Synthesis of a staurosporine analogue possessing a 7-azaindole unit instead of an indole moiety

Article abstract of DOI:10.1016/j.tetlet.2004.04.102

The synthesis of a new staurosporine analogue possessing a 7-azaindole unit instead of an indole moiety is described. This synthesis could be achieved by coupling a sugar moiety previously tosylated in 2′ position to the azaindolocarbazole aglycone. Nucle

Full text of DOI:10.1016/j.tetlet.2004.04.102

Tetrahedron
Letters
Tetrahedron Letters 45 (2004) 4643–4647
Synthesis of a staurosporine analogue possessing
a 7-azaindole unit instead of an indole moiety
Samir Messaoudi,a Fabrice Anizon,a Bruno Pfeiffer,b Roy Golsteynb
and Michelle Prudhommea,*
aUniversitꢀe Blaise Pascal, Synthꢁese et Etude de Systꢁemes ꢁa Intꢀer^et Biologique, UMR 6504 du CNRS, 63177 Aubiꢁere, France
bInstitut de Recherches Servier, Division Recherche Cancꢀerologie, 125 Chemin de ronde, 78290 Croissy sur Seine, France
Received 16April 2004; revised 19 April 2004; accepted 20 April 2004
Abstract—The synthesis of a new staurosporine analogue possessing a 7-azaindole unit instead of an indole moiety is described. This
synthesis could be achieved by coupling a sugar moiety previously tosylated in 20 position to the azaindolocarbazole aglycone.
Nucleophilic substitution on the carbon bearing the tosyl group yielded to the key cyclization leading to a compound in which the
carbohydrate part is linked to both indole and azaindole nitrogens.
Ó 2004 Elsevier Ltd. All rights reserved.
1. Introduction
viously obtained by semi-synthesis from rebeccamycin
seem to have multiple targets and in contrast with
rebeccamycin, they exhibit high selectivity toward the
different tumor cell lines tested.
Staurosporine, a microbial metabolite isolated from
cultures of Streptomyces staurosporeus, has been exten-
sively studied as a potent and nonselective kinase
inhibitor.1–3 Several academic and industrial groups
have synthesized a large number of staurosporine ana-
logues to obtain compounds exhibiting more selectivity
toward the various kinases.4 In the search for new
staurosporine analogues, we have previously synthesized
rebeccamycin derivatives in which the carbohydrate
moiety is linked to both indole nitrogens (Fig. 1).5;6
Rebeccamycin is an antitumor antibiotic produced from
cultures of Saccharothrix aerocolonigenes. Rebeccamy-
cin possesses an indolocarbazole framework onto which
is attached via a b-N-glycosidic bond a 4-O-methoxy-
glucose. Its antitumor activity is linked to its capacity to
inhibit topoisomerase I by forming a ternary DNA-
topoisomerase I-drug complex that prevents the religa-
tion of the DNA strand cleaved by the enzyme.7;8
Contrary to rebeccamycin, staurosporine has no effect
on topoisomerase I. Our staurosporine analogues pre-
Azaindoles, as biosters for indoles, present considerable
biological importance. We have recently synthesized
rebeccamycin analogues in which one or both indole
moieties have been replaced by a 7-azaindole unit (Fig.
1).9;10 The newly introduced nitrogen atom(s) could
modify the interactions with the target(s) enzyme(s).
In this Letter, we report the synthesis of a 7-aza-
staurosporine analogue 1 bearing a methyl group on the
imide nitrogen (Fig. 1).
2. Results and discussion
The previously achieved semi-synthesis of a stauro-
sporine analogue in three steps from rebeccamycin is
outlined in Scheme 1.5 Tosylation at 20 position on the
sugar part was carried out before reaction using sodium
azide, which led to two compounds, the major product
of the reaction was the bridged compound obtained via
deprotonation of the indole nitrogen followed by
nucleophilic substitution at C20. The minor product, 30-
azide, was formed via 20-30-epoxide. The last step was
the removal of the chlorine atoms.
Keywords: Staurosporine; Rebeccamycin; 7-Azaindole; Antitumor
compounds; Enzyme inhibitors.
