One-pot synthesis of 5-phenylimino, 5-thieno or 5-oxo-1,2,3-dithiazoles and evaluation of their antimicrobial and antitumor activity

Article abstract of DOI:10.1016/j.bmcl.2008.11.010

We here report the synthesis and biological evaluation of rare 4-substituted-5-phenylimino, 5-thieno- and 5-oxo-1,2,3-dithiazoles. Dithiazoles were selectively obtained in moderate to high yields (25-73%) via a one-pot reaction from various ethanoneoximes

Full text of DOI:10.1016/j.bmcl.2008.11.010

Bioorganic & Medicinal Chemistry Letters 19 (2009) 136–141
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
One-pot synthesis of 5-phenylimino, 5-thieno or 5-oxo-1,2,3-dithiazoles
and evaluation of their antimicrobial and antitumor activity
Lidia S. Konstantinova a, Oleg I. Bol’shakov a, Natalia V. Obruchnikova a, Hélène Laborie b, Annabelle Tanga b,
a,
Valérie Sopéna b, Isabelle Lanneluc b, Laurent Picot b, Sophie Sablé b, Valérie Thiéry b, , Oleg A. Rakitin
*
*
a N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Prospect, 47, 119991 Moscow, Russia
b Université de La Rochelle, UMR CNRS 6250, LIENSs, Bât. Curie, Equipe Molécules à Activités Biologiques, Avenue Michel Crépeau, F-17042 La Rochelle, France
a r t i c l e i n f o
a b s t r a c t
Article history:
We here report the synthesis and biological evaluation of rare 4-substituted-5-phenylimino, 5-thieno-
and 5-oxo-1,2,3-dithiazoles. Dithiazoles were selectively obtained in moderate to high yields (25–73%)
via a one-pot reaction from various ethanoneoximes with sulfur monochloride, pyridine in acetonitrile
followed by treatment by corresponding nucleophiles (aniline, thioacetamide and formic acid). All the
synthesized compounds were screened for their antibacterial (against bacteria Escherichia coli, Salmonella
enterica serovar Typhimurium, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus,
Enterococcus faecalis, Bacillus cereus and Listeria inocua), antifungal (against pathogenic strains Candida
albicans, Candida glabrata, Candida tropicalis and Issatchenkia orientalis) and antitumor (on human cell
lines MCF-7 and MDA-MB-231) activity. 4-(2-Pyridinyl)-5H-1,2,3-dithiazole-5-thione and 4-ethylcarb-
oxyl-5H-1,2,3-dithiazole-5-thione (5d, 5h) that are active against Gram-positive bacteria are significantly
active against fungi. 4-(2-Benzofuranyl)-5-phenylimino-5H-1,2,3-dithiazole (4e) exerts antiproliferative
activity.
Received 6 August 2008
Revised 30 October 2008
Accepted 2 November 2008
Available online 6 November 2008
Keywords:
1,2,3-Dithiazoles
Antibacterial activity
Antifungal activity
Antitumor activity
Ethanoneoximes
Sulfur monochloride
Antiproliferative activity
Ó 2008 Elsevier Ltd. All rights reserved.
Nitrogen-containing heterocycles with sulfur atom are an
important class of compounds in medicinal chemistry. Owing to
their growing use in compounds of therapeutic importance (anti-
bacterial, anticancer drugs), the synthesis of N-heteroimino-
1,2,3,-dithiazole derivatives has been actively pursued in the last
past decade.1 1,2,3-Dithiazoles have attracted much attention
among five-membered sulfur-nitrogen heterocycles because of
their interesting physical and biological properties and versatile
chemistry.2 The abundance of monocyclic dithiazole chemistry
has been derived from 4,5-dichloro-1,2,3-dithiazolium chloride 1
– Appel salt – which is readily prepared from chloroacetonitrile
and sulfur monochloride.3 The versatility springs from the suscep-
tibility of 1 to attack by nucleophiles at S-1, S-2, C-4 and C-5
atoms.4 A rank of 5-substituted 1,2,3-dithiazolium chlorides was
obtained from monosubstituted acetonitriles and sulfur monochlo-
ride.5 But these salts are not interesting from the synthetic point of
view. The chlorine atom in C-4 position on iminodithiazoles 2 can
not be displaced (Fig. 1). Stable 5-(arylimino)-4-chloro-5H-1,2,3-
dithiazoles 2 are interesting because of their biological importance
against some fungi, grasses and broad-leaved weeds.6 In order to
enhance potential antimicrobial activity of the dithiazole deriva-
tives, various research teams varied the structures of the aryl
groups with more complex aromatic moiety.1
In continuation of our work on bioactive 1,2,3-dithiazoles and
search for more potent derivatives, we report in this paper the ori-
ginal synthesis of novel 4- and 5-substituted-1,2,3-dithiazoles I, II,
III bearing at C-5 position an imino, a thioketone or an oxo func-
tionality (Fig. 2). Expecting an enhancement of the antimicrobial
potential, the antibacterial and antifungal activities were mea-
sured. We describe a systematic study of the reaction between
substituted ethanoneoximes and sulfur monochloride according
an easy one-pot protocol for the preparation of 5-phenylimino,
5-thione and 5-one-1,2,3-dithiazoles together with the scope and
limitations of this method.
