Synthesis of some galactofuranosyl disaccharides using a galactofuranosyl trichloroacetimidate as donor

Article abstract of DOI:10.1016/S0008-6215(98)00062-7

2,3,5-Tri-O-benzoyl-6-O-benzyl-β-D-galactofuranosyl trichloroacetimidate has been prepared for the first time and utilised as glycosyl donor for the synthesis of several disaccharides containing the β- linked galactofuranoside moiety.

Full text of DOI:10.1016/S0008-6215(98)00062-7

Carbohydrate Research 308 (1998) 207±211
Note
Synthesis of some galactofuranosyl
disaccharides using a galactofuranosyl
trichloroacetimidate as donor
Ambar Kumar Choudhury, Nirmolendu Roy*
Department of Biological Chemistry, Indian Association for the Cultivation of Science,
Calcutta 700 032, India
Received 30 September 1997; accepted in revised form 4 March 1998
Abstract
2,3,5-Tri-O-benzoyl-6-O-benzyl-ꢀ-d-galactofuranosyl trichloroacetimidate has been prepared
for the ®rst time and utilised as glycosyl donor for the synthesis of several disaccharides containing
the ꢀ-linked galactofuranoside moiety. # 1998 Elsevier Science Ltd. All rights reserved
Keywords: Galactofuranosyl trichloroacetimidate; Glycosidation; TMSOTf; Disaccharides
Synthesis of oligosaccharides containing
furanose units is a topic of increasing interest in the
®eld of glycobiology. d-Galactofuranoside moi-
eties are the constituents of many polysaccharides
of bacterial [1] and plant [2] origin as well as
Kinetoplastid parasites [3] and they were claimed
to be immunodominant in many bacterial antigens
[4]. Although not many oligosaccharides having
furanoside components have so far been prepared,
reports of the synthesis of disaccharides utilising
d-galactofuranose pentabenzoate [5] as donor are
available. Synthesis of oligosaccharides containing
galactofuranose have also been reported recently
using acylic glycosyl donors [6]. O-Pentenyl galac-
tofuranoside derivatives have been used for the
synthesis of some disaccharides and glycolipids [7].
We have recently [8] reported some novel dis-
accharides using ethyl 2,3,5,6-tetra-O-benzoyl-
1-thio-(methyl-ꢀ-d-galactofuranosiduronate)
as
donor. Although the preparation and glycosidation
of a ribofuranosyl trichloroacetimidate derivative
[9] and mannofuranosyl trichloroacetamidate [10]
has been already reported, no trichloroacetimidate
of galactofuranose derivatives have been described
so far. Since there is wide utilisation of pyranose
trichloroacetimidates as glycosyl donors, the pos-
sibility of using furanose trichloroacetimidate deri-
vatives in glycosidation reactions seems to be
highly promising. We report here the ®rst synthesis
of 2,3,5-tri-O-benzoyl-6-O-benzyl-ꢀ-D-galactofur-
anosyl trichloroacetimidate and its use as glycosyl
donor for the synthesis of disaccharides containing
ꢀ-d-galactofuranoside.
* Corresponding author.
0008-6215/98/$19.00 # 1998 Elsevier Science Ltd. All rights reserved
PII S0008-6215(98)00062-7

208
A.K. Choudhury, N. Roy/Carbohydrate Research 308 (1998) 207±211
1. Results and discussion
The ꢀ-galactofuranoside nature of the residues
in the disaccharide derivatives was con®rmed by
the presence of the characteristic 13C NMR signals
for C-10 (ꢂ 105±107), C-20 (ꢂꢁ81.6) and C-40 (ꢂ
82.4±83.0); the only exception being the 13C NMR
signal of C-1 in the (1!1) disaccharide 11, which
appeared at a much higher ®eld (ꢂ 101.4). This
deviation has, however, already been reported [5].
