Synthesis of new 3-substituted-5-(2-hydroxyethyl)-3,4,5,6-tetrahydro-2H-l, 3,5-thiadiazine-2-thione derivatives with potential antimicrobial activity

Article abstract of DOI:10.1002/ardp.200700195

The purpose of this study is based upon design and synthesis of a new series of flexible molecules of 3,4,5,6-tetrahydro-2H-1,3,5-thiadiazine-2-thione (THTT) derivatives depending upon incorporation of 2-aminoethanol as a part of the polar moiety in this nucleus. Thirteen derivatives of 3-substituted-5-(2- hydroxyethyl)-3,4,5,6-tetrahydro-2H-1,3,5-thiadiazine-2-thione were synthesized by reaction of the appropriate alkyl, cycloalkyl, aralkyl amine, or glycine with carbon disulphide, formaldehyde, and 2-aminoethanol. The structures of the target compounds were elucidated using spectral methods as well as elemental analyses. A mass-spectrometry study was carried out on representatives of the synthesized derivatives. The title compounds were tested for their antibacterial activity in vitro against some gram positive and gram negative bacteria. The in-vitro antifungal activity was tested against dermatophytic, saprophytic, phytopathogenic, and antagonistic fungi. In most cases, the newly synthesized compounds 4-16 exhibited a considerable inhibitory effect on the growth of some of the tested organisms in comparison to that of ampicillin or muconazole as reference drugs. Moreover, the results indicated that the polar hydroxyethyl group at the N5- and the lipophilic one at the N3-positions are essential for the antimicrobial activity of the tested compounds.

Full text of DOI:10.1002/ardp.200700195

370
Arch. Pharm. Chem. Life Sci. 2008, 341, 370–376
Full Paper
Synthesis of New 3-Substituted-5-(2-hydroxyethyl)-3,4,5,6-
tetrahydro-2H-l,3,5-thiadiazine-2-thione Derivatives with
Potential Antimicrobial Activity
Mostafa A. Hussein1 and Mohammed Hashem2
1 Department of Pharm. Organic Chemistry, Faculty of Pharmacy, Assiut University, Assiut, Egypt
2 Department of Botany, Faculty of Science, Assiut University, Assiut, Egypt
The purpose of this study is based upon design and synthesis of a new series of flexible mole-
cules of 3,4,5,6-tetrahydro-2H-1,3,5-thiadiazine-2-thione (THTT) derivatives depending upon
incorporation of 2-aminoethanol as a part of the polar moiety in this nucleus. Thirteen deriv-
atives of 3-substituted-5-(2-hydroxyethyl)-3,4,5,6-tetrahydro-2H-1,3,5-thiadiazine-2-thione were
synthesized by reaction of the appropriate alkyl, cycloalkyl, aralkyl amine, or glycine with car-
bon disulphide, formaldehyde, and 2-aminoethanol. The structures of the target compounds
were elucidated using spectral methods as well as elemental analyses. A mass-spectrometry
study was carried out on representatives of the synthesized derivatives. The title compounds
were tested for their antibacterial activity in vitro against some gram positive and gram negative
bacteria. The in-vitro antifungal activity was tested against dermatophytic, saprophytic, phytopa-
thogenic, and antagonistic fungi. In most cases, the newly synthesized compounds 4–16 exhib-
ited a considerable inhibitory effect on the growth of some of the tested organisms in compari-
son to that of ampicillin or muconazole as reference drugs. Moreover, the results indicated that
the polar hydroxyethyl group at the N5- and the lipophilic one at the N3-positions are essential
for the antimicrobial activity of the tested compounds.
