Synthesis and liquid crystallinity of dendronized carbohydrate liquid crystal

Article abstract of DOI:10.1016/j.carres.2011.10.042

A dendronized carbohydrate thermotropic liquid crystal was synthesized by attaching wedge-shaped mesogens onto a carbohydrate core. These molecules self-organize into chiral columnar hexagonal mesophase with each column slice (4.5 thicknesses) filled with average of two molecules. The supramolecular model was further optimized by molecular dynamics simulation. Moreover, chirality successfully expressed in columnar hexagonal mesophase by dendronized carbohydrate molecules may provide inspiration in searching for chiral mesophase of carbohydrate liquid crystals.

Full text of DOI:10.1016/j.carres.2011.10.042

Carbohydrate Research 347 (2012) 40–46
Contents lists available at SciVerse ScienceDirect
Carbohydrate Research
journal homepage: www.elsevier.com/locate/carres
Synthesis and liquid crystallinity of dendronized carbohydrate liquid crystal
Liulin Yang a,b, Yanming Dong a, , Xiaolan Hu a, Anhua Liu a
⇑
a College of Materials, Xiamen Univeristy, Xiamen University, Xiamen 361005, China
b College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 16 June 2011
Received in revised form 25 September 2011
Accepted 28 October 2011
Available online 6 November 2011
A dendronized carbohydrate thermotropic liquid crystal was synthesized by attaching wedge-shaped
mesogens onto a carbohydrate core. These molecules self-organize into chiral columnar hexagonal meso-
phase with each column slice (4.5 Å thicknesses) filled with average of two molecules. The supramolec-
ular model was further optimized by molecular dynamics simulation. Moreover, chirality successfully
expressed in columnar hexagonal mesophase by dendronized carbohydrate molecules may provide inspi-
ration in searching for chiral mesophase of carbohydrate liquid crystals.
Keywords:
Ó 2011 Elsevier Ltd. All rights reserved.
Dendronized carbohydrate liquid crystal
Chiral columnar hexagonal phase
Supramolecular chirality
1. Introduction
this theory, they have designed and synthesized a new class of
non-amphiphilic carbohydrate liquid crystals by embedding gluco-
The study of carbohydrate liquid crystals can be traced back to
1938 when some long-chain n-alkyl glucopyranosides were recog-
nized as thermotropic liquid crystals.1 However, it was not until
the last 30 years that carbohydrate liquid crystals had been paid
attention.2 So far, most of this kind of liquid crystals is composed
of sugar moiety partially substituted by n-alkyl chains (named as
amphiphilic glycolipids),3,4 and only several fully substituted
derivatives are reported to be discotic liquid crystals.5–7
Even few reports focused on the synthesis of glucose derivatives
with mesogenic side chains. Hirani et al.8 reported the first such
compounds which organize into chiral nematic phase or smectic
phase. Zhang et al.9 also reported star-shaped carbohydrate liquid
crystals with cholesterol as mesogenic side chains.
Given the above work we note that although the carbohydrate
liquid crystals have been discovered for several decades, there are
still quite limited categories in this liquid crystal library. However,
as described by Jeffrey, ‘carbohydrates are remarkable as a source of
mesogens’,10 since their great variety of isomers, polyfunctionality,
and adjustable degree of polymerization from mono-, di-, to oligo-
and polymer, while modified by alkyl chains or mesogens, thou-
sands of carbohydrate liquid crystals can be synthesized.
Furthermore, carbohydrates are chiral molecules, but chiral
mesophase behavior is rarely found. Kellogg and co-workers11 con-
sidered that, it is because the amphiphilic character of traditional
carbohydrate liquid crystals leads to rigidly packed double layers
that organize to smectic phase; whereas, supramolecular chirality
is in general more readily expressed in nematic phase. According to
pyranose ring in a trans-decalin structure to reduce hydrophilicity,
leading to chiral nematic phase.11 However, to our best knowledge,
there are still very few reports about carbohydrate chirality ex-
pressed in another mesophase.
Thereby, it is necessary to expand the carbohydrate liquid crys-
tal library. Carbohydrates modified by mesogenic side chains have
broad prospects. During our search for the mesogenic candidates,
‘Percec’-type supramolecular liquid crystalline dendrimers im-
pressed us deeply. These liquid crystalline dendrimers developed
by Percec and co-workers show the powerful ability of self-assem-
bly and self-organization.12 Variety of supramolecular structures
including disc, column, pyramid, and sphere can be achieved by
controlling the structure, generation, and molecular morphology
of dendrimers.
In this study, we synthesized a novel carbohydrate liquid crystal
by attaching wedge-shaped mesogen DOBOB (3,4,5-tris (p-dode-
cyloxybenzyloxy) benzoic acid) onto a carbohydrate core (N-acetyl
glucosamine), named as dendronized carbohydrate liquid crystal.
