Synthesis, metal ion complexation and antibacterial activities of some thiapodands with lipophilic amide and ester end groups

Article abstract of DOI:10.1080/17415993.2012.716843

A series of acyclic analogues of thiacrown ethers (podands) 7-12 with lipophilic amide and ester end groups were synthesized in high yield and in a simple way. Their transition metal ions complexation was studied using a conductometric method in acetonitrile at 25C. Podands 7 and 11 showed a continuous decrease in the molar conductances in their complexation with Ag ⁺, Cu²⁺, Cd²⁺, Hg²⁺, Zn²⁺ and Pb²⁺ which begins to level off at a mole ratio of 1:1 podand to metal indicating the formation of a stable 1:1 complexes. On the other hand, podand 9 also showed the formation of 1:1 complexes with above metal cations except with Hg²⁺ ion, which formed a 1:2 podand-to-metal ratio complex. An influence of end groups on metal ion selectivity is evident. Podands having ethoxy end groups (podands 8, 10 and 12 exhibit pronounced metal ion selectivity over podands having amino end groups (podands 7, 9 and 11). Compounds 10 and 12 with dithiaethylene units and ethoxy end groups provide the best selectivity for Hg²⁺ and Ag⁺ ions. These results suggest that podands 10 and 12 could be useful for the selective removal of Hg²⁺ and Ag⁺ ions from industrial waste that may contain a variety of toxic heavy and transition metal ions. The in vitro antibacterial activity of the investigated compounds was tested against several microorganisms such as Bacillus subtilis (ATCC 6633), Micrococcus luteus (ATCC 10240), Staphylococcus aureus (ATCC 43300), Escherichia coli (ATCC 25922) and Enterobacter aerogenes (ATCC 13048). The antibacterial activity of podand 10 is significant for M. luteus and B. subtilis compared with other podands under investigation.

Full text of DOI:10.1080/17415993.2012.716843

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Synthesis, metal ion complexation
and antibacterial activities of some
thiapodands with lipophilic amide and
ester end groups
Muhammad Ashram a , Shehadeh Mizyed b , Wael Zereini c & Abdel
Monem Rawashdeh b
a Chemistry Department , Mutah University , Mutah, Al-Karak ,
Jordan
b Chemistry Department , Yarmouk University , Irbid , Jordan
c Department of Biological Sciences , Mutah University , Mutah, Al-
Karak , Jordan
Published online: 18 Sep 2012.
To cite this article: Muhammad Ashram , Shehadeh Mizyed , Wael Zereini & Abdel Monem
Rawashdeh (2012) Synthesis, metal ion complexation and antibacterial activities of some
thiapodands with lipophilic amide and ester end groups, Journal of Sulfur Chemistry, 33:5, 561-571,
DOI: 10.1080/17415993.2012.716843
To link to this article: http://dx.doi.org/10.1080/17415993.2012.716843
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Journal of Sulfur Chemistry
Vol. 33, No. 5, October 2012, 561–571
Synthesis, metal ion complexation and antibacterial activities of
some thiapodands with lipophilic amide and ester end groups
Muhammad Ashrama*, Shehadeh Mizyedb, Wael Zereinic and Abdel Monem Rawashdehb
aChemistry Department, Mutah University, Mutah, Al-Karak, Jordan; bChemistry Department, Yarmouk
University, Irbid, Jordan; cDepartment of Biological Sciences, Mutah University, Mutah, Al-Karak, Jordan
(Received 9 June 2012; final version received 26 July 2012)
A series of acyclic analogues of thiacrown ethers (podands) 7–12 with lipophilic amide and ester end groups
were synthesized in high yield and in a simple way. Their transition metal ions complexation was studied
using a conductometric method in acetonitrile at 25◦C. Podands 7 and 11 showed a continuous decrease in
the molar conductances in their complexation withAg+, Cu2+, Cd2+, Hg2+, Zn2+ and Pb2+ which begins
to level off at a mole ratio of 1:1 podand to metal indicating the formation of a stable 1:1 complexes. On
the other hand, podand 9 also showed the formation of 1:1 complexes with above metal cations except
with Hg2+ ion, which formed a 1:2 podand-to-metal ratio complex. An influence of end groups on metal
ion selectivity is evident. Podands having ethoxy end groups (podands 8, 10 and 12 exhibit pronounced
metal ion selectivity over podands having amino end groups (podands 7, 9 and 11). Compounds 10 and 12
with dithiaethylene units and ethoxy end groups provide the best selectivity for Hg2+ and Ag+ ions. These
results suggest that podands 10 and 12 could be useful for the selective removal of Hg2+ andAg+ ions from
industrial waste that may contain a variety of toxic heavy and transition metal ions. The in vitro antibacterial
activity of the investigated compounds was tested against several microorganisms such as Bacillus subtilis
(ATCC 6633), Micrococcus luteus (ATCC 10240), Staphylococcus aureus (ATCC 43300), Escherichia
coli (ATCC 25922) and Enterobacter aerogenes (ATCC 13048). The antibacterial activity of podand 10 is
significant for M. luteus and B. subtilis compared with other podands under investigation.
X
S
S
S
S
O
O
O
O
O
O
O
O
Y
Y
Y
Y
7 Y=N(C2H5)2
8 Y=OC2H5
9
X =S;Y=N(C2H5)2
10 X = S;Y = OC2H5
11 X = O;Y = N(C2H5)2
12 X = O;Y = OC2H5
Keywords: thiapodands; transition metals; stability constant; conductivity; antibacterial activity
*Corresponding author. Email: ashram_1961@yahoo.com
ISSN 1741-5993 print/ISSN 1741-6000 online
© 2012 Taylor & Francis
http://dx.doi.org/10.1080/17415993.2012.716843
http://www.tandfonline.com

