Crystal and molecular structure of methyl L-glycero-α-D-manno- heptopyranoside, and synthesis of 1→7 linked L-glycero-D-manno-heptobiose and its methyl α-glycoside

Article abstract of DOI:10.1016/j.carres.2011.05.033

Methyl L-glycero-α-D-manno-heptopyranoside was synthesized in good yield by a Fischer-type glycosylation of the heptopyranose with methanol in the presence of cation-exchange resin under reflux and microwave conditions, respectively. The compound crystallized from 2-propanol in an orthorhombic lattice of space group P21212 showing a comparatively porous structure with a 2-dimensional O-H···O hydrogen bond network. As model compounds for the side chain domains of the inner core structure of bacterial lipopolysaccharide, L-glycero-α-D-manno-heptopyranosyl-(1→7)-L- glycero-D-manno-heptopyranose and the corresponding disaccharide methyl α-glycoside were prepared. The former compound was generated via glycosylation of a benzyl 5,6-dideoxy-hept-5-enofuranoside intermediate followed by catalytic osmylation and deprotection. The latter disaccharide was efficiently synthesized in good yield by a straightforward coupling of an acetylated N-phenyltrifluoroacetimidate heptopyranosyl donor to a methyl 2,3,4,6-tetra-O-acetyl heptopyranoside acceptor derivative followed by Zemplen deacetylation.

Full text of DOI:10.1016/j.carres.2011.05.033

Carbohydrate Research 346 (2011) 1739–1746
Contents lists available at ScienceDirect
Carbohydrate Research
journal homepage: www.elsevier.com/locate/carres
Crystal and molecular structure of methyl L-glycero-
side, and synthesis of 1?7 linked L-glycero-D-manno-heptobiose
and its methyl -glycoside
a-D-manno-heptopyrano-
a
Daniel Artner a, Christian Stanetty a, Kurt Mereiter b, Alla Zamyatina a, Paul Kosma a,
⇑
a Department of Chemistry, University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
b Institute of Chemical Technologies and Analytics, Vienna University of Technology, Getreidemarkt 9, A-1060 Vienna, Austria
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 20 April 2011
Received in revised form 26 May 2011
Accepted 27 May 2011
Available online 21 June 2011
Methyl
L
-glycero-
a
-
D
-manno-heptopyranoside was synthesized in good yield by a Fischer-type glycosyl-
ation of the heptopyranose with methanol in the presence of cation-exchange resin under reflux and
microwave conditions, respectively. The compound crystallized from 2-propanol in an orthorhombic lat-
tice of space group P21212 showing a comparatively porous structure with a 2-dimensional O–Hꢀ ꢀ ꢀO
hydrogen bond network. As model compounds for the side chain domains of the inner core structure
of bacterial lipopolysaccharide,
pyranose and the corresponding disaccharide methyl
L
-glycero-
a
-
D
-manno-heptopyranosyl-(1?7)-
L-glycero-D-manno-hepto-
Dedicated to András Lipták at the occasion
of his 75th birthday
a-glycoside were prepared. The former compound
was generated via glycosylation of a benzyl 5,6-dideoxy-hept-5-enofuranoside intermediate followed by
catalytic osmylation and deprotection. The latter disaccharide was efficiently synthesized in good yield
by a straightforward coupling of an acetylated N-phenyltrifluoroacetimidate heptopyranosyl donor to a
methyl 2,3,4,6-tetra-O-acetyl heptopyranoside acceptor derivative followed by Zemplén deacetylation.
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
Glycoside
Lipopolysaccharide
Heptose
Crystal structure
Glycosyl donor
1. Introduction
2. Results and discussion
Heptoses of the
important carbohydrate constituents of the lipopolysaccharide
(LPS) of many Gram-negative bacteria. As an example, -heptose
is found in a common branched trisaccharide [ -Hepp-(1?7)]-
L
- and
D
-glycero-
D
-manno configuration are
2.1. Preparation of methyl glycosides of
heptose
L-glycero-D-manno-
L,D
L
-a-
D
Previously, the
tained by chain elongation at position 6 of methyl
ranoside or via reaction of related
L,D
-Hepp methyl
a
-glycoside 4 had been ob-
-mannopy-
-heptosyl thioglycoside,
L
-
a
-
D
-Hepp-(1?3)-
L
-
a
-
D
-Hepp linked to position 5 of the lipid A-
a-D
connected Kdo residue in the inner core region of LPS.1
L,D
The heptosyl domain contributes to fundamental binding inter-
actions of LPS with components of the innate and adaptive im-
mune system. Recently, lectins, such as the human lung
surfactant protein (SP-D) as well as the Burkholderia cenocepacia
BC2L-C lectin have been found to bind to heptoses either via the
side chain diol system or via the trans-diol part of the pyranose
ring.2,3 In order to generate simple model glycosides for crystallo-
graphic as well as STD-NMR and lectin binding studies we have set
out to develop a straightforward preparation of mono- and disac-
charide methyl heptopyranosides.
chloride as well as trichloroacetimidate donors with methanol.4
A central synthetic intermediate within the Brimacombe approach
toward heptoses may be considered as a protected precursor for
Fischer-type heptoside synthesis and could also serve as a suitable
glycosyl acceptor for the synthesis of (1?7)-linked heptobiosides.
Thus, benzyl (E)-5,6-dideoxy-2,3-O-isopropylidene-a-D-lyxo-hept-
5-enofuranoside 1 was converted via catalytic osmylation into
the triol derivative 2 according to the literature.5,6 While the re-
ported two-step procedure, comprising hydrogenolysis of the ano-
meric benzyl group followed by acidic cleavage of the
isopropylidene group with H2SO4, had been applied for the prepa-
ration of the reducing L-glycero-D-manno heptose 3, monitoring of
the hydrogenolysis reaction by thin layer chromatography (TLC)
revealed a major highly polar fraction which had lost the isopro-
pylidene group. Hence, a direct conversion of 2 into the methyl gly-
coside was envisaged. In a model study, reducing heptose 3 was
⇑
Corresponding author. Tel.: +43 1 47654 6055; fax: +43 1 47654 6059.
E-mail address: paul.kosma@boku.ac.at (P. Kosma).
0008-6215/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2011.05.033

1740
D. Artner et al. / Carbohydrate Research 346 (2011) 1739–1746
subjected to treatment with Dowex 50 H+ cation-exchange resin
and methanol at 60 °C, which in the course of several hours re-
vealed the formation of four less polar products by TLC. Eventually,
the composition of the mixture converged into a main component
and a minor byproduct in 81% combined yield. 1H NMR analysis of
the mixture identified the presence of methyl L-glycero-a-D-man-
no-heptopyranoside 4 as the main isomer (H-1: d 4.565) and the
corresponding b-isomer 6 (H-1: d 4.32) as the minor constituent
2.2. Preparation of
glycoside
a-(1?7)-linked heptobiose and its methyl a-
Previously, the
a-(1?7)-linked heptobiose has been synthe-
sized by employing a benzyl 2,3,5,6-tetra-O-benzyl heptofurano-
side acceptor.9 In addition, 7-silane derivatives as well as
7-O-allyl, 7-O-tBDPSi, and 7-O-tBDMSi heptopyranoside deriva-
tives have served as suitable heptosyl precursors.10–14 The allylic
alcohol derivative 1, however, may also be regarded as an
implicitly protected heptose glycosyl acceptor. Previously a 7-O-
(a to b ratio 7:1). Reaction of 3 under microwave irradiation at
100 °C for 25 min furnished a 10:1 mixture of 4 and 6 containing
4% of the anomeric methyl heptofuranosides (H-1: d 5.27 and d
5.10) in a combined yield of 94%.7
phosphate derivative of
D-glycero-D-manno-heptose has been
synthesized via phosphorylation of 1 followed by osmylation and
deprotection.15 Compound 1 was subjected to a glycosylation reac-
tion with the known16 trichloroacetimidate donor 8 promoted by
TMSO-triflate in dichloromethane. In order to avoid orthoester for-
mation, the promoter had to be added in larger proportions
(ꢁ0.3 equiv), leading to partially deacetylated products. Subse-
For ease of purification, the mixture was acetylated with pyri-
dine–acetic anhydride–4-N,N-dimethylaminopyridine (DMAP) to
furnish a separable mixture of the penta-O-acetyl derivatives 5
and 7 in 81% yield (Scheme 1). Following separation of the isomers,
Zemplén deacetylation of 5 afforded known8 methyl
L
-glycero-a-D-
manno-heptopyranoside 4 in 73% yield, whereas deacetylation of 7
quent reacetylation afforded the
in 50% isolated yield (Scheme 1).
