Design, synthesis, and preliminary bioactivity evaluation of N-benzylpyrimidin-2-amine derivatives as novel histone deacetylase inhibitor

Article abstract of DOI:10.1111/cbdd.13019

Histone deacetylase (HDAC) inhibitors have been identified for the treatment of cancer. Lately, we designed and synthesized a series of substituted N-benzylpyrimidin-2-amine derivatives as potent HDAC inhibitors. In vitro HDAC inhibitory activities and an

Full text of DOI:10.1111/cbdd.13019

PROF. HAO FANG (Orcid ID : 0000-0002-2879-5146)
Article type
: Research Article
Design, synthesis and preliminary bioactivity evaluation of N-benzylpyrimidin-2-amine derivatives
as novel histone deacetylase (HDAC) inhibitor
†
†
Yi Zhou 1, , Yanyan Dun 1, , Huansheng Fu 1, Lei Wang 1, Xiaole Pan 1, Xinying Yang 1, Hao Fang1,*
1 Department of Medicinal Chemistry, Key Laboratory of Chemical Biology (Ministry of Education), School of
Pharmacy, Shandong University, Ji’nan, Shandong 250012, PR China
*Address correspondence to this author:
Prof. Hao Fang, Department of Medicinal Chemistry, School of Pharmacy, Shandong University, 44 West
Wenhua Road, Jinan, PR China.
E-mail: haofangcn@sdu.edu.cn
Tel. 86-531-88382019
Fax. 86-531-88382548
†Author Contributions:
†Y.Z. and Y.D. contributed equally.
Abstract: Histone deacetylase inhibitors have been identified for the treatment of cancer. Lately, we
designed and synthesized a series of substituted N-benzylpyrimidin-2-amine derivatives as potent HDAC
inhibitors. In vitro HDAC inhibitory activities and anti-proliferative activities of target compounds were
investigated. Some target compounds showed potent HDAC inhibitory activities and possessed obvious
anti-proliferative activity against tumor cells. Target compounds 6a, 6d, 8a, 8c and 8f not only exhibited
almost equally enzymatic inhibitory activity with SAHA, but showed better anti-proliferative activities.
Keyword: Histone deacetylase, Inhibitor, Anticancer, Tumor
Histone deacetylases (HDACs) have emerged as validated drug targets for treatment of cancers and other
diseases during past decade.1 As a family of epigenetic enzymes, HDACs are responsible for regulation of
gene expression by catalyzing deacetylation of N-acetyl lysine residues of histones and non-histone
proteins.2 High level of HDACs with concomitant down-regulation and/or mutations of histone
acetyltransferases (HATs) may associate with a condensed chromatin structure. This would prevent the
access of transcription factors to DNA during gene expression (e.g., tumor repressor genes), which results
This article has been accepted for publication and undergone full peer review but has not
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doi: 10.1111/cbdd.13019
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in cancer cells survival and progression.3 Currently, inhibition of HDACs has been identified for efficient
anticancer pathway on broad spectrum neoplasms in preclinical and clinical studies.4 Up to this time, there
are four HDAC inhibitors, Vorinostat (SAHA), Romidepsin (FK-228), Belinostat (PXD-101) and
Panobinostat (LBH-589), approved by FDA for the treatment of cutaneous T-cell lymphoma (CTCL),
peripheral T-cell lymphoma (PTCL) or multiple myeloma (MM).5-8 (Fig. 1)
Fig. 1 HDACs inhibitors pharmacophore model and approved agents
The common pharmacophore of HDAC inhibitors has been identified as four parts: a zinc-binding group
(ZBG), a hydrophobic linker, a polar connection unit (CU) and a surface recognition cap group (cap).3 (Fig.
1) Our group has already developed different kinds of novel potent HDAC inhibitors with hydroxamic acid
as ZBG according to the common pharmacophore model.9-14 And based on the common pharmacophore, a
novel series of N-benzylpyrimidin-2-amine hydroxamic acid derivatives has been designed. (Fig. 2)
Synthesis and preliminary biological evaluation of these substituted N-benzylpyrimidin-2-amine analogs
are reported in this article.
