Synthesis of oligosaccharides corresponding to Streptococcus pneumoniae type 9 capsular polysaccharide structures

Article abstract of DOI:10.1016/S0008-6215(02)00263-X

Two trisaccharides, α-D-Galp-(1→3)-β-D-ManpNAc-(1→4)-β-D-Glcp and α-D-Glcp-(1→3)-β-D-ManpNAc-(1→4)-β-D-Glcp, corresponding to structures from Streptococcus pneumoniae capsular polysaccharides type 9A, L, V and type 9N, respectively, have been synthesised

Full text of DOI:10.1016/S0008-6215(02)00263-X

Carbohydrate Research 337 (2002) 1715–1722
www.elsevier.com/locate/carres
Synthesis of oligosaccharides corresponding to Streptococcus
pneumoniae type 9 capsular polysaccharide structures
Mia Alpe, Stefan Oscarson*
Department of Organic Chemistry, Arrhenius Laboratory, Stockholm Uni6ersity, S-106 91 Stockholm, Sweden
Received 17 December 2001; accepted 6 August 2002
Abstract
Two trisaccharides, a-
D
-Galp-(1“3)-b-
D
-ManpNAc-(1“4)-b-
D
-Glcp and a-
D
-Glcp-(1“3)-b-
D
-ManpNAc-(1“4)-b-D-Glcp,
corresponding to structures from Streptococcus pneumoniae capsular polysaccharides type 9A, L, V and type 9N, respectively,
have been synthesised as 2-aminoethyl glycosides and as protected TMSE glycosides. Ethyl thioglycosides were used as glycosyl
donors and NIS/TfOH (in CH2Cl2 for b-linkages) and DMTST (in Et2O for a-linkages) as promoters in the glycosylations. The
b-ManNAc motif was introduced at the disaccharide level by azide displacement of a 2-O-triflate with b-D-gluco configuration.
The protecting group patterns allow continued syntheses of larger structures. © 2002 Elsevier Science Ltd. All rights reserved.
Keywords: Thioglycosides; Oligosaccharide synthesis; Glycoconjugate vaccines
1. Introduction
cosides, to allow conjugation to a carrier protein, as
well as TMSE glycosides to make transformation into
glycosyl donors possible.11 Also the protection pattern
is designed to permit continued synthesis of the com-
plete pentasaccharide units as well as larger structures.
The bacteria Streptococcus pneumoniae is a major
human pathogen.1 The bacteria is divided into
serotypes, each serotype corresponding to a unique
structure of the capsular polysaccharide (CPS) sur-
rounding the bacteria.2 Serotype 9 is one of the most
abundant serotypes comprising several variations: 9A,
9L, 9N, and 9V. These vary slightly in their CPS
structure (Fig. 1).3–6 9V is an acetylated version of 9A,
but the acetylation is believed to be not immunologi-
cally important.7
Streptococcus CPSs have been used as a polyvalent
vaccine against bacteria for a long time, and recently a
seven-valent glycoconjugate vaccine based on bacterial
CPS structures has been licensed in North America.8
Preliminary results for other serotypes indicate that also
much shorter parts of the CPS conjugated to a protein,
even down to only one or two repeating units, might be
enough to obtain a protective immunity against the
bacteria.9,10 To further investigate this we have synthe-
sised trisaccharide parts (residues III–I in Fig. 1) of the
pentasaccharide repeating units of serotypes 9A, L and
9N. The trisaccharides are synthesised as spacer gly-
2. Results and discussion
In spite of the importance of serotype 9 only one
synthesis of a type 9 part structure has been published,
a trisaccharide corresponding to residues II–V in Fig.
1.12 Since the biological repeating unit is not known, we
decided to choose the b-D-glucopyranosyl residue as
reducing end. This would allow starting from a com-
mon disaccharide precursor as well as choosing the, at
least in theory, most simple glycosidic linkage to con-
struct when later attempting planned block synthesis of
oligomers of the pentasaccharide repeating units.
The common disaccharide precursor was prepared as
outlined in Schemes 1–3. The known azidoethanol
glucoside 113 was benzylidenated and benzylated to give
the fully protected derivative 3, in which the azide was
reduced and the resulting amine protected as a benzyl
carbamate (“4, 45% overall yield from 1). Regioselec-
tive reductive opening of the benzylidene acetal14 then
afforded acceptor 5 almost quantitatively (Scheme 1).
* Corresponding author. Fax: 0046-8-154908
E-mail address: s.oscarson@organ.su.se (S. Oscarson).
0008-6215/02/$ - see front matter © 2002 Elsevier Science Ltd. All rights reserved.
PII: S0008-6215(02)00263-X

1716
M. Alpe, S. Oscarson / Carbohydrate Research 337 (2002) 1715–1722
Fig. 1. Repeating units of Streptococcus pneumoniae type 9 CPS.
Instead of working with mannosamine-type donors
b-glucosidic linkage and consecutive inversion of the
configuration at C-2, was employed.15 Thus, thioglu-
coside donor 8 was prepared from derivative 616 by
regioselective tin-promoted allylation at O-317 followed
and trying to optimise conditions for b-linkage forma-
tion,12 the other obvious approach, formation of a
by acetylation (Scheme 2).
NIS/TfOH-promoted glycosylation in CH2Cl2
18,19
of
acceptor 5 with donor 8 then gave the b-linked disac-
charide 9 (84%), which was transformed into the de-
sired precursor disaccharide acceptor 12, through
deacetylation, triflatation, azide displacement and deal-
lylation (Scheme 3, overall yield 58%).
At this stage the synthesis diverges, to obtain 9A and
L structures an a-linked galactose moiety is introduced,
whereas coupling with a glucose derivate yields a 9N
structure. The 3-O-acetyl thioglycoside derivatives 14
and 16 were prepared (Scheme 2) and used in DMTST-
promoted couplings in diethyl ether20,21 with acceptor
12 to produce the a-linked trisaccharides 17 and 21 in
excellent yields and stereoselectivity (Scheme 4). Azide
reduction followed by acetylation and O-deacetylation
then gave the two acceptors 19 and 23 ready for further
elongation. These derivatives were also fully depro-
tected by hydrogenolysis to yield the target trisaccha-
rides 20 (73%) and 24 (91%) both with a spacer
containing a free amino group for conjugation to a
protein to form immunogenic glycoconjugates.