Catalytic osmylation in the presence of NMO produced a
mixture of the diastereoisomeric diols in 97% yield, which was
resolved by repeated HPLC-separation to eventually furnish pure
a-(1?7)-linked disaccharide 9
gave methyl L-glycero-b-D-manno-heptopyranoside 6 in 91% yield,
respectively. 1H NMR and 13C NMR spectroscopic data as well as
the optical rotation values of 4 and 6 were in full agreement with
the assigned anomeric configuration.
Compound 4 could also be directly produced from intermediate
2 as follows. Hydrogenolysis of 2 was performed in methanol with
10% Pd–C at atmospheric pressure for 20 h at room temperature.
The catalyst was removed by filtration, cation-exchange resin
(H+) was then added and the filtrate was refluxed for 15 h. Filtra-
tion of the suspension and concentration furnished the anomeric
mixture of methyl glycosides in 84% yield, which crystallized from
hot 2-propanol to give compound 2 containing traces of b-isomer.
L-glycero-D-manno-isomer 10 in 46% yield. Deprotection of disac-
charide 10 was achieved by Zemplén deacetylation to afford 11
in 99% yield. Removal of the benzylic aglycon from 11 was accom-
plished by hydrogenolysis on 10% Pd/C which also led to partial
cleavage of the isopropylidene ketal to produce a 3:2 mixture of
the reducing heptobioses 12 and 13. Reductive removal of ketal
groups in the presence of Pd(OH)2 has previously been reported.17
Attempted acid-catalyzed hydrolysis of the isopropylidene group
OH
RO
RO
HO
HO
RO
RO
Ref. 6
b)
a)
OH
H
OH
+
OR
O
OH
O
O
O
OR
O
OBn
OBn
RO
RO
HO
HO
RO
RO
OMe
d)
H
OH
O
O
O
O
OMe
d)
OH
6 R = H
1
2
3
4 R = H
c)
c)
AcO
7 R = Ac
5 R = Ac
AcO
OAc
e)
+
O
AcO
AcO
CCl3
O
8
NH
AcO
AcO
RO
HO
HO
HO
OAc
O
RO
AcO
AcO
OR
HO
OH
O
OH
O
RO
RO
O
HO
HO
HO
HO
O
f)
g)
OBn
OH
O
O
+
9
OH
O
O
O
HO
O
OH
OH
H
OBn
O
H
HO
HO
OH
H
OH
O
O
O
O
10 R = Ac
11 R = H
O
13 R = H
O
12
OR
d)
14 R = Me
Scheme 1. Reagents and conditions: (a) H2, 10%Pd–C, MeOH, 20 h, rt; (b) MeOH, Dowex 50 H+, 60 °C, 12 h, 84% or MW, 100 °C, 25 min 94% for 4 and 6; (c) Ac2O, pyr., DMAP,
4 h, rt 81%; (d) 0.1 M NaOMe, MeOH, 3.5–5.5 h, rt, 73% for 4, 91% for 6, 99% for 11; (e) TMSOTf, CH2Cl2, molecular sieves 4 Å, 2 h, rt, then Ac2O, pyr, DMAP, 30 h, rt, 50% for 9; (f)
NMO, OsO4, CH2Cl2, 3.5 h rt; 95% (46% for isolated 10); (g) H2, 10%Pd–C, MeOH, 28 h, rt, 38% for 13.

D. Artner et al. / Carbohydrate Research 346 (2011) 1739–1746
1741
from 12 was tested under various conditions. Treatment of 12 with
10% aq TFA in CH2Cl2 or aq THF and 15% TFA in toluene consistently
resulted in concomitant hydrolysis of the interglycosidic linkage.
Treatment of 12 or 2 with Lewis acids did not lead to cleavage of
the acetonide (ZnCl2 in dichloromethane, FeCl3 in HOAc).18,19 The
isopropylidene group of 12 could also not be removed by micro-
wave treatment under aqueous conditions.20 Thus target com-
pound 13 was eventually isolated from the mixture obtained in
the hydrogenolysis step. Precipitation of 13 from a methanolic
solution containing the mixture of 12 and 13 with EtOAc followed
by purification on BioGel P-2 afforded 13 in 38% yield. 1H and 13C
NMR spectral data of 13 were in full agreement with published val-
A comparative experiment utilizing the trichloroacetimidate do-
nor 8 under analogous conditions led to a substantial amount of
6-linked disaccharide which was rather difficult to separate thus
leading to very low yields of isolated pure disaccharide 20. Small
amounts of (1?6) linked disaccharide were isolated by prepara-
tive HPLC to confirm its structure by 2D-NMR experiments.
Transesterification of 20 with sodium methoxide eventually
gave the known13 disaccharide glycoside 21 in 85% yield after final
purification on Bio-Gel P2.
2.3. Crystal structure of 4
ues of
L
-glycero-
a
-
D
-manno-heptopyranosyl-(1?7)-
L
-glycero-
a
-
D
-
Previously only the crystal structure of the b-anomeric hexa-O-
acetyl derivative of L-glycero-D-manno-heptose has been re-
manno-heptopyranose.21 The values of the heteronuclear coupling
constants were in agreement with the assigned anomeric configu-
ported.23 Compound 4 was crystallized from 2-propanol to give
prismatic crystals. Using this material, the crystal structure was
determined at T = 150 K as described in the experimental section.
A view of the molecular structure is shown in Figure 1. Selected
bond lengths and angles are given in Table 1. In the solid state, 4
adopts the usual chair conformation for the pyran ring with ring
bond lengths of 1.522–1.530 Å for C–C, and 1.408, and 1.438 Å
for C–O(5). The alternating positive and negative values of the ring
torsion angles vary between absolute values of 53.6° and 56.7°. The
methoxy oxygen O(1) and the hydroxyl oxygen O(2) are in axial
positions to the ring and mutually trans-configured, O(1)–C(1)–
C(2)–O(2) = 169.5°. The remaining ring substituents O(3), O(4),
and C(6) adopt equatorial positions. The dihydroxyethyl side chain
HO(6)–C(6)H–C(7)H2–O(7)H features an antiperiplanar conforma-
tion for the carbon chain moiety C(4)–C(5)–C(6)–C(7) (torsion an-
gle ꢂ169.3°) and the internal torsion angle O(6)–C(6)–C(7)–O(7) is
ꢂ64.2°. All five hydroxyl groups are involved in short intermolecu-
lar O–Hꢀ ꢀ ꢀO hydrogen bonds with Oꢀ ꢀ ꢀO distances of 2.658–2.789 Å
and O–Hꢀ ꢀ ꢀO angles between 149° and 175°. As visualized in
Figure 2, these hydrogen bonds link the heptose molecules into
double layers of molecules parallel to (0 0 1) with crystallographic
C2-symmetry perpendicular to (0 0 1). These double layers are cen-
tered at z ꢃ 0, 1, 2, etc., and are mutually held together only via Van
der Waals forces in the region of z ꢃ 1/2, 3/2, etc., where continu-
ous open channels parallel to the a-axis do exist. The channels,
which are centered at y,z = 0,0.56, ½,0.44, 1,0.56, etc., (Fig. 2), have
cross sections of ca. 1.5 Å too narrow to incorporate solvent mole-
cules, but they are responsible for a comparatively low X-ray den-
sity of the compound, 1.370 g cmꢂ3 at T = 297 K. This becomes
0
0
rations (JC-1 /H-1 174.2, JC-1/H-1
a
174.1, JC-1/H-1b 167.8 Hz).
-(1?7)-linked methyl heptobio-
Finally, the formation of the
a
sides 14 under conditions as described for the monosaccharide 4
was evaluated in a trial experiment. Thus treatment of 12 with
Dowex H+ resin in methanol at 50 °C for an extended period of
8 days indicated the presence of several components. Acetylation
of the mixture and flash chromatography afforded the correspond-
ing acetylated product amenable to NMR analysis. The 1H NMR
spectrum of the mixture revealed the peracetylated methyl a-hep-
tobioside as the main component (ꢁ50%). In conclusion, the recal-
citrant removal of the isopropylidene group at the disaccharide
stage disfavors the approach.
