Synthesis and evaluation of anti-acetylcholinesterase activity of some benzothiazole based new piperazine-dithiocarbamate derivatives.

Original Article

Synthesis and Evaluation of Anti-acetylcholinesterase Activity of Some Benzothiazole Based New Piperazinedithiocarbamate Derivatives

Affiliations

Key words

▶ benzothiazole ● ▶ piperazine ● ▶ dithiocarbamate ● ▶ cholinesterase inhibitors ●

U. A. Mohsen1, Z. A. Kaplancikli2, Y. Özkay2, L. Yurttaş2 1 2

Faculty of Pharmacy, Department of Pharmaceutical Chemistry, Al-Azhar University, Gaza, Palestine Faculty of Pharmacy, Department of Pharmaceutical Chemistry, Anadolu University, Eskişehir, Turkey

Abstract

▼

In this present study some benzothiazole derivatives bearing piperazine and thiocarbamate moieties were synthesized and their potential anticholinesterase properties were investigated. A set of 30 new compounds of 2-[(6-substituted benzothiazol-2-yl)amino]-2-oxoethyl 4-substituted piperazine-1-carbodithioate derivatives were synthesized by reacting 2-chloro-N-(6-substituted benzothiazole-2-yl)acetamide derivatives derivatives and sodium salts of appropriate N,N-disubstituted dithiocarbamic acids in ace-

Introduction

▼

received 24.02.2014 accepted 12.04.2014 Bibliography DOI http://dx.doi.org/ 10.1055/s-0034-1375613 Published online: 2014 Drug Res © Georg Thieme Verlag KG Stuttgart · New York ISSN 2194-9379 Correspondence L. Yurttaş Department of Pharmaceutical Chemistry Faculty of Pharmacy Anadolu University Yunusemre Campus 26470 Tepebaşı/Eskişehir Turkey Tel.: + 90/222/3350 580/3783 Fax: + 90/222/3350 750 [email protected]

In drug design; for a more efficient and beneficial therapy for the patients, it has become more important to discover novel and improved drugs, in means of selectivity and potency, through enz yme inhibition. Cholinesterase inhibitors (ChEIs) have appealed a great deal of interest among researchers owing to their importance in the treatment of myasthenia gravis, glaucoma and Alzheimer’s disease [1, 2]. Alzheimer’s disease is the most common age-related neurodegenerative disorder characterized by progressive deficits in memory and cognition, together with impairment in the ability to perform basic activities of daily living. Alzheimer’s disease has become an urgent public health problem due to the prevalence of Alzheimer’s disease worldwide [3–6]. Over the last 20 years, scientists have carried out considerable research for deciphering the underlying mechanisms of this devastating disease. Substantial evidence demonstrates that Alzheimer’s disease is associated with the deficiency in cholinergic neurotransmission and therefore current research interest in the design and synthesis of new cholinomimetics is focused on discovering agents that might be effective in the

tone. The structures of the obtained compounds were elucidated using FT-IR, 1H-NMR and MS spectral data and elemental analyses result. Each derivative was evaluated for its ability to inhibit acetylcholinesterase (AChE) using a modificated Ellman’s spectrophotometric method. Some of the compounds can be identified as anticholinesterase agents due to their inhibitory effect when compared with Donepezil. Compounds with dimethylamino ethyl or dimethylamino propyl substituents were defined as the anticholinesterase active compounds.

treatment of Alzheimer’s disease [7–10]. As known, in humans 2 cholinesterases are present: acetylcholinesterase (AChE), which selectively hydrolyses acetylcholine, and butyrylcholinesterase (BuChE), which is a non-specific cholinesterase. The main difference between 2 types of cholinesterase is the respective preferences for substrates: the former hydrolyses acetylcholine more quickly; the latter hydrolyses butyrylcholine more quickly. The main function of AChE is the termination of cholinergic neurotransmission, but the function of BuChE is not so clear [11]. Carbamates are the most widely studied class of anticholinesterase agents and considerable research on them in relation to Alzheimer’s disease has been accomplished. Rivastigmine possesses a carbamate moiety that resembles the ester linkage of acetylcholine. It is one of the most widely used anticholinesterase agents for the treatment of Alzheimer’s disease [12]. Dithiocarbamates are important pharmacophores owing to their lipophilicity, which is crucial for the delivery of central nervous system drugs to their site of action through the blood brain barrier. Medicinal chemists have studied dithiocarbamates extensively due to the fact that new effective compounds can be obtained by the bioisosteric replacement between carbamate and Mohsen UA et al. New Piperazine-Dithiocarbamates … Drug Res

Downloaded by: IP-Proxy ETH Zuerich, ETH-Bibliothek. Copyrighted material.

Authors

Original Article

Experımental

▼

All chemicals were purchased from Sigma-Aldrich Chemical Co (Sigma-Aldrich Corp., St. Louis, MO, USA) and Merck Chemicals (Merck KGaA, Darmstadt, Germany). All melting points (m.p.) were determined by Electrothermal 9100 digital melting point apparatus (Electrothermal, Essex, UK) and are uncorrected. All the reactions were monitored by thin-layer chromatography (TLC) using Silica Gel 60 F254 TLC plates (Merck KGaA, Darmstadt, Germany). Spectroscopic data were recorded with the following instruments: IR, Shimadzu 8400 S spectrophotometer (Shimadzu, Tokyo, Japan); NMR, Bruker DPX 500 NMR spectrometer (Bruker Bioscience, Billerica, MA, USA), in DMSO-d6, using TMS as internal standard; M + 1 peaks were determined by AB Sciex-3200 Q-TRAP LC/MS/MS system (AB Applied Biosystems Co., MA, USA). Elemental analyses were performed on a Leco TruSpec Micro CHN/CHNS elemental analyzer (Leco, Michigan, USA).

Synthesis of the compounds Synthesis of 2-chloro-N-(6-substituted benzothiazole-2-yl) acetamide derivatives (1a–f): Chloroacethyl chloride (0.2 mol, 16 mL) was added dropwise over 15 min to a magnetically stirring solution of 2-aminobenzothiazole derivative (0.2 mol) and triethylamine (0.2 mol, 28 mL) in dry THF (200 mL). After completion of the reaction, the solvent was evaporated under reduced pressure and then water was added to wash the resulting solid and the mixture was filtered, dried and recrystallized from ethanol to give compounds 1a–f [26]. Synthesis of sodium salts of 4-substituted piperazine-1-dithiocarbamic acids (2a–e): Sodium hydroxide (10 mmol) was dissolved in ethanol (80 mL) with constant stirring. After addition of the secondary amine (10 mmol) to this solution, carbon disulphide (100 mmol) was added dropwise in ice bath. The reaction mixture was stirred for 1 h in room temprature. The solvent was evaporated under reduced pressure and then the residue was washed with diethyl eter to obtain pure product.

d6, ppm): δ 2.63 (brs, 4H, piperazine CH2), 3.91 (brs, 2H, piperazine CH2), 4.10 (brs, 2H, piperazine CH2), 4.59 (s, 2H, COCH2), 6.71 (t, 1H, J: 4.68 Hz, Ar-H), 7.32 (t, 1H, J: 7.59 Hz, Ar-H), 7.45 (t, 1H, J: 7.45 Hz, Ar-H), 7.78 (d, 1H, J: 8.11 Hz, Ar-H), 7.99 (d, 1H, J: 7.78 Hz, Ar-H), 8.43 (d, 2H, J: 4.72 Hz, Ar-H), 12.69 (s, 1H, N-H). For C18H18N6OS3 calculated: 50.21 % C, 4.21 % H, 19.52 % N; found: 50.34 % C, 4.31 % H, 19.63 % N. MS [M + 1] + : m/z 431.

