Stereochemical effect of even-odd connecting links on supramolecular assemblies made of 1-glucosamide bolaamphiphiles

Article abstract of DOI:10.1021/ja961226y

Bolaamphiphiles with a 1-glucosamide-head group at each end, N,N'-bis(β-D-glucopyranosyl)alkane-1, n-dicarboxamide [Glc-NC(n)CN-Glc, n = 6, 9, 10, 11, 12, 13, and 14], have been synthesized. Self-assembled supramolecular structures in water strongly depend on whether n is even or odd, which respectively give rise to fibrous assemblies or planar platelets as well as amorphous solids. In connection with this even-odd effect of the hydrocarbon links, internal molecular arrangements of the solid fibers were investigated using FT-IR spectroscopy, X-ray diffraction and crystal analyses, and transmission electron microscopy. The oligomethylene groups of the Glc-NC(12)CN-Glc pack in a monoclinic or an orthorhombic mode in the fiber. We propose a possible self-assembled model based on a monolayer sheet, which is stabilized by hydrogen-bond networks via sugar-head and amide groups.

Full text of DOI:10.1021/ja961226y

2812
J. Am. Chem. Soc. 1997, 119, 2812-2818
Stereochemical Effect of Even-Odd Connecting Links on
Supramolecular Assemblies Made of 1-Glucosamide
Bolaamphiphiles
Toshimi Shimizu* and Mitsutoshi Masuda
Contribution from the Department of Organic Materials, National Institute of Materials and
Chemical Research, 1-1 Higashi, Tsukuba, Ibaraki 305, Japan
ReceiVed April 15, 1996. ReVised Manuscript ReceiVed January 22, 1997X
Abstract: Bolaamphiphiles with a 1-glucosamide-head group at each end, N,N′-bis(â-D-glucopyranosyl)alkane-1,
n-dicarboxamide [Glc-NC(n)CN-Glc, n ) 6, 9, 10, 11, 12, 13, and 14], have been synthesized. Self-assembled
supramolecular structures in water strongly depend on whether n is even or odd, which respectively give rise to
fibrous assemblies or planar platelets as well as amorphous solids. In connection with this even-odd effect of the
hydrocarbon links, internal molecular arrangements of the solid fibers were investigated using FT-IR spectroscopy,
X-ray diffraction and crystal analyses, and transmission electron microscopy. The oligomethylene groups of the
Glc-NC(12)CN-Glc pack in a monoclinic or an orthorhombic mode in the fiber. We propose a possible self-assembled
model based on a monolayer sheet, which is stabilized by hydrogen-bond networks via sugar-head and amide groups.
Introduction
phiphiles Glc-NC(n)CN-Glc (n ) 6, 9, 10, 11, 12, 13, and 14).
Very little is known about the molecular assemblies of glu-
cosamides12 in which the polysaccharide and protein interactions
are in some way combined. Furthermore, the relative orientation
of the two carbonyl dipoles13 should be controlled by the even
or odd number of carbons in the hydrocarbon links of the
bolaamphiphiles. We have recently revealed the hydrogen-bond
networks in the crystal structure of Glc-NC(11)CN-Glc.14 In
this paper, the formation of chiral assemblies is investigated
from the viewpoint of the even-odd effect of the connecting
links. Furthermore, we report internal molecular arrangements
of the self-assembled fibers.
Fibrous assemblies formed with synthetic amphiphiles1 have
recently provided a wide variety of well-defined and intriguing
nano- and microstructures.2 Particularly, enantiomeric am-
phiphiles are known to produce mirror image helices, whereas
racemates only give nonhelical platelets.2j,3-6 However, there
has been little investigation into a stereochemical effect of
even-odd hydrocarbon chains on chiral assemblies,7,8 as well
as their conformations in the fiber.9-11
To obtain crystalline fibers stabilized by multiple hydrogen
bonds, we have synthesized a series of 1-glucosamide bolaam-
X Abstract published in AdVance ACS Abstracts, March 1, 1997.
(1) Fuhrhop, J.-H.; Helfrich, W. Chem. ReV. 1993, 93, 1565-1582.
(2) For recent examples of molecular rods, see: (a) Pfannemueller, B.;
Welte, W. Chem. Phys. Lipids 1985, 37, 227-240. (b) Yanagawa, H.;
Ogawa, Y.; Furuta, H.; Tsuno, K. J. Am. Chem. Soc. 1989, 111, 4567-
4570. (c) Itojima, Y.; Ogawa, Y.; Tsuno, K.; Handa, N.; Yanagawa, H.
Biochemistry 1992, 31, 4757-4765. For molecular tubules, see: (d) Schnur,
J. M. Science 1993, 262, 1669-1676. (e) Harada, A.; Li, J.; Kamachi, M.
Nature 1993, 364, 516-518. (f) Thomas, B. N.; Safinya, C. R.; Plano, R.
