Benzoxazine and benzodioxine as indole isosteres in indolocarbazoles series: Synthesis and biological evaluation

Article abstract of DOI:10.2174/157017810790796291

New series of structure based on original benzodioxine and benzoxazine heterocycles were prepared leading to potential anticancer lead compounds. In this paper, we described a convenient approach via a Diels-Alder cycloaddition in order to efficiently provide three new indole isosteres in indolocarbazoles series. Their first cytotoxic evaluation was also reported.

Full text of DOI:10.2174/157017810790796291

Letters in Organic Chemistry, 2010, 7, 121-126
121
Benzoxazine and Benzodioxine as Indole Isosteres in Indolocarbazoles
Series: Synthesis and Biological Evaluation
Nathalie Ayerbe, Sylvain Routier*, Isabelle Gillaizeau*, Sébastien Tardy and Gérard Coudert
Institut de Chimie Organique et Analytique, UMR CNRS 6005,Université d'Orléans, BP 6759, F-45067 Orléans, France
Received August 26, 2009: Revised November 03, 2009: Accepted November 09, 2009
Abstract: New series of structure based on original benzodioxine and benzoxazine heterocycles were prepared leading to
potential anticancer lead compounds. In this paper, we described a convenient approach via a Diels-Alder cycloaddition in
order to efficiently provide three new indole isosteres in indolocarbazoles series. Their first cytotoxic evaluation was also
reported.
Keywords: Benzodioxine, benzoxazine, indolocarbazole, cytotoxicity.
R1
X
R2
INTRODUCTION
O
The chemistry and biology of indolocarbazole alkaloids
have attracted an increasing interest over the last 30 years
[1]. A broad range of structurally interesting indolocarbazole
alkaloids with useful biological activities has been isolated
from diverse natural sources. The pharmacological potential
of these natural products initiated the development of novel
synthetic methods for efficient routes to these alkaloids.
Since several years, we are engaged in an ongoing effort to
synthesize parented derivatives [2] (Fig. 1, carbazole I)
which exhibit protein kinase inhibitions and/or in vitro
cytotoxic effects [2f,g]. As an extension of our previous
work and taking into account our knowledge in the
functionalization of benzoxazine or benzodioxine moieties
[3], we want to report herein the synthesis and the cytotoxic
evaluation of new indolocarbazole isosteres II-IV (Fig. 1).
Our approach was to provide a design that would allow
compounds to be assembled quickly and efficiently. Among
all the versatile access to indolocarbazole series, the
preparation of original derivatives II-IV was envisioned via
a straightforward convenient Diels-Alder cycloaddition as
the key step from non-aromatic benzodioxinic and/or
benzoxazinic dienes (Fig. 2) [4].
O
II
III
IV
X,Y = O
X = NH, Y=O
X = NH, Y=NH
Diels-Alder
Y
Fig. (2). Retrosynthetic scheme.
RESULTS AND DISCUSSION
In order to perform the Diels-Alder cycloaddition, the
preparation of the required diene systems was carried out via
Stille palladium cross coupling reaction. To this aim, starting
from benzodioxine 1a [3e] or N-protected benzoxazine 1b
[3], vinylstannanes 2a, 2c and vinyliodides 2b were prepared
in fair to good yields under anionic conditions by using the
required electrophiles (Table 1). In each reaction, the nature
of the base (LDA or n-BuLi) and the time of the reaction
were optimized. As previously reported, 2-bromobenzo-
dioxine 2d was synthesized from 2,3-dibromo-2,3-dihydro-
1,4-benzodioxine [3d] and enol phosphate 2e was prepared
from the corresponding protected lactam [3c]. With all these
original functionalized benzodioxine and benzoxazine
derivatives 2a-c in hand, we next studied the Stille palladium
cross coupling reaction (Table 2). For efficiency’s sake, the
basic homocoupling of benzodioxine or benzoxazine
derivatives was first studied. The benzodioxinic diene
derivative 3a was thus prepared in good yield from 2-
bromobenzodioxine 2d and organostannane 2a in the
presence of Pd(PPh3)4 (10 mol%) and CuI (20 mol%) in
dioxane at 80°C. In order to achieve a good yield the
synthesis of the benzoxazinic diene derivative 3b, the
sterically hindered Boc protecting group was replaced by a
phenoxycarbonyl group. By slightly modifying the reaction
conditions and under microwave irradiations, the desired
diene 3b was isolated in 96% yield [6]. Our attention was
then focused on non-symmetrical diene 3c. The initial Stille
coupling process involving bromobenzodioxine 2d and
stannylated benzoxazine was found to be less convenient and
gave a lower yield (3c was recovered in 53% yield) than the
alternative process involving the palladium catalyzed cross-
R
R
N
O
O
O
N
O
O
O
Het/Ar
Y
X
N
H
I
R = H, CH3, (CH2)2N(CH3)2
R = H, CH3, (CH2)2N(CH3)2
Het/Ar = naphthalene, quinoline,
indane...