Supramolecular structure of this compound has been studied by
DSC, TPOM (thermal polarized optical microscopy), XRD, CD/UV
spectroscopy, and computer simulation. A phenomenon of chirality
transfer from the carbohydrate core to achiral branches (DOBOB
groups) leading to a chiral mesophase was observed, which is rare
for carbohydrate liquid crystals.
2. Molecular design and synthesis
DOBOB was synthesized by convergence method.13 The key
question is how to combine the two building blocks, DOBOB and
N-acetylglucosamine. This is a challenge not only because of the
⇑
Corresponding author. Tel.: +86 0592 2186095; fax: +86 0592 2183937.
E-mail address: ymdong@xmu.edu.cn (Y. Dong).
0008-6215/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2011.10.042

L. Yang et al. / Carbohydrate Research 347 (2012) 40–46
41
steric hindrance effect of bulky DOBOB group, but also the totally
different solubility of the two molecules. DOBOB can be easily dis-
solved in organic solvents such as chloroform or THF, but N-acetyl-
glucosamine is water soluble. Obviously, direct esterification will
encounter great difficulty since the reaction has to be carried out
in heterogeneous phase. In order to resolve the contradiction of
solubility, N-acetylglucosamine should be turned into organic sol-
vent soluble by chemical modification. Another key point is the
easy decomposition of DOBOB under acid condition, so the esteri-
fication of DOBOB catalyzed by acyl chloride can not proceed suc-
cessfully. Finally, the condensation reaction between carboxylic
acid and halogenated hydrocarbon catalyzed by KF and 18-C-6-E
was chosen to obtain the target product.
Therefore, halogenated alkyl segment, also acting as a spacer,
was introduced into N-acetylglucosamine by esterification
(Scheme 1). Reaction can be easily achieved in DMF/LiCl solvent
at room temperature. The hydroxyl groups were all esterified to
give tetrabromide 1, which dissolves in the organic solvent very
well. Then compound 2 was obtained from condensation of DOBOB
with compound 1 in DMF catalyzed by KF/18-C-6-E. The detailed
synthesis process and characterization are described in Section 5.
Figure 1. DSC traces of compound 2, both heating and cooling rates were 10 °C/
min. (a) The first heating trace; (b) the second heating trace; (c) the second cooling
trace.
at low magnification (Fig. 2 (a)). Generally, grainy texture is found
in nematic mesophase. However, XRD studies demonstrated a
columnar hexagonal structure for compound 2 (see Section 3.2).
The typical texture of columnar hexagonal mesophase is fan-
shaped focal conic or fan-shaped texture, such as DOBOB shows.14
Actually, it was found that this grainy-like texture formed by com-
pound 2 is composed of tiny broken-fan shaped monodomain
(Fig. 2 (b)) at high magnification. In addition, when a vertical pres-
sure was applied to the coverslip, the original texture turned into
colorful planar texture (Fig. 2 (c)), meaning molecules in monodo-
main can be reoriented under a mechanical field.
3. Results and discussion
The analysis of supramolecular structure was carried out by a
combination of DSC, TPOM, XRD, computer simulation and CD/
UV experiments.
3.1. Thermal analysis and mesophase texture
3.2. X-Ray diffraction studies
In the first heating trace of compound 2, weak peaks between
40 to 70 °C were observed; however, they were basically not de-
tected during the second heating-run. This is because of hot history
effect during sample preparation process. The second-run DSC
heating curve showed only one endothermic peak at about 90 °C
Wedge-shaped DOBOB15 and its derivatives,16 as well as full
acylation of carbohydrate discotic liquid crystals usually self-orga-
nize to form columnar hexagonal mesophase. Compound 2 can be
regarded as a quasi-disc molecule, and thus be rationally expected
to organize into hexagonal mesophase. XRD patterns of compound
2 recorded in the mesophase state exhibited a sharp reflection in
(
D
H = 18.9 kcal/mol), and an exothermic peak at about 46 °C
H = ꢀ25.5 kcal/mol) in a cooling curve (Fig. 1).
