Further structure-activity relationship studies on 4-((((3 S,6 S)-6-benzhydryltetrahydro-2 H -pyran-3-yl)amino)methyl)phenol: Identification of compounds with triple uptake inhibitory activity as potential antidepressant agents

Article abstract of DOI:10.1021/jm200020a

To investigate structural alterations of the lead triple uptake inhibitor molecule, disubstituted 4-((((3S,6S)-6-benzhydryltetrahydro-2H-pyran-3-yl)amino) methyl)phenol, we have carried out structure-activity relationship (SAR) studies to investigate the

Full text of DOI:10.1021/jm200020a

ARTICLE
pubs.acs.org/jmc
Further StructureÀActivity Relationship Studies on 4-((((3S,6S)-
6-Benzhydryltetrahydro-2H-pyran-3-yl)amino)methyl)phenol:
Identification of Compounds with Triple Uptake Inhibitory Activity as
Potential Antidepressant Agents
Bhaskar Gopishetty,† Stuart Hazeldine,† Soumava Santra,† Mark Johnson,† Gyan Modi,† Solav Ali,‡
Juan Zhen,‡ Maarten Reith,‡,§ and Aloke Dutta*,†
†Department of Pharmaceutical Sciences, Wayne State University, Detroit, Michigan 48202, United States
‡Department of Psychiatry and §Department of Pharmacology, New York University, New York, New York 10016, United States
S Supporting Information
b
ABSTRACT: To investigate structural alterations of the lead
triple uptake inhibitor molecule, disubstituted 4-((((3S,6S)-6-
benzhydryltetrahydro-2H-pyran-3-yl)amino)methyl)phenol, we
have carried out structureÀactivity relationship (SAR) studies to
investigate the effect of alteration of aromatic substitutions and
introduction of heterocyclic aromatic moieties on this molecular template. The novel compounds were tested for their affinities for
the dopamine transporter (DAT), serotonin transporter (SERT), and norepinephrine transporter (NET) in the brain by measuring
their potency in inhibiting the uptake of [3H]DA, [3H]5-HT, and [3H]NE, respectively. SAR results indicate dopamine
norepinephrine reuptake inhibitory (DNRI) type activity in thiophene (10g) and pyrrole (10i) derivatives. On the other hand,
3-hydroxyphenyl derivative 10f and 4-methoxyphenyl derivative 10j exhibited a triple reuptake inhibitory (TUI) activity profile, as
these molecules exhibited potent uptake inhibition for all the monoamine transporters (Ki of 31.3, 40, 38.5 and Ki of 15.9, 12.9, 29.3
for DAT, SERT, and NET for 10f and 10g, respectively). Compound 10f was further evaluated in the rat forced swim test to evaluate
its potential antidepressant effect. The results show significant reduction of immobility by TUI 10f at 10 mg/kg dose, indicating
potential antidepressant activity.
’ INTRODUCTION
reuptake inhibitors (SSRIs).12,13 Recently, TUIs have been shown
to be potent antidepressants in animal models and therefore are
being advanced as novel treatment tools offering certain
advantages.14À16 Because of their interaction at three mono-
amine transporters, this class of drug could potentially provide
faster onset of action. The enhanced efficacy of a TUI as an
antidepressant may be due to the additional dopaminergic
component, which can effectively relieve depression by activating
mesocorticolimbic dopaminergic pathways, reducing anhedonia
associated with a deficit in dopaminergic transmission.
Depression, especially major depression disorder, significantly
affects a high percentage of the population (15À20%) and is
regarded as a significant health problem. Unipolar depression is
ranked as number 1 before all other somatic and psychiatric
illnesses.1,2 It is believed that at least 20% of all individuals suffer
from a depressive episode at least once in their lifetime. Depres-
sion is potentially fatal, since most sufferers consider life threa-
tening acts and suicide.3,4
Selective monoamine uptake inhibitors have been used in the
treatment of depression.5 Among those, especially serotonin
(5-HT) and norepinephrine (NE) transporter blockers have
been used in the therapy for depression.6,7 However, in spite of
developments of different arrays of antidepressants, there still
remains a significant unmet need for more improved therapy, as a
large number of depressed people are still refractory to the
current existing therapies.8 Also, a significant number of people
relapse after treatment with current therapies.9 Although current
pharmacotherapies of depression do not address the dopami-
nergic component, there is ample clinical and biochemical
evidence pointing toward a strong dopaminergic component in
depression.10,11 It is hypothesized that a triple uptake inhibitor
(TUI) interacting with all three monoamine transporters would
display reduced side effects associated with selective serotonin
In recent years a number of TUIs, e.g., DOV 21,947 and
PRC200-SS, have been developed and have been characterized in
animal antidepressant models.17,18 Some of these molecules are
shown in Figure 1. In our previous studies on monoamine
transporters, we developed a unique pyran template as a bioi-
sosteric extension of piperidine derivatives, which we originally
synthesized for targeting the dopamine transporter (DAT).19À27
Initially, we identified unique asymmetric di- and trisubstituted
pyran derivatives inhibiting uptake of all three monoamine
transporters with higher potency for the 5-HT transporter
(SERT) and NE transporter (NET) and modest potency for
Received: January 9, 2011
Published: March 29, 2011
r
2011 American Chemical Society
2924
dx.doi.org/10.1021/jm200020a J. Med. Chem. 2011, 54, 2924–2932
|

Journal of Medicinal Chemistry
ARTICLE
the dopamine transporter (DAT). Dual acting inhibitors as
blockers of both SERT and NET as well as selective blockers
for NET were also identified. Asymmetric synthesis methods
have been developed by us to generate these molecules.26,27 The
results indicated stereospecific requirement for interaction of
these molecules with the monoamine transporters, as the inter-
action was mainly exhibited in the (À)-isomers. One of our lead
TUIs, 1c (D-161) (Figure 2), was recently shown to possess
antidepressant-like activity in animal studies.28
In our current work, we extended our SAR studies further with
asymmetric disubstituted pyran derivatives to understand the
effect of different aromatic substitutions on affinity and selectivity
for different monoamine transporters.
’ CHEMISTRY
Scheme 1 describes the synthesis of the key amine intermedi-
ate 8, which was used toward the synthesis of target compounds
as shown in Schemes 2 and 3. Briefly, regioselective ring-opening
of the (R)-epoxide 1 with allylmagnesium chloride in the
presence of a catalytic amount of copper(I) iodide afforded
alcohol 2 in good yield. Trans-vinylation of alcohol 2 with ethyl
vinyl ether in the presence of mercury(II) trifluoroacetate at
room temperature provided compound 3, which was immedi-
ately converted to cyclic olefin 4 by ring-closing metathesis.
Hydroboration of olefin 4 with 9-BBN in THF followed by
oxidation gave an inseparable mixture containing mostly trans-
isomer 5a. The mixture of compounds 5a and 5b was mesylated
with methanesulfonyl chloride in dichloromethane in the pre-
sence of triethylamine and separated by column chromatography
to give the trans-compound 6a in 74.7% yield and cis-compound
6b in 12.4% yield (trans/cis = 6:1). Compound 6a was then
treated with sodium azide in DMF to give azide 7, which was
finally hydrogenated with Pd/C in methanol to obtain the
optically active cis-amine intermediate 8 in quantitative yield.
Figure 1. Molecular structures of known clinical and preclinical
antidepressants.
Figure 2. Molecular structures of lead asymmetric pyran TUIs.
Scheme 1a
a Reagents and conditions: (a) allylmagnesium chloride, ether, À78 °C to room temp, overnight, 82.4%; (b) ethylvinyl ether, Hg(OCOCF3)2, room
temp, 4 h, 63.4%; (c) first generation Grubb's catalyst, benzene, reflux, 2 h, 67.6%; (d) (i) 9-BBN, THF, room temp, overnight; (ii) 10% NaOH, 30%
H2O2, 50 °C, 1 h, 90%; (e) CH3SO2Cl, Et3N, dichloromethane, room temp, 2 h, 74.7% for 6a, 12.4% for 6b; (f) NaN3, DMF, 80 °C, overnight, 81.1%;
(g) H2, PdÀC, MeOH, 50 psi, 2 h, quantitative yield.
2925
dx.doi.org/10.1021/jm200020a |J. Med. Chem. 2011, 54, 2924–2932

Journal of Medicinal Chemistry
ARTICLE
Scheme 2a
a Reagents and conditions: (a) epoxide, EtOH, reflux, overnight.
Scheme 3a
Scheme 2 describes epoxide ring-opening from 3,6-disubsti-
tuted amine precursor 8. The rationale behind designing these
compounds stems from the observation that in the GBR class of
compounds such side chain extension via opening of epoxide led
to development of potent molecules for DAT and SERT.29
Regioselective ring-opening of different substituted (R)-styrene
epoxides by the amine precursor 8 produced (R)-hydroxy
compounds 9a, 9c, and 9e. On the other hand, regioselective
ring-opening of similar (S)-epoxides by the same amine pre-
cursor yielded (S)-hydroxy compounds 9b, 9d, and 9f. None of
the (R)-hydroxy compounds exhibited potent activity except
4-fluorophenyl substituted compound 9c which displayed mod-
erate potency at DAT (Ki = 71 nM). Similarly, corresponding
diastereomers (S)-hydroxy compounds 9d and 9f did not exhibit
much potent activity except 9b which exhibited moderate
potency at DAT (Ki = 54 nM).