To be able to synthesise larger structures or
oligomers of the repeating unit, block donors corre-
sponding to the repeating units or parts of it were
necessary. Accordingly, the structures synthesized were
assembled not only as spacer glycosides but also as
their trimethylsilylethyl (TMSE) glycosides, which can
be selectively hydrolysed and transformed into various
donors or directly transformed into chloride donors.11
The only necessary difference in the TMSE-glycosides
as compared to the spacer glycosides is the introduction
of a participating group at O-2, to ensure b-selectivity
in future couplings. The known TMSE-glycoside 2522
was coupled with the earlier used donor 8 and under
identical conditions to give disaccharide 26, which was
then transformed as discussed for the corresponding
spacer derivative 9, into acceptor 29 (Scheme 5). This
time the deacetylation was performed using Mg(OMe)2
instead of NaOMe to avoid concomitant debenzoyla-
tion. Since the yield in the chemoselective deacylation
Scheme 1. (a) a,a-Dimethoxytoluene, pTsOH, DMF; (b)
BnBr, NaH, DMF; (c) 1. PPh3, CH2Cl2, 2. H2O, CH2Cl2,
reflux, 3. benzylchloroformate, pyridine; (d) NaCNBH3, HCl/
Et2O, THF.
Scheme 2. (a) 1. Bu2SnO, MeOH, reflux, 2. AllBr, CsF,
DMF; (b) Ac2O, pyridine; (c) 1. (Ph3P)3Rh(I)Cl, EtOH–tolu-
ene–H2O (6:3:1), 2. HgBr2.
,
Scheme 3. (a) NIS, TfOH, 4 A MS, CH2Cl2, −30°C; (b)
NaOMe, CH2Cl2–MeOH; (c) 1. Tf2O, CH2Cl2–pyridine, 0°C,
2. NaN3, DMF, 70°C; (d) 1. Ir-cat., H2, THF, 2. NIS, H2O.

M. Alpe, S. Oscarson / Carbohydrate Research 337 (2002) 1715–1722
1717
at the reducing end after transformation of the TMSE-
glycoside.
Originally these trisaccharide donor precursors were
designed as thioglycosides, since these can be activated
as donors directly.25 However, in spite of that the first
orthogonal coupling to give the corresponding disac-
charide proceeded excellent using a bromo sugar donor
and silver triflate as promoter (Scheme 7), the next
coupling to yield the trisaccharide surprisingly failed,
although the same coupling conditions were used. In
the latter coupling the thioglycoside acceptor was also
activated and the transglycosylated26 monosaccharide
33 was the main product, showing how even seemingly
small differences in donor and acceptor structure can
completely change the outcome of a glycosylation.
In summary, trisaccharide structures of S. pneumo-
niae type 9A, L, and N capsular polysaccharides have
Scheme 4. (a) DMTST, Et2O; (b) 1. NaBH4, NiCl2×6H2O,
EtOH–CH2Cl2, 2. Ac2O; (c) NaOMe, MeOH; (d) H2,
Pd(OH)2/C, AcOH/EtOH.
Scheme 6.
,
Scheme 5. (a) NIS, TfOH, 4 A MS, CH2Cl2, −30°C; (b)
Mg(OMe)2, CH2Cl2–MeOH; (c) 1. Tf2O, CH2Cl2–pyridine,
0°C, 2. NaN3, DMF, 70°C; (d) 1. Ir-cat., H2, THF, 2. NIS,
H2O.
step was not too high (67%) it was decided to use allyl
groups instead of acetyl groups as temporary protecting
groups in the next donors to ensure orthogonality.
Accordingly, the 3-O-allyl thioglycosides 1323 and 3024
were prepared. Once more DMTST-promoted cou-
plings in Et2O, this time with acceptor 29, afforded high
yields of the a-linked trisaccharides 31 (87%) and 32
(91%) (Scheme 6), both containing the possibility to be
elongated at the 3¦-position after deallylation as well as
Scheme 7.

1718
M. Alpe, S. Oscarson / Carbohydrate Research 337 (2002) 1715–1722
been synthesised, both as deprotected spacer derivatives
ready for conjugate formation, as partly protected
spacer-equipped acceptors ready for glycosylations, and
as differentially protected TMSE-glycosides ready for
elongation both at the non-reducing and reducing end.
water, dried and concentrated. The residue was purified
on silica gel (9:1 toluene–EtOAc) to give 2-(N-benzy-
loxycarbonyl)-aminoethyl 2,3-di-O-benzyl-4,6-O-ben-
zylidene-b- -glucopyranoside (4, 3.85 g, 6.2 mmol,
D
80%); 13C NMR (CDCl3): l 41.5 (CH2NHCOOBn),
66.5, 67.2, 69.1, 70.0, 75.5, 75.9, 81.4, 81.9, 82.4 (C-2-6,
OCH2CH2N, PhCH2O), 101.6 (benzylidene), 104.5 (C-
1), 126.4–138.8 (aromatic C), and 156.3 (NHCOOBn).
A solution of 4 (3.80 g, 6. 07 mmol), NaCNBH3 (3.87
3. Experimental
General methods.—TLC was carried out on Merck
precoated 60 F254 plates using UV-light and/or 8%
H2SO4 for visualization. Column chromatography was
performed on silica gel (0.040–0.063 mm, Amicon).
NMR spectra were recorded in CDCl3 (internal Me4Si,
l=0.00) or D2O (internal acetone 13C l=31.0, 1H
l=2.21) at 25 °C on a Varian 300 MHz or 400 MHz
instrument. Organic phases were dried over Na2SO4
before evaporation, which was performed under re-
duced pressure.
,
g, 61 mmol) and 3 A molecular sieves in distilled THF
(100 mL) was stirred at rt under an argon atmosphere
for 30 min. HCl in diethyl ether was added until pH 1.
After 4 h the reaction mixture was filtered through a
layer of Celite, concentrated and purified on silica gel
(3:1 toluene–EtOAc) to give 5 (3.77 g, 6.01 mmol, 99%)
as a white solid; [h]D −19° (c 1.0, CHCl3); 13C NMR
(CDCl3): l 41.4 (CH2NHCOOBn), 66.7, 69.8, 70.0,
71.1, 73.6, 74.0, 74.9, 75.3, 81.7, 83.9 (C-2-6,
OCH2CH2N, PhCH2O), 104.0 (C-1), 127.7–138.4 (aro-
matic C), and 156.6 (NHCOOBn).