(D
For TPOM study, sample was sandwiched between two glass
54.8 Å in company with three weak reflections at 31.3 Å, 26.0 Å
slides to make a liquid crystal cell. The cell was first heated above
90 °C while the sample melted into isotropic liquid, and then
cooled to room temperature. The sample finally turned to be a
translucent and ductile solid. A grainy-like texture was observed
pffiffiffi
and 20.8 Å (Fig. 3). According to the ratio of d-spacing (1:1/ 3:1/
pffiffiffi pffiffiffi
4:1/ 7), these peaks can be indexed in a hexagonal lattice as
(hkl) = (100), (110), (200) and (210) respectively. Furthermore,
two broad peaks with d-spacing of 4.5 Å (assigned to the average
O
O
OH
O
O
(CH2)10Br
Br(H2C)10
O
O
O
a
O
Br (CH2)10
+ HO
OH
(CH2)10Br
Br(H2C)10
O
Cl
O
NH
O
NH
HO
1
O
O
O
O
O
2 10
O
CH )
(
O
H3C(H2C)11
O
O
CH2O
CH2O
O
O
C)10
O
(H2
O
O
O
O
b
O
(H2C)10
O
H3C(H2C)11
O
1
COOH
+
O
O
O
NH
H3C(H2C)11
CH2O
O
2
DOBOB
O
O
refer to DOBOB group
Scheme 1. Synthesis route of dendronized carbohydrate liquid crystal. Reagents and conditions: (a) DMF/LiCl, Py, DMAP, rt, 48 h; (b) DMF, KF, 18-C-6-E, 100 °C, N2, 4 h.

42
L. Yang et al. / Carbohydrate Research 347 (2012) 40–46
Figure 2. (a) Grainy-like texture of compound 2 at low magnification; (b) tiny broken-fan texture of compound 2 at high magnification; (c) planar texture of compound 2
when a vertical pressure applied to the coverslip.
distance of alkyl chains) and 3.9 Å (assigned to the
aromatic groups) suggested a more liquid-like molecular stack
rather than crystalline.
p
–
p
stacking of
in liquid crystalline phase.17 First, molecular volume (Vmol) was cal-
culated according to equation: Vmol (in Å3) = M/(NA
ꢁ
q
ꢁ 10ꢀ24),17
where M is calculated molecular mass (Mcalcd = 4860), NA is Avoga-
The calculated column diameter D of compound 2 is 63.3 Å
pffiffiffi
dro number, q
is measured density (1.02 g/cm3). Then the volume
(D = 2 < d100 > / 3), which is significantly smaller than the theoret-
ical value. In fact, column diameter is usually less than that pre-
dicted from a structure in which the side chains radiate from the
backbone and have fully extended (all-trans) alkyl groups.16 This
is because the alkyl chains may contain significant numbers of
gauche conformation, or may interpenetrate each other between
columns. Otherwise, the dendron groups may be tilted downward,
like branches in a pine tree;16a or sideways, like propeller blades.
In order to understand the supramolecular structure within col-
umns, the number of dendrimers to fill a column slice (a = 63.3 Å,
c = 4.5 Å) was calculated. The slice thickness 4.5 Å corresponds to
the average correlations between the peripheral mesogenic groups
of one column slice with a thickness (h) of 4.5 Å was calculated from
Sꢂh, where S is the lattice area. Thus, the number of molecules per
slice (N) can be directly obtained by N = Sꢂh/Vmol. Calculated result
showed that average of two molecules is needed to fill such a col-
umn slice.
3.3. Computer simulation
The self-assembly model was further optimized by molecular
dynamics (MD) simulation. Before MD simulation, the key point
is to build a relatively rational molecular model as the preliminary
stage of simulation. As the supramolecular dendrimers described
by Percec et al.,18 columnar structures are generated from the
self-assembling of the most stable molecular conformations having
either a wedge-like or a half-disc shape. Therefore, we presumed
compound 2 adopts a flat conformation with different building
blocks (the flat dendrons and the quasi-disc acylation carbohydrate
core) lying more or less in a 2D hexagonal lattice. Considering the
calculation result of XRD data, two molecules that constitute a col-
umn slice may be essentially semicircular and lie side-by-side to
form a full ‘circle’ (Fig. 4). Such conformation facilitates the close
stacking of aromatic groups and alkyl chains leading to a more effi-
cient packing of space.
10000
8000
6000
4000
4.5 Å
3.9 Å
According to the XRD data, a hexagonal lattice with a = 63.3 Å,
c = 4.5 Å, filled with two dendrimers, was built. The supramolecu-
lar model was optimized by molecular mechanics calculation and
further molecular dynamics calculation. The detailed model build-
ing and simulation process are described in the Supplementary
data.
1
2
3
4
5
2000
0
0
10
20
30
40
50
Result of calculation evidenced a good filling of lattice space
(Fig. 5). Eight irregularly tilt dendron segments were annularly ar-
ranged around the c axis (the cylinder axis). Gauche conformation
2θ/°
Figure 3. XRD spectrum of compound 2 carried out in mesophase state.

L. Yang et al. / Carbohydrate Research 347 (2012) 40–46
43
phatic chains and the segregation between different constitutive
blocks.
