Stable analogues of nojirimycin-synthesis and biological evaluation of nojiristegine and manno-nojiristegine

Article abstract of DOI:10.1039/c5ob01281c

Two novel iminosugars called nojiristegines, being structural hybrids between nor-tropane alkaloid calystegine and nojirimycins, have been synthesised and found to be stable molecules despite the presence of a hemiaminal functionality. The synthesised iminosugars were evaluated against a panel of glycosidases and the best inhibition (IC₅₀), found against α-glucosidases, was in the micromolar region. The compounds were also evaluated as potential antibiotics but no useful level of activity was observed.

Full text of DOI:10.1039/c5ob01281c

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Stable analogues of nojirimycin – synthesis
and biological evaluation of nojiristegine
Cite this: DOI: 10.1039/c5ob01281c
and manno-nojiristegine†
Agnete H. Viuff,a Louise M. Besenbacher,a Akiko Kamori,b Mikkel T. Jensen,a
Mogens Kilian,c Atsushi Katob and Henrik H. Jensen*a
Two novel iminosugars called nojiristegines, being structural hybrids between nor-tropane alkaloid caly-
stegine and nojirimycins, have been synthesised and found to be stable molecules despite the presence
of a hemiaminal functionality. The synthesised iminosugars were evaluated against a panel of glycosidases
and the best inhibition (IC50), found against α-glucosidases, was in the micromolar region. The com-
pounds were also evaluated as potential antibiotics but no useful level of activity was observed.
Received 23rd June 2015,
Accepted 14th July 2015
DOI: 10.1039/c5ob01281c
www.rsc.org/obc
Despite their potent glycosidase inhibition, both nojiri-
mycin and manno-nojirimycin have little potential to be
Introduction
In 1965, the first naturally occurring iminosugar 5-amino-5- therapeutic candidates, due to their instability caused by their
deoxy-glucospyranose was found1 and subsequently named hemiaminal functionality, which eventually undergoes the
nojirimycin, after its isolation from Streptomyces nojiriensis.2 Amadori rearrangement.14,15 This inherent drawback of the
In 1984, the mannose derivative of nojirimycin (manno-nojiri- nojirimycins has been addressed by Inouye et al. through
mycin or nojirimycin B), was discovered by Niwa et al.3 who chemical reduction of nojirimycin to arrive at 1-deoxynojiri-
isolated it from Streptomyces lavendulae SF-425. One of the mycin (Fig. 1),16 which was later found by Yagi et al. to be
main reasons for the interest in these molecules was their naturally present in mulberry trees.17 The stability issue of
potent glycosidase inhibition established in 1970 by Niwa nojirimycins has probably caused the scientific community to
et al. for nojirimycin4 and by Legler and Jülich for manno- mainly focus on 1-deoxynojirimycin and its analogues at the
nojirimycin.5 These two prominent alkaloids of the imino- expense of nojirimycins. However, one finding often cited in
sugar/azasugar family6 have spawned a whole area of research the literature is the antibiotic activity of the nojirimycins,
mainly due to their potent inhibition of glycosidases. Several which was recognised very shortly after their discovery. Ishida
analogous molecules have been found in Nature or synthesised et al. reported nojirimycin to have antibiotic activity against
by creative chemists.7–9
bacterial strains from the otherwise dissimilar genera, Shigella
In general, iminosugars/azasugars have been reported to flexneri, Sarcina lutea and Xanthomonas oryzae. Surprisingly,
have important therapeutic potential in diseases such as dia- the compound had weak or no activity towards closely related
betes, cancer, lysosomal storage diseases, viral and bacterial bacteria such as Escherichia coli and even other strains of
diseases.10–12 Recently Warren et al. published their work on Shigella.18 Manno-nojirimycin was found by their discoverers
the iminosugar BCX4430 which is a broad spectrum antiviral to have weak antibiotic activity against Xanthomonas oryzae but
agent that inhibits infection with e.g. Ebola and other highly no activity against other bacteria tested.19
fatal viruses.13
The hemi-aminal functionality of alkaloids is not always as
unstable as that of nojirimycins. Among the naturally occur-
ring iminosugars, the calystegines possess a bicyclic structure
that prevents imine formation and thereby Amadori rearrange-
ment. Calystegines are glycosidase inhibitors, but have a
hydroxyl group in the place of the hydroxymethyl group of the
natural substrate.20 Inspired by the calystegine core structure
and the unstable noeuromycins from the Bols laboratories21
we previously reported on the synthesis of both glucose,
galactose and glucuronic acid configured synthetic hybrids of
aDepartment of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C,
Denmark. E-mail: hhj@chem.au.dk
bDepartment of Hospital Pharmacy, University of Toyama, 2630 Sugitani,
Toyama 930-01940, Japan
cDepartment of Biomedicine, Aarhus University, Wilhelm Meyers allé 4,
8000 Aarhus C, Denmark
†Electronic supplementary information (ESI) available. See DOI: 10.1039/
c5ob01281c
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Fig. 1 Structure of known iminosugars/azasugars. Box shows the structural hybrid molecules synthesised and evaluated in this study.
calystegines and noeuromycins (Fig. 1). These compounds
have been christened noeurostegines.22–24
The mixture of dienes 8 possessing a free secondary alcohol
proved incapable of undergoing ring-closing metathesis with
In this report we describe the synthesis, initial inhibitory the Grubbs–Hoveyda 2nd generation catalyst.28 Subsequent to
data and potential antibiotic activity of stable hybrids between alcohol acetylation with acetic anhydride, triethyl amine and
nojirimycin/manno-nojirimycin and calystegines. We here DMAP in 85% yield, the stereoisomers 9 could if needed be
refer to these molecules as nojiristegine (1) and manno-nojiris- separated and ring closing metathesis promoted by Grubbs–
tegine (2).
Hoveyda 2nd generation catalyst went smoothly in 93% yield
on the diastereoisomeric mixture from the previous reaction.
When working with the single isomers, the C6 stereochemistry
could be deduced by 1D and 2D 1H-NMR experiments and
assigned based on 3JHH coupling constants for 10 and 11. This
established the major product from the Barbier allylation to be
8S, but since both allylic alcohols (8R and 8S) eventually would
be oxidised to the same ketone, the synthesis of nojiristegine
(1) progressed with a mixture of isomers. The acetyl groups
were then removed from a mixture of ring closed acetates 10
and 11 by Zemplén conditions and the resulting alcohol was
next protected by the more robust p-methoxybenzyl (PMB)
ether with PMB-Cl/NaH in 57% yield over 2 steps. The cyclo-
heptene was next subjected to a hydroboration/oxidation
sequence to give the two regioisomeric secondary alcohols 13
and 14, of which each was found to be a single diastereo-
isomer. The ratio of the two secondary alcohols was found to
be different depending on whether the reaction was conducted
on the R or the S-isomer. The S-isomer gave 1 : 2.7 in favour of
the desired alcohol, while the R-isomer gave 1.7 : 1 in favour of
the undesired alcohol. Performing the reaction on the mixture
of stereoisomers originating from the Barbier reaction gave the
desired alcohol in a yield of 46%. The alcohol could now be
oxidised using Dess–Martin periodinane (DMP)29 to give the
ketones 15, which could be used as a precursor for the intro-
duction of both an azide and a hydroxymethyl substituent.
Accordingly, ketone 15 was first converted into the chloro-
epoxides30 17 by reaction with lithiated dichloromethane fol-
lowed by treatment with DBU. These compounds (17) were
Synthesis
The strategy for the synthesis of the nojiristegines was largely
inspired by our previously reported synthesis of noeuro-
stegine22 and calystegine A3.25 The synthesis of both target
molecules (1 and 2) was performed from methyl α-D-gluco-
pyranoside (3) and methyl α-D-mannopyranoside (4), respect-
ively. In a series of known steps26 these were separately
converted into 2,3,4-tri-O-benzyl-6-iodo-6-deoxy pyranosides 5
and 6 (Scheme 1).
For the synthesis of glucose-configured nojiristegine (1),
the 6-iodo-glucoside 5 was subjected to zinc-mediated frag-
mentation under sonication in THF–H2O27 giving an aldehyde,
which was used directly in the following Barbier reaction,
without further purification. This resulted in two diastereo-
isomeric allylic alcohols (8R and 8S) as an inseparable
2 : 3 mixture in 76% yield over 2 steps (Scheme 2).
Scheme 1 Synthesis of known 6-deoxy-6-iodo glycosides.
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Scheme 2 Synthesis of nojiristegine (1).
then reacted with tetrabutylammonium azide to give aldehydes thesis, since it was not possible to obtain crystals of high
18, which were reduced with NaBH4 and the resulting alcohols enough quality for a crystal structure.
protected as benzyl ethers to give the desired azides 20 in 34%
The PMB ether could now be deprotected using TFA and
over 6 steps. This sequence of known reactions was easily the resulting alcohol oxidised using DMP in 65% over two
monitored by TLC analysis but intermediate structural assign- steps. Basic hydrogenation with triethylamine resulted in
ment by NMR spectroscopy was highly challenging. Intermedi- reduction of the azide and spontaneous cyclisation into the
ates 16–18 were found to be unstable and chromatographic benzyl protected nojiristegine (22), as established by a hemi-
purification was therefore omitted. Identity was established by aminal 13C-NMR chemical shift of 92 ppm. Hydrogenolysis
mass spectrometry alone and the yield reported is for the full using Pearlman’s catalyst was then used to remove the
sequence (15–20).
remaining benzyl groups in quantitative yield. The presence
Given the nature of these reactions it cannot be ruled out, of exclusively large coupling constants as a result of axial–
that other isomers than the one shown in Scheme 2 was axial 1H–1H geometry verifies the stereochemistry of the
formed but none could be isolated. The stereochemistry of the quaternary centre originating from the introduction of the
product could not be verified until the last step of the syn- azido group.
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Nojiristegine (1) was hence successfully synthesised in 21 resulting ketone underwent the same sequence of reactions as
linear steps and was found to be fully shelf stable and stable in the nojiristegine synthesis (Scheme 2) to install benzyloxy-
in solution over several weeks.
methyl and azide substituents. Hence, 37 was treated with
The synthesis of the epimeric manno-nojirimycin (2) fol- lithiated dichloromethane and then DBU to give the chloro-
lowed a similar synthetic route. The iodide 6 (Scheme 1) was epoxide 39, which could be opened to compound 40 by treat-
subjected to zinc-mediated fragmentation and subsequent ment with tetrabutylammonium azide in DMSO. The aldehyde
Barbier reaction with allyl bromide.27 This resulted in two function was then reduced using sodium borohydride and the
inseparable diastereoisomers in a 2.2 : 1 mixture in 76% yield resulting alcohol protected as a benzyl ether. This gave the
(Scheme 3). The stereochemical outcome was established via desired product 42 in a 1.7 : 1 mixture with its epimer 43 in a
derivatisation at a later stage (vide infra). The diastereoisomeric total yield of 38% over 5 steps from ketone 37. The PMB ether
mixture was then acetylated using acetic anhydride and DMAP of 42 could now be deprotected using 2,3-dichloro-5,6-dicyano-
in pyridine and subsequently subjected to ring-closing meta- 1,4-benzoquinone (DDQ) and the resulting alcohol oxidised to
thesis. It was possible to separate the two stereoisomers (26 the ketone (44) in 39% over two steps. Azide reduction first
and 27) as the ring-closed acetates in 19% and 50% over two afforded the spontaneously cyclised 45 as shown by the pres-
steps, respectively (Scheme 3).
ence of a hemiaminal C-atom (δC 91.2 ppm) and next hydro-
For structural assignment, the two acetates (26 and 27) were genolysis to remove benzyl ether protection gave manno-
then individually deacylated by Zemplén conditions, O-benzyl- nojiristegine (2) in quantitative yield. The stereochemistry orig-
ated by NaH/BnBr and the double bond reduced. This gave inating from the azide introduction step could now be verified
two isomers (32 and 33) where one could be established by by analysis of coupling constants originating from the 1H nuclei
1
13C-NMR to be symmetrical. Consequently, the major/minor of the bicyclic molecule 2. The H-NMR spectrum showed one
isomer from the Barbier reaction was established as the 6R/6S small (4.0 Hz) and one large coupling constant (9.2 Hz) as
isomer, respectively (Scheme 3). As for the synthesis of nojiris- expected from an equatorial/axial (H2/H3) and axial/axial (H3/
tegine (1, Scheme 2) both diastereoisomers (26 and 27) could H4) arrangement, respectively. If the quaternary carbon atom
principally be used in the next steps but the synthesis was bearing the nitrogen had been opposite (46), two small coupling
completed with 27 alone (Scheme 4).
constants would be expected upon cyclisation (Scheme 5).
The synthesis produced manno-nojiristegine in 21 steps
The alcohol 29 was protected as a PMB ether in 84% over
two steps to give cycloheptene 34, which was subjected to from the unprotected methyl manno-pyranoside (4). The com-
hydroboration and oxidative work up to afford two regio- pound was stable and did not show any degradation after
isomeric alcohols in a 2.1 : 1 ratio as sole diasteroisomers in a several weeks on the shelf.
combined yield of 78%. The desired major alcohol isomer 36
Concerning the modest stereoselectivity in the Barbier reac-
was then oxidised using Dess–Martin periodinane (DMP). The tions of aldehydes 7 and 23, we found the two major products
Scheme 3 Synthesis towards manno-nojiristegine (2) and establishing the stereochemical outcome of the Barbier reaction.
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Scheme 4 Synthesis of manno-nojiristegine (2) from cycloheptenol 29.
Scheme 5 The different products formed from the two possible azide isomers 44 and 46.
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(8S and 24R) to possess opposite stereochemistry of the newly dence on C-α stereochemistry. This was also opposite to the
formed stereogenic centre (Table 1, entries 1 and 2). Interest- corresponding N-benzyl imine (entry 8).31
ingly, Skaanderup and Madsen found a more pronounced
Interestingly, the indium mediated Barbier allylation was
selectivity for both indium, magnesium and zinc in the analo- previously found to be dependent on the C-β stereochemistry
gous Barbier reaction with allyl bromide on the corresponding in the synthesis of noeurostegine and galacto-noeurostegine
N-benzyl imines (entries 6–8).31 Except for the metal zinc in reac- (entries 4 and 5), where the aldehyde is flanked by a benzyloxy
tion with the N-benzyl imine of 23, the stereochemical outcome group (Table 1).22,24 For these examples, the aldehyde leading
was reversed compared to the aldehyde substrates (7 and 23).
to noeurostegine (entry 4) having the same stereochemistry as
For a complete comparison, we also prepared the aldehyde 7, the S-product dominated, while the opposite was true for
analogous to 7 and 23 from D-galactose26 (entry 3) and again the aldehyde leading to galacto-noeurostegine (entry 5).
found the reaction to be selective for the C6–S isomer as com-
pound 7 originating from D-glucose demonstrating the depen-
Inhibition studies
The compounds 1 and 2 were tested for inhibitory activity
against a panel of glycosidases (Table 2), but in many cases no
Table 1 The stereoselectivity of the Barbier allylation of aldehydes
using different metals
inhibition was found. Nojiristegine (1) was, however, found to
Starting
material
be moderately active as an α-glucosidase inhibitor with an IC50
Entry Ref.
Product
Metal R/S
of 14 μM for rat intestinal sucrase, 27 μM for rice and 30 μM
for recombinant α-glucosidase alglycosidase alpha of which
the latter enzyme is used in enzyme replacement therapy for
Pompe disease. In comparison, 1-deoxynojirimycin is a strong
inhibitor of these enzymes (Ki 0.024 μM, Ki 0.01 μM, Ki
0.55 μM, respectively).35–37 which indicates that the steric
bulk of the ethylene bridge in nojiristegine (1) might interfere
with binding to the enzymes. Yeast α-glucosidase and
sweet almond β-glucosidase are both potently inhibited by
nojirimycin,5 whereas nojiristegine was largely inactive.
Human glucocerebrosidase was modestly inhibited by nojiris-
tegine (1, IC50 440 μM) but much less than what has been
found for noeurostegine (IC50 0.4 μM).38 Interstingly, nojiriste-
gine (1) was not found to be an inhibitor of coffee beans
α-galactosidase despite the fact that both calystegine B2 (Ki
0.86 μM),39 noeurostegine (Ki 2.5 μM)22 and 1-deoxynojiri-
mycin (Ki 23 μM)40 are all potent inhibitors of this enzyme
(Fig. 2). Since galacto-noeurostegine (4-epi-noeurostegine) is
not an inihibitor of green coffee beans α-galactosidase, but
calystegine and noeurostegine inhibit this enzyme potently, we
have previously speculated that the two former azasugars
would bind in a nojirimycin (NJ) binding mode24 placing the
ethylene bridge in the same position as nojiristegine (1). The
observation, that nojiristegine is not an inhibitor of this
enzyme, brings our previous suggestion into question.
1
2
This work
In
2 : 3
This work
In
2.2 : 1
3
4
This work
In
In
1 : 2.1
1 : 1.7
22
5
24
In
3 : 2
Manno-nojiristegine (2) did not show any activity against
tested mannosidases and most other glycosidases. Weak inhi-
bition of β-glucoronidase from E. coli and α,α-trehalase from
porcine kidney (IC50 of 810 μM and 400 μM, respectively) was
obtained.
6
7
31
31
In
Mg
Zn
1 : 0
16 : 1
5 : 1
In
Mg
Zn
0 : 1
1 : 8
8 : 1
Antibiotic studies
Nojiristegines 1 and 2 and the close structural analogue
1-deoxynojirimycin were evaluated for potential antibiotic
activity against a series of bacterial strains based on avail-
ability, clinical relevance and their close relation to original
8
31
In
Mg
Zn
1 : 0
8 : 1
2 : 1
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Table 2 Ki and IC50 values of iminosugars against various glycosidases
Values in μM
Enzyme
α-Glucosidase
Yeast
aNI b(16%)
IC50: 27
IC50: 181
NI (20%)
NI (12%)
NI (11%)
Ki: 6.35
85% at 100 μM32
Rice
Rat intestinal maltase
Rabbit small intestine maltase
Rat intestinal sucrase
Rabbit small intestine sucrase
IC50: 4.633
IC50: 14
NI (23%)
Ki: 0.1334
Amyloglucosidase
Aspergillus niger
NI (0%)
IC50: 30
NI (26%)
NI (0%)
NI (2%)
NI (9%)
Alglucosidase alfa
Human lysosome
α-Amylase
Porcine pancreas
β-Glucosidase
Sweet almond
Bovine liver
NI (28%)
NI (44%)
NI (21%)
NI (35%)
Ki: 0.95
Ki: 205
β-Glucocerebrosidase
Human lysosome
IC50: 440
NI (23%)
NI (21%)
NI (16%)
NI (24%)
NI (17%)
NI (20%)
NI (7%)
NI (0%)
NI (19%)
NI (4%)
NI (0%)
α-Galactosidase
Green coffee beans
α-Galactosidase A
Human lysosome
β-Galactosidase
Bovine liver
α-Mannosidase
Jack bean
Ki: 5005
Ki: 9005
Ki: 6.55
Ki: 7.75
β-Mannosidase
Snail
Aspergillus wentii
α-L-Rhamnosidase
Penicillium decumbens
NI (33%)
NI (43%)
NI (3%)
NI (2%)
α-L-Fucosidase
Bovine kidney
β-Glucuronidase
E. coli
Bovine liver
IC50: 620
NI (37%)
IC50: 810
NI (4%)
α,α-Trehalase
Porcine kidney
NI (8%)
NI (8%)
IC50: 420
NI (2%)
β-N-Acetyl-hexosaminidase
Human placenta
a NI: No inhibition (less than 50% inhibition at 1000 μM). b ( ): Inhibition % at 1000 μM.
