress protective activities. [1] Very
promising therapeutic applications have been obtained using the 1,4-dihydropyridine
system. The dihydropyridine skeleton is common in many drugs such as nifedipine (2),
Vol-3, Issue-4, Suppl-2, Nov 2012 ISSN: 0976-7908 Anand et al
www.pharmasm.com IC Value – 4.01 2764
felodipine (3), nicardipine (4), amlodipine (5), nitrendipine, nimodipine and others,
which are effective as cardiovascular agents and which are also used for the treatment of
hypertension.[2]
NH
MeO2C
H3C CH3
Nicardip ine
NO2
O
ON
CH2Ph
M e
4
Amlodipine
NH
ClCO2EtMeO2C
H3CO
NH2
5
NH
NO2
CO2MeMeO2C
H3C CH3
Nifedipine
2
NH
Cl
CO2EtMeO2C
H3C CH3
Felodipine
Cl
3
Ar = aryl aldehyde
where,
NH
Ar
COOC2H5C2H5OOC
H3C CH3
1,4-Dihydropyridine nucleus
1
Vol-3, Issue-4, Suppl-2, Nov 2012 ISSN: 0976-7908 Anand et al
www.pharmasm.com IC Value – 4.01 2765
The mannich reaction provides an excellent method for carbon-carbon bond
formation and its importance is reflected in the ever-increasing number of suitable
substrates and reaction conditions that have been developed.[3]In this context, literature
survey has revealed a number of reports on antimicrobial activity of N-mannich bases
derived from different heterocycles such as pyrrole, pyrazole, benzimidazole,
benzotriazole, etc. Mannich reaction of heterocyclic ring systems with formaldehyde and
primary or secondary amines have been tested for antibacterial, antifungal, antiviral,
anticancer, antileishmanial and antimalarial activity. [4]
In this regard in our present work we have synthesized some novel 1,4-
dihydropyridine derivatives from substituted quinoline aldehyde, its reaction with acetyl
acetone in presence of ammonia .The Mannich bases of these 1,4-dihydropyridines were
prepared in the second step by reacting these dihydropyridines with formaldehyde in a
base (scheme).
MATERIAL AND METHODS
Material: The chemicals and reagents used in the project work were of AR and LR
grade, procured from Astron chemicals, Ahmedabad and they are used as they obtained.
Equipments: Purity of compounds was checked by thin layer chromatography. Melting
points of synthesized compounds were determined by open capillary method. The IR
spectra of synthesized compounds were recorded on a Fourier-Transform IR
spectrophotometer (model-DRS 8400, Shimadzu) in the range of 400-4000 cm-1 using
KBr pellets. The 1H-NMR spectra of synthesized compounds were recorded on Bruker
Avance II 500MHz FT-NMR spectrophotometer (TOPSPIN 1.3 version) using DMSO-
d6 as solvent. Mass spectrum was recorded by MDS SCIEX API 2000 LCMS/MS
(Applied Biosystems) instrument.
Method:
STEP-I: Synthesis of 2-chloro-6-methylquinoline-3-carbaldehyde[5]
A Vilsmeier-Haack adduct prepared from phosphorus oxytrichloride (6.5 ml, 0.35 mol)
and N, N-dimethylformamide (2.3 ml, 0.125 mol) at 0 ºC was added to N-p-
tolylacetamide (1.49 gm, 0.05 mol) and refluxed for 10 h.The reaction mixture was
poured into ice followed by neutralization using sodium hydroxide. Crude product was
Vol-3, Issue-4, Suppl-2, Nov 2012 ISSN: 0976-7908 Anand et al
www.pharmasm.com IC Value – 4.01 2766
isolated and crystallised from ethanol. Molecular Formula: C11H8ClNO; Molecular
weight (g/mol): 205.64; Melting point: 120-122 ºC (Reported=120-125 ºC); Percentage
yield: 77.03 %; Rf: 0.41.
