Synthesis and anticonvulsant activity of bioisosteres of trimethadione, N-derivative-1,2,3-oxathiazolidine-4-one-2,2-dioxides from α-hydroxyamides

Article abstract of DOI:10.1016/j.bmc.2012.12.033

The synthesis and anticonvulsant activity of novel heterocycles N-derivative-1,2,3-oxathiazolidine-4-one-2,2-dioxides, bioisosteres of trimethadione (TMD, oxazolidine-2,4-dione) and phenytoin (PHE), are described. TMD is an anticonvulsant drug widely used against absences seizures in the early 80's and PHE is an antiepileptic drug with a wide spectrum activity. The intermediates of synthesis of N-derivative-1,2,3-oxathiazolidine-4-one-2,2- dioxides, α-hydroxyamides, were obtained using microwave assisted synthesis. Anticonvulsant screening was performed in mice after intraperitoneal administration in the maximal electroshock seizure test (MES) and subcutaneous pentylenetetrazole seizures test (scPTZ). These new compounds showed a wide spectrum activity and were no neurotoxic in the RotoRod test. α-Hydroxyamides and N-derivative-1,2,3-oxathiazolidine-4-one-2,2-dioxides were 3-4700 times more potent than valproic acid in the MES test. Quantification of anticonvulsant protection was calculated (ED₅₀) for the most active candidates; α-hydroxyamides 3a-c and 3e, and N-derivative- oxathiazolidine-4-one-2,2-dioxides 5a-c with ED₅₀ values of 9.1, 53.9, 44.6, 25.2, 15.1, 91.1 and 0.06 mg/kg, respectively, in the MES test.

Full text of DOI:10.1016/j.bmc.2012.12.033

Bioorganic & Medicinal Chemistry xxx (2013) xxx–xxx
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Synthesis and anticonvulsant activity of bioisosteres
of trimethadione, N-derivative-1,2,3-oxathiazolidine-4-
one-2,2-dioxides from
a-hydroxyamides
a
a
b
a
Valentina Pastore a,b, , Laureano Sabatier , Andrea Enrique , Mariel Marder , Luis E. Bruno-Blanch
⇑
a Química Medicinal, Departamento de Ciencias Biológicas, UNLP, calle 47 y 115, B1900BJW La Plata, Argentina
b Instituto de Química y Fisicoquímica Biológicas, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, C1113AAD Buenos Aires, Argentina
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis and anticonvulsant activity of novel heterocycles N-derivative-1,2,3-oxathiazolidine-4-
one-2,2-dioxides, bioisosteres of trimethadione (TMD, oxazolidine-2,4-dione) and phenytoin (PHE), are
described. TMD is an anticonvulsant drug widely used against absences seizures in the early 80’s and
PHE is an antiepileptic drug with a wide spectrum activity. The intermediates of synthesis of N-
Received 11 October 2012
Revised 13 December 2012
Accepted 22 December 2012
Available online xxxx
derivative-1,2,3-oxathiazolidine-4-one-2,2-dioxides,
a-hydroxyamides, were obtained using microwave
assisted synthesis. Anticonvulsant screening was performed in mice after intraperitoneal administration
in the maximal electroshock seizure test (MES) and subcutaneous pentylenetetrazole seizures test
(scPTZ). These new compounds showed a wide spectrum activity and were no neurotoxic in the RotoRod
Keywords:
N-derivative-1,2,3-oxathiazolidine-4-one-
2,2-dioxides
test.
more potent than valproic acid in the MES test. Quantification of anticonvulsant protection was calcu-
lated (ED50) for the most active candidates; -hydroxyamides 3a–c and 3e, and N-derivative-oxathiazoli-
a-Hydroxyamides and N-derivative-1,2,3-oxathiazolidine-4-one-2,2-dioxides were 3–4700 times
a-Hydroxyamides
Microwave synthesis
Anticonvulsant screening
a
dine-4-one-2,2-dioxides 5a–c with ED50 values of 9.1, 53.9, 44.6, 25.2, 15.1, 91.1 and 0.06 mg/kg,
respectively, in the MES test.
Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction
1912 and 1940, respectively.12,13 These two compounds were the
best choices for patients with epilepsy for many years. Even today
The past decades have witnessed many advances in the devel-
opment of new strategies for the treatment of epilepsy, mainly
focused in the prevention of seizures. New antiepileptics drugs
(AEDs) currently in used provide adequate seizure control in a sig-
nificant number of the patients.1–4 Between 1990 and 2011 fifteen
new antiepileptic drugs (AEDs) were approved: eslicarbazepine
acetate, felbamate, gabapentin, lacosamide, lamotrigine, leveti-
racetam, oxcarbazepine, pregabalin, retigabine, rufinamide, stirip-
entol, tiagabine, topiramate, vigabatrin and zonisamide. Many
AEDs enlarge serious side effects that are increased when a lifelong
medication is required.5 Pharmacoresistance and therapeutic fail-
ure in 20–25% of the patients remain the main reasons to continue
the search for safer and more efficacious drugs for this devastating
disease.6,7 As a result, intensive efforts are being devoted to find
new antiepileptic compounds with more selective activity and
lower toxicity.8
PHE is one of the major drugs used in epilepsy treatment. Although
both drugs have a broad anti-epileptic spectrum they have no
effect on absence seizures. In 1945, trimethadione (TMD) was
developed as the first drug specific for absence seizures.14,15 For
the next fifteen years many new antiepileptic drugs were devel-
oped by modification of these molecules that were effective
against different types of seizures.16
TMD is the most important of several antiepileptic oxazolidine-
diones.17 Its selective efficacy against absence seizure in man and
its profile of efficacy in experimental animal models were quickly
recognized and were the contrary for those of PHE. Although it
was the drug of choice, as it was the only truly effective drug for
treatment of absence seizures, interest in TMD has declined since
the introduction of ethosuximide and valproic acid. Moreover,
TMD caused ‘fetal trimethadione syndrome’ so this led to with-
drawal from the marketplace.18
Treatment of seizures with bromides in 1850 is considered the
first attempt for AED therapy.9–11 Phenobarbital (PB) and
phenytoin (PHE) were introduced as anticonvulsant agents in
Clinically the oxazolidinediones are effective in the control of
absence and related seizure types but not of partial or generalized
tonic–clonic seizures.19 N-Substituted oxazolidinediones, TMD
derivatives, were synthesized by the pyrolysis of carbonate esters
of the corresponding
a
-hydroxyamides20 and anticonvulsant activ-
⇑
Corresponding author. Tel.: +54 1149648289; fax: +54 1149625457.
E-mail address: vpastore@qb.ffyb.uba.ar (V. Pastore).
ity for some
a
-hydroxyamides have been already described.21
0968-0896/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmc.2012.12.033
Please cite this article in press as: Pastore, V.; et al. Bioorg. Med. Chem. (2013), http://dx.doi.org/10.1016/j.bmc.2012.12.033

2
V. Pastore et al. / Bioorg. Med. Chem. xxx (2013) xxx–xxx
Figure 1. Molecular structures of trimethadione, phenytoin and N-derivative-1,2,3-oxathiazolidine-4-one-2,2-dioxides.
In the present investigation we show some bioisosteres of TMD
The MW reaction conditions for the synthesis of a-hydroxya-
and PHE, called N-derivative-1,2,3-oxathiazolidine-4-one-2,2-
dioxides and 5,5-diphenyl-N-derivative-1,2,3-oxathiazolidine-4-
mides were selected in order to define the best possible proce-
dures. All the compounds were characterized by IR, 1H and 13C
NMR. The purity of the compounds was confirmed by elemental
analysis and the data were found in accordance with 0.3%.
N-derivative-oxathiazolidine-4-one-2,2-dioxides were obtained
with very good yields (75–95%) using ruthenium trichloride to oxi-
dize and sodium periodate as catalyst (Scheme 1). Previous studies
one-2,2-dioxides, respectively ( Fig. 1).
a-Hydroxyamides were
used to obtain the desired N-derivative-1,2,3-oxathiazolidine-4-
one-2,2-dioxide. Many different methods have been proved to
get an
a
-hydroxyamide function.22–24 Biological methods were
also described via Pseudomonas cepacia25 and biocatalytic methods
using Candida antarctica lipase.26 We found that microwave (MW)
reported that the cyclization of flexible 1,2 dioles and a-hydroxya-
radiation has simplified and improved the synthesis of
a-hydrox-
mides give very good yields comparing to those that used sulfuryl
yamides, with better yields, shortened reaction times compared
to traditional synthesis and reactions carried out without solvents
or catalysts.
chloride.
2.2. Anticonvulsant screening
Here we report the synthesis of TMD and PHE bioisosteres:
N-derivative-1,2,3-oxathiazolidine-4-one-2,2-dioxides, the tradi-
The biological evaluation of
a-hydroxyamides 3a–e, 3f and
tional and MW assisted synthesis of a-hydroxyamides, intermedi-
N-derivative-oxathiazolidine-4-one-2,2-dioxides
5a–c, was
ates of synthesis, and the evaluation of their anticonvulsant
activities.
performed in acute models, using the procedures proposed by
the National Institute of Health (NIH) via the Anticonvulsant
Screening Project (ASP).31 The primary evaluation (phase 1) in-
cludes the use of two anticonvulsant tests: Maximal Electroshock
Seizure test (MES) and subcutaneous Pentylenetetrazole Seizure
test (scPTZ). Toxicity is primary detected using the standardized
RotoRod test, which is also include in this phase.32
2. Results and discussion
2.1. Chemistry
It is well accepted that the MES test, which uses an electrical
stimulus, is related to the generalized tonic–clonic seizures. It is
used to identify those compounds that prevent seizures spread.
