Synthesis of β-(1→4)-oligo-d-mannuronic acid neoglycolipids

Article abstract of DOI:10.1016/j.carres.2007.10.007

Mammalian Toll-like receptors (TLRs) play important roles in host immune defense. The activation of TLR and down-stream signaling pathways have great impact on human physiology. Chemically diverse microbial products as well as synthetic ligands serve as a

Full text of DOI:10.1016/j.carres.2007.10.007

Available online at www.sciencedirect.com
Carbohydrate Research 343 (2008) 7–17
Synthesis of b-(1!4)-oligo-D-mannuronic acid neoglycolipids
Rongsong Xu and Zi-Hua Jiang*
Department of Chemistry, Lakehead University, 955 Oliver Road, Thunder Bay, Ontario, Canada P7B 5E1
Received 23 July 2007; received in revised form 5 October 2007; accepted 11 October 2007
Available online 22 October 2007
Abstract—Mammalian Toll-like receptors (TLRs) play important roles in host immune defense. The activation of TLR and down-
stream signaling pathways have great impact on human physiology. Chemically diverse microbial products as well as synthetic
ligands serve as agonists for these receptors. Recently, synthetic TLR ligands are being exploited as useful therapeutic agents for
a variety of diseases including infections, inflammatory diseases, and cancers. Alginate polymers and oligosaccharides are strong
immune stimulants mediated by TLR2/4, but synthesis of alginate oligomers is rarely studied. Reported here are the design and
chemical synthesis of two b-(1!4)-di- and b-(1!4)-tri-D-mannuronic acid neoglycolipids 1 and 2 as potential TLR ligands. By using
4,6-di-O-benzylidene-protected 1-thio mannoside 7 as a glycosyl donor, the diastereoselective b-D-mannosylation protocol provides
the b-(1!4)-D-mannobiose and b-(1!4)-D-mannotriose derivatives, which upon regioselective oxidation with TEMPO/BAIB oxi-
dation system yield the corresponding b-(1!4)-D-mannuronic acid containing neoglycolipids 1 and 2.
ꢀ 2007 Elsevier Ltd. All rights reserved.
Keywords: Alginate; D-Mannuronic acid; Oligosaccharide synthesis; Glycolipids; TLR ligand
1. Introduction
tory molecules potentially useful as vaccine adjuvants.7–9
To continue our studies in synthetic TLR ligands for
modulating immune responses, here we report the
design and synthesis of two alginate-derived neoglyco-
lipids 1 and 2 as potential ligands for TLRs (Chart 1).
Alginates are linear polysaccharides consisting of b-
(1!4)-linked D-mannuronic acid (M) residues and its
C-5-epimer a-(1!4)-linked L-guluronic acid (G) resi-
dues (Chart 1).10 In nature, alginates are produced by
marine macroalgae and some bacteria belonging to the
genera Azotobacter and Pseudomonas.11 Their composi-
tions are highly variable depending on the sources from
which they are isolated. Three types of polymeric blocks
have been reported for natural alginates: (a) poly-M
block which contains mainly D-mannuronic acid resi-
dues; (b) poly-G block consisting of mainly L-guluronic
acid residues; and (c) poly-GM block that contains
alternating D-mannuronic acid and L-guluronic acid
residues. Alginates from bacteria also display certain
degrees of acetylation at the O-2- and O-3-position of
D-mannuronic acid residues.12 Based on their gel-forming
properties, alginates have traditionally been widely
used as additives in the food industry,13 and more recently
in the biomedical industry as biocompatible materials
Mammalian Toll-like receptors (TLRs) are innate
pattern recognition receptors that play critical roles in
detecting invading pathogens and triggering of subse-
quent inflammatory and immune response. To date,
thirteen members of TLRs have been found in mice
and eleven in humans.1 Chemically diverse microbial
products as well as endogenous ligands such as heat
shock protein (HSP) serve as agonists for these recep-
tors.2 Activation of TLRs and downstream signaling
pathways lead to the expression of pro- and anti-inflam-
matory mediators, which have great impact on human
physiology. Conceivably, either naturally occurring or
synthetic ligands capable of regulating TLR signaling
pathways will be extremely useful in treating various dis-
eases including infection, chronic inflammation, and
cancers.3–5 As part of our synthetic vaccine program,6
we have previously reported a few lipid A-based syn-
thetic TLR 4 ligands, which are potent immune-stimula-
*
Corresponding author. Tel.: +1 807 766 7171; fax: +1 807 346
7775; e-mail: zjiang@lakeheadu.ca
0008-6215/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2007.10.007

8
R. Xu, Z.-H. Jiang / Carbohydrate Research 343 (2008) 7–17
HOOC
HOOC
O
HOOC
O
OH
OR
O
OR
O
OR
O
OH
OH
HOOC
OH
HOOC
O
HOOC
Alginate
O
O
O
O
H
O
O
RO
RO
RO
R = H, Ac
k
m
n
OH
OH
OH
Poly-L-guluronic acid (poly-G)
Poly-D-mannuronic acid (poly-M)
Poly-GM
O
O
O
OH
OH
OH
O
HO
HO
HO
HO
HO
1 n=0
2 n=1
O
O
O
O
O
O
O
HO
HO
n
OH
Chart 1. Structures of alginates and neoglycolipids 1 and 2.
for drug delivery14 and immobilization of microorgan-
isms and living cells.15 Recently, alginate polymers16,17
and alginate oligosaccharides18,19 have been reported
to be potent immune-stimulating agents in eliciting cyto-
kine production by monocytes. The immune-stimula-
tory potency depends on the content of M and G
residues of the polymeric blocks. TLR2 and TLR4 are
involved in mediating cytokine production induced by
both alginate polymers and alginate oligosaccha-
rides,17,19 suggesting that short oligosaccharides from
alginates may well serve as agonists or antagonists for
these receptors.
To better understand the biochemical properties of
alginates and the underlying mechanism of TLR-medi-
ated innate immune activation, it is highly desirable to
access chemically defined alginate fragments. However,
due to the challenge posed by constructing 1,2-cis b-glycos-
idic linkage of D-mannuronic acid as well as accessing L-
guluronic acid building blocks, synthesis of alginate olig-
omers has rarely been studied. During the course of our
investigation toward the synthesis of b-D-mannuronic
acid glycosides, van den Bos et al.20 reported an
elegant methodology, albeit unexpectedly, for the stereo-
controlled direct synthesis of b-D-mannuronic acid
glycosides. They found that 1-thio mannuronic acid
derivatives can be activated by either diphenyl sulfoxide–
trifluoromethanesulfonic acid anhydride (Ph2SO–Tf2O)
or N-iodosuccinimide–trimethylsilyl trifluoromethane-
sulfonate (NIS–TMSOTf) to produce b-D-mannuronic
acid glycosides in high yield and with excellent
b-selectivity. Recently, we have reported the synthesis
of two b-(1!4)-di-D-mannuronic acid glycosides through
b-D-mannobiose as the precursor.21 Presented here are
the full experimental results for the synthesis of two neo-
glycolipids 1 and 2 containing b-(1!4)-di- and b-(1!4)-
tri-D-mannuronic acid residues, respectively.
deemed to be poor drug candidates.22 Here we have
designed both compounds 1 and 2 as glycolipids in
which the conjugation with lipids may enhance the
stability and bioavailability of small carbohydrates in
the biological system. Glycolipids are also suitable for
liposome formulation, a drug delivery system proven
to be efficient in reducing toxicity and side effects.23 As
the lipid anchor capable of incorporating multiple lipid
chains, we have chosen the multifunctional pentaerythri-
tol, which has recently been used as a core to build
multivalent ligands.24,25 Thus, starting from the readily
available pentaerythritol ketal derivative 3,26 the lipidat-
ed pentaerythritol derivative 6 is prepared as the agly-
cone (Scheme 1). Lipidation of 3 is effected by the
treatment with 1-bromohexadecane and sodium hydride
in DMF to give 4 in 59% yield. The removal of the
cyclohexylidene group to liberate diol 5 is incomplete
when 4 is treated under these conditions: (a) 10:1:0.2
EtOAc–MeOH–H2O in the presence of a catalytic
amount of p-toluenesulfonic acid (p-TsOH) under
reflux; and (b) 2:1:0.3 ExOAc–hexane–ethylene glycol
in the presence of p-TsOH as the catalyst at room tem-
perature. Gratifyingly, diol 5 is obtained in 95% yield
through a trans-ketal reaction with neopentyl glycol in
anhyd CH2Cl2 in the presence of camphorsulfonic acid
(CSA). Diol 5 is then converted to the mono-benzylated
lipid aglycone 6 in 70% yield by treatment with dibutyl-
tin oxide (Bu2SnO), followed by benzyl bromide and
tetrabutylammonium bromide.27
O
O
OR
OR
3 R = H
a
4 R = n-C16H33
b
RO
HO
O
C16H33
C16H33
5 R = H
c
O
6 R = Bn
2. Results and discussion
Scheme 1. Reagents and conditions: (a) n-C16H33Br, DMF, NaH,
50 ꢁC, 59%; (b) neopentyl glycol, CSA, CH2Cl2, 35 ꢁC, 95%; (c) (i)
Bu2SnO, benzene, 90 ꢁC; (ii) BnBr, Bu4NBr, 90 ꢁC, 70%.
Naked small carbohydrate molecules are rapidly cleared
away from the biological system and therefore are

R. Xu, Z.-H. Jiang / Carbohydrate Research 343 (2008) 7–17
9
The strategy we employ to make the b-(1!4)-di- and
b-(1!4)-tri-D-mannuronic acid glycolipids 1 and 2 is to
first synthesize their corresponding b-(1!4)-D-manno-
sides as precursors, and then to convert all the mannose
residues to mannuronic acid residues through an oxida-
tion step. Diastereoselective synthesis of b-D-manno-
pyranoside has been a long-standing challenge in
carbohydrate chemistry.28 The methodology recently
developed by the group of Crich and co-workers29,30
by employing 4,6-di-O-benzylidene-protected 1-thio
and 1-sulfoxide mannoside donors offers an elegant
solution for the introduction of b-D-mannoside linkage.