Fig. 2 Design of novel N-benzylpyrimidin-2-amine derivatives
1. EXPERIMENTAL SECTION
1.1 Chemistry
All reagents and solvents were commercially available as well as analytically pure if not mentioned and
used without further purifications. All reactions were monitored by thin-layer chromatography (TLC) on
0.25 mm silica gel plates (GF-254). UV light, ferric chloride solution and iodine vaporization were used as
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visualization method. Melting points were measured in open capillaries and by RY-1 electrothermal
melting point apparatus. High-resolution mass spectra (HRMS) were conducted on an Agilent 6510
Quadrupole Time-of-Flight LC/MS deliver. All chemical shifts (in ppm) are reported relative to
tetramethylsilane as internal standard for solutions in DMSO-d6 or CDCl3 as the solvents. 1H and 13C NMR
spectra were recorded on a Brucker DRX spectrometer at 300 MHz or 400 MHz, d in parts per million and
J in hertz, using TMS as an internal standard. Significant 1H NMR data are reported in the following order:
multiplicity (s, singlet; d, doublet; t, triplet; m, multiplet) number of protons.
1.1.1 Procedure for the preparation of 2a
(E)-3-(dimethylamino)-1-(4-methoxyphenyl)prop-2-en-1-one (2a)
1-(4-methoxyphenyl)ethan-1-one (1a, 6.0 g, 20 mmol) was heated to 120°C in
1,1-dimethoxy-N,N-dimethylmethanamine (30.0 mL) for 7 h. After cooled to room temperature, the
reaction solution was diluted with ethyl acetate, washed three times by saturated sodium chloride solution
and then vacuum distillated to give crude product. Use flash chromatography for purification (PE:EA = 1:4)
to obtain 2a (9.09 g, yield: 55%).
1.1.2 General procedure for the preparation of 2b – 2h
(E)-3-(dimethylamino)-1-(5-methylfuran-2-yl)prop-2-en-1-one (2b)
The mixture of 1-(5-methylfuran-2-yl)ethan-1-one (1b, 2.5 mL, 20 mmol) and 1,1-dimethoxy-
N,N-dimethylmethanamine (8 mL) was heated to 115 °C for 12 h. After cooled to room temperature,
precipitate was filtrated and washed by ethyl acetate. Orange solid (3.25 g, yield 91%) was obtained after
drying up.
Compound 2c-2h were synthesized from 1c-1h in the same way to 2b.
1.1.3 General procedure for the preparation of 3a – 3g
4-(4-methoxyphenyl)-2-(methylthio)pyrimidine (3a)
The mixture of thiourea (3.04 g, 40 mmol), 20 mL EtOH, NaOH (1.6 g, 40 mmol) and 2a (4.1 g, 20 mmol)
was heated and refluxed for 24 h. After cooled to room temperature, solution was vacuum distillated to
give crude product. Dissolve solid in water and use 2 M HCl to adjust pH to 7. After filtration and
three-time washing, yellowish solid (3.88 g, 91%) was obtained. The yellow solid was then dissolved in
dimethyl sulfoxide and K2CO3 (2.74 g, 19.8 mmol), MeI (1.23 mL, 19.8 mmol) were added. After
overnight reacting under room temperature, solution was quenched by 50 mL water and filtered to give
crude product. Yellow solid 3a (3.49 g, 91%) was obtained after silica gel column chromatography.