562 M. Ashram et al.
1. Introduction
Acyclic analogues of crown ethers (podands) have received an important amount of interest by
research groups. Due to their low cost production, saving ring formation step(s) and their ability
to complex metal cations, anions and neutral guests, podands have became a significant type of
host in host–guest chemistry. A large number of podands with different end groups, chain length
and ligation atoms have been synthesized and their complexation properties were studied (1–6).
Several studies have focused on the determination of the selectivity and efficiency of the podand-
mediated extraction or transport of metal ions (4–6). Some of the crown ethers and their noncyclic
analogues proved to have different biological activities (7–9).
The stability and selectivity of the podands toward metal ions depend on several variables such
as chain length, identities of hetero-ligation atoms among the chain, the end groups and the type
of metal ions (10–15).
Previously, we have investigated the complexation of some transition metal cations (Ag+, Cu2+
,
Cd2+, Hg2+, Zn2+ and Pb2+) by two series of acyclic Schiff-base podands 1–6 with lipophilic
amide and ester end groups (Scheme 1) (15). The two series of podands show weak to good
complexation ability with poor selectivity toward metal cations studied. It was also found that
there was no large difference in the stability constants whether the Schiff-base podands ended
X
X
X
X
N
N
N
N
O
O
O
O
O
O
O
O
Y
Y
Y
Y
1 X =H;Y =OC2H5
2 X = H;Y= N(C2H5)2
3 X = Br;Y = N(C2H5)2
4
5
6
X
X
=
=
Br;Y
H;Y
H;Y
=
=
=
OC2H5
N(C2H5)2
N(C2H5)2
X
=
Scheme 1. Acyclic Schiff-base podands 1–6.
X
S
S
S
S
O
O
O
O
O
O
O
O
Y
Y
Y
Y
7 Y= N(C2H5)2
8 Y= OC2H5
9 X=S; Y=N(C2H5)2
10 X=S; Y=OC2H5
11 X=O; Y=N(C2H5)2
12 X=O; Y=OC2H5
Scheme 2. The synthesized acyclic thiacrown ethers 7–12.

