Novel conformationally constrained tropane analogues by 6-endo-trig radical cyclization anti stille coupling - Switch of activity toward the serotonin anti/or norepinephrine transporter

Article abstract of DOI:10.1021/jm0001121

A novel class of tricyclic tropane analogues has been synthesized by making use of radical cyclization technology in combination with the Stille coupling reaction. As hybrids between tropanes and quinuclidines, these tropaquinuclidines represent a significant structural departure from many of the other classes of tropane ligands synthesized to date. This structure class is characterized by the boat conformation of the tropane ring and the orientation of the additional bridge (and therefore of the nitrogen lone pair) together with the unusual placement of the aromatic moiety. All compounds were tested for their ability to inhibit monoamine reuptake under identical conditions. The ability to inhibit reuptake of dopamine in comparison to cocaine is generally decreased in this series but for one compound. (1S,3R,6S)-(Z)-9-(thienylmethylene)-7-azatricyclo[4.3.1.0]decane- 2β-carboxylic acid methyl ester (5h) exhibits reasonable activity at the dopamine transporter (DAT) (K(i) = 268 nM) and good activity at the norepinephrine transporter (NET) (K(i) = 26 nM). The potency and selectivity shown by some of these ligands for the NET, serotonine transporter (SERT), or NET/SERT is striking, particularly in view of the displacement of the aromatic ring in this series from its usual position at C-3 in the WIN analogues. Thus, (1S,3R,6S)-(Z)-9-(4-biphenylylmethylene)-7- azatricyclo[4.3.1.0]decane-2β-carboxylic acid methyl ester (5a) is a selective inhibitor of norepinephrine reuptake (K(i) = 12 nM). Its p-methoxy analogue 5c is a mixed inhibitor of norepinephrine and serotonin reuptake (K(i) = 187 nM at the NET and 56 nM at the SERT). The most active and selective compound we found in the present series is compound 8b [(1S,3R,6S)- 2-(acetoxymethyl)-(Z)9-(3,4-dichlorophenylmethylene)-7- azatricyclo[4.3.1.0]decane]. This compound is a potent (K(i) = 1.6 nM) and selective inhibitor of serotonin reuptake into rat midbrain synaptosomes. Its selectivity is about 400-fold over the NET and about 1000-fold over the DAT. The results of this study further demonstrate the possibility of tuning the selectivity of tropane analogues toward the SERT or NET binding site. The ligands disclosed herein provide additional pharmacological tools of use in attempting to correlate structure and transporter selectivity with in vivo studies of behavioral outcomes.

Full text of DOI:10.1021/jm0001121

2064
J . Med. Chem. 2000, 43, 2064-2071
Novel Con for m a tion a lly Con str a in ed Tr op a n e An a logu es by 6-en d o-tr ig Ra d ica l
Cycliza tion a n d Stille Cou p lin g - Sw itch of Activity tow a r d th e Ser oton in
a n d /or Nor ep in ep h r in e Tr a n sp or ter
Alexander Hoepping,† Kenneth M. J ohnson,‡ Clifford George,§ J udith Flippen-Anderson,§ and
Alan P. Kozikowski*,†
Drug Discovery Program, Georgetown University Medical Center, 3900 Reservoir Road, NW, Washington, D.C. 20007-2197,
Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, Texas 77555-1031,
and Laboratory for the Structure of Matter, Code 6030, Naval Research Laboratory, 4555 Overlook Avenue, SW,
Washington, D.C. 20375-5000
Received March 8, 2000
A novel class of tricyclic tropane analogues has been synthesized by making use of radical
cyclization technology in combination with the Stille coupling reaction. As hybrids between
tropanes and quinuclidines, these tropaquinuclidines represent a significant structural
departure from many of the other classes of tropane ligands synthesized to date. This structure
class is characterized by the boat conformation of the tropane ring and the orientation of the
additional bridge (and therefore of the nitrogen lone pair) together with the unusual placement
of the aromatic moiety. All compounds were tested for their ability to inhibit monoamine
reuptake under identical conditions. The ability to inhibit reuptake of dopamine in comparison
to cocaine is generally decreased in this series but for one compound. (1S,3R,6S)-(Z)-9-
(thienylmethylene)-7-azatricyclo[4.3.1.03,7]decane-2â-carboxylic acid methyl ester (5h ) exhibits
reasonable activity at the dopamine transporter (DAT) (Ki ) 268 nM) and good activity at the
norepinephrine transporter (NET) (Ki ) 26 nM). The potency and selectivity shown by some of
these ligands for the NET, serotonine transporter (SERT), or NET/SERT is striking, particularly
in view of the displacement of the aromatic ring in this series from its usual position at C-3 in
the WIN analogues. Thus, (1S,3R,6S)-(Z)-9-(4-biphenylylmethylene)-7-azatricyclo[4.3.1.03,7]-
decane-2â-carboxylic acid methyl ester (5a ) is a selective inhibitor of norepinephrine reuptake
(Ki ) 12 nM). Its p-methoxy analogue 5c is a mixed inhibitor of norepinephrine and serotonin
reuptake (Ki ) 187 nM at the NET and 56 nM at the SERT). The most active and selective
compound we found in the present series is compound 8b [(1S,3R,6S)-2-(acetoxymethyl)-(Z)-
9-(3,4-dichlorophenylmethylene)-7-azatricyclo[4.3.1.03,7]decane]. This compound is a potent (Ki
) 1.6 nM) and selective inhibitor of serotonin reuptake into rat midbrain synaptosomes. Its
selectivity is about 400-fold over the NET and about 1000-fold over the DAT. The results of
this study further demonstrate the possibility of tuning the selectivity of tropane analogues
toward the SERT or NET binding site. The ligands disclosed herein provide additional
pharmacological tools of use in attempting to correlate structure and transporter selectivity
with in vivo studies of behavioral outcomes.
In tr od u ction
prominent roles in cocaine addiction.3-5 Thus, the
selective transport inhibitors desipramine and fluoxet-
ine have been shown to shift cocaine’s dose-response
curve to the left, demonstrating that low doses of cocaine
that do not elicit cocaine-lever-appropriate responding
acquire full cocaine-like properties when combined with
selective inhibitors of the NET and the SERT, which
when administered alone produce only partial cocaine-
like responding.6,7 Furthermore, experiments with DAT
knockout mice suggest that a certain amount of redun-
dancy in the cocaine reward circuit may exist.8 To date,
antidepressant agents such as fluoxetine or desipramine
that interact selectively with biogenic amine transport-
ers have met with limited success in clinical trials.9,10
It may be that these agents do not possess the right
profile of inhibitory activity at these transporters, or it
could mean that this approach is simply without merit.
Currently, there are too little data to confirm either of
these hypotheses. To further study the role of the
different transport systems in cocaine reward and
craving, ligands exhibiting varying selectivities for one
Cocaine abuse remains a serious health and social
problem in the United States and worldwide, with an
estimated 1.5 million cocaine users in the United States
alone.1 As a consequence, it is obvious that immediate
strategies are needed for the treatment of cocaine
addiction to combat the destructive effects of this
reinforcing drug on individuals and on society at large.
According to the dopamine theory of addiction, cocaine
is believed to elicit its behavioral and pharmacological
effects primarily by binding to the dopamine transporter
(DAT) in the nucleus accumbens and striatum, thereby
inhibiting the removal of dopamine from the synaptic
cleft. In addition to the DAT, cocaine also binds with
high affinity to the serotonin (SERT) and the norepi-
nephrine transporters (NET).2 More recent work sug-
gests that both the SERT and the NET may also play
† Georgetown University Medical Center.
‡ University of Texas Medical Branch.
§ Naval Research Laboratory.
10.1021/jm0001121 CCC: $19.00 © 2000 American Chemical Society
Published on Web 05/03/2000

Novel Conformationally Constrained Tropanes
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 10 2065
F igu r e 2. Schematic overlay of 5 and 6 with a WIN com-
pound; distances between the nitrogen and centroid of the
aromatic ring: (1) 5.6 Å, (2) 7.6 Å, (3) 5.6 Å.
Sch em e 1
to contribute to binding at the monoamine transport-
ers.11 At the same time, the aromatic ring is displaced
from its original 3-position to a position above the basal
plane of the tropane ring without changing its ap-
proximate directionality. The distance between nitrogen
and the centroid of the aromatic ring in the WIN
compounds is about 5.63 Å and seems to be optimal for
high binding affinity.15 Since 3â-(phenyl)alkyltropanes16
or 3â-carbamoyl analogues of cocaine17,18 are in general
less active than WIN compounds, we regarded it as
necessary to maintain about the same interatomic
distance. Essentially the same distance of about 5.64 Å
is maintained by installation of a three-carbon linker
between the nitrogen and the aromatic ring in the N,-
C3-bridged19 compound possessing a Z-configured double
bond (Figure 2). For the E-configured compound 6 this
distance is enhanced to about 7.6 Å.
N, C3
F igu r e 1.
or more of the monoamine transporters will be valuable.
In fact, it is reasonable to suggest that drugs lacking
the ability to inhibit transport at all three monoamin-
ergic transporters would exhibit only partial cocaine-
like properties, and thus possibly serve as medications.
The present study was designed to provide additional
tools to investigate this largely untested hypothesis.
To date numerous tropane and non-tropane deriva-
tives have been prepared (Figure 1), both with the aim
to better understand structure-activity relationships
at the DAT and with the notion that the identification
of ligands of improved potency and DAT selectivity may
lead to “cocaine medications.”11,12 However, despite
these notable efforts, ligands that have targeted solely
the DAT have not at present led to a clinically useful
medication. Yet important progress has been made in
the synthesis of ligands that show improved selectivity
in the inhibition of either dopamine or serotonin re-
uptake.13 For example, we have recently shown that
constraint of the nitrogen lone pair by making “front-”
or “back-bridged” tropane analogues leads to compounds
with selectivity for either the SERT or the DAT.14 The
NET affinity was generally not influenced by this
structural change. Because of our interest in identifying
ligands showing diminished DAT activity, we chose to
further explore the SAR of the front-bridged tropanes.
In particular, we felt that a more dramatic departure
from the structure exhibited by the WIN analogues
might facilitate the identification of ligands showing
only partial cocaine-like effects. Thus, we chose to
introduce a ring constraint between the 3-position of the
tropane ring and the nitrogen atom which by necessity
forces the six-membered ring of the tropane moiety into
a boat conformation. These new N,C3-bridged com-
pounds can also be viewed as tropaquinuclidines, hy-
brids of tropanes and quinuclidines as illustrated in
Figure 1.
Ch em istr y
Retrosynthetic analysis of the envisioned N,C3-
bridged tropanes reveals that the installation of the new
bridge could be accomplished using an intramolecular
radical cyclization reaction starting from a propargyl-
substituted anhydroecgonine methyl ester. This would
lead to a tricyclic vinylstannane, which in turn would
be a suitable substrate to introduce a phenyl substituent
by means of a Stille coupling (Scheme 1).
The preparation of the bridged tropanes was ac-
complished using the general strategy outlined in
Scheme 2. Starting from cocaine (1), norcocaine was
prepared by N-demethylation with R-chloroethyl chlo-
roformate.20 Alkylation with propargyl bromide afforded
N-propargylnorcocaine in 84% yield. Saponification,
dehydration, and reesterification provided N-propar-
gylnoranhydroecgonine methyl ester (2). The key step
in the synthesis is a 6-endo-trig cyclization. It was
envisioned that the vinyl radical, generated by addition
of a stannyl radical to the triple bond, would react in
an endo manner with the double bond because of the
radical stabilizing effect of the ester group, thus pre-
venting a competing 5-exo-trig cyclization.21 The cycliza-
tion was carried out using syringe pump methodology,
an excess of tributyltin hydride, and equimolar amounts
of AIBN. The cyclization proceeded in good yield (73%)
and with high diastereoselectivity as relates to the
orientation of the ester group. Due to the bulky nature
Moreover, this modification would allow us to main-
tain the ester group at the 2-position, which is known

2066 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 10
Hoepping et al.
Sch em e 2a
Sch em e 3a
a
Reagents and conditions: (a) LiAlH4 or DIBAL-H/THF; (b)
pyridine, Ac2O, DMAP; E ) COOMe; a , Ar ) Ph; b, Ar ) 3,4-
dichlorophenyl.
orientation of the phenyl ring constitutes an important
structural determinant of transporter activity in this
ligand series.
Only one compound, 5h , shows higher activity at the
DAT than cocaine. This compound was derived from 5a
by bioisosteric replacement of the phenyl ring with a
thiophene ring. 5h exhibits improved activity at the
NET and, as a consequence of its significant DAT
activity, acts as a combined dopamine and norepineph-
rine reuptake inhibitor. The remaining compounds show
decreased activity at the DAT with Ki values from about
480 nM for 5a to 10 µM for 5e, thus confirming our
previous finding that a ring constraint over the three-
carbon bridge leads to compounds with reduced DAT
activity.14
a
Reagents and conditions: (a) CH3CH(Cl)OCOCl, 1,2-dichlo-
roethane, K2CO3; MeOH, 92%; (b) propargyl bromide, K2CO3,
MeCN, 84%; (c) 2 N HCl; POCl3; MeOH, -78 °C f rt, 82%; (d)
AIBN, n-Bu3SnH, PhH, 73%; (e) ArI, CuI, (o-Tol)3P, Pd2(dba)3,
DMF, 8-65%; a , Ar ) Ph; b, Ar ) 3,4-dichlorophenyl; c, Ar )
4-MeO-C6H4; d , Ar ) 4-F-C6H4; e, Ar ) 1-naphthyl; f, Ar )
2-furyl; g, Ar ) 3-furyl; h , Ar ) 2-thienyl; i, Ar ) biphenylyl.
The SAR for the NET and for the SERT is not as easy
to interpret. Compound 5a lacking substitution on the
phenyl ring shows potent inhibition of norepinephrine
reuptake. It is also reasonably selective, as its Ki values
at the SERT and DAT are 20-fold and 9-fold higher,
respectively. The thiophene derivative (5h ), already
mentioned above, exhibits an improved activity at the
NET and 100-fold selectivity over the SERT. The most
active compound at the NET binding site is the biphenyl
derivative 5i with good selectivity over the DAT (50-
fold) and SERT (50-fold). The p-methoxy-substituted
compound 5c as well as the two furyl analogues 5f and
5g still exhibit good activity for the NET. The remaining
compounds exhibit a dramatic drop in activity. Appar-
ently, the steric requirements for the hydrophobic
recognition pocket for the phenyl ring at the NET are
rather strict, allowing only para substitution. These
findings are further supported by the decreased activity
found for the 3,4-dichlorophenyl bearing analogue 5b
as well as the very poor activity shown by the naphthyl
analogue 5e. Moreover a certain electron density in the
phenyl ring seems to be necessary for binding, as a
fluoro substituent decreases norepinephrine reuptake
activity by a factor of about 10 (5d vs 5a ).
To investigate the influence of the ester group on
binding activity and selectivity, we converted 5a and
5b into their corresponding alcohols 7a and 7b. In
comparison to the ester 5a , a drastic loss in activity was
observed for the alcohol 7a . Also, conversion of the
alcohol 7a into the acetate 8a did not lead to a signi-
ficant regain in activity. At first sight the ester group
would seem to be essential for activity, even if all
possible chemical modifications have not been explored.
The size and orientation of the hydrophobic recogni-
tion pocket seems to be a major factor in differentiating
ligands for either the NET or the SERT. We found that
simple phenyl substitution does not lead to high activity
at the SERT. However, naphthyl substitution increases
the activity at the SERT by a factor of about 10 (5e vs
of the tributylstannyl residue, the cyclized radical is
trapped predominantly from the endo face of the tropane
ring, thus giving rise to the formation of the tricycles 3
and 4 with the ester group in a â-orientation.22 However,
two double bond isomers23,24 (3 and 4) were obtained in
an Z/ E ratio of about 2:1, and these were easily
separated by flash chromatography. No attempts were
made to assign the structure of the two isomers at this
stage. Next, we converted the vinylstannanes into the
phenyl derivatives 5a and 6 by means of a Stille
coupling with iodobenzene.
The use of DMF as solvent, tris(dibenzylideneac-
etone)dipalladium(0) as palladium source, tri(o-tolyl)-
phosphine as stabilizing ligand, and copper(I) iodide as
additive, as well as a strict temperature regimen, were
necessary to obtain the coupling products in acceptable
yields. The two stereoisomers were analyzed by NMR
methods using COSY, NOESY, and HETCOR. From the
NMR studies, 5a was assigned the Z-configuration and
6 the E-configuration (Figure 3). These assignments
were also confirmed by X-ray analysis.25 Since the Stille
reaction proceeds with retention of configuration, the
configurations of the starting vinylstannanes follow
from those of their phenyl derivatives.26 Compounds 7a
and 7b were obtained in good yields by reduction of the
ester group using either LiAlH4 or DIBAL-H in THF.
Acylation with acetic anhydride afforded the acetates
8a and 8b (Scheme 3).
Resu lts a n d Discu ssion
These novel ligands were tested for their inhibition
of reuptake of NE, 5-HT, and DA at their specific
transporters (Table 1).27,28
Compound 6 with the E-configured double bond is
only weakly active at all three transporters, whereas
compounds in the Z-series show high activity at the
monamine transport binding sites. As is apparent, the

Novel Conformationally Constrained Tropanes
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 10 2067
Ta ble 1. Inhibition of Reuptake at Monoamine Transporters, Ki ( SEM (nM)a
R1/R2
[3H]NE uptake
[3H]5-HT uptake
[3H]DA uptake
NE/DA
NE/5-HT
5-HT/DA
cocaine
5a
108 ( 3
53 ( 16
155 ( 1
1140 ( 70
423 ( 147
481 ( 11
0.2
0.11
0.7
0.05
0.37
2.36
R1 ) Ph
R2 ) COOMe
R1 ) 3,4-dichlorophenyl
R2 ) COOMe
R1 ) 4-MeO-C6H4
R2 ) COOMe
R1 ) 4-F-C6H4
R2 ) COOMe
R1 ) naphthyl
R2 ) COOMe
R1 ) 2-furyl
5b
5c
5d
5e
5f
5g
5h
5i
1000 ( 280
187 ( 5
20 ( 1
56 ( 4
1920 ( 260
3130 ( 160
6620 ( 460
9720 ( 700
2020 ( 190
1880 ( 10
268 ( 17
0.52
0.06
0.09
0.55
0.05
0.09
0.10
0.02
0.3
50.6
3.37
1.74
44.5
0.03
0.33
0.01
0.02
0.2
0.01
0.02
0.05
0.01
1.82
0.26
7.65
1.29
1.48
0.55
0.005
1.02
0.001
584 ( 163
5370 ( 580
111 ( 13
164 ( 3
335 ( 45
121 ( 3
3680 ( 190
498 ( 65
2050 ( 40
614 ( 105
7480 ( 250
5300 ( 180
96 ( 5
R2 ) COOMe
R1 ) 3-furyl
R2 ) COOMe
R1 ) 2-thienyl
R2 ) COOMe
R1 ) 4-biphenylyl
R2 ) COOMe
R1 ) Ph
26 ( 2
12 ( 1
477 ( 81
6
1530 ( 150
2830 ( 630
10500 ( 800
450 ( 18
638 ( 86
5070 ( 310
9690 ( 167
21300 ( 2180
1030 ( 70
1870 ( 90
R2 ) COOMe
R1 ) Ph
7a
7b
8a
8b
0.29
0.49
0.44
0.34
0.53
109.
0.43
412
R2 ) CH2OH
R1 ) 3,4-dichlorophenyl
R2 ) CH2OH
R1 ) Ph
1050 ( 190
1.6 ( 0.4
R2 ) CH2OAc
R1 ) 3,4-dichlorophenyl
R2 ) CH2OAc
a
Ki values are mean ( SEM from two to four independent experiments, each consisting of six drug concentrations (in triplicate) that
were selected on the basis of preliminary screening experiments to bracket the approximate IC50 value.
Ta ble 2. Binding and Inhibition of Reuptake Performed in Cells Expressing Human Transporters, Ki ( SEM (nM)a
HEK-hNET cells
HEK-hSERT cells
HEK-hDAT cells
selectivities (uptake)
[
125I]RTI-55
binding
[3H]NE
uptake
[
125I]RTI-55
binding
[3H]5-HT
uptake
[
125I]RTI-55
binding
[3H]DA
uptake
NE/DA
NE/5-HT
5-HT/DA
cocaine
5a
5b
1740 ( 180
1040 ( 360
3770 ( 390
5440 ( 470
264 ( 57
68 ( 13
640 ( 120
208 ( 75
343 ( 31
301 ( 53
2400 ( 1100
30.0 ( 8
258 ( 23
276 ( 22
910 ( 160
>10 µM
2330 ( 480
0.56 ( 0.01
42 ( 11
1570 ( 180
3320 ( 550
3600 ( 1600
0.07
0.06
0.06
0.03
21.3
3.9
2.6
0.03
0.01
5c
53 ( 14
3700 ( 520
a
Numbers represent the means ( SEM from at least three independent experiments, each conducted with duplicate (for binding
assays) or triplicate (for uptake assays) determination.
5a ), thus demonstrating the different shape of the
recognition site. Since 3,4-dichlorophenyl substitution
in the WIN series leads to some of the most DAT active
compounds to be reported (IC50 ) 0.79 nM),29 we decided
to explore this substitution pattern also in our series.
Compound 5b in fact exhibits remarkable potency and
selectivity for the SERT, showing about 100-fold higher
activity at the SERT vs the DAT and about 50-fold
higher activity at the SERT vs the NET. This activity
could further be improved by reducing the ester group
and acylating the obtained alcohol with acetic anhy-
dride. The resulting compound 8b is the most active and
selective compound in the present series. Its selectivity
for the SERT over the NET and DAT of about 410 and
1000 is intriguing. This good selectivity is also retained
in the alcohol 7b, which still has good activity at the
SERT. The 3,4-dichlorophenyl substituent pattern con-
stitutes therefore an important element for binding at
the SERT, which can be further fine-tuned by modifica-
tion of the ester group. Compound 5c has a SERT
activity between that of 8b and 5e, and its selectivity
over the DAT is still good (50-fold for SERT vs DAT).
Additionally, compounds 5a , 5b, and 5c were tested
by the Cocaine Treatment Discovery Program (CTDP)
of the National Institute on Drug Abuse (NIDA) for their
effects on radioligand binding and biogenic amine
uptake by HEK cells expressing cDNA for the human
DAT, SERT, and NET, respectively (Table 2).30 The
uptake data obtained using cells that express human
monoamine transporters correlate well with the data
obtained with rat synaptosomes, thus corroborating our
initial data. Slight inconsistencies are probably due to
species differences. These data revealed an excellent
binding affinity within the picomolar range at the
human SERT for compound 5b. The selectivity of this
compound over both DAT and NET is about 6000, hence
making it one of the most active and selective tropane
analogues identified to date at the SERT.
The compounds disclosed in the present series possess
several features which distinguish them from other

2068 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 10
Hoepping et al.
J ) 16.1, both parts d with J ) 2.4), 3.44 (br s, 1H), 3.72 (s,
3H), 3.95 (m, 1H), 5.27 (quin, J ) 5.8, 1H), 7.45 (t, J ) 7.8,
2H), 7.54 (t, J ) 7.3, 1H), 8.03 (d, J ) 7.3, 2H); 13C NMR δ
25.23, 25.92, 35.49, 41.82, 50.06, 51.33, 60.12, 61.95, 66.92,
71.25, 80.94, 128.25, 129.65, 130.18, 132.87, 166.1, 170.23.
tropane derivatives synthesized until now, particularly,
the additional bridge between the carbon atom 319 and
the nitrogen, which constrains the tropane ring in the
boat conformation. Recent reports on boatlike tropane
derivatives revealed a decreased binding at the SERT
in comparison to the DAT.31-33 However, due to the
orientation of the nitrogen lone pair over the two-carbon
bridge combined with the introduction of additional
steric bulk over the three-carbon bridge, these ligands
were anticipated to exhibit decreased activity at the
DAT, in analogy to the “front-bridged” compounds
(Figure 1).14 This hypothesis was confirmed, since all
of the compounds tested showed only moderate or low
inhibition of dopamine reuptake. On the other hand, the
activity and selectivity for the SERT and NET is mainly
influenced by the substitution pattern of the aromatic
ring. Initial data for variations of the ester group show
that fine-tuning for higher selectivity and activity is
possible.
In summary, the synthesis of a novel class of tricyclic
tropane analogues which can be viewed as hybrids
between tropanes and quinuclidines has been accom-
plished that makes use of radical cyclization technology
in combination with Stille coupling chemistry. These
new tropaquinuclidines represent a significant struc-
tural departure from many of the other classes of tro-
pane ligands synthesized to date. They are characterized
by the boat conformation of the tropane ring and the
orientation of the additional bridge (and therefore of the
nitrogen lone pair) together with the unusual placement
of the aromatic moiety. The potency and selectivity
shown by some of these ligands for the NET, SERT, or
NET/SERT are striking, particularly in view of the
displacement of the aromatic ring in this series from
its usual position at the C3 in the WIN analogues. These
ligands provide additional pharmacological tools of use
in attempting to correlate structure and transporter
selectivity with in vivo studies of behavioral outcomes.
N-P r op a r gyln or a n h yd r oecgon in e Meth yl Ester (2).
N-Propargylnorcocaine (2.43 g, 7.42 mmol) was refluxed in 2
N hydrochloric acid overnight. The solution was concentrated
to dryness, and the residue was dried at room temperature in
vacuo for 4 h. Phosphorus oxychloride (50 mL) was added, and
the mixture was refluxed for 2 h. The excess of phosphorus
oxychloride was removed under reduced pressure, and the
residue was dried for 1 h in vacuo. The gummy mass was
cooled in a dry ice/acetone bath, and methanol (50 mL) was
added very carefully with gentle shaking of the flask. The
solution was allowed to return to room temperature slowly and
stirred for 1 h at room temperature. The methanol was
evaporated, and the product was purified by flash chromatog-
raphy (ethyl acetate/hexane 1/3, Rf 0.24) to afford 4 (1.25 g,
82%) as a yellow oil: 1H NMR δ 1.52 (m, 1H), 1.84 (m, 2H),
2.15 (m, 2H), 2.21 (t, J ) 2.5, 1H), 2.6 (d, J ) 19.7, 1H), 3.24
and 3.31 (ABq, J ) 16.0, both parts d with J ) 2.6, 2H), 3.51
(t, J ) 5.1, 1H), 3.74 (s, 3H), 4.0 (d, J ) 5.0, 1H), 6.83 (brs,
1H); 13C NMR δ 29.71, 31.13, 34.18, 37.86, 51.48, 54.43, 56.48,
71.45, 80.52, 133.36, 135.91, 166.1.
Ra d ica l Cycliza tion of 2. Compound 2 (1.03 g, 5.02 mmol)
was dissolved in benzene (100 mL) and heated to reflux. AIBN
(824 mg, 5.02 mmol) and tri-n-butylstannane (2.75 mL, 10.0
mmol) were dissolved in benzene to the total volume of 50 mL
and added via syringe pump over 8 h to the refluxing solution
of 2. The mixture was refluxed for another 2 h, the solvent
was evaporated, and the residue was purified by flash chro-
matography employing a gradient (ethyl acetate/hexane 30/
70 to 100/0) to yield a mixture of 3 and 4.
(1S ,3R ,6S )-(Z)-9-[(Tr i-n -b u t ylst a n n yl)m e t h yle n e ]-7-
a za t r icyclo[4.3.1.03,7]d eca n e-2â-ca r b oxylic a cid m et h yl
ester (3): yield 1.23 g (51%); Rf 0.38 (ethyl acetate); 1H NMR
δ 0.75-1.7 (m, 30 H), 2.00 (ddd, J ) 22.5, 9.5, 2.2, 1H), 2.14
(m, 2H), 2.35 (t, J ) 2.9, 1H), 2.63 (m, 1H), 3.26 (m, 1H), 3.54
and 3.61 (ABq, J ) 17.3, both parts d with J ) 2.2, 2H), 3.63
(s, 3H), 3.77 (m, 1H), 5.52 (t, J ) 2.4, 1H with satellites from
J Sn-H ) 57.5); 13C NMR δ 9.67, 13.65, 27.24, 29.12, 31.95,
32.61, 36.52, 40.20, 50.34, 51.70, 52.40, 53.80, 55.9, 117.49,
155.96, 174.15.
(1S,3R,6S)-(E )-9-[(Tr i-n -b u t ylst a n n yl)m e t h yle n e ]-7-
a za t r icyclo[4.3.1.03,7]d eca n e-2â-ca r b oxylic a cid m et h yl
ester (4): yield 540 mg (22%); Rf 0.15 (ethyl acetate); 1H NMR
δ 0.75-1.7 (m, 30H), 1.95 (ddd, J ) 22.5, 9.5, 2.3, 1H), 2.15
(m, 2H), 2.40 (m, 2H), 3.25 (m, 1H), 3.64 (s, 1H), 3.58-3.8 (m,
3H), 5.47 (t, J ) 1.8, 1H with satellites from J Sn-H ) 62.6);
13C NMR δ 5.53, 9.22, 22.91, 24.67, 27.52, 28.22, 32.82, 33.30,
46.53, 47.27, 47.47, 49.26, 52.16, 112.27, 151.38, 169.98.
Stille Cou p lin g (Gen er a l P r oced u r e). The appropriate
aryl or hetaryl iodide (0.5 mmol), tris(o-tolyl)phosphine (8 mol
%), Pd2(dba)3 (2 mol %), and copper(I) iodide (8 mol %) were
dissolved in DMF (2 mL) and stirred at room temperature for
15 min under nitrogen. Then the stannane (0.5 mmol) in DMF
(2 mL) was added, and the mixture was stirred at 45-50 °C
for 12 h. The solution was poured into ice-cold hydrochloric
acid (2 N), and the aqueous phase was extracted with ether
(3 × 20 mL). The organic phase was reextracted with hydro-
chloric acid (2 × 15 mL), and the combined acidic solutions
were basified with NH4OH and extracted with ethyl acetate
(4 × 20 mL). The solution was dried over MgSO4, the solvent
was evaporated, and the residue was chromatographed on
silica gel using ethyl acetate/triethylamine 10/1.
Exp er im en ta l Section
NMR spectra were recorded on a Varian Unity Inova
spectrometer at 300 MHz for proton and 75.46 MHz for carbon-
13 spectra. CDCl3 was used as solvent. Chemical shifts are
reported in ppm relative to internal TMS. Coupling constants
are given in hertz (Hz). Analytical thin-layer chromatography
was performed using Merck silica gel 60F-254 plates; flash
chromatography was performed using Merck silica gel (60-
200 mesh). Mass spectra were measured in the EI mode at an
ionization potential of 70 eV. Starting materials were obtained
from Aldrich or Fluka. Solvents were obtained from Fisher
Scientific and were used without further purification unless
otherwise noted. DMF (DriSolv) was obtained from EM Sci-
ence. Norcocaine, 2-iodofuran, and 3-iodofuran were prepared
according to literature methods.20,34 To ensure proper elemen-
tal analyses and for easy handling in the biological assays, all
final compounds were converted into salts by common meth-
ods.
N-P r op a r gyln or coca in e. Norcocaine (2.57 g, 8.88 mmol),
propargyl bromide (1.18 mL, 10.6 mmol), and K2CO3 (1.46 g,
10.6 mmol) were refluxed in acetonitrile (50 mL) for 12 h. The
solvent was removed, and the residue was dissolved in ice-
cold ammonia solution (2% v/v). The aqueous solution was
extracted with ether (3 × 30 mL) and dried, and the solvent
was evaporated under reduced pressure. Flash chromatogra-
phy (ethyl acetate/hexane 1/3, Rf 0.34) afforded N-propargyl-
norcocaine (2.43 g, 84%) as slightly yellow crystals: 1H NMR
δ 1.77 (m, 2H), 1.91 (m, 1H), 2.02 (m, 2H), 2.18 (t, J ) 2.4,
1H), 2.45 (dd, J ) 11.7, 2.2), 3.05 (m, 1H), 3.09 and 3.19 (ABq,
(1S ,3R ,6S )-(Z)-9-(P h e n ylm e t h yle n e )-7-a za t r icyclo-
[4.3.1.03,7]d eca n e-2â-ca r boxylic a cid m eth yl ester (5a ):
yield 66%, colorless oil, solidifies upon standing (white crys-
1
tals); mp 97-98 °C; [R]25 +68.5 (c 0.35, CHCl3); H NMR δ
D
1.46 (m, 3H), 2.0-2.3 (m, 3H), 2.41 (t, J ) 3.2, 1H), 2.71 (dd,
J ) 5.9, 3.17, 1H), 3.28 (m, 1H), 3.65 (s, 3H), 3.79 (m, 1H),
3.92 and 4.05 (ABq, J ) 18.3, both parts d with J ) 2.4, 2H),
6.13 (t, J ) 2.3), 7.1-7.4 (m, 5H); 13C NMR δ 32.03, 32.65,

Novel Conformationally Constrained Tropanes
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 10 2069
36.59, 37.37, 48.26, 51.85, 52.41, 53.76, 56.28, 122.03, 126.15,
128.34, 128.36, 137.42, 140.59, 174.28. Anal. C, H, N.
(1S,3R,6S-(Z)-9-(4-Bip h en ylylm eth ylen e)-7-a za tr icyclo-
[4.3.1.03,7]d eca n e-2â-ca r boxylic a cid m eth yl ester (5i):
1
yield 64%; H NMR δ 1.50 (m, 3H), 2.1 (m, 1H), 2.2 (m, 2H),
(1S ,3R ,6S )-(Z)-9-(3,4-Dich lor op h e n ylm e t h yle n e )-7-
a za t r icyclo[4.3.1.03,7]d eca n e-2â-ca r b oxylic a cid m et h yl
2.42 (t, J ) 3.0, 1H), 2.75 (dd, J ) 5.8, 3.1, 1H), 3.3 (m, 1H),
3.79 (s, 3H), 3.8 (s, 1H) 3.96 and 4.09 (ABq, J ) 18.3, both
parts d with J ) 2.1, 2H), 6.17 (s, 1H), 7.2-7.65 (m, 9H); 13C
NMR δ 31.99, 32.61, 36.55, 37.40, 48.38, 51.88, 52.37, 53.74,
56.25, 121.61, 126.89, 127.00, 127.17, 128.73, 128.77, 136.42,
138.83, 140.67, 140.89, 174.27. Anal. C, H, N.
ester (5b): yield 61%; white crystals; mp 127-28 °C; [R]25
D
1
+64.6 (c 1.65, CHCl3); H NMR δ 1.50 (m, 3H), 2.05 (m, 1H),
2.17 (m, 2H) 2.42 (t, J ) 2.9, 1H), 2.69 (m, 1H), 3.28 (m, 1H),
3.65 (s, 3H), 3.76 (m, 1H), 3.86 and 3.99 (ABq, J ) 18.3, both
parts d with J ) 2.3, 2H), 6.03 (br s, 1H), 7.01 (dd, J ) 8.4,
1.8, 1H), 7.26 (d, J ) 1.8, 1H), 7.36 (d, J ) 8.1, 1H); 13C NMR
δ 31.94, 32.54, 36.28, 37.26, 48.15, 51.88, 52.12, 53.61, 56.27,
119.77, 127.41, 129.78, 130.01 130.13, 132.26, 137.29, 143.49,
174.15. Anal. C, H, N.
(1S ,3R ,6S )-(E )-9-(P h e n ylm e t h yle n e )-7-a za t r icyclo-
[4.3.1.0.3,7]d eca n e-2â-ca r boxylic a cid m eth yl ester (6):
yield 37%; [R]25 -52.8 (c 1.065, CHCl3); 1H NMR δ 1.48 (m, 3
D
H), 2.05 (m, 1H), 2.17 (m, 2H), 2.30 (t, J ) 3.1, 1H), 3.33 (m,
2H), 3.43 (s, 3H), 3.71 and 3.82 (ABq, J ) 17.7, both parts d
with J ) 2.1, 2H), 3.78 (m, 1H), 6.28 (s, 1H), 7.1-7.3 (m, 5H);
13C NMR δ 28.83, 31.98, 32.66, 35.60, 48.99, 51.08, 51.40,
53.85, 56.30, 121.21, 126.09, 128.08, 128.10, 137.06, 139.61,
174.22. Anal. C, H, N.
(1S ,3R ,6S )-(Z)-9-(4-Me t h o x y p h e n y lm e t h y le n e )-7-
a za t r icyclo[4.3.1.03,7]d eca n e-2â-ca r b oxylic a cid m et h yl
ester (5c): yield 59%; 1H NMR δ 1.49 (m, 3H), 2.07 (m, 1H),
2.17 (m, 2H), 2.39 (t, J ) 3.1, 1H), 2.68 (m, 1H), 3.28 (m, 1H),
3.64 (s, 3H), 3.77 (m, 1H), 3.80 (s, 3H), 3.89 and 4.02 (ABq, J
) 18.1, both parts d with J ) 2.4, 2H), 6.07 (br s, 1H), 6.86 (d,
J ) 8.7, 2H), 7.13 (d, J ) 8.7, 2H); 13C NMR δ 32.03, 32.67,
36.67, 37.28, 48.27, 51.85, 52.46, 53.76, 55.26, 56.23, 113.77,
121.29, 129.54, 130.25, 138.07, 157.85, 174.31. Anal. C, H, N.
(1S,3R,6S)-2-(Hydr oxym eth yl)-(Z)-9-(ph en ylm eth ylen e)-
7-a za tr icyclo[4.3.1.03,7]d eca n e (7a ). To a solution of 5a (0.5
mmol) in THF (10 mL) was added LiAlH4 (1.5 mmol) portion-
wise, and the mixture was stirred for 3 h. The mixture was
quenched with concentrated Rochelle salt solution (15 mL)
followed by extraction with EtOAc (3 × 10 mL). The organic
phase was washed with brine (20 mL), dried over MgSO4, and
concentrated under reduced pressure to afford the title com-
(1 S ,3 R ,6 S )-(Z )-9 -(4 -F l u o r o p h e n y l m e t h y l e n e )-7 -
a za t r icyclo[4.3.1.03,7]d eca n e-2â-ca r b oxylic a cid m et h yl
1
ester (5d ): yield 49%; H NMR δ 1.5 (m, 3H), 2.05 (m, 1H),
2.16 (m, 2H), 2.40 (t, J ) 3.2, 1H), 2.68 (dd, J ) 6.0, 3.1, 1H),
3.28 (m, 1H), 3.65 (s, 3H), 3.76 (m, 1H), 3.87 and 3.99 (ABq, J
) 18.2, both parts d with J ) 2.3, 2H), 6.1 (br s, 1H), 7.0 (t, J
) 8.8, 2H), 7.14 (dd, J ) 8.6, 5.6, 2H); 13C NMR δ 31.92, 32.55,
36.40, 37.17, 48.04, 51.77, 52.23, 53.65, 56.19, 115.12 (d, J )
21.32), 120.73, 129.75 (d, J ) 7.7), 133.43 (d, J ) 3.3), 140.12
(d, J ) 2.2), 161.0 (d, J ) 246.7), 174.23; MS m/z (%) 301 (M+,
34), 242 (59), 159 (29), 146 (45), 120 (46), 109 (39), 83 (100);
Anal. C, H, N.
1
pound as a colorless oil: quantitative yield; H NMR δ 1.4-
1.7 (m, 4H), 2.0-2.35 (m, 3H), 2.41 (dd, J ) 5.7, 3.1, 1H), 2.80
(m, 1H), 3.26 (m, 1H), 3.45 (m, 2H), 3.88 and 3.97 (ABq, J )
18.4, both parts d with J ) 2.5, 2H), 6.17 (t, J ) 2.3, 1H), 7.25
(m, 5H); 13C NMR δ 32.20, 32.89, 35.68, 37.26, 48.45, 48.72,
53.98, 58.07, 65.56, 121.85, 126.04, 128.22, 128.36, 137.30,
141.19. Anal. C, H, N.
(1S ,3R ,6S )-2-(H yd r ox ym e t h yl)-(Z)-9-(3,4-d ic h lo r o -
p h en ylm et h ylen e)-7-a za t r icyclo[4.3.1.03,7]d eca n e (7b ).
DIBAL-H (1.5 mmol) was added dropwise to a solution of 5b
(0.5 mmol) in THF (10 mL) under N2 at room temperature.
The reaction mixture was stirred for 3 h, quenched with
concentrated Rochelle salt solution (15 mL), and extracted with
EtOAc (3 × 10 mL). The organic phase was washed with brine
(20 mL), dried over MgSO4, and concentrated under reduced
pressure. Purification of the crude product by flash chroma-
tography on silica gel using EtOAc/NEt3 10/1 as eluent afforded
the title compound as a colorless oil: yield 89%; 1H NMR δ
1.2-1.4 (m, 4H), 2.0-2.35 (m, 3H), 2.43 (dd, J ) 6.1, 3.4, 1H),
2.81 (m, 1H), 3.30 (m, 1H), 3.5 (d, J ) 7.6, 2H), 3.85 and 3.93
(ABq, J ) 18.4, both parts d with J ) 2.5, 2H), 6.08 (t, J )
2.4, 1H), 7.05 (dd, J ) 8.4, 2.0, 1H), 7.3 (d, J ) 2.0, 1H), 7.4
(d, J ) 8.4, 1H); 13C NMR δ 32.20, 32.80, 35.73, 37.06, 48.44,
48.63, 54.00, 58.06, 65.53, 119.74, 127.36, 129.69, 129.93,
130.19, 132.33, 137.33, 144.23. Anal. C, H, N.
(1S,3R,6S)-(Z)-9-(1-Na p h th ylm eth ylen e)-7-a za tr icyclo-
[4.3.1.03,7]d eca n e-2â-ca r boxylic a cid m eth yl ester (5e):
1
yield 46%; H NMR δ 1.50 (m, 3H), 2.15 (m, 3H), 2.45 (t, J )
3.3, 1H), 2.9, (dd, J ) 6.0, 3.3, 1H), 3.69 and 3.83 (ABq, J )
18.5, both parts d with J ) 2.4, 2H), 3.74 (s, 3H), 3.76 (m,
1H), 6.68 (br s, 1H), 7.3-8.0 (m, 7H); 13C NMR δ 32.02, 32.56,
36.48, 36.75, 47.06, 51.9, 52.33, 53.82, 56.32, 119.25, 124.45,
125.31, 125.61, 125.66, 125.79, 126.98, 128.37, 131.47, 133.52,
133.83, 141.9, 174.40. Anal. C, H, N.
(1S ,3R ,6S )-(Z)-9-(2-F u r ylm e t h yle n e )-7-a za t r icyclo-
[4.3.1.03,7]d eca n e-2â-ca r boxylic a cid m eth yl ester (5f):
yield 28%; 1H NMR δ 1.49 (m, 3H), 2.0 (m, 1H), 2.18 (m, 2H),
2.39 (t, J ) 3.0, 1H), 2.68 (dd, J ) 6.0, 3.0, 1H), 3.30 (m, 1H),
3.64 (s, 3H), 3.76 (m, 1H), 3.88 and 3.95 (ABq, J ) 18.9, both
parts d with J ) 2.4, 2H), 6.02 (t, J ) 2.4, 1H), 6.07 (d, J ) 3,
1H), 6.37 (dd, J ) 3.2, 1.9, 1H), 7.35 (d, J ) 1.4, 1H); 13C NMR
δ 32.06, 32.62, 36.28, 36.52, 48.37, 51.88, 52.14, 53.71, 56.30,
107.76, 110.27, 111.23, 139.37, 141.13, 152.90, 174.16; MS m/z
(%) 273 (M+, 26), 214 (26), 69 (37), 68 (36), 43 (100). Anal. C,
H, N.
(1S,3R,6S)-2-(Acetoxym eth yl)-(Z)-9-(ph en ylm eth ylen e)-
7-a za tr icyclo[4.3.1.03,7]d eca n e (8a ). To a solution of 7a (0.1
mmol) in pyridine (1 mL) and acetic anhydride (0.25 mL) was
added DMAP (1 mg), and the solution was stirred for 2 h. The
mixture was concentrated under reduced pressure, diluted
with EtOAc (20 mL), and washed with a saturated solution of
NaHCO3 (2 × 10 mL). The organic solution was dried and
concentrated under reduced pressure. Purification of the crude
product by flash chromatography on silica gel using CHCl3/
MeOH 10/1 as eluent afforded the title compound as a colorless
(1S ,3R ,6S )-(Z)-9-(3-F u r ylm e t h yle n e )-7-a za t r icyclo-
[4.3.1.03,7]d eca n e-2â-ca r boxylic a cid m eth yl ester (5g):
yield 8%; 1H NMR δ 1.51 (m, 3H), 2.1 (ddd, J ) 12.5, 9.8, 2.3,
1H), 2.2 (m, 2H), 2.4 (t, J ) 3.1, 1H), 2.68 (dd, J ) 5.9, 3.0,
1H), 3.31 (m, 1H), 3.64 (s, 3H), 3.75 and 3.83 (ABq, J ) 17.9,
both parts d with J ) 2.0, 2H), 3.78 (m, 1H), 5.95 (s, 1H), 6.34
(s, 1H), 7.32 (s, 1H), 7.37 (s, 1H); 13C NMR δ 31.89, 32.50,
36.30, 36.40, 48.32, 51.87, 52.19, 53.85, 56.34, 110.47, 111.50,
122.46, 140.25, 142.74, 174.09; MS m/z (%) 273 (M+, 0.7), 214
(17), 85 (41), 83 (100), 68 (32). Anal. C, H, N.
1
oil: yield 73%; H NMR δ 1.5 (m, 3H), 1.77 (m, 1H), 2.04 (s,
3H), 2.05 (m, 3H), 2.36 (dd, J ) 5.8, 2.9, 1H), 2.85 (dd, J )
5.7, 2.8, 1H), 3.30 (m, 1H), 3.91 and 3.99 (ABq, J ) 18.2, both
parts d with J ) 2.8, 2H), 3.97 (d, J ) 7.8, 2H), 6.13 (t, J )
2.4, 1H), 7.1-7.4 (m, 5H); 13C NMR δ 20.89, 32.20, 32.80, 35.93,
37.20, 45.23, 48.50, 53.87, 67.22, 122.36, 126.10, 128.30,
128.37, 137.29, 140.44, 171.04. Anal. C, H, N.
(1S,3R,6S-(Z)-9-(2-Th ien ylm et h ylen e)-7-a za t r icyclo-
[4.3.1.03,7]d eca n e-2â-ca r boxylic a cid m eth yl ester (5h ):
yield 58%; 1H NMR δ 1.51 (m, 3H), 2.03 (m, 1H), 2.2 (m, 2H),
2.4 (t, J ) 2.9, 1H), 2.70 (dd, J ) 5.6, 2.7, 1H), 3.28 (m, 1H),
3.63 (s, 3H), 3.77 (s, 1H) 3.85 and 3.93 (ABq, J ) 18.4, both
parts d with J ) 2.2, 2H), 6.37 (s, 1H), 6.87 (d, J ) 3.4, 1H),
7.0 (t, J ) 3.7 1H), 7.5 (d, J ) 10, 1H); 13C NMR δ 32.01, 32.58,
36.48, 36.56, 48.43, 51.89, 52.76, 53.76, 56.32, 114.93, 124.80,
125.82, 126.99, 138.72, 140.83, 174.12. Anal. C, H, N.
(1S,3R,6S)-2-(Acet oxym et h yl)-(Z)-9-(3,4-d ich lor op h e-
n ylm eth ylen e)-7-azatr icyclo[4.3.1.03,7]decan e (8b) was pre-
1
pared in a similar manner as 8a : yield 80%; H NMR δ 1.5
(m, 3H), 1.78 (m, 1H), 2.05 (s, 3H), 2.1 (m, 3H), 2.35 (dd, J )
5.6, 2.9, 1H), 2.85 (dd, J ) 5.7, 3.1, 1H), 3.31 (m, 1H), 3.86
and 3.94 (ABq, J ) 18.4, both parts d with J ) 2.5, 2H), 3.95

2070 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 10
Hoepping et al.
(5) Spanagel, R.; Weiss, F. The dopamine hypothesis of reward: Past
and current status Trends Neurosci. 1999, 22, 521-527.
(6) Richardson, N. R.; Roberts, D. C. S. Fluoxetine pretreatment
reduces breaking points on a progressive ratio schedule rein-
forced by intravenous cocaine self-administration in the rat. Life
Sci. 1991, 49, 833-840.
(7) Cunningham, K. A.; Callahan, P. M. Monoamine reuptake
inhibitors enhance the discriminative stimulus state induced by
cocaine in the rat. Psychopharmacology 1991, 104, 177-180.
(8) Sora, I.; Wichems, C.; Takahashi, N.; Li, X. F.; Zeng, Z.; Revay,
R.; Lesch, K. P.; Murphy, D. L.; Uhl, G. R. Cocaine reward
models: Conditioned place preference can be established in
dopamine- and in serotonin-transporter knockout mice. Proc.
Natl. Acad. Sci. U.S.A. 1998, 95, 7699-7704.
(d, J ) 7.4, 2H), 6.04 (t, J ) 2.4, 1H), 7.02 (dd, J ) 8.2, 2.0,
1H), 7.29 (d, J ) 2.0, 1H), 7.38 (d, J ) 8.2, 1H); 13C NMR δ
20.90, 32.15, 32.74, 35.97, 36.97, 45.12, 48.39, 53.87, 58.15,
66.99, 120.29, 127.43, 129.85, 130.03, 130.23, 132.35, 137.22,
143.22, 171.01. Anal. C, H, N.
Syn a p tosom a l Up ta k e of [3H]Dop a m in e, [3H]5-Hy-
d r oxyt r yp t a m in e, a n d [3H ]Nor ep in ep h r in e. All com-
pounds were tested as their respective salts. The effect of
candidate compounds in antagonizing biogenic amine high-
affinity uptake was determined using a method similar to that
previously employed for [3H]DA uptake.27 Striatum, midbrain,
and parietal/occipital cortex were dissected and used as a
source of rat DAT, SERT, and NET, respectively. These brain
regions were homogenized with a Teflon-glass pestle in ice-
cold 0.32 M sucrose and centrifuged for 10 min at 1000g. The
supernatant was centrifuged at 17500g for 20 min. This P2
synaptosomal pellet was resuspended in 30 volumes of ice-
cold modified KRH buffer consisting of (in mM) NaCl (125),
KCl (4.8), MgSO4 (1.2), CaCl2 (1.3), KH2PO4 (1.2), glucose (5.6),
nialamide (0.01), and HEPES (25) (pH 7.4).28 An aliquot of the
synaptosomal suspension was preincubated with the buffer
and drug for 30 min at 4 °C and then for 15 min at 37 °C before
uptake was initiated by the addition of [3H]biogenic amine (∼5
nM for [3H]DA and [3H]5-HT, 9 nM for [3H]NE, final concen-
tration). After 5 min, uptake was terminated by adding 5 mL
of cold buffer containing glucosamine as a substitute for NaCl
and then finally by rapid vacuum filtration over GF-C glass-
fiber filters, followed by washing with two 5 mL volumes of
ice-cold, sodium-free buffer. The bound and free [3H]biogenic
amines were separated by rapid vacuum filtration over What-
man GF/C filters, using a Brandel M24R cell harvester,
followed by two washes with 5 mL of cold buffer. Radioactivity
on the filters was then extracted by allowing the filters to sit
overnight with 5 mL of scintillation fluid. The vials were
vortexed and counted. Specific uptake of [3H]DA was defined
as that which is sensitive to inhibition by 30 mM cocaine; 10
mM fluoxetine and 3 mM desipramine, respectively, were used
to define the specific uptake of [3H]5-HT and [3H]NE. In each
instance, it was virtually identical to that calculated by
subtracting the mean of identical tubes incubated at 0 °C. IC50
values were determined using the computer program LIGAND.
The Cheng-Prusoff equation for classic, competitive inhibition
was used for calculating Ki from IC50 values in uptake
experiments. The Km values used were about 67 nM for [3H]-
DA, 53 nM for [3H]5-HT, and 54 nM for [3H]NE.
(9) Carroll, K. M.; Rounsaville, B. J .; Gordon, L. T.; Nich, C.; J atlow,
P.; Bisighini, R. M.; and Gawin, F. H. Psychotherapy and
pharmacotherapy for ambulatory cocaine abusers. Arch. Gen.
Psychiatry 1994, 51, 177-187.
(10) (a) Batki, S. L.; Washburn, A. M.; Manfredi, L.; Murphy, J .;
Herbst, M. D.; Delucci, K.; J ones, T.; Nanda, N.; J acob, P.; and
J ones, R. T. Fluoxetine in primary and secondary cocaine
dependence: Outcome using quantitative benzoylecgonine con-
centration. In Problems of Drug Dependence, 1993: Proceedings
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Ack n ow led gm en t. We are indebted to the NIH,
National Institute on Drug Abuse (DA10458, DA05867,
and DA09045), and the Office of Naval Research for
their financial support. We thank Dr. Istvan Enedy for
the molecular modeling studies.
Su p p or tin g In for m a tion Ava ila ble: X-ray structures of
5a and 6, tables of crystal data, atomic coordinates, bond
lengths and angles, anisotropic and isotropic displacement
parameters, and hydrogen coordinates. This material is avail-
able free of charge via the Internet at http://pubs.acs.org.
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(25) Crystal data for 5a : A clear plate 0.72 × 0.12 × 0.08 mm, C18H21
-
NO2, FW ) 283.36, orthorhombic space group P212121; a ) 6.193-
(1), b ) 14.373(2), c ) 34.163(4) Å, V ) 3041.2(6) Å3, Z ) 8, dcalc
) 1.238 g/cm3; 2928 reflections were measured to 2qmax ) 115°.

Novel Conformationally Constrained Tropanes
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 10 2071
Refinement on F2, R ) 0.059, wR ) 0.122 for all 2687 unique
data. Crystal data for 6: A clear plate 0.44 × 0.09 × 0.07 mm,
C25H20NO5S, FW ) 455.55, orthorhombic space group P212121;
a ) 8.166(1), b ) 10.458(2), c ) 26.034(4) Å, V ) 2223.4(6) Å3,
Z ) 4, dcalc ) 1.361 gm/cm3; 7455 reflections were measured to
2qmax ) 113°. Refinement on F2, R ) 0.056, wR ) 0.128 for all
2633 unique data. Cystallographic coordinates have been de-
posited with the Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge CB2 1EZ, UK, deposit@ccdc.cam.ac.uk.
Additionally, crystallographic data have been deposited as
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J M0001121