2-[(Benzothiazol-2-yl)amino]-2-oxoethyl 4-(4-nitrophenyl) piperazine-1-carbodithioate (2): Yield 70–72 %, m.p. 256– 257 °C. IR (KBr, cm − 1): νmax 3 335 (amide N-H), 1 672 (C = O), 1 552–1 312 (C = C), 1 245–926 (C-N). 1H-NMR (500 MHz, DMSOd6, ppm): δ 2.62 (brs, 4H, piperazine CH2), 3.91 (brs, 2H, piperazine CH2), 4.11 (brs, 2H, piperazine CH2), 4.48 (s, 2H, COCH2), 6.96 (d, 2H, J: 9.41 Hz, Ar-H), 7.32 (t, 1H, J: 7.43 Hz, Ar-H), 7.45 (t, 1H, J: 7.30 Hz, Ar-H), 7.78 (d, 1H, J: 8.18 Hz, Ar-H), 7.99 (d, 1H, J: 7.78 Hz, Ar-H), 8.12 (d, 2H, J: 9.35 Hz, Ar-H), 12.69 (s, 1H, N-H). For C20H19N5O3S3 calculated: 50.72 % C, 4.04 % H, 14.79 % N; found: 50.82 % C, 4.11 % H, 14.61 % N. MS [M + 1] + : m/z 474. 2-[(Benzothiazol-2-yl)amino]-2-oxoethyl 4-[2-(N,N-dimethylamino)ethyl]piperazine-1-carbodithioate (3): Yield 71–73 %, m.p. 84–85 °C. IR (KBr, cm − 1): νmax 3 338 (amide N-H), 1 669 (C = O), 1 561–1 332 (C = C), 1 239–927 (C-N). 1H-NMR (500 MHz, DMSO-d6, ppm): δ 2.18 (s, 6H, N(CH3)2), 2.39–2.45 (m, 4H, (CH2)2), 2.63 (brs, 4H, piperazine CH2), 3.90 (brs, 2H, piperazine CH2), 4.11 (brs, 2H, piperazine CH2), 4.48 (s, 2H, COCH2), 7.31 (t, 1H, J: 7.99 Hz, Ar-H), 7.45 (t, 1H, J: 7.14 Hz, Ar-H), 7.75 (d, 1H, J: 7.82 Hz, Ar-H), 7.98 (d, 1H, J: 7.97 Hz, Ar-H), 12.69 (s, 1H, N-H). For C18H25N5OS3 calculated: 51.03 % C, 5.95 % H, 16.53 % N; found: 51.14 % C, 5.87 % H, 16.42 % N. MS [M + 1] + : m/z 424. 2-[(Benzothiazol-2-yl)amino]-2-oxoethyl 4-[3-(N,N-dimethylamino)propyl]piperazine-1-carbodithioate (4): Yield 73–76 %, m.p. 130–132 °C (decomp.). IR (KBr, cm − 1): νmax 3 358 (amide N-H), 1 672 (C = O), 1 537–1 315 (C = C), 1 248–926 (C-N). 1H-NMR (500 MHz, DMSO-d6, ppm): δ 1.35 (m, 2H, CH2), 2.20 (s, 6H, N(CH3)2), 2.39–2.45 (m, 4H, (CH2)2), 2.62 (brs, 4H, piperazine CH2), 3.91 (brs, 2H, piperazine CH2), 4.10 (brs, 2H, piperazine CH2), 4.49 (s, 2H, COCH2), 7.32 (t, 1H, J: 7.25 Hz, Ar-H), 7.45 (t, 1H, J: 7.25 Hz, Ar-H), 7.76 (d, 1H, J: 7.64 Hz, Ar-H), 7.97 (d, 1H, J: 8.79 Hz, Ar-H), 12.69 (s, 1H, N-H). For C19H27N5OS3 calculated: 52.14 % C, 6.22 % H, 16.00 % N; found: 52.24 % C, 6.37 % H, 16.21 % N. MS [M + 1] + : m/z 438.

General synthesis procedure for 2-[(6-substituted benzothiazol-2-yl)amino]-2-oxoethyl 4-substituted piperazine-1-carbodithioate derivatives (1–30): Compounds 1a–f (10 mmol) were stirred with appropriate sodium salts of dithiocarbamic acids (2a–e) (10 mmol) in acetone for 7 h. After TLC screening, the mixture was filtered and the obtained crude product was washed with water, then crystallized from ethanol.

2-[(Benzothiazol-2-yl)amino]-2-oxoethyl 4-cyclohexylpiperazine-1-carbodithioate (5): Yield 75–77 %, m.p. 203–206 °C. IR (KBr, cm − 1): νmax 3 341 (amide N-H), 1 670 (C = O), 1 521–1 305 (C = C), 1 251–927 (C-N). 1H-NMR (500 MHz, DMSO-d6, ppm): δ 1.21–1.28 (m, 5H, cyclohexyl C-H), 1.63–1.89 (m, 5H, cyclohexyl C-H), 2.23–2.29 (m, 1H, cyclohexyl C-H), 2.63 (brs, 4H, piperazine CH2), 3.93 (brs, 2H, piperazine CH2), 4.12 (brs, 2H, piperazine CH2), 4.51 (s, 2H, COCH2), 7.32 (t, 1H, J: 7.76 Hz, Ar-H), 7.45 (t, 1H, J: 8.09 Hz, Ar-H), 7.76 (d, 1H, J: 8.11 Hz, Ar-H), 7.98 (d, 1H, J: 7.92 Hz, Ar-H), 12.54 (s, 1H, N-H). For C20H26N4OS3 calculated: 55.27 % C, 6.03 % H, 12.89 % N; found: 55.20 % C, 6.09 % H, 12.75 % N. MS [M + 1] + : m/z 435.

2-[(Benzothiazol-2-yl)amino]-2-oxoethyl 4-(2-pyrimidinyl) piperazine-1-carbodithioate (1): Yield 74–76 %, m.p. 182– 185 °C. IR (KBr, cm − 1): νmax 3 328 (amide N-H), 1 670 (C = O), 1 534–1 305 (C = C), 1 258–927 (C-N). 1H-NMR (500 MHz, DMSO-

2-[(6-Ethoxy-2-benzothiazolyl)amino]-2-oxoethyl 4-(2-pyrimidinyl)piperazine-1-carbodithioate (6): Yield 71–73 %, m.p. 200–202 °C. IR (KBr, cm − 1): νmax 3 343 (amide N-H), 1 671 (C = O), 1 529–1 310 (C = C), 1 263–926 (C-N). 1H-NMR (500 MHz, DMSO-

Mohsen UA et al. New Piperazine-Dithiocarbamates … Drug Res


dithiocarbamate moieties [13–19]. Piperazine ring plays an important role for antiacetylcholinesterase activity [20–23]. Besides, it has been reported that benzothiazole ring possess an impact on antiacetylcholinesterase activity [24, 25]. On the basis of these findings and in the continuation of our ongoing research program synthesis and investigation of acetylcholinesterase inhibitor activity of the 2-[(6-substituted benzothiazol-2-yl) amino]-2-oxoethyl 4-substituted piperazine-1-carbodithioate derivatives (1–30) were reported in this study.

