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THIAZOLO [3, 2-α] PYRIMIDINE DERIVATIVES M. B. Buddh et al.
SYNTHESIS AND BIOLOGICAL EVALUATION OF THIAZOLO [3, 2-α α α α ] PYRIMIDINE DERIVATIVES AS A NEW TYPE OF
POTENTIAL ANTIMICROBIAL AGENTS
.M. B. Buddh, A. H. Bapodra
1and K. D. Ladva
2,*1M.D. Science College, Porbandar- 360575 (Gujarat)
2Shree M & N Virani Science College, Rajkot-360005 (Gujarat)
*E-mail: kdladva@vsc.edu.in
ABSTRACT
A series of 2-arylidene- 4-(4′-methoxyphenyl) - 5 - (3,4-dimethyl phenylamino) carbonyl – 6 - phenyl - 4,7 dihydro thiazolo [3,2-α] - pyrimidin 3-ones, were synthesized under reflux condition by a simple one pot condensation reaction of 4 – [(p-methoxyphenyl) -5- (3,4 – dimethyl) – phenyl amino carbonyl] – 6 – phenyl - 1,4 –dihydro pyrimidin -2(1H) –thiones and monochloro acetic acid, glacial acetic acid, acetic anhydride and different aromatic aldehydes in the presence of sodium acetate, where, thiopyrimidine derivatives were prepared by three component Biginelli reaction in presence of hydrochloric acid as a catalyst. The yield of both type of compounds thiopyrimidine derivatives and thiazolo pyrimidine derivatives following recrystallization from proper solvent were of the order 55 - 80%.All newly synthesized compounds were characterized by elemental analysis, IR, 1H-NMR, and Mass spectral analysis and purity of each compounds were checked by TLC using precoated silica gel plate. The synthesized compounds have been screened for their antimicrobial activies against various gram positive and gram negative bacteria and fungi. MIC of each compound was also determined.
Keywords: 1,4–dihydro pyrimidin -2(1H) –thiones, Thiazolo[3,2-α] pyrimidines, Antimicrobial activity studies.
© 2011 RASĀYAN. All rights reserved.
INTRODUCTION
The synthesis and pharmacological activity of condensed pyrimidine derivatives have been reported.
Thiazolo [3,2-α] pyrimidine derivatives are the bioisosteric analogues of purines and are potentially bioactive molecules. Many derivatives with different substitution patterns display interesting pharmacological activities. Thiazolopyrimidines have hypoglycemic and hypolipidemic and antidiabetic1 activities. Triazolopyrimidines have antifungal activity2 and pyrimidine derivatives have antileshimanial activity.3 Thus, these compounds have attracted our attention due to the wide range of biological activities associated with this scaffold. Various related compounds of these pyrimidine derivatives have biological activities ranging from kinase inhibitors, treatment of disease states associated with angiogenesis [plated derived growth factor, PDGFr, fibroplast growth factor, FGFr, and epiderma growth factor, (EGFr),4 the analogous mitogen-activated protein (CSBP/P38) kinase inhibitor,5 telomerase inhibitor 6], for treatment of arthritis, adult respiratory distress syndrome, chronic obstructive pulmonary disease, or Alzheimer’s diseae.7 Arylazopyrimidine derivatives showed antitumor activity 8-11 and anticancer activity.12
In light of these facts, the present work describes the synthesis of 4 – [(p-methoxyphenyl) -5- (3,4 – dimethyl) – phenyl amino carbonyl] – 6 – phenyl - 1,4 –dihydro pyrimidine -2(1H) –thione 1 and [2- arylidene- 4-(4′-methoxyphenyl) - 5 - (3,4-dimethyl phenylamino) carbonyl – 6 - phenyl - 4,7 dihydro thiazolo [3,2-α] – pyrimidine – 3 - ones] 2a-j and assesses their antimicrobial activity. The different aromatic aldehydes were used at second position of thiazolopyriomidine for structural modifications would inform the development of new agents with enhanced antimicrobial activity.
Chemistry
All thiazolopyrimidine derivatives have been synthesized by condensation of 4 - methoxyphenyl [5-(3,4–
dimethyl) – phenyl amino carbonyl] – 6– phenyl-1,4-dihydropyrimidine-2(1H)–thione with monochloro
THIAZOLO [3, 2-α] PYRIMIDINE DERIVATIVES M. B. Buddh et al. 825 acetic acid, anhydrous sodium acetate, glacial acetic acid, acetic anhydride and different aromatic aldehydes were heated to reflux , and work up to yielded 2-arylidene- 4- (4′-methoxyphenyl) - 5 - (3,4- dimethyl phenylamino) carbonyl – 6 - phenyl - 4,7 dihydro thiazolo [3,2-α] - pyrimidine 3-ones. The reaction scheme of synthesized thiazolo pyrimidines is as under.
