Synthesis of α-D-Galp-(1→3)-β-D-Galf-(1→3)-D-Man, a terminal trisaccharide of leishmania type-2 glycoinositolphospholipids

Article abstract of DOI:10.1021/jo016290z

The synthesis of α-D-Galp-(1→3)-β-D-Galf-(1→3)-D-Man, present in the type-2 glycoinositolphospholipids and in the core of the lipophosphoglycan of Leishmania, is described. The glycosyl aldonolactone approach, followed by reduction of the lactone with diisoamylborane, was utilized for the introduction of the internal galactofuranosyl unit and the trichloroacetimidate method for the O-glycosidation reaction. A high-yield synthesis of the β-D-Galf-(1-3)-D-Man unit, also present in the lipopeptidophosphoglycan of Trypanosoma cruzi, is reported.

Full text of DOI:10.1021/jo016290z

4430
J . Org. Chem. 2002, 67, 4430-4435
Syn th esis of r-D-Ga lp-(1f3)-â-D-Ga lf-(1f3)-D-Ma n , a Ter m in a l
Tr isa cch a r id e of Leish m a n ia Typ e-2 Glycoin ositolp h osp h olip id s
Lucia Gandolfi-Donadio, Carola Gallo-Rodriguez, and Rosa M. de Lederkremer*
CIHIDECAR, Departamento de Quı´mica Orga´nica, Facultad de Ciencias Exactas y Naturales,
Universidad de Buenos Aires, Ciudad Universitaria, Pabello´n II, 1428 Buenos Aires, Argentina
lederk@qo.fcen.uba.ar.
Received November 16, 2001
The synthesis of R-D-Galp-(1f3)-â-D-Galf-(1f3)-D-Man, present in the type-2 glycoinositolphos-
pholipids and in the core of the lipophosphoglycan of Leishmania, is described. The glycosyl
aldonolactone approach, followed by reduction of the lactone with diisoamylborane, was utilized
for the introduction of the internal galactofuranosyl unit and the trichloroacetimidate method for
the O-glycosidation reaction. A high-yield synthesis of the â-D-Galf-(1-3)-D-Man unit, also present
in the lipopeptidophosphoglycan of Trypanosoma cruzi, is reported.
In tr od u ction
did not express LPG, whereas the GIPLs, with the same
type of Galf-Man linkage, were unaffected. This implied
the existence of two different galactofuranosyl trans-
ferases.7 In contrast, in Mycobacterium tuberculosis a
bifunctional UDP-galactofuranosyltransferase was iden-
tified.8
Very recently, the synthesis of the Leishmania LPG
core heptasaccharyl myo-inositol was reported.9 They
used the thioglycoside method for the glycosidation of the
galactofuranose derivative, which was prepared in seven
steps from galactose. In our case, we used a D-galactono-
1,4-lactone derivative, easily prepared in two steps from
the commercial lactone, as the precursor of the furanoic
ring. The mild trichloroacetimidate method10 was em-
ployed for the O-glycosidation reaction.
Leishmania parasites are the agents of leishmaniasis,
a disease which in the mammalian host experiences
ailments ranging from cutaneous lesions to fatal visceral
infections. The life cycle of Leishmania consists of two
stages, the promastigote extracellular form, which is
present in the midgut of the sand fly vector, and the
intracellular amastigotes, which reside within the
phagolisosome in the mammalian macrophage. The gly-
coinositolphospholipids (GIPLs) are a family of low
molecular weight glycolipids1,2 that are major surface
constituents of promastigotes and amastigotes. On the
basis of the structure of the oligosaccharide, GIPLs are
classified into three types. Type 2 is characterized by the
R-D-Galp-(1-3)-â-D-Galf-(1-3)-D-Man (1) unit, which is
also internally present in the lipophosphoglycan (LPG).
Moreover, patients with leishmaniasis are known to have
elevated levels of antibodies directed against the GIPLs
containing the terminal R-D-Galp-(1-3)-D-Galf structure.1
The LPG is the predominant cell surface glycoconjugate
of Leishmania promastigotes, whereas it is substantially
down-regulated in amastigotes. The unusual feature of
LPG and GIPL-2 is the internal galactofuranose. Com-
pound 1 is the smallest moiety containing the sugar. The
biosynthesis of D-Galf containing glycoconjugates is a
topic of great interest, as the sugar in this configuration
is present in pathogenic microorganisms but not in
mammals.3 A UDP-Galp mutase that catalyzes intercon-
versions of UDP-Galp and UDP-Galf in bacteria was
described.4 A gene, LPG1, that encodes a putative ga-
lactofuranosyl transferase was described; in Leishma-
nia,5,6 however, a null mutant of L. major lacking LPG1
We report here for the first time the synthesis of R-D-
Galp(1-3)â-D-Galf(1-3)-D-Man (1). The R-D-Galp-(1-3)-
â-D-Galf derivative prepared by the glycosyl-aldonolac-
tone approach11,12 is a convenient intermediate for further
glycosylation of the reducing end.
Resu lts a n d Discu ssion
The synthesis of an oligosaccharide with internal
galactofuranose represents a challenge because of the
comparative instability of the glycofuranosidic linkage.
Thus, protective groups must be carefully chosen in order
(6) Turco, S. J .; Spa¨th, G. F.; Beverly, S. M. Trends Parasitol. 2001,
17, 233-226.
(7) Spa¨th, G. F.; Epstein, L.; Leader, B.; Singer, S. M.; Avila, H. A.;
Turco, S. J .; Beverly, S. M. Proc. Natl. Acad. Sci. U.S.A. 2000, 97,
9258-9263.
(8) Kremer, L.; Dover, L. G.; Morehouse, C.; Hitchin, P.; Everett,
M.; Morris, H. R.; Dell, A.; Brennan, P. J .; McNeil, M. R.; Flaherty,
C.; Duncan, K.; Besra, G. S. J . Biol. Chem. 2001, 276, 26430-26440.
(9) Ruda, K.; Lindberg, J .; Garreg, P. J .; Oscarson, S.; Konradsson,
P. J . Am. Chem. Soc. 2000, 122, 11067-11072.
* To whom correspondence should be addressed. Fax: 5411-4576-
3352.
(1) McConville, M. J .; Homans, S. W.; Thomas-Oates, J . E.; Dell,
A.; Bacic, A. J . Biol. Chem. 1990, 265, 7385-7394.
(2) McConville, M. J .; Ferguson, M. A. J . Biochem. J . 1993, 294,
305-324.
(3) Lederkremer, R. M.; Colli, W. Glycobiology 1995, 5, 547-552.