As second approach a straightforward strategy toward the
synthesis of methyl
a-disaccharide was then elaborated starting
from methyl glycoside 4, which was converted into the 7-O-
tertbutyldimethylsilyl ether derivative 15 by reaction with
tBDMSiCl/diazabicyclo[2.2.2]octane in MeCN in 86% yield
(Scheme 2). Subsequent acetylation with acetic anhydride–pyri-
dine–DMAP gave the tetra-O-acetyl derivative 16 (ꢁ98%). Re-
moval of the silyl group by the action of 2% HF in MeCN
afforded the glycosyl acceptor 17 which was immediately sub-
jected to the coupling reaction in order to prevent extensive
acetyl migration from the neighboring 6-position. As glycosyl
donors, the known21 trichloroacetimidate donor 8 and the novel
N-phenyltrifluoroacetimidate heptosyl donor 19 were employed.
The latter donor was obtained in near quantitative yield by the
reaction of hemiacetal 18 with N-phenyltrifluoroacetimidoyl
chloride/K2CO3 in acetone.22 The donor was isolated by silica
gel chromatography and was present as an anomeric mixture
clearly evident by comparison with the isochemical methyl
D-gly-
(a/b ratio 8:1). Glycosylation of 17 with donor 19 proceeded
cero-b- -gulo-heptopyranoside, C8H16O7, which crystallizes in the
D
at room temperature within 1.25 h and furnished the -(1?7)-
linked disaccharide 20, which was isolated in 51% yield
following extensive purification by column chromatography.
a
monoclinic space group P21 with a 3-dimensional hydrogen bond
network and has an X-ray density of 1.464 g cmꢂ3, by 6.8% larger
than for 4.24
R'O
RO
AcO
AcO
RO
a)
e)
OAc
O
4
OR
O
RO
OR
O
RO
RO
AcO
AcO
RO
RO
OR
OMe
O
18 R = H,
19 R = CF3C=NPh
15 R = H, R' = tBDMSi
16 R = Ac, R' = tBDMSi
b)
c)
d)
RO
OR
O
17
R = Ac, R'=H
RO
RO
OMe
20 R = Ac
21 R = H
f)
Scheme 2. Reagents and conditions: (a) MeCN, DABCO, tBDMSiCl, 20 h, rt 86% for 15; (b) Ac2O, pyr., DMAP, 3 h, rt ꢁquant.; (c) 2% HF, MeCN; (d) PhN = CCl(CF3), acetone,
K2CO3, 3 h, rt, ꢁquant. for 19; (e) TMSOTf, CH2Cl2, molecular sieves 4Å, 75 min, -10?0 °C, 65% (51% for isolated 20); (f) 0.1 M NaOMe, MeOH, 2 h, rt, 85% for 21.

1742
D. Artner et al. / Carbohydrate Research 346 (2011) 1739–1746
Table 1
Selected bond lengths and angles for 4
Bond lengths (Å)
C(1)–C(2)
C(2)–C(3)
C(3)–C(4)
C(4)–C(5)
C(5)–C(6)
C(6)–C(7)
C(1)–O(1)
C(1)–O(5)
C(2)–O(2)
C(3)–O(3)
C(4)–O(4)
C(5)–O(5)
C(6)–O(6)
C(7)–O(7)
C(8)–O(1)
1.523(2)
1.526(2)
1.522(2)
1.530(2)
1.526(2)
1.522(2)
1.410(2)
1.408(2)
1.419(2)
1.429(2)
1.427(2)
1.438(2)
1.429(2)
1.424(2)
1.421(2)
Bond angles (°)
C(5)–O(5)–C(1)
O(5)–C(1)–C(2)
C(1)–C(2)–C(3)
C(2)–C(3)–C(4)
C(3)–C(4)–C(5)
C(4)–C(5)–O(5)
O(1)–C(1)–O(5)
O(1)–C(1)–C(2)
O(2)–C(2)–C(1)
O(2)–C(2)–C(3)
O(3)–C(3)–C(2)
O(3)–C(3)–C(4)
O(4)–C(4)–C(3)
O(4)–C(4)–C(5)
C(6)–C(5)–C(4)
C(6)–C(5)–O(5)
C(5)–C(6)–C(7)
O(6)–C(6)–C(5)
O(6)–C(6)–C(7)
C(6)–C(7)–O(7)
C(1)–O(1)–C(8)
114.63(11)
111.80(12)
110.46(12)
110.30(12)
109.99(12)
111.47(11)
112.58(13)
106.58(13)
106.28(12)
111.82(12)
108.54(11)
110.59(13)
110.41(12)
106.66(11)
112.65(12)
105.48(11)
110.88(13)
109.72(12)
111.49(13)
112.99(15)
112.80(15)
Figure 1. Molecular structure of 4 showing 50% ellipsoids.
3. Experimental
3.1. General
Concentration of solutions was performed at reduced pressure
at temperatures <40 °C. Dichloromethane and dry pyridine were
dried by refluxing with CaH2 (5 g per L) for 16 h, then distilled
and stored under argon over molecular sieves 0.4 nm. Column
chromatography was performed on Silica Gel 60 (230–400 mesh,
Merck). Analytical TLC was performed using Silica Gel 60 F254
HPTLC plates with 2.5 cm concentration zone (Merck). Spots were
detected by treatment with anisaldehyde—H2SO4. Size-exclusion
chromatography was performed on Bio-GelÒ P-2 Gel, Extra fine
<45 lm (wet) from Bio-Rad Laboratories. Ion exchange treatment
Torsion angles (°)
was performed with Dowex 50 W X 8 resin, H+ form, 50–100 mesh.
Melting points were determined on a Kofler hot stage microscope
and are uncorrected. Optical rotations were measured with a Per-
kin–Elmer 243 B polarimeter. NMR spectra were recorded at
297 K in D2O, CD3OD, or CDCl3 with Bruker DPX 300, Avance II
400 and Avance III 600 spectrometers (1H at 300.13 MHz, 13C at
75.47 MHz or 1H at 400.13 MHz, 13C at 100.61 MHz, 1H at
600.13 MHz, 13C at 150.9 MHz), respectively, using standard Bru-
ker NMR software. 1H NMR spectra were referenced to tetrameth-
ylsilane (in CDCl3) or 2,2-dimethyl-2-silapentane-5-sulfonic acid
(in D2O). 13C NMR spectra were referenced to chloroform for solu-
tions in CDCl3 (d 77.00) or dioxane (d 67.40) for solutions in D2O.
HRMS analysis was carried out from H2O/MeCN solutions (concen-
tration 1 mg/L) using an HTC PAL system autosampler (CTC Analyt-
ics AG), an Agilent 1100/1200 HPLC with binary pumps, degasser,
and column thermostat (Agilent Technologies, Waldbronn, Ger-
many) and Agilent 6210 ESI-TOF mass spectrometer (Agilent Tech-
nologies, Palo Alto, US). The mass spectrometer was previously
tuned with Agilent tune mix and further reference masses were
added to the method to provide a mass accuracy below 2 ppm.
Data analysis was performed with Mass Hunter software (Agilent
Technologies). Elemental analyses were provided by Dr. J. Theiner,
Mikroanalytisches Laboratorium, Institut für Physikalische Chemie,
Universität Wien.
