Linear synthesis of the tumor-associated carbohydrate antigens Globo-H, Ssea-3, and Gb3

Article abstract of DOI:10.1021/jo025834+

The tumor-associated carbohydrate antigens Globo-H, SSEA-3, and Gb3 were synthesized in a linear fashion using glycosyl phosphate monosaccharide building blocks. All of the building blocks were prepared from readily available common precursors. The difficult α-(1→-4-cis)-galactosidic linkage was installed using a galactosyl phosphate donor with high selectivity. Introduction of the β-galactosamine unit required the screening a variety of amine protecting groups to ensure good donor reactivity and protecting group compatibility. An N-trichloroacetyl-protected galactosamine donor performed best for the installation of the β-glycosidic linkage. Conversion of the trichloroacetyl group to the N-acetyl group was achieved under mild conditions, fully compatible with the presence of multiple glycosidic bonds. This synthetic strategy is expected to be amenable to the synthesis of the globo-series of tumor antigens on solid-support.

Full text of DOI:10.1021/jo025834+

Lin ea r Syn th esis of th e Tu m or -Associa ted Ca r boh yd r a te An tigen s
Globo-H, SSEA-3, a n d Gb3
Folkert Bosse, Lisa A. Marcaurelle, and Peter H. Seeberger*
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
seeberg@mit.edu
Received April 17, 2002
The tumor-associated carbohydrate antigens Globo-H, SSEA-3, and Gb3 were synthesized in a linear
fashion using glycosyl phosphate monosaccharide building blocks. All of the building blocks were
prepared from readily available common precursors. The difficult R-(1f4-cis)-galactosidic linkage
was installed using a galactosyl phosphate donor with high selectivity. Introduction of the
â-galactosamine unit required the screening a variety of amine protecting groups to ensure good
donor reactivity and protecting group compatibility. An N-trichloroacetyl-protected galactosamine
donor performed best for the installation of the â-glycosidic linkage. Conversion of the trichloroacetyl
group to the N-acetyl group was achieved under mild conditions, fully compatible with the presence
of multiple glycosidic bonds. This synthetic strategy is expected to be amenable to the synthesis of
the globo-series of tumor antigens on solid-support.
In tr od u ction
cancer.7 A synthetic Globo-H construct is currently being
evaluated and has shown very promising results as an
antitumor vaccine in clinical trials.8-10 Gb5 is abundant
in testicular cancer11-13 and is present during embryonic
development.14 In recognition of this latter property, the
pentasaccharide moiety of Gb5 is often referred to as the
stage specific embryonic antigen-3 (SSEA-3). Finally, Gb3
is highly enriched in ovarian cancer and Burkitt’s B-cell
lymphoma.15
Due to their importance as tumor markers and poten-
tial anticancer vaccines, several members of the globo-
series of GSLs have been targets of total syntheses.
Globo-H was first synthesized by Danishefsky and co-
workers using the glycal assembly approach.16,17 Further
Altered glycosylation is a universal feature of cancer
cells, and certain carbohydrate structures are markers
of many tumors.1,2 Like normal cells during embryonic
development, tumor cells adhere to a variety of cell types,
invade tissues, and undergo activation and rapid growth.
Since changes in cellular glycosylation profiles are com-
mon during embryogenesis, it is not surprising that
altered glycosylation is also characteristic of malignant
transformation and tumor activation. A variety of changes
occur in malignant cells, such as the loss of expression
or excessive expression of certain structures, the per-
sistence of incomplete or truncated structures, and the
appearance of novel structures.3 Carbohydrates are
displayed on the surface of both normal and tumor cells
in the context of membrane glycosphingolipids (GSLs)
and glycoproteins. The carbohydrate epitopes of GSLs
have been analyzed following extraction from whole cells
and have been extensively studied for the treatment of
cancer by both passive and active immunotherapy.1,2
(7) Zhang, S.; Cordon-Cardo, C.; Zhang, H. S.; Reuter, V. E.; Adluri,
S.; Hamilton, W. B.; Lloyd, K. O.; Livingston, P. O. Int. J . Cancer 1997,
73, 42.
(8) Slovin, S. F.; Ragupathi, G.; Adluri, S.; Ungers, G.; Terry, K.;
Kim, S.; Spassova, M.; Bornmann, W. G.; Fazzari, M.; Dantis, L.;
Olkiewicz, K.; Lloyd, K. O.; Livingston, P. O.; Danishefsky, S. J .; Scher,
H. I. Proc. Natl. Acad. Sci. U.S.A. 1999, 96, 5710.
(9) Wang, Z. G.; Williams, L. J .; Zhang, X. F.; Zatorski, A.; Kudrya-
shov, V.; Ragupathi, G.; Spassova, M.; Bornmann, W.; Slovin, S. F.;
Scher, H. I.; Livingston, P. O.; Lloyd, K. O.; Danishefsky, S. J . Proc.
Natl. Acad. Sci. U.S.A. 2000, 97, 2719.
(10) Gilewski, T.; Ragupathi, G.; Bhuta, S.; Williams, L. J .; Musselli,
C.; Zhang, X. F.; Bencsath, K. P.; Panageas, K. S.; Chin, J .; Hudis, C.
A.; Norton, L.; Houghton, A. N.; Livingston, P. O.; Danishefsky, S. J .
Proc. Natl. Acad. Sci. U.S.A. 2001, 98, 3270.
One major class of GSLs is the globo-series of tumor
antigens. Some prominent members of this family include
Globo-H, Gb5, and Gb3 (Figure 1). Globo-H was first
isolated and identified as an antigen on breast cancer
cells4,5 and is also expressed in prostate6 and ovarian
(11) Olie, R. A.; Fenderson, B.; Daley, K.; Oosterhuis, J . W.; Murphy,
J .; Looijenga, L. H. Br. J . Cancer 1996, 74, 133.
(1) Hakomori, S. Adv. Cancer Res. 1989, 52, 257.
(2) Hakomori, S.; Zhang, Y. Chem. Biol. 1997, 4, 97.
(12) Wenk, J .; Andrews, P. W.; Casper, J .; Hata, J .; Pera, M. F.;
von Keitz, A.; Damjanov, I.; Fenderson, B. A. Int. J . Cancer 1994, 58,
108.
(13) Kannagi, R.; Cochran, N. A.; Ishigami, F.; Hakomori, S.;
Andrews, P. W.; Knowles, B. B.; Solter, D. EMBO J . 1983, 2, 2355.
(14) Solter, D.; Knowles, B. B. Proc. Natl. Acad. Sci. U.S.A. 1978,
75, 5565.
(15) Farkas-Himsley, H.; Hill, R.; Rosen, B.; Arab, S.; Lingwood, C.
A. Proc. Natl. Acad. Sci. U.S.A. 1995, 92, 6996.
(16) Bilodeau, M. T.; Park, T. K.; Hu, S.; Randolph, J . T.; Danishef-
sky, S. J .; Livingston, P. O.; Zhang, S. J . Am. Chem. Soc. 1995, 117,
7840.
(3) Varki, A. Glycosylation Changes in Cancer. In Essentials of
Glycobiology; Varki, A., Cummings, R. D., Esko, J ., Freeze, H., Hart,
G., Marth, J ., Eds.; Cold Spring Harbor Laboratory Press: Cold Spring
Harbor, 1999; pp 537-549.
(4) Kannagi, R.; Levery, S. B.; Ishijamik, F.; Hakomori, S.; Schev-
insky, L. H.; Knowles, B. B.; Solter, D. J . Biol. Chem. 1983, 258, 8934.
(5) Bremer, E. G.; Levery, S. B.; Sonnino, S.; Ghidoni, R.; Canevari,
S.; Kannagi, R.; Hakomori, S. J . Biol. Chem. 1984, 259, 14773.
(6) Zhang, S.; Zhang, H. S.; Reuter, V. E.; Slovin, S. F.; Scher, H. I.;
Livingston, P. O. Clin. Cancer Res. 1998, 4, 295.
10.1021/jo025834+ CCC: $22.00 © 2002 American Chemical Society
Published on Web 08/28/2002
J . Org. Chem. 2002, 67, 6659-6670
6659

Bosse et al.
F IGURE 1. Globo-series of tumor-associated antigens (R ) ceramide).
syntheses used trichloroacetimidate building blocks18 and
a two-directional glycosylation strategy.19 Most recently,
Wong and co-workers prepared Globo-H via a one-pot
strategy using the computer program OptiMer to aid in
synthesis planning.20 The pentasaccharide SSEA-3 has
been synthesized by Ogawa,21 Danishefsky,22 and Mag-
nusson,23 while the assembly of Gb3 has been reported
by several groups.24
expected to be amenable to the preparation of the target
tumor antigens on solid-support.
Resu lts a n d Discu ssion
In keeping with our goal of automating solution-phase
protocols on solid-support, six glycosyl donors were
selected as building blocks for a sequential assembly of
the Globo-H hexasaccharide 1 (Scheme 1). SSEA-3 and
Gb3 became accessible by deprotection of the correspond-
ing synthetic intermediates. This linear strategy differs
markedly from previous routes, which had been striving
for highest convergence. Acetyl and levulinoyl esters were
chosen as temporary hydroxyl protecting groups, given
their ease of removal29 and compatibility with solid-phase
synthesis.25,30 The n-pentenyl group was selected for
protection of the reducing end sugar in order to mimic
the linker used during automated solid-phase synthe-
sis.25,31 In addition, the n-pentenyl glycoside can serve
as a leaving group in a late-stage glycosylation32 or as a
handle for bioconjugation.33
Syn th esis of th e La ctose Disa cch a r id e. The con-
struction of the target oligosaccharides began with the
preparation of the reducing end lactose disaccharide. Two
monosaccharide building blocks had to be synthesized.
Glucosyl phosphate 2 (Scheme 2) and galactosyl phos-
phate 3 were prepared using a one-pot procedure starting
from 3,6-di-O-benzyl glucal 829 and 3,6-di-O-benzyl ga-
lactal 10,34 respectively. It should be emphasized that
while treatment of galactal 9 with benzyl bromide and
sodium hydride at 0 °C34 produced 10 in low yield (20%),
In this paper, we describe a solution-phase synthesis
of the tumor antigens Globo-H, SSEA-3, and Gb3. A
strictly linear strategy for the assembly of these oligo-
saccharides was investigated in anticipation of auto-
mating the synthesis on solid support.25 Given their
compatibility with solid-phase oligosaccharide chemistry,
glycosyl phosphates were employed as donors in our
solution-phase studies.26,27 Glycosyl phosphates can be
readily prepared from glycals using a one-pot procedure,27
as well as from glycosyl trichloroacetimidates.28 The use
of glycosyl phosphate building blocks enabled the suc-
cessful installation of the difficult R-galactosidic linkage,
as well as the â-galactosamine moiety, in good yield with
high stereoselectivity. The strategy described here is
(17) Park, T. K.; Kim, I. J .; Hu, S.; Bilodeau, M. T.; Randolph, J . T.;
Kwon, O.; Danishefsky, S. J . J . Am. Chem. Soc. 1996, 118, 11488.
(18) Lassaletta, J . M.; Schmidt, R. R. Liebigs Ann. 1996, 1417.
(19) Zhu, T.; Boons, G. J . Angew. Chem., Int. Ed. Engl. 1999, 38,
3495.
(20) Burkhart, F.; Zhang, Z.; Wacowich-Sgarbi, S.; Wong, C.-H.
Angew. Chem., Int. Ed. 2001, 40, 1274.
(21) Nunomura, S.; Ogawa, T. Tetrahedron Lett. 1988, 29, 5681.
(22) Park, T. K.; Kim, I. J .; Danishefsky, S. J . Tetrahedron Lett.
1995, 36, 9089.
(23) Nilsson, U.; Magnusson, G. Carbohydr. Res. 1995, 272, 9.
(24) (a) Koike, K.; Sugimoto, M.; Sato, S.; Ito, Y.; Nakahara, H.;
Ogawa, T. Carbohydr. Res. 1987, 163, 189l; (b) Nicolaou, K. C.;
Caulfield, T. J .; Katoaka, H. Carbohydr. Res. 1990, 202, 177. (c) Qui,
D.; Schmidt, R. R. Liebigs Ann. Chem. 1992, 217. (d) Hashimoto, S.;
Sakamoto, H.; Honda, T.; Abe, H.; Nakamura, S.; Ikegami, S. Tetra-
hedron Lett. 1997, 52, 8969.
(25) Plante, O. J .; Palmacci, E. R.; Seeberger, P. H. Science 2001,
291, 1523.
(26) Palmacci, E. R.; Plante, O. J .; Seeberger, P. H. Eur. J . Org.
Chem. 2002, 595.
(29) Love, K. R.; Andrade, R. B.; Seeberger, P. H. J . Org. Chem.
2001, 66, 8165.
(30) Hewitt, M. C.; Seeberger, P. H. Org. Lett. 2001, 3, 3699.
(31) Andrade, R. B.; Plante, O. J .; Melean, L. G.; Seeberger, P. H.
Org. Lett. 1999, 1, 1811.
(32) Fraser-Reid, B.; Udodong, U. E.; Wu, Z. F.; Ottosson, H.;
Merritt, J . R.; Rao, C. S.; Roberts, C.; Madsen, R. Synlett 1992, 927.
(33) (a) Allen, J . R.; Allen, J . G.; Zhang, X. F.; Williams, L. J .;
Zatorski, A.; Ragupathi, G.; Livingston, P. O.; Danishefsky, S. J . Chem.
Eur. J . 2000, 6, 1366. (b) Buskas, T.; So¨derberg, E.; Konradsson, P.;
Fraser-Reid, B. J . Org. Chem. 2000, 65, 958.
(27) Plante, O. J .; Palmacci, E. R.; Andrade, R. B.; Seeberger, P. H.
J . Am. Chem. Soc. 2001, 123, 9545.
(28) Schmidt, R. R.; Stumpp, M. Liebigs Ann. Chem. 1984, 680.
(34) Kessler, H.; Kling, A.; Kottenhahn, M. Angew. Chem., Int. Ed.
1990, 29, 425.
6660 J . Org. Chem., Vol. 67, No. 19, 2002

