Adamantane-pyrido[2,3-d]Pyrimidine Derivatives; Synthesis, Characterization and Investigation of Antimicrobial Study

Introduction

The research on biochemical importance of pyrimidines and pyrimidine derivatives have centered great importance because of the pyrimidines represent the main backbone in alkaloids and nucleic bases as well as their interesting powerful biological activities. Pyrimidine derivatives contain diversified applications as pharmaceuticals and occupy a unique place in heterocyclic and medicinal chemistry also^1-3. Combination of coumarin derivatives and pyrimidine derivatives has received considerable attention by researchers because of possessing so many biological important application and pharmacological activities^4-7. Various pyrimidine derivatives show very broad range of biological activities viz. antimicrobial activity⁸, anti-inflammatory⁹, anticancer¹⁰, antiviral¹¹, antitubercular¹², antihypertensive^13-14, anticonvulsant¹⁵, H¹-antihistamines¹⁶, 4-phosphodiester inhibitors^17-18 and antimalarial^19-20.

Materials and Methods

The synthesis was carried out using A R Grade reagents and solvents and were used without further purification. Open capillary method was used to take melting points and are uncorrected. TLC (thin layer chromatography) was used check the progress of reactions using silica gel plates GF254 (E. Merck). The solvent system comprised of methanol and toluene; the chromatograms visualized using source of UV light (254nm). FTIR spectra were recorded making use of KBr on pallets Perkin Elmer 1600 FTIR. ¹H NMR and ¹³C NMR spectra were obtained using Bruker 500 MHz, DMSO-d₆ as the solvent and TMS (tetra methyl silane) as internal standard. LCMS was used to carry out LC-MS.

Synthesis of 3-Acetyl-2H-chromen-2-one (1)

0.01 mole Salicylaldehyde and 0.01 mole EAA (Ethyl Acetoacetate) was mixed in 15mL in ethyl alcohol. 2mL DEA (diethyl aniline) was added in this mixture with continuous stirring at RT for about 2 hrs which yielded solid. The solid was filtered, recrystallized using ethyl alcohol as solvent.  Yield; 91 %, MP 113-115º C.

Preparation of various substituted chalcone derivatives (2a-k)

Base catalyzed Claisen-Schmidt condensation reaction was used to synthesize various chalcone derivatives of the appropriate substituted aldehydes and substituted acetophenone by reported literature method²¹.

3-Acetyl-2H-chromen-2-one (0.01mole) (1) and substituted benzaldehyde (0.01mole)  dissolved in 10 mL ethanol in RBF using a magnetic stirrer. Water bath was used to maintain the temperature of reaction at 20-25º C. 1 gm NaOH in 10 mL dist. H₂O was taken and this NaOH solution was drop wise added into to the reaction mixture for 30 minutes with continuous stirring. On completion of addition, solution was stirred further for 4-5 hrs and kept at RTfor 12 hrs. The final solution was dumped into chilled H₂O & neutralized using 0.1-0.2N HCl whereby solid obtained. The product was filtered & then dried in air. The crude was recrystallized by rectified spirit. Further purification was done by used ethyl acetate and n-hexane.

Preparation of various derivatives of 2-Amino-4-(2,4-substitutedphenyl)-6-(2-oxo-2H-chromen-3-yl) nicotinonitrile (3a-k)

Chalcone derivatives (2a-k) (0.01mole), malononitrile (0.01mole) and anhydrous ammonium acetate (0.02mole) were taken in RBF and dissolved in 20 mL absolute ethanol solvent. It was heated under reflux condition for 7-8 hours. Completion of reaction was confirmed by TLC. This reaction mixture was then cooled down to the RT. As solution attained RT, solid was formed which was filtered, then was washed with distilled water till free from impurities dried and ethanol was used for recrystallized to obtains compounds (3a-k)²².

Preparation of various derivatives of 5-(2,4-substitutedphenyl)-2-Methyl-7-(2-oxo-2H–

chromen-3-yl) Pyrido[2,3-d] Pyrimidin-4(3H)-one (4a-k)

The mixture of compound (3a-k) (0.01mole) and excess of glacial CH₃COOH (20mL) was heated maintaining reflux condition for 7-8 hours. Glacial CH₃COOH was self-solvent. On completion of the reaction, solution obtained was cooled down to RT. The resultant solution was added in to chilled H₂O. The solid formed was filtered, then washed with cold dist. H₂O several times, dried & recrystallization from dioxane yielded compounds (4a-k).

