Synthesis, spectroscopic and biological properties of bis(3- arylimidazolidinyl-1)methanes. A novel family of antimicrobial agents

Article abstract of DOI:10.1016/j.ejmech.2005.03.010

Synthesis, spectroscopic and biological properties of new bis(3-arylimidazolidinyl-1)methanes are described. These compounds were synthesized by condensation reaction between N-arylethylenediamines and formaldehyde. Chemical structures were confirmed by means of their ¹H- and ¹³C-NMR and mass spectroscopic data. Investigation of in vitro antimicrobial activity was performed using Gram-negative and Gram-positive bacteria as well as antifungal studies against Aspergillus niger and Candida albicans. Minimal inhibitory concentrations of active compounds were determined.

Full text of DOI:10.1016/j.ejmech.2005.03.010

European Journal of Medicinal Chemistry 40 (2005) 811–815
www.elsevier.com/locate/ejmech
Original article
Synthesis, spectroscopic and biological properties
of bis(3-arylimidazolidinyl-1)methanes.
A novel family of antimicrobial agents
Isabel Perillo a,*, Evangelina Repetto a, María Cristina Caterina a, Rosana Massa b,
Gabriel Gutkind b, Alejandra Salerno a
a Department of Organic Chemistry, Faculty of Pharmacy and Biochemistry, University of Buenos Aires, Junín 956 (1113) Buenos Aires, Argentina
b Department of Microbiology, Immunology and Biotechnology, Faculty of Pharmacy and Biochemistry, University of Buenos Aires,
Junín 956 (1113) Buenos Aires, Argentina
Received 6 December 2004; received in revised form 2 March 2005; accepted 7 March 2005
Available online 04 May 2005
Abstract
Synthesis, spectroscopic and biological properties of new bis(3-arylimidazolidinyl-1)methanes are described. These compounds were
synthesized by condensation reaction between N-arylethylenediamines and formaldehyde. Chemical structures were confirmed by means of
their 1H- and 13C-NMR and mass spectroscopic data. Investigation of in vitro antimicrobial activity was performed using Gram-negative and
Gram-positive bacteria as well as antifungal studies against Aspergillus niger and Candida albicans. Minimal inhibitory concentrations of
active compounds were determined.
© 2005 Published by Elsevier SAS.
Keywords: Imidazolidines; Bis(3-arylimidazolidinyl-1)methanes; Aminals; Antimicrobial activity
1. Introduction
In this work we present the synthesis of a series of unpub-
lished bis(3-arylimidazolidinyl-1)methanes 1a–j (Table 1)
obtained by reaction of N-arylethylenediamines 2 with an
excess of formaldehyde, their spectroscopic characterization
and microbiological assays which prove their bioactivity.
Compounds 1 are representative of a group of aminals char-
acterized by the presence of two saturated 1,3-azole ring con-
nected by a methylene bridge, some of them having antimi-
crobial activity [10].
Tetrahydroimidazoles (imidazolidines) result interesting
compounds due to their bioactivity, such as strogenic activity
[1] and mammary tumor inhibition [2], anti inflammatory and
analgesic activity [3]. Fungicide, bactericide and antiviral
activities had also been reported [3,4]. On the other hand,
they had been employed as carriers of pharmacologically
active ethylenediamines [5,6] or carbonyl compounds [7].
Stable 1,3-disubstituted imidazolidines are obtained from
N,N′-disubstituted ethylenediamines and aldehydes, what-
ever substituents are present in reactants [8]. Instead, in the
reaction of N-monosubstituted ethylenediamines with two or
more carbon aldehydes, the obtained imidazolidine is part of
a tautomeric equilibria with the corresponding aminoimine
(being one or both species detected by 1H-NMR) [8a,9]. To
our knowledge, there are no precedent studies of reaction
between N-monosubstituted ethylenediamines and formalde-
hyde.