O(5)–C(1)–C(2)–C(3)
C(1)–C(2)–C(3)–C(4)
C(2)–C(3)–C(4)–C(5)
C(3)–C(4)–C(5)–O(5)
C(4)–C(5)–O(5)–C(1)
C(5)–O(5)–C(1)–C(2)
O(1)–C(1)–C(2)–O(2)
O(5)–C(1)–C(2)–O(2)
O(2)–C(2)–C(3)–O(3)
O(3)–C(3)–C(4)–O(4)
O(4)–C(4)–C(5)–O(5)
O(5)–C(5)–C(6)–O(6)
O(6)–C(6)–C(7)–O(7)
O(4)–C(4)–C(5)–C(6)
C(4)–C(5)–C(6)–C(7)
C(4)–C(5)–C(6)–O(6)
C(5)–C(6)–C(7)–O(7)
54.34(17)
ꢂ53.59(16)
53.58(16)
ꢂ54.14(15)
56.72(16)
ꢂ56.65(17)
169.45(12)
ꢂ67.14(16)
ꢂ56.74(16)
ꢂ68.91(15)
ꢂ173.88(11)
ꢂ54.70(15)
ꢂ64.23(16)
67.77(15)
ꢂ169.31(12)
67.11(16)
173.20(12)
Hydrogen bonds (Å) with symmetry codes of the acceptor atoms
O(2)?O(3) [ꢂx+1,ꢂy,z]
2.754(2)
O(3)?O(7) [x+1,y,z]
2.704(2)
2.658(2)
2.789(2)
2.746(2)
O(4)?O(6) [x+½,ꢂy+½,ꢂz]
O(6)?O(2) [ꢂx,ꢂy,z]
O(7)?O(4) [ꢂx,ꢂy+1,z]
(k = 0.71073 Å) and
x-scan frames covering a 3/4 sphere of the re-
ciprocal space. After data integration with program SAINT,25 the
structure was solved by direct methods and refined on F2 with
the program package SHELX97.26 All non-hydrogen atoms were re-
fined anisotropically. Hydrogen atoms were inserted in idealized
positions and were treated as riding using the AFIX 83 restraint
for OH hydrogen atoms.26 Crystal data are: C8H16O7, Mr = 224.21,
orthorhombic, space group P21212 (no. 18), T = 150 K,
3.2. X-ray crystallographic study
Compound 4 was crystallized from 2-propanol to give excellent
prismatic colorless crystals. X-ray data were collected with an
oval of 0.51 ꢄ 0.43 ꢄ 0.35 mm on a Bruker Smart APEX CCD
diffractometer using graphite-monochromated Mo-K
a radiation
a = 8.9740(3) Å, b = 9.9424(4) Å, c = 11.9632(4) Å,
a = b = c = 90°,

D. Artner et al. / Carbohydrate Research 346 (2011) 1739–1746
1743
complete conversion of the starting material to a main product
along with the presence of one by-product. Work-up as described
for method A afforded a mixture of 4 and 6 (76 mg, 81%) as syrup.
Method C: A suspension of 3 (20 mg, 0.095 mmol) and DOWEX
H+ resin (ꢁ200 mg) in dry methanol (2 mL) was stirred in the
MW-oven at 100 °C for 25 min. After this time, TLC (3:7:0.5
MeOH–CHCl3–H2O) indicated almost complete conversion of the
starting material to a main product along with the presence of
two minor by-products and no further progress toward target com-
pound within the last 5 min. Work-up as described for method A
afforded a 10:1 mixture of 4 and 6 (21 mg, 94%) as a white solid.
3.4. Acetylation of the anomeric heptopyranosides
A solution of 4 and 6 (76 mg) and a catalytic amount of DMAP in
dry pyridine (5 mL) was stirred with Ac2O (0.5 mL) for 4 h at room
temperature. Methanol (0.1 mL) was added and the solution was
coevaporated with toluene (3 ꢄ 20 mL) and concentrated. Purifica-
tion of the residue by column chromatography (3:2 toluene/EtOAc)
afforded 5 as the major component (103 mg, 70%) followed by a
fraction containing mainly compound 7 (8.5 mg, 6%) and pure
compound 7 (7.5 mg, 5%). Data for 5: colorless syrup, ½a D20
ꢅ
+10 (c
0.75, CHCl3); lit.14: ½a D20
ꢅ
+22 (c 1.0, CHCl3). 1H NMR (400 MHz,
CDCl3): d = 5.33–5.24 (m, 4H, H-2, H-3, H-4, H-6), 4.745 (d, 1H,
J1,2 1.6 Hz, H-1), 4.31 (dd, 1H, J7a,6 5.8, J7a,7b 11.2 Hz, H-7a), 4.24
(dd, 1H, J6,7b 7.5 Hz, H-7b), 4.07–4.04 (m, 1H, H-5), 3.39 (s, 3H,
OMe), 2.17 (s, 3H), 2.14 (s, 3H), 2.05 (s, 3H), 2.01 (s, 3H) and 1.98
(s, 3H, 5 ꢄ Ac). Data for 7: colorless syrup, ½a D20
ꢂ75 (c 0.75, CHCl3).
ꢅ
1H NMR (400 MHz, CDCl3): d = 5.51 (dd, 1H, J1,2 1.1, J3,2 3.4 Hz, H-2),
5.31 (app. t, 1H, J3,4 10.2, J4,5 10.1 Hz, H-4), 5.31 (ddd, 1H, H-6), 5.06
(dd, 1H, H-3), 4.55 (d, 1H, H-1), 4.49 (dd, 1H, J7a,6 5.4, J7a,7b 11.4 Hz,
H-7a), 4.20 (dd, 1H, J6,7b 7.6 Hz, H-7b), 3.69 (dd, 1H, J5,6 2.4 Hz, H-
5), 3.54 (s, 3H, OMe), 2.22 (s, 3H), 2.14 (s, 3H), 2.07 (s, 3H), 2.03 (s,
3H) and 1.99 (s, 3H, 5 ꢄ Ac).
Figure 2. Packing diagram of 4 viewed along the a-axis and showing two double
layers of 2-dimensionally hydrogen bonded molecules extending parallel to (0 0 1)
at z ꢃ 0 and 1. Hydrogen bonds are indicated by red dashed lines, the channels
parallel to a by green rectangles. Crystallographic C2 axes extend parallel to c at
y = 0, ½, and 1.
3.5. Methyl L-glycero-a-D-manno-heptopyranoside (4)
V = 1067.39(7) Å3, Z = 4, dcalcd = 1.395 g/cm3,
9379 reflections collected up to hmax = 30.0°, 1791 were indepen-
dent, Rint = 0.0271, and 1636 were observed (I > 2 (I)); final R
data), wR2 =
(w(Fo2)2) = 0.100 (all data). Unit cell dimensions
at room temperature (297 K) are:
l
= 0.123 mmꢂ1. Of
A solution of 5 (99.8 mg, 0.27 mmol) in dry MeOH (10 mL) was
stirred with 0.1 M NaOMe solution (0.3 mL) at room temperature
for 5.5 h. DOWEX H+ resin was added until pH 6–7 was achieved.
The resin was removed and the filtrate was concentrated to afford
4. Crystallization of the residue from hot 2-propanol afforded
37.5 mg (73%) of 4, colorless plates, mp 133–134 °C (2-PrOH);
r
indices:
R
and density of
R1 =
R
R
||Fo| ꢂ |Fc||/
R
|Fo| = 0.044
(all
(w(Fo ꢂ Fc2)2/
2
4
a = 8.9929(1) Å, b = 9.9970(1) Å, c = 12.0940(2) Å, V = 1087.28 Å3,
and dcalcd = 1.370 g cmꢂ3. Atomic parameters and further details
of the structure determination have been deposited. CCDC
881898 contains the supplementary crystallographic data for this
paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
½
a 2D0
ꢅ
+79.5 (c 0.5, MeOH), lit.8: ½a D20
ꢅ
+70 (c 0.5, MeOH). 1H NMR
(400 MHz, CD3OD): d = 4.565 (d, 1H, J1,2 1.5 Hz, H-1), 3.88 (ddd,
1H, J5,6 1.2, J7b,6 6.5, J7a,6 7.4 Hz, H-6), 3.75 (app. t, 1H, J3,4 = J4,5
9.7 Hz, H-4), 3.68 (dd, 1H, J2,3 3.4 Hz, H-2), 3.595 (dd, 1H, J7a,7b
10.8 Hz, H-7a), 3.58 (dd, 1H, H-3), 3.54 (dd, 1H, H-7b), 3.44 (dd,
1H, H-5), 3.26 (s, 3H, OMe). 13C NMR (100 MHz, CD3OD):
d = 101.42 (C-1), 71.39 (C-3), 71.03 (C-5), 70.68 (C-2), 69.30 (C-6),
66.33 (C-4), 63.03 (C-7) and 53.91 (CH3O). Anal. Calcd for
C8H16O7: C, 42.86; H, 7.19. Found: C, 42.84; H, 7.01.
3.3. Methyl glycoside formation of
heptopyranose
L-glycero-D-manno-
Method A: A solution of 2 (3.31 g, 9.72 mmol) in dry methanol
(80 mL) was stirred with 10% Pd–carbon (400 mg) under H2 at
atmospheric pressure at room temperature for 20 h. The suspen-
sion was filtered over a bed of Celite and washed with methanol.
The solution was concentrated to give a syrupy residue (2.27 g).
A 1/3 aliquot (754 mg) of the debenzylated material was dissolved
in dry methanol (50 mL), Dowex 50 H+ resin (4 g) was added and
the suspension was stirred at 60 °C for 15 h. The resin was filtered
off and the filtrate was concentrated to give a 10:1 mixture of 4
and 6 (603 mg, 84% based on 2).