(4) Sanders, D. A. R.; Staines, A. G.; McMahon, S. A.; McNeil, M.
R.; Whitfield, C.; Naismith, J . H. Nat. Struct. Biol. 2001, 8, 858-863
and references therein.
(10) Schmidt, R. R.; Kinzy, W. Adv. Carbohydr. Chem. Biochem.
1994, 50, 21-123. Schmidt, R. R. In Modern Method in Carbohydrate
Synthesis; Khan, S. H., O’Neil, P. A., Eds.; Harwood Academic
Publishers: Amsterdam, 1996; pp 20-54. Schmidt, R. R.; J ung, K.-H.
In Preparative Carbohydrate Chemistry; Hanessian, S., Ed.; Marcel
Dekker: 1997; pp 283-312.
(11) Marino, C.; Chiocconi, A.; Varela, O.; Lederkremer, R. M.
Carbohydr. Res. 1998, 311, 183-189.
(5) Ryan, K. A.; Garraway, L. A.; Descoteaux, A.; Turco, S. J .;
Beverley, S. M. Proc. Natl. Acad. Sci. U.S.A. 1993, 90, 8609-8613.
(12) Lederkremer, R. M.; Marino, M.; Varela, O. Carbohydr. Res.
1990, 200, 227-230.
10.1021/jo016290z CCC: $22.00 © 2002 American Chemical Society
Published on Web 05/14/2002

Synthesis of a Trisaccharide of Leishmania GIPLs
J . Org. Chem., Vol. 67, No. 13, 2002 4431
lyst and donor 415 to afford the glycosyl lactone 5 in 74%
yield. The R-anomeric configuration was assigned on the
Sch em e 1. Syn th esis of th e r-D-Ga lp(1-3)-Ga lf
Un ita
1
basis of the NMR spectra. In the H NMR spectrum, the
H-1′ signal appeared as a doublet centered at 4.82 ppm
with J ) 3.8 Hz and the 13C NMR spectrum showed the
anomeric carbon at 99.1 ppm confirming the R assign-
ment.
Reduction of the glycosyl lactone 5 using diisoamyl-
borane (DSB) yielded the furanoic derivative 6 in 88%
yield. Careful quenching of this reaction was important
due to the removal of the isopropylidene funcionality that
showed hydrolysis even by weak acidic aqueous condi-
tions.
The straightforward formation of the trichloroacetim-
idate from the free sugar and the mild conditions for
glycosidation were notorious advantages for this route.
Thus, the trichloroacetimidate derivative of 6 was ob-
1
tained as an R/â mixture of anomers as shown by the H
NMR spectrum. The characteristic resonances due to the
anomeric protons were located at 6.46 ppm (bs, â anomer)
and 6.65 ppm (d, J ) 4.38 Hz, R anomer) in a 6:1 ratio.
Unfortunately, this compound was very unstable and
could not be used for the following step. However,
compound 6 is a good precursor for the disaccharide R-D-
galactopyranosyl-(1f3)-D-galactopyranose since after
deprotection, the reducing sugar would isomerize into the
more stable pyranose. The disaccharide is present in the
mucins of infective trypomastigotes of Trypanosoma cruzi
and represents the major target for trypanolytic anti
RGal antibodies from chagasic patients.16
Taking into account that trichloroacetimidates with a
benzoyl in OH-2 of galactofuranose have been success-
fully used for glycosidation,17 the benzoyl derivative 10
was synthesized. Benzoylation of 2 (45% yield) was not
as selective as pivaloylation, but it was a simple strategy
for obtaining the precursor 7 with the OH-3 free for
glycosidation.
a
Reagents: (i) RCl, C5H5N; (ii) TMSOTf, 4 Å molecular sieves,
ether, 0 °C; (iii) diisoamylborane.
to preserve the structure when the free oligosaccharide
is the target.
Coupling of 7 with the galactopyranosyl donor 4 gave
the R-lactonic disaccharide 9 in 60% yield. Reduction with
DSB produced the furanoic synthon 10. Treatment of 10
with trichloroacetonitrile and DBU gave the correspond-
ing trichloroacetimidate 11, which, in this case, could be
purified by column chromatography without decomposi-
tion.
To study the regioselectivity of glycosidation of the
mannose derivative 14 by the trichloroacetimidate method,
we performed the reaction with the simple galactofura-
nose derivative 13 (Scheme 2). Compound 13 was easily
prepared from the byproduct 8 (Scheme 1). Compound 8
could be obtained in high yield by benzoylation of 2 with
an excess of benzoyl chloride.18 The substituted disac-
charide 15 was obtained in 70% yield by selective
substitution at OH-3 (Scheme 2). Acetylation of OH-2 of
compound 15 and comparison of the spectra (Table 1)
confirmed the high selectivity of the reaction. Compound
15 was deprotected to yield methyl â-D-galactofuranosyl-
(1-3)-R-D-mannopyranoside (17). The 13C NMR spectrum
of 17 previously described19 was recorded at 70 °C; for
In the present work, a derivative of D-galactono-1,4-
lactone with free OH-3 was envisioned as a precursor of
an internal galactofuranose. This choice has the advan-
tage that once the former has been glycosylated with a
convenient derivative of galactopyranose to construct the
R linkage, reduction of the lactone would give the free
anomeric OH group. Indeed, D-galactone-1,4-lactone could
be considered as a virtually protected galactofuranose.
Taking into account that selective acylation of D-ga-
lactono-1,4-lactone gave the 2,5,6-tri-O-acyl derivative in
low yield,13 an alternative strategy was considered. Thus,
5,6-O-isopropylidene-D-galactono-1,4-lactone14 (2) was
selectively pivaloylated, foreseeing the higher reactivity
of OH-2 due to stereoelectronic effects, which increase
the nucleophilicity of the R-hydroxyl group. Treatment
of 2 with 1 equiv of pivaloyl chloride in pyridine at 0 °C
gave the 2-O-pivaloyl derivative 3 that crystallized from
the reaction mixture in 79% yield (Scheme 1). With the
aldonolactone acceptor 3 in hand, the next step was the
construction of the R-Galp-(1-3) linkage. We have previ-
ously described the use of aldonolactones as acceptors in
glycosidations with peracylated sugars as donors and
SnCl4 as promoter.11,12 In the present case, construction
of the R-D-Galp linkage was performed by the trichloro-
acetimidate method, using trimethylsilyl triflate as cata-
(15) Wegmann, B.; Schmidt, R. R. J . Carbohydr. Chem. 1987, 6,
357-375.
(16) Almeida, I. C.; Ferguson, M. A.; Schenkman, S.; Travassos, L.
