A family of low-molecular-weight organogelators based on Nα,Nε-diacyl-l-lysine: effect of alkyl chains on their organogelation behaviour

Article abstract of DOI:10.1016/j.tet.2008.08.061

A family of low-molecular-weight organogelators based on N^α,N^ε-diacyl-l-lysine was synthesized by acylation of N^ε-dodecyl-l-lysine with acyl chlorides through the one-pot synthetic procedure and their organogelation properties were examined. These compounds functioned as an organogelator; especially, l-lysine derivatives possessing the branched alkyl groups are a better organogelation property. The NMR and IR studies demonstrate that the organogelation occurred through hydrogen bonding interactions between the amide groups and between the carboxy groups.

Full text of DOI:10.1016/j.tet.2008.08.061

Tetrahedron 64 (2008) 10395–10400
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Tetrahedron
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A family of low-molecular-weight organogelators based on Na,N3-diacyl-
-lysine:
L
effect of alkyl chains on their organogelation behaviour
*
Masahiro Suzuki , Mariko Yumoto, Hirofusa Shirai, Kenji Hanabusa
Graduate School of Science and Technology, Shinshu University, Ueda, Nagano 386-8567, Japan
a r t i c l e i n f o
a b s t r a c t
A family of low-molecular-weight organogelators based on Na,N3-diacyl-
L-lysine was synthesized by
Article history:
Received 1 August 2008
Received in revised form 20 August 2008
Accepted 20 August 2008
Available online 26 August 2008
acylation of N3-dodecyl-
L
-lysine with acyl chlorides through the one-pot synthetic procedure and their
organogelation properties were examined. These compounds functioned as an organogelator; especially,
-lysine derivatives possessing the branched alkyl groups are a better organogelation property. The NMR
L
and IR studies demonstrate that the organogelation occurred through hydrogen bonding interactions
between the amide groups and between the carboxy groups.
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
wide applications to industrial fields, it is desirable that gelators
can be simply, cheaply and effectively synthesized and are envi-
Supramolecular gels, which are a quasi-solid containing much
solvents and made by low-molecular-weight gelators, have
attracted much interest because of their unique properties and
potential applications as new soft materials.1–8 A supramolecular
gel is formed by entrapping solvents into a three-dimensional
network created by entanglement of non-covalently self-assem-
bled nanofibers, so-called supramolecular polymers and called
organogels for organic solvents and oils as well as hydrogels for
aqueous solutions.1–9 Recently, the academic research results have
been reported in various fields; the use as organic templates for the
fabrication of mesoporous polymer materials10 and nano-scaled
designed inorganic materials,11–14 and the application to liquid
crystalline,15–19 photochemistry20–29 and electrochemistry.30–33
On the other hand, low-molecular-weight gelators have de-
veloped not only in academic interests but also in industrial fields
such as cosmetics, health care, textile, foods and oil.1–8 For example,
12-hydroxystearic acid is one of the most famous gelators34 and has
ronmentally friendly materials (having features such as bio-
degradiation and non-toxicity). We have already reported some
easily preparable L
-lysine based organogelators (Scheme 1).39,41,42
Gelator A was synthesized through a two-step procedure and an
all-powerful organogelator that formed the organogels in many
organic solvents and oils.41 Gelator B was easily prepared by mixing
of the isocyanated L-lysine derivative and alkyl amine and func-
tioned as a good organogelator.39,42 For both systems, isocyanate
derivatives were used in the synthetic procedures although they
were commercially available (relatively cheap). In this paper, we
describe that the one-step preparation of Na,N3-bis(acyl)-
L-lysine
from commercially available N3-lauroyl-
L-lysine in aqueous solu-
tions and their organogelation behaviour.
H
N
H
N
H
N
C18H37
O
O
been used for the treatment of domestic waste oils. N-Lauroyl-
L-
O
CH3O
A
glutamic acid- -bis(n-butylamide) is in practical use for the
a,g
treatment of oil spill. Furthermore, for cosmetics, paints and foods,
some low-molecular-weight gelators are used as gelators and
thickeners. The gelators used in academic researches generally
have a complex structure and are prepared via multi-synthetic
steps. Such gelators are not suitable for large-scale applications
(industrial applications). In contrast, some gelators, which can be
simply and cheaply prepared, have been reported and they show
a good gelation ability for many organic solvents and oils.35–40 As
H
N
H
N
H
H
N
N
C12H25
O
O
B
O
CH3O
Scheme 1. L-Lysine based organogelators.
2. Results and discussion
All diacyl-
L
-lysine derivatives were prepared by mixing of
* Corresponding author. Tel.: þ81 268 21 5415; fax: þ81 268 21 5608.