3.6. Methyl L-glycero-b-D-manno-heptopyranoside (6)
A solution of 7 (10.1 mg, 0.027 mmol) in MeOH (7 mL) was trea-
ted with 0.1 M methanolic NaOMe solution (0.08 mL) and pro-
cessed as described for the deacetylation of 5. Yield: 4.8 mg
(91%), colorless syrup,
½
a 2D0
ꢅ
ꢂ49 (c 0.5, CHCl3). 1H NMR
(400 MHz, CD3OD): d = 4.32 (d, 1H, J1,2 0.9 Hz, H-1), 3.84 (ddd,
1H, J5,6 1.6, J 6.9, J 8.5 Hz, H-6), 3.73 (dd, 1H, J2,3 3.2 Hz, H-2),
3.70 (app. t, 1H, J3,4 = J4,5 9.6 Hz, H-4), 3.56 (app. d, 2H, H-7a, H-
7b), 3.40 (s, 3H, OMe), 3.35 (dd, 1H, H-3), 3.16 (dd, 1H, H-5), 13C
NMR (100 MHz, CD3OD): d = 101.43 (C-1), 74.69 (C-5), 74.08 (C-
3), 71.01 (C-2), 69.33 (C-6), 66.20 (C-4), 62.77 (C-7) and 55.57
(CH3O). HR MS: m/z = 223.0834 [MꢂH]ꢂ; calcd 223.0739.
Method B: A suspension of 3 (88 mg, 0.42 mmol) and DOWEX H+
resin (ꢁ1 g) in dry methanol (5 mL) was stirred under reflux for
12 h. After this time, TLC (10:10:3 MeOH–CHCl3–H2O) indicated

1744
D. Artner et al. / Carbohydrate Research 346 (2011) 1739–1746
3.7. Benzyl 2,3,4,6,7-penta-O-acetyl-
heptopyranosyl-(1?7)-(E)-5,6-dideoxy-2,3-O-isopropylidene-
L
-glycero-
a
-
D
-manno-
J4,5 8.1, H-4), 3.96 (m, 2H, H-5, H-6), 3.80 (dd, 1H, J7a,6 5.0, J7a,7b
10.0 Hz, H-7a), 3.61 (dd, 1H, J7b,6 7.0 Hz, H-7b), 2.75 (br. signal,
1H, OH), 2.18 (s, 3H), 2.14 (s, 3H), 2.04 (s, 3H), 2.02 (s, 3H) and
1.98 (s, 3H, 5 ꢄ COCH3), 1.47 (s, 3H) and 1.33 [s, 3H, C(CH3)2]. 13C
NMR (100 MHz, CDCl3): d = 170.54, 170.25, 170.01, 169.85 and
169.57 (COCH3), 137.48 (Cq-Ph), 128.48, 128.41, 127.89 (CPh),
112.68 [C(CH3)2], 105.55 (C-1), 98.36 (C-10), 84.96 (C-2), 80.14 (C-
3), 78.75 (C-4), 69.84 (C-7), 69.71 (C-20), 69.40 (C-5, C-6), 69.36
(CH2Ph), 69.26 (C-30), 68.76 (C-50), 67.10 (C-60), 64.82 (C-40),
62.03 (C-70), 25.95, 24.59 [C(CH3)2], 20.34, 20.72 (d.i.) and 20.64
(d.i., total 5C, COCH3). Anal. Calcd for C34H46O18: C, 54.98; H,
6.24. Found: C, 54.40; H, 6.08.
a-
D-lyxo-hept-5-enofuranoside (9)
A suspension of the glycosyl acceptor 1 (181 mg, 0.59 mmol)
and trichloroacetimidate donor 8 (128 mg, 0.22 mmol) in freshly
distilled dichloromethane (5 mL) was stirred with powdered mol
sieves 4 Å at 0 °C for 3 h under Ar. TMSO-triflate (0.012 mL,
0.066 mmol) was added in three portions and the suspension
was stirred for 2 h at rt. Et3N (60 lL) was added, the suspension
was diluted with dichloromethane (20 mL), filtered over a bed of
CeliteÒ, and washed with dichloromethane (100 mL). The filtrate
was concentrated and the residue was purified by column chroma-
tography (toluene/EtOAc 5:1) to give 9 as colorless syrup (39.5 mg,
24.6%) as major compound and a partially deacetylated product
(49.4 mg) as by-product. The partially deacetylated glycoside was
taken up in pyridine (2 mL) and stirred with Ac2O (1 mL) for 30 h
at rt. The solution was cooled to ꢂ10 °C and MeOH (3 mL) was
added and the mixture was stirred for 15 min. The solution was
co-evaporated with toluene (3 ꢄ 50 mL) and concentrated. Flash
chromatography of the residue (toluene/EtOAc 5:1) gave a second
crop of 9 which crystallized from n-hexane/EtOAc as colorless nee-
3.9.
L-Glycero-
a-
D-manno-heptopyranosyl-(1?7)-benzyl 2,3-O-
isopropylidene-
L
-glycero- -manno-heptofuranoside (11)
a-D
A solution of 10 (36 mg, 0.049 mmol) in dry MeOH (1.5 mL) was
stirred with 1 M methanolic NaOMe (100 lL) for 3.5 h at rt. Dowex
50 H+ ion exchange resin was then added to adjust the pH ꢁ6. The
resin was filtered off and the filtrate was concentrated under re-
duced pressure giving 11 as colorless syrup. Yield: 26 mg (99%);
½
a 2D0 +37.4 (c 0.5, MeOH). 1H NMR (400 MHz, CD3OD): d = 7.39–
ꢅ
dles. Combined yield: 80 mg (50%); mp 114–115°; ½a D20
ꢅ
+35.6 (c
7.26 (m, 5H, Ph), 5.02 (s, 1H, H-1), 4.89–4.85 (m, 2H, H-3, H-10),
4.73 and 4.48 (AB system, 2H, JAB 11.8 Hz, CH2Ph), 4.64 (d, 1H,
J2,3 5.8 Hz, H-2), 4.19 (dd, 1H, J4,5 9.2, J4,3 3.2 Hz, H-4), 4.04–3.95
(m, 3H, H-5, H-6, H-60), 3.90–3.82 (m, 3H, H-40, H-20, H-7a), 3.74
0.5, CHCl3). 1H NMR (300 MHz, CDCl3): d = 7.34 (m, 5H, Ph), 5.91
(m, 2H, H-5, H-6), 5.36 (dd, 1H, J2 ,3 3.2, J3 ,4 9.7 Hz, H-30), 5.34–
0
0
0
0
5.26 (m, 3H, H-20, H-40, H-60), 5.10 (s, 1H, H-1), 4.92 (d, 1H, J1 ,2
0
0
1.5 Hz, H-10), 4.70 and 4.50 (AB system, 2H, JAB 11.7 Hz, CH2Ph),
4.70 (dd, 1H, J2,3 3.2, J3,4 5.9 Hz, H-3), 4.50 (dd, 1H, J4,5 6.0, H-4),
(dd, 1H, J5 ,6 3.4, J5 ,4 9.8 Hz, H-50), 3.71–3.66 (m, 3H, H-30, H-70a,
H-70b), 3.57 (dd, 1H, J7a,7b 9.5, J7b,6 6.8 Hz, H-7b), 1.44 (s, 3H) and
1.33 [s, 3H, C(CH3)2]. 13C NMR (100 MHz, CD3OD): d = 138.91 (Cq-
Ph), 129.31, 129.26, 129.70 (CPh), 113.49 [C(CH3)2], 106.51 (C-1),
102.25 (C-10), 86.28 (C-2), 81.26 (C-3), 79.92 (C-4), 72.84 (C-50),
72.53 (C-30), 72.13 (C-20), 70.59 and 70.51 (C-5, C-6), 70.26 (C-7),
69.57 (CH2Ph), 69.14 (C-60), 67.70 (C-40), 64.19 (C-70), 26.52 and
25.09 [C(CH3)2].
