Synthesis of a Trisaccharide Repeating Unit of the O-Antigen from Burkholderia multivorans and Its Oligomers

Article abstract of DOI:10.1002/ejoc.201500964

Burkholderia multivorans is a Gram-negative bacterium, and an important opportunistic human pathogen that can cause fatal infections. Its O-antigens are useful templates for the development of carbohydrate-based vaccines. A highly convergent and efficient

Full text of DOI:10.1002/ejoc.201500964

FULL PAPER
DOI: 10.1002/ejoc.201500964
Synthesis of a Trisaccharide Repeating Unit of the O-Antigen from
Burkholderia multivorans and Its Oligomers
Xin Zhang,[a] Guofeng Gu,*[a] and Zhongwu Guo[a]
Keywords: Synthesis design / Total synthesis / Diastereoselectivity / Carbohydrates / Glycosylation / Medicinal chemistry
Burkholderia multivorans is a Gram-negative bacterium, and
an important opportunistic human pathogen that can cause
fatal infections. Its O-antigens are useful templates for the
development of carbohydrate-based vaccines. A highly con-
vergent and efficient strategy was developed for the synthe-
sis of tri-, hexa-, and nonasaccharide fragments of the O-anti-
acetimidate donors, was used as a key building block.
Glycosylation of 3-azidopropanol with the trisaccharyl donor
followed by global deprotection gave the target trisacchar-
ide. The trisaccharyl donor was also used to elongate the
carbohydrate chain to obtain the dimer and trimer in a [3+3]
and [3+3+3] manner. All of the synthetic targets have a free
gen of B. multivorans species Y. In these syntheses, a tri- amino group at their reducing end to facilitate further
saccharyl thioglycoside, which was assembled from thio- derivatization, such as conjugation with other functional
mannoside acceptor and rhamnosyl and mannosyl trichloro- biomolecules.
For the development of new protective and therapeutic
Introduction
strategies against Gram-negative bacteria, their cell-surface
O-polysaccharides (OPSs), also known as O-antigens, are
useful targets. The OPS is a prominent part of the lipopoly-
saccharide (LPS), the major component of the bacterial cell
glycocalyx, and plays an important role in bacterial immu-
nology, such as protecting bacteria against the host’s im-
mune system and so on.[13,14] O-Antigens are exposed on
the bacterial cell surface, and thus are considered to be
attractive antigens for the development of bacterial vac-
cines.[15–17]
A number of Bcc O-antigens have been characterized to
date.[18] For example, Silipo and coworkers have recently
isolated and characterized two O-antigens from B. multivor-
ans strain C1576, with the following repeating-unit struc-
tures: Ǟ2)-α-d-Man-(1Ǟ2)-α-d-Rha-(1Ǟ3)-α-d-Man-(1Ǟ
(species Y), and Ǟ2)-α-d-Man-(1Ǟ2)-α-d-Aco-(1Ǟ3)-α-d-
Rha-(1Ǟ (species X; d-Aco = d-acofriose; Figure 1, a).[19]
Recently, synthetic oligosaccharide fragments of bacterial
polysaccharides have received considerable attention as
structurally defined antigens for the development of carbo-
hydrate-based antibacterial vaccines.[20–23] It has also been
found that the lengths[20–22] and sequences[23] of oligosac-
charides play a critical role in their immunogenicity. To fa-
cilitate a systematic and in-depth immunological study of B.
multivorans and the application of its O-antigen for vaccine
development, we describe in this paper the chemical synthe-
sis of a trisaccharide repeating unit 1 of the species Y O-
antigen, and of its dimer 2 and trimer 3 (Figure 1, b). The
oligosaccharide repeating unit structure of a polysaccharide
can be represented in different ways, and each possible
structure may have its own activity. This effect may be less
significant for oligomers of the repeating unit. This is why
The Burkholderia cepacia complex (Bcc) is a group of
closely related Gram-negative bacteria with similar pheno-
types but distinctly different genotypes.[1,2] The Bcc bacteria
occur widely in nature, and may have a large number of
applications,[3–6] as they have antimicrobial, nitrogen-fixing,
and other useful biological activities. Although the Bcc bac-
teria have potentially beneficial effects, they are also oppor-
tunistic human pathogens that can cause fatal infections in
vulnerable populations, such as those with chronic granulo-
matous disease (CGD) or with cystic fibrosis (CF).[3,7–10]
Occasionally, Bcc infection can result in rapid and clinically
uncontrollable “cepacia syndrome” in CF patients, resulting
in necrotizing pneumonia and septicaemia, which give rise
to high rates of mortality.[7] Of all the Bcc bacteria found
in CF patients, Burkholderia multivorans is one of the two
most frequently found and most pathogenic species. It ac-
counts for about 40% of Bcc infections in the United
States,[11] and the number of B. multivorans infections is
growing steadily. On the other hand, the pathogenic mecha-
nism of Bcc infection remains unclear, and there is also a
lack of effective therapies against it.[12] Consequently, de-
tailed studies of Bcc, and new strategies for the effective
prevention and treatment of Bcc infection are urgently
needed.
[a] National Glycoengineering Reseach Center, Shandong
University,
27 Shanda Nanlu, Jinan 250100, P. R. China
E-mail: guofenggu@sdu.edu.cn
http://www.glycoeng.sdu.edu.cn//artinfo.php?id=48
Supporting Information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201500964.
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X. Zhang, G. Gu, Z. Guo
FULL PAPER
2 and 3 were designed and synthesized in addition to re- (Scheme 2). Benzylation of 9 with benzyl bromide and so-
peating unit 1, which was selected merely because it is the dium hydride in DMF gave fully protected tosylate 10 in an
form described in the literature. The synthetic targets (i.e., excellent 98% yield. The tosyl group in 10 was then
1–3) were designed to have a free amino group linked to smoothly reduced with lithium aluminium hydride (LiAlH4)
their reducing end, which would enable their regioselective in THF[28] to give 6-deoxy sugar 11 in 83% yield. The
modification, such as coupling with carrier molecules for chemical shift of the 6-H signal (d, J = 6.2 Hz) at δ =
the development of conjugate vaccines and for other immu- 1.28 ppm in the 1H NMR spectrum of 11 indicated the for-
nological studies.
mation of a new methyl group. Removal of the isopropylid-
ene group in 11 by treatment with TFA (80% aq.) was fol-
lowed by regioselective benzylation of the resulting 2,3-diol
(i.e., 12) using Bu2SnO[29] and benzyl bromide (Ǟ13), and
then acetylation to protect the remaining hydroxyl group to
give fully protected rhamnose derivative 14. The downfield-
1
shifted 2-H signal in the H NMR spectrum of acetylated
14 compared to that of 13 confirmed that the benzylation
of 12 had proceeded with the correct regioselectivity.
Acetolysis of methyl glycoside 14 with 1% concentrated
H2SO4 in AcOH and Ac2O (1:1 v/v)[30] at 0 °C gave 15 as a
predominantly α product in an excellent yield (95%). Fi-
nally, 15 was converted into 7 in two steps, including selec-
tive removal of the anomeric acetyl group with hydrazine
acetate,[31] and then trichloroacetimidation[32] of the re-
sulting hemiacetal with trichloroacetonitrile and 1,8-diaza-
bicyclo[5.4.0]undec-7-ene (DBU) in CH2Cl2 at 0 °C.
Figure 1. The structures of (a) B. Multivorans O-antigens, and
(b) synthetic targets 1–3.
Results and Discussion
Mannosyl thioglycoside 8 was prepared by the procedure
outlined in Scheme 3. First, p-tolyl 1-thio-α-d-manno-
pyranoside 16[33] was converted into 17 by a tin-complex-
directed[29] regioselective 3-O-allylation in 55% yield. Com-
pound 17 was then benzoylated to give fully protected
mannose derivative 18. The downfield-shifted chemical
shifts of the 2-H and 4-H signals at δ = 5.83 ppm, and of
As shown in Scheme 1, retrosynthetic disconnection of
target molecules 1–3 resulted in trisaccharyl thioglycoside
4. Compond 4 could act as a common glycosyl donor for
the glycosylation of 5,[24] to introduce a latent amino group
at the reducing end of the carbohydrate chain, and for
oligomerization. In turn, trisaccharide 4 could be assembled
from monosaccharide building blocks 6,[25] 7, and 8. To fa-
cilitate stereoselective 1,2-trans glycosylation based on
neighboring-group participation, we planned to use benzoyl
and acetyl groups to protect the 2-O-positions in 6–8. The
acetyl groups at the 2-O-positions of the d-rhamnosyl and
d-mannosyl units could be selectively removed under acidic
conditions to allow further glycosylation at these positions.
1
6a-H and 6b-H signals at δ = 4.63 and 4.47 ppm, in the H
NMR spectrum of 18 confirmed that the 3-O-allylation had
proceeded with the correct regioselectivity. Deallylation of
18 with palladium chloride (0.5 equiv.) in methanol[34]
smoothly gave 8 in a good yield (63%).
With monosaccharyl building blocks 6–8 in hand, key
The synthesis began with the preparation of mannosyl trisaccharyl thioglycoside 4 was assembled by stepwise
donor 6 according to a reported procedure.[25] Next, the glycosylation (Scheme 4). The reaction of 8 with 7 pro-
synthesis of rhamnosyl donor 7 started from 9[26,27] moted by trimethylsilyl triflate (TMSOTf) at –78 °C gave 19
Scheme 1. Retrosynthetic analysis of target molecules 1–3.
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Synthesis of a Trisaccharide Repeating Unit
Scheme 2. Synthesis of rhamnosyl building block 7; TFA = trifluoroacetic acid; TBAI = tetrabutylammonium iodide.
Scheme 3. Synthesis of mannosyl building block 8; All = allyl.
in high yield (94%) and high stereoselectivity as a result of = 5.02 ppm), proved the regiochemistry of the deacylation
neighboring-group participation. The H-coupled gHSQC reaction. Next, 20 was coupled with 6[25] in a reaction
1
1
spectrum of 19 showed that the JC-1,H-1 coupling constant promoted by TMSOTf to give trisaccharide 4 in 91%
was 171.6 Hz, indicating an α configuration for the newly yield. This key intermediate was used as a common glycosyl
formed glycosidic bond.[35] Selective removal of the 2-O- donor for the construction of all three synthetic targets
acetyl group in 19 was achieved with 5% acetyl chloride 1–3.
(AcCl)[36] in CH2Cl2 and MeOH (1:1 v/v) to give 20 in 90%
A glycosylation reaction between 4 and 3-azido-1-prop-
yield. The upfield shift of the 2-H signal at δ = 3.72 ppm in anol 5,[24] using N-iodosuccinimide (NIS) and a catalytic
1
the H NMR spectrum of 20, as compared to that of 19 (δ amount of TMSOTf as promoters, gave trisaccharyl glycos-
Scheme 4. Synthesis of trisaccharide 1.
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X. Zhang, G. Gu, Z. Guo
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ide 21 in 79% yield. Finally, deacylation of 21 with sodium linkages in 23. Target compound 2 was obtained by global
methoxide, followed by hydrogenolytic debenzylation in deprotection in two steps, as described for the deprotection
acetic acid (10% aq.) with Pd/C (10%) as the catalyst gave of 1, in 65% overall yield.
the desired trisaccharide (i.e., 1), which was purified by size-
Similarly, treatment of 23 with 5% AcCl in CH2Cl2 and
exclusion chromatography on a Bio-Gel P-2 column.