Compound 3b-3g were synthesized from 2b-2g in the same way to 3a
1.1.4 General procedure for the preparation of 4a – 4h and 7a – 7f
Methyl 4-(((4-(5-methylfuran-2-yl)pyrimidin-2-yl)amino)methyl)benzoate (4b)
3b (0.54g, 2.6 mmol) was dissolved in 20 mL acetonitrile/water (1/1) and reacted with potassium hydrogen
peroxymonosulfate (1.6g, 5.2 mmol) on room temperature overnight. Reacting solution was vacuum
distillated and saturated sodium bicarbonate solution was added. Extract by ethyl acetate and vacuum
distillate organic layer to give crude intermediate. The mixture of the intermediate, 10 mL DMF, K2CO3
(0.31 g, 2.2 mmol) and methyl 4-(aminomethyl)benzoate (0.55 g, 3.3 mmol) was heated to 110 °C. After
10 h, reacting solution was quenched by water. After filtration and silica gel chromatography, orange solid
(4b, 0.24 g, yield: 28%) was obtained.
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Compound 4a-4f were synthesized from 3b-3g in the same way to 4b; synthesis of 4g and 4h from 3d and
3a was similar to 4b, only methyl 4-(aminomethyl)benzoate was changed to methyl
4-(hydroxymethyl)benzoate.
Compound 7a-7f were synthesized from 3a-3f in the same way to 4b, only methyl
4-(aminomethyl)benzoate was changed to methyl (E)-3-(4-(aminomethyl)phenyl)acrylate; synthesis of 7g
and 7h was similar to 4b, only methyl 4-(aminomethyl)benzoate was changed to methyl
(E)-3-(4-(hydroxymethyl)phenyl)acrylate.
1.1.5 General procedure for the preparation of 5a – 5e and 9a – 9c
Methyl 4-(((4-(5-methylfuran-2-yl)pyrimidin-2-yl)thio)methyl)benzoate (5c)
Thiourea (2.60 g, 34.2 mmol) was dissolved in 20 mL ethanol. NaOH (1.37 g, 34.2 mmol) and 1b (3.07 g,
17.1 mmol) were added. The mixture was heated to 90 °C and stirred for 24 h. After cooled to room
temperature, solvent was evaporated and solid was re-dissolved by water. Add hydrochloric acid to adjust
pH to 7, filter and wash three times by water. Yellow solid intermediate (2.80 g, 85.0%) was obtained after
drying. The mixture of this intermediate (0.55 g, 2.9 mmol), K2CO3 (0.48 g, 3.4 mmol), methyl
4-(bromomethyl)benzoate (0.66 g, 2.9 mmol) and acetone were heated to reflux for 12 h. Evaporate
solvent and white solid 5c (0.77 g, 79%) was obtained after column chromatography.
5a-5e and 9a-9c were synthesized in the same way to 5c.
1.1.6 General procedure for the preparation of 10a and 10b
Ethyl (E)-3-(4-((4-(5-methylfuran-2-yl)pyrimidin-2-yl)amino)phenyl)acrylate (10b)
The mixture of 2b (0.72 g, 4 mmol), 2-methoxyethanol (5 mL), Et3N (1.2 g, 12 mmol) and
methyl-3-(4-guanidinophenyl)acrylate (0.66 g, 3 mmol) were heated to 120 °C for 2 d. After cooled to
room temperature and diluted by dichloromethane, the reaction solution was washed by saturated brine and
dried by magnesium sulfate. Yellow solid 10b (0.09 g, yield: 7%) was obtained after filtration, evaporation
and column chromatography.
10a was synthesized from 2a in the same way to 10b
1.1.7 Procedure for the preparation of 10c
Methyl (E)-3-(4-((4-(furan-2-yl)pyrimidin-2-yl)amino)phenyl)acrylate (10c)
The mixture of 2c (0.66 g, 4 mmol), 2-methoxyethanol (3 mL), Et3N (1.2 g, 12 mmol) and
methyl-3-(4-guanidinophenyl)acrylate (0.66 g, 3 mmol) were heated to 130 °C for 2.5 h by microwave
reactor. After cooled to room temperature and diluted by dichloromethane, the reaction solution was
washed by saturated sodium chloride and dried by magnesium sulfate. Yellow solid 10c (0.17 g, yield:
18%) was obtained after filtration, evaporation and column chromatography.
