Inhibition of lactoperoxidase-catalyzed oxidation by imidazole-based thiones and selones: A mechanistic study

Article abstract of DOI:10.1002/asia.201300274

Herein, we describe the synthesis and biomimetic activity of a series of N,N-disubstituted thiones and selones that contain an imidazole pharmacophore. The N,N-disubstituted thiones do not show any inhibitory activity towards LPO-catalyzed oxidation reactions, but their corresponding N,N-disubstituted selones exhibit inhibitory activity towards LPO-catalyzed oxidation reactions. Substituents on the N atom of the imidazole ring appear to have a significant effect on the inhibition of LPO-catalyzed oxidation and iodination reactions. Selones 16, 17, and 19, which contain methyl, ethyl, and benzyl substituents, exhibit similar inhibition activities towards LPO-catalyzed oxidation reactions with IC₅₀ values of 24.4, 22.5, and 22.5 μM, respectively. However, their activities are almost three-fold lower than that of the commonly used anti-thyroid drug methimazole (MMI). In contrast, selone 21, which contains a N-CH₂CH₂OH substituent, exhibits high inhibitory activity, with an IC₅₀ value of 7.2 μM, which is similar to that of MMI. The inhibitory activity of these selones towards LPO-catalyzed oxidation/iodination reactions is due to their ability to decrease the concentrations of the co-substrates (H₂O₂ and I ₂), either by catalytically reducing H₂O₂ (anti-oxidant activity) or by forming stable charge-transfer complexes with oxidized iodide species. The inhibition of LPO-catalyzed oxidation/iodination reactions by N,N-disubstituted selones can be reversed by increasing the concentration of H₂O₂. Interestingly, all of the N,N-disubstituted selones exhibit high anti-oxidant activities and their glutathione peroxidase (GPx)-like activity is 4-12-fold higher than that of the well-known GPx-mimic ebselen. These experimental and theoretical studies suggest that the selones exist as zwitterions, in which the imidazole ring contains a positive charge and the selenium atom carries a large negative charge. Therefore, the selenium moieties of these selones possess highly nucleophilic character. The ⁷⁷Se NMR chemical shifts for the selones show large upfield shift, thus confirming the zwitterionic structure in solution. Stop, in the name of love: The inhibition of lactoperoxidase (LPO)-catalyzed reactions by a series of N,N-disubstituted thiones and selones that contain an imidazole pharmacophore is described. The inhibitory activity not only depends on the substituent that is attached to the nitrogen atom, but also on the nature of the chalcogen atom. The inhibition of LPO activity by selones is due to their ability to scavenge the substrate, hydrogen peroxide. Copyright

Full text of DOI:10.1002/asia.201300274

FULL PAPER
DOI: 10.1002/asia.201300274
Inhibition of Lactoperoxidase-Catalyzed Oxidation by Imidazole-Based
Thiones and Selones: A Mechanistic Study
Gouriprasanna Roy,*[a, b] P. N. Jayaram,[a] and Govindasamy Mugesh*[a]
Abstract: Herein, we describe the syn-
thesis and biomimetic activity of
a series of N,N-disubstituted thiones
and selones that contain an imidazole
pharmacophore. The N,N-disubstituted
thiones do not show any inhibitory ac-
tivity towards LPO-catalyzed oxidation
reactions, but their corresponding N,N-
disubstituted selones exhibit inhibitory
activity towards LPO-catalyzed oxida-
tion reactions. Substituents on the N
atom of the imidazole ring appear to
have a significant effect on the inhibi-
tion of LPO-catalyzed oxidation and
iodination reactions. Selones 16, 17,
and 19, which contain methyl, ethyl,
and benzyl substituents, exhibit similar
inhibition activities towards LPO-cata-
lyzed oxidation reactions with IC50
values of 24.4, 22.5, and 22.5 mm, re-
spectively. However, their activities are
almost three-fold lower than that of
the commonly used anti-thyroid drug
methimazole (MMI). In contrast,
ꢀ
LPO-catalyzed oxidation/iodination re-
actions by N,N-disubstituted selones
can be reversed by increasing the con-
centration of H2O2. Interestingly, all of
the N,N-disubstituted selones exhibit
high anti-oxidant activities and their
glutathione peroxidase (GPx)-like ac-
tivity is 4–12-fold higher than that of
the well-known GPx-mimic ebselen.
These experimental and theoretical
studies suggest that the selones exist as
zwitterions, in which the imidazole ring
contains a positive charge and the sele-
nium atom carries a large negative
charge. Therefore, the selenium moiet-
ies of these selones possess highly nu-
cleophilic character. The 77Se NMR
chemical shifts for the selones show
large upfield shift, thus confirming the
zwitterionic structure in solution.
selone 21, which contains
a
N
CH2CH2OH substituent, exhibits high
inhibitory activity, with an IC50 value of
7.2 mm, which is similar to that of MMI.
The inhibitory activity of these selones
towards LPO-catalyzed oxidation/iodi-
nation reactions is due to their ability
to decrease the concentrations of the
co-substrates (H2O2 and I2), either by
catalytically reducing H2O2 (anti-oxi-
dant activity) or by forming stable
charge-transfer complexes with oxi-
dized iodide species. The inhibition of
Keywords: bioorganic chemistry ·
chalcogens · heterocycles · inhibi-
tors · scavengers
Introduction
The overproduction of active thyroid hormone, which leads
to hyperthyroidism, can either be controlled by blocking the
biosynthesis of thyroid hormone (TH), catalyzed by thyroid
peroxidase (TPO), or by inhibiting iodothyronine deiodinas-
es 1 and 2 (ID-1 and ID-2), which are responsible for the
conversion of prohormone T4 into biologically active hor-
mone T3. Anti-thyroid drugs, such as methimazole (1,
MMI), 6-n-propyl-2-thiouracil (3, PTU), and carbimazole (5,
CBZ; Scheme 1), are typically employed for the treatment
of hyperthyroidism. Several mechanisms by which these thi-
Scheme 1. Selected commonly used anti-thyroid drugs and their selenium
analogues.
ourea drugs can inhibit the biosynthesis of TH have been
proposed.[1–3] Compounds 1 and 5 exert their inhibitory ac-
tivity by interacting with the oxidized heme group of TPO
or by binding to the heme group of the enzyme upon oxida-
tion.[1,2] Because some of these compounds have been shown
to form stable charge-transfer complexes with iodine, such
compounds may block the iodination in vivo by diverting
the reactive iodine species from the reaction site.[3] In anoth-
er mechanism, it has been proposed that TPO inactivation
may occur through a competitive coordination of the drug
to the iron center of the enzyme, which is assisted by hydro-
[a] Dr. G. Roy, P. N. Jayaram, Prof. Dr. G. Mugesh
Department of Inorganic and Physical Chemistry
Indian Institute of Science
Bangalore 560 012 (India)
E-mail: mugesh@ipc.iisc.ernet.in
[b] Dr. G. Roy
Department of Chemistry and Center for Informatics
School of Natural Sciences
Shiv Nadar University, Dadri 203207, Uttar Pradesh (India)
E-mail: gouriprasanna.roy@snu.edu.in
ꢀ
gen bonding between the free N H group of the drug and
the distal histidine group.[4] Therefore, the presence of a free
ꢀ
N H moiety appears to be important for the anti-thyroid
activity of MMI and its related compounds.
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/asia.201300274.
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Gouriprasanna Roy, Govindasamy Mugesh et al.
Hydrogen peroxide (H2O2), an essential co-substrate in
the TPO-catalyzed biosynthesis of TH, is produced in high
amounts by thyroid oxidases DUOX-1 and DUOX-2 in the
thyroid gland. During its normal physiological activity, the
thyroid gland is continuously exposed to relevant concentra-
tions of H2O2 and H2O2-derived reactive oxygen species
(ROS).[5] It has been reported that compounds 1 and 3 par-
tially inhibit the Ca2+/NADPH-dependent generation of
H2O2 in the thyroid, owing to their antioxidant properties.
The inhibition of the biosynthesis of TH by MMI in vivo
may arise from both a direct effect on TPO activity and its
ability to scavenge H2O2.[6,7] The selenium analogues of anti-
thyroid drugs MSeI (2), PSeU (4), and SeCBZ (6) have at-
tracted considerable attention. Because selones are typically
better nucleophiles than their corresponding thiones, the se-
lenium analogues of anti-thyroid drugs may exhibit better
inhibitory activity towards ID-1 than their sulfur analogues.
Recently, we reported that MSeI (2) and SeCBZ (6) inhibit-
ed the LPO-catalyzed oxidation of the ABTS reaction by
depleting the H2O2 in a model system.[8–11] Herein, we report
the synthesis and inhibition behavior of a series of N,N-dis-
Scheme 2. Synthesis of compounds 15–21 by using heterocyclic carbenes
that were generated in situ from their corresponding imidazolium salts.
Reagents and conditions: a) ethyl bromide, NaI, acetone, 12 h, RT (for
compound 8); chloroethanol, 808C (for compound 10); b) K2CO3, dry
MeOH, S or Se powder, reflux, 24 h.
ꢀ
ubstituted thiones and selones that do not contain a free N
H moiety. We also show that the selones exhibit significant
antioxidant activity in the presence of thiols.
Results and Discussion
Scheme 3. Synthesis of compound 24 by using a heterocyclic carbene that
was generated in situ from its corresponding imidazolium salt. Reagents
and conditions: a) chloroethanol, 808C; b) K2CO3, dry MeOH, Se
powder, reflux, 24 h.
N,N-disubstituted thiones and selones 15–21 were synthe-
sized by treating 1-methylimidazole with appropriate halides
to produce the corresponding imidazolium salts,[9a] followed
by their reactions with elemental sulfur or selenium to
afford the corresponding thiones and selones. In these reac-
tions, deprotonation of the imidazolium salts by a base leads
to an in situ generation of reactive carbenes, which, in turn,
react with elemental sulfur or selenium to afford the corre-
sponding thiones or selones (Scheme 2). Because com-
pounds 15–21 are readily soluble in organic solvents, such as
CH2Cl2, they can be easily separated from other salt-like im-
purities. These compounds were very stable in the presence
of air and no decomposition was observed. To understand
whether the replacement of the methyl group in MMI/MSeI
and related compounds by other substituents affected their
inhibition properties towards peroxidase-catalyzed oxidation
and iodination reactions, we synthesized compounds 20, 21,
and 24, which contained one or two CH2CH2OH moieties.
