One-pot synthesis of branched oligosaccharides by use of galacto- and mannopyranosyl thioglycoside diols as key glycosylating agents

Article abstract of DOI:10.1039/c3ob40421h

We describe in this paper the efficient four-component one-pot synthesis of three fully protected oligosaccharides 22, 36, and 50 with di-branched structures by employing d-galacto- and mannopyranosyl thioglycoside diols as central glycosylating agents. After global deprotection, they were converted respectively into the 3-aminopropyl linker-containing free oligosaccharide fragments 14, 24, and 38 structurally related to cell wall oligosaccharides from Atractylodes lancea DC, the marine fungus Lineolata rhizophorae and pathogenic Mycobacterium tuberculosis. The 3-aminopropyl linker at the anomeric carbon can enable conjugation of these synthetic oligomers to a suitable protein carrier. This journal is The Royal Society of Chemistry 2013.

Full text of DOI:10.1039/c3ob40421h

Organic &
Biomolecular Chemistry
View Article Online
View Journal | View Issue
PAPER
One-pot synthesis of branched oligosaccharides by use
of galacto- and mannopyranosyl thioglycoside diols
as key glycosylating agents†
Cite this: Org. Biomol. Chem., 2013, 11,
3903
Xing-Yong Liang, Qiang-Wei Liu, Hua-Chao Bin and Jin-Song Yang*
We describe in this paper the efficient four-component one-pot synthesis of three fully protected oligo-
saccharides 22, 36, and 50 with di-branched structures by employing D-galacto- and mannopyranosyl
thioglycoside diols as central glycosylating agents. After global deprotection, they were converted
respectively into the 3-aminopropyl linker-containing free oligosaccharide fragments 14, 24, and 38
structurally related to cell wall oligosaccharides from Atractylodes lancea DC, the marine fungus Lineolata
rhizophorae and pathogenic Mycobacterium tuberculosis. The 3-aminopropyl linker at the anomeric
carbon can enable conjugation of these synthetic oligomers to a suitable protein carrier.
Received 28th February 2013,
Accepted 5th April 2013
DOI: 10.1039/c3ob40421h
www.rsc.org/obc
another glycosyl donor 5. These three steps together work out
the branched sugar 6 (Scheme 1, eqn (1)).
Introduction
The oligosaccharide chains, typically conjugated to proteins
and lipids, play a significant role in cell recognition and signal method wherein several glycosylation steps are sequentially
transduction in numerous biological processes.1 Among these completed in
single reaction vessel shows particular
The solution-phase one-pot multi-step glycosylation
a
oligosaccharides, many have been found to have branched- efficiency in the rapid preparation of oligosaccharides.6 But
chain structures. For example, branched oligomannose resi- most of the one-pot glycosylation methods are based on
dues are a structural feature common to all asparagine-linked sequential activation of glycosyl donors to provide linear oligo-
glycans (N-glycans) widely distributed on mammalian cell saccharides. Few approaches involve the one-pot synthesis of
surface, and are crucial constituents of the HIV-associated branched sugars.7 In this respect, Takahashi and co-workers
envelope glycoprotein gp120.2 While 2,6- and 3,6-branched have focused on the branched-type one-pot approach based on
arabinogalactopyranosyl units are common structural com- the regioselective glycosylation of a diol glycoside acceptor.7b–d
ponents of arabinogalactans (AGs) present on the cell surface The reactivity differences between the two hydroxy (OH)
of plants including some traditional herbal medicines.3 More- groups toward a proper glycosyl donor are exploited to control
over, 3,6-di-O-(β-D-glucopyranosyl)-β-D-glucopyranosyl structure the one-pot glycosylation. The synthetic utility of this method-
is the characteristic of phytoalexin elicitor-active β-glucohepta- ology was exemplified by the one-pot assembly of a range of
saccharide isolated from mycelial walls of Phytophthora mega- branched galacto- and mannoside trisaccharides7b–d as well as
sperma f. sp. glycinea.4 Due to their occurrence in biological glycosyl amino acid derivatives.7f,g Furthermore, on the syn-
structures and their challenging branched framework,
a
thesis of the Lewis family of oligosaccharides, Huang and Ye
number of efforts have been made towards the synthesis of et al. have reported the construction of branched oligosacchar-
this type of oligosaccharides.5 Much of the work published so ides by a combination of preactivation and reactivity-based
far normally relied upon fragment couplings at the branching chemoselective one-pot glycosylations. The efficiency of this
sites and required multiple protection/deprotection steps for strategy was further demonstrated in the synthesis of two
elongation of the sugar chain, namely, glycosylation of a sugar branched oligosaccharides, i.e., LewisX pentasaccharide and
alcohol 1 with a glycosyl donor 2, then selective deprotection dimeric LewisX octasaccharide.7h
of the resulting 3 (→4), and a second glycosylation of 4 with
Very recently, we described the development of a novel
regioselective furanosylation methodology8 using partially pro-
tected arabino- and galactofuranosyl thioglycosides as central
glycosylating building blocks. This method has proven to be
very useful in one-pot preparation of a series of linear and
branched-type arabino- and galactofuranoses of bacterial and
plant origins. Here, the aim of our work is to apply this viable
Key Laboratory of Drug Targeting, Ministry of Education, and Department of
Chemistry of Medicinal Natural Products, West China School of Pharmacy, Sichuan
University, Chengdu 610041, P. R. China. E-mail: yjs@scu.edu.cn, yjscd@163.com
†Electronic supplementary information (ESI) available. See DOI: 10.1039/
c3ob40421h
This journal is © The Royal Society of Chemistry 2013
Org. Biomol. Chem., 2013, 11, 3903–3917 | 3903

View Article Online
Paper
Organic & Biomolecular Chemistry
Scheme 1 Strategies for synthesis of branched oligosaccharides.
synthetic method to the one-pot synthesis of pyranose counter-
parts. As outlined in Scheme 1, eqn (2), the principal of the
Results and discussion
strategy is built on the following considerations. Regio- and Arabinogalactans (AGs) are a class of polysaccharides mainly
chemoselective glycosylation of the primary alcohol on posi- consisting of a (1→4)- or (1→6)-β-D-galactopyranose backbone
tion 6 of the thioglycoside diol 7 with glycosyl trichloroacetimi- with α-linked L-arabinofuranose side chains at position 2 or
date donor 8 gives disaccharide 9 that is then coupled in situ 3.3c They are often found in higher plants and in some situ-
with the primary OH group of a glycosyl acceptor to form a tri- ations they occur in covalent association with protein as pro-
saccharide intermediate 11, which upon activation and coup- teoglycans (arabinogalactan proteins, AGPs). Although the
ling with the second thioglycosyl donor (the fourth most popular AGs have been used for food additives, other AG-
component) will provide the corresponding branched tetrasac- containing polysaccharides have been evaluated for their
charide 13. Compound 7 functions as an acceptor for the first pharmacological activity and medicinal uses. Yamada et al.9
glycosylation, a donor for the second glycosylation and again have reported that ALR-5IIa-1-1, an arabino-3,6-galactan,
an acceptor for the third glycosylation. In this way, three glyco- which was purified from the rhizomes of medicinal herb Atrac-
sidic linkages are sequentially constructed in a one-pot three- tylodes lancea DC, possesses intestinal immune system modu-
step reaction.
lating activity in mice. The analysis of the structure–activity
In this paper, we report the facile one-pot assembly of three relationships of ALR-5IIa-1-1 by glycosidase digestions revealed
branched oligosaccharides, i.e., 3,6-branched D-galacto- and that the β-(1→6)-linked 3-branched tetrasaccharide portion 14
mannosides (22 and 35, respectively), and 2,6-branched D-man- [β-D-Galp-(1→6)-[α-L-Araf-(1→3)]-β-D-Galp-(1→6)-β-D-Galp, Scheme 2]
noside (49) by application of the proposed regioselective glyco- in the non-reducing terminal side of ALR-5IIa-1-1 largely contri-
sylation approach. Global deprotection followed by trans- butes to expression of the activity.10
formation of the azido group into an amino group created
We chose 3,6-branched arabinogalactosyl glycoside 14 as
successfully 3-aminopropyl spacer-containing free sugars our initial synthetic target for its relatively structural simplicity
14, 24, and 38, whose structures are related to cell-surface would enable us to easily verify the basic principles of the
polysaccharides from Atractylodes lancea DC, the marine designed one-pot synthesis method. To date, chemical syn-
fungus Lineolata rhizophorae and Mycobacterium tuberculosis, thesis of some structurally different AG-type oligosaccharides
respectively. The amine spacer can ensure future conjugation has been reported.11 In general, the published works are
of these synthetic oligomers to a microarray or suitable protein typical examples of oligosaccharide synthesis involving
carrier for biological studies.
tediously selective protection and deprotection steps and
Scheme 2 Retrosynthetic analysis of tetraarabinogalactan 14.
3904 | Org. Biomol. Chem., 2013, 11, 3903–3917
This journal is © The Royal Society of Chemistry 2013

View Article Online
Organic & Biomolecular Chemistry
Paper
laborious intermediate purifications. We describe herein an triflate (TMSOTf), a versatile promoter for the chemoselective
alternative approach to 14 on the basis of the use of 3,6-dihy- activation of glycosyl trichloroacetimidate donors over thiogly-
droxy D-thioglycoside 15 as a key intermediate. We envisaged cosyl acceptors13 was chosen as the catalyst. Treatment of 15
that, due to the reactivity difference between the primary and with 16 (1.25 equiv.) in the presence of a catalytic amount of
the secondary OH groups, the glycosylation events of the TMSOTf (0.1 equiv.) and 4 Å molecular sieves (MS) in dry
former should be preferable over the later in regioselective gly- dichloromethane (CH2Cl2) at −80 to 0 °C for 1 h provided
cosylation reaction. As retrosynthetically shown in Scheme 2, (1→6)-linked disaccharide alcohol 20 as a single β-isomer in
the reaction sequence for 14 involves three steps: (i) chemo- good 89% yield. The stereochemical outcome resulted from
and regioselective glycosylation of the primary alcohol of thio- the neighboring group participation of the benzoyl group at
galactoside 15 in the presence of the secondary one with tri- the C-2 position of the donor. The regioselectivity in this
chloroacetimidate 16,12 followed by (ii) coupling of the process was assured by gHMBC experiment of 20, namely, the
resulting disaccharide thioglycoside with acceptor 1711e based strong correlation observed between the C-6 signal (δC
on the difference in reactivity between the secondary OH on 61.7 ppm) and the anomeric H-1′ resonance (δH 4.93 ppm, d,
donor and the primary OH on acceptor, and (iii) glycosylation JH1–H2 = 8.0 Hz) confirmed a (1→6) linkage. Products arising
of the remaining secondary alcohol of 15 with donor 188 to from the C-3 glycosylation and the intermolecular aglycon
give the protected form of 14.
transformation14 of 15 were not isolated. Next, condensation
Preparation of D-galactose diol derivative 15 was performed of 20 with primary OH-containing galactoside 17 was investi-
as detailed in Scheme 3. Selective 6-O-detritylation of the gated. We adopted the combination of N-iodosuccinimide
known suitably protected β-D-galactothiopyranoside 1911e (NIS) and catalytic triflic acid (TfOH), one of the most
under acidic hydrolysis followed by oxidative cleavage of the common reagent systems for activation of thioglycosides,13 as
2-naphthylmethyl (Nap) group in the presence of 2,3-dichloro- coupling promoter. Thus, treatment of thioglycoside 20 (1.25
5,6-dicyano-1,4-benzoquinone (DDQ) afforded the desired 15 equiv.) with acceptor 17 (1.0 equiv.) under the promotion of
in 79% yield over two steps.
NIS (1.20 equiv.), TfOH (0.1 equiv.), and 4 Å MS in CH2Cl2 at
Stepwise synthesis of the protected tetrasaccharide 22 was −20 to 0 °C for 1 h furnished trisaccharide alcohol 21 in excel-
undertaken (Scheme 4). We first examined the glycosylation of lent 94% yield. Importantly, no other coupled product was
the primary alcohol of thioglycoside 3,6-diol 15 with 1.25 detected under these reaction conditions. Finally, through the
equivalents of trichloroacetimidate donor 16. Trimethylsilyl same thioglycoside activation conditions, the desired pro-
tected 22 was obtained in 89% yield via glycosylation of the
remaining secondary alcohol of 21 with 2,3,5-perbenzoylated
L-arabinofuranose thioglycoside 18.
The one-pot synthesis of 22 was carried out with the same
reaction sequence as in the preliminary tests in Scheme 4. In
the event, imidate 16 was used to regioselectively and chemo-
Scheme 3 Preparation of monosaccharide building block 15.
selectively condense with diol 15 by activation with cat.
Scheme 4 Synthesis of tetrasaccharide 14.
This journal is © The Royal Society of Chemistry 2013
Org. Biomol. Chem., 2013, 11, 3903–3917 | 3905

