From mannose to morphan analogues: Methyl α-d-mannoside as chiral building block for the synthesis of mono- and bicyclic σ receptor ligands

Article abstract of DOI:10.1016/j.carres.2012.05.006

Previously the synthesis and high σ₁ receptor affinity of mannose derived pyrans 3-5 with equatorially oriented amino groups have been reported. Herein the synthesis and receptor affinities of the corresponding axially substituted pyrans and ox

Full text of DOI:10.1016/j.carres.2012.05.006

Carbohydrate Research 359 (2012) 24–29
Contents lists available at SciVerse ScienceDirect
Carbohydrate Research
journal homepage: www.elsevier.com/locate/carres
From mannose to morphan analogues: methyl
a-D-mannoside as chiral
building block for the synthesis of mono- and bicyclic
r receptor ligands
⇑
Kathrin Wiedemeyer, Bernhard Wünsch
Institut für Pharmazeutische und Medizinische Chemie der Universität Münster, Hittorfstraße 58-62, D-48149 Münster, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
Previously the synthesis and high r1 receptor affinity of mannose derived pyrans 3–5 with equatorially
oriented amino groups have been reported. Herein the synthesis and receptor affinities of the corre-
sponding axially substituted pyrans and oxa-morphans are described. Key step in the diastereoselective
synthesis was an SN2 substitution of tosylate 10 with NaN3. Heating of the azide 6 with acid led unexpect-
Received 26 March 2012
Received in revised form 3 May 2012
Accepted 4 May 2012
Available online 12 May 2012
edly to the oxa-morphan 13, which showed remarkable affinity toward the
r1 receptor (Ki = 860 nM). The
benzylamine 15 and the dimethylamine 16 were obtained by reduction of the azide 6 and subsequent
a
a
Keywords:
Mannose
Alloheptopyranosides
Diastereoselectivity
Bicyclic systems
Oxa-morphan
reductive alkylation. In contrast to the equatorial amines 3–5, the axial amines 15
a and 16a did not inter-
act with the r1 receptor or another investigated receptor system.
Ó 2012 Elsevier Ltd. All rights reserved.
r1 Receptor ligands
1. Introduction
ease, Parkinson’s disease) with r1 agonists. The reduction of
unpleasant and dangerous effects after withdrawal of ethanol,
amphetamine or cocaine from addicted animals was shown for
r1 receptor antagonists. Additionally, r1 antagonists are able to
potentiate opioid induced analgesia.3–6 Finally, some human tumor
cell lines express a large amount of r1 and r2 receptors, which
stimulate the development of r1 antagonist-based antitumor
drugs.7,8
Due to the high r1 receptor affinity of the glucoheptopyrano-
sides 3–5 with equatorially oriented amino moieties, the ketone
2 should be exploited for the synthesis of novel sugar derived r1
ligands. It was planned to transform the ketone 2 into the axial
azide 6, which should be used for bridging of the pyran ring, giving
access to conformationally rigid morphan analogues 7. Moreover,
the azide 6 should be converted into pyrans 8 with axially oriented
amino moieties. Although it was shown that the diastereomer of 4
with axially oriented methylamino moiety has only very low r1
receptor affinity,2 further derivatives with axially oriented amino
moieties are of interest. In particular amines with two substituents
(tertiary amines) and a larger substituent should be synthesized in
order to investigate whether the axial orientation or the substitu-
tion pattern is responsible for low r1 receptor affinity.
The class of naturally occurring carbohydrates contains numer-
ous enantiomerically pure building blocks. However, the chiral
information of the diverse and valuable mono- or disaccharides
is rarely exploited for the synthesis of pharmacologically active
agents. The antiepileptic drug topiramate and the antiviral drug
zanamivir represent prominent examples for sugar derived drugs.
Recently we have shown that the monosaccharide methyl
a-D-mannoside (1) can be used for the synthesis of sugar derived
amines 3–5 (Scheme 1). The key step of this synthesis was the
stereoselective reductive amination of the ketone 2, which had
been prepared in an eleven step sequence starting with methyl
a-D-mannoside (1). The reductive amination of ketone 2 took place
with high diastereoselectivity leading predominantly to glucohe-
ptopyranosides 3–5 with equatorially oriented amino moieties.
Recording of the r1 receptor affinity of the amines 3–5 led to
Ki-values lower than 100 nM. In particular the dimethylamine 5,
which was tested as mixture of
r1 receptor affinity with a Ki-value of 21 nM.1,2
Since the 1 receptor is a promising target for the development
a- and b-anomers, showed high
r
of innovative drugs for the treatment of various neurological and
neuropsychiatric diseases, we are particularly interested in novel
r1 receptor ligands. r1 Receptor agonists can be used as antide-
pressants and their antiamnesic and neuroprotective potential
permits the treatment of memory disorders (e.g., Alzheimer’s dis-
2. Results and discussion
2.1. Chemistry
Reduction of the ketone 2 with NaBH4 led predominantly to the
alcohol, 9 with equatorially oriented OH moiety. The reaction
⇑
Corresponding author. Tel.: +49 251 8333311; fax: +49 251 8332144.
E-mail address: wuensch@uni-muenster.de (B. Wünsch).