To obtain the never described class of compounds I, II, III, we
decided to form an Appel salt intermediate bearing an alkyl, aryl
functionality at C-4 position and to displace the chlorine atom at
Cl
NAr
Cl
Cl
+
R
NAr
+
-
ArNH2
N
S
N
S
N
S
S
Cl
S
1
S
2
* Corresponding authors. Tel.: +33 5 46 45 82 76; fax: +33 5 46 45 82 47.
E-mail addresses: valerie.thiery@univ-lr.fr (V. Thiéry), orakitin@ioc.ac.ru (O.A.
Rakitin).
Figure 1.
0960-894X/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2008.11.010

L. S. Konstantinova et al. / Bioorg. Med. Chem. Lett. 19 (2009) 136–141
137
R
NPh
R
S
R
O
R
NPh
R
O
PhNH2
R
Me
OH
HCO2H
10%
+
S2Cl2/Pyridine
N
S
N
S
N
S
N
S
N
S
N
S
I
S
II
S
III
S
S
(27-58%)
3a-3h
6a
4a-4h
CH3C(S)NH2
(25-73%)
R = aryl, alkyl, ester
a R = Ph
Figure 2.
b R = 4-NO2C6H4
c R = 4-FC6H4
R
S
S
d R = 2-pyridinyl
e R = 2-benzofuranyl
f R = 2-thiophenyl
g R = Me
R
Cl
Cl
+
N
R
X
R
Me
OH
S2Cl2/Base
PhNH2
S
-
N
N
S
N
S
5a-5h
S
S
CH3C(S)NH2
HCOOH
h R = CO2Et
4, 5, 6
X = PhN, S, O
IV
3
Scheme 1.
Figure 3.
Table 1
Preparation of the 4-substituted 5-phenyliminodithiazoles 4, 4-substituted-5H-1,2,3-
dithiazoles-5-thiones 5 and the 4-phenyl-5-phenylimino-5H-1,2,3-dithiazole 68.
the C-5 position by a nucleophilic system. Our retrosynthetic route
to targets compounds 4a–4h, 5a–5h and 6a is shown in Fig. 3.
Surprisingly, other than Appel salt 4-substituted 1,2,3-dithiazo-
lium chlorides IV are hardly available. 4-Phenyl- and 4-nitro-
phenyl-1,2,3-dithiazolium chlorides IV have been prepared from
the reaction of acetophenone oxime 3a and its 4-nitro derivative
3b with sulfur monochloride.7
These salts IV were found to be unstable and were converted to
stable 5-arylimino derivatives 4a, 4b by the reaction with primary
aromatic amines (Fig. 4). After optimization of the experimental
conditions, 5-phenylimino-1,2,3-dithiazoles 4a–4h and 5-thione-
1,2,3-dithiazoles 5a–5h were prepared from substituted ethanone-
oximes 3a–3h and sulfur monochloride following an easy one-pot
protocol (Scheme 1 and Table 1).
4-Chloro-5-thiodithiazoles can be prepared by treatment of Ap-
pel salt 1 with hydrogen sulfide in acetonitrile3 or with 2-cya-
nothioacetamide in dichloromethane.5 But both methods are
inconvenient because of toxicity of H2S and high price of the sec-
ond reagent. We decided to employ for this transformation thioac-
etamide which was successfully used by us in the preparation of
4,5-dichloro-3H-1,2-dithiole-3-thione from 3,4,5-trichlorodithioli-
um chloride.9 We checked this possibility by replacing formic acid
with thioacetamide solution in acetonitrile at the last step and
found that thione 5a was obtained in high yield (73%). This method
was extended to other ethanoneoximes. 1,2,3-Dithiazol-5-thiones
5 were formed selectively in high to moderate yields (Table 1
and Scheme 1).
Replacing thioacetamide with formic acid at the last step of the
reaction of ethanoneoximes with S2Cl2 led to imine 6a selectively
in poor yield. HCO2H which was not used before for the synthesis
of 1,2,3-dithiazol-5-ones gave the best yield of ketone 6a and facil-
itates the work-up procedure.
5-Phenylimino, 5-thione and 5-one-1,2,3-dithiazoles 4, 5, 6
were tested for their in vitro antibacterial activity against a panel
of Gram-positive and Gram-negative reference strains: all microbi-
ological products were purchased from Biokar except Mueller Hin-
ton Broth (Difco). Chemicals were of analytical grade from Sigma.
The microorganisms used in this study were Escherichia coli
ATCC25922, Pseudomonas aeruginosa ATCC27853, Staphylococcus
aureus ATCC25923, Candida albicans ATCC10231 from the Ameri-
Product
R
Yield %
mp (°C)
Formula
4a
4b
4c
4d
4e
4f
4g
4h
5a
5b
5c
5d
5e
5f
Ph
55
27
46
47
57
35
57
58
73
56
40
50
55
25
38
59
58
76
172
68
C14H10N2S2
C14H9N3O2S2
C14H9FN2S2
C13H9N3S2
C16H10N2OS
C12H8N2S3
C9H8N2S2
C11H10N2O2S2
C8H5NS3
C8H4N2O2S3
C8H4FNS3
C7H4N2S3
C10H5NOS3
C6H3NS4
C3H3NS3
C5H5NO2S3
C8H5NOS2
4-NO2C6H4
4-FC6H4
2-Pyridinyl
2-Furanyl
2-Thiophenyl
CH3
Oil
144
106
Oil
CO2Et
Ph
Oil
100
188
152
100
134
92
47
Oil
72
4-NO2C6H4
4-FC6H4
2-Pyridinyl
2-Benzofuranyl
2-Thiophenyl
CH3
5g
5h
6a
CO2Et
Ph
can Type Culture Collection, Klebsiella pneumoniae CIP53153, Sal-
monella enterica serovar Typhimurium CIP5858, Enterococcus
faecalis CIP103214 from the French ‘Collection de l’Institut Pasteur’,
Candida glabrata DSM6425, Candida tropicalis DSM1346, Issatchen-
kia orientalis DSM6128 from the ‘Deutsche Sammlung von Mikro-
organismen und Zellkulturen GmbH’, Bacillus cereus and Listeria
inocua from our laboratory collection. The bacteria were grown
for 24 h on nutritive agar medium (or tryptone soy agar medium
for E. faecalis and L. inocua), at 37 °C (or 30 °C forE. faecalis, L. inocua
and B. cereus). The yeasts were grown on yeast extract peptone
dextrose medium at 30 °C for 24 h. The compounds were dissolved
in DMSO 80% and 50
lg of each compound were tested for their
antibacterial and antifungal activity with the agar well diffusion
10
method.