E-mail address: msuzuki@shinshu-u.ac.jp (M. Suzuki).
commercially available N3-lauroyl-
L-lysine and alkanoyl chloride
0040-4020/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2008.08.061

10396
M. Suzuki et al. / Tetrahedron 64 (2008) 10395–10400
H
N
H
N
R
O
O
HO
O
1: R = n-C6H13
2: R = n-C12H25
4: R =
3: R =
5: R =
6: R =
Figure 1.
with a relatively high reaction yield. In addition, because these
syntheses were one-pot synthetic procedure and can also be car-
ried out at the large scale, it is suitable for industrial applications. In
these procedures, the reaction yield for each step was very high
(>98%) and total reaction yield was above 96% (Fig. 1).
Figure 2. TEM images of xerogels prepared from ethyl acetate gel of 1 (A) and 1,4-
dioxane gels of 2–6 (B–F).
The orgenogelation properties of 1–6 are listed in Table 1. These
compounds were readily soluble in alcohols and CHCl3. The orga-
nogelation properties significantly depended on the alkyl groups
linking to the Na position; the compounds, 3–6, having the
branched alkyl chains, showed the better organogelation ability43
than those of the linear alkyl chains (1 and 2). For 1 and 2, having
the linear alkyl chains, 1 had a relatively good organogelation
ability, and 2 (having long alkyl group) barely formed the organo-
gels. It is well-known that the organogelation ability depends on
a hydrophobic–hydrophilic balance of the molecule, namely, the
balance of polar hydrogen bonding units and non-polar alkyl chains
or that of strengths between hydrogen bonding and van der Waals
interaction.1–7,39,44 Because the difference of molecular structures is
the alkyl chain at the Na position in the present cases, the gelation
ability depends on the feature of their alkyl chains. Compound 1
has the suitable balance for organogelation, while the alkyl chain
length of 2 may be too long and tend to precipitate. Compounds 3–6
formed organogels in many organic solvents and oils such as
hydrocarbone, esters, ketones, cyclic ethers, aromatic solvents,
Table 1
Organogelation properties of 1–6 at 25 ꢀ
C
1
2
3
4
5
6
n-Hexane
c-Hexane
EtOH
AcOEt
Acetone
THF
1,4-Dioxane
Toluene
Nitrobenzene
DMSO
CH3CN
CCl4
Ins
d
d
15
45
d
d
45
3
Ins
d
d
d
P
Ins
d
d
30
20
20
25
40
40
d
P
45
25
P
30
45
10
P
30
10
Ins
40
d
30
40
15
Ins
1
20
13
d
18
35
d
30
3
3
7
d
30
25
10
15
10
35
d
P
d
15
15
30
15
20
10
15
P
20
8
4
20
8
8
6
6
5
7
5
3
15
15
3
d
7
35
10
d
P
PG
P
6
d
d
P
P
3
5
2
4
PC
15
30
d
10
10
d
15
40
Ins
6
20
10
d
30
2
g-BL
25
30
10
15
d
d
10
Ins
40
d
d
45
20
P
Oleic acid
Linseed oil
IPM
Liquid paraffin
Triolein
Silicone oil (KF56)
D4
Diesel oil
TEG
40
d
P
d
d
15
Ins
d
d
45
45
45
d
6
40
d
1
d
30
d
d
d
30
20
20
PEG400
MePEG550
PPG700
Values denote minimum gel concentration (MGC, g/L). Ins: insoluble; P: precipitate
after dissolution; PG: partial gel consisting of gel and solution; d: no gelation at
40 g/L; PC: propylene carbonate; g-BL: g-butyrolactone; IPM: myristic acid isopropyl
ester; D4: octamethylcyclotetrasiloxane; TEG: tetraethylene glycol; PEG400: poly-
ethylene glycol (MWz400); MePEG550: polyethylene glycol monomethyl ether
(MWz550); PPG700: polypropylene glycol (MWz700).
Figure 3. 1H NMR spectra of 1 (A) and 5 (B) in a mixture of CDCl3 and CCl4; CDCl3/CCl4
(vol/vol)¼100:0 (a), 70:30 (b), 50:50 (c), 30:70 (d) and 10:90 (e); [1]¼10 g/L, [5]¼5 g/L.

M. Suzuki et al. / Tetrahedron 64 (2008) 10395–10400
10397
Table 2
indication of restricted freedom of motion; therefore, it indicates
the presence of hydrogen bonding interaction.29,47–49 The similar
results were obtained for other compounds. In addition, the proton
of the carboxy group showed the similar shift; therefore, the in-
teraction of carboxy groups play an important role in the gelation.
