Synthesis, single crystal X-ray studies and antimicrobial activities of novel Indole barbiturates

Article abstract of DOI:10.1007/s00044-011-9827-6

A novel series of N-substituted 2-phenyl indole derivatives incorporating barbituric acid have been synthesised and the chemical structures of the resulting molecules were characterised by means of IR, NMR and mass spectra. The antimicrobial activities of these compounds were investigated. Significant improvement in the antimicrobial activity can be achieved, in the presence of Cl and Br substituents on phenacyl moiety at para position. Single crystal X-ray analysis was also performed for the compound 6b in order to determine the crystal structure. Springer Science+Business Media, LLC 2011.

Full text of DOI:10.1007/s00044-011-9827-6

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2012) 21:2896–2901
DOI 10.1007/s00044-011-9827-6
ORIGINAL RESEARCH
Synthesis, single crystal X-ray studies and antimicrobial activities
of novel Indole barbiturates
•
S. Vijaya Laxmi B. Janardhan B. Rajitha
•
•
•
P. Raghavaiah Prathima Srinivas
Received: 28 July 2011 / Accepted: 19 October 2011 / Published online: 30 October 2011
Ó Springer Science+Business Media, LLC 2011
Abstract A novel series of N-substituted 2-phenyl indole
derivatives incorporating barbituric acid have been syn-
thesised and the chemical structures of the resulting mol-
ecules were characterised by means of IR, NMR and mass
spectra. The antimicrobial activities of these compounds
were investigated. Significant improvement in the antimi-
crobial activity can be achieved, in the presence of Cl and
Br substituents on phenacyl moiety at para position. Single
crystal X-ray analysis was also performed for the com-
pound 6b in order to determine the crystal structure.
heterocyclic dyes, indole derivatives exhibit unique photo
responsive organic compounds (Yukinori Nagao et al., 2007;
Anon, 1971) which render them useful in a variety of
applications such as in light-emitting electrochemical cells,
(Qianqian Li et al., 2009) solid-state lasers, light-emitting
diodes, fluorescent labels, and probes in biology and medi-
cine, (Asefa and Singh, 2010; Lengvinaite et al., 2010; Chao
Zhang et al., 2010). On the other hand, barbituric acid has
been used as disperse dye with strong fluorescent and as
yellow organic pigment (Theford et al., 2003; Karci, 2008;
Wang and Kim, 2009). In continuation of our studies on
antimicrobial agents (Vijaya Laxmi et al., 2011; Suresh
kuarm et al., 2011) we assessed antibacterial and antifungal
activity of indole barbituric acid derivatives.
Keywords Antimicrobial activity Á Barbituric acid Á
Crystal structure Á 2-Phenyl-1H-Indole-3-carbaldehyde
Introduction
Results and discussion
Indole, a potent basic pharmacodynamic nucleus, has been
reported to possess a wide variety of biological properties,
viz., anti-inflammatory (Preeti Rani et al., 2004), anticancer
(Jing-Ru Weng et al., 2010; Mahboobi et al., 2005), anti-
depressant (Kar and Attah, 1991), antibacterial (Tiwari et al.,
2006; Deepa Sinha et al., 2008), and antifungal (El-Sawy
et al., 2006). Moreover, as an important class of organic
Synthesis of indole barbiturates
The synthesis of Indole-based barbituric acid derivatives
were carried out according to Scheme 1. The key inter-
mediate 1 (2-phenyl Indole) was synthesised based on lit-
erature method (Vogel’s, 2006).
2-Phenyl-1H-indole on vilsmeier formylation-afforded
compound 2, (2-phenyl-1H-indole-3-carbaldehyde). When
2-phenyl-1H-indole-3-carbaldehyde is treated with simple,
substituted phenacyl bromides, and alkyl bromides sepa-
rately under K2CO3 and phase transfer catalytic conditions
(PTC) with TBAB (tetra butyl ammonium bromide) in DMF
stirring at room temperature-afforded compounds 3(a–e)
and 4(a–c), respectively (Vijaya Laxmi and Rajitha, 2010).
