Synthesis of bridged piperazines with σ receptor affinity

Article abstract of DOI:10.1016/j.ejmech.2007.02.005

Bridged piperazines 4 were designed as conformationally restricted piperazine σ receptor ligands. The chiral pool synthesis started from (S)-glutamate, which was transformed in five reaction steps into the piperazinediones 5 bearing a propionic acid ester side chain. A two-step Dieckmann analogous cyclization provided the bicyclic ketones 7 as key intermediates. The alcohols 8 were prepared by LiAlH₄ reduction of the ketones 7. NaBH₄ reduction, Williamson ether synthesis and LiAlH₄ reduction led to the methyl and benzyl ethers 12 and 13. High σ₁ affinity is attained when one large substituent is introduced either at N-8 or O-2. The most potent σ₁ ligand in this series of compounds is the methyl ether 12b with the N-butyl substituent (K_i = 13.2 nM, selectivity σ₂:σ₁ = 16). Moreover, the N-methyl derivatives 13a (σ₂: K_i = 30.4 nM) and 12a (σ₂ preference) represent promising starting points for the development of potent and selective σ₂ ligands.

Full text of DOI:10.1016/j.ejmech.2007.02.005

European Journal of Medicinal Chemistry 42 (2007) 1247e1262
http://www.elsevier.com/locate/ejmech
Original article
Synthesis of bridged piperazines with s receptor affinity
*
Manuela Weigl, Bernhard Wunsch
¨
Institut fu¨r Pharmazeutische und Medizinische Chemie, Hittorfstrasse 58-62, 48149 Mu¨nster, Germany
Received 28 September 2006; received in revised form 6 February 2007; accepted 12 February 2007
Available online 25 February 2007
Abstract
Bridged piperazines 4 were designed as conformationally restricted piperazine s receptor ligands. The chiral pool synthesis started from
(S )-glutamate, which was transformed in five reaction steps into the piperazinediones 5 bearing a propionic acid ester side chain. A two-
step Dieckmann analogous cyclization provided the bicyclic ketones 7 as key intermediates. The alcohols 8 were prepared by LiAlH4 reduction
of the ketones 7. NaBH4 reduction, Williamson ether synthesis and LiAlH4 reduction led to the methyl and benzyl ethers 12 and 13. High s1
affinity is attained when one large substituent is introduced either at N-8 or O-2. The most potent s1 ligand in this series of compounds is the
methyl ether 12b with the N-butyl substituent (Ki ¼ 13.2 nM, selectivity s2:s1 ¼ 16). Moreover, the N-methyl derivatives 13a (s2:
Ki ¼ 30.4 nM) and 12a (s2 preference) represent promising starting points for the development of potent and selective s2 ligands.
Ó 2007 Elsevier Masson SAS. All rights reserved.
Keywords: s Receptor ligands; Structure/affinity relationships; 6,8-Diazabicyclo[3.2.2]nonane; Chiral pool synthesis; Dieckmann cyclization
1. Introduction
atypical antipsychotics [3], antidepressants [4], anti-cocaine
agents [5,6], and antitumor agents [7].
The huge group of cell surface receptors is divided into
three main families: G-protein coupled receptors, ligand gated
ion channels, and receptor protein kinases. However, s recep-
tors, which are located in the central nervous system and the
periphery, do not match this classification. Recently the s1
receptor of various tissues and species has been cloned [1].
It was shown that the resulting amino acid sequence is not
related to any known mammalian protein. The exact three-
dimensional structure of the s1 receptor protein as well as
the amino acid sequence of the s2 receptor still remains to
be elucidated [2]. Despite the fact that the exact physiological
role of s receptors is not yet completely understood the
involvement of s receptors in several physiological and patho-
physiological events is well documented. Therefore, ligands
interacting with s receptors are of interest for example as
Several s receptor ligands contain the piperazine heterocy-
cle and the 1,4-disubstituted piperazine derivatives 1 [8] and 2
[9] are among the most active s receptor ligands described so
far. Recently, we have shown that piperazine derivatives 3 with
an additional hydroxymethyl substituent in position 2 also
bind with high affinity at s receptors [10]. The piperazines
3 can adopt two chair conformations with an equatorially or
an axially oriented hydroxymethyl moiety. Moreover, free
rotation of the hydroxymethyl group around the indicated
bond is possible in both conformers (Fig. 1).
Herein we wish to report on the synthesis and s receptor
affinity of the bridged piperazine derivatives 4. In the bicyclic
compounds 4 the piperazine ring is forced into a boat like con-
formation leading to a somewhat different orientation of the N
substituents. Moreover, the substituent in the former 2-position
(of compound 3) is fixed in an axial orientation and the rota-
tion around the single bond is no longer possible. The confor-
mationally constrained piperazine derivatives 4 are planned in
order to learn more about the pharmacologically active confor-
mation, which interacts with the s receptor protein.
* Corresponding author. Tel.: þ49 251 8333311; fax: þ49 251 832144.
E-mail address: wuensch@uni-muenster.de (B. Wunsch).
¨
0223-5234/$ - see front matter Ó 2007 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2007.02.005

1248
M. Weigl, B. Wu¨nsch / European Journal of Medicinal Chemistry 42 (2007) 1247e1262
R
Cl
Cl
N
CH3
N
N
N
1
2
N
R
N
N
R
N
OH
HO
3
R3
N
R1
N
R2O
4
Fig. 1. Comparison of the lead compounds 1e3 with the novel s receptor ligands 4.
2. Chemistry
The bridged piperazinediones 7aec were reduced with
LiAlH4 in refluxing THF and the formed diastereomeric alco-
hols (2R)-8a/(2S )-8a and (2R)-8c/(2S )-8c were separated by
flash chromatography. The butyl derivative 8b was obtained
by LiAlH4 reduction of a 9b/11b mixture. In this case purifica-
tion by flash chromatography (fc) led only to a mixture of di-
astereomers in the ratio (2S )-8b:(2R)-8b ¼ 23:77 (Scheme 2).
In order to synthesize 2-alkoxy derivatives of the bicyclic
system the ketones 7aec were reduced with NaBH4 to afford
the alcohols 9aec as mixtures of diastereomers, respectively.
The ethers 10aec and 11aec were prepared by NaH de-
protonation of the corresponding alcohols 9aec and subse-
quent alkylation with methyl iodide and benzyl bromide,
Starting from the proteinogenic amino acid (S )-glutamate
the monocyclic piperazinedione derivatives 5aec with a pro-
pionic acid ester side chain were synthesized in five steps
[11]. The three-carbon bridge of 7aec was established by
the variation of the Dieckmann cyclization recently described
by us [12]. This Dieckmann cyclization consists of two steps:
at first treatment of 5aec with lithium hexamethyldisilazane
(LHMDS) and subsequent trapping of the intermediate diaster-
eoselectively [13] led to the mixed methyl silyl acetals 6aec.
Careful hydrolysis of 6aec with acid provided the bicyclic
ketones 7aec in very high yield (Scheme 1).
R
O
Bn
N
O
N
(S)-glutamate
N
R
H
O
H3CO
O
N
CO2CH3
O
Bn
5a-c
O
O
N
Bn
Bn
N
O
N
O
(a
)
(b)
N
R
R
5-7
R
a
b
c
CH3
H3CO
O
OSI(CH3)3
6a-
C4H9
CH2CH2C6H5
c
7a-c
Scheme 1. (a) LHMDS, THF, ꢀ78 ꢁC, then TMS-Cl, ꢀ78 ꢁC. (b) p-TolSO3H, THF, H2O, rt.

M. Weigl, B. Wu¨nsch / European Journal of Medicinal Chemistry 42 (2007) 1247e1262
1249
7a-c
(a)
O
N
Bn
N
O
(a)
R
7a-c
HO
9a-c
N
N
Bn
Bn
8
N
8
N
R
R
(b)
(c)
2
+
2
H
HO
O
N
O
N
OH
H
Bn
Bn
N
N
O
R
R
(2R)-8a-c
(2S)-8a-c
O
BnO
H3CO
8
R
10a-
c
1
1a-c(+9b)
CH3
a
b
c
C4H9
(d)
N
(d)
(d)
CH2CH2C6H5
8b
Scheme 2. (a) LiAlH4, THF, 66 ꢁC.
8
N
Bn
Bn
N
8
N
R
R
respectively. At last reduction of the dilactam systems with
LiAlH4 produced the diastereomeric methyl ethers (2R)-12/
(2S )-12 and benzyl ethers (2R)-13/(2S )-13 as inseparable
mixtures of diastereomers (Scheme 3).
2
BnO
2
H3CO
(2R+2S)-12a-c
(2R+2S)-13a-c
For the purpose of comparison the dimethoxy derivative
15a bearing a methyl group at the N-atom was synthesized
and pharmacologically evaluated. Transacetalization of the
mixed methyl/silyl acetal 6a with methanol and a catalytic
amount of p-toluenesulfonic acid afforded the ketone dimethyl
acetal 14a. During this transacetalization small amounts of the
ketone 7a were formed, which was separated after NaBH4
reduction. Finally, LiAlH4 reduction of the lactam carbonyl
moieties provided the bridged piperazine 15a with two
methoxy substituents in position 2 (Scheme 4).
9-13
R
a
b
c
CH3
C4H9
CH2CH2C6H5
Scheme 3. (a) NaBH4, THF, H2O, rt. (b) NaH, CH3I, THF, rt. (c) NaH,
PhCH2Br, Bu4NI, THF, rt. (d) LiAlH4, THF, 66 ꢁC.
3. Receptor binding studies
O
O
Bn
Bn
The s receptor affinity of the bridged piperazines was eval-
uated with receptor binding studies. In these assays the test
compounds compete with tritium labeled ligands for a limited
number of receptors. Homogenates of guinea pig brain and rat
liver were used as receptor material in the s1 assay and the s2
assay, respectively. In the s1 assay [3H]-(þ)-pentazocine was
employed as radioligand, and the non-specific binding was de-
termined in the presence of a large excess of haloperidol. Since
a s2 selective radioligand is not commercially available, the
non-selective radioligand [3H]-ditolylguanidine was employed
in the presence of a large excess of non-radiolabeled
(þ)-pentazocine (100 nM), which selectively occupies s1
receptors. Performing of the s2 assay in the presence of an
excess of non-tritiated 1,3-di(o-tolyl)guanidine led to the non-
specific binding of the radioligand [14].
N
N
O
N
N
(a)
H3C
H3C
+
7a
O
H3CO
H3CO
OSI(CH3)3
OCH3
6a
14a
(b)
N
Bn
H3C
N
2
H3CO
OCH3
15a
Since a structural relationship between s receptor ligands
and NMDA receptor antagonists as well as k Opioid receptor
Scheme 4. (a) CH3OH, THF, p-TolSO3H, rt. [then NaBH4]. (b) LiAlH4, THF,
66 ꢁC.

1250
M. Weigl, B. Wu¨nsch / European Journal of Medicinal Chemistry 42 (2007) 1247e1262
agonists exist the affinity of the bridged piperazines towards
these receptor systems was investigated as well. In the compe-
tition experiments the radioligands [3H]-MK801 (NMDA)
[15], [3H]-U69593 (k Opioid) [16], and [3H]-DAMGO
(m Opioid) [16] were employed.
substituent favours the interaction with the s1 receptor, but
a second large substituent disturbs binding at the s1 receptor
protein. The position of the large substituent (N-8 or O-2) is
of minor importance since 13a (N-methyl, O-benzyl, Ki ¼
16.2 nM) and 12b (N-butyl, O-methyl, Ki ¼ 13.2 nM) are
almost equipotent.
The s2 receptor affinities of diastereomeric alcohols (2R)-
8a and (2S )-8a as well as (2R)-8c and (2S )-8c do not differ
significantly. A large N-substituent leads to little increase of
the s2 affinity compared to the N-methyl derivatives. The s2
affinities of the butyl (8b) and 2-phenylethyl derivatives (8c)
are still in the high nanomolar range (Ki ¼ 340e590 nM).
The corresponding methyl ethers 12a, 12b and 12c reveal
very similar s2 affinity (Ki ¼ 327 nM, 219 nM, 297 nM,
respectively). In this series the nitrogen substituent has little
influence on the s2 affinity. Somewhat different properties
are observed in the benzyl ether series 13. Here the N-methyl
derivative 13a binds with extraordinarily high affinity towards
s2 receptors (Ki ¼ 30.4 nM) whereas the corresponding
N-butyl (13b) and N-phenylethyl derivatives (13c) are less
active. The benzyl ether 13a represents the most potent s2
ligand of this series.
Generally most of the bridged piperazines 8, 12, 13 and 15
interact selectively with s1 receptors. However, four com-
pounds (12a, 12b, 13a, 13b) will be discussed with respect
of their s1/s2 receptor selectivity. The most s1 selective com-
pounds are the butyl derivatives 12b and 13b (s2:s1 ¼ 16 and
21, respectively). Exchange of the N-butyl substituent of 12b
against a methyl group (12a) reduces the s1 affinity 100-fold
but retains the s2 affinity, which leads to a ligand with a 4-fold
preference for the s2 receptor over the s1 receptor. Compared
to the methyl ether 12a the s1 affinity of the benzyl ether 13a
is increased 100-fold and the s2 affinity 10-fold. Thus, the
benzyl ether 13a represents the most potent s2 ligand in this
4. Results and discussion
The receptor affinities of the bridged piperazines are
summarized in Table 1.
The s1 receptor affinity of the alcohols 8 hardly depends on
their stereochemistry: the diastereomeric alcohols with the
N-methyl group (2S )-8a and (2R)-8a as well as the diastereo-
meric N-phenylethyl alcohols (2S )-8c and (2R)-8c show very
similar Ki-values. Therefore, the receptor affinities of diaste-
reomeric mixtures were investigated when separation by flash
chromatography failed to give pure diastereomers (8b, 12b,
12c, 13b, 13c). In contrast the N-8-substituent strongly influ-
ences the s1 affinity. The bridged piperazines (2R)-8a and
(2S )-8a with the small methyl group display only low s1
receptor affinity (Ki ¼ 2.4 mM and 4.97 mM), whereas alcohols
bearing larger N-substituents (butyl 8b, 2-phenylethyl 8c)
interact with s1 receptors in the low nanomolar range.
The same tendency is observed for the methyl ether series
12. The s1 affinity of the N-methyl derivative 12a is rather
low, whereas the corresponding butyl derivative 12b (Ki ¼
13.2 nM) and the 2-phenylethyl derivative 12c (Ki ¼ 76 nM)
strongly bind at s1 receptors. An additional methoxy group
in position 2 (15a) does not raise the s1 affinity of N-methyl
derivatives.
In the benzyl ether series 13 the s1 affinity is reversed and
decreases with increasing size of the N-8-substituent. Thus the
N-methyl derivative 13a is the most potent compound
(Ki ¼ 16.2 nM) in the benzyl ether series. Obviously, one large
Table 1
Receptor affinity of the bridged piperazines
Compound
Ki ꢂ SEM [nM] (n ¼ 3)
s1 ([3H](þ)-pentazocine)
s2 ([3H]-ditolylguanidine)
k ([3H]-U69593)
m ([3H]-DAMGO)
NMDA ([3H]-MK801)
8a (2S )
4970 ꢂ 180
2400 ꢂ 300
23.4 ꢂ 6.9
33.3 ꢂ 6.9
29.5 ꢂ 8.5
1350 ꢂ 450
13.2 ꢂ 4.1
76 ꢂ 17.6
16.2 ꢂ 5.6
39.5 ꢂ 15.3
175 ꢂ 37
3500 ꢂ 500
2.20 ꢂ 0.31
3.58 ꢂ 0.20
164 ꢂ 47
e
2890 ꢂ 750
4180 ꢂ 780
447 ꢂ 31
343 ꢂ 58
588 ꢂ 81
327 ꢂ 57
219 ꢂ 108
297 ꢂ 107
30.4 ꢂ 3.6
820 ꢂ 250
628 ꢂ 79
1830 ꢂ 320
34.2 ꢂ 2.3
n.d.
n.d. 13.2%a
n.d. 12.6%a
1600 ꢂ 200
2460 ꢂ 790
1290 ꢂ 130
3590 ꢂ 450
157 ꢂ 21
5020 ꢂ 460
585 ꢂ 160
1110 ꢂ 450
2230 ꢂ 200
>10 mM
e
n.d. 4.7%a
n.d. 8.5%a
n.d. 37.9%a
4960 ꢂ 2410
4050 ꢂ 400
n.d. 21.5%a
n.d. 37.4%a
n.d. 68.6%a
n.d. 70.4%a
3320 ꢂ 1680
n.d. 34.8%a
n.d. 27.6%a
e
n.d. 13.7%a
n.d. 21.0%a
n.d. 52.3%a
n.d. 21.9%a
n.d. 20.6%a
n.d. 8.7%a
n.d. 55.5%a
n.d. 50.5%a
n.d. 0%a
n.d. 21.5%a
n.d. 16.4%a
n.d. 44.3%a
e
8a (2R)
8b (2S:2R ¼ 23:77)
8c (2S )
8c (2R)
12a (2R)
12b (2S:2R ¼ 25:75)
12c (2S:2R ¼ 23:77)
13a (2R)
13b (2S:2R ¼ 36:64)
13c (2S:2R ¼ 22:78)
15a
Haloperidol
(þ)-Pentazocine
Ditolylguanidine
U-50488
e
e
e
63.9 ꢂ 10.8
e
e
e
e
0.49 ꢂ 0.16
3.17
e
e
Naoxone
e
e
e
e
0.68 ꢂ 0.04
e
e
Phencyclidine
(S )-Ketamine
a
e
28 ꢂ 4.6
108 ꢂ 12
e
e
e
e
Inhibition of radioligand binding at a test compound concentration of 10 mM.

