Synthesis and anticholinesterase activities of novel 1,3,4-thiadiazole based compounds

Article abstract of DOI:10.3109/14756366.2012.688041

In the present study, new (1,3,4-thiadiazol-2-yl)benzene-1,3-diol based compounds have been synthesized and their potential anticholinesterases properties have been investigated using the modified of Ellman's spectrophotometric method. The compounds were obtained by the reaction of hydrazides or thiosemicarbazides with aryl-modified sulfinylbis[(2,4- dihydroxyphenyl)methanethione]s. Their chemical structures were elucidated by IR, ¹H-NMR, ¹³C-NMR and EI-MS spectral data and elemental analyses. Most of the compounds acted as acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitors in vitro, with IC50 values ranging from >500 to 0.053 μM and from >500 to 0.105 μM, respectively. The most potent compound 9 (IC50 = 0.053 μM) proved to be selective toward AChE, exhibiting selectivity ratios versus BuChE of ca. 950. The kinetic studies showed that it is a mixed-type of AChE inhibitor. Another compound (2) was active against both enzymes with IC50 values in the low nM range. The structure-activity relationships (SARs) of the compounds under consideration were discussed.

Full text of DOI:10.3109/14756366.2012.688041

Journal of Enzyme Inhibition and Medicinal Chemistry, 2013; 28(4): 816–823
© 2013 Informa UK, Ltd.
ISSN 1475-6366 print/ISSN 1475-6374 online
DOI: 10.3109/14756366.2012.688041
research arTIcLe
Synthesis and anticholinesterase activities of novel
1,3,4-thiadiazole based compounds
Alicja Skrzypek1, Joanna Matysiak1, Monika M. Karpińska2, and Andrzej Niewiadomy1,2
1Department of Chemistry, University of Life Sciences, Lublin, Poland and 2Institute of Industrial Organic Chemistry,
Warszawa, Poland
abstract
In the present study, new (1,3,4-thiadiazol-2-yl)benzene-1,3-diol based compounds have been synthesized and their
potential anticholinesterases properties have been investigated using the modified of Ellman’s spectrophotometric
method. The compounds were obtained by the reaction of hydrazides or thiosemicarbazides with aryl-modified
sulfinylbis[(2,4-dihydroxyphenyl)methanethione]s. Their chemical structures were elucidated by IR, 1H-NMR, 13C-NMR
and EI-MS spectral data and elemental analyses. Most of the compounds acted as acetylcholinesterase (AChE) and
butyrylcholinesterase (BuChE) inhibitors in vitro, with IC50 values ranging from >500 to 0.053 μM and from >500 to
0.105 μM, respectively. The most potent compound 9 (IC = 0.053 μM) proved to be selective toward AChE, exhibiting
selectivity ratios versus BuChE of ca. 950. The kinetic5s0 tudies showed that it is a mixed-type of AChE inhibitor.
Another compound (2) was active against both enzymes with IC50 values in the low nM range. The structure-activity
relationships (SARs) of the compounds under consideration were discussed.
Keywords: 1,3,4-Thiadiazole, synthesis, acetylcholinesterase, butyrylcholinesterase, inhibitor
Introduction
that in severe AD brains the levels of AChE are consider-
Acetylcholinesterase (AChE) inhibition is a major phar-
macological approach to the treatment of Alzheimer’s
disease (AD1,2). A common method for the treatment
of cognitive and behavioral symptoms of AD is the use
of structurally diverse group of cholinesterase inhibi-
tors (ChEIs) with an amine moiety and distinct modes
of action. Available ChEI drugs are tacrine (Cognex3),
donepezil (Aricept4) galanthamine (Reminyl) - revers-
ible inhibitors5 and rivastigmine (Exelon6) which acts
as a pseudo-irreversible ChEI, and differs in selectivity
toward AChE and butyrylcholinesterase (BuChE).
Two major evidences highlight the central role of
AChE in AD: (i) inhibitors, which increase synaptic levels
of available ACh by preventing its degradation and tem-
porarily retard the loss of cognitive function, (ii) AChE
induces the expression of the β-amyloid (Aβ) precursor
protein in glia and activates glial cells7. e second class
of compounds are the only approved drugs for the symp-
tomatic treatment of AD8. Recent research has revealed
ably reduced, whereas BuChE activity increases. BuChE
may then act as a compensatory mechanism for ACh
metabolism, aggravating the toxicity of Aβ .
9
To obtain more metabolically stable cholinomimetic
ligands, it is possible to replace the ester group with a
series of five-membered rings like oxadiazoles, thiadia-
zoles, triazoles and tetrazoles10. Some researchers have
studied thiadiazoles extensively and the compounds
bearing thiadiazole moiety have been reported to exhibit
significant anticholinesterase activity11,12
e antioxidant and muscarinic receptor binding
properties of 3-(thiadiazolyl)pyridine 1-oxides
.
were reported by Martinez et al13. as potential
acetylcholinesterase inhibitors. Sarkadi et al. studied
1-benzyl-4-[2-(5-phenyl-1,3,4-thiadiazol-2-yl)
aminoethyl]piperidines14. e thiadiazolidin-3,5-dione
(TDZD) derivatives were reported as the first non-ATP
competitive inhibitors of glycogen synthase kinase 3β
(GSK-3β) which is one of the most attractive therapeutic
Address for Correspondence: Joanna Matysiak, Department of Chemistry, University of Life Sciences, Akademicka 15, 20–950 Lublin, Poland.
Tel: +48 81 4456816, Fax: +4881 5333549. E-mail: joanna.matysiak@up.lublin.pl
(Received 10 March 2012; revised 17 April 2012; accepted 20 April 2012)
816

Synthesis of novel 1,3,4-thiadiazole based compounds 817
targets for the development of selective inhibitors of
Alzheimer’s disease treatment15. Misra and co-wokers
described thiadiazoloquinazolone derivatives as
AChEI12,16. Recently N-(benzothiazol-2-yl)-2-[(5-amino/
methyl-1,3,4-thiadiazol-2-yl)thio]acetamides have been
presented as AChEI with IC50 values in the low µM range17.
Synthesis of compounds
4-(5-Propyl-1,3,4-thiadiazol-2-yl)benzene-1,3-diol (1)
A mixture of butyrohydrazide (0.025 mol) (Alfa Aesar)
and STB (0.025 mol) in methanol (120 mL) was refluxed
(3 h). e hot mixture was filtered, water (40 mL) was
added to the filtrate and the mixture was left at room
temperature (24 h). Recrystallization from MeOH/H2O
(4:3) (70 mL) afforded 1.