R. Biochem. J . 1994, 304, 793-802.
(17) Gallo-Rodriguez, C.; Gandolfi, L.; Lederkremer, R. M. Org. Lett.
1999, 1, 245-247; Choudhury, A. K.; Roy, N. Carbohydr. Res. 1998,
308, 207-211.
(13) Gallo, C.; J eroncic, L.; Varela, O.; Lederkremer, R. M. J .
Carbohydr. Chem. 1993, 12, 841-851.
(14) Fleet, G. W. J .; Son, J . C. Tetrahedron 1988, 44, 2637-2647.
(18) Limberg, G.; Thiem, J . Carbohydr. Res. 1995, 275, 107-115.

4432 J . Org. Chem., Vol. 67, No. 13, 2002
Gandolfi-Donadio et al.
Ta ble 1. 1H NMR (500 MHz) Ch em ica l Sh ifts for Com p ou n d s 9, 15, 16, a n d 19-21
δ (ppm), J (Hz)a
H-1
(J 1,2
H-2
(J 2,3
H-3
H-4
H-5
H-6a
H-6b
(J 6a,6b)
compd
)
)
(J 3,4
)
(J 4,5
)
(J 5,6a
4.29
nd
3.93
(8.7)
3.87
(4.0)
4.29
(6.9)
3.9
(4.5)
4.32
(6.4)
3.87
(4.5)
4.07
(6.7)
4.27
(7.0)
)
(J 5,6b
)
9
Gal-one
Galp
Man
Galf
Man
Galf
Man
Galf
Galp
Man
Galf
Galp
Man
Galf
Galp
5.88
4.66
(7.2)
3.89
(2.7)
4.34
(9.7)
5.46
(5.2)
4.46
(9.9)
5.32
(4.8)
4.15
(9.2)
4.07
(4.9)
3.81
(2.9)
3.8
(9.3)
4.19
(5.5)
3.94
(2.8)
3.76
(9.1)
3.84
(7.0)
3.88
(2.6)
4.29
ndb
4.01
3.99-3.97
3.99-3.97
nd
(8.1)
4.03
(10.1)
4.12
(3.4)
4.42
(1.4)
5.36
(3.8)
5.37
(1.0)
3.8
(3.4)
5.67
(1.7)
4.08
(10.3)
3.67
(3.2)
5.57
(1.7)
4.05
(9.9)
3.8
nd
4.89
(3.7)
4.82
(1.3)
5.37
3.42
(5.0)
4.28
(10.2)
3.78
(6.5)
4.28
(10.0)
3.85
(6.1)
4.22
(10.1)
3.67
(6.9)
3.54
(4.9)
3.84
nd
3.18
(8.7)
3.84
(9.4)
3.76
(8.4)
3.83
(10.0)
3.77
(8.7)
3.73
(10.1)
3.57
(8.4)
3.49
(9.9)
3.84
nd
3.62-3.66
nd
3.41
(9.8)
3.83
nd
3.60-3.62
nd
3.24
(9.7)
15
16
19
4.04
(9.3)
4.37
(4.6)
3.96
(9.6)
4.35
(5.1)
3.91
(9.4)
4.32
(4.9)
3.87
4.7
(1.6)
5.35
4.9
(1.3)
5.11
-
5.21
(3.7)
4.8
(1.6)
5.17
-
5.02
(3.7)
4.83
(1.1)
5.02
(2.3)
4.85
(3.7)
20
21
3.91
(9.6)
4.42
(5.7)
3.92
3.62-3.66
nd
3.76
(5.2)
4.15
(6.7)
3.62-3.66
(5.0)
3.46
(5.4)
3.81
3.9
3.62-3.65
(3.2)
4.26
(4.2)
4.05
(10.2)
(9.6)
4.28
(4.4)
3.81
nd
nd
3.68
(4.6)
4.04-4.07
(8.3)
3.60-3.62
(4.5)
3.57
(3.2)
a
NMR assigments are derived from two-dimensional experiments. The signals for the protective groups are shown in the Experimental
b
Section. nd, not determined.
that reason, all our values are slightly shifted (0.8-1
ppm) to higher field. This synthesis is a good alternative
for the preparation of the disaccharide â-D-Galf(1f3)-D-
Manp11 present as external unit in the lipopeptidophos-
phoglycan of T. cruzi.20 The good yield obtained in the
coupling reaction proved that it was not necessary to
protect the OH-2 group of compound 14 as previously
described, using other glycosidation methods.21 It was
reported that glycosidation of methyl glycoside 14 by the
orthoacetate method also took place selectively at OH-
3.19
Sch em e 2. Syn th esis of Meth yl
â-D-Ga lf(1-3)-r-D-Ma n a
In agreement, glycosidation of benzyl mannopyrano-
side 18 with the disaccharide imidate 11 afforded 19 in
80% yield (Scheme 3). The aqueous acidic removal of both
acetal groups to afford 20 proceeded without galactofura-
nosidic cleavage. Debenzoylation of 20 and subsequent
catalytic hydrogenation produced the fully deprotected
trisaccharide 1, in good yield. The1H NMR spectrum of
1 was complex because signals correponding to both
anomers at the reducing end were shown. The anomeric
signals for the three monosaccharide units are in ac-
cordance with the structure. The 13C NMR spectrum
could be completely assigned showing signals for the
anomeric carbon of the internal galactofuranose at δ
105.8 and 105.4 ppm. The anomeric region also showed
the signals for the R-D-Galp at 100.5 ppm and two signals
at 94.7 and 94.5 ppm corresponding to the reducing end
(19) Gorin, P. A. J .; Barreto-Bergter, E. M.; Da Cruz, F. S. Carbo-
hydr. Res. 1981, 88, 177-188.
(20) Lederkremer, R. M.; Lima, C.; Ramirez, M. I.; Ferguson, M. A.
J .; Homans, S. W.; Thomas-Oates. J . Biol. Chem. 1991, 266, 23670-
23675.
(21) J ohnston, B. D.; Pinto, B. M. Carbohydr. Res. 1999, 315, 356-
360.
a
Reagents: (i) diisoamylborane; (ii) Cl3CCN, DBU, CH2Cl2; (iii)
TMSOTf, 4 Å molecular sieves, CH2Cl2, -10 °C; (iv) Ac2O, C5H5N;
(v) 65% aqueous AcOH, 80 °C; (vi) 0.5 M NaOMe in MeOH.

