Axially chiral facial amphiphiles with a dihydronaphthopentaphene structure as molecular tweezers for swnts

Article abstract of DOI:10.1002/chem.200901545

Syntheses of chiral 6,15dihydronaphtho[2,3-c]pentaphene derivatives of opposite configurations are reported. Starting from anthracene, the strategy involves two key steps: a Diels-Alder reaction on a prochiral dianthraquinone, and an enantiomeric resolution using (-)-menthol. The final molecules exhibit very strong optical activity, as shown by their circular dichroism spectra, and are examples of chiral facial amphiphiles. Their adsorption at the surface of single-walled carbon nanotubes (SWNTs) has also been studied, and has been found to occur preferentially on 0.8-1.0 nm diameter nanotubes among the population of a high-pressure CO conversion (HiPco) SWNT sample (0.8-1.2 nm). The synthesised facial amphiphiles act as nano-tweezers for the diameter-selective solubilisation of SWNTs in water. The expected optical activities of the SWNT samples solubilised by each of the chiral amphiphiles have been studied by circular dichroism spectroscopy, but the results are not yet conclusive.

Full text of DOI:10.1002/chem.200901545

FULL PAPER
DOI: 10.1002/chem.200901545
Axially Chiral Facial Amphiphiles with a Dihydronaphthopentaphene
Structure as Molecular Tweezers for SWNTs
Renaud Marquis,[a] Krystyna Kulikiewicz,[a] Sergei Lebedkin,[b] Manfred M. Kappes,[b]
Charles Mioskowski†,[a] Stꢀphane Meunier,*[a] and Alain Wagner[a]
In memory of Charles Mioskowski who initiated this work
Abstract: Syntheses of chiral 6,15-
dihydronaphtho[2,3-c]pentaphene de-
rivatives of opposite configurations are
reported. Starting from anthracene, the
chiral facial amphiphiles. Their adsorp-
tion at the surface of single-walled
carbon nanotubes (SWNTs) has also
been studied, and has been found to
occur preferentially on 0.8–1.0 nm di-
ameter nanotubes among the popula-
tion of a high-pressure CO conversion
(HiPco) SWNT sample (0.8–1.2 nm).
The synthesised facial amphiphiles act
as nano-tweezers for the diameter-se-
lective solubilisation of SWNTs in
water. The expected optical activities
of the SWNT samples solubilised by
each of the chiral amphiphiles have
been studied by circular dichroism
spectroscopy, but the results are not
yet conclusive.
ACHTUNGTRENNUNG
strategy involves two key steps:
a
Diels–Alder reaction on a prochiral di-
anthraquinone, and an enantiomeric
resolution using (À)-menthol. The final
molecules exhibit very strong optical
activity, as shown by their circular di-
chroism spectra, and are examples of
Keywords: amphiphiles
· anthra-
cenes · carbon nanotubes · chirality ·
pi interactions
Introduction
Pursuing our effort to design geometrically constrained
polyaromatic molecules for the supramolecular recognition
and sorting of single-walled carbon nanotubes (SWNTs),[4]
we conceived the facial amphiphiles (6R,15R)-1 and
(6S,15S)-1 (Figure 1). The structural control of SWNTs (di-
ameter and helicity) during their production is difficult.
Nevertheless, obtaining refined SWNT samples possessing
well-defined properties is a critical hurdle that has to be
overcome with regard to their fundamental study and for
many technological applications. For instance, discrimination
according to diameter is highly valuable for nanoelectronic
applications, since diameter plays a key role in determining
the electronic properties of carbon nanotube field-effect
transistors (on-current varying by several orders of magni-
tude depending on the SWNT band gap).[5] Therefore, the
development of methods for sorting SWNTs according to
their electronic properties and/or structural parameters has
attracted a lot of attention, the ultimate goal being the pro-
duction of samples of SWNTs with a single structure.[6] In
pursuit of this goal, “host–guest strategies” are the most so-
phisticated and promising; they have been adopted by sever-
al groups, including our own. These strategies involve the
use of small amphiphilic anchor molecules with constrained
shapes that are able to specifically solubilise a sub-popula-
tion of SWNTs in an as-produced SWNTs mixture. These
Typical amphiphiles, such as lipids, have a head-to-tail struc-
ture, usually consisting of a polar head-group and a long hy-
drocarbon chain; facial amphiphiles, on the contrary, present
a hydrophobic face and a hydrophilic face.[1] Bile salts and
certain helical peptides are natural examples of such com-
pounds.[2] Numerous original facial amphiphiles have been
synthesised and examined with regard to their two- and
three-dimensional assembly behaviour, their abilities to
solubilise specific types of molecules, and their lack of sus-
ceptibility to aggregation.[3]
[a] Dr. R. Marquis, Dr. K. Kulikiewicz, Dr. C. Mioskowski,
Dr. S. Meunier, Dr. A. Wagner
Laboratory of Functional Chemo-Systems, UMR 7199
Facultꢀ de Pharmacie, Universitꢀ de Strasbourg
74 Route du Rhin, BP 24, 67401 Illkirch (France)
Fax : (+33)390-24-43-06
E-mail: meunier@bioorga.u-strasbg.fr
[b] Dr. S. Lebedkin, Prof. Dr. M. M. Kappes
Institut fꢁr Nanotechnologie, Forschungszentrum Karlsruhe
76021 Karlsruhe (Germany)
[†] Deceased.
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.200901545.
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c]pentaphene derivatives.[9] They are not exact enantiomers
because the asymmetric centres of the nitrilotriacetic side
chains are of the same configuration in the two structures;
however, the two asymmetric carbons of the 6,15-
dihydronaphtho
Figure 1) are of opposite stereochemistry. To the best of our
knowledge, only one example of chiral 6,15-
dihydronaphtho[2,3-c]pentaphene has hitherto been de-
ACHTUNGTRENN[UNG 2,3-c]pentaphene fragment (C6 and C15,
a
AHCTUNGTRENNUNG
scribed in the literature. In 1976, Harada et al. reported the
synthesis of (6R,15R)-(+)-6,15-dihydro-6,15-ethanonaphtho-
AHCTUNGTREG[NNNU 2,3-c]pentaphene (Scheme 1a) from chiral (9R,10R)-(+)-
1,5-dimethoxycarbonyl-9,10-dihydro-9,10-ethanoanthracene
by a sequence of Grignard addition, oxidation, Friedel–
Crafts acylation, and aromatisation.[10] Notably, the opposite
enantiomer of the final product was not synthesised. Fur-
thermore, this hydrocarbon molecule does not bear chemical
functions that would enable the grafting of the polar head-
groups required in our application; thus, we had to follow a
completely different synthetic strategy. To access our target
molecules, and especially the two isomers of the dihydro-
naphthopentaphene, we envisaged using the dianthraqui-
none 4 as a key intermediate (Scheme 1b).