Journal of Sulfur Chemistry 563
with ester groups or ended with amino groups. To further probe the end group and the chain length
with different ligation hetero-atom effects, two series of podands with sulfur atoms embedded in
the chain and with lipophilic amide and ester end groups were synthesized (Scheme 2) and their
complexation with the above transition metal cations was studied using a conductometric method
in acetonitrile (AN) at 25◦C in addition to their antibacterial activity.
2. Results and discussion
2.1. Synthesis
The synthesis of podands 7, 9 and 11 was carried out in the same manner as the synthesis of 8,
10 and 12 (Schemes 3) (15). Treatment of 13 with two equivalents of NaBH4 in THF at 0–5◦C
produce compound 14 in more than 90% yield as an oily product. Treatment of 14 with freshly
distilled SOCl2 in dry CH2Cl2 at 5 ◦C for 15 min produce 15 in about 90% yield as an oily product.
When two equivalents of compound 15 were treated with one equivalent of ethane 1,2-dithiol or
bis(2-mercaptoethyl)sulfide or bis(2-mercaptoethyl) ether in the presence of one equivalent of
K2CO3 in refluxing anhydrous AN for 24 h, podands 7, 9 and 11 were produced, respectively,
in high yields. Compounds 7, 9 and 11 were fully characterized by 1H, 13C NMR, infrared (IR)
spectroscopy and elemental analysis.
O
Cl
O
OH
O
H
O
O
O
NaBH4, THF
SOCl2,CH2Cl2
O
(C2H5)2N
(C2H5)2N
(C2H5)2N
13
14
15
S
S
O
O
O
HSCH2CH2SH
K2CO3,CH3CN
O
(C2H5)2N
N(C2H5)2
Cl
O
7
O
X
S
S
(C2H5)2N
(HSCH2CH2)2X
K2CO3,CH3CN
O
O
O
O
(C2H5)2N
N(C2H5)2
9
X=S
11 X=O
Scheme 3. The synthesis of acyclic thiacrown ethers 7, 9 and 11.

564 M. Ashram et al.
2.2. Complexation studies
In this study, the conductometric method was used to
(1) establish the stoichiometry of the complexes formed between transition metals Ag+, Cu2+
,
Cd2+, Hg2+, Zn2+ and Pb2+ and podands 7–12.
(2) determine the stability constants of the formed complexes using a simplex program (16–22).
The variation of molar conductivity ꢀ with [L]T/[M]T for complexes of podands 7–12 and
metal cations mentioned above in AN were studied at 25◦C. [L]T and [M]T denote the total
concentrations of podands and metal cations, respectively. The resulting molar conductance–
mole ratio plots are shown in Figure 1 as an example. The addition of podand 10 to metal
cation solutions causes a continuous decrease in the molar conductance that begins to level
off at a mole ratio 1 of podand-to-metal ion indicating the formation of stable 1:1 complexes.
Anomalous behavior was observed in the complexation of other podands with metal cations
studied. Regarding 9-Hg2+ complex, the addition of podand 9 to Hg2+ salt solution indicates
that the change in the slope of the conductometric titration curve are observed at a ligand:metal
ratio of 0.5 which means the formation of 1:2 complex. To confirm the 1:2 complexation ratio
obtained by conductivity measurements, the complexation between ligand 9 and Hg2+ was
studied using Job’s plot (Figure 2). This figure shows that a maxima of about 0.25 is obtained
indicating 1:2 ligand-to-metal ratio. Furthermore, the complexation is also verified by changes
in the 1H NMR chemical shifts of the podands under investigation. The addition of Hg2+ ion
to podand 9 in CD3CN resulted in a chemical shift change for the benzylic protons of about
0.25 ppm. A complete complexation study using NMR will be published in due course. From
these experimental results, we deduce that the sulfur atoms of the bis(thiaethylene) unit spacer,
the oxygen atoms of the carbonyl groups and the nitrogen atoms of the amino amide groups are
participants in the coordination with Hg2+ ion. The contribution of the carbonyl groups in the
coordination is confirmed from the change in IR stretching of these groups upon complexation
as shown in Figure 3. Replacement of amino end groups in podand 9 by ethoxy end groups
in podand 10 gave 1:1 ligand-to-Hg2+ complexes indicating that the oxygen atoms of the
ethoxy groups do not participate in the interaction with the Hg2+ ion. This result is consistent
with a poor association of Hg2+ ion (soft ion) and oxygen atoms (hard atoms) according to
hard and soft acid-base theory (23).
380
330
280
230
<
180
Ag+
Hg2+
130
0
0.5
1
1.5
2
2.5
3
[L]T/[M]T
Figure 1. Molar conductance–mole ratio plots for 10 and metal cations in CH3CN at 25◦C.