J.; Clark, N. A. Science 1995, 267, 1635-1638. (g) Kimizuka, N.;
Kawasaki, T.; Hirata, K.; Kunitake, K. J. Am. Chem. Soc. 1995, 117, 6360-
6361. (h) Hartgerink, J. D.; Granja, J. R.; Milligan, R. A.; Ghadiri, M. R.
J. Am. Chem. Soc. 1996, 118, 43-50. (i) Shimizu, T.; Kogiso, M.; Masuda,
M. Nature 1996, 383, 487-488. For molecular scrolls, see: (j) Fuhrhop,
J.-H.; Demoulin, C.; Rosenberg, J.; Boettcher, C. J. Am. Chem. Soc. 1990,
112, 2827-2829. For molecular ribbons, see: (k) Shimizu, T.; Mori, M.;
Minamikawa, H.; Hato, M. J. Chem. Soc., Chem. Commun. 1990, 183-
185. (l) Imae, T.; Takahashi, Y.; Muramatsu, H. J. Am. Chem. Soc. 1992,
114, 3414-3419. (m) Shimizu, T.; Hato, M. Biochim. Biophys. Acta 1993,
1147, 50-58. (n) Frankel, D. A.; O’Brien, D. F. J. Am. Chem. Soc. 1994,
116, 10057-10069. (o) Endisch, C.; Bottcher, C.; Fuhrhop, J.-H. J. Am.
Chem. Soc. 1995, 117, 8273-8274.
Results and Discussion
Observation of Crystalline Fibers by Light Microscopy.
The bolaamphiphiles Glc-NC(n)CN-Glc (n ) 6, 9, 10, 11, 12,
13, and 14) proved to be soluble at least in hot water (up to
0.1% w/v for Glc-NC(14)CN-Glc at 70 °C, see Table 1).
However, they are insoluble in nonpolar solvents like chloroform
and hexane. When the saturated hot aqueous solutions of each
bolaamphiphile were allowed to slowly cool, they afforded
different types of crystalline and fibrous assemblies. Especially,
the fiber-growth feature strongly depends on both the lengths
of the alkylene chains and their even or odd carbon numbers.
The hexamethylene-group-spanned bolaamphiphile Glc-NC-
(6)CN-Glc is highly soluble in water at room temperature
(>50% w/v at room temperature, see Table 1). Upon successful
(3) Tachibana, T.; Yoshizumi, T.; Hori, K. Bull. Chem. Soc. Jpn. 1979,
52, 34-41.
(4) Nakashima, N.; Asakuma, S.; Kunitake, T. J. Am. Chem. Soc. 1985,
107, 509-510.
(5) Fuhrhop, J.-H.; Schnieder, P.; Rosenberg, J.; Boekema, E. J. Am.
Chem. Soc. 1987, 109, 3387-3390.
(6) Fuhrhop, J.-H.; Schnieder, P.; Boekema, E.; Helfrich, W. J. Am.
Chem. Soc. 1988, 110, 2861-2867.
(7) Yamada, N.; Kawasaki, M. J. Chem. Soc., Chem. Commun. 1990,
568-569.
(11) Terech, P.; Furman, I.; Weiss, R. G. J. Phys. Chem. 1995, 99, 9558-
9566.
(12) Fuhrhop, J.-H.; Koening, J. Membranes and Molecular Assemblies:
The Synkinetic Approach; The Royal Society of Chemistry: Cambridge,
1994.
(13) Leiserowitz, L.; Tuval, M. Acta Crystallogr., Sect. B 1978, 34,
1230-1247.
(14) Masuda, M.; Shimizu, T. Chem. Commun. 1996, 1057-1058.
(8) Yamada, N.; Okuyama, K.; Serizawa, T.; Kawasaki, M. J. Chem.
Soc., Perkin Trans. 2 1996, 2707-2714.
(9) Svenson, S.; Koening, J.; Fuhrhop, J.-H. J. Phys. Chem. 1994, 98,
1022-1028.
(10) Terech, P.; Rodriguez, V.; Barnes, J. D.; McKenna, G. B. Langmuir
1994, 10, 3406-3418.
S0002-7863(96)01226-7 CCC: $14.00 © 1997 American Chemical Society

1-Glucosamide Bolaamphiphiles
J. Am. Chem. Soc., Vol. 119, No. 12, 1997 2813
Table 1. Physical Properties of 1-Glucosamide Bolaamphiphiles and the Obtained Representative Morphologies of the Self-Assemblies from
Saturated Aqueous Solutions
bolaamphiphile
n
mp (°C)
solubility in water (w/v %)a
morphology
needle-like
amorphous solid
long thin fiber or gel fiber
twin and platelet
helical fiber
Glc-NC(6)CN-Glc
Glc-NC(9)CN-Glc
Glc-NC(10)CN-Glc
Glc-NC(11)CN-Glc
Glc-NC(12)CN-Glc
Glc-NC(13)CN-Glc
Glc-NC(14)CN-Glc
6
207.5-208.3 (dec)
212.6-217.6 (dec)
222.2-224.9 (dec)
213.4-220.4 (dec)
220.2-224.0 (dec)
226.3-227.3 (dec)
227.0-229.4 (dec)
>50 (at 25 °C)
ndb
9
10
11
12
13
14
ndb
0.52 (at 36 °C)
0.78 (at 36 °C)
0.11 (at 50 °C)
<0.1 (at 70 °C)
amorphous solid
“bow-tie”-like fiber or thin fiber
a Solubility was determined using constant-composition methods. b Not determined.