Keywords: Antimicrobial / Synthesis / Thiadiazine-2-thione /
Received: September 23, 2007; accepted: December 12, 2007
DOI 10.1002/ardp.200700195
Introduction
Tetrahydro-2H-l,3,5-thiadiazine-2-thione (THTT) deriv-
atives are known to display important biological activ-
ities. Numerous studies have been published on their
Figure 1. Lead structure I of synthesized compounds.
antibacterial [1–10], antifungal [11–16], anthelmintic
[17], antiprotozoal [18], and antituberculous [5] activity
as prodrugs [19–21]. The antimicrobial activity of these
compounds has been suggested to be based on isothiocya-
nates and dithiocarbamic acids, which are formed by
hydrolysis of the tetrahydro-2H-l,3,5-thiadiazine-2-thione
ring [15–21]. Some studies have pointed out the signifi-
cance of the nature of the substituents at the 3- and 5-
positions [3–5]. Lipophilic groups at both, the 3- and 5-
positions, lead to compounds with high antimicrobial
activities but also high toxicity. The toxicity of such com-
pounds was greatly altered by using polar groups at the
5-position [13] with the optimum structure-activity illus-
trated in Fig. 1. The previous studies revealed that inser-
tion of the carboxymethyl group at the 5-position would
reduce both the lipophilicity and the antimicrobial activ-
Correspondence: Mostafa A. Hussein, Department of Pharm. Organic
Chemistry, Faculty of Pharmacy, Assiut University, Assiut-71526, Egypt.
E-mail: mostafa1705@yahoo.com
Fax: +20 088 2332-776
Abbreviations: Tetrahydro-2H-l,3,5-thiadiazine-2-thione (THTT)
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Arch. Pharm. Chem. Life Sci. 2008, 341, 370–376
Antimicrobial l,3,5-Thiadiazine-2-thione
371
Table 1. Physicochemical data of compounds 4–16.
Compound
R
Molecular formula (MW)
Yielda) (%)
Mpb) (8C)
Rfc)
Clog P
4
5
6
7
8
CH3
C2H5
n-C3H7
i-C3H7
n-C4H9
i-C4H9
n-C5H11
n-C6H13
c-C6H13
C6H5CH2
2-C6H5C2H4
dl-1-C6H5C2H4
HOOCCH2
C6H12N2OS2 (192.30)
C7H14N2OS2 (192.30)
C8H16N2OS2 (192.30)
C8H16N2OS2 (192.30)
C9H18N2OS2 (192.30)
C9H18N2OS2 (192.30)
C10H20N2OS2 (192.30)
C10H22N2OS2 (192.30)
C11H20N2OS2 (192.30)
C12H16N2OS2 (192.30)
C13H18N2OS2 (192.30)
C13H18N2OS2 (192.30)
C7H12N2O3S2 (192.30)
78
75
90
90
83
80
70
83
80
92
85
80
65
liquid
liquid
118–119
121–122
93
0.31
0.32
0.35
0.41
0.51
0.52
0.58
0.56
0.52
0.49
0.45
0.43
0.27
0.448
1.027
1.556
1.330
2.085
1.865
2.614
3.143
2.439
2.138
2.445
2.447
–1.027
9
85–86
10
11
12
13
14
15
16
110–111
127–128
144–145
125–126
98–99
145–146
178–179
a)
The developing solvent system used is CHCl3 : CH3OH (5 : 3).
The boiling points of compounds 4 and 5 are 2158C/10 mm Hg and 2188C/10 mm Hg, respectively.
The crystallization solvent for the solid compounds is ethanol.
b)
c)
ity [19–21]. Accordingly, further tuning of the polarity of
the substituent group at the 5-position of the THTT moi-
ety seemed to be of interest. This work is concerned with
the incorporation of the hydroxyethyl group in the 5-
position of the flexible THTT nucleus. This will afford
analogues with modified lipophilic properties and the
testing of their antimicrobial activities, if present.
It is also of interest to investigate the mass-spectral
behavior of the representatives of the synthesized deriv-
atives for further exploration of the reported compounds
[22, 23].
R: 4 = CH3, 5 = C2H5, 6 = C3H7, 7 = i-C3H7, 8 = n-C4H9, 9 = i-C4H9, 10 = n-C5H11, 11 =
n-C6H13, 12 = cyclo-C6H13, 13 = C6H5CH2, 14 = 2- C6H5C2H4, 15 = 1-C6H5C2H4, 16 =
CH2COOH.