For each experiment, DMSO 80% alone was used as a
control. Determination of the minimum inhibitory concentration
(MIC), the minimum bactericidal concentration (MBC) or the
minimum fungicidal concentration (MFC) of the molecules was
made by macro-dilution broth method, according to Sham and
Washington11 for the bacteria or Shadomy and Pfaller12 for the
yeasts. The tested compounds were dissolved in DMSO. The maxi-
mum concentration of solvent used in liquid cultures (2.13%) did
not affect the growth of the microorganisms.
The in vitro antibacterial and antifungal activities of the com-
pounds were evaluated against pathogenic or opportunistic patho-
genic microorganisms from Gram-positive or Gram-negative
bacteria and yeasts.
Antibacterial activity. The antibacterial assays were first per-
formed by the agar diffusion method against Gram-negative bacte-
ria E. coli ATCC25922, S. enterica serovar Typhimurium CIP5858, K.
R
Cl
Cl
+
R
NPh
R
Me
OH
PhNH2
-
S2Cl2/Pyridine
+
N
N
S
N
S
S
S
IV
Figure 4.

138
L. S. Konstantinova et al. / Bioorg. Med. Chem. Lett. 19 (2009) 136–141
Table 4
pneumoniae CIP53153, P. aeruginosa ATCC27853, and Gram-posi-
tive bacteria S. aureus ATCC25923, E. faecalis CIP103214, B. cereus
and L. inocua. When a product was active, the minimum inhibitory
concentration (MIC) and the minimum bactericidal concentration
(MBC) were determined by the macro-dilution broth method.
MBC is defined as the lowest concentration of product that killed
99.99% of the inoculum. For the MIC, we did not test higher con-
Antimicrobial activity of the compounds 4, 5, 6 detected by the agar diffusion method.
Compound (50
l
g)
Yeasts
C. tropicalis
C. albicans
C. glabrata
I. orientalis
4a
4b
4c
4e
4f
4g
4h
5a
5b
5c
5d
5e
5f
À
À
À
À
À
À
À
À
++
À
À
À
++
À
À
À
+
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
centrations more than 48 lg/ml.
À
À
None of the tested iminodithiazoles 4a–4g had any effect on
the growth of the Gram-negative, Gram-positive bacteria and
yeasts. In contrast compound 4h bearing an ester group at C-4
position and thioketones 5a, 5d and 5h are moderately active
against Gram-positive. The results showed that Gram-positive
bacteria were more sensitive to different compounds than
Gram-negative bacteria (Tables 2 and 3). Compound 5h as well
6a exhibited a weak activity against the Gram-negative bacteria
E. coli (Table 3).
Antifungal activity. As for antibacterial activity, the antifungal
activity was initially tested using the agar diffusion method. The
assays were performed with the following pathogenic strains: C.
albicans ATCC10231, C. glabrata DSM6425, C. tropicalis DSM1346
and I. orientalis DSM6128. No activity was found with the iminodi-
thiazole substituted in C-4 position 4a–4g except for the iminodi-
thiazole 4h. Tested yeasts C. albicans, C. glabrata and C. tropicalis
were significantly inhibited by iminodithiazole 4h, and the thioke-
tones 5d, 5h (Table 4). These first results allowed us to select the
compounds and the fungi strains used for the determination of
the MIC and the minimum fungicidal concentration (MFC). The ra-
tio MFC/MIC was calculated in order to determine if the product
had a fungistatic (MFC/MIC P 4) or fungicidal (MFC/MIC 6 4)
À
À
+++
À
+++
À
À
À
À
À
+++
À
+++
À
À
À
5g
5h
6a
À
À
+++
À
++
À
À
Averaged diameter of the inhibition zone was measured in triplicate; À, inactive;
+, inhibition zone 6–9 mm; ++, inhibition zone 9–12 mm; +++, inhibition zone
>12 mm.
activity. The results are summarized in Table 5. Commercial antibi-
otics, Amphotericin B and fluconazole, were used as references for
inhibitory activity against yeasts. The three products 4h, 5d and
5h, showed significant antifungal activity (Table 5). Amphotericin
B and fluconazole have greater activity against pathogenic yeasts
than the tested compounds, but amphotericin is nephrotoxic and
fluconazole has only fungistatic activity.
Table 2
Antimicrobial activity of the compounds 4, 5, 6 detected by the agar diffusion method.