Unfortunately, 1H NMR of an organogel cannot be measured, be-
cause of its long relaxation time of amide protons.
1H NMR data of 1 and 5 in CDCl3/CCl4
CDCl3/CCl4
COOH
Na–H
N3–H
1
5
100:0
70:30
50:50
30:70
9.91
10.03
10.53
8.00
6.79
6.86
6.94
7.03
6.00
6.16
6.30
6.42
100:0
70:30
50:50
30:70
90:10
d
6.83
6.85
6.90
7.10
7.23
6.01
6.24
6.29
6.78
7.07
Further detailed study was carried out using FTIR spectropscopy.
FTIR spectroscopy is extensively used to investigate the organo-
gelation because the IR spectrum of the gel state in addition to
solution and solid states can be obtained. Figure 4 shows the FTIR
spectra of 1 and 5 in CHCl3 solution and CCl4 gel and these data are
listed in Table 3. In the CHCl3 solution, the typical IR bands were
observed around 3445 cmꢁ1, 1658 cmꢁ1 and 1520 cmꢁ1, arising
from the non-hydrogen bonded amide groups. In contrast, the IR
peaks of the hydrogen bonded amide groups appeared around
3300 cmꢁ1,1640 cmꢁ1 and 1550 cmꢁ1 in the CCl4 gels. These results
indicate the presence of hydrogen bonding interaction between the
amide groups in the organogel. In the CCl4 gels, the IR peak of the
hydrogen bonded amide I was observed at 1637 cmꢁ1 for 1 and at
1650 cmꢁ1 for 5. The branched alkylated gelators have a different
hydrogen bonding pattern from the linear alkylated gelators.
Probably, this is induced by steric effect of the branched alkyl chain.
In addition, the FTIR measurements also provide information on
the alkyl groups, and we obtained interesting results. For 1–3, the
absorption bands of the asymmetric (nas) and symmetric (ns) CH2
stretching vibrations in the CCl4 gel were observed around
2920 cmꢁ1 and 2851 cmꢁ1, while these bands appear at a low fre-
quency compared with those of free alkyl chains in CHCl3
7.90
7.90
8.50
10.74
propylene carbonate and g-butyrolactone, vegetable and mineral
oils and glycols; especially, 6, which has the isostearic acid group
(2-heptylundecanoyl group), showed the best organogelation
ability among 1–6. For gelators having the linear alkyl chains, the
hydrophobic–hydrophilic balance of the gelator molecule is im-
portant for the organogelation. However, the organogelation ability
for 3–6 increased with the increasing carbon numbers of the
branched alkyl chains. These results imply that the formation of
supramolecular gels (molecular aggregation) depends on not only
the hydrophobic–hydrophilic balance of the gelator molecule but
also other factors such as the size of alkyl chains, van der Waals
radius and steric hindrance for aggregation.
It is well-known that a gelator molecule constructs nanoscale
superstructures such as nanofibers, nanoribbons and nanosheets in
a supramolecular gel.1 Figure 2 shows the transmission electron
microscopic (TEM) images of xerogels prepared from ethyl acetate
gel of 1 and 1,4-dioxane gels of 2–6. In all supramolecular gels,
these gelators formed a supramolecular nanofiber with a diameter
of 10–40 nm, and their entanglements created a three-dimensional
network. Similar images were observed for other organogels such
as acetone and toluene. Therefore, the organogelation occurs by
immobilizing solvents in the nanospaces in the three-dimensional
networks.
The hydrogen bonding and van der Waals interactions are main
driving forces for self-assembly of the gelators into nanofibers.1,45,46
The NMR spectra can reveal hydrogen bonding interaction. Figure 3
shows the typical 1H NMR spectra of 1 and 5 in a mixture of CDCl3
and CCl4, and the NMR data are listed in Table 2. Here, 1 and 5 are
soluble in CDCl3 and forms an organogel in CCl4. Two NMR signals
of the amide protons were observed at 6.79 and 6.00 for 1 as well as
at 6.83 and 6.01 for 5 in the CDCl3 solution, corresponding to the
free amide proton. With the increasing content of CCl4, these peaks
shifted to the lower field and broadened. Such lower field shift and
broadening of the NMR resonance peaks can be interpreted as an
[2929 cmꢁ1 nas, C–H) and 2856 cmꢁ1
( (ns, C–H)]. Such a low fre-
quency shift shows the strong interaction between the alkyl chains
(van der Waals interaction).43 On the other hand, the IR bands of
the CH2 stretching vibration of 4–6, having the branched alkyl
chains, were independent of solvents (almost the same band in the
CHCl3 solution as that in the CCl4 gel). Compared with those of the
solid states, these bands appear at high frequency. This fact implies
that the branched alkyl chains are relatively fluidic in the CCl4 gel
and their molecular packing is more random than that of the solid
state; i.e., van der Waals interaction between the branched alkyl
chains is weak (or non). The fluidity of the branched alkyl chains
may give large spaces for trapping of solvent molecules, which
leads to a more effective organogelation than 1–3.
