Fluoroalkene modification of mercaptoacetamide-based histone deacetylase inhibitors

Article abstract of DOI:10.1016/j.bmc.2009.12.005

Inhibitors of histone deacetylases (HDAC) are emerging as a promising class of anti-cancer agents. The mercaptoacetoamide-based inhibitors are reported to be less toxic than hydroxamate and are worthy of further consideration. Therefore, we have designed a series of analogs as potential inhibitors of HDACs, in which the mercaptoacetamide group was replaced by (mercaptomethyl)fluoroalkene, and their HDAC inhibitory activity was evaluated. Subnanomolar inhibition was observed for all synthetic compounds.

Full text of DOI:10.1016/j.bmc.2009.12.005

Bioorganic & Medicinal Chemistry 18 (2010) 605–611
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Fluoroalkene modification of mercaptoacetamide-based histone
deacetylase inhibitors
a
b
b
a
Satoshi Osada a, , Satoshi Sano , Mariko Ueyama , Yoshiro Chuman , Hiroaki Kodama ,
*
Kazuyasu Sakaguchi b
a Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, 1 Honjo, Saga 840-8502, Japan
b Department of Biological Chemistry, Division of Chemistry, Graduate School of Science, Hokkaido University, Kita 8 Nishi 5, Sapporo 060-0808, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Inhibitors of histone deacetylases (HDAC) are emerging as a promising class of anti-cancer agents. The
mercaptoacetoamide-based inhibitors are reported to be less toxic than hydroxamate and are worthy
of further consideration. Therefore, we have designed a series of analogs as potential inhibitors of HDACs,
in which the mercaptoacetamide group was replaced by (mercaptomethyl)fluoroalkene, and their HDAC
inhibitory activity was evaluated. Subnanomolar inhibition was observed for all synthetic compounds.
Ó 2009 Elsevier Ltd. All rights reserved.
Received 22 October 2009
Revised 30 November 2009
Accepted 2 December 2009
Available online 28 December 2009
Keywords:
HDAC inhibitor
Fluoroalkene
1. Introduction
O
O
OH
N
H
Epigenetic regulation of gene expression is mediated by several
mechanisms, including DNA methylation, ATP-dependent chroma-
tin remodeling, and post-translational modifications of histones.1
Among several post-translational modification reactions, dynamic
N
Trichostatin A
O
H
OH
N
acetylation of e-amino groups of lysine residues on histone tails
N
H
O
is regulated by two opposing enzymes, histone acetyltransferase
and histone deacetylase (HDAC).2 Histone hyperacetylation by
HDAC inhibition neutralizes the positive charge of the lysine side
chain and is thought to be associated with change in the chromatin
structure and the consequential transcriptional activation of sev-
eral genes. One important outcome of histone hyperacetylation is
induction of the cyclin-dependent kinase inhibitory protein
p21Waf1/Cip1, which causes cell cycle arrest.3 Recently, HDAC inhib-
itors such as trichostatin A4 and suberoylanilide hydroxamic acid
(SAHA)5 have been reported to inhibit proliferation of tumor cells
by inducing terminal differentiation (Fig. 1). Thus, inhibitors of
HDACs are emerging as a promising class of anti-cancer agents.6,7
The co-crystal structure of the histone deacetylase-like protein
with SAHA reveals an active site consisting of a tubular pocket with
a zinc ion at the bottom of the pocket.8 While the hydroxamate
head group of SAHA interacts with the zinc ion of the active site,
the linker spans the tube-like portion of the binding pocket and
the aromatic cap-group makes contact with the surface of the en-
zyme. Although hydroxamic acids are effective metal binding
SAHA
Figure 1. Structures of HDAC inhibitors.
groups and are frequently employed as metalloprotease inhibitors,
they have been found to exhibit unfavorable pharmacokinetic
behavior including glucuronidation, sulfation, and metabolic
hydrolysis.9,10 Therefore, it is desirable to find replacement groups
that strongly inhibit HDACs.
Nonhydroxamate HDAC inhibitors such as o-aminoanilide,11 tri-
fluoromethyl ketones,12 ketoamides,13 phosphonates,14 and N-
formylhydroxylamine15 have been reported; however, they are less
potent than hydroxamates. The thiol group has been known to be a
good chelator for zinc-dependent enzymes, and therefore, thiol-
based SAHA analogs were recently developed.16 Thiol-based SAHA
analogs are reported to be potent HDAC inhibitors in spite of their
monodentate zinc binding ability in comparison to SAHA’s biden-
tate hydroxamic acid moiety. In searching for more effective units,
three groups have independently designed mercaptoacetamide-
based HDAC inhibitors that are supported by the ability of thiol
and carbonyl groups to interact with zinc ion in a chelating man-
ner.17–19 Furthermore, a cortical neuron neuroprotection study
* Corresponding author. Tel.: +81 952 28 8551; fax: +81 952 28 8548.
E-mail address: osadas@cc.saga-u.ac.jp (S. Osada).
0968-0896/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2009.12.005

606
S. Osada et al. / Bioorg. Med. Chem. 18 (2010) 605–611
revealed that the mercaptoacetoamide-based inhibitors are less
toxic than hydroxamate.20 Therefore, the thiol-based inhibitors
are thought to be worthy of further consideration.
O
O
N
H
SH
Supposing that the amide-bond in mercaptoacetamide located
in the catalytic gorge of the HDACs may be sensitive to hydrolytic
cleavage, we focused on replacing the amide functionality with a
mimetic structure. For an amide-bond surrogate, (Z)-fluoroalkene
(A) has been proposed to be equivalent to (s-Z)-amide (B) isostere
(Fig. 2).21 Since the first successful incorporation into a biologically
active peptide (substance P),22 the fluoroalkene unit has been ap-
plied to many peptidomimetics. Therefore, we have designed a ser-
ies of SAHA analogs as potential inhibitors of HDACs, in which the
hydroxamic acid was replaced by (mercaptomethyl)fluoroalkene
moieties (Fig. 3). Based on results of SAR studies on HDAC inhibi-
tors, the designed compounds focused on a 4-carbon or 5-carbon
chain linker unit, capped with an aromatic ring at the terminal end.
H
N
N
H
SH
O
H
X
SH
n
F
n = 1, 2
X = CONH, NHCO
Figure 3. Thiol-based HDAC inhibitors and fluoroalkene-modified inhibitors.
was determined using fluor-Lys as the substrate, and the result is
a 50% inhibition of HDAC activity (see values in Table 1). SAHA
was used as positive control, which had an IC50 value of 1.1 lM
2. Results and discussion
in our assays. According to the data, all synthetic compounds had
superior inhibitory activity than SAHA. As in the preceding case,
a five-carbon chain length proved better for the spacer unit. The
reversal of the amide linkage and the introduction of p-dimethyl-
aminophenyl moiety as found in trichostatin A did not influence
the inhibition ability. In the case of the previously reported mer-
captoacetamide analogs, significant activity drop was observed
when the linker length was reduced from five- to four-carbon
units.17,18 However, the inhibitory activity of fluoroalkene-based
inhibitors decreases less. In this context, the designed inhibitor
unit is substantially superior than mercaptoacetamide. We assume
that the chain-length dependency of mercaptoacetamide-based
inhibitors may be because of the bidentate coordination, which
may enforce to form an unfavorable conformation at the rim side
of the catalytic gorge. According to calculations based on MP2
and B3LYP levels of theory, the charge distribution indicates that
the fluoroalkene forms the proper polarity to mimic the polarity
of an amide but the magnitude of the charge separation is less.26
The synthesis of fluoroalkenes is outlined in Schemes 1 and 2,
and the compounds prepared for this study are listed in Table 1.
