Cyclic tertiary sulfamates: Selective inhibition of the tumor-associated carbonic anhydrases IX and XII by N- and O-substituted acesulfame derivatives

Article abstract of DOI:10.1016/j.ejmech.2014.07.014

Carbonic anhydrase (hCA) IX and XII isoforms are over-expressed both in primary and in metastatic cell lines of hypoxic tumors and are innovative targets for cancer diagnosis and treatment. On the basis of the importance of the pharmacophoric sulfamate moiety (bioisostere of the sulfonamide group) present in the structure of recent human CA inhibitors, we designed N-alkylated and O-alkylated derivatives of acesulfame, a cyclic tertiary sulfamate, assessing the inhibitory activity against the ubiquitous isoforms hCA I and II and the cancer-related isoforms hCA IX and XII. All derivatives were nanomolar inhibitors, with some of them possessing an outstanding selectivity towards the tumor-associated hCA IX and/or hCA XII isoforms.

Full text of DOI:10.1016/j.ejmech.2014.07.014

European Journal of Medicinal Chemistry 84 (2014) 240e246
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Short communication
Cyclic tertiary sulfamates: Selective inhibition of the tumor-associated
carbonic anhydrases IX and XII by N- and O-substituted acesulfame
derivatives*
,
Celeste De Monte a *, Simone Carradori a, Daniela Secci a, Melissa D'Ascenzio a,
, c, **
Daniela Vullo b, Mariangela Ceruso b, Claudiu T. Supuran b
a Sapienza University of Rome, Department of Drug Chemistry and Technologies, 00185 Roma, Italy
b
ꢀ
Universita degli Studi di Firenze, Polo Scientifico, Laboratorio di Chimica Bioinorganica, 50019 Florence, Italy
Universita degli Studi di Firenze, Neurofarba Department, Section of Pharmaceutical and Nutraceutical Sciences, Sesto Fiorentino, 50019 Florence, Italy
c
ꢀ
a r t i c l e i n f o
a b s t r a c t
Article history:
Carbonic anhydrase (hCA) IX and XII isoforms are over-expressed both in primary and in metastatic cell
lines of hypoxic tumors and are innovative targets for cancer diagnosis and treatment. On the basis of the
importance of the pharmacophoric sulfamate moiety (bioisostere of the sulfonamide group) present in
the structure of recent human CA inhibitors, we designed N-alkylated and O-alkylated derivatives of
acesulfame, a cyclic tertiary sulfamate, assessing the inhibitory activity against the ubiquitous isoforms
hCA I and II and the cancer-related isoforms hCA IX and XII. All derivatives were nanomolar inhibitors,
with some of them possessing an outstanding selectivity towards the tumor-associated hCA IX and/or
hCA XII isoforms.
Received 1 May 2014
Received in revised form
20 June 2014
Accepted 6 July 2014
Available online 8 July 2014
Keywords:
Acesulfame derivatives
Anticancer agents
N-alkylation
© 2014 Elsevier Masson SAS. All rights reserved.
O-alkylation
Selective hCA IX/hCAXII inhibitors
Sulfamate
1. Introduction
the hydroxylation and the degradation, and forms a dimer with
HIF-1b in the nucleus, interacting with co-activators in a tran-
Malignancies need new blood vessels to provide nutrients and
oxygen, but not all the cancer cells take enough amounts of oxy-
gen and so they become hypoxic [1]. As a consequence of hypoxia,
an upregulation of genes involved in anaerobic metabolism and
tumor vascularization occurs [2]. Hypoxia-inducible factor-1 (HIF-
1) is a protein transcription factor which presents two subunits,
scriptional complex which binds a hypoxia-response element
(HRE) in the promoter or enhancer regions of HIF target genes [3]
which are involved in angiogenesis, vascular tone, erythropoiesis
and in the production of glycolysis enzymes [4]. While in normal
tissues glucose is converted to glucose-6-phosphate and then to
pyruvate, that is oxidized in the mitochondria to carbon dioxide
and water, cancer cells in hypoxia produce energy from glycolysis
by lactic acid fermentation in the cytosol (the so-called Warburg
effect) [5]. The enhanced generation and export to the extracel-
lular environment of lactic and carbonic acids by glycolysis causes
an extracellular acidification: to cope with this unkind condition
and to maintain their intracellular pH weakly alkaline, tumor cells
use buffer systems, pumps and carbonic anhydrases (CAs) [6],
which are zinc metalloenzymes catalyzing the reversible hydra-
tion of carbon dioxide to bicarbonate and protons [7]. The known
the constitutive subunit HIF-1
HIF-1 , and controls the responses to a hypoxic microenviron-
ment. In normoxia, the hydroxylation of the prolines of HIF-1
b and the oxygen-regulated subunit
a
a
isoform is normally required to be recognized by the von Hip-
peleLindau (VHL) tumor suppressor protein for the proteasomal
degradation of HIF-1a. Under hypoxic conditions, HIF-1a eludes
*
We dedicate this paper to the 60th anniversary of Prof. Marius Andruh, close
friend and collaborator of Univ. of Bucharest, Romania.
* Corresponding author.
human CA (EC 4.2.1.1) isozymes belong to the a-class CA family
present in mammals and the most common ubiquitous isoforms
are the cytosolic hCA I and hCA II. On the other hand, CA IX and CA
XII isoforms have been validated as targets of antitumor agents [8].
In fact, the bicarbonate ion produced at the extracellular surface
ꢀ
** Corresponding author. Universita degli Studi di Firenze, Polo Scientifico, Labo-
ratorio di Chimica Bioinorganica, 50019 Florence, Italy.
E-mail addresses: celeste.demonte@uniroma1.it (C. De Monte), claudiu.
supuran@unifi.it (C.T. Supuran).
http://dx.doi.org/10.1016/j.ejmech.2014.07.014
0223-5234/© 2014 Elsevier Masson SAS. All rights reserved.

C. De Monte et al. / European Journal of Medicinal Chemistry 84 (2014) 240e246
241
by CA IX is transported into the cytosol to regulate intracellular pH
while the protons produced by CA IX contribute to diminish
extracellular pH, causing matrix breakdown and tumor invasion
and metastasis. According to these data, CA IX could be used as a
biomarker of hypoxic tumors and is an attractive target for anti-
cancer therapy [9]. Moreover, HIF-1 regulated the expression of CA
IX [10], that has been found in different forms of cancer such as
glioblastoma, colorectal and breast cancer and it is constitutively
present in renal carcinoma [11]. CA IX is also expressed in cancer-
associated fibroblasts and its activity leads to epi-
thelialemesenchymal transition in prostate carcinoma cells
causing major motility, survival and stemness [12]. It has been
demonstrated that the inhibition of CA IX supports anti-VEGF
therapy with bevacizumab [13]. Another tumor-related CA iso-
form is CA XII, which is over-expressed not only in gastric, colo-
rectal and breast cancer but also in T-cell Acute Lymphoblastic
Leukemia human samples [14].
