Synthesis of the two monomethyl esters of the disaccharide 4-O-α-D-galacturonosyl-D-galacturonic acid and of precursors for the preparation of higher oligomers methyl uronated in definite sequences

Article abstract of DOI:10.1016/S0008-6215(98)00312-7

Methyl (α-D-galactopyranosyluronic acid)-(1→4)-D-galactopyranuronate and methyl α-D-galactopyranosyluronate-(1→4)-D-galactopyranuronic acid have been synthesized by coupling methyl (benzyl 2,3-di-O-benzyl-β-D-galactopyranosid)uronate (3) or benzyl (benzyl 2,3-di-O-benzyl-β-D-galactopyranosid)uronate (4) with benzyl (phenyl 2,3,4-tri-O-benzyl-1-thio-β-D-galactopyranosid)uronate and methyl (phenyl 2,3,4-tri-O-benzyl-1-thio-β-D-galactopyranosid)uronate, respectively, using N-iodosuccinimide and trifluoromethanesulphonic acid as promoters, followed by removal of the benzyl groups. The 4'-OH unprotected dimers benzyl (methyl 2,3-di-O-benzyl-α-D-galactopyranosyluronate)-(1→4)-(benzyl 2,3-di-O-benzyl-β-D-galactopyranosid)uronate and methyl (benzyl 2,3-di-O-benzyl-α-D-galactopyranosyluronate)-(1→4)-(benzyl 2,3-di-O-benzyl-β-D-galactopyranosid)uronate were prepared from methyl (phenyl 2,3-di-O-benzyl-1-thio-4-O-trimethylsilyl-β-D-galactopyranosid)uronate and benzyl (phenyl 2,3-di-O-benzyl-1-thio-4-O-trimethylsilyl-β-D-galactopyranosid)uronate and acceptors 4 or 3, respectively. These compounds have been designed to serve as precursors for the preparation of higher-membered d-galacturonic acid oligomers methyl esterified in definite positions. Copyright (C) 1998 Elsevier Science Ltd.

Full text of DOI:10.1016/S0008-6215(98)00312-7

Carbohydrate Research 314 (1998) 189–199
Synthesis of the two monomethyl esters of the
disaccharide 4-O-a-
D
-galacturonosyl- -galacturonic acid
D
and of precursors for the preparation of higher
oligomers methyl uronated in definite sequences
Didier Magaud a, Cyrille Grandjean a, Alain Doutheau a,*, Daniel Anker a,
Vladimir Shevchik b, Nicole Cotte-Pattat b, Janine Robert-Baudouy b
a Laboratoire de Chimie Organique, EA 1844, Institut National des Sciences Applique´es, and UMR-CNRS-5622,
20 a6enue Albert Einstein, F-69621 Villeurbanne, France
b Laboratoire de Ge´ne´tique Mole´culaire des Microorganismes et des Interactions Cellulaires, UMR-CNRS-5577,
Institut National des Sciences Applique´es, 20 a6enue Albert Einstein, F-69621 Villeurbanne, France
Received 26 January 1998; accepted 13 November 1998
Abstract
Methyl (a-
uronate-(1“4)-
galactopyranosid)uronate (3) or benzyl (benzyl 2,3-di-O-benzyl-b-
2,3,4-tri-O-benzyl-1-thio-b- -galactopyranosid)uronate and methyl (phenyl 2,3,4-tri-O-benzyl-1-thio-b-
ranosid)uronate, respectively, using N-iodosuccinimide and trifluoromethanesulphonic acid as promoters, followed
by removal of the benzyl groups. The 4%-OH unprotected dimers benzyl (methyl 2,3-di-O-benzyl-a- -galactopyra-
nosyluronate)-(1“4)-(benzyl 2,3-di-O-benzyl-b- -galactopyranosid)uronate and methyl (benzyl 2,3-di-O-benzyl-a-
galactopyranosyluronate)-(1“4)-(benzyl 2,3-di-O-benzyl-b- -galactopyranosid)uronate were prepared from methyl
(phenyl 2,3-di-O-benzyl-1-thio-4-O-trimethylsilyl-b- -galactopyranosid)uronate and benzyl (phenyl 2,3-di-O-benzyl-
1-thio-4-O-trimethylsilyl-b- -galactopyranosid)uronate and acceptors 4 or 3, respectively. These compounds have
been designed to serve as precursors for the preparation of higher-membered
esterified in definite positions. © 1998 Elsevier Science Ltd. All rights reserved.
D
-galactopyranosyluronic acid)-(1“4)-
-galactopyranuronic acid have been synthesized by coupling methyl (benzyl 2,3-di-O-benzyl-b-
-galactopyranosid)uronate (4) with benzyl (phenyl
-galactopy-
D
-galactopyranuronate and methyl a-
D-galactopyranosyl-
D
D-
D
D
D
D
D
D-
D
D
D
D
-galacturonic acid oligomers methyl
Keywords: Pectins;
D-Galacturonic acid esters; Thioglycosides
properties and, thus, are used as thickening
agents in the food industry, and (b) their
degradation by certain fungi or bacteria
causes damage to plants in the field and dur-
ing storage. It is well recognized that the
proportion of methyl galacturonate units in
pectins greatly influence both the gel forma-
tion [2] and the activity of pectinases produced
by phytopathogenic microorganisms [3]. How-
ever, no systematic study concerning the im-
1. Introduction
Pectins, constituents of plant cell-walls, are
mainly composed of a backbone of partially
esterified a-(1“4)-linked
[1]. Pectins have aroused considerable interest
since (a) they possess pronounced gel-forming
D
-galacturonic acids
* Corresponding author.
0008-6215/98/$ - see front matter © 1998 Elsevier Science Ltd. All rights reserved.
PII: S0008-6215(98)00312-7

190
D. Magaud et al. / Carbohydrate Research 314 (1998) 189–199
portance of the position of the ester groups
for recognition and catalysis by these enzymes
has yet been published. Our continuing inter-
est in pectins [4] led us to further investigate
this aspect. Consequently, a method was
sought that would permit the synthesis of
oligomers bearing methyl esters in definite po-
sitions for enzyme assays.
dimer and the two O-protected a-(1“4)-
linked dimeric acceptors designed for the fur-
ther preparation of higher oligomers methyl
esterified in definite positions.
Preparation of glycosyl donors and accep-
tors.—We first focused on the preparation of
the two monomethyl esterified
acid dimers. To prepare the required donors
and acceptors we decided to use -galactose
D
-galacturonic
An obvious approach to our target com-
pounds is based on a-(1“4)-glycosylation be-
tween two suitably protected and differently
esterified galacturonic esters. Nakahara et al.
[5] attempted the glycosylation between two
D
as starting material and to carry out the oxi-
dation of the C-6 hydroxyl group into acid
later in the sequence1. Known methyl (benzyl
2,3-di-O-benzyl-b- -galactopyranosid)uronate
D
D-galacturonic acid methyl esters using
(3) [14] and the corresponding benzyl uronate
4 were obtained from the sodium salt of ben-
Mukaiyama’s conditions [6] but did not ob-
serve the formation of the expected dimer.
The first successful (1“4)-coupling between
zyl 2,3-di-O-benzyl-b-
nic acid (2). The latter compound was pre-
-galactose pentaacetate by the
D-galactopyranosiduro-
two -galacturonic acid esters was reported by
D
pared from b-
D
Pozsgay using a methyl 1-thioglycoside as the
donor [7]. However, no experimental details
were published. More recently, Vogel et al.
observed the formation of a mixture of three
different (1“4)-linked dimers in 45% overall
nine-step sequence of Turvey and Williams
[15] except that we found it easier to perform
the oxidation of the intermediate benzyl 2,3-
di-O-benzyl-b- -galactopyranoside (1) using
D
4-methoxy-2,2,6,6-tetramethyl-1-piperidiny-
loxy (4-MeO-TEMPO) [16] according to Anel-
li’s procedure2 [17].
yield [8] from
D-galacturonic acid-derived ac-
ceptors and donors, using the trityl-cya-
noethylidene condensation method [9].