This replacement was expected to increase the solubility of
these compounds in aqueous buffer. For the synthesis of
compound 24, we employed the 2-(1H-imidazol-1-yl)ethanol
(22) as the key starting material, which could be readily syn-
thesized by treating imidazole with sodium hydride, fol-
lowed by reaction with 2-chloroethanol in DMF (Scheme 3).
Compound 24 could also be directly synthesized from imida-
zole as a white solid by using slightly more than two equiva-
lents of 2-chloroethanol. In this reaction, we found that the
use of sodium hydride was not necessary for the replace-
ment of the hydrogen atom by a CH2CH2OH group.
To investigate the effect of the thione/selone moiety on
the inhibition of peroxidase-catalyzed oxidation and iodina-
tion reactions, several N,N-disubstituted thiones and selones
that contained more than one thione (C=S)/selone (C=Se)
moiety (compounds 27–29, 32–34, 36, and 37) were synthe-
sized. These compounds were synthesized from their corre-
sponding N-substituted imidazole by using appropriate hal-
ides, as shown in Scheme 4. Compounds 27–29 were synthe-
sized from the reactions of 1-methylimidazole or 1-benzyl
imidazole with 2-dibromoethane at reflux in dry THF. The
addition of elemental sulfur or selenium in dry MeOH
under basic conditions to halide salts 25 and 26 afforded
thione 28 and selones 27 and 29.[12] The reactions of 1-meth-
ylimidazole or compound 22 with 1,3-bis(bromomethyl)ben-
zene in dry THF, followed by the addition of sulfur or sele-
nium powder in dry MeOH under basic conditions produced
compounds 32–34. Similarly, the reaction of 1-methylimida-
zole with 1,3,5-tris(bromomethyl)-2,4,6-trimethyl benzene in
dry THF afforded the corresponding imidazolium salt (35),
which, upon treatment with elemental sulfur and selenium,
produced thione 36 and selone 37, respectively. To under-
stand the effect of the C=C double bond in the imidazole
ring on the inhibition of peroxidase-catalyzed reactions, we
ꢀ
synthesized compounds 41–43, which contained a C C
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Gouriprasanna Roy, Govindasamy Mugesh et al.
Table 1. Summary of the DFT calculations of selenium compounds at
the B3LYP/6-311+G
(d,p) level and GIAO 77Se NMR chemical shifts at
the B3LYP/6-311+G(d,p)//B3LYP/6-311+ +G(2d,p) level by using the
AHCTUNGTRENNUNG
A
ACHTUNGTRENNUNG
Gaussian 98 suite of quantum chemical calculations, as well as experi-
mental 77Se NMR chemical shifts.
ꢀ
ꢀ
Compound
C Se bond
length [ꢁ]
C Se bond
order
Charge on 77Se NMR
Se
[ppm]
Expt.
Calcd Calcd
Calcd
Expt.[a]
(calcd)[b]
2
1.848(4)[c] 1.835 1.371
1.843[d]
1.838 1.361
1.843(2)[c] 1.844 1.344
ꢀ0.262
ꢀ0.269
ꢀ0.272
ꢀ0.286
ꢀ0.289
ꢀ0.289
ꢀ0.244
ꢀ0.182
ꢀ5 (23)
ꢀ6 (39)
ꢀ3 (ꢀ2)
ꢀ9 (19)
ꢀ45[b] (ꢀ25)
0 (0)
16
19
21
24
27
41
42
1.854(4)
1.848(3)
1.841(3)
1.834(4)
1.844 1.341
1.848 1.335
1.844 1.339
1.837 1.405
63 (113)
161 (173)
1.828(4), 1.828 1.459
1.840(4)
[a] 77Se NMR data for all compounds were recorded in CDCl3, except for
compound 24, for which D2O was used. [b] Chemical shifts (d) are re-
ported referenced to dimethyl selenide. The calculated 77Se NMR chemi-
cal shift for dimethyl selenide at the B3LYP/6-311+G
ACHTUNGTREN(NGNU d,p)//B3LYP/6-
311+ +G(2d,p) level of theory is d=1637.6348 ppm. [c] Data taken from
AHCTUNGTRENNUNG
Ref. [9a]. [d] The C–Se bond length matches that reported previously in
Ref. [9c].
Scheme 4. Synthesis of N,N-disubstituted thiones and selones that con-
tained multiple thione (C=S)/selone (C=Se) moieties (27–29, 32–34, 36,
and 37) by using heterocyclic carbenes that were generated in situ from
their corresponding imidazolium salts. Reagents and conditions: a) 2-di-
bromoethane, THF; b) K2CO3, dry MeOH, S or Se powder; c) a,a’-dibro-
mo-m-xylene, THF; d) 1,3,5-tris(bromomethyl)-2,4,6-trimethylbenzene,
THF.
ized positive charge over the five-membered ring. The crys-
tal structures of selones 21 and 24 show some interesting
features: In compound 21, an intermolecular hydrogen bond
between the hydroxy group of one molecular unit and the
selenium atom of another molecular unit leads to the forma-
tion of a chain-like structure, as shown in Figure 1A. Al-
though the hydrogen bonding interactions do not appear to
ꢀ
single bond instead of a double bond. Compounds 41–43
could be synthesized by treating different amines (38–40)
with triethylorthoformate and selenium in a sealed Teflon
bomb and heating at 1908C for 8 h (Scheme 5).[13]
affect the nature of the C Se bond in compound 24, the
NCH2CH2OH substituent in the heterocycle does alter the
ꢀ
ꢀ
nature of the C Se bond in compound 21. The C Se bond
length (1.854 ꢁ) is slightly longer than that of other selones
Scheme 5. Synthetic route to compounds 41–43.
ꢀ
Single-crystal X-ray structural analysis shows that the C
Se bond lengths (1.841–1.854 ꢁ) in the N,N-disubstituted se-
lones (16, 19, 21, 24, and 27) are much longer than that of
a typical C=Se double bond (1.74 ꢁ) and are close to that of
[8]
ꢀ
ꢀ
a C Se single bond (1.88 ꢁ, Table 1). The C N bond
lengths (1.384–1.339 ꢁ) in the imidazole ring are significant-
ꢀ
ly shorter than that of a C N single bond (1.48 ꢁ) and
slightly longer than that of a C=N double bond (1.29 ꢁ).
ꢀ
Furthermore, the C2 C3 bond lengths (1.326, 1.325, and
Figure 1. A) Intermolecular H-bonding interaction between the OH
group of one molecular unit and the Se atom of another molecular unit
in compound 21; O···Se 3.345 ꢁ, OH···Se 2.558 ꢁ. B) Intermolecular H-
1.336 ꢁ) are significantly longer than that of a typical C=C
double bond (1.28 ꢁ). These observations suggest that these
N,N-disubstituted selones can be considered as zwitterions,
with a negative charge on the selenium atom and a delocal-
ꢀ
ꢀ
ꢀ
bonding interaction in compound 24; O H···OH 2.138 ꢁ, H O···O H
2.744 ꢁ.
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Gouriprasanna Roy, Govindasamy Mugesh et al.
ꢀ
and it is very close to that of a C Se single bond
(1.88 ꢁ).[8–11] The structure of compound 24 also indicates
the formation of an intermolecular hydrogen bond between
the hydroxy moieties of two adjacent molecular units (Fig-
ure 1B). However, in contrast to compound 21, the selenium
atom in compound 24 does not participate in hydrogen
bonding.
ꢀ
To further investigate the nature of the C Se bond and
the charge on the selenium atom in these N,N-disubstituted
selones, we performed quantum chemical calculations. So
far, theoretical investigations of selones have been highly
limited to compounds that contain simple substituents,
mainly owing to the requirements of large basis sets for the
calculations.[14] The bond order, the charges on the atoms,
and the 77Se NMR data of all of the compounds were calcu-
lated at the B3LYP level of theory by using the 6-311+ +G-
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
chemical shifts were calculated by using the gauge invariant
atomic orbitals (GIAO) method.[17] Experimental (X-ray)
ꢀ
and theoretical (DFT calculations) results of the C Se bond
Figure 2. Occupied p MOs of selone 21, which contain three bonding or-
bitals of the imidazole ring and one Se 4p orbital. The C atom and the
Se 4p orbital have poor p-overlap.
length, bond order, charge on the Se atom, and 77Se NMR
data of the selones are summarized in Table 1. Crystal-struc-
ture determination, as well as theoretical calculations, show
ꢀ
that the C Se bond lengths of these selones are intermedi-
ate between the values as predicted by the respective sum
of the covalent radii of carbon and selenium atom single
of various thiones and selones on peroxidase-catalyzed oxi-
dation reactions was studied in vitro by using spectroscopic
techniques. The enzyme-inhibition experiments were carried
out with heme-containing lactoperoxidase (LPO) because it
is readily available in its pure form. Furthermore, LPO has
been shown to behave very similarly to TPO with respect to
the oxidation of organic substrates and the iodination of thy-
roglobulin (a protein that is required for the synthesis of
thyroxine) and other iodide acceptors.[3b] In the LPO-cata-
lyzed oxidation reaction, we employed 2,2’-azio-bis-3-ethyl-
benthiazoline-6-sulfonic acid (ABTS) and H2O2 as sub-
strates to determine the half-maximal inhibitory concentra-
tion (IC50) of the test compounds. The IC50 values of all of
the thiones/selones that were tested for the inhibition of the
LPO-catalyzed oxidation of ABTS are listed in Table 2.