As mentioned above, the NMR study showed the change in the
proton of the carboxy group when increasing CCl4 content, and the
contribution of the carboxy group to the organogelation (self-as-
sembly into nanofibers) was indicated. Therefore, we focus also the
IR bands of the carboxy group. As shown in Figure 4, the IR peaks
Figure 4. FTIR spectra of 1 (A) and 5 (B) in CHCl3 solutions (dotted line) and CCl4 gels (solid line); [1]¼[5]¼10 g/L.

10398
M. Suzuki et al. / Tetrahedron 64 (2008) 10395–10400
Table 3
a better organogelation property, especially, 6 is excellent gelator
FTIR data of 1 and 5 in CHCl3 solution and CCl4 gels
that form organogels in many organic solvents and oils. The NMR
and IR studies demonstrate that the driving forces for the organo-
gelation are mainly hydrogen bonding interactions between the
amide groups and between the carboxy groups. It is found that the
1
5
CHCl3
CCl4
CHCl3
CCl4
Amide A (
nas C–H
ns C–H
COOH (
Amide I (
Amide II (
n
N–H)
3445
2928
2856
1722
1657
1519
3309
2920
2850
1733
1637
1553
3446
2928
2856
1725
1658
1520
3290
2928
2855
1738
1650
1544
introduction of the branched alkyl chain into L-lysine decreases the
van der Waals interaction between the alkyl chains due to its large
van der Waals radius and gives large spaces in the three-di-
mensional networks. Because these gelators can simply and
cheaply be synthesized with high reaction yield and the synthetic
procedure can undergo in large scale, it is expected the application
for many industrial fields.
n
C]O)
C]O)
C]O)
n
n
were observed at 1722 cmꢁ1 for 1 and 1725 cmꢁ1 for 5 in the CHCl3
solution, while they shifted to high frequency in the CCl4 gel; i.e.,
1733 cmꢁ1 for 1 and 1738 cmꢁ1 for 5. These bands are almost the
same as those in the solid state. This result indicates that the hy-
drogen bonding pattern between the carboxy groups in the CHCl3
solution is different from that in the CCl4 gel and the solid state;
namely, the hydrogen bonding becomes weak in the CCl4 gel
compared with that in CHCl3 solution. It is assumed that the for-
mation of intermolecular hydrogen bonding interaction inhibits the
interaction of the carboxy groups. In contrast, for 6, the IR bands of
the carboxy group in CHCl3 solution and CCl4 gel hardly change
(1721 cmꢁ1 in CHCl3 and 1718 cmꢁ1 in CCl4 gel), indicating that they
have almost the same hydrogen bonding pattern of the carboxy
groups.
4. Experimental
4.1. General
4.1.1. Materials
N3-Lauroyl-
L-lysine was kindly supplied from Ajinomoto Co., Inc.
The other chemicals were of the highest commercial grade avail-
able and were used without further purification. All solvents used
in the syntheses were purified, dried or freshly distilled as required.
4.1.2. Typical synthetic procedure
N3-Lauroyl-
L-lysine (65.7 g, 0.2 mol) was dissolved in NaOH aq
The NMR and IR studies led us to propose the gelation mecha-
nism. For 1 and 2 having a linear alkyl chain, the hydrogen bonding
between the amide groups, relatively weak hydrogen bonding be-
tween the carboxy groups and van der Waals interactions are the
driving forces for self-assembly into the nanofibers and then
organogelation. This is similar to the results reported pre-
viously.1,39,44 On the other hand, for 4–6, the carboxy groups un-
dergo a relatively strong hydrogen bonding interaction because the
amide groups do not have the hydrogen bonding interaction in the
CHCl3 solution. After dissolution of the gelators (4–6) in CCl4, hy-
drogen bonding interactions between the amide groups and be-
tween the carboxy groups lead to the formation of three-
dimensional networks by the self-assembled nanofibers. In this
case, the steric effect of the branched alkyl chains hinders the van
der Waals interaction of the alkyl chains and provides large spaces;
as a result, the effective organogelation is achieved (Scheme 2).
solution (80 g/700 mL) and ethyl ether (500 mL) was added. Alka-
noyl chloride (0.3 mol) was slowly added to the ether layer. The
biphasic solution was vigorously stirred at 0 ꢀC for 4 h and then at
room temperature for 20 h. The resulting solution was carefully
acidified by concd HCl to ca. pH¼1. White precipitate was filtered,
washed with water and then dried. The crude product was purified
by recrystallization from EtOH/ether.