Fig. 2 Inhibitory data for inhibition of α-galactosidase from green coffee beans.
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strains tested with nojirimycin (Pseudomonas aeruginosa strain ing in no activity against any of the strains of Pseudomonas aer-
PAO1, Escherichia coli strains VK98 and VK144, and Staphylo- uginosa, E. coli, and Staphylococcus aureus for neither 1 nor 2.
coccus aureus strain VK75). Nojirimycin has been found largely A careful literature survey revealed that literature only holds
inactive against non-resistant Shigella flexneri 2a, Shigella flex- very little information about the antibiotic activity of nojiri-
neri 6 Mita, Staphylococcus aureus Terashima and 209 P and mycin despite the fact that this compound is often referred to
E. coli Umezawa, but highly active against Xanthomonas oryzae, as an antibiotic. Given the current threat of resistant bacteria a
resistant Shigella flexneri 2a and Sarcina lutea PCI 1001.18
modern study of the nojirimycins would be in order to
Neither 1-deoxynojirimycin nor nojiristegine (1) showed confirm its activity and activity profile.
any antibiotic activity against the tested strains of Pseudomonas
aeruginosa, Staphylococcus aureus or E. coli up to concen-
trations of 500 μg mL−1. Lack of activity against E. coli and Sta-
Experimental
Inhibition studies
phylococcus aureus was also seen in the original results for
nojirimycin,18 but activity against E. coli could have been
The ability of the compounds to inhibit glycosidase activity
expected due its close genetic relation to Shigella flexneri.
Niwa et al. reported manno-nojirimycin to be weakly active
(50-fold less than nojirimycin) against Xanthomonas oryzae and
also tested other unspecified bacterial strains but found no
activity.19 Assuming that Niwa et al. tested the activity against
the same bacteria as Ishida et al.18 there seems to be a note-
worthy difference between the antibiotic activity of nojirimycin
and its manno-epimer, but this cannot, to the best of our
knowledge, be confirmed.
was carried out as previously described.23
Antibiotic studies
The ability of the compounds to inhibit bacterial growth was
tested on 5% blood agar plates (Statens Serum Institut, Copen-
hagen). The inoculum was a suspension of the respective
bacterial strains in sterile 0.9% saline at a density of approxi-
mately 107 bacteria per ml. The suspension was added to the
entire surface of the agar plate where upon excess fluid was
removed with a pipette. After drying of the plate filter paper
discs with a diameter of 5 mm were placed on the agar surface
and 200 ul of the respective dilutions of the compounds were
added. Potential inhibition zones were read after overnight
incubation at 37 °C.
In our test, manno-nojiristegine (2) did not show any
activity against the strains as investigated for 1.
While glycosidase inhibition has been carefully investi-
gated, our literature study has revealed that only little is
known about the antibiotic activity of nojirimycin and manno-
nojirimycin. In order to take advantages of this antibiotic
activity, it is evident that further studies must be conducted in
order to establish the mechanism for this activity.
The bacterial strains used in the inhibition experiments
were Pseudomonas aeruginosa strain PAO1, Escherichia coli
strains VK98 and VK144, and Staphylococcus aureus strain
VK75.
Conclusion
Organic synthesis
Two new iminosugars of the hemiaminal nortropane type have
General methods. All reactions with air- and moisture sensi-
been synthesised through 21 steps from methyl α-D-glucopyra- tive compounds were conducted in an atmosphere of nitrogen
noside and methyl α-D-mannopyranoside. The key transform- or argon. Dichloromethane, toluene, acetonitrile and THF
ation was the instalment of a nitrogen atom in form of an were dried over aluminum oxide via an MBraun SPS-800
azide at a quarternary carbon atom, which was performed over solvent purification system, other dry solvents were dried over
several steps from a ketone functionality.
molecular sieves. Evaporation of solvents was done under
The synthesised highly functionalised iminosugars were reduced pressure at 40 °C. Flash column chromatography was
named nojiristegine and manno-nojiristegine due to their carried out with a Merck silica gel (230–400 Mesh). TLC analy-
resemblance with both calystegines and nojirimycin. As a sis was carried out on silica gel on aluminum foil (Merck Kie-
result of the ethylene bridge inherited from calystegines, the selgel 60 F254). TLC plates were visualized by using ceric
synthesised molecules were found to be stable in aqueous sulfate/ammonium molybdate in 10% H2SO4 or ninhydrin in
medium for several days.
n-butanol/acetic acid and successive heating to dryness.
Apparatus. NMR spectra were recorded on a Varian Mercury
Nojiristegine (1) and its manno-configured isomer (2) were
both evaluated as potential glycosidase inhibitors, but only 400 spectrometer. 1H-, gCOSY-, and gHMQC-NMR were
weak inhibition was found. This shows that only limited space recorded at 400 MHz and 13C-NMR and DEPT-135 at 100 MHz.
is available in the glycosidase binding pocket, which only in Chemical shifts (δ) are given in ppm relative to the residual
certain cases can accommodate the ethylene bridge. Glycosi- solvent signals (CDCl3 (δ 7.26 ppm for proton and 77.16 ppm
dase inhibition by calystegines and noeuromycins has in for carbon resonances) and D2O (δ 4.79 ppm for proton).
general been found to be more potent that what was found for Assignment of NMR spectra is based on gCOSY, gHMQC and
the two nojiristegines investigated in this study.
DEPT-135 experiments. Mass spectra were recorded on a
The synthesised compounds (1 and 2) were also evaluated Micromass LC-TOF spectrometer with positive electronspray
as a potential antibiotics against a few bacterial strains, result- ionization. Melting points were measured on a Büchi B-450,
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and are not corrected. Optical rotations were measured on an H6eq), 4.05 (1H, t, J3,2 = J3,4 9.4 Hz, H3), 3.82 (1H, dt, J5,6eq
ADP440+ polarimeter and reported in units of deg cm2 g−1
4.6 Hz J5,6ax = J5,4 9.7 Hz, H5), 3.71 (1H, t, J6ax,5 = J6ax,6eq
.
Concentrations are given in g per 100 mL. IR spectra were 10.2 Hz, H6ax), 3.60 (1H, t, J4,5 = J4,3 10.2 Hz, H4), 3.56 (1H,
obtained as neat on a PerkinElmer FT-IR spectrometer (Spec- dd, J2,1 3.6 Hz J2,3 10.0 Hz, H2), 3.41 (3H, s, CH3). 13C-NMR
trum TWO/UATR TWO) and the wavelengths (νmax
)
are (100 MHz, CDCl3): δC 138.9 (Ar), 138.4 (Ar), 137.6 (Ar), 129.1
(Ar), 128.6 (Ar), 128.5 (Ar), 128.4 (Ar), 128.3 (Ar), 128.2 (Ar),
128.0 (Ar), 127.8 (Ar), 126.2 (Ar), 101.4 (CHPh), 99.4 (C1), 82.3
reported in cm−1
.
Synthesis
Methyl 4,6-O-benzylidene-α-D-glucopyranoside (48). Methyl (C4), 79.4 (C2), 78.8 (C3), 75.5 (CH2Ph), 73.9 (CH2Ph), 69.3
α-D-glucopyranoside (3) (5.11 g, 26.3 mmol) was dissolved in (C6), 62.5 (C5), 55.5 (CH3). LRMS (ESI): calcd for C28H30O6Na
freshly distilled acetonitrile (100 mL) and the mixture was 485.1935; found 484.9.
stirred vigorously under a nitrogen atmosphere. Benzaldehyde
NMR data was in accordance with previously reported
dimethyl acetal (7 mL, 46.6 mmol, 1.8 eq.) and 10-camphor- values.41
sulfonic acid (298 mg, 1.28 mmol, 5%) were added, and the
Methyl 2,3,4-tri-O-benzyl-α-D-glucopyranoside (50). BH3·THF
mixture was heated to reflux. After 45 min the reaction complex (1 M solution in THF, 80 mL, 80 mmol, 4.9 eq.) was
mixture was allowed to cool to r.t., neutralized by adding a few mixed with methyl 2,3-di-O-benzyl-4,6-O-benzylidene-α-D-gluco-
drops of triethylamine and concentrated under reduced pyranoside (49) (7.54 g, 16.3 mmol) under a nitrogen atmos-
pressure. The resulting white powder was dissolved in phere. The mixture was stirred for 10 min before Cu(OTf)2
ethyl acetate (250 mL), washed with brine, dried over MgSO4, (294 mg 0.810 mmol, 5%) was added and the reaction was
filtered and concentrated under reduced pressure. The result- then allowed to stir overnight. The reaction was quenched by
ing crystals were mixed with diethyl ether and filtered to adding triethylamine (2.3 mL) and methanol (29 mL), concen-
remove excess benzaldehyde dimethyl acetal. Methyl 4,6-O- trated under reduced pressure, added additional methanol
benzylidene-α-D-glucopyranoside (48) was isolated as white (25 mL) and concentrated again. Toluene was added and
crystals (7.43 g, 74%).
the mixture was concentrated and purified by flash column
1
Rf (methanol/EtOAc 1 : 9) 0.55; H-NMR (400 MHz, CDCl3): chromatography (pentane/ethyl acetate 2 : 1). Methyl 2,3,4-tri-
δH 7.51–7.34 (5H, m, ArH), 5.53 (1H, s, CHPh), 4.79 (1H, d, J1,2 O-benzyl-α-D-glucopyranoside (50) was isolated as white crys-
4.0 Hz, H1), 4.29 (1H, dd, J6eq,5 4.8 Hz, J6eq,6ax 9.8 Hz, H6eq), tals (6.48 g, 86%).
3.92 (1H, t, J3,2 = J3,4 9.2 Hz, H3), 3.81 (1H, dt, J5,6ax = J5,4
Rf (pentane/ethyl acetate 2 : 1) 0.29; 1H-NMR (400 MHz,
10.4 Hz, J5,6eq 4.5, H5), 3.74 (1H, t, J6ax,6eq = J6ax,5 9.7 Hz, CDCl3): δH 7.38–7.27 (15H, m, ArH), 4.99 (1H, d, J 10.8 Hz,
H6ax), 3.62 (1H, bred s, H2), 3.49 (1H, t, J4,5 = J4,3 9.2 Hz, H4), CHHPh), 4.89 (1H, d, CHHPh), 4.84 (1H, d, J 11.2 Hz, CHHPh),
3.44 (3H, s, CH3), 2.82 (1H, bs, OH), 2.34 (1H, bs, OH). 4.81 (1H, d, J 12.0 Hz, CHHPh), 4.67 (1H, d, CHHPh), 4.65 (1H,
13C-NMR (100 MHz, CDCl3): δC 137.2 (Ar), 129.4, 128.5, 126.6 d, CHHPh), 4.58 (1H, d, J1,2 3.6 Hz, H1), 4.01 (1H, t, J3,2 = J3,4
(Ar), 102.2 (CHPh), 100.0 (C1), 81.2 (C4), 73.0 (C2), 71.9 (C3), 9.4 Hz, H3), 3.77 (1H, dd, J6a,5 2.4 Hz, J6a,6b 11.7 Hz, H6a)
69.2 (C6), 62.6 (C5), 55.8 (CH3) LRMS (ESI): calcd for 3.73–3.63 (2H, m, H6b, H5), 3.53 (1H, t, J4,5 = J4,3 9.2 Hz, H4),
C14H18O6Na 305.0996; found 304.9;
3.51 (1H, dd, J2,1 3.6 Hz, J2,3 9.2 Hz, H2), 3.37 (3H, s, CH3).
NMR data were in accordance with previously reported 13C-NMR (100 MHz, CDCl3): δC 138.8 (Ar), 138.2 (Ar), 138.2
values.41
(Ar), 128.5 (Ar), 128.4 (Ar), 128.2 (Ar), 128.1 (Ar), 128.0 (Ar),
Methyl 2,3-di-O-benzyl-4,6-O-benzylidene-α-D-glucopyranoside 128.0 (Ar), 127.9 (Ar), 127.7 (Ar), 98.2 (C1), 82.0 (C3), 80.0 (C2),
(49). NaH (60%, 3.00 g 75.0 mmol, 3.9 eq.) was slowly added 76.8 (C4), 75.8 (CH2Ph), 75.1 (CH2Ph), 73.4 (CH2Ph), 70.7 (C5),
to a stirred solution of methyl 4,6-O-benzylidene-α-D-glucopyra- 61.9 (C6), 55.2 (CH3). LRMS (ESI): calcd for C28H32O6Na
noside 48 (5.35 g 19.0 mmol) in DMF (40 mL) under a nitrogen 487.2091; found 487.0.
atmosphere. The reaction mixture was cooled to 0 °C and BnBr
(7 mL, 58.9 mmol, 3.1 eq.) was added drop wise under for- values.41
mation of hydrogen gas. The mixture was allowed to slowly Methyl
NMR data were in accordance with previously reported
2,3,4-tri-O-benzyl-6-deoxy-6-iodo-α-D-glucopyranoside
heat to r.t. and after 45 min the mixture was diluted with water (5). Triphenylphosphine (8.88 g, 33.8 mmol, 2.5 eq.), imid-
and diethyl ether and extracted with diethyl ether. The com- azole (1.91 g, 28.0 mmol, 2.1 eq.) and iodine (3.78 g,
bined organic phases were washed with water, dried over 14.9 mmol, 1.1 eq.) were added to a solution of methyl 2,3,4-
MgSO4, filtered and concentrated under reduced pressure. The tri-O-benzyl-α-D-glucopyranoside (50) (6.30 g, 13.6 mmol) in
crude product was purified by flash column chromatography anhydrous toluene (150 mL) under a nitrogen atmosphere.
(pentane/ethyl acetate 8 : 1 → 6 : 1) to give the benzyl protected The mixture was heated to reflux for 2 hours, then cooled to
compound 49 as white crystals (7.63 g, 87%).
r.t. and added 5% aqueous sodium thiosulfate (130 ml). The
Rf (pentane/ethyl acetate 6 : 1) 0.39; Mp (uncorr.) organic phase was washed with brine, dried over MgSO4 and
96.8–97.8 °C (lit. 94–95 °C crystalised from MeOH); 1H-NMR concentrated. The crude product was purified by flash column
(400 MHz, CDCl3): δH 7.51–7.26 (15H, ArH), 5.55 (1H, s, CHPh), chromatography (pentane/ethyl acetate 15 : 1) to yield the
4.92 (1H, d, J 11.3 Hz, CHHPh), 4.86 (1H, d, J 12.1 Hz, iodide 5 as a white solid (5.35 g, 69%).
CHHPh), 4.84 (1H, d, CHHPh) 4.70 (1H, d, CHHPh), 4.60 (1H,
d, J1,2 3.6 Hz, H1), 4.27 (1H, dd, J6eq,5 4.8 Hz J6eq,6ax 9.6 Hz, CDCl3): δH 7.37–7.23 (15H, m, ArH), 4.98 (1H, d, J 10.8 Hz,
Rf (pentane/ethyl acetate 15 : 1) 0.16; 1H-NMR (400 MHz,
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CHHPh) 4.93 (1H, d, J 10.9 Hz, CHHPh), 4.80 (1H, d, J 10.8 Hz, According to NMR the product was a 2 : 3 mixture of R- and
CHHPh) 4.79 (1H, d, J 12.2 Hz, CHHPh), 4.68 (1H, d, J 9.1 Hz, S-diastereoisomers.
CHHPh), 4.65 (1H, d, J 10.2 Hz, CHHPh), 4.62 (1H, d, J1,2
Rf (pentane/ethyl acetate 11 : 1) 0.19, 1H-NMR (400 MHz,
2.6 Hz, H1), 4.02 (1H, t, J3,2 = J3,4 9.6 Hz, H3), 3.58 (1H, dd, J2,1 CDCl3): δH 7.43–7.21 (48.7H, m, ArH), 6.03–5.74 (3.9H, m), 5.67
3.6 Hz J2,3 9.6 Hz, H2), 3.49–3.42 (2H, m, H5, H6a), 3.42 (3H, s, (1.9H, ddt, J 17.4 Hz, J 10.6, J 7.0 Hz), 5.38–5.24 (6.1H, m),
CH3), 3.36–3.26 (2H, m, H4, H6b). 13C-NMR (100 MHz, CDCl3): 5.10–4.99 (6.1H, m), 4.83 (3.2H, dd, J 11.3 Hz, J 15.3 Hz), 4.72
δC 138.7 (Ar), 138.2 (Ar), 138.1 (Ar), 128.7 (Ar), 128.7 (Ar), 128.6 (3.2H, d, J 11.1 Hz), 4.68–4.51 (9.8H, m), 4.37 (3.1H, dd, J 23.1
(Ar), 128.2 (Ar), 128.2 (Ar), 128.1 (Ar), 127.9 (Ar), 98.3 (C1), 81.7 Hz, J 11.8 Hz), 4.19 (1H, dd, J 7.6 Hz, J 5.5 Hz), 4.02 (2.3H, dd,
(C4), 81.6 (C3), 80.3 (C2), 75.9 (CH2Ph), 75.5 (CH2Ph), 73.6 J 3.6 Hz, J 7.4 Hz), 3.87 (1H, bs), 3.80–3.72 (3.2H, m), 3.65
(CH2Ph), 69.5 (C5), 55.6 (CH3), 7.9 (C6). LRMS (ESI): calcd for (2.1H, dd, J 2.2 Hz, J 7.5 Hz), 3.60–3.49 (3.6H, m), 2.89 (0.8H,
C28H31O5INa 597.1108; found 596.6.
NMR data was in accordance with previously reported 138.5, 138.4, 138.2, 138.1, 138.0, 135.5, 135.5, 135.3, 135.1,
bs), 2.39–2.10 (7.7H, m); 13C-NMR (100 MHz, CDCl3): δC 138.7,
values.42
128.6, 128.6, 128.5, 128.5, 128.5, 128.4, 128.4, 128.4, 128.2,
(2R,3S,4R)-2,3,4-Tri-O-benzylhex-5-enal (7). Pre-activated Zn 128.1, 128.0, 128.0, 127.9, 127.9, 127.7, 119.1, 118.9, 117.4,
dust‡ (6.42 g, 98.2 mmol, 11 eq.) and water (25 mL) were 82.5, 81.4, 81.1, 80.9, 80.1, 79.6, 75.3, 75.1, 74.5, 73.0, 70.9,
added to a solution of the iodide 5 (5.14 g, 8.95 mmol) in THF 70.6, 70.5, 70.4, 39.1, 38.2. HRMS (ESI): calcd for C29H32O4Na
(230 mL). The mixture was sonicated at 40 °C for 1 h 35 min, 481.2346; found 481.2356.
then diluted with water and diethyl ether and filtered through
(3R,4S,5S,6R)-6-O-Acetyl-3,4,5-tri-O-benzyl-1,8-nonadiene(9R)
a pad of Celite®. The organic phase was washed with water and (3R,4S,5S,6S)-3,4,5-tri-O-benzyl-6-O-acetyl-1,8-nonadiene
and brine, dried over Na2SO4, filtered and concentrated under (9S). The alcohol 8 (1.09 g, 2.39 mmol) was dissolved in anhy-
reduced pressure to yield the aldehyde 7 (3.67 g) without drous dichloromethane under a nitrogen atmosphere before
further purification.
Ac2O (0.41 mL, 4.34 mmol, 1.8 eq.), Et3N (0.66 mL, 4.74 mmol,
Rf (pentane/ethyl acetate 1 : 5) 0.74; 1H-NMR (400 MHz, 2 eq.) and DMAP (27.7 mg, 0.23 mmol, 0.09 eq.) were added.