Further Knoevenegal condensation of intermediates 3(a–e)
and 4(a–c) with barbituric acid in methanol under reflux
furnished both alkyl and aryl indole barbiturates (5a–e) and
S. V. Laxmi Á B. Janardhan Á B. Rajitha (&)
Department of Chemistry, National Institute of Technology,
Warangal 506 004, India
e-mail: rajitabhargavi@yahoo.com
P. Raghavaiah
School of Chemistry, University of Hyderabad, Hyderabad, India
P. Srinivas (&)
Sri Venkateshwara College of Pharmacy, Osmania University,
Hyderabad, India
e-mail: drpssvcp@gmail.com
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Med Chem Res (2012) 21:2896–2901
2897
Scheme 1 Synthesis of indole barbiturates
(6a–c) in good yields. The Indole aldehydes 3(a–e) and
4(a–c) were colourless when condensed with barbituric acid
the compounds 5(a–e) and (6a–c) have shown yellow
and orange colours. We have ascribed structure 5(a–e) and
(6a–c) by spectral analysis. In the IR spectra, bands in the
region 3,180–3,220 cm-1 is attributed to NH of barbituric
acid, bands at 1,727 and 1,680 cm-1 confirmed the presence
of C=O group. In 1HNMR spectrum C=C–H, NH protons of
barbituric acid appeared as a singlet at d ppm 7.9, 11.1, and
11.2, respectively. All other aromatic and aliphatic protons
were observed at the expected region. In 13C-NMR spectra,
signal at d 161.4–162.4 and 163.9–164.1 ppm assign the
C=O groups in barbituric acid, while C=O of phenacyl group
appeared in the range of 191.5–192.9 ppm (5a–e). EIMS and
evaporation. Single crystal X-ray diffraction data was
collected on a CCD detector based diffractometer-SMART
APEX from Bruker-Nonius AXS using Mo-Ka radiation
˚
(k = 0.71073 A) at T = 293(2). The crystal structure was
solved by direct methods using SHELXS-97 program and
refinements of F2 were performed using SHELXL-97
program. A summary of the crystallographic data and
structure refinement details are given in Table 1. The
ORTEP representation of the molecular structure of 6b is
shown in Fig. 1. The crystal structure of 6b consists of
methanol sitting on the inversion center and water
molecule.
HRMS of the given compounds displayed (m?1) and (m?23
peaks, which confirmed their molecular weights.
)
Antimicrobial activity
The compounds were evaluated for antibacterial and anti-
fungal activities, according to standard cup plate method
(Granade and Artis, 1980). Nutrient broth and nutrient agar
were used and samples dissolved in 5 ml of dimethyl-
sulphoxide (DMSO). The solvent control DMSO did not
show any antimicrobial activity. The antimicrobial activity
X-ray crystallography
Prism-shaped single crystals of 6b were obtained from a
mixture of 1:1 ratio of chloroform and methanol by slow
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Med Chem Res (2012) 21:2896–2901
Table 1 Crystal data and summary of intensity data collection and
structure refinement for compound 6b
Empirical formula
C45H38N6O10
822.81
Formula weight
Temperature
293(2)
Crystal system, space group
Crystal description and colour
Triclinic, P-1
Prism, yellow colour
˚
Unit cell parameters (A,°)
a = 10.2849 (13)
b = 10.4038 (13)
c = 11.8742 (13)
a = 99.067 (10)
b = 101.513 (10)
c = 118.802 (13)
1042.3(2)
3
˚
Volume (A )
Fig. 1 ORTEP representation of compound 6b
Z
1
Crystal dimensions (mm)
Dcalc (Mg/m3)
0.42 9 0.32 9 0.28
1.311
antifungal activities, while compounds 5a and 5e were
inactive towards bacteria and fungi.
F (0 0 0)
430
0.094 mm-1
Absorption coefficient
Diffraction radiation wavelength
˚
(A)
0.71073
Conclusion
Reflections collected/unique
Extinction coefficient
Max. and min. transmission
Limiting indices
7625/4244 [R(int) = 0.0330]
0.010(3)
In this study, 2-phenyl indole barbituratic acid derivatives
(5a–e and 6a–c) were synthesised, identified by spectral
data and single crystal X-ray analysis (6b). Antimicrobial
activity of Indole barbiturates enhanced when chloro and
bromo substituents introduced into aryl moiety in 5b and
5c, respectively, while the activity was found to be
diminished in 5e due to the introduction of methoxy group.
From the results, we propose that the newly synthesised
Indole barbiturates 5b, 5c, and 6b can be considered as the
lead compounds for the development as potential antimi-
crobial agents in the treatment of different bacterial and
fungal infections.
0.9741 and 0.9614
-12 B h B 12,
-12 B k B 12,
212 B l B 14
R indices (all data)
R1 = 0.1291, wR2 = 0.1745
2h range for data collection (°)
Number of reflections
Completeness to theta = 26.37
Refined parameters
2.89–26.37
4244
99.9%
293
No. observed reflections
Goodness-of-fit on F2
Refinement Method
CCDC
I [ 2 s (I) 2406
1.047
Full-matrix least-squares on F2
816380
Experimental
General
was compared with known standard drugs at the same
concentration. The known concentrations of Ampicillin
and Ketoconazole (100, 200, 300 lg/ml) were used as
standard for bacteria and fungi, respectively. The test cul-
tures used were Eschereschia coli, Bacillus subtilis,
Staphylococcus aureus, Pseudomonas aeuroginosa, Pro-
teus vulgaris, Saccharomyces cerevesiae, and Candida
albicans. The results from the Table 2 reveals that the
compounds 5(a–e) and 6(a–c) exhibited antimicrobial
activity at 100–300 lg/ml concentration. In both the series
5b, 5c, 5d, 6b, and 6c displayed marked antibacterial
activity. Ampicillin was active as antibacterial agent and
Ketoconazole as antifungal agent, whereas compounds 5b,
5c, 5d, and 6b showed remarkable antibacterial and
Chemicals were purchased from Merck (purity 98%). All
melting points were determined with Quimis apparatus
(Model Q-340s 13) and were uncorrected. TLC was per-
formed on 2.0 9 6.0 cm aluminium sheets covered with
silica gel (Sorbent, with 200 lm thickness) under ultravi-
olet radiation. Ethyl acetate:Hexane (2:8) is used as a
mobile phase. Infrared (IR) spectra were obtained with
ABB spectro photometer (Model: FTLA 2000-100) using
KBr pellets. NMR, was measured on Brucker 300-MHz
spectrometer using DMSO as a solvent and TMS as
internal standard. Mass spectra were recorded on a Jeol
JMSD-300 spectrometer.
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Med Chem Res (2012) 21:2896–2901
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Table 2 In vitro antimicrobial activity (MIC) values for compounds 5a–e and 6a–c
Bacterial strains
Fungal strains
Compound
E. coli
B. subtilis
S. aureus
P. aeuroginosa
P. vulgaris
S. cerevesiae
C. albicans
lg/ml
5a
100, 200, 300
- - -
100, 200, 300
- - -
100, 200, 300
- - -
100, 200, 300
? ? ?
100, 200, 300
? - ?
100, 200, 300
? ? ??
? ? ??
?? ?? ??
? ? ??
- - ?
100, 200, 300
- - -
5b
?? ?? ??
? ? ??
? ? ??
- - -
? ? ??
? ? ??
? ? ?
? ? ?
? ? ?
? ? ?
? ? ?
5c
? ? ?
? ? ?
? ? ?
? ? ??
- - -
5d
? ? ?
- - ?
- ? ?
5e
- - ?
- - -
? ? ?
? ? ?
? ? ?
6a
- - -
- - ?
- - -
? ? ?
- - -
? ? ?
?? ? ?
?? ?? ??
? ? ?
6b
? ?? ??
?? ?? ??
?? ?? ??
ND
? ?? ??
? ? ??
?? ?? ??
ND
?? ?? ??
? ? ?
? ? ??
- - -
? ? ?
? ? ?
6c
? ? ?
- - -
Am
Kt
?? ?? ??
ND
?? ?? ??
ND
?? ?? ??
ND
ND
- - -
?? ?? ??
?? ?? ??
- resistant, ? moderately sensitive, ?? sensitive
Am ampicillin, Kt ketoconazole, ND not done
5-{1-[2-(4-Chloro-phenyl)-2-oxo-ethyl]-2-phenyl-1H-
indol-3-ylmethylene}-pyrimidine-2,4,6-trione (5b)
General synthetic procedure for the
compounds 5a–e and 6a–c
Yellowish solid; M.P 250–255°C; IR (KBr, tmax, cm-1):
3188,3086(N–H), 3050, (aromatic C–H) 2916, (aliphatic
C–H), 1735, 1694, 1656 (C=O), 1532, 1442, 1227, 1198,
Derivatives of 1-(2-oxo-2-phenyl–ethyl)-2-phenyl-1H-
indole-3-carbaldehyde (3a–e) or derivatives of 1-alkyl-2-
phenyl-1H-indole-3-carbaldehyde (4a–c) (1.0 mol) were
dissolved in methanol. An equimolar amount of barbituric
acid was added to it, and the mixture was heated under
reflux for 3–4 h. Product formation was confirmed by TLC,
the mixture was cooled and the solid obtained was filtered
and washed well with cold methanol. The characterisation
data of compounds 5(a–e), 6(a–c) is given below.
1
930, 747; H-NMR (400 MHz, DMSO-d6): d 5.97(s, 2H),
7.2–8.0 (m, 9H), 7.373 (d, 1H, J = 6 Hz),7.586(d, 1H,
J = 6 Hz), 7.681(d, 1H, J = 8.4), 7.98 (s, 1H), 8.081(d,
1H, J = 8.8), 11.05(s, 1H, NH),11.11(s, 1H, NH). 13C-
NMR (100 MHz, DMSO-d6): d 51.6, 111.2, 112.0, 113.1,
121.5, 123.3, 124.6, 125.0, 128.5, 128.7, 129.0, 130.1,
130.2, 132.6, 138.2, 139.2, 147.1, 150.4, 151.7, 161.4,
164.0, 192.6. MS ESI: 484 (m ? 1) (10%). For the M.F
C27H18ClN3O4, M.Wt 483.
Structural confirmations
5-[1-(2-Oxo-2-phenyl–ethyl)-2-phenyl-1H-indol-3-
ylmethylene]-pyrimidine-2,4,6-trione (5a)
5-{1-[2-(4-Bromo-phenyl)-2-oxo-ethyl]-2-phenyl-1H-
indol-3-ylmethylene}-pyrimidine-2,4,6-trione (5c)
Orange solid; M.P 265–270°C; IR (KBr, tmax, cm-1):
3184, 3118 (N–H), 3054,(aromatic C–H) 2936 (aliphatic
C–H), 1732, 1696 1665 (C=O), 1539, 1442,1299, 1202,
Yellowish solid; M.P 235–240°C; IR (KBr, tmax, cm-1):
3216, 3079 (N–H), 3057, (aromatic C–H) 2923(aliphatic
C–H), 1725, 1686,1652(C=O), 1577, 1424, 1228, 1098,
1
933, 749; H-NMR (300 MHz, DMSO-d6): d 5.96 (s, 2H),
1
931,750; H-NMR (400 MHz, DMSO-d6): d 5.96 (s, 2H),
7.19–8.20 (m, 9H),7.381(d,1H, J = 5.2 Hz), 7.546 (d,
1H, J = 8 Hz),7.61 (d, 1H, J = 8 Hz), 7.636(d,1H, J =
5.2 Hz), 7.98 (s,1H), 8.053(d,1H, J = 7.2 Hz), 11.02
(s, 1H, NH), 11.08(s, 1H, NH). 13C-NMR (75 MHz,
DMSO-d6): d 51.5, 111.2, 111.9, 113.1, 121.5, 123.3,
124.6, 125.0, 128.2, 128.5, 128.7, 128.9, 130.2, 130.7, 134,
134.2, 138.3, 147.1, 150, 151.8, 161.4, 164, 193.4. MS
HRMS: calculated m/z 449.14 found 449.056, 450.059
(m ? 1), 472.044 (m ? 23) For the M.F C27H19N3O4.
7.27–7.97. (m, 9H), 7.289(d, 1H, J = 5.2 Hz), 7.365
(d,1H, J = 6 Hz), 7.564 (d,1H, J = 5.2 Hz), 7.819 (d,1H,
J = 8.8 Hz), 7.98 (s, 1H), 11.03(s, 1H, NH), 11.10(s, 1H,
NH). 13C-NMR (100 MHz, DMSO-d6): d 51.6, 111.3,
112.1, 113.2, 121.6, 123.4, 124.7, 125.1, 128.5, 128.6,
128.8, 129.1, 130.3, 132.0, 138.3, 147.2, 150.5, 151.8,
161.5, 164.1, 192.8. MS ESI: 528 (m ? 1) (100%). For the
M.F C27H18BrN3O4, M.Wt 527.
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Med Chem Res (2012) 21:2896–2901
5-[1-(2-Biphenyl-4-yl-2-oxo-ethyl)-2-phenyl-1H-indol-3-
ylmethylene]-pyrimidine-2,4,6-trione (5d)
6.024 (m, 1H) 7.25–7.65 (m, 9H), 7.96 (s, 1H), 10.98 (s,1H,
NH), 11.05 (s, 1H, NH). 13C-NMR (100 MHz, DMSO-d6): d
46.9, 48.5, 111.5, 111.6, 112.9, 117.2, 121.6, 123.3, 124.7,
125.2, 128.7, 130.2, 130.9, 133.0, 137.4, 147.3, 150.4, 151.4,
161.4, 164. MS ESI 371 (m ?) (40%), 372(m ? 1) (20%).
