Application of glycosyl thioimidates in solid-phase oligosaccharide synthesis

Article abstract of DOI:10.1021/jo701902f

(Chemical Equation Presented) Two stable classes of thioimidoyl derivatives, S-benzoxazolyl (SBox) and S-thiazolinyl (STaz) glycosides, were investigated as glycosyl donors for solid-phase oligosaccharide synthesis. It was demonstrated that these derivatives are suitable for both glycosyl acceptor-bound and glycosyl donor-bound strategies, commonly employed in resin-supported oligosaccharide synthesis.

Full text of DOI:10.1021/jo701902f

Application of Glycosyl Thioimidates in Solid-Phase Oligosaccharide
Synthesis
M. Cristina Parlato,† Medha N. Kamat,† Haisheng Wang,† Keith J. Stine,†,‡ and
Alexei V. Demchenko*,†
Department of Chemistry and Biochemistry and Center for Nanoscience, UniVersity of MissourisSt. Louis,
One UniVersity BouleVard, St. Louis, Missouri 63121
demchenkoa@umsl.edu
ReceiVed August 29, 2007
Two stable classes of thioimidoyl derivatives, S-benzoxazolyl (SBox) and S-thiazolinyl (STaz) glycosides,
were investigated as glycosyl donors for solid-phase oligosaccharide synthesis. It was demonstrated that
these derivatives are suitable for both glycosyl acceptor-bound and glycosyl donor-bound strategies,
commonly employed in resin-supported oligosaccharide synthesis.
Introduction
allows the following: rapid synthesis of oligosaccharide se-
quences without the necessity of purifying (and characterizing)
the intermediates; ease of excess reagent removal; and perfor-
mance in an automated fashion that has the potential to
significantly reduce the labor associated with the whole
process.8-24 Nevertheless, there are some limitations: large
One of the main drawbacks in studying the biological
functions of glycoconjugates and oligosaccharides is their
limited availability in pure form from natural sources. Therefore,
there are expectations that efficient chemical or chemo-
enzymatic syntheses would make complex carbohydrates more
accessible to general chemical, biochemical, and industrial
audiences to keep in pace with the exploding area of glycobi-
ology.1 In spite of significant progress in the area of synthetic
carbohydrate chemistry, complex glycostructures remain among
the most challenging targets of modern synthetic chemistry.2,3
The past decade has witnessed an expansion of methods and
strategies used for both solution-phase4-6 and solid-phase
oligosaccharide synthesis.7
(7) Seeberger, P. H.; Haase, W. C. Chem. ReV. 2000, 100, 4349-4393.
(8) Sears, P.; Wong, C. H. Science 2001, 291, 2344-2350.
(9) Plante, O. J.; Palmacci, E. R.; Seeberger, P. H. Science 2001, 291,
1523-1527.
(10) Crich, D.; Smith, M. J. Am. Chem. Soc. 2002, 124, 8867-8869.
(11) Kanemitsu, T.; Wong, C. H.; Kanie, O. J. Am. Chem. Soc. 2002,
124, 3591-3599.
(12) Lam, S. N.; Gervay-Hague, J. Carbohydr. Res. 2002, 337, 1953-
1965.
(13) Manabe, S.; Ito, Y. J. Am. Chem. Soc. 2002, 124, 12638-12639.
(14) Majumdar, D.; Zhu, T.; Boons, G.-J. Org. Lett. 2003, 5, 3591-
3594.
Oligosaccharide synthesis on the solid phase by using
insoluble polymeric support is a very attractive technique that
(15) Ojeda, R.; de Paz, J. L.; Martin-Lomas, M. Chem. Commun. 2003,
2486-2487.
† Department of Chemistry and Biochemistry.
‡ Center for Nanoscience.
(16) Ojeda, R.; Terenti, O.; de Paz, J. L.; Martin-Lomas, M. Glycocon-
jugate J. 2004, 21, 179-195.
(1) Bertozzi, C. R.; Kiessling, L. L. Science 2001, 291, 2357-2364.
(2) Galonic, D. P.; Gin, D. Y. Nature 2007, 446, 1000-1007.
(3) Seeberger, P. H.; Werz, D. B. Nature 2007, 446, 1046-1051.
(4) Davis, B. G. J. Chem. Soc., Perkin Trans. 1 2000, 2137-2160.
(5) Nicolaou, K. C.; Mitchell, H. J. Angew. Chem., Int. Ed. 2001, 40,
1576-1624.
(17) Wu, X.; Schmidt, R. R. J. Org. Chem. 2004, 69, 1853-1857.
(18) Bauer, J.; Rademann, J. J. Am. Chem. Soc. 2005, 127, 7296-7297.
(19) Dondoni, A.; Marra, A.; Massi, A. Angew. Chem., Int. Ed. 2005,
44, 1672-1676.
(20) Hanashima, S.; Manabe, S.; Ito, Y. Angew. Chem., Int. Ed. 2005,
44, 4218-4224.
(6) Demchenko, A. V. Lett. Org. Chem. 2005, 2, 580-589.
10.1021/jo701902f CCC: $40.75 © 2008 American Chemical Society
Published on Web 02/01/2008
1716
J. Org. Chem. 2008, 73, 1716-1725

Solid-Phase Oligosaccharide Synthesis
SCHEME 1
reagent excess, limited use of molecular sieves, large volume
of waste solvent, cumbersome analysis of intermediates, lower
stereoselectivity, loss and poisoning of resin, reagent trapping,
etc. Some of these issues can be addressed by developing
versatile glycosyl donors that would be both stable and highly
reactive under certain reaction conditions. In spite of significant
progress in recent years, none of the currently employed methods
are capable of solving all of these challenges. Arguably, each
complex synthetic target still requires careful retroanalysis,
thorough preliminary studies, and cumbersome selection of the
reaction components: resins, linkers, building blocks, promoters,
solvents, etc.
Recently we demonstrated that two stable classes of thio-
imidoyl derivatives, S-benzoxazolyl (SBox)25 and S-thiazolinyl
(STaz)26 glycosides, are capable of very rapid and stereoselective
solution-phase glycosylations under mild reaction conditions.27
These positive characteristics stimulated our interest in testing
the glycosyl thioimidates in glycosylations on the solid phase.
Herein we report our studies demonstrating that the SBox and
STaz glycosides can serve as capable building blocks in a variety
of synthetic applications on the solid phase.
solution-phase activator, these reactions are often performed at
low temperatures to extend its survivability in the prolonged
experiments that are common for glycosylation on the solid
support.
In approach B, the glycosyl donor linked to the solid support
via a suitable hydroxyl group is reacted with the solution-phase
glycosyl acceptor. In principle, this approach would allow rapid
oligosaccharide synthesis by applying (chemo)selective activa-
tion strategies that would not require additional deprotection
steps. A principal drawback of this strategy resides in the fact
that most side reactions during glycosylation involve the
glycosyl donor,28 which in this application will result in the
termination of the chain elongation. As a result, the number of
glycosyl donors suitable for this approach pioneered by Dan-
ishefsky29 and Ogawa30 remains low.7 Two-directional tech-
niques combining approaches A and B are also known.31,32
Our intention was to evaluate the applicability of the
thioimidate methodology to both glycosyl acceptor-bound and
glycosyl donor-bound approaches to solid-phase oligosaccharide
synthesis. This paper highlights the most important results
acquired in our laboratory.
Acceptor-Bound Glycosylation Strategy. Having investi-
gated a number of options for the study of the glycosyl acceptor-
bound approach, we chose insoluble Merrifield and Tentagel
terminal amine resins due to their general versatility, compat-
ibility with a broad range of reaction conditions, relatively low
cost, and high loading capacity, 0.9-1.2 and 0.4-0.6 mmol/g,
respectively. The 3,6-diol building block 133 was reacted with
succinic anhydride in the presence of dimethylaminopyridine
(DMAP) in pyridine to afford derivative 2 containing a carboxyl
linker suitable for immobilization on the resin (Scheme 2). The
immobilization through the formation of an amide linkage
between the carboxyl of compound 2 and the amine group of
the resin was accomplished in the presence of 1,3-dicyclohexy-
lcarbodiimide (DCC). The loading capacity of the resulting
glycopolymers 3a and 3b was nearly quantitative for the upper
Results and Discussion
There are two main strategies for solid-phase oligosaccharide
synthesis differing in the type of attachment (Scheme 1). In
strategy A, the glycosyl acceptor unit is bound to the solid
support either through the anomeric carbon (A1) or via another
position, e.g., at C-6 (A2). In this case, the glycosyl donor and
promoter are in the solution and this offers an important
advantage as the couplings tend to be more predictable and the
results acquired in the solution-phase synthesis can be more
easily translated to the solid phase. As a result, a vast variety
of glycosyl donors have been investigated along this pathway.7
Since the glycosyl donor is exposed to a large amount of the
(21) Ako, T.; Daikoku, S.; Ohtsuka, I.; Kato, R.; Kanie, O. Chem. Asian
J. 2006, 1, 798-813.
(22) Jonke, S.; Liu, K. G.; Schmidt, R. R. Chem. Eur. J. 2006, 12, 1274-
(28) Bochkov, A. F.; Zaikov, G. E. Chemistry of the O-glycosidic bond:
formation and cleaVage; Pergamon Press: New York, 1979.