Figure 1. Chiral facial amphiphiles.
approaches often allow the attainment of high specificities
in the diameter or the helicity (e.g., zigzag or armchair) and
thus the conductivity of the selected SWNTs by virtue of
the precise molecular design of the anchor molecules.[7] The
most advanced development of such a “host–guest strategy”
was recently proposed by N. Komatsu, who reported the se-
lective solubilisation of optical isomers of SWNTs (left- or
right-handed helicity along the nanotube axis) by using
chiral zinc(II) diporphyrins.[8] To the best of our knowledge,
this is unique work concerning the separation of isomers of
SWNTs, and is noteworthy in that the corresponding anchor
molecules do not discriminate a particular helicity angle. In
our previous report, we presented two polyaromatic amphi-
philic molecules for the selection of either armchair or
zigzag SWNTs by virtue of optimised p–p stacking interac-
tions with the nanotube graphene-type atomic structure.[4] In
the work presented herein, the same strategy is followed,
but inspired by the pioneering work of N. Komatsu, we en-
visaged the sorting of SWNTs according to more advanced
structural parameters; we wished to design polyaromatic
molecules that would allow for
A report by Clar in 1948[11] suggests that the central an-
thracene ring in 4 should be the most favourable reactive
site in a Diels–Alder reaction. With diethyl acetylenedicar-
boxylate as the dienophile, (Æ)-5 would be obtained as a
racemic mixture. Reduction and aromatisation of this diqui-
none, followed by transesterification with a chiral alcohol,
should allow us to separate the two diastereoisomers of 7.
Each of them could subsequently be converted to the target
molecules 1.
Results and Discussion
Synthesis: Compound 4 was synthesised following the strat-
egy reported by Clar,[11] in two steps from anthracene 2
(Scheme 2). The diacid 3 was obtained among a mixture of
other regioisomers and could not be purified. Heating of the
the first time the diameter-se-
lective chiral discrimination of
SWNTs. Remarkably, in paral-
lel, N. Komatsu has recently
reported the enrichment of
larger diameter SWNTs using
chiral monoporphyrins.[8d] The
aim of this communication is
to describe the synthesis of the
two chiral facial amphiphiles
(6R,15R)-1 and (6S,15S)-1 and
to present the results of
SWNT-sorting experiments in
terms of diameter discrimina-
tion and optical enrichment.
Compounds 1 (Figure 1) are
two 6,15-dihydronaphtho
G
Scheme 1. Retrosynthetic strategy followed by a) Harada et al. and b) that used herein.
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Molecular Tweezers for SWNTs
FULL PAPER
dide-catalysed transesterifica-
tion reaction reported by Ranu
et al.,[13] using molten (À)-
menthol as the solvent. Indeed,
at 808C in molten (À)-men-
thol, indium triiodide, pre-
pared in situ by stirring indium
metal and iodine, efficiently af-
forded the di-(À)-menthyl
esters 7 from (Æ)-6 in 88%
yield (Scheme 3).
The resulting equimolar mix-
ture of the two diastereoiso-
mers could be very efficiently
separated by column chroma-
tography on silica gel, afford-
ing the two enantiomerically
Scheme 2. Synthesis of racemic 6,15-dihydronaphthopentaphene (Æ)-6. a) Phthalic anhydride, AlCl3, (CHCl2)2,
2 h at 958C; b) benzoyl chloride, ZnCl2, nitrobenzene, 30 min at 2058C; c) diethyl acetylenedicarboxylate, ni-
trobenzene, 45 h at 2108C; d) 1) NaBH4, MeOH/diglyme, À208C to RT; 2) SnCl2, aqueous 10% HCl.
mixture at 2058C for 30 min in
the presence of zinc(II) chlo-
ride and benzoyl chloride al-
lowed the formation of 4,
which could be cleanly isolated
as a purple solid after repeated
washing with nitrobenzene and
diethyl ether. A 1H NMR spec-
trum of this highly insoluble
compound could only be re-
Scheme 3. Synthesis and separation of diastereoisomers 7. a) (À)-menthol, In, I2, 48 h at 808C.
corded in deuterated nitroben-
zene by heating the sample to 1908C. Notably, the overall
yield of this synthesis of 4 was higher than that reported by
Clar (18% instead of 9%).
pure compounds (6R,15R)-7 and (6S,15S)-7 (de >99% by
HPLC; see the Supporting Information).
Each of the two diastereoisomers of 7 was quantitatively
saponified to afford the two enantiomers of diacid 8
(Scheme 4). Attempted bis-coupling of the tert-butyl-nitrilo-
triacetate (9)[14] with compounds 8 was unsuccessful using
the benzotriazole-1-yloxytris(dimethylamino)phosphonium
hexafluorophosphate (BOP) reagent or the 1-hydroxybenzo-
triazole (HOBt)/N’-(3-dimethylaminopropyl)-N-ethylcarbo-
diimide (EDC) coupling system in DMF, 1,4-dioxane, or 1,4-
dioxane/benzene (1:1) as solvents. In the presence of 6 equiv
of n-propylphosphonic anhydride (T3P, Scheme 4)[15] no re-
action was observed in 1,4-dioxane; however, the presence
of benzene as a co-solvent allowed the reaction to proceed
such that the two desired products (6R,15R)-10 and
(6S,15S)-10 were obtained in moderate yields. Benzene
might prevent compounds 8 from aggregating by keeping
them in solution by virtue of intermolecular p–p stacking in-
teractions. The specific rotations of the compounds 10 could
be measured in chloroform: for (6R,15R)-10: [a]D =+1828
(c=1.9ꢃ10À3, CHCl3) and for (6S,15S)-10: [a]D =À1908 (c=
0.6ꢃ10À3, CHCl3).
Diels–Alder reactions of acetylenes and 4 were found to
be regiospecific because of the high reactivity of the central
ring of the anthracene fragment, as previously reported.[12]
By heating 4 in nitrobenzene in the presence of 10 equiv of
diethyl acetylenedicarboxylate for 45 h in a sealed tube, rac-
emic compound (Æ)-5 could be obtained in a very good
yield (Scheme 2) and was thoroughly characterised after re-
crystallisation. Furthermore, the structure of (Æ)-5, and es-
pecially the dihedral angle (approximately 1208) formed by
the two anthraquinone units, was confirmed by X-ray crys-
tallographic analysis of monocrystals grown by diffusion of
petroleum ether into a solution in chloroform. Notably, the
Diels–Alder reaction of 4 with di-(À)-menthyl acetylenedi-
carboxylate was unsuccessful. Reduction of the two quinone
moieties of (Æ)-5 followed by the sensitive aromatisation of
the anthracene units to afford (Æ)-6 was performed in a
one-pot sequence.
