Tariquidar analogues: Synthesis by CuI-catalysed N/O-aryl coupling and inhibitory activity against the ABCB1 transporter

Article abstract of DOI:10.1002/ejoc.200700142

Less lipophilic and better water soluble tariquidar analogues were synthesised from one central anthranilic acid derived building block by Cu ^I-catalysed N/O-arylation reactions. The compounds were tested for their inhibitory activity against the ABCB1 transporter in a flow cytometric calcein-AM efflux assay. A correlation between their calculated log P values and their activities was observed, with the more lipophilic analogues being as potent as the reference substance tariquidar. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.

Full text of DOI:10.1002/ejoc.200700142

FULL PAPER
DOI: 10.1002/ejoc.200700142
Tariquidar Analogues: Synthesis by CuI-Catalysed N/O–Aryl Coupling and
Inhibitory Activity against the ABCB1 Transporter
Michael Egger,[a] Xuqin Li,[a] Christine Müller,[b] Günther Bernhardt,[b]
Armin Buschauer,*[b] and Burkhard König*[a]
In memory of Dr. Thomas Suhs
Keywords: Cross-coupling / Medicinal chemistry / Lipophilicity
Less lipophilic and better water soluble tariquidar analogues
were synthesised from one central anthranilic acid derived
building block by CuI-catalysed N/O–arylation reactions.
The compounds were tested for their inhibitory activity
against the ABCB1 transporter in a flow cytometric calcein-
AM efflux assay. A correlation between their calculated logP
values and their activities was observed, with the more lipo-
philic analogues being as potent as the reference substance
tariquidar.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2007)
with the anticancer drug paclitaxel, an ABCB1 substrate,
increased brain levels of the cytostatic in mice by a factor
of 6–8 relative to the treatment with paclitaxel alone.[8]
Moreover, in nude mice bearing orthotopically growing hu-
man glioblastoma the combination therapy led to a de-
crease in tumour volume by 90%, whereas application of
paclitaxel alone was ineffective.[8] The antitumour effect in
vivo could be clearly attributed to increased paclitaxel levels
in the brain as a result of inhibited ABCB1-mediated trans-
port at the BBB.[8]
However, paclitaxel levels also increased in liver, kidneys
and plasma relative to the control, so that systemic paclit-
axel toxicity became dose-limiting with valspodar, owing to
modulation of ABCB1 in liver, kidneys and bone marrow.
By using the more potent ABCB1 inhibitor tariquidar (1)
(Figure 1), a higher brain/plasma ratio of paclitaxel was de-
tected in mice.[9] However, despite the high tariquidar con-
centrations in the brain, paclitaxel brain levels did not in-
crease relative to the valspodar group.[9] The latter result
might be explained by the high lipophilicity of tariquidar,
which results in its accumulation in the lipid compartment
of the brain. Therefore, tariquidar might reach its target,
the ABCB1 transporter, at suboptimal concentration. To in-
vestigate this hypothesis we started a project to develop bet-
ter soluble tariquidar analogues with more favourable phar-
macokinetic properties.
Introduction
The mdr1 gene product ABCB1 (P-glycoprotein 170), a
member of the ABC transporter family of transmembrane
proteins, prevents the entry of a vast variety of structurally
diverse chemicals into the cell.[1] While protection of the
organism against potentially toxic compounds is an impor-
tant biological function, ABCB1 may also play a critical
role in drug treatment. The efflux of cytostatics as a result
of the (over)expression of ABC transporters such as
ABCB1 is a major limitation in cancer chemotherapy (clas-
sical multidrug resistance, MDR, of tumour cells).[1–6] In
addition to their contribution to drug resistance, these
transporters are highly expressed in the endothelial cells of
brain capillaries and represent important components of
the blood–brain barrier (BBB), which prevents the entry of
a broad variety of xenobiotics, including anticancer drugs
such as vinca alkaloids, anthracyclines, epipodophyllotox-
ins and taxanes, into the central nervous system. This leads
to very low drug concentrations in the brain and plays a
crucial role in the clinical resistance of malignant brain tu-
mours to chemotherapy.[7]
To improve drug uptake into the brain, several studies
explored the possibility of inhibiting ABCB1 in the capillar-
ies of the BBB.[4–8] We recently demonstrated that coappli-
cation of the 2nd generation ABCB1 inhibitor valspodar
The reported activity data of known tariquidar deriva-
tives suggested that modifications of the methoxy groups of
the central anthranilic amide are likely to be tolerated. Our
retrosynthetic approach uses bromo tariquidar 3 as a pre-
cursor that is converted by transition-metal-catalysed N– or
[a] Institut für Organische Chemie, Universität Regensburg,
Universitätsstrasse 31, 93040 Regensburg, Germany
Fax: +49-941-943-1717
E-mail: burkhard.koenig@chemie.uni-regensburg.de
[b] Institut für Pharmazie, Universität Regensburg,
Universitätsstrasse 31, 93040 Regensburg, Germany
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M. Egger, X. Li, C. Müller, G. Bernhardt, A. Buschauer, B. König
FULL PAPER
acid as the central moiety. 2-Amino-5-bromobenzoic acid
(5) was obtained by bromination of anthranilic acid (4) with
[bmim]Br3 according to the procedure described in the lit-
erature in good yield.[15] Boc-protection highly improved
the solubility of intermediate 7 and was crucial for the effi-
ciency of the subsequent coupling reaction. After deprotec-
tion and acylation with quinoline-2-carbonyl chloride,
bromo tariquidar analogue 3 was obtained in an overall
yield of 38% over five reaction steps (Scheme 1).
Figure 1. Structure of tariquidar (1).
O–aryl coupling into tariquidar derivatives with different
overall polarity (Figure 2). While the traditional Cu-medi-
ated Ullmann coupling reactions required high tempera-
tures and stoichiometric amounts of copper,[10] far more ef-
ficient methodologies using catalytic amounts of palladium
or copper salts have been developed for the coupling of
amines to aryl halides.[11] In most cases though, the re-
ported reaction conditions were optimised for rather simple
substrate combinations. Especially for the palladium chem-
istry, the proper choice of the catalyst system is crucial for
the success of the reactions,[12] and the combination of pal-
ladium source, ligand, their ratio, base and substrate might
be very sensitive to variations.[13] We have therefore tested
in this work a series of typical palladium- and copper-cata-
lysed N-arylation conditions for their application on ta-
riquidar.
Scheme 1. Synthesis of bromo tariquidar 3. Reagents and condi-
tions: a) [bmim]Br3, CH2Cl2, room temp., 40 min, 95%; b) Boc2O,
Na2CO3, CH2Cl2, room temp. to 40 °C, 60%; c) ArNH2, HBTU,
HOBt, DIPEA, CH2Cl2, 0 °C to room temp., 24 h, 85%; d) HCl/
Et2O, CH2Cl2, 0 °C to room temp., 95%; e) quinoline-3-carbonyl
chloride, NEt3, CH2Cl2/DMF, room temp., 70 h, 82%.
A primary (9), a secondary cyclic (10) and a secondary
acyclic (11) amine were selected for N–aryl coupling reac-
tions to probe different amine types and to obtain tariqui-
dar analogues with increased water solubility and decreased
lipophilicity (Figure 3).
Figure 2. Synthesis of tariquidar derivatives 2 by N– or O–aryl
coupling; X = O, N; R = alkyl.
Results and Discussion
Figure 3. Amines for N–aryl coupling reactions with compound 3.
Synthesis
The preparation of bromo tariquidar analogue 3 fol-
To compare different catalyst systems, bromo tariquidar
lowed the parent synthesis[14] in coupling the upper aniline precursor 6 was allowed to react with morpholine (10) and
part and the lower quinolone part to substituted anthranilic primary amine 9 (Scheme 2) with the use of copper and
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Synthesis of Tariquidar Analogues by CuI-Catalysed N/O–Aryl Coupling
FULL PAPER
palladium salts and the ligand systems given in Figure 4.
The para-amino substituent in compound 6 disfavours
The ligands were adopted from procedures described in the the N–aryl substitution reaction.[19] While the copper-cata-
literature for the coupling of aryl bromides with primary or lysed reaction for the primary amine still gave moderate
secondary aliphatic amines.[12,16–18]
coupling yields, the isolated product amounts from the pal-
ladium-catalysed reactions were disappointing. Another
drawback of the palladium-catalysed reactions is the typical
use of toluene as the solvent, in which compound 3 is only
sparingly soluble even at higher temperatures.
Compound 3 was coupled with primary amine 9 by using
CuI and N,N-diethylsalicylamide (L2) or 2-isobutyrylcy-
clohexanone (L1) as the ligand[16,20] to yield tariquidar ana-
logue 14, which shows improved solubility, in moderate
yields. Morpholine (10) was introduced as a substituent into
the tariquidar skeleton in good yields with -proline (L3)
as the ligand following the conditions recently described by
Ma.[18] The most critical substrates for these kinds of coup-
ling reactions are secondary acyclic amines. Several of the
above-discussed conditions were tested, but none of them
gave the desired product in satisfactory and isolatable
amounts (Scheme 3). The use of 3 in a CuCl-catalysed O–
aryl coupling was demonstrated in the reaction with alcohol
19 in an analogous coupling reaction.
Scheme 2. Model reactions with aryl bromide 6. Reagents and con-
ditions: a) CuBrϫDMS (20 mol-%), L2 (40 mol-%), K3PO4, DMF,
90 °C, 24 h; b) Pd2(dba)3 (2.5 mol-%), L4 (4.5 mol-%), NaOtBu,
toluene, 90 °C, 24 h; c) CuI (20 mol-%), L3 (40 mol-%), K3PO4,
DMSO, 90 °C, 24 h; d) Pd2(dba)3 (1 mol-%), L5 (4 mol-%), K3PO4,
toluene, 90 °C, 24 h.
Flow Cytometric Calcein-AM Efflux Assay (ABCB1
Assay)
In Kb-V1 cells, calcein-AM is extruded by ABCB1 be-
fore nonspecific esterases can cleave the ester bonds, and
calcein is not accumulated.[21] Therefore, ABCB1 inhibitors
can easily be recognised by flow cytometric determination
of intracellular calcein-AM levels. Depending on the modu-
lator concentration, the change in the calcein-AM efflux, or
rather in the relative fluorescence intensity of the cells, is
Figure 4. Ligands used for N–aryl coupling reactions.
Scheme 3. Ullmann-type coupling reactions of 3 with amines 9–11. Reagents and conditions: a) CuBrϫDMS (20 mol-%), L3 (40 mol-
%), K3PO4, DMSO, 90 °C; b) CuBrϫDMS (20 mol-%), L3 (40 mol-%), K3PO4, DMSO, 90 °C; c) CuI (40 mol-%), L1 (80 mol-%),
K3PO4, DMF, 90 °C; d) Pd2(dba)3 (1.5 mol-%), L4 (1.5 mol-%), NaOtBu, toluene, 90 °C; e) (i) 19, Na; (ii) CuCl (20 mol-%), DMF, 90 °C
(46% of 10 recovered); f) CuBrϫDMS (20 mol-%), L2 (40 mol-%), K3PO4, DMF, 90 °C (66% of 10 recovered); g) CuI (40 mol-%), L1
(75 mol-%), K3PO4, DMF, 90 °C (41% of 10 recovered).
Eur. J. Org. Chem. 2007, 2643–2649
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M. Egger, X. Li, C. Müller, G. Bernhardt, A. Buschauer, B. König
FULL PAPER
measured. The assay was performed as recently described to be more generally applicable for these substrate combina-
by Müller et al.[21]
tions than the Buchwald-Hartwig amination procedure
The resulting data of the new tariquidar analogues and using Pd0. For the Pd chemistry, the system of Pd source,
their calculated pharmacokinetic parameters (calculations ligand, base and solvent is probably more critical towards
were carried out with ACD Labs software) are shown in different substrate combinations and might need to be op-
Figure 5 and Table 1. Relative to tariquidar, both central timised for each reaction. The synthetic route described
building block 3 and aryl ether analogue 17 showed im- here allows quick access to new potential MDR modula-
proved activities in the calcein-AM efflux assay, whereas tors. The results from the calcein-AM efflux assay demon-
arylamine analogues 15 and 14 showed a decreased potency strate that structural changes in the chosen position are in-
relative to the reference substance tariquidar in inhibiting deed tolerated without considerable loss of activity. The
ABCB1. The desired decrease in lipophilicity was achieved series of new ABCB1 modulators is well suited to test the
in all three derivatives of 3. In the same order, as logP de- aforementioned BBB selectivity hypothesis in vivo as the
creases, the activity against ABCB1 drops. It is still dis- lipophilicities of the compounds range from logP = 7 to 4,
cussed in the literature whether high lipophilicity might be thereby including the value of tariquidar (logP = 6.1) on
an important criterion (amongst others) for the inhibition one end and that of valspodar (logP = 4.1) on the other
of ABC transporters.[22] The results obtained from this end. Further investigations on the new tariquidar-like
small series are in accordance to this hypothesis, under the ABCB1 inhibitors are in progress.
assumption that the newly introduced side chains only af-
fect physicochemical parameters.
Experimental Section
General: Commercial reagents and starting materials were pur-
chased from Aldrich, Fluka or Acros and used without further
purification. CH2Cl2 was distilled from CaH2, anhydrous DMF
was purchased from Fluka. Flash chromatography was performed
on silica gel (Merck silica gel Si 60 40–63 µm); products were de-
tected by TLC on alumina plates coated with silica gel (Merck silica
gel 60 F254, thickness 0.2 mm). The compounds were detected by
UV light (λ = 254 nm) and a solution of ninhydrine in ethanol.
Melting points were determined with a Büchi SMP 20 apparatus
and are uncorrected. NMR spectra were recorded with Bruker Av-
ance 300 (1H: 300.1 MHz, 13C: 75.5 MHz, T = 300 K), Bruker Av-
ance 400 (1H: 400.1 MHz, 13C: 100.6 MHz, T = 300 K) or Bruker
Avance 600 (1H: 600.1 MHz, 13C: 150.1 MHz, T = 300 K) instru-
ments. Chemical shifts are reported in δ/ppm relative to external
standards and coupling constants J are given in Hz. Abbreviations
for the characterisation of the signals: s = singlet, d = doublet, t =
Figure 5. ABCB1 inhibition by tariquidar and the new inhibitors
in dependence of their concentrations. Open circle 3, filled triangle
17, filled circle tariquidar, open triangle 15, filled square 14.
triplet, m = multiplet, br. s = broad singlet, dd = double of dou-
blets. The relative numbers of protons is determined by integration.
Error of reported values: chemical shift 0.01 ppm (1H NMR),
0.1 ppm (13C NMR), coupling constant 0.1 Hz. The used solvent
Table 1. Calculated properties of the new tariquidar analogues and
their biological activities as determined by the calcein-AM efflux
assay.
for each spectrum is reported. Mass spectra were recorded with
Finnigan MAT TSQ 7000 (ESI) or Finnigan MAT 90 (HRMS)
instruments, IR spectra with a Bio-Rad FT-IR-FTS 155 spectrome-
ter and UV/Vis spectra with a Cary BIO 50 UV/Vis/NIR spectrom-
eter (Varian). Compounds 9, 11 and 2-isobutyrylcyclohexanone
(L1) were prepared by the reported methods. The products of the
model reactions (12 and 13) were synthesised under the conditions
described above, and the experimental procedures were identical to
those of the final reactions.
Compound
logP
IC50
[nM]
Efficacy Hill coefficient
[%]
n
Tariquidar
3
17
15
14
6.1Ϯ1.1
7.1Ϯ1.0
6.0Ϯ1.0
5.1Ϯ1.0
223Ϯ8
145Ϯ12
181Ϯ6
102
98
116
109
105
2.6
1.9
2.7
2.9
2.3
5
3
3
3
3
593Ϯ21
4.3Ϯ1.1 1 575Ϯ98
5-Bromo-2-(tert-butoxycarbonylamino)benzoic Acid (6): 5-Bromo-
anthranilic acid (5) (4.35 g, 20 mmol) was dissolved in anhydrous
dichloromethane (150 mL), followed by the addition of Na2CO3
(2.36 g, 22 mmol) and di-tert-butyl dicarbonate (4.85 g, 22 mmol).
The solution was stirred at room temperature for 1 h under a nitro-
gen atmosphere and then heated at reflux for 24 h. The mixture
was washed with water, 1  citric acid and brine. The organic phase
was dried with Na2SO4, evaporated under reduced pressure and
separated by column chromatography on silica gel (hexane/acetone,
5:1, Rf = 0.35) to provide 6 as a white solid (3.8 g, 60%). M.p. 177–
Conclusions
We have shown that modern variants of the Ullmann re-
action can be used to prepare tariquidar analogues from
bromo tariquidar 3 and suitable amines in one step. Coup-
ling of a primary and a secondary cyclic amine as well as
an alcohol was achieved in one metal-catalysed reaction
1
178 °C. H NMR (300 MHz, CDCl3): δ = 1.52 (s, 9 H, Boc), 7.62
each. The Ullmann-type coupling reactions using CuI seem (dd, J = 9.1 Hz, J = 2.5 Hz, 1 H, Ar-H), 8.10 (d, J = 2.5 Hz, 1
3
4
4
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Synthesis of Tariquidar Analogues by CuI-Catalysed N/O–Aryl Coupling
FULL PAPER
H, Ar-H), 8.30 (d, 3J = 9.1 Hz) ppm. 13C NMR (75 MHz, CDCl3):
δ = 28.6 (+), 81.9 (Cquat), 114.3 (Cquat), 118.0 (Cquat), 121.4 (+),
CH2Cl2 and washed with a saturated aqueous solution of
NaHCO3. The organic phase was dried with MgSO4, and the sol-
134.9 (+), 137.9 (+), 142.7 (Cquat), 154.0 (Cquat), 170.0 (Cquat) ppm. vent was removed to obtain the pure product as a white solid (1.0 g,
IR (KBr): ν = 3330, 2978, 1729, 1682, 1578, 1516 cm–1. UV/Vis 95%). M.p. 157 °C. 1H NMR (300 MHz, CDCl3): δ = 2.74–2.94
˜
(MeOH): λ (logε) = 308 (3.514), 253 (4.280) nm. MS (ESI–, DCM/ (m, 8 H, 4 CH2), 3.65 (s, 2 H, NCH2), 3.84 (s, 3 H, OCH3), 3.85
MeOH + 10 mmol/L NH4Ac): m/z (%) = 314 (100) [(M – H)+]–,
316 (98) [(M – H)+]–. C12H14BrNO (316.15): calcd. C 45.59, H 4.46,
N 4.43; found C 45.12, H 4.55, N 4.24.
(s, 3 H, OCH3), 5.51 (br. s, 2 H, NH2), 6.54 (s, 1 H, Ar-H), 6.61
3
(s, 1 H, Ar-H), 6.61 (d, J = 8.8 Hz, 1 H, Ar-H), 7.23–7.26 (m, 2
H, Ar-H, AAЈBBЈ), 7.32 (dd, 4J = 2.2 Hz, 3J = 8.8 Hz, 1 H, Ar-
4
H), 7.46–7.49 (m, 2 H, Ar-H, AAЈBBЈ), 7.56 (d, J = 2.2 Hz, 1 H,
2-(tert-Butoxycarbonylamino)-5-[2-(2-methoxyethoxy)ethylamino]-
Ar-H), 7.65 (br. s, 1 H, CONH) ppm. 13C NMR (75 MHz, CDCl3):
δ = 28.6, 33.4, 51.1, 55.7, 55.9, 55.9, 60.1, 107.8, 109.5, 111.4, 117.8,
119.1, 121.0, 126.1, 126.3, 129.3, 129.7, 135.3, 135.6, 136.9, 147.2,
1
benzoic Acid (12): H NMR (300 MHz, CDCl3): δ = 1.52 (s, 9 H,
Boc), 3.29–3.33 (m, 2 H, CH2), 3.41 (s, 3 H, OCH3), 3.56–3.60 (m,
2 H, CH2), 3.64–3.68 (m, 2 H, CH2), 3.70–3.74 (m, 2 H, CH2), 6.93
147.6, 147.9, 166.3 ppm. IR (KBr): ν = 3470, 3373, 3302, 1638,
˜
3
4
4
(dd, J = 9.1 Hz, J = 3.0 Hz, 1 H, Ar-H), 7.35 (d, J = 3.3 Hz, 1
H, Ar-H), 8.24 (d, 3J = 9.1 Hz, 1 H, Ar-H), 9.65 (br. s, 1 H, CONH)
ppm. 13C NMR (75 MHz, CDCl3): δ = 28.4 (+), 44.4 (–), 59.1 (+),
69.3 (–), 70.2 (–), 71.9 (–), 80.3 (Cquat), 114.7 (Cquat), 115.2 (+),
120.6 (+), 121.7 (+), 134.5 (Cquat), 153.1 (Cquat), 172.2 (Cquat), 176.8
(Cquat) ppm. MS (CI, NH3): m/z (%) = 355 (100) [M + H]+.
1596, 1520, 818 cm–1. UV/Vis (CH2Cl2): λ (logε) = 346 (3.366),
264 (3.808), 229 (4.067) nm. MS (ESI, DCM/MeOH + 10 mmol/L
NH4Ac): m/z (%) = 510 (100) [M + H]+, 512 (98) [M + H]+.
N-(4-Bromo-2-{[4-(2-{6,7-dimethoxy-1,2,3,4-tetrahydroisoquinolin-
2-yl}ethyl)phenyl]-carbamoyl}phenyl)quinoline-3-carboxamide (3):
Compound 8 (702 mg, 1.4 mmol) and NEt3 (0.4 mL, 3 mmol) were
dissolved in a mixture of CH2Cl2 and anhydrous DMF (10 mL/
1 mL). Quinoline-3-carbonyl chloride hydrochloride (477 mg,
2.1 mmol) was added in small portions, and the mixture was stirred
at room temperature for 3 d. After dilution with CH2Cl2, the or-
ganic phase was washed with a saturated aqueous solution of
NaHCO3 and dried with MgSO4. Evaporation of the solvent and
purification by flash chromatography on silica gel (acetone/hex-
anes, 1:1, 1% NEt3, Rf = 0.27) yielded the product as a pale yellow
solid (761 mg, 82 %). M.p. 204–207 °C 1H NMR (300 MHz,
CDCl3): δ = 2.76–2.97 (m, 8 H, 4 CH2), 3.67 (s, 2 H, NCH2), 3.84
(s, 3 H, OCH3), 3.85 (s, 3 H, OCH3), 6.54 (s, 1 H, Ar-H), 6.61 (s,
1
2-(tert-Butoxycarbonylamino)-5-morpholinobenzoic Acid (13): H
NMR (300 MHz, CDCl3): δ = 1.53 (s, 9 H, Boc), 3.11–3.14 (m, 4
3
4
H, 2 CH2), 3.86–3.89 (m, 4 H, 2 CH2), 7.19 (dd, J = 9.3 Hz, J =
4
3
3.3 Hz, 1 H, Ar-H), 7.58 (d, J = 3.0 Hz, 1 H, Ar-H), 8.36 (d, J
= 9.3 Hz, 1 H, Ar-H), 9.79 (br. s, 1 H, CONH) ppm. 13C NMR
(75 MHz, CDCl3): δ = 28.5 (+), 50.3 (–), 67.1 (–), 80.7 (Cquat),
114.6 (Cquat), 118.2 (+), 120.5 (+), 124.2 (+), 136.5 (Cquat), 145.9
(Cquat), 153.2 (Cquat), 171.8 (Cquat) ppm. MS (CI, NH3): m/z (%) =
323 (83) [M + H]+, 266 (100) [M + H – C4H9]+.
tert-Butyl-4-bromo-2-({4-[2-(6,7-dimethoxy-1,2,3,4-tetrahydroiso-
quinolin-2-yl)ethyl]phenyl}carbamoyl)phenylcarbamate (7): Com-
pound 6 (886 mg, 2.8 mmol), HOBt (419 mg, 3.1 mmol) and
HBTU (1166 mg, 3.1 mmol) were added to an ice-cooled solution
of DIPEA (0.9 mL, 5.2 mmol) in CH2Cl2 (10 mL). The solution
was stirred for 10 min and 4-[2-(6,7-dimethoxy-1,2,3,4-tetra-
hydroisoquinolin-2-yl)ethyl]phenylamine (812 mg, 2.6 mmol) was
added in small portions. The reaction mixture was warmed to room
temperature and stirred for 24 h. The mixture was then diluted with
CH2Cl2, and the organic phase was washed with water, a saturated
aqueous solution of NaHCO3 (3ϫ) and dried with MgSO4. After
evaporation of the solvent, the crude product was purified by flash
chromatography on silica gel (EtOAc/NEt3, 99:1, Rf = 0.27) to ob-
tain a pale yellow solid (1.3 g, 85 %). M.p. 196 °C. 1H NMR
(300 MHz, CDCl3): δ = 1.49 (s, 9 H, Boc), 2.75–2.95 (m, 8 H, 4
CH2), 3.66 (s, 2 H, NCH2), 3.84 (s, 3 H, OCH3), 3.85 (s, 3 H,
OCH3), 6.54 (s, 1 H, Ar-H), 6.61 (s, 1 H, Ar-H), 7.26–7.29 (m, 2
H, Ar-H, AAЈBBЈ), 7.46–7.49 (m, 2 H, Ar-H, AAЈBBЈ), 7.56 (dd,
3
1 H, Ar-H), 7.31 (d, J = 8.5 Hz, 2 H, Ar-H, AAЈBBЈ), 7.57 (dd,
3
4J = 2.2 Hz, J = 8.8 Hz, 1 H, Ar-H), 7.61–7.67 (m, 1 H, Ar-H),
3
4
7.63 (d, J = 8.5 Hz, 2 H, Ar-H, AAЈBBЈ), 7.78 (d, J = 2.2 Hz, 1
H, Ar-H), 7.81–7.87 (m, 1 H, Ar-H), 7.99–8.02 (m, 1 H, Ar-H),
3
8.16–8.19 (m, 1 H, Ar-H), 8.47 (br. s, 1 H, CONH), 8.62 (d, J =
4
4
8.8 Hz, 1 H, Ar-H), 8.78 (d, J = 2.2 Hz, 1 H, Ar-H), 9.52 (d, J
= 2.2 Hz, 1 H, Ar-H), 12.07 (br. s, 1 H, CONH) ppm. 13C NMR
(75 MHz, CDCl3): δ = 28.7 (–), 33.5 (–), 51.1 (–), 55.7 (–), 55.9 (+),
55.9 (+), 60.1 (–), 109.5 (+), 111.4 (+), 116.1 (Cquat), 121.0 (+),
123.1 (Cquat), 123.6 (+), 126.1 (Cquat), 126.5 (Cquat), 126.7 (Cquat),
126.9 (Cquat), 127.6 (+), 129.2 (+), 129.5 (+), 129.5 (+), 130.0 (+),
131.7 (+), 135.2 (Cquat), 135.4 (+), 136.2 (+), 137.8 (Cquat), 138.3
(Cquat), 147.2 (Cquat), 147.6 (Cquat), 148.7 (+), 149.5 (Cquat), 164.1
(Cquat), 166.1 (Cquat) ppm. IR (KBr): ν = 2932, 1677, 1597, 1512,
˜
1464, 829 cm–1. UV/Vis (CH2Cl2): λ (log ε) = 287 (4.333), 238
(4.637) nm. C36H33BrN4O4 (665.59): calcd. C 64.96, H 5.00, N
8.42; found C 64.37, H 4.99, N 8.11. HRMS: calcd. for
C36H33BrN4O4 [M]+ 664.1685; found 664.1692.
3
4
4J = 2.5 Hz, J = 9.1 Hz, 1 H, Ar-H), 7.68 (d, J = 2.2 Hz, 1 H,
3
Ar-H), 7.74 (br. s, 1 H, CONH), 8.31 (d, J = 9.1 Hz, 1 H, Ar-H),
9.72 (br. s, 1 H, CONH) ppm. 13C NMR (75 MHz, [D6]DMSO): δ
= 27.8 (+), 28.2 (–), 32.4 (–), 50.5 (–), 55.0 (–), 55.3 (+), 55.3 (+),
59.5 (–), 80.1 (Cquat), 109.8 (+), 111.6 (+), 113.3 (Cquat), 120.9 (+),
121.3 (+), 123.4 (Cquat), 125.8 (Cquat), 126.5 (Cquat), 128.7 (+), 131.0
(+), 134.5 (+), 136.1 (Cquat), 136.5 (Cquat), 138.1 (Cquat), 146.7
(Cquat), 147.0 (Cquat), 151.9 (Cquat), 165.5 (Cquat) ppm. IR (KBr): ν
˜
= 3321, 2974, 2933, 1728, 1512, 1156 cm–1. UV/Vis (MeOH): λ
(logε) = 281 (4.107), 256 (4.300) nm. MS (ESI, DCM/MeOH +
10 mmol/L NH4Ac): m/z (%) = 610 (100) [M + H]+, 612 (97) [M
+ H]+.
2-Amino-5-bromo-N-(4-{-[6,7-dimethoxy-1,2,3,4-tetrahydroiso-quin-
olin-2-yl]ethyl}-phenyl)benzamide (8): Compound 7 (1.3 g,
2.2 mmol) was dissolved in CH2Cl2 (30 mL) and cooled in an ice-
bath. After the addition of HCl/Et2O, the mixture was stirred over-
night, concentrated in vacuo and the precipitate was suspended in
N-(2-{[4-(2-{6,7-Dimethoxy-1,2,3,4-tetrahydroisoquinolin-2-yl}-
ethyl)phenyl]carbamoyl}-4-{2-ethoxyethoxy}phenyl)quinoline-3-
carboxamide (17): A 25-mL three-necked flask was evacuated,
flushed with nitrogen (3 cycles) and charged with 2-ethoxyethanol
Eur. J. Org. Chem. 2007, 2643–2649
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
2647

M. Egger, X. Li, C. Müller, G. Bernhardt, A. Buschauer, B. König
(2 mL, 21 mmol) and Na (10 mg, 0.4 mmol). After the formation purified by flash chromatography on silica gel (EtOAc/EtOH, 4:1,
FULL PAPER
1
of H2 had ceased, DMF (0.5 mL), CuCl (4 mg, 0.04 mmol) and
compound 3 (122 mg, 0.2 mmol) were added under an atmosphere
of nitrogen. The flask was equipped with a condenser, and the reac-
tion mixture was stirred at 90 °C for 24 h. After cooling, the mix-
ture was diluted with CH2Cl2, washed with water and a saturated
aqueous solution of NaHCO3 (3ϫ), and the organic phase was
dried with MgSO4. The solvent was evaporated, and the remaining
solid was purified by flash chromatography on silica gel (acetone/
hexanes, 1:1, Rf = 0.31) to obtain a white solid (64 mg, 52%). M.p.
Rf = 0.29) to give a yellow solid (116 mg, 75%). M.p. 238 °C. H
NMR (600 MHz, CD2Cl2; HSQC, HMBC, COSY, ROESY): δ =
2.87–3.00 (m, 8 H, 4 CH2, 5-H, 6-H, 9-H, 10-H), 3.15 (m, 4 H, 2
CH2, 33-H, 34-H), 3.77 (s, 3 H, OCH3, 38-H), 3.78 (s, 3 H, OCH3,
37-H), 3.77–3.79 (m, 6 H, NCH2, 8-H, 2 CH2, 35-H, 36-H), 6.55
(s, 1 H, 1-HAr), 6.62 (s, 1 H, 4-HAr), 7.11 (dd, 3J = 9.0 Hz, 4J =
2.6 Hz, 1 H, 20-HAr), 7.26–7.30 (m, 3 H, 12-HAr, 12Ј-HAr, 18-HAr),
7.61–7.67 (m, 3 H, 13-HAr, 13Ј-HAr, 30-HAr), 7.81–7.85 (m, 1 H,
29-HAr), 8.00–8.03 (m, 1 H, 31-HAr), 8.11–8.14 (m, 1 H, 28-HAr),
8.51 (d, 3J = 9.0 Hz, 1 H, 21-HAr), 8.75–8.77 (m, 1 H, 32-HAr),
124–126 °C. 1H NMR (400 MHz, CD2Cl2; HSQC, HMBC, COSY,
3
ROESY): δ = 1.18 (t, J = 7.2 Hz, 3 H, CH3, 36-H), 2.76–2.84 (m, 9.30 (br. s, 1 H, 15-H), 9.38–9.40 (m, 1 H, 26-HAr), 11.70 (br. s, 1
6 H, 3 CH2, 4-H, 5-H, 9-H), 2.90–2.93 (m, 2 H, CH2, 10-H), 3.51 H, 23-H) ppm. 13C NMR (150 MHz, CD2Cl2): δ = 27.5 (C-5), 32.5
3
(q, J = 7.2 Hz, 2 H, OCH2, 35-H), 3.62 (s, 2 H, NCH2, 8-H), 3.64 (C-10), 49.8 (C-33, C-34), 50.9 (C-6), 54.9 (C-8), 56.1 (C-38), 56.2
(t, 3J = 4.8 Hz, 2 H, OCH2, 34-H), 3.78 (s, 3 H, OCH3, 38-H), 3.78 (C-37), 60.8 (C-9), 67.0 (C-35, C-36), 110.1 (C-1), 111.9 (C-4), 115.0
(s, 3 H, OCH3, 37-H), 4.07 (t, 3J = 4.8 Hz, 2 H, OCH2, 33-H), 6.54 (C-18), 119.9 (C-20), 121.8 (C-13, C-13Ј), 123.4 (C-21), 123.8 (C-
(s, 1 H, 1-HAr), 6.60 (s, 1 H, 4-HAr), 7.10 (dd, 3J = 9.2 Hz, 4J = 17), 124.5 (C-8a), 125.6 (C-4a), 127.4 (C-31a), 127.9 (C-25), 127.9
4
2.7 Hz, 1 H, 20-HAr), 7.28 (d, J = 2.7 Hz, 1 H, 18-HAr), 7.31 (d,
(C-30), 129.2 (C-28), 129.5 (C-31), 129.6 (C-12, C-12Ј), 131.6 (C-
22), 131.7 (C-14), 131.9 (C-29), 136.2 (C-32), 136.5 (C-11), 147.9
(C-2), 148.1 (C-19), 148.6 (C-3), 148.9 (C-26), 149.4 (C-27a), 163.7
3
3J = 8.3 Hz, 2 H, 12-HAr, 12Ј-HAr), 7.62 (d, J = 8.3 Hz, 2 H, 13-
HAr, 13Ј-HAr), 7.62–7.66 (m, 1 H, 30-HAr), 7.80–7.84 (m, 1 H, 29-
HAr), 7.99–8.02 (m, 1 H, 31-HAr), 8.13–8.15 (m, 1 H, 28-HAr), 8.38
(C-24), 168.4 (C-16) ppm. IR (KBr): ν = 2933, 1655, 1598, 1516,
˜
3
4
(br. s, 1 H, 15-H), 8.66 (d, J = 9.2 Hz, 1 H, 21-HAr), 8.75 (d, J =
1228, 1123 cm–1. UV/Vis (CH2Cl2): λ (logε) = 283 (4.245), 236
2.3 Hz, 1 H, 32-HAr), 9.43 (d, 4J = 2.3 Hz, 1 H, 26-HAr), 11.80 (br. (4.562) nm. HRMS: calcd. for C40H41N5O5 [M]+ 671.3108; found
s, 1 H, 23-H) ppm. 13C NMR (100 MHz, CD2Cl2): δ = 15.3 (+, C- 671.3122.
36), 29.0 (–, C-5), 33.5 (–, C-10), 51.4 (–, C-6), 55.9 (–, C-8), 56.2
(+, C-38), 56.2 (+, C-37), 60.2 (–, C-9), 67.1 (–, C-35), 68.5 (–, C-
N-(2-{[4-(2-{6,7-Dimethoxy-1,2,3,4-tetrahydroisoquinolin-2-yl}-
ethyl)phenyl]carbamoyl}-4-{2-[2-methoxyethoxy]ethylamino}phenyl)-
33), 69.1 (–, C-34), 110.2 (+, C-1), 112.1 (+, C-4), 114.2 (+, C-18),
quinoline-3-carboxamide (14): A 5-mL screw-capped glass vial with
118.3 (+, C-20), 121.3 (+, C-13, C-13Ј), 123.1 (Cquat, C-17), 123.6
stirring bar was charged with CuI (20 mg, 0.1 mmol), compound 3
(+, C-21), 126.7 (Cquat, C-4a), 127.2 (Cquat, C-25), 127.4 (Cquat, C-
(176 mg, 0.3 mmol) and K3PO4 (106 mg, 0.5 mmol). The vial was
8a), 127.7 (+, C-30), 127.8 (Cquat, C-31a), 129.5 (+, C-31), 129.8
put in a small Schlenk tube, evacuated and filled with argon (3
cycles). 2-Isobutyrylcyclohexanone (34 mg, 0.2 mmol), 2-(2-me-
(+, C-12, C-12Ј), 129.8 (+, C-28), 131.6 (+, C-29), 133.3 (Cquat, C-
22), 135.8 (Cquat, C-14), 135.9 (+, C-32), 138.2 (Cquat, C-11), 147.8
thoxyethoxy)ethylamine (60 mg, 0.5 mmol) and dry DMF were
(Cquat, C-2), 148.1 (Cquat, C-3), 149.0 (+, C-26), 149.8 (Cquat, C-
added by syringe under an atmosphere of argon; the vial was
27a), 154.9 (Cquat, C-19), 163.8 (Cquat, C-24), 167.5 (Cquat, C-16)
capped, and the reaction mixture was stirred at 90 °C for 48 h.
After cooling, the solution was diluted with CH2Cl2, washed with
water and a saturated aqueous solution of NaHCO3, and the or-
ganic phase was dried with MgSO4. Evaporation of the solvent and
ppm. IR (KBr): ν = 2931, 1633, 1597, 1517, 1408, 1127 cm–1. UV/
˜
Vis (CH2Cl2): λ (logε) = 282 (4.176), 238 (4.550) nm. HRMS: calcd.
for C40H42N4O6 [M]+ 674.3104; found 674.3106.
purification of the crude product by flash chromatography on silica
gel (EtOAc/MeOH, 4:1, 1% NEt3, Rf = 0.25) gave 19 as a yellow
1
solid (74 mg, 40%). M.p. 96 °C. H NMR (300 MHz, CDCl3): δ =
3
2.82–3.00 (m, 8 H, 4 CH2), 3.16 (t, J = 5.1 Hz, 2 H, CH2), 3.33
(s, 3 H, OCH3), 3.44–3.51 (m, 6 H, 3 CH2), 3.73 (s, 2 H, NCH2),
3.84 (s, 3 H, OCH3), 3.85 (s, 3 H, OCH3), 6.54 (s, 1 H, Ar-H), 6.61
3
4
(s, 1 H, Ar-H), 6.72 (dd, J = 9.1, J = 2.7 Hz, 1 H, Ar-H), 6.92
(d, 4J = 2.7 Hz, 1 H, Ar-H), 7.28 (d, 3J = 8.5 Hz, 2 H, Ar-H,
AAЈBBЈ), 7.59–7.65 (m, 1 H, Ar-H), 7.67 (d, 3J = 8.5 Hz, 2 H, Ar-
H, AAЈBBЈ), 7.78–7.83 (m, 1 H, Ar-H), 7.96–7.99 (m, 1 H, Ar-H),
3
8.14–8.17 (m, 1 H, Ar-H), 8.42 (d, J = 9.1 Hz, 1 H, Ar-H), 8.69
4
4
(br. s, 1 H, CONH), 8.73 (d, J = 2.2 Hz, 1 H, Ar-H), 9.49 (d, J
= 2.2 Hz, 1 H, Ar-H), 11.60 (br. s, 1 H, CONH) ppm. 13C NMR
(100 MHz, CD2Cl2): δ = 24.4, 30.4, 49.8, 52.6, 54.3, 56.2, 56.2,
56.3, 59.0, 68.3, 70.3, 72.2, 109.8, 111.7, 118.7, 122.1, 122.2, 123.0,
123.4, 123.4, 127.6, 128.0, 128.1, 128.2, 128.4, 129.5, 129.6, 129.6,
132.6, 133.0, 137.4, 137.5, 147.9, 147.9, 148.2, 149.0, 149.7, 163.2,
N-(2-{[4-(2-{6,7-Dimethoxy-1,2,3,4-tetrahydroisoquinolin-2-yl}-
ethyl)phenyl]carbamoyl}-4-morpholinophenyl)quinoline-3-carbox-
amide (15): A 5-mL screw-capped glass vial with stirring bar was
charged with CuBr–dimethylsulfide complex (10 mg, 0.05 mmol)
and put in a small Schlenk tube. The reaction vessel was heated
and evacuated until dimethylsulfide was removed completely and
the white solid had turned to green. After cooling, the vial was
evacuated and backfilled with argon (3 cycles) and -proline
(12 mg, 0.1 mmol), compound 3 (154 mg, 0.2 mmol), K3PO4
(106 mg, 0.5 mmol), morpholine (40 µL, 0.5 mmol) and anhydrous
DMSO (2 mL) were added under an atmosphere of argon. The vial
was closed, and the mixture was stirred at 90 °C for 44 hours, co-
oled and diluted with CH2Cl2. The organic phase was washed with
water and a saturated aqueous solution of NaHCO3 and dried with
MgSO4. After evaporation of the solvent, the remaining solid was
168.0 ppm. IR (KBr): ν = 2930, 1599, 1516, 1252, 1226 cm–1. UV/
˜
Vis (MeOH): λ (logε) = 281 (4.150), 236 (4.519) nm. HRMS: calcd.
for C41H45N5O6 [M]+ 703.3370; found 703.3376.
Cell Line and Culture Conditions: Kb-V1 cells, an ABCB1 overex-
pressing subclone[23] of Kb cells (ATCC CCL-17), were maintained
in DulbeccoЈs modified EagleЈs medium (Sigma, Deisenhofen, Ger-
many) supplemented with 10% FCS (Biochrom, Berlin, Germany)
and 300 ng/mL vinblastine. Cells were maintained in a water satu-
rated atmosphere (95% air/5% carbon dioxide) at 37 °C in 75-cm2
2648
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© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2007, 2643–2649

Synthesis of Tariquidar Analogues by CuI-Catalysed N/O–Aryl Coupling
FULL PAPER
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following trypsinisation by using 0.05% trypsin/0.02% EDTA (Ro-
che Diagnostics, Mannheim, Germany). Mycoplasma contami-
nation was routinely monitored by polymerase chain reaction
(Venor GeM, Minerva Biolabs GmbH, Berlin, Germany), and only
Mycoplasma-free cultures were used.
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This work was supported by the Deutsche Forschungsgemeinschaft
(GRK 760), the Asia Link programme of the European Union
(training fellowship for X. L.) and the Fonds der Chemischen Indu-
strie. M. E. thanks the Elitenetzwerk Bayern for a graduate fellow-
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Published Online: April 23, 2007
Eur. J. Org. Chem. 2007, 2643–2649
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
2649