View Article Online
Paper
Organic & Biomolecular Chemistry
Scheme 5 Retrosynthetic analysis of tetrasaccharide 24.
TMSOTf at −80 °C in CH2Cl2. On gradual warming to approxi- glycosylation steps: (i) chemo- and regioselective coupling of
mately 0 °C, disaccharide 20, as the only detected product, was the primary alcohol of 25 in the presence of the secondary one
visible on TLC. Next, the reaction mixture was re-cooled to with trichloroacetimidate 26,16 followed by (ii) reaction of the
−20 °C and subsequent addition of the acceptor 17 along with resulting 6-O-glycosylated disaccharide thioglycoside with
NIS–TfOH activating reagents to the reaction flask drove the acceptor 27, and (iii) condensation of the remaining secondary
second glycosylation reaction to proceed, giving rise to the tri- OH of 25 with donor 28.17
saccharide intermediate 21 as the sole product after 1 h.
The one-pot synthesis of tetrasaccharide 24 required the
Finally, NIS–TfOH-mediated glycosylation of the remaining preparation of monosaccharide building blocks 25 and 27
secondary OH group of 21 with donor 18 at −20 to 0 °C within (Scheme 6). Regioselective 3-O-monoalkylation of the known phenyl
1 h completed the synthesis of the perbenzoylated 22. Purifi- 1-thio-6-O-trityl-α-D-mannopyranoside (29)18 with (2-naphthyl)-
cation of the crude mixture was achieved by silica-gel column methyl (Nap) group via dibutylstannylene acetal formation19
chromatography to provide tetrasaccharide 22 as a colorless oil followed by 2,4-O-protection with benzoyl chloride (BzCl)
in a good 52% overall yield based on 15. All glycosylations formed 31 in 80% yield over two steps. Then, removal of
leading to 22 proceeded with exclusive β-anomeric stereo- the trityl (Tr) protecting group of 31 with 80% HOAc gave
selectivity as a result of neighboring group participation of C-2 sugar 32 (70% yield) which was subsequently deprotected with
benzoyl groups.
DDQ to afford the corresponding monomer 25 (91% yield). In
This four-component one-pot protocol illustrates the useful- addition, the synthesis of compound 27 began with regioselec-
ness of the diol 15, which is able to function consecutively as tive 6-O-tritylation of the known 2,3,4,6-tetraol 3020 followed by
an acceptor, a donor, and an acceptor. Overall, when com- benzoylation to give mannose derivative 33 in 69% yield over
pared with the existing method, the approach greatly speeds two steps. Benzoate 32 was subsequently detritylated by acid
up the preparation of the target molecule since the entire syn- hydrolysis to afford the required 27 in an 85% yield.
thetic route can be accomplished without the need of protect-
ing group manipulation and intermediate work-up, and thus with building blocks 25–28 is shown in Scheme 7. Thus, 1.25
offers more practical access to the 3,6-branched equivalents of trichloroacetimidate 26 was regioselectively
arabinogalactan. coupled to 1.0 equivalent of diol acceptor 25 activated with a
The successful implementation of the one-pot protocol
a
A complete deprotection of 22 was accomplished in two catalytic amount of TMSOTf in the presence of 4 Å MS at
steps as follows. First, the benzoyl groups were cleaved by −80 °C in CH2Cl2. On gradual warming to approximately 0 °C,
Zemplén transesterification (NaOCH3, CH3OH, rt, 2 h) to a new spot, thiodisaccharide 34 was visible on TLC. Next, the
secure 23 in 90% yield. Next, the azido group of polyol 23 was reaction mixture was re-cooled to −20 °C and subsequent
reduced by Pd–C-catalyzed hydrogenolysis (H2, Pd–C, CH3OH, addition of the acceptor 27 (1.0 equiv.) along with NIS–TfOH
30 °C, 24 h) to produce the target tetrasaccharide 14 in 84% to the mixture drove the second glycosylation to proceed and
yield. The structures of the compounds 23 and 14 were con-
firmed by comparison of their 1H and 13C NMR data with
those published in literature.11e
To ascertain the universality of this method, we next
applied it to the synthesis of branched mannosides. The novel
heterotetrasaccharide motif 24 [α-D-Manp-(1→6)-[β-D-Galf-
(1→3)]-α-D-Manp-(1→6)-α-D-Manp, Scheme 5] representing the
repeating unit found in cell wall polysaccharide of the marine
fungus Lineolata rhizophorae15 was chosen as the target mole-
cule. Here, we present a three-step one-pot synthetic route to
24 by taking advantage of 3,6-di-OHs D-mannose thioglycoside
25 as a core building block. As shown in Scheme 5, the
sequence of its assembly also includes three consecutive Scheme 6 Preparation of monosaccharide building blocks 25 and 27.
3906 | Org. Biomol. Chem., 2013, 11, 3903–3917
This journal is © The Royal Society of Chemistry 2013

View Article Online
Organic & Biomolecular Chemistry
Paper
Scheme 7 Synthesis of tetragalactomannan 24.
produced the trisaccharide 35 as a main product after 1 h. stereochemistry.22 The structure of 36 was further confirmed
Finally, NIS–TfOH (cat.)-mediated reaction of the remaining by its high-resolution MS at m/z 2124.6001 (M + Na)+, which
secondary OH group of 35 with 1.2 equivalents of D-galactofur- was in accordance with the calculated exact mass of the mole-
anosyl thioglycoside donor 28 at −20 to 0 °C within one hour cule (calcd 2124.6008).
completed the synthesis of the desired molecule. However,
At last, deblocking of tetrasaccharide 36 was also effected
upon purification by silica gel column chromatography, the in two steps involving debenzoylation by Zemplén transesterifi-
protected tetrasaccharide 36 along with a byproduct 36a were cation (NaOMe, 85% yield) and the resulting polyol 37 was
acquired as colorless oils in 41% and 1.6% overall yield based subjected to catalytic hydrogenation to give the deprotected
on 25, respectively. The tetrasaccharide 36a turned out to be saccharide 24 (76% yield).
the result of the double glycosylation of 26 with diol 25 fol-
Success in the one-pot assembly of two branched tetrasac-
lowed by coupling with glycosyl alcohol 27. Further optimiz- charides led us to further explore the synthesis of sugar 38
ation of the reaction revealed that the amount of imidate 26 containing more bulky architecture by use of all aspects of our
was critical to improving the regioselectivity of the first glycosy- regioselective glycosylation chemistry. Hexamannan motif 38,
lation step. Consequently, less amount of 26 (1.15 equiv.) was which has α-(1→2) and α-(1→6) branch points at the central
used instead and the one-pot synthesis process was repeated D-mannopyranose unit, is linked to the core arabinomannan
under the above-described glycosylation conditions, which led (AM) domain from Mycobacterium tuberculosis, a human patho-
to the formation of 36 as the sole isolated product in an gen causing severe tuberculosis (TB) infection.23 Such 2,6-
improved 45% overall yield after standard work-up and silica branched mannan structures are very common and important
gel column chromatography.
component of cell surface polysaccharides of Mycobacterium
The structure of 36 was elucidated through the use of 1D species.24 Synthesis of the molecule and its analogues will
(1H, 13C, 400 MHz) and 2D NMR spectroscopy (gCOSY, HMQC, eventually help to find a carbohydrate antigen for vaccinations
and gHMBC) and ESI-MS spectral analysis. The determination against TB.25 In 2006, a thiol spacer-linked mannohexasacchar-
of the anomeric configuration of the mannopyranoses was per- ide fragment with the same sugar array of 38 was prepared by
1
formed according to Bock and Petersen.21 Accordingly, the H the Seeberger laboratory26 to be used as an intermediate in the
NMR spectrum of 36 showed the H-1 signals of the D-mannosi- total synthesis of a core AM dodecasaccharide. Despite the flex-
dic linkages appeared as a singlet at δH 5.27, 5.18, and ible synthetic strategy they employed provided a ready access
4.82 ppm. In the 13C NMR spectrum, three anomeric signals to several different TB AMs for structure–activity relationship
appeared at δC 98.0, 97.8, and 97.2 ppm, and the 1JCH coupling studies, the tedious protecting group manipulation and inter-
constants between anomeric carbons and hydrogens were mediate purifications reduced its efficiency. We envisioned
determined to be 170.9, 171.6, and 171.6 Hz. Thus, these data that the incorporation of our regioselective glycosylation
confirm that all the mannosidic linkages are α. On the other method in the synthesis of 38 could simplify the complicated
hand, the H-1 and C-1 signals of the galactofuranosyl residue synthetic operation. Here, we present a new three-step one-pot
appeared as a singlet at δH 5.62 and at δC 102.6 ppm, respect- procedure to 38 following the protocols similar to those used
ively. Both are characteristic of β-galactofuranoside anomeric for the preparation of protected 22 and 36. Retrosynthetic
This journal is © The Royal Society of Chemistry 2013
Org. Biomol. Chem., 2013, 11, 3903–3917 | 3907

View Article Online
Paper
Organic & Biomolecular Chemistry
Scheme 8 Retrosynthetic analysis of hexamannan 38.
analysis indicated that the construction of 38, as shown in in a 89% yield of disaccharide thioglycoside 47, which was
Scheme 8, required the utility of four building blocks – diman- easily elaborated into the corresponding 40 in 77% yield by
nosyl trichloroacetimidate donor 3927 and 6-OH mannose exposure to hydrazine monoacetate (N2H4·HOAc) at ambient
acceptor 27 for the respective non-reducing and reducing term- temperature in CH2Cl2.
inal α-(1→6) mannan backbone, dimannose thioglycoside 40
With all building blocks available, we carried out the one-
with 2′,6′-hydroxy unprotected for the central 2,6-O-bis-glycosy- pot glycosylation as shown in Scheme 10 to obtain 50, a fully
lated mannosyl block, and mannosyl thioglycoside donor 4128 protected precursor of 38. First, 39 (1.15 equiv.) was used to
for the α-(1→2) linked monosaccharide moiety.
regioselectively glycosylate with disaccharide diol 40 (1.0
The preparation of the core disaccharide alcohol 40 is equiv.) by activation with TMSOTf (cat.) in CH2Cl2 at −80 °C to
depicted in Scheme 9. Compound 4229 was reacted with ambient temperature to deliver tetrasaccharide 48 as the only
p-methylphenol (PMP-OH) under the promotion of boron tri- detected product. Next, the reaction mixture was re-cooled to
fluoride etherate (BF3·Et2O) to yield glycoside 43 in good yield. −20 °C and subsequent addition of the acceptor 27 (1.0 equiv.)
Conventional modification of the 2- and 6-O-acetyl groups of along with NIS–TfOH reagent system to the reaction mixture
43 into Lev (levulinyl) function by methanolysis using NaOCH3 drove the second glycosylation to proceed and provided the
in CH3OH and subsequent esterification with levulinic acid pentasaccharide intermediate 49 as a main product after being
(LevOH) furnished levulinate 44 in 95% over two steps. Oxi- stirred at room temperature for 4 h. Finally, reaction of the
dative cleavage of the p-methoxyphenyl (PMP) group at the remaining axial secondary OH of 49 with donor 41 (1.2 equiv.)
anomeric carbon of 44 using ceric ammonium nitrate (CAN) in under NIS–TfOH activation conditions completed the syn-
aqueous acetonitrile (CH3CN) at 0 °C yielded an intermediate thesis of the desired 50. After work-up and purification by
hemiacetal. Activation of the obtained crude hemiacetal was column chromatography, 50 was acquired as a colorless oil in
performed by treatment with trichloroacetonitrile (CCl3CN) an acceptable 47% overall yield based on 40. In contrast to the
and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in CH2Cl2, thus existing method, the usage of the regioselective one-pot glyco-
forming imidate 45 as a single diastereomer (56% yield, two sylation procedure realizes the rapid assembly of the target
steps from 44). TMSOTf-catalyzed chemoselective glycosylation 2,6-O-disubstituted mannan structure, thereby improving the
of the obtained 45 with mannosyl thioglycoside 4630 resulted overall synthetic efficiency. The configuration of all mannosi-
1
dic linkages could be assigned by the JCH coupling constants
and the chemical shifts of the anomeric protons. In the 13C
NMR spectrum, all the anomeric carbon resonances appeared
1
clearly in the range of δC 97.8 to 100.1 ppm, and the JCH
values between anomeric protons and carbons are 169.9,
170.7, 170.9, 171.6, 172.1, and 172.1 Hz, proving that all D-gly-
1
cosidic linkages are α. Furthermore, in the H NMR spectrum,
six anomeric proton resonances of the D-mannosidic linkages
appeared as singlets at δH 5.26, 5.16, 5.13, 5.11, 5.11, and
5.07 ppm. The structure of 50 was further deduced by its high-
resolution MS at m/z 3044.9050 (M + Na)+, which was identical
with the calculated exact mass of the molecule (calcd
3044.9046). Then, by means of the same two-step deprotec-
tion protocol, the target free homohexasaccharide 38 was
Scheme 9 Preparation of disaccharide building block 40.
3908 | Org. Biomol. Chem., 2013, 11, 3903–3917
synthesized via intermediate 51 as a white solid after size-
This journal is © The Royal Society of Chemistry 2013

View Article Online
Organic & Biomolecular Chemistry
Paper
Scheme 10 Synthesis of hexamannan 38.
exclusion chromatography on a Sephadex LH-20 column with 10% (v/v) H2SO4 in EtOH or by UV detection. Solvents
(Scheme 10).
used in the reactions were distilled from appropriate drying
agents prior to use. Silica gel (200–300 mesh) was used for
column chromatography. Optical rotations were measured at
20 1 °C for solutions in a 1.0 dm cell. Infrared absorption
spectra were recorded as KBr discs using a FT-IR spectropho-
Conclusions
In conclusion, presented here is the facile one-pot preparation tometer. High resolution mass spectra (HRMS) were acquired
1
of protected 3,6-branched D-galacto- and mannosides (22 and in the ESI-TOF mode. H and 13C NMR spectra were recorded
36), and 2,6-branched D-mannoside (50). The synthesis fea- on a 400 MHz spectrometer in CDCl3 with tetramethylsilane
tures the highly regioselective glycosylation of the central 3,6- (TMS) as internal reference. Chemical shifts (δ) are expressed
and 2,6-dihydroxy-D-galacto- and mannothioglycoside building in ppm downfield from the internal TMS absorption. Standard
units, by which sequential construction of three branched-type splitting patterns are abbreviated: s (singlet), d (doublet), t
glycosidic bonds are achieved in a one-pot manner. The incor- (triplet), q (quartet), m (multiplet). J values are given in Hz.
poration of the 3-aminopropyl function at the reducing end of
Phenyl 2,4-di-O-benzoyl-1-thio-β-D-galactopyranoside (15)
the obtained carbohydrate molecules will allow for the attach-
ment of these compounds to macromolecular devices for bio- A solution of 19 (832 mg, 0.965 mmol) in 80% aq AcOH
logical testing. This synthetic technology, which omits the (9.7 mL) was stirred at 80 °C for 3 h and the mixture was then
protection/deprotection manipulations and purification of syn- concentrated. The crude residue was dissolved in 4 : 1 DCM–
thetic intermediate and permits the rapid assembly of both MeOH (19.4 mL), and then DDQ (349 mg, 1.54 mmol) and
homo- and heteroglycan core structures, represents an impor- H2O (0.1 mL) were added. After being stirred for 1 d at room
tant advance toward streamlining the synthesis of biologically temperature, the mixture was evaporated. The residue was
relevant branched-chain oligosaccharides. Application of this diluted with CH2Cl2, washed with satd aq NaHCO3 and brine.
new pathway to the synthesis of structurally diverse oligosac- The organic layer was separated and dried over anhydrous
charide libraries is currently under way.
Na2SO4, filtered, and concentrated in vacuo. The residue was
purified by column chromatography (5 : 2, petroleum ether–
EtOAc) to afford 15 (368 mg, 79% for two steps) as an amor-
phous solid. Rf 0.30 (2 : 1, petroleum ether–EtOAc). [α]2D0 +9.5 (c
Experimental section
1
0.95, CHCl3); H NMR (400 MHz, CDCl3) δ 8.12 (d, 2H, J = 8.0
All non-aqueous reactions were performed under a nitrogen Hz), 7.92 (d, 2H, J = 8.0 Hz), 7.65 (t, 2H, J = 7.2 Hz), 7.44–7.52
atmosphere and monitored by thin layer chromatography (m, 6H), 7.29–7.40 (m, 3H), 5.57 (d, 1H, J = 3.6 Hz), 5.29 (t, 1H,
(TLC) using Silica Gel GF254 plates with detection by charring J = 9.6 Hz), 4.91 (d, 1H, J = 9.6 Hz), 4.09–4.14 (m, 1H), 3.92 (t,
This journal is © The Royal Society of Chemistry 2013
Org. Biomol. Chem., 2013, 11, 3903–3917 | 3909