2. Chemistry
Bis(3-arylimidazolidinyl-1)methanes 1a–j were synthe-
sized by condensation of N-arylethylenediamines 2 with an
excess aqueous formaldehyde (37%) in ethanol under reflux.
Precursors N-arylethylenediamines 2 were prepared by ami-
nolysis of 2-bromoethylamine (hydrobromide) with the cor-
responding arylamine (Fig. 1) [11].
Attainment of bis(3-arylimidazolidinyl-1)methanes 1 may
be considered as a result of the condensation between
* Corresponding author.
E-mail address: iperillo@ffyb.uba.ar (I. Perillo).
0223-5234/$ - see front matter © 2005 Published by Elsevier SAS.
doi:10.1016/j.ejmech.2005.03.010

812
I. Perillo et al. / European Journal of Medicinal Chemistry 40 (2005) 811–815
Table 1
Melting points, yields (%) and molecular formula of bis (3-arylimidazolidinyl-1)methanes 1a–j
Compound
Ar
M.p. (°C)
141–143
138–140
144–146
190–192
153–155
191–193
178–180
131–133
138–140
192–194
Yield (%)
Molecular formula
1a
1b
1c
1d
1e
1f
1g
1h
1i
C6H5
78
75
84
79
81
85
79
86
89
87
C
C
C
C
C
C
C
C
C
C
19H24N4
4-CH3C6H4
4-CH3OC6H4
4-ClC6H4
3,4-Cl2 C6H3
4-NO2C6H4
4-BrC6H4
3-ClC6H4
3-BrC6H4
b-C10H7
21H28N4
21H28N4O2
19H22Cl2N4
19H20Cl4N4
19H22N6O4
19H22Br2N4
19H22Cl2N4
19H22Br2N4
27H28N4
1j
N-arylethylenediamines and formaldehyde which leads to
aminoimines 3. When aryl substituents allow subsequent
cyclization, NH imidazolidines 3 should be obtained, which
by intermolecular condensation with formaldehyde should
lead to bisimidazolidines 1 as final products. When at least
one of the ortho positions of the arylamine is substituted
(2-NO2, 2-Cl, 2-CH3), cyclization reaction does not occur,
and final products are the corresponding aminoimines 3
(Fig. 1).
The basic structures of compounds 1 were confirmed by
1H-NMR and 13C-NMR spectral data (Table 2). Assignment
of signals was performed by comparison with spectra of prop-
erly 1,3-disubstituted imidazolidines [12–14].
4. Results and discussion
Ten compounds (1) were screened for their antimicrobial
activity. Respect to antifungal activity, results shown that all
compounds were inactive frente a Candida albicans.
However, all derivatives resulted effective against Aspergil-
lus niger, being compounds 1a (MIC 16 ug/ml), 1e (MIC
4 ug/ml) and 1b (MIC 1 ug/ml) the most active. A moderate
activity (MIC 16–32 ug/ml) was observed for compounds 1c,
d, f–i.
All synthesized compounds showed antibacterial activity
against Escherichia coli, Micrococcus luteus, Bacillus sub-
tilis, Listeria monocytogenes, Pseudomonas aeruginosa and
Staphylococcus aureus. Compounds 1e and 1f proved to be
the most active for E. coli and M. luteus, respectively. Such
activity may be associated to the bactericidal action of related
compounds, due to a potential capability to liberate formal-
dehyde. Compounds of general formula A such as methylene-
bis heterocycles (A, Y = alkylene, arylene, etc.; X = O, S)
were described with bactericidal and fungicidal activity [10].
In particular, bis(5-methy1,3-oxazolidin-3-yl)methane (A,
Y = CH2–CH(CH3), X = O) was proposed as fungicide for
lubricants and starch pastes [10b].
Excepting compounds 1f and 1i, mass spectra of all com-
pounds display the molecular ion peak, having generally low
intensity. The main fragments as well as their relative inten-
sities are given in Table 3. The probable fragmentation path-
ways are depicted in Fig. 2.