Journal of Sulfur Chemistry 565
0.14
0.12
0.1
0.08
0.06
0.04
0.02
0
0
0.1
0.2
0.3
0.4
0.5
X9
0.6
0.7
0.8
0.9
1
Figure 2. Job’s plot of the complex of compound 9 with Hg2+ metal cation in CH3CN at 25◦C.
Figure 3. The change in IR stretching of carbonyl groups of 9 upon complexation with Hg2+
.
When a ligating agent complexes with a specific metal ion, many factors influence the stability
constants such as the radius of metal ion, the identity of the donor atoms and a macrocyclic effect
which involves the dimensional compatibility between the macrocycle and the size of the metallic
cation. As shown in Table 1, the order of stability constant of podands-Ag+ is 9>11>7 when the
end group is the amino group and 10>12>8 when the end group is the ethoxy group. From these
observations, we can conclude the following:
(a) The cavity size of podands that contain bis(thiaethylene) unit spacer (9, 10, 11 and 12) is more
flexible and, therefore, it has the ability to adopt a suitable orientation and wrap around the
metaliontoformmorestablecomplexeswithAg+ comparingtomorerigidcavitiesofpodands
7 and 8 that contain the monothiaethylene unit spacer. Indeed, when quantum mechanical
calculations were performed using the GAUSSIAN03 program package (24), they show that

566 M. Ashram et al.
Table 1. Log Kassoc for complexation of Ag+, Cu2+, Cd2+, Hg2+, Zn2+ and Pb2+ and with podands 7–12 in AN at
25◦C.
Compound
Ag+
Cu2+
Cd2+
Hg2+
Zn2+
Pb2+
7
8
9
10
11
12
4.42 0.11
2.77 0.07
5.24 0.12
4.76 0.11
5.00 0.11
3.95 0.09
6.57 0.16
3.38 0.08
5.76 0.14
5.38 0.13
5.24 0.12
(2:1)b
5.43 0.14
5.76 0.17
4.95 0.12
6.67 0.17
7.71 0.19
a
a
a
6.33 0.16
6.67 0.15
5.00 0.12
6.86 0.17
a
a
a
a
5.14 0.12
5.71 0.13
4.43 0.11
5.38 0.11
a
a
a
a
Notes: aNo change in molar conductance was observed.
bThe data cannot be fitted in equation.
the podand 9 complex with Ag+ has wrapped itself around the ion and formed a square
planar complex (Figure 4) with an S–Ag distance of 2.57Å. Podand 7 in its complex with
Ag+ formed a tetrahedral complex (Figure 5) with an S–Ag distance of 2.67Å. Comparing
those distances with the typical S–Ag distance which is 2.50Å shows that the former is more
stable (25).
(b) Replacement of one sulfur atom in bis(thiaethylene) unit space by one oxygen atom causes a
decrease in stability constants. Compare stability constants of 9 and 11, and 10 and 12.
(c) Replacement of amino end groups by ethoxy end groups causes a decrease in stability con-
stants. Compare stability constants of 7 and 8, 9 and 10, and 11 and 12. This tendency is
also observed for the stability constants of the complexes 7-Hg2+ and 8-Hg2+, and 7-Cu2+
and 8-Cu2+. These results give clear evidence that the nature of the end groups takes part in
determining the value of stability constants.
Figure 4. Speculated structure for 9-Ag complex showing square planar arrangement.
Figure 5. Predicted structure for 7-Ag complex with tetrahedral geometry.