0008-6215/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.carres.2012.05.006

K. Wiedemeyer, B. Wünsch / Carbohydrate Research 359 (2012) 24–29
25
Cl
Cl
Cl
Cl
O
O
OH
OH
11 steps
N
H
N
H
O
HO
HO
R2NH
O
O
NaBH3CN
R2N
OCH3
OCH3
O
OCH3
3: NR2 = NHBn
4: NR2 = NHCH
1
2
3
methyl α-D-mannoside
5: NR2 = N(CH3)2
Cl
Cl
Cl
Cl
O
O
O
N
N
H
N
H
R
O
O
O
OCH3
OCH3
R2N
N3
R2N
7
6
8
α: OCH3 axial
β: OCH3 equatorial
Scheme 1. Eleven reaction steps are required to transform methyl
a-D-mannoside (1) into ketone 2, which should serve as common intermediate for the synthesis oxa-
morphans 7, and pyrans with equatorially (3–5) and axially oriented (8) amino moieties.
mixture contained small amounts (ca. 15%) of the epimeric alcohol
epi-9 with axially oriented OH-moiety. After removal of epi-9 by
flash chromatography, alcohol 9 was isolated in 61% yield (Scheme
2). For the synthesis of the tosylate 10 the alcohol 9 was treated
with p-toluenesulfonyl chloride in the presence of triethylamine
and dimethylaminopyridine. In order to obtain high yields of the
tosylate 10 (80%) a mixture of diastereomeric alcohols 9 and
epi-9 (85:15) was used leading to an inseparable mixture of diaste-
reomeric tosylates 10 and epi-10 (ratio 85:15). The azide 6 with
axial position of the azido moiety was obtained by nucleophilic
substitution of the tosylate 10 with NaN3. Since the tosylate 10
contained small amounts (ca. 15%) of epi-10 with axially oriented
tosyloxy group, the corresponding diastereomer of azide 6 was also
formed and isolated (6%) during flash chromatographic
purification.
The 1H NMR spectrum of 10 clearly demonstrates the equatorial
position of the tosyloxy group in 3-position: The triplet of triplet at
4.56 ppm with two large 1,2-diaxial coupling constants of 11.6 Hz
is only possible for an axially oriented proton at 3-position. Addi-
tionally the equatorial orientation of 3-H after inversion of the con-
figuration to azide 6 is shown by the quintet type signals at
3.92 ppm (J = 3.4 Hz) and 4.09 ppm (J = 3.2 Hz). The rather small
Cl
Cl
Cl
Cl
O
O
N
H
N
H
O
(a)
O
(b)
HO
OCH3
OCH3
O
9
2
Cl
Cl
Cl
Cl
O
O
N
H
N
H
O
(c)
O
RSO2O
3
3
OCH3
10: R = pTol
OCH3
N3
6
α: OCH3 axial
β: OCH3 equatorial
Scheme 2. Reagents and conditions: (a) NaBH4, MeOH, rt, 7 h, 61%; (b) p-toluenesulfonyl chloride, NEt3, DMAP, CH2Cl2, reflux, 28 h, 80%; (c) NaN3, DMF, reflux, 8 h, 64% (6)
and 6% (epi-6).

26
K. Wiedemeyer, B. Wünsch / Carbohydrate Research 359 (2012) 24–29
coupling constants of 3.4/3.2 Hz are only compatible with an equa-
torial orientation of this proton.
2.2. Receptor binding studies
At first bridging of the sugar derived pyran ring of the azide 6 by
the amidoethyl side chain was investigated. In particular the oxa-
morphan derivative 11 was envisaged bearing an additional azide
moiety for further modifications. Compounds with the morphan
scaffold (morphine substructure) are of interest as analgesics9
The affinity of the oxa-morphan 13 and the amines 15
a
and 16
a
toward r1
experiments using the radioligands [3H]-(+)-pentazocine (
[3H]-ditolylguanidine (
, r2 and NMDA receptors was recorded in competition
r
1),
r
2),12–14 and [3H]-(+)-MK-801 (NMDA).15,16
The affinity data are summarized in Table 1. The mannose de-
rived ligands 15 and 16 with axially oriented amino moieties
did neither interact with r1 2 nor NMDA receptors. In the screen-
ing with test compound concentrations of 1.0 M ( 1) and 10
2, NMDA) they did not compete significantly with the radioli-
gands. Obviously, the orientation of the basic amino moiety is cru-
cial for the interaction with the 1 receptor protein. An equatorial
and as ligands for
r
receptors.10
a
a
Treatment of the azide 6 with p-toluenesulfonic acid or BF3 OEt2
led to decomposition of the educt 6. However heating of a solution
of 6 in toluene with an acidic ion exchange resin (Amberlyst-H15Ò)
produced a new product, which was isolated in 37% yield. Surpris-
ingly it turned out to be the oxa-morphan derivative 13 instead of
11 (Scheme 3). In the IR spectrum of 13 absorptions of an azido
moiety were not found and the 1H NMR spectrum did not show
a singlet for a methoxy group. Due to the existence of rotational
isomers around the exocyclic N–C@O bond, two sets of signals (ra-
tio 55:45) are seen in the NMR spectra. The signals for the protons
in 3-position (d = 6.65 ppm, d, J = 6.1 Hz (rotamer 1); d = 6.70 ppm,
d, J = 5.8 Hz (rotamer 2)), 4-position (d = 4.40–4.54 ppm, m (rot-
amer 1); d = 4.75 ppm, t, J = 5.9 Hz (rotamer 2)), and 5-position
(d = 4.26–4.32 ppm, m (rotamer 1); d = 5.24–5.27 ppm, m (rotamer
2)) confirm unequivocally the structure of 13. The existence of
rotational isomers was shown by recording the NMR spectra at ele-
vated temperature and the assignment of the signals was sup-
ported by 2D spectra.
, r
l
r
lM
(r
r
orientation of the benzylamino (3) or dimethylamino moiety (5)
led to high r1 affinity, whereas the corresponding diastereomers
15
most inactive at the r1 receptor.