Starting from commercially available diol 1a or 1b, one of the
hydroxyl groups was selectively brominated by treating with aque-
ous HBr in toluene to afford
x
-bromo alcohols 2.23 Then the other
hydroxyl was converted to carboxylic acids 3 by the Anelli oxida-
tion.24 The acids 3 were converted to acid chlorides and were trea-
ted with aniline in the presence of N-methylmorpholine to obtain
benzamides 4. The benzamides 4 were reacted with sulfoxide an-
ion, which is generated from ethyl phenylsulfinylfluoroacetate
and NaH in anhydrous DMF, and then the adducts thus formed were
heated to 95 °C to facilitate syn elimination, which results in the
selective formation of thermodynamically stable Z-fluoroalkenes
5. Obtained fluoroalkenes 5 were reduced to the allyl alcohols 6
using in situ formed LiBH4, and these were converted to bromides
7 via the Appel reaction. The bromides 7 were treated with potas-
sium thioacetate, and subsequent alkaline hydrolysis gave the de-
sired thiols 9 accompanied by a small amount of disulfide forms 10.
Recent inhibitor design has focused on the cap-group that is be-
lieved to be responsible for isozyme selectivity.25 Although it be-
comes an inverse amide for synthetic reasons, construction of the
fluoroalkene moiety prior to introduction of the capping group will
be an efficient route for making isozyme-selective inhibitors. N-
Boc-6-aminohexanoic acid methyl ester (11) was reduced by LiAlH4
to yield alcohol 12, which was transformed to bromide 13 via the
Appel reaction. The bromide 13 was converted to Z-fluoroalkene
14 using a procedure similar to the one described for 5, and the es-
ter functionality was again reduced with LiAlH4 to obtain allyl alco-
hol 15. After acidic removal of the Boc group, condensation with
benzoic acid derivatives gave benzamide derivatives 16. The termi-
nal alcohol was converted to a leaving group via the Appel reaction.
However, conversion of 16b to the corresponding bromide under
the Appel condition was unsuccessful, presumably because of the
formation of an insoluble salt caused by the presence of the dimeth-
ylamino group. In this case, the alcohol was activated as mesylate
17b. Displacement of these leaving groups by potassium thioace-
tate followed by alkaline hydrolysis gave thiols 18.
By nature, the fluoroalkene has a p-system that is able to interact
with aromatic rings located in the channel of the HDAC catalytic
pocket. Therefore, when the fluoroalkene inhibitor unit is obliged
to penetrate shallowly into the channel, the hydrophobic environ-
ment of the channel tolerates the unit and accommodates it, and
the unit is assumed to interact with zinc in a monodentate manner.
As the fluoroalkene is known for nonhydrolyzable amide mimetic,
it is stable with respect to hydrolytic cleavage. Cancellation of pos-
sibility of amide cleavage by the HDAC might be partly involved in
the less chain-length dependency. Consequentially, we believe the
fluoroalkene structure is a suitable mimic for delivering an amide-
like structure to the catalytic center through the hydrophobic
channel.
3. Conclusions
In conclusion, four fluoroalkene-containing analogs of merca-
ptoacetoamide-based inhibitors were synthesized and were as-
sayed as inhibitors of HDAC. Potent inhibition activities of all
four compounds suggest that the nonhydrolyzable fluoroalkenes
can mimic substrates for HDACs. Further biological study of these
compounds, such as isozyme selectivity, is underway.
Synthetic thiols were tested with an in vitro assay using a HeLa
nuclear extract. The HDAC inhibitory activity of these compounds
H
N
4. Experimental
H
N
H
Melting points (uncorrected) were recorded on a Yanako MPS3
micro-melting point apparatus. All commercial reagents were used
without further purification unless otherwise noted. 1H NMR, 13C
NMR, and 19F NMR spectra were obtained using a JEOL AL-300
O
F
O
A
B
Figure 2. Fluoroalkene as an amide surrogate.

S. Osada et al. / Bioorg. Med. Chem. 18 (2010) 605–611
607
O
h
O
O
O
d
F
a
b
c
COOEt
HO
e
OH
HO
F
Br
N
H
N
H
Br
HO
Br
F
n
n
n
n
n
n
F
1
2
3
4
5
f
O
O
O
g
N
H
Br
N
H
S
N
OH
+
n
n
H
6
7
8
O
F
O
H
N
S
a
: n =4
N
H
S
N
H
SH
n
O
n
n
b: n =5
F
F
9
10
Scheme 1. Reagents and conditions: (a) HBr, toluene; (b) TEMPO, NaOCl, n-Bu4NBr, AcOEt–water; (c) (i) SOCl2, CH2Cl2, (ii) PhNH2, NMM; (d) (i) NaH, PhSOCHFCOOEt, DMF,
(ii) 95 °C; (e) NaBH4, LiCl, THF–EtOH; (f) imidazole, Ph3P, CBr4, toluene; (g) AcSK, EtOH; (h) K2CO3, MeOH.
H
N
H
N
H
N
H
N
H
N
COOEt
d
a
b
c
COOMe
Boc
Boc
OH
Boc
e
Boc
OH
Boc
Br
5
5
5
5
5
F
F
11
12
13
14
15
R
R
R
H
N
H
H
N
f
g, h
N
SH
OH
X
5
5
5
O
F
O
F
O
F
16
17
18
a: R = H, X=Br
b: R = NMe2, X=OMs
Scheme 2. Reagents and conditions: (a) LiAlH4, THF; (b) imidazole, Ph3P, CBr4, toluene; (c) (i) NaH, PhSOCHFCOOEt, DMF, (ii) 95 °C; (d) LiAlH4, THF; (e) (i) HCl–dioxane, (ii)
PhCOOH, EDCI, HOBt, NMM, DMF; (f) imidazole, Ph3P, CBr4, toluene (for a) or MsCl, Et3N (for b); (g) AcSK, EtOH; (h) K2CO3, MeOH.
Table 1
ture was cooled to 0 °C. The mixture was stirred vigorously while
slowly adding 0.35 M NaOCl aqueous solution (30 mL). Stirring
Synthesized HDAC inhibitors and inhibiting activities
was continued for 90 min, and then the reaction was quenched
by adding aqueous Na2S2O3. The aqueous phase was separated,
washed with ether, acidified by adding 2 M HCl aqueous solution.
