Convergent synthesis of 4,5-branched inner-core oligosaccharides of lipopolyand lipooligosaccharides

Article abstract of DOI:10.1080/09168451.2015.1069698

The convergent synthesis of branched inner-core oligosaccharides of lipopoly-and lipooligosaccharide with a 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo) disaccharide acceptor was achieved. The L-glycero-D-manno-heptopyranose (Hep) units for the branched core

Full text of DOI:10.1080/09168451.2015.1069698

Bioscience, Biotechnology, and Biochemistry
ISSN: 0916-8451 (Print) 1347-6947 (Online) Journal homepage: http://www.tandfonline.com/loi/tbbb20
Convergent synthesis of 4,5-branched
inner-core oligosaccharides of lipopoly- and
lipooligosaccharides
Ruiqin Yi, Hirofumi Narimoto, Miku Nozoe & Tsuyoshi Ichiyanagi
To cite this article: Ruiqin Yi, Hirofumi Narimoto, Miku Nozoe & Tsuyoshi Ichiyanagi
(2015) Convergent synthesis of 4,5-branched inner-core oligosaccharides of lipopoly- and
lipooligosaccharides, Bioscience, Biotechnology, and Biochemistry, 79:12, 1931-1945, DOI:
10.1080/09168451.2015.1069698
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Date: 05 November 2015, At: 18:39

Bioscience, Biotechnology, and Biochemistry, 2015
Vol. 79, No. 12, 1931–1945
Convergent synthesis of 4,5-branched inner-core oligosaccharides of lipopoly-
and lipooligosaccharides
Ruiqin Yi1, Hirofumi Narimoto2, Miku Nozoe2 and Tsuyoshi Ichiyanagi2,*
2
1The United Graduate School of Agricultural Sciences, Tottori University, Tottori, Japan; Faculty of Agriculture,
Department of Life and Food Sciences, Tottori University, Tottori, Japan
Received May 9, 2015; accepted June 13, 2015
http://dx.doi.org/10.1080/09168451.2015.1069698
The convergent synthesis of branched inner-core
oligosaccharides of lipopoly- and lipooligosaccharide
with a 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo)
disaccharide acceptor was achieved. The L-glycero-D-
manno-heptopyranose (Hep) units for the branched
core oligosaccharide Galβ(1-4)Glcβ(1-4)Hep and
Hepα(1-3)Hep were prepared from the correspond-
ing Hep building blocks. To obtain 4,5-branched
core oligosaccharide structures, the common accep-
tor Kdoα(2-4)Kdo was glycosylated with the Hep
units.
described,9,10) there are few reports of branched inner-
core OS structures.11) In a recent paper, we reported
the synthesis of 4,5-branched inner-core trisaccharides
by coupling monosaccharides (Hep, Man, GalN3) with
a common Kdo acceptor 1 (Fig. 1).12,13) To extend
the utility of this approach, here we prepared more
complex 4,5-banched inner-core OS structures by
using the same Kdo disaccharide as the acceptor. A
lactose donor was initially chosen as
a model
compound to try to introduce branching structure.
Based on the model glycosylation, the corresponding
Hep units constructed from the Hep building blocks
were coupled with the Kdo moiety to obtain the
desired branched inner-core OS.
Key words: glycosylation; oligosaccharide; heptose;
lipopolysaccharide; lipooligosaccharide
Results and discussion
Synthesis of Hep units
Lipopolysaccharides (LPSs) and lipooligosaccharides
(LOSs) are the major glycolipids expressed in the
outer membrane of gram-negative bacteria.1) LPSs and
LOSs are the first line of defense for bacteria against
a range of environmental factors, including detergents
and antimicrobial agents,2,3) and also play an impor-
tant role in the pathogenesis of bacterial infections.
Structurally, an LPS consists of a lipid A, a core
oligosaccharide (core OS), and an O-antigen polysac-
charide, whereas LOS which is limited to 10 saccha-
ride units lacks an O-antigen polysaccharide.4) The
core OS can be further subdivided into the inner core
and outer core. The inner core consists of mostly the
higher carbon sugars 3-deoxy-D-manno-oct-2-ulosonic
acid (Kdo), and L-glycero-D-manno-heptopyranose
(Hep). In Fig. 1, for example, the inner core of LPSs/
LOSs from many gram-negative bacteria contains a
To install the Kdo moiety, the Hep units, Galβ(1-4)
Glcβ(1-4)Hep trisaccharide and Hepα(1-3)Hep disac-
charide, were prepared. All the Hep building blocks (3,
4, 7) required for the Hep units were obtained from
known methyl 6,7-di-O-acetyl-2-O-benzyl-L-glycero-
D-manno-heptopyranoside 214) (Scheme 1). Treatment
of 3,4-diol
2
with t-butyldimethylsilyl chloride
(TBDMSCl) and 1H-imidazole in N,N-dimethylfor-
mamide (DMF) at room temperature gave 3-O-TBDMS
ether 314) in 94% yield. The acetylation of 3 in acetic
anhydride (Ac2O)/pyridine and subsequent de-O-silyla-
tion of TBDMS group in aqueous trifluoroacetic acid
gave 3-OH product 414) in 88% yield. L-Glycero-
D-manno-heptosyl trichloroacetimidate 7 was also pre-
pared from 3,4-diol 2 in a 69% yield over four steps as
follows: sequential acetylation of 3,4-diol 2, acetolysis
of 5, selective anomeric deacetylation, and treatment of
hemiacetal 6 with trichloroacetonitrile in the presence
of potassium carbonate.
4,5-branched
Hepα(1-3)Hepα(1-5)[Kdoα(2-4)]Kdo
tetrasaccharide as the common structure.5) An R
(R = Lac, Glc, P) residue is usually substituted at the
4-O position of Hep I.6–8)
To develop vaccines, immunotherapeutics, and diag-
Next, glycosylation of 4-OH Hep building block 3
with hepta-O-acetyl-β-lactosyl trichloroacetimidate 815)
using TMSOTf as the catalyst in CH2Cl2 proceeded
smoothly to afford (1-4)-linked Galβ(1-4)Glcβ(1-4)Hep
nostics for pathogenic gram-negative bacteria,
a
detailed knowledge of branched inner-core OS struc-
tures is required. Although many chemical syntheses
of linear inner-core OS structures have been
trisaccharide 916) as
a Hep unit in 79% yield
*Corresponding author. Email: yanagi@muses.tottori-u.ac.jp
© 2015 Japan Society for Bioscience, Biotechnology, and Agrochemistry

1932
R. Yi et al.
(Scheme 2). The glucosyl-(1-4)-heptose linkage in
trisaccharide 9 was assigned as β based on the coupling
constant between H-1 and H-2 of the glucose residue
(3JH1,H2 = 8.0 Hz).17) Cleavage of the TBDMS group
in Galβ(1-4)Glcβ(1-4)Hep trisaccharide 9 with aqueous
trifluoroacetic acid produced the free 3-OH 1016) in
97% yield. To characterize the effect of the protecting
group of donor moiety on the glycosidation, two types
of Galβ(1-4)Glcβ(1-4)Hep donors (13 and 17) with the
different protecting groups at C-2 of the Hep residue
were prepared from 10, respectively, as follows.
Immediate acetylation of 10 with acetic anhydride in
pyridine gave 11 in 73% yield. Acetolysis of 11 in
H2SO4/Ac2O/AcOH and subsequent selective anomeric
deacetylation afforded hemiacetal 12. Galβ(1-4)Glcβ(1-
4)Hep hemiacetal 12 was transformed in quantitative
yield to the corresponding trichloroacetimidate 13. In
addition, to obtain a per-O-acetylated Galβ(1-4)Glcβ(1-
4)Hep donor, the benzyl group at C-2 of the Hep resi-
due in 10 was removed by hydrogenolysis (10% Pd/C
in EtOAc) to give 2,3-diol 1416) in 97% yield. Acetyla-
tion of 14 with acetic anhydride in pyridine, followed
by acetolysis, produced 15 in 67% yield. Selective
anomeric deacetylation of 15 with hydrazine acetate in
DMF at 0 °C gave hemiacetal 16 in 90% yield. Treat-
ment of 16 with trichloroacetonitrile in the presence of
K2CO3 gave per-O-acetylated Galβ(1-4)Glcβ(1-4)Hep
trichloroacetimidate 17 in 92% yield. Galβ(1-4)Glcβ(1-
4)Hep trichloroacetimidates 13 and 17 were expected
to undergo [3 + 2] coupling with the Kdo moiety.
Fig. 1. General inner-core oligosaccharide structure of LPS/LOS
and Kdoα(2-4)Kdo dimer 1.
Scheme 1. Conditions: (a) TBDMSCl, 1H-imidazole, DMF, rt, 4 h,
94%; (b) (i) Ac2O, DMAP, pyridine, 0 °C→ rt, 17 h, 95%; (ii) 90%
TFA aq., rt, 1 h, 93%; (c) Ac2O, DMAP, pyridine, 0 °C→ rt, 2 h,
94%; (d) (i) H2SO4, Ac2O, AcOH, rt, 2 h, 95%; (ii) hydrazine acet-
ate, 0 °C→ rt, DMF, 2 h, 80%; (e) Cl3CCN, K2CO3, CH2Cl2, rt,
22 h, 96%. TBDMSCl: t-butyldimethylsilyl chloride; DMF: N,N-
dimethylformamide; DMAP: N,N-dimethyl-4-aminopyridine; TFA:
trifluoroacetic acid.
The (1-3)-linked heptobiose unit 18 was prepared in
50% yield by glycosidation of imidate 7 with Hep
Scheme 2. Conditions: (a) TMSOTf, CH2Cl2, MS-AW 300 molecular sieves, 0 °C, 3 h, 79%; (b) TFA/H2O, 9:1, rt, 5 min, 97%; (c) Ac2O,
DMAP, pyridine, rt, 2 h, 73%; (d) (i) H2SO4, Ac2O, AcOH, rt, 3 h, 64%; (ii) hydrazine acetate, DMF, 0 °C, 8 h, 77%; (e) Cl3CCN, K2CO3,
CH2Cl2, rt, 13 h, quant; (f) 10% Pd/C, H2, ethyl acetate, rt, 3.5 h, 97%; (g) (i) Ac2O, pyridine, rt, 24 h; (ii) H2SO4, Ac2O, AcOH, rt, 15 h,
two steps: 67%; (h) hydrazine acetate, DMF, 0 °C, 8 h, 90%; (i) Cl3CCN, K2CO3, CH2Cl2, rt, 24 h, 92%. TMSOTf: trimethylsilyl
trifluoromethanesulfonate.

Synthesis of 4,5-branched inner-core OSs
1933
residue suggested the (1-3) linkage was an α-linkage.17)
No β-isomer was detected. Acetolysis of the methyl
ether in 18, followed by selective cleavage of the
anomeric acetyl group with hydrazine acetate in DMF
at 0 °C, produced disaccharide hemiacetal 19 in 78%
yield over two steps. Treatment of 19 with trichloroace-
tonitrile in the presence of K2CO3 gave Hep(1-3)Hep
trichloroacetimidate 20, which was expected to undergo
[2 + 2] coupling with the Kdo moiety.
Scheme 3. Conditions: (a) TMSOTf, CH2Cl2, 4Å molecular sieves,
−78 °C→ rt, 2 h, 50%; (b) (i) H2SO4, Ac2O, AcOH, rt, 2 h, (ii)
hydrazine acetate, DMF, 0 °C, 7 h, two steps: 78%; (c) Cl3CCN,
K2CO3, CH2Cl2, rt, 21 h, 80%, α/β = 6:1.
Synthesis of 4,5-branched inner-core OS structures
Next, we focused on the glycosylation of the Kdo
moiety with the Hep units. A model glycosylation using
a lactose derivative as a donor was performed to test
this convergent approach. Because the glycosidation of
building block 4 using TMSOTf as a promoter in
CH2Cl2 (Scheme 3). The coupling constant between
C-1 and H-1 (1JC,H = 174 Hz) of reducing heptose
Table 1. Glycosyl coupling of Kdoa(2-4)Kdo acceptor 1 and glycosyl donors 13,17, and 20–23.
Donor
Solvent
CH2Cl2
Time/h
2
Product
1/%
9
CH2Cl2
2
2
–
90
75
CH2Cl2/Et2O(3/1)
17 (α)
13 (α)
CH2Cl2
15
–
CH2Cl2
2
69
20 (α/β=6/1)
CH2Cl2
1
42

1934
R. Yi et al.
Scheme 4. Glycosylation of compound 1 with Donors 13, 17, and
20–23.
Hep imidate 21 containing acetyl groups could provide
Hepα(1-5)[Kdoα(2-4)]Kdo trisaccharide 24 in good
yield (Table 1), per-O-acetylated lactosyl imidate 22
was used for coupling with Kdoα(2-4)Kdo acceptor 1
(Scheme 4 and Table 1). However, no Lac-Kdo tetrasac-
charide was formed. The reactivity of the per-O-acety-
lated lactose donor was too low to form the linkage.
Therefore, a more reactive donor, hepta-O-benzyl-α-
lactosyl trichloroacetimidate 2318), was examined. To
increase the α-selectivity in the lactosylation, the
reaction was carried out in CH2Cl2/Et2O19) and gave
branched Galβ(1-4)Glc(1-5)[Kdoα(2-4)]Kdo tetrasac-
charide 25 in 20% yield as only a single isomer. The
coupling constant between H-1 and H-2 of the glucose
residue (3JH1,H2 = 3.4 Hz) indicated that the (1-5) link-
age was an α-linkage. The high stereoselectivity was
Fig. 2. Partial HMBC spectrum of tetrasaccharide 28 in CDCl3 at
25 °C.
Kdoα(2-4)Kdo acceptor 1 using 0.06 equiv of TMSOTf
as the activator. As expected, the introduction of the
dibenzyl group substantially increased the reactivity of
the Hepα(1-3)Hep unit to provide Hepα(1-3)Hep(1-5)
[Kdoα(2-4)]Kdo tetrasaccharide 28 in moderate yield
(57%) as only the α-isomer. The configuration of
tetrasaccharide 28 was confirmed by the coupling
constants between C-1 and H-1 of the corresponding
due to the anomeric effect20) and the solvent effect21,22)
.
The introduction of benzyl ethers meant that imidate 23
was more effective in providing desired tetrasaccharide
25, despite the high steric hindrance.
1
1
heptoses (Hep III: JC,H = 172 Hz, Hep IV: JC,
H = 174 Hz).
Following the model glycosylation, the [3 + 2] cou-
pling of the Lacβ(1-4)Hep unit with the Kdo moiety
was examined. According to the glycosidation results
of both Hep donor 7 and 21 giving products in high α-
selectivity in CH2Cl2, CH2Cl2 was used as a solvent
for the following heptosylation. The synthesis of
Lacβ(1-4)Hepα(1-5)[Kdoα(2-4)]Kdo pentasaccharide by
coupling of per-O-acetylated Galβ(1-4)Glcβ(1-4)Hep
trichloroacetimidate 17 with Kdo acceptor 1 failed. No
branched pentasaccharide was found and mainly
imidate 17 was recovered, even though the reaction
time was extended to 15 h. In addition, the decomposi-
tion of the acceptor 1 to lactone 26 was observed. The
donor was changed to Galβ(1-4)Glcβ(1-4)Hep imidate
13, which contained a benzyl group at C-2 of the
Hep residue, and desired Galβ(1-4)Glcβ(1-4)Hep(1-5)
[Kdoα(2-4)]Kdo pentasaccharide 27 was obtained in a
26% yield as the α-anomer. No β-isomer was detected.
The anomeric configuration of the Hep residue in pen-
tasaccharide 27 was confirmed by the coupling con-
stants between C-1 and H-1 of the heptose residue
(1JC,H = 174 Hz). This was consistent with the results
of the model glycosylation, which indicated that the
reactivity of the donor is important for this convergent
approach. The introduction of a benzyl ether at C-2 of
the Hep residue increased the reactivity of the Galβ(1-
4)Glcβ(1-4)Hep unit to provide the branched pentasac-
charide. Therefore, in our convergent approach, the
sterically crowded heptose unit can be added to the
Kdo moiety to produce the desired 4,5-branched core
OS structures. This approach was also expected to pro-
vide the common inner-core OS structure containing
the heptobiose unit. For this purpose, dibenzyl Hepα(1-
3)Hep trichloroacetimidate 20 was coupled with
Furthermore, all branched structures we synthesized
were characterized by analyzing the corresponding 2D
NMR spectra (COSY, HMQC, and HMBC). For exam-
ple, the existence of the (1-5) linkage in Hepα(1-3)
Hepα(1-5)[Kdoα(2-4)]Kdo tetrasaccharide 28 was sup-
ported by the HMBC analysis. The cross-relay peaks,
Kdo H-5I/Hep C-1III, Hep H-1III/Kdo C-5I, in the
HMBC spectrum (Fig. 2) confirmed that the Hep unit
is linked to the 5-position of the Kdo moiety.
These results suggest that it is possible to obtain 4,5-
branched inner-core OSs of LPS/LOS using common
Kdo dimer 1 as an acceptor via a convergent approach.
The Lac-Hep imidate 13 with a benzyl group at C-2 of
the reducing residue, other than the Lac-Hep peracetate
17, giving the desired product of glycoside indicates
that the effective improvement of the reactivity is sup-
ported by the benzyl group. Meanwhile, the glycosida-
tion of perbenzylated Lac imidate 23 giving less
product might indicate that the perbenzylated donor
should be too active to obtain the glycoside in good
yield. These results suggest that the introduction of
appropriate number of benzyl protecting groups appears
to be important for the yield of this convergent
glycosylation.
Finally,
deprotection
of
Hepα(1-3)Hepα(1-5)
[Kdoα(2-4)]Kdo tetrasaccharide 28 was performed over
three steps. Pd(OH)2/C-promoted hydrolysis of the ben-
zyl groups, acid hydrolysis of the isopropylidene group
with aqueous trifluoroacetic acid, and hydrolysis of the
ester group in 0.1 M NaOH produced the target
4,5-branched tetrasaccharide 29 in 90% yield as the
disodium salt.
Galβ(1-4)Glcβ(1-4)Hepα(1-5)[Kdoα(2-4)]Kdo pen-
tasaccharide 27 and Galβ(1-4)Glcα(1-5)[Kdoα(2-4)]Kdo