4.1.2.1. Na-Hexanoyl-N3-lauroyl-
L
-lysine (1). Yield 88%. IR (KBr):
N–H, amide A), 1733 cmꢁ1
C]O, –COOH),
C]O, amide I), 1555 cmꢁ1 N–H, amide II); 1H NMR
¼0.86–0.90 (m, 6H, CH3), 2.18 (t,
n
¼3311 cmꢁ1
(
n
(n
1638 cmꢁ1
(n
(d
(400 MHz, CDCl3, TMS, 25 ꢀC):
d
J¼7.3 Hz, 2H, CH2CONH), 2.24 (t, J¼7.0 Hz, 2H, NHCOCH2), 3.19–3.26
(m, 2H, NHCH2), 4.42–4.47 (m, 1H, CHNH), 6.30 (t, J¼5.6 Hz, 1H,
NaHCO), 6.85 (d, J¼7.3 Hz, 1H, CON3H), 9.37 (br, 1H; COOH). Ele-
mental analysis calcd (%) for C24H46N2O4 (426.63): C, 67.57; H,
10.87; N, 6.57. Found: C, 67.88; H, 10.99; N, 6.58.
3. Conclusions
4.1.2.2. Na,N3-Bis(lauroyl)-
L
-lysine (2). Yield 96%. IR (KBr):
N–H, amide A), 1713 cmꢁ1
C]O, –COOH),
C]O, amide I), 1557 cmꢁ1 N–H, amide II); 1H NMR
In conclusion, we reveal the preparation of a family of Na,N3-
n
¼3307 cmꢁ1
(
n
(n
diacyl-
on their organogelation behaviour. These compounds are prepared
by acylation of N3-dodecyl-
-lysine with acyl chlorides through the
one-pot synthetic procedure with low cost and high reaction yield.
-Lysine organogelators possessing the branched alkyl groups are
L-lysine based organogelators and effect of the alkyl chains
1645 cmꢁ1
(
n
(d
(400 MHz, CDCl3, TMS, 25 ꢀC):
d¼0.88 (t, J¼6.3 Hz, 6H, CH3), 2.18 (t,
L
J¼7.6 Hz, 2H, CH2CONH), 2.24 (t, J¼7.6 Hz, 2H, NHCOCH2), 3.17–3.29
(m, 2H, NHCH2), 4.51 (q, J¼4.8 Hz, 1H, CHNH), 6.22 (t, J¼5.6 Hz, 1H,
NaHCO), 6.82 (d, J¼7.6 Hz, 1H, CON3H), 10.63 (br, 1H, COOH).
L
Scheme 2. Organogelation mechanism.

M. Suzuki et al. / Tetrahedron 64 (2008) 10395–10400
10399
Elemental analysis calcd (%) for C30H58N2O4 (510.79): C, 70.54; H,
11.45; N, 5.48. Found: C, 70.66; H, 12.01; N, 5.55.
4.1.6. Gel strength
Samples wereprepared as follows:a mixture of aweighed gelator
in water (2 mL) in a sealed vial (15 mm in diameter) was heated at
90 ꢀC for 5 min. The resulting opaque solution was allowed to stand
at 25 ꢀC for 6 h. The gel strength was evaluated as the force necessary
to sink a cylinder bar (10 mm in diameter) 4 mm deep in the gel.
4.1.2.3. Na-Cyclohexylcarbonyl-N3-lauroyl-
L
-lysine (3). Yield 92%. IR
N–H, amide A), 1725 cmꢁ1
C]O, –COOH),
N–H, amide II); 1H NMR
¼0.88 (t, J¼6.6 Hz, 6H, CH3), 2.17–
(KBr):
n
¼3312 cmꢁ1
(
n
(n
1639 cmꢁ1 C]O, amide I), 1545 cmꢁ1
(n (d
(400 MHz, CDCl3, TMS, 25 ꢀC):
d
2.25 (m, 3H, CH2CONH, 1H, NHCOCH), 3.16–3.28 (m, 2H, NHCH2),
4.49 (q, J¼4.8 Hz, 1H, CHNH), 6.33 (t, J¼5.6 Hz, 1H, NaHCO), 6.74 (d,
J¼7.6 Hz, 1H, CON3H), 10.23 (br, 1H, COOH). Elemental analysis calcd
(%) for C25H46N2O4 (438.64): C, 68.45; H, 10.57; N, 6.39. Found: C,
68.49; H, 11.00; N, 6.34.
