Synthesis and cytotoxic activity evaluation of novel arylpiperazine derivatives on human prostate cancer cell lines

Article abstract of DOI:10.3390/molecules190812048

A series of novel arylpiperazine derivatives was synthesized. The in vitro cytotoxic activities of all synthesized compounds against three human prostate cancer cell lines (PC-3, LNCaP, and DU145) were evaluated by a CCK-8 assay. Compounds 9 and 15 exhibi

Full text of DOI:10.3390/molecules190812048

Molecules 2014, 19, 12048-12064; doi:10.3390/molecules190812048
OPEN ACCESS
molecules
ISSN 1420-3049
www.mdpi.com/journal/molecules
Article
Synthesis and Cytotoxic Activity Evaluation of Novel
Arylpiperazine Derivatives on Human Prostate Cancer
Cell Lines
Hong Chen †, Xue Liang †, Fang Xu, Bingbing Xu, Xuelan He, Biyun Huang and Mu Yuan *
Pharmaceutical Research Center, Guangzhou Medical University, 195# Dongfengxi Road,
Guangzhou 510182, China; E-Mails: chenwexpo@sina.com (H.C.); liangliang4983@163.com (X.L.);
sherrywon03@163.com (F.X.); yjxubb@163.com (B.X.); gzmc_xlhe@hotmail.com (X.H.);
guangyihby@126.com (B.H.)
†
These authors contributed equally to this work.
* Author to whom correspondence should be addressed; E-Mail: mryuanmu838@sina.com;
Tel./Fax: +86-20-8134-0727.
Received: 7 July 2014; in revised form: 4 August 2014/ Accepted: 6 August 2014/
Published: 12 August 2014
Abstract: A series of novel arylpiperazine derivatives was synthesized. The in vitro
cytotoxic activities of all synthesized compounds against three human prostate cancer cell
lines (PC-3, LNCaP, and DU145) were evaluated by a CCK-8 assay. Compounds 9 and 15
exhibited strong cytotoxic activities against LNCaP cells (IC50 < 5 μM), and compound 8
(IC50 = 8.25 μM) possessed the most potent activity against DU145 cells. However, these
compounds also exhibited cytotoxicity towards human epithelial prostate normal cells
RWPE-1. The structure–activity relationship (SAR) of these arylpiperazine derivatives was
also discussed based on the obtained experimental data.
Keywords: synthesis; arylpiperazine derivatives; cytotoxic activity; CCK-8;
structure-activity relationship
1. Introduction
Prostate cancer is the most common non-skin cancer in men and is the second-leading cause of
cancer-related deaths in the US [1]. The incidence of prostate cancer varies worldwide. Generally, the

Molecules 2014, 19
12049
incidence rate in Occidental countries is higher than that in Asian countries [2,3]. Old age [4], ethnicity [4],
family history [5,6] diet [7] hormones and other related factors [3] of this disease are the principal risk
factors of developing prostate cancer. Prostate cancer mortality typically results from the metastasis to
the bone and lymph nodes, as well as the progression from androgen-dependent to androgen-independent
prostatic growth [8]. Clinically, localized disease is potentially curable [9] through surgery or
radiotherapy to remove or destroy cancerous cells. However, metastatic prostate cancer remains
essentially incurable and androgen ablation therapy has been the standard therapy [10,11]. Although
various chemotherapeutic agents [12] are used solely or in combination with radiotherapy to treat
advanced diseases, none of the conventional approaches to cancer therapy have been proven to be
highly successful for prostate cancer. Other studies have shown once tumor cells have become
hormone refractory, the standard cytotoxic agents for hormone-refractory prostate cancer (HRPC) can
do little to improve the treatment outcomes or survival rates [13–15], although they can still relieve the
pain to some extent in some patients. Therefore, inventing and developing more effective and safe
anti-prostate cancer drugs are urgently needed.
Compounds with arylpiperazine moieties have a wide range of bioactivities including
antiarrhythmic [16] diuretic [17], antiallergic [18], antidepressant [19] anxiolytic [20] antipsychotic [21]
antimalarial [22] and antiplasmodial properties [23]. In addition, these compounds also exhibit
receptor-blocking properties [17,24–27]. Naftopidil (Figure 1), an arylpiperazine compound, is a
specific α1d receptor antagonist [28,29]. Previous studies have demonstrated that naftopidil has higher
affinity for the α1d-adrenergic receptor than for the α1a- and α1b-adrenergic receptor subtypes [30], and in
Japan it is one of the most widely used α1-adrenergic receptor antagonists for the treatment of benign
prostatic hyperplasia (BPH) [31,32].
Figure 1. Structure of naftopidil.
N
O
OH
N
O
Recent studies have shown that naftopidil could possibly exert an anticancer effect and inhibit
prostate cancer cell growth by arresting the G1 cell cycle phase [33,34]. In addition, naftopidil can also
decrease cell viability for bladder, prostate, and renal cancer cell lines [35], as well as induce apoptosis
in malignant mesothelioma cell lines [36]. These findings indicate that naftopidil might be useful as an
anti-cancer drug. Many studies have shown that arylpiperazine derivatives may act as potential α1a-
and/or α1a- + α1d-selective ligands for the treatment of BPH. However, there have been few studies on
cytotoxic activities of these compounds against human prostate cancer cells [37–42]. As part of our
group’s continuing efforts to study the core framework of naftopidil [43–46], herein we report the
synthesis of a series of novel arylpiperazinyl derivatives based on naftopidil (Scheme 1) to identify
new anti-prostate cancer drug candidates with potential for further development. All synthesized
compounds were evaluated for their cytotoxic activities against the androgen-insensitive human
prostate cancer cell line PC-3, the androgen-sensitive human prostate cancer cell line LNCaP, the
androgen-insensitive human prostate cancer cell line DU145, and the human prostate epithelial cell

Molecules 2014, 19
12050
line RWPE-1. The SAR was further discussed on the basis of the obtained experimental data. Some
compounds exhibited strong anti-cancer activities against the tested cancer cells and superior potency
than naftopidil.
Scheme 1. The synthesis route of compounds 5–29.
OH
O
OH
(ii)
(i)
O
O
OH
Ar
Br
Br
O
2
3
1
O
O
O
(iv)
O
(iii)
O
O
N
N
OTs
5-27
4
(v)
R
O
O
O
N
28, 29
N
N
8, Ar =
9, Ar =
7, Ar =
5, Ar =
6, Ar =
N
O
O
F
13, Ar =
14, Ar =
O
12, Ar =
10, Ar =
11, Ar =
Cl
F
F
CN
18, Ar =
23, Ar =
28, R = H
19, Ar =
24, Ar =
17, Ar =
22, Ar =
27, Ar =
15, Ar =
20, Ar =
16, Ar =
21, Ar =
26, Ar =
F
F
O
Cl
Cl
Cl
Br
Cl
Cl
F3C
25, Ar =
O
29, R = OH
CF3
Reagents and conditions: (i) BH3.S(CH3)2, THF, 0 °C for 1 h, and room temperature for 10 h; (ii) sesamol,
K2CO3, CH3CN, reflux, 16 h; (iii) TsCl, Et3N and 4-dimethylaminopyridine, Cl2CH2, 0 °C, 16 h;
(iv) arylpiperazines, K2CO3, CH3CN, reflux, 16 h; (v) phenylpiperidines, K2CO3, CH3CN, reflux, 16 h.
2. Results and Discussion
2.1. Chemistry
As depicted in Scheme 1, a series of novel arylpiperazine derivatives were synthesized in four steps
starting from the commercially available 2-(4-(bromomethyl)phenyl)acetic acid (1). First, compound 1
was reduced to alcohol 2 in the presence of a borane–methyl sulfide complex (2 M in tetrahydrofuran)
at 0 °C for 1 h and then at room temperature for 10 h. The intermediate 2 was directly used without
further purification. The nucleophilic substitution reaction of compound 2 with sesamol in the presence
of potassium carbonate (K2CO3) gave compound 3 (67% yield from compound 1) after 16 h at reflux.
Compound 3 was treated with 4-toluenesulfonyl chloride in the presence of triethylamine and a

Molecules 2014, 19
12051
catalytic amount of 4-dimethylaminopyridine at 0 °C for 16 h to generate compound 4 (95% yield).
Finally, the reactions of compound 4 with various arylpiperazines or phenyl-piperidines in the
presence of K2CO3 at reflux for 16 h gave arylpiperazine or phenylpiperidine derivatives 5 to 29
(55% to 82% yield; Scheme 1). The structures of all the compounds (as their HCl salts) were
confirmed using 1H-NMR, 13C-NMR, and elemental analyses (C, H, and N).
2.2. Cytotoxic Activity
The synthesized target compounds 5 to 29 were evaluated for their in vitro cytotoxic activities
against the three human prostate cancer cell lines (PC-3, LNCaP, and DU145), and compared with
their effects on human prostate epithelial cell line RWPE-1 by CCK-8 assay [47–49]. The results are
summarized in Table 1.
Table 1. In vitro cytotoxicity of compounds 5–29.
IC50 (μM) a
Compd.
PC-3 b
>50
LNCaP b
27.85 ± 1.72
27.70 ± 4.17
31.22 ± 0.63
26.60 ± 0.86
3.47 ± 0.36
31.94 ± 0.89
>50
DU145 b
>50
RWPE-1 b
>50
5
6
>50
28.92 ± 0.98
>50
38.78 ± 0.77
41.05 ± 0.54
31.69 ± 3.14
31.01 ± 1.57
>50
7
>50
8
>50
8.25 ± 0.16
>50
9
>50
10
11
>50
47.75 ± 2.02
>50
>50
>50
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
naftopidil
>50
30.73 ± 0.83
28.27 ± 0.49
>50
>50
>50
>50
>50
>50
>50
>50
38.95 ± 0.77
41.01 ± 0.47
>50
>50
1.25 ± 0.23
32.47 ± 1.04
26.76 ± 1.00
13.11 ± 0.51
26.58 ± 0.40
>50
>50
>50
>50
>50
26.83 ± 0.92
>50
23.94 ± 0.75
>50
26.89 ± 1.00
>50
>50
29.85 ± 0.80
>50
>50
>50
>50
25.28 ± 1.55
39.41 ± 0.54
33.25 ± 2.69
19.85 ± 1.01
32.96 ± 0.21
26.83 ± 1.51
>50
>50
>50
>50
>50
>50
>50
>50
35.89 ± 1.25
>50
>50
>50
>50
>50
18.94 ± 3.68
>50
>50
>50
24.95 ± 0.68
>50
>50
26.79 ± 3.01
28.46 ± 2.18
19.73 ± 0.01
>50
18.21 ± 1.88
42.98 ± 7.58
22.36 ± 0.61
24.71 ± 2.22
38.23 ± 2.45
>50
42.10 ± 0.79
34.58 ± 0.31
a
b
IC50 values are taken as means ± standard deviation from three experiments; PC-3, LNCaP and DU145,
human prostate cancer cell line; RWPE-1, the human prostate epithelial cell line.