2-(N-Benzyloxycarbonyl)-aminoethyl 2,3,6-tri-O-ben-
zyl-i- -glucopyranoside (5).—A catalytic amount of
D
Ethyl 2-O-acetyl-3-O-allyl-4,6-O-benzylidene-1-thio-
i- -glucopyranoside (8).—A mixture of 6 (9.30 g, 30.0
p-TsOH was added to a solution of 1 (4.6 g, 19 mmol)13
and a,a-dimethoxytoluene (3.37 g, 22 mmol) in DMF
(70 mL). The mixture was heated at 50 °C for 24 h, and
then co-concentrated with toluene. Silica gel chro-
matography (1:1 toluene–EtOAc) gave 2-azidoethyl
D
mmol)16 and dibutyltin oxide (8.89 g, 35.7 mmol) in
MeOH (200 mL) was refluxed. After 1 h the mixture
was concentrated. The residue was dissolved in DMF
(100 mL) and allyl bromide (3.05 mL, 36.0 mmol) and
CsF (5.92 g, 39.0 mmol) were added. The mixture was
stirred at rt overnight and then concentrated. The
residue was dissolved in CH2Cl2 and washed with KF
(aq, sat), dried and concentrated. Silica gel chromatog-
raphy (4:1 toluene–EtOAc) gave ethyl 3-O-allyl-4,6-O-
4,6-O-benzylidene-b- -glucopyranoside (2, 4.3 g, 13
D
mmol, 70%); 13C NMR l 50.7 (OCH2CH2N3), 66.4,
68.6, 68.9, 73.0, 74.5, 80.4 (C-2-6, OCH2CH2N3), 101.9
(benzylidene), 103.3 (C-1), and 126.3–136.9 (aromatic
C). A solution of 2 (3.48 g, 10.4 mmol) and BnBr (7.10
g, 42 mmol) in dry DMF (40 mL) was added dropwise
to a cold (0 °C) suspension of NaH (2.08 g, 52 mmol) in
DMF (30 mL). The mixture was stirred at room tem-
perature (rt) overnight before the addition of MeOH
(20 mL). Toluene was added and the mixture was
washed with a saturated aqueous NaHCO3 and water.
The organic layer was dried, concentrated and purified
by chromatography (10:1 toluene–EtOAc) to give 2-
benzylidene-1-thio-b- -glucopyranoside (7, 7.16 g, 20.3
D
mmol, 67%) as a white solid together with some start-
ing material (6, 2.23 g, 7.1 mmol, 24%). 7: 13C NMR
(CDCl3): l 15.3 (SCH2CH3), 24.6 (SCH2CH3), 68.7,
70.8, 72.9, 73.7, 81.3, 81.3 (C-2-6, allyl CH2), 86.6
(C-1), 101.3 (benzylidene), 117.4 (allyl), 126.0, 128.3,
129.0, 134.9, and 137.2 (aromatic C, allyl). Compound
7 (1.97 g, 5.59 mmol) was dissolved in pyridine (50 mL)
and cooled to 0 °C. Acetic anhydride (50 mL) was
added and the mixture was stirred at rt for 1 h, diluted
with toluene and concentrated. The residue was purified
on a silica gel column (10:1 toluene–EtOAc) to give 8
(2.14 g, 5.41 mmol, 97%); [h]D −45° (c 1.0, CHCl3);
13C NMR (CDCl3): l 14.9 (SCH2CH3), 21.0 (CH3CO),
24.0 (SCH2CH3), 68.6, 70.7, 71.2, 73.4, 79.8, 81.3 (C-2-
6, allyl CH2), 84.2 (C-1), 101.1 (benzylidene), 116.7
(allyl), 125.9, 128.1, 128.9, 134.6, 137.0 (aromatic C,
allyl), and 169.3 (CH3CO). Anal. Calcd for C20H26O6S:
C, 60.89; H, 6.64. Found: C, 61.06; H, 6.74.
azidoethyl
2,3-di-O-benzyl-4,6-O-benzylidene-b-D-
glucopyranoside (3, 4.25 g, 8.2 mmol, 79%) as a white
solid; 13C NMR (CDCl3): l 51.0 (OCH2CH2N3), 66.1,
68.5, 68.7, 75.1, 75.4, 80.8, 81.4, 82.1 (C-2-6,
OCH2CH2N3, PhCH2O), 101.1 (benzylidene), 104.0 (C-
1), and 126.0–138.4 (aromatic C). Triphenylphosphine
(3.03 g, 12 mmol) was added at rt to a stirred solution
of 3 (3.97 g, 7.7 mmol) in CH2Cl2 (100 mL) and stirring
was continued at rt overnight. Water (50 mL) was
added and stirring was continued under reflux for 20 h
until all phosphine imine was hydrolysed. The organic
layer was concentrated and then co-concentrated twice
with toluene. Benzylchloroformate (1.75 mL, 12.3
mmol) was added at 0 °C to a stirred solution of the
amine in pyridine (50 mL). More benzylchloroformate
(550 mL, 3.85 mmol) was added after 30 min. After 1 h
the mixture was diluted with CH2Cl2, washed with
2-(N-Benzyloxycarbonyl)-aminoethyl (2-azido-4,6-O-
benzylidene - 2 - deoxy - i -
2,3,6-tri-O-benzyl-i- -glucopyranoside (12).—A mix-
ture of 8 (980 mg, 2.48 mmol) and 5 (1.04 g, 1.66
D
- mannopyranosyl) - (1“4)-
D
mmol) in dry CH2Cl2 containing powdered molecular

M. Alpe, S. Oscarson / Carbohydrate Research 337 (2002) 1715–1722
1719
,
sieves (4 A) was stirred under argon at rt for 1 h. The
129.0, 134.3, 136.5–138.8 (aromatic C, allyl), 156.4
(NHCOOBn). Compound 11 (850 mg, 0.90 mmol) was
dissolved in distilled THF (10 mL) and palladium on
carbon was added. The mixture was stirred for 5 min at
rt and then filtered. [Bis(methyldiphenylphos-
phine)](1,5-cyclooctadiene)iridium(I)PF6 (76 mg, 90
mmol) was added and the mixture was degassed and
then treated with H2 for 20 min (until the red colour
disappeared), then it was degassed again and NIS (1.01
g, 4.51 mmol) and water (4.5 mL, 252 mmol) were
added. After 30 min the solution was diluted with
CH2Cl2 and washed with Na2S2O3 (10% aq), NaHCO3
(aq, sat), dried and evaporated. Purification by silica gel
chromatography (3:1 toluene–EtOAc) gave 12 (667 mg,
0.74 mmol, 82%); [h]D −26° (c 1.0, CHCl3); 13C NMR
(CDCl3): l 41.3 (CH2NHCOOBn), 64.7 (C-2%), 66.8,
66.9, 68.3, 69.8, 70.0, 73.7, 74.1, 75.1, 75.3, 77.8, 78.3,
81.7, 82.9 (C-2-6, 3%-6%, PhCH2O, OCH2CH2N), 100.6,
102.1, 103.9 (C-1, 1%, benzylidene), 126.2–129.3, 136.5–
138.9 (aromatic C), and 156.4 (NHCOOBn). Anal.
