De novo synthesis and lectin binding studies of unsaturated carba-pyranoses

Article abstract of DOI:10.1039/c003597a

Starting from branched para-benzoquinones a practical and highly flexible route is described for the preparation of unsaturated carbapyranoses. The potential of the synthesized galactose analogues to act as competitive inhibitors in lectin-carbohydrate interactions is investigated by means of Surface Plasmon Resonance (SPR) Spectroscopy.

Full text of DOI:10.1039/c003597a

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PAPER
www.rsc.org/obc | Organic & Biomolecular Chemistry
De novo synthesis and lectin binding studies of unsaturated carba-pyranoses†
Timo Leermann,*a Oliver Block,b Michael A. L. Podeschwa,c Uwe Pfu¨llerd and Hans-Josef Altenbacha
Received 26th February 2010, Accepted 4th June 2010
First published as an Advance Article on the web 30th June 2010
DOI: 10.1039/c003597a
Starting from branched para-benzoquinones a practical and highly flexible route is described for the
preparation of unsaturated carbapyranoses. The potential of the synthesized galactose analogues to act
as competitive inhibitors in lectin-carbohydrate interactions is investigated by means of Surface
Plasmon Resonance (SPR) Spectroscopy.
moiety (see Fig. 1). In connection with our general interest in
Introduction
carbohydrate mimics we wanted to prepare the whole series
A primary event in many biological processes involved in cell–
of unsaturated carba-pyranoses and also some representative 6-
cell recognition/adhesion is the specific attachment of proteins to
desoxy derivatives, a class of compounds which have not been
glycolipids or glycoproteins which are located in cell membranes.1
isolated from natural sources so far.
Lectins, a class of sugar binding proteins, show specificity to
terminal and/or subterminal carbohydrate residues and have at
least two sugar combining sites. Highly biological active lectins are
for example the lectins of European Mistletoe (ML I, ML II, ML
III) recognizing specifically galactosyl/N-acetylgalactosamine
residues.2 The mistletoe lectins are the main active principles
R
R
R
in preparations like Iscadorꢀ, Plenosolꢀ or Iscusinꢀ which are
therapeutically widely used in adjuvant cancer therapy.
Up to now the specific recognition of saccharides by lectins
has been the subject of many studies3 and it has been found
that even simple monosaccharides are selectively bound. However
the possible recognition of carbasugars and other carbohydrate
analogues by lectins has not been investigated so far.
Carbasugars4 in general are characterized by the replacement
of the ring oxygen atom of a furanoid or pyranoid sugar by a
methylene group.5 In an interesting manner, these molecules are
often recognized by sugar processing enzymes e.g. glycosidases
and glycotransferases instead of the original monosaccharide
and exhibit a large variety of biological activities, for example,
antibiotic, antiviral or plant growing inhibiting properties.6 Not
only saturated carbasugars have been isolated from natural
sources, but also unsaturated ones bearing a ring double bond.
Typical examples of unsaturated naturally occuring carbasugars
are streptol,7 valienamine,8 validamine,9 cyclophellitol,10 (+)-
MK760711 or the families of gabosines,12 pericosines13 and
piperinols.14 (+)-MK7607 shows effective herbicidal activity and
is the 4-epimer of streptol, a plant-growth inhibitor. But these
are just two of eight possible diastereoisomers within the class of
the unsaturated carba-pyranoses with an exocyclic hydroxymethyl
Fig. 1 Possible diastereoisomers of unsaturated carbasugars bearing a
hydroxymethyl side chain (only one enantiomer is shown).
Results and discussion
Preparation of unsaturated carbapyranoses
In analogy to the synthetic route towards conduritols, inositols
and derivatives thereof which was developed in our laboratory,15
we considered the possibility of preparing unsaturated carbapyra-
noses starting from substituted para-benzoquinones. After finding
that bromination of monosubstituted para-benzoquinones takes
place regioselectively at the unsubstituted double bond and
the reduction with sodium borohydride gives mainly the all-
trans diastereomer the branched intermediates 3 and 6 can be
stereoselectively synthesized in high yields (see Scheme 1). The
reaction of 3 and 6 with silver acetate in dry acetic acid (Pre´vost
conditions16) provides pentaacetate 7 and tetraacetate 8 which
both possess the all-trans configuration. Deacetylation is achieved
by reacting the acetates with sodium methanolate to deliver the
corresponding alcohols 9 and 10 respectively.
aBergische University Wuppertal, Gaussstrasse 20, 42097, Wuppertal,
Germany. E-mail: timo.leermann@broteleermann.de; Fax: +49 (0)202
439 2648
bMerck KGaA, Frankfurter Strasse 250, 64293, Darmstadt, Germany
cSanofi-Aventis, Industriepark Hoechst, 65926, Frankfurt, Germany
dUniversity Medical Center Hamburg, Zentrum fu¨r Experimentelle Medizin,
Institut fu¨r Anatomie II, PhytoLab, Martinistrasse 52, 20246, Hamburg,
Germany
Pentaacetate 11 and tetraacetate 12 with the cis,trans,cis
configuration can be prepared from the intermediates 3 and
6 by conversion with silver acetate in 90% aqueous acetic
acid (Woodward conditions17) followed by acetylation of the
† Electronic supplementary information (ESI) available: Synthetic proce-
dures, NMR spectra and representative SPR binding sensorgrams. See
DOI: 10.1039/c003597a
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Scheme 1 a) Br2, CH2Cl2, 5–10 ◦C, 98%; b) NaBH4, Et2O/H2O, -15 ◦C, 82%; c) Ac2O, pyridine, 0 ◦C – RT, 51%; d) Br2, CH2Cl2, 5–10 ◦C, 96%; e)
NaBH4, Et2O/H2O, -15 ◦C, 91%; f) Ac2O, pyridine, 0 ◦C–RT, 60%.
Scheme 2 a) AgOAc, AcOHabs., Ac2O, RF, 71%; b) NaOMe, MeOH, 0–5 ◦C, 100%; c) AgOAc, 90% AcOH, reflux, then Ac2O, pyridine, 35%; d)
NaOMe, MeOH, 0–5 ◦C, 82%; e) AgOAc, AcOHabs., Ac2O, reflux, 67%; f) NaOMe, MeOH, 0–5 ◦C, 88%; g) AgOAc, 90% AcOH, reflux, then Ac2O,
pyridine, 32%; h) NaOMe, MeOH, 0–5 ◦C, 88%.
crude material with acetic anhydride. Cleavage of the pro-
tecting groups under the above conditions gives pentol 13
(rac. MK7607) and the corresponding desoxy analogue 14 (see
Scheme 2).
Epoxides 15 and 16 can be prepared in high yields from 3 and
6 respectively by use of lithium hydroxide as base (see Scheme 3).
The regioselectivity of the epoxide formation was quite surprising.
However gs-HMBC (Gradient Selected Heteronuclear Multiple
Bond Coherence) NMR experiments show a coupling between
the methylene group (respectively the methyl group) and the
allylic proton H-6 which reveals the neighborship of the side
chain and the epoxy functionality. Nucleophilic ring opening
with water of epoxides 15 and 16 and subsequent peracetylation
with acetic anhydride delivers bromides 18 and 19. Conversion
of the bromides with silver acetate in 90% aqueous acetic acid
followed by acetylation of the crude material with acetic anhydride
yields compounds 20 and 21 which both possess the cis,trans,trans
configuration. Subsequent cleavage of the acetate protecting
groups by sodium methanolate gives pentol 22 (rac. streptol) and
the related desoxy analogue 23.