Original Article

2-[(6-Ethoxy-2-benzothiazolyl)amino]-2-oxoethyl 4-(4-nitrophenyl)piperazine-1-carbodithioate (7): Yield 74–76 %, m.p. 247–250 °C. IR (KBr, cm − 1): νmax 3 343 (amide N-H), 1 671 (C = O), 1 529–1 310 (C = C), 1 263–926 (C-N). 1H-NMR (500 MHz, DMSOd6, ppm): δ 1.35 (t, 3H, J = 7.4 Hz, CH3), 2.64 (brs, 4H, piperazine CH2), 3.87 (brs, 2H, piperazine CH2), 4.07 (q, 2H, J: 7.8 Hz, CH2), 4.12 (brs, 2H, piperazine CH2), 4.46 (s, 2H, COCH2), 6.96–7.04 (m, 3H, Ar-H), 7.55–7.64 (m, 2H, Ar-H), 8.12 (d, 2H, J: 9.32 Hz, Ar-H), 12.59 (s, 1H, N-H). For C22H23N5O4S3 calculated: 51.05 % C, 4.48 % H, 13.53 % N; found: 51.09 % C, 4.40 % H, 13.65 % N. MS [M + 1] + : m/z 518. 2-[(6-Ethoxy-2-benzothiazolyl)amino]-2-oxoethyl 4-[2-(N,Ndimethylamino)ethyl]piperazine-1-carbodithioate (8): Yield 68–70 %, m.p. 155–158 °C. IR (KBr, cm − 1): νmax 3 343 (amide N-H), 1 671 (C = O), 1 529–1 310 (C = C), 1 263–926 (C-N). 1H-NMR (500 MHz, DMSO-d6, ppm): δ 1.35 (t, 3H, J = 8.0 Hz, CH3), 2.15 (s, 6H, N(CH3)2), 2.39–2.45 (m, 4H, (CH2)2), 2.63 (brs, 4H, piperazine CH2), 3.87 (brs, 2H, piperazine CH2), 4.07 (q, 2H, J: 7.59 Hz, CH2), 4.12 (brs, 2H, piperazine CH2), 4.40 (s, 2H, COCH2), 7.02 (d, 1H, J: 8.67 Hz, Ar-H), 7.55 (s, 1H, Ar-H), 7.64 (d, 1H, J: 8.78 Hz, Ar-H), 12.59 (s, 1H, N-H). For C20H29N5O2S3 calculated: 51.36 % C, 6.25 % H, 14.97 % N; found: 51.29 % C, 6.39 % H, 14.85 % N. MS [M + 1] + : m/z 468. 2-[(6-Ethoxy-2-benzothiazolyl)amino]-2-oxoethyl 4-[3-(N,Ndimethylamino)propyl]piperazine-1-carbodithioate (9): Yield 77–78 %, m.p. 132–135 °C (decomp.). IR (KBr, cm − 1): νmax 3 342 (amide N-H), 1 671 (C = O), 1 529–1 310 (C = C), 1 263–926 (C-N). 1 H-NMR (500 MHz, DMSO-d6, ppm): δ 1.35 (t, 3H, J = 7.7 Hz, CH3), 2.15 (m, 2H, CH2), 2.18 (s, 6H, N(CH3)2), 2.38–2.44 (m, 4H, (CH2)2), 2.64 (brs, 4H, piperazine CH2), 3.87 (brs, 2H, piperazine CH2), 4.07 (q, 2H, J: 7.59 Hz, CH2), 4.12 (brs, 2H, piperazine CH2), 4.40 (s, 2H, COCH2), 7.02 (d, 1H, J: 8.48 Hz, Ar-H), 7.55 (s, 1H, Ar-H), 7.65 (d, 1H, J: 8.69 Hz, Ar-H), 12.58 (s, 1H, N-H). For C21H31N5O2S3 calculated: 52.36 % C, 6.49 % H, 14.54 % N; found: 52.44 % C, 6.58 % H, 14.54 % N. MS [M + 1] + : m/z 482. 2-[(6-Ethoxy-2-benzothiazolyl)amino]-2-oxoethyl 4-cyclohexylpiperazine-1-carbodithioate (10): Yield 74–75 %, m.p. 166– 168 °C. IR (KBr, cm − 1): νmax 3 341 (amide N-H), 1 670 (C = O), 1 529–1 310 (C = C), 1 263–926 (C-N). 1H-NMR (500 MHz, DMSOd6, ppm): δ 1.21–1.25 (m, 5H, cyclohexyl C-H), 1.35 (t, 3H, J = 7.5 Hz, CH3), 1.63–1.89 (m, 5H, cyclohexyl C-H), 2.24–2.29 (m, 1H, cyclohexyl C-H), 2.63 (brs, 4H, piperazine CH2), 3.88 (brs, 2H, piperazine CH2), 4.07 (q, 2H, J: 7.59 Hz, CH2), 4.12 (brs, 2H, piperazine CH2), 4.40 (s, 2H, COCH2), 7.02 (d, 1H, J: 8.69 Hz, Ar-H), 7.55 (s, 1H, Ar-H), 7.64 (d, 1H, J: 8.79 Hz, Ar-H), 12.51 (s, 1H, N-H). For C22H30N4O2S3 calculated: 55.20 % C, 6.32 % H, 11.70 % N; found: 55.31 % C, 6.45 % H, 11.54 % N. MS [M + 1] + : m/z 479.

2-[(6-Methyl-2-benzothiazolyl)amino]-2-oxoethyl 4-(2-pyrimidinyl)piperazine-1-carbodithioate (11): Yield 69–71 %, m.p. 202–204 °C. IR (KBr, cm − 1): νmax 3 348 (amide N-H), 1 670 (C = O), 1 532–1 313 (C = C), 1 260–927 (C-O, C-N). 1H-NMR (500 MHz, DMSO-d6, ppm): δ 2.27 (s, 3H, CH3), 2.61 (brs, 4H, piperazine CH2), 3.92 (brs, 2H, piperazine CH2), 4.11 (brs, 2H, piperazine CH2), 4.45 (s, 2H, COCH2), 6.71 (t, 1H, J: 4.68 Hz, Ar-H), 7.26 (d, 1H, J: 7.26 Hz, Ar-H), 7.65 (d, 1H, J: 8.16 Hz, Ar-H), 7.78 (s, 1H, Ar-H), 8.43 (d, 2H, J: 4.72 Hz, Ar-H), 12.61 (s, 1H, N-H). For C19H20N6OS3 calculated: 51.33 % C, 4.53 % H, 18.90 % N; found: 51.42 % C, 4.59 % H, 18.79 % N. MS [M + 1] + : m/z 445. 2-[(6-Methyl-2-benzothiazolyl)amino]-2-oxoethyl 4-(4-nitrophenyl)piperazine-1-carbodithioate (12): Yield 74–76 %, m.p. 249–250 °C. IR (KBr, cm − 1): νmax 3 352 (amide N-H), 1 673 (C = O), 1 571–1 321 (C = C), 1 243–927 (C-O, C-N). 1H-NMR (500 MHz, DMSO-d6, ppm): δ 2.41 (s, 3H, CH3), 2.63 (brs, 4H, piperazine CH2), 3.93 (brs, 2H, piperazine CH2), 4.12 (brs, 2H, piperazine CH2), 4.46 (s, 2H, COCH2), 6.96 (d, 2H, J: 9.47 Hz, Ar-H), 7.26 (d, 1H, J: 8.32 Hz, Ar-H), 7.65 (d, 1H, J: 8.12 Hz, Ar-H), 7.77 (s, 1H, Ar-H), 8.12 (d, 2H, J: 9.42 Hz, Ar-H), 12.61 (s, 1H, N-H). For C21H21N5O3S3 calculated: 51.73 % C, 4.34 % H, 14.36 % N; found: 51.62 % C, 4.48 % H, 14.73 % N. MS [M + 1] + : m/z 488. 2-[(6-Methyl-2-benzothiazolyl)amino]-2-oxoethyl 4-[2-(N,Nd i m e t hy l a m i n o ) e t hy l ] p i p e r a z i n e - 1 - c a r b o d i t h i o a t e (13): Yield 70–72 %, m.p. 156–158 °C. IR (KBr, cm − 1): νmax 3 338 (amide N-H), 1 670 (C = O), 1 565–1 318 (C = C), 1 237–926 (C-O, C-N). 1H-NMR (500 MHz, DMSO-d6, ppm): δ 2.16 (s, 6H, N(CH3)2), 2.39–2.45 (m, 7H, (CH2)2 and CH3), 2.62 (brs, 4H, piperazine CH2), 3.92 (brs, 2H, piperazine CH2), 4.11 (brs, 2H, piperazine CH2), 4.46 (s, 2H, COCH2), 7.26 (d, 1H, J: 8.35 Hz, Ar-H), 7.64 (d, 1H, J: 8.21 Hz, Ar-H), 7.77 (s, 1H, Ar-H), 12.61 (s, 1H, N-H). For C19H27N5OS3 calculated: 52.14 % C, 6.22 % H, 16.0 % N; found: 51.23 % C, 6.31 % H, 16.12 % N. MS [M + 1] + : m/z 438. 2-[(6-Methyl-2-benzothiazolyl)amino]-2-oxoethyl 4-[3-(N,Ndimethylamino)propyl]piperazine -1-carbodithioate (14): Yield 72–75 %, m.p. 149–151 °C. IR (KBr, cm − 1): νmax 3 345 (amide N-H), 1 671 (C = O), 1 557–1 324 (C = C), 1 241–927 (C-O, C-N). 1H-NMR (500 MHz, DMSO-d6, ppm): δ 1.58 (m, 2H, CH2), 2.16 (s, 6H, N(CH3)2), 2.38–2.43 (m, 7H, (CH2)2 and CH3), 2.64 (brs, 4H, piperazine CH2), 3.93 (brs, 2H, piperazine CH2), 4.10 (brs, 2H, piperazine CH2), 4.47 (s, 2H, COCH2), 7.26 (d, 1H, J: 8.05 Hz, Ar-H), 7.64 (d, 1H, J: 8.23 Hz, Ar-H), 7.77 (s, 1H, Ar-H), 12.61 (s, 1H, N-H). For C20H29N5OS3 calculated: 53.18 % C, 6.47 % H, 15.51 % N; found: 53.27 % C, 6.56 % H, 15.59 % N. MS [M + 1] + : m/z 452. 2-[(6-Methyl-2-benzothiazolyl)amino]-2-oxoethyl 4-cyclohexylpiperazine-1-carbodithioate (15): Yield 72–75 %, m.p. 187– 189 °C. IR (KBr, cm − 1): νmax 3 348 (amide N-H), 1 673 (C = O), 1 561–1 311 (C = C), 1 239–927 (C-O, C-N). 1H-NMR (500 MHz, DMSO-d6, ppm): δ 1.22–1.26 (m, 5H, cyclohexyl C-H), 1.64–1.88 (m, 5H, cyclohexyl C-H), 2.24–2.29 (m, 1H, cyclohexyl C-H), 2.41 (s, 3H, CH3), 2.62 (brs, 4H, piperazine CH2), 3.92 (brs, 2H, piperazine CH2), 4.11 (brs, 2H, piperazine CH2), 4.41 (s, 2H, COCH2), 7.26 (d, 1H, J: 8.05 Hz, Ar-H), 7.64 (d, 1H, J: 8.32 Hz, Ar-H), 7.77 (s, 1H, Ar-H), 12.58 (s, 1H, N-H). For C21H28N4OS3 calculated: 56.22 % C, 6.29 % H, 12.49 % N; found: 52.28 % C, 6.35 % H, 12.56 % N. MS [M + 1] + : m/z 449.