2. Results and discussion
In view of these literature data, we re-exam-
ined the coupling between two
D-galacturonic
acid esters. Attempted condensation of benzyl
-galacturonate derivatives bearing a variety
D
Benzyl (phenyl 2,3,4-tri-O-benzyl-1-thio-b-
of leaving groups at the anomeric carbon
(bromide, trichloroacetimidoyl, pentenyloxy)
with acceptor 4 proved to be unsuccessful.
Next we turned our attention to 1-thiogly-
cosides. Since they are sufficiently stable to
withstand protecting group manipulations and
can readily be activated, 1-thioglycosides have
been known for a long time to be powerful
glycosyl donors (for a recent review see [10]).
We therefore decided to examine the glycosy-
lation between phenyl 1-thioglycoside deriva-
D
-galactopyranosid)uronate (11) and methyl
(phenyl
2,3,4-tri-O-benzyl-1-thio-b-
D
-galac-
topyranosid)uronate (12) were prepared as
follows. Phenyl 1-thio-b- -galactopyranoside
D
(5)3 was first transformed (TrCl, Pyr., DMAP)
into the corresponding 6-O-trityl derivative 6
followed by benzylation (NaH, BnBr, DMF)
to afford phenyl 2,3,4-tri-O-benzyl-1-thio-6-
O-trityl-b- -galactopyranoside (7). Selective
D
tives of
D
-galacturonic esters as donors and
-galacturonic esters as ac-
1 Similar strategies were adopted by several authors. See for
example [13].
4-OH unprotected
D
2 We used Ca(OCl)2, more stable on storage, instead of
NaOCl which is advised by Anelli et al. [17].
3 This compound was obtained by Zemple´n deacetylation
of the corresponding tetraacetate prepared according to Ref.
[18].
ceptors promoted by N-iodosuccinimide and
trifluoromethanesulfonic acid [11,12]. We now
describe the preparation of the two mono-
methyl esters of a-(1“4)- -galacturonic acid
D

D. Magaud et al. / Carbohydrate Research 314 (1998) 189–199
191
removal of the trityl group (Amberlyst 15 H+,
MeOH) gave rise to phenyl 2,3,4-tri-O-benzyl-
benzyl-1-thio-b-
D
-galactopyranosid)uronate
(16) and benzyl (phenyl 2,3-di-O-benzyl-1-
thio-b- -galactopyranosid)uronate (17) was
1-thio-b- -galactopyranoside (8) in 70% over-
D
D
all yield4. Using Nilsson’s conditions [20]
(PDC, tert-BuOH, Ac2O), compound 8 was
directly transformed into tert-butyl (phenyl
formed in 38 and 35% yields, respectively. The
formation of this mixture was particularly ad-
vantageous in our case since the two esters
were both needed and proved to be readily
separable by silica gel column chromatogra-
phy. Next, 16 and 17 were quantitatively
transformed (TMSOTf, 2,6-lutidine, CH2Cl2,
−10 °C) into the corresponding 4-O-
trimethylsilyl derivatives 18 and 19.
2,3,4-tri-O-benzyl-1-thio-b- -galactopyra-
D
nosid)uronate (9) in 70% yield. This com-
pound was then converted (TFA 20%,
CH2Cl2) into the corresponding acid 10 which
was not purified but directly esterified (BnBr,
phase transfer conditions) to give 11 in 68%
overall yield. The tert-butyl ester 9 was also
directly transformed (anhyd HCl, MeOH) into
the corresponding methyl ester 12 in 96%
yield. The use of acidic conditions allowed us
to avoid a base-promoted b-elimination result-
ing in the formation of a double bond between
C-4 and C-5.
We thus obtained the two donors required
for the preparation of the two monomethyl
esterified
D-galacturonic acid dimers. To
achieve an access to higher oligomers, a
phenyl 1-thio-galactopyranosiduronate mono-
mer bearing a selectively removable protecting
group at the C-4 position was required. From
5, we first prepared known phenyl 2-O-benzyl-
Preparation of dimeric
D
-galacturonic acid
deri6ati6es.—The glycosylations were per-
formed at −60 °C using a mixture of diethyl
ether and methylene chloride as solvent and
N-iodosuccinimide and trifluoromethanesul-
fonic acid as promoters. The results are sum-
marized in Table 1. Reaction of the
thioglycoside donors 11 and 12 with the glyco-
syl acceptors 3 and 4, respectively, gave rise
stereoselectively to the corresponding dimers
20 and 21 in good yields (Table 1, entries 1
and 2). Coupling between 18 and 4 led to
dimer 22 after in situ removal of the
trimethylsilyl group (entry 3). Similarly, cou-
pling between 19 and 3 gave rise to 4%-OH
unprotected dimer 23 (entry 4).
3,4-O-isopropylidene-1-thio-b- -galactopyra-
D
noside (13) using the Fernandez-Mayoralas et
al. procedure [21]. Performing the benzylation
in dimethylformamide (instead of THF) and
using Amberlyst H+ (instead of CSA) as
acidic catalyst for removing the methoxy–iso-
propyl protective group, with careful monitor-
ing of the reaction by TLC, the yield was
improved from 59 to 69%. Compound 13 was
then oxidized in 61% yield into tert-butyl
(phenyl 2-O-benzyl-3,4-O-isopropylidene-1-
thio-b- -galactopyranosid)uronate (14) in the
D
usual conditions. Treatment of 14 in anhy-
drous methanolic hydrochloric acid solution
Hydrogenolysis of 20 and 21a using
Pd(OH)2/C as catalyst [24] afforded the two
gave methyl (phenyl 2-O-benzyl-1-thio-b- -
D
galactopyranosid)uronate (15) quantitatively.
The selective benzylation of the 3-OH group
could be achieved using the dibutyltin oxide
activation [22]. As observed by Vogel et al.
[23] with closely related galacturonic acid es-
ters, a mixture of methyl (phenyl 2,3-di-O-
monomethyl esters of
D-galacturonic acid di-
saccharide 24 and 25 in excellent yields and
1
high purity5. The H NMR data of dimer 24
5 NMR spectra of 24 and 25 exhibited unusually broad
lines that could be resolved after treatment with Dowex 50
H+ as suggested earlier for galacturonic acid containing
oligosaccharides [7].
4 This compound had been previously obtained by a differ-
ent route. See Ref. [19].