Compound (50
l
g)
Gram-negative bacteria
Gram-positive bacteria
E. coli
P. aeruginosa
K. pneumoniae
S. Typhimurium
E. faecalis
S. aureus
B. cereus
L. inocua
4a
4b
4c
4e
4f
4g
4h
5a
5b
5c
5d
5e
5f
À
À
À
À
À
À
À
À
À
À
+
À
À
À
++
+
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
À
+
À
À
À
À
À
À
À
À
À
À
+++
À
À
À
++
À
+
À
À
À
À
À
À
+
++
À
À
++
À
À
À
++
À
À
À
À
À
À
À
–
À
À
À
À
À
+
++
+
–
À
À
++
À
À
À
+
À
++
À
À
+
++
À
5g
5h
6a
À
À
Averaged diameter of the inhibition zone was measured in triplicate; À, inactive; +, inhibition zone 6–9 mm; ++, inhibition zone 9–12 mm; +++, inhibition zone >12 mm.
Table 3
Bactericidal activities, minimum inhibitory concentration and minimum bactericidal concentration (l
g/ml)*.
Compound
Bacteria tested
E. coli
E. faecalis
S. aureus
B. cereus
L. inocua
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
4h
5a
5d
5g
5h
6a
À
À
À
À
48
32
48
48
48
À
>48
>48
>48
>48
>48
À
48
>48
>48
>48
À
À
À
À
À
À
À
>48
>48
À
À
À
>48
À
>48
À
48
À
>48
À
16
À
>48
À
>48
>48
>48
>48
>48
À
>48
À
>48
À
>48
À
32
À
>48
À
*
Measured in triplicate.

L. S. Konstantinova et al. / Bioorg. Med. Chem. Lett. 19 (2009) 136–141
139
Pharmacological assay on cancer cells. The preliminary antiprolif-
erative activity of all the synthetized compounds 4, 5, 6 was tested
in vitro on two cell lines.
Cell lines. The antiproliferative activity of dithiazoles was stud-
ied on MCF-7 and MDA-MB-231 human breast cancer cell lines
(LGC Promochem). MCF-7 and MDA-MB-231 were grown in 1%
penicillin–streptomycin (Dutscher).
20 l
L of MTT salt solution (5 g LÀ1 in PBS 100 mM, pH 7.4, sterile,
protected from light) were added to each well, the plates were
incubated for a further 4 h to allow MTT metabolism to formazan
by the succinate-tetrazolium reductase system active only in via-
ble cells. After incubation, the cell culture medium was removed,
and cells were lysed with 100 lL DMSO. Plates were incubated
for 10 min at 37 °C to allow solubilization of formazan crystals,
and to remove bubbles from the wells. The optical densities
were read on a plate reader (VERSAmax, Molecular Devices) at
550 nm. Data were then analyzed to calculate the % of growth
inhibition through a comparison of samples with untreated cells
(cell culture medium containing 1% DMSO, 0% growth inhibition)
and lysed cells (cell culture medium containing 10% SDS, 100%
growth inhibition). Data are presented as the mean percentage
of growth inhibition SEM calculated from 24 measures from
three independent experiments.
Antiproliferative activity. Dithiazoles were dissolved in DMSO
(Sigma–Aldrich) to obtain 10À3 M stock solutions from which fur-
ther dilutions were made in the cell culture medium. A 50
lL ali-
quot of medium containing 2.10À5 M molecules was added to
each well of 96-well plates. After equilibration at 37 °C, 50 lL of
a 105 cell mLÀ1 suspension (5000 cells) were dispensed into all
wells of the pre-equilibrated 96-well plate, diluting dithiazoles
to a final concentration of 10À5 M. After 72 h growth, viable cells
were quantified using the MTT cell proliferation assay. Briefly,
Table 5
Fungicidal activities, minimum inhibitory concentration and minimum fungicidal concentration (l
g/ml)*.
Compound
Fungi tested*
C. glabrata
MFC
C. albicans
C. tropicalis
MIC
MFC
MFC/MIC
MIC
MFC/MIC
MIC
MFC
MFC/MIC
4h
5d
5h
48
32
48
0.25
2
>48
>48
>48
0.5
À
32
8
32
2
48
48
48
2
1.5
6
1.5
2
32
32
48
1
>48
48
>48
2
À
À
1.5
À
À
Amphotericin B
Fluconazole
2
2
>32
>128
>64
4
>128
>32
4
>128
*
Measured in triplicate.
MDA-MB-231
MCF-7
6a
5h
5g
5f
5e
5d
5c
5b
5a
4h
4g
4f
4e
4c
4b
4a
0
10
20
30
40
50
60
70
80
Growth inhibition % (72h)
Figure 5. Antiproliferative activity of dithiazoles 10À5 M on MCF-7 and MDA-MB-231 breast cancer cell lines. Data are presented as the mean percentage of growth
inhibition SEM calculated from 24 measures from three independent experiments.

140
L. S. Konstantinova et al. / Bioorg. Med. Chem. Lett. 19 (2009) 136–141
Bioassays databanks (Bioinfobank Institute, http://cancer.bioinfo.
Acknowledgments
pl/; Pubchem: http://pubchem.ncbi.nlm.nih.gov/) were screened
using the compare methodology (http://dtp.nci.nih.gov/docs/com-
pare/compare_methodology.html) to check the availability of anti-
proliferative data obtained with other dithiazoles, and specifically
1,2,3-dithiazoles.