MeOH (1:1 v/v) removed the acetyl group selectively to give
Alternatively, selective deacetylation of 21 with AcCl in 24 in 85% yield. The coupling reaction between 24 and 4
CH2Cl2 and MeOH (1:1 v/v) gave trisaccharide 22, which was also carried out with NIS and TMSOTf as promoters
could be used as a glycosyl acceptor for the synthesis of 2 to give fully protected nonasaccharide 25 in a very good
and 3 (Scheme 5). Glycosylation of 22 with 4 using NIS yield (82%). Compound 25 was finally subjected to global
and TMSOTf in CH2Cl2 gave hexasaccharide 23 in good deprotection as described above to give compound 3. All
1
yield (74%). Again, the JC-1,H-1 coupling constants in the the synthetic targets, as well as the synthetic intermediates
1
1H-coupled gHSQC spectrum of 23 were over 171 Hz, involved, were fully characterized by 1D and 2D H and
which confirmed the α configuration of all of the glycosidic 13C NMR spectrometry, and mass spectrometry.
Scheme 5. Synthesis of hexasaccharide 2 and nonasaccharide 3.
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Synthesis of a Trisaccharide Repeating Unit
(t, J = 6.0 Hz, 1 H, 3-H), 4.13 (dd, J = 10.5, 6.0 Hz, 1 H, 6b-H),
4.09 (d, J = 6.0 Hz, 1 H, 2-H), 3.74 (ddd, J = 10.2, 6.0, 1.8 Hz, 1
H, 5-H), 3.38 (dd, J = 10.2, 6.0 Hz, 1 H, 4-H), 3.31 (s, 3 H,
Conclusions
In summary, we have described the first synthesis of a
trisaccharide repeating unit of the O-antigen of B. multi- -OCH3), 2.42 (s, 3 H, ArCH3), 1.48, 1.34 [2 s, 2ϫ 3 H, C(CH3)2]
ppm. 13C NMR (150 MHz, CDCl3): δ = 144.71, 137.73, 132.90,
vorans (species Y), as well as a highly convergent and ef-
129.74, 128.31, 127.97, 127.94, 127.76, 109.53, 98.02, 78.49, 75.59,
ficient strategy for the assembly of oligomers of this repeat-
75.03, 72.55, 69.32, 66.55, 55.00, 27.90, 26.18, 21.64 ppm. HRMS
ing unit. In these syntheses, trisaccharyl thioglycoside 4 was
the key and common building block, which was used as a
(ESI): calcd. for [C24H30O8S + NH4]+ 496.2000; found 496.1996.
glycosyl donor not only for the glycosylation of aglycon 5
to prepare 1, but also for elongation of the carbohydrate (11): A mixture of LiAlH4 (1.0 g, 26.3 mmol) in THF (10 mL) was
Methyl
4-O-Benzyl-2,3-O-isopropylidene-α-D-rhamnopyranoside
added in portions to a solution of 10 (5.0 g, 10.5 mmol) in THF
(20 mL) at 0 °C. The mixture was warmed to 65 °C and stirred
for 3 h, after which time TLC (petroleum ether/ethyl acetate, 4:1)
indicated the disappearance of 10. The mixture was diluted with
EtOAc (150 mL), and washed with H2SO4 (1 m aq.; 2ϫ 100 mL).
The organic phase was dried with Na2SO4, and concentrated, and
the residue was purified by flash column chromatography (petro-
leum ether/ethyl acetate, 4:1) to give 11 (2.67 g, 83%) as a white
foamy solid. [α]2D5 = +56 (c = 1.8, CHCl3). 1H NMR (600 MHz,
CDCl3): δ = 7.38–7.22 (m, 5 H, ArH), 4.88 (d, J = 11.6 Hz, 1 H,
chain to achieve the convergent [3+3] and [3+6] construc-
tion of the target hexa- and nonasaccharides. Trisaccharide
4 was prepared by the stepwise assembly of monosaccharide
building blocks 6–8. All of the glycosylation reactions, in-
cluding those of complex oligosaccharides, were highly ef-
ficient and stereoselective, probably due to the presence of
acyl groups at the 2-O-position of the designed building
blocks, which guaranteed 1,2-trans-glycosylation as a result
of neighboring-group participation. Moreover, synthetic
targets 1–3 have a 3-aminopropyl linker at their reducing CH2Ph), 4.84 (s, 1 H, 1-H), 4.62 (d, J = 11.6 Hz, 1 H, CH2Ph),
4.24 (t, J = 6.4 Hz, 1 H, 3-H), 4.12 (d, J = 5.7 Hz, 1 H, 2-H), 3.65
(m, 1 H, 5-H), 3.35 (s, 3 H, -OCH3), 3.20 (dd, J = 9.6, 7.2 Hz, 1
H, 4-H), 1.50, 1.36 [2 s, 2ϫ 3 H, C(CH3)2], 1.28 (d, J = 6.2 Hz, 3
H, 6-H) ppm. 13C NMR (150 MHz, CDCl3): δ = 138.33, 128.25,
127.97, 127.60, 109.16, 97.99, 81.03, 78.64, 75.98, 72.90, 64.38,
54.76, 27.98, 26.31, 17.83 ppm. HRMS (ESI): calcd. for [C17H24O5
+ NH4]+ 326.1962; found 326.1963.
end, which allows further modifications through the unique
and reactive free amino group, such as coupling with bio-
molecules to generate glycoconjugates that could be used in
biological studies. We are currently working on coupling
1–3 with immunologically active carrier molecules for the
exploration of the immunology of B. multivorans, and the
development of vaccines based on the O-antigen of B.
multivorans. The results of these studies will be reported in
due course.
Methyl 4-O-Benzyl-α-D-rhamnopyranoside (12): A solution of 11
(1.4 g, 4.54 mmol) in TFA (80% aq.; 5 mL) was stirred at room
temp. for 1 h, and then the mixture was coevaporated with toluene
(50 mL) twice under reduced pressure. The residue was purified by
flash column chromatography (petroleum ether/ethyl acetate, 2:1)
to give 12 (975 mg, 80%) as a white foamy solid. [α]2D5 = +74 (c =
Experimental Section
1
1.0, CHCl3). H NMR (600 MHz, CDCl3): δ = 7.39–7.28 (m, 5 H,
General Methods: Optical rotations were determined at 25 °C with
a Rudolph Autopol I automatic polarimeter. 1H and 13C NMR
spectra were recorded with an Agilent 600 MHz spectrometer for
solutions in CDCl3 or D2O. Chemical shifts are given in ppm
downfield from Me4Si. Me4Si was used as an internal reference for
solutions in CDCl3, and the DHO signal was used as the reference
for solutions in D2O. Positive-mode electrospray ionization (ESI)
high-resolution mass spectra (HRMS) were recorded with a JEOL
JMS-DX-303HF spectrometer. Thin-layer chromatography (TLC)
was carried out on silica gel HF254 plates with detection by charring
using H2SO4 (30% v/v in MeOH) or using a UV detector. Silica
gel column chromatography was carried out with mixtures of ethyl
acetate and petroleum ether (b.p. 60–90 °C) or toluene as the el-
uents. Solutions were concentrated at Ͻ60 °C under diminished
pressure.
ArH), 4.75 (d, J = 11.4 Hz, 1 H, CH2Ph), 4.71 (d, J = 11.4 Hz, 1
H, CH2Ph), 4.65 (s, 1 H, 1-H), 3.91 (br. s, 1 H, 2-H), 3.87 (m, 1 H,
3-H), 3.70 (m, 1 H, 5-H), 3.34 (s, 3 H, -OCH3), 3.32 (t, J = 9.6 Hz,
1 H, 4-H), 2.26–2.21 (m, 2 H, -OH), 1.35 (d, J = 6.0 Hz, 3 H, 6-
H) ppm. 13C NMR (150 MHz, CDCl3): δ = 138.20, 128.64, 128.02,
127.93, 100.25, 81.63, 74.99, 71.41, 71.04, 66.95, 54.86, 18.00 ppm.
HRMS (ESI): calcd. for [C14H20O5 + NH4]+ 286.1649; found
286.1649.
Methyl 3,4-Di-O-Benzyl-α-D-rhamnopyranoside (13): A mixture of
12 (940 mg, 3.51 mmol) and Bu2SnO (873 mg, 3.51 mmol) in dry
toluene (15 mL) was heated at reflux for 4 h with azeotropic re-
moval of water using Dean–Stark tube. The mixture was then
cooled to 60 °C, and TBAI (1.29 g, 3.50 mmol) and BnBr (0.5 mL,
4.21 mmol) were added. The mixture was stirred at 60 °C over-
Methyl
4-O-Benzyl-2,3-O-isopropylidene-6-O-tosyl-α-d-manno- night, and then it was concentrated under reduced pressure. The
pyranoside (10): NaH (60% in oil; 865 mg, 21.6 mmol) and BnBr
(1.5 mL, 13 mmol) were added to a cooled solution of 9[27] (4.21 g,
10.8 mmol) in dry DMF (20 mL) at 0 °C. The mixture was stirred
at 0 °C for 30 min, then it was diluted with EtOAc (200 mL), and
washed successively with cooled water, HCl (1 m aq.), and brine.
The organic phase was dried with Na2SO4, and concentrated. The
residue was purified by flash column chromatography (petroleum
ether/ethyl acetate, 2:1) to give 10 (5.07 g, 98%) as a white foamy
residue was purified by column chromatography (petroleum ether/
ethyl acetate, 3:2) to give 13 (1.17 g, 93%) as a syrup. [α]2D5 = +57
1
(c = 0.5, CHCl3). H NMR (600 MHz, CDCl3): δ = 7.40–7.25 (m,
10 H, ArH), 4.87 (d, J = 10.8 Hz, 1 H, CH2Ph), 4.69 (s, 1 H, 1-H),
4.67 (s, 2 H, CH2Ph), 4.63 (d, J = 10.8 Hz, 1 H, CH2Ph), 4.01 (br.
s, 1 H, 2-H), 3.81 (dd, J = 9.0, 3.0 Hz, 1 H, 3-H), 3.69 (m, 1 H, 5-
H), 3.43 (t, J = 9.0 Hz, 4-H), 3.33 (s, 3 H, -OCH3), 1.31 (d, J =
6.0 Hz, 3 H, 6-H) ppm. 13C NMR (150 MHz, CDCl3): δ = 138.37,
137.88, 128.54, 128.52, 128.36, 127.92, 127.90, 127.81, 127.68,
126.96, 99.97, 80.02, 79.88, 75.32, 71.98, 68.44, 67.09, 54.73,
17.87 ppm. HRMS (ESI): calcd. for [C21H26O5 + NH4]+ 376.2118;
found 376.2123.
solid. [α]2D5 = +38 (c = 2.7, CHCl3). H NMR (600 MHz, CDCl3):
1
δ = 7.77 (d, J = 8.4 Hz, 2 H, ArH), 7.34–7.23 (m, 7 H, ArH), 4.84
(d, J = 11.4 Hz, 1 H, CH2Ph), 4.83 (s, 1 H, 1-H), 4.48 (d, J =
11.4 Hz, 1 H, CH2Ph), 4.29 (dd, J = 10.5, 1.8 Hz, 1 H, 6-Ha), 4.25
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Methyl 2-O-Acetyl-3,4-di-O-benzyl-α-
D
-rhamnopyranoside (14): A
75.66, 72.01, 70.71, 67.56, 21.01, 17.98 ppm. C24H26Cl3NO6
(530.83): calcd. C 54.31, H 4.94, N 2.64; found C 54.24, H 5.11, N
2.55.
solution of 13 (1.05 g, 2.93 mmol) in Ac2O (5 mL) and pyridine
(8 mL) was stirred at room temp. for 2 h, and then the mixture was
concentrated under reduced pressure. The residue was purified by
flash column chromatography (petroleum ether/ethyl acetate, 2:1)
to give 14 (1.13 g, 96%) as a syrup. [α]2D5 = +19 (c = 0.6, CHCl3).