192
D. Magaud et al. / Carbohydrate Research 314 (1998) 189–199
Table 1
Results of glycosylation reactions
Entry
Donor
Acceptor
Time (h)
Product
Yield (%)
1
2
3
4
11
12
18
19
3
4
4
3
2.5
2.5
1.5
1.5
20a
88
91
68
70
21 a/b=97/3b
22a
23a
a The b anomer was not detectable either by TLC of the crude glycosylation product or in the NMR spectra of the purified a
anomer.
b The two anomeric isomers were separated.
are in full agreement with selected data re-
ported for this compound isolated from pectin
degradation [25].
molybdic acid solution in EtOH containing
10% of H2SO4. Column chromatography was
performed on silica gel (Kieselgel 60, 0.04–
0.06 mm, E. Merck) using the following sol-
vent systems (v/v): (A1) 3:1, (A2) 1:1, and (A3)
1:2 pentane–Et2O; (B) Et2O; (C1) 4:1, (C2) 3:1
pentane–acetone; (D) 2:1 pentane–EtOAc;
(E) 6:1 CH2Cl2–MeOH;(F1) 60:1, (F2) 30:1
CH2Cl2–Et2O; (G1) 10:10:1, (G2) 10:10:2, (G3)
10:10:3 CH2Cl2–pentane–EtOAc; (H) 5:2:2 2-
propanol–H2O–AcOH. Organic solutions
were dried on MgSO4. Melting points were
determined with a Kofler hot-stage melting-
point apparatus. Optical rotations were mea-
sured with a Perkin-Elmer 241 polarimeter. IR
spectra were recorded on a Perkin–Elmer
In summary, the direct coupling between
two -galacturonic acid esters was achieved in
D
good yield using phenyl b-1-thioglycosides as
donors. This method allowed the two selec-
tively monomethyl esterified a-(1“4)-linked
D
-galacturonic acid dimers and two 4%-OH
unprotected dimeric acceptors to be prepared.
The latter compounds would permit the syn-
thesis of trimers and further higher oligomers
of
D
-galacturonic acid methyl esterified in
definite positions.
1
1310 spectrometer, and H NMR and 13C
3. Experimental
NMR spectra were recorded, in CDCl3 except
when otherwise stated, with either a Bruker
AM 200 or 300 spectrometer at room temper-
ature. Chemical shifts are given in ppm
downfield from internal Me4Si. Elemental
analyses were performed by the ‘Service Cen-
tral de Microanalyses du CNRS’ Solaize
(France).
General methods.—Aliquat 336 (tricapryl-
methylammonium chloride) and TEMPO
(2,2,6,6-tetramethyl-1-piperidinyloxy, free rad-
ical) were supplied by Aldrich Europ. Solvents
were dried as follows: MeOH distilled from
magnesium methoxide; pyridine and Et2O
from KOH; CH2Cl2 from P2O5 tert-butanol
distilled and DMF distilled and stored over 4
Methyl (benzyl 2,3-di-O-benzyl-i- -galac-
D
˚
topyranosid)uronate (3).—To a solution of 1
[15] (1 g, 2.2 mmol) in CH2Cl2 (2.8 mL) were
successively added, at 0 °C, a 0.016 M solu-
tion of 4-methoxy TEMPO [17] in CH2Cl2 (1.4
mL, 0.022 mmol), then 1.4 mL (0.11 mmol) of
A molecular sieves. Reaction mixtures were
magnetically stirred. The reactions were moni-
tored by TLC on Silica Gel 60 F254 (E. Merck)
and detection was carried out by UV exami-
nation and charring with a 5% phospho-

D. Magaud et al. / Carbohydrate Research 314 (1998) 189–199
193
a 0.08 M solution of Aliquat 336 in CH2Cl2,
and finally 0.45 mL (0.22 mmol) of a 0.5 M aq
solution of KBr. To this mixture were then
added a cooled (0 °C) solution of calcium
hypochlorite (0.796 g, 5.56 mmol) and of
NaHCO3 (0.796 g, 9.47 mmol) in 16 mL of
water. After 5 min, the reaction was complete
(TLC, solvent C2 and E) whereupon NaHCO3
(1.4 g) was added in order to adjust the pH to
7–8. Solvents were evaporated under reduced
pressure and DMF (10 mL) was added to the
residue. To this suspension was added 0.62
mL (9.9 mmol) of methyl iodide and the reac-
tion mixture was stirred and heated at 60 °C.
The reaction was complete after 2 h (TLC,
solvent C2). Solvent was evaporated under
reduced pressure and water (10 mL) and Et2O
(50 mL) were added to the residue. After
filtration through celite the organic phase was
washed with water (2×10 mL), dried, and
concentrated. Column chromatography (sol-
vent C1) gave 3 (0.640 g, 60%) as a white solid;
mp 110–111 °C (EtOH–water), lit. 111–
112 °C [14].
was stirred at room temperature for 3 days.
The reaction mixture was concentrated under
reduced pressure and Et2O (200 mL) was
added to the residue. The solution was washed
with a saturated aq NaHCO3 solution (2×30
mL), dried and concentrated under reduced
pressure to give a solid residue which was
dried (P2O5) and then dissolved in dry DMF
(90 mL). The resulting solution of crude 6 was
added to NaH (4.49 g of a 60% suspension in
oil, ca. 110 mmol, washed thrice with pentane)
in dry DMF (20 mL). A catalytic amount of
imidazole was added to the reaction mixture
stirred at 20 °C. After the evolution of H2
ceased, benzyl bromide (13.3 mL, 112.25
mmol) and a catalytic amount of Bu4NI were
added. After 4 h the starting material had
disappeared (TLC, solvent A2). Solvent was
evaporated under reduced pressure and Et2O
(200 mL) was added to the residue. Excess
NaH was destroyed by careful addition of
water (50 mL). The mixture was washed with
aq HCl 3 N (2×20 mL) dried, concentrated
and the residue was dissolved in 1:1 MeOH–
CHCl3 (200 mL). To this solution Amberlyst
15 H+ (15 g) was added and the reaction
mixture was gently stirred (rotatory evapora-
tor) and heated at 60 °C. After 1 h the reac-
tion was complete (TLC, solvent A2). The
resin was removed by filtration and washed
with MeOH (3×30 mL). The filtrate was
concentrated under reduced pressure in the
presence of a small amount of triethylamine at
40 °C giving a residue that was dissolved in
Et2O (100 mL). To this solution water (50
mL) was added and the organic phase was
separated, washed with water (3×10 mL)
dried and concentrated under reduced pres-
sure. Column chromatography of the crude
product (solvent A2 then solvent A3) gave 8
(11.8 g, 70% from 5) as a white solid. An
analytical sample was recrystallized from cy-
clohexane: mp 94–95 °C; lit. 94–95 °C [19].
tert-Butyl (phenyl 2,3,4-tri-O-benzyl-1-thio-
Benzyl (benzyl 2,3-di-O-benzyl-i- -galac-
D
topyranosid)uronate (4).—Prepared following
the same procedure as for 3 except that methyl
iodide was replaced by benzyl bromide (1.18
mL, 9.9 mmol; 60 °C, 2 h), resulting in 4
(0.788 g, 64%) as a white solid; mp 128–
129 °C (cyclohexane); [h]2D5−23° (c 0.7,
1
CHCl3); H NMR: l 7.37–7.25 (m, 20 H, H
aromatic); 5.28 (s, 2 H, CH2Ph); 5.04, 4.91
(2d, 2 H, J 11.0 Hz, CH2Ph); 4.74–4.64 (m, 4
H, 2 CH2Ph); 4.46 (d, 1 H, J1,2 7.6 Hz, H-1);
4.31 (broad d, 1 H, H-4); 4.07 (broad s, 1 H,
H-5); 3.58 (dd, 1 H, J2,3 9.3 Hz, H-2), 3.52
(dd, 1 H, J3,4 3.4 Hz, H-3); 2. 56 (s, 1 H, OH);
13C NMR: l 167.6 (C-6); 138.3, 137.6, 137.2,
135.3, 128.6, 128.5, 128.4, 128.3, 128.2, 128.0,
127.8, 127.7, 127.6 (C aromatic); 102.1 (C-1);
79.8, 78.2, 73.6, 67.9 (C-2,3,4,5); 75.2, 72.5,
71.0, 67.1 (4 CH2Ph). Anal. Calcd for
C34H34O7: C, 73.60; H, 6.10. Found: C, 73.78;
H, 6.11.