d6, ppm): δ 1.35 (t, 3H, J = 7.4, Hz, CH3), 2.64 (brs, 4H, piperazine CH2), 3.93 (brs, 2H, piperazine CH2), 4.07 (q, 2H, J: 7.5 Hz, CH2), 4.13 (brs, 2H, piperazine CH2), 4.45 (s, 2H, COCH2), 6.71 (t, 1H, J: 4.72 Hz, Ar-H), 7.03 (d, 1H, J: 7.74 Hz, Ar-H), 7.56 (s, 1H, Ar-H), 7.64 (d, 1H, J: 8.81 Hz, Ar-H), 8.43 (d, 2H, J: 4.74 Hz, Ar-H), 12.54 (s, 1H, N-H). For C20H22N6O2S3 calculated: 50.61 % C, 4.67 % H, 17.71 % N; found: 50.49 % C, 4.54 % H, 17.62 % N. MS [M + 1] + : m/z 475.

2-[(6-Methoxy-2-benzothiazolyl)amino]-2-oxoethyl 4-(2-pyrimidinyl)piperazine-1-carbodithioate (16): Yield 70–72 %, m.p. 200–203 °C. IR (KBr, cm − 1): νmax 3 345 (amide N-H), 1 671 (C = O), 1 552–1 303 (C = C), 1 248–927 (C-N). 1H-NMR (500 MHz, DMSO-d6, ppm): δ 2.61 (brs, 4H, piperazine CH2), 3.81 (s, 3H, OCH3), 3.92 (brs, 2H, piperazine CH2), 4.11 (brs, 2H, piperazine CH2), 4.46 (s, 2H, COCH2), 6.71 (t, 1H, J: 4.76 Hz, Ar-H), 7.04 (d, 1H, J: 8.90 Hz, Ar-H), 7.58 (s, 1H, Ar-H), 7.66 (d, 1H, J: 8.83 Hz, Ar-H), 8.42 (d, 2H, J: 4.74 Hz, Ar-H), 12.55 (s, 1H, N-H). For C19H20N6O2S3 calculated: 49.55 % C, 4.38 % H, 18.25 % N; found: 49.64 % C, 4.52 % H, 18.31 % N. MS [M + 1] + : m/z 461.

2-[(6-Chloro-2-benzothiazolyl)amino]-2-oxoethyl 4-(2-pyrimidinyl)piperazine-1-carbodithioate (21): Yield 70–72 %, m.p. 220–223 °C. IR (KBr, cm − 1): νmax 3 334 (amide N-H), 1 674 (C = O), 1 563–1 315 (C = C), 1 242–927 (C-N). 1H-NMR (500 MHz, DMSO-d6, ppm): δ 2.61 (brs, 4H, piperazine CH2), 3.92 (brs, 2H, piperazine CH2), 4.11 (brs, 2H, piperazine CH2), 4.46 (s, 2H, COCH2), 6.67 (t, 1H, J: 4.64 Hz, Ar-H), 7.46 (d, 1H, J: 7.85 Hz, Ar-H), 7.74 (d, 1H, J: 8.19 Hz, Ar-H), 8.11 (s, 1H, Ar-H), 8.43 (d, 2H, J: 4.73 Hz, Ar-H), 12.63 (s, 1H, N-H). For C18H17ClN6OS3 calculated: 46.49 % C, 3.68 % H, 18.07 % N; found: 46.58 % C, 3.54 % H, 18.34 % N. MS [M + 1] + : m/z 465.

2-[(6-Methoxy-2-benzothiazolyl)amino]-2-oxoethyl 4-(4-nitrophenyl)piperazine-1-carbodithioate (17): Yield 68–71 %, m.p. 243–246 °C. IR (KBr, cm − 1): νmax 3 352 (amide N-H), 1 670 (C = O), 1 564–1 318 (C = C), 1 247–927 (C-N). 1H-NMR (500 MHz, DMSOd6, ppm): δ 2.62 (brs, 4H, piperazine CH2), 3.76 (brs, 2H, piperazine CH2), 3.81 (s, 3H, OCH3), 4.18 (brs, 2H, piperazine CH2), 4.46 (s, 2H, COCH2), 6.96–7.05 (m, 3H, Ar-H), 7.57–7.67 (m, 2H, Ar-H), 8.12 (d, 2H, J: 9.42 Hz, Ar-H), 12.55 (s, 1H, N-H). For C21H21N5O4S3 calculated: 50.08 % C, 4.20 % H, 13.91 % N; found: 50.14 % C, 4.35 % H, 13.81 % N. MS [M + 1] + : m/z 504.

2-[(6-Chloro-2-benzothiazolyl)amino]-2-oxoethyl 4-(4-nitrophenyl)piperazine-1-carbodithioate (22): Yield 67–70 %, m.p. 146–150 °C (decomp.). IR (KBr, cm − 1): νmax 3 352 (amide N-H), 1 670 (C = O), 1 564–1 318 (C = C), 1 247–927 (C-N). 1H-NMR (500 MHz, DMSO-d6, ppm): δ 2.64 (brs, 4H, piperazine CH2), 3.78 (brs, 2H, piperazine CH2), 4.19 (brs, 2H, piperazine CH2), 4.47 (s, 2H, COCH2), 6.97–7.03 (m, 3H, Ar-H), 7.53–7.60 (m, 2H, Ar-H), 8.15 (d, 2H, J: 9.12 Hz, Ar-H), 12.63 (s, 1H, N-H). For C20H18ClN5O3S3 calculated: 47.28 % C, 3.57 % H, 13.79 % N; found: 47.35 % C, 3.43 % H, 13.87 % N. MS [M + 1] + : m/z 508.

