Synthesis and Antimicrobial Activity of Some New 2, 4, 6 -Trisubstituted Pyrimidines

 

N. Srinath1*, Y. Rajendra Prasad2, K. Mukkanti3 and N. K. Agarwal2

1Department of Pharmacy, Acharya Nagarjuna University, Guntur - 521250

2University College of Pharmaceutical Sciences, Andhra University, Visakhapatnam - 530003

3Centre for Pharmaceutical Sciences, J N T University, Hyderabad – 500085

*Corresponding Author E-mail: srinath_n2k@rediffmail.com

 

ABSTRACT:

A variety of 2-amino-4-(3'-methyl-4'-hydroxyphenyl)-6-(substituted) pyrimidines were synthesized by reacting various chalcones with guanidine hydrochloride. The required chalcones were prepared by condensation of 3'-methyl-4'-hydroxyacetophenone with various substituted aromatic / heteroaromatic aldehydes in the presence of alkali. All these compounds were characterized by IR, 1H NMR and Elemental analysis.  The newly synthesized compounds were evaluated for their antimicrobial activity and some of them have shown significant activity when compared with the standard.

 

KEYWORDS: Pyrimidines, Synthesis, Antimicrobial activity

 


 

INTRODUCTION:

Among a wide variety of heterocycles that have been explored for developing medicinally important molecules, pyrimidine derivatives occupy an important place in the present day therapeutics. They were reported to possess a broad spectrum of biological activities such as antimicrobial1,2, anti-inflammatory3, anticancer4, antiviral5, antitubercular6 and antimalarial7 properties. These observations prompted the authors to carryout the synthesis of some new 2-amino-4-(3'-methyl-4'-hydroxyphenyl)-6-(substituted) pyrimidines (B1P1 - B15P15), which were evaluated for their antimicrobial activity.

 

EXPERIMENTAL:

Chemicals and solvents were of reagent grade are used without further purification. Melting points were determined on a capillary melting point apparatus and are uncorrected. 1H NMR spectra were recorded in the indicated solvent on Bruker AMX 400MHz NMR Spectrometer with TMS as internal standard. IR spectra were recorded in KBr on Perkin Elmer – 337 Infrared Spectrophotometer. Microanalyses were performed on Perkin Elmer model 2400 series II apparatus and were within the ± 0.4% of the theoretical values. Column chromatography was performed on silica gel (Merck, 60-120 mesh).

 

GENERAL PROCEDURE FOR THE PREPARATION OF PYRIMIDINES:

A mixture of chalcones (B1-B15) of 3'-methyl-4'-hydroxyacetophenone (0.001 mol), guanidine hydrochloride (0.001 mol) in absolute ethanol (5 ml) and potassium hydroxide (0.002 mol) were refluxed on a water bath for 6 hours. The solvent was completely evaporated and the residue was poured into ice cold water, the precipitated solid was collected by filtration, purified by column chromatography and crystallized from suitable solvent to give pyrimidine derivatives8-12 (Scheme 1). The chemical and spectral data of the compounds (B1P1 - B15P15) are given in Table 1, Table 2 and Table 3.

 

ANTIMICROBIAL ACTIVITY

Cup plate method 13,14 using Mueller – Hinton agar medium was employed to study the preliminary antibacterial activity of newly synthesized pyrimidines (B1P1 - B15P15) against B. pumilis, B. subtilis, E. coli and P. vulgaris. The agar medium was purchased from Hi media Laboratories Ltd., Mumbai, India. Preparation of nutrient broth, subculture, base layer medium, agar medium and peptone waster was done as per the standard procedure. Each test compound (5mg) was dissolved in 5 ml of dimethyl sulfoxide (1000 µg/ml). Volumes of 0.05 ml and 0.1 ml of each compound were used for testing.

 

Same cup plate method using PDA medium was employed to study the preliminary antifungal activity of newly synthesized pyrimidines (B1P1 - B15P15) against A. niger and P. crysogenium.


Scheme 1

                              Chalcone                                                          Guanidine                                                     2, 4, 6 – trisubstituted pyrimidine                                                                                      

     (as hydrochloride salt)                                  

                                        (B1 - B15)                                                                                                                         (B1P1 - B15P15)

 


Where Ar =

                                       

The PDA medium was purchased from Hi media Laboratories Ltd., Mumbai, India. Preparation of nutrient broth, subculture, base layer medium and PDA medium was done as per the standard procedure. Each test compound (5mg) was dissolved in 5 ml of dimethyl sulfoxide (1000 µg/ml). Volumes of 0.05 ml (50µg) and 0.1 ml (100µg) of each compound were used for testing.