i-D
-galactopyranosid)uronate
(9).—To
a
Phenyl 2,3,4-tri-O-benzyl-1-thio-i-
D-galac-
stirred solution of 8 (1.1 g, 2.03 mmol) in dry
CH2Cl2 (26 mL) were added pyridinium
dichromate (PDC) (1.5 g, 4.1 mmol), acetic
anhydride (1.95 mL, 20.6 mmol) and tert-bu-
tanol (3.8 mL, 40.3 mmol). The starting mate-
rial had disappeared after 4 h of stirring (TLC
topyranoside (8).—To a solution of 5 [17]
(8.48 g, 31.17 mmol) in pyridine (180 mL),
were added trityl chloride (14.94 g, 53.60
mmol) and a catalytic amount of 4-dimethyl-
aminopyridine (DMAP). The reaction mixture

194
D. Magaud et al. / Carbohydrate Research 314 (1998) 189–199
CH2Ph); 4.59 (d, 1 H, J1,2 9.6 Hz, H-1); 4.30
(broad d, 1 H, H-4); 4.09 (broad s, 1 H, H-5);
3.92 (pt, 1 H, H-2); 3.63 (dd, 1 H, J2,3 9.2, J3,4
2.7 Hz, H-3). Anal. Calcd for C40H38O6S: C,
74.30; H, 5.88. Found: C, 73.96; H, 5.92.
Methyl (phenyl 2,3,4-tri-O-benzyl-1-thio-i-
solvent A2) and the mixture was applied on
the top of a silica gel column (200 g) in Et2O,
with a 5-cm layer of Et2O on the top of the
gel. The chromium compounds precipitated in
the presence of Et2O and after 15 min the
product was eluted with Et2O. The crude
product obtained after concentration of Et2O
solution was chromatographed on silica gel
(solvent A1) to give 9 (0.870 g, 70%) as a pale
D-galactopyranosid)uronate
(12).—To
a
stirred solution of 9 (1 g, 1.63 mmol) in dry
MeOH (20 mL), cooled to 0 °C, was added
dropwise, acetyl chloride (5 mL). After a few
minutes, the reaction mixture was allowed to
warm to room temperature. After 2.5 h, the
reaction was complete (TLC, solvent A2). The
solvent was evaporated under reduced pres-
sure at 40 °C. The white solid obtained was
recrystallized from cyclohexane to give 12
(0.89 g, 96%); mp 98–100 °C then solidifica-
tion; second mp at 110–112 °C; [h]2D5 +9.2° (c
1
yellow oil; [h]2D5 +20° (c 1.5, CHCl3); H
NMR: l 7.74−7.70 (m, 2 H, H aromatic);
7.4−7.15 (m, 18 H, H aromatic); 4.96–4.63
(m, 6 H, 3 CH2Ph); 4.57 (d, 1 H, J1,2 9.5 Hz,
H-1); 4.29 (broad s, 1 H, H-4); 3.95 (broad s,
1 H, H-5); 3.85 (pt, 1 H, H-2); 3.63 (dd, 1 H,
J2,3 9.2, J3,4 2.7 Hz, H-3); 1.46 (s, 9 H, 3 CH3,
tert-Bu); 13C NMR: l 166.9 (C-6); 138.4,
138.2, 138.0, 133.0, 133.1, 128.7, 128.4, 128.0,
127.7, 127.5, 127.3 (C aromatic); 87.0 (C-1);
83.5, 77.3, 76.4, 75.6 (C-2,3,4,5); 82.4
(C(CH3)3); 75.6, 74.5, 72.7 (3 CH2Ph); 28.0 (3
CH3, tert-Bu). Anal. Calcd for C37H40O6S: C,
72.55; H, 6.53. Found: C, 72.34; H, 6.34.
Benzyl (phenyl 2,3,4-tri-O-benzyl-1-thio-i-
1
0.9, CHCl3); H NMR: l 7.73–7.78 (m, 2 H,
H aromatic); 7.47–7.24 (m, 18 H, H aro-
matic); 4.97–4.78 (m, 6 H, 3CH2Ph); 4.66 (d,
1 H, J1,2 9.6 Hz, H-1); 4.37 (broad s, 1 H,
H-4); 4.1 (broad s, 1 H, H-5); 4.0 (pt, 1 H,
H-2); 3.74 (s, 3 H, OCH3); 3.69 (dd, 1 H, J2,3
9.2, J3,4 2.7 Hz, H-3); 13C NMR: l 168.4
(C-6); 138.3, 138.2, 137.9, 133.5, 132.4, 128.8,
128.5, 128.3, 128.1, 127.8, 127.7, 127.5, (C
aromatic); 87.7 (C-1); 83.3, 77.2, 76.6, 75.1
(C-2,3,4,5); 75.6, 74.4, 72.8 (3 CH2Ph); 52.4
(OCH3). Anal. Calcd for C34H34O6S: C, 71.58;
H, 5.96. Found: C, 71.27; H, 5.86.
D-galactopyranosid)uronate (11).—To a solu-
tion of 9 (6.35 g, 10.37 mmol) in CH2Cl2 (19.2
mL) was added trifluoroacetic acid (4.8 mL,
62.8 mmol). After 1 h at ambient temperature,
the starting material had disappeared (TLC,
solvent A2) and a more polar product was
formed (TLC, solvent E). The reaction mix-
ture was concentrated under reduced pressure
at 30 °C to give a residue that was dissolved in
CH2Cl2 (90 mL). To this solution were added
successively Aliquat 336 (2.46 g), sat aq
NaHCO3 sol (45 mL), a catalytic amount of
Bu4NI and benzyl bromide (1.5 mL, 12.61
mmol). After stirring overnight at room tem-
perature, the intermediate had disappeared
(TLC, solvent E) and a less polar product was
formed (TLC, solvent A2). The reaction mix-
ture was diluted with CH2Cl2 (50 mL) and the
organic phase was washed with aq 1 N HCl
(2×20 mL), dried, and concentrated under
reduced pressure. The crude product was
chromatographed (solvent A1) to give 11 (4.56
g, 68%) as a white solid. An analytical sample
was recrystallized from cyclohexane; mp 83–
tert-Butyl (phenyl 2-O-benzyl-3,4-O-iso-
propylidene-1-thio-i- -galactopyranosid)uron-
D
ate (14).—To a solution of 13 [22] (6.12 g,
15.2 mmol) in CH2Cl2 (15 mL) were succes-
sively added acetic anhydride (14.75 mL,
156.3 mmol), tert-butanol (21.25 mL, 222.2
mmol) and PDC (11.9 g, 31.15 mmol). The
reaction mixture was stirred at room tempera-
ture in the dark. After 3 h the reaction was
complete (TLC, solvent A2) and the mixture
was applied on the top of a silica gel column
(240 g) in EtOAc, with a 5-cm layer of EtOAc
on the top of the gel. The chromium com-
pounds precipitated in the presence of EtOAc
and after 15 min the product was eluted with
EtOAc. After solvent evaporation under re-
duced pressure at 35 °C the residue was di-
luted in 3:1 Et2O–CH2Cl2 (500 mL) and the
resulting solution washed with saturated aq
NaHCO3 (50 mL) then H2O (50 mL), HCl
1
84 °C; [h]2D5 +6.7° (c 1.07, CHCl3); H NMR:
l 7.68–7.64 (m, 2 H, H aromatic); 7.37–7.11
(m, 23 H, H aromatic); 5.19–4.51 (m, 8 H, 4

D. Magaud et al. / Carbohydrate Research 314 (1998) 189–199
195
mide (3.35 mL, 28.20 mmol). The mixture had
been stirred at this temperature for an addi-
tional period of 3 h. The methyl ester was first
formed (Rf 0.31) and then, gradually, the ben-
zyl ester (Rf 0.66) (solvent A3). The reaction
mixture was concentrated under reduced pres-
sure at 40 °C. A solution of the residue in
CH2Cl2 (100 mL) was sequentially extracted
with water (20 mL), an aq solution of sodium
metabisulfite (20 mL) and water (20 mL). The
organic phase was dried, concentrated and the
residue chromatographed (solvent G1 then G2
then G3). Compound 17 (0.8 g, 35%) was first
eluted and then 16 (0.75 g, 38%) which were
both crystallized in cyclohexane. Compound
17; mp 154–155 °C; [h]2D5 −18.8° (c 1.45,
3 N (50 mL), H2O (50 mL), saturated aq
NaHCO3 (50 mL), dried and concentrated.
