Total synthesis of indole-derived allocolchicine analogues exhibiting strong apoptosis-inducing activity

Article abstract of DOI:10.1002/chem.201200083

A series of novel pyrrolo-allocolchicine derivatives (containing a 1-methyl-1H-indol-5-yl moiety replacing ringa C) was synthesized. The tetracyclic ring system was constructed by Suzuki-Miyaura cross-coupling of a 1-methylindole-5-boronate with an ortho-

Full text of DOI:10.1002/chem.201200083

FULL PAPER
DOI: 10.1002/chem.201200083
Total Synthesis of Indole-Derived Allocolchicine Analogues Exhibiting
Strong Apoptosis-Inducing Activity
[
a]
[b]
[c]
[d]
[b]
Nikolay Sitnikov, Janna Velder, Liliane Abodo, Nicole Cuvelier, Jçrg Neudçrfl,
[b]
[
c]
[d]
[a]
Aram Prokop, Gꢀnter Krause, Aleksey Y. Fedorov,* and Hans-Gꢀnther Schmalz*
Abstract: A series of novel pyrrolo-al-
locolchicine derivatives (containing a
resulting ketone, the nitrogen function-
ality was introduced in a Mitsunobu-
type reaction by using zinc azide fol-
crystallography. The compounds syn-
thesized were then tested against
BJAB tumor cells and found to exhibit
pronounced cytotoxic activity (prolifer-
ation inhibition and apoptosis induc-
tion). The ketone 24b was even active
at sub-nanomolar concentration. In ad-
dition, the antitumor potential of the
compounds was confirmed by using B
lymphoid cell lines.
1-methyl-1H-indol-5-yl moiety replac-
ing ring C) was synthesized. The tetra-
cyclic ring system was constructed by
Suzuki–Miyaura cross-coupling of a 1-
methylindole-5-boronate with an ortho-
iodo-dihydrocinnamic acid derivative
and subsequent intramolecular Friedel–
Crafts acylation. After reduction of the
lowed by LiAlH reduction. Structural
4
assignments were supported by X-ray
Keywords: allocolchicinoids · atro-
pisomerism · cross-coupling · het-
erocycles · antitumor agents
Introduction
Due to the essential role of the mitotic spindle in cell divi-
sion, the microtubule dynamic is still regarded as one of the
[
1]
most relevant drug targets for the treatment of cancer.
[2]
Colchicine (1) (Figure 1), isolated from Colchicum autum-
nale, is a cytostatic drug that strongly binds to tubulin, the
[3]
main constitutive protein of microtubules. Although 1 is
frequently employed in the treatment of acute gout and
familial Mediterranean fever, a high general toxicity has
prevented its use in cancer chemotherapy. Nevertheless, 1
[4]
and its structural analogues, such as allocolchicine (2),
[5,6]
combretastatin A-4 (3),
and 4-arylcoumarins (for exam-
ple, 4 ), represent promising lead structures for the devel-
[7]
Figure 1. Chemical structure of the natural colchicinoids 1–4 and the
highly active analogues 5 and 6, which display an N-methylindole sub-
structure.
[
a] N. Sitnikov, Prof. Dr. A. Y. Fedorov
Department of Organic Chemistry
Nizhny Novgorod State University
Gagarina av. 23, Nizhny Novgorod 603950 (Russian Federation)
Fax : (+7)831-462-30-85
opment of new anticancer agents addressing the colchicine-
[7,8]
binding site of tubulin.
The structural similarity of these
E-mail: afnn@rambler.ru
compounds arises from the presence of two neighboring
[
b] Dr. J. Velder, Dr. J. Neudçrfl, Prof. Dr. H.-G. Schmalz
Department of Chemistry
polyoxygenated aromatic rings, A and C, arranged in a syn
[
3,7,9]
University of Cologne
Greinstrasse 4, 50939 Kçln (Germany)
Fax : (+49)221-470-3064
non-coplanar fashion within an appropriate distance.
Although a molecular-modeling study
[8a]
has suggested
certain key structural features as being responsible for
strong tubulin binding, the search for novel colchicinoids
with improved antitumor properties is still a rather empiric
enterprise and relies on the “educated intuition” of synthetic
chemists, in combination with biological screening.