4.1.7. FTIR study
The FTIR spectroscopy was performed using the spectroscopic
cell with a CaF2 window and 50 m
m spacers operating at a 2 cmꢁ1
resolution with 32 scans for solution and gel states and KBr method
for solid states.
4.1.2.4. Na-2-Ethylhexanoyl-N3-lauroyl-
L
-lysine (4). Yield 86%. IR
N–H, amide A), 1736 cmꢁ1
C]O, –COOH),
N–H, amide II); 1H NMR
¼0.84–0.90 (m, 9H, CH3), 2.18 (t,
4.1.8. VT-IR study
An automatic temperature-control cell unit (Specac Inc., P/N
20730) with a vacuum-tight liquid cell (Specac Inc., P/N 20502, path
length 50 mm) fitted with CaF2 windows was used to measure the IR
spectra at different temperatures.
(KBr):
n
¼3308 cmꢁ1
(
n
(n
1641 cmꢁ1 C]O, amide I), 1546 cmꢁ1
(n (d
(400 MHz, CDCl3, TMS, 25 ꢀC):
d
J¼7.7 Hz, 2H, CH2CONH), 3.23 (t, J¼6.2 Hz, 2H, NHCH2), 4.51–4.55 (m,
1H, CH), 6.34–6.38 (m,1H, N3H), 6.74–6.78 (m,1H, NaH), 9.29 (br,1H,
COOH). Elemental analysis calcd (%) for C26H50N2O4 (454.69): C,
68.68; H, 11.08; N, 6.18. Found: C, 68.77; H, 11.22; N, 6.19.
Acknowledgements
This work is supported by a grant-in-aid for Global COE program
and Scientific Research (B) (No. 20350091) from the Ministry of
Education, Culture, Sports, Science and Technology of Japan, and
Research Foundation for the Electrotechnology of Chubu.
4.1.2.5. Na-3,5,5-Trimethylhexanoyl-N3-lauroyl-
L
-lysine (5). Yield 94%.
N–H, amide A),1734 cmꢁ1
C]O, –COOH),
N–H, amide II); 1H NMR
¼0.86–0.91 (m, 15H, CH3), 2.16–2.22
IR (KBr):
n
¼3312 cmꢁ1
(
n
(n
1638 cmꢁ1 C]O, amide I), 1553 cmꢁ1
(n (d
(400 MHz, CDCl3, TMS, 25 ꢀC):
d
(m, 2H, CH2CONH), 3.18–3.29 (m, 2H, NHCH2), 4.50 (br, 1H, CH), 6.19
(br, 1H, N3H), 6.83 (d, J¼7.3 Hz, 1H, NaH), 8.23 (br, 1H, COOH). Ele-
mental analysis calcd (%) for C27H52N2O4 (468.39): C, 69.19; H, 11.18;
N, 5.98. Found: C, 69.22; H, 11.55; N, 5.98.
Supplementary data
Supplementary data associated with this article can be found in
the online version, at doi:10.1016/j.tet.2008.08.061.
4.1.2.6. Na-2-Heptylundecanoyl-N3-lauroyl-
L
-lysine (6). Yield 94%.
N–H, amide A), 1736 cmꢁ1
C]O,
N–H, amide II);
¼0.85–0.89 (m, 9H, CH3),
References and notes
IR (KBr):
n
¼3303 cmꢁ1
(
n
(n
–COOH), 1638 cmꢁ1
(n
C]O, amide I), 1544 cmꢁ1
(d
1. Molecular Gels: Materials with Self-assembled Fibrillar Networks; Weiss, R. G.,
Terech, P., Eds.; Springer: Dordrecht, 2006.
1H NMR (400 MHz, CDCl3, TMS, 25 ꢀC):
d
2. Low Molecular Mass Gelators: Design, Self-assembly, Function; Fages, F., Ed.;
Topics in Current Chemistry; Springer: New York, NY, 2005; vol. 256.
3. Terech, P.; Weiss, R. G. Chem. Rev. 1997, 97, 3133–3159.
4. van Esch, J. H.; Kellogg, R. M.; Feringa, B. L. Angew. Chem., Int. Ed. 2000, 39,
2263–2266.