View Article Online
Paper
Organic & Biomolecular Chemistry
1H, J = 7.2 Hz), 3.76–3.83 (m, 1H), 3.53–3.59 (m, 1H), 2.74–2.78 7.92–8.04 (m, 10H), 7.77 (d, 4H, J = 8.4 Hz), 7.35–7.62 (m,
(m, 2H); 13C NMR (100 MHz, CDCl3) δ 167.0, 166.6, 134.0, 23H), 7.21–7.26 (m, 4 H), 5.90 (d, 1H, J = 3.2 Hz), 5.85 (d, 1H,
133.7, 133.5, 130.7, 130.0, 129.9, 129.3, 128.8, 128.6, 128.5, J = 3.2 Hz), 5.65–5.71 (m, 3H), 5.50–5.57 (m, 2H), 5.32 (dd, 1H,
128.46, 128.4, 84.9, 77.7, 72.6, 71.4, 71.1, 60.5; IR (KBr) 3446, J = 4.0, 9.6 Hz), 4.71 (d, 1H, J = 8.0 Hz), 4.66 (d, 1H, J = 8.0 Hz),
2963, 2883, 1724, 1602, 1451, 1346 cm−1; HRMS (ESI) calcd for 4.62 (d, 1H, J = 8.0 Hz), 4.16–4.25 (m, 2H), 4.03–4.13 (m, 3H),
C26H24O7S [M + Na]+ 503.1140, found 503.1143.
3.94–3.98 (m, 2H), 3.90 (t, 1H, J = 6.0 Hz), 3.77 (dd, 1H, J = 7.2,
10.0 Hz), 3.64–3.69 (m, 1H), 3.61 (dd, 1H, J = 5.6, 10.0 Hz),
3.32–3.38 (m, 1H), 3.10 (t, 2H, J = 6.4 Hz), 2.77 (s 1H),
1.45–1.62 (m, 2H); 13C NMR (100 MHz, CDCl3) δ 166.3, 166.2,
Phenyl 2,3,4,6-tetra-O-benzoyl-β-D-galactopyranosyl-(1→6)-
2,3-di-O-benzoyl-1-thio-β-D-galactopyranoside (20)
A
mixture of trichloroacetimidate donor 16 (186 mg, 165.8, 165.4, 165.4, 165.3, 165.3, 165.3, 165.0, 133.5, 133.4,
0.251 mmol), diol thioglycoside acceptor 15 (95 mg, 133.3, 133.25, 133.2, 133.1, 133.0, 129.96, 129.8, 129.7, 129.6,
0.194 mmol), and freshly activated 4 Å molecular sieves 129.58, 129.5, 129.24, 129.2, 129.1, 128.9, 128.8, 128.61, 128.6,
(300 mg) in dry CH2Cl2 (4.0 mL) was cooled to −80 °C. The sus- 128.42, 128.4, 128.2, 128.16, 101.3, 100.8, 100.7, 73.1, 72.8,
pension was stirred for 15 min at the same temperature, then 72.3, 71.5, 71.1, 70.2, 69.8, 68.6, 67.8, 66.6, 66.2, 61.4, 47.7,
a solution of TMSOTf (4.6 μL, 0.025 mmol) in CH2Cl2 (1.0 mL) 28.6; IR (KBr) 3494, 2960, 2887, 2099, 1730, 1602, 1452,
was added dropwise. After being stirred for 1 h at the same 1108 cm−1; HRMS (ESI) calcd for C84H73N3O25 [M + Na]+
temperature, the mixture was warmed gradually to 0 °C. The 1546.4431, found 1546.4425.
reaction was quenched with triethylamine, diluted with
CH2Cl2 and filtered. The filtrate was concentrated to give a
residue, which was purified by column chromatography (8 : 3,
petroleum ether–EtOAc) to afford 20 as a colorless syrup
3-Azidopropyl 2,3,4,6-tetra-O-benzoyl-β-D-galactopyranosyl-
(1→6)-[2,3,5-tri-O-benzoyl-α-L-arabinofuranosyl-(1→3)]-2,4-di-
O-benzoyl-β-D-galactopyranosyl-(1→6)-2,3,4-tri-O-benzoyl-
β-D-galactopyranoside (22)
(185 mg, 89%). Rf 0.25 (2 : 1, petroleum ether–EtOAc).
[α]2D0 +51.0 (c 0.70, CHCl3); 1H NMR (400 MHz, CDCl3) δ 8.15 (d, Prepared from thioglycoside 18 (102 mg, 0.184 mmol) and
2H, J = 8.4 Hz), 8.09 (d, 2H, J = 8.4 Hz), 7.97–8.02 (m, 4H), 7.90 (d, acceptor 21 (217 mg, 0.142 mmol) following the procedure
2H, J = 8.4 Hz), 7.81 (d, 2H, J = 8.4 Hz), 7.24–7.66 (m, 23H), similar to that for 20→21. The resulting residue was purified
5.97 (d, 1H, J = 3.2 Hz), 5.84 (dd, 1H, J = 8.0, 10.4 Hz), 5.66 (d, by column chromatography (3 : 1, petroleum ether–EtOAc) to
1H, J = 2.8 Hz), 5.60 (dd, 1H, J = 3.2, 10.4 Hz), 5.25 (t, 1H, J = afford protected tetrasaccharide 22 (250 mg, 89%) as a color-
9.6 Hz), 4.93 (d, 1H, J = 8.0 Hz), 4.80 (d, 1H, J = 10.0 Hz), 4.44 less syrup. One-pot synthesis of the protected oligosaccharide
(dd, 1H, J = 8.4, 9.6 Hz), 4.22–4.22 (m, 2H), 3.99–4.13 (m, 3H), 22:
A
mixture of trichloroacetimidate 16 (312 mg,
4.44 (dd, 1H, J = 2.8, 10.4 Hz), 2.80 (d, 1H, J = 9.6 Hz); 13C 0.420 mmol), 3,6-diol thioglycoside 15 (166 mg, 0.340 mmol),
NMR (100 MHz, CDCl3) δ 166.5, 166.0, 165.9, 165.5, 165.47, and freshly activated 4 Å molecular sieves (800 mg) in dry
165.2, 133.9, 133.6, 133.5, 133.3, 133.25, 133.2, 131.0, 130.0, CH2Cl2 (7.4 mL) was stirred at room temperature for 15 min.
129.95, 129.92, 129.74, 129.72, 129.7, 129.4, 129.2, 129.0, Then the suspension was cooled to −80 °C, and a solution of
128.9, 128.6, 128.5, 128.4, 128.3, 128.2, 101.3, 84.9, 76.97, 72.8, TMSOTf (7.5 μL, 0.042 mmol) in CH2Cl2 (1 mL) was added
71.6, 71.3, 71.2, 70.8, 69.6, 68.1, 67.9, 61.7; IR (KBr) 3454, dropwise. After being stirred for 1 h at the same temperature,
2926, 2857, 1729, 1602, 1452, 1345 cm−1; HRMS (ESI) calcd for the reaction was gradually warmed to room temperature. The
C60H50O16S [M + Na]+ 1081.2717, found 1081.2717.
reaction mixture was stirred for a further 1 h at the same temp-
erature, at the end of which time TLC indicated the complete
consumption of the starting materials. The resulting slurry
was re-cooled to −20 °C, a solution of acceptor 17 (200 mg,
0.340 mmol) in CH2Cl2 (0.5 mL) was added. Then NIS (92 mg,
3-Azidopropyl 2,3,4,6-tetra-O-benzoyl-β-D-galactopyranosyl-
(1→6)-2,4-di-O-benzoyl-1-thio-β-D-galactopyranosyl-(1→6)-
2,3,4-tri-O-benzoyl-β-D-galactopyranoside (21)
A mixture of donor 20 (295 mg, 0.276 mmol), acceptor 17 0.410 mmol) and TfOH (3.0 μL, 0.034 mmol) were added at
(144 mg, 0.251 mmol), and freshly activated 4 Å molecular −20 °C. The reaction mixture was stirred for 1 h at 0 °C, at the
sieves (450 mg) in dry CH2Cl2 (10 mL) was cooled to −20 °C. end of which time TLC indicated it was finished. A solution of
The suspension was stirred for 15 min at −20 °C, then NIS thioglycoside donor 18 (232 mg, 0.420 mmol) in CH2Cl2
(74 mg, 0.330 mmol), TfOH (2.5 μL, 0.028 mmol) were added (0.5 mL) was added when the temperature was re-cooled to
and the resulting mixture was gradually warmed to 0 °C. The −20 °C. Then NIS (113 mg, 0.504 mmol) and TfOH (4 μL,
reaction mixture was stirred for 1 h at the same temperature, 0.042 mmol) were added. After being stirred for 1 h at 0 °C,
at the end of which time TLC indicated the complete con- the reaction was quenched with triethylamine, diluted with
sumption of the starting materials. The reaction was quenched CH2Cl2 and filtered. The filtrate was concentrated to give a
with triethylamine, diluted with CH2Cl2 and filtered. The fil- residue, which was purified by column chromatography (2 : 1,
trate was concentrated to give a residue, which was purified by petroleum ether–acetone) to afford 22 (349 mg, 52% for three
column chromatography (2 : 1, petroleum ether–EtOAc) to steps based on 17) as an amorphous solid. Rf 0.18 (3 : 1, pet-
afford protected trisaccharide 21 (361 mg, 94%) as a colorless roleum ether–EtOAc). [α]2D0 +58.0 (c 0.70, CHCl3); 1H NMR
syrup. Rf 0.18 (2 : 1, petroleum ether–EtOAc). [α]2D0 +81.5 (c 1.00, (400 MHz, CDCl3) δ 7.99–8.11 (m, 10H), 7.90–7.95 (m, 8H),
1
CHCl3); H NMR (400 MHz, CDCl3) δ 8.12 (d, 4H, J = 8.4 Hz), 7.87 (d, 2H, J = 7.6 Hz), 7.77 (d, 2H, J = 7.6 Hz), 7.76 (d, 2H,
3910 | Org. Biomol. Chem., 2013, 11, 3903–3917
This journal is © The Royal Society of Chemistry 2013