(29) Seeberger, P. H.; Eckhardt, M.; Gutteridge, C. E.; Danishefsky, S.
J. J. Am. Chem. Soc. 1997, 119, 10064-10072.
(30) Ito, Y.; Kanie, O.; Ogawa, T. Angew. Chem., Int. Ed. 1996, 35,
2510-2512.
(31) Zhu, T.; Boons, G. J. Angew. Chem., Int. Ed. 1998, 37, 1898-
1900.
(32) Zhu, T.; Boons, G. J. Angew. Chem., Int. Ed. Engl. 1999, 38, 3495-
3497.
1290.
(23) Branderhorst, H. A.; Liskamp, R. A. J.; Pieters, R. J. Tetrahedron
2007, 63, 4290-4296.
(24) Doi, T.; Kinbara, A.; Inoue, H.; Takahashi, T. Chem. Asian J. 2007,
2, 188-198.
(25) Demchenko, A. V.; Malysheva, N. N.; De Meo, C. Org. Lett. 2003,
5, 455-458.
(26) Demchenko, A. V.; Pornsuriyasak, P.; De Meo, C.; Malysheva, N.
N. Angew. Chem., Int. Ed. 2004, 43, 3069-3072.
(27) Pornsuriyasak, P.; Kamat, M. N.; Demchenko, A. V. ACS Symp.
Ser. 2007, 960, 165-189.
(33) Kuester, J. M.; Dyong, I. Justus Liebigs Ann. Chem. 1975, 2179-
2189.
J. Org. Chem, Vol. 73, No. 5, 2008 1717

Parlato et al.
SCHEME 2
capacity range (1.2 and 0.6 mmol/g, respectively). This was
determined by the treatment of the loaded beads with dilute
NaOMe solution in methanol and recovering compound 2 from
the conjugate 3a and 3b in 98% and 95% yield, respectively,
based on the expected maximal loading.
the SBox and STaz leaving groups, high donor-promoter
specificities have been discovered. Thus, switching the donor-
promoter combination resulted in significantly compromised
results; i.e., glycosidation of 4 in the presence of MeOTf or
glycosidation of 6 in the presence of TMSOTf afforded
disaccharide 5 in only 20% and 10%, respectively.
Having obtained sugar-coated resins 3a and 3b, we turned
our attention to the investigation of suitable reaction conditions
for glycosylations. For this purpose we initially selected five
glycosyl donors of the D-gluco series that have been developed
in our laboratory: SBox glycosides 4,34 7,35 and 10,25 as well
as STaz glycosides 6 and 9.26,36 It should be noted that the
selection of these building blocks was driven by the intention
to investigate the synthesis of both 1,2-trans and 1,2-cis
glycosides. Apparently, glycosyl donors bearing a nonparticipat-
ing group at C-2 (2-O-benzyl) 7, 9, and 10 are suitable
precursors for the synthesis of 1,2-cis glycosides, whereas their
2-O-benzoylated counterparts 4 and 6 are suitable for 1,2-trans
glycosylations.
All glycosyl donors under investigation provided very high
yields and stereoselectivities in the solution-based di- and
oligosaccharide syntheisis especially in the presence of silver-
(I) trifluormethanesulfonate (AgOTf) as promoter.27 However,
formation of the expected disaccharide 5 was not detected when
perbenzoylated glycosyl donors 4 or 6 were glycosidated with
3a in the presence of AgOTf (entries 1 and 2, Table 1). This
result is seemingly in contradiction with our earlier observation
for the solution-phase glycosylations that required very short
reaction times and provided the requisite glycosides in nearly
quantitative yields.25,26 Herein though, the high reactivity of
thioimidates in the presence of AgOTf in combination with the
low reactivity of the resin-bound secondary alcohol creates an
obvious mismatch. This reactivity difference results in rapid
side reactions including hydrolysis and self-condensation of the
solution-based glycosyl donor, rather than the anticipated
glycosylation. Therefore, we assumed that the competing side
reactions could be suppressed by using less reactive promoters
known from our studies of activation of the thioimidoyl moieties
in solution: Cu(OTf)2, MeOTf, NIS/TfOH, NIS/TMSOTf,
TfOH, and TMSOTf.36,37
Having established suitable reaction conditions for the
synthesis of 1,2-trans-linked disaccharides, we turned our
attention to investigating building blocks bearing a nonpartici-
pating 2-O-benzyl substituent. It is well-known that per-
benzylated compounds are significantly more reactive (armed)
than their acylated counterparts (disarmed).38 Therefore, we
suspected that the increased reactivity of the building blocks 7
and 9, in comparison to their per-benzoylated counterparts 4
and 6, would be detrimental for glycosylations of the resin-
bound acceptor. Indeed, when acceptor 3a was reacted with 7
(TMSOTf) or 9 (MeOTf) the disaccharide 8 was isolated in
significantly lower yields of 54% and 32%, respectively (entries
5 and 6, Table 1). These results prompted us to investigate
glycosyl donor 10 bearing the 2-O-benzyl-3,4,6-tri-O-acetyl
group pattern that was determined to be significantly less
reactive than its per-benzylated analogue 7.35 Indeed, this
glycosylation was significantly more successful and the
requisite disaccharide 11 was formed in a good yield of 80%
(entry 7, Table 1). In should be emphasized that the latter
glycosylation was completely R-stereoselective, whereas the
stereoselectivity achieved with per-benzylated glycosyl donors
7 and 9 was low.
Being encouraged by the preliminary results, we translated
our findings to the synthesis of other targets, in particular,
derivatives of the galacto and glucosamino series. For this
purpose, STaz glycoside 1226 and SBox glycosides 14,25 16,39
and 1839 were selected. The glycosylations of acceptor 3a were
uneventful, and the corresponding disaccharides 13, 15, 17, and
19 were obtained in 51-82% yield (entries 8-11, Table 1).
On a similar note, Tentagel-bound acceptor 3b was investi-
gated. In this case, NIS/TMSOTf-promoted glycosidations of
the SBox glycosides 4, 7, and 10 were the most advantageous.
As a result, disaccharides 5, 8, and 11 were obtained in good
yields of 78-98%; and in the case of glycosyl donors 4 and
10, excellent â- and R-stereoselectivity was achieved, respec-
tively. These results are summarized in Table 1, entries 12-
14.
The systematic screening resulted in the discovery of the
activation conditions, suitable for efficient glycosylation of the
Merrifield resin-bound acceptor 3a with SBox glycosyl donor
4 and its STaz counterpart 6. We determined that TMSOTf-
promoted glycosidation of 4 and MeOTf-promoted glycosidation
of 6 proceeded nearly quantitatively providing the disaccharide
5 in excellent yields of 95% and 98%, respectively (entries 3
and 4, Table 1). Interestingly, in spite of a structural parity of
Donor-Bound Glycosylation Strategy. For the study of the
glycosyl donor-bound approach, we chose differently protected
6-hydroxyl SBox building blocks 21a and 21b,35 capable of 1,2-
trans and 1,2-cis glycosylation, respectively. For the insoluble
(34) Demchenko, A. V.; Kamat, M. N.; De Meo, C. Synlett 2003, 1287-
1290.
(35) Kamat, M. N.; Demchenko, A. V. Org. Lett. 2005, 7, 3215-3218.
(36) Pornsuriyasak, P.; Demchenko, A. V. Chem. Eur. J. 2006, 12, 6630-
6646.
