Chiral lariat ethers as membrane carriers for chiral amino acids and their sodium and potassium salts

Article abstract of DOI:10.1016/j.tetasy.2009.01.005

Four chiral lariat ethers 8-11 containing a (p-methoxyphenoxy) methyl side arm were used for chiral discrimination of amino acids in their zwitterionic form or as potassium and sodium salts in transport across a bulk chloroform membrane with satisfactory selectivity. The carriers that were employed exhibited different transport selectivity relative to the amino acids and their salts under study. The d/l selectivity strongly depends on the amino acids or their salts, and in some cases reverse selectivity has been obtained. The best selectivity was obtained in the case of tyrosine and its potassium salts for all carriers. The transport rates of amino acids and their salts were found to be controlled by factors such as the structure of the carriers and amino acids or their salts. Among these factors, it was also found that the side arm of the lariat ethers plays an important role in the transport process. As a consequence, the main goal of our investigation was to separate the chiral amino acids through liquid membranes.

Full text of DOI:10.1016/j.tetasy.2009.01.005

Tetrahedron: Asymmetry 20 (2009) 179–183
Contents lists available at ScienceDirect
Tetrahedron: Asymmetry
journal homepage: www.elsevier.com/locate/tetasy
Chiral lariat ethers as membrane carriers for chiral amino acids
and their sodium and potassium salts
*
I ßs ıl Aydın, Tarık Aral, Mehmet Karakaplan , Halil Ho ßs gören
Department of Chemistry, Faculty of Science, Dicle University, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
Four chiral lariat ethers 8–11 containing a (p-methoxyphenoxy) methyl side arm were used for chiral dis-
crimination of amino acids in their zwitterionic form or as potassium and sodium salts in transport across
a bulk chloroform membrane with satisfactory selectivity. The carriers that were employed exhibited dif-
Received 6 November 2008
Accepted 19 January 2009
Available online 11 February 2009
ferent transport selectivity relative to the amino acids and their salts under study. The D/L selectivity
strongly depends on the amino acids or their salts, and in some cases reverse selectivity has been
obtained. The best selectivity was obtained in the case of tyrosine and its potassium salts for all carriers.
The transport rates of amino acids and their salts were found to be controlled by factors such as the struc-
ture of the carriers and amino acids or their salts. Among these factors, it was also found that the side arm
of the lariat ethers plays an important role in the transport process. As a consequence, the main goal of
our investigation was to separate the chiral amino acids through liquid membranes.
Ó 2009 Elsevier Ltd. All rights reserved.
1
. Introduction
The enantiomeric discrimination of chiral organic molecules has
nature of crown ethers, the rigidity of the microenvironment of their
cavity, and the quality of the side arm are all expected to play an
important role in enantiomeric recognition. The attachment of a side
arm with potential cation coordination sites produces complexing
attracted considerable attention over the past two decades due to
an urgent need to develop analytical tools for monitoring the enan-
tiomeric purity of chiral species of biochemical, pharmaceutical,
and agrochemical relevance, as well as the methodology for sepa-
rating enantiomers for commercial purposes. Amino acids are
important bioactive substances. A study on transport selectivity
and the kinetics of amino acids through the liquid membrane
would be helpful for separation and in understanding the transport
process of amino acids through the cell membrane.
Supramolecular chemistry is principally based on the concept of
molecular recognition, which is defined as a process of selective
binding and selection of substrates by a receptor. A new system of
recognition and separation could take advantage of the functional
9
agents called lariat ethers. For some lariat ethers, the presence of
a flexible side arm with an electron donor site is known well to
enhance the binding ability of the ligand by the participation of this
additional donor group in the complexation, providing three dimen-
sional cavities.
Several studies have been reported on the transport of amino
1
0–15
acids using crown ethers by different techniques.