The aqueous phase was extracted with ether and dried over
Na2SO4. The solvent was removed in vacuo to give the acid 3a as
a heavy viscous liquid (1.7 g, 80%). The spectral data were identical
to reported data.29
X
SH
n
F
R
Compd
n
R
X
IC50 (lM)
9a
9b
18a
18b
4
5
5
5
–H
–H
–H
NHCO
0.51
0.36
0.29
0.30
NHCO
CONH
CONH
–NMe2
4.2. 7-Bromoheptanoic acid (3b)
spectrometer (300 MHz, 75 MHz, and 283 MHz, respectively). All
chemical shifts are reported in ppm as d values relative to internal
tetramethylsilane (1H and 13C) or benzotrifluoride (19F) in CDCl3
unless otherwise noted. Multiplicities are described using the
abbreviations s, singlet; d, doublet, t, triplet; q, quartet; and m,
multiplet. HRMS spectra were acquired using a JEOL GCmateII
mass spectrometer or a JEOL JMS-700 mass spectrometer. Tetrahy-
drofuran was distilled from sodium benzophenone ketyl prior to
use. All the manipulations with air-sensitive reagents were per-
formed under a dry argon atmosphere. Analytical TLC was per-
formed using Merck Silica Gel 60 F254 plates (0.25 mm on glass).
Flash column chromatography was performed using either Wako-
gel C-300 (45–75 mm). Suberoylanilide hydroxamic acid was syn-
Starting from 2b (1.66 g, 8.5 mmol), 3b was obtained as a pale
yellow viscous liquid (1.50 g, 84%) following a procedure similar
to that described for 3a. The spectral data were identical to re-
ported data.28
4.3. (Z)-7-(N-Phenylcarbamoyl)-2-fluoro-2-heptenoic acid ethyl
ester (5a)
Sodium hydride (60% in mineral oil, 1.36 g, 30 mmol), in which
the oil was previously washed out with petroleum ether, was sus-
pended in 23 mL of DMF under argon atmosphere. The suspension
was cooled to 0 °C, and a solution of ethyl phenylsulfinylfluoroac-
etate (6.43 g, 28 mmol) in DMF (7.0 mL) was added in a dropwise
manner. The mixture was stirred for 30 min at 0 °C, and then com-
pound 4a (8.37 g, 31 mmol), which was dissolved in 10 mL of DMF,
was slowly added at 5 °C, and the reaction mixture was stirred for
12 h. The progress of adduct formation was monitored by TLC, and
then the reaction mixture was warmed up to 95 °C and maintained
for 3 h. After cooling to room temperature, the reaction was
quenched with the NH4Cl aqueous solution, and the solution was
extracted with AcOEt. The organic extracts were successively
washed with 1 M HCl, saturated NaHCO3 solution, and brine. After
thesized as previously described.27
x-Bromo alcohols 2a and 2b
were prepared according to reported procedures.23 x-Bromo carb-
oxybenzamides 4a and 4b were prepared in accordance with the
method described in the literature.28
4.1. 6-Bromohexanoic acid (3a)
To a solution of 6-bromohexanol (2.0 g, 11 mmol) dissolved in
EtOAc (30 mL) was added NaHCO3 (5.0 g, 59 mmol), TEMPO
(0.21 g, 1.3 mmol), and n-Bu4NBr (0.68 g, 2.1 mmol), and this mix-

608
S. Osada et al. / Bioorg. Med. Chem. 18 (2010) 605–611
drying the organic phase over Na2SO4, the solvent was removed in
vacuo and the residue was purified by flash chromatography (hex-
ane/ethyl acetate = 1:1) yielding 5a as colorless crystals (5.86 g,
72%). Mp 76–78 °C; 1H NMR d 7.45 (d, J = 8.1 Hz, 2H), 7.26 (t,
J = 6.3 Hz, 2H), 7.17 (s, 1H), 7.03 (t, J = 7.4 Hz, 1H), 6.10 (dt, J = 33,
7.8 Hz, 1H), 4.21 (t, J = 6.9 Hz, 2H), 2.18–2.33 (m, 4H), 1.66–1.76
(m, 2H), 1.45–1.53 (m, 2H), 1.23 (t, J = 7.1 Hz, 3H); 13C NMR d
171.1, 160.5 (d, J = 36 Hz), 146.4 (d, J = 266 Hz), 137.9, 128.9,
124.1, 124.1, 119.9 (d, J = 13 Hz), 61.5, 37.0, 27.7, 24.9, 23.8, 14.1;
19F NMR d À131.7 (d, J = 32 Hz); HRMS (FAB) M+ calculated for
C16H20NO3F 293.1427, found 294.1488.
3.9 mmol), and CBr4 (1.32 g, 3.9 mmol) at 0 °C, and this mixture
was stirred for 1 h at room temperature. The reaction mixture
was diluted with AcOEt, washed with brine, and dried over Na2SO4.
The solvent was removed in vacuo and the residue purified by flash
chromatography (hexane/ethyl acetate = 2:1), yielding 7a as color-
less crystals (0.66 g, 70%). Mp 84–85 °C; 1H NMR d 7.52 (d,
J = 7.2 Hz, 2H), 7.29–7.34 (m,3H), 7.10 (t, J = 7.5 Hz, 1H), 4.93 (dt,
J = 34, 7.7 Hz, 1H), 3.91 (d, J = 20 Hz, 2H), 2.37 (t, J = 7.4 Hz, 2H),
2.16 (q, J = 7.2 Hz, 2H), 1.76 (quin, J = 7.5 Hz, 2H), 1.49 (quin,
J = 7.5 Hz, 2H); 13C NMR d 170.9, 152.8 (d, J = 252 Hz), 137.9,
129.0, 124.2, 119.8, 110.5 (d, J = 16 Hz), 37.3, 28.7 (d, J = 17 Hz),
28.2, 24.8, 23.4; 19F NMR d À116.0 (dt, J = 35, 20 Hz); HRMS (FAB)
(M+H)+ calculated for C14H18NO79BrF 314.0558, found 314.0552.
4.4. (Z)-8-(N-Phenylcarbamoyl)-2-fluoro-2-octenoic acid ethyl
ester (5b)
4.8. (Z)-9-Bromo-8-fluoro-N-phenylnon-7-enamide (7b)
Starting from 4b (5.14 g, 22 mmol), 5b was obtained as colorless
crystals (5.44 g, 79%) following a procedure similar to that de-
scribed above. Mp 66–68 °C; 1H NMR d 7.50 (d, J = 7.9 Hz, 2H),
7.46 (br s, 1H), 7.30 (t, J = 7.5 Hz, 2H), 7.09 (t, J = 7.2 Hz, 1H), 6.05
(dt, J = 33, 7.9 Hz, 1H), 4.26 (q, J = 7.1 Hz, 2H), 2.35 (t, J = 7.5 Hz,
2H), 2.20–2.30 (m, 2H), 1.73 (quin, J = 7.5 Hz, 2H), 1.26–1.53 (m,
4H), 1.33 (t, J = 7.1 Hz, 3H); 13C NMR d 171.2, 16.6 (d, J = 36 Hz),
146.4 (d, J = 256 Hz), 137.9, 128.9, 124.1, 120.3 (d, J = 12 Hz),
119.8, 61.5, 37.4, 28.7, 28.0, 25.2, 24.0, 14.1; 19F NMR d À132.0
(d, J = 34 Hz); HRMS (FAB) (M+1)+ calculated for C17H23FNO3
308.1662, found 308.1658.
Starting from 6b (0.72 g, 2.7 mmol), 7b was obtained as color-
less crystals (0.66 g, 74%) following a procedure similar to that de-
scribed for 7a. Mp 96–98 °C; 1H NMR d 7.48 (d, J = 7.8 Hz, 2H),
7.24–7.32 (m, 3H), 7.08 (t, J = 7.2 Hz, 1H), 4.88 (dt, J = 35, 7.5 Hz,
1H), 3.87 (d, J = 20 Hz, 2H), 2.33 (t, J = 7.5 Hz, 2H), 2.09 (t,
J = 6.3 Hz 2H), 1.71 (quin, J = 7.2 Hz, 2H), 1.37–1.39 (m, 4H); 13C
NMR d 171.2, 152.6 (d, J = 252 Hz), 137.9, 129.0, 124.2, 119.8,
110.8 (d, J = 16 Hz), 37.6, 28.6 (d, J = 17 Hz), 28.5, 28.4, 25.2, 23.7;
19F NMR d À116.4 (dt, J = 35, 19 Hz); HRMS (FAB) (M+H)+ calcu-
lated for C15H20NO79BrF 328.0712, found 328.0720.
4.5. (Z)-7-(N-Phenylcarbamoyl)-2-fluoro-2-heptenol (6a)
4.9. (Z)-7-(Phenylcarbamoyl)-2-fluorohept-2-enyl
acetylsulfane (8a)
NaBH4 (0.55 g, 14 mmol) was slowly added to a solution of LiCl
(0.61 g, 14 mmol) dissolved in EtOH (9.2 mL). A solution of 5a
(1.05 g, 3.6 mmol) dissolved in THF (6.0 mL) was added to this sus-
pension, and this mixture was stirred for 24 h at room tempera-
ture. The reaction was quenched with aqueous NH4Cl and the
solution was evaporated to remove EtOH. The residue was ex-
tracted with AcOEt, and the organic extracts were successively
washed with saturated NaHCO3 solution and brine. After drying
the organic phase over Na2SO4, solvent was removed in vacuo
and the residue was purified by flash chromatography (hexane/
ethyl acetate = 1:1) yielding 6a as colorless crystals (0.76 g, 84%).
Mp 70–71 °C; 1H NMR d 7.48 (d, J = 7.8 Hz, 2H), 7.24–7.32 (m,
3H), 7.08 (t, J = 7.4 Hz, 1H), 4.76 (dt, J = 37 Hz, 7.5 Hz, 1H), 4.07
(dd, J = 16, 6.3 Hz, 2H), 2.34 (t, J = 7.2 Hz, 2H), 2.12 (t, J = 7.2 Hz,
2H), 1.96 (t, J = 6.6 Hz, 1H) 1.74 (quin, J = 7.5 Hz, 2H), 1.45 (quin,
J = 7.2 Hz, 2H); 13C NMR d 172.2, 156.3 (d, J = 256 Hz), 137.9,
128.9, 124.2, 120.0, 107.0 (d, J = 14 Hz), 60.6 (d, J = 33 Hz), 37.1,
28.4, 24.9, 22.8; 19F NMR d À121.9 (dt, J = 37 Hz, 16 Hz); HRMS
(FAB) (M+H)+ calculated for C14H19NO2F 252.1400, found 252.1378.
To a solution of 7a (0.53 g, 1.6 mmol) dissolved in EtOH (5.6 mL)
was added AcSK (0.70 g, 5.8 mmol), and the mixture was stirred for
19 h at room temperature. To this mixture was added THF–AcOEt,
washed with water and brine. After drying the organic phase over
Na2SO4, solvent was removed in vacuo and the residue purified by
flash chromatography (hexane/ethyl acetate = 3:2), yielding 8a as
colorless crystals (0.42 g, 84%). Mp 68–70 °C; 1H NMR d 7.50 (d,
J = 7.8 Hz, 2H), 7.32 (t, J = 8.0 Hz, 2H), 7.18 (br s, 1H), 7.10 (t,
J = 7.5 Hz, 1H), 4.76 (dt, J = 36, 7.8 Hz, 1H), 3.61 (d, J = 19 Hz, 2H),
2.32–2.37 (m, 5H), 2.11 (q, J = 7.5 Hz, 2H), 1.73 (quin, J = 7.5 Hz,
2H), 1.45 (quin, J = 7.5 Hz, 2H); 13C NMR d 194.5, 171.2, 152.7 (d,
J = 253 Hz), 137.9, 128.9, 124.1, 119.7, 108.2 (d, J = 15 Hz), 37.3,
30.4, 30.0, 28.4, 24.9, 23.3: 19F NMR d À113.5 (dt, J = 35, 19 Hz);
HRMS (FAB) (M+H)+ calculated for C16H21NO2FS 310.1277, found
310.1248.
4.10. (Z)-8-(Phenylcarbamoyl)-2-fluorooct-2-enyl acetylsulfane
(8b)
4.6. (Z)-8-(N-Phenylcarbamoyl)-2-fluoro-2-octenol (6b)
Starting from 7b (0.26 g, 0.80 mmol), 8b was obtained as color-
less crystals (0.25 g, 97%) by a similar procedure described for 8a.
Mp 53–54 °C; 1H NMR d 7.48 (d, J = 7.8 Hz, 2H), 7.29 (t, J = 7.8 Hz,
2H), 7.25 (br s, 1H), 7.07 (t, J = 7.9 Hz, 1H), 4.71 (dt, J = 36, 7.5 Hz,
1H), 3.58 (d, J = 19 Hz, 2H), 2.29–2.34 (m, 5H), 2.04–2.05 (m, 2H),
1.71 (quin, J = 7.2 Hz, 2H), 1.34–1.36 (m, 4H); 13C NMR d 194.3,
171.2, 152.6 (d, J = 252 Hz), 137.9, 129.0, 124.2, 119.8, 108.5 (d,
J = 15 Hz), 36.7, 30.4, 30.1, 28.6, 25.3, 23.5; 19F NMR d À113.2 (dt,
J = 37 Hz, 18 Hz); HRMS (FAB) (M+H)+ calculated for C17H23NO2FS
324.1234, found 324.1427.
Starting from 5b (1.46 g, 4.7 mmol), 6b was obtained as colorless
crystals (0.88 g, 70%) following a procedure similar to that described
for 6a. Mp 71–73 °C; 1H NMR d 7.50 (d, J = 7.8 Hz, 2H), 7.32 (t,
J = 8.0 Hz, 2H), 7.23 (br s, 1H), 7.10 (t, J = 7.4 Hz, 1H), 4.77 (dt,
J = 37, 7.5 Hz, 1H), 4.07 (d, J = 17 Hz, 2H), 2.35 (t, J = 7.4 Hz, 2H),
2.11 (t, J = 6.6 Hz 2H), 1.96 (br s, 1H) 1.74 (quin, J = 7.4 Hz, 2H),
1.35–1.43 (m, 4H); 13C NMR d 172.0, 156.1 (d, J = 256 Hz), 137.9,
128.8, 124.1, 120.0, 107.4 (d, J = 14 Hz), 60.7 (d, J = 33 Hz), 37.4,
28.6, 28.5, 25.3, 23.0; 19F NMR d À122.3 (dt, J = 37 Hz, 17 Hz); HRMS
(FAB) (M+H)+ calculated for C15H21NO2F 266.1556, found 266.1536.
4.11. (Z)-7-Fluoro-8-mercapto-N-phenyloct-6-enamide (9a)
and its dimer (10a)
4.7. (Z)-8-Bromo-7-fluoro-N-phenyloct-6-enamide (7a)
To a solution of compound 8a (0.40 g, 1.3 mmol) dissolved in
MeOH (12 mL) was added K2CO3 (0.10 g, 2.5 mmol), and this mix-
ture was stirred for 2 h at room temperature. The mixture was di-
To a solution of 6a (0.76 g, 3.0 mmol) dissolved in toluene
(30 mL) was added PPh3 (1.02 g, 3.9 mmol), imidazole (0.27 g,

S. Osada et al. / Bioorg. Med. Chem. 18 (2010) 605–611
609
luted with AcOEt, washed with water and brine, and dried over
Na2SO4. Solvent was removed in vacuo and the residue was puri-
fied by flash chromatography (hexane/ethyl acetate = 3:2), yielding
9a (0.27 g, 78%) as a white solid. Disulfide dimer 10a (0.06 g,
0.11 mmol, 17%) was also obtained as a white solid. 9a; mp 53–
55 °C; 1H NMR d 7.50 (d, J = 8.1 Hz, 2H), 7.32 (t, J = 8.0 Hz, 2H),
7.19 (br s, 1H), 7.10 (t, J = 7.4 Hz, 1H), 4.70 (dt, J = 36, 7.5 Hz, 1H),
3.20 (dd, J = 17, 8.1 Hz, 2H), 2.36 (t, J = 7.5 Hz, 2H), 2.12 (q,
J = 7.2 Hz, 2H), 1.70–1.82 (m, 3H), 1.46 (q, J = 7.4 Hz, 2H); 13C
NMR d 171.3, 155.6 (d, J = 252 Hz), 137.9, 128.9, 124.2, 119.8,
106.2 (d, J = 16 Hz), 37.3, 28.5 (d, J = 1.9 Hz), 25.6, 24.9, 23.2; 19F
NMR d À115.0 (dt, JHF = 37 Hz, 18 Hz); HRMS (FAB) (M+H)+ calcu-
lated for C14H19NOFS 268.1171, found 268.1168. Compound 10a;
mp 98–100 °C; 1H NMR d 7.47–7.50 (m, 6H), 7.27 (t, J = 7.4 Hz,
4H), 7.07 (t, J = 7.2 Hz, 2H), 4.68 (dt, J = 36, 7.5 Hz, 2H), 3.29 (d,
J = 20 Hz, 4H), 2.34 (t, J = 7.4 Hz, 4H), 2.12 (q, J = 7.1 Hz, 4H), 1.74
(quin, J = 7.5 Hz, 4H) 1.45 (quin, J = 7.7 Hz, 4H); 13C NMR d 171.3,
152.2 (d, J = 253 Hz), 137.9, 128.9, 124.2, 119.9, 109.6 (d,
J = 15 Hz), 40.3 (d, J = 31 Hz), 37.3, 28.6, 24.9, 23.5; 19F NMR d
À115.2 (dt, JHF = 35 Hz, 18 Hz); HRMS (FAB) (M+H)+ calculated for
C28H35N2O2F2S2 533.2108, found 533.2109.
(10 mL). The mixture was stirred for 40 min, and then quenched
with 10% KOH aqueous solution (20 mL) at 0 °C. Inorganic precip-
itates were filtered and the solution was concentrated. The oil
was dissolved in AcOEt, washed with 1 M HCl, saturated NaHCO3,
and brine, and then dried over Na2SO4. Solvent was removed in va-
cuo to give 12 as colorless crystals (2.11 g, 97%). Mp 36–37 °C; 1H
NMR analysis is consistent with published data.31
4.15. N-tert-Butoxycarbonyl-1-amino-6-bromohexane (13)
To a solution of 12 (4.26 g, 20.0 mmol) dissolved in toluene
(200 mL) was added triphenylphosphine (5.46 g, 21 mmol), imid-
azole (1.51 g, 23 mmol), and CBr4 (7.30 g, 22 mmol) at 0 °C, and
this mixture was stirred for 3 h. The reaction mixture was ex-
tracted with AcOEt, and the extract was washed with brine and
dried over Na2SO4. Solvent was removed in vacuo and the residue
was purified by flash chromatography (hexane/ethyl acetate = 2:2),
yielding 13 as a colorless oil (3.57 g, 65%). 1H NMR analysis is con-
sistent with published data.32
4.16. (Z)-8-(N-tert-Butoxycarbonyl)amino-2-fluoro-2-octenoic
acid ethyl ester (14)
4.12. (Z)-8-Fluoro-9-mercapto-N-phenylnon-7-enamide (9b)
and its dimer (10b)
Sodium hydride (60% in mineral oil, 0.56 g, 14 mmol), in which
oil was previously washed out with petroleum ether, was sus-
pended in 9 mL of DMF under an Ar atmosphere. The suspension
was cooled to 0 °C, and a solution of ethyl phenylsulfinylfluoroac-
etate (2.65 g, 12 mmol) dissolved in DMF (5 mL) was added drop-
wise. The mixture was stirred for 30 min at 0 °C, compound 13
(2.65 g, 13 mmol) dissolved in 3.3 mL of DMF was slowly added
at 5 °C, and the reaction mixture was stirred for 17 h. The progress
of adduct formation was monitored by TLC, and then the reaction
mixture was warmed to 95 °C and maintained at this temperature
for 3 h. After cooling to room temperature, the reaction was
quenched with the NH4Cl aqueous solution, and the mixture was
extracted with AcOEt. The organic extracts were washed with brine
and dried over Na2SO4. Solvent was removed in vacuo and the res-
idue was purified by flash chromatography (hexane/ethyl ace-
tate = 3:1), yielding 14 as a pale yellow oil (2.77 g, 79%). 1H NMR
d 6.16 (dt, J = 33, 7.5 Hz, 1H), 4.46 (br s, 1H), 4.29 (q, J = 7.1 Hz,
2H), 3.12 (q, J = 6.3 Hz, 2H), 2.21–2.29 (m, 2H), 1.29–1.54 (m,
6H), 1.44 (s, 9H), 1.33 (t, J = 7.2 Hz, 3H); 13C NMR d 160.6 (d,
J = 36 Hz), 155.9, 146.4 (d, J = 257 Hz), 120.2 (d, J = 12 Hz), 79.1,
61.5, 40.4, 29.8, 28.4, 27.9, 26.3, 24.1, 14.1; 19F NMR d À132.1 (d,
JHF = 34 Hz); HRMS (FAB) (M+H)+ calculated for C15H27NO4F
304.1924, found 304.1926.
By a treatment similar to that described for 9a, 8b (0.25 g,
0.76 mmol) gave 9b (0.19 g, 0.66 mmol, 87%) and disulfide dimer
10b (0.014 g, 0.02 mmol, 7%) as white solids. 9b: mp 67–69 °C; 1H
NMR d 7.50 (d, J = 7.5 Hz, 2H), 7.31 (t, J = 8.0 Hz, 2H), 7.25 (br s, 1H),
7.10 (t, J = 7.4 Hz, 1H), 4.67 (dt, J = 36, 7.5 Hz, 1H), 3.15–3.24 (m,
2H), 2.35 (t, J = 7.5 Hz, 2H), 2.05–2.10 (m, 2H), 1.68–1.81 (m, 3H),
1.38–1.42 (m, 4H); 13C NMR d 171.2, 155.4 (d, J = 252 Hz), 137.9,
128.9, 124.2, 119.7, 106.5 (d, J = 16 Hz), 37.7, 28.8 (d, J = 1.3 Hz),
28.6, 25.7, 25.2, 23.5; 19F NMR d À114.7 (dt, J = 37 Hz, 18 Hz); HRMS
(FAB) (M+H)+ calculated for C15H21NOFS 282.1328, found 232.1346.