Yield: 65%; HPLC: log k = −0.26; m.p.: 243–245°C; anal.
calc. for C11H12N2O2S (236.29): C, 55.91; H, 5.12; N, 11.86;
found: C, 56.02; H, 5.10; N, 11.80; H NMR (500 MHz,
DMSO-d6, ppm) δ: 11.04 (s, 1H, HO-C(3)), 9.97 (s, 1H,
HO-C(1)), 7.94 (m, 1H, H-C(5)), 6.47 (m, 1H, H-C(2)), 6.42
(m, 1H, H-C(6)), 3.04 (t, J = 7.46 Hz, 2H, CH2), 1.76 (sextet,
J = 7.43 Hz, 2H, CH2), 0.97 (t, J = 7.35 Hz, 3H, CH3); 13C
NMR (125 MHz, DMSO-d6, ppm) δ: 168.2, 162.6, 160.8,
156.2, 129.0, 108.4, 108.1, 102.4, 30.7 (CH2), 22.8 (CH2),
13.4 (CH3); IR (ATR, cm−1): 3162 (OH), 2962 (H-Ar), 1626
(C=N), 1598, 1552, 1529 (C=C), 1468, 1421, 1330, 1250,
1228, 1171 (C-O), 1133, 1054 (N=C-S-C=N), 986, 967, 845,
801, 745, 690 (C-S-C), 674; EI-MS (m/z, %): 236 (58), 235
(5), 221 (18), 210 (5), 209 (10), 208 (100), 207 (5), 184 (4),
167 (6), 153 (16), 136 (14), 135 (10), 80 (4), 69 (4), 52 (4),
41 (4).
In the previous studies, we found
a series of
4-(5-phenyl)-1,3,4-thiadiazol-2-yl)benzene-1,3-diols
substituted in the phenyl ring as in vitro AChE and
BuChE inhibitors of high potency18. Some of them were
efficient against both enzymes, others were character-
ized by high selectivity to AChE over to BuChE. With
the aim of gaining insights into the structure–activity
relationships and possibly identifying new leads in the
AChE/BuChE inhibitors, in the present work we synthe-
sized some new compounds from the (1,3,4-thiadiazol-
2-yl)benzene-1,3-diol group. We included derivatives
with 5-heterocyclic, aryl and alkyl substituents attached
directly to the 1,3,4-thiadiazole ring or by -NH- group as
well as the compounds with modified resorcinol moiety.
e inhibition mechanism for the chosen compounds
was studied.
1
Materials and methods
Chemistry
4-[5-(Naphthalen-2-yl)-1,3,4-thiadiazol-2-yl]benzene-
1,3-diol (3)
e IR spectra were recorded with a Perkin-Elmer
FT-IR 1725X spectrophotometer (Perkin-Elmer Ltd.,
Beaconsfield, Buckinghamshire, England) (in KBr) or
Varian 670 FT-IR spectrometer (ATR). e spectra were
A mixture of naphthalene-2-carbohydrazide (0.005 mol)
(Alfa Aesar) and STB (0.0037 mol) in methanol (35 mL)
was refluxed (1.5 h). e hot mixture was filtered, water
(50 mL) was added to the filtrate and the mixture was
left at room temperature (24 h). Recrystallization from
MeOH/H2O (1:1) (25 mL) afforded 3.
made in the range of 600–4000 cm−1. H NMR and 13C
1
NMR spectra were recorded in DMSO-d6 using a Varian
Mercury 400 or a Bruker DRX 500 (Bruker Daltoncs, Inc.
Billerica, MA) instrument. Chemical shifts (δ, ppm) were
given in relation to tetramethylsilane (TMS). e spectra
MS (EI, 70 eV) were recorded using the apparatus AMD-
604 (Intectra GmbH, Harpstedt, Germany). Elemental
analyses (C, H, N) were conducted using a Perkin-Elmer
2400 instrument (Perkin Elmer, Waltham, MA) and were
found to be in good agreement ( 0.4%) with the calcu-
lated values. e melting point (mp) was determined
using a Büchi B-540 (Flawil, Switzerland) melting point
apparatus.
e purity of the compounds was examined by a
liquid chromatograph Knauer (Berlin, Germany) with
a dual pump, a 20-μL simple injection valve and a
UV–visible detector (330 nm). e Hypersil Gold C18
(1.9 μm, 100 × 2.1 mm) column was used as the station-
ary phase. e mobile phase included different contents
of methanol and acetate buffer (pH 4, 20 nM) as the
aqueous phase. e flow rate was 0.5 mL min−1 at room
temperature. e retention time of an unretained solute
(t0) was determined by the injection of a small amount
of acetone dissolved in water. Log k values for 70% of
methanol (v/v) in the mobile phase are presented. Log
k values were calculated as log k = log (tR – to)/to, where:
tR = retention time of a solute, to = retention time of an
unretained solute.
Yield: 74%; HPLC: log k = 0.514; m.p.: 248–250°C;
anal. calc. for C18H12N2O2S (320.37): C, 67.48; H, 3.78; N,
8.74; found: C, 67.41; H, 3.80; N, 8.70; 1H NMR (500 MHz,
DMSO-d6, ppm) δ: 11.14 (s, 1H, HO-C(3)), 10.09 (s, 1H,
HO-C(1)), 8.58 (s, 1H, H-Ar), 8.19 (dd, J = 8.58 Hz and
J = 1.78 Hz, 1H, H-Ar), 8.14 (m, 3H, H-Ar), 8.02 (m, 1H,
H-CAr), 7.64 (m, 2H, H-Ar), 6.56 (d, J = 2.3 Hz, 1H, H-C(2)),
6.50 (dd, J = 8.66 Hz and J = 2.31 Hz, 1H, H-C(5)); 13C NMR
(125 MHz, DMSO-d6, ppm) δ: 166.3, 162.9, 161.4, 156.5,
133.8, 132.9, 129.0, 128.9, 128.6, 127.8, 127.7, 127.5, 127.4,
127.1, 123.9, 108.5, 108.4, 102.2; IR (KBr, cm−1): 3397, 3151
(OH), 1631 (C=N), 1600, 1527, 1473 (C=C), 1431, 1334,
1257, 1182 (C-O), 1140, 1052 (N=C-S-C=N), 1022, 986,
968, 939, 898, 852, 806, 743, 682 (C-S-C), 640, 611; EI-MS
(m/z, %): 320 (M+, 100), 186 (4), 185 (24), 171 (16), 167
(42), 160 (5), 154 (11), 153 (30), 149 (4), 140 (6), 139 (4),
135 (7), 127 (25), 126 (9), 119 (4), 107 (6), 86 (4), 77 (5), 69
(4), 63 (4), 52 (6), 51 (5), 40 (9), 39 (6).
4-[5-(1,3-Benzodioxol-5-yl)-1,3,4-thiadiazol-2-yl]benzene-
1,3-diol (4)
A mixture of 1,3-benzodioxole-5-carbohydrazide (0.005
mol) (Alfa Aesar) and STB (0.0037 mol) in methanol (30
mL) was refluxed (3 h). e hot mixture was filtered,
© 2013 Informa UK, Ltd.

818 A. Skrzypek et al.
water (30 mL) was added to the filtrate and the mixture
was left at room temperature (24 h). Recrystallization
from MeOH/H2O (2:1) (30 mL) afforded 4.