Preparation of various derivatives of 3-(2-Chloroacetyl)-5-(2,4-substitutedphenyl)-2-Methyl-7-(2-Oxo-2H– Chromen-3-yl) Pyrido[2,3-d]Pyrimidin-4(3H)-one (5a-k)

Sodium acetate was dissolved in 20mL glacial acetic acid in RBF. Compound (4a-k) (0.01mole) was dissolved in this mixture and was cooled 0-5º C. Chloroacetyl chloride (0.02mL) was added in this mixture at 0-5º C during 1 Hr. After the completion of addition, resultant solution was stirred for 30 mins. The temperature was raised to 80º C for heating up to 1.5 Hrs. & then was stirred at R.T. This solution was dumped into chilled H₂O, the solid thus formed was filtered, washed using chilled H₂O several times, dried, recrystallized from acetic acid to give compounds (5a-k).

Preparation of various derivatives N-(Hydroxyadamantan-1-yl)-5-(2,4-substituted phenyl)-2-Methyl-4-oxo-7-(2-Oxo-2H-Chromen-3-yl)Pyrido[2,3-d]Pyrimidine-3(4H) Carboxamide (6a-k)

Compound (5a-k) (0.01mole) was dissolved in 20mL DMF. Slow heating was started and mixture of 3-Aminoadamantan-1-ol (0.01mole) and K₂CO₃ (0.012mole) was mixed slot wise. On completion of addition, the resultant solution was refluxed for 5-6 Hrs. TLC was used to check completion of reaction. The resultant solution was allowed to cool to RT, then dumped into ice, the solid formed was filtered, then washed with dist. H₂O several times, dried, finally recrystallized using ethanol to yield compounds (6a-k).  

Reaction scheme

Scheme 1 Click here to View Scheme

Table 1: Physical properties of synthesized Adamantane-pyrido[2,3-d]pyrimidine derivatives (TT₁ to TT₁₁)

No	Sample	Sample Code	Molecular Formula	Substituent		Melting Point (°C)
				R1	R2
1	6a	TT1	C35H32N4O6	-H	-OCH3	278-280º C
2	6b	TT2	C34H29ClN4O5	-H	-Cl	285-287º C
3	6c	TT3	C36H35N5O5	-H	-N(CH3)2	272-274º C
4	6d	TT4	C34H30N4O6	-H	-OH	286-288º C
5	6e	TT5	C34H29N5O7	-H	-NO2	275-276º C
6	6f	TT6	C34H29BrN4O5	-H	-Br	266-268º C
7	6g	TT7	C34H30N4O6	-OH	-H	258-260º C
8	6h	TT8	C35H32N4O6	-H	-CH3	288-290º C
9	6i	TT9	C34H28Cl2N4O5	-Cl	-Cl	280-282º C
10	6j	TT10	C35H32N4O6	-CH3	-H	272-273º C
11	6k	TT11	C34H29BrN4O5	-Br	-H	255-257º C

 

Table 2: Elementary analysis data of Adamantane-pyrido[2,3-d]pyrimidine derivatives (TT₁ to TT₁₁).

No	Sample Code	Elementary Analysis
		Calculated (%)						Found (%)
		C	H	O	N	Cl	Br	C	H	N	O	Cl	Br
1	TT1	69.52	5.33	15.88	9.27	–	–	69.48	5.27	15.86	9.23	–	–
2	TT2	67.05	4.80	13.13	9.20	5.82	–	67.00	4.77	13.09	9.18	5.79	–
3	TT3	70.00	5.71	12.95	11.34	–	–	69.98	5.67	12.89	11.30	–	–
4	TT4	69.14	5.12	16.25	9.49	–	–	69.10	5.10	16.20	9.42	–	–
5	TT5	65.91	4.72	18.07	11.30	–	–	65.89	4.69	17.98	11.27	–	–
6	TT6	62.49	4.47	12.24	8.57	–	12.23	62.47	4.44	12.22	8.55	–	12.19
7	TT7	69.14	5.12	16.25	9.49	–	–	69.08	5.08	16.14	9.44	–	–
8	TT8	69.52	5.33	15.88	9.27	–	–	69.49	5.31	15.87	9.25	–	–
9	TT9	63.46	4.39	12.43	8.71	11.02	–	63.44	4.31	12.35	8.64	10.88	–
10	TT10	69.52	5.33	15.88	9.27	–	–	69.47	5.22	15.81	9.22	–	–
11	TT11	62.49	4.47	12.24	8.57	–	12.23	62.40	4.42	12.21	8.51	–	12.15

Table 3: Antibacterial activity of Adamantane-pyrido[2,3-d]pyrimidine derivatives (TT₁ to TT₁₁).