Synthesis of a Trisaccharide of Leishmania GIPLs
J . Org. Chem., Vol. 67, No. 13, 2002 4433
Sch em e 3a
a
Reagents: (i) Cl3CCN, DBU, CH2Cl2, 0 °C; (ii) TMSOTf, 4 Å molecular sieves, CH2Cl2, -10 °C; (iii) 65% aqueous AcOH, 80 °C; (iv) 0.5
M NaOMe in MeOH; (v) H2 (3 atm), 10% Pd(C), MeOH.
(ddd, J ) 7.4, 7.3, 2.1 Hz, 1 H), 4.38 (ddd, J ) 3.3, 6.7, 6.6 Hz,
1 H), 4.24 (dd, J ) 3.3, 7.3 Hz, 1 H), 4.14 (dd, J ) 6.7, 8.5 Hz,
1 H), 4.02 (dd, J ) 6.6, 8.5 Hz, 1 H), 3.51 (d, 1 H, J ) 2.1 Hz,
OH), 1.44 (s, 3 H), 1.39 (s, 3 H), 1.29 (s, 9 H); 13C NMR (CDCl3,
50.3 MHz) δ 179.4, 172.4, 110, 79.8, 76.8, 74.1, 73.4, 65.0, 38.9,
27.0, 26.0, 25.5. Anal. Calcd for C14H22O7: C, 55.62; H, 7.33.
Found: C, 55.76; H, 7.53.
of the Manp. The low field signals at 85.7 for C-4′ and
82.7 ppm for C-2′ are also characteristic of the galacto-
furanosyl unit and coincident with signals reported for
the Leishmania heptasaccharide containing the galacto-
furanosyl unit.9
Con clu sion s
2,3,4,6-Tetr a -O-ben zyl-r-D-ga la ctop yr a n osyl-(1f3)-5,6-
O-isopr opyliden e-2-O-pivaloyl-D-galacton o-1,4-lacton e (5).
A mixture of O-(2,3,4,6-tetra-O-benzyl-â-D-galactopyranosyl)-
trichloroacetimidate15 (4, 300 mg, 0.44 mmol), 3 (141 mg, 0.47
mmol), and powdered 4 Å molecular sieves (500 mg) in dry
ether was vigorously stirred at 0 °C under an argon atmo-
sphere. After 20 min, TMSOTf (25 µL, 0.14 mmol) was slowly
added, and the stirring was continued for 2 h. The suspension
was neutralized by addition of N,N-diisopropyl-N-ethylamine,
filtered through Celite, and concentrated under reduce pres-
sure. Column chromatography (20:1 toluene-EtOAc) of the
residue gave 5 (269 mg, 74%) as a colorless syrup: Rf 0.71
(5:1 toluene-EtOAc), [R]D +31.5° (c 1, CHCl3); 1H NMR
(CDCl3, 500 MHz) δ 7.42-7.23 (m, 20 H), 5.55 (d, J ) 7.7 Hz,
1 H), 4.92 (d, J ) 11.2 Hz, 1H), 4.87 (d, J ) 11.6 Hz, 1H), 4.82
(d, J ) 3.8 Hz, 1H), 4.78, 4.75 (2d, J ) 11.6 Hz, 2H), 4.60 (d,
J ) 11.6 Hz, 1H), 4.59 (d, J ) 11.2 Hz, 1H), 4.48 (d, J ) 11.6
Hz, 1H), 4.43 (dd, J ) 7.1, 7.7 Hz, 1H), 4.41 (d, J ) 11.6 Hz,
1H), 4.26 (dt, J ) 3.2, 6.6 Hz, 1H), 4.20 (dd, J ) 7.1, 3.2 Hz,
1H), 4.06 (bs, 1 H), 4.04 (dd, J ) 10.3, 3.8 Hz, 1H), 3.93-4.00
(m, 3H), 3.88 (dd, J ) 10.3, 2.6 Hz, 1H), 3.60 (t, J ) 8.7 Hz,
1H), 3.44 (dd, J ) 8.7, 5.0 Hz, 1H), 1.41, 1.34 (2s, 6 H, (CH3)2C),
1.20 (s, 9 H, ((CH3)3C); 13C NMR (CDCl3, 50.3 MHz) δ 176.7,
169.1, 138.5-127.3, 110.2 ((CH3)2C), 99.3, 78.8, 78.4, 76.2, 75.0,
74.4, 74.0, 73.9, 73.5, 73.1, 72.6, 70.1, 67.7, 64.9, 38.6, 26.9,
25.9, 25.4. Anal. Calcd for C48H56O12: C 69.88, H 6.84. Found:
C 69.92, H 7.09.
The synthesis of the trisaccharide containing the
internal galactofuranose present in Leishmania GIPLs
and in the core of the LPG is described for the first time.
The strategy was based on the synthesis of the glycosyl-
lactone as precursor for the galactofuranosyl ring. The
choice of the protecting groups facilitated the preparation
of the totally unprotected trisaccharide of special interest
for studies on the glycosyl transferases of Leishmania.
Exp er im en ta l Section
Gen er a l Meth od s. TLC was performed on 0.2 mm silica
gel 60 F254 (Merck) aluminum supported plates. Detection
was effected by exposure to UV light or by spraying with 5%
(v/v) sulfuric acid in EtOH and charring. Column chromatog-
raphy was performed on silica gel 60 (230-400 mesh, Merck).
Melting points were determined with a Thomas-Hoover ap-
paratus and are uncorrected. Optical rotations were measured
with a Perkin-Elmer 343 polarimeter. NMR spectra were
recorded with a Bruker AC 200 spectrometer at 200 MHz (1H)
and 50.3 MHz (13C) or with a Bruker AM 500 spectrometer at
500 MHz (1H) and 125 MHz (13C).
5,6-O-Isop r op ylid en e-2-O-p iva loyl-D-ga la cton o-1,4-la c-
ton e (3). To a stirred solution of 5,6-O-isopropylidene-D-
galactono-1,4-lactone14 (2; 1.1 g, 5.0 mmol) in dry pyridine (20
mL), cooled to 0 °C, was added pivaloyl chloride (0.68 mL, 5.5
mmol) during 1 h. After 1 h of stirring at room temperature,
the mixture was poured into ice-water (300 g) and the stirring
continued for 1 h. The mixture was extracted with CH2Cl2
(2 × 50 mL), and the organic layer was sequentially washed
with HCl 5% (100 mL), water (100 mL), saturated aqueous
NaHCO3 (100 mL), and water, dried (MgSO4), and concen-
trated. The residue crystallized upon addition of hexanes-
EtOAc to give 3 (1.2 g, 79%): mp 127-128 °C (hexanes-
EtOAc); Rf 0.5 (toluene-EtOAc 1:1); [R]D -73.3° (c 1, CHCl3);
1H NMR (CDCl3, 200 MHz) δ 5.22 (d, J ) 7.4 Hz, 1 H), 4.42
2,3,4,6-Tetr a -O-ben zyl-r-D-ga la ctop yr a n osyl-(1f3)-5,6-
O-isop r op ylid en e-2-O-p iva loyl-D-ga la ctofu r a n ose (6). To
a solution of bis(2-butyl-3-methyl)borane (1.6 mmol) in anhy-
drous THF (0.8 mL) cooled to 0 °C and under an argon
atmosphere was added a solution of 5 (132 mg; 0.16 mmol) in
anhydrous THF (1.5 mL), and the solution was stirred for 20
h at room temperature and then processed as already de-
scribed.22 The organic layer was washed with water, dried (Na2-
SO4), and concentrated. Boric acid was eliminated by coevap-
(22) Lerner, L. M. Methods Carbohydr. Chem. 1972, 6, 131-134.