Thus, by using the 1-thio mannoside 729 as the glycosyl-
ation donor and 1-benzenesulfinyl piperidine (BSP)
and Tf2O in the presence of the hindered base, 2,6-di-
tert-butyl-4-methylpyridine (DTBMP) as the promoting
system, the b-linked (1!4)-di-D-mannoside 11 and
(1!4)-tri-D-mannoside 14 can be prepared in a straight-
forward manner (Scheme 2). Activation of donor 7 in
dichloromethane at ꢀ60 ꢁC followed by the addition
of the glycosylation acceptor 6 at ꢀ78 ꢁC, gives the
desired b-D-mannoside 8b in 85% yield. a-Glycoside 8a
is also formed in 8% yield. The b-glycosidic linkage in
8b is confirmed by the characteristic H-5 signal29 (d
3.30, ddd, 1H, J 10.0, 10.0, 4.5 Hz) of its 1H NMR spec-
ence of 4-dimethylaminopyridine (DMAP) affords 6-O-
benzoyl derivative 10 in 70% yield.
Using the same glycosylation protocol as described
for the synthesis of 8a/8b, monosaccharide 10 is glycosyl-
ated with 1-thio mannoside donor 7 to give disaccha-
ride 11 in 67%. The newly formed b-linkage in 11 is
confirmed by the characteristic H-5 signal29 (d 3.05,
ddd, 1H, J = 10.0, 10.0, 4.5 Hz,) of the sugar residue
bearing the 4,6-di-O-benzylidene group, as well as the
presence of three acetal carbons (two anomeric carbons
1
and one in benzylidene group) with JC,H coupling con-
1
stants less than 160 Hz (d 101.57, JC,H = 157.5, Hz;
102.14, 1JC,H = 153.7 Hz; 102.48, 1JC,H = 155.4 Hz).29,31
A minor product formed in about 10% yield shows char-
acteristic signals of the a-isomer of the disaccharide in
its 1H and 13C NMR spectra, but its structure is not con-
firmed since the analytically pure compound has not
been obtained. Following the same sequence of reaction
steps as described for the transformation of 8b to 10,
disaccharide 11 is first converted to diol 12 (90%) and
then to 6-O-monobenzoate 13 in 94% yield. Using the
same glycosylation protocol, disaccharide 13 is reacted
with donor 7 to give the desired trisaccharide 14 in
51% yield (with 10% unreacted 13 recovered). The newly
formed b-linkage in 14 is similarly confirmed by the
characteristic H-5 signal of the 4,6-di-O-benzylidene-
bearing mannose residue (d 2.97, ddd, J 9.5, 9.5,
1
trum and the JC,H coupling constant of the anomeric
1
carbon29,31 (d 101.55, JC,H = 154.6 Hz and 103.44,
1JC,H = 155.8 Hz, C-1 and the acetal carbon of the ben-
zylidene group). The a-linkage in 8a is evidenced by the
1JC,H coupling constant of the anomeric carbon (d 99.61,
5.0 Hz, 1H) and by the JC,H coupling constant value
1
1
of the anomeric carbons (d 101.51, JC,H = 153.1 Hz;
1
1
101.57, JC,H = 151.6 Hz; 102.11, JC,H = 152.3 Hz,
102.49, 1JC,H = 156.5 Hz). Again, a minor product (pos-
sibly the a-isomer) has been detected, but its structure is
not established. Repeated chromatographic purification
of the trisaccharide 14 partly accounts for its relatively
low yield.
1
1JC,H = 167.1 Hz and 101.66, JC,H = 157.5 Hz). Com-
pound 8b is then converted to diol 9 in 90% yield by
treating with neopentyl glycol in the presence of CSA
in anhydrous dichloromethane. Regioselective benzoyl-
ation of 9 with benzoyl chloride and pyridine in the pres-
Ph
OBn
O
Ph
OBn
O
O
O
OC16H33
OC16H33
Ph
OBn
O
O
a
O
O
O
OC16H33
OC16H33
OBn
BnO
+
BnO
+
6
O
BnO
O
SPh
OBn
7
8α
8β
b
c
OBn
O
OC16H33
RO
HO
BnO
Ph
OBn
O
OBn
O
OC16H33
OC16H33
OBn
a
O
BzO
O
O
BnO
O
OC16H33
O
BnO
7
OBn
11
9 R = H
10 R = Bz
b
OBn
OBn
Ph
OBn
O
OBn
OBn
O
OC16H33
OC16H33
OBn
OC16H33
OC16H33
OBn
O
RO
HO
BnO
BzO
O
BzO
BzO
O
BnO
O
O
O
O
O
O
O
BnO
BnO
BnO
a
14
12 R = H
13 R = Bz
c
7
Scheme 2. Reagents and conditions: (a) BSP, DTBMP, Tf2O, CH2Cl2, ꢀ60 ꢁC then ꢀ78 ꢁC to 0 ꢁC, 8% for 8a and 85% for 8b; 67% for 11; and 51%
for 14; (b) neopentyl glycol, CSA, CH2Cl2, 35 ꢁC, 90% for both 9 and 12; (c) BzCl, pyridine, DMAP, CH2Cl2, ꢀ25 ꢁC to 0 ꢁC, 70% for 10 and 94%
for 13.

10
R. Xu, Z.-H. Jiang / Carbohydrate Research 343 (2008) 7–17
12
14
a
e
b
OBn
O
OBn
O
OC
H
OC
H
16 33
OBn
O
OBn
O
OBn
O
16 33
HO
HO
BnO
HO
HO
HO
BnO
HO
HO
O
O
O
O
OC H
16 33
O
OC H
16 33
BnO
BnO
BnO
18
15
OBn
OBn
b
O
O
O
O
O
OC
H
OBn
O
OBn
O
16 33
OC
H
OBn
O
OBn
O
OBn
O
RO
HO
BnO
RO
O
BnO
16 33
RO
HO
BnO
RO
O
BnO
RO
O
BnO
O
OC H
16 33
O
OC H
16 33
OBn
OBn
d
19 R = H
20 R = Bn
d
16 R = H
17 R = Bn
c
c
1
2
Scheme 3. Reagents and conditions: (a) NaOMe, 1:1 MeOH–CH2Cl2, rt, 100%; (b) BAIB, TEMPO, 2:1 CH2Cl2–H2O, rt, 95% for 16 and 70% for 19;
(c) BnBr, KF, DMF, rt, 78% for 17 and 80% for 20; (d). H2, Pd/C, 4:1 THF–H2O, rt, 90% for both 1 and 2; (e) (i) neopentyl glycol, CSA, CH2Cl2,
35 ꢁC; (ii) NaOMe, 1:1 MeOH–CH2Cl2, rt, two steps 83%.
With the desired b-(1!4)-D-mannobiose and b-
(1!4)-D-mannotriose on hand, the next step is to
convert the mannose residues to the mannuronic acid
residues. Thus, compounds 12 and 14 are transformed
to their 6-hydroxyl derivatives 15 and 18, respectively,
through standard protecting group manipulation
(Scheme 3). The primary hydroxyl groups in 15 and 18
are then regioselectively oxidized to carboxylic acid
functional groups by the combination of 2,2,6,6-tetra-
methylpiperidinyloxy free radical (TEMPO) and
[bis(acetoxy)iodo]benzene (BAIB),32 providing the
corresponding dicarboxylic acid 16 and tricarboxylic
acid 19 in 95% and 70% yield, respectively. For struc-
tural confirmation, both acids 16 and 19 are converted
into their benzyl esters 17 and 20 by the treatment with
benzyl bromide and potassium fluoride in DMF in 78%
and 80% yield, respectively. The TEMPO/BAIB oxida-
tion system provides a good yield in the simultaneous
oxidation of multiple primary hydroxyl groups to car-
boxylic acid functions in the presence of secondary
hydroxyl groups. Hydrogenolytic debenzylation of 17
and 20 in the presence of palladium-on-charcoal under
a hydrogen atmosphere gives the target glycolipids 1
and 2 in 90% yield. The structures of 1 and 2 have been
confirmed by mass spectroscopy data.
In conclusion, an efficient synthesis of b-(1!4)-di- and
b-(1!4)-tri-D-mannuronic acid neoglycolipids 1 and 2
has been reported. The strategy incorporates the dia-
stereoselective synthesis of b-(1!4)-D-mannobiose and
b-(1!4)-D-mannotriose using a 4,6-di-O-benzylidene-
protected 1-thio D-mannoside as the glycosyl donor, foll-
owed by simultaneous regioselective oxidation of all the
mannose residues to the mannuronic acid residues by the
TEMPO/BAIB oxidation system. The method described
here shall be applicable for synthesizing glycoconjugates
containing larger b-(1!4)-oligo-D-mannuronic acid
fragments. Ongoing research is devoted to the synthesis
of other types of alginate oligomers and the biological
investigation of these neoglycoconjugates in respect to
their immune-stimulating and/or -modulating properties
mediated with TLR2/4.
3. Experimental
3.1. General methods
All air- and moisture-sensitive reactions have been
performed under nitrogen atmosphere. Anhydrous
N,N-dimethylformamide (DMF) was purchased from
Aldrich Chemical Co., and other dry solvents were pre-
pared in accordance with standard procedures. ACS
grade solvents were purchased from Fisher Scientific
Co. and used for chromatography without distillation.