Compound 10b; mp 96–98 °C; 1H NMR d 7.45 (d, J = 7.8 Hz, 4H),
7.40 (br s, 2H), 7.23 (t, J = 7.8 Hz, 4H), 7.02 (t, J = 7.7 Hz, 2H), 4.74
(dt, J = 36, 7.5 Hz, 2H), 3.29 (d, J = 20 Hz, 4H), 2.28 (t, J = 7.5 Hz, 4H),
2.04–2.06 (m, 4H), 1.66 (quin, J = 7.2 Hz, 4H), 1.33–1.35 (m, 8H);
13C NMR d 171.4, 155.3 (d, J = 253 Hz), 137.9, 129.0, 124.2, 119.8,
109.9 (d, J = 16 Hz), 40.3 (d, J = 31 Hz), 37.7, 28.8, 28.7, 25.3, 23.7;
19F NMR d À114.9 (dt, J = 35 Hz, 18 Hz); HRMS (FAB) (M+H)+ calcu-
lated for C30H39N2O2F2S2 561.2421, found 561.2429.
4.13. N-tert-Butoxycarbonyl-6-aminohexanoic acid methyl
ester (11)
To a chilled solution of thionyl chloride (2.3 mL, 30 mmol) in
methanol (20 mL) was slowly added 6-aminohexanoic acid
(1.31 g, 10.0 mmol). The mixture was stirred for 24 h at room tem-
perature and then concentrated in vacuo to give a white solid. The
solid was suspended in 10 mL of THF. To this suspension was
added triethylamine (1.7 mL, 10 mmol) and di-tert-butyl-dicarbox-
ylate (2.31 g, 10.5 mmol). The solution was stirred overnight at
room temperature. Precipitates were filtered off and solvent was
removed with a rotary evaporator to give an oily product. The oil
was dissolved in AcOEt, washed with 1 M HCl, saturated NaHCO3,
and brine, and then dried over Na2SO4. Solvent was removed in va-
cuo to give 11 as a colorless oil (2.45 g). The compound was used
without further purification. Compound analysis is consistent with
published data.30
4.17. (Z)-8-(N-tert-Butoxycarbonyl)amino-2-fluoro-2-octenol
(15)
Compound 14 (0.64 g, 2.1 mmol) in THF (10 mL) was slowly
added to a stirring suspension of LiAlH4 (0.089 g, 2.3 mmol) in
THF (20 mL) so as not to exceed 40 °C. After 1.5 h, the reaction mix-
ture was cooled 0 °C, 10% KOH aqueous solution (5 mL) was added
cautiously. The formed precipitate was filtered off and the filtrate
was concentrated in vacuo. The residue was dissolved in AcOEt.
The organic solution was washed with brine and dried over Na2SO4.
Solvent was removed in vacuo to give 15 as a colorless oil (0.36 g,
65%). An analytical sample was purified by flash chromatography
(hexane/ethyl acetate = 1:1). 1H NMR d 4.74 (t, J = 37, 7.5 Hz, 1H),
4.50 (br s, 1H), 4.07 (dd, J = 16, 6.5 Hz, 2H), 3.07 (q, J = 6.6 Hz, 2H),
2.08 (q, J = 6.7 Hz, 2H), 1.90 (br s, 1H), 1.27–1.50 (m, 6H), 1.42 (s,
9H); 13C NMR d 159.5 (d, J = 255 Hz), 156.1, 107.4 (d, J = 13 Hz),
79.1, 61.0 (d, J = 33 Hz), 40.5, 29.7, 28.6, 28.4, 26.1, 23.1; 19F NMR
d À122.4 (dt, J = 37, 16 Hz); HRMS (FAB) (M+H)+ calculated for
C13H25NO3F 262.1813, found 262.1840.
4.14. N-tert-Butoxycarbonyl-6-aminohexanol (12)
To a suspension of LiAlH4 (0.37 g, 10.0 mmol) in THF (70 mL)
was slowly added a solution of 11 (2.45 g, 10.0 mmol) in THF

610
S. Osada et al. / Bioorg. Med. Chem. 18 (2010) 605–611
4.18. N-((Z)-7-Fluoro-8-hydroxyoct-6-enyl)benzamide (16a)
thioacetate was dissolved in MeOH (5.0 mL) and K2CO3 (34 mg,
0.25 mmol) was added to this solution. The mixture was stirred
for 30 min at room temperature, diluted with AcOEt, washed with
water and brine, and dried over Na2SO4. Solvent was removed in va-
cuo and the residue purified by flash chromatography (hexane/
ethyl acetate = 3:2) yielding 18a (0.12 g, 1.0 mmol, 78%) as a oil.
1H NMR d 7.72–7.76 (m, 2H), 7.37–7.50 (m, 3H), 6.13 (br s, 1H),
4.78 (dt, J = 36, 7.5 Hz, 1H), 3.34–3.47 (m, 2H), 3.13–3.23 (m, 2H),
2.09 (q, J = 6.3 Hz, 2H), 1.72–1.77 (m, 1H), 1.61 (quin, J = 6.8 Hz,
2H), 1.34–1.41 (m, 4H); 13C NMR d 167.5, 155.5 (d, J = 252 Hz),
134.8, 131.3, 128.5, 126.8, 106.5 (d, J = 16 Hz), 39.9, 29.4, 28.7,
26.3, 25.2, 23.4; 19F NMR d À115.3 (dt, J = 37, 18 Hz); HRMS (FAB)
(M+H)+ calculated for C15H21NOFS 282.1328, found 282.1331.
To a solution of 15 (0.37 g, 1.4 mmol) dissolved in dioxane
(2.5 mL) was slowly added 4 M HCl/dioxane (4.0 mL) at 0 °C and
the mixture was stirred for 1 h at room temperature. The reaction
mixture was diluted with methanol, concentrated in vacuo to give
a pale, yellow oil. The residue was dissolved in DMF (1.4 mL) and
cooled to 0 °C. To this solution was successively added N-methyl-
morpholine (0.15 mL, 1.4 mmol),
a solution of benzoic acid
(0.18 g, 1.5 mmol) and HOBt (0.25 g, 1.8 mmol) dissolved in DMF
(1.4 mL), and EDCI (0.28 g, 1.5 mmol). The reaction mixture was
stirred for 26 h at room temperature and diluted with AcOEt. The
organic solution was successively washed with water, saturated
NaHCO3 solution, 1 M aqueous HCl, and brine. After drying the or-
ganic phase over Na2SO4, solvent was removed in vacuo and the
residue was purified by flash chromatography (hexane/ethyl ace-
tate = 1:1) yielding 16a as colorless oil (0.30 g, 80%). 1H NMR d
7.71 (d, J = 8.4 Hz, 2H), 7.37–7.49 (m, 3H), 6.24 (br s, 1H), 4.73
(dt, J = 37, 7.5 Hz, 1H), 4.03 (d, J = 16 Hz, 2H), 3.40 (q, J = 6.6 Hz,
2H), 2.30 (br s, 1H), 2.08 (q, J = 6.6 Hz, 2H), 1.59 (quin, J = 6.9 Hz,
2H), 1.31–1.46 (m, 4H); 13C NMR d 167.6, 156.2 (d, J = 256 Hz),
134.8, 131.4, 128.5, 126.8, 107.4 (d, J = 14 Hz), 61.1 (d, J = 27 Hz),
39.9, 29.4, 28.6, 26.3, 23.1; 19F NMR d À122.2 (dt, J = 38, 16 Hz);
HRMS (FAB) (M+H)+ calculated for C15H21NO3F 266.1556, found
266.1557.
