Design, synthesis, and preliminary SAR study of 3- and 6-side-chain-extended tetrahydro-pyran analogues of cis- and trans-(6-benzhydryl-tetrahydropyran-3-yl)-benzylamine

Article abstract of DOI:10.1016/j.bmc.2006.01.051

In our effort to further understand interaction of novel pyran derivatives with monoamine transporters, we have designed, synthesized, and biologically characterized side-chain-extended derivatives of our earlier developed cis- and trans-(6-benzhydryl-tetrahydro-pyran-3-yl)-benzylamine derivatives. Both 3- and 6-position extensions were explored. All synthesized derivatives 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. Compounds were also tested for their binding affinity at the DAT by their ability to inhibit binding of [³H]WIN 35, 428. The results indicated that extension at the 3-position resulted in loss of activity compared to the original compound I. On the other hand, extension at the 6-position resulted in improvement of activity in the compound cis-12 by 2-fold over the parent compound I indicating favorable interaction. In addition, two glycoside derivatives were designed, synthesized, and biologically characterized. The glycosidic trans-isomer 24 exhibited highest potency for the NET in the current series of compounds.

Full text of DOI:10.1016/j.bmc.2006.01.051

Bioorganic & Medicinal Chemistry 14 (2006) 3953–3966
Design, synthesis, and preliminary SAR study of 3- and
6-side-chain-extended tetrahydro-pyran analogues of cis- and
trans-(6-benzhydryl-tetrahydropyran-3-yl)-benzylamine
Shijun Zhang,a Juan Zhen,b Maarten E. A. Reithb and Aloke K. Duttaa,*
aDepartment of Pharmaceutical Sciences, Wayne State University, Detroit, MI 48202, USA
bNew York University School of Medicine, Millhauser Laboratories, Department of Psychiatry, New York, NY 10016, USA
Received 16 December 2005; revised 18 January 2006; accepted 20 January 2006
Available online 14 February 2006
Abstract—In our effort to further understand interaction of novel pyran derivatives with monoamine transporters, we have
designed, synthesized, and biologically characterized side-chain-extended derivatives of our earlier developed cis- and trans-(6-benz-
hydryl-tetrahydro-pyran-3-yl)-benzylamine derivatives. Both 3- and 6-position extensions were explored. All synthesized derivatives
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. Compounds
were also tested for their binding affinity at the DAT by their ability to inhibit binding of [3H]WIN 35, 428. The results indicated that
extension at the 3-position resulted in loss of activity compared to the original compound I. On the other hand, extension at the
6-position resulted in improvement of activity in the compound cis-12 by 2-fold over the parent compound I indicating favorable
interaction. In addition, two glycoside derivatives were designed, synthesized, and biologically characterized. The glycosidic
trans-isomer 24 exhibited highest potency for the NET in the current series of compounds.
ꢀ 2006 Elsevier Ltd. All rights reserved.
1. Introduction
(Fig. 1).11–13 Recently, several review papers have been
published summarizing most of this work.12–14
Monoamine transporters play vital roles in maintaining
and terminating the action of biogenic amines including
dopamine (DA), serotonin (5-HT), and norepinephrine
(NE) in the synapse and are known as DAT, SERT,
and NET, respectively.1 Among these three transport-
ers, it is widely believed that DAT mediates cocaine’s
reinforcing and addictive properties.2–8 However, this
does not rule out the involvement of non-dopaminergic
systems in cocaine reinforcing effect. For example, the
serotonergic system has been shown to modulate some
of cocaine’s effects.9,10 Enormous efforts have been
devoted toward developing selective DAT inhibitors as
potential therapeutic agents to treat cocaine addiction.
To date, several structurally diverse compounds have
been synthesized and they can be classified in the follow-
ing categories: tropine, benztropin, GBR 12909, methyl-
phenidate, mazindol, and phencyclidine analogues
During the past 10 years, we have been focusing on
developing selective DAT blocker based on piperidine
derivatives,15–21 and recently, we have embarked on
the development of novel 3,6-disubstituted- and asym-
metric (2,4,5)-trisubstituted-tetrahydro-pyran deriva-
tives targeting monoamine transporter systems.22–24
Results of our work from these two series of tetrahy-
dro-pyran derivatives indicated that disubstituted and
trisubstituted tetrahydro-pyran derivatives exhibited
somewhat different activity profiles at the three mono-
amine transporters. In general, (À)-enantiomers of
(2,4,5)-trisubstituted tetrahydro-pyran derivatives, such
as compound (À)-III, turned out to be potent and selec-
tive at either NET or SERT or both,24 while 3,6-disub-
stituted tetrahydro-pyran derivatives, such as compound
I, exhibited potency and selectivity at either DAT or
NET (Fig. 2).22,23 On the other hand, we have observed
that the requirement of cis-configuration between the
benzhydryl substituent and the exocyclic N-substituent
and their similar relative positions on the tetrahydro-py-
ran ring was maintained in these two different templates
albeit III contained one additional hydroxyl substituent.
Keywords: Dopamine transporter; Serotonin transporter; Norepineph-
rine transporter; Cocaine.
*
Corresponding author. Tel.: +1 313 577 1064; fax: +1 313 577
2033; e-mail: adutta@wayne.edu
0968-0896/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2006.01.051

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S. Zhang et al. / Bioorg. Med. Chem. 14 (2006) 3953–3966
H C
basic nitrogen atom as shown in compounds 17 and
18 (Fig. 3). The rationale behind this design was same
as we described in our previous report.22 The N- and
O-atoms have different atom size, basicity, and hydro-
gen bonding capability. Therefore, this exchange might
lead to new binding and pharmacological results due
to different physicochemical and pharmacodynamic
properties.
3
N
H C
3
N
CO CH
2
3
O
Benztropine
WIN 35,065-2
F
(c) Finally, we have designed two glycoside derivatives
cis-24 and trans-24 (Fig. 4). The rationale behind this de-
sign was that diphenylmethoxy substitution will be in an
a-position which corresponds to an axial position in a
chair tetrahydro-pyran conformation in these two su-
gar-type molecules, and the results from these two com-
pounds will help us to understand the importance of the
relative positions of the diphenylmethoxy moiety and
the exocyclic N-atom on the tetrahydro-pyran back-
bone. Furthermore, such sugar-type compounds were
never explored for CNS activity including DAT block-
ade, and it would be interesting to examine binding
affinities of these glycoside derivatives for monoamine
transporter systems. This information will also shed
more light on possible interaction mechanisms of this
novel tetrahydro-pyran template.
O
N
N
N
H
CO CH
2
3
Methylphenidate
GBR 12909
Cl
F
NH
2
CH
3
N
HO
N
N
Mazindol
Normifensine
Figure 1. Different structures of DAT inhibitors.
However, series III molecules exhibited different activity
profiles indicating the presence of an additional hydroxy
substituent significantly altered interactions with the
binding domains. This further has indicated that an
optimal distance between aromatic rings in the benzhy-
dryl moiety and the exocyclic N-atom is an important
structural determinant for their affinities at monoamine
transporters. Subtle change in this distance might lead
to further optimization of binding and pharmacological
properties. In our current study with disubstituted pyran
derivatives, we wanted to explore the effects of change in
distance between the exocyclic N-atom and the two
aromatic rings in the benzhydryl moiety on their activi-
ties for monoamine transporter systems. The rationale
behind our design is described below.
2. Preliminary molecular modeling study of designed
compounds
In order to demonstrate the different separation of
distances between the exocyclic N-atom and the aro-
matic rings in benzhydryl moiety in our newly de-
signed molecules, we have carried out a preliminary
molecular modeling study using compounds I, 4,
and cis-12. The lowest energy conformations for these
three compounds were established using the same
procedure as we described in our earlier publica-
tion.21,23 Briefly, compounds were minimized first
with the SYBYL molecular modeling program (ver-
sion 6.9, 2002, Tripos Associates, Inc., St. Louis,
MO). Minimized molecules obtained from this opera-
tion were next subjected to a grid search protocol to
search for the lowest energy conformer. Grid search
operation was carried out with the change of torsion-
al angle from 0ꢁ to 360ꢁ with an increment of 10ꢁ.
The distances between the exocyclic N-atom and the
two aromatic rings in benzhydryl moiety in each mol-
ecule were measured, and the results are shown in
Figure 5.
(a) Compounds 4 and 12 have been designed by exten-
sion of either the 3- or 6-position and compound 12
has been designed both in the cis- and trans-configura-
tions, respectively (Fig. 3). Results from biological char-
acterization of these derivatives will aid us to
understand the importance of the distance between the
exocyclic N-atom and the aromatic ring in the benzhy-
dryl moiety in binding interaction. In addition, by
designing cis- and trans-12, we can further confirm
whether the cis-stereochemistry is still required in these
extended analogues for interaction with monoamine
transporters.
3. Chemistry
(b) In our next design, we replaced the oxygen atom in
the 6-position side chain in 12 by a bioisosteric more
The synthesis of final compound 4 with extended side
chain at the 3-position is shown in Scheme 1. Briefly,
OH
F
HN
F
N
O
O
O
H
HN
F
I
II
(-)-III
Figure 2. Di- and tri-substituted tetrahydro-pyran compounds.