3.4. Supramolecular chirality studied by CD/UV experiments
Dendrimers with chirality have a high scientific value for the
basic understanding of fundamental stereochemical issues; also
have many features that will be of crucial importance to other
fields where dendrimers are thought to be useful.20,21 Carbohy-
drates are appealing for the design of chiral dendrimers due to
their easy availability from the chiral pool and polyfunctionality.
Lindhorst had first synthesized a carbohydrate-centered PAMAM-
type dendrimer;22 however, no further chirality study was
reported.
In this study, CD/UV experiments were carried out in solvents
and on thin films. Films were cast on round quartz plates, with
thickness between 2 and 3 lm. All the films were annealed for
3 h in their isotropic phase before the test in order to eliminate po-
tential artificial orientation, and then cooled to room temperature.
As expected, no CD signal of DOBOB in solution or bulk can be
detected (Fig. 6 (a)). Even if the supramolecular columns generated
from DOBOB are chiral, they do not exhibit a CD spectrum since
they are racemic. However, for chiral molecules, such as carbohy-
drate liquid crystals, things may be different. A typical example
is penta-O-n-alkanoylglucopyranoses, which can self-organize into
columnar hexagonal mesophase that induced circular dichroism,
indicated a helical arrangement of the discotic molecules along
the column axis.5
Compound 2 also showed no detectable CD signal of aromatic
groups in chloroform solution (Fig. 6(b)), in other words, a failure
chirality transmission in solution. The result came as no surprise.
During the first studies of dendrimers incorporated a chiral core,
Seebach et al.23 had found a ‘loss’ of chiral information in solution
in the case of branched systems featuring an aliphatic spacer be-
tween achiral dendrons and chiral core unit. This phenomenon
was thought to be caused by the dilution effect and increased flex-
ibility of dendrons induced by aliphatic spacer linker, which can
also be a reasonable explanation for the case of compound 2 in
solution.
However, when we cast compound 2 into thin film from chloro-
form solution, an entirely different CD spectrum was obtained. CD
spectrum of film at room temperature showed three absorption
peaks at 230 nm, 273 nm and 302 nm which can be assigned to
the aromatic groups of DOBOB (Fig. 6(b)). According to the meso-
phase study mentioned above, compound 2 in the film had self-
assembled into supramolecular columns under this testing condi-
tion. Therefore, the CD signal of achiral dendron groups is most
probably derived from supramolecular chirality resulted from their
helical arrangement in the cylinder (Fig. 7). This hypothesis is also
supported by the temperature dependence of CD experiment
(Fig. 6(c)). Experiment was performed during cooling process after
the film was heated to isotropic phase. While it was in isotropic
phase, no CD signal was detected. This was quite analogous to
what happened in chloroform solution, while the alkyl spacer link-
ers were too flexible to transmit chirality information. As the tem-
perature decreased, until the sample came into columnar
hexagonal phase, the CD signal developed from scratch and in-
creased quickly. Thus, the chirality of carbohydrate core can be
transmitted to achiral dendron branches by their cooperative
self-assembly, and the chiral carbohydrate center most probably
plays the primary role of selecting the handedness of the helix. This
mechanism is also supported by the similar helical packing of
dendronized cyclotriveratrylenes in their Uiho phase.24
Figure 4. Two half-disc molecules form a full circle slice, and the slices self-
assemble into columns.
and interdigitation of terminal alkyl chains were also observed.
Moreover, the internal alkyl chains were twisted. This maybe re-
sulted from the micro-phase segregation19 and the mismatch be-
tween the surface areas of aromatic groups and the cross section
of aliphatic chains,17 which prevent the alkyl chains from adopting
all-trans conformation. The overall molecular conformation of the
dendrimers is driven by the steric congestion of the terminal ali-
Many materials have been reported to self-organize into helical
columnar mesophase, including lyotropic and thermotropic mate-
rials, such as foldamers,25 helicenes,26 and wedge-shaped
Figure 5. Snapshot of molecular conformation in Colh mesophase for compound 2
obtained by MD simulation.

44
L. Yang et al. / Carbohydrate Research 347 (2012) 40–46
a
b
c
12
6
0
230nm
20
10
0
273nm
30
20
Isotropic phase
during phase transition
-6
Col phase
-12
-18
-24
h
302nm
-10
-20
10
0
200 250 300 350 400 450 500
Wavelength/nm
200
250
300
350
400
-10
-20
-30
-40
-50
Wavelength/nm
0.8
0.6
0.4
0.2
0.0
1.6
1.2
0.8
0.4
0.0
film
solution
film
solution
200 250 300 350 400 450 500
Wavelength/nm
200
250
300
350
400
200 250 300 350 400 450 500
Wavelength/nm
Wavelength/nm
Figure 6. (a) CD/UV spectra of DOBOB film (2–3
l
m) and in CHCl3 solution (4.0 ꢁ 10ꢀ4g/mL) at room temperature; (b) CD/UV spectra of compound 2 film (2–3
lm) and in
CHCl3 solution (5.4 ꢁ 10ꢀ4g/mL) at room temperature; (c) CD spectra of compound 2 film (2–3
lm) in different phase state.
carbohydrate in the center of liquid crystalline dendrimer, and
found that the chirality of carbohydrate core can be transmitted to
achiral dendron branches by their cooperative self-assembly, and fi-
nally expressed in columnar hexagonal mesophase. Considering the
great variety of dendron mesogens as building blocks, this kind of
dendronized carbohydrate may provide inspiration in searching
for chiral mesophase of carbohydrate liquid crystals.
