An extended study of dimeric phenyl tropanes

Article abstract of DOI:10.1016/j.bmc.2009.06.007

A series of dimeric phenyl tropanes consisting of two molecules of 4-chloro, 4-iodo or 4-(3-thiopheno)-phenyl tropane tethered together at the carboxylic acid moiety by a diamine or diol linker were prepared. The diamines used were a variety of linear, cyclic and aromatic diamines, while the diol tethered compounds were prepared by 'click' chemistry and contained a triazole in the linker. The new compounds were tested for binding to hDAT, hSERT and hNET. Amide linked chlorophenyl tropanes with an aromatic linker was found to be potent and selective DAT inhibitors with the best K_i value for hDAT being 6 nM. The ester linked halophenyl tropanes were more potent but displayed little selectivity in inhibition of monoamine transporter binding. Among the studied compounds an ester linker of 10 atoms between the tropane moieties gave the highest affinity. One monomeric phenyl tropane was made for comparison and was found to be less potent than the dimeric counterparts towards SERT and NET but remain highly active against DAT. Dimeric thiophenophenyl tropanes were in general found to be comparatively poor monoamine transporter binders, but significant gains of affinity of up to 45-fold could be achieved with selected dimeric chlorophenyl tropanes compared to the parent monomer. This observation implies that a secondary binding site that has affinity for phenyl tropanes, most likely the putative S2 site, is located within 13 A of the primary central S1 binding site.

Full text of DOI:10.1016/j.bmc.2009.06.007

Bioorganic & Medicinal Chemistry 17 (2009) 4900–4909
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
An extended study of dimeric phenyl tropanes
Susan Nielsen a, Christian M. Pedersen a, Signe Grann Hansen a, Mikkel Due Petersen a, Steffen Sinning b,
c,
Ove Wiborg b, Henrik Helligsø Jensen a, , Mikael Bols
*
*
a Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
b Centre for Psychiatric Research, Psychiatric University Hospital, Skovagervej 2, DK-8240 Risskov, Denmark
c Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of dimeric phenyl tropanes consisting of two molecules of 4-chloro, 4-iodo or 4-(3-thiopheno)-
phenyl tropane tethered together at the carboxylic acid moiety by a diamine or diol linker were prepared.
The diamines used were a variety of linear, cyclic and aromatic diamines, while the diol tethered com-
pounds were prepared by ‘click’ chemistry and contained a triazole in the linker. The new compounds
were tested for binding to hDAT, hSERT and hNET. Amide linked chlorophenyl tropanes with an aromatic
linker was found to be potent and selective DAT inhibitors with the best Ki value for hDAT being 6 nM.
The ester linked halophenyl tropanes were more potent but displayed little selectivity in inhibition of
monoamine transporter binding. Among the studied compounds an ester linker of 10 atoms between
the tropane moieties gave the highest affinity. One monomeric phenyl tropane was made for comparison
and was found to be less potent than the dimeric counterparts towards SERT and NET but remain highly
active against DAT. Dimeric thiophenophenyl tropanes were in general found to be comparatively poor
monoamine transporter binders, but significant gains of affinity of up to 45-fold could be achieved with
selected dimeric chlorophenyl tropanes compared to the parent monomer. This observation implies that
a secondary binding site that has affinity for phenyl tropanes, most likely the putative S2 site, is located
within 13 Å of the primary central S1 binding site.
Received 6 January 2009
Revised 29 May 2009
Accepted 5 June 2009
Available online 10 June 2009
Keywords:
Monoamine transporter
Inhibition
Dimeric
Phenyl tropane
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
of novel SSRIs remains a very active research area in medicinal
chemistry.
The three biogenic monoamine neurotransmitters dopamine
(DA), serotonin (SER) and norepinephrine (NE) control a variety
of functions in the central nervous system. The transporter pro-
teins for these neurotransmitters, the dopamine, serotonin and
norepinephrine transporters (DAT, SERT and NET, respectively) be-
long to the class of Na+/Clꢀ dependent secondary active transport-
ers. Their role is to carry DA, SER and NE across cell membranes
and they therefore serve an important role in regulating the synap-
tic level of these neurotransmitters.
SERT plays a key role in many psychiatric diseases such as
depression,1 Parkinson’s2 and Alzheimer’s diseases.3 Significant
progress has been made in the area of monoamine transporter
inhibition and this has led to selective serotonin reuptake inhibi-
tors (SSRIs) that are now the most common pharmacological treat-
ment of mild and moderate depression offering several advantages
compared to traditional tricyclic antidepressants. Still the SSRIs
suffer from some limitations which are seen by a 2–6 weeks delay
in the onset of therapeutic effect, and that each SSRI currently on
the marked is only efficient in 60–70% of patients.4 Development
Studies have both shown that SERT furthermore is also partially
involved in mediating the stimulating and addictive properties of
cocaine,5 but that inhibition of DAT is pivotal6 in connection to this
widely abused drug. Although there currently exits no therapeutic
treatment for cocaine addiction it has been speculated it would be
possible to prepare compounds that could antagonize the effect of
cocaine while still allowing for DA transport. This idea has for a
number of years spawned the development of selective DAT bind-
ers with compounds of the phenyl tropane type of which chloro-
derivative 1 is a prime example (Fig. 1).7 Recent results, however,
have suggested that phenyl tropanes and dopamine have partially
overlapping binding sites on DAT indicating that this approach for
addiction treatment may be futile.8 Based on homology modeling
and biochemical experiments, however, the vestibule connecting
the central binding site and the extracellular space is large enough
to accommodate small molecules.9 Indeed, the existence of a vici-
nal modulatory substrate site in the homologous bacterial leucine
transporter (LeuT), the S2 site,10 that is also able to accommodate
tricyclic antidepressants11,12 implies that a similar site may be
present in both hDAT and hSERT. We hypothesized that a bivalent
ligand successfully utilizing both the central binding site (S1) and
the putative S2 site could potentially exhibit considerable gains
* Corresponding authors. Tel.: +45 89423963 (H.H.J.); tel.: +45 35321822 (M.B.).
E-mail addresses: hhj@chem.au.dk (H.H. Jensen), bols@kemi.ku.dk (M. Bols).
0968-0896/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2009.06.007

S. Nielsen et al. / Bioorg. Med. Chem. 17 (2009) 4900–4909
4901
O
OH
O
O
O
OMe
dioxane
/water
1) SOCl2
2)
R
R
N
N
R
S
N
rfx
88-100%
CH2OH
40-43%
4 R = Cl
1 R = Cl
7 R = Cl
8 R = I
5
2
R = I
6 R =
R = I
S
3 R =
O
N
O
N3
n
9
n = 0, R=Cl
10 n = 4, R=Cl
R
11
12
Cl
n = 5, R=
n = 9, R=I
Figure 1. Synthesis of building blocks for dimeric phenyl tropanes.
in affinity and selectivity compared to the parent monovalent com-
pounds (1–3, Fig. 1) only utilizing the central binding site. By uti-
lizing the well known high affinity of tropanes we aim to
establish a platform anchored to the central binding site from
which we by linkers can probe the affinity of different attachments
for the S2 site. The present study explores facile synthetic routes to
linking tropanes with different moieties in order to identify novel
ligands that also utilize the S2 site and by this strategy possibly
create stronger and more selective ligands for DAT and/or SERT
compared to the monovalent counterparts. Such compounds could
be valuable as biochemical tools or potential novel medicinal can-
didates. To a first approximation ligands of a bivalent nature,
which both has affinity for the S1 and S2 sites can be expected to
show increased binding provided that the linker only has an insig-
nificant effect. Fatty ester- or amide substituents in place of the
parent methyl ester of cocaine and cocaine analogues have previ-
ously been found to be well tolerated by DAT, while SERT/NET
binding was affected to a greater extent.7
rophenyl tropane, the 4-iodophenyl and 4-thiophenophenyl deriv-
atives were also included; the former was included because the 4-
iodo derivatives generally are more potent than 4-chloro deriva-
tives7 and the latter was included because a 4-thiophene group re-
cently has been shown to lead to strong and selective SERT
binding.15 The phenyl tropanes 1–3 were synthesized as previously
described.13,15 The hydrolysis of the methyl esters of these starting
materials was carried out by the refluxing the substrates in diox-
ane–water13 the basicity of the amine being the single means of
hydrolysis. The corresponding acids 4–6 were obtained in 88–
100% yield. These could be converted to propargyl esters 7 and 8
or azidoalkyl esters 9–12 (Fig. 1) by reaction with thionyl chloride
followed by treatment with propargyl or azidoalkyl alcohol. The
esters were obtained in 40–43% yield from the acids.
From these monomeric building blocks two sets of dimers could
be synthesized (Fig. 2). From the acids 4–6 and selected diamines,
the diamides 13–28 were prepared using coupling with benzotri-
zol-1-yloxy-tris(dimethylamino)phosphonium
hexafluorophos-
Bivalent ligands for monoamine transporters have previously
phate (BOP) in dichloromethane (DCM) in the presence of
triethylamine (TEA).13 A slight excess of diacid (1.1 equiv per ami-
no-group) was used. Purification of the products was not always
trivial, but chromatography in DCM containing small amounts of
TEA was generally found to be an efficient method. Nevertheless,
yields in these dimerizations varied widely. From 4-chlorophenyl
tropane 4 the dimers 13–18 were obtained in yields given in Figure
3. Likewise, from the 4-thiophenyl tropane 6 dimers 19–28 was ob-
tained in yields shown (Fig. 4). These yields reflect not only the dif-
ferent reactivity of the diamines, but also problems associated with
purification of some of the products.
been explored with some success.13,14
In the present work we report a broader study of dimeric phenyl
tropanes to establish the influence of (a) linker length beyond the 6
atoms used by Fandrick et al.,13 (b) linker rigidity and (c) changes
in attachment sites on binding affinity and selectivity. We here de-
scribe the synthesis of a number of these interesting dimeric mol-
ecules and a study of their binding to hDAT, hSERT and hNET.
2. Chemistry
The azido alkyl and propargyl esters of linker type B were pre-
A series of building blocks for the preparation of dimeric phenyl
tropanes were prepared as outlined in Figure 1. Besides the 4-chlo-
pared via CuSO4 and ascorbic acid catalyzed ‘click’ chemistry16 in
H
N
H
N
LINKERA
O
O
O
OH
BOP
R
R
R
N
N
N
DCM
TEA
4-6
13-28
LINKER B
O
O
O
O
Cu(I)
R
R
N
7-8 + 9-12
N
29-33
Figure 2. Synthesis of dimeric phenyl tropanes.

4902
S. Nielsen et al. / Bioorg. Med. Chem. 17 (2009) 4900–4909
O
O
N
N
H
N
N
N
O
N
O
N
H
N
H
Cl
Cl
Cl
13 (96%)
Cl
14 (39%)
N
N
O
O
N
H
N
H
m
n
m=0, n=0; 15 (46%)
m=0, n=1; 16 (80%)
m=0, n=2; 17 (63%)
m=1, n=2; 18 (47%)
Cl
Cl
Figure 3. Diamide dimers with linker type A prepared from 4. Values in brackets indicate isolated chemical yield for the coupling step.
O
H
N
O
N
N
O
N
O
N
N
H
N
H
N
H
n
S
S
n=1; 19 (31%)
n=3; 20 (84%)
n=5; 21 (22%)
S
S
22 (87%)
N
O
N
N
O
O
N
N
H
N
H
O
N
m
n
H
N
H
S
S
S
S
m=0, n=0; 23 (46%)
m=0, n=1; 24 (45%)
m=0, n=2; 25 (47%)
m=1, n=1; 26 (45%)
m=1, n=2; 27 (34%)
28 (34%)
Figure 4. Diamide dimers with linker type A prepared from 6. Values in brackets indicate isolated chemical yield for the coupling step.
water/tert-butanol to explore the effect of another type of linker on
monoamine transporter binding. This gave the 1,4-substituted tri-
azole-linked dimers 29–31 in fair to good yields as the only prod-
uct (Fig. 5). The coupling of 8 and 12, however, behaved sluggishly
and was accordingly carried out at elevated temperature which re-
sulted in the inseparable regioisomers 32 and 33 in a 69:31 ratio.
Due to sterical hindrance the 1,4-triazole would be expected to
be the major product, but no attempts were made to establish this.
To test the effect of having a dimeric as opposed to a monomeric
presentation of the phenyl tropane skeleton and to investigate
whether the linker functionality itself would have an effect on
monoamine transporter binding, compound 37 was prepared
(Fig. 6). Azido-alcohol was reacted with TMS–acetylene in the pres-
ence of CuSO4/sodium ascorbate to yield triazole alcohol 35 in 40%.
The silyl group was removed by treatment with tetrabutylammo-
nium fluoride (TBAF) in 96% yield and the resulting alcohol 36
was reacted with the acid chloride made from carboxylic acid 4.
This gave triazole tropane ester 37 in 68% yield.
3. Biology
Data for binding of the new compounds to DAT, SERT and NET
transporters were determined using competitive binding assays
with a radioactive ligand. Cloned human monoamine transporters
were expressed in the membrane of COS-1 cells and displacement
of radioligand 125I-(2) measured.
Compound 3 has been found to be a very potent and selective
rSERT inhibitor in a binding assay employing rat brain homoge-

S. Nielsen et al. / Bioorg. Med. Chem. 17 (2009) 4900–4909
4903
N
O
N
O
O
N
O
O
O
O
N
N
N
O
N
N
n
N
N
n
Cl
I
Cl
I
n=1; 29 (47%)
n=5; 30 (75%)
n=6; 31 (33%)
n=10; 32/33 (46%)
69/31 mixture of 1,4/1,5-regioisomers
Figure 5. Triazole dimers with linker type B prepared from compounds 7–11. Values in brackets indicate isolated chemical yield for the coupling step. Compound 32/33 was
prepared as a mixture of regioisomers.
1) NaN3, TBAI, DMF
N
HO
Cl
HO
N
2) TMSCCH, CuSO4
Na-ascorbate, 40%
N
TBAF/THF
96%
TMS
34
35
N
N
O
O
Acid chloride of 4,
N
TEA, THF, 68%
Cl
N
N
HO
N
N
TMS
36
37
Figure 6. Synthesis of triazole tropane monomer 37.
nates. Our assay confirmed that 3 is a potent SERT binder albeit the
binding was 30 times weaker on hSERT from a heterologous
expression system than previously found for rSERT from natural
sources (Table 1).15 Accordingly, the selectivity for the SERT is in
our assay also much lower than previous findings. The discrepancy
is presumably due to the difference in species and the source of
monoamine transporters.
The dimeric analogues of 1 (Fig. 3) 13–18 varied considerably in
binding affinity to DAT. Compounds 15–18 with an aromatic dia-
mine tether were considerably more potent than aliphatic tethered
compounds 13–14 consistent with favourable interactions with
the aromatic residues (Y156 and F266 in hDAT) lining the short ca-
nal between the central (S1) binding site and the putative (S2) ves-
tibular binding site.10 The results also indicate that a relatively
short tether, as in 13 and 15, results in poor binding, which is in
agreement with the previous study.13 SERT- and NET binding are
poor for all these compounds, making 16 and 17 quite selective
compounds for the DAT.
Table 1
Ki values for binding of hDAT, hSERT and hNET found as the mean value from at least
3 independent measurements
Substance
Ki binding (nM)
Selectivity
hNET/
hDAT
hSERT
hNET
hSERT/
hDAT
hDAT
1 (RTI-31)
2 (RTI-55)
3
2.7 1.1
3.9 1.1
2.5 1.8
21 0.5
4.2 0.3
0.58 0.2
39 28
19 2.8
26 11
7.8
1.1
0.24
14
4.9
10
The series of dimeric analogues of 3 (Fig. 4) compounds 19–28
are all quite poor monoamine transporter binders (Table 1). De-
spite the high affinity of the parent (3), analogues with very long
tethers, 19–21, are two orders of magnitude weaker against DAT
and NET, while SERT affinity is affected even more. A significant de-
crease in binding affinity compared to monovalent 3 against all
monoamine transporters is also observed for compounds 22–28
with benzene- or cyclohexyl containing linkers.
The triazole linked dimers 29–33 (Fig. 5) were, in terms of bind-
ing affinity, the most potent compounds in this study. The three
compounds derived from 1, 29–31 (Fig. 5), are strong DAT-binders
with the analogues with long tethers (compounds 30 and 31) being
the most effective albeit not significantly outstanding compared to
the parent compound (1) (Table 1). SERT binding is likewise strong
especially for compound 30 being 24-fold more potent than the
parent monomer (1). NET binding was found to be somewhat
weaker and for the best compounds (30 and 31) in the range of
monomeric affinity as found for DAT binding. Binding of the mix-
ture of iodinated regioisomers 32 and 33 is considerably weaker
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
890 570 4000 2800 4900 1900 4.6
180 100 2500 130 440 140 14
690 230 3200 320 5400 3300 4.6
5.5
2.5
7.8
39
21
6.6
20 16
9
4
1500 400
2600 1100
65 72
810 350
180 72
100 100
74
390
3.3
27
5.2
4.0
2.4
4.4
3.8
9.4
3.4
4.6
6.7
8.2
5.1
7.3
8.5
5.1
1.6
69
540 190 2100 1100 2200 650
4.0
690 230
350 110
1300 730
210 120
800 340
710 340
93 37
470 220
250
1700 400
1500 700
5000 2100 0.62
1900 550
2700 100
3300 580
620 84
1300 440
1200 760
120 36
0.68
0.72
9
810 210
270 76
730 230
340 150
160 80
62 59
860 600
27 12
0.86 0.79
1.3
0.92
0.48
1.7
0.38
3.7
160 17
230 170
29
30
31
32/33
37
16
1.0 0.6
3.9
140 140
5.5
9
1.6
8.5
20
2
8
0.86
0.89
0.91
3.6
2
3.5
3
120 51
20 18
220 140
380 200
2
Inhibition was found to be competitive. Uncertainty is reported as SEM.

4904
S. Nielsen et al. / Bioorg. Med. Chem. 17 (2009) 4900–4909
than 29–31, which must also be true for the individual compounds
even if there is a considerable difference in biological activity be-
tween them.
4. Experimental
4.1. General
The selectivity of compounds 30–33 is essentially identical but
due to their improved SERT affinity inverse that of the parent com-
pound (1).
All reactions were carried out under nitrogen atmosphere and
only dried glassware from the oven (ꢁ125–150 °C) was used. Evap-
oration on the evaporator to remove solvents was done under re-
duced pressure unless otherwise stated, and the temperature was
kept around 40 °C. Dry solvents were used for the reactions.
Dichloromethane was dried by distillation over CaH2 and diethyl
ether was dried over sodium wire. As the stationary phase for
the chromatography Fluka Silica Gel 60 (230–400 mesh) were
used. TLC-plates were performed on silica gel (Merck Kieselgel,
60 F254). 1H NMR and 13C NMR spectra were recorded at a Varian
Mercury 400 spectrometer. 1H NMR spectra were recorded at
400 MHz in chloroform-d or D2O. 13C NMR spectra were recorded
at 100 MHz in chloroform-d or D2O. HRMS spectra were recorded
at a Micromass LC-TOF instrument by using electro spray in posi-
tive ionization mode.
Monomeric phenyl tropane with a triazole linker (37) was
found to be a potent hDAT binder with a low nanomolar affinity.
For all three monoamine transporters the result of adding the lin-
ker as in monomeric 37 to the parent methylester (1) was found to
be inconsequential (DAT and SERT) or deleterious (NET). However,
the benchmark for the value of dimers can be found when compar-
ing 37 with 30 and 31. Compound 30 shows a moderate 5.5-fold
tighter binding affinity for hDAT compared to monovalent 37,
whereas a more significant increase was found towards hSERT
(23-fold) and even more pronounced hNET (45-fold).
Ligands selective for the putative S2 site over the S1 site of
monoamine transporters may have interesting pharmaceutical
prospects as well as applications in studying whether the S2 site
plays the same role for the transport mechanism of monoamine
transporters than what has been proposed for LeuT.10 Even though
small noncompetitive inhibitors and allosteric modulators of
monoamine transporters exist there is, however, no evidence for
these compounds binding selectively to S2. If such a S2 selective
compound was to be developed the screening for the desired selec-
tivity would be complicated. By using phenyl tropane as an anchor
to the primary site via a linker it would be possible to screen for
suitable lead compounds for S2 by determining the gain of affinity
contributed by the potential lead compound to a dimer with phe-
nyl tropane as the other subunit.
We set out to probe if a phenyl tropane in the primary binding
site8 could act as an anchor point for exploring affinity in the S2
site of different linked moieties and to identify which linker chem-
istries would be suitable. The considerable gains of affinity, up to
45-fold, of the dimer relative to the monomer suggest that im-
proved affinity is certainly obtainable using this strategy and that
phenyl tropane is also accepted in the juxtaposed site. We also
show that attention to the chemical characteristics and length of
the linker is very important to prevent that a poorly accepted lin-
ker cancels out the positive effects of the dimer approach.
The gains in affinity from homodimers of tropane analogues im-
ply that the second tropane may be a suitable ligand also for the S2
site. The S2 site appears to be highly promiscous in LeuT11,12,17 and
may be forgiving for a phenyl tropane even though it was originally
developed for high S1 site affinity. Accordingly, a second dimer sub-
unit more optimized for the S2 site may yield even greater gains of
affinity. The observations that antidepressants will bind to the S2
site of LeuT11,12 suggests that a bivalent ligand linking a tropane ana-
logue with anantidepressantanaloguemay exhibitthedesired gains
in affinity and selectivity should a similar site exist in the mono-
amine transporters. Inhibition data of the superior compound 30
(Table 1) imply that two sites are separated by 13 Å.18 Building on
the knowledge gathered in the present study linked bivalent tro-
pane-tricyclic antidepressants are being pursued by us.
In summary, we have synthesized a diverse series of bivalent
phenyl tropanes with different linkers to evaluate the effect of both
linker composition and a secondary tropane on inhibition of mono-
amine transporters. It was found that bivalent chlorophenyl tro-
panes with aromatic diamine linkers are potent and selective
binders of the hDAT. Chlorophenyl tropanes with intermediate
length ester tethers were likewise found to be strong hDAT bind-
ers, but for these compounds inhibition of hSERT and hNET was
also significant. Finally, it was observed that bivalent 3-thiophen-
ophenyl tropanes were poor monoamine transport binders despite
the high affinity of the parent monomeric 3-thiophenophenyl
tropane.
4.1.1. 3b-(4-Thiopheno-3-yl-phenyl) tropane-2b-carboxylic acid
(6)
To
a
flask with 2b-carbomethoxy-3b-(4-thiopheno-3-yl-
phenyl)tropane (3, 0.21 g, 0.62 mmol) was added 15 mL H2O and
15 mL dioxane. The mixture was refluxed overnight. The solvent
was removed under reduced pressure and lyophilized to dryness.
The product, 0.201 g of a white solid, 6 (0.61 mmol, 100%) was ob-
tained and used without further purification. 1H NMR (D2O) d 1.88
(1H, dt, Jd = 14.6 Hz and Jt = 4.0 Hz, H4endo), 2.09–2.21 (2H, m,
H6endo and H7endo), 2.31–2.49 (2H, m, H6exo and H7exo), 2.74 (1H,
dt, Jd = 2.8 Hz and Jt = 14.6 Hz, H4exo), 2.80 (1H, m, H2), 2.82 (3H,
s, NCH3), 3.42 (1H, dt, Jd = 13.2 Hz and Jt = 6.1 Hz, H3), 3.99 (2H,
m, H1 and H5), 7.36 (2H, dm, Jd = 8.6 Hz), 7.54–7.57 (2H, m), 7.68
(2H, dm, Jd = 8.6 Hz), 7.70 (1H, dd, Jd = 1.6 Hz and Jd = 2.8 Hz). 13C
NMR (D2O) d 23.5, 23.8, 32.2, 33.3, 38.3, 52.7, 63.5, 65.9, 120.9,
126.3, 126.4, 127.4, 128.5, 134.2, 139.5, 141.5, 179.3. HRMS(ES):
calculated for 6 + Na m/z 350.1191. Found m/z 350.1196.
4.2. General synthesis of 3b-(4-halophenyl) tropane-2b-
carboxylic acid prop-2-ynyl or azidoalkyl esters (7–12)19
To a flask containing 3b-(4-halophenyl)tropane-2b-carboxylic
acid (1 equiv, halo = Cl or I) was added 4 mL thionyl chloride. The
mixture was stirred for 90 min and excess of thionyl chloride
was removed under reduced pressure to afford 3b-(4-halophe-
nyl)tropane-2b-carbonyl chloride. This was dissolved in 10 mL
dichloromethane. Propargyl or azidoalkyl alcohol (5 equiv) was
added. Then triethylamine (5 equiv) and the mixture stirred over-
night. To the solution was added 20 mL H2O and the organic layer
was separated. The aqueous layer was extracted with 3 ꢂ 20 mL
dichloromethane, and the combined organic layers were dried over
magnesium sulfate and concentrated under reduced pressure.
4.2.1. 3b-(4-Chlorophenyl)tropane-2b-carboxylic acid prop-2-
ynyl ester (7)
The amount of starting material, 4 used for the reaction was
0.353 g (1.27 mmol). The product was purified by flash chromatog-
raphy (49.5% pentane–49.5% diethyl ether–1% triethylamine) to af-
ford 0.172 g of a white solid of 7 (0.54 mmol, 43%). 1H NMR (CDCl3)
d 1.49–1.68 (3H, m, H4endo, H6endo and H7endo), 1.89–2.20 (2H, m,
H6exo and H7exo), 2.15 (3H, s, NCH3), 2.32 (1H, m, –C„CH), 2.48
(1H, dt, Jd = 2.4 Hz and Jt = 12.4 Hz, H4exo), 2.84 (1H, m, H2), 2.90
(1H, dt, Jd = 12.4 Hz and Jt = 5.2 Hz, H3), 3.29 (1H, m, H5), 3.52
(1H, m, H1), 4.37 (1H, dd, Jd = 15.6 Hz and Jd = 12.8 Hz, OCH2–
C„CH), 4.53 (1H, dd, Jd = 15.6 Hz and Jd = 2.8 Hz, OCH2–C„CH),
7.11 (2H, dm, Jd = 8.2 Hz), 7.15 (2H, dm, Jd = 8.2 Hz). 13C NMR

S. Nielsen et al. / Bioorg. Med. Chem. 17 (2009) 4900–4909
4905
(CDCl3) d 25.1, 25.8, 33.2, 33.8, 41.8, 51.3, 52.4, 62.1, 65.0, 74.4,
77.8, 128.0, 128.7, 131.5, 141.2, 170.3. HRMS(ES) calculated for
7 + H m/z 318.1261. Found m/z 318.1265.
–C@O–NH–). 13C NMR (CDCl3) d 24.6, 25.9, 31.0, 31.5, 34.3, 35.0,
40.7, 46.0, 54.0, 60.9, 63.8, 128.2, 129.0, 132.2, 139.7, 171.4.
HRMS(ES) calculated for 13 + H m/z 637.3076. Found m/z 637.3077.
4.2.2. 3b-(4-Iodophenyl)tropane-2b-carboxylic acid prop-2-ynyl
ester (8)
4.3.2. 1-[3b-(4-Chlorophenyl)tropane-2b-carbonyl-amino]-2-
[3b-(4-chlorophenyl)tropane-2b-carbonyl-piperidine-4-yl]
ethane (14)
The amount of starting material 5 used for the reaction was
0.482 g (1.30 mmol). The product was purified by flash chromatog-
raphy (49.5% pentane–49.5% diethyl ether–1% triethylamine) to af-
ford 0.210 g of a white solid of 8 (0.51 mmol, 40%). 1H NMR (CDCl3)
d 1.58–1.75 (3H, m, H4endo, H6endo and H7endo), 2.05–2.26 (2H, m,
H6exo and H7exo), 2.23 (3H, s, NCH3), 2.39 (1H, m, –C„CH), 2.55
(1H, dt, Jd = 2.8 Hz and Jt = 12.4 Hz, H4exo), 2.92 (1H, m, H2), 2.95
(1H, dt, Jd = 12.8 Hz and Jt = 4.8 Hz, H3), 3.36 (1H, m, H5), 3.60
(1H, m, Jd = 6.4 Hz, H1), 4.45 (1H, dd, Jd = 15.6 Hz and Jd = 2.4 Hz,
OCH2–C„CH), 4.61 (1H, dd, Jd = 15.6 Hz and Jd = 2.4 Hz, OCH2–
C„CH), 7.01 (2H, dm, Jd = 8.4 Hz), 7.58 (2H, dm, Jd = 8.4 Hz). 13C
NMR (CDCl3) d 25.1, 25.8, 33.4, 33.6, 41.9, 51.4, 52.4, 62.1, 65.0,
74.5, 77.8, 91.2, 129.5, 136.9, 142.5, 170.3. HRMS(ES) calculated
for 8 + H m/z 410.0617. Found m/z 410.0619.
For this experiment 43 mg (0.21 mmol) of 2-piperidin-4-yl-eth-
ylamine was employed. The residue was purified by flash chroma-
tography (99% dichloromethane, 1% triethylamine) to afford 54 mg.
of a clear oil, 14 (0.083 mmol, 39%). 1H NMR (CDCl3) d 0.77 (1H, m),
0
1.00 (1H, m), 1.15–1.43 (4H, m), 1.58–1.75 (7H, m, H4endo, H4endo
,
,
0
0
0
H6endo, H6endo , H7endo, H7endo ), 2.04–2.32 (6H, m, H4exo, H4exo
0
0
H6exo, H6exo , H7exo and H7exo ), 2.21 (6H, s, NCH3), 2.45 (1H, m,
H2/H20), 2.82 (1H, dt, Jd = 12.2 Hz and Jt = 2.8 Hz), 2.92 (1H, m,
H2/H20), 2.93 (1H, dt, Jd = 12.8 Hz and Jt = 4.4 Hz), 3.08 (2H, m, H3
and H30), 3.14(2H, m), 3.25–3.32 (2H, m, H5 and H50), 3.29 (1H,
m, H1/H10), 3.38 (1H, m, H1/H10), 3.76 (1H, m), 4.46 (1H, m), 7.07
(2H, dm, Jd = 8.4 Hz), 7.15–7.20 (6H, m) 9.42 (1H, m, –C@O–NH–).
13C NMR (CDCl3) d 24.9, 26.2, 34.1, 34.4, 35.4, 36.2, 36.5, 41.3,
53.1, 54.3, 61.3, 62.3, 64.0, 128.1, 128.4, 128.9, 129.0, 131.2,
132.4, 139.9, 142.5, 171.4. HRMS(ES) calculated for 14 + H m/z
651.3232. Found m/z 651.3835.
4.2.3. Synthesis of 3b-(4-Iodophenyl)tropane-2b-carboxylic acid
9-azido-undecyl ester (12)
The amount of 3b-(4-iodophenyl)tropane-2b-carboxylic acid
used was 74 mg (0.2 mmol) leading to 108 mg of a yellow oil of
12. 1H NMR (CDCl3) d 0.93 (2H, quint, Jquint = 7.5 Hz, CH2–CH2–
CH2), 1.12–1.44 (13H, m, CH2–CH2–CH2) 1.57 (2H, quint,
Jquint = 7.5 Hz, CH2–CH2–CH2) 1.76 (1H, quint, Jquint = 7.5 Hz, CH2–
CH2–CH2), 2.07 (1H, dm, Jd = 14.4 Hz, H4endo), 2.26–2.42 (2H, m,
H6endo and H7endo), 2.51–2.63 (2H, m, H6exo and H7exo), 2.87 (1H,
dt, Jd = 2.8 Hz and Jt = 14.4 Hz, H4exo), 3.06 (3H, s, NCH3), 3.13
(1H, m, H2), 3.25 (1H, t, Jt = 7.0 Hz, CH2N3), 3.52 (1H, m, H3), 3.53
(1H, t, Jt = 7.0 Hz, CH2N3), 3.76 (1H, dt, Jd = 10.8 Hz and Jt = 6.8 Hz,
OCH2–), 3.89 (1H, dt, Jd = 10.8 Hz and Jt = 6.8 Hz, OCH2–), 4.25
(1H, m, H5), 4.32 (1H, m, H1), 7.05 (2H, dm, Jd = 8.4 Hz), 7.67
(2H, dm, Jd = 8.4 Hz). 13C NMR (CDCl3) d 24.2, 25.2, 25.5, 26.7,
26.9, 27.9, 28.9, 29.1, 29.3, 32.4, 32.7, 33.7, 41.3, 45.5, 49.1, 51.6,
64.6, 66.2, 67.0, 93.5, 129.8, 137.3, 138.0, 174.3. HRMS(ES) calcu-
lated for 12 + H m/z 567.2196. Found m/z 567.2192.
4.3.3. 1,4-Di[3b-(4-chlorophenyl)tropane-2b-carbonyl-amino]
benzene (15)
For this experiment 19 mg (0.18 mmol) of 1,4-diaminobenzene
was used. The product was purified by flash chromatography (99%
dichloromethane, 1% triethylamine) to afford 0.186 g of a red solid
of 15 (0.053 mmol, 46%). 1H NMR (CDCl3) d 1.56–1.76 (6H, m,
H4endo, H6endo and H7endo), 2.04–2.36 (6H, m, H4exo, H6exo and
H7exo), 2.38 (6H, s, NCH3), 2.54 (2H, m, H2), 3.17 (2H, dt,
Jd = 13.6 Hz and Jt = 6.4 Hz, H3) 3.44 (4H, m, H1 and H5), 7.11
(4H, dm, Jd = 8.4 Hz), 7.21 (4H, dm, Jd = 8.4 Hz) 7.34 (4H, s), 12.0
(2H, s, –C@O–NH–). 13C NMR (CDCl3) d 25.0, 26.3, 35.4, 35.5,
41.0, 55.0, 61.4, 63.8, 120.4, 128.5, 129.2, 132.6, 134.3, 139.7,
170.2. HRMS(ES) calculated for 15 + H m/z 630.2528. Found m/z
630.2542.
4.3.4. 1-[3b-(4-Chlorophenyl)tropane-2b-carbonyl-amino]-1-
[3b-(4-chlorophenyl)tropane-2b-carbonyl-aminobenzene-4-yl]
methane (16)
4.3. General synthesis of 1, N-di-3b-(4-chlorophenyl)tropane-
2b-carboxy amide linked molecules (13–18)
The reaction was performed with 40 mg (0.327 mmol) of 4-ami-
nobenzylamine. The residue was purified by flash chromatography
(99% dichloromethane, 1% triethylamine) to afford 0.168 g of a red
solid 16 (0.26 mmol, 80%). 1H NMR (CDCl3) d 1.56–1.84 (6H, m,
To a solution of benzotriazol-1-yloxytris(dimethylamino)phos-
phonium hexafluorophosphate, BOP (2.8 equiv) in 10 mL dichloro-
methane was added triethylamine (20 equiv) and the mixture was
stirred at 0 °C for 20 min. 3b-(4-Chlorophenyl)tropane-2b-carbox-
ylic acid, 4 (2.2 equiv) was added and the mixture was stirred at
0 °C for 30 min. The linker/diamine (1 equiv) was added and the
mixture was stirred over night at room temperature. H2O
(10 mL) was added to the reaction mixture and the organic layer
was separated. The aqueous layer was extracted with 3 ꢂ 10 mL
ethyl acetate. The combined organic layers was dried over magne-
sium sulfate and concentrated under reduced pressure.
0
0
0
H4endo, H4endo , H6endo, H6endo , H7endo and H7endo ), 2.04–2.32(5H,
0
0
0
m, H4exo/H4exo , H6exo, H6exo , H7exo and H7exo ), 2.21 (3H, s, NCH3),
0
2.40 (1H, m, H4exo/H4exo ), 2.41 (3H, s, NCH3), 2.57 (2H, m, H2
and H20), 3.10 (1H, dt, Jd = 14.0 Hz and Jt = 6.4 Hz, H3/H30), 3.19
(1H, dt, Jd = 14.0 Hz and Jt = 6.4 Hz, H3/H30), 3.30 (1H, m, H5/H50),
3.34 (1H, m, H5/H50), 3.45 (2H, m, H1 and H10), 4.29 (2H, d,
Jd = 6.0 Hz), 7.04 (2H, dm, Jd = 8.4 Hz), 7.12 (2H, dm, Jd = 8.8 Hz),
7.18 (4H, dm, Jd = 8.8 Hz), 7.20 (2H, dm, Jd = 8.8 Hz), 7.38 (2H,
dm, Jd = 8.4 Hz) 9.86 (1H, t, Jt = 6.0 Hz, –C@O–NH–CH2–), 12.08
(1H, s, –C@O–NH-C6H4–). 13C NMR (CDCl3): d 24.8, 24.9, 26.0,
26.1, 34.6, 35.2, 35.2, 40.8, 41.0, 46.2, 54.1, 54.9, 61.0, 61.2, 63.6,
63.8, 119.7, 128.2, 128.2, 128.3, 129.0, 129.0, 132.1, 132.4, 134.2,
137.3, 139.5, 139.6, 170.4, 172.1. HRMS(ES) calculated for 16 + H
m/z 645.2763. Found m/z 645.2753.
4.3.1. trans-1,4-Di[3b-(4-chlorophenyl)tropane-2b-carbonyl-
amino] cyclohexane (13)
The reaction was performed with 35 mg (0.31 mmol) of trans-
1,4-diaminocyclohexane. The residue was purified by flash chro-
matography (99% dichloromethane, 1% triethylamine) to afford
0.186 g. of white crystals, 13 (0.29 mmol, 96%). 1H NMR (CDCl3) d
1.25 (4H, m) 1.58–1.71 (6H, m, H4endo, H6endo and H7endo), 1.85
(4H, m), 2.00–2.24 (6H, m, H4exo, H6exo and H7exo), 2.20 (6H, s,
NCH3), 2.87 (2H, m, H2), 3.05 (2H, dt, Jd = 13.6 Hz and Jt = 5.6 Hz,
H3), 3.25 (2H, m, H5) 3.29 (2H, m, H1), 3.59 (2H, m), 7.07 (4H,
dm, Jd = 8.4 Hz), 7.19 (4H, dm, Jd = 8.4 Hz), 9.55 (2H, d, Jd = 8.0 Hz,
4.3.5. 1-[3b-(4-Chlorophenyl)tropane-2b-carbonyl-amino]-2-
[3b-(4-chlorophenyl)tropane-2b-carbonyl-aminobenzene-4-yl]
ethane (17)
Amount of 4-(2-amino-ethyl)phenyl amine (linker) added to
the reaction was 44 mg. (0.32 mmol). The residue was purified

4906
S. Nielsen et al. / Bioorg. Med. Chem. 17 (2009) 4900–4909
by flash chromatography (99% dichloromethane, 1% triethylamine)
Jd = 8.4 Hz), 7.25 (4H, m), 7.29 (2H, m), 7.40 (2H, dm, Jd = 8.4 Hz),
9.44 (2H, t, Jt = 5.4 Hz, –C@O–NH–). 13C NMR (CDCl3) d 24.6, 25.9,
26.7, 29.6, 34.7, 35.3, 38.5, 41.0, 54.1, 61.0, 63.9, 119.6, 125.5,
126.0, 126.1, 127.8, 133.9, 140.1, 142.1, 172.2. HRMS(ES) calculated
for 19 + H m/z 735.3766. Found m/z 735.3748.
to afford 0.134 g of a red solid, 17 (0.20 mmol, 63%). 1H NMR
0
0
(CDCl3) d 1.45–1.82 (6H, m, H4endo, H4endo , H6endo, H6endo , H7endo
0
0
0
and H7endo ), 1.88–2.34 (6H, m, H4exo, H4exo , H6exo, H6exo , H7exo
and H7exo), 2.07 (3H, s, NCH3), 2.38 (3H, s, NCH3), 2.43 (1H, m,
H2/H20), 2.55 (1H, m, H2/H20), 2.76 (2H, m), 3.00 (1H, dt,
Jd = 13.6 Hz and Jt = 6.2 Hz, H3/H30), 3.15 (2H, dt, Jd = 13.6 Hz and
Jt = 6.2 Hz, H3/H30), 3.19 (2H, m, H5 and H50), 3.42 (4H, m, H1,
H10), 6.88 (2H, dm, Jd = 8.8 Hz), 7.01 (2H, dm, Jd = 8.4 Hz), 7.06
(2H, dm, Jd = 8.4 Hz), 7.15 (4H, dm, Jd = 8.4 Hz), 7.16 (2H, dm,
Jd = 8.4 Hz), 7.39 (2H, dm, Jd = 8.8 Hz), 9.52 (1H, t, Jt = 5.0 Hz,
–C@O–NH–CH2–), 11.98 (1H, s, –C@O–NH–C6H4–). 13C NMR
(CDCl3) d 24.8, 25.0, 26.1, 26.2, 34.9, 34.9, 35.1, 35.2, 35.3, 40.4,
40.9, 41.0, 54.3, 55.0, 61.1, 61.3, 63.7, 119.8, 128.3, 128.4, 129.1,
129.1, 129.2, 132.2, 132.4, 134.7, 137.0, 139.6, 140.0, 170.3,
172.4. HRMS(ES) calculated for 17 + H m/z 659.2920. Found m/z
659.2835.
4.4.2. 1,8-Di[3b-(4-thiophene-3-yl-phenyl)tropane-2b-carbonyl-
amino] octane (20)
The experiment was performed with 22 mg (0.15 mmol) of 1,8-
aminooctane. The residue was purified by flash chromatography
(99% dichloromethane, 1% triethylamine) to afford 98 mg of a
white solid, 20 (0.05 mmol, 84%). 1H NMR (CDCl3) d 1.26–1.39
(8H, m), 1.50 (4H, m), 1.62–1.78 (6H, m, H4endo, H6endo and H7endo),
2.04–2.31 (6H, m, H4exo, H6exo and H7exo), 2.26 (6H, s, NCH3), 2.56
(2H, m, H2), 3.09–3.18 (6H, m, H3), 3.33 (4H, m, H1 and H5),
7.19 (4H, dm, Jd = 8.0 Hz), 7.33 (4H, m), 7.48 (2H, m), 7.48 (2H,
dm, Jd = 8.0 Hz), 9.51 (2H, t, Jt = 5.2 Hz, –C@O–NH–). 13C NMR
(CDCl3) d 24.9, 26.3, 27.3, 29.4, 29.8, 35.1, 35.7, 38.9, 41.3, 54.4,
61.3, 64.2, 119.9, 125.9, 126.3, 126.5, 128.2, 134.2, 140.4, 142.4,
172.6. HRMS(ES) calculated for 20 + H m/z 763.4079. Found m/z
763.4120.
4.3.6. 1-[3b-(4-Chlorophenyl)tropane-2b-carbonyl-amino]-2-
[3b-(4-chlorophenyl)tropane-2b-carbonyl-
aminomethylbenzene-4-yl] ethane (18)
The reaction was performed with 39 mg (0.176 mmol) of 2-(4-
aminomethylphenyl)-ethylamine. The residue was purified by
flash chromatography (99% dichloromethane, 1% triethylamine)
to afford 56 mg. of a red oil, 18 (0.083 mmol, 47%). 1H NMR (CDCl3)
4.4.3. 1,10-Di[3b-(4-thiophene-3-yl-phenyl)tropane-2b-
carbonyl-amino] decane (21)
The experiment was performed with 28 mg (0.161 mmol) of
1,10-aminodecane. The residue was purified by flash chromatogra-
phy (99% dichloromethane, 1% triethylamine) to afford 28 mg of a
white solid, 21 (0.035 mmol, 22%). 1H NMR (CDCl3) d 1.24 (12H, m),
1.43 (4H, m), 1.55–1.71 (6H, m, H4endo, H6endo and H7endo), 2.00–
2.28 (6H, m, H4exo, H6exo and H7exo), 2.20 (6H, s, NCH3), 2.52 (2H,
m, H2), 3.04–3.11 (6H, m, H3), 3.26 (4H, m, H1 and H5), 7.12
(4H, dm, Jd = 8.0 Hz), 7.26 (4H, m), 7.30 (2H, m) 7.40 (2H, dm,
Jd = 8.0 Hz), 9.43 (2H, t, Jt = 5.2 Hz, –C@O–NH–). 13C NMR (CDCl3)
d 25.0, 26.3, 27.4, 29.4, 29.7, 29.8, 35.1, 35.7, 39.0, 41.4, 54.4,
61.5, 64.3, 120.0, 125.9, 126.4, 126.5, 128.2, 134.3, 140.4, 142.4,
172.6. HRMS(ES) calculated for 21 + H m/z 791.4392. Found m/z
791.4378.
0
0
d 1.48–1.74 (6H, m, H4endo, H4endo , H6endo, H6endo , H7endo and
0
0
0
H7endo ), 1.98-2.26 (6H, m, H4exo, H4exo , H6exo, H6exo , H7exo and
H7exo), 2.02 (3H, s, NCH3), 2.18 (3H, s, NCH3), 2.45 (1H, m, H2/
H20), 2.59 (1H, m, H2/H20), 2.81 (2H, dt, Jd = 3.2 Hz and Jt = 7.0 Hz),
3.09 (1H, dt, Jd = 12.6 Hz and Jt = 6.2 Hz, H3/H30), 3.09 (2H, dt,
Jd = 12.6 Hz and Jt = 6.2 Hz, H3/H30), 3.18 (2H, m, H5 and H50),
3.25 (1H, m, H1/H10), 3.33 (1H, m, H1/H10), 3.40 (1H, dd, Jd = 6.0 Hz
and Jd = 12.0 Hz), 3.47 (1H, dd, Jd = 6.0 Hz and Jd = 12.0 Hz), 4.32
(2H, t, Jd = 6.0 Hz), 6.96 (2H, dm, Jd = 8.4 Hz), 7.05 (2H, dm,
Jd = 8.4 Hz), 7.17 (2H, dm, Jd = 8.4 Hz), 7.18 (2H, dm, Jd = 8.4 Hz),
7.20 (4H, s), 9.55 (1H, t, Jt = 5.6 Hz, –C@O–NH–CH2–), 9.90 (1H, t,
Jt = 5.6 Hz, –C@O–NH–CH2–). 13C NMR (CDCl3) d 24.5, 24.6, 25.8,
25.8, 34.4, 34.5, 34.9, 34.9, 35.0, 39.8, 40.7, 40.8, 42.3, 53.9, 54.0,
60.8, 60.9, 63.4, 63.6, 127.5, 128.0, 128.6, 128.7, 128.8, 132.0,
137.1, 138.1, 139.4, 139.5, 172.0, 172.1. HRMS(ES) calculated for
18 + H m/z 673.3076. Found m/z 673.3082.
4.4.4. trans-1,4-Di[3b-(4-thiophene-3-yl-phenyl)tropane-2b-
carbonyl-amino] cyclohexane (22)
The reaction was performed with 17 mg (0.15 mmol) of trans-
1,4-diamino cyclohexane. The product was purified by flash chro-
matography (99% dichloromethane, 1% triethylamine) to afford
95 mg of a white solid, 22 (0.13 mmol, 87%). 1H NMR (CDCl3) d
1.32 (4H, m), 1.63–1.77 (6H, m, H4endo, H6endo and H7endo) 1.92
(4H, m) 2.23–2.70 (4H, m, H6exo and H7exo), 2.20 (6H, s, NCH3),
2.29 (2H, dt, Jd = 6.8 Hz and Jt = 13.0 Hz, H4exo), 2.53 (2H, m, H2),
3.13 (2H, dt, Jd = 12.8 Hz and Jt = 6.2 Hz, H3), 3.29 (4H, m, H1 and
H5), 3.67 (2H, m), 7.07 (4H, dm, Jd = 8.4 Hz) 7.34 (2H, dd, Jd = 4.8 Hz
and Jd = 2.8 Hz), 7.35 (2H, dd, Jd = 4.8 Hz and Jd = 1.6 Hz), 7.39 (2H,
dd, Jd = 2.8 Hz and Jd = 1.6 Hz), 7.49 (4H, dm, Jd = 8.4 Hz), 9.59 (2H,
d, Jd = 8.0 Hz, –C@O–NH–). 13C NMR (CDCl3) d 24.9, 26.2, 31.3, 31.7,
34.9, 35.4, 41.0, 46.3, 54.3, 61.2, 63.2, 119.9, 125.9, 126.2, 126.5,
128.2, 134.2, 140.3, 142.4, 171.8. HRMS(ES) calculated for 22 + H
m/z 733.3610. Found m/z 733.3636.
4.4. General synthesis of dimers of 1,n-di-3b-(4-thiophene-3-yl-
phenyl)tropane-2b-carboxy amide linked molecules (19–28)
To a solution of benzotriazol-1-yloxytris(dimethylamino)phos-
phonium hexafluorophosphate, BOP (2.8 equiv) in 10 mL dichloro-
methane was added triethylamine (20 equiv) and the mixture was
stirred at 0 °C for 20 min. 2b-Carboxylic acid-3b-(4-thiophene-3-
yl-phenyl)tropane, 6 (2.2 equiv) was added and the mixture was
stirred at 0 °C for 30 min. The linker/diamine (1 equiv) was added,
and the mixture was stirred overnight at room temperature. H2O
(10 mL) was added to the reaction mixture, and the organic layer
separated. The aqueous layer was extracted with 3 ꢂ 10 mL ethyl
acetate. The combined organic layers was dried over magnesium
sulfate and concentrated under reduced pressure.
4.4.5. 1,4-Di[3b-(4-thiophene-3-yl-phenyl)tropane-2b-carbonyl-
amino] benzene (23)
4.4.1. 1,6-Di[3b-(4-thiophene-3-yl-phenyl)tropane-2b-carbonyl-
amino] hexane (19)
The experiment was performed with 16 mg (0.15 mmol) of 1,4-
diamino benzene. The residue was purified by flash chromatogra-
phy (99% dichloromethane, 1% triethylamine) to afford 50 mg of
a red solid, 23 (0.069 mmol, 46%). 1H NMR (CDCl3) d 1.70–1.88
(6H, m, H4endo, H6endo and H7endo) 2.12–2.34 (4H, m, H6exo and
H7exo), 2.40 (6H, s, NCH3), 2.43 (2H, tm, Jt = 12.8 Hz, H4exo), 2.62
(2H, m, H2), 3.23 (2H, dt, Jd = 12.8 Hz and Jt = 6.2 Hz, H3), 3.45
(2H, dm, Jd = 5.6 Hz, H5), 3.49 (2H, dm, Jd = 5.6 Hz, H1), 7.23 (4H,
The experiment was carried out with 19 mg (0.161 mmol) of 1,6-
amino hexane. The residue was purified by flash chromatography
(99% dichloromethane, 1% triethylamine) to afford 37 mg of a white
solid, 19 (0.05 mmol, 31%). 1H NMR (CDCl3) d1.29–1.33 (4H, m, H21)
1.44 (4H, m, H20) 1.58–1.68 (6H, m, H4endo, H6endo and H7endo), 2.00–
2.25 (6H, m, H4exo, H6exo and H7exo), 2.50 (6H, s, NCH3), 2.50 (2H, m,
H2), 3.02–3.13 (6H, m, H3), 3.25 (4H, m, H1 and H5), 7.12 (4H, dm,

S. Nielsen et al. / Bioorg. Med. Chem. 17 (2009) 4900–4909
4907
dm, Jd = 8.0 Hz), 7.33–7.41 (10H, m) 7.502 (4H, dm, Jd = 8.0 Hz),
12.0 (2H, s, -C@O–NH–). 13C NMR (CDCl3) d 24.7, 26.0, 35.3, 40.7,
53.2, 54.8, 61.1, 63.6, 119.7, 120.1, 125.6, 126.1, 128.0, 134.0,
134.1, 139.8, 142.0, 170.2. HRMS(ES) calculated for 23 + H m/z
727.3140. Found m/z 727.3151.
35.0, 35.5, 41.2, 42.8, 54.4, 61.3, 64.1, 120.0, 125.9, 126.4, 126.5,
127.9, 128.2, 134.2, 138.2, 140.2, 142.4, 172.6.
4.4.9. 1-[3b-(4-Thiophene-3-yl-phenyl)tropane-2b-carbonyl-
amino]-2-[3b-(4-thiophene-3-yl-phenyl)tropane-2b-carbonyl-
aminomethylbenzene-4-yl] ethane (27)
4.4.6. 1-[3b-(4-Thiophene-3-yl-phenyl)tropane-2b-carbonyl-
amino]-1-[3b-(4-thiophene-3-yl-phenyl)tropane-2b-carbonyl-
aminobenzene-4-yl] methane (24)
The experiment was performed with 15 mg (0.13 mmol) of 4-
aminobenzylamine. The residue was purified by flash chromatog-
raphy (99% dichloromethane, 1% triethylamine) to afford 44 mg
of an orange oil, 24 (0.057 mmol, 45%). 1H NMR (CDCl3) d 1.61–
The reaction was performed with 28 mg (0.126 mmol) of 2-(4-
aminomethylphenyl)-ethylamine. The product was purified by
flash chromatography (99% dichloromethane, 1% triethylamine)
to afford 33 mg of a clear oil, 27 (0.043 mmol, 34%). 1H NMR
0
0
(CDCl3) d 1.53–1.77 (6H, m, H4endo, H4endo , H6endo, H6endo , H7endo
0
0
0
and H7endo ), 1.98–2.29 (6H, m, H4exo, H4exo , H6exo, H6exo , H7exo
0
and H7exo ), 2.02 (3H, s, NCH3), 2.19 (3H, s, NCH3), 2.52 (2H, m,
0
0
0
1.88 (6H, m, H4endo, H4endo , H6endo, H6endo , H7endo and H7endo ),
H2/H20), 2.66 (2H, m, H2/H20), 2.84 (2H, m), 3.07 (1H, dt,
Jd = 12.4 Hz and Jt = 6.2 Hz, H3/H30), 3.15 (2H, dt, Jd = 12.4 Hz and
Jt = 6.2 Hz, H3/H30), 3.20 (2H, m, H5 and H50), 3.28 (1H, m, H1/
H10), 3.35 (1H, m, H1/H10), 3.40–3.60 (2H, m), 4.33 (1H, dd,
Jd = 6.0 Hz and Jd = 14.8 Hz), 4.39 (1H, dd, Jd = 6.0 Hz and
Jd = 14.8 Hz), 7.10 (2H, dm, Jd = 8.4 Hz), 7.18 (2H, dm, Jd = 8.4 Hz),
7.23 (4H, s), 7.34 (4H, m), 7.38 (2H, m), 7.46 (2H, dm, Jd = 8.4 Hz),
7.48 (2H, m), 9.54 (1H, t, Jt = 5.2 Hz, –C@O–NH–CH2–), 9.86 (1H,
t, Jt = 5.2 Hz, –C@O–NH–CH2–). 13C NMR (CDCl3) d 24.5, 24.5,
25.7, 25.8, 34.5, 34.7, 34.9, 34.9, 35.0, 39.7, 40.6, 40.8, 42.3, 53.9,
54.0, 60.9, 60.9, 63.5, 63.6, 119.5, 125.5, 125.5, 125.9, 126.0,
126.0, 127.4, 127.7, 127.8, 128.6, 132.5, 132.6, 137.0, 138.0,
139.8, 139.9, 141.9, 172.2, 172.3. HRMS(ES) calculated for 27 + H
m/z 769.3610. Found m/z 769.3601.
0
0
0
2.04–2.49 (6H, m, H4exo, H4exo , H6exo, H6exo , H7exo and H7exo ),
2.21 (3H, s, NCH3) 2.41 (3H, s, NCH3) 2.49 (2H, m, H2 and H20),
3.15 (1H, dt, Jd = 14.4 Hz and Jt = 6.2 Hz, H3/H30), 3.24 (1H, dt,
Jd = 14.4 Hz and Jt = 6.2 Hz, H3/H30), 3.30 (1H, m, H5/H50), 3.36
(1H, m, H5/H50), 3.47 (2H, m, H1 and H10), 4.30 (1H, dd, Jd = 5.6 Hz
and Jd = 14.8 Hz) 4.36 (1H, dd, Jd = 5.6 Hz and Jd = 14.8 Hz) 7.18 (2H,
dm, Jd = 8.0 Hz) 7.21 (2H, dm, Jd = 8.0 Hz), 7.22 (2H, dm, Jd = 8.0 Hz)
7.30–7.37 (4H, m), 7.40 (2H, m), 7.41 (2H, dm, Jd = 8.0 Hz), 7.48
(2H, dm, Jd = 8.0 Hz), 7.49 (2H, dm, Jd = 8.0 Hz), 9.87 (1H, t,
Jt = 5.0 Hz, –C@O–NH–CH2–), 12.07 (1H, s, –C@O–NH–C6H4–). 13C
NMR (CDCl3) d 24.5, 24.7, 25.8, 25.9, 34.5, 34.6, 35.1, 35.2, 40.6,
40.8, 42.3, 54.0, 54.7, 60.9, 61.0, 63.5, 63.6, 119.5, 119.6, 126.0,
126.0, 126.0, 127.8, 127.8, 127.9, 127.9, 133.8, 133.9, 134.0,
137.2, 139.6, 139.9, 142.0, 172.1. HRMS(ES) calculated for 24 + H+
m/z 741.3297. Found m/z 741.3314.
4.4.10. 1,3-Di[3-(4-thiophene-3-yl-phenyl)tropane-2-carbonyl-
aminomethyl] benzene (28)
4.4.7. 1-[3b-(4-Thiophene-3-yl-phenyl)tropane-2b-carbonyl-
amino]-2-[3b-(4-thiophene-3-yl-phenyl)tropane-2b-carbonyl-
aminobenzene-4-yl] ethane (25)
The reaction was performed with 17 mg (0.125 mmol) of 4-(2-
aminoethyl)phenyl amine. The product was purified by flash chro-
matography (99% dichloromethane, 1% triethylamine) to afford
44 mg. of a clear oil, 25 (0.059 mmol, 47%). 1H NMR (CDCl3) d
The reaction was performed with 20 mg (0.147 mmol) of meta-
xylylenediamine. The product was purified by flash chromatogra-
phy (99% dichloromethane, 1% triethylamine) to afford 50 mg of
a red solid, 28 (0.050 mmol, 34%). 1H NMR (CDCl3) d 1.64–1.78
(6H, m, H4endo, H6endo and H7endo), 2.04–2.30 (4H, m, H6exo and
H7exo), 2.20 (6H, s, NCH3), 2.27 (2H, dt, Jd = 2.4 Hz, Jd = 13.2 Hz,
H4exo), 2.68 (2H, m, H2), 3.17 (2H, dt, Jd = 13.2 Hz and Jt = 6.2 Hz,
H3), 3.29 (2H, m, H5), 3.39 (2H, m, H1), 4.34 (2H, dd, Jd = 6.0 Hz
and Jd = 14.8 Hz), 4.47 (2H, dd, Jd = 6.0 Hz and Jd = 14.8 Hz), 7.19
(8H, m) 7.36 (4H, m), 7.40 (2H, dd, Jd = 2.4 Hz and Jd = 1.6 Hz)
7.48 (4H, dm, Jd = 8.0 Hz) 9.95 (2H, t, Jt = 5.0 Hz, -C@O–NH–). 13C
NMR (CDCl3) d 24.9, 26.1, 34.9, 35.4, 41.1, 42.9, 54.3, 61.2, 64.0,
119.8, 125.8, 126.2, 126.3, 126.3, 126.8, 128.1, 128.7, 134.1,
139.7, 140.1, 142.3, 172.5.
0
0
1.44–1.82 (6H, m, H4endo, H4endo , H6endo, H6endo , H7endo and
0
0
0
H7endo ), 1.88–2.44 (6H, m, H4exo, H4exo , H6exo, H6exo , H7exo and
0
H7exo ), 2.08 (3H, s, NCH3) 2.40 (3H, s, NCH3) 2.56 (1H, m, H2/
H20), 2.61 (1H, m, H2/H20), 2.80 (2H, t, Jt = 6.6 Hz), 3.05 (1H, dt,
Jd = 13.6 Hz and Jt = 6.2 Hz, H3/H30), 3.21 (3H, m, H3/H30) 3.44
(4H, m, H5, H50, H1 and H10), 7.04 (2H, dm, Jd = 8.0 Hz), 7.14 (2H,
dm, Jd = 8.0 Hz), 7.19 (2H, dm, Jd = 8.0 Hz), 7.33 (6H, m), 7.38 (2H,
m), 7.44 (2H, dm, Jd = 8.0 Hz), 7.46 (2H, dm, Jd = 8.0 Hz), 9.53 (1H,
t, Jt = 4.8 Hz, –C@O–NH–CH2–), 11.97 (1H, s, –C@O–NH–C6H4–).
13C NMR (CDCl3) d 24.8, 25.0, 26.1, 26.2, 35.0, 35.1, 35.3, 35.4,
40.4, 40.9, 41.0, 54.4, 55.1, 61.2, 61.4, 63.8, 119.8, 125.7, 125.8,
126.2, 126.4, 128.1, 129.2, 132.8, 132.9, 134.6, 137.1, 139.9,
140.4, 142.2, 142.4, 170.5, 172.6. HRMS(ES) calculated for 25 + H
m/z 755.3453. Found m/z 755.3429.
4.5. General synthesis of 1-[3b-(4-chloro-phenyl)tropane-2b-
carbonyl-oxy]-n-[4-(3b-{4-chloro-phenyl}tropane-2b-carbonyl-
oxy-methyl)-(1,2,3)triazol-1-yl]alkane (29–33)
3b-(4-Halophenyl)tropane-2b-carboxylic acid prop-2-ynyl es-
ter, 7 or 8 (1 equiv) and 3b-(4-chlorophenyl)tropane-2b-carboxylic
acid
x-azidoalkyl ester (1 equiv) 9, 10, 11 or 12 were suspended in
4.4.8. 1,4-Di[3-(4-thiophene-3-yl-phenyl)tropane-2-carbonyl-
aminomethyl] benzene (26)
a 1:1 mixture of water and tert-butyl alcohol (4 mL). Ascorbic acid
(0.1 equiv) and copper(II) sulfate pentahydrate (0.05 equiv) was
added. The heterogeneous mixture was stirred for 44 h at room
temperature. The reaction mixture was diluted with 5 mL water
and basified to pH 9. The organic layer was separated and the aque-
ous layer was extracted with 3 ꢂ 5 mL dichloromethane. The com-
bined organic layers was dried over magnesium sulfate and
concentrated under reduced pressure.
The reaction was performed with 20 mg (0.147 mmol) of para-
xylylenediamine. The residue was purified by flash chromatogra-
phy (99% dichloromethane, 1% triethylamine) to afford 50 mg of
a white solid, 26 (0.066 mmol, 45%). 1H NMR (CDCl3) d 1.65–1.81
(6H, m, H4endo, H6endo and H7endo) 2.24–2.35 (4H, m, H6exo and
H7exo) 2.23 (6H, s, NCH3) 2.30 (2H, dt, Jd = 2.8 Hz, Jd = 12.8 Hz,
H4exo), 2.71 (2H, m, H2) 3.19 (2H, dt, Jd = 12.4 Hz and Jt = 6.4 Hz,
H3), 3.31 (2H, m, H5), 3.40 (2H, dm, Jd = 6.4 Hz, H1), 4.38 (2H, dd,
Jd = 5.6 Hz and Jd = 14.8 Hz) 4.46 (2H, dd, Jd = 5.6 Hz and
Jd = 14.8 Hz), 7.22 (4H, dm, Jd = 8.4 Hz), 7.27 (4H, s) 7.39 (4H, m),
7.43 (2H, dd, Jd = 2.4 Hz and Jd = 1.2 Hz), 7.52 (4H, dm, Jd = 8.4 Hz)
9.96 (2H, t, Jt = 5.6 Hz, –C@O–NH–). 13C NMR (CDCl3) d 25.0, 26.3,
4.5.1. 1-[3b-(4-Chloro-phenyl)tropane-2b-carbonyl-oxy]-2-[4-
(3b-{4-chloro-phenyl}tropane-2b-carbonyl-oxy-methyl)-
(1,2,3)triazol-1-yl]ethane (29)
Amount of reactants used for the reaction was; 3b-(4-chloro-
phenyl)tropane-2b-carboxylic acid prop-2-ynyl ester (7, 35 mg,

4908
S. Nielsen et al. / Bioorg. Med. Chem. 17 (2009) 4900–4909
0.11 mmol) and 3b-(4-chlorophenyl)tropane-2b-carboxylic acid 6-
azidoethyl ester (9, 42 mg, 0.11 mmol). The residue was purified by
flash chromatography (99% dichloromethane–1% triethylamine) to
afford 36 mg of a clear oil, 29 (0.052 mmol, 47%). 1H NMR (CDCl3) d
7.21 (2H, dm, Jd = 8.4 Hz), 7.24 (2H, dm, Jd = 8.4 Hz), 7.26 (2H,
dm, Jd = 8.4 Hz), 7.30 (1H, s). 13C NMR (CDCl3) d 25.1, 25.2, 25.6,
25.9, 26.4, 28.5, 28.6, 30.2, 33.2, 33.2, 33.9, 34.0, 41.8, 42.0, 50.2,
52.5, 52.7, 57.2, 62.1, 63.6, 65.0, 65.4, 123.1, 127.9, 127.8, 128.6,
128.7, 131.4, 141.6, 141.8, 143.3, 171.2, 171.5. HRMS(ES) calcu-
lated for 31 + H m/z 736.3396. Found m/z 736.3443.
0
0
0
1.56–1.72 (6H, m, H4endo, H4endo , H6endo, H6endo , H7endo and H7endo),
0
0
2.05–2.27 (4H, m, H6exo, H6exo , H7exo and H7exo ), 2.06 (3H, s, NCH3)
0
2.08 (3H, s, NCH3) 2.37 (1H, tm, Jt = 12.0 Hz, H4exo/H4exo ), 2.50 (1H,
0
0
dm, Jt = 12.0 Hz, H4exo/H4exo ), 3.81 (2H, m, H2 and H2 ), 3.89 (2H,
4.5.4. Synthesis of 1-[3b-(4-iodophenyl)tropane-2b-carbonyl-
oxy]-11-[4-(3b-{4-iodo-phenyl}tropane-2b-carbonyloxy-
methyl)-(1,2,3)triazol-1-yl] undecane (32) and 1-[3-(4-
iodophenyl)tropane-2-carbonyloxy]-11-[5-(3-{4-iodo-
phenyl}tropane-2-carbonyloxy-methyl)-(1,2,3)triazol-3-yl]
undecane (33)
From 3b-(4-iodophenyl)tropane-2b-carboxylic acid prop-2-ynyl
ester, 8 (53 mg, 0.130 mmol) and 3b-(4-iodo-phenyl)tropane-2b-
carboxylic acid 11-azido-undecyl ester, 12 (73 mg, 0.191 mmol)
were obtained a product was purified by flash chromatography
(99% dichloromethane–1% triethylamine) to afford 58 mg of a yel-
low oil consisting of 32 and 33 in a 69:31 regioisomeric ratio
(0.059 mmol, 46%). The exact structure of the major product was
not established. 1H NMR (CDCl3), 32 d 1.07–1.30 (14H, m) 1.38
dt, Jd = 12.8 Hz and Jt = 5.6 Hz, H3 and H30), 3.27 (2H, m, H5 and
H50), 3.39 (1H, m, H1/H10), 3.46 (1H, m, H1/H10), 4.18 (2H, m),
4.30 (1H, m), 4.39 (1H, m), 5.01 (2H, s), 7.06 (2H, dm, Jd = 8.4 Hz),
7.08 (2H, dm, Jd = 8.4 Hz), 7.11 (2H, dm, Jd = 8.4 Hz), 7.15 (2H,
dm, Jd = 8.4 Hz), 7.28 (1H, s). 13C NMR (CDCl3) d 24.6, 24.7, 25.4,
32.6, 32.7, 33.3, 33.4, 41.3, 41.3, 49.2, 52.0, 52.1, 57.1, 61.3, 61.6,
63.1, 64.5, 64.7, 123.4, 127.4, 127.6, 128.0, 128.2, 130.9, 131.1,
140.8, 141.0, 143.8, 170.6. HRMS(ES) calculated for 29 + H m/z
666.2614. Found m/z 666.2627.
4.5.2. 1-[3b-(4-Chloro-phenyl)tropane-2b-carbonyl-oxy]-6-[4-
(3b-{4-chloro-phenyl}tropane-2b-carbonyl-oxy-methyl)-
(1,2,3)triazol-1-yl]hexane (30)
0
0
Amount of reactants used for the reaction was; 3b-(4-chloro-
phenyl)tropane-2b-carboxylic acid prop-2-ynyl ester, 7 (66 mg,
0.208 mmol) and 3b-(4-chlorophenyl)tropane-2b-carboxylic acid
6-azido-hexyl ester 10 (84 mg, 0.208 mmol). The product was puri-
fied by flash chromatography (99% dichloromethane–1% triethyl-
amine) to afford 0.112 g of a white solid, 30 (0.155 mmol, 75%).
1H NMR (CDCl3) d 1.21 (4H, m), 1.42 (2H, quint, Jquint = 7.2 Hz),
(2H, m) 1.49–1.67 (6H, m, H4endo, H4endo , H6endo, H6endo , H7endo
0
0
and H7endo ), 1.78 (2H, m), 1.98–2.16 (4H, m, H6exo, H6exo , H7exo
and H7exo ), 2.07 (3H, s, NCH3), 2.14 (3H, s, NCH3), 2.46 (2H, m,
0
0
0
0
H4exo and H4exo ), 2.78–2.89 (2H, m, H2, H2 , H3 and H3 ), 3.28
(2H, m, H5 and H50), 3.48 (2H, m, H1 and H10), 3.73 (1H, dt,
Jt = 6.4 Hz and Jd = 10.8 Hz), 3.93 (1H, dt, Jt = 6.4 Hz and
Jd = 10.8 Hz), 4.21 (2H, t, Jt = 7.4 Hz), 4.99 (1H, d, Jd = 12.8 Hz),
5.05 (1H, d, Jd = 12.8 Hz), 7.91 (2H, dm, Jd = 8.0 Hz), 7.93 (2H, dm,
Jd = 8.0 Hz), 7.12 (1H, s), 7.47 (2H, dm, Jd = 8.0 Hz), 7.51 (2H, dm,
Jd = 8.0 Hz). 13C NMR (CDCl3), 32 d 24.6, 25.3, 25.9, 28.0, 28.4,
28.7, 28.8, 28.9, 29.8, 32.8, 32.8, 33.2, 33.3, 41.3, 41.4, 49.9, 51.9,
52.1, 56.7, 61.6, 63.3, 64.5, 64.8, 90.4, 122.6, 128.9, 129.0, 136.3,
142.6, 142.7, 170.7, 171.0. HRMS(ES) calculated for 32/33 + H m/z
976.2735. Found m/z 976.2748. 1H NMR (CDCl3), 33 d 1.07–1.30
0
0
0
1.54–1.74 (6H, m, H4endo, H4endo , H6endo, H6endo , H7endo and
0
H7endo ), 1.79 (2H, quint, Jquint = 7.2 Hz), 2.02–2.25 (4H, m, H6exo
,
0
0
H6exo , H7exo and H7exo ), 2.13 (3H, s, NCH3) 2.19 (3H, s, NCH3),
0
2.51 (1H, dt, Jd = 2.8 Hz and Jt = 12.8 Hz, H4exo/H4exo ), 2.54 (1H,
0
0
dt, Jd = 2.8 Hz and Jt = 12.8 Hz, H4exo/H4exo ), 2.85 (1H, m, H2/H2 ),
2.89 (1H, m, H2/H20), 2.93 (1H, m, H3/H30), 2.96 (1H, m, H3/H30),
3.33 (1H, m, H5/H50), 3.34 (1H, m, H5/H50), 3.52 (dm, Jd = 6.4 Hz,
H1/H10), 3.53 (dm, Jd = 6.4 Hz, H1/H10), 3.80 (dt, Jt = 6.4 Hz and
Jd = 10.0 Hz), 3.97 (dt, Jt = 6.4 Hz and Jd = 10.0 Hz), 4.22 (2H, t,
Jt = 7.2 Hz), 5.05 (1H, d, Jd = 12.8 Hz), 5.09 (1H, d, Jd = 12.8 Hz),
7.14 (2H, dm, Jd = 8.5 Hz), 7.16 (2H, dm, Jd = 8.5 Hz), 7.18 (2H,
dm, Jd = 8.5 Hz), 7.20 (2H, dm, Jd = 8.5 Hz), 7.20 (1H, s). 13C NMR
(CDCl3) d 24.8, 24.8, 24.9, 25.5, 25.7, 28.1, 29.7, 32.8, 33.5, 33.6,
41.5, 42.6, 49.8, 52.1, 52.3, 56.8, 61.8, 63.0, 64.6, 65.0, 122.7,
127.5, 127.6, 128.3, 128.4, 131.0, 141.2, 141.4, 142.9, 170.8,
171.1. HRMS(ES) calculated for 30 + H m/z 722.3240. Found m/z
722.3214.
(14H, m), 1.38 (2H, m), 1.49–1.67 (6H, m, H4endo, H4endo , H6endo
H6endo , H7endo and H7endo ), 1.78 (2H, m), 1.98–2.16 (4H, m, H6exo
,
,
0
0
0
H6exo‘, H7exo and H7exo ), 2.07 (3H, s, NCH3), 2.14 (3H, s, NCH3),
2.46 (2H, m, H4exo and H4exo‘), 2.78–2.89 (4H, m, H2, H20, H3 and
H30), 3.28 (2H, m, H5 and H50), 3.48 (2H, m, H1 and H10), 3.73
(1H, dt, Jt = 6.4 Hz and Jd = 10.8 Hz), 3.93 (1H, dt, Jt = 6.4 Hz and
Jd = 10.8 Hz), 4.27 (2H, t, Jt = 7.4 Hz), 4.92 (1H, d, Jd = 12.8 Hz),
4.96 (1H, d, Jd = 12.8 Hz), 7.91 (2H, dm, Jd = 8.0 Hz), 7.93 (2H, dm,
Jd = 8.0 Hz), 7.20 (1H, s), 7.47 (2H, dm, Jd = 8.0 Hz), 7.51 (2H, dm,
Jd = 8.0 Hz). 13C NMR (CDCl3), 33 d 24.6, 25.3, 25.9, 28.0, 28.4,
28.7, 28.8, 28.9, 29.8, 32.8, 32.8, 33.2, 33.3, 41.3, 41.4, 49.9, 51.9,
52.1, 56.7, 61.6, 63.3, 64.5, 64.8, 90.4, 128.9, 129.0, 129.1, 136.3,
136.7, 142.6, 170.7, 171.0.
4.5.3. 1-[3b-(4-Chloro-phenyl)tropane-2b-carbonyl-oxy]-7-[4-
(3b-{4-chloro-phenyl}tropane-2b-carbonyl-oxy-methyl)-
(1,2,3)triazol-1-yl] heptane (31)
The amounts used was for 3b-(4-chlorophenyl)tropane-2b-car-
boxylic acid prop-2-ynyl ester, 7 (53 mg, 0.17 mmol) and for 3b-(4-
chlorophenyl)tropane-2b-carboxylic acid 6-azidoheptyl ester 11
(58 mg, 0.17 mmol). The residue was purified with flash chroma-
tography (99% dichloromethane–1% triethylamine) to afford
37 mg of a clear oil, 31 (0.056 mmol, 33%). 1H NMR (CDCl3) d
1.28–1.56 (6H, m), 1.47 (2H, quint, Jquint = 7.2 Hz), 1.58–1.79 (6H,
4.5.5. 5-(4-Trimethylsilyl-1H-1,2,3-triazol-1-yl)pentan-1-ol (35)
A solution of 5-chloro-1-pentanol (34, 0.90 mL, 7.7 mmol), so-
dium azide (751 mg, 11.6 mmol) and tetrabutylammonium iodide
(291 mg, 0.79 mmol) in 4 mL DMF was stirred for 2 days at room
temperature. The mixture was diluted with 50 mL H2O and ex-
tracted with 5x25 mL diethyl ether. The combined organic phases
were washed with 25 mL H2O and 25 mL brine, dried over MgSO4.
Removal of the solvent at atmospheric pressure and room temper-
ature afforded 766 mg of 5-azidopentan-1-ol (5.93 mmol, 77%) as a
colourless oil. 1H NMR (CDCl3) d 1.35 (1H, br s, OH), 1.42–1.50 (2H,
m), 1.57–1.68 (4H, m), 3.29 (2H, t, J = 6.8 Hz), 3.67 (2H, t, J = 6.8 Hz,
H5). The crude 5-azidopent-1-ol (600 mg, 4.65 mmol) was taken
up in 10 mL H2O/tert-butanol (1:1). To the solution was added tri-
methylsilyl acetylene (0.66 mL, 4.67 mmol), CuSO4 (37 mg,
0.23 mmol) and sodium ascorbate (275 mg, 1.39 mmol). After 5 h
of stirring at room temperature, additionally CuSO4 (37 mg,
0.23 mmol) and sodium ascorbate (275 mg, 1.39 mmol) was
0
0
0
m, H4endo, H4endo , H6endo, H6endo , H7endo and H7endo ), 1.86 (2H,
0
quint, Jquint = 7.2 Hz), 2.08–2.29 (4H, m, H6exo, H6exo , H7exo and
0
H7exo ), 2.19 (3H, s, NCH3), 2.25 (3H, s, NCH3), 2.57 (1H, dt,
0
Jd = 2.4 Hz and Jt = 12.4 Hz, H4exo/H4exo ), 2.60 (1H, dt, Jd = 2.4 Hz
0
0
and Jt = 12.4 Hz, H4exo/H4exo ), 2.91 (1H, m, H2/H2 ), 2.94 (1H, m,
H2/H20), 2.99 (1H, m, H3/H30), 3.01 (1H, m, H3/H30), 3.39 (1H, m,
H5/H50), 3.40 (1H, m, H5/H50), 3.58 (1H, m, H1/H10), 3.60 (1H, m,
H1/H10), 3.85 (1H, dt, Jt = 6.6 Hz and Jd = 10.8 Hz), 3.93 (1H, dt,
Jt = 6.6 Hz and Jd = 10.8 Hz), 4.22 (2H, t, Jt = 7.2 Hz), 5.10 (1H, d,
Jd = 12.8 Hz), 5.15 (1H, d, Jd = 12.8 Hz), 7.19 (2H, dm, Jd = 8.4 Hz),

S. Nielsen et al. / Bioorg. Med. Chem. 17 (2009) 4900–4909
4909
added. The mixture was stirred for 12 h, diluted with 50 mL H2O
and extracted with 3 ꢂ 25 mL EtOAc. The combined organic layers
were washed with 25 mL 5% NH4OH and 25 mL brine and dried
over MgSO4 before the solvents were removed at reduced pressure.
Flash chromatography (60% EtOAc/40% CH2Cl2) afforded 35
(548 mg, 2.41 mmol, 52%) as a colourless oil. 1H NMR (CDCl3) d
0.31 (9H, s), 1.38–1.46 (2H, m), 1.57–1.64 (2H, m), 1.89 (1H, br s,
OH), 1.94 (2H, quint, J = 7.6 Hz), 3.64 (2H, t, J = 6.4 Hz), 4.37 (2H,
t, J = 7.6 Hz), 7.49 (1H, s). 13C NMR (CDCl3) d -1.0, 23.0, 30.4, 32.1,
49.8, 62.5, 128.9, 146.6. HRMS(ES) calculated for 35 + Na m/z
250.1352. Found m/z 250.1346.
in ice-cold PBSCM by centrifugation, homogenizing the cells in ice-
cold Harvest Buffer I (150 mM NaCl, 50 mM Tris, 20 mM EDTA)
using a Ultra-Turrax (Janke & Kunkel AG) for 60 s. Membrane
was pelleted by centrifugation at 12,000g for 10 min at 4 °C and
washed in ice-cold Harvest Buffer I. The membranes were pelleted
again and finally resuspended in PBSCM using the Ultraturrax
briefly. Membrane preparations were aliquoted into 2 mL portions
and stored at ꢀ80 °C until use. The concentration of total protein in
the membrane preparation was determined with the MicroBCA kit
(Pierce). A concentration of 5 lg/well of membrane preparation
was used with the nominated concentration of drug of interest in
combination with 0.1–0.25 nM 125I-(2). Membrane and ligands
were incubated for 1 h at 20 °C. Using a Filtermate cellharvester
(Packard) membranes were captured on GF/B 96-well filter plates
(Packard) pre-soaked with 0.5% polyethyleneimine (Merck) and
washed thrice with ice-cold water. The filter in each well was dis-
4.5.6. 5-(1H-1,2,3-Triazol-1-yl)pentan-1-ol (36)
To a solution of 5-(4-trimethylsilyl-1H-123-triazol-1-yl)pen-
tan-1-ol (35, 477 mg, 2.10 mmol)) in 10 mL THF was added tetra-
butylammonium fluoride (1 M in THF, 2.60 mL, 2.60 mmol), and
the reaction mixture was heated to 50 °C. After 18 h the crude mix-
ture was evaporated to dryness at reduced pressure. Flash chroma-
tography (5% methanol–95% dichloromethane) gave 36 (314 mg,
2.02 mmol, 96%) as a colourless oil. 1H NMR (CDCl3) d 1.38–1.46
(2H, m), 1.55 (1H, br s, OH), 1.61 (2H, m), 1.96 (2H, quint,
J = 7.2 Hz), 3.65 (2H, t, J = 6.4 Hz), 4.41 (2H, t, J = 7.2 Hz), 7.54
(1H, s), 7.70 (1H, s). 13C NMR (CDCl3) d 22.9, 30.2, 32.0, 50.2,
62.3, 123.4, 133.9. HRMS(ES) calculated for 36 + Na m/z
178.0956. Found m/z 178.0948.
solved in 40
mined with
l
L Microscint 20 and scintillation counts were deter-
a
Packard Topcounter. Precise concentration of
radioligand was quantified by liquid scintillation counting on a
Packard Tri-Carb.
Acknowledgements
We kindly acknowledge OChem Graduate School, Aarhus
University for support and Bente Ladegaard for skilful technical
assistance.
4.5.7. 1-[3b-(4-Chlorophenyl)tropane-2b-carbonyl-oxy]-5-
[(1,2,3)triazol-1-yl]pentane (37)
3b-(4-Chlorophenyl)tropane-2b-carboxylic acid (4, 240 mg,
0.86 mmol) was dissolved in 3.5 mL dry dichloromethane. Oxalyl
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.bmc.2009.06.007.
chloride (90
lL, 1.0 mmol) and dry DMF (20 lL, 0.26 mmol) and
the mixture was stirred at room temperature. After 3 h the reaction
mixture was evaporated to dryness at reduced pressure, and the
crude residue was taken up in 3 mL dry THF. 5-(1,2,3-Trizole-1-
yl)pentan-1-ol (36, 105 mg, 0.68 mmol) and freshly distilled trieth-
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Expression of the three monoamine transporters in COS-1 cells
was achieved by stable transfection with the pIRES vector (Invitro-
gen) carrying the cDNA of the transporters. Membrane prepara-
tions for the binding assay were produced by scraping the stably
transfected cells from cell culture dishes (Nunc), pelleting the cells