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NEW ANILIDES AS POTENTIAL
ANTIMICROBIAL AGENTS. NOTE 1
ILEANA CHIRIŢĂ1, AL. MISSIR1, CAMELIA ELENA STECOZA1, CARMEN
LIMBAN1, G. M. NIŢULESCU1, DIANA NUŢĂ1, L. MORUŞCIAG1,
CARMELLINA BĂDICEANU1, CORINA ILIE2, M.T. CĂPROIU3
1
Department of Pharmaceutical Chemistry, University of Medicine and
Pharmacy “Carol Davila”, Bucharest, Traian Vuia 6, sect. 2, 020956,
Romania
2
National Institute of Chemical and Pharmaceutical Research and
Development, Bucharest, Calea Vitan 112, sect.3, Romania
3
The Organic Chemistry Center of Romanian Academy "Costin C.D.
Nenitescu” Bucharest, Splaiul Independentei, 202B, 77208, Romania
Abstract
Based on our experience in the synthesis of N-(2-dialkylaminoethyl)benzanilides with antimicrobial effect, we developed some new compounds, amides of 2phenylthiomethyl-benzoic acid. These new substances were characterized by their physicochemical properties and by elemental analysis and spectrometric measurements: IR, 1HNMR and 13C-NMR.
Rezumat
Având în vedere experienţa noastră în sinteza N-(2-dialchilaminoetil)
benzanilidelor cu efecte antimicrobiene, am obţinut noi compuşi, amide ale acidului 2feniltiometil-benzoic. Noile amide au fost caracterizate prin proprietăţile lor fizico-chimice
şi prin analiză elementală şi spectrală: IR, 1H-RMN şi 13C-RMN.


amides of 2-phenylthio-methyl-benzoic acid
antimicrobial activity
INTRODUCTION
In the therapeutic field there are many amidic substances used as
germicides and fungicides. They have a higher skin retention time, even
after several washes with water and soap. These substances can be
incorporated in detergents or soaps, and also in plastic or rubber materials
used for toys manufacturing, food packing, single use dishes, thus
contributing to these products sterilization.
In previous papers [1- 3] we presented the synthesis of some
benzanilides with similar structures, having powerful bactericidal effect
against S. aureus and antifungal action against C. albicans.
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We continued our researches and there were synthesized new
amides of 2-phenylthiomethyl-benzoic acid with the general formula:
CH2-S
R= ethyl
R'= -H, -Cl
R1= -H, -CH3, -OCH3
R1
CO-N-CH2CH2-N(R)2
R'
MATERIALS AND METHODS
In order to obtain the new compounds (1a-e) we followed four
steps. The reactions are presented in Scheme 1 and Scheme 2.
- synthesis of the 2-phenylthiomethyl-benzoic acids (2a-c)
- synthesis of the mentioned acid chlorides (3a-c)
- synthesis of the N-(2-dialkylaminoethyl)-anilines (4a, 4b)
- synthesis of the original amides (hydrochlorides) (1a-e)
O
C
CH2OH
Zn; NaOH
-NH3
NH
C
CH2OH
H Cl
COO-Na+
-NaCl
COOH
O
HCl
-H2O
CH2
R1
HS
CH2-S
O
C
KOH
- +
COO K
O
CH2-S
COOH
2a R1= H
2b R1= -OCH3
2c R1= -CH3
SOCl2
H Cl
R1
-KCl
CH2-S
R1
COCl
R1
3a R1= H
3b R1= -OCH3
3c R1= -CH3
Scheme 1
Synthesis of the the 2-phenylthiomethyl-benzoic acids (2a-c)
and their acid chlorides (3a-c)
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NH2
+ Cl
Cl-CH2-CH2-NH(C2H5)2
R'
NH-CH2CH2-N(C2H5)2
R'
4a R'= H
4b R' = Cl
5a R'= H
5b R' = Cl
CH2-S
CH2-S
1) +
3a-c
COCl
2) + HCl (Et2O)
R1
R1
+
CO-N-CH2CH2-N(C2H5)2
H Cl
R'
1a: R1=H; R'=Cl
1b: R1=H; R'=H
1c: R1=-OCH3; R'=Cl
1d: R1=-CH3; R'=Cl
1e: R1=-CH3; R'=H
Scheme 2
Synthesis of the N-(2-dialkylaminoethyl)-anilines (4a, 4b)
and of the original amides (1a-e)
According to the methods described in the literature, the phtalide
was prepared by reducing the phtalimide with copper-activated zinc in
alkaline medium, because the method has good yields and goes without
secondary products and the resulted compounds have desired purity [4].