M. Weigl, B. Wu¨nsch / European Journal of Medicinal Chemistry 42 (2007) 1247e1262
1251
series, however due to its strong s1 affinity increase it shows
6.1.1. (1S,5S )-6-Benzyl-2-methoxy-8-methyl-2-(trimethyl-
little preference for the s1 receptor over the s2 receptor.
The bridged piperazines binding in the low nanomolar
range at s1 and/or s2 receptors are selective over k Opioid,
m Opioid, and NMDA receptors. Some of the compounds
show moderate k affinity in the low micromolar range (e.g.
8b: Ki ¼ 1600 nM). However, a surprisingly high k receptor
affinity was found for the methyl ether of the N-butyl deriva-
tive 12b. The Ki value of 157 nM is in the range of its s2
affinity (Ki ¼ 219 nM). Nevertheless, 12b is still 10-fold selec-
tive for the s1 receptor over the k receptor. In Table 1 the m
and NMDA receptor affinities are given as inhibition (in %)
of radioligand binding at a test compound concentration of
10 mM. It is shown that the investigated bridged piperazines
do not interact significantly with m Opioid, and NMDA recep-
tors. At a concentration of 10 mM the inhibition is generally
lower than 50% indicating an IC50 value greater than 10 mM.
siloxy)-6,8-diazabicyclo[3.2.2]nonane-7,9-dione (6a)
Under N2 a solution of lithium hexamethyldisilazane
(LHMDS, 1 M in THF; 3.30 mL, 3.30 mmol) was added drop-
wise to a solution of 5a [11] (877 mg, 2.88 mmol) in THF
(50 mL) at ꢀ78 ꢁC. After a reaction time of 30 min at
ꢀ78 ꢁC
a solution of chlorotrimethylsilane (1.15 mL,
8.97 mmol) in THF (6.0 mL) was added and the reaction mix-
ture was stirred for 30 min at ꢀ78 ꢁC, then for 60 min at room
temperature. The solvent was removed in vacuo and the resi-
due was dissolved in ethyl acetate (80 mL). The solution
was washed with NaOH (0.5 M, 2 ꢃ 50 mL), with HCl
(0.5 M, 2 ꢃ 50 mL) and with brine (50 mL), dried (Na2SO4)
and concentrated in vacuo. The resulting product 6a was char-
acterized and directly used for the next reaction without
further purification. Colorless solid, yield 1.05 g (97%);
tlc: ethyl acetate, Rf ¼ 0.50. C19H28N2O4Si (376.4). MS (EI):
m/z (%) ¼ 376 (M, 48), 361 (M ꢀ CH3, 15), 345 (M ꢀ OCH3,
25
5. Conclusion
12), 285 (M ꢀ CH2Ph, 4). [a] ¼ þ60.4 (c ¼ 0.56, CH2Cl2).
589
IR (film): ~n [cmꢀ1] ¼ 3032 (w, nCH arom.), 2959 (m, nCH aliph.),
1682 (s, nC]O, tert. amides), 1254, 1017 (m, nCOC), 733, 701 (m,
gmonosubst. arom.). 1H NMR (CDCl3): d ¼ 0.21 (s, 9H,
Si(CH3)3), 1.40e1.51 (m, 1H, 4-H), 1.65e1.89 (m, 3H, 4-H,
3-H), 3.00 (s, 3H, NCH3), 3.25 (s, 3H, OCH3), 3.82 (dd,
J ¼ 5.5/2.4 Hz, 1H, 5-H), 3.93 (s, 1H, 1-H), 4.30 (d,
J ¼ 14.6 Hz, 1H, NCH2Ph), 4.72 (d, J ¼ 14.6 Hz, 1H,
NCH2Ph), 7.20e7.36 (m, 5H, arom. H). 13C NMR (CDCl3):
d ¼ 1.3 (3C, Si(CH3)3), 24.2 (1C, C-4), 32.7 (1C, C-3), 33.1
(1C, NCH3), 48.6 (1C, NCH2Ph), 48.8 (1C, OCH3), 59.0
(1C, C-5), 69.5 (1C, C-1), 98.3 (1C, C-2), 127.7 (1C, arom.
CH), 128.3 (2C, arom. CH), 128.6 (2C, arom. CH), 135.8
(1C, arom. C), 166.0 (1C, C]O), 168.4 (1C, C]O).
The bridged piperazines represent a novel class of potent s
receptor ligands. High s1 affinity is attained when one large
substituent (butyl, benzyl) is attached either to N-8 or the
oxygen atom in position 2 (8b, 8c, 12b, 13a, 13b). Two large
substituents are not tolerated by the s1 receptor protein. The
benzyl ether 13a, the most potent s2 ligand of this series,
and the s2 selective methyl ether 12a represent promising
starting points for the development of potent and selective
s2 receptor ligands.
6. Experimental
6.1. Chemistry, general
6.1.2. (1S,5S )-6-Benzyl-8-butyl-2-methoxy-2-(trimethyl-
Unless otherwise noted, moisture sensitive reactions were
conducted under dry nitrogen. THF was distilled from so-
dium/benzophenone ketyl prior to use. Petroleum ether used
refers to the fraction boiling at 40e60 ꢁC. Thin layer chroma-
tography (tlc): silica gel 60 F254 plates (Merck). Flash chroma-
tography (fc) [17]: silica gel 60, 0.040e0.063 mm (Merck);
parentheses include: diameter of the column [cm], eluent, frac-
tion size [mL], Rf. Melting points: melting point apparatus
SMP 2 (Stuart Scientific), uncorrected. Optical rotation:
Polarimeter 241 (Perkin Elmer); 1.0 dm tube; concentration
c [g/100 mL]. Elemental analyses: CHN-Elementaranalysator
Rapid (Heraeus), Elemental Analyzer 240 (PerkineElmer)
and Vario EL (Elementaranalysesysteme GmbH). MS: MAT
312, MAT 8200, MAT 44, and TSQ 7000 (Finnigan); EI
¼ electron impact, CI ¼ chemical ionization. High resolution
MS (HR-MS): MAT 8200 (Finnigan). IR: IR spectrophotome-
ter 1600 FT-IR and 2000 FT-IR (PerkineElmer); s ¼ strong,
m ¼ medium, w ¼ weak. 1H NMR (300 MHz), 13C NMR
(75 MHz): Unity 300 FT NMR spectrometer (Varian), d in
parts per million related to tetramethylsilane, coupling con-
stants are given with 0.5 Hz resolution; the assignments of
siloxy)-6,8-diazabicyclo[3.2.2]nonane-7,9-dione (6b)
Under N2 a solution of LHMDS (1 M in THF; 17.5 mL,
17.5 mmol) was added dropwise to a solution of 5b [11]
(5.01 g, 14.5 mmol) in THF (140 mL) at ꢀ78 ꢁC. After a reac-
tion time of 60 min at ꢀ78 ꢁC a solution of chlorotrimethylsi-
lane (5.6 mL, 43.7 mmol) in THF (4 mL) was added and the
reaction mixture was stirred for 15 min at ꢀ78 ꢁC, then for
3 h at room temperature. The solvent was removed in vacuo
and the residue was dissolved in ethyl acetate (150 mL). The
solution was washed with HCl (0.5 M, 100 mL), with NaOH
(0.5 M, 100 mL), and with brine (100 mL), dried (Na2SO4)
and concentrated in vacuo. The resulting product 6b was
characterized and directly used for the next reaction
without further purification. Colorless oil, yield 5.33 g
(88%). C22H34N2O4Si (418.6). IR (film): ~n [cmꢀ1] ¼ 3028
(w, nCH arom.), 2958 (m, nCH aliph.), 1685 (s, nC]O, tert. amides),
1253 (m, nCOC), 1106 (m, OeSi), 733, 700 (m, gmonosubst. arom.).
1H NMR (CDCl3): d ¼ 0.22 (s, 9H, Si(CH3)3), 0.92
(t, J ¼ 7.2 Hz, 3H, NCH2CH2CH2CH3), 1.30 (sext, J ¼
7.3 Hz, 2H, NCH2CH2CH2CH3), 1.40e1.61 (m, 3H, 4-H,
NCH2CH2CH2CH3), 1.80e1.88 (m, 3H, 3-H, 4-H), 3.00
(ddd, J ¼ 13.9/7.9/6.0 Hz, 1H, NCH2CH2CH2CH3), 3.26
(s, 3H, OCH3), 3.80 (dt, J ¼ 14.3/7.7 Hz, 1H,
1
13C and of H NMR signals were supported by 2D NMR
techniques.

1252
M. Weigl, B. Wu¨nsch / European Journal of Medicinal Chemistry 42 (2007) 1247e1262
NCH2CH2CH2CH3), 3.81 (dd, J ¼ 6.4/1.5 Hz, 1H, 5-H), 3.98
(s, 1H, 1-H), 4.36 (d, J ¼ 14.6 Hz, 1H, NCH2Ph), 4.71 (d,
J ¼ 14.6 Hz, 1H, NCH2Ph), 7.23e7.36 (m, 5H, arom. H).
J ¼ 14.6 Hz, 1H, NCH2Ph), 7.21e7.36 (m, 5H, arom. H).
13C NMR (CDCl3): d ¼ 29.2 (1C, C-4), 32.9 (1C, NCH3),
36.9 (1C, C-3), 49.0 (1C, NCH2Ph), 59.1 (1C, C-5), 73.5
(1C, C-1), 128.3 (2C, arom. CH), 128.4 (1C, arom. CH),
129.1 (2C, arom. CH), 135.3 (1C, arom. C), 163.3 (1C,
C]O), 167.4 (1C, C]O), 199.2 (1C, C]Oketone).
6.1.3. (1S,5S)-6-Benzyl-2-methoxy-8-(2-phenylethyl)-2-(tri-
methylsilyloxy)-6,8-diazabicyclo[3.2.2]nonane-7,9-dione (6c)
Under N2 a solution of LHMDS (1 M in THF; 3.0 mL,
3.0 mmol) was added dropwise to a solution of 5c [11]
(1.02 g, 2.58 mmol) in THF (50 mL) at ꢀ78 ꢁC. After a reac-
tion time of 40 min at ꢀ78 ꢁC a solution of chlorotrimethyl-
silane (1.2 mL, 9.4 mmol) in THF (7 mL) was added and the
reaction mixture was stirred for 30 min at ꢀ78 ꢁC, then for
30 min at room temperature. The solvent was removed in
vacuo and the residue was dissolved in ethyl acetate
(70 mL). The solution was washed with NaOH (0.5 M,
2 ꢃ 40 mL), with HCl (0.5 M, 2 ꢃ 40 mL) and with brine
(40 mL), dried (Na2SO4) and concentrated in vacuo. The re-
sulting product 6c was characterized and directly used for
the next reaction without further purification. Colorless solid,
yield 1.19 g (99%), Rf ¼ 0.60 (ethyl acetate), Rf ¼ 0.66 (petro-
leum ether/ethyl acetate 3:7). C26H34N2O4Si (466.6). IR
(film): ~n [cmꢀ1] ¼ 3029 (w, nCH arom.), 2958 (w, nCH aliph.),
1682 (s, nC]O, tert. amides), 1254, 1208 (m, nCOC), 732, 698
(m, gmonosubst. arom.). 1H NMR (CDCl3): d ¼ 0.25 (s, 9H,
Si(CH3)3), 1.44e1.58 (m, 1H, 4-H), 1.78e1.96 (m, 3H, 3-H,
4-H), 2.82e3.02 (m, 2H, NCH2CH2Ph), 3.29 (s, 3H, OCH3),
3.22e3.36 (m, 1H, NCH2CH2Ph), 3.82 (dd, J ¼ 5.5/1.8 Hz,
1H, 5-H), 4.00 (s, 1H, 1-H), 4.09 (ddd, J ¼ 13.6/8.3/7.2 Hz,
1H, NCH2CH2Ph), 4.39 (d, J ¼ 14.6 Hz, 1H, NCH2Ph),
4.68 (d, J ¼ 14.6 Hz, 1H, NCH2Ph), 7.18e7.41 (m, 10H,
arom. H).
6.1.5. (1S,5S )-6-Benzyl-8-butyl-6,8-diazabicyclo[3.2.2]-
nonane-2,7,9-trione (7b)
A solution of the mixed acetal 6b (5.33 g, prepared from
5b, 5.0 g, 14.5 mmol) and p-toluenesulfonic acid (550 mg,
2.9 mmol) in THF (90 mL) and H2O (10 mL) was stirred for
16 h at room temperature. The mixture was concentrated in
vacuo and the residue was purified by fc (5 cm, ethyl acetate,
20 mL, Rf ¼ 0.53). Pale yellow solid, mp 89e93 ꢁC, yield
2.41 g (53% with regard to the monocyclic piperazinedione
20
5b). [a] ¼ þ22 (c ¼ 1.13, CH2Cl2). C18H22N2O3 (314.2).
589
HR-MS: Calcd. 314.163043 found 314.163155 (þ0.4 ppm).
MS (EI): m/z (%) ¼ 314 (M, 14), 223 (M ꢀ CH2Ph, 39), 195
(223-CO, 29). IR (film): ~n [cmꢀ1] ¼ 3033 (w, nCH arom.),
1
1727 (s, nC]O, ketone), 1683 (s, nC]O, tert. amides). H NMR
(CDCl3): d ¼ 0.88 (t, J ¼ 7.3 Hz, 3H, NCH2CH2CH2CH3),
1.26 (sext, J ¼ 7.3 Hz, 2H, NCH2CH2CH2CH3), 1.35e1.57
(m, 2H, NCH2CH2CH2CH3), 1.81 (dddd, J ¼ 14.4/9.7/7.0/
2.5 Hz, 1H, 4-H), 2.29 (ddt, J ¼ 14.6/8.5/4.2 Hz, 1H, 4-H),
2.43 (ddd, J ¼ 15.5/7.1/3.8 Hz, 1H, 3-H), 2.75 (ddd, J ¼
15.6/9.2/8.6 Hz, 1H, 3-H), 3.36 (ddd, J ¼ 14.1/8.4/5.9 Hz,
1H, NCH2CH2CH2CH3), 3.50 (ddd, J ¼ 13.9/8.6/6.2 Hz, 1H,
NCH2CH2CH2CH3), 4.05 (dd, J ¼ 4.4/2.9 Hz, 1H, 5-H), 4.26
(s, 1H, 1-H), 4.53 (d, J ¼ 14.6 Hz, 1H, NCH2Ph), 4.63 (d,
J ¼ 14.6 Hz, 1H, NCH2Ph), 7.19e7.43 (m, 5H, arom. H).
13C NMR (CDCl3): d ¼ 13.5 (1C, NCH2CH2CH2CH3),
19.8 (1C, NCH2CH2CH2CH3), 28.8 (1C, C-4), 29.6
(1C, NCH2CH2CH2CH3), 36.9 (1C, C-3), 45.9 (1C,
NCH2CH2CH2CH3), 49.0 (1C, NCH2Ph), 59.2 (1C, C-5),
72.0 (1C, C-1), 128.2 (2C, arom. CH), 128.3 (1C, arom.
CH), 129.0 (2C, arom. CH), 135.3 (1C, arom. C), 163.6 (1C,
C]O), 167.0 (1C, C]O), 199.8 (1C, C]Oketone).
6.1.4. (1S,5S )-6-Benzyl-8-methyl-6,8-diazabicyclo-
[3.2.2]nonane-2,7,9-trione (7a)
As described for 6a the piperazinedione 5a (8.28 g,
27.2 mmol) was reacted with LHMDS (30.0 mL, 30.0 mmol)
and chlorotrimethylsilane (11.2 mL, 87.4 mmol, in 8 mL
THF) to yield the mixed methyl silyl acetal 6a. Without puri-
fication 6a was dissolved in a mixture of THF (100 mL) and
water (10 mL), p-toluenesulfonic acid (1.00 g, 5.25 mmol)
was added and the mixture was stirred for 16 h at room tem-
perature. The solvent was removed under reduced pressure
and the residue was purified by fc (8 cm, ethyl acetate,
6.1.6. (1S,5S )-6-Benzyl-8-(2-phenylethyl)-6,8-diazabicyclo-
[3.2.2]nonane-2,7,9-trione (7c)
As described for the synthesis of 6c the monocyclic piper-
azinedione 5c (3.01 g, 7.62 mmol) was dissolved in THF
(80 mL) and at ꢀ78 ꢁC reacted with a 1 M LHMDS solution
in THF (8.7 mL, 8.7 mmol) and after 45 min with a solution
of chlorotrimethylsilane (3.0 mL, 23.4 mmol) in THF
(5 mL). After stirring for 20 min at ꢀ78 ꢁC and for 3 h at
room temperature the reaction mixture was worked up as de-
scribed for 6c. The resulting residue was dissolved in a mixture
of THF (100 mL) and H2O (10 mL), p-toluenesulfonic acid
(0.32 g, 1.7 mmol) was added and the mixture was stirred
for 8 h at room temperature. The mixture was concentrated
in vacuo and the residue was purified by fc (4 cm, ethyl
acetate, 20 mL, Rf ¼ 0.48). Colorless solid, mp 164e166 ꢁC,
100 mL, Rf ¼ 0.41). Colorless solid, mp 183e184 ꢁC, yield
25
6.70 g (90%, with regard to 5a). [a] ¼ þ5.2 (c ¼ 0.55,
589
CH2Cl2). C15H16N2O3 (272.3). Calcd. C 66.2 H 5.92 N 10.3
found C 65.9 H 6.41 N 10.4. MS (EI): m/z (%) ¼ 272 (M,
49), 215 (M ꢀ COeNCH3, 8), 181 (M ꢀ CH2Ph, 97). MS
(CI): m/z (%) ¼ 273 (MHþ, 100), 181 (MHþ ꢀ PhCH3, 2).
IR (film): ~n [cmꢀ1] ¼ 3030 (w, nCH arom.), 2975, 2935 (m,
nCH aliph.), 1728 (s, nC]O, ketone), 1682 (s, nC]O, tert. amides),
1
1253, 1177 (m, nCOC), 732 (m, gmonosubst. arom.). H NMR
(CDCl3): d ¼ 1.84 (dddd, J ¼ 14.5/8.8/7.2/3.3 Hz, 1H, 4-H),
2.28 (ddt, J ¼ 14.5/8.4/4.1 Hz, 1H, 4-H), 2.46 (ddd, J ¼ 15.5/
7.3/4.3 Hz, 1H, 3-H), 2.67 (dt, J ¼ 15.5/8.4 Hz, 1H, 3-H),
3.03 (s, 3H, NCH3), 4.03 (t, J ¼ 3.7 Hz, 1H, 5-H), 4.18 (s,
1H, 1-H), 4.53 (d, J ¼ 14.6 Hz, 1H, NCH2Ph), 4.66 (d,
yield 2.47 g, 90% related to the monocyclic piperazinedione
23
5c. [a] ¼ þ72 (c ¼ 0.68, CH2Cl2). C22H22N2O3 (362.4).
589
Calcd. C 72.91 H 6.12 N 7.73 found C 73.05 H 6.30 N