1H NMR (600 MHz, CDCl3): δ = 7.37–7.26 (m, 10 H, ArH), 5.36
(dd, J = 3.0, 1.2 Hz, 1 H, 2-H), 4.92 (d, J = 10.2 Hz, 1 H, CH2Ph),
4.69 (d, J = 11.4 Hz, 1 H, CH2Ph), 4.62 (br. s, 1 H, 1-H), 4.61 (d,
J = 10.2 Hz, 1 H, CH2Ph), 4.52 (d, J = 11.4 Hz, 1 H, CH2Ph), 3.92
(dd, J = 9.6, 3.0 Hz, 1 H, 3-H), 3.73 (m, 1 H, 5-H), 3.43 (t, J =
9.6 Hz, 1 H, 4-H), 2.15 (s, 3 H, -COCH3), 1.32 (d, J = 6.4 Hz, 3
H, 6-H) ppm. 13C NMR (150 MHz, CDCl3): δ = 170.43, 138.45,
137.98, 128.36, 128.34, 128.03, 127.89, 127.68, 127.65, 98.64, 79.98,
77.96, 75.37, 71.68, 68.84, 67.49, 54.81, 21.13, 17.96 ppm. HRMS
(ESI): calcd. for [C23H28O6 + NH4]+ 418.2224; found 418.2220.
p-Tolyl 3-O-Allyl-1-thio-α-D-mannopyranoside (17): Bu2SnO (2.5 g,
10 mmol) was added to a solution of 16[33] (2.86 g, 10 mmol) in dry
toluene (80 mL). The mixture was heated at reflux for 6 h with
azeotropic removal of water using Dean–Stark tube, and then it
was cooled to 60 °C. TBAI (3.69 g, 10 mmol) and allyl bromide
(1.3 mL, 15.0 mmol) were added. The mixture was stirred at 60 °C
overnight, and then it was concentrated under reduced pressure.
The residue was purified by flash column chromatography (ethyl
acetate) to give 17 (1.80 g, 55%). [α]2D5 = +155 (c = 0.2, CH3OH).
1H NMR (600 MHz, CD3OD): δ = 7.40 (d, J = 7.8 Hz, 2 H, ArH),
7.13 (d, J = 7.8 Hz, 2 H, ArH), 5.99 (m, 1 H, -OCH2CH=CH2),
5.48–5.33 (m, 2 H, 1-H and -OCH2CH=CH2), 5.20 (br. d, J =
10.8 Hz,
-OCH2CH=CH2), 4.14 (br. dd,
trated H2SO4 (0.1 mL) was added to a solution of 14 (980 mg, -OCH2CH=CH2), 4.05 (m, 1 H, 5-H), 3.82–3.77 (m, 2 H, 4-H and
1
H, -OCH2CH=CH2), 4.18 (m,
2
H, 2-H and
1,2-Di-O-acetyl-3,4-di-O-benzyl-
D-rhamnopyranose (15): Concen-
J
=
12.6, 6.0 Hz,
1
H,
2.45 mmol) in Ac2O and AcOH (1:1 v/v; 10 mL) at 0 °C, and the
mixture was stirred until TLC (petroleum ether/ethyl acetate, 4:1)
indicated that the reaction was complete. The solution was diluted
with CH2Cl2 (100 mL), and the organic phase was washed success-
ively with saturated aq. NaHCO3, water, and brine. The organic
phase was dried with Na2SO4, and concentrated. The residue was
subjected to silica gel column chromatography (petroleum ether/
ethyl acetate, 4:1) to give 15 (998 mg, 95%) as a white foamy solid.
[α]2D5 = +24 (c = 0.8, CHCl3). 1H NMR (600 MHz, CDCl3): δ =
7.36–7.26 (m, 10 H, ArH), 5.99 (s, 1 H, 1-H), 5.34 (br. s, 1 H, 2-
H), 4.91 (d, J = 10.2 Hz, 1 H, CH2Ph), 4.71 (d, J = 11.4 Hz, 1 H,
CH2Ph), 4.61 (d, J = 10.2 Hz, 1 H, CH2Ph), 4.54 (d, J = 11.4 Hz,
1 H, CH2Ph), 3.91 (dd, J = 9.6, 3.2 Hz, 1 H, 3-H), 3.79 (m, 1 H,
5-H), 3.46 (t, J = 9.6 Hz, 1 H, 4-H), 2.16 (s, 3 H, -COCH3), 2.06
(s, 3 H, -COCH3), 1.32 (d, J = 6.0 Hz, 3 H, 6-H) ppm. 13C NMR
(150 MHz, CDCl3): δ = 170.04, 168.53, 138.13, 137.66, 128.41,
128.06, 127.98, 127.83, 127.81, 91.07, 79.44, 77.54, 75.60, 71.87,
69.97, 67.73, 20.95, 20.89, 17.97 ppm. HRMS (ESI): calcd. for
[C24H28O7 + NH4]+ 446.2173; found 446.2174.
6a-H), 3.75 (dd, J = 12.0, 6.0 Hz, 1 H, 6b-H), 3.52 (dd, J = 9.6,
3.0 Hz, 1 H, 3-H), 2.32 (s, 3 H, -SPhCH3) ppm. 13C NMR
(150 MHz, CD3OD): δ = 137.56, 135.00, 132.11, 130.57, 129.34,
116.25, 89.25, 78.86, 74.23, 70.38, 69.18, 66.19, 61.19, 19.66 ppm.
HRMS (ESI): calcd. for [C16H22O5S + NH4]+ 344.1526; found
344.1527.
p-Tolyl
2,4,6-Tri-O-benzoyl-3-O-allyl-1-thio-α-D-mannopyranos-
ide (18): BzCl (2.0 mL, 17.2 mmol) was added dropwise to a solu-
tion of 17 (1.5 g, 4.60 mmol) in pyridine (10 mL) at 0 °C. The mix-
ture was stirred at room temp. for 2 h, then it was diluted with
CH2Cl2 (150 mL), and washed with HCl (1 m aq.), and brine. The
organic layer was dried with anhydrous Na2SO4, and concentrated.
The residue was purified by flash column chromatography (petro-
leum ether/ethyl acetate, 5:1) to give 18 (2.44 g, 83%) as a white
foamy solid. [α]2D5 = +97 (c = 1.3, CHCl3). 1H NMR (600 MHz,
CDCl3): δ = 8.09 (d, J = 8.4 Hz, 2 H, ArH), 8.07 (d, J = 8.4 Hz, 2
H, ArH), 8.03 (d, J = 8.4 Hz, 2 H, ArH), 8.13–8.08 (m, 3 H, ArH),
7.46 (t, J = 8.4 Hz, 2 H, ArH), 7.41–7.36 (m, 6 H, ArH), 6.98 (d,
J = 7.8 Hz, 2 H, ArH), 5.83 (m, 2 H, 2-H and 4-H), 5.77 (m, 1
2-O-Acetyl-3,4-di-O-benzyl-α-
D-rhamnopyranosyl
Trichloroacet- H, -OCH2CH=CH2), 5.62 (d, J = 1.2 Hz, 1 H, 1-H), 5.21 (m, 1
imidate (7): Hydrazine acetate (710 mg, 7.70 mmol) was added to
a solution of 15 (828 mg, 1.94 mmol) in DMF (5 mL) at 0 °C. The
mixture was stirred at 0 °C for 3 h, after which time TLC (petro-
leum ether/ethyl acetate, 2:1) showed that the reaction was com-
plete. The mixture was diluted with EtOAc (150 mL), and then
washed with water and brine. The organic phase was dried with
anhydrous Na2SO4, and concentrated, and the residue was purified
by silica gel column chromatography (petroleum ether/ethyl acetate,
2:1).
H, -OCH2CH=CH2), 5.11 (m, 1 H, -OCH2CH=CH2), 4.85 (ddd, J
= 9.6, 6.0, 2.4 Hz, 1 H, 5-H), 4.63 (dd, J = 12.0, 2.4 Hz, 1 H, 6a-
H), 4.47 (dd, J = 12.0, 6.0 Hz, 1 H, 6b-H), 4.14 (m, 1 H,
-OCH2CH=CH2), 4.12 (dd, J = 9.6, 3.6 Hz, 1 H, 3-H), 4.02 (m,
1 H, -OCH2CH=CH2), 2.23 (s, 3 H, -SPhCH3) ppm. 13C NMR
(150 MHz, CDCl3): δ = 166.18, 165.62, 165.43, 138.30, 133.91,
133.37, 133.35, 132.96, 132.52, 129.96, 129.92, 129.87, 129.79,
129.46, 129.44, 129.01, 128.59, 128.47, 128.31, 118.15, 86.61, 74.76,
70.87, 70.63, 69.79, 68.63, 63.37, 21.12 ppm. HRMS (ESI): calcd.
for [C37H34O8S + NH4]+ 656.2313; found 656.2318.
The product was then dissolved in anhydrous CH2Cl2 (5 mL), The
solution was cooled to 0 °C, and trichloroacetonitrile (1.0 mL,
10.0 mmol) and DBU (100 μL) were added. The mixture was
stirred for 30 min, and then it was concentrated. The residue was
purified by column chromatography (petroleum ether/ethyl acetate,
4:1) to give 7 (813 mg, 79% over two steps) as a white foamy solid.
[α]2D5 = +31 (c = 0.3, CHCl3). 1H NMR (600 MHz, CDCl3): δ =
p-Tolyl 2,4,6-Tri-O-benzoyl-1-thio-α-D-mannopyranoside (8): PdCl2
(177 mg, 1.0 mmol) was added to a solution of 18 (1.28 g,
2.0 mmol) in MeOH (20 mL) at room temp. The mixture was
stirred at room temp. for 3 h, after which time TLC (petroleum
ether/ethyl acetate, 3:1) indicated the disappearance of 18. The mix-
ture was diluted with CH2Cl2 (50 mL), and filtered through a Ce-
8.63 (s, 1 H, NH), 7.40–7.26 (m, 10 H, ArH), 6.16 (s, 1 H, 1-H), lite®454 pad. The filtrate was concentrated under reduced pressure.