2-[(6-Methoxy-2-benzothiazolyl)amino]-2-oxoethyl 4-[2-(N,Ndimethylamino)ethyl]piperazine-1-carbodithioate (18): Yield 71–72 %, m.p. 148–150 °C. IR (KBr, cm − 1): νmax 3 349 (amide N-H), 1 674 (C = O), 1 555–1 334 (C = C), 1 253–927 (C-N). 1H-NMR (500 MHz, DMSO-d6, ppm): δ 2.19 (s, 6H, N(CH3)2), 2.43 (m, 4H, (CH2)2), 2.62 (brs, 4H, piperazine CH2), 3.81 (s, 3H, OCH3), 3.91 (brs, 2H, piperazine CH2), 4.12 (brs, 2H, piperazine CH2), 4.41 (s, 2H, COCH2), 7.05 (d, 1H, J: 9.02 Hz, Ar-H), 7.58 (s, 1H, Ar-H), 7.65 (d, 1H, J: 8.83 Hz, Ar-H), 12.52 (s, 1H, N-H). For C19H27N5O2S3 calculated: 50.30 % C, 6.00 % H, 15.44 % N; found: 50.44 % C, 6.13 % H, 15.61 % N. MS [M + 1] + : m/z 454.

2-[(6-Chloro-2-benzothiazolyl)amino]-2-oxoethyl 4-[2-(N,Nd i m e t hy l a m i n o ) e t hy l ] p i p e r a z i n e - 1 - c a r b o d i t h i o a t e (23): Yield 71–72 %, m.p. 128–130 °C. IR (KBr, cm − 1): νmax 3 351 (amide N-H), 1 673 (C = O), 1 552–1 333 (C = C), 1 243–927 (C-N). 1 H-NMR (500 MHz, DMSO-d6, ppm): δ 2.21 (s, 6H, N(CH3)2), 2.44 (m, 4H, (CH2)2), 2.64 (brs, 4H, piperazine CH2), 3.95 (brs, 2H, piperazine CH2), 4.13 (brs, 2H, piperazine CH2), 4.44 (s, 2H, COCH2), 7.47 (d, 1H, J: 8.42 Hz, Ar-H), 7.95 (d, 1H, J: 8.59 Hz, Ar-H), 8.13 (s, 1H, Ar-H), 12.62 (s, 1H, N-H). For C18H24ClN5OS3 calculated: 47.20 % C, 5.28 % H, 15.29 % N; found: 47.27 % C, 5.38 % H, 15.41 % N. MS [M + 1] + : m/z 458.

2-[(6-Methoxy-2-benzothiazolyl)amino]-2-oxoethyl 4-[3-(N,Ndimethylamino)propyl]piperazine -1-carbodithioate (19): Yield 68–70 %, m.p. 135–136 °C. IR (KBr, cm − 1): νmax 3 334 (amide N-H), 1 672 (C = O), 1 546–1 329 (C = C), 1 252–926 (C-O, C-N). 1H-NMR (500 MHz, DMSO-d6, ppm): δ 1.60 (m, 2H, CH2), 2.18 (s, 6H, N(CH3)2), 2.39–2.45 (m, 4H, (CH2)2), 2.65 (brs, 4H, piperazine CH2), 3.83 (s, 3H, OCH3), 3.92 (brs, 2H, piperazine CH2), 4.11 (brs, 2H, piperazine CH2), 4.43 (s, 2H, COCH2), 7.06 (d, 1H, J: 8.74 Hz, Ar-H), 7.58 (s, 1H, Ar-H), 7.66 (d, 1H, J: 8.69 Hz, Ar-H), 12.52 (s, 1H, N-H). For C20H29N5OS3 calculated: 51.36 % C, 6.25 % H, 14.97 % N; found: 51.26 % C, 6.36 % H, 14.85 % N. MS [M + 1] + : m/z 468.

2-[(6-Chloro-2-benzothiazolyl)amino]-2-oxoethyl 4-[3-(N,Ndimethylamino)propyl]piperazine -1-carbodithioate (24): Yield 68–70 %, m.p. 130–131 °C. IR (KBr, cm − 1): νmax 3 342 (amide N-H), 1 671 (C = O), 1 538–1 312 (C = C), 1 245–927 (C-O, C-N). 1H-NMR (500 MHz, DMSO-d6, ppm): δ 1.60 (m, 2H, CH2), 2.18 (s, 6H, N(CH3)2), 2.39–2.45 (m, 4H, (CH2)2), 2.65 (brs, 4H, piperazine CH2), 3.92 (brs, 2H, piperazine CH2), 4.11 (brs, 2H, piperazine CH2), 4.43 (s, 2H, COCH2), 7.41 (d, 1H, J: 8.45 Hz, Ar-H), 7.80 (s, 1H, Ar-H), 8.12 (d, 1H, J: 8.56 Hz, Ar-H), 12.62 (s, 1H, N-H). For C19H26ClN5OS3 calculated: 48.34 % C, 5.55 % H, 14.83 % N; found: 48.22 % C, 5.67 % H, 14.93 % N. MS [M + 1] + : m/z 472.

2 - [ ( 6 - M eth ox y - 2 - b e nzoth iazo l y l ) a m i n o ] - 2 - oxo ethy l 4-cyclohexylpiperazine-1-carbodithioate (20): Yield 71–72 %, m.p. 157–158 °C. IR (KBr, cm − 1): νmax 3 351 (amide N-H), 1 674 (C = O), 1 548–1 321 (C = C), 1 252–926 (C-O, C-N). 1H-NMR (500 MHz, DMSO-d6, ppm): δ 1.24–1.27 (m, 5H, cyclohexyl C-H), 1.65–1.91 (m, 5H, cyclohexyl C-H), 2.25–2.30 (m, 1H, cyclohexyl C-H), 2.63 (brs, 4H, piperazine CH2), 3.82 (s, 3H, OCH3), 3.93 (brs, 2H, piperazine CH2), 4.11 (brs, 2H, piperazine CH2), 4.48 (s, 2H, COCH2), 7.04 (d, 1H, J: 9.03 Hz, Ar-H), 7.58 (s, 1H, Ar-H), 7.65 (d, 1H, J: 8.84 Hz, Ar-H), 12.58 (s, 1H, N-H). For C21H28N4O2S3 calculated: 54.28 % C, 6.07 % H, 12.06 % N; found: 54.37 % C, 6.18 % H, 12.14 % N. MS [M + 1] + : m/z 465.

2-[(6-Chloro-2-benzothiazolyl)amino]-2-oxoethyl 4-cyclohexylpiperazine-1-carbodithioate (25): Yield 71–72 %, m.p. 158– 160 °C. IR (KBr, cm − 1): νmax 3 343 (amide N-H), 1 671 (C = O), 1 534–1 312 (C = C), 1 263–927 (C-O, C-N). 1H-NMR (500 MHz, DMSO-d6, ppm): δ 1.26–1.29 (m, 5H, cyclohexyl C-H), 1.67–1.93 (m, 5H, cyclohexyl C-H), 2.29–2.34 (m, 1H, cyclohexyl C-H), 2.65 (brs, 4H, piperazine CH2), 3.94 (brs, 2H, piperazine CH2), 4.15 (brs, 2H, piperazine CH2), 4.47 (s, 2H, COCH2), 7.05 (d, 1H, J: 9.31 Hz, Ar-H), 7.59 (s, 1H, Ar-H), 7.66 (d, 1H, J: 8.88 Hz, Ar-H), 12.58 (s, 1H, N-H). For C20H25ClN4OS3 calculated: 51.21 % C, 5.37 % H, 11.94 % N; found: 51.34 % C, 5.46 % H, 11.84 % N. MS [M + 1] + : m/z 469.