* Corresponding author. Tel.: +33-4-7340-7124; fax: +33-4-7340-7717;
e-mail: mprud@chimie.univ-bpclermont.fr
0040-4039/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2004.04.102

4644
S. Messaoudi et al. / Tetrahedron Letters 45 (2004) 4643–4647
H
N
H
R1
N
N
O
O
O
O
O
R2
R2
N
N
N
N
N
N
O
O
H
Cl
HO
Cl
H3C
OH
O
OH
H3CO
OH
OCH3
NHCH3
R3
OCH3
staurosporine
rebeccamycin
staurosporine analogues
from rebeccamycin
R
N
R
R
N
N
O
O
O
O
O
O
R'
N
N
N
N
H
N
N
N
N
N
N
H
H
OH
OH
OH
O
O
O
R = H
HO
HO
HO
R = CH3
OH
OH
OH
OH
OH
OH
7-aza rebeccamycins
CH3
N
O
O
N
N
N
O
OH
HO
OH
7-aza staurosporine analogue 1
Figure 1.
H
N
H
O
O
N
O
O
K2CO3
p-TsCl
N
N
H
N
N
THF
Cl
H
Cl
Cl
Cl
O
O
OH
OTs
HO
CH3O
2'
NaN3
DMF
HO
CH3O
Rebeccamycin
OH
O
OH
O
H
H
N
N
O
H
O
N
O
O
HCOONH4
+
N
O
N
Pd/C, MeOH
N
O
N
2'
OH
OCH3
N
N
H
Cl
Cl
Cl
Cl
OH
OCH3
O
HO
HO
HO
HO
N3
3'
CH3O
Scheme 1.
For the synthesis of compound 1, we chose to use a-1-
chloro-1-deoxy-2-O-tosyl-3,4,6-tri-O-benzyl glucopyra-
nose 7, prepared from triacetylated glycal 2 as shown in
Scheme 2. Tribenzylated compound 3 was prepared

S. Messaoudi et al. / Tetrahedron Letters 45 (2004) 4643–4647
4645
O
O
OAc
O
OBn
O
OBn
O
OBn
O
1) MeONa, MeOH
2) NaH,BnBr
dimethyldioxirane
AcOH
OAc
OBn
OBn
OBn
OAc
O
NaHCO3
H2O
oxone
OAc
DMF
OBn
O
OBn
OBn
OH
5
4
3
2
TsCl, pyridine
CH2Cl2
OBn
OBn
O
O
HCl, Et2O
OBn
OBn
OAc
Cl
OTs
OBn
OBn
OTs
6
7
Scheme 2.
from commercial triacetylated glycal 2 according to a
known method.11 Epoxidation of 3 with dimethyldioxi-
rane12 provided the anhydro-sugar 4. Reaction of 4 with
glacial acetic acid led to compound 5 in 55% yield as a
mixture of both a and b anomers in 3:10 ratio, respec-
tively.13;14 Tosylation of 5 gave 615 in 84% yield as a
mixture of the a and b anomers in 5:8 ratio, respectively,
together with unreacted b anomer 5. The anomeric
mixture of 6 dissolved in diethylether was treated with
HCl gas according to a method previously described in
altro- and allo-pyranosyl series,16 to yield compound 717
in 66% yield as the a chloro anomer, the unreacted a 6
was recovered.
Coupling of the chloro-sugar 7 with the aglycone 818 was
achieved in a heterogeneous medium. The reaction did
not occur using KOH, Na2SO4 in acetonitrile as
described by Ohkubo et al.19;20 for the synthesis of
rebeccamycin analogues. The coupling reaction was
carried out in acetonitrile, using KOH and tris[2-(2-
methoxyethoxy)ethyl]amine (TDA-1) as a phase transfer
catalyst, according to the method described by Seela and
Bourgeois21 for the synthesis of nucleosides, to yield a
mixture, which was partly purified by chromatography.
The next step was the reaction with sodium azide in
dimethylformamide leading to the bridged compound
922 in only 12% yield for the two steps, however in the
OBn
CH3
N
CH3
N
O
OBn
O
O
CH3CN, KOH
O
O
1)
(
MeO
)3N
Cl
OTs
OBn
O
2)
NaN3, DMF
N
N
N
N
H
N
N
H
8
O
OBn
OBn
BnO
9
BBr3
CH2Cl2
CH3
N
O
O
N
N
N
O
OH
OH
HO
1
Scheme 3.