Calix[n]are-
nas have been employed for the selective transport of amino acid
1
6,17
18
methylesters
and amines, amino acids, and peptides. Gokel
et al. have reported the first enantioselective transport of Z-amino
+
acid and dipeptide K carboxylates through a bulk chloroform
1
9
membrane. Mendoza et al. reported the enantioselective trans-
1
20
features (binding and selections) of supramolecular species. Many
port of amino acids by guanidinium receptors. Amino acids and
studies were focused on the design and synthesis of a great variety
of functionalized macrocycles such as crown ethers, aza crown
ethers, cryptands, and calixarenes, which are able to recognize
and/or exhibit catalytic activities on biologically interesting ammo-
their sodium and potassium salts have been transported enanti-
oselectively through a liquid membrane by using chiral crown
1
0,21
ether derived from methyl
a
-D
-mannose
and chiral diaza-
2
2
crown ethers having arene side arm, respectively. In continuation
with our interest in this subject, we used one 15-crown-5 8 chiral
lariat ether and three 18-crown-6 9–11 chiral lariat ethers incorpo-
rating flexible donating side arm (p-methoxyphenoxy) methyl as a
chiral auxiliary, chosen due to its donor groups. Macrocycles 8–11
have been synthesized by ring closure of chiral subunit diol 1 pre-
pared from (S)-glycidol and p-methoxyphenol, as described in our
previous report, that exhibited good chiral recognition properties
2
–8
nium guests (amino acids, biogenic amines, and peptides).
The
attractive properties of synthetic macrocyclic receptors that are able
to form complexes with various compounds by non-covalent inter-
actions are used in understanding the phenomenon of biochemical
specificity, especially in the area of molecular recognition. The chiral
*
Corresponding author. Tel.: +90 4122488550; fax: +90 4122488039.
8
E-mail address: mkkaplan@dicle.edu.tr (M. Karakaplan).
toward amino acid methyl esters. Macrocycles 10 and 11 bear
0
957-4166/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2009.01.005

1
80
I. Aydın et al. / Tetrahedron: Asymmetry 20 (2009) 179–183
RO
RO
O
O
O
O
O
O
i
ii
OH + ROH
+
HO
OH
O
O
1
OTs
TsO
4
O
+
8
TsO
OTHP
2
RO
RO
RO
O
O
O
O
O
O
O
O
ii
O
O
ii
O
O
+
+
O
O
O
O
OH HO
O
OTs TsO
O
OTs TsO
3
7
6
+
OTs TsO
10
O
O
5
11
ii
O
O
O
OR
O
O
O
9
Scheme 1. R: p-MeOPh–, Reagents and condition: (i) piperidine hydrochloride, 70–80 °C, 4 h., (ii) NaH, THF, reflux, 56 h.
benzo and naphtho units as rigid and lipophilic groups, respec-
tively. The lariat crown ethers used in this study are shown in
Scheme 1.
Taking into account the transport experiments, it is clear that
the flux of -phenylglycine was found to be higher than that of
the -enantiomer, except in the case of host 11 for phenylglycine
Figs. 2–5). Conversely, with phenylalanine, hosts 9 and 10 enanti-
oselectively transport -phenylalanine over -phenylalanine (Figs.
and 4). However, the flux of -phenylalanine was found to be
higher than that of the -enantiomer for host 11 (Fig. 5). A high
selectivity was also found for phenylalanine, but a low and
D
L
(
L
D
2
. Results and discussion
3
D
L
In this study, chiral lariat hosts 8–11 have been prepared from
D/L
key intermediates 1 and 3 as shown in Scheme 1. Chiral subunit
diol 1 was synthesized by regioselective ring-opening reaction of
chiral glycidol, p-methoxyphenol, and catalytic amount of piperi-
dine hydrochloride in high enantiopurity. Chiral building block diol
reverse selectivity was found for its sodium and potassium salts
with the host 8 (Fig. 2). The reverse selectivity may be attributed
to the influence of the cation involved.