We gratefully acknowledge financial support from the Russian
Foundation for Basic Research (Grant No. 08-03-00003-a) and the
Royal Society of Chemistry (Research Fund Grant to O.A.R.).
M.A.B. team thank the Comité de Charente Maritime de la Ligue
Nationale Contre le Cancer and the Cancéropôle Grand Ouest for
financial support. V.T. also thank the Conseil Général de Charente
Maritime for financial Ph.D. Grant (H.L.).
Antiproliferative activity of dithiazoles is summarized in Figure
5. Most molecules exhibited a moderate to strong activity at
10À5 M. on MCF-7, with approximated GI50 equal to 10
l
M for
M for compounds
4f, 4g, 4h, 5 and 6. Dithiazoles also exerted a moderate activity
on MDA-MB-231 with GI50 superior to 10 M (0–30% growth inhi-
bition at 10 M). MDA-MB-231 were always more resistant than
compounds 4a, 4b, 4c, 4e and superior to 10
l
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l
l
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Taylor, R. J. K., Eds.; Elsevier: Oxford, 2008; Vol. 6, pp 1–36 (Chapter 6–01).
3. Appel, R.; Janssen, H.; Siray, M.; Knoch, F. Chem. Ber. 1985, 118, 1632.
4. (a) Barclay, T. M.; Beer, L.; Cordes, A. W.; Oakley, R. T.; Preuss, K. E.; Taylor, N. J.;
Reed, R. W. J. Chem. Soc. Chem. Commun. 1999, 531; (b) Koutentis, P. A.
Molecules 2005, 10, 346.
MCF-7 to the presence of dithiazoles in the culture medium, as
previously observed with various antiproliferative compounds
(thiazoloquinazolinones, thiazolocarbazoles).13,14 Molecules active
on MDA-MB-231 were then considered as good antiproliferative
compounds, showing interest for further pharmacomodulation,
as moreover, they were usually very active on MCF-7. Molecules
active on MDA-MB-231 were then considered as good antiprolifer-
ative compounds, showing interest for further pharmacomodula-
tion, as moreover, they were usually very active on MCF-7.
Molecules active on MDA-MB-231 were then considered as good
antiproliferative compounds, showing interest for further pharma-
comodulation, as moreover, they were usually very active on
MCF-7. The presence of an alkyl or benzyl substituent on the
dithiazole ring was associated to a weak activity (4a,4g,5a,5g,6a).
In the same way, substitution of the dithiazole ring by pyridine
(5d), fluorobenzyle (4c,5c) did not increase the antiproliferative
activity on MDA-MB-231. Molecules containing a thioketone sub-
stituent on the dithiazole ring (nitrobenzyl 5b, ethylcarboxylate
5h, benzofuranyl 5e, thienyl 5f) showed a better activity than the
corresponding compounds containing a ketone or imine substitu-
ent (4b,4h,4e,4f, respectively). As a conclusion, dithiazoles substi-
tuted with a thioketone exerted the best antiproliferative activity,
especially when benzofurane (5e), nitrobenzyle (5b), thiophene
(5f) and ethylcarboxylate (5h) substituents were present in the
structure. The benzofurane substituent could represent an inter-
esting candidate for further pharmacomodulation as the benzofu-
rane dithiazole containing an imine substituent (4e) was also
very active on both cell lines. The pharmacological targets of these
original heterocycles remain to be established.
5. Kim, K. Sulfur Rep. 1998, 21, 147.
6. (a) Moore, J. E. U.S. Patent 4059590, 1977; Chem. Abstr., 1978, 88, 50874.; (b)
Mayer, R.; Förster, E.; Matauschek, B. D. German Patent DD 212387, 1984;
Chem. Abstr., 1985, 102, 113064.
7. (a) Gray, M. A.; Rees, C. W.; Williams, D. J. Heterocycles 1994, 37, 1827; (b)
Emayan, K.; Rees, C. W. Bull. Soc. Chim. Belg. 1997, 106, 605.
8. General procedure for the synthesis of 4a–4h from ethanoneoximes: Pyridine
(3 mmol) was added dropwise at À5 to 0 °C to
a stirred solution of
ethanoneoxime (1 mmol) and sulfur monochloride (2 mmol) in acetonitrile
(10 ml) under inert atmosphere of argon. The mixture was stirred at 0 °C for
15 min. Then aniline (1 mmol) was added, the mixture was stirred at 0 °C for
30 min and followed by pyridine (2 mmol), filtered and solvents were
evaporated. The residue was separated by column chromatography (Silica gel
Merck 60, light petroleum and then light petroleum–CH2Cl2 mixtures).
N-[(5Z)-4-Phenyl-5H-1,2,3-dithiazol-5-ylidene]aniline, 4a: yield 55%. Bright
yellow crystals, mp 73–76 °C. Anal. Calcd for C14H10N2S2: C, 62.19; H, 3.73;
N, 10.36. Found: C, 62.25; H, 3.68; N, 10.62. 1H NMR (300 MHz, CDCl3) d: 7.19
(3H, m, Ph), 7.48 (5H, m, Ph), 8.22 (2H, m, Ph). 13C NMR (75.5 MHz, CDCl3) d:
119.0, 125.6, 128.1, 129.0, 129.8, 130.3 (10 CH, Ar), 132.6, 153.1, 159.2, 165.4 (4
sp2 tertiary C). MS (EI, 70 eV), m/z (%): 270 (M+, 96).