 

The cups each of 7 mm diameter were made by scooping out the medium with a sterilized cork borer in a petridish, which was streaked with the organisms. The solutions of each test compound (0.05 ml and 0.1 ml) were added separately in the cups and petridishes were subsequently incubated. Benzyl penicillin and Fluconazole were used as standard (reference) drugs for evaluation of antibacterial and antifungal activities respectively and dimethyl- sulfoxide as control, which did not reveal any inhibition. Zone of inhibition produced by each compound was measured in mm and the results are presented in Table 4 and Table 5.


Table 1. PHYSICAL CHARACTERIZATION DATA OF PYRIMIDINES

Compound

Ar

Formula

m.p

(OC)

Yield

(%)

B1P1

2''-pyridinyl

C16H14 N4O                    (C, H, N) a

157

76

B2P2

3''-pyridinyl

C16H14 N4O                    (C, H, N)

160

74

B3P3

4''-pyridinyl

C16H14 N4O                    (C, H, N)

149

75

B4P4

2''-furyl

C15H13 N3O2                             (C, H, N)

173

70

B5P5

2''-pyrrolyl

C15H14 N4O                    (C, H, N)

159

72

B6P6

2''-thienyl

C15H13 N3SO                  (C, H, N)

162

78

B7P7

2''-indolyl

C19H16 N4O                    (C, H, N)

195

68

B8P8

2''-quinolinyl

C20H16 N4O                    (C, H, N)

183

70

B9P9

9''-anthracenyl

C25H19 N3O                    (C, H, N)

170

66

B10P10

4''-fluorophenyl

C17H14 N3FO                  (C, H, N)

260

71

B11P11

4''-chlorophenyl

C17H14 N3ClO                (C, H, N)

145

73

B12P12

4''-bromophenyl

C17H14 N3BrO                (C, H, N)

252

70

B13P13

4''-methylphenyl

C18H17 N3O                    (C, H, N)

110

66

B14P14

4''-methoxyphenyl

C18H17 N3O2                             (C, H, N)

155

68

B15P15

3'',4'',5''-trimethoxyphenyl

C20H21 N3O4                             (C, H, N)

165

72

a Elemental analysis for C, H, N are within ± 0.4% of theoretical values

 

Table 2. IR SPECTRAL DATA OF PYRIMIDINES

Compound

Position of absorption band ( cm-1)

B1P1

3361 (NH2), 3499 (O-H), 1602 (C=N),

1573 (C=C Quadrant of Ar), 1508 (CH=CH)

B2P2

3362 (NH2), 3497 (O-H), 1600 (C=N),

1575 (C=C Quadrant of Ar),1505 (CH=CH)

B3P3

3364 (NH2), 3496 (O-H), 1602 (C=N),

1572 (C=C Quadrant of Ar), 1504 (CH=CH)

B4P4

3360 (NH2), 3498 (O-H), 1602 (C=N),

1573 (C=C Quadrant of Ar), 1504 (CH=CH), 1200 (-C-O-)

B5P5

3365 (NH2), 3499 (O-H), 1605 (C=N),

1574 (C=C Quadrant of Ar), 1505 (CH=CH)

B6P6

3361 (NH2), 3497 (O-H), 1602 (C=N),

1572 (C=C Quadrant of Ar), 1504 (CH=CH), 704 (C-S)

B7P7

 

3365 (NH2), 3495 (O-H), 1604 (C=N),

1575 (C=C Quadrant of Ar), 1506 (CH=CH)

B8P8

3361 (NH2), 3496 (O-H), 1603 (C=N),

1570 (C=C Quadrant of Ar),1503 (CH=CH)

B9P9

3363 (NH2), 3495 (O-H), 1601 (C=N),

1573 (C=C Quadrant of Ar), 1504 (CH=CH)

B10P10

3361 (NH2), 3498 (O-H), 1605 (C=N),

1574 (C=C Quadrant of Ar), 1505 (CH=CH), 1120 (C-F)

B11P11

3360 (NH2), 3496 (O-H), 1600 (C=N),

1572 (C=C Quadrant of Ar), 1505 (CH=CH), 853 (C-Cl)

B12P12

3362 (NH2), 3499 (O-H), 1604 (C=N),

1575 (C=C Quadrant of Ar), 1506 (CH=CH), 1020 (C-Br)

B13P13

3360 (NH2), 3497 (O-H), 1603 (C=N),

1572 (C=C Quadrant of Ar), 1505 (CH=CH)

