Synthesis, inhibition and binding of simple non-nitrogen inhibitors of monoamine transporters

Article abstract of DOI:10.1016/j.bmc.2007.03.069

A series of simple truncated analogues of phenyl tropanes, 2-arylcycloalk-1-enyl carboxylic acid methylesters, were prepared and investigated for their activity towards the dopamine, serotonin and norepinephrine transporters. The compounds were prepared f

Full text of DOI:10.1016/j.bmc.2007.03.069

Bioorganic & Medicinal Chemistry 15 (2007) 4159–4174
Synthesis, inhibition and binding of simple non-nitrogen
inhibitors of monoamine transporters
a
a
a
a
˚
Mikkel Due Petersen, Søren Valdgard Boye, Erik Holm Nielsen, Jeanette Willumsen,
Steffen Sinning,b Ove Wiborgb and Mikael Bolsa,*
aDepartment of Chemistry, University of Aarhus, Langelandsgade 140, DK-8000 Aarhus C, Denmark
bDepartment of Biological Psychiatry, Psychiatric, University Hospital, Skovagervej 2, DK-8240 Risskov, Denmark
Received 18 September 2006; revised 20 March 2007; accepted 23 March 2007
Available online 30 March 2007
Abstract—A series of simple truncated analogues of phenyl tropanes, 2-arylcycloalk-1-enyl carboxylic acid methylesters, were pre-
pared and investigated for their activity towards the dopamine, serotonin and norepinephrine transporters. The compounds were
prepared from cyclic ketoesters, which were converted to enolic triflates and reacted with arylboronates using the Suzuki coupling.
For comparison the corresponding piperidines were also made and investigated. The new compounds inhibit monoamine-transport-
ers with Ki values ranging from 0.1 to 1000 lM.
ꢀ 2007 Elsevier Ltd. All rights reserved.
1. Introduction
in vivo in various physiologic and pathologic conditions
such as psychiatric diseases and addiction.3
The three classical monoamine neurotransmitters dopa-
mine (DA), serotonin (5-HT) and norepinephrine (NE)
control a variety of functions such as appetite, sleep,
mood and locomotor activity in the central nervous sys-
tem. NE is also the major neurotransmitter in the post-
ganglionic synapses in the sympathetic nervous system.
The transporters for these three neurotransmitters, the
dopamine, serotonin and norepinephrine transporters
(DAT, SERT and NET, respectively) have an important
role in terminating the signals from neurons releasing
these neurotransmitters, and also serve as targets for
antidepressants and several addictive drugs.
Cocaine is a psychomotor stimulant, abuse of which is a
growing problem in the western world. Cocaine exerts
its effect by acting as an inhibitor of the monoamine
transporters, thereby increasing the concentration of
the monoamines in their respective synapses. It is mainly
the inhibition of DAT in the mesolimbic dopamine sys-
tem that is thought to be responsible for cocaine’s stim-
ulating and addictive properties,4 although SERT
inhibition probably also plays a role in the addictive
properties. The mesolimbic dopamine system is com-
prised of dopamine neurons that have their cell bodies
in the ventral tegmental area (VTA) of the midbrain
and these neurons projections to the limbic forebrain.
Especially the projection to the nucleus accumbens
(NAc) in the limbic forebrain is thought to be impor-
tant. The VTA-NAc is a key detector of rewarding stim-
ulus, and it is generally thought that NAc is the key
target for all substances of abuse, resulting in a change
in the biochemistry of the reward circuits.5 The impor-
tance of DAT in the rewarding effect of cocaine has been
confirmed in many experiments.6
In the early 1990s the genes coding for the three trans-
porters were cloned, which led to a significant increase
in our knowledge about the precise location of these
transporters (e.g., in situ hybridisation)1 and the role
of these transporters in addiction by the construction
of knockout mice.2
Later, PET (Positron Emission Tomography) studies
with DAT, SERT or NET selective PET ligands were
used to examine the activities of these transporters
Despite extensive research no pharmacologic treatment
for cocaine abuse currently exists. Several strategies
interfering with the dopamine system are currently
under investigation.7 One interesting strategy is the use
Keywords: Inhibitors; Monoamine transporters; Cocaine analogues;
Suzuki coupling.
*
Corresponding author. E-mail: mb@chem.au.dk
0968-0896/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2007.03.069

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M. D. Petersen et al. / Bioorg. Med. Chem. 15 (2007) 4159–4174
of a partial cocaine agonist: compounds that bind to
DAT and inhibit the uptake of dopamine, though less
effective than cocaine. Such a compound should have
a significantly better binding affinity for DAT than co-
caine, and ideally have long duration of action and a
slow absorption to the brain. To select such a compound
the discrimination ratio8 (DR) has been defined as the
compounds’ Ki for inhibition of dopamine uptake, di-
vided by the corresponding Ki for DAT binding.
Although the validity of the DR has been questioned9,
and some compounds with DR values more than 10
have shown in vivo pharmacological activity very simi-
lar to that of cocaine,10,11 a DR above 10 is still a useful
criterion for selecting a cocaine antagonist or partial
agonist.
or on substituents on the phenyl ring. These studies have
resulted in compounds with a high affinity and high
selectivity for each of the individual transporters.
Meltzer et al. have shown that the basic nitrogen in the
tropane skeleton is not essential for binding. Oxa and
carba analogues 1b and 1c (Fig. 2) were only four and
eight-fold less potent than 1a for binding to DAT.17–19
They also found that the unsaturated analogues 2a–c
had similar potency as 1a–c on DAT.17–19 Kozikowski
et al. have shown that the bicyclic system of the tropane
ring is not essential for binding. In one study they tested
compounds without the C6–C7 bridge, giving the mono-
cyclic piperidine analogue 3a,20 these compounds were
only slightly less potent than their tropane analogues.
Meltzer et al. have even shown that very simple biaryls
such as 4 (Fig. 2), which have no nitrogen and a mono-
cyclic core, bind to DAT and SERT from brain tissues
of cynomolgus monkey.18 They found this compound
to have an IC50 value for DAT binding that was 1.5
times higher than that of cocaine, which is surprisingly
potent.
PET studies have shown that the level of the monoamine
transporters in many psychiatric and neurological
conditions such as Parkinson disease, depression and
Attention-Deficit Hyperactivity Disorder (ADHD) is
altered.12 Polymorphisms in the genes coding for mono-
amine transporters are thought to be associated with in-
creased vulnerability to diseases such as depression and
ADHD.13
These findings led us to speculate as to the significance
of the bicyclic system and the significance of the nitro-
gen atom. We therefore decided to investigate a series
of simplified analogues 6, 7 and 8 (Fig. 2 and Table 1)
that more resemble tropane or piperidines than 4, but
nevertheless do not have the bicyclic system or the nitro-
gen. Compound 7 is a carba analogue of the piperidine 3
(with an additional unsaturation), while 8 can be seen as
an analogue of the phenyl tropane 2a with the nitrogen
bridge deleted. We have also prepared piperidine
analogues to 3 and unsaturated piperidines such as 5d
(Table 1), to see the effect of unsaturation and to gauge
the behaviour of these compounds in our assays. This is
likely to have only a marginal effect because studies have
shown this substitution does not affect binding in the
tropane family.14a Previous experience has shown us
that we often obtain higher Ki values than that obtained
in work with brain homogenates.21
Because of the variety of roles the monoamine trans-
porters play in neurophysiology, many different classes
of inhibitors have been developed.14 One potent class
of inhibitors is the phenyl tropanes such as RTI-5515
and WIN 35065-216 (Fig. 1). These compounds, struc-
turally based on cocaine, show an improved binding to
the monoamine transporters compared to cocaine and
display a varied selectivity for DAT.13 A great number
of compounds have been synthesized based on the phe-
nyl tropanes. Most of this research has focused on var-
iation on either the nitrogen substituent, the ester group
COOMe
OBz
COOMe
COOMe
I
MeN
MeN
MeN
In the present work, we report the synthesis of these
three types of very simplified phenyl tropane analogues
and their binding and inhibition on DAT, SERT and
WIN 35065-2
RTI-55
Cocaine
Figure 1. Cocaine and phenyltropanes.
COOMe
X
COOMe
COOMe
COOMe
MeN
Cl
Cl
X
Cl
Cl
Cl
Cl
4
3a
2a
2b
2c X=CH2
X=NCH3
X=O
1a
X=NCH3
1b X=O
1c
X=CH2
COOMe
COOMe
COOMe
COOMe
HN
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
5a
6a
7a
8a
Figure 2. Analogues of phenyltropanes and target compounds.

M. D. Petersen et al. / Bioorg. Med. Chem. 15 (2007) 4159–4174
4161
Table 1. Binding of piperidine derivatives 3, 5, 10 to monoamine
transportersa
respectively, of the para-iodinated compounds 3c and
10c of which 3c is a monocyclic analogue of RTI-55.
Binding[125I]RTI-55 Ki (lM)
We then synthesized a,b-unsaturated analogues of Kozi-
kowski’s piperidine 3 (Scheme 2). The Boc protected
piperidone 1122 was converted to the triflate 12 using tri-
flic anhydride/NaH,23 this triflate was used in a Suzuki
reaction to give 13a,d,q. Deprotection of 13a,d,q with
trifluoroacetic acid gave the products 5a,d,q. As seen
from Scheme 1 these compounds were synthesized as
the ethyl esters (unlike most of the compounds in this
study which were methyl esters), but this is likely to have
only a marginal effect, because studies have shown that
this substitution does not affect binding in the tropane
family.24
DAT
SERT
NET
Cocaine
RTI-55
3a
0.630 0.125
0.004 0.001
0.322 0.021
59.4 1.9
0.965 0.138
0.006 0.003
1.85 0.08
13.8 0.7
0.887 0.162
0.034 0.020
3.91 0.54
41.6 14.7
35.2 5.0
36.3 5.2
0.855 0.793
2.3 1.94
0.268 0.096
2.5
ent-3a
( )-3b
( )-10b
( )-3c
( )-10c
5d
8.51 0.33
17.4 1.1
27.0 1.0
46.7 3.2
0.323 0.194
1.25 0.681
0.079 0.017
0.922
0.287 0.202
2.81 0.21
0.440 0.155
0.217
5ab
5q
20.6 4.2
3.00 0.94
10.0 2.2
ent-3a is the enantiomer of 3a.
a Values are expressed as means SEM from at least three indepen-
dent experiments each conducted with duplicate determinations.
b The value is the result of a single experiment conducted with dupli-
cate determinations.
Synthesis of the carba-analogues 6–8 is outlined in
Scheme 3. This synthesis follows the same steps as the
synthesis of 5a–q. The commercially available ketoesters
14–16 were converted to the enoltriflates 17–19 using
triflic anhydride/NaH. This gave the triflates in 95–
99% yield.25,26 The triflates were used in a Suzuki cou-
pling with various aryl boronic acids, using Pd(OAc)2
as the palladium source and triphenylphosphine as the
ligand, to give the compounds 6–8. For comparison
compound 4 was prepared by published methods.19
NET. Although these compounds only bind with mod-
erate potency to the transporters, the manner in which
they bind is probably similar to cocaine.
2. Chemistry
Some of the coupling products were hydrogenated giv-
ing the saturated derivatives 21–22 (Scheme 4), that
are comparable to 3b. Attempts to saturate some of
the chlorinated compounds failed because dehalogen-
ation competed with hydrogenation of the double bond.
As control compounds for our assay we prepared Kozi-
kowsky’s saturated piperidines 3a and ent-3a according
to published methods.20 We also made the racemic phe-
nyl analogues 3b and 10b using this method (Scheme 1):
Arecholine was reacted with phenylmagnesium bromide
at À10 ꢁC giving after separation 20% cis-isomer 3b and
12% trans-isomer 10b. These compounds were iodinated
with iodine and silver triflate giving 58% and 44%,
It is known that the presence of an n-propyl group in the
2-position instead of the normal methylester group can
increase the DAT binding 25-fold for the piperidine
a
COOMe
Ph
COOMe
Ph
COOMe
MeN
MeN
MeN
+
b
b
9
3b
10b
COOMe
COOMe
MeN
MeN
I
I
10c
3c
Scheme 1. Synthesis of saturated piperidines. Reagents and conditions: (a) PhMgBr, À10 ꢁC; (b) I2, Ag(OTf)2, 25 ꢁC.
a
b
c
COOEt
OTf
COOEt
Ar
COOEt
Ar
COOEt
O
BocN
BocN
HN
BocN
11
13a,d,q
q:
12
Ar = 3,4-di-chlorophenyl,
5a,d,q
a:
d:
Ar = 2-naphthyl,
Ar = 3-nitro-phenyl
Scheme 2. Synthesis of a,b-unsaturated piperidines. Reagents and conditions: (a) NaH, Tf2O, Et2O, 0 ꢁC; (b) ArB(OH)2, Pd(OAc)2, PPh3, Na2CO3,
EtOH/Benzene, 65 ꢁC; (c) TFA, DCM.

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M. D. Petersen et al. / Bioorg. Med. Chem. 15 (2007) 4159–4174
n
n
n
a
b
COOMe
COOMe
COOMe
O
OTf
Ar
: n=1
: n=2
: n=3
: n=1
: n=2
: n=3
: n=1
6
: n=2
7
: n=3
8
14
15
16
17
18
19
Scheme 3. Synthesis of a,b-unsaturated b-arylesters. Reagents and conditions: (a) NaH, Tf2O, Et2O, 0 ꢁC; (b) ArB(OH)2, Pd(OAc)2, PPh3, Na2CO3,
EtOH/benzene, 65 ꢁC.
3.2. Uptake assay
n
n
a
For the uptake assay stably transfected cells were seeded
in 96 well microplates (Nunc) and grown at 37 ꢁC, 5%
CO2, 95% humidity for two days. Prior to the IC50 assay
the medium was aspired and the cells were washed in
PBSCM (137 mM NaCl, 2.7 mM KCl, 4.3 mM Na2H-
PO4, 1.4 mM KH2PO4, 0.1 mM CaCl2 and 1 mM
MgCl2,, pH 7.4) on an automatic microplate washer.
The dilution series of the drug in PBSCM were added
to the adhering cells for 30 min of preincubation to
allow equilibration of binding before the uptake was ini-
tiated by the addition of 30–100 nM tritiated 5-HT (Per-
kin–Elmer Life Sciences) or DA (Amersham Bisciences)
mixed with the dilution series of the drug. Accumulation
of 5-HT or DA was allowed to proceed for 10 min at
20 ꢁC and the assay was terminated by aspiration of
the uptake media and washing with PBSCM. Scintillant
(MicroScint 20 from Packard) was used to solubilize
cells and accumulated radioactivity was quantified on
a Packard Topcounter. Concentration of substrate was
quantified by liquid scintillation counting on a Packard
Tri-Carb.
COOMe
COOMe
Ar
Ar
: n=2
7
: n=3
8
: n=2
: n=3
21
22
Scheme 4. Preparation of saturated b-arylester. Reagents: (a) Pd/C,
H2, EtOH.
analogues 3,20 a trend not observed in the phenyl
tropanes27. To test this modification of our compounds,
25 was synthesized (Scheme 3) as a mixture of cis and
trans isomers (1:1). First the ester group in 7a was re-
duced with LiAlH4. The resulting primary alcohol 23
was converted to the aldehyde 24 by a Swern oxidation,
and 24 was finally converted to 25 by a Wittig reaction.
We chose not to reduce the double bond on the propyl
side chain, because of the risk of dehalogenation, so
25 was a 1:1 mixture of cis and trans isomers (Scheme 5).
3. Biology
3.3. Binding assay
3.1. Cell culture
Membrane preparations for the binding assay were pro-
duced by scraping the stably transfected cells from cell
culture dishes (Nunc), pelleting the cells in ice-cold
PBSCM by centrifugation and homogenising 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 Ultratur-
rax briefly. Membrane preparations were aliquoted into
2 mL portions and stored at À80 ꢁC until use. The con-
centration of total protein in the membrane preparation
was determined with the MicroBCA kit (Pierce).
Cell lines stably expressing hSERT, hDAT or hNET
were established by transfecting COS-1 cells with
hSERT/hDAT/hNET inserted in the pIRES vector
(BD Biosciences Clontech) also carrying a Blasticidin
resistance gene. Cells were cultured in DMEM (Bio-
Whitaker) supplemented with 10% FCS (Gibco Life
Technologies), 1% Penicillin/Streptomycin (BioWhitaker)
and 10 lg/mL of Blasticidin (Cayla) selection of trans-
fected cells. After 14 days of selection Blasticidin was
adjusted to 2 lg/mL in the culture medium and cells
were subcultured under this selection regime and grown
at 37 ꢁC, 5% CO2, 95% humidity.
COOMe
OH
O
a
b
c
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
7a
23
24
25
Scheme 5. Synthesis of 25. Reagents and conditions: (a) LiAlH4, ether, reflux; (b) DMSO, oxalylchloride, NEt3, À78 ꢁC; (c) EtPPh3Br, BuLi, 0 ꢁC.

M. D. Petersen et al. / Bioorg. Med. Chem. 15 (2007) 4159–4174
4163
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-RTI-55.
Membrane and ligands were incubated for 1 h at
20 ꢁC. Using a Filtermate cellharvester (Packard) mem-
branes were captured on GF/B 96-well filterplates
(Packard) presoaked with 0.5% polyethyleneimine
(Merck) and washed twice with ice cold water. The filter
in each well was dissolved in 40 lL Microscint 20 and
scintillationcounts were determined with a Packard
Topcounter. Precise concentration of radioligand was
quantified by liquid scintillation counting on a Packard
Tri-Carb.
linear regression tool in the Graphpad Prism 3 software.
From at least three independent experiments the result-
ing IC50 values were transformed to Ki values using the
equation described by Cheng and Prusoff.28
4. Results and discussion
The new compounds and the controls 3a, ent-3a, 4 were
screened for inhibition of RTI-55 binding, and in some
cases inhibition of uptake, on hDAT, hNET and
hSERT. The results of this are shown in Table 1 (piperi-
dines), Table 2 (unsaturated compounds) and Table 3
(saturated compounds).
3.4. Data analysis
First it is noted that the Ki values for hDAT of 3a and
ent-3a are over 10 times higher than the IC50 values
reported for binding to rat striatal membrane, which
Counts from the Packard Topcounter were fitted to a
sigmoidal dose–response curve using the built-in non-
Table 2. Binding and uptake of the non-nitrogen containing compounds 6–8 to monoamine transportersa
COOMe
COOMe
COOMe
X
X
X
Y
Y
Y
7
8
6
X
Y
Binding[125I]RTI-55 Ki (lM)
Uptake Ki (lM)
DAT
SERT
NET
[3H]DA
[3H]SER
[3H]DA (NET)
Co-caine
RTI-55
4b
0.630 0.125
0.004 0.001
4.06
0.965 0.138
0.006 0.003
620
0.887 0.162
0.034 0.020
46.7
0.347 0.150
0.009 0.006
—
0.524 0.223
0.004 0.003
0.182 0.058
0.010 0.008
—
—
—
6a
6b
Cl
Cl
H
Cl
H
1.9 0.3
785 268
2840 912
2240 443
417 188
2690 920
1460 380
3800 175
3388 315
296 62
11 11
5.5 0.4
2.1 0.8
3.3 1.2
7.0 0.7
6.3 3.9
—
28
178 70
5
18
34
9
8
420 28
470 215
39 52
—
—
6c
6d
Cl
285 138
26
–(CH)4–
4.1 0.4
140 52
302 87
2649 765
—
—
—
4
6f
6g
OMe
t-Bu
OCF3
SO2Me
COMe
H
H
550 57
789 122
2884 749
—
1390 45
—
—
H
—
—
6h
6i
H
—
—
H
—
1161 40
2904 826
—
6j
H
335 33
875 96
6.54 7.72
2.1 0.3
85 23
240 30
1318 211
111 45
49 17
121 29
—
646 99
247 32
—
6k
6p
NH2
H
1950 197
1141 400
228 34
NO2
Cl
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
7a
7b
Cl
H
14
5
0.625 0.245
0.589 0.021
4.9 28
314 82
871 524
Cl
H
1860 858
1180 629
109 29
993 278
339 146
81 19
7c
7d
Cl
–(CH@CH)2–
22 5
12 0.7
26 7
1.5 0.8
10
—
—
—
—
—
—
499
—
7
7e
7g
Ph
H
264 151
605 272
1660 270
630 186
1050 136
590 114
231 42
841 304
2250 1320
4680 702
668 177
5020 586
4710 657
573 49
215 78
1100 759
2540 451
2500 422
2110 270
2020 346
675 144
121 27
15 3.7
—
—
t-Bu
OCF3
H
H
7h
7l
H
—
—
H
7m
7n
H
CF3
H
—
—
CF3
OH
H
7o
7q
H
—
—
3
NO2
Cl
H
239 30
1.36 0.33
15 1.7
28.7 10.9
149 35
706 59
8a
8b
Cl
Cl
0.515 0.246
2.2 1.0
3.78 1.41
—
4.72 2.21
84 24
85 23
20 11
—
—
8c
8d
H
Cl
22
5
463 89
532 48
–(CH@CH)2–
Ph
t-Bu
392 57
2.0 0.1
884 140
68 0.2
13 1.3
8e
8g
H
32
3
0.81 0.35
—
42 70
3.9 2.3
—
—
H
1040 69
381 85
62 12
255 137
25
11
5
—, Not determined.
a Values are expressed as mean SEM from at least three independent experiments each conducted with duplicate determinations.
b The value is the result of two independent experiments each conducted with duplicate determinations.

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M. D. Petersen et al. / Bioorg. Med. Chem. 15 (2007) 4159–4174
Table 3. Binding and uptake of the saturated compounds 21–22 to monoamine transporters
COOMe
COOMe
X
X
Y
Y
22
21
Structure
Binding[125I]RTI-55 Ki (lM)
X
Y
DAT
SERT
NET
21e
21g
21h
21l
Ph
H
830 813
766 483
1180 297
975 323
569 140
222 58
390 78
9120 1670
605 168
1510 670
1910 399
185 40
658 76
675 356
719 317
1360 108
991 361
439 175
51 19
t-Bu
OCF3
H
H
H
H
21m
21n
22e
22g
H
CF3
H
CF3
Ph
H
313 103
1140 30
73 21
1800 320
t-Bu
H
94 33
Values are expressed as mean SEM from at least three independent experiments each conducted with duplicate determinations.
were 0.024 lM and 1.4 lM, respectively.20 This some-
what confirms our observation that many compounds
(but not all) frequently are less potent in the hDAT as-
say.21 Cocaine and RTI-55 are also 5–6 times less potent
in this study than values obtained with brain homoge-
nates,20,14 suggesting that the relative values of the dif-
ferent inhibitors remained constant. The unsubstituted
phenyl piperidines 3b and 10b give values in the low
micromolar range which is 25 times higher than the 4-
chlorophenyl derivative. The new iodophenylpiperidines
3c and 10c bind to the DAT with a potency equal to 3a,
but 3c is about 40 times weaker (bearing in mind that 3c
is racemic) than the tropane equivalent RTI-55. Thus,
our finding is that the piperidines are significantly weak-
er than the tropanes. The difference in binding between
cis and trans isomers (3b versus 10b, 3c versus 10c) is
comparatively small (2–10-fold) reflecting the greater
flexibility of these small molecules relative to the phenyl
tropanes.
to the monoamine transporters than the cyclohexene
analogues, showing that the nitrogen has a larger effect
on these monocyclic compounds than seen on the tro-
pane analogues.
Another interesting comparison is to compare 6–8 with
Meltzers 2-arylbenzoates since this reflects the influence
of saturation/unsaturation in the ring system. At first
sight compounds 6–8 appear weaker since a value of
150 nM has been reported for 4 on DAT binding, when
assayed on rat homogenates, and we obtained 4 and
12 lM for 6d and 7d. However, the necessity to compare
with data obtained under identical condition was once
more evident when we find that compound 4 in our
assay had a Ki for DAT binding of 4.06 lM (Table
2b). This value is close to what we find for 6d and 7d
meaning that there is little difference between a partially
saturated or aromatic ring in the binding to the DAT.
Confirming this is the observation that the change in
ring-size between 5-, 6- and 7-membered ring appears
unimportant. In general, the three series of compounds
6–8 display largely similar activity profiles, when substit-
uents are kept constant, with just a few exceptions.
The unsaturated piperidines (5a,d,q) were found to have
roughly a similar potency to the monoamine transporters
as saturated piperidines (Table 1). Though the study did
not include identical aromatic groups we can nevertheless
compare compounds with strong-binding aromatic groups
such as the saturated piperidine with iodophenyl 3c and the
unsaturated dichlorophenyl and naphthyl piperidines 5a
and 5d. These compounds bind to DAT with Ki values
varying with less than 1 order of magnitude, which reveals
that the double bond in the 2-position does not influence
activity much. Modifications in the aromatic moiety are
obviously much more crucial than introduction of this
double bond, since unsaturated 3-nitrophenyl piperidine
5q is 50–300 times weaker than 5d and 5a.
It is a general characteristic about the carba analogues
6–8 that the SERT binding is poor, so that the loss of
the nitrogen has introduced a degree of DAT and
NET selectivity. Compound 4 resembles 6–8 in this
respect.
Another characteristic for the compounds 6–8 is that the
aromatic substituent is extremely important for binding
and that 3,4-dichloro (6a, 7a and 8a) is 10–50-fold more
potent towards DAT than 3- or 4-chloro (6b, 6c, 7b, 7c,
8b and 8c), which is 10–50-fold better than the unsubsti-
tuted phenyl 7l. This general trend is more drastic than
is observed in the phenyl tropanes:14a in those com-
pounds halogenation of the phenyl group is also advan-
tageous, but introduction of one chlorine only increases
DAT binding 20-fold, and the 3,4-dichloro is only
slightly more active than the 4-chloro. This indicates
The importance of the nitrogen in the monocyclic com-
pounds in binding and uptake to the monoamine trans-
porters is addressed in the data for 6–8 (Table 2a and b).
The cyclohexenes 7 are direct analogues of 5 without the
nitrogen. Comparing 7a, 7d and 7q with the correspond-
ing piperidines 5a, 5d and 5q, we see that the unsatu-
rated piperidines bind with 20–30 times better potency

M. D. Petersen et al. / Bioorg. Med. Chem. 15 (2007) 4159–4174
4165
that the binding mode of the aromatic group is not iden-
tical in the two series of compounds.
chain, has a slightly decreased potency (DAT and
SERT) compared to the parent compound 7a.
Many different phenyl substituents were investigated
and some specific details can be noted: a trifluoromethyl
group is in general considered as a bioisostere of a chlo-
rine atom, the two compounds with a trifluoromethyl
group on the aromatic ring, 7m and 7n, bind worse than
their chlorine analogues 7b and 7c. The same effect has
however been observed in phenyltropanes, where the
4-CF3 substituted derivative was 10-fold less potent than
the 4-chlorine.14a It suggests that the function of chlo-
ride is related to its ability of electron donation through
conjugation; the only quality the CF3 group does not
possess.
In summary, this study confirms previous findings that
very simple truncated versions of phenyl tropanes can in-
hibit monoamine transporters albeit with low to moder-
ate potency. It was observed that a decrease of 40-fold in
binding occurs when the bicyclic tropane-structure is
transformed into a piperidine and another loss of 20–
30-fold when the piperidine nitrogen is replaced with car-
bon. While these decreases appear drastic they are never-
theless much smaller than the loss observed when the
aromatic group of a phenyltropane is replaced with al-
kyl.29 The fact that the compounds share the ester and
aromatic group with the phenyl tropanes implies the pos-
sibility of a similarity in the mode of binding. However,
in these non-nitrogen containing compounds the impor-
tance of the substituents in the aromatic group is greatly
enhanced, which suggests an altered or increased binding
towards this group. The same phenomenon was observed
by Meltzer for non-nitrogenous tropanes. We propose
that the non-nitrogen containing compounds obtain
compensation for the loss of binding to nitrogen by slid-
ing into a position with a more tightly bound aromatic
group. This implies that phenyltropanes do not have
optimal binding to the aromatic group, and indeed this
is supported by the observation that 3-phenethyltropane
is a stronger DAT inhibitor than the 3-phenyltropane.14a
The compounds 6k and 7o were made in order to test
the effect of having a hydroxyl or an amino group on
the phenyl ring. An amino and hydroxyl group can func-
tion as a hydrogen bond donor/acceptor, but both com-
pounds show a poor binding. This indicates that polar
substituents on the phenyl are unfavourable.
The compounds 6f–j, 7g–l and 8g were made in order to
test some new substituents on the phenyl ring, all of
these modifications resulted in poor binding with Ki
values higher than 100 lM.
The effect of saturation of the double bond is still un-
clear because most of the compounds that were satu-
rated have a weak binding in both their saturated and
unsaturated state. The exception to this is the biphenyl
8e. As can be seen from Table 3 the saturation of 8e–
22e (Scheme 1) decreases the Ki for binding to the
DAT more than 150-fold, while the binding to SERT
and NET was only decreased 2–4-fold. Although the
binding of 8e to the three transporters was decreased
by saturation, the effect was largest for binding to
DAT. Meltzer et al. have previously reported that for
the phenyl tropanes and the oxa and carba analogues
of these 1a–c, the saturation of the double bond results
in only a small decrease in DAT binding, but in a sub-
stantial improvement in SERT binding especially for
the oxa analogues.
5. Experimental
5.1. General
1
5.1.1. Apparatus. H NMR and 13C NMR spectra were
recorded on a Varian Gemini 2000 Spectrometer (400
and 100 MHz, respectively), using CDCl3 as solvent
and reference point (d 7.26 ppm and d 77.16 ppm,
respectively). Mass spectra were recorded on a Micro-
mass LC-TOF spectrometer. Melting points were mea-
sured on a Stuart Scientific Melting Point Apparatus
SMP3 and are not corrected.
5.1.2. Solvents. DCM was dried by distillation over
CaH2. Et2O was dried over sodium. Benzene was dried
˚
over molecular sieves (4 A).
Many of the compounds show considerably higher po-
tency for inhibition of dopamine uptake than binding
on DAT. The most extreme compound 7b shows around
150-fold lower Ki towards dopamine uptake inhibition
than inhibition of RTI-55 binding. This should be com-
pared to the almost equal Ki values for binding and up-
take for cocaine and RTI-55. Compound 7b seems in
fact to be very selective for DAT uptake inhibition since
it is much weaker towards SERT and NET. An explana-
tion for this potency is that 7b has multiple binding sites
or modes on DAT. One of these binding sites is proba-
bly capable of inhibiting uptake, but RTI-55 only has
low affinity (or no affinity at all) for this binding site,
and can therefore not displace 7b during the binding
studies, giving the high Ki value.
5.1.3. Chromatography. Flash column chromatography
was performed with a Merck silica gel (230–400 mesh).
TLC was performed on silica gel (Merck Kieselgel 60
F254) and for visualization of the spots either UV light
(254 nm), Ce-Mol solution (Ce(SO4)2 (10 g) and
(NH4)2MoO4 (15 g) dissolved in 10% H2SO4) or KMnO4
dissolved in ethanol were used. After application of the
solutions, the TLC-plates were heated to dryness.
5.1.4. Evaporation. Evaporation was done at reduced
pressure at 40 ꢁC.
5.1.5. Methyl 3,4-cis-N-methyl-4-phenylpiperidine-3-car-
boxylate (3b) and methyl 3,4-trans-N-methyl-4-phenylpi-
peridine-3-carboxylate (10b). A stirred solution of
phenylmagnesium bromide (36 mL, 1.35 M in Et2O) in
Finally it is noted that compound 25 (Table 2b), where
the ester group has been substituted with a propene

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M. D. Petersen et al. / Bioorg. Med. Chem. 15 (2007) 4159–4174
dry Et2O (219 mL) was cooled to À10 ꢁC. A solution of
arecoline (9) (4.02 g, 25.9 mmol) in dry Et2O (94 mL)
was added dropwise and stirred at À10 ꢁC for 11/2 h
(followed by TLC). The mixture was then poured onto
crushed ice and slowly treated with 10% HCl (62 mL).
The aqueous phase was separated, washed with Et2O
(62 mL), then while cooling in an ice bath slowly treated
with 50% Na2CO3 until pH 10–11, and then extracted
with Et2O (3 · 50 mL). The combined organic phases
were washed with brine (62 mL), dried over MgSO4
and concentrated in vacuo to give a crude mixture of
( )-3b and ( )-10b. Flash chromatography (diethyl
ether–pentane; 3:1 with Et3N in 1%) afforded the cis-iso-
mer ( )-3b (1.19 g, 20%) as a white solid, and the trans-
isomer ( )-10b (0.72 g, 12%) as colourless oil.
(977 mg, 3.85 mmol), CF3SO3Ag (988 mg, 3.85 mmol),
20 mL CH2Cl2 and 5 drops of CH3CO2H. The mix-
ture was stirred at room temperature overnight in
darkness, and then AgI was removed by filtration
and washed with CH2Cl2 (4 · 3 mL). The combined
organic phases were washed with diluted NH4OH, a
5% Na2S2O3 solution and water, dried over Na2SO4
and concentrated in vacuo. Flash chromatography
(diethyl ether–pentane; 1.7:1 with Et3N in 0.4%) affor-
ded the desired product ( )-10c (306 mg, 44%) as
yellow oil.
1H NMR (CDCl3) d: 7.52 (2H, d, J = 8.4 Hz); 7.01 (2H,
d, J = 8.4 Hz); 3.39 (3H, s); 3.25 (1H, br d, J = 10.8 Hz);
2.89–2.84 (2H, m); 2.80 (1H, dt, J2 = 4.0 Hz,
J1 = 11.2 Hz); 2.65 (1H, dq, J1 = 2.8 Hz, J2 = 11.6 Hz);
2.27 (3H, s); 2.10 (1H, t, J = 12.0 Hz); 2.04–1.98 (1H,
m); 1.76–1.68 (1H, m).
1
5.1.5.1. Compound ( )-3b. H NMR (CDCl3) d: 7.27–
7.09 (5H, m); 3.43 (3H, s); 3.11 (1H, br d, J = 11.2 Hz);
2.98–2.87 (2H, m); 2.80 (1H, dt, J1 = 4.0 Hz,
J2 = 11.6 Hz); 2.61 (1H, dq, J1 = 4.0 Hz, J2 = 11.6 Hz);
2.31 (1H, dd, J1 = 3.6 Hz, J2 = 11.6 Hz); 2.22 (3H, s);
2.03 (1H, dt, J1 = 2.8 Hz, J2 = 11.2 Hz); 1.79–1.73 (1H, m).
13C NMR (CDCl3) d: 171.5; 142.0; 136.0; 128.3; 90.6;
57.5; 54.8; 50.8; 46.3; 45.1; 40.2; 25.1.
HR-MS(ES): Calcd for C14H18NO2 + H+: m/z 360.0461.
Found m/z 360.0452.
13C NMR (CDCl3) d: 172.4; 144.5; 128.2; 127.9; 126.4;
59.0; 56.2; 51.5; 47.0; 46.2; 42.3; 26.0.
5.2. General method for triflation
5.1.5.2. Compound ( )-10b. 1H NMR (CDCl3) d: 7.40–
7.11 (5H, m); 3.35 (3H, s); 3.02 (1H, br d, J = 11.6 Hz);
2.96–2.82 (2H, m); 2.70 (1H, dt, J1 = 3.6 Hz,
J2 = 11.2 Hz); 2.46 (1H, dq, J1 = 4.0 Hz, J2 = 11.6 Hz);
2.23 (1H, dd, J1 = 3.6 Hz, J2 = 12.0 Hz); 2.28 (3H, s),
2.12 (1H, dt, J1 = 3.2 Hz, J2 = 11.2 Hz); 1.82–1.74 (1H, m).
NaH (60% w/w), 1 g, 25 mmol was washed with pentane
(3 · 20 mL) under a nitrogen atmosphere, then 20 mL of
ether was added and the slurry was cooled to 0 ꢁC. The
ketoester (5 mmol) dissolved in 15 mL ether was added
dropwise, and the reaction mixture was stirred at 0 ꢁC
for 30 min. Then Tf2O (1.70 mL, 10 mmol) was added
dropwise, and the reaction mixture was stirred for
60 min at 0 ꢁC after which 25 mL of H2O was added
slowly. The layers were separated the aqueous phase
was extracted with CH2Cl2 (3 · 15 mL). The combined
organic phases were dried with MgSO4 and concen-
trated in vacuo. Purification by Flash chromatography
(diethyl ether–pentane; 1:30) afforded the triflate as col-
ourless oil.
5.1.6. Methyl 3,4-cis-N-methyl-4-(4-iodophenyl)piperi-
dine-3-carboxylate (3c). To a dry round-bottom flask
were added ( )-3b (673 mg, 2.88 mmol), I2 (1.48 g,
5.84 mmol), CF3SO3Ag (1.49 g, 5.79 mmol), 20 mL
CH2Cl2 and 5 drops of CH3CO2H. The mixture was stir-
red in room temperature overnight in darkness, and then
AgI was removed by filtration and washed with CH2Cl2
(4 · 3 mL). The combined organic phases were washed
with diluted NH4OH, 5% Na2S2O3, and water, dried
over Na2SO4 and concentrated in vacuo. Flash chroma-
tography (diethyl ether–pentane; 2:1 with Et3N in 0.4%)
afforded the desired product ( )-3c (603 mg, 58%) as oil.
5.2.1. Methyl 2-(trifluoromethylsulfonyloxy)cyclopent-1-
enecarboxylate (17). The general method for triflation
with ketoester 14 afforded the triflate 17 as colourless
oil in 99% yield.
1H NMR (CDCl3) d: 7.58 (2H, d, J = 8.0 Hz); 7.01 (2H,
d, J = 8.4 Hz); 3.45 (3H, s); 3.25 (1H, br d, J = 11.2);
3.08–2.97 (2H, m); 2.89 (1H, dt, J1 = 4.0 Hz,
J2 = 11.2 Hz); 2.58 (1H, dq, J1 = 3.6 Hz, J2 = 11.6 Hz);
2.30 (1H, dd, J1 = 3.2 Hz, J2 = 11.2 Hz); 2.23 (3H, s);
2.03 (1H, dt, J1 = 2.8 Hz, J2 = 11.2 Hz); 1.72 (1H, dd,
J1 = 2.8 Hz, J2 = 12.4 Hz).
1H NMR (CDCl3) d: 3.80 (s, 3H); 2.73 (m, 4H); 2.02 (k,
2H, J = 7.8 Hz).
13C NMR (CDCl3) d: 162.6; 154.0; 123.0; 118.3 (q,
J = 318 Hz); 51.6; 32.6; 29.1; 18.7.
5.2.2. Methyl 2-(trifluoromethylsulfonyloxy)cyclohex-1-
enecarboxylate (18). The general method for triflation
with ketoester 15 afforded the triflate 18 as colourless
oil in 99% yield.
13C NMR (CDCl3) d: 171.5; 142.0; 136.0; 128.3; 90.6;
57.5; 54.8; 50.8; 46.3; 45.1; 40.2; 25.1.
HR-MS(ES): Calcd for C14H18NO2 + H+: m/z 360.0461.
Found: m/z 360.0452.
1H NMR (CDCl3) d: 3.76 (s, 3H); 2.47–2.35 (m, 4H);
1.79–1.61 (m, 4H).
5.1.7. Methyl 3,4-trans-N-methyl-4-(4-iodophenyl)piper-
idine-3-carboxylate (10c). To a dry round-bottomed-
flask were added ( )-10b (448 mg, 1.92 mmol), I2
13C NMR (CDCl3) d: 165.2; 152.0; 122.9; 118.4; 52.2;
28.7; 26.2; 22.4; 21.2.

M. D. Petersen et al. / Bioorg. Med. Chem. 15 (2007) 4159–4174
4167
5.2.3. Methyl 2-(trifluoromethylsulfonyloxy)cyclohept-1-
enecarboxylate (19). The general method for triflation
with ketoester 16 afforded the triflate 19 as colourless
oil in 95% yield.
HR-MS(ES): Calcd for C13H12Cl2O2 + Na+: m/z
293.0112. Found m/z 293.0118.
5.3.2. Methyl 2-(4-chlorophenyl)cyclopent-1-enecarboxy-
late (6b). Purification by Flash chromatography (diethyl
ether–pentane; 1:30) afforded 6b as colourless oil in 91%
yield.
1H NMR (CDCl3) d: 3.79 (s, 3H); 2.61–2.51 (m, 4H);
1.80–1.63 (m, 6H).
13C NMR (CDCl3) d: 165.8; 154.8; 127.6; 118.5; 51.8;
33.7; 30.4; 27.7; 25.0; 23.5.
1H NMR (CDCl3) d: 7.28 (m, 4H); 3.63 (s, 3H); 2.82 (t,
4H, J = 7.6 Hz); 1.98 (p, 2H, J = 7.6 Hz).
5.2.4. 1-tert-Butyl 3-ethyl 4-(trifluoromethylsulfonyloxy)-
5,6-dihydropyridine-1,3(2H)-dicarboxylate (12). NaH
(60% (w/w), 60 mg, 1.5 mmol) was washed with pentane
(3 · 5 mL) under a nitrogen atmosphere, 5 mL of ether
was added and the slurry was cooled to 0 ꢁC. Com-
pound 11 (200 mg, 0.74 mmol)22 in 3 mL ether was
added dropwise and the reaction mixture was stirred
for 90 min at room temperature. Then the mixture was
cooled to 0 ꢁC and Tf2O (0.14 mL, 0.83 mmol) in
3 mL anhyd Et2O was added dropwise followed by re-
moval of the cooling bath. The reaction mixture was
stirred for 40 min at 25 ꢁC after which 10 mL of satd
NH4Cl was added. The layers were separated, the aque-
ous phase extracted with 3 · 10 mL CH2Cl2, and the
combined organic phases were dried over MgSO4. Con-
centration under reduced pressure afforded 12 as a slight
yellow oil in 90% yield (266 mg). Compound 12 was
used in the following reactions without further
purification.
13C NMR (CDCl3) d: 166.3; 152.3; 135.3; 133.7; 129.4;
129.1; 127.9; 51.1; 40.0; 35.1; 21.8.
HR-MS(ES): Calcd for C13H13ClO2 + Na+: m/z
259.0502. Found m/z 259.0497.
5.3.3. Methyl 2-(3-chlorophenyl)cyclopent-1-enecarboxy-
late (6c). Purification by Flash chromatography (diethyl
ether–pentane; 1:30) afforded 6c as colourless oil in 94%
yield.
1H NMR (CDCl3) d: 7.30 (s, 1H); 7.26 (d, 2H,
J = 4.8 Hz); 7.20 (q, 1H, J = 4.8 Hz); 3.63 (s, 3H); 2.83
(t, 4H, J = 7.6 Hz); 1.99 (p, 2H, J = 7.6 Hz).
13C NMR (CDCl3) d: 166.1; 151.8; 138.7; 133.6; 130.0;
129.0; 127.8; 127.7; 125.9; 51.2; 40.2; 35.0; 21.9.
HR-MS(ES): Calcd for C13H13ClO2 + Na+: m/z
259.0502. Found m/z 259.0494.
1H NMR (CDCl3) d: 4.33–4.27 (m, 4H); 3.64–3.60 (m,
2H); 2.53–2.49 (m, 2H), 1.48 (s, 9H), 1.34 (t, 3H,
J = 7.2 Hz).
5.3.4. Methyl 2-(naphthalen-2-yl)cyclopent-1-enecarb-
oxylate (6d). Purification by Flash chromatography
(diethyl ether–pentane; 1:30) afforded 6d as colourless
oil in 85% yield.
13C NMR (CDCl3) d: 165.8; 154.8; 127.6; 118.5; 51.8;
33.7; 30.4; 27.7; 25.0; 23.5.
1H NMR (CDCl3) d: 7.81 (m, 4H); 7.47 (m, 3H); 3.63 (s,
3H); 2.97 (t, 2H, J = 7.7 Hz); 2.90 (t, 2H, J = 7.7 Hz);
2.05 (p, 2H, J = 7.7 Hz).
HR-MS(ES): Calcd for C14H20F3NO7S + Na+: m/z
426.0810. Found m/z 426.0812.
5.3. General method for Suzuki couplings
13C NMR (CDCl3) d: 166.7; 153.3; 134.5; 133.0; 132.9;
129.2; 128.2; 127.6; 127.1; 126.6; 126.2; 126.1; 126.0;
51.2; 40.2; 35.3; 22.0.
One equivalent of 17, 18, 19 or 12 (0.3 mmol) was added
to a tube (5–10 mL) with Na2CO3 (2 equiv), Pd(OAc)2
(0.05 equiv), the boronic acid (1.5 equiv) and dissolved
in ethanol–benzene (1:3). Finally PPh3 (0.1 equiv) was
added and the resulting mixture was flushed with nitro-
gen, and the tube sealed. The reaction mixture was stir-
red at 65 ꢁC for 20 h.
HR-MS(ES): Calcd for C17H16O2 + Na+: m/z 275.1048.
Found m/z 275.1048.
5.3.5. Methyl 2-(4-methoxyphenyl)cyclopent-1-enecarb-
oxylate (6f). Purification by Flash chromatography
(diethyl ether–pentane; 1:20) afforded 6f as colourless
oil in 98% yield.
5.3.1. Methyl 2-(3,4-dichlorophenyl)cyclopent-1-enecarb-
oxylate (6a). Purification by Flash chromatography
(diethyl ether–pentane; 1:30) afforded 6a as colourless
oil in 96% yield.
1H NMR (CDCl3) d: 7.33 (d, 2H, J = 8.8 Hz); 6.86
(d, 2H, J = 8.8 Hz); 3.81 (s, 3H); 3.65 (s, 3H); 2.83
(dq, 4H, J1 = 2.0 Hz, J2 = 7.4 Hz); 1.96 (p, 2H,
J = 7.7 Hz).
1H NMR (CDCl3) d: 7.42 (d, 1H, J = 2.1 Hz); 7.38 (d,
1H, J = 8.4 Hz); 7.17 (dd, 1H, J1 = 2.1 Hz,
J2 = 8.4 Hz); 3.64 (s, 3H); 2.81 (m, 4H);1.99 (p, 2H,
J = 7.6 Hz).
13C NMR (CDCl3) d: 166.8; 159.4; 153.1; 129.3; 129.0;
127.3; 113.1; 55.2; 51.0; 39.9; 35.2; 21.8.
13C NMR (CDCl3) d: 165.9; 150.8; 136.8; 131.8; 131.7;
130.5; 129.6; 127.3; 51.3; 39.9; 35.1; 21.8.
HR-MS(ES): Calcd for C14H16O3 + Na+: m/z 255.0997.
Found m/z 255.0995.

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M. D. Petersen et al. / Bioorg. Med. Chem. 15 (2007) 4159–4174
5.3.6. Methyl 2-(4-tert-butylphenyl)cyclopent-1-enecarb-
oxylate (6g). Purification by Flash chromatography
(diethyl ether–pentane; 1:30) afforded 6g as colourless
oil in 88% yield.
3.63 (s, 3H); 2.81 (t, 4H, J = 7.7 Hz); 1.97 (p, 2H,
J = 7.7 Hz).
13C NMR (CDCl3) d: 166.8; 153.5; 145.9; 138.0; 128.7;
118.1; 114.8; 114.3; 51.1; 40.1; 35.1; 21.9.
1H NMR (CDCl3) d: 7.37 (d, 2 H, J = 8.6 Hz); 7.32 (d,
2H, J = 8.6 Hz); 3.66 (s, 3H); 2.85 (m, 4 H); 1.98 (p,
2H, J = 7.3 Hz);1.34 (s, 9H).
HR-MS(ES): Calcd for C13H15NO2 + H+: m/z 218.1181.
Found m/z 218.1179.
13C NMR (CDCl3) d: 166.7; 153.5; 150.9; 133.6; 128.0;
127.6; 124.6; 51.1; 39.9; 35.2; 34.6; 31.2; 21.9.
5.3.11. Methyl 2-(4-nitrophenyl)cyclopent-1-enecarboxy-
late (6p). This reaction was performed using 4-nitroben-
zeneboronic ester (1.5 equiv) synthesized by the method
of Furstner and Gunter30 Purification by Flash chroma-
tography (EtOAc–pentane; 1:8) afforded 6p as a yellow
solid in 85% yield.
HR-MS(ES): Calcd for C17H22O2 + Na+: m/z 281.1517.
Found m/z 281.1516.
¨
¨
5.3.7. Methyl 2-(4-(trifluoromethoxy)phenyl)cyclopent-
1-enecarboxylate (6h). Purification by Flash chroma-
tography (diethyl ether–pentane; 1:30) afforded 6h as
colourless oil in 89% yield.
1H NMR (CDCl3) d: 8.19 (dd, 2H, J1 = 2.0 Hz,
J2 = 9.0 Hz); 7.46 (dd, 2H, J1 = 2.0 Hz, J2 = 9.0 Hz);
3.63 (s, 3H); 2.87 (m, 4H); 2.04 (m, 2H).
1H NMR (CDCl3) d: 7.37 (d, 2H, J = 8.6 Hz); 7.17 (d,
2H, J = 8.6 Hz); 3.64 (s, 3H); 2.84 (t, 4H, J = 7.6 Hz);
2.00 (p, 2H, J = 7.6 Hz).
13C NMR (CDCl3) d: 165.8; 151.4; 147.2; 144.0; 128.7;
128.4; 123.1; 51.4; 40.2; 35.1; 22.0.
HR-MS(ES): Calcd for C13H13NO4 + Na+: m/z
270.0742. Found m/z 270.0749.
13C NMR (CDCl3) d: 166.2; 152.2; 148.7; 135.5; 129.6;
129.3; 120.4 (q, J = 257 Hz); 120.1; 51.2; 40.1; 35.1; 21.9.
5.3.12. Methyl 2-(3,4-dichlorophenyl)cyclohex-1-enecarb-
oxylate (7a). Purification by Flash chromatography
(diethyl ether–pentane; 1:20) afforded 7a as colourless
oil in 95% yield.
HR-MS(ES): Calcd for C14H13F3O3 + Na+: m/z
309.0714. Found m/z 309.0718.
5.3.8. Methyl 2-(4-(methylsulfonyl)phenyl)cyclopent-1-
enecarboxylate (6i). Purification by Flash chromatog-
raphy (diethyl ether–pentane; 1:30) afforded 6i as
colourless oil in 89% yield.
1H NMR (CDCl3) d: 7.36 (d, 1H, J = 8.2 Hz); 7.22 (d, 1H,
J = 2.0 Hz); 6.96 (dd, 1H, J1 = 8.2 Hz, J2 = 2.0 Hz); 3.48
(s, 3H); 2.44–2.37 (m, 2H); 2.34–2.28 (m, 2H); 1.76.1.68
(m, 4H).
1H NMR (CDCl3) d: 7.89 (d, 2H, J = 8.5 Hz); 7.49 (d,
2H, J = 8.5 Hz); 3.62 (s, 3H); 3.05 (s, 3H); 2.85 (t, 4H,
J = 7.6 Hz); 2.02 (p, 2H, J = 7.6 Hz).
13C NMR (CDCl3) d: 169.3; 143.8; 143.3; 132.0; 130.8;
129.9; 128.8; 128.7; 126.3; 51.3; 32.6; 26.5; 22.2; 21.7.
13C NMR (CDCl3) d: 165.8; 151.7; 142.9; 139.4; 131.3;
128.6; 126.8; 51.3; 44.5; 40.2; 35.0; 21.9.
HR-MS(ES): Calcd for C14H14Cl2O2 + Na+: m/z
307.0269. Found m/z 307.0285.
HR-MS(ES): Calcd for C14H16O4S + Na+: m/z
303.0667. Found m/z 303.0669.
5.3.13. Methyl 2-(4-chlorophenyl)cyclohex-1-enecarboxylate
(7b). Purification by Flash chromatography (diethyl ether–
pentane; 1:20) afforded 7b as colourless oil in 99% yield.
5.3.9. Methyl 2-(4-acetylphenyl)cyclopent-1-enecarboxylate
(6j). Purification by Flash chromatography (diethyl ether–
pentane; 1:1) afforded 6j as colourless oil in 79% yield.
1H NMR (CDCl3) d: 7.27 (d, 2H, J = 8.4 Hz); 7.06 (d,
2H, J = 8.4 Hz); 3.45 (s, 3 H); 2.44–2.32 (m, 4 H);
1.78–1.65 (m, 4 H).
1H NMR (CDCl3) d: 7.92 (d, 2H, J = 8.5 Hz); 7.39 (d,
2H, 8.5 Hz); 3.62 (s, 3H); 2.85 (m, 4H); 2.59 (s, 3H);
2.01 (p, 2H, J = 7.7 Hz).
13C NMR (CDCl3) d: 169.8; 144.8; 141.8; 132.8; 128.2;
128.1; 51.3; 32.7; 26.6; 22.4 21.8.
13C NMR (CDCl3) d: 197.6; 166.1; 152.5; 142.0; 136.2;
130.5; 127.9; 127.8; 51.3; 40.0; 35.1; 26.6; 22.0.
HR-MS(ES): Calcd for C14H15ClO2 + Na+: m/z
273.0658. Found m/z 273.0657.
5.3.10. Methyl 2-(3-aminophenyl)cyclopent-1-enecarb-
oxylate (6k). Purification by Flash chromatography
(diethyl ether–pentane; 1:1) afforded 6k as colourless
oil in 86% yield.
5.3.14. Methyl 2-(3-chlorophenyl)cyclohex-1-enecarboxylate
(7c). Purification by Flash chromatography (diethyl ether–
pentane; 1:20) afforded 7c as colourless oil in 98% yield.
1H NMR (CDCl3) d: 7.24–7.21 (m, 2H); 7.14–7.12 (m,
1H); 7.02–6.98 (m, 1H); 3.45 (s, 3H); 2.45–2.40 (m,
2H); 2.38–2.32 (m, 2H); 1.78–1.70 (m, 4H).
1H NMR (CDCl3) d: 7.11 (t, 1H, J = 7.8 Hz); 6.70 (d,
1H, J = 7.6); 6.65 (s, 1H); 6.62 (d, 1H, J = 7.9 Hz);

M. D. Petersen et al. / Bioorg. Med. Chem. 15 (2007) 4159–4174
4169
13C NMR (CDCl3) d: 169.7; 145.2; 144.6; 133.8; 129.2;
128.4; 127.0; 126.9; 125.0; 51.2; 32.6; 26.6; 22.3; 21.8.
HR-MS(ES): Calcd for C15H15F3O3 + Na+: m/z
323.0871. Found m/z 323.0876.
HR-MS(ES): Calcd for C14H15ClO2 + Na+: m/z
273.0658. Found m/z 273.0660.
5.3.19. Methyl 2-phenylcyclohex-1-enecarboxylate (7l).
Purification by Flash chromatography (diethyl ether–
pentane; 1:20) afforded 7l as yellow oil in 85% yield.
5.3.15. Methyl 2-(naphthalen-2-yl)cyclohex-1-enecarb-
oxylate (7d). Purification by Flash chromatography
(diethyl ether–pentane; 1:20) afforded 7d as colourless
oil in 80% yield.
1H NMR (CDCl3) d: 8.11 (d, 1H, J = 7.6 Hz); 8.01 (s,
1H); 7.48 (m, 1H); 7.44 (dd, 1H, J = 1.4 Hz,
J = 7.6 Hz); 3.46 (s, 3H); 2.45 (m, 2H); 2.38 (m, 2H);
1.77 (m, 4H).
1H NMR (CDCl3) d: 7.83–7.78 (m, 3H); 7.61 (s, 1H);
7.48–7.43 (m, 2H); 7.29 (d, 1H, J = 8.5 Hz); 3.38 (s,
3H); 2.50–2.48 (m, 4H); 1.84–1.78 (m, 4H).
13C NMR (CDCl3) d: 170.39; 145.90; 143.44; 128.07;
127.79; 127.08; 126.80; 51.23; 32.68; 26.79; 22.58;
22.04.
13C NMR (CDCl3) d: 170.3; 145.7; 140.8; 133.2; 132.4;
128.1; 127.9; 127.6; 127.5; 126.0; 125.7; 125.7; 125.1;
51.4; 32.9; 27.0; 22.7; 22.1.
5.3.20. Methyl 2-(3-(trifluoromethyl)phenyl)cyclohex-1-
enecarboxylate (7m). Purification by Flash chromatog-
raphy (diethyl ether–pentane; 1:20) afforded 7m as col-
ourless oil in 95% yield.
HR-MS(ES): Calcd for C18H18O2 + Na+: m/z 289.1204.
Found m/z 289.1204.
1H NMR (CDCl3) d: 7.51 (d, 1H, J = 7.5 Hz); 7.42 (dd,
1H, J1 = 7.5 Hz, J2 = 7.7 Hz); 7.39 (s, 1H); 7.31 (d, 1H,
J = 7.7 Hz); 3.42 (s, 3H); 2.46–2.41 (m, 2H); 2.40–2.35
(m, 2H); 1.80–1.70 (m, 4H).
5.3.16. Methyl 2-(biphenyl-4-yl)cyclohex-1-enecarboxy-
late (7e). Purification by Flash chromatography (diethyl
ether–pentane; 1:20) afforded 7e as colourless oil in 83%
yield.
13C NMR (CDCl3) d: 169.5; 144.6; 144.1; 130.1; 128.8;
128.4; 124.1 (q, J = 272 Hz); 123.7; 123.7 123.6; 51.2;
32.6; 26.6; 22.3; 21.8.
1H NMR (CDCl3) d: 7.62 (d, 2H, J = 7.5 Hz); 7.56 (d,
2H, J = 8.0 Hz); 7.44 (t, 2H, J = 7.5 Hz); 7.34 (t, 1H,
7.5 Hz); 7.23 (d, 2H, 8.0 Hz); 3.47 (s, 3H); 2.48–2.42
(m, 4H); 1.81.1.74 (m, 4H).
HR-MS(ES): Calcd for C15H15F3O2 + Na+: m/z
307.0922. Found m/z 307.0927.
13C NMR (CDCl3) d: 170.4; 145.3; 142.3; 140.7; 139.7;
128.7; 127.8; 127.2; 127.0; 126.6; 51.2; 32.5; 26.8; 22.5; 21.9.
5.3.21. Methyl 2-(4-(trifluoromethyl)phenyl)cyclohex-1-
enecarboxylate (7n). Purification by Flash chromatogra-
phy (diethyl ether–pentane; 1:20) afforded 7n as colour-
less oil in 96% yield.
HR-MS(ES): Calcd for C20H20O2 + Na+: m/z 315.1361.
Found m/z 315.1366.
5.3.17. Methyl 2-(4-tert-butylphenyl)cyclohex-1-enecarb-
oxylate (7g). Purification by Flash chromatography
(diethyl ether–pentane; 1:20) afforded 7g as colourless
oil in 88% yield.
1H NMR (CDCl3) d: 7.56 (d, 2H, J = 8.1 Hz); 7.23 (d,
2H, J = 8.1 Hz); 3.43 (s, 3H); 2.46–2.42 (m, 2H); 2.38–
2.34 (m, 2H); 1.79–1.72 (m, 4H).
13C NMR (CDCl3) d: 169.4; 147.2; 145.2; 128.5; 127.1;
125.0; 124.9; 124.2 (q, J = 272 Hz); 51.2; 32.8; 26.5;
22.3; 21.8.
1H NMR (CDCl3) d: 7.32 (d, 2H, J = 8.3 Hz); 7.07 (d,
2H, J = 8.3 Hz); 3.42 (s, 3H); 2.44–2.37 (m, 4H); 1.77–
1.70 (m, 4H); 1.32 (s, 9H).
HR-MS(ES): Calcd for C15H15F3O2 + Na+: m/z
307.0922. Found m/z 307.0919.
13C NMR (CDCl3) d: 170.6; 149.8; 145.3; 140.1; 127.4;
126.4; 124.8; 51.1; 34.4; 32.3; 31.3; 26.8; 22.5; 21.9.
5.3.22. Methyl 2-(4-hydroxyphenyl)cyclohex-1-enecarb-
oxylate (7o). Purification by Flash chromatography
(diethyl ether–pentane; 1:1) afforded 7o as colourless
oil in 93% yield.
HR-MS(ES): Calcd for C18H24O2 + Na+: m/z 295.1674.
Found m/z 295.1669.
5.3.18. Methyl 2-(4-(trifluoromethoxy)phenyl)cyclohex-1-
enecarboxylate (7h). Purification by Flash chromatogra-
phy (diethyl ether–pentane; 1:20) afforded 7h as colour-
less oil in 83% yield.
1H NMR (CDCl3) d: 6.99 (d, 2H, J = 8.5 Hz); 6.70 (d,
2H, J = 8.5 Hz); 6.09 (s, 1H); 3.50 (s, 3H); 2.42–2.33
(m, 4H); 1.76–1.68 (m, 4H).
1H NMR (CDCl3) d: 7.14 (s, 4H); 3.42 (s, 3H); 2.45–2.40
(m, 2H); 2.38–2.33 (m, 2H); 1.79–1.72 (m, 4H).
13C NMR (CDCl3) d: 171.4; 155.2; 145.8; 135.1; 128.0;
127.0; 115.0; 51.5; 32.5; 26.8; 22.5; 21.9.
13CNMR(CDCl3)d: 169.8; 148.1; 144.7; 142.1; 128.4; 128.2;
120.5 (q, J = 257 Hz); 120.4; 51.1; 32.7; 26.6; 22.4; 21.8.
HR-MS(ES): Calcd for C14H16O3 + Na+: m/z 255.0997.
Found m/z 255.0991.

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M. D. Petersen et al. / Bioorg. Med. Chem. 15 (2007) 4159–4174
5.3.23. Methyl 2-phenylcyclohex-1-enecarboxylate (7q).
Purification by Flash chromatography (EtOAc–pentane;
1:10) afforded 7q as yellow oil in 53% yield.
5.3.27. Methyl 2-(naphthalen-2-yl)cyclohept-1-enecarb-
oxylate (8d). Purification by Flash chromatography
(CH2Cl2–pentane; 1:2) afforded 8d as colourless oil in
96% yield.
1H NMR (CDCl3) d: 8.11 (d, 1H, J = 7.6 Hz); 8.01 (s,
1H); 7.48 (m, 1H); 7.44 (dd, 1H, J = 1.4 Hz, J = 7.6
Hz); 3.46 (s, 3H); 2.45 (m, 2H); 2.38 (m, 2H); 1.77 (m,
4H).
1H NMR (CDCl3) d: 7.79 (m, 3H); 7.58 (s, 1H); 7.45 (m,
2H); 7.29 (m, 1H); 3.32 (s, 3H); 2.72–2.62 (m, 4H); 1.93–
1.87 (m, 2H); 1.75–1.68 (m, 4H).
13C NMR (CDCl3) d: 168.9; 148.1; 145.3; 144.7; 133.2;
129.2; 129.0; 122.0; 121.9; 51.5; 33.1; 26.6; 22.3; 21.9.
13C NMR (CDCl3) d: 171.6; 150.8; 142.0; 133.9; 133.2;
132.4; 128.0; 127.6; 126.1; 125.8; 125.4; 125.0; 51.3;
37.2; 32.4; 31.1; 26.5; 25.9.
HR-MS(ES): Calcd for C14H15NO4 + Na+: m/z
284.0899. Found m/z 284.0902.
HR-MS(ES): Calcd for C19H26O2 + Na+: m/z 303.1361.
Found m/z 303.1357.
5.3.24. Methyl 2-(3,4-dichlorophenyl)cyclohept-1-ene-
carboxylate (8a). Purification by Flash chromatography
(CH2Cl2-pentane; 1:3) afforded 8a as colourless oil in
90% yield.
5.3.28. Methyl 2-(biphenyl-4-yl)cyclohept-1-enecarboxy-
late (8e). Purification by Flash chromatography
(CH2Cl2–pentane; 1:2) afforded 8e as colourless oil in
75% yield.
1H NMR (CDCl3) d: 7.35 (d, 1H, J = 8.2 Hz); 7.22 (d,
1H, J = 2.0 Hz); 6.95 (dd, 1H, J = 2.0 Hz, J = 8.2 Hz);
3.46 (s, 3H); 2.58–2.55 (m, 4H); 1.89–1.83 (m, 2H);
1.67–1.62 (m, 4H).
1H NMR (CDCl3) d: 7.60 (d, 2H, J = 7.1 Hz); 7.54 (dd,
2H, J1 = 2.0 Hz, J2 = 8.4 Hz); 7.44 (t, 2H, J = 7.6 Hz);
7.34 (t, 1H, J = 7.3 Hz); 7.22 (dd, 2H, J1 = 2.0 Hz,
J2 = 8.4 Hz); 3.43 (s, 3H); 2.69–2.58 (m, 4H), 1.91–1.85
(m, 2H); 1.73–1.65 (m, 4H).
13C NMR (CDCl3) d: 170.6; 148.6; 144.5; 134.8; 132.1;
130.8; 130.0; 128.6; 126.2; 51.5; 36.9; 32.2; 30.8; 26.2;
25.6.
13C NMR (CDCl3) d: 171.6; 150.5; 143.4; 140.8; 139.7;
133.6; 128.8; 127.3; 127.2; 127.0; 126.7; 51.3; 37.1;
32.4; 31.1; 26.5; 25.8.
HR-MS(ES): Calcd for C15H16Cl2O2 + Na+: m/z
321.0425. Found m/z 321.0435.
HR-MS(ES): Calcd for C21H22O2 + Na+: m/z 329,1517.
Found m/z 329.1521.
5.3.25. Methyl 2-(4-chlorophenyl)cyclohept-1-enecarb-
oxylate (8b). Purification by Flash chromatography
(CH2Cl2–pentane; 1:2) afforded 8b as colourless oil in
90% yield.
5.3.29. Methyl 2-(4-tert-butylphenyl)cyclohept-1-enecarb-
oxylate (8g). Purification by Flash chromatography
(CH2Cl2–pentane; 1:2) afforded 8g as colourless oil in
74% yield.
1H NMR (CDCl3) d: 7.26 (d, 1H, J = 8.4 Hz); 7.06 (d,
2H, J = 8.4 Hz); 3.42 (s, 3H); 2.59–2.55 (m, 4H); 1.88–
1.82 (m, 2H); 1.68–1.62 (m, 4H).
1H NMR (CDCl3) d: 7.30 (d, 2H, J = 8.4 Hz); 7.07 (d,
2H, J = 8.4 Hz); 3.38 (s, 3H); 1.88–1.82 (m, 2H); 1.69–
1.62 (m, 4H); 1.63–1.55 (m, 4H); 3.38 (s, 3H); 1.31 (s,
9H).
13C NMR (CDCl3) d: 170.9; 149.6; 142.8; 133.8; 132.5;
128.0; 127.9; 51.1; 36.9; 32.1; 30.7; 26.2; 25.5.
HR-MS(ES): Calcd for C15H17ClO2 + Na+: m/z
287.0815. Found m/z 287.0812.
13C NMR (CDCl3) d: 171.9; 150.7; 149.8; 141.3; 133.1;
126.4; 124.8; 51.1; 37.0; 34.5; 32.4; 31.3; 31.1; 26.6; 25.9.
5.3.26. Methyl 2-(3-chlorophenyl)cyclohept-1-enecarb-
oxylate (8c). Purification by Flash chromatography
(CH2Cl2-pentane; 1:3) afforded 8c as colourless oil in
95% yield.
HR-MS(ES): Calcd for C19H26O2 + Na+: m/z 309.1830.
Found m/z 309.1823.
5.3.30. 1-tert-Butyl 3-ethyl 4-(naphthalen-2-yl)-5,6-dihy-
dropyridine-1,3(2H)-dicarboxylate (13d). Purification by
Flash chromatography (CH2Cl2-EtOAc; 20:1) afforded
13d as colourless oil in 76% yield.
1H NMR (CDCl3) d: 7.21 (m, 2H); 7.12 (dd, 1H,
J = 1.3 Hz, J = 2.2 Hz); 7.00 (ddd, 1H, J = 1.6 Hz,
J = 2.7 Hz, J = 6.0 Hz); 3.42 (s, 3H); 2.60–2.56 (m,
4H); 1.89–1.83 (m, 2H); 1.69–1.62 (m, 4H).
1H NMR (CDCl3) d: 7.83–7.77 (m, 3H); 7.60 (s, 1H);
7.49–7.44 (m, 2H); 7.29–7.26 (m, 1H); 4.31 (m, 2H);
3.90 (q, 2H, J = 7.1 Hz); 3.66 (dd, 2H, J = 5.7 Hz);
2.60 (m, 2H); 1.52 (s, 9H); 0.78 (m, 3H).
13C NMR (CDCl3) d: 171.0; 149.6; 146.3; 134.4; 133.9;
129.3; 127.0; 126.7; 124.9; 51.4; 37.0; 32.3; 30.9; 26.3;
25.7.
13C NMR (CDCl3) d: 167.0; 154.7; 146.0; 139.4; 133.2;
132.7; 127.9; 127.7; 127.7; 126.2; 126.0; 125.5; 125.4;
80.2; 60.4; 44.0; 39.6; 32.9; 28.5; 13.6.
HR-MS(ES): Calcd for C15H17ClO2 + Na+: m/z
287.0815. Found m/z 287.0806.

M. D. Petersen et al. / Bioorg. Med. Chem. 15 (2007) 4159–4174
4171
HR-MS(ES): Calcd for C23H27NO4 + Na+: m/z
404.1838. Found m/z 404.1840.
5.4.2. Methyl 2-(4-tert-butylphenyl)cyclohexanecarboxy-
late (21g). Purification by Flash chromatography
(diethyl ether–pentane; 1:20) afforded 21g as colourless
oil in 94% yield.
5.3.31. 1-tert-Butyl 3-ethyl 4-(3,4-dichlorophenyl)-5,6-
dihydropyridine-1,3(2H)-dicarboxylate (13a). Purifica-
tion by Flash chromatography (CH2Cl2–EtOAc; 6:1)
afforded 13a as colourless oil in 96% yield.
1H NMR (CDCl3) d: 7.29 (d, 2H, J = 8.3 Hz); 7.16
(d, 2H, J = 8.3 Hz); 3.43 (s, 3H); 2.96 (dd, 1H,
J1 = 7.7 Hz, J2 = 4.1 Hz); 2.87 (dt, 1H, J1 = 11.7 Hz,
J2 = 4.1 Hz); 2.36 (dq, 1H, J1 = 12.6 Hz, J2 = 3.5 Hz);
2.07–2.02 (m, 1H); 1.95–1.87 (m, 1H); 1.80–1.70 (m,
3H); 1.61–1.54 (m, 1H); 1.46–1.35 (m, 1H); 1.30 (s,
9H).
1H NMR (CDCl3) d: 7.40 (d, 1H, J = 8.4 Hz); 7.24 (d,
1H, J = 2.0 Hz); 6.97 (dd, 1H, J1 = 2.0 Hz,
J2 = 8.4 Hz); 4.25 (m, 2H); 4.00 (q, 2H, J = 7.2 Hz);
3.60 (m, 2H); 2.45 (m, 2H); 1.50 (s, 9H); 1.01 (t, 3H,
J = 7.2 Hz).
13C NMR (CDCl3) d: 174.6; 148.8; 141.3; 127.1; 124.9;
50.8; 46.0; 44.1; 34.3; 31.4; 29.0; 26.7; 25.9; 21.8.
13CNMR(CDCl3)d: 166.1; 154.5; 144.0; 141.9; 132.3; 131.5;
130.2; 129.0; 126.4; 80.4; 60.7; 43.8; 39.5; 32.8; 28.5; 13.8.
HR-MS(ES): Calcd for C18H26O2 + Na+: m/z 297.1830.
Found m/z 297.1833.
HR-MS(ES): Calcd for C19H23Cl2NO4 + Na+: m/z
422.0902. Found m/z422.0902.
5.4.3. Methyl 2-(4-(trifluoromethoxy)phenyl)cyclohexan-
ecarboxylate (21h). Purification by Flash chromatogra-
phy (diethyl ether–pentane; 1:20) afforded 21h as
colourless oil in 94% yield.
5.3.32. 1-tert-butyl 3-ethyl 4-(3-nitrophenyl)-5,6-dihydro-
pyridine-1,3(2H)-dicarboxylate (13q). Purification by
Flash chromatography (CH2Cl2–EtOAc; 6:1) afforded
13q as colourless oil in 87% yield.
1H NMR (CDCl3) d: 7.27 (d, 2H, J = 8.8 Hz); 7.14 (d,
2H, J = 8.8 Hz); 3.44 (s, 3H); 2.97 (dd, 1H,
J1 = 7.9 Hz, J2 = 3.9 Hz); 2.91 (dt, 1H, J1 = 12.0 Hz,
J2 = 4.2 Hz); 2.37 (dq, 1H, J1 = 13.0 Hz, J2 = 3.7 Hz);
2.12–2.05 (m, 1H); 1.98–1.90 (m, 1H); 1.82–1.72 (m,
3H); 1.63–1.56 (m, 1H); 1.50–1.35 (m, 1H).
1H NMR (CDCl3) d: 8.16 (dd, 1H, J = 8.0 Hz); 8.02 (d,
1H, J = 2.0 Hz); 7.52–7.45 (m, 2H); 4.29 (m, 2H), 3.97
(q, 2H, J = 7.2 Hz); 3.64 (dd, 2H, J = 5.6 Hz); 2.51 (m,
2H); 1.51 (s, 9H); 0.97 (t, 3H, 7.2 Hz).
13C NMR (CDCl3) d: 165.7; 154.5; 148.1; 144.5; 143.7;
133.1; 129.2; 122.3; 122.1; 80.4; 60.7; 43.8; 39.3; 33.1;
28.5; 13.8.
13C NMR (CDCl3) d: 174.5; 147.7; 143.4; 129.1; 120.8
(q, J = 256 Hz); 120.8; 51.1; 46.2; 44.2; 29.2; 26.8; 26.0;
21.8.
HR-MS(ES): Calcd for C19H24N2O6 + Na+: m/z
399.1532. Found m/z 399.1527.
HR-MS(ES): Calcd for C15H17F3O3 + Na+: m/z
325.1027. Found m/z 325.1025.
5.4. General method for reductive hydrogenation
5.4.4. Methyl 2-phenylcyclohexanecarboxylate (21l).
Purification by Flash chromatography (diethyl ether–
pentane; 1:20) afforded 21l as colourless oil in 91% yield.
The unsaturated compounds were stirred for 24 h in
methanol with 10% Pd/C (10 wt%) at atmospheric pres-
sure under H2. After filtration through Celite and con-
centration in vacuo the products were purified by
Flash chromatography.
1H NMR (CDCl3) d: 7.30–7.15 (m, 5H); 3.42 (s, 3H);
3.00–2.85 (m, 2H); 2.37 (q, 1H, J = 11.6 Hz); 2.08–2.02
(m, 1H); 1.96–1.88 (m, 1H); 1.80–1.70 (m, 3H); 1.62–
1.54 (m, 1H); 1.46–1.36 (m, 1H).
5.4.1. Methyl 2-(biphenyl-4-yl)cyclohexanecarboxylate (21e).
Purification by Flash chromatography (diethyl ether–pen-
tane; 1:20) afforded 21e as colourless oil in 70% yield.
13C NMR (CDCl3) d: 175.0; 144.6; 128.3; 127.7; 126.3;
51.0; 46.2; 44.8; 29.1; 26.7; 26.0; 21.8.
1H NMR (CDCl3) d: 7.58 (d, 2H, J = 8.0 Hz); 7.51 (d,
2H, J = 8.1 Hz); 7.42 (t, 2H, J = 7.2 Hz); 7.34–7.28 (m,
3H); 3.45 (s, 3H); 3.01 (dd, 1H, J1 = 7.8 Hz,
J2 = 4.2 Hz); 2.93 (dt, 1H, J1 = 11.8 Hz, J2 = 4.2 Hz);
2.40 (dq, 1H, J1 = 12.0 Hz, J2 = 2.8 Hz); 2.10–2.05 (m,
1H); 1.97–1.90 (m, 1H); 1.84–1.73 (m, 3H); 1.62–1.56
(m, 1H); 1.50–1.40 (m, 1H).
HR-MS(ES): Calcd for C14H18O2 + Na+: m/z 241.1204.
Found m/z 241.1197.
5.4.5. Methyl 2-(3-(trifluoromethyl)phenyl)cyclohexane-
carboxylate (21m). Purification by Flash chromatogra-
phy (diethyl ether–pentane; 1:20) afforded 21m as
colourless oil in 74% yield.
13C NMR (CDCl3) d: 174.5; 143.6; 141.0; 138.9; 128.7;
127.9; 127.0; 127.0 126.8; 50.9; 46.0; 44.3; 29.0; 26.7;
25.8; 21.7.
1H NMR (CDCl3) d: 7.47–7.35 (m, 5H); 3.42 (s, 3H);
3.00–2.90 (m, 2H); 2.37 (dq, 1H, J1 = 12.0 Hz,
J2 = 3.7 Hz); 2.12–2.04 (m, 1H); 1.98–1.89 (m, 1H);
1.81–1.72 (m, 3H); 1.63–1.56 (m, 1H); 1.48–1.36 (m,
1H).
HR-MS(ES): Calcd for C20H22O2 + Na+: m/z 317.1517.
Found m/z 317.1518.

4172
M. D. Petersen et al. / Bioorg. Med. Chem. 15 (2007) 4159–4174
13C NMR (CDCl3) d: 174.3; 145.5 131.2; 128.6; 124.5;
123.8; 51.1; 46.1; 44.6; 29.2; 26.6; 25.9; 21.7.
trated in vacuo and 10 mL of 1 M NaOH was added.
The aqueous phase was extracted with 3 · 10 mL
CH2Cl2 and the combined organic phases dried over
MgSO4 and concentrated in vacuo. Purification by
Flash chromatography (CH2Cl2–MeOH; 6:1) afforded
5d as a yellowish oil in 72% yield (26 mg).
HR-MS(ES): Calcd for C15H17F3O2 + Na+: m/z
309.1078. Found m/z 309.1071.
5.4.6. Methyl 2-(4-(trifluoromethyl)phenyl)cyclohexane-
carboxylate (21n). Purification by Flash chromatogra-
phy (diethyl ether–pentane; 1:20) afforded 21m as
colourless oil in 70% yield.
1H NMR (CDCl3) d: 7.83–7.78 (m, 3H); 7.61 (s, 1H);
7.48–7.43 (m, 2H); 7.30–7.28 (m, 1H); 3.87 (q, 2H,
J = 7.1 Hz); 3.77 (m, 2H); 3.14 (t, 2H, J = 5.5 Hz);
2.54 (m, 2H); 2.42 (br. s, 1H); (t, 3H, J = 7.1 Hz).
1H NMR (CDCl3) d: 7.53 (d, 2H, J = 8.3 Hz); 7.35 (d,
2H, J = 8.3 Hz); 3.43 (s, 3H); 3.00–2.90 (m, 2H); 2.38
(dq, 1H, J1 = 12.0 Hz, J2 = 3.7); 2.12–2.05 (m, 1H);
1.96–1.88 (m, 3H); 1.82–1.60 (m, 2H); 1.43–1.35 (m,
1H).
13C NMR (CDCl3) d: 167.8; 145.8; 139.9; 133.2; 132.6;
128.0; 127.8; 127.7; 127.6; 126.2; 126.0; 125.6; 125.4;
60.2; 45.9; 42.9; 32.8; 13.6.
HR-MS(ES): Calcd for C18H19NO2 + Na+: m/z
304.1313. Found m/z 304.1328.
13C NMR (CDCl3) d: 174.2; 148.7; 128.1; 125.1; 51.1;
46.0; 44.5; 29.2; 26.5; 25.8; 21.8.
5.4.10. Ethyl 4-(3,4-dichlorophenyl)-1,2,5,6-tetrahy-
dropyridine-3-carboxylate (5a). To a solution of 13a
(60 mg, 0.15 mmol) in 5 mL CH2Cl2 was added 1 mL
TFA (13.4 mmol) and the reaction mixture was stirred
for 17 h at room temperature. The mixture was con-
centrated in vacuo and 10 mL of 1 M NaOH was
added. The aqueous phase was extracted with
3 · 10 mL CH2Cl2 and the combined organic phases
dried over MgSO4 and concentrated in vacuo. Purifi-
cation by Flash chromatography (CH2Cl2–MeOH;
6:1) afforded 5a as a yellowish oil in 63% yield
(28 mg).
HR-MS(ES): Calcd for C15H17F3O2 + Na+: m/z
309.1078. Found m/z 309.1071.
5.4.7. Methyl 2-(biphenyl-4-yl)cycloheptanecarboxylate
(22e). Purification by Flash chromatography (CH2Cl2–
pentane; 1:1) afforded 22e as colourless oil in 80% yield.
1H NMR (CDCl3) d: 7.48 (d, 2H, J = 7.6 Hz); 7.40 (d,
2H, J = 8.2 Hz); 7.33 (t, 2H, J = 7.7 Hz); 7.23 (t, 1H,
J = 7.3 Hz); 7.18 (d, 2H, J = 7.8 Hz); 3.26 (s, 3H); 3.18
(ddd, 1H, J = 4.2 Hz, J = 6.5 Hz, J = 10.4 Hz); 2.92
(ddd, 1H, J = 4.2 Hz, J = 6.5 Hz, J = 10.4 Hz); 2.15–
1.82 (m, 8H); 1.39 (m, 2H).
1H NMR (CDCl3) d: 7.39 (d, 1H, J = 8.2 Hz); 7.25 (d,
1H, J = 1.8 Hz); 6.99 (d, 1H, J = 8.3 Hz); 3.97 (q, 2H,
J = 7.1 Hz); 3.74 (m, 2H); 3.26 (b. s, 1H); 3.12 (m,
2H); 2.44 (m, 2H); 0.98 (t, 3H, J = 7.1 Hz).
13C NMR (CDCl3) d: 175.6; 144.4; 141.1; 139.1; 128.8;
128.4; 127.1; 127.0; 126.8; 51.1; 50.2; 47.0; 32.2; 30.5;
28.6; 28.1; 27.5.
13C NMR (CDCl3) d: 166.6; 144.0; 142.2; 132.3; 131.5;
130.2; 129.0; 127.7; 126.5; 60.6; 45.3; 42.4; 32.4; 13.8.
HR-MS(ES): Calcd for C21H24O2 + Na+: m/z 331.1674.
Found m/z 331.1661.
HR-MS(ES): Calcd for C14H15Cl2NO2 + H+: m/z
300.0558. Found m/z 300.0552.
5.4.8. Methyl 2-(4-tert-butylphenyl)cycloheptanecarboxy-
late (22g). Purification by Flash chromatography
(CH2Cl2–pentane; 1:2) afforded 22g as colourless oil in
78% yield.
5.4.11. Ethyl 4-(3-nitrophenyl)-1,2,5,6-tetrahydropyri-
dine-3-carboxylate (5q). To a solution of 13c (48 mg,
0.13 mmol) in 5 mL CH2Cl2 was added 1 mL TFA
(13.4 mmol) and the reaction mixture was stirred for
17 h at room temperature. The mixture was concen-
trated in vacuo and 10 mL of 1 M NaOH was added.
The aqueous phase was extracted with 3 · 10 mL
CH2Cl2 and the combined organic phases dried over
MgSO4 and concentrated in vacuo. Purification by
Flash chromatography (CH2Cl2–MeOH; 6:1) afforded
5q as a yellowish oil in 82% yield (27 mg).
1H NMR (CDCl3) d: 7.27 (d, 2H, J = 8.2 Hz); 7.11 (d,
2H, J = 8.2 Hz); 3.29 (s, 3H); 3.18 (ddd, 1H, J = 4.2
Hz, J = 6.5 Hz, J = 10.6 Hz); 2.94 (ddd, 1H,
J = 4.2 Hz, J = 6.5 Hz, J = 10.6 Hz); 2.19–1.81 (m,
8H); 1.45 (m, 2H), 1.29 (s, 9H).
13C NMR (CDCl3) d: 175.7; 149.0; 142.1; 127.6; 124.9;
51.0; 50.3; 46.8; 34.4; 32.1; 31.5; 30.5; 28.6; 28.2; 27.4.
HR-MS(ES): Calcd for C19H28O2 + Na+: m/z 311.1987.
Found m/z 331.1982.
1H NMR (CDCl3) d: 8.15 (ddd, 1H, J = 1.9 Hz,
J = 1.9 Hz, J = 7.3 Hz); 8.03 (m, 1H); 7.52–7.46 (m,
2H); 3.94 (q, 2H, J = 7.1 Hz); 3.77 (m, 2H); 3.20 (br.
s, 1H); 3.14 (m, 2H); 2.49 (m, 2H); 0.93 (t, 3H,
J = 7.1 Hz).
5.4.9. Ethyl 4-(naphthalen-2-yl)-1,2,5,6-tetrahydropyri-
dine-3-carboxylate (5d). To a solution of 13d (49 mg,
0.13 mmol) in 5 mL CH2Cl2 was added 1 mL TFA
(13.4 mmol) and the reaction mixture was stirred for
30 min at room temperature. The mixture was concen-
13C NMR (CDCl3) d: 166.2; 148.2; 144.5; 144.1; 133.3;
129.1; 128.3; 122.3; 122.1; 60.6; 45.3; 42.4; 32.8; 13.8.

M. D. Petersen et al. / Bioorg. Med. Chem. 15 (2007) 4159–4174
4173
HR-MS(ES): Calcd for C14H16N2O4 + H+: m/z
277.1188. Found m/z 277.1183.
phase was extracted with ether (10 mL) and the combined
ether phases were dried (MgSO4). The solvent was re-
moved in vacuo and purification by Flash chromatogra-
phy (pentane) afforded 25 as colourless oil in 76% yield
(111 mg).
5.4.12. (2-(3,4-Dichlorophenyl)cyclohex-1-enyl)methanol
(23). 7a (250 mg, 0.88 mmol) dissolved in ether (5 mL)
was added to a suspension of LiAlH4 (250 mg,
6.58 mmol) in dry ether (10 mL). The mixture was re-
fluxed for 1 h and after cooling to 0 ꢁC quenched with
water. The water phase was made acidic by 2 M HCl
and the ether phase was isolated. The water phase was
extracted with ether (10 mL), and the combined ether
phases were dried (MgSO4). Removal of the solvent un-
der reduced pressure afforded 23 as a slightly yellow oil
in 99% yield (224 mg). Compound 23 was used without
further purification.
1H NMR (CDCl3) d: 7.31 (d, 0.5H, J = 8.2 Hz); 7.23
(d, 0.5H, J = 8.3 Hz); 7.21–7.17 (m, 1H); 6.92 (dt,
1H, J1 = 8.3 Hz, J2 = 2.1 Hz); 5.94 (d, 0.5H, J =
15.5 Hz); 5.70 (d, 0.5H, J = 11.5 Hz); 5.61 (dq, 0.5H,
J1 = 15.6 Hz,
J2 = 6.6 Hz);
5.18
(dq,
J1 = 11.6 Hz, J2 = 7.0 Hz); 2.25–2.12 (m, 4H); 1.70–
0.5H,
1.58 (m, 7H).
13C NMR (CDCl3) d: 144.5; 144.0; 133.8; 133.4; 133.1;
132.1; 131.8; 131.7; 130.9; 130.8; 130.7; 130.5; 130.3;
130.1; 129.8; 128.6; 128.1; 125.2; 123.9; 32.8; 31.5;
30.4; 25.7; 23.2; 23.2; 22.9; 22.7; 18.7; 15.1.
1H NMR (CDCl3) d: 7.37 (d, 1H, J = 8.2 Hz); 7.26 (d,
1H, J = 2.0 Hz); 7.00 (dd, 1H, J1 = 8.2 Hz,
J2 = 2.0 Hz); 3.92 (s, 2H); 2.27–2.21 (m, 4H); 1.74–1.69
(m, 4H).
HR-MS(ES): Calcd for C15H16Cl2 + Na+: m/z 289.0527.
Found m/z 289.0533.
13C NMR (CDCl3) d: 143.0; 134.7; 134.1; 132.2; 130.6;
130.2; 127.8; 63.8; 32.0; 27.1; 23.1; 22.6.
Acknowledgment
HR-MS(ES): Calcd for C13H14Cl2O + Na+: m/z
279.0319. Found m/z 279.0325.
We thank the Lundbeck foundation and FNU for
generous financial support.
5.4.13.
2-(3,4-Dichlorophenyl)cyclohex-1-enecarbalde-
hyde (24). Oxalylchloride (0.1 mL, 1.18 mmol) was dis-
solved in dry dichloromethane (5 mL) and, after
cooling to À78 ꢁC, DMSO was added (1 mL). The mix-
ture was stirred for 5 min at À78 ꢁC followed by addi-
tion of 23 (207 mg, 0.80 mmol) in dry DCM (3 mL).
The mixture was stirred for further 1 h at À78 ꢁC fol-
lowed by addition of Et3N (3 mL). The mixture was stir-
red at rt. for 1 h and thereafter diluted with
dichloromethane (10 mL). The organic solution was
washed with satd aq solution of Na2CO3 (3 · 10 mL)
and dried (MgSO4). The solvent was removed in vacuo
and purification by Flash chromatography (ether–pen-
tane; 1:5) afforded 24 as colourless oil in 69% yield
(142 mg).
Supplementary data
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/
j.bmc.2007.03.069.
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