The acids 2a-c resulted by phtalide condensation with a suspension
of potassium salt of the corresponding thiophenolate, that have a good
solubility in water and can be easily separated from xylene used as reaction
solvent. The acids precipitate after treating the reaction mixture with a
diluted hydrochloric acid solution [5].
The acid chlorides 3a-c resulted by treating the mentioned acids 2a-c
with thionyl chloride in excess.
The amines 4a-b were obtained by alkylation of corresponding anilines
5a-b with N-(2-chloroethyl)-N,N-diethylamine hydrochloride, in anhydrous
toluene, using sodium carbonate as hydrochloric acid acceptor [1, 2, 6].
The new amides resulted by coupling the acid chlorides 3a-c with
the anilines (4a, 4b) in anhydrous toluene in the presence of a base
(triethylamine). These amides were converted to the corresponding
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hydrochlorides (1a-e) by treating the etheric solution of amides with ethereal
hydrochloric acid, using a low temperature, under 5oC [1, 2, 6].
The synthesized compounds were characterized to establish their
structure and purity, using the FT-IR, 1H-NMR and 13C-NMR spectrometry.
The 1H-NMR and 13C-NMR spectra were registered with a Varian-Gemini300 BB spectrometer operating at 300.075 MHz for proton and 75.462 MHz
for carbon and an UNITY 400 plus, operating at 400 MHz for proton and
100 MHz for carbon. As solvents were used:
- deuterochloroform with a min. 99% isotopic purity;
- perdeuterated dimethylsulfoxyde with a min. 98% isotopic purity;
- trifluoroacetic acid with 99% purity.
Chemical shifts were recorded as δ values in parts per million
(ppm) relative to tetramethylsilane as internal standard. Multiplicities are
given together with the coupling constants (in Hz). The spectra were
recorded at 20oC ± 1 temperature. In order to perform the right attribution of
the signals, we used different techniques to simplify the spectra, like the
homonuclear decoupling and the specific deuteration. In some cases the
APT and COSY spectra were needed. The spectral assignments were
performed according to the general structure:
R1
20
CH2-S
16
17
18
26 25
21 24
22 23
15
19
14
11
13
7
9
8
10
CO-N-CH2-CH2-N
12
CH2-CH3
11'
12'
CH2-CH3
6
1
5 4
2
3
R'
The FT-IR spectra were recorded with a BRUKER Vertex-70
apparatus with an optical system with diamond. The ATR technique in the
solid phase was used and each spectrum is a result of 32 independent scans.
The melting points were measured in glass capillary tubes, using an
Electrothermal 9100 digital apparatus and are uncorrected.
RESULTS AND DISCUSSION
The synthesis of phtalide was performed according to the method
described in previous paper [4].
The synthesis of the 2-phenylthiomethyl-benzoic acid (2a), 2-(4methoxy-phenylthiomethyl)-benzoic
acid
(2b)
and
2-(4-methylphenylthiomethyl)-benzoic acid (2c) [5, 7].
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
2-Phenylthio-methyl-benzoic acid (2a)
In a round–bottom flask, equipped with water removing device is
dissolved 0.05 mol thiophenol in 30 mL xylene and 0.055 mol of potassium
hydroxide are added. The reaction mixture is refluxed until 0.9 mL resulting
water is removed by azeotropic distillation, while potassium thiophenolate
precipitates; 0.05 mol of phtalide are added and the mixture is refluxed until
it solidifies. The precipitate is dissolved in 10% potassium hydroxide and
than is diluted with 50 mL water.