Hence, pursuing our interest in the field of anticancer therapy
[15e17], we developed new selective tumor-associated CAs in-
hibitors [18e20] based on the two most important bioactive che-
motypes present in literature, the metal-complexing anions and
the sulfonamides [21]. Thanks to the encouraging results obtained
by the saccharin derivatives, and basing on the evidence that sul-
famates act as effective CA IX inhibitors [22,23], we decided to
modify the saccharin skeleton endowed with a cyclic tertiary sul-
fonamide moiety designing a bioisosteric series of N-alkylated and
O-alkylated derivatives of the well known sweetener acesulfame
[24], that bears the cyclic tertiary sulfamate group (Fig. 1). Then, we
assessed their inhibitory activity against the ubiquitous hCA I and II
and the cancer-related hCA IX and XII isoforms demonstrating their
outstanding selectivity towards the latter isozymes.
Scheme 1. Synthesis of acesulfame derivatives (sulfamate inhibitors).
3. Biological evaluation
3.1. Carbonic anhydrase inhibition
All the synthesized compounds of a series and b series and the
purchased potassium acesulfame were assayed to establish their
inhibitory effect against the ubiquitous off-target isoforms, CA I and
II, and the cancer-related ones, CA IX and XII by a stopped-flow, CO2
hydrase assay method [26] and the CA inhibition data are sum-
marized in Table 1.
In general, the introduction of an alkyl/benzyl substituent on the
parent compound led to better and selective CA inhibitors. A
comprehensive structureeactivity relationship for this series can
be described as follows.
(i) Most of the tested compounds were not active
(KI > 20000 nM) against two of the common off target CA I
and CA II isoenzymes. They also were more effective than the
starting compound potassium acesulfame and more selec-
tive than the reference drug acetazolamide for the inhibition
of the tumor-associated isoforms. Although weak inhibitory
effects were exerted on CA I by derivatives 3b and 4b
(KI ¼ 2900 and 2485 nM, respectively), and on CA II by 4a
(KI ¼ 2175 nM), these compounds also displayed a consid-
erable activity on the tumor-associated isoforms: 3b, which
contained a CN moiety, possessed a KI of 47 nM towards CA
IX, while the carbonylic derivatives 4a and 4b inhibited CA
XII (KI ¼ 159 and 157 nM, respectively). Compound 15a,
presenting the sterically hindered 30-nitroacetophenone in
the alkylating chain, was not selective towards the off-target
CA II and the tumor-associated CA IX and XII with KI values
ranging from 16.3 to 25.5 nM, and it was also slightly effec-
tive on CA I (1300 nM).
2. Results and discussion
2.1. Chemistry
Twenty-two compounds were synthesized according to the
general procedure reported in Scheme 1 based on a procedure
published in our previous work [20]. The reaction between po-
tassium acesulfame and the electrophile agents in N,N-dime-
thylformamide gave the resulting N-alkylated derivatives (a
series) and/or O-alkylated derivatives (b series). The formation of
a mixture of amide and imidate compounds or the generation of
only one of them depended not only on the thermodynamic sta-
bility of the products, but also on the nature and on the steric
hindrance of the electrophile reactant which could affect the
product distribution and selectivity [25]. These considerations
could explain the formation of the derivatives belonging to a se-
ries and/or b series starting from the ambident nucleophile po-
tassium acesulfame. All synthesized compounds have been fully
characterized by analytical and spectral data (see Section 5.1).
Potassium acesulfame was purchased by SigmaeAldrich® Italy and
used in the syntheses and in the biological assays without further
purification.
(ii) Compounds 1a, 1b, 2b, 7a, 8b, 9a, 10a, 13a, 14a and 14b
selectively inhibited both the tumor-related isozymes: CA IX
was inactivated in the range of 5.7e309 nM, whereas CA XII
in the range of 16.5e180 nM. When acesulfame derivatives
were functionalized with a phenyl ring bearing a bromine
(compounds 8b and 9a) or a cyano moiety (compound 13a),
they lost their selectivity against CA IX and XII. On the other
hand, even though with slight differences, O-alkylated
products 1b, that was functionalized with an allyl moiety,
and 2b, containing a propargyl group, were more active on
CA XII (85.8 and 178 nM respectively), while the O-alkylated
acetophenone derivative 14b was more selective on CA IX
with respect to the corresponding N-alkylated 14a at a
greater concentration (14a at 5.7 nM, while 14b at 15.3 nM).
(iii) Outstanding results for the inhibition of CA IX were reached
with derivatives 5a and 5b, bearing an ethyl ester moiety
(KI ¼ 47 and 43 nM respectively), and 6a and 6b, containing a
phenyl ring substituted in the ortho position with a nitro
group (KI ¼ 41 nM).
(iv) As regards the inhibitory activity against CA XII, it was
noteworthy that the O-alkylated derivative 7b was more
selective than its counterpart N-alkylated 7a: in fact the
former only inhibited this isoform (134 nM), while the latter
Fig. 1. Chemical evolution of novel CA IX and XII inhibitors.

242
C. De Monte et al. / European Journal of Medicinal Chemistry 84 (2014) 240e246
Table 1 (continued)
Table 1
Inhibitory activity of N-alkylated (a series) and O-alkylated (b series) acesulfame
derivatives, potassium acesulfame and the reference drug acetazolamide against
selected hCA isoforms by a stopped-flow CO2 hydrase assay.
Compound
R
KI (nM)
CA I
CA II
CA IX
CA XII
Compound
R
KI (nM)
CA I
CA II
CA IX
CA XII
15a
1300
25.5
16.8
16.3
1a
1b
>20,000 >20,000
>20,000 >20,000
114.4
103
Potassium acesulfame
Acetazolamide
>20,000 >20,000
250 12.1
2410
25.0
>20,000
5.7
199
85.8
both CA IX and XII as reported above. Furthermore, in order
to define a structureeactivity relationship, we could state
that the presence of the nitro group in the meta position
rather than in the ortho position of the phenyl ring reversed
the selectivity of action from CA IX (for derivatives 6a and 6b)
to CA XII (for 7a and 7b). Similarly, compound 11b, which
presented a phenyl ring with a fluorine at C3, had an inhib-
itory effect exclusively on CA XII with a KI of 91.5 nM,
whereas its N-alkylated counterpart 11a was only weakly
more selective on CA XII (18.3 nM) with respect to CA IX
(275 nM). Instead, product 10a, that contained the fluorine at
C2 of the aromatic nucleus, was active towards both CA IX
and XII (KI ¼ 285 and 180 nM, respectively). Finally, com-
pound 12a, presenting two fluorine atoms in the ortho po-
sitions of the aromatic ring, was an effective inhibitor
exclusively of CA XII isozyme (KI ¼ 170 nM).