In order to separate the two enantiomers of the 6,15-
dihydronaphthoACHTUNGTRENNUNG[2,3-c]pentaphene 6, twofold transesterifica-
tion of the ethyl esters with (À)-menthol was studied. Heat-
Since we observed a certain degree of retro Diels–Alder
reactions of 6,15-dihydronaphthopentaphenes 10 or similar
substrates when using sodium hydroxide, lithium hydroxide,
or potassium hydroxide, acidic conditions were preferred for
the deprotection of the 6-carboxylic acids of (6R,15R)-10
ing (Æ)-6 with (À)-menthol in the presence of a catalyst
such as TiCl4, TiACHTUNGTRENNUNG(OiPr)4, or p-toluenesulfonic acid (PTSA)
did not afford the expected menthyl esters. In order to
ACHTUNGTRENNUNGachieve this transformation, we extended the indium triio-
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S. Meunier et al.
dronaphthopentaphene moiet-
ies. Both CD spectra, recorded
in Tris buffer (pH 8), feature
very strong typical split Cotton
effects for such compounds in
the
220–300 nm
region
(Figure 2). By comparison with
the CD spectrum of (6R,15R)-
(+)-6,15-dihydro-6,15-etha
ACHTUNGTRENNUNGno-
A
ACHTUNGTRENNUNG
the (6R,15R)-1 configuration
was assigned to the sample dis-
playing a CD spectrum with a
positive first and a negative
second Cotton effect (De272
=
+255000,
De250 =À269000,
A(De272ÀDe250)=+524000).
The CD spectrum showing a
negative first and a positive
second Cotton effect (De272
=
Scheme 4. Synthesis of the two 6,15-dihydronaphthopentaphene diastereoisomers 10. a) LiOH, EtOH, 6 h at
reflux; b) 9, T3P, EDIPA, 1,4-dioxane/benzene 1:1, 4 d at RT.
À254000,
De250 =+277000,
A(De272ÀDe250)=À531000) was
assigned to the (6S,15S)-1 con-
figuration. Interestingly, de-
and (6S,15S)-10. Cleavage of the 6-tert-butyl esters was
achieved by treating each of the two compounds 10 in tri-
fluoroacetic acid for 30 h (HPLC monitoring; Scheme 5).
spite the fact that the two compounds are not strictly enan-
tiomers (the asymmetric centres of the nitrilotriacetic side
chains are of the same configuration), the CD spectra are
virtually identical but of opposite sign, showing that the op-
tical activity is largely dictated by the enantiomerically pure
6,15-dihydronaphthopentaphene fragments (similarly, the
UV/Vis absorption spectra are almost identical; Figure 2).
Notably, to the best of our knowledge, this is the first report
of a CD spectrum of a (6S,15S)-dihydronaphthopentaphene.
The absolute configurations of
ACHTUNGTRENNUNG
The structures of the obtained compounds, (6R,15R)-1 and
1
(6S,15S)-1, were confirmed by H and 13C NMR as well as
by mass spectrometry in negative-ion mode on a MALDI-
TOF instrument.
Circular dichroism (CD) spectra of compounds 1 allowed
assignment of the absolute configurations of the 6,15-dihy-
the synthesised intermediates
were determined on the basis
of the configuration of the
final compounds 1.
Selective
solubilisation
of
SWNTs: The properties of the
compounds 1 for the discrimi-
nation of SWNTs in terms of
diameter and chirality were
studied according to a previ-
ously reported strategy.[4] The
previously optimised protocol
was applied, starting from
high-pressure CO conversion
(HiPco) SWNTs dispersed in
an aqueous solution of sodium
dodecyl sulfate (SDS; 1 wt%).
Briefly, (6R,15R)-1 or (6S,15S)-
1 was added to a suspension of
SWNTs, SDS was removed by
extended dialysis, and finally
the samples were centrifuged
Scheme 5. Synthesis of the two 6,15-dihydronaphthopentaphene diastereoisomers 1. a) TFA, 30 h at RT.
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Molecular Tweezers for SWNTs
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Diels–Alder adducts serve as diameter-selective molecular
anchors for the separation of SWNTs in the 1–2 nm diame-
ter range,[7c] though we demonstrate here the finer selection
of smaller SWNTs in an HiPco mixture. In our case, the ob-
served selection in size could also be due to the three-di-
mensional shape of compounds 1, which makes them suita-
ble for effective interaction with the tubular shape of
SWNTs of optimum diameter (see the Supporting Informa-
tion for a schematic representation, Scheme S1). Notably, a
discrimination of SWNTs in favour of large helicity angle is
also observed with compounds 1, as tubes (7,6) show the
largest increases of abundance in comparison with the start-
ing mixture.
As shown in Figure 4, the selections achieved with com-
pounds 1 are very different from those obtained in previous
studies using a pentacene- or a quaterrylene-based amphi-
phile.[4] This confirms that the geometry of the polyaromatic
anchor molecule, most probably interacting by p–p stacking
with the nanotube wall, is a crucial factor for the tuning of
the SWNTs discrimination. Also, in comparison with previ-
ous amphiphiles used, running the sorting experiments with
1 was facilitated by virtue of their lower self-aggregating be-
haviour, a feature that is inherent to facial amphiphiles.
After having studied the diameter-based discrimination of
SWNTs achieved by compounds 1 by PL, the optical activity
of the purified nanotube samples was studied with the aim
of characterising the optical enrichment. We adopted the ex-
perimental set-up reported by Peng et al. in his pioneering
work on the preparation of optically active SWNT samples
using two enantiomers of chiral diporphyrins.[8] Thus, the op-
tical activities of SWNT samples extracted by using
(6R,15R)-1 and (6S,15S)-1 were studied by CD after remov-
al of compounds 1 from the samples (by repeated aqueous
and acidic methanolic washes).[4] Unfortunately, all our at-
tempts to record an unequivocal signal by CD (in the range
300–1100 nm) attributable to carbon nanotubes under the
conditions described by Peng et al. have been unsuccessful
due to the low SWNT contents in the final samples.[18]
Therefore, our experiments are not yet conclusive in terms
of optical enrichment in the SWNT samples purified by
compound 1.