CDCl3): δH 9.61 (1H, s, CHO), 7.33–7.18 (15H, m, ArH), 5.79 The mixture was allowed to stir overnight after which a small
(1H, ddd, J5,4 7.61 Hz, J5,6Z 11.0 Hz, J5,6E 16.7 Hz, H5), 5.24 amount of DMAP was added. After stirring for additional 2 h
(1H, d, J6Z,5 11.0 Hz, H6Z), 5.23 (1H, d, J6E,5 16.6 Hz, H6E), 4.68 the reaction was quenched by adding methanol and
(1H, d, J 11.7 Hz, CHHPh), 4.67 (d, J 11.8 Hz, 1H, CHHPh) 4.54 diluted with dichloromethane. The organic phase was washed
(1H, d, CHHPh), 4.50 (1H, d, J 11.5 Hz, CHHPh), 4.45 (1H, d, with 1 M aq. HCl and sat. aq. NaHCO3, dried over MgSO4, fil-
CHHPh), 4.33 (1H, d, CHHPh), 4.11 (1H, dd, J4,5 7.6 Hz, J4,3 tered and concentrated under reduced pressure. The crude
5.0 Hz, H4), 3.84 (1H, dd, J2,3 4.2 Hz, J2,1 0.6 Hz, H2), 3.76 (1H, product was purified by flash column chromatography
t, J3,2 = J3,4 4.6 Hz, H3). 13C-NMR (100 MHz, CDCl3): δC 201.7 (pentane/ethyl acetate 25 : 1) yielding the R (9R) and S (9S)
(CHO), 137.9 (Ar), 137.8 (Ar), 137.3 (Ar), 134.9 (C5), 128.7 (Ar), isomers of the product (1.02 g, 85%) which could be partly
128.6 (Ar), 128.5 (Ar), 128.5 (Ar), 128.4 (Ar), 128.3 (Ar), 128.2 separated.
(Ar), 128.0 (Ar), 127.7 (Ar), 119.5 (C6), 82.6 (C4), 82.0 (C3), 80.0
(C2), 74.7 (CH2Ph), 73.4 (CH2Ph), 71.1 (CH2Ph). HRMS (ESI): 11 : 1) 0.45; [α]2D93K −14.4 (c 1, CHCl3); 1H-NMR (400 MHz,
calcd for C27H28O4Na 439.1880; found 439.1885. CDCl3): δH 7.34–7.26 (15H, m, ArH), 5.91 (1H, ddd, J2,3 7.7 Hz,
NMR data was in accordance with previously reported J2,1Z 10.3 Hz, J2,1E 16.7 Hz, H2), 5.65 (1H, m, H8) 5.33 (1H, dd,
9S: colourless oil (0.550 g, 46%), Rf (pentane/ethyl acetate
values.43
J1Z,1E 1.1 Hz, H1Z), 5.30 (1H, dd, H1E), 5.21 (1H, dt, J6,7a = J6,5
(3R,4S,5S,6R/S)-3,4,5-Tri-O-benzyl-6-hydroxy-1,8-nonadiene (8). 3.5 Hz, J6,7b 9.1 Hz, H6), 4.99 (1H, dt, J9E,8 16.1 Hz J9E,7a = J9E,7b
Indium dust (1.96 g, 17.1 mmol, 1.9 eq.) and allyl bromide 1.6 Hz, H9E) 4.98 (1H, dt, J9Z,8 10.3 Hz J9Z,7a = J9Z,7b 0.94 Hz,
(2.3 mL, 27.1 mmol, 3 eq.) were added to a stirred solution of H9Z), 4.75 (1H, d, J 11.2 Hz, CHHPh), 4.71 (1H, d, J 11.4 Hz,
the crude aldehyde 7 (3.67 g, 8.81 mmol) in 50% aqueous THF CHHPh), 4.66 (1H, d, CHHPh), 4.61 (2H, d, J 12.2 Hz, CHHPh,
(64 mL). The reaction was stirred overnight at r.t. after which CHHPh) 4.36 (1H, d, CHHPh), 4.06 (1H, dd, J4,3 5.6 Hz, H3),
sat. aq. NH4Cl was added to the reaction mixture and the 3.76 (1H, dd, J5,4 5.6 Hz, H5), 3.62 (1H, t, H4), 2.48 (2H, m,
aqueous phase was neutralized with sat. aq. NaHCO3. The H7), 1.98 (1H, s, CH3). 13C-NMR (100 MHz, CDCl3): δH 170.1
resulting mixture was extracted with dichloromethane and the (CvO), 138.1 (Ar), 138.3 (Ar), 138.6 (Ar), 134.8 (C8/C2), 134.4
combined organic phases dried over MgSO4, filtered and con- (C2/C8), 128.2 (Ar), 128.2 (Ar), 127.9 (Ar), 127.7 (Ar), 127.5 (Ar),
centrated under reduced pressure. The crude product was puri- 127.5 (Ar), 127.4 (Ar), 119.4 (C1), 117.1 (C9), 81.8 (C3), 81.1
fied by flash column chromatography (pentane/ethyl acetate (C5), 80.5 (C4), 74.7 (CH2Ph), 74.1 (CH2Ph), 73.9 (C6), 70.7
11 : 1) to give the diene 8 as an oil (3.13 g, 76% over 2 steps). (CH2Ph), 34.0 (C7), 21.0 (CH3). HRMS (ESI): calcd for
C32H36O5Na 523.2455; found 523.2466.
9R: colourless oil (0.250 g, 21%), Rf (pentane/ethyl acetate
11 : 1) 0.31; [α]2D93K −9.2 (c 1, CHCl3); 1H-NMR (400 MHz,
CDCl3): δH 7.36–7.25 (15H, m, ArH), 5.97–5.83 (1H, m, H2),
‡Zinc dust (1.01 g) was mixed with 1 M HCl (10 mL) and stirred at r.t for
30 min. The mixture was then filtered and the zinc dust was washed with water
5.58–5.42 (1H, m, H8), 5.28 (1H, bs, H1a), 5.27 (1H, ddd,
J 6.8 Hz, J 1.8 Hz, J 0.9 Hz, H1b), 4.99–4.96 (1H, m, H9Z),
and diethyl ether. At last the zinc dust was dried under high vacuum with a heat
gun.
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4.96–4.92 (1H, m, H9E), 4.90 (1H, ddd, J6,7b 3.7 Hz, J6,7a 5.8 Hz,
(3R,4S,5S,6S/R)-3,4,5-Tri-O-benzyl-6-hydroxy-cycloheptene (51).
J6,5 7.4 Hz, H6), 4.82 (1H, d, J 11.5 Hz, CHHPh), 4.76 (1H, d, The acetyl protected compounds (10 and 11) (2.62 g,
J 11.3 Hz, CHHPh), 4.69 (1H, d, CHHPh), 4.64 (1H, d, J 11.9 5.54 mmol) was dissolved in anhydrous methanol (86 mL)
Hz, CHHPh), 4.63 (1H, d, CHHPh), 4.31 (1H, d, CHHPh), 3.97 under a nitrogen atmosphere. Sodium (52 mg) was added and
(1H, dd, J3,2 4.1 Hz, J3,4 7.5 Hz, H3), 3.79 (1H, dd, J5,4 3.9 Hz, the mixture was stirred for 6 h 20 min. The mixture was then
H5), 3.55 (1H, dd, H4), 2.29–2.19 (2H, m, H7), 1.98 (3H, s, concentrated under reduced pressure, added toluene and con-
CH3). 13C-NMR (100 MHz, CDCl3): δC 170.4 (CvO), 138.5 (Ar), centrated again. The crude product (51) was used directly in
138.2 (Ar), 138.0 (Ar), 135.5 (C2/C8), 133.6 (C8/C2), 128.3 (Ar), the next step without further purification.
128.3 (Ar), 128.2 (Ar), 128.0 (Ar), 127.7 (Ar), 127.6 (Ar), 127.6
(3R,4S,5S,6S)-3,4,5-Tri-O-benzyl-6-hydroxy-cycloheptene (51S). Rf
(Ar), 118.7 (C1), 117.7 (C9), 81.6 (C4), 79.8 (C3), 78.8 (C5), 74.9 (pentane/ethyl acetate 5 : 1) 0.25; [α]2D93K +2.1 (c 1, CHCl3);
(CH2Ph), 74.8 (CH2Ph), 72.6 (C6), 70.5 (CH2Ph), 35.5 (C7), 21.0 1H-NMR (400 MHz, CDCl3): δH 7.37–7.25 (15H, m, ArH), 5.81
(CH3). HRMS (ESI): calcd for C32H36O5Na 523.2455; found (1H, ddd, J2,3 1.5 Hz, J2,7 3.2 Hz, J2,1 11.5 Hz, H2), 5.72 (1H,
523.2463.
ddt, J1,7a 1.9 Hz, J1,7b = J1,3 5.7 Hz, H1), 4.92 (1H, d, J 10.8 Hz,
(3R,4S,5S,6S)-6-O-Acetyl-3,4,5-tri-O-benzyl-cycloheptene
(10) CHHPh), 4.85 (1H, d, J 11.5 Hz, CHHPh), 4.70 (1H, d, CHHPh),
and (3R,4S,5S,6R)-6-O-acetyl-3,4,5-tri-O-benzyl-cycloheptene (11). 4.70 (2H, s, CH2Ph), 4.66 (1H, d, CHHPh), 4.16 (1H, ddd, J3,4
The diene 9 (2.98 g, 5.94 mmol) was dissolved in anhydrous 9.1 Hz, H3), 4.06 (1H, d, J6,7a 8.4 Hz, H6), 3.78 (1H, dd, J4,5 7.2
toluene (21 mL) under a nitrogen atmosphere. Grubbs– Hz, H4), 3.67 (1H, dd, J5,6 3.2 Hz, H5), 2. 63 (1H, bs, OH), 2.52
Hoveyda 2nd generation catalyst (75 mg, 0.12 mmol, 2%) was (1H, ddt, J7a,7b 16.5 Hz, H7a), 2.19 (1H, dd, H7b). 13C-NMR
added to the reaction flask, which was immediately put (100 MHz, CDCl3): δC 138.8 (Ar), 138.5 (Ar), 138.5 (Ar), 132.3
in a preheated 80 °C oil bath. The mixture was stirred for (C2), 128.6 (Ar), 128.5 (Ar), 128.2 (Ar), 128.0 (Ar), 127.9 (Ar),
1 h 30 min, cooled down to r.t. and concentrated under 127.8 (Ar), 127.7 (Ar), 127.0 (C1), 85.2 (C5), 82.6 (C4), 75.3
reduced pressure. The crude product was purified by flash (CH2Ph), 78.6 (C3), 74.1 (CH2Ph), 72.9 (CH2Ph), 69.0 (C6), 31.4
column chromatography (pentane/ethyl acetate 15 : 1) to (C7). HRMS (ESI): calcd for C28H30O4Na 453.2036; found
give the cycloheptenes 10 and 11 (2.04 g, 73%) as a slightly 453.2044.
yellow oil.
(3R,4S,5S,6R)-3,4,5-Tri-O-benzyl-6-hydroxy-cycloheptene (51R).
(3R,4S,5S,6S)-6-O-Acetyl-3,4,5-tri-O-benzyl-cycloheptene (10). Rf Rf (pentane/ethyl acetate 5 : 1) 0.36; 1H-NMR (400 MHz,
(pentane/ethyl acetate 5 : 1) 0.56; [α]2D93K −6.4 (c 1, CHCl3); CDCl3): δH 7.45–7.29 (m, 15H, ArH), 5.91–5.82 (m, 2H, H1, H2),
1H-NMR (400 MHz, CDCl3): δH 7.37–7.26 (15H, m, ArH), 5.70 5.08 (d, J 11.3 Hz, 1H, CHHPh), 4.99 (d, J 10.7 Hz, 1H,
(1H, dd, J2,1 11.8 Hz, J2,3 1.0 Hz, H2), 5.62 (1H, dt, J1,7a = J1,7b CHHPh), 4.78 (d, 1H, CHHPh), 4.74 (s, 2H, CH2Ph), 4.69 (d,
5.5 Hz, J1,2 11.8 Hz, H1), 5.33 (1H, ddd, J6,7b/5 1.6 Hz, J6,7b/5 3.0 1H, CHHPh), 4.23 (d, J 8.8 Hz, 1H, H3), 3.67–3.56 (m, 2H, H4 +
Hz, J6,7a 9.8 Hz, H6), 4.77 (1H, d, J 11.1 Hz, CHHPh), 4.69 (2H, H6), 3.48 (dd, J 18.1 Hz, J 9.8 Hz, 1H, H5), 2.50–2.37 (m, 1H,
s, CH2Ph), 4.66 (2H, s, CH2Ph), 4.63 (1H, d, CHHPh), 4.30 (1H, H7a), 2.29–2.11 (m, 1H, H7b). 13C-NMR (100 MHz, CDCl3):
d, J5,4 9.2 Hz, H5), 3.79 (1H, dd, J3,4 4.7 Hz, H3), 3.74 (1H, dd, δC 138.6 (Ar), 138.4 (Ar), 138.4 (Ar), 133.7 (C2), 128.6 (Ar), 128.3
H4), 2.62 (1H, ddd, J7a,7b 16.7 Hz, H7a), 2.35 (1H, d, J7b,7a 16.7 (Ar), 128.0 (Ar), 127.8 (Ar), 127.8 (Ar), 127.7 (Ar), 127.5 (Ar),
Hz, H7b), 2.04 (3H, s, CH3). 13C-NMR (100 MHz, CDCl3): 127.5 (Ar), 126.8 (C1), 89.3 (C5), 83.4 (C4/C6), 78.4 (C3), 75.9
δC 170.1 (CvO), 138.6 (Ar), 138.5 (Ar), 138.3 (Ar), 131.2 (C2), (CH2Ph), 75.4 (CH2Ph), 72.7 (CH2Ph), 70.6 (C4/C6), 31.1 (C7).
128.3 (Ar), 128.3 (Ar), 128.0 (Ar), 127.9 (Ar), 127.6 (Ar), 127.5 HRMS (ESI): calcd for C28H30O4Na 453.2036; found 453.2044.
(Ar), 126.0 (C1), 83.3 (C4), 82.6 (C3), 79.0 (C5), 74.2 (CH2Ph),
72.8 (CH2Ph), 73.1 (CH2Ph), 71.2 (C6), 29.6 (C7), 21.2 (CH3). heptene (12). NaH (60%, 0.454 g, 18.92 mmol, 2 eq.) and
HRMS (ESI): calcd for C30H32O5Na 495.2142; found 495.2154. PMBCl (1.5 mL, 11.05 mmol, 2 eq.) were added to a cooled
(3R,4S,5S,6S/R)-3,4,5-Tri-O-benzyl-6-O-p-methoxybenzyl-cyclo-
(3R,4S,5S,6R)-6-O-Acetyl-3,4,5-tri-O-benzyl-cycloheptene (11). Rf (0 °C) and stirred solution of the crude alcohol (51)
(pentane/ethyl acetate 11 : 1) 0.33; [α]2D93K −2.9 (c 1, CHCl3); (5.54 mmol) in anhydrous DMF (27 mL) under a nitrogen
1H-NMR (400 MHz, CDCl3): δH 7.36–7.21 (m, 15H, ArH), 5.84 atmosphere. The reaction mixture was heated to r.t. and
(ddd, J2,1 11.3 Hz, J2,3 3.6 Hz, J 1.6 Hz, 1H, H2), 5.76–5.66 (m, stirred overnight. The next day more NaH was added. After
1H, H1), 4.95 (ddd, J6,7b 10.0 Hz, J6,5 7.2 Hz, J6,7a 2.8 Hz, 1H, 20 min the reaction mixture was quenched by addition of
H6), 4.87 (d, J 10.6 Hz, 1H, CHHPh), 4.82 (d, J 11.3 Hz, 1H, n-butylamine, diluted with EtOAc, washed with water and
CHHPh), 4.69 (d, J 10.7 Hz, 2H, 2 × CHHPh), 4.68 (d, J 11.5 Hz, brine, dried over MgSO4, filtered and concentrated under
2H, 2 × CHHPh), 4.20 (m, 1H, H4), 3.70–3.58 (m, 2H, H5, H3), reduced pressure. The crude product was purified by flash
2.37 (ddd, J7a,7b 15.6 Hz, J7a,1 6.6 Hz, 1H, H7a), 2.32–2.22 column chromatography (pentane/ethyl acetate 14 : 1) yielding
(m, 1H, H7b), 1.93 (s, 3H, CH3). 13C-NMR (100 MHz, CDCl3): the PMB ether (12) (1.75 g, 57% over 2 steps).
δC 170.1 (CvO), 138.8 (Ar), 138.7 (Ar), 138.6 (Ar), 134.0 (C2),
(3R,4S,5S,6S)-3,4,5-Tri-O-benzyl-6-O-p-methoxybenzyl-cyclohep-
128.4 (Ar), 128.4 (Ar), 128.2 (Ar), 127.8 (Ar), 127.6 (Ar), 127.6 tene (12S). Rf (pentane/ethyl acetate 14 : 1) 0.23; [α]2D93K −6.8
(Ar), 127.6 (Ar), 125.3 (C1), 85.8 (C5/C3), 84.3 (C5/C3), 77.9 (c 1, CHCl3); 1H-NMR (400 MHz, CDCl3): δH 7.38–7.25 (15H, m,
(C4), 75.8 (CH2Ph), 75.3 (CH2Ph), 73.0 (CH2Ph), 72.7 (C6), 29.4 ArH), 7.24–7.20 (2H, m, ArH from PMB), 6.87–6.82 (2H, m, ArH
(C7), 21.3 (CH3). HRMS (ESI): calcd for C30H32O5Na 495.2142; from PMB), 5.69–5.56 (2H, m, H1, H2), 4.76–4.59 (5H, m,
found 495.2146.
CHHAr), 4.54 (1H, d, J 11.2, CHHAr), 4.45 (2H, s, CH2Ar), 4.21
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(1H, d, J3,4 9.2 Hz, H3), 3.94 (1H, ddd, J6,5 1.0 Hz, J6,7 3.8 Hz, dd, J 4.8 Hz, J 4.1 Hz, H3), 3.79 (3H, s, CH3) 3.62 (1H, dd,
J6,7 10.0 Hz, H6), 3.88 (1H, dd, J5,4 3.8 Hz, H5), 3.8 (3H, s, J 10.8 Hz, J 3.3 Hz, H5/H1), 3.32 (1H, dd, J 9.5 Hz, J 4.9 Hz, H2/
CH3), 3.74 (1H, dd, H4), 2.61–2.51 (1H, m, H7a), 2.37 (1H, d, H4), 2.82 (1H, bs, OH), 2.13–1.99 (2H, m, H6a, H7a), 1.86–1.77
J7b,7a 18.0, H7b). 13C-NMR (100 MHz, CDCl3): δC 159.1 (Ar), (1H, m, H6b/H7b), 1.50–1.37 (1H, m, H6b/H7b). 13C-NMR
158.4 (Ar from PMB), 128.9 (Ar), 128.7 (Ar), 132.0 (Ar), 130.6 (100 MHz, CDCl3): δC 159.14 (Ar from PMB), 138.7 (Ar), 138.2
(C1/C2), 129.9 (Ar), 129.8 (Ar), 129.1 (Ar), 128.3 (Ar), 128.2 (Ar), (Ar), 138.0 (Ar), 130.8 (Ar), 129.1 (Ar), 128.6 (Ar), 128.6 (Ar),
128.0 (Ar), 127.8 (Ar), 127.6 (Ar), 127.5 (Ar), 127.4 (Ar), 127.4 128.4 (Ar), 127.9 (Ar), 127.8 (Ar), 127.6 (Ar), 113.8 (Ar from
(C1/C2), 127.0 (Ar), 113.7 (Ar from PMB), 113.5 (Ar from PMB), PMB), 89.3 (C2/C4), 82.8 (C3), 78.7 (C1/C5), 78.03 (C2/C4),
84.1 (C4), 82.0 (C5), 79.3 (C3), 76.0 (C6), 73.7 (CH2Ar), 73.2 74.22 (CH2Ar), 72.84 (CH2Ar), 72.32 (CH2Ar), 70.72 (CH2Ar),
(CH2Ar), 72.5 (CH2Ar), 70.6 (CH2Ar), 57.4 (C7), 55.2 (CH3). 69.44 (C1/C5), 53.3 (CH3), 31.0 (C6/C7), 24.8 (C6/C7). HRMS
HRMS (ESI): calcd for C36H38O5Na 573.2611; found 573.2619.