Scheme 1. Synthesis route of compounds 4–16.
Results and discussion
Chemistry
The target compounds were synthesized by reaction of
the appropriate alkyl, cyc1oalkyl, aralkyl amine, or gly-
cine la–m, with carbon disulphide and potassium
hydroxide. The resulting alkyl dithiocarbamate salts 2
were subjected to cyc1o-condensation reaction with
formaldehyde and 2-aminoethanol to provide the target
derivatives 4–16, Scheme 1. It was suggested that the
reaction proceeded through the formation of the inter-
mediate 3 in situ [l0–18]. The structures of the synthe-
sized compounds were verified on the basis of spectral
and elemental analyses. Table 1 shows the physicochemi-
cal data of compounds 4–16.
prominent strong absorption bands around 3500–
3450 cm– 1 (OH), in addition, an absorption band at about
1450 cm– 1 was attributed to a C=S bond. 1H-NMR spectra
revealed a common pattern of the THTT backbone and
the N5-substituent (CH2CH2OH). The differences in sets
and patterns were only attributed to the N3 alkyls, cyclo-
alkyl, or aralkyls, where they showed pattern in accord-
ance with the expected structures of the target com-
pounds (see Experimental).
On the other hand, trials for the preparation of some
derivatives with the hydroxyethyl moiety in position 3
were unsuccessful. The difficulty of preparation of such
compounds might be attributed to the salt formation of
2-aminoethanol in strong alkaline medium [3].
All the spectral data are in accordance with the pro-
posed structures. IR spectra of compounds 4–16 show
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372
M. A. Hussein and M. Hashem
Arch. Pharm. Chem. Life Sci. 2008, 341, 370–376
Scheme 2. Fragmentation patterns of compounds 7.
Scheme 3. Fragmentation patterns of compounds 13.
Moreover, the structures of the target compounds study the effect of the lipophilicity on the antimicrobial
were further confirmed on the basis of the MS (El) data of activity.
two representative compounds as given in the fragmen-
tation patterns of compounds 7 and 13 of Schemes 2 and Antimicrobial activity
3, respectively. The mass spectrum of 7 showed a weak The synthesized compounds 4–16 were evaluated in vitro
M+ –1 peak at m/z 219 (11.8%) as the deprotonation of the for their antibacterial and antifungal activities using the
substituent attached at N5 proceeded very easily, while standard agar diffusion method [25] according to the pro-
the mass spectrum showed the prominent peaks at m/z tocol mentioned below. Table 2, showed the antimicro-
118 (12.4%), 100 (39.5%), and 42 (100%) (base peak corre- bial activity of the tested compounds expressed as the
sponding to the fragment C3H6). On the other hand, the inhibition zone in mm.
mass spectrum of compound 13 showed a weak molecu-
lar ion peak at m/z 268 (4.6%) (Scheme 3).
The antibacterial activities of the target compounds
were tested against Bacillus cereus and Micrococcus roseus
as gram-positive and Serratia rodenii and Escherichia coli as
gram-negative bacterial species. The antifungal activity of
Lipophilicity
The lipophilicity of the target compounds 4–16 is the tested compounds was investigated in vitro against
expressed in the term of Clog P values (Table 1). The val- dermatophytes (Candida albicans, Microsporum canis,
ues were computed with a routine method called calcu- Microsporum gypseum, and Trichophyton rubrum), Sapro-
lated log P (Clog P) contained in a PC-software package as phytes (Aspergillus terreus and Penicillim chrysogenum),
mentioned in Experimental [24]. This work is devoted to phytopathogens (Drechslera spicifera and Fusarium oxyspo-
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Arch. Pharm. Chem. Life Sci. 2008, 341, 370–376
Antimicrobial l,3,5-Thiadiazine-2-thione
373
Table 2. Antimicrobial activity of the tested compounds 4–16 and the reference drugs. (All values are the average of three observa-
tions.)