In our next series, we planned to systematically explore the
influence of heterocyclic and substituted aromatic moieties in the
disubstituted pyran template. Since the initial development of
pyran derivatives, influences of N-heterocyclic substitutions have
not been explored. In the starting pyridine series, 2- (10a),
3- (10b), and 4-substituted (10c) pyridines were designed and
synthesized. Interestingly, the 4-pyridine substituted compound
10c exhibited selective interaction with DAT (Ki of 28.3, 889, and
462 for DAT, SERT, and NET, respectively (Tables 1 and 2))
whereas the other two pyridine compounds were weak at all
three transporters. This indicates the importance of the position
of the N-atom in the pyridine ring in interacting with the
monoamine transporters. In our next exploration of heterocyclic
aromatic moieties, thiophene derivative 10g, furan derivative
10h, and pyrrole derivative 10i were designed and synthesized.
Thiophene derivative 10g and pyrrole derivative 10i exhibited
interesting dual DAT/NET potency (Ki (DAT and NET) of 41.4
and 47.2 nM for 10g and 43.2 and 39.6 nM for 10i), whereas
furan derivative 10h exhibited 2-fold selective potency for NET
(Ki of 59.8 nM for NET vs Ki of 110 and 115 nM for DAT and
SERT, respectively (Tables 1 and 2).
a Reagents and conditions: (a) RCHO, NaCNBH3, AcOH, 1,2-di-
chloroethane, room temp, overnight.
Scheme 2 outlines the synthesis of the final compounds 9aÀf
by treating amine 8 with corresponding optically active (R)- and
(S)-epoxides.
Similarly, reductive amination of amine 8 with various alde-
hydes furnished target compounds 10aÀj as shown in Scheme 3.
’ RESULTS AND DISCUSSION
We have successfully developed an improved version of the
synthesis of asymmetric disubstituted pyran derivative precursor
as described in Scheme 1. This involved fewer synthetic steps to
make 3,6-disubstituted compounds compared to our previous
published report.27
In our previous SAR studies, we have shown that substitutions
on the N-benzylic aromatic ring had a significant influence on the
profile of monoamine uptake inhibition. One of the interesting
findings from those studies was that the presence of H-bond
forming functionality in the aromatic ring conferred higher
potency for the NET. Compounds 1d (D-185), 1b (D-168),
and 1c (Figure 2) with amino and hydroxyl groups at the para
position exhibited a TUI profile with potent activity at the
NET.27 In the current SAR studies, we wanted to further explore
3,6-disubstituted compounds by introducing various aromatic
substitutions and side chain expansion on the exocyclic N-atom.
In our next series of molecules, we focused on phenyl sub-
stituted compounds. In our exploration to evaluate the effect of
enhanced hydrophobicity on N-aromatic substitution, we re-
placed the phenyl moiety by a naphthalene ring to produce 10d.
However, such replacement only produced moderate potency
for SERT (Ki = 88.8 nM). Next we wanted to explore the
positional effect of the hydroxyl group on the aromatic ring in 1c,
2926
dx.doi.org/10.1021/jm200020a |J. Med. Chem. 2011, 54, 2924–2932

Journal of Medicinal Chemistry
ARTICLE
Table 1. Affinity of Drugs at DAT, SERT, and NET in Rat Brain
Ki, nM
DAT uptake, SERT uptake, [3H]- NET uptake,
compd
[3H]DAa
5-HTa
[3H]NEa
GBR 12909
16.2 ( 1.6
NDb
198 ( 19
503 ( 61
12.2 ( 2.4
14.7 ( 2.1
25.0 ( 8.4
29.1 ( 3.5
936 ( 68
796 ( 94
1,140 ( 208
825 ( 169
1,092 ( 161
646 ( 118
483 ( 63
152 ( 11
889 ( 61
88.8 ( 21.7
440 ( 96
40.1 ( 4.9
186 ( 43
115 ( 5
48.5 ( 7.4
0.826 ( 0.25
120 ( 41
29.3 ( 7.9
25.5 ( 9.6
30.5 ( 7.8
162 ( 34.6
298 ( 45
546 ( 97
222 ( 62
429 ( 245
299 ( 34
505 ( 220
353 ( 60
462 ( 86
232 ( 54
160 ( 38
38.5 ( 6.0
47.2 ( 15.4
59.8 ( 0.6
39.6 ( 3.5
29.3 ( 4.8
reboxetine
fluoxetine
1a
1092 ( 98
37.4 ( 3.9
85.2 ( 8.2
42.0 ( 3.3
145 ( 16
54.0 ( 8.5
71.8 ( 13.6
106 ( 28
125 ( 31
137 ( 9
1b
1c
Figure 3. Effect of subchronic administration of vehicle (10% β-
hydroxypropylcyclodextrin solution), 10f, and imipramine on the dura-
tion of immobility in the forced swimming test in rats. One-way ANOVA
analysis demonstrated significant effect among treatments: F(4,95) =
13.70 (P < 0.008). Dunnett’s analysis showed that the effect of 10f at 10
mg/kg dose on immobility was statistically significantly different com-
pared to vehicle (P < 0.01). The effect of imipramine (15 mg/kg) on
immobility was also statistically significantly different (P < 0.05) from
vehicle. Asterisks indicate a statistically significant difference toward
control group that received saline ip: (//) P < 0.05 or 0.01. Each
treatment group contained six to seven rats.
9a
9b
9c
9d
9e
9f
10a
10b
10c
10d
10e
10f
209 ( 20
145 ( 51
28.3 ( 11.6
473 ( 134
200 ( 28
31.3 ( 10.6
41.4 ( 8.9
110 ( 23
43.2 ( 1.8
15.9 ( 1.7
respectively) exhibited a TUI-like profile very similar to 1c,
whereas 2-hydroxyl substituted 10e was much less potent at
the three transporters. The low activity of 10e might be due to
the location of the hydroxyl group at the 2-position, giving rise to
an unfavorable steric interaction. Next we wanted to evaluate 10j,
which is a methoxylated derivative of 1c. The uptake inhibition
results indicate higher potencies for DAT and SERT compared
to 1c in the methoxylated derivative (Ki of 15.9 and 12.9 vs 42
and 29 nM for DAT and SERT, respectively, for 10j).
10g
10h
10i
141 ( 2
10j
12.9 ( 1.3
a For uptake by DAT, SERT, and NET, [3H]DA, [3H]-5-HT, and
[3H]NE accumulation was measured. Results are average ( SEM of
three to eight independent experiments assayed in triplicate. b Not done.
Finally, we subjected one of our lead TUIs, 10f, to the forced
swim test (FST) in rats to measure its potential antidepressant
effect. Extended CNS receptor screening of this compound at 10
μM indicated less than 50% inhibition with the majority of the
receptor target sites and greater than 50% inhibition at a few
other target sites (only marginally so in some cases; see Support-
ing Information for the data). The forced swim test has been used
widely as a preclinical model for screening drugs for antidepres-
sant activity and has been applied to characterize a broad spec-
trum of antidepressants.30,31 This assay, with some limitations, is
considered a very good predictor of antidepressant activity of a
test compound. On the basis of our previous experience, we
chose 10 mg/kg as a moderately high dose to study the effect of
this compound on immobility. It is evident from the results
(Figure 3) that compound 10f at 10 mg/kg exhibited significant
reduction of immobility compared to vehicle, as did the reference
drug imipramine at 15 mg/kg dose. Thus, the results suggest that
compound 10f may have antidepressant activity.
Table 2. Selectivity of Drugs (Ratio of Ki) in Inhibiting
Uptake by Monoamine Transporters
DAT uptake/SERT DAT uptake/NET SERT uptake/NET
compd
uptakea
uptakea
uptakea
9a
0.15
0.07
0.06
0.13
0.11
0.21
0.43
0.95
0.03
5.33
0.45
0.78
0.22
0.96
0.31
1.23
0.9
5.78
2.67
2.09
3.72
2.55
2.16
0.96
0.43
1.92
0.38
2.75
1.04
3.94
1.92
3.56
0.44
9b
0.18
0.13
0.48
0.29
0.46
0.41
0.41
0.06
2.04
1.25
0.81
0.88
1.84
1.09
0.54
9c
9d
9e
9f
10a
10b
10c
10d
10e
10f
10g
10h
10i
10j
’ CONCLUSION
We have carried out further SAR studies with disubstituted
pyran derivatives. Introduction of exocyclic hydroxyl groups on
the N-alkylphenyl moiety did not produce any further improve-
ment of activity. Replacement of the phenyl ring in compound 1c
by the heterocyclic 4-pyridine moiety produced potent activity
for the DAT in compound 10c. Further replacement by five-
membered heterocycles, e.g., furan, thiophene, and pyrole, pro-
duced interesting dopamine norepinephrine reuptake inhibitor
(DNRI) type activity in 10g and 10i. Furthermore, compounds
a Ratio of Ki values.
through compounds 10e and 10f. The 3-hydroxyl substituted
compound 10f (Ki of 31. 40 and 38 for DAT, SERT, and NET,
2927
dx.doi.org/10.1021/jm200020a |J. Med. Chem. 2011, 54, 2924–2932

Journal of Medicinal Chemistry
ARTICLE
10f and 10j exhibited triple uptake inhibitory activity. Finally, in
the rat FST experiment, compound 10f exhibited high efficacy in
reducing immobility, indicating a potential antidepressant effect.
In this regard, 10f was more efficacious than imipramine which
might indicate higher efficacy of TUI in this animal model. In the
near future we plan to examine this molecule further for its potential
antidepressant property.
88.20, 115.45, 126.72, 126.84, 128.56, 128.81, 128.85, 129.24, 138.22,
141.62, 142.28, 152.23.
(S)-2-Benzhydryl-3,4-dihydro-2H-pyran (4). To a stirred so-
lution of compound 3 (1.65 g, 5.93 mmol) in anhydrous benzene
(80 mL) was added Grubb’s (first generation) catalyst (0.24 g, 0.3
mmol) at room temperature under nitrogen atmosphere. The reaction
mixture was slowly heated to reflux, and the refluxing was continued for
2 h. After the mixture was cooled to room temperature, the solvent was
removed under reduced pressure. The crude residue was purified by
column chromatography using 5% ethyl acetate in hexanes and recrys-
tallized in hexanes to give compound 4 (1 g, 68%) as a white solid. Mp:
68À70 °C. 1H NMR (400 MHz, CDCl3): δ 1.52À1.62 (m, 1H),
1.72À1.82 (m, 1H), 1.92À2.10 (m, 2H), 4.05 (d, J = 8.8 Hz, 1H), 4.57
(dt, J = 2.4, 9.2 Hz, 1H), 4.67À4.72 (m, 1H), 6.35 (d, J = 6.0 Hz, 1H),
7.16À7.42 (m, 10H). 13C NMR (100 MHz, CDCl3): δ 20.01, 26.49,
56.46, 76.64, 100.86, 126.66, 126.85, 128.60, 128.70, 128.88, 142.12,
142.42, 144.06.
6-Benzhydryltetrahydro-2H-pyran-3-ol (Mixture of 5a and
5b). To a stirred solution of compound 4(2.8 g, 11.18 mmol) in anhydrous
THF (10 mL) was added 9-BBN (56 mL, 0.5 M solution in tetrahydrofur-
an, 27.96 mmol) under a nitrogen atmosphere. After being stirred overnight
at room temperature, the reaction mixture was cooled to 0 °C, quenched by
the addition of ethanol (15 mL), and stirred for 10 min. Next, aqueous 10%
NaOH solution (15 mL) and 30% H2O2 (10 mL) were added, and the
resulting solution was heated to 50 °C for 1 h. After cooling to room
temperature, the reaction mixture was treated with water (40 mL) and
extracted with ethyl acetate (3 Â 75 mL). The combined organic layers
were washed with water (40 mL), brine (40 mL) and dried over Na2SO4,
and the solvent was removed under reduced pressure. The crude residue
was purified by column chromatography using 25% ethyl acetate in hexanes
to give mixture of inseparable compounds 5a and 5b (2.7 g, 90%) as a thick
syrup. 1H NMR (400 MHz, CDCl3): δ 1.34À1.45 (m, 3H), 1.53À1.61
(m, 1H), 2.01À2.09 (m, 1H), 3.14 (t, J = 10.0 Hz, 1H), 3.62À3.70
(m, 1H), 3.91 (d, J = 9.2 Hz, 1H), 3.95À4.04 (m, 2H), 7.16À7.37
(m, 10H). 13C NMR (100 MHz, CDCl3): δ 29.68, 33.01, 57.55, 66.24,
73.18, 79.09, 126.68, 126.92, 128.73, 128.78, 128.81, 128.86, 128.99, 142.57,
142.64, 142.96.
’ EXPERIMENTAL SECTION
Reagents and solvents were obtained from commercial suppliers and
used as received unless otherwise indicated. Dry solvents were obtained
according to the standard procedures. All reactions were performed
under inert atmosphere (N2) unless otherwise noted. Analytical silica gel
coated TLC plates (Si 254F) were purchased from Baker Inc. and were
visualized with UV light or by treatment with phosphomolybdic acid
(PMA). Flash chromatography was carried out on Baker silica gel (40 μm).
1H NMR and 13C spectra were routinely recorded with a Varian 400
spectrometer operating at 400 and 100 MHz, respectively. The NMR
solvent used was CDCl3 as indicated. TMS was used as an internal
standard. NMR and rotation of free bases were recorded. Salts of free
bases were used for biological characterization. Elemental analyses were
performed by Atlantic Microlab Inc., and results were within (0.4% of
the theoretical value.
[Ring 2,5,6-3H]dopamine (38.7 Ci/mmol), [1,2-3H]serotonin (28.0
Ci/mmol), and levo-[ring-2,5,6-3H]norepinephrine (44.6 Ci/mmol)
were obtained from Perkin-Elmer (Boston, MA, U.S.). Imipramine,
fluoxetine, reboxetine, and GBR 12909 dihydrochloride (1-[2-[bis(4-
fluorophenyl)methoxy]ethyl]-4-[3-phenylpropyl]piperazine) were pur-
chased from Sigma-Aldrich (St. Louis, MO, U.S.).
(S)-1,1-Diphenylhex-5-en-2-ol (2). To a stirred solution of (R)-
2-benzhydryloxirane26 (4.5 g, 21.40 mmol) in anhydrous diethyl ether
(90 mL) was added copper(I) iodide (0.41 g, 2.14 mmol) and
allylmagnesium chloride (13.37 mL, 2 M solution in tetrahydrofuran,
26.75 mmol) at À78 °C. After being stirred overnight at room tem-
perature under nitrogen atmosphere, the reaction mixture at 0 °C was
quenched by addition of saturated NH4Cl solution (50 mL) and
extracted with ethyl acetate (3 Â 75 mL). The combined organic layers
were washed with water (50 mL), brine (50 mL) and dried over Na2SO4,
and solvent was removed under reduced pressure. The crude residue was
purified by silica gel column chromatography using 10% ethyl acetate in
hexanes to give compound 2 (4.45 g, 82%) as a thick colorless syrup. 1H
NMR (400 MHz, CDCl3): δ 1.44À1.64 (m, 3H), 2.12À2.21 (m, 1H),
2.25À2.34 (m, 1H), 3.89 (d, J = 8.4 Hz, 1H), 4.34À4.40 (m, 1H),
4.93À5.04 (m, 2H), 5.72À5.83 (m, 1H), 7.18À7.42 (m, 10H). 13C
NMR (100 MHz, CDCl3): δ 30.41, 34.42, 59.14, 73.40, 115.13, 126.82,
127.14, 128.50, 128.92, 129.05, 129.09, 138.72, 141.69, 142.60.
(S)-(2-(Vinyloxy)hex-5-ene-1,1-diyl)dibenzene (3). To a stir-
red solution of alcohol 2 (2.6 g, 10.30 mmol) in excess of ethyl vinyl
ether (100 mL) was added mercury(II) trifluoroacetate (0.88 g, 2.06
mmol) at room temperature, and stirring was continued for 4 h under a
nitrogen atmosphere. The solvent was removed under reduced pressure
at room temperature. The crude product was dissolved in 5% ethyl
acetate in hexanes and filtered through a basic alumina pad quickly, and
the filtrate was concentrated under reduced pressure at room tempera-
ture to give product 3 (1.82 g, 63%) as a thick light-yellow syrup. The
unreacted starting material 2 (0.65 g, 25%) was also recovered by
washing the used basic alumina pad with 15% ethyl acetate in hexanes.
1H NMR (400 MHz, CDCl3): δ 1.55À1.72 (m, 2H), 2.05À2.22
(m, 2H), 3.83 (dd, J = 1.6, 6.4 Hz, 1H), 4.10 (d, J = 7.6 Hz, 1H), 4.20
(dd, J = 1.6, 14.0 Hz, 1H), 4.45 (dt, J = 4.0, 7.6 Hz, 1H), 4.80À5.06
(m, 2H), 5.68À5.78 (m, 1H), 6.12 (dd, J = 6.4, 14.0 HZ, 1H), 7.16À7.36
(m, 10H). 13C NMR (100 MHz, CDCl3): δ 29.70, 32.57, 56.21, 82.10,
(3R,6S)-6-Benzhydryltetrahydro-2H-pyran-3-yl Methane-
sulfonate (6a). To an ice-cooled stirred mixture of compounds 5a and
5b (2.7 g, 10.06 mmol) and triethylamine (2.8 mL, 20.12 mmol) in
anhydrous dichloromethane (60 mL) was added methanesulfonyl
chloride (1.17 mL, 15.09 mmol) under a nitrogen atmosphere. After
being stirred for 2 h at room temperature, the reaction mixture was
extracted with ethyl acetate (3 Â 75 mL) and water (40 mL). The
combined organic layers were washed with water (40 mL), brine
(40 mL) and dried over Na2SO4, and the solvent was removed under
reduced pressure. The residue was purified by column chromatography
using 25% ethyl acetate in hexanes to elute the trans compound 6a
(2.6 g, 75%) first as a white solid followed by cis compound 6b (0.43 g,
12%) as a white solid. Spectral data for 6a. Mp: 110À112 °C. [R]25
D
(À)48.4° (c 0.5, MeOH). 1H NMR (400 MHz, CDCl3): δ 1.42À1.52
(m, 1H, H-5ax), 1.62À1.78 (m, 2H, H-4ax, H-5eq), 2.21À2.30 (m, 1H,
H-4eq), 2.99 (s, 3H, CH3), 3.37 (t, J = 10.4 Hz, 1H, H-2ax), 3.89 (d, J =
8.8 Hz, 1H, Ph2CH), 4.02 (dt, J = 2.0, 9.2 Hz, 1H, H-6ax), 4.10À4.18
(m, 1H, H-2eq), 4.58À4.66 (m, 1H, H-3ax), 7.14À7.32 (m, 10H,
aromatic). 13C NMR (100 MHz, CDCl3): δ 29.51, 30.58, 38.68, 57.12,
69.87, 75.27, 79.04, 126.73, 126.96, 128.59, 128.65, 128.68, 128.93,
141.97, 142.34.
(2S,5S)-5-Azido-2-benzhydryltetrahydro-2H-pyran (7). To
a stirred solution of compound 6a (2.5 g, 7.22 mmol) in DMF (60 mL)
was added sodium azide (2.35 g, 36.08 mmol). After being stirred
overnight at 80 °C, the reaction mixture was cooled to room tempera-
ture, treated with water (40 mL), and extracted with ethyl ether (3 Â
75 mL). The combined organic layers ware washed with water (40 mL),
2928
dx.doi.org/10.1021/jm200020a |J. Med. Chem. 2011, 54, 2924–2932

Journal of Medicinal Chemistry
ARTICLE
brine (40 mL) and dried over Na2SO4, and the solvent was removed
under reduced pressure. The crude residue was purified by column
chromatography using 5% ethyl acetate in hexanes to give compound 7
71.2, 79.3, 114.9, 115.2, 126.2, 126.4, 127.3, 127.4, 128.3, 128.4, 138.1,
141.9, 142.0, 160.9, 163.3. [R]25D (À)54.6° (c 1, MeOH). The product
was converted into the corresponding hydrochloride salt. Mp: 260À265 °C.
1
(1.72 g, 81%) as a white solid. Mp: 93À95 °C. H NMR (400 MHz,
Anal. (C26H28NO2F HCl) C, H, N.
3
CDCl3): δ 1.32À1.38 (m, 1H), 1.59À1.70 (m, 1H), 1.73À1.82 (m,
1H), 1.94À2.20 (m, 1H), 3.52À3.57(m, 1H), 3.63 (dd, J = 1.6, 12.0 Hz,
1H), 3.95À4.10 (m, 3H), 7.16À7.38 (m, 10H). 13C NMR (100 MHz,
CDCl3): δ 25.43, 27.68, 55.58, 57.55, 69.80, 79.45, 126.56, 126.81,
128.57, 128.64, 128.73, 128.84, 142.23.
(S)-2-(((3S,6S)-6-Benzhydryltetrahydro-2H-pyran-3-yl)amino)-
1-(4-fluorophenyl)ethanol (9d). Amine 8 (60 mg, 0.22 mmol) was
treated with (S)-2-(4-fluorophenyl)oxirane (35 mg, 0.25 mmol) in anhydrous
ethanol (3 mL) using procedure A. The residue was purified by silica gel
column chromatography using 3% methanol in ethyl acetate as the eluent to
afford compound 9d (48 mg, 56%) as a thick syrup. 1H NMR (400 MHz,
CDCl3): δ 1.17À1.38 (m, 2H), 1.56À1.76 (m, 1H), 1.96À2.08 (m, 1H),
2.75 (t from dd, J = 10.0 Hz, 1H), 2.88 (br s, 1H), 3.10 (dd, J = 2.3, 12.0 Hz,
1H), 3.44 (d, J = 12.3 Hz, 1H), 4.02À4.12 (m, 3H), 4.95 (d, J = 9.1 Hz, 1H),
5.63 (br s, 1H), 6.93À7.04 (m, 2H), 7.13À7.40 (m, 12H). 13C NMR (100
MHz, CDCl3):δ24.4, 25.4, 52.0, 54.1, 56.8, 69.2, 69.5, 69.6, 79.3, 115.1, 115.3,
126.2, 126.5, 127.3, 127.4, 128.2, 128.3, 128.4, 128.5, 136.9, 137.0, 141.8, 141.9,
(3S,6S)-6-Benzhydryltetrahydro-2H-pyran-3-amine (8). Azide
7 (0.65 g, 2.21 mmol) in methanol (40 mL) was hydrogenated (50 psi)
in the presence of 10% PdÀC (65 mg, 10 wt %) for 2 h. The reaction
mixture was filtered through a short bed of Celite, and the solvent was
removed under reduced pressure to afford amine 8 (0.65 g) as a light
yellow solid in quantitative yield. The product was pure enough for
continuation to the next step. Mp: 92À94 °C. [R]25D (À)76.8° (c 1.0,
MeOH). 1H NMR (400 MHz, CDCl3): δ 1.24À1.44 (m, 3H),
1.52À1.62 (m, 1H), 1.63À1.80 (m, 2H), 2.89 (br s, 1H), 3.62À3.66
(m, 1H), 3.74À3.80 (m, 1H), 3.96 (d, J = 8.8 Hz, 1H), 4.04 (dt, J = 2.4,
8.8 Hz, 1H), 7.12À7.37 (m, 10H). 13C NMR (100 MHz, CDCl3): δ
24.86, 31.06, 45.55, 57.58, 73.92, 79.60, 126.50, 126.69, 128.56, 128.72,
128.76, 142.40, 142.65.
160.9, 163.4. [R]25 (À)34.6° (c 1, MeOH). The product was convert-
D
ed into the corresponding hydrochloride salt. Mp: 248À256 °C. Anal.
(C26H28NO2F HCl 0.4H2O) C, H, N.
3
3
(R)-2-(((3S,6S)-6-Benzhydryltetrahydro-2H-pyran-3-yl)amino)-
1-(3-methoxyphenyl) ethanol (9e). Amine 8 (60 mg, 0.22 mmol) was
treated with (R)-2-(3-methoxyphenyl)oxirane (38 mg, 0.25 mmol) in anhy-
drous ethanol (3 mL) using procedure A. The residue was purified by silica gel
column chromatography using 3% methanol in ethyl acetate as the eluent to
afford compound 9e (55 mg, 59%) as a thick syrup. 1H NMR (400 MHz,
CDCl3): δ 0.76À0.89 (m, 1H), 1.10À1.50 (m, 3H), 1.56À1.74 (m, 1H),
1.80À1.98(m, 1H), 2.63À2.73 (m, 2H), 2.82 (dd, J= 3.5, 12.0 Hz, 1H), 3.41
(br s, 2H), 3.56 (dd, J = 1.5, 12.0 Hz, 1H), 3.74 (s, 3H), 3.82À3.96 (m, 2H),
3.96À4.07 (m, 1H), 4.69 (dd, J = 3.5, 9.1 Hz, 1H), 6.73À6.80 (m, 1H),
6.84À6.91 (m, 2H), 7.07À7.32 (m, 11H). 13C NMR (100 MHz, CDCl3): δ
24.7, 26.9, 51.3, 53.9, 55.1, 57.1, 68.9, 71.2, 79.3, 111.0, 113.2, 118.0, 126.2,
126.4, 128.2, 128.4, 129.3, 141.8, 143.6, 159.6. [R]25D (À)69.5° (c1, MeOH).
The product was converted into the corresponding hydrochloride salt. Mp:
140À150 °C. Anal. (C27H31NO3 HCl 0.2H2O) C, H, N.
Procedure A. (R)-2-((3S,6S)-6-Benzhydryltetrahydro-2H-
pyran-3-ylamino)-1-phenylethanol (9a). A mixture of amine 8
(50 mg, 0.19 mmol) and (R)-2-phenyloxirane (27 mg, 0.22 mmol) in
anhydrous ethanol (3 mL) was refluxed under nitrogen atmosphere
overnight. The solvent was removed under reduced pressure and the
crude residue was purified by column chromatography using 3%
methanol in ethyl acetate to afford compound 9a (40 mg, 56%) as a
thick syrup. 1H NMR (400 MHz, CDCl3): δ 1.28À1.34 (m, 1H),
1.45À1.55 (m, 1H), 1.67 (tt, J = 4.0, 13.6 Hz, 1H), 1.82À1.92 (m, 1H),
2.57 (dd, J = 9.6, 12.4 Hz, 1H), 2.65 (br s, 1H), 2.91 (dd, J = 3.6, 12.4 Hz,
1H), 3.58 (dd, J = 1.2, 11.6 Hz, 1H), 3.90À3.98 (m, 2H), 4.05 (dt, J =
2.0, 10.4 Hz, 1H), 4.63 (dd, J = 3.6, 9.6 Hz, 1H), 7.12À7.40 (m, 15H).
13C NMR (100 MHz, CDCl3): δ 24.63, 26.64, 51.16, 53.74, 57.12,
68.84, 71.83, 79.11, 125.66, 125.97, 126.28, 127.49, 128.02, 128.14,
3
3
(S)-2-(((3S,6S)-6-Benzhydryltetrahydro-2H-pyran-3-yl)amino)-
1-(3-methoxyphenyl)ethanol(9f). Compound 8 (0.18 g, 0.67 mmol)
was treated with (S)-2-(3-methoxyphenyl)oxirane (0.1 g, 0.67 mmol) in
anhydrous ethanol (10 mL) using procedure A. The residue was purified
by column chromatography using 5% methanol in ethyl acetate to afford
128.20, 128.29, 141.91, 142.00, 142.28. [R]25 (À)100.6° (c 0.5,
D
MeOH). The product was converted into the corresponding hydro-
chloride salt. Mp: 275À277 °C. Anal. (C26H29NO2 HCl) C, H, N.
3
1
compound 9f (0.16 g, 57%) as a thick syrup. H NMR (400 MHz,
(S)-2-((3S,6S)-6-Benzhydryltetrahydro-2H-pyran-3-ylamino)-
1-phenylethanol (9b). Amine 8 (0.1 g, 0.37 mmmol) was treated with
(S)-2-phenyloxirane (45 mg, 0.37 mmol) in anhydrous ethanol (5 mL)
using procedure A. The residue was purified by column chromatography
using 4% methanol in ethyl acetate to afford compound 9b (90 mg, 62%)
as a thick syrup. 1H NMR (400 MHz, CDCl3): δ 1.26À1.34 (m, 1H),
1.48À1.59(m, 1H), 1.67(tt, J= 4.0, 13.6 Hz, 1H), 1.92À1.99 (m, 1H), 2.65
(dd, J = 9.2, 12.0 Hz, 1H), 2.74 (br s, 1H), 3.05 (dd, J = 3.2, 12.0 Hz, 1H),
3.48À3.52 (m, 1H), 3.96À4.06 (m, 4H), 4.78 (dd, J = 2.8, 9.2 Hz, 1H),
7.12À7.38 (m, 15H). 13C NMR (100 MHz, CDCl3): δ 24.82, 26.47,
51.53, 54.37, 57.12, 70.12, 70.99, 79.30, 125.72, 126.23, 126.50, 127.51,
CDCl3): δ 1.24À1.34 (m, 2H), 1.42À1.56 (m, 1H), 1.65 (tt, J = 4.0,
13.2 Hz, 1H), 1.90À1.98 (m, 1H), 2.62 (dd, J = 9.6, 12.4 Hz, 1H), 2.71
(br s, 1H), 3.03 (dd, J = 3.2, 12.4 Hz, 1H), 3.48À3.54 (m, 1H), 3.80 (s,
3H), 3.94À4.08 (m, 3H), 4.72 (dd, J = 2.8, 9.2 Hz, 1H), 6.81 (dd, J = 2.4,
8.0 Hz, 1H), 6.90À6.96 (m, 2H), 7.12À7.34 (m, 11H). 13C NMR (100
MHz, CDCl3): δ 25.15, 26.92, 51.68, 54.60, 55.50, 57.46, 70.56, 71.37,
79.58, 111.25, 113.47, 118.29, 126.51, 126.77, 128.56, 128.66, 128.72,
128.81, 129.65, 142.32, 142.39, 144.14, 159.99. [R]25D (À)53.2° (c 0.5,
MeOH). The product was converted into the corresponding hydro-
chloride salt. Mp: 210À212 °C. Anal. (C27H31NO3 HCl) C, H, N.
3
128.28, 128.37, 128.40, 128.47, 128.53, 141.92, 142.04, 142.09. [R]25
Procedure B. (3S,6S)-6-Benzhydryl-N-(pyridin-2-ylmethyl)
tetrahydro-2H-pyran-3-amine (10a). To a stirred solution of
amine 8 (60 mg, 0.22 mmol) and 2-pyridinecarboxaldehyde (21 μL,
0.22 mmol) in 1,2-dichloroethane (6 mL) was added glacial acetic acid
(13 μL, 0.22 mmol). After the mixture was stirred for 30 min, NaCNBH3
(28 mg, 0.44 mmol) was added portionwise followed by methanol
(1 mL) and the mixture was stirred overnight at room temperature. The
reaction mixture was quenched with saturated NaHCO3 solution at 0 °C
and extracted with ethyl acetate (3 Â 75 mL). The combined organic
layers were washed with water, brine and dried over Na2SO4, and solvent
was removed under reduced pressure. Crude product was purified by
column chromatography using 3% methanol in dichloromethane to give
D
(À)40.6° (c 0.5, MeOH). The product was converted into the correspond-
ing hydrochloride salt. Mp: 215À217 °C. Anal. (C26H29NO2 HCl) C, H, N.
3
(R)-2-(((3S,6S)-6-Benzhydryltetrahydro-2H-pyran-3-yl)amino)-
1-(4-fluorophenyl)ethanol (9c). Amine 8 (60 mg, 0.22 mmol) was
treated with (R)-2-(4-fluorophenyl)oxirane (35 mg, 0.25 mmol) in
anhydrous ethanol (3 mL) using procedure A. The residue was purified
by silica gel column chromatography using 3% methanol in ethyl acetate
as the eluent to afford compound 9c (51 mg, 59%) as a thick syrup. 1H
NMR (400 MHz, CDCl3): δ 1.20À1.56 (m, 2H), 1.56À1.76 (m, 1H),
1.86À2.04 (m, 1H), 2.62À2.72 (m, 1H), 2.75 (s, 1H), 2.84 (dd, J = 3.5,
12.0 Hz, 1H), 3.25À3.65 (m, 3H), 3.82À3.94 (m, 2H), 3.97À4.09 (m,
1H), 4.75 (dd, J = 3.5, 9.4 Hz, 1H), 6.90À7.05 (m, 2H), 7.06À7.36 (m,
12H). 13C NMR (100 MHz, CDCl3): δ 24.8, 27.4, 51.0, 54.3, 57.2, 69.7,
1
compound 10a (45 mg, 56%) as a thick syrup. H NMR (400 MHz,
CDCl3): δ 1.28À1.36 (m, 1H), 1.50À1.74 (m, 1H), 1.91À2.04 (m,
2929
dx.doi.org/10.1021/jm200020a |J. Med. Chem. 2011, 54, 2924–2932

Journal of Medicinal Chemistry
ARTICLE
1H), 2.74 (s, 1H), 3.28 (br s, 1H), 3.58 (dd, J = 1.8, 12.0 Hz, 1H),
3.85À4.14 (m, 5H), 7.07À7.42 (m, 12H), 7.62 (t, J = 7.6 Hz, 1H), 8.52
(d, J = 3.9 Hz, 1H). 13C NMR (100 MHz, CDCl3): δ 25.0, 27.2, 51.1,
52.1, 57.0, 70.1, 79.3, 121.9, 122.1, 126.1, 126.4, 128.2, 128.5, 136.5,
142.2, 142.3, 149.1, 159.3. [R]25D (À)65.0° (c 1, MeOH). The product
was converted into the corresponding hydrochloride salt. Mp: 220À230 °C.
1H), 1.90À2.00 (m, 1H), 2.70 (br s, 1H), 3.54À3.60 (m, 1H),
3.90À3.96 (m, 2H), 4.00À4.12 (m, 3H), 6.78 (t, J = 7.6 Hz, 1H),
6.85 (d, J = 8.0 Hz, 1H), 6.97 (d, J = 6.8 Hz, 1H), 7.14À7.38 (m, 11H). 13
C
NMR (100 MHz, CDCl3): δ 25.48, 27.28, 49.61, 49.80, 57.89, 69.72, 79.69,
116.69, 119.20, 112.50, 126.63, 126.85, 128.58, 128.67, 128.86, 129.01,
142.21, 142.27, 158.72. [R]25D (À)86.2° (c 0.5, MeOH). The product was
converted into the corresponding hydrochloride salt. Mp: 315À317 °C
(dec). Anal. (C25H27NO2 HCl 0.3H2O) C, H, N.
Anal. (C24H26N2O 2HCl) C, H, N.
3
(3S,6S)-6-Benzhydryl-N-(pyridin-3-ylmethyl)tetrahydro-2H-
pyran-3-amine (10b). Compound 8 (60 mg, 0.22 mmol) was reacted
with 3-pyridinecarboxaldehyde (21 μL, 0.22 mmol), glacial acetic acid
(13 μL, 0.22 mmol), and NaCNBH3 (28 mg, 0.44 mmol)) in 1,2-
dichloroethane (6 mL) using procedure B. The crude residue was
purified by column chromatography using 3% methanol in dichloro-
3
3
3-((((3S,6S)-6-Benzhydryltetrahydro-2H-pyran-3-yl)amino)
methyl)phenol (10f). Compound 8 (60 mg, 0.22 mmol) was reacted
with 3-hydroxybenzaldehyde (24 μL, 0.22 mmol), glacial acetic acid
(13 μL, 0.22 mmol), and Na(OAc)3BH (84 mg, 0.44 mmol) in 1,2-
dichloroethane (6 mL) using procedure B. The crude residue was purified
by column chromatography using 2% methanol in dichloromethane to
afford compound 10f (64 mg, 76%) as a thick syrup. 1H NMR (400 MHz,
CDCl3): δ 1.29À1.39 (m, 1H), 1.44À1.58 (m, 1H), 1.68 (tt, J = 4.3, 13.7
Hz, 1H), 2.05À2.11 (m 1H), 2.82 (br s, 1H), 3.31À3.35 (m, 1H), 3.52 (d,
J = 12.5 Hz, 1H), 3.82 (dd, J = 13.1, 29.9 Hz, 2H), 3.94 (d, J = 9.2 Hz, 1H),
3.99À4.09 (m, 2H), 6.68 (d, J = 7.3 Hz, 1H), 6.74 (d, J = 8.2 Hz, 1H), 6.96
(s, 1H), 7.09À7.31 (m, 11H). 13C NMR (100 MHz, CDCl3): δ 24.5, 25.8,
49.2, 49.9, 56.9, 67.9, 79.4, 115.4, 115.7, 120.0, 126.3, 126.5, 128.2, 128.5,
129.8, 141.7, 141.8, 157.4. [R]25D (À)55.4° (c 0.5, MeOH). The product
was converted into the corresponding hydrochloride salt. Mp: 190À200 °C.
Anal. (C25H27NO2 HCl 0.5H2O) C, H, N.
1
methane to afford compound 10b (45 mg, 56%) as a thick syrup. H
NMR (400 MHz, CDCl3): δ 1.24À1.36 (m, 2H), 1.48À1.70 (m, 2H),
1.90À1.98 (m, 1H), 2.64 (br s, 1H), 3.56 (dd, J = 1.6, 12.0 Hz, 1H), 3.81
(br s, 2H), 3.94À4.10 (m, 3H), 7.10À7.38 (m, 11H), 7.72 (d, J = 7.2 Hz,
1H), 8.50 (d, J = 3.6 Hz, 1H), 8.54 (s, 1H). 13C NMR (100 MHz,
CDCl3): δ 25.35, 27.55, 48.26, 50.62, 57.50, 70.37, 79.53, 123.64, 126.52,
126.72, 128.56, 128.72, 128.75, 128.77, 136.11, 142.34, 142.57, 148.70,
149.92. [R]25 (À)77.2° (c 0.5, MeOH). The product was converted
D
into the corresponding hydrochloride salt. Mp: 258À260 °C. Anal.
(C24H26N2O 2HCl) C, H, N.
3
(3S,6S)-6-Benzhydryl-N-(pyridin-4-ylmethyl)tetrahydro-2H-
pyran-3-amine (10c). Compound 8 (60 mg, 0.22 mmol) was reacted
with 4-pyridinecarboxaldehyde (21 μL, 0.22 mmol), glacial acetic acid
(13 μL, 0.22 mmol), and NaCNBH3 (28 mg, 0.44 mmol) in 1,2-
dichloroethane (6 mL) using procedure B. The crude residue was
purified by column chromatography using 3% methanol in dichloro-
3
3
(3S,6S)-6-Benzhydryl-N-(thiophen-2-ylmethyl)tetrahydro-
2H-pyran-3-amine (10g). Compound 8 (60 mg, 0.22 mmol) was
reacted with 2-thiophenecarboxaldehyde (25 mg, 0.22 mmol), glacial
acetic acid (13 μL, 0.22 mmol), and NaCNBH3 (18 mg, 0.29 mmol) in
1,2-dichloroethane (6 mL) using procedure B. The crude residue was
purified by column chromatography using 3% methanol in dichloro-
1
methane to afford compound 10c (46 mg, 58%) as a thick syrup. H
1
NMR (500 MHz, CDCl3): δ 1.35À1.43 (m, 1H), 1.46À1.60 (m, 1H),
1.72 (tt, J = 4.0, 13.4 Hz, 1H), 1.86À1.95 (m, 1H), 2.58 (s, 1H), 3.61
(dd, J = 1.2, 11.6 Hz, 1H), 3.89À4.02 (m, 4H), 4.06À4.13 (m, 1H),
7.16À7.40 (m, 10H), 7.67 (d, J = 6.1 Hz, 2H), 8.48 (d, J = 6.1 Hz, 2H).
13C NMR (125 MHz, CDCl3): δ 25.1, 27.5, 49.1, 50.9, 57.4, 70.2, 79.3,
124.9, 126.3, 126.5, 128.3, 128.4, 128.6, 128.5, 141.9, 142.1, 146.7,
157.6. [R]25D (À)69.5° (c 1, MeOH). The product was converted into
the corresponding hydrochloride salt. Mp: 224À230 °C. Anal.
methane to afford compound 10g (65 mg, 79%) as a thick syrup. H
NMR (400 MHz, CDCl3): δ 1.24À1.34 (m, 1H), 1.44À1.58 (m, 1H),
1.64 (tt, J = 4.0, 13.2 Hz, 1H), 1.86À1.94 (m, 1H), 2.69 (br s, 1H), 3.55
(dd, J = 2.0, 12.0 Hz, 1H), 3.92À4.08 (m, 6H), 6.88À6.91 (m, 1H),
6.92À6.95 (m, 1H), 7.14À7.36 (m, 11H). 13C NMR (100 MHz,
CDCl3): δ 25.51, 27.87, 45.85, 50.22, 57.60, 70.43, 79.56, 124.53,
124.75, 126.54, 126.74, 126.83, 128.63, 128.78, 128.82, 142.49,
142.68, 145.09. [R]25 (À)78.4° (c 0.5, MeOH). The product was
D
(C24H26N2O 1.8HCl) C, H, N.
converted into the corresponding hydrochloride salt. Mp: 256À258 °C.
3
Anal. (C23H25NOS HCl 0.1H2O) C, H, N.
(3S,6S)-6-Benzhydryl-N-(naphthalen-1-ylmethyl)tetrahydro-
2H-pyran-3-amine (10d). Compound 8 (60 mg, 0.22 mmol) was
reacted with 1-naphthaldehyde (30 μL, 0.22 mmol), glacial acetic acid
(13 μL, 0.22 mmol), and NaCNBH3 (28 mg, 0.44 mmol) in 1,2-
dichloroethane (6 mL) using procedure B. The crude residue was
purified by column chromatography using 3% methanol in dichloro-
3
3
(3S,6S)-6-Benzhydryl-N-(furan-2-ylmethyl)tetrahydro-2H-
pyran-3-amine (10h). Compound 8 (50 mg, 0.19 mmol) was reacted
with furfural (18 mg, 0.19 mmol), glacial acetic acid (11 μL, 0.19 mmol),
and NaCNBH3 (24 mg, 0.37 mmol) in 1,2-dichloroethane (6 mL) using
procedure B. The crude residue was purified by column chromatography
using 45% ethyl acetate in hexanes to afford compound 10h (45 mg,
1
methane to afford compound 10d (51 mg, 56%) as a thick syrup. H
1
NMR (500 MHz, CDCl3): δ 1.33À1.41 (m, 1H), 1.55À1.66 (m, 1H),
1.73 (tt, J = 4.0, 13.4 Hz, 1H), 1.99À2.08 (m, 1H), 3.63 (dd, J = 1.2, 11.6
Hz, 1H), 4.01 (d, J = 8.9 Hz, 1H), 4.07À418 (m, 2H), 4.28 (dd, J = 13.1,
37.5 Hz, 2H), 7.17À7.35 (m, 8 H), 7.37À7.58 (m, 6 H), 7.81 (d, J = 8.2
Hz, 1H), 7.90 (d, J = 7.6 Hz, 1H), 8.19 (d, J = 8.2 Hz, 1H). 13C NMR
(125 MHz, CDCl3): δ 25.3, 27.7, 48.4, 50.9, 57.2, 70.1, 79.3, 123.7,
125.4, 125.9, 126.0, 126.2, 126.4, 127.7, 128.3, 128.4, 128.5, 128.6, 131.8,
133.8, 135.8, 142.2, 142.4. [R]25D (À)69.5° (c 1, MeOH). The product
was converted into the corresponding hydrochloride salt. Mp: 140À150 °C.
Anal. (C29H29NO HCl 0.4H2O) C, H, N.
69%) as a thick syrup. H NMR (400 MHz, CDCl3): δ 1.28À1.34
(m, 1H), 1.45À1.58 (m, 1H), 1.59À1.74 (m, 2H), 1.84À1.94 (m, 1H),
2.65 (br s, 1H), 3.55 (dd, J = 2.0, 12.0 Hz, 1H), 3.77 (dd, J = 14.4, 22.8
Hz, 2H), 3.90À4.00 (m, 2H), 4.02À4.10 (m, 1H), 6.15 (d, J = 2.8 Hz,
1H), 6.30 (t, J = 2.8 Hz, 1H), 7.10À7.40 (m, 11H). 13C NMR (100
MHz, CDCl3): δ 25.36, 27.82, 43.76, 50.50, 57.42, 70.30, 79.51, 106.96,
110.32, 126.47, 126.67, 128.55, 128.70, 128.72, 128.76, 141.98, 142.49,
142.65, 154.27. [R]25 (À)75.4° (c 0.5, MeOH). The product was
D
converted into the corresponding hydrochloride salt. Mp: 228À230 °C.
Anal. (C23H25NO2 HCl 0.3H2O) C, H, N.
3
3
3
3
2-(((3S,6S)-6-Benzhydryltetrahydro-2H-pyran-3-ylami-
no)methyl)phenol (10e). Compound 8 (60 mg, 0.22 mmol) was
reacted with 2-hydroxybenzaldehyde (24 μL, 0.22 mmol), glacial acetic
acid (13 μL, 0.22 mmol), and NaCNBH3 (28 mg, 0.44 mmol) in 1,2-
dichloroethane (6 mL) using procedure B. The crude residue was
purified by column chromatography using 2% methanol in dichloro-
methane to afford compound 10e (65 mg, 77%) as a thick syrup. H
NMR (400 MHz, CDCl3): δ 1.34À1.52 (m, 2H), 1.68 (tt, J = 4.0, 13.6,
(3S,6S)-N-((1H-Pyrrol-2-yl)methyl)-6-benzhydryltetrahydro-
2H-pyran-3-amine (10i). Compound 8 (50 mg, 0.19 mmol) was
reacted with pyrrole-2-carboxaldehyde (18 mg, 0.19 mmol), glacial
acetic acid (11 μL, 0.19 mmol), and NaCNBH3 (24 mg, 0.37 mmol)
in 1,2-dichloroethane (6 mL) using procedure B. The crude product was
purified by column chromatography using 5% methanol in ethyl acetate
to afford compound 10i (50 mg, 77%) as a thick syrup. 1H NMR (400
MHz, CDCl3): δ 1.32À1.36 (m, 1H), 1.64À1.68 (m, 2H), 1.96À2.00
1
2930
dx.doi.org/10.1021/jm200020a |J. Med. Chem. 2011, 54, 2924–2932

Journal of Medicinal Chemistry
ARTICLE
(m, 1H), 2.72 (br s, 1H), 3.46 (d, J = 12.4 Hz, 1H), 3.88À4.08 (m, 5H),
4.99 (br s, 1H), 6.07 (br s, 1H), 6.14 (br s, 1H), 6.77 (br s, 1H),
7.10À7.36 (m, 10H), 9.48 (br s, 1H). 13C NMR (100 MHz, CDCl3):
δ 25.11, 26.55, 43.13, 50.30, 57.43, 69.54, 79.63, 107.93, 108.22,
118.58, 126.48, 126.79, 127.41, 128.55, 128.67, 128.78, 128.83,
U.S.) weighing 200À225 g housed in cages for at least 1 week prior to
testing. Animals were maintained in a temperature-controlled environ-
ment under a 12 h light/dark cycle. All subjects were naive and used
only once.
Rats were transported to the testing room at least for 1 h prior to
testing for acclimatization and adaptation purposes. Experimental ses-
sions were conducted between 9 a.m. to 2 p.m. daily. Animals were
assigned randomly and were placed individually in a glass cylinder
(24.5 cm  35.5 cm) filled with water at room temperature to a depth of
22 cm. All the test sessions were recorded by a video camera. The water
was changed in the beginning of each session, and the temperature was
maintained constant at 24À25 °C. Rats were judged to be immobile if
making minimum movement to barely keep afloat.
The procedure consisted of a pretest and a test session separated by
24 h.30 During the pretest period, rats were placed in the swim chamber
for 15 min. Followed by the initial swim exposure, rats were patted dry
and were transferred to the individual cages. Drugs or vehicle was then
administered (ip) 15 min after the initial swim exposure, and the rats
were then transported to their home cages. On the following day the rats
were brought back to the testing room at least 1 h before the beginning of
test session. Rats were administered either drugs or vehicle 1 h before the
swim test. Each rat underwent a 5 min swim session, which was
videotaped and scored later. In the case of imipramine, the pretreatment
time was 30 min.
All drugs were prepared freshly on the test days. Compound 10f and
imipramine were dissolved in 10% β-hydroxypropylcyclodextrin solu-
tion. All drugs and vehicles were administered ip. 10f was administered
at a dose of 10 mg/kg and the volume of injections was maintained at
2 mL/kg. Imipramine was administered at 15 mg/kg. All drugs and
vehicles were administered 1 h prior to testing for FST. Imipramine was
administered 30 min prior to testing. An individual, blinded to the
treatment, scored the videotapes for immobility. Immobility scores were
analyzed by one-way ANOVA test.
142.34, 142.49. [R]25 (À)77.8° (c 0.5, MeOH). The product
D
was converted into the corresponding hydrochloride salt. Mp:
234À236 °C. Anal. (C23H26N2O HCl 0.3H2O) C, H, N.
3
3
(3S,6S)-6-Benzhydryl-N-(4-methoxybenzyl)tetrahydro-2H-
pyran-3-amine (10j). Compound 8 (60 mg, 0.22 mmol) was reacted
with 4-methoxybenzaldehyde (31 mg, 0.22 mmol), glacial acetic acid (13
μL, 0.22 mmol), and NaCNBH3 (28 mg, 0.44 mmol) in 1,2-dichlor-
oethane (6 mL) using procedure B. The crude residue was purified by
column chromatography using ethyl acetate to afford compound 10j (40
mg, 46%) as a thick syrup. 1H NMR (400 MHz, CDCl3): δ 1.28À1.36
(m, 1H), 1.50À1.70 (m, 2H), 1.81 (br s, 1H), 1.90À1.98 (m, 1H), 2.65
(br s, 1H), 3.57 (d, J = 11.6 Hz, 1H), 3.73 (dd, J = 12.8, 24.8 Hz, 2H),
3.82 (s, 3H), 3.96À4.10 (m, 3H), 6.88 (d, J = 8.8 Hz, 2H), 7.16À7.40
(m, 12H). 13C NMR (100 MHz, CDCl3): δ 25.45, 27.84, 50.40, 50.46,
55.51, 57.45, 70.49, 79.49, 114.01, 126.46, 126.64, 128.52, 128.73,
128.75, 128.82, 129.43, 132.96, 142.48, 142.76, 158.82. [R]25D (À) 67.3°
(c 1, MeOH). The product was converted into the corresponding hydro-
chloride salt. Mp: 136À138 °C. Anal. (C26H29NO2 HCl 0.3H2O) C, H, N.
3
3
In Vitro Experiments. Monoamine Transport Inhibition. The
ability of test compounds to inhibit substrate uptake by rat monoamine
transporters was monitored as described by us previously.28,32 Briefly,
uptake of [3H]dopamine by DAT was measured in rat striatum, and
uptake of [3H]serotonin by SERT and [3H]norepinephrine by NET was
monitored in rat cerebral cortex. At least five triplicate concentrations of
each test compound were studied, spaced evenly around the IC50. IC50
was estimated by nonlinear computer curve-fitting procedures and
converted to Ki with the ChengÀPrusoff equation, as we described
previously.32
CNS Receptor Screening. Compound 10f was characterized in several
CNS receptor binding assays to assess the selectivity and specific
interactions of 10f with the monoamine transporters. The assays were
carried out generously by the National Institute of Mental Health’s
Psychoactive Drug Screening Program, Contract NO1MH32004
(NIMH PDSP). The NIMH PDSP is Directed by Bryan L. Roth,
MD, Ph.D., at the University of North Carolina at Chapel Hill and
Project Officer Jamie Driscol at NIMH, Bethesda, MD, U.S. (http://
pdsp.med.unc.edu/).
’ ASSOCIATED CONTENT
S
Supporting Information. Spectral data for 6b, binding
b
affinity of 10f, and elemental analysis data for all final targets. This
material is available free of charge via the Internet at http://pubs.
acs.org.
’ AUTHOR INFORMATION
Compound 10f was evaluated in primary binding assays targeting,
among others, cloned human dopamine receptor subtypes, serotonin
receptor subtypes, R-adrenergic receptors, and opioid receptors. The
description of all receptors targeted and corresponding radioligand used
is provided in the Supporting Information. The default concentration for
primary binding experiments was 10 μM. Compounds with inhibition of
>50% in the primary assay were moved into the secondary assay with full
concentration curves of the test compound in order to calculate the Ki
value for inhibition. For experimental details refer to the PDSP Web site
http://pdsp.med.unc.edu/ and click on “Binding Assay” or “Functional
Assay” on the menu bar (experimental details have been updated!).
In Vivo Experiments. Animals. Male SpragueÀDawley rats
(200À225 g) were purchased from Harlan. Animals were housed in a
temperature and humidity controlled room with 12 h light/dark cycle.
Food and water were accessible to animals freely throughout the
duration of study. All testing occurred during the light component. All
animal procedures were reviewed and approved by Wayne State
University animal investigation committee consistent with AALAC
guidelines.
Corresponding Author
*Phone: 1-313-577-1064. Fax: 1-313-577-2033. E-mail: adutta@
wayne.edu.
’ ACKNOWLEDGMENT
This work is supported by National Institute of Mental
Health/The National Institutes of Health Grant MH084888
(A.D.).
’ ABBREVIATIONS USED
DAT, dopamine transporter; SERT, serotonin transporter; NET,
norepinephrine transporters; TUI, triple uptake inhibitor; SAR,
structureÀactivity relationship; GBR 12909 dihydrochloride,
(1-[2-[bis(4-fluorophenyl)methoxy]ethyl]-4-[3-phenylpropyl]pipe-
razine); SSRI, selective serotonin reuptake inhibitor; DNRI, do-
pamine norepinephrine reuptake inhibitor; NE, norepinephr-
ine; 5-HT, serotonin; FST, forced swim test
Effect of Compound 10f in the Rat Forced Swimming Test as
a Measure of Its Antidepressant Property. The subjects were male Swiss
SpragueÀDawley rats (Harlam SpragueÀDawley Inc., Indianapolis, IN,
2931
dx.doi.org/10.1021/jm200020a |J. Med. Chem. 2011, 54, 2924–2932

Journal of Medicinal Chemistry
ARTICLE
’ REFERENCES
(21) Ghorai, S. K.; Cook, C.; Davis, M.; Venkataraman, S. K.;
George, C.; Beardsley, P. M.; Reith, M. E.; Dutta, A. K. High affinity
hydroxypiperidine analogues of 4-(2-benzhydryloxyethyl)-1-(4-fluoro-
benzyl)piperidine for the dopamine transporter: stereospecific interac-
tions in vitro and in vivo. J. Med. Chem. 2003, 46, 1220–1228.
(22) Dutta, A. K.; Zhang, S.; Kolhatkar, R.; Reith, M. E. Dopamine
transporter as target for drug development of cocaine dependence
medications. Eur. J. Pharmacol. 2003, 479, 93–106.
(23) Zhang, S.; Reith, M. E.; Dutta, A. K. Design, synthesis, and
activity of novel cis- and trans-3,6-disubstituted pyran biomimetics of
3,6-disubstituted piperidine as potential ligands for the dopamine
transporter. Bioorg. Med. Chem. Lett. 2003, 13, 1591–1595.
(24) Kolhatkar, R.; Cook, C. D.; Ghorai, S. K.; Deschamps, J.;
Beardsley, P. M.; Reith, M. E.; Dutta, A. K. Further structurally constrained
analogues of cis-(6-benzhydrylpiperidin-3-yl)benzylamine with elucidation
of bioactive conformation: discovery of 1,4-diazabicyclo[3.3.1]nonane
derivatives and evaluation of their biological properties for the monoamine
transporters. J. Med. Chem. 2004, 47, 5101–5113.
(25) Zhang, S.; Zhen, J.; Reith, M. E.; Dutta, A. K. Structural
requirements for 2,4- and 3,6-disubstituted pyran biomimetics of
cis-(6-benzhydryl-piperidin-3-yl)-benzylamine compounds to interact
with monoamine transporters. Bioorg. Med. Chem. 2004, 12, 6301–6315.
(26) Zhang, S.; Zhen, J.; Reith, M. E.; Dutta, A. K. Discovery of novel
trisubstituted asymmetric derivatives of (2S,4R,5R)-2-benzhydryl-
5-benzylaminotetrahydropyran-4-ol, exhibiting high affinity for seroto-
nin and norepinephrine transporters in a stereospecific manner. J. Med.
Chem. 2005, 48, 4962–4971.
(27) Zhang, S.; Fernandez, F.; Hazeldine, S.; Deschamps, J.; Zhen, J.;
Reith, M. E.; Dutta, A. K. Further structural exploration of trisubstituted
asymmetric pyran derivatives (2S,4R,5R)-2-benzhydryl-5-benzylamino-
tetrahydropyran-4-ol and their corresponding disubstituted (3S,6S)
pyran derivatives: a proposed pharmacophore model for high-affinity
interaction with the dopamine, serotonin, and norepinephrine trans-
porters. J. Med. Chem. 2006, 49, 4239–4247.
(1) Kessler, R. C.; Berglund, P.; Demler, O.; Jin, R.; Koretz, D.;
Merikangas, K. R.; Rush, A. J.; Walters, E. E.; Wang, P. S. The epidemiology
of major depressive disorder: results from the National Comorbidity Survey
Replication (NCS-R). JAMA, J. Am. Med. Assoc. 2003, 289, 3095–3105.
(2) Lopez, A. D.; Murray, C. C. The global burden of disease,
1990À2020. Nat. Med. 1998, 4, 1241–1243.
(3) Dilsaver, S. C.; Chen, Y. W.; Swann, A. C.; Shoaib, A. M.;
Krajewski, K. J. Suicidality in patients with pure and depressive mania.
Am. J. Psychiatry 1994, 151, 1312–1315.
(4) Strakowski, S. M.; McElroy, S. L.; Keck, P. E., Jr.; West, S. A.
Suicidality among patients with mixed and manic bipolar disorder. Am. J.
Psychiatry 1996, 153, 674–676.
(5) Nemeroff, C. B. Psychopharmacology of affective disorders in
the 21st century. Biol. Psychiatry 1998, 44, 517–525.
(6) Iversen, L. Neurotransmitter transporters: fruitful targets for
CNS drug discovery. Mol. Psychiatry 2000, 5, 357–362.
(7) Schloss, P.; Williams, D. C. The serotonin transporter: a primary
target for antidepressant drugs. J. Psychopharmacol. 1998, 12, 115–121.
(8) Nierenberg, A. A.; Amsterdam, J. D. Treatment-resistant depres-
sion: definition and treatment approaches. J. Clin. Psychiatry 1990, 51
(Suppl.), 39–47; discussion 48À50.
(9) Nierenberg, A. A.; Quitkin, F. M.; Kremer, C.; Keller, M. B.; Thase,
M. E. Placebo-controlled continuation treatment with mirtazapine: acute
pattern of response predicts relapse. Neuropsychopharmacology 2004,
29, 1012–1018.
(10) D’Aquila, P. S.; Collu, M.; Gessa, G. L.; Serra, G. The role of
dopamine in the mechanism of action of antidepressant drugs. Eur. J.
Pharmacol. 2000, 405, 365–373.
(11) Papakostas, G. I. Dopaminergic-based pharmacotherapies for
depression. Eur. Neuropsychopharmacol. 2006, 16, 391–402.
(12) Clayton, A. H.; Warnock, J. K.; Kornstein, S. G.; Pinkerton, R.;
Sheldon-Keller, A.; McGarvey, E. L. A placebo-controlled trial of
bupropion SR as an antidote for selective serotonin reuptake inhibi-
tor-induced sexual dysfunction. J. Clin. Psychiatry 2004, 65, 62–67.
(13) Damsa, C.; Bumb, A.; Bianchi-Demicheli, F.; Vidailhet, P.;
Sterck, R.; Andreoli, A.; Beyenburg, S. “Dopamine-dependent” side
effects of selective serotonin reuptake inhibitors: a clinical review. J. Clin.
Psychiatry 2004, 65, 1064–1068.
(14) Skolnick, P.; Popik, P.; Janowsky, A.; Beer, B.; Lippa, A. S.
Antidepressant-like actions of DOV 21,947: a “triple” reuptake inhibitor.
Eur. J. Pharmacol. 2003, 461, 99–104.
(15) Shaw, A. M.; Boules, M.; Zhang, Y.; Williams, K.; Robinson, J.;
Carlier, P. R.; Richelson, E. Antidepressant-like effects of novel triple
reuptake inhibitors, PRC025 and PRC050. Eur. J. Pharmacol. 2007,
555, 30–36.
(28) Dutta, A. K.; Ghosh, B.; Biswas, S.; Reith, M. E. D-161, a novel
pyran-based triple monoamine transporter blocker: behavioral pharma-
cological evidence for antidepressant-like action. Eur. J. Pharmacol. 2008,
589, 73–79.
(29) Lewis, D. B.; Matecka, D.; Zhang, Y.; Hsin, L. W.; Dersch,
C. M.; Stafford, D.; Glowa, J. R.; Rothman, R. B.; Rice, K. C. Oxygenated
analogues of 1-[2-(diphenylmethoxy)ethyl]- and 1-[2-[bis(4-fluoro-
phenyl)methoxy]ethyl]-4-(3-phenylpropyl)piperazines (GBR 12935
and GBR 12909) as potential extended-action cocaine-abuse therapeutic
agents. J. Med. Chem. 1999, 42, 5029–5042.
(30) Porsolt, R. D.; Le Pichon, M.; Jalfre, M. Depression: a new
animal model sensitive to antidepressant treatments. Nature 1977,
266, 730–732.
(16) Skolnick, P.; Basile, A. S. Triple reuptake inhibitors (“broad
spectrum” antidepressants). CNS Neurol. Disord.: Drug Targets 2007,
6, 141–149.
(31) Cryan, J. F.; Markou, A.; Lucki, I. Assessing antidepressant
activity in rodents: recent developments and future needs. Trends
Pharmacol. Sci. 2002, 23, 238–245.
(17) Liang, Y.; Shaw, A. M.; Boules, M.; Briody, S.; Robinson, J.;
Oliveros, A.; Blazar, E.; Williams, K.; Zhang, Y.; Carlier, P. R.; Richelson,
E. Antidepressant-like pharmacological profile of a novel triple reuptake
inhibitor, (1S,2S)-3-(methylamino)-2-(naphthalen-2-yl)-1-phenylpro-
pan-1-ol (PRC200-SS). J. Pharmacol. Exp. Ther. 2008, 327, 573–583.
(18) Skolnick, P.; Krieter, P.; Tizzano, J.; Basile, A.; Popik, P.;
Czobor, P.; Lippa, A. Preclinical and clinical pharmacology of DOV
216,303, a “triple” reuptake inhibitor. CNS Drug Rev. 2006, 12, 123–134.
(19) Dutta, A. K.; Davis, M. C.; Reith, M. E. Rational design and
synthesis of novel 2,5-disubstituted cis- and trans-piperidine derivatives
exhibiting differential activity for the dopamine transporter. Bioorg. Med.
Chem. Lett. 2001, 11, 2337–2340.
(32) Cheng, Y.; Prusoff, W. H. Relationship between the inhibition
constant (K1) and the concentration of inhibitor which causes 50%
inhibition (I50) of an enzymatic reaction. Biochem. Pharmacol. 1973,
22, 3099–3108.
(20) Dutta, A. K.; Davis, M. C.; Fei, X. S.; Beardsley, P. M.; Cook, C. D.;
Reith, M. E. Expansion of structureÀactivity studies of piperidine analogues
of 1-[2-(diphenylmethoxy)ethyl]-4-(3-phenylpropyl)piperazine (GBR
12935) compounds by altering substitutions in the N-benzyl moiety and
behavioral pharmacology of selected molecules. J. Med. Chem. 2002,
45, 654–662.
2932
dx.doi.org/10.1021/jm200020a |J. Med. Chem. 2011, 54, 2924–2932