3. Pharmacology
Screening of in vitro antimicrobial activity of the synthe-
sized bis(3-arylimidazolidinyl-1)methanes 1 was performed
using the disk diffusion method employing representative
Gram-positive and Gram-negative bacteria, and filamentous,
fungi and yeasts. Those compounds which presented any inhi-
bition zone were evaluated by their minimal inhibitory con-
centration (MIC) using the dilution technique. Results are
shown in Table 4.
An analogous compound, taurolidine (bis-(1,1-
dioxoperhydro-1,2,4-thiazinyl-4)-methane) (A, X = NH, Y
= SO2CH2CH2) showed an important activity against P.
aeruginosa, E. coli, Proteus vulgaris and Salmonella typh-
imurium [15]. Such activity is based in the capability of this
compound to act as carrier of non-toxic formaldehyde, donat-
ing methylol groups to bacterial proteins and endotoxins [16]
causing their denaturalization and poly-condensation. Re-
cently, interest for this compound in prevention and treat-
ment of infections related to intravascular catheterization has
grown up [17].
Fig. 1. Synthetic pathways to compound 1.

Table 2
1H- and 13C-NMR data of compounds 1a–j
1H-NMR (d ppm) (J = Hz)
13C-NMR (d ppm)
Compound
A
B
C
D
Aromatics
others
A
B
C
D
Aromatics
others
1a
4.16, s
3.13, t
3.43, t
3.46, s
6.50 (d, 4H) J = 7.68
69.0
50.9
45.6
74.4
111.7, 113.8, 129.2, 146.5
J = 6.31 J = 6.31
6.71 (t, 2H) J = 7.12
7.24 (dd, 4H) J1 = 7.68, J2 = 7.12
6.47 (d, 4H) J = 8.43
1b
1c
1d
1e
4.14, s
4.12, s
4.11, s
4.10, s
3.12, t
J = 6.37 J = 6.37
3.12, t 3.37, t
J = 6.36 J = 6.36
3.12, t 3.37, t
J = 6.27 J = 6.27
3.12, t 3.36, t
J = 6.18 J = 6.18
3.39, t
3.46, s
3.47, s
3.44, s
3.43, s
2.25, s
CH3
69.3
69.7
69.0
68.8
50.9
50.9
50.8
50.7
45.9
46.4
45.8
45.7
74.6
74.7
74.1
73.1
111.8, 125.5, 129.7, 144.6
112.7, 114.9, 141.5, 151.3
112.6, 121.2, 129.0, 145.2
20.2
7.04 (d, 4H) J = 8.43
CH3
55.8
6.50 (dd, 4H) J1 = 6.80, J2 = 2.30
6.83 (dd, 4H) J1 = 6.80, J2 = 2.30
6.43 (d, 4H) J = 8.90
3.75, s
OCH3
OCH3
7.17 (d, 4H) J = 8.90
6.33 (dd, 2H) J1 = 8.72, J2 = 2.80
6.56 (s, 2H)
111.2, 112.9, 119.0, 130.5,
132.8, 145.6
7.23 (d, 2H) J = 8.72
1f
4.25, s
4.10, s
4.13, s
3.19, t
J = 6.41 J = 6.41
3.11, t 3.36, t
J = 6.40 J = 6.40
3.12, t 3.39, t
J = 6.37 J = 6.37
3.52, t
3.52, s
3.45, s
3.44, s
6.44 (d, 4H) J = 9.32
68.5
68.9
68.8
50.5
50.8
50.7
45.6
45.7
45.6
73.3
74.1
74.0
110.3, 126.3, 137.1, 150.3
111.5, 113.2, 131.8, 145.3
8.13 (d, 4H) J = 9.32