Calcd for C50H54N4O12: C, 66.51; H, 6.03. Found: C,
66.43; H, 6.20.
solution was cooled to −30 °C, NIS (559 mg, 2.48
mmol) and TfOH (73 mL, 0.83 mmol) were added and
the mixture was stirred for 1 h at −30 °C. The mixture
was neutralized with NEt3 and filtered through Celite.
The filtrate was washed with Na2S2O3 (10% aq),
NaHCO3 (aq, sat) and water, dried and evaporated.
Purification by silica gel chromatography (3:1 toluene–
EtOAc) gave 2-(N-benzyloxycarbonyl)-aminoethyl (2-
O-acetyl-3-O-allyl-4,6-O-benzylidene-b-
syl)-(1“4)-2,3,6-tri-O-benzyl-b- -glucopyranoside (9,
D-glucopyrano-
D
1.34 g, 1.40 mmol, 84%); 13C NMR (CDCl3): l 20.8
(CH3CO), 41.3 (CH2NHCOOBn), 66.0, 66.6, 67.6,
68.5, 69.7, 73.1, 73.3, 73.6, 74.6, 75.0, 75.3, 76.7, 78.7,
81.3, 81.5, 82.6 (C-2-6, 2%-6%, PhCH2O, OCH2CH2N,
allyl CH2), 100.7, 101.1, 103.7 (C-1, -1%, benzylidene),
116.5 (allyl), 126.0–128.9, 134.7, 136.5–138.9 (aromatic
C, allyl), 156.4 (NHCOOBn), 169.0 (CH3CO). Com-
pound 9 (1.34 g, 1.40 mmol) was dissolved in 1:1
MeOH–CH2Cl2 (50 mL) and the pH was adjusted to
12 by treatment with 1 M methanolic NaOMe. The
mixture was stirred at rt for 3 h, neutralized with
Dowex 50 (H+) ion exchange resin, filtered and concen-
trated. Silica gel chromatography (3:1 toluene–EtOAc)
gave 2-(N-benzyloxycarbonyl)-aminoethyl (3-O-allyl-
Ethyl
3-O-acetyl-2,4,6-tri-O-benzyl-1-thio-i-D-
glucopyranoside (14).—To a solution of 13 (550 mg,
1.03 mmol)23 in 6:3:1 EtOH–toluene–H2O (30 mL) was
added tris(triphenylphosphine)rhodium(I) chloride (381
mg, 0.41 mmol). After 4 h more Wilkinson’s catalyst
(170 mg) was added. The mixture was refluxed for 24 h
and then cooled to rt. HgBr2 (741 mg, 2.06 mmol) was
added and the mixture was stirred at rt overnight,
filtered through Celite and concentrated. The residue
was dissolved in pyridine (10 mL) and cooled to 0 °C.
Acetic anhydride (10 mL) was added and the mixture
was stirred at rt for 2 h, diluted with toluene and
concentrated. Silica gel chromatography (9:1 toluene–
EtOAc) gave 14 (348 mg, 0.65 mmol, 63%); [h]D +6°
(c 1.0, CHCl3); 13C NMR (CDCl3): l 15.1 (SCH2CH3),
21.0 (CH3CO), 25.2 (SCH2CH3), 68.7, 73.5, 74.3, 74.8,
76.1, 77.4, 78.9, 79.6 (C-2-6, PhCH2O), 85.1 (C-1),
127.7–138.1 (aromatic C), and 169.9 (CH3CO).
4,6-O-benzylidene-b-
tri-O-benzyl-b- -glucopyranoside (10, 1.193 g, 1.30
D
-glucopyranosyl)-(1“4)-2,3,6-
D
mmol, 93%) as a white solid; 13C NMR (CDCl3): l 41.3
(CH2NHCOOBn), 66.3, 66.7, 68.2, 68.5, 69.8, 73.5,
73.6, 74.4, 74.9, 75.1, 75.2, 80.1, 81.2, 81.9, 83.3 (C-2-6,
2%-6%, PhCH2O, OCH2CH2N, allyl CH2), 101.1, 103.5,
103.9 (C-1, -1%, benzylidene), 117.2 (allyl), 125.3–129.0,
134.9, 136.5–138.9 (aromatic C, allyl), 156.4
(NHCOOBn). Trifluoromethanesulfonic anhydride
(502 mL, 2.98 mmol) was added at 0 °C and under
argon to a stirred solution of 10 (1.095 g, 1.19 mmol) in
distilled 2:1 CH2Cl2–pyridine (18 mL). The reaction
mixture was then left stirring overnight, slowly attain-
ing rt. After 20 h the mixture was diluted with CH2Cl2,
washed with NaHCO3 (aq, sat), dried and concen-
trated. The crude triflate was dried for 2 h in vacuum.
The dried triflate was dissolved in dry DMF (40 mL)
and NaN3 (388 mg, 5.96 mmol) was added. The reac-
tion mixture was stirred at 70 °C for 3 h, cooled to
0 °C, diluted with toluene, filtered through Celite and
concentrated. Silica gel chromatography (3:1 toluene–
EtOAc) gave 2-(N-benzyloxycarbonyl)-aminoethyl (3-
Ethyl
3-O-acetyl-2,4,6-tri-O-benzyl-1-thio-i-D-
galactopyranoside (16).—To a solution of 15 (270 mg,
0.55 mmol)27 in pyridine (3 mL) at 0 °C was added
acetic anhydride (3 mL). The mixture was stirred at rt
for 3 h and then co-concentrated with toluene. Silica gel
chromatography (15:1 toluene–EtOAc) gave 16 (267
mg, 0.50 mmol, 91%) as a yellow oil; [h]D +37° (c 1.1,
CHCl3); 13C NMR (CDCl3): l 15.0 (SCH2CH3), 20.9
(CH3CO), 25.0 (SCH2CH3), 68.3, 73.5, 74.6, 74.9, 75.4,
76.6, 76.8 (C-2-6, PhCH2O), 85.3 (C-1), 127.7–138.2
(aromatic C), and 170.3 (CH3CO). Anal. Calcd for
C31H36O6S: C, 69.38; H, 6.76. Found: C, 69.20; H, 6.71.