0
0
0
0
4.30 (dd, 1H, J6 ,7a 6.0, J7a ,7b 11.3 Hz, H-7a0), 4.25 (dd, J6 ,7b
0
0
0
0
0
0
7.5 Hz, H-7b0), 4.23 (m, 1H, J7a,7b 12.7 Hz, H-7a), 4.13 (dd, J4 ,5
0
0
9.3, J5 ,6 2.0 Hz, H-50), 4.06 (m, 1H, H-7b), 2.18 (s, 3H), 2.15 (s,
3H), 2.06 (s, 3H), 2.03 (s, 3H) and 1.99 (s, 3H, 5 ꢄ COCH3), 1.46 (s.
3H) and 1.30 [s, 3H, C(CH3)2]. 13C NMR (75 MHz, CDCl3):
d = 170.43, 170.25, 170.07, 169.87, 169.65 (COCH3), 137.27 (Cq,
Ph), 129.35 (CPh), 128.50 (CPh), 128.41 (C-5), 128.01 (CPh),
127.88 (C-6), 112.63 [C(CH3)2], 105.25 (C-1), 97.19 (C-10), 85.38
(C-2), 81.27 (C-3), 80.00 (C-4), 69.58 (C-20), 69.26 (C-30), 68.99
(CH2Ph), 68.57 (C-50), 67.97 (C-7), 66.96 (C-60), 64.90 (C-40), 61.82
(C-70), 26.06, 24.84 [C(CH3)2], 21.00, 20.78, 20.76, 20.69 and
20.66 (COCH3). Anal. Calcd for C34H44O16: C, 57.62; H, 6.26. Found:
C, 57.56; H, 5.79.
0
0
3.10.
L-Glycero-a-D-manno-heptopyranosyl-(1?7)-L-glycero-D-
manno-heptopyranose (13)>
A suspension of heptobiose 11 (22 mg, 0.042 mmol) in dry
MeOH (3 mL) was stirred with 10% Pd–C (ꢁ50 mg) under hydrogen
at atmospheric pressure for 28 h at room temperature. The catalyst
was removed by filtration over a bed of CeliteÒ and the filtrate was
concentrated under reduced pressure. NMR analysis of the residue
indicated the presence of 12 and 13 (3:2 ratio). The residue was
dissolved in the minimal amount of MeOH and compound 13
was selectively precipitated by addition of EtOAc. The precipitate
was separated by centrifugation, dissolved in water and lyophi-
lized. The residue was purified over Bio-Rad Bio-GelÒ P2 column
(water, 5% EtOH) and lyophilized to give 13 as an amorphous solid.
3.8. Benzyl 2,3,4,6,7-penta-O-acetyl-
heptopyranosyl-(1?7)-2,3-O-isopropylidene-
manno-heptofuranoside (10)
L-glycero-
a-
D-manno-
L
-glycero-a-D-
N-Methylmorpholine-N-oxide (22 mg, 0.188 mmol) was added
to a solution of 9 (46 mg, 0.065 mmol) in 8:1 acetone/water
(20 mL). Upon complete dissolution a catalytic amount of OsO4
was added, the mixture turned slightly yellow and was stirred
for 3.5 h at rt. The mixture was diluted with CHCl3 (80 mL) and
was washed with 5 M HCl (10 mL). The organic phase was treated
vigorously with 45% aq Na2S2O5 and dried (Na2SO4). Concentration
gave a residue which was purified by column chromatography (tol-
Yield: 6.4 mg (38%); ½a D20
ꢅ
+24 (c 0.3, H2O, equilibrium after 15 h);
lit21: +45.4 (c 1.0, H2O). 1H NMR (300 MHz, D2O): d = 5.19 (d,
0.7H, J1
1.6 Hz, H-1
a
), 4.93 (m, 1H, H-10a, H-10b), 4.90 (d,
0.3H, J1b,2b 1.0 Hz, H-1b), 4.22–4.19 (m, 1H, H-6 H-6b),
4.02–4.06 (m, 1H, H-60a, H-60b), 4.00 (br m, 1H, H-20a, H-20b),
3.96–3.92 (br m, 1H, H-2 , H-2b), 3.90–3.59 (m, 9.7H, H-3 , H-
0a, H-4 , H-4b, H-40a, H-40b, H-30b, H-5 , H-7ab, H-70b
, H-7a
H-70bb, H-3b, H-50a, H-50b, H-7b
, H-7bb) and 3.35 (dd, 0.3H,
J5b,6b 1.8, J4b,5b 8.3 Hz, H-5b). 13C NMR (100 MHz, D2O): d = 101.04
(C-10a), 100.94 (C-10b), 94.81 (C-1
), 94.59 (C-1b), 75.35 (C-5b),
73.89 (C-3b), 72.11 (C-50b), 71.93 (2C, C-2b, C-50a), 71.73 (C-5
),
71.43 (2C, C-3 , C-2
), 71.16 (C-30a), 70.59 (2C, C-20a, C-20b),
69.57 (C-60b), 69.47 (C-60a), 69.32 (C-7
), 68.97 (C-7b), 67.87
a,2a
a,
uene/EtOAc 1:1) to afford an 8:1 isomeric mixture of the
L
-glycero-
a
a
D
-manno- and -glycero- -gulo-diastereomer. Yield: 54 mg (95%).
D
L
3
a
a
a
a,
Separation of the isomers was achieved by repeated HPLC chroma-
a
tography (toluene/EtOAc 1:1?1:2) to give 10 (28 mg, 46%) as the
less mobile isomer (Rf 0.31; toluene/EtOAc 1:1) as a syrup; ½a D20
ꢅ
a
+40.5 (c 0.4, CHCl3). 1H NMR (400 MHz, CDCl3): d = 7.38–7.15 (m,
a
5H, Ph), 5.33–5.27 (m, 4H, H-20, H-30, H-40, H-60), 5.11 (s, 1H, H-
a
a
1), 4.93 (d, 1H, J1 ,2 ꢁ1.0 Hz, H-10), 4.88 (dd, 1H, J2,3 6.0, J3,4
a
0
0
3.8 Hz, H-3), 4.67 (d, 1H, H-2), 4.65 and 4.53 (AB system, 2H, JAB
(C-6a), 67.70 (C-6b), 66.74 (2C, C-4a
, C-40a), 66.42 (2C, C-4b, C-
11.9 Hz, CH2Ph), 4.38 (dd, 1H, J6 ,7a 5.4, J7a ,7b 11.4 Hz, H-7a0),
40b), 63.71 (C-70b) and 63.57 (C-70a). ESI-TOF MS: m/z = 403.1339
0
0
0
0
4.24 (dd, 1H, J6 ,7b 7.6 Hz, H-7b0), 4.14 (m, 1H, H-50), 4.11 (dd, 1H,
[M+H]; calcd 403.1452.
0
0

D. Artner et al. / Carbohydrate Research 346 (2011) 1739–1746
1745
3.11. Methyl 7-O-tertbutyldimethylsilyl-
heptopyranoside (15)
L
-glycero-
a
-
D
-manno-
3H, 4 ꢄ COCH3). 13C NMR (100 MHz, CDCl3): d = 171.15, 170.03,
169.85 and 169.62 (C@O), 98.99 (C-1), 70.25 (C-6), 69.48 and
69.26 (C-3, C-2), 68.75 (C-5), 65.10 (C-4), 61.33 (C-7), 55.46
(CH3O), 20.90, 20.81, 20.62 and 20.60 (COCH3).