There is a good linearity between the selectivity for the
D-enan-
3
was prepared by the reaction of diol 1 and tosylate 2, which was
tiomers of tyrosine, over the -enantiomers for all hosts that were
L
obtained via monoprotection of ethylene glycol. Employed chiral
lariat hosts 8–11 were synthesized by a ring closure reaction of
chiral diols 1 and 3 and appropriate ditosylates 4–7 under high-
dilution conditions as described.8
Table 1 presents a set of transport data for phenylalanine,
phenylglycine, tyrosine, and tryptophan, and their sodium and
potassium salts, respectively. Four chiral lariat ethers bearing
investigated (Figs. 2–5). Not only are these regular correlations of
enantiomeric discrimination for tyrosine, but also the high flux val-
ues were obtained in the case of tyrosine. The tyrosine case
deserves particular attention, the highest enantiomeric discrimina-
tion was obtained for tyrosine and its potassium salt for all hosts
(Figs. 2–5). The much more pronounced enantioselectivity of tyro-
sine may be assessed with the three hydrogen bonding complexes
of tyrosine which contains the appropriate steric interactions that
cause specific conformational binding including the favorable p–p
interaction between flexible side arm of hosts and aromatic moiety
of guests. Many studies have reported the solid-state structures of
(p-methoxyphenoxy) methyl moiety, 15-crown-5 8, 18-crown 6
9, benzo-18-crown-6 10, and naphtho-18-crown-6 11 have been
employed as carriers in the chloroform membrane phase. The con-
centration of transported species was measured in the receiving
phase within 72 h.

I. Aydın et al. / Tetrahedron: Asymmetry 20 (2009) 179–183
181
Table 1
a,b
Transport data through liquid membrane
Amino acid
8
9
10
11
8
ꢁ2 ꢁ1
8
ꢁ2 ꢁ1
8
ꢁ2 ꢁ1
8
ꢁ2 ꢁ1
J
72 ꢀ 10 (mol m
s
)
a
T
J
72 ꢀ 10 (mol m
s
)
a
T
J
72 ꢀ 10 (mol m
s
)
a
T
J
72 ꢀ 10 (mol m
s
)
a
T
L
-PhGly
-PhGly
-PhGlyNa
-PhGlyNa
-PhGlyK
-PhGlyK
-PhAla
-PhAla
-PhAlaNa
-PhAlaNa
-PhAlaK
-PhAlaK
-Tyr
-Tyr
-TyrNa
-TyrNa
-TyrK
-TyrK
-Trp
-Trp
-Trp Na
-TrpNa
-Trp K
4.23
9.24
6.58
10.32
3.54
18.18
31.26
8.95
2.18
14.84
20.94
3.83
14.35
2.45
1.41
3.74
4.49
3.31
1.31
2.10
3.45
1.04
3.48
1.13
1.67
1.07
3.64
10.12
5.70
15.04
2.95
36.27
35.58
13.27
34.99
21.13
24.67
17.89
7.96
38.73
16.81
48.26
7.18
37.45
6.59
6.29
44.53
24.77
39.61
40.30
2.78
35.87
18.48
8.94
21.33
6.59
14.84
8.75
25.16
9.63
25.85
12.98
27.03
2.56
39.81
48.36
48.46
2.75
38.83
13.07
8.45
50.03
32.54
39.90
44.33
1.94
2.39
2.25
2.87
2.68
2.08
D
L
1.57
5.14
3.49
2.66
1.27
2.64
D
L
12.29
2.68
1.65
1.38
4.86
2.87
5.22
1.05
1.80
1.02
D
11.01
36.07
10.91
20.74
15.83
25.56
12.19
11.01
38.04
46.39
48.26
10.81
37.65
5.03
L
D
L
4.92
D
13.07
11.21
14.25
3.05
41.87
34.40
48.36
4.62
38.34
3.54
3.24
50.23
28.80
39.32
38.83
L
D
L
13.73
1.41
8.30
1.09
1.74
1.01
15.55
1.00
D
L
D
L
14.12
1.55
1.54
1.11
D
L
D
4.42
L
44.72
26.74
28.60
30.57
D
L
D
-Trp K
a
Transport experiments were obtained from three replicates, and estimated errors are <12%.
b
ꢁ2 ꢁ1
J
72 = Flux of transported amino acids after 72 h (mol m
T
s ); a = ratio of fluxes: higher/lower flux; PhGly = phenylglycine; PhAla = phenylalanine; Tyr = tyrosine;
Trp = tryptophan.
6
5
4
3
0
0
0
0
L
D
(
c)
(a)
20
1
0
0
Figure 2. Bar plots of fluxes of amino acids and their salts for host 8.