The colourless solid thus obtained was washed
with pentane (10 mL) and dried (P2O5) to give
14 (4.37 g, 61%); mp 132–133 °C (cyclohex-
1
ane/pentane); [h]2D5 −40.2° (c 1.2, CHCl3); H
NMR: l 7.67–7.60 (m, 2 H, H aromatic);
7.43–7.25 (m, 8 H, H aromatic); 4.78, 4.64
(2d, 2 H, J 11.3 Hz, 2 CH2Ph); 4.63 (d, 1 H,
J1,2 8.7 Hz, H-1); 4.48 (dd, 1 H, J3,4 5.8, J4,5
2.4 Hz, H-4); 4.30 (pt, 1 H, J2,3 6.0, H-3); 4.24
(d, 1 H, H-5); 3.58 (broad dd, 1 H, H-2); 1.50
(s, 9 H, 3 CH3, tert-Bu); 1.39, 1.34 (2 s, 2×3
H, 2 CH3). Anal. Calcd for C26H32O6S: C,
66.10 H; 6.78; S, 6.78. Found: C, 65.90; H,
6.65; S, 6.66.
1
Methyl (phenyl 2-O-benzyl-1-thio-i-
D-gal-
CHCl3); H NMR (CDCl3+D2O): l 7.67–
actopyranosid)uronate (15).—To a stirred so-
lution of 14 (3.34 g, 7.08 mmol) in dry MeOH
(67 mL) at 0 °C was added, dropwise, acetyl
chloride (16.7 mL, 234 mmol). The reaction
mixture was then allowed to reach ambient
temperature. After 2.5 h the reaction was
complete (TLC, solvent B) and the volatiles
were evaporated under reduced pressure.
Crystallization of the residue from cyclohex-
ane afforded 15 (2.7 g, 98%) as a white solid;
mp 137–138 °C; [h]2D5 −24.5° (c 1.06, CHCl3);
1H NMR (CDCl3 +D2O): l 7.77–7.72 (m, 2
H, H aromatic); 7.52–7.37 (m, 8 H, H aro-
matic); 4.96, 4.70 (2d, 2 H, J 11.3 Hz, 2
CH2Ph); 4.61 (d, 1 H, J1,2 9.2 Hz, H-1); 4.30
(dd, 1 H, J3,4 3.0, J4,5 1.2 Hz, H-4); 4.10 (d, 1
H, H-5); 3.83 (s, 3 H, OCH3); 3.71 (dd, 1 H,
J2,3 8.7 Hz, H-3); 3.63 (pt, 1 H, H-2). Anal.
Calcd for C20H22O6S: C, 61.52; H, 5.68; S,
8.21. Found: C, 61.56; H, 5.67; S, 8.42.
7.62 (m, 2 H, H aromatic); 7.37–7.23 (m, 18
H, H aromatic); 5.26 (s, 2 H, CH2Ph); 4.87–
4.63 (m, 4 H, 2CH2Ph); 4.57 (d, 1 H, J1,2 9.5
Hz, H-1); 4.39 (broad d, 1 H, H-4); 4.07
(broad s, 1 H, H-5); 3.74 (pt, 1 H, H-2); 3.61
(dd, 1 H, J2,3 8.9, J3,4 3.0 Hz, H-3). Anal.
Calcd for C33H32O6S: C, 71.22; H, 5.76; S,
5.76. Found: C, 70.93; H, 5.80; S, 5.55. Com-
pound 16; mp 128–130 °C; [h]2D5 −14.8° (c
1.3, CHCl3); 1H NMR (CDCl3+D2O): l
7.66–7.61 (m, 2 H, H aromatic); 7.38–7.25
(m, 13 H, H aromatic); 4.87–4.64 (m, 4 H, 2
CH2Ph); 4.59 (d, 1 H, J1,2 9.4 Hz, H-1); 4.39
(broad t, 1 H, H-4); 4.07 (d, 1 H, J4,5 1.1 Hz,
H-5); 3.83 (s, 3 H, OCH3); 3.75 (pst, 1 H,
H-2); 3.63 (dd, 1 H, J2,3 8.9, J3,4 3.1 Hz, H-3).
Anal. Calcd for C27H28O6S: C, 65.50; H, 5.83;
S, 6.67. Found: C, 66.95; H, 6.02; S, 6.92.
Methyl (phenyl 2,3-di-O-benzyl-1-thio-4-O-
trimethylsilyl-i- -galactopyranosid)uronate
D
Methyl (phenyl 2,3-di-O-benzyl-1-thio-i-
galactopyranosid)uronate (16) and benzyl
(phenyl 2,3-di-O-benzyl-1-thio-i- -galactopy-
D-
(18).—A stirred solution of 16 (0.5 g, 1.04
mmol) in dry CH2Cl2 (1 mL), was treated at
−10 °C with trimethylsilyl triflate (280 mL,
1.82 mmol) and 2,6-lutidine (305 mL, 2.6
mmol). After 5 min the reaction was complete
(TLC, solvent A3). The reaction mixture was
diluted with Et2O (10 mL) washed with aq
NaHCO3 (2 mL) dried and concentrated to
give 18 as a syrup (0.574 g, 100%); [h]2D5 −3.3°
D
ranosid)uronate (17).—A mixture of 15 (1.6 g,
4.1 mmol), Bu2SnO (1.18 g, 4.74 mmol), and
toluene (40 mL) was stirred under reflux using
a Dean–Stark separator between the reaction
flask and the condenser. When about the stoi-
chiometric amount of water had been distilled,
1
˚
4 A beads molecular sieves were added in the
(c 0.8, CHCl3); H NMR: l 7.72–7.68 (m, 2
receptor of the Dean–Stark separator and
heating was continued for 1 h. The reaction
mixture was cooled to 60 °C and treated with
Bu4NI (1.75 g, 4.74 mmol) and benzyl bro-
H, H aromatic); 7.42–7.28 (m, 13 H, H aro-
matic); 4.81–4.71 (m, 4 H, 2 CH2Ph); 4.62 (d,
1 H, J1,2 9.6 Hz, H-1); 4.49 (broad d, 1 H,
H-4); 4.08 (broad s, 1 H, H-5); 3.85 (broad

196
D. Magaud et al. / Carbohydrate Research 314 (1998) 189–199
reduced pressure and the crude product was
purified by column chromatography (solvent
F1 then F2) to give 20 (0.448 g, 88%) as a white
solid: mp 100 °C (MeOH); [h]2D5 +26.2° (c 1.0,
pst, 1 H, H-2); 3.82 (s, 3 H, OCH3); 3.51 (dd,
1 H, J2,3 9.2, J3,4 2.6 Hz, H-3); 0.10 (s, 9 H, 3
CH3Si). The compound was not stable enough
to obtain satisfactory elemental analysis.