E-mail: schmalz@uni-koeln.de
[
c] L. Abodo, Dr. A. Prokop
Department of Pediatric Hematology/Oncology
Childrenꢀs Hospital Kçln
Amsterdamer Strasse 59, 50735 Kçln (Germany)
[
d] N. Cuvelier, Dr. G. Krause
Some years ago, it was found that replacement of the 3-
hydroxy-4-methoxyphenyl fragment in molecules 3 and 4 by
a hydrophobic 1-methyl-1H-indol-5-yl group led to highly
Department I of Internal Medicine
Center for Integrated Oncology Kçln Bonn
University of Cologne, Kerpener Strasse 62, 50937 Kçln (Germany)
[10]
[11]
cytotoxic compounds 5 and 6, respectively, which were
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201200083.
found to inhibit microtubule assembly in vitro at nanomolar
Chem. Eur. J. 2012, 00, 0 – 0
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concentrations. The presence of the hydrophobic N-methyl
group in 5 and 6 turned out to be crucial for the biological
activity, because the corresponding compounds with a free
NÀH group did not exhibit notable degrees of cytotoxici-
“unsubstituted” position in ring A is protected by a bromine
atom. Biaryl derivative 9, in turn, could be prepared by
cross-coupling of suitable precursors, for instance, 5-bro-
moindole 10 and metalated A-ring synthon 13. Of course, 9
could alternatively be assembled from building blocks with
a reversed polarity, for example, from a metalated indole of
type 11 and iodoarene 12. Compounds 10 and 11 could be
prepared from commercial 5-bromoindole, whereas 3,4,5-tri-
methoxyphenylpropionic acid (14) represents a well-accessi-
ble starting material for the ring-A building block 12 and
metalated derivatives of type 13 (Scheme 1).
[
10,11]
ty.
It is noteworthy that the geometric parameters of the
neoflavonoid 6 (the torsion angle and the distances between
the centroids of rings A and C and the heteroatom substitu-
[11]
ents) were shown to closely resemble those of 1 and 3.
The remarkable activity of compounds 5 and 6 suggested
that allocolchicine analogues with an N-methylindole sub-
structure might also exhibit interesting biological properties.
After examining molecular models, we considered 7a and
its isomer 7b (Figure 2), in which the indole N atom takes a
We started our investigation with the conversion of 14
into the dihalosubstituted ester 12 through bromination (Br2
[13]
in AcOH), silver-assisted iodination (AgO(O)CCF /I ),
3
2
and
subsequent
esterification
with
diazomethane
(
Scheme 2).
Figure 2. Indole-derived allocolchicinoids 7a and 7b, the “designed”
target molecules of this study.
para position with respect to the biaryl bond, as particularly
promising structures. We report herein the total synthesis of
these “designed” natural product analogues. Moreover, we
disclose the results of a primary biological study, which re-
vealed compounds rac-7a, rac-7b, and some of their synthet-
ic precursors to exhibit powerful cytotoxic and apoptosis-in-
ducing activities against two different tumor cells lines.
Scheme 2. Synthesis of biaryl compound 17. Reagents and conditions:
a) Br , AcOH, 58C to RT, 2 h; b) I , AgO(O)CCF , CH Cl , RT, 6 h;
c) CH , Et O, RT, 72% (3 steps); d) 19b, Pd(OAc) (3 mol%), Ph
(9 mol%.), Cs CO (1.5 equiv), toluene, 1108C, 24 h, 96%.
2
2
3
2
2
2
N
2
2
A
H
N
T
E
N
N
2
3
P
Results and Discussion
2
3
The strategy of our synthesis of 7a and 7b is illustrated in
Scheme 1. By using ketones 8a and 8b, respectively, as pre-
target compounds, we envisioned that the formation of the
seven-membered B ring, which is the key challenge in any
For the preparation of biaryl 17, we then explored differ-
ent cross-coupling methodologies. Initially, we thought that
the electron-rich and sterically-hindered aryliodide 12 might
[12]
[14]
allocolchicine synthesis, could be achieved by intramolec-
not be a particularly good substrate for oxidative addition.
ular Friedel–Crafts acylation of precursor 9, in which the
Therefore, we converted 12 into the organozinc reagent 18
(
Figure 3) following either the procedure of Dexter and
[15]
[16]
Jackson
or the protocol of Knochel and co-workers.
Unfortunately, all attempts to achieve the Pd-catalyzed Ne-
gishi coupling of 18 with bromoindole 10 (even with the
[17]
conditions recently proposed by Knochel and co-workers)
failed and the desired product (17) was not formed to any
Figure 3. Possible organometallic reagents for the synthesis of biaryl com-
Scheme 1. Retrosynthetic analysis of the target compounds 7a and 7b.
pound 9.
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Antitumor-Active Indole-Derived Allocolchicine Analogues
FULL PAPER
significant extent. We thus returned to the aryliodide 12 and
tried to react it with an appropriate indole-derived metalat-
ed reagent under Stille or Suzuki cross-coupling con-
Moreover, when we tried to convert 9 into the correspond-
ing acid chloride by treatment with oxalyl chloride, rapid de-
composition was observed, even at À788C. However, from
the reaction of 9 with (1-chloro-2-methylpropenyl)dimethyl-
[14a]
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
ditions.
the boronate 19b (Figure 3) were prepared from N-methyl-
-bromoindole (10) by following common protocols. Disap-
Accordingly, the organotin compound 19a and
[22]
amine (Ghosez reagent) in CH Cl , a clear solution con-
2
2
5
taining acid chloride 20 (as proven by sample aminolysis
pointingly, the Stille coupling of 12 with 19a could not be
with HNEt ) was obtained (Scheme 3).
