Synthesis and antimicrobial activities of a new series of 4-S-[41-amino-51-oxo-61-substituted benzyl-41,51-dihydro-11,21,41-triazin-3-yl]mercaptoacetyl-3-arylsydnones

Article abstract of DOI:10.1016/j.ejmech.2008.02.003

The synthesis of some 4-S-(4¹-amino-5¹-oxo-6¹-substituted benzyl-4¹,5¹-dihydro-1¹,2¹,4¹-triazin-3-yl)mercaptoacetyl-3-arylsydnones by the reaction of 3-aryl-4-bromoacetylsydnones with 6-substituted-4-amino-3-mercapto-1,2,4-triazin-5-ones is described. The IR, ¹H NMR, mass spectra and elemental analysis characterized the newly synthesized compounds. The synthesized compounds were screened for their antimicrobial activity. All the compounds showed higher activity than that of standard drug during antimicrobial studies and the activity was comparable with the standard drug for antifungal activity.

Full text of DOI:10.1016/j.ejmech.2008.02.003

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European Journal of Medicinal Chemistry 43 (2008) 2831e2834
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Original article
Synthesis and antimicrobial activities of a new series
of 4-S-[41-amino-51-oxo-61-substituted benzyl-41,
51-dihydro-11,21,41-triazin-3-yl]mercaptoacetyl-3-arylsydnones
*
Jyothi C Hegde, K.S Girisha, Adithya Adhikari, Balakrishna Kalluraya
Department of Studies in Chemistry, Mangalore University, Mangalagangothri 574 199, Karnataka, India
Received 29 August 2007; received in revised form 4 February 2008; accepted 7 February 2008
Available online 4 March 2008
Abstract
The synthesis of some 4-S-(41-amino-51-oxo-61-substituted benzyl-41,51-dihydro-11,21,41-triazin-3-yl)mercaptoacetyl-3-arylsydnones by the
reaction of 3-aryl-4-bromoacetylsydnones with 6-substituted-4-amino-3-mercapto-1,2,4-triazin-5-ones is described. The IR, 1H NMR, mass
spectra and elemental analysis characterized the newly synthesized compounds. The synthesized compounds were screened for their antimicro-
bial activity. All the compounds showed higher activity than that of standard drug during antimicrobial studies and the activity was comparable
with the standard drug for antifungal activity.
Ó 2008 Elsevier Masson SAS. All rights reserved.
Keywords: Synthesis; Sydnones; Triazines; Antimicrobial activity
1. Introduction
2. Chemistry
Rapid development of resistance to the existing antimicro-
bial drugs poses a major threat to the public health. Recent
reports suggest that bacteria and fungi are developing resis-
tance to existing drugs [1,2]. Consequently, there is a pressing
need to develop new antimicrobial agents, which have a broad
spectrum of activity against the resistant micro-organisms.
Since their discovery, sydnones have shown diverse biologi-
cal activities and it is thought that the meso-ionic nature of
sydnone ring promote significant interactions with biological
systems. Some ofits derivativesare reported to possess activities
such as anticancer, antimicrobial and anti-inflammatory [3e6].
Similarly, 1,2,4-triazinone derivatives are known to be endowed
with wide spectrum of biological activities such as antitumor
and antimicrobial properties [7e9]. Keeping in view of these
observations and in continuation of our search for biologically
active sydnone derivatives [10,11], we synthesized a series of
the title compounds and studied their biological activity.
The synthetic routes followed for the preparation of triazi-
nones 3 and the title compounds 5 are outlined in Schemes 1
and 2. Arylidine oxazolones 1 and acetyl sydnones were pre-
pared following the literature methods [12,13]. Photochemical
bromination of 3-aryl-4-acetylsydnone afforded 3-aryl-4-bro-
moacetylsydnones 4 [10]. 6-Substituted-4-amino-3-mercapto-
1,2,4-triazine-5-ones 3 were obtained by direct one-pot
condensation of 4-arylidine-2-methyl-1,3-oxazol-5-ones 1
with thiocarbohydrazide 2 (Scheme 1). The condensation of
6-substituted-4-amino-3-mecapto-1,2,4-triazine-5-ones 3 with
3-aryl-4-bromoacetylsydnones 4 yielded S-substituted triazi-
none derivatives 5ael (Scheme 2). We expected the forma-
tion of cyclized triazinothiadiazines, but unexpectedly
S-substituted products were obtained instead of cyclized
product. Attempts were made to cyclize the newly synthe-
sized products, employing a variety of catalysts. However,
our all efforts did not succeed due to the sensitivity of the
sydnone ring towards acid, base and heat. The newly synthe-
sized compounds were well characterized by spectral and
analytical data.