Synthesis of 4,5-branched inner-core OSs
1935
60 (flash column: 0.040–0.063 mm; open column:
0.063–0.200 mm).
Methyl 3,4,6,7-tetra-O-acetyl-2-O-benzyl-l-glycero-α-
D-manno-heptopyranoside (5). A catalytic amount of
N,N-dimethyl-4-aminopyridine (DMAP) was added to a
solution of methyl 6,7-di-O-acetyl-2-O-benzyl-L-glyc-
ero-D-manno-heptopyranoside (2; 1.9 g, 4.8 mmol) in
acetic anhydride (4.5 mL)/pyridine (9.7 mL) at 0 °C.
After stirring for 2 h at room temperature, the mixture
was concentrated and purified by silica gel chro-
matography (ethyl acetate/hexane, 4:5) to give 5 (2.2 g,
94%). [α]25D = −19.2 (c 3.1, CHCl3), 1H NMR
(600 MHz, CDCl3): δ 1.96, 2.01, 2.05, 2.13 (s, 3H x 4,
Ac), 3.35 (s, 3H, OCH3), 3.82 (dd, 1H, J1,2 = 1.4 Hz,
J2,3 = 3.2 Hz, H-2), 3.99 (dd, 1H, J4,5 = 10.2 Hz,
J5,6 = 2.0 Hz, H-5), 4.25 (dd, 1H, J6,7a = 7.6 Hz,
J7a,7b = 11.2 Hz, H-7a), 3.34 (dd, 1H, J6,7b = 5.8 Hz,
J7a,7b = 11.2 Hz, H-7b), 4.63 (d, 1H, J = 12.4 Hz,
OCH2Ph), 4.69 (d, 1H, J = 12.4 Hz, OCH2Ph), 4.78 (d,
1H, J1,2 = 1.4 Hz, H-1), 5.19 (dd, 1H, J2,3 = 3.2 Hz,
J3,4 = 10.2 Hz, H-3), 5.27 (ddd, 1H, J5,6 = 2.0 Hz,
J6,7a = 7.6 Hz, J6,7b = 5.8 Hz, H-6), 5.44 (dd, 1H,
J3,4 = 10.2 Hz, J4,5 = 10.2 Hz, H-4), 7.29–7.37 (m, 5H,
Ph). 13C NMR (150 MHz, CDCl3): δ 20.6, 20.7, 20.8,
20.84 (Ac-CH3), 55.2 (OCH3), 62.0 (C-7), 65.2 (C-4),
67.1 (C-6), 68.5 (C-5), 71.5 (C-3), 73.2 (OCH2Ph),
74.9 (C-2), 99.4 (C-1), 128.0, 128.4, 129.9, 137.6 (Ph),
169.6, 170.2, 170.5, 170.51 (Ac: C=O). ESI-HRMS for
C23H30O11: 505.1686 [M + Na]+. Found 505.1644.
Scheme 5. Conditions: (a) Pd(OH)2/C, H2, MeOH, rt; (b) 80% TFA
aq., CH2Cl2, rt; (c) 0.1 M NaOH, MeOH, three steps: 29 (90%), 30
(53%), 31 (60%).
tetrasaccharide 25 were subjected to similar
deprotection to afford the corresponding deprotected
compounds, 30 (53%) and 31 (60%) (Scheme 5).
3,4,6,7-Tetra-O-acetyl-2-O-benzyl-L-glycero-D-manno-
heptopyranose (6). A mixture of H2SO4/AcOH/Ac2O
(9.0 mL, 2:50:25) was added to a solution of methyl
3,4,6,7-tetra-O-acetyl-2-O-benzyl-L-glycero-α-D-manno-
heptopyranoside (5; 2.2 g, 4.5 mmol) in acetic acid and
acetic anhydride (1:2, 10.0 mL). After stirring for 2 h
at room temperature, the reaction mixture was neutral-
ized by the addition of sodium acetate (3.5 g), poured
into saturated sodium hydrogen carbonate, and
extracted with dichloromethane. The combined organic
layer was washed with brine, dried over anhydrous
sodium sulfate, filtered, and concentrated. The residue
was purified by silica gel chromatography (ethyl acet-
ate/hexane, 4:5) to give a syrup (2.2 g, 95%). The
syrup was treated with hydrazine acetate (0.5 g,
5.6 mmol) in DMF (30.0 mL) for 2 h at room tempera-
ture. The reaction mixture was diluted with ethyl acet-
ate, washed with water and brine, dried over anhydrous
sodium sulfate, filtered, and concentrated. The residue
was purified by silica gel chromatography (ethyl acet-
ate/hexane, 1:1) to give 6 (1.6 g, 80%). 1H NMR
(600 MHz, CDCl3): δ 1.98, 2.02, 2.06, 2.14 (s, 3H x 4,
Ac), 3.86 (dd, 1H, J1,2 = 1.8 Hz, J2,3 = 3.2 Hz, H-2),
4.14 (dd, 1H, J6,7a = 7.0 Hz, J7a,7b = 11.4 Hz, H-7a),
4.18 (dd, 1H, J4,5 = 10.0 Hz, J5,6 = 2.0 Hz, H-5), 4.40
(dd, 1H, J6,7b = 5.4 Hz, J7a,7b = 11.4 Hz, H-7b), 4.64
(d, 1H, J = 12.4 Hz, OCH2Ph), 4.67 (d, 1H,
J = 12.4 Hz, OCH2Ph), 5.23 (ddd, 1H, J5,6 = 2.0 Hz,
J6,7a = 7.0 Hz, J6,7b = 5.4 Hz, H-6), 5.27 (dd, 1H,
J2,3 = 3.2 Hz, J3,4 = 10.2 Hz, H-3), 5.29 (d, 1H,
J1,2 = 1.8 Hz, H-1), 5.44 (dd, 1H, J3,4 = 10.2 Hz,
Experimental
General procedures. Optical rotation was measured
with a polarimeter (SEPA500, Horiba) in CHCl3. All
NMR spectra were recorded at 25 °C in CDCl3 or D2O
on a 600 MHz NMR spectrometer (Avance II, Bruker).
Me4Si was used as an internal standard for CDCl3, and
1% CH3CN (δ = 2.06 ppm for 1H; δ = 1.47 and
119.68 ppm for 13C) was used for D2O. Multiplicities
are quoted as singlet (s), broad singlet (brs), doublet (d),
doublet of doublet (dd), triplet (t), or multiplet (m). All
NMR chemical shifts (δ) are recorded in parts per mil-
lion (ppm), and coupling constants (J) are reported in
hertz (Hz). Mass spectrometry (MS) was performed by
positive- and negative-mode electrospray ionization
(LCT Premier, Waters). For high-precision measure-
ments, the mass spectra were obtained by scanning the
voltage over a narrow mass range at a resolution of
10,000. MALDI-TOF spectra (Autoflex-T2, Bruker)
were obtained using 3,5-dihydroxybenzoic acid as the
matrix. Elemental analysis was performed on two
different instruments (Vario ELCUBE and Vario EL III,
Elementar). Analytical TLC was performed on Silica
Gel 60 F254 glass plates. The TLC plates were visual-
ized with UV light and by staining with Hanessian solu-
tion (ceric sulfate and ammonium molybdate in aqueous
sulfuric acid) and then heating at 200–160°C for 3 min.
Column chromatography was performed on Silica Gel

1936
R. Yi et al.
J4,5 = 10.0 Hz, H-4), 7.30–7.37 (m, 5H, Ph). 13C NMR
(150 MHz, CDCl3): δ 20.7, 20.8, 20.85 (Ac-CH3), 62.8
(C-7), 65.5 (C-4), 67.2 (C-6), 68.7 (C-5), 71.4 (C-3),
73.2 (OCH2Ph), 75.6 (C-2), 93.0 (C-1), 127.9, 128.0,
128.4, 137.7 (Ph), 169.8, 170.3, 170.6, 171.3
(Ac: C=O). ESI-HRMS for C22H28O11: 491.1529
[M + Na]+. Found 491.1514.
79%). [α]25D = +1.0 (c 1.0, CHCl3), 1H NMR
(600 MHz, CDCl3): δ 0.08, 0.09 [s, 3H x 2, Si(CH3)2C
(CH3)3], 0.90 [s, 9H, Si(CH3)2C(CH3)3], 1.96, 1.98,
2.04, 2.05, 2.05, 2.06, 2.09, 2.13, 2.15 (s, 3H x 8, Ac),
3.33 (s, 3H, OCH3), 3.55 (ddd, 1H, J4,5 = 10.0 Hz,
J5,6a = 5.2 Hz, J5,6b = 2.0 Hz, H-5II), 3.56 (brs, 1H,
J
1,2 = 3.4 Hz, H-2I), 3.64 (dd, 1H, J4,5 = 8.8 Hz, H-5I),
3.76 (dd, 1H, J3,4 = 9.2 Hz, J4,5 = 10.0 Hz, H-4II), 3.80
(m, 1H, J4,5 = 8.8 Hz, H-4I), 3.86 (ddd, 1H,
J4,5 = 0.8 Hz, J5,6a = 7.4 Hz, J5,6b = 6.2 Hz, H-5III),
4.06 (m, 1H, H-3I), 4.07 (dd, 1H, J5,6a = 7.4 Hz,
J6a,6b = 11.2 Hz, H-6aIII), 4.09 (dd, 1H, J5,6a = 5.2 Hz,
J6a,6b = 10.2 Hz, H-6aII), 4.15 (dd, 1H, J5,6b = 6.2 Hz,
J6a,6b = 11.2 Hz, H-6bIII), 4.21 (dd, 1H, J6,7a = 7.4 Hz,
J7a,7b = 11.2 Hz, H-7aI), 4.33 (dd, 1H, J6,7b = 5.6 Hz,
J7a,7b = 11.2 Hz, H-7bI), 4.38 (dd, 1H, J5,6b = 2.0 Hz,
J6a,6b = 10.2 Hz, H-6bII), 4.48 (d, 1H, J1,2 = 8.0 Hz, H-
1III), 4.55 (d, 1H, J1,2 = 8.0 Hz, H-1II), 4.63 (d, 1H,
J = 11.8 Hz, OCH2Ph), 4.72 (d, 1H, J1,2 = 3.4 Hz, H-
1I), 4.77 (d, 1H, J = 11.8 Hz, OCH2Ph), 4.87 (dd, 1H,
J1,2 = 8.0 Hz, J2,3 = 9.4 Hz, H-2II), 4.93 (dd, 1H,
J2,3 = 10.4 Hz, J3,4 = 3.4 Hz, H-3III), 5.10 (dd, 1H,
J1,2 = 8.0 Hz, J2,3 = 10.4 Hz, H-2III), 5.18 (dd, 1H,
J2,3 = 9.4 Hz, J3,4 = 9.2 Hz, H-3II), 5.34 (dd, 1H,
J3,4 = 3.4 Hz, J4,5 = 0.8 Hz, H-4III), 5.35 (m, 1H,
J6,7a = 7.4 Hz, J6,7b = 5.6 Hz, H-6I), 7.24–7.36 (m, 5H,
Ph). 13C NMR (150 MHz, CDCl3): δ −4.8, −4.6 (Si
(CH3)2C(CH3)3), 18.1 (Si(CH3)2C(CH3)3), 20.5, 20.6,
20.67, 20.7, 20.85, 20.9, 25.9, 29.7 (Ac-CH3), 25.8 (Si
(CH3)2C(CH3)3), 55.2 (OCH3), 60.6 (C-6III), 62.3 (C-
6II), 62.5 (C-7I), 66.5 (C-4III), 68.7 (C-6I), 69.1 (C-2III),
70.2 (C-5I), 70.6 (C-5III), 70.9 (C-3III), 71.0 (C-3I),
71.9 (C-2II), 72.4 (C-5II), 72.9 (C-3II, CH2Ph), 76.5 (C-
4II), 77.4 (C-4I), 78.3 (C-2I), 100.3 (C-1I, C-1II), 100.9
(C-1III), 127.3, 127.37, 128.1, 138.5 (Ph), 169.0, 169.5,
169.7, 170.0, 170.1, 170.2, 170.23, 170.3, 170.36 (Ac:
C=O). Anal. Calcd for C51H74O26Si: C, 54.15; H, 6.59.
Found: C, 53.94; H, 6.48.
3,4,6,7-Tetra-O-acetyl-2-O-benzyl-L-glycero-α-D-manno-
heptopyranosyl trichloroacetimidate (7).
Compound
6 (1.5 g, 3.2 mmol) was dissolved in dry dichloro-
methane (3.0 mL). Potassium carbonate (2.2 g,
16.0 mmol) was added followed by trichloroacetonitrile
(3.2 mL, 32.0 mmol), and the mixture was stirred for
22 h at room temperature. The reaction mixture was fil-
tered through Celite. The solution was concentrated
and purified by silica gel column chromatography
(ethyl acetate/hexane, 2:3 + 1% Et3N) to give 7 (1.9 g,
96%). [α]25D = −13.4 (c 3.7, CHCl3), 1H NMR
(600 MHz, CDCl3): δ 1.96, 2.01, 2.02, 2.13 (s, 3H x 4,
Ac), 4.06 (dd, 1 H, J1,2 = 1.8 Hz, J2,3 = 3.4 Hz, H-2),
4.18 (dd, 1H, J6,7a = 7.6 Hz, J7a,7b = 11.4 Hz, H-7a),
4.20 (dd, 1H, J4,5 = 9.2 Hz, J5,6 = 2.0 Hz, H-5), 4.28
(dd, 1H, J6,7b = 5.6 Hz, J7a,7b = 11.4 Hz, H-7b), 4.65
(d, 1H, J = 12.2 Hz, OCH2Ph), 4.78 (d, 1H,
J = 12.2 Hz, OCH2Ph), 5.23 (dd, 1H, J2,3 = 3.4 Hz,
J3,4 = 10.2 Hz, H-3), 5.27 (ddd, 1H, J5,6 = 2.0 Hz,
J6,7a = 7.6 Hz, J6,7b = 5.6 Hz, H-6), 5.54 (dd, 1H,
J3,4 = 10.2 Hz, J4,5 = 9.2 Hz, H-4), 6.35 (d, 1H,
J1,2 = 1.8 Hz, H-1), 7.27–7.40 (m, 5H, Ph), 8.68 (s,
1H, OC(NH)CCl3). 13C NMR (150 MHz, CDCl3): δ
20.7, 20.8, 20.86 (Ac-CH3), 62.0 (C-7), 64.6 (C-4),
66.8 (C-6), 71.0 (C-5), 71.3 (C-3), 73.1 (OCH2Ph),
73.3 (C-2), 90.6 (OCNHCCl3), 95.3 (C-1), 128.1,
128.4, 137.2 (Ph), 160.0 (OCNHCCl3), 169.5, 170.4,
170.5 (Ac: C=O). ESI-HRMS for C24H28Cl3NO11:
634.0626 [M + Na]+. Found 634.0639.
Methyl (2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl)-
(1-4)-(2,3,6-tri-O-acetyl-β-D-glucopyranosyl)-(1-4)-6,7-
di-O-acetyl-2-O-benzyl-L-glycero-α-D-manno-heptopyra-
noside (10). Compound 9 (486.0 mg, 429.7 μmol) was
dissolved in a mixture of trifluoroacetic acid and water
(9:1, v/v, 10.0 mL) at room temperature. After stirring
for 5 min, the mixture was diluted with toluene and
concentrated. The residue was purified by flash column
chromatography (dichloromethane/acetone, 9:1) to give
Methyl (2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl)-
(1-4)-(2,3,6-tri-O-acetyl-β-D-glucopyranosyl)-(1-4)-6,7-di-
O-acetyl-2-O-benzyl-3-O-tert-butyldimethylsilyl-L-glycero-
α-D-manno-heptopyranoside (9). A mixture of methyl
6,7-di-O-acetyl-2-O-benzyl-3-O-tert-butyldimethylsilyl-L-
glycero-α-D-manno-heptopyranoside (3; 1.5 g, 2.9 mmol),
(2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl)-(1-4)-2,3,6-
tri-O-acetyl-β-D-glucopyranosyl trichloroacetimidate (8;
5.6 g, 7.2 mmol), and MS-AW 300 molecular sieves
(7.0 g) in dry dichloromethane (50.0 mL) was stirred
for 1 h under argon and then cooled to 0 °C. TMSOTf
(106.0 μL, 0.6 mmol) in dry dichloromethane (0.5 mL)
was added dropwise to the reaction mixture, and the
mixture was stirred for 3 h. The solution was neutral-
ized by the addition of triethylamine and saturated
sodium hydrogen carbonate and diluted with dichloro-
methane. The mixture was filtered through Celite,
and the filtrate was extracted with dichloromethane.
The organic phase was dried over anhydrous sodium
sulfate, filtered, and concentrated. Purification of
the residue by BioRad S-X1 size exclusion beads
(toluene/ethyl acetate, 1:1) and flash column chro-
matography (toluene/acetone, 5:1) afforded 9 (2.6 g,
1
10 (424.0 mg, 97%). [α]25D= +8.0 (c 1.0, CHCl3). H
NMR (600 MHz, CDCl3): δ 1.97, 2.04, 2.04, 2.05,
2.06, 2.09, 2.12, 2.13, 2.16 (s, 3H x 9, Ac), 3.30 (s,
3H, OCH3), 3.64 (m, 1H, J4,5 = 9.5 Hz, H-5I), 3.66
(dd, 1H, J3,4 = 9.5 Hz, J4,5 = 9.5 Hz, H-4I), 3.73 (ddd,
1H, J5,6a = 6.5 Hz, J5,6b = 2.0 Hz, H-5II), 3.76 (dd, 1H,
J3,4 = 9.5 Hz, H-4II), 3.77 (dd, 1H, J1,2 = 2.0 Hz,
J2,3 = 3.3 Hz, H-2I), 3.88 (ddd, 1H, J4,5 = 1.5 Hz,
J5,6a = 7.5 Hz, J5,6b = 6.5 Hz, H-5III), 3.92 (dd, 1H,
J2,3 = 3.3 Hz, J3,4 = 9.5 Hz, H-3I), 3.98 (d, 1H, J3-OH,H-
3 = 2.5 Hz, 3-OH), 4.04 (dd, 1H, J5,6a = 6.5 Hz,
J6a,6b = 12.0 Hz, H-6aII), 4.08 (dd, 1H, J5,6a = 7.5 Hz,
J6a,6b = 11.0 Hz, H-6aIII), 4.13 (dd, 1H, J5,6b = 6.5 Hz,
J6a,6b = 11.0 Hz, H-6bIII), 4.27 (dd, 1H, J6,7a = 6.5 Hz,
J7a,7b = 11.0 Hz, H-7aI), 4.30 (dd, 1H, J6,7b = 7.0 Hz,