2
achieved under a variety of conditions with different palladi-
In a first attempt to induce the projected Friedel–Crafts
um sources (Pd
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
[PPh ] , Pd (trans,trans-dibenzylideneace-
cyclization, we added ZnCl to a crude solution of 20 in
3
4
2
2
[18]
tone) , Pd(OAc) ), ligands (phosphine ligands, Ph As),
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
CH Cl at room temperature. However, the desired ketones
3
2
3
2
2
[19]
bases (K CO , Cs CO ), additives (CuI), and solvents (tol-
21a and 21b were obtained in only 5% yield (as a 4:1 mix-
ture), whereas the major products, formed in more than
50% combined yield (in a ratio of 1:3.5), turned out to be
compounds 22a and 22b, as unambiguously confirmed by
means of X-ray crystallography (Figure 4).
2
3
2
3
uene, MeCN, N-methylpyrrolidine). Only a side product re-
sulting from reductive dehalogenation of 12 was isolated,
which at least indicated the occurrence of the oxidative ad-
dition step. Encouraged by this observation, we finally tried
the Suzuki coupling between 12 and 1-methylindole-5-bor-
onic acid pinacol ester (19b). We were pleased to find that
the desired product 17 was formed in high yield when the
reaction was performed with Pd ACTHUNGTRNEUNG( OAc) (3 mol%) and Ph P
2 3
(
9 mol%) in the presence of Cs CO in toluene at 1108C
2 3
(
Scheme 2). In this reaction, the choice of base turned out
to be crucial, because no reaction was observed with K CO
2
3
instead of Cs CO . By following this protocol, the synthesis
2
3
of 17 could be easily performed on a multigram scale.
With compound 17 in our hands, the next goal was to
close ring B by means of Friedel–Crafts acylation. Although
a number of protocols employing esters as substrates in such
[20]
reactions have been reported, our initial attempts to di-
rectly cyclize ester 17 by treatment with a Lewis acid (AlCl3,
BF ·Et O, or ZnCl ) were not successful. Instead of the de-
3
2
2
sired products 21a/21b (Scheme 3), only complex product
mixtures were formed, presumably as a consequence of the
high reactivity and sensitivity of the electron-rich indole
system. The carboxylic acid 9, obtained from 17 by basic hy-
drolysis, also failed to give the desired cyclization products
Figure 4. Structures of compounds 22a and 22b in the crystalline state.
2
Sc
1a/21b upon treatment with either polyphosphoric acid or
ACHTUNGTRENNUNG( OTf) as the catalyst (Tf: trifluoromethanesulfonyl).
3
As compounds 22a and 22b probably result from reaction
of the indole part of 20 with unreacted Ghosez reagent in a
Vilsmeier/Haack type process (and concomitant hydrolysis
or aminolysis of the acid chloride function), we reduced the
amount of Ghosez reagent in the acid chloride forming step
to 1.1 equivalents and extended the reaction time to 12 h. In
[21]
addition, the resulting solution of 20 was diluted to a con-
À1
centration of 0.02 molL prior to addition of ZnCl at 08C
2
and further stirring for 2 h at room temperature. In this way,
ketones 21a and 21b were obtained (as a 4:1 mixture) in
4
0% yield on a gram scale. Other solvents (MeNO2,
PhNO ) and Lewis acids (AlCl , BF ·Et O, Sc(OTf) , Ti-
AHCTUNGTRENNUNG
2
3
3
2
3
AHCTUNGTRNNEG(U OiPr) , EtAlCl , Et AlCl) proved to be much less efficient.
4 2 2
Only ZnBr led to a comparable result. As we did not suc-
2
ceed in separating isomers 21a and 21b (either by column
chromatography or by preparative HPLC), we used the mix-
ture in the subsequent transformations.
Reductive amination with NaBH CN/NH OAc in
3
4
[23]
MeOH afforded rac-23a in 45% yield (56% with respect
to 21a) as the only amine formed under the reaction condi-
tions (Scheme 4). The interesting fact that ketone 21b did
not react to form the corresponding amine (even at elevated
Scheme 3. Synthesis of intermediates 21a and 21b. Reagents and condi-
tions: a) 1m LiOH (aq), THF/MeOH/H O, 50 8C; b) Ghosez reagent
1.1 equiv), CH Cl , 08C, 12 h; c) ZnCl (2 equiv), CH Cl , 08C to RT,
h. THF: tetrahydrofuran.