The reported 13C NMR signals [16] of C-1 and C-2
in methyl ꢁ-d-galactofuranoside are ꢂ 103.1 and
77.4, respectively, which are quite di€erent from
those of the methyl ꢀ-d-galactofuranoside. The
ꢀ-selectivity in the glycoside formation may be
explained by the participation of the C-2 benzoyl
group. Moreover, steric interaction of two large
groups in 1,2-cis con®guration in ꢁ-galactofuranoside
The known 1,2:3,4-di-O-isopropylidene-d-galac-
tose (1, Scheme 1) [11] was benzylated in the usual
way to give the 6-O-benzyl derivative 2. Treatment
of 2 with p-toluenesulfonic acid in methanol at
ꢀ
70 C gave methyl-6-O-benzyl-ꢀ-d-galactofurano-
side (3). The structure of 3 was con®rmed by GLC
1
and H NMR spectroscopy. Benzoylation of 3 fol-
lowed by acetolysis [12] of the product 4 furnished
the ꢀ-acetate 5. Treatment of 5 with hydrogen
bromide in acetic acid±acetic anhydride [13] a€or-
ded exclusively 2,3,5-tri-O-benzoyl-6-O-benzyl-d-
galactofuranose (6). No galactosyl bromide could
be detected in the reaction mixture. Compound 6
was allowed to react in dichloromethane with tri-
chloroacetonitrile in the presence of potassium
carbonate [14] giving 2,3,5-tri-O-benzoyl-6-O-ben-
zyl-ꢀ-d-galactofuranosyl trichloroacetimidate (7)
(85%) together with a small amount (8%) of its
ꢁ-anomer.
The trichloroacetimidate donor 7 (1.2 mmol) was
then allowed to react with 1 mmol each of the
acceptors 12 [15], 13, 14 [8] and 6, having primary
or secondary hydroxyl groups free and using
trimethylsilyl tri¯uoromethanesulfonate [14] as
promoter, giving the ꢀ-linked disaccharide deriva-
tives 8, 9, 10 and 11 (Scheme 2).
Scheme 1. Reageꢀnts: (a) NaH, BnBr, DMF; (b) 0.1 M p-
TsOH, MeOH, 70 C, 6 h, 65%; (c) BzCl, pyridine, 3 h, quan;
(d) 4:1:0.1 AcOH±Ac2O±concd H2SO4, 0 ꢀC!r.t., 2 h, 75%;
ꢀ
(e) 33% HBr±AcOH, Ac2O, CH2Cl2, 0 C, 74%; (f) CH2Cl2,
K2CO3, CCl3CN, r.t., 85%.
Scheme 2.

A.K. Choudhury, N. Roy/Carbohydrate Research 308 (1998) 207±211
209
may hinder their formation. This may explain the
exclusive formation of the ꢀ-glycoside 11 although
the acceptor contained 30% of ꢁ-galactofuranose
derivative.
The disaccharide derivatives 8, 9, 10 and 11 were
then hydrogenolysed and the products were treated
with sodium methoxide to a€ord the desired dis-
accharides in the form of their glycosides, namely
15, 16, 17 and 18. Compounds 16 and 18 had
identical physical data as reported earlier and all
(except 18) have characteristic signals at ꢂꢁ109
(C-10) and ꢂꢁ84 (C-40) in their 13 NMR spectra [5].
H, H-5), 5.64 (d, 1 H, J3,4 5 Hz, H-3), 5.44 (s, 1 H,
H-2), 5.22 (s, 1 H, H-1), 4.55 (dd, 1 H, J3,4 5 Hz,
J4,5 4 Hz, H-4), 4.50 (s, 2 H, CH2Ph), 3.80 (d, 2 H,
J5,6 6 Hz, H-6), 3.42 (s, 3 H, OCH3). Anal. Calcd
for C35H32O9: C, 70.45; H, 5.40. Found: C, 70.62;
H, 5.57.