X,Y = O
II
III
IV
X = NH, Y=O
X = NH, Y=NH
Fig. (1). Examples of indolocarbazoles analogues I-IV.
*Address correspondence to these authors at the Institut de Chimie
Organique et Analytique, UMR CNRS 6005,Université d'Orléans, BP 6759,
F-45067 Orléans, France; Tel: (33) 2 38 49 45 76; Fax: (33) 2 38 41 72 81;
E-mail: sylvain.routier@univ-orleans.fr; isabelle.gillaizeau@univ-orleans.fr
1570-1786/10 $55.00+.00
© 2010 Bentham Science Publishers Ltd.

122 Letters in Organic Chemistry, 2010, Vol. 7, No. 2
Ayerbe et al.
Table 1. Preparation of Intermediates 2 Under Anionic Conditions
O
O
1) Base (1.2 equiv)
E
2) E+ (1.5 equiv)
X
X
THF, -78°C
1a-b
2a-c
Entry
SM
Base
E+
Time
Products (Yields%)
1a
X=O
2a [2f,2g]
(E = SnMe3, 99%)
1
n-BuLi
Me3SnCl
I2
1.5h
1b
2b [5]
(E = I, 61%)
2
LDA
LDA
20 min
20 min
X= NCOPh
1b
2c [5]
(E = SnBu3, 75%)
3
Bu3SnCl
X= NCOPh
SM: Starting Material.
Table 2. Obtention of Dienes 3 via Stille Cross-Coupling Conditions
O
O
O
Pd(0)
Stille
E
X
X'
X
2
3
Entry
Reactants
Products (Yields%)d
O
O
O
O
O
O
1a
O
O
SnMe3
Br
2d
2a
3a (84 %)
O
O
O
O
2b
N
N
I
N
SnBu3
N
COPh
COPh
COPh
COPh
3b (96 %)
2b
2c
O
N
O
O
O
3c
O
N
OP(O)(OPh)2
O
SnMe3
Boc
Boc
2a
2e
3c [3b,3d] (93%)
Conditions: a2d (2 equiv.), 2a (1 equiv.), Pd(PPh3)4 (0.1 equiv), CuI (0.2 equiv), dioxane, 80°C, 18h. b2b (1 equiv.), 2c (1.2 equiv.), Pd(PPh3)2Cl2 (0.1 equiv), CuBr. Me2S (1 equiv),
DMF, μwave 150°C, 17 min. c2e (2 equiv.), 2a (1 equiv.), Pd(PPh3)4 (0.1 equiv), LiCl (3 equiv), THF, 60°C, 2h. d Isolated yield.
coupling reaction of the vinylphosphate derivative 2e (entry
3 3c, 93% yield) [3d].
benzodioxane or benzoxazine moiety (Scheme 1). In the case
of the symmetrical benzoxazine derivative 3b (Table 3, entry
2), the Diels-Alder cycloaddition yielded the desired
cycloadduct 5a (in low yield) accompanied with a non
separable mixture of the ring-opened phenol 5b and mono
protected derivative 5c. However, direct treatment of the
crude mixture (5a-c) with Et3N in dichloromethane gave 5c
isolated as the sole product in 94% yield [7]. By performing
the Diels-Alder cycloaddition in the presence of maleimide
or N-methylmaleimide as the dienophile (Table 3, entries 4-
5), the original cycloadducts 7-8 were isolated in fair to good
yields [8]. For compound 7, best yield was observed by
The next phase of our work for the construction of the
fused hexacyclic systems II-IV required a Diels-Alder
cycloaddition (Fig. 2 and Table 3). Reaction of symmetrical
and non-symmetrical dienes 3a, 3b, 3c with DMAD, used as
the dienophile, afforded in fair to good yields the
corresponding cycloadducts 4a, 5a (or 5c), 6a (Table 3,
entries 1-3). It is worth noting that during this cycloaddition
reaction, ring-opened phenols 4b, 5b (or 5c), 6b were
isolated as by-products. As previously demonstrated [3h]
these phenolic derivatives result from the ring opening of the

Synthesis and Biological Evaluation
Letters in Organic Chemistry, 2010, Vol. 7, No. 2
123
Table 3. Synthesis of Cycloadducts 4-8 via Diels-Alder Reaction
O
O
O
O
O
O
MeO2C
CO2Me
O
R
N
Y
X
or
O
Y
X
3a-c
4-8
Products (Yields%)e
CO2Me
Entry
Diene
3a
Dienophile (equiv)
CO2Me
CO2Me
OH
CO2Me
O
O
O
DMAD
(8.0)
1 a
O
O
O
O
4b (19%)
4a (82%)
CO2Me
CO2Me
CO2Me
OR
CO2Me
O
O
O
DMAD
(20.0)
2 b
3b
N
N
N
PhOC
5b R=H
N
R
R
H
5a R = COPh
5c R=COPh (94%)
CO2Me
CO2Me
CO2Me
OH
CO2Me
O
O
O
DMAD
(8.0)
3 a
3c
O
N
O
N
Boc
6a (85%)
Boc
6b (6%)
CH3
N
O
O
CH3
N
O
4 c
3a
O
7(88%)
O
O
(8.0)
O
O
R
R
N
N
O
O
O
O
O
5 d
3b
O
8a R = H (29%)
R = H
8b R = CH3 (44%)
R= CH3
N
N
(8.0)
COPh
COPh
a
c
Conditions: Toluene, sealed tube, 95°C, 4h. bConditions (a) (obtention of a mixture of 5a-c) then treatment with Et3N (1.5 equiv), CH2Cl2, r.t. 1h. 5c was isolated in 94% yield.
AlCl3 (0.2 equiv), toluene, r.t., 2h. dToluene, sealed tube, 95°C, 16h. eIsolated yield.
using a catalytic amount of AlCl3 in toluene at rt. The
moderate yield observed in the case of derivatives 8a and 8b
could be attributed to the steric hindrance of the two
protective groups borne by the nitrogen atom. Subsequent
aromatization of the highly reactive cycloadducts using
either DDQ at 70°C in toluene or radical conditions in the

124 Letters in Organic Chemistry, 2010, Vol. 7, No. 2
Ayerbe et al.
MeO2C
CO2Me
MeO2C
CO2Me
H
O
O
O
3a
3b
3c
Me2OC
CO2Me
Diels-Alder
Y
Y
OR 4b, 5b (or 5c), 6b
X
X
4a, 5a, 6a
Scheme 1. By products 4b, 5b (or 5c), 6b isolated by ring-opening of benzodioxane or benzoxazine moiety [3h]. Conditions: See Table 3,
entries 1-3.
presence of NBS and benzoyle peroxide under light
irradiation (60W) afforded derivatives 9-12 [9] in fair to
good yields (Scheme 2).
protected phenol 14b is not cytotoxic. Lack of a methyl
group induces a low level of cytotoxicity in agent 14c. The
appearance of this cell toxicity is mainly due to a newly
formed partially masked hydroquinonic system. The bis-
benzodioxino heterocyclic compounds 11 and 13b were
moderately cytotoxic. It is worth noting that substituting an
amino hydrophilic side chain for the methyl maleimide
group decreased cytotoxicity. Results concerning compound
15b were of higher interest. In the latter one of the two
benzodioxine moieties was replaced with a benzoxazine unit.
This modification regenerates a NH group such as it can be
MeO2C
CO2Me
O
O
i
4a or 6a
Y
9 X,Y=O
X
10 X=NBoc, Y=O
R
X
O
O
N
O
O
O
O
i
O
O
9
i or ii
O
O
7,8a or 8b
Y
X
13a X=O
13b X=NCH2CH2N(CH3)2
ii
11 X,Y=O, R=CH3
12a X,Y=NCOPh, R= H
12b X,Y=NCOPh, R=CH3
X
O
O
Scheme 2. Aromatization of the cycloadducts 4a,6a,7,8a or 8b.
Conditions: (i) DDQ (8.0 equiv), toluene; from 4a : 70°C, 19 h, 9
(87%); from 6a: 55°C, 3 days, 10 (74%); from 7: 85°C, 4h, 11
(93%); (ii) NBS (3.0 equiv), BzO2 (cat.), CCl4, 60W, 6 min.; from
8a: 12a (25%) or from 8b: 12b (80%).
OR
O
i
4b
4b
O
O
14a X=O, R=CH3
14b X=NCH2CH2N(CH3)2, R=CH3
14c X=NCH2CH2N(CH3)2, R=H
ii
In order to introduce diversity on the maleimide nitrogen,
anhydride 13a or 14a was generated in good yields from the
corresponding diesters using aqueous potassium hydroxide
in methanol at reflux, followed by a recyclization in acidic
medium (Scheme 3). Conversion of those anhydrides
respectively to imides 13b or 14b was achieved in good
yields by heating in the presence of primary amine [10].
Moreover, it appeared that the N,N-dimethylaminoethyl
chain could be directly introduced from diester derivatives
affording imides 14c (from 4b) and 15a (from 10). In the
case of compound 15a, partial cleavage of the Boc group
was observed during this reaction sequence. Total
deprotection of the nitrogen atom by use of formic acid gave
the target compound 15b in 81% yield, after neutralization.
Having in hand these original indole bioisosteres, we next
focused our attention on their biological evaluation. In vitro
cell cytotoxicity of the original polycyclic derivatives 11,
13b, 14b, 14c, 15b was carried out on the murine L1210
leukemia cell line (Table 4) [11]. In order to enhance their
solubility, compounds 13b and 15b were quantitatively
converted into their soluble chlorhydrate salts. The O-
ii
N
N
O
O
O
O
ii
10
O
X
15a X=NBoc
15b X=NH
iii
Scheme 3. Conditions: (i) KOH (10 equiv), MeOH/H2O 9/1, rflx
16 h. then Ac2O, rflx, 4h; from 9: 13a (97%); from 4b: (a) CH3I
(10.0 equiv), K2CO3 (5.0 equiv), acetone, rflx, 18h, (86%) then (i),
14a was isolated in 81% yield; (ii) NH2CH2CH2N(CH3)2, 95 °C
16h, then SiO2, CH2Cl2, r.t., 2h, from 13a: 13b (92%); from 14a:
14b (89%); from 4b: 14c (70%); from 10: mixture of 15a (53%)
and 15b (28%); (iii) HCOOH, r.t., 7h, 15b (81 %).

Synthesis and Biological Evaluation
Letters in Organic Chemistry, 2010, Vol. 7, No. 2
125
Table 4. Cytotoxicity on L1210 Cell Line
Entry
Compounds
Maleimide Substitution
(IC50, μM)
1
2
3
4
5
11
13b.HCl
14b
CH3
45.5
28.1
>100
22.4
1.0
(CH2)2N(CH3)2, HCl
(CH2)2N(CH3)2
14c
(CH2)2N(CH3)2
15b.HCl
(CH2)2N(CH3)2, HCl
pyrrolo[2,3-a]pyrrolo[3,4-c]-carbazoles,
leur
procédé
de
seen in the case of the indole moiety. Compound 15b
exhibited thus a cytotoxic activity rising to micromolar
value. In addition, its effect on cycle cell indicates an
accumulation in the G2/M phases such as described for the
related indolocarbazole (data not shown). Several enzymatic
assays (topoisomerase and kinase) and DNA interaction are
still in progress in order to elucidate the action of this new
lead compound 15b which is also a good candidate for
further structural modifications.
préparation et les compositions pharmaceutiques qui les
contiennent. FR Patent 2845997 ; Chem. Abstr. 2004, 140, 339333.
(a) Claveau, E.; Gillaizeau, I.; Blu, J.; Bruel, A.; Coudert, G. Easy
access to new heterocyclic systems: 1,4-oxazine and substituted
1,4-oxazines. J. Org. Chem. 2007, 72, 4832. (b) Buon, C.; Chacun-
Lefevre, L.; Rabot, R.; Bouyssou, P.; Coudert, G. Synthesis of 3-
substituted and 2,3-disubstituted-4H-1,4-benzoxazines. Tetra-
hedron 2000, 56, 605. (c) Lepifre, F.; Buon, C.; Rabot, R.;
Bouyssou, P.; Coudert, G. Palladium-catalysed coupling of vinyl
phosphates with aryl or heteroaryl boronic acids. Application to the
synthesis of substituted nitrogen containing heterocycles.
Tetrahedron Lett. 1999, 40, 6373. (d) Buon, C.; Bouyssou, P.;
Coudert, G. Synthesis of 3-substituted-4H-1,4-benzoxazines via
palladium-catalysed coupling reactions. Tetrahedron Lett. 1999,
40, 701. (e) Lepifre, F.; Buon, C.; Bouyssou, P.; Coudert, G.
Synthesis of 4H-pyrido[3,2-b][1,4]oxazine and 3-substituted-4H-
pyrido[3,2-b][1,4]oxazines via palladium-catalyzed reactions.
Heterocycl. Commun. 2000, 6, 397. (f) Chacun-Lefevre, L.; Buon,
C.; Bouyssou, P.; Coudert, G. Synthesis of 3-substituted-4H-1,4-
benzoxazines. Tetrahedron Lett. 1998, 39, 5763. (h) Lepifre, F.;
Buon, C.; Roger, P.-Y.; Bouyssou, P.; Coudert, G. Easy access to
N-aryl, N-heteroarylbenzoxazolinones and 4-aza analogues via
Diels–Alder cycloaddition reactions. Tetrahedron Lett. 2004, 45,
8257.
[3]
To sum up, we have developed the efficient synthesis of
three new scaffolds, bio-isosteres of indolocarbazoles.
Subsequently to our study, it is worth noting that the
presence of a nitrogen atom in benzoxazinic derivatives
makes such compounds useful for further structural
modifications (e.g. glycosylation or metal complexation
[12]). Experiments designed to explore the potentialities of
these original heterocyclic systems are in progress and will
be described in due course.
[4]
(a) Palmer, B.D.; Thompson, A.M.; Booth, R.J.; Dobrusin, E.M.;
Kraker, A.J.; Lee, H.H.; Lunney, E.A.; Mitchell, L.H.; Ortwine,
D.F.; Smaill, J.B.; Swan, L.M.; Denny, W.A. Structure-activity
relationships for chromophore modification and phenyl ring
substitution. J. Med. Chem. 2006, 49, 4896. (b) McCort, G.;
Duclos, O.; Cadilhac, C.; Guilpain, E. A versatile new synthesis of
4-aryl- and heteroaryl-[3,4-c]pyrrolocarbazoles by [4+2]
cycloaddition followed by palladium catalysed cross coupling.
Tetrahedron Lett. 1999, 40, 6211.(c) Conchon, E.; Anizon, F.;
Aboab, B.; Prudhomme, M. Synthesis and biological activities of
ACKNOWLEDGEMENTS
This research was supported by grants for S.R. from the
Association pour la Recherche sur le Cancer (ARC), le
Canceropôle Grand Ouest, (for SR and IG) La Ligue Contre
le Cancer (comité du Loiret) and for I.G. from la Fondation
pour la Recherche Médicale FRM section Orléans.
new checkpoint kinase
1 inhibitors structurally related to
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[2]
(a) Routier, S.; Coudert, G.; Mérour, J. Y.; Caignard, D. H. First
[5]
Representative procedure for the preparation of 2b-c. To a solution
of N-COPh Benzoxazine 1b [3b,3g] in THF at -78°C was added
dropwise 1.2 equiv of LDA. After stirring for 1h, tributyltin
chloride (1.5 equiv) was added at -78°C. After 20 min at -78°C, the
reaction was quenched by slow addition of water. The aqueous
phase was then extracted with EtOAc and the organic phase was
washed with brine. The organic phase was dried over anhydrous
MgSO4 and concentrated. Flash chromatography (petroleum
ether:EtOAc, 98/2) afforded 2c (75%) as a an yellow oil. 1H NMR
(250 MHz, CDCl3): ꢀ= 7.3-7.4 (m, 3H), 7.26-7.31 (m, 2H), 7.11
(dt, J = 1.25 and 8 Hz, 1H), 6.91 (dt, J = 1.5 and 8 Hz, 1H), 6.60
(dt, J = 1.5 and 8 Hz, 1H), 6.15 (dd, J = 1.5 and 7.5 Hz, 1H), 6.09
(s, 1H), 1.55 (m, 6H), 1.34 (m, 6H), 1.02 (t, J = 7 Hz, 6H), 0.87 (t,
synthesis
of
symmetrical
and
non-symmetrical
aza
indolocarbazoles derivatives. Tetrahedron Lett. 2002, 43, 2561. (b)
Routier, S.; Ayerbe, N.; Mérour, J. Y.; Coudert, G.; Bailly, C.;
Pierré, A.; Pfeiffer, B.; Caignard, D. H.; Renard, P. Synthesis and
biological evaluation of 7-azaindolocarbazoles. Tetrahedron 2002,
58, 6621. (c) Routier, S.; Peixoto, P.; Mérour, J. Y.; Coudert, G.;
Dias, N.; Bailly, C.; Leonce, S.; Caignard, D. H. Synthesis and
biological evaluation of novel naphthocarbazoles as potential
anticancer agents. J. Med. Chem. 2005, 48, 1401. (d) Lefoix, M.;
Coudert, G.; Routier, S.; Pfeiffer, B.; Caignard, D. H.; Hickman, J.;
Pierré, A.; Golsteyn, R. M.; Léonce, S.; Bossard, C.; Mérour, J. Y.
Novel 5-azaindolocarbazoles as cytotoxic agents and Chk1
inhibitors. Bioorg. Med. Chem. 2008, 16, 5303. (e) Bourderioux,
A.; Bénéteau, V.; Mérour, J.-Y.; Baldeyrou, B.; Ballot, C.;
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Nouveaux dérivés de type [1,4]benzodioxino[2,3-e]isoindoles
substitués pyrido-pyrrolo[3,2-g]pyrrolo[3,4-e]-indole et pyrido-
J = 8 Hz, 9H). 13C NMR (62.9 MHz, CDCl3): ꢀ= 166.7 (s), 149.7
(s), 140.8 (d), 134.9 (s), 130.8 (d), 129.2 (s), 128.7 (d), 128.4 (d),
126.0 (d), 123.5 (s), 123.4 (d), 122.8 (d), 116.8 (d), 29.2 (t), 27.5
(t), 13.9 (t), 12.7 (q). MS (IS) m/z = 527 [M+1]+.
[6]
Preparation of diene 3b. To a solution of stanylated benzoxazine 2c
(1,2 equiv) in distilled DMF (5 mL), under argon, were
successively added iodo benzoxazine 2b (0.7 mmol, 1 equiv),
palladium (II) dichlorobistriphenylphosphine (0.1 equiv) and

126 Letters in Organic Chemistry, 2010, Vol. 7, No. 2
Ayerbe et al.
CuBr.Me2S (1 equiv). Then the flask was evacuated and backfilled
with argon three times. The reaction mixture was heated under
microwaves in a sealed tube for 17 min. at 150 °C. The crude was
diluted with ethyl acetate. The organic phase was successively
washed with aqueous NH4OH (17%), then with a saturated solution
of KF and with brine. The organic phase was dried over anhydrous
MgSO4 and concentrated. Flash chromatography (petroleum ether
then petroleum ether:EtOAc, 90:10) afforded 3b (0.311 g, 96%
yield). Yellow solide m.p. 198-200°C. 1H NMR 250 MHz (CDCl3)
ꢀ(ppm): 7.88-7.95 (m, 2H), 7.25-7.28 (m, 4H), 7.06-7.09 (m, 2H),
7.03-7.06 (m, 4H), 6.88-6.95 (m, 4H), 6.68-6.72 (m, 2H), 5.97 (s,
2H). HRMS (IS) m/z [M+1]+ calcd for C30H21N2O4: 473.1501;
found 473.1514.
Representative procedure for Diels-Alder cycloaddition in the
presence of DMAD. Diene 3b (0.504 mmol) and DMAD (20
equiv) were heated at 95°C in a sealed tube in toluene (1 mL) for
4h. The crude mixture (containing 5a, 5b and 5c) was then
dissolved in dichloromethane (15 mL) in presence of triethylamine
(1 mL). After stirring for 1h at room temperature, the organic phase
was washed with a saturated aqueous solution of NH4Cl and with
brine. The organic phase was dried over anhydrous MgSO4 and
concentrated. Flash chromatography (petroleum ether then
petroleum ether:EtOAc, 90:10) afforded 5c (94% yield). Yellow
Flash chromatography (petroleum ether then petroleum
ether:EtOAc, 70:30) afforded 9 in 87% yield. White solid m.p. 225-
1
226°C. H NMR 250 MHz (CDCl3) ꢀ(ppm): 6.85-7.00 (m, 8H),
3.89 (s, 6H). 13C NMR 62.5 MHz (CDCl3) ꢀ(ppm) : 164.3 (s), 140.8
(s), 140.4 (s), 137.3 (s), 133.0 (d), 125.0 (d), 124.7 (d), 117.0 (d),
116.7 (d), 114.5 (d), 52.9 (q). HRMS (IS) m/z [M+Na]+ calcd for
C22H14O8Na: 429.0586; found 429.0606.
(b) To a solution of 8b (0.053 mmol) in CCl4 (3.5 mL) was
carefully added NBS (2,1 équiv.) and a catalytic quantity of
benzoyle peroxyde. The mixture was irradiated with a lamp (60W
power) during 6 min. After cooling, the mixture was diluted with
dichloromethane. The organic phase was washed with aqueous
NaHCO3 solution (10%), then with a solution of aqueous sodium
thiosulfite solution. The organic phase was dried over anhydrous
MgSO4 and concentrated. Flash chromatography (petroleum ether
then petroleum ether:EtOAc, 70:30) afforded 12b in 80% yield.
[7]
Yellow solid m.p. 230°C. 1H NMR 250 MHz (CDCl3) ꢀ(ppm):
7.21-7.4 (m, 6H), 7.08-7.18 (m, 10H), 6.93 (dt, J= 1.5 and 8.25Hz,
2H), 3.22 (s, 3H). 13C NMR 62.5 MHz (CDCl3) ꢀ(ppm) : 167.2 (s),
164.6 (s), 148.5 (s), 145.5 (s), 133.1 (s), 131.4 (d), 130.1 (s), 128.4
(d), 128.1 (s), 127.2 (d), 125.8 (d), 124.0 (d), 116.7 (d), 114.6 (s),
24.4 (q). HRMS (IS) m/z [M+1]+ calcd for C35H22N3O6: 580.1509;
found 580.1514.
solid m.p. 193-194°C. 1H NMR 250 (CDCl3) ꢀ(ppm): 8.07 (d, J=
6Hz, 2H), 7.25-7.51 (m, 10H), 7.04-7.17 (m, 4H), 6.62-6.71 (m,
3H), 6.53-6.56 (m, 1H), 3.92 (s, 3H), 3.70 (s, 3H). 13C NMR 62.5
MHz (CDCl3) ꢀ(ppm) : 171.0 (s), 166.9 (s), 166.5 (s), 164.5 (s),
145.2 (s), 142.7 (s), 141.7 (s), 134.3 (d), 134.2 (s), 132.7 (s), 131.8
(d), 130.5 (d), 128.9 (s), 128.7 (d), 128.5 (d), 128.1 (d), 127.9 (s),
127.7 (d), 126.0 (s), 124.5 (d), 123.8 (d), 122.9 (d), 121.9 (s), 118.2
(s), 115.8 (d), 114.9 (d), 52.9 (q), 52.3 (q). HRMS (IS) m/z [M+1]+
calcd for C36H27N2O8: 615.1767; found 615.1772.
[10]
[11]
(a) Representative procedure for the transimidification step, see ref.
1
[2e]. (b) Compound 13b: Yellow solid m.p. 254-255°C. H NMR
250 MHz (CDCl3) ꢀ(ppm): .6.97-7.08 m, 8H), 3.73 (t, J= 6.5 Hz,
2H), 2.55 (t, J= 6.5 Hz, 2H), 2.27 (s, 6H). 13C NMR 62.5 MHz
(CDCl3) ꢀ(ppm) : 164.8 (s), 140.2 (s), 140.1 (s), 138.8 (s), 135.4
(s), 125.4 (d), 125.2 (d), 117.4 (d), 117.0 (d), 110.4 (d), 57.1 (t),
45.6 (q), 36.0 (t). HRMS (IS) m/z [M+1]+ calcd for C24H19N2O6:
431.1243; found 431.1263.
(a) Bach, S.; Knockaert, M.; Reinhardt, J.; Lozach, O.; Schmitt, S.;
Baratte, B. Roscovitine targets, protein kinases and pyridoxal
kinase. J. Biol. Chem. 2005, 280, 31208. (b) Bettayeb, K.; Tirado,
O.M.; Marionneau-Lambert, S.; Ferandin, Y.; Lozach, O.; Morris,
J.C.; Mateo-Lozano, S.; Drueckes, P.; Schächtele, C.; Kubbutat,
M.; Liger, F.; Marquet, B.; Joseph, B.; Echalier, A.; Endicott, J.;
Notario, V.; Meijer, L. Meriolins, a new class of cell death–
inducing kinase inhibitors with enhanced selectivity for cyclin-
dependent kinases. Cancer Res. 2007, 67, 8325. (c) Reinhardt, J.;
Ferandin, Y.; Meijer, L. Purification CK1 by affinity
chromatography on immobilised axin. Protein Expr. Purif. 2007,
54, 101.
[8]
Representative procedure for Diels-Alder cycloaddition in the
presence of N-methylmaleimide. Diene 3b (0.125 mmol) and
dienophile (N-methylmaleimide, 8 equiv) were dissolved in toluene
(1 mL) in a sealed tube and heated at 90°C for 16h. After
evaporation of the solvent, the crude mixture was purified by flash
column chromatography (petroleum ether/ethyl acetate 7:3) to
afford cycoadduct 8b in 44% yield. Yellow solid m.p.114-115°C.
1H NMR 250 MHz (CDCl3) ꢀ(ppm): 8.18 (m, 2H), 7.57-7.65 (m,
1H), 7.43-7.49 (m, 3H), 7.20-7.33 (m, 12H), 7.02-7.14 (m, 4H),
6.68-6.79 (m, 4H), 5.13 (m, 2H), 3.68-3.70 (m, 2H), 2.59 (s, 3H).
13C NMR 62.5 MHz (CDCl3) ꢀ(ppm) : 172.9 (s), 166.3 (s), 148.9
(s), 134.9 (s), 133.7 (d), 130.3 (d), 130.2 (d), 128.6 (d), 128.2 (d),
128.1 (s), 126.7 (d), 126.2 (d), 122.7 (d), 118.9 (d), 75.9 (d), 42.9
(d), 25.0 (q). HRMS (IS) m/z [M+1]+ calcd for C35H26N3O6:
584.1822; found 584.1830.
[12]
Meggers, E.; Ekin Atilla-Gokcumen, G.; Bregman, H.;
Maksimoska, J.; Mulcahy, S.P.; Pagano, N.; Williams, D.S.
Exploring chemical space with organometallics: ruthenium
complexes as protein kinase inhibitors. Synlett 2007, 1177.
[9]
General procedure for the aromatisation of the cycloadducts. (a) A
solution of 4a in toluene was added DDQ (8.0 equiv) was heated at
70°C for 19h. After cooling, the solvent was evaporated. The
mixture was diluted with CH2Cl2 and the organic phase was washed
with aqueous NaHCO3 solution (10%), then with brine. The
organic phase was dried over anhydrous MgSO4 and concentrated.