View Article Online
Organic & Biomolecular Chemistry
Paper
J = 7.6 Hz), 7.15–7.56 (m, 36H), 5.83–5.87 (m, 2H), 5.82 (d, 1H, J = The obtained residue was dissolved in dry DMF (49 mL). To
3.2 Hz), 5.63–5.71 (m, 3H), 5.49–5.55 (m, 3H), 5.30 (s, 1 H), the resulting solution were added CsF (1.45 g, 9.54 mmol) and
5.25 (s, 1 H), 4.97–5.03 (m, 2H), 4.72–4.76 (m, 1H), 4.74 (d, 1H, 2-naphthylmethyl bromide (2.10 g, 9.59 mmol). After being
J = 8.0 Hz), 4.63 (d, 1H, J = 8.0 Hz), 4.60 (d, 1H, J = 8.0 Hz), stirred for 1 d at room temperature, the mixture was diluted
4.06–4.18 (m, 5H), 3.95–4.01 (m, 3 H), 3.56–3.74 (m, 3H), with CH2Cl2, washed with water and brine. The organic layer
3.26–3.31 (m, 1H), 3.06 (t, 1H, J = 6.8 Hz), 1.36–1.58 (m, 2H); was separated and dried over anhydrous Na2SO4, filtered, and
13C NMR (100 MHz, CDCl3) δ 166.1, 165.8, 165.7, 165.44, concentrated. The residue was directly used for the next step
165.4, 165.3, 165.3, 165.25, 165.2, 165.0, 164.9, 164.6, 133.3, without further purification. To a solution of the obtained
133.15, 133.1, 133.0, 132.9, 132.8, 130.1, 130.0, 129.8, 129.7, residue in pyridine (49 mL) was added benzoyl bromide
129.6, 129.55, 129.3, 129.2, 129.1, 128.9, 128.8, 128.7, 128.6, (4.5 mL, 38.8 mmol). After being stirred for 2 h at 50 °C, the
128.4, 128.39, 128.3, 128.2, 128.0, 107.6, 101.3, 101.2, 100.5, reaction was quenched with methanol, diluted with CH2Cl2,
82.5, 81.5, 77.5, 76.0, 73.0, 72.7, 71.6, 71.6, 71.5, 71.0, 69.84, and then the mixture was washed with aq 1 M HCl, satd aq
69.8, 69.5, 68.8, 68.1, 67.6, 66.3, 66.1, 63.2, 61.4, 47.7, 28.6; IR NaHCO3 and brine. The organic layer was separated and dried
(KBr) 2931, 2858, 2099, 1729, 1602, 1452, 1108 cm−1; HRMS over anhydrous Na2SO4, filtered, and concentrated in vacuo.
(ESI) calcd for C110H93N3O32 [M + Na]+ 1990.5640, found The residue was purified by column chromatography (10 : 1,
1990.5641.
petroleum ether–EtOAc) to afford compound 31 (3.354 g, 80%)
as a pale yellow oil. Rf 0.45 (4 : 1, petroleum ether–EtOAc).
[α]2D0 +14.2 (c 1.40, CHCl3); 1H NMR (400 MHz, CDCl3) δ 8.13–8.17
(m, 3H), 7.71–7.80 (m, 3H), 7.57–7.65 (m, 5H), 7.36–7.53 (m,
3-Azidopropyl β-D-galactopyranosyl-(1→6)-[α-L-arabinofuranosyl-
(1→3)]-β-D-galactopyranosyl-(1→6)-β-D-galactopyranoside (23)11e
To a stirred solution of the 22 (290 mg, 0.147 mmol) in 14H), 7.20–7.29 (m, 4H), 7.07–7.15 (m, 8H), 5.98 (dd, 1H, J =
CH3OH (14.7 mL) was added NaOCH3 (29 mg) at 0 °C, and the 1.6, 3.2 Hz), 5.81 (t, 1H, J = 10.0 Hz), 5.75 (d, 1H, J = 1.6 Hz),
resulting mixture was warmed gradually to room temperature. 4.85 (d, 1H, J = 12.0 Hz), 4.67 (d, 1H, J = 12.0 Hz), 4.51–4.56
The mixture was stirred for 2 h at the same temperature at the (m, 1H), 4.07 (dd, 1H, J = 3.2, 9.6 Hz), 3.29–3.34 (m, 2H); 13C
end of which time TLC indicated it was finished. The reaction NMR (100 MHz, CDCl3) δ 165.8, 165.1, 134.7, 133.6, 133.51,
was quenched with acetic acid and the resulting mixture was 133.5, 133.4, 133.0, 132.96, 132.9, 131.8, 130.2, 130.0, 129.8,
concentrated to dryness. The resulting residue was purified by 129.6, 129.5, 129.1, 128.6, 128.5, 128.4, 128.1, 127.9, 127.7,
Sephadex LH-20 (1 : 2, CH2Cl2–MeOH) to afford compound 23 127.6, 127.5, 126.8, 126.7, 125.9, 125.8, 86.1, 74.8, 71.7, 71.0,
(95 mg, 90%) as a gray amorphous solid. [α]2D0 −22.4 (c 0.20, 70.3, 68.3, 62.7; IR (KBr) 2924, 2879, 1727, 1599, 1583, 1447,
1
H2O); H NMR (400 MHz, D2O) δ 5.28 (s, 1H), 4.60 (d, 1H, J = 1346 cm−1; HRMS (ESI) calcd for C56H46O7S [M + Na]+
8.0 Hz), 4.52 (d, 1H, J = 8.0 Hz), 4.48 (d, 1H, J = 8.0 Hz), 4.22 (s, 885.2862, found 885.2863.
1H), 4.16–4.26 (m, 2H), 3.68–4.16 (m, 20H), 3.57–3.62 (m, 2H),
Phenyl 2,4-di-O-benzoyl-3-O-(2-naphthylmethyl)-1-thio-
α-D-mannopyranoside (32)
3.54 (t, 2H, J = 6.8 Hz), 1.94–2.00 (m, 2H); 13C NMR (100 MHz,
D2O) δ 111.7, 105.8, 105.5, 105.2, 86.2, 83.7, 82.6, 78.9, 77.5,
76.2, 75.9, 75.1, 75.0, 73.1, 72.2, 71.6, 71.4, 71.0, 70.8, 69.8, A solution of 31 (3.354 g, 3.89 mmol) in 80% aq AcOH (78 mL)
63.6, 63.4, 50.3, 30.6.
was stirred at 80 °C for 3 h, then the mixture was concentrated.
The crude residue was purified by column chromatography
(6 : 1, petroleum ether–EtOAc) to afford 32 as a colorless syrup
(1.69 g, 70.0%). Rf 0.50 (2 : 1, petroleum ether–EtOAc).
3-Aminopropyl β-D-galactopyranosyl-(1→6)-[α-L-arabinofuranosyl-
(1→3)]-β-D-galactopyranosyl-(1→6)-β-D-galactopyranoside (14)11e
To a solution of compound 23 (85 mg, 0.118 mmol) in MeOH [α]2D0 +9.7 (c 1.50, CHCl3); 1H NMR (400 MHz, CDCl3) δ 8.18 (d, 2H,
(11.8 mL) was added 10% Pd/C (17 mg). After being stirred for J = 8.0 Hz), 8.00 (d, 2H, J = 8.0 Hz), 7.79 (d, 1H, J = 8.4 Hz), 7.71
24 h under H2 at room temperature, the mixture was filtered (s 1H), 7.58–7.65 (m, 4H), 7.41–7.54 (m, 9H), 7.26–7.35 (m,
through sephadex LH-20 (MeOH) to afford compound 14 4H), 6.04 (dd, 1H, J = 1.6, 3.2 Hz), 5.78 (d, 1H, J = 1.6 Hz), 5.77
(69 mg, 84%) as a gray amorphous solid. [α]2D0 −23.8 (c 0.10, (t, 1H, J = 10.0 Hz), 4.92 (d, 1H, J = 12.4 Hz), 4.75 (d, 1H, J =
1
H2O); H NMR (400 MHz, D2O) δ 5.27 (s, 1H), 4.58 (d, 1H, J = 12.4 Hz), 4.39 (dt, 1H, J = 3.2, 10.0 Hz), 4.26 (dd, 1H, J = 3.2,
7.6 Hz), 4.50 (d, 1H, J = 6.8 Hz), 4.48 (d, 1H, J = 6.8 Hz), 4.25 (s, 9.6 Hz), 3.73–3.80 (m, 2H), 2.64 (s 1H); 13C NMR (100 MHz,
1H), 3.66–4.20 (m, 24H), 3.55–3.60 (m, 2H), 3.16 (t, 2H, J = CDCl3) δ 166.4, 165.6, 134.5, 133.5, 133.4, 133.0, 132.9, 132.8,
6.8 Hz), 2.01–2.07 (m, 2H); 13C NMR (100 MHz, D2O) δ 111.6, 131.8, 129.93, 129.9, 129.2, 129.16, 128.9, 128.5, 128.4, 128.2,
105.7, 105.4, 105.1, 86.1, 83.6, 82.5, 78.8, 77.5, 76.0, 75.9, 75.0, 127.9, 127.8, 127.5, 127.0, 126.0, 125.94, 125.9, 86.2, 74.1, 72.1,
74.8, 73.0, 72.95, 72.1, 71.7, 71.4, 70.9, 70.7, 70.3, 63.5, 63.3, 71.1, 70.0, 68.3, 61.3; IR (KBr) 3526, 2926, 2877, 1724, 1602,
39.9, 29.5.
1452, 1345 cm−1; HRMS (ESI) calcd for C37H32O7S [M + Na]+
643.1766, found 643.1770.
Phenyl 2,4-di-O-benzoyl-3-O-(2-naphthylmethyl)-6-O-trityl-
1-thio-α-D-mannopyranoside (31)
Phenyl 2,4-di-O-benzoyl-1-thio-α-D-mannopyranoside (25)
To a solution of compound 29 (2.51 g, 4.88 mmol) in toluene To a solution of 32 (1.6 g, 2.58 mmol) in 4 : 1 DCM–MeOH
(49 mL) was added dibutyltin oxide (2.1 g, 8.43 mmol). After (52 mL) were added DDQ (932 mg, 4.12 mmol) and H2O
being stirred for 3 h at 110 °C, the mixture was concentrated. (0.25 mL). After being stirred for 1 d at room temperature, the
This journal is © The Royal Society of Chemistry 2013
Org. Biomol. Chem., 2013, 11, 3903–3917 | 3911

View Article Online
Paper
Organic & Biomolecular Chemistry
mixture was evaporated. The residue was diluted with CH2Cl2, chromatography (7 : 2, petroleum ether–EtOAc) to afford com-
washed with satd aq NaHCO3 and brine. The organic layer was pound 27 (1.03 g, 85%) as colorless syrups. Rf 0.52 (3 : 2, pet-
separated and dried over anhydrous Na2SO4, filtered, and con- roleum ether–EtOAc). [α]2D0 −103.4 (c 1.35, CHCl3); 1H NMR
centrated in vacuo. The residue was purified by column chrom- (400 MHz, CDCl3) δ 8.12 (d, 2H, J = 8.4 Hz), 8.00 (d, 2H, J =
atography (7 : 2, petroleum ether–EtOAc) to yield 25 (1.13 g, 8.4 Hz), 7.84 (d, 2H, J = 8.4 Hz), 7.38–7.64 (m, 7H), 7.25–7.29
91%) as an amorphous solid. Rf 0.40 (2 : 1, petroleum ether– (m, 2H), 5.98 (dd, 1H, J = 3.6, 10.0 Hz), 5.87 (t, 1H, J = 10.0 Hz),
EtOAc). Rf 0.40 (2 : 1, petroleum ether–EtOAc). [α]2D0 +99.1 (c 5.68 (q, 1H, J = 3.6 Hz), 5.12 (s, 1H), 4.02 (dd, 1H, J = 2.0, 8.8
1.70, CHCl3); 1H NMR (400 MHz, CDCl3) δ 8.08 (s, 2H), 8.06 (s, Hz), 3.92–3.96 (m, 1H), 3.76–3.87 (m, 2H), 3.61–3.66 (m, 1H),
2H), 7.41–7.62 (m, 8H), 7.25–7.34 (m, 3H), 5.71 (s, 1H), 5.80 (t, 3.54 (t, 2H, J = 6.4 Hz), 2.65 (dd, 1H, J = 6.0, 8.4 Hz), 1.95–2.02
1H, J = 1.6 Hz), 4.39–4.47 (m, 2H), 3.73–3.79 (m, 2H), 2.95 (s, (m, 2H); 13C NMR (100 MHz, CDCl3) δ 166.5, 165.5, 165.0,
1H), 2.43 (s, 1H); 13C NMR (100 MHz, CDCl3) δ 167.2, 165.8, 133.7, 133.6, 133.2, 129.9, 129.6, 129.2, 129.0, 128.6, 128.5,
133.7, 133.6, 132.8, 132.0, 129.9, 129.8, 129.2, 129.0, 128.8, 128.3, 127.9, 127.0, 97.8, 71.1, 70.5, 69.6, 67.1, 65.0, 61.3, 48.2,
128.51, 128.5, 128.0, 85.9, 74.2, 71.6, 70.3, 69.3, 61.3; IR (KBr) 28.7; IR (KBr) 3529, 2929, 2883, 1729, 1602, 1452, 1112 cm−1
;
3447, 2923, 2877, 1722, 1602, 1451 cm−1; HRMS (ESI) calcd for HRMS (ESI) calcd for C30H29N3O9 [M + Na]+ 598.1801, found
C26H24O7S [M + Na]+ 503.1140, found 503.1140.
598.1802.
3-Azidopropyl 2,3,4-tri-O-benzoyl-6-O-trityl-α-D-
mannopyranoside (33)
One-pot synthesis of 3-azidopropyl 2,3,4,6-tetra-O-benzoyl-
α-D-mannopyranosyl-(1→6)-[2,3,5,6-tetra-O-benzoyl-β-D-
galactofuranosyl-(1→3)]-2,4-di-O-benzoyl-α-D-mannopyranosyl-
(1→6)-2,3,4-tri-O-benzoyl-α-D-mannopyranoside (36)
To a solution of 30 (1.01 g, 3.84 mmol) in pyridine (50 mL)
were added Ph3CCl (2.68 g, 9.60 mmol) and DMAP (46 mg,
0.38 mmol). The mixture was stirred for 1 d at 80 °C. Then Using the same procedures as described for the one-pot prepa-
benzoyl chloride (2.70 mL, 23.0 mmol) was added at 0 °C. The ration of 22, trichloroacetimidate 26 (242 mg, 0.326 mmol),
resulting mixture was warmed gradually to 55 °C. The reaction 3,6-diol thioglycoside 25 (136 mg, 0.283 mmol) were coupled
was stirred for 2 h at the same temperature, at the end of first by activation with TMSOTf (6.0 μL, 0.033 mmol), then the
which time TLC indicated it was finished. The reaction was resulting disaccharide thioglycoside 34 was glycosylated with
quenched with methanol, diluted with CH2Cl2, and then the the acceptor 27 (162 mg, 0.283 mmol) promoted by NIS
mixture was washed with aq 1 M HCl, satd aq NaHCO3 and (76 mg, 0.340 mmol) and TfOH (2.5 μL, 0.028 mmol) to give
brine. The organic layer was separated and dried over anhy- trisaccharide 35. Finally, thioglycoside donor 28 (229 mg,
drous Na2SO4, filtered, and concentrated in vacuo. The residue 0.326 mmol) and NIS (49.1 mg, 0.218 mmol)–TfOH (1.6 μL,
was purified by column chromatography (8 : 1, petroleum 0.018 mmol) were added to glycosylate with 35. The resulting
ether–EtOAc) to afford compound 33 (2.17 g, 69% for two residue was purified by column chromatograph (2 : 1, pet-
steps) as a yellow syrups. Rf 0.55 (3 : 1, petroleum ether–EtOAc). roleum ether–acetone) to afford 36 (268 mg, 45% for three
1
[α]2D0 +99.1 (c 1.70, CHCl3); H NMR (400 MHz, CDCl3) δ 8.19 steps based on 25) as a colorless syrup. Data for disaccharide
(d, 2H, J = 7.6 Hz), 7.87 (d, 2H, J = 7.6 Hz), 7.77 (d, 2H, J = intermediate 34: Rf 0.25 (3 : 1, petroleum ether–EtOAc). [α]D20
7.6 Hz), 7.65 (t, 1H, J = 7.2 Hz), 7.41–7.52 (m, 10H), 7.26–7.35 (m, −12.6 (c 1.20, CHCl3); 1H NMR (400 MHz, CDCl3) δ 8.22 (d, 2H,
4H), 7.09–7.18 (m, 9H), 6.10 (t, 1H, J = 10.0 Hz), 5.80 (dd, 1H, J = 8.0 Hz), 8.13 (d, 2H, J = 8.0 Hz), 8.00–8.05 (m, 6H), 7.89 (d,
J = 2.8, 10.0 Hz), 5.72 (s, 1H), 5.16 (s, 1H), 4.21 (dd, 1H, J = 2.8, 2H, J = 8.0 Hz), 7.25–7.63 (m, 18H), 6.14 (t, 1H, J = 10.0 Hz),
10.0 Hz), 3.98–4.03 (m, 1H), 3.65–3.71 (m, 1H), 3.55 (t, 2H, J = 6.04 (dd, 1H, J = 3.2, 10.0 Hz), 8.13 (t, 1H, J = 10.0 Hz),
6.4 Hz), 3.44 (d, 1H, J = 10.4 Hz), 3.32 (dd, 1H, J = 4.8, 10.4 Hz), 5.79–5.83 (m, 3H), 5.14 (s, 1H), 4.87 (dd, 1H, J = 3.2, 10.0 Hz),
2.02 (t, 2H, J = 6.0 Hz); 13C NMR (100 MHz, CDCl3) δ 165.6, 4.46 (td, 1H, J = 3.2, 4.8 Hz), 4.39 (dd, 1H, J = 2.0, 12.0 Hz),
165.5, 165.0, 143.6, 133.4, 133.1, 133.0, 129.9, 129.7, 129.6, 4.23 (dd, 2H, J = 4.0, 10.8 Hz), 4.14 (dd, 1H, J = 4.0, 12.0 Hz),
129.4, 129.2, 129.1, 128.6, 128.5, 128.2, 128.1, 127.7, 126.8, 3.79 (d, 1H, J = 10.8 Hz), 2.85 (d, 1H, J = 8.4 Hz); 13C NMR
97.6, 70.7, 70.5, 66.7, 64.7, 62.1, 48.3, 28.8; IR (KBr) 2930, (100 MHz, CDCl3) δ 166.8, 166.0, 165.9, 165.4, 165.13, 165.1,
2877, 2098, 1725, 1601, 1452, 1112 cm−1; HRMS (ESI) calcd for 133.8, 133.5, 133.45, 133.4, 133.1, 133.0, 131.9, 130.0, 129.9,
C49H43N3O9 [M + Na]+ 840.2897, found 840.2901.
129.87, 129.8, 129.75, 129.7, 129.68, 129.6, 129.3, 129.2,
129.11, 129.1, 128.94, 128.9, 128.8, 128.6, 128.5, 128.4, 128.38,
128.3, 128.0, 97.7, 86.3, 74.4, 70.1, 70.1, 70.1, 70.0, 69.8, 68.8,
3-Azidopropyl 2,3,4-tri-O-benzoyl-α-D-mannopyranoside (27)
To a solution of 33 (1.72 g, 2.11 mmol) in CH3CN (21 mL) was 66.6, 66.3, 62.2; IR (KBr) 3437, 2926, 2872, 1728, 1602, 1451,
added CF3COOH (5.4 mL) dropwise at 0 °C and the resulting 1369 cm−1; HRMS (ESI) calcd for C60H50O16S [M + Na]+
mixture was warmed gradually to 35 °C. The reaction was 1081.2717, found 1081.2721. Data for trisaccharide intermedi-
stirred for 4 h at the same temperature, at the end of which ate 35: Rf 0.28 (2 : 1, petroleum ether–EtOAc). [α]2D0 −30.3 (c
1
time TLC indicated it was finished. The reaction was quenched 1.20, CHCl3); H NMR (400 MHz, CDCl3) δ 8.13–8.18 (m, 6H),
with methanol, diluted with CH2Cl2, and then the mixture was 7.97–8.04 (m, 8H), 7.85–7.90 (m, 4H), 7.26–7.58 (m, 27H), 6.23
washed with satd aq NaHCO3 and brine. The organic layer was (t, 1H, J = 10.0 Hz), 6.07 (t, 1H, J = 10.0 Hz), 5.94 (dd, 1H, J =
separated and dried over anhydrous Na2SO4, filtered, and con- 2.8, 11.6 Hz), 5.93 (dd, 1H, J = 2.0, 9.6 Hz), 5.72–5.77 (m, 2 H),
centrated in vacuo. The residue was purified by column 5.63 (d, 1H, J = 2.4 Hz), 5.55 (t, 1H, J = 2.0 Hz), 5.19 (s, 1H),
3912 | Org. Biomol. Chem., 2013, 11, 3903–3917
This journal is © The Royal Society of Chemistry 2013