(
b)
6
5
4
0
0
0
L
Figure 1. Transport apparatus and detailed experimental conditions. (a) Source
D
ꢁ
3
phase (2 mL): amino acid or its salts (4 ꢀ 10 M) (by adding NaOH or KOH
ꢁ
3
(
4 ꢀ 10 M). (b) Organic carrier phase (2 mL): chloroform; carrier: lariat crown
ꢁ3
ethers (8–11) (2 ꢀ 10 M). (c) Receiving phase (2 mL): pure water.
30
2
0
0
0
lariat ether complexes in which the cation is
p
-coordinated by phe-
1
8,19
20
+
1
nyl,
for the Na arene interaction. In general, the higher enantioselec-
tivity of potassium salts can be explained by apical- or a sand-
phenol, or indoles with K ; few data have been reported
+
p
wich-type supramolecular complex which also causes specific
conformational binding as mentioned for tyrosine due to its larger
size. The tyrosine sodium salt is probably transported as a counter-
ion of phenolate ion in which the stereogenic center of tyrosine salt
orientated out of the complex; therefore, in this case the enantiose-
lectivity cannot be observed.
Figure 3. Bar plots of fluxes of amino acids and their salts for host 9.
potassium salt for host 11, where the situation is reversed. As in
the case of reversed situation of tyrosine, the enantiomeric
discrimination of tryptophan sodium salt was obtained moderately
higher than that of tryptophan and its potassium salt, which were
Taking into account the transport experiments of tryptophan
and its salts, it is clear that the flux of
L-trptophan is somewhat
higher than that of the -enantiomer for all hosts, opposite to its
D

1
82
I. Aydın et al. / Tetrahedron: Asymmetry 20 (2009) 179–183
60
50
40
30
20
10
0
agreement with those observations of solid-state lariat ether
complexes including side arm participation in metal–cation com-
L
2
3–25
D
plexation,
and increased stability constant in solution com-
9
pared with corresponding crown ether ligands. Thus, the highly
selective transport of amino acids and their salts was achieved as
zwitterionic forms via the three hydrogen bonds of the protonated
ammonium and the charge interactions of metal carboxylate with
chiral lariat ethers 8–11, respectively.
3
. Conclusion
In conclusion, liquid membranes are often used to simulate the
Figure 4. Bar plots of fluxes of amino acids and their salts for host 10.
membrane transport of organics of biological interest (amino acids,
organic acids, nucleotides, etc.) by employing macrocyclic recep-
tors, lipophilic charged carriers, or chiral receptors (for enantiose-
lective separations) as selective carriers. These membranes display
a high selectivity due to a specific complexation (hydrogen bond-
ing, electrostatic or hydrophobic interactions) of a solute by the
selective carriers. We have shown that lariat ethers 8–11 with a
flexible side arm not only increase the fluxes of amino acids, in
both zwitterionic and metal carboxylate forms, but also provide a
satisfactory enantiomeric discrimination as well. It is essential that
the complexation should occur from the more sterically hindered
side of the macrocyclic rings to effect steric discrimination interac-
tions between chiral auxiliary and the chiral guest molecules.
6
5
4
3
2
1
0
0
0
0
0
0
0
L
D
4
4
. Experimental
.1. Apparatus
Figure 5. Bar plots of fluxes of amino acids and their salts for host 11.
Melting points were determined with GALLENKAMP Model (UK)
apparatus with open capillaries. Infrared spectra were recorded on a
_
found to be quite low for all hosts. Noteworthy results were also
obtained for tryptophan when compared with its sodium and
potassium salts (Figs. 2–5). The lowest transport rate of tryptophan
indicated that intra-molecular hydrogen bonding or ion-dipole
interaction of zwitterionic form of tryptophan lead to no supramo-
lecular complexation between hosts 8–11. However, the sodium
and potassium salts of tryptophan were probably transported as
the counterion of non-specific conformational binding complexes
between the metal cation and hosts that also include more favor-
MIDAC-FTIR Model 1700 (Costa Mesa, CA, USA) spectrophotometer.