S. Zhang et al. / Bioorg. Med. Chem. 14 (2006) 3953–3966
3955
H
N
F
O
3-position side chain extension
4
F
HN
F
N
H
O
O
O
O
trans-12
cis-12
6-position side
chain extension
OH
F
HN
O
HN
N
O
N
H
H
18
17
Figure 3. The design of side-chain-extended tetrahydro-pyran compounds at either 3- or 6-position.
reaction with NaCN in dimethylformamide (DMF) at
100 ꢁC yielded 2. Raney-Ni catalyzed reduction gave
amine precursor cis-(6-benzhydryl-tetrahydro-pyran-3-
yl)-methylamine 3 which on reductive amination with
4-fluorobenzaldehyde, as we described in our earlier
publication,19 gave the final product (6-benzhydryl-tet-
rahydro-pyran-3-ylmethyl)-(4-fluorobenzyl)-amine 4.
F
HN
F
N
H
O
O
O
O
cis-24
trans-24
Scheme 2 describes the synthesis of trans-12 and cis-12.
3,4-Dihydro-2H-pyran-2-carbaldehyde 5 was reduced
by NaBH4 in ethanol to give alcohol intermediate (3,4-
dihydro-2H-pyran-2-yl)-methanol 6 in 85% yield.25 Pro-
tection of compound 6 with tert-butyl-(3,4-dihydro-2H-
pyran-2-yl-methoxy)-diphenyl-silane (TBDPS), fol-
lowed by hydroboration and oxidation, gave the trans-
product 6-(tert-butyl-diphenyl-silanyloxylmethyl)-tetra-
hydro-pyran-3-ol 8 as a major product.26 Compound 8
was subjected to Swern oxidation to give compound
Figure 4. The design of glycoside-type derivatives.
starting intermediate alcohol trans-6-benzhydryl-tetra-
hydro-pyran-3-ol 1 which was synthesized by us
earlier,22,23 was converted into cis-6-benzhydryl-tetrahy-
dro-pyran-3-carbonitrile 2 by two-step reactions. Thus,
mesylation with methanesulfonyl chloride in dichloro-
methane produced methanesulfonic acid 6-benzhydryl-
tetrahydro-pyran-3-ol ester which on SN2 substitution
Figure 5. Preliminary modeling study of different substituted tetrahydro-pyran derivatives.

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S. Zhang et al. / Bioorg. Med. Chem. 14 (2006) 3953–3966
NH
2
The synthesis of the final products 17 and 18 is shown in
CN
Scheme 3. Starting with the same reagent 3,4-dihydro-
2H-pyran-2-carbaldehyde 5, as we used in Scheme 2,
reductive amination with amino-diphenylmethane gave
intermediate benzhydryl-(3,4-dihydro-2H-pyran-2-ylm-
ethyl)-amine 13 in 85% yield.19 Hydroboration with
BH3 in THF followed by oxidation with NaOH and
H2O2 produced trans-6-[(benzhydryl-amino)-methyl]-
tetrahydro-pyran-3-ol 14 as the major product in 55%
yield.26 This trans-alcohol intermediate 14 was convert-
ed into cis-amine precursor 6-[(benzhydryl-amino)-
methyl]-tetrahydro-pyran-3-ylamine 15 through three
reactions which involved first mesylation with metha-
nesulfonyl chloride in dichloromethane followed by
SN2 substitution with NaN3 in DMF, and finally reduc-
tion by lithium aluminum hydride (LAH) in tetrahydro-
furan (THF). Reductive amination with 4-
fluorobenzaldehyde and 4-hydroxy-benzaldehyde gave
the final products cis-6-[(benzhydryl-amino)-methyl-tet-
rahydro-pyran-3-yl]-(4-fluorobenzyl)-amine 17 and cis-
6-[(benzhydryl-amino)-methyl-tetrahydro-pyran-3-yl]-
(4-hydroxy-benzyl)-amine 18, both in 85% yield,
respectively.
c
O
O
a,b
O
OH
3
1
2
d
F
H
N
O
4
Scheme 1. Reagents and conditions: (a) CH3SO2Cl, Et3N/CH2Cl2,
room temperature, 4 h, 77.8%; (b) NaCN/DMF, 100 ꢁC, 85%; (c)
Raney-Ni; 4-fluorobenzaldehyde,
ClCH2CH2Cl, room temperature, 65%.
(d)
AcOH,
NaCNBH3/
6-(tert-butyl-diphenyl-silanyloxylmethyl)-dihydro-pyran-
3-one 9. Reductive amination of compound 9 with 4-flu-
orobenzylamine gave trans-[6-(tert-butyl-diphenyl-silan-
yloxylmethyl)-tetrahydro-pyran-3-yl]-(4-fluorobenzyl)-
amine and cis-[6-(tert-butyl-diphenyl-silanyloxylmeth-
yl)-tetrahydro-pyran-3-yl]-(4-fluorobenzyl)-amine
10,
respectively, which were carefully separated by chroma-
tography in 55% and 40% yield, respectively. Deprotec-
tion of trans-10 with tetra-n-butylammonium fluoride
(TBAF) in THF gave trans-[5-(4-fluorobenzylamino)-
tetrahydro-pyran-2-yl]-methanol 11 in 70% yield, and
the same procedure starting from cis-10 afforded cis-[5-
(4-fluorobenzylamino)-tetrahydro-pyran-2-yl]-methanol
cis-11 in 75% yield. Williamson condensation with benz-
hydrol starting from trans-11 and cis-11, respectively,
gave the final products trans-(6-benzhydryloxymethyl-
Lastly, the synthesis of sugar-type derivatives cis-(6-ben-
zhydryloxy-tetrahydro-pyran-3-yl)-(4-fluorobenzyl)-
amine 24 and trans-(6-benzhydryloxy-tetrahydro-pyran-
3-yl)-(4-fluorobenzyl)-amine 24 is shown in Scheme 4.
Starting from commercially available furfuryl alcohol
19, reaction in the presence of N-bromosuccinimide
(NBS), NaHCO3, and NaOAc followed by the addition
of acetic anhydride gave acetic acid 5-oxo-5,6-dihydro-
2H-pyran-2-yl ester 20 in 64% yield. This ester 20 was
reacted with benzhydrol in the presence of SnCl4 to pro-
duce 6-benzhydryloxy-6H-pyran-3-one 21 in 90%
tetrahydro-pyran-3-yl)-(4-fluorobenzyl)-amine,
trans-
12, and cis-(6-benzhydryloxymethyl-tetrahydro-pyran-
3-yl)-(4-fluorobenzyl)- amine, cis-12, in 70% and 65%
yield, respectively.
O
OTBDPS
d
b,c
a
HO
OTBDPS
O
OH
H
O
O
O
8
9
6
O
5
e
F
HN
F
N
H
O
O
TBDPSO
+
TBDPSO
cis-10
trans-10
f
f
F
F
HN
N
O
HO
H
O
trans-11
HO
cis-11
g
g
F
HN
F
N
O
O
H
O
O
cis-12
trans-12
Scheme 2. Reagents and conditions: (a) NaBH4/EtOH, À78 ꢁC to room temperature, 4 h, 85%; (b) TBDPSCI, imidazole/DMF, room temperature,
quantitative yield; (c) i—BH3/THF; ii—NaOH, H2O2, 92.4%; (d) oxalyl chloride, DMSO, Et3N/CH2Cl2, À78 ꢁC to room temperature, 30 min, 81%;
(e) 4-fluorobenzylamine, AcOH, NaCNBH3/ClCH2CH2Cl, room temperature, 55% and 40%; (f) TBAF/THF, 0 ꢁC to room temperature, 70–75%; (g)
benzhydrol, TsOH/benzene, azotropic distillation, 65–70%.

S. Zhang et al. / Bioorg. Med. Chem. 14 (2006) 3953–3966
3957
H
a
H
b
H
N
c,d,e
N
N
H
O
O
O
HO
O
O
NH
2
14
13
5
15
f
H
N
17 R=
18 R=
F
OH
O
NH
R
Scheme 3. Reagents and condition: (a) benzhydrylamine, AcOH, NaCNBH3/ClCH2CH2Cl; (b) i—BH3/THF; ii—NaOH, H2O2; (c) CH3SO2Cl,
Et3N/CH2Cl2; (d) NaN3/DMF; (e) LAH/THF; (f) aldehyde, AcOH, NaCNBH3/ClCH2CH2Cl.
O
O
H
O
O
a
b
F
c
O
O
O
O
OH
22
O
21
19
OAc
20
g
d,e,f
NH
2
N
O
O
h
O
O
H
O
O
O
25
cis-24
23
h
F
HN
O
O
trans-24
Scheme 4. Reagents and conditions: (a) i—NBS, NaHCO3, NaOAc/MeOH/H2O; ii—AC2O; (b) SnCl4, benzhydrol/CH2Cl2; (c) BF3/Et2O,
NaCNBH3/THF; (d) CH3SO2Cl, Et3N/CH2Cl2; (e) NaN3/DMF; (f) LAH/THF; (g) L-selectride/THF; (h) aldehyde or amine, AcOH, NaCNBH3/
ClCH2CH2Cl.
yield.27 Starting from this enone intermediate 21, two
different methods have been employed to synthesize
cis-24 and trans-24. Reduction of this enone 21 under
the same condition as we used in our previous reported
method, gave predominantly cis-6-benzhydryloxy-tetra-
hydro-pyran-3-ol 22 in 70% yield.22 The conversion of
cis-22 into trans-6-benzhydryloxy-tetrahydro-pyran-3-
yl-amine 23 was achieved under the same set of reaction
conditions as we employed for the conversion of trans-
14 into cis-15 shown in Scheme 3. Thus, mesylation with
methanesulfonyl chloride in dichloromethane followed
by SN2 substitution with NaN3 in DMF and reduction
with LAH in THF yielded 23. Reductive amination of
trans-23 with 4-fluorobenzaldehyde produced the final
compound trans-(6-benzhydryloxy-tetrahydro-pyran-3-
yl)-(4-fluorobenzyl)-amine 24 in 81% yield. For the syn-
thesis of cis-24, 6-benzhydryloxy-6H-pyran-3-one 21
was reduced to 6-benzhydryloxy-dihydro-pyran-3-one
25 with L-selectride in THF in 80% yield. Reductive
amination of this keto compound 25 with 4-fluoroben-
zylamine gave only the final product cis-(6-benzhydryl-
oxy-tetrahydro-pyran-3-yl)-(4-fluorobenzyl)-amine 24
in 80% yield.
All the synthesized compounds were characterized by
1H NMR and 13C NMR, and their elemental analysis
results are shown in Table 4 of the supplemental section.
3.1. In vitro characterization
All the synthesized molecules were tested for their in vi-
tro binding affinity at rat DAT by measuring their abil-
ity to compete for the high-affinity binding of the
radioligand [3H]WIN35,428 and the uptake of dopa-
mine, serotonin, and norepinephrine as we described in
our earlier report. The results are shown in Table 1.
4. Discussion
In our earlier reports, we have established two different
types of substituted tetrahydro-pyran pharmacophoric
structures with different potency and selectivity at
monoamine transporter systems.22–24 Even though the
3,6-disubstituted tetrahydro-pyran derivatives exhibited
preferential potency and selectivity at DAT or NET,
while the (2,4,5)-trisubstituted tetrahydro-pyran deriva-