For the field of helical columnar mesophase, an interesting work
about helicene that self-assembles into helical columns was re-
ported.26 Both enantiopure and racemic helicenes were synthesized
to compare their supramolecular structures. However, it is difficult
for carbohydrates to obtain opposite enantiomer or racemer. Most
of carbohydrates are obtained from natural resources. They are usu-
ally only present in one type of enantiomer. Nevertheless, consider-
ing the great number of isomers of carbohydrates, two isomers with
opposite rotatory direction can be chosen to compare their helical
sense. Furthermore, these two isomers can be mixed together to
find whether the isomers separate in separate columns of opposite
helical sense, or whether columns loose helicity.
Figure 7. Chiral columnar hexagonal phase self-organized by compound 2.
molecules.27 Wedge-shaped molecules (either free or attached to
core molecule) that assemble into helical columns have been stud-
ied in depth. For example, polymethacrylate grafted by DOBOB
assembles into a tubular structure with branches helically stacked
around the backbone.27 Triphenylene attached by wedge-shaped
or taper-shaped dendrons self-assemble into helical pyramidal col-
umns or chiral spheres.24 In these cases, ‘helical arrangement ap-
pears to have an advantage over the stacked-disk model in that
they can more easily accommodate the propagation of the side
chains along the backbone in the core of the cylinders’.27 Therefore,
according to these references and the results of CD experiments, it
is rational to present the helical arrangement model for dendron-
ized carbohydrate liquid crystal.
5. Experimental
5.1. Techniques
Product purification was performed by JAI LC-9104 Recycling
Preparative GPC, using chloroform as mobile phase. 1H NMR
(400 MHz) and 13C NMR (100 MHz) spectra were recorded on a
Bruker Avance IIDMX 400 instrument. The purity of products was
determined by High Pressure Liquid Chromatography (HPLC) using
THF as mobile phase at 1 mL/min, on a Waters 510 High Pressure
Liquid Chromatograph, and a Waters 410 Differential Refractome-
ter. Polystyrene is used as standard sample. Elementary analysis
was determined on Elementar Vario EL III CHNS Analyzer.
4. Conclusion
We have synthesized a novel carbohydrate thermotropic liquid
crystal by attaching wedge-shaped mesogens onto a carbohydrate
core, named as dendronized carbohydrate liquid crystal. Based on
the XRD data, computer simulations and CD/UV data, we propose
a structure model that these molecules self-assemble into helical
supramolecular columns, and further self-organize into chiral
columnar hexagonal mesophase.
Chiral mesophase of carbohydrate liquid crystal is rarely re-
ported. So far, there are only several examples with chirality ex-
pressed in nematic phase. In this study, we embedded
Thermal transition was detected by NETZSCH DSC 204 Cell dif-
ferential scanning calorimeter (DSC) equipped with a refrigerated
cooling system with 10 °C minꢀ1 heating and cooling rate. Indium
was used as the calibration standard. The transition temperatures
were calculated as the maxima and minima of their endothermic
and exothermic peaks.
A NIKON ME600 optical microscope
equipped with a Mettler FP82HT hot stage and a Mettler Toledo
FP90 Central Processor were used to verify thermal transitions
and to characterize anisotropic textures. Density measurements
were carried out by Satorius BS 210s Specific Gravity Balance.

L. Yang et al. / Carbohydrate Research 347 (2012) 40–46
45
X-ray diffraction (XRD) measurements were performed using
Cu-K radiation from a Panalytical X’pert rotating anode X-ray
ortho to COOH), 7.32 (d, 20H, ortho to CH2OAr, 3, 5 positions),
7.24 (d, 10H, ortho to CH2OAr, 4 position), 6.88 (d, 20H, meta to
CH2OAr, 3, 5 positions), 6.74 (d, 10H, meta to CH2OAr, 4 position),
a
1
source with X-ray generator working at 40 kV, 30 mA. Samples
were held on glass slides which were annealed at 100 °C before
test. XRD spectrum analysis was performed using X’per Highscore
Plus software. Molecular simulation was done by using Materials
Studio modeling software version 4.0.