Molecules 2014, 19
12052
As shown in Table 1, some compounds exhibited moderate to strong cytotoxic activities against the
tested cancer cell lines, and even exhibited much better activity than naftopidil. For example,
compounds 9 and 15 exhibited strong cytotoxic activities against LNCaP cells (IC50 < 5 μM) and these
compounds showed excellent selective activity for LNCaP cells over the other tested cancer cells.
However, compounds 9 and 15 exhibited cytotoxic effects on normal RWPE-1 human epithelial
prostate cells. Moreover, compound 8 (IC50 = 8.25 μM) showed the most potent activity against
DU145 cells and a marked selectivity for DU145 cells over the other tested cancer cells.
The SAR analysis revealed the following: (1) phenylpiperazine derivative 5 exhibited similar
cytotoxic activities against LNCaP cells compared with benzylpiperazine derivative 6, however, these
activities decreased significantly in DU145 cells; (2) compound 8 exhibited a more effective cytotoxic
activity than compounds 5 and 7 against DU145 cells. These results suggest that the introduction of a
pyrimidinyl moiety at the 4-position of piperazine ring was beneficial for anti-cancer activity.
Moreover, compound 8 showed excellent selective activity for DU145 cells over the other tested
cancer cells; (3) compound 11 lost potency (IC50 > 50 μM) against LNCaP cells compared with
compounds 9 and 10 (IC50 = 3.47 and 31.94 μM, respectively). The activity profiles indicated that a
methyl at the m-position on the phenyl group was inauspicious for anti-cancer activity. A similar
potency profile was observed in compounds 12, 13, and 14; (4) Moreover, compounds containing an o-
methyl-substituted phenyl group showed better activity for LNCaP cells than did the p-methyl-
substituted group for LNCaP cells, as exemplified by compound 9 which showed significantly
improved activity, while compound 10 exhibited moderate cytotoxic activity. A similar potency profile
was also observed in compound 15 (IC50 = 1.25 μM) vs. 16 (IC50 = 32.47 μM), as well as 19
(IC50 = 26.58 μM) vs. 20 (IC50 > 50 μM); (5) Compared to compounds 16 and 24 (IC50 = 19.85 μM),
compound 20 (IC50 > 50 μM) lost potency against LNCaP cells. The obtained results suggested that a
chloro group in the p-position on the phenyl group was not favorable for anti-cancer activity; (6) Although
compounds 22 (IC50 = 39.41 μM), 23 (IC50 = 33.25 μM), 25 (IC50 = 32.96 μM), and 26 (IC50 = 26.83 μM)
demonstrated moderate cytotoxic activities against LNCaP cells, these compounds had improved
selectivity for LNCaP cells over the other cancer cells; (7) The compounds with methyl or fluoro
groups at the o-position on the phenyl group exhibited a relatively strong cytotoxicity against LNCaP
cells (IC50 < 5 μM); (8) Phenylpiperidine derivatives 28 and 29 (Scheme 1) were synthesized to
compare the anti-cancer activity of arylpiperazine derivatives. As shown in Table 1, compounds 28
and 29 exhibited moderate cytotoxic activities against LNCaP and DU145 cells. However, these
compounds also exhibited cytotoxic effect on human prostate epithelial cell line.
3. Experimental Section
3.1. General Information
Reagents and solvents were commercially available. Solvents were dried and purified prior to use
using standard procedures. Melting points were determined on a SGW X-4 micro melting point
apparatus (Shanghai Precision & Scientific Instrument Co., Ltd, Shanghai, China) and are uncorrected.
NMR spectra were determined on a Bruker AV-400 NB spectrometer (Faellanden, Switzerland)
in DMSO-d6 using TMS as internal standard, and coupling constants (J) are in Hz. EI mass spectra

Molecules 2014, 19
12053
were recorded on a DSQ mass spectrometer. Elemental analyses (C, H, N) were performed on an
Elementar Vario EL elemental analyzer and the analytical results were within ±0.4% of the theoretical
values for the formula given unless otherwise listed. Flash column chromatography was performed
with silica gel (300–400 mesh, Qing Dao Ocean Chemical Factory, Qingdao, China) eluted with
petroleum ether–ethyl acetate.
3.1.1. 2-(4-(Bromomethyl)phenyl)ethanol (2)
To a cooled (0 °C) solution of carboxylic acid 1 (5 g, 0.021 mol) in dry tetrahydrofuran (THF, 100 mL)
borane-dimethyl sulfide complex (21.9 mL, 0.042 mol, 2 M in THF) was added dropwise. The reaction
mixture was stirred at 0 °C for 1 h and at room temperature for 10 h. Water (20 mL) was added slowly
and extracted with ethyl acetate (3 × 100 mL). The combined organic phase was successively washed
with water, brine, dried over anhydrous magnesium sulfate, and concentrated in vacuo. The resulting
residue was directly used without further purification in the following step.
3.1.2. 2-(4-((Benzo[d][1,3]dioxol-5-yloxy)methyl)phenyl)ethanol (3)
To a solution of compound 2 (4 g, 18.7 mmol) in acetone (100 mL) sesamol (2.58 g, 18.7 mmol）
and potassium carbonate (10.32 g, 74.8 mmol) were added, and the reaction mixture was stirred at
reflux for 16 h. After cooling to ambient temperature, the reaction mixture was filtered through a
Buchner funnel. After filtration the filtrate was concentrated in vacuo and the residue was purified by
silica gel column chromatography using ethyl acetate/petroleum ether (1/10, v/v) as eluent to afford
4.06 g of compound 3 (67% from compound 1) as a white solid. m.p. 102–103 °C; 1H-NMR (400 MHz,
DMSO-d6) δ in ppm: 7.32 (d, J = 8.0 Hz, 2H, Ar-H), 7.22 (d, J = 8.0 Hz, 2H, Ar-H), 6.79 (d, J = 8.5 Hz,
1H, Ar-H), 6.68 (d, J = 2.5 Hz, 1H, Ar-H), 6.43 (dd, J = 8.5, 2.5 Hz, 1H, Ar-H), 5.94 (s, 2H, CH2), 4.97
(s, 2H, CH2), 4.60 (t, J = 5.2 Hz, 1H, OH), 3.60 (td, J = 7.0, 5.2 Hz, 2H, CH2), 2.72 (t, J = 7.0 Hz, 2H,
CH2); 13C-NMR (101 MHz, DMSO-d6) δ in ppm: 154.25, 148.34, 141.64, 139.65, 135.07, 129.33,
128.09, 108.46, 106.64, 101.42, 98.55, 70.39, 62.57; MS (EI, m/z): 272 (M+), 167, 149, 135 (100%),
117, 105, 97, 79.
3.1.3. 2-(4-((Benzo[d][1,3]dioxol-5-yloxy)methyl)phenyl)ethyl 4-methylbenzenesulfonate (4)
To a solution of compound 3 (4 g, 14.7 mmol), triethylamine (5.94 g, 58.8 mmol) and
4-dimethyl- aminopyridine (0.18 g, 1.47 mmol) in dry dichloromethane (CH2Cl2, 100 mL) at 0 °C was
added dropwise a solution of 4-toluenesulfonyl chloride (4.19 g, 22.1 mmol) in CH2Cl2 (10 mL). The
reaction mixture was stirred at 0 °C for 16 h. Water (20 mL) was added slowly and the reaction
mixture was extracted with CH2Cl2 (3 × 100 mL). The combined organic phase was successively
washed with water and brine, dried over anhydrous magnesium sulfate, and concentrated in vacuo.
The residue was purified by silica gel column chromatography using ethyl acetate/petroleum ether
(1/15, v/v) as eluent to afford 5.76 g (95%) of compound 4 as a white solid. m.p. 90–91 °C; 1H-NMR
(400 MHz, DMSO-d6) δ in ppm: 7.65 (d, J = 8.0 Hz, 2H, Ar-H), 7.40 (d, J = 8.0 Hz, 2H, Ar-H), 7.30 (d,
J = 8.0 Hz, 2H, Ar-H), 7.15 (d, J = 8.0 Hz, 2H, Ar-H), 6.80 (d, J = 8.5 Hz, 1H, Ar-H), 6.69 (d, J = 2.5 Hz,
1H, Ar-H), 6.44 (dd, J = 8.5, 2.5 Hz, 1H, Ar-H), 5.95 (s, 2H, CH2), 4.98 (s, 2H, CH2), 4.23 (t, J = 6.4 Hz,