4434 J . Org. Chem., Vol. 67, No. 13, 2002
Gandolfi-Donadio et al.
oration with MeOH (5 × 3 mL), and the product was purified
by column chromatography (7:1 toluene-EtOAc) to give 6 (117
mg; 88%) as an amorphous solid: Rf 0.33 toluene-EtOAc; [R]D
lized from EtOH: mp 136-138 °C (EtOH); Rf 0.30 (5:1
toluene-EtOAc); [R]D +65.5° (c 1, CHCl3); 1H NMR (CDCl3,
200 MHz) anomeric region δ 5.58 (d, J ) 4.0 Hz, R anomer,
0.3 H, H-1), 5.45 (d, J ) 1.1 Hz, â anomer, 0.7 H, H-1), 5.38
(s, â anomer, 0.7 H, H-2), 5.22 (dd, J ) 6.6, 4.6 Hz, R anomer,
0.3 H, H-2), 5.07 (d, J ) 3.6 Hz, 0.7 H, H-1′), 1.44, 1.42, 1.36,
1.33 (4s, 6 H); 13C NMR (CDCl3, 50.3 MHz) δ 165.4, 138.6-
127.4, 109.8 ((CH3)2C), 100.9 (C-1â), 98.7, 97.6 (C-1′ of R and
â anomers), 95.1 (C-1R), 83.0, 82.0, 80.5, 79.3, 78.9, 78.8, 78.7,
76.2, 75.4, 74.9, 74.7, 73.9, 73.7, 73.4, 73.3, 72.9, 70.1, 69.0,
68.3, 65.5, 26.4, 26.1, 25.5, 25.2. Anal. Calcd for C50H54O12: C
70.91, H 6.43. Found: C 70.85, H 6.29.
1
+43.3° (c 1, CHCl3); H NMR (CDCl3, 500 MHz) δ 7.36-7.29
(m, 20 H), 5.45 (d, 0.4 H, J ) 4.5 Hz, H-1R), 5.21 (s, 0.6 H,
H-1â), 5.16 (d, J ) 1 Hz, 1H), 4.98 (d, J ) 3.8 Hz, 1H), 4.92-
3.80 (m), 3.60-3.40 (m), 1.45, 1.37 (2s, 6 H), 1.21,1.20 (2s, 9
H); 13C NMR (CDCl3, 50.3 MHz) δ 177.2, 138.6-127.4, 109.8
((CH3)2C), 101.0 (C-1â), 98.1, 97.2 (C-1′of R and â anomers),
95.2 (C-1R), 83.4, 81.7, 81.4, 80.2, 79.3, 78.8, 78.6, 78.4, 76.6,
76.2, 75.5, 74.9, 74.7, 73.9, 73.8, 73.5, 72.9, 70.0, 69.0, 68.2,
65.6, 38.6, 38.5, 27.1, 27.0, 26.4, 26.1, 25.5, 25.2. Anal. Calcd
for C48H58O12: C 69.71, H 7.07. Found: C 69.57, H, 7.15.
2-O-Ben zoyl-5,6-O-isop r op ylid en e-D-ga la cton o-1,4-la c-
ton e (7) a n d 2,3-Di-O-ben zoyl-5,6-O-isop r op ylid en e-D-
ga la cton o-1,4-la cton e (8). To a suspension of d-galactono-
1,4-lactone (3 g, 16.8 mmol) in a mixture of acetone-2,2-
dimethoxypropane 3:1 (40 mL) cooled at 0 °C was added
concentrated H2SO4 (0.03 mL). After 30 min, NH4OH was
added to pH 7, and the suspension was filtered and concen-
trated. The syrup was dissolved in dry pyridine (15 mL) and
cooled to -10 °C, benzoyl chloride (2.4 mL, 20.7 mmol) was
slowly added during 30 min, and stirring was continued for
additional 30 min. The reaction mixture was processed as
described for 3, and the resulting syrup was purified by column
chromatography (7:1 toluene-EtOAc and then 6:1 toluene-
EtOAc). The fastest migrating component (Rf 0.71, 6:1 toluene-
EtOAc) was identified as 2,3-di-O-benzoyl-5,6-O-isopropylidene-
D-galactono-1,4-lactone (8, 1.81 g, 25%), which after crystalliza-
tion from hexanes-ethyl acetate gave the following data: mp
112-113 °C; [R]D +87.2° (c 1, CHCl3) (lit.18 [R]D +59.0° (c 1,
CHCl3)); 1H NMR was identical as decribed;18 13C NMR (50.35
MHz, CDCl3) δ 169.0 (C-1), 165.5, 165.0, 133.8-128.4, 110.5
((CH3)2C), 79.8, 74.4, 72.4, 65.0, 25.8, 25.3.
2,3-Di-O-ben zoyl-5,6-O-isop r op ylid en e-D-ga la ctofu r a -
n ose (12). Compound 8 (0.72 g) was reduced with bis(2-butyl-
3-methyl)borane (18.7 mmol) as described for compound 6 and
purified by column chromatography (7:1 toluene-EtOAc) to
give 12 (0.51 g; 70%) as a hygroscopic syrup: Rf 0.33 (4:1
toluene-EtOAc); [R]D +59.0° (c 1, CHCl3); 1H NMR (CDCl3,
200 MHz) anomeric region δ 5.84 (dd, J ) 5.8, 4.4 Hz, R
anomer, 0.4 H, H-2), 5.72 (d, J ) 4.4 Hz, R anomer, 0.4 H,
H-1), 5.66 (bs, â anomer, 0.6 H, H-1), 1.50, 1.46, 1.44, 1.39
(4s, 6 H); 13C NMR (CDCl3, 50.3 MHz): δ 166.1-165.4, 137.8-
125.2, 110.2, 109.9 ((CH3)2C), 100.9 (C-1â), 95.4 (C-1R), 83.2,
82.6, 80.2, 78.3, 77.8, 77.2, 75.7, 75.6, 65.6, 26.2, 26.0, 25.4,
25.3. Anal. Calcd for
Found: C 62.68, 5.83.
C
23H24O8‚1/2H2O: C 63.15, H 5.76.
Meth yl â-D-Ga la ctofu r a n osyl-(1f3)-r-D-m a n n op yr a n o-
sid e (17). To a stirred solution of 12 (0.22 g, 0.56 mmol) and
trichloroacetonitrile (3.4 mL, 3.4 mmol) in CH2Cl2 (20 mL)
cooled to 0 °C was slowly added DBU (0.033 mL, 0.22 mmol).
After 40 min, the solution was concentrated under reduced
pressure, and the residue was purified by column chromatog-
raphy (25:1:0.25 toluene-EtOAc-TEA) to give 0.26 g (80%)
of O-(2,3-di-O-benzoyl-5,6-O-isopropylidene-D-galactofurano-
syl)trichloroacetimidate 13 as a syrup: Rf 0.75 (4:1 toluene-
The next fraction from the column (Rf 0.29, 6:1 toluene-
EtOAc) afforded crystalline 7 (2.44 g, 45%): mp 94-95 °C
(benzene); [R]D -95.9° (c 1, CH Cl3); 1H NMR (200 MHz, CDCl3)
δ 8.08 (d, J ) 7.7 Hz, 2 H), 7.7.64-7.41 (m, 3 H), 5.55 (d, J )
7.7 Hz, 1 H), 4.61 (J ) 7.7 Hz, 1 H), 4.38 (dt, J ) 3.3, 6.6 Hz,
1 H), 4.28 (dd, J ) 3.3, 7.7 Hz, 1 H), 4.13 (dd, J ) 6.6, 8.4 Hz,
1 H), 4.03 (dd, J ) 6.6, 8.4 Hz, 1 H), 3.7 (bs, 1 H,), 1.43 (s, 3
H), 1.37 (s, 3 H); 13C NMR (CDCl3, 50.3 MHz) δ 168.9 (C-1),
166.7, 134.1, 130.1, 128.5, 128.0, 110.3 ((CH3)2C), 79.9, 77.0,
73.9, 73.2, 64.9, 25.9, 25.3, 25.5. Anal. Calcd for C16H18O7: C
59.62, H 5.63. Found: C 59.96, H 5.73.
1
EtOAc); H NMR (CDCl3, 200 MHz) δ 8.70 (NH, 1H), 8.13-
7.42 (m, 10 H), 6.64 (bs, 1 H), 5.71 (bs, 1 H), 5.61 (d, J ) 3.3
Hz, 1H), 4.60 (ddd, J ) 5.1, 6.2, 6.6 Hz, 1H), 4.54 (dd, J ) 5.1,
3.3, 1 H), 4.15 (dd, J ) 6.6, 8.4 Hz, 1H), 4.06 (dd, J ) 6.2, 8.4
Hz, 1H), 1.45, 1.40 (2s, 6H); 13C NMR (CDCl3, 50.3 MHz) δ,
165.6, 133.7-128.5, 110.1 ((CH3)2C), 103.2 (C-1â), 86.0, 80.5,
80.2, 75.1, 65.5, 26.3, 26.0.
A vigorously stirred suspension of dried 13 (0.26 g, 0.45
mmol), methyl 4,6-O-benzylidene-D-mannopyranoside23 (14,
0.24 g, 0.85 mmol), and 4 Å powdered molecular sieves (0.4 g)
in anhydrous CH2Cl2 (15 mL) was cooled to -10 °C, and
TMSOTf (15 µL, 0.083 mmol) was slowly added. After 40 min,
the mixture was quenched by addition of saturated aqueous
NaHCO3 (10 mL). After dilution with CH2Cl2 (150 mL) and
additional saturated aqueous NaHCO3, the organic phase was
separated, washed with water, dried (Na2SO4), and concen-
trated. The residue was purified by column chromatography
(7:1 toluene-EtOAc) to give 243 mg of amorphous methyl 2,3-
di-O-benzoyl-5,6-O-isopropylidene-â-D-galactofuranosyl-(1f3)-
4,6-O-benzylidene-R-D-mannopyranoside (15, 70% yield): Rf
0.25 (4:1 toluene-EtOAc), [R]D 9.3° (c 1, CHCl3); 1H NMR
(CDCl3, 500 MHz, Table 1) only the values for the protecting
groups are listed δ 8.06-7.97 (m, 4H), 5.44 (CHPh, 1H), 3.38
(s, 3H), 1.37, 1.36 (2s, 6H); 13C NMR (CDCl3, 125 MHz) δ 165.9,
165.5, 137.4-126.0, 109.8 ((CH3)2C), 102.5, 102.0, 101.2 (C-1,
C-1′, PhCH), 82.5, 82.3, 77.3, 76.9, 74.9, 71.7, 67.0, 68.7, 65.5,
65.6, 55.0, 26.2, 24.4.
2,3,4,6-Tetr a -O-ben zyl-r-D-ga la ctop yr a n osyl-(1f3)-5,6-
O-isopr opyliden e-2-O-ben zoyl-D-galacton o-1,4-lacton e (9).
To a stirred mixture of O-(2,3,4,6-tetra-O-benzyl-â-D-galacto-
pyranosyl)trichloroacetimidate (4, 3.4 g, 5.0 mmol) and 5,6-
O-isopropylidene-2-O-benzoyl-D-galactono-1,4-lactone (7; 2.36
g, 7.3 mmol) in anhydrous ether (80 mL), cooled to 0 °C under
argon, was slowly added TMSOTf (0.355 mL, 2.0 mmol). After
2 h, saturated aqueous NaHCO3 was added (100 mL) and the
stirring continued for 20 min. The product was extracted with
CH2Cl2 (200 mL), and the extract was washed with water
(4 × 100 mL), dried (Na2SO4), and concentrated. Column
chromatography (20:1 toluene-EtOAc and then 15:1 toluene-
EtOAc) of the residue gave 9 (2.52 g, 60%) that crystallized
upon addition of EtOH: Rf 0.56 (6:1 toluene-EtOAc); mp 133-
1
134 °C (ethanol); [R]D +53.3° (c 1, CHCl3); H NMR (CDCl3,
500 MHz, Table 1) only the values for protecting groups are
listed δ 8.04 (d, J ) 7.3 Hz, 2H), 7.65-7.00 (m, 23 H), 4.86,
4.60 (2d, J ) 11.7 Hz, 2H), 4.86, 4.48 (2d, J ) 11.4 Hz, 2H),
4.77, 4.73 (2d, J ) 11.7 Hz, 2H), 4.18, 4.10 (2d, J ) 11.7 Hz,
2H), 1.43, 1.37 (2s, 6 H); 13C NMR (CDCl3, 200 MHz) δ 168.4
(C-1), 165.0, 138.5-125.4, 110.3 ((CH3)2C), 99.6 (C-1′), 78.7,
78.6, 78.4, 76.1, 74.9, 74.4, 74.1, 73.6, 73.4, 73.2, 72.6, 70.1,
67.7, 65.0, 26.0, 25.5. Anal. Calcd for C50H52O12: C 71.07; H
6.30. Found: C 71.00; H 6.16.
Usual acetylation of 15 in dry pyridine with acetic anhydride
gave methyl 2,3-di-O-benzoyl-5,6-O-isopropylidene-â-D-galacto-
furanosyl-(1f3)-2-O-acetyl-4,6-O-benzylidene-R-D-mannopyra-
noside (16): 1H NMR spectrum is described in Table 1; 13C
NMR (CDCl3, 125 MHz) δ 170.1, 165.4, 165.1, 137.3-125.9,
109.8 ((CH3)2C), 102.3 (C-1′), 101.9 (CHPh), 99.9 (C-1), 82.7,
81.6, 77.9, 77.2, 75.2, 69.0, 68.9, 68.8, 65.6, 63.7, 55.1, 26.3,
25.4, 20.9.
Unreacted 7 (1.2 g) was recovered from the column by
further elution with 1:1 toluene-EtOAc.
2,3,4,6-Tetr a -O-ben zyl-r-D-ga la ctop yr a n osyl-(1f3)-5,6-
O-isop r op ylid en e-2-O-b en zoyl-D-ga la ct ofu r a n ose (10).
Compound 9 (1.42 g) was reduced as described for 6 to give
10 (0.97 g; 68%) as an amorphous solid that slowly crystal-
Compound 15 was further treated with AcOH/H2O at 80 °C
and then debenzoylated with 0.5 M NaOMe in methanol to
(23) Buchanan, J . G.; Schwarz, J . C. P. J . Chem. Soc. 1962, 4770-
4777.

Synthesis of a Trisaccharide of Leishmania GIPLs
J . Org. Chem., Vol. 67, No. 13, 2002 4435
give methyl â-D-galactofuranosyl-(1-3)-R-D-mannopyranose
(17, 88% yield): Rf 0.25 (7:3:1:0.5 EtOAc-EtOH-H2O-NH3);
EtOAc) of the residue afforded 20 (222 mg, 84%) as a
hygroscopic syrup: Rf 0.33 (1:5 toluene-EtOAc); [R]D +26.6°
(c 1, CHCl3); 1H NMR (CDCl3, 500 MHz, Table 1) only the
values for the protecting groups are listed δ 4.88, 4.49 (2d,
J ) 11.5 Hz, 2H), 4.82, 4.65 (2d, J ) 11.7 Hz, 2H), 4.77, 4.75
(2d, J ) 11.7 Hz, 2H), 4.43, 4.65 (2d, J ) 12.0 Hz, 2H), 4.37,
4.27 (2d, J ) 11.4 Hz, 2H); 13C NMR (CDCl3, 125 MHz) δ 165.7
(PhCO), 137.9-127.5, 104.7 (C-1′), 99.3, 98.9 (C-1, C-1′′), 83.8,
83.4, 81.8, 79.5, 79.1, 75.9, 74.7, 74.6, 74.1, 73.8, 72.8 (CH2-
Ph), 72.2, 71.7, 70.5, 69.9, 69.0 (CH2Ph), 68.6, 66.5, 63.5, 62.7.
Anal. Calcd for C60H66O17‚1/2H2O: C, 66.35; H, 6.40. Found:
C, 66.10; H, 6.17.
Ben zyl 2,3,4,6-Tet r a -O-b en zyl-r-D-ga la ct op yr a n osyl-
(1f3)-â-D -ga la ct ofu r a n osyl-(1f3)-r-D -m a n n op yr a n o-
sid e (21). To a solution of 20 (134 mg, 0.127 mmol) in
anhydrous MeOH (0.7 mL), cooled at 0 °C, was added 0.5 M
NaOMe in MeOH (0.6 mL). After the mixture was stirred at
room temperature for 1 h, H2O (0.1 mL) was added. The
solution was passed through a column (1.5 × 4 cm) containing
Amberlite IR-120 plus (H+) resin and the latter washed with
MeOH. The solvent was evaporated and the methyl benzoate
eliminated by five successive coevaporations with H2O. Column
chromatography of the residue (1:5 toluene-EtOAc) afforded
21 (0.120 mg, 99%) as a hygroscopic syrup: Rf 0.19 (1:5
toluene-EtOAc); [R]D +10.8° (c 1, CHCl3); 1H NMR (CDCl3, 500
MHz, Table 1) only the values for the protecting groups are
listed δ 4.89, 4.50 (2d, J ) 11.7 Hz, 2H), 4.80, 4.64 (2d, J )
11.7 Hz, 2H), 4.78, 4.72 (2d, J ) 11.7 Hz, 2H), 4.67, 4.46 (2d,
J ) 11.7 Hz, 2H), 4.46, 4.36 (2d, J ) 11.7 Hz, 2H); 13C NMR
(CDCl3, 125 MHz) δ 138.4-127.6, 107.5 (C-1′), 99.6, 98.9 (C-
1, C-1′′), 86.8, 82.2, 80.1, 80.0, 79.0, 75.7, 74.9, 74.6, 74.1, 73.8,
73.2, 72.1, 72.0, 70.7, 70.2, 69.5, 69.2, 66.2, 63.5, 62.4. Anal.
Calcd for C53H62O16‚1/2H2O: C, 66.03; H, 6.59. Found: C,
65.96; H, 6.57.
1
[R]D -49° (c 1,water) (lit.19 [R]D -37° (c 0.6, water)); H NMR
(D2O, 200 MHz) anomeric region δ 5.03 (d, J ) 1.5 Hz, 1H,
H-1′), 4.7 (d, J ) 1.8 Hz, 1H, H-1), 3.32 (bs, OCH3, 3 H); 13C
NMR (D2O, 25 °C, 50.3 MHz), δ 105.4 (C-1′), 101.5 (C-1), 83.9,
82.2, 77.9, 76.4, 73.4, 71.7, 67.5, 66.0, 63.7, 61.9, 55.7. The 13C
NMR spectrum of the literature was recorded at 70 °C; for
that reason, all our values are shifted 0.8-1 ppm to higher
field.