N-[(5Z)-4-(4-Nitrophenyl)-5H-1,2,3-dithiazol-5-ylidene]-N-phenylamine,
4b:
yield 27%. Orange crystals, mp 171-172 °C. Anal. Calcd for C8H4N2O2S3: C,
37.49; H, 1.57; N, 10.93. Found: C, 37.62; H, 1.73; N, 11.05. 1H NMR (300 MHz,
CDCl3) d: 7.23 (3H, m, Ph), 7.48 (2H, m, Ph), 8.31 (2H, d, J 8.3, Ar), 8.49 (2H, d, J
8.3, Ar). 13C NMR (75.5 MHz, CDCl3) d: 124.2, 128.6, 135.3, 135.4 and 131.0 (9
CH, Ar), 143.5, 153.4, 157.9, 162.5, 164.0, 170.4 (6 sp2 tertiary C). MS (EI, 70 eV),
m/z (%): 315 (M+, 13), 167 (54).
Databanks screening. Using the Bioinfobank Institute databank,
antiproliferative data on NCI cancer cells lines were found for 33
molecules containing
a thiazole ring (http://cancer.bioinfo.pl/
N-[(5Z)-4-(4-Fluorophenyl)-5H-1,2,3-dithiazol-5-ylidene]-N-phenylamine,
4c:
drugs?search=thiazole) but no data were available for dithiazoles
or bithiazoles. The Pubchem database (http://pubchem.ncbi.nlm.
nih.gov/, search for the term ‘dithiazole’), reports potential antican-
cer activity for various dithiazoles, some of them exerting a good
antiproliferative activity on various NCI cell lines. However, the
main conclusion of this databank screening is that the antiprolifer-
ative activity of 1,2,3-dithiazoles remains to be established for
most molecules. Our study thus provides one of the first reports
of in vitro antiproliferative activity of 1,2,3-dithiazoles on human
breast cancer cell lines.
In conclusion, we described the antimicrobial and antitumor
activity of according to us, never reported 1,2,3-dithiazoles func-
tionalized at C-4 and C-5 positions. We reported an efficient one-
step protocols to 1,2,3-dithiazole-5-phenylimines, 5-thiones and
5-ones from readily available substituted methyl ketone oximes.
The thioketones 5d and 5h appear to be the most active of the ser-
ies tested against Gram-positive microorganisms and yeasts. De-
tailed studies determining the mechanism of action of these
compounds on the bacteria will be published later. As regards
the antitumor interest of compound 4e, biological testing on differ-
ent cell lines should be in progress.
yield 46%. Bright yellow crystals, mp 65–68 °C. Anal. Calcd for C14H9FN2S2: C,
58.31; H, 3.15; F, 6.59; N, 9.71; S, 22.24. Found: C, 58.45; H, 3.26; N, 9.92. 1H
NMR (300 MHz, CDCl3) d: 7.17 (5H, m, Ph), 7.47 (2H, m, Ar), 8.27 (2H, v, Ar). 13
C
NMR (75.5 MHz, CDCl3) d: 115.2, 118.9, 125.8, 128.2, 131.1 (9 CH, Ar), 152.9,
157.9, 157.9, 166.2 and 166.4 (5 sp2 tertiary C). MS (EI, 70 eV), m/z (%): 288 (M+,
34), 167((78).
N-[(5Z)-4-Pyridin-2-yl-5H-1,2,3-dithiazol-5-ylidene]aniline, 4d yield 47%. Red oil.
Anal. Calcd for C13H9N3S2: C, 39.60; H, 1.90; N, 13.19. Found: C, 39.72; H, 2.12;
N, 13.31. 1H NMR (300 MHz, CDCl3) d: 7.16 (3H, m, Ar), 7.43 (3H, m, Ar), 7.82
(1H, m, Ar), 8.04 (1H, d, J 8.5, Py), 8.76 (1H, d, J 3.9, Py). 13C NMR (75.5 MHz,
CDCl3) d: 119.0, 124.9, 125.6, 130.8, 136.2 150.2, 154.0 (9 CH, Ar), 148.2, 151.9,
154.1, 171.1 (4 sp2 tertiary C). MS (EI, 70 eV), m/z (%): 271 (M+, 46).
N-[(5Z)-4-(1-Benzofuran-2-yl)-5H-1,2,3-dithiazol-5-ylidene]-N-phenylamine, 4e:
yield 57%. Red crystals, mp 138–144 °C. Anal. Calcd for C16H10N2OS2: C, 61.91;
H, 3.25; N, 9.02. Found: C, 61.82; H, 3.48; N, 8.79. 1H NMR (300 MHz, CDCl3) d:
7.50 (9H, m, Ar), 8.21 (1H, s, Ar). 13C NMR (75.5 MHz, CDCl3) d: 110.0, 110.2,
111.7, 119.3, 122.9, 123.6, 126.1 and 126.8 (10 CH, Ar), 127.8, 130.3, 148.8,
150.1, 152.6 and 155.4 (6 sp2 tertiary C). MS (EI, 70 eV), m/z (%): 310 (M+, 89).
N-[(5Z)-4-Thien-2-yl-5H-1,2,3-dithiazol-5-ylidene]aniline, 4f, yield 35%. Red
crystals, mp 108 °C. Anal. Calcd for C12H8N2S3: C, 52.14; H, 2.92; N, 10.13.