Molecules 2014, 19
12054
2H, CH2), 2.89 (t, J = 6.4 Hz, 2H, CH2), 2.40 (s, 3H, CH3); 13C-NMR (101 MHz, DMSO-d6) δ in ppm:
154.22, 148.36, 145.23, 141.68, 136.78, 135.90, 132.78, 130.52, 129.28, 128.21, 127.89, 108.47,
106.64, 101.44, 98.55, 71.43, 70.27, 34.55, 21.53; MS (EI, m/z): 426 (M+), 289, 254, 155, 137, 117
(100%), 104, 91.
3.1.4. General Procedure for the Preparation of Compounds 5–29
To a solution of 4 (100 mg, 0.23 mmol) in acetonitrile (CH3CN, 10 mL) was added the
corresponding arylpiperazine or phenylpiperidine (1.2 equiv) and potassium carbonate (6.0 equiv). The
reaction mixture was stirred at reflux for 16 h. After cooling to ambient temperature, the reaction
mixture was filtered through a Buchner funnel. After filtration the filtrate was concentrated in vacuo
and the residue was purified by silica gel column chromatography using ethyl acetate/petroleum ether
(1/5, v/v) as eluent to afford the corresponding products, and all compounds were recrystallized from
trichloromethane and n-hexane.
1-(2-(4-((Benzo[d][1,3]dioxol-5-yloxy)methyl)phenyl)ethyl)-4-phenylpiperazine (5). Yield: 65%, m.p.
195–196 °C (HCl salt); 1H-NMR (400 MHz, DMSO-d6) δ in ppm: 11.51 (s, 1H, N+H), 7.40 (d, J = 8.0 Hz,
2H, Ar-H), 7.30 (d, J = 8.0 Hz, 2H, Ar-H), 7.27 (dd, J = 8.0, 7.3 Hz, 2H, Ar-H), 7.02 (d, J = 8.0 Hz, 2H,
Ar-H), 6.87 (t, J = 7.3 Hz, 1H, Ar-H ), 6.80 (d, J = 8.5 Hz, 1H, Ar-H), 6.68 (d, J = 2.5 Hz, 1H,
Ar-H), 6.43 (dd, J = 8.5, 2.5 Hz, 1H, Ar-H), 5.95 (s, 2H, CH2), 5.00 (s, 2H, CH2), 3.82 (d, J = 10.4 Hz,
2H, CH2), 3.62 (d, J = 10.4 Hz, 2H, CH2), 3.40–3.09 (m, 8H, CH2); 13C-NMR (101 MHz, DMSO-d6) δ
in ppm: 154.07, 149.87, 148.26, 141.60, 137.07, 136.08, 129.49, 129.09, 128.40, 120.45, 116.40,
108.38, 106.61, 101.36, 98.49, 70.13, 56.36, 50.92, 45.80, 29.33; Anal. Calc. for C26H28N2O3·2HCl: C,
63.80; H, 6.18; N, 5.72. Found: C, 63.64; H, 6.12; N, 5.58.
1-(2-(4-((Benzo[d][1,3]dioxol-5-yloxy)methyl)phenyl)ethyl)-4-benzylpiperazine (6). Yield: 80%, m.p.
177–178 °C (HCl salt); 1H-NMR (400 MHz, DMSO-d6) δ in ppm: 12.00 (s, 1H, N+H), 7.71–7.42 (m,
5H, Ar-H), 7.39 (d, J = 8.0 Hz, 2H, Ar-H), 7.30 (d, J = 8.0 Hz, 2H, Ar-H), 6.80 (d, J = 8.5 Hz, 1H,
Ar-H), 6.68 (d, J = 2.5 Hz, 1H, Ar-H), 6.43 (dd, J = 8.5, 2.5 Hz, 1H, Ar-H), 5.95 (s, 2H, CH2), 5.00
(s, 2H, CH2), 4.34 (s, 2H, CH2), 3.94–2.93 (m, 12H, CH2); Anal. Calc. for C27H30N2O3·2HCl: C, 64.41;
H, 6.41; N, 5.56. Found: C, 63.98; H, 6.45; N, 5.31.
1-(2-(4-((Benzo[d][1,3]dioxol-5-yloxy)methyl)phenyl)ethyl)-4-(pyridin-2-yl)piperazine (7). Yield: 70%,
m.p. 185–186 °C (HCl salt); 1H-NMR (400 MHz, DMSO-d6) δ in ppm: 11.92 (s, 1H, N+H), 8.13 (dd,
J = 5.6, 1.2 Hz, 1H, pyridine H), 7.96 (t, J = 7.6 Hz, 1H, pyridine H), 7.41–7.30 (m, 5H, Ar-H and
pyridine H ), 6.98 (t, J = 6.4 Hz, 1H, pyridine H), 6.80 (d, J = 8.5 Hz, 1H, Ar-H), 6.69 (d, J = 2.5 Hz,
1H, Ar-H), 6.44 (dd, J = 8.5, 2.5 Hz, 1H, Ar-H), 5.95 (s, 2H, CH2), 5.00 (s, 2H, CH2), 4.54 (d, J = 10.6 Hz,
2H, CH2), 3.78–3.09 (m, 10H, CH2); 13C-NMR (101 MHz, DMSO-d6) δ in ppm: 154.16, 148.35,
141.69, 137.09, 136.19, 129.17, 128.50, 114.40, 108.47, 106.69, 101.45, 98.58, 70.22, 56.47, 50.38,
43.40, 40.66, 29.38; Anal. Calc. for C25H27N3O3·2.8HCl: C, 57.79; H, 5.78; N, 8.09. Found: C, 57.78;
H, 6.06; N, 7.86.

Molecules 2014, 19
12055
2-(4-(2-(4-((Benzo[d][1,3]dioxol-5-yloxy)methyl)phenyl)ethyl)piperazin-1-yl)pyrimidine (8). Yield: 65%,
1
m.p. 181–182 °C (HCl salt); H-NMR (400 MHz, DMSO-d6) δ in ppm: 11.36 (s, 1H, N+H), 8.45 (d,
J = 4.4 Hz, 2H, pyrimidine H), 7.39 (d, J = 7.5 Hz, 2H, Ar-H), 7.29 (d, J = 7.5 Hz, 2H, Ar-H),
6.85–6.37 (m, 4H, Ar-H and pyrimidine H), 5.94 (s, 2H, CH2), 5.00 (s, 2H, CH2), 4.70 (d, J = 11.4 Hz,
2H, CH2), 3.64–3.05 (m, 10H, CH2); 13C-NMR (101 MHz, DMSO-d6) δ in ppm: 161.07, 158.61,
154.14, 145.81, 141.68, 137.02, 136.20, 129.16, 128.49, 111.79, 108.46, 106.69, 101.45, 98.57, 70.20,
56.59, 50.85, 29.41; Anal. Calc. for C24H26N4O3·1.5HCl: C, 60.92; H, 5.86; N, 11.84. Found: C, 60.67;
H, 5.98; N, 11.61.
1-(2-(4-((Benzo[d][1,3]dioxol-5-yloxy)methyl)phenyl)ethyl)-4-o-tolylpiperazine (9). Yield: 80%, m.p.
202–203 °C (HCl salt); 1H-NMR (400 MHz, DMSO-d6) δ in ppm: 11.16 (s, 1H, N+H), 7.42 (d, J = 8.1 Hz,
2H, Ar-H), 7.32 (d, J = 8.1 Hz, 2H, Ar-H), 7.10 (m, 4H, Ar-H), 6.81 (d, J = 8.5 Hz, 1H, Ar-H), 6.69 (d,
J = 2.5 Hz, 1H, Ar-H), 6.44 (dd, J = 8.5, 2.5 Hz, 1H, Ar-H), 5.96 (s, 2H, CH2), 5.01 (s, 2H, CH2), 3.62
(d, J = 10.9 Hz, 2H, CH2), 3.43–3.08 (m, 10H, CH2), 2.28 (s, 3H, CH3); 13C-NMR (101 MHz, DMSO-d6)
δ in ppm: 155.55, 151.59, 149.74, 143.08, 138.51, 137.58, 133.84, 132.86, 130.58, 129.89, 128.55,
125.62, 120.84, 109.85, 108.08, 102.83, 99.96, 71.59, 57.99, 53.31, 50.02, 30.88, 19.26; Anal. Calc.
for C27H30N2O3·2HCl: C, 64.41; H, 6.41; N, 5.56. Found: 64.63; H, 6.45; N, 5.44.
1-(2-(4-((Benzo[d][1,3]dioxol-5-yloxy)methyl)phenyl)ethyl)-4-p-tolylpiperazine (10). Yield: 70%, m.p.
184–185 °C (HCl salt); 1H-NMR (400 MHz, DMSO-d6) δ in ppm: 11.30 (s, 1H, N+H), 7.40 (d, J = 8.0 Hz,
2H, Ar-H), 7.30 (d, J = 8.0 Hz, 2H, Ar-H), 7.08 (d, J = 8.3 Hz, 2H, Ar-H), 6.92 (d, J = 8.3 Hz, 2H, Ar-H),
6.79 (d, J = 8.5 Hz, 1H, Ar-H), 6.68 (d, J = 2.5 Hz, 1H, Ar-H), 6.43 (dd, J = 8.5, 2.5 Hz, 1H, Ar-H),
5.94 (s, 2H, CH2), 5.00 (s, 2H, CH2), 3.75 (d, J = 9.2 Hz, 2H, CH2), 3.62 (d, J = 9.2 Hz, 2H, CH2),
3.40–3.07 (m, 8H, CH2), 2.22 (s, 3H, CH3); 13C-NMR (101 MHz, DMSO-d6) δ in ppm: 154.15, 148.34,
147.73, 141.69, 137.12, 136.17, 130.02, 129.62, 129.18, 128.49, 116.79, 108.47, 106.71, 101.45, 98.58,
70.22, 56.48, 51.05, 46.41, 29.44, 20.51; Anal. Calc. for C27H30N2O3·2HCl: C, 64.41; H, 6.41; N, 5.56.
Found: C, 64.40; H, 6.43; N, 5.36.
1-(2-(4-((Benzo[d][1,3]dioxol-5-yloxy)methyl)phenyl)ethyl)-4-m-tolylpiperazine (11). Yield: 82%, m.p.
171–172 °C (HCl salt); 1H-NMR (400 MHz, DMSO-d6) δ in ppm: 11.61 (s, 1H, N+H), 7.40 (d, J = 8.0 Hz,
2H, Ar-H), 7.30 (d, J = 8.0 Hz, 2H, Ar-H), 7.15 (t, J = 7.6 Hz, 1H, Ar-H), 6.93–6.62 (m, 5H,
Ar-H), 6.43 (dd, J = 8.5, 2.5 Hz, 1H, Ar-H), 5.95 (s, 2H, CH2), 5.00 (s, 2H, CH2), 3.80 (d, J = 11.2 Hz,
2H, CH2), 3.62 (d, J = 11.2 Hz, 2H, CH2), 3.41–3.06 (m, 8H, CH2), 2.27 (s, 3H, CH3); 13C-NMR
(101 MHz, DMSO-d6) δ in ppm: 154.17, 149.89, 148.35, 141.69, 138.78, 137.18, 136.15, 129.42, 129.17,
128.49, 121.45, 117.19, 113.80, 108.47, 106.70, 101.45, 98.58, 70.23, 56.45, 50.97, 46.01, 29.41, 21.80;
Anal. Calc. for C27H30N2O3·2HCl: C, 64.41; H, 6.41; N, 5.56. Found: C, 64.54; H, 6.44; N, 5.44.
1-(2-(4-((Benzo[d][1,3]dioxol-5-yloxy)methyl)phenyl)ethyl)-4-(2-methoxyphenyl)piperazine (12). Yield:
75%, m.p. 173–174 °C (HCl salt); 1H-NMR (400 MHz, DMSO-d6) δ in ppm: 11.50 (s, 1H, N+H), 7.40
(d, J = 8.0 Hz, 2H, Ar-H), 7.31 (d, J = 8.0 Hz, 2H, Ar-H), 7.07–6.88 (m, 4H, Ar-H), 6.80 (d, J = 8.5 Hz,
1H, Ar-H), 6.69 (d, J = 2.5 Hz, 1H, Ar-H), 6.43 (dd, J = 8.5, 2.5 Hz, 1H, Ar-H), 5.95 (s, 2H, CH2),
5.01 (s, 2H, CH2), 3.80 (s, 3H, OCH3), 3.62 (d, J = 10.8 Hz, 2H, CH2), 3.51 (d, J = 10.8 Hz, 2H, CH2),
13
3.39–3.10 (m, 8H, CH2); C-NMR (101 MHz, DMSO-d6) δ in ppm: 154.16, 152.31, 148.35, 141.69,