TLC plates (Silica Gel 60F254, thickness 0.25 mm) and
Silica Gel 60 (40–63 lm) for flash column chromatogra-
phy were purchased from Silicycle, Inc., Canada. 1H and
13C NMR spectra were recorded on a Varian Unity Ino-
va 500-MHz spectrometer, and tetramethylsilane (TMS,
d 0.00 ppm) and chloroform (d 77.23 ppm) were used as
internal standards for 1H and 13C chemical shifts,
respectively. Multiplicity of proton signals are indicated
as follows: s (singlet), d (doublet), t (triplet), q (quartet),
m (multiplet), and br (broad). Sugar units are designated
as I, II, and III (as superscripts), beginning at the reduc-
ing end of the molecule, according to the Whelan system
(Rule 2-Carb-37.2).33 Optical rotations were measured
on a Perkin–Elmer 241 polarimeter at room temperature
(20–22 ꢁC). Elemental analysis was carried out on a
CEC (SCP) 240-XA Analyzer at Lakehead University
Instrumentation Laboratory (LUIL). Low-resolution
MALDI mass spectra were obtained from a Biflex-IV

R. Xu, Z.-H. Jiang / Carbohydrate Research 343 (2008) 7–17
11
MALDI linear/reflector instrument at the University of
Manitoba, Canada, and high-resolution electrospray-
ionization (HRESI) mass spectra were measured on
the Applied Biosystems Mariner Biospectrometry
Workstation at the University of Alberta, Canada.
reflux at 90 ꢁC for 16 h with removal of water by a
Dean–Stark trap. Then Bu4NBr (3.22 g, 10.0 mmol)
and PhCH2Br (2.38 mL, 20.0 mmol) were added, and
the mixture was stirred under reflux for 5 h. The solvent
was then removed in vacuum, and the residue was redis-
solved in EtOAc (150 mL) and washed with satd aq
NaHCO3. The organic layer was dried with Na2SO4
and concentrated in vacuum. The residue was purified
by flash chromatography (20:1 and then 12:1 hexane–
EtOAc) to provide 6 (4.72 g, 70%) as a syrup. Rf 0.36
3.2. 3,3-Dihexadecyloxymethyl-1,5-dioxaspiro[5,5]
undecane (4)
To a completely dissolved solution of 1-bromohexa-
decane (26.20 mL, 85.44 mmol) in anhyd DMF
(60 mL) was carefully added sodium hydride (2.60 g,
102.65 mmol), followed by dropwise addition of 3
(9.25 g, 42.77 mmol, dissolved in 20 mL of DMF). The
mixture was heated at 50 ꢁC and stirred for 16 h. The
mixture was then poured into ice-water (400 mL),
extracted with EtOAc (300 mL · 3), and the combined
organic layer was dried over Na2SO4 and concentrated
in vacuum. The residue was purified by flash chromato-
graphy (30:1 and then 20:1 hexane–EtOAc) to provide 4
(14.31 g, 59%) as a colored syrup. Rf 0.41 (20:1 hexane–
1
(10:1 hexane–EtOAc); H NMR (500 MHz, CDCl3): d
0.88 (t, 6H, J 6.5 Hz, 2CH3), 1.25 (m, 52H, 26CH2),
1.52 (m, 5H, 2CH2, OH), 3.38 (t, 4H, J 6.5 Hz,
2CH2O), 3.47 (s, 4H, 2CH2O), 3.52 (s, 2H, CH2OH),
3.73 (s, 2H, CH2O), 4.50 (s, 2H, CH2Ph), 7.27–7.35
(m, 5H, Ar-H). 13C NMR (125 MHz, CDCl3): d 14.38,
22.95, 26.42, 29.62, 29.74, 29.83, 29.89, 29.91, 29.93,
29.96, 32.19, 45.10, 66.84, 71.01, 71.88, 72.05, 73.71,
126.60, 127.71, 128.54, 138.76. Anal. Calcd for
C44H82O4 (675.13): C, 78.28; H, 12.24. Found: C,
77.92; H, 12.14.
1
EtOAc); H NMR (500 MHz, CDCl3): d 0.90 (t, 6H, J
6.5 Hz, 2CH3), 1.20 (m, 56H, 26CH2), 1.30 (m, 2H,
CH2), 1.40 (m, 8H, 4CH2), 3.30 (m, 8H, 4CH2O), 3.60
(s, 4H, 2CH2O). 13C NMR (125 MHz, CDCl3): d
14.40, 22.83, 22.96, 25.98, 26.43, 29.64, 29.77, 29.82,
29.91, 29.93, 29.98, 32.19, 32.87, 39.23, 62.30, 70.61,
71.88, 98.21. Anal. Calcd for C43H84O4Æ0.5H2O
(665.10): C, 76.60; H, 12.70. Found: C, 76.97; H, 12.33.
3.5. 3-Benzyloxy-2,2-dihexadecyloxymethylpropyl 2,3-
di-O-benzyl-4,6-di-O-benzylidene-a-D-mannopyranoside
(8a) and 3-benzyloxy-2,2-dihexadecyloxymethylpropyl
2,3-di-O-benzyl-4,6-di-O-benzylidene-b-D-mannopyrano-
side (8b)
To a solution of 729 (1.63 g, 3.01 mmol) in anhyd
CH2Cl2 (50 mL) were added 1-benzenesulfinylpiperidine
(BSP, 0.69 g, 3.3 mmol), 2,6-di-tert-butyl-4-methylpyr-
idine (DTBMP, 1.26 g, 6.12 mmol), and molecular
3.3. 2,2-Dihexadecyloxymethyl-1,3-propanediol (5)
˚
To a solution of 4 (14.31 g, 21.52 mmol) and neopentyl
glycol (9.0 g, 86.1 mmol) in anhyd CH2Cl2 (200 mL) was
added camphorsulfonic acid (CSA, 1.0 g, 4.3 mmol).
The mixture was stirred at 35 ꢁC under an N2 atmo-
sphere for 16 h. The mixture was then washed with satd
aq NaHCO3 (100 mL), and the organic extract was
dried over Na2SO4 and concentrated. The residue was
purified by flash chromatography (2:1 hexane–EtOAc)
to give 5 (12.1 g, 95%) as a white powder. Rf 0.45 (2:1
sieves (4 A, 2.0 g). The mixture was stirred at room tem-
perature under N2 atmosphere for 1 h. Trifluorometh-
anesulfonic acid anhydride (Tf2O, 0.56 mL, 3.30 mmol)
was added dropwise at ꢀ60 ꢁC, and the mixture was stir-
red for 5 min. The mixture was cooled to ꢀ78 ꢁC, and a
solution of 6 (1.35 g, 2.00 mmol, dissolved in 10 mL of
dry CH2Cl2) was added dropwise. The mixture was kept
stirring at ꢀ78 ꢁC for 2 h and then warmed up to room
temperature before quenched with satd aq NaHCO3
(30 mL). The organic layer was separated, and the aque-
ous layer was extracted with CH2Cl2 (2 · 30 mL). The
combined organic layer was dried over Na2SO4, and
concentrated, and the residue was purified by flash chro-
matography (20:1 and then 10:1 hexane–EtOAc) to pro-
vide compound 8b (2.10 g, 85%) as a syrup. The minor
isomer was further purified by flash chromatography
(12:1 hexane–EtOAc) to give analytical pure compound
8a (190 mg, 8%). For 8a: Rf 0.39 (8:1 hexane–EtOAc);
1
hexane–EtOAc); H NMR (500 MHz, CDCl3): d 0.88
(t, 6H, 2CH3), 1.26 (m, 52H, 26CH2), 1.55 (m, 4H,
2CH2), 2.80 (t, 2H, J 6.0 Hz, 2OH), 3.42 (t, 4H, J
6.0 Hz, 2CH2O), 3.51 (s, 4H, 2CH2O), 3.64 (d, 4H, J
6.0 Hz, 2CH2OH). 13C NMR (125 MHz, CDCl3): d
14.14, 22.71, 29.38, 29.45, 29.52, 29.61, 29.64, 29.68,
29.70, 29.72, 31.94, 31.98, 44.50, 65.48, 72.06, 73.23.
Anal. Calcd for C37H76O4 (585.10): C, 75.97; H, 13.09.
Found: C, 75.85; H, 12.87.
22
½aꢁD +15.8 (c 0.26, CHCl3); 1H NMR (500 MHz,
3.4. 3-Benzyloxy-2,2-dihexadecyloxymethyl-1-propanol
(6)
CDCl3): d 0.88 (t, 6H, J 6.5 Hz, 2CH3), 1.26 (m, 52H,
26CH2), 1.51 (m, 4H, 2CH2), 3.28–3.35 (m, 9H), 3.39
(s, 2H), 3.73 (m, 2H), 3.79 (ddd, 1H, J 10.0, 10.0,
4.5 Hz, H-5), 3.85 (dd, 1H, J 9.5, 9.5 Hz), 3.88 (dd,
1H, J 9.5, 3.5 Hz, H-2), 4.21–4.25 (m, 2H), 4.43 (d,
A solution of 5 (5.85 g, 10.0 mmol) and dibutyltin oxide
(2.49 g, 10.0 mmol) in benzene (100 mL) was kept at

12
R. Xu, Z.-H. Jiang / Carbohydrate Research 343 (2008) 7–17
1H, J 12.0 Hz, PhCHH), 4.47 (d, 1H, J 12.0 Hz,
PhCHH), 4.63 (d, 1H, J 12.0 Hz, PhCHH), 4.72 (d,
1H, J 12.0 Hz, PhCHH), 4.76 (d, 1H, J 1.5 Hz, H-1),
4.79 (d, 1H, J 12.0 Hz, PhCHH), 4.83 (d, 1H, J
12.0 Hz, PhCHH), 5.63 (s, 1H, CHPh), 7.23–7.50 (m,
20H, Ar-H). 13C NMR (125 MHz, CDCl3): d 14.39,
22.96, 26.48, 29.63, 29.80, 29.90, 29.93, 29.98, 32.18,
45.25, 64.32, 66.41, 66.87, 69.12, 69.47, 71.86, 73.45,
73.53, 73.57, 76.56, 76.90, 79.44, 99.61 (1JC,H
167.1 Hz), 101.66 (1JC,H 157.5 Hz), 126.35, 127.55,
127.59, 127.75, 127.92, 127.96, 128.16, 128.34, 128.49,
128.59, 128.96, 138.10, 138.44, 138.90, 139.05. HRE-
SIMS: [M+Na]+ calcd for C71H108O9Na, 1127.7885;
found (positive-ion mode): 1127.7884. For 8b: Rf 0.35
1H, J 12.0 Hz, PhCHH), 4.45 (d, 1H, J 12.0 Hz,
PhCHH), 4.52 (d, 1H, J 12.0 Hz, PhCHH), 4.69 (d,
1H, J 12.0 Hz, PhCHH), 4.91 (d, 1H, J 12.0 Hz,
PhCHH), 7.23–7.39 (m, 15H, Ar-H). Anal. Calcd for
C64H104O9 (1017.52): C, 75.55; H, 10.30. Found: C,
75.07; H, 10.13.