Antibacterial Activity
Minimum Inhibition Concentration
Sample	Sample Code	E. Coli MTCC443	P. Aeruginosa MTCC1688	S. Aureus MTCC96	S. Pyogenes MTCC442
6a	TT1	50	62.5	100	62.5
6b	TT2	100	100	200	62.5
6c	TT3	62.5	50	200	100
6d	TT4	100	62.5	100	200
6e	TT5	100	200	200	200
6f	TT6	50	100	250	200
6g	TT7	100	200	250	200
6h	TT8	50	62.5	200	62.5
6i	TT9	50	100	50	100
6j	TT10	62.5	100	100	100
6k	TT11	100	200	100	200
Ampicillin		100	100	250	100
Chloramphenicol		50	50	50	50
Norfloxacin		10	10	10	10
Ciprofloxacin		25	25	50	50

Table 4: Antifungal activity and antitubercular of synthesized Adamantane-pyrido[2,3-d]pyrimidine derivatives (TT₁ to TT₁₁).

Antifungal activity & Antitubercular Activity
Minimum Inhibition Concentration
Sample	Sample Code	C. Albicans MTCC227	A. Niger MTCC282	A. Clavatus MTcc1323	H37RV MIC µg/mL
6a	TT1	100	100	50	100
6b	TT2	50	62.5	100	62.5
6c	TT3	200	100	200	100
6d	TT4	100	100	250	500
6e	TT5	62.5	50	62.5	100
6f	TT6	50	100	100	200
6g	TT7	100	100	200	62.5
6h	TT8	62.5	100	50	100
6i	TT9	200	200	200	500
6j	TT10	200	250	100	100
6k	TT11	100	100	100	62.5
Nystatin		100	100	100	–
Griseofulvin		500	100	100	–
Rifampicin		–	–	–	40
Isoniazid		–	–	–	0.2

Table 5: Antimalarial activity of synthesized Adamantane-pyrido[2,3-d]pyrimidine derivatives (TT₁ to TT₁₁).

Antimalarial Activity
Minimum Inhibition Concentration
Sample	Sample Code	Mean Values
6a	TT1	0.88µg/mL
6b	TT2	0.25µg/mL
6c	TT3	1.01µg/mL
6d	TT4	0.98µg/mL
6e	TT5	0.74µg/mL
6f	TT6	0.42µg/mL
6g	TT7	0.35µg/mL
6h	TT8	0.46µg/mL
6i	TT9	0.31µg/mL
6j	TT10	0.52µg/mL
6k	TT11	0.23µg/mL
Chloroquine		0.020 µg/mL
Quinine		0.268 µg/mL

 

¹H NMR spectral data of Adamantane-pyrido[2,3-d]pyrimidine derivatives

Figure:1 1H NMR spectral data of TT1 Click here to View Figure

¹H NMR data (500 MHz, DMSO – d₆) δ

1.57-2.24(m, 14H of adamantane), 3.47 (s, OH group of admentanol), 7.35 (s, 1H of NH group of adamantane), 3.07 (s, 3H of -CH₃ of pyrimidine), 3.90 (s, 3H of CH₃ of methoxy group), 6.94-8.59 (m, 10H of Aromatic group).

Figure 2: 1H NMR spectral data of TT3 Click here to View Figure

¹H NMR data (500 MHz, DMSO – d₆) δ

1.55-2.24(m, 14H of adamantane), 3.43 (s, OH group of admentanol), 7.41 (s, 1H of NH group of admantan), 3.09 (s, 3H of CH₃ of pyrimidine), 3.92 (s, 6H of N(CH₃)₂ group), 6.75-8.51 (m, 10H of Aromatic group).