Ben zyl 2,3,4,6-Tet r a -O-b en zyl-r-D-ga la ct op yr a n osyl-
(1f3)-2-O-ben zoyl-5,6-O-isop r op ylid en e-â-D-ga la ctofu r a -
n osyl-(1f3)-4,6-O-ben zyliden e-r-D-m an n opyr an oside (19).
To a stirred solution of 10 (0.55 g, 0.65 mmol) and trichloro-
acetonitrile (0.39 mL, 3.9 mmol) in CH2Cl2 (20 mL), cooled to
0 °C, was slowly added DBU (0.038 mL, 0.256 mmol), and the
stirring was continued for 30 min. The solution was concen-
trated under reduced pressure, and the residue was purified
by column chromatography (15:1:0.5 toluene-EtOAc-TEA) to
1
give 0.57 g (88%) of syrupy 11. H NMR (CDCl3, 200 MHz): δ
8.60 (NH, 1H), 6.47 (s, H-1, 1H), 5.66 (s, H-2, 1H), 5.09 (d,
J ) 3.3 Hz, Η-1′, 1H), 4.95-3.52 (m, 21H), 1.35, 1.24 (2s, 6H).
To a vigorously stirred suspension of dried 11 (0.57 g, 0.58
mmol), benzyl 4,6-O-benzylidene-R-D-mannopyranoside24 (18,
0.33 g, 1.17 mmol), and 4 Å powdered molecular sieves in Cl2-
CH2 (13 mL) cooled to -10 °C was added TMSOTf (10 µL,
0.055 mmol). After 30 min, TLC showed the absence of
trichloroacetimidate 11. The mixture was quenched by addi-
tion of saturated solution of NaHCO3 (10 mL). After dilution
with CH2Cl2 (150 mL) and additional saturated NaHCO3
solution, the organic phase was separated and washed with
water, dried (Na2SO4) and concentrated. The residue was
purified by column chromatography (13:1 toluene-EtOAc) to
give 553 mg of amorphous solid 19 (81% yield): Rf 0.40 (4:1
toluene-EtOAc); [R]D +38.3° (c 1, CHCl3); 1H NMR (CDCl3,
500 MHz, Table 1) only the values for the protecting groups
are listed δ 5.34 (CHPh), 4.94, 4.54 (2d, J ) 11.6 Hz, 2H), 4.78,
4.63 (2d, J ) 11.6 Hz, 2H), 4.70, 4.49 (2d, J ) 11.9 Hz, 2H),
4.65, 4.56 (2d, J ) 11.9 Hz, 2H), 4.40, 4.33 (2d, J ) 11.4 Hz,
2H), 1.26, 1.22 (2s, 6H); 13C NMR (CDCl3, 125 MHz) δ 165.8
(PhCO), 138.8-126.0, 109.3 ((CH3)2C), 102.7 (C-1′, âGalf),
101.6 (CHPh), 99.6 (C-1, Man), 98.8 (C-1′′, RGalp), 84.0 (C-
3′), 82.1 (C-4′), 80.9 (C-2′), 78.8 (C-3′′), 77.0 (C-4), 76.5 (C-2′′),
75.5 (C-4′′), 75.0 (C-5′), 74.5, 73.8, 73.2, 72.8 (CH2Ph), 72.3 (C-
3), 70.4 (C-6′′), 70.3 (C-5′′), 69.2 (CH2Ph), 68.7 (C-6, C-2), 65.2
(C-6′), 63.8 (C-5), 26.1, 25.4 ((CH3)2C). Anal. Calcd for
r-D-Galactopyr an osyl-(1f3)-â-D-galactofu r an osyl-(1f3)-
D-m a n n op yr a n ose (1). A suspension of compound 21 (76 mg,
0.080 mmol) in MeOH (5.5 mL) and 10% Pd/C (30 mg) was
hydrogenated at 45 psi (3 atm) for 4 h at room temperature.
After filtration of the catalyst, the filtrate was evaporated
under vacuum to give an amorphous solid that was dissolved
in water (1 mL), passed through
a C8-Maxi-Clean, and
lyophilized. Trisaccharide 1 (39.3 mg, 98%) was obtained as a
high hygroscopic syrup: Rf 0.17 (7:1:1 n-propanol-MeOH-
H2O); [R]D +28.3° (c 1, H2O); 1H NMR (D2O, 500 MHz)
anomeric region for the R anomer δ 5.13 (d, J ) 1.9 Hz, H-1,
Man), 5.10 (bs, Galf), 5.00 (d, J ) 3.5 Hz, H-1, Galp); 13C NMR
(D2O, 50.34 MHz) δ 105.8, 105.4 (C-1′); 100.5 (C-1′′, Galp); 94.7
(C-1R), 94.5 (C-1 â), 85.7, 82.7, 80.4, 76.1, 73.4, 72.3, 71.7, 70.1,
C
70H74O17: C, 70.81; H, 6.28. Found: C, 71.04; H, 6.48.
Ben zyl 2,3,4,6-Tet r a -O-b en zyl-r-D-ga la ct op yr a n osyl-
69.1, 68.4, 66.1, 63.7, 62.1, 61.9. Anal. Calcd for C18H32O16
H2O: C, 41.38; H, 6.56. Found: C, 41.09; H, 6.40.
‚
(1f3)-2-O-ben zoyl-â-D-ga la ctofu r a n osyl-(1f3)-r-D-m a n -
n op yr a n osid e (20). To a stirred solution of 19 (297 mg, 0.25
mmol) in HOAc (2 mL) at 80 °C was slowly added H2O (0.65
mL) until turbidity, and heating was continued for 30 min.
The mixture was cooled and concentrated, and the residue was
subjected to successive dissolution and evaporation with
toluene (3 × 5 mL). Column chromatography (1:4 toluene-
Ack n ow led gm en t. This work was supported by
grants from the Agencia Nacional de Promocio´n Cien-
t´ıfica y Tecnolo´gica (ANPCyT, BID 1201/OC-AR, PICT
06-05133) and Universidad de Buenos Aires. C.G.-R.
and R.M.d.L. are research members of CONICE T. L.G.-
D. is a research fellow from CONICET.
(24) Shaban, M. A.; Ary, I. E.; J eanloz, D. A.; J eanloz, R. W.
Carbohydr. Res. 1975, 45, 105-114.
J O016290Z