(37) Kamat, M. N.; Rath, N. P.; Demchenko, A. V. J. Org. Chem. 2007,
72, 6938-6946.
(38) Fraser-Reid, B.; Wu, Z.; Udodong, U. E.; Ottosson, H. J. Org. Chem.
1990, 55, 6068-6070.
(39) Bongat, A. F. G.; Kamat, M. N.; Demchenko, A. V. J. Org. Chem.
2007, 72, 1480-1483.
1718 J. Org. Chem., Vol. 73, No. 5, 2008

Solid-Phase Oligosaccharide Synthesis
TABLE 1. Synthesis of Disaccharides by the Acceptor-Bound Approach
a All glycosylations were performed in dichloromethane under argon at room temperature in the presence of molecular sieves (MS): 3 Å with AgOTf or
MeOTf and 4 Å with TMSOTf or NIS/TMSOTf. b The product was N,O-acetylated (Ac2O/pyridine) to simplify the purification. c The product after cleavage
and acetylation was obtained as a separable mixture of 19 and 20 (1/2), the total disaccharide yield is given.
J. Org. Chem, Vol. 73, No. 5, 2008 1719

Parlato et al.
SCHEME 3
SCHEME 4
polymeric support we chose Merrifield terminal amine resin.
The SBox glycosides 21a and 21b were reacted with succinic
anhydride in the presence of DMAP in pyridine to afford the
corresponding derivatives 22a and 22b bearing a carboxyl linker
suitable for immobilization on the resin (Scheme 2). The
immobilization through the formation of an amide linkage
between the carboxyl of compounds 22a or 22b and the amine
group of the resin was accomplished as described for the
synthesis of 3a. The loading capacity of the resulting glyco-
polymers 23a and 23b (Scheme 3) was nearly quantitative for
the upper capacity range (1.2 mmol/g). This conclusion was
based on the recovery of the corresponding methyl glycosides
(∼95%) resulting from the displacement of the SBox moiety
during the prolonged deacylation/cleavage with MeOTf.
Having obtained glycosyl donor-coated resins 23a and 23b,
we turned our attention to investigating suitable reaction
conditions for their glycosidations. For this purpose, we initially
selected a number of common glycosyl acceptors 24,33 26,40
28,41 30,42 32, and 34. It should be noted that the selection of
these building blocks was driven by the intention to investigate
the scope and limitation of the methodology toward the synthesis
of various glycosidic linkages. Bearing in mind our experience
with the acceptor-bound approach, we carefully approached the
task of identifying suitable promoters. Upon screening a variety
of conditions, we determined that in most part AgOTf or
TMSOTf provide the highest yields. All glycosidations of 2-O-
benzoylated donor 23a were â-stereoselective. These studies
are summarized in Table 2, entries 1-6.
TMSOTf-promoted glycosylations provided the desired products
37 and 39 in moderate yields of 37% and 25%, respectively
(entries 7 and 8, Table 2). The latter reaction was complicated
by partial activation of the STaz moiety of the glycosyl acceptor
due to apparent cross-reactivity of the SBox and STaz moieties
under TMSOTf-promoted glycosylation conditions. If the reac-
tion time was doubled, no disaccharide 39 could be detected
due to the activation of the STaz moiety resulting in the
formation of higher oligomers.
Glycosidation of 2-O-benzylated resin bound glycosyl donor
23b was rather disappointing due to relatively low yields and
poor stereoselectivity in a majority of test reactions attempted.
A representative example of these studies is shown in Table 2,
entry 9. Surprizingly, when S-ethyl glycosyl acceptor 36 was
glycosylated, complete R-stereoselectivity was detected; unfor-
tunately, the yield of this transformation was low (entry 10,
Table 2). Very comparable results have been obtained with
glycosyl donors 22a and 22b immobilized on Tentagel resin.
These glycosylations were performed in the presence of NIS/
TMSOTf or MeOTf as promoters and afforded the requisite
disaccharide derivatives in 50-75% yield.
Application to Multistep Synthesis. The results of the
selective activation of the resin-bound SBox glycosyl donor over
the glycosyl acceptor bearing an S-ethyl anomeric moiety
prompted us to investigate the multistep oligosaccharide syn-
thesis. For this purpose, we performed coupling of glycosyl
donor 23a and glycosyl acceptor 36 and, without isolating the
intermediate, the next glycosylation step was attempted. This
involved reaction between the immobilized intermediate dis-
accharide donor with added glycosyl acceptor 24 in the presence
of NIS/TfOH, common activation conditions for glycosidation
of thioglycosides (Scheme 4).44 The resulting glycopolymer was
subjected to cleavage with MeONa and subsequent per-O-
acetylation to afford the trisaccharide 42 in 30% yield overall.
Along similar lines, we performed glycosylations of glycosyl
acceptors bearing a temporary anomeric substituent, which under
an appropriate set of reaction conditions can be turned into a
potent leaving group. For these studies we chose partially
protected S-ethyl glycoside 3643 and STaz glycoside 38.36
(40) Garegg, P. J.; Hultberg, H. Carbohydr. Res. 1981, 93, C10-C11.
(41) Koto, S.; Takebe, Y.; Zen, S. Bull. Chem. Soc. J. 1972, 45, 291-
293.
(42) Sollogoub, M.; Das, S. K.; Mallet, J.-M.; Sinay, P. C. R. Acad. Sci.
Ser. 2 1999, 2, 441-448.
(43) Veeneman, G. H.; van Boom, J. H. Tetrahedron Lett. 1990, 31,
275-278.
(44) Garegg, P. J. AdV. Carbohydr. Chem. Biochem. 1997, 52, 179-
205.
1720 J. Org. Chem., Vol. 73, No. 5, 2008

Solid-Phase Oligosaccharide Synthesis
TABLE 2. Synthesis of Disaccharides by the Donor-Bound Approach
a The disaccharide was O-acetylated (Ac2O/pyridine) to simplify the purification.
In addition, disaccharide 43 was also formed (15% yield) as a
result of coupling between glycosyl donor 23a, remaining after
the first glycosylation step, with added glycosyl acceptor 24.
stereoselective with both STaz and SBox glycosides. These
compounds were sufficiently stable under reaction conditions
that withstood prolonged glycosylation experiments at room
temperature. These observations differ significantly from those
made with other commonly employed glycosyl donors including
sulfoxides (-78 °C),45 phosphates (-50 °C),46 or trichloroace-
timidates (-40 °C).22 The glycosyl donor-bound approach for
Conclusions
Many common glycosyl donors can be used in solid-phase
oligosaccharide synthesis via acceptor-bound approaches, and
the glycosyl thioimidates investigated herein are no exception.
A variety of applications were proven to be highly efficient and
(45) Yan, L.; Taylor, C. M.; Goodnow, R.; Kahne, D. J. Am. Chem.
Soc. 1994, 116, 6953-6954.
J. Org. Chem, Vol. 73, No. 5, 2008 1721

Parlato et al.
170.0, 170.1, 171.9, 176.3 ppm; HR-FAB MS calcd for C28H30-
NO11S [M + H]+ 588.1540, found 588.1561.
resin-supported oligosaccharide synthesis is by far more chal-
lenging overall, and this is reflected in the low number of reports
dedicated to these studies. Only stable glycosyl donors such as
glycals, thioglycosides, or fluorides that are less prone to having
side reactions can be used along this strategy. We demonstrated
that the SBox glycosides also fit in this rare category, and
provide good yields throughout. One of the important charac-
teristics of the thioimidoyl moiety is that it can be selectively
activated over alkyl/aryl thioglycosides and this advantageous
feature was explored herein by synthesizing a trisaccharide
derivative via selective activation in two glycosylation steps.
General Procedure for the Immobilization on the Resin:
Preparation of Glycopolymer Conjugates 3a, 3b, 23a, and 23b.
Aminomethyl polymer resin (50 mg, 0.04-0.06 mmol of NH2
functional group) was swollen in dry dichloromethane (2 mL) for
30 min at room temperature. Then a mixture of succinoylated sugar
2, 22a, or 22b (0.18 mmol) and 1,3-dicyclohexylcarbodiimide (48
mg, 0.18 mmol) in dry dichloromethane (2 mL) was added. The
resulting reaction mixture was agitated for 72 h, then the resin was
separated by sintered filter, washed successively with methanol (5
× 5 mL) and dichloromethane (5 × 5 mL), and dried in vacuo.
