A strategy for chemical synthesis of selectively methyl-esterified oligomers of galacturonic acid

Article abstract of DOI:10.1039/b006981g

The synthesis of monomethyl-esterified trigalacturonans 1-3 is described as part of a general strategy towards pectic oligosaccharides. The necessary monomeric building blocks were all prepared on a large scale from galactose pentaacetate. The glycosylations were carried out between galactose glycosyl donors and acceptors using the n-pentenyl glycosylation technique. Yields of the desired α-anomers were in the 50 to 74% range. The trigalactans thus obtained were then subjected to oxidation at C-6. Depending on the protecting group at this position the oxidation either produced the carboxylic acid or the corresponding methyl ester. Hereby, oligomers of galacturonic acid can be prepared with methyl esters introduced in a regiocontrolled fashion.

Full text of DOI:10.1039/b006981g

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A strategy for chemical synthesis of selectively methyl-esterified
oligomers of galacturonic acid
Mads H. Clausen, Malene R. Jørgensen, Jesper Thorsen and Robert Madsen*
1
Department of Organic Chemistry, Technical University of Denmark, DK-2800 Lyngby,
Denmark
Received (in Cambridge, UK) 29th August 2000, Accepted 18th January 2001
First published as an Advance Article on the web 13th February 2001
The synthesis of monomethyl-esterified trigalacturonans 1–3 is described as part of a general strategy towards
pectic oligosaccharides. The necessary monomeric building blocks were all prepared on a large scale from galactose
pentaacetate. The glycosylations were carried out between galactose glycosyl donors and acceptors using the
n-pentenyl glycosylation technique. Yields of the desired α-anomers were in the 50 to 74% range. The trigalactans
thus obtained were then subjected to oxidation at C-6. Depending on the protecting group at this position the
oxidation either produced the carboxylic acid or the corresponding methyl ester. Hereby, oligomers of galacturonic
acid can be prepared with methyl esters introduced in a regiocontrolled fashion.
Introduction
Pectin is one of the main gelling agents used in the food indus-
try and a major polysaccharide in primary plant cell walls.1 Its
main structural feature is a linear chain of α(1→4)-linked
D-galacturonic acids, which are partially methyl esterified. Pec-
tin is degraded by a number of pectic enzymes including pectin
lyase, polygalacturonase, and pectin esterase.1 Pectin is an
extremely complex polysaccharide and degradation products
from pectin are very inhomogeneous. Several analytical tech-
niques have been applied to the analysis of smaller fragments of
pectin.2 However, the vast majority of pectin research so far
has concentrated on investigating pectin and pectic enzymes
from various sources on a macroscopic level.1 Owing to the
lack of well-defined and homogeneous fragments of pectin
few studies have been carried out on a molecular level.3
A particularly important task is to examine and understand
the substrate specificity of pectic enzymes using well-defined
galacturonans.4
The purpose of our programme is to use chemical synthesis
for de novo design of well-defined and partially esterified
monomer will then dictate whether these positions are oxidised
to the carboxylic acid or to its methyl ester. Acetyl groups and
p-methoxyphenyl (PMP) groups were chosen for the C-6
protection. These are orthogonal protecting groups which
are stable to the strongly acidic conditions used in glycosyl-
ation reactions. In addition, they are sterically non-demanding
groups and should not provide any significant hindrance for the
glycosylation at the 4-position, which was intended to be carried
out with pent-4-enyl galactosides. The n-pentenyl glycosyl-
ation technique8 was chosen because it provides a minimum of
manipulations at the anomeric center, and here, the n-pentenyl
group serves a dual function. First, it protects the anomeric
center during synthesis of the monomeric building blocks, and
secondly, at the time of the glycosylation it is also capable of
activating the anomeric center in the presence of strong electro-
philes. Three different monomeric building blocks are needed: a
benzyl galactoside C to serve as glycosyl acceptor for the
reducing end and two glycosyl donors A and B, the former for
the non-reducing end.
oligomers of galacturonic acid. Previously,
a synthetic
strategy towards larger oligomers of galacturonic acid was
developed, but with no partial esterification of the carboxylic
acids.5 Recently, an interesting method was demonstrated by
coupling of protected galacturonic acid glycosyl donors and
acceptors.6 However, these are not very reactive and as a result
not well suited for coupling of larger units. Instead, we decided
to concentrate on the use of galactose glycosyl donors and
acceptors which are significantly more reactive. For our
exploratory studies we decided to focus on the synthesis of
monomethylated trigalacturonates 1–3. These could be used to
demonstrate that methyl ester groups can be introduced at any
place in the galacturonic acid oligomer. In addition, com-
pounds 1–3 have very recently been used as the first partially
methyl esterified galacturonans in the study of pectic enzymes
from several fungi and bacteria.7
Monomer syntheses
These monomers were all prepared from galactose pentaacetate
(Scheme 2). Treatment with pent-4-enyl alcohol and BF3ؒ
OEt2 followed by deacetylation gave crystalline pent-4-enyl
β-galactoside 4. This can bifurcate to form glycosyl donors A
and B. For preparation of the former, the primary position was
first protected with a trityl group to give crystalline 5. Benzyl-
ation followed by subsequent removal of the trityl group gave 6.
Results and discussion
Retrosynthesis
The strategy requires a protected galactose oligomer to be
assembled (Scheme 1). The protecting groups at C-6 in each
DOI: 10.1039/b006981g
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This journal is © The Royal Society of Chemistry 2001
543

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Scheme 1
Scheme 2 Reagents and conditions: (i) pent-4–en-1-ol, BF3ؒOEt2, CH2Cl2; then NaOMe, MeOH; (ii) TrCl, pyridine, 90 ЊC; (iii) BnBr, NaH, Bu4NI,
DMF; then H2SO4, MeOH; (iv) Ac2O, Et3N, CH2Cl2; (v) p-methoxyphenol, PPh3, DEAD, THF; (vi) PhCH(OMe)2, CSA, CHCl3, 60 ЊC; (vii) BnBr,
NaH, Bu4NI, DMF; (viii) propane-1,3-diol, PTSA, MeOH, CH2Cl2; (ix) TsCl, pyridine; then p-methoxyphenol, NaH, DMF; (x) (ClCH2CO)2O,
Et3N, DMAP, CH2Cl2; (xi) BnOH, BF3ؒOEt2, CH2Cl2; then NaOMe, MeOH.
This could then be converted into the C-6 acetyl and PMP
glycosyl donors 7a and 7b.
promoter. First, PMP-protected glycosyl donor 11b and
acceptor 13b were coupled to give disaccharide 14 in 74% yield
of the pure α-anomer (Scheme 3). No attempts have been made
to isolate and identify a possible β-anomer in these couplings.
Subsequent removal of the chloroacetyl group gave alcohol 15.
In a similar manner, disaccharides 21 and 28 were prepared in
good yields by coupling of 11a and 13b as well as 11b and 13a.
However, the subsequent dechloroacetylation of 21 and 28 did
not proceed very well with thiourea and NaHCO3 in MeOH
due to concomitant partial removal of the primary acetates.
Instead, we discovered that thiourea in THF could effectively
promote the removal of chloroacetate if a catalytic amount of
Bu4NI was added. Hereby, disaccharide alcohols 22 and 29
were obtained in good yields. These were then ready for the next
coupling with 7b to produce trisaccharides 23 and 30. Both
coupling products were isolated as inseparable mixtures of α-
and β-anomers which were separated in the next reaction after
removal of the primary acetyl group. The last trisaccharide 16
was isolated as the pure α-anomer in 54% yield after coupling
of 7a and 15. In general, all these glycosylations proceeded well
with the desired α-anomers formed in yields ranging from 50
to 74%. The strategy should thus hold great promise for
future couplings to larger oligomers. In every coupling the
α-configuration at the newly generated stereogenic center has
been verified by NMR spectroscopy, and this is most easily
done by 13C NMR. For all di- and trigalactans the α-linked
anomeric carbons resonate at δC 99.5–101.0 while the β-linked
anomeric carbon at the reducing end is always found at
δC 102.5–103.5. This is in accord with literature observations for
galactose-containing oligosaccharides.11
For synthesis of glycosyl donor B, pent-4-enyl galactoside
4 was first temporarily protected with a 4,6-O-benzylidene
acetal. This was conveniently installed by reflux in chloroform
solution9 and the product 8 isolated by direct crystallisation.
Benzylation (to 9) and removal of the benzylidene acetal then
gave diol 10. Cleavage of the 4,6-benzylidene acetal did not go
to completion in acidic methanol alone and required the
addition of propane-1,3-diol to further shift the equilibrium.
Diol 10 was then selectively acetylated or p-methoxyphenylated
at the primary position. For protection of the 4-position a
chloroacetyl group was chosen to give glycosyl donors 11a and
11b. The chloroacetyl group has previously been removed
selectively in the presence of acetyl groups.10
For synthesis of glycosyl acceptor C, galactose pentaacetate
was treated with benzyl alcohol followed by deacetylation to
give benzyl β--galactopyranoside. This was subsequently
treated in the same way as the corresponding pent-4-enyl
galactoside 4 to provide diol 12. Selective acetylation or
p-methoxyphenylation then gave acceptors 13a and 13b. It is
noteworthy that most of the compounds for these monomer
syntheses are crystalline, thus making it easy to perform the
syntheses on a large scale.
Oligomer assembly
All glycosylation reactions were performed in CH2Cl2 at
Ϫ20 ЊC using N-iodosuccinimide (NIS) and a catalytic amount
of triethylsilyl trifluoromethanesulfonate (TESOTf) as the
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Scheme 3 Reagents and conditions: (i) NIS, TESOTf, CH2Cl2, Ϫ20 ЊC; (ii) thiourea, NaHCO3, MeOH, CH2Cl2; (iii) K2CO3, MeOH; (iv) Dess–
Martin periodinane, CH2Cl2, then NaClO2, NaH2PO4, 2-methylbut-2-ene, ButOH, aq. THF; then TMSCHN2, MeOH; (v) CAN, aq. MeCN, Ϫ10 ЊC;
(vi) Dess–Martin periodinane, CH2Cl2; then NaClO2, NaH2PO4, 2-methylbut-2-ene, ButOH, aq. THF; (vii) Pd/C, H2, aq. MeOH; (viii) thiourea,
NaHCO3, Bu4NI, THF, 55 ЊC.
