2-Aroylindoles and 2-aroylbenzofurans with N-hydroxyacrylamide substructures as a novel series of rationally designed histone deacetylase inhibitors

Article abstract of DOI:10.1021/jm0703136

Histone deacetylase (HDAC) inhibitors are considered to be drugs for targeted cancer therapy and second-generation HDIs are currently being tested in clinical trials. Here, we report on the synthesis and biological evaluation of a novel HDAC inhibitor sca

Full text of DOI:10.1021/jm0703136

J. Med. Chem. 2007, 50, 4405-4418
4405
2-Aroylindoles and 2-Aroylbenzofurans with N-Hydroxyacrylamide Substructures as a Novel
Series of Rationally Designed Histone Deacetylase Inhibitors†
Siavosh Mahboobi,*,‡ Andreas Sellmer,‡ Heymo Ho¨cher,‡ Christian Garhammer,‡ Herwig Pongratz,‡ Thomas Maier,§
Thomas Ciossek,§ and Thomas Beckers*,§
Department of Pharmaceutical Chemistry I, UniVersity of Regensburg, D-93040 Regensburg, Germany, and Therapeutic Area Oncology,
ALTANA Pharma, a Member of the NYCOMED Group, D-78467 Konstanz, Germany
ReceiVed March 19, 2007
Histone deacetylase (HDAC) inhibitors are considered to be drugs for targeted cancer therapy and second-
generation HDIs are currently being tested in clinical trials. Here, we report on the synthesis and biological
evaluation of a novel HDAC inhibitor scaffold with the hydroxamate Zn2+ complexing headgroup, selected
from the 2-aroylindol motif. Inhibition of nuclear extract HDAC and recombinant HDAC 1 as well as
induction of histone H3K9+14 hyperacetylation mediated by E-N-hydroxy-(2-aroylindole)acrylamides or E-N-
hydroxy-(2-aroylbenzofuran)acrylamides were studied. Moreover, the cytotoxic activity, the effects on the
cell cycle, and histone H3S10 phosphorylation of selected compounds were determined. By use of a panel
of 24 different human tumor cell lines, mean IC50 values of the most potent analogues 6c and 7b were 0.75
and 0.65 µM, respectively. The novel compounds were shown to be no substrates of the P-glycoprotein
drug transporter. Comparable to N1-hydroxy-N8-phenyloctanediamide “2 (SAHA)”, cells in the S phase of
the cell cycle are depleted, with partial arrest in G1 and G2/M and finally induction of massive apoptosis.
Introduction
by histone acetyltransferases (HATs) and histone deacetylases
(HDACs), respectively. Mammalian HDAC isoenzymes fall into
four distinct classes with at least 18 members.5 HDAC class I
(HDACs 1-3, 8), class II (HDACs 4-7, 9, 10), and class IV
(HDAC11) enzymes are functionally related Zn2+-containing
amidohydrolases and are inhibited by the natural compound
trichostatin A (TSA). They are part of multiprotein complexes
examplified by interaction with transcriptional corepressors and
transcription factors.6 The function of HDAC class I enzymes
in normal and pathological conditions was intensively studied.
For example, targeted deletion of HDAC1 is followed by
embryonic lethality in mice,7 and HDAC 1-3 isoenzymes are
highly expressed in prostate adenocarcinoma with HDAC 2
expression as an independent prognostic factor correlating with
survival.8 HDAC class II isoenzmyes are less well characterized,
with HDAC 6 having substrates different from histone proteins
like the mitotic spindle protein R-tubulin.9 HDAC inhibitors
(HDIs) effect the transcriptional regulation and induce or repress
genes involved in differentiation, proliferation, cell cycle
regulation, protein turnover, and apoptosis.10 As such, they are
considered as drugs for targeted cancer therapy.11 HDAC
inhibiting compounds are highly divergent in structure and
comprise short-chain fatty acids and derivatives, hydroxamic
acids, cyclic tetrapeptides/peptolides, benzamides, and others.
Various agents are currently in clinical development, namely,
the hydroxamte analogues (E)-3-(4-(((2-(1H-indol-3-yl)ethyl)-
(2-hydroxyethyl)amino)methyl)phenyl)-N-hydroxyacrylamide “1c
(LBH589)” (phase I, Novartis12), N-hydroxy-3-(3-(N-phenyl-
sulfamoyl)phenyl)acrylamide “1d (PXD101)” (phase II, Topo-
target/Curagen13), N1-hydroxy-N8-phenyloctanediamide “2 (SAHA,
vorinostat (Zolinza))” (phase II/III, Merck Inc.),14 and N-(2-(4-
(hydroxycarbamoyl)phenoxy)ethyl)-3-(isopropylamino)benzo-
furan-2-carboxamide hydrochloride “3 (CRA024781)” (phase
I, Pharmacyclics Inc.15), the benzamide analogues (4-(2-ami-
nophenylcarbamoyl)benzylamino)methyl nicotinate “3a (MS275)”
(phase II, Bayer-Schering AG16) and N-(2-aminophenyl)-4-((4-
(pyridin-3-yl)pyrimidin-2-ylamino)methyl)benzamide“3b(MGCD0103)”
(phase II, Methylgene17), the cyclic peptolide “3c (depsipeptide/
Within the past decade our understanding of malignant cell
growth and the underlying molecular alterations has offered new
opportunities for molecular targeted cancer therapy. These new
targeted approaches complement traditional chemotherapeutic
drugs with the promise of a broader therapeutic window and
efficacy in late-stage or therapy-resistant cancer patients.
Carcinogenesis and tumor progression are controlled by both
genetic and epigenetic events. Unlike genetic events, epigenetic
aberrations such as DNA methylation evident in cancer cells
can usually be reversed, thus reactivating epigenetically silenced
genes.1 On the basis of this rationale, the DNA methyltransferase
(DNMTa) inhibitors 5-aza-3′-deoxycytidine 1a2 and 5-azacyti-
dine 1b,2 acting as suicide inhibitors of DNMT1 and DNMT3a/
b, are approved drugs for the treatment of patients with
myelodysplastic syndrome2 (MDS).
Another important epigenetic modification is based on the
reversible acetylation of the N-terminal tails of core histone
proteins H2A/B, H3, and H4.3 In general, histone hyperacety-
lation is correlated with gene activation, whereas histone
hypoacetylation mediates transcriptional repression.4 The revers-
ible acetylation and deacetylation of lysine residues are catalyzed
† This paper is dedicated to Professor Wolfgang Wiegrebe on the occasion
of his 75th birthday.
* To whom correspondence should be addressed. For S.M. on chemical
aspects: phone, (+49) (0) 941-9434824; fax, (+49) (0) 941-9431737;
e-mail, siavosh.mahboobi@chemie.uni-regensburg.de. For T.B. on biological
aspects: phone, (+49) (0) 7531 842974; fax, (+49) (0) 7531 8492974;
e-mail, Thomas.Beckers@altanapharma.com.
‡ University of Regensburg.
§ ALTANA Pharma, a Member of the NYCOMED Group.
a Abbreviations:: ARK-B, Aurora kinase B; BOP, (benzotriazol-1-yloxy)-
tris(dimethylamino)phosphonium hexafluorophosphate; CTCL, cutaneous
T-cell lymphoma; DNMT, DNA methyltransferase; HAT, histone acetyl-
transferases; HDAC, histone deacetylases; HDI, histone deacetylase inhibi-
tor; MDS, myelodysplastic syndrome; NFkB, nuclear factor κ B; NH2OTHP,
O-(tetrahydropyran-2-yl)hydroxylamine; NSCLC, non-small-cell lung can-
cer; PBS, phosphate buffered saline; STAT, signal transducer and activator
of transcription; Pgp, P-glycoprotein; SAHA, suberoylanilidhydroxamic acid;
SDS-PAGE, sodium dodecyl sulfate polyacrylamide gel electrophoresis;
TSA, trichostatin A.
10.1021/jm0703136 CCC: $37.00 © 2007 American Chemical Society
Published on Web 08/11/2007

4406 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 18
Mahboobi et al.
Table 1. Chemical Structures and Chemical Classes, Their Mode-of-Action, Specificity, and Development Status
FK228)” (phase II, Gloucester/NCI18), and finally butyrate
analogues like valproic acid “3d (VPA)” (phase II, Topotar-
get19). Suberoylanilidhydroxamic acid (2) was recently approved
for treatment of refractory cutaneous T-cell lymphoma (CTCL20).
It is important to note that except for benzamide analogues 3a
and 3b, all hydroxamate-based HDIs in clinical development
are unselective inhibitors of HDAC class I and class II enzymes.
Nevertheless, it appears to be a common property of unselective
as well as class I selective HDIs to induce alterations of gene
expression with a similar final outcome, namely, cell cycle
alterations, induction of differentiation, and apoptosis.1,21 In
contrast to antimitotic agents, proliferating as well as arrested
(dormant) tumor cells are killed with similar potency.21,22 From
recent studies it is now evident that the antitumor activity of
HDIs cannot be explained by epigenetic mechanisms alone. In
melanoma cells, interaction of NFκB p65 with STAT1 (signal
transducer and activator of transcription) is dependent on CBP
(CRE binding protein)/HDAC regulated STAT1 acetylation
controlling the nuclear translocation and antiapoptotic function
of NFκB.23 In another study, interaction of HDAC 3 with the
mitotic kinase Aurora B (ARK-B) and HDAC 3 dependent
phosphorylation of histone H3S10 by ARK-B were shown,
giving a hint to the partial M-phase arrest seen by many HDIs.24
An overview of the reference compounds as discussed with their
mode-of-action and specificity is compiled in Table 1.
Here, we report on a novel HDAC inhibitor scaffold with
the hydroxamate Zn2+ complexing headgroup (“warhead”). The
new scaffold was selected from the 2-aroylindol motif (Chart
1), described to be highly active as an antimitotic agent by
destabilizing tubulin polymerization.25 Combining both structural
elements abolished the tubulin binding activity, leading to
HDAC inhibitors with an in vitro potency equal or superior to
2 as the most advanced HDAC inhibitor.
Chemistry
The synthetic route to obtain the desired target compounds
is given in the following: The substituted 2-aroylindole deriva-
tives 13a-c were easily prepared by coupling the lithiated indole