2
(
2
2
2
2
2
2
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A. Y. Fedorov, H.-G. Schmalz et al.
led to the indole-derived allocolchicinoids rac-7a and rac-7b
in 87% and 89% yield, respectively (Scheme 5).
We briefly also explored the possibility of enantioselec-
tively introducing the stereogenic center at the C7 position
through asymmetric reduction of ketones 24a or 24b. Both
[26]
the Noyori transfer hydrogenation
Bakshi–Shibata (CBS) reduction
and the Corey–
were reported to give
low selectivities with related allocolchicine-type substra-
[27]
Scheme 4. Synthesis of 23a by reductive amination. Reagents and condi-
tions: a) NaBH CN, NH OAc, MeOH, 3 ꢂ molecular sieves, 508C,
days, 56% (with respect to 21a).
3
4
4
[12h]
tes,
so we tested the more
[
12b,f,h]
promising
method of Sin-
garam and co-workers, that is,
temperatures) presumably results from the steric shielding
of its carbonyl group.
Radical dehalogenation of the 4:1 mixture of 21a/21b by
using tributylstannane in the presence of azobisisobutyroni-
trile (AIBN) afforded a mixture of isomers 24a/24b, which
the use of LiBH (2.5 equiv) in
4
the presence of 2-(3-nitrophen-
yl)-1,3,2-dioxaborolane-4R,5R-
dicarboxylic acid ((+)-TarB-
Figure 5. Structure
+)-TarB-NO , which was used
for the enantioselective LiBH
reduction of ketones 21a/21b
of
(
2
[28]
NO2, 27; 2.0 equiv)
as a
4
could be separated by column chromatography on SiO /
KF to yield the pure ketones 24a (73%) and 24b (18%;
chiral Lewis acid (Figure 5).
2
[
24]
However, the reduction of and 24a.
Scheme 5).
either 21a/21b or 24a under
these conditions proceeded
only with moderate yields (56–59%) and rather low enan-
tioselectivities (53% and 37% ee, respectively), as deter-
mined by means of HPLC on a chiral stationary phase.
The constitution of the various pyrrolo-allocolchicinoids
prepared was proven by NMR spectroscopy, and the assign-
ments were additionally confirmed by X-ray crystal struc-
ture analysis of ketones 21a and 24b (Figure 6).
Scheme 5. Synthesis of various pyrrolo-allocolchicinoids. Reagents and
conditions: a) AIBN, HSnBu
b) NaBH , THF/MeOH/H O, RT, 3 h; c) Zn(N
uene, RT, 0.5 h; d) 1m LiAlH in Et O, THF, RT, 24 h; then Ac
dine, CH Cl , RT, 0.5 h. Yields: 24a: 73%; 24b: 18%; 25a: 92%; 25b:
3%; 26a: 89%; 26b: 68%; rac-7a: 87%; rac-7b: 89%. py: pyridine;
3
,
then separation by chromatography;
·2py, PPh , DIAD, tol-
O, pyri-
Figure 6. Structures of ketones 21a (left) and 24b (right) in the crystal-
line state.
4
2
3
)
2
3
4
2
2
2
2
9
[29]
DIAD: diisopropylazodicarboxylate.
An interesting fact is that, in contrast to colchicine (1),
1
13
two diastereomers are observed in the H and C NMR
spectra of compounds rac-25a, rac-25b, rac-26a, rac-26b,
rac-7a, and rac-7b under ambient conditions. This can be at-
tributed to a less pronounced energy difference between the
atrop-diastereomers although the rotational barrier around
As the reductive amination proved to be troublesome
with this kind of substrate (see above), ketones 24a and
4b, respectively, were transformed into the target com-
2
pounds 7a and 7b by using an S 2 amination approach
the chiral biaryl axis is still high enough to prevent rapid in-
N
[12b]
[12,30]
(
Scheme 5).
For this reason, the carbonyl functions in
terconversion on the NMR timescale (Figure 7).
The
2
4a and 24b were first reduced with NaBH to give the al-
ratio of the atrop-diastereomers varies strongly with the po-
larity of the solvent used (CDCl or CD OD), possibly as a
4
cohols rac-25a and rac-25b, respectively, in almost quantita-
tive yield. Subsequent nucleophilic displacement of the hy-
droxy groups by azides under Mitsunobu conditions
forded rac-26a and rac-26b in 89% and 68% yield, respec-
tively. Finally, reduction of the azide group with LiAlH in
Et O and subsequent acetylation of the resulting amino
function with acetic anhydride in the presence of pyridine
3
3
31]
[
consequence of subtle solvation effects. In the case of rac-
7a and rac-7b, the NMR spectra are additionally complicat-
ed by the presence of Z/E isomers of the acetamido group.