The aqueous phase is separated and acidulated with 1M
hydrochloric acid (pH=3), when 2-phenylthiomethyl-benzoic acid (2a)
precipitates. The resulting product is purified from ethanol:water (3:1); acid
2a is obtained as crystalline powder, with m.p. 109-111oC (75% yield).
Similarly to the previous case, using 4-methoxy-thiophenol or 4methyl-thiophenol, the following acids were obtained:
 2-(4-Methoxy-phenylthiomethyl)-benzoic acid (2b), white crystals,
m.p. 133-135oC (ethanol: water= 3:1) (81% yield).
 2-(4-Methyl-phenylthiomethyl)-benzoic acid (2c), white crystals,
m.p. 124-126oC (ethanol: water= 3:1) (71% yield).
The synthesis of chlorides of 2-phenylthiomethyl-benzoic acid (3a),
2-(4-methoxy-phenylthiomethyl)-benzoic acid (3b) and 2-(4-methylphenylthiomethyl)-benzoic acid (3c) [5]
In a round–bottom flask, equipped with condenser and drying tube
is placed a mixture of the acid (2a-2c) and thionyl chloride, in molar ratio
1:10; the mixture was refluxed for 90 minutes, then the thionyl chloride was
removed under reduced pressure and the crude chlorides 3a-3c were
obtained and were used without any purification in the next step of
synthesis.
The synthesis of N-(2-diethylaminoethyl)-anilines (4a, 4b).
These amines were obtained using the methods described in our
previous paper [5].
The synthesis of the original amidic compouns (1a-e)
N-(2-diethylaminoethyl)-N-phenyl-2-(phenylthiomethyl)benzamide hydrochloride (1a)
To a stirred solution of 1.45g (0.00633 mol) N-(2diethylaminoethyl)-3-chloraniline (5b) and 1.11g (1.5 mL) (0.011 mol)
triethylamine in 20 mL dry toluene is added 2.5g (0.0095 mol) 2phenylthiomethyl-benzoic acid chloride (3a). The mixture is refluxed for
10h. After cooling at room temperature and filtering the triethylamine
hydrochloride, the toluene is evaporated in vacuum with a rotary evaporator;
FARMACIA, 2008, Vol.LVI, 5
537
the residue is taken up in 30 mL chloroform and it is washed with 10%
sodium carbonate solution (3x50 mL) and then with water. The chloroform
solution is dried on anhydrous sodium sulfate and then the solvent is
evaporated under vacuum. The resulting basic amide is brown-yellow oil,
which was transformed in the corresponding hydrochloride by treating the
etheric solution of basic amide with a saturated solution of hydrochloric acid
in anhydrous ether which is dropwise added. Thus was obtained a white
crystaline compound, m.p. 118-120oC (acetone) (75% yield).
TLC: single spot Rf=0.75 (eluent chloroform: methanol=4:1,
developing system: UV, iodine atmosphere)
Elemental analysis: N% theoretical/experimental 5.72/5.78
1
H-RMN(dmso-d6, δ ppm, J Hz): 11.29(bs, 1H, HN+); 7.45-7.90(m, 14H,
Harom); 4.41(s, 2H, H-20); 4.30(bs, 2H, H-8); 3.25(bs, 2H, H-9); 3.12(bs,
4H, H-11-11’); 1.20(bs, 6H, H-12-12’).
13
C-RMN(dmso-d6, δ ppm): 169.19(C-13); 141.94(Cq); 136.01(Cq);
135.37(Cq); 134.80(Cq); 130.03(CH); 129.12(CH); 128.73(CH);
128.72(CH); 128.27(CH); 127.67(CH); 127.31(CH); 126.36(CH);
126.07(CH); 126.06(CH); 46.61(C-9); 46.50(C-11-11’); 43.78(C-8);
34.29(C-20); 8.38(C-12-12’).