1.1.8 General procedure for the preparation of 6a – 6m, 8a – 8k and 11a – 11c
N-hydroxy-4-(((4-(5-methylfuran-2-yl)pyrimidin-2-yl)amino)methyl)benzamide (6b)
Solution A was prepared by dissolution of hydroxylamine hydrochloride (4.67 g, 67 mmol) in methanol
(24 ml). Potassium hydroxide (6.60 g, 100 mmol) was diluted in methanol (14 ml) to develop solution B,
which was added dropwise to the solution A at 0 °C. The reaction mixture was stirred for 30 min at 0 °C
and filtered to give the solution C free hydroxylamine in methanol. 5b (0.20 g, 0.6 mmol) and 10 mL
solution C were stirred for 1 h. Solution was evaporated, diluted with little water and adjusted to pH 6 with
hydrochloric acid. After filtration and silica column chromatography, 6b (0.14g, 70%) was obtained.
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6a-6m were synthesis from 4a-4h and 5a-5e in the same way to 6b; 8a-8k were synthesized in the same
way to 6b from 7a-7h and 9a-9c. 11b-11c were synthesized in the same way to 6b from 10a-10c.
1.2 In vitro HDAC assay
1.2.1 HeLa nuclear extract
The HDAC inhibitory activities of all the final products and the positive control drug SAHA was evaluated
by the Color de LysTM assay (BMLAK501, EnzoTM Life Sciences). According to the HDAC kit instruction,
HeLa cell nucleus extracts (mainly HDAC1&2), Color de Lys substrate and compounds to be tested
(including SAHA) were diluted to needed concentrations. First, HeLa cell nucleus extracts (15 μL/well)
o
were incubated with different concentrations of tested compounds (10 μL/well) at 37 C for 5 min in the
o
96-well plate. Then substrate (25 μL/well) was added and the mixture was incubating at 37 C for 30 min.
At last, the mixture of Color de Lys Developer and TSA (50 μL/well) was added and incubated for 30 min,
the absorption was measured on a microplate reader at 405 nm. The inhibition ratios were calculated from
the absorption of inhibited wells and control ones. A regression analysis method between the concentration
and inhibition rate was used to obtain the IC50 values.
1.2.2 HDAC1, HDAC6 and HDAC8
o
All the enzymatic reactions were conducted at 37 C for 30 min. The 50 μL reaction mixture contains 25
mM Tris, pH 8.0, 1 mM MgCl2, 0.1 mg/ml BSA, 137 mM NaCl, 2.7 mM KCl, HDAC and the enzyme
substrate. The compounds were diluted in 10% DMSO and 5 μL of the dilution was added to a 50 μL
reaction so that the final concentration of DMSO is 1% in all of reactions. The assay was performed by
quantitating the fluorescent product amount of in solution following an enzyme reaction. Fluorescence is
then analyzed with an excitation of 350-360 nm and an emission wavelength of 450-460 nm at SpectraMax
M5 microtiter plate reader. The IC50 values were calculated using nonlinear regression with normalized
dose-response fit in Prism GraphPad software.
1.3 MTT assay
The antiproliferative activities of representative compounds and positive control SAHA were evaluated by
the MTT (3-[4,5-dimethyl-2-thiazolyl]-2,5-diphenyl-2H-tetrazolium bromide) assay. All cell lines were
cultured in RPMI1640 medium containing 10% FBS at 37 oC in a 5% CO2 humidified incubator. In short,
cancer cells were plated at 3000-4000 cells per well (100 μL/well) in 96-well plates for 8 h and then
incubated with different concentrations of compounds (100 μL/well) for 48 h. 0.5% MTT solution (10
μL/well) was added and incubation for 4 h. Finally, the formed formazan in every well was dissolved in
150 μL DMSO and mixed for 15 min. Absorbance data was measured by microtiter-plate reader at 570 nm.