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Scheme 3 a) LiOH, Et2O/MeOH, -15–10 ◦C, 83%; b) p-TsOH, H2O, 0 ◦C–RT, then Ac2O, pyridine, 51%; c) AgOAc, 90% AcOH, reflux, then Ac2O,
pyridine, 65%; d) NaOMe, MeOH, 0–5 ◦C, 81%; e) LiOH, Et2O/MeOH, 0 ◦C, 72%; f) CBr4, H2O, 35 ◦C, then Ac2O, pyridine, 37%; g) AgOAc, 90%
AcOH, reflux, then Ac2O, pyridine, 38%; h) NaOMe, MeOH, 0–5 ◦C, 88%.
Scheme 4 a) K2CO3, MeOH, 0 ◦C, 100%; b) 2,2-dimethoxypropane, p-TsOH, acetone (abs.), 100%; c) NaOH, Et2O/H2O, room temperature; d) AcOH,
H2O, then Ac2O, pyridine, 52%; e) AgOAc, 90% AcOH, reflux, then Ac2O, pyridine, 54%; f) NaOMe, MeOH, 0–5 ◦C, 79%.
Acetal 25 can be synthesized in two steps from intermediate
3 (see Scheme 4). Cleavage of the acetate protecting groups
by potassium carbonate followed by conversion of the resulting
triol 24 with 2,2-dimethoxypropane delivers acetal 25. Epoxide
26 is prepared by reacting 25 with sodium hydroxide. Selective
opening of the epoxide in the allylic position and hydrolysis
of the acetal moiety is achieved by the addition of acetic acid
and the resulting crude material is peracetylated with acetic
anhydride to yield tetraacetate 27. Conversion of 27 with silver
acetate in 90% aqueous acetic acid followed by acetylation of the
crude material delivers pentaacetate 28. Subsequent cleavage of
the acetate protecting groups with sodium methanolate delivers
pentol 29 (rac.1-epi-MK7607) which possesses the trans,trans,cis
configuration.
in solution to a ligand immobilized on the sensor chip. We used this
technique to investigate the potential of some of the synthesized
racemic carbasugars to be recognized by the galactose-specific
Misteltoe Lectin I (ML I) and the N-acetylgalactosamine-specific
Misteltoe Lectin III (ML III). Asialofetuin, with its large number
of galactose moieties, is used as the immobilized ligand. As shown
by X-ray crystallography of ML I in complex with galactose the
3- and 4-hydroxyl groups of galactose are responsible for the
binding to the lectin.18 Therefore, with the exception of 9, from
the synthesized racemic carba-pyranoses only compounds which
exhibit the a- or b-galactose configuration were chosen for testing
and compared with the enantiopure unbranched compounds
(+)-30, (-)-30, (+)-31 and (-)-31 with such galacto-configuration
(see Fig. 2).
The measurements with ML I show a remarkable inhibition
of the lectin-ASF interaction by compounds 13 and 29 whereas
compounds 14 and (+)-31 exhibit a weaker inhibition (see Fig. 3).
Almost no inhibition is obtained with compound 9, which is the
only tested compound not exhibiting a galactose configuration
demonstrating the high specificity for this configuration also with
carbasugars.
Lectin binding studies
The Biological Interaction Analysis (BIA) via Surface Plasmon
Resonance (SPR) Spectroscopy allows the continuous monitoring
of interactions between two or more molecules. The SPR technique
detects changes expressed in response units (RU) in the interfacial
effective refractive index resulting from the binding of an analyte
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Fig. 4 Inhibition of the ASF-ML III interaction.
wich are lacking the ring double bond, show no affinity towards
ML I. This result implies that the steric and electronic environment
of the unsaturated carbapyranoses seems to be more similar to that
of the natural substrate than that of the corresponding saturated
carbasugars. In the case of enantiopure compounds, such as (+)-
31 and (-)-31, the lectin selectively binds to the enantiomer which
exhibits the D-galactose configuration.
Fig. 2 Carbasugars used for lectin binding studies.
Conclusions
The present work shows the potential of 3 and 6 as versatile
building blocks in the construction of unsaturated carbapyranoses
bearing an exocyclic hydroxymethyl or methyl moiety. Initial
results of the lectin binding studies prove that some of the
synthesized carbasugars show interesting inhibitory properties.
Future work will focus on the preparation of amino- or halogeno-
functionalized derivatives to provide a larger variety of com-
pounds for the further exploration of sugar binding sites in lectins
via SPR Spectroscopy.
Experimental
Fig. 3 Inhibition of the ASF-ML I interaction.
General
The second measurement using ML III instead of ML I shows
that an inhibition of the ASF-ML III interaction can not be
efficiently achieved by any of the tested compounds with this lectin
(see Fig. 4).
All NMR spectra were recorded on a Bruker ARX 400 (400 MHz)
1
spectrometer. Beside H and 13C experiments, 2D COSY (1H–
1
1H and H–13C), gs-HMBC (1H–13C) and DEPT spectra for the
unequivocal correlation of the hydrogen and carbon atoms were
recorded. The chemical shifts are given in ppm downfield of TMS,
although the solvents actually served as internal standard. The
multiplicity is given by the following symbols: s (singlet), d (dou-
blet), t (triplet), q (quartet), m (multiplet) and yt (pseudotriplet for
unresolved dd). The coupling constant J is given in Hz. Elemental
analysis was performed on a Perkin–Elmer elemental analyzer
240B. All organic extracts were dried over Na2SO4, filtered and
concentrated with a rotary evaporator under reduced pressure.
Only distilled solvents were used. The racemic Carba-a-galactose
and Carba-a-glucose have been synthesized following a procedure
published by Ogawa.19
The higher inhibition of the ASF-ML I interaction by branched
sugar mimetics, such as 13 and 29, in comparison to 14 or
the corresponding unbranched system (+)-31 indicates that the
hydroxymethyl side chain seems to be helpful for the binding to
the lectin. The comparison between 13 (a-galactose configuration)
and 29 (b-galactose configuration) on the one hand and 9 (a-
glucose configuration) on the other shows that the configuration
of the hydroxy groups at C-3 and C-4 is also crucial for the
recognition by ML I. Remarkably all compounds which exhibit an
affinitytowardsthelectinspossessaringdoublebond. Theracemic
carba-a-galactose (rac. C-Gal) and carba-a-glucose (rac. C-Gluc),
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BIAcore measurements
mixture is stirred for 12 h. Ice (100 g) is added and after stirring
for 15 min dichloromethane (100 mL) is added. The layers are
separated and the aqueous layer is extracted with dichloromethane
(2 ¥ 50 mL). The combined organic layer is washed with 0.75 N
HCl (3 ¥ 50 mL), saturated aquoeus NaHCO3 (3 ¥ 50 mL) and
brine (50 mL), dried over Na2SO4 and filtered. After evaporation,
the resulting residue is recrystallized from EtOH to yield 8.6 g
(20.1 mmol, 51%) of the desired product as colourless crystals.