1g
1h
6.49 (d, 4H) J = 8.71
7.26 (d, 4H) J = 8.71
6.36 (dd, 2H) J1 = 8.30, J2 = 1.97
6.48 (s, 2H)
109.8, 111.5, 116.2, 130.1,
135.0, 147.3
6.67 (dd, 2H) J1 = 7.18, J2 = 1.97
7.12 (t, 2H) J = 8.10
1i
Ij
4.12, s
4.30, s
3.11, t
3.38, t
3.43, s
3.58, s
6.42 (dd,2H) J1 = 7.95, J2 = 2.25
6.64 (t, 2H) J = 2.25
68.8
69.2
50.7
50.9
45.5
45.9
74.0
74.2
110.2, 114.3, 119.1, 123.3,
130.4, 147.4
J = 6.42 J = 6.42
6.81 (dd, 2H) J1 = 7.69, J2 = 2.25
7.06 (t, 2H) J = 7.95
3.20, t
3.54, t
6.74 (d, 2H) J = 2.20
105.5, 115.3, 121.7, 125.2,
125.8, 126.3, 127.6, 129.0,
135.0, 144.3
J = 6.45 J = 6.45
6.90 (dd, 2H) J1 = 9.06, J2 = 2.20
7.20 (t, 2H) J = 6.90
7.37 (td, 2H) J1 = 6.90, J2 = 1.30
7.60-7.75 (m, 6H)

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I. Perillo et al. / European Journal of Medicinal Chemistry 40 (2005) 811–815
Table 3
Select fragments in the EI mass spectra of compounds 1a–j
Compound
M+•
A
B a
C b
D
E
F
Others
1a
1b
1c
1d
308 (24.4)
336 (55.5)
368 (7.9)
376 (0.6)
378 (0.4)
444 (0.02)
446 (0.04)
448 (0.01)
398 (–)
161 (100)
175 (100)
191 (100)
195 (100)
197 (32.2)
229 (58.1)
231 (43.9)
162 (55.5)
176 (22.2)
192 (10.5)
196 (31.4
)198 (9.1)
230 (100)
232 (56.4)
148 (34.4)
162 (27.8)
178 (25.5)
182 (–)
147 (41.1)
161 (28.6)
177 (27.4)
181 (40.8)
183 (12.5)
215 (17.1)
217 (14.6)
106 (33.3)
120 (13.5)
136 (18.8)
140 (25.1)
142 (7.8)
174 (53.2)
176 (34.0)
56 (12.2)
56 (8.4)
56 (12.1)
56 (11.3)
107 (28.5)
121 (10.6)
137 (21.1)
184 (–)
1e
1f
216(31.3)
218 (19.2)
56 (25.8)
56 (–)
43 (19.0)
206 (3.4)
207 (4.9)
193 (24.2)
192 (17.4)
151 (100)
43 (74.7)
105 (42.7)
194 (41.6)
160 (16.5)
1g
464 (0.03)
466 (0.13)
468 (0.02)
376 (1.7)
378 (0.7)
464 (–)
239 (100)
241 (94.1)
240 (31.5
242 (–) c
226 (12.8
228 (10.0)
225 (27.2)
227 (21.1)
184 (37.4)
186 (37.0)
56 (37.8)
1h
1i
195 (64.7)
197 (29.3)
239 (100)
241 (97.2)
196 (100)
198 (30.8)
240 (–) d
182 (–)
181 (46.0)
183 (14.2)
225 (42.3)
227 (26.4)
140 (4.4)
142 (1.6)
184 (51.2)
186 (53.0)
56 (7.8)
184 (–)
226 (25.8)
228 (16.6)
56 (11.9)
466 (–)
242 (12.0)
468 (–)
1j
408 (0,9)
211 (100)
212 (30.2)
198 (36.9)
197 (52.9)
156 (93.3)
56 (11.0)
127 (15.7)
a This ion has the same mass that the isotopic peak of A.
b This ion has the same mass that the isotopic peak of D.
c The absence of m/z 242 indicates that m/z peak 240 do not correspond to B ion.
d The absence of m/z 240 indicates that m/z peak 242 do not correspond to B ion.