In the light of reports by N. Komatsu, we had not antici-
pated that the amount of purified SWNT necessary for CD
studies would have been higher than the amount of material
that our experimental strategy can deliver (after extensive
washings of compound 1). Instead of pursuing an optimisa-
tion of the experimental procedure, this observation and the
very promising selection results shown above led us to re-
think our strategy toward our foremost objective, which is
to deliver a large-scale preparative procedure based on our
amphiphilic anchor molecules for the fine selection of
SWNTs. To this end, we are currently working on a support-
ed version of our amphiphiles and on the adaptation of our
experimental procedures to a pH-dependent continuous-ex-
traction set-up.
Figure 2. CD (left axis) and UV (right axis) spectra of (6R,15R)-1 (red
trace) and (6S,15S)-1 (blue trace) in Tris buffer (pH 8).
to separate the solubilised fraction of SWNTs remaining in
the supernatant from the aggregated SWNTs in the pellet.
Control experiments in the absence of facial amphiphiles 1
showed that no SWNTs remained in the supernatant at this
stage. The aqueous supernatants obtained, containing the
SWNTs selected by (6R,15R)-1 or (6S,15S)-1, were dialysed
against D2O in order to reach an H2O content below 0.2%
and to allow their analysis by photoluminescence (PL). This
experiment permits analysis of the semiconducting (n,m)
SWNT population and thus allows comparison of the two
obtained samples with the population of the starting HiPco
nanotubes in terms of diameter selection (photolumines-
cence phenomena would be expected to be identical for two
enantiomeric SWNTs). The PL protocol involves measuring
the luminescence of the sample using excitation wavelengths
in the range 500–900 nm (in 3 nm increments). The result is
a three-dimensional map showing absorption peaks that can
be precisely assigned to a specific nanotube structure
(n,m).[16] The PL experimental conditions used herein cover
the whole distribution of the (n,m) semiconducting nano-
tubes in the HiPco material (note that metallic tubes are not
detected by this technique).[17]
The PL results show that the fractions of SWNTs solubi-
lised by compounds (6R,15R)-1 and (6S,15S)-1 are virtually
identical since the maps recorded for these two samples are
very similar (Figure 3b, c). Under the hypothesis that the
solubilisation of SWNTs is driven by the two enantiomeri-
cally pure 6,15-dihydronaphthopentaphene fragments of 1,
this demonstrates the specificity of our sorting procedure.[4]
Comparing the population of SWNTs sorted by one of the
two compounds 1 with the starting HiPco mixture (Fig-
ure 3a/b or a/c), a clear selection in terms of diameter is ob-
served, since only nanotubes in the range 0.8–1.0 nm are de-
tected. These results can be related to the work of Tromp
et al., in which it was reported that pentacene–maleimide
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S. Meunier et al.
Figure 3. Photoluminescence spectra of HiPco SWNT samples before and after the selection protocol. a) PL intensity versus excitation and emission
wavelengths for a HiPco SWNT sample suspended in SDS and deuterium oxide (the colours from blue to red indicate the strength of the emission). b),
c) Spectra of the extracted fractions of the previous HiPco SWNT sample using the reported selection protocol[4] and starting with facial amphiphile
(6R,15R)-1 (b) or (6S,15S)-1 (c) at a concentration of 2ꢃ10À4 molLÀ1. PL emission intensities are reported in Hamada plots to illustrate the selections
obtained.
Conclusion
agents for SWNTs and have demonstrated that compounds
1 permit very fine size selections. Theoretical calculations
are ongoing for the further interpretation of this experimen-
tal result. CD experiments on the final samples, which were
not conclusive in terms of SWNT optical enrichment, have
encouraged us to pursue our effort towards the development
of preparative methods based on our collection of amphi-
philic anchor molecules for the sorting of various types of
A pair of chiral facial amphiphiles with a dihydronaphtho-
pentaphene structure has been synthesised for the first time.
Compounds (6R,15R)-1 and (6S,15S)-1 exhibit very high op-
tical activities and could be of utility in studies of optical de-
vices or for the selective solubilisation of chiral guest mole-
cules. In this report, we have focused on their use as sorting
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Molecular Tweezers for SWNTs
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Figure 4. Selection of SWNTs from HiPco samples by using a pentacene-based (top) or quaterrylene-based (bottom) amphiphile. PL emission intensities
are reported in Hamada plots to illustrate the selections obtained. For spectra, refer to ref. [4].
trifuged. The solids recovered from the centrifugation and the organic
phases were combined and dried under reduced pressure. The obtained
residue was washed with acetic acid and diethyl ether to afford crude 1,5-
bis(2-carboxybenzoyl)anthracene as a light-brown solid (5.22 g). This res-
idue (5.22 g, 11 mmol based on the sole presence of 1,5-bis(2-carboxyben-
SWNTs, with the ultimate goal being the delivery of bulk
quantities of a single-structure SWNT.
zoyl)anthracene) was mixed with benzoyl chloride (17.6 mL, 154 mmol,
14 equiv), zinc(II) chloride (3.07 g, 22.5 mmol, 2.05 equiv), and nitroben-
Experimental Section
zene (60 mL). The resulting mixture was gradually heated to 2058C and
kept at this temperature for 30 min. After cooling to 60–808C, the reac-
General: All experiments were carried out under an argon atmosphere.
TLC was performed on Merck silica gel 60F254 and spots were revealed
tion mixture was filtered. The brown residue was washed with nitroben-
by exposure to UV at 254 nm and vanillin. Silica gel (Merck 60, 40–
zene and diethyl ether to afford 4 as a violet solid (2.41 g, 5.5 mmol, 18%
63 mm) was used for flash column chromatography. For the separation of
from anthracene). M.p.> 3508C; 1H NMR (300 MHz, [D5]nitrobenzene,
compounds (6R,15R)-7 and (6S,15S)-7, a finer silica gel (Merck 60, 14–
1908C, TMS): d=10.6 (s, 2H; H6,15), 8.60–8.68 (m, 2H; H7,16), 8.52–
40 mm) was preferred. NMR spectra were recorded at 300 or 200 MHz
1
8.60 (m, 2H; H8,17), 8.44–8.52 (m, 2H; H4,13), 8.34–8.41 (m, 2H;
for H and at 75 or 50 MHz for 13C. Infra-red spectra were recorded on a
H1,10), 7.82–7.99 ppm (m, 4H; H2,3,11,12); IR: n˜ =1668 (C=O), 1591,
Perkin–Elmer spectrometer (1600 FT-IR) from samples in KBr discs.
Melting points were measured on a Bibby Sterilin device (Stuart Scientif-
ic SMP3). Elemental analyses were performed by the Service Central
dꢄAnalyses du CNRS at Vernaison. High-resolution mass spectra were re-
corded using a MicroTOF instrument (Bruker). UV/Vis absorption spec-
tra were recorded on a UVIkon XL instrument (BioTek). CD spectra
were recorded on a Jasco spectrometer (J-810).