3.7. 3-Benzyloxy-2,2-dihexadecyloxymethylpropyl 6-O-
benzoyl-2,3-di-O-benzyl-b-D-mannopyranoside (10)
A solution of 9 (480 mg, 0.48 mmol) and 4-(dimethyl-
amino)pyridine (DMAP, 7.6 mg, 0.048 mmol) in dry
pyridine (5 mL) was cooled to ꢀ25 ꢁC and benzoyl chlo-
ride (0.061 mL, 0.53 mmol, dissolved in 5 mL of anhyd
CH2Cl2) was added dropwise. The reaction mixture
was kept to stir for 2 h at ꢀ25 ꢁC and then warmed up
to room temperature and stirred at room temperature
for 16 h. The mixture was then diluted with EtOAc
(100 mL) and washed successively with 4 M HCl
(30 mL), ice-water (30 mL), and satd aq NaHCO3
(30 mL). The organic layer was dried over Na2SO4
and concentrated in vacuum. The residue was purified
by flash chromatography (10:1 and then 4:1 hexane–
EtOAc) to give compound 10 (370 mg, 70%) as a syrup.
22
(8:1 hexane–EtOAc); ½aꢁD ꢀ15.7 (c 0.66, CHCl3); 1H
NMR (500 MHz, CDCl3): d 0.88 (t, 6H, J 6.5 Hz,
2CH3), 1.25 (m, 52H, 26CH2), 1.52 (m, 4H, 2CH2),
3.30 (ddd, 1H, J 10.0, 10.0, 4.5 Hz, H-5), 3.32–3.38
(m, 4H, 2CH2O), 3.39–3.54 (m, 8H, 4CH2O), 3.83 (d,
1H, J 3.0 Hz, H-2), 3.92 (dd, 1H, J 10.0, 10.0 Hz),
3.99 (d, 1H, J 10.0 Hz), 4.30 (dd, 1H, J 10.0, 4.5 Hz),
4.37 (s, 1H, H-1), 4.41 (d, 1H, J 12.0 Hz, PhCHH),
4.50 (d, 1H, J 12.0 Hz, PhCHH), 4.57 (d, 1H, J
12.0 Hz, PhCHH), 4.68 (d, 1H, J 12.0 Hz, PhCHH),
4.79 (d, 1H, J 12.0 Hz, PhCHH), 4.95 (d, 1H, J
12.0 Hz, PhCHH), 5.60 (s, 1H, CHPh), 7.21–7.50 (m,
20H, Ar-H). 13C NMR (125 MHz, CDCl3): d 14.36,
22.93, 26.49, 29.61, 29.77, 29.87, 29.90, 29.92, 29.95,
32.18, 45.46, 67.76, 68.83, 69.81, 69.88, 69.90, 70.65,
71.80, 71.81, 72.62, 73.50, 74.81, 76.04, 78.28, 78.87,
101.55 (1JC,H 154.6 Hz), 103.44 (1JC,H 155.8 Hz),
126.26, 127.55, 127.57, 127.71, 127.72, 128.35, 128.43,
128.49, 128.75, 129.00, 137.86, 138.61, 138.72, 139.07.
Anal. Calcd for C71H108O9 (1105.63): C, 77.13; H,
9.85. Found: C, 76.93; H, 9.81.
22
Rf 0.63 (2:1 hexane–EtOAc); ½aꢁD ꢀ35.0 (c 0.38, CHCl3);
1H NMR (500 MHz, CDCl3): d 0.88 (t, 6H, J 6.5 Hz,
2CH3), 1.26 (m, 52H, 26CH2), 1.49 (m, 4H, 2CH2),
2.90 (br s, 1H, OH), 3.30–3.56 (m, 13H), 3.85 (d, 1H,
J 3.0 Hz, H-2), 4.01–4.04 (m, 2H), 4.39 (d, 1H, J
12.0 Hz, PhCHH), 4.46 (d, 1H, J 12.0 Hz, PhCHH),
4.49 (s, 1H, H-1), 4.52 (dd, 1H, J 12.0, 6.0 Hz, H-6),
4.59 (d, 1H, J 12.0 Hz, PhCHH), 4.61 (d, 1H, J
12.0 Hz, PhCHH), 4.66 (dd, 1H, J 12.0, 3.5 Hz, H-6),
4.68 (d, 1H, J 12.0 Hz, PhCHH), 4.92 (d, 1H, J
12.0 Hz, PhCHH), 7.20–7.48 (m, 18H, Ar-H), 8.05 (d,
2H, J 8.0 Hz, Ar-H). 13C NMR (125 MHz, CDCl3): d
14.30, 22.85, 26.38, 29.52, 29.68, 29.77, 29.82, 29.85,
29.87, 32.09, 45.35, 64.35, 66.95, 69.77, 69.84, 69.86,
70.18, 71.35, 71.69, 71.71, 73.39, 73.53, 73.94, 74.45,
81.56, 102.86 (1JC,H 154.6 Hz, C-1), 126.99, 127.40,
127.47, 127.85, 127.96, 128.19, 128.27, 128.32, 128.34,
128.58, 129.96, 132.91, 137.89, 138.93, 138.99, 166.82
(CO). Anal. Calcd for C71H108O10 (1121.63): C, 76.03;
H, 9.71. Found: C, 75.85; H, 9.49.
3.6. 3-Benzyloxy-2,2-dihexadecyloxymethylpropyl 2,3-
di-O-benzyl-b-D-mannopyranoside (9)
To a solution of 8b (2.10 g, 1.92 mmol) and neopentyl
glycol (0.80 g, 7.68 mmol) in anhyd CH2Cl2 (20 mL)
was added camphorsulfonic acid (0.30 g, 1.15 mmol).
The mixture was stirred at 35 ꢁC under an N2 atmos-
phere for 16 h, and the reaction was quenched with satd
aq NaHCO3 (10 mL). The organic layer was dried over
Na2SO4, and concentrated in vacuum, and the residue
was purified by flash chromatography (5:1 and then
2:1 hexane–EtOAc) to give 9 (1.74 g, 90%) as a syrup.
3.8. 3-Benzyloxy-2,2-dihexadecyloxymethylpropyl 2,3-
di-O-benzyl-4,6-di-O-benzylidene-b-D-mannopyranosyl-
(1!4)-6-O-benzoyl-2,3-di-O-benzyl-b-D-mannopyran-
oside (11)
22
Rf 0.36 (5:4 hexane–EtOAc); ½aꢁD ꢀ40.4 (c 0.37, CHCl3);
1H NMR (500 MHz, CDCl3): d 0.88 (t, 6H, J 6.5 Hz,
2CH3), 1.25 (m, 52H, 26CH2), 1.52 (m, 4H, 2CH2),
2.34 (dd, 1H, J 6.0, 6.0 Hz, OH), 3.25 (dd, 1H, J 9.5,
3.0 Hz, H-3), 3.29 (m, 1H, H-5), 3.34–3.54 (m, 11H),
3.80 (dd, 1H, J 9.5, 4.5 Hz), 3.84 (d, 1H, J 3.0 Hz,
H-2), 3.90 (m, 2H), 3.99 (d, 1H, J 9.0 Hz), 4.24 (d,
1H, J 12.0 Hz, PhCHH), 4.39 (s, 1H, H-1), 4.44 (d,
To a solution of 729 (245 mg, 0.41 mmol) in anhyd
CH2Cl2 (10 mL) were added 1-benzenesulfinylpiperidine
(BSP, 103 mg, 0.45 mmol), 2,6-di-tert-butyl-4-methyl-
pyridine (DTBMP, 187 mg, 0.83 mmol), and molecular
˚
sieves (4 A, 1.0 g). The mixture was stirred at room tem-
perature under an N2 atmosphere for 30 min and then

R. Xu, Z.-H. Jiang / Carbohydrate Research 343 (2008) 7–17
13
cooled to ꢀ60 ꢁC followed by the addition of trifluoro-
methanesulfonic acid anhydride (0.08 mL, 0.45 mmol).