2b
3b
>20,000 >20,000
2900 >20,000
252
47
178
2900
4a
4b
5a
5b
6a
6b
7a
7b
8b
15,650
2175
>20,000
>20,000
47
159
157
2485 >20,000
>20,000 >20,000
>20,000 >20,000
>20,000 >20,000
>20,000 >20,000
>20,000 >20,000
>20,000 >20,000
>20,000 >20,000
4530
2710
2170
2830
177
43
41
41
These encouraging biological results demonstrated that this
series of N- and O-alkylated acesulfame derivatives could represent
an important starting point for the development of new anticancer
agents.
266.6
>20,000
134
249
180
4. Conclusions
A new series of twenty-two acesulfame derivatives were
designed, synthesized and assayed against four human carbonic
anhydrases: CA IX and XII that are the two tumor-associated iso-
zymes, and CA I and II which represent the most common off-
targets for the development of selective anticancer CA inhibitors.
Most of the compounds had no affinity for hCA I and II, and they all
possessed an inhibitory effect selectively on CA IX and/or CA XII in
the nanomolar range.
9a
>20,000 >20,000
>20,000 >20,000
284
285
170
180
10a
These CAIs should be further studied not only for their phar-
macological importance, but also to elucidate their mechanism of
action. As we already did for other selective CA XII inhibitors that
we synthesized in the past [19], computational investigation with
molecular modeling and docking studies could be used to investi-
gate their selective interaction with CA IX and CA XII in order to
understand if they could be involved or not in a direct binding with
the active site of the enzyme. Therefore, the promising biological
in vitro results demonstrated that this novel class of sulfamate
compounds could represent an innovative and attractive tool for
the development of new antitumor agents based on the inhibition
of the cancer-related isoforms of human carbonic anhydrase.
11a
11b
12a
>20,000 >20,000
>20,000 >20,000
>20,000 >20,000
275
>20,000
>20,000
18.3
91.5
170
13a
>20,000 >20,000
309
136
5. Experimental protocols
14a
14b
>20,000 >20,000
>20,000 >20,000
5.7
16.5
5.1. Chemistry
Solvents were used as supplied without further purification.
Where mixtures of solvents are specified, the stated ratios are
volume:volume. Reagents were used directly as supplied by
15.3
126

C. De Monte et al. / European Journal of Medicinal Chemistry 84 (2014) 240e246
243
SigmaeAldrich® Italy. Column chromatography was carried out
using SigmaeAldrich® silica gel (high purity grade, pore size 60 Å,
230e400 mesh particle size). Analytical thin-layer chromatography
was carried out on SigmaeAldrich® silica gel on TLA aluminum foils
with fluorescent indicator. Visualization was carried out under
ultra-violet irradiation (254 nm). NMR spectra were recorded on a
Bruker AV400 (1H: 400 MHz, 13C: 101 MHz). Coupling constants J
chromatography on silica gel (ethyl acetate:petroleum ether, 1:2)
gave compound 2b as a light yellow oil (73% yield); IR n max 3291 (
n
C
speH), 3108 (
1378 (nas SO2), 1190 (ns SO2), 1159 (
NMR (400 MHz, CDCl3)
2H, CH2), 5.84 (s, 1H, CH]); 13C NMR (101 MHz, CDCl3)
n
C
sp2eH), 2131 (
n
C^C), 1650 (
n
C]N), 1558 (
n
C]C),
n
CeOeC), 726 (
n
OeS) cmꢀ1; 1H
d
2.25 (s, 3H, CH3), 2.64 (s,1H, CH^), 4.94 (s,
20.63
d
(CH3), 56.14 (CH2), 75.48 (CH^), 77.23 (C^CH), 95.31 (CH]),
168.52 (CH3C]), 169.46 (C]N). Anal. Calcd for C7H7NO4S: C, 41.79;
H, 3.51; N, 6.96. Found: C, 41.55; H, 3.24; N, 7.12.
are valued in Hertz (Hz). Chemical shifts are expressed as
d units
(parts per millions), based on appearance rather than interpreta-
tion, and are referenced to the residual non deuterated solvent
peak. IR spectra were recorded on a FT-IR PerkineElmer Spectrum
One equipped with ATR system. Absorption maxima (nmax) are re-
ported in wavenumbers (cmꢀ1). All melting points were measured
on a Stuart® melting point apparatus SMP1, and are uncorrected.
Temperatures are reported in ꢁC. Where given, systematic com-
pound names are those generated by ChemSketch following IUPAC
conventions.
5.1.1.3. [(6-Methyl-2,2-dioxido-1,2,3-oxathiazin-4-yl)oxy]acetonitrile
(3b). Chloroacetonitrile (2.0 eq) was added portionwise to a stir-
ring solution of potassium acesulfame (1.0 eq) in 10 mL of dry N,N-
dimethylformamide. The reaction mixture was stirred at 80 ꢁC for
72 h, poured on ice and extracted with dichloromethane
(3 ꢂ 20 mL). The organics were reunited, dried over sodium sulfate
and concentrated in vacuo. Purification by column chromatography
on silica gel (ethyl acetate:n-hexane, 1:1) gave compound 3b as a
5.1.1. General procedure for the synthesis of acesulfame derivatives
Up to 2.5 eq of the corresponding electrophile were added
portionwise to a stirring solution of potassium acesulfame (1.0 eq)
in 10 mL of dry N,N-dimethylformamide and the reaction mixture
was stirred under nitrogen for 24e72 h at 80 ꢁC, with the exception
of derivatives 1a, 1b and 2b, for which the reaction was carried out
at room temperature because of the low thermostability of the
reagents. Then, the mixture was poured on ice and the resulting
product was extracted or filtered and purified by column chroma-
tography on silica gel.
light brown oil (64% yield); IR n max 2920 (
1649 ( C]N), 1566 ( C]C), 1385 (nas SO2), 1263 (
ns SO2), 930 ( OeS), 734 (
sp2eH) cmꢀ1 1H NMR (400 MHz,
CD2Cl2):
2.31 (s, 3H, CH3), 5.05 (s, 2H, CH2), 5.94 (s, 1H, CH]); 13
NMR (101 MHz, CDCl3) 20.80 (CH3), 51.76 (CH2), 94.60 (CH]),
112.79 (CN), 167.87 (CH3C]), 170.89 (C]N). Anal. Calcd for
C6H6N2O4S: C, 35.64; H, 2.99; N, 13.86. Found: C, 35.40; H, 3.17; N,
14.05.
n
C
sp2eH), 2350 (
n C^N),
n
n
n
CeOeC), 1194
(
n
d
C
;
d
C
d
5.1.1.4. 6-Methyl-3-(2-oxopropyl)-1,2,3-oxathiazin-4(3H)-one 2,2-
dioxide (4a) and 1-[(6-methyl-2,2-dioxido-1,2,3-oxathiazin-4-yl)
oxy]propan-2-one (4b). Chloroacetone (1.1 eq) was added por-
tionwise to a stirring solution of potassium acesulfame (1.0 eq) in
10 mL of dry N,N-dimethylformamide. The reaction mixture was
stirred at 80 ꢁC for 48 h, poured on ice and extracted with chloro-
form (3 ꢂ 20 mL). The organics were reunited, dried over sodium
sulfate and concentrated in vacuo. Purification by column chro-
matography on silica gel (ethyl acetate:petroleum ether, 1:2) gave
compounds 4a and 4b.