Journal of Sulfur Chemistry 567
An influence of end groups on metal ion selectivity is evident. As shown in Table 1, podands
having ethoxy end groups (podands 8, 10 and 12) exhibit pronounced metal ion selectivity over
podands having amino end groups (podands 7, 9 and 11). Among the three podands 8, 10 and 12,
podands 10 and 12 exhibit the highest Hg2+ and Ag+ ion selectivity. These results suggest that
podands 10 and 12 could be useful for the selective removal of Hg2+ andAg+ ions from industrial
waste which may contains a variety of toxic heavy and transition metal ions.
2.3. Antibacterial activity
ThesynthesizedpodandsshowedweaktomoderateactivitiesagainstGram-positivebacteria, espe-
cially Micrococcus luteus. Compounds 10 and 12 revealed a very weak activity against B. subtilis.
The multidrug-resistant Staphylococcus aureus and Gram-negative bacteria were resistant to the
applied test substances. The bioactivity of these compounds is shown in Tables 2 and 3.
It is clear that these compounds were selectively active against M. luteus. Compound 10 was
the most potent bioactive agent against M. luteus in agar diffusion test (Figure 6). Although some
of these compounds exhibit antibacterial activities at concentrations more than 100 μg ml−1 (i.e. 7
and 8), their minimum inhibitory concentration (MIC) values were around or even lower than that
concentration with a static effect. Such finding may be attributed to their low diffusion ability in
the agar plate test and their lipophilic nature.As shown in Table 3, the potency of these compounds
to inhibit M. luteus growth increased when there are more than two sulfur atoms present in the
bridge. Moreover, sulfur containing podand esters are 4–8-fold more active than the amide ones.
The activity of these compounds could be attributed to their ability to bind and complex with
metal ions in the cell that may disturb the ionic homeostasis in the bacterial cells or inhibit the
activities of some crucial bacterial enzymes. Such findings are in agreement with the results of
Federova et al. (8).They noticed anincreaseinthetuberculostatic activityof theoxygencontaining
crown esters upon going from cyclic crowns to their acyclic analogs and that their activity exceeds
the amino analogs (8). In addition, Tochtrop et al. (26) reported that the presence of sulfur atoms
as ligating sites in a podand makes it more lipophilic and increase its efficiency to extract and
transport cations.
Table 2. Bioactivity of the synthesized compounds against the susceptible bacterial strains.
Micrococcus luteus (μg disc−1
)
Bacillus subtilis (μg disc−1
)
Compound
100
300
500
100
300
500
7
9
11
8
10
12
–
11
15
15
–
25
14
11
16
15
10
25
14
–
–
–
–
–
–
–
–
–
–
8
9
–
–
–
–
9
13
12
–
23
12
10
Note: –, No activity.
Table 3. MIC of the synthesized compounds in the serial dilution assay with the susceptible bacterial strains.
MIC (μg ml−1
)
Organisms
7
9
11
8
10
12
St
Micrococcus luteus
Bacillus subtilis
125s
–
31.5s
–
31.5s
–
31.5s
–
3.9s
–
3.1s
–
<0.4
<0.4
Note: St, streptomycin; s, bacteriostatic; –, >1000 μg ml−1
.

568 M. Ashram et al.
Figure 6. Inhibition zones indicating the activity of compound 10 against M. luteus. Left zone: 50 μg disc−1, right zone:
100 μg disc−1
.
3. Conclusion
A series of podands in which the length of ethereal linkage connecting the two benzo-moieties is
varied to contain mono- and dithiaethylene units with different ending groups were synthesized
in a simple way and in high yields. A conductometric titration technique was used to determine
the stability constants in AN at 25◦C and the L:M mole ratio for the complexation of podands 7,
8, 9, 10, 11 and 12 with Ag+, Cu2+, Cd2+, Hg2+, Zn2+ and Pb2 ions. Podands 10 and 12 with
dithiaethylene units and ethoxy end groups provide the best selectivity for Hg2+ and Ag+ ions.
The antimicrobial activity of these podands was tested. Podand 10 shows a significant activity for
M. luteus and B. subtilis compared with other podands.
4. Experimental
Melting points are uncorrected and obtained on electrothermal melting point apparatus. 1H and
13C NMR spectra were recorded on 300 and 50 MHz NMR spectrometers, respectively. Unless
otherwise noted, samples were dissolved in CDCl3. Chemical shifts are reported in ppm relative
to TMS used as internal standard. Elemental analyses (C, H, N and S) were performed on Euro
elemental analysis 3000 from Euro Vector S.P.A. SN 8910. All reagents were of analytical grade
and used without further purification. Ethane 1,2-dithiol or bis(2-mercaptoethyl)sulfide or bis(2-
mercaptoethyl) ether were obtained from Aldrich; salicylaldehyde was from Lancaster; ethyl
bromoacetate from Merck and anhydrous potassium carbonate from SureChem. The solvents
were used without further purification.
The following salts were purchased from the companies indicated: AgNO3 (Degussa),
Cu(ClO4)2·6H2O (Aldrich), Pb(ClO4)2·3H2O (Aldrich), Zn(ClO4)2·6H2O (Aldrich), Cd(ClO4)2
(Aldrich) and Hg(ClO4)2.xH2O (Aldrich). For the conductivity measurements, AN was used after
fractional distillation. The conductivity of the CH3CN was less than 1 ×10−7 S cm−1. Solutions
having metal ion concentrations of approximately 1.0–1.1 × 10−4 M were prepared by dissolving
a known mass of each salt in the respective solvent. These solutions were also used as solvents
for preparing the thiapodand solutions with concentrations of approximately 1.5–1.6 × 10−3 M.
The description of the conductometer and the details of the conductance measurements have been
given previously (16). Compounds 8, 10, 12 and 13 were prepared according to the literature
procedures (15, 17).