IR(ATR in solid, cm-1): 3422; 3051; 2947; 2881; 2648; 2494; 1745; 1718;
1631; 1588; 1486; 1439; 1382; 1320; 1282; 1224; 1229; 1090; 1025; 908;
775; 736; 698; 654; 607; 528; 478; 445; 420.
All the original amides (hydrochlorides) 1b-e were obtained using
the same method of synthesis, and they are presented as it follows:
N-(2-diethylaminoethyl)-N-phenyl-2-(phenylthiomethyl)benzamide hydrochloride (1b)
- white crystals, m.p. 88-91oC (ethanol abs.) (70% yield).
- TLC: single spot Rf=0.8 (the same visualisation)
- elemental analysis: N% t/e: 6.16/6.25
1
H-RMN(dmso-d6, δ ppm, J Hz): 11.29(bs, 1H, HN+); 7.45-7.90(m, 14H,
Harom); 4.41(s, 2H, H-20); 4.30(bs, 2H, H-8); 3.25(bs, 2H, H-9); 3.12(bs,
4H, H-11-11’); 1.20(bs, 6H, H-12-12’).
13
C-RMN(dmso-d6, δ ppm): 169.19(C-13); 141.94(Cq); 136.01(Cq);
135.37(Cq); 134.80(Cq); 130.03(CH); 129.12(CH); 128.73(CH);
128.72(CH); 128.27(CH); 127.67(CH); 127.31(CH); 126.36(CH);
126.07(CH); 126.06(CH); 46.61(C-9); 46.50(C-11-11’); 43.78(C-8);
34.29(C-20); 8.38(C-12-12’).
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IR(ATR in solid, cm-1): 3422; 3051; 2947; 2881; 2648; 2494; 1745; 1718;
1631; 1588; 1486; 1439; 1382; 1320; 1282; 1224; 1229; 1090; 1025; 908;
775; 736; 698; 654; 607; 528; 478; 445; 420.
N-(2-diethylaminoethyl)-N-(3-chlorophenyl)-2-(4-methoxyphenylthiomethyl)-benzamide hydrochloride (1c)
- yellow crystals, m.p. 94-96oC (chromatografic purification,
chloroform/methanol 4:1 eluent) (35% yield).
- TLC: single spot Rf=0.76 (the same visualisation)
- elemental analysis: N% t/e: 5.39/5.28
1
H-RMN(dmso-d6, δ ppm, J Hz): 7.62(bs, 1H, H-27.32(d, 2H, H-22-26,
8.7); 6.95-7.30(m, 7H, Harom); 6.91(d, 2H, H-23-25, 8.7); 4.27(s, 2H, H-20);
4.27(s, 2H, H-8); 3.75(s, 3H, H-27); 3.29(bs, 2H, H-9); 3.15(bs, 4H, H-1212’); 1.21(bs, 6H, H-12-12’).
13
C-RMN(dmso-d6, δ ppm): 170.21(C-13); 158.63(C-24); 143.42(C-1);
137.35(Cq); 136.22(Cq); 134.18(Cq); 132.35(CH); 132.34(C-22-26);
130.59(CH); 130.21(CH); 129.27(CH); 127.71(CH); 127.40(CH);
126.52(CH); 125.54(CH); 125.27(Cq); 114.82(C-23-25); 55.25(C-27);
46.84(C-9); 46.46(C-11-11’); 44.08(C-8); 36.49(C-20); 8.45(C-12-12’).
IR(ATR in solid, cm-1): 3411; 3052; 2977; 2944; 2905; 2833; 2354; 1626;
1586; 1472; 1387; 1311; 1289; 1245; 1170; 1123; 1099; 1027; 887; 861;
828; 784; 760; 719; 686; 628; 523; 495; 444.
N-(2-diethylaminoethyl)-N-(3-chlorophenyl)-2-(4-methylphenylthiomethyl)-benzamide hydrochloride (1d)
- white-yellow crystals, m.p. 114-116oC (ethyl ether) (80% yield).