1-O-Acetyl-2,3,5-tri-O-benzoyl-6-O-benzyl-b-d-
galactofuranose (5).ÐTo a solnꢀ of 4 (500 mg,
0.84 mmol) in AcOH (4 mL) at 0 C, Ac2O (1 mL)
and concd H2SO4 (0.1 mL) were added and the
mixture was stirred for 30 miꢀn. The temperature
was then allowed to rise to 25 C, and after 90 min
the reaction was quenched with crushed ice. The
mixture was extracted with CH2Cl2 (3Â10 mL) and
the organic layer was washed successively with ice
water, aq NaHCO3 and water, dried and con-
2. Experimental
General.ÐAll reactions were monitored by TLC
on silica gel G (E. Merck). Column chromato-
graphy was performed on 100±200 mesh silica gel
(SRL, India). All solvents were distilled and/or
dried before useꢀand all evaporations were con-
ducted below 40 C under reduced pressure unless
stated otherwise. Optical rotations were measured
with a Perkin-Elmer model 241 MC polarimeter.
1H and 13C NMR spectra were recorded on a Jeol
FX-100 or Bruker 300 MHz spectrometer using
CDCl3 as solvent (internal standard Me4Si) unless
otherwise stated. Melting points were determined
on a paran oil bath and are uncorrected.
centrated. Column chromatography (toluene±
25
EtOAc 10:1) gave 5 (395 mg, 75.2%) as foam. ‰ꢁŠ
D
4.8ꢀ (c 1.3, CHCl3); 1H NMR: ꢂ 7.19±8.08 (m, 20
H, aromatic protons), 6.48 (s, 1 H, H-1), 5.81 (m, 1
H, H-5), 5.66 (d, 1 H, J3,4 4 Hz, H-3), 5.56 (bs, 1 H,
H-2), 4.81 (t, 1 H, J 4 Hz, H-4), 4.56 (s, 2 H,
CH2Ph), 3.85 (d, 2 H, J5,6 6 Hz, H-6), 2.30 (s, 3H,
OAc). Anal. Calcd for C36H32O10: C, 69.22; H,
5.16. Found: C, 69.10; H, 5.38.
2,3,5-Tri-O-benzoyl-6-O-benzyl-d-galactofuranose
(6).ÐTo a solꢀn of 5 (400 mg, 0.64 mmol) in CH2Cl2
(10 mL) at 0 C, Ac2O (0.5 mL) and 33% HBr in
AcOH (3 mL) were added. The mixture was stirred
for 2 h and then diluted with CH2Cl2 (15 mL),
washed successively with ice-water, cold saturated
NaHCO3 and cold water. The organic layer was
dried, ®ltered and then concentrated to a syrup.
Methyl 6-O-benzyl-b-d-galactofuranoside (3).ÐA
soln of 2 (2 g, 5.7 mmol) and p-TsOH (760 mg) in
MeOH (40 mL) was re¯uxed for 6 h. The soln was
then neutralized with Et3N and concentrated to a
syrup. Column chromatography (EtOAc) gave 3
Column chromatography (5:1 toluene±EtOAc)
25
D
25
D
1
(1.05 g, 64.8%). ‰ꢁŠ
76.2ꢀ (c 2.6, CHCl3); H
gave pure 6 (277 mg, 74.2%) as a syrup. ‰ꢁŠ
ꢀ
1
NMR: ꢂ 7.33 (s, 5 H, aromatic protons) 5.03 (s, 1
H, H-1), 3.36 (s, 3 H, OCH3). Anal. Calcd for
C14H20O6: C, 59.14; H, 7.09. Found: C, 58.95; H,
7.18.
+10.8 (c 0.4, CHCl3); H NMR: ꢂ 7.23±8.00 (m,
20 H, aromatic protons), 6.14 (m, 1 H, H-5), 5.75
(d, 1 H, J3,4 4 Hz, H-3), 5.65 (d, 1 H, J1,2 6 Hz, H-2,
a), 5.60 (bs, 1 H, H-2, ꢀ), 5.53 (d, 1 H, J1,2 6 Hz, H-
1, ꢁ), 5.36 (s, 1 H, H-1), 4.75 (t, 1 H, J 4 Hz, H-4),
4.50 (s, 2 H, CH2Ph), 3.82 (d, 2 H, J5,6 6 Hz, 6-H).