Journal of Sulfur Chemistry 569
4.1. Synthesis
4.1.1. Synthesis of O-(N,N-diethylacetamidooxy)benzyl alcohol (14)
To a solution of 13 (0.51 g, 2.12 mmol) in THF (10 ml) was added NaBH4 (0.16 g, 4.24 mmol) at
0–5◦C. The reaction was stirred for 15 min and then for 45 min at room temperature. The reaction
mixture was quenched by adding2 mlofcold water, followedby aqueous5%HCl until thesolution
become acidic to pH paper. The mixture was extracted with CHCl3. The organic layer was dried
1
over anhydrous MgSO4 and evaporated to give 14 as a colorless oil in 95% yield; H NMR
δH 1.14 (t, J = 6 Hz, 3H, NCH2CH3), 1.20 (t, J = 6 Hz, 3H, NCH2CH3), 3.41 (q, J = 6 Hz,
4H, NCH2CH3), 4.68 (s, 2H), 4.70 (s, 2H), 6.81 (d, J = 4 Hz, 1H), 6.93 (t, J = 6 Hz, 1H),
7.20–7.25 (m, 2H); 13C NMR δC 12.86, 14.42, 40.19, 41.28, 60.5, 67.67, 111.2, 121.23, 128.11,
128.24, 129.61, 136.50, 168.51.
4.1.2. Synthesis of O-(N,N-diethylacetamidooxy)benzyl chloride (15)
To a solution of 14 (0.45 g, 1.9 mmol) in dry CH2Cl2 (30 ml) at 0◦C was added freshly distilled
SOCl2 (0.28 ml, 3.8 mmol). The reaction mixture was stirred at 0◦C for 15 min and then was
quenched by adding 20 ml of cold water. The organic layer was washed with water until the
aqueous layer was neutral to pH paper. The organic layer was dried over anhydrous MgSO4
1
and evaporated to give 15 as a colorless oil in 92% yield; H NMR δH 1.13 (t, J = 6 Hz, 3H,
NCH2CH3), 1.20 (t, J = 6 Hz, 3H, NCH2CH3), 3.39 (q, J = 6 Hz, 4H, NCH2CH3), 4.69 (s, 2H),
4.71 (s, 2H), 6.79 (d, J = 4 Hz, 1H), 6.90 (t, J = 6 Hz, 1H), 7.20–7.30 (m, 2H); 13C NMR δC
12.84, 14.42, 40.15, 41.26, 41.61, 67.72, 113.62, 120.66, 125.90, 128.15, 128.65, 135.58, 167.54.
4.1.3. General procedure for synthesis of acyclic thiacrown ether podands 7, 9 and 11
In a 100 ml one-necked flask equipped with a magnetic stirrer bar and a reflux condenser, the chlo-
ride amide compound 15 (0.75 g, 2.94 mmol), ethane 1,2-dithiol or bis(2-mercaptoethyl)sulfide
or bis(2-mercaptoethyl) ether (1.47 mmol) and anhydrous K2CO3(0.41 g, 2.94 mmol) were mixed
in anhydrous CH3CN (50 ml). The mixture was refluxed for 24 h. The mixture was filtered and the
filtrate was evaporated to dryness. The 1H NMR and 13C NMR, IR analysis and elemental anal-
ysis measured for the obtained products are consistent very well with the corresponding acyclic
thiacrown ether podand formula.
4.1.4. 1,2-Bis[2-(N,N-diethylacetamidooxy)thiabenzyl]ethane 7
Pale brown semi-solid (92%); Fourier transform infrared spectroscopy (FT-IR) (KBr, cm−1): 1659
1
[CON(C2H5)2]; H NMR (CDCl3): δ 1.13 (t, J = 8 Hz, 6H, CH2CH3), 1.19 (t, J = 6 Hz, 6H,
CH2CH3), 2.68 (s, 4H, SCH2CH2S), 3.40 (q, J = 6 Hz, 8H, CH2CH3), 3.80 (s, 4H, CH2Ph), 4.71
(s, 4H, OCH2CO), 6.86 (d, J = 6 Hz, 2H), 6.91–6.94 (m, 2H), 7.17–7.28 (m, 4H); 13C NMR
(CDCl3): δ 12.86, 14.42, 30.08, 31.22, 40.06, 41.03, 67.77, 112.21, 121.39, 127.26, 128.41,
130.46, 156.32, 167.88. Anal. Calcd for C28H40N2S2O4 (%): C 63.13, H 7.57, N 5.26, S 12.04;
found (%):C 63.01, H 7.44, N 5.19, S 11.97.
4.1.5. 1,5-Bis[2-(N,N-diethylacetamidooxy)thiabenzyl]-3-thiapentane 9
Pale yellow oil (89%); FT-IR (KBr, cm−1): 1658 [CON(C2H5)2]; H NMR (CDCl3): δ 1.15
1
(t, J = 8 Hz, 6H, CH2CH3), 1.21 (t, J = 6 Hz, 6H, CH2CH3), 2.67 (m, 8H, (SCH2CH2)2S), 3.41