Linear Synthesis of Globo-H, SSEA-3, and Gb3
SCHEME 1. Retr osyn th esis of th e P r otected Globo-H Hexa sa cch a r id e
SCHEME 2. Syn th esis of Bu ild in g Block s 2 a n d 3
upon deprotection with hydrazine yielded 95% of acceptor
16.
In sta lla tion of th e r-Ga la ctosid ic Lin k a ge. A
major challenge in the synthesis of the globo-series of
tumor antigens is the installation of the R-(1f4-cis)-
galactosidic linkage of the reducing end trisaccharide.
While R-galactosidic linkages have been formed using a
variety of glycosylating agents, the stereochemical out-
come of this coupling is difficult to predict and is highly
dependent on the glycosyl acceptor. High selectivity for
all glycosylation reactions is mandatory, since this strat-
egy is being developed for use on solid-support and cannot
take advantage of the purification of reaction intermedi-
ates. To install the difficult R-linkage, we chose to explore
the use of glycosyl phosphate 4, given its compatibility
with solid-phase oligosaccharide synthesis.
Since the presence of a benzyl ether at C2 was required
to favor R-selectivity, donor 4 could not be synthesized
directly from a glycal using the standard one-pot proce-
dure27,35 but was generated from a glycosyl trichloro-
acetimidate.28 Hence, 4,6-di-O-benzyl galactal 11 was
protected as the p-methoxybenzyl (PMB) ether 1717 (97%)
and then converted to the allyl glycoside 18 (R:â ) 1:5,
79%) by epoxidation with DMDO and solvolysis with allyl
alcohol (Scheme 4). Installation of the C2 benzyl group
19 (71%), followed by exchange of the PMB ether for a
levulinoyl ester, furnished 20 in 93% yield. Palladium-
mediated cleavage of the allyl glycoside afforded the
intermediate lactol, which was immediately converted to
trichloroacetimidate 21 (76%, two steps) by reaction with
trichloroacetonitrile and DBU. Transformation of the
R-trichloroacetimidate (21) to the â-phosphate (4) was
achieved in 90% yield upon exposure to dibutyl phos-
two other important intermediates, 4,6-di-O-benzyl ga-
lactal 11 (36%) and tri-O-benzyl galactal 12 (26%), were
also generated in this reaction and were easily separated
by column chromatography. Therefore, this procedure
served as a starting point for the preparation of all four
galactosyl building blocks (3-6) used in this synthesis.
Protection of galactal 10 as the levulinate ester 13 (92%),
followed by subsequent conversion to the glycosyl phos-
phate and esterification, produced 3 in 52% yield.
The assembly of the lactose disaccharide commenced
with the installation of the n-pentenyl glycoside, followed
by removal of the levulinoyl ester as described previously
(Scheme 3).29 Union of phosphate 3 with pentenyl gly-
coside 14 afforded lactose disaccharide 15 (82%), which
(35) Treatment of the intermediate glycosyl phosphate with sodium
hydride and benzyl bromide leads to migration of the phosphate to
yield the C2 phosphoryl benzyl glycoside.
J . Org. Chem, Vol. 67, No. 19, 2002 6661

Bosse et al.
SCHEME 3. Syn th esis of th e La ctose Disa cch a r id e
SCHEME 4. Syn th esis of th e C2 Ben zyl-P r otected Ga la ctose Don or
TABLE 1. Cou p lin g Con d ition s Used To Gen er a te th e
Gb3 Tr isa cch a r id e
SCHEME 5. Dep r otection of th e Gb3
Tr isa cch a r id e
the yield and stereoselectivity of the reaction improved
when a mixture of ether/dichloromethane was used (79%,
R:â ) 20:1). Reaction temperature proved crucial for
achieving high R-selectivity. When the reaction was
carried out at -20 °C, a 1:1 mixture of R- and â-anomers
was obtained. The intermediate trichloroacetimidate 21
also proved to be a suitable glycosylating agent for the
preparation of trisaccharide 22. Reaction of 21 with
disaccharide 16 at 0 °C in dichloromethane yielded
R-linked trisaccharide 22 in 54% yield.
Removal of all ester and benzyl ether protecting groups
of trisaccharide 22 was accomplished by a dissolving-
metal reduction (Scheme 5). Subsequent treatment with
acetic anhydride in pyridine furnished the peracetylated
Gb3 trisaccharide 23 in 43%.
Syn th esis of th e Ga la ctosa m in e Bu ild in g Block .
Having installed the challenging R-galactosidic linkage,
we turned our attention to the synthesis of a suitable
glycosylating agent for the introduction of the galac-
tosamine unit. An important consideration in designing
the galactosamine building block was the selection of an
amine protecting group. A number of strategies for
masking the C2 amino group were investigated, including
protection as the N-carbamate (Troc and Cbz), N-tri-
donor
solvent
CH2Cl2
CH2Cl2/THF
CH2Cl2/THF
CH2Cl2/Et2O
CH2Cl2
temp (°C) R:â selectivity
yield (%)
4
4
4
4
21
-78
-20
-78
-78
0
11:1
1:1
20:1
20:1
R only
58
80
61
79
54
phate. It should be noted that attempts to generate the
glycosyl phosphate directly from the lactol led to the
formation of 1,1 coupled disaccharides.
Syn th esis of th e Gb3 Tr isa cch a r id e. With the
desired glycosyl phosphate in hand, conditions for gly-
cosylation of the hindered lactose acceptor 16 were
explored (Table 1). Initial reaction conditions employing
TBSOTf as a promoter in dichloromethane at -78 °C led
to the formation of target trisaccharide 22 in 58% yield
but with only moderate R-selectivity (R:â ) 11:1). Both
6662 J . Org. Chem., Vol. 67, No. 19, 2002

Linear Synthesis of Globo-H, SSEA-3, and Gb3
SCHEME 6. Syn th esis of N-TCA-P r otected Ga la ctosa m in e Don or 5
SCHEME 7. In sta lla tion of N-TCA-P r otected Ga la ctosa m in e
SCHEME 8. Syn th esis of C2 Ester -P r otected
Ga la ctose Don or s 6 a n d 34
chloroacetamide, N-phthalimide, and azide. Glycosyl
phosphate 5 bearing a C2 N-trichloroacetamide per-
formed best. The N-trichloroacetyl (TCA) group has been
reported to ensure high â-selectivity in glycosylation
reactions, can be converted directly into the correspond-
ing N-acetyl group under mild conditions that are fully
compatible with sensitive glycosidic bonds, and has been
used in the synthesis of several complex oligosaccha-
rides.36-39
reacetylated with acetic anhydride in pyridine to procure
N-TCA protected 28 in 40% yield. Removal of the ano-
meric TDS group under the agency of TBAF (91%)
followed by reaction of lactol 29 with trichloroacetonitrile
in the presence of DBU afforded trichloroacetimidate 30
in 70% yield. Conversion of 30 into glycosyl phosphate 5
was accomplished in good yield (74%) by reaction with
dibutyl phosphate.
Reaction of trisaccharide 22 with hydrazine acetate
provided acceptor 31 in 62% yield (Scheme 7). Glycosyl-
ation of 31 with 5 at -78 °C in the presence of TMSOTf
proceeded in excellent yield (93%) to afford exclusively
the desired â-linked product 32. In comparison, attempts
to glycosylate 31 with trichloroacetimidate donor 30
using a catalytic amount of TMSOTf resulted only in
acceptor decomposition. Deacetylation of tetrasaccharide
32 with sodium methoxide provided acceptor 33 in 88%
yield.
The synthesis of the required galactosamine donor
commenced with 4,6-di-O-benzyl galactal 11, which was
protected as the C3 acetate 2440 and then subjected to
an azidonitration reaction (Scheme 6). The resulting
product (25) was hydrolyzed by exposure to thiophenol
in the presence of diisopropylethylamine (DIEA), and
lactol 26 was protected as the anomeric silyl ether (27)
using thexyldimethylsilyl (TDS) chloride (96%). Reduc-
tion of the azido group with sodium borohydride in
ethanol afforded the C2 amine, which was then treated
with trichloroacetyl (TCA) chloride in the presence of
triethylamine. Due to partial de-O-acetylation during the
reaction with sodium borohydride, the crude mixture was
(36) Blatter, G.; Beau, J . M.; J acquinet, J . C. Carbohydr. Res. 1994,
260, 189.
(37) Pekari, K.; Tailler, D.; Weingart, R.; Schmidt, R. R. J . Org.
Chem. 2001, 66, 7432.
(38) Blatter, G.; J acquinet, J . C. Carbohydr. Res. 1996, 288, 109.
(39) Sherman, A.; Yudina, O. N.; Mironov, Y. V.; Sukhova, E. V.;
Shashkov, A. S.; Menshov, V. M.; Nifantiev, N. E. Carbohydr. Res.
2001, 336, 13.
(40) Greilich, U.; Brescello, R.; J ung, K.-H.; Schmidt, R. R. Liebigs
Ann. 1996, 663.
Syn th esis of th e SSEA-3 P en ta sa cch a r id e. Elabo-
ration of tetrasaccharide 33 to the SSEA-3 precursor
required the introduction of a galactose unit at the C3
position of the terminal galactosamine residue. To achieve
J . Org. Chem, Vol. 67, No. 19, 2002 6663

Bosse et al.
SCHEME 9. Com p letion of th e SSEA-3 P en ta sa cch a r id e
SCHEME 10. Com p letion of th e Globo-H Hexa sa cch a r id e
high â-selectivity in the glycosylation reaction, we inves-
tigated the use of a galactose building block bearing a
C2 ester. Initially, a benzoate group was chosen as a
means of protection for the C2 hydroxyl group. Building
block 3427 was synthesized in one-pot starting from tri-
O-benzyl galactal 12 (Scheme 8). While the union of
phosphate 34 with tetrasaccharide 33 proceeded smoothly
(90% yield) (Scheme 9), subsequent deprotection of the
C2 benzoyl ester (35) proved problematic. Complete
removal of the benzoate could not be achieved without
concomitant loss of the pivaloyl esters. Replacement of
the C2 benzoyl group of donor 34 with an acetate (6)
enabled the successful synthesis of the target penta-
saccharide. Glycosylation of tetrasaccharide 33 with
phosphate donor 6 under the agency of TMSOTf provided
pentasaccharide 36 in good yield (88%). Deacetylation of
36 with sodium methoxide cleanly afforded compound 37
(76%).
and reaction with acetic anhydride. It is important to note
that prior conversion of the N-TCA-group to the N-
acetamide was crucial for the success of this reaction
sequence. Subjection of N-TCA-protected pentasaccharide
37 to dissolving-metal reduction led to cleavage of the
â-galactosamine linkage, producing trisaccharide 23 after
peracetylation.
Com p letion of th e Globo-H Hexa sa cch a r id e. Fu-
cosyl phosphate 7 had performed well previously for the
installation of R-(1f2-cis) glycosidic linkages29 and was
employed for the completion of the target hexasaccharide.
Glycosylation of pentasaccharide 37 with fucosyl phos-
phate 7 provided protected Globo-H hexasaccharide 1 in
66% yield with complete R-selectivity (Scheme 10).
Deprotection of 1 via dissolving-metal reduction as above
provided peracetylated Globo-H 39 in 40% yield. NMR
and mass spectral analysis of 39 was in accordance with
previously reported data.33
Following conversion of the N-TCA group to the cor-
responding N-acetamide with tributylstannane and AIBN,
the protected pentasaccharide was converted to peracet-
ylated SSEA-3 38 (40%) by a dissolving-metal reduction
Con clu sion s
In summary, the synthesis of three members of the
globo-series of tumor antigens was accomplished in a
6664 J . Org. Chem., Vol. 67, No. 19, 2002