O-allyl-2-azido-4,6-O-benzylidene-2-deoxy-b-
D-manno-
pyranosyl)-(1“4)-2,3,6-tri-O-benzyl-b- -glucopyrano-
D
side (11, 0.85 g, 0.90 mmol, 76%) as a white solid
together with some starting material 10 (93 mg, 0.10
mmol, 8%). 11: 13C NMR (CDCl3):
l
41.3
(CH2NHCOOBn), 63.5 (C-2%), 66.7, 67.2, 68.3, 68.4,
69.8, 71.9, 73.6, 74.1, 75.0, 75.3, 76.6, 78.4, 81.7, 82.9
(C-2-6, 3%-6%, PhCH2O, OCH2CH2N, allyl CH2), 100.2,
101.5, 103.9 (C-1, 1%, benzylidene), 117.1 (allyl), 125.9–
2-(N-Benzyloxycarbonyl)-aminoethyl
benzyl-h- -glucopyranosyl)-(1“3)-(2-acetamido-4,6-
O-benzylidene-2-deoxy-i- -mannopyranosyl)-(1“4)-
2,3,6-tri-O-benzyl-i- -glucopyranoside (19).—A solu-
(2,4,6-tri-O-
D
D
D

1720
M. Alpe, S. Oscarson / Carbohydrate Research 337 (2002) 1715–1722
tion of 14 (150 mg, 0.28 mmol) and 12 (126 mg, 0.14
mmol) in 6:1 dry diethyl ether–CH2Cl2 (3.5 mL) con-
2-Aminoethyl h-
D
-glucopyranosyl-(1“3)-2-acetam-
-glucopy-
ido-2-deoxy-i- -mannopyranosyl-(1“4)-i-
D
D
,
taining powdered molecular sieves (4 A) was stirred at
ranoside (20).—To a solution of 19 (41 mg, 30 mmol)
dissolved in EtOH (3 mL) and AcOH (2 mL) was
added palladium hydroxide on activated carbon pow-
der and the mixture was hydrogenolyzed at 100 psi for
48 h. Additional catalyst was added after 24 h. The
mixture was centrifuged and the pellets were washed
once with EtOH. The supernatants were combined and
concentrated. The residue was dissolved in water and
washed with EtOAc, concentrated, and purified on a
Bio-Gel P-2 column to give, after freeze-drying, 20 (13
mg, 22 mmol, 73%); [h]D +123° (c 0.83, H2O); 13C
NMR (D2O): l 22.7 (CH3CON), 40.1 (CH2NH2), 53.5
(C-2%), 60.6, 61.0, 61.1, 66.5, 67.1, 70.0, 72.2, 72.9, 73.4,
73.5, 74.7, 75.1, 76.9, 79.0, 79.3 (C-2-6, 3%-6%, 2¦-6¦
OCH2CH2), 100.1, 101.2, 102.6 (C-1, 1%, 1¦), and 175.5
rt under an argon atmosphere for 1 h. To the mixture
was added DMTST (145 mg, 0.56 mmol) and the
stirring was continued for 30 min. After neutralization
with NEt3 (0.5 mL), the mixture was filtered through
Celite and concentrated. The residue was purified on a
silica gel column (4:1 toluene–EtOAc) to yield 2-(N-
benzyloxycarbonyl)-aminoethyl (3-O-acetyl-2,4,6-tri-O-
benzyl-a-
benzylidene - 2 - deoxy - b -
2,3,6-tri-O-benzyl-b- -glucopyranoside (17, 183 mg,
D
-glucopyranosyl)-(1“3)-(2-azido-4,6-O-
D
- mannopyranosyl) - (1“4)-
D
0.13 mmol, 93%); 13C NMR, l 21.0 (CH3CO), 41.3
(CH2NHCOOBn), 64.3 (C-2%), 66.7, 67.1, 68.4, 68.5,
69.7, 70.3, 70.7, 72.7, 73.6, 73.6, 74.2, 74.3, 75.1, 75.2,
75.3, 75.5, 75.8, 76.0, 78.1, 81.7, 82.9 (C-2-6, 3%-6%, 2¦-6¦,
OCH2CH2N, PhCH2O), 97.4 (C-1¦), 100.0, 102.2, 103.9
(C-1, 1%, benzylidene), 126.2–138.9 (aromatic C), 156.4
(NHCOOBn), 169.7 (CH3CO). To a solution of 17 (187
mg, 0.14 mmol) in EtOH (10 mL) and CH2Cl2 (2 mL)
were added NaBH4 (10 mg, 0.27 mmol) and a catalytic
amount of NiCl2·6H2O. After 3 h more NaBH4 (20 mg)
was added. The reaction mixture was stirred at rt for 6
h, when Ac2O (300 mL) was added. After 30 min the
reaction mixture was diluted with toluene and concen-
trated. Silica gel chromatography (1:1 toluene–EtOAc)
gave 2-(N-benzyloxycarbonyl)-aminoethyl (3-O-acetyl-
1
(CH3CON); H (selected signals), l 4.50 (d, 1 H, J1,2
7.7 Hz, H-1), 4.63 (d, 1 H, J2,3 4 Hz, H-2%), 4.88 (s, 1 H,
H-1%), 5.22 (d, 1 H, J1,2 3.8 Hz, H-1¦). MALDI-TOF
MS: Calcd for C22H40N2NaO16 ([M+Na]+): 611.23,
found 610.87.