Elongation of the spanned alkylene chain by two methylene
groups allowed the formation of right-handed twisted or helical
ribbons from the bolaamphiphile Glc-NC(12)CN-Glc. They
are of light-microscopic dimensions. Their helical pitches vary
widely from 1 to 10 µm. This feature shows a good contrast
to uniform helical rods and ribbons of electron-microscopic
dimensions1 (Figure 2a). The obtained chiral structures will
come from both the amide hydrogen bond chains and the
stereoselective hydrogen bonds between the glucopyranosyl head
groups. Polarized light microscopy of the dried helical fibers
exhibited birefringence, indicative of an extended crystalline
structure (Figure 2b). The octaacetylated derivative of Glc-
NC(12)CN-Glc did not crystallize in any nonpolar solvents but
caused an extended gelation with, e.g., an ethyl acetate/n-hexane
mixture (1/4, v/v) or tetrachloromethane. This implies that the
existence of the free hydroxyl groups is responsible for the
effective fiber formation in water. The maximum width of the
ribbons is as large as 3 µm, and the length-to-width ratio reaches
to several thousands. It is noteworthy that several bifurcated
fibers were found (Figure 2c). During the course of fiber
growth, two thinner separate fibers grew independently with
twisting. The simultaneous occurrence of more than one
crystalline form is called polymorphism in crystal engineering.17
It is unknown whether the bifurcated fibers are derived from
conformational or orientational polymorphism. Presumably,
thermodynamic and kinetic contributions to crystal growth are
complicatedly connected. As will be detailed later, the undeca-
methylene-group-spanned bolaamphiphile Glc-NC(11)CN-Glc
also tends to afford crystal polymorphism evidenced by the
appearance of twin crystals. The chiral fiber formation of the
1-glucosamide bolaamphiphiles is thus delicately affected by
the chemical and physical conditions in the growing media.
Figure 1. (a) Needle-like fibers made of Glc-NC(6)CN-Glc observed
using polarized light microscopy (at 25 °C in water). (b) Flexible and
thin fibrous assemblies made of Glc-NC(10)CN-Glc observed using
polarized light microscopy (at 25 °C in water).
Dehydrated fibers made of Glc-NC(12)CN-Glc are somewhat
fragile but extremely stable for a long term (>1 year) at
temperatures lower than 220 °C in atmospheric pressure.
Differential scanning calorimetry showed that Glc-NC(12)CN-
Glc has no phase transition in water from 20 °C to 120 °C; no
melting occurs up to 220 °C. Many helical microstructures have
been obtained from chiral amphiphilic compounds. However,
most of them are stable under limited conditions in an aqueous
environment,2k,4 or they form gel fibers in nonpolar solvents.18,19
crystallization, it gave a common needle-like microcrystal
(Figure 1a). Helical structures can be randomly seen. On the
other hand, very flexible and long thin fibers, hundreds of
micrometers in length, were obtained in water from the
decamethylene-group-spanned bolaamphiphile Glc-NC(10)CN-
Glc (Figure 1b). The fiber morphologies apparently resemble
the noncovalently prepared organic fibers.15,16 Helical mor-
phologies can also be observed using the light microscope
although they are ill-defined. The formation of these thin fibers
competes with an extended hydrogelation by the same bolaam-
phiphiles, critically depending on the concentration, the cooling
rate, and preparation method of the sample. Even if we dissolve
the dehydrated hydrogels into water, no crystalline fibers can
be obtained.
We also found interesting “bow-tie”-like structures by the
self-assembly of Glc-NC(14)CN-Glc. High-powered polarized
light microscopy clearly revealed that several columnar as-
semblies grow and project radially from a central nucleus or
associate with each other (Figure 3). However, controlled slow
cooling and the subsequent slow evaporation of the saturated
aqueous solution gave twisted thin fibers for Glc-NC(14)CN-
Glc (cooling rate <0.1 °C/min).
(17) MacDonald, J. C.; Whitesides, G. M. Chem. ReV. 1994, 94, 2383-
2420.
(18) Hidaka, H. Colloid Surface 1991, 58, 1-7.
(19) Hanabusa, K.; Yamada, M.; Kimura, M.; Shirai, H. Angew. Chem.,
Int. Ed. Engl. 1996, 35, 1949-1951.