Synthesis of 4,5-branched inner-core OSs
1937
J7a,7b = 11.0 Hz, H-7bI), 4.49 (d, 1H, J1,2 = 8.0 Hz, H-
1III), 4.54 (d, 1H, J1,2 = 8.0 Hz, H-1II), 4.59 (dd, 1H,
J5,6b = 2.0 Hz, J6a,6b = 12.0 Hz, H-6bII), 4.70 (d, 1H,
J = 12.0 Hz, OCH2Ph), 4.75 (d, 1H, J1,2 = 2.0 Hz, H-
1I), 4.84 (d, 1H, J = 12.0 Hz, OCH2Ph), 4.94 (dd, 1H,
J1,2 = 8.0 Hz, J2,3 = 9.5 Hz, H-2II), 4.97 (dd, 1H,
72.1 (C-5II), 72.7 (OCH2Ph), 73.3 (C-3II), 73.9 (C-4I),
75.2 (C-2I), 76.2 (C-4II), 99.1 (C-1I), 99.9 (C-1II),
101.1 (C-1III), 127.8, 127.9, 128.4, 137.7 (Ph), 169.1,
169.7, 169.9, 170.2, 170.3, 170.4, (Ac: C=O). ESI-
HRMS for C47H62O27: 1067.3376 [M + Na]+. Found
1081.3368.
J
2,3 = 10.8 Hz, J3,4 = 3.5 Hz, H-3III), 5.19 (dd, 1H,
J1,2 = 8.0 Hz, J2,3 = 10.8 Hz, H-2III), 5.22 (dd, 1H,
J2,3 = 9.5 Hz, J3,4 = 9.5 Hz, H-3II), 5.25 (ddd, 1H,
J6,7a = 6.5 Hz, J6,7b = 7.0 Hz, H-6I), 5.35 (dd, 1H,
J3,4 = 3.5 Hz, J4,5 = 1.5 Hz, H-4III), 7.38–7.25 (m, 5H,
Ph). 13C NMR (150 MHz, CDCl3): δ 20.3, 20.34, 20.4,
20.5, 20.6, 20.7 (Ac-CH3), 55.0 (OCH3), 60.7 (C-6III),
61.8 (C-6II), 62.0 (C-7I), 66.5 (C-4III), 68.0 (C-6I), 68.4
(C-5I), 69.0 (C-2III), 69.8 (C-3I), 70.6 (C-5III), 70.8
(C-3III), 71.3 (C-2II), 72.55 (C-5II), 72.6 (C-3II),
73.0 (OCH2Ph), 76.0 (C-2I), 76.2 (C-4II), 79.6
(C-4I), 99.0 (C-1I), 100.4 (C-1II), 100.9 (C-1III), 127.3,
127.34, 128.1, 138.4 (Ph), 168.9, 169.3, 169.87, 169.9,
170.0, 170.1, 170.2, 170.23 (Ac: C=O). ESI-HRMS
for C45H60O26: 1039.3271 [M + Na]+. Found:
1039.3303.
(2,3,4,6-Tetra-O-acetyl-β-D-galactopyranosyl)-(1-4)-
(2,3,6-tri-O-acetyl-β-D-glucopyranosyl)-(1-4)-3,6,7-tri-
O-acetyl-2-O-benzyl-L-glycero-D-manno-heptopyranose
(12). A solution of 11 (195.0 mg, 184.1 μmol) in a
mixture of H2SO4/AcOH/Ac2O (4.0 mL, 0.1:6:14) was
stirred for 3 h at room temperature. The reaction mix-
ture was neutralized by the addition of sodium acetate,
poured into saturated sodium hydrogen carbonate, and
extracted with dichloromethane. The combined organic
layer was washed with brine, dried over anhydrous
sodium sulfate, filtered, and concentrated. The residue
was purified by flash column chromatography (ethyl
acetate/hexane, 2:1) to give a syrup (124.5 mg, 64%).
The syrup was treated with hydrazine acetate (13.0 mg,
120.4 μmol) in DMF (1.0 mL) for 8 h at 0 °C. The
reaction mixture was diluted with ethyl acetate, washed
with water and brine, dried over anhydrous sodium sul-
fate, filtered, and concentrated. The residue was puri-
fied by silica gel column chromatography (ethyl
acetate/hexane, 2:1) to give 12 (89.1 mg, 77%). 1H
NMR (600 MHz, CDCl3): δ 1.96, 1.98, 2.04, 2.06,
2.06, 2.07, 2.15, 2.15 (s, 3H x 10, Ac), 3.37 (brs, 1H,
OH), 3.61 (ddd, 1H, J4,5 = 10.0 Hz, J5,6a = 4.6 Hz,
Methyl (2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl)-
(1-4)-(2,3,6-tri-O-acetyl-β-D-glucopyranosyl)-(1-4)-3,6,7-
tri-O-acetyl-2-O-benzyl-L-glycero-α-D-manno-heptopyra-
noside (11).
Compound 10 (280.3 mg, 275.8 μmol)
was acetylated with pyridine/Ac2O (1:1, v/v, 1.6 mL)
in the presence of a catalytic amount of N,N-dimethyl-
4-aminopyridine (DMAP) over 2 h. After removing the
solvent, the residue was purified by flash column chro-
matography (dichloromethane/ethyl acetate, 5:2) to give
J
5,6b = 2.0 Hz, H-5II), 3.79 (dd, 1H, J1,2 = 2.8 Hz,
J2,3 = 3.2 Hz, H-2I), 3.85 (dd, 1H, J3,4 = 9.0 Hz,
J4,5 = 10.0 Hz, H-4II), 3.86 (ddd, 1H, J4,5 = 1.2 Hz,
J5,6a = 7.6 Hz, J5,6b = 6.2 Hz, H-5III), 3.89 (dd, 1H,
J3,4 = 8.6 Hz, J4,5 = 9.8 Hz, H-4I), 3.98 (dd, 1H,
J4,5 = 9.8 Hz, H-5I), 4.07 (dd, 1H, J5,6a = 7.6 Hz,
J6a,6b = 11.0 Hz, H-6aIII), 4.09 (dd, 1H, J5,6a = 4.6 Hz,
J6a,6b = 12.0 Hz, H-6aII), 4.15 (dd, 1H, J5,6b = 6.2 Hz,
J6a,6b = 11.0 Hz, H-6bIII), 4.15 (dd, 1H, J6,7a = 7.0 Hz,
J7a,7b = 11.0 Hz, H-7aI), 4.38 (dd, 1H, J6,7b = 6.2 Hz,
J7a,7b = 11.0 Hz, H-7bI), 4.39 (dd, 1H, J5,6b = 2.0 Hz,
J6a,6b = 12.0 Hz, H-6bII), 4.48 (d, 1H, J1,2 = 8.0 Hz, H-
1III), 4.56 (d, 1H, J = 12.2 Hz, OCH2Ph), 4.57 (d, 1H,
J1,2 = 7.2 Hz, H-1II), 4.63 (d, 1H, J = 12.2 Hz,
OCH2Ph), 4.82 (dd, 1H, J1,2 = 7.2 Hz, J2,3 = 8.4 Hz,
H-2II), 4.93 (dd, 1H, J2,3 = 10.4 Hz, J3,4 = 3.4 Hz, H-
3III), 5.10 (dd, 1H, J1,2 = 8.0 Hz, J2,3 = 10.4 Hz, H-
2III), 5.15 (dd, 1H, J2,3 = 8.4 Hz, J3,4 = 9.0 Hz, H-3II),
5.27 (d, 1H, J1,2 = 2.8 Hz, H-1I), 5.33 (dd, 1H,
J3,4 = 3.4 Hz, J4,5 = 1.2 Hz, H-4III), 5.33 (dd, 1H,
J2,3 = 3.2 Hz, J3,4 = 8.6 Hz, H-3I), 5.37 (ddd, 1H,
J6,7a = 7.0 Hz, J6,7b = 6.2 Hz, H-6I), 7.27–7.33 (m, 5H,
Ph). 13C NMR (150 MHz, CDCl3): δ 20.5, 20.6, 20.65,
20.66, 20.7, 20.79, 20.8, 20.9 (Ac-CH3), 60.7 (C-6III),
62.4 (C-6II), 62.6 (C-7I), 66.6 (C-4III), 68.1 (C-6I), 69.0
(C-2III), 69.3 (C-3I), 70.5 (C-5III), 70.6 (C-5I), 71.0
(C-3III), 71.9 (C-2II), 72.0 (C-5II), 72.7 (OCH2Ph), 73.2
(C-3II), 74.0 (C-4I), 75.7 (C-2I), 76.2 (C-4II), 92.4
(C-1I), 99.8 (C-1II), 101.1 (C-1III), 127.7, 127.8, 128.4,
137.7 (Ph), 169.2, 169.66, 169.7, 170.0, 170.15,
170.2, 170.24, 170.4, 170.9 (Ac: C=O). ESI-HRMS
for C46H60O27: 1067.3220 [M + Na]+. Found
1067.3226.
1
11 (180.9 mg, 73%). [α]25D = +6.1 (c 0.8, CHCl3), H
NMR (600 MHz, CDCl3): δ 1.96, 1.97, 2.04, 2.05,
2.06, 2.08, 2.09, 2.15, 2.16 (s, 3H x 10, Ac), 3.34 (s,
3H, OCH3), 3.61 (ddd, 1H, J4,5 = 10.0 Hz,
J5,6a = 4.8 Hz, J5,6b = 1.8 Hz, H-5II), 3.76 (dd, 1H,
J1,2 = 2.4 Hz, J2,3 = 3.4 Hz, H-2I), 3.80 (dd, 1H,
J4,5 = 9.6 Hz, J5,6 = 1.0 Hz, H-5I), 3.84 (dd, 1H,
J3,4 = 8.6 Hz, J4,5 = 10.0 Hz, H-4II), 3.86 (ddd, 1H,
J4,5 = 0.8 Hz, J5,6a = 7.6 Hz, J5,6b = 6.6 Hz, H-5III),
3.88 (dd, 1H, J3,4 = 8.4 Hz, J4,5 = 9.6 Hz, H-4I), 4.07
(dd, 1H, J5,6a = 7.6 Hz, J6a,6b = 11.4 Hz, H-6aIII), 4.10
(dd, 1H, J5,6a = 5.4 Hz, J6a,6b = 12.0 Hz, H-6aII), 4.12
(dd, 1H, J5,6b = 6.6 Hz, J6a,6b = 11.4 Hz, H-6bIII), 4.25
(dd, 1H, J6,7a = 7.4 Hz, J7a,7b = 11.2 Hz, H-7aI), 4.32
(dd, 1H, J6,7b = 6.0 Hz, J7a,7b = 11.2 Hz, H-7bI), 4.38
(dd, 1H, J5,6b = 1.8 Hz, J6a,6b = 12.0 Hz, H-6bII), 4.47
(d, 1H, J1,2 = 8.0 Hz, H-1III), 4.55 (d, 1H, J = 12.2 Hz,
OCH2Ph), 4.57 (d, 1H, J1,2 = 7.2 Hz, H-1II), 4.64 (d,
1H, J = 12.2 Hz, OCH2Ph), 4.77 (d, 1H, J1,2 = 2.4 Hz,
H-1I), 4.82 (dd, 1H, J1,2 = 7.2 Hz, J2,3 = 8.2 Hz, H-2II),
4.93 (dd, 1H, J2,3 = 10.4 Hz, J3,4 = 3.4 Hz, H-3III),
5.10 (dd, 1H, J1,2 = 8.0 Hz, J2,3 = 10.4 Hz, H-2III),
5.15 (dd, 1H, J2,3 = 8.2 Hz, J3,4 = 8.6 Hz, H-3II), 5.27
(dd, 1H, J2,3 = 3.4 Hz, J3,4 = 8.4 Hz, H-3I), 5.34 (dd,
1H, J3,4 = 3.4 Hz, J4,5 = 0.8 Hz, H-4III), 5.39 (ddd, 1H,
J5,6 = 1.0 Hz, J6,7a = 7.2 Hz, J6,7b = 6.0 Hz, H-6I),
7.26–7.33 (m, 5H, Ph). 13C NMR (150 MHz, CDCl3):
δ 20.5, 20.6, 20.68, 20.7, 20.74, 20.8, 20.9 (Ac-CH3),
55.3 (OCH3), 60.7 (C-6III), 62.2 (C-6II), 62.4 (C-7I),
66.6 (C-4III), 68.1 (C-6I), 69.0 (C-2III), 69.3 (C-3I),
70.6 (C-5III), 70.7 (C-5I), 71.0 (C-3III), 71.9 (C-2II),