The loading capacity of the resulting glycopolymer was determined
by cleavage off the beads by the general procedures provided below.
General Procedures for Glycosylation on the Resin: Prepa-
ration of Disaccharides. Method A: AgOTf-Promoted Glyco-
sylation. A mixture of resin-bound glycosyl acceptor (or donor,
0.06 mmol), glycosyl donor (or acceptor, 0.18 mmol), coevaporated
with toluene (3 × 10 mL) and dried in vacuo for 2 h directly prior
to application, and molecular sieves (3 Å, 200 mg) in dry
dichloromethane (4 mL) was agitated for 12 h at room temperature.
Then AgOTf (0.24 mmol) was added and the mixture was agitated
for 48 h at room temperature under argon. After that, glycosyl donor
(0.18 mmol) in dry dichloromethane (1 mL) and AgOTf (0.24
mmol) were added and the reaction mixture was agitated for an
additional 48 h. The resin was separated by sintered filter, washed
successively with methanol (5 × 5 mL) and dichloromethane (5 ×
5 mL), and dried in vacuo. The residual resin was suspended in
dry dichloromethane (2 mL) before adding 1 N sodium methoxide
solution in methanol (2 mL). The reaction mixture was agitated at
room temperature for 48 h; the pH was monitored and adjusted
within pH ∼8-9 range with 1 N sodium methoxide solution, if
needed. The resin was separated by sintered filter, washed succes-
sively with methanol (3 × 5 mL) and dichloromethane (3 × 5 mL),
and dried in vacuo. The combined filtrate was neutralized with
Dowex (H+), the resin was filtered off, and the solvent was removed
under reduced pressure. The residue was subjected to column
chromatography on silica gel (methanol/dichloromethane or ethyl
acetate/hexane gradient elution) to provide the requisite disaccharide
derivative.
Experimental Section
General Procedure for Introducing the Succinoyl Linker:
Preparation of Building Blocks 2, 22a, and 22b. 4-(N,N-
Dimethylamino)pyridine (0.169 mmol) and succinic anhydride (1.69
mmol) were added to a stirred solution of partially protected
derivative (1, 21a, or 21b, 1.69 mmol) in dry pyridine (10 mL) at
room temperature under argon. The reaction mixture was stirred
for 16 h at room temperature under argon. Upon completion (∼16
h), the reaction mixture was concentrated under reduced pressure,
then the residue was dissolved in dichloromethane (60 mL) and
washed with water (3 × 10 mL). The organic phase was separated,
dried over MgSO4, and concentrated in vacuo, and the residue was
purified by column chromatography on silica gel (ethyl acetate/
hexane, 1/1, v/v) to afford compounds 2, 22a, or 22b, respectively.
Methyl 2,4-di-O-benzyl-6-O-(3-hydroxycarbonylpropanoyl)-
R-D-glycopyranoside (2): The title compound was obtained from
methyl 2,4-di-O-benzyl-R-D-glycopyranoside (1)33 in 75% yield as
a white amorphous solid. Analytical data for 2: Rf 0.37 (methanol/
1
dichloromethane, 1/9, v/v); [R]29 +59.6 (c 1, CHCl3); H NMR
D
(CDCl3) δ 2.51-2.53 (m, 4H), 3.23 (s, 3H), 3.25-3.35 (m, 2H),
3.70 (m, 1H), 4.02 (dd, 1H, J ) 9.8 Hz), 4.16-4.28 (m, 2H), 4.52-
4.67 (m, 4H), 4.81 (d, 1H, J ) 11.1 Hz), 7.18-7.29 (m, 10H) ppm;
13C NMR (CDCl3) δ 28.9, 29.0, 55.4, 63.6, 68.4, 73.3, 73.8, 74.7,
76.8, 79.8, 97.6, 128.1, 128.3 (×3), 128.4 (×3), 128.7 (×2), 128.8,
138.0, 138.3, 172.0, 177.5 ppm; HR-FAB MS calcd for C25H29-
Na2O9 [M - H + 2Na]+ 519.1607, found 519.1586.
Benzoxazolyl 2,3,4-tri-O-benzoyl-6-O-(3-hydroxycarbonylpro-
panoyl)-â-D-glycopyranoside (22a): The title compound was
obtained from benzoxazolyl 2,3,4-tri-O-benzoyl-â-D-glycopyrano-
side (21a)35 in 80% yield as a white amorphous solid. Analytical
data for 22a: Rf 0.43 (ethyl acetate/hexane, 3/2, v/v); [R]26D +83.4
(c 1, CHCl3); 1H NMR (CDCl3) δ 2.47-2.57 (m, 4H), 4.19-4.32
(m, 3H), 5.59 (dd, 1H, J ) 9.6 Hz), 5.67 (dd, 1H, J ) 9.8 Hz),
5.91 (d, 1H, J ) 7.7 Hz), 5.95 (dd, 1H, J ) 9.4 Hz), 7.17-7.85
(19H) ppm; 13C NMR (CDCl3) δ, 27.9, 27.8, 61.6, 67.8, 69.4, 72.7,
75.6, 82.8, 109.2, 117.8, 123.6, 123.7, 127.3 (×2), 127.4 (×2),
127.5 (×2), 127.6 (×3), 128.7 (×2), 128.8 (×2), 128.9, 132.3,
132.5, 132.6, 140.2, 147.1, 150.8, 160.3, 164.2, 164.6 (×2), 170.7,
175.7 ppm; HR-FAB MS calcd for C38H30NNa2O12S [M - H +
Na]+ 770.1284, found 770.1299.
Method B: TMSOTf-Promoted Glycosylation. A mixture of
resin-bound glycosyl acceptor (or donor, 0.06 mmol), glycosyl
donor (or acceptor, 0.18 mmol), coevaporated with toluene (3 ×
10 mL) and dried in vacuo for 2 h directly prior to application,
and molecular sieves (4 Å, 200 mg) in dry dichloromethane (4 mL)
was agitated for 12 h at room temperature. Then TMSOTf (0.24
mmol) was added and the mixture was agitated for 48 h at room
temperature under argon. After that, glycosyl donor (0.18 mmol)
in dry dichloromethane (1 mL) and TMSOTf (0.24 mmol) were
added and the reaction mixture was agitated for an additional 48
h. The resin was separated by sintered filter, washed successively
with methanol (5 × 5 mL) and dichloromethane (5 × 5 mL), and
dried in vacuo. The residual resin was subjected to NaOMe
treatment and purification as described for Method A to afford the
requisite disaccharide.
Method C: MeOTf-Promoted Glycosylation. A mixture of
resin-bound glycosyl acceptor (0.06 mmol), glycosyl donor (0.18
mmol), coevaporated with toluene (3 × 10 mL) and dried in vacuo
for 2 h directly prior to application, and molecular sieves (3 Å,
200 mg) in dry dichloromethane (4 mL) was agitated for 12 h at
room temperature. Then MeOTf (0.24 mmol) was added and the
mixture was agitated for 48 h at room temperature under argon.
After that, glycosyl donor (0.18 mmol) in dry dichloromethane (1
mL) and MeOTf (0.24 mmol) were added and the reaction mixture
was agitated for an additional 48 h. The resin was separated by
sintered filter, washed successively with methanol (5 × 5 mL) and
dichloromethane (5 × 5 mL), and dried in vacuo. The residual resin
was subjected to NaOMe treatment and purification as described
for Method A to afford the requisite disaccharide.
Benzoxazolyl 3,4-di-O-acetyl-2-O-benzyl-6-O-(3-hydroxycar-
bonylpropanoyl)-â-D-glycopyranoside (22b): The title compound
was obtained from benzoxazolyl 3,4-di-O-acetyl-2-O-benzyl-â-D-
glycopyranoside (21b)35 in 78% yield as a white amorphous solid.
Analytical data for 22b: Rf 0.30 (methanol/dichloromethane, 1/6,
1
v/v); [R]26 +10.5 (c 1, CHCl3); H NMR (CDCl3) δ 1.86, 1.96
D
(2s, 3H), 2.51-2.53 (m, 4H), 3.79 (dd, 1H, J ) 9.0 Hz), 3.85 (m,
1H), 4.13-4.15 (m, 2H), 4.64 (dd, 2H, J ) 11.2 Hz), 5.03 (dd,
1H, J ) 9.8 Hz), 5.25 (dd, 1H, J ) 9.5 Hz), 5.40 (d, 1H, J ) 10.0
Hz), 7.16-7.25 (9H) ppm; 13C NMR (CDCl3) δ 20.8, 20.9, 29.2,
29.3, 62.5, 68.4, 75.5, 75.8, 76.4, 77.6, 78.3, 84.9, 110.4, 119.2,
124.9 (×2), 128.3 (×2), 128.7 (×2), 137.2, 141.5, 151.9, 161.3,
(46) Palmacci, E. R.; Plante, O. J.; Seeberger, P. H. Eur. J. Org. Chem.