Due to its pharmacophoric (3,4-dichlorophenylacetyl) resi-
a and 16a with axial orientation of the amino moiety were al-
r
due17,18 and its analogy to morphans, the oxa-morphan 13 was in-
cluded into the receptor binding studies. A r1 receptor affinity of
860 nM was found, which is remarkable, since 13 does not contain
a basic amino functionality. It can be concluded that the three
dimensional morphan structure and the r1 pharmacophoric
dichlorophenylacetyl residue are responsible for the interaction
with the
r1 receptor. However, it should be noted that amine-free
neurosteroids (e.g., progesterone, dehydroepiandrosterone), which
are discussed as endogenous r1 ligands,19,20 show similar r1
receptor affinities as the oxa-morphan 13.
We assume that the formation of 13 started with an acid in-
duced elimination of methanol. Subsequently, the azido group
was cleaved off leading to the stabilized cation 12, which was
trapped intramolecularly by the amide N-atom.
3. Conclusion
Reduction of the azide 6 with H2 in the presence of Raney-Ni
afforded the primary amine 14 in 77% yield (Scheme 4). The
monobenzylamine 15 was prepared by condensation of the pri-
mary amine 14 with benzaldehyde and subsequent NaBH4 reduc-
tion. Due to substantial epimerization during this reaction step,
fc separation and purification of the product were difficult and
Instead of the azido substituted oxa-morphan 11, the regioiso-
meric oxa-morphan 13 was formed upon heating of azide 6 with
acid. Although 13 does not contain a basic amino functionality, it
showed an unexpectedly high r1 affinity of 860 nM. Changing
the potent
r
1 receptor ligands 3–5 (amino group in equatorial po-
led finally to the pure diastereomer 15a with both the benzyl-
sition) into analogues 15
a
and 16 with axially oriented amino
a
amino and methoxy groups in axial position. Reductive methyla-
tion of the primary amine 14 was performed with a large excess
of formaldehyde and NaBH3CN11 giving 37% yield of the dimethyl-
groups led to almost complete loss of r1 affinity. These results
prove that the axial orientation and not the substitution pattern
of the amino moiety at 3-position is responsible for the low r1
affinity.
amine 16
a
with axially oriented methoxy group.
Cl
Cl
Cl
Cl
O
O
O
N
H
N
H
Cl
N
Cl
OCH3
O
O
O
OCH3
N3
N3
N3
6
11
(a)
Cl
O
Cl
Cl
O
7
N
Cl
N
8
H
1
5
O
+
O2
4
3
12
13
Scheme 3. Reagents and conditions: (a) Amberlyst H15Ò, toluene, 60 °C, 6 days, 37%.

K. Wiedemeyer, B. Wünsch / Carbohydrate Research 359 (2012) 24–29
27
Cl
Cl
Cl
O
O
Cl
N
H
N
H
(a)
(b) or (c)
6
O
O
OCH3
OCH3
NH2
R2N
15: NR2 = NHBn
16: NR2 = N(CH3)2
14
α: OCH3 axial
β: OCH3 equatorial
Scheme 4. Reagents and conditions: (a) H2, Raney-Ni, MeOH, NaOH, rt, balloon, 22 h, 77%; (b) PhCH@O, Na2SO4, CH2Cl2, rt, 7 days; then NaBH4, MeOH, rt, 21 h, 9% (15
a
), 31%
(mixture of diastereomers); (c) CH2@O, NaBH3CN, MeOH, rt, 28 h, 37% (16a), 29% (mixture of diastereomers).
Table 1
mixture was stirred for additional 3.5 h. The solvent was removed
in vacuo, the residue was dissolved in water (10 mL) and the aque-
ous layer was extracted with Et2O (2 ꢀ 20 mL). The organic layers
were dried (MgSO4), concentrated in vacuo and the residue was
purified by fc (2 cm, TBME–acetone 70/30, fractions 5 mL,
Rf = 0.28). Colorless oil, that became solid in the refrigerator, yield
242 mg (61%). MS (EI): m/z [%] 361/363 [M+, 4/2.9], 330/332/334
[MꢁOCH3, 12.1/8.5/2.1], 159/161/163 [–CH2PhCl2+, 73/49/14]. MS
(CI, NH3): m/z [%] 379/381/383 [M +NH4+, 4.1/2.6/0.4]. Anal. Calcd
for C16H21Cl2NO4 (362.3): C, 53.05; H, 5.84; N, 3.87. Found: C,
~
r1, r2 and NMDA receptor affinity
Compd
NR2
Ki SEM (nM); n = 3
r1
r2
NMDA (PCP)
3b2
NHBn
NHCH3
N(CH3)2
—
NHBn
N(CH3)2
83 32
2520 960
>10
>10
>10
>10
>10
>10
n.d.
n.d.
n.d.
n.d.
l
l
l
l
l
l
M
M
M
M
M
M
4
5
a
a
/b2
/b2
69 5.0
21 1.0
860 396
>1.0
>1.0
3.6 0.20
2.2 0.31
661 115
n.d.
>10
>10
>10
>10
>10
n.d.
lM
lM
lM
lM
lM
13
15
16
a
a
l
l
M
M
(+)-Pentazocine
Haloperidol
Progesterone
Ditolylguanidine
Phencyclidine
34 2.3
n.d.
64 11
n.d.
53.15; H, 6.16; N, 3.73. IR (ATR, film):
m
3293 (
m
N–H), 1647
C–O). 1H
+b-is.), 1.49–
+b-is. or 2-Heq +b-
+b-is. or 2-Heq +b-is.), 3.12–3.64
+b-is.), 3.14 (s, 2ꢀ0.5H, COCH2Ph,
(
m
O@C–NH, amide I), 1553 (d N–H, amide II), 1034 (
NMR (CDCl3): d 1.16–1.46 (m, 2H, 2-Hax + 4-Hax
1.92 (m, 2H, CH2CH2NH, +b-is./1H, 4-Heq
is.), 2.00–2.20 (m, 1H, 4-Heq
(m, 1H, CH2CH2NH,
m
,
a
n.d.