STEP-II: Synthesis of 1,1'-(4-(2-chloro-6-methylquinolin-3-yl)-2,6-dimethyl-1,4-
dihydropyridine-3,5-diyl)diethanone
A mixture of 2-chloro-6-methylquinoline-3-carbaldehyde (20.5 gm, 0.1 mol), acetyl
acetone (20.0 ml, 0.2 mol) and ammonium hydroxide (0.35 gm, 0.1 mol) in methanol was
heated under reflux for 4 hours. To the resulting mixture, warm water was added and then
allowed to cool. The product was filtered off, washed with aqueous ethanol and
recrystallized from alcohol. Molecular Formula: C21H21ClN2O2; Molecular weight
(g/mol): 368.86; Melting point: 138-140 ºC; Percentage yield: 90.25 %; Rf: 0.73.
STEP-III: Synthesis of Mannich bases
A mixture of 1,1'-(4-(2-chloro-6-methylquinolin-3-yl)-2,6-dimethyl-1,4-dihydropyridine-
3,5-diyl)diethanone (0.01 mol), different bases (0.01 mol) and paraformaldehyde (0.02
mol) was taken in methanol and heated under reflux for 4 hours. The reaction mixture
was cooled and poured into crushed ice. The product was filtered and recrystallized from
aqueous ethanol.
Vol-3, Issue-4, Suppl-2, Nov 2012 ISSN: 0976-7908 Anand et al
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Scheme: Synthesis of Mannich bases of 1,4-dihydropyridine:
Different substitutents (R) are introduced through phthalimide, p-aminobenzoic acid,
morpholine, sulphanilamide, benzimidazole, benzotriazole.
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TABLE 1: PHYSICAL CONSTANT DATA TABLE OF MANNICH BASES
DERIVATIVES
No. Name (R) Molecular formula
Melting Point (°C)
Yield %
Rf Value
1 Phthalimide C30H26N3O4Cl 200-206 43.65%
0.26 Hexane:Ethyl acetate ::8:2
2 p-Amino benzoic acid
C29H28N3O4Cl 136-140 45.52%
0.55 Hexane:Ethyl acetate ::3:7
3 Morpholine C26H30N3O3Cl 152-156 43.70% 0.38 Acetone:Benzene ::9:1
4 Sulphanilamide C28H29N4O4SCl 236-242 50.24%
0.61 Hexane:Ethyl acetate ::8:2
5 Benzimidazole C29H27N4O2Cl 122-128 42.46% 0.53 Acetone:Benzene ::9:1
6 Benzotriazole C28H26N5O2Cl 136-140 52.97% 0.60 Acetone:Benzene ::9:1
(1a) 2-((3,5-Diacetyl-4-(2-chloro-6-methylquinolin-3-yl)-2,6-dimethylpyridin-1(4H)-
yl) methyl) isoindoline-1,3-dione
IR (KBr, cm-1): 1307 (C-N str), 1743 (C=O str in amide), 3248 (N-H str), 752 (C-Cl str),
1423 (-CH3 str), 1600, 1527, 1491 (Aromatic); 1H NMR (δ ppm, DMSO): 2.27 (s, 6H,
COCH3), 2.40 (s, 9H, -CH3), 4.74 (s, 1H,-CH-), 5.01 (s, 2H,-CH2); Mass: (m/e) 528 (M+),
301.2(100).
(1b) 4-(((3,5-Diacetyl-4-(2-chloro-6-methylquinolin-3-yl)-2,6-dimethylpyridin-1(4H)-
yl) methyl)amino)benzoic acid
IR (KBr, cm-1): 3215 (N-H str), 1718(-COOH str), 1672(-C=O str), 752(C-Cl str), 1423(-
CH3 str), 1491(C=N str), 1600,1527,1491(Aromatic); 1H NMR (δ ppm, DMSO): 2.27 (s,
Vol-3, Issue-4, Suppl-2, Nov 2012 ISSN: 0976-7908 Anand et al
www.pharmasm.com IC Value – 4.01 2769
9H, -CH3), 4.0 (s, 2H, -CH2), 4.15 (t, 1H, -NH), 6.2-8.23 (m, 10H, Ar-H), 4.74 (s, 1H, -
CH); Mass: (m/e) 516.5(M-1), 367.2(100).
(1c) 4-(((3,5-Diacetyl-4-(2-chloro-6-methylquinolin-3-yl)-2,6-dimethylpyridin-1(4H)-
yl) methyl)amino)benzenesulfonamide
IR (KBr, cm-1): 1155 & 1330 (SO2NH2 str), 665 (C-S str), 1215 (S=O str), 3228 (-NH
str).