Original Article

Original Article

2-[(6-Nitro-2-benzothiazolyl)amino]-2-oxoethyl 4-(4-nitrophenyl)piperazine-1-carbodithioate (27): Yield 67–70 %, m.p. 174–176 °C. IR (KBr, cm − 1): νmax 3 352 (amide N-H), 1 670 (C = O), 1 543–1 303 (C = C), 1 256–927 (C-N). 1H-NMR (500 MHz, DMSOd6, ppm): δ 2.61 (brs, 4H, piperazine CH2), 3.74 (brs, 2H, piperazine CH2), 4.12 (brs, 2H, piperazine CH2), 4.35 (s, 2H, COCH2), 6.96 (d, 2H, J: 9.40 Hz, Ar-H), 7.60 (d, 1H, J: 8.32 Hz, Ar-H), 8.12 (d, 1H, J: 9.32 Hz, Ar-H), 8.16 (d, 2H, J: 8.34 Hz, Ar-H), 8.79 (s, 1H, Ar-H), 13.13 (s, 1H, N-H). For C20H18N6O5S3 calculated: 46.32 % C, 3.50 % H, 16.21 % N; found: 46.45 % C, 3.41 % H, 16.33 % N. MS [M + 1] + : m/z 519. 2-[(6-Nitro-2-benzothiazolyl)amino]-2-oxoethyl 4-[2-(N,Nd i m e t hy l a m i n o ) e t hy l ] p i p e r a z i n e - 1 - c a r b o d i t h i o a t e (28): Yield 67–70 %, m.p. 213–214 °C. IR (KBr, cm − 1): νmax 3 343 (amide N-H), 1 670 (C = O), 1 568–1 314 (C = C), 1 254–927 (C-N). 1 H-NMR (500 MHz, DMSO-d6, ppm): δ 2.32–2.43 (m, 10H, N(CH3)2 and (CH2)2), 2.65 (brs, 4H, piperazine CH2), 3.98 (brs, 2H, piperazine CH2), 4.15 (brs, 2H, piperazine CH2), 4.47 (s, 2H, COCH2), 7.81 (d, 1H, J: 8.84 Hz, Ar-H), 8.25 (d, 1H, J: 8.22 Hz, Ar-H), 8.97 (s, 1H, Ar-H), 12.62 (s, 1H, N-H). For C18H24N6O3S3 calculated: 46.13 % C, 5.16 % H, 17.93 % N; found: 46.23 % C, 5.24 % H, 17.99 % N. MS [M + 1] + : m/z 469. 2-[(6-Nitro-2-benzothiazolyl)amino]-2-oxoethyl 4-[3-(N,Ndimethylamino)propyl]piperazine -1-carbodithioate (29): Yield 65–67 %, m.p. 188–190 °C. IR (KBr, cm − 1): νmax 3 351 (amide N-H), 1 670 (C = O), 1 545–1 310 (C = C), 1 243–927 (C-O, C-N). 1H-NMR (500 MHz, DMSO-d6, ppm): δ 1.58 (m, 2H, CH2), 2.18 (s, 6H, N(CH3)2), 2.39–2.45 (m, 4H, (CH2)2), 2.67 (brs, 4H, piperazine CH2), 3.96 (brs, 2H, piperazine CH2), 4.19 (brs, 2H, piperazine CH2), 4.45 (s, 2H, COCH2), 7.42 (d, 1H, J: 8.45 Hz, Ar-H), 7.83 (s, 1H, Ar-H), 8.15 (d, 1H, J: 8.56 Hz, Ar-H), 12.62 (s, 1H, N-H). For C19H26N6O3S3 calculated: 47.28 % C, 5.43 % H, 17.41 % N; found: 47.17 % C, 5.62 % H, 17.83 % N. MS [M + 1] + : m/z 483. 2-[(6-Nitro-2-benzothiazolyl)amino]-2-oxoethyl 4-cyclohexylpiperazine-1-carbodithioate (30): Yield 68–71 %, m.p. 127– 130 °C (decomp.). IR (KBr, cm − 1): νmax 3 345 (amide N-H), 1 672 (C = O), 1 556–1 309 (C = C), 1 245–927 (C-O, C-N). 1H-NMR (500 MHz, DMSO-d6, ppm): δ 1.27–1.31 (m, 5H, cyclohexyl C-H), 1.67–1.93 (m, 5H, cyclohexyl C-H), 2.29–2.34 (m, 1H, cyclohexyl C-H), 2.65 (brs, 4H, piperazine CH2), 3.85 (s, 3H, OCH3), 3.94 (brs, 2H, piperazine CH2), 4.15 (brs, 2H, piperazine CH2), 4.47 (s, 2H, COCH2), 7.45 (d, 1H, J: 8.84 Hz, Ar-H), 8.10 (d, 1H, J: 8.22 Hz, Ar-H), 8.72 (s, 1H, Ar-H), 12.59 (s, 1H, N-H). For C20H25N5O3S3 calculated: 50.08 % C, 5.25 % H, 14.60 % N; found: 50.21 % C, 5.34 % H, 14.46 % N. MS [M + 1] + : m/z 480.

Biology AChE inhibition All compounds were subjected to a slightly modified method of Ellman’s test [27] in order to evaluate their potency to inhibit the AChE. The spectrophotometric method is based on the reaction of released thiocholine to give a coloured product with a chromogenic reagent 5,5-dithio-bis(2-nitrobenzoic)acid (DTNB). AChE, (E.C.3.1.1.7 from Electric Eel, 500 units), and Donepezil hydrochloride were purchased from Sigma-Aldrich (Steinheim, Germany). Potassium dihydrogen phosphate, DTNB, potassium hydroxide, sodium hydrogen carbonate, gelatine, acetylthiocholine iodide (ATC) were obtained from Fluka (Buchs, Switzerland). Spectrophotometric measurements were performed on a 1700 Shimadzu UV-1700 UV–Vis spectrophotometer. Cholinesterase activity of the compounds (1–30) was measured in 100 mM phosphate buffer (pH 8.0) at 25 °C, using ATC as substrates, respectively. DTNB (10 mM) was used in order to observe absorbance changes at 412 nm. Donepezil hydrochloride was used as a positive control [28].

Enzymatic assay Enzyme solutions were prepared in gelatin solution (1 %), at a concentration of 2.5 units/mL. AChE and compound solution (50 μL) which is prepared in 2 % DMSO at a concentration range of 0.001–100 μM were added to 3.0 mL phosphate buffer (pH 8 ± 0.1) and incubated at 25 °C for 5 min. The reaction was started by adding DTNB) (50 μL) and ATC (10 μL) to the enzyme-inhibitor mixture. The production of the yellow anion was recorded for 10 min at 412 nm. As a control, an identical solution of the enzyme without the inhibitor is processed following the same protocol. The blank reading contained 3.0 mL buffer, 50 μL 2 % DMSO, 50 μL DTNB and 10 μL substrate. All processes were assayed in triplicate. The inhibition rate ( %) was calculated by the following equation: Inhibition % = (AC–AI)/AC × 100 Where AI is the absorbance in the presence of the inhibitor, AC is the absorbance of the control and AB is the absorbance of blank reading. Both of the values are corrected with blank-reading value. SPSS for Windows 15.0 was used for statistical analysis. Data were expressed as Mean ± SD.

Results and Discussions

▼

Chemistry The synthesis of the 2-[(6-substituted benzothiazol-2-yl) amino]-2-oxoethyl 4-substituted piperazine-1-carbodithioate derivatives (1–30) were carried out in accordance with the ▶ Fig. 1. The starting materials sequence of reaction depicted in ● 2-chloro-N-(6-substituted benzothiazole-2-yl)acetamide derivatives (1a–f) were prepared via acetylation reaction of 2-aminobenzothiazole derivatives with chloroacetyl chloride in tetrahidrofuran and trietilamin. Sodium salts of 4-substituted piperazine-1-dithiocarbamic acids (2a–e) were prepared from secondary amines with carbon disulphide in basic medium. These 2 obtained groups were reacted with each other in acetone with the presence of potassium carbonate to gain final ▶ Table 1). The structures of the obtained compounds (1–30) (● compounds were elucidated using spectral data. In the IR spec-



2-[(6-Nitro-2-benzothiazolyl)amino]-2-oxoethyl 4-(2-pyrimidinyl)piperazine-1-carbodithioate (26): Yield 70–72 %, m.p. 244–245 °C. IR (KBr, cm − 1): νmax 3 338 (amide N-H), 1 671 (C = O), 1 566–1 310 (C = C), 1 245–927 (C-N). 1H-NMR (500 MHz, DMSOd6, ppm): δ 2.61 (brs, 4H, piperazine CH2), 3.92 (brs, 2H, piperazine CH2), 4.11 (brs, 2H, piperazine CH2), 4.46 (s, 2H, COCH2), 6.72 (t, 1H, J: 4.63 Hz, Ar-H), 7.90 (d, 1H, J: 8.88 Hz, Ar-H), 8.28 (d, 2H, J: 8.03 Hz, Ar-H), 8.43 (d, 2H, J: 4.63 Hz, Ar-H), 9.04 (s, 1H, Ar-H), 13.13 (s, 1H, N-H). For C18H17N7O3S3 calculated: 45.46 % C, 3.60 % H, 20.62 % N; found: 45.57 % C, 3.69 % H, 20.54 % N. MS [M + 1] + : m/z 476.