ꢀ
ꢀ
and double bonds (dACTHNUGRTENUNG(C Se)=1.94 ꢁ for a single C Se bond
ꢀ
ꢀ
and d
(C Se)=1.74 ꢁ for a C=Se double bond). The C Se
bond orders of all of the selones lie in between single and
double bonds (1.33–1.46), in agreement with the X-ray crys-
tal-structure analysis. The selenium moiety of these N,N-dis-
ubstituted selones contains a large negative charge, ranging
from ꢀ0.262 to ꢀ0.289, where the selenium moiety behaves
as a nucleophile (Table 1). The occupied p molecular orbi-
tals (MOs) of selone 21 indicate that there is relatively little
p overlap between the Se 4p orbital and the adjacent carbon
atom of the aromatic ring (Figure 2). Therefore, both the
crystal-structure analysis and theoretical calculations clearly
suggest that the N,N-disubstituted selones can be best as-
cribed as zwitterions with a negative charge on the selenium
atom and a delocalized positive charge over the five-mem-
ꢀ
bered ring (see above). The C Se double bond in these se-
Table 2. Inhibition of the LPO-catalyzed oxidation of ABTS by various
thiones and selones.
ꢀ
lones is very weak and they do not have pure C Se double-
bond character. However, in the case of selones that lack
Compound
IC50 [mm][a]
Compound
IC50 [mm][a]
18.8
(ꢁ1.9)
7.3
(ꢁ0.7)
inactive
7.7
inactive
ꢀ
ꢀ
the C C double bond in the ring (41 and 42), the C Se
bond lengths are a little shorter and the charge on the sele-
nium atom in these compounds is smaller compared to the
other selones (from ꢀ0.182 to ꢀ0.244). These observations
suggest that the zwitterionic character in compounds 41 and
42 is less compared to that of the other selones that have
1
2
7.0
A
24
27
28
29
32
33
34
41
42
ACHTUNGTRENNUNG
16.4
A
ACHTUNGTRENNUNG
15
16
17
18
19
20
21
inactive
24.4
22.5
U
ACHTUNGTRENNUNG
inactive
22.6
inactive
7.2
5.2
3.2
ACHTUNGTRENNUNG
N
ACHTUNGTRENNUNG
ꢀ
a C C double bond in the imidazole ring.
84.3
90.0
ACHTUNGTRENNUNG
The mechanism by which anti-thyroid drugs inhibit the
biosynthesis of thyroid hormone is currently an active area
of research. We have previously shown that the selenium an-
alogue of MMI inhibits the peroxidase-catalyzed reaction
through a different mechanism to that of MMI. The effect
E
ACHTUNGTRENNUNG
[a] The reactions were performed in a 1 mL cuvette and the change in
UV absorption owing to the oxidation of ABTS was followed at 411 nm.
The assay mixture contained 12.9 nm LPO, 28.7 mm H2O2, 1.4 mm ABTS,
and 1–200 mm thione/selone. [b] Data taken from Ref. [9a].
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Gouriprasanna Roy, Govindasamy Mugesh et al.
It has been proposed that the activation of the iron center
in TPO/LPO must proceed through an interaction of the
FeIII atom with H2O2 and that the inactivation of TPO by
MMI may occur through a competitive coordination of the
drug to the iron center, assisted by a hydrogen-bonding in-
ted against the concentration of H2O2. As expected for irre-
versible inhibitors, the LPO activity was completely inhibit-
ed by MMI at a concentration of 12 mm and the enzyme ac-
tivity could not be recovered by increasing the concentra-
tion of H2O2. The enzymatic activity was also almost com-
pletely inhibited at a 12 mm concentration of selone 34. This
particular compound exhibited the highest inhibitory activity
(IC50: 3.2 mm) among all of the selones in this study. Howev-
er, the enzyme activity could be completely recovered by in-
creasing the concentration of H2O2, although the inhibitory
activity of selone 34 was found to be almost twice as high as
that of MMI. The effect of H2O2 concentration on the inhib-
ition of LPO-catalyzed oxidation of ABTS at different con-
centrations of selone 34 is shown in Figure 3. We observed
ꢀ
teraction between the free N H group of MMI and a histi-
dine residue of the TPO enzyme. In agreement with this as-
ꢀ
sumption, MMI, which contains a free N H group, inhibited
the LPO-catalyzed oxidation of ABTS with an IC50 value of
7.0 mm, whereas all of the N,N-disubstituted thiones (15, 18,
ꢀ
20, 28, and 32), which lacked any free N H groups on the
heterocycle, were found to be inactive towards LPO-cata-
lyzed oxidation. In contrast, the N,N-disubstituted selones
exhibited excellent inhibitory activity towards LPO-cata-
lyzed oxidation (Table 2). The substituents that are attached
on the nitrogen atom in the heterocycle (imidazole ring)
play an important role in the inhibition of the LPO-cata-
lyzed oxidation of ABTS. Among the compounds with one
selone (C=Se) moiety, compound 21, which contained a 2-
hydroxyethyl (CH2CH2OH) group at the N1 position, exhib-
ited an almost-three-times larger inhibitory activity (IC50 =
7.2 mm) than that of the methyl- (16), ethyl- (17), and
benzyl-substituted compounds (19). The activity of selone 21
is comparable to that of the most-potent commercially avail-
able anti-thyroid drug, MMI (7.0 mm). However, selone 24,
which contained a 2-hydroxyethyl group on both nitrogen
atoms of the imidazole ring, exhibited much lower inhibitory
activity (18.8 mm) than that of compound 21, thus indicating
that the increased hydrophilic nature of selone 24 did not
enhance its inhibitory activity.
Figure 3. Effect of H2O2 on the inhibition of the LPO-catalyzed oxidation
of ABTS by compound 34: a) control sample (0 mm); b) 12 mm of com-
pound 34; c) 15 mm of compound 34; d) 20 mm of compound 34; and
e) 12 mm of MMI (1).
ꢀ
Compounds 2 and 24, which had similar C Se bond
lengths (1.848 ꢁ), exhibited similar inhibitory activities to-
wards the LPO-catalyzed oxidation reaction, with IC50
values of 16.4 and 18.8 mm, respectively; the inhibitory activ-
ity of selone 34 (3.2 mm), which contained a 2-hydroxyethyl
group, was almost twice that of selone 21. This result is
probably due to the fact that compound 34 contains two imi-
dazole moieties, whereas selone 21 only contains a single
selone unit. Similarly, compounds 27, 29, and 33, which con-
tain two selone units with methyl and benzyl substituents on
the nitrogen atoms, exhibited excellent inhibitory activities
towards the LPO-catalyzed oxidation reaction. The inhibito-
ry activities of these compounds are almost 2–3-times higher
than those of compounds 16 and 19. The IC50 values for
compounds 27 and 29 are 7.3 and 7.7 mm, respectively, which
are similar to that of MMI. This result indicates that the
selone moieties in these compounds are responsible for the
inhibitory activity towards the LPO-catalyzed oxidation re-
action. Reliable inhibition data could not be obtained for
compound 37, owing to its poor solubility in the assay sol-
vent.
that the enzyme activity could be recovered to a large
extent by increasing the concentration of H2O2 up to a cer-
tain inhibitor concentration (20 mm for selone 34). The
amount of H2O2 that was required for complete recovery of
the enzyme activity correlates well with the amount of in-
hibitor used. The control experiments indicate that it is the
depletion of H2O2 and not the enzyme inactivation that is
responsible for the deviations from the control rates. The
sigmoidal behavior of the graph for compound 34 is proba-
bly due to the utilization of H2O2 for the oxidation of sele-
nenic acid into other oxidized products at lower concentra-
tions of the peroxide. Similar effects of H2O2 were also ob-
served for other selones. These observations strongly suggest
that MMI does not act on H2O2, but rather that it acts on
the enzyme itself, thus leading to irreversible inhibition, as
previously proposed. On the other hand, the inhibition by
various selones is mainly due to their ability to react with
H2O2 that is present in the assay mixture.[1i,18]
To understand the nature of the inhibition of LPO-cata-
lyzed oxidation reactions by N,N-disubstituted selones, we
performed further experiments at different concentrations
of H2O2 because the selenium moiety in the selones are
known to react with peroxides. The initial rates (vo), which
were obtained at various concentrations of H2O2, were plot-
As discussed in the Introduction, one of the possible
mechanisms by which anti-thyroid drugs inhibit the biosyn-
thesis of thyroid hormone is through the diversion of the
oxidized iodides away from thyroglobulin (Tg) by forming
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Gouriprasanna Roy, Govindasamy Mugesh et al.
stable electron-donor/electron-acceptor complexes with diio-
dine (I2).[3a,b] Anti-thyroid drugs, which are oxidized by the
TPO/H2O2 system, may form stable donor–acceptor com-
plexes with either diiodine (I2) or activated iodine (I+, pro-
duced by TPO/H2O2/Iꢀ). Because the oxidized drug mole-
cules may react further with TPO/H2O2/Iꢀ in vivo to form
some other metabolites, it is important to identify the spe-
cies that are produced in the reaction of anti-thyroid drugs
with TPO/H2O2/Iꢀ. To this end, selone 19 was treated with
the LPO/H2O2/Iꢀ system in phosphate buffer at pH 7.4, simi-
lar to the assay conditions that are employed for LPO-cata-
lyzed iodination reactions. The treatment of selone 19 with
LPO/H2O2/Iꢀ produced a bright-orange-colored compound.