5.1.1.1. 6-Methyl-3-(prop-2-en-1-yl)-1,2,3-oxathiazin-4(3H)-one 2,2-
dioxide (1a) and 6-methyl-4-(prop-2-en-1-yloxy)-1,2,3-oxathiazine
2,2-dioxide (1b). Allyl bromide (2.5 eq) was added portionwise to
a stirring solution of potassium acesulfame (1.0 eq) in 10 mL of dry
N,N-dimethylformamide. The reaction mixture was stirred at room
temperature for 48 h, poured on ice and extracted with chloroform
(3 ꢂ 20 mL). The organics were reunited, dried over sodium sulfate
and concentrated in vacuo. Purification by column chromatography
on silica gel (ethyl acetate:petroleum ether, 1:2) gave compounds
1a and 1b.
4a: light yellow powder (28% yield); mp 83e86 ꢁC; IR nmax 3103
(
n
C
sp2eH), 1732 (
CeN), 1197 (ns SO2), 925 (
d6) 2.19 (s, 3H, CH3), 2.28 (s, 3H, CH3), 4.80 (s, 2H, CH2), 6.31 (s, 1H,
CH]); 13C NMR (101 MHz, DMSO-d6)
19.49 (CH3), 27.14 (COCH3),
n
C]O), 1697 (
n C]O), 1395 (nas SO2), 1315 (n
1a: light yellow oil (48% yield); IR nmax 3093 (
C]O),1401 (nas SO2), 1314 ( CeN),1198 (ns SO2), 930 (
sp2eH) cmꢀ1; 1H NMR (400 MHz, CDCl3)
2.18 (s, 3H, CH3), 4.40 (s,
n
C
sp2eH), 1702 (
n
n
OeS) cmꢀ1; 1H NMR (400 MHz, DMSO-
n
n
OeS), 908 (d
d
C
d
d
2H, CH2), 5.25 (d, Jcis ¼ 10.4 Hz, 1H, ]CH2), 5.33 (d, Jtrans ¼ 17.2 Hz,
1H, ]CH2), 5.79 (s, 1H, CH ¼ ), 5.81e5.88 (m, 1H, CH]); 13C NMR
51.46 (CH2), 104.07 (CH]), 159.93 (CH3C]), 163.56 (C]O), 200.20
(C]O). Anal. Calcd for C7H9NO5S: C, 38.35; H, 4.14; N, 6.39. Found:
C, 38.57; H, 4.39; N, 6.62.
(101 MHz, CDCl3)
d 19.62 (CH3), 45.04 (CH2), 104.39 (CH]), 119.79
(CH]), 130.55 (CH2]), 159.85 (CH3C]), 161.92 (C]O). Anal. Calcd
for C7H9NO4S: C, 41.37; H, 4.46; N, 6.89. Found: C, 41.19; H, 4.75; N,
6.61.
4b: yellow oil (35% yield); IR nmax 3022 (
n
C
sp2eH), 1742 (
C]C),1386 (nas SO2),1214 ( CeOeC),1196 (ns
1H NMR (400 MHz, CDCl3)
2.22 (s, 3H,
n C]O),
1652 (
SO2), 745 (
n
C]N),1567 (
n
n
n
OeS) cmꢀ1
;
d
1b: yellow oil (21% yield); IR nmax 3103 (
1553 ( C]C), 1374 (nas SO2), 1271 ( CeOeC), 1187 (ns SO2), 967 (
sp2eH), 932 ( OeS), 910 (
sp2eH) cmꢀ1 1H NMR (400 MHz,
CDCl3)
2.17 (s, 3H, CH3), 4.77 (s, 2H, CH2), 5.30 (d, Jcis ¼ 10.4 Hz,1H,
]CH2), 5.36 (d, Jtrans ¼ 17.2 Hz, 1H, ]CH2), 5.76 (s, 1H, CH]),
5.89e5.95 (m, 1H, CH]); 13C NMR (101 MHz, CDCl3)
20.44 (CH3),
n Csp2eH), 1648 (n C]N),
CH3), 2.26 (s, 3H, CH3), 4.96 (s, 2H, CH2), 5.93 (s, 1H, CH]); 13C NMR
n
n
d
(101 MHz, CDCl3)
d 20.66 (CH3), 26.12 (COCH3), 70.97 (CH2), 95.28
C
n
d
C
;
(CH]), 168.78 (CH3C]), 169.69 (C]N), 198.91 (C]O). Anal. Calcd
for C7H9NO5S: C, 38.35; H, 4.14; N, 6.39. Found: C, 38.10; H, 3.89; N,
6.17.
d
d
60.30 (CH2), 95.58 (CH]), 120.54 (CH]), 130.04 (CH2]), 168.77
(CH3C]), 169.01 (C]N). Anal. Calcd for C7H9NO4S: C, 41.37; H, 4.46;
N, 6.89. Found: C, 41.60; H, 4.22; N, 7.07.
5.1.1.5. Ethyl (6-methyl-2,2-dioxido-4-oxo-1,2,3-oxathiazin-3(4H)-
yl)acetate (5a) and ethyl [(6-methyl-2,2-dioxido-1,2,3-oxathiazin-4-
yl)oxy]acetate (5b).
a-Bromoethyl acetate (2.0 eq) was added to a
5.1.1.2. 6-Methyl-4-(prop-2-yn-1-yloxy)-1,2,3-oxathiazine 2,2-
dioxide (2b). Propargyl bromide (1.1 eq) was added portionwise
to a stirring solution of potassium acesulfame (1.0 eq) in 10 mL of
dry N,N-dimethylformamide. The reaction mixture was stirred at
room temperature for 24 h, poured on ice and extracted with
chloroform (3 ꢂ 20 mL). The organics were reunited, dried over
sodium sulfate and concentrated in vacuo. Purification by column
stirring solution of potassium acesulfame (1.0 eq) in 10 mL of dry
N,N-dimethylformamide. The reaction mixture was stirred at 80 ꢁC
for 24 h, poured on ice and extracted with dichloromethane
(3 ꢂ 20 mL). The organics were reunited, dried over sodium sulfate
and concentrated in vacuo. Purification by column chromatography
on silica gel (ethyl acetate:n-hexane, 1:1) gave compounds 5a and
5b.