The relative configuration of the preferred atrop-diaster-
eomer of rac-7b was found to be (aR,7S) by means of an X-
ray structure analysis of a crystal obtained from CDCl3
[25]
af-
4
2
(
Figure 8). The dihedral angle along the chiral axis between
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Antitumor-Active Indole-Derived Allocolchicine Analogues
FULL PAPER
cytotoxicity and apoptosis-inducing activity than their a-type
isomers. Also, the functional group at the C7 position signif-
icantly affected the biological properties. Among all of the
compounds investigated, ketone 24b exhibited the most
powerful activity by causing 83% inhibition of cell prolifera-
tion and 64% apoptosis induction (after 72 h) at 1 nm con-
centration, whereas virtually no unspecific cytotoxicity was
detected after 1 h in a control experiment (LDH assay).
In a second series of biological investigations, the activity
of the indole-derived allocolchicinoids against lymphoid cell
lines was assessed. Initially, Mec-1 cells were incubated for
4
8 h with the different compounds at a standard concentra-
tion of 50 nm and the metabolic activity of the cells was then
determined through 2,3-bis-(2-methoxy-4-nitro-5-sulfo-
phenyl)-2H-tetrazolium-5-carboxanilide (XTT) assay
Table 2). For colchicine (1, used as a reference) and rac-
Figure 7. Equilibrium between atrop-diastereomers of pyrrolo-allocolchi-
cinoids (R: OH, N , or NHAc).
3
a
(
Table 2. Cytotoxicity of various pyrrolo-allocolchicinoids on lymphoid
Mec-1 cells.
[
a]
[b]
Compound
Metabolic activity [%]
IC50 [mm]
1
2
2
10
100
32
35
26
98
77
82
0.013 (0.010)
–
–
–
4a
4b
Figure 8. Structure of rac-7b in the crystalline state.
rac-25a
rac-25b
rac-26a
rac-7a
0.011 (0.011)
–
–
–
the benzene and the indole ring (approximately 508) was
found to be very similar to that of natural colchicine (1) and
combretastatin A-4 (3). Thus, the structural requirements
for efficient interaction with tubulin should be fulfilled.
The antitumor properties of compounds 24a/b, rac-25a/b,
rac-26a, and rac-7a/b were first investigated by using BJAB
rac-7b
[
a] Mec-1 cells were incubated with 50 nm concentration of the com-
pounds and the metabolic activity (relative to an untreated control) was
determined by means of an XTT assay. [b] Apoptosis induction (IC )
was determined by flow cytometric cell-cycle analysis after 48 h (values
in brackets refer to SU-DHL-5 cells).
5
0
[32]
tumor cells (Burkitt-like lymphoma cells). The induction
of apoptosis (AC ) was determined by using a DNA frag-
50
mentation assay, whereas proliferation inhibition (IC ) was
25b (the most active sample), flow cytometric analysis (after
48 h, staining with annexin V and 7-aminoactinomycin D (7-
ADD)) revealed comparable levels of apoptosis induction
(IC50 values of 13 nm for 1 and 11 nm for rac-25b, respective-
ly). In order to detect possible differences in the biological
effects on two distinct B lymphoid cell lines, the dose-de-
pendent apoptosis induction assay was repeated with the
human B cell lymphoma cell line SU-DHL-5 (Table 2,
values given in brackets). The effect of 50 nm of colchicine
and rac-25b on the distribution of cell-cycle phases was ex-
amined by analysis of the DNA content of the SU-DHL-5
cells and was found to be equivalent.
5
0
determined by cell counting (see Table 1). All compounds
were found to exhibit strong antitumor activity at nanomo-
lar or even sub-nanomolar (in the case of 24b) concentra-
tions and to display a particularly low unspecific cytotoxici-
ty, as determined by lactate dehydrogenase (LDH) release
measurements (see the Supporting Information). Com-
pounds of the b series (for example, 24b) displayed a higher
Table 1. Antitumor activity of pyrrolo-allocolchicinoids rac-7a/b and the
synthetic precursors 24a/b, rac-25a/b, and rac-26a on the BJAB tumor
cell line.
[
a]
[b]
Compound
IC50 [mm]
AC50 [mm]
1
2
2
0.02
0.0025
<0.001
0.03
0.008
0.2
0.03
0.005
<0.001
0.1
0.01
0.5
Conclusion
4a
4b
rac-25a
rac-25b
rac-26a
rac-7a
In conclusion, we have designed, synthesized, and biologi-
cally assessed a new class of indole-containing allocolchicine
analogues. By starting from commercial 3,4,5-trimethoxy-
phenylpropionic acid (14), the target compounds rac-7a and
rac-7b were obtained in 11 steps with overall yields of 14%
and 3%, respectively, by using a Suzuki coupling and a Frie-
del–Crafts cyclization as the key CÀC bond-forming reac-
0.08
0.03
0.5
0.05
rac-7b
[
a] The proliferation inhibition (IC50) after 24 h was determined by using
a CASY cell counter. [b] Apoptosis induction (AC50) was measured after
2 h by DNA fragmentation of BJAB cells on a single cell level.