Single crystals suitable for X-ray analysis were obtained by
the slow evaporation of the solvent. X-ray crystal-structure
analysis indicated the formation of complex 44, which con-
tained a diselenide dication and two Iꢀ ions as counterions
(Scheme 6, Figure 4). In this reaction, selone 19 was oxi-
dized by the LPO/H2O2/I2 system into its corresponding dis-
elenide, which produced a charge-transfer complex (44) with
ously exposed to relevant concentrations of H2O2, which can
freely diffuse into the cytoplasm and the nucleus, where it
may lead to aberrant oxidation and iodination of the pro-
teins and lipids, trigger apoptosis, and might induce DNA
damage.[5a] However, the thyroid gland, which contains the
highest amount of selenium among other endocrine tissues,
contains at least 11 different selenoproteins, including gluta-
thione peroxidases GPx1, GPx3, and GPx4, thioredoxin re-
ductase (TrxR), the Se-transport protein SePP, and seleno-
protein 15 (SeP15). These proteins catalyze redox reactions
in various physiological processes, such as controlling the
H2O2 level in the thyroid gland and the scavenging of reac-
tive oxygen species (ROS), TH metabolism, and others.[5] To
understand the antioxidant activities of thiones and selones
and to understand the mechanism by which the N,N-disub-
stituted selones exhibit an inhibitory effect towards the
LPO-catalyzed oxidation and iodination reactions, we inves-
tigated the glutathione peroxidase (GPx)-like activity of the
thiones and selones. The GPx-like activity was studied by
using H2O2 as a substrate and PhSH as a cofactor. The
amount of diphenyl disulfide (PhSSPh) that was
formed during the course of reaction was monitored
by HPLC and the activities were compared with
the well-known GPx-mimic ebselen.[20,21] Interest-
ingly, all of the N,N-disubstituted selones, which are
potent inhibitors of LPO-catalyzed reactions, exhib-
it high GPx-like activity. The activity of all of the
N,N-disubstituted selones were 4–12-times higher
than that of ebselen (Table 3). Among the selones
that contained one C=Se moiety, compound 17,
Scheme 6. Charge-transfer complexes of selone 19 with the LPO/H2O2/I2 system (44)
and with molecular iodine (45).
Table 3. GPx-like activity for ebselen, thiones, and selones.[a]
Compound
Rate [mmminꢀ1
]
Compound
Rate [mmminꢀ1
]
ebselen
MMI (1)
MSeI (2)
2.9
–
231.7
–
16.3
29.1
–
11.2
–
N
27
28
29
32
33
34
36
37
41
42
43
19.9
–
14.3
–
26.5
25.3
–
35.5
12.7
13.9
14.9
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
15
16
17
18
19
20
21
24
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
20.8
15.2
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
Figure 4. X-ray crystal structure of compound 44, which shows an intra-
molecular Se···I interaction.
[a] The concentration of the test compounds was 100 mm.
oxidized iodine. It should be noted that the reaction of com-
pound 19 with molecular iodine produces a completely dif-
ferent complex (45, Scheme 6).[19]
which contained an ethyl substituent, exhibited the highest
GPx activity (29.1 mmminꢀ1). The GPx activity of compound
21 (20.8 mmminꢀ1) was almost seven-times higher than that
of ebselen (2.9 mmminꢀ1). Substituents on the nitrogen atom
of the imidazole ring play an important role in their antioxi-
dant activities. Compounds 16 and 24 exhibited almost-simi-
lar GPx-like activities (16.3 and 15.2 mmminꢀ1, respectively).
The introduction of a benzyl group appeared to lower the
GPx activity because the activity of compound 19
(11.2 mmminꢀ1) was much lower than that of alkyl-based
compounds 16, 17, and 21. However, this compound was
found to be almost four-times more active than ebselen.
Recent biochemical studies on the metabolism of thyroid
hormone suggest that glutathione peroxidases (GPx), a sele-
noenzyme that is present in the thyroid gland, degrades in-
tracellular H2O2 and inhibits the biosynthesis of thyroid hor-
mones.[6c] Hydrogen peroxide is an essential co-substrate for
the biosynthesis of thyroid hormone as produced by the
NADPH-dependent flavoproteins thyroid oxidase DUOX
(dual oxidases) 1 and 2. Thus, as a consequence of its
normal physiological activity, the thyroid gland is continu-
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The GPx-like activities of compounds that contained two
selone moieties (27, 29, 33, and 34) were also found to be 7–
9-times higher than that of ebselen. Compound 34, which
exhibited promising LPO-inhibitory activity, was about nine-
fold more active (25.3 mmminꢀ1) than ebselen. Compound
37, which contained three selone moieties, also exhibited
high GPx-like activity, with an initial rate of 35.5 mmminꢀ1.
The activities of compounds 41, 42, and 43 were found to be
slightly lower than those of the selones that contained a C=
C double bond in the imidazole ring. It should be noted that
compounds 41 and 42 exhibited very weak inhibitory activi-
ty toward LPO-catalyzed reactions. In contrast to the se-
lones, all of the N,N-disubstituted thiones did not show GPx
activity under identical experimental conditions. Interesting-
stituted selones is mainly due to their ability to react with
co-substrates H2O2 (antioxidant activity) and diiodine (or
oxidized iodide). In contrast to the selones, the N,N-disubsti-
tuted thiones do not exhibit GPx-like activity, which is in
agreement with their effect on LPO-catalyzed reactions.
Experimental Section
General Procedure
Lactoperoxidase from bovine milk and ABTS (2,2’-azino-bis-3-ethylbens-
thiazoline sulfonic acid) were purchased from Fluka Chemical Co. n-
Butyl lithium was purchased from Acros Chemical Co. (Belgium) and se-
lenium powder was purchased from Sigma–Aldrich. Ethylene chlorohy-
drine, sodium hydride (NaH), sodium borohydride (NaBH4), benzyl chlo-
ride, and other chemicals were obtained from local companies. All ex-
periments were performed under anhydrous and anaerobic conditions by
using standard Schlenk techniques. Melting points were determined in
open tubes on a Buchi melting point B-540 apparatus and are uncorrect-
ed. Mass spectroscopy was performed on a Q-TOF Micro mass spectrom-
eter with electrospray ionization (ESI). In the case of isotopic patterns,
the reported values are of the most-intense peaks. Elemental analysis
was performed on a Thermo Finigan FLASH EA 1112 CHNS analyser.
Solution-state NMR spectra were recorded in CDCl3, [D4]MeOH, D2O,
ꢀ
ly, MSeI (2), which has a free N H group in the imidazole
ring, is almost 80-times more active than ebselen (Table 3).
These observations suggest that the mechanism for the GPx-
like activity of MSeI is different from that of the N,N-disub-
stituted selones. The mechanism for the reduction of H2O2
by MSeI may involve the formation of selenenic acid
(SeOH) and selenenyl sulfide intermediates, as previously
shown for other GPx mimics.[21] Unfortunately, our attempts
to detect these intermediates by 77Se NMR spectroscopy
were unsuccessful. However, in the absence of PhSH, the re-
actions of the selones with H2O2 produced the correspond-
ing seleninic acids (SeO2H), thus indicating that the rapid
reaction of the selenenic acid with PhSH may prevent the
further oxidation of SeOH into SeO2H.
1
or [D6]DMSO. H (400 MHz), 13C (100 MHz), and 77Se NMR (76.3 MHz)
spectra were recorded on a Bruker Avance 400 NMR Spectrometer. 1H
and 13C NMR spectra are referenced to the solvent peak as an internal
standard and the chemical shifts are reported relative to tetramethylsi-
lane (TMS). 77Se NMR spectra were referenced to diphenyl diselenide as
an external standard and the chemical shifts are reported relative to di-
methyl selenide (d=0 ppm) by assuming that the resonance of the stan-
dard is d=461.0 ppm. In most cases, the 77Se NMR experiments were run
overnight to obtain good-quality spectra. UV/Vis experiments were per-
formed on
a Varian CARY 300 Bio spectrophotometer that was
equipped with a temperature-controlled multi-cell assembly. Thin-layer
chromatography analysis was performed on pre-coated silica gel plates
(Merck) and spots were visualized by using UV irradiation. Column
chromatography was performed on glass columns that were loaded with
silica gel or on an automated flash chromatography system (Biotage) by
using preloaded silica cartridges. High-performance liquid chromatogra-
phy (HPLC) experiments were performed on a Waters Alliance System
(Milford, MA), which consisted of a 2690 separation module, a 2690 pho-
todiode-array detector, and a fraction collector. The assays were per-
formed in 1.8 mL sample vials and a built-in autosampler was used for
sample injection. The Alliance HPLC System was controlled with EM-
POWER software (Waters Corporation, Milford, MA). Compounds 15,
16, 18, and 19 were synthesized according to a literature procedure.[9a]
Conclusions
Herein, we have described the synthesis, characterization,
and biomimetic activity of a series of N,N-disubstituted thio-
nes and selones. Whereas methimazole (MMI) strongly and
irreversibly inhibits lactoperoxidase (LPO)-catalyzed oxida-
ꢀ
tion reactions, the replacement of the N H group in MMI
by alkyl or benzyl substituents abolishes this inhibitory
effect. In contrast, the N,N-disubstituted selones exhibit sig-
nificant inhibitory effect on LPO-catalyzed oxidation reac-
tions and the IC50 values for these compounds not only
depend on the number of selone moieties, but also on the
nature of the C=Se bond in the molecule. Experimental and
theoretical studies have indicated that the selones exist as
zwitterions, in which the heterocyclic ring contains a partial
positive charge and the selenium atom carries a large nega-
tive charge. Owing to their highly nucleophilic character,
the selone moieties readily react with H2O2 and diiodine (or
oxidized iodide). The 77Se NMR chemical shifts for the se-
lones show large upfield shifts with respect to their related
selenocarbonyl compounds, thus confirming the zwitterionic
structure in solution. In addition to the LPO inhibition, the
N,N-disubstituted selones exhibit good glutathione perox-
idase (GPx)-like activity and the activities of all of the se-
lones are higher than that of ebselen, a well-known GPx
mimic. These observations suggest that the inhibition of
LPO-catalyzed oxidation/iodination reactions by N,N-disub-
Synthesis of 1-Ethyl-3-methyl-1H-imidazole-2ACTHUNRTGNEUNG(3H)-selone (17)
Step 1: A solution of ethyl bromide (7.29 g, 66.98 mmol) in acetone
(30 mL) was added to a two-necked flask that contained sodium iodide
(10.04 g, 66.98 mmol) and 1-methylimidazole 5.00 g, 60.89 mmol) and the
reaction mixture was stirred for 12 h at RT. The solvent was removed
under vacuum and the resulting residue was treated with CH2Cl2. The
mixture was stirred for 5 min and the precipitated sodium chloride was
removed by filtration through a pad of Celite. The solvent CH2Cl2 was
evaporated under reduced pressure to yield a pale-yellow powder, which
was used in the next step without any further purification. Step 2: The
yellow solid as obtained from the first step was placed in a 250 mL two-
necked round-bottomed flask that was fitted with a reflux condenser and
dry MeOH (75 mL) was added. The resulting slurry was treated with se-
lenium powder (4.8 g, 60.89 mmol) and anhydrous potassium carbonate
(8.42 g, 60.89 mmol) and the reaction mixture was heated at reflux for
24 h. The brown solution was hot filtered through a pad of Celite and
washed twice with dry MeOH. The desired compound was obtained as
a white crystalline solid upon cooling at 48C. The small impurities in the
sample could be removed by column chromatography on silica gel
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Gouriprasanna Roy, Govindasamy Mugesh et al.