After stirring at ꢀ60 ꢁC for 5 min, the mixture was
cooled to ꢀ78 ꢁC, and a solution of 10 (330 mg,
0.27 mmol, dissolved in 3 mL of CH2Cl2) was added
dropwise. The mixture was kept to stir at ꢀ78 ꢁC for
an additional 2 h and then warmed up to room temper-
ature. The reaction was quenched by adding satd aq
NaHCO3 (10 mL). The organic layer was separated,
and the aqueous layer was extracted with CH2Cl2
(10 mL · 2). The combined organic layer was dried over
Na2SO4 and concentrated in vacuum and the residue
was purified by flash chromatography (10:1 and then
5:1 hexane–EtOAc,) to provide compound 11 (291 mg,
Usual workup and flash chromatographic purification
(2:1 and then 5:4 hexane–EtOAc) provided 12 (2.64 g,
22
96%) as a syrup. Rf 0.38 (5:3 hexane–EtOAc); ½aꢁD
1
ꢀ39.0 (c 0.34, CHCl3); H NMR (500 MHz, CDCl3): d
0.88 (t, 6H, J 6.5 Hz, 2CH3), 1.25 (m, 52H, 26CH2),
1.48 (m, 4H, 2CH2), 3.07 (m, 1H, H-5), 3.20 (dd, 1H,
J 9.5, 3.5 Hz, H-3), 3.25–3.35 (m, 4H, 2OCH2), 3.38–
3.42 (m, 4H, 2OCH2), 3.44–3.56 (m, 6H), 3.62–3.66
(m, 2H), 3.72 (dd, 1H, J 12.5, 3.5 Hz), 3.86 (d, 1H, J
3.0 Hz, H-2), 3.88 (dd, 1H, J 9.5, 9.5 Hz), 3.92 (d, 1H,
J 3.0 Hz, H-2), 4.00 (d, 1H, J 9.5 Hz), 4.23 (dd, 1H, J
9.5, 9.5 Hz), 4.31 (d, 1H, J 12.0 Hz, PhCHH), 4.40 (d,
1H, J 12.0 Hz, PhCHH), 4.42 (s, 1H, H-1), 4.47 (d,
1H, J 12.0 Hz, PhCHH), 4.48 (d, 1H, J 12.0 Hz,
PhCHH), 4.50 (m, 1H, H-6I), 4.54 (s, 1H, H-1), 4.55
(d, 1H, J 12.0 Hz, PhCHH), 4.65 (dd, J 12.0, 3.0 Hz,
H-6I), 4.68 (d, 1H, J 12.0 Hz, PhCHH), 4.72 (d, 1H, J
12.0 Hz, PhCHH), 4.76 (d, 1H, J 12.0 Hz, PhCHH),
4.83 (d, 1H, J 12.0 Hz, PhCHH), 4.92 (d, 1H, J
12.0 Hz, PhCHH), 7.22–7.55 (m, 27H, Ar-H), 7.54 (t,
1H, J 7.5 Hz, Ar-H), 8.05 (d, 2H, J 8.5 Hz, Ar-H). 13C
NMR (125 MHz, CDCl3): d 14.36, 22.93, 26.43, 29.59,
29.75, 29.85, 29.88, 29.91, 29.93, 32.15, 45.44, 61.42,
62.65, 64.17, 67.07, 69.75, 69.80, 70.14, 71.37, 71.74,
71.76, 72.35, 73.39, 73.58, 74.10, 74.44, 74.60, 75.74,
75.18, 75.94, 79.55, 81.94, 101.41 (1JC,H 155.7), 102.57
(1JC,H 157.2 Hz), 127.49, 127.52, 127.58, 127.66,
127.76, 127.85, 128.00, 128.16, 128.29, 128.36, 128.41,
128.42, 128.56, 128.71, 128.75, 129.98, 130.06, 133.42,
137.80, 138.48, 138.74, 138.99, 139.11, 166.66 (CO).
HRESIMS: [M+Na]+ calcd for C91H130O15Na,
1485.9301; found (positive-ion mode): 1485.9301. Anal.
Calcd for C91H130O15: C, 74.66; H, 8.95. Found: C,
74.46; H, 8.74.
22
67%) as a syrup. Rf 0.64 (5:2 hexane–EtOAc); ½aꢁD
1
ꢀ26.8 (c 0.40, CHCl3); H NMR (500 MHz, CDCl3): d
0.88 (t, 6H, J 6.5 Hz, 2CH3), 1.25 (m, 52H, 26CH2),
1.46 (m, 4H, 2CH2), 3.05 (ddd, 1H, J 9.5, 9.5, 4.5 Hz,
H-5II), 3.26–3.32 (m, 4H, 2OCH2), 3.36–3.43 (m, 4H,
2CH2O), 3.43–3.52 (m, 6H), 3.54 (dd, 1H, J 9.5,
3.0 Hz, H-3), 3.59 (dd, 1H, J 9.5, 3.0 Hz, H-3), 3.69
(dd, 1H, J 10.0, 10.0 Hz), 3.83 (d, 1H, J 3.0 Hz, H-2),
3.93 (d, 1H, J 3.0 Hz, H-2), 3.99 (dd, 1H, J 10.0,
4.5 Hz, H-6II), 4.01 (d, 1H, J 10.0 Hz), 4.10 (dd, 1H, J
9.0, 9.0 Hz, H-4), 4.16 (dd, 1H, J 9.0, 9.0 Hz, H-4),
4.38 (d, 1H, J 12.0 Hz, PhCHH), 4.42 (s, 1H, H-1),
4.43 (d, 1H, J 12.0 Hz, PhCHH), 4.50 (m, 2H, 2H-6I),
4.55 (d, 1H, J 12.0 Hz, PhCHH), 4.57 (d, 1H, J
12.0 Hz, PhCHH), 4.60 (s, 1H, H-1), 4.66 (d, 1H, J
12.0 Hz, PhCHH), 4.67 (d, 1H, J 12.0 Hz, PhCHH),
4.69 (d, 1H, J 12.0 Hz, PhCHH), 4.83 (d, 1H, J
12.0 Hz, PhCHH), 4.88 (d, 1H, J 12.0 Hz, PhCHH),
4.89 (d, 1H, J 12.0 Hz, PhCHH), 5.51 (s, 1H, PhCH),
7.23–7.52 (m, 32H, Ar-H), 7.53 (t, 1H, J 7.5 Hz,
Ar-H), 8.03 (d, 2H, J 8.0 Hz, Ar-H). 13C NMR
(125 MHz, CDCl3): d 14.40, 22.95, 26.45, 29.63, 29.79,
29.89, 29.92, 29.95, 29.97, 32.18, 45.43, 64.09, 67.63,
68.74, 69.86, 69.89, 70.23, 71.81, 71.83, 72.10, 72.56,
73.47, 73.54, 73.98, 74.78, 75.39, 76.16, 77.32, 77.47,
78.55, 78.67, 80.03, 101.57 (1JC,H 157.5, Hz), 102.14
(1JC,H 153.7 Hz), 102.48 (1JC,H 155.4 Hz), 126.32,
127.40, 127.49, 127.52, 127.68, 127.72, 127.75, 128.02,
128.31, 128.37, 128.43, 128.54, 128.55, 128.63, 129.05,
130.01, 130.17, 133.24, 137.79, 138.54, 138.77, 138.82,
139.10, 139.12, 166.55 (CO). Anal. Calcd for
C98H134O15ÆH2O (1552.13): C, 74.97; H, 8.73. Found:
C, 74.98; H, 9.07.
3.10. 3-Benzyloxy-2,2-dihexadecyloxymethylpropyl 6-O-
benzoyl-2,3-di-O-benzyl-b-D-mannopyranosyl-(1!4)-6-
O-benzoyl-2,3-di-O-benzyl-b-D-mannopyranoside (13)
In a similar way as described for the preparation of 10,
compound 12 (310 mg, 0.21 mmol) was treated with 4-
(dimethylamino)pyridine (DMAP, 13.8 mg, 0.11 mmol)
and benzoyl chloride (0.08 mL, 0.69 mmol) in dry pyr-
idine (5 mL) at ꢀ25 ꢁC. Usual workup and flash
chromatographic purification (8:1 and then 5:1 hex-
ane–EtOAc) afforded compound 13 (310 mg, 94%) as a
22
syrup. Rf 0.72 (5:3 hexane–EtOAc); ½aꢁD ꢀ58.7 (c 0.29,
1
CHCl3); H NMR (500 MHz, CDCl3): d 0.86 (t, 6H, J
3.9. 3-Benzyloxy-2,2-dihexadecyloxymethylpropyl 2,3-di-
O-benzyl-b-D-mannopyranosyl-(1!4)-6-O-benzoyl-2,3-
di-O-benzyl-b-D-mannopyranoside (12)
6.5 Hz, 2CH3), 1.23–1.30 (m, 52H, 26CH2), 1.46 (m,
4H, 2CH2), 3.20–3.23 (m, 1H), 3.24–3.46 (m, 12H),
3.59 (dd, 1H, J 9.5, 4.0 Hz, H-3), 3.65 (m, 1H), 3.80
(d, 1H, J 4.0 Hz, H-2), 3.92 (d, 1H, J 4.0 Hz, H-2),
4.00 (m, 2H), 4.24 (dd, 1H, J 9.5, 9.5 Hz), 4.33 (d, 1H,
J 12.0 Hz, PhCHH), 4.36 (s, 1H, H-1), 4.37 (d, 1H, J
12.0 Hz, PhCHH), 4.44 (m, 3H, 3H-6), 4.51 (d, 1H, J
12.0 Hz, PhCHH), 4.58 (d, 1H, J 12.0 Hz, PhCHH),
In a similar way as described for the preparation of 9,
compound 11 (2.92 g, 1.84 mmol) was treated with neo-
pentyl glycol (783 mg, 7.54 mmol) in dry CH2Cl2
(20 mL) at 35 ꢁC under an N2 atmosphere for 16 h.

14
R. Xu, Z.-H. Jiang / Carbohydrate Research 343 (2008) 7–17
4.59 (s, 1H, H-1), 4.60 (m, 1H, H-6), 4.61 (d, 1H, J
12.0 Hz, PhCHH), 4.64 (d, 1H, J 12.0 Hz, PhCHH),
4.68 (d, 1H, J 12.0 Hz, PhCHH), 4.75 (d, 1H, J
12.0 Hz, PhCHH), 4.84 (d, 1H, J 12.0 Hz, PhCHH),
4.86 (d, 1H, J 12.0 Hz, PhCHH), 7.19–7.39 (m, 29H,
Ar-H), 7.44 (t, 1H, J 7.5 Hz, Ar-H), 7.51 (t, 1H, J
7.5 Hz, Ar-H), 7.95 (d, 2H, J 7.5 Hz, Ar-H) 8.04 (d,
2H, J 7.5 Hz, Ar-H). 13C NMR (125 MHz, CDCl3): d
14.35, 22.92, 26.41, 29.59, 29.75, 29.85, 29.88, 29.91,
29.93, 32.15, 45.41, 61.64, 63.99, 64.22, 66.38, 69.84,
69.87, 70.14, 71.45, 71.79, 71.81, 72.01, 73.45, 73.57,
73.89, 74.49, 74.54, 74.65, 74.79, 75.64, 79.27, 81.67,
101.54 (1JC,H 156.4 Hz, C-1), 102.40 (1JC,H 158.2 Hz,
C-1), 127.47, 127.48, 127.62, 127.75, 127.94, 128.05,
128.07, 128.17, 128.29, 128.31, 128.40, 128.46, 128.52,
128.61, 128.75, 133.12, 133.24, 137.75, 138.60, 138.99,
139.05, 139.10, 166.57 (CO), 166.92 (CO). Anal. Calcd
for C98H134O16 (1568.13): C, 75.06; H, 8.64. Found: C,
74.94; H, 8.86.