Found: C, 51.92; H, 2.88; N, 10.39. 1H NMR (300 MHz, CDCl3) d: 7.16 (1H, m, Ar),
7.29 (3H, m, Ar), 7.51 (4H, m, Ar), 8.34 (1H, d, J 4.9, Ar). 13C NMR (75.5 MHz,
CDCl3) d: 119.6, 126.1, 127.2, 129.9, 130.0, 13.1 (8 CH, Ar); 135.0, 151.9, 154.3,
163.0 (4 sp2 tertiary C). MS (EI, 70 eV), m/z (%): 276 (M+, 42), 173 (–PhNC, 8), 167
(–ThCN, 53), 109(–PhNCSS, 55).
N-[(5Z)-4-Methyl-5H-1,2,3-dithiazol-5-ylidene]-N-phenylamine, 4g: yield 57%.
Red oil. Anal. Calcd for C9H8N2S2: C, 51.90; H, 3.87; N, 13.45. Found: C, 52.07;

L. S. Konstantinova et al. / Bioorg. Med. Chem. Lett. 19 (2009) 136–141
141
H, 3.98; N, 13.70. 1H NMR (300 MHz, CDCl3) d: 2.54 (3H, s, CH3), 7.22 (3H, m, Ph),
7.46 (2H, m, Ph). 13C NMR (75.5 MHz, CDCl3) d: 18.6 (CH3), 119.5, 125.9, 129.8 (5
CH, Ph), 152.4, 161.9, 166.3 (3 sp2 tertiary C). MS (EI, 70 eV), m/z (%): 208 (M+,
38), 167 (55).
Ethyl (5Z)-5-(phenylimino)-5H-1,2,3-dithiazole-4-carboxylate, 4h: yield 58%. Red
oil. Anal. Calcd for C11H10N2O2S2: C, 49.61; H, 3.78; N, 10.52; O, 12.01; S, 24.08.
Found: C, 49.88; H, 4.02; N, 10.42. 1H NMR (300 MHz, CDCl3) d: 1.43 (3H, t, J
7.34, CH3), 4.38 (2H, q, J 7.34, CH2), 7.16 (3H, m, Ph), 7,46 (2H, m, Ph). 13C NMR
(75.5 MHz, CDCl3) d:14.2 (CH3), 63.0 (CH2), 119.3 (2CH, Ph), 126.4 (CH), 129.8
(2CH, Ph), 139.4, 152.1, 153.3 and 160.4 (4 sp2 tertiary C). MS (EI, 70 eV), m/z (%):
266 (M+, 40), 167 (80).
132.9, 140.8, 147.6 and 168.7 (4 sp2 tertiary C), 205.2 (C@S). MS (EI, 70 eV), m/z
(%): 251 (M+, 23), 175 (59), 143 (58).
4-Thien-2-yl-5H-1,2,3-dithiazole-5-thione, 5f: yield 25%. Red crystals, mp 89–
92 °C. Anal. Calcd for C6H3NS4: 216.9148. Found: 246.9151. 1H NMR (300 MHz,
CDCl3) d: 7.14 (1H, m, Th), 7.53 (1H, d, J 5.1, Th), 8.36 (1H, d, J 4.4, Th). 13C NMR
(75.5 MHz, CDCl3) d: 127.2, 130.7, 131.7 (3 CH, Th), 133.9, 164.0 (2 sp2 tertiary
C), 205.6 (C@S). MS (EI, 70 eV), m/z (%): 217 (M+, 73), 141 (100), 109 (53).
4-Methyl-5H-1,2,3-dithiazole-5-thione, 5g: yield 38%. Red crystals, mp 45–47 °C.
Anal. Calcd for C3H3CNS3: C, 24.14; H, 2.03; N, 9.38. Found: C, 23.68; H, 2.21; N,
8.83. 1H NMR (300 MHz, CDCl3) d: 2.56 (3H, s, CH3). 13C NMR (75.5 MHz, CDCl3)
d: 18.5 (CH3); 169.8 (sp2 tertiary C); 206.6 (C@S). MS (EI, 70 eV), m/z (%): 149
(M+, 58), 85 (24).
General procedure for the synthesis of 5a–5h from ethanoneoximes: Pyridine
(3 mmol) was added dropwise at À5 to 0 °C to
a
stirred solution of
Ethyl 5-thioxo-5H-1,2,3-dithiazole-4-carboxylate, 5h: yield 59%. Red oil. Anal.
Calcd for C5H5NO2S3: C, 28.97; H, 2.43; N, 6.76. Found: C, 29.26; H, 2.68; N, 7.03.
ethanoneoxime (1 mmol) and sulfur monochloride (2 mmol) in acetonitrile
(10 ml) under an inert atmosphere of argon. The mixture was stirred at 0 °C for
15 min. Then thioacetamide (1.1 mmol) was added, the mixture was stirred at
r.t. for 2 h, filtered and solvents were evaporated. The residue was separated by
column chromatography (Silica gel Merck 60, light petroleum and then light
petroleum–CH2Cl2 mixtures). Yields are given.
1H NMR (300 MHz, CDCl3) d: 1.42 (3H, t, J 7.3, CH3), 4.43 (2H, q, J 7.3, CH2). 13
C
NMR (75.5 MHz, CDCl3) d:14.1 (CH3), 63.4 (CH2), 160.1, 169.4 (2 sp2 tertiary C),
204.6 (C@S). MS (EI, 70 eV), m/z (%): 207 (M+, 53), 179 (6), 163 (20), 149 (65).