15 3.1
a
,
a
, a
The exact Ki-values were recorded only, when a significant reduction of the radi-
oligand binding was observed at a test compound concentration of 1 M ( 1) or
10 M ( 2, NMDA).
,
a
, a
l
r
a
a
a
/b-is.),
/b-is.),
l
r
n.d. = not determined.
3.20 (s, 2ꢀ0.5H, COCH2Ph,
a
/b-is.), 3.43 (s, 3ꢀ0.5H, OCH3,
/b-is.), 3.69–3.85 (m, 1H, 5-H,
+b-is.), 4.23 (dd, J = 9.6/2.0 Hz, 0.5H, 1-
-is.), 5.95 (s,
/b-is.), 7.11
/b-is.), 7.12 (d, J = 8.2 Hz, 0.5H,
/b-is.), 7.36 (d, J = 1.5 Hz, 0.5H, arom. H, 20-H,
b-is.), 7.37 (d, J = 2.1 Hz, 0.5H, arom. H, 20-H,
/b-is.), 7.40 (d,
J = 8.2 Hz, 0.5H, arom. H, 50-H,
/b-is.), 7.41 (d, J = 8.2 Hz, 0.5H,
arom. H, 50-H,
/b-is.); a signal for the OH-proton is not seen in
the spectrum. Ratio of 9 -anomer): 9b (b-anomer) is 50:50.
3.49 (s, 3ꢀ0.5H, OCH3,
a
a
a+b-is.),
3.98–4.08 (m, 1H, 3-H,
4. Experimental
Hax, b-is.), 4.58 (t, broad, J = 3.1 Hz, 0.5H, 1-Heq, a
broad, 0.5H, NH,
a/b-is.), 6.11 (s, broad, 0.5H, NH, a
4.1. Chemistry, general
(d, J = 8.2 Hz, 0.5H, arom. H, 60-H,
a
arom. H, 60-H,
a
a/
Unless otherwise noted, moisture-sensitive reactions were con-
ducted under dry nitrogen. Thin-layer chromatography (tlc): silica
gel 60 F254 plates (E.Merck). Flash chromatography (fc): silica gel
a
a
a
60, 40–63
l
m (E.Merck); parentheses include: diameter of the col-
a (a
umn (cm), eluent, fraction size (mL), and Rf-value. Melting points
(mp): melting point apparatus SMP2 (Stuart Scientific), uncor-
rected. Optical rotation: Polarimeter 241 (Perkin–Elmer), 1.0 dm
tube; concentration c (g/100 mL); temperature 20 °C. Elemental
analyses (CHN): Vario EL (Elementaranalysesysteme GmbH) and
Elemental Analyzer 240 (Perkin–Elmer). Mass spectra: Finnigan
MAT 44S, MAT 312, MAT 8200, and TSQ 7000, electron-impact
(EI) or chemical ionization (CI) or electro-spray-ionization (LC-
ESI/ESI-direct) or atmospheric pressure chemical ionization
(APCI/FIA-APCI/LC-APCI) mode. IR spectroscopy: 1605 FT-IR spec-
trometer (Perkin–Elmer) with Universal ATR sampling accessory.
1H NMR spectra (300 MHz), 13C NMR spectra (75 MHz): Unity
300 FT NMR spectrometer (Varian); d in parts per million (ppm)
relative to tetramethylsilane; coupling constants J (in Hz) are given
with 0.5 Hz resolution; the assignment of 1H and 13C NMR signals
was supported by 2D NMR techniques.
4.3. Methyl 7-[(3,4-dichlorophenyl)acetylamino]-3-O-tosyl-
2,4,6,7-tetradeoxy- - and b- -glucoheptopyranoside (10)
a
D
Crude alcohol 9 (970 mg, 2.7 mmol) was dissolved in CH2Cl2
(50 mL). Then p-toluenesulfonyl chloride (3.27 g, 17.2 mmol) and
NEt3 (4.7 mL, 33.7 mmol) were added. Under ice cooling 4-dimeth-
ylaminopyridine (1.6 g, 13.1 mmol) was added and the mixture
was stirred at 0 °C for 10 min. Then it was heated to reflux for
28 h. The mixture was washed with 1 M HCl (25 mL) and a satu-
rated solution of NaHCO3 (25 mL). The organic layer was dried
(MgSO4), concentrated in vacuo and the residue was purified by
fc (3 cm, EtOAc–acetone 80/20, fractions 10 mL, Rf = 0.51). Pale yel-
low oil, yield 1.1 g (80%). C23H27Cl2NO6S (516.4). MS (EI): m/z [%]
159/161/163 [–CH2PhCl2+, 58/37/6.5]. MS (LC/ESI): m/z [%] 538/
540/542 [M+Na+, 100/63/11]. MS (CI, isobutane): m/z [%] 314/
316/318 [MH+ꢁOTosꢁOCH3, 100/61/10.2]. HRMS (EI): Calcd for
4.2. Methyl 7-[(3,4-dichlorophenyl)acetylamino]-2,4,6,7-
C
15H15Cl2NO2 (MꢁTosOHꢁHOCH3), 311.0480. Found: 311.0477.