N, 13.52; found: C, 52.25; H, 3.42; N, 13.48; 1H NMR (500
MHz, DMSO-d6, ppm) δ: 10.97 (s, 2H, HO-C(3)), 10.01 (s,
2H, HO-C(1)), 7.95 (d, 2H, J = 8.69 Hz, H-C(5)), 6.48 (d,
2H, J = 2.31 Hz, H-C(2)), 6.42 (dd, 2H, J = 8.68 Hz and J =
2.32 Hz, H-C(6)), 3.60 (s, 4H, CH2); 13C NMR (500 MHz,
DMSO-d6, ppm) δ: 166.4, 163.3, 161.0, 156.2, 128.9, 108.4,
108.2, 102.3, 28.6 (2C, CH2); IR (KBr, cm−1): 3556 (OH),
3038, 2942 (CAr-H), 1605 (C=N, C=C), 1521, 1475 (C=C),
1432, 1343, 1319, 1277, 1214, 1184 (C-O), 1122 (CAr-H),
1084, 987, 970, 867 (CAr-H), 813, 723, 708, 663 (C-S-C),
618; EI-MS (m/z, %): ESI-MS (m/z): 413.1 [M-H]-, 827.1
[2M-H]-.
Yield: 82%; HPLC: log k = 0.118; m.p.: 308–310°C;
anal. calc. for C15H10N2O4S (314.32): C, 57.32; H, 3.21; N,
8.91; found: C, 57.40; H, 3.19; N, 8.95; 1H NMR (500 MHz,
DMSO-d6, ppm) δ: 11.06 (s, 1H, HO-C(3)), 10.04 (s, 1H,
HO-C(1)), 8.02 (d, J = 8.67 Hz, 1H, H-C(5)), 7.55 (d, J =
1.74 Hz, 1H, H-C(4’)), 7.50 (dd, J = 8.07 Hz and J = 1.78
Hz, 1H, H-C(6’)), 7.07 (d, J = 8.10 Hz, 1H, H-C(7’)), 6.51
(d, J = 2.32 Hz, 1H, H-C(2)), 6.47 (dd, J = 8.68 Hz and J
= 2.32 Hz, 1H, H-C(6)), 4.16 (s, 2H, CH2); 13C NMR (125
MHz, DMSO-d6) δ: 165.8, 162.2, 161.2, 156.2, 149.4, 148.1,
128.8, 124.2, 122.3, 109.0, 108.4, 108.3, 106.7, 102.3, 101.8;
IR (KBr, cm−1): 3484, 3394, 3047 (OH), 3047 (H-Ar), 2921
(CH), 1612 (C=N), 1509 (C=C), 1448, 1321, 1285, 1263,
1229, 1178 (C-O), 1128, 1099, 1038, 1006, 986, 971, 937,
876, 858, 805, 725, 670 (C-S-C); EI-MS (m/z, %): 314 (M+,
100), 285 (4), 179 (14), 178 (21), 167 (36), 165 (16), 153 (8),
148 (7), 147 (16), 146 (15), 135 (9), 134 (5), 121 (8), 119 (4),
108 (5), 107 (9), 106 (4), 80 (5), 79 (4), 75 (5), 69 (7), 65 (5),
63 (15), 62 (7), 52 (9), 51 (6), 39 (8), 38 (4).
4-(5-(4-(Trifluoromethyl)phenylamino)-1,3,4-thiadiazol-2-yl)
benzene-1,3-diol (8)
A mixture of 4-(4-(trifluoromethyl)phenyl)-3-thiosemi-
carbazide (0.004 mol) (Alfa Aesar) and STB (0.003 mol)
in methanol (30 mL) was refluxed (3h). e hot mixture
was filtered, water (50 mL) was added to the filtrate and
it was left at room temperature (24 h). Recrystallization
from MeOH/H2O (2:1) (30 mL) afforded 8.
Yield: 72%; HPLC: log k = 0.292; m.p.: 234–236°C;
anal. calc. for C15H10F3N3O2S (353.32): C, 50.99; H, 2.85;
N, 11.89; found: C, 51.08; H, 2.86; N, 11.81; 1H NMR (500
MHz, DMSO-d6, ppm) δ: 10.89 (s, 1H, HO-C(3)), 10.68 (s,
1H, HO-C(1)), 9.23 (s, 1H, NH), 7.86 (m, 3H, H-CAR), 7.71
(m, 2H, H-CAR), 6.46 (d, J = 2.39 Hz, 1H, H-C(2)), 6.41 (dd,
J = 8.62 Hz and J = 2.39 Hz, 1H, H-C(6)); 13C NMR (125
MHz, DMSO-d6, ppm) δ: 162.9, 160.4, 155.6, 155.4, 144.2,
128.5, 126.3, 126.2, 121.3, 121.0, 116.7, 116.6, 108.4, 108.1,
102.4; IR (KBr, cm−1): 3400, 3255 (OH, NH), 3024 (CAR-H),
1619 (C=N, C=C), 1573 (C=C), 1476, 1440, 1413, 1330
(CF3), 1247, 1216, 1168 (C-O), 1061 (N=C-S-C=N), 1012,
987, 970, 937, 832, 805, 736, 679 (C-S-C); EI-MS (m/z, %):
353 (M+, 100), 352 (9), 334 (4), 219 (4), 218 (34), 198 (7),
191 (4), 153 (5), 150 (4), 145 (5), 136 (5), 94 (6), 66 (4).
4,4’-[5,5’-methylenedi-(1,3,4-thiadiazole-2-yl)]
di(benzene-1,3-diol)
A mixture of propanedihydrazide (0.01 mol) (Alfa Aesar)
and STB (0.015 mol) in methanol (80 mL) was refluxed
(4 h). e removed compound was filtered and washed
with water. Recrystallization from MeOH/H2O (1:1)
(40 mL) afforded 5.
Yield: 84%; HPLC: log k = −0.446; m.p.: 277–279°C;
anal. calc. for C17H12N4O4S2 (400.43): C, 50.99; H, 3.02;
N, 13.99; found: C, 51.18; H, 3.00; N, 14.05; 1H NMR (500
MHz, DMSO-d6, ppm) δ: 11.02 (s, 2H, HO-C(3)), 10.09 (s,
2H, HO-C(1)), 8.02 (d, 2H, J = 8.71 Hz, H-C(5)), 6.49 (d,
2H, J = 2.32 Hz, H-C(2)), 6.45 (dd, 2H, J = 8.70 Hz and J =
2.31 Hz, H-C(6)), 5.03 (s, 2H, CH2); 13C NMR (125 MHz,
DMSO-d6, ppm) δ: 163.9 (2C), 161.2 (2C), 156.2 (2C),
128.8 (2C), 123.1 (2C), 108.3 (2C), 108.2 (2C), 102.3 (2C),
29.3 (CH2); IR (KBr, cm−1): 3257 (OH), 1630 (C=N), 1522,
1470 (C=C), 1414, 1327, 1281, 1246, 1209, 1188 (C-O),
1136, 1108 (CAr-H), 986, 969, 852 (CAr-H), 799, 749, 730,
669 (C-S-C), 627, 601; EI-MS (m/z, %): 400 (M+, 100), 371
(4), 238 (4), 234 (13), 233 (16), 232 (12), 208 (4), 207 (7),
204 (5), 167 (12), 154 (4), 153 (43), 136 (12), 135 (45), 108
(14), 107 (12), 106 (7), 97 (9), 84 (8), 80 (10), 79 (7), 69
(12), 66 (5), 65 (6), 63 (6), 52 (17), 50 (4), 45 (5), 39 (13).