Scheme-1
EXPERIMENTAL
Preparation of 4 –[(p-methoxyphenyl)-5 - (3,4–dimethyl) –phenyl amino carbonyl] – 6 – phenyl - 1,4 –dihydropyrimidin -2(1H) –thiones
A mixture of thiourea (1.2gm, 0.015mole), 4-methoxy benzaldehyde (1.5gm, 0.01mole) and N-(3,4- dimethylphenyl)-3-oxo-3-phenylpropanamide (2.67gm, 0.01 mole) in 15 ml of ethanol containing few drops of concentrated hydrochloric acid was refluxed for 8 hrs. The solution was allowed to stand for 12 hrs. at room temperature and the resulting solid mass separated was filtered and crystallized from dioxane.
Yield 67%, m.p.265˚C, [C26H25N3O2S, required N =9.47 %; found N= 9.42 %].
General process for preparation of 2-arylidene – 4- (p-methoxyphenyl) - 5 - (3,4-dimethyl phenylamino)carbonyl - 6-phenyl - 4,7 dihydro thiazolo [3,2-α] –pyrimidin- 3-ones
A mixture of compound -1 (0.01 mole), monochloro acetic acid (0.015 mole), anhydrous sodium acetate (2 gm), glacial acetic acid (20 ml), acetic anhydride (15 ml) and different aromatic aldehydes (0.01 mole)
O H
O C H3
NH2 S N H2 NH
O
O H5C6 C
H3
C H3
NH
N H H5C6
O NH C
H3 C H3
O C H3
S
N
N H H5C6
O NH C
H3 C H3
O C H3
S O
R H+ Ethanol
ClCH2COOH
CH3COONa R-CHO
(CH3CO)2O/CH3COOH
R=aryl
+
Compound-1
Compound-2a-j
THIAZOLO [3, 2-α] PYRIMIDINE DERIVATIVES M. B. Buddh et al. 826 were heated to reflux for 3-4 hr. The reaction mixture was cooled to room temperature and poured on to crushed ice with vigorous stirring. The precipitated solid was filtered under suction, washed with cold water and isolate the product, 2a-j. The physical constants of compounds are given in Table – 1.The reaction was monitored by TLC using ethyl acetate: ethylene dichloride.
Table-1: Physical constants of compounds 2a-j
% of Nitrogen
S.No. R
Molecular
Formula M.P. 0C Yield % Calcd. Found
2a 4-OCH3-C6H4- C36H31N3O4S 152 78 6.98 6.96
2b C6H5- C35H29N3O3S 183 75 7.35 7.37
2c 3-C6H5-O-C6H4 C41H33N3O4S 228 68 6.33 6.39
2d 3,4-(OCH3)2-C6H4 C37H33N3O5S 212 71 6.65 6.69
2e 4-OH,3-OCH3-C6H3 C36H31N3O5S 220 58 6.8 6.84
2f 3-NO2-C6H4- C35H28N4O5S 135 62 9.09 9.13
2g C4H7S C33H27N3O3S2 176 65 7.27 7.24
2h 4-OH-C6H5- C35H29N3O4S 210 60 7.15 7.11
2i 4-N(CH3)2-C6H4 C37H34N4O3S 178 72 9.11 9.08
2j 4-Cl- C6H4 C35H28ClN3O3S 182 70 6.93 6.98
Spectral data
4-[(p-methoxyphenyl)-5-(3,4–dimethyl) –phenyl amino carbonyl]-6- phenyl-1,4 -dihydropyrimidin - 2(1H)-thiones (1)
IR (KBr, cm-1): 2958, 2875, 3079, 1530, 3068, 3398, 1706, 1651, 1015, 1H NMR (300 MHz) δ (ppm) : [2.10 (6H, d), 2 x(CH3) moiety], [ 3.80 (3H, S), Ar-OCH3 ], [5.30 (1H, S), -CH -pyrimi.], [6.91-7.50 (12H, m), Ar-H], [9.10 (1H, S), -NH (pyrimi.)], [9.62 (1H, S), -NH (pyrimi.)] [10.21 (1H, S), -NH (- NHCO)]; MS m/z = 433 (M+); Anal. Calcd. for C26H25N3O2S: N, 9.47 %;. Found: N, 9.42 %].
2-arylidene-4- (p-methoxyphenyl) - 5 - (3,4-dimethyl phenylamino)carbonyl - 6-phenyl - 4,7 dihydro thiazolo [3,2-α] –pyrimidin- 3-ones (2a)
IR (KBr, cm-1): 2967, 2831, 3082, 1553, 3082, 3302, 1673, 1660, 1000
1H NMR (300 MHz) δ (ppm) : [2.10 (6H, d), 2 x (CH3) moiety], [ 3.68 (3H, s), Ar-OCH3 ], [3.80 (3H, s), (OCH3)], [6.18 (1H, s), -CH (pyrimi.)], [6.78 -7.72 (16H, m) Ar-H], [7.80 (1H, S) -NH (-NHCO)], [9.58 (1H, S), -CH (Vinyl)]
MS m/z = 602 (M+); Anal. Calcd. for C36H31N3O4S: N, 6.98 %;. Found: N, 6.96 %].