Methyl esters can now be introduced at the positions where
acetyl groups are placed. On all three trisaccharides 16, 23, and
30 these acetyl groups were removed by transesterification with
K2CO3 in MeOH. Several procedures were investigated for oxi-
dation of the primary alcohol to the corresponding carboxylic
acid methyl ester. The oxidation turned out to be most
efficiently carried out by a one-pot three-step procedure. First,
the primary alcohols were oxidised to their corresponding
aldehydes with the Dess–Martin periodinane.12 The Swern
procedure13 worked equally well for this oxidation, but for
preparative purposes the Dess–Martin protocol was found to
be the most convenient. The aldehydes were not purified, but
treated directly with NaClO2 in the presence of 2-methylbut-2-
ene as scavenger14 to produce the corresponding carboxylic
acids. Severe oxidation of the benzyl groups occurred if
the scavenger was not added. These carboxylic acids were
then methyl esterified by (trimethylsilyl)diazomethane
(TMSCHN2)15 to produce trisaccharides 18, 25, and 32 in satis-
factory overall yields from the corresponding alcohols. The
remaining PMP-protected C-6 positions were now oxidised to
carboxylic acid. The PMP ethers were cleaved with cerium()
ammonium nitrate (CAN) to give diols 19, 26, and 33. These
were then oxidised in a one-pot two-step procedure using the
Dess–Martin periodinane followed by NaClO2 treatment to
give diacids 20, 27, and 34. Here, the neutral conditions of the
Dess–Martin oxidation turned out to be crucial. If the Swern
procedure was used for this oxidation to aldehyde, signifi-
cant decomposition occurred, presumably due to base-induced
β-elimination from the methyl esters. Final removal of the
benzyl groups proceeded cleanly via catalytic hydrogenation
to give selectively methyl-esterified trigalacturonans 1–3 with
NMR spectra in accordance with literature data.7
Conclusions
In conclusion, we have completed the synthesis of monomethyl-
esterified trigalacturonans 1–3 from D-galactose. The monomer
building blocks for the synthesis were easily prepared on a large
scale from galactose pentaacetate. The couplings were carried
out using pent-4-enyl glycosides to give good yields of the
desired α-anomers. Finally, oxidation of the C-6 positions was
performed under mild conditions, either to the methyl ester
or to the corresponding carboxylic acid. The present strategy
is believed to be a viable technique for preparation of larger
J. Chem. Soc., Perkin Trans. 1, 2001, 543–551
545

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oligomers of selectively methyl-esterified galacturonic acids.
Synthesis of these larger units is currently in progress.
(1 g, 2.7 mmol). The mixture was stirred at rt overnight, and
then quenched with MeOH, diluted with Et2O (700 cm3) and
washed with water (700 cm3). The organic layer was dried, con-
centrated and the residue was dissolved in 1% H2SO4 in MeOH
(290 cm3). After stirring of the mixture at rt for 1 h, solid
Na2CO3 (15 g) was added and the stirring was continued until
neutral pH was attained. The mixture was filtered and the fil-
trate concentrated to a syrup. This was dissolved in CH2Cl2 (300
cm3), washed with water (200 cm3), dried, concentrated, and
purified by flash chromatography (hexane–EtOAc; 2:1) to give
6 (14.5 g, 83%) as a syrup; Rf 0.31; [α]D20 Ϫ23.8 (c 0.8, CHCl3);
δH (CDCl3) 7.41–7.25 (m, 15H), 5.89–5.74 (m, 1H), 5.05–4.92
(m, 4H), 4.85–4.64 (m, 4H), 4.36 (d, 1H, J 7.6), 3.95 (dt, 1H,
J 9.5, 6.4), 3.84 (dd, 1H, J 9.7, 7.7), 3.81–3.73 (m, 2H), 3.57–
3.46 (m, 3H), 3.37 (t, 1H, J 6.2), 2.16 (m, 2H), 1.75 (m, 2H);
δC (CDCl3) 138.5, 138.3, 138.1, 138.0, 128.6–127.5 (15C), 114.7,
103.9, 82.1, 79.5, 75.1, 74.3, 74.0, 73.3, 72.6, 69.2, 61.9, 30.1,
28.8 (Calc. for C32H38O6: C, 74.11; H, 7.39%. Found: C, 74.14;
H, 7.39).
Experimental
General
Optical rotations were determined with a Perkin-Elmer 241
polarimeter. [α]D-Values are in units of 10Ϫ1 deg cm2 gϪ1. NMR
spectra were recorded on a Varian Mercury 300 spectrometer.
Chemical shifts were measured in ppm and coupling constants
(J) in Hz. For 13C NMR spectra in CDCl3 (δC = 76.9) and
CD3OD (δC = 49.0) the solvent was used as internal reference.
Mass spectra were obtained at Danisco Biotechnology by
MALDI-TOF on a Perseptive Biosystems Voyager-De instru-
ment in positive-ion mode using α-cyano-4-hydroxycinnamic
acid as the matrix. TLC was performed on aluminium sheets
precoated with silica gel (Merck 1.05554). Compounds were
visualised by charring after dipping in a solution of cerium()
sulfate (2.5 g) and ammonium molybdate (6.25 g) in 10% aq.
H2SO4 (250 cm3). Flash column chromatography was per-
formed using silica gel 60 (Amicon 85040). Microanalyses were
performed at the Department of Chemistry at the University of
Copenhagen.
Pent-4-enyl 6-O-acetyl-2,3,4-tri-O-benzyl-ꢀ-D-galactopyrano-
side 7a
A solution of 6 (4.0 g, 7.71 mmol), Ac2O (1.0 cm3, 10.6 mmol),
Et3N (1.6 cm3, 11.4 mmol) and 4-(dimethylamino)pyridine
(DMAP) (16 mg) in CH2Cl2 (75 cm3) was stirred at rt for 2 h
and then concentrated, and purified by flash chromatography
(hexane–EtOAc; 3:1) to give 7a (4.1 g, 95%) as a syrup; Rf 0.35;
[α]D20 Ϫ22.0 (c 1.3, CHCl3); δH (CDCl3) 7.40–7.20 (m, 15H), 5.79
(m, 1H), 5.11–4.88 (m, 4H), 4.80–4.62 (m, 4H), 4.33 (d, 1H,
J 8.0), 4.20 (dd, 1H, J 8.0, 11.0), 4.05 (dd, 1H, J 8.0, 11.0), 4.08–
3.70 (m, 3H), 3.58–3.40 (m, 3H), 2.15 (m, 2H), 1.95 (s, 3H), 1.75
(m, 2H); δC (CDCl3) 170.4, 138.6, 138.3, 138.1 (2C), 128.5–
127.5 (15C), 114.7, 103.9, 82.2, 79.4, 75.1, 74.2, 73.3, 72.8, 71.9,
69.3, 62.9, 30.1, 28.8, 20.7 (Calc. for C34H40O7: C, 72.83; H,
7.19%. Found: C, 72.25; H, 7.24).
Pent-4-enyl ꢀ-D-galactopyranoside 4
To a solution of galactose pentaacetate (35 g, 89.7 mmol) and
pent-4-en-1-ol (20 cm3, 194 mmol) in CH2Cl2 (250 cm3) was
added BF3ؒOEt2 (14 cm3, 110 mmol). The mixture was stirred at
rt under an atmosphere of nitrogen for 10 h, and then diluted
with CH2Cl2 (100 cm3) and washed with saturated aq. NaHCO3
(350 cm3). The organic layer was dried and concentrated. The
syrupy residue was dissolved in 0.04 M NaOMe in MeOH (300
cm3) and the solution stirred for 2 h. The mixture was quenched
with Amberlite IR-120 (Hϩ) (15 cm3) and stirred for an addi-
tional 30 min. The resin was filtered off and the filtrate concen-
trated, and purified by flash chromatography (CH2Cl2–MeOH;
6:1) to give 17.5 g of a greasy solid; Rf 0.30. Recrystallisation
from EtOAc afforded 4 (12.5 g, 56%) as white crystals; mp 88–
90 ЊC; [α]D20 Ϫ10.0 (c 1.6, H2O) [lit.,16 Ϫ9.02 (c 1.23, H2O)];
δH (D2O) 5.82 (m, 1H), 5.01 (d, 1H, J 17.4), 4.94 (d, 1H, J 10.2),
4.30 (d, 1H, J 8.0), 3.84 (m, 2H), 3.72–3.51 (m, 5H), 3.42 (t, 1H,
J 8.9), 2.07 (m, 2H), 1.65 (m, 2H); δC (D2O) 139.1, 115.0, 103.0,
75.3, 73.1, 71.0, 70.1, 68.9, 61.1, 29.6, 28.3 (Calc. for C11H20O6:
C, 53.22; H, 8.12%. Found: C, 53.42; H, 7.98).
Pent-4-enyl 2,3,4-tri-O-benzyl-6-O-(4-methoxyphenyl)-ꢀ-D-
galactopyranoside 7b
To a solution of 6 (5.9 g, 11.4 mmol), PPh3 (6.0 g, 23 mmol),
and p-methoxyphenol (5.8 g, 47 mmol) in dry THF (45 cm3)
was added diethyl azodicarboxylate (DEAD) (3.6 cm3, 23
mmol). The mixture was stirred at rt for 2 days during which
time additional amounts of PPh3 (3 g) and DEAD (1.8 cm3)
were added. Concentration and purification by flash chrom-
atography (hexane–EtOAc; 4:1) afforded 7b (5.2 g, 73%) as a
solid; Rf 0.54; mp 77.5–79 ЊC (from EtOH); [α]D20 Ϫ15.3 (c 0.8,
CHCl3); δH (CDCl3) 7.40–7.18 (m, 15H), 6.78 (m, 4H), 5.81 (m,
1H), 5.05–4.91 (m, 4H), 4.80 (d, 1H, J 12.0), 4.79 (d, 1H,
J 11.1), 4.75 (d, 1H, J 11.5), 4.62 (d, 1H, J 11.5), 4.40 (d,
1H, J 7.7), 3.99 (m, 3H), 3.95 (m, 1H), 3.86 (t, 1H, J 8.5), 3.78
(s, 3H), 3.69 (t, 1H, J 6.2), 3.58 (m, 1H), 3.54 (m, 1H), 2.16 (m,
2H), 1.75 (m, 2H); δC (CDCl3) 154.3, 152.8, 139.0, 138.7, 138.6,
138.4, 128.7–127.7 (15C), 115.7, 115.0, 114.8, 104.3, 82.5, 79.8,
75.4, 74.8, 73.5, 73.4, 73.1, 69.6, 67.1, 56.0, 30.5, 29.2 (Calc. for
C39H44O7: C, 74.98; H, 7.10%. Found: C, 74.73; H, 7.02).