Synthesis of 6a from ethanoneoximes: Pyridine (3 mmol) was added dropwise at
À5 to 0 °C to
a stirred solution of ethanoneoxime (1 mmol) and sulfur
4-Phenyl-5H-1,2,3-dithiazole-5-thione, 5a: yield 73%. Brown scales 95–100 °C.
Anal. Calcd for C8H5NS3: C, 45.47; H, 2.38; N, 6.63. Found: C, 45.55; H, 2.43; N,
6.70. 1H NMR (300 MHz, CDCl3) d: 7.36 (3, m, Ph), 7.47 (2H, m, Ph). 13C NMR
(75.5 MHz, CDCl3) d: 128.0, 129.4 (4 CH, Ph); 130.5 (CH, Ph); 131.3, 179.3 (2 sp2
tertiary C); 208.0 (C@S). MS (EI, 70 eV), m/z (%): 211 (M+, 100), 135 (95), 103
(30).
monochloride (2 mmol) in acetonitrile (10 ml) under argon. The mixture was
stirred at 0 °C for 15 min. Then formic acid (5 mmol) was added, the mixture
was stirred at 0 °C for 30 min and refluxed for 1 h, filtered and solvents were
evaporated. The residue was separated by column chromatography (Silica gel
Merck 60, light petroleum and then light petroleum–CH2Cl2 mixtures). Yield is
given.
4-(4-Nitrophenyl)-5H-1,2,3-dithiazole-5-thione, 5b: yield 56%. Black-brown
crystals, mp 182–190 °C. Anal. Calcd for C8H4N2O2S3: C, 37.49; H, 1.57; N,
10.93. Found: C, 37.62; H, 1.73; N, 11.05. 1H NMR (300 MHz, CDCl3) d: 8.15 (2H,
d, J 9.2, Ar), 8.31 (2H, d, J 9.2, Ar). 13C NMR (75.5 MHz, CDCl3) d: 122.5 and 123.5
(4 CH); 126.4, 130.1, 163.1 (3 sp2 tertiary C), 207.3 (C@S). MS (EI, 70 eV), m/z (%):
256 (M+, 38), 180 (100).
4-Phenyl-5H-1,2,3-dithiazole-5-one, 6a: yield 58%. Light yellow crystals, mp 70–
72 °C. Anal. Calcd for C8H5NOS2: C, 49.21; H, 2.58; N, 7.17. Found: C, 49.13; H,
2.73; N, 7.30. 1H NMR (300 MHz, CDCl3) d: 7.48 (3H, m, Ph), 8.15 (2H, m, Ph). 13
C
NMR (75.5 MHz, CDCl3) d: 128.0, 128.8, 131.0 (5 CH, Ph); 130.9, 155.0 (2 sp2
tertiary C); 189.4 (C@O). MS (EI, 70 eV), m/z (%): 195 (M+, 20), 167 (30), 135 (7),
103 (37).
4-(4-Fluorophenyl)-5H-1,2,3-dithiazole-5-thione, 5c: yield 40%. Brown crystals,
mp 148–152 °C. Anal. Calcd for C8H4FNS3: C, 41.90; H, 1.76; N, 6.11. Found: C,
41.83; H,1.89; N, 6.30. 1H NMR (300 MHz, CDCl3) d: 7.15 (2H, t, J 8.80, Ar), 7,98
(2H, m, Ar). 13C NMR (75.5 MHz, CDCl3) d: 115.4, 131.7 (4 CH, Ar), 130.2 (sp2
tertiary C), 150.9, 140.6, 165.7 (3 sp2 tertiary C), 208.0 (C@S). MS (EI, 70 eV), m/z
(%): 229 (M+, 78), 209 (10), 185(12), 153 (89).
4-(2-Pyridinyl)-5H-1,2,3-dithiazole-5-thione, 5d: yield 50%. Red crystals, mp 99–
100 °C. Anal. Calcd for C7H4N2S3: C, 39.60; H, 1.90; N, 13.19. Found: C, 39.72; H,
2.12; N, 13.31. 1H NMR (300 MHz, CDCl3) d: 7.41 (1H, m, Py), 7.82 (1H, m, Py),
8.04 (1H, d, J 8.5, Py), 8.76 (1H, d, J 3.9, Py). 13C NMR (75.5 MHz, CDCl3) d: 124.9,
136.2, 150.2, 154.0 (4 CH, Py), 154.1, 171.1 (2 sp2 tertiary C), 203.4 (C@S). MS (EI,
70 eV), m/z (%): 212 (M+, 46), 168 (15), 136(77).
4-(1-Benzofuran-2-yl)-5H-1,2,3-dithiazole-5-thione, 5e: yield 55%. Red crystals,
mp 132–134 °C. Anal. Calcd for C10H5NOS3: C 47.79; H, 2.01; N, 5.57; O, 6.37; S,
38.27. Found: C, 47.92; H, 2.23; N, 6.76. 1H NMR (300 MHz, CDCl3) d: 7.32 (1H,
m, Bzf), 7.44 (1H, m, Bzf), 7.62 (1H, d, J 8.1, Bzf), 7.73 (1H, d, J 7.3, Bzf), 8.50 (1H, s,
Bzf). 13C NMR (75.5 MHz, CDCl3) d:110.7, 111.4, 122.9, 123.6, 127.1 (5 CH, Bzf),
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