2-arylidene-4- (3,4-dimethoxyphenyl) - 5 - (3,4-dimethyl phenylamino)carbonyl - 6-phenyl - 4,7 dihydro thiazolo [3,2-α] –pyrimidin- 3-ones(2d)
IR (KBr, cm-1): 2969, 2838, 3088, 1550, 3089, 3313, 1678, 1665, 1011
1H NMR (300 MHz) δ (ppm) : [2.18 (6H, d), 2 x (CH3) moiety], [3.72 (3H, S), Ar-OCH3 ], [3.82 (6H, d), 2 x OCH3], [6.25 (1H, S), -CH -pyrimi.], [6.81 -7.78 (15H, m), Ar-H], [7.85 (1H, S, -NH (NHCO)], [9.62 (1H, S), -CH (vinyl)].
MS m/z = 632 (M+); Anal. Calcd. for C37H33N3O5S: N, 6.65 %;. Found: N, 6.69 %].
Antimicrobial activity
The antimicrobial activity of newly synthesized compounds was determined using Broth dilution method13-15. The standard strains used for the activity were procured from institute of Microbial
THIAZOLO [3, 2-α] PYRIMIDINE DERIVATIVES M. B. Buddh et al. 827 Technology, Chandigarh. In this method each synthesized drug was diluted obtaining 2000 microgram/ml concentration, as a stock solution. The 10 µL suspensions from each well were further inoculated on appropriate media and growth was noted after 24 and 48 hrs at 37˚C. The lowest concentration, which showed no growth after spot subculture was considered as MBC / MFC for each drug. The result of this test is affected by the size of inoculums. The test mixture should contain 108organism/ml. In this method the results are recorded in the form of primary and secondary screening.
Antibacterial activity
In vitro antibacterial activity of the compounds was carried out against culture of Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and S.pyogenus at concentrations of 1000, 500, 200, 100, 50, 25, 12.5µg/ml respectively. The drugs Ampicillin, Chloremphenicol, Ciprofloxacin, and Norfloxacin were used as a standard for antibacterial activity at different concentration indicated in Table- 2.
Antifungal activity
In vitro antifungal activity of same synthesized compounds was tested against C.albicans, Aspergillus’s niger and A.clavatus. The compounds were tested at different concentrations 1000, 500, 200, 100, 50, 25, 12.5 µg/ml respectively. The drugs Nystatin and Greseofulvin were used as a standard for antifungal activity at different concentration indicated in Table-2.
Table-2: Antimicrobial screening results of compounds 2a-j.
RESULTS AND DISCUSSION
Antibacterial activity
It has been observed from the experimental data that all compounds 2a-j were found to be mild to moderately active against Gram positive and Gram negative bacterial strains. The maximum activity was
Antibacterial activity is expressed in the form of Minimal Bactericidal Concentration (MBC) in µl
Antifungal activity is expressed in the form of
Minimal Fungicidal (MFC) Concentration in µl Compd. E.coli
MTCC 442
P.aeruginosa MTCC
441
S.aureus MTCC
96
S.pyogenus MTCC
443
C.albicans MTCC
227
A.niger MTCC 282
A.clavatus MTCC
1323
2a 200 250 500 100 250 500 500
2b 500 500 250 500 500 500 500
2c 250 250 500 250 250 250 500
2d 500 1000 250 500 1000 1000 1000
2e 200 250 100 500 1000 500 500
2f 500 100 500 500 1000 500 250
2g 500 250 250 500 500 500 500
2h 200 250 200 100 500 1000 500
2i 500 1000 1000 500 1000 1000 500
2j 250 250 250 500 250 500 500
Gentamycin 0.05 1 0.25 0.5 - - -
Ampicillin 100 100 250 100 - - -
Chloramphenicol 50 50 50 50 - - -
Ciprofloxacin 25 25 50 50 - - -
Norfloxacin 10 10 10 10 - - -
Nystatin - - - - 100 100 100
Greseofulvin - - - - 500 100 100
THIAZOLO [3, 2-α] PYRIMIDINE DERIVATIVES M. B. Buddh et al. 828 observed in compounds bearing R=p-methoxy phenyl, m-phenoxy phenyl, p-hydroxy phenyl, and p- chloro phenyl substitutes against E.coli. & P. aeruginosa in comparision to standard drug Ampicillin.
However the compounds bearing phenyl, 3, 4- dimethoxy phenyl, p-hydroxy phenyl and p-chloro phenyl substitutes are giving significant activity against E .coli. & S. aureus. The significant activity was displayed by the compounds bearing R= p-methoxy phenyl and p-hydroxy phenyl substitutes against S.
pyogenus in comparision to standard drug Ampicillin.
Antifungal activity
The antifungal data revealed that compounds were least toxic to the fungal strain. However the compounds bearing R= p-methoxy phenyl, m-phenoxy phenyl, 2- thiophene and p-chloro phenyl indicate maximum activity in comparision to Nystatin and significant activity in comparision to Greseofulvin against C.albicans. While compounds bearing R= m-phenoxy substitute was displayed maximum activity against A.niger and m-nitro substitute against A. clavatus in comparision to Greseofulvin and Nystatin.
ACKNOWLEDGEMENTS
The authors are thankful to Krishna chemical Industries, Baroda for providing research facilities
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