Linear Synthesis of Globo-H, SSEA-3, and Gb3
68.12, 67.34, 66.09, 38.18, 32.28. 32.21, 30.00, 28.17, 27.33,
linear fashion using six glycosyl phosphate building
blocks. In the context of these syntheses, methods for the
installation of R-galactosidic and â-galactosamine link-
ages using glycosyl phosphates were developed. The
strategy devised for this solution-phase synthesis is
currently being applied to the synthesis of the globo-
series of tumor antigens on solid-support in a fully
automated fashion.
18.78, 18.75, 13.77, 13.74. 31P NMR (120 MHz, CDCl3):
δ
-2.12. ESI-MS: m/z (M + Na)+ calcd 757.3323, obsd 757.3313.
n -P en ten yl 3,6-Di-O-ben zyl-4-O-levu lin oyl-2-O-pivaloyl-
â-D-ga la ctop yr a n osyl-(1f4)-3,6-d i-O-ben zyl-2-O-p iva loyl-
â-D-glu cop yr a n osid e 15. Glycosyl phosphate 3 (1.83 g, 2.49
mmol) and monosaccharide 1429 (1.44 g, 2.81 mmol) were
coevaporated three times with toluene, dissolved in CH2Cl2
(60 mL), and cooled to -78 °C. TBSOTf (0.83 mL, 3.61 mmol)
was added and the mixture was warmed slowly to -60 °C.
After 1 h Et3N (5 mL) was added and the mixture was poured
into a saturated solution of NaHCO3 (100 mL). The aqueous
phase was extracted twice with CH2Cl2, dried over MgSO4,
filtered, and concentrated under reduced pressure. The residue
was purified by flash chromatography (3:1 hexane/EtOAc) to
afford 2.12 g (82%) of 15 as a colorless oil. [R]D: -1.03 (c )
1.28, CH2Cl2). IR (thin film): 3438, 2970, 2932, 2871, 1738,
1367, 1277 cm-1. 1H NMR (400 MHz, CDCl3): δ 7.38-7.20 (m,
20 H), 5.76-5.38 (m, 1 H), 5.59 (d, J ) 3.0 Hz, 1 H), 5.10 (dd,
J ) 10.0, 8.1 Hz, 1 H), 4.95-5.04 (m, 4 H), 4.77 (d, J ) 12.1
Hz, 1 H), 4.69 (d, J ) 11.4 Hz, 1 H), 4.56 (d, J ) 10.7 Hz, 1 H),
4.46-4.36 (m, 4 H), 4.32-4.29 (m, 2 H), 4.07 (app t, J ) 9.3
Hz, 1 H), 3.89-3.83 (m, 1 H), 3.77-3.70 (m, 2 H), 3.65-3.60
(m, 1 H), 3.54-3.51 (m, 1 H), 3.47-3.42 (m, 1 H), 3.38-3.28
(m, 4 H), 2.73-2.49 (m, 4 H), 2.08 (s, 3 H), 2.13-2.06 (m, 2
H), 1.72-1.64 (m, 2 H), 1.18 (s, 9 H), 1.15 (s, 9 H). 13C NMR
(100 MHz, CDCl3): δ 206.85, 176.97, 176.75, 172.11, 138.89,
138.26, 138.12, 138.02, 137.63, 128.73, 128.65, 128.57, 128.41,
128.36, 128.26, 128.19, 128.03, 127.89, 127.87, 127.81, 127.69,
127.47, 127.39, 75.39, 75.31, 74.62, 73.76, 72.39, 72.24, 71.41,
71.15, 69.07, 68.05, 67.44, 66.31, 38.93, 38.89, 38.15, 30.21,
29.87, 28.93, 28.10, 27.43, 27.33.
n -P en ten yl 3,6-Di-O-ben zyl-2-O-p iva loyl-â-D-ga la cto-
p yr a n osyl-(1f4)-3,6-d i-O-ben zyl-2-O-p iva loyl-â-D-glu co-
p yr a n osid e 16. Disaccharide 15 (1.98 g, 1.91 mmol) was
dissolved in CH2Cl2 (100 mL). A solution of hydrazine acetate
(193 mg, 2.10 mmol) in MeOH (10 mL) was added, and the
mixture was stirred for 1 h at room temperature and concen-
trated. The residue was purified by flash chromatography (4:1
hexane/EtOAc), yielding 1.70 g (95%) of 16 as a colorless oil.
[R]D: +13.5 (c ) 0.80, CH2Cl2). IR (thin film): 2928, 1738,
1134, 1062 cm-1. 1H NMR (400 MHz, CDCl3): δ 7.39-7.19 (m,
20 H), 5.83-5.76 (m, 1 H), 5.20 (dd, J ) 9.8, 8.1 Hz, 1 H),
5.05-4.95 (m, 4 H), 4.76 (d, J ) 12.1 Hz, 1 H), 4.65 (d, J )
11.8 Hz, 1 H), 4.56 (d, J ) 10.9 Hz, 1 H), 4.51 (d, J ) 11.8 Hz,
1 H), 4.47-4.38 (m, 3 H), 4.36 (d, J ) 8.0 Hz, 1 H), 4.31 (d, J
) 11.9 Hz, 1 H), 4.05 (app t, J ) 9.3 Hz, 1 H), 4.02-4.01 (m,
1 H), 3.89-3.83 (m, 1 H), 3.63 (app t, J ) 9.1 Hz, 1 H), 3.57
(dd, J ) 9.5, 6.6 Hz, 1 H), 3.47-3.31 (m, 5 H), 2.25 (br s, 1 H),
2.13-2.06 (m, 2 H), 1.68-1.64 (m, 4 H), 1.19 (s, 9 H), 1.18 (s,
9 H). 13C NMR (100 MHz, CDCl3): δ 177.08, 176.82, 139.00,
138.31, 138.29, 138.21, 137.50, 128.69, 128.63, 128.57, 128.24,
128.17, 127.95, 127.90, 127.88, 127.80, 127.69, 127.28, 114.99,
101.51, 99.79, 81.05, 79.42, 75.40, 75.35, 74.74, 73.76, 73.74,
73.35, 72.51, 71.57, 71.15, 69.09, 68.46, 68.18, 65.78, 38.98,
38.91, 30.24, 28.96, 27.47, 27.34. ESI-MS: m/z (M + Na)+ calcd
961.4709, obsd 961.4725.
Exp er im en ta l Section
Gen er a l Meth od s. All chemicals were reagent grade and
used as supplied, unless otherwise noted. Dichloromethane
(CH2Cl2), tetrahydrofuran (THF), diethyl ether (Et2O), and
toluene were purified by a J T Baker Cycle-Trainer Solvent
Delivery System. Analytical thin-layer chromatography was
performed on silica gel 60 F254 plates (0.25 mm). Compounds
were visualized by dipping the plates in a cerium sulfate-
ammonium molybdate solution followed by heating. Flash
chromatography was performed using forced flow of the
indicated solvent on Silicylce silica (230-400 mesh). NMR
spectra (1H at 400 MHz, 13C at 100 MHz) were recorded in
CDCl3 as the solvent and chemical shifts are reported in parts
per million (δ) relative to CHCl3 as an internal reference. 31P
spectra (120 MHz) are reported in δ relative to H3PO4 (0.0
ppm) as an external reference. Optical rotations were meas-
ured at 24 °C.
3,6-Di-O-ben zyl-4-O-levu lin oyl-D-ga la ct a l 13. Galactal
1034 (3.94 g, 10.7 mmol) was dissolved in CH2Cl2 (80 mL) and
cooled to 0 °C. DCC (3.53 g, 17.1 mmol), DMAP (131 mg, 1.07
mmol), and levulinic acid (1.5 mL, 15.0 mmol) were added,
and the mixture was stirred for 14 h at room temperature.
The mixture was filtered, washed twice with water, dried over
MgSO4, filtered, and concentrated under reduced pressure. The
residue was purified by flash chromatography (3:1 hexane/
EtOAc) to afford 4.20 g (92%) of 13 as a pale yellow oil. [R]D:
+1.13 (c ) 1.6, CH2Cl2). IR (thin film): 2920, 1738, 1717, 1362,
1155, 1099 cm-1. 1H NMR (400 MHz, CDCl3): δ 7.28-7.18 (m,
10 H), 6.32 (dd, J ) 6.3, 1.8 Hz, 1 H), 5.56-5.52 (m, 1 H),
4.68-4.65 (m, 1 H), 4.57 (d, J ) 11.8 Hz, 1 H), 4.50 (d, J )
11.7 Hz, 1 H), 4.45 (d, J ) 11.7 Hz, 1 H), 4.39 (d, J ) 11.8 Hz,
1 H), 4.17-4.15 (m, 1 H), 4.12-4.08 (m, 1 H), 3.60 (dd, J )
9.8, 6.2 Hz, 1 H), 3.50 (dd, J ) 9.8, 6.3 Hz, 1 H), 2.67-2.53
(m, 4 H), 2.07 (s, 3 H). 13C NMR (100 MHz, CDCl3): δ 206.55,
172.47, 144.65, 138.18, 137.86, 128.62, 128.57, 128.26, 128.01,
127.87, 101.35, 74.56, 73.87, 71.15, 69.63, 68.61, 63.57, 38.17,
30.00, 28.29. ESI-MS: m/z (M + Na)+ calcd 447.1778, obsd
447.1752.
Dibu tyl 3,6-Di-O-ben zyl-4-O-levu lin oyl-2-O-p iva loyl-â-
D-ga la ctop yr a n osid e P h osp h a te 3. Galactal 13 (0.831 g,
2.55 mmol) was dissolved in CH2Cl2 (15 mL) and cooled to 0
°C. DMDO (0.08 M in acetone, 45 mL, 3.6 mmol) was added
and the reaction was stirred for 20 min. The solvent was
evaporated at 0 °C and the residue dissolved in CH2Cl2 (40
mL) and cooled to -78 °C. A solution of dibutyl phosphate (0.56
mL, 2.8 mmol) in CH2Cl2 (10 mL) was added dropwise. After
stirring for 10 min, the mixture was warmed to 0 °C, and
DMAP (1.24 g, 10.2 mmol) and pivaloyl chloride (0.63 mL, 5.10
mmol) were added. After stirring for 14 h the solvent was
removed in vacuo, and the residue was purified by flash
chromatography (1:1 hexane/EtOAc), yielding 980 mg (52%)
of 3 as a colorless oil. [R]D: +25.2 (c ) 1.28, CH2Cl2). IR (thin
film): 2928, 1740, 1494, 1277, 1050 cm-1. 1H NMR (400 MHz,
CDCl3): δ 7.37-7.23 (m, 10 H), 5.67-5.66 (m, 1 H), 5.23-
5.21 (m, 2 H), 4.69 (d, J ) 11.4 Hz, 1 H), 4.51-4.50 (m, 2 H),
4.38 (d, J ) 11.4 Hz, 1 H), 4.06-3.98 (m, 4 H), 3.88-3.87 (m,
1 H), 3.65-3.54 (m, 3 H), 2.74-2.62 (m, 4 H), 2.15 (s, 3 H),
1.63-1.58 (m, 4 H), 1.40-1.32 (m, 4 H), 1.19 (s, 9 H), 0.93-
0.87 (m, 6 H). 13C NMR (100 MHz, CDCl3): δ 206.56, 177.17,
172.05, 137.77, 137.26, 128.62, 128.58, 128.50, 128.28, 128.23,
128.09, 128.05, 128.01, 96.97, 77.15, 73.10, 71.71, 70.31, 68.21,
Allyl 4,6-Di-O-b en zyl-3-O-p -m et h oxyb en zyl-r/â-D-ga -
la ctop yr a n osid e 18. To a solution of di-O-benzyl galactal 1134
(1.26 g, 3.86 mmol) in DMF (20 mL) were added NaH (176
mg, 4.4 mmol), p-methoxybenzyl chloride (600 µL, 4.4 mmol),
and TBAI (70 mg, 0.19 mmol) at 0 °C. The reaction was stirred
for 16 h at room temperature, diluted with EtOAc, washed
three times with water, and dried over MgSO4. The organic
phase was concentrated in vacuo and the crude residue was
purified by flash chromatography (6:1 hexanes/EtOAc) to
afford 1.65 g (97%) of 1717 as a colorless oil. Compound 17 (1.65
g, 3.70 mmol) was dissolved in CH2Cl2 (30 mL) and cooled to
0 °C. A solution of DMDO (0.08 M in acetone, 60 mL, 4.8 mmol)
was added and the mixture was stirred for 10 min and then
concentrated in vacuo at 0 °C. The resulting residue was
dissolved in allyl alcohol (30 mL) and stirred at room temper-
J . Org. Chem, Vol. 67, No. 19, 2002 6665