13C NMR: ꢂ 165.6±166.4 (COPh) 127.6±137.7
(aromatic carbons), 100.8 (C-1, ꢀ, 75%), 95.8 (C-1,
ꢁ, 25%), 83.0 (C-4), 81.6 (C-2), 78.8 (C-3), 76.6,
73.4, 71.5, 68.5 (C-6). Anal. Calcd for C34H30O9:
C, 70.09; H, 5.19. Found: C, 70.15; H, 5.32.
Methyl 2,3,5-tri-O-benzoyl-6-O-benzyl-b-d-gal-
actofuranoside (4).ÐTo a soln of 3 (500 mg,
1.76 mmol) in pyridine (20 mL), benzoyl cꢀhloride
(1 mL, 8.6 mmol) was added dropwise at 0 C and
the mixture was stirred for 1 h. Water (1 mL) was
added and stirring was continued for another
30 min. The mixture was concentrated to a small
vol., diluted with CH2Cl2, washed with aq NaHCO3
and water. The soln was ®ltered, dried and then
concentrated. Column chromatography (10:1
2,3,5-Tri-O-benzoyl-6-O-benzyl-b-d-galactofuran-
osyl trichloroacetimidate (7).ÐTo a soln of 6
(375 mg, 0.64 mmol) in CH2Cl2 (3 mL), K2CO3
(450 mg) and trichloroacetonitrile (0.35 mL,
3.4 mmol) were added. The mixture was stirred at
room temperature for 6 h, then ®ltered through
toluene±EtOAc) gave 4 (1.03 g, 98%) as an amor-
25
D
phous solid. ‰ꢁŠ
17ꢀ (c 5.2, CHCl3); 1H NMR: ꢂ
7.20±8.06 (m, 20 H, aromatic protons), 5.66 (m, 1

210
A.K. Choudhury, N. Roy/Carbohydrate Research 308 (1998) 207±211
Celite. The ®ltrate was diluted with CH2Cl2,
washed three times with water, dried and con-
centrated. Column chromatography of the result-
ing syrup (10:1 toluene±EtOAc) gave 7 (395 mg,
84.9%) together with its ꢁ-anomer (38 mg, 8.1%).
Anal. Calcd for C53H52O16S: C, 65.15; H, 5.36.
Found: C, 65.02; H, 5.50.
Methyl 2,3,5-tri-O-benzoyl-6-O-benzyl-b-d-gal-
actofuranosyl-(1!6)-2,3,5-tri-O-benzyl-b-d-galacto-
25
D
furanoside (9).Ð164 mg, 85%; ‰ꢁŠ
6.7ꢀ (c 1.6,
25
‰ꢁŠ
30.7ꢀ (c 0.2, CHCl3); H NMR: ꢂ 8.78 (s, 1
CHCl3); H NMR: ꢂ 7.25±8.06 (m, 20 H, aromatic
protons), 5.80 (m, 2 H, H-5, H-50), 5.75 (bs, 1 H,
1
1
D
H, CONHCCl3), 7.40±8.10 (m, 20 H, aromatic
protons), 6.70 (s, 1 H, H-1), 5.86 (m, 1 H, H-5),
5.76 (d, 1 H, J3,4 4 Hz, H-3), 5.70 (s, 1 H, H-2), 4.88
(t, 1 H, J 4 Hz, H-4), 4.56 (s, 2 H, CH2Ph), 3.84 (d,
2 H, J5,6 6 Hz, H-6). 13C NMR: ꢂ 166.2±165.6
(COPh), 160.8 (C ˆ NH), 125.8±138.2 (aromatic
carbons), 103.5 (C-1), 85.0 (C-4), 81.5 (C-2), 77.7
(Ccl3), 77.1 (C-3), 73.7 (C-5), 63.5 (C-6). Anal.