(ESI): calcd for C36H40O6Na 591.2717; found 591.2715.
(3R,4S,5S,6R)-3,4,5-Tri-O-benzyl-6-O-p-methoxybenzyl-cyclohep-
(2R,3S,4S,5R)-2,3,4-Tri-O-benzyl-5-O-p-methoxybenzyl-cyclohep-
tene (12R). Rf (pentane/ethyl acetate 13 : 1) 0.33; [α]2D93K −4.1 tane-1-ol (13R). Colourless oil; Rf (pentane/ethyl acetate 4 : 1)
(c 1, CHCl3); Mp (uncorr.) 73.8–78.4 °C; 1H-NMR (400 MHz, 0.42; [α]2D93K +20.4 (c 1, CHCl3); 1H-NMR (400 MHz, CDCl3):
CDCl3): δH 7.31–7.19 (15H, m, ArH), 7.19–7.14 (2H, m, ArH δH 7.30–7.18 (m, 15H, ArH), 7.14 (d, J 8.3, 2H, ArH from PMB),
from PMB), 6.85–6.76 (2H, m, ArH from PMB), 5.79 (1H, ddd, 6.79–6.73 (m, 2H, ArH from PMB), 4.69–4.52 (m, 5H, CH2Ar),
J2,1 11.4 Hz, J2,7 3.5 Hz, J2,3 1.0 Hz, H2), 5.65 (1H, dtd, J1,7 4.51–4.42 (m, 2H, CH2Ar), 4.37 (d, J 10.9 Hz, 1H, CH2Ar),
6.1 Hz, J 2.0 Hz, H1), 4.85 (1H, d, J 10.8 Hz, CHHAr), 4.76 (1H, 4.11–4.01 (m, 1H, H1/H5), 3.99 (dt, J 6.7 Hz, J 3.3 Hz, 1H, H1/
d, J 11.0 Hz, CHHAr), 4.73 (1H, d, CHHAr), 4.70 (1H, d, H5), 3.95–3.89 (m, 1H, H2/H4), 3.82 (dd, J 6.8 Hz, J 2.6 Hz, 1H,
CHHAr), 4.70 (1H, d, J 12.1 Hz, CHHAr), 4.63 (1H, d, CHHAr), H3), 3.77 (dd, J 7.4 Hz, J 2.5 Hz, 1H, H2/H4), 3.74 (s, 3H, CH3),
4.48 (2H, s, CH2Ar), 4.26 (1H, dd, J3,4 8.9 Hz, H3), 3.76 (3H, s, 2.12–1.94 (m, 4H, H6/H7). 13C-NMR (100 MHz, CDCl3):
CH3), 3.72–3.60 (2H, m, H4, H5), 3.55 (1H, ddd, J 8.7 Hz, J 6.4 δC 159.3 (Ar from PMB), 138.8 (Ar), 138.7 (Ar), 138.5 (Ar), 130.3
Hz, J 2.4 Hz, H6), 2.39 (1H, dd, J7a,7b 15.9 Hz, J7a,1 6.2 Hz, (Ar), 129.6 (Ar), 128.5 (Ar), 128.4 (Ar), 128.4 (Ar), 128.0 (Ar),
H7a), 2.32–2.21 (1H, m, H7b). 13C-NMR (100 MHz, CDCl3): 127.9 (Ar), 127.9 (Ar), 127.7 (Ar), 127.7 (Ar), 127.5 (Ar), 113.9
δC 159.2 (Ar from PMB), 139.1 (Ar), 138.8 (Ar), 133.4 (C2), 130.7 (Ar from PMB), 84.2 (C2/C4), 81.6 (C3), 78.8 (C2/C4), 77.0
(Ar), 129.4 (Ar), 128.4 (Ar), 128.4 (Ar), 128.1 (Ar), 127.9 (Ar), (C1/C5), 73.3 (CH2Ar), 72.7 (CH2Ar), 72.0 (CH2Ar), 71.7
127.9 (Ar), 127.6 (Ar), 125.9 (C1), 113.9 (Ar from PMB), 87.0 (CH2Ar), 67.0 (C1/C5), 55.4 (CH3), 36.6 (C6/C7), 35.8 (C6/C7).
(C4/C5), 84.6 (C4/C5), 78.7 (C6), 78.2 (C3), 75.6 (CH2Ar), 75.2 HRMS (ESI): calcd for C36H40O6Na 591.2717; found 591.2710.
(CH2Ar), 73.1 (CH2Ar), 71.7 (CH2Ar), 55.4 (CH3), 29.3 (C7).
(3R,4S,5S,6S)-3,4,5-Tri-O-benzyl-6-O-p-methoxybenzyl-cyclo-
HRMS (ESI): calcd for C36H38O5Na 573.2611; found 573.2617.
heptane-1-ol (14S). Oil; Rf (pentane/ethyl acetate 4 : 1) 0.06;
(2R,3S,4S,5S/R)-2,3,4-tri-O-benzyl-5-O-p-methoxybenzyl-cyclo- [α]2D93K −0.9 (c 1, CHCl3); 1H-NMR (400 MHz, CDCl3):
heptane-1-ol (13) and (3R,4S,5S,6S/R)-3,4,5-tri-O-benzyl-6-O-p- δH 7.37–7.25 (15H, m, ArH), 7.23–7.19 (2H, m, ArH from PMB),
methoxybenzyl-cycloheptane-1-ol (14). The alkene 12 (1.75 g, 6.87–6.82 (2H, m, ArH from PMB), 4.68 (1H, d, J 12.2 Hz,
3.17 mmol) was dissolved in anhydrous THF (61 mL) and CHHAr), 4.61 (1H, d, J 11.6 Hz, CHHAr), 4.61 (1H, d, CHHAr)
BH3·THF complex (1 M solution in THF, 12.7 mL, 12.7 mmol, 4.61 (2H, s, CH2Ar), 4.55 (1H, d, CHHAr), 4.42 (2H, s, CH2Ar),
4 eq.) was added drop wise at 0 °C under a nitrogen atmos- 4.18 (1H, bd, J 4.1 Hz, H1), 3.94 (1H, dd, J 7.3 Hz, J 9.5 Hz, H3/
phere. After stirring for 1 h 10 min more BH3·THF complex H6) 3.90 (1H, d, J 2.5 Hz, H5/H4), 3.85 (1H, dd, J 2.7 Hz, J 11.5
(2 mL) was added. After additional 1 h 45 min the reaction was Hz, H6/H3), 3.80 (3H, s, CH3), 3.73 (1H, dd, J 7.1 Hz, J 2.7 Hz,
added 2 M NaOH (6.5 mL) and 35% aqueous H2O2 (13 mL) H4/H5), 2.38 (1H, ddd, J 14.8 Hz, J 11.6 Hz, J 4.0 Hz, H7a/H2a),
and the reaction was allowed to stir at r.t. for additional 3 h 2.17 (1H, ddd, J 1.3 Hz, J 11.0 Hz, J 14.3 Hz, H2a/H7a), 1.94
15 min. The mixture was then diluted with diethyl ether and (1H, dd, J 14.3 Hz, J 6.0 Hz, H2b/H7b), 1.84 (1H, d, J 14.2 Hz,
the organic phase was washed with water and brine, dried over H7b/H2b). 13C-NMR (100 MHz, CDCl3): δC 159.1 (Ar from
MgSO4, filtered and concentrated under reduced pressure. The PMB), 138.9 (Ar), 138.7 (Ar), 138.6 (Ar), 130.8 (Ar), 129.2 (Ar),
crude product was purified by flash column chromatography 128.4 (Ar), 128.4 (Ar), 128.3 (Ar), 127.9 (Ar), 127.9 (Ar), 127.7
(pentane/ethyl acetate 4 : 1) to give the two regioisomers 13 (Ar), 127.5 (Ar), 113.8 (Ar from PMB), 83.5 (C4/C5), 79.8
(830 mg, 46%) and 14 (340 mg, 19%) which were easily (C5/C4), 77.4 (C6/C3), 74.5 (C3/C6), 72.7 (CH2Ar), 72.4 (CH2Ar),
separated.
71.9 (CH2Ar), 70.9 (CH2Ar), 65.1 (C1), 55.3 (CH3), 37.2 (C2/C7),
(2R,3S,4S,5S)-2,3,4-Tri-O-benzyl-5-O-p-methoxybenzyl-cyclohep- 35.6 (C7/C2). HRMS (ESI): calcd for C36H40O6Na 591.2717;
tane-1-ol (13S). Oil; Rf (pentane/ethyl acetate 4 : 1) 0.17; found 591.2726.
[α]D293K +12.8 (c 1, CHCl3); 1H-NMR (400 MHz, CDCl3): δH
(3R,4S,5S,6R)-3,4,5-Tri-O-benzyl-6-O-p-methoxybenzyl-cyclohep-
7.38–7.22 (15H, m, ArH), 7.22–7.18 (2H, m, ArH from PMB), tane-1-ol (14R). Colourless oil; Rf (pentane/ethyl acetate 4 : 1)
6.87–6.82 (2H, m, ArH from PMB), 4.77 (1H, d, J 12.2 Hz, 0.14; [α]2D93K +1.0 (c 1, CHCl3); 1H-NMR (400 MHz, CDCl3):
CHHAr), 4.75 (1H, d, J 11.2 Hz, CHHAr), 4.63 (1H, d, CHHAr), δH 7.35–7.15 (m, 18H, ArH), 6.82 (2H, m, ArH from PMB), 4.92
4.54 (1H, d, CHHAr), 4.47 (2H, s, CH2Ar), 4.44 (1H, d, J 11.8 (1H, d, J 11.1 Hz, CHHAr), 4.72 (1H, d, J 11.2 Hz, CHHAr), 4.65
Hz, CHHAr), 4.38 (1H, d, CHHAr), 3.98 (1H, dd, J 2.3 Hz, J 9.6 (1H, d, CHHAr), 4.59 (1H, d, J 11.5 Hz, CHHAr), 4.54 (1H, d,
Hz, H1/H5), 3.96 (1H, dd, J 8.3 Hz, J 4.2 Hz, H4/H2), 3.82 (1H, CHHAr), 4.53 (1H, d, CHHAr) 4.48 (1H, d, J 11.5 Hz, CHHAr),
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4.44 (1H, d, CHHAr), 3.76 (3H, s, CH3), 3.76–3.72 (2H, m), 3.70 of freshly prepared LDA in THF (∼0.37 M, 2.0 mL, 0.740 mmol,
(1H, d, J 8.3 Hz) 3.65 (1H, dd, J 8.4 Hz, J 4.4 Hz), 3.63–3.58 (1H, 2 eq.) at −78 °C. The mixture was stirred for 10 min and then a
m), 1.92–1.81 (2H, m, H2/H7), 1.81–1.71 (2H, m, H2/H7). solution of the ketone 15 (208 mg, 0.367 mmol) in THF
13C-NMR (100 MHz, CDCl3): δC 159.2 (Ar from PMB), 138.6 (1.8 mL) was added. After stirring for 8 h more LDA was added
(Ar), 138.5 (Ar), 138.5 (Ar), 130.7 (Ar), 129.2 (Ar), 128.6 (Ar), (2 mL) at −78 °C and the reaction was left to stir overnight.
128.5 (Ar), 128.1 (Ar), 127.9 (Ar), 127.8 (Ar), 127.7 (Ar), 127.7 The next morning more LDA (2 mL) and dichloromethane
(Ar), 113.8 (Ar from PMB), 84.8, 83.9, 83.0, 77.4, 75.5 (CH2Ar), (0.2 mL) was added and the reaction heated to 0 °C. After 2 h
74.5 (CH2Ar), 73.1 (CH2Ar), 71.7, 70.8 (CH2Ar), 55.4 (CH2Ar), the reaction was quenched with sat. aq. NH4Cl, diluted with
27.3 (C2/C7), 22.8 (C2/C7). HRMS (ESI): calcd for C36H40O6Na ethyl acetate, washed with water and brine, dried over MgSO4,
591.2717; found 591.2718.
filtered and concentrated under reduced pressure to give the
(2S,3R,4S,5S/R)-2,3,4-Tri-O-benzyl-5-p-methoxybenzyl-cyclohep- crude alcohol (16).
tanon (15). The alcohol 13 (830 mg, 1.46 mmol) was dissolved
Crude alcohol 16 was dissolved in anhydrous DMSO (2 mL)
in dichloromethane (45 mL) and Dess–Martin periodinane and added DBU (90 μL, 0.602 mmol, 1.7 eq.) and stirred for
(1.24 g, 2.93 mmol, 2 eq.) was added. The mixture was stirred 1 h 40 min. The mixture was then diluted with ethyl acetate
for 40 min after which it was quenched by adding Na2S2O3 (s) and washed with water and brine. The combined aqueous
and sat. aq. NaHCO3. The mixture was allowed to stir for phases were extracted with ethyl acetate and the combined
35 min and was then extracted with dichloromethane, dried organic phases were now dried over MgSO4, filtered and con-
over MgSO4, filtered and concentrated under reduced pressure centrated under reduced pressure to give the crude chloro-
giving the ketone 15 (919 mg). The crude product was used epoxide (17).
directly in the next step without further purification.
Crude 17 was dissolved in anhydrous DMF (2.4 mL) and
(2S,3R,4S,5S)-2,3,4-Tri-O-benzyl-5-p-methoxybenzyl-cycloheptanon added TBAN3 (322 mg, 1.13 mmol, 3.1 eq.) under a nitrogen
(15S). Rf (pentane/ethyl acetate 4 : 1) 0.26; [α]2D93K −15.3 (c 1, atmosphere. The mixture was heated to 50 °C and after 10 min
CHCl3); 1H-NMR (400 MHz, CDCl3): δH 7.36–7.20 (13H, m, cooled to r.t., diluted with ethyl acetate, washed with water,
ArH), 7.18–7.12 (4H, m, ArH), 6.83–6.78 (2H, m, ArH from dried over MgSO4, filtered and concentrated under reduced
PMB), 4.77 (1H, d, J 11.9 Hz, CHHAr), 4.65 (1H, d, J 12.3 Hz, pressure.
CHHAr), 4.57 (1H, d, CHHAr), 4.51 (1H, d, CHHAr), 4.44–4.37
The resulting aldehyde 18 was then dissolved in methanol
(4H, m, CH2Ar), 4.08 (1H, d, J2,3 3.7 Hz, H2) 3.92–3.84 (3H, m, (3.5 mL) and NaBH4 (98.6 mg, 2.60 mmol, 7 eq.) was added
H3, H4, H5), 3.76 (3H, s, CH3), 2.54 (1H, ddd, J7a,6a 4.5 Hz, and the mixture stirred at 0 °C for 2 h. More NaBH4 was then
J7a,6b 7.3 Hz, J7a,7b 13.2 Hz, H7a), 2.31 (1H, ddd, J7b,6b 4.9 Hz, added and after another 10 min at 0 °C and 15 min at room
J7b,6a 10.4 Hz, H7b), 2.08 (1H, ddt, J6a,5 10.4 Hz, J6a,6b 14.0 Hz, temperature the mixture was quenched with water, concen-
H6a), 1.84 (1H, ddt, J6b,5 7.3 Hz, H6b). 13C-NMR (100 MHz, trated under reduced pressure, redissolved in ethyl acetate,
CDCl3): δC 206.7 (CvO), 159.3 (Ar from PMB), 138.4 (Ar), 137.9 washed with water, dried over MgSO4, filtered and concen-
(Ar), 129.3 (Ar), 128.5 (Ar), 128.3 (Ar), 128.3 (Ar), 127.9 (Ar), trated under reduced pressure to give the crude alcohol (19).
127.9 (Ar), 127.7 (Ar), 127.5 (Ar), 113.9 (Ar), 86.5 (C2), 80.4
19 was then dissolved in anhydrous DMF (1.9 mL) and
(2 × C, C3/C4/C5), 76.2 (C3/C4/C5), 73.2 (CH2Ar), 72.7 (CH2Ar), cooled to 0 °C. NaH (60%, 53.7 mg, 1.34 mmol, 3.7 eq.) and
72.5 (CH2Ar), 70.8 (CH2Ar), 55.4 (CH3), 37.0 (C7), 24.2 (C6). then benzyl bromide (65 μL, 0.547 mmol, 1.5 eq.) was added
HRMS (ESI): calcd for C36H38O6Na 589.2561; found 589.2563.
under a nitrogen atmosphere. The reaction was stirred over-
(2S,3R,4S,5R)-2,3,4-Tri-O-benzyl-5-p-methoxybenzylcycloheptanon night and then quenched with water, diluted with ethyl
(15R). Rf (pentane/ethyl acetate 3 : 1) 0.63; [α]2D93K −1.8 (c 1, acetate, washed with water, dried over MgSO4, filtered and con-
CHCl3); 1H-NMR (400 MHz, CDCl3): δH 7.35–7.18 (m, 15H, centrated under reduced pressure. The crude product was puri-
ArH), 7.18–7.13 (m, 2H, ArH from PMB), 6.83–6.77 (m, 2H ArH fied by flash column chromatography (pentane/ethyl acetate
from PMB), 4.66 (1H, d, J 11.8 Hz, CHHAr), 4.66 (1H, d, 20 : 1) to give the product (20) (81 mg, 34% over 6 steps).
CHHAr), 4.58 (1H, d, J 10.5 Hz, CHHAr), 4.56 (1H, d, CHHAr),
(1R,2R,3S,4S,5R)-1-Azido-2,3,4-tri-O-benzyl-1-(benzyloxy)methyl-
4.49 (1H, d, J 11.3, CHHAr), 4.47–4.40 (4H, m), 3.86 (1H, dd, 5-O-p-methoxybenzyl-cycloheptane (20R). Rf (pentane/ethyl
J 7.2 Hz, J 3.4 Hz), 3.81 (1H, t, J 4.8 Hz), 3.80–3.76 (1H, m) 3.77 acetate 20 : 1) 0.23; [α]2D93K +6.0 (c 1, CHCl3); 1H-NMR
(3H, s, CH3), 2.58–2.39 (2H, m, H7), 2.12–1.95 (2H, m, H6). (400 MHz, CDCl3): δH 7.39–7.19 (m, 20H, ArH), 7.19–7.12
13C-NMR (100 MHz, CDCl3): δC 207.3 (CvO), 159.3 (Ar from (m, 2H, ArH from PMB), 6.86–6.78 (m, 2H, ArH from PMB),
PMB), 138.2 (Ar), 138.1 (Ar), 137.7 (Ar), 130.5 (Ar), 129.4 (Ar), 4.84 (d, J 10.7 Hz, 1H, CHHAr), 4.73 (d, J 11.5 Hz, 1H,
128.5 (Ar), 128.4 (Ar), 128.4 (Ar), 128.1 (Ar), 128.0 (Ar), 127.9 CHHAr)), 4.72 (d, 1H, CHHAr), 4.69 (d, J 12.0 Hz, 1H, CHHAr),
(Ar), 127.8 (Ar), 127.8 (Ar), 113.8 (Ar from PMB), 86.1, 81.3, 4.61 (d, 1H, CHHAr), 4.57 (d, J 11.1 Hz, 1H, CHHAr), 4.52 (d,
81.0, 78.8, 73.6 (CH2Ar), 73.1 (CH2Ar), 72.5 (CH2Ar), 71.4 J 11.9 Hz, 2H, CHHAr, CHHAr), 4.47 (d, 1H, CHHAr), 4.28 (d,
(CH2Ar), 55.4 (CH3), 37.4 (C7), 24.5 (C6). HRMS (ESI): calcd for 1H, CHHAr), 3.94 (d, J 4.4 Hz, 1H, H2/H3), 3.87 (dd, J 8.4 Hz,
C36H38O6Na 589.2561; found 589.2569.