Bosse et al.
ature for 16 h. The solution was concentrated and the crude
product was purified by flash chromatography (3:1 hexanes/
EtOAc) to afford 1.52 g (79%, R:â ) 1:5) of 18 as a colorless
oil. IR (thin film): 3460, 2914, 2869, 2107, 1612, 1513, 1454,
added, followed by NaOAc (290 mg, 3.54 mmol) and PdCl2 (314
mg, 1.77 mmol), and the mixture was stirred for 16 h at room
temperature. The reaction mixture was diluted with EtOAc
and washed with water, saturated aqueous NaHCO3, and
brine. The organic phase was dried over MgSO4, filtered, and
concentrated to give the desired lactol as a pale yellow oil. The
crude lactol was dissolved in CH2Cl2 (10 mL), and trichloro-
acetonitrile (5 mL) and DBU (10 µL) were added. The mixture
was stirred for 1 h at room temperature and concentrated. The
resulting residue was purified by flash chromatography (2:1
hexanes/EtOAc, 2% Et3N) to yield 794 mg (76%) of compound
21 as a colorless oil. [R]D: +67.9 (c ) 1.90, CH2Cl2). IR (thin
film): 3337, 2920, 2871, 1739, 1718, 1672, 1353, 1289, 1155,
1103, 1074, 1027 cm-1. 1H NMR (400 MHz, CDCl3): δ 8.57 (s,
1 H), 7.36-7.28 (m, 15 H), 6.54 (d, J ) 3.5 Hz, 1 H), 5.39 (dd,
J ) 10.5, 2.9 Hz, 1 H), 4.76 (d, J ) 11.3 Hz, 1 H), 4.73 (d, J )
10.3 Hz, 1 H), 4.64 (d, J ) 12.1 Hz, 1 H), 4.57 (d, J ) 11.4 Hz,
1 H), 4.50 (d, J ) 11.8 Hz, 1 H), 4.43 (d, J ) 11.8 Hz, 1 H),
4.30 (app t, J ) 6.6 Hz, 1 H), 4.24 (dd, J ) 10.5, 3.5 Hz, 1 H),
4.17 (app d, J ) 2.3 Hz, 1 H), 3.59-3.56 (m, 2 H), 2.81-2.75
(m, 1 H), 2.66-2.40 (m, 3 H), 2.17 (s, 3 H). 13C NMR (100 MHz,
CDCl3): δ 206.80, 172.66, 161.71, 138.58, 138.36, 138.11,
128.83, 128.76, 128.67, 128.63, 128.54, 128.39, 128.24, 128.19,
128.15, 128.12, 127.95, 95.02, 91.63, 75.68, 75.32, 73.77, 73.62,
73.18, 72.80, 71.85, 68.21, 60.83, 38.18, 30.25, 28.32. ESI-MS:
m/z (M + Na)+ calcd 714.1399, obsd 714.1370.
1248, 1078 cm-1 1H NMR (400 MHz, CDCl3, â-anomer): δ
.
7.39-7.28 (m, 14 H), 6.91 (app d, J ) 8.6 Hz, 2 H), 5.98-5.92
(m, 1 H), 5.32 (dd, J ) 17.2, 1.4 Hz, 1 H), 5.21 (app d, J ) 10.4
Hz, 1 H), 4.91 (d, J ) 11.6 Hz, 1 H), 4.71-4.59 (m, 2 H), 4.52-
4.44 (m, 2 H), 4.42-4.36 (m, 1 H), 4.32 (d, J ) 7.7 Hz, 1 H),
4.16-4.12 (m, 1 H), 4.00-3.97 (m, 1 H), 3.93 (app d, J ) 2.5
Hz, 1 H), 3.38 (s, 3 H), 3.66-3.59 (m, 2 H), 3.44 (dd, J ) 9.8,
2.8 Hz, 1 H), 2.42 (br s, 1 H). 13C NMR (100 MHz, CDCl3): δ
159.75, 138.92, 138.26, 130.48, 129.29, 128.88, 128.69, 128.62,
128.34, 128.26, 128.23, 128.00, 118.25, 114.35, 114.30, 102.42,
82.05, 75.09, 74.38, 74.16, 73.99, 73.14, 72.45, 71.60, 70.39,
69.15, 55.71, 21.51, 14.64. ESI-MS: m/z (M + Na)+ calcd
543.2359, obsd 543.2359.
Allyl 2,4,6-Tr i-O-ben zyl-3-O-p-m eth oxyben zyl-r/â-D-ga -
la ctop yr a n osid e 19. To a solution of 18 (1.5 g, 2.9 mmol) in
DMF (20 mL) were added NaH (140 mg, 3.5 mmol) and benzyl
bromide (420 µL, 3.5 mmol) at 0 °C. The mixture was stirred
for 4 h and then quenched with water, diluted with EtOAc,
and washed twice with water and once with brine. The organic
phase was dried over MgSO4, filtered, and concentrated in
vacuo. The residue was purified by flash chromatography (6:1
hexanes/EtOAc) to afford 1.60 g (71%, R:â ) 1:5) of 19 as a
white solid. IR (thin film): 2915, 2867, 2360, 2341, 1513, 1454,
Dibu tyl 2,4,6-Tr i-O-ben zyl-3-O-levu lin oyl-â-D-ga la cto-
p yr a n osid e P h osp h a te 4. Glycosyl trichloroacetimidate 21
(425 mg, 0.613 mmol) was dissolved in CH2Cl2 (5 mL) and
cooled to 0 °C. Dibutyl phosphate (135 µL, 0.675 mmol) was
added and the mixture was stirred for 1 h and concentrated.
The residue was purified by flash chromatography (1:1 hexane/
EtOAc, 2% Et3N) to afford 410 mg (90%) of 4 as a colorless
oil. [R]D: +28.8 (c ) 0.92, CH2Cl2). IR (thin film): 2927, 1717,
1248, 1099, 1077 cm-1 1H NMR (400 MHz, CDCl3, â-ano-
.
mer): δ 7.43-7.28 (m, 19 H), 6.90 (d, J ) 11.6 Hz, 1 H), 6.89
(d, J ) 11.5 Hz, 1 H), 6.01-5.93 (m, 1 H), 5.35 (dd, J ) 18.0,
2.0 Hz, 1 H), 5.20 (dd, J ) 12.2, 1.4 Hz, 1 H), 4.97 (d, J ) 11.7
Hz, 1 H), 4.96 (d, J ) 10.8 Hz, 1 H), 4.80 (d, J ) 10.8 Hz, 1 H),
4.47-4.42 (m, 3 H), 4.17-4.13 (m, 1 H), 3.90-3.86 (m, 1 H),
3.84 (s, 3 H), 3.61 (dd, J ) 6.3, 3.0 Hz, 1 H), 3.57-3.52 (m, 2
H). 13C NMR (100 MHz, CDCl3): δ 159.56, 139.21, 139.08,
138.34, 134.63, 131.04, 129.64, 129.58, 128.86, 128.80, 128.71,
128.67, 128.59, 128.44, 128.32, 128.22, 128.16, 127.98, 127.95,
117.47, 103.38, 82.31, 80.02, 75.70, 74.86, 73.97, 73.84, 73.39,
73.15, 69.34, 68.63, 55.70. ESI-MS: m/z (M + Na)+ calcd
633.2823, obsd 633.2828.
1
1494, 1262, 1050 cm-1. H NMR (400 MHz, CDCl3): δ 7.36-
7.27 (m, 15 H), 5.18 (app t, J ) 7.0 Hz, 1 H), 4.96 (dd, J )
10.2, 3.1 Hz, 1 H), 4.86 (d, J ) 11.6 Hz, 1 H), 4.72 (d, J ) 11.6
Hz, 1 H), 4.67 (d, J ) 11.6 Hz, 1 H), 4.56 (d, J ) 11.6 Hz, 1 H),
4.47 (d, J ) 11.8 Hz, 1 H), 4.42 (d, J ) 11.8 Hz, 1 H), 4.10-
3.98 (m, 5 H), 3.91 (dd, J ) 10.2, 7.8 Hz, 1 H), 3.84-3.80 (m,
1 H), 3.61-3.59 (m, 2 H), 2.70-2.32 (m, 4 H), 2.13 (s, 3 H),
1.63-1.56 (m, 4 H) 1.38-1.24 (m, 4 H), 0.89 (t, J ) 7.4 Hz, 3
H) 0.86 (t, J ) 7.4 Hz, 6 H). 13C NMR (100 MHz, CDCl3): δ
206.38, 172.25, 138.38, 138.29, 137.78, 128.58, 128.44, 128.42,
128.17, 127.95, 127.84, 127.83, 127.77, 99.13, 77.00, 75.21,
75.16, 74.88, 74.22, 73.85, 73.55, 67.87, 67.77, 37.86, 32.29,
32.25, 29.93, 27.92, 18.72, 13.75, 13.72. 31P NMR (120 MHz,
CDCl3): δ -1.66. ESI-MS: m/z (M + Na)+ calcd 763.3218, obsd
763.3227.
Allyl 2,4,6-Tr i-O-b en zyl-3-O-levu lin oyl-r/â-D-ga la ct o-
p yr a n osid e 20. To a solution of 19 (1.20 g, 1.96 mmol) in
CH2Cl2 (20 mL) were added water (1.0 mL) and DDQ (556 mg,
2.45 mmol). The reaction was stirred for 1 h at room temper-
ature and then poured into a saturated solution of NaHCO3
and extracted three times with CH2Cl2. The organic phases
were combined, dried over MgSO4, filtered, and concentrated.
The crude residue was dissolved in CH2Cl2 (20 mL), and
levulinic acid (318 mg, 2.74 mmol), DIC (490 µL, 3.14 mmol),
and DMAP (24 mg, 0.20 mmol) were added. The mixture was
stirred for 16 h at room temperature and then diluted with
CH2Cl2, washed with H2O and saturated aqueous NaHCO3,
dried over MgSO4, and filtered. The solvent was removed in
vacuo and the residue was purified by flash chromatography
(3:1 f 2:1 hexanes/EtOAc) to afford 1.07 g (93%, R:â ) 1:5) of
20 as a colorless oil. IR (thin film): 2920, 1738, 1718, 1361,
n -P en t en yl 2,4,6-Tr i-O-b en zyl-3-O-levu lin oyl-r-D-ga -
la ct op yr a n osyl-(1f4)-3,6-d i-O-b en zyl-2-O-p iva loyl-â-D-
ga la ctop yr a n osyl-(1f4)-3,6-d i-O-ben zyl-2-O-p iva loyl-â-D-
glu cop yr a n osid e 22. P r oced u r e A. Disaccharide 16 (980
mg, 0.945 mmol) and glycosyl phosphate 4 (2.39 g, 3.22 mmol)
were coevaporated three times with toluene, dissolved in
CH2Cl2/Et2O (1:4, 50 mL), and cooled to -78 °C. TBSOTf (740
µL, 3.2 mmol) was added and the mixture was stirred for 2 h
while warming to -20 °C. Triethylamine (5 mL) was added
and the mixture was concentrated under reduced pressure.
The residue was purified by flash chromatography (4:1 f 3:1
hexane/EtOAc) to afford 1.10 g (79%) of 22 as a colorless oil.
P r oced u r e B. Disaccharide 16 (78 mg, 0.083 mmol) and
trichloroacetimidate 21 (105 mg, 0.166 mmol) were coevapo-
rated three times with toluene, dissolved in CH2Cl2 (4 mL),
and cooled to 0 °C. TMSOTf (5 µL, 0.025 mmol) was added
and the mixture was stirred for 40 min at 0 °C. Triethylamine
(50 µL) was added and the mixture was concentrated under
reduced pressure. The residue was purified by flash chroma-
tography (4:1 f 3:1 hexane/EtOAc) to afford 66 mg (54%) of
22 as a colorless oil.
1209, 1158, 1074 cm-1 1H NMR (400 MHz, CDCl3, â-ano-
.
mer): δ 7.38-7.28 (m, 15 H), 5.98-5.93 (m, 1 H), 5.35 (dd, J
) 17.2, 1.6 Hz, 1 H), 5.20 (dd, J ) 10.5, 1.4 Hz, 1 H), 4.97-
4.91 (m, 2 H), 4.73-4.66 (m, 2 H), 4.57-4.42 (m, 5 H), 4.17-
4.14 (m, 1 H), 3.96 (app d, J ) 2.9 Hz, 1 H), 3.84 (dd, J ) 10.2,
7.7 Hz, 1 H), 3.69-3.76 (m, 1 H), 3.62-3.55 (m, 2 H), 2.76-
2.39 (m, 4 H), 2.15 (s, 3 H). 13C NMR (100 MHz, CDCl3): δ
206.74, 172.64, 138.99, 138.70, 138.25, 134.39, 128.85, 128.77,
128.67, 128.63, 128.54, 128.46, 128.40, 128.31, 128.24, 128.20,
128.12, 128.02, 127.97, 117.63, 103.21, 77.30, 75.59, 75.34,
75.10, 74.82, 73.89, 73.79, 73.57, 70.63, 68.78, 38.19, 30.24,
28.38, 28.30. ESI-MS: m/z (M + Na)+ calcd 611.2615, obsd
611.2619.
2,4,6-Tr i-O-b en zyl-3-O-levu lin oyl-r-D-ga la ct op yr a n o-
syl Tr ich lor a cetim id a te 21. Compound 20 (906 mg, 1.54
mmol) was dissolved in AcOH (9 mL). Water (300 µL) was
[R]D: +23.7 (c ) 0.91, CH2Cl2). IR (thin film): 2930, 2870,
1
1740, 1132, 1095, 1054 cm-1. H NMR (400 MHz, CDCl3): δ
6666 J . Org. Chem., Vol. 67, No. 19, 2002

Linear Synthesis of Globo-H, SSEA-3, and Gb3
7.40-7.16 (m, 35 H), 5.88-5.81 (m, 1 H), 5.40-5.35 (m, 2 H),
5.16 (d, J ) 12.1 Hz, 1 H), 5.08-5.00 (m, 4 H), 4.81 (d, J )
12.1 Hz, 1 H), 4.80 (d, J ) 12.1 Hz, 1 H), 4.65-4.51 (m, 8 H),
4.41-4.33 (m, 3 H), 4.23-4.22 (m, 2 H), 4.15-4.16 (m, 1 H),
4.13-4.06 (m, 5 H), 3.92-3.81 (m, 3 H), 3.71-3.67 (m, 1 H),
3.52-3.41 (m, 5 H), 3.32 (dd, J ) 10.4, 2.4 Hz, 1 H), 3.12 (dd,
J ) 8.9, 4.9 Hz, 1 H), 2.57-2.54 (m, 1 H), 2.49-2.31 (m, 3 H),
2.17-2.14 (m, 2 H), 2.11 (s, 3 H), 1.72-1.69 (m, 2 H), 1.22 (s,
9 H), 1.18 (s, 9 H). 13C NMR (100 MHz, CDCl3): δ 206.64,
176.88, 176.54, 171.64, 139.56, 138.98, 138.70, 138.48, 138.41,
138.37, 138.33, 138.01, 128.60, 128.57, 128.53, 128.44, 128.31,
128.30, 128.22, 128.08, 127.99, 127.97, 127.89, 127.84, 127.79,
127.73, 127.71, 127.47, 127.45, 126.90, 114.96, 104.41, 101.45,
100.79, 81.29, 80.27, 76.35, 75.88, 75.41, 75.29, 75.13, 74.88,
74.65, 73.68, 73.63, 73.41, 73.24, 73.12, 72.62, 71.87, 71.31,
69.08, 68.66, 68.36, 67.70, 67.49, 38.93, 38.88, 37.97, 30.27,
29.99, 28.98, 28.00, 27.56, 27.31. ESI-MS: m/z (M + Na)+ calcd
1491.7013, obsd 1491.7052.
n -P en ten yl 2,3,4,6-Tetr a -O-a cetyl-r-D-ga la ctop yr a n o-
syl-(1f4)-2,3,6-t r i-O-a cet yl-â-D-ga la ct op yr a n osyl-(1f4)-
2,3,6-tr i-O-a cetyl-â-D-glu cop yr a n osid e 23. To a deep blue
solution of sodium in liquid ammonia (ca. 7 mL) was added
trisaccharide 22 (125 mg, 0.085 mmol) in dry THF (5 mL)
under N2 at -78 °C. After 45 min the reaction was quenched
with MeOH (5 mL) and most of the ammonia was removed
with a stream of N2. The mixture was diluted with MeOH,
treated with Dowex 50-X8 ion-exchange resin (washed and
dried), filtered, and rinsed thoroughly with MeOH. The solu-
tion was concentrated in vacuo, and the resulting residue was
dissolved in pyridine (3 mL) and treated with Ac2O (2 mL) in
the presence of DMAP (one crystal) at room temperature for
18 h. Flash chromatography of the crude material (1:1 f 1:2
hexanes/EtOAc) afforded 36 mg (43%) of 23 as a colorless oil.
[R]D: +44.9 (c ) 1.20, CH2Cl2). IR (thin film): 2926, 1750,
1700, 1653, 1558, 1540, 1495, 1373, 1230, 1050 cm-1. 1H NMR
(400 MHz, CDCl3): δ 5.80-5.76 (m, 1 H), 5.60 (d, J ) 1.8 Hz,
1 H), 5.40 (dd, J ) 11.0, 2.9 Hz, 1 H), 5.24-5.17 (m, 2 H), 5.11
(dd, J ) 10.5, 8.1 Hz, 1 H), 5.04-4.96 (m, 3 H), 4.90 (m, 1 H),
4.73 (app d, J ) 10.8 Hz, 1 H), 4.54-4.27 (m, 4 H), 4.18-4.09
(m, 4 H), 4.02 (app s, 1 H), 3.87-3.77 (m, 4 H), 3.78-3.62 (m,
1 H), 3.52-3.46 (m, 1 H) 2.14 (s, 3 H), 2.13 (s, 3 H), 2.09-2.06
(m, 23 H), 2.13 (s, 3 H), 1.71-1.62 (m, 2 H). 13C NMR (100
MHz, CDCl3): δ 170.69, 170.51, 170.47, 170.10, 169.72, 169.69,
169.54, 168.87, 137.81, 115.07, 101.10, 100.53, 99.63, 73.14,
72.81, 72.45, 71.79, 71.74, 70.21, 69.30, 68.93, 68.82, 67.85,
67.09, 67.04, 62.23, 61.26, 60.39, 60.23, 53.44, 29.82, 28.56,
20.95, 20.88, 20.72, 20.69, 20.65, 20.61, 20.52. ESI-MS: m/z
(M + Na)+ calcd 1015.3265, obsd 1015.3253.
EtOAc) to give 1.16 g (91%, R:â ) 2:1) of 26 as a white solid.
IR (thin film): 3399, 3031, 2872, 2112, 1745, 1231, 1045 cm-1
.
1H NMR (400 MHz, CDCl3, selected peaks): δ 5.38 (d, J ) 3.4
Hz, 1 H, R H-1), 5.32 (dd, J ) 11.0, 2.9 Hz, 1 H, R H-3), 4.74
(dd, J ) 10.8, 3.1 Hz, 1 H, â H-3), 4.06 (app d, J ) 2.3 Hz, R
H-4), 3.94 (app d, J ) 3.3 Hz, 1 H, â H-4), 3.92 (dd, J ) 11.1,
3.5 Hz, R H-2), 3.07 (br s, 1 H, OH). ESI-MS: m/z (M + Na)+
calcd 450.1636, obsd 450.1628.
Dim eth ylth exylsilyl 3-O-Acetyl-2-a zid o-4,6-d i-O-ben -
zyl-2-d eoxy-â-D-ga la ctop yr a n osid e 27. To 1.16 g (2.70
mmol) of 26 in DMF (25 mL) were added imidazole (551 mg,
8.10 mmol) and thexyldimethylsilyl chloride (TDS-Cl) (800
µL, 4.07 mmol). The mixture was stirred at room temperature
for 12 h, diluted with EtOAc, and washed with water,
saturated aqueous NaHCO3, water, and brine. The organic
phase was dried over MgSO4, concentrated, and purified by
flash chromatography (8:1 hexanes/EtOAc) to afford 1.48 g
(96%) of 27 as a colorless oil. [R]D: +2.4 (c ) 1.32, CH2Cl2). IR
(thin film): 2927, 2112, 1749, 1653, 1558, 1455, 1259, 1090
cm-1. 1H NMR (400 MHz, CDCl3): δ 7.49-7.22 (m, 10 H), 4.70
(dd, J ) 11.1, 2.7 Hz, 1 H), 4.63-4.40 (m, 5 H), 3.94 (app s, 1
H), 3.74 (dd, J ) 8.0, 2.4 Hz, 1 H), 3.66-3.59 (m, 3 H), 2.04 (s,
3 H), 1.69 (m, 1 H), 0.90 (m, 12 H), 0.21 (s, 6 H). 13C NMR
(100 MHz, CDCl3): δ 170.25, 138.08, 137.95, 137.74, 137.70,
129.34, 128.61, 128.46, 128.43, 128.38, 128.18, 128.15, 128.07,
127.86, 127.79, 127.74, 126.05, 97.31, 75.30, 75.24, 75.05,
73.58, 73.53, 73.47, 73.33, 72.41, 68.48, 68.23, 67.38, 63.83,
33.80, 24.81, 20.87, 19.95, 19.83, 18.50, 18.40, 1.03, -1.91,
-3.25, -3.27. ESI-MS: m/z (M + Na)+ calcd 592.2813, obsd
592.2805.
Dim eth ylth exylsilyl 3-O-Acetyl-4,6-di-O-ben zyl-2-deoxy-
2-tr ich lor oa ceta m id o-â-D-ga la ctop yr a n osid e 28. To a so-
lution of 27 (1.34 g, 2.35 mmol) in EtOH (20 mL) were added
NaBH4 (444 mg, 11.8 mmol) and NiCl2 (56 mg, 0.24 mmol).
The solution was stirred for 90 min at room temperature then
neutralized with AcOH and concentrated to dryness. The
residue was precipitated with CH2Cl2, filtered over a pad of
Celite, and concentrated. To a solution of the crude amine in
CH2Cl2 (20 mL) was added Et3N (975 µL, 7.00 mmol) and
trichloroacetyl chloride (310 µL, 2.80 mmol) at 0 °C. The
reaction mixture was stirred for 20 min at 0 °C and then
diluted with CH2Cl2 and washed with water, saturated aque-
ous NaHCO3, and water. The organic phase was dried over
MgSO4 and concentrated. The resulting residue was dissolved
in pyridine (10 mL) and treated with Ac2O (5 mL). After 12 h
the reaction mixture was concentrated, coevaporated with
toluene, and purified by flash chromatography (4:1 hexanes/
EtOAc) to yield 648 mg (40%) of 28 as a colorless oil. [R]D: -5.3
(c ) 0.89, CH2Cl2). IR (thin film): 2926, 2862, 1717, 1653, 1558,
3-O-Acetyl-2-a zid o-4,6-d i-O-ben zyl-2-d eoxy-r/â-D-ga la c-
top yr a n osyl Nitr a te 25. Galactal 2440 (3.03 g, 8.22 mmol)
was dissolved in CH3CN (60 mL) and cooled to -15 °C. CAN
(13.5 g, 24.7 mmol) and NaN3 (800 mg, 12.3 mmol) were added,
and the mixture was stirred vigorously using a mechanical
stirrer. After 4 h the reaction mixture was diluted with ice-
cold Et2O, washed twice with ice-water, dried over Na2SO4,
and concentrated. The crude residue was purified by flash
chromatography (5:1 hexanes/EtOAc) to afford 1.7 g (45%) of
25 (R:â ) 4:1) as a colorless oil. IR (thin film): 2922, 2116,
1
1540, 1403, 1050 cm-1. H NMR (400 MHz, CDCl3): δ 7.36-
7.27 (m, 10 H), 6.67 (d, J ) 9.0 Hz, 1 H), 5.19 (dd, J ) 11.3,
2.3 Hz, 1 H), 4.85 (d, J ) 7.8 Hz, 1 H), 4.75 (d, J ) 11.7 Hz, 1
H), 4.60 (d, J ) 11.7 Hz, 1 H), 4.53 (d, J ) 11.7 Hz, 1 H), 4.47
(d, J ) 11.7 Hz, 1 H), 4.31-4.24 (m, 1 H), 3.98 (app s, 1 H),
3.77-3.74 (m, 1 H), 3.68 (app t, J ) 8.8 Hz, 1 H), 3.64-3.62
(m, 1 H), 2.00 (s, 3 H), 1.65-1.62 (m, 1 H), 0.88-0.85 (m, 12
H), 0.20 (s, 3 H), 0.16 (s, 3 H). 13C NMR (100 MHz, CDCl3): δ
171.34, 161.98, 138.38, 138.19, 129.44, 128.87, 128.78, 128.68,
128.25, 128.19, 96.52, 93.02, 75.37, 74.06, 73.98, 73.92, 68.73,
55.86, 34.23, 25.16, 21.22, 20.45, 20.36, 18.98, 18.96, -1.22,
-2.86. ESI-MS: m/z (M + Na)+ calcd 710.1845, obsd 710.1867.
1
1748, 1652, 1280, 1223, 1102, 1028 cm-1. H NMR (400 MHz,
CDCl3, selected peaks): δ 6.30 (d, J ) 4.1 Hz, 1 H, R H-1),
5.54 (d, J ) 8.8 Hz, 1 H, â H-1), 5.19 (dd, J ) 11.3, 2.9 Hz, 1
H, R H-3), 4.86 (dd, J ) 11.0, 3.0 Hz, 1 H, â H-3), 4.29 (dd, J
) 11.3, 4.2 Hz, 1 H, R H-2), 4.18 (app d, J ) 2.9 Hz, 1 H, R
H-4), 4.07 (app d, J ) 2.9 Hz, 1 H, â H-4), 4.00 (dd, J ) 11.0,
8.8 Hz, 1 H, â H-2). ESI-MS: m/z (M + Na)+ calcd 495.1486,
obsd 495.1469.
3-O-Ace t yl-2-a zid o-4,6-d i-O-b e n zyl-2-d e oxy-D-ga la c-
tose 26. To a solution of 25 (1.42 g, 3.00 mmol) in CH3CN (30
mL) were added thiophenol (900 µL, 9.00 mmol) and DIEA
(525 µL, 3.00 mmol) at 0 °C. After 90 min the reaction mixture
was concentrated under reduced pressure and the crude
residue purified by flash chromatography (6:1 f 2:1 hexanes/
3-O-Ace t yl-4,6-d i-O-b e n zyl-2-d e oxy-2-t r ich lor oa ce t -
a m id o-r-D-ga la ctop yr a n osyl Tr ich lor oa cetim id a te 30. To
a solution of compound 28 (740 mg, 1.07 mmol) in dry THF
(10 mL) were added AcOH (75 µL, 1.3 mmol) and a 1.0 M
solution of tetrabutylammonium fluoride in THF (1.3 mL, 1.3
mmol). The mixture was stirred at room temperature for 20
h, diluted with EtOAc, washed with saturated aqueous
NaHCO3, water, and brine, dried over MgSO4, and concen-
trated. Purification of the resulting residue by flash chroma-
tography (8:1 f 4:1 hexanes/EtOAc) yielded 530 mg (91%) of
29 as a colorless oil. To a solution of lactol 29 (527 mg, 0.96
J . Org. Chem, Vol. 67, No. 19, 2002 6667

Bosse et al.
mmol) in CH2Cl2 (10 mL) was added trichloroacetonitrile (5
mL) and DBU (10 µL). The mixture was stirred at room
temperature for 2 h and then concentrated. Purification of the
crude residue by flash chromatography (4:1 hexanes/EtOAc)
yielded 461 mg (70%) of 30 as a colorless foam. [R]D: +65.1 (c
) 0.83, CH2Cl2). IR (thin film): 2926, 1717, 1684, 1558, 1494,
1452, 1403, 1050 cm-1. 1H NMR (400 MHz, CDCl3): δ 8.73 (s,
1 H), 7.39-7.27 (m, 10 H), 6.93 (d, J ) 8.9 Hz, 1 H), 6.47 (d,
J ) 3.5 Hz, 1 H), 5.42 (dd, J ) 11.3, 2.7 Hz, 1 H), 4.90-4.87
(m, 1 H), 4.82 (d, J ) 11.4 Hz, 1 H), 4.62 (d, J ) 11.4 Hz, 1 H),
4.52-4.49 (m, 2 H), 4.44 (d, J ) 11.7 Hz, 1 H), 4.25 (dd, J )
7.8, 5.7 Hz, 1 H), 4.12 (d, J ) 2.4 Hz, 1 H), 3.70 (app t, J ) 9.0
Hz, 1 H), 3.61 (dd, J ) 9.1, 5.4 Hz, 1 H), 2.06 (s, 3 H). 13C
NMR (100 MHz, CDCl3): δ 171.86, 162.44, 160.67, 138.06,
137.94, 128.89, 128.87, 128.58, 128.39, 128.34, 128.28, 95.32,
92.46, 91.22, 77.64, 75.65, 74.06, 73.92, 72.47, 70.95, 67.80,
50.92, 21.28. ESI-MS: m/z (M + Na)+ calcd 710.9763, obsd
710.9763.
zyl-r-D-ga la ctop yr a n osyl-(1f4)-3,6-d i-O-ben zyl-2-O-p iv-
a loyl-â-D-ga la ct op yr a n osyl-(1f4)-3,6-d i-O-b en zyl-2-O-
p iva loyl-â-D-glu cop yr a n osid e 32. Trisaccharide 31 (308 mg,
0.230 mmol) and glycosyl phosphate 5 (196 mg, 0.270 mmol)
were coevaporated three times with toluene, dissolved in
CH2Cl2 (4 mL), and cooled to -78 °C. TMSOTf (50 µL, 0.270
mmol) was added and the mixture was stirred for 30 min.
Triethylamine (200 µL) was added and the mixture was
directly purified by flash chromatography (4:1 f 2:1 hexane/
EtOAc) to afford 405 mg (93%) of 32 as a white solid. [R]D:
-15.2 (c ) 1.00, CH2Cl2). IR (thin film): 1734, 1521, 1455,
1
1364, 1231, 1093 cm-1. H NMR (400 MHz, CDCl3): δ 7.46-
7.18 (m, 45 H), 6.54 (d, J ) 9.8 Hz, 1 H), 5.85-5.78 (m, 1 H),
5.36 (dd, J ) 9.9, 8.3 Hz, 1 H), 5.06-4.96 (m, 4 H), 4.84-4.74
(m, 6 H), 4.66-4.47 (m, 8 H), 4.38-4.02 (m, 17 H), 4.02-3.99
(m, 2 H), 3.89 (app s, 1 H), 3.90-3.80 (m, 2 H), 3.78-3.51 (m,
3 H), 3.48-3.35 (m, 4 H), 3.28 (app d, J ) 10.2 Hz, 1 H), 3.05
(dd, J ) 8.5, 5.1 Hz, 1 H), 2.12-2.08 (m, 2 H), 2.00 (s, 3 H),
1.71-1.66 (m, 2 H), 1.18 (s, 9 H), 1.26 (s, 9 H). 13C NMR (100
MHz, CDCl3): δ 171.27, 171.13, 163.83, 162.32, 139.08, 138.55,
138.50, 138.46, 138.43, 138.37, 129.72, 129.15, 129.04, 128.93,
128.89, 128.86, 128.83, 128.65, 128.63, 128.45, 128.40, 128.29,
128.25, 128.21, 128.15, 128.13, 128.03, 127.94, 127.92, 127.85,
127.80, 127.57, 127.42, 115.26, 102.34, 101.73, 101.00, 92.84,
80.41, 80.00, 79.64, 77.72, 77.64, 75.48, 75.39, 75.27, 75.15,
74.89, 74.24, 73.96, 73.93, 73.85, 73.80, 73.61, 73.50, 73.38,
73.04, 73.01, 72.33, 72.16, 71.84, 71.76, 69.34, 69.13, 68.48,
68.17, 67.93, 67.64, 53.65, 39.19, 39.09, 30.49, 29.21, 27.76,
27.67, 27.58, 21.32. ESI-MS: m/z (M + Na)+ calcd 1920.7315,
obsd 1920.7340.
Dibu tyl 3-O-Acetyl-4,6-di-O-ben zyl-2-deoxy-2-tr ich lor o-
a ceta m id o-â-D-ga la ctop yr a n osyl P h osp h a te 5. To a solu-
tion of imidate 30 (453 mg, 0.66 mmol) in CH2Cl2 (5 mL) at 0
°C was added dibutyl phosphate (150 µL, 0.72 mmol). The
mixture was stirred for 1 h and then directly loaded onto a
short column of silica gel and eluted with 1:1 hexanes/EtOAc
to afford 360 mg (74%) of phosphate 5 as a white solid. [R]D:
+13.8 (c ) 0.82, CH2Cl2). IR (thin film): 2928, 1718, 1540,
1
1494, 1454, 1260, 1028 cm-1. H NMR (400 MHz, CDCl3): δ
8.08 (d, J ) 9.5 Hz, 1 H), 7.35-7.26 (m, 10 H), 5.53 (app t, J
) 7.8 Hz, 1 H), 5.25 (d, J ) 10.9 Hz, 1 H), 4.71 (d, J ) 11.6
Hz, 1 H), 4.63-4.55 (m, 1 H), 4.50 (d, J ) 11.2 Hz, 1 H), 4.47
(d, J ) 10.9 Hz, 1 H), 4.38 (d, J ) 11.7 Hz, 1 H), 4.09 (m, 2 H),
4.02-3.99 (m, 2 H), 3.82 (app s, 2 H), 3.64-3.60 (m, 1 H), 3.53-
3.49 (m, 1 H), 2.01 (s, 3 H), 1.64-1.59 (m, 4 H), 1.38-1.36 (m,
n -P en ten yl 4,6-Di-O-ben zyl-2-d eoxy-2-tr ich lor oa cet-
a m id o-â-D-ga la ct op yr a n osyl-(1f3)-2,4,6-t r i-O-b en zyl-r-
D-ga la ct op yr a n osyl-(1f4)-3,6-d i-O-b en zyl-2-O-p iva loyl-
â-D-ga la ctop yr a n osyl-(1f4)-3,6-d i-O-ben zyl-2-O-p iva loyl-
â-D-glu cop yr a n osid e 33. To a solution of tetrasaccharide 32
(305 mg, 0.160 mmol) in MeOH (15 mL) was added a solution
of NaOMe in MeOH (180 µL, 0.80 mmol, 25% by wt). The
reaction mixture was stirred at room temperature for 1 h and
then quenched with Dowex 50-X8 ion-exchange resin, filtered,
and concentrated. The crude residue was purified by flash
chromatography (3:1 hexanes/EtOAc) to afford 262 mg (88%)
of tetrasaccharide 33 as a white solid. [R]D: -6.6 (c ) 1.10,
4 H), 0.94-0.88 (m, 6 H). 13C NMR (100 MHz, CDCl3):
δ
170.41, 163.73, 162.42, 137.60, 128.35, 128.29, 128.19, 127.82,
127.70, 127.53, 96.77, 96.72, 92.62, 91.97, 74.92, 73.31, 73.04,
72.81, 68.34, 68.27, 68.14, 68.10, 68.03, 67.66, 52.72, 52.63,
31.93, 31.86, 20.68, 18.49, 18.46, 13.49. 31P NMR (120 MHz,
CDCl3): δ -2.62. ESI-MS: m/z (M + Na)+ calcd 760.1582, obsd
760.1559.
n -P en t en yl 2,4,6-Tr i-O-b en zyl-r-D-ga la ct op yr a n osyl-
(1f4)-3,6-d i-O-ben zyl-2-O-p iva loyl-â-D-ga la ctop yr a n osyl-
(1f4)-3,6-d i-O-b e n zyl-2-O-p iva loyl-â-D -glu cop yr a n o-
sid e 31. Trisaccharide 22 (1.10 g, 0.746 mmol) was dissolved
in CH2Cl2 (20 mL). A solution of hydrazine acetate (122 mg,
1.33 mmol) in MeOH (4 mL) was added and the mixture was
stirred for 12 h. The mixture was diluted with CH2Cl2 (100
mL) and washed twice with water, dried over MgSO4, filtered,
and concentrated under reduced pressure. The residue was
purified by flash chromatography (4:1 f 2:1 hexane/EtOAc)
to afford 634 mg (62%) of 31 as a colorless oil. [R]D: +25.1 (c
) 1.00, CH2Cl2). IR (thin film): 3030, 2871, 1737, 1130, 1094
CH2Cl2). IR (thin film): 2870, 1735, 1454, 1366, 1094 cm-1
.
1H NMR (400 MHz, CDCl3): δ 7.45-7.18 (m, 45 H), 6.37 (d, J
) 8.7 Hz, 1 H), 5.86-5.76 (m, 1 H), 5.37 (app t, J ) 8.2 Hz, 1
H), 5.04-4.90 (m, 5 H), 4.80-4.65 (m, 6 H), 4.56-4.30 (m, 8
H), 4.24 (app s, 1 H), 4.16-4.00 (m, 11 H), 3.86-3.67 (m, 6
H), 3.66-3.57 (m, 2 H), 3.44-3.28 (m, 5 H), 3.17 (app d, J )
10.5 Hz, 1 H), 3.08 (dd, J ) 8.3, 5.4 Hz, 1 H), 2.34 (br s, 1 H),
1.87-1.89 (m, 2 H), 1.88 (s, 9 H), 1.69-1.64 (m, 2 H), 1.13 (s,
9 H). 13C NMR (100 MHz, CDCl3): δ 176.84, 176.81, 139.44,
139.31, 138.79, 138.31, 138.24, 138.20, 138.15, 138.09, 129.44,
128.72, 128.66, 128.61, 128.58, 128.38, 128.24, 128.18, 128.09,
128.04, 127.97, 127.93, 127.86, 127.73, 127.66, 127.60, 127.38,
127.25, 114.98, 101.66, 101.43, 100.30, 100.07, 92.47, 79.83,
79.59, 79.20, 75.61, 75.51, 75.27, 75.14, 73.78, 73.71, 73.64,
73.48, 73.36, 73.17, 72.93, 72.81, 72.30, 71.64, 71.42, 69.03,
68.26, 67.87, 67.85, 67.42, 56.52, 38.93, 38.83, 30.22, 28.94,
28.30, 27.52, 27.32, 22.89, 14.43. ESI-MS: m/z (M + Na)+ calcd
1878.7209, obsd 1878.7262.
cm-1 1H NMR (400 MHz, CDCl3): δ 7.37-7.16 (m, 35 H),
.
5.83-5.67 (m, 1 H), 5.27 (dd, J ) 10.4, 7.9 Hz, 1 H), 5.14 (d,
J ) 11.9 Hz, 1 H), 5.04-4.94 (m, 4 H), 4.78 (d, J ) 12.2 Hz, 1
H), 4.77 (d, J ) 12.1 Hz, 1 H), 4.66 (d, J ) 11.3 Hz, 1 H), 4.56-
4.45 (m, 6 H), 4.38-4.34 (m, 2 H), 4.24-4.20 (m, 3 H), 4.12-
3.99 (m, 5 H), 3.96-3.95 (m, 1 H), 3.88-3.81 (m, 1 H), 3.73-
3.79 (m, 3 H), 3.62 (app t, J ) 9.0 Hz, 1 H), 3.50-3.34 (m, 5
H), 3.27 (dd, J ) 10.4, 2.5 Hz, 1 H), 3.07 (dd, J ) 8.8, 4.9 Hz,
1 H), 2.12-2.05 (m, 2 H), 1.78-1.62 (m, 3 H), 1.17 (s, 9 H),
1.12 (s, 9 H). 13C NMR (100 MHz, CDCl3): δ 176.90, 176.74,
139.44, 139.01, 138.62, 138.36, 138.32, 138.29, 138.24, 138.13,
128.61, 128.42, 128.39, 128.31, 128.28, 128.21, 128.17, 128.11,
127.92, 127.86, 127.75, 127.68, 127.60, 127.46, 127.30, 127.16,
114.96, 101.47, 100.19, 99.94, 81.35, 80.03, 75.40, 75.33, 75.30,
74.60, 74.48, 73.68, 73.51, 73.31, 73.12, 73.12, 72.36, 71.75,
71.30, 70.09, 69.08, 68.94, 68.30, 67.69, 67.55, 30.23, 28.93,
28.93, 27.25. ESI-MS: m/z (M + Na)+ calcd 1393.6645, obsd
1393.6612.
Dibu tyl 2-O-Acetyl-3,4,6-tr i-O-ben zyl-â-D-ga la ctop yr a n -
osyl P h osp h a t e 6. Tri-O-benzyl galactal 12 (644 mg, 1.55
mmol) was dissolved in CH2Cl2 (15 mL) and cooled to 0 °C.
DMDO (0.08 M in acetone, 30 mL, 2.4 mmol) was added and
the reaction was stirred for 10 min. The solvent was evapo-
rated at 0 °C, and the resulting residue was dissolved in
CH2Cl2 (15 mL) and cooled to -78 °C. Dibutyl phosphate (340
µL, 1.7 mmol) was added and the mixture was stirred for 10
min. After warming to 0 °C DMAP (758 mg, 6.20 mmol) and
acetyl chloride (220 µL, 3.10 mmol) were added, and the
reaction mixture was stirred for 2 h and concentrated.
Purification of the crude residue by flash chromatography (1:1
n -P en ten yl 3-O-Acetyl-4,6-di-O-ben zyl-2-deoxy-2-tr ich lo-
r oa ceta m id o-â-D-ga la ctop yr a n osyl-(1f3)-2,4,6-tr i-O-ben -
6668 J . Org. Chem., Vol. 67, No. 19, 2002

Linear Synthesis of Globo-H, SSEA-3, and Gb3
hexane/EtOAc) afforded 769 mg (73%) of phosphate 6 as a
colorless oil. [R]D: +25.9 (c ) 0.93, CH2Cl2). IR (thin film):
127.01, 114.75, 104.39, 101.17, 100.07, 99.99, 92.57, 80.99,
79.80, 79.68, 79.56, 78.25, 75.81, 75.55, 75.06, 74.88, 74.59,
74.47, 73.35, 73.92, 73.87, 73.57, 73.46, 73.34, 73.28, 73.22,
72.93, 72.85, 72.71, 72.39, 72.26, 71.70, 71.40, 71.15, 68.91,
68.79, 68.72, 68.25, 68.15, 67.82, 67.47, 38.68, 38.59, 31.90,
31.56, 30.02, 29.67, 29.34, 29.25, 28.74, 28.10, 27.30, 27.10,
22.63, 22.42, 21.05, 14.17, 14.12, 13.97. ESI-MS: m/z (M +
Na)+ calcd 2310.9146, obsd 2310.9136.
1
2927, 1751, 1558, 1494, 1452, 1403, 1050 cm-1. H NMR (400
MHz, CDCl3): δ 7.54-7.28 (m, 15 H), 5.46 (dd, J ) 10.0, 8.0
Hz, 1 H), 5.16 (app t, J ) 7.5 Hz, 1 H), 4.96 (d, J ) 11.5 Hz,
1 H), 4.69 (d, J ) 12.4 Hz, 1 H), 4.62 (d, J ) 11.4 Hz, 1 H),
4.53 (d, J ) 12.2 Hz, 1 H), 4.45 (app s, 2 H), 4.07-3.95 (m, 5
H), 3.71-3.65 (m, 2 H), 3.62-3.55 (m, 2 H), 2.05 (s, 3 H), 1.62-
1.40 (m, 4 H), 1.38-1.35 (m, 4 H), 0.95-0.87 (m, 6 H). 13C NMR
(100 MHz, CDCl3): δ 169.48, 138.24, 137.61, 137.59, 128.44,
128.22, 127.85, 127.64, 127.51, 127.37, 96.97, 79.64, 74.63,
74.13, 73.49, 72.20, 72.08, 67.94, 67.87, 67.81, 32.08, 32.01,
31.94, 20.92, 18.55, 13.55, 13.53. 31P NMR (120 MHz, CDCl3):
δ -2.26. ESI-MS: m/z (M + Na)+ calcd 707.2956, obsd
707.2931.
n -P en ten yl 2,3,4,6-Tetr a -O-a cetyl-â-D-ga la ctop yr a n o-
syl-(1f3)-4,6-d i-O-a cetyl-2-d eoxy-2-a ceta m id o-â-D-ga la c-
topyr an osyl-(1f3)-2,4,6-tr i-O-acetyl-r-D-galactopyr an osyl-
(1f4)-2,3,6-tr i-O-a cetyl-â-D-ga la ctop yr a n osyl-(1f4)-2,3,6-
tr i-O-a cetyl-â-D-glu cop yr a n osid e 38. Pentasaccharide 37
(35 mg, 15 µmol), Bu3SnH (50 µL, 160 µmol), and a catalytic
amount of AIBN were dissolved in dry toluene (3 mL), and
the solution was vigorously stirred for 20 min under a stream
of N2. After heating to 100 °C for 1 h, another 20 µL of Bu3SnH
and a catalytic amount of AIBN were added. After 1 h the
reaction mixture was cooled to room temperature and concen-
trated under reduced pressure. The residue was purified by
flash chromatography (10:1 f 4:1 f 2:1 hexanes/EtOAc) to
afford 18 mg (55%) of the desired product. To a deep blue
solution of sodium in liquid ammonia (ca. 7 mL) was added
the above compound in dry THF (3 mL) under N2 at -78 °C.
After 45 min, the reaction was quenched with MeOH (4 mL)
and most of the ammonia was removed with a stream of N2.
The mixture was diluted with MeOH, treated with Dowex 50-
X8 ion-exchange resin (washed and dried), filtered, and rinsed
with a solution of NH3 in MeOH. The solution was concen-
trated in vacuo and coevaporated with toluene. The resulting
residue was dissolved in pyridine (2 mL) and treated with Ac2O
(1 mL) in the presence of DMAP (one crystal) at room
temperature for 20 h. Flash chromatography of the crude
material (2:1 EtOAc/hexanes f 100% EtOAc) gave 5 mg (40%)
of pentasaccharide 38 as a white solid. IR (thin film): 1745,
n -P en ten yl 2-O-Acetyl-3,4,6-tr i-O-ben zyl-â-D-ga la cto-
p yr a n osyl-(1f3)-4,6-d i-O-b e n zyl-2-d e oxy-2-t r ich lor o-
a ceta m ido-â-D-ga la ctop yr a n osyl-(1f3)-2,4,6-tr i-O-ben zyl-
r-D-ga la ct op yr a n osyl-(1f4)-3,6-d i-O-b en zyl-2-O-p iva l-
oyl-â-D-galactopyranosyl-(1f4)-3,6-di-O-benzyl-2-O-pivaloyl-
â-D-glu cop yr a n osid e 36. Tetrasaccharide 33 (89 mg, 48
µmol) and glycosyl phosphate 6 (66 mg, 96 µmol) were
coevaporated three times with toluene, dissolved in CH2Cl2 (4
mL), and cooled to -50 °C. TMSOTf (18 µL, 96 µmol) was
added and the mixture was stirred for 20 min. Triethylamine
(100 µL) was added and the mixture was directly purified by
flash chromatography (4:1 hexanes/EtOAc) to afford 99 mg
(88%) of pentasaccharide 36 as a colorless foam. [R]D: +1.8 (c
) 1.00, CH2Cl2). IR (thin film): 2926, 1734, 1700, 1653, 1558,
1
1495, 1455, 1400, 1050 cm-1. H NMR (400 MHz, CDCl3): δ
7.35-7.18 (m, 60 H), 6.22 (d, J ) 8.9 Hz, 1 H), 5.84-5.77 (m,
1 H), 5.45 (app t, J ) 8.6 Hz, 1 H), 5.32 (app t, J ) 8.8 Hz, 1
H), 5.04-4.96 (m, 6 H), 4.86-3.53 (m, 48 H), 3.43-3.36 (m, 5
H), 3.26-3.24 (m, 2 H), 3.15-3.13 (m, 1 H), 2.10-2.06 (m, 2
H), 2.06 (s, 3 H), 1.70-1.65 (m, 2 H), 1.15 (s, 9 H), 1.12 (s, 9
H). 13C NMR (100 MHz, CDCl3): δ 176.55, 176.37, 169.76,
160.94, 139.34, 139.18, 139.02, 138.63, 138.57, 138.45, 138.40,
138.06, 137.87, 137.74, 137.65, 128.74, 128.52, 128.49, 128.37,
128.34, 128.31, 128.26, 128.21, 128.13, 128.07, 127.99, 127.91,
127.88, 127.84, 127.81, 127.73, 127.66, 127.58, 127.52, 127.41,
127.35, 127.11, 127.02, 126.90, 114.75, 101.24, 101.15, 100.76,
100.10, 92.68, 79.64, 78.06, 77.00, 76.49, 75.88, 75.07, 74.81,
74.77, 74.49, 73.87, 73.58, 73.46, 73.24, 73.16, 72.96, 72.72,
72.33, 71.84, 71.43, 71.10, 70.79, 68.94, 68.80, 68.46, 68.40,
67.60, 55.20, 38.67, 38.60, 30.02, 29.68, 29.26, 28.75, 28.10,
27.30, 27.10, 22.43, 21.10, 13.98. ESI-MS: m/z (M + Na)+ calcd
2352.9251, obsd 2352.9288.
1
1548, 1370, 1229, 1066 cm-1. H NMR (400 MHz, CDCl3): δ
5.85-5.75 (m, 1 H), 5.67 (d, J ) 7.2 Hz, 1 H), 5.61 (app s, 1
H), 5.42 (app s, 1 H), 5.36 (app d, J ) 2.1 Hz, 1 H), 5.32-4.89
(m, 10 H), 4.77 (app d, J ) 9.4 Hz, 1 H), 4.70 (app d, J ) 8.4
Hz, 1 H), 4.63 (app d, J ) 7.7 Hz, 1 H), 4.55 (d, J ) 7.6 Hz, 1
H), 4.48 (app d, J ) 8.0 Hz, 1 H), 4.44-4.37 (m, 2 H), 4.24-
4.02 (m, 9 H), 3.96-3.93 (m, 1 H), 3.89-3.86 (m, 2 H), 3.81-
3.77 (m, 2 H), 3.65-3.62 (m, 2 H), 3.52-3.48 (m, 1 H), 3.28-
3.23 (m, 1 H), 2.16-1.96 (m, 48 H), 1.75-1.65 (m, 2 H), 1.61
(s, 3 H). ESI-MS: m/z (M + Na)+ calcd 1590.5115, obsd
1590.5170.
n -P en ten yl 2-O-Ben zyl-3,4-di-O-pivaloyl-r-L-fu copyr an -
osyl-(1f2)-3,4,6-tr i-O-ben zyl-â-D-ga la ctop yr a n osyl-(1f3)-
4,6-d i-O-ben zyl-2-d eoxy-2-tr ich lor oa ceta m id o-â-D-ga la c-
topyr an osyl-(1f3)-2,4,6-tr i-O-ben zyl-r-D-galactopyr an osyl-
(1f4)-3,6-d i-O-b en zyl-2-O-p iva loyl-â-D-ga la ct op yr a n o-
syl-(1f4)-3,6-di-O-ben zyl-2-O-pivaloyl-â-D-glu copyr an oside
1. Pentasaccharide 37 (54 mg, 24 µmol) and fucosyl phosphate
7 (44 mg, 71 µmol) were coevaporated three times with toluene,
dissolved in CH2Cl2 (2 mL), and cooled to -50 °C. TMSOTf
(13 µL, 71 µmol) was added and the mixture was stirred for
45 min while warming to -20 °C. Triethylamine (200 µL) was
added and the mixture was directly purified by flash chroma-
tography (8:1 f 5:1 hexanes/EtOAc) to afford 42 mg (66%) of
hexasaccharide 1 as a colorless foam. [R]D: -20.6 (c ) 1.00,
CH2Cl2). IR (thin film): 2926, 1734, 1558, 1494, 1403, 1262
cm-1. 1H NMR (400 MHz, CDCl3): δ 7.56 (d, J ) 6.7 Hz, 1 H),
7.38-7.15 (m, 60 H), 7.03-7.00 (m, 5 H), 5.86-5.72 (m, 1 H),
5.65 (d, J ) 2.6 Hz, 1 H), 5.51 (app d, J ) 10.6 Hz, 1 H), 5.30
(app t, J ) 9.1 Hz, 1 H), 5.22 (app s, 1 H), 5.17-5.13 (m, 2 H),
5.07-4.86 (m, 7 H), 4.78-3.92 (m, 38 H), 3.92-3.58 (m, 10
H), 3.47-3.38 (m, 7 H), 3.24-3.18 (m, 2 H), 2.09-2.07 (m, 2
H), 1.67-1.64 (m, 2 H), 1.60 (s, 9 H), 1.15 (s, 9 H), 1.11 (s, 9
H), 1.04 (s, 9 H), 0.70 (d, J ) 6.2 Hz, 3 H). 13C NMR (100 MHz,
CDCl3): δ 178.46, 177.26, 177.03, 176.69, 162.79, 140.06,
139.30, 139.18, 139.04, 138.78, 138.63, 138.56, 138.37, 138.24,
138.21, 128.95, 128.93, 128.86, 128.78, 128.75, 128.71, 128.62,
n -P en t en yl 3,4,6-Tr i-O-b en zyl-â-D-ga la ct op yr a n osyl-
(1f3)-4,6-d i-O-ben zyl-2-d eoxy-2-tr ich lor oa ceta m id o-â-D-
ga la ct op yr a n osyl-(1f3)-2,4,6-t r i-O-b en zyl-r-D-ga la ct o-
p y r a n o s y l-(1f4)-3,6-d i -O -b e n z y l-2-O -p i v a lo y l-â-D -
ga la ctop yr a n osyl-(1f4)-3,6-d i-O-ben zyl-2-O-p iva loyl-â-D-
glu cop yr a n osid e 37. To a solution of pentasaccharide 36 (98
mg, 42 µmol) in MeOH (3 mL) was added a solution of NaOMe
in MeOH (48 µL, 21 µmol, 25% by wt). The reaction mixture
was stirred at room temperature for 12 h and then quenched
with Dowex 50-X8 ion-exchange resin, filtered, and concen-
trated. The crude residue was purified by flash chromatogra-
phy (4:1 hexanes/EtOAc) to afford 73 mg (76%) of pentasac-
charide 37 as a colorless foam. [R]D: -0.3 (c ) 1.00, CH2Cl2).
IR (thin film): 2926, 1734, 1558, 1494, 1403, 1261, 1050 cm-1
.
1H NMR (400 MHz, CDCl3): δ 7.38-7.16 (m, 60 H), 6.51 (d, J
) 8.5 Hz, 1 H), 5.84-5.74 (m, 1 H), 5.32 (app t, J ) 8.4 Hz, 1
H), 4.99-4.88 (m, 7 H), 4.76-4.25 (m, 22 H), 4.18-3.74 (m,
17 H), 3.60-3.54 (m, 8 H), 3.41-3.34 (m, 5 H), 3.26-3.24 (m,
2 H), 3.10 (dd, J ) 8.6, 5.2 Hz, 1 H), 2.44 (br s, 1 H), 2.09-
2.06 (m, 2 H), 1.67-1.65 (m, 2 H), 1.16 (s, 9 H), 1.12 (s, 9 H).
13C NMR (100 MHz, CDCl3): δ 176.55, 176.42, 162.11, 139.26,
139.16, 139.01, 138.66, 138.61, 138.38, 138.38, 138.26, 138.05,
138.03, 137.88, 137.73, 128.97, 128.55, 128.47, 128.42, 128.39,
128.34, 128.24, 128.15, 128.07, 128.00, 127.93, 127.91, 127.83,
127.76, 127.67, 127.61, 127.52, 127.40, 127.35, 127.10, 127.05,
J . Org. Chem, Vol. 67, No. 19, 2002 6669