H-20), 5.63 (d, 1 H, J1 ,2 1.2 Hz, H-10), 5.62 (bs, 1
H, H-2), 5.10 (d, 1 H, J1,2 1.2 Hz, H-1), 4.97 (t, 1
H, J 3 Hz, H-40), 4.67 (t, 1 H, J 3.6 Hz, H-4), 3.79
(d, 2 H, J5,6 6 Hz, H-60), 3.40 (s, 3 H, OCH3). 13C
NMR: ꢂ 166.3±165.8 (6 COPh), 133.8±127.9 (aro-
matic carbons), 106.8 (C-10), 105.5 (C-1), 82.3 (C-
40), 82.2 (C-4), 81.6 (2 C, C-20, C-2), 77.5, 73.7,
73.1, 71.2 (C-6), 68.4 (C-60), 54.9 (OCH3). Anal.
Calcd for C62H54O17: C, 69.52; H, 5.08. Found: C,
69.35; H, 5.27.
0
0
Calcd for C36H30O9NCl3: C, 59.47; H, 4.16.
25
Found: C, 59.66; H, 4.31. ꢁ-Anomer of 7: ‰ꢁŠ
D
+27.0ꢀ (c 0.44, CHCl3); H NMR: ꢂ 8.56 (s, 1 H,
1
CONHCCl3), 7.50±8.08 (m, 20 H, aromatic pro-
tons) 6.86 (d, 1 H, J1,2 4 Hz, H-1), 6.30 (t, 1 H, J
6 Hz, H-3), 5.82 (dd, 1 H, J1,2 4 Hz, J2,3 6 Hz, H-2),
5.64 (m, 1 H, H-5), 4.82 (t, 1 H, J 6 Hz, H-4), 4.48
(s, 2 H, CH2Ph), 3.92 (d, 2 H, J5,6 6 Hz, H-6). Anal.
Calcd for C36H30O9NCl3: C, 59.47; H, 4.16.
Found: C, 59.60; H, 4.27.
General procedure for glycosidation.ÐA mixture
of donor 7 (0.22 mmol), the acceptor (0.18 mmol),
4 A molecular sieves in CH2Cl2 (3 mL) was stirred
for 3 h at 25 ꢀC. The mixture was cooled to 20 ꢀC
and TMSOTf (0.10 mmol) was added upon stir-
ring. After 20 min of continued stirring, the reac-
tion mixture was diluted with CH2Cl2, ®ltered and
washed successively with saturated NaHCO3
and water. The organic layer was dried and then
concentrated. Column chromatography (8:1
toluene±EtOAc) gave the pure disaccharide deri-
vatives. The physical data of the compounds are
given below.
Methyl 2,3,5-tri-O-benzoyl-6-O-benzyl-b-d-galacto-
furanosyl-(1!4)-2,3-di-O-benzoyl-a-d-fucopyrano-
side (10).Ð105 mg, 78%; ‰ꢁŠ
79.5ꢀ (c 0.9,
D
1
CHCl3); H NMR: ꢂ 1.44 (7.10±8.00 (m, 20 H,
aromatic protons), 5.75 (m, 1 H, H-50), 5.69 (d, 1
H, J3,4 4 Hz, H-30), 5.56 (bs, 1 H, H-20), 5.39 (bs, 1
H, H-10), 5.17 (d, 1 H, J1,2 3.0 Hz, H-1), 4.45 (t, 1
H, J 4 Hz, H-40), 3.44 (s, 3 H, OCH3), 1.44 (d, 3 H,
J5,6 6.6 Hz, H-6). 13C NMR: ꢂ 165.8±165.3 (5
COPh), 133.4±127.3 (aromatic carbons), 107.1 (C-
10), 97.5 (C-1), 83.1 (C-40), 81.8 (C-20), 77.3, 76.5,
72.6, 71.3, 70.2, 68.9, 68.7 (C-60), 65.8 (C-6), 55.4
(OCH3), 16.4 (CCH3). Anal. Calcd for C55H50O15:
C, 69.46; H, 5.30. Found: C, 69.32; H, 5.41.