J 6.9 Hz, 1H, H2/H3), 3.81–3.76 (m, 4H, CH3, H4), 3.63 (d, J8a,8b
(1R,2R,3S,4S,5R/S)-1-Azido-2,3,4-tri-O-benzyl-1-(benzyloxy)methyl- 9.6 Hz, 1H, H8a), 3.60 (d, 1H, H8b), 3.57 (td, J 8.6 Hz, J 2.7 Hz,
5-O-p-methoxybenzyl-cycloheptane (20). Anhydrous dichloro- 1H, H5), 1.93–1.71 (m, 3H, H6/H7), 1.55 (dd, J 11.3 Hz,
methane (0.23 mL, 3.60 mmol, 9.8 eq.) was added to a solution J 6.7 Hz, 1H, H6/H7). 13C-NMR (100 MHz, CDCl3): δC 159.2
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(Ar from PMB), 139.1 (Ar), 138.6 (Ar), 138.1 (Ar), 138.0 (Ar), filtered of through a syringe filter and the filtrate concentrated
131.1 (Ar), 129.4 (Ar), 128.5 (Ar), 128.4 (Ar), 128.4 (Ar), 128.4 under reduced pressure to give the crude hemiaminal (22)
(Ar), 128.2 (Ar), 127.8 (Ar), 127.8 (Ar), 127.7 (Ar), 127.7 (Ar), (38.8 mg).
127.6 (Ar), 113.8 (Ar from PMB), 87.7 (C2/C3), 82.9 (C4), 80.4
Rf (pentane/ethyl acetate 1 : 1) 0.36; [α]2D93K +15.4 (c 1,
(C2/C3), 78.8 (C5), 75.5 (CH2Ar), 74.5 (CH2Ar), 73.8 (CH2Ar), CHCl3); 1H-NMR (400 MHz, CDCl3): δH 7.43–7.16 (m, 20H,
73.8 (C8), 73.4 (CH2Ar), 72.5 (CH2Ar), 67.1 (C1), 55.4 (CH3), ArH), 5.04 (d, J 11.4 Hz, 1H, CHHPh), 4.92 (d, J 10.8 Hz, 1H,
26.9 (C6/C7), 26.7 (C6/C7). HRMS (ESI): calcd for CHHPh), 4.81 (d, J 11.1 Hz, 1H, CHHPh), 4.79 (d, J 10.8 Hz,
C44H47N3O6Na 736.3357; found 736.3363.
(1R,2R,3S,4S,5S)-1-Azido-2,3,4-tri-O-benzyl-1-(benzyloxy)methyl- 1H, CHHPh), 4.43 (d, 1H, CHHPh), 3.75 (d, J6a,6b 9.0 Hz, 1H,
5-O-p-methoxybenzyl-cycloheptane (20S). Rf (pentane/ethyl H6a), 3.74 (d, J2,3 8.2 Hz, 1H, H2), 3.65 (t, J3,4 8.3 Hz, 1H, H3),
2H, CHHPh, CHHPh), 4.60 (d, 1H, CHHPh), 4.53 (d, J 11.7 Hz,
acetate 20 : 1) 0.10; 1H-NMR (400 MHz, CDCl3): δH 7.46–7.20 3.53 (d, 1H, H4), 3.36 (d, 1H, H6b), 2.34 (ddd, J8a,8b 12.0 Hz,
(m, 23H, ArH), 6.82–6.71 (m, 2H, ArH from PMB), 4.73–4.52 J8a,7a 9.9 Hz, J8a,7b 4.0 Hz, 1H, H8a), 1.90 (ddd, J7a,7b 12.6 Hz,
(m, 9H), 4.48 (d, J 11.1 Hz, 1H), 4.07–3.95 (m, 4H), 3.81 (s, 3H, J7a,8b 4.5 Hz, 1H, H7a), 1.66 (td, J8b,7b 12.2 Hz, 1H, H8b), 1.56
CH3), 3.83–3.78 (m, 1H) 3.73 (d, J 9.8 Hz, 1H), 2.31 (ddd, J 14.7 (td, 1H, H7b). 13C-NMR (100 MHz, CDCl3): δC 139.1 (Ar), 138.9
Hz, J 11.0 Hz, J 4.1 Hz, 1H, H6a/H7), 2.04–1.90 (m, 1H, (Ar), 138.9 (Ar), 138.1 (Ar), 128.5 (Ar), 128.5 (Ar), 128.4 (Ar),
H6a/H7), 1.79 (ddt, J 14.7 Hz, J 11.2 Hz, J 3.9 Hz, 1H, 128.1 (Ar), 127.9 (Ar), 127.8 (Ar), 127.8 (Ar), 127.7 (Ar), 127.6
H6b), 1.40–1.27 (m, 1H, H6a/H7). HRMS (ESI): calcd for (Ar), 127.6 (Ar), 91.7 (C1), 87.2 (C2), 84.9 (C3), 82.8 (C4), 77.4
C44H47N3O6Na 736.3357; found 736.3385.
(CH2Ph), 75.7 (CH2Ph), 74.7 (CH2Ph), 73.5 (CH2Ph), 73.2
(2R,3S,4R,5R)-5-Azido-2,3,4-tri-O-benzyl-5-(benzyloxy)methyl- (CH2Ph), 62.9 (C5), 31.7 (C8), 25.5 (C7). HRMS (ESI): calcd for
cycloheptanon (21). The PMB ether (20) (69.6 mg, 97.6 μmol) C36H39NO5H 566.2901; found 566.2910.
was mixed with trifluoroacetic acid/dichloromethane 1 : 1
(1S,2R,3S,4R,5R)-5-(Hydroxymethyl)-8-azabicyclo[3.2.1]octane-
(7.6 mL) at 0 °C. After 1 h 10 min the mixture had turned dark 1,2,3,4-tetraol – nojiristegine (1).
purple and was concentrated under reduced pressure. The
crude alcohol was redissolved in dichloromethane (4.4 mL)
and added Dess–Martin periodinate (109 mg, 0.255 mmol,
2.6 eq.). After 30 min the reaction was quenched with sat. aq.
NaHCO3 and Na2S2O3. The mixture was left to stir for 1 h and
then extracted with dichloromethane, dried over MgSO4,
filtered and concentrated under reduced pressure. The crude
product was combined with another batch (18 μmol) and puri- The crude benzyl protected compound (21) (66.8 μmol) was
fied by flash column chromatography (pentane/ethyl acetate dissolved in methanol/ethyl acetate 1 : 1 (2.6 mL) and added
8 : 1) to give the ketone (21) (43.2 mg, 65% over 2 steps).
20% Pearlmans catalyst (10.2 mg, 14.5 μmol, 22%). The
Rf (pentane/ethyl acetate 6 : 1) 0.36; [α]2D93K +33.0 (c 1, mixture was bubbled through with hydrogen and stirred under
CHCl3); 1H-NMR (400 MHz, CDCl3): δH 7.45–7.21 (m, 18H, a hydrogen atmosphere for 3 h 50 min. 2 drops of concen-
ArH), 7.08 (dd, J 6.6 Hz, J 2.9 Hz, 2H, ArH), 4.78 (d, J 11.8 Hz, trated hydrochloric acid was then added and the reaction left
1H, CHHPh), 4.71 (d, J 11.6 Hz, 2H, 2 × CHHPh), 4.69 (d, overnight. The next morning the catalyst was filtered of
J2,3 5.6 Hz, 1H, H2), 4.48 (d, J 12.0 Hz, 1H, CHHPh), 4.45 (d, through a syringe filter and the filtrate concentrated under
J 11.3 Hz, 2H, 2 × CHHPh), 4.42 (d, J 10.3 Hz, 1H, CHHPh), reduced pressure. The crude compound was purified by flash
4.11 (d, J 11.4 Hz, 1H, CHHPh), 4.01 (d, J3,4 3.7 Hz, 1H, H4), column chromatography (5% NH4OH in ethanol) to give
3.89 (dd, 1H, H3), 3.61 (d, J8a,8b 9.6 Hz, 1H, H8a), 3.47 (d, nojiristegine (1) (16.5 mg, quant.).
H8b), 2.60–2.38 (m, 2H, H6/H7), 1.99 (ddd, J 14.1 Hz, J 9.1 Hz,
Rf (5% NH4OH in ethanol) 0.31; [α]2D93K −2.4 (c 1, H2O);
J 4.7 Hz, 1H, H6/H7), 1.75 (ddd, J 14.5 Hz, J 7.9 Hz, J 5.3 Hz, 1H-NMR (400 MHz, D2O): δH 3.78 (d, J6a,6b 12.2 Hz, 1H, H6a),
1H, H6/H7). 13C-NMR (100 MHz, CDCl3): δC 205.9 (CvO), 3.68 (d, J 8.7 Hz, 1H, H2), 3.58 (d, J 8.7 Hz, 1H, H4), 3.56 (d,
137.9 (Ar), 137.7 (Ar), 137.7 (Ar), 137.3 (Ar), 128.5 (Ar), 128.5 1H, H6b), 3.46 (t, J2,3 8.7 Hz, 1H, H3), 2.28–2.14 (m, 1H, H8a),
(Ar), 128.4 (Ar), 128.4 (Ar), 128.2 (Ar), 128.2 (Ar), 128.0 (Ar), 1.88–1.73 (m, 2H, H7a + H8b), 1.73–1.62 (m, 1H, H7b).
128.0 (Ar), 127.9 (Ar), 127.9 (Ar), 127.6 (Ar), 87.3 (C2), 80.0 (C3), 13C-NMR (100 MHz, D2O): δC 91.5 (C1), 75.9 (C2), 74.9 (C3),
78.4 (C4), 74.4 (C8), 74.0 (CH2Ar), 73.4 (CH2Ar), 73.2 (CH2Ar), 72.1 (C4), 65.3 (C5), 62.3 (C6), 28.3 (C8), 23.2 (C7). HRMS (ESI):
72.5 (CH2Ar), 66.1 (C5), 37.6 (C6/C7), 26.0 (C6/C7). HRMS calcd for C8H15NO5H 206.1023; found 206.1023.
(ESI): calcd for C36H37N3O5Na 614.2625; found 614.2623.
Methyl 6-O-trityl-α-D-mannopyranoside (52). Commercially
(1S,2R,3S,4R,5R)-2,3,4-Tris(benzyloxy)-5-((benzyloxy)methyl)-8- available methyl α-D-mannopyranoside (4) (4.96 g, 25.5 mmol)
azabicyclo[3.2.1]octan-1-ol (22). The ketone (21) (42.2 mg, was dissolved in anhydrous pyridine (40 mL). Trityl chloride
71.3 μmol) was dissolved in methanol/ethyl acetate 1 : 1 (10.8 g, 38.7 mol, 1.5 eq.) and DMAP (634 mg, 5.15 mmol,
(2.6 mL). Three drops of triethylamine and then 20% Pearl- 0.2%) were added and the reaction mixture was stirred at room
mans catalyst (12.5 mg, 0.0178 mmol, 20%) were added. The temperature overnight under a nitrogen atmosphere. The pyri-
mixture was bubbled through with hydrogen and stirred under dine was then removed under reduced pressure and the
a hydrogen atmosphere for 15 min. The catalyst was then residue was diluted with dichloromethane. The organic phase
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was washed with 1 M aq. HCl, sat. aq. NaHCO3 and brine and mixture was heated to reflux. The reaction was stirred for 1 h
the organic layer was dried over MgSO4, filtered and concen- 30 min., and then cooled to room temperature. Na2S2O3 (aq)
trated under reduced pressure giving the tritylated crude com- (300 mL) was added and the mixture was washed with water
pound (52) (18.1 g) as a white solid.
and brine, dried with MgSO4, filtered and concentrated. The
Rf (ethyl acetate/pentane 1 : 1) 0.39. HRMS (ESI): calcd for crude product was purified by flash column chromatography
C26H28O6Na 459.1778; found 459.1782.
(ethyl acetate/pentane 1 : 20 → 1 : 2) to give the iodide (6) as a
Rf (ethyl acetate/pentane 1 : 19) 0.32; 1H-NMR (400 MHz,
Methyl
2,3,4-Tri-O-benzyl-6-O-trityl-α-D-mannopyranoside yellow oil (28.1 g, 93%).
(53). The crude compound 52 was dissolved in anhydrous
DMF (110 mL) under a nitrogen atmosphere. The mixture was CDCl3): δH 7.44–7.28 (15H, m, ArH), 5.01 (1H, d, J 11.0 Hz,
cooled to 0 °C and 60% sodium hydride in mineral oil (6.20 g, CHHPh), 4.78 (d, J 12.5 Hz, 1H, CHHPh), 4.77 (1H, d, J 1.8 Hz,
156 mmol, 6 eq.) was slowly added, followed by dropwise H1). 4.73 (1H, d, CHHPh), 4.70 (1H, d, CHHPh), 4.62 (2H, s,
addition of benzyl bromide (13.9 mL, 117 mmol, 4.5 eq.) CH2Ph) 3.91 (1H, dd, J3,4 9.3 Hz, J3,2 3.0 Hz, H3), 3.84–3.77
under formation of hydrogen gas. The reaction mixture was (2H, m, H4, H2), 3.63–3.51 (2H, m, H6a, H5) 3.39 (3H, s, CH3)
then allowed slowly to warm to room temperature and react 3.35 (1H, dd, J6a,6b 10.2 Hz, J5,6b 2.4 Hz, H6b). 13C-NMR
overnight. The mixture was quenched by addition of methanol (100 MHz, CDCl3): δC 138.4 (Ar), 138.3 (Ar), 138.3 (Ar), 128.6
(30 mL) and then evaporated under reduced pressure. The (Ar), 128.5 (Ar), 128.5 (Ar), 128.1 (Ar), 127.9 (Ar), 127.8 (Ar),
residue was diluted with diethyl ether and washed with water. 127.8 (Ar), 127.7 (Ar), 99.1 (C1), 80.0 (C3), 78.7 (C4), 75.5
The aqueous phase was extracted with diethyl ether and the (CH2Ph), 74.6 (C2), 72.8 (CH2Ph), 72.2 (CH2Ph), 71.5 (C5), 55.2
combined organic phases were washed with brine, dried over (CH3), 7.2 (C6). HRMS (ESI): calcd for C28H31O5INH4 592.1554;
MgSO4, filtered and concentrated under reduced pressure found 592.1554.
yielding the crude compound (53) (32.6 g) as a brown oil.
Rf (ethyl acetate/pentane 1 : 1) 0.39. HRMS (ESI): calcd for values.42
C47H50O6NH4 724.3633; found 724.3640. (2S,3S,4R)-2,3,4-Tri-O-benzylhex-5-enal (23). A solution of
2,3,4-tri-O-benzyl-6-hydroxy-α-D-mannopyranoside iodide 6 (541 mg, 0.934 mmol) in anhydrous THF (20 mL) and
NMR data was in accordance with previously reported
Methyl
(54). The crude compound (53) was dissolved in methanol/ water (5 mL) was degassed in a sonication bath. Then preacti-
dichloromethane 2 : 1 and then p-toluenesulfonic acid was vated zinc dust (625 mg, 10.3 mmol, 11 eq.)§ was added and
added until pH < 4. The reaction was stirred overnight. The the mixture sonicated at 40 °C for 1 h 30 min. The reaction
mixture was then neutralised with triethylamine and evapor- mixture was diluted with water and diethyl ether and filtered
ated under reduced pressure. The residue was diluted with through a pad of Celite®. The organic phase was washed with
ethyl acetate and washed with water. The aqueous phase was water and brine, dried over Na2SO4, filtered and concentrated
extracted with ethyl acetate and the combined organic phases under reduced pressure to yield the aldehyde (23) (394 mg) as
were washed with brine, dried with MgSO4, filtered and con- a clear oil without further purification.
centrated. The crude product was purified by flash column
chromatography (ethyl acetate/pentane 1 : 10 → 1 : 1) to give 54 CDCl3): δH 9.66 (1H, s, CHO), 7.35–7.26 (15H, m, ArH), 5.87
as a yellow oil (7.86 g, 65% over 3 steps). (1H, ddd, J5,4 8.0 Hz, J5,6Z 10.4 Hz, J5,6E 17.6 Hz, H5), 5.37 (1H,
Rf (ethyl acetate/pentane 1 : 11) 0.34; 1H-NMR (400 MHz,
Rf (ethyl acetate/pentane 1 : 3) 0.27; 1H-NMR (400 MHz, d, J6E,5 17.3 Hz, H6E), 5.35 (1H, d, J6Z,5 10.3 Hz, H6Z) 4.72–4.61
CDCl3): δH 7.40–7.27 (15H, m, ArH), 4.97 (1H, d, J 10.9 Hz, (4H, m, 2 × CHHPh), 4.49 (1H, d, J 11.7 Hz, CHHPh), 4.37 (1H,
CHHPh), 4.81 (1H, d, J 12.3 Hz, CHHPh), 4.72 (1H, s, H1), 4.71 d, J 11.8 Hz, CHHPh), 4.11 (1H, m, H4) 4.07 (1H, dd, J2,3
(1H, d, CHHPh), 4.68 (1H, d, CHHPh), 4.66 (2H, s, CH2Ph), 3.7 Hz, J2,1 1.2 Hz, H2), 3.89 (1H, dd, J3,4 5.6 Hz, H3). 13C-NMR
4.00 (1H, t, J4,3 = J4,5 9.5 Hz, H4), 3.93 (1H, dd, J3,2 2.9 Hz, H3), (100 MHz, CDCl3): δC 201.8 (CHO), 138.2 (Ar), 138.0 (Ar), 137.5
3.87 (1H, dd, J2,1 9.2 Hz, H2), 3.83–3.78 (1H, m, H6), 3.65 (1H, (Ar), 135.3 (C5), 128.6 (Ar), 128.5 (Ar), 128.4 (Ar), 128.2 (Ar),
ddd, J5,6a 4.4 Hz, J5,6b 3.1 Hz, H5), 3.22 (3H, s, CH3), 2.16 (1H, 128.1 (Ar), 128.0 (Ar), 127.9 (Ar), 127.7 (Ar), 120.0 (C6), 83.8
bs, OH). 13C-NMR (100 MHz, CDCl3): δC 138.6 (Ar), 138.5 (Ar), (C4), 83.0 (C3), 80.7 (C2), 74.3 (CH2Ph), 73.0 (CH2Ph), 70.9
138.3 (Ar), 128.5 (Ar), 128.5 (Ar), 128.5 (Ar), 128.3 (Ar), 128.1 (CH2Ph). HRMS (ESI): calcd for C27H28O4Na 439.1880; found
(Ar), 128.0 (Ar), 127.8 (Ar), 127.7 (Ar), 99.4 (C1), 80.3 (C3), 75.3 439.1880.
(CH2Ph), 75.0 (C4), 74.8 (C2), 73.0 (CH2Ph), 72.3 (CH2Ph), 72.2
NMR data was in accordance with previously reported
(C6), 62.5 (C6), 54.9 (CH3). HRMS (ESI): calcd for C28H32O6NH4 values.43
482.2537; found 482.2546.
(4R/S,5R,6S,7R)-5,6,7-Tri-O-benzyl-1,8-nonadiene-4-ol (24). To
NMR data was in accordance with previously reported a stirred solution of the crude aldehyde (23) (0.934 mmol) in
values.44
50% aqueous THF (14 mL) was added indium dust (227 mg,
Methyl 2,3,4-tri-O-benzyl-6-deoxy-6-iodo-α-D-mannopyranoside 1.98 mmol, 2 eq.) and allyl bromide (0.30 mL, 3.47 mmol,
(6). Methyl 2,3,4-tri-O-benzyl-α-D-mannopyranoside (54) (24.3 g,
52.5 mmol) was dissolved in anhydrous toluene (300 mL)
under a nitrogen atmosphere. Triphenylphosphine (34.5 g,
§Zinc dust (2.06 g) was mixed with 1 M HCl (20 mL) and stirred at room temp-
erature for 1 hour. Then the mixture was filtered and the zinc dust was washed
131 mmol, 2.5 eq.), imidazole (8.59 g, 126 mmol, 2.4 eq.) and
with water and diethyl ether. The zinc dust was dried under high vacuum at
iodine (14.7 g, 57.8 mmol, 1.1 eq.) were added and the reaction about 30 min and in the first 5 min heated with a heat gun.
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4 eq.). The mixture was stirred overnight at room temperature. 117.9 (CH2vCH), 81.7, 80.8, 78.1, 74.9 (CH2Ph), 73.8, 72.4
Sat. aq. NaHCO3 (5 mL) was added to neutralise the reaction (CH2Ph), 70.5 (CH2Ph), 36.3 (C3), 21.4 (CH3). Major isomer +
mixture, which was then extracted with chloroform and the minor isomer: 13C-NMR (100 MHz, CDCl3): δC 128.5 (Ar), 128.5
combined organic phases dried over MgSO4, filtered and con- (Ar), 128.4 (Ar), 128.4 (Ar), 128.4 (Ar), 128.2 (Ar), 128.1 (Ar),
centrated. The crude product was purified by flash column 128.1 (Ar), 128.1 (Ar), 127.9 (Ar), 127.9 (Ar), 127.8 (Ar), 127.7
chromatography (ethyl acetate/pentane 1 : 20) to give the (Ar), 127.7 (Ar), 127.6 (Ar). HRMS (ESI): calcd for C32H36O5NH4
product (24) as a colourless oil (310 mg, 76% over 2 steps). 518.2901; found 518.2903.
According to NMR the product was a 1 : 2.2 mixture of S- and
R-diastereoisomers.
(3R,4S,5R,6S)-6-O-Acetyl-3,4,5-tri-O-benzyl-cycloheptene (26) and
(3R,4S,5R,6R)-6-O-acetyl-3,4,5-tri-O-benzyl-cycloheptene (27). The
Rf (ethyl acetate/pentane 1 : 9) 0.40; 1H-NMR (400 MHz, crude acetate (25) (5.81 mmol)) was dissovled in anhydrous
CDCl3): δH 7.27–7.09 (30H, m, ArH), 5.87–5.58 (4H, m), toluene (30 mL) under an atmosphere of nitrogen. Grubbs–
5.28–5.19 (4H, m), 5.01–4.87 (4H, m), 4.66 (4H, dt, J 18.6 Hz, Hoveyda 2nd generation catalyst (35.7 mg, 54.8 μmol, 1 mol%)
J 11.5 Hz), 4.55 (2H, d, J 11.8 Hz), 4.39–4.34 (4H, m), 4.28 (q, was added to the mixture which was immediately put on a pre-
J 11.0 Hz), 4.04 (1H, dd, J 7.4 Hz, J 5.8 Hz), 3.97 (1H, dd, heated 80 °C oil bath. The mixture stirred for 2 h before more
J 7.9 Hz, J 5.0 Hz), 3.85 (2H, dd, J 10.2 Hz, J 7.4 Hz), 3.74–3.69 catalyst was added. After additional 1 h 30 min the reaction
(2H, m), 3.53–3.47 (2H, m), 2.96 (1H, s), 2.57 (1H, s), 2.43–2.36 was concentrated under reduced pressure and the crude
(1H, m), 2.27–2.11 (3H, m). Major isomer: 13C-NMR (100 MHz, product was purified by flash column chromatography (diethyl
CDCl3): δC 138.3 (Ar), 138.3 (Ar), 138.3 (Ar), 136.0 (CHvCH2), ether/chloroform 0 : 1 → 1 : 40) yielding 27 and 26 (1.96 g, 71%
135.5 (CHvCH2), 119.1 (CHvCH2), 117.4 (CHvCH2), 82.9, over 2 steps) which were partly separated.
81.5, 81.5, 74.7, 72.9, 71.1, 70.6, 37.7 (C3). Minor isomer:
(3R,4S,5R,6S)-6-O-Acetyl-3,4,5-tri-O-benzyl-cycloheptene
(26).
13C-NMR (100 MHz, CDCl3): δC 138.2 (Ar), 138.1 (Ar), 138.0 Colourless oil (53.7 mg, 19% over 2 steps); Rf (ethyl acetate/
(Ar), 135.7 (CHvCH2), 135.2 (CHvCH2), 119.3 (CHvCH2), pentane 1 : 13) 0.38; [α]2D98K −1.2 (c 1.0, CHCl3). 1H-NMR
117.2 (CHvCH2), 82.1, 81.0, 78.1, 75.3, 73.0, 70.7, 70.3, 38.7 (400 MHz, CDCl3): δH 7.38–7.23 (m, 15H, ArH), 5.81 (1H, dd,
(C3). Major isomer + minor isomer: 13C-NMR (100 MHz, J2,1 11.7 Hz, J2,3 4.1 Hz, H2), 5.72 (1H, ddd, J1,7b 6.9 Hz, J1,7a 1.2
CDCl3): δC 128.4 (Ar), 128.4 (Ar), 128.3 (Ar), 128.3 (Ar), 128.1 Hz, H1), 5.15 (1H, td, J6,5 = J6,7b 6.9 Hz, J6,7a 3.2 Hz, H6), 4.78
(Ar), 128.0 (Ar), 128.0 (Ar), 128.0 (Ar), 127.9 (Ar), 127.8 (Ar), (1H, d, J 9.7 Hz, CHHPh), 4.75 (1H, d, CHHPh), 4.73 (1H, d,
127.8 (Ar), 127.7 (Ar), 127.6 (Ar), 127.6 (Ar). HRMS (ESI): calcd J 12.2 Hz, CHHPh), 4.66 (1H, d, CHHPh), 4.62 (1H, d, J 11.8
for C30H34O4Na 481.2349; found 481.2350.
Hz, CHHPh), 4.55 (1H, d, CHHPh), 4.35 (1H, dd, J3,4 7.2 Hz,
(4R/S,5R,6S,7R)-5,6,7-Tri-O-benzyl-1,8-nonadiene-4-acetate (25). H3), 3.96 (1H, dd, J5,4 1.8 Hz, H5), 3.91 (1H, dd, H4), 2.56 (1H,
The alcohol (24) (2.67 g, 5.81 mmol) was dissolved in anhy- dddt, J7a,7b 15.6 Hz, H7a), 2.33 (1H, dt, H7b), 1.96 (3H, s, CH3).
drous pyridine (20 mL) under an atmosphere of nitrogen. 13C-NMR (100 MHz, CDCl3): δC 169.9 (CvO), 138.6 (Ar), 138.6
Acetic anhydride (20 mL) and DMAP (35.2 mg, 0.293 mmol, (Ar), 138.5 (Ar), 132.2 (CHvCH), 128.2 (Ar), 128.2 (Ar), 127.7
5 mol%) were added and stirred at room temperature for 3 h (Ar), 127.6 (Ar), 127.5 (Ar), 127.4 (Ar), 126.2 (CHvCH), 80.5
30 min. The reaction was cooled on a water bath and (C5), 78.3 (C4), 75.9 (C3), 73.4 (CH2Ph), 73.3 (CH2Ph), 71.8
quenched by slow addition of water (20 mL) and then diluted (CH2Ph/C6), 71.8 (CH2Ph/C6), 28.2 (C7), 21.1 (CH3). HRMS
with ethyl acetate. The organic phase was washed with 1 M aq. (ESI): calcd for C30H32O5Na 495.2142; found 495.2147.
HCl and sat. aq. NaHCO3, dried over MgSO4, filtered and
concentrated under reduce pressure to yield the acetylated Colourless oil (1.37 g, 50% over 2 steps); Rf (ethyl acetate/
compound (25) (2.93 g) without further purification.
pentane 1 : 13) 0.38; [α]2D98K −4.0 (c 1.0, CHCl3); 1H-NMR
(3R,4S,5R,6R)-6-O-Acetyl-3,4,5-tri-O-benzyl-cycloheptene (27).
Rf (ethyl acetate/pentane 1 : 15) 0.32; 1H-NMR (400 MHz, (400 MHz, CDCl3): δH 7.42–7.23 (15H, m, ArH), 5.76 (1H, dt,
CDCl3): δH 7.33–7.13 (m, 20.4H), 5.86 (tdd, J 17.7 Hz, J 10.3 Hz, J2,1 12.4 Hz, J2,3 2.7 Hz, H2), 5.62 (1H, m, H1), 4.92 (1H, d,
J 7.7 Hz, 1.3H), 5.61 (ddt, J 17.3 Hz, J 10.6 Hz, J 7.1 Hz, 1.3H), J 11.9 Hz, CHHPh), 4.84 (1H, d, J 11.7 Hz, CHHPh), 4.79 (1H,
5.36–5.17 (m, 3.7H), 4.96–4.89 (m, 2.4H), 4.71 (d, J 11.4 Hz, d, CHHPh), 4.76 (1H, d, J 11.4 Hz, CHHPh), 4.75 (1H, dt, J6,7a
0.9H), 4.64 (d, J 11.4 Hz, 1H), 4.63–4.47 (m, 3.1H), 4.48 (s, 11.4 Hz, J6,7b = J6,5 1.3 Hz, H6), 4.68 (1H, d, CHHPh) 4.68 (1H,
0.5H), 4.31 (d, J 11.3 Hz, 1H), 4.27 (d, J 11.9 Hz, 1.1H), 4.09 d, CHHPh), 4.60 (1H, dq, J3,4 9.2 Hz, H3), 4.14 (1H, s, H5), 3.56
(dd, J 7.9 Hz, J 4.0 Hz, 0.3H), 4.04 (dd, J 7.7 Hz, J 4.9 Hz, 0.9H), (1H, dd, J4,5 1.4 Hz H4), 2.78 (1H, ddq, J7a,7b 14.6 Hz, J7a,1
3.77 (dd, J 6.0 Hz, J 3.3 Hz, 1H), 3.69 (dd, J 6.8 Hz, J 2.8 Hz, 2.9 Hz, H7a), 2.05 (1H, dddd, J7b,1 8.8 Hz, J7b,1 3.5 Hz, H7b),
0.3H), 3.62–3.58 (m, 0.2H), 3.56 (dd, J 6.0 Hz, J 4.9 Hz, 1H), 1.99 (3H, s, CH3). 13C-NMR (100 MHz, CDCl3): δC 170.4 (CvO),
2.39 (t, J 6.7 Hz, 0.9H), 2.34 (t, J 7.0 Hz, 0.4H), 1.89 (s, 1.1H), 139.0 (Ar), 138.9 (Ar), 134.5 (CHvCH), 128.4 (Ar), 128.4 (Ar),
1.89 (s, 2.7H). Major isomer: 13C-NMR (100 MHz, CDCl3): 128.3 (Ar), 128.0 (Ar), 127.9 (Ar), 127.7 (Ar), 127.6 (Ar),
δC 170.1 (CvO), 138.6 (Ar), 138,5 (Ar), 138.4 (Ar), 136.0 124.1 (CHvCH), 83.1 (C4), 80.1 (C5), 77.1 (C3), 74.7 (CH2Ph),
(CH2vCH), 134.6 (CH2vCH), 119.0 (CH2vCH), 117.4 73.7 (CH2Ph), 73.4 (CH2Ph), 73.2 (C6), 26.9 (C7), 21.4
(CH2vCH), 81.9, 81.1, 79.6, 74.5 (CH2Ph), 73.5 (CH2Ph), 73.0, (CH3). HRMS (ESI): calcd for C30H32O5Na 495.2142; found
70.6 (CH2Ph), 34.6 (C3), 21.2 (CH3). Minor isomer: 13C-NMR 495.2143.
(100 MHz, CDCl3): δC 170.7 (CvO), 138.5 (Ar), 138.4 (Ar), 138.3
(3R,4S,5R,6R)-3,4,5-Tri-O-benzyl-6-hydroxy-cycloheptene (29).
(Ar), 136.3 (CH2vCH), 134.0 (CH2vCH), 119.1 (CH2vCH), Sodium (70.2 mg, 2.96 mmol, 1 eq.) was dissolved in
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anhydrous methanol (10 mL). The sodium methoxide solution p-methoxybenzyl-cycloheptane-1-ol (36). The alkene (34) (1.33 g,
(10 mL) was added to the acetylated compound (27) (1.36 g, 2.42 mmol, 1 eq.) was dissovled in anhydrous THF (50 mL)
2.88 mmol) under an atmosphere of nitrogen. The reaction under an atmosphere of nitrogen. The stirred reaction mixture
mixture was stirred overnight at room temperature. The was cooled to 0 °C and then BH3·THF (1 M in THF, 7.3 mL,
mixture was concentrated under reduced pressure, diluted 7.3 mmol, 3 eq.) was added drop wise. The reaction was left at
with dichloromethane and washed with water, dried with 0 °C for 2 hours 30 min, then 35% H2O2 (11 mL) and 2 M
MgSO4, filtered and concentrated. The deacetylated crude NaOH (6.6 mL) were added drop wise at 0 °C and the mixture
product (29) (1.22 g) was used without further purification.
was stirred at room temperature overnight. The mixture was
Rf (diethyl ether/chloroform 1 : 40) 0.23; 1H-NMR (400 MHz, then diluted with diethyl ether (50 mL) and washed with water
CDCl3): δH 7.39–7.27 (15H, m, ArH), 5.87–5.75 (2H, m, and brine, dried over MgSO4, filtered and concentrated. The
CHvCH), 4.92 (1H, d, J 11.9 Hz, CHHPh), 4.84 (1H, d, J 11.9 crude product was purified by flash column chromatography
Hz, CHHPh), 4.78 (1H, d, CHHPh), 4.73 (1H, d, CHHPh), 4.65 (ethyl acetate/pentane 1 : 3 → 1 : 1) to yield the two regio-
(1H, d, J 11.8 Hz, CHHPh), 4.58 (1H, d, CHHPh), 4.42 (1H, dd, isomeres 35 and 36 (1.07 g, 78%) as a 1 : 2.1 mixture which
J3,4 8.0 Hz, J3,2 3.7 Hz, H3), 4.04 (1H, t, J5,4 = J5,6 1.8 Hz, H5), were partly separated.
3.86 (1H, ddt, J6,OH 9.6 Hz, J6,7b 7.2 Hz, J6,5 2.4 Hz, H6), 3.80
(3R,4S,5R,6R)-3,4,5-Tri-O-benzyl-6-O-p-methoxybenzyl-cyclohep-
(1H, dd, H4), 2.89 (1H, d, JOH,6 9.7 Hz, OH), 2.64–2.55 (1H, m, tane-1-ol (35). Colourless oil (61.4 mg, 4%); Rf (ethyl acetate/
H7a), 2.19 (1H, ddd, J7b,7a 14.3 Hz, J7b,1 2.6 Hz, H7b). 13C-NMR pentane 1 : 3) 0.24; 1H-NMR (400 MHz, CDCl3): δH 7.48–7.26
(100 MHz, CDCl3): δC 139.0 (Ar), 138.7 (Ar), 138.7 (Ar), 132.8 (15H, m, ArH), 7.26–7.20 (2H, m, ArH from PMB), 6.92–6.86
(CHvCH), 128.5 (Ar), 128.5 (CHvCH), 128.4 (Ar), 128.2 (Ar), (2H, m, ArH from PMB), 4.87 (1H, d, J 12.2 Hz, CHHPh), 4.82
128.0 (Ar), 127.8 (Ar), 127.8 (Ar), 127.7 (Ar), 127.7 (Ar), 127.6 (d, CHHPh), 4.69 (d, J 11.4 Hz, CHHPh), 4.64 (d, CHHPh), 4.60
(Ar), 81.9 (C4, C5), 75.1 (C3), 74.2 (CH2Ph), 73.6 (CH2Ph), 72.2 (d, J 11.8 Hz, CHHPh), 4.52 (d, CHHPh), 4.42 (d, J 11.6 Hz,
(CH2Ph), 70.8 (C6), 31.3 (C7). HRMS (ESI): calcd for CHHPh), 4.36 (d, CHHPh), 4.29 (1H, m, H1), 4.14 (1H, bs, H4/
C28H30O4Na 453.2036; found 453.2040.
H5), 3.99–3.91 (1H, m, H3/H6), 3.81 (3H, s, CH3), 3.74 (1H, dd,
(3R,4S,5R,6R)-3,4,5-Tri-O-benzyl-6-O-p-methoxybenzyl-cyclohep- J 10.8 Hz, J 5.5 Hz, H3/H6), 3.70 (dd, J 6.9 Hz, J 1.1 Hz, H4/H5),
tene (34). The crude alcohol (29) (2.88 mmol) was dissolved in 2.54 (1H, bs, OH), 2.29 (1H, dd, J 14.7 Hz, J 4.3 Hz, H2/H7),
anhydrous DMF (20 mL) under an atmosphere of nitrogen and 2.21–2.07 (2H, m, H2/H7), 2.03–1.95 (1H, m, H2/H7). 13C-NMR
cooled to 0 °C. Sodium hydride (234 mg, 5.74 mmol, 2 eq.) (100 MHz, CDCl3): δC 159.2 (Ar from PMB), 139.2 (Ar), 138.7
and p-methoxybenzyl chloride (0.77 mL, 5.71 mmol, 2 eq.) (Ar), 138.6 (Ar), 130.7 (Ar), 129.3 (Ar), 128.5 (Ar), 128.4 (Ar),
were added to the reaction mixture which was heated to room 128.2 (Ar), 127.9 (Ar), 127.8 (Ar), 127.7 (Ar), 127.7 (Ar), 127.6
temperature. The mixture was stirred for 4 h 30 min and was (Ar), 127.3 (Ar), 113.9 (Ar PMB), 85.5 (C4/C5), 81.5 (C4/C5), 79.5
quenched by addition of n-butylamine (5 mL), diluted with (C1), 77.0 (CH2Ph), 73.4 (CH2Ph), 72.7 (CH2Ph), 72.6 (CH2Ph),
ethyl acetate, washed with 1 M aq. HCl and sat. aq. NaHCO3, 71.0 (C3/C6), 66.7 (C3/C6), 55.4 (OCH3), 37.3 (C2/C7), 36.1
dried over MgSO4, filtered and concentrated under reduced (C2/C7). HRMS (ESI): calcd for C36H40O6Na 591.2717; found
pressure. The crude product was purified by flash column 591.2724.
chromatography (ethyl acetate/pentane 1 : 25 → 1 : 15) yielding
the PMB-ether (34) (1.33 g, 84% over 2 steps) as a clear oil.