Figure 3: 1H NMR spectral data of TT5 Click here to View Figure

¹H NMR data (500 MHz, DMSO – d₆) δ

1.55-2.24 (m, 14H of adamantane), 3.55 (s, OH group of admentanol), 7.41 (s, 1H of NH group of admantan), 3.13 (s, 3H of CH₃ of pyrimidine), 7.35-8.60 (m, 10H of Aromatic group).

Figure 4: 1H NMR spectral data of TT8 Click here to View Figure

¹H NMR data (500 MHz, DMSO – d₆) δ

1.55-2.37 (m, 14H of adamantane), 3.55 (s, OH group of admentanol), 7.35 (s, 1H of NH group of admantan), 3.13 (s, 3H of CH₃ of pyrimidine), 7.10-8.60 (m, 10H of Aromatic group), 2.73 (s, 3H of CH₃ group).

¹³C NMR spectral data of Adamantane- pyrido[2,3-d]pyrimidine derivatives

Figure 5: 13C NMR spectral data of TT1 Click here to View Figure

Compound-TT₂

22.40, 29.71, 35.98, 43.07, 44.40, 47.56, 50.50, 55.35, 68.80, 113.88, 114.98, 119.95, 120.24, 122.36, 125.51, 127.56, 129.59, 131.33, 132.68, 143.60, 145.30, 148.78, 152.96, 153.90, 154.04, 158.73, 159.49, 163.34, 164.02

IR Spectra of Adamantane-pyrido[2,3-d]pyrimidine derivatives

Figure 6: IR Spectra of TT1 Click here to View Figure

Compound-TT₁: IR (KBr, cm^-1)

ν = C-H 1271, N-H 1526 secondary amine, O-H 3924, C-H 2855 of OCH₃, C-H 3413, C-Br 738, C-H 2922 of methyl group.

Figure 7: IR Spectra of TT3 Click here to View Figure

Compound-TT₃: IR (KBr, cm^-1)

ν = C-H 1275, N-H 1541 secondary amine, O-H 3926, C-H 3413, C-Br 738, C-H 2925 of methyl group. C-H 2925 of N(CH₃)₂

LCMS Spectra of Adamantane- pyrido[2,3-d]pyrimidine derivatives

Figure 8: LCMS Spectra of TT1 and TT3 Click here to View Figure

Graph 1: Antimicrobial activity of Adamantane-pyrido[2,3-d]pyrimidine derivatives (TT1 to TT11) Click here to View Graph

Graph 2: Antifungal activity of Adamantane-pyrido[2,3-d]pyrimidine derivatives (TT1 to TT11). Click here to View Graph

Graph 3: Anti Tubercular activity of Adamantane-pyrido[2,3-d]pyrimidine derivatives (TT1 to TT11) Click here to View Graph

Results and discussion

3-Acetyl-2H-Chromen-2-one resultedby the reaction of Ethylacetoacetate (EAA) & Salicylaldehyde. (DEA) Diethyl Aniline then was mixed with continuous stirring dropwise at RT to obtain solid. Various chalcone compounds were prepared using Claisen-Schmidt (base catalyzed) condensation reaction of selected substituted aldehyde and substituted acetophenone by known literature method¹⁹. Substituted benzaldehyde and 3-Acetyl-2H-Chromen-2-one was mixed in ethanol using magnetic stirrer. Water bath was used to maintain the reaction temperature between 20-25º C on the magnetic stirrer. 1 gm NaOH was added to 10 mL distilled water and the resulted aqueous NaOH solution was dropwise added into the to the reaction mixture and when addition was completed this solution was stirred further for 4-5 Hrs and kept for 12 Hrs. The mixture was made neutral with 0.1 – 0.2N HCl till the solidification obtained. The resulted mixture was filtered then dried in air finally recrystallized using rectified spirit. Further carried out from purification was Ethyl Acetate & n-Hexane.

Chalcone derivatives (2a-k), malononitrile and anhydrous ammonium acetate were taken in RBF and absolute ethanol was used as solvent. This mixture was refluxed for 7-8 Hrs. then cooled to RT. As solution attained RT, solid was obtained. Filtration & washing was done with dist. H₂O thoroughly, recrystallization from Ethanol to yielded compounds (3a-k)²³.