(EtOAc/petroleum ether, 1:2). Yield: 7.5 g (65%); M.p. 52–558C;
1H NMR (CDCl3): d=1.41 (t; 3H of NCH2CH3), 3.71 (s; 3H of NCH3),
4.18 (q; 2H of NCH2CH3), 6.87 ppm (s, 2H; CH of imidazole ring);
13C NMR (CDCl3): d=14.5, 37.0, 44.9, 118.0, 120.0, 154.7 ppm; 77Se NMR
(CDCl3): d=ꢀ14 ppm; HRMS (TOF): m/z calcd for C6H10N2Se: 191.0087
[M+H]+; found: 191.0094.
and anhydrous potassium carbonate (1.23 g, 8.92 mmol). Then, the reac-
tion mixture was heated at reflux for 24 h before being hot filtered
through Celite. The desired compound was obtained from the filtrate as
a white solid and it was crystallized by the slow evaporation of its solu-
1
tion in MeOH. The H NMR spectrum of this sample indicated the pres-
ence of some impurities, which were removed by column chromatogra-
phy on silica gel (EtOAc/petroleum ether, 1:2). Yield: 1.45 g (69%);
M.p. 100–1028C; 1H NMR (D2O): d=3.89 (t, 4H; CH2OH), 4.23 (t, 4H;
NCH2), 7.23 ppm (2H; CH of the imidazole ring); 13C NMR (D2O): d=
Synthesis of 1-(2-Hydroxyethyl)-3-methyl-(1H)-imidazole-2
ACHTUNGTRENUN(NG 3H)-thione
(20)
50.4, 58.7, 120.2, 148.6 ppm (1J
ACTHNUTRGNEU(GN Se,C)=216 Hz; C=Se of the imidazole
A 250 mL two-necked flask that was fitted with a reflux condenser and
septum was charged with 1-methylimidazole (5.0 g, 60.9 mmol), ethylene
chlorohydrine (4.83 g, 60.9 mmol) was added, and the reaction mixture
was heated at 808C for 96 h to produce a white solid, which was filtered
and used in the next step without any further purification. The solid com-
pound was placed in a 250 mL two-necked round-bottomed flask that
was fitted with a reflux condenser and treated with dry MeOH (70 mL),
sulfur powder (1.9 g, 60 mmol), and anhydrous potassium carbonate
(7.6 g, 55 mmol). Then, the reaction mixture was heated at reflux for 20 h
before being hot filtered through Celite. The desired compound was ob-
tained from the filtrate as a white crystalline solid upon cooling at 48C.
ring); 77Se NMR (D2O): d=ꢀ45 ppm; HRMS (TOF): m/z calcd for
C7H12N2O2Se: 258.9962 [M+Na]+; found: 258.9952.
Method B: A mixture of imidazole (1.00 g, 14.68 mmol) and chloroetha-
nol (2.96 g, 36.72 mmol) was placed in a 250 mL two-necked round-bot-
tomed flask that was fitted with a reflux condenser and septum and the
mixture was warmed to 808C for 96 h to produce a brown solid. The
solid was placed in a 250 mL two-neck round bottom flask that was fitted
with a reflux condenser and treated with dry MeOH (25 mL), selenium
powder (1.15 g, 14.68 mmol), and anhydrous potassium carbonate (2.02 g,
14.68 mmol). Then, the reaction mixture was heated at reflux for 24 h
before being hot filtered through Celite. The desired compound was ob-
tained from the filtrate as a white solid and it was crystallized by the
slow evaporation of its solution in MeOH. Yield: 1.89 g (55%).
1
The H NMR spectrum of this sample indicated the presence of some im-
purities, which were removed by column chromatography on silica gel
(EtOAc/petroleum ether, 1:2). Yield: 6.0 g (62%); M.p. 82–848C;
1H NMR (CDCl3): d=3.43 (br s, 1H; OH), 3.61 (s; 3H of NCH3), 3.94 (t,
Synthesis of Compound 27[12]
J
N
ACHTUNGTREN(UNNG H,H)=4.8 Hz, 2H; CH2OH),
Step 1: To a solution of 1,2-dibromoethane (5.72 g, 30.44 mmol) in THF
(35 mL) was added 1-methylimidazole (5.00 g, 60.89 mmol). Then, the re-
action mixture was heated at reflux for 3 h to afford a white crystalline
product, which was filtered, washed with ether, and dried under vacuum
for 1 h. Step 2: The solid compound as obtained in the first step was
placed in a 250 mL two-necked round-bottom flask that was fitted with
a reflux condenser and treated with dry MeOH (40 mL), anhydrous po-
tassium carbonate (8.41 g, 60.89 mmol), and selenium powder (4.8 g,
60.89 mmol). The reaction mixture was heated at reflux for 24 h and then
cooled. MeOH was evaporated under reduced pressure and the residue
was extracted with CHCl3. The combined organic extracts were filtered
through Celite and the desired compound was obtained from the filtrate
as a white solid, which was purified by column chromatography on silica
gel (EtOAc/petroleum ether). Yield: 12.0 g (57%); M.p. 190–1938C;
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
(NCH3), 50.32 (N-CH2), 61.1 (CH2OH), 117.8 (CH of the imidazole
ring), 118.2 (CH of the imidazole ring), 161.7 ppm (C=S of the imidazole
ring); HRMS (TOF): m/z calcd for C6H10N2OS: 181.0412 [M+Na]+;
found: 181.0415.
Synthesis of 1-(2-Hydroxyethyl)-3-methyl-(1H)-imidazole-2
ACHTUNGTRENUN(NG 3H)-selone
(21)
This compound was synthesized according to the procedure described for
the corresponding thione. For this reaction, 1-methylimidazole (5.0 g,
60.9 mmol), ethylene chlorohydrine (4.83 g, 60.9 mmol), selenium powder
(4.74 g, 60 mmol), and anhydrous potassium carbonate (7.6 g, 55 mmol)
were used. The final product was purified by column chromatography on
silica gel (EtOAc/petroleum ether, 1:2). Yield: 7.5 g (60%); M.p. 64–
668C; 1H NMR (CDCl3): d=3.15 (br s, 1H; OH), 3.65 (s; 3H of NCH3),
1H NMR (CDCl3): d=3.67 (s, 6H), 4.58 (s, 4H), 6.76 (d, J
ACTHNUGRTENUNG(H,H)=2.4 Hz,
2H), 6.80 ppm (d, JACTHNUTRGNEUNG
(H,H)=2.4 Hz, 2H); 13C NMR (CDCl3): d=37.1,
47.3, 119.8, 119.9, 155.7 ppm; 77Se NMR (D2O): d=4 ppm; HRMS
(TOF): m/z calcd for C10H14N4Se2: 350.9627 [M+H]+; found: 350.9634.
3.91 (t,
CH2OH), 6.84 (d, J
6.97 ppm (d, J
(H,H)=2.0 Hz, 1H; CH of the imidazole ring); 13C NMR
(CDCl3): d=37.2 (NCH3), 51.9 (NCH2), 60.8 (CH2OH), 119.8 (CH of the
J
G
JACTHUNGTERNNU(G H,H)=5.2 Hz, 2H;
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
Synthesis of Compound 28
A mixture of 1-benzyl imidazole (0.75 g, 4.74 mmol) and 1,2-dibromo-
ethane (0.21, 2.37 mmol) was heated at reflux in dry THF (20 mL)for
2 days. The white solid that formed was filtered, washed with dry THF,
and dried under vacuum. The white powder was placed in a 100 mL two-
necked round-bottomed flask that was fitted with a reflux condenser, dry
MeOH (30 mL) was added, and the mixture was stirred at RT for 5 min.
To the stirring solution were added sulfur powder (0.15 g, 4.74 mmol)
and anhydrous potassium carbonate (0.6 g, 4.30 mmol) and the mixture
was heated at reflux for 24 h. The unreacted sulfur powder was removed
by passing through a pad of Celite and washed with dry MeOH. Small
impurities could be removed by column chromatography on silica gel
(petroleum ether/EtOAc, 3:1). The desired product was obtained as
a white crystalline solid. Yield: 0.73 g (38%); M.p. 157–1598C; 1H NMR
(CDCl3): d=4.56 (s; 4H of NCH2CH2N), 5.22 (s, 4H; NCH2Ph), 6.45 (d,
imidazole ring), 120.4 (CH of the imidazole ring), 154.7 ppm (1J
ACTHNUTRGNEU(GN Se,C)=
227 Hz; C=Se of the imidazole ring); 77Se NMR (CDCl3): d=ꢀ9 ppm;
HRMS (TOF): m/z calcd for C6H10N2OSe: 228.9856 [M+Na]+; found:
228.9857.