2-(N-Benzyloxycarbonyl)-aminoethyl
benzyl-h- -galactopyranosyl)-(1“3)-2-acetamido-4,6-
O-benzylidene-2-deoxy-i- -mannopyranosyl-(1“4)-
2,3,6-tri-O-benzyl-i- -glucopyranoside (23).—Donor
(2,4,6-tri-O-
D
D
D
16 (214 mg, 0.40 mmol) and acceptor 12 (180 mg, 0.20
mmol) was coupled as described above for compounds
14 and 12 to yield 2-(N-benzyloxycarbonyl)-aminoethyl
2,4,6-tri-O-benzyl-a-
mido-4,6-O-benzylidene-2-deoxy-b-
(1“4)-2,3,6-tri-O-benzyl-b- -glucopyranoside (18, 142
D
-glucopyranosyl)-(1“3)-(2-aceta-
D
-mannopyranosyl)-
(3-O-acetyl-2,4,6-tri-O-benzyl-a-
(1“3) - (2 - azido - 4,6 - O - benzylidene - 2 - deoxy - b -
mannopyranosyl)-(1“4)-2,3,6-tri-O-benzyl-b- -gluco-
D-galactopyranosyl)-
D
D-
mg, 0.10 mmol, 72%); 13C NMR (CDCl3): l 21.1
(CH3CO), 22.8 (CH3CON), 41.3 (CH2NHCOOBn),
51.3 (C-2%), 66.7, 68.2, 68.5, 69.1, 70.0, 70.5, 72.5, 73.2,
73.6, 74.0, 74.6, 75.0, 75.2, 75.6, 76.2, 76.4, 80.0, 82.1,
83.4 (C-2-6, 3%-6%, 2¦-6¦, OCH2CH2N, PhCH2O), 96.8
(C-1¦), 100.1, 102.1, 103.9 (C-1, 1%, benzylidene), 126.1–
138.8 (aromatic C), 156.4 (NHCOOBn), 169.9, 170.6
(CH3CO and CH3CON). Compound 18 (80 mg, 57
mmol) was dissolved in 1:1 MeOH–CH2Cl2 (4 mL) and
the pH was adjusted to 12 by treatment with 1 M
methanolic NaOMe. The mixture was stirred at rt for 4
h, neutralized with Dowex 50 (H+) ion exchange resin,
filtered and concentrated. Silica gel chromatography
(1:3 toluene–EtOAc) gave 19 (59 mg, 44 mmol, 77%);
[h]D +26° (c 1.0, CHCl3); 13C NMR (CDCl3): l 23.1
(CH3CON), 41.3 (CH2NHCOOBn), 52.0 (C-2%), 66.5,
66.7, 68.1, 68.5, 68.9, 69.6, 70.0, 70.6, 72.4, 73.3, 73.5,
73.6, 74.5, 75.0, 75.1, 76.1, 77.5, 77.8, 79.8, 81.9, 83.3
(C-2-6, 3%-6%, 2¦-6¦, OCH2CH2N, PhCH2O), 96.9 (C-1¦),
99.9, 102.4, 103.9 (C-1, 1%, benzylidene), 126.3–138.9
(aromatic C), 156.4 (NHCOOBn) and 170.2
(CH3CON). Anal. Calcd for C79H86N2O18: C, 70.21; H,
6.41. Found: C, 69.93; H, 6.52. MALDI-TOF MS:
Calcd for C79H86N2NaO18 ([M+Na]+): 1373.58, found
1372.86.
D
pyranoside (21, 256 mg, 0.19 mmol, 93%) as a white
solid; 13C NMR (CDCl3): l 21.0 (CH3CO), 41.3
(CH2NHCOOBn), 64.3 (C-2%), 66.7, 67.1, 68.2, 68.4,
69.9, 70.9, 71.9, 72.4, 73.5, 74.3, 74.4, 74.6, 75.1, 75.4,
75.5, 75.8, 76.6, 77.8, 81.6, 82.8 (C-2-6, 3%-6%, 2¦-6¦,
OCH2CH2N, PhCH2O), 98.6 (C-1¦), 99.8, 102.1, 103.8
(C-1, 1%, benzylidene), 126.3–138.9 (aromatic C), 156.4
(NHCOOBn), and 170.3 (CH3CO). The azido group in
21 (166 mg, 0.12 mmol) was converted to an acetamido
group as described above for compound 17 to give
2-(N-benzyloxycarbonyl)-aminoethyl (3-O-acetyl-2,4,6-
tri-O-benzyl-a-
mido-4,6-O-benzylidene-2-deoxy-b-
(1“4)-2,3,6-tri-O-benzyl-b- -glucopyranoside (22, 130
D
-galactopyranosyl)-(1“3)-(2-aceta-
D
-mannopyranosyl)-
D
mg, 93 mmol, 78%) as a white solid; 13C NMR (CDCl3):
l 21.0 (CH3CO), 23.1 (CH3CON), 41.3 (CH2NH-
COOBn), 52.1 (C-2%), 66.5, 66.7, 68.2, 68.8, 69.2, 69.6,
70.7, 71.2, 73.0, 73.6, 74.3, 75.0, 75.1, 75.8, 76.2, 79.7,
81.8, 83.1 (C-2-6, 3%-6%, 2¦-6¦, OCH2CH2N, PhCH2O),
97.4 (C-1¦), 99.5, 102.2, 103.8 (C-1, 1%, benzylidene),
126.3–138.9 (aromatic C), 156.4 (NHCOOBn), 169.9
and 170.8 (CH3CO and CH3CON). Compound 22 (89
mg, 64 mmol) was deacetylated as 18 above to yield 23
(75 mg, 55 mmol, 86%); [h]D +27° (c 1.0, CHCl3); 13C

M. Alpe, S. Oscarson / Carbohydrate Research 337 (2002) 1715–1722
1721
NMR (CDCl3): l 23.5 (CH3CON), 41.6 (CH2NH-
COOBn), 52.9 (C-2%), 67.0, 68.4, 68.9, 69.8, 69.9, 70.2,
70.6, 73.3, 73.7, 74.6, 75.2, 75.3, 76.9, 79.9, 82.0, 83.4
(C-2-6, 3%-6%, -2¦-6¦, OCH2CH2N, PhCH2O), 97.4 (C-
1¦), 99.6, 102.6, 104.1 (C-1, 1%, benzylidene), 126.5–
139.3 (aromatic C), 156.7 (NHCOOBn), and 170.7
of 10“11. 28: 13C NMR (CDCl3): l −1.5 (CH3Si),
17.9 (CH2Si), 63.5 (C-2%), 67.2, 68.3, 68.7, 71.9, 73.5,
73.7, 74.6, 74.7, 77.8, 78.4, 81.2 (C-2-6, 3%-6%, PhCH2O,
allyl CH2, OCH2CH2Si), 100.4, 100.7, 101.5 (C-1, 1%,
benzylidene), 117.2 (allyl), 125.3–130.0, 132.9, 134.3,
137.3, 137.9, 138.3 (aromatic C, allyl), and 165.1
(PhCO). Compound 28 (188 mg, 0.21 mmol) was deal-
lylated as described for compound 11 to yield 29 (146
mg, 0.17 mmol, 82%); 13C NMR (CDCl3): l −1.4
(CH3Si), 18.0 (CH2Si), 64.7 (C-2%), 66.9, 67.2, 68.3,
68.5, 70.1, 73.4, 73.7, 74.6, 78.3, 80.9 (C-2-6, 3%-6%,
PhCH2O, OCH2CH2Si), 100.6, 100.7, 102.0 (C-1, 1%,
benzylidene), 126.1–130.0, 132.8, 136.8, 137.6, 138.2
(aromatic C), and 164.9 (PhCO). MALDI-TOF MS:
Calcd for C45H53N3NaO11Si ([M+Na]+): 862.33,
found 861.87.