1332, 1300, 1271, 709 cmÀ1
.
Diquinone (Æ)-5: A mixture of compound 4 (220 mg, 0.50 mmol), diethyl
acetylenedicarboxylate (0.80 mL, 4.7 mmol, 9.4 equiv), and nitrobenzene
(1.5 mL) was heated at 2108C in a sealed tube for 45 h. The crude prod-
uct was purified by flash chromatography on silica, eluting first with
ethyl acetate/dichloromethane/cyclohexane 1:80:19 and then with ethyl
acetate/dichloromethane (gradient to 4:96). The obtained solid was re-
crystallised twice from ethyl acetate/cyclohexane 3:2 to yield (Æ)-5 as a
brown solid (260 mg, 0.43 mmol, 88%). Rf =0.25 (AcOEt/CH2Cl2/cyclo-
NaphthoACHTUNGTRENNUNG[2,3-c]pentaphene-5,18:9,14-diquinone (4): A mixture of anthra-
cene (5.4 g, 30.3 mmol) and phthalic anhydride (10.3 g, 69.5 mmol,
2.3 equiv) was heated to 1508C under vigorous stirring. 1,1,2,2-Tetrachlo-
ACHTUNGTRENNUNGroethene (120 mL) was then slowly added, the resulting mixture was
cooled to 958C, and freshly prepared finely divided aluminium chloride
(18 g, 135 mmol, 1.5 equiv) was added portionwise. The reaction mixture
was stirred for 2 h at 958C, then cooled, diluted with chloroform
(300 mL), and hydrolysed with 10% HCl (300 mL) for 12 h under vigo-
rous stirring. The aqueous phase was extracted with chloroform; the ob-
tained emulsions were collected at each extraction step, pooled, and cen-
hexane, 1:80:19); 1H NMR (300 MHz, CDCl3, 208C, TMS): d=8.34 (d,
3
3J
(d, 3J
7.85–7.79 (m, 2H; H3,12), 7.82–7.75 (m, 2H; H2,11), 7.79 (s, 2H; H6,15),
(H,H)=8.2 Hz, 2H; H4,13), 8.26 (d, J
N
ACHUTNGRENNUG ACHTUNGTRENN(UGN H,H)=7.8 Hz, 2H; H8,17),
(H,H)=7.8 Hz, 2H; H7,16), 7.95 (d, 3J
4.29 (q, 3J(H,H)=7.1 Hz, 4H; 2ꢃCH2), 1.31 ppm (t, 3J
ACTHNUTRGENNUG ACHUTTGNREN(NUGN H,H)=7.1 Hz,
6H; 2ꢃCH3); 13C NMR (75 MHz, CDCl3, 208C, TMS): d=185.2, 182.8,
165.2 (2ꢃCO2Et), 151.9 (2ꢃCCO2Et), 146.6, 145.9, 134.5 (C4a,13a), 134.5
Chem. Eur. J. 2009, 15, 11187 – 11196
ꢂ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
11193

S. Meunier et al.
(C4,13), 133.3 (C5a,14a), 132.1 (C8a,17a), 130.2 (C1,10), 128.8 (C9a,18a),
127.8 (C2,3,11,12), 127.3 (C8,17), 127.1 (C7,16), 62.2 (2ꢃCH2), 48.6
(C6,15), 14.4 ppm (2ꢃCH3); elemental analysis calcd (%) for C38H24O8:
C 74.99, H 3.97; found: C 74.2, H 4.1; MS (CI): m/z: 609 [M++H], 608
[M+].
(2ꢃOCHCH2CH), 41.0 (2ꢃOCHCHCH2CH2), 34.3 (2ꢃOCHCHCH2),
31.6 (2ꢃ(CH3)2CH), 26.0 (2ꢃOCHCH), 23.2 (2ꢃOCHCH2), 22.2 (2ꢃ
CHCHCH3), 20.9 (2ꢃCHCHCH3), 16.2 ppm (2ꢃCH2CHCH3).
Diacid (6R,15R)-8: Lithium hydroxide (50 mg, 2.3 mmol, 23 equiv) was
added to a solution of (6R,15R)-7 (76 mg, 0.10 mmol, 1.0 equiv) in etha-
nol (20 mL) and the mixture was refluxed for 6 h. Water (60 mL) and 1 n
HCl were then added to the cooled reaction mixture, and the aqueous
phase was extracted with ethyl acetate. The combined organic phases
were dried over sodium sulfate, filtered, and concentrated to dryness.
The crude residue was purified by flash chromatography on silica eluting
with methanol/ethyl acetate (gradient from 0:100 to 40:60). The purified
product was dried under reduced pressure and redissolved in chloroform
(10 mL). The solution obtained was filtered to remove the silica and con-
centrated once more to afford (6R,15R)-8 (49 mg, 0.10 mmol, 99%). Rf =
0.20 (MeOH/AcOEt, 5:95); 1H NMR (300 MHz, CD3OD, 208C, TMS):
Diethyl ester (Æ)-6: Sodium borohydride (62 mg, 1.6 mmol, 12 equiv)
was added portionwise to a suspension of (Æ)-5 (100 mg, 0.16 mmol) in
dry methanol (3.5 mL) at À208C over 15 min. After a further 15 min of
stirring, diglyme (3 mL) was added. After the addition of further sodium
borohydride, the reaction was monitored by TLC until complete con-
sumption of the starting material. Once homogeneous, the reaction mix-
ture was warmed to À58C, diluted with cold dry methanol (3.5 mL), and
slowly poured into a cold (58C) saturated solution of tin(II) chloride in
10% HCl (100 mL) under stirring. The aqueous phase was extracted with
chloroform. The combined organic layers were dried over sodium sulfate,
filtered, and concentrated and the residue was purified by flash chroma-
tography on silica eluting with dichloromethane/cyclohexane 70:30 to
d=9.04 (s, 2H; H5,14), 8.38 (s, 2H; 2ꢃH9,17), 8.12 (d, 3J
2H; H4,13), 7.90 (d, 3J(H,H)=8.3 Hz, 2H; H1,10), 7.81 (d, 3J
8.3 Hz, 2H; H7,16), 7.72 (d, 3J
(H,H)=8.3 Hz, 2H; H8,17), 7.47–7.40 (m,
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
afford (Æ)-6 as
(CH2Cl2/cyclohexane, 70:30); 1H NMR (300 MHz, CDCl3, 208C, TMS):
d=8.90 (s, 2H; H5,14), 8.42 (s, 2H; H9,18), 8.13 (d, 3J
(H,H)=8.7 Hz,
2H; H4,13), 7.94 (d, 3J(H,H)=8.1 Hz, 2H; H1,10), 7.79 (d, 3J
(H,H)=
8.6 Hz, 2H; H7,16), 7.76 (d, 3J
(H,H)=8.6 Hz, 2H; H8,17), 7.53–7.45 (m,
2H; H3,12), 7.49–7.41 (m, 2H; H2,11), 6.72 (s, 2H; H6,15), 4.28 (q, 3J-
(H,H)=7.1 Hz, 4H; 2ꢃCH2), 1.28 ppm (t, 3J
(H,H)=7.1 Hz, 6H; 2ꢃ
a yellow solid (85 mg, 0.15 mmol, 94%). Rf =0.20
AHCTUNGTRENNUNG
2H; H3,12), 7.42–7.35 (m, 2H; H2,11), 7.29 ppm (s, 2H; H6,15);
13C NMR (75 MHz, CD3OD, 208C, TMS): d=169.5 (2ꢃCO2H), 154.2
(2ꢃCCO2H), 145.2, 145.0, 133.4 (C4a,13a), 132.5 (C5a,14a), 131.6
(C8a,17a), 129.4 (C4,13), 129.2 (C9a,18a), 129.1 (C1,10), 128.2 (C9,18),
126.6, 126.4, 126.2 (C8,17), 123.8 (C7,16), 121.4 (C5,14), 53.0 ppm
(C6,15); HRMS: calcd for C34H20O4: 491.1278 [M++H]; found (ESI-
TOF): m/z: 491.1286.