4.22. 4-(Dimethylamino)-N-((Z)-7-fluoro-8-mercaptooct-6-
enyl)benzamide (18b)
To a solution of 16b (130 mg, 0.42 mmol) and Et3N (0.09 mL,
0.64 mmol) dissolved in THF (3.7 mL) was slowly added MeSO2Cl
(50 lL, 0.63 mmol) at 0 °C. After the addition, the mixture was stir-
red for 2 h at room temperature. The precipitate was filtered off
and the filtrate was concentrated in vacuo. The residue was dis-
solved in ethanol (3.0 mL), AcSK (240 mg, 2.1 mmol) was added
to the solution, and the mixture was stirred for 20 h at room tem-
perature. This mixture was diluted with AcOEt, washed with water
and brine. After drying the organic phase over Na2SO4, solvent was
removed in vacuo and the residue purified by flash chromatogra-
phy (hexane/ethyl acetate = 3:2) yielding a thioacetate derivative
as a colorless oil. The oil was dissolved MeOH (2.2 mL) and
K2CO3 (14 mg, 0.10 mmol) was added. After the mixture was stir-
red for 30 min at room temperature, it was diluted with AcOEt,
washed with water and brine, and dried over Na2SO4. Solvent
was removed in vacuo and the residue purified by flash chroma-
tography (hexane/ethyl acetate = 3:2) yielding 18b (32 mg, 46%)
as a white solid. Mp 84–86 °C; 1H NMR d 7.57–7.62 (m, 2H),
6.56–6.61 (m, 2H), 5.97 (br s, 1H), 4.72 (dt, J = 36, 7.5 Hz, 1H),
3.36 (q, J = 6.5 Hz, 2H), 3.14 (dd, J = 14, 8.1 Hz, 2H), 2.94 (s, 6H),
1.97–2.03 (m, 2H), 1.70 (t, J = 8.0 Hz, 1H), 1.48–1.55 (m, 2H),
1.31–1.33 (m, 4H); 13C NMR d 167.4, 155.4 (d, J = 252 Hz), 152.4,
128.2, 121.6, 111.0, 106.6 (d, J = 16 Hz), 40.1, 39.7, 29.6, 28.8,
26.4, 25.2, 23.5; 19F NMR d -115.4 (dt, J = 37, 18 Hz); HRMS (FAB)
(M+H)+ calculated for C17H26N2OFS 325.1750, found 325.1748.
4.19. 4-(Dimethylamino)-N-((Z)-7-fluoro-8-hydroxyoct-6-
enyl)benzamide (16b)
Starting from 15 (0.46 g, 1.8 mmol), 16b was obtained as a
white powder (0.34 g, 62%) following a procedure similar to that
described for 16a. Mp 89–90 °C; 1H NMR d 7.61–7.66 (m, 2H),
6.61–6.66 (m, 3H), 6.06 (br s, 1H), 4.85 (dt, J = 37, 7.5 Hz, 1H),
4.08 (d, J = 15 Hz, 2H), 3.40 (q, J = 6.7 Hz, 2H), 2.98 (s, 6H), 2.44
(br s, 1H), 2.09 (q, J = 6.5 Hz, 2H), 1.57 (quin, J = 6.9 Hz, 2H),
1.33–1.41 (m, 4H); 13C NMR d 167.6, 156.3 (d, J = 256 Hz), 152.3,
128.3, 121.4, 111.1, 107.2 (d, J = 14 Hz), 60.9 (d, J = 33 Hz), 40.1,
39.7, 29.5, 28.6, 26.2, 23.1; 19F NMR d À122.2 (m); HRMS (FAB)
(M+H)+ calculated for C17H26FN2O2 309.1978, found 309.1981.
4.20. N-((Z)-8-Bromo-7-fluorooct-6-enyl)benzamide (17a)
To a solution of 16a (0.29 g, 1.1 mmol) dissolved in toluene
(11 mL) was added PPh3 (0.36 g, 1.4 mmol), imidazole (0.10 g,
1.4 mmol), and CBr4 (0.45 g, 1.4 mmol) at 0 °C, and the mixture
was stirred for 3 h at room temperature. The reaction mixture
was diluted with AcOEt, washed with brine, and dried over Na2SO4.
The solvent was removed in vacuo and the residue purified by flash
chromatography (hexane/ethyl acetate = 1:1) yielding 17a as color-
less crystals (0.20 g, 60%). 1H NMR d 7.72–7.76 (m, 2H), 7.37–7.50
(m, 3H), 6.14 (br s, 1H), 4.89 (dt, J = 34, 7.5 Hz, 1H), 3.87 (d,
J = 20 Hz, 2H), 3.42 (q, J = 7.2 Hz, 2H), 2.10 (q, J = 6.9 Hz, 2H), 1.61
(quin, J = 6.6 Hz, 2H), 1.35–1.44 (m, 4H); 13C NMR d 167.7, 159.3,
134.5, 131.4, 128.5, 126.9, 110.8 (d, J = 16 Hz), 40.0, 29.3, 28.8,
28.4, 26.3, 23.4; 19F NMR d À115.8 (dt, J = 35, 20 Hz); HRMS (FAB)
(M+H)+ calculated for C15H20NOBrF 328.0712, found 328.0678.
4.23. HDAC inhibition assay
The HDAC activity assay was performed using an HDAC fluores-
cent activity assay/drug discovery kit (AK-500, BIOMOL Research
Laboratories). HeLa cell nuclear extract was used as the source of
HDAC activity. Test compounds were prepared as 5 mM stock solu-
tions in EtOH. HeLa nuclear extracts (15
lL) were incubated at
37 °C with 25 L of Fluor de Lys substrate and various concentra-
l
tions of samples. The reaction was allowed to proceed for 10 min
at room temperature before stopping the reaction by adding Fluor
de Lys Developer with trichostatin A. Twenty minutes after addi-
tion of this developer, the mixture was diluted with 150 lL of buf-
fer, and then the fluorescence was measured on a fluorometric
reader with excitation set at 360 nm and emission detection set
at 460 nm. The concentration of the compound, which results in
50% inhibition, was determined by plotting as a logistic function
of the log[Inh] and the % inhibition. We report the means values
of the three independent experiments.