Compound (3a-k) and excess of glacial CH₃COOH were mixed and then refluxed condition for 7-8 Hrs. Glacial acetic acid was self-solvent. After the completion of reaction, solution was cooled to RT. Solid thus obtained, was filtered, then washed thoroughly with cold dist. H₂O several times, dried, Dioxane was used for recrystallization to give compounds (4a-k).

Various derivatives of 3-(2-Chloroacetyl)-5-(2,4-substitutedphenyl)-2-Methyl-7-(2-Oxo-2H-Chromen-3-yl)Pyrido[2,3-d]Pyrimidin-4(3H)-one (5a-k) were synthesized from compounds (4a-j). Saturated solution of sodium acetate was prepared in glacial acetic acid. Compound (4a-k) was dissolved drop wise to the mixture and then was cooled at 0-5º C. Chloroacetyl chloride was dropwise added in the solution at 0-5º C during 1 Hr. time period. When addition was completed, this reaction mixture was heated at 80º C for 1.5 Hrs. & this solution was stirred at RT for 12 Hrs. which gave compounds (5a-k).

Various derivatives of N-(Hydroxyadamantan-1-yl)-5-(2,4-substituted phenyl)-2-Methyl-4-Oxo-7-(2-Oxo-2H-Chromen-3-yl)Pyrido[2,3-d]Pyrimidine-3(4H) carboxamide (6a-k) were synthesized by reaction between the mixture of 3-aminoadamantan-1-ol and K₂CO₃. This was refluxed for 5-6 hours, and then the solution was cooled to RT. Then this mixture was dumped into ice to obtain solid, which was filtered & washed with distilled water, dried and finally recrystallization was carried out using Ethanol to yield (6a-k) products.

The compounds were confirmed by study of FT-IR spectra, using KBr discs. on Perkin-Elmer 1600 FTIR, ¹H NMR and ¹³C NMR spectra were measured on Bruker 500 MHz in DMSO -d₆ as solvent was used and TMS – tetra methyl silane was internal standard respectively. LC-MS were carried out on LCMS. According to NMR data presence of methyl group showed value of δ near 2.92-3.09, proton of the secondary of NH group showed value of δ near 6.76-7.35, -OH group pf adamantane showed value of δ near 3.43-3.47, -OCH₃ showed value of δ near 3.79-3.90 and 5H of coumarin showed value of δ 6.75-8.59. Figure 1 to 4 shows ¹H NMR spectra of the compounds TT₁, TT₃, TT₅ and TT₈ respectively. Figure 5 shows ¹³C NMR spectra of the compound TT₁. Figure 6 and 7 shows IR spectra of the compounds TT₁ and TT₃ respectively. Figure 8 represents LCMS spectra of the compounds TT₁ and TT₃ respectively.

Biological activity

Antibacterial activity

Table-3 shows MIC (minimum inhibition concentration) of the N-(3-Hydroxyadamantan-1-yl) – 5 – (2,4-substitutedphenyl)-2-Methyl-4-Oxo-7-(2-Oxo-2H-Chromen-3-yl)Pyrido[2,3-d]Pyrimidine-3(4H)Carboxamide (6a-k) (Graph-1). Majority of the molecules which were tested, showed noticeable activities against E. Coli, P. Aeruginosa, S. Aureus & S. Pyogenes. From the results of antibacterial study of these N-(Hydroxyadamantan-1-yl)-5-(2,4-substitutedphenyl)-2-Methyl-4-Oxo-7-(2-oxo-2H-Chromen-3-yl)Pyrido[2,3-d]Pyrimidine- 3(4H)carboxamide (6a-k) derivatives such as TT₁ (R₁ = -H and R₂ = -OCH₃), TT₆ (R₁ = -H and R₂ = -Br), TT₈ (R₁ = -H and R₂ = -CH₃) and TT₉ (R₁ = -Cl and R₂ = -Cl) showed better activity at 50µg/mL; TT₃ (R₁ = -H and R₂ = (CH₃)₂N-) and TT₁₀ (R₁ = -Br and R₂ = -H) showed better activity at 62.5µg/mL; TT₂ (R₁ = -H and R₂ = -Cl), TT₄ (R₁ = -H and R₂ = -OH), TT₅ (R₁ = -H and R₂ = -NO₂), TT₇ (R₁ = -OH and R₂ = -H) and TT₁₁ (R₁ = -Br and R₂ = -H) showed better activity at 100µg/mL against E. Coli as comparing with Ampicillin (MIC=100µg/mL).