1H, J 12.0 Hz, PhCHH), 5.48 (s, 1H, CHPh), 7.04–
7.43 (m, 39 H, Ar-H), 7.47 (t, 1H, J 7.5 Hz, Ar-H),
7.51 (t, 1H, J 7.5 Hz, Ar-H), 7.94 (d, 2H, J 7.5 Hz,
Ar-H), 8.04 (d, 2H, J 7.5 Hz, Ar-H). 13C NMR
(125 MHz, CDCl3): d 14.38, 22.93, 26.42, 29.62, 29.78,
29.88, 29.91, 29.94, 29.96, 32.15, 45.41, 63.68, 64.13,
67.57, 68.66, 69.85, 70.18, 71.80, 71.81, 72.10, 72.15,
72.46, 73.45, 73.48, 73.55, 73.55, 73.95, 74.57, 74.81,
75.36, 75.53, 75.89, 75.99, 77.20, 78.44, 78.56, 80.15,
101.51 (1JC,H 153.1 Hz), 101.57 (1JC,H 151.6 Hz),
102.11 (1JC,H 152.3 Hz), 102.49 (1JC,H 156.5 Hz),
126.3, 127.42, 127.44, 127.47, 127.50, 127.66, 127.68,
127.71, 127.85, 128.06, 128.26, 128.30, 128.33, 128.41,
128.48, 128.51, 128.63, 129.89, 130.00, 133.26, 133.29,
137.81, 138.56, 138.65, 138.78, 138.79, 139.11, 139.12,
139.19, 166.43 (CO), 166.52 (CO). HRESIMS:
[M+Na]+ calcd for C125H160O21Na, 2020.1344; found
(positive-ion mode): 2020.1345. Anal. Calcd for
C
125H160O21 (1998.63): C, 75.12; H, 8.07. Found: C,
75.38; H, 8.22.
3.11. 3-Benzyloxy-2,2-dihexadecyloxymethylpropyl 2,3-
di-O-benzyl-4,6-di-O-benzylidene-b-D-mannopyranosyl-
(1!4)-6-O-benzoyl-2,3-di-O-benzyl-b-D-mannopyran-
osyl-(1!4)-6-O-benzoyl-2,3-di-O-benzyl-b-D-manno-
pyranoside (14)
3.12. 3-Benzyloxy-2,2-dihexadecyloxymethylpropyl 2,3-
di-O-benzyl-b-D-mannopyranosyl-(1!4)-2,3-di-O-benzyl-
b-D-mannopyranoside (15)
Compound 12 (370 mg, 0.253 mmol) was dissolved in
2:1 MeOH–CH2Cl2 (30 mL), and NaOMe in MeOH
was added until pH 10. The mixture was kept to stir
for 17 h and then neutralized with weakly acidic resin
(IRC-50, H+ form). The crude product was purified by
flash chromatography (1:1 and then 1:2 hexane–EtOAc)
to provide 15 (319 mg, 92%) as a white power. Rf 0.21
Using the same glycosylation protocol as described for
the preparation of 8a/8b, the 1-thio donor 729
(70.3 mg, 0.13 mmol) was activated by BSP (29.3 mg,
0.14 mmol) and Tf2O (0.08 mL, 0.45 mmol) in the pres-
ence of DTBMP (55.4 mg, 0.27 mmol) at ꢀ60 ꢁC for
5 min, followed by addition of the glycosylation accep-
tor 13 (110 mg, 0.07 mmol) at ꢀ78 ꢁC. The crude prod-
uct was purified by repeated flash chromatography (5:1
hexane–EtOAc; 7:1 hexane–EtOAc; and 5:0.8:0.5 hex-
ane–EtOAc–CH2Cl2) to give 14 (71.7 mg, 51%) along
with unreacted 13 (11 mg, 10%). The yield of 14 was
61% based on the amount of 13 that reacted. Rf 0.26
22
(1:1 hexane–EtOAc); ½aꢁD ꢀ42.0 (c 0.29, CHCl3); 1H
NMR (500 MHz, CDCl3): d 0.88 (t, 6H, J 6.5 Hz,
2CH3), 1.25 (m, 52H, 26CH2), 1.51 (m, 4H, 2CH2),
2.24 (br s, 3H, 3OH), 3.19 (m, 1H), 3.29–3.51 (m,
13H), 3.69–3.74 (m, 2H), 3.81–3.88 (m, 2H), 3.91–3.96
(m, 2H), 4.11 (dd, 1H, J 9.5, 9.5 Hz), 4.15 (dd, 1H, J
9.5, 9.5 Hz), 4.37 (s, 1H, H-1), 4.38 (d, 1H, J 12.0 Hz,
PhCHH), 4.43 (d, 1H, J 12.0 Hz), 4.49 (d, 1H, J
12.0 Hz, PhCHH), 4.50 (d, 1H, J 12.0 Hz, PhCHH),
4.56 (d, 1H, J 12.0 Hz, PhCHH), 4.59 (s, 1H, H-1),
4.67 (d, 1H, J 12.0 Hz, PhCHH), 4.73 (d, 1H, J
12.0 Hz, PhCHH), 4.78 (d, 1H, J 12.0 Hz, PhCHH),
4.85 (d, 1H, J 12.0 Hz, PhCHH), 4.88 (d, 1H, J
12.0 Hz, PhCHH), 7.24–7.34 (m, 25H, Ar-H). 13C
NMR (125 MHz, CDCl3): d 14.37, 22.93, 26.47, 29.61,
29.77, 29.87, 29.90, 29.93, 29.95, 32.16, 45.55, 62.09,
63.01, 67.56, 69.68, 69.72, 71.54, 71.89, 72.43, 73.02,
73.52, 74.20, 74.49, 74.52, 74.83, 75.37, 75.71, 75.76,
76.64, 80.29, 82.20, 101.60 (C-1), 102.56 (C-1), 127.21,
127.43, 127.52, 127.61, 127.63, 127.72, 127.73, 127.78,
127.80, 127.92, 128.19, 128.23, 128.36, 128.38, 128.46,
128.47, 128.54, 128.78, 137.88, 138.68, 138.75, 139.06.
Anal. Calcd for C84H126O14ÆH2O (1359.92): C, 73.70;
H, 9.34. Found: C, 73.65; H, 9.16.
22
(5:0.7:0.5 hexane–EtOAc–CH2Cl2); ½aꢁD ꢀ23.6 (c 0.41,
1
CHCl3); H NMR (500 MHz, CDCl3): d 0.88 (t, 6H, J
6.5 Hz, 2CH3), 1.24 (m, 52H, 26CH2), 1.46 (m, 4H,
2CH2), 2.97 (ddd, 1H, J 9.5, 9.5, 5.5 Hz, H-5III), 3.26–
3.45 (m, 14H), 3.54–3.61 (m, 4H,), 3.78 (d, 1H, J
3.0 Hz, H-2), 3.86 (d, 1H, J 3.0 Hz, H-2), 3.89 (d, 1H,
J 3.0 Hz, H-2), 3.89 (dd, 1H, J 9.5, 9.5 Hz), 3.97 (d,
1H, J 10.0 Hz), 4.06 (dd, 1H, J 9.5, 9.5 Hz), 4.16 (m,
2H), 4.30 (d, 1H, J 12.0 Hz, PhCHH), 4.33 (m, 2H),
4.36 (s, 1H, H-1), 4.36 (d, 1H, J 12.0 Hz, PhCHH),
4.44 (d, 1H, J 12.0 Hz, PhCHH), 4.47 (s, 1H, H-1),
4.50 (d, 1H, J 12.0 Hz, PhCHH), 4.54 (d, 1H, J
12.0 Hz, PhCHH), 4.55 (m, 1H), 4.56 (d, 1H, J
12.0 Hz, PhCHH), 4.63 (d, 1H, J 12.0 Hz, PhCHH),
4.64 (m, 1H), 4.65 (d, 1H, J 12.0 Hz, PhCHH), 4.69
(d, 1H, J 12.0 Hz, PhCHH), 4.77 (d, 1H, J 12.0 Hz,
PhCHH), 4.78 (s, 1H, H-1), 4.79 (d, 1H, J 12.0 Hz,
PhCHH), 4.82 (d, 1H, J 12.0 Hz, PhCHH), 4.87 (d,

R. Xu, Z.-H. Jiang / Carbohydrate Research 343 (2008) 7–17
15
1
3.13. 3-Benzyloxy-2,2-dihexadecyloxymethylpropyl
benzyl 2,3-di-O-benzyl-b-D-mannopyranosyluronate-
(1!4)-benzyl 2,3-di-O-benzyl-b-D-mannopyranosidur-
onate (17)
CHCl3); H NMR (500 MHz, CDCl3): d 0.88 (t, 6H, J
7.0 Hz, 2CH3), 1.25 (br s, 52H, 26CH2), 1.48 (m, 4H,
2CH2), 2.77 (d, 1H, J 2.5 Hz, OH), 3.10 (dd, 1H, J
10.0, 3.0 Hz, H-3), 2.28–3.49 (m, 13H), 3.64 (d, 1H, J
3.0 Hz, H-2), 3.65 (d, 1H, J 3.0 Hz, H-2), 3.81 (d, 1H,
J 9.5 Hz, H-5), 4.00 (d, 1H, J 9.5 Hz, H-5), 4.18 (ddd,
1H, J 10.0, 9.5, 2.5 Hz, H-4II), 4.32 (s, 1H, H-1), 4.40
(m, 3H), 4.45 (m, 2H), 4.46 (s, 1H, H-1), 4.47 (d, 1H,
J 12.0 Hz, PhCHH), 4.49 (d, 1H, J 12.0 Hz, PhCHH),
4.64 (d, 1H, J 12.0 Hz, PhCHH), 4.68 (d, 1H, J
12.0 Hz, PhCHH), 4.71 (d, 1H, J 12.0 Hz, PhCHH),
4.85 (d, 1H, J 12.0 Hz, PhCHH), 5.00 (d, 1H, J
12.0 Hz, PhCHH), 5.01 (d, 1H, J 12.0 Hz, PhCHH),
5.10 (d, 1H, J 12.0 Hz), 5.20 (d, 1H, J 12.0 Hz, PhCHH),
7.25 (m, 35H, Ar-H). 13C NMR (125 MHz, CDCl3): d
14.1, 22.7, 26.2, 29.3, 29.5, 29.6, 29.7, 31.9, 45.2, 66.9,
67.1, 68.0, 69.6, 70.5, 71.6, 72.3, 73.2, 73.7, 74.2, 74.6,
74.8, 75.0, 75.1, 79.4, 80.1, 102.1 (C-1), 102.9 (C-1),
127.2, 127.3, 127.4, 127.6, 127.7, 127.8, 128.0, 128.1,
128.2, 128.27, 128.3, 128.4, 128.5, 128.6, 135.1, 135.3,
138.0, 138.6, 138.7, 138.9, 168.1 (CO), 169.1 (CO).