Indoles and Furans as Inhibitors
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 18 4407
Chart 1. Chemical Structures of Selected Hydroxamate-Based
HDAC Inhibitors in Clinical Development (1-3), Selected
Aroylindoles (4), and Novel Rationally Designed Compounds
(5-10)
Scheme 1. Synthesis of
E-N-Hydroxy-(2-aroylindole)acrylamidesa
a (a) BuLi, -78 °C, THF; (b) HClO4 (37%), CH2Cl2, 0 °C, 2 h; (c)
NaOH, NEt3, H2O, 20 °C; (d) (1) CF3COOH, 20 °C, (2) H2O; (e) BOP,
DMF, NEt3, room temp, 1 h; (f) HCl, MeOH, 20 °C, 24 h.
species with the respective acid chlorides (12, 12c) bearing a
protected aldehyde group. Deprotection of the aldehydes (13a-
c) with perchloric acid followed by Wittig olefination26 and
cleavage of the resulting trans-oriented acrylic acid tert-butyl
esters (15a-c) with trifluoroacetic acid yielded the correspond-
ing acrylic acids (16a-c). To obtain the N-dephenylsulfonated
carboxylic acids (17a-c), deprotection with NaOH in water/
methanol was performed. Amidation of 16a-c or 17a-c with
commercially available NH2OTHP (O-(tetrahydropyran-2-yl)-
hydroxylamine) by use of BOP {(benzotriazol-1-yloxy)tris-
(dimethylamino)phosphonium hexafluorophosphate} as a cou-
pling reagent27 and cleavage of the tetrahydropyran-2-yl protected
acrylamides (18a-c and 19a-c) led to the N-hydroxyacryla-
mides 5a-c and 6a-c.
Scheme 2. Synthesis of Acid Chlorides (12, 12c) Bearing a
Protected Aldehyde Groupa
a (a) 1,2-ethandiol, Al2O3, toluene, ∆, 48 h; (b) pyridine, SOCl2, 20 °C,
30 min.
The respective acid chlorides 12 and 12c, which were used
for the coupling reaction described in Scheme 1, were prepared
as shown in Scheme 2 by protection of the commercially
available formylbenzoic acids (20, 20c) with ethylene glycol
according to Kamitori28 and by treatment of the resulting [1,3]-
dioxolan-2-ylbenzoic acids (21, 21c) with thionyl chloride in
THF/pyridine solution.
Following the strategy described in Scheme 1, the N-
hydroxyacrylamide substituent was introduced at C-5 of the
indole nucleus (Scheme 3). Lithiation of 1-benzenesulfonyl-5-
[1,3]dioxolan-2-yl-1H-indole29 (24), coupling with the respective
acid chlorides, and cleavage of the resulting [1,3]dioxolanes
(25a,b) by perchloric acid yielded the aldehydes (26a,b), which
were converted to the E-N-hydroxyacrylamides (8a,b and 9a,b)
in four steps.
N-hydroxyacrylamide substituent was performed in the same
manner (Scheme 4) as described for the indole nucleus and led
to the desired compounds 36a and 36b.
Again, introduction of the N-hydroxyacrylamide substituent
was performed at C-5 of the 2-aroylbenzofuranyl nucleus
(Scheme 5) following the general synthetic strategy described
in Scheme 4. Thus, 4-hydroxybenzene-1,3-dicarbaldehyde (38)
used in this sequence was easily accessible from 4-hydroxy-
benzaldehyde (39) according to Stille.30
Results and Discussion
The in vitro data for inhibition of HeLa nuclear extract HDAC
activity (a mixture of HDAC isoenzymes 1-3, 5, and 8) and
recombinant HDAC 1 (rHDAC 1) in comparison with 2 as a
reference compound are compiled in Tables 2-5. To assess the
cellular efficacy of HDAC inhibition, EC50 and IC50 values for
the induction of histone H3K(Ac)9+14 hyperacetylation and
cytotoxicity vs HeLa cells are also given. Mean data from two
experiments are shown. Respective concentration-effect curves
derived from the histone H3 hyperacetylation assay for selected
The corresponding benzofuran-2-carbonylbenzaldehydes (34a,b)
were prepared from salicylic aldehyde (32) and the respective
substituted ω-bromoacetophenones (33a,b) under basic condi-
tions in acetonitrile (Scheme 4) according to Stille et al.30 The
ω-bromoacetophenones (33a,b) thereby were prepared by
bromination in CH2Cl2 with bromine. Introduction of the

4408 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 18
Mahboobi et al.
Scheme 3. Preparation of E-3-(2-Benzoyl-1H-indol-5-yl)-N-hydroxyacrylamidesa
a (a) NaOH, CH2Cl2, PhSO2Cl; (b) 1,2 ethandiol, Al2O3, toluene, ∆, 48 h; (c) n-BuLi, -78 °C, THF; (d) HClO4 (37%), CH2Cl2, 0 °C, 2 h; (e) NaOH,
NEt3, H2O, 20 °C; (f) (1) CF3COOH, 20 °C; (2) H2O; (g) BOP, DMF, NEt3, room temp, 1 h; (h) HCl, MeOH, 20 °C, 24 h.
Scheme 4a
When we investigated 2-aroylindoles 4a-c,25 removal of the
N-phenylsulfonyl protection group resulted in 40- to 100-fold
higher activity mediated by inhibition of tubulin polymerization.
Here, however, no effect of the phenylsulfonyl group on
biological activity can be observed when comparing derivatives
5a-c with their corresponding N-unsubstituted derivatives 6a-
c. Interestingly, by comparison of the biological data for the
compounds being substituted by the trans-oriented E-N-hy-
droxyacrylamide motif in position 4 (5a and 6a) with the
respective compounds being substituted in position 3 of the
benzoyl system (5c and 6c), the change in position led to about
10-fold higher inhibition of nuclear extract HDAC and rHDAC
1 activity as well as to a significant increase of H3K hyper-
acetylation and cytotoxicity. When the biological data for the
unsubstituted compounds 5a and 6a were compared with data
for 5b and 6b, substitution in position 5 of the indolyl system
by a methoxy group (5b and 6b), again in contrast to the findings
for the 2-aroylindole compounds 4a-c,25 did not exhibit any
effects. When these effects and the results obtained for the E-N-
hydroxy-(2-aroylbenzofuran)acrylamides 7a and 7b (Table 3)
were evaluated, the same trend is seen. For the carboxylic acids
(16c, 17c) structurally related to the most potent hydroxamates
(5c, 6c), no significant inhibition of HDAC has been observed.
a (a) K2CO3, CH3CN, ∆; (b) NaOH, NEt3, H2O, 20 °C; (c) (1) CF3COOH,
20 °C, (2) H2O; (d) BOP, DMF, NEt3, room temp, 1 h; (e) HCl, MeOH, 20
°C, 24 h.
compounds (2, 6c, 7b, 9a, and 10c) are shown in Figure 1.
Combining the structural features of 2-aroylindoles with an E-N-
hydroxyacrylamide motif leads to compounds with a concentra-
tion-dependent inhibition of nuclear extract HDAC and rHDAC
1 in the submicromolar range and significant H3K hyperacety-
lation correlating well with cytotoxicity against HeLa cells.
Compounds 6c and 7b were also tested for inhibition of
rHDAC 3 and 8 isoenzymes as additional class I representatives.
rHDAC 3 and 8 were inhibited by 6c and 7b with IC50 values

Indoles and Furans as Inhibitors
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 18 4409
Scheme 5. Preparation of E-3-(2-Benzoylbenzofuran-5-yl)-N-hydroxyacrylamides 10a-ca
a (a) K2CO3, CH3CN, ∆; (b) NaOH, NEt3, H2O, 20 °C; (c) (1) CF3COOH, 20 °C, (2) H2O; (d) BOP, DMF, NEt3, room temp, 1 h; (e) HCl, MeOH, 20
°C, 24 h.
Table 2. Inhibition of Nuclear Extract HDAC and rHDAC 1 and Induction of H3K(Ac)9+14 Hyperacetylation and Cytotoxicity Against HeLa Cells
Mediated by E-N-Hydroxy-(2-aroylindole)acrylamidesa
a Mean data from at least two experiments are shown.
of 0.05 µM/0.032 µM and 0.079 µM/0.079 µM, respectively.
Thus, both compounds behave as pan HDAC inhibitors like 2.
the potency in inhibition of nuclear extract HDAC and rHDAC
1, cytotoxicity against HeLa cells is highest for 8a and 8b.
Substitution patterns in the benzoyl system had no significant
effect on biological activity, as seen for 8a and 8b or 10a and
10b. Considering the fact that small-molecule HDAC inhibitors
in general are known to be built from a cap group, a spacer,
and a Zn2+ chelating headgroup like the hydroxamic acid motif,
this can be most likely explained by an outside orientation of
Substitution by the N-hydroxyacrylamide motif in position 5
of the indolyl sytem (Tables 4 and 5, compounds 8a-10c) also
led to potent HDAC inhibition and cellular activity. Inhibition
of HDAC enzymatic activity was the most distinct in the case
of the N-phenylsulfonated indolyl compounds 8a,b, followed
by 9a,b and the benzofuranyl compounds 10a-c. Reflecting

4410 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 18
Mahboobi et al.
Table 3. Inhibition of Nuclear Extract HDAC and rHDAC 1 and Induction of H3K(Ac)9+14 Hyperacetylation and Cytotoxicity Against HeLa Cells of
E-N-Hydroxy-(2-aroylbenzofurane)acrylamides 7a and 7ba
a Mean data from at least two experiments are shown.
Table 4. Inhibition of Nuclear Extract HDAc and rHDAC 1 and Induction of H3K(Ac)9+14 Hyperacetylation and Cytotoxicity Against HeLa Cells of
E-3-(2-Benzoyl-1H-indol-5-yl)-N-hydroxyacrylamides 8a,b and 9a,ba
a Mean data from at least two experiments are shown.
Table 5. Inhibition of Nuclear Extract HDAC and rHDAC 1 and Induction of H3K(Ac)9+14 Hyperacetylation and Cytotoxicity on HeLa Cells of
E-3-(2-Benzoylbenzofuran-5-yl)-N-hydroxyacrylamides 10a-ca
a Mean data from at least two experiments are shown.
the benzoyl system as the cap group. As a consequence, the
cap group interacts with the solvent accessible surface of the
HDAC enzyme, which is in proximity to the active site as shown
for hydroxamate analogues, binding to the class I isoenzyme
HDAC 8.31 Since this region of the HDAC enzyme is highly
malleable, modification of the aromatic system would result only
in a minor influence on the binding affinity.
PC3 (androgen-independent prostate carcinoma). Both analogues
are no substrate of the P-glycoprotein (P-gp) drug transporter,
since the sensitivities toward vincristine-resistent P-gp overex-
The biological profile of the most potent analogues 6c and
7b with the indolyl or benzofuran scaffold was investigated in
more detail. The antiproliferative/cytotoxic activity was deter-
mined by using a broad panel of 24 different human tumor cell
lines emenating from 16 different solid and hematological tumor
entities (Table 6). The mean IC50 values were calculated as 0.75
µM for 6c and 0.65 µM for 7b, which is about 5 times more
potent as 2 with a mean IC50 of 3.3 µM. Cell lines with the
highest sensitivity (IC50 < 0.3 µM) are K562 (chronic myeloid
leukemia/CML), EOL1 (acute myeloid eosinophilic leukemia/
AML), CCRF-CEM (acute T-lymphoblastic leukemia/ALL), and
Figure 1. Induction of histone H3K hyperacetylation in HeLa cells.
HeLa cervical carcinoma cells were treated with compounds 6c (2),
7b (b), 9a ([), 10c (1), and SAHA/2 (9) as reference for 24 h before
fixation, staining with a H3K(Ac)9+14 specific antibody and using single
cell image analysis with the Cellomics array scan device. EC50 values
were calculated by nonlinear regression analysis using the program
GraphPad prism.

Indoles and Furans as Inhibitors
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 18 4411
Table 6. Cytotoxicity Profilea
a The antiproliferative, cytotoxic activity of selected compounds was evaluated using a panel of 24 different human tumor cell lines. Further information
on the different cell lines is given in the Experimental Section. nd: not determined.
pressing CCRF-CEM cells and the parental cell line are similar.
Cytotoxicity toward RKO colon carcinoma cells is only slightly
affected by addition of 40 vol % human serum, pointing toward
low serum protein binding. Finally, 6c, 7b, and 2 depict a cell
cycle independent cytotoxic activity as shown by using the
RKOp21waf1 model.32 Proliferation of arrested p21waf1 expressing
and proliferating RKO cells is inhibited with nearly equal
potency (Figure 2).
The effect of 6c and 7b on the cell cycle of A549 non-small-
cell lung cancer cells (NSCLC) by flow cytometry was studied
next. Asynchronous proliferating A549 cells were treated for
Figure 2. Cytotoxicity in the RKOp21waf1 cell line model. The effect
24 h before staining of nuclear DNA with propidium iodide.
As shown in Figure 3, both compounds at g1 µM deplete cells
in the S-phase (>2 N and <4 N DNA content). A partial arrest
and transient in G1 (2 N DNA content) and G2/M (4 N DNA
of 2 (0), 6c (4), and 7b (3) on arrested and proliferating RKOp21waf1
cells after treatment for 72 h was determined using the Alamar blue
assay. IC50 values were calculated by nonlinear regression analysis using
the program GraphPad prism.

