Slow-onset, long-duration 3-(3′,4′-dichlorophenyl)-1-indanamine monoamine reuptake blockers as potential medications to treat cocaine abuse

Article abstract of DOI:10.1021/jm000201d

A series of 3-(3′,4′-dichlorophenyl)-1-indanamine monoamine reuptake blockers have been synthesized in an effort to develop a compound that could be used as a maintenance therapy to treat cocaine abuse. Since the effects of cocaine on dopamine (DA) and serotonin (5HT) transporters are important components of its pharmacological activity, the focus was on nonselective inhibitors of monoamine transport. To reduce or eliminate the abuse potential of a DA reuptake blocker, the compounds were designed to be slow-onset, long-duration prodrugs whose N-demethylated metabolites would have increased activity over the parent compound with the ideal being a parent compound that has little or no activity. To achieve this, pairs of compounds with different groups on the amine nitrogen and with and without an additional N-methyl group were synthesized. All of the synthesized compounds were screened for binding and reuptake at the cloned human DA, 5HT, and norepinephrine (NE) transporters. As previously found, trans isomers are nonselective blockers of DA, 5HT, and NE reuptake, cis isomers with small N-alkyl groups are selective blockers of 5HT reuptake, and tertiary amines of the trans compounds are less potent than the corresponding N-demethylated secondary amines as blockers of DA reuptake. Larger N-alkyl groups in both the trans and cis series were found to reduce activity for the 5HT and NE transporters with less effect at DA transporters. Selected trans compounds were also screened for locomotor activity in mice and generalization to a cocaine-like profile in rats. With intraperitoneal administration, all of the trans isomers showed a slow onset of at least 20 min and an extremely long duration of action in the locomotor assays. Several of the trans compounds also fully generalized to a cocaine-like pharmacological profile. An initial lead compound, the N,N-dimethyl analogue trans-1b, was resolved into chirally pure enantiomers. Surprisingly, both enantiomers were found to have significant affinity for the DA transporter and to cause locomotor activation. This is in contrast to the N-methyl compound in which only the (+)-enantiomer had significant activity. The absolute configuration of the more active enantiomer was determined by X-ray crystallography to be 3R,1S.

Full text of DOI:10.1021/jm000201d

J . Med. Chem. 2000, 43, 4981-4992
4981
Slow -On set, Lon g-Du r a tion 3-(3′,4′-Dich lor op h en yl)-1-in d a n a m in e Mon oa m in e
Reu p ta k e Block er s a s P oten tia l Med ica tion s To Tr ea t Coca in e Abu se
Mark Froimowitz,*,† Kuo-Ming Wu,† Adel Moussa,† Reem M. Haidar,† J urjus J urayj,† Clifford George,‡ and
Eliot L. Gardner#
Pharm-Eco Laboratories, 25 Patton Road, Devens, Massachusetts 01432, Laboratory for the Structure of Matter,
Naval Research Laboratory, Washington, D.C. 20375-5341, and Intramural Research Program, National Institute on
Drug Abuse, Baltimore, Maryland 21224
Received May 9, 2000
A series of 3-(3′,4′-dichlorophenyl)-1-indanamine monoamine reuptake blockers have been
synthesized in an effort to develop a compound that could be used as a maintenance therapy
to treat cocaine abuse. Since the effects of cocaine on dopamine (DA) and serotonin (5HT)
transporters are important components of its pharmacological activity, the focus was on
nonselective inhibitors of monoamine transport. To reduce or eliminate the abuse potential of
a DA reuptake blocker, the compounds were designed to be slow-onset, long-duration prodrugs
whose N-demethylated metabolites would have increased activity over the parent compound
with the ideal being a parent compound that has little or no activity. To achieve this, pairs of
compounds with different groups on the amine nitrogen and with and without an additional
N-methyl group were synthesized. All of the synthesized compounds were screened for binding
and reuptake at the cloned human DA, 5HT, and norepinephrine (NE) transporters. As
previously found, trans isomers are nonselective blockers of DA, 5HT, and NE reuptake, cis
isomers with small N-alkyl groups are selective blockers of 5HT reuptake, and tertiary amines
of the trans compounds are less potent than the corresponding N-demethylated secondary
amines as blockers of DA reuptake. Larger N-alkyl groups in both the trans and cis series
were found to reduce activity for the 5HT and NE transporters with less effect at DA
transporters. Selected trans compounds were also screened for locomotor activity in mice and
generalization to a cocaine-like profile in rats. With intraperitoneal administration, all of the
trans isomers showed a slow onset of at least 20 min and an extremely long duration of action
in the locomotor assays. Several of the trans compounds also fully generalized to a cocaine-
like pharmacological profile. An initial lead compound, the N,N-dimethyl analogue trans-1b,
was resolved into chirally pure enantiomers. Surprisingly, both enantiomers were found to
have significant affinity for the DA transporter and to cause locomotor activation. This is in
contrast to the N-methyl compound in which only the (+)-enantiomer had significant activity.
The absolute configuration of the more active enantiomer was determined by X-ray crystal-
lography to be 3R,1S.
In tr od u ction
to result in drug-seeking behavior.5 Indeed, intracranial
microdialysis studies of rats trained to self-administer
cocaine intravenously found reduced levels of extracel-
lular nucleus accumbens DA during cocaine withdrawal
though basal levels of DA were elevated in the cocaine-
experienced rats as compared with drug-na¨ıve controls.6
Similarly, rats trained to self-administer cocaine intra-
venously were found to have elevated intracranial self-
stimulation thresholds during cocaine withdrawal sug-
gesting a “postcocaine anhedonia”.7,8 There is also
evidence that there may be a genetic component to drug
abuse vulnerability9,10 and that some human abuse of
drugs may be an effort at self-medication for depressed
individuals.11 A recent report, in which [11C]PET imag-
ing was used to quantitate the number of striatal DA
D2 receptors in human subjects who had not previously
abused drugs, reinforces the conclusion that genetic
differences may account for different propensities to
abuse drugs since individuals who reported “liking” the
effects of intravenous methylphenidate were found to
have significantly lower levels of D2 receptors than
those that found the effects to be neutral or unpleas-
The illicit abuse of cocaine is a major problem
throughout the world. The ability of cocaine to bind to
the dopamine (DA) transporter and, therefore, to block
the reuptake of DA into presynaptic neurons that
release DA appears to be responsible for its abuse
potential.1-3 For example, the potencies of cocaine-like
drugs in self-administration studies correlate best with
their affinities for binding to the DA transporter as
labeled with tritiated mazindol or cocaine.1,4 As a
consequence, the acute use of cocaine increases synaptic
DA, and this activates the brain reward loci that are
believed to cause the euphoria associated with cocaine
abuse.2 With chronic use, however, it has been sug-
gested that synaptic DA may become depleted during
cocaine abstinence and that these reduced levels of
synaptic DA may then be associated with craving and
* To whom correspondence should be addressed. Tel: 978-784-5384.
Fax: 978-784-5500. E-mail: markf@pharmeco.com.
† Pharm-Eco Laboratories.
‡ Naval Research Laboratory.
#
National Institute on Drug Abuse.
10.1021/jm000201d CCC: $19.00 © 2000 American Chemical Society
Published on Web 11/29/2000

4982 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 26
Froimowitz et al.
ant.12 For all of these reasons, a nonaddictive and
nonabusable DA reuptake blocker that raises DA levels
and relieves the dysphoria/craving that habitual users
of cocaine feel may be useful in treating cocaine abuse.
Unlike the situation with other drugs of abuse, there
are currently no safe and effective pharmacotherapies
available to aid habitual users of cocaine who want to
stop their usage of the drug. A number of possible
pharmacotherapeutic approaches have been sug-
gested.13-15 One popular approach is to develop a
cocaine antagonist that blocks cocaine binding to the
DA transporter without inhibiting DA reuptake. Such
a compound would antagonize cocaine binding without
having a cocaine-like pharmacological effect. This kind
of compound would have a high “uptake-to-binding
ratio”, though, as has been pointed out, this ratio may
be highly dependent on the assay conditions.16 There
have been some claims of modest success with this
approach.17 A second possible approach is the develop-
ment of a maintenance pharmacotherapy that would
reduce the dysphoria that the chronic use of cocaine
engenders which may then also reduce craving for
cocaine and relapse to cocaine use. This approach has
been most successful in the treatment of opiate and
nicotine addicts. For a maintenance therapy to be
beneficial, however, it should be less medically deleteri-
ous than the drug of abuse that it is replacing. For
example, methadone and LAAM are orally active opioids
that reduce the craving of heroin addicts who want to
stop their intravenous injections of heroin. Similarly,
nicotine patches allow the absorption of nicotine through
the skin which is less deleterious than obtaining it by
smoking cigarettes.
F igu r e 1. Dopamine reuptake blockers.
12909, a slow-release formulation, which has been
reported to decrease cocaine self-administration for up
to 1 month following a single injection.23
It is becoming increasingly clear that the pharmaco-
dynamics of a drug of abuse is important for its
abusability with those that have rapid onsets and short
durations of action appearing to have the highest abuse
potential.18,19 Relevant to this is the recent report that
humans who lack an enzyme that metabolically inac-
tivates nicotine are less likely to become addicted to
cigarette smoking.20 Thus, our approach for a mainte-
nance therapy for cocaine users has been to try to design
slow-onset, long-duration DA reuptake blockers. In this,
we were inspired by the development of LAAM for
treating heroin addicts. While LAAM has been reported
to have little intrinsic activity at opioid receptors, its
two N-demethylated metabolites have significant activ-
ity,21,22 and this offers advantages over methadone
maintenance. Since LAAM has little or no initial activ-
ity, potential abusers do not get the “rush” associated
with intravenous heroin or methadone. Nevertheless,
its slow metabolism to more active compounds is suf-
ficient to relieve the symptoms of opioid withdrawal. On
the basis of the LAAM model, we have tried to design
compounds that would require in vivo metabolism before
they have their maximum effect. That is, they would
be prodrugs whose activity would increase with time.
An agonist therapy, by addressing the underlying
dysphoric state, may be superior to an antagonist
strategy by analogy to pharmacotherapies for heroin
addiction since maintenance therapies, such as metha-
done and LAAM, are more widely accepted by addicts
than opioid antagonists such as naltrexone. A similar
approach is being tried with a decanoate ester of GBR
We were aided in our design of slow-onset compounds
by a pharmacophore model developed for DA reuptake
blockers of diverse structural classes.24 Starting from
cocaine and the related tropane CFT, the model encom-
passes other classes of compounds including 3-phenyl-
1-indamines, 1-amino-4-phenyltetralins, and hexahy-
dropyrrolo[2,1-a]isoquinolines (Figure 1). The model has
been extended to include methylphenidate,25 correctly
predicting the decrease in potency of N-methyl deriva-
tives of its analogues,26 and to bupropion, in which both
enantiomers fit the model equally well,27 and this is
consistent with the finding that the enantiomers have
similar potencies as DA reuptake blockers.28 Most
recently, BTCP and its analogues have been incorpo-
rated into the pharmacophore model.29
We were further aided in our efforts by a report which
indicated that the 3-aryl-1-indamine LU-19005 (also
known as indatraline) is a slow-onset, long-duration DA
reuptake blocker.30 Based on the original report of
compounds in this series,31 it also appears that second-
ary amines in this series are consistently more potent
than the corresponding tertiary amine. This can be
understood with the pharmacophore model in that the
additional methyl group of tertiary amines appears to
be preferentially placed in the position required for an
ammonium hydrogen.24 Thus, we decided to synthesize
a series of indanamines with different groups on the
amine nitrogen with and without the additional methyl
group. Specifically, we were looking for compounds in

Slow-Onset, Long-Duration MO Reuptake Blockers
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 26 4983
Sch em e 1
Sch em e 2
which the tertiary amine had minimal activity as a DA
reuptake blocker but the corresponding secondary amine
has potent activity. Since N-demethylation is one of the
most common forms of human metabolism,32 the ter-
tiary amine would be expected to be a prodrug with the
desired pharmacokinetic profile.
While the abuse potential of cocaine is primarily
believed to be due to its action at the DA transporter,
cocaine also has significant effects at serotonin (5HT)
and norepinephrine (NE) transporters. There is evi-
dence that the effect of cocaine on 5HT contributes to
its discriminative and behavioral effects.33,34 5HT ago-
nists and antagonists have also been shown to have
important modulatory effects on DA levels.35-37 This is
one possible explanation for the finding that DA trans-
porter knockout mice continue to self-administer co-
caine.38 For these reasons, it may be important for a
pharmacotherapy that treats cocaine abuse to have a
5HT component. In any case, there do not appear to be
any serious toxicity problems associated with 5HT
reuptake blockers, and their antidepressant effects may
be beneficial given the prevalence of depression in drug
abusers.11
Analogues with a variety of substituents on the
pendent phenyl ring have previously been made in the
3-phenyl-1-indanamine series.31 The 3′,4′-diCl group
was chosen here since this was optimal in this series.
Interestingly, the same phenyl substitution is consis-
tently optimal or near optimal in a variety of DA
reuptake blockers including the 1-amino-4-phenyltetra-
lins,39 pyrroloisoquinolines,40 3-phenyltropanes,41 meth-
ylphenidate analogues,42 mazindol analogues,43 and
3-phenylbicyclo[2.2.2]- and -[2.2.1]alkanes.44 Similarly,
a CF3 phenyl substitution consistently decreases activity
in all of these series in which it has been synthesized.
This suggests that the phenyl ring is probably making
similar interactions with the DA transporter in the
various series. In the 3-aryl-1-indamine series, the trans
isomers were generally found to be nonselective re-
uptake blockers at the DA, 5HT, and NE transporters
whereas the cis isomers were selective for the 5HT
transporter.31 Since the Medications Development Divi-
sion of the National Institute on Drug Abuse was
interested in compounds with both pharmacological
profiles, both isomers were synthesized and assayed.
Ch em istr y
Initial chemical syntheses were based on a published
procedure shown in Scheme 1.31 Intermediate 8 was
produced by the reaction of benzaldehyde with ethyl
cyanoacetate. This was coupled with the Grignard
reagent 9 to produce the acid 10 after hydrolysis and
decarboxylation. The acid 10 was cyclized with poly-
phosphoric acid to produce the ketone 11. The ketone
was reduced with NaBH4 to produce the alcohol 12
which was converted to the chloride 13 with SOCl2.
Reflux in THF with the appropriate amine produced the
desired amines 1-6. To achieve high purity, HPLC was
utilized to separate the trans and cis isomers with the
former being the major product. The iodo derivative 7b
was synthesized by reacting trans-1b with I2, NaIO3,
and H2SO4 in HOAc (Scheme 2).45 The position of the
iodine atom was determined by NMR and confirmed by
X-ray crystallography. Chiral column Chiralcel OD was
used to resolve trans-1b into its enantiomers using
hexanes, 2-PrOH, and trifluoroacetic acid (90/10/0.1) as
the mobile phase with the (+)-enantiomer being eluted
first.
After trans-1b was chosen as an initial lead com-
pound, process development was performed and a
method developed for its large-scale synthesis as out-
lined in Scheme 3. This synthetic method produces the
desired trans isomer without requiring chromatographic
separation of the geometric and optical isomers. 3,4-
Dichlorocinnamic acid (14) is reacted with H2SO4 and
benzene to produce the acid 10 which was cyclized to
produce the ketone 11 by treatment with ClSO3H.
NaBH4 reduction produces the alcohol 12 with a cis/
trans ratio of 92:7 (as measured by HPLC). After
purification by crystallization from EtOAc/heptane, the
ratio was 99.5:0.5. The cis alcohol 12 was then stereo-

4984 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 26
Ta ble 1. Synthesized Compounds
Froimowitz et al.
anal.
compd
R1
R2
R3
salt
mp, °C
C,H,N,Cl
trans-1a
trans-1b
methyl
methyl
H
H
H
chloride
hydrogen
maleate
chloride
chloride
chloride
chloride
hydrogen
maleate
chloride
hydrogen
oxalate
175-177
155-156
C
16H16NCl3
methyl
C21H21NO4Cl2
(-)-trans-1b
(+)-trans-1b
cis-1a
cis-1b
trans-7b
methyl
methyl
methyl
methyl
methyl
methyl
methyl
H
methyl
methyl
H
H
H
H
I
196-199
195-197
228-229
204-207
122-123
C17H18NCl3
C17H18NCl3
C16H16NCl3
C17H18NCl3
C21H20NO4Cl2
trans-2a
trans-2b
ethyl
ethyl
H
H
H
217-225
96-102
C17H18NCl3
C20H21NO4Cl2
methyl
cis-2a
cis-2b
trans-3a
trans-3b
cis-3a
ethyl
ethyl
propyl
propyl
propyl
H
H
H
H
H
H
chloride
chloride
chloride
chloride
hydrogen
maleate
chloride
chloride
chloride
chloride
chloride
chloride
chloride
chloride
chloride
chloride
chloride
chloride
chloride
>240
C17H18NCl3
C18H20NCl3
C18H20NCl3
C19H22NCl3
C22H23NO4Cl2
methyl
H
methyl
H
196-198
195-196
182-184
188-189
cis-3b
propyl
methyl
H
methyl
H
methyl
H
methyl
H
methyl
H
methyl
H
H
H
H
H
H
H
H
H
H
H
H
H
H
>206
C19H22NCl3
C18H20NCl3
C19H22NCl3
C18H20NCl3
C19H22NCl3
C19H22NCl3
trans-4a
trans-4b
cis-4a
isopropyl
isopropyl
isopropyl
isopropyl
tert-butyl
tert-butyl
tert-butyl
tert-butyl
benzyl
147-150
196-197
>212
cis-4b
>206
>243
trans-5a
trans-5b
cis-5a
a
201-205
>243
C20H24NCl3
C19H22NCl3
C20H24NCl3
C22H20NCl3
C23H22NCl3
C22H20NCl3
C23H22NCl3
cis-5b
222-223
>238
trans-6a
trans-6b
cis-6a
benzyl
benzyl
benzyl
203-205
222-226
192-199
cis-6b
methyl
a
The elemental analysis could be made to fit the theoretical values by including 0.23 mol equiv of ethyl acetate and 0.021 mol equiv
of diethyl ether that were observable by NMR and assuming 0.2 mol equiv of water.
Sch em e 3
Resu lts a n d Discu ssion
The results of the binding and reuptake assays for
the monoamine transporters for the synthesized trans
and cis isomers are shown in Tables 2 and 3, respec-
tively. As previously reported,31 the trans isomers were
generally nonselective blockers of monoamine reuptake
while the more potent cis isomers were selective for the
5HT transporter. Some of the trans isomers were
considerably more potent in the DA assays than cocaine
itself (Table 2). As previously noted, trans tertiary
amines with an extra N-methyl group were consistently
less potent than the corresponding secondary amines
in blocking the reuptake of DA.24,31 Larger N-alkyl
groups reduced DA reuptake only slightly until the
N-methyl, N-tert-butyl compound 5b which had greatly
decreased activity. For the 5HT and NE transporters,
larger N-alkyl groups such as an N-tert-butyl or N-
benzyl group reduced activity by greater amounts,
particularly for the former. The deleterious effect of
large groups on the nitrogen is also seen in the cis
isomers and results in a loss of selectivity toward the
5HT transporter. The iodo compound trans-7b was
synthesized as an intermediate in a procedure to
produce tritiated compound. When the compound was
submitted for biological testing, the effect of the iodine
was found to greatly decrease the activity at the 5HT
and NE transporters but to have a relatively small effect
selectively converted to the desired trans-1b by convert-
ing the alcohol to the mesylate which was then reacted
with the required amine via an SN2 reaction. Purifica-
tion of the final products was by crystallization of the
hydrogen maleate salt. It was also possible to resolve
the enantiomers of trans-1b by fractional crystallization
with di-p-toluoyltartaric acid with the D-acid precipitat-
ing out the (+)-enantiomer. Unlike trans-1b, the HCl
salts of the resolved enantiomers were solids.

Slow-Onset, Long-Duration MO Reuptake Blockers
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 26 4985
Ta ble 2. Binding of Trans Isomers to DA, 5HT, and NE Cloned Human Transporters Using 40-80 pM [125I]RTI and Inhibition of
[3H]DA (20 nM), [3H]5HT (20 nM), and [3H]NE (20 nM) Uptake
binding Ki, nM
dopamine
uptake
serotonin
norepinephrine
binding uptake
uptake IC50, nM
uptake/
binding
uptake/
binding
uptake/
binding 5HT/DA NE/DA
compd
binding
binding
uptake
cocaine 300 ( 10
330 ( 30
23 ( 10
200 ( 70
650 ( 170
120 ( 33
1.1
0.85
11
17
14
0.94
7.5
6.9
0.24
1.4
1.6
1.1
2.8
3.0
1.6
4.6
500 ( 50
5.0 ( 0.8
0.33 ( 0.11
3.6 ( 1.5
0.06 ( 0.03
17 ( 7
2.0 ( 0.8
16 ( 0.8
130 ( 40
91 ( 9
93 ( 9
44 ( 6
310 ( 40
4.8 ( 1.5
65 ( 12
0.62 2700 ( 350
190 ( 50
15 ( 6
0.07
0.68
0.36
1.0
0.40
2.3
0.58
0.60
2.4
1.6
0.68
1.6
2.1
2.3
0.94
0.21
0.033
0.020
0.053
0.58
0.65
0.17
0.20
0.18
1a
27 ( 6
19 ( 7
38 ( 12
0.96
200
22 ( 7
95 ( 23
130 ( 35
52 ( 7
1b
(-)-1b
(+)-1b 8.7 ( 0.8
34 ( 8
130 ( 60
6.3 ( 2.4
36
110
130 ( 50
21 ( 6
7b
2a
2b
3a
3b
4a
4b
5a
5b
6a
6b
310 ( 210 290 ( 40
3700 ( 1600 220
13 ( 4
24 ( 7
480 ( 30
190 ( 40
240 ( 70
1500 ( 500
1400 ( 600 3200 ( 1100
13
11
8.1 ( 1.3
39 ( 7
61 ( 12
270 ( 30
53 ( 1
340 ( 10
51 ( 21
6.5
48 ( 29
250 ( 10
55 ( 28
400 ( 100
110 ( 50
260 ( 80
150 ( 50
440 ( 80
28 ( 14
150 ( 50
130 ( 70
640 ( 330
75 ( 35
420 ( 220
310 ( 50
1000 ( 400
0.21
0.089
9.1
0.56
4.7
0.46
0.56
2.5
1.9
1.5
2.2
0.84
0.37
12
2.9
1.5
3.7
2.1
2.6
34.
4.2
220 ( 20
250 ( 30
32 ( 6
180 ( 100 190 ( 60
7.9
8.4
130 ( 90
370 ( 170
740 ( 260 3100 ( 1200
890 ( 280 2700 ( 1500
4700 ( 300
380 ( 140
180 ( 45
>10 µM
>10 µM
3700 ( 1300
80 ( 20
120 ( 3
130 ( 50
550 ( 200
460 ( 180 2600 ( 240
2800 ( 1900 1600 ( 240
5.7
0.57
21
6.7
Ta ble 3. Binding of Cis Isomers to DA, 5HT, and NE Cloned Transporters Using 40-80 pM [125I]RTI and Inhibition of [3H]DA (20
nM), [3H]5HT (20 nM), and [3H]NE (20 nM) Uptake
binding Ki, nM
dopamine
uptake
serotonin
norepinephrine
binding uptake
uptake IC50, nM
binding 5HT/DA NE/DA
uptake/
binding
uptake/
binding
uptake/
compd
binding
binding
uptake
1a
1b
2a
2b
3a
3b
4a
4b
5a
5b
6a
6b
290 ( 40
63 ( 16
140 ( 4
500 ( 110
550 ( 130
1.7
8.7
38 ( 8
4.0 ( 2.0
5.5 ( 1.4
19 ( 7
0.11
2.3
4.0
5.5
2.6
4.0
2.3
600 ( 200
150 ( 40
130 ( 70
86 ( 58
0.22
0.57
0.008
0.010
0.02
0.14
2.1
0.80
0.21
1.9
0.26
0.16
0.17
8.3
1.0
0.54
1.1
2.4 ( 1.0
4.7 ( 1.0
13 ( 1
1000 ( 200 11.
170 ( 50
660 ( 190 530 ( 90
280 ( 60 620 ( 60
0.80
2.2
0.83
3.1
1.4
2.3
72 ( 23
2400 ( 1200 4400 ( 2900
540 ( 210
2000 ( 600
3500 ( 2100 1500 ( 500
650 ( 100 1800 ( 300
1100 ( 500 1800 ( 20
2200 ( 500
4800 ( 400
>10 µM
1.8
1.2
0.27
0.43
2.8
500 ( 30 1300 ( 400
630 ( 150
540 ( 180
1200 ( 300 1000 ( 60
450 ( 120 1400 ( 300
680 ( 210 960 ( 110
650 ( 110 1500 ( 900
2800 ( 900
1100 ( 200 5300 ( 600
>10 µM
200 ( 60
130 ( 30
810 ( 120
300 ( 80
73 ( 11 1800 ( 600 25
1.9
1.2
1700 ( 300
>10 µM
2100 ( 200
300 ( 90
>10 µM
1.6
>10 µM
>10 µM
>10 µM
>10 µM
4.8
>10 µM
700 ( 240
2.3
F igu r e 2. Stereoscopic image of the more active (+)-enantiomer of trans-1b showing the 3R,1S absolute configuration.
at the DA transporter. This suggests that large N-alkyl
groups and steric bulk on the unsubstituted phenyl ring
may be used to decrease activity at the 5HT and NE
transporters in nonselective monoamine reuptake block-
ers if that is desired. As indicated above, our intention
is to retain activity at the 5HT transporter since this
component of the action of cocaine contributes signifi-
cantly to its overall pharmacological effects.
For the resolved enantiomers of trans-1b, the (+)-
enantiomer was the more potent one. Somewhat sur-
prisingly, however, the (-)-enantiomer showed consid-
erable affinity and potency in blocking the reuptake of
all three monoamines. Given the 99.2% ee purity of the
(-)-enantiomer, this is clearly not due to the presence
of the (+)-enantiomer. This is unlike the situation for
the N-methyl analogue trans-1a in which the (+)-
enantiomer is about 50 times as potent as the (-)-
enantiomer in blocking the reuptake of DA.31 The
absolute configuration of the more active (+)-enantiomer
was determined by X-ray crystallography to be 3R,1S
(Figure 2), as was also found previously for the more
active enantiomer of the N-methyl analogue trans-1a .31
The conformation of the N-methyl groups in the crystal
structure is similar to the preferred conformation
predicted by the MM2-87 calculations which was sug-
gested to be unfavorable for binding to the transporter.24
In the previous study of 3-phenyl-1-indanamines,31
among the compounds that were synthesized and as-

4986 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 26
Froimowitz et al.
F igu r e 4. Effect of (+)-trans-1b on horizontal activity counts/
10 min as a function of dose and time during an 8-h session
in mice; *p < 0.05 compared with vehicle (210-240 min).
F igu r e 3. Effect of cocaine on horizontal activity counts/10
min as a function of dose and time during an 8-h session in
mice; *p < 0.05 compared with vehicle (0-30 min).
sayed for pharmacological activity were the cis and trans
isomers of 1a , 1b, 2a , and 3a . In that study, the DA,
NE, and 5HT reuptake assays utilized rat synaptosomal
tissue, whereas the reuptake assays in this work used
cloned human transporters. There was reasonable agree-
ment for the common compounds in both studies.
The effects of cocaine and (+)-trans-1b on locomotor
activity in mice are shown in Figures 3 and 4, respec-
tively. It can be seen that the cocaine already has a
substantial effect at the first data point of 10 min. In
fact, the onset of cocaine is believed to be considerably
faster than that. It can also be seen that most of its
stimulatory effects are gone within 2 h. In contrast, (+)-
trans-1b appears to have an onset of action of at least
20 min since locomotor activity is still going down at
that point. Thereafter, the stimulatory effect appears
to be present throughout the 8 h of the testing session.
(The reduced activity at the highest doses appears to
be due to stereotypy which occurs in rodents with high
levels of released DA.) Thus, (+)-trans-1b can be seen
to have the desired slow-onset, long-duration profile.
The other trans-3-phenyl-1-indanamines synthesized
also showed similar slow-onset, long-duration pharma-
cological profiles, and their ED50 values are shown in
Table 4. Most of the compounds in this class appear to
be cocaine-like and produce maximum locomotor stimu-
lation similar to that of cocaine. However, this is less
true for the compounds with large groups on the
ammonium nitrogen. Both enantiomers of trans-1b also
Ta ble 4. ED50 Values ((SEM) of Compounds on 8-h Locomotor
Assay (Mice) and for Generalization to 10 mg/kg Cocaine (Rat)
ED50, mg/kg
compd
cocaine
locomotor activity
generalization
7.92 ( 0.22a
1.2 ( 0.5
2.4 ( 0.4
0.96 ( 0.40
1.0 ( 0.3
2.7 ( 0.3
8.1 ( 1.6
1.7 ( 0.4
3.1 ( 0.4
2.9 ( 0.4
g28
3.61 ( 0.14b
trans-1a
trans-1b
(+)-trans-1b
trans-2a
trans-2b
trans-3a
trans-3b
trans-4a
trans-4b
trans-5a
trans-6a
trans-6b
trans-7b
1.3 ( 0.5
2.3 ( 0.5
1.5 ( 0.5
3.3 ( 0.4
c
d
g20
5.7 ( 0.5
g17
e
a
Standard error of the population of 72 independent determina-
b
tions. Standard error of the population of 88 independent
determinations. c Partial substitution at 25 mg/kg. Partial sub-
d
stitution at 5-10 mg/kg. e Partial substitution at 10-25 mg/kg.
produced locomotor stimulation in a 1-h locomotor assay
with ED50 values of 3.4 and 5.0 mg/kg for the (+)- and
(-)-enantiomers, respectively (not shown). On the 8-h
locomotor assay, the ED50 value for the (+)-enantiomer
was 0.96 mg/kg (Table 4). However, the less potent (-)-
enantiomer showed considerably more toxicity at a high
dose of 100 mg/kg than the (+)-enantiomer (not shown).

Slow-Onset, Long-Duration MO Reuptake Blockers
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 26 4987
This suggests that it may be toxicologically advanta-
geous to use the (+)-enantiomer rather than the race-
mate.
DA reuptake blockers may have similar binding affini-
ties.52 It is even possible to achieve high potency in
compounds in which the nitrogen of 3-phenyltropanes
has been replaced by an oxygen or carbon atom.53-56
This might argue against the pharmacophore model.
Nevertheless, the importance of directionality of the
ammonium hydrogen (or amine lone pair) was recently
shown by the synthesis and testing of cocaine analogues
in which additional rigidification produced defined
directions of the ammonium hydrogen (or amine lone
pair).57 It was found that “back-bridged” analogues
(Figure 1), in which the ammonium hydrogen was
consistent with the pharmacophore model, had higher
affinities for the DA transporter and were more selective
for it relative to the 5HT transporter. In contrast, “front-
bridged” analogues had higher affinities for the 5HT
transporter and were more selective for it relative to
the DA transporter. (Both classes of compounds had
approximately equal high affinities for the NE trans-
porter, suggesting that the differences in orientation of
the ammonium hydrogen did not play a major role for
the latter.) These preferences were not absolute, how-
ever, and “front-bridged” analogues still had consider-
able affinity at the DA transporter.
Several of the compounds were also tested in an in
vivo cocaine generalization assay in rats trained to
discriminate cocaine from saline (Table 4). The com-
pounds were perceived as being cocaine-like with race-
mic trans-1b being the most potent of these with an
ED50 of 1.3 mg/kg. This is interesting in that, while the
compounds are perceived as being cocaine-like in this
assay and reduce the self-administration of cocaine in
both rodents46,47 and primates,48 they do not fully
eliminate cocaine self-administration despite cocaine-
like pharmacological profiles. The persistent, though
reduced, self-administration of cocaine by these animals
may be attributed to residual, rapid phasic fluctuations
in DA levels superimposed on the tonic elevation of DA
produced by the long-duration profile of the compounds.
Interestingly, racemic trans-1b appears to be especially
efficacious in reducing the self-administration of cocaine
in Lewis rats, a hypodopaminergic strain which displays
more self-administration and more conditioned place
preferences than other strains of rats for drugs which
increase levels of DA in brain reward regions.49 Racemic
trans-1b was also tested in rodents trained to self-
administer cocaine to see if the compound, when sub-
stituted for cocaine, would itself be self-administered.
Using a dose of racemic trans-1b that produces equiva-
lent decreases of electrical brain stimulation reward
thresholds and equivalent increases of nucleus accum-
bens DA as a dose of cocaine that is robustly self-
administered, we found that the compound is only self-
administered at levels comparable to their self-
administration of saline.46 This last result suggests that
slow-onset, long-duration DA reuptake blockers will be
nonabusable.
Exp er im en ta l Section
Ch em istr y. Column chromatography was carried out with
Baker 40-µm silica gel. Melting points were obtained using a
Thomas-Hoover capillary melting point apparatus and are
corrected. NMR spectra were recorded on a Bruker 300-MHz
FT-NMR spectrometer. The HPLC system used contains an
Eldex Duros Series pump as the feeding pump, two Rainin
SD-1 pumps, a Rainin UV-1 detector, and a Rainin FC-1
fraction collector. Elemental analyses were obtained from
Atlantic Microlabs, Atlanta, GA, and were within (0.4% of
theoretical values.
Syn th esis of tr a n s-1b by Sch em e 3. 3-(3′,4′-Dich lo-
r op h en yl)-3-p h en ylp r op a n oic Acid (10). A mixture of 3,4-
dichlorocinnamic acid (14; 95% trans, 50 g, 0.23 mol), benzene
(150 mL), and concentrated H2SO4 (100 mL) was stirred at
85-95 °C in a three-neck round-bottom flask. When the level
of 14 was e1%, the reaction mixture was cooled to room
temperature and slowly poured onto ice. The mixture was
stirred for 30 min and then transferred into a separatory
funnel. The aqueous layer was drained and extracted twice
with EtOAc. The organic solutions were combined and washed
five times with water and twice with brine. The solvent was
then evaporated under reduced pressure and the residue dried
under high vacuum at room temperature for 24 h. The desired
acid 10 (65.8 g, 96% yield) was obtained as a thick oil: 1H
NMR (DMSO-d6) δ 12.23 (s, 1 H), 7.66 (d, 1 H, J ) 2 Hz), 7.54
(d, 1 H, J ) 9 Hz), 7.40-7.13 (m, 6 H), 4.49 (t, 1 H, J ) 9 Hz),
One potential problem with the use of a long-duration
reuptake blocker as a medication for cocaine abuse is
that a long-lasting stimulant effect may interfere with
sleep in those that use it. For that reason, this approach
will only work if the stimulatory effects can wear off by
the end of the day or if substimulatory doses can have
the desired therapeutic effects. To that end, our results
with Lewis rats are promising. As indicated above,
Lewis strain rats, due to a hypodopaminergic genetic
fault, are believed to be a potential model for humans
who have a propensity to abuse drugs. The effects of
these slow-onset, long-duration compounds appeared to
be particularly effective in reducing the self-administra-
tion of cocaine in this rat strain, and this occurred at
doses which in themselves were not stimulatory to the
animals.
3.18-3.00 (m, 2 H); IR (KBr) 3500-2200, 1718 cm-1
.
3-(3′,4′-Dich lor op h en yl)in d a n -1-on e (11). Chlorosulfonic
acid (66 mL, 0.99 mol) was added slowly to a solution of the
acid 10 (65 g, 0.22 mol) in dichloromethane (330 mL) at room
temperature. After the reaction was complete, the reaction
mixture was slowly poured onto ice, stirred for 15 min, and
transferred to a separatory funnel. The cloudy bottom layer
was drained and the dichloromethane removed under reduced
pressure to give a light yellow solid which was dissolved in
EtOAc. The top aqueous layer was extracted twice with EtOAc.
The combined organic layers were washed with water five
times and twice with brine. The EtOAc solution was evapo-
rated to dryness and the obtained solid was stirred for one hr
with 100 mL of 1:9 EtOAc:heptane at room temperature.
Stirring was continued for 4 h at 5-10 °C. The mixture was
filtered and the filter cake washed twice with a cold solution
of 1:9 EtOAc:heptane. After drying under high vacuum for 16
h, 45.6 g (71%) of the desired ketone 11 was obtained as an
As indicated above, a pharmacophore has been pro-
posed for compounds that bind to the DA transporter.24
After superposition of the key features of the molecules
in their biologically active conformer, the direction of
the ammonium hydrogen (or lone pair for the free base)
was proposed as a crucial feature. However, there has
recently been a drastic modification in thinking about
the structural requirements of binding to the DA
transporter with regard to the amine group. For ex-
ample, introducing groups that reduce nitrogen basicity
does not preclude high potency.50,51 It has also recently
been suggested that the cationic and neutral forms of

4988 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 26
Froimowitz et al.
1
off-white solid: 97% pure by HPLC; H NMR (CDCl3) δ 7.85
isomers of other analogues with small N-alkyl groups could
be separated in a similar fashion.
(d, 1 H, J ) 9 Hz), 7.62 (t, 1 H, J ) 9 Hz), 7.50 (t, 1 H, J ) 9
Hz), 7.40 (d, 1 H, J ) 9 Hz), 7.30-7.20 (m, 2 H), 6.95 (dd, 1 H,
J ) 9, 2 Hz), 4.56 (dd, 1 H, J ) 9, 4 Hz), 3.25 (dd, 1 H, J ) 21,
HP LC Resolu tion of (+)- a n d (-)-tr a n s-N,N-Dim eth yl-
[3-(3′,4′-d ich lor op h en yl)in d a n -1-yl]a m in e. A Chiralcel OD
column (10 µm, 10 mm × 250 mm) was used with the UV
detector set at 260 nm. The purified trans amine was dissolved
in 10% 2-PrOH/hexanes (∼2 mg/mL) and filtered through a
0.2-µL filter. For each injection, ∼1.5 mg of the amine was
loaded. The mobile phase contained hexanes, 2-PrOH, and
trifluoroacetic acid in a ratio of 90/10/0.1 with a flow rate of 4
mL/min. The (+)-salt eluted out at about 15 min and the (-)-
salt at about 17 min. Fractions of each peak were combined,
the solvent evaporated, treated with saturated NaHCO3(aq)
to produce the free bases, extracted with EtOAc, dried over
MgSO4, vacuum filtered, and the solvent evaporated. After
conversion to the HCl salts, the optical purities were 100% ee
for the (+)-salt and 99% ee for the (-)-salt, respectively, as
measured by chiral HPLC.
Ch em ica l Resolu tion of (+)- a n d (-)-tr a n s-N,N-Di-
m eth yl-[3-(3′,4′-d ich lor op h en yl)in d a n -1-yl]a m in e. To a
solution of the racemate (10.5 g/100 mL of acetone) was added
a solution of Di-p-toluoyl-L-tartaric acid (14.5 g/100 mL of
acetone). A white solid formed immediately. The mixture was
stirred at room temperature for 1 h and then filtered. The filter
cake was washed with 50 mL of acetone and then stirred with
200 mL of acetone at room temperature for 12 h. Vacuum
filtration gave 9.03 g of product. The obtained salt was stirred
in 200 mL of acetone at room temperature for 12 h. The
mixture was filtered and dried under reduced pressure to give
8.37 g of the di-p-toluoyl tartarate salt. This was converted to
the free base by stirring with saturated NaHCO3(aq) (50 mL).
The free base was extracted with EtOAc (2 × 50 mL). The
EtOAc layer was washed with water (100 mL) and brine (100
mL). After drying over anhydrous sodium sulfate, removal of
solvent gave 3.71 g (71%) of the (+)-free base in 99.4%
enantiomeric purity. The (-)-enantiomer was prepared simi-
larly using di-p-toluoyl-D-tartaric acid.
Novel Com p ou n d s Syn th esized . Note that most of the
compounds with asymmetric alkyl groups on the amine showed
two sets of NMR signals. We believe that this is due to
significant concentrations of the different epimers in which
the asymmetric N-alkyl groups are interchanged.
tr a n s-N-Eth yl-N-m eth yl-3-(3′,4′-d ich lor op h en yl)-1-in -
d a n a m in e h yd r ogen oxa la te (tr a n s-2b): 1H NMR (DMSO-
d6) δ 1.18 (3H, t, J ) 7.2 Hz), 3.09 (1H, dt, J ) 15.7 Hz, 8.3
Hz), 1.7-1.9 (2H, m), 2.9-3.3 (3H, m), 4.73 (1H, t, J ) 7.8
Hz), 5.19 (1H, d, J ) 7.6 Hz), 7.0 (1H, m), 7.17 (1H, d, J ) 8.3
Hz), 7.4 (2H, m), 7.47 (1H, s), 7.60 (1H, d, J ) 8.2 Hz), 7.7
(1H, m).
cis- N-Eth yl-N-m eth yl-3-(3′,4′-d ich lor op h en yl)-1-in d a n -
a m in e h yd r och lor id e (cis-2b): 1H NMR (DMSO-d6; two sets
of signals in a ratio of ∼35/65 were detected) δ 1.31 (1.05H, t,
J ) 7.1 Hz), 1.42 (1.95H, t, J ) 7.1 Hz), 2.18 (0.35H, t, J ) 9.7
Hz), 2.22 (0.65H, t, J ) 9.7 Hz), 2.55 (1.95H, d, J ) 4.6 Hz),
2.8-3.1 (1.7H, m), 3.1-3.3 (1.35H, m), 4.42 (1H, t, J ) 8.9
Hz), 5.16 (0.35H, t, J ) 8.9 Hz), 5.24 (0.65H, t, J ) 8.3 Hz),
6.9 (1H, m), 7.3 (1H, m), 7.4 (2H, m), 7.4 (2H, m), 7.59 (1H, d,
J ) 1.8 Hz), 7.65 (1H, d, J ) 8.3 Hz), 8.12 (0.35H, d, J ) 7.3
Hz), 8.19 (0.65H, d, J ) 7.0 Hz), 11.84 (1H, s).
tr a n s-N-Meth yl-N-p r op yl-3-(3′,4′-d ich lor op h en yl)-1-in -
d a n a m in e h yd r och lor id e (tr a n s-3b): 1H NMR (DMSO-d6;
two sets of signals in a ratio of ∼1/1 were detected) δ 0.87
(1.5H, t, J ) 7.5 Hz), 0.92 (1.5H, t, J ) 7.5 Hz), 1.7-1.9 (2H,
m), 2.3-2.5 (1H, m), 2.5 (1.5H, under DMSO-d5), 2.69 (1.5H,
d, J ) 4.6 Hz), 2.7-2.9 (0.5H, m), 2.9-3.1 (2H, m), 3.1-3.2
(0.5H, m), 4.76 (1H, q, J ) 8.5 Hz), 5.19 (0.5H, d, J ) 8.3 Hz),
5.29 (0.5H, d, J ) 8.3 Hz), 7.0 (1H, m), 7.18 (1H, dd, J ) 1.9
Hz, 8.3 Hz), 7.4 (2H, m), 7.48 (1H, d, J ) 1.9 Hz), 7.61 (1H,
dd, J ) 1.1 Hz, 8.3 Hz), 7.9 (0.5H, m), 8.0 (0.5H, m), 10.98
(1H, s).
9 Hz), 2.62 (dd, 1 H, J ) 21, 4 Hz); IR (KBr) 1699 cm-1
.
cis-3-(3′,4′-Dich lor op h en yl)in d a n -1-ol (12). A solution of
the ketone 11 (25 g, 0.09 mol) in 250 mL of THF was stirred
at -5 °C. A solution of NaBH4 (6.8 g, 018 mol) in water (28
mL) was cooled to 0 °C and then added dropwise while
maintaining the temperature of the reaction mixture below 0
°C. After all of the NaBH4 solution was added, the cooling bath
was removed and the reaction mixture stirred for 2 h. The
reaction mixture was diluted with ice-cold water and stirred
for 1 h. THF was removed under reduced pressure and the
mixture extracted twice with EtOAc. The EtOAc solution was
washed twice with water, twice with brine, and then evapo-
rated to dryness. The oily mixture that was obtained was
stirred with a solution (100 mL) of 1:9 EtOAc:heptane for 1 h
and at 5-10 °C for 4 h. The mixture was filtered and the filter
cake washed with ice-cold solution of 1:9 EtOAc:heptane. After
drying, 18.8 g (74%) of the cis alcohol 12 was obtained with a
purity of 98.5% with the undesired trans alcohol being e1%:
1H NMR (DMSO-d6) δ 7.60 (d, 1 H, J ) 9 Hz), 7.50 (d, 1 H, J
) 2 Hz), 7.40 (d, 1 H, J ) 9 Hz), 7.30-7.15 (m, 3 H), 6.85 (d,
1 H, J ) 9 Hz), 5.53 (d, 1 H, J ) 9 Hz), 5.15-5.05 (m, 1 H),
4.25 (t, 1 H, J ) 9 Hz), 2.92-2.78 (m, 1 H), 1.86-1.73 (m, 1
H); IR (KBr) 3300 cm-1
.
tr a n s-N,N-Dim et h yl[3-(3′,4′-d ich lor op h en yl)in d a n -1-
yl]a m in e (1b). A solution of the cis alcohol 12 (22.7 g, 0.081
mol) and triethylamine (45 mL, 0.325 mol) in THF (350 mL)
was stirred at -15 °C under argon. A solution of methane-
sulfonyl chloride (12.6 mL, 0.162 mol) in THF (150 mL) was
cooled to -60 °C and then added slowly to the alcohol solution
maintaining the temperature below 0 °C. The reaction mixture
was stirred for 10 min at 0 °C and then purged with
dimethylamine gas (56 g, 1.21 mol). The reaction mixture was
allowed to warm to room temperature and stirred for 6 h. THF
was removed under reduced pressure and the mixture was
extracted three times with EtOAc. The combined EtOAc
solutions were washed twice with brine, dried over anhydrous
sodium sulfate, and evaporated to dryness to give 26 g of the
desired trans amine (trans:cis ratio of 96.6:3.4) as a brown oil.
The crude amine was stirred with 5 mL of EtOAc and then 45
mL of heptane was added. The mixture was stirred for 1 h at
15 °C, filtered, and the filter cake washed with 40 mL heptane.
The solid was dried under high vacuum to give 14 g of the
desired trans-1b (56%, first crop). The mother liquor was
evaporated to dryness and the obtained oil was stirred with
10% EtOAc in heptane (15 mL) for 1 h at 15 °C. The formed
solid was then filtered, the filter cake washed with heptane,
and dried under high vacuum, to give 5.2 g of a second crop
(21%). Both crops contained 0.6% of the undesired cis isomer
as indicated by HPLC. After an additional washing, filter, and
drying step, we obtained 15 g (60% yield) of the desired trans-
1b amine that was 94% pure and contained 0.2% of the
undesired cis isomer as determined by HPLC: 1H NMR
(CDCl3) δ 7.45 (dd, 1 H, J ) 9, 2 Hz), 7.35 (d, 1 H, J ) 9 Hz),
7.30-7.20 (m overlapping CHCl3 singlet, 2 H), 7.18 (d, 1 H, J
) 2 Hz), 6.98-6.90 (m, 2 H), 4.48-4.35 (m, 2 H), 2.72-2.60
(m, 1 H), 2.25 (s, 6 H), 2.05-1.90 (m, 1 H).
HP LC Sep a r a tion of cis- a n d tr a n s-N,N-Dim eth yl-[3-
(3′,4′-d ich lor op h en yl)in d a n -1-yl]a m in e. A Phenomenex
Primesphere column (silica, 5 µm, 110 Å, 21.2 mm × 250 mm)
was used with the UV detector set at 268 nm. The mixture of
amines, which had been partially purified by chromatography,
was dissolved in EtOAc (∼103 mg/mL) and filtered through a
0.2-µm filter. For each injection, ∼100 mg of the amine was
loaded. The mobile phase contained EtOAc and Et3N in a ratio
of 100/0.05 with a flow rate of 10 mL/min. The cis amine eluted
out at 17 min and the trans amine at 20 min. Solvent
evaporation afforded the desired cis and trans amines. Using
this method, it was possible to obtain an essentially complete
separation of the cis and trans isomers. The cis and trans
cis-N-Met h yl-N-p r op yl-3-(3′,4′-d ich lor op h en yl)-1-in -
d a n a m in e h yd r och lor id e (cis-3b): 1H NMR (DMSO-d6; two
sets of signals in a ratio of ∼4/6 were detected) δ 0.87 (1.2H,
t, J ) 7.5 Hz), 0.93 (1.8H, t, J ) 7.4 Hz), 1.7-1.9 (1.2H, m),

Slow-Onset, Long-Duration MO Reuptake Blockers
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 26 4989
1.9-2.1 (0.8H, m), 2.1-2.3 (1H, m), 2.56 (1.8H, d, J ) 4.7 Hz),
2.83 (1.2H, d, J ) 4.6 Hz), 2.7-3.2 (3H, m), 4.42 (1H, t, J )
8.8 Hz), 5.14 (0.4H, t, J ) 8.4 Hz), 5.23 (0.6H, t, J ) 8.5 Hz),
6.9 (1H, m), 7.28 (1H, dd, J ) 1.9 Hz, 8.3 Hz), 7.4 (2H, m), 7.6
(1H, m), 7.65 (1H, d, J ) 8.3 Hz), 8.08 (0.4H, d, J ) 6.5 Hz),
8.19 (0.6H, d, J ) 7.5 Hz), 11.72 (0.4H, s), 11.85 (0.6H, s).
t r a n s-N -Isop r op yl-3-(3′,4′-d ich lor op h e n yl)-1-in d a n -
a m in e h yd r och lor id e (tr a n s-4a ): 1H NMR (DMSO-d6) δ 1.37
(3H, d, J ) 6.4 Hz), 1.41 (3H, d, J ) 6.4 Hz), 2.43 (1H, dt, J )
14.1 Hz, 7.3 Hz), 3.5 (1H, m), 2.78 (1H, ddd, J ) 3.3 Hz, 8.2
Hz, 14.4 Hz), 3.5 (1H, m), 4.87 (1H, t, J ) 7.6 Hz), 5.0 (1H,
m), 7.0 (1H, m), 7.17 (1H, dd, J ) 2.1 Hz, 8.4 Hz), 7.4 (2H, m),
7.44 (1H, d, J ) 2.0 Hz), 7.60 (1H, d, J ) 8.2 Hz), 7.9 (1H, m),
9.35 (1H, s), 9.48 (1H, s).
s), 1.74 (1.44H, s), 2.02 (1H, dt, J ) 13 Hz, 9.9 Hz), 2.65 (2.52H,
d, J ) 5.2 Hz), 2.69 (0.48H, d, J ) 5.4 Hz), 2.93 (0.84H, dt, J
) 12.8 Hz, 7.6 Hz), 3.32 (0.16H, dt, J ) 7.3 Hz, 3 Hz), 4.15
(0.16H, dd, J ) 7.5 Hz, 10.0 Hz), 4.32 (0.84H, t, J ) 8.6 Hz),
5.09 (0.16H, dd, J ) 7.5 Hz, 10.0 Hz), 5.40 (0.84H, t, J ) 8.5
Hz), 6.94 (0.84H, d, J ) 7.7 Hz), 7.2 (1.32H, m), 7.3-7.5 (4.16H,
m), 9.01 (0.84H, d, J ) 7.8 Hz), 11.89 (0.84H, s), 12.01 (0.16H,
s).
t r a n s-N -B e n zy l-3-(3′,4′-d ic h lo r o p h e n y l)-1-in d a n -
a m in e h yd r och lor id e (tr a n s-6a ): 1H NMR (DMSO-d6) δ 2.6
(1H, m), 2.95 (1H, ddd, J ) 2.8 Hz, 8.2 Hz, 14.6 Hz), 4.21 (2H,
s), 4.89 (1H, t, J ) 7.7 Hz), 5.36 (1H, d, J ) 6.0 Hz), 7.0 (1H,
m), 7.26 (1H, dd, J ) 2.0 Hz, 8.3 Hz), 7.4-7.5 (6H, m), 7.61
(1H, d, J ) 8.2 Hz), 7.7 (2H, m), 7.9 (1H, m), 10.04 (2H, s).
tr a n s-N-Isop r oyl-N-m eth yl-3-(3′,4′-d ich lor op h en yl)-1-
in d a n a m in e h yd r och lor id e (tr a n s-4b): 1H NMR (DMSO-
d6; two sets of signals in a ratio of ∼3/7 were detected) δ 1.32
(0.9H, d, J ) 6.5 Hz), 1.41 (2.1H, d, J ) 6.4 Hz), 1.47 (3H, d,
J ) 6.5 Hz), 2.36 (0.3H, t, J ) 7.7 Hz), 2.41 (0.7H, t, J ) 8.0
Hz), 2.48 (2.1H, d, J ) 5.0 Hz), 2.51 (0.9H, d, J ) 3.9 Hz),
2.96 (0.7H, ddd, J ) 2.8 Hz, 8.5 Hz, 15.1 Hz), 3.04 (0.3H, dd,
J ) 8.4 Hz, 15.3 Hz), 3.59 (0.7H, m, J ) 6.3 Hz), 3.7 (0.3H,
m), 4.81 (0.7H, t, J ) 6.0 Hz), 5.03 (0.3H, t, J ) 8.4 Hz), 5.15
(0.3H, dd, J ) 5.3 Hz, 6.9 Hz), 5.4 (0.7H, m), 7.0 (1H, m), 7.17
(0.3H, dd, J ) 2.1 Hz, 8.4 Hz), 7.19 (0.7H, dd, J ) 2.1 Hz, 8.4
Hz), 7.4 (2H, m), 7.44 (0.3H, d, J ) 2.1 Hz), 7.47 (0.7H, d, J )
2.0 Hz), 7.61 (0.7H, d, J ) 8.3 Hz), 7.62 (0.3H, d, J ) 8.3 Hz),
7.8 (0.3H, m), 8.1 (0.7H, m), 10.96 (0.3H, s), 11.13 (0.7H, s).
ci s-N -I s o p r o p y l-3-(3′,4′-d ic h lo r o p h e n y l)-1-in d a n -
a m in e h yd r och lor id e (cis-4a ): 1H NMR (DMSO-d6) δ 1.41
(3H, d, J ) 6.2 Hz), 1.43 (3H, d, J ) 6.2 Hz), 2.16 (1H, q, J )
10.7 Hz), 2.97 (1H, dt, J ) 12.5 Hz, 7.3 Hz), 3.5 (1H, m), 4.40
(1H, t, J ) 8.8 Hz), 4.96 (1H, q, J ) 6.8 Hz), 6.84 (1H, d, J )
7.2 Hz), 7.4 (3H, m), 7.60 (1H, d, J ) 1.9 Hz), 7.66 (1H, d, J )
8.3 Hz), 8.13 (1H, d, J ) 7.2 Hz), 9.28 (1H, t, J ) 9.0 Hz),
10.14 (1H, t, J ) 7.7 Hz).
cis-N-Isop r oyl-N-m eth yl-3-(3′,4′-d ich lor op h en yl)-1-in -
d a n a m in e h yd r och lor id e (cis-4b): 1H NMR (DMSO-d6; two
sets of signals in a ratio of ∼1/9 were detected) δ 1.31 (0.3H,
d, J ) 6.5 Hz), 1.44 (0.3H, d, J ) 6.6 Hz), 1.47 (2.7H, d, J )
6.4 Hz), 1.54 (2.7H, d, J ) 6.4 Hz), 2.21 (1H, dt, J ) 12.9 Hz,
9.8 Hz), 2.58 (2.7H, d, J ) 4.9 Hz), 2.79 (0.3H, d, J ) 4.7 Hz),
2.84 (0.9H, dt, J ) 14.2 Hz, 7.4 Hz), 3.04 (0.1H, dt, J ) 13.1
Hz, 7.5 Hz), 3.48 (0.9H, m, J ) 6.5 Hz), 3.8 (0.1H, m), 4.36
(0.1H, t, J ) 8.9 Hz), 4.20 (0.9H, t, J ) 8.9 Hz), 5.19 (0.1H, t,
J ) 9.1 Hz), 5.37 (0.9H, t, J ) 8.1 Hz), 6.9 (1H, m), 7.3-7.4
(3H, m), 7.9 (0.1H, m), 8.29 (0.9H, d, J ) 6.6 Hz), 11.26 (0.1H,
s), 11.68 (0.9H, s).
tr a n s-N-ter t-Bu t yl-3-(3′,4′-d ich lor op h en yl)-1-in d a n -
a m in e h yd r och lor id e (tr a n s-5a ): 1H NMR (DMSO-d6) δ
1.47 (9H, s), 2.40 (1H, dt, J ) 14.2 Hz, 8.0 Hz), 2.99 (1H, ddd,
J ) 1.6 Hz, 8.1 Hz, 13.9 Hz), 5.1 (2H, m), 7.0 (1H, m), 7.16
(1H, dd, J ) 2.1 Hz, 8.4 Hz), 7.4 (3H, m), 7.6 (2H, m), 8.43
(1H, d, J ) 12.2 Hz), 9.9 (1H, m).
tr a n s-N-ter t-Bu t yl-N-m et h yl-3-(3′,4′-d ich lor op h en yl)-
1-in d a n a m in e h yd r och lor id e (tr a n s-5b): 1H NMR (DMSO-
d6; two sets of signals in a ratio of ∼3/7 were detected) δ 1.66
(6.3H, s), 1.70 (2.7H, s), 1.9 (0.3H, m), 2.25 (2.1H, d, J ) 5.1
Hz), 2.3 (0.7H, m), 2.57 (0.9H, s), 2.84 (0.3H, bs), 3.74 (0.7H,
dd, J ) 6.7 Hz, 14.2 Hz), 4.56 (0.3H, bs), 5.01 (0.7H, d, J ) 6.8
Hz), 5.12 (0.7H, dd, J ) 6.8 Hz, 9.7 Hz), 5.44 (0.3H, d, J ) 7.0
Hz), 6.85 (0.3H, d, J ) 7.0 Hz), 7.00 (0.3H, d, J ) 7.3 Hz),
7.1-7.5 (6.1H, m), 8.63 (0.3H, d, J ) 7.6 Hz), 11.63 (0.3H, s),
11.71 (0.7H, s).
tr a n s-N-Ben zyl-N-m eth yl-3-(3′,4′-d ich lor op h en yl)-1-in -
d a n a m in e h yd r och lor id e (tr a n s-6b): 1H NMR (DMSO-d6;
two sets of signals in a ratio of ∼1/1 were detected) δ 2.30
(0.5H, t, J ) 7.9 Hz), 2.35 (0.5H, t, J ) 8.0 Hz), 2.44 (1.5H, d,
J ) 4.8 Hz), 2.57 (1.5H, d, J ) 4.7 Hz), 3.18 (0.5H, d, J ) 8.4
Hz), 3.23 (0.5H, t, J ) 9.2 Hz), 4.2 (1H, m), 4.30 (0.5H, dd, J
) 6.5 Hz, 13.0 Hz), 4.43 (0.5H, dd, J ) 5.3 Hz, 13.0 Hz), 4.79
(0.5H, t, J ) 7.8 Hz), 4.90 (0.5H, t, J ) 7.9 Hz), 5.07 (0.5H, d,
J ) 8.0 Hz), 5.28 (0.5H, d, J ) 8.4 Hz), 7.0 (1H, m), 7.20 (1H,
dt, J ) 2.0 Hz, 8.9 Hz), 7.3-7.5 (6H, m), 7.6-7.7 (2H, m), 7.8
(1H, m), 8.0 (0.5H, m), 8.1 (0.5H, m), 11.61 (0.5H, s), 11.73
(0.5H, s).
cis-N-Ben zyl-3-(3′,4′-d ich lor op h en yl)-1-in da n a m in e h y-
d r och lor id e (cis-6a ): 1H NMR (DMSO-d6) δ 2.35 (1H, dt, J
) 12.4 Hz, 10.0 Hz), 3.02 (1H, dt, J ) 12.6 Hz, 7.7 Hz), 4.30
(2H, s), 4.41 (1H, t, J ) 8.8 Hz), 4.83 (1H, s), 6.84 (1H, d, J )
6.8 Hz), 7.3-7.5 (6H, m), 7.63 (1H, d, J ) 2.0 Hz), 7.67 (1H, d,
J ) 8.3 Hz), 7.7 (2H, m), 8.09 (1H, d, J ) 6.7 Hz), 10.11 (1H,
s), 10.51 (1H, s).
cis-N-Ben zyl-N-m et h yl-3-(3′,4′-d ich lor op h en yl)-1-in -
d a n a m in e h yd r och lor id e (cis-6b): 1H NMR (DMSO-d6; two
sets of signals in a ratio of ∼2/3 were detected) δ 2.4 (1H, m),
2.69 (1.2H, d, J ) 2.3 Hz), 2.8-3.0 (1H, m), 3.38 (1.8H, s),
4.18 (0.8H, s), 4.4 (2.2H, m), 5.02 (0.6H, t, J ) 7.4 Hz), 5.25
(0.4H, t, J ) 7.7 Hz), 6.91 (0.6H, d, J ) 6.0 Hz), 6.97 (0.4H, d,
J ) 7.0 Hz), 7.2-7.7 (9H, m), 7.92 (1H, d, J ) 3.7 Hz), 8.23
(0.4H, d, J ) 6.8 Hz), 8.30 (0.6H, d, J ) 6.4 Hz), 11.92 (0.4H,
s), 12.05 (0.6H, s).
tr a n s-N,N-Dim eth yl-3-(3′,4′-d ich lor op h en yl)-6-iod o-1-
in d a n a m in e h yd r ogen m a lea te (tr a n s-7b): 1H NMR (DM-
SO-d6) δ 2.35 (1H, dt, J ) 7.8 Hz, 15.2 Hz), 2.7 (6H, bs), 2.91
(1H, dd, J ) 8.1 Hz, 14.4 Hz), 4.65 (1H, t, J ) 8.2 Hz), 5.08
(1H, d, J ) 6.8 Hz), 6.04 (2H, s), 6.82 (1H, d, J ) 8.1 Hz), 7.18
(1H, dd, J ) 2.5 Hz, 8.9 Hz), 7.48 (1H, d, J ) 1.7 Hz), 7.61
(1H, d, J ) 8.3 Hz), 7.76 (1H, d, J ) 7.8 Hz), 8.02 (1H, s).
Cr ysta llogr a p h y. C17H18Cl2N+Cl-, fw ) 342.67, monoclinic
space group P212121; a ) 5.747(1), b ) 11.397(1), c ) 26.484(3)
Å; V ) 1734.7(3) Å3, Z ) 4, Fcalc ) 1.312 mg mm-3; λ(Cu KR)
) 1.54178 Å, µ ) 4.712 mm-1, F(000) ) 712, T ) 223 K.
A clear colorless crystal was used for data collection on an
automated Bruker P4 diffractometer equipped with an incident
beam monochromator. Lattice parameters were determined
from 40 centered reflections within 15° < 2θ < 56°. The data
collection range had a {(sin θ)/λ}max ) 0.55. Three standards,
monitored after every 97 reflections, corrected for a decay of
3.2% during the data collection. A set of 1345 reflections was
collected in the θ/2θ scan mode, with an ω-scan rate (a function
of count rate) from 7.5 to 30.0°/min. There were 1282 unique
reflections. Corrections were applied for Lorentz, polarization,
and absorption effects. The maximum and minimum trans-
missions were 0.416 and 0.194, respectively. The structure was
solved with SHELXTL58 and refined with the aid of the
SHELX97 system of programs. The full-matrix least-squares
refinement on Fo2 varied 194 atom coordinates and anisotropic
thermal parameters for all non-H atoms. H atoms were
included using a riding model [coordinate shifts of C applied
to attached H atoms, C-H distances set to 0.96, H angles
idealized, Uiso(H) were set to 1.2-1.5 Ueq(C)]. Final residuals
were R1 ) 0.074 for the 1128 observed data with Fo >4σ(Fo)
and 0.080 for all data. Final difference Fourier excursions of
ci s-N -t er t -B u t y l-3-(3′,4′-d ic h lo r o p h e n y l)-1-in d a n -
a m in e h yd r och lor id e (cis-5a ): 1H NMR (DMSO-d6) δ 1.49
(9H, s), 2.5 (1H, m), 3.07 (1H, dt, J ) 12.6 Hz, 7.7 Hz), 3.36
(1H, s), 4.38 (1H, t, J ) 9.0 Hz), 5.04 (1H, q, J ) 8.0 Hz), 6.87
(1H, d, J ) 7.3 Hz), 7.3-7.4 (3H, m), 7.60 (1H, d, J ) 2.0 Hz),
7.66 (1H, d, J ) 8.3 Hz), 8.05 (1H, d, J ) 7.3 Hz), 8.80 (1H, d,
J ) 12.0 Hz), 9.63 (1H, t, J ) 10.4 Hz).
cis-N-ter t-Bu tyl-N-m eth yl-3-(3′,4′-d ich lor op h en yl)-1-in -
d a n a m in e h yd r och lor id e (cis-5b): 1H NMR (DMSO-d6; two
sets of signals in a ratio of ∼16/84 were detected) δ 1.71 (7.56H,

4990 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 26
Froimowitz et al.
0.66 and -0.35 eÅ-3. The anomalous scattering was suf-
ficiently accurate to determine the absolute configuration using
the method of Flack,59 and the absolute structure parameter
was 0.01(6). Tables of coordinates, bond distances and angles,
and anisotropic thermal parameters have been deposited with
the Crystallographic Data Centre, Cambridge CB2 1EW,
England.
Bin d in g a n d Reu p ta k e Assa ys. For the DA transporter
assays, two different cell lines that express recombinant
human DA (hDAT) transporters were utilized. Initially, C6
cells were used and HEK293 cells were used thereafter. A
HEK293 cell line that expresses recombinant human serotonin
(hSERT) and norepinephrine (hNET) transporters was used
for all 5HT and NE transporter assays. The same cell lines
were used for both the binding and reuptake assays. Test drugs
(10 mM stock solution) were dissolved in DMSO. Pipetting was
performed with a Biomek 2000 robotic workstation.
For the binding assays, C6-hDAT, HEK-hDAT, HEK-
hSERT, or HEK-hNET cells were grown on 150-mm diameter
tissue culture dishes. Medium was poured off the plate, the
plate washed with 10 mL of phosphate-buffered saline (PBS),
and 10 mL of lysis buffer (2 mM HEPES, 1 mM ETDA) added.
After 10 min, cells were scraped from plates, poured into
centrifuge tubes, and centrifuged for 20 min at 30000g.
Supernatant was removed and the pellet was resuspended in
20-32 mL 0.32 M sucrose depending on the density of binding
sites in a given cell line (i.e. a resuspension volume which
results in binding e 10% of the total radioactivity) with a
Polytron at setting 7 for 10 s. Each assay contained 50 µL of
membrane preparation (approximately 15 µg protein), 25 µL
of test drug, and 25 µL of [125I]RTI-55 (40-80 pM final
concentration) in a final volume of 250 µL. Krebs HEPES was
used for all assays. Membranes were preincubated with test
drug for 10 min prior to addition of the [125I]RTI-55. The
mixture was incubated for 90 min at room temperature in the
dark and was terminated by filtration onto GF/C filters using
a Tomtech harvester. Scintillation fluid was added to each
square and radioactivity remaining on the filter was deter-
mined using a Wallac µ- or â-reader. Competition experiments
were conducted with duplicate determinations. Data were
analyzed using GraphPAD Prism with IC50 values converted
to Ki values with the Cheng-Prusoff equation.
For the reuptake assays, C6-hDAT, HEK-hDAT, HEK-
hSERT, or HEK-hNET cells were plated on 150-mm dishes
and grown till confluent. The medium was removed and cells
were washed twice with room-temperature PBS. Following the
addition of 3 mL of PBS, the plates were placed in a 25 °C
water bath for 5 min. The cells were gently scraped and then
triturated with a pipet. Cells from multiple plates were
combined. One plate provided enough cells for 48 wells which
tested two drug curves. The assay was conducted in 96 1-mL
vials and used the Tomtech harvester and betaplate reader.
Krebs HEPES (350 µL) and test drugs (50 µL) were added to
the vials and placed in a 25 °C water bath. Cells (50 µL) were
added, preincubated for 10 min, and [3H]DA, [3H]5HT, or [3H]-
NE (50 µL, 20 nM final concentration) was added. Uptake was
terminated after 10 min by filtration on the Tomtech harvester
using filters presoaked in 0.05% polyethylenimine. Assays
were conducted in triplicate with six test drug concentrations.
Data were analyzed using GraphPAD Prism.
one mouse per activity chamber. ED50 values, doses producing
one-half maximal stimulant activity (maximum - mean
control/10 min), were estimated from a linear regression
against log doses of the ascending portion of the dose-response
curves.
Gen er a liza tion Assa ys. Six male Sprague-Dawley rats
were trained to discriminate cocaine (10 mg/kg) from saline
using a two-lever choice paradigm. Food was available as a
reinforcer under a fixed ratio 10 schedule when responding
occurred on the injection-appropriate lever. All tests were
performed in standard, commercially available chambers
(Coulbourn Instruments) using 45-mg food pellets (Bioserve)
as reinforcers. Training sessions occurred in a double alternat-
ing fashion and tests were conducted between pairs of identical
training sessions (i.e. between either two saline or two cocaine
training sessions). Tests occurred only if, in the two preceding
training sessions, subjects met the criteria of emitting 85% of
responses on the injection-appropriate lever for both the first
reinforcer (first fixed ratio) and the total session. Test sessions
lasted for 20 min or until 20 reinforcers had been obtained.
Intraperitoneal injections of test drug or its vehicle (methyl-
cellulose) were performed 60 min prior to the start of the test
session. A second injection of either saline or cocaine occurred
10 min prior to the start of the test session. The range of doses
of the test compounds was chosen from inactive doses to those
that had biological activity as evidenced by full substitution.
ED50 values were estimated from a linear regression against
log doses.
Ack n ow led gm en t. This work was supported by
National Institute on Drug Abuse Contract N01DA-4-
8313 to M.F. and Contract DA 09045 to C.G. and the
Aaron Diamond Foundation (to E.L.G.). C.G. also ac-
knowledges the support of the Naval Research Labora-
tory. The pharmacological assays were provided by the
National Institute on Drug Abuse as follows: trans-
porter binding and reuptake assays under Contract
N01DA-3-8303; mouse locomotor assays under Con-
tracts N01DA-2-9305 and N01DA-7-8076 and by the
NIDA Intramural Research Program, Psychobiology
Section; and rat discrimination assays under Contracts
N01DA-2-9305 and N01DA-7-8076.
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