The IC50 values were calculated according to the inhibition ratios.
2. RESULT AND DISCUSSION
2.1 Chemistry
Synthetic routes were illustrated in Scheme 1-3. Various arylethylketone (1a-1h) were treated with
1,1-dimethoxy-N,N-dimethylmethanamine to give intermediates 2a-2h. Then 2a-2h reacted with thiourea
and iodomethane successively to obtain intermediates 3a-3g. Compounds 3a-3h were oxidized by
potassium peroxymonosulfate, and then treated with substituted benzylamine and benzyl alcohol to gain
4a-4h and 7a-7h by SNAr reaction. On the other hand, 2a-2e were cyclized and then substituted by various
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benzyl bromide to give 5a-5e and 9a-9c. Intermediates 2 converted to 10a-10c by heating with
methyl-3-(4-guanidinophenyl)acrylate. To give target compounds 6a-6m, 8a-8k as well as 11a-11c,
intermediates 4a-4h, 5a-5e, 7a-7k, 10a-10c were reacted with hydroxylamine in potassium hydroxide
solution respectively.15
Scheme 1. Reagents and conditions: (a) 1,1-dimethoxy-N,N-dimethylmethanamine, 100-120°C; (b) i)
thiourea, NaOH, EtOH, reflux; ii) MeI, K2CO3, DMSO, R.T.; (c) i) oxone, acetonitrile/H2O, R.T.; ii)
methyl-4-(aminomethyl)-benzoate or methyl-4-(hydroxymethyl)benzoate , K2CO3, DMF, 110°C, or
microwave, 110 °C; (d) H2NOH·HCl, KOH, MeOH, R.T.; (e) i) thiourea, NaOH, EtOH, reflux; ii)
methyl-4-(bromomethyl)benzoate, K2CO3, acetone, reflux.
Scheme 2. Reagents and conditions: (a) i) NaOH, EtOH, reflux; ii) MeI, K2CO3, DMSO, R.T.; (b) i) oxone,
acetonitrile/H2O,
R.T.;
ii)
methyl
(E)-3-(4-(aminomethyl)phenyl)acrylate
or
methyl-3-(4-(hydroxymethyl)phenyl)acrylate , K2CO3, DMF, 110°C, or microwave, 110 °C; (c) i) NaOH,
EtOH, reflux; ii) methyl-4-(bromomethyl)benzoate, K2CO3, acetone, reflux; (d) H2NOH·HCl, NaOH,
MeOH, R.T..
Scheme 3. Reagents and conditions: (a) methyl-3-(4-guanidinophenyl)acrylate, triethylamine,
2-methoxyethanol, microwave or heated, 130°C; (b) H2NOH·HCl, NaOH, MeOH, R.T..
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2.2 HDAC inhibitory activities of target compounds
HDAC inhibitory activities of all target compounds were evaluated by the Color de Lys™ assay, using
SAHA as positive control and the result listed in Table 1 and 2. It indicated that the linkers, connection
units (X moiety) and the substituents of pyrimidine (Ar group) all significantly influence on the inhibitory
activities against HDAC. Generally speaking, N-hydroxybenzamide compounds showed higher HDAC
inhibition activity than N-hydroxycinnamamide.
Methylene between phenyl and pyrimidine was necessary for HDAC inhibitory activities. If nitrogen of
2-position of pyrimidine directly linked to phenyl (n = 0), HDAC inhibitory would decrease, perhaps
owing to unappropriated length of linker. Compared with other series target compound, 11a-11c showed
poor HDAC inhibitory activities. Heteroatom of X moiety preferred nitrogen instead of sulfur or oxygen
for satisfactory inhibitory activity of HDAC.
As for Ar group, aryl or other heterocycle fragment was introduced in 4-position of pyrimidine in this
study. Usually, heterocycle fragment, such as furan and thiazole, exhibit poor potency compared with
substituted phenyl ring. According to the substitution in phenyl ring, para-substitution (i.e. 6d) are more
favorable than ortho-substituted phenyl (i.e. 6e).