4-{5-[5-(4-Bromophenyl)-1,2-oxazol-3-yl]-1,3,4-thiadiazol-
2-yl}benzene-1,3-diol (10)
A mixture of 5-(4-bromophenyl)isoxazole-3-carboxylic
acid hydrazide (0.01mol) (Alfa Aesar) and STB (0.01 mol)
in methanol (45 mL) was refluxed (3 h). e removed solid
was filtered and washed with water. Recrystallization
from MeOH (40 mL) afforded 10.
Yield: 62%; HPLC: log k = 0.692; m.p.: 345–347°C;
anal. calc. for C17H10BrN3O3S (416.25): C, 49.05; H, 2.42;
N, 10.09; found: C, 49.25; H, 4.43; N, 10.06; 1H NMR (500
MHz, DMSO-d6, ppm): δ 11.37 (s, 1H, HO-C(3)), 10.18
(s, 1H, HO-C(1)), 8.16 (d, 1H, J = 8.62 Hz, H-C(5)), 7.98
(m, 2H, H-C(2’, 6’)), 7.83 (s, 1H, H-isoxazole), 7.80 (m,
2H, H-C(3’, 5’), 6.54 (d, 1H, J = 2.28 Hz, H-C(2)), 6.49 (dd,
J = 8.71 and 2.27 Hz, 1H, H-C(6)); 13C NMR (125 MHz,
DMSO-d6, ppm) δ: 169.7, 163.8, 161.9, 156.9, 156.8, 154.9,
132.4 (2C), 129.1, 127.9 (2C), 125.4, 124.5, 108.6, 107.9,
102.3, 99.2; IR (ATR, cm−1): 3358 (OH), 2916 (H-Ar), 2850
(CH), 1605 (C=N), 1525 (C=C), 1474, 1444, 1421, 1392,
1351, 1272, 1219, 1187 (C-O), 1107, 1039 (N=C-S-C=N),
4,4’-{[5,5’-(ethane-1,2-diyl)]di(1,3,4-thiadiazol-2-yl)}
di(benzene-1,3-diol)
A mixture of succinic dihydrazide butanedihydrazide
(0.01 mol) (Aldrich) and STB (0.015 mol) in methanol
(80 mL) was refluxed (2 h). e removed compound was
filtered and washed with water. Recrystallization from
MeOH/H2O (1:1) (50 mL) afforded 6.
Yield: 89%; HPLC: log k = 0.802; m.p.: 316–319°C;
anal. calc. for C18H14N4O4S2 (414.46): C, 52.16; H, 3.40;
Journal of Enzyme Inhibition and Medicinal Chemistry

Synthesis of novel 1,3,4-thiadiazole based compounds 819
1008, 947, 933, 870, 831, 797, 685 (C-S-C); EI-MS (m/z, %):
416 (M+, 21), 415 (100), 235 (6), 208 (6), 207 (5), 185 (39),
183 (40), 167 (18), 157 (10), 155 (10), 153 (10), 135 (15),
108 (4), 107 (5), 89 (13), 75 (5), 69 (4), 52 (5), 39 (74).
was refluxed (3 h). e removed solid was filtered,
washed with water. Recrystallization from MeOH/H2O
(3:1) (10 mL) afforded 13.
Yield: 60%; HPLC: log k = 0.087; m.p.: 189–190°C; anal.
calc. for C15H11ClN2O2S (318.78): C, 56.52; H, 3.48; N,
8.79; found: C, 56.59; H, 3.46; N, 8.76; 1H NMR (500 MHz,
DMSO-d6, ppm) δ: 11.31 (s, 1H, HO-C(3)), 10.76 (s, 1H,
HO-C(1)), 8.05 (s, 1H, H-C(5)), 7.35 (d, 4H, J = 4.42 Hz,
H-C(Ar’)), 7.27 (m, 1H, H-C(Ar’)), 6.68 (s, 1H, C(2)), 4.45
(s, 2H, CH2); 13C NMR (125 MHz, DMSO-d6, ppm) δ: 168.6,
162.1, 156.1, 154.6, 138.0, 128.9 (2C), 128.8 (2C), 127.8,
127.1, 111.8, 109.5, 103.6, 34.7 (CH2); IR (ATR, cm−1): 3100
(OH), 3028 (CAr-H), 2870, 2851 (CH), 1625 (C=N), 1604,
1587 (C=C), 1480, 1467, 1442, 1426, 1407, 1391, 1384,
1371, 1352, 1296, 1256, 1223, 1191 (C-O), 1162, 1095, 971,
871, 843 (CAr-H), 805, 730, 700, 678 (C-S-C); EI-MS (m/z,
%): 318 (M+, 59), 317 (10), 169 (9), 150 (12), 149 (100), 148
(6), 141 (5), 122 (22), 121 (9), 117 (7), 116 (9), 91 (37), 89
(7), 78 (5), 69 (7), 65 (12), 63 (5), 51 (10), 39 (7).
4-{5-[5-(4-Fluorophenyl)thiophen-2-yl]-1,3,4-thiadiazol-2-yl}
benzene-1,3-diol (11)
A mixture of 5-(4-fluorophenyl)thiophene-2-carboxylic
acid hydrazide (0.01mol) (Alfa Aesar) and STB (0.01 mol)
in methanol (55 mL) was refluxed (3 h). e removed solid
was filtered and washed with water. Recrystallization
from MeOH (40 mL) afforded 11.
Yield: 65%; HPLC: log k = 0.609; m.p.: 312–314°C; anal.
calc. for C18H11FN2O2S2 (370.42): C, 58.36; H, 2.99; N,
7.56; found: C, 58.51; H, 3.01; N, 7.54; 1H NMR (500 MHz,
DMSO-d6, ppm) δ: 11.17 (s, 1H, HO-C(3)), 10.09 (s, 1H,
HO-C(1)), 8.06 (d, 1H, J = 8.71 Hz, H-C(5)), 7.82 (m, 2H,
H-C(2’, 6’), 7.76 (d, 1H, J = 3.89 Hz, H-C(thioph)), 7.60 (d,
1H, J = 3.89 Hz, H-C(thioph)), 7.31 (m, 2H, H-C(3’, 5’)),
6.53 (d, 1H, J = 2.29 Hz, H-C(2)), 6.46 (dd, J = 8.69 and 2.29
Hz, 1H, H-C(6)); 13C NMR (125 MHz, DMSO-d6, ppm) δ:
162.1, 161.4, 161.2, 160.1, 156.4, 144.5, 131.4, 130.7, 129.5,
128.9, 127.8, 127.7, 124.9, 116.3, 116.1, 108.5, 108.2, 102.3;
IR (ATR, cm−1): 3157 (OH), 3097 (CAR-H), 2917 (CH), 2850
(CH), 1636 (C=N), 1601, 1547 (C=C), 1468, 1445, 1411,
1352, 1249, 1176 (C-O), 1098, 967, 912, 874, 823, 792, 681
(C-S-C); EI-MS (m/z, %): 370 (M+, 100), 234 (8), 221 (7),
203 (9), 167 (8), 153 (4), 133 (6), 69 (5).