N-(Hydroxyadamantan-1-yl)-5-(2,4-substitutedphenyl)-2-Methyl-4-Oxo-7-(2-Oxo-2H-Chromen -3-yl)Pyrido[2,3-d]Pyrimidine-3(4H) Carboxamide (6a-k) derivatives such as TT₃ (R₁ = -H and R₂ = (CH₃)₂N-) showed better activity at 50µg/mL; TT₁ (R₁ = -H and R₂ = -OCH₃) and TT₈ (R₁ = -H and R₂ = -CH₃) showed better activity at 62.5µg/mL; TT₂ (R₁ = -H and R₂ = -Cl), TT₆ (R₁ = -H and R₂ = -Br), TT₉ (R₁ = -Cl and R₂ = -Cl) and TT₁₀ (R₁ = -CH₃ and R₂ = -H) showed better activity at 100µg/mL against P. Aeruginosa as comparing with Ampicillin (MIC = 100 µg / mL) and equivalent as Chloramphenicol (MIC = 50 µg / mL).

N-(Hydroxyadamantan-1-yl)-5-(2,4-substitutedphenyl)-2-Methyl-4-Oxo-7-(2-Oxo-2H-Chromen -3-yl)Pyrido[2,3-d]Pyrimidine-3(4H) Carboxamide (6a-k) derivatives such as TT₉ (R₁ = -Cl and R₂ = -Cl) showed better activity at 50µg/mL; TT₁ (R₁ = -H and R₂ = -OCH₃), TT₄ (R₁ = -H and R₂ = -OH), TT₁₀ (R₁ = -Br and R₂ = -H) and  TT₁₁ (R₁ = -Br and R₂ = -H) showed better activity at 100µg/mL against S. Aureus as comparing with Ampicillin (MIC = 100 µg / mL) and N-(3-Hydroxyadamantan-1-yl)-5-(2,4-substitutedphenyl)-2-Methyl-4-Oxo-7-(2-Oxo-2H-Chromen-3-yl)Pyrido[2,3-d]Pyrimidine-3(4H) Carboxamide (6a-k) derivatives such as TT₁ (R₁ = -H and R₂ = -OCH₃), TT₂ (R₁ = -H and R₂ = -Cl) and TT₈ (R₁ = -H and R₂ = -CH₃) showed better activity at 62.5µg/mL; TT₃ (R₁ = -H and R₂ = (CH₃)₂N-), TT₉ (R₁ = -Cl and R₂ = -Cl) and TT₁₀ (R₁ = -Br and R₂ = -H) showed better activity at 100µg/mL against S. pyogenes as compared to Ampicillin (MIC = 100 µg / mL).