(1d) 1,1'-(4-(2-Chloro-6-methylquinolin-3-yl)-2,6-dimethyl-1-(morpholine- methyl)-
1,4-dihydropyridine-3,5-diyl)diethanone
IR (KBr, cm-1): 1334(C-N str), 1222(C-O-C str), 3220 (N-H str), 740(C-Cl str), 1420(-
CH3 str), 1596, 1530, 1490(Aromatic); 1H NMR (δ ppm, DMSO): 3.64(t, 4H, O-CH2),
2.5(t, 4H, N-CH2), 3.70 (s, 2H,-CH2); Mass: (m/e) 466.3(M-1), 367.2(100).
(1e) 1,1'-(1-((1H-benzo[d]imidazol-1-yl)methyl)-4-(2-chloro-6-methylquinolin-3-yl)-
2,6-dimethyl-1,4-dihydropyridine-3,5-diyl)diethanone
IR (KBr, cm-1): 3218 (N-H str), 1330 (C=N str), 735(C-Cl str), 1425(-CH3 str), 1604,
1527, 1470(Aromatic); Mass: (m/e) 503.3(M+), 301.2(100).
(1f) 1,1'-(1-((1H-benzo[d][1,2,3]triazol-1-yl)methyl)-4-(2-chloro-6-methylquinolin-3-
yl)-2,6-dimethyl-1,4-dihydropyridine-3,5-diyl)diethanone
IR (KBr, cm-1): 1610 (N=N str), 1220 (Azide), 3220 (N-H str), 740(C-Cl str), 1420(-CH3
str), 1596, 1530, 1490(Aromatic); Mass: (m/e) 499.7 (M+), 301.2(100).
RESULTS AND DISCUSSION
Biological Evaluations
Microbial Screening:
The synthesized compounds were screened for their anti-microbial activity by Agar
diffusion method and Disc diffusion method using medium F and Sabouraud’s agar
medium for bacteria and fungi respectively. Anti microbial activity was evaluated by
measuring the diameter of zone of inhibition against test organisms. Based on the results
it is refered that synthesis of some 1,4-dihydropyridine derivatives have significant
inhibition effect on the growth of bacteria like Bacillus cereus, Staphylococus aureus,
Bacillus subtillus and Escherichia coli and fungi like Candida albicans. The results were
tabulated in table. The results showed that the compound Ib, Ic and If showed very good
Vol-3, Issue-4, Suppl-2, Nov 2012 ISSN: 0976-7908 Anand et al
www.pharmasm.com IC Value – 4.01 2770
activity when compare to that the standard (Streptomycin, Tetracycline and Miconazole).
The activity was due to the presence of carboxylic acid group in compound Ib,
sulphonamide group in compound Ic and triazole ring in compound If.
TABLE 2: ANTIBACTERIAL ACTIVITY (ZONES OF INHIBITION) OF
SYNTHESISED COMPOUNDS
Compound code
Conc. (µg/ml)
Zone of inhibition(mm)
Gram +ve Gram –ve
B.cereus S.aureus B.subtillus E.coli
Ia
64 8 7 7 7 80 - - - - 100 9 8 9 9 125 10 11 11 10 156 12 12 12 12
Ib
64 10 10 11 11 80 - - 12 12 100 13 12 15 14 125 14 14 16 15 156 15 16 16 17
Ic
64 11 11 - - 80 13 12 11 12 100 14 13 13 13 125 15 14 15 15 156 16 17 17 16
Id
64 - 8 8 - 80 9 - - 10 100 10 10 10 10 125 12 11 11 11 156 13 14 13 13
Ie
64 9 8 9 9 80 11 10 11 10 100 12 11 12 11 125 14 13 13 12 156 15 15 15 14
If
64 10 9 11 10 80 11 10 12 12 100 12 12 13 12 125 15 14 14 14 156 16 15 15 15
Streptomycin
25 10 8 - - 50 12 10 - - 75 18 14 - - 100 24 20 - -
Tetracycline
25 - - - 11 50 - - - 14 75 - - - 20 100 - - - 22
Vol-3, Issue-4, Suppl-2, Nov 2012 ISSN: 0976-7908 Anand et al
www.pharmasm.com IC Value – 4.01 2771
Degree of activity was measured by the zone of inhibition (mm), (--) No inhibition
Figure 1 Antibacterial activity chart of B.cereus Gram +ve bacteria of synthesized test compounds (Note: Concentration of streptomycin and tetracycline were considered at 25, 50, 75 and
100 μg/ml instead of 64, 80, 100, 125 and 156 μg/ml respectively).