M. Weigl, B. Wu¨nsch / European Journal of Medicinal Chemistry 42 (2007) 1247e1262
1253
7.86. MS (EI): m/z (%) ¼ 362 (M, 10), 271 (M ꢀ CH2Ph, 18),
243 (M ꢀ NCH2CH2Ph, 38). IR (film): ~n [cmꢀ1] ¼ 3055
(w, nCH arom.), 1720 (m, nC]O, ketone), 1688 (s, nC]O, tert. amides).
1H NMR (CDCl3): d ¼ 1.79 (dddd, J ¼ 14.3/9.5/6.9/2.7 Hz,
1H, 4-H), 2.24 (ddt, J ¼ 14.3/8.2/4.1 Hz, 1H, 4-H), 2.37
(ddd, J ¼ 15.7/7.1/3.6 Hz, 1H, 3-H), 2.57 (dt, J ¼ 15.6/8.9 Hz,
1H, 3-H), 2.88 (t broad, J ¼ 7.3 Hz, 2H, NCH2CH2Ph), 3.69
(dt, J ¼ 14.0/7.2 Hz, 1H, NCH2CH2Ph), 3.85 (dt, J ¼ 13.7/
7.1 Hz, NCH2CH2Ph), 3.98 (dd, J ¼ 4.3/3.2 Hz, 1H, 5-H),
4.21 (s, 1H, 1-H), 4.53 (d, J ¼ 14.6 Hz, 1H, NCH2Ph), 4.63
(d, J ¼ 14.6 Hz, 1H, NCH2Ph), 7.15e7.38 (m, 10H, arom. H).
NCH2Ph), 4.02 (dt, J ¼ 7.3/5.2 Hz, 1H, 2-H), 7.20e7.37 (m,
5H, arom. H). 13C NMR (CDCl3): d ¼ 29.5 (1C, C-3), 29.8
(1C, C-4), 44.5 (1C, NCH3), 46.1 (1C, C-7), 53.4 (1C, C-9),
53.9 (1C, C-5), 60.8 (1C, NCH2Ph), 63.6 (1C, C-1), 74.8
(1C, C-2), 126.9 (1C, arom. CH), 128.2 (2C, arom. CH), 128.4
(2C, arom. CH), 139.6 (1C, arom. C).
6.1.8. (1R,2S,5S)-6-Benzyl-8-(2-phenylethyl)-6,8-diazabi-
cyclo[3.2.2]nonan-2-ol ((2S)-8c) and (1R,2R,5S )-6-benzyl-
8-(2-phenylethyl)-6,8-diazabicyclo[3.2.2]nonan-2-ol ((2R)-8c)
Under N2 a solution of LiAlH4 (1 M in THF, 5.0 mL,
5.0 mmol) was added to an ice-cold solution of the ketone
7c (392 mg, 1.08 mmol) in THF (50 mL). The reaction mix-
ture was stirred for 90 h at reflux temperature. The excess of
LiAlH4 was carefully (ice bath) destroyed by addition of
3 M NaOH (3 mL) and H2O (3 mL) and subsequent warming
for 30 min. The mixture was filtered and concentrated in
vacuo. The residue ((2S )-8c:(2R)-8c ¼ 30:70) was purified
by fc (2 cm, petroleum ether:ethyl acetate ¼ 3:7).
6.1.7. (1R,2S,5S )-6-Benzyl-8-methyl-6,8-diazabicyclo-
[3.2.2]nonan-2-ol ((2S )-8a) and (1R,2R,5S )-6-benzyl-8-
methyl-6,8-diazabicyclo[3.2.2]nonan-2-ol ((2R)-8a)
Under N2 a tablet of LiAlH4 (800 mg, 21.1 mmol) was added
to an ice-cold solution of 7a (888 mg, 3.26 mmol) in THF
(80 mL). The mixture was stirred for 30 min at 0 ꢁC and for
68 h at reflux temperature. Then the excess of LiAlH4 was care-
fully (ice bath, N2) destroyed by addition of Na2SO4$10H2O
(4.8 g). The mixture was heated to reflux (30 min), filtered and
the solvent was removed in vacuo. The residue ((2S )-8a:
(2R)-8a ¼ 27:73) was purified by fc (2 cm, ethyl acetate:
C2H5OH ¼ 9:1 þ 1% dimethylethylamine, 5 mL).
(2S )-8c (Rf ¼ 0.44): Pale yellow oil, yield 71 mg (20%).
18
[a] ¼ þ34.8 (c ¼ 0.39, CH2Cl2). C22H28N2O (336.2). HR-
589
MS: Calcd. 336.220163 found 336.220322 (þ0.5 ppm). MS
(EI): m/z (%) ¼ 336 (M, 7), 277 (M ꢀ CH2CH2CH2OH, 3)
245 (M ꢀ CH2Ph, 100), 154 (M ꢀ 2ꢃ CH2Ph, 10). IR (film):
~n [cmꢀ1] ¼ 3380 (m, nOH), 3027 (w, nCH arom.), 2925,
(2S )-8a (Rf ¼ 0.45): Pale yellow oil, yield 160 mg (20%).
20
[a] ¼ þ24.2 (c ¼ 0.55, CH2Cl2). C15H22N2O (246.2).
589
1
HR-MS: Calcd. 246.173213 found 246.173131 (ꢀ0.3 ppm).
MS (EI): m/z (%) ¼ 246 (M, 9), 228 (M ꢀ H2O, 1), 217
(M ꢀ NCH3, 2), 187 (M ꢀ CH2CH2CH2OH, 11), 155
(M ꢀ CH2Ph, 22). IR (film): ~n [cmꢀ1] ¼ 3371 (m, nOH),
2807 (m, nCH aliph.), 733, 700 (s, gmonosubst. arom.). H NMR
(CDCl3): d ¼ 1.50e1.64 (m, 2H, 4-H, 3-H), 1.72e1.84 (m,
1H, 4-H), 2.12 (ddt, J ¼ 14.0/8.6/4.9 Hz, 1H, 3-H), 2.78e
3.00 (m, 10H, 7-H (2H), 9-H (2H), NCH2CH2Ph (3H), 5-H,
1-H, CHOH ) 3.06 (dt, J ¼ 12.1/5.5 Hz, 1H, NCH2CH2Ph),
3.74 (s, 2H, NCH2Ph), 3.77 (td, J ¼ 5.5/1.8 Hz, 1H, 2-H),
7.20e7.39 (m, 10H, arom. H). 13C NMR (CDCl3): d ¼ 27.9
(1C, C-4), 30.0 (1C, C-3), 34.5 (1C, NCH2CH2Ph), 49.3
(1C, C-7), 51.5 (1C, C-9), 53.7 (1C, C-5), 59.5 (1C,
NCH2CH2Ph), 60.6 (1C, NCH2Ph), 61.2 (1C, C-1), 67.5
(1C, C-2), 126.3 (1C, arom. CH), 126.9 (1C, arom. CH),
128.2 (2C, arom. CH), 128.3 (2C, arom. CH), 128.5 (4C,
arom. CH), 139.7 (2C, arom. C).
1
3027 (w, nCH arom.), 732, 698 (m, gmonosubst. arom.). H NMR
(CDCl3): d ¼ 1.54ꢀ1.70 (m, 2H, 4-H, 3-H), 1.71e1.83 (m,
1H, 4-H), 2.11 (dddd, J ¼ 13.6/8.4/6.7/4.4 Hz, 1H, 3-H),
2.47 (s, 3H, NCH3), 2.65 (dt, J ¼ 4.9/2.1 Hz, 1H, 1-H), 2.73
(d broad, J ¼ 2.4 Hz, 2H, 9-H), 2.80e2.93 (m, 3H, 5-H,
7-H), 3.68 (d, J ¼ 13.4 Hz, 1H, NCH2Ph), 3.73 (d, J ¼
13.4 Hz, 1H, NCH2Ph), 3.80 (td, J ¼ 4.8/1.8 Hz, 1H, 2-H),
4.40e4.57 (broad, 1H, CHOH ), 7.19e7.36 (m, 5H, arom.
H). 13C NMR (CDCl3): d ¼ 27.9 (1C, C-4), 30.1 (1C, C-3),
44.9 (1C, NCH3), 48.1 (1C, C-7), 53.8 (1C, C-9), 53.9 (1C,
C-5), 60.6 (1C, NCH2Ph), 61.8 (1C, C-1), 70.2 (1C, C-2),
126.8 (1C, arom. CH), 128.2 (2C, arom. CH), 128.3 (2C,
arom. CH), 139.9 (1C, arom. C).
(2R)-8c (Rf ¼ 0.23): Pale yellow oil, yield 146 mg (40%).
18
[a] ¼ þ23.5 (c ¼ 0.95, CH2Cl2). C22H28N2O (336.2). HR-
589
MS: Calcd. 336.220163 found 336.220322 (þ0.5 ppm). MS
(EI): m/z (%) ¼ 336 (M, 7), 277 (M ꢀ CH2CH2CH2OH, 5),
245 (M ꢀ CH2Ph, 100), 154 (M ꢀ 2ꢃ CH2Ph, 10). IR (film):
~n [cmꢀ1] ¼ 3379 (m, nOH), 3026 (w, nCH arom.), 2929, 2802
(m, nCH aliph.), 732, 699 (s, gmonosubst. arom:). 1H NMR
(CDCl3): d ¼ 1.60e1.73 (m, 1H, 4-H), 1.80e1.95 (m, 2H,
4-H, 3-H), 2.10e2.20 (m, 1H, CHOH ), 2.15 (dtd, J ¼ 11.8/
5.9/2.7 Hz, 1H, 3-H), 2.86e2.98 (m, 9H, NCH2CH2Ph (4H),
9-H (2H), 7-H, 5-H, 1-H), 3.19 (dd, J ¼ 11.3/2.4 Hz, 1H,
7-H), 3.75 (d, J ¼ 14.6 Hz, 1H, NCH2Ph), 3.80 (d, J ¼
14.6 Hz, 1H, NCH2Ph), 4.03 (dt, J ¼ 6.7/5.4 Hz, 1H, 2-H),
7.20e7.45 (m, 10H, arom. H). 13C NMR (CDCl3): d ¼ 29.4
(1C, C-3), 29.9 (1C, C-4), 34.7 (1C, NCH2CH2Ph), 47.2
(1C, C-7), 51.1 (1C, C-9), 54.0 (1C, C-5), 58.8 (1C,
NCH2CH2Ph), 60.7 (1C, NCH2Ph), 61.5 (1C, C-1), 75.0
(1C, C-2), 125.9 (1C, arom. CH), 126.9 (1C, arom. CH),
(2R)-8a (Rf ¼ 0.34): Colorless oil, yield 422 mg (53%).
20
[a] ¼ þ33.3 (c ¼ 0.47, CH2Cl2). C15H22N2O (246.2).
589
HR-MS: Calcd. 246.173213 found 246.173131 (ꢀ0.3 ppm).
MS (EI): m/z (%) ¼ 246 (M, 5), 228 (M ꢀ H2O, 2), 187
(M ꢀ CH2CH2CH2OH, 12), 155 (M ꢀ CH2Ph, 20). IR (film): ~n
[cmꢀ1] ¼ 3358 (m, nOH), 3028 (w, nCH arom.), 2927 (s, nCH aliph.),
1
730, 698 (m, gmonosubst. arom.). H NMR (CDCl3): d ¼ 1.61
(dddd, J ¼ 15.7/11.0/4.9/1.7 Hz, 1H, 4-H), 1.77e1.90 (m, 2H,
4-H, 3-H), 2.09 (tdd, J ¼ 10.7/4.7/1.8 Hz, 1H, 3-H),
2.27e2.36 (broad, 1H, CHOH ), 2.41 (s, 3H, NCH3), 2.64
(dt, J ¼ 4.6/2.5 Hz, 1H, 1-H), 2.74 (d broad, J ¼ 2.4 Hz, 2H,
9-H), 2.75 (dd, J ¼ 11.3/2.7 Hz, 1H, 7-H), 2.84 (tt, J ¼
4.7/2.6 Hz, 1H, 5-H), 3.08 (dd, J ¼ 11.3/2.4 Hz, 1H, 7-H),
3.67 (d, J ¼ 13.4 Hz, 1H, NCH2Ph), 3.73 (d, J ¼ 13.4 Hz, 1H,

1254
M. Weigl, B. Wu¨nsch / European Journal of Medicinal Chemistry 42 (2007) 1247e1262
128.2 (4C, arom. CH), 128.4 (2C, arom. CH), 128.6 (2C,
arom. CH), 139.4 (1C, arom. C), 140.4 (1C, arom. C).
In addition to the pure products a mixture of (2S )-8c and
(2R)-8c was isolated by fc. Yield 82 mg (22%); total yield
299 mg (82%).
Additionally a mixture of (2S )-9a and (2R)-9a was iso-
lated. Colorless solid, yield 0.78 g (40%); total yield 1.51 g
(77%).
6.1.10. (1S,2S,5S )-6-Benzyl-8-butyl-2-hydroxy-6,8-diazabi-
cyclo[3.2.2]nonane-7,9-dione ((2S )-9b and (1S,2R,5S )-6-
benzyl-8-butyl-2-hydroxy-6,8-diazabicyclo[3.2.2]nonane-
7,9-dione ((2R)-9b)
NaBH4 (370 mg, 9.7 mmol) was added to a cooled (ice
bath) solution of 7b (506 mg, 1.61 mmol) in a mixture of
THF (45 mL) and H2O (5 mL) and the mixture was stirred
for 20 h at room temperature. The solvent was removed in
vacuo, the residue was dissolved in ethyl acetate (80 mL),
and the mixture was washed with H2O (3 ꢃ 50 mL). After dry-
ing (Na2SO4) the solution was concentrated in vacuo to afford
a mixture of the diastereomeric alcohols (2S )-9b and
6.1.9. (1S,2S,5S )-6-Benzyl-2-hydroxy-8-methyl-6,8-diazabi-
cyclo[3.2.2]nonane-7,9-dione ((2S )-9a) and (1S,2R,5S )-6-
benzyl-2-hydroxy-8-methyl-6,8-diazabicyclo[3.2.2]nonane-
7,9-dione ((2R)-9a)
NaBH4 (0.83 g, 21.9 mmol) was added to a cooled (ice bath)
solution of 7a (1.95 g, 7.16 mmol) in a mixture of THF/propan-
2-ol/H2O (100 mL, 20 mL, 5 mL). After stirring for 16 h at
room temperature the solvent was removed invacuo, the residue
was dissolved in ethyl acetate (80 mL) and washed with H2O
(2 ꢃ 50 mL) and HCl (0.5 M, 1 ꢃ 50 mL). The organic layer
was dried (Na2SO4) and concentrated invacuo to yield a mixture
ofthediastereomericalcohols(2S )-9aand(2R)-9aasacolorless
solid. The diastereomers (2S )-9a and (2R)-9a (ratio 15:85 ac-
cording to 1H NMR spectrum) were separated by fc (4 cm, ethyl
acetate:acetone ¼ 1:1, 20 mL).
(2R)-9b (18:82). Colorless oil, yield 403 mg (80%), Rf ¼ 0.46/
24
589
0.43 with tailing (ethyl acetate:acetone ¼ 1:1). [a]
¼
þ97.7 (18:82 diastereomeric mixture, c ¼ 0.84, CH2Cl2).
C18H24N2O3 (316.4). Calcd. C 68.33 H 7.65 N 8.85 found C
68.19 H 7.42 N 8.65. MS (CI): m/z (%) ¼ 334 (M þ NHþ4 , 11),
317 (MHþ, 100), 261 (MHþ ꢀ CH2CH2CH2CH3, 2), 225
(M ꢀ CH2Ph, 7). IR (film): ~n [cmꢀ1] ¼ 3407 (s, nOH), 3064,
3031 (w, nCH arom.), 2934, 2869 (each m, nCH aliph.), 1667
(2S )-9a (Rf ¼ 0.45): Colorless solid, mp 171e173 ꢁC, yield
23
0.20 g (10%). [a] ¼ þ88.1 (c ¼ 0.50, CH2Cl2). C15H18N2O3
589
(274.3). Calcd. C 65.7 H 6.61 N 10.2 found C 65.4 H 6.61 N
10.2. MS (EI): m/z (%) ¼ 274 (M, 79), 246 (M ꢀ CO, 6), 217
(M ꢀ CH3NCO, 23), 183 (M ꢀ CH2Ph, 52). IR (film):
~n [cmꢀ1] ¼ 3394 (m, nOH), 3063, 3030 (w, nCH arom.), 2934
1
(s, nC]O, tert. amides), 732, 701 (m, gmonosubst. arom.). H NMR
(CDCl3): d ¼ 0.91 (t, J ¼ 7.3 Hz, 3H, NCH2CH2CH2CH3), 1.29
(sext, J ¼ 7.3 Hz, 2H, NCH2CH2CH2CH3), 1.47e1.76 (m, 5H,
NCH2CH2CH2CH3 (2H), 4-H (2H), 3-H (1H)), 1.97 (ddd,
J ¼ 14.5/9.7/4.8 Hz, 0.8H, 3-H), 1.86e1.95* (m, 0.2H, 3-H),
2.49* (s broad, 0.2H, CHOH ), 3.16 (dt, J ¼ 13.9/6.9 Hz,
0.8H, NCH2CH2CH2CH3), 3.19* (dt, J ¼ 13.9/7.0 Hz,
0.2H, NCH2CH2CH2CH3), 3.58 (dt, J ¼ 13.6/7.5 Hz, 1H,
NCH2CH2CH2CH3), 3.86 (dd, J ¼ 5.5/2.6 Hz, 1H, 5-H),
3.78e3.84 (m, 1H, 2-H), 4.03 (d, J ¼ 3.3 Hz, 0.8H, 1-H),
4.12* (d, J ¼ 1.1 Hz, 0.2H, 1-H), 4.23 (d broad, J ¼ 3.7 Hz,
0.8H, CHOH ), 4.44* (d, J ¼ 14.6 Hz, 0.2H, NCH2Ph), 4.51
(d, J ¼ 14.6 Hz, 0.8H, NCH2Ph), 4.59* (d, J ¼ 14.6 Hz, 0.2H,
NCH2Ph), 4.67 (d, J ¼ 14.3 Hz, 0.82H, NCH2Ph), 7.14e7.38
(m, 5H, arom. H). 13C NMR (CDCl3): d ¼ 13.6 (1C,
NCH2CH2CH2CH3), 19.8 (1C, NCH2CH2CH2CH3), 23.1
(0.8C, C-4), 24.5* (0.2C, C-4), 29.0* (0.2C, C-3), 29.1 (0.8C,
(m, nCH aliph.), 1668 (s, nC]O,
amides), 737, 701 (m,
tert.
1
gmonosubst. arom.). H NMR (CDCl3): d ¼ 1.23e1.38 (m, 1H,
4-H), 1.49e1.71 (m, 1H, 3-H), 1.85e1.98 (m, 2H, 3-H,
4-H), 3.11 (s, 3H, NCH3), 3.36e3.54 (broad, 1H, CHOH ),
3.82 (dd, J ¼ 4.9/2.4 Hz, 1H, 5-H), 4.05 (d, J ¼ 1.8 Hz, 1H,
1-H), 4.14 (ddd, J ¼ 8.5/4.8/1.9 Hz, 1H, 2-H), 4.43 (d,
J ¼ 14.6 Hz, 1H, NCH2Ph), 4.58 (d, J ¼ 14.6 Hz, 1H,
NCH2Ph), 7.11e7.35 (m, 5H, arom. H). 13C NMR (CDCl3):
d ¼ 24.5 (1C, C-4), 29.1 (1C, C-3), 34.5 (1C, NCH3), 48.5
(1C, NCH2Ph), 59.0 (1C, C-5), 67,2 (1C, C-2), 69.6 (1C,
C-1), 128.1 (1C, arom. CH), 128.2 (2C, arom. CH), 128.9
(2C, arom. CH), 135.4 (1C, arom. C), 167.9 (1C, C]O),
168.3 (1C, C]O).
(2R)-9a (Rf ¼ 0.38): Colorless solid, mp 165e167 ꢁC, yield
25
0.53 g (27%). [a] ¼ þ166 (c ¼ 1.06, CH2Cl2). C15H18N2O3
C-3),
29.8
(1C,
NCH2CH2CH2CH3),
45.2
(1C,
589
(274.3). Calcd. C 65.7 H 6.61 N 10.2 found C 65.7 H 6.55 N
10.1. MS (EI): m/z (%) ¼ 274 (M, 35), 217 (M ꢀ CH3NCO, 9),
183 (M ꢀ CH2Ph, 39). IR (film): ~n [cmꢀ1] ¼ 3419 (m, nOH),
NCH2CH2CH2CH3), 48.5* (0.2C, NCH2Ph), 48.7 (0.8C,
NCH2Ph), 59.3 (1C, C-5), 65.9 (0.8C, C-1), 66.9* (0.2C, C-1),
66.7 (0.8C, C-2), 67.7* (0.2C, C-2), 128.0 (1C, arom. CH),
128.3 (2C, arom. CH), 128.8 (2C, arom. CH), 135.5* (0.2C,
arom. C), 135.7 (0.8C, arom. C), 167.8* (0.2C, C]O), 167.9
(0.8C, C]O), 168.5* (0.2C, C]O), 169.1 (0.8C, C]O).
* ¼ Signals of the minor diastereomer.
3055 (w, nCH arom.), 2976 (w, nCH aliph.), 1678 (s, nC]O, tert. amides),
1
737, 700 (m, g
). H NMR (CDCl3): d ¼ 1.48e1.75
monosubst. arom:
(m, 3H, 4-H, 3-H), 1.90e2.02 (m, 1H, 3-H), 2.99 (s, 3H,
NCH3), 3.35e3.45 (broad, 1H, CHOH ), 3.82 (dt, J ¼ 4.6/
3.3 Hz, 1H, 2-H), 3.86 (dd, J ¼ 5.4/2.4 Hz, 1H, 5-H), 4.00
(d, J ¼ 3.1 Hz, 1H, 1-H), 4.50 (d, J ¼ 14.3 Hz, 1H, NCH2Ph),
4.68 (d, J ¼ 14.6 Hz, 1H, NCH2Ph), 7.22e7.36 (m, 5H, arom.
H); 13C NMR (CDCl3): d ¼ 23.4 (1C, C-4), 29.1 (1C, C-3),
32.7 (1C, NCH3), 48.7 (1C, NCH2Ph), 59.0 (1C, C-5), 65.8
(1C, C-2), 67.7 (1C, C-1), 128.1 (1C, arom. CH), 128.4 (2C,
arom. CH), 128.9 (2C, arom. CH), 135.6 (1C, arom. C),
167.7 (1C, C]O), 169.5 (1C, C]O).
6.1.11. (1S,2S,5S )-6-Benzyl-2-hydroxy-8-(2-phenylethyl)-
6,8-diazabicyclo[3.2.2]nonane-7,9-dione ((2S )-9c) and
(1S,2R,5S )-6-benzyl-2-hydroxy-8-(2-phenylethyl)-6,8-
diazabicyclo[3.2.2]nonane-7,9-dione ((2R)-9c)
NaBH4 (505 mg, 13.3 mmol) was added to a cooled (ice
bath) solution of ketone 7c (1.02 g, 2.81 mmol) in a mixture
of THF (50 mL) and H2O (5 mL) and the mixture was stirred

M. Weigl, B. Wu¨nsch / European Journal of Medicinal Chemistry 42 (2007) 1247e1262
1255
for 4 h at room temperature. The solvent was removed in va-
cuo and the residue was purified by fc (3 cm, ethyl
acetate:acetone ¼ 8:2, 20 mL, Rf ¼ 0.43/0.38). Colorless solid,
yield 0.93 g (91%), ratio of diastereomers (2S )-9c:(2R)-
9c ¼ 25:75. C22H24N2O3 (364.2). Calcd. C 72.51 H 6.64 N
7.68 found C 72.49 H 6.69 N 7.58. The diastereomers were
separated by a second fc (3 cm, ethyl acetate:acetone ¼ 8:2,
10 mL).
(3 cm, ethyl acetate:acetone ¼ 1:1, 10 mL, Rf ¼ 0.46). Col-
orless solid, mp 136e139 ꢁC, yield 192 mg (73%). [a]25389
¼
þ151 (c ¼ 0.57, CH2Cl2). C16H20N2O3 (288.1). HR-MS:
Calcd. 288.147393 found 288.147343 (ꢀ0.2 ppm). MS (EI):
m/z (%) ¼ 288 (M, 18), 256 (M ꢀ CH3OH, 19), 197
(M ꢀ CH2Ph, 44), 169 (M ꢀ PhCH2NCH2, 64). IR (film):
~n [cmꢀ1] ¼ 3056 (w, nCH arom.), 2937 (w, nCH aliph.), 1682 (s,
nC]O,
amides), 736, 703 (m, gmonosubst. arom.). 1H NMR
tert.
(2S )-9c (Rf ¼ 0.43): Colorless solid, mp 157e161 ꢁC, yield
(CDCl3): d ¼ 1.47e1.70 (m, 3H, 4-H, 3-H), 1.80e1.91 (m,
1H, 3-H), 2.96 (s, 3H, NCH3), 3.29 (ddd, J ¼ 8.1/4.8/3.2 Hz,
1H, 2-H), 3.40 (s, 3H, OCH3), 3.82 (dd, J ¼ 5.5/2.4 Hz, 1H,
5-H), 3.97 (d, J ¼ 2.7 Hz, 1H, 1-H), 4.41 (d, J ¼ 14.3 Hz,
1H, NCH2Ph), 4.70 (d, J ¼ 14.6 Hz, 1H, NCH2Ph), 7.19e
7.34 (m, 5H, arom. H). 13C NMR (CDCl3): d ¼ 23.3 (1C,
C-4), 26.4 (1C, C-3), 32.4 (1C, NCH3), 48.6 (1C, NCH2Ph),
57.0 (1C, OCH3), 58.9 (1C, C-5), 64.4 (1C, C-1), 75.0 (1C,
C-2), 127.9 (1C, arom. CH), 128.3 (2C, arom. CH), 128.7
(2C, arom. CH), 135.8 (1C, arom. C), 166.5 (1C, C]O),
169.5 (1C, C]O).
20
61 mg (5.9%). [a] ¼ þ19.1 (c ¼ 0.48, CH2Cl2).
589
C22H24N2O3 (364.2). HR-MS: Calcd. 364.178693 found
364.179092 (þ1.1 ppm). MS (EI): m/z (%) ¼ 364 (M, 23), 273
(M ꢀ CH2Ph, 26), 245 (M ꢀ NCH2CH2Ph, 22). IR (film): ~n
[cmꢀ1] ¼ 3423 (s, nOH), 3030 (w, nCH arom.), 2933 (w, nCH aliph.),
1
), 735, 700 (s, gmonosubst. arom.). H NMR
1660 (s, n
C]O, tert. amides
(CDCl3): d ¼ 1.23e1.40 (m, 1H, 4-H), 1.55e1.73 (m, 1H,
3-H), 1.86e2.02 (m, 2H, 3-H, 4-H), 2.65 (d broad, J ¼ 4.3 Hz,
1H, CHOH ), 2.95 (t, J ¼ 7.5 Hz, 2H, NCH2CH2Ph), 3.46 (dt,
J ¼ 13.7/7.3 Hz, 1H, NCH2CH2Ph), 3.78 (dd, J ¼ 5.3/2.3 Hz,
1H, 5-H), 4.00 (d, J ¼ 1.5 Hz, 1H, 1-H), 4.03e4.13 (m, 1H,
2-H), 4.09 (dt, J ¼ 13.7/7.3 Hz, 1H, NCH2CH2Ph), 4.40 (d,
J ¼ 14.6 Hz, 1H, NCH2Ph), 4.60 (d, J ¼ 14.6 Hz, 1H, NCH2Ph),
7.13e7.40 (m, 10H, arom. H).
6.1.13. (1S,2S,5S )-6-Benzyl-8-butyl-2-methoxy-6,8-diazabi-
cyclo[3.2.2]nonane-7,9-dione ((2S )-10b) and (1S,2R,5S )-6-
benzyl-8-butyl-2-methoxy-6,8-diazabicyclo[3.2.2]nonane-
7,9-dione ((2R)-10b)
(2R)-9c (Rf ¼ 0.37): Colorless solid, mp 152e156 ꢁC, yield
20
113 mg (11%). [a] ¼ þ53.5 (c ¼ 0.51, CH2Cl2).
589
C22H24N2O3 (364.2). HR-MS: Calcd. 364.178693 found
364.179092 (þ1.1 ppm). MS (EI): m/z (%) ¼ 364 (M,
33), 273 (M ꢀ CH2Ph, 11). IR (film): ~n [cmꢀ1] ¼ 3410 (s,
nOH), 3058, 3024 (w, nCH arom.), 2956 (w, nCH aliph.), 1664 (s,
NaH (270 mg, 11.3 mmol) prepared from NaH dispersion
(80% in oil, 340 mg) was slowly added to a cooled (0 ꢁC) so-
lution of (2S )-9b/(2R)-9b (356 mg, 1.13 mmol) in THF
(40 mL). After stirring for 15 min at 0 ꢁC a solution of CH3I
(0.35 mL, 5.63 mmol) in THF (4.5 mL) was added and the
mixture was stirred for 16 h at room temperature. The mixture
was concentrated in vacuo, the residue was dissolved in
CH2Cl2 (70 mL) and the solution was washed with H2O
(2 ꢃ 40 mL). The organic layer was dried (Na2SO4), filtered,
concentrated in vacuo and the residue was purified by fc
(2 cm, ethyl acetate, 2 mL, Rf ¼ 0.39-0.37). Colorless solid,
nC]O,
amides), 738, 700 (s, gmonosubst. arom.). 1H NMR
tert.
(CDCl3): d ¼ 1.46e1.78 (m, 3H, 3-H, 4-H), 1.95 (dq,
J ¼ 14.0/4.8 Hz, 1H, 3-H), 2.90 (t broad, J ¼ 7.6 Hz, 2H,
NCH2CH2Ph), 3.42 (ddd, J ¼ 14.0/7.9/6.7 Hz, 1H, NCH2
CH2Ph), 3.71e3.80 (m, 1H, 2-H), 3.83 (dd, J ¼ 5.7/2.5 Hz,
1H, 5-H), 3.90 (dt, J ¼ 13.7/7.6 Hz, 1H, NCH2CH2Ph), 4.02
(d, J ¼ 3.4 Hz, 1H, 1-H), 4.52 (d, J ¼ 14.6 Hz, 1H, NCH2Ph),
4.64 (d, J ¼ 14.6 Hz, 1H, NCH2Ph), 7.18e7.37 (m, 10H,
arom. H). A signal for the OH-proton was not found.
In addition to the pure products a mixture of (2S )-9c and
(2R)-9c was isolated. Colorless solid, yield 0.72 g (70%); total
yield 0.894 g (87%).
mp 91e92 ꢁC, yield 237 mg (64%), ratio of diastereomers
25
(2S )-10b:(2R)-10b ¼ 22:78. [a] ¼ þ126 (22:78 diastereo-
589
meric mixture, c ¼ 0.54, CH2Cl2). C19H26N2O3 (330.4).
Calcd. C 69.07 H 7.93 N 8.47 found C 69.19 H 7.76 N
8.29. MS (EI): m/z (%) ¼ 330 (M, 24), 298 (M ꢀ CH3OH,
3), 259 (M ꢀ NCH2CH2CH2CH3, 41), 239 (M ꢀ CH2Ph, 67).
IR (film): ~n[cmꢀ1] ¼ 2932, 2869 (m, nCH aliph.), 1680 (s,
6.1.12. (1S,2R,5S )-6-Benzyl-2-methoxy-8-methyl-6,8-
nC]O,
amides), 733, 701 (m, gmonosubst. arom.). 1H NMR
tert.
diazabicyclo[3.2.2]nonane-7,9-dione ((2R)-10a)
(CDCl3): d ¼ 0.93* (t, J ¼ 7.2 Hz, 3ꢃ 0.2H, NCH2CH2CH2
CH3), 0.95 (t, J ¼ 7.2 Hz, 3ꢃ 0.8H, NCH2CH2CH2CH3),
1.32* (sext, J ¼ 7.3 Hz, 2ꢃ 0.2H, NCH2CH2CH2CH3), 1.34
(sext, J ¼ 7.3 Hz, 2ꢃ 0.8H, NCH2CH2CH2CH3), 1.50e1.77
(m, 5H, NCH2CH2CH2CH3 (2H), 4-H (2H), 3-H (1H)), 1.93
(ddt, J ¼ 13.4/8.2/5.0 Hz, 0.8H, 3-H), 1.94e2.02* (m, 0.2H,
3-H), 3.12 (ddd, J ¼ 13.9/7.5/6.4 Hz, 0.8H, NCH2CH2CH2
CH3), 3.14* (ddd, J ¼ 13.9/7.3/6.8 Hz, 0.2H, NCH2CH2
CH2CH3), 3.34 (ddd, J ¼ 7.9/4.3/3.5 Hz, 0.8H, 2-H), 3.39*
(s, 3ꢃ 0.2H, OCH3), 3.45 (s, 3ꢃ 0.8H, OCH3), 3.52* (ddd,
J ¼ 9.6/4.9/1.2 Hz, 0.2H, 2-H), 3.62 (dt, J ¼ 13.6/7.7 Hz,
0.8H, NCH2CH2CH2CH3), 3.68e3.79* (m, 0.2H, NCH2CH2
CH2CH3), 3.81* (dd, J ¼ 5.7/2.0 Hz, 0.2H, 5-H), 3.85
A solution of (2R)-9a (250 mg, 0.91 mmol, with a little
amount of the diastereomeric alcohol (2S )-9a) in THF
(15 mL) was slowly added to a cooled (0 ꢁC) suspension of
NaH (165 mg, 6.7 mmol) prepared from NaH dispersion
(80% in oil, 206 mg) in THF (10 mL). After stirring for
20 min a solution of CH3I (0.17 mL, 2.73 mmol) in THF
(0.8 mL) was added and the mixture was stirred for 16 h at
room temperature. The mixture was concentrated in vacuo,
the residue was dissolved in CH2Cl2 (60 mL) and the solution
was washed with 0.5 M HCl (40 mL), 0.5 M NaOH (40 mL),
and brine (40 mL). The organic layer was dried (Na2SO4), fil-
tered, concentrated in vacuo and the residue was purified by fc

1256
M. Weigl, B. Wu¨nsch / European Journal of Medicinal Chemistry 42 (2007) 1247e1262
(dd, J ¼ 5.3/2.6 Hz, 0.8H, 5-H), 4.05 (d, J ¼ 3.4 Hz, 0.8H,
1-H), 4.12* (d, J ¼ 0.9 Hz, 0.2H, 1-H), 4.46 (d, J ¼ 14.6 Hz,
0.8H, NCH2Ph), 4.48* (d, J ¼ 14.6 Hz, 0.2H, NCH2Ph),
4.59* (d, J ¼ 14.6 Hz, 0.2H, NCH2Ph), 4.76 (d, J ¼ 14.6 Hz,
0.8H, NCH2Ph), 7.20e7.38 (m, 5H, arom. H). * ¼ Signals of
the minor diastereomer.
mixture was stirred for 16 h at room temperature. The solvent
was removed under reduced pressure, the residue was dis-
solved in CH2Cl2 (60 mL) and the solution was washed with
H2O (2 ꢃ 40 mL), 0.5 M HCl, (40 mL) and 0.5 M NaOH
(40 mL). The organic layer was dried (Na2SO4), filtered, con-
centrated in vacuo and the residue was purified by fc (2 cm,
petroleum ether:ethyl acetate ¼ 1:9, 20 mL).
(2S )-11a (Rf ¼ 0.50): Colorless solid, mp 141e142 ꢁC,
6.1.14. (1S,2S,5S )-6-Benzyl-2-methoxy-8-(2-phenylethyl)-
6,8-diazabicyclo[3.2.2]nonane-7,9-dione ((2S )-10c) and
(1S,2R,5S )-6-benzyl-2-methoxy-8-(2-phenylethyl)-6,8-
23
yield 42 mg (13%). [a] ¼ þ43.1 (c ¼ 0.31, CH2Cl2).
589
C22H24N2O3 (364.2). HR-MS: Calcd. 364.178693 found
364.179092 (þ1.1 ppm). MS (EI): m/z (%) ¼ 364 (M, 8),
273 (M ꢀ CH2Ph, 24). IR (film): ~n [cmꢀ1] ¼ 3030 (w,
diazabicyclo[3.2.2]nonane-7,9-dione ((2R)-10c)
A solution of (2S )-9c/(2R)-9c (437 mg, 1.20 mmol) in THF
(10 mL) was slowly added to a cooled (0 ꢁC) suspension of
NaH (370 mg, 15 mmol) prepared from NaH dispersion
(80% in oil, 460 mg) in THF (20 mL). After stirring for
15 min a solution of CH3I (0.38 mL, 6.1 mmol) in THF
(1.6 mL) was added and the mixture was stirred for 7 h at
room temperature. The mixture was concentrated in vacuo,
the residue was dissolved in ethyl acetate (80 mL), the solution
was washed with H2O (2 ꢃ 50 mL), dried (Na2SO4), filtered,
concentrated in vacuo and the residue was purified by fc
(2 cm, ethyl acetate, 5 mL, Rf ¼ 0.43/0.38). Colorless oil,
nCH arom.), 2934 (m, nCH aliph.), 1678 (s, nC]O,
amides),
tert.
1
701 (m, gmonosubst. arom.). H NMR (CDCl3): d ¼ 1.24e1.38
(m, 1H, 4-H), 1.60e1.79 (m, 1H, 3-H), 1.89e2.01 (m, 2H,
3-H, 4-H), 3.10 (s, 3H, NCH3), 3.79 (ddd, J ¼ 8.9/4.6/
1.8 Hz, 1H, 2-H), 3.83 (dd, J ¼ 5.2/2.1 Hz, 1H, 5-H), 4.15
(d, J ¼ 1.5 Hz, 1H, 1-H), 4.46 (d, J ¼ 14.6 Hz, 1H, NCH2Ph),
4.56 (d, J ¼ 11.9 Hz, 1H, OCH2Ph), 4.63 (d, J ¼ 11.9 Hz, 1H,
OCH2Ph), 4.60 (d, J ¼ 14.6 Hz, 1H, NCH2Ph), 7.21e7.40 (m,
10H, arom. H). 13C NMR (CDCl3): d ¼ 24.6 (1C, C-4), 26.6
(1C, C-3), 33.9 (1C, NCH3), 48.3 (1C, NCH2Ph), 58.7 (1C,
C-5), 66.3 (1C, C-1), 70.9 (1C, OCH2Ph), 74.1 (1C, C-2),
127.3 (2C, arom. CH), 127.7 (1C, arom. CH), 127.9 (1C,
arom. CH), 128.1 (2C, arom. CH), 128.3 (2C, arom. CH),
128.8 (2C, arom. CH), 135.4 (1C, arom. C), 137.3 (1C,
arom. C), 167.3 (1C, C]O), 168.1 (1C, C]O).
yield 396 mg (87%), ratio of diastereomers (2S )-10c:
20
(2R)-10c ¼ 22:78. [a] ¼ þ78.9 (22:78 diastereomeric mix-
589
ture, c ¼ 0.29, CH2Cl2). C23H26N2O3 (378.2). HR-MS: Calcd.
378.194343 found 378.194455 (þ0.3 ppm). MS (EI): m/z
(%) ¼ 378 (M, 35), 307 (M ꢀ CH2CHCHOCH3, 21), 287
(M ꢀ CH2Ph, 30), 202 (307-CH2CH2Ph, 30). IR (film): ~n
[cmꢀ1] ¼ 3055 (w, nCH arom.), 2932 (w, nCH aliph.), 1679 (s,
(2R)-11a (Rf ¼ 0.32): Colorless solid, mp 158e160 ꢁC,
23
yield 234 mg (71%). 1 [a] ¼ þ136 (c ¼ 0.75, CH2Cl2).
589
C22H24N2O3 (364.2). HR-MS: Calcd. 364.178693 found
364.179092 (þ1.1 ppm). MS (EI): m/z (%) ¼ 364 (M, 6),
273 (M ꢀ CH2Ph, 30), 245 (273-NCH3, 21). IR (film): ~n
[cmꢀ1] ¼ 3030 (w, nCH arom.), 2937 (m, nCH aliph.), 2868 (w,
nNCH3), 1681 (s, nC]O, tert. amides), 733, 701 (m, gmonosubst. arom.).
1H NMR (CDCl3): d ¼ 1.48e1.73 (m, 3H, 4-H, 3-H),
1.79e1.92 (m, 1H, 3-H), 2.88 (s, 3H, NCH3), 3.46e3.53 (m,
1H, 2-H), 3.84 (dd, J ¼ 5.3/2.6 Hz, 1H, 5-H), 4.03 (d,
J ¼ 3.4 Hz, 1H, 1-H), 4.40 (d, J ¼ 14.6 Hz, 1H, NCH2Ph),
4.57 (d, J ¼ 12.2 Hz, 1H, OCH2Ph), 4.71 (d, J ¼ 12.2 Hz,
1H, OCH2Ph), 4.79 (d, J ¼ 14.6 Hz, 1H, NCH2Ph), 7.22e
7.42 (m, 10H, arom. H). 13C NMR (CDCl3): d ¼ 23.5 (1C,
C-4), 27.0 (1C, C-3), 32.5 (1C, NCH3), 48.9 (1C, NCH2Ph),
59.2 (1C, C-5), 64.9 (1C, C-1), 71.2 (1C, OCH2Ph), 72.2
(1C, C-2), 127.8 (2C, arom. CH), 128.0 (1C, arom. CH),
128.1 (1C, arom. CH), 128.5 (4 C, arom. CH), 128.8 (2C,
arom. CH), 136.0 (1C, arom. C), 137.4 (1C, arom. C), 166.7
(1C, C]O), 169.6 (1C, C]O).
nC]O,
amides), 736, 695 (m, gmonosubst. arom.). 1H NMR
tert.
(CDCl3): d ¼ 1.20e1.35* (m, 0.2H, 4-H), 1.46-1.72 (m,
2.6H, 4-H (2ꢃ 0.8H), 3-H (1H)), 1.75e2.02 (m, 1.2H, 3-H
(1H), 4-H (0.2H)), 2.88 (t, J ¼ 7.3 Hz, 2ꢃ 0.8H,
NCH2CH2Ph), 2.90* (t, J ¼ 7.3 Hz, 2ꢃ 0.2H, NCH2CH2Ph),
3.10e3.18 (m, 0.8H, NCH2CH2Ph), 3.30e3.42 (m, 1H, 2-
H), 3.35 (s, 3H, OCH3), 3.48* (ddd, J ¼ 9.7/4.9/1.1 Hz,
0.2H, NCH2CH2Ph), 3.75* (dd, J ¼ 5.6/2.0 Hz, 0.2H, 5-H),
3.79 (dd, J ¼ 5.3/2.7 Hz, 0.8H, 5-H), 3.88 (dt, J ¼
13.7/7.7 Hz, 0.8H, NCH2CH2Ph), 3.95e4.05* (m, 0.2H,
NCH2CH2Ph), 4.00 (d, J ¼ 3.7 Hz, 0.8H, 1-H), 4.04* (d,
J ¼ 0.9 Hz, 0.2H, 1-H), 4.36* (d, J ¼ 14.6 Hz, 0.2H,
NCH2Ph), 4.45 (d, J ¼ 14.6 Hz, 0.8H, NCH2Ph), 4.59* (d,
J ¼ 14.9 Hz, 0.2H, NCH2Ph), 4.66 (d, J ¼ 14.6 Hz, 0.8H,
NCH2Ph), 7.12e7.34 (m, 10H, arom. H). * ¼ Signals of the
minor diastereomer.
6.1.15. (1S,2S,5S )-6-Benzyl-2-benzyloxy-8-methyl-6,8-
diazabicyclo[3.2.2]nonane-7,9-dione ((2S )-11a) and
(1S,2R,5S )-6-benzyl-2-benzyloxy-8-methyl-6,8-diazabi-
cyclo[3.2.2]nonane-7,9-dione ((2R)-11a)
A solution of (2S )-9a/(2R)-9a (247 mg, 0.91 mmol) in THF
(6 mL) was slowly added to a cooled (0 ꢁC) suspension of
NaH (120 mg, 5 mmol) prepared from NaH dispersion (80%
in oil, 153 mg) in THF (10 mL). After stirring for 20 min a so-
lution of Bu4NþIꢀ (43 mg, 0.12 mmol) and benzyl bromide
(0.35 mL, 3.0 mmol) in THF (2 mL) was added and the
6.1.16. (1S,2S,5S )-6-Benzyl-2-benzyloxy-8-butyl-6,8-
diazabicyclo[3.2.2]nonane-7,9-dione ((2S )-11b) and
(1S,2R,5S )-6-benzyl-2-benzyloxy-8-butyl-6,8-diazabicyclo-
[3.2.2]nonane-7,9-dione ((2R)-11b)
NaH (ca. 300 mg, 12.5 mmol), which had been prepared by
washing a NaH dispersion (80% in oil, 380 mg) with petro-
leum ether, was added to a cooled (0 ꢁC) solution of
(2S )-9b/(2R)-9b (400 mg, 1.26 mmol) in THF (15 mL). After

M. Weigl, B. Wu¨nsch / European Journal of Medicinal Chemistry 42 (2007) 1247e1262
1257
23
stirring for 15 min at 0 ꢁC a solution of Bu4NþIꢀ (190 mg,
0.5 mmol) and benzyl bromide (0.75 mL, 6.4 mmol) in THF
(2 mL) was added and the mixture was stirred for 6 h at
room temperature. Then the mixture was concentrated in va-
cuo, the residue was dissolved in ethyl acetate (100 mL), the
organic layer was washed with H2O (2 ꢃ 70 mL), dried
(Na2SO4), filtered and concentrated in vacuo. The residue
was purified by fc (4 cm, petroleum ether:ethyl acetate ¼ 1:1,
20 mL, Rf ¼ 0.43e0.45 with tailing). Colorless solid, mp
103e105 ꢁC, yield 375 mg (73%). According to the 1H
[a] ¼ þ98.7 (23:77 mixture of diastereomers, c ¼ 0.68,
589
CH2Cl2). C29H30N2O3 (454.2). HR-MS: Calcd. 454.225643
found 454.225684 (þ0.1 ppm). MS (EI): m/z (%) ¼ 454 (M,
12), 363 (M ꢀ CH2Ph, 62), 348 (M ꢀ CH3CH2Ph, 26), 257
(348-CH2Ph, 4), 227 (M ꢀ CH2PheCH3CH2OCH2Ph, 37).
IR (film): ~n [cmꢀ1] ¼ 3060, 3029 (w, nCH arom.), 2935, 2866
(m, nCH aliph.), 1678 (s, nC]O,
amides), 1251, 1082 (m,
tert.
nCOC), 733, 700 (m, gmonosubst. arom.). 1H NMR (CDCl3):
d ¼ 1.23e1.36* (m, 0.2H, 4-H), 1.49e1.72 (m, 3ꢃ 0.8H,
4-H, 3-H), 1.75e1.89 (m, 1H, 3-H), 1.90e2.02* (m, 2ꢃ
0.2H, 3-H, 4-H), 2.81 (t broad, J ¼ 7.9 Hz, 2ꢃ 0.8H,
NCH2CH2Ph), 2.87e2.95* (m, 2ꢃ 0.2H, NCH2CH2Ph), 3.25
(ddd, J ¼ 13.9/7.9/6.1 Hz, 0.8H, NCH2CH2Ph), 3.33e3.40
(m, 0.8H, 2-H), 3.41e3.48* (m, 0.2H, NCH2CH2Ph), 3.70e
3.88 (m, 2H, 5-H, NCH2CH2Ph (0.8H), 2-H (0.2H)), 4.00*
(ddd, J ¼ 13.7/8.1/7.0 Hz, 0.2H, NCH2CH2Ph), 4.06 (d,
J ¼ 3.7 Hz, 0.8H, 1-H), 4.11* (d, J ¼ 1.2 Hz, 0.2H, 1-H),
4.37* (d, J ¼ 14.6 Hz, 0.2H, NCH2Ph), 4.41 (d, J ¼ 14.6 Hz,
0.8H, NCH2Ph), 4.52 (d, J ¼ 11.9 Hz, 0.8H, OCH2Ph), 4.56*
(d, J ¼ 11.0 Hz, 0.2H, OCH2Ph), 4.61* (d, J ¼ 11.9 Hz,
0.2H, OCH2Ph), 4.62* (d, J ¼ 15.2 Hz, 0.2H, NCH2Ph), 4.67
(d, J ¼ 11.9 Hz, 0.8H, OCH2Ph), 4.77 (d, J ¼ 14.6 Hz, 0.8H,
NCH2Ph), 7.13e7.44 (m, 15H, arom. H). * ¼ Signals of the
minor diastereomer.
NMR spectrum the ratio of diastereomers (2S )-11b:(2R)-
23
11b ¼ 22:78. [a] ¼ þ43.1 (22:78 mixture of diastereomers,
589
c ¼ 0.31, CH2Cl2). C25H30N2O3 (406.5). Calcd. C 73.87 H
7.44 N 6.89 found C 73.67 H 7.29 N 7.06. MS (CI): m/z
(%) ¼ 407 (MHþ, 70), 315 (M ꢀ CH2Ph, 6), 287
(MHþ ꢀ CHOCH2Ph, 8). IR (film): ~n [cmꢀ1] ¼ 3031 (w,
nCH arom.), 2932, 2868 (m, nCH aliph.), 1678 (s, nC]O, tert. amides),
1
735, 700 (m, gmonosubst. arom.). H NMR (CDCl3): d ¼ 0.91 (t,
J ¼ 7.3 Hz, 3H, NCH2CH2CH2CH3), 1.28 (sext, J ¼ 7.3 Hz,
2ꢃ 0.8H, NCH2CH2CH2CH3), 1.30* (sext, J ¼ 7.4 Hz,
2ꢃ 0.2H, NCH2CH2CH2CH3), 1.40e2.05 (m, 6H,
NCH2CH2CH2CH3 (2H), 4-H (2H), 3-H (2H)), 2.99 (ddd,
J ¼ 13.6/8.0/6.1 Hz, 0.8H, NCH2CH2CH2CH3), 3.18* (dt,
J ¼ 13.7/7.0 Hz, 0.2H, NCH2CH2CH2CH3), 3.46e3.60 (m,
2ꢃ 0.8H, NCH2CH2CH2CH3, 2-H), 3.75* (dd broad,
J ¼ 4.7/1.4 Hz, 0.2H, 2-H), 3.76* (dt, J ¼ 13.7/7.8 Hz, 0.2H,
NCH2CH2CH2CH3), 3.81* (dd, J ¼ 5.8/1.8 Hz, 0.2H, 5-H),
3.85 (dd, J ¼ 5.3/2.6 Hz, 0.8H, 5-H), 4.07 (d, J ¼ 3.4 Hz,
0.8H, 1-H), 4.17* (d, J ¼ 1.2 Hz, 0.2H, 1-H), 4.42 (d, J ¼
14.6 Hz, 0.8H, NCH2Ph), 4.45* (d, J ¼ 14.6 Hz, 0.2H,
NCH2Ph), 4.57* (d, J ¼ 11.6 Hz, 0.2H, OCH2Ph), 4.60 (d,
J ¼ 11.9 Hz, 0.8H, OCH2Ph), 4.61* (d, J ¼ 14.3 Hz, 0.2H,
NCH2Ph), 4.63* (d, J ¼ 11.9 Hz, 0.2H, OCH2Ph), 4.73 (d,
J ¼ 12.2 Hz, 0.8H, OCH2Ph), 4.82 (d, J ¼ 14.3 Hz, 0.8H,
NCH2Ph), 7.20e7.42 (m, 10H, arom. H). * ¼ Signals of the
minor diastereomer.
6.1.18. (1R,2R,5S )-6-Benzyl-2-methoxy-8-methyl-6,8-diaza-
bicyclo[3.2.2]nonane ((2R)-12a)
Under N2 a solution of 1 M LiAlH4 in THF (3.0 mL,
3.0 mmol) was added to a cold solution of (2R)-10a
(175 mg, 0.61 mmol) in THF (60 mL). After 15 min the
mixture was heated to reflux for 90 h. The excess of LiAlH4
was destroyed by careful addition of Na2SO4$10H2O (3.6 g),
the suspension was heated to reflux for 30 min and filtered.
The filtrate was concentrated in vacuo and the residue was
purified by fc (2 cm, ethyl acetate þ 1% ethyldimethylamine,
2 mL, Rf ¼ 0.25). Colorless oil, yield 59 mg (37%).
22
6.1.17. (1S,2S,5S )-6-Benzyl-2-benzyloxy-8-(2-phenylethyl)-
6,8-diazabicyclo[3.2.2]nonane-7,9-dione ((2S )-11c) and
(1S,2R,5S )-6-benzyl-2-benzyloxy-8-(2-phenylethyl)-6,8-
diazabicyclo[3.2.2]nonane-7,9-dione ((2R)-11c)
[a] ¼ þ58.9 (c ¼ 0.38, CH2Cl2). C16H24N2O (260.2). HR-
589
MS: Calcd. 260.188863 found 260.188372 (ꢀ1.9 ppm). MS
(EI): m/z (%) ¼ 260 (M, 100), 187 (M ꢀ CH2CH2CH2OCH3,
23), 169 (M ꢀ CH2Ph, 50), 137 (169-CH3OH, 15). IR (film):
~n [cmꢀ1] ¼ 3028 (w, vCH arom.), 2937, 2870 (s, nCH aliph.),
2794 (m, nOCH =NCH ), 1261, 1098 (m, nCOC), 729, 697 (m,
NaH dispersion (80% in oil, 414 mg) was washed with
petroleum ether and subsequently (ca. 330 mg, 13.7 mmol)
suspended in THF (20 mL) at 0 ꢁC. Then a solution of (2S )-
9c/(2R)-9c (500 mg, 1.37 mmol) in THF (20 mL) was added.
After stirring for 10 min at 0 ꢁC a solution of Bu4NþIꢀ
(197 mg, 0.5 mmol) and benzyl bromide (0.8 mL, 6.9 mmol)
in THF (4 mL) was added and the mixture was stirred for
15 min at 0 ꢁC and for 16 h at room temperature. The mixture
was concentrated in vacuo, the residue was dissolved in ethyl
acetate (80 mL) and the organic layer was washed with 0.5 M
NaOH (50 mL), 0.5 M HCl (50 mL) and brine (mL). The or-
ganic layer was dried (Na2SO4), filtered, concentrated in vacuo
and the residue was purified by fc (3 cm, petroleum ether:ethyl
acetate ¼ 1:1, 20 mL, Rf ¼ 0.31e0.34 with tailing). Colorless
3
3
gmonosubst. arom.). 1H NMR (CDCl3): d ¼ 1.52 (td broad,
J ¼ 13.0/5.2 Hz, 1H, 4-H), 1.84e2.05 (m, 3H, 4-H, 3-H),
2.48 (s, 3H, NCH3), 2.61e2.70 (m, 2H, 1-H, 9-H), 2.80 (dd,
J ¼ 11.0/3.6 Hz, 1H, 9-H), 2.83 (dd, J ¼ 11.6/1.7 Hz, 1H,
7-H), 2.86e2.90 (m, 1H, 5-H), 3.09 (dd, J ¼ 11.3/2.1Hz,
1H, 7-H), 3.36 (s, 3H, OCH3), 3.42 (ddd, J ¼ 9.2/7.0/2.4 Hz,
1H, 2-H), 3.68 (d, J ¼ 14.0 Hz, 1H, NCH2Ph), 3.73 (d,
J ¼ 14.0 Hz, 1H, NCH2Ph), 7.19e7.44 (m, 5H, arom. H).
13C NMR (75.4 MHz, CDCl3): d ¼ 26.4 (1C, C-3), 28.2
(1C, C-4), 44.3 (1C, NCH3), 47.2 (1C, C-7), 53.0 (1C, C-5),
54.0 (1C, C-9), 56.4 (1C, OCH3), 60.4 (1C, NCH2Ph),
60.5 (1C, C-1), 84.3 (1C, C-2), 126.7 (1C, arom. CH),
128.1 (2C, arom. CH), 128.3 (2C, arom. CH), 140.0 (1C,
arom. C).
1
oil, yield 378 mg (61%). According to the H NMR spectrum
the ratio of diastereomers (2S )-11c:(2R)-11c ¼ 23:77.

1258
M. Weigl, B. Wu¨nsch / European Journal of Medicinal Chemistry 42 (2007) 1247e1262
6.1.19. (1S,2S,5S )-6-Benzyl-8-butyl-2-methoxy-6,8-diazabi-
cyclo[3.2.2]nonane ((2S )-12b) and (1S,2R,5S )-6-benzyl-8-
butyl-2-methoxy-6,8-diazabicyclo[3.2.2]nonane ((2R)-12b)
Under N2 a solution of 1 M LiAlH4 in THF (4.0 mL,
4.0 mmol) was added to a cold solution of 10b (168 mg,
0.51 mmol) in THF (40 mL). The mixture was stirred for
30 min at 0 ꢁC and then it was heated to reflux for 140 h. After
careful addition of 3 M NaOH (2 mL) and H2O (2 mL) the
mixture was heated to reflux for 15 min. It was filtered, the fil-
trate was concentrated in vacuo, the residue was dissolved in
ethyl acetate (80 mL) and H2O (50 ml), the organic layer
was separated and the aqueous layer was extracted with ethyl
acetate (2 ꢃ 50 mL). The organic layer was dried (Na2SO4),
concentrated in vacuo and the residue was purified by fc
(2 cm, ethyl acetate:acetone ¼ 8:2, 2 mL, Rf ¼ 0.51*/0.34
with tailing). Pale yellow oil, yield 73 mg (47.4%). According
0.36 mmol) in THF (30 mL). The mixture was stirred for
15 min at 0 ꢁC and then it was heated to reflux for 75 h. After
careful addition of 3 M NaOH (1 mL) and H2O (1 mL) the
mixture was heated to reflux for 15 min. It was filtered and
the filtrate was concentrated in vacuo. Pale yellow oil, yield
124 mg (98%), Rf ¼ 0.57*/0.48 ethyl acetate:acetone ¼ 8:2,
1
with tailing. According to the H NMR spectrum the ratio
20
of diastereomers (2S )-12c:(2R)-12c ¼ 23:77. [a] ¼ þ20.3
589
(23:77 mixture of diastereomers, c ¼ 0.67, CH2Cl2).
C23H30N2O (350.2). HR-MS: Calcd. 350.235813 found
350.236364 (þ1.6 ppm). MS (EI): m/z (%) ¼ 350 (M, 34),
259 (M ꢀ CH2Ph, 100), 168 (M ꢀ 2ꢃ CH2Ph, 6). IR (film):
~n [cmꢀ1] ¼ 3060, 3026 (w, nCH arom.), 2927 (s, nCH aliph.),
2807 (m, nOCH3), 1255 (m, nCOC), 1096 (s, nCOC), 731, 699
(s, gmonosubst. arom.). 1H NMR (CDCl3): d ¼ 1.48e1.60 (td
broad, J ¼ 12.4/5.8 Hz, 0.8H, 4-H), 1.65e1.77* (m, 2ꢃ
0.2H, 4-H), 1.82e2.05 (m, 2.8H, 4-H (0.8H), 3-H (2H)),
2.71 (dd, J ¼ 10.1/2.7 Hz, 0.8H, 9-H), 2.76e2.94 (m, 7.4H,
NCH2CH2Ph (4H), 7-H (1.2H), 5-H, 1-H (0.8H), 9-H (2ꢃ
0.2H)), 2.98 (dd, J ¼ 10.1/2.7 Hz, 0.8H, 9-H), 2.99e3.05*
(m, 0.2H, 1-H), 3.16 (dd, J ¼ 14.0/4.5 Hz, 0.8H, 7-H), 3.34*
(s, 3ꢃ 0.2H, OCH3), 3.37 (s, 3ꢃ 0.8H, OCH3), 3.33e3.41
(m, 0.8H, 2-H), 3.52e3.61* (m, 0.2H, 2-H), 3.65e3.78 (m,
2H, NCH2Ph), 7.17e7.44 (m, 10H, arom. H). 13C NMR
(CDCl3): d ¼ 25.9* (0.2C, C-3), 26.5 (0.8C, C-3), 28.3
(0.8C, C-4), 31.3* (0.2C, C-4), 34.8 (0.8C, NCH2CH2Ph),
35.1* (0.2C, NCH2CH2Ph), 48.4 (0.8C, C-7), 50.3* (0.2C,
C-7), 51.4* (0.2C, C-9), 51.7 (0.8C, C-9), 53.2 (0.8C, C-5),
54.5* (0.2C, C-5), 56.0* (0.2C, OCH3), 56.4 (0.8C, OCH3),
58.5 (0.8C, C-1), 58.8 (0.8C, NCH2CH2Ph), 59.4* (0.2C,
NCH2CH2Ph), 60.5 (1C, NCH2Ph), 61.0* (0.2C, C-1), 84.8
(0.8C, C-2), 85.9* (0.2C, C-2), 125.8* (0.2C, arom. CH),
125.9 (0.8C, arom. CH), 126.7 (0.8C, arom. CH), 126.8*
(0.2C, arom. CH), 128.1 (2C, arom. CH), 128.3 (2ꢃ
0.8C þ 2C, arom. CH), 128.6* (2ꢃ 0.2C, arom. CH), 128.7
(2ꢃ 0.8C, arom. CH), 128.8* (2ꢃ 0.2C, arom. CH), 139.7*
(0.2C, arom. C), 140.0 (0.8C, arom. C), 140.5 (0.8C, arom.
C), 140.8* (0.2C, arom. C). * ¼ Signals of the minor
diastereomer.
to the 1H NMR spectrum the ratio of diastereomers (2S )-
20
12b:(2R)-12b ¼ 25:75. [a] ¼ þ35.3 (25:75 mixture of dia-
589
stereomers, c ¼ 0.52, CH2Cl2). C19H30N2O (302.5). Calcd. C
75.45 H 10.00 N 9.26 found C 75.25 H 9.83 N 9.56. MS
(EI): m/z (%) ¼ 302 (M, 100), 259 (M ꢀ CH2CH2CH3, 6),
229 (M ꢀ H2NCH2CH2CH2CH3, 23), 211 (M ꢀ CH2Ph, 90).
IR (film): ~n [cmꢀ1] ¼ 3027 (w, nCH arom.), 2927, 2870, 2804 (s,
nCH aliph.), 1149, 1100 (m, nCOC), 730, 698 (m, gmonosubst. arom.).
1H NMR (CDCl3): d ¼ 0.91* (t, J ¼ 7.1 Hz, 3ꢃ 0.25H,
CH2CH2CH2CH3), 0.93 (t, J ¼ 7.2 Hz, 3ꢃ 0.75H,
NCH2CH2CH2CH3), 1.25e1.60 (m, 4.75H, NCH2CH2CH2CH3
(4H), 4-H (0.75H)), 1.65e1.73* (m, 2ꢃ 0.25H, 4-H), 1.78e2.01
(m, 2.75H, 3-H (2H), 4-H (0.75H)), 2.50e2.66 (m, 2.75H,
NCH2CH2CH2CH3 (2H), 9-H (0.75H)), 2.68e2.96 (m, 4.5H,
7-H (0.75H, 2ꢃ 0.25H), 9-H (0.75H, 2ꢃ 0.25H), 1-H (1H), 5-
H (1H)), 3.10 (dd, J ¼ 12.7/3.5 Hz, 0.75H, 7-H), 3.31* (s, 3ꢃ
0.25H, OCH3), 3.36 (s, 3ꢃ 0.75H, OCH3), 3.32e3.40 (m,
0.75H, 2-H), 3.52* (q, J ¼ 5.2 Hz, 0.25H, 2-H), 3.64e3.74
(m, 2H, NCH2Ph (2H)), 7.18e7.39 (m, 5H, arom. H). 13C
NMR (CDCl3): d ¼ 14.0 (1C, NCH2CH2CH2CH3), 20.4 (1C,
NCH2CH2CH2CH3), 26.0* (0.25C, C-3), 26.6 (0.75C, C-3),
28.4 (0.75C, C-4), 30.2 (0.75C, NCH2CH2CH2CH3), 30.5*
(0.25C, NCH2CH2CH2CH3), 31.7* (0.25C, C-4), 48.1 (0.75C,
C-7), 50.1* (0.25C, C-7), 51.2* (0.25C, C-9), 51.7 (0.75C,
C-9), 53.2 (0.75C, C-5), 54.6* (0.25C, C-5), 55.9
(0.75C, OCH3), 56.4* (0.25C, OCH3), 56.6 (0.75C,
NCH2CH2CH2CH3), 57.2* (0.25C, NCH2CH2CH2CH3),
58.1 (0.75C, C-1), 60.4* (0.25C, C-1), 60.6 (0.75C,
NCH2Ph), 61.1* (0.25C, NCH2Ph), 85.2 (0.75C, C-2), 86.0*
(0.25H, C-2), 126.6 (0.75C, arom. CH), 126.7* (0.25C,
arom. CH), 128.1 (2C, arom. CH), 128.3 (2ꢃ 0.75C, arom.
CH), 128.6* (2ꢃ 0.25C, arom. CH), 139.9* (0.25C, arom.
C), 140.2 (0.75C, arom. C). * ¼ Signals of the minor
diastereomer.
6.1.21. (1R,2R,5S )-6-Benzyl-2-benzyloxy-8-methyl-6,8-
diazabicyclo[3.2.2]nonane ((2R)-13a)
Under N2 a solution of 1 M LiAlH4 in THF (2.5 mL,
2.5 mmol) was added to a cold solution of (2R)-11a
(171 mg, 0.47 mmol) in THF (40 mL). The mixture was
stirred for 10 min at 0 ꢁC and then it was heated to reflux
for 50 h. After careful addition of Na2SO4$10H2O (1.5 g)
the mixture was heated to reflux for 20 min. It was filtered,
the filtrate was concentrated in vacuo and the residue was
purified by fc (2 cm, petroleum ether:ethyl acetate ¼ 8:2 þ 1%
ethyldimethylamine, 2 mL, Rf ¼ 0.22). Colorless oil, yield
22
6.1.20. (1R,2S,5S )-6-Benzyl-2-methoxy-8-(2-phenylethyl)-
6,8-diazabicyclo[3.2.2]nonane ((2S )-12c) and (1R,2R,5S )-
6-benzyl-2-methoxy-8-(2-phenylethyl)-6,8-
diazabicyclo[3.2.2]nonane ((2R)-12c)
Under N2 a solution of 1 M LiAlH4 in THF (1.5 mL,
1.5 mmol) was added to a cold solution of 10c (136 mg,
100 mg (63%). [a] ¼ þ54.6 (c ¼ 0.67, CH2Cl2).
589
C22H28N2O (336.2). HR-MS: Calcd. 336.220163 found
336.220322 (þ0.5 ppm). MS (EI): m/z (%) ¼ 336 (M, 16),
245 (M ꢀ CH2Ph, 10), 187 (M ꢀ CH2CH2CH2OCH2Ph, 12),
154 (M ꢀ 2ꢃ CH2Ph, 67). IR (film): ~n [cmꢀ1] ¼ 3061, 3028
(w, nCH arom.), 2926, 2867 (s, nCH aliph.), 2791 (m, nNCH3),

M. Weigl, B. Wu¨nsch / European Journal of Medicinal Chemistry 42 (2007) 1247e1262
1259
1
1261, 1072 (m, nCOC), 732, 697 (s, gmonosubst. arom.). H NMR
(CDCl3): d ¼ 1.50 (td, J ¼ 12.8/5.2 Hz, 1H, 4-H), 1.82e1.94
(m, 1H, 4-H), 1.95e2.12 (m, 2H, 3-H), 2.43 (s, 3H, NCH3),
2.60e2.68 (m, 2H, 1-H, 9-H), 2.78e2.85 (m, 3H, 5-H, 7-H,
9-H), 3.18 (dd, J ¼ 11.3/1.8 Hz, 1H, 7-H), 3.63 (ddd,
J ¼ 9.5/7.2/2.4 Hz, 1H, 2-H), 3.68 (d, J ¼ 14.9 Hz, 1H,
NCH2Ph), 3.73 (d, J ¼ 14.9 Hz, 1H, NCH2Ph), 4.53 (d,
J ¼ 11.9 Hz, 1H, OCH2Ph), 4.59 (d, J ¼ 11.9 Hz, 1H,
OCH2Ph), 7.18e7.42 (m, 10H, arom. H). 13C NMR
(CDCl3): d ¼ 26.8 (1C, C-3), 28.3 (1C, C-4), 44.3 (1C,
NCH3), 47.4 (1C, C-7), 53.0 (1C, C-5), 54.0 (1C, C-9), 60.5
(1C, NCH2Ph), 61.0 (1C, C-1), 70.7 (1C, OCH2Ph), 82.1
(1C, C-2), 126.7 (1C, arom. CH), 127.4 (1C, arom. CH),
127.5 (2C, arom. CH), 128.1 (2C, arom. CH), 128.3 (2C,
arom. CH), 128.4 (2C, arom. CH), 139.1 (1C, arom. C),
140.1 (1C, arom. C).
28.5 (0.6C, C-4), 30.2 (0.6C, NCH2CH2CH2CH3), 30.6*
(0.4C, NCH2CH2CH2CH3), 31.6* (0.4C, C-4), 48.3 (0.6C,
C-7), 50.1* (0.4C, C-7), 51.3* (0.4C, C-9), 51.8 (0.6C,
C-9), 53.2 (0.6C, C-5), 54.6* (0.4C, C-5), 56.5 (0.6C,
NCH2CH2CH2CH3), 56.9* (0.4C, NCH2CH2CH2CH3), 58.7
(0.6C, C-1), 60.6 (0.6C, NCH2Ph), 60.7* (0.4C, NCH2Ph),
61.0* (0.4C, C-1), 70.0* (0.4C, OCH2Ph), 70.7 (0.6C,
OCH2Ph), 82.9* (0.4C, C-2), 83.9 (0.6H, C-2), 127.3
(2C, arom. CH), 127.5 (1C, arom. CH), 128.1 (2C, arom.
CH), 128.2 (1C, arom. CH), 128.3 (4C, arom. CH), 139.2
(0.6C, arom. Cbenzyl ether), 139.5* (0.4C, arom. Cbenzyl ether),
139.9* (0.4 C, arom. Cbenzylamine), 140.3 (0.6C, arom. Cbenzylamine).
* ¼ Signals of the minor diastereomer.
Compound 8b (Rf ¼ 0.22*/0.19 with tailing): pale yellow
1
oil, yield 58 mg (34%). According to the H NMR spectrum
21
the ratio of (2S )-8b:(2R)-8b ¼ 23:77. [a] ¼ þ29.9 (23:77
589
mixture of diastereomers, c ¼ 0.46, CH2Cl2). C18H28N2O
(288.2). HR-MS: Calcd. 288.220163 found 288.219629
(ꢀ1.9 ppm). MS (EI): m/z (%) ¼ 288 (M, 36), 245
(M ꢀ CH2CH2CH3, 9), 229 (M ꢀ CH2CH2CH2OH, 28), 197
(M ꢀ CH2Ph, 84), 179 (197-H2O, 72). IR (film): ~n
[cmꢀ1] ¼ 3369 (m, nOH), 3028 (w, nCH arom.), 2929,
2870, 2802 (m, nCH aliph.), 1145, 1053 (m, nCO), 732, 698 (s,
6.1.22. (1R,2S,5S )-6-Benzyl-2-benzyloxy-8-butyl-6,8-
diazabicyclo[3.2.2]nonane ((2S )-13b) and (1R,2R,5S )-6-
benzyl-2-benzyloxy-8-butyl-6,8-diazabicyclo[3.2.2]nonane
((2R)-13b) and (1R,2S,5S )-6-benzyl-8-butyl-6,8-diazabi-
cyclo[3.2.2]nonane-2-ol ((2S )-8b) and (1R,2R,5S )-6-
benzyl-8-butyl-6,8-diazabicyclo[3.2.2]nonane-2-ol ((2R)-8b)
Under N2 a solution of 1 M LiAlH4 in THF (4.0 mL,
4.0 mmol) was added to a cold solution of 11b containing
small amounts of 9b (208 mg, 0.51 mmol in THF (40 mL).
The mixture was stirred for 30 min at 0 ꢁC and then it was
heated to reflux for 140 h. After careful addition of 3 M
NaOH (2 mL) and H2O (2 mL) the mixture was heated to
reflux for 15 min. It was filtered, the filtrate was concentrated
in vacuo and the residue was purified by fc (2 cm, ethyl ace-
tate, 2 mL).
1
gmonosubst. arom.). H NMR (CDCl3): d ¼ 0.91 (t, J ¼ 7.0 Hz,
3ꢃ 0.8H, NCH2CH2CH2CH3), 0.93 (t, J ¼ 7.0 Hz, 3ꢃ 0.2H,
NCH2CH2CH2CH3), 1.24e1.53 (m, 5H, NCH2CH2CH2CH3
(4H), CHOH (1H)), 1.54e1.68 (m, 1.2H, 4-H (1H),
3-H (0.2H)), 1.71e1.88 (m, 1.8H, 3-H (0.8H), 4-H
(1H)), 2.04e2.19 (m, 1H, 3-H), 2.51 (t, J ¼ 7.2 Hz, 2ꢃ
0.8H, NCH2CH2CH2CH3), 2.54* (t, J ¼ 7.0 Hz, 2ꢃ 0.2H,
NCH2CH2CH2CH3), 2.65e2.94 (m, 5.2H, 9-H (2H), 7-H
(0.8H), 7-H (2ꢃ 0.2H), 5-H (1H), 1-H (1H)), 3.09 (dd,
J ¼ 11.0/2.1 Hz, 0.8H, 7-H), 3.67 (d, J ¼ 13.4 Hz, 1H,
NCH2Ph), 3.72 (d, J ¼ 13.4 Hz, 1H, NCH2Ph), 3.79* (t broad,
J ¼ 5.0 Hz, 0.2H, 2-H), 3.97 (dt, J ¼ 7.0/5.2 Hz, 0.8H, 2-H),
7.19e7.37 (m, 5H, arom. H). * ¼ Signals of the minor
diastereomer.
Compound 13b (Rf ¼ 0.64*/0.53 with tailing): colorless oil,
20
1
yield 47 mg (24%). According to the H NMR spectrum the
ratio of (2S )-13b:(2R)-13b ¼ 36:64. [a] ¼ þ25.0 (36:64
589
mixture of diastereomers, c ¼ 0.51, CH2Cl2). C25H34N2O
(378.3). HR-MS: Calcd. 378.267113 found 378.266927
(ꢀ0.5 ppm). MS (EI): m/z (%) ¼ 378 (M, 90), 287
(M ꢀ CH2Ph, 35), 229 (287-CH3CH2CH2CH3, 11), 196 (M ꢀ
2ꢃ CH2Ph, 100). IR (film): ~n [cmꢀ1] ¼ 3028 (w, nCH arom.),
2927, 2867, 2800 (m, nCH aliph.), 1072 (s, nCOC), 733, 698 (s,
gmonosubst. arom.). 1H NMR (CDCl3): d ¼ 0.92 (t broad,
J ¼ 7.0 Hz, 3H, NCH2CH2CH2CH3), 1.25e1.58 (m, 4.6H,
NCH2CH2CH2CH3 (4H), 4-H (0.6H)), 1.60e1.78* (m, 2ꢃ
0.4H, 4-H), 1.80e2.14 (m, 2.6H, 3-H (2H), 4-H (0.6H)),
2.50e2.72 (m, 3H, NCH2CH2CH2CH3 (2H), 7-H (0.4H),
9-H (0.6H)), 2.72e3.00 (m, 4.4H, 7-H (1H), 9-H (0.6H, 2ꢃ
0.4H), 1-H (1H), 5-H (1H)), 3.22 (dd, J ¼ 12.5/3.7 Hz, 0.6H,
7-H), 3.56 (ddd, J ¼ 9.3/7.2/1.5 Hz, 0.6H, 2-H), 3.66* (d,
J ¼ 13.4 Hz, 0.4H, NCH2Ph), 3.68 (d, J ¼ 14.9 Hz, 0.6H,
NCH2Ph), 3.72* (d, J ¼ 13.3 Hz, 0.4H, NCH2Ph), 3.73 (d,
J ¼ 14.9 Hz, 0.6H, NCH2Ph), 3.76* (q, J ¼ 5.0 Hz, 0.4H,
2-H), 4.53* (s, 2ꢃ 0.4H, OCH2Ph), 4.55 (d, J ¼
11.9 Hz, 0.6H, OCH2Ph), 4.60 (d, J ¼ 11.9 Hz, 0.6H,
OCH2Ph), 7.18e7.39 (m, 10H, arom. H). 13C NMR
(CDCl3): d ¼ 14.1 (1C, NCH2CH2CH2CH3), 20.4 (1C,
NCH2CH2CH2CH3), 26.5* (0.4C, C-3), 26.9 (0.6C, C-3),
6.1.23. (1R,2S,5S )-6-Benzyl-2-benzyloxy-8-(2-phenylethyl)-
6,8-diazabicyclo[3.2.2]nonane ((2S )-13c) and (1R,2R,5S )-
6-benzyl-2-benzyloxy-8-(2-phenylethyl)-6,8-
diazabicyclo[3.2.2]nonane (((2R)-13c)
Under N2 a solution of 1 M LiAlH4 in THF (3.5 mL,
3.5 mmol) was added to a cold solution of 11c (316 mg,
0.70 mmol) in THF (60 mL). The mixture was stirred for
15 min at 0 ꢁC and then it was heated to reflux for 65 h. After
careful addition of Na2SO4$10H2O (4 g) the mixture was
heated to reflux for 30 min. It was filtered, the filtrate was con-
centrated in vacuo and the residue was purified by fc (2 cm,
ethyl acetate, 2 mL, Rf ¼ 0.65*/0.58 with tailing). Pale yellow
1
oil, yield 219 mg (74%). According to the H NMR spectrum
20
589
the ratio of diastereomers (2S )-13c:(2R)-13c ¼ 22:78. [a]
¼
þ25.9 (22:78 mixture of diastereomers, c ¼ 0.51, CH2Cl2).
C29H34N2O (426.3). HR-MS: Calcd. 426.267113 found
426.267320 (þ0.5 ppm). MS (EI): m/z (%) ¼ 426 (M, 53),
335 (M ꢀ CH2Ph, 93), 244 (M ꢀ 2ꢃ CH2Ph, 55), 229
(335-CH3CH2Ph, 12), 153 (M ꢀ 3ꢃ CH2Ph, 56). IR (film): ~n

1260
M. Weigl, B. Wu¨nsch / European Journal of Medicinal Chemistry 42 (2007) 1247e1262
[cmꢀ1] ¼ 3061, 3027 (w, nCH arom.), 2927, 2801 (m, nCH aliph.),
1072 (s, nCOC), 732, 697 (s, gmonosubst. arom.). 1H NMR
(CDCl3): d ¼ 1.49 (td, J ¼ 12.5/4.7 Hz, 0.8H, 4-H), 1.62e
1.75* (m, 2ꢃ 0.2H, 4-H), 1.80e2.12 (m, 2.8H, 3-H (2H), 4-
H (0.8H)), 2.62e3.08 (m, 9.2H, NCH2CH2Ph (4H), 9-H
(2H), 7-H (1.2H), 5-H, 1-H), 3.23 (dd, J ¼ 13.7/4.2 Hz,
0.8H, 7-H), 3.54 (t broad, J ¼ 7.3 Hz, 0.8H, 2-H), 3.66e3.80
(m, 2.2H, NCH2Ph (2H), 2-H (0.2H)), 4.47e4.60* (m, 2ꢃ
0.2H, OCH2Ph), 4.51 (d, J ¼ 12.1 Hz, 0.8H, OCH2Ph), 4.58
(d, J ¼ 12.1 Hz, 0.8H, OCH2Ph), 7.14e7.41 (m, 15H, arom.
H). 13C NMR (CDCl3): d ¼ 26.4* (0.2C, C-3), 26.9 (0.8C,
C-3), 28.4 (0.8C, C-4), 31.3* (0.2C, C-4), 34.7 (0.8C,
NCH2CH2Ph), 35.1* (0.2C, NCH2CH2Ph), 48.6 (0.8C, C-7),
50.4* (0.2C, C-7), 51.5* (0.2C, C-9), 51.7 (0.8C, C-9), 53.2
(0.8C, C-5), 54.4* (0.2C, C-5), 58.7 (0.8C, NCH2CH2Ph),
59.1 (0.8C, C-1), 59.2* (0.2C, NCH2CH2Ph), 60.5 (0.8C,
NCH2Ph), 60.9* (2ꢃ 0.2C, C-1, NCH2Ph), 70.1* (0.2C,
OCH2Ph), 70.8 (0.8C, OCH2Ph), 82.7 (0.8C, C-2), 84.0*
(0.2C, C-2), 125.8* (0.2C, arom. CH), 125.9 (0.8C, arom.
CH), 126.7* (0.2C, arom. CH), 127.2* (0.2C, arom. CH),
127.4 (2ꢃ 0.8C, arom. CH), 127.5 (2ꢃ 0.8C, arom. CH),
128.2 (2C, arom. CH), 128.3 (4.4 C, arom. CH (4ꢃ 0.8C,
6ꢃ 0.2C)), 128.4 (2C, arom. CH), 128.7 (2ꢃ 0.8C, arom.
CH), 128.8* (2ꢃ 0.2C, arom. CH), 139.2 (0.8C, arom. C),
139.4* (0.2C, arom. C), 140.1 (1C, arom. C), 140.5 (0.8C,
arom. C), 140.9* (0.2C, arom. C). * ¼ Signals of the minor
diastereomer.
J ¼ 5.6/2.0 Hz, 1H, 5-H), 4.06 (s, 1H, 1-H), 4.42 (d,
J ¼ 14.6 Hz, 1H, NCH2Ph), 4.66 (d, J ¼ 14.9 Hz, 1H,
NCH2Ph), 7.21e7.35 (m, 5H, arom. H).
(2S )-9a (Rf ¼ 0.46): Colorless solid, yield 0.37 g (11%).
(2R)-9a (Rf ¼ 0.39): Colorless solid, yield 0.99 g (30%).
6.1.25. (1R,5S )-6-Benzyl-8-methyl-6,8-diazabicyclo[3.2.2]-
nonane-2-one dimethyl acetal (15a)
Under N2 a solution of 1 M LiAlH4 in Et2O (1.5 mL,
1.5 mmol) was added to a cold solution of 14a (83 mg,
0.26 mmol) in THF (20 mL). The mixture was stirred for
30 min at 0 ꢁC and then it was heated to reflux for 60 h. After
careful addition of Na2SO4$10H2O (2.5 g) the mixture was
heated to reflux for 30 min. It was filtered, the filtrate was
concentrated in vacuo and the residue was purified by fc
(2 cm, ethyl acetate þ 1% NH3 conc., 2 mL, Rf ¼ 0.45).
Colorless solid, yield 55 mg (73%), mp 60e61 ꢁC.
23
[a] ¼ þ31.9 (c ¼ 0.39, CH2Cl2). C17H26N2O2 (290.2).
589
HR-MS: Calcd. 290.199428 found 290.198867 (ꢀ1.9 ppm).
MS (EI): m/z (%) ¼ 290 (M, 57), 259 (M ꢀ OCH3, 14), 184
(M ꢀ NHCH2Ph, 100), 167 (M ꢀ CH3OHeCH2Ph, 23). IR
(film): ~n [cmꢀ1] ¼ 3026 (w, nCH arom.), 2935 (s, nCH aliph.),
2794 (m, nOCH =NCH ), 1104, 1051 (m, nCOC), 731, 698 (m,
3
3
1
gmonosubst. arom.). H NMR (CDCl3): d ¼ 1.55e1.68 (m, 1H,
4-H), 1.74e1.90 (m, 2H, 4-H, 3-H), 2.10e2.22 (m, 1H,
3-H), 2.50 (s, 3H, NCH3), 2.62 (s broad, 1H, 1-H), 2.68e
2.75 (m, 1H, 9-H), 2.77e2.88 (m, 3H, 9-H, 7-H, 5-H), 3.03
(dd, J ¼ 10.1/1.5 Hz, 1H, 7-H), 3.23 (s, 3H, OCH3), 3.24 (s,
3H, OCH3), 3.65 (d, J ¼ 13.4 Hz, 1H, NCH2Ph), 3.72 (d,
J ¼ 13.7 Hz, 1H, NCH2Ph), 7.22e7.36 (m, 5H, arom. H).
13C NMR (CDCl3): d ¼ 27.3 (1C, C-4), 30.3 (1C, C-3), 44.9
(1C, NCH3), 47.2 (1C, C-7), 48.1 (1C, OCH3), 48.4 (1C,
OCH3), 52.5 (1C, C-5), 53.6 (1C, C-9), 60.0 (1C, NCH2Ph),
61.8 (1C, C-1), 105.0 (1C, C-2), 126.8 (1C, arom. CH),
128.2 (2C, arom. CH), 128.4 (2C, arom. CH), 139.9 (1C,
arom. C).
6.1.24. (1S,5S )-6-Benzyl-2,2-dimethoxy-8-methyl-6,8-diaza-
bicyclo[3.2.2]nonane-7,9-dione (14a)
A solution of 6a (4.52 g, 12.0 mmol) and p-toluenesulfonic
acid (450 mg, 2.4 mmol) in THF (80 mL) and CH3OH (80 ml)
was stirred for 16 h at room temperature. After evaporation of
the solvent the residue was purified by fc (6 cm, ethyl acetate,
40 mL, Rf ¼ 0.41). The isolated product (yield 2.19 g, 63%)
was an inseparable mixture of ketone 7a and dimethyl acetal
14a. In order to get the pure dimethyl acetal 14a the residue
was dissolved in THF (80 mL) and H2O (80 mL), NaBH4
(1.47 g, 38.9 mmol) was added and the mixture was stirred
for 16 h at room temperature. The organic part of the solvent
was removed in vacuo, the aqueous layer was extracted
with ethyl acetate (100 mL), the organic layer was dried
(Na2SO4), concentrated in vacuo and the residue (mixture of
14a and 9a) was purified by fc (6 cm, ethyl acetate:acetone ¼
1:1, 30 mL).
6.2. Receptor binding studies, general
Tefloneglass-homogenizer: PotterÒS (B. Braun Biotech
International). Rotor/stator homogenizer: UltraturraxÒ T25
basic (Ika Labortechnik). Centrifuge: high speed refrigerating
centrifuge model J2-HS (Beckman). Filter: Whatman glass
fibre filters GF/B, presoaked in 0.5% polyethylenimine (in
water) for 2 h at 4 ꢁC before use. Filtration was performed
with a Brandel 24-well cell harvester. Scintillation cocktail:
Rotiszint eco plus (Roth). Liquid scintillation analyzer: Tri-
Carb 2100 TR (Canberra Packard), counting efficiency 66%.
All experiments were carried out in triplicates. IC50-values
were determined from competition experiments with at least
six concentrations of test compounds and were calculated
with the curve-fitting program GraphPad PrismÒ 3.0 (Graph-
Pad Software) by nonlinear regression analysis. Ki-values
were calculated according to Cheng and Prusoff [18]. For
compounds with high affinity (low Ki-values) mean val-
ues ꢂ SEM from at least three independent experiments are
given.
Compound 14a (Rf ¼ 0.58): colorless oil, yield 0.83 g
23
(22%). [a] ¼ þ73.9 (c ¼ 0.65, CH2Cl2). C17H22N2O4
589
(318.4). Calcd. C 64.14 H 6.97 N 8.79 found C 63.85 H
7.03 N 8.37. MS (EI): m/z (%) ¼ 318 (M, 28), 303
(M ꢀ CH3, 4), 287 (M ꢀ OCH3, 12), 217 (M ꢀ CH2
CHC(OCH3)2, 17). IR (film): ~n [cmꢀ1] ¼ 2943 (m, nCH aliph.),
2837 (w, nOCH =NCH ), 1683 (s, nC]O, tert. amides), 1260, 1104,
3
3
1041 (m, nCOC), 736, 702 (m, gmonosubst. arom.). 1H NMR
(CDCl3): d ¼ 1.43 (dddd, J ¼ 13.8/11.5/5.1/2.1 Hz, 1H, 4-H),
1.65 (ddd, J ¼ 14.1/11.6/5.2 Hz, 1H, 3-H), 1.77e1.87 (m,
1H, 4-H), 1.92 (dt, J ¼ 14.1/4.6 Hz, 1H, 3-H), 3.00 (s, 3H,
NCH3), 3.21 (s, 3H, OCH3), 3.33 (s, 3H, OCH3), 3.81 (dd,

M. Weigl, B. Wu¨nsch / European Journal of Medicinal Chemistry 42 (2007) 1247e1262
1261
6.3. Investigation of s1 receptor affinity
Performance of the s2 assay: The membrane preparation
(about 60 mg protein) was incubated with 3 nM [3H]-ditolyl-
guanidine (di-[p-ring-3H]-1,3-di-o-tolylguanidine, 2220 GBq/
mmol; American Radiolabeled Chemicals Inc.) and different
concentrations of test compounds in buffer (50 mM Trise
HCl, pH 8.0) in the presence of 100 nM (þ)-pentazocine.
The total volume was 250 mL. The incubation (120 min,
25 ꢁC) was stopped by addition of 2 mL of ice cold buffer
(10 mM TriseHCl, pH 8.0) followed by rapid filtration
through presoaked Whatman GF/B filters using a cell har-
vester. After washing three times with 2 mL of cold buffer
3 mL of scintillation cocktail were added to the filters. After
at least 8 h bound radioactivity trapped on the filters was
counted in a liquid scintillation analyzer. Non-specific binding
was determined with 10 mM non-radiolabeled ditolylguani-
dine. The Kd-value of [3H]-ditolylguanidine is 17.9 nM.
[3H]-(þ)-Pentazocine binding to guinea pig brain mem-
brane preparations was performed according to the procedure
described in Ref. [14].
Membrane preparation: Thawed guinea pig brains (Dunkin
Hartley, Harlan-Sera-Lab) were homogenized with an Ultra-
turrax (8000 rpm) in 10 volumes of cold 0.32 M sucrose.
The homogenate was centrifuged at 1000 g for 10 min at
4 ꢁC. The supernatant was separated and centrifuged at
22,000 g for 20 min at 4 ꢁC. The pellet was resuspended in
10 volumes of buffer (50 mM TriseHCl, pH 7.4) with an
Ultraturrax (8000 rpm), incubated for 30 min at 25 ꢁC and
centrifuged at 22,000 g (20 min, 4 ꢁC). The pellet was resus-
pended in buffer, the protein concentration was determined ac-
cording to the method of Bradford [19] using bovine serum
albumin as standard, and subsequently the preparation was
frozen (ꢀ83 ꢁC) in 5 mL portions of about 2 mg protein/mL.
Performance of the s1 assay: The test was performed with
the radioligand [ring-1,3-3H]-(þ)-pentazocine (1036 GBq/
mmol; NEN Life Science Products). The thawed membrane
preparation (about 150 mg of the protein) was incubated with
various concentrations of test compounds, 3 nM [3H]-(þ)-pen-
tazocine and buffer (50 mM TriseHCl, pH 7.4) in a total vol-
ume of 500 mL for 150 min at 37 ꢁC. The incubation was
terminated by rapid filtration through presoaked Whatman
GF/B filters using a cell harvester. After washing four times
with 2 mL of cold buffer 3 mL of scintillation cocktail were
added to the filters. After at least 8 h bound radioactivity trap-
ped on the filters was counted in a liquid scintillation analyzer.
Non-specific binding was determined with 10 mM haloperidol.
The Kd-value of [3H]-(þ)-pentazocine is 2.9 nM.
6.5. Investigation of k receptor affinity
[3H]-U-69593 binding to guinea pig brain membrane prep-
arations was performed according to standard procedure
described in Ref. [16].
6.6. Investigation of m receptor affinity
[3H]-DAMGO binding to guinea pig brain membrane prep-
arations was performed according to standard procedure
described in Ref. [16].
6.7. Investigation of NMDA receptor-affinity
[3H]-(þ)-MK-801 binding to guinea pig brain membrane
preparations was performed according to standard procedure
described in Ref. [15].
6.4. Investigation of s2 receptor affinity
s2 Receptor affinity was determined using rat liver mem-
branes with [3H]-ditolylguanidine in the presence of 100 nM
(þ)-pentazocine to mask s1-binding sites. The assay was per-
formed according to the procedure described in Ref. [14].
Membrane preparation: One frozen rat liver (Sprague Daw-
ley, Harlan-Sera-Lab) was allowed to thaw slowly on ice. Then
it was homogenized with a potter (800 rpm) in 10 volumes of
cold buffer (10 mM TriseHCl/0.32 M sucrose, pH 7.4). The
homogenate was centrifuged at 1000 g for 10 min at 4 ꢁC.
The supernatant was separated and saved on ice. The pellet
was resuspended in 30 mL of cold buffer and centrifuged
again. Both supernatants were then centrifuged at 31,000 g
for 20 min at 4 ꢁC. The pellet was resuspended in 30 mL of
buffer (10 mM TriseHCl, pH 7.4) by vortexing and gentle
potter homogenization. Then it was incubated for 15 min at
25 ꢁC and centrifuged at 31,000 g (20 min, 4 ꢁC). The pellet
was resuspended in buffer, the protein concentration was
determined according to the method of Bradford [19] using
bovine serum albumin as standard, and subsequently the prep-
aration was frozen (ꢀ83 ꢁC) in 5 mL portions of about 2.5 mg
protein/mL.
Acknowledgement
Financial support of this work by the Deutsche Forschungs-
gemeinschaft, the Fonds der Chemischen Industrie and the
Wissenschaftliche Gesellschaft Freiburg is gratefully acknow-
ledged. Thanks are also due to the Degussa AG, Janssen-Cilag
GmbH, and Bristol-Myers Squibb for donation of chemicals
and reference compounds.
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