7
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A. Y. Fedorov, H.-G. Schmalz et al.
tions. Structural assignments were proven by X-ray crystal-
[10] L. Wang, K. W. Woods, Q. Li, K. J. Barr, R. W. Mc Croskey, S. M.
Hannick, L. Gherke, R. B. Credo, I. H. Hui, K. Marsh, R. Warner,
J. Y. Lee, N. Zielinski-Mozng, D. Frost, S. H. Rosenberg, H. L.
Sham, J. Med. Chem. 2002, 45, 1697–1711.
[33]
lography of various intermediates.
Biological tests with
BJAB (Burkitt-like lymphoma) and two distinct B lymphoid
cell lines revealed that all compounds exhibited cytotoxic
and apoptosis-inducing activity. Ketone 24b and alcohol rac-
[
11] O. G. Ganina, E. Daras, V. Bourgarel-Rey, V. Peyrot, A. N. Andre-
suk, J.-P. Finet, A. Yu. Fedorov, I. P. Beletskaya, S. Combes, Bioorg.
Med. Chem. 2008, 16, 8806–8812.
25b were identified as the most active compounds, with the
[
12] a) J. S. Sawyer, T. L. Macdonald, Tetrahedron Lett. 1988, 29, 4839–
former acting against BJAB cells even at sub-nanomolar
concentration. The new type of highly active indole-derived
4
842; b) A. V. Vorogushin, A. V. Predeus, W. D. Wulff, H.-J. Hansen,
J. Org. Chem. 2003, 68, 5826–5831; c) M. Leblanc, K. Fagnou, Org.
Lett. 2005, 7, 2849–2852; d) G. Besong, K. Jarowicki, P. J. Kocienski,
E. Sliwinski, F. T. Boyle, Org. Biomol. Chem. 2006, 4, 2193–2207;
e) W. M. Seganish, P. DeShong, Org. Lett. 2006, 8, 3951–3954;
f) S. D. Broady, M. D. Golden, J. Leonard, J. C. Muir, M. Maudet,
Tetrahedron Lett. 2007, 48, 4627–4630; g) S. Djurdjevic, J. R. Green,
Org. Lett. 2007, 9, 5505–5508; h) G. Besong, D. Billen, I. Dager, P.
Kocienski, E. Sliwinski, L. R. Tai, F. T. Boyle, Tetrahedron 2008, 64,
4700–4710; i) F.-D. Boyer, I. Hanna, Eur. J. Org. Chem. 2008, 4938–
[34]
antimitotic compounds
discovered in the course of this
study challenges additional synthetic and biological investi-
gations in the future.
Acknowledgements
4
948; j) S. Djurdjevic, F. Yang, J. R. Green, J. Org. Chem. 2010, 75,
We gratefully acknowledge financial support from the Russian Federal
Target Program (16.740.11.0476 and 14.740.12.1382), the Russian Founda-
tion for Basic Research (12-03-00214-a), and the German Academic Ex-
change Service (DAAD fellowship to N.S.). We also thank Dr. A. Gav-
rushin for fruitful discussions. We thank Chemetall GmbH for the dona-
tion of chemicals.
8241–8251.
[13] D. E. Jansen, C. V. Wilson, Org. Synth. 1956, 36, 46.
[14] a) J. Hassan, M. Sevignon, C. Gozzi, E. Schultz, M. Lemaire, Chem.
Rev. 2002, 102, 1359–1469; b) I. P. Beletskaya, O. G. Ganina, A. V.
Tsvetkov, A. Yu. Fedorov, J.-P. Finet, Synlett 2004, 2797–2799.
[15] C. S. Dexter, F. W. Jackson, J. Org. Chem. 1999, 64, 7579–7585.
[
16] A. Krasovskiy, V. Malakhov, A. Gavryushin, P. Knochel, Angew.
Chem. 2006, 118, 6186–6190; Angew. Chem. Int. Ed. 2006, 45, 6040–
6044.
[
1] a) M. A. Jordan, Curr. Med. Chem. Anti-Cancer Agents 2002, 2, 1–
7; b) M. A. Jordan, L. Wilson, Nat. Rev. Cancer 2004, 4, 253–265;
c) C. Dumontet, M. A. Jordan, Nat. Rev. Drug Discovery 2010, 9,
90–803; d) M. Kavallaris, Nat. Rev. Cancer 2010, 10, 194–204.