View Article Online
Organic & Biomolecular Chemistry
Paper
5.16 (d, 1H, J = 1.2 Hz), 4.86 (d, 1H, J = 1.2 Hz), 4.62 (td, 1H, J = 3.6, 129.22, 129.14, 129.1, 129.04, 129.0, 128.9, 128.3, 128.23,
10.0 Hz), 4.43 (d, 1H, J = 10.0 Hz), 4.39 (dd, 1H, J = 2.0, 8.0 Hz), 128.22, 128.2, 128.1, 99.8, 97.8, 97.4, 77.5, 71.8, 70.43, 70.4,
4.22–4.26 (m, 3H), 4.13 (dd, 1H, J = 4.0, 12.0 Hz), 3.95–4.00 70.2, 70.12, 70.05, 69.5, 69.3, 68.7, 68.0, 66.5, 66.4, 66.1, 66.0,
(m, 2H), 3.84 (d, 1H, J = 9.6 Hz), 3.65–3.70 (m, 1H), 65.0, 62.4, 62.3, 48.1, 29.5; IR (KBr) 2931, 2858, 2099, 1726,
3.51 (t, 2H, J = 6.4 Hz), 3.45 (d, 1H, J = 10.0 Hz), 2.51 (d, 1H, J = 1602, 1452, 1119 cm−1; HRMS (ESI) calcd for C118H99N3O34
8.4 Hz), 1.99 (t, 2H, J = 6.4 Hz); 13C NMR (100 MHz, CDCl3) δ [M + Na]+ 2124.6008, found 2124.5999.
166.7, 165.98, 165.95, 165.56, 165.53, 165.5, 165.3, 165.2,
165.0, 133.7, 133.6, 133.57, 133.5, 133.4, 133.38, 133.2, 133.01,
133.0, 129.9, 129.87, 129.8, 129.77, 129.76, 129.7, 129.65,
3-Azidopropyl α-D-mannopyranosyl-(1→6)-[β-D-arabinofuranosyl-
(1→3)]-α-D-mannopyranosyl-(1→6)-α-D-mannopyranoside (37)
129.3, 129.2, 129.17, 129.1, 129.0, 128.98, 128.73, 128.7, 128.5, Prepared from 36 (210 mg, 0.100 mmol) following the pro-
128.4, 128.3, 128.29, 97.8, 97.77, 97.2, 72.7, 70.4, 70.3, 70.1, cedure similar to that for 22→23. The resulting residue was
69.9, 69.89, 69.5, 69.2, 69.1, 68.7, 66.5, 66.4, 66.1, 65.8, 65.4, purified by Sephadex LH-20 (1 : 2, CH2Cl2–MeOH) to afford
65.0, 62.2, 48.2, 28.8; IR (KBr) 2925, 2875, 2098, 1727, 1601, compound 37 as an amorphous solid (64 mg, 85%). [α]2D0 +26.4
1451, 1106 cm−1; HRMS (ESI) calcd for C84H73N3O25 [M + Na]+ (c 0.80, MeOH); 1H NMR (400 MHz, D2O) δ 5.22 (s, 1H), 5.00 (s,
1546.4431, found 1546.4425. Date for tetrasaccharide 36: Rf 1H), 4.98 (s, 1H), 4.93 (s, 1H), 4.26 (s, 1H), 4.22 (s, 1H),
0.30 (1 : 1, petroleum ether–EtOAc). [α]2D0 −25.2 (c 1.00, CHCl3); 4.11–4.15 (m, 2H), 3.65–4.05 (m, 22H), 3.60–3.75 (m, 4H), 3.55
1H NMR (400 MHz, CDCl3) δ 8.22 (d, 2H, J = 7.2 Hz), 8.19 (d, (t, 2H, J = 6.0 Hz), 1.98 (s, 2H); 13C NMR (100 MHz, D2O) δ
2H, J = 7.2 Hz), 8.14 (d, 2H, J = 7.2 Hz), 8.09 (d, 2H, J = 7.2 Hz), 102.5, 98.1, 97.5, 97.3, 81.0, 79.6, 75.2, 73.7, 70.8, 69.1, 69.0,
8.04 (d, 2H, J = 7.6 Hz), 7.99 (d, 4H, J = 8.0 Hz), 7.94 (d, 2H, J = 68.8, 68.1, 64.8, 63.9, 63.4, 62.9, 60.9, 60.0, 46.3, 26.0; HRMS
8.0 Hz), 7.82–7.92 (m, 8H), 7.77 (d, 2H, J = 7.2 Hz), 7.13–7.61 (ESI) calcd for C27H47N3O21 [M + Na]+ 772.2600, found 772.2593.
(m, 39H), 6.37 (t, 1H, J = 10.0 Hz), 6.14 (t, 1H, J = 10.0 Hz),
3-Aminopropyl α-D-mannopyranosyl-(1→6)-[β-D-arabinofuranosyl-
5.93–6.00 (m, 3H), 5.88 (d, 1H, J = 1.6 Hz), 5.83 (t, 1H, J = 10.0
(1→3)]-α-D-mannopyranosyl-(1→6)-α-D-mannopyranoside (24)
Hz), 5.78 (d, 1H, J = 1.6 Hz), 5.64 (s, 1H), 5.62 (d, 1H, J = 2.0 Hz),
5.47 (d, 1H, J = 4.8 Hz), 5.35 (s, 1H), 5.27 (s, 1H), 5.18 (s, 1H), Prepared from 37 (42 mg, 0.056 mmol) following the pro-
4.97 (dd, 1H, J = 2.4, 12.0 Hz), 4.89 (dd, 1H, J = 3.2, 10.0 Hz), cedure similar to that for 23→14. The mixture was filtered
4.82 (s, 1H), 4.68 (q, 1H, J = 4.0 Hz), 4.52–4.58 (m, 2H), through Sephadex LH-20 (MeOH). The filtrate was concen-
4.44–4.48 (m, 2H), 4.37 (td, 1H, J = 4.0, 10.8 Hz), 4.12–4.16 (m, trated. The residue was lyophilized to give 24 (31 mg, 76%) as
1H), 3.91–4.03 (m, 3H), 3.66–3.71 (m, 1H), 3.49 (t, 2H, J = 6.8 a white solid. [α]2D0 +21.0 (c 0.10, H2O); 1H NMR (400 MHz,
Hz), 3.39 (d, 1H, J = 9.2 Hz), 1.99 (t, 2H, J = 6.8 Hz); 13C NMR D2O) δ 5.20 (s, 1H), 4.98 (s, 1H), 4.96 (s, 1H), 4.91 (s, 1H), 4.25
(100 MHz, CDCl3) δ 166.0, 165.9, 165.61, 165.6, 165.59, 165.5, (s, 1H), 4.21 (s, 1H), 3.60–4.13 (m, 24H), 3.15–3.25 (m, 2H),
165.3, 165.26, 165.2, 165.07, 165.06, 164.6, 133.6, 133.5, 133.4, 2.02–2.10 (m, 2H); 13C NMR (100 MHz, D2O) δ 106.8, 102.4,
133.3, 133.2, 133.1, 133.05, 133.02, 133.0, 132.8, 130.1, 130.0, 101.9, 101.7, 85.4, 83.9, 79.5, 78.0, 75.1, 73.3, 73.2, 73.0, 72.4,
129.95, 129.83, 129.8, 129.7, 129.68, 129.6, 129.5, 129.4, 129.3, 69.1, 69.0, 68.4, 68.1, 67.8, 67.7, 67.1, 65.3, 46.1, 36.2, 28.5;
129.2, 129.1, 129.0, 128.6, 128.5, 128.4, 128.3, 128.2, 128.16, HRMS (ESI) calcd for C27H49NO21 [M + H]+ 724.2875, found
128.0, 102.6, 98.0, 97.8, 97.2, 82.4, 81.5, 77.3, 71.3, 70.6, 70.4, 724.2908.
70.2, 70.1, 70.0, 69.6, 69.4, 68.7, 67.9, 67.1, 66.5, 66.1, 66.0,
65.0, 64.1, 63.2, 62.5, 48.1, 28.8; IR (KBr) 2926, 2857, 2099,
p-Methoxyphenyl 2,6-di-O-acetyl-3,4-di-O-benzyl-α-D-
mannopyranoside (43)
1729, 1602, 1452, 1110 cm−1
C
; HRMS (ESI) calcd for
118H99N3O34 [M + Na]+ 2124.6008, found 2124.6001. Date for To a solution of 42 (1.76 g, 3.62 mmol) in CH2Cl2 (18 mL) was
byproduct 36a: Rf 0.28 (1 : 1, petroleum ether–EtOAc). added PMPOH (0.75 g, 6.05 mmol) at 0 °C. The reaction
1
[α]2D0 −42.4 (c 0.50, CHCl3); H NMR (400 MHz, CDCl3) δ 8.32 (d, mixture was stirred for 15 min at 0 °C, then BF3·Et2O (0.75 mL,
2H, J = 7.2 Hz), 8.19 (d, 2H, J = 7.2 Hz), 8.24 (d, 2H, J = 7.6 Hz), 5.94 mmol) was slowly added and the resulting mixture was
8.04–8.07 (m, 8H), 8.04 (t, 4H, J = 7.2 Hz), 7.95 (d, 2H, J = 7.6 warmed gradually to room temperature. The mixture was
Hz), 7.89 (d, 2H, J = 7.6 Hz), 7.86 (d, 2H, J = 7.6 Hz), 7.73 (d, stirred for 2 h at the same temperature, at the end of which
2H, J = 7.6 Hz), 7.69 (d, 2H, J = 7.2 Hz), 7.53–7.60 (m, 6H), time TLC indicated that it was finished. The reaction was
7.17–7.52 (m, 32H), 7.14 (t, 1H, J = 7.2 Hz), 6.21 (t, 1H, J = 10.0 Hz), quenched with Et3N and the mixture was concentrated. The
6.13 (td, 2H, J = 3.2, 10.0 Hz), 5.90–5.94 (m, 3H), 5.84 (s, crude product was purified by column chromatography (6 : 1,
1H), 5.75 (s, 1H), 5.75 (dd, 1H, J = 2.8, 10.0 Hz), 5.56 (s, 1H), petroleum ether–EtOAc) to give 43 as a colorless syrup (1.73 g,
5.44 (s, 1H), 5.38 (s, 1H), 5.26 (s, 1H), 5.14 (s, 1H), 4.81 (s, 1H), 87%). Rf 0.25 (5 : 1, petroleum ether–EtOAc). [α]2D0 +45.7 (c 0.70,
1
4.74 (dd, 2H, J = 3.2, 9.6 Hz), 4.57 (t, 2H, J = 9.6 Hz), 4.41–4.48 CHCl3); H NMR (400 MHz, CDCl3) δ 7.26–7.38 (m, 10H), 6.97
(m, 3H), 4.18–4.31 (m, 4H), 3.95–4.02 (m, 2H), 3.89 (t, 1H, J = (d, 2H, J = 9.2 Hz), 6.82 (d, 2H, J = 9.2 Hz), 5.56 (dd, 1H, J = 2.0,
10.4 Hz), 3.65–3.70 (m, 1H), 3.40–3.45 (m, 3H), 1.98 (t, 2H, J = 3.2 Hz), 5.41 (d, 1H, J = 1.6 Hz), 4.95 (d, 1H, J = 10.8 Hz), 4.79
6.8 Hz); 13C NMR (100 MHz, CDCl3) δ 166.0, 165.99, 165.9, (d, 1H, J = 10.8 Hz), 4.63 (d, 1H, J = 10.8 Hz), 4.59 (d, 1H, J =
165.7, 165.53, 165.52, 165.5, 165.4, 165.2, 165.01, 165.0, 164.7, 10.8 Hz), 4.37 (dd, 1H, J = 4.8, 12.0 Hz), 4.29 (dd, 1H, J = 2.0,
164.6, 133.6, 133.4, 133.3, 133.1, 133.0, 132.97, 132.8, 130.1, 12.0 Hz), 4.22 (dd, 1H, J = 3.2, 9.6 Hz), 3.99–4.03 (m, 1H), 3.84
130.0, 129.9, 129.8, 129.74, 129.7, 129.65, 129.5, 129.24, (d, 1H, J = 9.6 Hz), 3.76 (s, 3H), 2.19 (s, 3H), 2.02 (s, 3H);
This journal is © The Royal Society of Chemistry 2013
Org. Biomol. Chem., 2013, 11, 3903–3917 | 3913