AHCTUNGTRENNUNG
A
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
A
ACHTUNGTRENNUNG
CH3); 13C NMR (75 MHz, CDCl3, 208C, TMS): d=166.0 (2ꢃCO2Et),
149.2 (2ꢃCCO2Et), 143.41, 143.36, 132.1 (C4a,13a), 131.3 (C5a,14a),
130.3 (C6a,17a), 128.5 (C4,13), 128.3 (C1,10), 127.8 (C9a,18a), 127.5
(C9,18), 125.8 (C2,3,11,12), 125.5 (C8,17), 122.8 (C7,16), 120.3 (C5,14),
61.7 (2ꢃCH2), 50.5 (C6,15), 14.2 ppm (2ꢃCH3); MS (CI): m/z: 548 [M+].
Diacid (6S,15S)-8: Following the same procedure as that used for the syn-
thesis of (6R,15R)-8, but using (6S,15S)-7 (77 mg, 0.10 mmol, 1.0 equiv)
instead of (6R,15R)-7, gave (6S,15S)-8 (49 mg, 0.10 mmol, 99%). HRMS
(ESI-TOF): m/z: 491.1314 [M++H].
Di(À)-menthyl esters (6R,15R)-7 and
ACHTUNGTNER(NUNG 6S,15S)-7: Powdered indium
Compound (6R,15R)-10: The formate salt of tert-butyl (S)-6-amino-2-
{bis[(tert-butoxycarbonyl)methyl]amino}hexanoate[14] (115 mg, 0.22 mmol,
6.4 equiv) was dissolved in a saturated aqueous solution of potassium car-
bonate (20 mL), which was then extracted with ethyl acetate. The com-
bined organic phases were dried over magnesium sulfate, filtered, and
concentrated to dryness to give the free base, which was redissolved in
benzene (5.5 mL) and 1,4-dioxane (5.5 mL) and added to a solution of
(163 mg, 1.4 mmol, 3.7 equiv) and doubly sublimed iodine (540 mg,
2.1 mmol, 5.6 equiv) were added to molten (À)-menthol (3.5 g, 22 mmol,
60 equiv) at 458C. The reaction mixture was stirred at 458C for 30 min
and then (Æ)-6 (210 mg, 0.38 mmol) was added. The resulting mixture
was stirred at 808C for 40 h. Most of the excess of (À)-menthol was re-
moved by sublimation. The remaining material was dissolved in diethyl
ether, and the solution was washed with a saturated solution of sodium
thiosulfate and brine, dried over sodium sulfate, filtered, and concentrat-
ed. The residue was purified by flash chromatography on silica eluting
with ethyl acetate/dichloromethane (gradient from 1:99 to 4:96) to afford
(6R,15R)-7 and (6S,15S)-7 (255 mg, 0.33 mmol, 88%). The two diastereo-
isomers were separated by column chromatography on fine silica eluting
with ethyl acetate/cyclohexane 90:10 (de >99%, Chiralcel OD-H
(6R,15R)-8 (17 mg, 0.034 mmol, 1.0 equiv) in
a mixture of benzene
(1.5 mL) and 1,4-dioxane (1.5 mL). A 50% solution of n-propylphos-
phonic anhydride (T3P) in ethyl acetate (61 mL, 0.66 mmol, 3.0 equiv)
was added, followed by N-ethyl-N,N-diisopropylamine (42 mL, 1.54 mmol,
7.0 equiv). More T3P (61 mL, 0.66 mmol, 3.0 equiv) was added after 2 h
of stirring at room temperature. Once all of the starting material and in-
termediates (TLC on silica, methanol/ethyl acetate, 10:90, Rf =0.5) had
been consumed, the reaction mixture was washed with brine (2ꢃ10 mL).