5. Experimental protocols
(dd) and triplet (t). Mass spectra (EI) were recorded with a
GC–MS Shimadzu QP-1000 spectrometer operating at 20 eV.
Microanalytical data (C, H, N) agreed with the proposed struc-
tures within 0.4% of the theoretical values. TLC analyses
5.1. Chemistry
Melting points were determined with a Büchi capillary
apparatus and are uncorrected. NMR spectra were recorded
on a Bruker MSL 300 MHz spectrometer using deuteriochlo-
roform as the solvent. Chemical shifts are reported in ppm
relative to TMS as an internal standard. Splitting multiplici-
ties are reported as singlet (s), doublet (d), double doublet
were carried out on aluminum sheets silica gel 60 F254
.
5.1.1. Bis(3-arylimidazolidinyl-1)methanes 1a–j.
General procedure
Aqueous formaldehyde (3 mmol) was added dropwise to
a stirred solution of the appropriate N-arylethylenediamine
Fig. 2. Probable fragmentation pathways of compound 1.

I. Perillo et al. / European Journal of Medicinal Chemistry 40 (2005) 811–815
815
Table 4
MIC (ug/ml) values of compounds 1a–j
Microorganism
1a
32
16
32
32
32
32
16
1b
32
16
32
32
32
32
1
1c
32
8
1d
32
8
1e
8
1f
32
4
1g
128
32
1h
128
32
1i
128 >256
32 >64
1j
E. coli ATCC 11105 CCM-A-424
M. luteus ATCC 9341 CCM-A-45
B. subtilis ATCC 6633 CCM-A-10
L. monocytogenes ATCC 9027 CCM-A-39
P. aeruginosa ATCC 9027 CCM-A-39
S. aureus ATCC 6538P CCM-A-424
A. niger ATCC 16404
8
32
32
32
32
64
16
32
32
32
32
16
16
32
16
4
32
16
32
32
32
128
128
128
128
64
128
128
128
128
64
128 >256
128 >256
32
128 >256
64 >256
>128
[11] (1 mmol) in ethanol. Reaction was monitored by TLC
using benzene/methanol (9:1) as elution solvent until disap-
pearance of the starting diamine (ca. 20 min). Compounds 1
crystallize by cooling the mixture. The solid was filtered and
recrystallized from ethanol. Melting points, yields and
molecular formula of bis(3-arylimidazolidinyl-1)methanes
1a–j are given in Table 1.
Acknowledgements
This work was financially supported by the University of
Buenos Aires.
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Ar = 2-nitrophenyl). M.p. 118–120 °C. 1H-NMR (CDCl3) d
ppm: 2.90 (t, 2H), 3.30 (t, 2H), 3.65 (s, 2H), 6.60 (t, 1H),
6.80 (d, 1H), 7.45 (t, 1H), 8.10 (d, 1H), 8.40 (bs, 1H). MS:
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(s, 2H), 5.00 (bs, 1H), 6.60 (m, 2H), 7.10 (t, 1H), 7.40 (d,
1H). MS: m/z 182 (M+•).
5.1.2.3. 2-(2-Methylphenyl)-1-methyleneaminoethane (3,
Ar = 2-methylphenyl). This compound was isolated as and
oil.
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(t, 2H), 3.20 (s, 2H), 4.30 (bs, 1H), 6.60 (d, 1H), 6.75 (t, 1H),
7.20-7.35 (m, 2H). MS: m/z 162 (M+•).
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Antimicrobial activity was tested by the disk diffusion
method, with Antibiotic Medium number 1 (pH 6.5) and 11
(pH 7.9). The assayed microorganisms were B. subtilisATCC
6633 CCM-A-10, P. aeruginosa ATCC 9027 CCM-A-39, M.
luteusATCC 9341 CCM-A-45, S. aureusATCC 6538P CCM-
A-424, L. monocytogenes ATCC 9027 CCM-A-39, C. albi-
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0.25 µg/ml and cultures were incubated at 24 h at 37 °C.