Diazabicyclo[2.2.2]octane (86 mg, 0.77 mmol) was added at
room temperature to a solution of 4 (0.15 g, 0.669 mmol) in dry
acetonitrile (2.7 mL), followed by addition of tBDMS-chloride
(111 mg, 0.736 mmol). After 2 h additional MeCN (2.5 mL) was
added followed by addition of DABCO (53 mg, 0.468 mmol) and
tBDMSCl (71 mg, 0.468 mmol) in two portions after 5 h and 7 h,
respectively. The suspension was stirred overnight at room tem-
perature. MeOH (5 mL) was added and stirring was continued for
1 h. The suspension was concentrated and the residue was applied
3.14. 2,3,4,6,7-Penta-O-acetyl-L-glycero-D-manno-
heptopyranosyl N-phenyltrifluoroacetimidate (19)
A solution of 18, prepared according to lit.27, (96 mg,
0.228 mmol) in acetone (1.8 mL) was stirred with K2CO3 (63 mg)
and N-phenyltrifluoroacetimidoyl chloride (95 mg, 0.457 mol) for
3 h at room temperature. The solids were filtered over a bed of Cel-
iteÒ and the filtrate was concentrated. The residue was purified by
silica gel chromatography (5:1 toluene/EtOAc) to furnish 135 mg
(ꢁquant.) of 19 as a syrup. 1H NMR (400 MHz, CDCl3): d = 7.32 (t,
2H, J 8.8 Hz, PhH-3, PhH-5), 7.13 (t, 1H, J 6.9 Hz, PhH-4), 6.81 (t,
2H, J 8.0 Hz, PhH-2, PhH-6), 6.26 (br. s, 1H, H-1), 5.49 (dd, 1H, J2,3
2.6, J2,1 1.6 Hz, H-2), 5.40–4.38 (m, 2H, H-3, H-4), 5.28 (dt, 1H, J6,5
2.0, J6,7a 6.8 Hz, H-6), 4.24 (dd, 1H, J7a,7b 11.0 Hz, H-7a), 4.22 (dd,
1H, J6,7b 7.0 Hz, H-7b), 4.19–4.16 (m, 1H, H-5), 2.20 (s, 3H), 2.14
(s, 3H), 2.06 (s, 3H), 2.03 (s, 3H) and 2.02 (s, 3H, 5 ꢄ CH3CO). 13C
NMR (100 MHz, CDCl3): d = 170.31, 170.07, 170.01, 169.76,
169.67 and 169.49 (COCH3), 142.74 (C1-Ph), 128.94 (C3-Ph, C-
5Ph), 124.77 (C4-Ph), 119.14 (C2-Ph, C-6Ph), 93.49 (C-1), 70.56
(C-5), 68.93 (C-3), 68.02 (C-2), 66.45 (C-6), 64.23 (C-4), 61.08 (C-
7), 20.76, 20.63, 20.58 and 20.48 (COCH3).
on
a column of silica gel and eluted with EtOAc/MeOH
100:15?100:25?MeOH. Appropriate fractions were pooled and
concentrated to give 15 as a crystalline solid. Yield: 194 mg
(86%); mp 166–167 °C (EtOAc), ½a D20
ꢅ
+59 (c 0.3, CHCl3). 1H NMR
(400 MHz, CD3OD): d = 4.65 (d, 1H, J1,2 1.6 Hz, H-1), 3.94 (ddd,
1H, J5,6 1.3, J7b,6 6.5, J7a,6 7.9 Hz, H-6), 3.84 (app. t, 1H, J3,4 = J4,5
9.7 Hz, H-4), 3.76 (dd, 1H, J2,3 3.4 Hz, H-2), 3.74 (dd, 1H, J7a,7b
9.7 Hz, H-7a), 3.69 (dd, 1H, H-7b), 3.68 (dd, 1H, H-3), 3.63 (dd,
1H, H-5), 3.36 (s, 3H, OCH3), 0.92 (s, 9H, tBu), 0.10 (s, 3H) and
0.08 (s, 3H, 2 ꢄ SiMe). 13C NMR (100 MHz, CD3OD): d = 102.83 (C-
1), 72.86 (C-3), 72.18 (C-2), 71.61 (C-5), 70.36 (C-6), 67.63 (C-4),
64.67 (C-7), 55.31 (CH3O), 26.40 [C(CH3)3], 19.16 [C(CH3)3], ꢂ5.14
and ꢂ5.29 (SiCH3). HR MS: m/z = 337.1713 [MꢂH]ꢂ; calcd
337.1682.
3.12. Methyl 2,3,4,6-tetra-O-acetyl-7-O-tertbutyldimethylsilyl-
L
-
3.15. Methyl 2,3,4,6,7-penta-O-acetyl-
L
-glycero-
a-
D-manno-
glycero- -manno-heptopyranoside (16)
a
-
D
heptopyranosyl-(1?7)-2,3,4,6-tetra-O-acetyl-
L
-glycero-a-D-
manno-heptopyranoside (20)
A solution of 15 (180 mg, 0.532 mmol) in dry pyridine (5 mL)
was stirred with Ac2O (1 mL, 14 mmol) and a catalytic amount of
4-N,N-dimethylaminopyridine for 3 h at room temperature. The
solution was cooled to 0 °C, MeOH (2 mL) was added and stirring
was continued for 20 min. The solution was concentrated and
coevaporated with toluene. The residue was purified by silica gel
chromatography (n-hexane/EtOAc 2:1) to furnish 270 mg
Dry toluene was added to 17 (39 mg, 0.099 mmol) and donor 19
(88 mg, 0.148 mmol) and the solution was coevaporated several
times with addition of toluene and then concentrated. The residue
was dissolved in dry dichloromethane (1.6 mL) and a spatula tip of
ground activated molecular sieves 4 Å was added. The suspension
was stirred under Ar at 0 °C for 30 min and TMSO-triflate (10 lL,
(ꢁquant.) of 16 as colorless solid, mp 86–88 °C (CH2Cl2); ½a D20
ꢅ
0.049 mmol) was added via a syringe. The suspension was slowly
warmed to room temperature and stirred for 75 min. Et3N
(0.1 mL) was added and the suspension was filtered over a bed of
CeliteÒ and washed with dichloromethane (5 mL). The filtrate
was washed with satd aq NaHCO3, dried (Na2SO4), and concen-
trated to give 135 mg of an oily residue. Purification by silica gel
chromatography (toluene/EtOAc 2:1?1.5:1?1:1) afforded crude
20 (51 mg, 65%). In order to remove traces of a more polar by-prod-
uct, the disaccharide was further purified by chromatography
using 15:1 CH2Cl2/acetone as eluant, which furnished 40 mg
(51%) of pure disaccharide 20 and additional fractions containing
+31.5 (c 0.6, CHCl3). 1H NMR (400 MHz, CDCl3): d = 5.34 (dd, 1H,
J3,4 10.0, J2,3 3.4 Hz, H-3), 5.29 (app. t, 1H, J4,5 8.9 Hz, H-4), 5.26
(dd, 1H, J1,2 1.5 Hz, H-2), 4.95 (ddd, 1H, J5,6 1.8, J7b,6 6.0, J7a,6
9.0 Hz, H-6), 4.76 (d, 1H, H-1), 4.16 (dd, 1H, H-5), 3.81 (dd, 1H,
J7a,7b 9.7 Hz, H-7a), 3.70 (dd, 1H, H-7b), 3.42 (s, 3H, OCH3), 2.20
(s, 3H), 2.12 (s, 3H), 2.03 (s, 3H), 1.98 (s, 3H, CH3CO), 0.89 (s, 9H,
tBu), 0.08 (s, 3H) and 0.06 (s, 3H, 2 ꢄ SiMe). 13C NMR (100 MHz,
CDCl3): d = 170.30, 170.08, 169.91 and 169.66 (C@O), 98.88 (C-1),
69.65 (C-2), 69.59 (C-3), 69.50 (C-6), 66.98 (C-5), 65.06 (C-4),
59.28 (C-7), 55.28 (CH3O), 25.73 [C(CH3)3], 20.93, 20.79, 20.65
and 20.59 (COCH3), 18.09 [C(CH3)3], ꢂ5.36 and ꢂ5.49 (SiCH3)2.
HR MS: m/z = 507.2281 [M+H]+; calcd 507.2261.