B14P14

3361 (NH2), 3495 (O-H), 1602 (C=N),

1571 (C=C Quadrant of Ar), 1507 (CH=CH), 1070 (-O-CH3)

B15P15

3365 (NH2), 3498 (O-H), 1604 (C=N),

1570 (C=C Quadrant of Ar), 1504 (CH=CH), 1072 (-O-CH3)

 

 


RESULTS AND DISCUSSION:

From the results, it is evident that the compounds B8P8, B4P4 and B10P10 exhibited moderate antibacterial activity, at a concentration of 0.1ml dose level and is comparable to that of standard drug, benzyl penicillin at a concentration of 100 µg/ml. The other compounds also showed antibacterial activity less when compared to other pyrimidine derivatives. Compounds B10P10, B11P11 and B12P12 exhibited moderate antifungal activity and are comparable to that of fluconazole. The results are consistent with the biological activity of the existing drugs. Further studies have to be conducted to explore the mechanism of action of these compounds.


 

Table 3. 1H NMR SPECTRAL DATA OF PYRIMIDINES

Compound

Chemical shift ( δ ) in ppm

B1P1

8.28 (1H,s, C-5-H),5.40 (2H,s, C-2-NH2)

7.87 (1H,s,C-2'-H),2.32 (3H,s,C-3'-CH3)

7.20 (1H,d,J=8.8Hz,C-5'-H),7.90 (1H,d,J=8.8Hz,C-6'-H)

8.57 (1H,d,J=8Hz,C-3''-H),7.67 (1H,t,J=8Hz,C-4''-H)

7.47 (1H,m,J=7.5Hz,C-5''-H),8.68 (1H,d,J=7.8Hz, C-6''-H)

B2P2

7.71 (1H,s, C-5-H),5.30 (2H,s, C-2-NH2)

7.84 (1H,s,C-2'-H),2.32 (3H,s,C-3'-CH3)

7.20 (1H,d,J=8.8Hz,C-5'-H),7.94 (1H,d,J=8.8Hz,C-6'-H)

9.19 (1H,s,C-2''-H),8.31 (1H,d,J=8.2Hz,C-4''-H)

7.42 (1H,m ,J=8.2Hz,C-5''-H),8.69 (1H,d,J=7.8Hz, C-6''-H)

B3P3

7.86  (1H,s, C-5-H),5.30  (2H,s, C-2-NH2)

7.83 (1H,s,C-2'-H),2.33 (3H,s,C-3'-CH3)

7.20 (1H,d,J=8.8Hz,C-5'-H),7.94 (1H,d,J=8.8Hz,C-6'-H)

8.75 (1H,d, J=8.1Hz ,C-2''-H),7.93 (1H,d,J=8.1Hz,C-3''-H)

8.09 (1H,d ,J=8.1Hz,C-5''-H),8.61 (1H,d,J=8.2Hz, C-6''-H)

B4P4

8.00 (1H,s, C-5-H),5.25 (2H,s, C-2-NH2),7.83 (1H,s,C-2'-H)

2.32 (3H,s,C-3'-CH3),7.20 (1H,d,J=8.8Hz,C-5'-H)

7.87 (1H,d,J=8.8Hz,C-6'-H),7.00 (1H,d, J=6.8Hz ,C-3''-H)

7.41 (1H,d,J=6.7Hz,C-4''-H),7.70 (1H,d,J=6.7Hz,C-5''-H)

B5P5

7.80 (1H,s, C-5-H),5.30 (2H,s, C-2-NH2),7.77 (1H,s,C-2'-H)

2.32 (3H,s,C-3'-CH3),7.20 (1H,d,J=8.8Hz,C-5'-H)

8.00 (1H,d,J=8.8Hz,C-6'-H),6.87 (1H,d, J=6.7Hz ,C-3''-H)

6.18 (1H,m,J=6.8Hz,C-4''-H),6.69 (1H, d, J=6.7Hz,C-5''-H)

B6P6

7.40 (1H,s, C-5-H),5.18 (2H,s, C-2-NH2),7.82 (1H,s,C-2'-H)

2.32 (3H,s,C-3'-CH3),7.20 (1H,d,J=8.8Hz,C-5'-H)

7.90 (1H,d,J=8.8Hz,C-6'-H),7.89 (1H,d, J=6.6Hz ,C-3''-H)

7.21 (1H,m,J=6.7Hz,C-4''-H),7.57 (1H, d, J=6.6Hz,C-5''-H)