The combined aqueous phases were extracted with ethyl acetate
(10 mL). The combined organic phases were dried over sodium sulfate,
filtered, and concentrated to dryness. The crude residue was purified by
flash chromatography on silica eluting with ethyl acetate/dichlorome-
thane 10:90 to afford (6R,15R)-10 (9 mg, 0.007 mmol, 20%) as a yellow
column, 0.46ꢃ25 cm, 0.5 mLminÀ1, ethanol/hexane (0.8:99.2), tR(6R,15R)-7
=
14.1 min and tR(6S,15S)-7 =15.4 min; see the Supporting Information for
chromatograms). Data for (6R,15R)-7: Rf =0.29 (AcOEt/cyclohexane,
1
10:90); H NMR (200 MHz, CDCl3, 208C, TMS): d=8.83 (s, 2H; H5,14),
ACTHNUTRGNEUNG
8.35 (s, 2H; H9,18), 8.05 (d, 3J(H,H)=8.2 Hz, 2H; H4,13), 7.87 (d, 3J-
ACHTUNGTRENNUNG
1
solid. Rf =0.20 (AcOEt/CH2Cl2, 5:95); H NMR (300 MHz, CDCl3, 208C,
A
ACHTUNGTRENNUNG
TMS): d=8.95 (s, 2H; H5,14), 8.41 (s, 2H; H9,18), 8.13 (d, 3J
ACHTUNGTRENNUNG
36H); 13C NMR (50 MHz, CDCl3, 208C, TMS): d=165.3 (2ꢃCO2), 149.0
(2ꢃCCO2), 143.44, 143.38, 132.1 (C4a,13a), 131.3 (C5a,14a), 130.3
(C8a,17a), 128.4 (C4,13), 128.3 (C1,10), 127.9 (C9a,18a), 127.4 (C9,18),
125.8, 125.7, 125.4 (C8,17), 122.8 (C7,16), 120.2 (C5,14), 76.0 (2ꢃOCH),
50.7 (C6,15), 47.1 (2ꢃOCHCH2CH), 41.0 (2ꢃOCHCHCH2CH2), 34.4
(2ꢃOCHCHCH2), 31.6 (2ꢃ(CH3)2CH), 26.2 (2ꢃOCHCH), 23.3 (2ꢃ
OCHCH2), 22.2 (2ꢃCHCHCH3), 21.1 (2ꢃCHCHCH3), 16.4 ppm (2ꢃ
CH2CHCH3). Data for (6S,15S)-7: Rf =0.29 (AcOEt/cyclohexane, 10:90);
1H NMR (200 MHz, CDCl3, 208C, TMS): d=8.83 (s, 2H; 2ꢃH5,14), 8.33
8.1 Hz, 2H; H4,13), 7.94 (d, 3J
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
A
R
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
13C NMR (50 MHz, CDCl3, 208C, TMS): d=172.4 (2ꢃCO2tBu), 170.8
(4ꢃCO2tBu), 166.6 (2ꢃCON), 149.4 (2ꢃCCON), 143.7, 143.4, 132.2
(C4a,13a), 131.3 (C5a,14a), 130.3 (C8a,17a), 128.5 (C4,13), 128.3
(C9a,18a), 127.8 (C1,10), 127.5 (C9,18), 125.9, 125.7, 125.5 (C8,17), 123.0
(s, 2H; H9,18), 8.07 (d, 3J
8.0 Hz, 2H; H1,10), 7.76 (d, 3J
(H,H)=8.4 Hz, 2H; H8,17), 7.48–7.38 (m, 2H; 2ꢃH3,12), 7.43–7.33 (m,
2H; H2,11), 6.67 (s, 2H; H6,15), 4.85 (td, 3J(H,H)=10.8 Hz, 3J
(H,H)=
A
ACHTUNGTRNE(NUNG H,H)=
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG
(C7,16), 120.1 (C5,14), 81.2 (2ꢃC
ACHTUNTGRENGU(N CH3)3), 80.8 (4ꢃCACHTUNGTRNEN(UGN CH3)3), 65.3 (2ꢃ
A
ACHTUNGTRENNUNG
4.1 Hz, 2H; 2ꢃOCH), 2.21–0.70 ppm (m, 36H); 13C NMR (50 MHz,
CDCl3, 208C, TMS): d=165.5 (2ꢃCO2), 148.6 (2ꢃCCO2), 143.5
(C5b,6a,14b,15a), 132.0 (C4a,13a), 131.2 (C5a,14a), 130.3 (C8a,17a), 128.4
(C4,13), 128.3 (C1,10), 127.8 (C9a,18a), 127.4 (C9,18), 125.8, 125.7, 125.4
(C8,17), 122.9 (C7,16), 120.1 (C5,14), 76.0 (2ꢃOCH), 50.6 (C6,15), 46.9
NCH), 53.8 (2ꢃN(CH2)2), 51.6 (C6,15), 40.0 (2ꢃNHCH2), 30.4 (2ꢃ
AHCTUNGTRENNUNG
NHCH2CH2), 29.2 (2ꢃNCHCH2), 28.3 (6ꢃCH3), 28.2 (12ꢃCH3),
23.5 ppm (2ꢃNHCH2CH2CH2); UV/Vis (1,4-dioxane/chloroform, 92:8):
lmax (e)=484 (10000), 404 (200000), 384 (220000), 366 (200000), 346
(160000), 272 nm (3700000 molÀ1 m3 cmÀ1); HRMS: calcd for
11194
www.chemeurj.org
ꢂ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 11187 – 11196

Molecular Tweezers for SWNTs
FULL PAPER
C78H100N4O14: 1317.7309 [M++H]; found (ESI-TOF): m/z: 1317.7236.
The CD spectrum is displayed in the Supporting Information.
ion mode, HCCA, MeCN/H2O, 99:1): m/z: 979 [M+ÀH]. The CD and
absorbance spectra are displayed in Figure 2.
Compound (6S,15S)-10: Following the same procedure as that used for
the synthesis of (6R,15R)-10, but using (6S,15S)-8 (22 mg, 0.044 mmol,
1.0 equiv) instead of (6R,15R)-8, gave (6S,15S)-10 (12 mg, 0.009 mmol,
20%) as
(300 MHz, CDCl3, 208C, TMS): d=8.96 (s, 2H; H5,14), 8.41 (s, 2H;
H9,18), 8.14 (d, 3J(H,H)=8.1 Hz, 2H; H4,13), 7.93 (d, 3J
(H,H)=8.1 Hz,
2H; H1,10), 7.84 (d, 3J(H,H)=8.4 Hz, 2H; H7,16), 7.75 (d, 3J
(H,H)=
8.4 Hz, 2H; H8,17), 7.52–7.45 (m, 2H; H3,12), 7.47–7.40 (m, 2H; H2,11),
7.18 (brm, 2H; 2ꢃNH), 6.86 (s, 2H; H6,15), 3.50 (d, 3J
(H,H)=17.6 Hz,
4H; 2ꢃN (H,H)=17.6 Hz, 4H; 2ꢃN(CHAHB)2),
(CHAHB)2), 3.43 (d, 3J
3.45–3.20 (m, 6H; 2ꢃNHCH2, 2ꢃNCH), 1.42 (s, 18H; 2ꢃC(CH3)3), 1.39
(s, 36H; 4ꢃC(CH3)3), 1.65–1.20 ppm (m, 12H; 2ꢃNHCH2CH2CH2CH2);
a
yellow solid. Rf =0.20 (AcOEt/CH2Cl2, 5:95); 1H NMR
Acknowledgements
A
U
The authors are grateful to Sergio Abbate and Ettore Castiglioni of the
Universitꢅ di Brescia, Italy, for performing CD experiments on the
SWNT samples sorted by compounds 1 and for helpful discussions.
A
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
G
A
ACHTUNGTRENNUNG
T
[1] Y. Cheng, D. M. Ho, G. R. Gottlieb, D. Kahne, J. Am. Chem. Soc.