Molecules 2014, 19
12056
139.69, 137.17, 136.17, 129.18, 128.49, 124.06, 121.33, 118.80, 112.50, 108.47, 106.70, 101.45, 98.58,
70.22, 56.62, 55.88, 51.52, 47.36, 29.43; Anal. Calc. for C27H30N2O4·2HCl: C, 62.43; H, 6.21; N, 5.39.
Found: C, 62.37; H, 6.19; N, 5.25.
1-(2-(4-((Benzo[d][1,3]dioxol-5-yloxy)methyl)phenyl)ethyl)-4-(4-methoxyphenyl)piperazine (13). Yield:
70%, m.p. 174–175 °C (HCl salt); 1H-NMR (400 MHz, DMSO-d6) δ in ppm: 11.62 (s, 1H, N+H), 7.40
(d, J = 8.0 Hz, 2H, Ar-H), 7.31 (d, J = 8.0 Hz, 2H, Ar-H), 7.05 (d, J = 9.0 Hz, 2H, Ar-H), 6.89 (d,
J = 9.0 Hz, 2H, Ar-H), 6.80 (d, J = 8.5 Hz, 1H, Ar-H), 6.68 (d, J = 2.5 Hz, 1H, Ar-H), 6.43 (dd, J = 8.5,
2.5 Hz, 1H, Ar-H), 5.95 (s, 2H, CH2), 5.00 (s, 2H, CH2), 3.71 (s, 3H, OCH3), 3.66 (t, J = 9.0 Hz, 4H,
13
CH2), 3.40–3.10 (m, 8H, CH2); C-NMR (101 MHz, DMSO-d6) δ in ppm: 154.30, 153.66, 147.84,
142.69, 141.19, 136.63, 135.66, 128.68, 127.98, 118.48, 114.47, 107.96, 106.19, 100.95, 98.08, 69.72,
55.88, 55.25, 50.41, 47.06, 28.93; Anal. Calc. for C27H30N2O4·1.9HCl: C, 62.87; H, 6.23; N, 5.43.
Found: C, 62.90; H, 6.20; N, 5.25.
1-(2-(4-((Benzo[d][1,3]dioxol-5-yloxy)methyl)phenyl)ethyl)-4-(3-methoxyphenyl)piperazine (14). Yield:
72%, m.p. 171–172 °C (HCl salt); 1H-NMR (400 MHz, DMSO-d6) δ in ppm: 11.56 (s, 1H, N+H), 7.40
(d, J = 8.0 Hz, 2H, Ar-H), 7.30 (d, J = 8.0 Hz, 2H, Ar-H), 7.17 (t, J = 8.0 Hz, 1H, Ar-H), 6.80 (d,
J = 8.4 Hz, 1H, Ar-H), 6.69 (d, J = 2.4 Hz, 1H, Ar-H), 6.60 (dd, J = 8.4, 2.0 Hz, 1H, Ar-H), 6.55 (t,
J = 2.0 Hz, 1H, Ar-H), 6.50–6.37 (m, 2H, Ar-H), 5.95 (s, 2H, CH2), 5.00 (s, 2H, CH2), 3.83 (d,
J = 11.2 Hz, 2H, CH2), 3.74 (s, 3H, OCH3), 3.61 (d, J = 11.2 Hz, 2H, CH2), 3.41–3.06 (m, 8H, CH2);
13C-NMR (101 MHz, DMSO-d6) δ in ppm: 160.46, 153.86, 151.00, 148.05, 141.39, 136.88, 135.86,
130.03, 128.87, 128.19, 108.60, 108.17, 106.40, 105.53, 102.39, 101.15, 98.28, 69.93, 56.15, 55.18,
50.65, 45.51, 29.11; Anal. Calc. for C27H30N2O4·2HCl: C, 62.43; H, 6.21; N, 5.39. Found: C, 62.41; H,
6.19; N, 5.27.
1-(2-(4-((Benzo[d][1,3]dioxol-5-yloxy)methyl)phenyl)ethyl)-4-(2-fluorophenyl)piperazine (15). Yield:
65%, m.p. 187–188 °C (HCl salt); 1H-NMR (400 MHz, DMSO-d6) δ in ppm: 11.46 (s, 1H, N+H), 7.40
(d, J = 8.0 Hz, 2H, Ar-H), 7.30 (d, J = 8.0 Hz, 2H, Ar-H), 7.23–6.96 (m, 4H, Ar-H), 6.79 (d, J = 8.5 Hz, 1H,
Ar-H), 6.68 (d, J = 2.5 Hz, 1H, Ar-H), 6.43 (dd, J = 8.5, 2.5 Hz, 1H, Ar-H), 5.94 (s, 2H, CH2), 5.00 (s,
2H, CH2), 3.63 (d, J = 9.7 Hz, 2H, CH2), 3.50 (d, J = 9.7 Hz, 2H, CH2), 3.42–3.09 (m, 8H, CH2);
13C-NMR (101 MHz, DMSO-d6) δ in ppm: 156.27, 153.89, 148.08, 141.42, 138.50, 138.42, 136.83,
135.91, 128.91, 128.22, 125.18, 125.16, 123.65, 123.58, 119.80, 116.44, 116.24, 108.20, 106.44,
101.18, 98.31, 69.95, 56.31, 51.05, 47.16, 29.13; Anal. Calc. for C26H27FN2O3·2HCl: C, 61.54; H, 5.76;
N, 5.52. Found: C, 61.38; H, 5.56; N, 5.33.
1-(2-(4-((Benzo[d][1,3]dioxol-5-yloxy)methyl)phenyl)ethyl)-4-(4-fluorophenyl)piperazine (16). Yield:
60%, m.p. 196–197 °C (HCl salt); 1H-NMR (400 MHz, DMSO-d6) δ in ppm: 11.55 (s, 1H, N+H), 7.40
(d, J = 7.9 Hz, 2H, Ar-H), 7.30 (d, J = 7.9 Hz, 2H, Ar-H), 7.15–7.00 (m, 4H, Ar-H), 6.79 (d, J = 8.5 Hz,
1H, Ar-H), 6.68 (d, J = 2.5 Hz, 1H, Ar-H), 6.43 (dd, J = 8.5, 2.5 Hz, 1H, Ar-H), 5.94 (s, 2H, CH2),
5.00 (s, 2H, CH2), 3.74 (d, J = 8.8 Hz, 2H, CH2), 3.62 (d, J = 8.8 Hz, 2H, CH2), 3.40–3.08 (m, 8H,
CH2); 13C-NMR (101 MHz, DMSO-d6) δ in ppm: 157.75, 155.40, 153.64, 147.83, 146.32, 141.17,
136.65, 135.64, 128.65, 127.97, 117.90, 117.82, 115.55, 115.33, 107.95, 106.18, 100.94, 98.06, 69.71,