View Article Online
Paper
Organic & Biomolecular Chemistry
13C NMR (100 MHz, CDCl3) δ 170.6, 170.2, 155.2, 149.7, 137.8, 1H), 5.47 (d, 1H, J = 2.0 Hz), 4.92 (d, 1H, J = 11.2 Hz), 4.73 (d,
137.6, 128.43, 128.4, 128.1, 128.0, 127.9, 117.8, 114.5, 96.8, 1H, J = 11.2 Hz), 4.60 (t, 2H, J = 11.2 Hz), 4.29–4.36 (m, 2H),
77.9, 75.2, 73.8, 71.9, 70.2, 68.3, 63.0, 55.6, 21.0, 20.8; IR (KBr) 3.99–4.04 (m, 2H), 3.86 (t, 1H, J = 10.0 Hz), 2.70–2.78 (m, 6H),
2936, 2848, 1744, 1506, 1455, 1369 cm−1; HRMS (ESI) calcd for 2.58 (t, 2H, J = 6.4 Hz), 2.16 (s, 3H), 2.15 (s, 3H); 13C NMR
C31H34O9 [M + Na]+ 573.2101, found 573.2099.
(100 MHz, CDCl3) δ 206.2, 205.9, 172.2, 171.6, 159.6, 137.6,
137.2, 128.3, 128.28, 128.2, 128.18, 127.83, 127.8, 94.7, 77.0,
75.3, 73.0, 72.2, 71.7, 67.2, 62.7, 37.7, 37.6, 27.8, 27.6; IR (KBr)
p-Methoxyphenyl 2,6-di-O-levulinoyl-3,4-di-O-benzyl-α-D-
mannopyranoside (44)
2932, 2858, 1739, 1715, 1599, 1118, 1092, 1030 cm−1
.
To a solution of 43 (1.42 g, 2.58 mmol) in 1 : 2 DCM–MeOH
(25.8 mL) was added CH3ONa (2 8 mg, 0.520 mmol). The reac-
tion was stirred at room temperature for 1 h, at the end of
Phenyl 3,4-di-O-benzyl-2,6-di-O-levulinoyl-α-D-mannopyranosyl-
(1→6)-2,3,4-tri-O-benzoyl-1-thio-α-D-mannopyranoside (47)
which time TLC indicated it was finished. The reaction was The donor 45 (810 mg, 1.15 mmol) and the acceptor 46
diluted with CH2Cl2, and then the mixture was washed with (560 mg, 0.959 mmol) were dried together under high vacuum
water and brine. The organic layer was separated and dried for 0.5 h. The mixture was dissolved in CH2Cl2 (22 mL) and fol-
over anhydrous Na2SO4, filtered, and concentrated. The crude lowed by addition of freshly activated 4 Å molecular sieves
residue was dissolved in dry CH2Cl2 (25 mL), then DCC (7.0 g, (1.50 g). The resulting slurry was cooled to −80 °C, then a solu-
34.0 mmol) and LevOH (1.14 mL, 9.80 mmol) were added to tion of TMSOTf (22.0 μL, 0.118 mmol) in CH2Cl2 (1.0 mL) was
the reaction. The resulting mixture was stirred for 4 h at room added dropwise. After being stirred for 2 h at the same temp-
temperature, at the end of which time TLC indicated that it erature, the mixture was warmed gradually to 0 °C. The reac-
was finished. The reaction was diluted with CH2Cl2, and then tion was quenched with triethylamine, diluted with CH2Cl2
the mixture was filtered through celite and concentrated in and filtered. The filtrate was concentrated to give a residue,
vacuo. The crude product was purified by column chromato- which was purified by column chromatography (2 : 1, pet-
graphy (2 : 1, petroleum ether–EtOAc) to give 44 as a colorless roleum ether–EtOAc) to afford 47 as a colorless syrup (960 mg,
syrup (1.55 g, 95%). Rf 0.48 (1 : 1, petroleum ether–EtOAc). [α]2D0 89%). Rf 0.30 (3 : 2, petroleum ether–EtOAc). [α]D20 +14.9 (c 1.05,
1
1
+22.9 (c 0.70, CHCl3); H NMR (400 MHz, CDCl3) δ 7.26–7.38 CHCl3); H NMR (400 MHz, CDCl3) δ 8.09 (d, 2H, J = 8.0 Hz),
(m, 10H), 6.97 (d, 2H, J = 8.8 Hz), 6.81 (d, 2H, J = 9.2 Hz), 5.54 8.01 (d, 2H, J = 8.0 Hz), 7.86 (d, 2H, J = 8.0 Hz), 7.41–7.56 (m,
(dd, 1H, J = 2.0, 3.2 Hz), 5.40 (d, 1H, J = 1.6 Hz), 4.93 (d, 1H, J = 7H), 7.25–7.34 (m, 16H), 7.19 (t, 1H, J = 7.6 Hz), 6.03 (t, 1H, J =
11.2 Hz), 4.77 (d, 1H, J = 11.2 Hz), 4.60 (dd, 1H, J = 2.0, 11.2 10.0 Hz), 5.96 (q, 1H, J = 1.6 Hz), 5.84 (dd, 1H, J = 3.2, 10.4 Hz),
Hz), 4.37 (dd, 1H, J = 4.8, 11.6 Hz), 4.28 (dd, 1H, J = 1.6, 11.6 5.76 (d, 1H, J = 1.2 Hz), 5.37 (q, 1H, J = 1.6 Hz), 4.91 (d, 1H, J =
Hz), 4.19 (dd, 1H, J = 3.2, 8.8 Hz), 3.96–3.98 (m, 1H), 3.81 (t, 10.4 Hz), 4.80–4.82 (m, 2H), 4.56 (d, 1H, J = 11.2 Hz), 4.53 (d,
1H, J = 9.6 Hz), 3.75 (s, 3H), 2.66–2.76 (m, 6H), 2.52–2.57 (m, 1H, J = 11.2 Hz), 4.35 (d, 1H, J = 10.4 Hz), 4.30 (dd, 1H, J = 4.8,
2H), 2.17 (s, 3H), 2.15 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 12 Hz), 4.18 (d, 1H, J = 10.4 Hz), 3.96–4.00 (m, 2H), 3.78–3.80
206.3, 206.2, 172.3, 172.0, 155.1, 149.6, 137.8, 137.7, 128.3, (m, 1H), 3.65–3.73 (m, 2H), 2.63–2.73 (m, 6H), 2.46–2.52 (m,
128.1, 127.8, 117.7, 117.4, 96.6, 77.8, 75.2, 73.8, 71.7, 70.1, 2H), 2.14 (s, 3H), 2.13 (s, 3H); 13C NMR (100 MHz, CDCl3) δ
68.5, 63.1, 55.5, 37.9, 37.7, 29.7, 29.7, 28.0, 27.7; IR (KBr) 2932, 206.2, 206.17, 172.3, 171.7, 165.4, 165.3, 165.25, 138.1, 137.8,
2860, 1741, 1719, 1602, 1506, 1363 cm−1; HRMS (ESI) calcd for 133.5, 133.45, 133.2, 133.1, 131.4, 129.8, 129.7, 129.6, 129.3,
C37H42O11 [M + Na]+ 685.2625, found 633. 685.2629.
129.1, 128.74, 128.7, 128.6, 128.4, 128.2, 128.1, 127.9, 127.8,
127.7, 127.6, 97.7, 85.8, 78.3, 75.1, 73.6, 71.9, 71.6, 70.4, 69.7,
68.3, 67.0, 66.6, 63.1, 37.9, 37.7, 29.74, 29.7, 28.0, 27.6; IR
(KBr) 2927, 2858, 1731, 1602, 1453, 1362 cm−1; HRMS (ESI)
3,4-Di-O-benzyl-2,6-di-O-levulinoyl-α-D-mannopyranosyl
trichloroacetimidate (45)
To a solution of 44 (1.55 g, 2.34 mmol) in CH3CN (37.5 mL) and calcd for C63H62O17S [M + Na]+ 1145.3605, found 1145.3608.
H2O (9.30 mL) was added CAN (3.20 g, 5.85 mmol). The reaction
mixture was stirred at 0 °C for 40 min, at the end of which time
TLC indicated it was finished. The mixture was diluted with
Phenyl 3,4-di-O-benzyl-α-D-mannopyranosyl-(1→6)-2,3,4-tri-O-
benzoyl-1-thio-α-D-mannopyranoside (40)
EtOAc, and then the mixture was washed with satd aq NaHCO3 To a solution of 47 (960 mg, 0.855 mmol) in DCM (17 mL) and
and brine. The organic layer was separated and dried over anhy- MeOH (0.3 mL) was added AcOH·NH2NH2 (315 mg,
drous Na2SO4, filtered, and concentrated. The crude residue was 3.42 mmol). The reaction was stirred overnight at room temp-
dissolved in dry CH2Cl2 (11.8 mL), then Cl3CCN (1.18 mL, erature. Then the reaction mixture was quenched with acetone
mmol) and DBU (0.24 mL) were added. The mixture was stirred and concentrated to dryness. The resulting residue was puri-
for 1 h at room temperature, at the end of which time TLC indi- fied by column chromatography (3 : 2, CH2Cl2–MeOH) to
cated it was finished. The reaction was concentrated and puri- afford compound 40 (610 mg, 77%) as an amorphous solid. Rf
fied by column chromatography (5 : 3, petroleum ether–EtOAc) 0.35 (1 : 1, petroleum ether–acetone). [α]2D0 +18.4 (c 1.00,
1
to give 45 (920 mg, 56% for two steps) as a colorless syrup. Com- CHCl3); H NMR (400 MHz, CDCl3) δ 8.10 (d, 2H, J = 8.0 Hz),
pound 45 was unstable and should be used for the next step 8.02 (d, 2H, J = 8.0 Hz), 7.89 (d, 2H, J = 8.0 Hz), 7.44–7.58 (m,
quickly. Rf 0.40 (1 : 1, petroleum ether–EtOAc). 1H NMR 7H), 7.26–7.39 (m, 16H), 7.23 (t, 1H, J = 7.6 Hz), 4.92 (d, 1H, J =
(400 MHz, CDCl3) δ 8.72 (s, 1H), 7.26–7.35 (m, 10H), 6.24 (s, 1.2 Hz), 4.89 (d, 1H, J = 10.8 Hz), 4.78–4.83 (m, 1H), 4.66 (d,
3914 | Org. Biomol. Chem., 2013, 11, 3903–3917
This journal is © The Royal Society of Chemistry 2013