~
m
tetradeoxy-
a
- and b-
D
-glucoheptopyranoside (9)
IR (ATR, film):
3290 (
m
N–H), 1648 (
m
O@C–NH, amide I), 1548 (d
N–H, amide II), 1352 (R–SO2–OR0), 1174 (
mC–O), 730, 670 (cCHoop,
NaBH4 (117 mg, 3.1 mmol) was added to a solution of ketone 2
(393 mg, 1.1 mmol) in MeOH (15 mL) and the mixture was stirred
at rt for 3.5 h. Then NaBH4 (130 mg, 3.4 mmol) was added and the
arom.). 1H NMR (CDCl3): d 1.36–2.11 (m, 2H, 2-Hax + 2-Heq, isomer
1, 2, 3/2H, CH2CH2NH, isomer 1, 2, 3/2H, 4-Hax + 4-Heq, isomer 1, 2,
3), 2.44 (s, 3ꢀ0.4H, PhCH3, isomer 2), 2.45 (s, 3ꢀ0.45H, PhCH3,

28
K. Wiedemeyer, B. Wünsch / Carbohydrate Research 359 (2012) 24–29
isomer 1), 2.49 (s, 3ꢀ0.15H, PhCH3, isomer 3), 3.08–3.60 (m, 2H,
CH2CH2NH, isomer 1, 2, 3/0.45H, 5-Hax isomer 1), 3.10 (s,
1.27 (q, J = 12.0 Hz, 1H, 4-Hax), 1.46 (td, J = 12.8/3.7 Hz, 1H, 2-
,
Hax), 1.52–1.75 (m, 2H, CH2CH2NH), 1.81–1.89 (m, 1H, 2-Heq o. 4-
3 ꢀ 0.15H, OCH3, isomer 3), 3.14 (s, 3 ꢀ 0.4H, OCH3, isomer 2),
3.38 (s, 3 ꢀ 0.45H, OCH3, isomer 1), 3.45 (s, 2 ꢀ 0.45H, COCH2Ph,
isomer 1), 3.47 (s, 2 ꢀ 0.15H, COCH2Ph, isomer 3), 3.48 (s,
2 ꢀ 0.4H, COCH2Ph, isomer 2), 3.65–3.77 (m, 0.15H, 5-H, isomer
3), 4.02–4.11 (m, 0.4H, 5-H, isomer 2), 4.15 (dd, J = 9.8/1.8 Hz,
0.45H, 1-Hax, isomer 1), 4.45 (d, J = 4.0 Hz, 0.4H, 1-Heq, isomer 2),
4.52 (d, J = 2.1 Hz, 0.15H, 1-Heq, isomer 3), 4.56 (tt, J = 11.6/
5.1 Hz, 0.45H, 3-Hax, isomer 1), 4.76–4.81 (m, 0.15H, 3-Hax, isomer
3/0.4H, 3-Heq, isomer 2), 5.86 (s, broad, 0.45H, NH, isomer 1), 5.99
(s, broad, 0.15H, NH, isomer 3), 6.08 (s, broad, 0.4H, NH, isomer 2),
7.07–7.12 (m, 1H, arom. H, 60-H, isomer 1, 2, 3), 7.31–7.35 (m, 2H,
arom. H, Tosyl-H, m-pos., isomer 1, 2, 3/1H, arom. H, 50-H, isomer 1,
2, 3), 7.38–7.41 (m, 1H, arom. H, 20-H, isomer 1, 2, 3), 7.75–7.79 (m,
2H, arom. H, Tosyl-H, o-pos., isomer 1, 2, 3). According to the 1H
NMR spectrum around 15% of the epimer epi-10 with axially ori-
H
eq), 1.98–2.05 (m, 1H, 2-Heq o. 4-Heq), 3.10–3.22 (m, 1H,
CH2CH2NH), 3.15 (s, 3H, OCH3), 3.49 (s, 2H, COCH2Ph), 3.51–3.65
(m, 1H, CH2CH2NH), 3.68–3.79 (m, 2H, 3-H and 5-H), 4.57 (d,
J = 3.1 Hz, 1H, 1-Heq), 6.09 (s, broad, 1H, NH), 7.10 (dd, J = 8.2/
2.1 Hz, 1H, arom. H, 60-H), 7.35 (d, J = 1.8 Hz, 1H, arom. H, 20-H),
7.42 (d, J = 8.2 Hz, 1H, arom. H, 50-H).
4.5. 2-(3,4-Dichlorophenyl)-1-[(1R,5S)-2-oxa-6-
azabicyclo[3.3.1]non-3-en-6-yl]ethan-1-one (13)
A mixture of azide 6 (169 mg, 0.44 mmol), acidic ion-exchange
resin Amberlyst-H15Ò (154 mg, 0.7 meq), and toluene (20 mL) was
heated to 60 °C for 5 days. A further amount of Amberlyst-H15Ò
(168 mg, 0.76 meq) was added and the mixture was heated for an-
other day. After filtration, the organic layer was removed in vacuo
and the residue was purified by fc (2 cm, EtOAc–petroleum ether
70/30, fractions 5 mL, Rf = 0.52). Colorless solid, mp 77 °C, yield
ented tosyloxy group are present. Ratio of 10a (a-anomer): 10b
(b-anomer): epi-10 is 45:40:15.