Compound
Bacteria
Gram negative
B. cereus M. roseus S. rodenii E. coli
Fungi
Gram positive
Dermatophytes
C. albicans T. rub- M. gyp-
Saprophytes
Phytopathogens
Antagonist
D. spici- T. harzia-
M. canis A. terreus P. chryso- F. oxy-
rum
seum
genum
sporum
fera
num
4
5
6
7
8
8a)
11
0
0
0
8
0b)
13
0
10
8
7
6
10
10
12
20
0
10
15
10
17
20
7
7
10
10
7
20
10
15
15
20
23
20
15
0
10
15
7
8
8
10
12
12
0
0
9
15
13
14
0
15
13
12
15
18
12
9
15
18
20
15
9
7
10
10
11
13
0
12
13
12
15
18
12
9
15
18
20
15
9
0
7
7
8
8
12
10
15
12
11
7
10
9
7
13
15
15
18
–
15
10
10
16
12
12
15
0
10
0
7
12
–
10
10
12
9
15
16
15
12
10
8
10
22
15
13
16
18
21
20
16
0
9
0
8
10
11
12
13
14
15
16
0
0
7
0
11
15
0
11
12
8
15
20
20
13
8
15
20
22
18
7
0
–
25
10
15
10
12
0
0
–
25
13
18
22
12
0
0
–
15
0
0
–
25
0
–
25
0
–
25
c)
Ampicillin 14
Muconazole
10
–
–
26
–
27
–
7
a)
Inhibition zone in mm; disc diameter is 6 mm.
0 = no inhibition.
– = not tested.
b)
c)
rum), and an antagonist (Trichoderma harzianum). The though they have a reasonable antifungal activity against
results of the antimicrobial activity of the tested com- most of the studied fungi. Accordingly, the tested com-
pounds are given in Table 2, in comparison with the pounds can be considered as promising candidates for
reference drugs.
antifungal agents or for the use in plant-diseases inte-
The antibacterial and antifungal activities vary with grated control programs.
the variation of the N3 substituents of the THTT moiety
against the tested microbial strains. Most of the com-
pounds gave antibacterial activity comparable to the
reference drug ampicillin, further, some showed potency
Conclusion
against Micrococcus roseus and Escherichia coli.
We conclude that a new series of 3-substituted-5-(2-
Again, highly antifungal activities were obtained for hydroxyethyl)-3,4,5,6-tetrahydro-2H-l,3,5-thiadiazine-2-
the tested compounds on comparison to the reference thione derivatives was synthesized and tested for their
drug muconazole with no constant pattern. The study antimicrobial activity. The chemical structures of the tar-
revealed an interesting finding that compound 16 has no get compounds were elucidated utilizing the spectral as
inhibitory effect on the utilized fungal species, the struc- well as the elemental methods of analysis. Moreover, MS
ture of this compound includes two polar groups at N3 assured the expected structures. The antimicrobial activ-
(CH2COOH) and N5 (CH2CH2OH). This finding indicates ity varied with the N-3 substituent groups on THTT, and
that one of the two substituents at N3 or N5 must be non- the microorganisms used in comparison with the refer-
polar for activity, a result which is in accordance with ence drugs. Most of the tested compounds exhibited pro-
the lipophilicity concept. Generally, compounds such as nounced antimicrobial activities with no or weak inhibi-
7, 8, 13, and 14 of high Clog P values showed the best anti- tory activity against Trichoderma harzianum. Accordingly,
microbial activities, because of the ease of penetration they can be considered as promising candidates to be
into the lipophilic cell wall, whereas compound 16 with used either as antimicrobial agents and/or in plant-dis-
the lowest Clog P value had nearly of the lowest antimi- eases integrated control programs. Moreover, the results
crobial activity among the tested compounds. Interest- of study revealed the essentiality of the lipophilic group
ingly, the antifungal activities of the tested compounds at N3 and a polar substituent at N5 positions for good
are more pronounced than their antibacterial activity.
However, most of the tested compounds revealed no or
antimicrobial activity.
weak inhibitory activity against Trichoderma harzianum, The authors have declared no conflict of interest.