1H-NMR (CDCl3): d 2.04 (s, 3H, CH3), 2.11 (s, 3H, CH3), 2.12
(s, 3H, CH3), 4.24–4.32 (AB, 2H, H-5 and H-6), 4.36 (d, 1H, J =
13.5 Hz, H-7a), 4.62 (d, 1H, J = 13.5 Hz, H-7b), 5.68 (m, 1H,
H-1 or H-4), 5.80 (s, 1H, H-3), 5.89 (d, 1H, J = 5.9 Hz, H-1
or H-4). 13C-NMR (CDCl3): d 20.5, 20.6, 20.7 (3 ¥ CH3), 51.6,
52.7 (C-5 and C-6), 62.5 (C-7), 71.7, 72.8 (C-1 and C-4), 126.4
A BIAcore XTM system (Pharmacia Biosensor AB, Sweden)
was used to investigate the potential of the synthesized galactose
analogues to act as competitive inhibitors in lectin-carbohydrate
interactions. The asialofetuin (ASF type II, Sigma–Aldrich) was
amine-coupled to a CM5 sensor chip (Pharmacia Biosensor
AB, Sweden) according to the manufacturer’s instructions. The
coupling level was 1100 resonance units (RU) after blocking
of the active coupling surface with ethanolamine. The empty
activated and blocked channel was used as the background surface.
HBS buffer (0.01 M HEPES, pH 7.4, 0.15 M NaCl, 3 mM
EDTA, 0.005% Surfactant P20) was used as running buffer. For
the specificity measurements a 1 : 1 (v/v) mixture of an analyte
solution (ML I or ML III, 5 mg ml-1 in HBS) and a solution
of a sugar (D-galactose, D-glucose, D-fucose, 50 mM in HBS) or
a carba-sugar (50 mM in HBS for enantiopure compounds and
100 mM in HBS for racemic compounds) was prepared. Prior to
use the mixture is filtered through a 0.22 mm filter and degased.
The injection volume was 20 ml. All measurements were performed
=
(C-3), 134.7 (C-2), 169.5, 169.7, 170.1 (3 ¥ C O). Anal. calcd. for
C13H16Br2O6: C, 36.48; H, 3.77. Found: C, 36.49; H, 3.75%.
(1SR,2RS,3RS,4SR)-5-[(Acetyloxy)methyl]cyclohex-5-ene-
1,2,3,4-tetrayl tetraacetate (7)
◦
To a suspension of 3.30 g (19.8 mmol) silver acetate in 20 mL
of dry acetic acid 200 mL of acetic anhydride are added and the
mixture is refluxed for 1h. After cooling of the suspension 3.15 g
(7.3 mmol) of 3 are added and the mixture is refluxed for 14 h.
After cooling in an ice bath 200 mL diethyl ether are added. The
reaction mixture is filtered and the residue is washed with 200 mL
of diethyl ether. The combined organic phases are washed with
saturated NaHCO3-solution (3 ¥ 50 ;mL) and once with brine
(50 mL). Removal of the solvent yields a colourless oil which can
be recrystallized from EtOH to yield 2.0 g (5.2 mmol, 71%) of a
at a flow rate of 20 ml min-1 at 25 C. The response is measured
after 180 s using the BIA evaluation software 3.0. For regeneration
a solution of D-galactose (50 mM in HBS) was used.
[(4RS,5RS)-4,5-Dibromo-3,6-dioxocyclohex-1-ene-1-yl]methyl
acetate (1)
8.1 g (50.4 mmol) bromine in 15 mL dichloromethane are added
dropwise over 1 h to a cooled (5–10 ◦C) solution of 8.9 g
(49.4 mmol) 3,6-Dioxocyclohexa-1,4-diene-1-yl)methyl acetate in
90 mL dichloromethane. The reaction mixture is allowed to warm
to RT and stirred for another 1.5 h. The dichloromethane is
evaporated to give 15.8 g (48.1 mmol, 98%) of the desired product
as a brown oil, which is immediately used for reduction without
further purification.
1
colourless solid. H-NMR (CDCl3): d 1.98 (s, 3H, CH3), 1.99 (s,
3H, CH3), 2.01 (s, 3H, CH3),2.02 (s, 3H, CH3), 2.03 (s, 3H, CH3),
4.36 (d, 1H, J = 13.4 Hz, H-7a), 4.65 (d, 1H, J = 13.4 Hz, H-7b),
5.31 (AB, 2H, H-2 and H-3), 5.55 (d, 1H, J = 5.8 Hz, H-1), 5.72
(s, 1H, H-6), 5.75 (d, 1H, J = 7.1 Hz, H-4). 13C-NMR (CDCl3): d
20.5, 20.5, 20.6, 20.8 (5 ¥ CH3), 62.4 (C-7), 70.2 (C-4), 70.7 (C-1),
70.8 (C-2), 72.0 (C-3), 126.2 (C-5), 133.7 (C-6), 169.7, 169.9, 169.9,
[(3RS,4SR,5SR,6RS)-4,5-Dibromo-3,6-dihydroxy-cyclohex-1-
ene-1yl]methyl acetate (2)
=
170.1, 170.2 (5 ¥ C O). Anal. calcd. for C17H22O10: C, 52.85; H,
5.74. Found: C, 52.96; H, 5.78%.
A solution of 15.8 g (48.1 mmol) 1 in 125 mL diethyl ether is cooled
to -15 ◦C. During a period of 1 h a solution of 3.9 g (103.1 mmol)
sodium borohydride in 55 mL H2O is added dropwise to the
vigorously stirred solution. The reaction mixture is allowed to
warm to room temperature and stirred for additional 2 h. The
etheral phase is separated and the aqueous layer is extracted with
diethyl ether (5 ¥ 50 ml). The combined organic phases are dried
over Na2SO4, filtered and the solvent is evaporated to yield 13.0 g
(1SR,2RS,3RS,4SR)-5-(Hydroxymethyl)cyclohex-5-ene-1,2,3,4-
tetrol (9)
To a solution of 1.02 g (2.6 mmol) 7 in 50 mL MeOH 1.1 mL
of a 1 N methanolic NaOMe-solution are added at 0 ◦C and
the reaction mixture is stirred for 14 h at approx. +5 ◦C. After
neutralization of the solution by addition of Dowex 50 ¥ 8 (H+)
and filtration, the solvent is evaporated to yield 470 mg (2.6 mmol,
100%) of the desired pentol as a colourless oil which can be
1
(39.5 mmol, 82%) of the desired compound as a brown oil. H-
NMR (DMSO-d6): d 2.02 (s, 3H, CH3), 4.11–4.31 (m, 4H, H-3,
H-4, H-5 and H-6), 4.49 (d, 1H, J = 13.5 Hz, H-7a), 4.57 (d, 1H,
J = 13.5 Hz, H-7b), 5.61 (s, 1H, H-2). 13C-NMR (DMSO-d6): d
20.6 (CH3), 61.0, 61.5 (C-4 and C-5), 62.8 (C-7), 71.6, 72.7 (C-3
1
recrystallized from EtOH. H-NMR (D2O): d 3.43 (yt, 1H, H-
2 or H-3), 3.49 (yt, 1H, H-2 or H-3), 4.06 (d, 1H, J = 13.9 Hz,
H-7a), 4.15–4.19 (m, 3H, H-1, H-4 and H-7b), 5.58 (s, 1H, H-6).
13C-NMR (D2O): d 63.3 (C-7), 73.6, 74.2 (C-1 and C-4), 77.4, 77.8
(C-2 and C-3), 127.2 (C-6), 140.6 (C-5). Anal. calcd. for C7H12O5:
C, 47.73; H, 6.87. Found: C, 47.75; H, 6.88%.
=
and C-6), 128.1 (C-2), 135.1 (C-1), 169.9 (C O). Anal. calcd. for
C9H12Br2O4: C, 31.42; H, 3.52. Found: C, 31.45; H, 3.47%.