4412 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 18
Mahboobi et al.
arrest in G2/M, this result is unexpected. One possible explana-
tion is an arrest in G2. Another hypothesis is based on the
concept that only hypoacetylated histone H3 N-terminal tails
are good substrates for ARK-B as described recently by Li et
al.24 Since 6c and 7b potently induce H3 hyperacetylation, this
antagonizes ARK-B activity and as a consequence causes low
or undetectable histone H3S10 phosphorylation.
Conclusion
We conclude that 2-aroylindoles as 6c and 2-aroylbenzofurans
as 7b with the hydroxamate headgroup constitute a new class
of potent HDAC class I/II inhibitors with a cell-cycle-
independent and broad cytotoxicity superior to that of SAHA
(2) as an approved drug for cutaneous T-cell lymphoma
treatment.
Experimental Section
Biological Methods. Biochemical HDAC Assays. HDAC
activity was determined by using nuclei isolated from the cervical
carcinoma cell line HeLa (ATCC CCL2) according to a modified
method first described by Dignam et al.33 For recombinant HDAC1
expression, a clonal HEK293 (ATCC CRL1573) human kidney cell
line expressing the human HDAC1 isoenzyme bearing a C-terminal
FLAG epitope was provided by E. Verdin, The Gladstone Institute,
San Francisco, CA. The rHDAC1 protein was purified by M2
affinity gel chromatography according to the manufacturer’s
protocol (Sigma no. A2220). Purified HDAC protein samples were
routinely analyzed by SDS-PAGE (12.5% or 10% Laemmli gels)
followed by Coomassie stain and Western blotting using a FLAG-
specific antibody (anti-M2-POX antibody, Sigma no. A8592)
followed by ECL detection (GE Healthcare). In addition, protein
batches were analyzed by Western blotting for various HDAC
isoenzymes including HDAC1.
Figure 3. Flow cytometric analysis of A549 NSCLC cells. A549 cells
treated for 24 h with 6c and 7b at selected concentrations were analyzed
for cell populations in the G1, S, and G2/M stages of the cell division
cycle. Also, apoptotic cells with a subG1 DNA content were determined.
A column representation is given in part A, and selected histograms
and cell pictures by phase contrast microscopy are shown in part B.
The biochemical HDAC activity assay was essentially done as
described by Wegener et al.34 The overall reproducibility was very
high (standard error of the mean in the used test systems was e25%,
and mean values of the test compounds in general were within the
standard error of the mean of the test system). For details, see
Supporting Information.
Cellular Histone H3 Hyperacetylation Assay. To assess the
cellular efficacy of a histone deacetylase inhibition, an assay was
set up for use on the Cellomics “ArrayScan II” platform for a
quantitative calculation of histone acetylation as described.35 The
overall reproducibility was very high (standard error of the mean
in the used test systems was e25%, and mean values of the test
compounds in general were within the standard error of mean of
the test system). For details, see Supporting Information.
Figure 4. Analysis of histone H3K9+14 acetylation and H3S10 phos-
phorylation in RKO and A549 cells. RKO colon carcinoma (A) and
A549 NSCLC (B) cell lines were treated with selected concentrations
of 6c and 7b for 16 h before cell lysis and Western blot analysis,
detecting histone H3K(Ac)9+14 acetylation and H3S10 phosphorylation.
Samples of 10 µM SAHA/2 and 20 nM paclitaxel as an tubulin
stabilizing, antimitotic agent were included as controls.
Cellular Proliferation Assay. The antiproliferative cytotoxic
activity of selected compounds was evaluated using the tumor cell
lines HeLa (cervical carcinoma, ATCC CCL-2), H460 (non-small-
cell lung cancer, ATCC HTB-177), A549 (NSCLC, ATCC CCL-
185), MCF7 (breast carcinoma, ATCC HTB-22), MDA-MB468
(breast carcinoma, ATCC HTB-132), MDA-MB435 (breast carci-
noma, ATCC HTB-129), MDA-MB231 (breast carcinoma, ATCC
HTB-26), SKBR-3 (breast carcinoma, ATCC HTB-30), SKOV-3
(ovarian carcinoma, ATCC HTB-77), RKOp21 (colon carcinoma32),
HCT-15 (colon carcinoma, ATCC CCL-225), PC3 (prostate
carcinoma, ATCC CRL-1435), AsPC1 (pancreatic carcinoma,
ATCC CRL-1682), Cal27 (tongue carcinoma, ATCC CRL-2095),
A-431 (vulva carcinoma, ATCC CRL-2592), Hec1A (endometrial
carcinoma, ATCC HTB-112), Saos-2 (osteosarcoma, ATCC HTB-
85), U87MG (glioblastoma, ATCC HTB-14), WM266-4 (mela-
noma, ECACC 91061233), K562 (chronic myeloid carcinoma,
DSZM ACC 10), EOL1 (acute hypereosinophilic myeloid leukemia,
DSZM ACC386), and CCRF-CEM and CCRF-CEM VCR1000
(acute lymphoblastic leukemia sensitive and resistant toward
vincristine, DSZM 240). For quantification of cellular proliferation/
cytotoxicity, the Alamar blue (resazurin) cell viability assay was
applied.36 Cell lines were seeded at their respective density into
content) are evident at 3.2 µM (Figure 3B), with massive
apoptosis (subG1 cell population, <2 N DNA content) at 10
µM. This massive apoptosis affected the cell cycle analysis by
an overestimation of cells in the S and G1 phases (Figure 3A).
SAHA (2) as a reference behaved quite similarly, also
depleting S phase cells and partially arresting at G1 and G2/M
(data not shown). Finally, histone H3S10 phosphorylation as a
marker for ARK-B activation and mitotic arrest was studied in
RKO and A549 cells. As shown in Figure 4, 6c and 7b induce
a strong histone H3 hyperacetylation with maximum levels
reached in both cell lines between 1 and 3 µM. In parallel,
histone H3S10 phosphorylation was nearly completely inhibited
at 10 µM and below the level of untreated, cycling control cells.
The opposite is true for the antimitotic agent paclitaxel, showing
a strong induction of histone H3S10 phosphorylation as a
hallmark of mitotic arrest. Since both HDIs induce a partial

Indoles and Furans as Inhibitors
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 18 4413
96-well flat bottom plates (Costar no. 3598) in a volume of 200
µL per well. Twenty-four hours after seeding, 1 µL each of the
compound dilutions was added in duplicate and incubation con-
tinued for 72 h at 37 °C in a humidified atmosphere containing
5% CO2. Finally, an amount of 20 µL of resazurin solution (90
mg/mL in PBS) was added, and after 4 h of incubation at 37 °C,
the fluorescence was measured at an excitation λ of 544 nm and
an emission λ of 590 nm using a Wallac Victor V reader. For
calculation of cell viability, the emission from untreated cells was
set to 100% and from medium-only samples to 0% viability. The
viability in % was calculated using the formula
4-[1,3]Dioxolan-2-ylbenzoic acid (21) was prepared from 4-car-
boxybenzaldehyd (Acros) and ethane-1,2-diol according to the
literature.28
1H-Indole-5-carbaldehyde (22)39 was prepared from 5-bro-
moindole (Acros) according to the literature.39
1-Benzenesulfonyl-1H-indole-5-carbaldehyde (23) was pre-
pared from 1H-Indole-5-carbaldehyde (22)39 according to the
literature.29
5-(1,3-Dioxolan-2-yl)-1-(phenylsulfonyl)-1H-indole (24) was
prepared from 23 according to the analogous literature28 as described
1
for 21c. H NMR (DMSO-d6): δ (ppm) ) 8.25 (s, 1H), 8.17-
8.16 (m, 2H), 8.10-7.93 (m, 4H), 7.78-7.51 (m, 3H), 4.11-4.09
(m, 2H), 4.08-4.06 (m, 2H). Anal. (C17H15NO4S) C, H, N.
2-Bromo-1-phenylethanone (33c) (Acros) and 2-bromo-1-(3-
methoxyphenyl)ethanone (33d) (Alfa Aesar) were commercially
available, and 2-bromo-1-(3,4,5-trimethoxyphenyl)ethanone (33e)
was prepared according to the literature.40
4-Hydroxybenzene-1,3-dicarbaldehyde (38). 38 was prepared
from 4-hydroxybenzaldehyde according to the literature.30
3-[1,3]Dioxolan-2-ylbenzoic Acid (21c). 21c was prepared from
3-carboxybenzaldehyde (Aldrich) according to the analogous
literature.28 For details, see Supporting Information. 1H NMR
(DMSO-d6): δ (ppm) ) 13.09 (s, 1H), 8.00 (t, 1H, J ) 1.6 Hz),
7.96 (d,t 1H, Jd ) 7.7 Hz, Jt ) 1.5 Hz), 7.68 (d,t, 1H, Jd ) 7.7 Hz,
Jt ) 1.4 Hz), 7.53 (t, 1H, J ) 7.7 Hz), 5.80 (s, 1H), 4.10-4.02 (m,
2H), 4.02-3.94 (m, 2H). Anal. (C10H10O4) C, H.
Preparation of [1,3]Dioxolan-2-ylaroyl Chlorides 12 and 12c.
The respective aroylic acid (20.0 mmol) was dissolved in dry THF
and pyridine (60.0 mmol, 4.84 mL). SOCl2 (40.0 mmol, 2.90 mL)
was added, and the mixture was stirred for 30 min at room
temperature. The precipitating pyridininium hydrochloride was
filtered off. The solvent and excess reagent were removed in vacuo
at room temperature, and the aroylic acid chlorides were purified
by short-way column chromatography (SiO2, CH2Cl2).
4-[1,3]Dioxolan-2-ylbenzoyl Chloride (12). 1H NMR
(CDCl3): δ (ppm) ) 8.13 (d, 2H, J ) 8.5 Hz), 7.62 (d, 2H, J )
8.2 Hz), 5.88 (s, 1H), 4.12-4.10 (m, 2H), 4.08-4.06 (m,.2H). Anal.
(C10H9ClO3) C, H.
E590nmX - E590nmC0
E590nmC100 - E590nmC0
× 100
Flow Cytometric Analysis. A549 NSCLC cells were seeded at
5 × 105 cells/10 cm cell culture dish 24 h before treatment to allow
logarithmic proliferation during the experiment. After 24 h, cells
were treated with test compound (after an additional 24 and 48 h),
the culture medium was collected, and floating cells were collected
by short centrifugation (5 min at 1200 rpm). Attached cells were
washed once with 5 mL of PBS, detached by treatment with 3 mL
of trypsin/EDTA solution (short incubation for 3-5 min), and
together with detached floating cells, transferred into 15 mL Falcon
tubes. The cell culture dish was washed with 10 mL of DMEM to
collect all remaining cells. After centrifugation for 5 min at 1200rpm
at room temperature, the supernatant was discarded and the cell
pellet washed twice with 10 mL of PBS. The supernatant was
discarded, the cells resuspended in 4 mL of ice-cold fixation solution
(70 vol % ethanol, 30 vol% H2O). Next an amount of 10 mL of
PBS (4 °C) was added to the cells before centrifugation for 5 min
at 1200rpm. The supernatant was discarded, the cell pellet washed
once with 10 mL of PBS (4 °C), and the cell pellet finally
resuspended in 1 mL of staining solution (10 µg/mL RNAse A, 10
µg/mL propidiumiodide in PBS). After incubation for 30 min at
room temperature in the dark, cells were stored on ice and analyzed
using the Becton Dickinson FACS Canto device. Analysis was done
at an exitation λ of 488 nm with emission set at a λ of 600 nm.
Western Blot Analysis. For Western blot analysis, 2 × 105/
well A549 or 3 × 105/well RKOp21 carcinoma cells in six-well
cell culture plates were treated with the test compounds for 16 h.
Attached cells were lysed in 150 µL of lysis buffer (50 mM Tris-
HCl, pH 8, 150 mM NaCl, 1 v/v NP-40, 0.5% w/v Na desoxy-
cholate, 0.2% w/v disodium dodecyl sulfate (SDS), 0.02% w/v
NaN3, 1 mM Na vanadate, 20 mM NaF, 100 µg/mL PMSF, protease
inhibitor mix/Roche, and 50 U/mL Benzonase) at 4 °C. Equal
amounts of protein were separated by SDS-PAGE before transfer
to polyvinylidene difluoride (PVDF) membrane (Biorad no. 162-
0177) by semidry blotting.37 The following antibodies were used:
monoclonal antibody specific for â-actin (clone AC-12, Sigma no.
A-5441), polyclonal antibody specific for H3K(Ac)9+14 (Calbiochem
no. 382158), polyclonal antibody specific for H3S10p (Cell Signaling
no. 9701), goat antirabbit IgG-HRP conjugated (Biorad, 170-6515),
and goat-anti-mouse IgG-HRP conjugated (Biorad, 170-6516).
3-[1,3]Dioxolan-2-ylbenzoyl Chloride (12c). 1H NMR
(CDCl3): δ (ppm) ) 8.22 (t, 1H, J ) 1.6 Hz), 8.11 (dt, 1H, Jd )
7.8 Hz, Jt ) 1.6 Hz), 7.79 (d, 1H, Jd ) 7.8 Hz), 7.53 (t, 1H, J )
7.8 Hz), 5.86 (s, 1H), 4.18-4.11 (m, 2H), 4.09-34.02 (m, 2H).
Anal. (C10H9ClO3) C, H.
Preparation of (1-Phenylsulfonyl-1H-2-indolyl)arylmetha-
nones (13a-c and 25a,b) by Reaction of 1-Phenylsulfonyl-1H-
indolyles with Carboxylic Acid Chlorides. The compounds were
prepared according to the analogous literature.25 For details, see
Supporting Information.
(1-Benzenesulfonyl-1H-indol-2-yl)-(4-[1,3]dioxolan-2-ylphenyl)-
1
methanone (13a). H NMR (DMSO-d6): δ (ppm) ) 8.09-7.91
(m, 5H), 7.55-7.19 (m, 7H), 6.86 (d, 1H, J ) 0.8 Hz), 5.84 (s,
1H), 4.07-4.04 (m, 2H), 4.02-3.99 (m, 2H). Anal. (C24H19NO5S)
C, H, N.
(1-Benzenesulfonyl-5-methoxy-1H-indol-2-yl)-(4-[1,3]dioxolan-
1
2-ylphenyl)methanone (13b). H NMR (DMSO-d6): δ (ppm) )
7.95-7.87 (m, 5H), 7.74-7.58 (m, 5H), 7.24 (s, 1H), 7.19 (d, 1H,
J ) 2.5 Hz), 7.12 (dd, 1H, J ) 9 Hz, J ) 2.7 Hz), 5.87 (s, 1H),
4.08-4.05 (m, 2H), 4.03-3.97 (m, 2H), 3.77 (s, 3H). Anal. (C25H21-
NO6S) C, H, N.
Chemical Procedures. General. NMR spectra were recorded
with a Bruker Avance 300 MHz spectrometer at 300 K, using TMS
as an internal standard. IR spectra (KBr or pure solid) were
measured with a Bruker Tensor 27 spectrometer. Melting points
were determined with a Bu¨chi B-545. MS spectra were measured
with a Finnigan MAT 95 (EI, 70 eV, and HR-MS spectra) or with
a Finnigan Thermo Quest TSQ 7000 (ESI) (CH2Cl2/MeOH + 10
mmol/L NH4Ac). All reactions were carried out under nitrogen
atmosphere. Elemental analyses were performed by the Analytical
Laboratory of the University of Regensburg.
(1-Benzenesulfonyl-1H-indol-2-yl)-(3-[1,3]dioxolan-2-ylphenyl)-
1
methanone (13c). H NMR (DMSO-d6): δ (ppm) ) 8.08-7.34
(m, 13H), 7.31 (s, 1H), 5.86 (s, 1H), 4.08-4.05 (m, 2H), 4.0-
3.97 (m, 2H). Anal. (C24H19NO5S) C, H, N.
(1-Benzenesulfonyl-5-[1,3]dioxolan-2-yl-1H-indol-2-yl)phenyl-
methanone (25a). 25a was used in the next step without further
purification because of chemical instability.
(1-Benzenesulfonyl-5-[1,3]dioxolan-2-yl-1H-indol-2-yl)-(3-
methoxyphenyl)methanone (25b). 1H NMR (DMSO-d6): δ (ppm)
) 8.09 (d, 1H, J ) 9.0 Hz), 7.81-7.70 (m, 2H), 7.69-7.41 (m,
6H), 7.37-7.30 (m, 2H), 5.82 (s, 1H), 4.10-3.93 (m, 6H), 3.84
(s, 3H). Anal. (C25H21NO6S‚0.75H2O) C, H, N.
1-Benzenesulfonyl-1H-indole (11a) was prepared from indole
(Acros) according to procedures earlier described.38
1-Benzenesulfonyl-5-methoxy-1H-indole (11b) was prepared
from 5-methoxyindole (Biosynth) according to procedures38 de-
scribed earlier.

4414 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 18
Mahboobi et al.
Preparation of (1-Benzenesulfonyl-1H-indole-2-carbonyl)-
arylaldehydes (14a-c, 26a, and 26b) by Cleavage of the Respec-
tive [1,3]Dioxolanes. To a solution of the respective [1,3]dioxolanes
(12.5 mmol) in CH2Cl2 (40 mL) was added HClO4 (37%, 4.0 mL).
The mixture was stirred at 0 °C for 1-2 h until TLC indicated
complete consumption of the [1,3]dioxolane. The mixture was
poured into water (100 mL), and the organic layer was separated,
washed with saturated NaHCO3 (50 mL), and dried (Na2SO4). The
solvent was removed under reduced pressure, and the crude product
so obtained was purified by column chromatography (SiO2/CH2-
Cl2) and crystallization from diethyl ether.
4-(1-Benzenesulfonyl-1H-indole-2-carbonyl)benzaldehyde (14a).
1H NMR (CDCl3): δ (ppm) ) 10.14 (s, 1H), 8.16-8.03 (m, 3H),
8.02-7.99 (m, 4H), 7.61-7.56 (m, 2H), 7.53-7.46 (m, 3H), 7.32
(t, 1H, J ) 7.6 Hz), 7.02 (d, 1H, 0.5 Hz). Anal. (C22H15NO4S) C,
H, N.
3-[1-Benzenesulfonyl-2-(3-methoxybenzoyl)-1H-indol-5-yl]-
acrylic Acid tert-Butyl Ester (27b). 1H NMR (DMSO-d6): δ (ppm)
) 8.10-8.00 (m, 4H), 7.95-7.85 (m, 1H), 7.80-7.25 (m, 10H),
6.55 (d, 1H, J ) 16.2 Hz), 3.85 (s, 1H), 1.49 (s, 9H).
3-[4-(Benzofuran-2-carbonyl)phenyl]acrylic Acid tert-Butyl
1
Ester (35a). H NMR (DMSO-d6): δ (ppm) ) 8.02 (d, 2H, J )
8.2 Hz), 7.98 (d, 2H, J ) 8.2 Hz), 7.87-7.85 (m, 2H), 7.81 (d,
1H, J ) 8.5 Hz), 7.67 (d, 1H, J ) 16.2 Hz), 7.59 (t, 1H, J ) 7.8
Hz), 7.41 (t, 1H, J ) 7.1 Hz), 6.72 (d, 1H, J ) 16.2), 1.51 (s, 9H).
Anal. (C22H20O4) C, H.
3-[3-(Benzofuran-2-carbonyl)phenyl]acrylic Acid tert-Butyl
1
Ester (35b). H NMR (DMSO-d6): δ (ppm) ) 8.25 (s,1H), 8.07
(d, H, J ) 7.9 Hz), 7.98 (d, 1H, J ) 7.9 Hz), 7.90-7.85 (m, 2H),
7.80 (d, 1H, J ) 8.5 Hz), 7.73-7.57 (m, 3H), 7.41 (t, 1H, J ) 7.5
Hz), 6.67 (d, 1H, J ) 16.2), 1.50 (m, 9H). Anal. (C22H20O4) C, H.
3-(2-Benzoylbenzofuran-5-yl)acrylic Acid tert-Butyl Ester
(41a). 1H NMR (DMSO-d6): δ (ppm) ) 8.19-7.57 (m, 10H), 6.57
(d, 1H, J ) 15.9 Hz), 1.49 (s, 9H). Anal. (C22H20O4) C, H.
3-[2-(3-Methoxybenzoyl)benzofuran-5-yl]acrylic Acid tert-
4-(1-Benzenesulfonyl-5-methoxy-1H-indole-2-carbonyl)ben-
1
zaldehyde (14b). H NMR (CDCl3): δ (ppm) ) 10.13 (s, 1H),
8.10 (d, 2H, J ) 8.2 Hz), 8.02 (t, 3H, J ) 8.1 Hz), 7.92 (d, 2H, J
) 7.9 Hz), 7.59-7.53 (m, 1H), 7.46 (t, 2H, J ) 7.5 Hz), 7.10 (d,d,
1H, J ) 2.73 Hz, J ) 9.1 Hz), 6.98-6.96 (m, 2H), 3.82 (s, 3H).
Anal. (C23H17NO5S) C, H, N.
1
Butyl Ester (41b). H NMR (DMSO-d6): δ (ppm) ) 8.13-7.24
(m, 9H), 6.55 (d, 1H, J ) 16 Hz), 3.85 (s, 3H), 1.49 (s, 9H). Anal.
(C23H22O5) C, H.
3-(1-Benzenesulfonyl-1H-indole-2-carbonyl)benzaldehyde (14c).
1H NMR (DMSO-d6): δ (ppm) ) 10.13 (s, 1H), 8.40 (t, 1H, J )
1.5 Hz), 8.26-8.22 (m, 2H), 8.08 (d, 1H, J ) 8.5 Hz), 7.98 (d,
2H, J ) 7.1 Hz), 7.84 (t, 1H, J ) 7.7 Hz), 7.76-7.71 (m, 2H),
7.63 (t, 2H, J ) 7.5 Hz), 7.55 (t, 1H, J ) 7.7 Hz), 7.40-7.36 (m,
2H). Anal. (C22H15NO4S) C, H, N.
3-[2-(3,4,5-Trimethoxybenzoyl)benzofuran-5-yl]acrylic Acid
1
tert-Butyl Ester (41c). H NMR (DMSO-d6): δ (ppm) ) 8.17-
8.13 (m, 1H), 8.01-7.95 (m, 1H), 7.90-7.68 (m, 4H), 7.32 (s,
2H), 6.58 (d, 1H, J ) 16.1 Hz), 3.89 (s, 6H), 3.80 (s, 3H), 1.50 (s,
9H). Anal. (C25H26O7) C, H.
Preparation of the Acrylic Acids (16a-c, 28a,b, 36a,b, 42a-
c) by Cleavage of the Respective Acrylic Acid tert-Butyl Esters.
A solution of the respective acrylic acid tert-butyl ester (15.0 mmol)
in 50 mL of TFA was stirred at room temperature for 1 h. The
mixture was added to water (100 mL) with stirring, and the
precipitating product was removed by filtration and dried in vacuum.
3-[4-(1-Benzenesulfonyl-1H-indole-2-carbonyl)phenyl]acryl-
ic Acid (16a). 1H NMR (DMSO-d6): δ (ppm) ) 8.05 (d, 1H, J )
9.0 Hz), 7.98-7.92 (m, 6H), 7.75-7.61 (m, 5H), 7.53 (t, 1H, J )
7.8 Hz), 7.45-7.31 (m, 2H), 6.72 (d, 1H, J ) 16.2 Hz). Anal.
(C28H25NO5S) C, H, N.
1-Benzenesulfonyl-2-benzoyl-1H-indole-5-carbaldehyde (26a).
1H NMR (DMSO-d6): δ (ppm) ) 10.09 (s, 1H), 8.33-8.22 (m,
2H), 8.12-7.92 (m, 5H), 7.81-7.74 (m, 2H), 7.71-7.59 (m, 4H),
7.41 (s, 1H). Anal. (C22H15NO4S) C, H, N.
1-Benzenesulfonyl-2-(3-methoxybenzoyl)-1H-indole-5-carbal-
1
dehyde (26b). H NMR (DMSO-d6): δ (ppm) ) 10.07 (s, 1H),
8.33-8.25 (m, 2H), 8.11-8.02 (m, 3H), 7.82-7.64 (m, 3H), 7.55-
7.44 (m, 4H), 7.38-7.32 (m, 1H), 3.82 (s, 3H). Anal. (C23H17-
NO5S) C, H, N
Preparation of Acrylic Acid tert-Butyl Esters (15a-c, 27a,b,
35a,b, and 41a-c) by Wittig Olefination of the Respective
Aldehydes. To a mixture of the pertinent aldehydes (12.0 mmol)
were added (tert-butoxycarbonylmethyl)triphenylphosphonium chlo-
ride (Lancaster) (4.96 g, 12.0 mmol) in CH2Cl2 (100 mL), NaOH
(0,98 g, 24mmol) in H2O (50 mL), and NEt3 (5 mL). The mixture
was stirred at room temperature for 1 h. The organic layer was
separated and washed with 1 M HCl (50 mL) and saturated aqueous
NaHCO3 (2 × 100 mL). The combined organic layers were dried
(Na2SO4) and concentrated to give a crude product, which was
purified by flash column chromatography (SiO2, CH2Cl2) to afford
the pure compound.
3-[4-(1-Benzenesulfonyl-1H-indole-2-carbonyl)phenyl]acryl-
ic Acid tert-Butyl Ester (15a). 1H NMR (DMSO-d6): δ (ppm) )
8.05 (d, 1H, J ) 9.0 Hz), 7.98-7.92 (m, 6H), 7.75-7.61 (m, 5H),
7.53 (t, 1H, J ) 7.8 Hz), 7.39-7.34 (m, 2H), 6.72 (d, 1H, J )
16.2 Hz), 1.50 (s, 9H). Anal. (C28H25NO5S) C, H, N.
3-[4-(1-Benzenesulfonyl-5-methoxy-1H-indole-2-carbonyl)-
1
phenyl]acrylic Acid Monohydrate (16b). H NMR (DMSO-d6):
δ (ppm) ) 7.93-7.85 (m, 6H), 7.73-7.57 (m, 5H), 7.25 (s, 1H),
7.19 (d, 1H,J ) 2.5 Hz), 7.14-7.11 (m 1H), 6.71 (d, 1H, J ) 15.9
Hz), 3.77 (s, 3H).
3-[3-(1-Benzenesulfonyl-1H-indole-2-carbonyl)phenyl]acryl-
1
ic Acid (16c). H NMR (DMSO-d6): δ (ppm) ) 12.54 (s, 1H),
8.11 (s, 1H), 8.08 (t, 2H, J ) 8.4 Hz), 7.41 (d, 2H, J ) 7.4 Hz),
7.95 (d, 1H, J ) 7.9 Hz), 7.76-7.71 (m 2H), 7.68-7.62 (m, 4H),
7.54 (t, 1H, J ) 7.3 Hz), 7.39-7.35 (m, 2H), 6.64 (d, 1H, J )
16.2 Hz). Anal. (C24H17NO5S) C, H, N.
3-(1-Benzenesulfonyl-2-benzoyl-1H-indol-5-yl)acrylic Acid (28a).
1H NMR (DMSO-d6): δ (ppm) ) 12.45 (s, br, 1H), 8.09-7.85
(m, 7H), 7.79-7.58 (m, 7H), 7.29 (s, 1H), 6.55 (d, 1H, J ) 16.2
Hz). Anal. (C24H17NO5S‚0.25H2O) C, H, N.
3-[1-Benzenesulfonyl-2-(3-methoxybenzoyl)-1H-indol-5-yl]-
3-[3-(1-Benzenesulfonyl-1H-indole-2-carbonyl)phenyl]acryl-
ic Acid tert-Butyl Ester (15b). 15b was prepared as described
1
acrylic Acid (28b). H NMR (DMSO-d6): δ (ppm) ) 12.30 (s,
1
br, 1H), 8.10-8.02 (m, 4H), 7.92-7.87 (m, 1H), 7.78-7.63 (m,
4H), 7.55-7.41 (m, 3H), 7.37-7.29 (m, 2H), 6.55 (d, 1H, J )
15.9 Hz), 3.85 (s, 3H). Anal. (C25H19NO6S‚0.75H2O) C, H, N.
3-[4-(Benzofuran-2-carbonyl)phenyl]acrylic Acid (36a). 1H
NMR (DMSO-d6): δ (ppm) ) 12.63 (s, 1H), 8.03 (d, 2H, J ) 8.5
Hz), 7.93 (d, 2H, J ) 8.5 Hz), 7.89-7.85 (m, 2H), 7.79 (d, 1H, J
) 8.5 Hz), 7.71 (d, 1H, J ) 16.2 Hz), 7.59 (t, 1H, J ) 7.1 Hz),
7.41 (t, 1H, J ) 7.1 Hz), 6.72 (d, 1H, J ) 16.1 Hz). Anal.
(C18H12O4) C, H.
above. The reaction time was 4 days. H NMR (DMSO-d6): δ
(ppm) ) 8.20 (s, 1H), 8.11-8.01 (m, 4H), 7.93 (d, 1H, J ) 7.9
Hz), 7.83 (d, 2H, J ) 7.8 Hz), 7.66-7.61 (m, 4H), 7.53 (t, 1H, J
) 7.3 Hz), 7.39-7.30 (m, 2H), 6.63 (d, 1H, J ) 16.2 Hz), 1.48 (s,
9H). Anal. (C25H19NO6S) C, H, N.
3-[4-(1-Benzenesulfonyl-5-methoxy-1H-indole-2-carbonyl)-
1
phenyl]acrylic Acid tert-Butyl Ester (15c). H NMR (DMSO-
d6): δ (ppm) ) 8.12-7.86 (m, 6H), 7.73-7.60 (m, 4H), 7.25-
7.09 (m, 4H), 6.70 (d, 1H, J ) 16.2 Hz), 3.77 (s, 3H), 1.49 (s,
9H). Anal. (C25H19NO6S) C, H, N.
1
3-[3-(Benzofuran-2-carbonyl)phenyl]acrylic Acid (36b). H
3-(1-Benzenesulfonyl-2-benzoyl-1H-indol-5-yl)acrylic Acid tert-
Butyl Ester (27a). H NMR (DMSO-d6): δ (ppm) ) 8.05-8.00
(m, 4H), 7.95-7.90 (m, 2H), 7.80-7.72 (m, 2H), 7.70-7.58 (m,
6H), 7.28 (s, 1H), 6.55 (d, 1H, J ) 16.0 Hz), 1.48 (s, 9H). Anal.
(C28H25NO5S) C, H, N.
NMR (DMSO-d6): δ (ppm) ) 12.55 (s, 1H), 8.24 (s, 1H), 8.07
(d, 1H, J ) 7.7 Hz), 8.00 (d, 1H, J ) 7.3 Hz), 7.90-7.85 (m, 2H),
7.80 (d, 1H, J ) 8.5 Hz), 7.74 (d, 1H, J ) 16.2 Hz), 7.66 (t, 1H,
J ) 7.7 Hz), 7.60 (t, 1H, J ) 7.8 Hz), 7.41 (t, 1H, J ) 7.5 Hz),
6.69 (d, 1H, J ) 16.1 Hz). Anal. (C18H12O4) C, H.
1