Pent-4-enyl 6-O-trityl-ꢀ-D-galactopyranoside 5
A mixture of 4 (10.2 g, 41.1 mmol) and TrCl (12.6 g, 45.2
mmol) in dry pyridine (130 cm3) was heated at 90 ЊC for 3 h, and
then concentrated and co-concentrated with toluene. The resi-
due was dissolved in CH2Cl2 (150 cm3) and washed with water
(150 cm3). The organic layer was dried and concentrated. The
residue was crystallised from Et2O and recrystallised from
EtOAc–hexane to give 5 (17.6 g, 87%); Rf 0.48 (EtOAc); mp
89.0–91.5 ЊC; [α]D20 Ϫ27.6 (c 0.7, CHCl3); δH (CDCl3) 7.48–7.42
(m, 6H), 7.34–7.21 (m, 9H), 5.83 (m, 1H), 5.02 (dq, 1H, J 17.2,
1.7), 4.96 (dq, 1H, J 10.2, 1.7), 4.20 (d, 1H, J 7.2), 4.02 (t, 1H,
J 3.3), 3.93 (dt, 1H, J 9.7, 6.2), 3.65–3.35 (m, 6H), 2.55 (br d,
1H, J 5.9), 2.37 (br s, 1H), 2.28 (d, 1H, J 4.3), 2.13 (m, 2H), 1.75
(m, 2H); δC (CDCl3) 141.3 (3C), 135.5, 126.1 (6C), 125.3 (6C),
124.5 (3C), 112.4, 100.6, 84.3, 71.2, 71.1, 69.1, 66.8, 66.7, 60.2,
27.5, 26.2; m/z 513.30 (M ϩ Naϩ). Calc. for C30H34O6 ϩ Naϩ:
m/z, 513.23.
Pent-4-enyl 4,6-O-benzylidene-ꢀ-D-galactopyranoside 8
To a solution of PhCH(OMe)2 (33 cm3, 220 mmol) and
camphor-10-sulfonic acid (CSA) (450 mg) in CHCl3 (980 cm3)
was added 4 (38.5 g, 155 mmol). The flask was equipped with a
distillation head and the mixture heated at reflux for 1.5 h
during which time about 250 cm3 of a CHCl3–MeOH mixture
distilled off. The reaction mixture was quenched with Et3N (0.7
cm3) and concentrated to a solid, which was recrystallised from
EtOAc to give 8 (51.7 g, 99%); Rf 0.53 (EtOAc); mp 158–160 ЊC,
[α]D20Ϫ36.5 (c 1.5, CHCl3); δH (CDCl3) 7.49 (m, 2H), 7.35 (m,
3H), 5.81 (m, 1H), 5.54 (s, 1H), 5.04 (dq, 1H, J 17.1, 1.7), 4.97
(dq, 1H, J 10.4, 1.7), 4.32 (dd, 1H, J 12.5, 1.5), 4.26 (d, 1H,
J 7.3), 4.20 (dd, 1H, J 3.6, 1.5), 4.07 (dd, 1H, J 12.5, 1.9), 3.98
Pent-4-enyl 2,3,4-tri-O-benzyl-ꢀ-D-galactopyranoside 6
To a solution of 5 (16.5 g, 33.7 mmol) in DMF (130 cm3) was
added NaH (8 g of ~50% oil dispersion, 167 mmol). The
mixture was stirred at rt for 30 min and then cooled to 0 ЊC
followed by addition of BnBr (18 cm3, 152 mmol) and Bu4NI
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(dt, 1H, J 9.7, 6.6), 3.74 (dd, 1H, J 9.6, 7.3), 3.69 (dd, 1H, J 9.6,
3.6), 3.52 (dt, 1H, J 9.4, 7.0), 3.46 (m, 1H), 2.24–2.06 (br m,
4H), 1.76 (m, 2H); δC (CDCl3) 138.4, 137.8, 129.4, 128.4 (2C),
126.7 (2C), 115.1, 103.1, 101.6, 75.7, 73.0, 72.0, 69.6, 69.4, 66.9,
30.4, 28.9 (Calc. for C18H24O6: C, 64.27; H, 7.19%. Found: C,
64.51; H, 7.23).
and washed with 1 M aq. HCl (2 × 75 cm3). The organic phase
was dried and concentrated. To a solution of the residue in
DMF (10 cm3) was added a solution of sodium p-methoxy-
phenolate in DMF (prepared from 2.5 g of p-methoxyphenol
and 1.2 g of ~50% NaH oil dispersion in 15 cm3 of DMF). The
mixture was stirred for 2 days and then diluted with Et2O (100
cm3) and washed with water (2 × 60 cm3). The organic layer was
dried, concentrated, and purified by flash chromatography
(hexane–EtOAc; 4:1) to give 4.43 g of a syrup. This was treated
overnight with (ClCH2CO)2O (2.2 g), Et3N (1.8 cm3), and
DMAP (20 mg) in CH2Cl2 (50 cm3) followed by evaporation of
the solvent and flash chromatography (hexane–EtOAc; 5:1) to
afford 11b (4.77 g, 67%) as an oil; Rf 0.35; [α]D20 ϩ2.5 (c 0.9,
CHCl3); δH (CDCl3) 7.36–7.27 (m, 10H), 6.87–6.80 (m, 4H),
5.82 (m, 1H), 5.72 (d, 1H, J 2.4), 5.00 (m, 2H), 4.88 (d, 1H,
J 11.0), 4.78 (d, 1H, J 11.1), 4.74 (d, 1H, J 11.1), 4.57 (d, 1H,
J 11.5), 4.43 (d, 1H, J 7.3), 4.11 (m, 1H), 4.10 (s, 2H), 4.01–3.87
(m, 3H), 3.77 (s, 3H), 3.60 (m, 3H), 2.17 (m, 2H), 1.77 (m, 2H);
δC (CDCl3) 167.1, 154.6, 152.6, 138.6, 138.1, 137.8, 128.6–127.9
(10C), 116.2, 115.2, 114.9, 104.0, 79.3, 79.0, 75.6, 72.7, 71.6,
70.0, 69.2, 67.1, 55.9, 41.0, 30.4, 29.2 (Calc. for C34H39ClO8: C,
66.82; H, 6.43%. Found: C, 66.75; H, 6.53).
Pent-4-enyl 2,3-di-O-benzyl-4,6-O-benzylidene-ꢀ-D-galacto-
pyranoside 9
A mixture of 8 (51.6 g, 153 mmol) and NaH (28 g of ~50% oil
dispersion, 583 mmol) in DMF (500 cm3) was stirred at rt for
30 min and then cooled to 0 ЊC. BnBr (55 cm3, 462 mmol)
and Bu4NI (4 g, 11 mmol) were added and the solution stirred
at rt overnight before being quenched with MeOH, diluted
with CH2Cl2 (750 cm3) and washed with water (750 cm3).
The organic phase was dried, concentrated, and the residue was
crystallised from EtOAc–hexane to afford 9 (71.2 g, 90%); Rf
0.33 (hexane–EtOAc; 3:1); mp 114–117 ЊC, [α]D20 Ϫ27.8 (c 1.5,
CHCl3); δH (CDCl3) 7.55 (m, 2H), 7.41–7.26 (m, 13H), 5.82 (m,
1H), 5.50 (s, 1H), 5.07–4.90 (m, 3H), 4.81–4.72 (m, 3H), 4.39 (d,
1H, J 8.0), 4.31 (d, 1H, J 12.0), 4.12–3.96 (m, 3H), 3.84 (t, 1H,
J 8.7), 3.58–3.50 (m, 2H), 3.32 (s, 1H), 2.19 (m, 2H), 1.77 (m,
2H); δC (CDCl3) 139.1, 138.7, 138.4, 138.1, 129.1, 128.6 (2C),
128.5 (2C), 128.3 (2C), 128.2 (2C), 128.0 (2C), 127.9, 127.8,
126.8 (2C), 115.1, 103.9, 101.6, 79.4, 78.7, 75.6, 74.2, 72.3, 69.5
(2C), 66.6, 30.5, 29.2 (Calc. for C32H36O6: C, 74.40; H, 7.02%.
Found: C, 74.17; H, 6.73).
Benzyl 2,3-di-O-benzyl-ꢀ-D-galactopyranoside 12
A solution of galactose pentaacetate (25 g, 64 mmol), BnOH
(12 cm3, 116 mmol) and BF3ؒOEt2 (10 cm3, 79 mmol) in CH2Cl2
(200 cm3) was stirred at rt for 12 h, and then worked up and
deacetylated as described above for 4. Purification by flash
chromatography (acetone–EtOAc; 1:1) gave 15.8 g of a solid,
which on recrystallisation from MeCN gave 12.4 g of benzyl
β--galactopyranoside, mp 106–108 ЊC (lit.,17 99–100 ЊC).
A mixture of this material (10 g, 37 mmol), PhCH(OMe)2
(7.5 cm3, 50 mmol) and CSA (200 mg) in CHCl3 (175 cm3) was
heated at reflux for 1 h in a flask equipped with a distillation
head. About 50 cm3 of a CHCl3–MeOH mixture distilled off.
Benzyl 4,6-O-benzylidene-β--galactopyranoside crystallised
directly, 12.4 g, mp 195–198 ЊC (lit.,17 209–210 ЊC).
This was benzylated as described above for 8 to give, after
direct crystallisation from EtOAc, 16.8 g of benzyl 2,3-di-
O-benzyl-4,6-O-benzylidene-β--galactopyranoside, mp 162–
164 ЊC (lit.,17 169.5–170.5 ЊC).
This was deprotected as described above for 9 to give, after
direct crystallisation from EtOAc–hexane, 13.6 g of 12, mp
113–115 ЊC (lit.,17 116–117 ЊC).
Pent-4-enyl 2,3-di-O-benzyl-ꢀ-D-galactopyranoside 10
A solution of 9 (13.0 g, 25.2 mmol), propane-1,3-diol (9.1 cm3,
126 mmol) and toluene-p-sulfonic acid (PTSA) (100 mg, 0.6
mmol) in CH2Cl2 (70 cm3)–MeOH (70 cm3) was heated at reflux
for 96 h. The mixture was cooled, concentrated and purified by
flash chromatography (EtOAc–hexane; 1:1) to afford 10 (8.11
g, 75%) as a solid, Rf 0.15; mp 59–63 ЊC (from EtOAc); [α]D20
Ϫ2.5 (c 1.6, CHCl3); δH (CDCl3) 7.40–7.27 (m, 10H), 5.81 (m,
1H), 5.07–4.90 (m, 3H), 4.77–4.71 (m, 3H), 4.37 (d, 1H, J 7.7),
4.01–3.93 (m, 3H), 3.82 (dd, 1H, J 11.5, 4.8), 3.69–3.42 (m, 4H),
2.37 (br s, 2H), 2.16 (m, 2H), 1.76 (m, 2H); δC (CDCl3) 138.8,
138.2, 138.0, 128.7–127.8 (10C), 115.1, 104.0, 80.7, 79.1, 75.4,
74.2, 72.8, 69.6, 67.7, 62.8, 30.4, 29.2 (Calc. for C25H32O6: C,
70.07; H, 7.53%. Found: C, 69.88; H, 7.56).