Molecules 2014, 19
12057
55.90, 50.51, 46.07, 28.90; Anal. Calc. for C26H27FN2O3·1.9HCl: C, 61.99; H, 5.78; N, 5.56. Found: C,
62.02; H, 5.77; N, 5.41.
1-(2-(4-((Benzo[d][1,3]dioxol-5-yloxy)methyl)phenyl)ethyl)-4-(2,4-difluorophenyl)piperazine (17). Yield:
67%, m.p. 169–170 °C (HCl salt); 1H-NMR (400 MHz, DMSO-d6) δ in ppm: 11.42 (s, 1H, N+H), 7.40
(d, J = 8.0 Hz, 2H, Ar-H), 7.30 (d, J = 8.0 Hz, 2H, Ar-H), 7.28–7.00 (m, 3H, Ar-H), 6.80 (d, J = 8.5 Hz,
1H, Ar-H), 6.68 (d, J = 2.5 Hz, 1H, Ar-H), 6.43 (dd, J = 8.5, 2.5 Hz, 1H, Ar-H), 5.95 (s, 2H, CH2),
5.00 (s, 2H, CH2), 3.63 (d, J = 8.6 Hz, 2H, CH2), 3.43 (d, J = 8.6 Hz, 2H, CH2), 3.40–3.09 (m, 8H,
CH2); 13C-NMR (101 MHz, DMSO-d6) δ in ppm: 158.98, 158.93, 158.86, 156.58, 156.47, 156.24,
156.12, 153.84, 148.04, 141.38, 136.77, 135.88, 135.37, 135.34, 135.28, 135.25, 128.86, 128.18,
120.82, 120.80, 120.74, 120.70, 111.50, 111.47, 111.28, 111.26, 108.15, 106.38, 105.24, 104.98,
104.73, 101.14, 98.26, 69.90, 56.23, 51.03, 47.44, 29.10; Anal. Calc. for C26H26F2N2O3·1.25HCl: C,
62.70; H, 5.51; N, 5.62. Found: C, 62.85; H, 5.61; N, 5.42.
4-(4-(2-(4-((Benzo[d][1,3]dioxol-5-yloxy)methyl)phenyl)ethyl)piperazin-1-yl)-3-fluorobenzonitrile (18).
1
Yield: 75%, m.p. 182–183 °C (HCl salt); H-NMR (400 MHz, DMSO-d6) δ in ppm: 11.54 (s, 1H,
N+H), 7.77 (dd, J = 13.1, 1.2 Hz, 1H, Ar-H), 7.63 (dd, J = 8.4, 1.2 Hz, 1H, Ar-H), 7.40 (d, J = 8.0 Hz,
2H, Ar-H), 7.30 (d, J = 8.0 Hz, 2H, Ar-H), 7.25 (t, J = 8.4 Hz, 1H, Ar-H), 6.80 (d, J = 8.5 Hz, 1H,
Ar-H), 6.68 (d, J = 2.5 Hz, 1H, Ar-H), 6.43 (dd, J = 8.5, 2.5 Hz, 1H, Ar-H), 5.95 (s, 2H, CH2), 5.00 (s,
2H, CH2), 3.72 (d, J = 12.0 Hz, 2H, CH2), 3.64 (d, J = 12.0 Hz, 2H, CH2), 3.45–3.09 (m, 8H, CH2);
13C-NMR (101 MHz, DMSO-d6) δ in ppm: 154.39, 153.64, 151.94, 147.83, 142.35, 141.17, 136.53,
135.68, 129.90, 128.65, 127.98, 120.02, 119.92, 119.77, 118.07, 107.95, 106.17, 103.59, 100.94, 98.06,
69.69, 56.02, 50.43, 46.10, 28.88; Anal. Calc. for C27H26FN3O3·1HCl: C, 65.38; H, 5.49; N, 8.47.
Found: C, 65.12; H, 5.45; N, 8.24.
1-(2-(4-((Benzo[d][1,3]dioxol-5-yloxy)methyl)phenyl)ethyl)-4-(2-chlorophenyl)piperazine (19). Yield:
78%, m.p. 176–177 °C (HCl salt); 1H-NMR (400 MHz, DMSO-d6) δ in ppm: 11.27 (s, 1H, N+H), 7.46
(dd, J = 8.0, 1.6 Hz, 1H, Ar-H), 7.41 (d, J = 8.0 Hz, 2H, Ar-H), 7.35 (td, J = 8.0, 1.6 Hz, 1H, Ar-H),
7.31 (d, J = 8.0 Hz, 2H, Ar-H), 7.23 (dd, J = 8.0, 1.2 Hz, 1H, Ar-H), 7.12 (td, J = 8.0, 1.2 Hz, 1H,
Ar-H), 6.80 (d, J = 8.5 Hz, 1H, Ar-H), 6.69 (d, J = 2.5 Hz, 1H, Ar-H), 6.43 (dd, J = 8.5, 2.5 Hz, 1H,
Ar-H), 5.95 (s, 2H, CH2), 5.01 (s, 2H, CH2), 3.66 (d, J = 8.4 Hz, 2H, CH2), 3.44 (d, J = 8.4 Hz, 2H,
13
CH2), 3.41–3.08 (m, 8H, CH2); C-NMR (101 MHz, DMSO-d6) δ in ppm: 154.16, 148.35, 147.88,
141.70, 137.08, 136.20, 130.93, 129.20, 128.72, 128.50, 128.04, 125.29, 121.52, 108.47, 106.70,
101.46, 98.58, 70.22, 56.59, 51.66, 48.15, 29.51; Anal. Calc. for C26H27ClN2O3·1.25HCl: C, 62.89; H,
5.73; N, 5.64. Found: C, 62.95; H, 5.70; N, 5.47.
1-(2-(4-((Benzo[d][1,3]dioxol-5-yloxy)methyl)phenyl)ethyl)-4-(4-chlorophenyl)piperazine (20). Yield:
70%, m.p. 164–165 °C (HCl salt); 1H-NMR (400 MHz, DMSO-d6) δ in ppm: 11.64 (s, 1H, N+H), 7.40
(d, J = 8.0 Hz, 2H, Ar-H), 7.33–7.26 (m, 4H, Ar-H), 7.03 (d, J = 9.0 Hz, 2H, Ar-H), 6.80 (d, J = 8.5 Hz,
1H, Ar-H), 6.69 (d, J = 2.5 Hz, 1H, Ar-H), 6.43 (dd, J = 8.5, 2.5 Hz, 1H, Ar-H), 5.95 (s, 2H, CH2),
5.00 (s, 2H, CH2), 3.83 (d, J = 11.4 Hz, 2H, CH2), 3.62 (d, J = 11.4 Hz, 2H, CH2), 3.40–3.09 (m, 8H,
CH2); 13C-NMR (101 MHz, DMSO-d6) δ in ppm: 153.66, 148.37, 147.84, 141.19, 136.66, 135.65,

Molecules 2014, 19
12058
128.76, 128.66, 127.98, 123.52, 117.47, 107.96, 106.19, 100.95, 98.08, 69.72, 55.91, 50.33, 45.16,
28.89; Anal. Calc. for C26H27ClN2O3·2HCl: C, 59.61; H, 5.58; N, 5.35. Found: C, 59.66; H, 5.59; N, 5.19.
1-(2-(4-((Benzo[d][1,3]dioxol-5-yloxy)methyl)phenyl)ethyl)-4-(3-chlorophenyl)piperazine (21). Yield:
65%, m.p. 177–178 °C (HCl salt); 1H-NMR (400 MHz, DMSO-d6) δ in ppm: 11.60 (s, 1H, N+H), 7.40
(d, J = 8.0 Hz, 2H, Ar-H), 7.30 (d, J = 8.0 Hz, 2H, Ar-H), 7.25 (t, J = 8.4 Hz, 1H, Ar-H), 7.06 (t,
J = 2.4 Hz, 1H, Ar-H), 6.97 (dd, J = 8.4, 2.4 Hz, 1H, Ar-H), 6.87 (dd, J = 7.6, 1.2 Hz, 1H, Ar-H), 6.80
(d, J = 8.5 Hz, 1H, Ar-H), 6.68 (d, J = 2.5 Hz, 1H, Ar-H), 6.43 (dd, J = 8.5, 2.5 Hz, 1H, Ar-H), 5.95 (s,
2H, CH2), 5.00 (s, 2H, CH2), 3.90 (d, J = 11.6 Hz, 2H, CH2), 3.60 (d, J = 11.6 Hz, 2H, CH2), 3.40–3.07
(m, 8H, CH2); 13C-NMR (101 MHz, DMSO-d6) δ in ppm: 154.16, 151.27, 148.35, 141.69, 137.16,
136.16, 134.42, 131.08, 129.17, 128.49, 119.66, 115.76, 114.64, 108.47, 106.70, 101.45, 98.58, 70.22,
56.42, 50.77, 45.31, 29.40; Anal. Calc. for C26H27ClN2O3·2HCl: C, 59.61; H, 5.58; N, 5.35. Found: C,
59.55; H, 5.58; N, 5.18.
1-(2-(4-((Benzo[d][1,3]dioxol-5-yloxy)methyl)phenyl)ethyl)-4-(2,3-dichlorophenyl)piperazine
(22).
1
Yield: 60%, m.p. 177–178 °C (HCl salt). H-NMR (400 MHz, DMSO-d6) δ in ppm: 10.78 (s, 1H,
N+H), 7.41–7.30 (m, 6H, Ar-H), 7.22 (dd, J = 7.2, 2.8 Hz, 1H, Ar-H), 6.79 (d, J = 8.5 Hz, 1H, Ar-H),
6.68 (d, J = 2.5 Hz, 1H, Ar-H), 6.43 (dd, J = 8.5, 2.5 Hz, 1H, Ar-H), 5.94 (s, 2H, CH2), 5.00 (s, 2H,
CH2), 3.66 (d, J = 10.0 Hz, 2H, CH2), 3.27–3.04 (m, 10H, CH2); 13C-NMR (101 MHz, DMSO-d6) δ in
ppm: 155.53, 151.34, 149.73, 143.08, 140.49, 137.62, 134.60, 130.60, 130.50, 129.89, 127.95, 127.19,
121.74, 109.86, 108.09, 102.83, 99.95, 71.58, 57.99, 53.07, 49.66, 30.95; Anal. Calc. for
C26H26Cl2N2O3·1HCl: C, 59.84; H, 5.21; N, 5.37. Found: C, 60.04; H, 5.27; N, 5.16.
1-(2-(4-((Benzo[d][1,3]dioxol-5-yloxy)methyl)phenyl)ethyl)-4-(5-chloro-2-methoxyphenyl)piperazine
(23). Yield: 65%, m.p. 177–178 °C (HCl salt); 1H-NMR (400 MHz, DMSO-d6) δ in ppm: 11.46 (s, 1H,
N+H), 7.40 (d, J = 8.0 Hz, 2H, Ar-H), 7.30 (d, J = 8.0 Hz, 2H, Ar-H), 7.05 (dd, J = 8.7, 2.4 Hz, 1H, Ar-H),
6.99 (d, J = 8.7 Hz, 1H, Ar-H), 6.94 (d, J = 2.4 Hz, 1H, Ar-H), 6.80 (d, J = 8.5 Hz, 1H, Ar-H), 6.68 (d,
J = 2.5 Hz, 1H, Ar-H), 6.43 (dd, J = 8.5, 2.5 Hz, 1H, Ar-H), 5.95 (s, 2H, CH2), 5.00 (s, 2H, CH2), 3.80
(s, 3H, OCH3), 3.60 (d, J = 10.8 Hz, 2H, CH2), 3.55 (d, J = 10.8 Hz, 2H, CH2), 3.39–3.08 (m, 8H,
CH2); 13C-NMR (101 MHz, DMSO-d6) δ in ppm: 154.16, 151.12, 148.35, 141.69, 141.14, 137.14,
136.18, 129.18, 128.49, 124.99, 122.98, 118.68, 113.74, 108.47, 106.70, 101.45, 98.58, 70.22, 56.55,
56.27, 51.37, 47.01, 29.43; Anal. Calc. for C27H29ClN2O4·1.8HCl: C, 59.33; H, 5.68; N, 5.12. Found: C,
59.26; H, 5.79; N, 4.87.
1-(2-(4-((Benzo[d][1,3]dioxol-5-yloxy)methyl)phenyl)ethyl)-4-(4-bromophenyl)piperazine (24). Yield:
1
72%, m.p. 173–174 °C (HCl salt); H-NMR (400 MHz, DMSO-d6) δ in ppm: 11.62 (s, 1H, N+H),
7.43–7.35 (m, 4H, Ar-H), 7.29 (d, J = 8.0 Hz, 2H, Ar-H), 6.97 (d, J = 9.0 Hz, 2H, Ar-H), 6.79 (d,
J = 8.5 Hz, 1H, Ar-H), 6.67 (d, J = 2.5 Hz, 1H, Ar-H), 6.42 (dd, J = 8.5, 2.5 Hz, 1H, Ar-H), 5.94 (s, 2H,
CH2), 4.99 (s, 2H, CH2), 3.82 (d, J = 11.3 Hz, 2H, CH2), 3.60 (d, J = 11.3 Hz, 2H, CH2), 3.38–3.07 (m,
8H, CH2); 13C-NMR (101 MHz, DMSO-d6) δ in ppm: 154.16, 149.23, 148.35, 141.69, 137.17, 136.16,
132.14, 129.17, 128.49, 118.40, 111.72, 108.47, 106.70, 101.45, 98.58, 70.22, 56.42, 50.79, 45.53,
29.40; Anal. Calc. for C26H27BrN2O3·2HCl: C, 54.95; H, 5.14; N, 4.93. Found: C, 54.93; H, 5.15; N, 4.76.