1
[17] G. Manolikakes, M. A. Schade, C. M. Hernandez, H. Mayr, P. Kno-
chel, Org. Lett. 2008, 10, 2765–2768.
7
[18] a) C. Amatore, A. A. Bahsoun, A. Jutand, G. Meyer, A. N. Ntepe,
L. Ricard, J. Am. Chem. Soc. 2003, 125, 4212–4222; b) V. Farina, B.
Krishann, J. Am. Chem. Soc. 1991, 113, 9585–9595.
[
2] a) H.-G. Capraro, A. Brossi in The Alkaloids, Vol. 23 (Eds.: A.
Brossi), Academic Press, New York, 1984, pp. 1–70; b) T. Graening,
H.-G. Schmalz, Angew. Chem. 2004, 116, 3292–3318; Angew. Chem.
Int. Ed. 2004, 43, 3230–3256; c) B. Bhattacharyya, D. Panda, S.
Gupta, M. Banerjee, Med. Res. Rev. 2008, 28, 155–183.
[
19] V. Farina, S. Kapadia, B. Krishnan, C. Wang, L. S. Liebeskind, J.
Org. Chem. 1994, 59, 5905–5911.
[
20] See, for example: a) J. P. Hwang, G. K. Surya Prakash, G. A. Olah,
Tetrahedron 2000, 56, 7199–7203; b) H. W. Pinnick, S. P. Brown,
E. A. McLean, L. W. Zoller III, J. Org. Chem. 1981, 46, 3758–3760;
c) R. R. Poondra, P. M. Fisher, N. J. Turner, J. Org. Chem. 2004, 69,
[
3] K. W. Wood, W. D. Cornwell, J. R. Jackson, Curr. Opin. Pharmacol.
2
001, 1, 370–377.
[
4] a) O. Boye, A. Brossi in The Alkaloids, Vol. 41 (Eds.: A. Brossi,
J. A. Cordell), Academic Press, New York, 1992, p. 125; b) B. Pꢃrez-
Ramꢄrez, M. J. Gorbunoff, S. N. Timasheff, Biochemistry 1998, 37,
6
920–6922; d) K. Gewald, O. Calderon, H. Schaefer, U. Hain, Lie-
bigs Ann. Chem. 1984, 1390–1394; e) Y. Nishimoto, S. A. Babu, M.
Yasuda, A. Baba, J. Org. Chem. 2008, 73, 9465–9468.
1
646–1661.
[
5] a) G. R. Pettit, S. B. Singh, E. Hamel, C. M. Lin, D. S. Alberts, D.
Garcia-Kendall, Experientia 1989, 45, 209–211; b) G. R. Pettit, S. B.
Singh, M. R. Boyd, E. Hamel, R. K. Pettit, J. M. Schmidt, F. Hogan,
J. Med. Chem. 1995, 38, 1666–1672.
6] For reviews on combretastatin A-4 and structural analogues, see:
a) N. H. Nam, Curr. Med. Chem. 2003, 10, 1697–1722; b) G. C. Tron,
T. Pirali, G. Sorba, F. Pagliai, S. Busacca, A. Genazzani, J. Med.
Chem. 2006, 49, 3033–3044; c) H. P. Hsieh, J. P. Liou, N. Mahindroo,
Curr. Pharm. Des. 2005, 11, 1655–1677.
[
[
21] S. Kobayashi, Eur. J. Org. Chem. 1999, 15–27.
22] a) A. Devos, J. Remion, A. M. Frisque-Hesbain, A. Colens, L.
Ghosez, J. Chem. Soc. Chem. Commun. 1979, 1180–1181; b) B. Ha-
veaux, A. Dekoker, M. Rens, A. R. Sidani, J. Toye, L. Ghosez, Org.
Synth. 1979, 59, 26.
[
[
23] a) D. M. Ryckman, R. V. Stevens, J. Org. Chem. 1987, 52, 4274–
4
279; b) R. F. Borch, M. D. Bernstein, H. D. Durst, J. Am. Chem.
Soc. 1971, 93, 2897–2904.
[
[
[
24] D. C. Harrowven, I. L. Guy, Chem. Commun. 2004, 1968–1969.
25] M. C. Viaud, P. Rollin, Synthesis 1990, 130–132.
26] R. Noyori, T. Ohkuma, Angew. Chem. 2001, 113, 40–75; Angew.
Chem. Int. Ed. 2001, 40, 40–73.
[
[
[
7] a) C. Bailly, C. Bal, P. Barbier, S. Combes, J.-P. Finet, M.-P. Hilde-
brand, V. Peyrot, N. Wattez, J. Med. Chem. 2003, 46, 5437–5444;
b) C. Rappl, P. Barbier, V. Bourgarel-Rey, C. Gregoire, R. Gilli, M.