(15) Menger, F. M.; Lee, S. J. J. Am. Chem. Soc. 1994, 116, 5987-
5988.
(16) Nuckolls, C.; Katz, T. J.; Castellanos, L. J. Am. Chem. Soc. 1996,
118, 3767-3768.

2814 J. Am. Chem. Soc., Vol. 119, No. 12, 1997
Shimizu and Masuda
Figure 3. “Bow-tie”-like fibrous assemblies made of Glc-NC(14)-
CN-Glc observed using polarized light microscopy (at 25 °C in water).
This 1-glucosamide bolaamphiphile also forms long thin fibers by
careful cooling of the saturated aqueous solution.
Figure 4. Representative twin crystal formed with Glc-NC(11)CN-
Glc. Successfully obtained single crystal was subjected to X-ray crystal
analysis.14
axes of each platelet vary from 10° to 30°. X-ray crystal-
lographic analysis of the single crystal revealed a hydrogen-
bond-assisted layered structure.14 In the solid state, the alkylene
chains are arranged in an antiparallel pleated sheet. In addition,
cooperative and complementary hydrogen-bonding networks
stabilize the amphiphilic crystal structure via the sugar hydroxyl
and the amide groups.
Even-Odd Effect of Connecting Links. Table 1 sum-
marizes the light microscopic morphologies of the supra-
molecular structures from a series of 1-glucosamide bola-
amphiphiles. One notices an interesting tendency (Table 1);
the fibrous assemblies are formed when n is even, and platelets
or amorphous solids are formed when n is odd. On the other
hand, monoheaded enantiomeric amphiphiles are known to form
chiral fibers, whereas racemates precipitate as platelets without
any curvature.2j,3-6 These reports indicate that the chirality of
the amphiphiles strongly affect the curvature of the generated
molecular assemblies. However, in the present bolaamphiphile,
the stereochemistry of two terminal sugar-head groups are of
the same D-configuration. Therefore, the above tendency shows
the first example of this stereochemical effect by the even-
odd connecting links on the supramolecular assemblies.
Figure 2. (a) A wide variety of crystalline and right-handed helical
fibers made of Glc-NC(12)CN-Glc observed using polarized light
microscopy (at 25 °C in water). Periodical structures of the fibers are
denoted by arrows. (b) Polarized light micrographs of representative
dehydrated and right-handed fibers from Glc-NC(12)CN-Glc: (upper)
photographed through cross-polarized filters and (lower) through plane-
polarized filters. (c) Polarized light micrograph of a bifurcated dry
fiber from Glc-NC(12)CN-Glc.
In contrast to the fiber formation from the even-numbered
bolaamphiphiles Glc-NC(n)CN-Glc (n ) 6, 10, 12, and 14),
amorphous solids or planar platelets were formed from the
bolaamphiphiles Glc-NC(n)CN-Glc (n ) 9, 11, and 13) with
odd-numbered methylene carbons. Surprisingly, most of the
crystals (>90%) from Glc-NC(11)CN-Glc exist as a twin in
water. Figure 4 shows the stacked platelets with two different
directions of crystal growth. The angles between the two long
The crystal packing mode of Glc-NC(11)CN-Glc14 provides
valuable information about the networks and directions of the
amide hydrogen bond chains (Figure 5a). The molecules within
each layer are identical and related by translations, whereas the

1-Glucosamide Bolaamphiphiles
J. Am. Chem. Soc., Vol. 119, No. 12, 1997 2815
axes of the amide hydrogen bonds. Although no crystal
structures are yet available for the even-numbered 1-glucosamide
bolaamphiphiles, we have recently succeeded in the X-ray
single-crystal analysis of an even-numbered 1-D-galactosamide
derivative, N,N′-bis(â-D-galactopyranosyl)dodecane-1,12-dicar-
boxamide [Gal-NC(12)CN-Gal].20 If one does not take into
account the difference in the diastereomeric structures, these
two crystal structures will enable us to make reasonable
discussions about the even-odd effect of the connecting links.
The Gal-NC(12)CN-Gal molecules are found to pack in a
parallel sheet (Figure 5b). In addition, the connecting oligo-
methylene chains take an all-trans zigzag conformation. The
two carbonyl dipoles compensate each other within a molecule,
and eventually the antiparallel linear chains of hydrogen bonds
are formed in each molecule and within layer. Thus, the even-
odd effect of the hydrocarbon links would partly reflect the
difference in the relative orientation of the two carbonyl dipoles
within a molecule.