(CH3CON).
MALDI-TOF
MS:
Calcd
for
C79H86N2NaO18 ([M+Na]+): 1373.58, found 1372.88.
Anal. Calcd for C79H86N2O18: C, 70.21; H, 6.41.
Found: C, 70.05; H, 6.55.
2-Aminoethyl
amido - 2 - deoxy - i -
h-
D
D
-galactopyranosyl-(1“3)-2-acet-
- mannopyranosyl - (1“4) - i -
D
-
glucopyranoside (24).—Compound 23 (33 mg, 24 mmol)
was deprotected as descibed for compound 19 above to
give, after purification on a Bio-Gel P-2 column, 24 (13
mg, 22 mmol, 91%) after freeze-drying; [h]D +15° (c
1.0, H2O); 13C NMR (D2O): l 22.6 (CH3CON), 40.1
(CH2NH2), 53.5 (C-2%), 60.6, 60.9, 62.2, 66.5, 67.3, 69.0,
69.9, 70.0, 72.0, 73.5, 74.7, 75.2, 77.0, 77.9, 79.3 (C-2-6,
3%-6%, 2¦-6¦ OCH2CH2), 100.1, 101.0, 102.7 (C-1, 1%, 1¦)
and 175.6 (CH3CON); 1H (selected signals), l 4.52 (d, 1
H, J1,2 8 Hz, H-1), 4.66 (d, 1 H, J2,3 4 Hz, H-2%), 4.91
(s, 1 H, H-1%), and 5.28 (d, 1 H, J1,2 3.6 Hz, H-1¦).
MALDI-TOF MS: Calcd for C22H40N2NaO16 ([M+
Na]+): 611.23, found 610.87.
2-(Trimethylsilyl)ethyl (3-O-allyl-2,4,6-tri-O-benzyl-
h-
dene-2-deoxy-i-
zoyl-3,6-di-O-benzyl-i-
D
-glucopyranosyl)-(1“3)-(2-azido-4,6-O-benzyli-
-mannopyranosyl)-(1“4)-2-O-ben-
-glucopyranoside (31).—
D
D
Donor 13 (38 mg, 71 mmol) and acceptor 29 (30 mg, 36
mmol) was coupled as described above for compounds
14 and 12 to yield 31 (41 mg, 31 mmol, 87%); 13C NMR
(CDCl3): l −1.4 (CH3Si), 18.0 (CH2Si), 64.4 (C-2%),
67.1, 68.3, 70.8, 71.2, 73.4, 73.5, 74.3, 74.4, 74.5, 74.6,
74.8, 75.0, 75.9, 77.4, 78.3, 78.3, 80.8, 80.9 (C-2-6, 3%-6%,
2¦-6¦, PhCH2O, OCH2CH2Si, allyl CH2), 97.5 (C-1¦),
100.1, 100.6, 102.2 (C-1, 1%, benzylidene), 116.5 (allyl),
126.2–138.3 (aromatic C, allyl), and 165.0 (PhCO).
MALDI-TOF MS: Calcd for C75H85N3NaO16Si ([M+
Na]+): 1334.56, found 1334.52.
2-(Trimethylsilyl)ethyl (2-azido-4,6-O-benzylidene-2-
deoxy-i-
D
-mannopyranosyl)-(1“4)-2-O-benzoyl-3,6-
di-O-benzyl-i-
D
-glucopyranoside (29).—Donor 8 (167
mg, 0.42 mmol) and acceptor 25 (159 mg, 0.28 mmol)22
was coupled as described above for compounds 8 and 5
to give 2-(trimethylsilyl)ethyl (2-O-acetyl-3-O-allyl-4,6-
2-(Trimethylsilyl)ethyl (3-O-allyl-2,4,6-tri-O-benzyl-
O-benzylidene-b-
D
-glucopyranosyl)-(1“4)-2-O-ben-
-glucopyranoside (26, 200 mg,
h-
dene-2-deoxy-i-
zoyl-3,6-di-O-benzyl-i-
D
-galactopyranosyl)-(1“3)-(2-azido-4,6-O-benzyli-
-mannopyranosyl)-(1“4)-2-O-ben-
-glucopyranoside (32).—
zoyl-3,6-di-O-benzyl-b-
D
D
0.22 mmol, 79%); 13C NMR (CDCl3): l −1.5 (CH3Si),
17.9 (CH2Si), 20.9 (CH3CO), 66.1, 67.0, 67.9, 68.5,
73.2, 73.3, 73.4, 73.7, 74.5, 75.3, 78.7, 80.6, 81.4 (C-2-6,
2%-6%, PhCH2O, allyl CH2, OCH2CH2Si), 100.6, 100.9,
101.1 (C-1, 1%, benzylidene), 116.6 (allyl), 126.0–130.2,
132.8, 134.8, 137.2, 138.1, 138.4 (aromatic C, allyl),
165.0 (PhCO), and 169.2 (CH3CO). Compound 26 (404
mg, 0.45 mmol) was deacetylated as described for com-
pound 9 but using Mg(OMe)2 instead of NaOMe to
obtain 2-(trimethylsilyl)ethyl (3-O-allyl-4,6-O-benzyli-
D
Donor 30 (42 mg, 79 mmol)24 and acceptor 29 (33 mg,
39 mmol) was coupled as described above for com-
pounds 14 and 12 to yield 32 (47 mg, 36 mmol, 91%);
13C NMR (CDCl3): l −1.3 (CH3Si), 18.0 (CH2Si), 64.6
(C-2%), 67.0, 67.1, 68.3, 68.4, 70.2, 70.6, 71.2, 72.2, 73.3,
73.5, 74.5, 74.5, 74.8, 75.0, 75.1, 75.3, 77.1, 77.8, 78.0,
80.8 (C-2-6, 3%-6%, 2¦-6¦, PhCH2O, OCH2CH2Si, allyl
CH2), 98.6 (JC-1, H-1 174 Hz) (C-1¦), 99.7 (JC-1, H-1 162
Hz), 100.6 (JC-1, H-1 165 Hz), 101.9 (JC-1, H-1 157 Hz)
(C-1, 1%, benzylidene), 116.2 (allyl), 126.2–138.4 (aro-
matic C, allyl), 164.9 (PhCO). MALDI-TOF MS: Calcd
for C75H85N3NaO16Si ([M+Na]+): 1334.56, found
1334.89.