Pent-4-enyl 6-O-acetyl-2,3-di-O-benzyl-4-O-chloroacetyl-ꢀ-D-
galactopyranoside 11a
Benzyl 6-O-acetyl-2,3-di-O-benzyl-ꢀ-D-galactopyranoside 13a
A solution of 10 (2.0 g, 4.67 mmol), Ac2O (0.5 cm3, 5.3 mmol)
and Et3N (1 cm3, 7.2 mmol) in dry CH2Cl2 (25 cm3) was stirred
overnight and then quenched with a drop of MeOH. After stir-
ring of the mixture for an additional 1 h, (ClCH2CO)2O (1.2 g,
7.0 mmol), Et3N (1 cm3) and DMAP (10 mg) were added. The
mixture was stirred for 3 h, and then concentrated, and purified
by flash chromatography (hexane–EtOAc; 3:1) to give 11a
(2.4 g, 94%) as a syrup; Rf 0.44; [α]D20 ϩ17.5 (c 1.1, CHCl3);
δH (CDCl3) 7.36–7.27 (m, 10H), 5.81 (m, 1H), 5.53 (m, 1H),
5.06–4.95 (m, 2H), 4.87 (d, 1H, J 11.0), 4.74 (d, 1H, J 11.0),
4.72 (d, 1H, J 11.0), 4.55 (d, 1H, J 11.0), 4.38 (m, 1H), 4.21–
4.14 (m, 4H), 3.94 (dt, 1H, J 9.5, 6.4), 3.80 (dt, 1H, J 0.9, 6.8),
3.62–3.52 (m, 3H), 2.16 (m, 2H), 2.07 (s, 3H), 1.76 (m, 2H);
δC (CDCl3) 170.6, 167.2, 138.6, 138.1, 137.7, 128.6–127.9 (10C),
115.2, 104.0, 79.1, 78.9, 75.6, 72.8, 70.6, 70.0, 68.9, 61.9, 41.1,
30.4, 29.1, 21.0 (Calc. for C29H35ClO8: C, 63.67; H, 6.45%.
Found: C, 63.25; H, 6.47).
A mixture of 12 (3.0 g, 6.7 mmol), Ac2O (0.7 cm3, 7.4 mmol)
and Et3N (1.4 cm3, 10 mmol) in dry CH2Cl2 (20 cm3) was stirred
overnight and then quenched with MeOH. The solution was
diluted with CH2Cl2 (30 cm3) and washed with water (30 cm3).
The organic phase was dried and concentrated to give a solid,
which was recrystallised from EtOAc–hexane to afford 13a (3.1
g, 95%); Rf 0.31 (hexane–EtOAc; 2:1); mp 99–103 ЊC; [α]D20
Ϫ17.7 (c 1.5, CHCl3); δH (CDCl3) 7.42–7.25 (m, 15H), 4.96 (d,
1H, J 11.0), 4.94 (d, 1H, J 11.0), 4.77–4.65 (m, 4H), 4.45 (d, 1H,
J 7.8), 4.37 (m, 2H), 3.93 (dd, 1H, J 3.6, 0.9), 3.72 (dd, 1H,
J 9.4, 7.8), 3.59 (dt, 1H, J 0.9, 6.3), 3.50 (dd, 1H, J 9.4, 3.5), 2.10
(s, 3H); δC (CDCl3) 171.0, 138.7, 138.0, 137.5, 128.7–127.8
(15C), 102.5, 80.7, 79.0, 75.4, 72.9, 72.1, 71.1, 67.0, 63.3, 21.1
(Calc. for C29H32O7: C, 70.72; H, 6.55%. Found: C, 70.62; H,
6.62).
Benzyl 2,3-di-O-benzyl-6-O-(4-methoxyphenyl)-ꢀ-D-galacto-
pyranoside 13b
Pent-4-enyl 2,3-di-O-benzyl-4-O-chloroacetyl-6-O-(4-methoxy-
phenyl)-ꢀ-D-galactopyranoside 11b
To an ice-cooled solution of 12 (3.5 g, 7.77 mmol) in dry
pyridine (10 cm3) was added TsCl (2.08 g, 10.9 mmol). The
mixture was stirred at rt for 6 h and then diluted with CH2Cl2
(60 cm3) and washed with 1 M aq. HCl (3 × 50 cm3). The
To an ice-cooled solution of 10 (5.0 g, 11.7 mmol) in pyridine
(35 cm3) was added TsCl (3.3 g, 17.3 mmol). The mixture was
stirred at rt overnight and then diluted with CH2Cl2 (100 cm3)
J. Chem. Soc., Perkin Trans. 1, 2001, 543–551
547

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organic phase was dried and concentrated. To a solution of
the residue in DMF (15 cm3) was added a solution of sodium
δH (CDCl3) 7.44–7.11 (m, 40H), 6.78 (s, 4H), 6.65–6.44 (m,
4H), 5.07 (m, 2H), 5.00–4.81 (m, 5H), 4.81–4.36 (m, 15H),
4.29–4.17 (m, 3H), 4.14–3.79 (m, 8H), 3.78–3.63 (m, 3H),
3.76 (s, 3H), 3.67 (s, 3H), 3.49 (dd, 1H, J 9.9, 2.8), 1.78
(s, 3H); δC (CDCl3) 170.0, 154.2, 154.0, 152.7, 152.5, 139.0–
137.8 (8C), 128.6–127.3 (40C), 115.6 (4C), 114.9 (2C), 114.7
(2C), 103.2, 100.6, 99.6, 81.2, 79.5, 79.0, 77.5, 77.3, 76.1, 75.3
(2C), 75.0 (2C), 74.7, 74.3, 73.7, 73.2, 73.0 (2C), 72.6, 71.2, 69.7,
68.5, 65.8, 64.9, 62.5, 56.0, 55.9, 20.9; m/z 1502.91 (M ϩ Naϩ).
Calc. for C90H94O19 ϩ Naϩ: m/z, 1501.63.
p-methoxyphenolate in DMF (prepared from 1.4
g of
p-methoxyphenol and 0.54 g of ~50% NaH oil dispersion in
5 cm3 of DMF). The mixture was stirred for 16 h and then
diluted with Et2O (70 cm3) and washed with water (2 × 50 cm3).
The organic layer was dried, concentrated, and purified by flash
chromatography (hexane–EtOAc; 3:1) to give 13b (3.37 g, 78%)
as an oil, which crystallised from EtOH to give 3.12 g of title
compound; Rf 0.31; mp 87–87.5 ЊC; [α]D20 Ϫ34.4 (c 1.0, CHCl3);
δH (CDCl3) 7.41–7.28 (m, 15H), 6.88 (m, 4H), 4.96 (d, 1H,
J 12.2), 4.95 (d, 1H, J 11.0), 4.75 (m, 3H), 4.69 (d, 1H, J 11.8),
4.51 (d, 1H, J 7.7), 4.31–4.18 (m, 2H), 4.11 (d, 1H, J 3.3), 3.79
(s, 3H), 3.74 (m, 2H), 3.56 (dd, 1H, J 9.7, 3.5), 2.09 (br s, 1H);
δC (CDCl3) 154.4, 153.0, 138.7, 138.0, 137.6, 128.7–127.8 (15C),
116.1, 114.9, 102.7, 80.9, 79.2, 75.5, 73.0, 72.9, 71.1, 67.7, 66.9,
56.0 (Calc. for C34H36O7: C, 73.36; H, 6.52%. Found: C, 73.47;
H, 6.55).
Benzyl O-(2,3,4-tri-O-benzyl-ꢁ-D-galactopyranosyl)-(1→4)-O-
[2,3-di-O-benzyl-6-O-(4-methoxyphenyl)-ꢁ-D-galactopyranosyl]-
(1→4)-2,3-di-O-benzyl-6-O-(4-methoxyphenyl)-ꢀ-D-galacto-
pyranoside 17
A mixture of 16 (530 mg, 0.358 mmol) and K2CO3 (150 mg) in
MeOH (15 cm3) was stirred overnight and then filtered and
concentrated. The residue was purified by flash chromato-
graphy (hexane–EtOAc; 2:1) to afford 17 (507 mg, 98%) as a
foam; Rf 0.45; [α]D20 ϩ31.9 (c 2.3, CHCl3); δH (CDCl3) 7.44–7.12
(m, 40H), 6.76 (s, 4H), 6.65–6.46 (m, 4H), 5.08 (d, 1H, J 13.5),
5.07 (d, 1H, J 13.5), 4.98 (d, 1H, J 11.9), 4.91–4.83 (m, 4H),
4.79–4.44 (m, 14H), 4.30–4.21 (m, 3H), 4.11–4.02 (m, 3H),
3.98–3.90 (m, 3H), 3.87–3.62 (m, 4H), 3.76 (s, 3H), 3.67 (s, 3H),
3.50 (m, 1H), 3.33 (m, 2H), 0.9 (br s, 1H); δC (CDCl3) 154.2,
153.9, 152.7, 152.6, 138.9–137.8 (8C), 128.6–127.4 (40C), 115.6
(2C), 115.5 (2C), 114.9 (2C), 114.7 (2C), 103.2, 100.5, 99.9,
81.1, 79.4, 79.0, 77.5, 76.2, 75.9 (2C), 75.5, 75.3, 75.1, 74.7,
73.7, 73.2, 73.1, 73.0 (2C), 72.9, 71.2, 70.8, 69.8, 65.9, 65.0, 62.5,
56.0, 55.9; m/z 1460.49 (M ϩ Naϩ). Calc. for C88H92O18 ϩ Naϩ:
m/z, 1459.62.
General procedure for glycosylation reactions
A mixture of the donor (1 mmol) and the acceptor (0.77 mmol)
was dried azeotropically with toluene, and then subjected
to high vacuum for 2 h. The mixture was dissolved in dry
CH2Cl2 (10 cm3), cooled to Ϫ20 ЊC, and treated with NIS (230
mg, 1.02 mmol) and TESOTf (0.03 cm3, 0.13 mmol). The reac-
tion mixture was stirred at Ϫ20 ЊC until TLC revealed full con-
version of the donor (15–45 min). The solution was diluted
with CH2Cl2 (15 cm3) and washed successively with 10% aq.
Na2S2O3 (15 cm3) and saturated aq. NaHCO3 (15 cm3). The
organic phase was dried and concentrated and the residue
purified by flash chromatography.