HRESIMS: [M+Na]+ calcd for C98H134O16Na,
1589.9564; found (positive-ion mode): 1589.9565. Anal.
Calcd for C98H134O16: C, 75.06; H, 8.61. Found: C,
74.79; H, 8.67.
3.13.1. 3-Benzyloxy-2,2-dihexadecyloxymethylpropyl 2,3-
di-O-benzyl-b-D-mannopyranosyluronic acid-(1!4)-2,3-
di-O-benzyl-b-D-mannopyranuronic acid (16). To
a
flask charged with 15 (300.0 mg, 0.22 mmol), 2,2,6,6-
tetramethylpiperidinyloxy free radical (TEMPO)
(21.0 mg, 0.132 mmol) and [bis(acetoxy)iodo]benzene
(BAIB) (425.0 mg, 1.32 mmol) was added 2:1 CH2Cl2–
water (6 mL), and the mixture was stirred at room tem-
perature for 2 h. The reaction was quenched with 10%
aq Na2S2O3 (20 mL), and the mixture was extracted with
CH2Cl2 (20 mL · 3). The organic layer was washed with
water, dried over Na2SO4, and concentrated in vacuum.
The residue was purified by flash column chromato-
graphy (3:1:0.1:0.2 hexane–EtOAc–MeOH –HOAc) to
give 16 (291 mg, 95%). Rf 0.32 (3:1:0.1:0.2 hexane–
1
EtOAc–MeOH –HOAc); H NMR (500 MHz, CDCl3):
d 0.88 (t, 6H, J 6.5 Hz, 2CH3), 1.25 (m, 52H, 26CH2),
1.48 (m, 4H, 2CH2), 3.31–3.47 (m, 12H), 3.57 (d, 1H,
J 9.5 Hz, H-5), 3.71 (d, 1H, J 9.5 Hz, H-5), 3.79 (br s,
1H, H-2), 3.91–3.96 (m, 2H, H-3I, H-3II), 3.97 (d, 1H,
J 3.0 Hz, H-2), 4.19 (dd, 1H, J 9.5, 9.5 Hz, H-4), 4.34
(dd, 1H, J 9.5, 9.5 Hz, H-4), 4.41 (d, 1H, J 12.0 Hz,
PhCHH), 4.48 (d, 1H, J 12.0 Hz, PhCHH), 4.48 (d,
1H, J 12.0 Hz, PhCHH), 4.49 (s, 1H, H-1), 4.53 (d,
1H, J 12.0 Hz, PhCHH), 4.58 (d, 1H, J 12.0 Hz,
PhCHH), 4.64 (d, 1H, J 12.0 Hz, PhCHH), 4.66 (d,
1H, J 12.0 Hz, PhCHH), 4.73 (d, 1H, J 12.0 Hz,
PhCHH), 4.77 (s, 1H, H-1), 4.78 (d, 1H, J 12.0 Hz,
PhCHH), 4.80 (d, 1H, J 12.0 Hz, PhCHH), 7.12–7.38
(m, 25H, Ar-H), 10.20 (s, 2H, 2COOH). 13C NMR
(125 MHz, CDCl3): d 14.32, 22.89, 26.40, 29.65, 29.73,
29.83, 29.85, 29.89, 29.91, 32.12, 45.67, 68.53, 69.11,
69.25, 70.35, 71.94, 71.97, 72.54, 72.79, 73.21, 73.53,
74.11, 74.29, 74.56, 74.98, 75.06, 76.21, 77.93, 80.62,
100.97 (1JC,H 153.4 Hz, C-1), 101.99 (1JC,H 156.7 Hz,
C-1), 127.61, 127.64, 127.68, 127.82, 128.00, 128.03,
128.23, 128.33, 128.45, 128.53, 128.55, 128.57, 137.46,
138.07, 138.25, 138.71, 138.79, 172.02 (CO), 176.93 (CO).
3.14. 3-Benzyloxy-2,2-dihexadecyloxymethylpropyl 2,3-
di-O-benzyl-b-D-mannopyranosyl-(1!4)-2,3-di-O-benzyl-
b-D-mannopyranosyl-(1!4)-2,3-di-O-benzyl-b-D-manno-
pyranoside (18)
To a solution of 14 (220 mg, 0.11 mmol) and neopentyl
glycol (75 mg, 0.72 mmol) in anhyd CH2Cl2 (10 mL)
was added camphorsulfonic acid (37.5 mg, 0.16 mmol).
The mixture was stirred at 35 ꢁC under an N2 atmo-
sphere for 16 h and then washed with satd aq NaHCO3
(10 mL). The aqueous layer was further extracted with
CH2Cl2 (10 mL · 2), and the combined organic layer
was dried over Na2SO4 and concentrated in vacuum.
The residue was dried under high vacuum to give the diol
intermediate (400 mg) that was then treated with a cata-
lytic amount of NaOMe in 2:1 MeOH–CH2Cl2 (30 mL,
pH 10.0) for 17 h. The reaction mixture was neutralized
with a weakly acidic resin (IRC-50, H+ form) and the
crude product was purified by flash chromatography
(1:1:0.5 hexane–EtOAc–CH2Cl2) to afford 18 (155 mg,
83%, two steps) as a white powder. Rf 0.38 (1:2:0.5 hex-
3.13.2. Benzyl esterification of 16. To a solution of 16
(266 mg, 0.19 mmol) and potassium fluoride (220 mg,
3.80 mmol) in dry DMF (5 mL) was added PhCH2Br
(0.23 mL, 1.90 mmol). The mixture was kept to stir for
16 h until TLC indicated complete reaction. The DMF
was removed under high vacuum, and water (25 mL)
was added. The mixture was extracted with CH2Cl2
(25 mL · 3), and the organic layer was dried over
Na2SO4. The residue was purified by flash chromatogra-
phy (5:1 and then 7:2 hexane–EtOAc) to give compound
17 (234 mg, 78%) as a syrup. Rf 0.69 (2:1:0.05:0.05
1
ane–EtOAc–CH2Cl2); H NMR (500 MHz, CDCl3): d
0.88 (t, 6H, J 7.0 Hz, 2CH3), 1.25 (br s, 52H, 26CH2),
1.51 (m, 4H, 2CH2), 2.30 (br s, 4H, 4OH), 3.19 (m,
2H), 3.24 (m, 1H), 3.28 (dd, 1H, J 9.5, 3.0 Hz, H-3),
3.34–3.50 (m, 14H), 3.62–3.66 (m, 2H), 3.70–3.72 (m,
2H), 3.80–3.84 (m, 3H), 3.86–3.88 (m, 2H), 3.96 (d, 1H,
J 9.5 Hz), 4.08 (dd, 1H, J 9.0, 9.0 Hz, H-4), 4.13 (d,
1H, J 9.0, 9.0 Hz, H-4), 4.34 (d, 1H, J 12.5 Hz, PhCHH),
4.37 (s, 1H, H-1), 4.44 (d, 1H, J 12.5 Hz, PhCHH), 4.49
22
hexane–EtOAc–MeOH–HOAc); ½aꢁD ꢀ76.5 (c 0.11,

16
R. Xu, Z.-H. Jiang / Carbohydrate Research 343 (2008) 7–17
(d, 1H, J 12.5 Hz, PhCHH), 4.50 (s, 1H, H-1), 4.50 (d,
1H, J 12.5 Hz, PhCHH), 4.54 (d, 1H, J 12.5 Hz,
PhCHH), 4.55 (d, 1H, J 12.5 Hz, PhCHH), 4.59 (s, 1H,
H-1), 4.73 (d, 1H, J 12.5 Hz, PhCHH), 4.74 (d, 1H, J
12.5 Hz, PhCHH), 4.75 (d, 1H, J 12.5 Hz, PhCHH),
4.79 (d, 1H, J 12.5 Hz, PhCHH), 4.80 (d, 1H, J
12.5 Hz, PhCHH), 4.83 (d, 1H, J 12.5 Hz, PhCHH),
4.87 (d, 1H, J 12.5 Hz, PhCHH), 4.89 (d, 1H, J
12.5 Hz, PhCHH), 7.24–7.40 (m, 35H, Ar-H). 13C
NMR (125 MHz, CDCl3): d 14.38, 22.93, 26.42, 29.62,
29.78, 29.88, 29.91, 29.95, 29.96, 32.15, 45.41, 62.11,
62.23, 63.03, 67.56, 69.69, 69.73, 70.21, 71.55, 71.91,
72.45, 73.03, 73.54, 74.22, 74.50, 74.55, 74.84, 75.39,
75.39, 75.70, 75.73, 75.73, 75.78, 76.65, 80.13, 80.30,
82.22, 101.20 (C-1), 101.61 (C-1), 102.58 (C-1), 127.23,
127.45, 127.53, 127.63, 127.65, 127.73, 127.75, 127.79,
127.81, 127.94, 128.20, 128.25, 128.37, 128.40, 128.47,
128.49, 128.55, 128.56, 128.80, 137.88, 138.72, 138.78,
138.82, 138.85, 138.90, 139.06. Anal. Calcd for
3.68 (d, 2H, J 3.0 Hz, 2H-2), 3.75 (d, 1H, J 9.5 Hz,
H-5), 4.00 (d, 1H, J 9.5 Hz, H-5), 4.13 (ddd, 1H, J 9.5,
9.5, 2.5 Hz, H-4III), 4.26 (dd, 1H, J 9.5, 9.5 Hz, H-4),
4.28 (s, 1H, H-1), 4.31 (s, 1H, H-1), 4.34 (dd, 1H, J 9.5,