B7P7

7.38 (1H,s, C-5-H),5.44 (2H,s, C-2-NH2),7.86 (1H,s,C-2'-H)

2.32 (3H,s,C-3'-CH3),7.15 (1H,d,J=8.8Hz,C-5'-H)

7.91 (1H,d,J=8.8Hz,C-6'-H),8.21 (1H,m,C-2''-H)

8.60  (1H,d,J=7.7Hz,C-4''-H),7.05 (1H,t, J=7.7Hz,C-5''-H)

7.22 (1H,t, J=7.9Hz,,C-6''-H),7.44 (1H,d, J=7.9Hz,C-7''-H)

B8P8

8.31 (1H,s, C-5-H),5.35 (2H,s, C-2-NH2),

7.87 (1H,s,C-2'-H),2.32 (3H,s,C-3'-CH3)

7.20 (1H,d,J=8.8Hz,C-5'-H),7.90 (1H,d,J=8.8Hz,C-6'-H)

8.50 (1H,d, J=8.1Hz, C-3''-H),8.30 (1H,d,J=8.1Hz,C-4''-H)

7.85(1H,d, J=7.9Hz,C-5''-H),7.55 (1H,t, J=7.9Hz,C-6''-H)

7.73 (1H,t, J=7.9Hz,C-7''-H),8.26 (1H,d,J=7.9Hz, C-8''-H)

B9P9

7.82 (1H,s, C-5-H),5.02 (2H,s, C-2-NH2),7.90 (1H,s,C-2'-H)

2.32 (3H,s,C-3'-CH3),7.10 (1H,d,J=8.8Hz,C-5'-H)

7.91 (1H,d,J=8.8Hz,C-6'-H),7.81 (1H,d, J=7.8Hz ,C-1''-H)

7.18 (1H,m, J=8.1Hz ,C-2''-H),7.48 (1H,m, J=8.1Hz ,C-3''-H)

8.23 (1H,d,J=8.1Hz,C-4''-H),8.23 (1H,d, J=8.1Hz,C-5''-H)

7.48 (1H,m, J=8.1Hz,C-6''-H),7.18 (1H,m, J=7.8Hz,C-7''-H)

7.82 (1H,d,J=7.8Hz, C-8''-H),8.70 (1H,s, C-10''-H)

B10P10

7.84 (1H,s, C-5-H),5.45 (2H,s, C-2-NH2),

7.84 (1H,s,C-2'-H),2.32 (3H,s,C-3'-CH3)

6.89 (1H,d,J=8.8Hz,C-5'-H),7.94 (1H,d,J=8.8Hz,C-6'-H)

8.10 (1H,d,J=8.6Hz,C-2''-H),7.29 (1H,d,J=8.6Hz,C-3''-H)

7.29 (1H,d, J=8.6Hz,C-5''-H),7.99 (1H,d, J=8.6Hz,C-6''-H)

B11P11

7.81 (1H,s, C-5-H),5.42 (2H,s, C-2-NH2)

7.84 (1H,s,C-2'-H),2.32 (3H,s,C-3'-CH3)

7.15 (1H,d,J=8.8Hz,C-5'-H),7.94 (1H,d,J=8.8Hz,C-6'-H)

7.85 (1H,d,J=8.4Hz,C-2''-H),7.60 (1H,d,J=8.4Hz,C-3''-H)

7.60 (1H,d, J=8.4Hz,C-5''-H),7.99 (1H,d, J=8.4Hz,C-6''-H)

B12P12

7.79 (1H,s, C-5-H),5.30 (2H,s, C-2-NH2)

7.84 (1H,s,C-2'-H),2.32 (3H,s,C-3'-CH3)

7.30 (1H,d,J=8.8Hz,C-5'-H),7.94 (1H,d,J=8.8Hz,C-6'-H)

8.12 (1H,d,J=8.2Hz,C-2''-H),7.53 (1H,d,J=8.2Hz,C-3''-H)

7.53 (1H,d, J=8.2Hz,C-5''-H),8.12 (1H,d, J=8.2Hz,C-6''-H)

B13P13

7.72 (1H,s, C-5-H),5.43 (2H,s, C-2-NH2),7.84 (1H,s,C-2'-H)

2.32 (3H,s,C-3'-CH3),6.89 (1H,d,J=8.8Hz,C-5'-H)

7.94 (1H,d,J=8.8Hz,C-6'-H),8.05 (1H,d,J=8.1Hz,C-2''-H)

7.36 (1H,d,J=8.1Hz,C-3''-H),2.41 (3H,s, C-4''-CH3)