2,3,5-tri-O-benzoyl-6-O-benzyl-b-d-galactofuran-
osyl-(1!1)-2,3,5-tri--O-benzoyl-6-O-benzyl-b-d-gal-
actofuranoside (11).Ð148 mg, 72%; [a]D 16.4ꢀ (c
1
4.56, CHCl3); H NMR: ꢂ 7.20±8.12 (m, 40 H,
aromatic protons), 5.87 (m, 2 H, H-5, 50), 5.73 (s, 2
H, H-2, 20), 5.69 ((d, 2 H, J3,4 5.1 Hz, H-3, 30), 5.57
(s, 2 H, H-1, 10), 4.90 (t, 2 H, J 4.5 Hz, H-4, 40),
4.56 (dd, 4 H, J 12 Hz, 2 CH2C6H5), 3.90 (d, 4 H, J
6 Hz, H-6, 60). 13C NMR: ꢂ 166.3±165.8 (COPh),
128.0±138.2 (aromatic carbons), 101.4 (C-1, 10),
82.9 (C-4, 40), 82.6 (C-2, 20), 73.8, 73.7, 71.8 (C-5,
50), 69.0 (C-6, 60). Anal. Calcd for C68H58O17: C,
71.19; H, 5.09. Found: C, 71.11; H, 5.23.
1-S-p-Tolyl 2,3,5-tri-O-benzoyl-6-O-benzyl-b-d-gal-
actofuranosyl-(1!3)-2,4,6-tri-O-acetyl-b-d-galacto-
25
pyranoside (8).Ð144 mg, 82%; ‰ꢁŠ +8.3ꢀ (c 1.4,
D
1
CHCl3); H NMR: ꢂ 7.10±8.13 (m, 24 H, aromatic
protons), 5.46 (d, 1 H, J3,4 3.6 Hz, H-3), 5.36 (d, 1
H, J 0.9 Hz, H-20), 5.31 (t, 1 H, J 12 Hz, H-2), 5.26
(d, 1 H, J1 ,2 0.9 Hz, H-10), 4.89 (dd, 1 H, J3,4
3.6 Hz, J4,5 5.1 Hz, H-4), 4.63 (dd, 2 H, CH2C6H5),
4.55 (d, 1 H, J1,2 12 Hz, H-1), 2.34 (s, 3 H,
SC6H4CH3), 2.21, 2.08 and 2.05 (3 s, 9 H, 3 OAc).
13C NMR: ꢂ 170.2±165.3 (3 COCH3, 3 COPh)
126.6±137.9 (aromatic carbons), 107.4 (C-10),
87.0 (C-1), 82.8 (C-40), 82.4 (C-20), 77.5, 76.4, 74.8,
73.0, 71.2, 69.2, 68.8, 68.3 (C-60), 62.3 (C-6), 21.0
(SC6H4CH3), 20.8, 20.5 and 20.4 (3 COCH3).
0
0
1-S-p-Tolyl b-d-galactofuranosyl-(1!3)-b-d-gal-
actopyranoside (15).ÐTo a soln of 8 (75 mg,
0.08 mmol) in 2:1:1 1-propanol±AcOH±H2O [17]
(5 mL) was addedꢀ10% Pd/C (75 mg). The mixture
was stirred at 80 C for 20 h, then cooled, ®ltered
through Celite, and concentrated to dryness. The
product was puri®ed by column chromatography
(EtOAc) and then treated with 0.05 M MeONa in

A.K. Choudhury, N. Roy/Carbohydrate Research 308 (1998) 207±211
211
MeOH (4 mL). After 2 h, the soln was made neu-
tral by the addition of Amberlite IR-120 (H+)
resin, ®ltered and the solvent was evaporated to
provide the product which was puri®ed by column
(D2O): ꢂ 104.7 (C-1, 10), 84.4 (C-4, 40), 82.2 (C-2,
20), 78.0, 72.0, 64.1 (C-6, 60). Anal. Calcd for
C12H22O11: C, 42.11; H, 6ꢀ.48. Found: C, 41.82; H,
6.65. Lit [5] mp 206±208 C (MeOH); [ꢁ]D 150ꢀ
(H2O).