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374
M. A. Hussein and M. Hashem
Arch. Pharm. Chem. Life Sci. 2008, 341, 370–376
CH2CH2CH3 and CH2CH2OH), 4.65 (4H, s, 2CH2). Anal. calcd. for
C8H16N2OS2: C, 43.60; H, 7.32; N, 12.71; Found: C, 43.64; H, 7.63;
N, 12.60.
Experimental
Chemistry
Melting points were determined on an electrothermal melting
point apparatus (Sturat Scientific, UK) and were uncorrected.
Precoated silica gel plates (silica gel 0.25 mm, 60G F254; Merck,
Germany) were used for thin layer chromatography. As develop-
ing solvent system chloroform/methanol (5 : 3) was used and the
spots were detected by ultraviolet light and/or iodine. IR spectra
(KBr disc) were recorded on an IR-470 Shimadzu spectrometer
(Shimadzu, Tokyo, Japan). 1H-NMR spectra were measured on a
Varian EM-360 L NMR spectrometer (60 MHz), (Varian, USA).
Chemical shifts are expressed in d-values (ppm) relative to TMS
as an internal standard, using CDCl3 as a solvent. Mass spectra
were made on a JEOL JMS600 (El) mass spectrometer (JEOL,
Japan) at Assiut University Central Laboratory, Assiut, Egypt. Ele-
mental analyses were performed at the Department of Chemis-
try, Faculty of Science, Assiut University, and the Micro Analyti-
cal Center, Faculty of Science, Cairo University, Egypt. The anti-
microbial activity was performed at the Department of Botany,
Faculty of Science, Assiut University, Assiut, Egypt.
5-(2-Hydroxyethyl)-3-i-propyl-3,4,5,6-tetrahydro-2H-
1,3,5-thiadiazine-2-thione 7
1H-NMR: 1.35 (6H, d, 2CH3), 2.40 (1H, br s, OH), 3.15 (2H, t,
CH2CH2OH), 3.95 (2H, t CH2CH2OH), 4.65 (4H, s, 2CH2), 6.20-6.80
(1H, m, CHMe2). Anal. calcd. for C8H16N2OS2: C, 43.60; H, 7.32; N,
12.71; Found: C, 43.67; H, 7.83; N, 12.64.
4.1.1.5 3-n-Butyl-5-(2-hydroxyethyl)-3,4,5,6-tetrahydro-
2H-1,3,5-thiadiazine-2-thione 8
1H-NMR: 1.05 (3H, t, CH3), 1.30-2.15 (4H, m, CH2(CH2)2CH3), 2.90
(1H, br s, OH), 3.15 (2H, t, CH2CH2OH), 3.65-4.40 (4H, m,
CH2(CH2)2CH3 and CH2CH2OH), 4.75 (4H, s, 26CH2). Anal. calcd.
for C9H18N2OS2: C, 46.12; H, 7.74 ; N, 11.95; Found: C, 46.01; H,
8.38; N, 12.19.
Synthesis of 3-substituted-5-(2-hydroxyethyl)-3,4,5,6-
tetrahydro-2H-1,3,5-thiadiazine-2-thione derivatives
4–16
3-i-Butyl-5-(2-hydroxyethyl)-3,4,5,6-tetrahydro-2H-1,3,5-
thiadiazine-2-thione 9
1H-NMR: 1.15 (6H, d, CH3), 2.20–2.80 (2H, m, CH and OH), 3.25
(2H, t, CH2CH2OH), 3.80-4.35 (4H, m, CH2CH and CH2CH2OH), and
4.75 (4H, s, 2CH2). Anal. calcd. for C9H18N2OS2: C, 46.12; H, 7.74;
N, 11.95; Found: C, 46.55; H, 7.83; N, 11.56.