(1RS,4RS,5SR,6SR)-2-[(Acetyloxy)methyl]-5,6-dibromo-cyclo-
(1RS,2RS,3RS,4RS)-5-[(Acetyloxy)methyl]cyclohex-5-ene-
hex-2-ene-1,4-diyl diacetate (3)
1,2,3,4-tetrayl tetraacetate (11)
◦
13.0 g (39.4 mmol) 2 are dissolved in a cooled mixture (0 C) of
To a solution of 1.0 g (2.3 mmol) 3 in 20 mL 90% aqueous acetic
16 mL of pyridine and 16 mL of acetic anhydride. The reaction
acid is added 5.0 g (30.0 mmol) silver acetate and the reaction
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mixture is refluxed for 20 h. After cooling 150 mL ethyl acetate
are added and the reaction mixture is filtered. The solvent is
evaporated and 10 mL acetic anhydride and 10 mL pyridine are
added to the residue. After stirring for 45 min all volatiles are
removed in vacuo and the residue is taken up in 100 mL diethyl
ether and 100 mL brine. The organic phase is separated, dried over
Na2SO4, filtered and the solvent is removed to yield a brown oil
which can be recrystallized from EtOH to give 306 mg (0.8 mmol,
(1SR,2RS,3SR,4RS)-6-[(Acetyloxy)methyl]-3-bromocyclohex-5-
ene-1,2,4-triyl triacetate (18)
A solution of 0.52 g (2.35 mmol) 15 in 30 mL of destilled water
is cooled to 0 ◦C and 30 mg p-toluenesulfonic acid are added.
After stirring the reaction mixture for 14 h at room temperature
50 mg solid NaHCO3 are added and the water is removed by
lyophilization. To the remaining brown oil 10 mL acetic anhydride
and 10 mL pyridine are added. After 2 h all volatiles are removed
in vacuo and the residue is taken up in 20 mL diethyl ether. The
organic phase is washed with saturated NaHCO3-solution (2 ¥
20 mL) and brine (2 ¥ 20 mL), dried over Na2SO4, filtered and
the solvent is removed. The remaining yellow oil is purified by
column chromatography (cyclohexane:ethyl acetate 7 : 3) to yield
1
35%) of the desired compound as colourless crystals. H-NMR
(CDCl3): d 1.96 (s, 3H, CH3), 1.98 (s, 3H, CH3), 2.02 (s, 3H, CH3),
2.03 (s, 3H, CH3), 2.04 (s, 3H, CH3), 4.44 (d, 1H, J = 13.9 Hz,
H-7a), 4.53 (d, 1H, J = 13.9 Hz, H-7b), 5.34–5.42 (AB, 2H, H-2
and H-3), 5.65 (m, 1H, H-1), 5.72 (d, 1H, J = 3.6 Hz, H-4), 5.89
(d, 1H, J = 5.0 Hz, H-6). 13C-NMR (CDCl3): d 20.5, 20.5, 20.6,
20.6 (5 ¥ CH3), 63.2 (C-7), 65.5, 65.6 (C-1 and C-4), 66.2, 66.5
(C-2 and C-3), 125.3 (C-6), 135.4 (C-5), 169.7, 169.8, 170.0, 170.1
1
0.5 g (1.2 mmol, 51%) of a colourless oil. H-NMR (CDCl3): d
2.04 (s, 3H, CH3), 2.07 (s, 3H, CH3), 2.10 (s, 3H, CH3), 2.11 (s, 3H,
CH3), 4.34 (dd, 1H, J = 6.4 and 2.7 Hz, H-3), 4.42 (d, 1H, J =
13.8 Hz, H-7a), 4.60 (d, 1H, J = 13.8 Hz, H-7b), 5.30 (dd, 1H, J =
5.2 and 2.7 Hz, H-2), 5.56 (d, 1H, J = 5.2 Hz, H-1), 5.61 (m, 1H,
H-4), 5.89 (d, 1H, J = 3.0 Hz, H-5). 13C-NMR (CDCl3): d 20.6,
20.7, 20.8 (4 ¥ CH3), 47.0 (C-3), 63.2 (C-7), 67.6 (C-1), 70.8 (C-4),
71.2 (C-2), 125.8 (C-5), 134.3 (C-6), 169.4, 169.6, 169.8, 170.2 (4 ¥
=
(5 ¥ C O). Anal. calcd. for C17H22O10: C, 52.85; H, 5.74. Found:
C, 52.74; H, 5.66%.
(1RS,2RS,3RS,4RS)-5-(Hydroxymethyl)cyclohex-5-ene-1,2,3,4-
tetrol (13)
=
C O). Anal. calcd. for C15H19BrO8: C, 44.24; H, 4.70. Found: C,
To a solution of 408 mg (1.1 mmol) 11 in 25 mL MeOH 0.5 ml
of a 1 N methanolic NaOMe-solution are added at 0 ◦C and
the reaction mixture is stirred for 14 h at approx. +5 ◦C. After
neutralizing of the solution by addition of Dowex 50 ¥ 8 (H+) and
filtration, the solvent is evaporated to yield a brown oil which can
be recrystallized from EtOH to give 155 mg (0.9 mmol, 82%) of a
beige solid. 1H-NMR (D2O): d 3.81–3.89 (AB, 2H, H-2 and H-3),
4.12 (s, 2H, H-7), 4.23 (d, 1H, J = 2.9 Hz, H-4), 4.29 (yt, 1H,
H-1), 5.83 (m, 1H, H-6). 13C-NMR (D2O): d 64.3 (C-7), 68.3 (C-
1), 68.9 (C-4), 70.6, 70.9 (C-2 and C-3), 126.3 (C-6), 142.5 (C-5).
Anal. calcd. for C7H12O5: C, 47.73; H, 6.87. Found: C, 47.59; H,
6.72%.
44.73; H, 4.83%.
(1SR,2SR,3SR,4RS)-5-[(Acetyloxy)methyl]cyclohex-5-ene-
1,2,3,4-tetrayl tetraacetate (20)
To a solution of 0.5 g (1.23 mmol) 18 in 10 mL 90% aqueous
acetic acid are added 1.8 g (10.8 mmol) silver acetate and the
reaction mixture is refluxed for 20 h. After cooling 50 mL ethyl
acetate are added and the reaction mixture is filtered. The solvent
is evaporated and 5 mL acetic anhydride and 5 mL pyridine are
added to the residue. After stirring for 45 min all volatiles are
removed in vacuo and the residue is taken up in 50 mL diethyl
ether and 50 mL brine. The organic phase is separated, dried over
Na2SO4, filtered and the solvent is removed to yield a brown oil
which is purified by column chromatography (cyclohexane:ethyl
acetate 3 : 2) to give 310 mg (0.8 mmol, 65%) of a colourless oil.
1H-NMR (CDCl3): d 2.00 (s, 3H, CH3), 2.01 (s, 3H, CH3), 2.04 (s,
3H, CH3), 2.05 (s, 3H, CH3), 2.09 (s, 3H, CH3), 4.40 (d, 1H, J =
13.5 Hz, H-7a), 4.69 (d, 1H, J = 13.5 Hz, H-7b), 5.14 (dd, 1H, J =
10.9 and 3.9 Hz, H-2), 5.51 (dd, 1H, J = 10.9 and 7.3 Hz, H-3),
5.60 (yt, 1H, H-1), 5.67 (d, 1H, J = 7.3 Hz, H-4), 5.95 (d, 1H, J =
5.6 Hz, H-6). 13C-NMR (CDCl3): d 20.5, 20.6, 20.6, 20.7, 20.8 (5 ¥
CH3), 62.6 (C-7), 65.3 (C-1), 68.1 (C-2), 69.9 (C-3), 70.4 (C-4),
(1RS,2RS,3RS,6RS)-2-Bromo-5-(hydroxymethyl)-7-oxa-
bicyclo[4.1.0]hept-4-en-3-ol (15)
A solution of 3.77 g (8.8 mmol) 3 in 70 mL diethyl ether and
◦
30 mL MeOH is cooled to -15 C, 650 mg (27.1 mmol) lithium
hydroxide is added and the reaction mixture is allowed to warm
to◦+10 ◦C over a period of 3.5 h. After cooling the mixture to
0
C 250 mL of a buffer solution (pH 7, 50 mmol L-1 KH2PO4
and 60 mmol L-1 Na2HPO4) is added and the aqueous phase is
made alkaline (pH 7–8) by addition of approx. 800 mg Na2HPO4.
Extraction with ethyl acetate (3 ¥ 150 mL) and removal of the
solvent yields 1.62 g (7.3 mmol, 83%) of a brown oil which is
used for the next reaction step without further purification. For
analytical purposes the crude product can be purified by column
chromatography (cyclohexane: ethyl acetate 2 : 3) and subsequent
recrystallization from chloroform/acetone. 1H-NMR (DMSO-
d6): d 3.44 (dd, 1H, J = 4.0 and 2.3 Hz, H-6), 3.71 (d, 1H, J =
4.0 Hz, H-1), 4.00 (d, 2H, J = 5.6 Hz, CH2), 4.11 (m, 2H, H-
2 and H-3), 5.01 (t, 1H, J = 5.6 Hz, OH), 5.56 (m, 1H, OH),
5.59 (s, 1H, H-4). 13C-NMR (DMSO-d6): d 52.6 (C-6), 55.2 (C-
1), 56.8 (C-2), 62.1 (C-7), 69.6 (C-3), 128.9 (C-4), 135.7 (C-5).
Anal. calcd. for C7H9BrO3: C, 38.04; H, 4.11. Found: C, 37.92; H,
4.00%.
=
123.6 (C-6), 137.7 (C-5), 169.7, 170.0, 170.1, 170.2 (5 ¥ C O).
Anal. calcd. for C17H22O10: C, 52.85; H, 5.74. Found: C, 53.37; H,
5.95%.
(1SR,2SR,3SR,4RS)-5-(Hydroxymethyl)cyclohex-5-ene-1,2,3,4-
tetrol (22)
To a solution of 227 mg (0.59 mmol) 20 in 15 mL MeOH 0.3 mL
of a 1 N methanolic NaOMe-solution are added at 0 ◦C and
the reaction mixture is stirred for 14 h at approx. +5 ◦C. After
neutralization of the solution by addition of Dowex 50 ¥ 8 (H+)
and filtration, the solvent is evaporated to yield a colourless oil
which can be recrystallized from EtOH to give 84 mg (0.48 mmol,
1
81%) of a colourless powder. H-NMR (D2O): d 3.55 (ddd, 1H,
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J = 10.6, 4.0 and 0.8 Hz, H-2), 3.68 (dyt, 1H, H-3), 4.05 (d, 1H,
J = 7.7 Hz, H-4), 4.11 (d, 1H, J = 14.2 Hz, H-7a), 4.20 (d, 1H, J =
14.2 Hz, H-7b), 4.25 (yt, 1H, H-1), 5.82 (m, 1H, H-6). 13C-NMR
(D2O): d 63.5 (C-7), 68.3 (C-1), 72.9 (C-2), 74.4 (C-4), 74.7 (C-3),
124.4 (C-6), 144.3 (C-5). Anal. calcd. for C7H12O5: C, 47.73; H,
6.87. Found: C, 47.46; H, 6.87%.
Anal. calcd. for C15H19BrO8: C, 44.24; H, 4.70. Found: C, 44.59; H,
4.27%.
(1RS,2SR,3SR,4SR)-5-[(Acetyloxy)methyl]cyclohex-5-ene-
1,2,3,4-tetrayl tetraacetate (28)
To a solution of 464 mg (1.14 mmol) 27 in 8 mL 90% aqueous
acetic acid are added 1.5 g (9.0 mmol) silver acetate and the
reaction mixture is refluxed for 20 h. After cooling 50 mL ethyl
acetate are added and the reaction mixture is filtered. The solvent
is evaporated and 5 mL acetic anhydride and 5 mL pyridine are
added to the residue. After stirring for 45 min all volatiles are
removed in vacuo and the residue is taken up in 50 mL diethyl
ether and 50 mL brine. The organic phase is separated, dried
over Na2SO4, filtered and the solvent is removed to yield a brown
oil which is recrystallized from EtOH to give 240 mg (0.62 mmol,
54%) of colourless crystals. 1H-NMR (CDCl3): d 1.97 (s, 3H, CH3),
2.02 (s, 3H, CH3), 2.05 (s, 3H, CH3), 2.06 (s, 3H, CH3), 2.10 (s, 3H,
CH3), 4.47 (d, 1H, J = 13.7 Hz, H-7a), 4.54 (d, 1H, J = 13.7 Hz,
H-7b), 5.11 (m, 1H, H-2), 5.48–5.52 (AB, 2H, H-3 and H-4), 5.69
(d, 1H, J = 3.8 Hz, H-1), 5.81 (s, 1H, H-6). 13C-NMR (CDCl3):
d 20.4, 20.7, 20.7, 20.8 (5 ¥ CH3), 63.4 (C-7), 65.5 (C-1), 68.5 (C-
2), 68.9 (C-3), 71.2 (C-4), 128.0 (C-6), 132.7 (C-5), 169.7, 170.0,
(1SR,4SR,5RS,6RS)-5,6-Dibromo-1,7-O-isopropylidene-2-
hydroxymethyl-cyclohex-2-ene-1,4-diol (25)
A solution of 3.0 g (7.0 mmol) 3 in 50 mL MeOH is cooled to 0 ◦C
and 310 mg K2CO3 are added. The reaction mixture is stirred for
4 h, acidified by the addition of 7 mL 1 N HCl and the solvent is
removed in vacuo. The residue is taken up in 50 mL ethyl acetate
and 50 mL brine, the phases are separated and the aqueous layer is
extracted with ethyl acetate (4 ¥ 50 mL). The organic phase is dried
over Na2SO4, filtered and the solvent is evaporated to yield 2.1 g
(7.0 mmol, 100%) of the corresponding triol 24 as a colourless
foam. The foam is dissolved in 20 mL dry acetone and 10 mL 2,2-
dimethoxypropane and 20 mg p-toluenesulfonic acid are added.
The reaction mixture is stirred for 1.5 h at room temperature before
50 mL saturated NaHCO3-solution and 50 mL diethyl ether are
added. The layers are separated and the organic phase is washed
with brine (2 ¥ 50 mL), dried over Na2SO4, filtered and the solvent
is evaporated to yield 2.4 g (7.0 mmol, 100%) of a brown oil which
can be recrystallized from diethyl ether for analytical purposes.
1H-NMR (CDCl3): d 1.43 (s, 3H, CH3), 1.51 (s, 3H, CH3), 2.75
(d, 1H, J = 4.1 Hz, OH), 4.14–4.18 (m, 3H, H-5, H-6 and H-7a),
4.41 (m, 1H, H-7b), 4.56 (m, 1H, H-4), 4.62 (dd, 1H, J = 5.3
and 1.0 Hz, H-1), 5.55 (m, 1H, H-3). 13C-NMR (CDCl3): d 20.4,
27.4 (2 ¥ CH3), 54.0, 60.6 (C-5 and C-6), 62.1 (C-7), 73.2 (C-1),
73.5 (C-4), 100.4 (OCO), 121.5 (C-3), 134.8 (C-2). Anal. calcd. for
C10H14Br2O3: C, 35.12; H, 4.13. Found: C, 34.93; H, 4.16%.
=
170.2, 170.2 (5 ¥ C O). Anal. calcd. for C17H22O10: C, 52.85; H,
5.74. Found: C, 52.97; H, 5.78%.
(1RS,2SR,3SR,4SR)-5-(Hydroxymethyl)cyclohex-5-ene-1,2,3,4-
tetrol (29)
To a solution of 222 mg (0.57 mmol) 28 in 15 mL MeOH 0.3 mL
of a 1 N methanolic NaOMe-solution are added at 0 ◦C and
the reaction mixture is stirred for 14 h at approx. +5 ◦C. After
neutralization of the solution by addition of Dowex 50 ¥ 8 (H+)
and filtration, the solvent is evaporated to yield a colourless oil
which can be recrystallized from EtOH to yield 80 mg (0.45 mmol,
79%) of a colourless powder. 1H-NMR (D2O): d 3.52 (dd, 1H, J =
10.8 and 4.0 Hz, H-3), 3.61 (dd, 1H, J = 10.8 and 7.7 Hz, H-2),
4.05 (d, 1H, J = 7.7 Hz, H-1), 4.11 (s, 2H, H-7), 4.18 (d, 1H, J =
4.0 Hz, H-4), 5.68 (s, 1H, H-6). 13C-NMR (D2O): d 64.2 (C-7), 68.9
(C-4), 73.1 (C-3), 74.0 (C-1), 74.7 (C-2), 129.3 (C-6), 139.9 (C-5).
Anal. calcd. for C7H12O5: C, 47.73; H, 6.87. Found: C, 47.55; H,
6.74%.
(1RS,2SR,3RS,4SR)-5-[(Acetyloxy)methyl]-3-bromocyclohex-5-
ene-1,2,4-triyl triacetate (27)
To a solution of 1.0 g (2.9 mmol) 25 in 60 mL diethyl ether are
added 60 mL of a 1 N aqueous NaOH-solution and the reaction
mixture is stirred at ambient temperature for 4 h. The phases are
separated and the aqueous layer is extracted with diethyl ether (3 ¥
50 mL). The diethyl ether is evaporated and 10 mL water and 5 mL
acetic acid are added to the resulting residue (epoxide 26). The
reaction mixture is stirred at ambient temperature for 14 h and all
volatiles are removed in vacuo. 15 mL acetic anhydride and 15 mL
pyridine are added to the resulting oil and the mixture is stirred
for 1 h. All volatiles are removed in vacuo and the residue is taken
up in 50 mL diethyl ether and 50 mL brine. The organic layer is
dried over Na2SO4, filtered and the solvent is evaporated to deliver
a brown oil which can be purified by column chromatography
(cyclohexane:ethyl acetate 3 : 1) to yield 605 mg (1.5 mmol, 52%)
(5RS,6RS)-5,6-Dibromo-2-methylcyclohex-2-ene-1,4-
dione (4)
32.6 g (204.0 mmol) bromine in 50 mL dichloromethane are
added dropwise over 1h to a cooled (5–10 ◦C) solution of
24.4 g (200.0 mmol) 2-methylbenzo-1,4-quinone in 350 mL
dichloromethane. The reaction mixture is allowed to warm to RT
and stirred for another 1.5 h. The dichloromethane is evaporated
to give 54.0 g (191.5 mmol, 96%) of crude (5RS,6RS)-5,6-dibromo-
2-methylcyclohex-2-ene-1,4-dione as a brown solid, which is
immediately used for reduction without further purification.
1
of a colourless oil. H-NMR (CDCl3): d 2.03 (s, 3H, CH3), 2.04
(s, 3H, CH3), 2.08 (s, 3H, CH3), 2.09 (s, 3H, CH3), 4.36 (dd, 1H,
J = 4.4 and 3.0 Hz, H-3), 4.45 (d, 1H, J = 13.7 Hz, H-7a), 4.56
(d, 1H, J = 13.7 Hz, H-7b), 5.19 (dd, 1H, J = 6.7 and 3.0 Hz,
H-2), 5.52 (d, 1H, J = 6.7 Hz, H-1), 5.59 (d, 1H, J = 4.4 Hz,
H-4), 5.88 (m, 1H, H-6). 13C-NMR (CDCl3): d 20.6, 20.7, 20.8
(4 ¥ CH3), 47.4 (C-3), 63.4 (C-7), 69.1 (C-1), 70.0 (C-2), 70.2 (C-
(1RS,4RS,5SR,6SR)-5,6-Dibromo-2-methylcyclohex-2-ene-1,4-
diol (5)
A solution of 54.0 g (191.5 mmol) 4 in 500 mL diethyl ether is
cooled to -15 ◦C. During a period of 1h a solution of 15.5 g
=
4), 126.7 (C-6), 132.8 (C-5), 169.7, 169.8, 169.9, 170.2 (4 ¥ C O).
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(409.7 mmol) sodium borohydride in 220 mL H2O is added
dropwise to the vigorously stirred solution. The reaction mixture
is allowed to warm to room temperature and stirred for additional
3 h. The ether phase is separated and the aqueous layer is extracted
with diethylether (5 ¥ 100 ml). The combined organic phases
are dried over Na2SO4, filtered and the solvent is evaporated
to yield 50.0 g (174.8 mmol, 91%) of the raw diol, which can
mixture is stirred for 14 h at approx. +5 ◦C. After neutralization
of the solution by addition of Dowex 50 ¥ 8 (H+) and filtration,
the solvent is evaporated to yield 210 mg (1.3 mmol, 88%) of a
1
beige solid. H-NMR (MeOH-d4): d 1.74 (s, 3H, CH3), 3.34 (m,
2H, H-2 and H-3), 3.90 (d, 1H, J = 6.1 Hz, H-1 or H-4), 4.01 (m,
1H, H-1 or H-4), 4.79 (s, 4H, OH), 5.29 (m, 1H, H-6). 13C-NMR
(MeOH-d4): d 18.9 (CH3), 73.3, 76.0 (C-1 and C-4), 77.3, 77.5
(C-2 and C-3), 126.3 (C-6), 137.6 (C-5). Anal. calcd. for C7H12O4:
C, 52.49; H, 7.55 Found: C, 52.23; H, 7.38%.
1
be recrystallized from toluene for analytical purposes. H-NMR
(DMSO-d6): d 1.66 (s, 3H, CH3), 4.06–4.25 (m, 4H, H-1, H-4, H-5
and H-6), 5.34 (m, 1H, H-3), 5.56 (d, 1H, J = 7.1 Hz, OH), 5.69 (d,
1H, J = 7.6 Hz, OH). 13C-NMR (DMSO-d6): d 18.8 (CH3), 61.8,
61.9 (C-5 and C-6), 71.9, 74.6 (C-1 and C-4), 126.5 (C-3), 136.6
(C-2). Anal. calcd. for C7H10Br2O2: C, 29.40; H, 3.52. Found: C,
29.39; H, 3.53%.
(1RS,2RS,3RS,4RS)-5-Methylcyclohex-5-ene-1,2,3,4-tetrayl
tetraacetate (12)
To a solution of 1.7 g (4.7 mmol) 6 in 40 mL 90% aqueous acetic
acid are added 10 g (60 mmol) silver acetate and the reaction
mixture is refluxed for 20 h. After cooling 300 mL ethyl acetate
are added and the reaction mixture is filtered. The solvent is
evaporated and 20 mL acetic anhydride and 20 mL pyridine are
added to the residue. After stirring for 45 min all volatiles are
removed in vacuo and the residue is taken up in 200 mL diethyl
ether and 200 mL brine. The organic phase is separated, dried over
Na2SO4, filtered and the solvent is removed to yield a yellow oil
which can be recrystallized from diisopropyl ether/EtOH to give
500 mg (1.5 mmol, 32%) of a colourless solid. 1H-NMR (CDCl3):
d 1.71 (s, 3H, CH3), 1.96 (s, 3H, CH3), 1.97 (s, 3H, CH3), 2.03 (s,
3H, CH3), 2.06 (s, 3H, CH3), 5.33 (dd, 1H, J = 10.7 and 4.1 Hz,
H-2 or H-3), 5.40 (dd, 1H, J = 10.7 and 4.1 Hz, H-2 or H-3), 5.57
(yt, 2H, H-1 and H-4), 5.62 (dd, 1H, J = 5.1 and 1.5 Hz, H-6).
13C-NMR (CDCl3): d 20.1, 20.4, 20.5, 20.6, 20.7 (5 ¥ CH3), 66.1
(C-1 or C-4), 66.3, 66.6 (C-2 and C-3), 69.1 (C-1 or C-4), 123.1
(1RS,4RS,5SR,6SR)-5,6-Dibromo-2-methylcyclohex-2-ene-1,4-
diyl diacetate (6)
32.7 g (114.5 mmol) 5 are dissolved in a cooled mixture (0 ◦C) of
52 mL of pyridine and 52 mL of acetic anhydride. The reaction
mixture is stirred for 12 h. Ice (200 g) is added and after stirring
for 15 min dichloromethane (200 mL) is added. The layers are
separated and the aqueous layer is extracted with dichloromethane
(2 ¥ 100 mL). The combined organic layer is washed with 0.75 N
HCl (3 ¥ 100 mL), saturated aqueous NaHCO3 (3 ¥ 100 mL) and
brine (50 mL), dried over Na2SO4 and filtered. After evaporation,
the resulting residue is recrystallized from EtOH to yield 25.4 g
(68.7 mmol, 60%) of colourless crystals. 1H-NMR (DMSO-d6): d
1.57 (s, 3H, CH3), 2.04 (s, 3H, CH3), 2.09 (s, 3H, CH3), 4.66 (AB,
2H, H-5 and H-6), 5.47 (m, 1H, H-3), 5.63 (m, 1H, H-1 or H-4),
5.78 (yd, 1H, H-1 or H-4). 13C-NMR (DMSO-d6): d 18.0, 20.4,
20.6 (3 ¥ CH3), 53.8, 54.5 (C-5 and C-6), 73.2, 74.7 (C-1 and C-4),
=
(C-6), 137.0 (C-5), 169.8, 169.9, 170.2, 170.4 (4 ¥ C O). Anal.
calcd. for C15H20O8: C, 54.87; H, 6.14. Found: C, 54.84; H, 6.19%.
=
123.9 (C-3), 135.5 (C-2), 169.4, 169.6 (2 ¥ C O). Anal. calcd. for
C11H14Br2O4: C, 35.70; H, 3.81. Found: C, 35.72; H, 3.80%.
(1RS,2RS,3RS,4RS)-5-Methylcyclohex-5-ene-1,2,3,4-tetrol (14)
(1RS,2SR,3SR,4RS)-5-Methylcyclohex-5-ene-1,2,3,4-tetrayl
tetraacetate (8)
To a solution of 0.5 g (1.5 mmol) 12 in 30 mL MeOH 0.6 mL
of a 1 N methanolic NaOMe-solution are added at 0 ◦C and
the reaction mixture is stirred for 14 h at approx. +5 ◦C. After
neutralization of the solution by addition of Dowex 50 ¥ 8 (H+)
and filtration, the solvent is evaporated to yield 208 mg (1.3 mmol,
To a suspension of 3.3 g (19.8 mmol) silver acetate in 20 mL of
dry acetic acid 200 mL of acetic anhydride are added and the
mixture is refluxed for 1 h. After cooling of the suspension 2.7 g
(7.3 mmol) of 6 are added and the mixture is refluxed for 14 h.
After cooling in an ice bath 200 mL diethyl ether are added. The
reaction mixture is filtered and the residue is washed with 200 mL
of diethyl ether. The combined organic phases are washed with
saturated NaHCO3-solution (3 ¥ 50 mL) and once with brine
(50 mL). Removal of the solvent yields a colourless oil which
can be recrystallized from diisopropyl ether/EtOH to yield 1.6 g
(4.9 mmol, 67%) of a colourless solid. 1H-NMR (CDCl3): d 1.63
(s, 3H, CH3), 1.96 (s, 3H, CH3), 1.97 (s, 3H, CH3), 1.99 (s, 3H,
CH3), 2.01 (s, 3H, CH3), 5.24 (AB, 2H, H-2 and H-3), 5.41 (m,
1H, H-6), 5.50 (m, 1H, H-1 or H-4), 5.62 (yd, 1H, H-1 or H-4).
13C-NMR (CDCl3): d 18.2, 20.4, 20.5, 20.5, 20.8 (5 ¥ CH3), 71.2
(C-1 or C-4), 71.3, 71.7 (C-2 and C-3), 72.9 (C-1 or C-4), 122.9
1
88%) of an offwhite solid. H-NMR (MeOH-d4): d 1.81 (s, 3H,
CH3), 3.81 (m, 2H, H-2 and H-3), 4.01 (d, 1H, J = 3.6 Hz, H-1
or H-4), 4.15 (m, 1H, J = 4.1 Hz, H-1 or H-4), 4.76 (s, 4H, OH),
5.53 (m, 1H, H-6). 13C-NMR (MeOH-d4): d 20.9 (CH3), 67.9 (C-1
or C-4), 70.3, 70.6 (C-2 and C-3), 71.7 (C-1 or C-4), 125.7 (C-6),
139.0 (C-5). Anal. calcd. for C7H12O4: C, 52.49; H, 7.55 Found: C,
52.28; H, 7.42%.
(1RS,2SR,3RS,6RS)-2-Bromo-5-methyl-7-oxabicyclo-[4.1.0]hept-
4-en-3-ol (16)
A solution of 13.0 g (35.0 mmol) 6 in 200 mL diethyl ether and
100 mL MeOH is cooled to 0 ◦C, 1.88 g (78.5 mmol) lithium
hydroxide are added and the reaction mixture is stirred for 1.5 h at
this temperature. 300 mL H2O are added to the reaction mixture,
the phases are separated and the aqueous phase is extracted with
diethyl ether (2 ¥ 200 mL). The combined organic phase is dried
over Na2SO4, filtered and the solvent is evaporated to yield 5.17 g
(25.2 mmol, 72%) of a colourless solid. 1H-NMR (DMSO-d6): d
1.83 (d, 3H, J = 1.5 Hz, CH3), 3.36 (dd, 1H, J = 4.1 and 2.0 Hz,
=
(C-6), 135.0 (C-5), 169.7, 169.8, 170.1, 170.2 (4 ¥ C O). Anal.
calcd. for C15H20O8: C, 54.87; H, 6.14. Found: C, 54.86; H, 6.19%.
(1SR,2RS,3RS,4SR)-5-Methylcyclohex-5-ene-1,2,3,4-tetrol (10)
To a solution of 0.5 g (1.5 mmol) 8 in 30 mL MeOH 0.6 mL of a 1 N
◦
methanolic NaOMe-solution are added at 0 C and the reaction
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=
H-6), 3.67 (yd, 1H, J = 4.1 Hz, H-1), 4.08 (m, 2H, H-2 and H-
3), 5.45 (m, 1H, H-4), 5.50 (d, 1H, J = 5.9 Hz, OH). 13C-NMR
(DMSO-d6): d 20.5 (CH3), 55.1 (C-6), 55.4 (C-1), 56.8, 69.6 (C-2
and C-3), 130.0 (C-4), 130.8 (C-5). Anal. calcd. for C7H9BrO2: C,
41.00; H, 4.42. Found: C, 41.12; H, 4.31%.
5), 169.7, 170.0, 170.1, 170.2 (4 ¥ C O). Anal. calcd. for C15H20O8:
C, 54.87; H, 6.14. Found: C, 54.90; H, 6.10%.
(1SR,2SR,3SR,4RS)-5-Methylcyclohex-5-ene-1,2,3,4-tetrol (23)
To a solution of 0.5 g (1.5 mmol) 21 in 30 mL MeOH 0.6 mL
of a 1 N methanolic NaOMe-solution are added at 0 ◦C and
the reaction mixture is stirred for 14 h at approx. +5 ◦C. After
neutralization of the solution by addition of Dowex 50 ¥ 8 (H+)
and filtration, the solvent is evaporated to yield 210 mg (1.3 mmol,
88%) of a beige solid. 1H-NMR (MeOH-d4): d 1.77 (s, 3H, CH3),
3.42 (dd, 1H, J = 10.2 and 4.1 Hz, H-2), 3.67 (dd, 1H, J = 10.2
and 7.6 Hz, H-3), 3.77 (d, 1H, J = 6.6 Hz, H-4), 4.10 (t, 1H,
J = 4.6 Hz, H-1), 4.85 (s, 4H, OH), 5.53 (m, 1H, H-6). 13C-NMR
(MeOH-d4): d 19.2 (CH3), 68.1 (C-1), 72.8 (C-2), 74.1 (C-3), 76.1
(C-4), 123.7 (C-6), 141.3 (C-5). Anal. calcd. for C7H12O4: C, 52.49;
H, 7.55 Found: C, 52.27; H, 7.44%.
(1RS,2SR,3RS,4SR)-3-Bromo-6-methylcyclohex-5-ene-1,2,4-triol
(17)
2.3 g (11.2 mmol) 16 are suspended in 20 mL H2O, 0.4 g (0.6 mmol)
tetrabromomethane are added and the suspension is heated to
35 ◦C for 14 h. The aqueous layer is extracted with tert-butyl
methyl ether (10 mL) and the water is evaporated to yield 1.4 g
(6.3 mmol, 56%) of a colourless oil. 1H-NMR (DMSO-d6): d 1.65
(s, 3H, CH3), 3.67 (d, 1H, J = 4.1 Hz, H-1), 3.76 (yd, 1H, J =
4.1 Hz, H-2), 4.14 (ys, 2H, H-3 and H-4), 5.29 (ys, 1H, H-5). 13C-
NMR (DMSO-d6): d 19.9 (CH3), 60.6 (C-3), 69.0 (C-4), 72.5,
73.2 (C-1 and C-2), 125.5 (C-5), 135.5 (C-6). Anal. calcd. for
C7H11BrO3: C, 37.69; H, 4.97. Found: C, 37.71; H, 4.30%.
Acknowledgements
The authors would like to thank Dr Karola Pfu¨ller (Institute
of Phytochemistry, Private University Witten/Herdecke) for per-
forming the lectin binding studies.
(1RS,2SR,3RS,4SR)-3-Bromo-6-methylcyclohex-5-ene-1,2,4-triyl
triacetate (19)
1.4 g (6.3 mmol) 17 are dissolved in a cooled mixture (0 ◦C) of
27 mL pyridine and 27 mL acetic anhydride and the reaction
mixture is stirred for 14 h. Ice (100 g) is added and after stirring
for 15 min dichloromethane (100 mL) is added. The layers are
separated and the aqueous layer is extracted with dichloromethane
(2 ¥ 50 mL). The combined organic layer is washed with 0.75 N
HCl (3 ¥ 50 mL), saturated aqueous NaHCO3 (3 ¥ 50 mL) and
brine (50 mL), dried over Na2SO4 and filtered. After evaporation,
the resulting residue is recrystallized from ethanol to yield 1.5 g
Notes and references
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3 For review see: H. Lis and N. Sharon, Chem. Rev., 1998, 98, 637.
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1
(4.2 mmol, 66%) of colourless crystals. H-NMR (DMSO-d6): d
1.65 (s, 3H, CH3), 2.04 (s, 6H, 2 ¥ CH3), 2.06 (s, 3H, CH3), 4.46
(dd, 1H, J = 5.6 Hz and 3.1 Hz, H-3), 5.18 (dd, 1H, J = 5.6 Hz
and 3.1 Hz, H-2), 5.30 (d, 1H, J = 5.6 Hz, H-1), 5.41 (m, 1H, H-4),
5.62 (m, 1H, H-5). 13C-NMR (DMSO-d6): d 18.7, 20.4, 20.5, 20.6
(4 ¥ CH3), 48.6 (C-3), 70.1, 70.2 (C-1 and C-2), 70.8 (C-4), 122.6
=
(C-5), 135.7 (C-6), 169.3, 169.5, 169.8 (3 ¥ C O). Anal. calcd. for
C13H17BrO6: C, 44.72; H, 4.91. Found: C, 44.69; H, 4.95%.
(1SR,2SR,3SR,4RS)-5-Methylcyclohex-5ene-1,2,3,4-tetrayl
tetraacetate (21)
To a solution of 1.4 g (3.9 mmol) 19 in 30 mL 90% aqueous
acetic acid are added 5.7 g (34.2 mmol) silver acetate and the
reaction mixture is refluxed for 20 h. After cooling 200 mL ethyl
acetate are added and the reaction mixture is filtered. The solvent
is evaporated and 15 mL acetic anhydride and 15 mL pyridine
are added to the residue. After stirring for 45 min all volatiles are
removed in vacuo and the residue is taken up in 100 mL diethyl
ether and 100 mL brine. The organic phase is separated, dried over
Na2SO4, filtered and the solvent is removed to yield a yellow oil
which can be recrystallized from diisopropyl ether/EtOH to give
503 mg (1.5 mmol, 38%) of a colourless solid. 1H-NMR (CDCl3):
d 1.68 (s, 3H, CH3), 1.96 (s, 3H, CH3), 1.99 (s, 3H, CH3), 2.04 (s,
3H, CH3), 2.05 (s, 3H, CH3), 5.08 (dd, 1H, J = 10.2 and 3.6 Hz,
H-2), 5.47–5.54 (m, 3H, H-1, H-3 and H-4), 5.63 (m, 1H, H-6).
13C-NMR (CDCl3): d 18.5, 20.4, 20.5, 20.6, 20.8 (5 ¥ CH3), 66.0
(C-3), 68.6 (C-2), 69.8, 73.4 (C-1 and C-4), 120.9 (C-6), 139.2 (C-
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