Characterization of Fiber Structures. As already men-
tioned, we obtained three dehydrated crystalline fibers for Glc-
NC(n)CN-Glc (n ) 6, 12, and 14) and one lyophilized gel fiber
for Glc-NC(10)CN-Glc. Furthermore, we have a single crystal
for Glc-NC(11)CN-Glc and crystalline powders for Glc-NC-
(n)CN-Glc (n ) 9 and 13). Although the crystallinities of the
obtained self-assemblies are not uniform, both a Fourier-
transform infrared spectroscopy (FT-IR) and powder X-ray
diffraction studies should be useful in the establishment of the
internal molecular arrangements of the fibrous assemblies.
Therefore, we focused our attention upon the influence of the
even-odd numbers of the methylene chains on the conformation
and their packing.
FT-IR Spectroscopy. FT-IR spectroscopy for the dehydrated
fibers from Glc-NC(n)CN-Glc (n ) 10, 12, and 14) showed
the appearance of the amide I and II bands at 1657-1659 and
1534-1551 cm-1, respectively (see Table 2). This finding
strongly supports the existence of the amide hydrogen bonds.
In addition, the peak frequencies of the amide I and II bands
clearly show an even-odd effect for the chain length (n)
(n g 11) (Figure 6). The absorption frequencies of the CdO
stretching band (amide I) should decrease with the hydrogen-
bond formation, whereas those of the N-H deformation band
(amide II) should increase. Therefore, it can be at least said
that the Glc-NC(n)CN-Glc molecules (n ) 12 and 14) form
weaker hydrogen bonding between the amide groups than the
odd-numbered derivatives (n ) 11 and 13). A similar even-
odd effect on the amide absorption bands has been reported for
the cast films of azobenzene containing amphiphiles.8
X-ray Diffraction. By taking advantage of the crystallinity,
we carried out low- and wide-angle powder X-ray diffraction
experiments with the dehydrated fibers and crystals from the
1-glucosamide bolaamphiphiles. The observed characteristic
diffraction data are also listed in Table 2. The low-angle
diffraction comes from the characteristic lattice repeat, i.e., the
long-range ordering of the bolaamphiphiles, whereas the wide-
angle region is indicative of the hydrocarbon chain packing,
i.e., the short-range ordering.
Representative X-ray diffraction diagrams are shown in Figure
7 for the dehydrated fibers from Glc-NC(n)CN-Glc (n ) 12,
13, and 14). The diffraction patterns of all the samples show
Bragg peaks typical of crystalline or solid systems. Each low-
angle region is characterized by one sharp and two narrow
reflections. By using Bragg’s equation, we deduced the
characteristic 2.45-, 2.61-, and 2.60-nm long spacing for the
fibers from Glc-NC(n)CN-Glc (n ) 12, 13, and 14, respec-
Figure 5. Crystal packing patterns of (a) Glc-NC(11)CN-Glc14 and
(b) Gal-NC(12)CN-Gal,20 viewed along the c-axis. The amide
hydrogen bond chains run roughly along the c-axis. The symbols (X)
and (.) represent the amide group in which the carbonyl oxygen atom
is placed below and above the plane, respectively.
molecules in successive layers have opposite orientations. The
layers are arranged in a pleated sheet. The directions of the
amide hydrogen bond chains are the same within the individual
layer and alternate between the layers. As a consequence, the
macrodipoles of the layers compensate each other. Namely,
when n is odd, the generated macrodipoles allow the layers to
extend through the planes that are perpendicular to the chain
(20) Masuda, M.; Shimizu, T. Unpublished results.

2816 J. Am. Chem. Soc., Vol. 119, No. 12, 1997
Shimizu and Masuda
Table 2. FT-IR Spectroscopic Absorption Bands and X-ray Diffraction Data for the Self-Assemblies from 1-Glucosamide Bolaamphiphiles
FT-IR data (cm-1
)
representative X-ray diffraction (nm)
short spacing packing mode
bolaamphiphile
sample nature
amide I
amide II
long spacing
Glc-NC(6)CN-Glc
Glc-NC(9)CN-Glc
Glc-NC(10)CN-Glc
Glc-NC(11)CN-Glc
Glc-NC(12)CN-Glc
Glc-NC(13)CN-Glc
Glc-NC(14)CN-Glc
dehydrated fiber
crystalline powder
dehydrated fiber
crystalline powder
dehydrated fiber
crystalline powder
dehydrated fiber
1657
1665
1659
1640
1659
1638
1657
1559, 1540
1557
1551
1547
1536
1549
1534
2.16
2.52
2.67
2.43
2.45
2.61
2.60
0.447
0.448
b
0.465
0.439
b
0.418
0.400
b
0.401
0.414
b
0.37
0.38
b
0.382
0.389
b
O
or M|
T|
Dha
T|
O
or M|
or M|
Dha
O
0.425
0.403
0.38
a Distorted hexagonal. b No well-defined peaks were obtained because of the broadening.
Figure 6. FT-IR peak frequencies of amide I and II bands as a function
of the chain length (n) of the 1-glucosamide bolaamphiphiles.