The elemental analyses were performed with CARLO-ERBA Model
1
13
1108 (Rodano, Milan, Italy) apparatus. H NMR (400 MHz) and
C
NMR (100 MHz) spectra were recorded on a BRUKER DPX-400
high-performance digital FT-NMR (Bremen, Germany) spectrome-
ter, with tetramethysilane as the internal standard solution in deu-
teriochloroform. Optical rotations were recorded by using PERKIN
ELMER Model 341 (Beaconsfield, Bocks, UK) polarimeter. UV analy-
sis for transport experiments were performed with PERKIN ELMER
Lambda 35 UV (Beaconsfield, Bocks, UK) spectrometer. All chemicals
were of reagent grade unless otherwise specified. THF was dried (on
sodium benzophenone ketyl) and distilled prior to use.
able p–p interactions as mentioned above for the tyrosine sodium
salt than in the cases of the phenylglycine and phenylalanine.
There are many factors that favor the complexation strength,
such as (i) solvent polarity, (ii) a good size correspondence between
guest and host, (iii) lack of strain in the host, and (iv) the presence of
donor groups in the host and in the side arm which are appropriate
fortheguest. Althoughthepotassiumand sodiumionsformstronger
complexes with 18-crown-6 and 15-crown-5, respectively, there is
unlikely to be a correlation between the cation size and enantiose-
lectivity. This result is in agreement with those of a previous
4.2. Synthesis
Compounds 1–7 were synthesized as described in our previous
8
report.
4.2.1. (S)-2-[(4-Methoxyphenoxy)methyl]-15-crown-5 8
2
1
report. The results also show that no significant
exists between the aromatic residue of the amino acid and receptors
0 and 11, having benzo and naphtho units related to hosts 8 and 9.
p
–
p
interaction
To a suspension of 0.88 g (29.00 mmol 80% in mineral oil) of
NaH in 150 mL of the dry THF at 0 °C was added a solution of
(S)-3-(p-methoxyphenoxy)-1,2-propanediol 1 (1.30 g, 6.56 mmol)
in 250 mL of THF. The reaction mixture was refluxed for 2 h. After
cooling to 0 °C, a solution of tetra (ethylene glycol) di-(p-toluene-
sulfonate) (3.29 g, 6.56 mmol) in 250 mL of THF was slowly added.
The suspension was refluxed for 48 h. The solvent was evaporated
after adding 100 mL of water to the residue. The mixture was
1
However, benzo-andnaphtho-18-crown-610and11generallyhave
a better flux of phenylglycine or its salts than hosts 8 and 9. This indi-
cates a strong p–p stacking interaction. The investigated carrier sys-
tems exhibited satisfactory transport rates and enantiomeric
discriminations for all amino acids and their salts when compared
with the previously reported data.1
0,21,22
It is difficult to say that
extracted with CH
ers were washed with 50 mL of water and dried over MgSO
2 2
Cl
(4 ꢀ 20 mL), and the combined organic lay-
the transport rates depend on the hydrophobicity of the amino acids
4
, and
1
7
as the opposite statement was reported by the previous report.
These results significantly indicate the influence of side arm which
might be providing steric hindrance, and cation– and stacking
interactions by its electron donor capacity. These results are also in
the solvent was evaporated. The crude product was purified by col-
umn chromatography (eluent: EtoAc/hexane/triethylamine: 5/5/1)
3
D
0
p
p
–p
to yield 0.91 g (39%) of pure product as a viscous oil. ½
aꢂ
¼ ꢁ14:0
1
3
(c 7.0, CHCl ). H NMR d (ppm): 3.64–4.03 (m, 24H); 6.81–6.88 (m,

I. Aydın et al. / Tetrahedron: Asymmetry 20 (2009) 179–183
183
4
7
6
1
6
H); 13C NMR d (ppm): 153.89, 153.06, 115.60, 114.60, 78.17,
quid membrane consisted of 2 mL of chloroform containing the
ꢁ3
6.72, 71.09, 70,83, 70,79, 70.56, 70.54, 70.48, 70.41, 68.97,
crown ethers 8–11 at a concentration of 2 ꢀ 10 M. The mem-
brane was stirred magnetically at 300 rpm. The source phase
(2 mL) contained the amino acid, or its salt at a concentration of
ꢁ1
8.42, 55.73. IR
m (cm ): 3043, 2940, 2874, 1602, 1509, 1463,
233, 1133, 1041, 941, 829, 743. Anal. Calcd for C18
28 7
H O : C,
ꢁ3
0.66; H, 7.87. Found: C, 60.45; H, 7.95.