Figure 2 Antibacterial activity chart of S.aureus Gram +ve bacteria of synthesized test compounds (Note: Concentration of streptomycin and tetracycline were considered at 25, 50, 75 and
100 μg/ml instead of 64, 80, 100, 125 and 156 μg/ml respectively).
Vol-3, Issue-4, Suppl-2, Nov 2012 ISSN: 0976-7908 Anand et al
www.pharmasm.com IC Value – 4.01 2772
Figure 3 Antibacterial activity chart of B.subtillus Gram +ve bacteria of synthesized test
compounds (Note: Concentration of streptomycin and tetracycline were considered at 25, 50, 75 and 100 μg/ml instead of 64, 80, 100, 125 and 156 μg/ml respectively).
Figure 4 Antibacterial activity chart of E.coli Gram -ve bacteria of synthesized test compounds
(Note: Concentration of streptomycin and tetracycline were considered at 25, 50, 75 and 100 μg/ml instead of 64, 80, 100, 125 and 156 μg/ml respectively)
Vol-3, Issue-4, Suppl-2, Nov 2012 ISSN: 0976-7908 Anand et al
www.pharmasm.com IC Value – 4.01 2773
TABLE 3: ANTIFUNGAL ACTIVITY (ZONES OF INHIBITION) OF
SYNTHESISED COMPOUNDS
Compound code
Conc. (µg/ml)
Zone of inhibition(mm)
Compound code
Conc. (µg/ml)
Zone of inhibition(mm)
C. albicans C. albicans
Ia
50 -
Id
50 - 100 - 100 - 150 8 150 10 200 10 200 14
Ib
50 8
Ie
50 8 100 10 100 9 150 16 150 10 200 18 200 14
Ic
50 8
If
50 8 100 13 100 12 150 16 150 14 200 17 200 15
Degree of activity was measured by the zone of inhibition (mm), (--) No inhibition
Figure 5 Antifungal activity chart of C. albicans fungi of synthesized test compounds.
CONCLUSION
In summary, most of the synthesized compounds showed significant antibacterial activity
and antifungal activity within the series against both of Gram +ve and Gram –ve bacteria
Vol-3, Issue-4, Suppl-2, Nov 2012 ISSN: 0976-7908 Anand et al
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at 156 and 125 μg/ml concentrations and antifungal activity of fungi at 150 and 200
μg/ml concentrations.
ACKNOWLEDGEMENT
The authors are thankful to L.J.Institute of Pharmacy for providing facilities for synthesis
and biological screening.
REFERENCES
1. Swarnalatha G, Prasanthi G, Sirisha N and Chetty CM: 1, 4-dihydropyridines: a
multifunctional molecule – A review. International Journal of ChemTech
Research 2011; 3(1): 75-89.
2. Prakash, Hussain K, Kumar R, Wadhwa D, Sharma C and Aneja KR: Synthesis
and antimicrobial evaluation of new 1,4-dihydro-4-pyrazolylpyridines and 4-
pyrazolylpyridines. Organic and Medicinal Chemistry Letters 2011; 1-6.
3. Velazquez AMa, Torres LA, Diaz G and Ramirez A: A novel one pot, solvent-
free Mannich synthesis of methylpiperidinylphenols,
methylphenylmorpholinylphenols and methylthiophenylmorpholinylphenols
using infrared light irradiation. Arkivoc 2006; 2: 150-161.
4. Shah TB, Gupte A, Patel MR, Chaudhari VS, Patel H and Patel VC: Synthesis
and in vitro study of biological activity of heterocyclic N-Mannich Bases. Indian
Journal of Chemistry 2009; 48B: 88-96.
5. Khan FN, Subashini R, Roopan SM, Hathwar VR and Ng SW: 2-Chloro-6-
methylquinoline-3-carbaldehyde. Acta Crystallography 2009; E65: o2686.
For Correspondence: Kinjal A. Anand Email: [email protected]