Bosse et al.
128.58, 128.55, 128.49, 128.40, 128.35, 128.27, 128.24, 128.07,
128.02, 127.97, 127.91, 127.84, 127.76, 127.69, 127.52, 127.45,
127.41, 127.34, 127.19, 115.19, 102.74, 101.52, 101.16, 100.91,
100.06, 96.93, 84.12, 80.68, 78.51, 78.16, 77.65, 76.66, 76.51,
75.69, 75.56, 75.44, 74.96, 74.85, 74.72, 74.52, 74.44, 74.00,
73.88, 73.72, 73.37, 73.11, 73.05, 72.39, 72.15, 71.94, 71.81,
71.75, 70.54, 69.25, 69.09, 68.86, 68.59, 68.31, 65.67, 39.30,
39.14, 39.08, 32.02, 30.50, 29.22, 27.73, 27.63, 27.57, 27.51,
23.09, 15.74, 14.57. ESI-MS: m/z (M + 2Na)2+ calcd 1369.0618,
obsd 1369.0602.
n -P en ten yl 2,3,4-Tr i-O-a cetyl-r-L-fu cop yr a n osyl-(1f2)-
3,4,6-tr i-O-acetyl-â-D-galactopyr an osyl-(1f3)-2-acetam ido-
4,6-d i-O-a cetyl-2-d eoxy-â-D-ga la ctop yr a n osyl-(1f3)-2,4,6-
tr i-O-acetyl-r-D-galactopyr an osyl-(1f4)-2,3,6-tr i-O-acetyl-
â-D -g a la c t o p y r a n o s y l-(1f4)-2,3,6-t r i -O -a c e t y l-â-D -
glu cop yr a n osid e 39.33 Hexasaccharide 1 (21 mg, 7.8 µmol),
Bu3SnH (25 µL, 80 µmol), and a catalytic amount of AIBN were
dissolved in dry toluene (3 mL), and the solution was vigor-
ously stirred for 20 min under a stream of N2. After heating
to 100 °C for 1 h, another 25 µL of Bu3SnH and a catalytic
amount of AIBN were added. After 1.5 h the reaction mixture
was cooled to room temperature and concentrated under
reduced pressure. The residue was purified by flash chroma-
tography (10:1 f 4:1 f 2:1 hexanes/EtOAc) to afford 12 mg
(60%) of the desired product. To a deep blue solution of sodium
in liquid ammonia (ca. 7 mL) was added the above compound
in dry THF (3 mL) under N2 at -78 °C. After 45 min the
reaction was quenched with MeOH (4 mL) and most of the
ammonia was removed with a stream of N2. The mixture was
diluted with MeOH, treated with Dowex 50-X8 ion-exchange
resin (washed and dried), filtered, and rinsed with a solution
of NH3 in MeOH. The solution was concentrated in vacuo and
coevaporated with toluene. The resulting residue was dissolved
in pyridine (2 mL) and treated with Ac2O (1 mL) in the
presence of DMAP (one crystal) at room temperature for 16
h. Flash chromatography of the crude material (2:1 EtOAc/
hexanes f 100% EtOAc) afforded 4 mg (40%) of hexasaccha-
1
ride 39 as a white solid. H NMR (400 MHz, CDCl3): δ 6.69
(d, J ) 6.8 Hz, 1 H), 5.82-5.75 (m, 1 H), 5.61 (app s, 1 H),
5.48 (app d, J ) 3.3 Hz, 1 H), 5.41 (app d, J ) 2.4 Hz, 1 H),
5.31-4.85 (m, 12 H), 4.78-4.74 (m, 1 H), 4.54-4.40 (m, 6 H),
4.37-4.35 (m, 1 H), 4.26 (dd, J ) 10.5, 2.5 Hz, 1 H), 4.21-
3.96 (m, 8 H), 3.90-3.73 (m, 5 H), 3.64-3.60 (m, 1 H), 3.52-
3.46 (m, 1 H), 3.08-3.04 (m, 1 H), 2.16-1.90 (m, 53 H), 1.68-
1.64 (m, 2 H), 1.60 (s, 3 H), 1.15 (d, J ) 6.2 Hz, 3 H). ESI-MS:
m/z (M + Na)+ calcd 1820.5906, obsd 1820.5949.33
Ack n ow led gm en t. This research was supported by
the David Koch Research Fund. P.H.S. is a Glaxo-
Smith-Kline Research Scholar and an Alfred P. Sloan
Scholar. L.A.M. is supported by a NIH Cancer Research
Training Grant. Funding for the MIT-DCIF Advance
(DPX)400 was provided byNIH (Award no.1S10RR13886-
01). Funding for the Mercury-DCIF Mercury 300 was
provided by NSF (Award no. CHE-9808061) and NSF
(Award no. DBI-9729592).
Su p p or t in g In for m a t ion Ava ila b le: 1H NMR and 13C
NMR spectral data for all described compounds. This material
is available free of charge via the Internet at http://pubs.acs.org.
J O025834+
6670 J . Org. Chem., Vol. 67, No. 19, 2002