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S. Zhang et al. / Bioorg. Med. Chem. 14 (2006) 3953–3966
Table 1. Affinity of drugs at dopamine, serotonin, and norepinephrine transporters in rat striatum
Compound
DAT binding,
IC50, nM, [3H]WIN 35, 428a
DAT uptake,
IC50, nM, [3H]DAa
SERT uptake,
IC50, nM, [3H]5-HTa
NET uptake,
IC50, nM [3H]NEa
Cocaine
GBR 12909
266 37
10.6 1.9
313 71b
163 29b
308 25c
398 33
737 160a
101.4 14.2
3130 550b
114 36
14.2 2.9
II
I
III
156 36
169 20
215 14
104 49
165 17
676 33
4400
13.3 1.0
3432 1752
1328 592
1435
4
cis-12
trans-12
17
80.4 17.4
162 19
>10,000
>10,000
110
6
168
239
9
9
3570 664
1477 224
1660 150
2977 229
1489 133
536 45
18
cis-24
trans-24
247 23
520 47
366 52
213 38
309 16
1689 503
290 59
a For binding, the DAT was labeled with [3H]WIN 35, 428. For uptake by DAT, SERT and NET, [3H]DA, [3H]5-HT and [3H]NE accumulation were
measured. Results are averages SEM of three to eight independent experiments assayed in triplicate.
b Results are from Ref. 23.
c Results are from Ref. 24.
tives exhibited potency and selectivity at either NET or
SERT, still an overall cis-stereochemistry between the
benzhydryl substituent and the exocyclic N-substituent
in tetrahydro-pyran ring was maintained in these two
series of derivatives.24 These results indicated that the
distance between these two groups and their orientation
which is controlled by their positions in tetrahydro-py-
ran ring are important structural determinants required
for their affinities at monoamine transporter systems. To
further explore the effects of the change in distance be-
tween these two groups on their potency and selectivity
for monoamine transporter systems, we have designed
and biologically characterized various side-chain-ex-
tended analogues at either 3- or 6-positions on the tetra-
hydro-pyran ring (Table 1).
Following the above results, compounds 17 and 18
were designed to investigate whether the replacement
of the O-atom by a bioisosteric NH will alter inter-
action with monoamine transporters especially with
DAT. In these N-version analogues, we also wanted
to examine introduction of p-hydroxy-benzyl substi-
tution as shown in compound 18. In this regard,
in our previous study, we found that introduction
of a hydroxyl substitution in the para-position of
the N-benzyl moiety in cis-3,6-disubstituted pyran
derivatives could shift potency selectivity in favor
of NET.23 Results from compound 17 indicated that
replacement of the oxygen-atom by a more basic
NH moiety in 6-position side chain marginally de-
creased its activity at the DAT, and this compound
exhibited little or no activity at SERT and NET.
This slight loss in DAT activity compared to com-
pound cis-12 might be caused by the subtle change
in interactions caused by replacement of the O-atom
by a more basic N-atom. However, the binding
activity of this compound is still greater than its
parent compound I which further indicated that 6-
position-side-chain modification might lead to more
potent and selective molecules at DAT. Interestingly,
compound 18 exhibited 3-fold decrease in DAT
binding activity when compared with compound
cis-12 while its NET activity was increased by 2.5
times as found in our earlier work.23 However, the
selectivity of compound 18 was exhibited still in fa-
vor of DAT in spite of its increase in NET activity.
These results indicated that even though hydroxyl
substitution in the para-position of benzyl phenyl
ring could decrease DAT activity and increase
NET activity, it could not reverse the selectivity as
shown in our previous 3,6-disubstituted compound.
This further indicated the existence of different inter-
action modes between these side-chain derivatives
and our first-generation cis-3,6-disubstituted tetrahy-
dro-pyran derivatives. More work will be needed to
map out the molecular determinant requirements in
Compound 4 exhibited decreased activities compared to
its parent compound I at all three transporters including
DAT (Table 1, DAT; IC50, 215 vs 156 nM). Results from
compound 4 indicated that side-chain extension at the 3-
position of tetrahydro-pyran ring adversely affected the
binding activity of this molecule and that the direct link-
age between the exocyclic N-substituent and the tetrahy-
dro-pyran ring is important for interaction with
monoamine transporters. On the other hand, compounds
trans-12 and cis-12 both exhibited increased activity at
DAT compared to their parent compounds II and I,
respectively, and the increase in DAT binding activity
was 2-fold for both the compounds (162 and 80.4 vs 313
and 163 nM). It is also interesting to note that the cis-
stereochemical preference for DAT activity was still
maintained in these side-chain-extended derivatives as
cis-isomer of 12 was two times more active at the DAT
compared to its trans-version. The increase in DAT activ-
ity in this 6-position side-chain-extended template might
be caused by conformational changes due to the introduc-
tion of more flexible side chain, or additional hydrogen
bonding interaction with the newly incorporated side-
chain oxygen-atom. These results also indicated that
side-chain modification at the 6-position on this new cis-
tetrahydro-pyran template might lead to development
of more potent and selective molecules at the DAT.
this
template.
new
side-chain-extended
tetrahydro-pyran

S. Zhang et al. / Bioorg. Med. Chem. 14 (2006) 3953–3966
3959
Glycoside derivatives cis-24 and trans-24 exhibited inter-
esting results. cis-24 exhibited weak activity at DAT and
no activity at SERT and NET; however, a separation in
DAT binding and dopamine uptake activity in this com-
pound was noticed, and the selectivity was reversed in fa-
vor of uptake inhibition. On the other hand, trans-24
exhibited relatively higher activity at both DAT and
NET. The activity for NET in trans-24 was substantially
higher compared to that in cis-24 (290 vs 1689 nM). It is
interesting to note that even though the activity of these
two compounds was low, stereochemical preference for
the overall monoamine transporter activity was found
in the trans-version.
6.1. Synthesis of 6-benzhydryl-tetrahydro-pyran-3-carbo-
nitrile (2)
6.1.1. Procedure A. Synthesis of methanesulfonic acid
trans-6-benzhydryl-tetra-hydropyran-3-yl ester. Metha-
nesulfonyl chloride (0.62 g, 5.41 mmol) dissolved in
dry methylene chloride (10 ml) was added dropwise
to a mixture of trans-6-benzhydryl-tetrahydro-pyran-
3-ol
1 (0.73 g, 2.71 mmol), triethylamine (0.41 g,
4.06 mmol) in methylene chloride (10 ml) and was
cooled to 0 ꢁC. After 1 h, the reaction was brought
to room temperature over a period of 4 h. Additional
methylene chloride (20 ml) was added to the reaction
mixture, and the mixture was washed in turn with sat-
urated aqueous sodium bicarbonate, brine, and water,
and then dried over anhydrous sodium sulfate. The
solvent was removed under reduced pressure, and
purification by flash chromatography gave methane-
sulfonic acid trans-6-benzhydryl-tetrahydro-pyran-3-yl
ester (0.94 g, quantitative yield).
5. Conclusion
In our current study, the effects of the change in distance
between the exocyclic N-atom and the benzhydryl
moiety on activity at monoamine transporters were
explored, and results from this study indicated that
side-chain extension at 6-position of tetrahydro-pyran
ring could lead to increase in DAT activity as shown
in compound cis-12, while 3-position extension
adversely affected activity at all three transporters. In
two glycoside derivatives, cis-24 exhibited weak activity
at DAT, while trans-24 exhibited dual weak activity at
both DAT and NET. In general, cis-stereochemistry
between two substituents on the tetrahydro-pyran
ring is a preferential pharmacophoric requirement for
interacting with DAT.
1H NMR (300 Hz, CDCl3): 1.50 (m, 1H, H-5), 1.60–1.80
(m, 2H, H-4, H-5), 2.26 (m, 1H, H-4), 2.98 (s, 3H,
CH3SO2), 3.38 (t, J = 10.50 Hz, 1H, H-2ax), 3.91 (d,
J = 9.30 Hz, 1H, Ph2CH), 4.03 (dt, J = 1.80 Hz,
9.50 Hz, 1H, H-6), 4.15 (m, 1H, H-2eq), 4.63 (m, 1H,
H-3), 7.16–7.38 (m, 10H, aromatic-CH).
13C NMR (75 MHz, CDCl3): 29.51, 30.59, 38.69, 57.11,
69.87, 75.25, 79.04, 126.71, 126.95, 128.57, 128.62,
128.66, 128.92, 141.62, 141.77.
6.1.2. Procedure B. Synthesis of 6-benzhydryl-tetrahydro-
pyran-3-carbonitrile (2). Into a solution of methanesulf-
onic acid trans-6-benzhydryl-tetrahydropyran-3-yl ester
(0.1 g, 0.29 mmol) in dry DMF was added NaCN
(0.03 g, 0.58 mmol). The mixture was heated at 100 ꢁC
overnight. The mixture was diluted with ethyl ether
(50 ml), and was washed in turn with water, saturated
NaHCO3, and brine, and then was dried over anhydrous
Na2SO4. Removal of the solvent and purification
by flash chromatography (hexane/ethyl acetate 7:3)
gave cis-6-benzhydryl-tetrahydropyran-3-carbonitrile 2
(0.07 g, 85% yield).
6. Experimental details
Reagents and solvents were obtained from commercial
suppliers and used as received unless otherwise indicat-
ed. Dry solvent was obtained according to the standard
procedure as in Vogel’s. All reactions were performed
under inert atmosphere (N2) unless otherwise noted.
Analytical silica gel-coated TLC plates (Si250F) were
purchased from Baker, Inc. and were visualized with
UV light or by treatment with phosphomolybdic acid
(PMA) and ninhydrin solution. Flash chromatography
1
was carried out on Baker silica gel 40 mm. H NMR
and 13C NMR spectra were routinely obtained at GE-
300 MHz FT NMR, Varian Unity-300/500, and Varian
Mercury-400 NMR. The NMR solvents used were
CDCl3, CD3OD, or deuterium-acetone as indicated.
TMS was used as an internal standard. Elemental anal-
yses were performed by Atlantic Microlab, Inc. and
were within 0.4% of the theoretical values. Yield is of
purified product.
1H NMR (300 MHz, CDCl3): 1.50 (m, 1H, H-5), 1.62–
1.84 (m, 2H, H-4, H-5), 2.08 (m, 1H, H-4), 2.71 (m,
1H, H-3), 3.55 (dd, J = 1.80 Hz, 11.70 Hz, 1H, H-2),
4.00–4.20 (m, 3H, H-2, H-6, Ph2CH), 7.06–7.40 (m,
10H, aromatic-CH).
6.1.3. Synthesis of cis-(6-benzhydryl-tetrahydro-pyran-3-
yl)-methylamine (3). cis-6-Benzhydryl-tetrahydropyran-
3-carbonitrile 2 (0.6 g, 0.22 mmol) dissolved in ethanol
was hydrogenated in the presence of Raney-Ni (70 mg,
wet weight) overnight (60 psi pressure) to give cis-
[3H]WIN 35,428 (87.0 Ci/mmol), [3H]dopamine (59.4 Ci/
mmol), [3H]serotonin (30.0 Ci/mmol), and [3H]norepi-
nephrine (52.0 Ci/mmol) were obtained from Dupont-
New England Nuclear (Boston, MA, USA). (À)-Co-
caine hydrochloride, WIN 35,428 naphthalene sulfo-
nate, and GBR 12909 dihydrochloride (1-[2-[bis(4-
fluorophenyl)methoxy]ethyl]-4-[3-phenylpropyl]piperazine)
were purchased from SIGMA–ALDRICH (St. Louis,
MO).
(6-benzhydryl-tetrahydro-pyran-3-yl)-methylamine
(0.5 g, 82% yield).
3
1H NMR (400 MHz, CDCl3): 1.26 (m, 1H, H-5), 1.37
(m, 1H, H-5), 1.58–1.76 (m, 3H, H-4, H-3), 2.59 (m,
1H, CH2NH2), 2.73 (m, 1H, CH2NH2), 3.60 (m, 1H,
H-2), 3.80 (d, J = 12.00 Hz, H-2), 3.92 (m, 1H,

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S. Zhang et al. / Bioorg. Med. Chem. 14 (2006) 3953–3966
Ph2CH), 4.11 (m, 1H, H-6), 7.00–7.40 (m, 10 H, aro-
matic-CH).
6.3. Synthesis of trans-6-(tert-butyl-diphenyl-silanyl-
oxymethyl)-tetrahydro-pyran-3-ol (8)
13C NMR (100 MHz, CDCl3): 25.66, 25.79, 33.56,
47.13, 57.32, 69.38, 79.51, 125.95, 126.26, 127.98,
128.33, 128.42, 128.69, 141.90.
6.3.1. (a) Synthesis of tert-butyl-(3,4-dihydro-2H-pyran-
2-yl-methoxy)-diphenyl-silane. Into a solution of 3,4-di-
hydyo-2H-pyran-2-yl-methanol 6 (1 g, 8.8 mmol) and
imidazole (1.32 g, 19.36 mmol) in dry DMF (50 ml)
was added tert-butyl-diphenylsilylchloride (2.65 g,
9.6 mmol) at 0 ꢁC. The reaction mixture was allowed
to reach room temperature and was continued for 2 h.
Removal of the solvent and purification by flash chro-
matography (hexane/ether 20:1) gave pure product
tert-butyl-(3,4-dihydro-2H-pyran-2-yl-methoxy)-diphenyl-
silane 3.09 g (quantitative yield).
6.1.4. Procedure C. Synthesis of (6-benzhydryl-tetrahy-
dro-pyran-3-ylmethyl)-(4-fluorobenzyl)-amine (4). A solu-
tion
of
cis-(6-benzhydryl-tetrahydro-pyran-3-yl)-
methylamine 3 (0.04 g, 0.14 mmol), 4-fluorobenzalde-
hyde (0.02 g, 0.14 mmol), and glacial acetic acid
(0.01 g, 0.14 mmol) in dry CH2Cl2 (20 ml) was stirred
at room temperature for 2 h. NaCNBH3 (0.01 g,
0.21 mmol) in methanol (5 ml) was added into above
solution, and the mixture was stirred at room tempera-
ture for 4 h. Water was added to quench the reaction
and the mixture was stirred for 30 min at 0 ꢁC. Then
the mixture was basified with saturated aqueous NaH-
CO3 and extracted thrice with CH2Cl2 (3· 30 ml). The
combined organic phase was washed with brine, water
and dried over anhydrous Na2SO4. Solvent was re-
moved to collect the crude residue. The residue was puri-
fied by flash chromatography (hexane/ethyl acetate/
triethylamine 3:2:0.2) to give (6-benzhydryl-tetrahydro-
1H NMR (400 MHz, CDCl3): 1.47 (s, 9H, 3CH3), 1.79
(m, 1H, H-3), 2.00 (m, 2H, H-3, H-4), 2.11 (m, 1H, H-
4), 3.76 (m, 1H, CH2OH), 3.87 (m, 1H, CH2OH), 4.71
(m, 1H, H-5), 6.44 (d, J = 5.60 Hz, 1H, H-6), 7.20–
7.80 (m, 10H, aromatic-CH).
6.3.2. (b) Procedure D. Synthesis of trans-6-(tert-butyl-
diphenyl-silanyloxymethyl)-tetrahydro-pyran-3-ol
(8).
Into a solution of tert-butyl-(3,4-dihydro-2H-pyran-2-
yl-methoxy)-diphenyl-silane (0.31 g, 0.88 mmol) in dry
THF was added BH3/THF drop by drop (4.4 ml of
1.0 M BH3/THF, 4.4 mmol) at 0 ꢁC. After addition,
the mixture was brought to room temperature and the
reaction was continued at room temperature overnight.
The reaction mixture was then oxidized by adding
NaOH (1.76 ml of 3 N NaOH, 5.28 mmol) and H2O2
(0.24 g, 7.04 mmol), and the reaction was kept at 55 ꢁC
for 1 h. K2CO3 was added at 0 ꢁC and the mixture
was stirred for 30 min. The reaction mixture was extract-
ed with ethyl acetate (3· 30 ml). The combined organic
phase was dried over anhydrous Na2SO4. Removal of
the solvent and purification by flash chromatography
(hexane/ethyl acetate 1:1) gave pure trans-6-(tert-butyl-
pyran-3-ylmethyl)-(4-fluorobenzyl)-amine
65% yield).
4
(0.03 g,
1H NMR (400 MHz, CDCl3): 1.20–1.46 (m, 2H, H-5),
1.60–1.82 (m, 3H, H-3, H-4), 2.66 (m, 1H, –CH2NH–),
2.81 (m, 1H, –CH2NH–), 3.61 (dd, J = 2.80 Hz,
11.60 Hz, 1 H, H-2), 3.73 (m, 2H, (F)PhCH2), 3.92 (m,
2H, Ph2CH, H-2), 4.03 (dt, J = 2.00 Hz, 9.60 Hz, 1H,
H-6), 6.80–7.40 (m, 14H, aromatic-CH).
13C NMR (100 MHz, CDCl3): 26.00, 26.08, 34.00,
49.79, 53.59, 57.49, 70.13, 79.57, 115.22, 115.43,
126.43, 126.61, 128.54, 128.71, 129.77, 129.85.
diphenyl-silanyloxymethyl)-tetrahydro-pyran-3-ol
(0.3 g, 92.4% yield).
8
Free base was converted into oxalate in ethanol: mp 136–
138 ꢁC. Anal. [C25H27NO2Æ(COOH)20.4H2O] C, H, N.
1H NMR (300 MHz, CDCl3): 1.06 (s, 9H, 3CH3), 1.39
(m, 1H, H-5), 1.83 (m, 2H, H-5, H-4), 2.13 (m, 1H, H-
4), 3.10 (t, J = 10.50 Hz, 1H, H-2), 3.37 (m, 1H, H-6),
3.54 (m, 1H, CH2OTBDPS), 3.62–3.78 (m, 2H,
CH2OTBDPS, H-3), 3.99 (m, 1H, H-2), 7.20–7.80 (m,
10H, aromatic-CH).
6.2. Synthesis of 3,4-dihydro-2H-pyran-2-yl-methanol (6)
Into a solution of 3,4-dihydro-2H-pyran-2-carbaldehyde
5 (1 g, 8.93 mmol) in ethanol (25 ml) at À78 ꢁC was add-
ed NaBH4 (1.01 g, 26.8 mmol) in portionwise manner.
After 1 h, the mixture was brought to room temperature
over a period of 4 h. Saturated NaHCO3 was added and
the resulting solution was concentrated under reduced
pressure. The aqueous phase was extracted with ethyl
acetate (3· 30 ml), and the combined organic phase
was dried over anhydrous Na2SO4. Removal of the sol-
vent and purification by flash chromatography (hexane/
ethyl acetate 7:3) gave pure product 0.87 g (85% yield).
13C NMR (75 MHz, CDCl3): 27.10, 27.42, 32.72, 66.63,
66.88, 72.77, 77.71, 127.88, 129.88, 133.81, 133.84,
135.85.
6.4. Synthesis of 6-(tert-butyl-diphenyl-silanyloxymethyl)-
tetrahydro-pyran-3-one (9)
Into a solution of dimethylsulfoxide (DMSO) (0.15 g,
1.94 mmol) in dry CH2Cl2 (20 ml) at À78 ꢁC was added
oxylyl chloride (0.13 g, 0.97 mmol) in dry CH2Cl2 in a
dropwise manner. trans-6-(tert-Butyl-diphenyl-silanyl-
oxymethyl)-tetrahydro-pyran-3-ol 8 (0.32 g, 0.88 mmol)
in dry CH2Cl2 (10 ml) was then added via syringe. After
15 min, Et3N (0.44 g, 4.4 mmol) was added drop by
drop. After 5 min at À78 ꢁC, the reaction mixture was
1H NMR (400 MHz, CDCl3): 1.61 (m, 1H, H-3), 1.72
(m, 1H, H-3), 1.90 (m, 1H, H-4), 2.03 (m, 1H, H-4),
2.95 (s, 1H, OH), 3.59 (m, 2H, CH2OH), 3.83 (m, 1H,
H-2), 4.62 (M, 1H, H-5), 6.30 (d, J = 5.6 Hz, 1H, H-6).
13C NMR (100 MHz, CDCl3): 19.57, 24.07, 65.37,
75.81, 100.97, 143.48.

S. Zhang et al. / Bioorg. Med. Chem. 14 (2006) 3953–3966
3961
brought to room temperature over a period of 30 min.
The mixture was washed in turn with saturated NaH-
CO3, brine, and water, and then dried over anhydrous
Na2SO4. Removal of the solvent and purification by
chromatography (hexane/ethyl acetate 7:3) gave pure
6-(tert-butyl-diphenyl-silanyloxymethyl)-tetrahydro-py-
ran-3-one 9 (0.26 g, 81% yield).
1H NMR (500 MHz, CDCl3): 1.45 (m, 1H, H-3), 1.56–
1.72 (m, 2H, H-3, H-4), 2.08 (m, 1H, H-4), 2.67 (m,
1H, H-5), 3.10 (t, J = 11.00 Hz, 1H, H-6), 3.36 (m, 1H,
H-2), 3.49 (m, 1H, CH2OH), 3.60 (m, 1H, CH2OH),
3.78 (m, 2H, PhCH2), 4.08 (m, 1H, H-6), 6.90–7.40
(m, 4H, aromatic-CH).
13C NMR (125 MHz, CDCl3): 27.76, 27.79, 49.87,
50.59, 57.57, 70.50, 79.54, 126.56, 126.73, 127.57,
128.59, 128.72, 128.77, 130.11, 130.45, 130.79, 132.54,
141.34, 142.33, 142.59.
1H NMR (300 MHz, CDCl3): 1.09 (s, 9H, 3CH3), 1.96
(m, 1H, H-5), 2.12 (m, 1H, H-5), 2.47 (m, 1H, H-4),
2.62 (m, 1H, H-4), 3.71 (m, 1H, H-6), 3.82 (m, 2H,
CH2OTBDPS), 3.96 (m, 1H, H-2), 4.15 (m, 1H, H-2),
7.20–7.80 (m, 10H, aromatic-CH).
6.6. Synthesis of cis-[5-(4-fluorobenzylamino)-tetrahydro-
pyran-2-yl]-methanol (cis-11)
6.5. Synthesis of trans-[6-(tert-butyl-diphenyl-silanyl-
oxymethyl)-tetrahydro-pyran-3-yl]-(4-fluorobenzyl)-
amine (10) and cis-[6-(tert-butyl-diphenyl-silanyloxy-
methyl)-tetrahydro-pyran-3-yl]-(4-fluorobenzyl)-amine
(10)
cis-[6-(tert-Butyl-diphenyl-silanyloxymethyl)-tetrahydro-
pyran-3-yl]-(4-fluorobenzyl)-amine (0.09 g, 0.19 mmol)
was reacted with TBAF (0.1 g, 0.38 mmol) at 0 ꢁC in dry
THF (Procedure E) to give cis-[5-(4-fluorobenzylamino)-
tetrahydro-pyran-2-yl]-methanol 11 (0.03 g, 75% yield).
6-(tert-Butyl-diphenyl-silanyloxymethyl)-tetrahydro-py-
ran-3-one 9 (0.26 g, 0.7 mmol) was reacted with 4-fluo-
robenzylamine (0.09 g, 0.7 mmol) in the presence of
glacial acetic acid (0.04 g, 0.7 mmol) in 1,2-dichloroeth-
ane (10 ml) and then reduced by NaCNBH3 (0.05 g,
0.84 mmol) in methanol (5 ml) (Procedure B) to give a
mixture of cis-[6-(tert-butyl-diphenyl-silanyloxymeth-
yl)-tetrahydro-pyran-3-yl]-(4-fluorobenzyl)-amine and
trans-[6-(tert-butyl-diphenyl-silanyloxymethyl)-tetrahy-
dro-pyran-3-yl]-(4-fluorobenzyl)-amine.
1H NMR (400 MHz, CDCl3): 1.16–1.40 (m, 2H, H-3),
1.55 (m, 1H, H-4), 2.02 (m, 1H, H-4), 2.59 (m, 1H, H-
5), 3.04 (t, J = 10.40 Hz, 1H, H-6), 3.26-3.54 (m, 3H,
H-2, CH2OH), 3.72 (m, 2H, PhCH2), 4.01 (m, 1H,
H-6), 6.90–7.40 (m, 4H, aromatic-CH).
6.6.1. Procedure F. Synthesis of trans-(6-benzhydryloxym-
ethyl-tetrahydro-pyran-3-yl)-(4-fluorobenzyl)-amine (trans-
12). A mixture of trans-[5-(4-fluorobenzylamino)-tetra-
hydro-pyran-2-yl]-methanol 11 (0.16 g, 0.67 mmol),
benzhydrol (0.12 g, 0.67 mmol), and p-toluenesulfanic
acid (0.15 g, 0.8 mmol) in benzene was refluxed under
azotropic distillation condition overnight. Removal of
solvent and purification by chromatography (hexane/
ethyl acetate/Et3N 7:3:0.3) gave pure trans-(6-benzhyd-
ryloxymethyl-tetrahydro-pyran-3-yl)-(4-fluorobenzyl)-
amine 12 (0.19 g, 70% yield).
cis-[6-(tert-Butyl-diphenyl-silanyloxymethyl)-tetrahydro-
pyran-3-yl]-(4-fluorobenzyl)-amine was eluted first
(0.13 g, 40% yield).
1H NMR (300 MHz, CDCl3): 1.05 (s, 9H, 3CH3), 1.27
(m, 1H, H-5), 1.50–1.70 (m, 2H, H-4, H-5), 1.98 (m,
1H, H-4), 2.64 (m, 1H, H-3), 3.40–3.80 (m, 6H, H-2,
H-6, CH2OTBDPS, PhCH2), 3.97 (m, 1H, H-2), 6.90–
7.80 (m, 14H, aromatic-CH).
1H NMR (400 MHz, CDCl3): 1.32 (m, 1H, H-4), 1.47
(dq, 1H, J = 2.40 Hz and 12.0 Hz, H-5ax), 1.80 (m,
1H, H-5eq), 2.10 (m, 1H, H-4), 2.70 (tt, 1H, J =
4.0 Hz and 10.40 Hz, H-3), 3.12 (t, J = 10.40 Hz, 1H,
H-2ax), 3.45 (m, 1H, CH2OR), 3.52–3.62 (m, 2H, H-6,
CH2OR), 3.80 (m, 2H, PhCH2), 4.13 (m, 1H, H-2eq),
5.44 (s, 1H, Ph2CH), 6.90–7.42 (m, 14H, aromatic-CH).
Eluted second was trans-[6-(tert-butyl-diphenyl-silanyl-
oxymethyl)-tetrahydro-pyran-3-yl]-(4-fluorobenzyl)-
amine (0.19 g, 55% yield).
1H NMR (500 MHz, CDCl3): 1.08 (s, 9H, 3CH3), 1.24–
1.42 (m, 2H, H-5), 1.81 (m, 1H, H-4), 2.07 (m, 1H, H-4),
2.66 (m, 1H, H-3), 3.06 (t, J = 10.50 Hz, 1H, H-2), 3.39
(m, 1H, H-6), 3.55 (m, 1H, CH2OTBDPS), 3.70–3.82
(m, 3H, CH2OTBDPS, PhCH2), 4.06 (M, 1H, H-2),
6.90–7.80 (m, 14H, aromatic-CH).
13C NMR (100 MHz, CDCl3): 28.12, 31.13, 50.86,
53.46, 72.44, 72.85, 76.97, 84.35, 115.39, 115.61,
127.34, 127.38, 127.72, 128.64, 129.79, 129.87, 142.41.
Free base was converted into oxalate salt from ethanol:
mp 207–208 ꢁC. Anal. [C26H28NFO2Æ(COOH)2] C, H, N.
6.5.1. Procedure E. Synthesis of trans-[5-(4-fluor-
obenzylamino)-tetrahydro-pyran-2-yl]-methanol (trans-
11). Into a solution of trans-[6-(tert-butyl-diphenyl-sila-
nyloxymethyl)-tetrahydro-pyran-3-yl]-(4-fluorobenzyl)-
amine 10 (0.09 g, 0.19 mmol) in dry THF (10 ml) was
added TBAF (0.1 g, 0.38 mmol) at 0 ꢁC. The reaction
mixture was brought to room temperature over a period
of 2 h. Removal of the solvent and purification by chro-
matography (hexane/ethyl acetate/Et3N 7:3:0.3) gave
pure trans-[5-(4-fluorobenzylamino)-tetrahydro-pyran-
2-yl]-methanol 11 (0.03 g, 70% yield).
6.7. Synthesis of cis-(6-benzhydryloxymethyl-tetrahydro-
pyran-3-yl)-(4-fluorobenzyl)-amine (cis-12)
cis-[5-(4-Fluorobenzylamino)-tetrahydro-pyran-2-yl]-
methanol (0.16 g, 0.67 mmol) was reacted with benzhy-
drol (0.12 g, 0.67 mmol) in the presence of p-toluenesulf-
onic acid (0.15 g, 0.8 mmol) in benzene (Procedure F) to
give pure cis-(6-benzhydryloxymethyl-tetrahydro-pyran-
3-yl)-(4-fluorobenzyl)-amine 12 (0.18 g, 65% yield).

3962
S. Zhang et al. / Bioorg. Med. Chem. 14 (2006) 3953–3966
1H NMR (400 MHz, CDCl3): 1.50–1.62 (m, 2H, H-5),
1.68 (tt, 1H, J = 4.80 Hz and 12.80 Hz, H-4ax), 1.97
(m, 1H, H-4eq), 2.64 (m, 1H, H-3), 3.41 (m, 1H,
CH2OR), 3.50–3.58 (m, 2H, H-2, CH2OR), 3.63 (m,
1H, H-6), 3.78 (m, 2H, PhCH2), 4.00 (m, 1H, H-2),
5.44 (s, 1H, Ph2CH), 6.90–7.42 (m, 14H, aromatic-CH).
nyl chloride (0.06 g, 0.53 mmol), triethylamine (0.04 g,
0.35 mmol) (Procedure A) to give methanesulfonic acid
trans-6-[(benzhydryl-amino)-methyl]-tetrahydro-pyran-
3-yl ester (0.11 g, 85%).
1H NMR (400 MHz, CDCl3): 1.53 (m, 1H, H-5), 1.72
(m, 2H, H-4, H-5), 1.93 (br s, 1H, NH), 2.28 (m, 1H,
H-4), 2.60 (m, 2H, CH2NHR), 2.99 (s, 3H, CH3SO2),
3.33 (t, J = 10.40 Hz, 1H, H-2), 3.48 (m, 1H, H-6),
4.12 (m, 1H, H-2), 4.61 (m, 1H, H-3), 4.79 (s, 1H,
Ph2CH), 7.10–7.60 (m, 10H, aromatic-CH).
13C NMR (100 MHz, CDCl3): 23.67, 27.27, 50.31,
50.66, 70.26, 72.42, 84.28, 115.25, 115.46, 127.08,
127.20, 127.29, 127.67, 128.60, 129.76, 129.84, 142.42.
Free base was converted into oxalate salt from ethanol:
mp 203–204 ꢁC. Anal. [C26H28NFO2Æ(COOH)20.7H2O]
C, H, N.
13C NMR (100 MHz, CDCl3): 28.43, 30.31, 38.74,
52.60, 67.77, 69.55, 75.20, 127.26, 127.29, 127.48,
127.52, 128.72, 128.76, 144.04, 144.23.
6.8. Synthesis of benzhydryl-(3,4-dihydro-2H-pyran-2-yl-
methyl)-amine (13)
6.10.2. (2) Synthesis of cis-(5-azido-tetrahydro-pyran-2-
yl-methyl)-benzhydryl-amine. Methanesulfonic acid
trans-6-[(benzhydryl-amino)-methyl]-tetrahydro-pyran-
3-yl ester (0.25 g, 0.68 mmol) was reacted with sodium
azide (0.13 g, 2.03 mmol) (Procedure B) to give cis-(5-az-
ido-tetrahydro-pyran-2-yl-methyl)-benzhydryl-amine
(0.19 g, 90% yield).
3,4-Dihydro-2H-pyran-2-carbaldehyde
5
(1.5 g,
13.39 mmol) was reacted with benzhydrylamine (2.45 g,
13.39 mmol) in the presence of glacial acetic acid (0.8 g,
13.39 mmol) in 1,2-dichloroethane (50 ml) and then re-
duced by NaCNBH3 (1.01 g, 16.1 mmol) in methanol
(5 ml) (Procedure B) to give benzhydryl-(3,4-dihydro-
2H-pyran-2-yl-methyl)-amine 13 (3.17 g, 85% yield).
1H NMR (400 MHz, CDCl3): 1.42 (m, 1H, H-3), 1.60–
1.84 (m, 2H, H-3, H-4), 2.00 (m, 1H, H-4), 2.13 (br s,
1H, NH), 2.57–2.74 (m, 2H, CH2NHR), 3.52–3.64 (m,
3H, H-2, H-5, H-6), 3.98 (m, 1H, H-6), 4.81 (s, 1H,
Ph2CH), 7.10–7.60 (m, 10H, aromatic-CH).
1H NMR (400 MHz, CDCl3): 1.64–1.84 (m, 2H, H-3),
1.90–2.16 (m, 2H, H-4), 2.73 (m, 2H, CH2NHR), 4.01 (m,
1H, H-2), 4.68 (m, 2H, H-5), 4.85 (s, 1H, Ph2CH), 6.37 (d,
J = 4.00 Hz, 1H, H-6), 7.10–7.60 (m, 10H, aromatic-CH).
13C NMR (100 MHz, CDCl3): 24.65, 27.29, 53.42,
55.83, 67.88, 69.48, 77.29, 127.20, 127.25, 127.54,
127.59, 128.70, 128.73, 144.08, 144.48.
13C NMR (100 MHz, CDCl3): 19.87, 26.14, 52.58,
67.69, 74.73, 100.84, 127.21, 127.24, 127.53, 127.57,
128.70, 128.73, 143.78, 144.29.
6.10.3. (3) Procedure G. Synthesis of cis-6-[(benzhydryl-
amino)-methyl]-tetrahydro-pyran-3-ylamine (15). Into a sus-
pension of LiAlH4 (0.06 g, 1.49 mmol) in dry ethyl ether
(20 ml) was added a solution of cis-(5-azido-tetrahydro-py-
ran-2-yl-methyl)-benzhydryl-amine (0.12 g, 0.37 mmol) in
dry ethyl ether (25 ml) at 0 ꢁC under N2. The reaction mix-
ture was brought to room temperature over a period of 5 h.
The reaction was quenched by the addition of 10% NaOH
drop by drop. The mixture was dried over anhydrous
Na2SO4. Removal of the solvent and purification by
chromatography (ethyl acetate/methanol/triethylamine
8.8:1:0.2) gave cis-6-[(benzhydryl-amino)-methyl]-tetrahy-
dro-pyran-3-yl-amine 15 (0.09 g, 80% yield).
6.9. Synthesis of trans-6-[(benzhydryl-amino)-methyl]-
tetrahydro-pyran-3-ol (14)
Benzhydryl-(3,4-dihydro-2H-pyran-2-yl-methyl)-amine
13 (0.6 g, 2.25 mmol) in dry THF was reacted with BH3/
THF (11.2 ml 1.0 M BH3/THF, 11.2 mmol) at 0 ꢁC,
then followed by addition of NaOH (3.7 ml of 3 N
NaOH, 11.2 mmol) and H2O2 (1.27 g, 11.2 mmol) to
give pure trans-6-[(benzhydryl-amino)-methyl]-tetrahy-
dro-pyran-3-ol 14 (0.35 g, 55% yield) (Procedure D).
1H NMR (400 MHz, CDCl3): 1.39 (m, 2H, H-5), 1.62 (m,
1H, H-4), 1.92 (br s, 2H, NH, OH), 2.08 (m, 1H, H-4),
2.58 (m, 2H, CH2NHR), 3.10 (t, J = 10.40 Hz, 1H, H-2),
3.43 (m, 1H, H-6), 3.64 (m, 1H, H-3), 3.96 (m, 1H, H-2),
4.78 (s, 1H, Ph2CH), 7.10–7.60 (m, 10H, aromatic-CH).
1H NMR (400 MHz, CDCl3): 1.34 (m, 1H, H-5), 1.56
(m, 1H, H-5), 1.66–1.84 (m, 2H, H-4), 2.48–2.66 (m,
2H, CH2NHR), 2.82 (m, 1H, H-3), 3.51 (m, 1H, H-6),
3.60 (m, 1H, H-2), 3.73 (m, 1H, H-2), 4.81 (s, 1H,
Ph2CH), 7.10–7.60 (m, 10H, aromatic-CH).
13C NMR (100 MHz, CDCl3): 28.57, 32.89, 53.06,
66.59, 67.86, 72.77, 127.19, 127.24, 127.53, 127.57,
128.68, 128.72, 144.31.
13C NMR (100 MHz, CDCl3): 23.85, 29.00, 45.38,
52.78, 67.88, 72.00, 76.89, 127.20, 127.25, 127.54,
127.59, 128.70, 128.73, 144.08, 144.48.
6.10. Synthesis of cis-6-[(benzhydryl-amino)-methyl]-tet-
rahydro-pyran-3-ylamine (15)
6.11. Synthesis of cis-{6-[(benzhydryl-amino)-methyl]-tet-
rahydro-pyran-3-yl}-(4-fluorobenzyl)-amine (17)
6.10.1. (1) Synthesis of trans-methanesulfonic acid 6-
[(benzhydryl-amino)-methyl]-tetrahydro-pyran-3-yl ester.
trans-6-[(Benzhydryl-amino)-methyl]-tetrahydro-pyran-
3-ol (0.1 g, 0.35 mmol) was reacted with methanesulfo-
cis-6-[(Benzhydryl-amino)-methyl]tetrahydro-pyran-3-
yl-amine 15 (0.27 g, 0.91 mmol) was reacted with 4-flu-

S. Zhang et al. / Bioorg. Med. Chem. 14 (2006) 3953–3966
3963
orobenzaldehyde (0.11 g, 0.91 mmol) in the presence of
glacial acetic acid (0.05 g, 0.91 mmol) and then reduced
by NaCNBH3 (0.07 g, 1.1 mmol) in methanol (5 ml)
(Procedure C) to give cis-{6-[(benzhydryl-amino)-meth-
The reaction mixture was neutralized by the addition
of saturated NaHCO3 and was extracted with ethyl ace-
tate (3· 50 ml). The combined organic phase was
washed in turn with brine and water, and then dried
over anhydrous Na2SO4. Removal of the solvent and
purification by chromatography (hexane/ethyl acetate
1:1) gave pure product acetic acid 5-oxo-5,6-dihydro-
2H-pyran-2-yl ester 20 (6.1 g, 64% yield).
yl]tetrahydro-pyran-3-yl}-(4-fluorobenzyl)-amine
(0.32 g, 85% yield).
17
1H NMR (400 MHz, CDCl3): 1.37 (m, 1H, H-5eq), 1.56
(m, 1H, H-5ax), 1.65 (tt, 1H, J = 3.60 Hz and 12.80 Hz,
H-4ax), 1.84–1.96 (m, 3H, H-4, NH), 2.53–2.67 (m, 3H,
H-3, CH2NHR), 3.48–3.58 (m, 2H, H-2, H-6), 3.75 (m,
2H, PhCH2), 3.93 (m, 1H, H-2), 4.78 (s, 1H, Ph2CH),
6.90–7.60 (m, 14H, aromatic-CH).
1H NMR (500 MHz, CDCl3): 2.12 (s, 3H, CH3CO), 4.20
(d, J = 17.00 Hz, 1H, H-6), 4.48 (d, J = 17.00 Hz, 1H,
H-6), 6.25 (d, J = 10.50 Hz, 1H, H-2), 6.46 (d,
J = 3.00 Hz, 1H, H-4), 6.91 (dd, J = 3.50 Hz, 10.00 Hz,
1H, H-3).
13C NMR (100 MHz, CDCl3): 24.70, 27.27, 50.31,
50.72, 53.52, 67.89, 70.31, 115.21, 115.43, 127.15,
127.20, 127.54, 127.56, 128.66, 128.69, 129.73, 129.80,
126.47, 136.50, 144.17, 144.48, 160.87, 163.30.
13C NMR (125 MHz, CDCl3): 21.11, 67.58, 86.81,
94.99, 128.98, 142.47.
6.14. Synthesis of 6-benzhydryloxy-6H-pyran-3-one (21)
Free base was converted into oxalate salt from ethanol:
mp 171–175 ꢁC. Anal. [C26H29N2FOÆ(COOH)20.7H2O]
C, H, N.
A solution of SnCl4 (0.51 g, 1.96 mmol) in CH2Cl2
(5 ml) was added slowly to a stirred solution of acetic
acid 5-oxo-5,6-dihydro-2H-pyran-2-yl ester (6.1 g,
39.1 mmol) and benzhydrol (36 g, 195 mmol) in CH2Cl2
(100 ml). The reaction mixture was stirred at room tem-
perature for 5 h, which was followed by quenching of
the reaction with saturated NaHCO3 solution (100 ml)
and the resulting oil was extracted with ethyl acetate
(3· 60 ml). The organic phase was washed in turn with
saturated NaHCO3, brine, and water, and then dried
over anhydrous Na2SO4. Removal of the solvent and
purification by chromatography (hexane/ethyl acetate
4:1) gave pure 6-benzhydryloxy-6H-pyran-3-one 21
(9.8 g, 90% yield).
6.12. Synthesis of cis-{6-[(benzhydryl-amino)-methyl]-tet-
rahydro-pyran-3-yl}-(4-hydroxy-benzyl)-amine (18)
cis-6-[(Benzhydryl-amino)-methyl]tetrahydro-pyran-3-
yl-amine 15 (0.27 g, 0.91 mmol) was reacted with 4-hy-
droxy-benzaldehyde (0.11 g, 0.91 mmol) in the presence
of glacial acetic acid (0.05 g, 0.91 mmol), and then re-
duced by NaCNBH3 (0.07 g, 1.1 mmol) in methanol
(5 ml) (Procedure C) to give cis-{6-[(benzhydryl-ami-
no)-methyl]tetrahydro-pyran-3-yl}-(4-fluorobenzyl)-
amine 18 (0.32 g, 85% yield).
1H NMR (400 MHz, CDCl3): 1.38 (m, 1H, H-5eq), 1.56
(dq, 1H, J = 3.60 Hz and 14.20 Hz, H-5ax), 1.65 (tt, 1H,
J = 4.0 Hz and 14.20 Hz, H-4ax), 1.97 (m, 1H, H-4),
2.60 (m, 2H, CH2NHR), 2.68 (m, 1H, H-3), 3.50 (m,
1H, H-2), 3.53 (m, 1H, H-6), 3.68 (m, 2H, PhCH2),
3.95 (m, 1H, H-2), 4.78 (s, 1H, Ph2CH), 6.50–7.60 (m,
14H, aromatic-CH).
1H NMR (300 MHz, CDCl3): 4.09 (d, J = 17.10 Hz, 1H,
H-2), 4.47 (d, J = 16.50 Hz, 1H, H-2), 5.27 (d,
J = 3.30 Hz, 1H, H-4), 5.89 (s, 1H, Ph2CH), 6.17 (d,
J = 10.50 Hz, 1H, H-6), 6.90 (dd, J = 3.60 Hz,
10.50 Hz, 1H, H-5), 7.20–7.46 (m, 10H, aromatic-CH).
6.15. Synthesis of 6-benzhydryloxy-tetrahydro-pyran-3-ol
(22)
13C NMR (100 MHz, CDCl3): 24.62, 27.03, 50.51,
50.81, 53.37, 67.89, 69.90, 115.92, 127.19, 127.23,
127.54, 127.57, 128.69, 128.71, 129.82, 131.15, 143.98,
144.29, 155.71.
NaCNBH3 (0.42 g, 6.64 mmol) was added portionwise
to
a
mixture of 6-benzhydryloxy-6H-pyran-3-one
(0.062 g, 2.2 mmol) and BF3/Et2O (1.11 g, 7.8 mmol) in
dry THF (30 ml) cooled to À78 ꢁC. The reaction mix-
ture was allowed to come to room temperature over a
period of 4 h. The reaction was quenched with saturated
aqueous NaHCO3 (30 ml). The organic phase was sepa-
rated, and the aqueous phase was extracted with ethyl
ether (3· 20 ml). The combined organic phase was dried
over anhydrous Na2SO4. Removal of the solvent under
reduced pressure, and purification by flash chromatog-
raphy (hexane/ethyl acetate 4:1) afforded pure product
6-benzhydryloxy-tetrahydro-pyran-3-ol 22 (0.44 g, 70%
yield).
Free base was converted into oxalate salt from ethanol,
mp 200–204 ꢁC. Anal. [C26H30N2FO2Æ(COOH)21.05-
H2O] C, H, N.
6.13. Synthesis of acetic acid 5-oxo-5,6-dihydro-2H-
pyran-2-yl ester (20)
Into a solution of furfuryl alcohol (6 g, 61.2 mmol) in
THF/H2O (4:1, 100 ml) was added portionwise finely
mixed
N-bromo
succinimide
(NBS)
(11.43 g,
64.2 mmol), NaHCO3 (10.3 g, 122.4 mmol), and NaOAc
(5.02 g, 61.2 mmol) at 0 ꢁC. After 10 min, acetic anhy-
dride (18.74 g, 183.6 mmol) was added in a portionwise
manner. The mixture was brought to room temperature
gradually and stirred overnight at room temperature.
1H NMR (400 MHz, CDCl3): 1.68 (m, 1H, H-5), 1.76–1.94
(m, 3H, H-4, H-5), 2.03 (br s, 1H, OH), 3.58 (d, J = 6.40 Hz,
2H, H-2), 3.68 (m, 1H, H-3), 4.65 (m, 1H, H-6), 5.78 (s, 1H,
Ph2CH), 7.10–7.60 (m, 10H, aromatic-CH).

3964
S. Zhang et al. / Bioorg. Med. Chem. 14 (2006) 3953–3966
13C NMR (100 MHz, CDCl3): 28.26, 28.57, 65.86,
66.18, 78.63, 94.38, 126.99, 127.43, 127.87, 127.96,
128.18, 128.76, 128.82, 141.58, 142.68.
hyde (0.02 g, 0.15 mmol) in the presence of glacial
acetic acid (0.009 g, 0.15 mmol) and then reduced by
NaCNBH3 (0.02 g, 0.30 mmol) in methanol (1 ml)
(Procedure C) to give trans-(6-benzhydryloxy-tetrahy-
dro-pyran-3-yl)-(4-fluorobenzyl)-amine 24 (0.05 g, 81%
yield).
6.16. Synthesis of trans-6-benzhydryloxy-tetrahydro-py-
ran-3-yl-amine (23)
6.16.1. (1)Synthesisofmethanesulfonic acid cis-6-benzhyd-
ryloxy-tetrahydro-pyran-3-yl ester. cis-6-Benzhydryloxy-
tetrahydro-pyran-3-ol 22 (0.09 g, 0.31 mmol) was reacted
with methanesulfonyl chloride (0.07 g, 0.61 mmol) in the
presence of triethylamine (0.05 g, 0.45 mmol) (Procedure
A) to give methanesulfonic acid cis-6-benzhydryloxy-tet-
rahydro-pyran-3-yl ester (0.1 g, 90%).
1H NMR (400 MHz, CDCl3): 1.53 (m, 2H, H-5,
NH), 1.65 (m, 1H, H-5), 1.92 (m, 1H, H-4), 2.09
(m, 1H, H-4), 2.71 (m, 1H, H-3), 3.70 (dd, J = 4.80 Hz
and 11.20 Hz, 1H, H-2ax), 3.76 (s, 2H, PhCH2),
3.99 (m, 1H, H-2eq), 4.65 (t, 1H, J = 3.60 Hz, H-6),
5.82 (s, 1H, Ph2CH), 6.80–7.50 (m, 14H, aromatic-
CH).
1H NMR (400 MHz, CDCl3): 1.77 (m, 1H, H-5), 1.92–2.10
(m, 2H, H-4, H-5), 2.19 (m, 1H, H-4), 2.99 (s, 3H, CH3SO2),
3.70–3.85 (m, 2H, H-2), 4.65–4.73 (m, 2H, H-3, H-6), 5.75
(s, 1H, Ph2CH), 7.10–7.60 (m, 10H, aromatic-CH).
13C NMR (100 MHz, CDCl3): 25.33, 27.21, 50.73,
51.51, 65.42, 78.87, 96.23, 115.30, 115.51, 127.01,
127.38, 127.87, 127.92, 127.45, 127.74, 129.73, 129.82,
141.64, 142.77.
13C NMR (100 MHz, CDCl3): 25.94, 28.67, 38.89,
52.76, 62.69, 74.68, 78.92, 93.88, 126.91, 127.56,
127.80, 128.10, 128.57, 128.85, 128.91, 141.33, 142.46.
Free base was converted into oxalate salt from ethanol:
mp 178–180 ꢁC Anal. [C25H26NFO2Æ(COOH)20.3H2O]
C, H, N.
6.16.2. (2) Synthesis of trans-5-azido-2-benzhydryloxy-
tetrahydro-pyran. Methanesulfonic acid cis-6-benzhyd-
ryloxy-tetrahydro-pyran-3-yl ester (0.12 g, 0.33 mmol)
was reacted with sodium azide (0.09 g, 1.33 mmol)
(Procedure B) to give cis-(5-azido-2-benzhydryloxy-tet-
rahydro-pyran (0.09 g, 91% yield).
6.18. Synthesis of 6-benzhydryloxy-dihydro-pyran-3-one
(25)
Into a solution of 6-benzhydryloxy-6H-pyran-3-one 21
(0.15 g, 0.53 mmol) in dry THF (20 ml) was added
L-selectride (0.53 ml of 1.0 M solution in THF,
0.53 mmol) drop by drop at À78 ꢁC. After 20 min, the
reaction was quenched with saturated NH4Cl. The mix-
ture was extracted by ethyl acetate (3· 20 ml). The com-
bined organic phase was washed with brine and water,
and then dried over anhydrous Na2SO4. Removal of
the solvent and purification by chromatography (hex-
ane/ethyl acetate 4:1) gave pure 6-benzhydryloxy-dihy-
dro-pyran-3-one 25 (0.12 g, 80% yield).
1H NMR (400 MHz, CDCl3): 1.69 (m, 2H, H-3), 2.00
(m, 1H, H-4), 2.22 (m, 1H, H-4), 3.47–3.60 (m, 2H, H-
5, H-6), 3.96 (dd, J = 2.40 Hz, 12.00 Hz, 1H, H-6),
4.76 (m, 1H, H-2), 5.77 (s, 1H, Ph2CH), 7.10–7.60 (m,
10H, aromatic-CH).
13C NMR (100 MHz, CDCl3): 23.34, 26.06, 55.83,
62.64, 78.93, 94.96, 126.94, 127.50, 127.81, 128.03,
128.54, 128.80, 141.49, 142.70.
1H NMR (400 MHz, CDCl3): 2.14 (m, 1H, H-5), 2.26
(m, 1H, H-5), 2.48 (m, 1H, H-4), 2.67 (m, 1H, H-4),
3.91 (d, J = 16.80 Hz, 1H, H-2), 4.17 (d, J = 16.80 Hz,
1H, H-2), 5.06 (m, 1H, H-6), 5.82 (s, 1H, Ph2CH),
7.10–7.60 (m, 10H, aromatic-CH).
6.16.3. (3) Synthesis of trans-6-benzhydryloxy-tetrahy-
dro-pyran-3-yl-amine (23). trans-(5-Azido-2-benzhydryl-
oxy-tetrahydro-pyran (0.08 g, 0.27 mmol) was reduced
by LiAlH4 (0.04 g, 1.07 mmol) in dry ethyl ether (5 ml)
to give trans-6-[(benzhydryloxy-tetrahydro-pyran-3-yl-
amine 23 (0.072 g, 95%) (Procedure G).
13C NMR (100 MHz, CDCl3): 28.44, 34.03, 67.79,
79.44, 93.86, 126.85, 127.67, 127.74, 128.16, 128.61,
128.88, 141.19, 142.25.
1H NMR (400 MHz, CD3OD): 1.47 (m, 1H, H-5), 1.64 (m,
1H, H-5), 1.92 (m, 1H, H-4), 2.12 (m, 1H, H-4), 2.91 (m,
1H, H-3), 3.25 (m, 1H, H-2), 3.96 (m, 1H, H-2), 4.62 (m,
1H, H-6), 4.79 (s, 1H, Ph2CH), 7.10–7.60 (m, 10H, aromat-
ic-CH).
6.19. Synthesis of cis-(6-benzhydryloxy-tetrahydro-pyran-
3-yl)-(4-fluorobenzyl)-amine (cis-24)
6-Benzhydryloxy-dihydro-pyran-3-one
25
(0.05 g,
0.16 mmol) was reacted with 4-fluorobenzylamine
(0.02 g, 0.16 mmol) in the presence of glacial acetic acid
(0.009 g, 0.16 mmol) and then reduced by NaCNBH3
(0.01 g, 0.21 mmol) in methanol (1 ml) (Procedure C)
to give cis-(6-benzhydryloxy-tetrahydro-pyran-3-yl)-
(4-fluorobenzyl)-amine 24 (0.05 g, 80% yield).
13C NMR (100 MHz, CD3OD): 26.32, 26.51, 45.92,
66.22, 79.20, 96.22, 126.63, 127.05, 127.41, 127.64,
128.03, 128.40, 141.67, 142.79.
6.17. Synthesis of trans-(6-benzhydryloxy-tetrahydro-
pyran-3-yl)-(4-fluorobenzyl)-amine (trans-24)
1H NMR (400 MHz, CDCl3): 1.62–1.92 (m, 4H, H-4, H-
5), 2.72 (tt, 1H, J = 4.0 Hz and 9.60 Hz, H-3), 3.54 (t,
J = 10.40 Hz, 1H, H-2ax), 3.65 (m, 1H, H-2eq), 3.77
trans-6-Benzhydryloxy-tetrahydro-pyran-3-yl-amine 23
(0.04 g, 0.15 mmol) was reacted with 4-fluorobenzalde-

S. Zhang et al. / Bioorg. Med. Chem. 14 (2006) 3953–3966
3965
(m, 2H, PhCH2), 4.74 (t, 1H, J = 2.40 Hz, H-6), 5.76 (s,
1H, Ph2CH), 6.80–7.50(m, 14H, aromatic-CH).
below respective Kd or Km values in the protocols
used.24
13C NMR (100 MHz, CDCl3): 26.15, 29.39, 50.56,
52.91, 65.02, 78.32, 94.01, 115.31, 115.53, 126.98,
127.32, 127.88, 128.45, 128.71, 129.70, 129.79, 141.75,
142.87.
Supplementary data
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/
j.bmc.2006.01.051.
Free base was converted into oxalate salt from ethanol.
Anal. [C25H26NFO2Æ(COOH)20.5H2O] C, H, N.
6.20. Molecular modeling
References and notes
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In order to demonstrate the difference in distances be-
tween the exocylic N-atom in benzyl substitution and
the two phenyl rings of benzhydryl substituion, we
have carried out a preliminary molecular modeling
study. Side-chain-extended derivatives at 3- and 6-po-
sition 4 and cis-12, and the 3,6-disubstituted com-
pound 16b were chosen for this study. Compounds
were minimized first with the SYBYL molecular mod-
eling program (version 6.9, 2002, Tripos Associates,
Inc., St. Louis, MO). Minimized molecules obtained
from this operation were next subjected to a grid
search protocol to search for the lowest-energy con-
former. Grid search operation was carried out with
the change of torsional angle from 0ꢁ to 360ꢁ with
an increment of 10ꢁ comprising of atoms a–b–c–d as
shown in Figure 5 for all three compounds. This oper-
ation resulted in the generation of lowest energy with
a corresponding torsional angle for each of these three
compounds. In the final step, the distance between the
exocyclic N atom and two phenyl rings in benzhydryl
moiety was measured and the value is shown in
Figure 5. It was quite evident that the measured dis-
tances in three compounds were quite different.
8. Witkin, J. M.; Nichols, D. E.; Terry, P.; Katz, J. L.
J. Pharmacol. Exp. Ther. 1991, 257, 706–713.
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Transporter Uptake Blockers: Structure Activity Rela-
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Transporter Uptake Blockers: Structure Activity Rela-
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654–662.
6.21. Biological experiment
All transporter assays were performed exactly as we
described previously.24 Briefly, binding of [3H]WIN
35,428 was measured in rat striatal membrane prepa-
rations with [Na+] at 30 mM at 0–4 ꢁC for a period
of 2 h; nonspecific binding was defined with 100 lM
cocaine. Rat striatal synaptosomes were used for mea-
suring uptake of [3H]DA; incubation with test com-
pounds for 5 min was followed by the additional
presence of [3H]DA for 4 min at 25 ꢁC. Nonspecific
uptake was defined with 100 lM cocaine. For uptake
assays with [3H]serotonin and [3H]NE, synaptosomes
were prepared from rat cerebral cortex, with nonspe-
cific uptake defined by 10 lM citalopram and 10 lM
desipramine, respectively. Test compounds were dis-
solved in dimethylsulfoxide (DMSO) and diluted out
in 10% (v/v) DMSO. Additions from the latter stocks
resulted in a final concentration of DMSO of 0.5%,
which by itself did not interfere with transporter mea-
sures. At least five triplicate concentrations of each
test compound were studied, spaced evenly around
the IC50 value. The latter was estimated by nonlinear
computer curve-fitting procedures as we detailed previ-
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