chromatography (19:1 EtOAc±EtOH) yielding
25
D
pure 15 (23 mg, 67%) as an amorphous solid; ‰ꢁŠ
ꢀ
1
+25 (0.9, CHCl3). H NMR (D2O): ꢂ 5.30 (bs, 1
H, H-10), 4.48 (d, 1 H, J1,2 12 Hz, H-1), 4.29 (bs, 1
H, H-4), 1.78 (s, 3 H, SC6H4CH3). 13C NMR
(D2O): ꢂ 127±135 (aromatic carbons), 109.7 (C-10),
88.4 (C-1), 84.6 (C-40), 82.3 (C-20), 77.1, 75.4, 73.5,
72.0, 71.0, 69.5, 63.4 (C-6, C-60), 62.0, 20.7
(SC6H4CH3). Anal. Calcd for C19H28O10S:
C,50.88; H, 6.29. Found: C, 50.62; H, 6.48.
Acknowledgements
We thank the Department of Science and Tech-
nology, New Delhi (Project No. SP/S1/G14/95) for
®nancial support.
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Pd/C (60 mg) in a Paar apparatus overnight. The
product was puri®ed by column chromatography
and debenzoylated with MeONa as described for
the preparation of 15 giving pure 16 (19.8 mg,
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25
87ꢀ (c 1, H2O). H
1
72%) as colourless glass; ‰ꢁŠ
D
NMR (D2O): ꢂ 5.43 (bs, 1 H, H-10), 5.20 (bs, 1 H,
H-1), 3.42 (s, 3 H, OCH3). 13C NMR (D2O): ꢂ
109.6 (C-1, 10), 109.2, 84.5 (C-4, C-40), 82.5 (C-2,
C-20), 82.2, 78.5, 78.2, 72.4, 71.1, 70.6 (C-6), 64.3
(C-60), 56.5 (CH3O). Anal. Calcd for C13H24O11
:
C, 43.82; H, 6.79. Found: C, 44.15; H, 6.90. Lit [5]
[a]D 90ꢀ (H2O).
Methyl
b-d-galactofuranosyl-(1!4)-a-l-fuco-
pyranose (17).ÐA soln of 10 (72 mg, 0.07 mmol)
was hydrogenolysed and debenzoylated as descri-
bed for the preparation of 16 to a€ord pure 17
25
ꢀ
1
(18 mg, 70%); ‰ꢁŠ
18.8 (c 0.8, H2O); H NMR
D
(D2O): ꢂ 5.32 (bs, 1 H, H-10), 5.10 (d, 1 H, J1,2
2.5 Hz, H-1), 3.40 (s, 3 H, OCH3), 1.42 (d, 3 H, J5,6
6 Hz, H-6). 13C NMR (D2O): ꢂ 109.8 (C-10) 98.1
(C-1), 84.1 (C-40), 79.0, 75.9, 75.3, 71.5, 70.3, 70.1,
68.0, 64.2 (C-60), 63.1 (C-6), 55.6 (OCH3), 16.1
(CCH3). Anal. Calcd for C13H24O10: C, 45.88; H,
7.11. Found: C, 45.65; H, 7.32.
b-d-galactofuranosyl-(1!1)-b-d-galactofurano-
side (18).ÐA soln of 11 (82 mg, 0.07 mmol) was
hydrogenolysed and debenzoylated as described
for the preparation of 16 to a€ord pure 18
(19.6 mg, 80%) as an amorphous solid which crys-
25
D
ꢀ
tallised from MeOH; mp 203±205 C; ‰ꢁŠ
148ꢀ
1
(c 0.9, H2O). H NMR (D2O): ꢂ 5.25 (s, 2 H, H-1,
10), 3.88 (d, 4 H, J 6.5 Hz, H-6, 60). 13C NMR