Benzyl O-[2,3-di-O-benzyl-4-O-chloroacetyl-6-O-(4-methoxy-
phenyl)-ꢁ-D-galactopyranosyl]-(1→4)-2,3-di-O-benzyl-6-O-
(4-methoxyphenyl)-ꢀ-D-galactopyranoside 14
Benzyl O-(methyl 2,3,4-tri-O-benzyl-ꢁ-D-galactopyranosyl-
uronate)-(1→4)-O-[2,3-di-O-benzyl-6-O-(4-methoxyphenyl)-ꢁ-
D-galactopyranosyl]-(1→4)-2,3-di-O-benzyl-6-O-(4-methoxy-
phenyl)-ꢀ-D-galactopyranoside 18
Syrup; Rf 0.54 (hexane–EtOAc; 2:1); [α]D20 ϩ18.5 (c 3.3, CHCl3);
δH (CDCl3) 7.47–7.09 (m, 25H), 6.83–6.49 (m, 8H), 5.81 (d, 1H,
J 2.0), 5.05–4.44 (m, 13H), 4.19 (m, 1H), 4.12 (d, 1H, J 7.0),
4.08–3.96 (m, 2H), 3.95 (s, 2H), 3.83–3.45 (m, 12H); δC (CDCl3)
166.5, 153.9 (2C), 152.2 (2C), 138.3–137.3 (5C), 128.3–127.2
(25C), 115.5 (2C), 115.2 (2C), 114.5 (2C), 114.3 (2C), 102.9,
100.5, 80.6, 78.5, 76.2, 75.3, 74.9, 74.8, 73.3, 73.0, 72.8, 71.9,
71.0, 69.9, 67.0, 65.9, 65.2, 55.5 (2C), 40.7 (Calc. for C63H65-
ClO14: C, 69.96; H, 6.06%. Found: C, 69.57; H, 6.14).
To a suspension of the Dess–Martin periodinane (259 mg,
0.611 mmol) in CH2Cl2 (10 cm3) was added a solution of 17
(585 mg, 0.407 mmol) in CH2Cl2 (7 cm3). The mixture was
stirred for 20 min and then quenched by addition of Et2O
(12 cm3) and saturated aq. NaHCO3 containing 3 g of Na2S2O3
(12 cm3). After being stirred for an additional 2 h the solution
was diluted with Et2O (10 cm3) and washed successively with
saturated aq. NaHCO3 (10 cm3) and water (10 cm3). The
organic phase was dried and concentrated. To a solution of the
residue in ButOH (7 cm3), THF (3 cm3), and 2-methylbut-2-ene
(2.2 cm3) were added NaClO2 (368 mg, 4.07 mmol) and NaH2-
PO4ؒH2O (0.4 g) in water (3 cm3). The mixture was stirred over-
night and then quenched with 1 M aq. HCl (10 cm3) and
extracted with EtOAc (2 × 20 cm3). The organic extracts were
dried and concentrated. To a solution of the residue in MeOH
(30 cm3) was added a 2 M solution of TMSCHN2 in hexanes
(3.2 cm3, 6.4 mmol). After being stirred overnight the solution
was concentrated, and purified by flash chromatography
(hexane–EtOAc; 3:1) to give 18 (339 mg, 57%) as a foam; Rf
0.14; [α]D20 ϩ3.5 (c 2.4, CHCl3); δH (CDCl3) 7.41–7.04 (m,
40H), 6.78 (s, 4H), 6.65–6.47 (m, 4H), 5.18 (d, 1H, J 3.8),
5.07 (d, 1H, J 3.4), 4.99–4.81 (m, 6H), 4.76–4.41 (m, 13H),
4.35 (br d, 1H, J 1.7), 4.24–4.17 (m, 3H), 4.09–4.04 (m, 2H),
3.97 (dd, 1H, J 10.7, 3.4), 3.88 (dd, 1H, J 10.7, 3.4), 3.80 (dd,
1H, J 10.3, 3.4), 3.76 (s, 3H), 3.75–3.62 (m, 4H), 3.67 (s, 3H),
3.48 (dd, 1H, J 10.0, 2.8), 3.22 (s, 3H); δC (CDCl3) 169.5,
154.0, 153.8, 152.5, 152.2, 138.6–137.6 (8C), 128.3–126.9
(40C), 115.3 (4C), 114.7 (2C), 114.5 (2C), 102.9, 100.5, 99.4,
81.0, 78.6 (2C), 77.9, 76.7, 74.9 (3C), 74.5, 74.4, 74.3, 73.6,
73.0, 72.8, 72.7 (2C), 71.8, 71.5, 71.0, 69.1, 65.4, 64.2, 55.7,
55.6, 51.7; m/z 1487.29 (M ϩ Naϩ). Calc. for C89H92O19 ϩ
Naϩ: m/z, 1487.61.
Benzyl O-[2,3-di-O-benzyl-6-O-(4-methoxyphenyl)-ꢁ-D-galacto-
pyranosyl]-(1→4)-2,3-di-O-benzyl-6-O-(4-methoxyphenyl)-ꢀ-D-
galactopyranoside 15
A mixture of 14 (1.81 g, 1.67 mmol), thiourea (1.3 g, 17 mmol)
and NaHCO3 (0.7 g, 8.3 mmol) in MeOH (25 cm3)–CH2Cl2 (25
cm3) was heated at 50 ЊC overnight and then diluted with
CH2Cl2 (150 cm3) and washed with saturated aq. NaHCO3
(150 cm3). The organic phase was dried, concentrated and puri-
fied by flash chromatography (hexane–EtOAc; 3:1) to give 15
(1.29 g, 77%) as a foam; Rf 0.32; [α]D20 ϩ21.6 (c 2.6, CHCl3);
δH (CDCl3) 7.44–7.13 (m, 25H), 6.76–6.57 (m, 8H), 5.07–4.40
(m, 14H), 4.26 (m, 1H), 4.18 (d, 1H, J 3.0), 4.12–3.42 (m, 14H),
2.05 (br s, 1H); δC (CDCl3) 153.8 (2C), 152.6, 152.6, 138.4–
137.4 (5C), 128.3–127.2 (25C), 115.3 (4C), 114.5 (2C), 114.3
(2C), 102.8, 100.3, 80.7, 78.7, 77.7, 75.6, 75.0 (2C), 73.3, 72.9,
72.6, 72.0, 71.0, 68.0, 66.8, 66.6, 65.6, 55.6 (2C) (Calc. for
C61H64O13: C, 72.89; H, 6.42%. Found: C, 72.43; H, 6.28).
Benzyl O-(6-O-acetyl-2,3,4-tri-O-benzyl-ꢁ-D-galactopyranosyl)-
(1→4)-O-[2,3-di-O-benzyl-6-O-(4-methoxyphenyl)-ꢁ-D-galacto-
pyranosyl]-(1→4)-2,3-di-O-benzyl-6-O-(4-methoxyphenyl)-
ꢀ-D-galactopyranoside 16
Syrup; Rf 0.49 (hexane–EtOAc; 2:1); [α]D20 ϩ36.1 (c 1.1, CHCl3);
548
J. Chem. Soc., Perkin Trans. 1, 2001, 543–551

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Benzyl O-(6-O-acetyl-2,3-di-O-benzyl-ꢁ-D-galactopyranosyl)-
(1→4)-2,3-di-O-benzyl-6-O-(4-methoxyphenyl)-ꢀ-D-galacto-
Benzyl O-(methyl 2,3,4-tri-O-benzyl-ꢁ-D-galactopyranosyl-
uronate)-(1→4)-O-(2,3-di-O-benzyl-ꢁ-D-galactopyranosyl)-
(1→4)-2,3-di-O-benzyl-ꢀ-D-galactopyranoside 19
pyranoside 22
To a solution of 18 (303 mg, 0.207 mmol) in MeCN (7 cm3) at
Ϫ10 ЊC was added aq. CAN (1.2 g, 2.2 mmol in 2 cm3). The
mixture was stirred at Ϫ10 ЊC for 30 min and then diluted with
CHCl3 (20 cm3) and washed with water (2 × 15 cm3). The
organic phase was dried, concentrated and purified by flash
chromatography (hexane–EtOAc; 3:2) to give 19 (210 mg, 81%)
as a foam; Rf 0.12; [α]D20 ϩ48.3 (c 0.8, CHCl3); δH (CDCl3) 7.42–
7.22 (m, 40H), 5.01 (d, 1H, J 3.4), 4.98 (d, 1H, J 3.4), 4.93 (d,
1H, J 7.3), 4.91–4.55 (m, 16H), 4.41 (d, 1H, J 7.7), 4.34 (t, 1H,
J 2.1), 4.14 (dd, 1H, J 10.2, 3.4), 4.08 (d, 1H, J 2.9), 4.04 (t, 1H,
J 6.2), 4.00–3.95 (m, 3H), 3.88 (dd, 1H, J 10.7, 3.2), 3.72–3.62
(m, 4H), 3.59 (dd, 1H, J 11.1, 6.0), 3.48–3.37 (m, 2H), 3.43 (s,
3H), 1.73 (br s, 2H); δC (CDCl3) 169.7, 138.9–137.8 (8C), 128.9–
127.4 (40C), 103.3, 100.5, 100.3, 80.8, 79.4, 78.9, 77.6, 77.1,
76.8, 76.4, 76.2, 75.7, 75.4, 75.0, 74.7, 74.6, 74.3, 73.1 (2C), 72.0
(3C), 71.5, 61.6, 60.5, 52.3; m/z 1276.27 (M ϩ Naϩ). Calc. for
C75H80O17 ϩ Naϩ: m/z, 1275.53.
To a solution of 21 (1.0 g, 0.98 mmol) in THF (12 cm3) were
added thiourea (150 mg, 2.0 mmol), NaHCO3 (180 mg, 2.1
mmol) and Bu4NI (18 mg, 0.05 mmol). The mixture was heated
at 55 ЊC overnight and then diluted with CH2Cl2 (50 cm3) and
washed with water (50 cm3). The organic layer was dried, con-
centrated, and purified by flash chromatography (hexane–
EtOAc; 3:1) to afford 22 (790 mg, 85%) as a foam; Rf 0.25; [α]D20
ϩ32.7 (c 0.8, CHCl3); δH (CDCl3) 7.46–7.25 (m, 25H), 6.78–
6.68 (m, 4H), 5.05 (d, 1H, J 3.5), 4.99 (d, 1H, J 11.4), 4.98
(d, 1H, J 11.4), 4.97 (s, 1H), 4.86 (d, 1H, J 12.6), 4.85 (d, 1H,
J 10.9), 4.80–4.67 (m, 5H), 4.59 (d, 1H, J 12), 4.57 (d, 1H,
J 7.5), 4.45 (m, 2H), 4.48–4.02 (m, 6H), 3.89–3.67 (m, 3H),
3.76 (s, 3H), 3.51 (dd, 1H, J 9.8, 2.9), 1.94 (s, 3H); δC (CDCl3)
170.7, 154.2, 152.6 (2C), 138.9, 138.6, 138.3, 137.7, 128.7–127.6
(25C), 115.8 (2C), 114.9 (2C), 103.1, 100.2, 80.4, 79.2, 77.8,
76.1, 75.2 (2C), 73.7, 73.3, 72.7, 72.5, 71.3, 68.0, 67.4, 66.3, 63.0,
56.0, 21.1 (Calc. for C56H60O13: C, 71.47; H, 6.43%. Found: C,
71.02; H, 6.47).