Benzyl (phenyl 2,3-di-O-benzyl-1-thio-4-O-
1
CHCl3); H NMR: l 7.42–7.12 (m, 35 H, H
aromatic); 5.23 (d, 1 H, J1%,2% 3 Hz, H-1%);
5.09–4.40 (m, 14 H, 7CH2Ph); 4.97 (d, 1 H,
J4%,5% 1.1 Hz, H-5%); 4.50 (broad s, 1 H, H-4);
4.44 (d, 1 H, J1,2 7.7 Hz, H-1); 4.30 (broad pst,
1 H, H4%); 4.10 (dd, 1 H, J2%,3% 9.9 Hz, H-2%);
4.04 (dd, 1 H, J3%,4% 2.6 Hz, H-3%); 3.94 (broad
s, 1 H, H-5); 3.70 (dd, 1 H, J2,3 9.9 Hz, H-2);
3.55 (s, 3 H, OCH3); 3.55 (dd, 1 H, J3,4 2.6 Hz,
H-3); 13C NMR: l 168.9 (C-6); 168.2 (C-6%);
138.7, 138.6, 138.5, 138.0, 137.5, 135.3, 128.7,
128.5, 128.4, 128.3, 128.2, 128.1, 128.0, 127.8,
127.6, 127.5, 127.4, 127.3 (C aromatic); 102.8
(C-1); 99.8 (C-1%); 79.6, 78.3, 77.9, 76.5, 75.3,
74.7, 73.6, 71.6 (C-2,3,4,5,2%,3%,4%,5%); 75.0,
74.5, 73.0, 72.8, 72.1, 71.3, 66.7 (7 CH2Ph);
52.3 (OCH3). Anal. Calcd for C62H62O13 (0.5
H2O): C, 72.72; H, 6.15. Found: C, 72.70; H,
6.16.
trimethylsilyl-i- -galactopyranosid)uronate
D
(19).—A stirred solution of 17 (0.5 g, 0.89
mmol) in dry CH2Cl2 (1 mL) was treated at
−10 °C with trimethylsilyl triflate (245 mL,
1.57 mmol) and 2,6-lutidine (262 mL, 2.26
mmol). After 10 min the reaction was com-
plete (TLC, solvent A3). The reaction mixture
was diluted with Et2O (10 mL) washed with
aq saturated NaHCO3 (2 mL), dried and con-
centrated giving 19 as a syrup (0.564 g, 100%);
1
[h]2D5 −1.6° (c 0.9, CHCl3); H NMR: l 7.72–
7.68 (m, 2 H, H aromatic); 7.40–7.20 (m, 18
H, H aromatic); 5.24 (s, 2 H, CH2Ph ester);
4.83–4.67 (m, 4 H, 2 CH2Ph); 4.60 (d, 1 H,
J1,2 9.5 Hz, H-1); 4.49 (broad d, 1 H, H-4);
4.09 (broad s, 1 H, H-5); 3.81 (pst, 1 H, H-2);
3.51 (dd, 1 H, J2,3 9.2, J3,4 2.6 Hz, H-3); 0.03
(s, 9 H, 3 CH3Si). The compound was not
stable enough to obtain satisfactory elemental
analysis.
Benzyl (methyl 2,3,4-tri-O-benzyl-h-
actopyranosyluronate)-(1“4)-(benzyl 2,3-di-
O-benzyl-i- -galactopyranosid)uronate (21a)
and benzyl (methyl 2,3,4-tri-O-benzyl-i-
galactopyranosyluronate) - (1“4) - (benzyl 2,3 -
di - O - benzyl - i - - galactopyranosid)uronate
D-gal-
Methyl (benzyl 2,3,4-tri-O-benzyl-h-
actopyranosyluronate)-(1“4)-(benzyl 2,3-di-
O-benzyl-i- -galactopyranosid)uronate (20).
D-gal-
D
D
-
D
—Compounds 11 (0.387 g, 0.6 mmol) and 3
(0.239 g, 0.5 mmol) were dried (vacuum dessi-
cator; P2O5; 0.1 mmHg) for 24 h and then
dissolved freshly distilled (P2O5) CH2Cl2 (4
mL). Under dry nitrogen, to this solution were
added N-iodosuccinimide (NIS) (0.15 g, 0.66
mmol) (crystallized from dioxane–CCl4 and
dried with P2O5) and dried (300 °C, 1 h, 0.1
D
(21b).—These compounds were prepared fol-
lowing the same procedure as for 20 from
donor 12 (0.561 g, 0.984 mmol) and acceptor
4 (0.544 g, 0.982 mmol) using 0.272 g (1.21
mmol) of NIS, 6 mL of CH2Cl2, 12 mL of
˚
Et2O, 1.3 g of 4 A powder molecular sieves
and 0.3 mL (0.1 mmol) of a solution of 0.03
mL of TfOH in CH2Cl2 (1 mL). The reaction
was complete after 2.5 h. The crude reaction
mixture was purified by two silica gel chro-
matographies (solvent F2 then A2). During the
second chromatography, we first eluted 21a
(0.884 g, 88%) as a syrup and then 21b (0.030
g, 3%) as a syrup. 21a; [h]2D5 +36.2° (c 0.8,
˚
mmHg) 4 A powder molecular sieves (0.9 g)
and the reaction mixture was diluted with
freshly distilled (LiAlH4) Et2O (8 mL). To this
cooled (−60 °C) stirred solution was added
(syringe) 200 mL (0.06 mmol) of a solution of
0.03 mL of TfOH in of CH2Cl2 (1 mL). The
temperature of the solution was maintained
below −55 °C. After 2.5 h, the donor had
disappeared (TLC, solvent F2), and the reac-
tion mixture was poured into a saturated aq
NaHCO3 solution (50 mL) and Et2O (100
mL). A small amount of Na2S2O5 was added
until decoloration. After extraction with Et2O
(3×50 mL), the organic layers were pooled
and dried. The solvent was evaporated under
1
CHCl3); H NMR: l 7.40–7.14 (m, 35 H, H
aromatic); 5.25 (d, 1 H, J1%,2% 3 Hz, H-1%);
5.05–4.50 (m, 14 H, 7 CH2Ph); 4.92 (d, 1 H,
J4%,5% 1.5 Hz, H-5%); 4.48 (broad s, 1 H, H-4);
4.43 (d, 1 H, J1,2 7.6 Hz, H-1); 4.28 (broad pt,
1 H, H-4%); 4.12 (dd, 1 H, J2%,3% 10.2 Hz, H-2%);
4.06 (dd, 1 H, J3%,4% 2.4 Hz, H-3%); 3.94 (broad
s, 1 H, H-5); 3.72 (dd, 1 H, J2,3 9.9 Hz, H-2);

D. Magaud et al. / Carbohydrate Research 314 (1998) 189–199
197
3.42 (dd, 1 H, J3,4 3 Hz, H-3); 3.35 (s, 3 H,
NMR: l 169.4, 164.3 (C-6,6%); 138.4, 138.3,
137.9, 137.3, 137.2, 128.6, 128.5, 128.4, 128.3,
128.1, 128.0, 127.9, 127.8, 127.6, 127.5, 127.4,
(C aromatic); 102.7 (C-1); 99.5 (C-1%); 80.0,
77.8, 76.9, 75.5, 74.3, 73.5, 70.5, 68.4 (C-
2,3,4,5,2%,3%,4%,5%); 75.0, 73.0, 72.5, 72.4, 71.2,
66.9 (6 CH2Ph); 52.1 (OCH3). Anal. Calcd for
C55H56O13: C, 71.43; H, 6.06. Found: C, 71.25;
H, 6.16.