View Article Online
Organic & Biomolecular Chemistry
Paper
1H, J = 10.8 Hz), 4.55 (d, 1H, J = 11.2 Hz), 4.50 (d, 1H, J = 11.2 133.4, 133.2, 133.1, 133.02, 133.0, 131.9, 130.0, 129.9, 129.81,
Hz), 3.96–4.00 (m, 2H), 3.82–3.88 (m, 2H), 3.63–3.72 (m, 4H), 129.79, 129.7, 129.69, 129.6, 129.58, 129.33, 129.31, 129.2,
2.60 (s, 1H), 2.40 (s, 1H); 13C NMR (100 MHz, CDCl3) δ 165.41, 129.17, 129.1, 129.05, 129.0, 128.95, 128.8, 128.5, 128.46,
165.4, 165.3, 138.3, 137.8, 133.6, 133.5, 133.1, 131.6, 129.81, 128.4, 128.3, 128.2, 127.9, 127.8, 127.77, 127.6, 99.4, 97.9, 97.4,
129.8, 129.7, 129.3, 129.2, 128.9, 128.8, 128.6, 128.48, 128.46, 86.2, 80.5, 75.0, 74.1, 72.2, 71.7, 70.9, 70.7, 70.4, 70.1, 70.0,
128.3, 128.0, 127.9, 127.86, 127.7, 127.68, 99.2, 85.9, 80.0, 75.1, 69.2, 68.8, 68.0, 66.7, 66.6, 66.41, 66.4, 66.3, 65.9, 62.4; IR
73.7, 72.0, 71.9, 71.7, 70.5, 70.4, 68.1, 67.3, 66.4, 61.7; IR (KBr) (KBr) 3441, 2922, 2853, 1730, 1602, 1453 cm−1; HRMS (ESI)
3430, 2925, 2858, 1730, 1600, 1451, 1362 cm−1; HRMS (ESI) calcd for C114H98O30S [M + Na]+ 2001.5761, found 2001.5767.
calcd for C53H50O13S [M + Na]+ 949.2870, found 949.2850.
Data for pentasaccharide intermediate 49: Rf 0.25 (1 : 1, pet-
roleum ether–EtOAc). [α]2D0 −12.1 (c 1.60, CHCl3); 1H NMR
(400 MHz, CDCl3) δ 8.18–7.84 (m, 26H), 7.21–7.59 (m, 49H),
6.08–6.14 (m, 3H), 6.05 (d, 1H, J = 10.0 Hz), 6.01 (dd, 1H, J =
3.2, 10.0 Hz), 5.96 (dd, 1H, J = 3.2, 10.0 Hz), 5.93 (dd, 1H, J =
3.2, 10.0 Hz), 5.87 (dd, 1H, J = 3.2, 10.4 Hz), 5.82–5.84 (m, 1H),
5.74–5.77 (m, 2H), 5.68 (d, 1H, J = 1.6 Hz), 5.18 (s, 1H), 5.13 (d,
1H, J = 1.2 Hz), 5.04 (d, 1H, J = 12.0 Hz), 5.01 (s, 1H), 5.00 (s,
One-pot synthesis of 3-azidopropyl 2,3,4,6-tetra-O-benzoyl-
α-D-mannopyranosyl-(1→6)-2,3,4-tri-O-benzoyl-α-D-
mannopyranosyl-(1→6)-[2,3,4,6-tetra-O-benzoyl-α-D-
mannopyranosyl-(1→2)]-3,4-di-O-benzyl-α-D-mannopyranosyl-
(1→6)-2,3,4-tri-O-benzoyl-α-D-mannopyranosyl-(1→6)-2,3,4-tri-
O-benzoyl-α-D-mannopyranoside (50)
A mixture of trichloroacetimidate 39 (86 mg, 0.069 mmol), 2,6- 1H), 4.97 (s, 1H), 4.71 (d, 1H, J = 11.6 Hz), 4.61 (d, 1H, J = 11.6 Hz),
diol thioglycoside 40 (56 mg, 0.061 mmol), and freshly acti- 4.57 (d, 1H, J = 11.6 Hz), 4.42 (dd, 1H, J = 2.0, 12.0 Hz),
vated 4 Å molecular sieves (300 mg) in dry CH2Cl2 (1.0 mL) 4.24–4.36 (m, 4H), 4.23 (dd, 1H, J = 4.0, 12.0 Hz), 4.12–4.16 (m,
was stirred at room temperature for 15 min. Then the suspen- 1H), 4.03 (s, 1H), 4.00–3.85 (m, 6H), 3.80 (dd, 1H, J = 1.6, 10.0 Hz),
sion was cooled to −80 °C, and a solution of TMSOTf (1.3 μL, 3.55–3.69 (m, 5H), 3.51 (d, 2H, J = 10.8 Hz), 1.99 (t, 2H, J =
0.007 mmol) in CH2Cl2 (0.3 mL) was added dropwise. After 6.8 Hz); 13C NMR (100 MHz, CDCl3) δ 165.9, 165.6, 165.5,
being stirred for 2 h at the same temperature, the reaction was 165.46, 165.43, 165.42, 165.4, 165.33, 165.31, 165.2, 165.1,
gradually warmed to room temperature. The reaction mixture 138.6, 138.0, 133.5, 133.4, 133.3, 133.1, 133.0, 132.9, 130.0,
was stirred for a further 1 h at the same temperature, at the 129.9, 129.8, 129.75, 129.7, 129.66, 129.4, 129.3, 129.25, 129.2,
end of which time TLC indicated the complete consumption 129.1, 129.0, 128.95, 128.91, 128.7, 128.67, 128.5, 128.44,
of the starting materials. The resulting slurry was re-cooled to 128.39, 128.35, 128.3, 128.2, 128.1, 127.8, 127.7, 127.68, 127.6,
−20 °C, a solution of acceptor 27 (35 mg, 0.061 mmol) in 127.5, 99.5, 98.1, 98.0, 97.86, 97.85, 80.3, 74.9, 73.8, 71.4, 70.8,
CH2Cl2 (0.2 mL) was added. Then NIS (17 mg, 0.075 mmol) 70.5, 70.4, 70.3, 70.2, 70.1, 69.7, 69.1, 68.8, 67.8, 66.9, 66.63,
and TfOH (1 μL, 0.011 mmol) were added at −20 °C. The reac- 66.62, 66.4, 66.3, 65.5, 65.1, 62.3, 60.3, 48.2, 28.7; IR (KBr)
tion mixture was stirred for 4 h at room temperature, at the 3436, 2924, 2853, 2099, 1729, 1602, 1452, 1106 cm−1; HRMS
end of which time TLC indicated it was finished. A solution of (ESI) calcd for C138H121N3O39 [M + Na]+ 2466.7475, found
thioglycoside donor 41 (50 mg, 0.073 mmol) in CH2Cl2 2466.7483. Data for hexasaccharide 50: Rf 0.25 (1 : 1, petroleum
1
(0.2 mL) was added when the temperature was re-cooled to ether–EtOAc). [α]2D0 −12.1 (c 1.60, CHCl3); H NMR (400 MHz,
−20 °C. Then NIS (20 mg, 0.088 mmol) and TfOH (1.2 μL, CDCl3) δ 8.17–7.84 (m, 34H), 7.20–7.60 (m, 61H), 7.16 (t, 1H,
0.013 mmol) were added. After being stirred for 2 h at room J = 7.6 Hz), 7.11 (t, 1H, J = 7.6 Hz), 7.01–7.16 (m, 2H), 6.72–6.79
temperature. The reaction was quenched with triethylamine, (m, 2H), 6.29 (q, 1H, J = 10.0 Hz), 6.06–16 (m, 3H), 6.05 (dd,
diluted with CH2Cl2 and filtered. The filtrate was concentrated 1H, J = 3.6, 10.0 Hz), 5.99 (dd, 1H, J = 2.8, 10.4 Hz), 5.83–5.94
to give a residue, which was purified by column chromato- (m, 4H), 5.74–5.76 (m, 2H), 5.26 (s, 1H), 5.16 (s, 1H), 5.13 (s,
graphy (2 : 1, petroleum ether–acetone) to afford 50 (86 mg, 1H), 5.11 (s, 2H), 5.07 (s, 1H), 4.92 (d, 1H, J = 12.0 Hz), 4.77 (t,
47% for three steps based on 40) as an amorphous solid. Data 1H, J = 11.6 Hz),4.75 (d, 1H, J = 11.6 Hz), 4.71 (d, 1H, J = 11.6
for tetrasaccharide intermediate 48: Rf 0.30 (1 : 1, petroleum Hz), 4.60 (d, 1H, J = 11.2 Hz), 4.38–4.45 (m, 2H), 4.30–4.32 (m,
ether–EtOAc). [α]2D0 −7.9 (c 0.90, CHCl3); 1H NMR (400 MHz, 2H), 4.22 (d, 1H, J = 10.0 Hz), 4.16 (dd, 2H, J = 3.6, 10.4 Hz),
CDCl3) δ 8.21 (d, 2H, J = 8.0 Hz), 8.12 (d, 2H, J = 8.0 Hz), 3.93–4.08 (m, 5H), 3.67–3.86 (m, 5H), 3.48–3.63 (m, 5H), 2.04 (t
8.01–8.05 (m, 8H), 7.85–7.95 (m, 8H), 7.14–7.61 (m, 45H), 6.30 2H, J = 6.8 Hz); 13C NMR (100 MHz, CDCl3) δ 166.0, 165.9,
(t, 1H, J = 10.0 Hz), 6.14 (t, 1H, J = 10.4 Hz), 6.12 (t, 1H, J = 10.4 165.6, 165.5, 165.45, 165.4, 165.3, 165.28, 165.24, 165.22,
Hz), 6.03 (dd, 1H, J = 3.2, 10.4 Hz), 6.01 (d, 1H, J = 3.2 Hz), 5.90 165.04, 165.0, 164.8, 164.7, 138.9, 138.0, 133.5, 133.4, 133.36,
(td, 2H, J = 3.2, 8.0 Hz), 5.82–5.84 (m, 2H), 5.60 (dd, 1H, J = 133.3, 133.27, 133.1, 132.9, 132.8, 132.14, 132.1, 130.0, 129.9,
1.6, 2.8 Hz), 5.13 (s, 1H), 5.05 (s, 1H), 5.05 (d, 1H, J = 2.8 Hz), 129.86, 129.7, 129.66, 129.6, 129.34, 129.3, 129.1, 129.05,
5.01 (s, 1H), 4.89 (s, 1H), 4.65–4.68 (m, 3H), 4.45 (dd, 1H, J = 129.0, 128.8, 128.7, 128.66, 128.4, 128.34, 128.3, 128.2, 128.1,
2.0, 12.0 Hz), 4.31–4.37 (m, 2H), 4.22–4.28 (m, 2H), 4.14–4.16 127.6, 127.4, 127.35, 100.1, 99.2, 98.3, 98.0, 97.84, 97.81, 80.4,
(m, 1H), 4.08 (dd, 1H, J = 3.2, 9.2 Hz), 4.02 (dd, 1H, J = 4.0, 77.4, 74.9, 74.0, 72.6, 71.3, 70.7, 70.6, 70.4, 70.3, 70.2, 70.1,
11.2 Hz), 3.94 (t, 1H, J = 9.2 Hz), 3.87 (dd, 1H, J = 6.4, 10.8 Hz), 69.8, 69.3, 69.0, 68.7, 66.8, 66.7, 66.4, 66.3, 66.2, 65.9, 65.3,
3.74–3.79 (m, 1H), 3.68 (d, 1H, J = 10.0 Hz), 3.56 (d, 1H, J = 65.2, 62.5, 62.1, 48.2, 28.7; IR (KBr) 2928, 2853, 2099, 1730,
10.0 Hz); 13C NMR (100 MHz, CDCl3) δ 166.0, 165.5, 165.48, 1603, 1453, 1105 cm−1; HRMS (ESI) calcd for C172H147N3O48
165.43, 165.4, 165.39, 165.3, 165.2, 165.1, 138.6, 138.0, 133.5, [M + Na]+ 3044.9046, found 3044.9058.
This journal is © The Royal Society of Chemistry 2013
Org. Biomol. Chem., 2013, 11, 3903–3917 | 3915