Carbon disulfide (4.8 mL, 80 mmol) was added portionwise to a
well-stirred mixture of alkyl, cycloalkyl, aralkyl amine, or gly-
cine la–m, (20 mmol) and potassium hydroxide (5.5 mL, 40%
aqueous solution, 40 mmol); stirring was continued at 08C for
2 h. To the above mixture, formaldehyde solution (3.8 mL, 35%,
44 mmol) was added and the stirring was continued for further
3 h. The resulting solution was added dropwise to a solution of
2-aminoethanol (1.2 mL, 20 mmol) in phosphate buffer (pH 7.8,
5 mL) at 08C. After stirring for 5 h at ambient temperature, the
medium was rendered nearly neutral and the formed precipi-
tates were collected by filtration, washed with aqueous metha-
nol, dried, and crystallized from ethanol. On the other hand,
liquid products were obtained by extraction of the reaction mix-
ture with chloroform. The combined organic extract was
washed with brine and dried (Na2SO4). Concentration and col-
umn chromatography (CHCl3/MeOH, 10 : 2) afforded the target
compounds. Yields, melting points, and physical data are given
in Table 1.
5-(2-Hydroxyethyl)-3-n-pentyl-3,4,5,6-tetrahydro-2H-
1,3,5-thiadiazine-2-thione 10
1H-NMR: 1.00 (3H, t, CH3), 1.25–2.05 (6H, m, CH2(CH2)3CH3), 2.85
(1H, br s, OH), 3.15 (2H, t, CH2CH2OH), 3.65–4.40 (4H, m,
CH2(CH2)3CH3 and CH2CH2OH), 4.75 (4H, s, 26CH2). Anal. calcd.
for C10H20N2OS2: C, 48.35; H, 8.12; N, 11.28; Found: C, 48.50; H,
8.00; N, 11.50.
3-n-Hexyl-5-(2-hydroxyethyl)-3,4,5,6-tetrahydro-2H-
1,3,5-thiadiazine-2-thione 11
1H-NMR: 0.95 (3H, t, CH3), 1.20–2.00 (8H, m, CH2(CH2)4CH3), 3.15
(2H, t, CH2CH2OH), 3.54 (1H, br s, OH), 3.70–4.35 (4H, m,
CH2(CH2)4CH3 and CH2CH2OH), 4.65 (4H, s, 26CH2). Anal. calcd.
for C11H22N2OS2: C, 50.34; H, 8.45; N, 10.67; Found: C, 50.44; H,
8.34; N, 10.78.
5-(2-Hydroxyethyl)-3-methyl-3,4,5,6-tetrahydro-2H-1,3,5-
thiadiazine-2-thione 4
1H-NMR: 3.15 (2H, t, CH2CH2OH), 3.65 (3H, s, CH3), 3.85–4.25 (3H,
m, CH2CH2OH), 4.75 (4H, s, 2CH2). Anal. calcd. for C6H12N2OS2: C,
37.47; H, 6.29; N, 14.57; Found: C, 37.40; H, 6.04; N, 14.55.
3-Cyclohexyl-5-(2-hydroxyethyl)-3,4,5,6-tetrahydro-2H-
1,3,5-thiadiazine-2-thione 12
1H-NMR: 1.00–2.25 (10H, m, c-hexyl), 2.45 (1H, br s, OH), 3.15 (2H,
t, CH2CH2OH), 3.85 (2H, t, CH2CH2OH), 4.55 (4H, s, 2CH2), 5.75–
6.30 (1H, m, CHN of c-hexyl). Anal. calcd. for C11H20N2OS2: C,
50.73; H, 7.74; N, 10.76; Found: C, 50.51; H, 8.41; N, 10.55.
3-Ethyl-5-(2-hydroxyethyl)-3,4,5,6-tetrahydro-2H-1,3,5-
thiadiazine-2-thione 5
1H-NMR: 1.25 (3H, t, CH3), 2.85 (1H, br s, OH), 3.05 (2H, t,
CH2CH2OH), 3.80–4.15 (4H, m, CH2CH2OH and CH2CH3), (4H, s,
26CH2). Anal. calcd. for C7H14N2OS2: C, 40.75; H, 6.84; N, 13.58.
Found: C, 41.05; H, 6.73; N, 13.55.