The scPTZ test involves a chemical induction to generate the con-
vulsion and is related to myoclonic seizures. It helps to identify
those compounds that may act raising seizure threshold.33–36
The compounds were administrated intraperitoneally (ip) to
adult male Swiss Albino mice (18–23 g) at the doses of 30 and
100 mg/kg and the assays were performed 0.5 and 4 h later.
Phase 2 of ASP was also performed, where the Maximal Time
Effect (MTE) and the Median Effective Dose (ED50) in MES test
Ammonolysis of 2-hidroxyisobutyl methyl ester, 2-hydroxyiso-
butyric acid and methyl benzylate with primary amines to ob-
tained
a-hydroxyamides (3a–f) were tested in (a) reflux system
in a proper solvent where reaction time varies from 2 to 7 days27
and (b) solvent free microwave reactor (Discover CEM) where reac-
tion time varies from 15 to 25 min (Scheme 1). When necessary,
boric acid was used as catalyst. Time and temperature conditions
were previously determined. This is the first report of the MW syn-
thesis of these types of a-hydroxyamides.
Cyclization with thionyl chloride (compounds 4a–d) and oxida-
tion with sodium periodate catalyzed by ruthenium trichloride
(compounds 5a–d) (Scheme 1) were conducted accordingly to pre-
viously reported procedures with slight modifications.28–30
The conditions used in the MW reactor for compund 3a–g are
shown in Table 1. Melting points were recorded on Electrothermal
IA6034 apparatus and are uncorrected.
was evaluated for
a-hydroxyamides 3a–c and 3e and N-deriva-
tive-oxathiazolidine-4-one-2,2-dioxides 5a–c.
The tested compounds can be classified into four classes accord-
ing to their activity,36 (1) anticonvulsant activity at 100 mg/kg or
less; (2) anticonvulsant activity at doses higher than 100 mg/kg;
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V. Pastore et al. / Bioorg. Med. Chem. xxx (2013) xxx–xxx
3
Scheme 1. Synthesis of the compounds.
threshold seizure (single episode of clonic spasms of at least 5 s
duration) (Table 2). Compounds 3d and 3f and 5d did not evidence
any anticonvulsant activity in the PTZ test.
Neither of the compounds tested showed any failure to main-
tain balance on the rotating rod of the RotoRod assay evidencing
that the compounds did not produce neurological deficits.
Table 1
MW reaction conditions for the synthesis of
a-hydroxyamides
Compound
Reaction time (min)
Reaction temperature (°C)
Mpa (°C)
3a
3b
3c
3d
3eb
3f
15
15
15
25
15
10
150
150
150
150
150
150
67–68.5
103–105
58–59
54–55
81–82.5
66–67
2.2.2. MES test
The absence of tonic extension of the hind legs after an electro-
shock by ear clips means that the compounds administrated pro-
tect against this test. All the evaluated compounds showed this
protection. Therefore, they could be classified in class 1, as they
protected against the MES test at doses lower than 100 mg/kg.
Compounds 3a–c, 3e–f were active at 0.5 h with a 100% of pro-
tection at 100 mg/kg, while compounds 3d, 3e–3f and 5a showed
100% of protection at 30 mg/kg after 4 h of its ip administration
(Table 2).
a
Melting point of the a-hydroxyamides synthesized.
Boric acid as catalyst.
b
(3) compound inactive at any doses up to 300 mg/kg; (4) com-
pound inactive at 300 mg/kg and toxic at 30 mg/kg or less.
2.2.1. PTZ test
The PTZ test, induced seizure entailed the subcutaneous (sc)
administration of 85 mg/kg of PTZ as a 0.5% solution in 0.9% saline
in the posterior midline of the mice. The animals were observed for
30 min. Protection was defined as the failure to observe even a
MTE and ED50 in MES test were evaluated only for those
N-derivative-oxathiazolidine-4-one-2,2-dioxides whose
a-hydrox-
yamide precursors showed activity in both MES and PTZ tests.
Table 2
Pharmacological profile, MTE and ED50 (mg/kg) of a-hydroxyamides and N-derivatives-1,2,3-oxathiazolidine-4-one-2,2-dioxides and their MlogP values
f
Compound
MlogPa
Dose (mg/kg)
MESb
PTZc
Neurotoxicity screend
MTEe (h)
ED50 (mg/kg)
0.5 h
4 h
0.5 h
4 h
0.5 h
4 h
3a
3b
3c
3d
3e
3f
1.44
1.72
0.82
0.46
1.44
2.99
1.72
1.99
1.06
0.73
30
100
30
100
30
100
30
100
30
100
30
100
30
100
30
3/3
3/3
1/3
3/3
0/3
3/3
1/3
1/3
1/3
3/3
1/3
3/3
1/3
2/3
2/3
2/3
1/3
0/3
1/3
1/3
1/3
0/3
1/3
1/3
2/3
2/3
3/3
0/3
3/3
2/3
3/3
2/3
2/3
3/3
1/2
2/3
2/3
2/3
0/3
1/3
2/2
2/2
0/2
2/2
1/2
0/2
0/2
0/2
0/2
0/2
0/2
0/2
0/2
1/2
2/2
1/2
1/2
0/2
0/2
0/2
0/2
2/2
0/2
2/2
2/2
2/2
0/2
0/2
0/2
0/2
0/2
0/2
0/2
0/2
0/2
1/2
1/2
1/2
0/2
0/2
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0.25
1
9.1
53.9
44.6
nd
6
nd
0.5
nd
4
25.2
nd
5a
5b
5c
5d
15.1
91.1
0.06
nd
2
100
30
100
30
2
nd
100
Values represent number of mice protected from seizures or with neurotoxic effects divided by the number of mice tested.