1938
R. Yi et al.
(2,3,4,6-Tetra-O-acetyl-β-D-galactopyranosyl)-(1-4)-
(2,3,6-tri-O-acetyl-β-D-glucopyranosyl)-(1-4)-3,6,7-tri-O-
acetyl-2-O-benzyl-L-glycero-α-D-manno-heptopyranosyl
(d, 1H, J2-OH,H-2 = 1.5 Hz, 2-OH), 3.35 (s, 3H, OCH3),
3.55 (dd, 1H, J3,4 = 8.0 Hz, J4,5 = 9.8 Hz, H-4I), 3.71
(dd, 1H, J4,5 = 9.8 Hz, J5,6 = 1.0 Hz, H-5I), 3.72 (ddd,
1H, J4,5 = 10.0 Hz, J5,6a = 5.5 Hz, J5,6b = 2.0 Hz, H-5II),
3.78 (dd, 1H, J3,4 = 9.0 Hz, J4,5 = 10.0 Hz, H-4II), 3.81
(dd, 1H, J2,3 = 3.5 Hz, J3,4 = 8.0 Hz, H-3I), 3.96 (dd,
1H, J1,2 = 1.0 Hz, J2,3 = 3.5 Hz, H-2I), 3.88 (ddd, 1H,
J4,5 = 1.0 Hz, J5,6a = 7.5 Hz, J5,6b = 6.5 Hz, H-5III),
4.03 (dd, 1H, J5,6a = 5.5 Hz, J6a,6b = 12.0 Hz, H-6aII),
4.08 (dd, 1H, J5,6a = 7.5 Hz, J6a,6b = 11.3 Hz, H-6aIII),
4.14 (dd, 1H, J5,6b = 6.5 Hz, J6a,6b = 11.3 Hz, H-6bIII),
4.22 (m, 1H, J5,6 = 1.0 Hz, H-6I), 4.29 (m, 2H, H-7aI,
H-7bI), 4.30 (d, 1H, J3-OH,H-3 = 1.0 Hz, 3-OH), 4.46 (d,
1H, J1,2 = 8.0 Hz, H-1II), 4.51 (d, 1H, J1,2 = 8.5 Hz,
H-1III), 4.65 (dd, 1H, J5,6b = 2.0 Hz, J6a,6b = 12.0 Hz,
H-6bII), 4.80 (d, 1H, J1,2 = 1.0 Hz, H-1I), 4.93 (dd, 1H,
J1,2 = 8.0 Hz, J2,3 = 9.5 Hz, H-2II), 4.97 (dd, 1H,
J2,3 = 10.5 Hz, J3,4 = 3.5 Hz, H-3III), 5.11 (dd, 1H,
J1,2 = 8.5 Hz, J2,3 = 10.5 Hz, H-2III), 5.22 (dd, 1H,
J2,3 = 9.5 Hz, J3,4 = 9.0 Hz, H-3II), 5.35 (dd, 1H,
J3,4 = 3.5 Hz, J4,5 = 1.0 Hz, H-4III). 13C NMR
(150 MHz, CDCl3): δ 20.4, 20.42, 20.5, 20.54, 20.6,
20.64, 20.9 (Ac-CH3), 55.2 (OCH3), 60.7 (C-6III), 61.6
(C-6II), 62.0 (C-7I), 66.5 (C-4III), 67.7 (C-5I), 67.9 (C-
6I), 69.0 (C-2III), 69.5 (C-3I), 69.5 (C-2I), 70.8 (C-3III),
71.0 (C-5III), 71.2 (C-2II), 72.5 (C-3II), 72.8 (C-5II),
76.0 (C-4II), 79.0 (C-4I), 100.1 (C-1I), 100.6 (C-1II),
100.9 (C-1III), 169.0, 169.3, 170.0, 170.04, 170.16,
170.2, 170.26, 170.3 (Ac: C=O). ESI-HRMS for
C38H54O26: 949.2801 [M + Na]+. Found 949.2766.
trichloroacetimidate (13).
Trichloroacetonitrile (85.0
μL, 842.1 μmol) was added to a solution of 12 (88.0 mg,
84.2 μmol) in dry dichloromethane (0.8 mL) under
argon. Potassium carbonate (58.0 mg, 421.0 μmol) was
added to the reaction mixture. After stirring for 13 h at
room temperature, the mixture was filtered through
Celite. The solution was concentrated and purified by sil-
ica gel column chromatography (ethyl acetate/hexane,
2:1) to give 13 (96.0 mg, 100%). [α]25D = −5.7 (c 1.3,
CHCl3), 1H NMR (600 MHz, CDCl3): δ 1.96, 1.99,
2.00, 2.06, 2.04, 2.04, 2.04, 2.05, 2.06, 2.07, 2.15, 2.15
(s, 3H x 10, Ac), 3.65 (ddd, 1H, J4,5 = 10.0 Hz,
J5,6a = 4.8 Hz, J5,6b = 1.6 Hz, H-5II), 3.84 (dd, 1H,
J3,4 = 9.2 Hz, J4,5 = 10.0 Hz, H-4II), 3.87 (ddd, 1H,
J5,6a = 7.6 Hz, J5,6b = 6.2 Hz, H-5III), 3.88 (dd, 1H,
J3,4 = 5.6 Hz, J4,5 = 9.4 Hz, H-4I), 3.94 (dd, 1H,
J4,5 = 9.4 Hz, J5,6 = 0.8 Hz, H-5I), 4.04 (dd, 1H,
J1,2 = 3.6 Hz, J2,3 = 2.8 Hz, H-2I), 4.07 (dd, 1H,
J5,6a = 7.6 Hz, J6a,6b = 11.2 Hz, H-6aIII), 4.09 (dd, 1H,
J5,6a = 4.8 Hz, J6a,6b = 12.0 Hz, H-6aII), 4.14 (dd, 1H,
J5,6b = 6.2 Hz, J6a,6b = 11.2 Hz, H-6bIII), 4.16 (dd, 1H,
J6,7a = 7.2 Hz, J7a,7b = 11.4 Hz, H-7aI), 4.22 (dd, 1H,
J6,7b = 5.8 Hz, J7a,7b = 11.4 Hz, H-7bI), 4.47 (dd, 1H,
J5,6b = 1.6 Hz, J6a,6b = 12.0 Hz, H-6bII), 4.49 (d, 1H,
J1,2 = 8.0 Hz, H-1III), 4.61 (d, 1H, J1,2 = 7.6 Hz, H-1II),
4.63 (d, 1H, J = 12.0 Hz, OCH2Ph), 4.68 (d, 1H,
J = 12.0 Hz, OCH2Ph), 4.85 (dd, 1H, J1,2 = 7.6 Hz,
J2,3 = 8.6 Hz, H-2II), 4.94 (dd, 1H, J2,3 = 10.4 Hz,
J3,4 = 3.6 Hz, H-3III), 5.10 (dd, 1H, J1,2 = 8.0 Hz,
J2,3 = 10.4 Hz, H-2III), 5.16 (dd, 1H, J2,3 = 8.6 Hz,
J3,4 = 9.2 Hz, H-3II), 5.29 (ddd, 1H, J5,6 = 0.8 Hz,
J6,7a = 7.2 Hz, J6,7b = 6.2 Hz, H-6I), 5.33 (dd, 1H,
J3,4 = 3.6 Hz, H-4III), 5.48 (dd, 1H, J2,3 = 2.8 Hz,
J3,4 = 5.6 Hz, H-3I), 6.31 (d, 1H, J1,2 = 3.6 Hz, H-1I),
7.26–7.34 (m, 5H, Ph), 8.68 (NH). 13C NMR (150 MHz,
CDCl3): δ 20.5, 20.54, 20.7, 20.74, 20.76, 20.79, 20.8,
20.9, 21.0 (Ac-CH3), 60.7 (C-6III), 62.1 (C-7I and C-6II),
66.6 (C-4III), 67.9 (C-6I), 69.3 (C-2III), 69.9 (C-3I), 70.6
(C-5III), 71.0 (C-3III), 71.5 (C-2II), 71.6 (C-5II), 72.4
(-OCH2Ph and C-5I), 73.0 (C-3II), 74.0 (C-4I), 74.9 (C-
2I), 76.0 (C-4II), 90.8 (OCNHCCl3), 96.0 (C-1I), 99.2
(C-1II), 101.1 (C-1III), 127.9, 128.0, 128.4, 137.2 (Ph),
160.5 (OCNHCCl3), 169.0, 169.6, 169.8, 169.9, 170.1,
170.13, 170.16, 170.2, 170.24, 170.4 (Ac: C=O). ESI-
HRMS for C48H60Cl3NO27: 1210.2316 [M + Na]+.
Found 1210.2294.
(2,3,4,6-Tetra-O-acetyl-β-D-galactopyranosyl)-(1-4)-
(2,3,6-tri-O-acetyl-β-D-glucopyranosyl)-(1-4)-1,2,3,6,
7-penta-O-acetyl-L-glycero-α-D-manno-heptopyranose
(15). Compound 14 (342.0 mg, 0.4 mmol) was trea-
ted with acetic anhydride (1.0 mL) and pyridine
(2.0 mL) at room temperature. The reaction mixture
was stirred overnight and concentrated. The residue was
purified by silica gel column chromatography (dichloro-
methane/acetone, 4:1) to give a syrup. The syrup was
dissolved in a mixture of H2SO4/AcOH/Ac2O (8.0 mL,
0.1:6:14) at room temperature. After stirring for 15 h,
the reaction mixture was neutralized by the addition of
sodium acetate (0.2 g), poured into saturated sodium
hydrogen carbonate, and extracted with chloroform.
Combined organic phase was washed with brine, dried
over anhydrous sodium sulfate, filtered, and concen-
trated. The residue was purified by silica gel column
chromatography (dichloromethane/acetone, 4:1) to give
1
15 (257.0 mg, 67%). [α]25D = +29.0 (c 1.0, CHCl3), H
NMR (600 MHz, CDCl3): δ 1.97, 1.99, 2.03, 2.05,
2.06, 2.07, 2.08, 2.13, 2.14, 2.15, 2.16, 2.18 (s, 3H x
12, Ac), 3.61 (ddd, 1H, J4,5 = 9.5 Hz, J5,6a = 7.0 Hz,
J5,6b = 5.5 Hz, H-5II), 3.82 (dd, 1H, J3,4 = 8.5 Hz,
J4,5 = 9.5 Hz, H-4II), 3.85–3.88 (m, 2H, H-5III, H-4I),
3.91 (dd, 1H, J4,5 = 9.5 Hz, J5,6 = 1.2 Hz, H-5I), 4.05–
4.09 (m, 2H, H-6aIII, H-7aI), 4.13 (dd, 1H,
J5,6b = 6.2 Hz, J6a,6b = 11.0 Hz, H-6bIII), 4.19 (dd, 1H,
J5,6a = 7.0 Hz, J6a,6b = 11.5 Hz, H-6aII), 4.24 (dd, 1H,
J5,6b = 5.5 Hz, J6a,,6b = 11.5 Hz, H-6bII), 4.40 (dd, 1H,
J6,7b = 2.0 Hz, J7a,7b = 12.0 Hz, H-7bI), 4.49 (d, 1H,
J1,2 = 8.0 Hz, H-1III), 4.61 (d, 1H, J1,2 = 7.5 Hz, H-1II),
4.82 (dd, 1H, J1,2 = 7.5 Hz, J2,3 = 8.0 Hz, H-2II), 4.95
Methyl (2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl)-
(1-4)-(2,3,6-tri-O-acetyl-β-D-glucopyranosyl)-(1-4)-6,7-
di-O-acetyl-L-glycero-α-D-manno-heptopyranoside (14).
Compound 10 (227.0 mg, 0.2 mmol) was hydrogenated
in the presence of 10% Pd/C (100.0 mg) in ethyl acet-
ate (15.0 mL) under atmospheric pressure of hydrogen.
After stirring for 3.5 h at room temperature, the reac-
tion mixture was filtered through Celite and concen-
trated. The residue was purified by flash column
chromatography (dichloromethane/acetone, 3:1) to give
1
14 (198.0 mg, 97%). [α]25D = +26.0 (c 1.0, CHCl3), H
NMR (600 MHz, CDCl3): δ 1.97, 2.04, 2.04, 2.05,
2.07, 2.12, 2.14, 2.16, 2.17 (s, 3H x 9, Ac), 2.55

Synthesis of 4,5-branched inner-core OSs
1939
(dd, 1H, J2,3 = 10.5 Hz, J3,4 = 3.4 Hz, H-3III), 5.11 (dd,
1H, J1,2 = 8.0 Hz, J2,3 = 10.5 Hz, H-2III), 5.16 (dd, 1H,
J2,3 = 8.0 Hz, J3,4 = 8.5 Hz, H-3II), 5.22 (dd, 1H,
J1,2 = 2.5 Hz, J2,3 = 9.0 Hz, H-2I), 5.32–5.36 (m, 3H,
H-6I, H-4III, H-3I), 6.06 (d, 1H, J1,2 = 2.5 Hz, H-1I).
13C NMR (150 MHz, CDCl3): δ 20.5, 20.51, 20.6,
20.65, 20.7, 20.8, 20.81, 20.9, 21.1 (Ac-CH3), 60.7 (C-
6III), 62.2 (C-6II), 62.3 (C-7I), 66.6 (C-4III), 67.9 (C-3I),
68.4 (C-6I), 68.9 (C-2III), 69.1 (C-2I), 70.6 (C-5III), 71.0
(C-3III), 71.4 (C-5I), 71.9 (C-2II), 72.2 (C-5II), 73.1 (C-
3II), 73.2 (C-4I), 76.0 (C-4II), 90.4 (C-1I), 99.8 (C-1II),
101.2 (C-1III), 168.3, 169.1, 169.5, 169.53, 169.6,
169.8, 170.1, 170.14, 170.2, 170.3, 170.4 (Ac: C=O).
ESI-HRMS for C43H58O29: 1061.2961 [M + Na]+.
Found 1061.2981.
argon. Potassium carbonate (39.3 mg, 284.4 μmol) was
added to the reaction mixture. After stirring for 24 h at
room temperature, the mixture was filtered through
Celite. The solution was concentrated and purified by
silica gel column chromatography (ethyl acetate/hex-
ane, 2:1) to give 17 (60.2 mg, 92%). [α]25D = +2.4 (c
1.0, CHCl3), 1H NMR (600 MHz, CDCl3): δ 1.97,
2.00, 2.00, 2.04, 2.07, 2.12, 2.15, 2.19 (s, 3H x 11,
Ac), 3.63 (ddd, 1H, J4,5 = 10.0 Hz, J5,6a = 4.0 Hz,
J5,6b = 2.0 Hz, H-5II), 3.84–3.89 (m, 3H, H-4II, H-5III,
H-4I), 4.01 (dd, 1H, J4,5 = 9.8 Hz, J5,6 = 1.4 Hz, H-5I),
4.06 (dd, 1H, J5,6a = 7.2 Hz, J6a,6b = 11.2 Hz, H-6aIII),
4.09 (dd, 1H, J5,6a = 4.0 Hz, J6a,6b = 12.2 Hz, H-6aII),
4.14 (dd, 1H, J5,6b = 6.2 Hz, J6a,6b = 11.2 Hz, H-6bIII),
4.17 (dd, 1H, J6,7a = 7.2 Hz, J7a,7b = 11.4 Hz, H-7aI),
4.21 (dd, 1H, J6,7b = 6.0 Hz, J7a,7b = 11.4 Hz, H-7bI),
4.47 (dd, 1H, J5,6b = 2.0 Hz, J6a,6b = 12.2 Hz, H-6bII),
4.53 (d, 1H, J1,2 = 8.0 Hz, H-1III), 4.61 (d, 1H,
J1,2 = 7.0 Hz, H-1II), 4.83 (dd, 1H, J1,2 = 7.0 Hz,
J2,3 = 7.8 Hz, H-2II), 4.95 (dd, 1H, J2,3 = 10.6 Hz,
J3,4 = 3.4 Hz, H-3III), 5.10 (dd, 1H, J1,2 = 8.0 Hz,
J2,3 = 10.6 Hz, H-2III), 5.16 (dd, 1H, J2,3 = 7.8 Hz,
J3,4 = 10.4 Hz, H-3II), 5.34 (dd, 1H, J4,5 = 0.8 Hz,
J3,4 = 3.4 Hz, H-4III), 5.37 (ddd, 1H, J5,6 = 1.4 Hz,
J6,7a = 7.2 Hz, J6,7b = 6.0 Hz, H-6I), 5.43 (dd, 1H,
J1,2 = 2.2 Hz, J2,3 = 3.4 Hz, H-2I), 5.44 (dd, 1H,
J2,3 = 3.4 Hz, H-3I), 6.23 (d, 1H, J1,2 = 2.2 Hz, H-1I),
8.74 (NH). 13C NMR (150 MHz, CDCl3): δ 20.5,
20.57, 20.6, 20.7, 20.74, 20.8 (Ac-CH3), 60.7 (C-6III),
62.0 (C-6II), 62.1 (C-7I), 66.6 (C-4III), 67.8 (C-2I), 67.9
(C-6I), 69.0 (C-3I and C-2III), 70.6 (C-5III), 71.0 (C-
3III), 71.6 (C-2II), 71.7 (C-5II), 72.1 (C-5I), 73.1 (C-3II),
73.3 (C-4I), 75.8 (C-4II), 90.5 (OCNHCCl3), 94.6 (C-
1I), 99.9 (C-1II), 101.1 (C-1III), 160.0 (OCNHCCl3),
169.1, 169.4, 169.42, 169.67, 169.7, 170.0, 170.1,
170.2, 170.3, 170.4 (Ac: C=O). ESI-HRMS for
(2,3,4,6-Tetra-O-acetyl-β-D-galactopyranosyl)-(1-4)-
(2,3,6-tri-O-acetyl-β-D-glucopyranosyl)-(1-4)-2,3,6,7-tetra-
O-acetyl-L-glycero-D-manno-heptopyranose (16). Com-
pound 15 (256.6 mg, 247.0 μmol) was treated with
hydrazine acetate (45.5 mg, 494.0 μmol) in DMF
(3.0 mL) for 8 h at 0 °C. The reaction mixture was
diluted with ethyl acetate, washed with water and brine,
dried over anhydrous sodium sulfate, filtered, and con-
centrated. The residue was purified by silica gel column
chromatography (acetone/dichloromethane, 1:4) to give
16 (223.4 mg, 90%). 1H NMR (600 MHz, CDCl3): δ
1.96, 1.98, 2.04, 2.06, 2.07, 2.08, 2.13, 2.16, 2.19 (s,
3H x 11, Ac), 3.27 (brs, 1H, OH), 3.62 (ddd, 1H,
J4,5 = 10.0 Hz, J5,6a = 4.6 Hz, J5,6b = 1.6 Hz, H-5II),
3.81 (dd, 1H, J3,4 = 9.4 Hz, J4,5 = 10.0 Hz, H-4II), 3.87
(ddd, 1H, J5,6a = 7.8 Hz, J5,6b = 6.2 Hz, H-5III), 3.88
(dd, 1H, J4,5 = 9.8 Hz, H-4I), 4.06 (dd, 1H,
J5,6a = 4.6 Hz, J6a,6b = 12.0 Hz, H-6aII), 4.07 (dd, 1H,
J5,6a = 7.8 Hz, J6a,6b = 11.2 Hz, H-6aIII), 4.09 (dd, 1H,
J4,5 = 9.8 Hz, H-5I), 4.12 (dd, 1H, J5,6b = 6.2 Hz,
J6a,6b = 11.2 Hz, H-6bIII), 4.16 (dd, 1H, J6,7a = 6.8 Hz,
J7a,7b = 11.4 Hz, H-7aI), 4.38 (dd, 1H, J5,6b = 1.6 Hz,
J6a,6b = 12.0 Hz, H-6bII), 4.39 (dd, 1H, J6,7b = 5.8 Hz,
J7a,7b = 11.4 Hz, H-7bI), 4.49 (d, 1H, J1,2 = 8.0 Hz, H-
1III), 4.60 (d, 1H, J1,2 = 6.8 Hz, H-1II), 4.80 (dd, 1H,
J1,2 = 6.8 Hz, J2,3 = 8.2 Hz, H-2II), 4.94 (dd, 1H,
J2,3 = 10.4 Hz, J3,4 = 3.4 Hz, H-3III), 5.11 (dd, 1H,
C43H56Cl3NO28:
1162.1940.
1162.1952
[M + Na]+.
Found
Methyl (3,4,6,7-tetra-O-acetyl-2-O-benzyl-L-glycero-
α-D-manno-heptopyranosyl)-(1-3)-4,6,7-tri-O-acetyl-2-
O-benzyl-L-glycero-α-D-manno-heptopyranoside (18).
A
mixture of 7 (188.0 mg, 308.0 μmol), methyl 4,6,7-tri-
O-acetyl-2-O-benzyl-L-glycero-α-D-manno-heptopyra-
noside (4; 135.0 mg, 308.0 μmol), and 4 Å molecular
sieves (135.0 mg) was suspended in dry dichloro-
methane (0.9 mL). The reaction mixture was stirred for
1 h under argon and then cooled to -78 °C. TMSOTf
(2.2 μL, 12.3 μmol) in dichloromethane was added
dropwise to the reaction mixture. The reaction was
warmed to room temperature and stirred for 2 h. The
reaction was neutralized by the addition of a few drops
of triethylamine and aqueous saturated sodium hydro-
gen carbonate. The reaction mixture was diluted with
dichloromethane and filtered through Celite. The filtrate
was extracted twice with dichloromethane. The com-
bined organic phase was dried over anhydrous sodium
sulfate, filtered, and concentrated. The residue was
purified by BioRad S-X3 size exclusion beads (toluene/
ethyl acetate, 1:1) to give 18 (136.6 mg, 50%).
[α]25D = +41.2 (c 1.0, CHCl3), 1H NMR (600 MHz,
CDCl3): δ 1.77, 1.94, 1.96, 2.04, 2.05, 2.09, 2.13
(s, 3H x 7, Ac), 3.31 (s, 3H, OCH3), 3.66 (dd, 1H,
J
1,2 = 8.0 Hz, J2,3 = 10.4 Hz, H-2III), 5.15 (dd, 1H,
J2,3 = 8.2 Hz, J3,4 = 9.4 Hz, H-3II), 5.22–5.23 (m, 2H,
H-6I, H-4III), 5.34 (d, 1H, J1,2 = 3.2 Hz, H-1I), 5.40
(dd, 1H, H-3I), 5.41 (dd, 1H, J1,2 = 3.2 Hz, H-2I). 13C
NMR (150 MHz, CDCl3): δ 20.5, 20.6, 20.8, 20.9,
20.92 (Ac-CH3), 60.7 (C-6III), 62.5 (C-6II), 62.8 (C-7I),
66.6 (C-4III), 68.3 (C-6I), 68.96 (C-3I), 69.0 (C-2III),
69.1 (C-2I), 70.4 (C-5I), 70.6 (C-5III), 71.0 (C-3III),
71.9 (C-2II), 71.92 (C-5II), 73.1 (C-3II), 73.3 (C-4I),
76.0 (C-4II), 92.0 (C-1I), 99.1 (C-1II), 101.1 (C-1III),
169.2, 169.7, 169.8, 170.0, 170.1, 170.2, 170.4, 170.5
(Ac: C=O). ESI-HRMS for C41H56O28: 1019.2856
[M + Na]+. Found 1019.2848.
(2,3,4,6-Tetra-O-acetyl-β-D-galactopyranosyl)-(1-4)-
(2,3,6-tri-O-acetyl-β-D-glucopyranosyl)-(1-4)-2,3,6,7-
tetra-O-acetyl-L-glycero-α-D-manno-heptopyranosyl trich-
loroacetimidate (17).
Trichloroacetonitrile (57.0 μL,
565.6 μmol) was added to a solution of 16 (57.1 mg,
57.3 μmol) in dry dichloromethane (1.0 mL) under

1940
R. Yi et al.
J1,2 = 1.6 Hz, J2,3 = 3.0 Hz, H-2I), 3.76 (dd, 1H,
J4,5 = 10.0 Hz, J5,6 = 1.8 Hz, H-5II), 3.81 (dd, 1H,
J1,2 = 1.6 Hz, J2,3 = 3.0 Hz, H-2II), 3.87 (dd, 1H,
J4,5 = 10.0 Hz, J5,6 = 2.0 Hz, H-5I), 4.02 (dd, 1H,
J6,7a = 6.4 Hz, J7a,7b = 11.2 Hz, H-7aII), 4.07 (dd, 1H,
J2,3 = 3.0 Hz, J3,4 = 9.8 Hz, H-3I), 4.11 (dd, 1H,
J4,5 = 10.0 Hz, H-4II), 5.47 (dd, 1H, J3,4 = 7.0 Hz,
J4,5 = 10.2 Hz, H-4I), 7.30–7.46 (m, 10H, Ph). 13C
NMR (150 MHz, CDCl3): δ 20.6, 20.7, 20.75, 20.9,
21.5 (Ac-CH3), 61.7 (C-7II), 62.6 (C-7I), 65.5 (C-4II),
67.1 (C-6I), 67.16 (C-6II), 68.0 (C-4I), 68.9 (C-5I), 69.3
(C-5II), 70.7 (C-3II), 72.6 (OCH2Ph), 73.4 (OCH2Ph),
74.2 (C-3I), 75.4 (C-2I), 75.5 (C-2II), 92.9 (C-1I), 99.4
(C-1II), 128.0, 128.2, 128.25, 128.5, 128.7, 129.1,
137.4, 137.6 (Ph), 169.4, 169.5, 169.8, 170.4, 170.7,
171.1 (Ac: O=C). ESI-HRMS for C42H52O20: 899.2950
[M + Na]+. Found 899.2930.
J
6,7b = 6.8 Hz, J7a,7b = 11.2 Hz, H-7bII), 4.23 (dd, 1H,
J6,7a = 7.6 Hz, J7a,7b = 11.2 Hz, H-7aI), 4.32 (dd, 1H,
J6,7b = 5.6 Hz, J7a,7b = 11.2 Hz, H-7bI), 4.59, 4.64 (d,
2H, J = 12.2 Hz, OCH2Ph), 4.76 (d, 1H, J1,2 = 1.6 Hz,
H-1I), 4.82, 4.84 (d, 2H, J = 12.8 Hz, OCH2Ph), 5.03
(d, 1H, J1,2 = 1.6 Hz, H-1II), 5.05 (ddd, 1H,
J5,6 = 1.8 Hz, J6,7a = 6.4 Hz, J6,7b = 6.8 Hz, H-6II), 5.21
(ddd, 1H, J5,6 = 2.0 Hz, J6,7a = 7.6 Hz, J6,7b = 5.6 Hz,
H-6I), 5.31 (dd, 1H, J2,3 = 3.0 Hz, J3,4 = 10.0 Hz, H-
3II), 5.40 (dd, 1H, J3,4 = 9.8 Hz, J4,5 = 10.0 Hz, H-4II),
5.47 (dd, 1H, J3,4 = 9.8 Hz, J4,5 = 10.0 Hz, H-4I),
7.28–7.45 (m, 10H, Ph). 13C NMR (150 MHz, CDCl3):
δ 20.4, 20.66, 20.69, 20.7, 20.8, 20.83 (Ac-CH3), 55.1
(OCH3), 61.5 (C-7II), 62.0 (C-7I), 65.5 (C-4II), 66.9 (C-
6I), 67.1 (C-6II), 67.8 (C-4I), 68.8 (C-5I), 69.2 (C-5II),
70.8 (C-3II), 72.6 (OCH2Ph), 73.4 (OCH2Ph), 74.4 (C-
3I), 75.1 (C-2I), 75.5 (C-2II), 99.2 (C-1II), 99.4 (C-1I),
128.0, 128.1, 128.2, 128.4, 128.7, 129.0, 137.4, 137.6
(Ph), 169.3, 169.4, 169.7, 170.1, 170.3, 170.5, 170.6
(Ac: O=C). ESI-HRMS for C43H54O20: 913.3106
[M + Na]+. Found 913.3093.
(3,4,6,7-Tetra-O-acetyl-2-O-benzyl-L-glycero-α-D-manno-
heptopyranosyl)-(1-3)-4,6,7-tri-O-acetyl-2-O-benzyl-L-
glycero-D-manno-heptopyranosyl trichloroacetimidate
(20). Trichloroacetonitrile (192.0 μL, 1.9 mmol) was
added to a solution of 19 (139.9 mg, 160.0 μmol) in
dry dichloromethane (1.6 mL) under argon. Potassium
carbonate (113.0 mg, 0.8 mmol) was added to the reac-
tion. After stirring for 21 h at room temperature, the
mixture was filtered through Celite. The solution was
concentrated and purified by flash column chromatogra-
phy (ethyl acetate/hexane, 1:1) to give 20α (111.0 mg,
66%)
and
20β
(18.5 mg,
14%).
α-isomer:
[α]25D = +18.6 (c 1.5, CHCl3), 1H NMR (600 MHz,
CDCl3): δ 1.90, 1.94, 1.97, 2.01, 2.05, 2.06, 2.13 (s,
3H
J5,6 = 2.0 Hz, H-5II), 3.75 (dd, 1H, J1,2 = 1.4 Hz,
2,3 = 3.0 Hz, H-2II), 3.89 (dd, 1H, J6,7a = 4.0 Hz,
J7a,7b = 11.6 Hz, H-7aII), 3.94 (dd, 1H, J1,2 = 1.6 Hz,
2,3 = 3.2 Hz, H-2I), 4.05 (dd, 1H, J2,3 = 3.2 Hz,
x
7, Ac), 3.40 (dd, 1H, J4,5 = 10.0 Hz,
(3,4,6,7-Tetra-O-acetyl-2-O-benzyl-L-glycero-α-D-manno-
heptopyranosyl)-(1-3)-4,6,7-tri-O-acetyl-2-O-benzyl-L-
glycero-D-manno-heptopyranose (19). Compound 18
(158.5 mg, 178.0 μmol) was dissolved in a mixture of
H2SO4/AcOH/Ac2O (4.0 mL, 0.1:6:14) and stirred for
2 h at room temperature. The reaction mixture was neu-
tralized by the addition of sodium acetate (1.2 g),
poured into saturated sodium hydrogen carbonate, and
extracted with dichloromethane. The combined organic
layer was washed with brine, dried over anhydrous
sodium sulfate, filtered, and concentrated to a syrup
(156.5 mg). The crude syrup was treated with hydra-
zine acetate (20.4 mg, 221.0 μmol) in DMF (1.2 mL)
for 7 h at 0 °C. The reaction mixture was diluted with
ethyl acetate, washed with water and brine, dried over
anhydrous sodium sulfate, filtered, and concentrated.
The residue was purified by silica gel column chro-
matography (ethyl acetate/hexane, 1:1) to give 19
J
J
J3,4 = 6.6 Hz, H-3I), 4.08 (dd, 1H, J4,5 = 10.0 Hz,
J5,6 = 2.0 Hz, H-5I), 4.11 (dd, 1H, J6,7b = 7.2 Hz,
J7a,7b = 11.6 Hz, H-7bII), 4.16 (dd, 1H, J6,7a = 7.6 Hz,
J7a,7b = 11.4 Hz, H-7aI), 4.27 (dd, 1H, J6,7b = 5.4 Hz,
J7a,7b = 11.4 Hz, H-7bI), 4.60, 4.62 (d, 2H,
J = 12.2 Hz, OCH2Ph), 4.73, 4.91 (d, 2H, J = 12.4 Hz,
OCH2Ph), 4.98 (ddd, 1H, J5,6 = 2.0 Hz, J6,7a = 4.0 Hz,
J6,7b = 8.6 Hz, H-6II), 5.02 (d, 1H, J1,2 = 1.4 Hz, H-1II),
5.20 (dd, 1H, J2,3 = 3.0 Hz, J3,4 = 10.2 Hz, H-3II), 5.21
(ddd, 1H, J5,6 = 2.0 Hz, J6,7a = 7.6 Hz, J6,7b = 5.4 Hz,
H-6I), 5.31 (dd, J3,4 = 10.2 Hz, J4,5 = 10.0 Hz, H-4II),
5.52 (dd, J3,4 = 6.6 Hz, J4,5 = 10.0 Hz, H-4I), 6.40 (d,
1H, J1,2 = 1.6 Hz, H-1I), 7.27–7.50 (m, 10H, Ph), 8.80
(s, 1H, NH). 13C NMR (150 MHz, CDCl3): δ 20.6,
20.7, 20.76, 20.8 (Ac-CH3), 62.1 (C-7I), 62.6 (C-7II),
65.3 (C-4II), 66.7 (C-6I), 66.9 (C-4I), 67.2 (C-6II), 69.8
(C-5II), 70.8 (C-3II), 71.5 (C-5I), 72.2 (OCH2Ph), 73.5
(OCH2Ph), 73.7 (C-2I), 75.3 (C-3I), 75.8 (C-2II), 90.6
(OCNHCCl3), 95.0 (C-1I), 100.2 (C-1II), 127.8, 128.0,
128.2, 128.5, 128.6, 128.9, 136.9, 137.4 (Ph), 159.5
(OCNHCCl3), 169.4, 169.7, 170.2, 170.5 (Ac: O=C).
ESI-HRMS for C44H52Cl3NO20: 1042.2046 [M + Na]+.
Found 1042.2051. β-isomer: [α]25D = −12.6 (c 0.3,
CHCl3), 1H NMR (600 MHz, CDCl3): δ 1.75, 1.88,
1.90, 1.97, 1.98, 2.02, 2.05 (s, 3H x 7, Ac), 3.52 (dd,
1H, J4,5 = 9.8 Hz, J5,6 = 2.0 Hz, H-5II), 3.64 (dd, 1H,
J4,5 = 10.0 Hz, J5,6 = 2.6 Hz, H-5I), 3.74 (dd, 1H,
J1,2 = 2.0 Hz, J2,3 = 3.0 Hz, H-2II), 3.78 (dd, 1H,
J2,3 = 2.8 Hz, J3,4 = 9.6 Hz, H-3I), 3.89 (dd, 1H,
J1,2 = 0.6 Hz, J2,3 = 2.8 Hz, H-2I), 4.00 (dd, 1H,
J6,7a = 7.8 Hz, J7a,7b = 11.6 Hz, H-7aI), 4.03 (dd, 1H,
J6,7a = 6.6 Hz, J7a,7b = 11.2 Hz, H-7aII), 4.11 (dd, 1H,
1
(122.4 mg, 78%). H NMR (600 MHz, CDCl3): δ 1.82,
1.95, 1.96, 2.05, 2.06, 2.10, 2.15 (s, 3H x 7, Ac), 3.03
(s, 1H, OH), 3.70 (dd, 1H, J1,2 = 2.0 Hz, J2,3 = 2.6 Hz,
H-2I), 3.72 (dd, 1H, J4,5 = 10.0 Hz, J5,6 = 1.8 Hz, H-
5II), 3.81 (dd, 1H, J1,2 = 1.6 Hz, J2,3 = 3.0 Hz, H-2II),
4.07 (dd, 1H, J4,5 = 10.2 Hz, J5,6 = 2.0 Hz, H-5I), 4.10
(dd, 1H, J6,7a = 5.2 Hz, J7a,7b = 11.4 Hz, H-7aII), 4.14
(dd, 1H, J7a,7b = 11.4 Hz, H-7bII), 4.14 (dd, 1H,
J7a,7b = 11.4 Hz, H-7aI), 4.16 (dd, 1H, J2,3 = 2.6 Hz,
J3,4 = 7.0 Hz, H-3I), 4.38 (dd, 1H, J6,7b = 5.4 Hz,
J7a,7b = 11.4 Hz, H-7bI), 4.59, 4.64 (d, 2H,
J = 12.2 Hz, OCH2Ph), 4.82, 4.85 (d, 2H, J = 12.8 Hz,
OCH2Ph), 5.04 (ddd, 1H, J5,6 = 1.8 Hz, J6,7a = 5.2 Hz,
H-6II), 5.06 (d, 1H, J1,2 = 1.6 Hz, H-1II), 5.18 (ddd,
1H, J5,6 = 2.0 Hz, J6,7b = 5.4 Hz, H-6I), 5.30 (d, 1H,
J1,2 = 2.0 Hz, H-1I), 5.31 (dd, 1H, J2,3 = 3.0 Hz,
J3,4 = 10.2 Hz, H-3II), 5.40 (dd, 1H, J3,4 = 10.2 Hz,