4-Chloro-6-(5-(4-fluorophenylamino)-1,3,4-thiadiazol-2-yl)
benzene-1,3-diol (14)
A
mixture of 4-fluorophenyl-3-thiosemicarbazide
(0.003 mol) (Alfa Aesar) and SClTB (0.002 mol) in metha-
nol (25 mL) was refluxed (3 h). e removed solid was
filtered and washed with water. Recrystallization from
MeOH (10 mL) afforded 14.
Yield: 64%; HPLC: log k = 0.146; m.p.: 261–262°C;
anal. calc. for C14H9ClFN3O2S (337.76): C, 49.78; H, 2.69;
N, 12.44; found: C, 49.84; H, 2.71; N, 12.38; 1H NMR (500
MHz, DMSO-d6, ppm) δ: 11.03 (s, 1H, HO-C(1)), 10.64
(s, 1H, HO-C(3)), 10.27 (s, 1H, NH), 7.92 (s, 1H, H-C(5)),
7.66 (m, 2H, CAR-H), 7.19 (m, 2H, CAr-H), 6.67 (s, 1H,
H-C(2)); 13C NMR (125 MHz, DMSO-d6, ppm) δ: 163.6,
160.4, 157.9, 155.7, 154.8, 137.4, 128.5, 108.9, 108.8, 115.7,
115.5, 111.6, 109.9, 103.6; IR (ATR, cm−1): 3374 (OH), 3020
(H-Ar), 1617 (C=N), 1567 (C=C), 1444, 1432, 1411, 1240,
1211, 1164 (C-O), 1059 (N=C-S-C=N), 1010, 988, 975, 942,
912, 828, 801, 726, 674 (C-S-C), 612, 587. EI-MS (m/z, %):
337 (M+, 100), 336 (9), 189 (6), 187 (13), 184 (5), 170 (8),
169 (18), 168 (65), 155 (8), 154 (8), 141 (20), 136 (19), 130
(8), 128 (20), 121 (5), 114 (9), 110 (16), 100 (15), 95 (20), 83
(20), 75 (14), 69 (15), 63 (5), 57 (6), 51 (8), 40 (16), 39 (5).
4-{5-[5-(4-Bromophenyl)thiophen-2-yl]-1,3,4-thiadiazol-2-yl}
benzene-1,3-diol (12)
A mixture of 5-(4-bromophenyl)thiophene-2-carboxylic
acid hydrazide (0.01mol) (Aldrich) and STB (0.01 mol) in
methanol (40 mL) was refluxed (3 h). e removed solid
was filtered and washed with water. Recrystallization
from MeOH (40 mL) afforded 12.
Yield: 62%; HPLC: log k = 0.899; m.p.: 253–254°C; anal.
calc. for C18H11BrN2O2S2 (431.33): C, 50.12; H, 2.57; N,
6.49; found: C, 50.30; H, 2.59; N, 6.44; 1H NMR (500 MHz,
DMSO-d6, ppm) δ: 11.21 (s, 1H, HO-C(3)), 10.12 (s, 1H,
HO-C(1)), 8.06 (d, 1H, J = 8.70 Hz, H-C(5)), 7.78 (d, 1H, J
= 3.91 Hz, H-C(thioph)), 7.73 (m, 2H, H-C(2’, 6’), 7.67 (m,
3H, H-C(3’, 5’, thioph)), 6.55 (d, 1H, J = 2.26 Hz, H-C(2)),
6.46 (dd, J = 8.70 and 2.27 Hz, 1H, H-C(6)); 13C NMR (125
MHz, DMSO-d6, ppm) δ: 162.1, 161.4, 159.0, 156.3, 144.4,
132.2 (2C), 132.1, 131.8, 130.8, 128.9, 127.6 (2C), 125.6,
121.6, 108.4, 108.2, 102.3; IR (ATR, cm−1): 3352 (OH), 2946
(CAR-H), 2835 (CH), 1660, 1630 (C=N), 1603, 1529 (C=C),
1462, 1450, 1415, 1226, 1035, 685 (C-S-C); EI-MS (m/z,
%): 431 (M+, 20), 430 (100), 297 (12), 295 (11), 283 (13),
281 (10), 266 (5), 265 (21), 264 (5), 263 (17), 216 (6), 199
(4), 172 (5), 171 (5), 167 (30), 158 (7), 153 (11), 140 (10),
135 (4), 107 (4), 69 (10), 40 (10).
4-Chloro-6-(5-(3-chlorophenylamino)-1,3,4-thiadiazol-2-yl)
benzene-1,3-diol (15)
A
mixture of 4-(3-chlorophenyl-3-thiosemicarbazide
(0.01 mol) (Alfa Aesar) and SClTB (0.01 mol) in methanol
(50 mL) was refluxed (3 h). e hot mixture was filtered
and water (50 mL) was added to the filtrate. e formed
solid was filtered off and crystallized from methanol (4:1)
(50 mL). e formed solid was boiled in chloroform (30
mL) and filtered. Recrystallization from MeOH/H2O (1:1)
(50 mL) afforded 15.
4-(5-Benzyl-1,3,4-thiadiazol-2-yl)-6-chlorobenzene-1,3-diol
Yield: 60%; HPLC: log k = 0.392; m.p.: 300–302°C; anal.
(13)
calc. for C14H9C12O2S (354.21): C,47.47; H, 2.56; N, 11.86;
found: C, 47.58; H, 2.54; N, 11.89; H NMR (500 MHz,
1
A
mixture of phenylacetic hydrazide (0.016 mol)
(Aldrich) and SClTB (0.012 mol) in methanol (80 mL)
DMSO-d6, ppm) δ: 11.10 (s, 1H, HO-C(1)), 10.68 (s, 1H,
© 2013 Informa UK, Ltd.

820 A. Skrzypek et al.
945, 883, 806, 689 (C-S-C); EI-MS (m/z, %): 437 (M+, 25),
219 (35), 178 (6), 177 (18), 164 (18), 163 (7), 150 (9), 148
(17), 147 (12), 146 (72), 145 (100), 132 (9), 131 (9), 129
(11), 121 (9), 120 (11), 104 (7), 102 (13), 91 (5), 77 (7), 51
(6), 45 (13), 44 (23), 42 (11), 39 (6), 36 (27), 34 (11).