51 mg (37%). [
a
]
-113.0 (c 1.026, MeOH). MS (EI): m/z [%] 159/
589
4.4. Methyl 3-azido-7-[(3,4-dichlorophenyl)acetylamino]-
2,3,4,6,7-pentadeoxy- - and b- -alloheptopyranoside (6) and
methyl 3-azido-7-[(3,4-dichlorophenyl)acetylamino]-2,3,4,6,7-
pentadeoxy- - and b- -glucoheptopyranoside (epi-6)
161/163 [–CH2PhCl2+, 37/23/3]. MS (LC/ESI): m/z [%] 312/314/316
+
a
D
[MH+, 100/68/11]. MS (CI, NH3): m/z [%] 329/331/333 [M+NH4
,
5.8/3.5/0.6], 312/314/316 [MH+, 100/66/12]. Anal. Calcd for
a
D
C
15H15Cl2NO2 (312.2): C 57.71 H 4.84 N 4.49. Found C 57.31 H
~
4.87 N 4.88. IR (ATR, neat):
1028 (
m
1628 (
m
O@C–N, amide I), 1236,
A mixture of tosylate 9 (617 mg, 1.2 mmol), NaN3 (849 mg,
13.1 mmol), and DMF (25 mL) was heated to reflux for 8 h. After
addition of H2O (25 mL), the mixture was extracted with Et2O
(3 ꢀ 25 mL). The organic layer was dried (MgSO4), concentrated
in vacuo and the residue was purified by fc (2 cm, EtOAc, fractions
5 mL).
m
C–O). 1H NMR (CDCl3): d 1.53 (tdd, J = 13.2/7.0/2.5 Hz,
0.55H, 8-CH2, rotamer 2), 1.48–2.02 (m, 1H, 8-CH2, rotamer 1+2/
0.45H, 8-CH2, rotamer 1/2H, 9-CH2, rotamer 1+2), 3.48 (td,
J = 13.0/4.0 Hz, 1H, 7-CH2, rotamer 1+2), 3.59 (dd, J = 13.0/6.8 Hz,
1H, 7-CH2, rotamer 1+2), 3.65 (s, 2 ꢀ 0.55H, COCH2Ph, rotamer 2),
3.71 (s, 2 ꢀ 0.45H, COCH2Ph, rotamer 1), 4.26–4.32 (m, 0.45H, 5-
H, rotamer 1), 4.40–4.54 (m, 0.45H, 4-H, rotamer 1/1H, 1-H, rot-
amer 1+2), 4.75 (t, J = 5.9 Hz, 0.55H, 4-H, rotamer 2), 5.24–5.27
(m, 0.55H, 5-H, rotamer 2), 6.65 (d, J = 6.1 Hz, 0.45H, 3-H, rotamer
1), 6.70 (d, J = 5.8 Hz, 0.55H, 3-H, rotamer 2), 7.09 (dd, J = 8.5/
1.7 Hz, 0.55H, arom. H, 60-H, rotamer 2), 7.12 (dd, J = 8.5/2.1 Hz,
0.45H, arom. H, 60-H, rotamer 1), 7.34 (d, J = 1.8 Hz, 1H, arom. H,
20-H, rotamer 1+2), 7.39 (d, J = 8.2 Hz, 0.55H, arom. H, 50-H, rotamer
2), 7.40 (d, J = 8.2 Hz, 0.45H, arom. H, 50-H, rotamer 1). Ratio of rot-
amer 1 and rotamer 2 is 45:55. 13C NMR (CDCl3): d 29.3 (0.45C, C-
9), 30.0 (0.55C, C-9), 31.9 (0.45C, CH2CH2NH), 32.8 (0.55C,
CH2CH2NH), 38.7 (1H, C-7), 39.1 (0.55C, C-5), 40.2 (0.45C,
COCH2Ph), 40.5 (0.55C, COCH2Ph), 44.1 (0.45C, C-5), 67.9 (0.55C,
C-1), 68.0 (0.45C, C-1), 96.9 (0.45C, C-4), 97.8 (0.55C, C-4), 128.1,
128.9, 130.5, 130.7, 130.9, 132.6, 135.3 (6C, arom. C), 148.5 (1C,
C-3), 168.1 (1C, NHCOCH2).
Compound 6 (axial azide, Rf = 0.51): Colorless solid, mp 104 °C,
yield 269 mg (64%). MS (EI): m/z [%] 356/358 [MH+ꢁOCH3, 5.6/1.6],
314/316 [MH+ꢁOCH3ꢁN3, 6.3/1.5], 159/161/163 [–CH2PhCl2+, 73/
48/9]. MS (APCI): m/z [%] 387/389/391 [MH+, 100/51/7]. MS (CI,
NH3): m/z [%] 404/406/408 [M+NH4+, 9/6/1], 387/389/391 [MH+,
47/32/6], 329/331/333 [MꢁN3ꢁCH3, 40/26/5]. Anal. Calcd for
C
16H20Cl2N4O3 (387.3): C 49.62 H 5.21 N 14.47. Found C 50.41 H
~
5.36 N 13.85. IR (ATR, neat):
m
3301 (
m
N–H), 2093 (
m
N3), 1646
C–O).
+b-is./2H,
(mO@C–NH, amide I), 1551 (d N–H, amide II), 1121, 1039 (m
1H NMR (CDCl3): d 1.45–1.97 (m, 2H, 2-Hax + 2-Heq
,
a
CH2CH2NH,
CH2CH2NH,
a
a
+b-is./2H, 4-Hax + 4-Heq
+b-is.), 3.19 (s, 3ꢀ0.45H, OCH3,
,
a
+b-is.), 3.11–3.64 (m, 2H,
a-is.), 3.42 (s,
3 ꢀ 0.55H, OCH3, b-is.), 3.46 (s, 2 ꢀ 0.55H, COCH2Ph, b-is.), 3.49
(s, 2 ꢀ 0.45H, COCH2Ph, -is.), 3.75 (ddt, J = 11.6/8.0/3.0 Hz,
0.55H, 5-H, b-is.), 3.92 (‘quint’, J = 3.4 Hz, 0.45H, 3-H, -is.), 4.00
(tt, J = 9.6/3.4 Hz, 0.45H, 5-H, -is.), 4.09 (‘quint’, J = 3.2 Hz, 0.55H,
3-H, b-is.), 4.49 (d, J = 2.7 Hz, 0.45H, 1-Heq -is.), 4.52 (dd, J = 9.6/
2.0 Hz, 0.55H, 1-Hax, b-is.), 5.91 (s, broad, 0.55H, NH, b-is.), 6.07
(s, broad, 0.45H, NH, -is.), 7.11 (dd, J = 8.2/2.1 Hz, 0.45H, arom.
H, 60-H, -is.), 7.12 (dd, J = 8.2/2.1 Hz, 0.55H, arom. H, 60-H, b-is.),
7.36 (d, J = 2.1 Hz, 0.45H, arom. H, 20-H,
-is.), 7.37 (d, J = 2.1 Hz,
0.55H, arom. H, 20-H, b-is.), 7.40 (d, J = 8.2 Hz, 0.55H, arom. H, 50-
H, b-is.), 7.41 (d, J = 8.2 Hz, 0.45H, arom. H, 50-H,
-is.). Ratio of
-anomer): 6b (b-anomer) is 45:55. 13C NMR (CDCl3): d 31.5,
a
a
a
,
a
4.6. Methyl 3-amino-7-[(3,4-dichlorophenyl)acetylamino]-
2,3,4,6,7-pentadeoxy-a- and b-D-alloheptopyranoside (14)
a
a
A mixture of azide 6 (50 mg, 0.13 mmol), Raney-Ni, 5 M NaOH
(1 mL), and MeOH (5 mL) was stirred under a H2 atmosphere (bal-
loon) at rt for 22 h. Raney-Ni was removed by filtration through
CeliteÒAFA and the solvent was removed in vacuo. After addition
of H2O (5 mL), the mixture was extracted with CH2Cl2
(4 ꢀ 20 mL). The organic layer was dried (MgSO4), concentrated
in vacuo and the resulting product was directly used for the next
step without further purification. Colorless oil (yield 36 mg, 77%).
a
a
6a (a
34.2, 34.5, 34.6, 34.8 (3C, C-2, C-4, CH2CH2NH), 37.0 (0.55C,
CH2CH2NH), 37.6 (0.45C, CH2CH2NH), 42.8 (1C, COCH2Ph), 52.7
(0.45C, C-3), 56.0 (0.55C, C-3), 55.1 (0.45C, OCH3), 56.3 (0.55C,
OCH3), 63.4 (0.45C, C-5), 69.7 (0.55C, C-5), 97.2 (0.45C, C-1), 99.3
(0.55C, C-1), 126.6 (0.55C, arom. C, 60-C), 128.9 (0.45C, arom. C,
60-C), 130.7, 131.1, 131.4, 131.5, 132.8 (4C, arom. C, 30-C, 50-C.40,
20-C), 135.1 (0.55C, arom. C, 10-C), 135.2 (0.45C, arom. C, 10-C),
169.3 (0.45C, NHCOCH2), 169.5 (0.55C, NHCOCH2).
C
16H22Cl2N2O3 (361.3). MS (EI): m/z [%] 329/331/333 [MꢁOCH3,
4/2/0.4], 159/161/163 [–CH2PhCl2+, 38/24/4]. MS (CI, isobutane):
m/z [%] 361/363/365 [MH+, 44/26/4], 329/331/333 [MꢁOCH3,
~
m
100/77/15]. IR (ATR, film):
3284 (
m
N–H), 1644 (
m
O@C–NH, amide
I), 1555 (d N–H, amide II), 1119, 1032 (
1.19–1.76 (m, 2H, 2-Hax + 2-Heq +b-is./2H, CH2CH2NH,
2H, 4-Hax + 4-Heq +b-is.), 1.87 (s, broad, 2H, NH2, +b-is.), 3.06–
3.64 (m, 2H, CH2CH2NH, +b-is./0.4H, 5-H, b-is./0.4H, 3-Heq, b-
m
C–O). 1H NMR (CDCl3): d
+b-is./
epi-6 (equatorial azide, Rf = 0.45): Colorless oil, that became so-
lid in the refrigerator, yield 25 mg (6%). C16H20Cl2N4O3 (387.3). MS
(APCI): m/z [%] 387/389/391 [MH+, 100/51/7]. 1H NMR (CDCl3): d
,
a
a
,
a
a
a

K. Wiedemeyer, B. Wünsch / Carbohydrate Research 359 (2012) 24–29
29
~
is.), 3.14 (s, 3 ꢀ 0.6H, OCH3,
3.45 (s, 2 ꢀ 0.4H, COCH2Ph, b-is.), 3.48 (s, 2 ꢀ 0.6H, COCH2Ph,
is.), 3.73 (ddt, J = 11.3/8.2/2.4 Hz, 0.6H, 5-H, -is.), 3.91–4.03 (m,
0.6H, 3-Heq -is.), 4.52 (d, J = 4.0 Hz, 0.6H, 1-Heq -is.), 4.72 (dd,
J = 9.5/2.4 Hz, 0.4H, 1-Hax, b-is.), 6.22 (s, broad, 0.6H, NH, -is.),
6.37 (s, broad, 0.4H, NH, b-is.), 7.11 (dd, J = 8.2/2.1 Hz, 0.4H, arom.