Synthesis of 4,5-branched inner-core OSs
1941
J6,7b = 6.4 Hz, J7a,7b = 11.2 Hz, H-7bII), 4.38 (dd, 1H,
J6,7b = 5.0 Hz, J7a,7b = 11.6 Hz, H-7bI), 4.53, 4.55 (d,
2H, J = 12.8 Hz, OCH2Ph), 4.98 (ddd, 1H,
J5,6 = 2.0 Hz, J6,7a = 6.6 Hz, J6,7b = 6.4 Hz, H-6II),
4.93, 4.98 (d, 2H, J = 12.6 Hz, OCH2Ph), 4.97 (d, 1H,
J1,2 = 2.0 Hz, H-1II), 5.20 (ddd, 1H, J5,6 = 2.0 Hz,
J6a,6b = 8.8 Hz, H-6bIV), 3.64 (dd, 1H, J5,6a = 1.6 Hz,
J6a,6b = 9.2 Hz, H-6aIII), 3.69 (dd, 1H, J4,5 = 3.0 Hz,
J5,6 = 1.2 Hz, H-5I), 3.74 (dd, 1H, J1,2 = 7.8 Hz,
J2,3 = 9.8 Hz, H-2IV), 3.86 (dd, 1H, J5,6 = 1.6 Hz,
J6,7 = 7.6 Hz, H-6II), 3.86 (dddd, 1H, J = 1.4, 3.2, 4.8,
13.0 Hz, OCH2-), 3.90 (dd, 1H, J3,4 = 2.8 Hz, H-4IV),
3.90 (dd, 1H, J2,3 = 9.8 Hz, H-3III), 3.94 (dd, 1H,
J6a,6b = 9.2 Hz, H-6bIII), 3.94 (ddd, 1H, J3a,4 = 2.4 Hz,
J3b,4 = 3.4 Hz, H-4II), 3.95 (dddd, 1H, OCH2-), 4.03
(dd, 1H, J5,6 = 1.2 Hz, J6,7 = 9.4 Hz, H-6I), 4.04 (dd,
1H, J5,6 = 1.6 Hz, H-5II), 4.05 (dd, 1H, J4,5 = 10.0 Hz,
H-4III), 4.11 (ddd, 1H, J4,5 = 10.0 Hz, J5,6a = 1.6 Hz,
H-5III), 4.25, 4.37 (d, 2H, J = 11.8 Hz, CH2Ph), 4.28
(dd, 1H, J7,8a = 3.4 Hz, J8a,8b = 12.6 Hz, H-8aI), 4.35
(d, 1H, J1,2 = 7.8 Hz, H-1IV), 4.36, 4.60 (d, 2H,
J = 12.0 Hz, CH2Ph), 4.46 (dd, 1H, J7,8b = 2.6 Hz,
J8a,8b = 12.6 Hz, H-8bI), 4.55, 4.97 (d, 2H,
J = 11.2 Hz, CH2Ph), 4.58 (dd, 1H, J7,8a = 4.6 Hz,
J8a,8b = 12.8 Hz, H-8aII), 4.62, 4.66 (d, 2H,
J = 12.0 Hz, CH2Ph), 4.70 (ddd, 1H, J3a,4 = 5.0 Hz,
J3b,4 = 11.8 Hz, J4,5 = 3.0 Hz, H-4I), 4.70, 5.01 (d, 2H,
J = 10.4 Hz, CH2Ph), 4.77, 5.00 (d, 2H, J = 12.4 Hz,
CH2Ph), 4.86, 4.87 (d, 2H, CH2Ph), 4.86 (dddd, 1H,
=CH2), 4.88 (d, 1H, J1,2 = 3.4 Hz, H-1III), 4.93 (dddd,
1H, J = 1.6, 1.6, 3.2, 17.2 Hz,=CH2), 5.30 (dd, 1H,
J7,8b = 2.6 Hz, J8a,8b = 12.8 Hz, H-8bII), 5.58–5.64 (m,
J
6,7a = 7.8 Hz, J6,7b = 5.0 Hz, H-6I), 5.25 (dd, 1H,
J2,3 = 3.0 Hz, J3,4 = 10.2 Hz, H-3II), 5.32 (dd, 1H,
J3,4 = 10.2 Hz, J4,5 = 9.8 Hz, H-4II), 5.46 (dd, 1H,
J3,4 = 9.6 Hz, J4,5 = 10.0 Hz, H-4I), 5.72 (d, 1H,
J1,2 = 0.6 Hz, H-1I), 7.19–7.48 (m, 10H, Ph), 8.69 (s,
1H, NH). 13C NMR (150 MHz, CDCl3): δ 19.5, 19.7,
19.71, 19.8, 19.83, 19.9 (Ac-CH3), 60.0 (C-7I), 61.3
(C-7II), 64.4 (C-4II), 65.6 (C-6I), 66.0 (C-4I), 66.5 (C-
6II), 68.1 (C-5II), 69.5 (C-3II), 72.4 (C-5I), 72.5
(OCH2Ph), 72.53 (OCH2Ph), 73.1 (C-2I), 74.5 (C-3I),
75.9 (C-2II), 89.4 (OCNHCCl3), 96.0 (C-1I), 98.4 (C-
1II), 126.8, 127.0, 127.0, 127.4, 127.6, 136.3, 136.4
(Ph), 159.7 (OCNHCCl3), 168.2, 168.4, 168.7, 169.1,
169.2, 169.6, 169.8 (Ac: O=C). ESI-HRMS for
C44H52Cl3NO20:
1042.2012.
1042.2046
[M + Na]+.
Found
(2,3,4,6-Tetra-O-benzyl-β-D-galactopyranosyl)-(1-4)-
(2,3,6-tri-O-benzyl-α-D-glucopyranosyl)-(1-5)-[methyl O-
[methyl (7,8-di-O-benzoyl-4,5-O-isopropylidene-3-deoxy-
α-D-manno-2-octulopyranosyl)onate]]-(2-4)-(allyl 7,8-
di-O-benzoyl-3-deoxy-α-D-manno-2-octulopyranosid)onate
(25). A mixture of methyl O-[methyl (7,8-di-O-ben-
zoyl-4,5-O-isopropylidene-3-deoxy-α-D-manno-2-octu-
lopyranosyl)onate]-(2-4)-(allyl 7,8-di-O-benzoyl-3-deoxy-
α-D-manno-2-octulopyranosid)onate (1; 10.0 mg, 10.2
μmol), (2,3,4,6-tetra-O-benzyl-β-D-galactopyranosyl)-(1-
4)-2,3,6-tri-O-benzyl-α-D-glucopyranosyl trichloroace-
timidate (23; 34.1 mg, 30.5 μmol), and MS-AW 300
molecular sieves (10.0 mg) was suspended in diethyl
ether and dichloromethane (3:1, 0.4 mL). The reaction
mixture was stirred for 1 h under argon and cooled to
0 °C. Then, 0.01 M TMSOTf (60.0 μL, 0.6 μmol) in
dichloromethane was added dropwise to the reaction
mixture. After stirring for 1 h, the reaction was warmed
to room temperature and stirred for 1 h. The reaction
solution was neutralized by the addition of a few drops
of triethylamine and aqueous saturated sodium hydro-
gen carbonate. The reaction mixture was diluted with
dichloromethane and was filtered through Celite. The
filtrate was extracted twice with dichloromethane. The
combined organic phase was dried over anhydrous
sodium sulfate, filtered, and concentrated. The residue
was purified by BioRad S-X1 size exclusion beads
(toluene/ethyl acetate, 1:1) and TLC chromatography
(ethyl acetate/hexane, 1:3) to give 25 (4.0 mg, 20%).
[α]25D = +41.0 (c 0.5, CHCl3), 1H NMR (600 MHz,
1H,
-CH=),
5.59
(ddd,
1H,
J6,7 = 7.6 Hz,
J7,8a = 4.6 Hz, J7,8b = 2.6 Hz, H-7II), 5.75 (ddd, 1H,
J6,7 = 9.4 Hz, J7,8a = 3.4 Hz, J7,8b = 2.6 Hz, H-7I),
7.03–7.56 (m, 47H, Ar), 7.84–8.00 (m, 8H, Ar). 13C
NMR (150 MHz, CDCl3): δ 24.6 and 25.1 (Isop-Me),
31.4 (C-3II), 34.4 (C-3I), 52.0 (OMeI), 52.1 (OMeII),
62.1 (C-8I), 62.1 (C-8II), 64.7 (OCH2-), 67.7 (C-4I),
67.9 (C-6III), 68.1 (C-6IV), 69.3 (C-7I), 69.8 (C-4II),
69.9 (C-6II), 70.66 (C-7II), 70.7 (C-6I), 71.0 (C-5III),
72.03 (C-5I), 72.06 (C-5II), 72.3, 72.6, 73.0, 73.4, 74.4,
74.7, 75.3 (OCH2Ph), 72.9 (C-5IV), 73.7 (C-4IV), 76.2
(C-4III), 78.9 (C-2III), 80.2 (C-2IV), 80.3 (C-3III), 82.3
(C-3IV), 96.2 (C-2II), 98.3 (C-1III), 98.8 (C-2I), 102.7
(C-1IV), 109.6 (Cisop), 116.2 (=CH2), 126.3, 126.7,
126.9, 127.3, 127.4, 127.5, 127.7, 127.8, 127.9, 128.0,
128.1, 128.14, 128.2, 128.3, 128.31, 128.4, 128.40,
128.45, 128.6, 129.6, 129.65, 129.7, 129.75, 129.8,
130.0, 130.3, 132.9, 133.0, 133.1, 133.4 (Ar), 133.6
(-CH=), 138.14, 138.2, 138.5, 139.0, 139.1, 139.3,
139.9 (Ar), 164.8, 165.1, 165.8, 166.1 (Bz: C=O),
167.7 (C-1I), 168.7 (C-1II). MALDI-TOF MS for
C113H116O29: 1959.750 [M + Na]+. Found 1959.300.
(2,3,4,6-Tetra-O-acetyl-β-D-galactopyranosyl)-(1-4)-
(2,3,6-tri-O-acetyl-β-D-glucopyranosyl)-(1-4)-(3,6,7-tri-
O-acetyl-2-O-benzyl-L-glycero-α-D-manno-heptopyra-
nosyl)-(1-5)-[methyl O-[methyl (7,8-di-O-benzoyl-4,5-
O-isopropylidene-3-deoxy-α-D-manno-2-octulopyranosyl)
onate]]-(2-4)-(allyl 7,8-di-O-benzoyl-3-deoxy-α-D-manno-
CDCl3):
δ
0.98
(dd,
1H,
J3a,3b = 15.4 Hz,
J3a,4 = 2.4 Hz, H-3aII), 1.18 (s, 3H, Me), 1.34 (s, 3H,
Me), 2.23 (dd, 1H, J3a,3b = 12.4 Hz, J3a,4 = 5.0 Hz,
H-3aI), 2.26 (dd, 1H, J3a,3b = 12.4 Hz, J3b,4 = 11.8 Hz,
H-3bI), 2.59 (dd, 1H, J3a,3b = 15.4 Hz, J3b,4 = 3.4 Hz,
H-3bII), 3.31 (ddd, 1H, J5,6a = 5.0 Hz, H-5IV), 3.32 (dd,
1H, J2,3 = 9.8 Hz, J3,4 = 2.8 Hz, H-3IV), 3.38 (dd, 1H,
J5,6a = 5.0 Hz, J6a,6b = 8.8 Hz, H-6aIV), 3.38 (s, 3H,
OMeI), 3.48 (s, 3H, OMeII), 3.51 (dd, 1H,
J1,2 = 3.4 Hz, J2,3 = 9.8 Hz, H-2III), 3.56 (dd, 1H,
2-octulopyranosid)onate (27).
A mixture of 1
(42.0 mg, 42.7 μmol), 13 (96.0 mg, 84.1 μmol), and
MS-AW 300 molecular sieves (43.0 mg) was sus-
pended in dry dichloromethane (1.6 mL). The reaction
mixture was stirred for 1 h under argon, and then
0.01 M TMSOTf (260.0 μL, 2.5 μmol) in dichloro-
methane was added dropwise to the reaction mixture.
After stirring for 2 h, the reaction was neutralized by