Original Article

O N

N

i

NH2

NH

S

R

Fig. 1 Synthesis of the compounds.

Cl

S

R

1a-f

R : H, CH 3, OCH 3, C l, OC 2H5, NO2

R'

N

S

ii

NH

R'

N

N + S - Na

2a-e R ': 2-pyrimidinyl, 4-nitrophenyl, cyclohexyl, C H2CH 2N(C H3)2, CH 2C H2C H2N(CH 3) 2 R'

1a-f

+

O

iii

2a-e

N

N NH R

S

1-30

Table 1 2-[(6-Subsituted benzothiazol-2-yl)amino]-2-oxoethyl 4-substituted piperazine-1-carbodithioate and derivatives. Comp.

R

R′

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

– – – – – 6-Ethoxy 6-Ethoxy 6-Ethoxy 6-Ethoxy 6-Ethoxy 6-Methyl 6-Methyl 6-Methyl 6-Methyl 6-Methyl 6-Methoxy 6-Methoxy 6-Methoxy 6-Methoxy 6-Methoxy 6-Chloro 6-Chloro 6-Chloro 6-Chloro 6-Chloro 6-Nitro 6-Nitro 6-Nitro 6-Nitro 6-Nitro

2-pyrimidinyl 4-nitrophenyl -CH2CH2N(CH3)2 -CH2 CH2CH2N(CH3)2 cyclohexyl 2-pyrimidinyl 4-nitrophenyl -CH2CH2N(CH3)2 -CH2 CH2CH2N(CH3)2 cyclohexyl 2-pyrimidinyl 4-nitrophenyl -CH2CH2N(CH3)2 -CH2 CH2CH2N(CH3)2 cyclohexyl 2-pyrimidinyl 4-nitrophenyl -CH2CH2N(CH3)2 -CH2 CH2CH2N(CH3)2 cyclohexyl 2-pyrimidinyl 4-nitrophenyl -CH2CH2N(CH3)2 -CH2 CH2CH2N(CH3)2 cyclohexyl 2-pyrimidinyl 4-nitrophenyl -CH2CH2N(CH3)2 -CH2 CH2CH2N(CH3)2 cyclohexyl

tra, the characteristic N-H bands and amide carbonyl functions were observed in 3 358–3 328 cm − 1 and 1 674–1 669 cm − 1 regions, respectively. The NMR spectra of the compounds 1–30


S S

exhibited aliphatic and aromatic peaks. In aliphatic region, peaks resulting from resonances of the piperazine and CH2CO protons were observed at about 2.61–4.19 ppm and at about 4.35–4.59 ppm. The peaks belonging to aromatic protons were seen at the range of 6.71–9.04 ppm. M + 1 peaks in MS spectra were in agreement with the calculated molecular weight of the title compounds (1–30) and elemental analysis results for C, H, and N elements were satisfactory with calculated values of the compounds.

Anticholinesterase activity In the present study some novel benzothiazole based piperazinecarbodithionic acid ester derivatives were tested for their AChE inhibitory activities by slightly modified Ellman’s assay. Initially, all compounds were tested for their inhibition potency against AChE at a single dose of 100 μM. Then the compounds 3, 4, 8, 9, 13, 14, 18, 19, 23, 24, 28, and 29 showing greater than 50 % enzyme inhibition were assayed at 10–0.001 μM concentration range and IC50 values were calculated. Donepezil was used as a control agent. Anticholinesterase inhibitory activity of the ▶ Table 2. synthesized compounds is presented in ● ▶ Table 2, the compound 28 was the most active As seen in the ● derivative in the series with a IC50 of 4.27 μM. This compound showed very closed inhibition potency to donepezil at the concentrations of 100 and 10 μM. Besides the compounds 8, 13, 18, and 23 displayed IC50 values lower than 10 μM. All of these compounds exhibited significant inhibitory activity ( > 90 %) at 100 μM concentration. The compounds 3, 4, 9, 14, 19, 24, and 29 were the other derivatives which showed higher inhibition potency than 50 % at 100 μM concentration. However, these compounds had low inhibitory activity at further concentrations. Structure activity relationships of the compounds clearly showed that aliphatic side chain located fourth position of the piperazine moiety enhances the biological activity since all of the active compounds bear dimethylamino ethyl or dimethylamino propyl groups. On the other hand phenyl or cyclohexyl


N

Original Article

Compound

100

10

1

0.1

0.01

0.001

IC50 (μM)*

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Donepezil

10.62 ± 0.19 21.44 ± 0.22 88.20 ± 0.75 54.64 ± 1.49 12.35 ± 0.91 17.77 ± 2.56 17.96 ± 1.98 93.37 ± 0.58 50.57 ± 2.56 39.23 ± 1.80 29.34 ± 1.82 20.54 ± 0.52 92.29 ± 0.29 75.88 ± 0.72 18.82 ± 2.15 19.53 ± 1.59 8.02 ± 0.87 95.55 ± 0.27 67.21 ± 1.03 26.93 ± 0.76 16.72 ± 0.17 20.39 ± 0.56 91.10 ± 0.13 54.53 ± 0.59 16.62 ± 2.47 19.12 ± 7.30 13.08 ± 1.32 96.18 ± 0.19 78.68 ± 0.25 23.39 ± 1.12 99.00 ± 0.28

ND* ND 36.28 ± 2.81 41.72 ± 1.45 ND ND ND 67.46 ± 1.31 24.05 ± 1.98 ND ND ND 65.60 ± 1.02 17.77 ± 1.32 ND ND ND 76.83 ± 0.84 12.45 ± 2.17 ND ND ND 59.00 ± 1.02 14.42 ± 2.24 ND ND ND 85.77 ± 0.34 28.75 ± 0.96 ND 96.93 ± 0.28

ND ND 23.12 ± 1.19 28.68 ± 0.96 ND ND ND 15.71 ± 1.49 14.42 ± 0.43 ND ND ND 11.54 ± 3.04 13.11 ± 0.98 ND ND ND 18.96 ± 3.03 9.42 ± 1.12 ND ND ND 7.88 ± 0.81 9.24 ± 1.43 ND ND ND 29.65 ± 1.33 19.42 ± 1.75 ND 79.99 ± 1.66





*ND: Not determined *IC50: 50 % inhibitory concentration (means ± SD of 3 independent experiments) of AChE

Fig. 2 Structures of the compound 28 and acetylcholine.

N

+N O

N

O

O N

N NH O2N

S 28

S S Acetylcholine

substituted piperazine containing compounds did not showed notable enzyme inhibitory activity. Among the aliphatic side chain carrying compounds, the compounds 3, 8, 13, 18, 23, and 28 substituted with dimethylamino ethyl, displayed higher activity than the dimethylamino propyl substituted compounds 4, 9, 14, 19, 24, and 29. This result suggest that increase of carbon number in the aliphatic side chain causes an activity loss. Similarity between acetylcholine and dimethylaminoethyl side chain may explain the increasing enzyme inhibitory activity of the compounds 3, 8, 13, 18, 23, and 28. Additionally, substituents on benzothiazole ring have an impact on enzyme inhibition activity. It seems that nitro group on benzothiazole ring has ▶ Fig. 2). more influence than other substituents (●

Declaration of Interest

▼

The authors report no conflicts of interest.

References 1 Silverman RB. The Organic Chemistry of Drug Design and Drug Action. 2nd ed. Elsevier Academic Press, Burlington: 2004 2 Shen ZX. Brain Cholinesterases: III. Future perspectives of AD research and clinical practice. Med Hypotheses 2004; 63: 298–307 3 Martinez A, Castro A. Novel cholinesterase inhibitors as future effective drugs for the treatment of Alzheimer’s disease. Expert Opin Investig Drugs 2006; 15: 1–12 4 Giacobini E. Cholinesterases: New roles in brain function and in Alzheimer’s Disease. Neurochem Res 2003; 28: 515–522



Table 2 AChE Inhibition potency of the compounds at 0.001–100 μM concentrations.