5.47 (br. s, 1 H, 2-H), 4.92 (d, J = 10.8 Hz, 1 H, CH2Ph), 4.72 (d, The residue was purified by column chromatography (petroleum
J = 11.4 Hz, 1 H, CH2Ph), 4.62 (d, J = 10.8 Hz, 1 H, CH2Ph), 4.52 ether/ethyl acetate, 4:1) to give 8 (755 mg, 63%) as a white foamy
(d, J = 11.4 Hz, 1 H, CH2Ph), 3.98 (dd, J = 9.6, 2.4 Hz, 1 H, 3-
H), 3.93 (m, 1 H, 5-H), 3.51 (t, J = 9.6 Hz, 1 H, 4-H), 2.18 (s, 3 H,
solid. [α]2D5 = +145 (c = 1.0, CHCl3). 1H NMR (600 MHz, CDCl3):
δ = 8.10 (d, J = 8.4 Hz, 2 H, ArH), 8.04 (d, J = 8.4 Hz, 2 H, ArH),
-COCH3), 1.34 (d, J = 6.0 Hz, 3 H, 6-H) ppm. 13C NMR 8.01 (d, J = 8.4 Hz, 2 H, ArH), 7.64–7.53 (m, 3 H, ArH), 7.51–
(150 MHz, CDCl3): δ = 170.04, 160.08, 138.10, 137.50, 128.45,
128.43, 128.31, 128.14, 127.99, 127.92, 95.14, 90.82, 79.32, 77.15,
7.44 (m, 2 H, ArH), 7.43–7.35 (m, 6 H, ArH), 7.00 (d, J = 7.8 Hz,
2 H, ArH), 5.71 (t, J = 9.6 Hz, 1 H, 4-H), 5.69 (dd, J = 2.4, 1.2 Hz,
7080
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Eur. J. Org. Chem. 2015, 7075–7085

Synthesis of a Trisaccharide Repeating Unit
1 H, 2-H), 5.66 (s, 1 H, 1-H), 4.99 (ddd, J = 9.6, 5.4, 2.0 Hz, 1 H,
4.28 (d, J = 11.3 Hz, 1 H, CH2Ph), 3.74 (m, 1 H, 5Ј-H), 3.72 (br.
5-H), 4.65 (dd, J = 12.0, 2.0 Hz, 1 H, 6a-H), 4.52 (dd, J = 12.0, s, 1 H, 2Ј-H), 3.62 (dd, J = 9.2, 3.0 Hz, 1 H, 3Ј-H), 3.32 (t, J =
5.4 Hz, 1 H, 6b-H), 4.39 (dd, J = 9.6, 3.0 Hz, 1 H, 3-H), 2.27 (s, 3
H, -SPhCH3) ppm. 13C NMR (150 MHz, CDCl3): δ = 166.92,
166.12, 165.76, 138.33, 133.75, 133.59, 133.07, 132.57, 129.97,
9.2 Hz, 1 H, 4Ј-H), 2.27 (s, 3 H, -SPhCH3), 1.16 (d, J = 6.2 Hz, 3
H, 6Ј-H) ppm. 13C NMR (150 MHz, CDCl3): δ = 166.16, 165.56,
165.41, 138.38, 138.33, 137.67, 133.71, 133.45, 133.01, 132.60,
129.83, 129.75, 129.19, 128.95, 128.58, 128.36, 86.25, 74.27, 70.72, 129.97, 129.86, 129.81, 129.75, 129.36, 129.03, 128.88, 128.72,
69.80, 69.28, 63.21, 21.12 ppm. HRMS (ESI): calcd. for 128.59, 128.38, 128.33, 128.20, 127.81, 127.73, 127.60, 127.47,
[C34H30O8S + H]+ 599.1734; found 599.1736; calcd. for [C34H30O8S 101.12 (C-1Ј), 86.17 (C-1), 79.36 (C-3Ј), 79.25 (C-4Ј), 75.66 (C-3),
+ NH4]+ 616.2000; found 616.2001.
74.59 (CH2Ph), 73.36 (C-2), 71.88 (CH2Ph), 69.68 (C-5), 68.84 (C-
4), 68.56 (C-5Ј), 68.46 (C-2Ј), 63.20 (C-6), 21.12 (-SPhCH3), 17.65
(C-6Ј) ppm. HRMS (ESI): calcd. for [C54H52O12S + NH4]+
942.3518; found 942.3534.
p-Tolyl 2-O-Acetyl-3,4-di-O-benzyl-α-D-rhamnopyranosyl-(1Ǟ3)-
2,4,6-tri-O-benzoyl-1-thio-α-D-mannopyranoside (19): TMSOTf
(9 μL, 0.05 mmol) was added to
a
solution of (300 mg,
8
0.50 mmol) and 7 (293 mg, 0.55 mmol) in anhydrous CH2Cl2
(8 mL) at –78 °C under a nitrogen atmosphere. The mixture was
stirred at –78 °C for 2 h, then it was neutralized with Et3N, and
then concentrated. The residue was purified by column chromatog-
raphy (petroleum ether/ethyl acetate, 5:1) to give 19 (455 mg, 94%)
as a white foamy solid. [α]2D5 = +27 (c = 0.5, CHCl3). 1H NMR
p-Tolyl 2-O-Acetyl-3,4,6-tri-O-benzyl-α-
3,4-di-O-benzyl-α- -rhamnopyranosyl-(1Ǟ3)-2,4,6-tri-O-benzoyl-1-
thio-α-
D-mannopyranosyl-(1Ǟ2)-
D
D
-mannopyranoside (4): TMSOTf (25 µL, 0.135 mmol) was
added to a solution of 20 (358 mg, 0.386 mmol) and 6[25] (860 mg,
1.35 mmol) in anhydrous CH2Cl2 (10 mL) (7 μL, 0.038 mmol) at
–78 °C under a nitrogen atmosphere. The mixture was stirred for
(600 MHz, CDCl3): δ = 8.11 (d, J = 8.4 Hz, 2 H, ArH), 8.07 (d, J 2 h, then it was neutralized with Et3N, and then concentrated. The
= 8.4 Hz, 2 H, ArH), 8.02 (d, J = 8.4 Hz, 2 H, ArH), 7.61–7.54 residue was purified by flash column chromatography (petroleum
(m, 3 H, ArH), 7.47 (t, J = 7.8 Hz, 2 H, ArH), 7.40–7.37 (m, 6 H,
ArH), 7.27–7.23 (m, 3 H, ArH), 7.20–7.16 (m, 3 H, ArH), 7.13–
ether/ethylacetate,3:1)togive4(492 mg,91%)asawhitefoamysolid.
[α]2D5 = +47 (c = 0.5, CHCl3). 1H NMR (600 MHz, CDCl3): δ =
7.11 (m, 2 H, ArH), 7.09–7.06 (m, 2 H, ArH), 6.99 (d, J = 8.0 Hz, 8.08 (br. d, J = 5.5 Hz, 4 H, ArH), 8.02 (d, J = 7.6 Hz, 2 H, ArH),
2 H, ArH), 5.91 (t, J = 9.9 Hz, 1 H, 4-H), 5.74 (dd, J = 3.2, 1.8 Hz,
1 H, 2-H), 5.65 (d, J = 1.2 Hz, 1 H, 1-H), 5.02 (dd, J = 3.2, 1.8 Hz,
7.60–7.54 (m, 2 H, ArH), 7.48 (t, J = 7.1 Hz, 1 H, ArH), 7.43–7.20
(m, 25 H, ArH), 7.19–7.12 (m, 6 H, ArH), 7.11–7.08 (m, 2 H, ArH),
1 H, 2Ј-H), 4.95 (d, J = 1.6 Hz, 1 H, 1Ј-H), 4.85 (ddd, J = 9.9, 5.6, 6.98 (d, J = 7.6 Hz, 2 H, ArH), 5.87 (t, J = 9.6 Hz, 1 H, 4-H), 5.74
2.4 Hz, 1 H, 5-H), 4.72 (d, J = 11.2 Hz, 1 H, CH2Ph), 4.62 (dd, J
= 12.2, 2.4 Hz, 1 H, 6a-H), 4.49 (dd, J = 12.2, 5.6 Hz, 1 H, 6b-H),
4.44 (d, J = 11.2 Hz, 1 H, CH2Ph), 4.41 (dd, J = 9.9, 3.2 Hz, 1 H,
(br. s, 1 H, 2-H), 5.64 (s, 1 H, 1-H), 5.37 (br. s, 1 H, 2ЈЈ-H), 5.09
(s, 1 H, 1Ј-H), 4.81 (d, J = 10.8 Hz, 1 H, CH2Ph), 4.80 (m, 1 H, 5-
H), 4.73–4.67 (m, 3 H, CH2Ph), 4.67 (s, 1 H, 1ЈЈ-H), 4.57 (br. d, J
3-H), 4.19 (d, J = 11.0 Hz, 1 H, CH2Ph), 4.10 (d, J = 11.0 Hz, 1 = 11.9 Hz, 1 H, 6a-H), 4.52–4.43 (m, 4 H, 6b-H and CH2Ph), 4.41
H, CH2Ph), 3.73 (m, 1 H, 5Ј-H), 3.69 (dd, J = 9.4, 3.2 Hz, 1 H, 3Ј- (d, J = 10.8 Hz, 1 H, CH2Ph), 4.37 (br. d, J = 8.5 Hz, 1 H, 3-H),
H), 3.27 (t, J = 9.4 Hz, 1 H, 4Ј-H), 2.27 (s, 3 H, -SPhCH3), 1.92
(s, 3 H, -COCH3), 1.12 (d, J = 6.2 Hz, 3 H, 6Ј-H) ppm. 13C NMR
(150 MHz, CDCl3): δ = 169.75, 166.14, 165.54, 165.44, 138.46,
138.34, 137.75, 133.61, 133.46, 132.98, 132.59, 129.96, 129.93,
129.84, 129.76, 129.25, 129.02, 128.86, 128.62, 128.60, 128.33,
4.32 (d, J = 11.6 Hz, 1 H, CH2Ph), 4.16 (d, J = 11.6 Hz, 1 H,
CH2Ph), 3.88 (br. d, J = 7.2 Hz, 1 H, 3ЈЈ-H), 3.78 (t, J = 9.5 Hz, 1
H, 4ЈЈ-H), 3.71 (m, 1 H, 5ЈЈ-H), 3.68–3.62 (m, 3 H, 2Ј-H, 3Ј-H, and
5Ј-H), 3.55 (dd, J = 10.8, 3.6 Hz, 1 H, 6aЈЈ-H), 3.38 (br. d, J =
10.8 Hz, 1 H, 6bЈЈ-H), 3.28 (t, J = 9.4 Hz, 1 H, 4Ј-H), 2.26 (s, 3
128.17, 128.13, 127.95, 127.51, 127.38, 99.48 (C-1Ј), 86.13 (C-1), H, -SPhCH3), 2.08 (s, 3 H, -COCH3), 1.07 (d, J = 6.0 Hz, 3 H, 6Ј-
79.36 (C-4Ј), 77.33 (C-3Ј), 76.19 (C-3), 74.54 (CH2Ph), 73.08 (C-2), H) ppm. 13C NMR (150 MHz, CDCl3): δ = 169.96, 166.18, 165.59,
71.43 (CH2Ph), 69.65 (C-5), 68.93 (C-5Ј), 68.68 (C-2Ј), 68.63 (C-4), 165.46, 138.52, 138.35, 138.27, 138.18, 138.13, 137.86, 133.66,
63.16 (C-6), 21.11 (-SPhCH3), 20.77 (-COCH3), 17.69 (C-6Ј) ppm. 133.47, 133.01, 132.50, 129.95, 129.91, 129.84, 129.75, 129.31,
HRMS (ESI): calcd. for [C56H54O13S + NH4]+ 984.3623; found
984.3639.