1942
R. Yi et al.
the addition of a few drops of triethylamine and aque-
ous saturated sodium hydrogen carbonate. The reaction
mixture was diluted with dichloromethane and filtered
through Celite. The filtrate was extracted twice with
dichloromethane. The combined organic phase was
dried over anhydrous sodium sulfate, filtered, and con-
centrated. The residue was purified by BioRad S-X1
size exclusion beads (toluene/ethyl acetate, 1:1) and
TLC chromatography (ethyl acetate/hexane, 2:1) to
give 27 (22.8 mg, 26%). [α]25D = +2.9 (c 1.9, CHCl3),
1H NMR (600 MHz, CDCl3): δ 1.22 (s, 3H, Me), 1.41
(s, 3H, Me), 1.90, 1.91, 1.95, 1.99, 2.01, 2.02, 2.03,
2.03, 2.05, 2.14 (s, 3H x 10, Ac), 2.02 (dd, 1H,
J3a,3b = 15.6 Hz, J3a,4 = 2.2 Hz, H-3aII), 2.18 (dd, 1H,
J3a,3b = 12.6 Hz, J3a,4 = 12.4 Hz, H-3aI), 2.38 (dd, 1H,
J3a,3b = 12.6 Hz, J3b,4 = 4.4 Hz, H-3bI), 2.91 (dd, 1H,
J3a,3b = 15.6 Hz, J3b,4 = 3.4 Hz, H-3bII), 3.49 (s, 3H,
OMeI), 3.55 (s, 3H, OMeII), 3.54 (ddd, 1H,
J4,5 = 9.6 Hz, J5,6a = 5.0 Hz, J5,6b = 1.6 Hz, H-5IV),
3.79 (dd, 1H, H-5I), 3.79 (dd, 1H, J3,4 = 9.0 Hz,
J4,5 = 9.6 Hz, H-4IV), 3.82 (ddd, 1H, J4,5 = 0.6 Hz,
J5,6a = 7.2 Hz, J5,6b = 6.2 Hz, H-5 V), 3.82 (dd, 1H,
J1,2 = 1.6 Hz, J2,3 = 2.8 Hz, H-2III), 3.85 (dd, 1H,
J3,4 = 9.4 Hz, J4,5 = 10.2 Hz, H-4III), 3.91 (dddd, 1H,
OCH2-), 3.92 (dd, 1H, J6,7a = 7.8 Hz, J7a,7b = 11.4 Hz,
H-7aIII), 3.95 (dd, 1H, J4,5 = 10.2 Hz, H-5III), 3.97
(dddd, 1H, OCH2-), 4.07 (dd, 1H, J5,6a = 7.2 Hz,
J6a,6b = 11.2 Hz, H-6aV), 4.08 (dd, 1H, J6,7 = 9.4 Hz,
H-6I), 4.08 (dd, 1H, J5,6a = 5.0 Hz, J6a,6b = 12.0 Hz, H-
6aIV), 4.11 (dd, 1H, J5,6b = 6.2 Hz, J6a,6b = 11.2 Hz, H-
6bV), 4.22 (dd, 1H, J6,7b = 5.2 Hz, J7a,7b = 11.4 Hz, H-
7bIII), 4.30 (dd, 1H, J5,6 = 1.6 Hz, J6,7 = 6.0 Hz, H-6II),
4.38 (dd, 1H, J4,5 = 7.8 Hz, J5,6 = 1.6 Hz, H-5II), 4.47
(d, 1H, J1,2 = 7.8 Hz, H-1IV), 4.35 (dd, 1H,
J5,6b = 1.6 Hz, J6a,6b = 12.0 Hz, H-6bIV), 4.43 (d, 1H,
J1,2 = 8.0 Hz, H-1 V), 4.45, 4.54 (d, 2H, J = 12.0 Hz,
CH2Ph), 4.46 (ddd, 1H, J3a,4 = 12.4 Hz, J3b,4 = 4.4 Hz,
H-4I), 4.55 (ddd, 1H, J3a,4 = 2.2 Hz, J3b,4 = 3.4 Hz,
J4,5 = 7.8 Hz, H-4II), 4.62 (dd, 1H, J7,8a = 6.2 Hz,
J8a,8b = 12.4 Hz, H-8aII), 4.63 (dd, 1H, J7,8a = 3.8 Hz,
J8a,8b = 12.4 Hz, H-8aI), 4.79 (dd, 1H, J1,2 = 7.8 Hz,
J2,3 = 8.8 Hz, H-2IV), 4.88 (dd, 1H, J7,8b = 2.4 Hz,
J8a,8b = 12.4 Hz, H-8bI), 4.91 (dd, 1H, J2,3 = 10.4 Hz,
J3,4 = 3.4 Hz, H-3 V), 4.93 (dddd, 1H, J = 1.4 Hz,
=CH2), 5.01 (d, 1H, J1,2 = 1.6 Hz, H-1III), 5.05 (dddd,
1H, J = 1.6, 1.6, 3.2, 17.2 Hz,=CH2), 5.08 (dd, 1H,
J1,2 = 8.0 Hz, J2,3 = 10.4 Hz, H-2 V), 5.12 (dd, 1H,
J2,3 = 8.8 Hz, J3,4 = 9.0 Hz, H-3IV), 5.18 (dd, 1H,
J7,8b = 2.2 Hz, J8a,8b = 12.4 Hz, H-8bII), 5.30 (ddd, 1H,
J6,7a = 7.8 Hz, J6,7b = 5.2 Hz, H-6III), 5.33 (dd, 1H,
J3,4 = 3.4 Hz, J4,5 = 0.6 Hz, H-4 V), 5.34 (dd, 1H,
J2,3 = 2.8 Hz, J3,4 = 9.4 Hz, H-3III), 5.58 (ddd, 1H,
J6,7 = 9.4 Hz, J7,8a = 3.8 Hz, J7,8b = 2.4 Hz, H-7I),
5.63–5.69 (m, 1H, -CH=), 5.75 (ddd, 1H, J6,7 = 6.0 Hz,
J7,8a = 6.2 Hz, J7,8b = 2.2 Hz, H-7II), 7.27–7.57 (m,
17H, Ar), 7.94–8.00 (m, 8H, Ar). 13C NMR
(150 MHz, CDCl3): δ 20.5, 20.54, 20.7, 20.8, 20.84,
20.9, 23.0, 23.8 (Ac-CH3), 24.6 and 25.1 (Isop-Me),
32.0 (C-3II), 34.7 (C-3I), 52.2 (OMeII), 52.3 (OMeI),
64.5 (OCH2-), 60.7 (C-6 V), 62.3 (C-6IV), 62.4 (C-8I),
63.2 (C-8II), 63.5 (C-7III), 66.6 (C-4 V), 68.2 (C-6III),
68.22 (C-4I), 69.0 (C-2 V), 69.67 (C-7I), 69.7 (C-3III),
70.0 (C-4II), 70.5 (C-6I), 70.6 (C-5 V), 70.91 (C-7II),
70.9 (C-5III), 71.0 (C-3 V), 71.0 (C-6II), 71.4 (C-5I),
71.8 (C-2IV), 72.1 (C-5IV), 72.3 (OCH2Ph), 72.5
(C-5II), 73.3 (C-3IV), 73.9 (C-4III), 76.9 (C-2III), 76.3
(C-4IV), 97.88 (C-2II), 97.9 (C-1III), 98.7 (C-2I), 100.2
(C-1IV), 101.1 (C-1 V), 109.5 (Cisop), 116.0 (=CH2),
127.4, 127.6, 128.2, 128.3, 128.4, 128.5, 128.6, 128.8,
129.4, 129.7, 129.8, 130.1, 130.2, 130.9, 132.8, 133.0,
133.2, 133.5 (Ar), 133.53 (-CH=), 138.4 (Ar), 165.2,
165.3, 166.0, 166.2 (Bz: C=O), 167.6 (C-1I), 169.1 (C-
1II), 169.6, 169.6, 169.7, 170.1, 170.2, 170.3, 170.4,
170.4 (Ac: C=O). MALDI-TOF MS for C98H112O45:
2031.638 [M + Na]+. Found 2030.629.
(3,4,6,7-Tetra-O-acetyl-2-O-benzyl-L-glycero-α-D-manno-
heptopyranosyl)-(1-3)-(2-O-benzyl-4,6,7-tri-O-acetyl-
L-glycero-α-D-manno-heptopyranosyl)-(1-5)-[methyl O-
[methyl (7,8-di-O-benzoyl-4,5-O-isopropylidene-3-deoxy-
α-D-manno-2-octulopyranosyl)onate]]-(2-4)-(allyl 7,8-
di-O-benzoyl-3-deoxy-α-D-manno-2-octulopyranosid)
onate (28). A mixture of 1 (62.3 mg, 63.4 μmol), 20
(129.5 mg, 126.8 μmol, α/β = 6:1), and MS-AW 300
molecular sieves (62.0 mg) was suspended in dichloro-
methane (2.7 mL). The reaction mixture was stirred for
1 h under argon, and then 0.01 M TMSOTf (380.0 μL,
3.8 μmol) in dichloromethane was added dropwise to
the reaction mixture. After stirring for 1 h, the reaction
was neutralized by the addition of a few drops of tri-
ethylamine and aqueous saturated sodium hydrogen
carbonate. The reaction mixture was diluted with
dichloromethane and filtered through Celite. The filtrate
was extracted twice with dichloromethane. The com-
bined organic phase was dried over anhydrous sodium
sulfate, filtered, and concentrated. The residue was
purified by BioRad S-X1 size exclusion beads (toluene/
ethyl acetate, 1:1) and TLC chromatography (ethyl
acetate/hexane, 3:2) to give 28 (66.9 mg, 57%).
[α]25D = −7.0 (c 1.0, CHCl3), 1H NMR (600 MHz,
CDCl3): δ 1.19 (s, 3H, Me), 1.36 (s, 3H, Me), 1.88,
1.93, 1.94, 1.97, 1.99, 2.01, 2.11 (s, 3H x 7, Ac), 2.02
(dd, 1H, J3a,3b = 15.6 Hz, J3a,4 = 2.6 Hz, H-3aII), 2.08
(dd, 1H, J3a,3b = 12.4 Hz, J3a,4 = 12.2 Hz, H-3aI), 2.25
(dd, 1H, J3a,3b = 12.4 Hz, J3b,4 = 4.0 Hz, H-3bI), 2.96
(dd, 1H, J3a,3b = 15.6 Hz, J3b,4 = 3.6 Hz, H-3bII), 3.38
(s, 3H, OMeI), 3.43 (s, 3H, OMeII), 3.69 (dd, 1H,
J4,5 = 2.2 Hz, H-5I), 3.80 (dd, 1H, J1,2 = 1.8 Hz,
J2,3 = 3.0 Hz, H-2IV), 3.89 (dddd, 1H, J = 1.6, 3.0, 4.8,
13.0 Hz, OCH2-), 3.94 (dddd, 1H, J = 1.4, 2.8, 5.6 Hz,
OCH2-), 3.95 (dd, 1H, J4,5 = 9.8 Hz, J5,6 = 8.2 Hz, H-
5IV), 3.95 (dd, 1H, J1,2 = 1.6 Hz, J2,3 = 2.4 Hz, H-2III),
4.06 (dd, 1H, J2,3 = 2.4 Hz, J3,4 = 10.0 Hz, H-3III),
4.09 (dd, 1H, J6,7 = 9.6 Hz, H-6I), 4.10 (dd, 1H,
J4,5 = 9.8 Hz, J5,6 = 8.6 Hz, H-5III), 4.21 (dd, 1H,
J6,7a = 6.0 Hz, H-7aIV), 4.21 (dd, 1H, J6,7b = 2.0 Hz, H-
7bIV), 4.24 (dd, 1H, J6,7a = 5.8 Hz, J7a,7b = 11.8 Hz, H-
7aIII), 4.26 (dd, 1H, J5,6 = 1.8 Hz, J6,7 = 7.2 Hz, H-6II),
4.32 (dd, 1H, J6,7b = 3.4 Hz, J7a,7b = 11.8 Hz, H-7bIII),
4.35 (dd, 1H, J4,5 = 7.8 Hz, J5,6 = 1.8 Hz, H-5II), 4.49
(ddd, 1H, J3a,4 = 2.6 Hz, J3b,4 = 3.6 Hz, J4,5 = 7.8 Hz,
H-4II), 4.59 (dd, 1H, J7,8a = 3.8 Hz, J8a,8b = 12.4 Hz,
H-8aI), 4.61 (dd, 1H, J7,8a = 4.2 Hz, J8a,8b = 12.4 Hz,
H-8aII), 4.61, 4.68 (d, 2H, CH2Ph), 4.62, 4.70 (d, 2H,
CH2Ph), 4.67 (ddd, 1H, J3a,4 = 12.2 Hz, J3b,4 = 4.0 Hz,
J4,5 = 2.2 Hz, H-4I), 4.80 (dd, 1H, J7,8b = 2.6 Hz,
J8a,8b = 12.4 Hz, H-8bI), 4.93 (dddd, 1H, J = 1.2, 1.6,