Carre, S. Combes, J.-P. Finet, V. Peyrot, Biochemistry 2006, 45,
[
[
27] E. J. Corey, C. J. Helal, Angew. Chem. 1998, 110, 2092–2118;
Angew. Chem. Int. Ed. 1998, 37, 1986–2012.
9
210–9218; c) S. Combes, P. Barbier, S. Douillard, A. McLeer-
Florin, V. Bourgarel-Rey, J.-T. Pierson, A. Yu. Fedorov, J.-P. Finet,
J. Boutonnat, V. Peyrot, J. Med. Chem. 2011, 54, 3153–3162.
28] a) J. T. Suri, T. Vu, A. Hernandez, J. Congdon, B. Singaram, Tetrahe-
dron Lett. 2002, 43, 3649–3652; b) D. B. Cordes, T. M. Nguyen, T. J.
Kwong, J. T. Suri, B. Singaram, Eur. J. Org. Chem. 2005, 5289–5295.
29] The correct assignment of the axial stereochemistry of natural col-
chicine was reported in 1999: a) U. Berg, H. Bladh, Helv. Chim.
Acta 1999, 82, 323–325; b) A. Brossi, K.-H. Lee, H. J. C. Yeh, Helv.
Chim. Acta 1999, 82, 1223–1224.
8] a) T. L. Nguyen, C. McGrath, A. R. Hermone, J. C. Burnett, D. W.
Zaharevitz, B. W. Day, P. Wipf, E. Hamel, R. Gussio, J. Med. Chem.
[
2
005, 48, 6107–6116; b) O. N. Zefirova, A. G. Diikov, N. V. Zyk,
N. S. Zefirov, Russ. Chem. Bull. 2007, 56, 680–695; c) D. G. I. King-
ston, J. Nat. Prod. 2009, 72, 507–515; d) N. Nicolaus, J. Zapke, P.
Riesterer, J.-M. Neudçrfl, A. Prokop, H. Oschkinat, H.-G. Schmalz,
ChemMedChem 2010, 5, 661–665.
[30] a) H. Rapoport, J. B. Lavigne, J. Am. Chem. Soc. 1956, 78, 2455–
2459; for configurationally stable allocolchicine-related atropisom-
ers, see: b) A. V. Vorogushin, W. D. Wulff, H.-J. Hansen, J. Org.
Chem. 2003, 68, 9618–9623.
9] a) C. M. Lin, S. B. Singh, P. S. Chu, R. O. Dempcy, J. M. Schmidt,
G. R. Pettit, E. Hamel, Mol. Pharmacol. 1988, 34, 200–208; b) K.
Gaukroger, J. A. Hadfield, L. A. Hepworth, N. J. Lawrence, A. T.
McGown, J. Org. Chem. 2001, 66, 8135–8138.
[31] F. Pietra, J. Phys. Org. Chem. 2007, 20, 1102–1107.
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Chem. Eur. J. 0000, 00, 0 – 0
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Antitumor-Active Indole-Derived Allocolchicine Analogues
FULL PAPER
[
[
32] T. Wieder, A. Prokop, B. Bagci, F. Essmann, D. Bernicke, K.
Schulze-Osthoff, B. Dorken, H.-G. Schmalz, P. T. Daniel, G. Henze,
Leukemia 2001, 15, 1735–1742.
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif.
[34] A. Brancale, R. Silvestri, Med. Res. Rev. 2007, 27, 209–238.
33] CCDC 836615 (22b), 836616 (22a), 836617 (21a), 836618 (24b), and
8
36619 (rac-7) contain the supplementary crystallographic data for
Received: January 9, 2012
Revised: June 21, 2012
this paper. These data can be obtained free of charge from the Cam-
Published online: && &&, 0000
Chem. Eur. J. 2012, 00, 0 – 0
ꢁ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
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These are not the final page numbers!

A. Y. Fedorov, H.-G. Schmalz et al.
Natural Product Analogues
N. Sitnikov, J. Velder, L. Abodo,
N. Cuvelier, J. Neudçrfl, A. Prokop,
G. Krause, A. Y. Fedorov,*
Induced suicide of tumor cells: Ana-
logues of the natural product allocol-
chicine containing an N-methylindole
substructure (see scheme) were synthe-
sized and found to exhibit pronounced
cytotoxic and apoptosis-inducing activ-
ity against different tumor cell lines at
low nanomolar or even sub-nanomolar
concentrations.
H.-G. Schmalz* .............. &&&& — &&&&
Total Synthesis of Indole-Derived
Allocolchicine Analogues Exhibiting
Strong Apoptosis-Inducing Activity
&
8
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www.chemeurj.org
ꢁ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 0000, 00, 0 – 0
ÝÝ
These are not the final page numbers!