4 ꢀ 10 M. The receiving phase was 2 mL of pure water. Blank
tests indicated that the transport of amino acids was negligible.
The concentration of the amino acids and their salts in the receiv-
ing phase and the source phase was assessed by UV spectropho-
tometer. The transport apparatus and detailed experimental
conditions are shown in Figure 1.
4
.2.2. (S)-2-[(4-Methoxyphenoxy)methyl]-18-crown-6 9
Compound 9 was prepared in a manner similar to that described
for the preparation of (S)-8 by using diol 3 (1.45 g, 5.00 mmol) and tri
(
ethylene glycol) di(p-toluenesulfonate) (2.80 g, 5.00 mmol) to give
3
D
0
1
0
6
1
7
3
9
.35 g, (18%) of pure 9. ½
a
ꢂ
¼ ꢁ8:8 (c 4.66, CHCl
3
). H NMR d (ppm):
13
.71–6.78 (m, 4H); 3.54–3.97 (m, 28H) C NMR d (ppm): 153.84,
Acknowledgment
52.99, 115.53, 114.55, 77.82, 77.74, 77.34, 71.31, 70.96, 70.85,
ꢁ
1
0.83, 70.72, 70.69, 70.65, 70.10, 68.67, 67.90, 55.68. IR
049, 2937, 2871, 1602, 1516, 1470, 1358, 1290, 1238, 1120, 1041,
88, 948, 829,750. Anal. Calcd for C20 : C, 60.0; H, 8.00. Found:
m
(cm ):
This research was supported by the Research Project Council of
Dicle University (DÜAPK) (Project No.: DÜAPK-04-FF-50).
32 8
H O
C, 59.87; H, 8.11.
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.
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4
.2.3. (S)-12-[(4-Methoxyphenoxy)methyl]-2,3-benzo-18-
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,3-bis-[2-(p-tolylsulfonyl)ethoxy]benzene (1.77 g, 3.50 mmol) to
2.
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1
.
Vögtle, F.; Wallon, A.; Müller, W. M.; Werner, U.; Nieger, M. J. Chem. Soc., Chem.
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2
give 0.20 g (12%) of pure 10as a viscous oil, which was purifiedby sil-
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9
3
D
0
1
EtOAc/triethylamine: 80/17/3). ½
a
ꢂ
¼ ꢁ2:7 (c 2.0, CHCl
3
). H NMR
d (ppm): 3.71–3.84 (m, 12H); 3.89–4.01 (m, 8H); 4.15–4.20 (m,
4
1
7
5
1
7
H); 6.78–6.85 (m, 4H); 6.90–6.94 (m, 4H). 13C NMR d (ppm):
52.96, 151.94, 149.43, 121.63, 114.31, 113.85, 113.38, 73.80,
1.93, 70.95, 70.42, 70.02, 69.97, 69.88, 69.32, 67.52, 67.34, 66.82,
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9
.
.
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ꢁ
1
4.20. IR
m
(cm ): 3069, 2924, 2871, 1615, 1509, 1451, 1233,
133, 1041, 935, 829, 750. Anal. Calcd for C24
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Recognit. Chem. 1998, 30, 69–77.
32 8
H O : C, 64.28; H,
1
1
1
1. Barboiu, M.; Guizard, C.; Hovnanian, N.; Palmeri, J.; Reibel, C.; Cot, L.; Luca, C. J.
Membr. Sci. 2000, 172, 103.
2. Barboiu, M.; Guizard, C.; Hovnanian, N.; Cot, L. Sep. Purif. Technol. 2001, 25,
.14. Found: C, 64.38; H, 7.24.
211–218.