13
OCH3); C NMR: l 169.3 (C-6); 167.1 (C-6%);
138.5, 138.4, 138.3, 137.9, 137.2, 135.1; 128.4,
128.3, 128.2, 128.1, 128.0, 127.9, 127.8, 127.7,
127.5, 127.4, 127.3, 127.2 (C aromatic); 102.5
(C-1); 99.6 (C-1%); 79.9, 77.9, 77.8, 76.3, 75.2,
74.9, 73.4, 71.5 (C-2,3,4,5,2%,3%,4%,5%); 74.9,
74.5, 72.9, 72.7, 72.2, 71.1, 66.8 (7 CH2Ph);
51.7 (OCH3). Anal. Calcd for C62H62O13: C,
73.37; H, 6.11. Found: C, 73.03; H, 6.24. 21b;
1H NMR: l 7.48–7.09 (m, 35 H, H aromatic);
5.33–4.44 (m, 14 H, 7 CH2Ph); 4.97 (d, 1 H,
J1%,2% 7.6, H-1%); 4.86 (broad dd, 1 H, J3,4 2.9,
J4,5 1.2 Hz, H-4); 4.5 (d, 1 H, J1,2 7.6 Hz, H-1);
4.17 (broad dd, 1 H, J3%,4% 3.1, J4%,5% 1.2 Hz,
H-4%); 4.13 (broad d, 1 H, H-5); 3.86 (dd, 1 H,
J2,3 9.8 Hz, H-2); 3.80 (dd, 1 H, J2%,3% 9.8 Hz,
H-2%); 3.74 (broad d, 1 H, H-5%); 3.6 (s, 3 H,
OCH3); 3.59 (dd, 1 H, H-3); 3.48 (dd, 1 H,
H-3%).
Methyl (benzyl 2,3-di-O-benzyl-h-
topyranosyluronate)-(1“4)-(benzyl 2,3-di-O-
benzyl - i - - galactopyranosid)uronate (23).—
D-galac-
D
This compound was prepared, as described for
22, from donor 19 (0.254 g, 0.4 mmol) and
acceptor 3 (0.162 g, 0.337 mmol) using 0.111 g
˚
(0.49 mmol) of NIS, 0.6 g of 4 A powder
molecular sieves, 2.5 mL of CH2Cl2, 5 mL of
Et2O, and 0.135 mL of a solution of 0.03 mL
of TfOH in CH2Cl2 (1 mL). The reaction was
complete in 1.5 h (TLC, solvent A2). After
cleavage of the trimethylsilyl group as for 22
the residue was chromatographed (solvent A3)
to give 23 as a syrup (0.220 g, 70%): [h]D25
Benzyl (methyl 2,3-di-O-benzyl-h-
topyranosyluronate)-(1“4)-(benzyl 2,3-di-O-
benzyl - i - - galactopyranosid)uronate (22).—
D-galac-
D
1
+28.2° (c 1.15, CHCl3); H NMR: l 7.43–
This compound was prepared as described for
20 from donor 18 (0.55 g, 0.996 mmol) and
acceptor 4 (0.46 g, 0.830 mmol) using 0.237 g
(1.05 mmol) of NIS, 6 mL of CH2Cl2, 12 mL
7.20 (m, 30 H, H aromatic); 5.22 (d, 1 H, J1%,2%
3.3 Hz, H-1%); 5.12–4.50 (m, 12 H, 6 CH2Ph);
5.01 (broad s, 1 H, H-5%); 4.46 (broad d, 1 H,
H-4); 4.45 (d, 1 H, J1,2 7.7 Hz, H-1); 4.39
(broad s, 1 H, H-4%); 4.00 (dd, 1 H, J2%,3% 9.9,
J3%,4% 3.3 Hz, H-3%); 3.95 (s, 1 H, H-5); 3.87 (dd,
1 H, H-2%); 3.70 (dd, 1 H, J2,3 9.9 Hz, H-2);
3.57 (s, 3 H, OCH3); 3.43 (dd, 1 H, J3,4 2.6 Hz,
˚
of Et2O, 1.3 g of 4 A powder molecular sieves
and 0.335 mL (0.11 mmol) of a solution of
0.03 mL of TfOH in 1 mL of CH2Cl2. The
reaction was complete after 1.5 h (1:1 pen-
tane–Et2O). After the usual treatment, the
crude product was dissolved in MeOH (30
mL) and the resulting solution was occasion-
ally stirred with Amberlyst 15 H+ resin (0.5
g). After 15 min the cleavage of the
trimethylsilyl group was complete (TLC, sol-
vent A2). The resin was filtered off and washed
with methanol (3×30 mL). The filtrate was
concentrated and the residue was chro-
matographed (solvent D) to give 0.527 g
(68%) of 22 as a syrup; [h]2D5 +38.2° (c 1.0,
13
H-3); C NMR: l 168.9, 168.2 (C-6,6%); 138.5,
138.4, 138.0, 137.9, 137.4, 135.5, 128.6, 128.5,
128.4, 128.3, 128.2, 128.1, 128.0, 127.9, 127.7,
127.6, (C aromatic); 102.8 (C-1); 99.7 (C-1%);
79.6, 77.8, 77.1, 75.6, 74.1, 73.6, 70.6, 68.5
(C-2,3,4,5,2%,3%,4%,5%); 75.0, 73.0, 72.5, 72.2,
71.4, 66.8 (6 CH2Ph); 52.4 (OCH3). Anal.
Calcd for C55H56O13: C 71.43; H 6.06. Found:
C 71.03; H 6.06.
Methyl (h-
(1“4)-h,i- -galactopyranuronate (24).—To
D
-galactopyranosyluronic acid)-
1
D
CHCl3); H NMR: l 7.40–7.18 (m, 30 H, H
a solution of dimer 20 (0.2 g, 0.19 mmol) in
EtOAc (5 mL) were added 3:1:1 2-propanol–
water–acetic acid (34 mL) and Pd(OH)2/C
(20%, 0.2 g). The reaction mixture was stirred
under hydrogen (105 Pa) until TLC analysis
(solvent H) showed one spot (8 h). The cata-
lyst was removed by filtration and washed
with water. The combined filtrates were con-
aromatic); 5.23 (d, 1 H, J1%,2% 3.4 Hz, H-1%);
5.04–4.56 (m, 12 H, 6 CH2Ph); 4.96 (broad s,
1 H, H-5%); 4.48 (broad d, 1 H, J3,4 2.5 Hz,
H-4); 4.43 (d, 1 H, J1,2 7.6 Hz, H-1); 4.37
(broad s, 1 H, H-4%); 4.02 (dd, 1 H, J2%,3% 10,
J3%,4% 3.3 Hz, H-3%); 3.95 (s, 1 H, H-5); 3.85 (dd,
1 H, H-2%); 3.72 (dd, 1 H, J2,3 10 Hz, H-2);
13
3.53 (s, 3 H, OCH3); 3.43 (dd, 1 H, H-3); C

198
D. Magaud et al. / Carbohydrate Research 314 (1998) 189–199
emental analysis for this very hygroscopic
compound was not obtained.
centrated under reduced pressure to give crude
24 (72 mg, 95%) as a colorless solid. In order
to get correctly resolved NMR spectra, a solu-
tion of 24 in water was treated with Dowex 50
H+ (0.2 g) for 10 min. Then the resin was
filtered off and washed with water. After con-
centration the residue was thrice dissolved in
D2O (2 mL) and the resulting solution was
concentrated under reduced pressure before
recording the NMR spectra. [h]2D5 +135° (c
Acknowledgements
The authors gratefully acknowledge the
European Community (Contract AIR2-CT94-
1345) and the Centre National de la
Recherche Scientifique for financial sup-
port.