a
MlogP: coefficient of partition octane–water calculated with Moriguchi method.37
Maximal electroshock seizure.
b
c
Pentylenetetrazol test.
d
Toxicity evaluated in RotoRod test.28
e
MTE: maximal time effect.
f
ED50: median effective dose. nd: not determined. MTE and ED50 values for phenytoin and trimethadione are 1 h and 5.54 mg/kg,41 0.5 h and 627 mg/kg,34 respectively.
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4
V. Pastore et al. / Bioorg. Med. Chem. xxx (2013) xxx–xxx
Valproic acid, a typical antiepileptic drug of broad spectrum in
clinical practice, showed an ED50 of 283 mg/kg in the MES test.
The -hydroxyamides and the N-derivative-1,2,3-oxathiazolidine-
(TLC) and spots were visualized under UV light and revealed by
sulfomolibdic acid solution. Elemental analysis was carried out
on CHNS Carlo Erba EA 1108 and the results were within 0.3%
of the theoretical values. IR spectra were recorded in Bruker IFS
66 FT/IR spectrophotometer as KBr disc. 1H NMR and 13C NMR
spectra were recorded on Bruker AC-200 MHz and Bruker AC-
50 MHz spectrometer respectively using CDCl3 as a solvent and tri-
methylsilane (TMS) as an internal standard. Splitting patterns are
designated as follows: s, singlet; d, doublet; t, triplet, m, multiplet.
a
4-one-2,2-dioxides studied here are more active than this classical
anticonvulsant actually in use. For example, compound 3a is 30
times more active than valproic acid. On the other hand, TMD
and PHE showed ED50 values of 627 and 5.5 mg/kg, respectively,
in the MES test.34 Compound 5a, a bioisostere of TMD, is almost
19 times more active than valproic acid and 40 times more active
than TMD. Outstandingly, compound 5c demonstrated a striking
effect in the MES test, as it showed the most anticonvulsant effect,
being almost 90 times more active than PHE, 4700 times more ac-
tive than valproic acid and 10,000 times more active than TMD.
It is also important to stress here that none of the mice treated
Chemical shift are given in ppm. ESI-MS spectra of the a-hydroxya-
mides were recorded on a LCQ Duo (ESI-Trap) Thermo and in an
Agilent 1100 LC system (Agilent Technologies, USA) coupled with
a MSD VL quadrupole (Agilent Technologies, USA) for the N-deriv-
atives 1,2,3-oxathiazolidin-4-one-2-oxide and N-derivatives
1,2,3-oxathiazolidin-4-one-2,2-dioxides.
with the
a-hydroxyamides or the N-derivative-1,2,3-oxathiazoli-
dine-4-one-2,2-dioxides studied died during the assays.
It is known that the CNS action of a drug, including its anticon-
vulsant activity, depends on its lipophilicity, which enables the
compound to cross the blood brain barrier (BBB) and to reach the
cellular site of action. The calculated lipophilicities, MLogP, of
the present series of compounds are shown in Table 2 and were
estimated using the HyperChem QSAR Properties, version 7.01,
Hypercube, Inc.37,38 It has been determined that a logP = 2 is the
best value for a compound to have passive diffusion through the
BBB. Compounds 3a–f and 5a–d, with broad structural variations,
showed a wide range of MLogP values (2.99 to 0.46). Although
no relation between MlogP values and anticonvulsant activity
could be established, it could be assume that these values are high
enough to allow the delivery of the compounds to the active site.
We also observe that a difference of one methylene group in com-
pounds 3a and 3b; and in compounds 5a and 5b; benzyl or phen-
ethyl group, respectively; decrease in 6 times the activity of the
compounds (ED50 3a: 9.1 mg/kg; ED50 3b: 53.9 mg/kg and ED50
5a: 15.1 mg/kg; ED50 5b: 91.1 mg/kg).
4.2. Synthesis of
(3a–f)
a-hydroxyamides using microwave reactor
MW-assisted free solvent synthesis was performed by means of
the following procedure: -hydroxyacid, -hydroxyisobutyl
a
a
methyl ester or methyl benzilate were put into a dry vessel with
the corresponding primary amine and a Teflon-coated magnetic
stirring bar. The reactor was set at 300 W and 250 psi. Reaction
time for compounds 3a–c and 3e was 15 min; 3d 25 min, and for
compound 3f 10 min; all at 150 °C. The reaction mixture was
monitored by TLC. The compounds were purified on column chro-
matography silica gel 60 (70–230 mesh, Merck). A white solid was
obtained in all cases except for compounds 5c and 5d that were ob-
tained as oil. Crystallization was carried out using the appropriate
solvent where necessary. As cyclohexylamine is little reactive, bo-
ric acid was used as catalyst for the synthesis of the
mide 3e.
a-hydroxya-
4.2.1. N-Benzyl-2-hydroxyisobutylamide (3a)
3. Conclusion
Yield 60% (hexane); mp: 67–68.5; Anal. Calcd for C11H15NO2: C
66.6, H 7.8, O 17.8, N 7.8. Found: C 66.9, H 8.1, O 17.5, N 7.5%; IR
(cmÀ1): 3408 (NH), 3306–3327 (OH), 2947–3076 (Ar), 1660
(C@O), 1541 (band II NH). 1H NMR (CDCl3) d (ppm): 7.40–7.20
(m, Ar), 7.08 (s, OH), 4.45 (d, J = 7.1 Hz –NH–CH2–Ar), 2.55 (s,
NH), 1.50 (s, CH3); 13C NMR (CDCl3) d (ppm): 176.5 (CO), 138.4–
128.9–127.9–127.7 (Ar), 73.9 ((CH3)2–C–OH), 43.5 (–NH–CH2–Bz),
28.2 (CH3). MS (ESI): m/z 194.1 [M+1]+.
In this study a series of novel N-derivative-1,2,3-oxathiazoli-
dines-4-one-2,2-dioxides bioisostere of TMD and PHE, were syn-
thesized with good yields.
these syntheses, were obtained with good yields by a MW reactor
with a non contaminated, reproducible, versatile and fast method.
These intermediates also showed anticonvulsant activities in both
MES and PTZ tests, were not neurotoxic and showed better biolog-
ical activities compared to antiepileptic drugs use in clinical
nowadays.
a-Hydroxyamides, intermediates of
4.2.2. N-Phenethyl-2-hydroxyisobutylamide (3b)
Yield 40% (acetonitrinile); mp: 103–105 °C; Anal. Calcd for
C12H17NO2: C 69.5, H 8.3, O 15.4, N 6.7. Found: C 69.5, H 8.1, O
15.6, N 6.8.%; IR (cmÀ1): 3357 (NH), 3228 (OH), 3037.6 (Ar), 2970
(alcane), 1650 (C@O), 1547.7 (NH band II); 1H NMR (CDCl3) d
(ppm): 7.40–7.20 (m, 5H, Ar), 6.85 (s, 1H, OH), 3.20 (s, 1H, –NH),
3.54–3.15 (m, 2H, –NH–CH2–CH2–), 2.80 (t, 2H, J = 7.1 Hz, –CH2–
CH2–Bz), 1.40 (s, 6H, (CH3)2); 13CNMR (CDCl3) d (ppm): 176.9
(CO), 129.8–128.9–128.8–127.3 (Ar), 74.5 ((CH3)2–C –OH), 42.1
(–NH–CH2–CH2–Bz), 35.9 (–NH–CH2–CH2–Bz), 28.1 (CH3). MS
(ESI): m/z 208.1 [M+1]+.
a-Hydroxyamides 3a–c, 3e, and compounds 5a–5c show an
astounding anticonvulsant effect in the MES test. Moreover,
compound 5c the most active drug obtained, with an ED50 of
60 lg/kg, was 10,000 more active than TMD the reference
compound in this work and 90 times more active than valproic
acid, an anticonvulsant drug presently in use in clinic.
The obtained results showed that
a-hydroxyamides and
N-derivative-1,2,3-oxathiazolidine-4-one-2,2-dioxides could be
useful as a template for future design, modification and investiga-
tion to produce more active analogs.
4.2.3. N-Butyl-2-hydroxyisobutylamide (3c)
Yield 40% (dichloromethane); mp: 58–59 °C; Anal. Calcd for
C8H17NO2: C 60.3, H 10.8, O 20.2, N 8.7. Found: C 60.3, H 10.6, O
20.7, N 8.4%; IR (cmÀ1): 3346.7 (NH), 3254.5 (OH), 2937–2973
(alcane), 2876 (CH3), 1647.7 (C@O). 1H NMR (CDCl3) d (ppm):
6.86 (s, 1H, OH), 3.57 (s, 1H, –NH–), 3.29–3.19 (dd, 2H,
J1 = 6.79 Hz, J2 = 12.83 Hz –NH–CH2–), 1.46–1.33 (m, 2H, –CH2–),
1.46–1.39 (m, 2H, –CH2–CH3), 1.41 (s, 6H, (CH3)2), 0.96–0.89
4. Experimental protocols
4.1. Chemistry
All the required chemicals were purchased from Sigma–Aldrich
and Acros Company. Precoated aluminium sheets (silica gel 60
F254, Merck, ref 1.05554) were use for thin layer chromatography
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V. Pastore et al. / Bioorg. Med. Chem. xxx (2013) xxx–xxx
5
(t, 3H, J = 7.1 Hz, –CH3); 13C NMR (CDCl3) d (ppm):176.9 (CO), 73.5
(–C–OH), 39.2 (–NH–CH2–), 31.8 (–NH–CH2–CH2–), 28.0 ((CH3)2),
20.2 (–CH2–CH3), 13.9 (–CH2–CH3). MS (ESI): m/z 160.1 [M+1]+.