3-Benzyl-5-(2-hydroxyethyl)-3,4,5,6-tetrahydro-2H-1,3,5-
thiadiazine-2-thione 13
1H-NMR: 1.95 (1H, br s, OH), 2.90(2H, t, CH2CH2OH), 3.70 (2H, t,
CH2CH2OH), 4.50 (2H, s, CH2 ring), 4.55 (2H, s, CH2 ring), 5.55 (2H,
s, CH2Ph), 7.60 (5H, s, C6H5). Anal. calcd. for C12H16N2OS2: C, 53.70;
H, 6.01; N; 10.44; Found: C, 53.83; H, 6.11; N, 10.23.
5-(2-Hydroxyethyl)-3-n-propyl-3,4,5,6-tetrahydro-2H-
1,3,5-thiadiazine-2-thione 6
1H-NMR: 1.00 (3H, t, CH3), 1.50–2.10 (2H, m, CH2CH2CH3), 2.85
(1H, br s, OH), 3.10 (2H, t, CH2CH2OH), 3.75–4.30 (4H, m,
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Arch. Pharm. Chem. Life Sci. 2008, 341, 370–376
Antimicrobial l,3,5-Thiadiazine-2-thione
375
centration was approximately 105 spores/mL. About 15 mL of
growth medium was introduced into sterilized plates of 9 cm
diameter and inoculated with 1 mL of spore or cell suspension.
Plates were shaken gently to homogenize the medium.
5-(2-Hydroxyethyl)-3-phenacyl-3,4,5,6-tetrahydro-2H-
1,3,5-thiadiazine-2-thione 14
1H-NMR: 2.35 (1H, br s, OH), 2.80–3.45 (4H, m, CH2CH2OH and
CH2CH2Ph), 3.80 (2H, t, CH2CH2OH), 4.20–4.65 (6H, m, 2CH2 ring
and CH2CH2Ph), 7.50 (5H, s, C6H5). Anal. calcd. for C13H18N2OS2: C,
55.28; H, 6.42; N, 9.92; Found: C, 54.95; H, 6.50; N, 9.71.
The antimicrobial activity of the tested compounds was per-
formed by the standard agar disc diffusion method [25] as fol-
lows: Sterile 6 mm filter paper discs (Whatman) were impreg-
nated with solutions of the tested compound as well as the refer-
ence drugs (10 lM/mL in DMSO). In addition, other discs were
impregnated with the solvent (DMSO) and served as control. The
impregnated discs were then dried for 1 h and placed in the cen-
ter of each plate. The seeded plates were incubated at 28 l 28C
for 7 days in case of fungi and 2 days at 37 l28C in case of bacte-
ria. The radii of the inhibition zones (in mm) were measured at
successive intervals during the incubation period. Triplicate sets
were applied for each treatment and the results are given in
Table 2.
5-(2-Hydroxyethyl)-3-(1-dl-phenacyl)-3,4,5,6-tetrahydro-
2H-1,3,5-thiadiazine-2-thione 15
1H-NMR: 1.55 (3H, d, CH3), 1.95 (1H, br s, OH), 2.35–2.95 (2H, t,
CH2CH2OH), 3.35 (2H, t, CH2CH2OH), 4.25–4.65 (5H, m, 2CH2 and
CHPh), 7.50 (5H, s, C6H5). Anal. calcd. for C13H18N2OS2: C, 55.28; H,
6.42; N, 9.92; Found: C, 55.65; H, 6.50; N, 10.11.
3-Carboxymethyl-5-(2-hydroxyethyl)-3,4,5,6-tetrahydro-
2H-1,3,5-thiadiazine-2-thione 16
1H-NMR: 3.05 (2H, t, CH2CH2OH), 3.75 (2H, t, CH2CH2OH), 4.55-
4.80 (6H, m, 2CH2 and CH2COOH), 5.45 (2H, br s, COOH and OH).
Anal. calcd. for C7H12N2O3S2: C, 35.58; H, 5.12; N, 11.85; Found: C,
35.50; H, 5.13; N, 12.05.
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