1
0.83, water); H NMR (D2O): l 5.35 (d, 0.4
H, J1,2 3.7 Hz, a H-1); 5.04 (s, 0.4 H, a H-5%);
5.03 (s, 0.6 H, b H-5%); 4.94 (broad d, 1 H,
H-1%); 4.82 (broad s, 0.4 H, a H-5); 4.66 (d, 0.6
H, J1,2 7.8 Hz, b H-1); 4.49 (s, 0.6 H, b H-5);
4.44 (broad d, 0.4 H, a H-4); 4.38 (broad d,
0.6 H, b H-4); 4.33–4.32 (m, 1 H, H-4%); 4.02
(dd, 0.4 H, J2,3 10.6, J3,4 3.1 Hz, a H-3);
3.95–3.88 (m, 1 H, H-3%); 3.81, 3.80 (2s, 3 H,
CH3O); 3.80–3.75 (m, 1 H, a H-2, b H-3);
3.71–3.70 (m, 1 H, H-2%); 3.48 (dd, 0.6 H, J2,3
10.1 Hz, b H-2); 13C NMR (D2O): l 173.3,
171.2, 170.3 (C-6,6%); 100.9 (C-1%); 96.9 (b C-
1); 92.9 (a C-1); 79.5, 78.6, 73.7, 71.8, 71.5,
71.4, 70.4, 70.3, 69.2, 68.3, 68.2, 68.1 (C-
2,3,4,5,2%,3%,4%,5%); 53.5, 53.4 (CH3O). Satisfac-
tory elemental analysis for this very
References
[1] R. Stuart, J.N. BeMiller, in: M.L. Fishman, J.J. Jen
(Eds.), Chemistry and Function of Pectins, ACS Symp.
Ser. 310, 1986, pp. 2–12.
[2] C. Rolin, B.U. Nielsen, P.-E. Glahn, Pectin, in S. Du-
mitriu (Ed.), Polysaccharides, Marcel Dekker, New
York, 1998, pp. 377–431.
[3] J.K. Burns, The polygalacturonases and lyases, in R.H.
Walter (Ed.), The Chemistry and Technology of Pectin,
Academic Press, New York, 1991, pp. 165–187.
[4] F. Alessi, A. Doutheau, D. Anker, G. Condemine, J.
Robert-Baudouy, Tetrahedron, 52 (1996) 4625–4636
and references therein.
[5] Y. Nakahara, T. Ogawa, Carbohydr. Res., 173 (1988)
306–315.
[6] T. Mukaiyama, Y. Murai, S. Shoda, Chem. Lett.,
(1981) 431–432.
[7] V. Pozsgay, Synthesis of oligosaccharides related to
plant, vertebrate, and bacterial cell-wall glycans, in H.
Ogura, A. Hasegawa, T. Suami-Kodansha (Eds.), Car-
bohydrates, Synthetic Methods and Application in
Medicinal Chemistry, VCH, Weinheim, 1992, pp. 188–
227.
[8] C. Vogel, C. Bergemann, H. Boye, H.A.Y. Ott, V.I.
Betaneli, N.K. Kotchekov, J. Carbohydr. Chem., 13
(1994) 47–62.
[9] N.K. Kochetkov, Tetrahedron, 43 (1987) 2389–2436.
[10] P.J. Garegg, Ad6. Carbohydr. Chem. Biochem., 52
(1997) 179–205.
[11] P. Konradson, U.E. Udodong, B. Fraser-Reid, Tetra-
hedron Lett., 31 (1990) 4313–4316.
[12] D. Magaud, C. Grandjean, A. Doutheau, D. Anker, V.
Shevchik, N. Cotte-Pattat, J. Robert-Baudouy, Tetra-
hedron Lett., 38 (1997) 241–244.
[13] C.H. Vogel, H. Boye, H. Kristen, J. Pratkt. Chem.,
332 (1990) 28–36 and ref. [19].
[14] R.H. Shah, F. Loewus, Carbohydr. Res., 4 (1967) 402–
407.
[15] J.R. Turvey, T.P. Williams, J. Chem. Soc., (1962)
2119–2122.
[16] T. Miyazawa, T. Endo, S. Siihashi, M. Okawara, J.
Org. Chem., 50 (1985) 1332–1334.
[17] P.L. Anelli, C. Biffi, F. Montanari, S. Quici, J. Org.
Chem., 52 (1987) 2559–2562.
1
hygroscopic compound was not possible. H
NMR data of this dimer are in full agreement
with selected reported values [25].
Methyl h-
4)-h,i- -galactopyranuronic acid (25).—This
D
-galactopyranosyluronate-(1“
D
compound was obtained from 21 (0.1 g), as
described for 24, as a colorless solid (0.034 g,
1
90%); [h]2D5 +113° (c 0.43, water); H NMR
(D2O): l 5.35 (d, 0.4 H, J1%,2% 3.8 Hz, a H-1);
5.13 (broad s, 1 H, H-5%); 5.06 (broad d, 1 H,
H-1%); 4.76 (broad s, 0.4 H, a H-5); 4.66 (d, 0.6
H, J1,2 7.8 Hz, b H-1); 4.45 (broad d, 0.4 H, a
H-4); 4.42 (s, 0.6 H, b H-5); 4.39 (broad d, 0.6
H, b H-4); 4.33–4.34 (m, 1 H, H-4%); 4.03 (dd,
0.4 H, J2,3 10.5, J3,4 3.1 Hz, a H-3); 3.98-3.90
(m, 1H, H-3%); 3.84–3.78 (m, 1 H, a H-2, b
H-3); 3.80 (s, 3 H, OCH3); 3.73 (dd, 0.6 H,
J1%,2% 3.9, J2%,3% 10.6 Hz, b H-2%); 3.72 (dd, 0.4 H,
J1%,2% 3.9, J2%,3% 10.5 Hz, a H-2%); 3.49 (dd, 0.6 H,
J2,3 10.2 Hz, b H-2); 13C NMR (D2O): l 172.5,
171.9, 171.6 (C-6,6%); 100.6 (C-1%); 96.8 (b C-
1); 92.8 (a C-1); 79.0, 78.2, 73.3, 72.0, 71.7,
71.5, 70.5, 69.8, 69.1, 69.0, 68.3, 68.2 (C-
2,3,4,5,2%,3%,4%,5%); 53.3 (CH3O). Satisfactory el-
[18] Y.E. Tsvetkov, N.E. Byramova, L.V. Backinowsky,
Carbohydr. Res., 115 (1983) 254–258.
[19] A. Lipta´k, I. Jodal, J. Harangi, P. Nanasi, Acta Chim.
Hung., 113 (1983) 415–422.

D. Magaud et al. / Carbohydrate Research 314 (1998) 189–199
199
[20] M. Nilsson, C.-M. Svahn, J. Westman, Carbohydr. Res.,
246 (1995) 161–172.
[21] A. Fernandez-Mayoralas, A. Marra, M. Trumtel,
A. Veyrie`res, P. Sinay¨, Carbohydr. Res., 188 (1989) 81–
95.
[23] C. Vogel, W. Steffan, A.Y. Ott, V.I. Betaneli, Carbohydr.
Res., 237 (1992) 115–129.
[24] N.C.R. van Straten, H.I. Duynstee, E. de Vrom, G.A.
van der Marel, J.H. van Boom, Liebigs Ann./Recueil,
(1997) 1215–1220.
[22] S. David, A. Thieffry, A Veyrie`res, J. Chem. Soc., Perkin
Trans. 1, (1981) 1796–1801.
[25] S.B. Tjan, A.G.J. Voragen, W. Pilnik, Carbohydr. Res.,
34 (1974) 15–23.
.