Figure 8. Dependence of both the fully extended molecular lengths
(L) and the d-spacings obtained from X-ray diffraction on the chain
length (n) of the 1-glucosamide bolaamphiphiles.
methylene carbons (n g 11). Taking into account an all-trans
conformation in all cases, one can presume that bolaamphiphiles
with a longer alkyl chain are arranged by inclining against a
layer plane within the fiber. In other words, the obtained
d-spacings correspond to either a thickness of a molecular sheet
or a diameter of a micellar rod. Within this monolayer sheet
or the micellar rod, the interlipid interval via the amide hydrogen
bonds would retain a certain backbone-backbone distance
(0.47-0.49 nm).13
In the wide-angle region, we observed remarkable differences
in the molecular packing of the hydrocarbon chains for the even-
and odd-numbered bolaamphiphiles (Table 2). Sharp reflections
appeared at 2θ corresponding to d ) 0.465, 0.401, and 0.382
nm in the diffraction diagram for the crystalline Glc-NC(11)-
CN-Glc. The occurrence of these three peaks corresponds to a
triclinic packing of the hydrocarbon chains, designated by
T//.21 The same packing mode was assumed for Glc-NC(9)-
CN-Glc based on the similarity of the peak occurrence. On
the other hand, we found another series of reflections, i.e., three
characteristic reflections at 2θ corresponding to d ) 0.439,
0.414, and 0.389 nm for the dehydrated fiber of Glc-NC(12)-
CN-Glc (Figure 7a). By comparison with the X-ray diffraction
data of related long-chain amphiphiles,22-24 we can propose an
orthorhombic (O ) or a monoclinic (M|) hydrocarbon-chain
packing for this fiber. Similar results were obtained for the
fibers from Glc-NC(n)CN-Glc (n ) 6 and 14) (see Table 2
and Figure 7c). In contrast, the broad and complicated
Figure 7. Powder X-ray diffraction diagrams of the dehydrated fibers
from Glc-NC(n)CN-Glc [(a) n ) 12, (b) n ) 13, and (c) n ) 14]. For
reference, the inserts represent related arrangements of the oligometh-
ylene chains.
tively). The long-range ordering for the assemblies from Glc-
NC(n)CN-Glc (n ) 6, 9, 10, and 11) was also similarly
evaluated and summarized in Table 2. The obtained 2.43-nm
d-spacing from Glc-NC(11)CN-Glc corresponds to the half size
of the b-axis in the crystal cell.14 This implies that the high
and sharp reflections at about ≈3.5° (2θ) will come from the
(020) plane. Figure 8 compares both the obtained d-spacings
and the estimated lengths (L) of the fully extended molecules
as a function of the chain length (n). The dependence of the
d-spacings significantly deviates from a linear relationship
between L and n (n g 11). It is noteworthy that the d-spacings
alternate between the even and odd numbers for the higher
(21) Vand, V. Acta Crystallogr. 1951, 4, 104-105.
(22) Goto, M. J. Jpn. Oil Chem. Soc. (YUKAGAKU) 1970, 19, 583-
599, and references cited therein.
(23) Goto, M.; Asada, E. Bull. Chem. Soc. Jpn. 1978, 51, 2456-2459.
(24) Garti, N.; Sato, K. Crystallization and Polymorphism of Fats and
Fatty Acids; Marcel Dekker: 1988.

1-Glucosamide Bolaamphiphiles
J. Am. Chem. Soc., Vol. 119, No. 12, 1997 2817
Figure 10. A possible self-assembling model based on the monolayered
chiral sheet of Glc-NC(12)CN-Glc. The hydrogen-bond networks
between the sugar-head groups are tentatively depicted by reference to
those in the crystal structure14 of Glc-NC(11)CN-Glc.
bolaamphiphiles pack side by side to form the monolayer sheet.
In addition, the molecules are tilting their hydrocarbon chains
against the monolayer plane. The inclination is estimated to
be 45-50° with respect to the plane normal. Their packing
modes in the fibers should be orthorhombic or monoclinic. As
for the intermolecular hydrogen bonds between the gluco-
pyranosyl groups, we can refer to the crystal structure of Glc-
NC(11)CN-Glc.14 According to the analysis, the atomic
distances between the hydroxyl oxygen at the 3- and 5-positions
(2.830 Å), at the 3- and 6-positions (2.911 Å), and at the 4-
and 6-positions (2.957 Å) are indicative of the existence of
intralayer and intermolecular hydrogen bonds. Similar hydrogen
bonds between the sugar-head groups could also be formed in
the fibers, contributing to the formation of the characteristic
helical fibers on the light microscopic scale.
Similarly, the combined attraction forces of the intermolecular
hydrogen bonds and hydrophobic interactions promote additional
association between the monolayered micellar rods. Fiber
formation via this self-assembling process is exemplified by the
R-amino-ω-lysine bolaamphiphile,25 arborols,26 and phospho-
lipids with a nucleotide-head group.2b,2c
In summary, the noncovalent construction of solid-like fibrous
assemblies by novel 1-glucosamide bolaamphiphiles have been
described. The chiral-achiral effect of the even and odd
connecting links on the supramolecular structures is reported
for the first time.
Figure 9. Transmission electron micrographs of (a) unstained fibrous
assemblies made of Glc-NC(12)CN-Glc and (b) negatively stained
fibers with 2%-phosphotungstic acid. When the width of the unstained
fiber is greater than 50 nm in length, helical morphologies can be
detected.
reflections indicate the existence of a disordered hexagonal
packing of the methylene chains for Glc-NC(n)CN-Glc (n )
10 and 13) (see Table 2 and Figure 7b). The above results
demonstrate that the hydrocarbon-chain packing within the fibers
from Glc-NC(n)CN-Glc (n ) 10, 12 and 14) is different from
that of the odd-numbered bolaamphiphiles (n ) 9 and 11).
Electron Microscopy. Polarized and phase-contrast light
microscopies demonstrate that the crystalline fibers formed with
Glc-NC(12)CN-Glc retain a characteristic helical microstruc-
ture. To explore the fine fiber structures, we carried out
transmission electron microscopy (TEM) for the unstained
fibers. The TEM clearly shows that the thinnest width of the
fiber is about 30-35 nm (Figure 9a). We found a wide variety
of fibers with nonuniform widths. The growth of a unit fiber
into higher ordered assemblies appears to be uncontrollable.
Helical morphologies are visible for the fibers with more than
a 50-nm width. The length of the fully extended Glc-NC(12)-
CN-Glc molecule is approximately 2.9 nm based on molecular
modeling (Figure 8). Therefore, the observed minimum width
(≈30 nm) of the fiber corresponds to the lengths of ten extended
bolaamphiphiles. Negatively stained fibers proved to retain a
helical morphology. The width of the thinnest specimen is about
35 nm (Figure 9b). A monolayered helical sheet structure can
be supported by the appearance of dark helical edges, whose
width is about 3 nm.
Experimental Section
General Methods. 1H-NMR spectra were recorded with a Bruker
AMX 300 spectrometer by using the 3-(trimethylsilyl)propionic acid-
d4 sodium salt as an internal standard for the aqueous solutions. For
the FT-IR and DSC measurements, a JASCO FT/IR-5300 spectrometer
(resolution ) 4 cm-1) and a Seiko Denshi SSC 560U calorimeter
(scanning rate ) 1.0°/min) were used, respectively.
Synthesis of 1-D-Glucosamide Bolaamphiphiles. The 1-D-glu-
cosamide bolaamphiphiles Glc-NC(n)CN-Glc (n ) 6, 9, 10, 11, 12,
13, and 14) were synthesized according to the following scheme. In a
typical synthesis, a commercially available acetobromo-R-D-glucose was
treated with sodium azide to give a crystalline â-1-azide derivative of
the tetraacetylated glucose. The stereochemical purity of this azide
Internal Molecular Arrangements of Fibers. We carried
out an FT-IR spectroscopy, X-ray diffraction study, and electron
microscopy for the dehydrated fibers from the 1-glucosamide
bolaamphiphiles. Consequently, we could collect several
evidence to depict a possible self-assembling model based on
the monolayered sheet structure. It is illustrated in Figure 10
for the fiber made of Glc-NC(12)CN-Glc. The 2.45-nm long
spacing represents the width of the monolayer sheet. The
1
was checked by H-NMR spectra. It clearly revealed the presence of
(25) Fuhrhop, J.-H.; Spiroski, D.; Boettcher, C. J. Am. Chem. Soc. 1993,
115, 1600-1601.
(26) Newkome, G. R.; Baker, G. R.; Arai, S.; Saunders, M. J.; Russo,
P. S.; Theriot, K. J.; Moorefield, N.; Rogers, L. E.; Miller, J. E.; Lieux, T.
R.; Murray, M. E.; Philips, B.; Pascal, L. J. Am. Chem. Soc. 1990, 112,
8458-8465.