Indoles and Furans as Inhibitors
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 18 4415
3-(2-Benzoylbenzofuran-5-yl)acrylic Acid (42a). 1H NMR
(DMSO-d6): δ (ppm) ) 12.45 (s, 1H), 8.20-7.58 (m, 11H), 6.58
(d, 1H, J ) 15.9 Hz). Anal. (C18H12O4) C, H.
J ) 9.2 Hz), 6.68 (d, 1H, J ) 15.9 Hz), 4.95 (s, 3H), 3.97 (m,
1H), 3.57-3.53 (m, 1H), 1.71 (m, 3H), 1.55 (m, 3H). Anal.
(C30H28N2O7S) C, H, N.
3-[2-(3-Methoxybenzoyl)benzofuran-5-yl]acrylic Acid (42b).
1H NMR (DMSO-d6): δ (ppm) ) 12.50 (s, br, 1H), 8.17-8.14
(m, 1H), 8.02-7.94 (m, 1H), 7.88-7.78 (m, 2H), 7.74 (d, 1H, J )
15.9 Hz), 7.62-7.47 (m, 3H), 7.35-7.28 (m, 1H), 6.59 (d, 1H, J
) 15.9 Hz), 3.87 (s, 3H). Anal. (C19H14O5‚0.25H2O) C, H.
3-[2-(3,4,5-Trimethoxybenzoyl)benzofuran-5-yl]acrylic Acid
3-[3-(1-Benzenesulfonyl-1H-indole-2-carbonyl)phenyl]-N-(tet-
1
rahydropyran-2-yloxy)acrylamide (18c). H NMR (DMSO-d6):
δ (ppm) ) 11.27 (s, 1H), 8.13-8.01 (m, 4H), 7.96-7.90 (m, 2H),
7.77-7.72 (m, 2H), 7.68-7.62 (m 4H), 7.58-7.52 (m, 1H), 7.40-
7.35 (m, 2H), 6.62 (d, 1H, J ) 15.9 Hz), 4.92 (s, 1H), 3.04-3.94
(m, 1H), 3.55-3.52 (m, 1H), 1.69 (m, 3H), 1.54 (m, 3H). Anal.
(C29H26N2O6) C, H, N.
1
(42c). H NMR (DMSO-d6): δ (ppm) ) 12.45 (s, br, 1H), 8.17-
8.13 (m, 1H), 7.99-7.03 (m, 1H), 7.90-7.81 (m, 2H), 7.75 (d,
1H, J ) 15.9 Hz), 7.31 (s, 2H), 6.58 (d, 1H, J ) 15.9 Hz), 3.89 (s,
6H), 3.80 (s, 3H). Anal. (C21H18O7‚0.25H2O) C, H.
3-[4-(1H-Indole-2-carbonyl)phenyl]-N-(tetrahydropyran-2-
yloxy)acrylamide (19a). 1H NMR (DMSO-d6): δ (ppm) ) 12.02
(s, 1H), 11.38 (s, 1H), 7.98 (d, 2H, J ) 8.2 Hz), 7.79 (d, 2H, J )
8.2 Hz), 7.73 (d, 1H, J ) 7.9 Hz), 7.60 (d, 1H, J ) 15.6 Hz),
7.250 (d, 1H, J ) 8.5 Hz), 7.33 (t, 1H, J ) 7.6 Hz), 7.18 (d, 1H,
J ) 1.4 Hz), 7.11 (t, 1H, J ) 7.5 Hz), 6.67 (d, 1H, J ) 15.6 Hz),
4.95 (s, 1H), 3.97 (m, 1H), 3.57-3.54 (m, 1H), 1.71 (m, 3H), 1.55
(m, 3H). Anal. (C23H22N2O4) C, H, N.
3-[4-(5-Methoxy-1H-indole-2-carbonyl)phenyl]-N-(tetrahy-
dropyran-2-yloxy)acrylamide (19b). 1H NMR (DMSO-d6): δ
(ppm) ) 11.89 (s, 1H), 11.37 (s, 1H), 7.96 (d, 2H, J ) 8.3 Hz),
7.78 (d, 2H, J ) 8.2 Hz), 7.60 (d, 1H, J ) 16.2 Hz), 7.40 (d 1H,
J ) 8.8 Hz), 7.15 (d, 1H, J ) 2.2 Hz), 7.16 (d, 1H, J ) 2.2 Hz),
7.04 (d,d, 1H, J ) 2.5 Hz, J ) 9.1 Hz), 6.67 (d, 1H, J ) 15.9 Hz),
4.94 (s, 1H), 4.00-3.97 (m, 1H), 3.86 (s, 3H), 3.63-3.57 (m, 1H),
1.71 (m, 3H), 1.55 (m, 3H). Anal. (C24H24N2O5) C, H, N.
3-[3-(1H-Indole-2-carbonyl)phenyl]-N-(tetrahydropyran-2-
yloxy)acrylamide (19c). 1H NMR (DMSO-d6): δ (ppm) ) 12.04
(s, 1H), 11.27 (s, 1H), 8.10 (s, 1H), 7.92 (t, 2H, J ) 9.3 Hz), 7.74
(d, 1H, J ) 8.0 Hz), 7.67-7.60 (m, 2H), 7.51 (d, 1H, J ) 8.2 Hz),
7.33 (t, 1H, J ) 7.7 Hz), 7.18 (d, 1H, J ) 1.4 Hz), 7.11 (t, 1H, J
) 7.1 Hz), 6.65 (d, 1H, J ) 15.7 Hz), 4.93 (s, 1H), 3.95 (m, 1H),
3.56-3.52 (m, 1H), 1.70 (m, 3H), 1.54 (m, 3H). Anal. (C23H22N2O4)
C, H, N.
Preparation of 3-[4-(1H-Indole-2-carbonyl)phenyl]acrylic Ac-
ids by Cleavage of the Benzenesulfonyl Group. The N-protected
methanone derivative X (1.5 mmol) was heated in methanol (50
mL) and 10% aqueous NaOH (50 mL) under reflux for 12 h. The
organic solvent was removed under reduced pressure, and the
aqueous solution was acidified (HCl, 37%). The yellow precipitating
crystals were removed by filtration, washed with diluted HCl, and
dried in vacuo. Thus, compounds 17a-c and 29a,b were prepared.
3-[4-(1H-Indole-2-carbonyl)phenyl]acrylic Acid (17a). 1H
NMR (DMSO-d6): δ (ppm) ) 12.02 (s, 1H), 7.92 (d, 2H, J ) 8.2
Hz), 7.72 (d, 3H, J ) 8.2 Hz), 7.51 (d, 1H, J ) 8.0 Hz), 7.34-
7.24 (m, 2H), 7.18 (d, 1H, J ) 1.4 Hz), 7.10 (t, 1H, J ) 7.5 Hz),
6.61 (d, 1H, J ) 15.9 Hz). Anal. (C18H13NO3‚H2O) C, H, N.
3-[4-(5-Methoxy-1H-indole-2-carbonyl)phenyl]acrylic Acid
1
(17b). H NMR (DMSO-d6): δ (ppm) ) 12.59 (s, 1H, exchange-
able), 11.89 (d, 1H, J ) 1.6 Hz, exchangeable), 7.94 (d, 2H, J )
7.9 Hz), 7.90 (d, 2H, J ) 7.9 Hz), 7.70 (d, 1H, J ) 16.0 Hz), 7.40
(d, 1H, 8.8 Hz), 7.16 (d, 1H, J ) 2.5 Hz), 7.06 (d, 1H, J ) 1.6
Hz), 6.99 (dd, 1H, J ) 8.8 Hz, J ) 2.5 Hz), 6.70 (d, 1H, J ) 16.0
Hz), 3.77 (s, 3H). Anal. (C19H15NO4‚1/6H2O) C, H, N.
3-[3-(1H-Indole-2-carbonyl)phenyl]acrylic Acid Hydrate (17c).
1H NMR (DMSO-d6): δ (ppm) ) 12.18 (s, 1H), 8.00 (s, 1H), 7.85-
7.81 (m,2H), 7.74 (d, 1H, J ) 8.2 Hz), 7.56 (t, 2H, J ) 8.1 Hz),
7.35-7.30 (m, 2H), 7.15-7.07 (m, 2H), 6.68 (d, 1H, J ) 15.9).
Anal. (C18H13NO3‚3/2H2O) C, H, N.
3-(2-Benzoyl-1H-indol-5-yl)-N-(tetrahydropyran-2-yloxy)-
acrylamide (30a). 1H NMR (DMSO-d6): δ (ppm) ) 12.20 (s, br,
1H), 11.18 (s, br, 1H), 7.96-7.93 (m, 3H), 7.74-7.67 (m, 1H),
7.63-7.52 (m, 5H), 7.18 (s, 1H), 6.45 (d, 1H, J ) 15.4 Hz), 4.91
(s, 1H), 4.10-3.90 (m, 1H), 3.58-3.50 (m, 1H), 1.77-1.63 (m,
3H), 1.63-1.48 (m, 3H). HR-PI-LSI-MS calcd for C23H23N2O4
[MH+•]: 391.1658. Found 391.1669.
3-(2-Benzoyl-1H-indol-5-yl)acrylic Acid (29a). 1H NMR (DMSO-
d6): δ (ppm) ) 12.27 (s, br, 1H), 12.22 (s, 1H), 8.04-7.92 (m,
3H), 7.75-7.50 (m, 6H), 7.20-7.17 (m, 1H), 6.45 (d, 1H, J )
15.9 Hz). Anal. (C18H13NO3‚0.5H2O) C, H, N.
3-[1-Benzenesulfonyl-2-(3-methoxybenzoyl)-1H-indol-5-yl]-N-
1
3-[2-(3-Methoxybenzoyl)-1H-indol-5-yl]acrylic Acid (29b). 1H
NMR (DMSO-d6): δ (ppm) ) 12.30 (s, br, 1H), 12.21 (s, 1H),
8.07 (s, 1H), 7.75-7.49 (m, 6H), 7.43-7.40 (m, 1H), 7.30-7-23
(m, 1H), 7.21-7.18 (m, 1H), 6.45 (d, 1H, J ) 15.9 Hz), 3.86 (s,
3H). Anal. (C19H15NO4‚0.5H2O) C, H, N.
(tetrahydropyran-2-yloxy)acrylamide (30b). H NMR (DMSO-
d6): δ (ppm) ) 11.25 (s, br, 1H), 8.12-7.90 (m, 3H), 7.95-7.88
(m, 1H), 7.78-7.72 (m, 2H), 7.70-7.46 (m, 5H), 7.45-7.41 (m,
1H), 7.37-7.30 (m, 2H), 6.53 (d, 1H, J ) 15.7 Hz), 4.92 (s, br,
1H), 4.03-3.90 (m, 1H), 3.83 (s, 3H), 3.60-3.50 (m, 1H), 1.75-
1.45 (m, 6H). Anal. (C30H28N2O7S) C, H, N.
Preparation of N-(Tetrahydropyran-2-yloxy)acrylamides by
Amidation of the Respective Acrylic Acids (18a-c, 19a-c,
30a,b, 31a,b, 37a,b, 43a-c). To a solution of the respective acrylic
acid (7.1 mmol), BOP {(benzotriazol-1-yloxy)tris(dimethylamino)-
phosphonium hexafluorophosphate} (3.32 g, 7.5 mmol), and NEt3
(2.3 mL, 17.04 mmol) in dry THF or DMF (30 mL) was added
NH2OTHP {O-(tetrahydropyran-2-yl)hydroxylamine, Aldrich} (1.0
g, 8.5 mmol). The mixture was stirred for 1-2 h (TLC control)
and then poured into water (100 mL) with stirring. The precipitating
crude product was removed by filtration and dried in vacuo.
Purification by column chromatography (SiO2, ethyl acetate)
afforded the pure title product as a colorless solid.
3-(2-Benzoyl-1H-indol-5-yl)-N-(tetrahydropyran-2-yloxy)-
acrylamide (31a). 1H NMR (DMSO-d6): δ (ppm) ) 12.20 (s, br,
1H), 11.18 (s, br, 1H), 7.96-7.93(m, 3H), 7.73-7.68 (m, 1H),
7.62-7.52 (m, 5H), 7.19 (s, 1H), 6.45 (d, 1H, J ) 15.4 Hz), 4.91
(s, 1H), 4.01-3.91 (m, 1H), 3.56-3.52 (m, 1H), 1.71-1.54 (m,
6H). IR (KBr): ν (cm-1) ) 3290, 2948, 1652, 1625. HR-PI-EI-
MS calcd for C23H22N2O4 [M+•]: 390.1580. Found 390.1580.
3-[2-(3-Methoxybenzoyl)-1H-indol-5-yl]-N-(tetrahydropyran-
2-yloxy)acrylamide (31b). 1H NMR (DMSO-d6): δ (ppm) ) 12.20
(s, br, 1H), 11.18 (s, br, 1H), 7.93 (s, 1H), 7.63-7.50 (m, 5H),
7.43-7.38 (m, 1H), 7.30-7.24 (m, 1H), 7.20 (s, 1H), 6.45 (d, 1H,
J ) 15.6 Hz), 4.91 (s, 1H), 4.03-3.90 (m, 1H), 3.85 (s, 3H), 3.60-
3.50 (m, 1H), 1.78-1.47 (m, 6H). Anal. (C24H24N2O5‚0.5H2O) C,
H, N.
3-[4-(Benzofuran-2-carbonyl)phenyl]-N-(tetrahydropyran-2-
yloxy)acrylamide (37a). 1H NMR (DMSO-d6): δ (ppm) ) 11.39
(s, 1H), 8.06 (d, 2H, J ) 8.2 Hz), 7.89-7.78 (m, 5H), 7.41 (t, 1H,
J ) 7.5 Hz), 6.69 (d, 1H, J ) 15.9 Hz), 4.95 (s, 1H), 3.99 (m,
1H), 3.58-3.54 (m, 1H), 1.72 (m, 3H), 1.56 (m, 3H). Anal. (C23H21-
NO5‚1/4H2O) C, H, N.
3-[4-(1-Benzenesulfonyl-1H-indole-2-carbonyl)phenyl]-N-(tet-
1
rahydropyran-2-yloxy)acrylamide (18a). H NMR (DMSO-d6):
δ (ppm) ) 11.40 (s, 1H, exchangeable), 8.06 (d, 1H, J ) 8.4 Hz),
7.98-7.93 (m, 4H), 7.79 (d, 2H, J ) 8.5 Hz), 7.73-7.70 (m, 2H),
7.66-7.49 (m, 4H), 7.39-7.33 (m, 2H), 6.68 (d, 1H, J ) 15.9
Hz), 4.94 (s, 1H), 3.97 (m, br, 1H), 3.55 (d, br, 1H, J ) 11.0 Hz),
1.71 (s, br, 3H), 1.55 (s, br, 3H). Anal. (C29H26N2O6S) C, H, N.
3-[4-(1-Benzenesulfonyl-5-methoxy-1H-indole-2-carbonyl)-
phenyl]-N-(tetrahydropyran-2-yloxy)acrylamide (18b). 1H NMR
(DMSO-d6): δ (ppm) ) 11.40 (s, 1H), 7.96-7.88 (m, 5H), 7.79
(d, 2H, J ) 8.3 Hz), 7.72 (t, 1H, J ) 7.4 Hz), 7.63-7.58 (m 3H),
7.25 (s, 1H), 7.19 (d, 1H, J ) 2.5 Hz), 7.12 (d,d, 1H, J ) 2.5 Hz,
3-[3-(Benzofuran-2-carbonyl)phenyl]-N-(tetrahydropyran-2-
yloxy)acrylamide (37b). 1H NMR (DMSO-d6): δ (ppm) ) 11.29
(s, 1H), 8.16 (s, 1H), 7.99 (d, 1H, J ) 7.7 Hz), 7.93 (d, 1H, J )