244
C. De Monte et al. / European Journal of Medicinal Chemistry 84 (2014) 240e246
5a: light yellow oil (20% yield); IR nmax 3104 (
n
C
sp2eH), 1751 (
C]C), 1320 (nas SO2), 1195 ( CeO),
OeS) cmꢀ1; 1H NMR (400 MHz,
n
(
C
ns SO2), 923 (
n
OeS), 812 (dm
C
sp2eH), 763 (dm
Csp2eH), 686 (dm
C]O), 1703 (
1175 (ns SO2), 1020 (
CD2Cl2):
n
C]O), 1659 (
n
n
sp2eH) cmꢀ1; 1H NMR (400 MHz, CDCl3)
d
2.23 (s, 3H, CH3), 5.06 (s,
n
CeN), 925 (
n
2H, CH2), 5.89 (s, 1H, CH]), 7.57 (t, J ¼ 7.8 Hz, 1H, benzene), 7.78 (d,
d
1.31 (t, 3H, J ¼ 7.2 Hz, CH3), 2.28 (s, 3H, CH3), 4.26 (q, 2H,
J ¼ 7.6 Hz,1H, benzene), 8.21 (d, J ¼ 8.0 Hz,1H, benzene), 8.30 (s,1H,
J ¼ 7.2 Hz, CH2), 4.54 (s, 2H, NeCH2), 5.92 (s, 1H, CH]); 13C NMR
benzene); 13C NMR (101 MHz, CDCl3)
d 19.79 (CH3), 45.20 (CH2),
(101 MHz, CDCl3)
d
14.02 (CH3), 19.85 (CH3), 43.37 (CH2), 62.28
104.44 (CH]), 123.51 (CH-benzene), 123.70 (CH-benzene), 129.85
(CH-benzene), 134.72 (CH-benzene), 136.71 (C-benzene), 148.44 (C-
benzene), 160.04 (CH3C]), 162.34 (C]O). Anal. Calcd for
(CH2), 104.34 (CH]), 159.80 (CH3C]), 162.52 (C]O), 166.22 (C]O).
Anal. Calcd for C8H11NO6S: C, 38.55; H, 4.45; N, 5.62. Found: C,
38.21; H, 4.74; N, 5.93.
C
11H10N2O6S: C, 44.29; H, 3.38; N, 9.39. Found: C, 44.46; H, 3.15; N,
9.05.
7b: yellow powder (17% yield); mp 115e123 ꢁC; IR nmax 3120 (
sp2eH), 1645 ( C]N), 1555 ( C]C), 1529 (nas NeO), 1353 (ns
NeO), 1340 (nas SO2), 1180 (ns SO2), 1166 ( CeOeC), 964 ( OeS),
822 (dm sp2eH), 741 (dm sp2eH), 699 (dm
sp2eH) cmꢀ1; 1H NMR
(400 MHz, CD2Cl2) 2.28 (s, 3H, CH3), 5.50 (s, 2H, CH2), 5.94 (s, 1H,
5b: light yellow oil (51% yield); IR nmax 3113 (
C]O), 1647 ( C]N), 1557 ( C]C), 1371 (nas SO2), 1185 (
1158 (ns SO2), 1037 ( CeOeC), 931 (
OeS) cmꢀ1 1H NMR
(400 MHz, CD2Cl2):
1.32 (t, 3H, J ¼ 7.2 Hz, CH3), 2.28 (s, 3H, CH3),
4.28 (q, 2H, J ¼ 7.2 Hz, CH2), 4.91 (s, 2H, OeCH2), 5.97 (s, 1H, CH]);
13C NMR (101 MHz, CDCl3)
14.03 (CH3), 20.62 (CH3), 62.05 (CH2),
n
Csp2eH), 1753 (
n
n
n
n
CeO),
n
n
n
;
C
n
n
d
n
n
C
C
C
d
d
63.74 (CH2), 95.24 (CH]), 165.93 (CH3C]), 168.85 (C]O), 169.69
(C]N). Anal. Calcd for C8H11NO6S: C, 38.55; H, 4.45; N, 5.62. Found:
C, 38.79; H, 4.22; N, 5.36.
CH]), 7.66 (t, J ¼ 7.8 Hz, 1H, benzene), 7.80 (d, J ¼ 7.6 Hz, 1H,
benzene), 8.27 (d, J ¼ 8.4 Hz, 1H, benzene), 8.32 (s, 1H, benzene);
13C NMR (101 MHz, DMSO-d6)
d 20.36 (CH3), 67.39 (CH2), 95.89
(CH]), 125.58 (CH-benzene), 129.84 (CH-benzene), 130.61 (CH-
benzene), 130.91 (CH-benzene), 134.80 (C-benzene), 148.01 (C-
benzene), 169.75 (CH3C]), 170.41 (C]N). Anal. Calcd for
5.1.1.6. 6-Methyl-3-(2-nitrobenzyl)-1,2,3-oxathiazin-4(3H)-one 2,2-
dioxide (6a) and 6-methyl-4-[(2-nitrobenzyl)oxy]-1,2,3-oxathiazine
2,2-dioxide (6b). 2-Nitrobenzyl chloride (1.1 eq) was added to a
stirring solution of potassium acesulfame (1.0 eq) in 10 mL of dry
N,N-dimethylformamide. The reaction mixture was stirred at 80 ꢁC
for 72 h and poured on ice. The resulting suspension was filtered
and washed with water, petroleum ether and diethyl ether. Puri-
fication by column chromatography on silica gel (diethyl ether:-
petroleum ether, 2:1) gave compounds 6a and 6b.
C11H10N2O6S: C, 44.29; H, 3.38; N, 9.39. Found: C, 44.07; H, 3.10; N,
9.58.
5.1.1.8. 4-[(2-Bromobenzyl)oxy]-6-methyl-1,2,3-oxathiazine 2,2-
dioxide (8b). 2-Bromobenzyl bromide (1.1 eq) was added to a stir-
ring solution of potassium acesulfame (1.0 eq) in 10 mL of dry N,N-
dimethylformamide. The reaction mixture was stirred at 80 ꢁC for
24 h, poured on ice and extracted with dichloromethane
(3 ꢂ 20 mL). The organics were reunited, dried over sodium sulfate
and concentrated in vacuo. Purification by column chromatography
on silica gel (ethyl acetate:n-hexane, 1:2) gave compound 8b as a
6a: light yellow powder (11% yield); mp 100e104 ꢁC; IR nmax
3090 (
ns NeO), 1305 (
cmꢀ1; 1H NMR (400 MHz, DMSO-d6)
n
C
sp2eH), 1705 (
CeN), 1199 (ns SO2), 926 (
2.31 (s, 3H, CH3), 5.39 (s, 2H,
n
C]O), 1527 (nas NeO), 1394 (nas SO2), 1344
(
n
n
OeS), 725 (do sp2eH)
C
d
CH2), 6.39 (s, 1H, CH]), 7.46 (d, J ¼ 7.2 Hz, 1H, benzene), 7.63 (t,
J ¼ 7.2 Hz, 1H, benzene), 7.80 (t, J ¼ 8.4 Hz, 1H, benzene), 8.13 (d,
white powder (81% yield); mp 95e96 ꢁC; IR nmax 1651 (
n
C]N),
J ¼ 8.4 Hz, 1H, benzene); 13C NMR (101 MHz, DMSO-d6)
d
19.53
1556 (
CeOeC), 934 (
DMSO-d6)
n
C]C), 1527 (
n
C]C), 1344 (nas SO2), 1190 (ns SO2), 1162 (
n
(CH3), 43.06 (CH2), 104.18 (CH]), 125.68 (CH-benzene), 128.86 (CH-
benzene), 129.76 (CH-benzene), 130.39 (CH-benzene), 134.77 (C-
benzene), 148.17 (C-benzene), 160.33 (CH3C]), 163.85 (C]O). Anal.
Calcd for C11H10N2O6S: C, 44.29; H, 3.38; N, 9.39. Found: C, 44.55; H,
3.11; N, 9.02.
n
OeS), 760 (do
C
sp2eH) cmꢀ1;1H NMR (400 MHz,
d
2.27 (s, 3H, CH3), 5.44 (s, 2H, CH2), 6.42 (s, 1H, CH]),
7.39 (t, J ¼ 7.6 Hz,1H, benzene), 7.47 (t, J ¼ 7.4 Hz,1H, benzene), 7.62
(d, J ¼ 7.6 Hz, 1H, benzene), 7.72 (d, J ¼ 8.0 Hz, 1H, benzene); 13C
NMR (101 MHz, DMSO-d6) d 20.34 (CH3), 69.45 (CH2), 95.91 (CH]),
6b: light yellow powder (72% yield); mp 141e144 ꢁC; IR nmax
124.19 (C-benzene), 128.56 (CH-benzene), 131.71 (CH-benzene),
132.16 (CH-benzene), 133.30 (CH-benzene), 133.64 (C-benzene),
169.86 (CH3C]), 170.34 (C]N). Anal. Calcd for C11H10BrNO4S: C,
39.77; H, 3.03; N, 4.22. Found: C, 39.98; H, 3.34; N, 4.01.
3112 (
ns NeO), 1344 (nas SO2), 1191 (ns SO2), 1163 (
735 (do
sp2eH) cmꢀ1; 1H NMR (400 MHz, DMSO-d6)
n
C
sp2eH), 1646 (
n
C]N), 1562 (
n
C]C), 1527 (nas NeO), 1356
CeOeC), 933 ( OeS),
2.29 (s, 3H,
(
n
n
C
d
CH3), 5.73 (s, 2H, CH2), 6.45 (s, 1H, CH]), 7.71 (t, J ¼ 7.8 Hz, 1H,
benzene), 7.79 (d, J ¼ 7.2 Hz, 1H, benzene), 7.86 (t, J ¼ 7.6 Hz, 1H,
benzene), 8.18 (d, J ¼ 8.0 Hz, 1H, benzene); 13C NMR (101 MHz,
5.1.1.9. 3-(3-Bromobenzyl)-6-methyl-1,2,3-oxathiazin-4(3H)-one
2,2-dioxide (9a). 3-Bromobenzyl bromide (1.1 eq) was added to a
stirring solution of potassium acesulfame (1.0 eq) in 10 mL of dry
N,N-dimethylformamide. The reaction mixture was stirred at 80 ꢁC
for 72 h, poured on ice and extracted with dichloromethane
(3 ꢂ 20 mL). The organics were reunited, dried over sodium sulfate
and concentrated in vacuo. Purification by column chromatography
on silica gel (ethyl acetate:n-hexane, 1:1) gave compound 9a as a
DMSO-d6)
d 20.36 (CH3), 67.39 (CH2), 95.89 (CH]), 125.58 (CH-
benzene), 129.84 (CH-benzene), 130.61 (CH-benzene), 130.91 (CH-
benzene),134.80 (C-benzene),148.01 (C-benzene),169.75 (CH3C]),
170.41 (C]N). Anal. Calcd for C11H10N2O6S: C, 44.29; H, 3.38; N,
9.39. Found: C, 43.98; H, 3.04; N, 9.67.
5.1.1.7. 6-Methyl-3-(3-nitrobenzyl)-1,2,3-oxathiazin-4(3H)-one 2,2-
dioxide (7a) and 6-methyl-4-[(3-nitrobenzyl)oxy]-1,2,3-oxathiazine
2,2-dioxide (7b). 3-Nitrobenzyl bromide (1.1 eq) was added to a
stirring solution of potassium acesulfame (1.0 eq) in 10 mL of dry
N,N-dimethylformamide. The reaction mixture was stirred at 80 ꢁC
for 72 h, poured on ice and extracted with chloroform (3 ꢂ 20 mL).
The organics were reunited, dried over sodium sulfate and
concentrated in vacuo. Purification by column chromatography on
silica gel (ethyl acetate:petroleum ether, 1:2) gave compounds 7a
and 7b.
white powder (73% yield); mp 71e76 ꢁC; IR nmax 3089 (
1706 ( C]O), 1387 (nas SO2), 1315 ( CeN), 1193 (ns SO2), 926 (
OeS), 870 (dm sp2eH), 791 (dm sp2eH), 696 (dm
sp2eH) cmꢀ1;1H
NMR (400 MHz, DMSO-d6) 2.28 (s, 3H, CH3), 5.02 (s, 2H, CH2), 6.35
(s, 1H, CH]), 7.34e7.37 (m, 2H, benzene), 7.53e7.54 (m, 2H, ben-
zene); 13C NMR (101 MHz, DMSO-d6)
19.47 (CH3), 45.18 (CH2),
n Csp2eH),
n
n
n
C
C
C
d
d
104.21 (CH]), 122.17 (C-benzene), 127.32 (CH-benzene), 131.04
(CH-benzene), 131.32 (CH-benzene), 131.42 (CH-benzene), 138.38
(C-benzene), 160.36 (CH3C]), 163.59 (C]O). Anal. Calcd for
7a: white powder (71% yield); mp 93e97 ꢁC; IR nmax 1696 (
O), 1530 (nas NeO), 1396 (nas SO2), 1351 (ns NeO), 1303 ( CeN), 1196
n
C]
C11H10BrNO4S: C, 39.77; H, 3.03; N, 4.22. Found: C, 39.53; H, 3.27; N,
n
4.44.

C. De Monte et al. / European Journal of Medicinal Chemistry 84 (2014) 240e246
245
5.1.1.10. 3-(2-Fluorobenzyl)-6-methyl-1,2,3-oxathiazin-4(3H)-one
2,2-dioxide (10a). 2-Fluorobenzyl chloride (1.1 eq) was added to a
stirring solution of potassium acesulfame (1.0 eq) in 10 mL of dry
N,N-dimethylformamide. The reaction mixture was stirred at 80 ꢁC
for 72 h and poured on ice. The resulting suspension was filtered
and washed with water and petroleum ether to give compound 10a
111.21 (CH-benzene), 112.28 (2ꢂ CH-benzene), 131.70 (C-benzene),
159.81 (CH3C]), 161.39 (d, J ¼ 258.36 Hz, 2ꢂ C-benzene), 163.36
(C]O). Anal. Calcd for C11H9F2NO4S: C, 45.68; H, 3.14; N, 4.84.
Found: C, 45.44; H, 3.32; N, 5.02.
5.1.1.13. 4-[(6-Methyl-2,2-dioxido-4-oxo-1,2,3-oxathiazin-3(4H)-yl)
methyl]benzonitrile (13a). 4-(Bromomethyl)benzonitrile (1.1 eq)
was added to a stirring solution of potassium acesulfame (1.0 eq) in
10 mL of dry N,N-dimethylformamide. The reaction mixture was
stirred at 80 ꢁC for 72 h, poured on ice and extracted with chloro-
form (3 ꢂ 20 mL). The organics were reunited, dried over sodium
sulfate and concentrated in vacuo. Purification by column chro-
matography on silica gel (ethyl acetate:petroleum ether, 1:2) gave
compound 13a as a white powder (82% yield); mp 85e87 ꢁC; IR
as an orange powder (81% yield); mp 44e45 ꢁC; IR nmax 3097 (
sp2eH), 1703 ( C]O), 1494 ( C]C), 1395 (nas SO2), 1299 ( CeN),
1192 (ns SO2), 1161 ( C sp2-F), 922 ( OeS), 756 (do
sp2eH) cmꢀ1;1H
NMR (400 MHz, DMSO-d6) 2.54 (s, 3H, CH3), 5.34 (s, 2H, CH2), 6.61
(s, 1H, CH]), 7.48e7.53 (m, 2H, benzene), 7.63e7.66 (m, 2H, ben-
zene); 13C NMR (101 MHz, DMSO-d6)
19.43 (CH3), 34.58 (CH2),
n
C
n
n
n
n
n
C
d
d
104.22 (CH]), 115.88 (CH-benzene), 116.08 (CH-benzene), 122.38
(CH-benzene), 122.52 (C-benzene), 125.05 (CH-benzene), 130.71 (C-
benzene), 160.18 (CH3C]), 163.47 (C]O). Anal. Calcd for
nmax 3092 (
1311 ( CeN), 1199 (ns SO2), 926 (
NMR (400 MHz, DMSO-d6) 2.29 (s, 3H, CH3), 5.12 (s, 2H, CH2), 6.36
(s, 1H, CH]), 7.51 (d, J ¼ 7.6 Hz, 2H, benzene), 7.86 (d, J ¼ 7.6 Hz, 2H,
benzene); 13C NMR (101 MHz, DMSO-d6)
19.48 (CH3), 45.39 (CH2),
n
Csp2eH), 2235 (
n
C^N), 1694 (
n
C]O), 1395 (nas SO2),
C
11H10FNO4S: C, 48.70; H, 3.72; N, 5.16. Found: C, 48.94; H, 3.55; N,
n
n
OeS), 796 (dp
C
sp2eH) cmꢀ1;1H
5.31.
d
5.1.1.11. 3-(3-Fluorobenzyl)-6-methyl-1,2,3-oxathiazin-4(3H)-one
2,2-dioxide (11a) and 4-[(3-fluorobenzyl)oxy]-6-methyl-1,2,3-
oxathiazine 2,2-dioxide (11b). 3-Fluorobenzyl chloride (1.1 eq)
was added to a stirring solution of potassium acesulfame (1.0 eq) in
10 mL of dry N,N-dimethylformamide. The reaction mixture was
stirred at 80 ꢁC for 48 h, poured on ice and extracted with
dichloromethane (3 ꢂ 20 mL). The organics were reunited, dried
over sodium sulfate and concentrated in vacuo. Purification by
column chromatography on silica gel (ethyl acetate:petroleum
ether, 1:3) gave compounds 11a and 11b.
d
104.16 (CH]), 111.27 (C-benzene), 119.00 (C-benzene), 128.92
(2ꢂ CH-benzene), 133.08 (2ꢂ CH-benzene), 141.25 (CN), 160.32
(CH3C]), 163.69 (C]O). Anal. Calcd for C12H10N2O4S: C, 51.79; H,
3.62; N, 10.07. Found: C, 51.50; H, 3.36; N, 9.84.
5.1.1.14. 6-Methyl-3-(2-oxo-2-phenylethyl)-1,2,3-oxathiazin-4(3H)-
one 2,2-dioxide (14a) and 2-[(6-methyl-2,2-dioxido-1,2,3-oxathiazin-
4-yl)oxy]-1-phenylethanone (14b). 2-Bromoacetophenone (1.1 eq)
was added to a stirring solution of potassium acesulfame (1.0 eq) in
10 mL of dry N,N-dimethylformamide. The reaction mixture was
stirred at 80 ꢁC for 24 h, poured on ice and extracted with chloro-
form (3 ꢂ 20 mL). The organics were reunited, dried over sodium
sulfate and concentrated in vacuo. Purification by column chro-
matography on silica gel (ethyl acetate:petroleum ether, 1:2) gave
compounds 14a and 14b.
11a: yellow oil (41% yield); IR nmax 1703 (
1402 (nas SO2), 1265 ( CeN), 1198 (ns SO2), 1167 (
OeS), 800 (dm sp2eH), 732 (dm sp2eH), 703 (dm
NMR (400 MHz, CDCl3) 2.25 (s, 3H, CH3), 5.00 (s, 2H, CH2), 5.87 (s,
n
C]O), 1593 (
Csp2-F), 928 (
sp2eH) cmꢀ1;1H
n C]C),
n
n
n
C
C
C
d
1H, CH]), 7.04 (t, J ¼ 8.4 Hz, 1H, benzene), 7.15 (d, J ¼ 9.2 Hz, 1H,
benzene), 7.22 (d, J ¼ 7.6 Hz, 1H, benzene), 7.31e7.36 (m, 1H, ben-
zene); 13C NMR (101 MHz, CDCl3)
d
19.76 (CH3), 45.63 (CH2), 104.52
14a: light yellow powder (63% yield); mp 109e113 ꢁC; IR nmax
(CH]), 115.39 (C-benzene), 115.60 (CH-benzene), 115.83 (CH-ben-
zene), 124.35 (CH-benzene), 130.27 (CH-benzene), 130.36 (C-ben-
zene), 160.09 (CH3C]), 162.01 (C]O). Anal. Calcd for C11H10FNO4S:
C, 48.70; H, 3.72; N, 5.16. Found: C, 48.91; H, 3.43; N, 5.42.