2818 J. Am. Chem. Soc., Vol. 119, No. 12, 1997
Shimizu and Masuda
only one doublet with J ) ≈8.6 Hz for the anomeric proton, indicating
a 100% â-glycosidic linkage. This compound was hydrogenated in
the presence of platinum oxide into a â-1-amino derivative, which was
directly condensed with a corresponding long-chain R,ω-dicarboxylic
acid chloride (20-60% yield). Purification of the octaacetylated
derivatives by silica-gel column chromatography (eluent: chloroform/
methanol ) 20/1, V/V) and the succeeding deacetylation produced the
raw bolaamphiphiles. Purification by silica-gel column chromatography
(eluent: chloroform/methanol/water ) 6/4/1, V/V) affords the requisite
1-D-glucosamide bolaamphiphiles. The 100% â-configuration of each
bolaamphiphile was also confirmed by an anomer proton signal in 1H-
NMR spectra. The purity was confirmed by thin-layer chromatography
on silica gel plates (Merck F60 254) and MALD-TOFMS (Shimadzu/
Kratos KOMPACT MALDI III) using sinapinic acid as a matrix. 1H
NMR of Glc-NC(12)CN-Glc (300 MHz, D2O, 83 °C): δ 4.95 (d, J )
9.1 Hz, 2H, H-1), 3.88 (dd, J ) 11.9 and 2.0 Hz, 2H, H-6b), 3.72 (dd,
J ) 11.9 and 5.2 Hz, 2H, H-6a), 3.55 (dd, J ) 9.3 and 9.1 Hz, 2H,
H-3), 3.50 (m, J ) 8.8, 5.2, and 2.0 Hz, 2H, H-5), 3.42 (dd, J ) 9.3
and 8.8 Hz, 2H, H-4), 3.40 (dd, J ) 9.1 and 9.1 Hz, 2H, H-2), 2.32 (t,
J ) 7.3 and 7.4 Hz, 4H, -CH2CONH-), 1.61 (m, 4H, -CH2CH2-
instrument (TEAC MV-70) as a freeze picture and printed out using a
Color Video Copy Processor (Mitsubishi CP-2000). The overall
magnification on the picture monitor was from 1000X to 5500X.
Transmission Electron Microscopy. The unstained specimen for
the electron microscopy was prepared by supplying a drop of
supernatant in a fiber-containing dispersion onto a grid coated with a
conductive osmium plasma film.27,28 The grids were blotted off with
filter paper and dried in air. Negatively stained samples were prepared
using phosphotungstic acid (2%). A small amount of staining solution
was applied on the same carbon films and immediately drained off.
The transmission electron microscope was a Zeiss CEM-902 with an
accelerating voltage of 80 KV. The observation was carried out at
room temperature. The magnification was from 5000X to 130 000X.
X-ray Diffraction. Dehydrated samples of the fibrous assemblies
were prepared by the isolation of the fibers and their subsequent
lyophilization. The dried fibers were cautiously powdered. All powder
spectra were taken on a Rigaku RAD-C powder diffractometer using
graphite-monochromated CuKR radiation (40 KV, 30 mA). The spectra
were measured at room temperature between 1° and 41° in the 2θ/θ-
scan mode with steps of 0.01° in 2θ and 0.6-s measurement time per
step.
CONH), 1.30 (m, 16H, -CH2-). [R]25 ) -15.2 (c 0.303). Anal.
D
Calcd for C26H48N2O12: C, 53.78; H, 8.33; N, 4.82. Found: C, 53.90,
H, 8.33; N, 4.77. In the same way, the other purified bolaamphiphiles
gave satisfactory H-NMR spectra and elemental analyses.
Acknowledgment. This work was partly supported by the
New Energy and Industrial Technology Development Organiza-
tion (Advanced Industrial Technology Research, “Synthesis of
Polymer Objects”). We thank colleagues Dr. K. Yase for the
skillful electron microscopy and Dr. M. Goto for her valuable
discussion concerning the X-ray diffraction study.
1
Preparation of Solid-like Fibers and Light Microscopy. The
crystalline fibrous assemblies were formed by heating the saturated
aqueous solutions to 100 °C and slowly cooling them to room
temperature. The cooling rate was controlled within 1-2 °C/min, and
the aqueous solution was slowly evaporated. For the light microscopy
measurement, a drop of the dispersion containing the fibrous assemblies
was placed on the slide glass, covered with a coverslip, and sealed at
the edges with adhesive tape. The samples were examined using a
phase-contrast light microscope (Olympus BX50, UPlanF1 20X, 40X,
100X objective) and polarized light microscope (Olympus BX50,
LMPlanF1, 20X, 50X objective). The micrograph images were
recorded either by a highly sensitive camera with automatic exposure
adjustments (Olympus PM30) or a 3-CCD Color Video Camera
(Olympus CS520MD) equipped with variable gain and offset adjust-
ments and monitored on a 21-in. color monitor (Ikegami TM2150M).
The picture images were stored using a magneto-optical disk-drive
Supporting Information Available: Graphical data of the
molecular structures and the crystal packing of the Glc-NC-
(11)CN-Glc, Gal-NC(10)CN-Gal, and Gal-NC(12)CN-Gal
molecules (6 pages). See any current masthead page for
ordering and Internet access instructions.
JA961226Y
(27) Tanaka, A. J. Electron Microsc. 1994, 43, 177-182.
(28) Yase, K.; Horiuchi, S.; Kyotani, M.; Yamamoto, K.; Yaguchi, A.;
Futaesaku, Y.; Suwa, T.; Kakimoto, M.; Imai, Y. Jpn. J. Appl. Phys. 1996,
35, L657-L660.