Synthesis of 1,3-Bis(2-hydroxyethyl)-1H-imidazole-2ACTHNUTRGNE(NUG 3H)-selone (24)
Method A Step 1: Preparation of 2-(1H-imidazol-1-yl)ethanol (22). A so-
lution of sodium hydride (2.98 g, 1.28 mol) in dry DMF (150 mL) was
added into a 500 mL two-necked round-bottomed flask that was fitted
with a sidearm. To this solution was slowly added imidazole (7.67 g,
1.13 mol) in dry DMF (25 mL) and the mixture was warmed to 908C for
1 h and then cooled. Then, a solution of chloroethanol (9.02 g, 1.13 mol)
in DMF (25 mL) was slowly added to the reaction mixture, which was
stirred at 908C for 24 h. After cooling to RT, the mixture was filtered
and the filtrate was evaporated under reduced pressure to yield crude
compound 22, which was purified by column chromatography on neutral
aluminum oxide (CHCl3/MeOH, 5:1) and then further used in the next
step. Step 2: A mixture of compound 22 (1.00 g, 8.92 mmol) and chloroe-
thanol (0.79 g, 9.81 mmol) in a 250 mL two-necked flask that was fitted
with a reflux condenser and a septum was warmed to 808C for 96 h to
produce a brown solid. This solid compound was placed in a 250 mL two-
necked round-bottom flask that was fitted with a reflux condenser and
treated with dry MeOH (25 mL), selenium powder (0.71 g, 8.92 mmol),
JACTHNUTRGENN(UG H,H)=2.4 Hz, 2H; CH of the imidazole ring), 6.54 (d, JACHTUGNTREN(NUGN H,H)=2.4 Hz,
2H; CH of the imidazole ring), 7.33 ppm (m, 10H; CH of the benzene
ring); 13C NMR (CDCl3): d=45.23 (NCH2CH2N), 51.10 (CH2 of the
benzyl group), 116.34, 118.27, (CH of the imidazole ring), 128.20, 128.23,
128.86, 135.63 (CH of the benzene ring), 162.37 ppm (C=S of the imida-
zole ring); elemental analysis calcd for C22H22N4S: C 64.99, H 5.45,
N 13.78; found: C 64.04, H 5.32, N 13.69.
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Gouriprasanna Roy, Govindasamy Mugesh et al.
Synthesis of Compound 29
tion was slowly added a solution of imidazole (7.67 g, 1.13 mol) in dry
DMF (25 mL) and the mixture was warmed at 908C for 1 h and then
cooled. A solution of chloroethanol (9.02 g, 1.13 mol) in DMF (25 mL)
was slowly added to the reaction mixture, which was stirred for 24 h at
908C. After cooling to RT, the mixture was filtered and the filtrate was
evaporated under reduced pressure to yield crude compound 22, which
was purified by column chromatography on neutral aluminum oxide
(CHCl3/MeOH, 5:1) and then further used in the next step. Step 2: To
a solution of a,a’-dibromo-m-xylene (1.17 g, 4.46 mmol) in THF (25 mL)
was dropwise added 2-(1H-imidazol-1-yl)ethanol (22, 1.00 gmL,
8.92 mmol) in THF (10 mL). The reaction mixture was heated at reflux
for 3 h and the white crystalline product was filtered, washed with ether,
and dried in vacuo for 1 h. Step 3: The solid compound as obtained from
the previous step was placed in a 250 mL two-necked round-bottomed
flask that was fitted with a reflux condenser and treated with dry MeOH
(40 mL), anhydrous potassium carbonate (1.23 g, 8.92 mmol), and sulfur
powder (0.71 g, 8.92 mmol). The reaction mixture was heated at reflux
for 24 h and then cooled. MeOH was evaporated under reduced pressure
and the residue was extracted with CHCl3. The combined organic ex-
tracts were filtered through Celite and the desired compound was ob-
tained from the filtrate as a white solid, which was purified by column
chromatography on silica gel (EtOAc/petroleum ether). Yield: 2.5 g
A mixture of 1-benzyl imidazole (0.75 g, 4.74 mmol) and 1,2-dibromo-
ethane (0.21, 2.37 mmol) was heated at reflux in dry THF (20 mL) for
2 days. The white solid that formed was filtered, washed with dry THF,
and dried under vacuum. The white powder was placed in a 100 mL two-
necked round-bottomed flask that was fitted with a reflux condenser, dry
MeOH (30 mL) was added, and the mixture was stirred at RT for 5 min.
To the stirring solution were added selenium powder (0.38 g, 4.74 mmol)
and anhydrous potassium carbonate (0.6 g, 4.30 mmol) and the mixture
was heated at reflux for 24 h. Unreacted selenium powder was removed
by passing the mixture through a pad of Celite and washing with dry
MeOH. Small impurities could be removed by column chromatography
on silica gel (petroleum ether/EtOAc, 5:1). The desired product was ob-
tained as a white crystalline solid. Yield: 0.83 g (35%); M.p. 162–1648C;
1H NMR (CDCl3): d=4.70 (s; 4H of NCH2CH2N), 5.32 (s, 4H;
NCH2Ph), 6.58 (d, J
ACHTUNGTRENNUNG(H,H)=2 Hz, 2H; CH of the imidazole ring), 6.80
(d, J(H,H)=2 Hz, 2H; CH of the imidazole ring), 7.33 ppm (m, 10H;
ACHTUNGTRENNUNG
CH of the benzene ring); 13C NMR (CDCl3): d=47.03 (NCH2CH2N),
53.08 (CH2 of the benzyl group), 118.46, 120.54, (CH of the imidazole
ring), 128.37, 128.46, 128.97, 135.32 (CH of the benzene ring), 156.04 ppm
(C=Se of the imidazole ring); 77Se NMR (CDCl3): d=7.5 ppm; elemental
analysis calcd for C22H22N2Se: C 52.81, H 4.43, N 11.20; found: C 52.68,
H 3.93, N 11.26.
1
(58%); M.p. 140–1428Cl H NMR ([D6]DMSO): d=3.68 (q, 4H), 4.11 (t,
4H), 4.94 (t, 2H), 5.30 (s, 4H), 7.20 (d, 2H), 7.29 (m, 5H), 7.38 ppm (s,
1H); 13C NMR ([D6]DMSO): d=48.3, 50.9, 51.1, 58.4, 118.7, 120.9, 126.7,
127.1, 128.5, 136.7, 154.5 ppm; 77Se NMR ([D6]DMSO): d=ꢀ0.8 ppm;
HRMS (TOF): m/z calcd for C18H22N4O2Se2: 508.9971 [M+Na]+; found:
509.0016.
Synthesis of Compound 32
Step 1: To a solution of a,a’-dibromo-m-xylene (1.59 g, 6.1 mmol) in THF
(25 mL) was added 1-methylimidazole (1.00 gmL, 12.17 mmol). The reac-
tion mixture was heated at reflux for 3 h and the white crystalline prod-
uct was filtered, washed with ether, and dried in vacuo for 1 h. Step 2:
The solid compound as obtained in the previous step was placed in
a 250 mL two-necked round-bottomed flask that was fitted with a reflux
condenser and treated with dry MeOH (40 mL), anhydrous potassium
carbonate (1.68 g, 12.2 mmol), and sulfur powder (0.39 g, 12.17 mmol).
The reaction mixture was heated at reflux for 24 h and then cooled.
MeOH was evaporated under reduced pressure and the residue was ex-
tracted with CHCl3. The combined organic extracts were filtered through
Celite and the desired compound was obtained from the filtrate as
a white solid, which was purified by column chromatography on silica gel
Synthesis of Compound 36
Step 1: To a solution of 1,3,5-tris(bromomethyl)-2,4,6-trimethylbenzene
(1.60 g, 4.05 mmol) in THF (25 mL) was added 1-methylimidazole
(1.00 gmL, 12.17 mmol). Then, the reaction mixture was heated at reflux
for 3 h and the white crystalline product was filtered, washed with ether,
and dried under vacuum for 1 h. Step 2: The solid compound as obtained
from the first step was placed in a 250 mL two-necked round-bottomed
flask that was fitted with a reflux condenser and treated with dry MeOH
(40 mL), anhydrous potassium carbonate (1.68 g, 12.2 mmol), and sulfur
powder (0.39 g, 12.17 mmol). The reaction mixture was heated at reflux
for 24 h and then cooled. MeOH was evaporated under reduced pressure
and the residue was extracted with CHCl3. The combined organic ex-
tracts were filtered through Celite and the desired compound was ob-
tained from the filtrate as a white solid, which was purified by column
chromatography on silica gel (EtOAc/petroleum ether). Yield: 3.0 g
(51%); M.p. 250–2558C; 1H NMR (CDCl3): d=2.05 (s, 9H), 3.65 (s,
1
(EtOAc/petroleum ether). Yield: 1.9 g (46%); M.p. 175–1788C; H NMR
(CDCl3): d=3.65 (s, 6H), 5.24 (s, 4H), 6.60 (d, J
ACHTUNGTREN(NUNG H,H)=2 Hz, 2H), 6.68
(d, J
ACHTUNGTRENNUNG
35.4, 51.13, 116.5, 118.2, 127.9, 129.5, 136.6, 163.0 ppm; HRMS (TOF): m/
z calcd for C16H18N4S2: 331.1051 [M+H]+; found: 331.1058.
Synthesis of Compound 33
9H), 5.21 (s, 6H), 6.09 (d, JACTHNUTRGNENG(U H,H)=2 Hz, 3H), 6.63 ppm (d, JACHTUNGTRENNUNG(H,H)=
2 Hz, 3H); 13C NMR (CDCl3): d=16.7, 35.15, 47.0, 114.4, 118.1, 131.3,
139.8, 162.3 ppm; HRMS (TOF): m/z calcd for C24H30N6S3: 499.1772
[M+H]+; found: 499.1769.
This compound was synthesized according to the procedure described for
the corresponding thione; because the first step is identical to that of
thione 32, only the second step is described here. The solid compound
that was obtained from the first step was placed in a 250 mL two-necked
round-bottomed flask that was fitted with a reflux condenser and treated
with dry MeOH (40 mL), anhydrous potassium carbonate (1.68 g,
12.2 mmol), and selenium powder (0.96 g, 12.17 mmol). The reaction mix-
ture was heated at reflux for 24 h and then cooled. MeOH was evaporat-
ed under reduced pressure and the residue was extracted with CHCl3.