HO-C(3)), 10.49 (s, 1H, NH), 7.98 (m, 1H, H-C(5)), 7.95 (t,
1H, J = 1.93 Hz, H-C(2’)), 7.47 (m, 1H, H-C(6’)), 7.37 (t, 1H,
J = 8.10 Hz, H-C(5’)), 7.04 (m, 1H, H-C(4’)), 6.70 (s, 1H,
H-C(2)); 13C NMR (125 MHz, DMSO-d6, ppm) δ: 163.9,
155.4, 153.9, 152.9, 142.1, 133.5, 130.6, 127.3, 121.0, 116.6,
115.7, 111.7, 109.8, 103.6; IR (ATR, cm−1): 3369 (OH), 3018
(Ar-H), 1619 (C=N), 1569 (C=C), 1440, 1438, 1421, 1235,
1220, 1168 (C-O), 1057 (N=C-S-C=N), 1009, 997, 985, 937,
922, 838, 810, 731, 664 (C-S-C), 620, 614, 594, 578; EI-MS
(m/z, %): 354 (M+, 25), 353 (100), 321 (5), 319 (14), 189 (5),
187 (14), 184 (69), 171 (7), 170 (10), 169 (11), 159 (12), 157
(10), 155 (5), 152 (7), 149 (23), 130 (5), 128 (14), 127 (5),
122 (7), 113 (5), 111 (12), 100 (9), 90 (4), 69 (7).
Compounds:
benzene-1,3-diol (2), 4,4’-{[5,5’-(benzene-1,4-diyl)]
bis(1,3,4-thiadiazol-2-yl)}di(benzene-1,3-diol) (7)
and 4-(2,4-dichlorophenoxymethyl)benzene-1,3-diol
(9) were prepared according to the procedure already
described19,20
4-(5-heptyl-1,3,4-thiadiazol-2-yl)
.
Measurement of ChEs activities
Acetylcholinesterase (AChE, E.C. 3.1.1.7, from the
electric eel), butylcholinesterase (BuChE, E.C. 3.1.1.8,
from equine serum), acetylthiocholine iodide (ATCh),
butylthiocholine iodide (BTCh), 5,5’-dithiobis-(2-ni-
trobenzoic acid) (DTNB), neostigmine bromide and
donepezil hydrochloride monohydrate were purchased
from Sigma-Aldrich (Steinheim, Germany). e inhibi-
tory activities against AChE and BuChE of the prepared
compounds were performed by means of the method
previously developed by Ellman et al., using donepezil
and neostigmine as the reference compounds21. is is
based on the reaction of released thiocholine to give a
coloured product with a chromogenic reagent. Seven dif-
ferent concentrations of the synthesized compounds in
the range 10−3–10−9 M were measured at 412 nm. All the
assays were under 0.1 M KH2PO4/K2HPO4 buffer (pH = 8)
using a Varian Cary 50 Spectrophotometer. Enzyme solu-
tions were prepared to give 2 units/mL in 2 mL aliquots.
e assay medium contained phosphate buffer, pH
8.0 (1 mL), 50 μL of 0.01 M DTNB, 10 μL of enzyme,
50 μL of acetylthiocholine iodide (ATCh) and 50 μL of the
test compound solution. ATCh was added to the assay
medium after 10 min of incubation time. e activity was
determined by measuring the increase in absorbance at
412 nm for 1 min interval at 37 0.2°C. For determining
the blank value, additionally 50 μL buffer replaced the
enzyme solution. In vitro the BuChE assay uses the simi-
lar method to that described above.
4-Chloro-6-(5-(3,4-dihydroxyphenyl)-1,3,4-thiadiazol-2-yl)
benzene-1,3-diol (16)
A mixture of 3,4-dihydroxybenzhydrazide (0.015 mol)
(Alfa Aesar) and SClTB (0.015 mol) in methanol (75 mL)
was refluxed (3 h). e hot mixture was filtered, water (40
mL) was added to the filtrate and it was left at room tem-
perature (24 h). Recrystallization from MeOH (40 mL)
afforded 16.
Yield: 62%; HPLC: log k = 0.11; m.p.: 280–282°C; anal.
calc. for C14H9ClN2O4S (336.75): C, 49.93; H, 2.69; N, 8.32;
found: C, 50.03; H, 2.68; N, 8.36; 1H NMR (500 MHz,
DMSO-d6, ppm) δ: 11.30 (s, 1H, HO-C(1)), 10.83 (s, 1H,
HO-C(3)), 9.58 (s, 1H, HO-C(3’)), 9.41 (s, 1H, HO-C(4’)),
8.10 (s, 1H, C(5)), 7.43 (d, J = 2.18 Hz, 1H, H-C(2’)), 7.26
(dd, J = 8.18 Hz, J = 2.16 Hz, 1H, H-C(6’)), 6.87 (d, J =
8.20, 1H, H-C(5’)), 6.77 (s, 1H, H-C(2)); 13C NMR (125
MHz, DMSO-d6, ppm) δ: 166.6, 160.2, 156.4, 154.8, 148.5,
145.8, 127.7, 121.4, 119.5, 116.3, 114.1, 111.8, 109.5, 104.0;
IR (ATR, cm−1): 3350 (OH), 3093 (CH), 2851 (CH), 1626
(C=N), 1605 (C=C), 1502 (C=C), 1461, 1450, 1400, 1385,
1319, 1297, 1280, 1253, 1231, 1187 (C-O), 1157, 1110, 978,
903, 875, 852, 827, 791, 721, 684 (C-S-C); EI-MS (m/z, %):
336 (M+, 100), 303 (8), 302 (8), 201 (19), 187 (6), 168 (6),
167 (18), 153 (12), 136 (5), 135 (9), 121 (4), 63 (4).
3-{5-[4-(Dimethylamino)phenyl]-1,3,4-thiadiazol-2-yl}
biphenyl-2,3’,4,5’,6-pentol (17)
Each concentration was analyzed in triplicate. e
50% inhibitory concentration (IC50) was calculated from
a dose–response curve obtained by plotting the percent-
age of inhibition versus the log concentration with the
use of GraFit 4.09 software22. e results were expressed
as the mean standard deviation (SD).
A mixture of 4-dimethylaminobenzhydrazide (0.014
mol) (Aldrich) and 2,3’,4,5’,6-pentahydroxybiphenyl-
3-carbodithioic acid (0.014 mol) in methanol (70 mL)
was refluxed (2.5 h). e removed compound was filtered
and washed with water. Recrystallization from MeOH (40
mL) afforded 17.
Yield: 65%; HPLC: log k = -0.26; m.p.: 236–238°C;
anal. calc. for C22H19N3O5S (437.47): C, 60.40; H, 4.38; N,
9.61; found: C, 60.54; H, 4.36; N, 9.57;1H NMR (500 MHz,
DMSO-d6, δ): 12.66 (s, 1H, HO), 11.33 (s, 1H, HO), 9.80
(s, 1H, HO), 8.98 (s, 2H, HO), 7.82 (d, J = 8.90 Hz, 2H,
H-C(Ar)), 6.82 (d, J = 9.00 Hz, 2H, H-C(Ar)), 6.26 (s, 1H,
H-C(Ar)), 6.16 (d, J = 2.18 Hz, 2H, H-C(Ar)), 6.12 (t, J =
2.15 Hz, 1H, H-C(Ar)), 3.01 (s, 6H, CH3); IR (ATR, cm−1):
3200 (OH), 2930 (Ar-H), 1640, 1630 (C=N), 1605 (C=C),
1483, 1468, 1461, 1443, 1426, 1413, 1390, 1371, 1334, 1249,
1231, 1200, 1156 (C-O), 1070, 1043 (N=C-S-C=N), 1006,
results and discussion
5-Substituted (1,3,4-thiadiazol-2-yl)benzene-1,3-diols
were obtained by the reaction of the commercially
available hydrazides or thiosemicarbazides with
sulfinylbis[(2,4-dihydroxyphenyl)methanethione]
(STB) or with its analogue sulfinylbis[(5-chloro-2,4-
dihydroxyphenyl)methanethione] (SClTB) in methanol
under reflux (1.5–4 h) in moderate to good yields (60–
89%) as outlined in Figure 1. e key intermediates were
Journal of Enzyme Inhibition and Medicinal Chemistry

Synthesis of novel 1,3,4-thiadiazole based compounds 821
Figure 1. Synthesis scheme of (1,3,4-thiadiazol-2-yl)benzene-1,3-diol derivatives.
obtained from 2,4-dihydroxybenzenecarbodithioic acids
and SOCl2 in diethyl ether23. e substituents panel of
compounds is shown in Figure 1. Purity of compounds
was monitored by the reversed-phase (RP-18) HPLC
chromatography (methanol–water).
for H-C(isoxazole) at 7.88 ppm in the case of compound
10. Protons of 2,5-disubstituted thiophene appeared as
two doublets at ca. 7.77 and 7.63 ppm with J = 3.9 Hz(11,12)
.
In the 13C NMR spectrum characteristic signals of substi-
tuted 1,3,4-thiadiazole ring carbon atoms appear in the
range 169-162 ppm.
All new compounds showed analytical and spec-
troscopic data in good accordance with the proposed
structure. In the 1H NMR spectra the OH protons are usu-
ally detected as broad bands in the range ca. 11 and 10
ppm. e resonance signals of aromatic protons of the
β-resorcinol moiety appear as two characteristic dublets
at ca. 8 ppm (J = 8.7 Hz) and 6.5 ppm (J = 2.3 Hz) cor-
responding to H-C(5) and H-C(2), respectively and as
doublet of doublets at ca. 6.45 ppm (J = 8.7 and 2.3 Hz) of
H-C(6). In the case of additional substitution in position 5
by chlorine atom protons of that ring appear as two char-
acteristic singlets at ca. 6.7 and 8 ppm corresponding to
H-C(2) and H-C(5), respectively13–16. Singlet is registered
In the IR spectrum there are strong bands in the region
about 3400–3100 corresponding to ν (O-H) and addition-
ally ν (N-H) in the case of compounds 8, 14, 15. Band of ν
(C=N) appears in the region 1635–1610 cm−1.
e mass spectra (EI) of the compounds show molec-
ular ion peaks, however, with various intensities. e
major fragmentation pathway of 4-(1,3,4-thiadiazol-2-yl)
benzene-1,3-diols involves the cleavage of the C(2)-N(3)
and S-C(5) bonds 1,3,4-thiadiazole ring with the for-
mation of (OH)2C6H3CS+ (m/z 153) ion. e cleavage of
S-C(2) and N-N bonds which directs to (OH)2C6H3CN+
(m/z 135) fragmentation is also observed. Characteristic
© 2013 Informa UK, Ltd.

822 A. Skrzypek et al.
relatively strong band corresponding to tropylic cation
C7H7+ (m/z 91) is observed for benzyl derivative13. It is the
effect of α and β atoms disconnection in relation to the
phenyl ring.
with two 1,3,4-thiadiazole rings(5,6,7) compound 7 with
benzene as a link shows the highest affinity for AChE.
Derivative 9 with the 2,4-dichlorophenoxymethyl sub-
stituent is the most active against AChE of all compounds
of 1,3,4-thiadiazole series. e presence of the additional
heterocyclic ring (oxazolyl, thiophenyl) does not improve
activities of compounds. Placement of chlorine atom in the
benzenodiole moiety does not change substantially affinity
of compounds for both enzymes(13–16). e analogs possess-
ing naphthalenyl(3) or biphenylyl(12) substituent are inactive.
e linear Lineweaver-Burk equation which is
a double reciprocal form of the Michaelis-Menten
equation was used to evaluate the type of inhibition.
e graphical analysis of steady-state inhibition data for
representative compounds 2 and 7 is shown in Figure 2A
and 2B, respectively. In Figure 2A the graph shows that
the mechanism of AChE inhibition of compound 2 is the
mixed-type. In Figure 2B the lines crossing the x axis in
the same point indicate unchanged KM and decreased
Vmax with the increasing inhibitor concentrations. is
is a typical trend of non-competitive inhibition which is
similar to that of donepezil4.
All compounds have been evaluated as AChE
and BuChE inhibitors. eir inhibitory potency was
expressed as the half of maximal inhibitory concentra-
tion, IC50. It was determined by the modified Ellman’s
method21. Donepezil and neostigmine were used as the
reference drugs. Table 1 shows that most of the studied
compounds were able to inhibit in vitro both enzymes
– AChE and BuChE but in a very broad range of concen-
trations. e IC50 values for AChE are ranged from > 500
to 0.053 μM and for BuChE from > 500 to 0.105 μM. At
the same it proves that all synthesized particles are sig-
nificantly more active towards AChE than BuChE, with
the exception of compounds 5 and 14. Compound 9 of
the highest activity against AChE shows inhibition effect
similar to that of neostigmine. Simultaneously it is 947-
fold more active against AChE compared to BuChE. at
compound can serve as a selective inhibition agent for
AChE over BuChE.
To find the influence of the type of 1,3,4-thiadiazole
ring substitution on potency of compounds the structure-
activity analyses SAR have been performed. To obtain bet-
ter results some previously described compounds were
included in the biological screening. SAR shows that alkyl
derivatives(compounds1and2)aregoodinhibitorsofboth
enzymes. Compound 2 with the heptyl substituent is one of
the most active derivatives. From the group of compounds
Table 1. In vitro inhibition (IC50, μM) and selectivity of the studied
compounds on AChE and BuChE.
IC50 for
Selectivity for
AChE***
No.
IC50 for AChE* [μM] BuChE** [μM]
1.
0.109 0.02
0.060 0.003
>500
18.2 0.1
0.24 0.02
>500
166.9
4.0
2.
3.
—
4.