Circular dichroism (CD) and UV spectroscopy measurements
were carried out by Jasco J-720 Spectropolarimeter and Cary 50
UV–Vis spectrophotometer in solutions and on thin films. Films
were cast on round quartz plates. Sample (5 mg) was dissolved
6.18 (d, H (a-anomer)), 5.66 (d, H (b-anomer), J = 8.8 Hz), 5.57–
5.09 (m, overlapped, NH & 2H in glucose ring), 5.04 (s, 20H, CH2OAr,
3, 5 positions), 4.99 (m, 10H, CH2OAr, 4 position), 4.48–3.74 (over-
lapped m, 4H of glucosamine), 4.26 (t, 10H, ArCOOCH2), 3.98 & 3.90
(two overlapped t, 30H, RCH2OAr), 2.43–2.22 (m, 8H, OOCCH2), 2.05
(t, 2H, COCH3), 1.77 (overlapped m, 10H+30H, CH2), 1.62 (over-
lapped m, 10H, CH2), 1.48–1.28 (overlapped m, 270H + 60H, CH2),
0.90 (t, 45H, CH3); 13C NMR (100 MHz, CDCl3, ppm): d = 177.5,
175.1, 174.6, 173.9, 173.7, 173.4, 173.1, 172.2, 171.9, 171.4 (COO-
in 500 lL of CHCl3, and 50 lL of the solution (containing 1 mg of
sample) was dropped homogeneously onto the quartz plate. The
glucosamine, a and b-anomer), 166.3 (Ar-COO-alkyl chain), 159.1
quartz plate was then annealed in Mettler FP82HT hot stage for 3 h.
(para to CH2OAr), 152.6 (meta to COOCH2), 142.5 (para to COOCH2),
130.3 (ipso to CH2OAr, 3, 5 positions), 129.5 (ipso to CH2OAr, 4 posi-
tion), 129.3 (ortho to CH2OAr, 3, 5 positions), 128.6 (ortho to
CH2OAr, 4 position), 125.4 (ipso to COOCH2), 114.5 (meta to CH2OAr,
3, 5 positions), 114.1 (meta to CH2OAr, 4 position), 109.2 (ortho to
COOCH2), 92.7 & 90.5 (C1 of glucosamine), 74.7 (ArCH2OAr, 4 posi-
tion), 72.8 &72.5 (C3 of glucosamine), 71.1 (ArCH2OAr, 3, 5 posi-
tions), 68.0 (CH2CH2OAr, 3,5-40 positions), 70.5 & 69.9 (C5 of
glucosamine), 67.6 & 67.3 (C4 of glucosamine), 65.2 (CH2OOCAr),
61.5 & 61.4 (C6 of glucosamine), 52.8 & 51.2 (C2 of glucosamine),
34.0 (CH2COO-glucose ring), 32.7 (COOCH2CH2), 32.0 (CH2CH2CH3),
29.8–28.8 (CH2), 26.9 (ArCOOCH2CH2CH2), 26.2 (CH2CH2CH2OAr),
25.1–24.6 (CH2CH2COO), 22.8 (CH3CH2), 14.2 (CH3). IR (cmꢀ1):
2955, 2921, 2852, 1742, 1713, 1659. Elemental Analysis calcd (%)
for C308H471NO42: C, 76.12; H, 9.77; N, 0.29; found (%): C, 75.93;
H, 9.70; N, 0.30.
5.2. Synthesis
5.2.1. Synthesis of compound 1
11-Bromoundecanoyl acid (4.7 g, 18 mmol) was dissolved in
10 mL dry dichloromethane. Then oxalyl chloride (2.36 mL,
27 mmol) was dropped slowly into the solution under room tem-
perature, using DMF as catalyst. The reaction was completed after
1 h. The solvent and the residue oxalyl chloride were removed by
vacuum distillation to obtained 11-bromoundecanoyl chloride
(4.8 g, 95%) as a light yellow viscous liquid. N-Acetyl glucosamine
(0.66 g, 3 mmol) was dissolved in 10 mL, 10 w/v% DMF/LiCl solu-
tion at 50 °C, and then cooled to 0 °C under ice-water bath. Dis-
tilled pyridine (2.9 mL) and 4-dimethylaminopyridine (DMAP)
(0.12 g, 1 mmol) were added. Then 11-bromoundecanoyl chloride
was dropped slowly into the solution with magnetic stirring. The
mixture was stirred in a closed vessel for 48 h under room temper-
ature. After the reaction was completed, the mixture was poured
into 50 mL water, extracted by CH2Cl2, washed sequentially with
30 mL of 5% aqueous HCl, 2 ꢁ 30 mL of 5% ammonia water, and
30 mL of saturated salt solution. The organic layer was dried (anhy-
drous MgSO4) and evaporated to residue. The crude product was
purified by column chromatography on silica gel (eluent CHCl3)
to obtain compound 1 (2.5 g, 60%) as a yellow viscous solid. 1H
Acknowledgments
We acknowledge Wei-shi Li researcher of Shanghai Institute of
Organic Chemistry, Chinese Academy of Science, for his great help
in product purification. Financial supported by the National Natu-
ral Science Foundation of China (20774077).