The combined organic extracts were filtered through Celite and the de-
sired compound was obtained as a white solid, which was purified by
column chromatography on silica gel (EtOAc/petroleum ether). Yield:
Synthesis of Compound 37
In the second step, the solid compound as obtained from the first step
was placed in a 250 mL two-necked round-bottomed flask that was fitted
with a reflux condenser and treated with dry MeOH (40 mL), anhydrous
potassium carbonate (1.68 g, 12.2 mmol), and selenium powder (0.96 g,
12.17 mmol). The reaction mixture was heated at reflux for 24 h and then
cooled. MeOH was evaporated under reduced pressure and the residue
was extracted with CHCl3. The combined organic extracts were filtered
through Celite and the desired compound was obtained from the filtrate
as a white solid, which was purified by column chromatography on silica
gel (EtOAc/petroleum ether). Yield: 4.2 g (54%); M.p. 2858C; 1H NMR
1
2.4 g (48%); M.p. 185–1888C; H NMR (CDCl3): d=3.74 (s, 6H), 5.34 (s,
4H), 6.78 (d, JACHTUNGTRENNUNG(H,H)=1.6 Hz, 2H), 6.86 (d, JACHUTNGTREN(NNGU H,H)=1.6 Hz, 2H), 7.28–
7.33 ppm (m, 4H); 13C NMR (CDCl3): d=37.4, 53.0, 118.6, 120.3, 128.2,
129.6, 136.4, 156.7 ppm; 77Se NMR (CDCl3): d=ꢀ0.8 ppm; HRMS
(TOF): m/z calcd for C16H18N4Se2: 426.9940 [M+H]+; found: 426.9951.
(CDCl3): d=2.19 (s, 9H), 3.72 (s, 9H), 5.27 (s, 6H), 6.24 (d, JACHTUNGTRENNUNG
1.6 Hz, 3H), 6.80 ppm (d, JACHTGNUTRENNUNG
17.0, 37.2, 49.2, 116.6, 120.1, 131.3, 140.2, 156.2 ppm; 77Se NMR (CDCl3):
d=8 ppm; HRMS (TOF) m/z calcd for C24H30N6Se3: 664.9926 [M+Na]+;
found: 664.9916.
Synthesis of Compound 34
Step 1: Preparation of 2-(1H-Imidazol-1-yl)ethanol (22). As mentioned
during the synthesis of compound 24, a solution of sodium hydride
(2.98 g, 1.28 mol) in dry DMF (150 mL) was placed in a 500 mL two-
necked round-bottomed flask that was fitted with a sidearm. To this solu-
Chem. Asian J. 2013, 8, 1910 – 1921
1918
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemasianj.org
Gouriprasanna Roy, Govindasamy Mugesh et al.
Synthesis of Compounds 41–43
oxidation reaction was calculated by following the increase in UV absorp-
tion at 411 nm. All of the solutions were freshly prepared as mentioned
above. In a typical experiment, for a 1 mL incubation mixture, 12.9 nm
LPO, 1.4 mm ABTS, and a fixed concentration of inhibitor were incubat-
ed for 1 min at 258C. The reaction was initiated with different concentra-
tions of hydrogen peroxide. The rates were calculated at different con-
centrations of hydrogen peroxide and were plotted against various con-
centrations of hydrogen peroxide.
General Procedure
A mixture of the amine (50.0 mmol for monoamines, 25.0 mmol for dia-
mines) triethylorthoformate (50 mmol, 100% excess), and selenium
(25.0 mmol) was sealed in a Teflon-lined bomb and heated at 1908C for
8 h under autogenous pressure, followed by slow cooling to RT. The cold
reaction mixture was dried under an oil vacuum for 3 h, dissolved in the
minimum amount of ether/EtOH (3:1), decolorized with charcoal, and
filtered. Slow evaporation gave the selenoureas as colorless crystalline
solids.[13]
Glutathione Peroxidase-Like Activity
In this assay, we employed a mixture of PhSH and H2O2 (1:2 molar ratio)
in MeOH/CH2Cl2 (1:1) at RT as a model system. Experiments were per-
formed with and without different catalysts under the same conditions.
Periodically, aliquots were removed and the concentrations of the di-
phenyl disulfide (PhSSPh) product were determined by reversed-phase
HPLC, by using pure PhSSPh as an external standard. The amount of di-
sulfide that formed during the course of the reaction was calculated from
the calibration plot for each standard.
1,3-Dimethyl-imidazolidine-2-selone (41)
ACTHNUTRGNEUNG
1H NMR (CDCl3): d=3.19(s, 6H), 3.55 ppm (s, 4H); 13C NMR (CDCl3):
d=36.9 (CH3), 49.3 (CH2 of the imidazolidine ring), 181.4 ppm (C=Se);
77Se NMR (CDCl3): d=62.8 ppm.
1,3-Diphenyl-imidazolidine-2-selone (42)
ACTHNUTRGNEUNG
1H NMR (CDCl3): d=4.19(s, 4H), 7.31–7.58 ppm (m, 10H); 13C NMR
Computational Methods
(CDCl3): d=51.1 (CH2 of the imidazolidine ring), 126.5, 127.3, 129.0,
141.4 (C of the benzene ring), 180.5 ppm (C=Se); 77Se NMR (CDCl3):
d=161.1 ppm.
All of the calculations were performed by using the Gaussian 03 suite of
quantum chemical programs.[23] The hybrid Becke’s three-parameter func-
tional with the Lee–Yang–Parr correlation functional (B3LYP) was ap-
plied for the DFT calculations. Geometries were fully optimized at the
1,3-Di-tert-butyl-imidazolidine-2-selone (43)
B3LYP level of theory by using the 6-311+ +GACTHNUTRGNEUNG
(d,p) basis sets.[15] All sta-
1H NMR (CDCl3): d=1.69 (s, 18H), 3.48 ppm (s, 4H); 13C NMR
(CDCl3): d=29.0 (CH3), 45.6 (CH2 of the imidazolidine ring), 58.0 (NC-
tionary points were characterized as minima by their corresponding Hes-
sian indices. The NMR calculations were performed at B3LYP/6-311+ +
ACHTUNGTRENNUNG
(CH3)3), 178.9 ppm (C=Se); 77Se NMR (CDCl3): d=266.8 ppm.
G
N
ACHTUNGTRENN(UNG d,p)-optimized geometries by using
Synthesis of Complex 44[19]
ACHTUNGTRENNUNG
To a solution of compound 19 (100 mg, 0.39 mmol) in CH2Cl2 (10 mL)
was added a solution of I2 (99 mg, 0.39 mmol) in CH2Cl2 (25 mL) drop-
wise under a nitrogen atmosphere at 08C. The red–brown solution was
stirred at RT for 3 h. The resulting solution was concentrated to obtain
a red–brown solid product. The product was recrystallized from CH2Cl2
to afford black crystals. Yield: 90 g (80%).
level of theory and charges were calculated by natural population analy-
sis (NPA).[25]
X-ray Crystallography
X-ray crystallographic studies were performed on a Bruker CCD diffrac-
tometer (graphite-monochromated MoKa radiation, l=0.71073 ꢁ) that
was controlled by a Pentium-based PC with the SMART software pack-
age.[26] Single crystals were mounted at RT onto the ends of glass fibers
and the data were collected at RT. The structures were solved by using
direct methods and refined by using the SHELXTL software package.
All non-hydrogen atoms were refined anisotropically and hydrogen
atoms were assigned at idealized locations. Empirical absorption correc-
tions were applied to all structures by using SADABS.[27–31]
Synthesis of Complex 45
To a solution LPO/H2O2/KI in phosphate buffer (50 mm, pH 7.4),[22] a so-
lution of compound 19 in MeOH was added dropwise with stirring. The
final mixture was allowed to stand at RT for slow evaporation of the sol-
vent. Upon evaporation of the solvent, bright-orange crystals were ob-
tained in quantitative yield.
Inhibition of the LPO-Catalyzed Oxidation of ABTS
Crystal Data for Compound 21
The LPO-inhibition experiments were performed in phosphate buffer
(pH 7) at 258C. The spectroscopic measurements were performed on
a UV/Vis spectrophotometer and the assay of LPO enzyme activity was
followed by catalysis of the oxidation of ABTS. The initial rate of the ox-
idation reaction was calculated by following the increase in UV absorp-
tion at 411 nm. The enzyme activity after the addition of various inhibi-
tors was expressed as a percentage of that observed in the absence of in-
hibitors. The concentration of peroxide was always present in excess with
respect to the enzyme. The inhibition plots were obtained by using
Origin 6.1 software and these plots were used for the calculation of the
IC50 values. In a typical experiment, 100 mm ABTS (from its diammoni-
um salt) and 30 mm hydrogen peroxide solutions (from a 30% w/w solu-
tion) were freshly prepared in deionized water. A solution of the lacto-
peroxidase enzyme (0.15–0.25 unitmLꢀ1) was prepared in cold deionized
water and used immediately for the assay. In a 1 mL reaction mixture,
the final concentrations were 12.9 nm LPO, 28.7 mm H2O2, 1.4 mm ABTS,
and 1–200 mm of the inhibitor.
C6H10N2OSe; Mw =205.12; orthorhombic; space group Pbca; a=14.74(2),
b=7.487(10), c=15.08(2) ꢁ; a=b=g=90.008; V=1665(4) ꢁ3; 1calcd
=
1.637 mgmꢀ3
;
Z=8;
m
G
;
reflns collected/unique
reflns: 13348/1995; parameters: 90; Rint =0.0901; R(observed data)[a]
:
R1 =0.0444, wR2 =0.0800; RACHTNUGRTNEUNG
(all data)[b]: R1 =0.0901, wR2 =0.0930; GOF
on F2: 1.036; D1min/max: ꢀ0.312/0.610 eꢁꢀ3 [32]
Crystal Data for Compound 24
C7H12N2O2Se; Mw =235.15; orthorhombic; space group Pbc21; a=
5.9400(17), b=16.674(5), c=9.506(3) ꢁ; a=b=g=90.008; V=
941.6(5) ꢁ3; 1calcd =1.659 mgmꢀ3; Z=4; m(MoKa)=3.952 mmꢀ1; reflns col-
AHCTUNGTRENNUNG
lected/unique reflns: 7580/2120; parameters: 109; Rint =0.0338; R(ob-
ACTHNUTRGNEUNG
served data)[a]: R1 =0.0281, wR2 =0.0837; R(all data)[b]: R1 =0.0338, wR2 =
[32]
0.0914; GOF on F2: 0.707; D1min/max: ꢀ0.307/0.394 eꢁꢀ3
.