Molecules 2014, 19
12059
1-(2-(4-((Benzo[d][1,3]dioxol-5-yloxy)methyl)phenyl)ethyl)-4-(2-(trifluoromethyl)phenyl)piperazine (25).
1
Yield: 75%, m.p. 171–172 °C (HCl salt); H-NMR (400 MHz, DMSO-d6) δ in ppm: 11.35 (s, 1H,
N+H), 7.60–7.56 (m, 6H, Ar-H), 7.31 (d, J = 8.0 Hz, 2H, Ar-H), 6.80 (d, J = 8.5 Hz, 1H, Ar-H), 6.69 (d,
J = 2.5 Hz, 1H, Ar-H), 6.43 (dd, J = 8.5, 2.5 Hz, 1H, Ar-H), 5.95 (s, 2H, CH2), 5.01 (s, 2H, CH2), 3.63
13
(d, J = 11.2 Hz, 2H, CH2), 3.45–3.34 (m, 4H, CH2), 3.23–3.07 (m, 6H, CH2); C-NMR (101 MHz,
DMSO-d6) δ in ppm: 154.17, 150.95, 148.35, 141.69, 137.11, 136.18, 134.37, 129.21, 128.49, 127.59,
127.54, 126.58, 124.91, 108.47, 106.70, 101.45, 98.58, 70.22, 56.49, 51.95, 50.22, 29.55; Anal. Calc.
for C27H27F3N2O3·1HCl: C, 62.25; H, 5.42; N, 5.38. Found: C, 62.41; H, 5.40; N, 5.24.
1-(2-(4-((Benzo[d][1,3]dioxol-5-yloxy)methyl)phenyl)ethyl)-4-(4-(trifluoromethyl)phenyl)piperazine (26).
1
Yield: 55%, m.p. 176–177 °C (HCl salt); H-NMR (400 MHz, DMSO-d6) δ in ppm: 11.45 (s, 1H,
N+H), 7.57 (d, J = 8.8 Hz, 2H, Ar-H), 7.40 (d, J = 8.0 Hz, 2H, Ar-H), 7.30 (d, J = 8.0 Hz, 2H, Ar-H),
7.17 (d, J = 8.8 Hz, 2H, Ar-H), 6.80 (d, J = 8.5 Hz, 1H, Ar-H), 6.69 (d, J = 2.5 Hz, 1H, Ar-H), 6.43 (dd,
J = 8.5, 2.5 Hz, 1H, Ar-H), 5.95 (s, 2H, CH2), 5.00 (s, 2H, CH2), 4.03 (d, J = 11.6 Hz, 2H, CH2), 3.64
(d, J = 11.6 Hz, 2H, CH2), 3.43–3.06 (m, 8H, CH2); 13C-NMR (101 MHz, DMSO-d6) δ in ppm: 153.64,
151.95, 147.83, 141.18, 136.60, 135.66, 128.66, 127.98, 126.28, 114.88, 107.95, 106.18, 100.94, 98.06,
69.70, 55.94, 50.19, 44.21, 28.93; Anal. Calc. for C27H27F3N2O3·1.25HCl: C, 61.18; H, 5.37; N, 5.28.
Found: C, 61.49; H, 5.42; N, 5.19.
1-(4-(4-(2-(4-((Benzo[d][1,3]dioxol-5-yloxy)methyl)phenyl)ethyl)piperazin-1-yl)phenyl)ethanone (27).
1
Yield: 60%, m.p. 183–184 °C (HCl salt); H-NMR (400 MHz, DMSO-d6) δ in ppm: 11.22 (s, 1H,
N+H), 7.86 (d, J = 8.8 Hz, 2H, Ar-H), 7.40 (d, J = 8.0 Hz, 2H, Ar-H), 7.30 (d, J = 8.0 Hz, 2H, Ar-H),
7.08 (d, J = 8.8 Hz, 2H, Ar-H), 6.80 (d, J = 8.5 Hz, 1H, Ar-H), 6.68 (d, J = 2.5 Hz, 1H, Ar-H), 6.43 (dd,
J = 8.5, 2.5 Hz, 1H, Ar-H), 5.95 (s, 2H, CH2), 5.00 (s, 2H, CH2), 4.09 (d, J = 11.6 Hz, 2H, CH2), 3.64
(d, J = 11.6 Hz, 2H, CH2), 3.36–3.10 (m, 8H, CH2), 2.48 (s, 3H, CH3); 13C-NMR (101 MHz, DMSO-d6)
δ in ppm: 195.72, 153.63, 152.54, 147.82, 141.17, 136.52, 135.67, 130.00, 128.65, 127.97, 127.78,
113.87, 107.94, 106.17, 100.93, 98.05, 69.68, 55.94, 50.25, 43.92, 28.94, 26.13; Anal. Calc. for
C28H30N2O4·1.5HCl: C, 65.52; H, 6.19; N, 5.46. Found: C, 65.78; H, 6.47; N, 5.31.
1-(2-(4-((Benzo[d][1,3]dioxol-5-yloxy)methyl)phenyl)ethyl)-4-phenylpiperidine (28). Yield: 75%, m.p.
183–184 °C (HCl salt); 1H-NMR (400 MHz, DMSO-d6) δ in ppm: 11.04 (s, 1H, N+H), 7.59–7.08 (m,
9H, Ar-H), 6.80 (d, J = 8.5 Hz, 1H, Ar-H), 6.69 (d, J = 2.5 Hz, 1H, Ar-H), 6.44 (dd, J = 8.5, 2.5 Hz, 1H,
Ar-H), 5.95 (s, 2H, CH2), 5.01 (s, 2H, CH2), 3.64 (d, J = 11.6 Hz, 2H, CH2), 3.30–3.00 (m, 6H, CH2),
13
2.90–2.78 (m, 1H, CH), 2.10–2.08 (m, 4H, CH2); C-NMR (101 MHz, DMSO-d6) δ in ppm: 153.85,
148.04, 144.41, 141.38, 136.98, 135.83, 128.86, 128.70, 128.18, 126.71, 108.16, 106.39, 101.14, 98.27,
69.91, 56.73, 52.08, 29.93, 29.26; Anal. Calc. for C27H29NO3·1HCl: C, 71.75; H, 6.69; N, 3.10. Found:
C, 71.25; H, 6.69; N, 2.98.
1-(2-(4-((Benzo[d][1,3]dioxol-5-yloxy)methyl)phenyl)ethyl)-4-phenylpiperidin-4-ol (29). Yield: 80%,
m.p. 194–195 °C (HCl salt); 1H-NMR (400 MHz, DMSO-d6) δ in ppm: 11.11 (s, 1H, N+H), 7.55–7.20
(m, 9H, Ar-H), 6.80 (d, J = 8.5 Hz, 1H, Ar-H), 6.69 (d, J = 2.5 Hz, 1H, Ar-H), 6.43 (dd, J = 8.5, 2.5 Hz,
1H, Ar-H), 5.95 (s, 2H, CH2), 5.47 (s, 1H, OH), 5.00 (s, 2H, CH2), 3.49 (d, J = 11.0 Hz, 2H, CH2),
13
3.43–3.06 (m, 8H, CH2), 1.82 (d, J = 11.0 Hz, 2H, CH2); C-NMR (101 MHz, DMSO-d6) δ in ppm:

Molecules 2014, 19
12060
153.65, 147.88, 147.83, 141.17, 136.77, 135.61, 128.67, 128.03, 127.95, 126.77, 124.51, 107.95,
106.18, 100.93, 98.07, 69.71, 68.00, 56.32, 48.25, 34.96, 29.17; Anal. Calc. for C27H29NO4·1HCl: C,
69.29; H, 6.46; N, 2.99. Found: C, 69.20; H, 6.45; N, 2.85.
3.2. In Vitro Cytotoxic Assay
3.2.1. Cell Culture
PC-3 and RWPE-1 cells were cultured in Dulbecco’s modification Eagle’s medium (DMEM,
Invitrogen, Carlsbad, CA, USA) supplemented with 10% fetal bovine serum (FBS, Hyclone, Logan,
UT, USA), 100 U/mL penicillin and 0.1 mg/mL streptomycin (Invitrogen). DU145 cells were cultured
in RPMI1640 media supplemented with 10% fetal bovine serum (FBS, Hyclone), 100 U/mL penicillin
and 0.1 mg/mL streptomycin (Invitrogen). LNCaP cells were cultured in F12 media supplemented with
10% fetal bovine serum (FBS, Hyclone), 100 U/mL penicillin and 0.1 mg/mL streptomycin
(Invitrogen). The cells were incubated at 37 °C in a humidified atmosphere with 5% CO2.
3.2.2. Assessment of Antitumor Activity by CCK-8 Assay
Cell proliferation was measured with the Cell Counting Kit-8 (CCK-8) assay kit (Dojindo Corp.,
Kumamoto, Japan). Cells were harvested during logarithmic growth phase and seeded in 96-well plates
at a density of 1 × 105 cells/mL, and cultured at 37 °C in a humidified incubator (5% CO2) for 24 h,
followed by exposure to various concentrations of compounds tested for 24 h. Subsequently 10 μL of
CCK-8 (Dojindo) was added to each well, the cells were then incubated for an additional 1 h at 37 °C
to convert WST-8 into formazan. Cell growth inhibition was determined by measuring the absorbance
(Abs) at λ = 450 nm using amicroplate reader. Three independent experiments were performed. Cell
growth inhibition was calculated according to the following equation:
Growth inhibition = (1 − OD of treated cells/OD of control cells) × 100%
The half maximal inhibitory concentrations (IC50) were obtained from linear regression analysis of
the concentration-response curves plotted for each tested compound.
4. Conclusions
In summary, this study reported the synthesis and biological evaluation against three human
prostate cancer cells and human prostate epithelial cells of a novel class of arylpiperazine derivatives.
The results showed that the majority of the compounds exhibited excellent selective activity for
LNCaP cells over the other tested cancer cells. The compounds with methyl (9) or fluoro (15) groups
at the o-position on the phenyl group demonstrated a relatively strong cytotoxicity against LNCaP cells.
It would be of interest to develop arylpiperazine derivatives for the treatment of the corresponding
tumors. Designing more efficient derivatives from arylpiperazines based on the current study may
successfully lead to the development of a potent anti-cancer agent. Further research involving other
class of arylpiperazine derivatives, and preparation of analogs with aryl groups instead of a
1,3-benzodioxolyl group are in progress.

Molecules 2014, 19
12061
Acknowledgments
The project was supported by the Technological Innovation Project of Colleges and Universities in
Guangdong Province (No. cx2d1127), the China Postdoctoral Science Foundation (Nos. 2013M542165
and 2013M531837), the National Science Foundation of Guangdong Province (No. S2013040014088)
and the Guangzhou Postdoctoral Scientific Research Foundation (Nos. Q130 and Q074).
Author Contributions
Conceived and designed the experiments: Mu Yuan, Hong Chen and Xue Liang. Hong Chen, Xue Liang,
Fang Xu, Bingbing Xu, Biyun Huang, and Xuelan He performed most experiments. Hong Chen and
Xue Liang wrote the paper. Mu Yuan read and approved the final manuscript.
Conflicts of Interest
The authors declare no conflict of interest.
References
1. Greenlee, R.T.; Murray, T.; Hill-Harmon, M.B.; Thun, M.J. Cancer statistics, 2001. CA: Cancer
J. Clin. 2001, 51, 15–36.
2. Quinn, M.; Babb, P. Patterns and trends in prostate cancer incidence, survival, prevalence and
mortality. Part I: International comparisons. BJU Int. 2002, 90, 162–173.
3. Gronberg, H. Prostate cancer epidemiology. Lancet 2003, 361, 859–864.
4. American Cancer Society. Cancer Facts & Figures 2003; American Cancer Society: Atlanta, GA,
USA, 2003.
5. Steinberg, G.D.; Carter, B.S.; Beaty, T.H.; Childs, B.; Walsh, P.C. Family history and the risk of
prostate cancer. Prostate 1990, 17, 337–347.
6. Bratt, O. Hereditary prostate cancer: Clinical aspects. J. Urol. 2002, 168, 906–913.
7. Whittemore, A.; Kolonel, L.N.; Wu, A.H.; John, E.M.; Gallagher, R.P.; Howe, G.R.; Burch, J.D.;
Hankin, J.; Dreon, D.M.; West, D.W. Prostate cancer in relation to diet, physical activity, and body
size in blacks, whites, and Asians in the United States and Canada. J. Natl. Cancer Inst. 1995, 87,
652–661.
8. Isaacs, J.T. Role of androgens in prostatic cancer. Vitam. Horm. 1994, 49, 433–502.
9. Frydenberg, M.; Stricker, P.D.; Kaye, K.W. Prostate cancer diagnosis and management. Lancet
1997, 349, 1681–1687.
10. Akduman, B.; Crawford, E.D. The management of high risk prostate cancer. J. Urol. 2003, 169,
1993–1998.
11. Huggins, C.; Hodges, C.V. Studies on prostatic cancer. I. The effect of castration, of estrogen and
of androgen injection on serum phosphatases in metastatic carcinoma of the prostate. 1941.
J. Urol. 2002, 167, 948–951.
12. Beedassy, A.; Cardi, G. Chemotherapy in advanced prostate cancer. Semin. Oncol. 1999, 26, 428–438.
13. Denmeade, S.R.; Lin, X.S.; Isaacs, J.T. Role of programmed (apoptotic) cell death during the
progression and therapy for prostate cancer. Prostate 1996, 28, 251–265.

Molecules 2014, 19
12062
14. Tang, D.G.; Porter, A.T. Target to apoptosis: A hopeful weapon for prostate cancer. Prostate 1997,
32, 284–293.
15. Craft, N.; Chhor, C.; Tran, C.; Belldegrun, A.; DeKernion, J.; Witte, O.N.; Said, J.; Reiter, R.E.;
Sawyers, C.L. Evidence for clonal outgrowth of androgen-independent prostate cancer cells from
androgen-dependent tumors through a two-step process. Cancer Res. 1999, 59, 5030–5036.
16. Szkaradek, N.; Rapacz, A.; Pytka, K.; Filipek, B.; Siwek, A.; Cegła, M.; Marona, H. Synthesis and
preliminary evaluation of pharmacological properties of some piperazine derivatives of xanthone.
Bioorg. Med. Chem. 2013, 21, 514–522.
17. Cecchetti, V.; Fravolini, A.; Schiaffella, F.; Tabarrini, O.; Bruni, G.; Segret, G.
o-Chlorobenzenesulfonamidic derivatives of (aryloxy)propanolamines as beta-blocking/diuretic
agents. J. Med. Chem. 1993, 36, 157–161.
18. Walsh, D.A.; Chen, Y.H.; Green, J.B.; Nolan, J.C.; Yannit, J.M. The synthesis and antiallergy
activity of 1-(aryloxy)-4-(4-arylpiperazinyl)-2-butanol derivatives. J. Med. Chem. 1990, 33,
1823–1827.
19. Seo, H.J.; Park, E.J.; Kim, M.J.; Kang, S.Y.; Lee, S.H.; Kim, H.J.; Lee, K.N.; Jung, M.E.; Lee, M.;
Kim, M.S.; et al. Design and synthesis of novel arylpiperazine derivatives containing the imidazole
core targeting 5-HT(2A) receptor and 5-HT transporter. J. Med. Chem. 2011, 54, 6305–6318.
20. Kikumoto, R.; Tobe, A.; Fukami, H.; Egawa, M. Synthesis and antianxiety activity of
(omega-piperazinylalkoxy)indan derivatives. J. Med. Chem. 1983, 26, 246–250.
21. Jaen, J.C.; Wise, L.D.; Heffner, T.G.; Pugsley, T.A.; Meltzed, L.T. Dopamine autoreceptor agonists
as potential antipsychotics. 1. (Aminoalkoxy)anilines. J. Med. Chem. 1988, 31, 1621–1625.
22. Cross, R.M.; Namelikonda, N.K.; Mutka, T.S.; Luong, L.; Kyle, D.E.; Manetsch, R. Synthesis,
antimalarial activity, and structure-activity relationship of 7-(2-phenoxyethoxy)-4(1H)-quinolones.
J. Med. Chem. 2011, 54, 8321–8327.
23. Clarkson, C.; Musonda, C.C.; Chibale, K.; Campbella, W.E.; Smitha, P. Synthesis of totarol amino
alcohol derivatives and their antiplasmodial activity and cytotoxicity. Bioorg. Med. Chem. 2003,
11, 4417–4422.
24. Leopoldo, M.; Lacivita, E.; Passafiume, E.; Contino, M.; Colabufo, N.A.; Berardi, F.; Perrone, R.
4-[omega-[4-arylpiperazin-1-yl]alkoxy]phenyl)imidazo[1,2-a]pyridine derivatives: Fluorescent
high-affinity dopamine D3 receptor ligands as potential probes for receptor visualization.
J. Med. Chem. 2007, 50, 5043–5047.
25. Chen, X.; Sassano, M.F.; Zheng, L.Y.; Setola, V.; Chen, M.; Bai, X.; Frye, S.V.; Wetsel, W.C.;
Roth, B.L.; Jin, J. Structure-functional selectivity relationship studies of β-arrestin-biased
dopamine D₂ receptor agonists. J. Med. Chem. 2012, 55, 7141–7153.
26. Romeiro, L.A.; da Silva Ferreira, M.; da Silva, L.L.; Castro, H.C.; Miranda, A.L.; Silva, C.L.;
Noël, F.; Nascimento, J.B.; Araújo, C.V.; Tibiriçá, E.; et al. Discovery of LASSBio-772, a
1,3-benzodioxole N-phenylpiperazine derivative with potent alpha 1A/D-adrenergic receptor
blocking properties. Eur. J. Med. Chem. 2011, 46, 3000–3012.
27. Baran, M.; Kepczynska, E.; Zylewski, M.; Siwek, A.; Bednarski, M.; Cegla, M.T. Studies on
novel pyridine and 2-pyridone derivatives of N-arylpiperazine as α-adrenoceptor ligands. Med. Chem.
2014, 10, 144–153.

Molecules 2014, 19
12063
28. Dellabella, M.; Milanese, G.; Muzzonigro, G. Efficacy of tamsulosin in the medical management
of juxtavesical ureteral stones. J. Urol. 2003, 170, 2202–2205.
29. Morita, T.; Wada, I.; Saeki, H.; Tsuchida, S.; Weiss, R.M. Ureteral urine transport: Changes in
bolus volume, peristaltic frequency, intraluminal pressure and volume of flow resulting from
autonomic drugs. J. Urol. 1987, 137, 132–135.
30. Takei, R.; Ikegaki, I.; Shibata, K.; Tsujimoto, G.; Asano, T. Naftopidil, a novel alpha1-adrenoceptor
antagonist, displays selective inhibition of canine prostatic pressure and high affinity binding to
cloned human alpha1-adrenoceptors. Jpn. J. Pharmacol. 1999, 79, 447–454.
31. Nishino, Y.; Masue, T.; Miwa, K.; Takahashi, Y.; Ishihara, S.; Deguchi, T. Comparison of
two alpha1-adrenoceptor antagonists, naftopidil and tamsulosin hydrochloride, in the treatment of
lower urinary tract symptoms with benign prostatic hyperplasia: A randomized crossover study.
BJU Int. 2006, 97, 747–751.
32. Kojima, Y.; Sasaki, S.; Kubota, Y.; Hayase, M.; Hayashi, Y.; Shinoura, H.; Tsujimoto, G.; Kohri, K.
Expression of alpha1-adrenoceptor subtype mRNA as a predictor of the efficacy of subtype
selective alpha1-adrenoceptor antagonists in the management of benign prostatic hyperplasia.
J. Urol. 2008, 179, 1040–1046.
33. Hori, Y.; Ishii, K.; Kanda, H.; Iwamoto, Y.; Nishikawa, K.; Soga, N.; Kise, H.; Arima, K.;
Sugimura, Y. Naftopidil, a selective {alpha}1-adrenoceptor antagonist, suppresses human prostate
tumor growth by altering interactions between tumor cells and stroma. Cancer Prev. Res (Phila).
2011, 4, 87–96.
34. Kanda, H.; Ishii, K.; Ogura, Y.; Imamura, T.; Kanai, M.; Arima, K.; Sugimura, Y. Naftopidil, a
selective alpha-1 adrenoceptor antagonist, inhibits growth of human prostate cancer cells by G1
cell cycle arrest. Int. J. Cancer 2008, 122, 444–451.
35. Gotoh, A.; Nagaya, H.; Kanno, T.; Nishizaki, T. Antitumor action of α(1)-adrenoceptor blockers
on human bladder, prostate and renal cancer cells. Pharmacology 2012, 90, 242–246.
36. Masachika, E.; Kanno, T.; Nakano, T.; Gotoh, A.; Nishizaki, T. Naftopidil induces apoptosis in
malignant mesothelioma cell lines independently of α1-adrenoceptor blocking. Anticancer Res.
2013, 33, 887–894.
37. Li, S.; Chiu, G.; Pulito, V.L.; Liu, J.; Connolly, P.J.; Middleton, S.A. 1-Arylpiperazinyl-4-
cyclohexylamine derived isoindole-1,3-diones as potent and selective alpha-1a/1d adrenergic
receptor ligands. Bioorg. Med. Chem. Lett. 2007, 17, 1646–1650.
38. Chiu, G.; Li, S.; Connolly, P.J.; Pulito, V.; Liu, J.; Middleton, S.A. (Arylpiperazinyl)cyclo-
hexylsufonamides: Discovery of alpha(1a/1d)-selective adrenergic receptor antagonists for the
treatment of Benign Prostatic Hyperplasia/Lower Urinary Tract Symptoms (BPH/LUTS).
Bioorg. Med. Chem. Lett. 2007, 17, 3292–3297.
39. Kuo, G.H.; Prouty, C.; Murray, W.V.; Pulito, V.; Jolliffe, L.; Cheung, P.; Varga, S.; Evangelisto, M.;
Shaw, C. Design, synthesis and biological evaluation of pyridine-phenylpiperazines: A novel
series of potent and selective alpha1a-adrenergic receptor antagonist. Bioorg. Med. Chem. 2000, 8,
2263–2275.
40. Khatuya, H.; Hutchings, R.H.; Kuo, G.H.; Pulito, V.L.; Jolliffe, L.K.; Li, X.; Murray, W.V.
Arylpiperazine substituted heterocycles as selective alpha(1a) adrenergic antagonists. Bioorg. Med.
Chem. Lett. 2002, 12, 2443–2446.

Molecules 2014, 19
12064
41. Konkel, M.J.; Wetzel, J.M.; Cahir, M.; Craig, D.A.; Noble, S.A.; Gluchowski, C. Synthesis and
structure-activity relationship of fluoro analogues of 8-{2-[4-(4-methoxyphenyl)piperazin-
1yl]ethyl}-8-azaspiro[4.5]decane-7,9-dione as selective alpha(1d)-adrenergic receptor antagonists.
J. Med. Chem. 2005, 48, 3076–3079.
42. Romeo, G.; Materia, L.; Modica, M.N.; Pittalà, V.; Salerno, L.; Siracusa, M.A.; Manetti, F.; Botta, M.;
Minneman, K.P. Novel 4-phenylpiperidine-2,6-dione derivatives. Ligands for α₁-adrenoceptor
subtypes. Eur. J. Med. Chem. 2011, 46, 2676–2690.
43. Huang, J.J.; Huang, Y.J.; Zhu, L.; Yuan, M. Design, synthesis and α1-adrenoreceptor blocking
activity of new arylpiperazines containing acetophenone substituents. Pharmazie 2014, 69, 1–7.
44. Liu, X.W.; Zhang, Y.Y.; Yuan, M.; Sun, Y.X. Determination of naftopidil enantiomers in rat
plasma using chiral solid phases and pre-column derivatization high-performance liquid
chromatography. J. Chromatogr. B 2012, 907, 140–145.
45. Zhao, X.; Chen, M.S.; Huang, B.Y.; Ji, H.; Yuan, M. Comparative Molecular Field Analysis
(CoMFA) and Comparative Molecular Similarity Indices Analysis (CoMSIA) studies on
α(1A)-adrenergic receptor antagonists based on pharmacophore molecular alignment. Int. J. Mol. Sci.
2011, 12, 7022–7037.
46. Zhao, X.; Yuan, M.; Huang, B.Y.; Ji, H.; Zhu, L. Ligand-based pharmacophore model of N-Aryl
and N-Heteroaryl piperazine alpha 1A-adrenoceptors antagonists using GALAHAD. J. Mol.
Graph. Model. 2010, 29, 126–136.
47. Kaspers, G.J.; Veerman, A.J.; Pieters, R.; van Zantwijk, C.H.; Smets, L.A.; van Wering, E.R.;
van der Does-Van Den Berg, A. In vitro cellular drug resistance and prognosis in newly diagnosed
childhood acute lymphoblastic leukemia. Blood 1997, 90, 2723–2729.
48. Kaspers, G.J.; Pieters, R.; van Zantwijk, C.H.; VanWering, E.R.; van der Does-Van Den Berg, A.;
Veerman, A.J. Prednisolone resistance in childhood acute lymphoblastic leukemia: Vitro-vivo
correlations and cross-resistance to other drugs. Blood 1998, 92, 259–266.
49. Ding, J.; Huang, S.L.; Wu, S.Q.; Zhao, Y.J.; Liang, L.H.; Yan, M.X.; Ge, C.; Yao, J.; Chen, T.Y.;
Wan, D.F.; et al. Gain of miR-151 on chromosome 8q24.3 facilitates tumour cell migration and
spreading through downregulating RhoGDIA. Nat. Cell Biol. 2010, 12, 390–399.
Sample Availability: Samples of the compounds are available from the authors.
© 2014 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article
distributed under the terms and conditions of the Creative Commons Attribution license
(http://creativecommons.org/licenses/by/3.0/).