Supplementary data
NMR (400 MHz, CDCl3, TMS, ppm): d = 6.19 (d, H (a-anomer),
J = 3.6 Hz), 5.67 (d, H (b-anomer), J = 8.8 Hz), 5.57–5.10 (m, over-
lapped, NH & 2H in glucose ring), 4.50–4.28 (m, H), 4.24–4.10
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.carres.2011.10.042.
(m, 2H), 3.96 (m, 2H (
a-anomer)), 3.78 (m, 2H (b-anomer)), 3.55
(t, 8H, CH2Br), 2.44–2.25 (m, 8H, CH2COO), 1.91 (s, 3H, COCH3
(a-
References
anomer)), 1.89 (s, 3H, COCH3 (b-anomer)), 1.76 (m, 8H, CH2),
1.68–1.55 (m, 8H, CH2), 1.42–1.28 (m, 48H, (CH2)6); 13C NMR
(100 MHz, CDCl3, ppm): d = 175.9, 174.3, 173.7, 173.2, 172.1,
171.8, 171.7, 171.4, 169.99, 169.95 (COO), 92.3 & 90.3 (C1 of gluco-
samine), 72.7 &72.4 (C3 of glucosamine), 70.3 & 69.8 (C5 of gluco-
samine), 67.6 & 67.2 (C4 of glucosamine), 61.5 & 61.4 (C6 of
glucosamine), 52.7 & 51.1 (C2 of glucosamine), 44.9 (CH2Br), 33.9
1. Noller, C. R.; Rockwell, W. C. J. Am. Chem. Soc. 1938, 60, 2076–2077.
2. Jeffrey, G. A. Acc. Chem. Res. 1986, 19, 168–173.
3. Vill, V.; Hashim, R. Curr. Opin. Colloid & Interface Sci. 2002, 7, 395–409.
4. Goodby, J. W.; Gortz, V.; Cowling, S. J.; Mackenzie, G.; Martin, P.; Plusquellec,
D.; Benvegnu, T.; Boullanger, P.; Lafont, D.; Queneau, Y.; Chambert, S.;
Fitremann, J. Chem. Soc. Rev. 2007, 36, 1971–2032.
5. Morris, N. L.; Zimmermann, R. G.; Jameson, G. B.; Dalziel, A. W.; Reuss, P. M.;
Weiss, R. G. J. Am. Chem. Soc. 1988, 110, 2177–2185.
(CH2COO),
32.5
(CH2CH2Br),
29.3–28.8
[(CH2)5],
26.8
6. Kohne, B.; Praefcke, K. Angew. Chem., Int. Edit. 1984, 23, 82–83.
7. (a) Sugiura, M.; Minoda, M.; Fukuda, T.; Miyamoto, T.; Watanabe, J. Liq. Cryst.
1992, 12, 603–611; (b) Sugiura, M.; Minoda, M.; Watanabe, J.; Miyamoto, T.
Polym. J. (Tokyo) 1994, 26, 1236–1243; (c) Takaragi, A.; Sugiura, M.; Minoda, M.;
Miyamoto, T.; Watanabe, J. Macromol. Chem. Phys. 1997, 198, 2583–2598.
8. Hirani, B.; Nakata, Y.; Watanabe, J. Mol. Cryst. Liq. Cryst. 1996, 288, 223–236.
9. Zhang, B.; Xiao, W.; Cong, Y.; Zhang, Y. Liq. Cryst. 2007, 34, 1129–1136.
10. Jeffrey, G. A.; Wingert, L. M. Liq. Cryst. 1992, 12, 179–202.
(CH2CH2CH2Br), 24.8–24.5 (CH2CH2COO); IR (cmꢀ1): 2926, 2854,
1746 (COO), 1670 (CONH), 723, 651 (CBr).
5.2.2. Synthesis of compound 2
DOBOB acid (0.4 g, 0.4 mmol) and compound
1 (0.12 g,
0.1 mmol) was dissolved in 5 mL DMF, then 18-C-6-E (0.1 g,
0.4 mmol) with KF (0.05 g, 0.8 mmol) was added. The mixture
was stirred at 100 °C under N2 atmosphere for 4 h. Then the mixture
was poured into 50 mL water, extracted by CHCl3, washed with 5%
aqueous HCl and water. The organic layer was dried (anhydrous
MgSO4) and evaporated to residue. The crude product was purified
by column chromatography on silica gel (eluent CHCl3) and then
recycling preparative GPC to obtain pure compound 2 (0.20 g,
41%) as a light yellow solid. Mw = 6404, Mn = 5946 (Mcalcd = 4860),
d = 1.08. 1H NMR (400 MHz, CDCl3, TMS, ppm): d = 7.35 (s, 10H,
11. Doren, H. A. V.; Smits, E.; Pestman, J. M.; Engberts, J. B. F. N.; Kellogg, R. M.
Chem. Soc. Rev. 2000, 29, 183–199.