5. Estroff, L. A.; Hamilton, A. D. Chem. Rev. 2004, 104, 1201–1217.
6. Sangeetha, N. M.; Maitra, U. Chem. Soc. Rev. 2005, 34, 821–836.
7. de Loos, M.; Feringa, B. L.; van Esch, J. H. Eur. J. Org. Chem. 2005, 3615–3631.
8. George, M.; Weiss, R. G. Acc. Chem. Res. 2006, 39, 489–497.
9. Low Molecular Weight Organic Gelators, Special Issue; Smith, D. K., Ed.; Tetra-
hedron; 2007; 63, 7285–7494.
10. Suzuki, M.; Sakakibara, Y.; Kobayashi, S.; Kimura, M.; Shirai, H.; Hanabusa, K.
Polym. J. 2003, 34, 474–477.
11. Kobayashi, S.; Hamasaki, N.; Suzuki, M.; Kimura, M.; Shirai, H.; Hanabusa, K.
J. Am. Chem. Soc. 2002, 124, 6550–6551.
12. Llusar, M.; Roux, C.; Pozzo, J.-L.; Sanchez, C. J. Mater. Chem. 2003, 13, 442–444.
13. Jung, J. H.; Shinkai, S.; Shimizu, T. Chem. Mater. 2003, 15, 2141–2145.
14. Yang, Y.; Suzuki, M.; Kimura, M.; Shirai, H.; Hanabusa, K. Chem. Commun. 2004,
1332–1333.
2.12–2.20 (m, 3H, CH2CONH, NHCOCH), 3.23 (q, J¼6.8 Hz, 2H,
NHCH2), 4.51 (q, J¼6.7 Hz, 1H, CH), 6.20 (br, 1H, N3H), 6.65 (d,
J¼6.8 Hz, 1H, NaH), 8.31 (br, 1H, COOH). Elemental analysis calcd (%)
for C36H70N2O4 (594.95): C, 72.68; H, 11.86; N, 4.71. Found: C, 72.99;
H, 12.11; N, 4.77.
4.1.3. Instrumentation and techniques
The elemental analyses were performed using a Perkin–Elmer
series II CHNS/O analyzer 2400. The VT-IR spectra were recorded on
a JASCO FS-420 spectrometer. The TEM observations were carried
out using a JEOL JEM-2010 electron microscope at 200 kV. The FE-
SEM observation was carried out using a Hitachi S-5000 field
emission scanning electron microscope. The 1H NMR spectra were
measured using a Bruker AVANCE 400 spectrometer with TMS as
the standard. The UV–vis spectra were measured using a JASCO
15. Kato, T. Science 2002, 295, 2414–2418.
16. van Bruggen, M. P. B.; Lekkerkerker, H. N. W. Langmuir 2002, 18, 7141–7145.
17. Camerel, F.; Faul, C. F. J. Chem. Commun. 2003, 1958–1959.
18. Tong, X.; Zhao, Y.; An, B.-K.; Park, S. Y. Adv. Funct. Mater. 2006, 16, 1799–1804.
19. Mizoshita, N.; Kato, T. Adv. Funct. Mater. 2006, 16, 2218–2224.
20. de Jong, J. J. D.; Lucas, L. N.; Kellogg, R. M.; van Esch, J. H.; Feringa, B. L. Science
2004, 304, 278–281.
21. Ryu, S. Y.; Kim, S.; Seo, J.; Kim, Y.-W.; Kwon, O.-H.; Jang, J.-D.; Park, S. Chem.
Commun. 2004, 70–71.
22. Ikeda, M.; Takeuchi, M.; Shinkai, S. Chem. Commun. 2003, 1354–1355.
23. George, M.; Weiss, R. G. Chem. Mater. 2003, 15, 2879–2888.
24. Koshima, H.; Matsusaka, W.; Yu, H. J. Photochem. Photobiol., A: Chem. 2003,156, 83–90.
25. Tsou, C.-C.; Sun, S.-S. Org. Lett. 2006, 8, 387–390.
V-570 UV/VIS/NIR spectrophotometer with
controller (JASCO ETC-505T). The gel strength measurements were
performed using a Sun Science Sun Rheo Meter CR-500DX.
a temperature-
4.1.4. Gelation test
A weighed gelator in solvent (1 ml) in a sealed test tube was
heated until the gelator dissolved. After allowing the solutions to
stand at 25 ꢀC for 6 h, the state of the solution was evaluated by the
‘test tube inversion’ method.
26. Yagai, S.; Iwashita, T.; Kishikawa, K.; Nakahara, S.; Karatsu, T.; Kitamura, A.
Chem.dEur. J. 2006, 12, 3984–3994.