Benzyl O-(methyl 2,3,4-tri-O-benzyl-ꢁ-D-galactopyranosyl-
uronate)-(1→4)-O-(2,3-di-O-benzyl-ꢁ-D-galactopyranosyluronic
acid)-(1→4)-2,3-di-O-benzyl-ꢀ-D-galactopyranosyluronic acid 20
Benzyl O-[2,3,4-tri-O-benzyl-6-O-(4-methoxyphenyl)-ꢁ-D-
galactopyranosyl]-(1→4)-O-(6-O-acetyl-2,3-di-O-benzyl-ꢁ-D-
galactopyranosyl)-(1→4)-2,3-di-O-benzyl-6-O-(4-methoxy-
phenyl)-ꢀ-D-galactopyranoside 23
Diol 19 (192 mg, 0.153 mmol) was oxidised with the Dess–
Martin periodinane (195 mg, 0.460 mmol) and then with
NaClO2 (278 mg, 3.07 mmol) as described above for 17 to give
20 (141 mg, 72%) after purification by flash chromatography
(EtOAc–hexane; 2:1 ϩ 3% AcOH); Rf 0.15; [α]D20 ϩ72.6 (c 0.6,
CHCl3); δH (CDCl3) 7.52–7.08 (m, 40H), 5.38 (br s, 1H), 5.23
(d, 1H, J 3.3), 5.05 (d, 1H, J 11.7), 4.94–4.39 (m, 20H), 4.18–
4.11 (m, 3H), 3.90 (s, 3H), 3.86 (m, 1H), 3.69–3.52 (m, 4H);
δC (CD3OD) 170.8, 170.4, 170.0, 138.9–137.9 (8C), 128.6–127.2
(40C), 102.8, 98.3, 97.7, 79.7, 77.8, 77.6, 76.6, 76.1, 76.0, 75.1,
74.6 (2C), 74.5, 73.2, 73.1, 73.0, 72.4 (2C), 72.2, 71.5, 71.3, 71.2,
70.8, 51.2; m/z 1304.46 (M ϩ Naϩ). Calc. for C75H76O19 ϩ Naϩ:
m/z, 1303.49.
Syrup; Rf 0.15 (hexane–EtOAc; 3:1); [α]D20 ϩ14.7 (c 0.9, CHCl3);
δH (CDCl3) 7.46–7.12 (m, 40H), 6.82–6.54 (m, 8H), 5.11 (d, 1H,
J 3.3), 5.05–3.54 (m, 35H), 3.78 (s, 3H), 3.77 (s, 3H), 3.49 (dd,
1H, J 9.8, 2.9), 1.93 (s, 3H); δC (CDCl3) 170.1, 154.0 (2C), 152.8,
152.7, 139.1–137.9 (8C), 128.9–127.5 (40C), 115.7 (2C), 115.5
(2C), 114.9 (2C), 114.7 (2C), 103.1, 100.6, 100.3, 79.9, 79.7,
79.3, 77.9, 76.5, 75.9, 75.2, 75.0, 74.8, 74.5, 74.2, 73.6, 73.3,
73.2, 72.9, 72.8, 72.5, 71.3, 69.5, 69.4, 66.1, 65.7, 62.1, 56.0,
55.9, 21.2 (Calc. for C90H94O19: C, 73.05; H, 6.40%. Found: C,
72.99; H, 6.56).
Benzyl O-[2,3,4-tri-O-benzyl-6-O-(4-methoxyphenyl)-ꢁ-D-
galactopyranosyl]-(1→4)-O-(2,3-di-O-benzyl-ꢁ-D-galacto-
pyranosyl)-(1→4)-2,3-di-O-benzyl-6-O-(4-methoxyphenyl)-ꢀ-D-
galactopyranoside 24
O-(Methyl ꢁ-D-galactopyranosyluronate)-(1→4)-O-(ꢁ-D-
galactopyranosyluronic acid)-(1→4)-D-galactopyranuronic acid 1
A solution of 20 (280 mg, 0.219 mmol) in MeOH (40 cm3)–
water (10 cm3) was hydrogenated over 10% Pd/C (200 mg) at 1
atm H2 pressure for 7 h. The catalyst was removed by filtration
through Celite and rinsed successively with MeOH and water.
The filtrate was concentrated to give 1 (107 mg, 87%) as a foam,
which was pure by NMR; Rf 0.43 (MeOH–H2O; 2:1 ϩ 3%
AcOH); δH (D2O) 5.26 (d, 0.4H, J 3.7, H1α), 5.07 (m, 2H), 5.03
(d, 1H, J 3.8, H1Ј), 4.76 (d, 0.4H, J 0.8), 4.71 (s, 1H), 4.68–4.63
(signals hidden under HDO peak), 4.55 (d, 0.6H, J 8.0, H1β),
4.40–4.32 (m, 2.6H), 4.27 (m, 1H), 4.01–3.92 (m, 2H), 3.87 (dd,
1H, J 10.3, 3.4), 3.77 (m, 0.6H), 3.74 (s, 3H), 3.72–3.68 (m,
1.6H), 3.67 (dd, 1H, J 10.0, 3.8), 3.44 (dd, 0.6H, J 9.5, 8.0);
δC (D2O) 175.4, 174.6, 171.7, 99.6, 99.3, 99.1, 96.4, 92.4, 78.8,
78.2, 77.3, 74.4, 72.5, 71.7, 71.6, 71.4, 70.8, 70.3, 69.0 (2C), 68.4,
68.2, 53.0.
Deacetylation of 23 as described above for 16 gave 24 as a
foam; Rf 0.50 (hexane–EtOAc; 2:1); [α]D20 ϩ20.0 (c 0.8, CHCl3);
δH (CDCl3) 7.48–7.17 (m, 40H), 6.87–6.55 (m, 4H), 6.78 (s, 4H),
5.09–4.52 (m, 19H), 4.38 (m, 1H), 4.29–3.45 (m, 23H), 3.24 (br
s, 1H); δC (CDCl3) 154.2, 154.1, 152.8, 152.7, 139.0–137.9 (8C),
128.9–127.2 (40C), 115.7 (2C), 115.5 (2C), 114.9 (2C), 114.8
(2C), 103.2, 101.0, 100.7, 80.4, 79.6, 79.1 (2C), 78.1, 76.7, 75.6,
75.3 (2C), 75.0, 74.7 (2C), 73.5, 73.3, 72.9, 72.8, 72.7, 71.3, 71.0,
69.8, 65.9 (2C), 61.3, 56.0 (2C) (Calc. for C88H92O18: C, 73.52;
H, 6.45%. Found: C, 72.99; H, 6.38).
Benzyl O-[2,3,4-tri-O-benzyl-6-O-(4-methoxyphenyl)-ꢁ-D-
galactopyranosyl]-(1→4)-O-(methyl 2,3-di-O-benzyl-ꢁ-D-
galactopyranosyluronate)-(1→4)-2,3-di-O-benzyl-6-O-
(4-methoxyphenyl)-ꢀ-D-galactopyranoside 25
Benzyl O-(6-O-acetyl-2,3-di-O-benzyl-4-O-chloroacetyl-ꢁ-D-
galactopyranosyl)-(1→4)-2,3-di-O-benzyl-6-O-(4-methoxy-
phenyl)-ꢀ-D-galactopyranoside 21
Oxidation and methyl esterification of 24 as described above for
17 gave 25 as a syrup; Rf 0.42 (hexane–EtOAc; 3:1); [α]D20 ϩ21.9
(c 1.3, CHCl3); δH (CDCl3) 7.36–7.03 (m, 40H), 6.75–6.40 (m,
4H), 6.69 (s, 4H), 5.11 (d, 1H, J 3.1), 4.95–4.36 (m, 20H), 4.29
(dd, 1H, J 8.3, 5.2), 4.21 (d, 1H, J 3.3), 4.08–3.34 (m, 12H), 3.67
(s, 3H), 3.66 (s, 3H), 3.17 (s, 3H); δC (CDCl3) 169.5, 154.3,
154.0, 152.9, 152.5, 139.2–137.8 (8C), 128.7–127.3 (40C), 115.6
(4C), 115.0 (2C), 114.7 (2C), 103.3, 100.3, 100.1, 80.4, 79.5,
78.6, 77.9, 77.6, 76.0, 75.2 (2C), 75.0, 74.9, 74.3, 74.0, 73.5 (2C),
73.1, 72.9, 72.2, 71.6, 71.4, 69.8, 66.2, 65.0, 56.0, 55.9, 52.1
(Calc. for C89H92O19: C, 72.93; H, 6.33%. Found: C, 72.67;
H, 6.50).
Syrup; Rf 0.37 (hexane–EtOAc; 3:1); [α]D20 ϩ43.9 (c 0.9, CHCl3);
δH (CDCl3) 7.45–7.16 (m, 25H), 6.72 (m, 4H), 5.61 (m, 1H),
4.99 (m, 3H), 4.88–4.43 (m, 11H), 4.20–4.09 (m, 4H), 4.05–3.97
(m, 4H), 3.81–3.63 (m, 2H), 3.75 (s, 3H), 3.50 (dd, 1H, J 10.9,
2.9), 1.95 (s, 3H); δC (CDCl3) 170.3, 167.1, 154.3, 152.5, 138.8,
138.6, 138.4, 138.0, 137.7, 128.7–127.6 (25C), 115.7 (2C), 114.9
(2C), 103.2, 100.3, 80.4, 79.0, 76.2, 75.2 (3C), 73.7, 73.3, 73.2,
72.3, 71.4, 70.0, 66.7, 65.7, 61.4, 56.0, 41.0, 20.9 (Calc. for
C58H61ClO14: C, 68.46; H, 6.04%. Found: C, 68.08; H, 5.94).
J. Chem. Soc., Perkin Trans. 1, 2001, 543–551
549

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Benzyl O-(2,3,4-tri-O-benzyl-ꢁ-D-galactopyranosyl)-(1→4)-O-
(methyl 2,3-di-O-benzyl-ꢁ-D-galactopyranosyluronate)-(1→4)-
2,3-di-O-benzyl-ꢀ-D-galactopyranoside 26
J 9.9, 2.9), 2.05 (s, 3H), 1.70 (br s, 1H); δC (CDCl3) 170.4, 153.7,
152.6, 138.3–137.3 (5C), 128.3–127.5 (25C), 115.3 (2C), 114.3
(2C), 102.6, 100.6, 80.5, 78.5, 76.3, 75.9, 75.6, 74.9, 73.7, 72.8,
72.2, 72.1, 71.0, 68.1, 66.8, 66.6, 52.3, 55.5, 20.8 (Calc. for
C56H60O13: C, 71.47; H, 6.43%. Found: C, 71.35; H, 6.37).
Deprotection of 25 as described above for 18 gave 26 as a foam;
Rf 0.12 (EtOAc–hexane; 3:2); [α]D20 ϩ39.0 (c 0.9, CHCl3); δH
(CDCl3) 7.41–7.23 (m, 40H), 5.13 (s, 1H), 5.02 (d, 1H, J 3.0),
4.95 (d, 1H, J 8.9), 4.93–4.86 (m, 3H), 4.84–4.53 (m, 13H), 4.47
(s, 1H), 4.43 (d, 1H, J 7.5), 4.06–3.89 (m, 6H), 3.85 (s, 1H), 3.79
(m, 2H), 3.69–3.54 (m, 2H), 3.44–3.31 (m, 3H), 3.37 (s, 3H),
2.12 (br s, 2H); δC (CDCl3) 169.1, 138.7–138.1 (8C), 128.7–
127.6 (40C), 103.2, 100.1, 99.7, 80.2, 79.3, 79.0, 77.8, 77.4, 76.8,
76.0, 75.8, 75.7, 75.2, 74.7, 74.5, 74.4, 73.6 (2C), 73.1, 72.4, 71.9,
71.5 (2C), 62.8, 60.9, 52.2 (Calc. for C75H80O17: C, 71.87; H,
6.43%. Found: C, 71.45; H, 6.41).
Benzyl O-[2,3,4-tri-O-benzyl-6-O-(4-methoxyphenyl)-ꢁ-D-
galactopyranosyl]-(1→4)-O-[2,3-di-O-benzyl-6-O-(4-methoxy-
phenyl)-ꢁ-D-galactopyranosyl]-(1→4)-6-O-acetyl-2,3-di-O-
benzyl-ꢀ-D-galactopyranoside 30
Foam; Rf 0.13 (hexane–EtOAc; 3:1); [α]D20 ϩ15.9 (c 1.1, CHCl3);
δH (CDCl3) 7.42–7.08 (m, 40H), 6.75–6.58 (m, 4H), 6.55–6.48
(m, 4H), 5.30 (m, 1H), 5.08–3.36 (m, 36H), 3.74 (s, 3H), 3.64
(s, 3H), 2.10 (s, 3H); δC (CDCl3) 170.7, 153.9 (2C), 152.8, 152.6,
139.0–137.7 (8C), 128.5–127.4 (40C), 115.5 (2C), 115.4 (2C),
114.7 (4C), 102.9, 101.1, 100.3, 80.9, 79.7, 78.9, 78.3, 76.1,
76.0, 75.7, 75.2 (2C), 75.0, 74.5, 73.7, 73.5, 73.0, 72.9, 72.7,
72.6, 71.2, 69.8, 69.2, 65.6, 64.9, 62.7, 56.0, 55.9, 22.9
(Calc. for C90H94O19: C, 73.05; H, 6.40%. Found: C, 72.51; H,
6.46).
Benzyl O-(2,3,4-tri-O-benzyl-ꢁ-D-galactopyranosyluronic acid)-
(1→4)-O-(methyl 2,3-di-O-benzyl-ꢁ-D-galactopyranosyl-
uronate)-(1→4)-2,3-di-O-benzyl-ꢀ-D-galactopyranosyluronic
acid 27
Oxidation of 26 as described above for 19 gave 27 as a foam; Rf
0.11 (EtOAc–hexane; 2:1 ϩ 3% AcOH); [α]D20 ϩ65.2 (c 0.6,
CHCl3); δH (CD3OD) 7.51–7.20 (m, 40H), 5.30 (d, 1H, J 2.8),
5.10 (d, 1H, J 11.5), 4.98 (d, 1H, J 3.3), 4.90–4.78 (6H, hidden
under HDO signal), 4.75–4.50 (m, 13H), 4.34–4.21 (m, 3H),
3.95–3.81 (m, 3H), 3.69–3.54 (m, 3H), 3.19 (s, 3H); δC (CDCl3)
172.0, 169.5, 169.0, 138.7–137.4 (8C), 128.9–127.4 (40C), 103.1,
99.8, 99.1, 79.3, 78.6, 77.7, 77.6, 76.3, 75.4, 75.2 (2C), 74.6 (2C),
73.7 (2C), 73.3, 73.0, 72.9, 72.6, 72.4, 72.2, 71.6, 71.4, 52.1; m/z
1304.54 (M ϩ Naϩ). Calc. for C75H76O19 ϩ Naϩ: m/z, 1303.49.
Benzyl O-[2,3,4-tri-O-benzyl-6-O-(4-methoxyphenyl)-ꢁ-D-
galactopyranosyl]-(1→4)-O-[2,3-di-O-benzyl-6-O-(4-methoxy-
phenyl)-ꢁ-D-galactopyranosyl]-(1→4)-2,3-di-O-benzyl-ꢀ-D-
galactopyranoside 31
Deacetylation of 30 as described above for 16 gave 31 as a
foam; Rf 0.10 (hexane–EtOAc; 2:1); [α]D20 ϩ22.5 (c 0.8, CHCl3);
δH (CDCl3) 7.42–7.15 (m, 40H), 6.76–6.55 (m, 8H), 5.14 (d, 1H,
J 2.9), 5.07 (d, 1H, J 3.0), 4.96–4.50 (m, 16H), 4.45 (d, 1H,
J 7.5), 4.37–4.30 (m, 3H), 4.21 (br s, 1H), 4.11–3.97 (m, 5H),
3.91 (t, 1H, J 8.8), 3.83–3.62 (m, 5H), 3.75 (s, 3H), 3.66 (s, 3H),
3.53–3.42 (m, 3H), 3.33 (br s, 1H); δC (CDCl3) 154.0 (2C), 152.8
(2C), 139.0–137.8 (8C), 128.8–127.5 (40C), 115.6 (2C), 115.5
(2C), 114.8 (2C), 114.7 (2C), 103.2, 100.6, 100.5, 81.2, 79.5,
79.3, 78.1, 76.4 (2C), 76.0, 75.8, 75.2 (2C), 74.6 (2C), 74.4, 73.8,
73.1, 72.8, 72.5, 71.4, 70.2, 69.5, 65.9, 65.5, 60.5, 56.0, 55.9
(Calc. for C88H92O18: C, 73.52; H, 6.45%. Found: C, 73.22; H,
6.26).
O-(ꢁ-D-Galactopyranosyluronic acid)-(1→4)-O-(methyl ꢁ-D-
galactopyranosyluronate)-(1→4)-D-galactopyranuronic acid 2
Hydrogenation of 27 gave 2 as a foam; Rf 0.51 (MeOH–water;
2:1 ϩ 3% AcOH); δH (D2O) 5.29 (d, 0.4H, J 4.1, H1α), 5.09 (s,
1H), 5.06 (d, 1H, J 3.9, H1Ј), 4.94 (br s, 1H), 4.88 (d, 1H, J 3.9,
H1Љ), 4.70–4.63 (signals hidden under HDO-peak), 4.59 (d,
0.6H, J 7.7, H1β), 4.42–4.39 (m, 1.6H), 4.35 (d, 0.6H, J 2.8), 4.27
(m, 1.6H), 4.00 (dd, 1H, J 10.5, 3.3), 3.85 (dd, 1H, J 10.3, 3.3),
3.76 (s, 3H), 3.74 (dd, 1H, J 10.0, 3.2), 3.70 (m, 1H), 3.67 (dd,
1H, J 10.7, 4.0), 3.43 (dd, 0.6H, J 10.1, 7.7); δC (D2O) 175.9,
175.6, 174.8, 173.5, 103.1, 102.7, 99.0, 95.1, 81.5 (2C), 80.7,
76.0, 74.5, 74.0, 73.4, 72.9, 72.5, 71.6, 70.7 (2C), 70.6, 55.7.
Benzyl O-[2,3,4-tri-O-benzyl-6-O-(4-methoxyphenyl)-ꢁ-D-
galactopyranosyl]-(1→4)-O-[2,3-di-O-benzyl-6-O-(4-methoxy-
phenyl)-ꢁ-D-galactopyranosyl]-(1→4)-(methyl 2,3-di-O-benzyl-
ꢀ-D-galactopyranosyluronate) 32
Oxidation and methyl esterification of 31 as described above for
17 gave 32 as a foam; Rf 0.11 (hexane–EtOAc; 3:1); [α]D20 ϩ15.0
(c 0.9, CHCl3); δH (CDCl3) 7.48–7.07 (m, 40H), 6.68 (m, 4H),
6.53 (m, 4H), 5.19 (d, 1H, J 3.1), 5.04 (m, 2H), 4.92–4.37 (m,
19H), 4.29 (m, 2H), 4.15 (s, 1H), 4.06–3.92 (m, 4H), 3.91–3.73
(m, 4H), 3.77 (s, 3H), 3.67 (s, 3H), 3.65 (s, 3H), 3.50 (m, 2H);
δC (CDCl3) 168.7, 153.9 (2C), 152.8 (2C), 139.1–137.7 (8C),
128.6–127.4 (40C), 115.6 (2C), 115.4 (2C), 114.7 (4C), 103.0,
100.2, 99.7, 80.7, 79.6, 78.5, 78.0, 77.5, 76.2, 75.9, 75.7, 75.3,
75.1, 74.9, 74.5, 74.0, 73.7, 72.9, 72.8, 72.7, 71.4, 70.1, 69.2,
65.5, 65.4, 56.0, 55.9, 52.6 (Calc. for C89H92O19: C, 72.93; H,
6.33%. Found: C, 72.57; H, 6.42).
Benzyl O-[2,3-di-O-benzyl-4-O-chloroacetyl-6-O-(4-methoxy-
phenyl)-ꢁ-D-galactopyranosyl]-(1→4)-6-O-acetyl-2,3-di-O-
benzyl-ꢀ-D-galactopyranoside 28
Foam; Rf 0.10 (hexane–EtOAc; 3:1); [α]D20 ϩ21.9 (c 0.6, CHCl3);
δH (CDCl3) 7.35–7.09 (m, 25H), 6.65–6.45 (m, 4H), 5.72 (br d,
1H, J 2), 5.19 (s, 1H), 4.93–4.47 (m, 11H), 4.38 (m, 3H), 4.05
(m, 1H), 3.91 (s, 2H), 3.84 (d, 1H, J 2.9), 3.73 (dd, 1H, J 10.3,
3.5), 3.65 (m, 1H), 3.61 (s, 3H), 3.59–3.42 (m, 3H), 3.33 (dd, 1H,
J 9.9, 2.7), 1.98 (s, 3H); δC (CDCl3) 170.7, 166.8, 154.2, 152.5,
138.5–137.6 (5C), 128.7–127.9 (25C), 115.9 (2C), 114.7 (2C),
103.0, 101.0, 80.8, 78.7, 76.6, 76.5, 75.3 (2C), 74.2, 73.5,
72.5, 72.3, 71.4, 70.2, 67.5, 66.3, 62.4, 55.9, 41.1, 21.2; m/z
1060.98 (M Ϫ Hϩ ϩ 2Naϩ). Calc. for C58H60ClO14 ϩ 2Naϩ:
m/z, 1061.35.
Benzyl O-(2,3,4-tri-O-benzyl-ꢁ-D-galactopyranosyl)-(1→4)-O-
(2,3-di-O-benzyl-ꢁ-D-galactopyranosyl)-(1→4)-(methyl 2,3-di-
O-benzyl-ꢀ-D-galactopyranosyluronate) 33
Benzyl O-[2,3-di-O-benzyl-6-O-(4-methoxyphenyl)-ꢁ-D-galacto-
pyranosyl]-(1→4)-6-O-acetyl-2,3-di-O-benzyl-ꢀ-D-galacto-
pyranoside 29
Deprotection of 32 as described above for 18 gave 33 as a foam;
Rf 0.09 (hexane–EtOAc; 2:1); [α]D20 ϩ34.3 (c 0.8, CHCl3); δH
(CDCl3) 7.45–7.23 (m, 40H), 5.14–5.05 (m, 2H), 4.96–4.87 (m,
4H), 4.83–4.60 (m, 12H), 4.48 (d, 1H, J 7.6), 4.41 (d, 1H, J 2.2),
4.15 (t, 1H, J 6.0), 4.08 (dd, 1H, J 10.2, 3.5), 4.02–3.91 (m, 5H),
3.87 (m, 1H), 3.84–3.73 (m, 2H), 3.66–3.50 (m, 3H), 3.54 (s,
3H), 3.47 (dd, 1H, J 9.7, 2.6), 3.30 (dd, 1H, J 11.2, 4.1), 2.3 (br s,
2H); δC (CDCl3) 168.5, 139.2–137.7 (8C), 128.8–127.6 (40C),
103.0, 100.8, 99.1, 80.2, 79.7, 79.4, 78.7, 77.3, 77.1, 76.4, 75.7,
Dechloroacetylation of 28 as described above for 21 gave 29 as
a foam, which was crystallised from EtOH; Rf 0.08 (hexane–
EtOAc; 3:1); mp 103–104 ЊC; [α]D20 ϩ22.3 (c 0.8, CHCl3);
δH (CDCl3) 7.43–7.18 (m, 25H), 6.74–6.61 (m, 4H), 5.02–4.61
(m, 11H), 4.52–4.43 (m, 4H), 4.25 (m, 1H), 4.08–3.91 (m, 4H),
3.77–3.72 (m, 2H), 3.70 (s, 3H), 3.54 (t, 1H, J 6.5), 3.42 (dd, 1H,
550
J. Chem. Soc., Perkin Trans. 1, 2001, 543–551

View Article Online
2 For some recent examples, see: R. Körner, G. Limberg, T. M. I. E.
Christensen, J. Dalgaard Mikkelsen and P. Roepstorff, Anal.
Chem., 1999, 71, 1421; P. J. H. Daas, P. W. Arisz, H. A. Schols,
G. A. De Ruiter and A. G. J. Voragen, Anal. Biochem., 1998, 257,
195.
75.4, 75.2, 74.8, 74.7, 73.9, 73.2, 73.2, 73.1, 72.9, 72.3, 71.5,
71.0, 62.9, 61.4, 52.5 (Calc. for C75H80O17: C, 71.87; H, 6.43%.
Found: C, 71.53; H, 6.32).
Benzyl O-(2,3,4-tri-O-benzyl-ꢁ-D-galactopyranosyluronic acid)-
(1→4)-O-(2,3-di-O-benzyl-ꢁ-D-galactopyranosyluronic acid)-
(1→4)-(methyl 2,3-di-O-benzyl-ꢀ-D-galactopyranosyluronate) 34
3 T. Sakai, T. Sakamoto, J. Hallaert and E. J. Vandamme, Adv. Appl.
Microbiol., 1993, 39, 213.
4 L. Parenicová, J. A. E. Benen, H. C. M. Kester and J. Visser,
Biochem. J., 2000, 345, 637; C. Roy, H. Kester, J. Visser, V. Shevchik,
N. Hugouvieux-Cotte-Pattat, J. Robert-Baudouy and J. Benen,
J. Bacteriol., 1999, 181, 3705; V. E. Shevchik, H. C. M. Kester,
J. A. E. Benen, J. Visser, J. Robert-Baudouy and N. Hugouvieux-
Cotte-Pattat, J. Bacteriol., 1999, 181, 1652; J. A. E. Benen, H. C. M.
Kester and J. Visser, Eur. J. Biochem., 1999, 259, 577; E. M. W. Chen
and A. J. Mort, Carbohydr. Polym., 1996, 29, 129.
5 Y. Nakahara and T. Ogawa, Carbohydr. Res., 1990, 205, 147;
Y. Nakahara and T. Ogawa, Carbohydr. Res., 1990, 200, 363; Y.
Nakahara and T. Ogawa, Carbohydr. Res., 1989, 194, 95.
6 D. Magaud, C. Grandjean, A. Doutheau, D. Anker, V. Shevchik,
N. Cotte-Pattat and J. Robert-Baudouy, Carbohydr. Res., 1998,
314, 189; D. Magaud, C. Grandjean, A. Doutheau, D. Anker,
V. Shevchik, N. Cotte-Pattat and J. Robert-Baudouy, Tetrahedron
Lett., 1997, 38, 241.
Oxidation of 33 as described above for 19 gave 34 as a foam; Rf
0.10 (EtOAc–hexane; 2:1 ϩ 3% AcOH); [α]D20 ϩ80.6 (c 0.9,
CHCl3); δH (CDCl3) 7.50–7.18 (m, 40H), 5.31–5.07 (m, 3H),
4.95–4.41 (m, 20H), 4.28 (s, 1H), 4.05–3.60 (m, 6H), 3.69 (s, 3H),
3.47 (m, 1H); δC (CDCl3) 177.2, 170.3, 168.5, 138.7–137.5 (8C),
128.8–127.5 (40C), 102.9, 99.5, 99.0, 79.1, 78.4, 78.1, 76.4, 76.3,
76.2, 75.6, 75.3 (2C), 75.1, 73.7 (3C), 73.1 (3C), 72.8, 71.5 (2C),
71.1, 52.7; m/z 1304.60 (M ϩ Naϩ). Calc. for C75H76O19 ϩ Naϩ:
m/z, 1303.49.
O-(ꢁ-D-Galactopyranosyluronic acid)-(1→4)-O-(ꢁ-D-galacto-
pyranosyluronic acid)-(1→4)-(methyl D-galactopyranuronate) 3
7 H. C. M. Kester, J. A. E. Benen, J. Visser, M. E. Warren,
R. Orlando, C. Bergmann, D. Magaud, D. Anker and A. Doutheau,
Biochem. J., 2000, 346, 469; L. Parenicová, H. C. M. Kester, J. A. E.
Benen and J. Visser, FEBS Lett., 2000, 467, 333; H. C. M. Kester,
D. Magaud, C. Roy, D. Anker, A. Doutheau. V. Shevchik,
N. Hugouvieux-Cotte-Pattat, J. A. E. Benen and J. Visser, J. Biol.
Chem., 1999, 274, 37053.
8 B. Fraser-Reid, U. E. Udodong, Z. Wu, H. Ottosson, J. R. Merritt,
C. S. Rao, C. Roberts and R. Madsen, Synlett, 1992, 927.
9 V. Ferro, M. Mocerino, R. V. Stick and D. M. G. Tilbrook, Aust. J.
Chem., 1988, 41, 813.
Hydrogenation of 34 gave 3 as a foam; Rf 0.28 (MeOH–water;
3:1 ϩ 3% AcOH); δH (D2O) 5.30 (d, 0.4H, J 3.8, H1α), 5.01–
4.97 (m, 3H), 4.92 (d, 1H, J 3.5, H1Љ), 4.79–4.53 (signals hidden
under HDO peak), 4.45–4.34 (m, 2.6H), 4.26 (d, 1H, J 2.2),
3.98 (m, 0.4H), 3.95 (m, 1H), 3.86 (dd, 1H, J 10.5, 3.4), 3.77–
3.64 (m, 3.4H), 3.75 (s, 1.8H), 3.75 (s, 1.2H), 3.42 (dd, 0.6H,
J 10.0, 7.7); δC (D2O) 172.9, 172.2, 170.9, 170.0, 100.6, 100.1,
96.6, 92.6, 79.2, 78.4, 73.4, 71.5, 71.3, 71.1, 70.4, 70.1 (2C), 70.0,
68.9, 68.2, 68.0 (2C), 67.8, 53.2, 53.1.
10 M. Bertolini and C. P. J. Glaudemans, Carbohydr. Res., 1970, 15,
263.
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12 D. B. Dess and J. C. Martin, J. Am. Chem. Soc., 1991, 113, 7277.
13 A. J. Mancuso, S.-L. Huang and D. Swern, J. Org. Chem., 1978, 43,
2480.
Acknowledgements
We thank the Danish Research Agency for financial support
through a centercontract grant.
14 G. A. Kraus and B. Roth, J. Org. Chem., 1980, 45, 4825.
15 N. Hashimoto, T. Aoyama and T. Shioiri, Chem. Pharm. Bull., 1981,
29, 1475.
16 U. E. Udodong, C. S. Rao and B. Fraser-Reid, Tetrahedron, 1992,
48, 4713.
17 J. R. Turvey and T. P. Williams, J. Chem. Soc., 1962, 2119.
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