2002, 595-606.
1722 J. Org. Chem., Vol. 73, No. 5, 2008

Solid-Phase Oligosaccharide Synthesis
Method D: NIS/TMSOTf-Promoted Glycosylation. A mixture
of resin-bound glycosyl acceptor 3b (0.03 mmol), glycosyl donor
(0.09 mmol), coevaporated with toluene (3 × 5 mL) and dried in
vacuo for 2 h directly prior to application, and molecular sieves (4
Å, 200 mg) in dry dichloromethane (4 mL) was agitated for 12 h
at room temperature. Then NIS (0.12 mmol) and TMSOTf (0.0012
mmol) were added and the mixture was agitated for 24 h at room
temperature under argon. The resin was separated by sintered filter,
washed successively with methanol (5 × 5 mL) and dichlo-
romethane (5 × 5 mL), and then re-suspended in dichloromethane
and agitated for several minutes to allow the resin swallow. The
resin was collected by using a plastic pipet and so was separated
from molecular sieves, and dried in vacuo for 24 h. The glycosy-
lation-filtration cycle was repeated twice. The residual resin was
swollen in methanol and subjected to NaOMe treatment and
purification as described for Method A to afford the requisite
disaccharide.
Methyl 2,4-di-O-benzyl-3-O-(â-D-glucopyranosyl)-R-D-glu-
copyranoside (5): The title compound was obtained from 3a and
434 by Method B in 95% yield, 3a and 636 by Method C in 98%
yield, or 3b and 4 by Method D in 98% yield as a white amorphous
solid. Analytical data for 5: Rf 0.34 (methanol/dichloromethane,
1/6, v/v); [R]26D +17.5 (c 1, MeOH); 1H NMR (CD3OD) δ 3.22-
3.36 (m, 6H), 3.37-3.83 (m, 8H), 4.27 (m, 1H), 4.59-4.68 (m,
3H), 4.79-4.84 (m, 2H), 5.08 (d, 1H, J ) 10.2 Hz), 7.27-7.46
(m, 10H) ppm; 13C NMR (CD3OD) δ 50.0, 55.6, 62.2, 63.5, 72.5,
74.3, 76.2, 76.7, 77.9, 78.2, 78.6, 78.9, 81.9, 99.1, 104.2, 129.1,
129.2, 129.5 (×2), 129.6 (×2), 129.8 (×2), 130.1 (×2), 139.5, 139.8
ppm; HR-FAB MS calcd for C27H36NaO11 [M + Na]+ 559.2155,
found 559.2168.
3a and 1425 by Method B in 52% (R/â ) 5/1) yield as a white
amorphous solid. Analytical data for R-15: Rf 0.25 (methanol/
1
dichloromethane, 1/9, v/v); H NMR (CD3OD) δ 3.25-3.30 (m,
4H), 3.43-3.77 (m, 8H), 3.86-3.89 (m, 1H), 4.12-4.19 (m, 2H),
4.36-4.51 (m, 5H), 4.62 (d, 1H, J ) 3.4 Hz), 4.78 (d, 1H, J )
11.8 Hz), 5.53 (d, 1H, J ) 3.0 Hz), 7.07-7.25 (15H) ppm; 13C
NMR (CD3OD) δ 55.3, 61.6, 63.4, 67.9 (×2), 70.6, 71.8, 73.1,
73.7, 73.7, 75.1, 76.3, 78.6, 79.1, 97.3, 97.5, 127.0 (×2), 127.7,
128.0, 128.1 (×2), 128.2 (×2), 128.5 (×2), 128.6 (×2), 128.7 (×2),
128.8, 137.6, 138.0, 138.2 ppm; HR-FAB MS calcd for C34H42O11-
Na [M + Na]+ 649.2625, found 649.2637.
Methyl 3-O-(2-methoxycarbamoyl-3,4,6-tri-O-acetyl-2-deoxy-
â-D-glucopyranosyl)-6-O-acetyl-2,4-di-O-benzyl-R-D-glucopyra-
noside (17): The title compound was obtained from 3a and 1639
by Method B followed by acetylation (see below) in 51% yield as
a white amorphous solid. General acetylation procedure: The
residue, recovered from the cleavage off the resin-bound disaccha-
ride, was dissolved in dry pyridine (1 mL) and acetic anhydride
(0.5 mL) was added at 0 °C. The reaction was allowed to gradually
warm to room temperature and kept for an additional 12 h. The
reaction was quenched by adding methanol (2 mL) then cooled to
room temperature, and the volatiles were removed under reduced
pressure. The residue was coevaporated with toluene (3 × 5 mL)
and then purified by column chromatography on silica gel (ethyl
acetate/hexane gradient elution) to afford the requisite per-acetylated
compound. Analytical data for 17: Rf 0.36 (ethyl acetate/hexanes,
1
3/2, v/v); [R]27 +21.7 (c 1, CHCl3); H NMR (CDCl3) δ 1.97,
D
2.01, 2.02, 2.03 (4s, 12H), 3.30 (s, 3H), 3.44-3.58 (m, 2H), 3.58-
3.63 (m, 1H), 3.74 (s, 3H), 3.77-3.79 (m, 2H), 4.02 (dd, 1H, J )
2.2 Hz, J ) 12.2 Hz), 4.20-4.28 (m, 4H), 4.50 (d, 1H, J ) 10.8
Hz), 4.57-4.68 (m, 3H), 4.83 (d, 1H, J ) 8.5 Hz), 4.87 (dd, 1H,
J ) 10.2), 5.04-5.10 (m, 2H), 7.25-7.42 (m, 10H) ppm; 13C NMR
(CDCl3) δ 20.8, 20.9, 21.1, 29.6, 29.9, 52.7, 55.3, 63.2, 68.6 (×2),
71.8, 73.1, 73.4, 74.9, 75.3, 76.8, 80.0, 81.1, 97.2, 102.2, 128.0,
128.2, 128.5 (×3), 128.6 (×2), 128.7, 129.1 (×2), 137.8, 138.4,
156.9, 169.6, 170.9 (×3) ppm; HR-FAB MS calcd for C37H47-
NNaO16 [M + Na]+ 784.2793, found 784.2829.
Methyl 2,4-di-O-benzyl-3-O-(2,3,4,6-tetra-O-benzyl-D-glu-
copyranosyl)-R-D-glucopyranoside (8): The title compound was
obtained from 3a and 735 by Method B in 54% yield (R/â ) 3/2),
3a and 936 by Method C in 32% yield (R/â ) 1/1), or 3b and 7 by
Method D in 78% yield (R/â ) 1.2/1) as a white amorphous solid.
Selected analytical data for 8: Rf 0.34 (ethyl acetate/hexanes, 2/3,
1
v/v); H NMR (CDCl3) δ, 5.72 (d, 1H, J ) 7.0 Hz), 4.98 (d, 1H,
J ) 4.2 Hz), 5.72 (d, 1H, J ) 3.5 Hz) ppm; 13C NMR (CDCl3) δ
97.6, 97.8, 98.0, 102.8 ppm; HR-FAB MS calcd for C55H60NaO11
[M + Na]+ 919.4033, found 919.4067.
Methyl 6-O-acetyl-3-O-(3,4,6-tri-O-acetyl-2-deoxy-2-phthal-
imido-â-D-glucopyranosyl)-2,4-di-O-benzyl-R-D-glucopyrano-
side (19): The title compound was obtained from 3a and 1839 by
Method B and acetylated prior to isolation as described for the
synthesis of 17 in 75% yield as a foam. Further analysis of the
disaccharide fraction showed the presence of two compounds, 19
and methyl 6-O-acetyl-3-O-[3,4,6-tri-O-acetyl-2-deoxy-2-(o-meth-
oxycarbonyl)benzamido-â-D-glucopyranosyl]-2,4-di-O-benzyl-R-D-
glucopyranoside (20), which were isolated by additional column
chromatography on silica gel (ethyl acetate/hexane slow gradient
elution) in 25% and 50%, respectively; both compounds were
Methyl 2,4-di-O-benzyl-3-O-(2-O-benzyl-R-D-glucopyranosyl)-
R-D-glucopyranoside (11): The title compound was obtained from
3a and 1025 by Method B in 80% yield (R only) or 3b and 10 by
Method D in 89% yield (R/â ) 5/1) as a white amorphous solid.