Crystal Data for Compound 27
C10H14N4Se2; Mw =348.17; monoclinic; space group P21/c; a=4.8188(10),
b=19.537(5), c=7.1988(16) ꢁ; b=90.008; V=647.8(2) ꢁ3; 1calcd
1.785 mgmꢀ3 (MoKa)=5.687 mmꢀ1
Z=2; reflns collected/unique
reflns: 5045/1315; parameters: 74; Rint =0.0412; R(observed data)[a]: R1 =
Effect of H2O2 Concentration on the Inhibition of the LPO-Catalyzed
Oxidation of ABTS
=
;
m
G
;
The effect of hydrogen-peroxide concentration on the inhibition of the
LPO-catalyzed oxidation of ABTS was performed on a UV/Vis spectro-
photometer in phosphate buffer (pH 7) at 258C. The initial rate of the
0.0285, wR2 =0.0929; RACTHNUTRGNEUNG
(all data)[b]: R1 =0.0412, wR2 =0.1063; GOF on F2:
0.795; D1min/max: ꢀ0.465/0.298 eꢁꢀ3
.
[32]
Chem. Asian J. 2013, 8, 1910 – 1921
1919
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemasianj.org
Gouriprasanna Roy, Govindasamy Mugesh et al.
Crystal Data for Compound 28
[3] a) J. Buxeraud, A. C. Absil, J. Claude, C. Raby, G. Catanzano, C.
Beck, Eur. J. Med. Chem. 1985, 20, 43–50; b) C. Raby, J. F. Lagorce,
A. C. Jambut-Absil, J. Buxeraud, G. Catanzano, Endocrinology
1990, 126, 1683–1691; c) M. C. Aragoni, M. Arca, F. Demartin, F. A.
Devillanova, A. Garau, F. Isaia, V. Lippolis, G. Verani, J. Am.
Chem. Soc. 2002, 124, 4538–4539; d) F. Cristiani, F. A. Devillanova,
F. Isaia, V. Lippolis, G. Verani, Polyhedron 1995, 14, 2937–2943;
e) F. Cristiani, F. Demartin, F. A. Devillanova, F. Isaia, G. Saba, G.
Verani, J. Chem. Soc. Dalton Trans. 1992, 3553–3560; f) F. Cristiani,
F. A. Devillanova, F. Demartin, F. Isaia, V. Lippolis, G. Verani,
Inorg. Chem. 1994, 33, 6315–6324.
C22H22N4S2; Mw =406.56; monoclinic; space group P21/c; a=8.8133(9),
b=9.9281(10), c=24.024(2) ꢁ; b=90.071(2)8; V=2102.1(4) ꢁ3; 1calcd
=
1.285 mgmꢀ3
;
Z=4;
m
(MoKa)=0.268 mmꢀ1
;
reflns collected/unique
reflns: 17660/4943; parameters: 253; Rint =0.028; R(observed data)[a]
:
R1 =0.0567, wR2 =0.1420; RACHTNUGRTNEUNG
(all data)[b]: R1 =0.0955, wR2 =0.1686; GOF
on F2: 0.888; D1min/max: ꢀ0.174/0.294 eꢁꢀ3 [32]
.
Crystal Data for Compound 41
C5H10N2Se; Mw =177.11; monoclinic; space group P21/n; a=10.547(3),
b=6.2838(16), c=11.672(3) ꢁ; b=112.938(4)8; V=712.4(3) ꢁ3; 1calcd
1.651 mgmꢀ3 (MoKa)=5.173 mmꢀ1
Z=4; reflns collected/unique
reflns: 5851/1664; parameters: 75; Rint =0.0848; R(observed data)[a]: R1 =
=
[4] Although there is no conclusive evidence for the coordination of the
;
m
U
;
ꢀ
thione moiety of anti-thyroid drugs to iron, iron sulfur coordinate
interactions are frequently observed in metalloenzymes; see: a) C.
Laurence, M. J. El Ghomari, M. Berthelot, J. Chem. Soc. Perkin
Trans. 2 1998, 1163–1166; b) C. Laurence, M. J. El Ghomari, J.-Y.
Le Questel, M. Berthelot, R. Mokhlisse, J. Chem. Soc. Perkin Trans.
2 1998, 1545–1551.
0.0434, wR2 =0.0875; RACHTUNGTRENNUNG
(all data)[b]: R1 =0.0848, wR2 =0.1019; GOF on F2:
0.998; D1min/max: ꢀ0.348/0.486 eꢁꢀ3
.
[32]
Crystal Data for Compound 42
C15H14N2Se; Mw =301.24; monoclinic; space group P21/n; a=5.9711(7),
b=21.688(3), c=20.463(3) ꢁ; b=90.971(2)8; V=2649.5(5) ꢁ3; 1calcd
1.510 mgmꢀ3 (MoKa)=2.817 mmꢀ1
Z=8; reflns collected/unique
reflns: 22876/6220; parameters: 325; Rint =0.1227; R(observed data)[a]
[5] a) C. Schmutzler, B. Mentrup, L. Schomburg, C. Hoang-Vu, V.
Herzog, J. Kçhrle, Biol. Chem. 2007, 388, 1053–1059; b) J. Aaseth,
H. Frey, E. Glattre, G. Norheim, J. Ringstad, Y. Thomassen, Biol.
Trace Elem. Res. 1990, 24, 147–152; c) J. Kçhrle, F. Jakob, B. Con-
temprꢂ, J. E. Dumont, Endocr. Rev. 2005, 26, 944–984.
[6] a) U. Bjçrkman, R. Ekholm, Endocrinology 1992, 130, 393–399;
b) U. Bjçrkman, R. Ekholm, Mol. Cell. Endocrinol. 1995, 111, 99–
107; c) R. Ekholm, U. Bjçrkman, Endocrinology 1997, 138, 2871–
2878.
[7] A. C. F. Ferreira, L. D. Cardoso, D. Rosenthal, D. P. Carvalho, Eur.
J. Biochem. 2003, 270, 2363–2368, and references therein.
[8] a) G. Roy, M. Nethaji, G. Mugesh, J. Am. Chem. Soc. 2004, 126,
2712–2713; b) G. Roy, G. Mugesh, J. Am. Chem. Soc. 2005, 127,
15207–15217.
[9] a) G. Roy, D. Das, G. Mugesh, Inorg. Chim. Acta 2007, 360, 303–
316; b) P. N. Jayaram, G. Roy, G. Mugesh, J. Chem. Sci. 2008, 120,
143–154; c) D. J. Williams, M. R. Fawcett-Brown, R. R. Raye, D.
VanDerveer, Y. T. Pang, R. L. Jones, K. L. Bergbauer, Heteroat.
Chem. 1993, 4, 409–414.
=
;
m
G
;
:
R1 =0.0493, wR2 =0.0916; RACHTNUGRTNEUNG
(all data)[b]: R1 =0.1227, wR2 =0.1242; GOF
on F2: 0.986; D1min/max: ꢀ0.346/0.519 eꢁꢀ3 [32]
.
Crystal Data for Compound 44
C22H24I2N4OSe2; Mw =772.17; monoclinic; space group P21/c; a=
10.2868(9), b=28.487(3), c=10.3754(9) ꢁ; b=116.488; V=2721.3(4) ꢁ3;
ACTHNUTRGNEUNG
1calcd =1.885 mgmꢀ3; Z=4; m(MoKa)=5.006 mmꢀ1; reflns collected/unique
reflns: 23718/6394; parameters: 282; Rint =0.1313; R(observed data)[a]
:
R1 =0.029, wR2 =0.093; RACHTNUTGRNEUNG
(all data)[b]: R1 =0.041, wR2 =0.106; GOF on
F2: 0.981; D1min/max: ꢀ0.593/0.883 eꢁꢀ3
.
[a] R1 =Sj jFo jꢀjFc j j/SjFo j ; wR2 ={S[w
4s(Fo).
N
(F2o)2]}1/2. [b] Fo >
ACHTUNGTRENNUNG
c
[10] D. Das, G. Roy, G. Mugesh, J. Med. Chem. 2008, 51, 7313–7317.
[11] G. Roy, M. Nethaji, G. Mugesh, Org. Biomol. Chem. 2006, 4, 2883–
2887.
[12] K. P. Bhabak, K. Satheeshkumar, S. Jayavelu, G. Mugesh, Org.
Biomol. Chem. 2011, 9, 7343–7350.
[13] Y. Zhou, M. K. Denk, Tetrahedron Lett. 2003, 44, 1295–1299.
[14] a) H. Bock, S. Aygen, P. Rosmus, B. Solouki, E. Weissflog, Chem.
Ber. 1984, 117, 187–202; b) S. Collins, T. G. Back, A. Rauk, J. Am.
Chem. Soc. 1985, 107, 6589–6592; c) S. Dapprich, G. Frenking,
Chem. Phys. Lett. 1993, 205, 337–342; d) J. S. Kwiatkowski, J. Leszc-
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Phys. 1994, 181, 47–55; f) E. D. Jemmis, K. T. Giju, J. Leszczynski, J.
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Acknowledgements
This study was supported by a grant from AstraZeneca Pharmaceuticals.
G.M. acknowledges the DST for the award of a Swarnajayanti Fellow-
ship. G.R. thanks the Council of Scientific and Industrial Research
(CSIR), New Delhi, for a research fellowship.
[1] a) B. Davidson, M. Soodak, J. T. Neary, H. V. Strout, J. D. Kieffer,
H. Mover, F. Maloof, Endocrinology 1978, 103, 871–883; b) A.
Taurog, M. L. Dorris, F. S. Guziec, Jr., Endocrinology 1989, 124, 30–
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Received: March 1, 2013
Revised: April 8, 2013
Published online: June 4, 2013
Chem. Asian J. 2013, 8, 1910 – 1921
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ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim