Thiophene bioisosteres of GluN2B selective NMDA receptor antagonists: Synthesis and pharmacological evaluation of [7]annuleno[b]thiophen-6-amines

Article abstract of DOI:10.1016/j.bmc.2019.115245

Thiophene bioisosteres of potent GluN2B receptor negative allosteric modulators were prepared and evaluated pharmacologically. The five-step synthesis of 4,5,7,8-tetrahydro[7]annuleno[b]thiophen-6-one (10) was considerably improved by carboxylation of thiophene-3-carboxylic acid (8) in the first reaction step. Reductive amination and alkylation led to three homologous series of secondary and tertiary phenylalkylamines 5, 11 and 12. Metalation, reaction with 1-formylpiperidine and subsequent reduction provided hydroxymethyl derivatives 15 and 16, which had been designed as bioisosteres of phenols. 2-Bromo derivatives 18 were obtained by bromination of ketone 10 with NBS and subsequent reductive amination. High GluN2B affinity was achieved with [7]annuleno[b]thiophenes bearing a 3-phenylpropylamino or 4-phenylbutylamino moiety (e.g. 5c: K_i = 5.9 nM; 11d: K_i = 9.0 nM). Tertiary ethylamines 12 showed lower GluN2B affinity than tertiary methylamines 11 or secondary amines 5 (e.g. 5c: K_i = 5.9 nM; 11c: K_i = 6.0; 12c: K_i = 51 nM). A Br-atom or a hydroxymethyl moiety in 2-position were less tolerated by the GluN2B receptor. Very similar relationships between the structure and GluN2B affinity and structure and σ affinity, in particular σ₂ affinity, were detected. A slight preference for the ifenprodil binding site of GluN2B receptors over σ₁ and σ₂ receptors was found for methylamines 11c (≈2-fold) and 11d (≈1.5–2-fold) as well as for bromo derivative 18c (≈3-fold).

Full text of DOI:10.1016/j.bmc.2019.115245

Bioorganic&MedicinalChemistryxxx(xxxx)xxxx
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Thiophene bioisosteres of GluN2B selective NMDA receptor antagonists:
Synthesis and pharmacological evaluation of [7]annuleno[b]thiophen-6-
amines
⁎
Sören Baumeistera, Dirk Schepmanna, Bernhard Wünscha,b,
a Institut für Pharmazeutische und Medizinische Chemie, Westfälische Wilhelms-Universität Münster, Corrensstraße 48, D-48149 Münster, Germany
b Cells-in-Motion Cluster of Excellence (EXC 1003 – CiM), Westfälische Wilhelms-Universität Münster, Germany
A R T I C L E I N F O
A B S T R A C T
Keywords:
Thiophene bioisosteres of potent GluN2B receptor negative allosteric modulators were prepared and evaluated
pharmacologically. The five-step synthesis of 4,5,7,8-tetrahydro[7]annuleno[b]thiophen-6-one (10) was con-
siderably improved by carboxylation of thiophene-3-carboxylic acid (8) in the first reaction step. Reductive
amination and alkylation led to three homologous series of secondary and tertiary phenylalkylamines 5, 11 and
12. Metalation, reaction with 1-formylpiperidine and subsequent reduction provided hydroxymethyl derivatives
15 and 16, which had been designed as bioisosteres of phenols. 2-Bromo derivatives 18 were obtained by
bromination of ketone 10 with NBS and subsequent reductive amination. High GluN2B affinity was achieved
NMDA receptor
GluN2B subunit
Selective GluN2B antagonists
Negative allosteric modulators
Ifenprodil binding site
Thiophene bioisosteres
Hydroxymethyl derivatives
[7]annuleno[b]thiophen-6-amines
Structure affinity relationships, σ receptor
affinity
with [7]annuleno[b]thiophenes bearing
a 3-phenylpropylamino or 4-phenylbutylamino moiety (e.g. 5c:
Ki = 5.9 nM; 11d: Ki = 9.0 nM). Tertiary ethylamines 12 showed lower GluN2B affinity than tertiary me-
thylamines 11 or secondary amines 5 (e.g. 5c: Ki = 5.9 nM; 11c: Ki = 6.0; 12c: Ki = 51 nM). A Br-atom or a
hydroxymethyl moiety in 2-position were less tolerated by the GluN2B receptor. Very similar relationships
between the structure and GluN2B affinity and structure and σ affinity, in particular σ2 affinity, were detected. A
slight preference for the ifenprodil binding site of GluN2B receptors over σ1 and σ2 receptors was found for
methylamines 11c (≈2-fold) and 11d (≈1.5–2-fold) as well as for bromo derivative 18c (≈3-fold).
Receptor selectivity
1. Introduction
neuronal cell damage followed by apoptosis) resulting from high con-
centrations of the excitatory neurotransmitter (S)-glutamate are termed
The N-methyl-D-aspartate (NMDA) receptor is one of the three io-
notropic receptors for the excitatory neurotransmitter (S)-glutamate.
Four special features of the NMDA receptor lead to its importance for
learning and memory: (1) two agonists, (S)-glutamate and glycine, are
required to open the ligand-gated ion channel; (2) Mg2+-ions block the
ion channel at resting membrane potential and have to be removed by
depolarization of the surrounding membrane (voltage-dependent acti-
vation); (3) the NMDA receptor controls the influx of Ca2+-ions; and (4)
the NMDA receptor presents several binding sites for ligands, which are
able to modulate the opening state of the ion channel.1–3
excitotoxicity. These excitotoxic processes play a crucial role in the
development and progression of neurodegenerative disorders including
Alzheimer’s and Parkinson’s disease, and other CNS disorders such as
stroke/ischemia, depression and alcohol withdrawal symptoms. HYP-
4–6
ERLINK "SPS:refid::bib4_bib5_bib6"
The NMDA receptor in the adult brain is composed of four proteins,
two GluN1 and two GluN2 subunits. The GluN1 subunit is encoded by
only one gene, which is expressed throughout the CNS, but the final
protein exists in eight posttranslational splice variants (GluN1a-h). On
the other hand, four different genes encode for four different GluN2
subunits, which are termed GluN2A-D. The expression level of the
different GluN2 subunits in the CNS is quite different.6–9 We are par-
ticular interested in negative allosteric modulators (NAMs) of NMDA
receptors containing the GluN2B subunit (here shortly: “GluN2B re-
ceptor”), since this subunit is only expressed in some regions of the CNS
Whereas Ca2+-ions have beneficial effects on neuronal development
in the central nervous system (CNS), elevated neuronal Ca2+-ion con-
centrations resulting from opening of the NMDA receptor associated ion
channel by increased concentration of (S)-glutamate in the synaptic
cleft induce neurotoxic effects. These neurotoxic effects (severe
⁎ Corresponding author at: Institut für Pharmazeutische und Medizinische Chemie, Westfälische Wilhelms-Universität Münster, Corrensstraße 48, D-48149
Münster, Germany.
E-mail address: wuensch@uni-muenster.de (B. Wünsch).
https://doi.org/10.1016/j.bmc.2019.115245
Received 14 October 2019; Received in revised form 26 November 2019; Accepted 27 November 2019
0968-0896/©2019ElsevierLtd.Allrightsreserved.
Pleasecitethisarticleas:SörenBaumeister,DirkSchepmannandBernhardWünsch,Bioorganic&MedicinalChemistry,
https://doi.org/10.1016/j.bmc.2019.115245

S. Baumeister, et al.
Bioorganic&MedicinalChemistryxxx(xxxx)xxxx
including cortex, hippocampus and striatum. Moreover, there is a spe-
cial binding site located at the interface between the GluN1 and GluN2B
subunit (ifenprodil binding site) which allows addressing selectively
GluN2B subunit containing NMDA receptors without touching NMDA
receptors with other GluN2 subunits.10,11 Such types of NAMs possess
therapeutic potential for the treatment of Parkinson’s disease, migraine,
alcohol dependence symptoms, and stroke. HYPERLINK "SPS:re-
difficult to remove from the product mixture. Therefore, an alternative
synthesis of dicarboxylic acid 9 starting with thiophene-3-carboxylic
acid (8) was envisaged. In 8, the 2-position is activated twice by the
carboxylate moiety and the adjacent S-atom, which resulted in con-
siderably higher regioselectivity. Thus, reaction of thiophene-3-car-
boxylic acid (8) with two equivalents of n-BuLi and subsequently with
CO2 provided the dicarboxylic acid 9 in 77% yield. (Scheme 1) The
increased yield of dicarboxylic acid 9 (77% instead of 5%) together
with the convenient work-up and purification procedure allowed the
synthesis of the key ketone 10 in large and reproducible amounts and
thus the investigation of thorough structure affinity relationships by
diverse structural modifications.
5–9
fid::bib5_bib6_bib7_bib8_bib9"
Very recently, we have introduced the class of tetrahydro-benzo[7]
annulen-7-amines showing high affinity towards GluN2B receptors.
Benzo[7]annulene cis-1 with relative cis-configuration of OH and NHR
moieties represents the first lead compound of this series with a GluN2B
affinity of 16 nM (Fig. 1). Moreover, cis-1 inhibits glutamate/glycine
induced cytotoxicity with an IC50-value of 12 nM.12 The GluN2B affi-
nity can be modulated by the substituent in 2-position. The benzo[7]
annulenamine 2 without substituents in 2- and 5-position revealed the
same nanomolar affinity Ki = 16 nM) as cis-1. An H-bond donating OH
moiety as in the GluN2B NAMs ifenprodil and Ro 25–6981, led to a Ki
value of 28 nM (3a). The electron withdrawing NO2 group (3b) and Cl-
atom (3c) resulted in very high GluN2B affinity of 1.6 and 2.1 nM,
respectively.13,14 In order to imitate the electronic properties of the
methoxyphenyl moiety of 1, the thiophene bioisostere 4 was prepared
showing an unexpectedly low GluN2B affinity of 204 nM. However,
removal of the benzylic OH moiety as in the benzene analogs 2 and 3
increased the GluN2B affinity of 5a 8-fold (Ki = 26 nM). HYPERLINK
Reductive amination of ketone 10 with homologous phenylalk-
17
ylamines and NaBH(OAc)3 led to the secondary amines 5a-d with
different length of the spacer. An additional methyl group was in-
troduced by reductive methylation of secondary amines 5a-d using
formalin and NaBH(OAc)3.17 The corresponding ethyl derivatives 12a-
d were obtained by reductive ethylation of secondary amines 5a-d with
acetaldehyde and NaBH(OAc)3.17 (Scheme 1).
In addition to modification of the substituents at the amino moiety,
modifications at 2–position should be performed at the very end of the
synthesis, i.e. diversification should be introduced at late stage of the
synthesis. For this purpose, secondary and tertiary amines 5c,d and
11b,c were treated with n-BuLi and 1-formylpiperidine to afford the
aldehydes 13c,d and 14b,c. Subsequent reduction of the aldehydes
13c,d and 14b,c with NaBH4 led to the hydroxymethyl derivatives
15
"SPS:refid::bib15″
Fig. 1. Lead compounds for the development of thiophene bioisosteric NAMs 6 of GluN2B receptors.
Herein, we wish to report the synthesis, GluN2B affinity and re-
ceptor selectivity of [7]annuleno[b]thiophen-6-amines of type 6. In
particular, various phenylalkyl substituents with longer alkyl spacers
should be introduced at the exocyclic amino moiety, which are more
related to the phenylpropyl moiety of benzo[7]annulenamines 1–3. The
GluN2B affinity and selectivity of tertiary amines bearing small alkyl
substituents will be investigated. Finally, the effect of further sub-
stituents at the thiophene ring will be studied.
15c,d and 16b,c, respectively (Scheme 2). It should be noted that li-
thiation of the secondary amines 5c,d required an excess of n–BuLi to
afford the aldehydes 13c,d in acceptable yields (44%, 31%). The hy-
droxymethyl derivatives 15c,d and 16b,c were designed as phenol
bioisosteres, since introduction of an OH moiety directly at 2-position
of the thiophene ring would result in a thiolactone tautomer. The
concept of bioisosteric replacement of an aromatic OH moiety by a
CH2OH moiety has been successfully realized for GluN2B antagonists
with benzo[7]annulenamine structure.18
2. Synthesis
In order to introduce further substituents in 2-position, ketone 10
was reacted with NBS to afford 2-bromoketone 17 in 83% yield.
Reductive amination of the bromoketone 17 with phenylpropyl- and
phenylbutylamine and NaBH(OAc)3 led to the brominated amines 18c
and 18d. Suzuki Miyaura reaction19 of the bromoketone 17 with (4-
hydroxyphenyl)boronic acid and Pd(dppf)Cl2 led to the arylated ketone
19, which was reductively aminated with phenylpropylamine and
NaBH(OAc)3 yielding the amine 20c (Scheme 3). Due to the amphoteric
properties of aminophenol 20c, its purification turned out to be rather
problematic leading finally to a yield of only 10%. The brominated
amines 18c and 18d were envisaged, as the chloro derivative 3c
showed very high GluN2B affinity. The OH moiety of the hydro-
xyphenyl derivative 20c should imitate the phenol of the potent
For the synthesis of secondary amines 5 and tertiary amines 11 and
12 ketone 10 served as key intermediate. (Scheme 1) As previously
described, ketone 10 was prepared starting from dicarboxylic acid 9 in
a four-step reaction sequence comprising LiAlH4 reduction, transfor-
mation of diol into dibromide by PBr3, reaction of dibromide with di-
methyl 3-oxoglutarate and, finally, ester hydrolysis and decarboxyla-
15
tion. HYPERLINK "SPS:refid::bib15"
However, the synthesis of dicarboxylic acid 9 by carboxylation of
thiophene-2-carboxylic acid (7)16 with n-BuLi and CO2 gave only very
low yields of approx. 5%.15 The low yield was due to formation of
thiophene-2,5-dicarboxylic acid as side product, which was very
2

S. Baumeister, et al.
Bioorganic&MedicinalChemistryxxx(xxxx)xxxx
Scheme 1. Synthesis of amines 5, 11 and 12.
Reagents and reaction conditions: (a) 1. n–BuLi,
THF, −78 °C, 1.5 h, 2. CO2, THF, −78 °C → rt,
6 h, 5%. (b) 1. n–BuLi, THF, –78 °C, 1,5h, 2. CO2,
THF, –78 °C → rt, 24 h, 77%. (c) 4 steps ac-
cording to Ref.15: 1. LiAlH4, reflux; 2. PBr3, 0 °C;
3. dimethyl 3-oxoglutarate, K2CO3, reflux; 4.
HCl. (d) Ph(CH2)nNH2, NaBH(OAc)3, CH2Cl2, rt,
20 h, 57–73%. (e) H2C]O, NaBH(OAc)3, rt,
24–116 h, 71–95%. (f) H3CCH]O, NaBH(OAc)3,
rt, 20–24 h, 27–87%.
GluN2B antagonists 3a, ifenprodil and Ro 25–6981, even if the distance
between the H-bond donating OH moiety to the basic amine is con-
siderably increased in 20c.
group and the terminal phenyl ring. After forming a strong H-bond
interaction between the protonated amino moiety and the carbonyl
moiety of Gln110, the terminal phenyl ring of the phenylpropyl side
chain can nicely occupy a lipophilic pocket of the ifenprodil binding
12–14
site. HYPERLINK "SPS:refid::bib12_bib13_bib14"
3. Receptor affinity
Bioisosteric replacement of the benzene ring of benzo[7]annulena-
mine 2 (Ki = 16 nM, Fig. 1)13,14 by the thiophene ring led to 5c with
increased GluN2B affinity (Ki = 5.9 nM). Even the more electron rich
phenol 3a (Ki = 28 nM, Fig. 1)13,14 shows lower GluN2B affinity in-
dicating that the electron density of the annulated aromatic ring alone
is not responsible for the high GluN2B affinity of thiophene derivatives
5c and 11c.
3.1. GluN2B affinity
The affinity towards GluN2B subunit containing NMDA receptors
was determined in receptor binding studies using the radioligand [3H]
ifenprodil. Membrane fragments containing NMDA receptors with two
GluN1a and two GluN2B subunits served as receptor material. These
membrane fragments were obtained from mouse fibroblast cells (L(tk-)
cells) stably transfected with the dexamethasone-inducible eukaryotic
expression vectors pMSG GluN1a, pMSG GluN2B (1:5 ratio).20 The
GluN2B affinity of the newly synthesized [7]annulene[b]thiophenes
together with some reference compounds is given in Table 1.
In the series of homologous secondary amines 5 the phenylpropy-
lamine 5c (Ki = 5.9 nM) and phenylbutylamine 5d (Ki = 11 nM) show
very high GluN2B affinity, which is in the same range as the GluN2B
affinity of the lead compounds ifenprodil (Ki = 10 nM) and eliprodil
(Ki = 13 nM). A shorter distance between the basic amino moiety and
the terminal phenyl ring as in the benzylamine 5a (Ki = 26 nM) and
phenylethylamine 5b (Ki = 33 nM) reduced the GluN2B affinity 3–6-
fold.
Introduction of a hydroxymethyl moiety as H-bond donating func-
tional group imitating a phenolic OH moiety resulted in considerably
reduced GluN2B affinity. The phenylpropylamines 15c and 16c showed
Ki values of 183 and 141 nM, respectively, whereas the corresponding
shorter phenylethylamine 16b and longer phenylbutylamine 15d have
Ki values higher than 700 nM.
For benzo[7]annulen-7-amines a Cl-atom increased the GluN2B af-
finity up to the low nanomolar range (3c, Ki = 2.1 nM). Therefore, the
Br-derivatives 18c and 18d were envisaged. The GluN2B affinity of
both Br-derivatives 18c and 18d is approx. two-fold reduced compared
to the GluN2B affinity of the unsubstituted derivatives 5c and 5d.
The introduction of a phenol as enlarged H-bond donating system
(20c) led to decreased GluN2B affinity.
The same trend was found for the homologous series of tertiary
methylamines 11a-d and ethylamines 12a-d. Whereas the methylated
phenylpropyl- and -butylamines 11c and 11d reveal almost the same
GluN2B affinity as the secondary amines 5c and 5d, the corresponding
ethyl derivatives 12c and 12d show considerably lower GluN2B affi-
nity. The high GluN2B affinity of the phenylpropylamines 5c and 11c is
explained by the optimal CH2CH2CH2-distance between the amino
3.2. σ1- and σ2-receptor affinity
Due to the high σ affinity of several GluN2B ligands including
ifenprodil,21 the σ1 and σ2 affinity of the thiophene derivatives were
recorded as well in receptor binding studies. In the σ1 and σ2 assays,
[3H](+)-pentazocine and [3H]di-o-tolylguanidine (+excess of
Scheme 2. Synthesis of hydroxymethyl substituted [7]annuleno[b]thiophenes 15 and 16. Reagents and reaction conditions: (a) n-BuLi, 1-formylpiperidine, THF, 1 h,
19–44%. (b) NaBH4, CH3OH, rt, 3–4 h, 47–84%
3

S. Baumeister, et al.
Bioorganic&MedicinalChemistryxxx(xxxx)xxxx
Scheme 3. Introduction of further sub-
stituents in 2-position of [7]annuleno[b]
thiophenes. Reagents and reaction condi-
tions: (a) NBS, CH2Cl2, rt, 18 h, 83%. (b) Ph
(CH2)nNH2, NaBH(OAc)3, CH2Cl2, rt, 20 h,
73–74%. (c) (4–hydroxyphenyl)boronic
acid, Pd(dppf)Cl2, K2CO3, H2O, THF, 24 h,
27%. (d) Ph(CH2)3NH2, NaBH(OAc)3,
CH2Cl2, rt, 20 h, 10%.
receptors the methylamines 11c (≈2-fold) and 11d (≈1.5–2-fold) as
well as the bromo derivative 18c (≈3-fold) are the most promising
GluN2B ligands. The ethylamines 12c (≈2-3-fold) and 12d (≈3-4-fold)
represent the most σ1 selective ligands of this series. A weak σ2 pre-
ference was found for the secondary amines 5d [2-fold (GluN2B), 10-
fold (σ1)] and 15c [6-fold (GluN2B), 2-fold (σ1)].
Table 1
GluN2B and σ receptor affinity of [7]annuleno[b]thiophen-6-amines.
Compd.
R1
R2
n
Ki
GluN2B
SEM [nM] (n = 3)
4. Conclusion
σ1
σ2
Bioisosteric replacement of the benzene ring of the benzo[7]annu-
lene structure of potent GluN2B ligands 2 and 3 by a thiophene ring was
well tolerated by the ifenprodil binding site of NMDA receptors con-
taining GluN2B subunits. Whereas the benzene derivative 2 displayed a
Ki-value of 16 nM, the GluN2B affinity of the thiophene annulated
analog 5c is almost 3-fold higher (Ki = 5.9 nM). For the thiophene
derivatives an OH moiety in benzylic position as in 1 (Ki = 12 nM) was
not necessary to achieve high GluN2B affinity.
5a15
5b
H
H
1
2
3
4
1
2
3
4
1
2
3
4
3
4
2
3
3
4
3
26
3
79
11
50
23
10
H
H
33
2
133
56
5c
H
H
5.9
11
0.6 187
5.1
5.7
91
2.1
5d
H
H
3
62
49
9
2.9
11a
11b
11c
11d
12a
12b
12c
12d
15c
15d
16b
16c
18c
18d
20c
CH3
CH3
CH3
CH3
C2H5
C2H5
C2H5
C2H5
H
H
72
7
17
2
16
H
130
6.0
9.0
61
16 42
63
20
3
H
0.3 10
2.1 17
2
13
H
3
12
2
H
2
60
2
149
141
33
40
A hydroxymethyl moiety in 2-position of the thiophene ring (15c:
Ki = 183 nM) cannot be regarded as bioisosteric to a phenolic OH
moiety (2a: Ki = 28 nM). Introduction of a Cl-atom in 2-position of
benzo[7]annulenamines (3c: Ki = 2.1 nM) as well as introduction of a
Br-atom in 2-position of thiophene derivatives (18c: Ki = 13 nM) re-
sulted in very high GluN2B affinity.
H
196
51
12 59
8.0
6
H
17
17
5
H
33
13
12
2
46
11
2
CH2OH
CH2OH
CH2OH
CH2OH
Br
183#
764#
726#
141#
13
61
14
30
H
84†
56†
6.4†
41
73†
48†
21†
43
CH3
CH3
H
Unexpectedly, a parallel development of GluN2B affinity and σ af-
finity, in particular σ2 affinity, was observed upon structural mod-
ifications. Thus, a slightly preferred interaction with the ifenprodil
binding site of GluN2B subunit containing NMDA receptors could only
be observed for the methylamines 11c (≈2-fold) and 11d
(≈1.5–2–fold) and the bromo derivative 18c (≈3-fold). On the other
hand, the tertiary ethylamines 12c and 12d showed a 3-fold preference
for σ1 over GluN2B receptors. A 2- and 6-fold preference for σ2 over
GluN2B receptors was detected for secondary phenylbutylamine 5d and
hydroxymethyl derivative 15c, respectively.
7
15
2
11
3
H
Br
23
0.3
14
13
H
60#
181
63
ifenprodil
eliprodil
10
13
nd
nd
nd
0.7
2.5
125
nd
24 98
34
nd
(+)-pentazocine
haloperidol
5.4
6.3
89
0.5 nd
1.6 78
2.3
18
di-o-tolylguanidine
29
57
nd = not determined.
#
†
Due to low GluN2B affinity, Ki values were recorded only once.
Due to low GluN2B affinity and insufficient purity, the σ affinity of the
5. Experimental
corresponding compounds was not further pursued.
5.1. Chemistry, general
(+)-pentazocine) were employed as radioligands and membrane pre-
parations from guinea pig brain and rat liver as receptor material, re-
spectively.22–24
Unless otherwise noted, moisture sensitive reactions were con-
ducted under dry nitrogen. CH2Cl2 was distilled over CaH2·THF was
distilled over sodium/benzophenone. Et2O and toluene were dried over
molecular sieve 0.4 Å. Thin layer chromatography (tlc): Silica gel 60
F254 plates (Merck). Flash chromatography (fc): Silica gel 60,
40–64 µm (Merck); parentheses include: diameter of the column (d),
length of the stationary phase, fraction size (V), eluent. Melting point:
Melting point apparatus Mettler Toledo MP50 Melting Point System,
uncorrected. MS: microOTOF–Q II (Bruker Daltonics); APCI, atmo-
spheric pressure chemical ionization. IR: FT-IR spectrophotometer
MIRacle 10 (Shimadzu) equipped with ATR technique. Nuclear mag-
netic resonance (NMR) spectra were recorded on Agilent 600-MR
(600 MHz for 1H, 151 MHz for 13C) or Agilent 400-MR spectrometer
Unexpectedly, the σ1 and σ2 affinities of the homologous series of
phenylalkylamines 5, 11 and 12 exhibited the same trends found for
GluN2B affinity: Phenylpropyl- and phenylbutylamines showed high σ1
and σ2 affinities, whereas the σ1 and σ2 affinities of the shorter homo-
logs were lower. Although the compounds have been designed as
GluN2B ligands, some compounds displayed higher σ1 and/or σ2 affi-
nity than GluN2B affinity (e.g. 5d: Ki(GluN2B)
= 11 nM,
Ki(σ2) = 5.7 nM; 12c: Ki(GluN2B) = 51 nM, Ki(σ1) = 17 nM;
Ki(σ2) = 33 nM). The hydroxymethyl derivatives 15c and 16c showed
an even higher preference for both σ1 and σ2 receptors over GluN2B
receptors.
With respect to selectivity for GluN2B receptors over σ1 and σ2
(400 MHz for 1H, 101 MHz for 13C);
δ in ppm related to
4

S. Baumeister, et al.
Bioorganic&MedicinalChemistryxxx(xxxx)xxxx
tetramethylsilane and measured referring to CHCl3 (δ = 7.26 ppm (1H
NMR) and δ = 77.2 ppm (13C NMR)), CHD2OD (δ = 3.31 ppm (1H
NMR) and δ = 49.0 ppm (13C NMR)) and DMSO‑d6 (δ = 2.54 ppm (1H
NMR) and δ = 39.5 ppm (13C NMR)); coupling constants are given with
0.5 Hz resolution; the assignments of 13C and 1H NMR signals were
supported by 2-D NMR techniques where necessary.
(d, J = 5.0 Hz, 1H, 3-Hthioph), 6.86 (d, J = 5.0 Hz, 1H, 2-Hthioph),
7.19–7.24 (m, 3H, 2,4,6-HPh), 7.28–7.33 (m, 2H, 3,5-HPh). A signal for
the NH proton is not seen in the spectrum. 13C NMR (101 MHz, CDCl3):
δ (ppm) = 25.5 (C-8), 26.4 (C-4), 34.0 (C-5), 34.4 (C-7), 36.7 (CH2-
CH2-Ph), 48.5 (CH2-CH2-Ph), 61.1 (C-6), 119.9 (C-2thioph), 126.3 (C-
4Ph), 128.6 (C-3Ph, C-5Ph), 128.8 (C-2Ph, C-6Ph), 130.4 (C-3thioph), 138.8
(C-3athioph), 139.9 (C-8thioph), 140.1 (C-1Ph). Exact MS (APCI): m/
z = 272.1453 (calcd. 272.1467 for C17H22NS+ [M+H]+). FT-IR
(neat): ṽ (cm−1) = 3023 (NeH), 2922 (CeH).
5.2. HPLC method for the determination of purity
Pump: LPG-3400SD, degasser: DG-1210, autosampler: ACC-3000 T,
UV-detector:
5.3.4. N-(3-Phenylpropyl)-5,6,7,8-tetrahydro-4H-[7]annuleno[b]
thiophen-6-amine (5c)
VWD-3400RS, interface: DIONEX UltiMate 3000, data acquisition:
Chromeleon 7 (Thermo Fisher Scientific); column: LiChrospher® 60 RP-
select B (5 µm), LiChroCART® 250–4 mm cartridge; guard column:
LiChrospher® 60 RP-select B (5 µm), LiChroCART® 4–4 mm cartridge
(No.: 1.50963.0001), manu-CART® NT cartridge holder; flow rate:
1.0 mL/min; injection volume: 5.0 µL; detection at λ = 210 nm; sol-
vents: A: method 1: water with 0.05% (v/v) trifluoroacetic acid;
method 2: water; B: method 1: acetonitrile with 0.05% (v/v) tri-
fluoroacetic acid; method 2: acetonitrile: gradient elution: (A%):
0–4 min: 90%, 4–29 min: 90 → 0%, 29–31 min: 0%, 31–31.5 min: 0 →
90%, 31.5–40 min: 90%. The purity of all compounds was determined
by this method. The purity of all test compounds is higher than 95%
(unless otherwise noted).
Ketone 10 (60 mg, 0.36 mmol) was dissolved in dry CH2Cl2 (6 mL).
Under N2, 3–phenylpropan-1-amine (82 μL, 0.58 mmol) and NaBH
(OAc)3 (122 mg, 0.58 mmol) were added and the mixture was stirred
for 3 h at room temperature. A saturated NaHCO3 solution (aq., 10 mL)
was added. The mixture was extracted with CH2Cl2 (3 × 10 mL), the
organic layer was dried (Na2SO4) and concentrated in vacuo. The re-
sidue was purified by flash column chromatography (ø = 0,5 cm,
l = 15 cm, fraction size = 3 mL, cyclohexane/ethyl acetate 4:1 + 1%
N,N-dimethylethanamine, Rf = 0.18). Colorless oil, yield 75 mg (73%),
Purity (HPLC): 99%, (tR = 18.9 min), C18H23NS (285.5 g/mol). 1H
NMR (600 MHz, CDCl3): δ (ppm) = 1.36–1.47 (m, 2H, 5-H, 7-H), 1.82
(quint, J = 7.3 Hz, 2H, NCH2CH2CH2Ph), 1.92–2.02 (m, 2H, 5-H, 7-H),
2.48 (ddd, J = 15.4/11.3/2.0 Hz, 1H, 4-H), 2.67 (m, 5H, 8-H,
NCH2CH2CH2Ph), 2.73 (tt, J = 9.3/3.0 Hz, 1H, 6-H), 2.85 (ddd,
J = 15.4/7.7/1.9 Hz, 1H, 4-H), 2.92 (ddd, J = 15.8/7.7/2.0 Hz, 1H, 8-
H), 6.72 (d, J = 5.1 Hz, 1H, 3-Hthioph), 6.84 (d, J = 5.0 Hz, 1H, 2-
5.3. Synthetic procedures
5.3.1. Thiophene-2,3-dicarboxylic acid (9)16
n-BuLi (7.8 mL, 20 mmol, 2.5 mol/L) was added dropwise to a
stirring solution of thiophene-3-carboxylic acid (8, 1 g, 8 mmol) in dry
THF (22 mL) at −78 °C. After 2 h, solid dry ice was added. After an-
other 30 min, the cooling bath was removed, and the mixture could
warm to ambient temperature. HCl (aq., 1 M, 50 mL) was added. The
mixture was extracted with ethyl acetate (3 × 25 mL), dried (Na2SO4)
and concentrated in vacuo. The resulting solid was used without further
purification. Rf = 0.06 (CH2Cl2/ MeOH 1:1 + 1% HCOOH). Colorless
Hthioph), 7.14–7.19 (m, 3H, 2,4,6-HPh), 7.23–7.27 (m, 2H, 3,5-HPh). A
signal for the NH proton is not seen in the spectrum. 13C NMR
(151 MHz, CDCl3):
δ (ppm) = 25.5 (C-8), 26.3 (C-4), 32.0
(NCH2CH2CH2Ph), 33.8 (NCH2CH2CH2Ph), 34.0 (C-7), 34.4 (C-5), 46.7
(NCH2CH2CH2Ph), 61.2 (C-6), 119.8 (C-2thioph), 125.9 (C-4Ph), 128.4
(2C, C-3Ph, C-5Ph), 128.5 (2C, C-2Ph, C-6Ph), 130.3 (C-3thioph), 138.7 (C-
3athioph), 139.9 (C-8athioph), 142.2 (C-1Ph). Exact MS (APCI): m/
z = 286.1621 (calcd. 286.1624 for C18H24NS+ [M+H]+). FT-IR
(neat): ṽ (cm−1) = 3024 (NeH), 2924 (CeH).
solid, mp 250 °C, yield 1.03
g (77%), Purity (HPLC): 75%,
(tR
=
16.8 min), C6H4O4S (172.2 g/mol). 1H NMR (400 MHz,
MeOH‑d4): δ (ppm) = 7.55 (d, J = 5.3 Hz, 1H, 4Hthioph), 7.60 (d,
J = 5.3 Hz, 1H, 5Hthioph). A signal for the CO2H proton is not seen in
the spectrum. 13C NMR (101 MHz, MeOH‑d4): δ (ppm) = 131.3 (C-5),
133.3 (C-4), 136.9 (C-2 or C-3), 141.9 (C-2 or C-3), 166.1 (3-CO2H),
167.7 (2-CO2H). Exact MS (APCI): m/z = 172.9897 (calcd. 172.9903
for C6H5O4S + [M+H]+). FT-IR (neat): ṽ (cm−1) = 1670 (C]O).
5.3.5. N-(4-Phenylbutyl)-5,6,7,8-tetrahydro-4H-[7]annuleno[b]thiophen-
6-amine (5d)
Ketone 19 (33.4 mg, 0.20 mmol) was dissolved in CH2Cl2 (6 mL).
Under N2, 4–phenylbutan-1-amine (51 μL, 0.32 mmol) and NaBH
(OAc)3 (68 mg, 0.32 mmol) were added and the mixture was stirred for
3 h at room temperature. A saturated NaHCO3 solution (aq., 10 mL) was
added. The mixture was extracted with CH2Cl2 (3 × 10 mL), the or-
ganic layer was dried (Na2SO4) and concentrated in vacuo. The residue
was purified by flash column chromatography (ø = 1 cm, l = 12 cm,
fraction size = 3 mL, cyclohexane/ethyl acetate 4:1 + 1% N,N-di-
methylethanamine, Rf = 0.13). Colorless oil, yield 37 mg (62%), Purity
(HPLC): 96.6%, (tR = 19.3 min), C19H25NS (299.5 g/mol). 1H NMR
(400 MHz, CDCl3): δ (ppm) = 1.37–1.50 (m, 2H, 5-H, 7-H), 1.50–1.60
(m, 2H, NCH2CH2CH2CH2Ph), 1.63–1.72 (m, 2H, NCH2CH2CH2CH2Ph),
1.94–2.06 (m, 2H, 5-H, 7-H), 2.51 (ddd, J = 15.5/11.3/2.0 Hz, 1H, 4-
H), 2.60–2.71 (m, 5H, 8-H, NCH2CH2CH2CH2Ph), 2.72–2.83 (m, 1H, 6-
H), 2.88 (ddd, J = 15.4/7.7/2.0 Hz, 1H, 4-H), 2.95 (ddd, J = 15.9/7.6/
2.1 Hz, 1H, 8-H), 6.75 (d, J = 5.0 Hz, 1H, 3-Hthioph), 6.87 (d,
J = 5.0 Hz, 1H, 2-Hthioph), 7.15–7.20 (m, 3H, 2,4,6-HPh), 7.26–7.30 (m,
5.3.2. 4,5,7,8-Tetrahydro-[7]annuleno[b]thiophen-6-one (10)15
Ketone 10 was prepared in three reaction steps from dicarboxyic
acid 9 as described in Ref.15
5.3.3. N-(2-Phenylethyl)-5,6,7,8-tetrahydro-4H-[7]annuleno[b]thiophen-
6-amine (5b)
Ketone 10 (58.2 mg, 0.35 mmol) was dissolved in dry CH2Cl2
(4 mL). Under N2, 2–phenylethan-1-amine (71 μL, 0.56 mmol) was
added and the mixture was stirred for 60 min at room temperature.
Afterwards, NaBH(OAc)3 (118.7 mg, 0.56 mmol) was added and the
mixture was stirred overnight at room temperature. A saturated
NaHCO3 solution (aq., 10 mL) was added. The mixture was extracted
with CH2Cl2 (3 × 10 mL), the organic layer was dried (Na2SO4) and
concentrated in vacuo. The residue was purified by flash column
chromatography (ø = 0.5 cm, l = 10 cm, fraction size = 5 mL, cy-
2H, 3,5-HPh). A signal for the NH proton is not seen in the spectrum. 13
C
NMR (101 MHz, CDCl3): δ (ppm) = 25.6 (C-8), 26.4 (C-4), 29.5
(NCH2CH2CH2CH2Ph), 30.2 (NCH2CH2CH2CH2Ph), 34.1 (C-7), 34.5 (C-
5), 36.0 (NCH2Ch2CH2CH2Ph), 47.2 (NCH2CH2CH2CH2Ph), 61.3 (C-6),
119.8 (C-2thioph), 125.9 (C-4Ph), 128.4 (2C, C-3Ph, C-5Ph), 128.6 (2C, C-
clohexane/ethyl acetate 4:1
+
1% N,N-dimethylethanamine,
Rf = 0.13). Colorless oil, yield 54 mg (57%), Purity (HPLC): 96.2%,
(tR = 18.2 min), C17H21NS (271.4 g/mol). 1H NMR (400 MHz, CDCl3):
δ (ppm) = 1.37–1.52 (m, 2H, 5-H, 7-H), 1.93–2.06 (m, 2H, 5-H, 7-H),
2.50 (ddd, J = 15.6/11.4/2.0 Hz, 1H, 4-H), 2.66 (ddd, J = 15.9/11.1/
1.8 Hz, 1H, 8-H), 2.75–2.99 (m, 7H, 4-H, 6-H, 8-H, NCH2CH2Ph), 6.74
2
Ph, C-6Ph), 130.4 (C-3thioph), 138.8 (C-3athioph), 140.0 (C-8athioph),
142.6 (C-1Ph). Exact MS (APCI): m/z = 300.1764 (calcd. 300.1780 for
C
19H26NS+ [M+H]+). FT-IR (neat): ṽ (cm−1) = 3020 (NeH), 2924
(CeH).
5

S. Baumeister, et al.
Bioorganic&MedicinalChemistryxxx(xxxx)xxxx
5.3.6. N-Benzyl-N-methyl-5,6,7,8-tetrahydro-4H-[7]annuleno[b]thiophen-
6-amine (11a)
(m, 2H, 5-H, 7-H), 1.78–1.84 (m, 2H, NCH2CH2CH2Ph), 1.99–2.08 (m,
2H, 5-H, 7-H), 2.25 (s, 3H, NCH3), 2.41–2.47 (m, 1H, 4-H), 2.49 (t,
J = 7.9 Hz, 2H, NCH2CH2CH2Ph), 2.60–2.66 (m, 3H, NCH2CH2CH2Ph,
8-H), 2.71 (tt, J = 11.0/2.4 Hz, 1H, 6-H), 2.92 (ddd, J = 10.1/6.5/
1.9 Hz, 1H, 4-H), 2.95 (ddd, J = 10.5/6.5/1.9 Hz, 1H, 8-H), 6.74 (d,
J = 5.1 Hz, 1H, 3-Hthioph), 6.89 (d, J = 5.0 Hz, 1H, 2-Hthioph),
7.13–7.17 (m, 1H, 4-HPh), 7.18–7.22 (m, 2H, 2,6-HPh), 7.23–7.27 (m,
2H, 3,5-HPh). 13C NMR (151 MHz, MeOH‑d4): δ (ppm) = 27.6 (C-8),
28.5 (C-4), 30.7 (NCH2CH2CH2Ph), 30.8 (C-5), 31.1 (C-7), 34.7
(NCH2CH2CH2Ph), 37.9 (NCH3), 54.0 (NCH2CH2CH2Ph), 68.9 (C-6),
120.6 (C-2thioph), 126.8 (C-4Ph), 129.4 (2C, C–3Ph, C–5Ph), 129.4 (2C, C-
2Ph, C-6Ph), 131.1 (C-3thioph), 139.5 (C-3athioph), 141.1 (C-8athioph),
143.3 (C–1Ph). Exact MS (APCI): m/z = 300.1776 (calcd. 300.1780 for
Benzylamine 5a (70 mg, 0.27 mmol) was dissolved in ethanol
(10 mL). A formaldehyde solution (aq., 37%, 33 μL, 0.44 mmol) and
aBH(OAc)3 (92 mg, 0.44 mmol) were added and the mixture was stirred
overnight at room temperature. A saturated NaHCO3 solution (aq.,
10 mL) was added. The mixture was extracted with CH2Cl2
(3 × 10 mL), the organic layer was dried (Na2SO4) and concentrated in
vacuo. The residue was purified by flash column chromatography
(ø = 1 cm, l = 15 cm, fraction size = 3 mL, cyclohexane/ethyl acetate
2:1, Rf = 0.5). Colorless solid, yield 66 mg (90%), Purity (HPLC):
92.8%, (tR = 16.6 min), C17H21NS (271.4 g/mol). 1H NMR (600 MHz,
CDCl3): δ (ppm) = 1.48–1.62 (m, 2H, 5-H, 7-H), 2.14 (ddd, J = 14.4/
5.2/1.9 Hz, 2H, 5-H, 7-H), 2.21 (s, 3H, NCH3), 2.40–2.48 (m, 1H, 4-H),
2.60–2.66 (m, 1H, 8-H), 2.72 (tt, J = 10.9/2.4 Hz, 1H, 6-H), 2.98 (ddd,
J = 15.1/6.5/2.1 Hz, 2H, 4-H, 8–H), 3.58 (s, 2H, PhCH2N), 6.78 (d,
J = 5.0 Hz, 1H, 3-Hthioph), 6.88 (d, J = 5.0 Hz, 1H, 2-Hthioph), 7.24 (tt,
J = 8.6/1.6 Hz, 1H, 4-HPh), 7.29–7.38 (m, 4H, 2,3,5,6-HPh). 13C NMR
(151 MHz, CDCl3): δ (ppm) = 27.0 (C-8), 27.8 (C-4), 30.3 (C-5), 30.8
(C-7), 37.8 (NCH3), 57.8 (PhCH2N), 67.6 (C-6), 119.7 (C-2thioph), 126.9
(C-4Ph), 128.4 (2C, C–3Ph, C-5Ph), 128.8 (2C, C-2Ph, C-6Ph), 130.4 (C-
C
19H26NS+ [M+H]+). FT-IR (neat): ṽ (cm−1) = 2928 (CeH), 1450
(CeH).
5.3.9. N-Methyl-N-(4-phenylbutyl)-5,6,7,8-tetrahydro-4H-[7]annuleno[b]
thiophen-6-amine (11d)
Phenylbutylamine 5d (50 mg, 0.17 mmol) was dissolved in me-
thanol (10 mL). A formaldehyde solution (aq., 37%, 20, μL, 0.27 mmol)
and NaBH(OAc)3 (58 mg, 0.27 mmol) were added and the mixture was
stirred for 44 h at room temperature. A saturated NaHCO3 solution (aq.,
10 mL) was added. The mixture was extracted with CH2Cl2
(3 × 10 mL), the organic layer was dried (Na2SO4) and concentrated in
vacuo. The residue was purified by flash column chromatography
(ø = 1 cm, l = 15 cm, fraction size = 3 mL, cyclohexane/ethyl acetate
4:1 + 1% N,N-dimethylethanamine, Rf = 0.44).
3
thioph), 139.0 (C-3athioph), 140.1 (C-8athioph), 140.3 (C-1Ph). Exact MS
(APCI): m/z = 272.1464 (calcd. 272.1467 for C17H22NS+ [M+H]+).
FT-IR (neat): ṽ (cm−1) = 2924 (CeH).
5.3.7. N-Methyl-N-(2-phenylethyl)-5,6,7,8-tetrahydro-4H-[7]annuleno[b]
thiophen-6-amine (11b)
Phenylethylamine 5b (73 mg, 0.27 mmol) was dissolved in ethanol
(10 mL). A formaldehyde solution (aq., 37%, 33 μL, 0.44 mmol) and
NaBH(OAc)3 (111 mg, 0.53 mmol) were added and the mixture was
stirred for 48 h at room temperature. A saturated NaHCO3 solution (aq.,
10 mL) was added. The mixture was extracted with CH2Cl2
(3 × 10 mL), the organic layer was dried (Na2SO4) and concentrated in
vacuo. The residue was purified by flash column chromatography
(ø = 1 cm, l = 15 cm, fraction size = 3 mL, cyclohexane/ethyl acetate
1:1 + 0,5% N,N–dimethylethanamine, Rf = 0.33). Yellow oil, yield
68 mg (88%), Purity (HPLC): 96.5%, (tR = 18.2 min), C18H23NS
(285.5 g/mol). 1H NMR (600 MHz, CDCl3): δ (ppm) = 1.40–1.54 (m,
3H, 2 × 5-H, 7-H), 1.98–2.08 (m, 1H, 7-H), 2.35 (s, 3H, NCH3),
2.41–2.46 (m, 1H, 4-H), 2.62 (ddd, J = 15.0/12.0/2.0 Hz, 1H, 8-H),
2.65–2.71 (m, 3H, 6-H, NCH2CH2Ph), 2.78 (t, J = 7.0 Hz, 2H,
NCH2CH2Ph), 2.92 (ddd, J = 15.2/6.5/2.0 Hz, 1H, 4-H), 2.97 (ddd,
J = 15.6/6.5/2.1 Hz, 1H, 8-H), 6.76 (d, J = 5.0 Hz, 1H, 3-Hthioph), 6.87
(d, J = 5.0 Hz, 1H, 2-Hthioph), 7.18–7.22 (m, 3H, 2,4,6-HPh), 7.28 (td,
Colorless oil, yield 36 mg (71%), Purity (HPLC): 99.5%,
(tR = 18.7 min), C20H27NS (313.5 g/mol). 1H NMR (400 MHz,
MeOH‑d4): δ (ppm) = 1.28–1.47 (m, 2H, 5-H, 7-H), 1.47–1.57 (m, 2H,
NCH2CH2CH2CH2Ph), 1.59–1.69 (m, 2H, NCH2CH2CH2CH2Ph),
1.97–2.09 (m, 2H, 5-H, 7-H), 2.22 (s, 3H, NCH3), 2.39–2.50 (m, 3H, 4-
H,
NCH2CH2CH2CH2Ph),
2.57–2.72
(m,
4H,
6-H,
8-H,
NCH2CH2CH2CH2Ph), 2.89–2.99 (m, 2H, 4-H, 8-H), 6.74 (d,
J = 5.1 Hz, 1H, 3-Hthioph), 6.89 (d, J = 5.0 Hz, 1H, 2-Hthioph),
7.11–7.20 (m, 3H, 2,4,6–HPh), 7.22–7.27 (m, 2H, 3,5-HPh). 13C NMR
(101 MHz, MeOH‑d4):
δ
(ppm)
=
27.6 (C-8), 28.3
(NCH2CH2CH2CH2Ph), 28.6 (C-4), 30.6 (NCH2CH2CH2CH2Ph), 30.7 (C-
5), 31.1 (C-7), 36.7 (NCH2CH2CH2CH2Ph), 37.9 (NCH3), 54.3
(NCHCH2CH2CH2Ph), 68.7 (C-6), 120.6 (C-2thioph), 126.7 (C-4Ph),
129.3 (2C, C-3Ph, C-5Ph), 129.5 (2C, C-2Ph, C-6Ph), 131.1 (C–3thioph),
139.5 (C-3athioph), 141.1 (C-8athioph), 143.6 (C-1Ph). Exact MS (APCI):
m/z = 314.1935 (calcd. 314.1937 for C20H28NS+ [M+H]+). FT-IR
(neat): ṽ (cm−1) = 2928 (CeH), 1450 (CeH).
J
=
7.3/1.3 Hz, 2H, 3,5-HPh). 13C NMR (151 MHz, CDCl3): δ
(ppm)
=
27.0 (C-8), 27.9 (C-4), 30.1 (C-5), 30.5 (C-7), 35.5
5.3.10. N-Benzyl-N-ethyl-5,6,7,8-tetrahydro-4H-[7]annuleno[b]thiophen-
6-amine (12a)
(NCH2CH2Ph), 37.8 (NCH3), 55.9 (NCH2CH2Ph), 68.2 (C-6), 119.8 (C-
2
6
1
thioph), 126.1 (C-4Ph), 128.5 (2C, C-3Ph, C-5Ph), 128.9 (2C, C-2Ph, C-
Ph), 130.4 (C-3thioph), 138.9 (C–3athioph), 140.1 (C-8athioph), 140.7 (C-
Benzylamine 5a (70 mg, 0.26 mmol) was dissolved in CH2Cl2
(6 mL). Under N2, acetaldehyde (46 μL, 0.83 mmol) and NaBH(OAc)3
(90 mg, 0.42 mmol) were added and the mixture was stirred over night
at room temperature. A saturated NaHCO3 solution (aq., 10 mL) was
added. The mixture was extracted with CH2Cl2 (3 × 10 mL), the or-
ganic layer was dried (Na2SO4) and concentrated in vacuo. The residue
was purified by flash column chromatography (ø = 0.5 cm, l = 18 cm,
fraction size = 3 mL, cyclohexane/ethyl acetate 2:1 + 0,5% N,N-di-
methylethanamine, Rf = 0.64). Yellow oil, yield 19 mg (27%), Purity
(HPLC): 91.5%, (tR = 18.2 min), C18H23NS (285.5 g/mol). 1H NMR
(600 MHz, CDCl3): δ (ppm) = 1.01 (t, J = 7.1 Hz, 3H, NCH2CH3),
1.41–1.55 (m, 2H, 5-H, 7-H), 2.10 (m, 2H, 5-H, 7-H), 2.40 (ddd,
J = 14.6/12.3/1.9 Hz, 1H, 4-H), 2.52 (q, J = 7.1 Hz, 2H, NCH2CH3),
2.55–2.63 (m, 1H, 8–H), 2.72–2.77 (m, 1H, 6-H), 2.91 (ddd, J = 15.2/
6.7/1.2 Hz, 1H, 4-H), 2.96 (ddd, J = 15.6/6.4/1.2 Hz, 1H, 8-H), 3.61
(s, 2H, PhCH2N), 6.76 (d, J = 5.0 Hz, 1H, 3-Hthioph), 6.86 (d,
J = 5.0 Hz, 1H, 2-Hthioph), 7.19–7.24 (m, 1H, 4-HPh), 7.27–7.32 (m, 2H,
3,5-HPh), 7.36 (d, J = 7.5 Hz, 2H, 2,6-HPh). 13C NMR (151 MHz,
CDCl3): δ (ppm) = 14.7 (NCH2CH3), 27.2 (C-8), 28.1 (C-4), 30.7 (C-5),
Ph). Exact MS (APCI): m/z
= 286.1623 [calcd. 286.1624 for
C18H24NS+ [M+H]+). FT-IR (neat): ṽ (cm−1) = 2928 (CeH), 1442
(CeH).
5.3.8. N-Methyl-N-(3-phenylpropyl)-5,6,7,8-tetrahydro-4H-[7]annuleno
[b]thiophen-6-amine (11c)
Phenylpropylamine 5c (55 mg, 0.19 mmol) was dissolved in me-
thanol (10 mL). A formaldehyde solution (aq., 37%, 23 μL, 0.31 mmol)
and NaBH(OAc)3 (66 mg, 0.81 mmol) were added and the mixture was
stirred for 116 h at room temperature. A saturated NaHCO3 solution
(aq., 10 mL) was added and the mixture was extracted with CH2Cl2
(3 × 10 mL), the organic layer was dried (Na2SO4) and concentrated in
vacuo. The residue was purified by flash column chromatography
(ø = 1 cm, l = 15 cm, fraction size = 3 mL, dichlormethane/methanol
98:2 + 2% N,N-dimethylethanamin, Rf = 0.40). Yellow oil, yield
55 mg (95%), Purity (HPLC): 97.9%, (tR = 18.4 min), C19H25NS
(299.5 g/mol). 1H NMR (600 MHz, MeOH‑d4): δ (ppm) = 1.32–1.47
6

S. Baumeister, et al.
Bioorganic&MedicinalChemistryxxx(xxxx)xxxx
31.3 (C-7), 44.2 (NCH2CH3), 54.3 (PhCH2N), 63.9 (C-6), 119.6
5.3.13. N-Ethyl-N-(4-phenylbutyl)-5,6,7,8-tetrahydro-4H-[7]annuleno[b]
(C–2thioph), 126.6 (C-4Ph), 128.2 (2C, C-3Ph, C-5Ph), 128.4 (2C, C-2Ph, C-
thiophen-6-amine (12d)
6
1
Ph), 130.4 (C–3thioph), 139.0 (C-3athioph), 140.2 (C-8athioph), 141.8 (C-
Phenylbutylamine 5d (50 mg, 0.17 mmol) was dissolved in CH2Cl2
(6 mL). Under N2, acetaldehyde (15 μL, 0.27 mmol) and NaBH(OAc)3
(58 mg, 0.27 mmol) were added and the mixture was stirred overnight
at room temperature. A saturated NaHCO3 solution (aq., 12 mL) was
added. The mixture was extracted with CH2Cl2 (3 × 10 mL), the or-
ganic layer was dried (Na2SO4) and concentrated in vacuo. The residue
was purified by flash column chromatography (ø = 1 cm, l = 10 cm,
fraction size = 3 mL, cyclohexane/ethyl acetate 4:1 + 1% N,N-di-
methylethanamine, Rf = 0,53). Yellow oil, yield 48 mg (87%), Purity
(HPLC): 94.6%, (tR = 20.7 min), C21H29NS (327.5 g/mol). 1H NMR
(600 MHz, MeOH‑d4): δ (ppm) = 1.05 (t, J = 7.2 Hz, 3H, NCH2CH3),
1.28–1.43 (m, 2H, 7-H, 5-H), 1.44–1.52 (m, 2H, NCH2CH2CH2CH2Ph),
1.63 (quint, J = 7.6 Hz, 2H, NCH2CH2CH2CH2Ph), 1.99 (dddd,
J = 13.1/6.4/2.4/1.9 Hz, 1H, 5-H), 2.03 (dddd, J = 13.1/6.5/2.2/
1.9 Hz, 1H, 7-H), 2.38–2.49 (m, 3H, 4-H, NCH2CH2CH2CH2Ph), 2.52 (q,
Ph). Exact MS (APCI): m/z
= 286.1621 (calcd. 286.1624 for
C
18H24NS+ [M+H]+). FT-IR (neat): ṽ (cm−1) = 2924 (CeH), 1450
(CeH).
5.3.11. N-Ethyl-N-(2-phenethyl)-5,6,7,8-tetrahdro-4H-[7]annuleno[b]
thiophen-6-amine (12b)
Phenylethylamin 5b (73 mg, 0.27 mmol) was dissolved in CH2Cl2
(6 mL). Under N2, acetaldehyde (46 μL, 0.83 mmol) and NaBH(OAc)3
(92 mg, 0.44 mmol) were added and the mixture was stirred overnight
at room temperature. A saturated NaHCO3 solution (aq., 12 mL) was
added. The mixture was extracted with CH2Cl2 (3 × 6 mL), the organic
layer was dried (Na2SO4) and concentrated in vacuo. The residue was
purified by flash column chromatography (ø = 1 cm, l = 15 cm,
fraction size = 3 mL, cyclohexane/ethyl acetate: 4:1, Rf = 0.33).
Colorless oil, yield 42.1 mg (52%), Purity (HPLC): 96.2%,
(tR = 18.6 min), C19H25NS (299.5 g/mol). 1H NMR (600 MHz,
MeOH‑d4): δ (ppm) = 1.12 (t, J = 7.2 Hz, 3H, NCH2CH3), 1.35–1.48
(m, 2H, 5-H, 7-H), 2.05 (dddd, J = 13.1/6.5/2.2/2.0 Hz, 1H, 5-H), 2.09
(dddd, J = 13.2/6.5/2.3/2.0 Hz, 1H, 7-H), 2.45 (ddd, J = 14.9/12.2/
1.7 Hz, 1H, 4-H), 2.61–2.68 (m, 3H, 8-H, NCH2CH2Ph), 2.68–2.80 (m,
4H, NCH2CH2Ph, NCH2CH3), 2.87 (m, 1H, 6-H), 2.94 (ddd, J = 9.8/
6.4/1.9 Hz, 1H, 4-H), 2.96 (ddd, J = 10.1/6.5/2.0 Hz, 1H, 8-H), 6.76
(d, J = 5.0 Hz, 1H, 3-Hthioph), 6.90 (d, J = 5.0 Hz, 1H, 2-Hthioph),
7.15–7.19 (m, 1H, 4-HPh), 7.19–7.22 (m, 2H, 2,6-HPh), 7.27 (t,
J
=
7.3 Hz, 2H, NCH2CH3), 2.56–2.66 (m, 3H, 8-H,
NCH2CH2CH2CH2Ph), 2.76 (tt, J = 11.0/2.4 Hz, 1H, 6-H), 2.91 (ddd,
J = 12.7/6.3/1.7 Hz, 1H, 4-H), 2.94 (ddd, J = 12.6/6.2/1.8 Hz, 1H, 8-
H), 6.74 (d, J = 5.0 Hz, 1H, 3-Hthioph), 6.89 (d, J = 5.0 Hz, 1H, 2-
H
H
δ
thioph), 7.13 (td, J = 7.2/1.4 Hz, 1H, 4-HPh), 7.16–7.18 (m, 2H, 2,6-
Ph), 7.24 (t, J = 7.6 Hz, 2H, 3,5-HPh). 13C NMR (151 MHz, MeOH‑d4):
(ppm)
= 14.3 (NCH2CH3), 27.9 (C-8), 28.8 (C-4), 29.3
(NCH2CH2CH2CH2Ph), 30.6 (NCH2CH2CH2CH2Ph), 31.3 (C-5), 31.7 (C-
7),
36.7
(NCH2CH2CH2CH2Ph),
45.5
(NCH2CH3),
51.3
(NCH2CH2CH2CH2Ph), 65.7 (C-6), 120.6 (C-2thioph), 126.7 (C-4Ph),
129.3 (2C, C-3Ph, C-5Ph), 129.4 (2C, C-2Ph, C-6Ph), 131.1 (C–3thioph),
139.6 (C-3athioph), 141.1 (C-8athioph), 143.7 (C-1Ph). Exact MS (APCI):
m/z = 328.2086 (calcd. 328.2093 for C21H30NS+ [M+H]+). FT-IR
(neat): ṽ (cm−1) = 2932 (CeH), 1439 (CeH).
J
=
7.9 Hz, 2H, 3,5-HPh). 13C NMR (151 MHz, MeOH‑d4):
δ
(ppm) = 14.3 (NCH2CH3), 27.8 (C-8), 28.7 (C-4), 31.5 (C-5), 31.9 (C-
7), 36.8 (NCH2CH2Ph), 45.6 (NCH2CH3), 53.8 (NCH2CH2Ph), 66.1 (C-
6), 120.6 (C-2thioph), 127.0 (C-4Ph), 129.4 (2C, C-3Ph, C-5Ph), 129.8 (2C,
C-2Ph, C–6Ph), 131.1 (C-3thioph), 139.6 (C–8athioph), 141.1 (C-3athioph),
141.8 (C-1Ph). Exact MS (APCI): m/z = 300.1779 (calcd. 300.1780 for
C19H26NS+ [M+H]+). FT-IR (neat): ṽ (cm−1) = 2924 (CeH), 1443
(CeH).
5.3.14. 6-[N-(3-Phenylpropyl)amino]-5,6,7,8-tetrahydro-4H-[7]annuleno
[b]thiophene-2-carbaldehyde (13c)
n-BuLi (0.3 mL, 0.7 mmol, 2.5 mol/L) was added dropwise to a
solution of propylamine 5c (101 mg, 0.4 mmol) in dry THF (5 mL) at
0 °C. After 5 min, 1–formylpiperidine (79 µL, 0.7 mmol) was added at
0 °C. The solution was stirred for 1 h at 0 °C. Afterwards, ethyl acetate
(10 mL) was added. The organic layer was washed with brine
(3 × 5 mL), dried (Na2SO4) and concentrated in vacuo. The crude
product was purified by flash column chromatography (ø = 2 cm,
l = 15 cm, fraction size = 5 mL, cyclohexane/ethyl acetate 1:4 + 1%
N,N–dimethylethanamine, Rf = 0.11). Bright yellow oil, yield 49 mg
(44%), Purity (HPLC): 73%, (tR = 16.8 min), C19H23NOS (313.5 g/
mol). 1H NMR (400 MHz, MeOH‑d4): δ (ppm) = 1.27–1.44 (m, 2H, 5-H,
7-H), 1.80–1.90 (m, 2H, NCH2CH2CH2Ph), 2.01–2.15 (m, 2H, 5-H, 7-
H), 2.54–2.63 (m, 1H, 4-H), 2.65–2.70 (m, 4H, NCH2CH2CH2Ph),
2.74–2.84 (m, 2H, 6-H, 8-H), 2.96 (ddd, J = 15.4/7.3/1.9 Hz, 1H, 4-H),
3.04 (ddd, J = 15.9/7.3/1.9 Hz, 1H, 8-H), 7.13–7.19 (m, 1H, 4-HPh),
7.19–7.23 (m, 2H, 2,6-HPh), 7.23–7.29 (m, 2H, 3,5-HPh), 7.60 (s, 1H, 3-
Hthioph), 9.69 (s, 1H, CHO). A signal for the NH proton is not seen in the
spectrum. 13C NMR (101 MHz, MeOH‑d4): δ (ppm) = 27.1 (C-4), 27.5
(C-8), 32.5 (NCH2CH2CH2Ph), 34.3 (C-5), 34.3 (C-7), 34.7
(NCH2CH2CH2Ph), 47.4 (NCH2CH2CH2Ph), 62.5 (C-6), 126.9 (C-4Ph),
129.4 (2C, C-3Ph, C-5Ph), 129.4 (2C, C-2Ph, C-6Ph), 139.7 (C-2thioph),
141.4 (C-3thioph), 143.3 (C-1Ph), 143.8 (C-3athioph), 153.3 (C-8athioph),
184.7 (CHO). Exact MS (APCI): m/z = 314.1579 (calcd. 314.1573 for
5.3.12. N-Ethyl-N-(3-phenylpropyl)-5,6,7,8-tetrahydro-4H-[7]annuleno
[b]thiophen-6-amine (12c)
Phenylpropylamine 5c (145 mg, 0.51 mmol) was dissolved in
CH2Cl2 (12 mL). Under N2, acetaldehyde (46 μL, 0.83 mmol) and NaBH
(OAc)3 (174 mg, 0.82 mmol) were added and the mixture was stirred
overnight at room temperature. A saturated NaHCO3 solution (aq.,
20 mL) was added. The mixture was extracted with CH2Cl2
(3 × 20 mL), the organic layer was dried (Na2SO4) and concentrated in
vacuo. The residue was purified by flash column chromatography
(ø = 1 cm, l = 15 cm, fraction size = 5 mL, cyclohexane/ethyl acetate
4:1 + 1% N,N-dimethylethanamine, Rf = 0,42). Yellow oil, yield
81 mg (51%), Purity (HPLC): 97%, (tR = 19.8 min), C20H27NS
(313.5 g/mol). 1H NMR (400 MHz, MeOH‑d4): δ (ppm) = 1.05 (t,
J = 7.2 Hz, 3H, NCH2CH3), 1.27–1.44 (m, 2H, 5-H, 7-H), 1.79 (tt,
J = 10.0/6.5 Hz, 2H, NCH2CH2CH2Ph), 1.96–2.07 (m, 2H, 5-H, 7-H),
2.38–2.66 (m, 8H, NCH2CH2CH2Ph, NCH2CH3, 4-H, 8–H), 2.79 (dd,
J = 12.2/9.7 Hz, 1H, 6-H), 2.90 (td, J = 7.9/6.8/1.9 Hz, 1H, 4-H), 2.94
(ddd, J = 7.9/6.3/2.0 Hz, 1H, 8-H), 6.74 (d, J = 5.1 Hz, 1H, 3-Hthioph),
6.89 (d, J = 5.0 Hz, 1H, 2-Hthioph), 7.11–7.20 (m, 3H, 2,4,6-HPh),
7.21–7.28 (m, 2H, 3,5-HPh). 13C NMR (101 MHz, MeOH‑d4):
δ
C
19H24NOS+ [M+H]+). FT-IR (neat): ṽ (cm−1): 3395 (NeH), 2924
(ppm) = 14.4 (NCH2CH3), 27.9 (C-8), 28.8 (C-4), 31.4 (C-5), 31.8 (2C,
C-7, NCH2CH2CH2Ph), 34.8 (NCH2CH2CH2Ph), 45.6 (NCH2CH3), 50.9
(NCH2CH2CH2Ph), 66.0 (C-6), 120.6 (C-2thioph), 126.8 (C-4Ph), 129.3
(2C, C-3Ph, C–5Ph), 129.4 (2C, C-2Ph, C-6Ph), 131.1 (C-3thioph), 139.6 (C-
3athioph), 141.1 (C-8athioph), 143.5 (C–1Ph). Exact MS (APCI): m/
(CeH), 1659 (C]O).
5.3.15. 6-[N-(4-Phenylbutyl)amino]-5,6,7,8-tetrahydro-4H-[7]annuleno
[b]thiophene-2-carbaldehyde (13d)
n-BuLi (0.2 mL, 0.5 mmol, 2.5 mol/L) was added dropwise to a
solution of butylamine 5d (78 mg, 0.3 mmol) in dry THF (3 mL) at 0 °C.
After 5 min, 1–formylpiperidine (84 µL, 0.5 mmol) was added at 0 °C.
The solution was stirred for 1 h at 0 °C. Afterwards, ethyl acetate (8 mL)
z = 314.1934 (calcd. 314.1937 for C
H
20 28
NS+ [M+H]+). FT-IR
(neat): ṽ (cm−1) = 2928 (CeH), 1443 (CeH).
7

S. Baumeister, et al.
Bioorganic&MedicinalChemistryxxx(xxxx)xxxx
was added. The organic layer was washed with brine (3 × 5 mL), dried
(Na2SO4) and concentrated in vacuo. The residue was purified by flash
column chromatography (ø = 2 cm, l = 13 cm, fraction size = 3 mL,
J = 7.6 Hz, 2H, NCH2CH2CH2Ph), 2.72–2.81 (m, 2H, 8-H, 6-H), 3.02
(ddd, J = 15.2/6.6/1.9 Hz, 1H, 4-H), 3.08 (ddd, J = 15.7/6.6/1.9 Hz,
1H, 8-H), 7.16 (m, 1H, 4–HPh), 7.20–7.22 (m, 2H, 2,6-HPh), 7.25–7.29
(m, 2H, 3,5–HPh), 7.62 (s, 1H, 3-Hthioph), 9.71 (s, 1H, CHO). 13C NMR
(151 MHz, MeOH‑d4): δ (ppm) = 28.2 (C-4), 28.6 (C-8), 30.5 (C-5),
30.6 (C-7), 30.7 (NCH2CH2CH2Ph), 34.6 (NCH2CH2CH2Ph), 37.8
(NCH3), 54.0 (NCH2CH2CH2Ph), 68.4 (C-6), 126.9 (C-4Ph), 129.4 (2C,
C-3Ph, C-5Ph), 129.4 (2C, C-2Ph, C-6Ph), 139.6 (C–2thioph), 141.4 (C-
cyclohexane/ethyl acetate 1:4
+ 1% N,N-dimethylethanamine,
Rf = 0.09). Bright yellow oil, yield 25 mg (31%), Purity (HPLC): 54%,
(tR = 17.7 min), C19H23NOS (313.2 g/mol). 1H NMR (600 MHz,
MeOH‑d4): δ (ppm) = 1.30–1.38 (m, 1H, 7-H), 1.41 (dddd, J = 13.6/
11.9/10.0/1.9 Hz, 1H, 5-H), 1.53–1.64 (m, 2H, NCH2CH2CH2CH2Ph),
1.67–1.75 (m, 2H, NCH2CH2CH2CH2Ph), 2.09 (dddd, J = 13.8/7.0/
3.6/1.8 Hz, 1H, 7-H), 2.15 (dddd, J = 13.7/7.0/3.3/1.8 Hz, 1H, 5-H),
2.57–2.63 (m, 1H, 4-H), 2.64–2.72 (m, 4H, NCH2CH2CH2CH2Ph), 2.82
(m, 2H, 6-H, 8-H), 2.96–3.01 (m, 1H, 4-H), 3.03–3.09 (m, 1H, 8-H),
7.14–7.18 (m, 1H, 4-HPh), 7.18–7.22 (m, 2H, 2,6-HPh), 7.23–7.28 (m,
2H, 3,5-HPh), 7.62 (s, 1H, 3-Hthioph), 9.71 (s, 1H, CHO). A signal for the
NH proton is not seen in the spectrum. 13C NMR (151 MHz, MeOH‑d4):
δ (ppm) = 27.1 (C-4), 27.4 (C-8), 30.1 (NCH2CH2CH2CH2Ph), 30.4
3thioph), 143.3 (C-1Ph), 143.8 (C-3athioph), 153.3 (C-8athioph), 184.7
(CHO). Exact MS (APCI): m/z = 328.1732 (calcd. 328.1730 for
C
20H26NOS+ [M+H]+). FT-IR (neat): ṽ (cm−1) = 2924 (CeH), 1670
(C]O).
5.3.18. 1-{6-[N-(3-Phenylpropyl)amino]-5,6,7,8-tetrahydro-4H-[7]
annuleno[b]thiophen-2-yl}methanol (15c)
Aldehyde 13c (35 mg, 0.11 mmol) was dissolved in dry MeOH
(4 mL). Under ice cooling, NaBH4 (10 mg, 0.26 mg) was added. The
transformation was monitored by IR spectroscopy. Once the carbonyl
band (approx. 1700 cm−1) had disappeared, EtOAc (6 mL) was added.
The mixture was washed with saturated NaHCO3 (aq., 3 × 3 mL), dried
(Na2SO4) and concentrated in vacuo. The residue was purified via flash
column chromatography (ø = 1 cm, h = 10 cm, fraction size = 3 mL,
cyclohexane/ethyl acetate 1:4 + 1% DMEA). Rf = 0.45 (cyclohexane/
ethyl acetate 1:1 + 1%/N,N-dimethylethanamine). Colorless oil, yield
16 mg (47%), Purity (HPLC): 96.7%, (tR = 15.9 min), C19H25NOS
(315.5 g/mol). 1H NMR (600 MHz, MeOH‑d4): δ (ppm) = 1.26–1.34
(m, 1H, 7-H), 1.34–1.40 (m, 1H, 5-H), 1.82–1.89 (m, 2H,
NCH2CH2CH2Ph), 2.00 (dddd, J = 13.5/6.9/3.4/1.5 Hz, 1H, 7-H), 2.05
(dddd, J = 13.4/6.9/3.3/1.9 Hz, 1H, 5-H), 2.46–2.51 (m, 1H, 4-H),
2.65–2.75 (m, 6H, 6-H, 8-H, NCH2CH2CH2Ph), 2.82 (ddd, J = 15.3/
7.1/1.9 Hz, 1H, 4-H), 2.87 (ddd, J = 15.8/7.1/2.0 Hz, 1H, 8-H), 4.59
(s, 2H, CH2OH), 6.66 (s, 1H, 3-Hthioph), 7.15–7.19 (m, 1H, 4-HPh),
7.21–7.23 (m, 2H, 2,6-HPh), 7.27 (tt, J = 7.2/1.5 Hz, 2H, 3,5-HPh). A
signal for the OH and NH protons are not seen in the spectrum. 13C
NMR (151 MHz, MeOH‑d4): δ (ppm) = 26.6 (C-8), 27.4 (C-4), 32.4
(NCH2CH2CH2Ph), 34.6 (C-7), 34.7 (NCH2CH2CH2Ph), 34.9 (C-5), 47.4
(NCH2CH2CH2Ph), 59.9 (CH2OH), 63.0 (C-6), 126.9 (C-4Ph), 129.4 (2C,
C-3Ph, C-5Ph), 129.4 (2C, C-2Ph, C-6Ph), 129.6 (C-3thioph), 139.7 (C-
3athioph), 139.9 (C-2thioph), 140.7 (C–8athioph), 143.3 (C-1Ph). Exact MS
(APCI): m/z = 316.1722 (calcd. 316.1730 for C19H26NOS+ [M+H]+).
FT-IR (neat): ṽ (cm−1) = 3341 (OeH), 3325 (NeH), 2932 (CeH).
(NCH2CH2CH2CH2Ph),
34.0
(C-7),
34.1
(C-5),
36.7
(NCH2CH2CH2CH2Ph), 47.6 (NCH2CH2CH2CH2Ph), 62.5 (C-6), 126.8
(C-4Ph), 129.3 (2C, C-3Ph, C-5Ph), 129.5, (2C, C-2Ph, C-6Ph), 139.7 (C-
2thioph), 141.3 (C-3thioph), 143.6 (C-1Ph), 143.7 (C-8athioph), 153.2 (C-
3athioph), 184.7 (CHO). Exact MS (APCI): m/z = 328.1745 (calcd.
328.1730 for C20H26NOS+ [M+H]+). FT-IR (neat): ṽ (cm−1) = 3445
(NeH), 2928 (CeH), 1720 (C]O).
5.3.16. 6-[N-Methyl-N-(2-phenylethyl)amino]-5,6,7,8-tetrahydro-4H-[7]
annuleno[b]thiophene-2-carbaldehyde (14b)
n-BuLi (84 µL, 0.21 mmol, 2.5 mol/L) was added dropwise to a
solution of amine 11b (60 mg, 0.21 mmol) in dry THF (4 mL) at 0 °C.
After 3 min, 1–formylpiperidine (26 µL, 0.23 mmol) was added at 0 °C.
The solution was stirred for 2 h at 0 °C. Afterwards, ethyl acetate
(10 mL) was added. The organic layer was washed with brine
(2 × 3 mL), dried (Na2SO4) and concentrated in vacuo. The residue was
purified by flash column chromatography (ø = 1 cm, l = 15 cm,
fraction size
= 3 mL, cyclohexane/ethyl acetate 1:4 + 1%
N,N–dimethylethanamine, Rf = 0.35). Yellow oil, yield 24 mg (36%),
Purity (HPLC): 72%, (tR = 16.5 min), C19H23NOS (313.5 g/mol). 1H
NMR (400 MHz, MeOH‑d4): δ (ppm) = 1.40–1.57 (m, 2H, 2 × 5-H),
2.07–2.16 (m, 2H, 2 × 7-H), 2.38 (s, 3H, NCH3), 2.54 (ddd, J = 14.5/
12.1/2.0 Hz, 1H, 4-H), 2.70–2.88 (m, 6H, 8-H, 6-H, NCH2CH2Ph), 3.04
(ddd, J = 14.41/6.70/1.67 Hz, 1H, 4-H), 3.10 (ddd, J = 15.86/6.81/
1.78 Hz, 1H, 8-H), 7.20 (tt, J = 7.1/1.6 Hz, 1H, 4-HPh), 7.22–7.27 (m,
2H, 2,6-HPh), 7.27–7.33 (m, 2H, 3,5-HPh), 7.64 (s, 1H, 3-Hthioph), 9.73
(s, 1H, CHO). 13C NMR (101 MHz, MeOH‑d4): δ (ppm) = 28.2 (C-4),
28.6 (C-8),30,8 (2C, C-5, C-7), 35.6 (NCH2CH2Ph), 37.9 (NCH3), 56.7
(NCH2CH2Ph), 68.4 (C-6), 127.1 (C-4Ph), 129.4 (2C, C–3Ph, C-5Ph),
129.7 (2C, C-2Ph, C-6Ph), 139.6 (C-2thioph), 141.4 (C-3thioph), 141.5 (C-
1Ph), 143.8 (C-8athioph), 153.3 (C-3athioph), 184.7 (CHO). Exact MS
(APCI): m/z = 314.1575 (calcd. 314.1573 for C19H24NOS+ [M+H]+).
FT-IR (neat): ṽ (cm−1) = 2927 (CeH), 1663 (C]O).
5.3.19. 1-{6-[N-(4-Phenylbutyl)amino]-5,6,7,8-tetrahydro-4H-[7]
annuleno[b]thiophen-2-yl}methanol (15d)
Aldehyde 13d (25 mg, 0.08 mmol) was dissolved in dry MeOH
(2 mL). Under ice cooling, NaBH4 (10 mg, 0.26 mg) was added. The
transformation was monitored by IR spectroscopy. Once the carbonyl
band (approx. 1700 cm−1) had disappeared, EtOAc (6 mL) was added.
The mixture was washed with saturated NaHCO3 (aq., 3 × 3 mL), the
organic layer was dried (Na2SO4) and concentrated in vacuo. The re-
sidue was purified by flash column chromatography (ø = 1 cm,
h = 15 cm, fraction size = 3 mL, CH2Cl2/MeOH 98:2 + 1% DMEA,
Rf = 0.09). Colorless oil, yield 16 mg (47%), Purity (HPLC): 85%,
(tR = 17.2 min), C20H27NOS (329.5 g/mol). 1H NMR (400 MHz,
MeOH‑d4): δ (ppm) = 1.28–1.46 (m, 2H, 5-H, 7-H), 1.53–1.63 (m, 2H,
NCH2CH2CH2CH2Ph), 1.65–1.74 (m, 2H, NCH2CH2CH2CH2Ph),
2.01–2.15 (m, 2H, 5-H, 7-H) 2.44–2.54 (m, 1H, 8-H), 2.62–2.70 (m, 3H,
4-H, NCH2CH2CH2CH2Ph), 2.71–2.78 (m, 2H, NCH2CH2CH2CH2Ph),
2.80–2.93 (m, 3H, 4-H, 6-H, 8-H), 4.58 (s, 2H, CH2OH), 6.66 (s, 1H, 3-
5.3.17. 6-[N-Methyl-N-(3-phenylpropyl)amino]-5,6,7,8-tetrahydro-4H-
[7]annuleno[b]thiophene-2-carbaldehyde (14c)
n-BuLi (70 µL, 0.18 mmol, 2.5 mol/L) was added dropwise to a
solution of amine 11c (50 mg, 0.17 mmol) in dry THF (3 mL) at 0 °C.
After 3 min, 1–formylpiperidine (21 µL, 0.19 mmol) was added at 0 °C.
The solution was stirred for 2 h at 0 °C. Afterwards, ethyl acetate
(10 mL) was added. The organic layer was washed with brine
(2 × 4 mL), dried (Na2SO4) and concentrated in vacuo. The residue was
purified by flash column chromatography (ø = 1 cm, l = 15 cm,
fraction size
=
3
mL, cyclohexane/ethyl acetate 1:4
+
1%
H
H
thioph), 7.15 (tt, J = 6.8/1.4 Hz, 1H, 4-HPh), 7.17–7.21 (m, 2H, 2,6-
N,N–dimethylethanamine, Rf = 0.38). Yellow oil, yield 10 mg (19%),
Purity (HPLC): 78%, (tR = 17.6 min), C20H25NOS (327.5 g/mol). 1H
NMR (600 MHz, MeOH‑d4): δ (ppm) = 1.37–1.43 (m, 1H, 5-H), 1.47
(dddd, J = 13.3/12.2/11.1/2.1 Hz, 1H, 7-H), 1.83 (quint, J = 7.7 Hz,
2H, NCH2CH2CH2Ph), 2.04–2.09 (m, 1H, 5-H), 2.10–2.15 (m, 1H, 7-H),
2.28 (s, 3H, NCH3), 2.49–2.56 (m, 3H, 4-H, NCH2CH2CH2Ph), 2.65 (t,
Ph), 7.22–7.28 (m, 2H, 3,5-HPh). A signal for the OH and NH protons
are not seen in the spectrum. 13C NMR (101 MHz, MeOH‑d4): δ
(ppm) = 26.5 (C-4), 27.2 (C-8), 29.5 (NCH2CH2CH2CH2Ph), 30.2
(NCH2CH2CH2CH2Ph), 33.9 (C-5 or C-7), 34.2 (C-5 or C-7), 36.6
(NCH2CH2CH2CH2Ph), 47.3 (NCH2CH2CH2CH2Ph), 59.9 (CH2OH),
62.9 (C-6), 126.8 (C-4Ph), 129.3 (2C, C-3Ph, C-5Ph), 129.5 (2C, C-2Ph, C-
8

S. Baumeister, et al.
Bioorganic&MedicinalChemistryxxx(xxxx)xxxx
6Ph), 129.5 (C–3thioph), 139.4 (C-8athioph),140.2 (C-2thioph), 140.5 (C-
3athioph), 143.4 (C-1Ph). Exact MS (APCI): m/z = 330.1887 (calcd.
330.1886 for C20H28NOS+ [M+H]+). FT-IR (neat): ṽ (cm−1) = 3339
(NeH), 3316 (OeH), 2924 (CeH).
washed with CH2Cl2 (3 × 10 mL). The combined organic layers were
dried (Na2SO4) concentrated in vacuo and the residue was purified by
flash column chromatography (ø = 1 cm, l = 12 cm, fraction
size = 3 mL, cyclohexane/ethyl acetate 5:1, Rf = 0.23). Yellow oil,
yield 123 mg (83%), Purity (HPLC): 84.1%, (tR = 20.2 min), C9H9BrOS
(245,1 g/mol). 1H NMR (600 MHz, CDCl3): δ (ppm) = 2.71–2.76 (m,
4H, 2 × 5-H, 2 × 7-H), 2.84–2.88 (m, 2H, 2 × 4-H), 2.93–2.99 (m, 2H,
2 × 8-H), 6.76 (s, 1H, 3-Hthioph). 13C NMR (151 MHz, CDCl3): δ
(ppm) = 24.4 (C-8), 25.6 (C-4), 42.5 (C-7), 43.4 (C-5), 107.7 (C-
5.3.20. 1-{6-[N-Methyl-N-(2-phenethyl)amino]-5,6,7,8-tetrahydro-4H-
[7]annuleno[b]thiophen-2-yl}methanol (16b)
Aldehyde 14b (24 mg, 0.08 mmol) was dissolved in dry MeOH
(2 mL). Under ice cooling, NaBH4 (10 mg, 0.26 mg) was added. The
transformation was monitored by IR spectroscopy. Once the carbonyl
band (approx. 1700 cm−1) had disappeared, EtOAc (10 mL) was added.
The mixture was washed with saturated NaHCO3 (aq., 3 × 6 mL), dried
2
thioph), 132.7 (C-3thioph), 138.0 (C-3athioph or C-8athioph), 138.2 (C-
3athioph or C–8athioph), 211.9 (C-6). Exact MS (APCI): m/z = 244.9615
(calcd. 244.9630 for C9H10BrOS+ [M+H]+). FT-IR (neat):
ṽ
(Na2SO4) and concentrated in vacuo. Rf
=
0.25 (CH2Cl2/MeOH
(cm−1) = 2943 (CeH), 1698 (C]O).
9:1 + 1% N,N-diethylethanamine). Colorless oil, yield 21 mg (84%),
Purity (HPLC): 74%, (tR = 15.5 min), C19H25NOS (315.5 g/mol). 1H
NMR (600 MHz, MeOH‑d4): δ (ppm) = 1.33–1.41 (m, 1H, 5-H),
1.41–1.48 (m, 1H, 7-H), 2.00–2.05 (m, 1H, 5-H), 2.07 (dddd, J = 12.9/
6.7/4.6/2.1 Hz, 1H, 7-H), 2.33 (s, 3H, NCH3), 2.38–2.44 (m, 1H, 4-H),
2.59–2.65 (ddd, J = 17.2/11.9/1.8 Hz, 1H, 8-H), 2.67–2.71 (m, 2H,
NCH2CH2Ph), 2.72–2.81 (m, 3H, 6–H, NCH2CH2Ph), 2.86 (ddd,
J = 13.6/6.6/2.0 Hz, 1H, 4-H), 2.90 (ddd, J = 15.2/6.6/1.9, 1H, 8-H),
4.58 (s, 2H, CH2OH), 6.66 (d, J = 2.8 Hz, 1H, 3-Hthioph), 7.16–7.19 (m,
1H, 4-HPh), 7.20–7.22 (m, 2H, 2,6-HPh), 7.25–7.29 (m, 2H, 3,5-HPh). A
signal for the OH proton is not seen in the spectrum. 13C NMR
(151 MHz, MeOH‑d4): δ (ppm) = 27.8 (C-8), 28.5 (C-4), 30.9 (C-7),
31.2 (C-5), 35.6 (NCH2CH2Ph), 37.9 (NCH3), 56.7 (NCH2CH2Ph), 59.9
(CH2OH), 68.8 (C-6), 127.1 (C-4Ph), 129.4 (2C, C-3Ph, C-5Ph), 129.7 (C-
5.3.23. 2-Bromo-N-(3-phenylpropyl)-5,6,7,8-tetrahydro-4H-[7]annuleno
[b]thiophen-6-amine (18c)
Bromoketone 17 (58 mg, 0.24 mmol) was dissolved in dry CH2Cl2
(5 mL). Under N2, 3-phenylpropan-1-amine (54 μL, 0.38 mmol) and
NaBH(OAc)3 (81 mg, 0.38 mmol) were added and the mixture was
stirred for 20 h at room temperature. A saturated NaHCO3 solution (aq.,
7 mL) was added. The mixture was extracted with CH2Cl2 (3 × 7 mL),
the organic layer was dried (Na2SO4) and concentrated in vacuo. The
residue was purified by flash column chromatography (ø = 1 cm,
l = 18 cm, fraction size = 3 mL, cyclohexane/ethyl acetate 1:2 + 1%
N,N-dimethylethanamine, Rf = 0,30). Brown oil, yield 64 mg (74%),
Purity (HPLC): 95%, (tR = 20.7 min), C18H21BrOS (365.3 g/mol). 1H
NMR (600 MHz, MeOH‑d4): δ (ppm) = 1.32 (dddd, J = 21.2/12.0/10.0/
1.7 Hz, 1H, 5–H), 1.38 (dddd, J = 21.6/11.4/9.8/2.1 Hz, 1H, 7-H),
1.83–1.89 (m, 2H, NCH2CH2CH2Ph), 2.01 (dddd, J = 13.4/7.2/3.2/
1.7 Hz, 1H, 5-H), 2.06 (dddd, J = 13.5/7.0/3.3/1.8 Hz, 1H, 7-H),
2.47–2.52 (m, 1H, 4-H), 2.64 (ddd, J = 16.1/11.5/1.9 Hz, 1H, 8-H), 2.69
(q, J = 7.5 Hz, 4H, NCH2CH2CH2Ph), 2.76 (tt, J = 10.3/3.0 Hz, 1H, 6-
H), 2.82 (ddd, J = 15.0/7.5/2.0 Hz, 1H, 4-H), 2.85 (ddd, J = 15.4/7.4/
2.1 Hz, 1H, 8-H), 6.76 (s, 1H, 3-Hthioph), 7.14–7.20 (m, 1H, 4-HPh),
7.20–7.23 (m, 2H, 2,6-HPh), 7.25–7.29 (m, 2H, 3,5-HPh). A signal for the
NH proton is not seen in the spectrum. 13C NMR (151 MHz, MeOH‑d4): δ
(ppm) = 26.2 (C-8), 27.1 (C-4), 32.2 (NCH2CH2CH2Ph), 34.1 (C-5), 34.4
(C-7), 34.7 (NCH2CH2CH2Ph), 47.3 (NCH2CH2CH2Ph) 62.6 (C-6), 106.3
(C-2thioph), 126.9 (C-4Ph), 129.4 (2C, C-2Ph, C-6Ph), 129.4 (2C, C-3Ph, C-
3
thioph), 129.7 (2C, C-2Ph, C-6Ph), 139.7 (C-3athioph), 139.9 (C-2thioph),
140.7 (C-8athioph), 141.5 (C-1Ph). Exact MS (APCI): m/z = 312.1731
(calcd. 316.1730 for
C
19H26NOS+ [M+H]+). FT-IR (neat):
ṽ
(cm−1) = 3333 (OeH).
5.3.21. 1-{6-[N-Methyl-N-(3-phenylpropyl)amino]-5,6,7,8-tetrahydro-
4H-[7]annuleno[b]thiophen-2-yl}methanol (16c)
Aldehyde 14c (10.4 mg, 0.03 mmol) was dissolved in dry MeOH
(2 mL). Under ice cooling, NaBH4 (12 mg, 0.32 mg) was added. The
transformation was monitored by IR spectroscopy. Once the carbonyl
band (approx. 1700 cm−1) had disappeared, EtOAc (8 mL) was added.
The mixture was washed with saturated NaHCO3 (aq., 3 × 7 mL), the
organic layer was dried (Na2SO4) and concentrated in vacuo. Rf = 0.17
5
Ph), 133.9 (C–3thioph), 141.5 (C-4athioph or C-8athioph), 142.0 (C–4athioph
(cyclohexane/ethyl acetate 1:4
+
1% N,N-dimethylethanamine).
or C-8athioph), 143.2 (C-1Ph). Exact MS (APCI): m/z = 364.0720 (calcd.
364.0729 for C18H23BrNS+ [M+H]+). FT-IR (neat): ṽ (cm−1) = 2924
(CeH), 1443 (CeH), 698 (CeBr).
Colorless oil, yield 6.4 mg (65%), Purity (HPLC): 74%, (tR = 16.2 min),
C
20H27NOS (329.5 g/mol). 1H NMR (600 MHz, MeOH‑d4):
δ
(ppm) = 1.34–1.40 (m, 1H, 7-H), 1.40–1.47 (m, 1H, 5-H), 1.80–1.86
(m, 2H, NCH2CH2CH2Ph), 2.02 (dddd, J = 14.8/6.6/4.3/2.2 Hz, 1H, 7-
H), 2.07 (dddd, J = 14.8/6.5/4.2/2.0 Hz, 1H, 5-H), 2.29 (s, 3H, NCH3),
2.40–2.46 (m, 1H, 4-H), 2.53 (t, J = 9.4 Hz, 2H, NCH2CH2CH2Ph),
2.60–2.68 (m, 3H, 8-H, NCH2CH2CH2Ph), 2.70–2.79 (m, 1H, 6-H), 2.87
(ddd, J = 13.8/6.5/2.0 Hz, 1H, 4-H), 2.91 (ddd, J = 15.1/6.5/2.1 Hz,
1H, 8-H), 4.59 (s, 2H, CH2OH), 6.67 (s, 1H, 3-Hthioph), 7.17 (tt, J = 7.2/
1.4 Hz, 1H, 4-HPh), 7.19–7.22 (m, 2H, 2,6-HPh), 7.25–7.29 (m, 2H, 3,5-
5.3.24. 2-Bromo-N-(4-phenylbutyl)-5,6,7,8-tetrahydro-4H-[7]annuleno
[b]thiophen-6-amine (18d)
Bromoketone 17 (58 mg, 0.24 mmol) was dissolved in CH2Cl2
(7 mL). Under N2, 4–phenylbutan-1-amine (61 μL, 0.38 mmol) and
NaBH(OAc)3 (81 mg, 0.38 mmol) were added and the mixture was
stirred for 21 h at room temperature. A saturated NaHCO3 solution (aq.,
8 mL) was added. The mixture was extracted with CH2Cl2 (3 × 8 mL),
the organic layer was dried (Na2SO4) and concentrated in vacuo. The
residue was purified by flash column chromatography (ø = 1 cm,
l = 19 cm, fraction size = 3 mL, cyclohexane/ethyl acetate 1:2 + 1%
N,N-dimethylethanamine, Rf = 0,33). Brown oil, yield 65 mg (73%),
H
Ph). A signal for the OH proton is not seen in the spectrum. 13C NMR
(151 MHz, MeOH‑d4):
δ (ppm) = 27.7 (C-8), 28.5 (C-4), 30.6
(NCH2CH2CH2Ph), 30.7 (C-7), 31.1 (C-5), 34.6 (NCH2CH2CH2Ph), 37.9
(NCH3), 53.9 (NCH2CH2CH2Ph), 59.9 (CH2OH), 68.9 (C-6), 126.9 (C-
4
3
Ph), 129.4 (2C, C-3Ph, C-5Ph), 129.4 (2C, C-2Ph, C-6Ph), 129.6 (C-
thioph), 139.7 (C-3athioph), 139.9 (C-2thioph), 140.7 (C–8athioph), 143.2
Purity (HPLC): 96.6%, (tR = 20.9 min), C19H23BrOS (379.4 g/mol). 1
H
NMR (600 MHz, MeOH‑d4): δ (ppm) = 1.32 (dddd, J = 21.6/11.8/
10.0/1.9 Hz, 1H, 5-H), 1.37 (dddd, J = 21.5/11.6/9.9/2.0 Hz, 1H, 7-
H), 1.53–1.58 (m, 2H, NCH2CH2CH2CH2Ph), 1.65–1.72 (m, 2H,
NCH2CH2CH2CH2Ph), 1.98–2.09 (m, 2H, 5-H, 7-H), 2.46–2.52 (m, 1H,
4-H), 2.61–2.68 (m, 5H, NCH2CH2CH2CH2Ph, 8-H), 2.71 (tt, J = 9.9/
3.0 Hz, 1H, 6-H), 2.82 (ddd, J = 14.0/7.4/1.9 Hz, 1H, 4-H), 2.85 (ddd,
J = 14.4/7.5/1.9 Hz, 1H, 8-H), 6.76 (s, 1H, 3-Hthioph), 7.14–7.17 (m,
1H, 4-HPh), 7.18–7.21 (m, 2H, 2,6-HPh), 7.24–7.28 (m, 2H, 3,5-HPh). A
signal for the NH proton is not seen in the spectrum. 13C NMR
(C-1Ph). Exact MS (APCI): m/z = 330.1882 (calcd. 330.1886 for
C20H28NOS+ [M+H]+). FT-IR (neat): ṽ (cm−1) = 2924 (CeH).
5.3.22. 2-Bromo-4,5,7,8-tetrahydro-[7]annuleno[b]thiophen-6-one (17)
The reaction was conducted under the exclusion of UV light.
N-Bromosuccinimide, recrystallized from H2O, (107 mg, 0.6 mmol)
was added to a solution of ketone 10 (91 mg, 0.55 mmol) in CH2Cl2
(4 mL). The mixture was stirred for 18 h at room temperature.
Afterwards, the mixture was filtrated through cotton wool and the filter
(151 MHz, MeOH‑d4):
δ (ppm) = 26.3 (C-8), 27.2 (C-4), 30.2
9

S. Baumeister, et al.
Bioorganic&MedicinalChemistryxxx(xxxx)xxxx
(NCH2CH2CH2CH2Ph), 30.4 (NCH2CH2CH2CH2Ph), 34.3 (C-5), 34.6 (C-
7), 36.8 (NCH2CH2CH2CH2Ph), 47.7 (NCH2CH2CH2CH2Ph), 62.6 (C-6),
106.2 (C-2thioph), 126.7 (C–4Ph), 129.3 (2C, C-3Ph, C-5Ph), 129.5 (2C, C-
Declaration of Competing Interest
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influ-
ence the work reported in this paper.
2
Ph, C-6Ph), 133.9 (C-3thioph), 141.5 (C-4athioph or C-8athioph), 142.1 (C-
4athioph or C-8athioph), 143.6 (C-1Ph). Exact MS (APCI): m/z = 378.0885
(calcd. 378.0886 for C19H25BrNS+ [M+H]+). FT-IR (neat):
ṽ
(cm−1) = 1450 (CeH), 924 (CeH), 698 (CeBr).
Acknowledgements
5.3.25. 2.-(4-Hydroxyphenyl)-4,5,7,8-tetrahydro-[7]annuleno[b]
thiophen-6-one (19)
This work was supported by the Deutsche Forschungsgemeinschaft
Germany (DFG), which is gratefully acknowledged.
Bromoketone 17 (90 mg, 0.37 mmol) was dissolved in THF (10 mL).
Under N2, (4–hydroxyphenyl)boronic acid (53 mg, 0.37 mmol), Pd
(dppf)Cl2 (5 mg, 2 mol-%), K2CO3 (126 mg, 0.93 mmol), and a few
drops of H2O were added and the mixture was heated to 80 °C over-
night. Afterwards, the mixture was washed with water (3 × 4 mL). The
aqueous layer was extracted with ethyl acetate (3 × 5 mL), the com-
bined organic layers were dried (Na2SO4) and concentrated in vacuo.
The residue was purified by flash column chromatography (ø = 1 cm,
l = 12 cm, fraction size = 3 mL, CH2Cl2/MeOH 99:1, Rf = 0,36).
Yellow solid, yield 26 mg (27%), C15H14O2S (258.3 g/mol). 1H NMR
(400 MHz, CD3OD): δ (ppm) = 2.76–2.79 (m, 4H, 2 × 5-H, 2 × 7-H),
2.92–2.97 (m, 2H, 2 × 4-H), 3.04–3.09 (m, 2H, 2 × 8-H), 6.78–6.81
(m, 2H, 2,6-HPh), 6.96 (s, 1H, 3-Hthioph), 7.38–7.41 (m, 2H, 3,5-HPh). A
signal for the OH proton is not seen in the spectrum. 13C NMR
(101 MHz CD3OD): δ (ppm) = 25.2 (C-8), 26.6 (C-4), 43.4 (C-5), 44.3
(C-7), 116.6 (2C, C-2Ph, C-6Ph), 125.5 (C-3thioph), 127.7 (C-2thioph),
127.7 (2C, C-3Ph, C-5Ph), 135.7 (C-3athioph or C-8athioph), 139.3 (C-
3athioph or C-8athioph), 141.5 (C-1Ph), 158.2 (C–4Ph), 215.2 (C-6). FT-IR
(neat): ṽ (cm−1): 2943 (CeH), 1697 (C]O).
Appendix A. Supplementary material
Supplementary data to this article can be found online at https://
doi.org/10.1016/j.bmc.2019.115245.
References
1. Danysz W, Parsons CG. Glycine and N-methyl-D-aspartate receptors: physiological
significance and possible therapeutic applications. Pharmacol Rev. 1998;50:597–664.
2. Bräuner-Osborne H, Egebjerg J, Nielsen EO, Madsen U, Krogsgaard-Larsen P. Ligands
for glutamate receptors: design and therapeutic prospects. J Med Chem.
2000;43:2609–2645.
3. Stark H, Reichert U, Struktur Graßmann S. Funktion Und potentielle Therapeutische
Bedeutung von NMDA-Rezeptoren, Teil 1. Pharm Unserer Zeit. 2000;2:159–166.
4. Zhou X, Hollern D, Liao J, Andrechek E, Wang H. NMDA receptor-mediated ex-
citotoxicity depends on the coactivation of synaptic and extrasynaptic receptors. Cell
Death Dis. 2013;4:e560.
5. Mony L, Kew JNC, Gunthorpe MJ, Paoletti P. Allosteric modulators of NR2B-con-
taining NMDA receptors: molecular mechanisms and therapeutic potential. Br J
Pharmacol. 2009;157:1301–1317.
6. Wu L-J, Zhuo M. Targeting the NMDA receptor subunit NR2B for the treatment of
neuropathic pain. Neurotherapeutics. 2009;6:693–702.
7. Paoletti P, Bellone C, Zhou Q. NMDA receptor subunit diversity: impact on receptor
properties, synaptic plasticity and disease. Nat Rev. 2013;14:383–400.
8. Paoletti P, Neyton J. NMDA receptor subunits: function and pharmacology. Curr Opin
Pharmacol. 2007;7:39–47.
5.3.26. 4-{6-[N-(3-Phenylpropyl)amino]-5,6,7,8-tetrahydro-4H-[7]
annuleno[b]thiophen-2-yl}phenol (20c)
9. Stark H, Reichert U, Graßmann S. Struktur, Funktion und potentielle Therapeutische
Bedeutung von NMDA-Rezeptoren, Teil 2. Pharm Unserer Zeit. 2000;2:228–236.
10. Lee C-H, Lü W, Michel JC, et al. NMDA receptor structures reveal subunit arrange-
ment and pore architecture. Nature. 2014;511:191–197.
Ketone 19 (26.3 mg, 0.1 mmol) was dissolved in CH2Cl2 (2 mL).
Under N2, 3-phenylpropan-1-amine (14 μL, 0.1 mmol) and NaBH(OAc)3
(35 mg, 0.16 mmol) were added. The mixture was stirred for 21 h at
room temperature. A saturated NaHCO3 solution (aq., 8 mL) was added.
The mixture was extracted with CH2Cl2 (3 × 5 mL), the organic layer
was dried (Na2SO4) and concentrated in vacuo. The residue was purified
by flash column chromatography (ø = 1 cm, l = 12 cm, fraction
size = 3 mL, CH2Cl2/MeOH 6:1, Rf = 0.42). Yellow solid, mp, yield
4 mg (10%), Purity (HPLC): 81.3%, (tR = 19.3 min), C24H27NOS
(377.6 g/mol). 1H NMR (600 MHz, MeOH‑d4): δ (ppm) = 1.46–1.58 (m,
2H, 5-H, 7-H), 1.96 (tt, J = 9.9/6.9 Hz, 2H, NCH2CH2CH2Ph), 2.15–2.25
(m, 2H, 5-H, 7-H), 2.56 (ddd, J = 15.2/12.0/1.9 Hz, 1H, 4-H), 2.70–2.78
(m, 3H, NCH2CH2CH2Ph, 8-H), 2.90–2.98 (m, 4H, 4-H, 8-H,
NCH2CH2CH2Ph), 3.14–3.19 (m, 1H, 6-H), 6.74–6.77 (m, 2H,
2,6–Hphenol), 6.90 (s, 1H, 3-Hthioph), 7.17–7.21 (m, 1H, 4-Hphenyl),
7.22–7.25 (m, 2H, 2,6-Hphenyl), 7.27–7.31 (m, 2H, 3,5-Hphenyl), 7.33–7.36
(m, 2H, 3,5-Hphenol). Signals of the OH and NH protons are not seen in
this spectrum. 13C NMR (151 MHz, MeOH‑d4): δ (ppm) = 26.0 (C-8),
27.0 (C-4), 30.3 (NCH2CH2CH2Ph), 32.5 (C-5 or C-7), 32.9 (C-5 or C-7),
34.0 (NCH2CH2CH2Ph), 46.1 (NCH2CH2CH2Ph), 62.9 (C-6), 116.6 (2C,
C-2phenol, C-6phenol),125.6 (C-3thioph), 127.2 (C–4phenyl), 127.3 (C-1phenol),
127.6 (2C, C-3phenol, C-5phenol), 129.4 (2C, C-2phenyl, C–6phenyl), 129.6
(2C, C-3phenyl, C-5phenyl), 137.0 (C-8athioph), 140.7 (C-2thioph), 141.4
(C–3athioph), 142.1 (C–1phenyl), 158.0 (C-4phenol). Exact MS (APCI): m/
z = 378.1870 (calcd. 378.1886 for C24H28NOS+ [M+H]+). FT-IR
(neat): ṽ (cm−1) = 3113 (NeH), 3021 (OeH), 2924 (CeH).
11. Karakas E, Simorowski N, Furukawa H. Subunit arrangement and phenylethanola-
mine binding in GluN1/GluN2B NMDA receptors. Nature. 2011;475:249–253.
12. Benner A, Bonifazi A, Shirataki C, et al. GluN2B-selective N-methyl-D-aspartate
(NMDA) receptor antagonists derived from 3-benzazepines: synthesis and pharma-
cological evaluation of benzo[7]annulen-7-amines. ChemMedChem. 2014;9:741–751.
13. Gawaskar S, Temme L, Schreiber JA, et al. Design, synthesis, pharmacological eva-
luation and docking studies of GluN2B-selective NMDA receptor antagonists with a
benzo[7]annulen-7-amine scaffold. ChemMedChem. 2017;12:1212–1222.
14. Gawaskar S, Schepmann D, Bonifazi A, Wünsch B. Synthesis, GluN2B affinity and
selectivity of benzo[7]annulen-7-amines. Bioorg Med Chem. 2014;22:6638–6646.
15. Baumeister S, Schepmann D, Wünsch B. Synthesis and receptor binding of thiophene
bioisosteres of potent GluN2B ligands with a benzo[7]annulene-scaffold.
MedChemComm. 2019;10:315–325.
16. Dey R, Navarathne D, Invernale MA, Berghorn ID, Sotzing GA. Versatile synthesis of
3,4-b diheteropentalenes. Tetrahedron Lett. 2010;51:2089–2091.
17. Abdel-Magid AF, Mehrman SJ. A review on the use of sodium triacetoxyborohydride
in the reductive amination of ketones and aldehydes. Org Process Res Dev.
2006;10:971–1031.
18. Temme L, Frehland B, Schepmann D, Robaa D, Sippl W, Wünsch B. Hydroxymethyl
bioisosteres of phenolic GluN2B-selective NMDA receptor antagonists: design,
synthesis and pharmacological evaluation. Eur J Med Chem. 2018;144:672–681.
19. Miyaura N, Suzuki A. Palladium-catalyzed cross-coupling reactions of organoboron
compounds. Chem Rev. 1995;95:2457–2483.
20. Schepmann D, Frehland B, Lehmkuhl K, Tewes B, Wünsch B. Development of a se-
lective competitive receptor binding assay for the determination of the affinity to
NR2B containing NMDA receptors. J Pharm Biomed Anal. 2010;53:603–608.
21. Hashimoto K, London ED. Interactions of erythro-ifenprodil, threo-ifenprodil, ery-
thro-iodoifenprodil, and eliprodil with subtypes of σ receptors. Eur J Pharmacol.
1995;273:307–310.
22. Meyer C, Neue B, Schepmann D, et al. Improvement of σ1 receptor affinity by late-
stage C-H-bond arylation of spirocyclic lactones. Bioorg Med Chem.
2013;21:1844–1856.
23. Miyata K, Schepmann D, Wünsch B. Synthesis and σ receptor affinity of regioisomeric
spirocyclic furopyridines. Eur J Med Chem. 2014;83:709–716.
5.4. Receptor binding studies
24. Hasebein P, Frehland B, Lehmkuhl K, Fr R, Schepmann D. Synthesis and pharma-
cological evaluation of like- and unlike-configured tetrahydro-2-benzazepines with
the α-substituted benzyl moiety in the 5-position. Org Biomol Chem.
2014;12:5407–5426.
Details on the assay to determine the affinity towards the ifenprodil
binding site of GluN2B subunit containing NMDA receptors are given in
Ref.20
Details on σ1 and σ2 receptor assays are given in Ref.22–24
10