Analytical data for R-11: Rf 0.24 (methanol/dichloromethane, 1/9,
v/v); [R]29D +24.7 (c 1, MeOH); 1H NMR (CD3OD) δ, 3.29-3.34
(m, 4H), 3.46-3.79 (m, 8H), 3.96 (dd, 1H, J ) 9.2 Hz), 4.13-
4.17 (m, 1H), 4.28 (dd, 1H, J ) 8.6 Hz), 4.44 (d, 1H, J ) 11.9
Hz), 4.56-4.71 (m, 5H), 4.94 (d, 1H, J ) 11.9 Hz), 5.56 (d, 1H,
J ) 3.4 Hz), 6.92-7.39 (m, 15H) ppm; 13C NMR (CD3OD) δ 55.4,
61.8, 62.5, 70.5, 70.6, 71.4, 73.4 (×2), 73.5, 73.7, 76.2, 78.6, 78.9,
79.2, 97.1, 97.8, 126.9 (×3), 127.7, 128.2 (×2), 128.4, 128.6 (×2),
128.7 (×2), 128.8, (×4), 137.8, 137.9, 138.4 ppm; HR-FAB MS
calcd for C34H42NaO11 [M + Na]+ 649.2625, found 649.2603.
Methyl 2,4-di-O-benzyl-3-O-(â-D-galactopyranosyl)-R-D-glu-
copyranoside (13): The title compound was obtained from 3a and
1226 by Method C in 82% yield as a white amorphous solid.
obtained as foams. Analytical data for 19: Rf 0.22 (ethyl acetate/
1
hexanes, 2/3 v/v); [R]26 +9.0 (c 1, CHCl3); H NMR (CDCl3) δ
D
1.88, 1.94, 2.00, 2.00 (4s, 12H), 3.08 (s, 3H), 3.17 (dd, 1H, J )
3.5 Hz, J ) 9.6 Hz), 3.30 (dd, 1H, J ) 8.8 Hz, J ) 9.9 Hz), 3.75
(m, 1H), 3.79 (d, 1H, J ) 12.5 Hz), 3.86 (m, 1H), 4.04-4.14 (m,
4H), 4.28-4.38 (m, 2H), 4.40 (dd, 1H, J ) 8.4 Hz, J ) 10.7 Hz),
4.58 (d, 1H, J ) 11.2 Hz), 4.66 (d, 1H, J ) 12.5 Hz), 5.04 (d, 1H,
J ) 11.2 Hz), 5.20 (dd, 1H, J ) 9.9 Hz), 5.82 (d, 1H, J ) 8.4 Hz),
5.57-6.01 (dd, 1H, J ) 10.7 Hz, J ) 9.1 Hz), 7.12-8.00 (m, 14H)
ppm; 13C NMR (CDCl3) δ 20.7, 20.9 (×2), 21.0, 29.9, 55.0, 55.7,
62.1, 63.2, 68.2, 69.3, 70.8, 71.60, 74.1, 74.7, 75.4, 76.8, 78.4, 80.9,
97.7, 98.3, 123.9, 128.0, 128.3 (×6), 128.6 (×2), 128.7 (×3), 138.3
(×2), 138.4, 167.7 (×2), 169.9, 170.3, 170.8, 170.9 ppm; HR-FAB
MS calcd for C43H47NNaO16 [M + Na]+ 856.2793, found 856.2769.
Analytical data for 13: Rf 0.27 (methanol/dichloromethane, 1/6,
1
v/v); [R]27 +22.5 (c 1, MeOH); H NMR (CD3OD) δ, 3.31 (s,
D
3H), 3.32-3.84 (m, 11H), 4.25 (m, 1H), 4.55 (d, 1H, J ) 10.9
Hz), 4.58 (d, 1H, J ) 3.8 Hz), 4.63 (d, 1H, J ) 11.6 Hz), 4.77-
4.87 (m, 2H), 5.14 (d, 1H, J ) 9.8 Hz), 7.25-7.53 (m, 10H) ppm;
13C NMR (CD3OD) δ 55.6, 62.2, 63.0, 70.6, 72.5, 73.5, 74.4, 75.1,
76.7, 77.3, 77.9, 79.2, 82.1, 99.2, 105.1, 129.1, 129.2, 129.4, 129.5,
129.6, 129.7, 129.8, 129.9, 130.0, 130.5, 139.6, 139.9 ppm; HR-
FAB MS calcd for C27H36O11Na [M + Na]+ 559.2155, found
559.2147.
Analytical data for 20: Rf 0.28 (ethyl acetate/hexanes, 3/2, v/v);
1
[R]26 +0.4 (c 1, CHCl3); H NMR (CDCl3) δ 1.93, 1.94, 1.97,
D
2.00 (4s, 12H), 3.22 (s, 3H), 3.45 (dd, 1H, J ) 8.7 Hz), 3.54 (dd,
1H, J ) 3.4 Hz, J ) 9.5 Hz), 3.63 (m, 1H), 3.72 (m, 1H), 3.82 (s,
3H), 3.98-4.06 (m, 2H), 4.13-4.25 (m, 3H), 4.32-4.42 (m, 2H),
4.50 (d, 1H, J ) 10.8 Hz), 4.58 (d, 1H, J ) 3.3 Hz), 4.88-4.95
(m, 2H), 5.04 (d, 1H, J ) 11.1 Hz), 5.12 (dd, 1H, J ) 9.6 Hz),
Methyl 2,4-di-O-benzyl-3-O-(2-O-benzyl-D-galactopyranosyl)-
R-D-glucopyranoside (15): The title compound was obtained from
J. Org. Chem, Vol. 73, No. 5, 2008 1723

Parlato et al.
5.40 (d, 1H, J ) 9.5 Hz), 6.91-7.92 (m, 14H) ppm; 13C NMR
(CDCl3) δ 20.8 (×2), 21.0, 21.1, 52.6, 54.4, 55.3, 62.3, 63.2, 68.6,
68.7, 71.9, 72.0, 73.4, 75.0 (×2), 80.0, 81.2, 97.0, 102.0, 127.0
(×2), 127.5, 128.0, 128.3, 128.5 (×2), 128.7 (×2), 129.0 (×2),
129.8, 130.0, 130.1, 132.1, 137.6, 138.1, 138.4, 166.8, 169.0, 169.5,
170.8 (×2), 180.0 ppm; HR-FAB MS calcd for C44H51NNaO17 [M
+ Na]+ 888.3055, found 888.3066.
Methyl 2,3,4-tri-O-benzyl-6-O-(â-D-glucopyranosyl)-R-D-glu-
copyranoside (25): The title compound was obtained from 23a
and 2433 by Method A in 87% yield as a white amorphous solid.
Hz), 3.25-3.32 (m, 3H), 3.63-3.70 (m, 2H), 3.88 (dd, 1H, J )
11.3 Hz), 4.03-4.10 (m, 2H), 4.28-4.33 (m, 2H), 4.39 (dd, 1H, J
) 2.4 Hz, J ) 5.0 Hz), 4.64 (dd, 1H, J ) 2.4 Hz, J ) 7.9 Hz),
5.52 (d, 1H, J ) 5.0 Hz) ppm; 13C NMR (CD3OD) δ 24.7, 25.3,
26.4, 62.9, 69.0, 70.0, 71.8, 72.1 (×2), 72.6, 75.2, 77.9, 78.1, 97.9,
104.9, 110.2, 110.6 ppm; HR-FAB MS calcd for C18H30NaO11 [M
+ Na]+ 445.1686, found 445.1688.