5 Sing M, Kaur M, Kukreja H et al. Acetylcholinesterase inhibitors as Alzheimer therapy: From nerve toxins to neuroprotection. Eur J Med Chem 2013; 70: 165–188 6 Grutzendler J, Morris JC. Cholinesterase inhibitors for Alzheimer’s disease. Drugs 2001; 61: 41–52 7 Pepeu G, Giovannini MG. Cholinesterase inhibitors and beyond. Curr Alzheimer Res 2009; 6: 86–96 8 Standridge JB. Pharmacotherapeutic approaches to the treatment of Alzheimer’s Disease. Clin Ther 2004; 26: 615–630 9 Johannsen P. Long-term cholinesterase inhibitor treatment of Alzheimer’s Disease. CNS Drugs 2004; 18: 757–768 10 Grossberg GT. Cholinesterase inhibitors for the treatment of Alzheimer’s Disease: – Getting on and staying on. Curr Ther Res Clin Exp 2003; 64: 216–235 11 Wilkinson DG, Francis PT, Schwam E et al. Cholinesterase inhibitors used in the treatment of Alzheimer’s disease: the relationship between pharmacological effects and clinical efficacy. Drugs Aging 2004; 21: 453–478 12 Lemke TL, Williams DA. Foye’s Principles of Medicinal Chemistry. 7th ed. Lippincott Williams & Wilkin, Baltimore: 2008 13 Madalageri PM, Kotresh O. Synthesis, DNA protection and antimicrobial activity of some novel chloromethyl benzimidazole derivatives bearing dithiocarbamates. J Chem Pharm Res 2012; 4: 2697–2703 14 Waterbeemd H, Mannhold R. In: Lipophilicity in Drug Action and Toxicology. Pliska V, Testa B, Waterbeemd H (ed.). VCH Publishers, New York: 1996; 401–418 15 Tokuyama R, Takahashi Y, Tomita Y et al. Structure-activity relationship (SAR) studies on oxazolidinone Antibacterial agents. 2. Relationship between lipophilicity and antibacterial activity in 5-thiocarbonyl oxazolidinones. Chem Pharm Bull 2001; 49: 353–360 16 Patani GA, LaVoie EJ. Bioisosterism: A rational approach in drug design. Chem Rev 1996; 96: 3147–3176 17 Duan YC, Ma YC, Zhang E et al. Design and synthesis of novel 1,2,3-triazole-dithiocarbamate hybrids as potential anticancer agents. Eur J Med Chem 2013; 62: 11–19 18 Bacharaju K, Jambula SR, Sivan S et al. Design, synthesis, molecular docking and biological evaluation of new dithiocarbamates substituted benzimidazole and chalcones as possible chemotherapeutic agents. Bioorg Med Chem Lett 2012; 22: 3274–3277


19 Turan-Zitouni G, Ozdemir A, Guven K. Synthesis of some 1-[(N,N-disubstituted thiocarbamoylthio)acetyl]-3-(2-thienyl)-5-aryl-2-pyrazoline derivatives and investigation of their antibacterial and antifungal activities. Arch Pharm Chem Life Sci 2005; 338: 96–104 20 Sadashiva CT, Narendra Sharath Chandra JN. Synthesis and efficacy of 1-[bis(4-fluorophenyl)-methyl]piperazine derivatives for acetylcholinesterase inhibition, as a stimulant of central cholinergic neurotransmission in Alzheimer’s disease. Bioorg Med Chem Lett 2006; 16: 3932–3936 21 Yurttaş L, Özkay Y, Kaplancikli ZA. Design, synthesis and evaluation of new thiazole-piperazines as acetylcholinesterase inhibitors. J Enzyme Inhib Med Chem 2013; 28: 1040–1047 22 Varadaraju KR, Kumar JR, Mallesha L et al. Virtual screening and biological evaluation of piperazine derivatives as human acetylcholinesterase inhibitors. Int J Alzheimers Dis 2013, early online doi:10.1155/2013/653962 23 Mohammadi-Farani A, Ahmadi A, Nadri H et al. Synthesis, docking and acetylcholinesterase inhibitory assessment of 2-(2-(4-benzylpiperazin-1-yl)ethyl)isoindoline-1,3-dione derivatives with potential anti-Alzheimer effects. Daru 2013; 21: 21–47 24 Keri RS, Quintanova C, Marques SM et al. Design, synthesis and neuroprotective evaluation of novel tacrine-benzothiazole hybrids as multitargeted compounds against Alzheimer’s disease. Bioorg Med Chem 2013; 21: 4559–4569 25 Özkay-Demir Ü, Can ÖD, Özkay Y et al. Effect of benzothiazole/piperazine derivatives on intracerebroventricular streptozotocin-induced cognitive deficits. Pharmacol Rep 2012; 64: 634–847 26 Yurttaş L, Özkay Y, Akalın-Çiftci G et al. Synthesis and anticancer activity evaluation of N-[4-(2-methylthiazol-4-yl)phenyl]acetamide derivatives containing (benz)azole moiety. J Enzyme Inhib Med Chem 2014; 29: 175–184 27 Ellman GL, Courtney KD, Andres V et al. A new and rapid colorimetric determination of acetylcholinesterase activity. Biochem Pharmacol 1961; 7: 88–95 28 Perry NSL, Houghton PJ, Theobald AE et al. In-vitro inhibition of human erythrocyte acetylcholinesterase by salvia lavandulaefolia essential oil and constituent terpenes. J Pharm Pharmacol 2000; 52: 895–902


Original Article

Synthesis and antitumor activity evaluation of new 2-(4-aminophenyl)benzothiazole derivatives bearing different heterocyclic rings.

Synthesis and in vitro antiproliferative evaluation of some B-norcholesteryl Benzimidazole and Benzothiazole derivatives.

Synthesis and in vitro antitumor activity of new series of benzothiazole and pyrimido[2,1-b]benzothiazole derivatives.

Synthesis and Antimicrobial Activity of Some New Quinoxaline Derivatives.

Synthesis and biological activity of some new 2-chlorophenothiazine derivatives.

Cytotoxic activities of some benzothiazole-piperazine derivatives.

Synthesis and antimicrobial activity of some new diphenylamine derivatives.

Synthesis and in vivo diuretic activity of some new benzothiazole sulfonamides containing quinoxaline ring system.

Synthesis and anti-cancer activity evaluation of new aurone derivatives.

Novel Ru(III) Complexes with Some Benzothiazole Derivatives: Synthesis, Physicochemical and Pharmacological Investigations.

Synthesis and herbicidal evaluation of novel benzothiazole derivatives as potential inhibitors of D1 protease.

Synthesis and evaluation of some water-soluble prodrugs and derivatives of taxol with antitumor activity.

Design, synthesis, biological evaluation and preliminary mechanism study of novel benzothiazole derivatives bearing indole-based moiety as potent antitumor agents.

Synthesis and evaluation of the anxiolytic activity of some phthalimide derivatives in mice model of anxiety.

Synthesis of some new quinazolinone derivatives and evaluation of their antimicrobial activities.

Synthesis and biological evaluation of some dibenzofuran-piperazine derivatives.

Synthesis and evaluation of antidepressant-like activity of some 4-substituted 1-(2-methoxyphenyl)piperazine derivatives.

Synthesis and biological evaluation of some cyclic phosphoramidate nucleoside derivatives.

Synthesis and antimicrobial activity of some new nitro derivatives of 4-quinazolone.

Synthesis and antinociceptive activity of novel mannich base derivatives of some new fused 3,5-pyrazolidinedione.

Synthesis, characterization and antimicrobial activity of some novel benzimidazole derivatives.

Synthesis and antihypertensive activity of some imidazoindole derivatives.

Synthesis, anticancer activity and UPLC analysis of the stability of some new benzimidazole-4,7-dione derivatives.

Synthesis and hypocholesterolemic activity of some N-diphenylmethylpiperazine derivatives.