H, 60-H, b-is.), 7.12 (dd, J = 8.2/2.1 Hz, 0.6H, arom. H, 60-H,
-is.),
7.35 (d, J = 2.1 Hz, 0.4H, arom. H, 20-H, b-is.), 7.36 (d, J = 2.4 Hz,
0.6H, arom. H, 20-H, -is.), 7.39 (d, J = 8.2 Hz, 0.4H, arom. H, 50-H,
b-is.), 7.40 (d, J = 8.2 Hz, 0.6H, arom. H, 50-H,
-is.). Ratio of 14
-anomer): 14b (b-anomer) is 60:40.
a
-is.), 3.17 (s, 3 ꢀ 0.4H, OCH3, b-is.),
m
3279 (mN–H), 1646 (
m
O@C–NH, amide I), 1555 (d N–H, amide
a
-
II), 1132, 1032 (
d 1.51–1.83 (m, 2H, 4-Hax + 4-Heq/2H, 2-Hax + 2-Heq/2H,
mC–O), 831, 707 (c
CHoop, arom.). 1H NMR (CDCl3):
a
,
a
,
a
CH2CH2NH), 2.35 (s, 6H, N(CH3)2), 3.19–3.57 (m, 2H, CH2CH2NH/
1H, 3-Heq), 3.26 (s, 3H, OCH3), 3.51 (s, 2H, COCH2Ph), 4.07-4.17
(m, 1H, 5-H), 4.57 (t, J = 4.9 Hz, 1H, 1-Heq), 6.27 (s, broad, 1H,
NH), 7.15 (dd, J = 8.2/2.1 Hz, 1H, arom. H, 60-H), 7.37 (d,
J = 2.1 Hz, 1H, arom. H, 20-H), 7.40 (d, J = 8.2 Hz, 1H, arom. H, 50-
H). Only 16a (a-anomer) was isolated. In addition to 16a a mixture
of diastereomeric dimethylamines was isolated as yellow oil
(Rf = 0.14), yield 11 mg (29%).
a
a
a
a
a
(a
4.7. Methyl 3-benzylamino-7-[(3,4-dichlorophenyl)acetyl-
amino]-2,3,4,6,7-pentadeoxy- -alloheptopyranoside (15a)
5. Receptor binding studies
a-
D
5.1. r1 and r2 assays
The primary amine 14 (77 mg, 0.22 mmol) was dissolved in
CH2Cl2 (7 mL). Anhydrous Na2SO4 (150 mg, 1.9 mmol), anhydrous
Na2CO3 (75 mg, 1.9 mmol), and benzaldehyde (0.5 mL, 5.0 mmol)
were added and the mixture was stirred at rt for 7 days. The solid
was filtered off and the solvent was evaporated in vacuo. The res-
idue was dissolved in MeOH (7 mL) and NaBH4 (25 mg, 0.67 mmol)
was added. After stirring at rt for 21 h, the solvent was evaporated,
2 M NaOH (7 mL) was added and the aqueous layer was extracted
with CH2Cl2 (3 ꢀ 10 mL). The organic layer was dried (MgSO4),
concentrated in vacuo and the residue was purified by fc (2 cm,
CH2Cl2–MeOH 95/5, fractions 2 mL, Rf = 0.32). Pale yellow oil, yield
The
r1 and r2 assays were performed as described in Refs. 12–
14.
5.2. NMDA assay
The affinity toward the phencyclidine (PCP) binding site of the
NMDA receptor was determined as described in Refs. 15,16.
Acknowledgements
9 mg (9%). C23H28Cl2N2O3 (451.4). [a]589 +33.4 (c 0.162, MeOH). MS
Thanks are due to the Deutsche Forschungsgemeinschaft for
financial support of this project. Donation of chemicals and refer-
ence compounds by Degussa AG, Janssen-Cilag GmbH, and Bristol-
Myers Squibb is gratefully acknowledged.
(EI): m/z [%] 106 [PhCH2NH+, 63], 91 [PhCH2+, 100]. MS (CI, NH3):
+
~
m
m/z [%] 451/453/455 [MH , 100/50/9]. IR (ATR, film):
3289 (mN-
H), 1645 (
1033 ( C–O), 732 (
J = 13.7/11.9/4.0 Hz, 1H, 4-Hax), 1.53–1.90 (m, 1H, 4-Heq/2H, 2-
ax + 2-Heq/2H, CH2CH2NH), 2.89–2.94 (m, 1H, 3-H), 3.07-3.34
m
O@C–NH, amide I), 1555 (d N–H, amide II), 1121,
m
c
CHoop, arom.). 1H NMR (CDCl3): d 1.43 (ddd,
References
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(s, 2H, NHCH2Ph), 4.46 (d, J = 3.4 Hz, 1H, 1-Heq), 6.21 (s, broad,
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In addition to 15 a mixture of diastereomeric benzylamines was
a
isolated as colorless oil (Rf = 0.44), yield 30 mg (31%).
4.8. Methyl 3-dimethylamino-7-[(3,4-dichlorophenyl)acetyl-
amino]-2,3,4,6,7-pentadeoxy-a-D-alloheptopyranoside (16a)
A solution of primary amine 14 (36 mg, 0.10 mmol), formalde-
hyde solution (37% in water, 0.15 mL, 1.8 mmol), and NaBH3CN
(60 mg, 0.9 mmol) in MeOH (5 mL) was stirred at rt for 28 h. Then
2 M NaOH (5 mL) was added and the mixture was concentrated in
vacuo to around 2 mL, which was extracted with CH2Cl2
(3 ꢀ 10 mL). The organic layer was dried (MgSO4), concentrated
in vacuo and the residue was purified by fc (1 cm, CH2Cl2–MeOH
80/20, fractions 2 mL, Rf = 0.39). Pale yellow oil, yield 14 mg
(37%). [
a
]
+25.1 (c 0.018, MeOH). MS (EI): m/z [%] 373/375/377
589
[MꢁCH3, 8/6/0.7], 159/161/163 [–CH2PhCl2+, 47/27/4]. MS (CI, iso-
butane): m/z [%] 389/391/393 [MH+, 34/18/3], 357/359/361
[MꢁOCH3, 100/59/11]. Anal. Calcd for C18H26Cl2N2O3 (389.3): C
55.53 H 6.73 N 7.20. Found C 54.87 H 6.84 N 7.30. IR (ATR, film):