7.36 (1H,d, J=8.1Hz,C-5''-H),8.05 (1H,d, J=8.1Hz,C-6''-H)

B14P14

7.75 (1H,s, C-5-H),5.45 (2H,s, C-2-NH2),7.84 (1H,s,C-2'-H)

2.32 (3H,s,C-3'-CH3),7.10 (1H,d,J=8.8Hz,C-5'-H)

7.94 (1H,d,J=8.8Hz,C-6'-H),8.10 (1H,d,J=7.9Hz,C-2''-H)

7.05 (1H,d,J=7.9Hz,C-3''-H),3.80 (3H,s, C-4''-OCH3); 7.05 (1H,d, J=7.9Hz,C-5''-H),7.99 (1H,d, J=7.9Hz,C-6''-H)

B15P15

7.57 (1H,s, C-5-H),5.25 (2H,s, C-2-NH2),7.84 (1H,s,C-2'-H); 2.32 (3H,s,C-3'-CH3),7.15 (1H,d,J=8.8Hz,C-5'-H)

7.94 (1H,d,J=8.8Hz,C-6'-H),7.61 (1H,s,C-2''-H); 3.93 (3H,s,C-3''-OCH3),3.94 (3H,s, C-4''-OCH3)

3.93 (3H,s, C-5''-OCH3),7.61 (1H,s, C-6''-H)

* s, singlet;  d, doublet; m, multiplet



Table 4. ANTIBACTERIAL ACTIVITY OF PYRIMIDINE DERIVATIVES

 

Compound

 

 

Ar

Zone of inhibition in mm

Quantity in µg/ml

B. pumilis

B. subtilis

E. coli

P. vulgaris

50

100

50

100

50

100

50

100

B1P1

2''-pyridinyl

04

06

05

07

05

09

09

10

B2P2

3''-pyridinyl

04

05

05

06

05

07

08

09

B3P3

4''-pyridinyl

05

06

05

07

06

08

08

10

B4P4

2''-furyl

12

14

13

17

15

17

13

15

B5P5

2''-pyrrolyl

05

08

06

09

07

11

09

12

B6P6

2''-thienyl

05

07

05

08

06

10

10

11

B7P7

2''-indolyl

09

12

10

13

13

16

10

12

B8P8

2''-quinolinyl

13

15

14

17

16

18

14

16

B9P9

9''-anthracenyl

04

05

04

05

05

06

07

08

B10P10

4''-fluorophenyl

12

15

13

16

16

17

12

15

B11P11

4''-chlorophenyl

11

14

12

16

15

16

12

14

B12P12

4''-bromophenyl

10

14

12

15

14

16

11

13

B13P13

4''-methylphenyl

06

09

08

11

09

14

09

11

B14P14

4''-methoxyphenyl

05

09

07

10

08

13

09

10

B15P15

3'',4'',5''-trimethoxyphenyl

07

10

08

12

10

15

08

12

Benzyl penicillin(standard)

15

18

16

19

18

22

17

20

Control (DMSO)

-

-

-

-

-

-

-

-

 

 

 


 

 


Table 5. ANTIFUNGAL ACTIVITY OF PYRIMIDINE DERIVATIVES

 

Compound

 

Ar

Zone of inhibition in mm

Quantity in µg/ml

A. niger

P. crysogenium

50

100

50

100

B1P1

2''-pyridinyl

04

05

05

07

B2P2

3''-pyridinyl

04

06

05

06

B3P3

4''-pyridinyl

04

05

06

07

B4P4

2''-furyl

09

12

08

10

B5P5

2''-pyrrolyl

05

07

05

06

B6P6

2''-thienyl

05

06

05

07

B7P7

2''-indolyl

08

11

07

09

B8P8

2''-quinolinyl

10

12

09

11

B9P9

9''-anthracenyl

04

05

05

06

B10P10

4''-fluorophenyl

13

16

12

14

B11P11

4''-chlorophenyl

12

15

12

13

B12P12

4''-bromophenyl

11

14

11

12

B13P13

4''-methylphenyl

06

09

06

07

B14P14

4''-methoxyphenyl

05

08

06

07

B15P15

3'',4'',5''-trimethoxyphenyl

07

10

07

08

Fluconazole (standard)

17

21

15

18

Control (DMSO)

-

-

-

-

 


 

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Received on 06.12.2010        Modified on 18.12.2010

Accepted on 25.12.2010        © AJRC All right reserved

Asian J. Research Chem. 4(2): February 2011; Page 329-333