(CO), 134.8–129.2–128.6–128.5 (Ar), 86.9 (CH3)2–C–O–), 44.3
(–N–CH2–Ar), 28.0 (CH3). MS (ESI): m/z 240.1 [M+1]+.
4.3.2. N-phenethyl-1,2,3-oxathiazolidine-4-one-2-oxide (4b)
Yield: 25%. Rf (1): 0.79 and Rf (2): 0.70 (dichloromethane). IR
(cmÀ1): 2925–3025 (CH Ar), 2880 (CH alcane), 1775 (CO), 1340
(SO). 1H NMR (CDCl3) d (ppm): 7.36–7.17 (m, 5H Ar), 4.03–3.89
(q, 1H, J1 = 6.76 Hz, J2 = 7.17 Hz –N–CH2–), 3.69–3.58 (q,
J1 = 6.45 Hz, J2 = 7.46 Hz, –N–CH2–), 3.02–2.95 (t, 2H, J = 7.05 Hz,
–CH2–), 1.67 (s, 3H, CH3), 1.47 (s, 3H, CH3). 13C NMR (CDCl3):
174.2 (CO), 137.5–129.0–128.9–127.2 (Ar), 86.5 ((CH3)2–C–O–),
42.0 (–N–CH2–CH2–Ar), 34.9 (–N–CH2–CH2–Ar), 27.9 (CH3), 25.6
(CH3). MS (ESI): m/z 254.1 [M+1]+.
4.2.4. N-Propyl-2-hydroxyisobutylamide (3d)
Yield 30% (hexane); mp: 54–55 °C; Anal. Calcd for C7H15NO2: C
57.9, H 10.4, O 22.1, N 9.6. Found: C 57.7, H 10.3, O 22.4, N 9.6%; IR
(cmÀ1): 3400.7 (NH), 3300.5 (OH), 2950–2975–2875 (CH3), 1650
(C@O), 1550.7 (NH band II); 1H NMR (CDCl3) d (ppm): 6.95 (s,
1H, OH), 3.66 (s, 1H, NH), 3.21–3.11 (dd, 2H, J1 = 6.91 Hz,
J2 = 13.13 Hz –NH–CH2–), 1.55–1.44 (m, 2H, –CH2–), 1.40 (s, 6H,
(CH3)2), 0.92–0.85 (t, 3H, J = 7.34 Hz CH3); 13C NMR (CDCl3) d
(ppm): 176.9 (CO), 73.5 (–C–OH), 41.1 (–NH–CH2–), 28.1 (CH3)2),
22.9 (–CH2–CH3), 11.4 (CH3). MS (ESI): m/z 146.1 [M+1]+.
4.4. Synthesis of N-derivative-1,2,3-oxathiazolidine-4-one-2,2-
dioxides (5a–d)
4.2.5. N-Cyclohexyl-2-hydroxyisobutylamide (3e)
Yield 5% (acetonitrile); mp: 81–82.5 °C; Anal. Calcd for
C10H19NO2: C 64.8, H 10.3, O 17.2, N 7.6. Found: C 64.9, H 10.4, O
17.3, N 7.4%; IR (cmÀ1): 3400(NH), 3100 (OH), 2850–2950 (alcane),
1600 (C@O); 1H NMR (CDCl3) d (ppm): 6.76 (s, 1H, OH), 3.75–3.61
(m, 1H, –CH– cyclohexyl), 2.92–1.31(m, 10 H, cyclohexyl), 3.16 (s,
1H, NH), 1.40 (s, 6H, (CH3)2), 13C NMR (CDCl3) d (ppm):184.1 (CO),
72.5 (–C–OH), 50.5 (–NH–C H–), 31.4–28.1–25.0 (C, cyclohexyl),
24.6 ((CH3)2). MS (ESI): m/z 186.1 [M+1]+.
The dioxides were obtained after oxidation with NaIO4R-
uCl3Á6H2O. Column chromatography on silica gel 60 (70–230 mesh,
Merck) afforded the N-derivative-1,2,3-oxathiazolidine-4-one-2,2-
dioxide as white solids.
To a solution of N-derivative-1,2,3-oxathiazolidine-4-one-2-
oxides (4.5 mmol) in acetonitrile (6 ml) and dichloromethane
(6 ml) at 0 °C an aqueous solution of NaIO4 (7 mmol) and ruthe-
nium chloride ca was added dropwise. The mixture was warm to
room temperature and an hour later extracted twice with dichloro-
methane. The organic phases were combined, washed with water
and brine, dried (Na2SO4) and concentrated to dryness. The residue
obtained was flash chromatographed on silica-gel 60 (70–
230 mesh, Merck) to give a white solid which was recristallized
from hexane.
4.2.6. N-Butyl-2,2-diphenyl-2-hydroxyacetamide (3f)
Yield 20% (dichloromethane/hexane); mp: 66–67 °C; Anal.
Calcd for C18H21NO2; C 76.3, H 7.5, O 11.3, N 4.9. Found: C 76.2,
H 7.6, O 11.5, N 4.7%; IR (cmÀ1): 3360-(NH), 3275 (OH), 3095–
3050 (Ar), 2875–2950 (alcane), 1625 (C@O), 1550 (band II NH);
1H NMR (CDCl3) d (ppm): 7.40–7.34 (m, 6H, Ar), 6.30 (s, 1H, OH),
4.00 (s, 1H, NH), 3.35–3.25 (dd, 2H, J1 = 6.95 Hz, J2 = 12.97 Hz
–NH–CH2–), 1.55–1.41 (m, 2H, –CH2–), 1.36–1.29 (m, 2H, –CH2–),
0.92–0.89 (t, 3H, J = 7.13 Hz, CH3); 13C NMR (CDCl3) d (ppm):
173.4 (CO), 143.2–128.6–127.7 (Ar), 81.6 (–C–OH), 40.0
(–CH2–), 31.7 (–CH2–), 20.2 (–CH2–), 13.9 (CH3). MS (ESI): m/z
284.1 [M+1]+.
4.4.1. 3-Benzyl-5,5-dimethyl-1,2,3-oxathiazolidine-4-one-2,2-
dioxide (5a)
Yield: 80%. Rf: 0.84 (dichloromethane). mp: 71–72.5 °C. Anal.
Calcd for C11H13NO4S. C: 51.8, H: 5.1, O: 25.0, N: 5.5, S: 12.6. Found:
C: 51.8, H: 5.1, N: 5.3, O: 25.4, S: 12.4. IR cmÀ1: 2996–3094 (CH Ar),
1754 (CO), 1357 (SO2). 1H NMR (CDCl3) d (ppm): 7.44–7.24 (m, 5H,
Ar), 4.78 (s, 2H, –N–CH2–Bz), 1.66 (s, 3H, CH3). 13C NMR (CDCl3):
168.7 (C@O), 133.4–129.8–129.1–128.9 (Ar), 93.6 ((CH3)2–C–O–),
45.7 (–N–CH2–Bz), 27.9 (CH3), 24.5 (CH3). MS (ESI): m/z 254.1
[MÀ1]+.
4.3. Synthesis of N-derivative-1,2,3-oxathiazolidine-4-one-2-
oxide (4a–d)
The monoxides were synthesized as previously described for
cyclic sulfamates.26 The product was extracted twice with dichlo-
romethane and concentrated to dryness under reduce pressure.
Silica gel 60 (70–230 mesh, Merck, ref 1.07734.1000) column
chromatography yields yellow oil products. The monoxide isomers
obtained in the synthesis were not separated.39,40
To a mixture of N-benzyl-2-hydroxyisobutylamide (3 mmol)
and triethylamine (6.5 mmol) in CH2Cl2 anhydrous (8 ml) at
À15 °C thionyl chloride (4 mmol) in CH2Cl2 anhydrous (2 ml)was
added dropwise, followed by triethylamine (6.5 mmol) in CH2Cl2
(2 ml). The mixture was stirred under N2 overnight, concentrated
to dryness under reduce pressure and the residue was chromato-
graphed on a silica-gel silica gel 60 (70–230 mesh, Merck) column
to give N-derivative-1,2,3oxatiazolidine-4-one-2-oxides as yellow
oils.
4.4.2. 3-Phenethyl-5,5-dimethyl-1,2,3-oxathiazolidine-4-one-
2,2-dioxide (5b)
Yield: 25%. Rf: 0.75 (dichloromethane), mp: 57–58 °C. Anal.
Calcd for C12H15NO4S C: 53.6, H: 5.6, N: 5.2, O: 25.5, S: 10.1. Found:
C: 53.8, H: 5.8, N: 5.0, O: 25.7, S: 9.7%. IR cmÀ1: 3032 (CH Ar),
2939.6 (CH alcane), 1743 (CO), 1356 (SO2). 1H NMR (CDCl3), d
ppm: 7.32–7.23 (m, 5H, Ar), 3.92–3.84 (t, 2H, J = 6.43 Hz, –N–
CH2–CH2–Bz), 3.10–3.03 (t, 2H, J = 6.39 Hz, –N–CH2–CH2–Bz),
1.66 (CH3). 13C NMR (CDCl3): 168.4 (CO), 138.8–129.2–128.8–
127.3 (Ar), 93.8 ((CH3)2–C–O–), 42.9 (–N–CH2–CH2–Bz), 34.0
(–N–CH2–CH2–Bz), 24.5 (CH3). MS (ESI): m/z 268.0 [M-1]+.