Antifungal activity

The minimum inhibition concentration of the N-(3-Hydroxyadamantan-1-yl)-5-(2,4-substitutedphenyl)-2-Methyl-4-oxo-7-(2-Oxo-2H-Chromen-3-yl)Pyrido[2,3-d] Pyrimidine-3(4H) Carboxamide (6a-k) is shown in Table-4 (Graph-2). Most of the compounds tested, exhibited considerable activities against C. Albicans, A. Niger & A. Clavatus. Antifungal activity results of N-(3-Hydroxyadamantan-1-yl)-5-(2,4-substitutedphenyl)-2-Methyl-4-Oxo-7-(2-Oxo-2H-Chromen-3-yl)Pyrido[2,3-d]Pyrimidine-3(4H)-Carboxamide (6a-k) derivative such as TT₂ (R₁ = -H and R₂ = -Cl) and TT₆ (R₁ = -H and R₂ = -Br)  showed better activity at 50 µg/mL; TT₅ (R₁ = -H and R₂ = -NO₂) and TT₈ (R₁ = -H and R₂ = -CH₃) showed better activity at 62.5µg/mL; TT₁ (R₁ = -H and R₂ = -OCH₃), TT₄ (R₁ = -H and R₂ = -OH), TT₇ (R₁ = -OH and R₂ = -H) and TT₁₁ (R₁ = -Br and R₂ = -H) showed better activity at 100µg/mL against C. Albicans as compared Nystatin (MIC = 100 µg / mL) and Griseofulvin (MIC = 500 µg / mL). N-(3-Hydroxyadamantan-1-yl)-5-(2,4-substitutedphenyl)-2-Methyl-4-Oxo-7-(2-Oxo-2H-Chromen-3-yl)Pyrido[2,3-d]Pyrimidine-3-(4H)-Carboxamide (6a-k) derivative such as TT₅ (R₁ = -H and R₂ = -NO₂) better activity at 50 µg/mL; TT₂ (R₁ = -H and R₂ = -Cl)showed better activity at 62.5µg/mL; TT₁ (R₁ = -H and R₂ = -OCH₃), TT₃ (R₁ = -H and R₂ = (CH₃)₂N-), TT₄ (R₁ = -H and R₂ = -OH), TT₆ (R₁ = -H and R₂ = -Br), TT₇ (R₁ = -OH and R₂ = -H) and TT₁₁ (R₁ = -Br and R₂ = -H) showed better activity at 100µg/mL against A. Niger as comparing with Nystatin (MIC = 100 µg / mL) and Griseofulvin (MIC = 500 µg / mL). N-(3-Hydroxyadamantan-1-yl)-5-(2,4-substitutedphenyl)-2-Methyl-4-Oxo-7-(2-Oxo-2H-Chromen-3-yl)Pyrido[2,3-d]Pyrimidine-3(4H)-Carboxamide (6a-k) derivative such as TT₁ (R₁ = -H and R₂ = -OCH₃) and TT₈ (R₁ = -H and R₂ = -CH₃) showed better activity at 50µg/mL; TT₅ (R₁ = -H and R₂ = -NO₂) better activity at 62.5µg/mL; TT₂ (R₁ = -H and R₂ = -Cl), TT₆ (R₁ = -H and R₂ = -Br), TT₁₀ (R₁ = -Br and R₂ = -H) and TT₁₁ (R₁ = -Br and R₂ = -H) showed better activity at 100µg/mL against A. Clavatus as comparing with Nystatin (MIC = 100 µg / mL) and Griseofulvin (MIC = 500 µg / mL).

Anti Tubercular activity

Very promising results of antibacterial activity test of N-3-Hydroxyadamantan-1-yl)-5-(2,4-substitutedphenyl)-2-Methyl-4-Oxo-7-(2-Oxo-2H-Chromen-3-yl)Pyrido[2,3-d]Pyrimidine-3(4H)Carboxamide (6a-k) directed to study out more primary screening against M. tuberculosis. The antitubercular activity results of Pyrido[2,3-d]Pyrimidine derivatives (6a-k) presented in Table-4 (Graph-3). For the screening trials, concentration of exhibiting compounds was 1000, 500 and 250 µg/mL. From these, the compounds exhibiting good activity in the primary screening were considered for secondary screening against M. tuberculosis H₃₇RV in the L. J. Medium. The results of the antitubercular activity were matched with Rifampicin at the concentration 40 µg/mL. N-(3-Hydroxyadamantan-1-yl)-5-(2,4-substitutedphenyl)-2-Methyl-4-Oxo-7-(2-Oxo-2H-Chromen-3-yl)Pyrido[2,3-d]Pyrimidine-3(4H) carboxamide (6a-k) such as TT₁, TT₇ and TT₁₁ containing bromo, hydroxy and methoxy substituted derivatives exhibited M. tuberculosis MIC values in around 62.5 µg/mL producing 95-99% better results. But the other compounds exhibited moderate to poor activity against M. tuberculosis H₃₇RV.

Anti Malarial activity

Antimalarial activity of Pyrido[2,3-d]Pyrimidine derivatives (6a-k) is shown in Table-5. Chloroquine and Quinine were the standard drugs used to compare antimalarial activity. The values of MIC are 0.020 µg/mL and 0.268 µg/mL respectively. Pyrido[2,3-d]Pyrimidine derivatives no. 1 & 2, 4 to 11 showed better activity at 0.88µg/mL, 0.25µg/mL, 0.98µg/mL, 0.74µg/mL, 0.42µg/mL, 0.35µg/mL, 0.46µg/mL, 0.31µg/mL, 0.52µg/mL and 0.23µg/mL respectivelyas antimalarial activity comparing with to Quinine (MIC=0.268 µg/mL).

Acknowledgement

Authors are thankful to Dr. A. S. Patel (Principal, Navyug science college, surat) who provided all facilities for research.

Conflict of Interest

There are no conflict of interest.

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