dene-b-
D
-glucopyranosyl)-(1“4)-2-O-benzoyl-3,6-di-
-glucopyranoside (27, 257 mg, 0.30 mmol,
O-benzyl-b-
D
67%); 13C NMR (CDCl3): l −1.5 (CH3Si), 17.9
(CH2Si), 66.3, 67.1, 68.2, 68.6, 73.5, 73.6, 74.4, 74.8,
75.1, 77.6, 80.1, 81.3, 81.6 (C-2-6, 2%-6%, PhCH2O, allyl
CH2, OCH2CH2Si), 100.7, 101.1, 103.6 (C-1, 1%, benzyl-
idene), 117.2 (allyl), 126.0–130.0, 132.9, 134.9, 137.3.
137.7, 138.2 (aromatic C, allyl), and 165.0 (PhCO).
Compound 27 (239 mg, 0.28 mmol) was converted to
2-(trimethylsilyl)ethyl (3-O-allyl-2-azido-4,6-O-benzyli-
Acknowledgements
Financial support from EU (Contract Number BIO 4
CT 960158), from the Swedish Foundation for Strategic
Research (the Glycoconjugates in Biological Systems
programme) and from the Swedish Natural Science
Research Council are gratefully acknowledged.
dene-2-deoxy-b-
zoyl-3,6-di-O-benzyl-b-
0.24 mmol, 84%) as described above for the conversion
D
-mannopyranosyl)-(1“4)-2-O-ben-
D
-glucopyranoside (28, 208 mg,

1722
M. Alpe, S. Oscarson / Carbohydrate Research 337 (2002) 1715–1722
15. Pozsgay, V. Stereoselective Synthesis of b-Mannosides. In
References
Carbohydrates in Chemistry and Biology: A Comprehen-
si6e Handbook; Ernst, B.; Hart, G.; Sinay¨, P., Eds.;
Wiley-VCH: Weinheim, 2000; Vol. 1, pp 319–344.
16. Garegg, P. J.; Kvarnstro¨m, I.; Niklasson, A.; Niklasson,
G.; Svensson, S. C. T. J. Carbohydr. Chem. 1993, 12,
933–953.
1. Streptococcus pneumoniae, Thomasz, A., Ed.; Molecular
Biology & Mechanisms of Disease, Mary Ann Liebert,
Inc.: New York, 2000.
2. Lindberg, B.; Kenne, L. In The Polysaccharides; Aspinall,
G. O., Ed.; Academic Press: New York, 1995; Vol. 2, pp
287–363.
3. Kamerling, J. P. Pneumococcal Polysaccharides: A Chem-
ical View, In Ref. 1, pp. 81–114.
4. Jones, C.; Mulloy, B.; Wilson, A.; Dell, A.; Oates, J. E. J.
Chem. Soc., Perkin Trans. 1 1985, 1665–1673.
5. Richards, J. C.; Perry, M. B.; Kniskern, P. J. Can. J.
Biochem. 1984, 62, 1309–1320.
6. Perry, M. B.; Daoust, V.; Carlo, D. J. Can. J. Biochem.
1981, 59, 524–533.
7. McNeely, T. B.; Staub, J. M.; Rusk, C. M.; Blum, M. J.;
Donnelly, J. J. Infect. Immun. 1998, 66, 3705–3710.
8. Wyeth-Lederle: information available through: http://
www.prevnar.com.
9. Laferrie`re, C. A.; Sood, R. K.; deMuys, J.-M.; Michon,
F.; Jennings, H. J. Vaccine 1997, 15, 179–186.
10. Benaissa-Trouw, B.; Lefeber, D. J.; Kamerling, J. P.;
Vliegenthart, J. F. G.; Kraaijeveld, K.; Snippe, H. Infect.
Immun. 2001, 69, 4698–4701.
11. Jansson, K.; Ahlfors, S.; Frejd, T.; Kihlberg, J.; Magnus-
son, G. J. Org. Chem. 1988, 53, 5629–5647.
12. Paulsen, H.; Helpap, B.; Lorentzen, J. P. Carbohydr. Res.
1988, 179, 173–197.
17. Grindley, T. B. Ad6. Carbohydr. Chem. Biochem. 1998,
53, 17–142.
18. Konradsson, P.; Udodong, U. E.; Fraser-Reid, B. Tetra-
hedron Lett. 1990, 31, 4313–4316.
19. Veeneman, G. H.; van Boom, J. H. Tetrahedron Lett.
1990, 31, 275–278.
20. Fu¨gedi, P.; Garegg, P. J. Carbohydr. Res. 1986, 149,
C9–C12.
21. Garegg, P. J.; Oscarson, S.; Ritze´n, H.; Szo¨nyi, M.
Carbohydr. Res. 1992, 228, 121–128.
22. Hada, N.; Kuroda, M.; Takeda, T. Chem. Pharm. Bull.
2000, 48, 1160–1165.
23. Slaghek, T. M.; vanVliet, M. J.; Maas, A. M. M.; Kamer-
ling, J. P.; Vliegenhart, J. F. G. Carbohydr. Res. 1989,
195, 75–86.
24. Das, S. K.; Ghosh, R.; Roy, N. J. Carbohydr. Chem.
1993, 12, 693–701.
25. Oscarson, S. Thioglycosides. Glycosylation Methods. In
Carbohydrates in Chemistry and Biology: A Comprehen-
si6e Handbook; Ernst, B.; Hart, G.; Sinay¨, P., Eds.;
Wiley-VCH: Weinheim, 2000; Vol. 1, pp 93–116.
26. Lo¨nn, H. Chem. Commun. Stockholm Uni6. 1984, 2,
1–30.
13. Susaki, H.; Suzuki, K.; Ikeda, M.; Yamada, H.; Watan-
abe, H. K. Chem. Pharm. Bull. 1994, 42, 2090–2096.
14. Garegg, P. J.; Hultberg, H.; Wallin, S. Carbohydr. Res.
1982, 108, 97–101.
27. van Dorst, J. A. L. M.; van Heusden, C. J.; Tikkanen, J.
M.; Kamerling, J. P.; Vliegenthart, J. F. G. Carbohydr.
Res. 1997, 3, 209–228.