(2R,3S,4R,5R)-2,3,4-Tri-O-benzyl-5-O-p-methoxybenzyl-cyclohep-
tane-1-ol (36). Colourless oil (0.181 g, 13%); Rf (ethyl acetate :
Rf (ethyl acetate/pentane 1 : 12) 0.28; [α]2D98K +7.6 (c 1.0, pentane 1 : 5) 0.28; 1H-NMR (400 MHz, CDCl3): δH 7.45–7.24
CHCl3); 1H-NMR (400 MHz, CDCl3): δH 7.35–7.15 (15H, m, (15H, m, ArH), 7.16 (2H, d, J 8.6 Hz, ArH from PMB), 6.88–6.82
ArH), 7.09 (2H, d, J 8.6 Hz, ArH from PMB), 6.77 (2H, d, J 8.6 (2H, m, ArH from PMB), 4.90 (1H, d, J 11.8 Hz, CHHPh), 4.86
Hz, ArH from PMB), 5.60 (1H, dt, J 12.5 Hz, J 2.5 Hz, H2), 5.50 (1H, d, CHHPh), 4.69 (2H, s, CH2Ph), 4.57 (1H, d, J 11.8 Hz,
(1H, m, H1), 4.81 (2H, s, CH2Ph), 4.72 (1H, d, J 11.9 Hz, CHHPh), 4.46 (1H, d, CHHPh), 4.34 (1H, d, JOH,1 10.1 Hz, OH),
CHHPh) 4.68 (1H, d, J 11.6 Hz, CHHPh), 4.59 (1H, d, CHHPh), 4.32 (1H, d, J 11.7 Hz, CHHPh), 4.26 (1H, d, CHHPh), 4.11 (1H,
4.53–4.46 (2H, m, H3, CHHPh), 4.30 (1H, d, J 11.7 Hz, s, H2), 3.89 (1H, ddd, J1,7a 7.2 Hz, J1,7b 2.8 Hz, H1), 3.83 (1H,
CHHPh), 4.26 (1H, d, CHHPh), 4.08 (1H, s, H5), 3.71 (3H, s, dd, J4,3 7.3 Hz, J4,5 2.4 Hz, H4), 3.75 (3H, s, CH3), 3.42 (1H, d,
CH3), 3.29 (1H, dd, J 9.3 Hz, J 1.0 Hz, H4), 3.21 (1H, dd, H3), 3.27 (1H, dd, J5,6a 11.2 Hz, J5,6b 5.0 Hz, H5), 2.04 (1H,
J 10.7 Hz, J 3.2, H6), 2.67–2.57 (1H, m, H7a), 2.07 (1H, ddd, dtd, J6a,6b 14.3 Hz, J6a,5 = J6a,7b 11.8 Hz, J6a,7a 3.0 Hz, H6a),
J 15.1 Hz, J 8.6 Hz, J 2.9 Hz, H7b). 13C-NMR (100 MHz, CDCl3): 1.93 (1H, dtd, J7a,7b 14.5 Hz, J7a,1 = J7a,6b 7.1 Hz, H7a),
δC 159.3 (Ar from PMB), 139.5 (Ar), 139.1 (Ar), 139.0 (Ar), 133.4 1.86–1.73 (1H, m, H6b), 1.61 (1H, ddd, H7b). 13C-NMR
(C2), 130.6 (Ar), 129.2 (Ar), 128.5 (Ar), 128.4 (Ar), 128.4 (Ar), (100 MHz, CDCl3): δC 159.2 (Ar from PMB), 138.5 (Ar), 138.4
128.2 (Ar), 127.9 (Ar), 127.9 (Ar), 127.9 (Ar), 127.6 (Ar), 127.5 (Ar), 137.7 (Ar), 130.4 (Ar), 129.1 (Ar), 129.0 (Ar), 128.4 (Ar),
(Ar), 127.3 (Ar), 125.0 (C1), 113.9 (Ar from PMB), 83.3 (C4), 80.1 128.4 (Ar), 128.2 (Ar), 127.9 (Ar), 127.8 (Ar), 127.8 (Ar), 127.7
(C5), 78.5 (C6), 74.2 (C3), 73.6 (CH2Ph), 73.4 (CH2Ph), 70.5 (Ar), 127.6 (Ar), 113.8 (Ar from PMB), 87.5 (C4), 84.4 (C3),
(CH2Ph), 55.4 (CH3), 27.7 (C7). HRMS (ESI): calcd for 80.1 (C2), 79.8 (C5), 73.8 (CH2Ph), 73.3 (CH2Ph), 73.0
C36H38O5Na 573.2611; found 573.2613.
(CH2Ph), 70.5 (CH2Ph), 68.8 (C1), 55.2 (CH3) 25.8 (C7), 22.3
(3R,4S,5R,6R)-3,4,5-Tri-O-benzyl-6-O-p-methoxybenzyl-cyclo- (C6). HRMS (ESI): calcd for C36H40O6Na 591.2717; found
heptane-1-ol (35) and (2R,3S,4R,5R)-2,3,4-tri-O-benzyl-5-O- 591.2720.
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(2S,3R,4R,5R)-2,3,4-Tri-O-benzyl-5-p-methoxybenzyl-cyclohepta-
The crude epoxide (39) (1.65 mmol) was dissolved in
none (37). The alcohol (36) (177 mg, 0.311 mmol) was dis- anhydrous DMSO (33 mL) and tetra-butylammonium azide
solved in dichloromethane (9.4 mL) and stirred at room (2.23 g, 7.9 mmol, 4.8 eq.) was added. The reaction was stirred
temperature. Freshly prepared Dess–Martin periodinane at 50 °C under an atmosphere of nitrogen. After 312 h the reac-
(269 mg 0.634 mmol, 2 eq.) was added and after 20 min the tion was quenched by addition of water and diluted with
reaction was quenched by addition of Na2S2O3(aq) and ethyl acetate. The organic phase was washed with water,
sat. aq. NaHCO3, stirred for 10 min and then extracted with dried over MgSO4, filtered and concentrated to give the crude
dichloromethane, dried over MgSO4, filtered and con- aldehyde (40).
centrated under reduced pressure. The crude product was
Rf (ethyl acetate/pentane 1 : 7) 0.34; HRMS (ESI): calcd for
purified by flash column chromatography (ethyl acetate/ C37H39N3O6Na 644.2731; found 644.2727.
pentane 1 : 10) yielding the product (37) (0.152 g, 87%) as a
colourless oil.
The crude aldehyde (40) (1.65 mmol) was dissolved in anhy-
drous methanol (40 mL) and stirred under an atmosphere of
Rf (ethyl acetate/pentane 1 : 6) 0.48; [α]2D98K +0.6 (c 1.0, nitrogen at 0 °C. The mixture was added NaBH4 (555 mg,
CHCl3); 1H-NMR (400 MHz, CDCl3): δH 7.40–7.29 (15H, m, 15.0 mmol, 9.1 eq.) and stirred for 1 h 15 min before it was
ArH), 7.18 (2H, d, J 8.6 Hz, ArH from PMB), 6.88 (2H, d, quenched by addtion of water and diluted with dichloro-
J 8.6 Hz, ArH from PMB), 4.84 (2H, s, CH2Ph), 4.68 (1H, d, methane. The mixture was extracted with dichloromethane,
J 12.0 Hz, CHHPh), 4.63 (1H, d, J 11.4 Hz, CHHPh), 4.58 (1H, dried over MgSO4, filtered and concentrated under reduced
d, CHHPh), 4.54 (1H, d, CHHPh), 4.34 (2H, s, CH2Ph), 4.12 pressure to give the crude alcohol (41) (0.873 g).
(1H, s, H4), 4.09 (1H, d, J 7.2 Hz, H2), 3.82 (3H, s, CH3), 3.69
Rf (ethyl acetate : pentane 1 : 6) 0.23; 1H-NMR (400 MHz,
(1H, d, J3,2 7.3 Hz, H3), 3.47 (1H, dd, J5,6 10.6 Hz, J5,6 5.0 Hz, CDCl3): δH 7.38 (1H, d, J 6.8 Hz, ArH), 7.28–7.18 (14H, m, ArH),
H5), 2.55 (td, J7a,7b = J7a,6a 11.8, J7a,6b 4.2 Hz, H7a), 2.47 (1H, 7.12 (2H, d, J 8.6 Hz, ArH from PMB), 6.79 (2H, d, J 8.6 Hz, ArH
ddd, J7b,6b 6.9 Hz, J7b,6a 3.8 Hz, H7b), 2.13 (1H, ddd, J6a,6b 14.4 from PMB), 4.91–4.79 (3H, m, CH2Ar), 4.65 (1H, d, J 12.0 Hz,
Hz, H6a), 2.09–1.98 (1H, d, H6b). 13C-NMR (100 MHz, CDCl3): CHHAr), 4.58 (1H, d, J 10.2 Hz, CHHAr), 4.47 (1H, d, CHHAr),
δC 206.0 (C1), 159.3 (Ar from PMB), 138.6 (Ar), 138.3 (Ar), 137.7 4.37–4.24 (3H, m), 4.05 (1H, s, J 14.0 Hz), 3.74 (3H, s, CH3),
(Ar), 130.2 (Ar), 129.2 (Ar), 128.4 (Ar), 128.2 (Ar), 128.1 (Ar), 3.71 (1H, d, J 5.2 Hz), 3.57 (1H, d, J 11.6 Hz), 3.40 (1H, d,
127.9 (Ar), 127.8 (Ar), 127.7 (Ar), 127.4 (Ar), 113.9 (Ar from J 9.2 Hz), 3.15 (1H, ddd, J 10.5 Hz, J 4.2 Hz, J 2.7 Hz), 1.95–1.65
PMB), 86.3 (C2), 82.6 (C3), 79.8 (C5), 79.5 (C4), 73.1 (CH2Ph), (4H, m), 1.26 (1H, ddd, J 15.3 Hz, J 9.3 Hz, J 2.2 Hz),
73.1 (CH2Ph), 72.7 (CH2Ph), 70.8 (CH2Ph), 55.3 (CH3), 35.5 0 0.84–0.72 (1H, m). HRMS (ESI): calcd for C37H41N3O6NH4
(C7), 26.8 (C6). HRMS (ESI): calcd for C28H32O6NH4 589.2561; 641.3334; found 641.3334.
found 589.2565.
The crude alcohol (41) (1.65 mmol) was dissolved in anhy-
(1R,2R,3S,4R,5R)-1-Azido-2,3,4-tri-O-benzyl-1-(benzyloxy)methyl- drous DMF and cooled to 0 °C. Sodium hydride (2.8 mmol,
5-p-methoxybenzyl-cycloheptane (42) and (1S,2R,3S,4R,5R)-1- 1.7 eq.) was slowly added under a nitrogen atmosphere. Benzyl
azido-2,3,4-tri-O-benzyl-1-(benzyloxy)methyl-5-p-methoxybenzyl- bromide (0.25 mL, 2.1 mmol, 1.3 eq.) was then slowly added
cycloheptane (43). Anhydrous dichloromethane (1.02 mL, and the mixture stirred overnight. The reaction was quenched
15.9 mmol, 9.6 eq.) was slowly added to a solution of freshly with methanol and concentrated under reduced pressure. The
prepared LDA (∼0.37 M in THF, 8.6 mL, 3.18 mmol, 1.9 eq.) at residue was redissolved in diethyl ether and washed with
−78 °C under nitrogen atmosphere. The mixture was stirred water. The combined aqueous phases were extracted with
for 10 min and then a solution of the ketone (37) (936 mg, ether and the combined organic phases washed with brine,
1.65 mmol) in THF (7.8 mL) was added. After 50 min at dried over MgSO4, filtered and concentrated under reduced
−78 °C the reaction was removed from cooling, quenched with pressure. The crude product was purified by flash column
sat. aq. NH4Cl and diluted with ethyl acetate. The mixture chromatography (20 : 1 → 10 : 1 pentane : ethyl acetate) to give
was washed with water and brine, dried over MgSO4, filtered an approximately 1 : 1.7 mixture of epimers (42 and 43), which
and concentrated under reduced pressure to give the crude was partly separated (444 mg, 38% over 5 steps).
alcohol (38).
Rf (ethyl acetate/pentane 1 : 10) 0.23; HRMS (ESI): calcd. for 5-p-methoxybenzyl-cycloheptane (42). (154 mg, 13%), Rf
C37H40O6Cl2Na 673.2094; found 673.2099.
(pentane/ethyl acetate 4 : 1) 0.5; 1H-NMR (400 MHz, CDCl3):
(1R,2R,3S,4R,5R)-1-Azido-2,3,4-tri-O-benzyl-1-(benzyloxy)methyl-
The crude alcohol (38) (1.65 mmol) was dissolved in an- δH 7.41 (d, J 7.1 Hz, 2H, ArH), 7.37–7.09 (m, 20H, ArH), 6.83 (d,
hydrous DMSO (11 mL) and stirred at room temperature under J 8.5 Hz, 2H, ArH), 4.87 (d, J 8.6 Hz, 1H, CHHAr) 4.86 (s, 2H,
nitrogen atmosphere. DBU (0.40 mL, 2.69 mmol, 1.6 eq.) was CH2Ar), 4.69 (d, J 10.8 Hz, 1H, CHHAr), 4.66 (d, J 12.2 Hz, 1H,
added and the reaction stirred until TLC analysis showed full CHHAr), 4.58 (d, J 12.0 Hz, 1H, CHHAr), 4.42 (d, J 12.1 Hz, 1H,
consumption of starting material. The reaction was then CHHAr), 4.41 (d, J 11.9 Hz, 1H, CHHAr) 4.32 (d, J 11.8 Hz, 1H,
quenched by addition of water and diluted with ethyl acetate. CHHAr), 4.26 (d, J 11.7 Hz, 1H, CHHAr), 4.15 (d, J2,3 9.1 Hz,
The organic phase was washed with water, dried over MgSO4, 1H, H2), 4.04 (s, 1H, H4), 3.74 (s, 3H, CH3), 3.70 (d, J8a,8b 10.1
filtered and concentrated under reduced pressure to give the Hz, 1H, H8a), 3.66 (d, 1H, H8b), 3.51 (d, J2,3 9.1 Hz, 1H, H3),
crude epoxide (39).
3.24 (bt, J 6.8 Hz, 1H, H5), 2.13–1.97 (m, 1H, H7a), 1.97–1.69
(m, 3H, H6, H7b). 13C-NMR (100 MHz, CDCl3): δC 159.2 (Ar
Rf (ethyl acetate/pentane 1 : 4) 0.25.
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from PMB), 139.2 (Ar), 138.8 (Ar), 138.7 (Ar), 137.9 (Ar), 130.6 periodinane (146 mg, 0.345 mmol, 1.6 eq.). Stirred for 50 min
(Ar), 129.1 (Ar), 128.5 (Ar), 128.4 (Ar), 128.3 (Ar), 128.2 (Ar), and then quenched with Na2S2O3 and sat. aq. NaHCO3. Stirred
128.2 (Ar), 128.2 (Ar), 128.1 (Ar), 128.0 (Ar), 127.9 (Ar), 127.8 for 10 min at r.t. and left at 4 °C for 2 weeks. The mixture was
(Ar), 127.8 (Ar), 127.7 (Ar), 127.6 (Ar), 127.6 (Ar), 127.5 (Ar), then extracted with dichloromethane, dried over MgSO4, fil-
127.4 (Ar), 113.8 (Ar form PMB), 82.1 (C2), 80.7 (C3), 79.4 (C4), tered and concentrated. The crude compound was purified by
79.3 (C5), 75.9 (CH2Ar), 74.2 (CH2Ar), 73.8 (CH2Ar), 73.7 flash column chromatography to give the ketone (44) (50.3 mg,
(CH2Ar), 71.6 (C8), 70.4 (CH2Ar), 68.8 (C1), 55.3 (CH3), 29.0 39% over 2 steps).
(C7), 24.1 (C6). HRMS (ESI): calcd for C44H47N3O6NH4
731.3803; found 731.3612.
Rf (pentane/ethyl acetate 8 : 1) 0.32; [α]2D98K +19.2 (c 1,
CHCl3); 1H-NMR (400 MHz, CDCl3): δH 7.37–7.13 (m, 18H,
(1S,2R,3S,4R,5R)-1-Azido-2,3,4-tri-O-benzyl-1-(benzyloxy)methyl-5- ArH), 7.05–6.96 (m, 2H, ArH), 4.76 (d, J 11.9 Hz, 1H, CHHAr),
p-methoxybenzyl-cycloheptane (43). (54.9 mg, 5%), Rf (pentane/ 4.67 (d, J 12.1 Hz, 1H, CHHAr), 4.67 (s, 1H, H2), 4.53 (d, 1H,
1
ethyl acetate 4 : 1) 0.8; H-NMR (400 MHz, CDCl3): δH 7.39 (d, CHHAr), 4.50 (d, 1H, CHHAr), 4.45 (d, J 11.9 Hz, 1H, CHHAr),
J 6.5 Hz, 1H, ArH), 7.36–7.12 (m, 20H, ArH), 6.83 (d, J 8.5, 1H, 4.43 (d, J 11.0 Hz, 1H, CHHAr), 4.38 (d, 1H, CHHAr), 4.27 (d,
ArH from PMB), 4.91 (d, J 11.4 Hz, 1H, CHHAr), 4.84 (s, 2H, 1H, CHHAr), 4.05 (d, J 5.0 Hz, 1H, H3/H4), 4.00 (d, J 5.1 Hz,
CH2Ar), 4.63 (d, 1H, CHHAr), 4.51 (d, J 11.2 Hz, 1H, CHHAr), 1H, H3/H4), 3.78 (d, J 9.1 Hz, 1H, H8a), 3.29 (d, J 9.1 Hz, 1H,
4.48 (d, 1H, CHHAr), 4.45 (s, 2H, CH2Ar), 4.34 (d, J 11.6 Hz, H8b), 2.74 (ddd, J6a,6b 19.3 Hz, J6a,7a 12.6 Hz, J6a,7b 3.2 Hz, 1H,
1H, CHHAr), 4.28 (d, 1H, CHHAr), 4.06 (s, 1H, H2), 3.82 (d, H7a), 2.21 (ddd, J6b,7b 5.5 Hz, J6b,7a 2.7 Hz, 1H, H7b), 1.88
J3,4 8.9 Hz, 1H, H4), 3.77 (s, 3H, CH3), 3.66–3.56 (m, 4H, H5 + (ddd, J7a,7b 15.2 Hz, 1H, H6a), 1.27 (bd, 1H, H6b). 13C-NMR
H3 + H8), 2.24–2.14 (m, 1H, H7a), 2.06–1.86 (m, 2H, H6a, (100 MHz, CDCl3): δC 207.2 (CvO), 137.9 (Ar), 137.9 (Ar), 137.7
H7b), 1.82–1.70 (m, 1H, H6b). 13C-NMR (100 MHz, CDCl3): (Ar), 137.6 (Ar), 128.6 (Ar), 128.5 (Ar), 128.5 (Ar), 128.3 (Ar),
δC 159.2 (Ar from PMB), 139.3 (Ar), 138.7 (Ar), 138.6 (Ar), 137.9 128.3 (Ar), 128.1 (Ar), 127.9 (Ar), 127.9 (Ar), 127.8 (Ar), 127.8
(Ar), 130.8 (Ar), 129.3 (Ar), 129.1 (Ar), 128.5 (Ar), 128.4 (Ar), (Ar), 127.7 (Ar), 82.9 (C2), 79.2 (C3/C4), 76.4 (C8), 75.3 (C3/C4),
128.4 (Ar), 128.2 (Ar), 128.2 (Ar), 128.0 (Ar), 127.8 (Ar), 127.8 74.0 (CH2Ar), 73.6 (CH2Ar), 73.5 (CH2Ar), 72.3 (CH2Ar), 66.0
(Ar), 127.7 (Ar), 127.6 (Ar), 127.6 (Ar), 127.5 (Ar), 127.3 (Ar), (C5), 35.6 (C7), 23.9 (C6). HRMS (ESI): calcd for
113.9 (Ar from PMB), 83.5 (C5/C3), 82.2 (C4), 79.6 (C2), 78.2 C36H37N3O5NH4 609.3071; found 609.3078.