- TLC: single spot Rf=0.72 (the same visualisation)
- elemental analysis: N% t/e: 5.56/5.64
1
H-RMN(dmso-d6, δ ppm, J Hz): 11.15(bs, 1H, H-N+); 7.53(bs, 1H, H-2);
7.28(d, 2H, H-22-26, 8.1); 7.14(d, 2H, H-23-25, 8.1); 6.95-7.35(m, 7H,
Harom); 4.34(s, 1H, H-20); 4.27(bs, 2H, H-8); 3.27(bs, 2H, H-9); 3.16(bs,4H,
H-11-11’); 2.26(s, 3H, H-27); 1.22(bs, 6H, H-12-12’).
13
C-RMN(dmso-d6, δ ppm): 169.12(C-13); 147.62(Cq); 139.56(Cq);
135.85(Cq); 133.18(Cq); 132.01(Cq); 130.55(CH); 130.16(CH); 129.77(C22-26); 129.77(CH); 129.32(CH); 129.13(C-23-25); 128.63(CH);
127.70(CH); 127.38(CH); 126.52(CH); 126.42(Cq); 46.79(C-9); 46.45(C11-11’); 44.05(C-8); 34.92(C-20); 20.56(C-27); 8.42(C-12-12’).
IR(ATR in solid, cm-1): 3052; 2979; 2881; 2336; 1626; 1587; 1491; 1474;
1442; 1392; 1321; 1244; 1177; 1122; 1101; 1078; 1034; 1017; 890; 839;
803; 784; 763; 751; 721; 692; 675; 625; 491.
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539
N-(2-diethylaminoethyl)-N-phenyl-2-(4-methyl-phenylthiomethyl)benzamide hydrochloride (1e)
-white-yellow crystals, m.p. 94-97oC (anhydrous toluene) (60% yield).
- TLC: single spot Rf=0.78 (the same visualisation)
- elemental analysis: N% t/e: 5.97/6.10
1
H-RMN(dmso-d6, δ ppm, J Hz): 7.32(d, 1H, H-19, 7.2); 7.27(d, 2H, H-2226, 8.0); 7.14(d, 2H, H-23-25, 8.0); 7.01(dl, 1H, H-16, 6.8); 6.95(t, 1H, H17, 6.8); 7.34-7.07(m, 6H, H-2÷6, H-18); 4.34(s, 2H, H-20); 4.22(tl, 2H, H8, 5.8); 3.28(tl, 2H, H-9, 5.8); 3.16(ql, 4H, H-11-11’, 6.3); 2.26(s, 3H, H27); 1.19(t, 6H, H-12-12’, 6.3).
13
C-RMN(dmso-d6, δ ppm): 169.44(C-13); 142.07(Cq); 135.90(Cq);
135.77(Cq); 134.72(Cq); 132.23(Cq); 130.15(CH); 129.85(CH);
129.24(CH); 129.15(CH); 129.11(CH); 128.82(CH); 127.71(CH);
127.43(CH); 126.36(CH); 46.85(C-9); 46.70(C-11-11’); 43.95(C-8);
35.03(C-20); 20.64(C-24); 8.52(C-12-12’).
IR(ATR in solid, cm-1): 3369; 2986; 2943; 2884; 2392; 1634; 1590; 1492;
1449; 1419; 1383; 1306; 1276; 1231; 1173; 1124; 1090; 1031; 896; 799;
769; 733; 697; 647; 612; 582; 486.
The antimicrobial activity [8] of these new benzamides showed a
good action, all amides being active against the reference strains and also
against gram-negative clinical strains; all of them exhibit antifungal activity.
CONCLUSIONS
In this paper we presented the synthesis of new amides of 2phenylthiomethyl-benzoic acid, using the optimized synthesis methods. The
compounds were physico-chemical characterized and their structure and
purity were established using the elemental analysis, TLC method and 1HNMR, 13C-NMR and IR spectral analysis. The antimicrobial tests confirmed
that these amides have a significant bactericidal and antifungal action.
The present research was financed by research contract CEEX 85/2006
between University of Medicine and Pharmacy “Carol Davila” and The
Medical Science Academy, the authority of Programme “Excellence
Research Projects”.
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