Synthesis of 4,5-branched inner-core OSs
1943
2.8, 10.6 Hz,=CH2), 4.98 (dddd, 1H, J = 1.6, 1.6, 3.2,
17.2 Hz,=CH2), 5.07 (d, 1H, J1,2 = 1.6 Hz, H-1III), 5.15
(dd, 1H, J2,3 = 3.0 Hz, J3,4 = 10.0 Hz, H-3IV), 5.20
(ddd, 1H, J5,6 = 8.2 Hz, J6,7a = 6.0 Hz, J6,7b = 2.0 Hz,
H-6IV), 5.21 (d, 1H, J1,2 = 1.8 Hz, H-1IV), 5.27 (dd,
1H, J7,8b = 2.4 Hz, J8a,8b = 12.4 Hz, H-8bII), 5.31 (ddd,
1H, J5,6 = 8.6 Hz, J6,7a = 5.8 Hz, J6,7b = 3.4 Hz, H-6III),
5.41 (dd, J3,4 = 10.0 Hz, J4,5 = 9.8 Hz, H-4IV), 5.52
(dd, J3,4 = 10.0 Hz, J4,5 = 9.8 Hz, H-4III), 5.57 (ddd,
1H, J6,7 = 9.6 Hz, J7,8a = 3.8 Hz, J7,8b = 2.6 Hz, H-7I),
5.63–5.69 (m,1H, -CH=), 5.68 (ddd, 1H, J6,7 = 7.2 Hz,
J7,8a = 4.2 Hz, J7,8b = 2.4 Hz, H-7II), 7.21–7.60 (m,
22H, Ar), 7.94–8.04 (m, 8H, Ar). 13C NMR
(150 MHz, CDCl3): δ 20.6, 20.8, 20.83, 20.87, 20.9
(Ac-CH3), 24.6 and 25.1 (Isop-Me), 32.0 (C-3II), 34.5
(C-3I), 52.1 (OMeII), 52.2 (OMeI), 62.4 (C-8II), 62.6
(C-8I), 63.5 (C-7IV), 64.1 (C-7III), 64.8 (OCH2-), 65.3
(C-4IV), 66.9 (C-4III), 67.6 (C-4I), 67.7 (C-6III), 68.0
(C-6IV), 69.0 (C-7I), 69.9 (C-4II), 70.0 (C-5IV), 70.1
(C-3III), 70.3 (C-6I, C-5III, C-6II), 70.6 (C-7II), 71.2 (C-
3IV), 72.1 (OCH2Ph), 72.2 (C-5II), 72.9 (OCH2Ph),
74.1 (C-5I), 75.5 (C-2IV), 77.2 (C-2III), 97.0 (C-2II),
98.8 (C-2I), 99.0 (C-1IV), 99.2 (C-1III), 109.6 (Cisop),
116.4 (=CH2), 127.3, 127.4, 127.7, 127.8, 128.3,
128.32, 128.4, 128.6, 128.8, 128.9, 129.5, 129.6,
129.7, 129.75, 129.9, 130.1, 132.9, 133.0, 133.3 (Ar),
133.4 (-CH=), 133.8, 137.8, 138.3 (Ar), 165.2, 165.4,
165.8, 166.2 (Bz: C=O), 167.4 (C-1I), 169.4 (C-1II),
169.6, 169.7, 169.8, 170.4, 170.5, 170.7, 170.8 (Ac:
C=O). MALDI-TOF MS for C94H104O38: 1863.611
[M + Na]+. Found 1862.589.
J8a,8b = 11.8 Hz, H-8aII), 3.66 (dd, 1H, J6,7 = 8.2 Hz,
H-6II), 3.68 (dd, 1H, J6,7a = 5.7 Hz, J7a,7b = 10.8 Hz,
H-7aIII), 3.73–3.77 (m, 4H, H-7bIII, H-7aIV, H-7bIV,
H-5III), 3.81 (dd, 1H, J7,8a = 6.4 Hz, J8a,8b = 11.6 Hz,
H-8aI), 3.84–3.98 (m, 8H, H-7I, H-3III, H-4III, H-7II,
H-8bII, H-4IV, H-5IV, H-8bI), 4.01–4.06 (m, 4H, H-5II,
H-3IV, H-6III, H-6IV), 4.07 (dd, 1H, J1,2 = 1.2 Hz,
J2,3 = 3.2 Hz, H-2III), 4.09 (ddd, 1H, J3a,4 = 12.6 Hz,
J3b,4 = 4.8 Hz, J4,5 = 3.0 Hz, H-4II), 4.13 (dd, 1H,
J1,2 = 1.6 Hz, J2,3 = 3.0 Hz, H-2IV), 4.22 (brs, 1H,
J4,5 = 2.2 Hz, H-5I), 4.26 (ddd, 1H, J3a,4 = 12.4 Hz,
J3b,4 = 4.2 Hz, J4,5 = 2.2 Hz, H-4I), 5.17 (d, 1H,
J1,2 = 1.2 Hz, H-1III), 5.29 (d, 1H, J1,2 = 1.6 Hz,
H-1IV). 13C NMR (150 MHz, D2O): δ 10.9 (CH3), 23.9
(CH2), 35.2 (C-3I, C-3II), 63.5 (C-7IV, C-8I), 64.0
(C-8II), 64.6 (C-7III), 65.4 (OCH2,), 66.4 (C-4III), 66.8
(C-4II), 66.81 (C-5II), 67.0 (C-4IV), 69.4 (C-6III), 69.7
(C-7I), 70.0 (C-6IV), 70.1 (C-4I), 70.6 (C-2III), 70.8
(C-2IV), 70.83 (C-7II), 71.1 (C-3IV), 72.4 (C-5III), 72.6
(C-6I), 72.62 (C-6II), 73.3 (C-5IV and C-5I), 79.2 (C-3III),
100.5, 100.7 (C-2I, C-2II), 101.3 (C-1III), 103.0 (C-1IV),
175.6, 175.9 (C-1I, C-1II). ESI-HRMS for C33H55O27:
883.2931 [M-2Na + H]-. Found 883.2929.
(β-D-Galactopyranosyl-(1-4)-β-D-glucopyranosyl)-(1-
4)-(L-glycero-α-D-manno-heptopyranosyl)-(1-5)-[O-(-
sodium 3-deoxy-α-D-manno-2-octulopyranosylonate)]-
(2-4)-sodium (propyl 3-deoxy-α-D-manno-2-octulopyra-
noside)onate (30). Compound 27 (9.0 mg, 4.5 μmol)
was hydrogenated in the presence of Pd(OH)2-C (20%,
0.2 mg) in dry methanol (0.5 mL) under atmospheric
pressure of hydrogen for 2 days at room temperature.
The reaction mixture was filtered through Celite and
concentrated. The residue was dissolved in dichloro-
methane (0.6 mL) and aqueous 80% trifluoroacetic acid
(70.0 μL) was added at room temperature. After stirring
for 1 h, the solvent was removed by evaporation under
an argon stream to give a crude compound that was
not subjected to further purification. The crude com-
pound was dissolved in methanol (1.0 mL), and then
0.1 M sodium hydroxide (1.4 mL, 0.14 mmol) was
added at room temperature. After stirring for 24 h, the
mixture was concentrated by evaporation. The residue
(L-Glycero-α-D-manno-heptopyranosyl)-(1-3)-(L-glyc-
ero-α-D-manno-heptopyranosyl)-(1-5)-[O-(sodium 3-deoxy-
α-D-manno-2-octulopyranosylonate)]-(2-4)-sodium (propyl
3-deoxy-α-D-manno-2-octulopyranoside)onate (29).
Compound 28 (10.0 mg, 5.4 μmol) in dry methanol
(0.3 mL) was added to a suspension of Pd(OH)2-C
(20%, 0.3 mg) in dry methanol (0.2 mL), under a H2
atmosphere with stirring at room temperature. After
stirring for 3 days, insoluble materials were removed
by filtration through Celite and the filtrate was evapo-
rated. The residue was dissolved in dichloromethane
(0.7 mL) and aqueous 80% trifluoroacetic acid (80.0
μL) was added at room temperature. After stirring for
1 h, the solvent was removed by evaporation under an
argon stream to give a crude compound that was not
subjected to further purification. The crude compound
was dissolved in methanol (1.0 mL), and then 0.1 M
sodium hydroxide (1.3 mL, 0.13 mmol) was added at
room temperature. After stirring for 24 h, the mixture
was concentrated by evaporation. The residue was
passed through a Bio-Gel P-2 column (2.5 × 100 cm,
H2O) and a Sep-Pak C18 column (H2O) to give 29
(4.5 mg, 90%) as a colorless powder. [α]25D = +127.6
was passed through
a
Bio-Gel P-2 column
(2.5 × 100 cm, H2O) and a Sep-Pak C18 column (H2O)
to give 30 (2.5 mg, 53%) as a colorless powder.
[α]25D = +17.4 (c 0.3, H2O), 1H NMR (600 MHz,
D2O): δ 0.91 (t, 3H, J = 7.4 Hz, CH3), 1.55–1.62 (m,
2H,
CH2),
1.77
(dd,
1H,
J3a,3b = 12.8 Hz,
J3a,4 = 12.6 Hz, H-3aII), 1.92 (dd, 1H, J3a,3b = 12.8 Hz,
J3a,4 = 12.0 Hz, H-3aI), 2.07 (dd, 1H, J3a,3b = 12.8 Hz,
J3b,4 = 4.4 Hz, H-3bI), 2.18 (dd, 1H, J3a,3b = 12.8 Hz,
J3b,4 = 4.6 Hz, H-3bII), 3.19–3.24 (m, 1H, OCH2),
3.26–3.30 (m, 1H, OCH2), 3.39 (dd, 1H, J1,2 = 8.0 Hz,
J2,3 = 8.8 Hz, H-2IV), 3.54 (dd, 1H, J1,2 = 7.8 Hz,
J2,3 = 10.0 Hz, H-2 V), 3.58 (dd, 1H, J6,7 = 8.4 Hz,
H-6I), 3.59 (dd, 1H, J7,8a = 6.2 Hz, J8a,8b = 11.6 Hz,
H-8aII), 3.64–3.84 (m, 14H, H-3 V, H-6II, H-3IV, H-6aIV,
H-6bIV, H-5 V, H-4IV, H-6aV, H-6bV, H-7aIII, H-5III,
H-7bIII, H-8aI, H-7I), 3.89 (dd, 1H, J7,8b = 2.6 Hz,
J8a,8b = 11.6 Hz, H-8bII), 3.91–3.99 (m, 4H, H-4 V,
H-7II, H-5IV, H-8bI), 4.00–4.07 (m, 3H, H-4III, H-3III,
H-5II), 4.09 (brs, 1H, J1,2 = 1.6 Hz, H-2III), 4.10 (ddd,
1
(c 0.5, H2O), H NMR (600 MHz, D2O): δ 0.92 (t, 3H,
J = 7.4 Hz, CH3), 1.54–1.61 (m, 2H, CH2), 1.76 (dd,
1H, J3a,3b = 13.2 Hz, J3a,4 = 12.6 Hz, H-3aII), 1.93 (dd,
1H, J3a,3b = 12.6 Hz, J3a,4 = 12.4 Hz, H-3aI), 2.06 (dd,
1H, J3a,3b = 12.6 Hz, J3b,4 = 4.2 Hz, H-3bI), 2.20 (dd,
1H, J3a,3b = 13.2 Hz, J3b,4 = 4.8 Hz, H-3bII), 3.21–3.24
(m, 1H, OCH2), 3.28–3.32 (m, 1H, OCH2), 3.57 (dd,
1H, J6,7 = 9.4 Hz, H-6I), 3.61 (dd, 1H, J7,8a = 6.2 Hz,

1944
R. Yi et al.
1H, J3a,4 = 12.6 Hz, J3b,4 = 4.6 Hz, J4,5 = 3.0 Hz, H-
4II), 4.14 (ddd, 1H, J6,7a = 7.8 Hz, J6,7b = 4.8 Hz, H-
6III), 4.21 (brs, 1H, J4,5 = 2.2 Hz, H-5I), 4.24 (ddd, 1H,
J3a,4 = 12.0 Hz, J3b,4 = 4.4 Hz, J4,5 = 2.2 Hz, H-4I),
4.44 (d, 1H, J1,2 = 7.8 Hz, H-1 V), 4.58 (d, 1H,
J1,2 = 8.0 Hz, H-1IV), 5.32 (d, 1H, J1,2 = 1.6 Hz, H-
1III). 13C NMR (150 MHz, D2O): δ 10.8 (CH3), 23.8
(CH2), 35.0, 35.3 (C-3I, C-3II), 60.6 (C-6IV), 61.6 (C-
6 V), 63.5 (C-8I), 64.0 (C-8II), 64.6 (C-7III), 65.4
(OCH2), 66.9 (C-4II), 67.0 (C-5II), 69.2 (C-6III), 69.7
(C-7I), 69.9 (C-4 V), 70.2 (C-4I), 70.3 (C3III), 70.5
(C-2III), 70.7 (C-7II), 71.6 (C-5III), 72.0 (C-2 V), 72.3
(C-5IV), 72.6 (C-6I), 72.7 (C-6II), 73.1 (C-4III), 73.4
(C-5I), 74.6 (C-3IV), 75.5 (C-2IV), 76.0 (C-3 V), 76.5
(C-5 V), 78.8 (C-4IV), 100.5, 100.8 (C-2I, C-2II), 101.0
(C-1III), 103.0 (C-1IV), 103.6 (C-1 V), 175.5, 175.9 (C-1I,
C-1II). ESI-HRMS for C38H63O31: 1015.3353
[M-2Na + H]-. Found 1015.3370.
C-1II).
ESI-HRMS
for
C31H51O25:
823.2719
[M-2Na + H]-. Found 823.2732.
Conclusion
The convergent synthetic strategy using Kdoα(2-4)
Kdo as a common acceptor was used to prepare more
complex 4,5-branched inner-core OS structures. Model
glycosylation using a lactose derivative as a test com-
pound suggested that the reactivity of the donor was
important for this convergent synthesis, and this was
supported by the subsequent glycosylation. Based on
the convergent approach, the first synthesis of 4,5-
branched inner-core OSs, namely Galβ(1-4)Glcβ(1-4)
Hepα(1-5)[Kdoα(2-4)]Kdo pentasaccharide and a com-
mon inner-core Hepα(1-3)Hepα(1-5)[Kdoα(2-4)]Kdo
tetrasaccharide, was accomplished by coupling the cor-
responding Hep units with Kdoα(2-4)Kdo. These results
suggested that Kdoα(2-4)Kdo 1 is a useful intermediate
for the synthesis of 4,5-branched core OS structures.
(β-D-Galactopyranosyl)-(1-4)-(α-D-glucopyranosyl)-
(1-5)-[O-(sodium 3-deoxy-α-D-manno-2-octulopyranosy-
lonate)]-(2-4)-sodium (propyl 3-deoxy-α-D-manno-2-
octulopyranoside)onate (31). Compound 25 (5.3 mg,
2.7 μmol) was hydrogenated in the presence of Pd
(OH)2-C (20%, 1.5 mg) in dry methanol (0.4 mL)
under atmospheric pressure of hydrogen for 1 day at
room temperature. The reaction mixture was filtered
through Celite and concentrated. The residue was trea-
ted with aqueous 80% trifluoroacetic acid (40.0 μL) at
room temperature. After stirring for 5 min, the solvent
was removed by evaporation under an argon stream to
give a crude compound that was not subjected to fur-
ther purification. The crude compound was dissolved in
methanol (0.8 mL), and then 0.1 M sodium hydroxide
(0.5 mL, 0.05 mmol) was added at room temperature.
After stirring for 24 h, the mixture was concentrated by
evaporation. The residue was purified by a Bio-Gel P-2
column (2.5 × 100 cm, H2O) and a Sep-Pak C18 col-
umn (H2O) to give 31 (1.4 mg, 60%) as a colorless
powder. [α]25D = +20.1 (c 0.1, H2O), 1H NMR
(600 MHz, D2O): δ 0.90 (t, 3H, J = 7.4 Hz, CH3),
1.53–1.60 (m, 2H, CH2), 1.80 (dd, 1H,
J3a,3b = 12.8 Hz, J3a,4 = 12.6 Hz, H-3aII), 2.02 (dd, 1H,
J3a,3b = 12.6 Hz, H-3aI), 2.06–2.08 (m, 2H, H-3bI, H-
3bII), 3.21–3.30 (m, 2H, OCH2), 3.55 (dd, 1H,
J1,2 = 7.8 Hz, J2,3 = 10.2 Hz, H-2IV), 3.56–3.60 (m,
3H, H-2III, H-6I, H-8aII), 3.66 (dd, 1H, J2,3 = 10.2 Hz,
J3,4 = 3.4 Hz, H-3IV), 3.72–3.82 (m, 6H, H-6II, H-4III,
H-6aIV, H-6bIV, H-5IV, H-8aI), 3.89–4.01 (m, 9H, H-
8bI, H-7II, H-4IV, H-6aIII, H-6bIII, H-3III, H-8bII, H-5II,
H-4I), 4.06 (ddd, 1H, J6,7 = 9.0 Hz, J7,8a = 3.0 Hz, J7,
8b = 2.4 Hz, H-7I), 4.09–4.12 (m, 1H, J3a,4 = 12.6 Hz,
J3b,4 = 4.8 Hz, J4,5 = 2.2 Hz, H-4II), 4.23 (brs, 1H, H-
5I), 4.23–4.26 (m, 1H, H-5III), 4.47 (d, 1H,
J1,2 = 7.8 Hz, H-1IV), 5.28 (dd, 1H, J1,2 = 3.6 Hz, H-
1III). 13C NMR (150 MHz, D2O): δ 10.8 (CH3), 22.8
(CH2), 35.2 (C-3I, C-3II), 60.2 (C-6III), 61.7 (C-6IV),
63.3 (C-8I), 64.0 (C-8II), 65.3 (OCH2), 66.7 (C-4II),
67.5 (C-5II), 69.2 (C-7I), 69.3 (C-4IV), 70.1, 71.3, 71.6,
71.8, 72.0, 72.3, 72.4, 73.0, 73.2 (C-4I, C-7II, C-2IV,
C-5III, C-6II, C-6I, C-2III, C-3III, C-5I), 74.0 (C-3IV),
75.9 (C-5IV), 78.5 (C-4III), 99.6, 100.5 (C-2I, C-2II),
102.3 (C-1III), 103.5 (C-1IV), 175.9 and 176.1 (C-1I,
Author contribution
Ruiqin Yi and Tsuyoshi Ichiyanagi planned the
experiments. Ruiqin Yi, Hirofumi Narimoto, and Miku
Nozoe performed the experiments. Ruiqin Yi and
Tsuyoshi Ichiyanagi analyzed the data. Ruiqin Yi,
Hirofumi Narimoto, and Miku Nozoe contributed
reagents or other essential material. Ruiqin Yi and
Tsuyoshi Ichiyanagi wrote the paper.
Acknowledgment
We thank Professors Jun-ichi Tamura and Toshiki
Nokami for helpful discussions and are also grateful to
Ms. Maki Taniguchi for technical assistance.
Disclosure statement
No potential conflict of interest was reported by the
authors.
Funding
This work was supported by JSPS KAKENHI [grant num-
ber 23580474 and 15K01822].
Supplemental material
The supplemental material for this paper is available
at http://dx.doi.org/10.1080/09168451.2015.1069698.
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