(3â)-Cholest-5-en-3-yl 2,3,4,6-tetra-O-acetyl-â-D-glucopyra-
noside (35): The title compound was obtained from 23a and
commercial 34 by Method A and acetylated prior to isolation as
described for the synthesis of 17 in 51% yield as a white amorphous
solid. Partial characterization data for compound 35 have been
reported previously.49 Spectral data for 35: 1H NMR (CDCl3) δ
0.68-2.23 (m, 43H, cholestenyl), 3.49 (m, 1H, OCH cholestenyl),
3.69 (m, 1H, H-5), 4.12 (dd, 1H, J5,6a ) 2.4 Hz, H-6a), 4.27 (dd,
1H, J5,6b ) 4.8 Hz, H-6b), 4.60 (d, 1H, J1,2 ) 8.0 Hz, H-1), 4.93-
4.99 (m, 1H, J2,3 ) 9.5 Hz, H-2), 5.08 (dd, 1H, J4,5 ) 9.5 Hz,
H-4), 5.21 (dd, 1H, J3,4 ) 9.5 Hz, H-3′), 5.36 (br d, 1H, dCH-
cholestenyl) ppm; 13C NMR (CDCl3) δ 12.1, 18.9, 19.6 (×2), 20.8
(×2), 20.7, 20.9 (×2), 21.0 (×2), 22.8, 23.0 (×2), 24.0 (×2), 28.2,
29.7 (×2), 32.1, 36.0, 36.9, 39.7 (×2), 42.5, 50.4, 53.6, 56.4, 57.0,
68.8, 71.7, 71.9, 73.1, 76.8, 80.3, 99.9, 122.4, 140.6, 169.5, 169.6,
170.6, 170.9 ppm; HR-FAB MS calcd for C41H64NaO10 [M + Na]+
739.4397, found 739.4365.
Analytical data for 25: Rf 0.30 (methanol/dichloromethane, 1/6,
1
v/v); [R]29 +3.9 (c 1, MeOH); H NMR (CD3SOCD3) δ 2.96-
D
3.17 (m, 4H), 3.26-3.38 (m, 4H), 3.40-3.50 (m, 2H), 3.57-3.78
(m, 4H), 4.00 (d, 1H, J ) 9.8 Hz), 4.15 (d, 1H, J ) 7.7 Hz), 4.50
(dd, 1H, J ) 5.8 Hz), 4.61-4.86 (m, 7H, J ) 4.2 Hz), 4.90 (d, 1H,
J ) 4.2 Hz), 4.95 (d, 1H, J ) 4.5 Hz), 5.15 (d, 1H, J ) 4.9 Hz),
7.26-7.37 (m, 15H) ppm; 13C NMR (CD3SOCD3) δ 54.6, 61.0,
67.4, 69.7, 70.0, 71.3, 73.4, 74.0, 74.4, 76.6, 76.9, 77.0, 79.4, 81.2,
96.9, 103.4, 127.4, 127.5, 127.6 (×6), 128.1 (×3), 128.2 (×2), 128.2
(×2), 138.5, 138.8, 138.8; HR-FAB MS calcd for C34H42NaO11
[M + Na]+ 649.2625, found 649.2640.
Methyl 2,3,6-tri-O-benzyl-4-O-(â-D-glucopyranosyl)-R-D-glu-
copyranoside (27): The title compound was obtained from 23a
and 2640 by Method A in 56% yield as a white amorphous solid.
Partial characterization data for compound 27 have been reported
previously.47 Spectral data for 27: 1H NMR (CD3OD) δ 3.14-
3.34 (m, 3H), 3.38 (s, 3H), 3.47-3.57 (m, 2H), 3.68-3.90 (m,
4H), 3.94-4.01 (m, 2H), 4.41 (d, 1H, J ) 7.4 Hz), 4.51-4.75 (m,
6H), 4.77 (d, 1H, J ) 3.7 Hz), 4.97 (d, 1H, J ) 10.4 Hz), 6.61-
7.43 (m, 15H) ppm; 13C NMR (CD3OD) δ 55.7, 63.4, 69.5, 71.8,
72.3, 74.3, 74.4, 75.9, 76.7, 77.4, 78.1, 78.9, 80.9, 81.8, 99.2, 103.7,
128.9, 129.0 (×2), 129.1 (×2), 129.3 (×2), 129.4 (×2), 129.6 (×4),
130.1 (×2), 139.7, 139.7 (×2) ppm; HR-FAB MS calcd for C34H42-
NaO11 [M + Na]+ 649.2625, found 649.2603.
Methyl 2,4,6-tri-O-benzyl-3-O-(â-D-glucopyranosyl)-R-D-glu-
copyranoside (29): The title compound was obtained from 23a
and 2841 by Method A in 98% yield as a white amorphous solid.
Analytical data for 29: Rf 0.33 (methanol/dichloromethane, 1/6,
v/v); [R]26D +11.4 (c 1, MeOH); 1H NMR (CD3OD) δ 3.10-3.28
(m, 6H), 3.42-3.71 (m, 8H), 4.13 (dd, 1H, J ) 10.4 Hz), 4.36-
4.58 (m, 5H), 4.68-4.77 (m, 2H), 4.87 (d, 1H, J ) 11.4 Hz), 7.18-
7.35 (m, 15H) ppm; 13C NMR (CD3OD) δ 55.7, 63.4, 70.0, 71.4,
72.5, 74.4, 74.6, 76.2, 76.7, 78.0, 78.1, 78.6, 78.9, 81.9, 99.2, 104.2,
129.0, 129.1, 129.2, 129.3 (×2), 129.5 (×2), 129.6 (×4), 129.8
(×2), 130.2 (×2), 139.3, 139.6, 139.8 ppm; HR-FAB MS calcd
for C34H42NaO11 [M + Na]+ 649.2625, found 649.2655.
Methyl 3,4,6-tri-O-benzyl-2-O-(â-D-glucopyranosyl)-R-D-glu-
copyranoside (31): The title compound was obtained from 23a
and 3042 by Method B in 49% yield as a white amorphous solid.
Analytical data for 31: Rf 0.29 (methanol/dichloromethane, 1/6,
v/v); [R]27D +17.2 (c 1, MeOH); 1H NMR (CD3OD) δ 3.11-3.32
(m, 6H), 3.44 (dd, 1H, J ) 9.3 Hz), 3.53-3.84 (m, 8H), 4.36-
4.64 (m, 5H), 4.64 (dd, 2H, J ) 12.3 Hz), 4.82 (d, 1H, J ) 3.5
Hz), 5.02 (d, 1H, J ) 11.5 Hz), 7.04-7.29 (m, 15H) ppm; 13C
NMR (CD3OD) δ 55.7, 62.9, 70.0, 71.6, 71.8, 74.5, 75.3, 76.2,
76.6, 78.2 (×2), 79.4, 81.0, 83.0, 101.3, 105.7, 128.7, 128.8, 128.9,
129.0 (×2), 129.2 (×2), 129.4 (×2), 129.5 (×2), 129.6 (×2), 129.7-
(×2), 139.6, 139.8, 140.3; HR-FAB MS calcd for C34H42NaO11
[M + Na]+ 649.2625, found 649.2602.
Ethyl 2,3,4-tri-O-acetyl-6-O-(2,3,4,6-tetra-O-acetyl-â-D-glu-
copyranosyl)-1-thio-â-D-glucopyranoside (37): The title com-
pound was obtained from 23a and 3643 by Method B and acetylated
prior to isolation as described for the synthesis of 17 in 37% yield
as a white amorphous solid. The isolated sample was essentially
the same as described previously.50
2-Thiazolinyl 2,3,4-tri-O-acetyl-6-O-(2,3,4,6-tetra-O-acetyl-â-
D-glucopyranosyl)-1-thio-â-D-glucopyranoside (39): The title
compound was obtained from 23a and 3836 by Method B and
acetylated prior to isolation as described for the synthesis of 17 in
25% yield as a white amorphous solid. Analytical data for 39: Rf
0.28 (ethyl acetate/hexanes, 3/2, v/v); [R]28 -10.5 (c 1, CHCl3);
D
1H NMR (CDCl3) δ 2.00, 2.02, 2.04, 2.05, 2.06, 2.07, 2.10 (7s,
21H), 3.44 (m, 2H), 3.60-3.71 (m, 2H), 3.77-3.84 (m, 2H), 4.11-
4.42 (m, 4H), 4.67 (d, 1H, J ) 8.0 Hz), 4.90-4.99 (m, 2H), 5.04-
5.20 (m, 3H), 5.26 (dd, 1H, J ) 10.3 Hz), 5.47 (d, 1H, J ) 10.4
Hz) ppm; 13C NMR (CDCl3) δ 20.8 (×4), 20.9 (×2), 21.0, 35.5,
61.9, 64.4, 67.8, 68.5, 68.9, 69.5, 71.3, 72.1, 73.1, 73.9, 76.8, 78.2,
83.0, 100.3, 169.6 (×2), 169.7, 169.8, 170.2, 170.5, 170.9 ppm;
HR-FAB MS calcd for C29H39NNaO17S2 [M + Na]+ 760.1557,
found 760.1539.