129.06, 128.98, 128.77, 128.62, 128.35, 128.29, 128.19, 128.18,
128.13, 127.89, 127.72, 127.66, 127.62, 127.37, 100.58 (C-1Ј), 99.47
(C-1ЈЈ), 86.09 (C-1), 79.08 (C-4Ј), 79.00 (C-3Ј), 77.69 (C-3ЈЈ), 76.08
(C-3), 75.33 (C-2Ј), 75.07 (CH2Ph), 74.32 (CH2Ph), 74.10 (C-4ЈЈ),
73.37 (CH2Ph), 73.26 (C-2), 71.79 (CH2Ph), 71.73 (C-5ЈЈ), 71.63
(CH2Ph), 69.72 (C-5), 69.12 (C-5Ј), 68.64 (C-4), 68.52 (2 C, C-2ЈЈ
and C-6ЈЈ), 63.23 (C-6), 21.12 (-SPhCH3), 21.09 (-COCH3), 17.74
(C-6Ј) ppm. HRMS (ESI): calcd. for [C83H82O18S + NH4]+
1416.5560; found 1416.5563.
p-Tolyl 3,4-Di-O-benzyl-α-
D-rhamnopyranosyl-(1Ǟ3)-2,4,6-tri-O-
benzoyl-1-thio-α- -mannopyranoside (20): Acetyl chloride (1.0 mL)
D
was slowly added to a solution of 19 (427 mg, 0.442 mmol) in
MeOH and CH2Cl2 (1:1 v/v; 20 mL) at 0 °C. The mixture was
stirred at room temp. overnight, and then it was neutralized with
saturated aq. NaHCO3, and extracted with CH2Cl2 (2ϫ 100 mL).
The combined organic phases were dried with anhydrous Na2SO4,
and concentrated. The residue was purified by column chromatog-
raphy (toluene/ethyl acetate, 10:1) to give 20 (368 mg, 90%) as a
white foamy solid. [α]2D5 = +14 (c = 0.2, CHCl3). 1H NMR
3-Azidopropyl 2-O-Acetyl-3,4,6-tri-O-benzyl-α-
yl-(1Ǟ2)-3,4-di-O-benzyl-α- -rhamnopyranosyl-(1Ǟ3)-2,4,6-tri-O-
benzoyl-α- -mannopyranoside (21): NIS (146 mg, 0.652 mmol) and
D-mannopyranos-
D
D
(600 MHz, CDCl3): δ = 8.10 (d, J = 8.4 Hz, 2 H, ArH), 8.08 (d, J TMSOTf (6 μL, 0.033 mmol) were added to a solution of 4
= 8.4 Hz, 2 H, ArH), 8.02 (d, J = 8.4 Hz, 2 H, ArH), 7.62–7.54 (456 mg, 0.326 mmol) and 5[24] (165 mg, 1.63 mmol) in anhydrous
(m, 3 H, ArH), 7.48 (t, J = 7.8 Hz, 2 H, ArH), 7.43–7.37 (m, 6 H,
ArH), 7.28–7.24 (m, 3 H, ArH), 7.22–7.20 (m, 3 H, ArH), 7.16 (d,
J = 7.2 Hz, 2 H, ArH), 7.13–7.11 (m, 2 H, ArH), 7.00 (d, J =
7.8 Hz, 2 H, ArH), 5.91 (t, J = 9.8 Hz, 1 H, 4-H), 5.74 (br. s, 1 H,
2-H), 5.65 (br. s, 1 H, 1-H), 5.00 (d, J = 1.6 Hz, 1 H, 1Ј-H), 4.86
(ddd, J = 9.8, 6.0, 2.0 Hz, 1 H, 5-H), 4.71 (d, J = 11.3 Hz, 1 H,
CH2Ph), 4.59 (dd, J = 12.2, 2.0 Hz, 1 H, 6a-H), 4.50 (d, J =
11.3 Hz, 1 H, CH2Ph), 4.49 (dd, J = 12.2, 6.0 Hz, 1 H, 6b-H), 4.43
(dd, J = 9.8, 3.0 Hz, 1 H, 3-H), 4.38 (d, J = 11.3 Hz, 1 H, CH2Ph),
CH2Cl2 (10 mL) at –15 °C under a nitrogen atmosphere. The mix-
ture was slowly heated to 40 °C, and stirred for 4 h, after which
time TLC indicated the complete disappearance of 4. The mixture
was then neutralized with Et3N, and concentrated. The residue was
purified by flash column chromatography (petroleum ether/ethyl
acetate, 2:1) to give 21 (355 mg, 79 %) as a white foamy solid.
[α]2D5 = +11 (c = 1.7, CHCl3). 1H NMR (600 MHz, CDCl3): δ =
8.08 (d, J = 8.1 Hz, 2 H, ArH), 8.02 (d, J = 8.1 Hz, 4 H, ArH),
7.58 (t, J = 8.4 Hz, 1 H, ArH), 7.54 (t, J = 8.4 Hz, 1 H, ArH), 7.46
Eur. J. Org. Chem. 2015, 7075–7085
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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7081

X. Zhang, G. Gu, Z. Guo
FULL PAPER
(t, J = 8.4 Hz, 1 H, ArH), 7.43–7.19 (m, 22 H, ArH), 7.18–7.14 (m,
D-mannopyranoside (22): Acetyl chloride (1.0 mL) was added to a
3 H, ArH), 7.13–7.06 (m, 6 H, ArH), 5.84 (t, J = 9.9 Hz, 1 H, 4- solution of 21 (300 mg, 0.22 mmol) in MeOH and CH2Cl2 (1:1 v/
H), 5.48 (br. s, 1 H, 2-H), 5.36 (br. s, 1 H, 2ЈЈ-H), 5.06 (s, 1 H, 1Ј-
H), 5.02 (s, 1 H, 1-H), 4.79 (d, J = 11.2 Hz, 1 H, CH2Ph), 4.70 (d,
J = 11.2 Hz, 1 H, CH2Ph), 4.68 (s, 1 H, 1ЈЈ-H), 4.67 (d, J = 11.2 Hz,
1 H, CH2Ph), 4.63 (d, J = 12.4 Hz, 1 H, CH2Ph), 4.60 (dd, J =
v; 20 mL) at 0 °C. The solution was stirred at room temp. over-
night, and then it was neutralized with saturated aq. NaHCO3. The
mixture was extracted with CH2Cl2 (2 ϫ 100 mL). The organic
phase was dried with anhydrous Na2SO4, and concentrated. The
12.2, 2.3 Hz, 1 H, 6a-H), 4.46 (d, J = 11.2 Hz, 2 H, CH2Ph), 4.44– residue was purified by flash column chromatography (petroleum
4.34 (m, 4 H, 3-H, 6b-H, and CH2Ph), 4.30 (d, J = 11.6 Hz, 1 H, ether/ethyl acetate, 2:1) to give 22 (232 mg, 80%) as a white foamy
solid. [α]2D5 = +8 (c = 0.8, CHCl3). H NMR (600 MHz, CDCl3): δ
1
CH2Ph), 4.19 (m, 1 H, 5-H), 4.15 (d, J = 11.6 Hz, 1 H, CH2Ph),
3.86 (dd, J = 9.6, 3.2 Hz, 1 H, 3ЈЈ-H), 3.82 (m, 1 H, -OCH2-), 3.76 = 8.11–8.02 (m, 6 H, ArH), 7.58 (t, J = 7.2 Hz, 1 H, ArH), 7.54
(t, J = 9.6 Hz, 1 H, 4ЈЈ-H), 3.70–3.60 (m, 4 H, 2Ј-H, 3Ј-H, 5Ј-H, (t, J = 7.2 Hz, 1 H, ArH), 7.50 (t, J = 7.2 Hz, 1 H, ArH), 7.44–
and 5ЈЈ-H), 3.55 (m, 1 H, -OCH2-), 3.52 (dd, J = 10.5, 4.2 Hz, 1 7.20 (m, 22 H, ArH), 7.19–7.15 (m, 3 H, ArH), 7.14–7.11 (m, 2 H,
H, 6aЈЈ-H), 3.36 (t, J = 6.5 Hz, 2 H, -CH2N3), 3.32 (br. d, J =
ArH), 7.10–7.02 (m, 4 H, ArH), 5.84 (t, J = 10.0 Hz, 1 H, 4-H),
10.5 Hz, 1 H, 6bЈЈ-H), 3.25 (t, J = 9.7 Hz, 1 H, 4Ј-H), 2.08 (s, 3 H, 5.49 (br. s, 1 H, 2-H), 5.13 (s, 1 H, 1Ј-H), 5.02 (s, 1 H, 1-H), 4.76
-COCH3), 1.84 (m, 2 H, -OCH2CH2CH2N3), 1.04 (d, J = 6.2 Hz, (d, J = 10.7 Hz, 1 H, CH2Ph), 4.70 (br. s, 1 H, 1ЈЈ-H), 4.68–4.62
3 H, 6Ј-H) ppm. 13C NMR (150 MHz, CDCl3): δ = 169.92, 166.16, (m, 4 H, CH2Ph), 4.60 (dd, J = 12.2, 2.0 Hz, 1 H, 6a-H), 4.47 (d,
165.72, 165.39, 138.56, 138.33, 138.21, 138.14, 137.84, 133.58, J = 12.5 Hz, 1 H, CH2Ph), 4.45–4.35 (m, 4 H, 3-H, 6b-H, and
133.42, 133.03, 129.84, 129.66, 129.34, 129.15, 128.73, 128.59, CH2Ph), 4.23 (d, J = 11.5 Hz, 1 H, CH2Ph), 4.19 (m, 1 H, 5-H),
128.39, 128.34, 128.28, 128.17, 128.09, 127.87, 127.71, 127.67, 4.10 (d, J = 11.5 Hz, 1 H, CH2Ph), 3.94 (br. s, 1 H, 2ЈЈ-H), 3.81
127.61, 127.58, 127.34, 127.32, 127.29, 100.55 (C-1Ј), 99.29 (C-1ЈЈ), (m, 1 H, -OCH2-), 3.79–3.71 (m, 3 H, 3ЈЈ-H, 4ЈЈ-H, and 5ЈЈ-H),
97.35 (C-1), 79.08 (C-4Ј), 79.05 (C-3Ј), 77.66 (C-3ЈЈ), 75.71 (C-3), 3.67–3.62 (m, 2 H, 2Ј-H and 3Ј-H), 3.61 (m, 1 H, 5Ј-H), 3.58–3.49
75.07 (2 C, C-2Ј and CH2Ph), 74.23 (CH2Ph), 74.06 (C-4ЈЈ), 73.14 (m, 2 H, -OCH2- and 6aЈЈ-H), 3.42 (br. d, J = 10.8 Hz, 1 H,
(CH2Ph), 71.78 (C-2), 71.73 (CH2Ph), 71.69 (C-5ЈЈ), 71.55
6bЈЈ-H), 3.33 (t, J = 6.5 Hz, 2 H, -CH2N3), 3.20 (t, J = 9.6 Hz, 1
(CH2Ph), 68.97 (2 C, C-5 and C-5Ј), 68.45 (C-2ЈЈ), 68.42 (C-6ЈЈ), H, 4Ј-H), 1.83 (m, 2 H, -OCH2CH2CH2N3), 1.04 (d, J = 6.2 Hz, 3
68.33 (C-4), 65.10 (-OCH2-), 63.08 (C-6), 48.20 (-CH2N3), 28.65 H, 6Ј-H) ppm. 13C NMR (150 MHz, CDCl3): δ = 166.15, 165.74,
(-OCH2CH2CH2N3), 21.07 (-COCH3), 17.74 (C-6Ј) ppm. HRMS 165.53, 138.64, 138.20, 138.08, 137.85, 133.66, 133.38, 133.01,
(ESI): calcd. for [C79H81N3O19 + NH4]+ 1393.5803; found
1393.5803.