slightly contaminated material. ½a D20
ꢅ
+22 (c 0.5, CHCl3). 1H NMR
(600 MHz, CDCl3): d = 5.34 (dd, 1H, J2,3 3.2, J3,4 10.0 Hz, H-3), 5.31
(t, 1H, J4,5 9.4 Hz, H-4), 5.29 (t, 1H, J4 ,5 9.9 Hz, H-40), 5.29–5.27
0
0
(m, 2H, H-2, H-60), 5.24 (dd, 1H, J2 ,3 3.4, J4 ,3 10.1 Hz, H-30), 5.21
0
0
0
0
3.13. Desilylation of 16
(dd, 1H, H-20), 5.20 (ddd, 1H, H-6), 4.90 (d, 1H, J1 ,2 0.7 Hz, H-10),
0
0
0
0
0
0
A solution of 16 (50 mg, 0.1 mmol) in dry MeCN was placed in a
teflon vessel and stirred with 2% HF in MeCN (1.2 mL) for 3 h at
room temperature. A spatula tip of solid NaHCO3 was added and
stirring was continued for 20 min. Filtration, washing of solids with
dry CH3CN (5 mL), and concentration of the filtrate gave a crude
material which was dried and directly submitted to the ensuing
glycosylation reaction. Material 17 was immediately used for the
subsequent glycosylation step. 1H NMR (400 MHz, CDCl3):
d = 5.35–5.29 (m, 2H, H-3, H-4), 5.26 (dd, 1H, J2,3 3.1 J1,2 1.7 Hz,
H-2), 5.02 (dt, 1H, J5,6 2.0, J7b,6 = J7a,6 8.1 Hz, H-6), 4.76 (d, 1H, H-
1), 4.14–4.11 (m, 1H, H-5), 3.91–3.80 (m, 2H, H-7a, H-7b), 3.42
(s, 3H, OMe), 2.17 (s, 3H), 2.16 (s, 3H), 2.02 (s, 3H) and 1.98 (s,
4.79 (d, 1H, J1,2 1.8 Hz, H-1), 4.34 (dd, 1H, J7 a,7 b 11.4, J7 a,6 5.1 Hz,
H-70a), 4.19 (dd, 1H, J7 b,6 7.8 Hz, H-70b), 4.10 (dd, 1H, J5,4 9.8, J5,6
0
0
2.2 Hz, H-5), 4.08 (dd, 1H, J5 ,6 1.8 Hz, H50), 3.85 (dd, 1H, J7a,7b
10.2, J7a,6 7.0 Hz, H-7a), 3.68 (dd, 1H, J6,7b 7.2 Hz, H-7b), 3.47 (s,
3H, OCH3), 2.18 (s, 3H), 2.17 (s, 3H), 2.16 (s, 3H), 2.14 (s, 3H),
2.053 (s, 3H), 2.050 (s, 3H), 2.01 (s, 3H), 1.988 (s, 3H), 1.986 (s,
3H, 9 ꢄ COCH3). 13C NMR (150 MHz, CDCl3): d = 170.39, 170.20
(d.i.), 170.01, 169.92, 169.81, 169.68 (d.i.) and 169.47 (COCH3),
98.98 (C-1), 98.24 (C-10), 69.37 (C-20), 69.27 (C-3, C-2), 68.98 (C-
30), 68.88 (C-50), 67.88 (C-5), 67.28 (C-6), 66.92 (C-60), 64.94 (C-
7), 64.82 and 64.72 (C-40, C-4), 62.10 (C-70), 55.57 (OCH3), 20.94,
20.92, 20.72 (d.i.), 20.69 (triple intensity) and 20.61 (d.i., COCH3).
0
0

1746
D. Artner et al. / Carbohydrate Research 346 (2011) 1739–1746
2. Wang, H.; Head, J.; Kosma, P.; Brade, H.; Müller-Loennies, S.; Sheikh, S.;
McDonald, B.; Smith, K.; Cafarella, T.; Seaton, B.; Crouch, E. Biochemistry 2008,
47, 710–720.
3.16. Methyl L-glycero-a-D-manno-heptopyranosyl-(1?7)-L-
glycero-a-D-manno-heptopyranoside (21)
3. Sulak, O.; Cioci, G.; Lameignere, E.; Aubert, D.; Marolda, C.; Gutsche, I.; Round,
A.; Delia, M.; Kosma, P.; Balloy, V.; Chignard, M.; Valvano, M.; Wimmerova, M.;
Imberty, A. Glycobiol. 2010, 20, 1527.
A solution of 20 (28 mg, 0.0352 mmol) in dry MeOH (1.5 mL)
was stirred with 0.1 M methanolic NaOMe (0.4 mL) for 3 h at room
temperature and processed as described for the deacetylation of 5.
Final purification was achieved on a BioGel P-2 column (28 ꢄ 1 cm,
H2O) to give 12.5 mg (85%) of 21 as an amorphous solid after
4. (a) Hansson, J.; Oscarson, S. Curr. Org. Chem. 2000, 4, 535–564; (b) Kosma, P.
Curr. Org. Chem. 2008, 12, 1021–1039. and references cited therein.
5. Brimacombe, J. S.; Kabir, A. K. M. Carbohydr. Res. 1986, 152, 329–334.
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8. (a) Yamasaki, R.; Takajyo, A.; Kubo, H.; Matsui, T.; Ishii, K.; Yoshida, M. J.
Carbohydr. Chem. 2001, 20, 171–180; (b) Boons, G. J. P. H.; van der Marel, G. A.;
Poolman, J. T.; Van Boom, J. H. Rec. Trav. Chim. Pays-Bas 1989, 108, 339–343; (c)
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Paulsen, H.; Wulff, A.; Heitmann, A. Liebigs Ann. Chem. 1988, 1073–1078.
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Chim. Pays-Bas 1992, 111, 144–148.
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1572.
12. Martin, P.; Lequart, V.; Cecchelli, R.; Boullanger, P.; Lafont, D.; Banoub, J. Chem.
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15. Güzlek, H.; Graziani, A.; Kosma, P. Carbohydr. Res. 2005, 340, 2808–2811.
16. Nepogod’ev, S. A.; Backinowsky, L. V.; Grzeszczyk, B.; Zamojski, A. Carbohydr.
Res. 1994, 254, 43–60.
lyophilization. ½a D20
ꢅ
+68 (c 0.3, H2O); Lit.14: ½a D20
ꢅ
+65 (c 1.0, H2O).
1H NMR (600 MHz, MeOD): d = 4.73 (d, 1H, J1 ,2 1.3 Hz, H-10),
4.55 (d, 1H, J1,2 1.5 Hz, H-1), 4.02 (ddd, 1H, J7b,6 7.6, J7a,6 5.4, J5,6
0
0
1.6 Hz, H-6), 3.85 (td, 1H, J6 ,5 1.5 Hz, H-60), 3.75–3.74 (m, 1H,
H-2), 3.75, 3.74 (2 ꢄ app. t, 1H, J 9.7 Hz, H-4, H-40), 3.68 (dd,
0
0
1H, J7a,7b 10.5 Hz, H-7a), 3.66 (dd, 1H, J3 ,2 3.4 Hz, H-20), 3.62 (dd,
0
0
1H, J3 ,4 9.6 Hz, H-30), 3.56 (dd, 1H, J7 a,7 b 10.9, J7 a,6 6.7 Hz,
H-70a), 3.56 (dd, 1H, J3,2 3.8 Hz, H-3), 3.54–3.50 (m, 3H, H-50,
H-7b, H-70b), 3.38 (dd, 1H, J5,4 9.8 Hz, H-5), 3.26 (s, 3H, OCH3).
13C NMR (150 MHz, MeOD): d = 102.97 (C-1), 102.50 (C-10), 72.95
(C-50), 72.81 (d.i.) and 72.75 (C-5, C-30, C-3), 72.09 and 72.07
(C-2, C-20), 70.79 (C-60), 70.67 (C-7), 68.91 (C-6), 67.76 and 67.68
(C-4, C-40), 64.47 (C-70) and 55.51 (OCH3). HR MS: m/z = 415.1505
[MꢂH]ꢂ; calcd 415.1451.
0
0
0
0
0
0
17. Murali, C.; Shashidhar, M. S.; Gopinath, C. S. Tetrahedron 2007, 63, 4149–4155.
18. Ribes, C.; Falomir, E.; Murga, J. Tetrahedron 2006, 62, 1239–1244.
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Kongkathip, N.; Ley, S. V. Synlett 2008, 1293–1296.
20. Procopio, A.; Gaspari, M.; Nardi, M.; Oliverio, M.; Tagarelli, A.; Sindona, G.
Tetrahedron Lett. 2007, 48, 8623–8627.
21. Paulsen, H.; Heitmann, A. Liebigs Ann. Chem. 1988, 1061–1071.
22. Yu, B.; Jiansong, S. Chem. Commun. 2010, 46, 4668–4679.
23. Duda, A.; Luger, P.; Paulsen, H. Acta Crystallogr., Sect. C 1986, 42, 1600–1602.
24. Mo, F.; Berg, O.; Gaasdal, A.; Sallam, M. A. E. Acta Chem. Scand. A 1981, 35, 239–
246.
25. Bruker programs: SMART, version 5.629; SAINT, version 6.45; SADABS, version
2.10; XPREP, version 6.1; SHELXTL, version 6.14 (Bruker AXS Inc., Madison, WI,
2003).
Acknowledgments
Authors are grateful to Martin Pabst for providing the MS data.
Technical support by Andreas Hofinger, Sarah Holliday, Gregor
Tegl, Alexander Gadinger, and Maria Hobel is gratefully acknowl-
edged. The authors thank the Austrian Science Fund FWF for finan-
cial support (grant P 22909).
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