4
.2.4. (S)-12-[(4-Methoxyphenoxy)methyl]-2,3-naphtho-18-
3. Buscmann, H.-J.; Mutihac, L.; Jansen, K. J. J. Inclusion Phenom. Mol. Recognit.
Chem. 2001, 39, 1–11.
crown-6 11
Compound 11 was prepared in a manner similar to that de-
scribed for the preparation of (S)-9 by using diol 3 (1.45 g,
.00 mmol) and 2,3-bis-[2-(p-tolylsulfonyl)ethoxy]naphthalene 4
2.72 g, 5.00 mmol) to give 0.30 g (12%) of pure 11 as a white solid,
which was purified by crystallization in ethanol, mp 88–89 °C.
14. Buscmann, H.-J.; Mutihac, L. Anal. Chim. Acta 2002, 466, 101–108.
1
1
1
5. Pichler, U.; Scrimin, P.; Tecilla, P.; Tonellato, U.; Veronese, A.; Verzini, M.
Tetrahedron Lett. 2004, 45, 1643–1646.
6. Mutihac, L.; Mutihac, R. J. Inclusion Phenom. Macrocycl. Chem. 2007, 59, 177–
181.
5
(
7. Oshima, T.; Inoue, K.; Furusaki, A.; Goto, M. J. Membr. Sci. 2003, 217, 87–97.
3
D
0
1
18. Mutihac, L.; Buscmann, H.-J.; Mutihac, R.-C.; Schollmeyer, E. J. Inclusion
Phenom. Macrocycl. Chem. 2005, 51, 1–10.
19. Zinic, M.; Frkanec, L.; Skaric, V.; Trafton, J.; Gokel, G. W. J. Chem. Comp. 1990,
1726–1728.
½
a
7
ꢂ
¼ ꢁ8:6 (c 3.76, CHCl
3
). H NMR d (ppm): 7.58–7.56 (dd, 2H);
.16–7.25 (dd, 2H); 7.01–7.02 (d, 2.8 Hz, 2H); 6.60–6.69 (m, 4H);
.12–4.20 (m, 4H); 3.80–3.94 (m, 8H); 3.59–3.75 (m, 12H).
1
3
4
C
2
0. Breccia, P.; Van Gool, M.; Perez-fernandez, R.; Martin-Santamaria, S.; Gago, F.;
Prados, P.; de Mendoza, C. J. Am. Chem. Soc. 2003, 125, 8270–8284.
1. Pietraszkiewicz, M.; Kozbial, M.; Pietraszkiewicz, O. J. Membr. Sci. 1998, 138,
109–113.
NMR d (ppm): 153.83, 152.97, 149.12, 149.10, 129.33, 129.31,
1
7
2
26.33, 124.18, 115.48, 106.87, 78.01 71.59, 71.32, 71.13, 71.03,
2
ꢁ1
0.23, 69.55, 69.41, 68.80, 68.68, 68.46, 55.66. IR
931, 2884, 1610, 1516, 1457, 1240, 1120, 1060, 941, 823, 743.
: C, 67.46; H, 6.82. Found: C, 67.05; H, 6.42.
m (cm ): 3056,
2
2
2. Demirel, N.; Bulut, Y.; Ho sß gören, H. Tetrahedron: Asymmetry 2004, 15, 2045.
3. (a) Atwood, J. L.; Crissinger, K. D.; Rogers, R. D. J. Organomet. Chem. 1978, 155,
34 8
Anal. Calcd for C28H O
1
4
–14; (b) Hrncir, D. C.; Rogers, R. D.; Atwood, J. L. J. Am. Chem. Soc. 1981, 103,
277; (c) Atwood, J. L. Inclusion Phenom. 1985, 3, 13.
24. Muraoka, M.; Ueda, A.; Zhang, W.; Kida, T.; Nakatsuji, Y.; Ikeda, I.; Kanehisa, N.;
Kai, Y. Tetrahedron Lett. 1998, 39, 9493–9496.
4
.3. Transport experiments
2
5. (a) Meadows, E. S.; De Wall, S. L.; Barbour, L. J.; Gokel, G. W. J. Am. Chem. Soc.
2001, 123, 3092; (b) De Wall, S. L.; Meadows, E. S.; Barbour, L. J.; Gokel, G. W. J.
Am. Chem. Soc. 1999, 121, 5613–5614.
Transport experiments were run at 25 °C in the custom-made,
U-shaped glass apparatus of 10 mm diameter for 72 h. The bulk li-