27. Tam, A. Y.-Y.; Wongm, K. M.-C.; Wang, G.; Yam, V. W.-W. Chem. Commun. 2007,
2028–2030.
28. Yang, H.; Yi, T.; Zhou, Z.; Zhou, Y.; Wu, J.; Xu, M.; Li, F.; Huang, C. Langmuir 2007,
23, 8224–8230.
29. Xue, P.; Lu, R.; Chen, G.; Zhang, Y.; Nomoto, H.; Takafuji, M.; Ihara, H. Chem.d
Eur. J. 2007, 13, 8231–8239.
4.1.5. Transmission electron microscope (TEM)
Samples of organogels were prepared as follows: benzene, 1,4-
dioxane or tetrachloromethane of the gelators were dropped on
a collodion- and carbon-coated 400 mesh grid and quickly dried in
vacuo for 24 h. After negative staining by osmic acid overnight, the
grids were dried under reduced pressure for 2 h.
30. Hanabusa, K.; Hiratsuka, K.; Kimura, M.; Shirai, H. Chem. Mater.1999,11, 649–655.

10400
M. Suzuki et al. / Tetrahedron 64 (2008) 10395–10400
31. Kubo, W.; Kambe, S.; Nakade, S.; Kitamura, T.; Hanabusa, K.; Wada, Y.; Yanagida,
S. J. Phys. Chem. B 2003, 107, 4374–4381.
32. Shibata, Y.; Kato, T.; Kado, T.; Shiratuchi, R.; Takashima, W.; Kaneto, K.; Hayase,
S. Chem. Commun. 2003, 2730–2731.
33. Li, X.-Q.; Stepanenko, V.; Chen, Z.; Prins, P.; Siebbeles, L. D. A.; Wu¨rthner, F.
Chem. Commun. 2006, 3871–3873.
34. Tachibana, T.; Mori, T.; Hori, K. Bull. Chem. Soc. Jpn. 1980, 53, 1714–1720.
35. Bhattacharya, S.; Krishnan-Ghosh, Y. Chem. Commun. 2001, 185–186.
36. Ballabh, A.; Trivedi, D. R.; Dastidar, P. Chem. Mater. 2003, 15, 2136–2140.
37. George, M.; Snyder, S. L.; Terech, P.; Glinka, C. J.; Weiss, R. G. J. Am. Chem. Soc.
2003, 125, 10275–10283.
41. Hanabusa, K.; Nakayama, H.; Kimura, M.; Shirai, H. Chem. Lett. 2000, 1070–1071.
42. Suzuki, M.; Nakajima, Y.; Yumoto, M.; Kimura, M.; Shirai, H.; Hanabusa, K.
Langmuir 2003, 19, 8622–8624.
43. In the present case, the gelation ability is regarded as the ability of the gelator
that can gel many kinds of organic fluids.
44. Suzuki, M.; Yumoto, M.; Kimura, M.; Shirai, H.; Hanabusa, K. Chem.dEur. J.
2003, 9, 348–354.
45. Timioka, K.; Sumiyoshi, T.; Narui, S.; Nagaoka, Y.; Iida, A.; Miwa, Y.; Taga, T.;
Nakano, M.; Handa, T. J. Am. Chem. Soc. 2001, 123, 11817–11818.
46. Sumiyoshi, T.; Nishimura, K.; Nakano, M.; Handa, T.; Miwa, Y.; Timioka, K. J. Am.
Chem. Soc. 2003, 123, 12137–12142.
38. Kiyonaka, S.; Shinkai, S.; Hamachi, I. Chem.dEur. J. 2003, 9, 976–983.
39. Suzuki, M.; Nakajima, Y.; Yumoto, M.; Kimura, M.; Shirai, H.; Hanabusa, K. Org.
Biomol. Chem. 2004, 2, 1155–1159.
47. Dunchan, D. C.; Whitten, D. G. Langmuir 2000, 16, 6445–6452.
48. Makarevic´, J.; Jokic´, M.; Raza, Z.; Stefanic´, Z.; Kojic´-Prodic´, B.; Zinic´, M. Chem.d
Eur. J. 2003, 9, 5567–5580.
ˇ
ˇ
40. D’Ale´o, A.; Pozzo, J.-L.; Fages, F.; Schmutz, M.; Mieden-Gundert, G.; Vo¨gtle, F.;
49. Suzuki, M.; Yumoto, M.; Kimura, M.; Shirai, H.; Hanabusa, K. Helv. Chim. Acta
2004, 87, 1–10.
Caplar, V.; Zinic, M. Chem. Commun. 2004, 190–191.