0.22 0.01
0.26 0.02
3.11 0.06
0.092 0.004
3.24 0.01
0.053 0.003
45.2 0.52
37.2 0.31
0.125 0.01
18.0 0.14
0.143 0.02
2.68 0.02
1.27 0.01
>500
25.1 0.02
0.184 0.01
14.3 0.20
15.21 0.42
1.32 0.01
50.20 0.20
193.4 1.13
> 500
114.1
0.71
4.59
165.3
0.41
947.2
4.3
5.
6.
7.
8.
9.
10.
11.
>13.44
148.8
2.45
0.73
186.5
27.72
—
12.
18.6 0.23
44.2 0.72
0.105 0.01
>500
13.
14.
15.
16.
35.20 0.24
>500
17.
neostigmine
donepezil
0.05 0.007
0.02 0.008
0.07 0.009
7.52 0.20
1.4
376
*IC50: 50% inhibitory concentration (means SD of three
experiments) of AChE.
**IC50: 50% inhibitory concentration (means SD of three
experiments) of BuChE.
***Selectivity for AChE = IC50 (BuChE)/IC50 (AChE).
Figure 2. Steady state inhibition of 2 (A) and 7 (B) against AChE.
Plot A shows the mixed-type inhibition and plot B the non-
competitive inhibition.
Journal of Enzyme Inhibition and Medicinal Chemistry

Synthesis of novel 1,3,4-thiadiazole based compounds 823
10. Ciapetti P, Giethlen B. Molecular Variations Based on Isosteric
Replacements. In: Wermuth CM. e Practice of Medicinal
Chemistry, USA: Academic Press Burlington, 2008:290–342.
11. Sengupta AK, Garg M. New 5-arylamino-2 N-(2’-
mercaptoacetylamino-4’-arylthiazolo)-thiadiazoles(III) - as AChE
inhibitors. J Indian Chem Soc 1980;57:1241–1242.
12. Misra HK. Synthesis of some new substituted 1,3,4-oxadiazoles
as potential insecticidal, antibacterial and anti-acetylcholine
esterase agents. Arch Pharm (Weinheim) 1983;316:487–493.
13. Martinez A, Alonso D, Castro A, Arán VJ, Cardelús I, Baños
JE et al. Synthesis and potential muscarinic receptor binding
and antioxidant properties of 3-(thiadiazolyl)pyridine 1-oxide
compounds. Arch Pharm (Weinheim) 1999;332:191–194.
conclusion
In conclusion, we synthesized new (1,3,4-thiadiazol-2-yl)
benzene-1,3-diol derivatives and evaluated their anticho-
linesterase activities. e results indicate that compound 9
is the most potent inhibitor of AChE being 947-fold more
active against AChE than BuChE. at compound can serve
as a selective inhibition agent. Whereas the heptyl deriva-
tive shows comparable high affinity for both enzymes in the
low nM range. e kinetic studies suggest that in a series of
the investigated compounds, inhibition mechanisms can
be various. e obtained results could be useful for design-
ing of new AChE and BuChE inhibitors, resulting in greater
selectivity as well as the increasing inhibitory potency.
14. Sarkandi DN, Firoozpour L, Asadipour A, Sheibani V, Asli MAM,
Davood A, Shafiee A, Foroumadi A. Synthesis of 1-benzyl-4-
2-(5-phenyl-1,3,4-thiadiazole-2-yl)aminoethyl piperidine as
potential Alzheimer’s disease modifying agent. Asian J Chem
2011;23:2503–2505.
Declaration of interest
15. Alonso M, Martinez A. GSK-3 inhibitors: discoveries and
developments. Curr Med Chem 2004;11:755–763.
e authors declared no conflict of interest.
16. Gupta AK, Misra HK. Synthesis and evaluation of substituted
quinazolone derivatives for antibacterial, antifungal, and
antiacetylcholinesterase activities. J Pharm Sci 1980;69:1313–1317.
17. Altintop MD, Kaplancikli ZA, Ozdemir A, Turan-Zitouni G, Temel
HE, Akalin G. Synthesis and anticholinesterase activity and
cytotoxicity of novel amide derivatives. Arch Pharm (Weinheim)
2012;345:112–116.
references
1. Carreiras MC, Marco JL. Recent approaches to novel anti-
Alzheimer therapy. Curr Pharm Des 2004;10:3167–3175.
2. O’Neill MF. Difficult times for Alzheimer’s treatments. Drug Discov
Today 2005;10:1333–1335.
3. Davis KL, Powchik P. Tacrine. Lancet 1995;345:625–630.
4. Tsuno N. Donepezil in the treatment of patients with Alzheimer’s
disease. Expert Rev Neurother 2009;9:591–598.
5. Kavanagh S, Gaudig M, Van Baelen B, Adami M, Delgado
A, Guzman C et al. Galantamine and behavior in Alzheimer
disease: analysis of four trials. Acta Neurol Scand 2011;124:
302–308.
18. Skrzypek A. Zastosowanie spektrofotometrycznej metody Ellmana
w ocenie właściwości inhibicyjnych nowych 2,5 – dipodstawionych
1,3,4-tiadiazoli w stosunku do acetylocholinoesterazy. III Sympozjum
Naukowego: Nauka i Przemysł – metody spektroskopowe w praktyce,
nowe wyzwania i możliwości. 2010, p 229–234.
19. Matysiak J, Skrzypek A, Niewiadomy A. Synthesis and antifungal
activity of novel 5-substituted 4-(1,3,4-thiadiazol-2-yl) benzene-
1,3-diols. Heteroat Chem 2010;7:533–540.
20. Matysiak J, Nasulewicz A, Pelczynska M, Switalska M, Jaroszewicz
I, Opolski A. Synthesis and antiproliferative activity of some
6. Farlow MR, Grossberg GT, Meng X, Olin J, Somogyi M. Rivastigmine
transdermal patch and capsule in Alzheimer’s disease: influence
of disease stage on response to therapy. Int J Geriatr Psychiatry
2011;26:1236–1243.
5-substituted 2-(2,4-dihydroxyphenyl)-1,3,4-thiadiazoles. Eur
Med Chem 2006;41:475–482.
J
21. Ellman GL, Courtney KD, Andres V Jr, Feather-Stone RM. A new
and rapid colorimetric determination of acetylcholinesterase
activity. Biochem Pharmacol 1961;7:88–95.
7. Grossberg GT. e ABC of Alzheimer’s disease: behavioral
symptoms and their treatment. Int Psychogeriatr 2002;14 Suppl
1:27–49.
22. Leatherbarrow RJ, Stains, UK: Erithacus Software Ltd; 1999.
23. Matysiak J, Niewiadomy A. Application of sulfinyl bis(2,4-
dihydroxythiobenzoyl) in the synthesis of N-substituted 2-amino-
5-(2,4-dihydroxyphenyl)-1,3,4-thiadiazoles. Synth Commun
2006;36:1621–1630.
8. Michaelis ML. Drugs targeting Alzheimer’s disease: some things
old and some things new.
897–904.
J Pharmacol Exp er 2003;304:
9. Darvesh S, Hopkins DA, Geula C. Neurobiology of
butyrylcholinesterase. Nat Rev Neurosci 2003;4:131–138.
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