* Corresponding author. Tel.: þ91 824 228 7262; fax: þ91 824 228 7367.
E-mail address: bkalluraya_2001@yahoo.com (B. Kalluraya).
0223-5234/$ - see front matter Ó 2008 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2008.02.003

2832
Ar
J.C. Hegde et al. / European Journal of Medicinal Chemistry 43 (2008) 2831e2834
appeared as a singlet at d, 3.78 integrating for 3 protons.
O
Two doublets centered at d, 6.86 and d, 7.36 integrating for
2 protons each corresponding to ortho and meta protons of
p-anisyl moiety. The aromatic protons of phenyl ring reso-
nated as multiplets at d, 7.16e7.33 integrating for 5 protons.
Further evidence for the assigned structure has been drawn
from the mass spectral data.
S
N
O
NH
NH2
H2N
NH
+
H3C
(1)
(2)
3.2. Antimicrobial activity
O
The new compounds 5ael were subjected for in vitro anti-
bacterial and antifungal studies by serial dilution method
[14,15] against both Gram þve and Gram ꢀve bacteria. Anti-
bacterial activity was determined against Staphylococus
aureus (ATCC-25923), Bacillus subtilis (Recultured), P. aeru-
ginosa (ATCC-27853) and Eschercia coli (ATCC-25922),
and antifungal activity was determined against Candida albi-
cans (NCIM No. 3100). Nitrofurazone and Fluconazole were
employed as standard drugs. Peptoneewater and DMF were
used as medium and solvent control. The results of biological
study are summarized in Table 1. From the data, it is clear that
all the compounds showed good activity against both fungus
and bacteria, particularly showed a significant antimicrobial
activity much higher than that of the standard drug.
Ar
NH2
N
N
N
SH
(3)
Scheme 1.
3. Results and discussion
3.1. Chemistry
Reaction of 3-aryl-4-bromoacetylsydnones 4 with 6-
substituted-4-amino-3-mercapto-1,2,4-triazine-5-ones 3 gave
S-substituted triazinone derivatives 5ael. The IR spectra of
compounds 5 showed absorption bands at 1780e1790,
1680e1690 and 1624e1637 cmꢀ1 for the C]O stretching
frequency of sydnone, triazinone and eCH2eCOe, respec-
tively. The peaks between 3200 and 3320 cmꢀ1 showed the
presence of eNH2 group thereby indicating that cyclization
has not taken place.
4. Conclusion
In conclusion the reaction of 6-substituted-4-amino-3-
mercapto-1,2,4-triazine-5-ones 3 with 3-aryl-4-bromoacetyl-
sydnones
4
gave 4-S-(41-amino-51-oxo-61-substituted
benzyl-41,51-dihydro-11,21,41-triazin-3-yl)mercaptoacetyl-3-
arylsydnones 5 rather than the cyclized products. The micro-
bial evaluation of these compounds indicated that they are
more potent antimicrobial agents than the standard drug.
1
In a typical example, H NMR of 5j showed a singlet at d,
4.4 integrating for 2 protons of eSCH2 group. The signal due
to NH2 protons appeared at d, 4.7 while CH2 protons came
into resonance at d, 4.0 as a singlet. The eOCH3 protons
5. Experimental section
5.1. General
R
O
Br
O
Melting points were determined in open capillary tubes and
are uncorrected. The purity of the compounds is confirmed by
Ar
NH2
SH
N
N
1
thin layer chromatography using silica gel plates. H NMR
+
N
+
N
N
spectra were recorded on a 300 MHz NMR spectrometer and
the 13C NMR spectra were recorded on a 400 MHz NMR
spectrometer. TMS was employed as internal standard. Chem-
ical shift values are expressed in d scale down field from TMS.
The IR spectra [KBr disc] were recorded on JASCO FTIR-430
spectrophotometer and the mass spectra were recorded on
a Jeol-JMS D-300 mass spectrometer operating at 70 eV.
CHN analysis was carried on a Vairo-El-Elementa model
analyzer.
-
O
O
(3)
(4)
AcONa/EtOH
O
-
O
+
NH2
Ar
O
N
N
N
N
N
5.1.1. Synthesis of 6-substituted-4-amino-3-mecapto-1,2,
4-triazin-5-ones 3
S
CH2
O
A solution of thiocarbohydrazide 2 (0.1 mol) dissolved in
minimum amount of hot water was added dropwise to a solu-
tion of oxazole derivative 1 (0.1 mol) in ethanol (50 ml). The
(5)
R
Scheme 2.

J.C. Hegde et al. / European Journal of Medicinal Chemistry 43 (2008) 2831e2834
2833
19.19; Calculated: C: 55.04, H: 3.66, N: 19.26; 1H NMR
300 MHz, CDCl3: d: 4.09 (s, 2H, CH2), d: 4.46 (s, 2H, Se
CH2), d: 4.79 (s, 2H, NH2); d: 7.30e7.60 (m, 10H, ArH).
13C NMR 400 MHz, DMSO: d: 39.76 (SeCH2e), d: 40.18
(AreCH2e), d: 107 (triazine-3C), d: 125e136 (10C-aro-
matic), d: 152 (triazine-6C), d: 156 (Sydnone-4C), d: 161
(Sydnone-5C), d: 166 (eCOe, triazine-5C), d: 179 (eCOe).
IR (KBr): nCO (sydnone) 1784 cmꢀ1, nCO (triazinone)
1685 cmꢀ1, nCeO (eCH2eCOe) 1631 cmꢀ1 Mass: m/z, 436
(MF: C20H16N6O4S).
Table 1
Antibacterial and Antifungal activity data in MIC (mg/ml)
Compound no. Antibacterial activity data
Antifungal
activity data
S. aureus P. aeruginosa E. coli B. Subtilis C. albicans
5a
5b
5c
5d
5e
5f
0.25
0.25
0.25
0.25
0.5
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.5
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.5
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
e
0.25
0.25
0.25
0.25
0.25
0.25
0.25
Compound 5b: Ar ¼ p-bromophenyl, R ¼ H; m.p. ¼ 178e
5g
5h
5i
180 ꢁC; yield 65%; CHN analysis e Found: C: 46.61, H:
1
2.81, N: 16.30; Calculated: C: 46.69, H: 2.91, N: 16.34; H
5j
NMR 300 MHz, CDCl3: d: 4.05 (s, 2H, CH2), d: 4.49 (s,
2H, SeCH2), d: 4.82 (s, 2H, NH2), d: 7.24 (d, 2H, ortho pro-
tons of p-bromophenyl), d: 7.43 (d, 2H, meta protons of p-
bromophenyl), d: 7.49e7.66 (m, 5H, ArH); Mass: m/z, 514/
516 (MF: C20H15BrN6O4S).
5k
5l
Nitrofurazone 0.5
(Std.)
Fluconazole
(Std.)
e
e
e
e
e
e
e
0.25
Compound 5c: Ar ¼ p-chlorophenyl, R ¼ H; m.p. ¼ 183e
Solvent control
(DMF)
e
e
184 ꢁC; yield 67%; CHN analysis e Found: C: 51.12, H:
1
3.14, N: 17.78; Calculated: C: 51.06, H: 3.18, N: 17.85; H
Index for antibacterial and antifungal activity e Method: minimum inhibitory
concentration by serial dilution method. Medium used: peptoneewater. Sol-
vent control: DMF. Std. for antibacterial: nitrofurazone. Std. for antifungal:
fluconazole.
NMR 300 MHz, CDCl3: d: 4.12 (s, 2H, CH2), d: 4.38 (s,
2H, SeCH2), d: 4.91 (s, 2H, NH2), d: 7.04 (d, 2H, ortho
protons of p-chlorophenyl), d: 7.51 (d, 2H, meta protons of
p-chlorophenyl), d: 7.54e7.68 (m, 5H, AreH); Mass: m/z,
470/472 (MF: C20H15ClN6O4S).
reaction mixture was refluxed for 2 h. Solid separated upon
cooling was collected by filtration. Further, the products
were purified by crystallization in ethanoledioxane mixture
and characterized by their melting points and reference to
literature [16].
Compound 5d: Ar ¼ 3,4-methylenedioxyphenyl, R ¼ H;
m.p. ¼ 162e163 ꢁC; yield 72%; CHN analysis e Found: C:
52.23, H: 3.28, N: 17.47 Calculated: C: 52.50, H: 3.33, N:
1
17.50; H NMR 300 MHz, CDCl3: d: 4.01 (s, 2H, CH2), d:
Compound 3a: 6-benzyl-4-amino-3-mercapto-1,2,4-tri-
azine-5-ones. Yield 78%, m.p. 204e205 ꢁC (lit. m.p. 205 ꢁC).
Compound 3b: 6-( p-bromobenzyl)-4-amino-3-mercapto-
1,2,4-triazine-5-ones. Yield 82%, m.p. 220e221 ꢁC (lit. m.p.
220e223 ꢁC).
Compound 3c: 6-( p-chlorobenzyl)-4-amino-3-mercapto-
1,2,4-triazine-5-ones. Yield 80%, m.p. 217 ꢁC (lit. m.p.
218 ꢁC).
4.49 (s, 2H, SeCH2), d: 4.82 (s, 2H, NH2), d: 5.93 (s, 2H,
OeCH2eO), d: 6.76e7.53 (m, 8H, ArH); Mass: m/z, 480
(MF: C21H16N6O6S).
Compound 5e: Ar ¼ p-nitrophenyl, R ¼ H; m.p. ¼ 211e
212 ꢁC; yield 69%; CHN analysis e Found: C: 49.78, H:
1
3.06, N: 20.42; Calculated: C: 49.89, H: 3.11, N: 17.37; H
NMR 300 MHz, CDCl3: d: 3.98 (s, 2H, CH2), d: 4.73 (s,
2H, SeCH2), d: 5.01 (s, 2H, NH2), d: 6.81e7.07 (m, 9H,
AreH); IR (KBr): nCO (sydnone) 1780 cmꢀ1, nCO (triazinone)
1689 cmꢀ1, nCeO (eCH2eCOe) 1637 cmꢀ1; Mass: m/z, 481
(MF: C20H15N7O6S).
Compound 3d: 6-(3,4-methylenedioxybenzyl)-4-amino-3-
mercapto-1,2,4-triazine-5-ones. Yield 69%, m.p. 221e223 ꢁC
(lit. m.p. 223 ꢁC).
Compound 5f: Ar ¼ phenyl, R ¼ CH3; m.p. ¼ 188e189 ꢁC;
yield 65%; CHN analysis e Found: C: 56.11, H: 4.07, N:
18.58; Calculated: C: 56.00, H: 4.00, N: 18.66; IR (KBr):
nCO (sydnone) 1787 cmꢀ1, nCO (triazinone) 1689 cmꢀ1, nCeO
Compound 3e: 6-( p-nitrobenzyl)-4-amino-3-mercapto-
1,2,4-triazine-5-ones. Yield 75%, m.p. 204e206 ꢁC (lit. m.p.
205 ꢁC).
5.1.2. Synthesis of 4-S-[41-amino-51-oxo-61-substituted
benzyl-41,51-dihydro-11,21,41-triazin-3-yl]
(eCH2eCOe) 1624 cmꢀ1 1H NMR 300 MHz, CDCl3: d:
;
2.42 (s, 3H, CH3), d: 4.09 (s, 2H, CH2), d: 4.51 (s, 2H, Se
CH2), d: 4.79 (s, 2H, NH2), d: 7.22e7.39 (m, 9H, ArH);
Mass: m/z, 450 (MF: C21H18N6O4S).
mercaptoacetyl-3-arylsydnone 5ael
To a solution of triazinenone 3 (0.01 mol) and bromoacetyl-
sydnones 4 (0.01 mol) in ethanol (20 ml), anhydrous sodium
acetate (0.41 g, 0.005 mol) was added. The solution was
stirred at room temperature for 2e3 h. The solid product
separated was collected by filtration, washed with water, dried
and recrystallised from ethanol. Compounds prepared as per
this procedure are as follows.
Compound
5g:
Ar ¼ p-bromophenyl,
R ¼ CH3;
m.p. ¼ 194e195 ꢁC; yield 67%; CHN analysis e Found: C:
47.64, H: 3.29, N: 15.83; Calculated: C: 47.72, H: 3.21, N:
19.90; IR (KBr): nCO (sydnone) 1786 cmꢀ1, nCO (triazinone)
1683 cmꢀ1, nCeO (eCH2eCOe) 1626 cmꢀ1
;
1H NMR
300 MHz, CDCl3: d: 2.51 (s, 3H, CH3), d: 4.24 (s, 2H,
CH2), d: 4.63 (s, 2H, SeCH2), d: 4.83 (s, 2H, NH2), d: 6.98
(d, 2H, ortho protons of p-bromophenyl), d: 7.68 (d, 2H,
Compound 5a: Ar ¼ phenyl, R ¼ H; m.p. ¼ 188e189 ꢁC;
yield 68%; CHN analysis e Found: C: 55.01, H: 3.56, N:

2834
J.C. Hegde et al. / European Journal of Medicinal Chemistry 43 (2008) 2831e2834
meta protons of p-bromophenyl), d: 7.11 (d, 2H, ortho protons
of p-tolyl), d: 7.34 (d, 2H, meta protons of p-tolyl); Mass: m/z,
528/530 (MF: C21H17BrN6O4S).
50.38, H: 3.30, N: 16.71; Calculated: C: 50.34, H: 3.39, N:
16.78; IR (KBr): nCO (sydnone) 1780 cmꢀ1, nCO (triazinone)
1685 cmꢀ1, nCeO (eCH2eCOe) 1627 cmꢀ1
;
1H NMR
Compound
5h:
Ar ¼ p-chlorophenyl,
R ¼ CH3;
300 MHz, CDCl3: d: 3.93 (s, 3H, OeCH3), d: 4.21 (s, 2H,
CH2), d: 4.49 (s, 2H, SeCH2), d: 5.01 (s, 2H, NH2), d:
6.74e7.03 (m, 8H, AreH); Mass: m/z, 500/502 (MF:
C21H17ClN6O5S).
m.p. ¼ 188e189 ꢁC; yield 71%; CHN analysis e Found: C:
52.14, H: 3.54, N: 17.41; Calculated: C: 52.01, H: 3.50, N:
17.33; IR (KBr) nCO (sydnone) 1790 cmꢀ1, nCO (triazinone)
1680 cmꢀ1, nCeO (eCH2eCOe) 1631 cmꢀ1
;
1H NMR
300 MHz, CDCl3: d: 2.31 (s, 3H, CH3), d: 4.23 (s, 2H,
CH2), d: 4.63 (s, 2H, SeCH2), d: 5.03 (s, 2H, NH2), d:
7.86e7.58 (m, 8H, AreH); Mass: m/z, 484/486 (MF:
C21H17ClN6O4S).
Compound 5i: Ar ¼ 3,4-methylenedioxyphenyl, R ¼ CH3;
m.p. ¼ 184e185 ꢁC; yield 69%; CHN analysis e Found: C:
53.35, H: 3.57, N: 17.21; Calculated: C: 53.44, H: 3.64, N:
17.28; IR (KBr) (sydnone) 1789 cmꢀ1, nCO (triazinone)
1686 cmꢀ1, nCeO (eCH2eCOe) 1636 cmꢀ1; Mass: m/z, 494
(MF: C22H18N6O6S).
References
[1] D. Niccolai, L. Tarsi, R.J. Thomas, Chem. Commun. (1997) 2333e2342.
[2] D.T.W. Chu, J.J. Plattner, L. Kats, J. Med. Chem. 39 (1996) 3853e3874.
[3] S.G. Mallur, B.V. Badami, Il Farmaco 55 (1) (2000) 65e67.
[4] M.A. Moustafa, M.N. Nasr, M.M. Gineinah, W.A.H. Bayoumi, Arch.
Pharm. Pharm. Med. Chem. 337 (2004) 164e170.
[5] M.A. Moustafa, M.N. Nasr, M.M. Gineinah, W.A.H. Bayoumi, Arch.
Pharm. Pharm. Med. Chem. 337 (2004) 427e433.
[6] C.S. Dunkley, C.J. Thoman, Bioorg. Med. Chem. Lett. 13 (2003)
2899e2901.
Compound 5j: Ar ¼ phenyl, R ¼ OCH3; m.p. ¼ 175e
176 ꢁC; yield 69%; CHN analysis e Found: C: 54.15, H:
3.92, N: 18.13; Calculated: C: 54.07, H: 3.86, N: 18.02; IR
[7] A.M. Abdel-Halim, Z. El-Gendy, R.M. Abdel-Rahman, Pharmazie 50
(1995) 726e729.
[8] M. Kidwai, R. Kumar, A. Srivastava, H.P. Gupta, Bioorg. Chem. 26
(1998) 289e294.
[9] B.S. Holla, M.K. Shivananda, B. Veerendra, B.K. Subramanya, Indian J.
Chem. 42B (2003) 2649e2651.
(KBr): nCO (sydnone) 1793 cmꢀ1
,
nCO (triazinone)
1683 cmꢀ1, nCeO (eCH2eCOe) 1631 cmꢀ1; Mass: m/z, 466
(MF: C21H18N6O5S).
[10] B. Kalluraya, A.M. Rahiman, Pol. J. Chem. 71 (1997) 1049.
[11] B. Kalluraya, A.M. Rahiman, D. Banji, Arch. Pharm. Pharm. Med.
Chem. 334 (2001) 263e268.
Compound
5k:
Ar ¼ p-bromophenyl,
R ¼ OCH3;
m.p. ¼ 194e195 ꢁC; yield 71%; CHN analysis e Found: C:
56.26, H: 3.03, N: 15.49; Calculated: C: 56.32, H: 3.12, N:
15.44; IR (KBr): nCO (sydnone) 1779 cmꢀ1, nCO (triazinone)
[12] B.S. Furniss, A.J. Hannaford, P.W.G. Smith, Vogel’s Text Book of
Organic Chemistry, fifth ed. Longman Group Limited, London, 1989,
p. 1155 (Chapter 8).
1680 cmꢀ1, nCeO (eCH2eCOe) 1625 cmꢀ1
;
1H NMR
[13] C.Y. Gerco, J. Tobias, L.B. Kier, J. Heterocycl. Chem. 4 (1967) 160.
[14] Z.K. Khan, In vitro and vivo screening techniques for bioactivity screen-
ing and evaluation, Proceedings of the International Workshop, UNIDO e
CDRI, 1997, p. 210.
300 MHz, CDCl3: d: 3.81 (s, 3H, OeCH3), d: 4.3 (s, 2H,
CH2), d: 4.58 (s, 2H, SeCH2), d: 4.89 (s, 2H, NH2), d:
6.93e7.88 (m, 8H, AreH); Mass: m/z, 544/546 (MF:
C21H17BrN6O5S).
[15] R.S. Verma (Ed.), Antifungal Agents: Past, Present and Future Prospec-
tus, National Academy of Chemistry and Biology, Lucknow, India, 1998.
[16] B.S. Holla, R. Gonsalves, B.K. Sarojini, Indian J. Chem. 36B (1997)
943e946.
Compound
5l:
Ar ¼ p-chlorophenyl,
R ¼ OCH3;
m.p. ¼ 196e197 ꢁC; yield 66%; CHN analysis e Found: C: