Combinatorial synthesis of benztropine libraries and their evaluation as monoamine transporter inhibitors

Article abstract of DOI:10.1039/b405768f

A combinatorial synthesis of benztropine analogues is presented. Radical azidonation of 3-benzyloxy-8-azabicyclo[3.2.1]octane-8-carboxylic acid tert-butyl ester 3 to 3-(1-azidobenzyloxy)-8-azabicyclo[3.2.1]octane-8- carboxylic acid terf-butyl ester 4 was used as a key step in the synthesis. This step was optimized by adding 10% DMF to the reaction. Reaction of 4 with phenyl magnesium bromide followed by Boc removal and N-methylation gave benztropine 1. Reaction of five-component Grignard reagents with 4 was used to create a two-dimensional library of 25 N-normethylbenztropine analogues. Further reaction of this library with five alkyl bromides was carried out to create a three-dimensional library containing 125 compounds. Screening of the libraries towards binding and inhibition of uptake of the human dopamine (hDAT), serotonin (hSERT) and norepinephrine transporters (hNET) was carried out. None of the synthesized compounds were found to be stronger than benztropine, and none were selective for inhibition of binding over monoamine uptake.

Full text of DOI:10.1039/b405768f

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A R T I C L E
Combinatorial synthesis of benztropine libraries and their evaluation
as monoamine transporter inhibitors†
Hanne Pedersen,a Steffen Sinning,b Anne Bülow,a Ove Wiborg,b Lise Falborgc and Mikael Bols*a
a
Department of Chemistry, University of Aarhus, Langelandsgade 140, DK-8000, Aarhus C.
E-mail: mb@chem.au.dk
Department of Biological Psychiatry, Risskov Psychiatric Hospital, DK-8240, Risskov
Department of Clinical Physiology and Nuclear Medicine, Aarhus Kommunehospital,
b
c
Nørrebrogade 44, DK-8000, Aarhus C
Received 19th April 2004, Accepted 30th July 2004
First published as an Advance Article on the web 6th September 2004
A combinatorial synthesis of benztropine analogues is presented. Radical azidonation of 3-benzyloxy-8-
azabicyclo[3.2.1]octane-8-carboxylic acid tert-butyl ester 3 to 3-(1-azidobenzyloxy)-8-azabicyclo[3.2.1]octane-8-
carboxylic acid tert-butyl ester 4 was used as a key step in the synthesis. This step was optimized by adding 10%
DMF to the reaction. Reaction of 4 with phenyl magnesium bromide followed by Boc removal and N-methylation
gave benztropine 1. Reaction of five-component Grignard reagents with 4 was used to create a two-dimensional
library of 25 N-normethylbenztropine analogues. Further reaction of this library with five alkyl bromides was
carried out to create a three-dimensional library containing 125 compounds. Screening of the libraries towards
binding and inhibition of uptake of the human dopamine (hDAT), serotonin (hSERT) and norepinephrine
transporters (hNET) was carried out. None of the synthesized compounds were found to be stronger than
benztropine, and none were selective for inhibition of binding over monoamine uptake.
prepare substituted benzyl ethers,8 thereby allowing us to pre-
Introduction
pare libraries of type A (Fig. 1). This synthesis would allow us
to prepare alkylphenylmethyl ethers while the classical synthesis
of benztropines, by reaction of tropine with diarylcarbinols or
diarylmethyl halides, would be difficult or even impossible in
the more hindered cases. It is thus interesting to note that while
the literature contains hundreds of benztropines containing the
diarylmethoxy ether moiety, just a single alkylarylmethyl ether
(the hydroxymethyl analogue) has been disclosed. In this paper
we present an efficient synthesis of these compounds and their
use in preparation of libraries containing both alkylaryl and
diaryl benztropines.
Combinatorial chemistry represents a series of synthetic
techniques that have the potential to facilitate the drug dis-
covery process significantly.1 Usually, combinatorial chemistry
combines multiple reactions and building blocks in order to
create many compounds. Both classical synthesis of individual
compounds using automated procedures and synthesis of com-
pound mixtures are today classified as combinatorial chemistry,2
but in the present work combinatorial chemistry describes work
with mixtures. Recently, our laboratory has reported a combi-
natorial method that uses multi-component Grignard reagents
to readily create mixed libraries.3 Due to the versatility of the
Grignard reaction, this method can be applied to many inter-
esting targets. We have demonstrated the use of this technique
in a two- and three-dimensional screening protocol to discover
new phenyltropanes.4 In the present work the application of this
method to benztropine analogues is presented.
Benztropine (1) is a well known anti-Parkinsonian drug that
has structural similarities to cocaine. Indeed, it has been found
that 1, similarly to cocaine, inhibits the re-uptake of dopamine
by binding to the dopamine transporter (DAT).5 As the ability
to inhibit dopamine re-uptake is thought to underlie cocaine’s
liability in drug abuse, the fact that 1 competes for the same
binding site on the DAT as cocaine makes 1 and its analogues
potential agents in an anti-cocaine treatment, particularly if
compounds can be found that inhibit cocaine’s binding without
disrupting dopamine transport. Furthermore, interestingly, the
behavioural effects of benztropine analogues have been found to
be different from those of cocaine, which is another reason why
a replacement therapy could work.6 The search for benztropine
analogues with potency and selectivity for the DAT is therefore
a worthwhile goal, and in the present work we report a combi-
natorial approach to benztropine analogues.
Fig. 1 Cocaine, benztropine and the target library.
Results and discussion
The strategy for the synthesis simply consisted in converting
tropine to a benzyl ether that by a-azidonation and substitution
could be converted to the desired libraries. To this end, tropine
was subjected to demethylation using chloroethyl chloroformate
followed by methanolysis, and the resulting amine was pro-
tected to give the N-Boc derivative 2 in 77% yield from tropine
(Scheme 1). Benzylation with NaH/BnBr uneventfully gave 3 in
85% yield.
The radical azidonation of 3 required study in more detail
(Table 1). As it turned out, azidonation at the conditions reported
originally, which included the use of 3 equivalents of IN3
(entry 1), did not give a satisfactorily high yield of 4. An increase
in the concentration of reactants (entries 2 and 3) increased the
conversion but also led to the formation of byproducts. With
an increase in concentration combined with a short reaction
time (entries 4 and 5) it was possible to increase the yield some-
what. Change of the solvent to one favouring radical reactions
(entry 6) was however counterproductive, presumably because
The chemical rationale behind the work was that our recently
developed radical azidonation reaction7 could be employed to
† Electronic supplementary information (ESI) available: (1) Ki values
for the 2D and 3D libraries, (2) ESI and GCMS spectra for sublibraries
I–V, a–e, and Z, and (3) 13C NMR spectra for 3, 5, 7, 8, 9, 10, 12a, 13a,
16 and 17. See http://www.rsc.org/suppdata/ob/b4/b405768f/
T h i s j o u r n a l i s
©
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 4
O r g . B i o m o l . C h e m . , 2 0 0 4 , 2 , 2 8 6 1 – 2 8 6 9
2 8 6 1

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Table 1 Radical azidonation of 3 (Scheme 1). Unless otherwise noted azidonation was performed at reflux (80 °C) using 3 equivalents of IN3, made
in situ from premixing 3 equivalents of iodine monochloride (ICl) and 7 equivalents of NaN3 in MeCN at −10 °C. Yields are isolated yields after
chromatography
Entry
Solvent
Additive
Concentration of 3/M
Time/min
Yield of 4
1
2
3
4
5
6
7
8
9
MeCN
MeCN
MeCN
MeCN
MeCN
CCl4
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
—
—
—
—
—
—
0.11
0.24
0.42
0.46
0.82
0.15
0.27
0.24
0.26
0.29
0.24
0.31
60
60
60
30
20
30
40
70
120
300
120
40
52%
51%
43%
59%
58%
37%
71%
73%
72% (corr.)
43% (corr.)
67% (corr.)
46% (corr.)
5% DMF
10% DMF
50% DMF
10% DMF (2.2 eq. IN3)
10% DMA
10
11
12
1.1 eq. 2,6-di-tert-butylpyridine
(corr.) means that the yield has been corrected by the subtraction of re-isolated starting material from consumed substrate.
under conditions9,10 (lutidine, TMSOTf) selective for its removal
in the presence of an acid-sensitive benzhydryl ether, giving 6 in
94% yield. Reaction of this amine with methyl chloroformate in
pyridine gave an 83% yield of methyl carbamate 7, which was
reduced to 1 with LiAlH4 in 83% yield.
Now the combinatorial synthesis outlined in Scheme 3
was investigated. Azide 4 was reacted with a 5-component
Grignard reagent to give library IV in Boc-protected form.
After removal of the Boc groups with lutidine/TMSOTf, library
IV was analysed by ESI mass spectroscopy and GCMS (EI) (see
Supplementary material†), both of which showed the presence
of all 5 expected compounds. NMR spectroscopy on this library
revealed the presence of each of the expected compounds in
equimolar amounts.
Scheme 1 Synthesis of azidoether 4 from tropine. The conditions
investigated for the azidonation are shown in Table 1.
of the necessity to keep azide ions dissolved during the reaction.
This observation supports the hypothesis that the reaction leads
to a benzylic iodide that is substituted by azide and thus involves
an ionic step as well.
To further improve the reaction, various additives were added,
rationalized from two working hypotheses. The hypothesis that
the formation of acid during the reaction was leading to decom-
position of the product led us to add a hindered pyridine to the
reaction (entry 12), but this was not an advantage compared
to the corresponding experiment with no additive. Another
hypothesis was that side reactions were occurring in the tropane
skeleton, starting with abstraction of a hydrogen atom a to the
amine nitrogen. This led to the idea of adding an amide, DMF,
that might compete with this abstraction. Indeed, addition of
small amounts of DMF led to the best yields (entries 7 and
8), while larger amounts slowed the reaction (entry 9). DMA
(dimethylacetamide, entry 11) did not have an effect on the yield
of 4, and the effect of DMF may therefore be due to reaction
of one of the methyl hydrogen atoms rather than the hydrogen
atom a to the carbonyl group.
Scheme 3 Combinatorial synthesis of normethyl benztropine
analogues from the azidoether 4.
This 5-component synthesis (Scheme 3) was repeated with
4 other sets of Grignard reagents to obtain the libraries I, II,
III and V containing the compounds shown as rows in Table 2.
These libraries were characterized with ESI and GC-MS in the
same way as library IV, confirming, with a single exception
(compound IIe), the presence of all compounds (see Supple-
mentary material†). Similarly, the reaction was carried out 5
times to create the libraries a–e, shown as columns in Table 2,
so that altogether the 25 compounds shown were made twice in
the form of 10 sublibraries of 5 compounds. One of the com-
pounds in the library was the known 4-chlorophenyl analogue
11, which was included as a positive control. This compound has
been reported to have a binding to the DAT from rat brain of
36.8 nM.11 The remaining compounds were new. It is noteworthy
that the library displays a considerable variation its structure and
includes both aryl, linear and cycloalkyl derivatives (Table 2).
Screening of the 10 sublibraries towards binding and uptake
to hDAT, hSERT and hNET was performed and the measured
Ki values are shown in the Supplementary material (Table S1).†
None of the 10 libraries showed potent binding to or inhibition
With an efficient preparation of 4 complete, we established
its conversion to benztropine (1) (Scheme 2). The azidoether 4
was reacted with phenylmagnesium bromide in toluene8 to give
diphenyl derivative 5 in 64% yield. The Boc group was removed
Scheme 2 Synthesis of benztropine from the azidoether 4.
O r g . B i o m o l . C h e m . , 2 0 0 4 , 2 , 2 8 6 1 – 2 8 6 9
2 8 6 2

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Table 2 Contents of the two-dimensional library contained in the sublibraries I–V (rows) and a–e (columns)
a
b
c
d
e
I
II
III
IV
V
Table 3 Binding and uptake of 8–11 to monoamine transporters
Ki/nM
Binding [125I]RTI-55
Uptake
[3H]DA
DAT
741 ± 363
391 ± 132
927 ± 119
862 ± 71
SERT
NET
[3H]5-HT
[3H]DA (NET)
Cocaine
1352 ± 407
24945 ± 102
16185 ± 913
7040 ± 266
5522 ± 936
4080 ± 380
1675 ± 477
573 ± 166
1560 ± 255
558 ± 62
1106 ± 124
952 ± 135
198 ± 71
629 ± 173
1095 ± 98
690 ± 93
22616 ± 2184
1178 ± 340
493 ± 221
22611 ± 3761
30038 ± 4184
5772 ± 991
512 ± 249
940 ± 148
2782 ± 238
823 ± 91
1
8
9
10
11
11061 ± 1529
604 ± 78
13594 ± 2706
10380 ± 844
1815 ± 277
1562 ± 626
of re-uptake to any of the monoamine transporters, with Ki
values of 6–700 nM being the lower limit. It is therefore evident
that no extraordinary differences in biological activity appear
to exist among the 25 compounds. Thus the significance of
changing one phenyl group in the benzhydryl ether moiety
appears to be limited. The data indicate that compounds Ic
and IIIc (Table 2) are the more potent compounds in the series
towards DAT binding and uptake, that compound Va is more
potent towards SERT binding and uptake, and that Ic is the
strongest with regard to net binding and uptake.
The individual compounds 8 (IIIc), 9 (Ic), 10 (IIc) and 11
(IVe) (Table 2) were prepared from 4 using the procedure out-
lined in Scheme 2, and were obtained in 63%, 61%, 59% and
69% yield, respectively, over two steps. Similarly, synthesis of
12 (Ia) and 13 (Id) was demonstrated through the intermediacy
of the corresponding Boc derivatives 12a and 13a, which were
obtained in 98% and 52% yield from 4, respectively. The test
results from some of these individual compounds are shown in
Table 3. Towards the DAT, the two aliphatic compounds 8 and
9 were slightly weaker than benztropine 1 and cocaine, and also
slightly weaker than the positive control 11, an observation that
was not displayed in the two-dimensional screening. However,
the differences are so small that the two-dimensional screening
was unable to detect them, as they are hidden in effects from
other compounds. The o-ethylbenzhydryl analogue 10 is, how-
ever, a remarkably poor inhibitor of the DAT.
norepinephrine transporter, being 3 times stronger than the
closely related isobutyl analogue 8 (IIIc). None of the com-
pounds show any significant selectivity between binding and
uptake.
The study was extended to the investigation of the effect of
substitution on the nitrogen atom. It was envisaged that this
could be carried out by a simple substitution at nitrogen with
various alkyl bromides. To investigate the feasibility of this reac-
tion, the model experiments outlined in Scheme 4 were carried
out. Compound 3 was deprotected with TFA to give 14, which
was reacted with allyl bromide and potassium carbonate in DMF
to give 15 in excellent yield. Consequently the five-component
alkylation of 14 was attempted (Scheme 4). Reaction of 14 with
a mixture of equimolar amounts (0.22 equivalents each) of
propargyl, allyl, isopentyl, phenylpropyl and butyl bromide in
the presence of 2 equivalents of K2CO3 gave model library Z,
for which NMR and MS showed that the 5 expected compounds
were formed in good yield and in equimolar amounts. There are
rate differences in the reaction of these different bromides with
14, but the fact that only a very slight excess of electrophile is
used ensures that products are evenly formed.
Using this chemistry, the two-dimensional library (Table 2)
was modified on the nitrogen atom with these 5 electrophiles
in order to create the three-dimensional library shown in
Fig. 2. The 125 compounds contained were prepared 3 times
as 5 sublibraries with 25 compounds either as the layers shown
as entries along the Z axis (Z1–Z5) or as slices made along the
X (X1–X5) or Y axes (Y1–Y5), respectively. These libraries were
None of the compounds are potent against SERT. The propyl
analogue 9 (Ic) is the most potent compound for binding to the
O r g . B i o m o l . C h e m . , 2 0 0 4 , 2 , 2 8 6 1 – 2 8 6 9
2 8 6 3

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Scheme 5 Synthesis of libraries X1 to Z5.
Scheme 4 Model experiments with the synthesis of the N-alkylated
From the data it was clear that the difference in binding
among the 125 analogues appeared limited, or at least no com-
pound was significantly more potent than others in the 6 assays.
According to the test results from the Z-libraries it appeared
that the N-butyl analogues (Z1) were more potent. Therefore the
compounds 16 (X1, Y3, Z1) and 17 (X3, Y3, Z1) were chosen for
individual synthesis. These compounds were prepared from 9 by
alkylation with butyl bromide and isopentyl bromide (respec-
tively) and K2CO3 in DMF. Testing of these two compounds
showed that they had no particularly strong inhibitory effect
(Table 4); compound 16 had a Ki of 1604 nM towards the DAT,
while 17 was weaker. The biological activities of each compound
are close to the average of the X and Y libraries.
library.
synthesized as shown in Scheme 5. The libraries X1–X5 were
made by carrying out N-alkylation with the 5 bromides of the
libraries I–V individually. Similarly, the libraries Y1–Y5 were
obtained from 5 reactions of each of libraries a to e with the 5
electrophiles. Finally the libraries Z1–Z5 were obtained by mix-
ing libraries I–V and reacting them with one of the 5 bromides
(Scheme 5). Characterization of these 25-membered sublibraries
could not be as good as in the smaller libraries, but the products
were subjected to GCMS, which revealed masses corresponding
to the presence of 20 or more of the expected compounds in
each library. With this documentation, and due to the similarity
of the model compound 14 and the library members of Table 2
in the vicinity of the nitrogen, it is reasonable to assume that the
expected 125 compounds were synthesized 3 times.
It is surprising that we find a relatively low potency of
benztropines compared to previous studies. For example, com-
pound 11 has been reported to inhibit the DAT with a Ki of
36 nM,11 while we find a 20-fold higher value. This discrepancy
is likely to be due to two differences: 1) that previous studies were
The 15 libraries were then screened and the results are shown
in Table S2 (see Supplementary material†).
Fig. 2 The three-dimensional library.
2 8 6 4
O r g . B i o m o l . C h e m . , 2 0 0 4 , 2 , 2 8 6 1 – 2 8 6 9

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Table 4 Ki values for binding and uptake at hDAT, hSERT or hNET
Ki/nM
Binding [125I]RTI-55
Uptake
[3H]DA
DAT
SERT
NET
[3H]5-HT [3H]DA (NET)
16
17
1604
3641
5149
6235
3857
3784
2173
8403
4698
18257
13570
24919
made with brain homogenates while we used a cloned trans-
porter, and 2) prior work was performed with the monoamine
transporters from rat while we used human transporters. It is
well known that discrepancies can be observed between the work
made with brain homogenates and cloned transporters, possibly
due to the presence of other material in the homogenates affect-
ing the assay. However, for cocaine the difference between the
two test systems is not as large. Also for benztropine (1) itself
the difference is not as large.
Sciences) or DA (Amersham Bisciences), applied to the cells
adhering to the bottom of the microplate wells to initiate up-
take. Accumulation of 5-HT or DA was allowed to proceed
for 10 min at 20 °C and the assay was terminated by aspiration
of the uptake media and washing with PBSCM. Scintillant
(MicroScint 20 from Packard Bell) was used to solubilise cells,
and accumulated radioactivity was quantifed on a Packard
Topcounter. Concentration of substrate was quantified by liquid
scintillation counting on an Packard Tri-Carb.
The binding of 1 to DAT gave a Ki of 197 nM using rat
homogenates and 412 nM with monkey brain homogenates,12
which is not far from the value of 391 nM we find for 1. There-
fore the discrepancies we find for 11 and other compounds are
compound specific and therefore appear to be associated with
differences in specific interaction of these compounds with the
transporters from the two species. A closer comparison of the
effects of these compounds with cloned human and rat trans-
porter might be worthwhile. Secondly, it is noted that no signifi-
cant selectivity between binding and uptake is was observed in
the studied compounds.
In summary, we have developed a new combinatorial synthesis
of benztropine analogues employing radical azidonation as the
key step. The azidonation reaction was improved by addition
of 10% DMF. Our approach can also be employed to combi-
natorial synthesis of analogues of other benzhydryl ethers, of
which the pharmaceutical literature contains many. We found
that substitution of one phenyl group in benztropine with many
other functionalities did not improve (and in most cases did not
decrease) inhibition and uptake of hDAT, hSERT or hNET. The
results show somewhat surprisingly that the two phenyl groups
in 1 are not necessary and may be replaced with little effect. Our
results also confirm the results from others that, in many cases,
changes in the N-substituents do not change the effect on the
transporter.
Binding assay
Membrane preparations for the binding assay were produced
by scraping the stably transfected cells from cell culture dishes
(Nunc), pelleting the cells in ice-cold PBSCM by centrifugation,
homogenising the cells in ice-cold Harvest Buffer I (150 mM
NaCl, 50 mM Tris, 20 mM EDTA) using a Ultra-Turrax
(Janke & Kunkel AG) for 60 s. The membrane was pelleted
by centrifugation at 12000 g for 10 min at 4 °C and washed
in ice-cold Harvest Buffer I, the membrane pelleted again and
the membrane pellet resuspended in PBSCM, briefly using the
Ultraturrax. Membrane preperations were aliquoted into 2 mL
portions and stored at −80 °C until use. The concentration of
total protein in the membrane preparation was determined with
a MicroBCA kit (Pierce).
A concentration of 5 lg per well of membrane preparation
was used with the nominated concentration of drug of interest
in combination with 0.1–0.25 nM [125I]-RTI-55. Membrane and
ligands were incubated for 1 h at 20 °C. Using a Filtermate Cell-
harvester (Packard), membranes were captured on GF/B 96-well
filterplates (Packard) presoaked with 0.5% polyethyleneimine
(Merck) and washed thrice with ice-cold water. The filter in
each well was dissolved in 40 lL Microscint 20 and scintillation
counts were determined with a Packard Topcounter. Precise
concentration of radioligand was quantified by liquid scintilla-
tion counting on a Packard Tri-Carb.
Experimental
Cell culture
3a-Hydroxy-8-azabicyclo[3.2.1]octane-8-carboxylic acid tert-
Cells stably expressing hSERT, hDAT or hNET were pro-
duced by transfecting COS-7 cells with hSERT/hDAT/hNET
inserted in the pIRES vector (BD Biosciences Clontech) also
bearing a Blasticidin resistance gene. Cells were cultured in
DMEM (BioWhitaker) supplemented with 10% FCS (Gibco
Life Technologies), 1% Penicillin/Streptomycin (BioWhitaker)
and 10 lg mL−1 of Blasticidin (Cayla) for negative selection
of nontransfected cells. After 14 days of selection Blasticidin
was adjusted to 2 lg mL−1 in the culture medium and cells were
subcultured under this selection regime and grown at 37 °C, 5%
CO2, and 95% humidity.
butyl ester (2)13
To a solution of tropine (prepared from azeotropically distilling
a mixture of tropine hydrate in toluene (4.98 g, 35.3 mmol))
in 1,2-dichloroethane (12 mL) was added dropwise 1-chloro-
ethyl chloroformate (6.3 mL, 58.39 mmol) at 0 °C. The mix-
ture obtained was refluxed for 1 h and then concentrated in
vacuo. The residue was dissolved in MeOH (15 mL), refluxed
for 45 min and concentrated in vacuo again. The residue was
taken into acetone (15 mL) and water (15 mL) and stirred
for 1 h. NaHCO3 (11.80 g, 141.2 mmol) and (Boc)2O (16.5 g,
75.53 mmol) were added. The mixture was stirred overnight and
concentrated in vacuo in order to remove acetone. The aqueous
phase was extracted with CHCl3 (4 × 20 mL). The combined
organic phases were dried over MgSO4 and concentrated in
vacuo. Chromatography (CH2Cl2/EtOAc, 6:1, Rf = 0.2) gave
the desired product (6.14 g, 77%) as a colourless solid. M.p.
141.5 °C, 1H NMR (CDCl3, 400 MHz) d = 4.16 (1H, br. s, H-3),
4.09 (2H, br. s, H-1,5), 2.14–1.66 (8H, m, H2-2,4,6,7), 1.41 (9H,
s, C(CH3)3, Boc) ppm. 13C NMR (CDCl3, 100 MHz) d = 153.6
(CO, Boc), 79.3 (C(CH3)3, Boc), 65.3 (C-3), 53.3/52.4* (C-1,5),
38.8/38.3* (C-2,4), 28.7 ((CH3)3C, Boc), 28.7/28.1* (C-6,7) ppm.
Uptake assay
For the uptake assay stably transfected cells were seeded in 96
well microplates (Nunc) and grown at 37 °C, 5% CO2, and 95%
humidity for two days. Before the IC50 assay the medium was
aspired and the cells were washed in PBSCM (137 mM NaCl,
2.7 mM KCl, 4.3 mM Na2HPO4, 1.4 mM KH2PO4, 0.1 mM
CaCl2, 1 mM MgCl2, pH 7.4) on a BioTek ELX50 microplate
washer, and the dilution series of the drug in PBSCM supple-
mented with 30–100 nM tritiated 5-HT (Perkin-Elmer Life
O r g . B i o m o l . C h e m . , 2 0 0 4 , 2 , 2 8 6 1 – 2 8 6 9
2 8 6 5

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(* The spectrum showed two rotamers.) HRMS (ES): calculated
solution kept refluxing. After addition the mixture was refluxed
for C12H21NO3Na (M + Na): 250.1419. Found: m/z 250.1396.
for 2 h. The Grignard reagent was taken out using a syringe and
titrated before use.
3-Benzyloxy-8-azabicyclo[3.2.1]octane-8-carboxylic acid tert-
butyl ester (3)
Titration of Grignard reagents
A
solution of
3a-hydroxy-8-azabicyclo[3.2.1]octane-8-
To a solution of menthol (156 mg, 1 mmol) and 1,10-phenan-
throline (5 mg) in dry THF (10 mL), the Grignard reagent was
added dropwise through a syringe. The equivalence point was
read when the mixture turned pink and the colour lasted for a
minimum of 1 min.14
carboxylic acid tert-butyl ester (2, 3.30 g, 14.7 mmol) in dry
DMF (20 mL) was cooled to 0 °C. NaH (2.81 g, 58.6 mmol,
50%) was added with continuous stirring. The cooling bath was
removed and stirring was continued at room temperature for 1 h.
A solution of BnBr (3.48 mL, 29.30 mmol) in dry DMF (5 mL)
was added and the mixture was stirred overnight. 1 M HCl was
added until a neutral pH value was obtained. The mixture was
extracted with Et2O (3 × 25 mL). The combined organic phases
were dried (MgSO4), evaporated in vacuo and the residue was
purified by chromatography (DCM/EtOAC, 100:1, Rf = 0.28)
to give the product (3.94 g, 85%) as a colourless solid. M.p.
Substitution of azide by single-component Grignard reagents
The reactions were carried out by dissolving approxi-
mately 100 mg (0.3 mmol) of 3-(Azidophenylmethoxy)-8-
azabicyclo[3.2.1]octane-8-carboxylic acid tert-butyl ester (4) in
3 mL of dry toluene. A freshly prepared ether solution of the
desired Grignard reagents (2 equivalents) was slowly added with
continuous stirring at room temperature. The addition caused
the clear colourless solution to become yellow. After stirring for
1 h the reactions were quenched by adding 1 mL of saturated
NH4Cl and 1 mL of water. The mixtures were extracted with
Et2O (3 × 10 mL), dried over MgSO4, evaporated in vacuo and
purified by chromatography.
1
61.5 °C, H NMR (CDCl3, 400 MHz) d = 7.35–7.26 (5H, m,
Ph–H), 4.49 (2H, s, O–CH2–Ph), 4.17 (2H, m, H-1,5), 3.71 (1H,
br. s, H-3), 2.17–1.85 (8H, m, H2-2,4,6,7), 1.46 (9H, s, (CH3)3,
Boc) ppm. 13C NMR (CDCl3, 200 MHz) d = 153.7 (CO, Boc),
139.2 (C(Ph)), 128.5; 127.5; 127.2 (CH(Ph)), 79.2 (C(CH3)3,
Boc), 72.8 (O–CH2–Ph), 70.9 (C-3), 53.4/52.6* (C-1.5), 35.7/
34.6* (C-2,4), 28.8 ((CH3)3C, Boc), 28.8/28.1* (C-6,7) ppm.
(* The spectrum showed two rotamers.) HRMS (ES); calculated
for C19H27NO3Na (M + Na): 340.1889. Found: m/z 340.1885.
3-Benzhydryloxy-8-azabicyclo[3.2.1]octane-8-carboxylic acid
tert-butyl ester (5)
3-(1-Azidobenzyloxy)-8-azabicyclo[3.2.1]octane-8-carboxylic
acid tert-butyl ester (4)
Chromatography (pentane/EtOAc, 15:1, Rf = 0.25) gave the
product 5 (76 mg, 64%) as a colourless solid. M.p. 92.4 °C, 1H
NMR (CDCl3, 200 MHz) d = 7.30–7.13 (10H, m, Ph–H), 5.36
(1H, s, O–CH–(Ph)2), 4.09 (2H, m, H-1,5), 3.61 (1H, s, H-3),
2.17–1.83 (8H, m, H2-2,4,6,7), 1.38 (9H, s, (CH3)3, Boc) ppm.
13C NMR (CDCl3, 50 MHz) d = 153.3 (CO, Boc), 142.7
(C(Ph)), 128.2; 127.2; 126.7 (CH(Ph)), 81.0 (O–CH–(Ph)2), 78.9
(C(CH3)3, Boc), 69.8 (C-3), 53.1/52.3* (C-1,5), 35.6/34.8* (C-
2,4), 28.4/27.7* ((CH3)3C, Boc), 28.4/27.7* (C-6,7) ppm. (* The
spectrum showed two rotamers.) HRMS (ES); calculated for
C25H31NONa (M + Na): 416.2206. Found: m/z 416.2202.
A solution of iodine monochloride (131 mg, 0.81 mmol) in
dry CH3CN (1 mL) was cooled to −10 °C. NaN3 (122 mg,
1.88 mmol) was added with continuous stirring. After 15 min,
the cooling bath was removed and DMF (0.1 mL) and 3a-
benzyloxy-8-azabicyclo[3.2.1]octane-8-carboxylic acid tert-
butyl ester (3, 85 mg, 0.27 mmol) were added. The mixture was
refluxed for 70 min (monitored by TLC) and then cooled to
room temperature. CH2Cl2 (10 mL) was added and the mixture
was washed with a solution of 5% Na2S2O3 (10 mL). This proce-
dure resulted in the brown organic phase becoming yellow and
the colourless water phase becoming orange. The water phase
was extracted with DCM (2 × 10 mL) and the combined organic
phases were dried over MgSO4 and evaporated in vacuo. The
residue was purified by chromatography (pentane/EtOAc, 10:1,
Rf = 0.26) to give the product (69 mg, 73%) as a clear colourless
oil. 1H NMR (CDCl3, 400 MHz) d = 7.45–7.36 (5H, m, Ph–H),
5.39 (1H, s, O–CHN3–Ph), 4.19 (2H, br. s, H-1,5), 4.13 (1H, t, H-
3, J = 4.4 Hz), 2.22–1.78 (8H, m, H2-2,4,6,7), 1.46 (9H, s, (CH3)3,
Boc) ppm. 13C NMR (CDCl3, 200 MHz) d = 153.6 (CO, Boc),
137.5 (C(Ph)), 129.3; 129.2; 128.9 (CH(Ph)), 91.5 (O–CHN3–
Ph), 79.4 (C(CH3)3, Boc), 72.4 (C-3), 53.1/52.3* (C-1,5), 37.2/
36.4* (C-2,4), 35.3/34.4* (C-6,7), 28.7/28.0 ((CH3)3C, Boc) ppm.
(* The spectrum showed two rotamers.) HRMS (ES); calculated
for C19H26N4O3Na (M + Na): 381.1904. Found: m/z 381.1903.
IR (film) m = 3444, 2978, 2103, 1694, 1652, 1548 cm−1.
3-(1-Phenylethoxy)-8-azabicyclo[3.2.1]octane-8-carboxylic acid
tert-butyl ester (12a)
Chromatography (pentane/EtOAc, 20:1, Rf = 0.39), gave
1
the product 12a (99 mg, 91%) as a colourless oil. H NMR
(CDCl3, 200 MHz) d = 7.29–7.20 (5H, m, Ph–H), 4.44 (1H, q,
O–CH(Me)–Ph, J = 6.4 Hz), 4.11 (2H, br. s, H-1,5), 3.48 (1H,
br. s, H-3), 2.19–1.63 (8H, m, H2-2,4,6,7), 1.40 (9H, s, (CH3)3,
Boc), 1.35 (3H, d, CH3, J = 6.4 Hz) ppm. 13C NMR (CDCl3,
50 MHz) d = 153.3 (CO, Boc), 144.2 (C(Ph)), 128.2; 127.1;
126.0 (CH(Ph)), 78.8 (C(CH3)3, Boc), 74.9 (O–CH(Me)–Ph),
69.3 (C-3), 53.1/52.3* (C-1,5), 37.0/36.1* (C-2,4), 34.2/33.4*
(C-6,7), 28.4/27.8* ((CH3)3C, Boc), 24.4 (CH3). (* The spec-
trum showed two rotamers.) HRMS (ES), Calculated for
C20H29NO3Na (M + Na): 354.2045. Found: m/z 354.2045.
3-(1-Phenylpentyloxy)-8-azabicyclo[3.2.1]octane-8-carboxylic
acid tert-butyl ester (13a)
Preparation of single-component Grignard reagents
Mg turnings (20 mmol) were suspended in dry Et2O (10 mL) in a
two necked round bottomed flask fitted with a reflux condenser.
The halide (10 mmol) was added at such a rate that the mixture
kept refluxing. After addition the mixture was refluxed for 2 h.
The Grignard reagent was taken out using a syringe and titrated
before use in order to determine the concentration.
Chromatography (pentane/EtOAc, 20:1, Rf = 0.29), gave the
product 13a (120 mg, 52%) as a colourless solid. M.p. 71.6 °C,
1H NMR (CDCl3, 200 MHz) d = 7.34–7.23 (5H, m, Ph–H),
4.27 (1H, t, J = 6.8 Hz, O–CH(Bu)–Ph), 4.14 (2H, br. s, H-1,5),
3.46 (1H, br. s, H-3), 2.21–1.85 (8H, m, H2-2,4,6,7), 1.72–1.52
(4H, m, CH2–CH2 butyl), 1.42 (9H, s, (CH3)3, Boc), 1.30 (2H,
q, J = 5.6 Hz, CH2–CH3 butyl), 0.86 (3H, t, J = 5.6 Hz, CH3
butyl) ppm. 13C NMR (CDCl3, 200 MHz) d = 153.6 (CO,
Boc), 143.5 (C(Ph)), 128.4; 127.4; 127.0 (CH(Ph)), 80.0
(O–CH(Bu)–Ph), 79.1 (C(CH3)3, Boc), 69.6 (C-3), 53.3/52.6*
(C-1,5), 38.7 (CH2), 37.6/35.9* (C-2,4), 34.1/33.4* (C-6,7),
28.7/28.2* ((CH3)3C, Boc), 28.2 (CH2), 22.9 (CH2), 14.2
Preparation of multiple-component Grignard reagents
Mg turnings (20 mmol) were suspended in dry Et2O (10 mL) in a
two necked round bottomed flask fitted with a reflux condenser.
Several different halides were added dropwise one by one in
mole-equivalent amounts (10 mmol total) at such a rate that the
2 8 6 6
O r g . B i o m o l . C h e m . , 2 0 0 4 , 2 , 2 8 6 1 – 2 8 6 9

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(CH3) ppm. (* The spectrum showed two rotamers.) HRMS
(ES); calculated for C23H35NO3Na (M + Na): 396.2518. Found:
m/z 396.2515.
3-[(2-Ethylphenyl)phenylmethoxy]-8-azabicyclo[3.2.1]octane (10)
1
Rf = 0.28. Yield 59% (2 steps). H NMR (CDCl3, 400 MHz)
d = 7.50–7.08 (9H, m, Ph–H), 5.57 (1H, s, O–CH–Ph), 3.56 (1H,
br. s, H-3), 3.42 (2H, br. s, H-1,5), 2.65 (1H, br. s, NH), 2.64–2.45
(2H, m, CH2), 1.92–1.61 (8H, m, H2-2,4,6,7), 0.98 (3H, t, CH3,
J = 7.6 Hz) ppm. 13C NMR (CDCl3, 100 MHz) d = 142.7; 141.6;
139.8 (C(Ph)), 128.8; 128.3; 127.9; 127.7; 127.5; 127.2; 126.1
(CH(Ph)), 77.6 (O–CH–Ph), 69.7 (C-3), 53.9; 53.7 (C-1,5), 37.8;
36.5 (C-2,4), 29.5; 29.2 (C-6,7), 25.1 (CH2), 15.0 (CH3) ppm.
HRMS (ES); calculated for C22H28NO (M + H): 322.2171.
Found: m/z 322.2171.
Synthesis of N-Boc-protected libraries I–V and a–e
The reactions were carried out by dissolving approxi-
mately 200 mg (0.6 mmol) of 3-(azidophenylmethoxy)-8-
azabicyclo[3.2.1]octane-8-carboxylic acid tert-butyl ester (4) in
5 mL of dry toluene. A freshly prepared ether solution of the
desired multiple-component Grignard reagents (2 equivalents)
were slowly added (ca. 2 h) with continuous stirring at room
temperature. The halides used in the Grignard reactions were
mixed according to Table 2. The additions of the Grignard
reagents caused a colour change from colourless to yellow.
After the additions the reactions were quenched by adding 1 mL
saturated solution of NH4Cl and 1 mL of water. The mixtures
were extracted with Et2O (3 × 10 mL), dried over MgSO4 and
evaporated to dryness. The crude compound was used without
further purification.
3-[(4-Chlorophenyl)phenylmethoxy]-8-azabicyclo[3.2.1]octane
(11)11
1
Rf = 0.28. Yield 69% (2 steps). H NMR (CDCl3, 400 MHz)
d = 7.22–7.15 (9H, m, Ph–H), 5.29 (1H, s, O–CH–Ph), 4.36
(1H, br. s, NH), 3.55 (1H, t, H-3, J = 3.2 Hz), 3.41 (2H, br. s,
H-1,5), 2.18–1.61 (8H, m, H2-2,4,6,7) ppm. 13C NMR (CDCl3,
100 MHz) d = 142.4; 141.6 (C(Ph)), 133.0 (C(Ph–Cl), 128.6;
128.5; 128.2; 127.6; 126.8 (CH(Ph)), 80.3 (O–CH–Ph), 69.7 (C-
3), 54.0; 53.7 (C-1,5), 36.7; 36.4 (C-2,4), 29.0; 28.2 (C-6,7) ppm.
HRMS (ES); calculated for C20H23ClNO (M + H): 328.1468.
Found: m/z 328.1468.
Deprotection of a single amine compound
The Boc-protected compound (0.6 mmol) was dissolved in
CH2Cl2 (5 mL). 2,6-Lutidine (8 eq.) and TMSOTf (5 eq.) were
added at 0 °C. The reaction was allowed to reach room tempera-
ture over 45 min. After stirring for another 10 min (monitored
by TLC) the reaction was quenched by adding a saturated solu-
tion of NaHCO3 (8 mL) and extracted with DCM (3 × 10 mL).
The dried (MgSO4) organic layer was evaporated in vacuo and
the residue was purified by chromatography (MeOH, 2% Et3N)
to give the product as clear colourless oil.
3-Benzyloxy-8-azabicyclo[3.2.1]octane (14)
3a-Benzyloxy-8-azabicyclo[3.2.1]octane-8-carboxylic acid tert-
butyl ester (3, 238 mg, 0.75 mmol) was dissolved in DCM (2 mL),
and TFA (2 mL) was added. The mixture was stirred at room
temperature for 1 h. The reaction was quenched by adding a
saturated solution of NaHCO3 (8 mL) and extracted with DCM
(3 × 10 mL). The dried (MgSO4) organic layer was evaporated
in vacuo. Purification by chromatography (MeOH, 2% Et3N,
Rf = 0.12) gave the product (153 mg, 94%) as a clear colourless
oil. 1H NMR (CDCl3, 400 MHz) d = 7.36–7.30 (5H, m, Ph–H),
4.46 (1H, s, O–CH2–Ph), 3.67 (1H, br. t, J = 4.4 Hz, H-3), 3.49
(2H, br. s, H-1,5), 2.31 (1H, br. s, NH), 2.21–1.73 (8H, m, H2-
2,4,6,7) ppm. 13C NMR (CDCl3, 100 MHz) d = 139.4 (C(Ph)),
128.5; 127.4; 127.2 (CH(Ph)), 72.8 (O–CH2–Ph), 70.6 (C-3), 54.0
(C-1,5), 37.1 (C-2,4), 29.6 (C-6,7) ppm. HRMS (ES); calculated
for C14H20NO (M + H): 218.1546. Found: m/z 218.1545.
3-Benzhydryloxy-8-azabicyclo[3.2.1]octane (6)15
1
Rf = 0.29 (MeOH, 2% Et3N). Yield 94%. H NMR (CDCl3,
200 MHz) d = 7.31–7.10 (10H, m, Ph–H), 5.35 (1H, s, O–CH–
(Ph)2), 3.57 (1H, br. s, H-3), 3.44 (2H, br. s, H-1,5), 3.01 (1H, br.
s, NH), 2.25–1.66 (8H, m, H2-2,4,6,7) ppm. 13C NMR (CDCl3,
50 MHz) d = 142.9 (C(Ph)), 128.2; 127.1; 126.7 (CH(Ph)), 80.7
(O–CH–(Ph)2), 69.6 (C-3), 53.5 (C-1,5), 36.8 (C-2,4), 29.1 (C-
6,7) ppm. HRMS (ES); calculated for C20H23NONa (M + Na):
294.1853. Found: m/z 294.1858.
3-(1-Phenylethoxy)-8-azabicyclo[3.2.1]octane (12)
3-(3-Methyl-1-phenylbutoxy)-8-azabicyclo[3.2.1]octane (8)
Chromatography (MeOH, 2% Et3N, Rf = 0.31) gave the product
(55 mg, 57% over 2 steps) as a clear colourless oil. H NMR
1
Rf = 0.28 (MeOH, 2% Et3N). Yield 63% (2 steps). H NMR
1
(CDCl3, 400 MHz) d = 7.24–7.17 (5H, m, Ph–H), 4,31 (1H, br.
s, NH), 4.26 (1H, dd, J = 5.2 Hz, J = 7.6 Hz, O–CH(Ph)–CH2),
3.52 (2H, br. s, H-1,5), 3.37 (1H, t, J = 4.4 Hz, H-3), 2.01–1.73
(8H, m, H2-2,4,6,7), 1.65–1.62 (2H, m, CH2 isobutyl), 1.29 (1H,
sep, CH2–CH–(CH3)2, J = 5.2), 0.86 (6H, t, CH3–CH–CH3,
J = 5.2 Hz) ppm. 13C NMR (CDCl3, 100 MHz) d = 143.8
(C(Ph)), 128.5; 127.5; 127.0 (CH(Ph)), 78.0 (O–CH–Ph), 69.1
(C-3), 54.1; 53.9 (C-1,5), 48.5 (2H, CH2 isobutyl), 40.0; 38.5 (C-
2,4), 29.0; 28.7 (C-6,7), 24.6 (CH), 23.5 (CH3), 22.5 (CH3) ppm.
HRMS (ES); calculated for C18H28NO (M + H): 274.2177.
Found: m/z 274.2171.
(CDCl3, 400 MHz) d = 7.25–7.17 (10H, m, Ph–H), 4.37 (1H, q,
J = 6.4 Hz, O–CH–Ph), 3.40 (1H, s, H-3), 3.37 (2H, m, H-1,5),
1.95 (1H, br. s, NH), 2.17–1.69 (8H, m, H2-2,4,6,7), 1.29 (3H, d,
J = 6.4 Hz, CH3) ppm. 13C NMR (CDCl3, 100 MHz) d = 136,7
(C(Ph)), 128.5; 127.3; 126.3 (CH(Ph)), 74.8 (O–CH–(Ph)2),
69.6 (C-3), 54.0 (C-1,5), 38.9; 36.2 (C-2,4), 29.8; 29.5 (C-6,7),
24.8 (CH3) ppm. HRMS (ES); calculated for C15H21NONa
(M + Na): 254.1521. Found: m/z 254.1525.
Compound library
The crude library from the multicomponent Grignard reaction
(0.5 mmol) was dissolved in DCM (5 mL). 2,6-Lutidine (8 eq.)
and TMSOTf (5 eq.) were added at 0 °C. The reaction was
allowed to reach room temperature over 1 h. The reaction was
quenched by adding a saturated solution of NaHCO3 (8 mL)
and extracted with DCM (3 × 10 mL). The dried (MgSO4)
organic layer was evaporated in vacuo and purified by chromato-
graphy (MeOH, 2% Et3N) to give the library as a clear colourless
or yellow oil in a yield of 56–70% over 2 steps.
3-(1-Phenylbutoxy)-8-azabicyclo[3.2.1]octane (9)
1
Rf = 0.28 (MeOH, 2% Et3N). Yield 61% (2 steps). H NMR
(CDCl3, 400 MHz) d = 7.26–7.14 (5H, m, Ph–H), 4.20 (1H,
dd, O–CH–Ph, J = 5.2 Hz, J = 7.6 Hz), 3.41 (2H, br. s, H-1,5),
3.36 (1H, t, J = 4.4 Hz, H-3), 2.35 (1H, br. s, NH), 2.19–2.15
(2H, m, CH2), 1.88–1.61 (8H, m, H2-2,4,6,7), 1.51–1.09 (2H,
m, CH2), 0.83 (3H, t, CH3, J = 7,6 Hz). 13C NMR (CDCl3,
100 MHz) d = 143.6 (C(Ph)), 128.2; 127.1; 126.8 (CH(Ph)), 79.2
(O–CH–Ph), 69.4 (C-3), 53.9; 53.7 (C-1,5), 41.1; 40.8 (C-2,4),
39.0 (CH2), 29.4; 29.1 (C-6,7), 19.1 (CH2), 14.2 (CH3) ppm.
HRMS (ES); calculated for C17H26NO (M + H): 260.2014.
Found: m/z 260.2010.
8-Allyl-3-benzyloxy-8-azabicyclo[3.2.1]octane (15)
3-Benzyloxy-8-azabicyclo[3.2.1]octane (72 mg, 0.33 mmol) was
dissolved in dry DMF (3 mL). K2CO3 (91 mg, 0.66 mmol) and
O r g . B i o m o l . C h e m . , 2 0 0 4 , 2 , 2 8 6 1 – 2 8 6 9
2 8 6 7

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was purified by chromatography (MeOH/DCM, 2:1, Rf = 0.29),
to give the product (82 mg, 57%) as a colourless oil. H NMR
allyl bromide (31 lL, 0.37 mmol) were added. The reaction was
stirred at room temperature for 1 h. The reaction was quenched
by addition of water (10 mL) and extracted with Et2O (3 ×
10 mL). The dried (MgSO4) organic layer was evaporated in
vacuo and purified by chromatography (MeOH/DCM, 2:1,
Rf = 0.32) to give the product (79 mg, 93%) as a clear colourless
oil. 1H NMR (CD3OD, 400 MHz) d = 7.31–7.23 (5H, m, Ph–H),
5.91 (1H, m, vinyl), 5.21 (2H, m, vinyl), 4.43 (2H, s, O–CH2–Ph),
3.62 (1H, m, H-3), 3.26 (2H, m, H-1,5), 3.07 (2H, d, allyl, J =
6.4 Hz), 2.14–1.91 (8H, m, H2-2,4,6,7) ppm. 13C NMR (CD3OD,
100 MHz) d = 139.2 (C(Ph)), 134.1 (CH vinyl) 128.1; 127.2
(CH(Ph)), 118.4 (CH2 vinyl), 71.7 (O–CH2–Ph), 70.4 (C-3), 58.3
(allyl), 54.9 (C-1,5), 35.0 (C-2,4), 25.3 (C-6,7), 24.8 (CH3) ppm.
HR-MS (ES); calculated for C15H21NONa (M + Na): 258.1858.
Found: m/z 258.1850.
1
(CDCl3, 400 MHz) d = 7.26–7.08 (30H, m, Ph–H), 5.89–5.79
(1H, m, R3), 5.11–5.02 (2H, m, R3), 4.39 (10H, s, O–CH2–Ph),
3.55 (5H, br. s, H-3), 3.11–3.10 (10H, m, H-1,5), 2.93 (2H, d, R3,
J = 6.4 Hz), 2.58 (1H, t, J = 8.0 Hz, R4), 2.32–2.21 (6H, m, CH2
R5), 2.04–1.70 (40H, m, H2-2,4,6,7), 1.56–1.17 (12H, m, CH2 R1,
CH2 R2, CH2 R4), 0.85 (3H, t, CH3 R1, J = 7.6 Hz), 0.83 (6H, d,
J = 6.4 Hz, CH3 R2) ppm. HRMS (ES); found: m/z 256.1; 258.1;
274.2; 288.2; 336.1.
Synthesis of libraries X1–X5 and Y1–Y5
One library of I–V or a–e (approx. 100 mg, 0.5 mmol) was
dissolved in dry DMF (5 mL), and 2 eq. K2CO3 were added.
Five alkyl bromides (1-bromobutane, 1-bromo-3-methylbutane,
3-bromopropene, 3-bromopropyne, (3-bromopropyl)benzene)
were added in mole-equivalent amounts (1.1 eq. total). The
mixtures were stirred at room temperature for 40 h. The
reactions were quenched by addition of water (10 mL) and
extracted with Et2O (3 × 10 mL). The dried (MgSO4) organic
layers was evaporated to dryness. The libraries were synthesized
in 70–90% yield.
3-Benzhydryloxy-8-azabicyclo[3.2.1]octane-8-carboxylic acid
methyl ester (7)
To a solution of 3-benzhydryloxy-8-azabicyclo[3.2.1]octane (6,
45 mg, 0.15 mmol) in pyridine (0.5 mL) was added dropwise
methyl chloroformate (0.1 mL) at 0 °C. The addition caused
the clear colourless solution to be red. After stirring for addi-
tionally 30 min at room temperature (monitored by TLC) the
reaction was quenched by addition of water (5 mL). 1 M HCl
was added until a neutral pH value was obtained. The mixture
was extracted with DCM (3 × 10 mL). The dried (MgSO4)
organic layer was evaporated in vacuo and the residue was
purified by chromatography (pentane/EtOAc, 8:1, Rf = 0.24),
Synthesis of libraries Z1–Z5
Libraries I to V were combined (approx. 100 mg, 0.3 mmol) and
dissolved in dry DMF (5 mL), divided into 5 equal portions and
2 eq. K2CO3 were added to each reaction. Five alkyl bromides
(1-bromobutane, 1-bromo-3-methylbutane, 3-bromopropene,
3-bromopropyne, (3-bromopropyl)benzene) were added
separately to the five reactions in 1.1 mole-equivalent amounts.
The five mixtures were stirred at room temperature until TLC
analysis showed that the reactions were finished (1–40 h). The
reactions were quenched by the addition of water (10 mL) and
extracted with Et2O (3 × 10 mL). The dried (MgSO4) organic
layers was evaporated to dryness. The libraries were synthesized
in 71–88% yield.
1
to give the product (44 mg, 83%) as a clear colourless oil. H
NMR (CDCl3, 200 MHz) d = 7.30–7.12 (10H, m, Ph–H),
5.36 (1H, s, O–CH–(Ph)2), 4.17 (2H, m, H-1,5), 3.63 (1H, s,
H-3), 3.60 (3H, s, Me), 2.19–1.66 (8H, m, H2-2,4,6,7) ppm.
13C NMR (CDCl3, 50 MHz) d = 154.0 (CO), 142.6 (C(Ph)),
128.2; 127.2; 126.7 (CH(Ph)), 81.0 (O–CH–(Ph)2), 69.7 (C-3),
52.7 (Me), 52.7/52.0* (C-1,5), 35.8/35.0* (C-2,4), 28.6/27.8*
(C-6,7) ppm. (* The spectrum showed two rotamers.) HR-MS
(ES); calculated for C22H25NO3Na (M + Na): 374.1729. Found:
m/z 374.1732.
8-Butyl-3-(3-methyl-1-phenylbutoxy)-8-azabicyclo[3.2.1]octane
(16)
3-Benzhydryloxy-8-methyl-8-azabicyclo[3.2.1]octane
(benztropine, 1)16
Rf = 0.18. Yield 71%. 1H NMR (CDCl3, 400 MHz) d = 7.29–7.15
(5H, m, Ph–H), 4.27 (1H, dd, J = 5.2 Hz, J = 8.0 Hz, O–CH(Ph)–
CH2), 3.30 (1H, br. s, H-3), 3.07 (2H, br. s, H-1,5), 2.27–2.22
(2H, m, N–CH2), 2.07–1.73 (8H, m, H2-2,4,6,7), 1,69–1.62 (2H,
m, CH2 isobutyl), 1.55–1.51 (1H, m, CH isobutyl), 1.41–1.21
(4H, m, CH2 butyl), 0.86 (6H, t, CH3 isobutyl, J = 6.4 Hz),
0.83 (3H, t, J = 7.2 Hz, CH3 butyl) ppm. 13C NMR (CDCl3,
100 MHz) d = 144.0 (C(Ph)), 128.2; 127.1; 126.8 (CH(Ph)),
77.5 (O–CH–Ph), 69.2 (C-3), 58.3; 57.9 (C-1,5), 51.7 (N–CH2),
48.5 (CH2 isobutyl), 39.5; 37.3 (C-2,4), 31.1 (CH2 butyl), 26.2;
26.0 (C-6,7), 24.3; 23.4 (CH3 isobutyl), 22.3 (CH isobutyl), 21.0
(CH2 butyl), 14.1 (CH3 butyl) ppm. HRMS (ES); calculated for
C22H35NO (M + H): 330.2757. Found: m/z 330.2784.
LiAlH4 (108 mg, excess) was suspended in dry Et2O (3 mL).
3-Benzhydryloxy-8-azabicyclo[3.2.1]octane-8-carboxylic acid
methyl ester (33 mg, 0.094 mmol) was added and the mixture
was refluxed for 2 h. Adding a saturated solution of NH4Cl
until all the LiAlH4 was deactivated quenched the reaction.
The mixture was extracted with Et2O (3 × 10 mL). The dried
(MgSO4) organic layer was evaporated in vacuo and the resi-
due was purified by chromatography (pentane/EtOAc, 5:1,
Rf = 0.38), to give the product (24 mg, 83%) as a colourless oil.
1H NMR (CDCl3, 200 MHz) d = 7.31–7.14 (10H, m, Ph–H),
5.34 (1H, s, O–CH–(Ph)2), 3.50 (1H, s, H-3), 3.01 (2H, m,
H-1,5), 2.19 (3H, s, Me), 2.10–1.81 (8H, m, H2-2,4,6,7) ppm.
13C NMR (CDCl3, 200 MHz) d = 143.4 (C(Ph)), 128.5; 127.4;
127.0 (CH(Ph)), 80.9 (O–CH–(Ph)2), 69.4 (C-3), 60.4 (CH3),
40.7 (C-1,5), 36.6 (C-2,4), 26.0 (C-6,7) ppm. HRMS (ES);
calculated for C21H25NONa (M + Na): 308.2015. Found: m/z
308.2014.
8-(3-Methylbutyl)-3-(3-methyl-1-phenylbutoxy)-8-azabicyclo-
[3.2.1]octane (17)
1
Rf = 0.20. Yield 62%. H NMR (CDCl3, 400 MHz) d = 7.28–
7.14 (5H, m, Ph–H), 4.26 (1H, dd, J = 5.2 Hz, J = 8.0 Hz,
O–CH(Ph)–CH2), 3.30 (1H, br. s, H-3), 3.07 (2H, br. s,
H-1,5), 2.28–2.24 (2H, m, N–CH2), 2.09–1.73 (8H, m, H2-
2,4,6,7), 1.70–1.60 (2H, m, CH2 isobutyl), 1.55–1.45 (2H, m,
CH isobutyl, CH 3-methylbutyl), 1.33–1.24 (2H, m, CH2 3-
methylbutyl), 0.86 (6H, t, CH3 isobutyl, J = 6,4 Hz), 0.82 (6H,
t, J = 7.2 Hz, CH3 3-methylbutyl) ppm. 13C NMR (CDCl3,
100 MHz) d = 144.0 (C(Ph)), 128.2; 127.1; 126.8 (CH(Ph)), 77.5
(O–CH–Ph), 69.2 (C-3), 58.3; 57.9 (C-1,5), 50.1 (N–CH2), 48.5
(CH2 isobutyl), 39.5; 37.8 (C-2,4), 37.2 (CH2 3-methylbutyl),
26.8 (CH 3-methylbutyl), 26.2; 26.0 (C-6,7), 24.3; 23.4 (CH3
Synthesis of model library Z
3-Benzyloxy-8-azabicyclo[3.2.1]octane (14, 110 mg, 0.51 mmol)
was dissolved in dry DMF (3 mL), and K2CO3 (140 mg,
1.02 mmol) was added. Five alkyl bromides (1-bromobutane, 1-
bromo-3-methyl-butane, 3-bromopropene, 3-bromopropyne, (3-
bromopropyl)benzene) were added in mole-equivalent amounts
(0.56 mmol total). The mixture was stirred at room temperature
overnight. The reaction was quenched by addition of water
(10 mL) and extracted with Et2O (3 × 10 mL). The dried
(MgSO4) organic layer was evaporated in vacuo and the residue
2 8 6 8
O r g . B i o m o l . C h e m . , 2 0 0 4 , 2 , 2 8 6 1 – 2 8 6 9

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isobutyl), 22.8 (CH3 3-methylbutyl), 22.3 (CH isobutyl) ppm.
HRMS (ES), Calculated for C23H37NO (M + H): 344.2953.
Found: m/z 344.2981.
References
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Synthesis of [125I]-RTI-55 {[125I]-(1R,2S,3S,5S)-3-(4-
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Acknowledgements
We thank the Lundbeck foundation for financial support.
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O r g . B i o m o l . C h e m . , 2 0 0 4 , 2 , 2 8 6 1 – 2 8 6 9
2 8 6 9