Besides, two of most potent target compounds, 6d and 8a, were chosen for the HDAC isoforms selective
inhibition experiments. According to results shown in Table 3, both two compounds exhibit more potent
inhibitory activity toward HDAC1, 6 and 8 than SAHA. On the other hand, these two compounds showed
higher HDAC1, 6 inhibitory activity than HDAC8.
Table 1 HDAC inhibitory activity of N-hydroxybenzamide derivatives
IC50 of HDACsa (μM)
Compd.
Ar
X
4-nitrophenyl
5-methylfuran-2-yl
furan-2-yl
NH
NH
NH
NH
NH
NH
O
0.413±0.207
0.296±0.062
0.186±0.108
0.175±0.049
>1
6a
6b
6c
4-chlorophenyl
6d
2,4-dichlorophenyl
4-methyl-2-(methylamino)thiazol-5-yl
4-chlorophenyl
6e
0.199±0.048
>1
6f
6g
4-methoxyphenyl
4-methoxyphenyl
4-chlorophenyl
O
>1
6h
S
>1
6i
S
>1
6j
5-methylfuran-2-yl
3-methoxyphenyl
4-methyl-2-(methylamino)thiazol-5-yl
-
S
0.424±0.086
>1
6k
S
6l
S
0.361±0.024
0.217±0.027
6m
SAHA
-
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a IC50 values of HDACs inhibition activity were expressed as the mean ± standard deviation of three separate
determinations.
Table 2 HDAC inhibitory activity of N-hydroxycinnamamide derivatives
n
IC50 of HDACsa (μM)
Compd.
Ar
X
1
1
1
1
1
1
1
1
1
1
1
0
0
0
4-methoxyphenyl
5-methylfuran-2-yl
furan-2-yl
NH
NH
NH
NH
NH
NH
O
0.246±0.081
8a
8b
>1
0.148±0.055
8c
4-chlorophenyl
>1
8d
2,4-dichlorophenyl
4-methyl-2-(methylamino)thiazol-5-yl
4-chlorophenyl
>1
8e
0.581±0.039
8f
>1
8g
5-methylfuran-2-yl
5-methylfuran-2-yl
furan-2-yl
O
>1
8h
S
>1
8i
S
0.418±0.204
8j
4-methyl-2-(methylamino)thiazol-5-yl
4-methoxyphenyl
5-methylfuran-2-yl
furan-2-yl
S
>1
8k
NH
NH
NH
-
>1
>1
11a
11b
11c
SAHA
>1
-
0.217±0.027
a IC50 values of HDACs inhibition activity were expressed as the mean ± standard deviation of three separate
determinations.
Table 3 HDAC isoforms inhibitory activity of cpd. 6d and 8a
IC50 (nM) a
Compd.
HDAC1
11.8±0.9
13.6±1.5
32.3±3.8
HDAC6
10.3±0.5
7±0.5
HDAC8
920±30
1000±0
1650±50
6d
8a
SAHA
17.4±1.4
a IC50 values of HDAC isoforms inhibition activity were expressed as the mean ± standard deviation of two
separate determinations.
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2.3 MTT assay
Five target compounds, 6a, 6d, 8a, 8c and 8f, were selected to evaluated their antiproliferative activities
using five tumor cell lines which include A549 (non-small-cell lung carcinoma cell), MDA-MB-231(breast
cancer cell), KG1(acute myelogenous leukemia cell), HCT116 (colon cancer cell) and PC-3(prostatic
cancer cell). As shown in Table 4, most of selected target compounds exhibited potent antiproliferative
activities. Compound 6a and 8f showed similar IC50 values with SAHA. Especially, 6d, 8a and 8c showed
significant inhibition activity better than SAHA. And it should be pointed out that the most potent
compound 8a possessed 6-fold antiproliferative activities against MDA-MB-231 and 5-fold against KG1
compared with SAHA.