4.21. N-((Z)-7-Fluoro-8-mercaptooct-6-enyl)benzamide (18a)
To a solution of 17a (0.19 g, 0.57 mmol) dissolved in EtOH
(2.0 mL) was added AcSK (0.24 g, 2.1 mmol) and the mixture was
stirred for 20 h at room temperature. To this mixture was added
THF–AcOEt, washed with water and brine. After drying of the or-
ganic phase over Na2SO4, solvent was removed in vacuo and the
residue purified by flash chromatography (hexane/ethyl ace-
tate = 3:2) yielding a thioacetate derivative as a colorless oil. The
Acknowledgments
A preliminary biological assay of 9a was examined by the
Screening Committee of Anticancer Drugs supported by Grant-in-

S. Osada et al. / Bioorg. Med. Chem. 18 (2010) 605–611
611
13. Wada, C. K.; Frey, R. R.; Ji, Z.; Curtin, M. L.; Garland, R. B.; Holms, J. H.; Li, J.;
Pease, L. J.; Guo, J.; Glaser, K. B.; Marcotte, P. A.; Richardson, P. L.; Murphy, S. S.;
Bouska, J. J.; Tapang, P.; Magoc, T. J.; Albert, D. H.; Davidsen, S. K.; Michaelides,
M. R. Bioorg. Med. Chem. Lett. 2003, 13, 3331.
14. Kapustin, G. V.; Fejer, G.; Gronlund, J. L.; McCafferty, D. G.; Seto, E.; Etzkorn, F.
A. Org. Lett. 2003, 5, 3053.
Aid for Scientific Research on Priority Area ‘Cancer’ from The Min-
istry of Education, Culture, Sports, Science and Technology, Japan.
The authors appreciate Professor Teruo Shinmyozu (Institute for
Materials Chemistry and Engineering, Kyushu University) for mass
spectral measurements.
15. Wu, T. Y.; Hassig, C.; Wu, Y.; Ding, S.; Schultz, P. G. Bioorg. Med. Chem. Lett.
2004, 14, 449.
16. Suzuki, T.; Kouketsu, A.; Matsuura, A.; Kohara, A.; Ninomiya, S.; Kohda, K.;
Miyata, N. Bioorg. Med. Chem. Lett. 2004, 14, 3313.
References and notes
17. Suzuki, T.; Matsuura, A.; Kouketsu, A.; Nakagawa, H.; Miyata, N. Bioorg. Med.
Chem. Lett. 2005, 15, 331.
18. Chen, B.; Petukhov, P. A.; Jung, M.; Velena, A.; Eliseeva, E.; Dritschilo, A.;
Kozikowski, A. P. Bioorg. Med. Chem. Lett. 2005, 15, 1389.
19. Anandan, S. K.; Ward, J. S.; Brokx, R. D.; Bray, M. R.; Patel, D. V.; Xiao, X. X.
Bioorg. Med. Chem. Lett. 2005, 15, 1969.
20. Kozikowski, A. P.; Chen, Y.; Gaysin, A.; Chen, B.; D’Annibale, M. A.; Suto, C. M.;
Langley, B. C. J. Med. Chem. 2007, 50, 3054.
21. Allmendinger, T.; Furet, P.; Hungerbühler, E. Tetrahedron Lett. 1990, 31, 7297.
22. Allmendinger, T.; Felder, E.; Hungarbühler, E. Tetrahedron Lett. 1990, 31, 7301.
23. Chong, J. M.; Heuft, M. A.; Rabbat, P. J. Org. Chem. 2000, 65, 5837.
24. Lucio Anelli, P.; Biffi, C.; Montanari, F.; Quici, S. J. Org. Chem. 1987, 52, 2559.
25. Estiu, G.; Greenberg, E.; Harrison, C. B.; Kwiatkowski, N. P.; Mazitschek, R.;
Bradner, J. E.; Wiest, O. J. Med. Chem. 2008, 51, 2898.
26. Urban, J. J.; Tillman, B. G.; Cronin, W. A. J. Phys. Chem. A 2006, 110, 11120.
27. Gediya, L. K.; Chopra, P.; Purushottamachar, P.; Maheshwari, N.; Njar, V. C. J.
Med. Chem. 2005, 48, 5047.
1. Spencer, V. A.; Davie, J. R. Gene 1999, 240, 1.
2. Mai, A.; Massa, S.; Rotili, D.; Cerbara, I.; Valente, S.; Pezzi, R.; Simeoni, S.; Ragno,
R. Med. Res. Rev. 2005, 25, 261.
3. Sambucetti, L. C.; Fischer, D. D.; Zabludoff, S.; Kwon, P. O.; Chamberlin, H.;
Trogani, N.; Xu, H.; Cohen, D. J. Biol. Chem. 1999, 274, 34940.
4. Yoshida, M.; Kijima, M.; Akita, M.; Beppu, T. J. Biol. Chem. 1990, 265, 17174.
5. Kelly, W. K.; O’Connor, O. A.; Krug, L. M.; Chiao, J. H.; Heaney, M.; Curley, T.;
MacGregore-Cortelli, B.; Tong, W.; Secrist, J. P.; Schwartz, L.; Richardson, S.;
Chu, E.; Olgac, S.; Marks, P. A.; Scher, H.; Richon, V. M. J. Clin. Oncol. 2005, 23,
3923.
6. Miller, T. A.; Witter, D. J.; Belvedere, S. J. Med. Chem. 2003, 46, 5097.
7. Villar-Garea, A.; Esteller, M. Int. J. Cancer 2004, 112, 171.
8. Finnin, M. S.; Donigian, J. R.; Cohen, A.; Richon, V. M.; Rifkind, R. A.; Marks, P. A.;
Breslow, R.; Pavletich, N. P. Nature 1999, 401, 188.
9. Mulder, G. J.; Meerman, J. H. Environ. Health Perspect. 1983, 49, 27.
10. Michaelides, M. R.; Dellaria, J. F.; Gong, J.; Holms, J. H.; Bouska, J. J.; Stacey, J.;
Wada, C. K.; Heyman, H. R.; Curtin, M. L.; Guo, Y.; Goodfellow, C. L.; Elmore, I.
B.; Albert, D. H.; Magoc, T. J.; Marcotte, P. A.; Morgan, D. W.; Davidsen, S. K.
Bioorg. Med. Chem. Lett. 2001, 11, 1553.
28. Suzuki, T.; Nagano, Y.; Kouketsu, A.; Matsuura, A.; Maruyama, S.; Kurotaki, M.;
Nakagawa, H.; Miyata, N. J. Med. Chem. 2005, 48, 1019.
29. Nanda, S.; Yadav, J. S. Tetrahedron: Asymmetry 2003, 14, 1799.
11. Suzuki, T.; Ando, T.; Tsuchiya, K.; Fukazawa, N.; Saito, A.; Mariko, Y.;
Yamashita, T.; Nakanishi, O. J. Med. Chem. 1999, 42, 3001.
12. Frey, R. R.; Wada, C. K.; Garland, R. B.; Curtin, M. L.; Michaelides, M. R.; Li, J.;
Pease, L. J.; Glaser, K. B.; Marcotte, P. A.; Bouska, J. J.; Murphy, S. S.; Davidsen, S.
K. Bioorg. Med. Chem. Lett. 2002, 12, 3443.
30. Hagen, T. Synlett 1990, 63.
31. Forbes, C. C.; DiVittorio, K. M.; Smith, B. D. J. Am. Chem. Soc. 2006, 128, 9211.
32. Egbertson, M. S.; Chang, C. T.; Duggan, M. E.; Gould, R. J.; Halczenko, W.;
Hartman, G. D.; Laswell, W. L.; Lynch, J. J., Jr.; Lynch, R. J.; Manno, P. D., et al J.
Med. Chem. 1994, 37, 2537.