4646
S. Messaoudi et al. / Tetrahedron Letters 45 (2004) 4643–4647
7. Bush, J. A.; Long, B. H.; Catino, J. J.; Bradner, W. T.;
8.89
132.1
Tomita, K. J. Antibiot. 1987, 40, 668–678.
8. Bailly, C.; Riou, J.-F.; Colson, P.; Houssier, C.; Rodri-
gues-Pereira, E.; Prudhomme, M. Biochemistry 1997, 36,
3917–3929.
CH3
N
116.9
O
O
7.49
152.8
H
ꢀ
ꢀ
ꢀ
9. Marminon, C.; Pierre, A.; Pfeiffer, B.; Perez, V.; Leonce,
S.; Renard, P.; Prudhomme, M. Bioorg. Med. Chem. 2003,
11, 679–687.
H
H
ꢀ
ꢀ
ꢀ
10. Marminon, C.; Pierre, A.; Pfeiffer, B.; Perez, V.; Leonce,
S.; Joubert, A.; Bailly, C.; Renard, P.; Hickman, J.;
Prudhomme, M. J. Med. Chem. 2003, 46, 609–622.
11. Bovin, N. V.; Zurabyan, S. E.; Khorlin, A. Y. Carbohydr.
Res. 1981, 98, 25–35.
N
N
N
8.63
H
H
146.9
6.42
84.6
O
OH
5.25
12. Murray, R. W.; Singh, M. Org. Synth. 1997, 74, 91–
97.
59.2
OH
13. Timer, C. M.; van Straten, N. C. R.; van der Marel, G. A.;
van Boom, J. H. J. Carbohydr. Chem. 1998, 17, 471–
487.
14. Takahashi, T.; Ebata, S.; Yamada, H. Synlett 1998, 381–
382.
HO
Scheme 4. Correlations observed in NMR experiments (chemical shifts
in ppm).
15. Spectral data of 6: IR (film, NaCl) mc@o 1739, 1760 cmÀ1
.
HRMS (FAB+) (M+Na)þ calcd for C36H38NaO9S
669.2134, found 669.2147.
coupling step, the unreacted aglycone 8 could be
recovered (Scheme 3). The last step was the removal of
the benzyl groups on the carbohydrate moiety using
boron tribromide in dichloromethane.23 Compound 124
was obtained in 90% yield. The structure of compound 1
was assigned from 1H COSY, HSQC, and HMBC NMR
experiments (Scheme 4). These experiments allowed the
assignment of the protons of the azaindole moiety. The
correlations allowed the identification of the quaternary
carbon at 152.8 ppm. A correlation was observed
1H NMR (400 MHz, CDCl3) bmajor anomer, aminor
anomer:
1.92 (3Hb, s, CH3), 2.11 (3Ha, s, CH3), 2.35 (3Hb, s, CH3
of OTs), 2.39 (3Ha, s, CH3 of OTs), 3.54–3.86(m,
5Hb+5Ha), 4.43–4.82 (m, 7Hb+7Ha), 5.65 (1Hb, d,
J ¼ 8:0 Hz, Hb1), 6.18 (1Ha, d, J ¼ 3:5 Hz, Ha1), 7.04–7.10
(m, 2Hb+2Ha), 7.14–7.36(15H b+15Ha), 7.73–7.79 (m,
2Hb+2Ha).
13C NMR (100 MHz, CDCl3): 20.7, 20.9, 21.6, 21.8 (CH3),
67.7, 67.8 (C6), 73.6, 73.7, 75.2, 75.4, 75.5, 75.7 (CH2 of
OBn), 72.6, 75.8, 77.0, 77.4, 78.1, 79.5, 79.7, 82.4, 89.6,
91.5 (C1, C2, C3, C4, C5), 127.6–128.6, 129.7, 130.0 (C tert
arom), 133.2, 134.7, 137.6, 137.7, 137.8, 137.9, 144.7, 145.3
(C quat arom), 168.6, 169.3 (C@O).
0
between this carbon and H2 . The regioselectivity of the
coupling reaction with the sugar moiety is consistent
with that already observed in the coupling using a het-
erogeneous medium in 7-azaindole series: the compound
in which the sugar part is linked to the indole moiety
was the major product of the reaction.10
16. Du, Y.; Mao, F.; Kong, F. Carbohydr. Res. 1996, 282,
315–323.
17. Spectral data of 7: IR (film, NaCl) mc@o 1739 cmÀ1
.
HRMS (FAB+) (M+Na)þ calcd for C34H35ClNaO7S
645.1690, found 645.1699.
In conclusion, we have successfully developed a method
for the synthesis of 7-aza staurosporine analogues,
which will be applied to prepare a new series by modi-
fying the substituent at the imide nitrogen and/or by
various substitutions on the aromatic rings and on the
sugar moiety. The biological properties of these new
azaindolocarbazoles will be evaluated.
1H NMR (400 MHz, CDCl3): 2.39 (3H, s, CH3), 3.66 (1H,
dd, J1 ¼ 11:0 Hz, J2 ¼ 2:0 Hz), 3.76–3.83 (2H, m), 4.05
(1H, t, J ¼ 9:5 Hz), 4.10 (1H, m), 4.48 (1H, d,
J ¼ 10:5 Hz), 4.48 (1H, d, J ¼ 12; 0 Hz), 4.60 (1H, d,
J ¼ 12:0 Hz), 4.60 (1H, dd, J1 ¼ 9:5 Hz, J2 ¼ 4:0 Hz), 4.69
(1H, d, J ¼ 11:0 Hz), 4.74 (1H, d, J ¼ 11:0 Hz), 4.75 (1H,
d, J ¼ 10:5 Hz), 6.21 (1H, d, J ¼ 4:0 Hz, H1), 7.08–7.11
(2H, m), 7.16–7.23 (4H, m), 7.25–7.37 (11H), 7.80 (2H, d,
J ¼ 8:5 Hz).
13C NMR (100 MHz, CDCl3): 21.7 (CH3 of OTs), 67.4
(C6), 73.6, 75.4, 75.6 (CH2 of OBn), 73.4, 76.6, 78.6, 79.1,
91.8 (C1, C2, C3, C4, C5), 127.7, 127.8–128.1, 128.3, 128.4,
128.5 (C tert arom), 133.0, 137.5, 137.6, 137.7, 145.3 (C
quat arom).
References and notes
1. Omura, S.; Iwai, Y.; Hirano, A.; Nakagawa, A.; Awaya,
J.; Tsuchiya, H.; Takahashi, Y.; Masuma, R. J. Antibiot.
1977, 30, 275–282.
ꢀ
18. Routier, S.; Ayerbe, N.; Merour, J.-Y.; Coudert, G.;
2. Tamaoki, T.; Nomoto, H.; Takahashi, I.; Kato, Y.;
Morimoto, M.; Tomita, F. Biochem. Biophys. Res. Com-
mun. 1986, 135, 397–402.
ꢀ
Bailly, C.; Pierre, A.; Pfeiffer, B.; Caignard, D.-H.;
Renard, P. Tetrahedron 2002, 58, 6621–6630.
19. Ohkubo, M.; Nishimura, T.; Jona, H.; Nakano, M.;
Honma, T.; Morishima, H. Tetrahedron 1996, 52, 8099–
8112.
3. Prudhomme, M. Curr. Pharm. Des. 1997, 3, 265–290.
€
4. Knolker, H. J.; Reddy, K. R. Chem. Rev. 2002, 102, 4003–
4427.
5. Anizon, F.; Moreau, P.; Sancelme, M.; Voldoire, A.;
ꢁ
20. Ohkubo, M.; Kawamoto, H.; Ohno, T.; Nakano, M.;
Morishima, H. Tetrahedron 1997, 53, 585–592.
21. Seela, F.; Bourgeois, W. Synthesis 1990, 945–950.
22. Spectral data of 9: Mp 67–69 °C.
Prudhomme, M.; Ollier, M.; Severe, D.; Riou, J.-F.;
Bailly, C.; Fabbro, D.; Meyer, T.; Aubertin, A.-M. Bioorg.
Med. Chem. 1998, 6, 1597–1604.
6. Marminon, C.; Anizon, F.; Moreau, P.; Leonce, S.; Pierre,
A.; Pfeiffer, B.; Renard, P.; Prudhomme, M. J. Med.
Chem. 2002, 45, 1330–1339.
IR (KBr) mC@O 1700 cmÀ1
.
ꢀ
ꢀ
HRMS (FAB+) (M+H)þ calcd for C47H39N4O6 755.2870,
found 755.2871.

S. Messaoudi et al. / Tetrahedron Letters 45 (2004) 4643–4647
4647
1H NMR signals of the sugar part were assigned from 1H–
1H COSY.
23. Ward, D. E.; Gai, Y.; Kaller, B. F. J. Org. Chem. 1995, 60,
7830–7836.
1H NMR (400 MHz, CDCl3): 3.30 (3H, s, CH3), 3.79 (1H,
d, J ¼ 11:0 Hz), 3. 91 (1H, dd, J1 ¼ 10:5 Hz, J2 ¼ 5:5 Hz,
24. Spectral data for 1: Mp 245–250 °C (decomposition)
IR (KBr) mC@O 1700 cmÀ1, mOH 3040–3680 cmÀ1
.
H6 ), 3.96–4.03 (2H, m, H3 , H6 ), 4.09 (1H, t, J ¼ 9:5 Hz,
HRMS (FAB+) (M+H)þ calcd for C26H21N4O6 485.1461,
found 485.1465.
0
0
0
0
0
H4 ), 4.42 (1H, m, H5 ), 4.44 (1H, d, J ¼ 10:5 Hz), 4.65
(1H, d, J ¼ 11:0 Hz), 4.67 (1H, d, J ¼ 12:0 Hz), 4.75 (1H,
d, J ¼ 12:0 Hz), 4.92 (1H, d, J ¼ 11:0 Hz), 5.53 (1H, m,
1H NMR (400 MHz, DMSO-d6): 3.19 (3H, s, NCH3),
3.59–3.66 (2H, m), 3.79 (1H, m), 3.95–3.98 (1H, m), 4.06
0
0
0
(1H, m), 5.18–5.28 (3H, m, 2OH+H2 ), 5.40 (1H, d,
H2 ), 6.15 (1H, d, J ¼ 3:5 Hz, H1 ), 6.45 (2H, d,
J ¼ 7:0 Hz), 6.89 (2H, t, J ¼ 7:5 Hz), 7.03 (1H, t,
J ¼ 7:5 Hz), 7.14–7.18 (2H, m), 7.24–7.28 (3H, m), 7.32–
7.39 (2H, m), 7.40–7.49 (6H, m), 8.00 (1H, m), 8.52 (1H, d,
J ¼ 4; 0 Hz), 8.82 (1H, m), 8.95 (1H, dd, J1 ¼ 8:0 Hz,
J2 ¼ 1:0 Hz).
0
J ¼ 5:5 Hz, OH), 6.42 (1H, d, J ¼ 4:0 Hz, H1 ), 7.49 (1H,
dd, J1 ¼ 8:0 Hz, J2 ¼ 5:0 Hz), 7.51 (1H, t, J ¼ 7:5 Hz), 7.64
(1H, dt, J1 ¼ 7:5 Hz, J2 ¼ 1:0 Hz), 8.24 (1H, d,
J ¼ 8:0 Hz), 8.63 (1H, dd, J1 ¼ 5:0 Hz, J2 ¼ 1:5 Hz), 8.72
(1H, d, J ¼ 7:5 Hz), 8.89 (1H, dd, J1 ¼ 8:0 Hz,
13C NMR (100 MHz, CDCl3): 23.9 (NCH3), 58.3, 74.5,
J2 ¼ 1:5 Hz).
13
0
0
0
0
0
0
0
78.3, 80.4, 85.0 (C1 , C2 , C3 , C4 , C5 ), 68.9 (C6 ), 73.8,
75.1, 75.9 (CH2 of OBn), 110.4, 113.3, 116.5, 117.7, 121.9,
125.3, 127.4, 130.2, 136.1, 137.6, 137.9, 143.3, 152.3 (C
quat arom), 113.6, 117.3, 122.9, 125.6, 127.7–128.7, 134.1,
146.5 (C tert arom), 170.0, 170.1 (C@O).
C NMR (100 MHz, DMSO-d6): 23.6(CH ), 61.1 (C6 ),
3
0
0
0
0
0
59.2 (C2 ), 70.1, 73.6, 76.8 (C3 , C4 , C5 ), 84.6(C 1 ), 109.2,
114.6, 116.1, 120.1, 120.9, 124.4, 127.6, 130.2, 143.0, 152.8
(C quat arom), 114.1, 116.9, 122.1, 124.2, 127.7, 132.1,
146.9 (C tert arom), 169.5, 169.6 (C@O).