(C5/C3), 75.8 (CH2Ar), 73.9 (2C, C8, CH2Ar), 73.7 (CH2Ar), 73.5
(1S,2S,3S,4R,5R)-2,3,4-Tris(benzyloxy)-5-((benzyloxy)methyl)-8-
(CH2Ar), 70.8 (CH2Ar), 67.1 (C1), 55.4 (CH3), 28.1 (C7), 25.5 azabicyclo[3.2.1]octan-1-ol (45). The ketone (44) (50.3 mg,
(C6). HRMS (ESI): calcd for C44H47N3O6NH4 731.3803; found 85 μmol) was dissolved in methanol/ethyl acetate 1 : 1 (3 mL)
731.3611.
and added 3 drops of triethyl amine and 20% Pearlman’s cata-
(1R,2R,3S,4R,5R)-1-Azido-2,3,4-tri-O-benzyl-1-(benzyloxy)methyl-
lyst (11.8 mg, 16.8 μmol, 20%). The atmosphere was exchanged
cycloheptane (55). The PMB-ether (42) (154 mg, 0.216 mmol) for hydrogen and the reaction stirred for 5 h. The mixture was
was dissolved in dichloromethane (2.8 mL) and water then filtered through Celite® and concentrated under reduced
(0.12 mL) and DDQ (69 mg, 0.302 mmol, 1.4 eq.) was added. pressure, to give the crude product (45) (48.3 mg).
The reaction was stirred vigorously for 4 h and then quenched
Rf (pentane/ethylacetat 1 : 1 + 1% triethyl amine) 0.27;
with sat. aq. NaHCO3, diluted with dichloromethane and [α]2D98K −12 (c 1, CHCl3); 1H-NMR (400 MHz, CDCl3): δH
washed with brine. The organic phase was dried over MgSO4, 7.38–7.09 (m, 2H, ArH), 4.96 (d, J 11.9, 1H, CHHAr), 4.83 (d,
filtered and concentrated to give the crude alcohol (55) J 10.8 Hz, 1H, CHHAr), 4.81 (d, 1H, 11.7 CHHAr), 4.60 (d,
which was used directly in the next step without further J 11.6 Hz, 1H, CHHAr), 4.56 (d, J 11.7 Hz, 2H, 2 × CHHAr), 4.51
purification.
(d, J 11.9 Hz, 1H, CHHAr), 4.41 (d, 1H, CHHAr), 3.91 (d, J2,3 9.2
Rf (pentane/ethyl acetate 4 : 1) 0.32, 1H-NMR (400 MHz, Hz, 1H, H2), 3.79 (d, J3,4 3.7 Hz, 1H, H4), 3.74 (d, J6a,6b 8.9 Hz,
CDCl3): δH 7.89–7.78 (m, 2H, ArH), 7.40–7.17 (m, 19H, ArH), 1H, H6a), 3.62 (dd, 1H, H3), 3.27 (d, 1H, H6b), 1.83–1.72 (m,
7.08–6.94 (m, 2H, ArH), 4.93 (d, J 11.8 Hz, 1H), 4.82 (t, J 10.8 2H, H7a, H8a), 1.70–1.59 (m, 1H, H7b/H8b), 1.48–1.30 (m, 1H,
Hz, 2H), 4.71 (d, J 11.7 Hz, 1H), 4.68–4.52 (m, 7H), 4.24 (d, H7b/H8b). 13C-NMR (100 MHz, CDCl3): δC 139.2 (Ar), 138.9
J 8.0 Hz, 1H), 4.03–3.93 (m, 2H), 3.85 (s, 3H, CH3), 3.78 (d, J 9.8 (Ar), 138.5 (Ar), 138.3 (Ar), 128.6 (Ar), 128.5 (Ar), 128.4 (Ar),
Hz, 1H), 3.72–3.63 (m, 1H), 1.97–1.80 (m, 2H), 1.73 (dddd, 128.4 (Ar), 128.3 (Ar), 127.9 (Ar), 127.8 (Ar), 127.8 (Ar), 127.7
J 31.1 Hz, J 15.2 Hz, J 10.0 Hz, J 4.6 Hz, 2H). 13C-NMR (Ar), 127.7 (Ar), 127.5 (Ar), 91.2 (C1), 80.9 (C3), 79.9 (C2), 79.8
(100 MHz, CDCl3): δC 164.6, 138.4, 138.3, 138.2, 137.8, 134.4, (C4), 74.9 (CH2Ar), 74.7 (CH2Ar), 73.6 (CH2Ar), 73.4 (C6), 72.5
132.0, 129.9, 129.7, 129.0, 128.6, 128.5, 128.5, 128.4, 128.4, (CH2Ar), 63.3 (C5), 33.6 (C7/C8), 24.5 (C7/C8). HRMS (ESI):
128.4, 128.3, 128.3, 128.3, 128.2, 128.2, 128.1, 127.9, 127.9, calcd for C36H39NO5H 566.2901; found 566.2907.
127.9, 127.9, 127.8, 127.8, 127.8, 127.7, 127.7, 127.7, 127.6,
127.6, 127.6, 127.5, 114.3, 80.3, 79.6, 78.8, 75.2, 75.1, 74.2, 1,2,3,4-tetraol
73.7, 73.6, 73.2, 71.5, 68.5, 55.5, 27.4, 26.4. HRMS (ESI): calcd protected compound (45) (85 μmol) was dissolved in 1 : 1
for C36H39N3O5Na 616.2782; found 616.2785. methanol : ethyl acetate (3 mL) and added 20% Pearlmans
(1S,2S,3S,4R,5R)-5-(Hydroxymethyl)-8-azabicyclo[3.2.1]octane-
–
manno-nojiristegine (2). The crude benzyl
(2R,3S,4R,5R)-5-Azido-2,3,4-tri-O-benzyl-1-(benzyloxy)methyl- catalyst (12.1 mg, 17 μmol, 20%) and 1 drop of concentrated
cycloheptanone (44). The crude alcohol (55) (0.216 mmol) was hydrochloric acid. The mixture was bubbled through with
dissolved in dichloromethane (9 mL) and added Dess–Martin hydrogen and stirred under a hydrogen atmosphere. After 5 h
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the reaction was concentrated under reduced pressure, re- concentrated under reduced pressure. The crude product was
dissolved in methanol and filtered through Celite®. The fil- purified by flash column chromatography (ethyl acetate/
trate was concentrated under reduced pressure, dissolved in pentane 1 : 25 → 1 : 15) yielding the product (31) (20.9 mg,
water and filtered through a syringe filter (VWR 0.2 μM cellu- 45% over 2 steps) as a clear oil.
lose acetate) to give the product hydrochloric salt with no
further purification (2) (20.6 mg, quant.) as a yellow solid.
Rf (ethyl acetate/pentane 1 : 10) 0.41; [α]2D98K +4.0 (c 1.0,
CHCl3); 1H-NMR (400 MHz, CDCl3): δH 7.35–7.15 (20 H, m,
Rf (5% NH4OH in ethanol) 0.22; [α]2D98K −16.2 (c 1, H2O); ArH), 5.60 (1H, dt, J 12.5 Hz, J 2.5 Hz, H2), 5.54–5.47 (1H, m,
1H-NMR (400 MHz, D2O): δH 4.00 (d, J2,3 4.0 Hz, 1H, H2), 3.86 H1), 4.82 (2H, s, CH2Ph), 4.73 (1H, d, J 11.9 Hz, CHHPh), 4.68
(d, J4,3 9.2 Hz, 1H, H4), 3.84 (d, J6a,6b 12.5 Hz, 1H, H6a), 3.78 (1H, d, J 11.6 Hz, CHHPh), 4.60 (1H, d, CHHPh), 4.52 (1H,
(dd, 1H, H3), 3.69 (d, 1H, H6b), 2.25–2.08 (m, 2H, H7/H8), CHHPh) 4.54–4.46 (1H, m, H3), 4.37 (1H, d, J 12.1 Hz,
2.03–1.93 (m, 1H, H8/H7), 1.93–1.81 (m, 1H, H8/H7). 13C-NMR CHHPh), 4.32 (1H, d, CHHPh), 4.11 (1H, s, H5), 3.31 (1H, dd,
(100 MHz, D2O): δC 96.5 (C1), 75.4 (C2), 72.3 (C3), 71.8 (C4), J 9.3 Hz, J 1.0 Hz, H4), 3.23 (1H, dd, J 11.1 Hz, J 2.7 Hz, H6),
69.3 (C5), 63.2 (C6), 31.8 (C7/C8), 24.1 (C8/C7). HRMS (ESI): 2.73–2.53 (1H, m, H7a), 2.10 (1H, ddd, J 15.1 Hz, J 8.6 Hz, J 2.8
calcd for C8H15NO5H 206.1023; found 206.1024.
Hz, H7b). 13C-NMR (100 MHz, CDCl3): δC 139.5 (Ar), 139.1 (Ar),
(3R,4S,5R,6S)-3,4,5,6-Tetra-O-benzyl-cycloheptene
(30). The 139.1 (Ar), 138.7 (Ar), 133.6 (CHvCH), 128.5 (Ar), 128.4 (Ar),
alcohol (28) (50.2 mg, 0.116 mmol) was dissolved in anhydrous 128.4 (Ar), 128.2 (Ar), 127.9 (Ar), 127.9 (Ar), 127.7 (Ar), 127.6
DMF (4 mL) under a nitrogen atmosphere and stirred at 0 °C. (Ar), 127.5 (Ar), 127.3 (Ar), 124.9 (CHvCH), 83.4 (C4), 80.3
60% NaH in mineral oil (9.76 mg, 0.232 mmol, 2 eq.) was (C5), 79.0 (C6), 77.4 (CH2Ph) 74.3 (CH2Ph), 73.7 (C3), 73.4
slowly added and then BnBr (29.1 mg, 0.170 mmol, 1.5 eq.) (CH2Ph), 70.9 (CH2Ph), 27.6 (C7). HRMS (ESI): calcd for
was under the formation of hydrogen gas. The mixture was C35H36O4Na 543.2506; found 543.2506.
stirred overnight. The reaction was quenched by addtion of
(1R,2S,3R,4S)-1,2,3,4-Tetra-O-benzl-cycloheptane
(32). The
methanol (2 mL) and the mixture was then diluted with alkene (30) (25 mg, 48 μmol) was dissolved in anhydrous
diethyl ether and washed with water. The aqueous phase was methanol (0.5 mL) and stirred under a nitrogen atmosphere at
extracted with diethyl ether and the combined organic phases room temperature. Triethylamine (5 µL, 37 μmol, 0.77 eq.) and
were washed with brine, dried with MgSO4, filtered and con- a catalytic amount of Pearlman’s catalyst were added to the
centrated under reduced pressure. The crude product was puri- mixture. The atmosphere was exchanged for hydrogen gas and
fied by flash column chromatography (ethyl acetate/pentane the reaction was stirred for 1 h 30 min hours before exchan-
1 : 15) yielding the product (30) (28.1 mg, 47% over 2 steps) as ging the atmosphere to nitrogen and diluting with methanol.
a clear oil.
The mixture was then filtrated through cotton wool and
Rf (ethyl acetate/pentane 1 : 10) 0.41; [α]2D98K +7.8 (c 1.0, concentrated under reduced pressure. The crude product was
CHCl3); 1H-NMR (400 MHz, CDCl3): δH 7.28–7.17 (20H, m, purified by flash column chromatography (ethyl acetate/
ArH), 5.73 (1H, ddd, J1,2 11.7 Hz, J2,3 3.8 Hz, J 1.0 Hz, pentane 1 : 30) yielding the product (32) (15.2 mg, 61%) as a
CHvCH), 5.65–5.58 (1H, m, CHvCH), 4.73 (2H, d, J 11.9 Hz, colourless oil.
2 × CHHPh), 4.63 (1H, d, CHHPh), 4.61 (1H, d, CHHPh), 4.55
Rf (ethyl acetate/pentane 1 : 20) 0.35; 1H-NMR (400 MHz,
(2H, s, CH2Ph), 4.43 (1H, d, J 11.9 Hz, CHHPh), 4.38 (1H, d, CDCl3): δH 7.40–7.15 (10H, m, ArH), 4.72 (1H, d, J 12.0 Hz,
CHHPh), 4.42–4.32 (m, 1H, H3), 3.90 (2H, ddd, J4,3 9.8 Hz, J5,6 CHHPh), 4.67 (1H, d, CHHPh), 4.58 (d, J 11.8 Hz, CHHPh),
7.1 Hz, J4,5 1.8 Hz, H4, H5), 3.62 (1H, td, J6,7 2.8 Hz, 1H), 4.50 (1H, d, CHHPh), 4.09 (1H, d, J 6.4 Hz, H1/H2), 3.81 (1H,
2.50–2.37 (1H, m, H7a), 2.34–2.18 (1H, m, H7b). 13C-NMR dd, J 6.3 Hz, J 3.8 Hz, H1/H2), 1.99–1.90/1H, m, H5/H6/H7)
(100 MHz, CDCl3): δC 139.3 (Ar), 139.2 (Ar), 139.0 (Ar), 138.8 1.87–1.68 (2H, m, H5/H6/H7). 13C-NMR (100 MHz, CDCl3):
(Ar), 132.8 (Ar), 128.4 (Ar), 128.4 (Ar), 128.4 (Ar), 128.4 (Ar), δC 139.2 (Ar), 139.2 (Ar), 128.4 (Ar), 128.4 (Ar), 127.7 (Ar), 127.7
127.9 (Ar), 127.9 (Ar), 127.8 (Ar), 127.7 (Ar), 127.6 (Ar), 127.5 (Ar), 127.5 (Ar), 127.4 (Ar), 81.8 (C1/C2), 73.1 (CH2Ph), 71.5
(Ar), 127.5 (Ar), 126.3 (Ar), 81.7 (C4/C5), 79.7 (C4/C5), 77.8 (C6), (CH2Ph), 31.0 (C5/C6/C7), 17.4 (C5/C6/C7). HRMS (ESI): calcd
76.9 (CH2Ph), 73.9 (C3), 73.8 (CH2Ph), 72.3 (CH2Ph), 71.6 for C35H38O4Na 545.2662; found 545.2660.
(CH2Ph), 28.1 (C7). HRMS (ESI): calcd for C28H32O6NH4
543.2506; found 543.2506.
(3R,4S,5R,6R)-3,4,5,6-Tetra-O-benzyl-cycloheptene
(1R,2S,3R,4R)-1,2,3,4-Tetra-O-benzyl-cycloheptane
alkene (31) (20.9 mg, 40 μmol) was dissolved in anhydrous
(31). The methanol (0.5 mL) and stirred under a nitrogen atmosphere
(33). The
alcohol (29) (39.4 mg, 91.1 mmol) was dissolved in anhydrous at room temperature. Triethylamine (4 µL, 30 μmol, 0.77 eq.)
DMF (4 mL) under a nitrogen atmosphere and stirred at 0 °C. and a catalytic amount of Pearlman’s catalyst were added to
60% NaH in mineral oil (7.53 mg, 0.181 mmol, 2 eq.) was the mixture. The atmosphere was exchanged for hydrogen
slowly added and then BnBr (23.8 mg, 0.136 mmol, 1.5 eq.) gas and the reaction was stirred for 3 hours before exchan-
was added under formation of hydrogen gas. The mixture was ging the atmosphere to nitrogen and diluting with methanol.
stirred overnight. The reaction was quenched by addtion of The mixture was then filtrated through cotton wool and con-
methanol (2 mL) and the mixture was then diluted with centrated under reduced pressure. The crude product was
diethyl ether and washed with water. The aqueous phase was purified by flash column chromatography (ethyl acetate/
extracted with diethyl ether and the combined organic phases pentane 1 : 30) yielding the (33) (9.52 mg, 45%) as a colour-
were washed with brine, dried with MgSO4, filtered and less oil.
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Paper
Rf (ethyl acetate/pentane 1 : 20) 0.35. 1H-NMR (400 MHz,
CDCl3): δH 7.36–7.15 (20H, m, ArH), 4.79 (1H, d, J 12.3 Hz,
CHHPh), 4.75 (1H, d, J 12.3 Hz, CHHPh), 4.55 (1H, d, J 11.8
X. Chen, B. R. Taubenheim, L. S. Welch, D. M. Minning,
Y. S. Babu, W. P. Sheridan and S. Bavari, Nature, 2014, 508,
402–405.
Hz, CHHPh), 4.54 (1H, d, J 11.4 Hz, CHHPh) 4.48 (1H, d, J 11.4 14 K. Kondo, Bioorg. Med. Chem., 2001, 9, 1091–1095.
Hz, CHHPh), 4.46 (1H, d, J 11.8 Hz, CHHPh), 4.31 (2H, s, 15 H. Paulsen, Liebigs Ann. Chem., 1965, 683, 187–198.
CH2Ph), 4.05 (1H, s, C2/C3), 3.78–3.71 (1H, m, C2/C3), 3.39 16 S. Inouye, T. Tsuruoka, T. Ito and T. Niida, Tetrahedron,
(1H, dd, J 7.2 Hz, J 0.8 Hz, C1/C4), 3.30–3.24 (1H, m, C1/C4),
2.00–1.50 (6H, m, C5, C6, C7). 13C-NMR (100 MHz, CDCl3): 17 M. Yagi, K. Tatsuhiko, Y. Aoyagi and H. Murai, Nippon
δC 139.5 (Ar), 139.2 (Ar), 139.0 (Ar), 138.8 (Ar), 128.5 (Ar), 128.4 Nogei Kagaku Kaishi, 1967, 50, 571.
(Ar), 128.4 (Ar), 128.2 (Ar), 128.0 (Ar), 127.9 (Ar), 127.7 (Ar), 18 N. Ishida, K. Kumagai, T. Niida, T. Tsuroka and H. Yomoto,
127.6 (Ar), 127.6 (Ar), 127.5 (Ar), 127.3 (Ar), 85.3 (C1/C4), 82.5 J. Antibiot. Ser. A, 1967, 20, 66.
(C2/C3), 81.1 (C1/C4), 79.9 (C2/C3), 73.4 (CH2Ph), 73.0 19 T. Niwa, T. Tsuruoka, H. Goi, Y. Kodama, J. Itoh, S. Inouye,
1968, 24, 2125–2144.
(CH2Ph), 72.1 (CH2Ph), 71.0 (CH2Ph), 30.2 (C5/C6/C7), 29.8
(C5/C6/C7), 18.6 (C5/C6/C7). HRMS (ESI): calcd for C35H38O4H
523.2843; found 523.2843.
Y. Yamada, T. Niida, M. Nobe and Y. Ogawa, J. Antibiot.,
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20 T. M. Gloster, R. Madsen and G. J. Davies, ChemBioChem,
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21 H. Liu, X. Liang, H. Søhoel, A. Bülow and M. Bols, J. Am.
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22 T. S. Rasmussen and H. H. Jensen, Org. Biomol. Chem.,
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23 T. S. Rasmussen, H. Koldsø, S. Nakagawa, A. Kato,
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Acknowledgements
We are grateful for support from the graduate school of
science and technology, Aarhus University.
24 S. Salamone, L. L. Clement, A. H. Viuff, O. J. Andersen,
F. Jensen and H. H. Jensen, Org. Biomol. Chem., 2015, 13,
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