4416 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 18
Mahboobi et al.
8.0 Hz), 7.89-7.86 (m, 2H), 7.80 (d, 1H, J ) 8.5 Hz), 7.68-7.57
(m, 3H), 7.41 (t, 1H, J ) 7.5 Hz), 6.66 (d, 1H, J ) 15.9 Hz), 4.93
(s, 1H), 3.96 (m, 1H), 3.56-3.52 (m, 1H), 1.70 (m, 3H), 1.54 (m,
3H). Anal. (C23H21NO5) C, H, N.
3-(2-Benzoylbenzofuran-5-yl)-N-(tetrahydropyran-2-yloxy)-
acrylamide (43a). 1H NMR (DMSO-d6): δ (ppm) ) 11.29 (s, 1H),
8.04-7.97 (m, 3H), 7.85-7.81 (m, 3H), 7.69-7.58(m, 4H), 6.55
(d, 1H, J ) 15.7 Hz), 4.93 (s, 1H), 3.66-3.46 (m, 1H), 1.78-1.47
(m, 7H). Anal. (C23H21NO5) C, H, N.
3-[2-(3-Methoxybenzoyl)benzofuran-5-yl]-N-(tetrahydropyran-
2-yloxy)acrylamide (43b). 1H NMR (DMSO-d6): δ (ppm) ) 11.30
(s, br, 1H), 8.07 (s, 1H), 7.87-7.81 (m, 3H), 7.63-7.47 (m, 4H),
7.34-7.28 (m, 1H), 6.55 (d, 1H, J ) 15.6 Hz), 4.93 (s, 1H), 4.05-
3.92 (m, 1H), 3.86 (s, 3H), 3.60-3.52 (m, 1H), 1.78-1.45 (m,
6H). Anal. (C24H23NO6‚1/3H2O) C, H, N.
(C19H16N2O4‚1/2H2O) C, H, N. IR (KBr): ν (cm-1) ) 3264, 1679,
1653, 1611. ES-MS (CH2Cl2/MeOH + 10 mmol/L NH4Ac) m/z
(%): 336 (21) [M]+, 335 (100).
N-Hydroxy-3-[3-(1H-indole-2-carbonyl)phenyl]acrylamide
Monohydrate (6c). Yield: 0.14 g (96%). Mp: 190.6-203.2 °C.
1H NMR (DMSO-d6): δ (ppm) ) 12.04 (s, 1H), 10.80 (s, 1H),
9.13 (s, 1H), 8.08 (s, 1H), 7.94-7.87 (m, 2H), 7.74 (d, 1H, J )
8.0 Hz), 7.64 (t, 1H, J ) 7.7 Hz), 7.60 (d, 1H, J ) 15.6 Hz), 7.52
(d, 1H, J ) 8.2 Hz), 7.33 (d, 1H, J ) 7.1 Hz), 7.18 (d, 1H, J ) 1.4
Hz), 7.11 (t, 1H J ) 7.1 Hz), 6.60 (d, 1H, J ) 15.6 Hz). Anal.
(C18H14N2O3) C, H, N. IR (KBr): ν (cm-1) ) 1659, 1624. ES-MS
(CH2Cl2/MeOH + 10 mmol/L NH4Ac) m/z (%): 307 (100) [M +
H+]+.
3-[4-(Benzofuran-2-carbonyl)phenyl]-N-hydroxyacrylamide
1
(7a). Yield: 0.17 g (89%). Mp: 177 °C (dec). H NMR (DMSO-
d6): δ (ppm) ) 10.93 (s, 1H), 8.04 (d, 2H, J ) 8.5 Hz), 7.88-
7.77 (m, 5H), 7.61-7.55 (m, 2H), 7.41 (t, 1H, J ) 7.5 Hz), 6.65
(d, 1H, J ) 15.9 Hz). Anal. (C18H13NO4‚1/4H2O) C, H, N. IR
(KBr): ν (cm-1) ) 1653, 697. ES-MS (CH2Cl2/MeOH + 10
mmol/L NH4Ac) m/z (%): 308 (100) [M + H+]+.
N-(Tetrahydropyran-2-yloxy)-3-[2-(3,4,5-trimethoxybenzoyl)-
benzofuran-5-yl]acrylamide (43c). 1H NMR (DMSO-d6): δ (ppm)
) 11.28 (s, br, 1H), 8.05 (s, br, 1H), 7.91 (s, 1H), 7.88-7.77 (m,
2H), 7.63 (d, 1H, J ) 15.8 Hz), 7.31 (s, 2H), 6.55 (d, 1H, J ) 15.8
Hz), 4.93 (s, br, 1H), 4.05-3.90 (m, 1H), 3.89 (s, 6H), 3.80 (s,
3H), 3.59-3.51 (m, 1H), 1.78-1.47 (m, 6H). Anal. (C26H27NO8‚
1.5H2O) C, H, N.
3-[3-(Benzofuran-2-carbonyl)phenyl]-N-hydroxyacrylamide
1
(7b). Yield: 0.27 g (98%). Mp: 170.7 °C. H NMR (DMSO-d6):
δ (ppm) ) 10.81 (s, 1H), 9.15 (s, 1H), 8.15 (s, 1H), 7.97 (d, 1H,
J ) 7.7 Hz), 7.93-7.85 (m, 3H), 7.80 (d, 1H, J ) 8.2 Hz), 7.67-
7.57 (m, 3H), 7.41 (t, 1H, J ) 7.5 Hz), 6.60 (d, 1H, J ) 15.6 Hz).
Anal. (C18H13NO4) C, H, N. IR (KBr): ν (cm-1) ) 1642, 761.
ES-MS (CH2Cl2/MeOH + 10 mmol/L NH4Ac) m/z (%): 615 (100)
[2M + H]+, 325 (31) [M + NH4+]+, 308 (100) [M + H]+.
3-(1-Benzenesulfonyl-2-benzoyl-1H-indol-5-yl)-N-hydroxy-
acrylamide (8a). Yield: 0.48 g (77%). Mp: 170-172 °C. 1H NMR
(DMSO-d6): δ (ppm) ) 10.79 (s, br, 1H), 9.05 (s, br, 1H), 8.10-
7.85 (m, 6H), 7.80-7.50 (m, 8H), 7.31 (s, 1H), 6.45 (d, 1H, J )
15.9 Hz). IR (KBr): ν (cm-1) ) 2950, 1664, 1630. EI-MS m/z
(%): 446 (25) [M]+•, 428 (80), 287 (75), 105 (100). HR-PI-EI-
MS calcd for C24H18N2O5S [M+•]: 446.0936. Found 446.0929.
3-[1-Benzenesulfonyl-2-(3-methoxybenzoyl)-1H-indol-5-yl]-N-
hydroxyacrylamide (8b). Yield: 0.06 g of colorless crystals (43%).
Mp: 135-138 °C. 1H NMR (DMSO-d6): δ (ppm) ) 10.79 (s, br,
1H), 9.06 (s, br, 1H), 8.12-7.97 (m, 3H), 7.89 (s, 1H), 7.80-7.42
(m, 8H), 7.35-7.28 (m, 2H), 6.48 (d, 1H, J ) 15.9 Hz), 3.84 (s,
3H). IR (KBr): ν (cm-1) ) 2833, 1660. PI-LSI-MS m/z (%): 477
(90) [MH+•]. HR-PI-LSI-MS calcd for C25H21N2O6S [MH]+•:
477.1120. Found 477.1118.
Synthesis of N-Hydroxyacrylamides by Cleavage of N-(Tet-
rahydropyran-2-yloxy)acrylamides (5a-c, 6a-c, 7a,b, 8a,b,
9a,b, 10a-c). The respective N-(tetrahydropyran-2-yloxy)acryla-
mides (0.25 mmol) were dissolved in MeOH (20.0 mL). HCl (0.6
N, 20.0 mL) was added, and the mixture was stirred over night at
room temperature. The precipitating crystals were filtered off,
washed with HCl (0.6 N), and dried in vacuo.
3-[4-(1-Benzenesulfonyl-1H-indole-2-carbonyl)phenyl]-N-hy-
droxyacrylamide Semihydrate (5a). Yield: 1.76 g (80%). Mp:
149.7-151.3 °C. 1H NMR (DMSO-d6): δ (ppm) ) 10.91 (s, 1H),
9.17 (s, 1H), 8.05 (d, 1H, J ) 8.5 Hz), 7.99-7.93 (m, 6H), 7.79-
7.59 (m, 5H), 7.53 (t, 1H, J ) 7.8 Hz), 7.39-7.33 (m, 2H), 6.63
(d, 1H, J ) 15.9 Hz). Anal. (C24H18N2O6S‚0.5H2O) C, H, N. IR
(KBr): ν (cm-1) ) 1659, 1627. EI-MS (70 eV) m/z (%): 446 (4.8)
[M]+•, 77 (100).
3-[4-(1-Benzenesulfonyl-5-methoxy-1H-indole-2-carbonyl)-
phenyl]-N-hydroxyacrylamide (5b). Yield: 0.47 g (56%). Mp:
141.8-142.0 °C. 1H NMR (DMSO-d6): δ (ppm) ) 10.92 (s, 1H),
9.17 (s,1H), 7.96-7.88 (m, 6H), 7.79-7.69 (m, 3H), 7.61 (t, 2H,
J ) 7.5 Hz), 7.24 (s, 1H), 7.19 (d, 1H, J ) 7.2 Hz), 7.12 (d,d, 1H,
J ) 2.7 Hz, J ) 9.0 Hz), 3.77 (s, 3H). Anal. (C25H20N2O6S) C, H,
N. IR (KBr): ν (cm-1) ) 1659, 726. ES-MS (CH2Cl2/MeOH +
10 mmol/L NH4Ac) m/z (%): 477 (100) [M + H+]+.
3-(2-Benzoyl-1H-indol-5-yl)-N-hydroxyacrylamide
(9a).
Yield: 0.13 g of yellow crystals (53%). Mp: 214-216 °C. 1H NMR
(DMSO-d6): δ (ppm) ) 12.19 (s, br, 1H), 10.69 (s, br, 1H), 9.00
(s, br, 1H), 7.98-7.87 (m, 3H), 7.73-7.50 (m, 6H), 7.18 (s, 1H),
6.40 (d, 1H, J ) 15.7 Hz). Anal. (C18H14N2O3) C, H, N. IR (KBr):
ν (cm-1) ) 3322, 1610. ESI-MS m/z (%): 307 (100) [MH]+•.
N-Hydroxy-3-[2-(3-methoxybenzoyl)-1H-indol-5-yl]acryla-
mide (9b). Yield: 0.03 g of yellow crystals (53%). Mp: 155-156
3-[3-(1-Benzenesulfonyl-1H-indole-2-carbonyl)phenyl]-N-hy-
droxyacrylamide Semihydrate (5c). Yield: 0.27 g (73%). Mp:
123.0-129.1 °C. 1H NMR (DMSO-d6): δ (ppm) ) 10.78 (s, 1H),
9.12 (s, 1H), 8.11-8.00 (m, 4H), 7.95-7.88 (m, 2H), 7.77-7.72
(m, 2H), 7.67-7.60 (m 3H), 7.56-7.52 (m, 3H), 7.40-7.35 (m,
2H), 6.57 (d, 1H, J ) 15.9 Hz), 4.95 (s, 1H), 3.97 (m, 1H), 3.57-
3.53 (m, 1H), 1.71 (m, 3H), 1.55 (m, 3H). Anal. (C24H18N2O5S‚1/
2H2O) C, H, N. IR (KBr): ν (cm-1) ) 3214, 1665, 1596. ES-MS
(CH2Cl2/MeOH + 10 mmol/L NH4Ac) m/z (%): 464 (100) [M +
NH4+]+, 447 (77) [M + H+]+.
1
°C. H NMR (DMSO-d6): δ (ppm) ) 12.17 (s, br, 1H), 10.70 (s,
br, 1H), 8.99 (s, br, 1H), 7.91 (s, 1H), 7.62-7.47 (m, 5H), 7.44-
7.39 (m, 1H), 7.32-7.23 (m, 1H), 7.22-7.18 (m, 1H), 6.40 (d,
1H, J ) 15.7 Hz), 3.86 (s, 3H). Anal. (C19H16N2O4‚0.5H2O) C, H,
N. IR (KBr): ν (cm-1) ) 3311, 1613. ESI-MS m/z (%): 673 (45)
[2MH]+•, 337 (100) [MH]+•.
N-Hydroxy-3-[4-(1H-indole-2-carbonyl)phenyl]acrylamide (6a).
1
Yield: 0.04 g (85%). Mp: 183.9-192.8 °C. H NMR (DMSO-
d6): δ (ppm) ) 10.92 (s, 1H), 7.98 (d, 2H, J ) 8.5 Hz), 7.77 (d,
2H, J ) 8.5 Hz), 7.73 (d, 1H, J ) 8.2 Hz), 7.57 (d 1H, J ) 15.9
Hz), 7.51 (d, 1H, J ) 7.5 Hz), 7.32 (t, 1H, J ) 7.7 Hz), 7.18 (d,
1H, J ) 1.4 Hz), 7.09 (t,1H, J ) 7.3 Hz), 6.60 (d, 1H, J ) 15.9).
Anal. (C18H14N2O3) C, H, N. IR (KBr): ν (cm-1) ) 1617, 1520.
ES-MS (CH2Cl2/MeOH + 10 mmol/L NH4Ac) m/z (%): 307 (100)
[M + H+]+.
3-(2-Benzoylbenzofuran-5-yl)-N-hydroxyacrylamide (10a). Crys-
tallization from ethanol/H2O (1:1) afforded 0.03 g (53%) of colorless
crystals. Mp: 151 °C. 1H NMR (DMSO-d6): δ (ppm) ) 10.80 (s,
1H), 9.07 (s, 1H), 8.06-7.97 (m, 3H), 7.86-7.79 (m, 3H), 7.73
(d, 1H, J ) 7.4 Hz), 7.66-7.62 (m, 2H), 7.59 (d, 1H, J ) 6.9 Hz),
6.50 (d, 1H, J ) 15.8 Hz). Anal. (C18H13NO4‚0.5EtOH) C, H, N.
IR (KBr): ν (cm-1) ) 3578, 3431, 1645. ES-MS (CH2Cl2/MeOH/
CH3COONH4) m/z (%): 306 (100) [M - H+]-.
N-Hydroxy-3-[4-(5-methoxy-1H-indole-2-carbonyl)phenyl]-
acrylamide Semihydrate (6b). Yield: 0.06 g (75%). Mp: 204.2-
N-Hydroxy-3-[2-(3-methoxybenzoyl)benzofuran-5-yl]acryla-
mide (10b). Yield: 0.75 g colorless crystals (55%). Mp: 138-
1
204.3 °C. H NMR (DMSO-d6): δ (ppm) ) 11.88 (s, 1H), 10.89
1
(s, 1H), 9.17 (s, 1H), 7.9 (d, 2H, J ) 8.2 Hz), 7.77 (d, 2H, J ) 8.2
Hz), 7.57 (d, 1H, J ) 15.9 Hz), 7.40 (d, 1H, J ) 9.0 Hz), 7.15 (d,
1H, J ) 2.2 Hz), 7.07 (d, 1H, J ) 1.4 Hz), 6.99 (dd, 1H, J ) 2.5
Hz, J ) 9.1 Hz), 6.62 (d, 1H, J ) 15.7), 3.76 (s, 3H). Anal.
140 °C. H NMR (DMSO-d6): δ (ppm) ) 10.80 (s, br, 1H), 9.12
(s, br, 1H), 8.05 (s, 1H), 7.88-7.76 (m, 3H), 7.65-7.47 (m, 4H),
7.33-7.27 (m, 1H), 6.50 (d, 1H, J ) 15.9 Hz). Anal. (C19H15NO5‚
0.75H2O) C, H, N. IR (KBr): ν (cm-1) ) 3325, 1682, 1645. ES-