12. Rosen, B. M.; Wilson, C. J.; Wilson, D. A.; Peterca, M.; Imam, M. R.; Percec, V.
Chem. Rev. 2009, 109, 6275–6540.
13. Percec, V.; Heck, J. J. Polym. Sci., Part A: Polym. Chem. 1991, 29, 591–597.
14. Laschat, S.; Baro, A.; Steinke, N.; Giesselmann, F.; Hagele, C.; Scalia, G.; Judele,
R.; Kapatsina, E.; Sauer, S.; Schreivogel, A.; Tosoni, M. Angew. Chem., Int. Edit.
2007, 46, 4832–4887.
15. Malthete, J.; Collet, A.; Levelut, A. Liq. Cryst. 1989, 5, 123–131.
16. (a) Percec, V.; Heck, J.; Tomazos, D.; Falkenberg, F.; Blackwell, H.; Ungar, G. J.
Chem. Soc., Perkin Trans. 1 1993, 2799–2811; (b) Chvalun, S. N.; Blackwell, J.;
Cho, J. D.; Kwon, Y. K.; Percec, V.; Heck, J. A. Polym. 1998, 39, 4515–4522.

46
L. Yang et al. / Carbohydrate Research 347 (2012) 40–46
17. (a) Gehringer, L.; Bourgogne, C.; Guillon, D.; Donnio, B. J. Am. Chem. Soc. 2004,
126, 3856–3867; (b) Rueff, J.; Barbera, J.; Marcos, M.; Omenat, A.; Martin-
Rapun, R.; Donnio, B.; Guillon, D.; Serrano, J. L. Chem. Mater. 2006, 18, 249–254.
18. Percec, V.; Won, B. C.; Peterca, M.; Heiney, P. A. J. Am. Chem. Soc. 2007, 129,
11265–11278.
24. (a) Percec, V.; Imam, M. R.; Peterca, M.; Wilson, D. A.; Heiney, P. A. J. Am. Chem.
Soc. 2009, 131, 1294–1304; (b) Percec, V.; Imam, M. R.; Peterca, M.; Wilson, D.
A.; Graf, R.; Spiess, H. W.; Balagurusamy, V. S. K.; Heiney, P. A. J. Am. Chem. Soc.
2009, 131, 7662–7677; (c) Peterca, M.; Percec, V.; Imam, M. R.; Leowanawat, P.;
Morimitsu, K.; Heiney, P. A. J. Am. Chem. Soc. 2008, 130, 14840–14852.
25. (a) Smaldone, R. A.; Moore, J. S. Chem. -Eur. J. 2008, 14, 2650–2657; (b) Gellman,
S. H. Acc. Chem. Res. 1998, 31, 173–180.
26. Shcherbina, M. A.; Zeng, X.; Tadjiev, T.; Ungar, G.; Eichhorn, S. H.; Phillips, K. E.
S.; Katz, T. J. Angew. Chem., Int. Ed. 2009, 48, 7837–7840.
27. (a) Kwon, Y. K.; Chvalun, S. N.; Blackwell, J.; Percec, V.; Heck, J. A.
Macromolecules 1995, 28, 1552–1558; (b) Kwon, Y. K.; Chvalun, S.; Schneider,
A.; Blackwell, J.; Percec, V.; Heck, J. A. Macromolecules 1994, 27, 6129–6132.
19. Tschierske, C. J. Mater. Chem. 2001, 11, 2647–2671.
20. Peerlings, H. W. I.; Meijer, E. W. Chem. - Eur. J. 1997, 3, 1563–1570.
21. Romagnoli, B.; Hayes, W. J. Mater. Chem. 2002, 12, 767–799.
22. Dubber, M.; Lindhorst, T. K. Chem. Commun. 1998, 1265–1266.
23. (a) Murer, P.; Seebach, D. Angew. Chem., Int. Edit. 1995, 34, 2116–2119; (b)
Seebach, D.; Lapierre, J.; Greiveldinger, G.; Skobridis, K. Helv. Chim. Acta 1994,
77, 1673–1688; (c) Seebach, D.; Lapierre, J.; Skobridis, K.; Greiveldinger, G.
Angew. Chem., Int. Edit. 1994, 33, 440–442.