129.85, 129.83, 129.66, 129.35, 129.20, 128.76, 128.58, 128.47,
128.38, 128.33, 128.22, 128.07, 127.93, 127.87, 127.74, 127.68,
127.59, 127.48, 127.33, 127.25, 100.99 (C-1ЈЈ), 100.76 (C-1Ј), 97.35
(C-1), 79.56 (C-3ЈЈ), 79.44 (C-4Ј), 78.95 (C-3Ј), 76.20 (C-3), 75.46
(C-2Ј), 75.05 (CH2Ph), 74.18 (C-4ЈЈ), 74.08 (CH2Ph), 73.11
(CH2Ph), 72.01 (CH2Ph), 71.81 (C-2), 71.70 (CH2Ph), 71.36 (C-
5ЈЈ), 68.96 (C-5), 68.89 (C-5Ј), 68.60 (C-6ЈЈ), 68.33 (C-2ЈЈ), 68.26
(C-4), 65.12 (-OCH2-), 63.11 (C-6), 48.17 (-CH2N3), 28.64
(-OCH2CH2CH2N3), 17.74 (C-6Ј) ppm. HRMS (ESI): calcd. for
[C77H79N3O18 + NH4]+ 1351.5693; found 1351.5719.
3-Aminopropyl α-
D-Mannopyranosyl-(1Ǟ2)-α-D-rhamnopyranos-
yl-(1Ǟ3)-α- -mannopyranoside (1): Compound 21 (40 mg,
D
0.029 mmol) was dissolved in MeOH (5 mL), and NaOMe (1 m in
MeOH) was added dropwise until the pH reached 10. The mixture
was stirred at room temp. for 8 h, and then it was neutralized with
Amberlite IR 120 (H+). The solution was filtered and concentrated.
The residue was briefly purified by column chromatography
(CH2Cl2/MeOH, 20:1).
3-Azidopropyl 2-O-Acetyl-3,4,6-tri-O-benzyl-α-
yl-(1Ǟ2)-3,4-di-O-benzyl-α- -rhamnopyranosyl-(1Ǟ3)-2,4,6-tri-O-
benzoyl-α- -mannopyranosyl-(1Ǟ2)-3,4,6-tri-O-benzyl-α- -manno-
pyranosyl-(1Ǟ2)-3,4-di-O-benzyl-α- -rhamnopyranosyl-(1Ǟ3)-
2,4,6-tri-O-benzoyl-α- -mannopyranoside (23): NIS (100 mg,
D-mannopyranos-
The product was dissolved in a mixture of AcOH and H2O (1:9 v/
v; 5 mL), and then Pd/C (10%; 10 mg) was added. The suspension
was stirred under a hydrogen atmosphere at room temp. overnight.
The solid materials were filtered off, and the filtrate was concen-
trated. The residue was purified by size-exclusion chromatography
on a Bio-Gel P-2 column with distilled water as the eluent. Prod-
uct-containing fractions were then lyophilized to give 1 (12.4 mg,
D
D
D
D
D
0.45 mmol) and TMSOTf (4.2 μL, 0.023 mmol) were added to a
solution of 22 (214 mg, 0.16 mmol) and 4 (312 mg, 0.22 mmol) in
dry CH2Cl2 (8 mL) at –15 °C under a nitrogen atmosphere. The
mixture was warmed slowly to room temp., and stirred for 30 h,
after which time TLC indicated the disappearance of 4. The mix-
ture was then neutralized with Et3N, and concentrated. The residue
was purified by column chromatography (petroleum ether/ethyl
acetate, 3:1) to give 23 (310 mg, 74 %) as a white foamy solid.
[α]2D5 = +10 (c = 0.2, CHCl3). 1H NMR (600 MHz, CDCl3): δ =
8.16–8.02 (m, 8 H, ArH), 7.99 (d, J = 7.4 Hz, 2 H, ArH), 7.86 (d,
J = 7.4 Hz, 2 H, ArH), 7.61 (t, J = 7.4 Hz, 1 H, ArH), 7.58 (t, J
= 7.4 Hz, 1 H, ArH), 7.54 (t, J = 7.4 Hz, 1 H, ArH), 7.52 (t, J =
7.4 Hz, 1 H, ArH), 7.43–7.07 (m, 59 H, ArH), 6.98 (d, J = 7.5 Hz,
2 H, ArH), 6.89 (t, J = 7.6 Hz, 2 H, ArH), 6.64 (t, J = 7.5 Hz, 1
H, ArH), 5.89 (t, J = 9.9 Hz, 1 H, 4ЈЈЈ-H), 5.84 (t, J = 9.9 Hz, 1
H, 4-H), 5.59 (br. s, 1 H, 2ЈЈЈ-H), 5.49 (br. s, 1 H, 2-H), 5.41 (br. s,
1 H, 2ЈЈЈЈЈ-H), 5.06 (s, 1 H, 1Ј-H), 5.03 (br. s, 2 H, 1-H and 1ЈЈ-H),
4.98 (s, 2 H, 1ЈЈЈ-H and 1ЈЈЈЈ-H), 4.90 (s, 1 H, 1ЈЈЈЈЈ-H), 4.81 (br.
d, J = 10.8 Hz, 1 H, CH2Ph), 4.78 (d, J = 11.4 Hz, 2 H, CH2Ph),
4.68 (d, J = 11.4 Hz, 1 H, CH2Ph), 4.66 (d, J = 11.4 Hz, 1 H,
1
78% over two steps) as a white foamy solid. H NMR (600 MHz,
D2O): δ = 5.09 (s, 1 H, 1Ј-H), 4.88 (d, J = 1.2 Hz, 1 H, 1-H), 4.67
(d, J = 1.2 Hz, 1 H, 1ЈЈ-H), 3.94 (dd, J = 3.0, 1.6 Hz, 1 H, 2Ј-H),
3.91 (dd, J = 3.2, 1.8 Hz, 1 H, 2-H), 3.86 (dd, J = 3.0, 1.5 Hz, 1
H, 2ЈЈ-H), 3.78 (dd, J = 9.8, 3.2 Hz, 1 H, 3Ј-H), 3.72 (dd, J = 12.0,
1.5 Hz, 1 H, 6a-H), 3.70–3.63 (m, 5 H, 3-H, 3ЈЈ-H, 5Ј-H, 6aЈЈ-H,
and -OCH2-), 3.63–3.55 (m, 3 H, 4ЈЈ-H, 6b-H, and 6bЈЈ-H), 3.53–
3.50 (m, 2 H, 4-H and 5-H), 3.49–3.40 (m, 2 H, 5ЈЈ-H and -OCH2-),
3.33 (t, J = 9.7 Hz, 1 H, 4Ј-H), 2.97 (m, 2 H, -CH2NH2), 1.83 (m,
2 H, -OCH2CH2CH2NH2), 1.13 (d, J = 6.2 Hz, 3 H, 6Ј-H) ppm.
13C NMR (150 MHz, D2O): δ = 102.33 (C-1), 100.84 (C-1Ј), 99.53
(C-1ЈЈ), 78.62 (C-3), 78.36 (C-2Ј), 73.19 (C-5), 72.86 (C-5ЈЈ), 71.97
(C-4Ј), 70.21 (C-3ЈЈ), 69.81 (C-2), 69.76 (C-3Ј), 69.65 (C-2ЈЈ), 69.10
(C-5Ј), 66.50 (C-4), 65.89 (C-4ЈЈ), 64.77 (-OCH2-), 60.80 (C-6ЈЈ),
60.73 (C-6), 37.36 (-CH2NH2), 26.57 (-OCH2CH2CH2NH2), 16.54
(C-6Ј) ppm. HRMS (ESI): calcd. for [C21H39NO15 + H]+ 546.2392;
found 546.2388.
3-Azidopropyl 3,4,6-Tri-O-benzyl-α-
D
-mannopyranosyl-(1Ǟ2)-3,4- CH2Ph), 4.63 (br. s, 2 H, CH2Ph), 4.62–4.58 (m, 2 H, 6a-H and
CH2Ph), 4.57–4.52 (m, 2 H, 3ЈЈЈ-H and CH2Ph), 4.49 (d, J =
di-O-benzyl-α- -rhamnopyranosyl-(1Ǟ3)-2,4,6-tri-O-benzoyl-α-
D
7082
www.eurjoc.org
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2015, 7075–7085

Synthesis of a Trisaccharide Repeating Unit
12.6 Hz, 1 H, CH2Ph), 4.46–4.38 (m, 7 H, 3-H, 6b-H, and CH2Ph),
HRMS (ESI): calcd. for [C39H69NO29 + H]+ 1016.4028; found
4.32 (d, J = 10.2 Hz, 1 H, CH2Ph), 4.31 (d, J = 10.8 Hz, 1 H, 1016.4045.
CH2Ph), 4.25–4.14 (m, 4 H, 5-H, 5ЈЈЈ-H, 6aЈЈЈ-H, and CH2Ph), 4.12
3-Azidopropyl 3,4,6-Tri-O-benzyl-α-
(1Ǟ2)-3,4-di-O-benzyl-α- -rhamnopyranosyl-(1Ǟ3)-2,4,6-tri-O-
benzoyl-α- -mannopyranosyl-(1Ǟ2)-3,4,6-tri-O-benzyl-α- -manno-
pyranosyl-(1Ǟ2)-3,4-di-O-benzyl-α- -rhamnopyranosyl-(1Ǟ3)-
2,4,6-tri-O-benzoyl-α- -mannopyranoside (24): Acetyl chloride
D-mannopyranosyl-
(d, J = 12.2 Hz, 1 H, CH2Ph), 4.07 (d, J = 11.2 Hz, 1 H, CH2Ph),
4.00 (br. d, J = 11.0 Hz, 1 H, 6bЈЈЈ-H), 3.93 (br. s, 1 H, 2Ј-H), 3.91
(m, 1 H, 3ЈЈ-H), 3.90–3.81 (m, 5 H, 4ЈЈ-H, 3ЈЈЈЈЈ-H, 4ЈЈЈЈЈ-H, 5ЈЈЈЈ-
H, and -OCH2-), 3.80 (br. s, 1 H, 2ЈЈЈЈ-H), 3.72 (dd, J = 9.6, 2.4 Hz,
1 H, 3ЈЈЈЈ-H), 3.70 (br. s, 1 H, 2ЈЈ-H), 3.64 (m, 1 H, 5Ј-H), 3.61
(dd, J = 9.6, 2.4 Hz, 2 H, 3Ј-H and 5ЈЈ-H), 3.56 (m, 1 H, -OCH2-),
3.43 (dd, J = 10.7, 4.2 Hz, 1 H, 6aЈЈЈЈЈ-H), 3.40–3.32 (m, 4 H, 4ЈЈЈЈ-
H, 5ЈЈЈЈЈ-H, and -CH2N3), 3.23 (br. d, J = 10.7 Hz, 1 H, 6bЈЈЈЈЈ-
H), 3.20–3.13 (m, 2 H, 4Ј-H and 6aЈЈ-H), 2.86 (br. d, J = 10.6 Hz,
1 H , 6 b Ј Ј - H ) , 2 . 0 3 ( s, 3 H , - C O C H 3 ) , 1 . 8 5 ( m , 2 H ,
-OCH2CH2CH2N3), 1.10 (d, J = 6.1 Hz, 3 H, 6ЈЈЈЈ-H), 1.07 (d, J =
6.1 Hz, 3 H, 6Ј-H) ppm. 13C NMR (150 MHz, CDCl3): δ = 169.93,
166.15, 165.94, 165.67, 165.42, 165.22, 165.08, 138.70, 138.60,
138.31, 138.23, 138.12, 137.88, 137.79, 133.57, 133.49, 133.40,
133.30, 133.01, 132.85, 130.08, 129.88, 129.83, 129.79, 129.67,
129.66, 129.61, 129.37, 129.09, 129.02, 128.72, 128.68, 128.59,
128.57, 128.45, 128.42, 128.38, 128.35, 128.33, 128.29, 128.21,
128.20, 128.15, 128.13, 128.07, 127.87, 127.85, 127.78, 127.67,
127.62, 127.55, 127.48, 127.34, 127.26, 127.24, 127.12, 125.29,
100.53 (C-1ЈЈ), 99.90 (2 C, C-1Ј and C-1ЈЈЈЈ), 98.86 (2 C, C-1ЈЈЈ and
C-1ЈЈЈЈЈ), 97.39 (C-1), 79.62, 79.55, 79.23, 78.94, 78.42, 77.65,
76.81, 75.18, 74.99, 74.92, 74.34, 74.29, 74.28, 74.08, 73.64, 73.14,
73.09, 72.62, 72.19, 72.01, 71.96, 71.83 (2 C), 71.79 (2 C), 71.68 (2
C), 69.26, 69.10, 69.04 (2 C), 68.63, 68.50, 68.47, 68.32 (C-6ЈЈЈЈЈ),
67.69 (C-6ЈЈ), 65.08 (-OCH2-), 63.13 (C-6), 62.31 (C-6ЈЈЈ), 48.19
(-CH2N3), 28.68 (-OCH2CH2CH2N3), 21.10 (-COCH3), 17.76 (C-
6Ј), 17.72 (C-6ЈЈЈЈ) ppm. HRMS (ESI): calcd. for [C153H153N3O36
+ 2NH4]2+ 1322.0455; found 1322.0473.