Indoles and Furans as Inhibitors
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 18 4417
MS (CH2Cl2/MeOH/CH3COONH4) m/z (%): 675 (17) [2M + H]+•,
338 (100) [MH]+•.
8.00 (d, 1H, J ) 8.5 Hz), 7.32 (s, 2H), 3.90 (s, 6H), 3.80 (s, 3H).
Anal. (C19H16O6) C, H. IR (pure solid): ν (cm-1) ) 2830, 1691,
1649. EI-MS (70 eV) m/z (%): 340 (100) [M]+, 269 (20), 173
(60).
N-Hydroxy-3-[2-(3,4,5-trimethoxybenzoyl)benzofuran-5-yl]-
acrylamide (10c). Yield: 0.23 g of colorless crystals (58%). Mp:
1
192 °C. H NMR (DMSO-d6): δ (ppm) ) 10.80 (s, br, 1H), 9.09
Acknowledgment. We thank E. Verdin, Gladstone Institute
for Virology and Immunology, San Francisco, CA, for providing
rHDAC1 and rHDAC6 expressing Hek293 cell lines. We also
thank colleagues at ALTANA Discovery Research, in particular
U. Bosch and G. Quintini for providing HDAC preparations as
well as H. Wieland and H. Julius for excellent technical
assistance.
(s, br, 1H), 8.04 (s, 1H), 7.91 (s, 1H), 7.85-7.76 (m, 2H), 7.61 (d,
1H, J ) 15.8 Hz), 7.31 (s, 2H), 6.50 (d, 1H, J ) 15.8 Hz), 3.89 (s,
6H), 3.80 (s, 3H). IR (KBr): ν (cm-1) ) 3444, 3309, 1676. PI-
LSI-MS m/z (%): 398 (85) [MH]+. HR-PI-LSI-MS calcd for
C21H20NO7 [MH+•]: 398.1140. Found 398.1230.
Preparation of 3- and 4-(2-Bromoacetyl)benzaldehyde (33a
and 33b). To a solution of the respective acetylbenzaldehyde (5.00
g, 33.75 mmol, Aldrich) in CH2Cl2 (40 mL) a few drops of a
bromine solution (33.75 mmol, 1.72 mL) in CH2Cl2 (10 mL) were
added at room temperature. After consumption of the added
bromine, the mixture was cooled to 0 °C and the remaining bromine
solution was added dropwise within half an hour. The mixture was
poured into water, and the organic layer was separated, washed
with saturated brine (2 × 50 mL), and dried (Na2SO4). The solvent
was removed under reduced pressure, and the product was purified
by column chromatography (SiO2, CH2Cl2).
Supporting Information Available: Additional experimental
details for syntheses, analytical data, combustion analysis results,
and details of biological test systems. This material is available
free of charge via the Internet at http://pubs.acs.org.
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4-(2-Bromoacetyl)benzaldehyde (33a). Yield: 4.60 g (60%).
1
Mp: 154.2 °C (dec). H NMR (DMSO-d6): δ (ppm) ) 10.13 (s,
1H), 8.20 (d, 2H, J ) 8.3 Hz), 8.07 (d, 2H, J ) 8.4 Hz), 5.03 (s,
2H). Anal. (C9H7BrO2) C, H. IR (KBr): ν (cm-1) ) 1692, 1208.
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3-(2-Bromoacetyl)benzaldehyde (33b). Yield: 3.70 g (49%)
1
of colorless crystals. Mp: 55.4-57.5 °C. H NMR (CDCl3): δ
(ppm) ) 10.11 (s, 1H), 8.48 (t, 1H, J ) 1.6 Hz), 8.27 (dt, 1H, J )
7.7 Hz, J ) 1.5 Hz), 8.14 (dt, 1H, J ) 7.7 Hz, J ) 1.5 Hz), 7.71
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1692, 1176. CI-MS (NH3) m/z (%): 244 (59) [M + NH4]+, 133
(100).
Preparation of (Benzofuran-2-carbonyl)arylaldehydes.40 The
benzofuran-2-carbonylarylaldehydes were prepared according to the
analogous literature30 as follows: A mixture of the respective
2-bromoacetophenone (33.6 mmol), the suitable substituted 2-hy-
droxybenzenealdehyde (33.6 mmol), and K2CO3 (4.66 g, 33.7
mmol) in CH3CN (100 mL) was refluxed for 3-5 h (TLC; SiO2,
CH2Cl2). The mixture was cooled to room temperature, and H2O
(200 mL) was added. The precipitating product was removed by
filtration and purified by column chromatography (SiO2, CH2Cl2)
to yield colorless crystals.
4-(Benzofuran-2-carbonyl)benzaldehyde (34a). Yield: 1.04 g
1
(28%). Mp: 153.5-153.6 °C. H NMR (DMSO-d6): δ (ppm) )
10.17 (s, 1H), 8.20-8.11 (m, 4H), 7.90-7.86 (m, 2H), 7.80 (d,
1H, J ) 8.4 Hz), 7.61 (t, 1H, J ) 7.8 Hz), 7.42 (t, 1H, J ) 7.5
Hz). Anal. (C16H10O3) C, H. IR (KBr): ν (cm-1) ) 1651, 1607.
EI-MS (70 eV) m/z (%): 250 (100) [M]+.
3-(Benzofuran-2-carbonyl)benzaldehyde (34b). Yield: 1.82 g
1
(49%). Mp: 102.2-103.3 °C. H NMR (DMSO-d6): δ (ppm) )
10.15 (s, 1H), 8.50 (t, 1H, J ) 1.5 Hz), 8.31 (d,t, 1H, Jd ) 7.7 Hz,
Jt ) 1.5 Hz), 8.23 (d,t, 1H, Jd ) 7.9 Hz, Jt ) 1.5 Hz), 7.91-7.78
(m, 4H), 7.60 (t, 1H, J ) 7.8 Hz), 7.42 (t, 1H, J ) 7.5 Hz). Anal.
(C16H10NO3) C, H, N. IR (KBr): ν (cm-1) ) 1704, 1689. EI-MS
(70 eV) m/z (%): 250 (100) [M + H]+.
2-Benzoylbenzofuran-5-carbaldehyde (40a).30 Yield: 7.40 g
(88%) of colorless crystals. Mp: 155.0-157.2 °C. 1H NMR
(DMSO-d6): δ (ppm) ) 10.11 (s, 1H), 8.46 (s, 1H), 8.16-7.58
(m, 8H). Anal. (C16H10O3) C, H. IR (pure solid): ν (cm-1) ) 2823,
1698, 1641. EI-MS (70 eV) m/z (%): 250 (29) [M]+, 77 (100).
2-(3-Methoxybenzoyl)benzofuran-5-carbaldehyde
(40b).
Yield: 3.54 g (53%) of colorless crystals. Mp: 137.6 °C. 1H NMR
(DMSO-d6): δ (ppm) ) 10.14 (s, 1H), 8.50 (d, 1H, J ) 1.3 Hz),
8.13 (dd, 1H, J ) 1.6 Hz, J ) 8.8 Hz), 8.05-7.95 (m, 2H), 7.69-
7.50 (m, 3H), 7.39-7.31 (m, 1H), 3.90 (s, 3H). Anal. (C16H10O3)
C, H. IR (pure solid): ν (cm-1) ) 2841, 1698, 1656. CI-MS (NH3)
m/z (%): 281 (20) [M + H+]+, 298 (100) [M + NH4+]+.
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