Table 4 Antiproliferative activities of representative target compounds
IC50 (μM)a
Compd.
A549
MDA-MB-231
2.88±0.51
0.17±0.09
0.20±0.08
0.32±0.03
1.15±0.32
1.32±0.34
KG1
HCT116
4.76±1.07
2.34±0.07
2.92±0.19
3.29±0.36
2.83±0.39
10.40±1.86
PC-3
6a
6d
3.29±0.69
0.47±0.060
0.23±0.058
0.37±0.056
4.33±1.32
1.71±0.14
15.36±1.30
4.57±0.11
1.96±0.44
5.27±0.03
6.80±1.22
10.36±0.09
3.41±1.06
1.18±0.11
1.00±0.03
0.76±0.08
7.24±0.34
3.88±0.49
8a
8c
8f
SAHA
a
IC50 of antiproliferative activities were expressed as the mean ± standard deviation of three separate
determinations.
3. CONCLUSIONS
In summary, a novel series of N-benzylpyrimidin-2-amine derivatives was designed and prepared for their
evaluation on antiproliferative activities. We changed cap region, CU and linker to discuss structure and
activity relationship. Among them, 6a, 6d, 8a, 8c and 8f showed better antipreliferative activities than
SAHA. Especially, 6d and 8a performed 7-fold and 6-fold antipreliferative activities against
MDA-MB-231 compared with SAHA. Compound 6d and 8a would be selected as novel lead compounds
for further developing and investigating.
ACKNOWLEDGEMENT
This work was supported by National Natural Science Foundation of China (Grant No. 81373281) and the
Fundamental Research Funds of Shandong University (Grant No. 2016JC018).
CONFLICT OF INTEREST
The authors declare no conflict of interest.
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Legends
Fig. 1 HDACs inhibitors pharmacophore model and approved agents
Fig. 2 Design of novel N-benzylpyrimidin-2-amine derivatives
Scheme 1. Reagents and conditions: (a) 1,1-dimethoxy-N,N-dimethylmethanamine, 100-120°C; (b) i)
thiourea, NaOH, EtOH, reflux; ii) MeI, K2CO3, DMSO, R.T.; (c) i) oxone, acetonitrile/H2O, R.T.; ii)
methyl-4-(aminomethyl)-benzoate or methyl-4-(hydroxymethyl)benzoate , K2CO3, DMF, 110°C, or
microwave, 110 °C; (d) H2NOH·HCl, KOH, MeOH, R.T.; (e) i) thiourea, NaOH, EtOH, reflux; ii)
methyl-4-(bromomethyl)benzoate, K2CO3, acetone, reflux.
Scheme 2. Reagents and conditions: (a) i) NaOH, EtOH, reflux; ii) MeI, K2CO3, DMSO, R.T.; (b) i) oxone,
acetonitrile/H2O,
R.T.;
ii)
methyl
(E)-3-(4-(aminomethyl)phenyl)acrylate
or
methyl-3-(4-(hydroxymethyl)phenyl)acrylate , K2CO3, DMF, 110°C, or microwave, 110 °C; (c) i) NaOH,
EtOH, reflux; ii) methyl-4-(bromomethyl)benzoate, K2CO3, acetone, reflux; (d) H2NOH·HCl, NaOH,
MeOH, R.T..
Scheme 3. Reagents and conditions: (a) methyl-3-(4-guanidinophenyl)acrylate, triethylamine,
2-methoxyethanol, microwave or heated, 130°C; (b) H2NOH·HCl, NaOH, MeOH, R.T..
Table 1 HDAC inhibitory activity of N-hydroxybenzamide derivatives
Table 2 HDAC inhibitory activity of N-hydroxycinnamamide derivatives
Table 3 HDAC isoforms inhibitory activity of cpd. 6d and 8a
Table 4 Antiproliferative activities of representative target compounds
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