For the M.F C22H17N3O3 M.Wt 371.
Orange solid; M.P 250–255°C; IR (KBr, tmax, cm-1):
3225, 3192 (N–H), 3070(aromatic C–H), 2929(aliphatic
C–H), 1709, 1672,1665(C=O), 1538, 1447, 1284, 1187, 944,
1
753; H-NMR (400 MHz, DMSO-d6): d 6(s, 2H), 7.3–7.76
(m, 16H), 7.89(d, 1H, J = 8.4 Hz) 7.99 (s, 1H), 8.147
(d, 1H, J = 8.4 Hz), 11.03(s, 1H, NH), 11.09(s, 1H, NH).
13C-NMR (100 MHz, DMSO-d6): d 51.6, 111.2, 111.9,
113.1, 121.5,123.3, 124.6, 125.1, 127.0, 128.5, 128.7, 128.9,
129.1, 130.2, 130.4, 130.7, 132.7, 138.3, 138.6, 145.6, 147.2,
150.4, 151.9, 161.4, 164.0, 192.9. MS ESI: 526 (m ? 1)
(10%). For the M.F C33H23N3O4, M.Wt 525.
5-(1-Butyl-2-phenyl-1H-indol-3-ylmethylene)-pyrimidine-
2,4,6-trione (6c)
Orange solid; M.P 220–230°C; IR (KBr, tmax, cm-1): 3203,
3080 (N–H), 2931 (aliphatic C–H), 1727, 1688 (C=O),
1
1550, 1443, 1295, 970, 749; H-NMR (400 MHz, DMSO-
d6): d 0.691 (t, J = 7.2 Hz, 3H, CH3–CH2), 1.07 (m, 2H),
1.58 (m, 2H), 4.272 (t, J = 7.2 Hz, 2H, CH2–CH2), 7.2–7.7
(m, 9H), 7.9 (s, 1H), 10.96 (s, 1H, NH), 11.03 (s, 1H, NH).
13C-NMR (100 MHz, DMSO-d6): d 13.1, 19.1, 31.0, 43.9,
110.9, 111.3, 112.9, 121.5, 123.3, 124.9, 125.2, 128.7,
130.1, 131.0, 137.3, 147.3, 150.4, 151.9, 161.4, 164.1. MS
HRMS Calculated 387.16 found 387.084, 388.09 (m ? 1),
410.077 (m ? 23) For the M.FC23H21N3O3.
5-{1-[2-(4-Methoxy-phenyl)-2-oxo-ethyl]-2-phenyl-1H-
indol-3-ylmethylene]-pyrimidine-2,4,6-trione (5e)
Yellowish solid, M.P 265–270°C, IR (KBr, tmax, cm-1):
3179, 3104, (N–H) 3030(aromatic C–H), 2932(aliphatic
C–H), 1729, 1693, 1650(C=O),1513, 1440, 1220, 1081,
1
938, 760. H-NMR (400 MHz, DMSO-d6): d 3.8 (s, 3H)
Acknowledgments The authors wish to thank Dr. B. Srinivas, NIT
Warangal for interpreting the single crystal X-ray analysis, one of the
authors S.V thanks the Ministry of Human Resource Development for
providing the fellowship.
5.8 (s, 2H), 7.0–8.0 (m, 10H), 7.565 (d, 1H, J = 6 Hz),
7.101 (d, 1H, J = 8.8 Hz), 7.97 (s, 1H), 8.041 (d,1H,
8.8 Hz), 11.02 (s, 1H, NH), 11.08 (s, 1H, NH). 13C-NMR
(100 MHz, DMSO-d6): d 51.2, 55.6, 111.2, 111.8, 113.1,
114.1, 121.5, 123.3, 124.6, 125.0, 126.8, 128.5, 128.7,
130.2, 130.6, 130.7, 138.3, 147.2, 150.4, 152.0, 161.4,
163.9, 164.0, 191.5. MS ESI: 502 (m ? 23) (60%). For the
M.F C28H21N3O5, M.Wt 479.
Declaration of interest The author reports no conflicts of interest.
The author alone hereby stands responsible for the contents of this
scientific paper.
5-(1-Ethyl-2-phenyl-1H-indol-3-ylmethylene)-pyrimidine-
2,4,6-trione (6a)
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