9.5 Hz, H-4), 4.38 (d, 1H, J 12.5 Hz, PhCHH), 4.39 (d,
1H, J 12.5 Hz, PhCHH), 4.40 (d, 1H, J 12.5 Hz,
PhCHH), 4.41 (d, 1H, J 12.5 Hz, PhCHH), 4.42 (d,
1H, J 12.5 Hz, PhCHH), 4.45 (d, 1H, J 12.5 Hz,
PhCHH), 4.46 (d, 1H, J 12.5 Hz, PhCHH), 4.57 (d,
1H, J 12.5 Hz, PhCHH), 4.65 (s, 1H, H-1), 4.67 (d, 1H,
J 12.5 Hz, PhCHH), 4.69 (d, 1H, J 12.5 Hz, PhCHH),
4.71 (d, 1H, J 12.5 Hz, PhCHH), 4.72 (dd, 1H, J
12.5 Hz, PhCHH), 4.75 (dd, 1H, J 12.5 Hz, PhCHH),
4.79 (d, 1H, J 12.5 Hz, PhCHH), 4.85 (d, 1H, J
12.5 Hz, PhCHH), 4.92 (dd, 1H, J 12.5 Hz, PhCHH),
4.98 (d, 1H, J 12.5 Hz, PhCHH), 5.03 (dd, 1H, J
12.5 Hz, PhCHH), 5.07 (d, 1H, J 12.5 Hz, PhCHH),
5.16 (d, 1H, J 12.5 Hz, PhCHH), 7.12–7.35 (m, 50H,
Ar-H). 13C NMR (125 MHz, CDCl3): d 14.39, 22.94,
26.47, 29.62, 29.80, 29.89, 29.93, 29.95, 29.97, 32.18,
45.46, 66.97, 67.06, 67.14, 68.12, 69.68, 69.72, 69.75,
70.66, 71.71, 71.72, 71.51, 72.51, 72.72, 73.36, 73.84,
74.62, 74.69, 74.93, 74.96, 75.08, 75.17, 76.11, 77.25,
77.29, 77.36, 79.50, 79.75, 80.24, 102.25 (1JC,H 157.7,
C-1), 102.45 (1JC,H 155.6, C-1), 103.21 (1JC,H 155.3 Hz,
C-1), 127.49, 127.53, 127.56, 127.64, 127.82, 127.96,
128.02, 128.19, 128.29, 128.34, 128.40, 128.53, 128.64,
128.66, 128.70, 128.74, 128.78, 128.83, 128.86, 135.39,
135.48, 135.49, 138.26, 138.81, 139.10, 139.15, 139.20,
139.21, 168.17 (CO), 168.22 (CO), 169.28 (CO). Anal.
Calcd for C125H160O22Æ0.5H2O (2014.63): C, 74.19; H,
8.01. Found: C, 74.12; H, 7.89.
C
104H148O19Æ0.5H2O (1702.31): C, 72.99; H, 8.77.
Found: C, 72.88; H, 8.51.
3.15. 3-Benzyloxy-2,2-dihexadecyloxymethylpropyl
benzyl 2,3-di-O-benzyl-b-D-mannopyranosyluronate-
(1!4)-benzyl 2,3-di-O-benzyl-b-D-mannopyranosyluro-
nate-(1!4)-benzyl 2,3-di-O-benzyl-b-D-mannopyranosid-
uronate (20)
3.15.1. Oxidation of 18. Compound 18 (155 mg,
0.091 mmol), TEMPO (11.5 mg, 0.074 mmol), and
BAIB (232 mg, 0.72 mmol) were dissolved in 2:1
CH2Cl2–MeOH (6 mL), and the mixture was stirred at
room temperature for 4 h. The mixture was diluted with
CH2Cl2 (40 mL) and washed successively with 10% aq
Na2S2O3 (20 mL) and ice-water (10 mL). The organic
layer was dried through Na2SO4 and concentrated in
vacuum. The residue was purified by flash chromato-
graphy (6:1:0.1:0.2 hexane–EtOAc–MeOH–HOAc) to
give tricarboxylic acid 19 (111 mg, 70%). Rf 0.28
(3:1:0.1:0.2 hexane–EtOAc–MeOH–HOAc).
3.16. 3-Hydroxy-2,2-dihexadecyloxymethylpropyl b-D-
mannopyranosyluronic acid-(1!4)-b-D-mannopyranos-
iduronic acid (1)
Compound 17 (14 mg, 8.92 lmol) was dissolved in
freshly distilled THF (16 mL), and palladium-on-char-
coal (20 mg) was added. The mixture was stirred under
an H2 atmosphere for 2 h, and then water (4 mL) was
added. The mixture was stirred under an H2 atmosphere
for an additional 16 h. The solid was then filtered off and
washed with 1:1 THF–MeOH (20 mL). The filtrate was
concentrated in vacuum to give 1 (7.5 mg, 90%) as white
powder. Rf 0.46 (4:2:0.4:0.4 CHCl3–CH3OH–H2O–
3.15.2. Benzyl esterification of 19. To a solution of 19
(101 mg, 0.058 mmol) in dry DMF (8 mL) were added
potassium fluoride (158 mg, 2.7 mmol) and PhCH2Br
(0.19 mL, 1.6 mmol). The mixture was kept to stir at
room temperature for 16 h and worked up in a
similar way as described for the preparation of com-
pound 17. Chromatographic purification (7:1 hexane–
EtOAc) afforded 20 (93 mg, 80%) as a colorless syrup.
Rf 0.70 (3:1:0.1:0.2 hexane–EtOAc–MeOH–HOAc);
22
HOAc); ½aꢁD ꢀ116.0 (c 0.05, 2:1 MeOH–CHCl3);
MALDITOF MS: calcd for C49H92O16, 936.63 [M]+;
found, 959.63 [M+Na]+, 981.62 [MꢀH+2Na]+.
22
½aꢁD ꢀ39.6 (c 0.66, CHCl3). 1H NMR (500 MHz,
3.17. 3-Hydroxy-2,2-dihexadecyloxymethylpropyl b-D-
mannopyranosyluronic acid-(1!4)-b-D-mannopyranosy-
luronic acid-(1!4)-b-D-mannopyranosiduronic acid (2)
CDCl3): d 0.88 (t, 6H, J 7.0 Hz, 2CH3), 1.25 (br s,
52H, 26CH2), 1.48 (m, 4H, 2CH2), 2.74 (d, 1H, J
2.5 Hz, OH), 3.03 (dd, 1H, J 9.0, 2.5 Hz, H-3), 3.22
(dd, 1H, J 9.0, 2.5 Hz, H-3), 3.28–3.48 (m, 13H), 3.62
(d, 1H, J 9.5 Hz, H-5), 3.62 (d, 1H, J 3.0 Hz, H-2),
Compound 20 (14 mg, 6.95 lmol) was dissolved in THF
(32 mL) and treated with palladium on charcoal (48 mg)

R. Xu, Z.-H. Jiang / Carbohydrate Research 343 (2008) 7–17
17
9. Jiang, Z.-H.; Budzynski, W. A.; Qiu, D.; Yalamati, D.;
Koganty, R. R. Carbohydr. Res. 2007, 342, 784–796.
10. Moe, S. T.; Draget, K. I.; Skjak-Braek, G.; Smidsrød, O.
In Food and Polysaccharides and Their Applications;
Stephen, A. M., Ed.; Dekker: New York, 1995; pp 245–
286.
under an H2 atmosphere for 2 h. Then water (6 mL) was
added, and the mixture was stirred for an additional
24 h under an H2 atmosphere. The catalyst was filtered
off and washed with THF–MeOH (15 mL). The filtrate
was passed through a short filtration silica gel column
and concentrated in vacuum. The residue was freeze-
dried from 1,4-dioxane to give 2 (7.0 mg, 90%) as a
white powder. Rf 0.38 (7:2:0.1 2-PrOH–water–NH4OH);
11. Gacesa, P. Microbiology 1998, 144, 1133–1143.
˚
12. Skjak-Bræk, G.; Brasdaken, H.; Larsen, B. Carbohydr.
Res. 1986, 154, 239–250.
13. Relm, B. H. A.; Valla, S. Appl. Microbiol. Biotechnol.
1997, 48, 281–288.
14. Uludag, H.; De Vos, P.; Tresco, P. A. Adv. Drug Deliv.
Rev. 2000, 42, 29–64.
15. Smithrød, O.; Skjaek-Braek, G. Trends Biotechnol. 1990,
8, 71–76.
22
½aꢁD +47.3 (c 0.08, 2:1 MeOH–CHCl3). MALDITOF
MS: calcd for C55H100O22, 1112.67 [M]+; found,
1136.05 [M+Na]+, 1158.06 [MꢀH+2Na]+.
˚
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Acknowledgments
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the Ontario Graduate Scholarship (OGS) during the
course of his graduate studies.
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