View Article Online
Paper
Organic & Biomolecular Chemistry
3-Azidopropyl α-D-mannopyranosyl-(1→6)-α-D-
mannopyranosyl-(1→6)-[α-D-mannopyranosyl-(1→2)]-3,4-di-O-
benzyl-α-D-mannopyranosyl-(1→6)-α-D-mannopyranosyl-(1→6)-
α-D-mannopyranoside (51)
K. Tatsuta and J. Thiem, Springer, Berlin, 2001, vol. 3,
pp. 1993–2004.
2 (a) C. N. Scanlan, J. Offer, N. Zitzmann and R. A. Dwek,
Nature, 2007, 446, 1038–1045; (b) L.-X. Wang, Curr. Opin.
Drug Discovery Dev., 2006, 9, 194–206; (c) D. A. Calarese,
H. K. Lee, C.-Y. Huang, M. D. Best, R. D. Astronomo,
R. L. Stanfield, H. Katinger, D. R. Burton, C. H. Wong and
I. A. Wilson, Proc. Natl. Acad. Sci. U. S. A., 2005, 102, 13372–
13377; (d) M. Mandal, V. Y. Dudkin, X.-D. Geng and
S. J. Danishefsky, Angew. Chem., Int. Ed., 2004, 43, 2557–2561.
3 (a) D. Egert and N. Beuscher, Planta Med., 1992, 58, 163–
172; (b) B. S. Paulsen, Curr. Org. Chem., 2001, 5, 939–950;
(c) S. Alban, B. Classen, G. Brunner and W. Blaschek,
Planta Med., 2002, 68, 1118–1124.
4 (a) J. K. Sharp, B. Valent and P. Albersheim, J. Biol. Chem.,
1984, 259, 11312–11320; (b) J. K. Sharp, M. McNeil and
P. Albersheim, J. Biol. Chem., 1984, 259, 11321–11336;
(c) J. K. Sharp, P. Albersheim and B. Lindberg, J. Biol.
Chem., 1984, 259, 11341–11345.
Prepared from 50 (302 mg, 0.100 mmol) following the pro-
cedure similar to that for 23→14. The resulting residue was
purified by Sephadex LH-20 (MeOH) to afford compound 51
(95 mg, 76%) as an amorphous solid. [α]2D0 +57.4 (c 1.25,
MeOH); 1H NMR (400 MHz, D2O) δ 7.35–7.45 (m, 10H), 5.18 (s,
1H), 5.02 (s, 1H), 4.95 (s, 1H), 4.92 (s, 1H), 4.86 (s, 2H), 4.78 (d,
1H, J = 11.6 Hz), 4.71 (d, 1H, J = 11.6 Hz), 4.63 (d, 1H, J = 10.8
Hz), 4.24 (s, 1H), 4.09 (s, 2H), 4.05 (s, 3H), 3.70–3.98 (m, 31H),
3.63 (d, 1H, J = 11.6 Hz), 3.52–3.55 (m, 1H), 3.32–3.33 (m, 2H),
1.84 (dd, 2H, J = 6.4, 12.4 Hz); 13C NMR (100 MHz, D2O) δ
134.9, 134.8, 126.3, 126.2, 126.0, 125.8, 125.7, 99.6, 97.6, 97.57,
97.05, 97.0, 95.6, 76.2, 73.1, 72.2, 71.4, 70.81, 70.8, 70.1, 69.4,
68.7, 68.5, 68.4, 68.1, 68.0, 67.8, 67.6, 67.4, 64.3, 64.2, 63.9,
63.7, 62.9, 62.7, 62.2, 58.6, 58.4, 45.5, 25.4; HRMS (ESI) calcd
for C53H79N3O31 [M + Na]+ 1276.4595, found 1276.4601.
5 Selected examples. Stepwise approach: (a) N. Teumelsan
and X.-F. Huang, J. Org. Chem., 2007, 72, 8976–8979;
(b) A. Koizumi, N. Hada, A. Kaburaki, K. Yamano,
F. Schweizer and T. Takeda, Carbohydr. Res., 2009, 344,
856–868. Layered approach: (c) X.-D. Geng, V. Y. Dudkin,
M. Mandal and S. J. Danishefsky, Angew. Chem., Int. Ed.,
3-Aminopropyl α-D-mannopyranosyl-(1→6)-α-D-
mannopyranosyl-(1→6)-[α-D-mannopyranosyl-(1→2)]-α-D-
mannopyranosyl-(1→6)-α-D-mannopyranosyl-(1→6)-α-D-
mannopyranoside (38)
To a solution of compound 51 (23 mg, 0.018 mmol) in MeOH
(3.6 mL) were added 10% Pd(OH)2/C (9 mg) and AcOH
(0.36 mL). After being stirred under a hydrogen atmosphere of
30 atm at room temperature for 24 h, the mixture was neutral-
ized and filtered. The filtrate was concentrated. The resulting
residue was purified by Sephadex LH-20 (MeOH) to give 37
(15 mg, 68%) as a white solid. [α]2D0 +33.6 (c 0.25, H2O); 1H
NMR (400 MHz, D2O) δ 5.19 (s, 1H), 5.09 (s, 1H), 4.97 (s, 2H),
4.95 (s, 1H), 4.91 (s, 1H), 4.13 (s, 1H), 3.97–4.05 (m, 11H),
3.75–3.95 (m, 22H), 3.60–3.75 (m, 4H), 3.06–3.08 (m, 2H), 1.99
(t, 2H, J = 6.8 Hz); 13C NMR (100 MHz, D2O) δ 104.7, 102.4,
102.0, 101.8, 101.7, 100.5, 75.7, 75.1, 73.4, 73.3, 73.26, 73.2,
73.1, 72.9, 72.8, 72.4, 69.1, 69.0, 68.9, 68.3, 68.0, 67.9, 67.6,
63.5, 63.3, 40.0, 29.9; HRMS (ESI) calcd for C39H69NO31 [M +
Na]+ 1070.3751, found 1070.3782.
2004,
43,
2562–2565.
Regioselective
strategy:
(d) K. N. Jayaprakash, S. R. Chaudhuri, C. V. S. R. Murty
and B. Fraser-Reid, J. Org. Chem., 2007, 72, 5534–5545;
(e) K. N. Jayaprakash, J. Lu and B. Fraser-Reid, Angew.
Chem., Int. Ed., 2005, 44, 5894–5898. Convergent strategy:
(f) V. K. Rajput and B. Mukhopadhyay, J. Org. Chem., 2008,
73, 6924–6927; (g) R. Geurtsen, F. Côté, M. G. Hahn and
G.-J. Boons, J. Org. Chem., 1999, 64, 7828–7835;
(h) K. Pekari and R. R. Schmidt, J. Org. Chem., 2003, 68,
1295–1308; (i) Y. Xing and J. Ning, Tetrahedron: Asymmetry,
2003, 14, 1275–1283; ( j) J. Ning, L.-S. Heng and K.-F. Kong,
Carbohydr. Res., 2002, 337, 1159–1164; (k) A. Düffels,
L. G. Green, S. V. Ley and A. D. Miller, Chem.–Eur. J., 2000,
6, 1416–1430; (l) P. Grice, S. V. Ley, J. Pietruszka and
H. W. M. Priepke, Angew. Chem., Int. Ed., 1996, 35, 197–200;
(m) A. A. Karelin, Y. E. Tsvetkov, L. Paulovicová, S. Bystricky,
E. Paulovicová and N. E. Nifantiev, Carbohydr. Res., 2010,
345, 1283–1290; (n) L. V. Backinowsky, P. I. Abronina,
A. S. Shashkov, A. A. Grachev, N. K. Kochetkov,
S. A. Nepogodiev and J. F. Stoddart, Chem.–Eur. J., 2002, 8,
4412–4423. Orthogonal protecting groups strategy:
(o) T. J. Boltje, C.-X. Li and G.-J. Boons, Org. Lett., 2010, 12,
4636–4639; (p) C. H. Wong, X.-S. Ye and Z.-Y. Zhang, J. Am.
Chem. Soc., 1998, 120, 7137–7138; (q) Y.-G. Du,
M.-M. Zhang and F.-Z. Kong, Org. Lett., 2000, 2, 3797–3800.
Solid-phase synthesis: (r) O. J. Plante, E. R. Palmacci and
P. H. Seeberger, Science, 2001, 291, 1523–1527;
(s) K. C. Nicolaou, N. Winssinger, J. Pastor and F. DeRoose,
J. Am. Chem. Soc., 1997, 119, 449–450.
Acknowledgements
We appreciate financial support from NSFC (21172156,
21021001), the National Basic Research Program of China (973
Program, 2010CB833202), Ministry of Education (NCET-08-
0377, 20100181110082), and Sichuan Province (08ZQ026-029)
of China.
Notes and references
1 (a) A. Varki, Glycobiology, 1993, 3, 97–130; (b) R. A. Dwek,
Chem. Rev., 1996, 96, 683–720; (c) S. Nishimura, in Glycoscience:
Chemistry and Chemical Biology, ed. B. Fraser-Reid,
6 Recent reviews on one-pot glycosylation: (a) B. Yu,
Z.-Y. Yang and H.-Z. Cao, Curr. Org. Chem., 2005, 9, 179–194;
3916 | Org. Biomol. Chem., 2013, 11, 3903–3917
This journal is © The Royal Society of Chemistry 2013

View Article Online
Organic & Biomolecular Chemistry
Paper
(b) Y.-H. Wang, X.-S. Ye and L.-H. Zhang, Org. Biomol. Chem., 16 M. A. Brimble, R. Kowalczyk and V. J. Muir, Org. Biomol.
2007, 5, 2189–2200. Chem., 2008, 6, 112–121.
7 For one-pot syntheses of branched oligopyranoses, see: 17 G. C. Completo and T. L. Lowary, J. Org. Chem., 2008, 73,
(a) H. Yamada, T. Harada and T. Takahashi, J. Am. Chem. 4513–4525.
Soc., 1994, 116, 7919–7920; (b) H. Yamada, T. Kato and 18 T. Ziegler and G. Lemanski, Tetrahedron, 2000, 56, 563–579.
T. Takahashi, Tetrahedron Lett., 1999, 40, 4581–4584; 19 T. B. Grindley, Adv. Carbohydr. Chem. Biochem., 1998, 53,
(c) T. Takahashi, M. Adachi, A. Matsuda and T. Doi, Tetrahe-
dron Lett., 2000, 41, 2599–2603; (d) H. Tanaka, N. Matoba 20 V. Ladmiral and D. M. Haddleton, J. Am. Chem. Soc., 2006,
and T. Takahashi, Chem. Lett., 2005, 400–401; 128, 4823–4830.
(e) H. Tanaka, M. Adachi, H. Tsukamoto, T. Ikeda, 21 (a) K. Bock and C. Petersen, J. Chem. Soc., Perkin Trans. 2,
17–142.
H. Yamada and T. Takahashi, Org. Lett., 2002, 4, 4213–
4216; (f) H. Tanaka, M. Adachi and T. Takahashi, Tetrahe-
1974, 293–297; (b) J. Ø. Duus, C. H. Gotfredsen and
K. Bock, Chem. Rev., 2000, 100, 4589–4614.
dron Lett., 2004, 45, 1433–1436; (g) H. Tanaka, M. Adachi 22 (a) K. Mizutani, R. Kasai, M. Nakamura, O. Tanaka and
and T. Takahashi, Chem.–Eur. J., 2005, 11, 849–862;
(h) A. Miermont, Y.-L. Zeng, Y.-Q. Jing, X.-S. Ye and
X.-F. Huang, J. Org. Chem., 2007, 72, 8958–8961.
H. Matsuura, Carbohydr. Res., 1989, 185, 27–38; (b) M. T. de
Oliveira, D. L. Hughes, S. A. Nepogodiev and R. A. Field,
Carbohydr. Res., 2008, 343, 211–220.
8 L.-M. Deng, X. Liu, X.-Y. Liang and J.-S. Yang, J. Org. Chem., 23 (a) P. J. Brennan, Annu. Rev. Biochem., 1995, 64, 29–63;
2012, 77, 3025–3037.
(b) A. Vercellone, J. Nigou and G. Puzo, Front. Biosci., 1998,
3, 149–163; (c) D. Chatterjee, Curr. Opin. Chem. Biol., 1997,
1, 579–588; (d) T. L. Lowary, J. Carbohydr. Chem., 2002, 21,
691–722; (e) R. R. Gadikota, C. S. Callam, B. J. Appelmelk
and T. L. Lowary, J. Carbohydr. Chem., 2003, 22, 459–480.
9 (a) K. W. Yu, H. Kiyohara, T. Matsumoto, H. C. Yang and
H. Yamada, Planta Med., 1998, 64, 714–719; (b) K. W. Yu,
H. Kiyohara, T. Matsumoto, H. C. Yang and H. Yamada,
Carbohydr. Polym., 2001, 46, 147–156.
10 I. Taguchi, H. Kiyohara, T. Matsumoto and H. Yamada, 24 (a) T. L. Lowary, in Glycoscience: Chemistry and Chemical
Carbohydr. Res., 2004, 339, 763–770.
11 (a) A. Borbás, L. Jánossy and A. Lipták, Carbohydr. Res.,
1999, 318, 98–109; (b) M. Csávás, A. Borbás, L. Jánossy,
Biology, ed. B. Fraser-Reid, K. Tatsuta and J. Thiem,
Springer, Berlin, 2001, p. 2005; (b) P. J. Brennan, Tuberculo-
sis, 2003, 83, 91–97.
Gy. Batta and A. Lipták, Carbohydr. Res., 2001, 336, 107– 25 (a) A. K. Pathak, V. Pathak, J. A. Maddry, W. J. Suling,
115; (c) M. Csávás, A. Borbás, L. Szilágyi and A. Lipták,
Synlett, 2002, 887–890; (d) M. Csávás, A. Borbás, L. Jánossy
and A. Lipták, Tetrahedron Lett., 2003, 44, 631–635;
(e) A. Fekete and A. Lipták, Carbohydr. Res., 2009, 344,
1434–1441; (f) G. Gu, F. Yang, Y.-G. Du and F.-Z. Kong, Car-
bohydr. Res., 2001, 336, 99–106; (g) J. Ning, H. Wang and
Y. Yi, Tetrahedron Lett., 2002, 43, 7349–7352; (h) A. Li and
F.-Z. Kong, Carbohydr. Res., 2004, 339, 1847–1856; (i) A. Li
and F.-Z. Kong, Carbohydr. Res., 2005, 340, 1949–1962;
( j) A. Li and F.-Z. Kong, Bioorg. Med. Chem., 2005, 13, 839–
853.
S. S. Gurcha, G. S. Besra and R. C. Reynolds, Bioorg. Med.
Chem., 2001, 9, 3129–3143; (b) A. K. Pathak, V. Pathak,
W. J. Suling, S. S. Gurcha, C. B. Morehouse, G. S. Besra,
J. A. Maddry and R. C. Reynolds, Bioorg. Med. Chem., 2002,
10, 923–928; (c) J. Han, R. R. Gadikota, P. R. McCarren and
T. L. Lowary, Carbohydr. Res., 2003, 338, 581–588;
(d) A. K. Pathak, V. Pathak, J. R. Riordan, W. J. Suling,
S. S. Gurcha, G. S. Besra and R. C. Reynolds, Bioorg. Med.
Chem. Lett., 2007, 17, 4527–4530; (e) A. K. Pathak,
V. Pathak, W. J. Suling, J. R. Riordan, S. S. Gurcha,
G. S. Besra and R. C. Reynolds, Bioorg. Med. Chem., 2009,
17, 872–881.
12 (a) F. Bien and T. Ziegler, Tetrahedron: Asymmetry, 1998, 9,
781–790; (b) P. Wayne and P. V. Murphy, J. Org. Chem., 26 A. Hölemann, B. L. Stocker and P. H. Seeberger, J. Org.
2010, 75, 6747–6755. Chem., 2006, 71, 8071–8088.
13 K. Toshima and K. Tatsuta, Chem. Rev., 1993, 93, 1503–1531. 27 R. Kowalczyk and M. A. Brimble, Synthesis, 2009, 2210–
14 For examples of aglycon transfer reactions of thioglyco- 2222.
sides, see: (a) H. Yu, B. Yu, X.-Y. Wu, Y.-Z. Hui and 28 O. Arjona, A. de Dios, C. Montero and J. Plumet, Tetrahe-
X.-W. Han, J. Chem. Soc., Perkin Trans. 1, 2000, 1445–1453; dron, 1995, 51, 9191–9200.
(b) T. Zhu and G. J. Boons, Carbohydr. Res., 2000, 329, 709– 29 (a) R. Verduyn, J. J. A. Beliën and J. H. van Boom, Tetrahe-
715; (c) Z.-T. Li and J. C. Gildersleeve, J. Am. Chem. Soc.,
2006, 128, 11612–11619.
dron Lett., 1991, 32, 6637–6640; (b) R. N. Shah, J. Carbohydr.
Chem., 1987, 6, 645–660.
15 M. I. Gimenez-Abián, J. A. Leal and A. Prieto, Carbohydr. 30 M. K. Christensen, M. Meldal and K. Bock, J. Chem. Soc.,
Res., 2007, 342, 2599–2603.
Perkin Trans. 1, 1993, 13, 1453–1460.
This journal is © The Royal Society of Chemistry 2013
Org. Biomol. Chem., 2013, 11, 3903–3917 | 3917