Flexible and biomimetic analogs of triple uptake inhibitor 4-((((3S,6S)-6-benzhydryltetrahydro-2H-pyran-3-yl)amino)methyl)phenol: Synthesis, biological characterization, and development of a pharmacophore model

Article abstract of DOI:10.1016/j.bmc.2013.11.017

In this study we have generated a pharmacophore model of triple uptake inhibitor compounds based on novel asymmetric pyran derivatives and the newly developed asymmetric furan derivatives. The model revealed features important for inhibitors to exhibit a

Full text of DOI:10.1016/j.bmc.2013.11.017

Bioorganic & Medicinal Chemistry 22 (2014) 311–324
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Flexible and biomimetic analogs of triple uptake inhibitor
4-((((3S,6S)-6-benzhydryltetrahydro-2H-pyran-3-yl)amino)methyl)
phenol: Synthesis, biological characterization, and development
of a pharmacophore model
Horrick Sharma a, Soumava Santra a, Joy Debnath a, Tamara Antonio b, Maarten Reith b,c, Aloke Dutta a,
⇑
a Wayne State University, Department of Pharmaceutical Sciences, Applebaum College of Pharmacy & Health Sciences, Rm# 3128, Detroit, MI 48202, United States
b New York University, Department of Psychiatry, New York, NY 10016, United States
c New York University, Department of Pharmacology, New York, NY 10016, United States
a r t i c l e i n f o
a b s t r a c t
Article history:
In this study we have generated a pharmacophore model of triple uptake inhibitor compounds based on
novel asymmetric pyran derivatives and the newly developed asymmetric furan derivatives. The model
revealed features important for inhibitors to exhibit a balanced activity against dopamine transporter
(DAT), serotonin transporter (SERT), and norepinephrine transporter (NET). In particular, a ‘folded’ con-
formation was found common to the active pyran compounds in the training set and was crucial to triple
uptake inhibitory activity. Furthermore, the distances between the benzhydryl moiety and the N-benzyl
group as well as the orientation of the secondary nitrogen were also important for TUI activity. We have
validated our findings by synthesizing and testing novel asymmetric pyran analogs. The present work has
also resulted in the discovery of a new series of asymmetric tetrahydrofuran derivatives as novel TUIs.
Lead compounds 41 and 42 exhibited moderate TUI activity. Interestingly, the highest TUI activity by lead
tetrahydrofuran compounds for example, 41 and 42, was exhibited in a stereochemical preference similar
to pyran TUI for example, D-161.
Received 28 September 2013
Revised 2 November 2013
Accepted 11 November 2013
Available online 19 November 2013
Keywords:
Depression
Antidepressants
Triple uptake inhibitors
Asymmetric synthesis
Pharmacophore model
Computational analysis
Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction
increasing serotonin (5-HT) and norepinephrine (NE) neurotrans-
mission.5,6 Monoamine oxidase inhibitors (MAOIs) were the first
Major depressive disorder is a debilitating illness affecting 15–
20% of the population in the United States.1 According to the World
Health Organization by 2020 it would be the second-most leading
cause of disability worldwide making it a global health problem. It
is believed that 20% of all individuals suffer from a major mood dis-
order at least once in their lifetime.
The ‘monoamine’ hypothesis has been the gold standard in
understanding the underlying cause of depression. It is built on
the idea that depression results from a deficiency in monoamine
neurotransmission, by a reduction of monoamine levels in the
synaptic cleft2,3 or, consonant with monoaminergic volume
transmission, a reduction in extracellular monoamine levels.4
Consequently, drug development efforts have centered on
class of antidepressants used.7 They increased monoamine levels
by preventing their metabolism. MAOIs were replaced by tricyclic
antidepressants (TCAs) that block the reuptake of 5-HT and NE into
the nerve terminal by inhibiting both 5-HT and NE transporters.
TCAs were plagued by their non-specific interactions in the CNS
including antagonism of adrenergic, histamine, and cholinergic
receptors.8 TCAs were subsequently superseded by selective sero-
tonin reuptake inhibitors (SSRIs) and serotonin/norepinephrine
reuptake inhibitors (SNRIs) which were developed as second-gen-
eration antidepressants.9–13 It has been shown that venlafaxine, an
SNRI, exhibits greater response and remission rates than SSRIs.14
Although SSRIs and SNRIs by virtue of their selective interactions
at the 5-HT and NE transporters exhibited an improved profile with
less adverse effects, they were not without shortcomings.15,16 Fore-
most, these agents have failed to improve the efficacy and exhibit
delayed onset of antidepressant response.17 Moreover, because of
relapse and unwanted side effects associated with SSRIs there is
an unmet need to discover newer agents for the treatment of
depression.18,19
Abbreviations: SSRI, selective serotonin reuptake inhibitors; SNRI, serotonin/
norepinephrine reuptake inhibitors; MAO, monoamine oxidase inhibitors; TCA,
tricyclic antidepressants; DAT, dopamine transporter; SERT, serotonin transporter;
NET, norepinephrine transporters; TUI, triple uptake inhibitor; SAR, structure–
activity relationship.
Current treatment aims at alleviating the extraneuronal
concentration 5-HT and NE but does not include a dopaminergic
⇑
Corresponding author. Tel.: +1 313 577 1064; fax: +1 313 577 2033.
E-mail address: adutta@wayne.edu (A. Dutta).
0968-0896/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmc.2013.11.017

312
H. Sharma et al. / Bioorg. Med. Chem. 22 (2014) 311–324
element. Preclinical and clinical studies have demonstrated that
antidepressants can sensitize mesolimbic postsynaptic dopamine
depression.37,38 In our continuous efforts to develop effective drugs
to combat depression, in the present structure–activity relation-
ship (SAR) study, we have carried out synthesis to further explore
the structural requisites of asymmetric pyran derivatives, discov-
ered new asymmetric tetrahydrofuran derivatives as TUIs, and
developed a pharmacophore model.
receptors thereby implicating
a dopaminergic component in
depression.20–23 Mesolimbic dopamine is associated with motiva-
tion and reward-related behavior and, therefore, including dopa-
minergic activity should improve anhedonia that is the central
component in depression.24 This is validated by the findings that
adjunct administration of the dopamine transporter blocker bupro-
pion and an SSRI enhanced efficacy in patients refractory to
SSRIs.25,26 Moreover, Pramipexole, a D3 preferring agonist, was
found to be effective in both unipolar and bipolar depression.27
Thus, an attractive strategy entails inhibiting the reuptake of all
three monoamines: 5-HT, NE, and dopamine, and developing triple
uptake inhibitors (TUIs) for the treatment of depression.28,29 Inhib-
iting all the three transporters simultaneously is challenging and
the desired ratio of relative potencies is still debated. It has been
hypothesized that the TUIs, with their broad spectrum activity,
would be able to provide faster onset, enhanced efficacy, and ad-
dress anhedonia with reduced side effects that are associated with
currently available antidepressants.30 Recent efforts in this
direction have led to the discovery of few potent TUIs (Fig. 1) that
have proved to be efficacious in animal models of depression.
These include DOV 216,303, PRC200-SS, JNJ-7925476, and
GSK-372,475.31,32 DOV 216,303 is currently undergoing clinical
development and has been shown to possess promising pharmaco-
kinetic properties and found to be as efficacious as citalopram.32
In our earlier studies we have synthesized piperidine deriva-
tives against dopamine transporters (DAT). Further, optimization
resulted in the discovery of a unique di- and tri-substituted pyran
template, several derivatives of which (Fig. 1) inhibited the uptake
of all three monoamine transporters.33–36 Dual acting inhibitors as
blockers of both 5-HT and NE transporters (SNRIs) or NE and dopa-
mine transporters (DNRIs) have also been identified. Two of our
lead TUIs D-142 and D-161 have shown to possess antidepressant
activity and were found to be efficacious in animal models of
2. Material and methods
2.1. Chemistry
Scheme 1 shows the synthesis of (R)-epoxide starting materials
4a and 4b which were used to make target compounds 15 and 16,
respectively. Reaction of diphenylmethane with allyl bromide and
4-bromobut-1-ene in the presence of n-butyl lithium in anhydrous
ether yielded alkene intermediates 2a and 2b, respectively,
which upon epoxidation with m-CPBA gave the corresponding
racemic epoxides 3a and 3b. The racemates 3a and 3b were
resolved by hydrolytic kinetic resolution using Jacobsen catalyst,
(R,R)-N,N0-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanedi-
aminocobalt, to yield (R)-4a,(S)-5a and (R)-4b, (S)-5b, respectively,
in high enantioselectivity.
The synthesis of target compounds 15 and 16 is described in
Scheme 2. The regioselective epoxide ring opening of 15 and 16
with allyl magnesium chloride and a catalytic amount of copper(I)
iodide resulted in alcohol intermediates 6a and 6b in 93% yields.
O-vinylation of 6a and 6b with ethyl vinyl ether and catalytic
amount of mercury(II) trifluoroacetate at room temperature gave
vinyl ethers 7a (77%) and 7b (74%), respectively. Intermediates
7a and 7b were immediately subjected to ring-closing metathesis
(RCM) in the presence of Grubbs catalyst (1st generation) in reflux-
ing anhydrous benzene to yield corresponding cyclic dihydropyran
intermediates 8a and 8b in 95% and 96% yields, respectively.
Intermediate 8a was then subjected to hydroboration reaction
with 9-BBN in anhydrous THF, followed by oxidation to give a
Cl
OH
HN
N
NH
NHCH3
Cl
Cl
O
GSK-372,475
Cl
PRC200-SS
DOV 216,303
JNJ-7925476
NH
R4
F
O
HN
R1
HN
R5
O
HN
O
O
OH
R3
D-168
F
D-478
R2
: R1 = H; R2 = H; R3 = H; R4 = H; R5 = OH
: R1 = H; R2 = H; R3 = OH; R4 = H; R5 = OCH3
: R1 = H; R2 = H; R3 = H; R4 = H; R5 = NH2
D-161
D-142
D-185
D-411: R1 = H; R2 = H; R3 = H; R4 = H; R5 = OCH3
D-391: R1 = H; R2 = H; R3 = H; R4 = OH; R5 = H
D-199: R1 = H; R2 = H; R3 = H; R4 = H; R5 = NO2
D-471: R1 = F; R2 = F; R3 = OH; R4 = H; R5 = OH
1 = F; R2 = F; R3 = H; R4 = H; R5 = NH2
D-451:
R
Figure 1. Structures of known and lead pyran-based TUIs.

H. Sharma et al. / Bioorg. Med. Chem. 22 (2014) 311–324
313
c
OH
a
b
n
n
n
n
O
+
O
OH
n = 1, 5a
n = 2, 5b
n = 1, 3a
n = 2, 3b
n = 1, (R)-4a
n = 2, (R)-4b
n = 1, 2a
n = 2, 2b
1
Scheme 1. Reagents and conditions: (a) Anhyd THF, ꢀ78 °C, n-BuLi, allylbromide or 4-bromobut-1-ene, overnight, 83% for 2a, 87% for 2b; (b) Anhyd CH2Cl2, 0 °C, m-CPBA,
overnight, 96% (c) (R,R)-(ꢀ)N,N/-bis(3,5-di-tert-butylsalicylidine)-1,2-cyclohexane diaminocobalt (Jacobsen’s catalyst), H2O, THF, over 99% ee and 46% yield for both 4a and
4b, 47% for both 5a and 5b.
c
a
b
n
n
n
OH
n
O
O
O
n = 1, 6a
n = 2, 6b
n = 1, 7a
n = 2, 7b
n = 1, (R)-4a
n = 2, (R)-4b
n = 1, 8a
n = 2, 8b
OMs
O
OH
O
OMs
O
O
OH
n
n
d
e
n
n
+
+
11a
n = 1,
n = 2, 11b
12a
n = 1,
n = 1, 9a
n = 2,
n = 1, 10a
10b
n = 2, 12b
9b
n = 2,
NH2
N3
HN
O
O
O
f
g
h
11a
11b
OH
n
n
n
n = 1, 14a
n = 2, 14b
n = 1, 15
n = 2, 16
n = 1, 13a
n = 2, 13b
Scheme 2. Reagents and conditions: (a) allylmagnesium chloride, CuI, anhyd THF, ꢀ78 °C to rt, 24 h, 93% for 6a, 84% for 6b; (b) Ethylvinyl ether, Hg(OCOCF3)2,0 °C to rt, 4 h,
77% for 7a, 74% for 7b; (c) Grubb’s catalyst (1st gen), anhyd benzene, reflux, 2 h, 95% for 8a, 96% for 8b; (d) (i) 9-BBN, anhyd THF, 0 °C to rt, overnight; (ii) 10% NaOH, 30% H2O2,
50 °C, 1 h, 95% for a mixture of 9a and 10a, 84% for a mixture of 9b and 10b; (e) CH3SO2Cl, Et3N, anhyd DCM, rt, 0 °C 2 h, 69% for 11a, 15% for 12a, 67% for 11b, 17% for 12b; (f)
NaN3, DMF, 80 °C, 24 h, 86% for 13a, 88% for 13b; (g) H2, Pd/C, MeOH, 1 atm, overnight, 98% for 14a, 97% for 14b; (h) RCHO, Na(OAc)3 BH, AcOH, 1,2-dichloroethane/MeOH,
3:1, rt, overnight, 46% for 15, 47% for 16.
mixture of inseparable diastereomers (95%) exclusively in the
favor of the trans isomer 9a. Similarly, intermediate 8b, upon
hydroboration and oxidation reaction yielded inseparable diaste-
reomers (84%) predominantly favoring the trans isomer 9b. The
diasteromeric mixture of 9a and 10a were then mesylated with
methanesulfonyl chloride using triethylamine in anhydrous
dichloromethane (DCM) and separated by column chromatogra-
phy to afford compound 11a as the major isomer in 69% and 12a
as the minor isomer in 15% yields. Similarly, diasteromeric mixture
of 9b and 10b, upon mesylation gave separable isomers 11b and
12b in 67% and 17% yields, respectively. The stereochemistry of
the trans isomer 9a has been thoroughly established in our previ-
ous studies.35 Major isomers 11a and 11b were then subjected to
SN2 nucleophilic substitution reaction using sodium azide in anhy-
drous DMF to give intermediates 13a and 13b in 86% and 88%
yields, respectively. Hydrogenation of 13a and 13b with 10% Pd/C
in methanol resulted in corresponding cis-amines 14a and 14b in
quantitative yields. Finally, 14a and 14b were subjected to reduc-
tive amination reaction with benzaldehyde in the presence of so-
dium triacetoxyborohydride and acetic acid catalyst to yield
corresponding final compounds 15 and 16 in 46% and 47% yields,
respectively.
Scheme 3 shows the synthesis of compound 27. The (R)-epoxide
17 was reacted with allyl magnesium chloride in the presence of
copper(I) iodide catalyst to yield intermediate 18 which upon viny-
lation with ethylvinyl ether and mercury(II) trifluoroacetate, gave
intermediate 19. RCM reaction gave intermediate 20, followed by
regio- and stereo-specific hydroboration and oxidation that re-
sulted in a mixture of inseparable diastereomers 21 and 22. Mesy-
lation reaction gave diastereomers 23 and 24 which were
separated by column chromatography. The trans intermediate 23
was subjected to SN2 nucleophilic substitution reaction using
sodium azide to yield intermediate 25 which gave the cis-amine
26 upon hydrogenation with 10% Pd/C in methanol. Compound
27 was synthesized via reductive amination reaction by reacting
26 with benzaldehyde using sodium cyanoborohydride and cata-
lytic amount of acetic acid.
The synthesis of tetrahydrofuran compounds 40–46 required
some modifications in our reaction conditions and is depicted in
scheme 4. Briefly, the epoxide ring in (R)-2-benzhydryloxirane
(28)36 was regioselectively opened with vinyl magnesium bromide
and a catalytic amount of copper(I) iodide resulting in (S)-alcohol
intermediate 29 in 75% yield. The alcohol intermediate was then
subjected to trans-vinylation using ethyl vinyl ether and a catalytic
amounts of mercury(II) trifluoroacetate. The reaction yielded the
desired intermediate 30 in low yields (8–10%) along with the forma-
tion of an acetal side product that resulted from the reaction of
in situ generated trifluoroacetic acid. Moreover, unreacted alcohol
was also recovered in significant amounts. It was noted that addi-
tion of triethylamine neutralized free acid and significantly
reduced the formation of the acetal side product.39 The reaction
was carried out in a sealed tube and heated to 50 °C to force the
equilibrium in the forward direction. Thus, 30 was obtained in mod-
erate yield (50%) along with the recovery of unreacted alcohol (38%)
which was recycled in the synthesis. The unstable intermediate 30
was immediately subjected to RCM reaction in the presence of
Grubbs catalyst (1st generation) at room temperature. The reaction
was optimized by warming to 50 °C and carrying out for a longer
time period (6 h) along with the portion-wise addition of the cata-
lyst over 3 h. The resulting intermediate 31, obtained in 53% yields,
was then reacted with 9-BBN followed by oxidation to obtain an
inseparable mixture of diastereomers 32 and 33. The diasteromeric

314
H. Sharma et al. / Bioorg. Med. Chem. 22 (2014) 311–324
b
c
a
O
O
OH
O
18
20
19
(R)-17
OMs
OH
O
O
OMs
O
O
e
OH
+
d
+
24
23
22
21
Minor
Major
NH2
N3
HN
O
O
h
O
g
OH
f
23
26
25
27
Scheme 3. Reagents and conditions: (a) allylmagnesium chloride, anhyd Ditheyl ether, ꢀ78 °C to rt, overnight, 78%; (b) ethylvinyl ether, Hg(OCOCF3)2, rt, 4 h, 83%; (c) Grubb’s
catalyst (1st gen), anhyd benzene, reflux, 3 h, 84%; (d) (i) 9-BBN, anhyd THF, rt, overnight; (ii) 10% NaOH, 30% H2O2, 50 °C, 1 h, 86%; (e) CH3SO2Cl, Et3N, DCM, rt, 2 h, 69% for 23,
14% for 24; (f) NaN3, DMF, 80 °C, overnight, 83%; (g) H2, Pd/C, MeOH, 50 psi, 2 h, quantitative yield; (h) 4-hydroxy benzaldehyde, NaCNBH3, AcOH, 1,2-dichloroethane, rt,
overnight, 70%.
O
a
b
c
d
f
OH
O
O
31
30
( )-28
R
29
e
OH
OH
OMs
OMs
+
+
O
O
O
34
O
35
33
32
h
NH2
g
N3
NH2
+
N3
+
O
O
O
36
38
39
37
(minor)
(major)
R
R
+
R=OH;
40
n= 1,
n= 2,
NH
NH
R=OH 45
n= 1,
n= 2,
;
R= OH; 41
R= H 46
O
;
O
n
n
n= 2, R= OCH3; 42
n= 2, R= F;
R= H
43
44
n= 2,
;
Scheme 4. Reagents and conditions: (a) vinylmagnesium bromide, CuI, anhyd THF, ꢀ78 °C to rt, overnight, 75%; (b) Ethylvinyl ether, Hg(OCOCF3)2, 50 °C, 12 h, 50%; (c)
Grubb’s catalyst (1st gen), anhyd benzene, 50 °C, 6 h, 53%; (d) (i) 9-BBN, anhyd THF, rt, overnight; (ii) 10% NaOH, 30% H2O2, 50 °C, 1 h, 53% for mixture of 32 and 33; (e)
CH3SO2Cl, Et3N, DCM, rt, 2 h; (f) NaN3, DMF, 80 °C, overnight, overall 36.0% for 36, 12.6% for 37; (g) H2, 10% Pd/C, MeOH, 1 atm, overnight, quantitative yield for 38, 80% for 39;
(h) aldehyde, NaCNBH3/Na(OAc)3BH,AcOH, 1,2-dichloroethane/MeOH, 3:1, rt, overnight, 35–45%.
mixture was mesylated with methanesulfonyl chloride using trieth-
ylamine in anhydrous dichloromethane. In contrast to the pyran
derivatives, the resulting diastereomers 34 and 35 were inseparable
at this stage, and were thus carried to the next step without
further purification. The SN2 nucleophilic substitution reaction with
sodium azide gave separable diastereomers 36 (major) and 37
(minor) which were purified by column chromatography. The
assignment of absolute stereochemistry and structural elucidation
of major diasteromer 36 was performed using 1H and 2D NMR
experiments and details has been provided in the Supplementary
data. Similar experiments were performed to characterize the min-
or azide diasteromer 37. After determining their stereochemistry,
the azide intermediates 36 and 37 were hydrogenated to obtain
the corresponding amines 38 and 39 in quantitative yields. The
amines were then subjected to reductive amination reaction with
appropriate aldehydes according to the method described above
to furnish the final compounds 40–46 in 35–45% yields.
be H-2 which is next to the H-1 (3.92 ppm) of the benzhydryl
group. The splitting was doublet of triplet (dt) from couplings with
H-1, H-3a (2.25 ppm), and H-3b (2.00 ppm) protons (Table 1).
Furthermore, 2D gradient double quantum-filtered correlation
spectroscopy (2D-gDQFCOSY) and 1H–1H homonuclear decoupling
experiments also supported this observation. The decoupling
experiment revealed that irradiation of protons at 1.75 and
2.25 ppm separately, has collapsed the doublet of triplet peak of
H-2 into a triplet. This validated that the protons at 1.75 and
2.25 ppm, are the immediate neighbouring protons of H-2. Further
experiments confirmed that the protons at 2.25 ppm is H-3a and
1.75 ppm is H-3b. The assignment of the remaining proton signals
with their coupling constants are summarized in Table 1. The H-4
proton occurs as a multiplet at 4.04 ppm in the 1H NMR (CD3OD)
spectrum resulting from the coupling interactions with H-3a,
H-3b, H-5a, and H-5b protons. To determine through-space
coupling and elucidate the absolute stereochemistry at the C-4
(Table 1) asymmetric center, nuclear Overhauser experiments
(NOE) was performed. The NOE revealed that irradiation of the
proton at 4.66 ppm (H-1) (in CD3OD spectra) produced diagnostic
NOEs between H-2 and H-4 with 1% enhancement of the H-4
multiplet signal at 4.05–4.10 ppm, suggesting that H-4 is cis to
H-2. Since stereochemistry at the C-2 carbon has (S) configuration,
2.2. Stereochemical assignment of the intermediate 36
Structural elucidation for compound 36 is summarized. By the
knowledge of chemical shift, in the aliphatic region the most
downfield proton at 4.66 ppm (1H NMR (CDCl3) spectrum) should

H. Sharma et al. / Bioorg. Med. Chem. 22 (2014) 311–324
315
Table 1
1H NMR (CDCl3) signals of respective protons and NOE correlation observed in major- and minors-azides 36 and 37
H-4
H-4
H-3b
H-3b
N3
H-3a
H-2
N3
H-3a
H-2
4
3
4
3
H-5a
H-5a
5
5
H-1
H-5b
2
O
H-5b
2
O
H-1
37
36
Proton
Compound 36 (ppm)
3.92a (d, J = 9.7 Hz)
Compound 37 (ppm)
H-1
3.94 (d, J = 8.4 Hz)
H-2
4.66 (dt, J1 = 9.7 Hz, J2 = 7.3 Hz)
2.25 (dt, J1 = 13.7 Hz, J2 = 7.3 Hz)
4.86 (dt, J1 = 9.4 Hz, J2 = 7.3 Hz)
2.00 (dd, J1 = 13.7 Hz, J2 = 5.5 Hz)
1.87 (ddd, J1 = 13.7 Hz, J2 = 9.4 Hz, J3 = 6.4 Hz)
4.08–4.12 (m)
H-3a
H-3b
H-4
1.75 (ddd, J1 = 11.3 Hz, J2 = 7.0 Hz,J3 = 4.0 Hz)
4.05–4.10a (m)
H-5a
H-5b
3.84 (dd, J1 = 10.0 Hz, J2 = 5.5 Hz)
3.96 (dd, J1 = 9.7 Hz, J2 = 2.4 Hz)
3.83 (dd, J1 = 9.7 Hz, J2 = 5.2 Hz)
4.02 (dd, J1 = 9.7 Hz, J2 = 2.2 Hz)
a
CD3OD solvent.
H-4 would be b with respect to the tetrahydrofuran ring; thus giv-
ing an (S) configuration at the C-4 chiral center and completing the
assignment of absolute (+)(2S,4S) stereochemistry for the major
isomer 36. As expected, for the minor diasteromer 37, irradiation
of the H-2 proton did not produce any enhancement of the H-4
The compound was found to be inactive against DAT (Ki 0.92
lM)
and SERT (Ki 2.49 M) and weakly active (Ki 240 nM) against
l
NET. This data underscores the importance of a benzhydryl group
in potent inhibition of monoamine uptake. In the pursuit of
expanding our SAR studies on pyran-based compounds further,
we decided to substitute the pyran template with a novel di-
substituted tetrahydrofuran moiety. Some modification of synthe-
sis was adopted to synthesize the tetrahydrofuran derivatives. Our
first attempt resulted in synthesis of trans compound 40 which,
however, was inactive against all the three transporters with Ki up-
proton. It suggested that the H-4 proton is faced
a-with respect
to the plane of tetrahydrofuran ring installing an (R) configuration
at the C-4 chiral center. The absolute configuration (ꢀ)(2S,4R) was
thus assigned for the minor isomer.
3. Results and discussion
take inhibition values of 0.94 lM, 1.15 lM, and 1.51 lM for DAT,
SERT, and NET, respectively. The loss of activity might be due to
less than optimal separation of pharmacophoric groups consisting
of the benzhydryl and N-benzyl moieties compared to the pyran
template. With an aim to bring the inter-pharmacophoric feature
distances to an optimum range comparable to pyran derivatives,
we designed tetrahydrofuran compounds with a phenyl ethyl
moiety instead of our benzyl group. Such modification significantly
enhanced activity at all the three transporters. Thus, when com-
pared to 40, compound 41 was about four times more active
against DAT(Ki 260 nM), almost eight times more active against
SERT (Ki 150 nM), and nine times more potent against NET
(Ki 165 nM). It should be noted that similar to the pyran analogs,
compounds 40 and 41 both have (S,S) stereochemistry at the C-2
and C-4 chiral centers, indicating similar stereospecificity for their
interactions with the monoamine transporters. Further, structural
modifications around N-phenylethyl moiety led to synthesis of
compounds 42–44. Substitution of a methoxy group at the para
position in compound 42 also displayed moderate inhibition of
uptake (Ki; 266 nM for DAT, 358 nM for SERT, and 198 nM for
NET) at all the three transporters. Substitution of a p-fluoro group
(compound 43) was tolerated by NET (Ki; 196 nM) but resulted in a
3.1. Structure–activity relationship (SAR)
Our SAR study is designed to investigate: (1) the role of dis-
tances between the phenyl rings of the benzhydryl moiety and
the N-benzyl group for a balanced TUI activity; (2) the importance
of the benzhydryl pharmacophoric feature and effects of introduc-
ing more flexibility in this part of the molecule for TUI activity, and
(3) the effects of bioisosteric replacement of pyran ring with a five
member tetrahydrofuran template on the activity for the mono-
amine transporters. In order to address these questions a series
of novel pyran and tetrahydrofuran derivatives were synthesized,
biologically screened, and conformationally analyzed. As described
below orientation of the benzhydral moiety with respect to the
pyran ring resulted in two distinct conformations. Our goal is to
study the effect of introducing more flexibility in this part of the
molecule.
When compared to D-161, which exhibited potent triple uptake
activity (Table 2), compound 15 had an additional methylene
group in between the benzhydral moiety and the pyran ring. It re-
sulted in the loss of activity for all the three transporters, being
only moderately active with Ki values of 245 nM, 346 nM, and
181 nM for the dopamine transporter (DAT), SERT, and NET respec-
tively. The additional methylene perturbed the distances between
the benzhydryl moiety and the N-benzyl group, the likely reason
for its loss of activity. Introduction of a more flexible ethylene
group in compound 16 gave an interesting biological profile. The
compound was selectively potent against DAT and NET with Ki val-
ues of 45.7 nM and 37.7 nM, respectively and was weak against
SERT (Ki of 473 nM). Thus, compound 16 exhibited a dopamine
norepinephrine reuptake inhibitor (DNRI) profile.
loss of activity for DAT and SERT (Ki; 586 nM and 1.35 lM, respec-
tively). Our previous studies have shown that H-bonding and ionic
interactions at this position brings selective activity against NET
and gives support to our assumption that (2S,4S)-N-phenylethyl
tetrahydrofuran derivatives may interact with monoamine trans-
porters in a similar binding mode as their pyran counterparts.40
Unsubstituted compound 44 was inactive against SERT and
showed weak activity against DAT and NET which is similar to
the corresponding pyran derivative (Ki; 303 nM for DAT, 1577 nM
for SERT, and 274 nM for NET, see Ref. 40). In our further goal to
investigate stereochemical preference in binding of tetrahydrofu-
ran compounds, minor diasteromeric compounds, with (2S,4R) ste-
reochemistry, 45 and 46 were also synthesized. When compared to
Further, to validate the importance of the benzhydryl group for
activity for the monoamine transporters, compound 27 bearing a
single phenyl group on the methylene spacer, was synthesized.

316
H. Sharma et al. / Bioorg. Med. Chem. 22 (2014) 311–324
Table 2
Binding affinity at DAT, SERT, and NET in rat brain
Compound
DAT uptake, Ki, nM, [3H]DAa
SERT uptake, Ki, nM, [3H]5-HTa
NET uptake, Ki, nM [3H]DAa
15 (D-488)
16 (D-487)
27 (D-504)
40 (D-452)
41 (D-470)
42 (D-561)
43 (D-562)
44 (D-560)
45 (D-469)
46 (D-564)
D-185b
245 80
45.7 23.4
920 89.0
943 238
260 62
266 70
586 92
642 161
3690 513
454 55
62.4 5.6
15.9 1.7
42.0 3.3
37.4 3.9
34.6 6.5
31.3 10.6
38.4 2.6
11.2 2.8
32.5 4.3
85.2 8.2
1092 98
346 52
473 126
2496 519
1147 158
150 37
181 41
37.7 10.6
240 38
1511 686
165 26
198 16
196 52
427 80
975 250
739 176
12.6 3.7
29.3 4.8
30.5 7.8
29.3 7.9
54.3 9.8
38.5 6.0
4.20 2.3
6.1 2.4
358 48
1353 234
2046 406
408 138
844 187
16.1 1.6
12.9 1.3
29.1 3.5
14.7 2.1
19.9 1.5
40.1 4.9
58.4 4.0
3.0 0.3
D-411c
D-161b
D-142c
D-199d
D-391c
D-471b
D-478b
D-451b
69.1 19.8
25.0 8.4
12.2 2.4
503 61
8.4 1.7
D-168b
25.5 9.6
158 58
0.69 0.21
Fluoxetine
Reboxetine
>10,000
a
Uptake by DAT, SERT and NET in rat brain tissue was monitored with [3H]DA, [3H]5-HT and [3H]DA as described in Section 2. Results are average SEM of three to eight
independent experiments assayed in triplicate.
b
Previously reported compound.42
Previously reported compound.34
c
Previously reported compound.33
d
their (2S,4S) diasteromeric counterparts compounds 40 and 44,
biological results for 45 and 46 indicated no significant preference
for the either isomer for activity.
hydrophobic features (H), and one cationic (+) feature (see Fig. 2a
and c). The two aromatic features mapped over the benzyl group
and ring A of the benzhydryl group, respectively. One hydrophobic
feature resulted from ring B of the benzhydryl moiety while an-
other hydrophobic region came from the pyran ring. Finally, the
cationic feature superimposed well on the secondary nitrogen.
The inter-pharmacophoric feature distances of the pharmacophore
model 1 are listed in Table 3. Similarly, pharmacophore elucidation
with the extended conformation was also performed (see Supple-
mentary data, Fig. S2). However, we presumed that model 1 result-
ing from the lowest energy conformations was more plausible
since the query included a pharmacophore for the pyran ring
which is a characteristic molecular template of our TUIs; and a cat-
ionic feature which is a common element present in most mono-
amine transporter inhibitors. The computational study was
further extended to include selected pyran and tetrahydrofuran
derivatives synthesized in the present study. Conformational anal-
ysis of 16, the most active compound of the series at DAT and NET,
revealed that its lowest energy conformer assumed an extended
orientation (Supplementary data, Fig. S3) with ring A of the benz-
hydryl moiety swung by 90° to lie in the plane of the pyran ring;
thereby significantly altering the torsions and inter-pharmaco-
phoric feature distances (refer Supplementary data, Table S1).
Furthermore, because of conformational flexibility, no folded con-
formation, which was predominantly present in the pyran TUI
compounds, was observed. It could imply that DAT and NET can
accommodate inhibitors with multiple binding modes, including
those with relatively extended conformations. On the other hand
this may not be the case for SERT which appears to prefer inhibi-
tors with ‘folded’ conformation. This could be one of the reasons
why GBR 12909, a known selective DAT blocker, which is reported
to adopt several flexible conformations, was most active for DAT
(Ki 16.2 nM), followed by NET (Ki 48.5 nM), but only moderately ac-
tive (Ki 198.0 nM), against SERT.41 As expected, compound 16
which was identified as a DNRI could not be accommodated into
TUI pharmacophore model 1, developed based on ‘folded
conformations’.
3.2. Computational analysis
A pharmacophore model of monoamine triple uptake inhibitors
was built using a training set of ten potent pyran compounds
(Fig. 1) which we have reported in our previous studies.34,37,38,42
The training set consisted of compounds with diverse structural
features and included both 3,6-di- and tri-substituted classes of
pyran derivatives. Furthermore, the training set compounds exhib-
ited balanced potencies (Table 2) against all the three transporters
and thus are representative of the TUIs developed in our labora-
tory. Analysis of conformations within dE of 3 kcal/mol revealed
that pyran compounds in the training set (Fig. 1) existed in two
distinct conformations. The lowest energy conformation of each
molecule adopted a ‘folded’ orientation (Fig. 2a) in which ring A
of the benzhydryl moiety was at 90° to the plane of the pyran ring
and lied parallel to the N-benzyl group. It was observed that for all
compounds, this conformation was favored and occurred predom-
inantly. The next distinct conformations were within an energy
difference of 2.3–2.8 kcal/mol from their respective lowest energy
conformations. In this orientation, compounds assumed an
extended conformation in which ring A of the benzhydryl group
was tilted to lie in the plane of the pyran ring (see Supplementary
data, Fig. S2). Thus, for this series of compounds, the orientation of
the benzhydryl moiety with respect to the pyran ring resulted in
two different conformations. Since a bioactive conformation does
not always need to be of lowest energy, both conformations of
the training set molecules were used for pharmacophore modeling.
Pharmacophore elucidation with the lowest energy conformations
gave 107 queries and top ten were considered for further analysis.
Based on our structure–activity relationship (SAR) data, the
number of coverage and degree of overlap, the second-ranked
query (RRHH+) was selected as the representative pharmacophore.
The query (model 1) consisted of two aromatic features (R), two

H. Sharma et al. / Bioorg. Med. Chem. 22 (2014) 311–324
317
Figure 2. (a) Pharmacophore model 1 resulting from lowest energy folded conformations of pyran derivatives in the training set; (b) common pharmacophore model 2
resulting from lowest energy folded conformations of pyran and tetrahydrofuran derivatives. The pharmacophore color coding is represented as: green for hydrophobic;
brown for aromatic; blue for cationic. Atoms in ligands are represented as: O, red; N, blue; C, gray; (c) pharmacophore features of model 1; (d) pharmacophore features of
model 2.
In the light of the development of novel tetrahydrofuran deriv-
Table 3
atives with moderate TUI profile, conformational analysis of com-
pound 41 was also performed. We observed that similar to the
pyran derivatives, 41 also predominantly, including the minimum
energy, adopted a ‘folded’ conformation. Thus, a ‘folded’ orienta-
tion with an optimum distance between the benzhydryl moiety
and the N-benzyl group is one of the critical requirements for this
series of compounds to exhibit a balanced activity against all three
transporters. In an attempt to find a possible reason for its dimin-
ished (while transporter-balanced) activity with respect to the pyr-
an compounds in the training set, we decided to map compound 41
over the pyran pharmacophore. A revised common pharmacophore
model was attempted with 12 compounds using ten potent pyran
derivatives in the training set, a moderately active tetrahydrofuran
derivative 41, and an inactive compound 40. Pharmacophore
Inter-pharmacophore feature distances of pharmacophore model 1 and 2
Pharmacophore features
Model 1
Model 2
distances (Å)
distances (Å)
Distances (Å)
PF1 aromatic/hydrophobic (ring C)–PF2
aromatic (ring A)
5.07
5.19
PF1 aromatic–PF3 hydrophobic (ring B)
PF1 aromatic–PF4 hydrophobic (pyran)
PF1 aromatic–PF5 cationic
PF2 aromatic–PF3 hydrophobic
PF2 aromatic–PF4 hydrophobic
PF2 aromatic–PF5 cationic
PF3 hydrophobic–PF4 hydrophobic
PF3 hydrophobic–PF5 cationic
PF4 hydrophobic–PF5 cationic
9.03
5.60
3.34
5.15
4.45
3.37
5.51
6.15
2.41
7.84
4.48
2.90
5.15
4.46
4.81
4.73
5.97
1.74

318
H. Sharma et al. / Bioorg. Med. Chem. 22 (2014) 311–324
elucidation resulted in 66 queries and the representative pharma-
cophore (model 2) is shown in Figure 2b and d. Model 2 consisted
of five (RHHH+) features which were mostly similar to those ob-
served in model 1, except that the aromatic feature of the benzyl
group in model 1 was substituted with a hydrophobic feature in
model 2. Comparison of the two models (Table 3) further revealed
that the optimum separation between the key features was per-
turbed which might explain the diminished activity of compound
41 with respect to their pyran counterparts. However, tetrahydro-
furan derivative 41, included in model 2, retained the required
conformation and the essential pharmacophoric features of our
pyran-based compounds giving support to their further investiga-
tion as potential novel TUIs.
bromide (12.2 mL, 141.2 mmol) was added slowly via a syringe.
The ice-bath was removed and the resulting solution was stirred
at room temperature for 24 h. Next, the reaction mixture was
cooled to 0 °C and quenched by slow addition of methanol
(5 mL), followed by water (150 mL). The organic layer was sepa-
rated and the aqueous layer was extracted with ethyl ether
(2 ꢁ 100 mL). The organic layers were combined and washed with
brine (100 mL). The organic layer was separated again, dried over
Na2SO4, and concentrated over rotary evaporator. The crude
product was sufficiently pure (16.4 g, 83%) and used in the next
step without further purification. 1H NMR (400 MHz, CDCl3):
d
7.12–7.38 (m, 10H), 5.74 (ddd, J = 17.0, 9.8, 3.5 Hz, 1H),
4.80–5.17 (m, 2H), 4.03 (t, J = 7.9 Hz, 1H), 2.84 (t, J = 7.6 Hz, 2H).
5.1.2. Pent-4-ene-1,1-diyldibenzene (2b)
4. Conclusion
Diphenylmethane (15.0 g, 89.16 mmol) in anhydrous THF
(174 mL) was reacted with n-BuLi (144.5 mL, 222.9 mmol) in anhy-
drous THF (1.6 M) and allyl bromide (9.98 mL, 98.45 mmol) follow-
ing procedure A. The crude product was sufficiently pure (17.3 g,
87%) and used in the next step without further purification. 1H
NMR (400 MHz, CDCl3): d 6.90–7.72 (m, 10H), 5.61–6.15 (m, 1H)
4.91–5.07 (m, 2H), 3.50–4.20 (m, 1H), 1.73–2.59 (m, 4H).
In conclusion, in this study we have generated a TUI pharmaco-
phore model revealing features important for inhibitors to exhibit
a balanced activity against DAT, SERT, and NET. In particular, a
‘folded’ conformation was found common to the active pyran com-
pounds in the training set and was crucial to triple uptake inhibi-
tory activity. Furthermore, the distances between the benzhydryl
moiety and the N-benzyl group as well as the orientation of the
secondary nitrogen were also important for TUI activity. We have
validated these findings by synthesizing and testing novel pyran
analogs. This study has revealed conformational preference of
inhibitors for DAT/NET over SERT and suggests that DAT/NET could
accommodate flexible ligands with multiple binding modes; thus
providing insights to guide the design of novel TUI as well as selec-
tive transporter blockers. The present work has also resulted in the
discovery of a new series of asymmetric tetrahydrofuran deriva-
tives as novel TUIs. Interestingly, the highest TUI activity was
exhibited in a stereochemical preference similar to pyran TUI for
example, D-161.
5.1.3. Procedure B. 2-(2,2-Diphenylethyl)oxirane (3a)
m-CPBA (29.0 g, 116.67 mmol, 70% wt/wt in water) was added
to a solution of 2a (16.2 g, 77.77 mmol) in DCM (173 mL) at 0 °C.
The ice-bath was removed and the resulting solution was stirred
at room temperature for 24 h. Next, the reaction mixture was
cooled to 0 °C and quenched with saturated NaHCO3 (100 mL).
The organic layer was separated and the aqueous layer was ex-
tracted with additional DCM (2 ꢁ 50 mL). The organic layers were
combined and washed with brine (100 mL). The organic layer was
separated, dried over Na2SO4, and concentrated over rotary evapo-
rator. The crude product was purified via gradient silica gel column
chromatography using 10–50% ethyl acetate in hexanes to obtain
pure racemic epoxide 3a (16.7 g, 96%). 1H NMR (400 MHz, CDCl3):
d 7.10–7.45 (m, 10H), 4.23 (t, J = 7.9 Hz, 1H), 2.78–2.96 (m, 1H),
2.70 (t, J = 4.7 Hz, 1H), 2.44 (dd, J = 4.7, 2.6 Hz, 1H), 2.21–2.36 (m,
2H)
5. Experimental
5.1. Chemistry
Reagents and solvents were obtained from commercial suppli-
ers and used as received unless otherwise indicated. Anhydrous
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 (silica gel
60 F254) were purchased from EM Science and were visualized
with UV light or by treatment with either phosphomolybdic acid
(PMA) or ninhydrin. Flash chromatography was carried out on
5.1.4. 2-(3,3-Diphenylpropyl)oxirane (3b)
m-CPBA (28.52 g, 115.60 mmol, 70% wt/wt in water) was re-
acted with
a solution of 2b (17.0 g, 76.47 mmol) in DCM
(170 mL) using procedure B. The crude product was purified via
gradient silica gel column chromatography using 1–50% ethyl ace-
tate in hexanes to obtain 17.5 g (96%) of pure racemic epoxide 3b.
1H NMR (400 MHz, CDCl3): d 1H NMR (400 MHz, CDCl3): d 6.90–
7.72 (m, 10H), 3.98 (t, J = 8.0 Hz, 1H), 2.84–3.05 (m, 1H), 2.74
(dd, J = 5.2, 3.6 Hz, 1H), 2.44 (dd, J = 4.8, 2.8 Hz, 1H), 1.98–2.42
(m, 2H), 1.34–1.79 (m, 2H).
Baker Silica Gel 40 l
M. 1H NMR and 13C spectra were routinely
recorded with a Varian 400/500 spectrometer operating at 400/
500 and 100/125 MHz, respectively. The NMR solvent used was
either CDCl3 or CD3OD or 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 were within
0.4% of the theoretical value. Optical rotations were recorded on a
Perkin–Elmer 241 polarimeter.
5.1.5. Procedure C. (R)-2-(2,2-Diphenylethyl)oxirane (4a)
(R,R)-(ꢀ)-N,N0-Bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohex-
ane diaminocobalt(II) (1.0 g, 1.52 mmol) was taken in a round bot-
tom flask and dissolved in DCM (60 mL). After the addition of acetic
acid (180 lL, 3.12 mmol), the mixture was stirred at room temper-
ature for 1 h. Then, the solvent was removed on a rotary evaporator
under reduced pressure and the residue was dried in air thor-
oughly for 2–3 days to obtain the activated catalyst. This solid res-
idue (0.30 g, 0.46 mmol) was added to the racemic epoxide 3a
(20.4 g, 91.03 mmol) and the reaction mixture was cooled down
in an ice bath. Next, THF (1.15 mL, 63.72 mmol) and H2O
(1.15 mL, 62.72 mmol) were added dropwise and the ice bath
was removed. The reaction mixture was stirred at room tempera-
ture for 21 days following which the enantio-enriched epoxide
was separated from the diol (5a) via gradient silica gel column
5.1.1. Procedure A. But-3-ene-1,1-diyldibenzene (2a)
To an oven-dried round bottom flask containing magnetic stir
bar, diphenylmethane (16.0 g, 117.67 mmol) was taken and dis-
solved in anhydrous THF (140 mL) under a continuous flow of
nitrogen. After cooling the solution to 0 °C, n-BuLi (181.8 mL,
294.17 mmol) in anhydrous THF (1.6 M) was slowly added. The
ice-bath was then removed, and the mixture was stirred at room
temperature for 1 h. The mixture was cooled to 0 °C again and allyl

H. Sharma et al. / Bioorg. Med. Chem. 22 (2014) 311–324
319
chromatography using 1–100% ethyl acetate in hexanes. To the
enantio-enriched epoxide (13.76 g, 61.34 mmol), additional
amount of the activated catalyst (0.095 g, 0.15 mmol), H2O
(0.38 mL, 20.72 mmol), and THF (0.38 mL, 20.72 mmol) were
added and the mixture was stirred for additional 7 days at room
temperature. The residue was purified by gradient silica gel col-
umn chromatography using 1–5% ethyl acetate in hexanes to give
compound 4a (9.96 g, 46%) and compound 5a (9.98 g, 47%).
of N2. After cooling the solution to 0 °C, excess of ethyl vinyl ether
(29 mL) was added. The ice-bath was removed and stirring was
continued for 4–5 h under a nitrogen atmosphere until TLC showed
maximum conversion. The reaction mixture was concentrated un-
der reduced pressure on a rotary evaporator at room temperature.
The crude product was dissolved in 5% ethyl acetate in hexanes and
filtered through a pad of basic alumina quickly. The filtrate was
concentrated under reduced pressure at room temperature to give
intermediate 7a (0.7 g, 77%). The starting material was recovered
from the alumina pad by eluting with ethyl acetate which was then
concentrated and recycled again.
½
a 2D5 +26.6 (c 1, MeOH). 1H NMR for (R)-4a (400 MHz, CDCl3):
ꢂ
d 7.10–7.45 (m, 10H), 4.23 (t, J = 7.9 Hz, 1H), 2.78–2.96 (m, 1H), 2.70
(t, J = 4.7 Hz, 1H), 2.44 (dd, J = 4.7, 2.6 Hz, 1H), 2.21–2.36 (m, 2H).
5.1.6. R)-2-(3,3-Diphenylpropyl)oxirane (4b)
5.1.10. (S)-(4-(Vinyloxy)oct-7-ene-1,1-diyl)dibenzene (7b)
Alcohol 9b (1.07 g, 3.83 mmol), mercury(II) trifluoroacetate
(0.12 g, 0.382 mmol), and excess ethyl vinyl ether (36 mL) were re-
acted following procedure E to give intermediate 7b (0.87 g, 74%)
which was immediately taken to the next step.
(R,R)-(ꢀ)-N,N’-Bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohex-
ane diaminocobalt(II) (1.0 g, 1.52 mmol), acetic acid (180 lL,
3.12 mmol) in DCM (60 mL) was reacted following procedure C
to obtain the activated catalyst. This solid residue (0.24 g,
0.37 mmol) was added to the racemic epoxide 3b (17.4 g,
73.01 mmol) and reaction was continued using procedure C. The
residue thus obtained was purified by gradient silica gel column
chromatography using 1–5% ethyl acetate in hexanes to give com-
5.1.11. Procedure F. (S)-2-(2,2-Diphenylethyl)-3,4-dihydro-2H-
pyran (8a)
The vinyl ether 7a (1.58 g, 5.4 mmol) was immediately dis-
solved in anhydrous benzene (59 mL) under a continuous flow of
N2 and Grubb’s catalyst (1st generation, 0.223 g, 0.27 mmol) was
added. The solution mixture was then refluxed at 90 °C for 2 h.
The reaction mixture was then cooled and the solvent was re-
moved under reduced pressure on a rotary evaporator. The black
residue was purified by gradient column chromatography using
1–10% ethyl acetate in hexanes to obtain the cyclic olefin 8a as a
pound 4b (8.0 g, 46%) and compound 5b (8.18 g, 47%). ½a D25
ꢂ
+3.4
(c 1, MeOH). 1H NMR for (R)-4b (400 MHz, CDCl3): d 1H NMR
(400 MHz, CDCl3): d 6.90–7.72 (m, 10H), 3.98 (t, J = 8.0 Hz, 1H),
2.84–3.05 (m, 1H), 2.74 (dd, J = 5.2, 3.6 Hz, 1H), 2.44 (dd, J = 4.8,
2.8 Hz, 1H), 1.98–2.42 (m, 2H), 1.34–1.79 (m, 2H).
5.1.7. Procedure D. (S)-1,1-Diphenylhept-6-en-3-ol (6a)
In an oven-dried round bottom flask equipped with magnetic
stir-bar, enantiomerically enriched (R)-epoxide 4a (6.77 g,
30.18 mmol), and copper(I) iodide (0.58 g, 3.05 mmol) were taken
and dissolved in anhydrous THF (64 mL) under a continuous flow
of N2. After cooling the solution to ꢀ78 °C, allylmagnesium chlo-
ride (18.75 mL, 2 M solution in THF, 37.12 mmol) was added
dropwise. The reaction mixture was slowly allowed to reach
room temperature and stirred overnight under a continuous flow
of N2. The reaction mixture was then cooled to 0 °C and quenched
by the addition of saturated NH4Cl solution (50 mL) and extracted
with ethyl acetate (3 ꢁ 75 mL). The combined organic layer was
washed with water and brine, dried over Na2SO4, and concen-
trated under reduced pressure on a rotary evaporator. The crude
residue was purified by gradient silica gel column chromatogra-
phy using 2–50% ethyl acetate in hexanes to give compound 6a
white solid (1.35 g, 95%). ½a D25
ꢂ
+67.0 (c 1, MeOH). 1H NMR
(400 MHz, CDCl3): d 6.96–7.44 (m, 10H), 6.29 (d, J = 5.9 Hz, 1H),
4.41–4.62 (m, 1H), 4.18 (dd, J = 10.3, 5.6 Hz, 1H), 3.42–3.62 (m,
1H), 2.19–2.36 (m, 1H), 2.04–2.17 (m, 1H), 1.80–1.96 (m, 2H),
1.66–1.77 (m, 1H), 1.46–1.62 (m, 1H).
5.1.12. (S)-2-(3,3-Diphenylpropyl)-3,4-dihydro-2H-pyran (8b)
The vinyl ether 7b (1.58 g, 5.2 mmol) was immediately reacted
with Grubb’s catalyst (1st generation, 0.212 g, 0.26 mmol) in anhy-
drous benzene (60 mL) following procedure F. The black residue
was purified by gradient column chromatography using 1–10%
ethyl acetate in hexanes to obtain the cyclic olefin 8b as white solid
(1.37 g, 96%). ½a D25
ꢂ
+30.3 (c 1, MeOH). 1H NMR (400 MHz, CDCl3): d
6.69–7.38 (m, 10H), 6.34 (d, J = 5.9 Hz, 1H), 4.50–4.69 (m, 1H), 3.89
(t, J = 7.9 Hz, 1H), 3.69–3.83 (m, 1H), 1.29–2.39 (m, 8H).
(7.5 g, 93%) as a colorless syrup. ½a D25
ꢂ
ꢀ17.6 (c 1, MeOH). 1H
NMR (400 MHz, CDCl3):
d
7.05–7.40 (m, 10H), 5.78 (ddd,
5.1.13. Procedure G. 6-(2,2-Diphenylethyl)tetrahydro-2H-pyran-
3-ol (mixture of 9a and 10a)
J = 17.0, 9.9, 3.2 Hz, 1H), 4.84–5.07 (m, 2H), 4.23 (dd, J = 10.0,
5.8 Hz, 1H), 3.36–5.57 (m, 1H), 2.04–2.32 (m, 4H), 1.52–1.65
(m, 1H), 1.42 (d, J = 4.1 Hz, 1H).
Compound 8a (1.353 g, 5.12 mmol) was taken in an oven-dried
round bottom flask equipped with magnetic stir-bar and dissolved
in anhydrous THF (20 mL) under a continuous flow of N2. After
cooling the solution to 0 °C, 9-BBN (25.6 mL, 0.5 M solution in
THF, 12.8 mmol) was added slowly. The ice-bath was removed
and the reaction mixture was stirred overnight at room tempera-
ture. Then, the reaction mixture was cooled to 0 °C, quenched by
the addition of ethanol (8 mL) and stirred for 10 min. Next,
aqueous 10% NaOH solution (8 mL) and 30% H2O2 (7.3 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 (50 mL) and extracted with ethyl acetate (3 ꢁ 50 mL).
The combined organic layer was washed with brine (100 mL), the
organic layer was separated and dried over Na2SO4. The solvent
was removed under reduced pressure on a rotary evaporator. The
crude residue was purified by column chromatography using 25%
ethyl acetate in hexanes to give compounds 9a (major) and 10a
(minor) (1.36 g, 95%) as a mixture. NMR data for major isomer
9a: 1H NMR (400 MHz, CDCl3): d 7.05–7.35 (m, 10H), 4.20 (dd,
J = 10.0, 5.9 Hz, 1H), 3.92 (ddd, J = 8.8, 4.7, 1.8 Hz, 1H), 3.32–3.63
5.1.8. (S)-1,1-Diphenyloct-7-en-4-ol (6b)
Epoxide 4b (8.0 g, 33.57 mmol) and CuI (0.64 g, 3.35 mmol) in
anhydrous THF (85 mL) was reacted with reacted with allyl mag-
nesium chloride (84.0 mL, 1 M solution in THF, 84.0 mmol) using
procedure D. The syrupy residue obtained was purified by gradient
silica gel column chromatography using a mixture of 10–25% ethyl
acetate in hexanes to afford corresponding allylic alcohol 6b as col-
orless syrup (7.99 g, 84%). ½a D25
ꢂ
+5.8 (c 1, MeOH). 1H NMR
(400 MHz, CDCl3): d 7.00–7.40 (m, 10H), 5.64–5.91 (m, 1H),
4.71–5.17 (m, 2H), 3.88 (t, J = 7.6 Hz, 1H), 3.46–3.72 (m, 1H),
1.80–2.39 (m, 4H), 1.19–1.71 (m, 4H).
5.1.9. Procedure E. (S)-(3-(Vinyloxy)hept-6-ene-1,1-
diyl)dibenzene (7a)
The alcohol 6a (0.833 g, 3.13 mmol) and mercury(II) trifluoro-
acetate (0.1 g, 0.313 mmol) were taken in an oven-dried round bot-
tom flask equipped with magnetic stir bar under a continuous flow

320
H. Sharma et al. / Bioorg. Med. Chem. 22 (2014) 311–324
(m, 1H), 2.85–3.05 (m, 2H), 2.67 (br s, 1H), 2.05–2.25 (m, 2H),
1.90–2.01 (m, 1H), 1.11–1.40 (m, 2H).
evaporator. The crude product was purified by gradient silica gel
column chromatography using 1–10% ethyl acetate in hexanes to
afford compound 13a (1.25 g, 86%). ½a D25
ꢂ
ꢀ24.4 (c 1, MeOH). 1H
5.1.14. 6-(3,3-Diphenylpropyl)tetrahydro-2H-pyran-3-ol
(mixture of 9b and 10b)
NMR (400 MHz, CDCl3): d 7.05–7.50 (m, 10H), 4.26 (dd, J = 10.6,
5.3 Hz, 1H), 3.89–4.07 (m, 1H), 3.32–3.62 (m, 2H), 2.90–3.20 (m,
1H), 2.06–2.32 (m, 2H), 1.86–2.04 (m, 1H), 1.58–1.80 (m, 2H),
1.38–1.54 (m, 1H).
Intermediate 8b (0.746 g, 2.68 mmol) in anhydrous THF (11 mL)
was reacted with 9-BBN (13.4 mL, 0.5 M solution in THF,
6.70 mmol) according to procedure G. The crude residue was puri-
fied by column chromatography using 25% ethyl acetate in hexanes
to yield compounds 9b (major) and 10b (minor) (0.67 g, 84%) as a
mixture. NMR data for major isomer 9b: 1H NMR (400 MHz,
5.1.18. (2R,5S)-5-Azido-2-(3,3-diphenylpropyl)tetrahydro-2H-
pyran (13b)
Intermediate 11b (1.06 g, 2.81 mmol), sodium azide (0.92 g,
14.17 mmol) in anhydrous DMF (20 mL) was reacted according to
procedure I. The crude product was purified by gradient silica gel
column chromatography using a mixture of 1–10% of ethyl acetate
CDCl3):
d 7.05–7.37 (m, 10H), 3.85–3.97 (m, 1H), 3.83 (t,
J = 7.9 Hz, 1H), 3.49–3.63 (m, 1H), 3.10–3.21 (m, 1H), 3.01 (t,
J = 10.6 Hz, 1H), 2.48 (s, 1H), 2.13–2.32 (m, 2H), 1.13–1.53 (m, 5H).
in hexanes to afford compound 13b (0.81 g, 88%). ½a D25
ꢀ8.0 (c 1,
ꢂ
5.1.15. Procedure H. (3R,6S)-6-(2,2-Diphenylethyl)tetrahydro-
2H-pyran-3-yl methanesulfonate (11a)
MeOH). 1H NMR (400 MHz, CDCl3): d 7.05–7.48 (m, 10H), 3.91–
4.01 (m, 1H), 3.86 (t, J = 7.8 Hz, 1H), 3.45–3.63 (m, 2H), 3.18–3.36
(m, 1H), 2.17–2.34 (m, 1H), 1.90–2.14 (m, 2H), 1.67–1.82 (m,
1H), 1.30–1.66 (m, 4H).
The mixture of compounds 9a and 10a (1.94 g, 5.30 mmol) was
dissolved in anhydrous DCM (46 mL) following which triethyl-
amine (1.48 mL, 10.6 mmol) was added at 0 °C under a continuous
flow of nitrogen. Then, methanesulfonyl chloride (0.53 mL,
6.89 mmol) was added dropwise. Thereafter, the ice-bath was re-
moved and the mixture was stirred for 2 h at room temperature.
The reaction mixture was quenched by the addition of saturated
NaHCO3 (30 mL) and extracted with DCM (3 ꢁ 40 mL). The organic
layers were combined and washed with brine (100 mL). The organ-
ic layer was separated, dried over Na2SO4, and the solvent was
removed under reduced pressure on a rotary evaporator. The iso-
mers were separated from the crude product by gradient silica
gel column chromatography using 2–50% of ethyl acetate in hex-
anes as eluent to first obtain the trans compound 11a (1.71 g,
69%) followed by the cis compound 12a (0.37 g, 15%). NMR data
5.1.19. Procedure J. (3S,6S)-6-(2,2-Diphenylethyl)tetrahydro-2H-
pyran-3-amine (14a)
The azide 13a (0.887 g, 2.80 mmol) was dissolved in methanol
(59 mL) and the mixture was hydrogenated (1 atm) in the presence
of 10% Pd-C (88 mg, 10 wt %) for overnight. Then, the reaction mix-
ture was filtered through a short bed of celite, and the filtrate was
concentrated under reduced pressure on a rotary evaporator to af-
ford the amine 14a (0.79 g, 98%) as an off-white solid. The product
was sufficiently pure and used in the next step without further
purification. ½a D25
ꢂ
+24.6 (c 1, MeOH). 1H NMR (400 MHz, CDCl3): d
8.50 (br s, 2H), 6.75–7.65 (m, 10H), 3.98–4.46 (m, 2H), 3.20–3.57
(m, 2H), 2.80–3.10 (m, 1H), 1.80–2.48 (m, 4H), 1.28–1.72 (m, 2H).
for the major isomer 11a: ½a D25
ꢂ
+40.6 (c 1, MeOH). 1H NMR
(400 MHz, CDCl3): d 7.16–7.45 (m, 10H), 4.53–4.71 (m, 1H), 4.20
(dd, J = 10.0, 5.9 Hz, 1H), 4.13 (ddd, J = 11.1, 5.0, 2.1 Hz, 1H), 3.19
(t, J = 10.6 Hz, 1H), 2.92–3.08 (m, 4H), 2.06–2.33 (m, 3H), 1.72–
1.83 (m, 1H), 1.57–1.68 (m, 1H), 1.43–1.54 (m, 1H).
5.1.20. (3S,6R)-6-(3,3-Diphenylpropyl)tetrahydro-2H-pyran-3-
amine (14b)
The azide 13b (0.80 g, 2.70 mmol) was hydrogenated using pro-
cedure J to afford the amine 14b (0.71 g, 97%) as an off-white solid.
The product was sufficiently pure and used in the next step with-
5.1.16. (3R,6R)-6-(3,3-Diphenylpropyl)tetrahydro-2H-pyran-3-yl
methanesulfonate (11b)
out further purification. ½a D25
ꢂ
+3.6 (c 1, MeOH). 1H NMR (400 MHz,
CDCl3): d 8.40 (br s, 2H), 6.95–7.45 (m, 10H), 4.13 (d, J = 12.6 Hz,
1H), 3.81 (t, J = 7.6 Hz, 1H), 3.31–3.60 (m, 2H), 3.05–3.30 (m, 1H),
1.88–2.38 (m, 3H), 1.24–1.86 (m, 5H).
The mixture of compounds 9b and 10b (1.25 g, 3.31 mmol), tri-
ethylamine (0.92 mL, 6.62 mmol), and methanesulfonyl chloride
(0.33 mL, 4.30 mmol) in anhydrous DCM (28 mL) was reacted
using procedure H to yield trans compound 11b (1.06 g, 67%)
which eluted first followed by the cis compound 12b (0.26 g,
5.1.21. Procedure K. 4-((((3S,6S)-6-(2,2-
Diphenylethyl)tetrahydro-2H-pyran-3-yl)amino)methyl)phenol
(15)
4-Hydroxy-benzaldehyde (66 mg, 0.57 mmol) was dissolved in
a mixture of 1,2-dichloroethane (3 mL)/methanol (1 mL) and gla-
cial acetic acid (32 lL, 0.57 mmol) was added. Then, amine 14a
(0.107 g, 0.38 mmol) was added and the solution stirred at room
temperature for 2 h following which Na(OAc)3BH (0.12 g,
0.57 mmol) was added. The resulting mixture was then stirred at
room temperature for 24 h, cooled to 0 °C, diluted with DCM
(20 mL) and quenched by the addition of water (30 mL). The organ-
ic layer was separated and the aqueous layer was extracted with
additional DCM (3 ꢁ 30 mL). The organic layers were combined,
dried over Na2SO4, and concentrated under reduced pressure on
a rotary evaporator. The crude residue was purified by gradient sil-
ica gel column chromatography using 1–10% methanol in DCM as
17%). NMR data for the major isomer 11b: ½a D25
ꢂ
+23.2 (c 1, MeOH).
1H NMR (400 MHz, CDCl3): d 7.10–7.35 (m, 10H), 4.50–4.66 (m,
1H), 4.10 (ddd, J = 11.1, 4.91, 2.34 Hz, 1H), 3.85 (t, J = 7.6, 1H),
3.28 (t, J = 10.5 Hz, 1H), 3.17–3.27 (m, 1H), 2.97 (s, 3H), 2.14–
2.34 (m, 2H), 1.96–2.12 (m, 1H), 1.59–1.81 (m, 2H), 1.26–1.55
(m, 3H). NMR data for the minor isomer 12b: ½a D25
ꢀ13.9 (c 1,
ꢂ
MeOH). 1H NMR (400 MHz, CDCl3): d 7.06–7.42 (m, 10H), 4.70 (t,
J = 19.9 Hz, 1H), 4.04–4.20 (m, 1H), 3.81–3.91 (m, 1H), 3.53 (d,
J = 13.2 Hz, 1H), 3.20–3.33 (m, 1H), 2.98 (s, 3H3H), 1.96–2.38 (m,
2H), 1.20–1.88 (m, 6H).
5.1.17. Procedure I. (2S,5S)-5-Azido-2-(2,2-
diphenylethyl)tetrahydro-2H-pyran (13a)
Compound 11a (1.70 g, 4.72 mmol) was dissolved in anhydrous
DMF (25 mL) and sodium azide (1.54 g, 23.62 mmol) was added at
once. The mixture was then stirred overnight at 80 °C under a con-
tinuous flow of N2, cooled to room temperature, and quenched
with water (200 mL). The solution was extracted with diethyl ether
(3 ꢁ 60 mL), the organic layers were combined and washed with
brine (100 mL). The organic layer was separated, dried over Na2-
the eluent to afford compound 15 (68 mg, 46%). ½a D25
ꢂ
+20.6 (c 1,
MeOH). 1H NMR (400 MHz, CDCl3): d 6.98–7.40 (m, 12H), 6.81 (d,
J = 8.5 Hz, 2H), 4.20 (dd, J = 10.6, 5.3 Hz, 1H), 3.94 (dd, J = 41.6,
12.6 Hz, 2H), 3.58 (br s, 1H), 3.28–3.46 (m, 2H), 2.90–3.15 (m,
2H), 1.90–2.34 (m, 4H), 1.45–1.77 (m, 2H). 13C NMR (100 MHz,
CDCl3): d 157.8, 144.6, 144.0, 131.2, 128.4, 128.3, 127.9, 127.5,
126.2, 126.1, 121.7, 116.0, 75.8, 66.7, 50.5, 48.6, 46.2, 41.3, 25.7,
SO4, and concentrated under reduced pressure on
a rotary

H. Sharma et al. / Bioorg. Med. Chem. 22 (2014) 311–324
321
24.7. The free base was converted into corresponding hydrochlo-
ride salt. Mp = 180–185 °C. Anal. (C26H29NO2ꢃHCl) C, H, N.
1.34–1.41 (m, 1H), 1.45–1.51 (m, 1H), 1.67–1.74 (m, 1H), 2.06–
2.12 (m, 1H), 2.66 (dd, J = 13.6, 5.6 Hz, 1H), 2.88 (dd, J = 13.6,
6.4 Hz, 1H), 3.10 (t, J = 10.4 Hz, 1H), 3.40–3.49 (m, 1H), 3.64–3.77
(m, 1H), 4.00 (ddd, J = 7.2, 4.8, 2.4 Hz, 1H), 7.18–7.32(m, 5H).
5.1.22. 4-((((3S,6R)-6-(3,3-Diphenylpropyl)tetrahydro-2H-
pyran-3-yl)amino)methyl)phenol (16)
Amine intermediate 14b (0.112 g, 0.38 mmol) and 4-hydroxy
benzaldehyde (66 mg, 0.57 mmol) were dissolved in DCM (3 mL).
5.1.27. (3R,6S)-6-Benzyltetrahydro-2H-pyran-3-yl
methanesulfonate (23)
MeOH (1 mL) and AcOH (33
l
L) were then added and reaction stir-
To an ice cooled stirred mixture of compounds 21 and 22 (0.5 g,
2.60 mmol) and triethylamine (0.72 mL, 5.20 mmol) in anhydrous
DCM (15 mL) was added methanesulfonyl chloride (0.3 mL,
3.90 mmol) and reaction continued following procedure H. The
residue was purified by column chromatography using 25% ethyl
acetate in hexanes to elute the trans compound 23 (0.48 g, 69%)
first as a white solid followed by the cis compound 24 (95 mg,
14%) as a white solid. Spectral data for 23: 1H NMR (400 MHz,
CDCl3): d 1.41–1.52 (m, 1H), 1.62–1.72 (m 1H), 1.76–1.82 (m,
1H), 2.22–2.31 (m, 1H), 2.67 (dd, J = 14.0, 5.6 Hz, 1H), 2.88 (dd,
J = 13.6, 6.4 Hz, 1H), 3.01 (s, 3H), 3.32 (t, J = 10.4 Hz, 1H), 3.45–
3.53 (m, 1H), 4.13 (ddd, J = 7.6, 4.8, 2.4 Hz, 1H), 4.63 (ddd,
J = 15.2, 10.8, 4.8 Hz, 1H), 7.17–7.32 (m, 5H).
red for 2 h. Na(OAc)3BH (0.115 g, 0.545 mmol) was thereafter
added and reaction continued following procedure K. The crude
residue thus obtained was purified by gradient silica gel column
chromatography using 1–10% methanol in DCM as the eluent to af-
ford compound 16 (68 mg, 47%). ½a D25
ꢀ4.5 (c 1, MeOH). MS (ESI):
ꢂ
m/z 402.4 [M+H]+. 1H NMR (400 MHz, CDCl3): d 6.91–7.40 (m,
12), 6.72 (d, J = 7.9 Hz, 2H), 5.03 (br s, 3H), 3.84–4.42 (m, 3H),
3.80 (t, J = 7.6 Hz, 1H), 3.32–3.50 (m, 1H), 2.94–3.30 (m, 2H),
1.82–2.26 (m, 3H), 1.18–1.80 (m, 5H). 13C NMR (100 MHz, CDCl3):
d 157.4, 144.8, 131.6, 128.4, 127.8, 126.1, 116.3, 78.4, 66.6, 51.8,
51.1, 49.0, 34.0, 31.3, 25.5, 24.3. The free base was converted
into corresponding hydrochloride salt. Mp = 210–218 °C. Anal.
(C27H31NO2.1.4HCl, 0.7H2O) C, H, N.
5.1.28. (2S,5S)-5-Azido-2-benzyltetrahydro-2H-pyran (25)
A stirred solution of compound 23 (0.45 g, 1.66 mmol) in DMF
(10 mL) was reacted with sodium azide (0.54 g, 8.30 mmol) using
procedure I. The crude residue thus obtained was purified by col-
umn chromatography using 5% ethyl acetate in hexanes to give
compound 25 (0.3 g, 83%) as a white solid. 1H NMR (400 MHz,
CDCl3): d 1.46–1.54 (m, 1H), 1.60–1.79 (m, 2H), 2.00 (dt, J = 8.8,
3.2 Hz, 1H), 2.68 (dd, J = 14.0, 6.4 Hz, 1H), 2.95 (dd, J = 13.6,
6.4 Hz, 1H), 3.48–3.60 (m, 3H), 3.99 (dd, J = 10.8, 2.4 Hz, 1H),
7.18–7.32 (m, 5H).
5.1.23. (S)-1-Phenylhex-5-en-2-ol (18)
A stirred solution of (R)-(2,3-epoxypropyl)benzene 18 (4.0 g,
29.81 mmol) in anhydrous diethyl ether (40 mL) was reacted with
copper(I) iodide (0.57 g, 2.98 mmol) and allylmagnesium chloride
(2 M solution in THF, 18.90 mL, 37.81 mmol) following procedure
D. The crude residue obtained was purified by silica-gel column
chromatography using 10% ethyl acetate in hexanes to give com-
pound 18 (4.1 g, 78%) as
a
thick colorless syrup. 1H NMR
(400 MHz, CDCl3): d 1.52–1.66 (m, 3H3H), 2.11–2.32 (m, 2H),
2.67(dd, J = 13.2, 8.4 Hz, 1H), 2.84 (dd, J = 13.2, 4.0 Hz, 1H), 3.78–
3.90 (m, 1H), 4.94–5.00 (m, 1H), 5.04 (t, J = 1.6 Hz, 1H), 5.05–5.09
(m, 1H), 5.78–5.90 (m 1H), 7.20–7.34 (m, 5H).
5.1.29. (3S,6S)-6-Benzyltetrahydro-2H-pyran-3-amine (26)
Azide 25 (0.3 g, 1.38 mmol) in methanol (25 mL) was hydroge-
nated with 10% Pd-C (30 mg, 10 wt %) using procedure J to afford
amine 26 (0.3 g) as a light yellow solid in quantitative yield. The
product was pure enough for continuation to the next step. 1H
NMR (400 MHz, CDCl3): d 1.40–1.48 (m, 1H), 1.50–1.62 (m, 3H),
1.65–1.74 (m, 2H), 2.69 (dd, J = 14.0, 6.4 Hz, 1H), 2.88 (br s, 1H),
2.91 (dd, J = 14.0, 6.4 Hz, 1H), 3.44–3.55 (m, 1H), 3.58 (dd,
J = 12.0, 2.4 Hz, 1H), 3.74 (d, J = 11.2 Hz, 1H), 7.18–7.30 (m, 5H).
5.1.24. (S)-(2-(Vinyloxy)hex-5-en-1-yl)benzene (19)
To a stirred solution of alcohol 16 (2.2 g, 12.48 mmol) in excess
of ethylvinyl ether (80 mL) was added mercury(II) trifluoroacetate
(1.06 g, 2.50 mmol) at room temperature, and stirring was contin-
ued for 4 h according to procedure E. The crude product was dis-
solved in 5% ethyl acetate in hexanes, filtered through a basic
alumina pad quickly, and the filtrate was concentrated under re-
duced pressure at room temperature to give product 19 (2.1 g,
83%) as a thick light-yellow syrup. Compound 19 was carried out
to next step without purification and characterization.
5.1.30. 4-((((3S,6S)-6-Benzyltetrahydro-2H-pyran-3-
yl)amino)methyl)phenol (27)
To a stirred solution of amine 26 (60 mg, 0.31 mmol) and 4-hy-
droxy benzaldehyde (38 mg, 0.31 mmol) in 1,2-dichloroethane
5.1.25. (S)-2-Benzyl-3,4-dihydro-2H-pyran (20)
(6 mL) glacial acetic acid (18 lL, 0.31 mmol) was added. After being
To a stirred solution of compound 19 (2.1 g, 10.38 mmol) in
anhydrous benzene (100 mL) was added Grubb’s (1st generation)
catalyst (0.43 g, 0.52 mmol). The reaction mixture was slowly
heated to reflux following procedure F. The crude residue was puri-
fied by column chromatography using 5% ethyl acetate in hexanes
and recrystallized in hexanes to give compound 20 (1.52 g, 84%) as
a white solid. 1H NMR (400 MHz, CDCl3): d 1.52–1.63 (m, 1H),
1.78–1.88 (m, 1H), 1.90–2.06 (m, 2H), 2.78 (dd, J = 12.8, 6.4 Hz,
1H), 2.99 (dd, J = 14.0, 6.4 Hz, 1H), 3.94–4.06 (m, 1H), 4.64–4.70
(m, 1H), 6.34 (d, J = 6.4 Hz, 1H), 7.18–7.34 (m, 5H).
stirred for 30 min, NaCNBH3 (26 mg, 0.41 mmol) was added por-
tion-wise followed by methanol (1 mL) and reaction stirred follow-
ing procedure K. Crude product was purified by column
chromatography using 1–5% methanol in ethyl acetate to give com-
pound 27 (65 mg, 70%) as a thick syrup. ½a D25
ꢀ11.8 (c 0.5, MeOH).
ꢂ
MS (ESI): m/z 298.4 [M+H]+. 1H NMR (400 MHz, CDCl3 and few drops
of CD3OD): d 1.30–1.40 (m, 2H), 1.42–1.54 (m, 1H), 1.78–1.88 (m,
1H), 2.53 (dd, J = 6.4, 14.0 Hz, 1H), 2.58 (br s, 1H), 2.73 (dd, J = 6.4,
13.6 Hz, 1H), 3.35 (dd, J = 1.6, 12.0 Hz, 1H), 3.38–3.42 (m, 1H),
3.58–3.64 (m, 2H), 3.82 (d, J = 12.8 Hz, 1H), 4.40 (br s, 2H), 6.64 (d,
J = 8.0 Hz, 2H), 6.98–7.23 (m, 7H). 13C (100 MHz, CDCl3 and few
drops of CD3OD): d 25.64, 26.09, 42.26, 49.59, 50.17, 68.91, 78.93,
115.56, 126.31, 128.31, 129.36, 130.14, 138.16, 156.68. The product
was converted into the corresponding hydrochloride salt; Mp 170–
172 °C. Anal. (C19H23NO2ꢃHClꢃ0.7H2O) C, H, N.
5.1.26. 6-Benzyltetrahydro-2H-pyran-3-ol (mixture of 21 and
22)
A stirred solution of compound 20 (1.5 g, 8.62 mmol) in anhy-
drous THF (10 mL) was reacted with 9-BBN (0.5 M solution in
THF, 43 mL, 21.54 mmol) following procedure G. The crude residue
was purified by column chromatography using 30% ethyl acetate in
hexanes to give mixture of inseparable compounds 21 and 22
(1.42 g, 86%) as a thick syrup. 1H NMR (400 MHz, CDCl3): d
5.1.31. (S)-1,1-Diphenylpent-4-en-2-ol (29)
A
stirring solution of (R)-2-benzhydryloxirane 28 (5.14 g,
24.47 mmol) and copper(I) iodide (0.49 g, 2.61 mmol) in THF

322
H. Sharma et al. / Bioorg. Med. Chem. 22 (2014) 311–324
(50 mL) was reacted with vinyl magnesium bromide (1 M solution
in THF, 32.73 mL, 32.73 mmol) at ꢀ78 °C following procedure D.
The crude thus obtained was purified by column chromatography
using 10% ethyl acetate in hexanes to afford compound 29
10.27 mmol) using procedure I. The crude residue thus obtained
was purified by column chromatography using 1–5% ethyl acetate
in hexanes to give two separable diastereomers in an isomeric ratio
of about 3:1. Compound 36 (0.26 g, overall 36%) was obtained as a
major component and compound 37 as a minor diastereomer
(4.37 g, 75%) as colorless liquid. ½a D25
ꢂ
ꢀ30.6 (c 0.5, MeOH). 1H
NMR (400 MHz, CDCl3): d 2.08–2.16 (m, 1H), 2.25–2.32 (m, 1H),
3.91 (d, J = 8.4 Hz, 1H), 4.38–4.43 (m, 1H), 5.03–5.12 (m, 2H),
5.89 (sextet, J = 6.4 Hz, 1H), 7.16–7.47 (m, 10H).
(0.090 g, overall 12%). For compound 36 ½a D25
ꢂ
+9.8 (c 1, MeOH);
for compound 37 ½a D25
ꢀ13.8 (c 0.5, MeOH).
ꢂ
5.1.37. (2S,4S)-4-Azido-2-benzhydryltetrahydrofuran (36)
1H NMR (500 MHz, CDCl3): d 1.75 (ddd, J = 13.4 Hz, 7.0 Hz,
3.6 Hz, 1H), 2.25 (dt, J = 13.7 Hz, 7.3 Hz, 1H), 3.84 (dd, J = 10.0 Hz,
5.5 Hz, 1H), 3.96 (dd, J = 9.7 Hz, 2.4 Hz, 1H), 4.05–4.10 (m, 2H),
4.66 (dt, J = 9.4 Hz, 7.3 Hz, 1H), 7.16–7.36 (m, 10H). 13C NMR
(CDCl3) d 37.3, 57.0, 61.2, 73.0, 81.3, 126.8, 127.0, 128.5, 128.6,
128.7, 128.9, 142.2, 142.4.
5.1.32. (S)-(2-(Vinyloxy)pent-4-ene-1,1-diyl)dibenzene (30)
In a sealed tube fitted with a screw-cap was taken excess ethyl
vinyl ether (10.0 mL). Mercury(II) trifluoroacetate (0.14 g,
0.33 mmol) was then added followed by alcohol 29 (0.8 g,
3.35 mmol) and triethylamine (0.14 mL, 1.00 mmol). The reaction
mixture was heated to 50 °C and stirred for 6 h. Thereafter, another
portion of ethyl vinyl ether (10.0 mL), mercury(II) trifluoroacetate
(0.14 g, 0.33 mmol) and triethylamine (0.14 mL, 1.00 mmol) was
added and the reaction stirred at 50 °C for another 6 h. After the
reaction, the reaction mixture was concentrated under reduced
pressure. The crude obtained was purified by eluting a short bed
of three-fourth silica and one-fourth charcoal with 3% ether in hex-
anes. Purified compound 30 (0.44 g, 50%), along with unreacted
alcohol 29 (0.34 g, 38%), was obtained as colorless oil (unstable)
and was immediately taken to the next step. The reaction was done
in parallel batches to obtain a total of 2.4 g of compound 30. 1H
NMR (400 MHz, CDCl3): d 2.15–2.28 (m,1H), 2.36–2.43 (m, 1H),
3.92 (d, J = 7.2 Hz, 1H), 4.14 (d, J = 8.4 Hz, 1H), 4.24 (dd,
J = 14.4 Hz, 1.6 Hz, 1H), 4.51–4.55 (m,1H), 5.0 (dd, J = 17.2 Hz,
1.6 Hz, 1H), 5.05–5.13 (m, 1H), 5.78–5.91 (m, 1H), 6.19 (dd,
J = 13.6 Hz, 6.4 Hz, 1H), 7.18–7.40 (m, 10H).
5.1.38. (2S,4R)-4-Azido-2-benzhydryltetrahydrofuran (37)
1H NMR (500 MHz, CDCl3): d 1.81–1.86 (m, 1H1H), 1.99 (dd,
J = 13.2 Hz, 5.2 Hz, 1H), 3.83 (dd, J = 10.0 Hz, 2.4 Hz, 1H), 3.92 (d,
J = 8.4 Hz, 1H), 3.98 (dd, J = 9.7 Hz, 5.2 Hz, 1H1H), 4.08–4.12 (m,
1H), 4.84 (dt, J = 9.4 Hz, 7.3 Hz, 1H), 7.12–7.36 (m, 10H). 13C NMR
(CDCl3) d 34.0, 56.9, 61.6, 72.8, 80.5, 126.8, 127.0, 128.5, 128.7,
128.7, 128.9, 142.0, 142.4.
5.1.39. (3S,5S)-5-Benzhydryltetrahydrofuran-3-amine (38)
Compound 36 (0.26 g, 0.73 mmol) was hydrogenated with 10%
Pd/C (26 mg, 10 wt %) using procedure J to afford compound 38
(0.23 g) as colorless oil in quantitative yield which was pure en-
ough for the next step. 1H NMR (400 MHz, CDCl3): d 1.36–1.41
(m, 1H), 2.11–2.19 (m, 1H1H), 3.29–3.34 (m, 1H), 3.44–3.51 (m,
1H), 3.78–3.81 (m, 1H), 4.01–4.07 (m, 1H1H), 4.63–4.69 (m, 1H),
7.12–7.35 (m, 10H).
5.1.33. (S)-2-Benzhydryl-2,3-dihydrofuran (31)
Compound 27 (2.4 g, 9.07 mmol) was dissolved in benzene
(40 mL) and Grubb’s (1st gen) catalyst (2.24 g, 2.72 mmol) was
added portion-wise over 3 h. The reaction mixture was heated at
50 °C for 6 h under N2 atmosphere. The reaction mixture was then
filtered over a short bed of Celite and the filtrate concentrated un-
der reduced pressure. The crude obtained was purified by column
chromatography using 5% ether in hexanes to afford compound 31
(1.14 g, 53%) as a white solid. 1H NMR (400 MHz, CDCl3): d 2.33–
2.41 (m, 1H), 2.56–2.65 (m, 1H), 4.12 (d, J = 9.2 Hz, 1H), 4.84 (q,
J = 2.4 Hz, 1H), 5.31 (q, J = 9.2 Hz, 1H), 6.32 (q, J = 2.4 Hz, 1H),
7.16–7.36 (m, 10H).
5.1.40. (3R,5S)-5-Benzhydryltetrahydrofuran-3-amine (39)
Compound 37 (0.09 g, 0.32 mmol) was stirred with 10% Pd/C
(9 mg, 10 wt %) under hydrogen atmosphere following procedure
J to yield compound 39 (0.065 g, 80.2%) which was taken to the
next step without further purification. 1H NMR (400 MHz, CDCl3):
d 1.39–1.46 (m, 1H), 2.17–2.24 (m, 1H), 3.54–3.59 (m, 2H),
3.81–3.87 (m, 1H), 4.08 (d, J = 8.3 Hz, 1H1H), 4.60–4.66 (m, 1H),
7.12–7.35 (m, 10H).
5.1.41. 3-((((3S,5S)-5-Benzhydryltetrahydrofuran-3-
yl)amino)methyl)phenol (40)
5.1.34. 5-Benzhydryltetrahydrofuran-3-ol (mixture of 32 and
33)
Amine intermediate 38 (20 mg, 0.06 mmol) and 4-hydroxy-
benzaldehyde (10 mg, 0.06 mmol) were dissolved in DCM
A stirred solution of compound 31 (1.14 g, 4.82 mmol) in THF
(15 mL) was reacted with 9-BBN (0.5 M solution in THF, 14.47 mL,
7.23 mmol) following procedure G. The crude was purified by col-
umn chromatography using 15% ether in hexanes to yield a mixture
of two inseparable diastereomer 32 and 33 (0.65 g, 53%); which was
taken to the next step without further purification.
(1.3 mL). MeOH (0.3 mL) and AcOH (3.2 lL) were then added and
reaction stirred for 30 min. NaCNBH3 (10 mg, 0.09 mmol) was
added and reaction continued following procedure K to obtain
crude which was purified by column chromatography using 1–5%
MeOH in DCM to afford target compound 40 (10 mg, 36%). ½a D25
ꢂ
ꢀ2.62 (c 0.5, MeOH). MS (ESI): m/z 360.4 [M+H]+. 1H NMR
(400 MHz, CDCl3): d 1.49–1.56 (m, 1H), 2.17–2.24 (m, 1H), 3.41
(quintet, J = 6.4 Hz, 1H), 3.53–3.61 (m, 2H), 3.76 (dd, J = 8.8,
4.0 Hz, 1H), 3.81 (dd, J = 9.2, 6.0 Hz, 1H), 4.06 (d, J = 8.4 Hz, 1H),
4.62 (q, J = 8.4 Hz, 1H), 6.61 (d, J = 8.4 Hz, 2H), 7.02–7.34 (m,
12H). 13C NMR (CDCl3) d 38.4, 51.9, 57.2, 58.2, 73.1, 81.2, 115.8,
126.7, 126.8, 128.6, 128.7, 128.8, 129.9, 142.3, 142.7. The free base
was converted into its corresponding hydrochloride salt. Mp
142–148 °C. Anal. (C24H25NO3ꢃHClꢃ1.8H2O) C, H, N.
5.1.35. 5-Benzhydryltetrahydrofuran-3-yl methanesulfonate
(mixture of 34 and 35)
A stirred solution of a mixture of compounds 32 and 33 (0.65 g,
2.55 mmol), triethylamine (0.70 mL, 5.10 mmol) and methanesul-
fonyl chloride (0.236 mL, 3.06 mmol) was reacted using procedure
H. The crude (0.91 g) containing a mixture of two diastereomers 34
and 35 was inseparable chromatographically and was taken to the
next step without purification.
5.1.42. 4-(2-(((3S,5S)-5-Benzhydryltetrahydrofuran-3-
yl)amino)ethyl)phenol (41)
Compound 38 (30 mg, 0.12 mmol) and 4-hydroxyphenyl acetal-
dehyde (20 mg, 0.12 mmol) were dissolved in DCM (2.4 mL).
5.1.36. (2S,4S)-4-Azido-2-benzhydryltetrahydrofuran (36) and
(2S,4R)-4-azido-2-benzhydryltetrahydrofuran (37)
A stirred solution of a mixture of compounds 34 and 35 (0.90 g,
crude) in DMF (20 mL) was reacted with sodium azide (0.668 g,
MeOH (0.6 mL) and AcOH (15 lL) were then added and reaction

H. Sharma et al. / Bioorg. Med. Chem. 22 (2014) 311–324
323
stirred for 30 min. NaCNBH3 (10.0 mg, 0.18 mmol) was added and
reaction continued according to procedure K. The crude obtained
was purified by column chromatography using 1–5% MeOH in
DCM to afford target compound 41 (20 mg, 46%) as colorless oil.
(dd, J = 8.8, 6.0 Hz, 1H), 3.97 (d, J = 8.8 Hz, 1H), 4.61 (q, J = 9.2 Hz,
1H), 7.19–7.34 (m, 15H). 13C NMR (CD2Cl2)
33.3, 35.1,
47.7, 55.9, 58.0, 70.3, 81.0, 126.6, 126.7, 126.9, 128.2, 128.3,
128.3, 128.4, 128.6, 128.6, 128.7, 141.6, 141.7. The free base
was converted into its corresponding hydrochloride salt.
Mp = 132–134 °C. Anal. C25H27NOꢃHClꢃ0.1H2O. C, H, N.
d
½
a 2D5
ꢂ
ꢀ0.6 (c 0.5, MeOH). 1H NMR (400 MHz, CDCl3): d 1.43–1.50
(m, 1H), 2.12–2.17 (m, 1H), 2.59–2.74 (m, 4H), 3.35–3.40 (m,
1H), 3.72 (dd, J = 9.2, 4.4 Hz, 1H), 3.81 (dd, J = 9.2, 6.0 Hz, 1H),
3.98 (d, J = 8.8 Hz, 1H), 4.59 (q, J = 8.4 Hz, 1H), 6.70 (d, J = 8.4 Hz,
2H), 6.83 (d, J = 8.0 Hz, 2H) 7.15–7.31 (m, 10H). 13C NMR (CDCl3)
d 35.2, 38.1, 49.7, 57.2, 58.8, 73.0, 81.2, 115.8, 126.7, 126.8,
128.6, 128.7, 128.7, 129.9, 131.0, 142.4, 142.7, 154.9. The free base
was converted into its corresponding hydrochloride salt.
Mp = 152–158 °C. Anal. (C25H27NO3ꢃHClꢃ0.8H2O) C, H, N.
5.1.46. 3-((((3R,5S)-5-Benzhydryltetrahydrofuran-3-
yl)amino)methyl)phenol (45)
Compound 39 (20 mg, 0.14 mmol) and 4-hydroxyphenyl acetal-
dehyde (20 mg, 0.14 mmol) were dissolved in DCM (1.3 mL).
MeOH (0.6 Ml) and AcOH (20 lL) were then added and reaction
stirred for 30 min. NaCNBH3 (10.0 mg, 0.21 mmol) was added
and reaction continued according to procedure K. The crude ob-
tained was purified by column chromatography using 1–5% MeOH
in DCM to afford target compound 45 (10 mg, 19%) as colorless li-
quid. 1H NMR (400 MHz, CD3OD): d 1.26–1.38 (m, 1H), 1.97 (m,
1H), 3.44–3.51 (m, 1H), 3.74–3.77 (m, 1H), 3.93–4.03 (m, 2H),
4.21–4.27 (m, 1H), 4.31–4.48 (m, 2H), 6.87–6.95 (m, 4H),
7.10–7.37 (m, 10H). 13C NMR (CD3OD) d 38.4, 51.9, 57.2, 58.2,
73.1, 81.2, 115.8, 126.7, 126.8, 128.6, 128.7, 128.8, 129.9, 142.3,
142.7. The free base was converted into its corresponding hydro-
chloride salt. Mp = 132–138 °C. HRMS calcd for C24H25NO3 (M+):
359.19. Found: 359.18.
5.1.43. (3S,5S)-5-Benzhydryl-N-(4-
methoxyphenethyl)tetrahydrofuran-3-amine (42)
Amine intermediate 38 (70 mg, 0.27 mmol) and 4-methoxy-
phenyl acetaldehyde (50 mg, 0.33 mmol) were dissolved in 1,2-
DCE (7 mL). MeOH (0.5 mL) and AcOH (16 lL) were then added
and reaction stirred for 30 min. Na(OAc)3BH (0.117 g, 0.54 mmol)
was thereafter added and reaction continued using procedure K.
The crude obtained was purified by column chromatography using
1–5% MeOH in DCM to afford target compound 42 (43 mg, 41%).
½
a 2D5
ꢂ
ꢀ10.3 (c 0.82, DCM). MS (ESI): m/z 388.5 [M+H]+. 1H NMR
(400 MHz, CD2Cl2): d 1.35–1.50 (m, 1H), 2.09–2.16 (m, 1H),
2.65–2.75 (m, 4H), 3.35–3.41 (m, 1H), 3.64 (dd, J = 8.8, 4.0 Hz,
1H), 3.78 (s, 3H), 3.76–3.80 (m, 1H), 3.97 (d, J = 8.8 Hz, 1H), 4.59
(q, J = 8.8 Hz, 1H), 6.83 (d, J = 8.8 Hz, 2H), 7.11 (d, J = 8.0 Hz, 2H)
7.17–7.21 (m, 2H), 7.27–7.34 (m, 8H). 13C NMR (CDCl3) d 35.3,
38.2, 49.7, 55.1, 57.2, 58.6, 73.1, 80.8, 113.7, 126.2, 126.4, 128.2,
128.2, 128.3, 128.4, 129.5, 131.9, 142.7, 142.9, 158.0. The free base
was converted into its corresponding hydrochloride salt.
Mp = 172–174 °C. Anal. (C26H29NO2ꢃHClꢃ0.1H2O) C, H, N.
5.1.47. (3R,5S)-5-Benzhydryl-N-benzyltetrahydrofuran-3-amine
(46)
Compound 39 (36 mg, 0.14 mmol) and phenylacetaldehyde
(20 mg, 0.17 mmol) were dissolved in DCM (3.5 mL). MeOH
(0.6 mL) and AcOH (10 lL) were then added and reaction stirred
for 30 min. Na(OAc)3BH (36 mg, 0.17 mmol) was thereafter added
and reaction continued following procedure K. The crude obtained
was purified by column chromatography using 1–5% MeOH in
DCM to afford target compound 46 (15 mg, 31%) as colorless liquid.
1H NMR (400 MHz, CD2Cl2): d 1.68–1.78 (m, 2H), 2.70–2.84 (m, 4H),
3.94 (m, 1H), 3.52 (m, 1H), 3.79 (m, 1H), 3.97 (m, 1H), 4.61 (m, 1H),
7.15–7.35 (m, 15H). 13C NMR (CDCl3) d 36.7, 38.5, 49.8, 57.5, 58.8,
73.9, 80.5, 126.4, 126.5, 126.7, 128.5, 128.6, 128.7, 128.7, 128.8,
128.9, 140.5, 143.1, 143.3. The free base was converted into its cor-
responding hydrochloride salt. Mp = 112–114 °C. HRMS calcd for
5.1.44. (3S,5S)-5-Benzhydryl-N-(4-
fluorophenethyl)tetrahydrofuran-3-amine (43)
Amine intermediate 38 (70 mg, 0.27 mmol) and 4-fluoro phenyl
acetaldehyde (46 mg, 0.33 mmol) were dissolved in 1,2-DCE
(6 mL). MeOH (0.5 mL) and AcOH (16 lL) were then added and
reaction stirred for 30 min. Na(OAc)3BH (70 mg, 0.33 mmol) was
thereafter added and reaction continued following procedure K.
The crude obtained was purified by column chromatography using
C
25H28NO (M+): 358.2162. Found: 358.2171.
1–5% MeOH in DCM to yield compound 43 (40 mg, 39%). ½a D25
ꢂ
ꢀ2.7
5.2. Transporter assays
(c 0.78, DCM). MS (ESI): m/z 376.5 [M+H]+. 1H NMR (400 MHz,
CD2Cl2): d 1.33–1.41 (m, 1H), 2.09–2.16 (m, 1H), 2.66–2.77 (m,
4H), 3.39 (quintet, J = 6.12 Hz, 1H), 3.64 (dd, J = 8.8, 4.4 Hz, 1H),
3.79 (dd, J = 8.8, 6.11 Hz, 1H), 3.97 (d, J = 8.8 Hz, 1H), 4.61 (q,
J = 8.56 Hz, 1H), 7.00 (t, J = 8.8 Hz, 2H), 7.19 (m, 4H), 7.26–7.36
(m, 8H). 13C NMR (CD2Cl2) d 36.0, 38.7, 49.9, 57.6, 59.0, 73.5,
81.2, 115.2, 115.4, 126.6, 126.8, 128.5, 128.6, 128.7, 128.8, 130.4,
130.5, 136.3, 143.1, 143.2. The free base was converted into its
corresponding hydrochloride salt. Mp = 168–170 °C. Anal.
(C25H26FNO1ꢃHClꢃ0.1H2O)C, H, N.
The ability of test compounds to inhibit substrate uptake by rat
monoamine transporters was monitored exactly as described by us
previously.42 Briefly, accumulation was measured of [3H]DA ([Ring
2,5,6-3H]dopamine (45.0 Ci/mmol, Perkin–Elmer, Boston, MA,
U.S.A.) for 5 min for monitoring DAT (rat striatum), and 7 min for
NET (rat cerebral cortex) (please note that DA is an excellent sub-
strate for NET, for our previous discussion see Ref. 43). Uptake of
[3H]5-HT ([1,2-3H]serotonin (27.9 Ci/mmol, Perkin–Elmer) was
measured for 10 min for monitoring SERT (rat cerebral cortex).
Drug stocks contained an additional 0.01% (w/v) bovine serum
albumin in order to reduce absorption of drug to the walls of the
assay plates. At least five triplicate concentrations of each test
compound were studied, spaced evenly around the IC50 value
which was converted to Ki with the Cheng–Prusoff equation.43
With observed Km values and [3H]ligand concentrations used, the
conversion factors (multipliers applied to IC50 for calculating Ki)
were P0.84.
5.1.45. (3S,5S)-5-Benzhydryl-N-phenethyltetrahydrofuran-3-
amine (44)
Amine intermediate 38 (30 mg, 0.118 mmol) and phenyl acetal-
dehyde (17 mg, 0.142 mmol) were dissolved in 1,2-DCE (3 mL).
MeOH (0.3 mL) and AcOH (8 lL) were then added and reaction stir-
red for 30 min. Na(OAc)3BH (10 mg, 0.142 mmol) was thereafter
added and reaction continued following procedure K. The crude
obtained was purified by column chromatography using 1–5%
MeOH in DCM to yield compound 44 (15 mg, 36%). ½a D25
ꢂ
ꢀ12.7 (c
5.3. Pharmacophore model
0.66, DCM). MS (ESI): m/z 358.5 [M+H]+. 1H NMR (400 MHz, CD2-
Cl2): d 1.33–1.40 (m, 1H), 2.09–2.16 (m, 1H), 2.69–2.78 (m, 4H),
3.39 (quintet, J = 6.40 Hz, 1H), 3.64 (dd, J = 8.8, 4.8 Hz, 1H), 3.79
Computational studies were conducted on Hewlett–Packard
xw4300 computer workstation under the Red Hat Enterprise Linux

324
H. Sharma et al. / Bioorg. Med. Chem. 22 (2014) 311–324
4. Bel, N.; Artigas, F. J. Pharmacol. Exp. Ther. 1996, 278, 1064.
5. Richelson, E. J. Clin. Psychiatry 2003, 64, 5.
6. Svensson, T. H. Acta Psychiatr. Scand. Suppl. 2000, 402, 18.
7. Shulman, K. I.; Herrmann, N.; Walker, S. E. CNS Drugs 2013.
8. Rose, J. B. Clin. Toxicol. 1977, 11, 391.
5 operating system using Molecular Operating Environment (MOE,
2012.10 from chemical computing group, Montreal, Canada) soft-
ware package. Structures, drawn using the Builder module, were
assigned partial atomic charges and then energy minimized using
the MMFF94x force field available in MOE. The secondary amines
were converted into their respective protonated states. Conforma-
tional search was performed using systemic and stochastic method
both of which generated similar output of conformers. Stochastic
method was preferred over systemic for further analysis as it is
computationally less expensive and is a method of choice to locate
the global energy minima for small molecules. Moreover, literature
studies have suggested that systemic search algorithm may pres-
ent difficulties in compounds containing tetrahydropyran or other
aliphatic rings.43 Stochastic search generates conformations by a
random (usually 30 degrees) increment of rotatable bonds (includ-
ing rings). RMS gradient of 0.005 and an iteration limit of 10,000
were kept for energy minimization. The conformational limit was
set to 500. Rejection limit cut off prior to termination was kept
at 100. Energy window cut off of E = 10 kcal/mol of the lowest en-
ergy was kept to access all reasonable conformations and rmsd of
60.1 Å was used to remove all duplicate conformations. The se-
lected conformations were subjected to flexible alignment and
aligned molecules were subsequently used to build pharmaco-
phore model using pharmacophore elucidator module in MOE.
The elucidator identifies common functional groups and aligns
the pharmacophoric features present in the molecules. Unified
scheme with default parameters were used for the pharmacophore
development.
9. Spinks, D.; Spinks, G. Curr. Med. Chem. 2002, 9, 799.
10. Wong, D. T.; Bymaster, F. P. Adv. Exp. Med. Biol. 1995, 363, 77.
11. Hiemke, C.; Hartter, S. Pharmacol. Ther. 2000, 85, 11.
12. Owens, M. J.; Nemeroff, C. B. Depress Anxiety 1998, 8, 5.
13. Di Giovanni, G.; Esposito, E.; Di Matteo, V. CNS Neurosci. Ther. 2010, 16, 179.
14. Thase, M. E.; Entsuah, A. R.; Rudolph, R. L. Br. J. Psychiatry 2001, 178, 234.
15. Barbey, J. T.; Roose, S. P. J. Clin. Psychiatry 1998, 59, 42.
16. Goldstein, B. J.; Goodnick, P. J. J. Psychopharmacol. 1998, 12, S55.
17. Gumnick, J. F.; Nemeroff, C. B. J. Clin. Psychiatry 2000, 61, 5.
18. Steffens, D. C.; Krishnan, K. R.; Helms, M. J. Depress Anxiety 1997, 6, 10.
19. Rush, A. J.; Trivedi, M. H.; Wisniewski, S. R.; Nierenberg, A. A.; Stewart, J. W.;
Warden, D.; Niederehe, G.; Thase, M. E.; Lavori, P. W.; Lebowitz, B. D.; McGrath,
P. J.; Rosenbaum, J. F.; Sackeim, H. A.; Kupfer, D. J.; Luther, J.; Fava, M. Am. J.
Psychiatry 1905, 2006, 163.
20. D’Aquila, P. S.; Collu, M.; Gessa, G. L.; Serra, G. Eur. J. Pharmacol. 2000, 405,
365.
21. Papakostas, G. I. Eur. Neuropsychopharmacol. 2006, 16, 391.
22. Dunlop, B. W.; Nemeroff, C. B. Arch. Gen. Psychiatry 2007, 64, 327.
23. Nutt, D.; Demyttenaere, K.; Janka, Z.; Aarre, T.; Bourin, M.; Canonico, P. L.;
Carrasco, J. L.; Stahl, S. J. Psychopharmacol. 2007, 21, 461.
24. Nestler, E. J.; Carlezon, W. A., Jr. Biol. Psychiatry 2006, 59, 1151.
25. Mischoulon, D.; Nierenberg, A. A.; Kizilbash, L.; Rosenbaum, J. F.; Fava, M. Can. J.
Psychiatry 2000, 45, 476.
26. Ascher, J. A.; Cole, J. O.; Colin, J. N.; Feighner, J. P.; Ferris, R. M.; Fibiger, H. C.;
Golden, R. N.; Martin, P.; Potter, W. Z.; Richelson, E., et al J. Clin. Psychiatry 1995,
56, 395.
27. Sporn, J.; Ghaemi, S. N.; Sambur, M. R.; Rankin, M. A.; Recht, J.; Sachs, G. S.;
Rosenbaum, J. F.; Fava, M. Ann. Clin. Psychiatry 2000, 12, 137.
28. Marks, D. M.; Pae, C. U.; Patkar, A. A. Curr. Neuropharmacol. 2008, 6, 338.
29. Guiard, B. P.; El Mansari, M.; Blier, P. Curr. Drug Targets 2009, 10, 1069.
30. Prins, J.; Olivier, B.; Korte, S. M. Exp. Opin. Investig. Drugs 2011, 20, 1107.
31. Liang, Y.; Shaw, A. M.; Boules, M.; Briody, S.; Robinson, J.; Oliveros, A.; Blazar,
E.; Williams, K.; Zhang, Y.; Carlier, P. R.; Richelson, E. J. Pharmacol. Exp. Ther.
2008, 327, 573.
Acknowledgment
32. Skolnick, P.; Krieter, P.; Tizzano, J.; Basile, A.; Popik, P.; Czobor, P.; Lippa, A. CNS
Drug Rev. 2006, 12, 123.
33. Zhang, S.; Fernandez, F.; Hazeldine, S.; Deschamps, J.; Zhen, J.; Reith, M. E.;
Dutta, A. K. J. Med. Chem. 2006, 49, 4239.
34. Gopishetty, B.; Hazeldine, S.; Santra, S.; Johnson, M.; Modi, G.; Ali, S.; Zhen, J.;
Reith, M.; Dutta, A. J. Med. Chem. 2011, 54, 2924.
This work is supported by National Institute of Mental Health/
National Institute of Health MH084888 (A.K.D.).
Supplementary data
35. Zhang, S.; Zhen, J.; Reith, M. E.; Dutta, A. K. J. Med. Chem. 2005, 48, 4962.
36. Gopishetty, B.; Gogoi, S.; Dutta, A. Tetrahedron: Asymmetry 2011, 22, 1081.
37. Dutta, A. K.; Ghosh, B.; Biswas, S.; Reith, M. E. Eur. J. Pharmacol. 2008, 589,
73.
38. Dutta, A. K.; Gopishetty, B.; Gogoi, S.; Ali, S.; Zhen, J.; Reith, M. Eur. J. Pharmacol.
2011, 671, 39.
Supplementary data (2D stereochemical characterization of the
major azide intermediate 36, molecular modeling, and elemental
analysis data for final targets) associated with this article can be
found, in the online version, at http://dx.doi.org/10.1016/
j.bmc.2013.11.017.
39. Bosch, M.; Schlaf, M. J. Org. Chem. 2003, 68, 5225.
40. Zhang, S.; Zhen, J.; Reith, M. E.; Dutta, A. K. Bioorg. Med. Chem. 2004, 12, 6301.
41. Pandit, D.; Roosma, W.; Misra, M.; Gilbert, K. M.; Skawinski, W. J.; Venanzi, C. A.
J. Mol. Model. 2011, 17, 181.
42. Santra, S.; Gogoi, S.; Gopishetty, B.; Antonio, T.; Zhen, J.; Reith, M. E.; Dutta, A.
K. ChemMedChem 2012, 7, 2093.
References and notes
43. Chen, I. J.; Foloppe, N. J. Chem. Inf. Model. 2008, 48, 1773.
1. Millan, M. J. Neurotherapeutics 2009, 6, 53.
2. Coppen, A. Br. J. Psychiatry 1967, 113, 1237.
3. Hensler, J. G. Life Sci. 2003, 72, 1665.