D
D
D
D
D
(0.5 mL) was added to a solution of 23 (246 mg, 0.094 mmol) in
MeOH and CH2Cl2 (1:1 v/v; 10 mL) at 0 °C. The mixture was
stirred at room temp. for 36 h, then it was neutralized with satu-
rated aq. NaHCO3, and extracted with CH2Cl2 (2ϫ 60 mL). The
organic phase was dried with anhydrous Na2SO4, and concen-
trated. The residue was purified by flash column chromatography
(petroleum ether/ethyl acetate, 2:1) to give 24 (206 mg, 85%) as a
white foamy solid. [α]2D5 = +19 (c = 0.3, CHCl3). 1H NMR
(600 MHz, CDCl3): δ = 8.13–8.02 (m, 8 H, ArH), 7.99 (d, J =
7.8 Hz, 2 H, ArH), 7.87 (d, J = 8.4 Hz, 2 H, ArH), 7.60 (t, J =
7.2 Hz, 1 H, ArH), 7.57 (t, J = 7.8 Hz, 1 H, ArH), 7.54 (t, J =
7.2 Hz, 1 H, ArH), 7.49 (t, J = 7.2 Hz, 1 H, ArH), 7.43–7.07 (m,
59 H, ArH), 6.97 (d, J = 7.8 Hz, 2 H, ArH), 6.88 (t, J = 7.5 Hz, 2
H, ArH), 6.64 (t, J = 7.5 Hz, 1 H, ArH), 5.88 (t, J = 9.6 Hz, 1 H,
4ЈЈЈ-H), 5.84 (t, J = 9.9 Hz, 1 H, 4-H), 5.58 (br. s, 1 H, 2ЈЈЈ-H),
5.48 (br. s, 1 H, 2-H), 5.06 (s, 1 H, 1Ј-H), 5.02 (br. s, 3 H, 1-H, 1ЈЈ-
H, and 1ЈЈЈЈ-H), 4.99 (s, 1 H, 1ЈЈЈ-H), 4.91 (s, 1 H, 1ЈЈЈЈЈ-H), 4.81
(br. d, J = 9.6 Hz, 1 H, CH2Ph), 4.74 (d, J = 10.8 Hz, 1 H, CH2Ph),
4.70 (d, J = 11.4 Hz, 1 H, CH2Ph), 4.68 (d, J = 12.6 Hz, 1 H,
CH2Ph), 4.65–4.56 (m, 6 H, 6a-H and CH2Ph), 4.53 (dd, J = 9.7,
2.6 Hz, 1 H, 3ЈЈЈ-H), 4.49 (d, J = 12.6 Hz, 1 H, CH2Ph), 4.45 (d, J
= 11.4 Hz, 1 H, CH2Ph), 4.45–4.37 (m, 5 H, 3-H, 6b-H, and
CH2Ph), 4.35 (d, J = 10.8 Hz, 1 H, CH2Ph), 4.33 (d, J = 12.0 Hz,
1 H, CH2Ph), 4.27 (d, J = 11.4 Hz, 1 H, CH2Ph), 4.22 (m, 1 H,
3-Aminopropyl α-
(1Ǟ3)-α- -mannopyranosyl-(1Ǟ2)-α-
-rhamnopyranosyl-(1Ǟ3)-α- -mannopyranoside (2): Compound 23
(45 mg, 0.017 mmol) was dissolved in MeOH (5 mL), and
NaOMe (1 m in MeOH) was added dropwise until the pH reached
D
-Mannopyranosyl-(1Ǟ2)-α-
D-rhamnopyranosyl- 5ЈЈЈ-H), 4.21–4.12 (m, 4 H, 5-H, 6aЈЈЈ-H, and CH2Ph), 4.05 (d, J
D
D
-mannopyranosyl-(1Ǟ2)-α-
= 11.8 Hz, 1 H, CH2Ph), 4.01 (br. d, J = 12.0 Hz, 1 H, 6bЈЈЈ-H),
3.93 (br. s, 2 H, 2Ј-H and 2ЈЈЈЈЈ-H), 3.91–3.81 (m, 4 H, 3ЈЈ-H, 4ЈЈ-
H, 4ЈЈЈЈЈ-H, and -OCH2-), 3.80–3.67 (m, 5 H, 2ЈЈ-H, 2ЈЈЈЈ-H, 3ЈЈЈЈ-
H, 3ЈЈЈЈЈ-H, 5ЈЈЈ-H, and 5ЈЈЈЈ-H), 3.67–3.52 (m, 4 H, 3Ј-H, 5Ј-H,
D
D
10. The mixture was stirred at room temp. for 24 h, and then it was 5ЈЈ-H, and -OCH2-), 3.46–3.38 (m, 2 H, 5ЈЈЈЈЈ-H and 6aЈЈЈЈЈ-H),
neutralized with Amberlite IR 120 (H+). The solution was filtered
and concentrated. The residue was purified by flash column
chromatography (CH2Cl2/MeOH, 25:1).
3.35 (t, J = 6.5 Hz, 2 H, -CH2N3), 3.26 (t, J = 9.6 Hz, 1 H, 4ЈЈЈЈ-
H), 3.22 (br. d, J = 10.8 Hz, 1 H, 6bЈЈЈЈЈ-H), 3.20–3.13 (m, 2 H, 4Ј-
H and 6aЈЈ-H), 2.94 (br. d, J = 10.8 Hz, 1 H, 6bЈЈ-H), 1.85 (m, 2 H,
-OCH2CH2CH2N3), 1.10 (d, J = 6.0 Hz, 3 H, 6ЈЈЈЈ-H), 1.07 (d, J =
6.0 Hz, 3 H, 6Ј-H) ppm. 13C NMR (150 MHz, CDCl3): δ = 166.14,
165.94, 165.66, 165.42, 165.23, 165.15, 138.69, 138.60, 138.32,
138.28, 138.24, 138.07, 137.96, 137.77, 133.57, 133.51, 133.39,
133.27, 133.00, 132.84, 130.08, 129.86, 129.83, 129.78, 129.65,
129.37, 129.08, 129.02, 128.72, 128.68, 128.58, 128.56, 128.45,
128.43, 128.40, 128.37, 128.34, 128.28, 128.23, 128.22, 128.19,
128.13, 128.10, 128.06, 127.88, 127.81, 127.77, 127.73, 127.64,
127.56, 127.53, 127.48, 127.45, 127.34, 127.29, 127.25, 127.22,
125.28, 100.50 (2 C, C-1ЈЈ and C-1ЈЈЈЈЈ), 100.04 (C-1ЈЈЈЈ), 99.85 (C-
1Ј), 98.84 (C-1ЈЈЈ), 97.39 (C-1), 79.60, 79.46, 79.42, 79.37, 79.22,
78.39, 76.19, 75.16, 74.93, 74.87, 74.48, 74.35, 74.28, 74.15, 73.77,
73.15 (2 C), 73.08 (2 C), 72.17, 72.03, 71.95 (3 C), 71.82, 71.78,
71.47, 69.19, 69.09, 69.04 (2 C), 69.00, 68.56, 68.50 (2 C), 68.36,
6 7 . 8 1 , 6 5 . 0 8 , 6 3 . 1 2 , 6 2 . 3 4 , 4 8 . 1 9 ( - C H 2 N 3 ) , 2 8 . 6 7
(-OCH2CH2CH2N3), 17.75 (2 C, C-6Ј and C-6ЈЈЈЈ) ppm. HRMS
(ESI): calcd. for [C151H151N3O35 + 2NH4]2+ 1301.0402; found
1301.0423.
The product was dissolved in a mixture of AcOH and H2O (1:9 v/
v; 5 mL), and Pd/C (10%; 15 mg) was added. The suspension was
stirred under a hydrogen atmosphere at room temp. overnight. The
solid materials were filtered off, and the solution was concentrated.