570 M. Ashram et al.
(q, J = 6 Hz, 8H, CH2CH3), 3.83 (s, 4H, CH2Ph), 4.73 (s, 4H, OCH2CO), 6.87 (d, J = 6 Hz,
2H), 6.94 (m, 2H), 7.19–7.27 (m, 4H); 13C NMR (CDCl3): δ 12.89, 14.45, 30.33, 31.43, 31.79,
40.29, 41.38, 67.78, 112.24, 121.45, 127.19, 128.49, 130.50, 156.05, 166.89. Anal. Calcd for
C30H44N2S3O4 (%): C 60.78, H 7.48, N 4.73, S 16.22; found (%):C 60.63, H 7.39, N 4.85,
S 16.09.
4.1.6. 1,5-Bis[2-(N,N-diethylacetamidooxy)thiabenzyl]-3-oxapentane 11
Pale yellow oil (95%); FT-IR (KBr, cm−1): 1657 [CON(C2H5)2]; 1H NMR (CDCl3): δ 1.15–1.20
(m, 12H, CH2CH3), 2.66 (t, J = 5 Hz, 4H, SCH2CH2OCH2CH2S), 3.42 (q, J = 6 Hz, 4H), 3.58
(t, J = 6 Hz, 4H, SCH2CH2OCH2CH2S), 3.84 (s, 4H, CH2Ph), 4.73 (s, 4H, OCH2CO), 6.88 (d,
J = 6 Hz, 2H), 6.92–6.96 (m, 2H), 7.18–7.23 (m, 2H), 7.27–7.29 (m, 2H); 13C NMR (CDCl3):
δ 12.84, 14.42, 30.68, 30.81, 31.09, 40.31, 41.44, 67.88, 70.44, 112.21, 121.37, 127.31, 128.34,
130.56, 156.04, 167.02. Anal. Calcd for C30H44N2S2O5 (%): C 62.47, H 7.69, N 4.86, S 11.12;
found (%): C 62.53, H 7.49, N 4.91, S 11.18.
4.2. In vitro antibacterial activity
The antibacterial activity of these compounds was determined by measuring the inhibition zones
in agar diffusion test and calculating the MIC by serial dilution assay as described earlier (27).
Streptomycin was used as a positive control.
The tested microorganisms were B. subtilis (ATCC 6633), M. luteus (ATCC 10240), S. aureus
(ATCC 43300), Escherichia coli (ATCC 25922) and Enterobacter aerogenes (ATCC 13048). The
applied concentrations on the blank 6 mm disks were 100, 300 and 500 μg ml−1
.
Acknowledgements
We thank Deanship of the Academic Research at Mutah University and Scientific Research for financial support.
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