4.4.3. 3-Butyl-5,5-dimethyl-1,2,3-oxathiazolidine-4-one-2,2-
dioxide (5c)
N-butyl-1,2,3-oxathiazolidine-4-one-2-oxide (4c), with Rf (1) of
0.86 and Rf (2) of 0.66 (dichloromethane); and N-propyl-1,2,3-oxa-
thiazolidine-4-one-2-oxide (4d), with Rf (1) of 0.85 and Rf (2) of
0.76 (dichloromethane); were directly cyclized.
Yield: 75%. Rf: 0.46 (dichloromethane), oil. Anal. Calcd for
C8H15NO4S C: 43.4, H: 6.8, O: 28.9, N: 6.3, S: 14.5. Found: C: 43.4,
H: 6.8, O: 28.8, N: 6.5, S: 14.5% IR cmÀ1:2990–2940 (CH alcane),
2883 (CH3), 1756 (CO), 1357 (SO2). 1H NMR (CDCl3), d ppm:
3.68–3.62 (t, 2H, J = 7.32 Hz, –N–CH2–), 1.85–1.68 (m, 2H, (–CH2–),
1.48–1.41 (m, 2H, –CH2–), 0.99–0.92 (t, 3H, J = 7.32 Hz, CH3).
13C NMR (CDCl3): 168.8 (CO), 93.5 ((CH3)2–C–O–), 42.0 (–N–CH2–
CH2–), 29.8 (–N–CH2–CH2–), 24.5 (CH3), 19.9 (–CH2–CH3), 13.6
(–CH2–CH3). MS (ESI): m/z 220.1 [MÀ1]+.
4.3.1. N-benzyl-1,2,3-oxathiazolidine-4-one-2-oxide (4a)
Yield: 70% R (1): 0.76 and R (2): 0.67 (dichloromethane). IR (cmÀ1):
f
f
2910–3050 (Ar), 1721 (CO), 1330 (SO), 1451.4, (C–N). 1H NMR
(CDCl3) d (ppm): 7. 41–7. 25 (m, 5H Ar), 4.45–4.42 (d, 2H,
J = 5.88 Hz, –N–CH2–Ar), 1.48 (s, 6H, CH3).13CNMR (CDCl3): 174.2
Please cite this article in press as: Pastore, V.; et al. Bioorg. Med. Chem. (2013), http://dx.doi.org/10.1016/j.bmc.2012.12.033

6
V. Pastore et al. / Bioorg. Med. Chem. xxx (2013) xxx–xxx
4.4.4. 3-Propyl-5,5-dimethyl-1,2,3-oxathiazolidine-4-one-2,2-
dioxide (5d)
Supplementary data
Yield: 29% Rf: 0.68 (dichloromethane), oil. Anal. Calcd for
C7H13NO4S C: 40.6, H: 6.3, O: 30.9, N: 6.7, S: 15.5% found C: 40.8,
H: 6.8, O: 30.6, N: 6.9, S: 15.4%.IR cmÀ1: 2939.6–2960.3 (CH al-
cane), 2883 (CH3), 1743.5 (CO), 1367–1346 (SO2). 1H NMR (CDCl3),
d, ppm: 3.65–3.58 (t, 2H, J = 6.6 Hz, –N–CH2–), 1.83–1.75 (m, 2H,
–CH2–), 1.73 (s, 6H, (CH3)2), 1.01–0.97 (t, 3H, J = 7.34 Hz, CH3). 13C
NMR (CDCl3): 168.8 (CO), 93.5 ((CH3)2–C–O–), 43.7 (–N–CH2–
CH2–CH3), 24.6 (–N–CH2–CH2–CH3), 21.3 ((CH3)2–C–O–), 11.2
(CH3). MS (ESI): m/z 206.1 [MÀ1]+.
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.bmc.2012.12.033.
These data include MOL files and InChiKeys of the most important
compounds described in this article.
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Dr. L.E. Bruno-Blanch is a member of the Faculty of Exact Sci-
ence, National University of La Plata; Dr. V. Pastore is fellowship
holders of Consejo Nacional de Investigaciones Científicas y Técni-
cas, Argentina (CONICET). This research was supported in part
through grants from Agencia de Promoción Científica y Tecnológ-
ica, CONICET, University of Buenos Aires and National University
of La Plata, Argentina.
Dr. M. Marder is a member of the Faculty of Pharmacy and
Biochemistry of National University of Buenos Aires and researcher
of CONICET. Authors are in debt to LANAIS-PRO EM, IQUIFIB-
CONICET, and Dr. Damián J. Marino from Faculty of Exact Science,
National University of La Plata for performing MS spectra.
Please cite this article in press as: Pastore, V.; et al. Bioorg. Med. Chem. (2013), http://dx.doi.org/10.1016/j.bmc.2012.12.033