The residue was purified by size-exclusion chromatography on a
Bio-Gel P-2 column with distilled water as the eluent. Product-
containing fractions were lyophilized to give 2 (11.4 mg, 65% over
two steps) as a white solid. 1H NMR (600 MHz, D2O): δ = 5.12 (s,
1 H, 1-H), 5.10 (s, 1 H, 1-H), 5.07 (s, 1 H, 1-H), 4.87 (s, 1 H, 1-
H), 4.85 (s, 1 H, 1-H), 4.67 (s, 1 H, 1-H), 3.96 (br. s, 1 H, 2-H),
3.94 (br. s, 1 H, 2-H), 3.93 (br. s, 1 H, 2-H), 3.91 (br. s, 2 H, 2ϫ
2-H), 3.85 (br. s, 1 H, 2-H), 3.80–3.74 (m, 3 H, 3ϫ 3-H), 3.74–3.63
(m, 10 H, 3ϫ 3-H, 2ϫ 5-H, 4ϫ 6a-H, and -OCH2-), 3.62–3.53 (m,
8 H, 4-H, 3ϫ 5-H, and 4ϫ 6b-H), 3.52–3.40 (m, 5 H, 3ϫ 4-H, 5-
H, and -OCH2-), 3.32 (t, J = 9.6 Hz, 2 H, 2ϫ 4-H), 2.97 (m, 2 H, -
CH2NH2), 1.83 (m, 2 H, -OCH2CH2CH2NH2), 1.14 (br. d, J =
6.0 Hz, 3 H, 6-H), 1.13 (br. d, J = 5.4 Hz, 3 H, 6-H) ppm. 13C
NMR (150 MHz, D2O): δ = 102.31 (C-1), 101.88 (C-1), 100.79 (C-
1), 100.76 (C-1), 100.62 (C-1), 99.50 (C-1), 78.64, 78.58, 78.49,
78.42, 78.34, 78.31, 73.22, 73.16, 72.81, 71.95 (2 C), 70.18, 69.83,
69.80, 69.71 (2 C), 69.63, 69.60 (2 C), 69.09 (2 C), 66.68, 66.50,
3-Azidopropyl 2-O-Acetyl-3,4,6-tri-O-benzyl-α-
(1Ǟ2)-3,4-di-O-benzyl-α- -rhamnopyranosyl-(1Ǟ3)-2,4,6-tri-O-
benzoyl-α- -mannopyranosyl-(1Ǟ2)-3,4,6-tri-O-benzyl-α- -manno-
65.85 (2 C), 64.7 (-OCH2-), 60.77 (4 C, 4ϫ C-6), 37.33 (-CH2NH2), pyranosyl-(1Ǟ2)-3,4-di-O-benzyl-α- -rhamnopyranosyl-(1Ǟ3)-
26.54 (-OCH2 CH2 CH2 NH2 ), 16.52 (2 C, 2 ϫ C-6) ppm. 2,4,6-tri-O-benzoyl-α- -mannopyranosyl-(1Ǟ2)-3,4,6-tri-O-benzyl-
D-mannopyranosyl-
D
D
D
D
D
Eur. J. Org. Chem. 2015, 7075–7085
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
7083

X. Zhang, G. Gu, Z. Guo
FULL PAPER
α-
D
-mannopyranosyl-(1Ǟ2)-3,4-di-O-benzyl-α-
D-rhamnopyranosyl-
tion was filtered and concentrated. The residue was purified by
(1Ǟ3)-2,4,6-tri-O-benzoyl-α-D-mannopyranoside (25): NIS (70 mg, flash column chromatography (CH2Cl2/MeOH, 25:1).
0.312 mmol) and TMSOTf (3.0 μL, 0.017 mmol) were added to a
solution of 24 (200 mg, 0.078 mmol) and 4 (218 mg, 0.156 mmol)
in dry CH2Cl2 (8 mL) at –15 °C under a nitrogen atmosphere. The
mixture was stirred for 5 h, after which time TLC indicated the
disappearance of 24. The mixture was then neutralized with Et3N,
and concentrated. The residue was purified by column chromatog-
raphy (petroleum ether/ethyl acetate, 3:1) to give 25 (245 mg, 82%)
as a white foamy solid. [α]2D5 = +9 (c = 0.2, CHCl3). 1H NMR
(600 MHz, CDCl3): δ = 8.19–7.95 (m, 14 H, ArH), 7.80 (d, J =
8.4 Hz, 2 H, ArH), 7.77 (d, J = 7.8 Hz, 2 H, ArH), 7.63 (t, J =
7.5 Hz, 1 H, ArH), 7.59 (t, J = 7.5 Hz, 2 H, ArH), 7.55 (t, J =
7.5 Hz, 2 H, ArH), 7.49 (t, J = 7.2 Hz, 1 H, ArH), 7.43–7.07 (m,
84 H, ArH), 7.06–7.00 (m, 4 H, ArH), 6.99 (d, J = 7.8 Hz, 2 H,
ArH), 6.90 (t, J = 7.5 Hz, 2 H, ArH), 6.85 (t, J = 7.5 Hz, 2 H,
ArH), 6.66 (t, J = 7.2 Hz, 1 H, ArH), 6.56 (t, J = 7.2 Hz, 1 H,
ArH), 5.89 (t, J = 9.6 Hz, 1 H, 4-H), 5.87–5.82 (m, 2 H, 2ϫ 4-H),
5.58 (s, 1 H, 2-H), 5.57 (s, 1 H, 2-H), 5.50 (s, 1 H, 2-H), 5.41 (s, 1
H, 2-H), 5.27 (s, 1 H, 1-H), 5.06 (br. s, 2 H, 2ϫ 1-H), 5.04 (s, 1 H,
1-H), 4.98 (s, 1 H, 1-H), 4.96 (s, 1 H, 1-H), 4.94 (s, 1 H, 1-H), 4.90
(s, 1 H, 1-H), 4.88 (s, 1 H, 1-H), 4.87–4.72 (m, 4 H, CH2Ph), 4.72–
4.37 (m, 23 H, 2ϫ 3-H, 6-H, and CH2Ph), 4.36–4.26 (m, 3 H, 5-
H and CH2Ph), 4.25–4.13 (m, 8 H, 2ϫ 5-H, 2ϫ 6-H, and CH2Ph),
4.12–3.98 (m, 7 H, 2ϫ 2-H, 3-H, 2ϫ 5-H, and 2ϫ 6-H), 3.89–3.76
(m, 8 H, 2ϫ 2-H, 3ϫ 3-H, 2ϫ 5-H, and -OCH2-), 3.74–3.69 (m,
2 H, 2-H and 5-H), 3.68–3.54 (m, 5 H, 3ϫ 3-H, 5-H, and -OCH2-),
3.46 (dd, J = 10.6, 4.0 Hz, 1 H, 6-H), 3.41–3.31 (m, 4 H, 2ϫ 4-H
and -CH2N3), 3.27 (br. d, J = 10.6 Hz, 1 H, 6-H), 3.23 (t,
J = 9.6 Hz, 2 H, 2ϫ 4-H), 3.19 (t, J = 9.6 Hz, 2 H, 2ϫ 4-H),
3.15 (br. d, J = 10.8 Hz, 1 H, 6-H), 3.02 (br. d, J = 11.2 Hz,
1 H, 6-H), 2.83 (br. d, J = 10.8 Hz, 1 H, 6-H), 2.65 (br. d, J =
11.2 Hz, 1 H, 6-H), 2.03 (s, 3 H, -COCH3), 1.86 (m, 2 H,
-OCH2CH2CH2N3), 1.16 (d, J = 6.0 Hz, 3 H, 6-H), 1.10 (d, J =
6.0 Hz, 3 H, 6-H), 1.09 (d, J = 6.0 Hz, 3 H, 6-H) ppm. 13C NMR
(150 MHz, CDCl3): δ = 169.92, 166.16, 165.95, 165.92, 165.68,
165.46, 165.26, 165.15, 165.11, 165.00, 138.74, 138.64, 138.61,
138.39, 138.34, 138.31, 138.23, 138.22, 138.15, 137.90, 137.81,
137.74, 133.59, 133.47, 133.41, 133.29, 133.02, 132.83, 130.15,
130.10, 129.91, 129.84, 129.80, 129.67, 129.64, 129.59, 129.53,
129.38, 129.11, 129.00, 128.88, 128.69, 128.65, 128.60, 128.57,
128.46, 128.43, 128.39, 128.36, 128.34, 128.32, 128.31, 128.29,
128.24, 128.20, 128.17, 128.15, 128.12, 128.10, 128.08, 128.02,
127.86, 127.81, 127.74, 127.72, 127.68, 127.66, 127.61, 127.60,
127.55, 127.50, 127.43, 127.40, 127.34, 127.29, 127.26, 127.23,
127.13, 100.58 (C-1), 99.95 (C-1), 99.78 (2 C, 2ϫ C-1), 99.08 (2 C,
2ϫ C-1), 98.90 (C-1), 98.86 (C-1), 97.41 (C-1), 79.76, 79.66, 79.54,
79.51, 79.24, 78.99, 78.22, 77.67, 77.37, 76.96, 75.25, 75.03, 75.00,
74.95, 74.43, 74.37, 74.31, 74.24 (2 C), 73.97, 73.90, 73.64, 73.12 (3
C), 73.07, 72.62, 72.56, 72.19, 72.05 (2 C), 72.01, 71.97, 71.79 (5
C), 71.69, 71.08, 69.47, 69.25, 69.18, 69.11, 69.06 (2 C), 68.96,
68.65, 68.57, 68.51, 68.36, 67.68, 67.59, 65.10, 63.15, 62.59, 62.28,
The product was dissolved in a mixture of AcOH and H2O (1:9 v/
v; 4 mL), and Pd/C (10%; 12 mg) was added. The suspension was
stirred under a hydrogen atmosphere at room temp. for 36 h. The
solid materials were filtered off, and the solution was concentrated.
The residue was purified by size-exclusion chromatography on a
Bio-Gel P-2 column with distilled water as the eluent. Product-
containing fractions were lyophilized to give 3 (18.1 mg, 61% over
two steps) as a white solid. 1H NMR (600 MHz, D2O): δ = 5.13 (s,
2 H, 2ϫ 1-H), 5.10 (br. s, 2 H, 2ϫ 1-H), 5.08 (s, 1 H, 1-H), 4.88
(s, 1 H, 1-H), 4.86 (s, 2 H, 2ϫ 1-H), 4.67 (s, 1 H, 1-H), 3.98 (br. s,
2 H, 2ϫ 2-H), 3.95 (br. s, 2 H, 2ϫ 2-H), 3.93 (br. s, 1 H, 2-H),
3.91 (br. s, 3 H, 3ϫ 2-H), 3.86 (br. s, 1 H, 2-H), 3.80–3.75 (m, 4
H, 4ϫ 3-H), 3.74–3.40 (m, 35 H, 5ϫ 3-H, 7ϫ 4-H, 9ϫ 5-H, 12ϫ
6-H, and -OCH2-), 3.32 (t, J = 9.7 Hz, 2 H, 2ϫ 4-H), 2.96 (m, 2
H, -CH2NH2), 1.83 (m, 2 H, -OCH2CH2CH2NH2), 1.14 (br. d, J
= 6.0 Hz, 6 H, 2ϫ 6-H), 1.13 (br. d, J = 5.4 Hz, 3 H, 6-H) ppm.
13C NMR (150 MHz, D2O): δ = 102.32 (C-1), 101.89 (2 C, 2ϫ C-
1), 100.81 (C-1), 100.77 (2 C, 2ϫ C-1), 100.62 (2 C, 2ϫ C-1), 99.52
(C-1), 78.65 (2 C), 78.59, 78.56, 78.51, 78.43, 78.38 (2 C), 73.24 (3
C), 73.17, 72.84, 71.99 (3 C), 70.2, 69.86, 69.83, 69.74 (3 C), 69.65
(3 C), 69.40 (2 C), 69.12 (3 C), 66.75, 66.72, 66.53, 65.87 (3 C),
64.76 (-OCH2-), 60.81 (6 C, 6ϫ C-6), 37.36 (-CH2NH2), 26.57
(-OCH2CH2CH2NH2), 16.54 (3 C, 3ϫ C-6) ppm. HRMS (ESI):
calcd. for [C57H99NO43 + H]+ 1486.5664; found 1486.5684.
Acknowledgments
This work was supported by the National Major Scientific and
Technological Special Project for Significant New Drugs Develop-
ment (grant number 2012ZX09502001-005) and by the National
Basic Research (973) Program of China (grant number
2012CB822102).
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mannopyranosyl-(1Ǟ2)-α- -rhamnopyranosyl-(1Ǟ3)-α- -manno-
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7084
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Eur. J. Org. Chem. 2015, 7075–7085

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Received: July 22, 2015
Published Online: October 12, 2015
Eur. J. Org. Chem. 2015, 7075–7085
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
7085