11b: light yellow powder (29% yield); mp 61e63 ꢁC; IR nmax 3088
3098 (
CeN), 1193 (ns SO2), 920 (
cmꢀ1; 1H NMR (400 MHz, DMSO-d6)
n
C
sp2eH), 1709 (
n
C]O), 1693 (
OeS), 751 (
2.33 (s, 3H, CH3), 5.50 (s, 2H,
n
C]O), 1396 (nas SO2), 1318 (
n
n
d
C
sp2eH), 685 ( sp2eH)
d C
d
CH2), 6.37 (s, 1H, CH]), 7.59 (t, J ¼ 7.6 Hz, 2H, benzene), 7.73 (t,
J ¼ 7.2 Hz, 1H, benzene), 8.07 (d, J ¼ 7.6 Hz, 2H, benzene); 13C NMR
(
n
C
sp2eH), 1651 (
SO2),1263 ( C sp2-F),1193 (ns SO2),1179 (
dm sp2eH), 785 (dm sp2eH), 690 (dm
(400 MHz, DMSO-d6) 2.27 (s, 3H, CH3), 5.40 (s, 2H, CH2), 6.41 (s,
n
C]N), 1542 (
n
C]C), 1441 (
CeOeC), 918 (
sp2eH) cmꢀ1
n
C]C), 1351 (nas
OeS), 868
1H NMR
(101 MHz, DMSO-d6) d 19.55 (CH3), 49.64 (CH2), 104.19 (CH]),
n
n
n
128.74 (2ꢂ CH-benzene), 129.44 (2ꢂ CH-benzene), 134.17 (CH-
benzene), 134.83 (C-benzene), 160.17 (CH3C]), 163.68 (C]O),
191.43 (C]O). Anal. Calcd for C12H11NO5S: C, 51.24; H, 3.94; N, 4.98.
Found: C, 51.02; H, 3.69; N, 4.72.
(
C
C
C
;
d
1H, CH]), 7.24 (t, J ¼ 8.4 Hz, 1H, benzene), 7.34 (t, J ¼ 9.2 Hz, 2H,
benzene), 7.45e7.49 (m, 1H, benzene); 13C NMR (101 MHz, DMSO-
14b: yellow powder (26% yield); mp 132e134 ꢁC; IR nmax 3118 (
n
d6)
d
20.31 (CH3), 69.74 (CH2), 71.86 (CH]), 96.09 (CH-benzene),
C
sp2eH), 1701 (
1374 (nas SO2), 1229 (
OeS), 738 ( sp2eH), 690 (
DMSO-d6) 2.32 (s, 3H, CH3), 5.94 (s, 2H, CH2), 6.55 (s, 1H, CH]),
n
C]O), 1655 (
CeOeC), 1193 (ns SO2), 963 (
sp2eH) cmꢀ1 1H NMR (400 MHz,
n
C]N), 1560 (
n
C]C), 1449 (
n C]C),
116.03 (C-benzene), 125.21 (CH-benzene), 131.16 (CH-benzene),
137.30 (CH-benzene), 162.51 (d, J ¼ 244.82 Hz, C-benzene), 169.89
(CH3C]), 170.06 (C]N). Anal. Calcd for C11H10FNO4S: C, 48.70; H,
3.72; N, 5.16. Found: C, 48.51; H, 3.99; N, 4.92.
n
d
C
sp2eH), 921 (
n
d
C
d
C
;
d
7.60 (t, J ¼ 7.6 Hz, 2H, benzene), 7.73 (t, J ¼ 7.4 Hz,1H, benzene), 8.00
(d, J ¼ 7.2 Hz, 2H, benzene); 13C NMR (101 MHz, DMSO-d6)
d 20.36
5.1.1.12. 3-(2,6-Difluorobenzyl)-6-methyl-1,2,3-oxathiazin-4(3H)-
one 2,2-dioxide (12a). 2,6-Difluorobenzyl chloride (1.1 eq) was
added to a stirring solution of potassium acesulfame (1.0 eq) in
10 mL of dry N,N-dimethylformamide. The reaction mixture was
stirred at 80 ꢁC for 48 h and poured on ice. The resulting suspension
was filtered and washed with water and n-hexane to give com-
pound 12a as a white powder (78% yield); mp 65e66 ꢁC; IR nmax
(CH3), 70.68 (CH2), 95.91 (CH]), 128.41 (2ꢂ CH-benzene), 129.48
(2ꢂ CH-benzene), 133.85 (CH-benzene), 134.79 (C-benzene), 170.00
(CH3C]), 170.62 (C]N), 191.44 (C]O). Anal. Calcd for C12H11NO5S:
C, 51.24; H, 3.94; N, 4.98. Found: C, 51.55; H, 4.15; N, 5.17.
5.1.1.15. 6-Methyl-3-[2-(3-nitrophenyl)-2-oxoethyl]-1,2,3-
oxathiazin-4(3H)-one
2,2-dioxide
(15a).
3098 (
CeN), 1193 (ns SO2), 1068 (
do sp2eH), 785 (do ;
sp2eH) cmꢀ1
n
C
sp2eH), 1716 (
n
C]O), 1470 (
C sp2-F), 990 (
1H NMR (400 MHz, DMSO-d6)
n
C]C), 1386 (nas SO2), 1316 (
n
2-Bromo-30-nitroacetophenone (1.1 eq) was added to a stirring
solution of potassium acesulfame (1.0 eq) in 10 mL of dry N,N-
dimethylformamide. The reaction mixture was stirred at 80 ꢁC for
24 h, poured on ice and extracted with chloroform (3 ꢂ 20 mL). The
organics were reunited, dried over sodium sulfate and concen-
trated in vacuo. Purification by column chromatography on silica gel
n
n
C sp2-F), 918 ( OeS), 808
n
(
C
C
d
2.25 (s, 3H, CH3), 5.10 (s, 2H, CH2), 6.31 (s, 1H, CH]), 7.12 (t,
J ¼ 8.0 Hz, 2H, benzene), 7.45e7.49 (m, 1H, benzene); 13C NMR
(101 MHz, DMSO-d6)
d 19.37 (CH3), 34.59 (CH2), 104.19 (CH]),

246
C. De Monte et al. / European Journal of Medicinal Chemistry 84 (2014) 240e246
(ethyl acetate:petroleum ether, 1:2) gave compound 15a as a light
yellow powder (87% yield); mp 145e147 ꢁC; IR nmax 3088 (
sp2eH), 1709 ( C]O), 1693 ( C]O), 1526 (nas NeO), 1348 (ns
NeO), 1320 (nas SO2), 1204 (ns SO2), 927 ( OeS), 821 (dm sp2eH),
792 (dm sp2eH), 670 (dm
sp2eH) cmꢀ1; 1H NMR (400 MHz, DMSO-
d6) 2.33 (s, 3H, CH3), 5.65 (s, 2H, CH2), 6.39 (s, 1H, CH]), 7.89e7.91
(m, 1H, benzene), 8.48e8.56 (m, 2H, benzene), 8.77 (s, 1H, ben-
zene); 13C NMR (101 MHz, DMSO-d6)
19.84 (CH3), 49.73 (CH2),
104.35 (CH]), 123.22 (CH-benzene), 129.61 (CH-benzene), 131.79
(CH-benzene), 135.71 (CH-benzene), 148.45 (C-benzene), 160.20 (C-
benzene),164.12 (CH3C]),184.95 (C]O),190.82 (C]O). Anal. Calcd
for C12H10N2O7S: C, 44.17; H, 3.09; N, 8.59. Found: C, 44.42; H, 3.28;
N, 8.84.
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Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.ejmech.2014.07.014.