Methyl 2,3,4-tri-O-benzyl-6-O-(2-O-benzyl-â-D-glucopyrano-
syl)-D-glucopyranoside (40): The title compound was obtained
from 23b and 2433 by Method A in 54% yield (anomeric mixture
R/â ≈ 1/1) as a white amorphous solid. Selected analytical data
1
for 40: Rf 0.25 (methanol/dichloromethane, 1/9, v/v); H NMR
(CD3OD) δ 4.23 (d, 1H, J ) 9.0 Hz), 4.56 (d, 1H, J ) 3.6 Hz),
4.60 (d, 1H, J ) 3.5 Hz), 4.95 (d, 1H, J ) 3.4 Hz) ppm; 13C NMR
(CD3OD) δ 98.6, 99.3, 99.3, 105.0 ppm; HR-FAB MS calcd for
C41H48NaO11 [M + Na]+ 739.3094, found 739.3099.
Ethyl 2,3,4-tri-O-acetyl-6-O-(2-O-benzyl-3,4,6-tri-O-acetyl-R-
D-glucopyranosyl)-1-thio-â-D-glucopyranoside (41): The title
compound was obtained from 23b and 3643 by Method B and
acetylated prior to isolation as described for the synthesis of 17 in
35% yield as a colorless foam. Analytical data for 41: Rf 0.25 (ethyl
1
acetate/hexanes, 2/3, v/v); [R]26 +39.0 (c 1, CHCl3); H NMR
D
6-O-(â-D-Glucopyranosyl)-1,2:3,4-O-isopropylidene-R-D-ga-
lactopyranose (33): The title compound was obtained from 23a
and commercial 32 by Method A in 45% yield as a white
(CDCl3) δ 1.19 (t, 3H), 1.93, 1.94, 1.97, 1.98, 1.99, 2.01 (6s, 18H),
2.63 (m, 2H), 3.41 (dd, 1H, J ) 2.1 Hz, J ) 10.3 Hz), 3.50 (dd,
amorphous solid. Analytical data for 33:48 Rf 0.24 (methanol/
1
dichloromethane, 1/6, v/v); [R]26 -50.8 (c 1, CHCl3); H NMR
(48) Hanessian, S.; Bacquet, C.; Lehong, N. Carbohydr. Res. 1980, 80,
D
c17-c22.
(CD3OD) δ 1.34, 1.35, 1.41, 1.53 (4s, 12H), 3.21 (dd, 1H, J ) 7.8
(49) Wulff, G.; Roehle, G.; Krueger, W. Chem. Ber. 1972, 105, 1097-
1110.
(47) Takeo, K.; Okushio, K.; Fukuyama, K.; Kuge, T. Carbohydr. Res.
1983, 121, 163-173.1290.
(50) Singh, S.; Scigelova, M.; Critchley, P.; Crout, D. H. G. Carbohydr.
Res. 1998, 305, 363-370.
1724 J. Org. Chem., Vol. 73, No. 5, 2008

Solid-Phase Oligosaccharide Synthesis
1H, J ) 3.5 Hz, J ) 10.0 Hz), 3.61-3.76 (m, 2H), 3.95 (dd, 1H,
J ) 1.9 Hz, J ) 12.3 Hz), 4.07 (m, 1H), 4.21 (dd, 1H, J ) 4.0 Hz,
J ) 12.4 Hz), 4.45 (d, 1H, J ) 10.1 Hz), 4.55 (dd, 2H), 4.71 (d,
1H, J ) 3.4 Hz), 4.83-4.93 (m, 3H), 5.17 (dd, 1H, J ) 9.3 Hz),
5.36 (dd, 1H, J ) 9.6 Hz), 7.21-7.28 (m, 5H) ppm; 13C NMR
(CDCl3) δ 15.1, 20.8 (×2), 20.9 (×2), 21.0, 24.7, 62.0, 67.4, 67.5
(×2), 68.6, 69.6, 70.2, 71.9, 73.3, 74.0, 76.8, 77.9, 83.6, 96.8, 128.0
(×2), 128.2, 128.7 (×2), 137.9, 169.6, 169.8, 169.9, 170.2, 170.3,
170.8 ppm; HR-FAB MS calcd for C33H44NaO16S [M + Na]+
751.2248, found 751.2263.
Methyl O-(2,3,4,6-tetra-O-acetyl-â-D-glucopyranosyl)-(1f6)-
O-(2,3,4-tri-O-acetyl-â-D-glucopyranosyl)-(1f6)-2,3,4-tri-O-ben-
zyl-â-D-glucopyranoside (42): Building blocks 23a and 36 were
reacted in accordance with Method B. Prior to cleaving off the
solid support, the dried residue containing the immobilized
intermediate disaccharide (0.06 mmol) was mixed with glycosyl
acceptor 24 (0.18 mmol) and molecular sieves (4 Å, 200 mg), and
the resulting mixture was agitated in dry dichloromethane (4 mL)
for 12 h at room temperature. Then NIS (0.24 mmol) and TfOH
(0.0024 mmol) were added and the reaction mixture was agitated
for 72 h at room temperature under argon. The resin was separated
by sintered filter, washed successively with methanol (5 × 5 mL)
and dichloromethane (5 × 5 mL), and dried in vacuo. The residual
resin was then subjected to treatment with NaOMe as described
for Method A followed by acetylation as described for the synthesis
of 17. The crude residue was purified by column chromatography
to afford the title trisaccharide 42 and methyl 6-O-(2,3,4,6-tetra-
O-acetyl-â-D-glucopyranosyl)-2,3,4-tri-O-benzyl-R-D-glucopyrano-
side (43) as colorless foams in 30% and 15%, respectively.
1.92, 1.94, 1.95, 2.00 (7s, 21H), 3.30 (s, 3H), 3.38-3.47 (m, 2H),
3.52-3.78 (m, 6H), 3.90 (dd, 1H, J ) 9.3 Hz), 3.98-4.06 (m,
2H), 4.18 (dd, 1H, J ) 4.8 Hz, J ) 12.3 Hz), 4.44-4.54 (m, 4H),
4.57 (d, 1H, J ) 13.5 Hz), 4.70-5.12 (m, 10H), 7.17-7.31 (m,
15H) ppm; 13C NMR (CDCl3) δ 14.3, 20.8 (×6), 20.9 (×2), 29.9
(×2), 55.5 (×2), 62.0, 68.45, 69.2 (×2), 71.3, 71.6, 72.2, 72.9,
73.2, 73.7, 73.8, 75.9, 77.6, 82.1, 98.5, 100.9, 127.8, 127.9, 128.1
(×2), 128.2, 128.4, 128.6, 128.7, 128.8, 138.3 (×2), 138.4 (×2),
138.9 (×2), 169.2, 169.3, 169.6, 169.8, 170.2, 170.6, 170.1, 170.3,
170.5, 170.8 ppm; HR-FAB MS calcd for C54H66NaO23 [M + Na]+
1105.3893, found 1105.3871.
Characterization data for 43 were essentially the same as those
reported previously.51
Acknowledgment. The authors thank the National Institutes
of General Medical Sciences (GM072693) and the Department
of Chemistry and Biochemistry for financial support of this
research, NSF for grants to purchase the NMR spectrometer
(CHE-9974801) and the mass spectrometer (CHE-9708640)
used in this work, and Dr. R. E. K. Winter and Mr. J. Kramer
for HRMS determinations.
Supporting Information Available: Spectra for all new
compounds. This material is available free of charge via the Internet
at http://pubs.acs.org.
JO701902F
Analytical data for 42: Rf 0.46 (ethyl acetate/hexanes, 1/1, v/v);
(51) Ito, Y.; Ogawa, T.; Numata, M.; Sugimoto, M. Carbohydr. Res.
1990, 202, 165-175.
1
[R]27 -0.62 (c 1, CHCl3); H NMR (CDCl3) δ 1.81, 1.91, 191,
D
J. Org. Chem, Vol. 73, No. 5, 2008 1725