1992, 114, 7319–7320.
ACHTUNGTRENNUNG
13C NMR (50 MHz, CDCl3, 208C, TMS): d=172.4 (2ꢃCO2tBu), 170.8
(4ꢃCO2tBu), 166.6 (2ꢃCON), 149.4 (2ꢃCCON), 143.7, 143.4, 132.2
(C4a,13a), 131.3 (C5a,14a), 130.4 (C8a,17a), 128.6 (C4,13), 128.3
(C9a,18a), 127.8 (C1,10), 127.5 (C9,18), 125.9, 125.7, 125.4 (C8,17), 123.0
[2] a) E. T. Kaiser, F. J. Kezdy, Science 1984, 223, 249–255; b) S. Taka-
hashi, Biochemistry 1990, 29, 6257–6264.
[3] a) F. M. Menger, J. L. Sorrells, J. Am. Chem. Soc. 2006, 128, 4960–
4961; b) U. Taotafa, D. B. McMullin, S. C. Lee, L. D. Hansen, P. B.
Sauvage, Org. Lett. 2000, 2, 4117–4120; c) J. Lu, S.-Z. Kang, S. L.
Xu, Q.-D. Zeng, C. Wang, L.-J. Wan, C.-L. Bai, Chem. Commun.
2003, 1498–1499; d) Z. Zhong, J. Yan, Y. Zhao, Langmuir 2005, 21,
6235–6239; e) S.-L. Xu, S.-Z. Kang, J. Lu, Y.-H. Liu, C. Wang, L.-J.
Wan, C.-L. Bai, Surfactant Sci. Ser. 2003, 527, L171–L176.
[4] R. Marquis, C. Greco, I. Sadokierska, S. Lebedkin, M. M. Kappes, T.
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Lett. 2008, 8, 1830–1835.
(C7,16), 120.2 (C5,14), 81.2 (2ꢃC
ACHTUNTGRENGU(N CH3)3), 80.8 (4ꢃCACHTUNGTRNEN(UGN CH3)3), 65.4 (2ꢃ
NCH), 53.9 (2ꢃN(CH2)2), 51.6 (C6,15), 40.0 (2ꢃNHCH2), 30.4 (2ꢃ
ACHTUNGTRENNUNG
NHCH2CH2), 29.2 (2ꢃNCHCH2), 28.34 (6ꢃCH3), 28.25 (12ꢃCH3),
23.6 ppm (2ꢃNHCH2CH2CH2); UV/Vis (1,4-dioxane/chloroform, 92:8):
lmax (e)=484 (10000), 404 (220000), 384 (240000), 366 (220000), 346
(180000), 272 nm (4100000 molÀ1 m3 cmÀ1); HRMS: calcd for
C78H100N4O14: 1339.7128 [M++Na]; found (ESI-TOF): m/z: 1339.7078.
The CD spectrum is displayed in the Supporting Information.
[5] Z. Chen, J. Appenzeller, J. Knoch, Y.-M. Lin, P. Avouris, Nano Lett.
2005, 5, 1497–1502.
Compound (6R,15R)-1: A large excess of trifluoroacetic acid (1 mL) was
added to a solution of (6R,15R)-10 (16 mg, 0.012 mmol, 1.0 equiv) in
chloroform (0.05 mL). The reaction mixture was stirred for 30 h at room
temperature, and then diethyl ether (2 mL) was added and the resulting
mixture was concentrated under reduced pressure. Twice more, diethyl
ether (2 mL) was added and the solution obtained was concentrated to
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Hersam, Nat. Nanotechnol. 2006, 1, 60–65; d) M. S. Strano, M.
Zheng, A. Jagota, G. B. Onoa, D. A. Heller, P. W. Barone, M. L.
Usrey, Nano Lett. 2004, 4, 543–550; e) A. Nish, J.-Y. Hwang, J.
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2007, 2, 640–646; b) F. Chen, B. Wang, Y. Chen, L.-J. Li, Nano Lett.
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Jpn. 1977, 50, 2033–2038.
dryness to yield a yellow solid (12 mg, 0.012 mmol, 99%). tR(6R,15R)-10
=
16.4 min (Dionex Acclaim 120-C18, 0.46ꢃ25 cm, 1.0 mLminÀ1, acetoni-
trile/50 mm AcONH4, pH 6.8, gradient from 0:100 to 100:0 in 30 min);
1H NMR (300 MHz, CD3OD, 208C, TMS): d=9.04 (s, 2H; H5,14), 8.39
(s, 2H; H9,18), 8.14 (d, 3J
8.7 Hz, 2H; H1,10), 7.87 (d, 3J
(H,H)=8.1 Hz, 2H; H8,17), 7.50–7.35 (m, 6H; H2,3,11,12, 2ꢃNH), 6.80
(s, 2H; H6,15), 3.85–3.50 (m, 14H; 2ꢃNHCH2, 2ꢃNCH, 2ꢃN(CH2)2),
A
ACHTUNGTRNE(NUNG H,H)=
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
1.90–1.10 ppm (m, 12H; 2ꢃNHCH2CH2CH2CH2); 13C NMR (75 MHz,
CD3OD, 208C, TMS): d=172.8 (2ꢃCO2H), 174.5 (4ꢃCO2H), 168.7 (2ꢃ
CON), 150.5 (2ꢃCCON), 145.2, 145.1, 133.5 (C4a,13a), 132.6 (C5a,14a),
131.6 (C8a,17a), 129.4 (C4,13), 129.2 (C9a,18a), 129.0 (C1,10), 128.3
(C9,18), 126.8, 126.6, 126.4 (C8,17), 123.8 (C7,16), 121.3 (C5,14), 67.0 (2ꢃ
NCH), 55.2 (2ꢃNACHTUNGTRENNUNG(CH2)2), 52.0 (C6,15), 40.4 (2ꢃNHCH2), 30.5 (2ꢃ
NHCH2CH2), 29.8 (2ꢃNCHCH2), 24.7 ppm (2ꢃNHCH2CH2CH2); MS
(MALDI-TOF negative-ion mode, a-cyano-4-hydroxycinnamic acid
(HCCA), MeCN/H2O, 99:1): m/z: 979 [M+ÀH]. The CD spectrum is dis-
played in Figure 2.
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Compound (6S,15S)-1: Following the same procedure as that used for the
synthesis of (6R,15R)-1, but using (6S,15S)-10 (20 mg, 0.015 mmol,
1.0 equiv) instead of (6R,15R)-10, gave (6S,15S)-1 (15 mg, 0.015 mmol,
99%) as a yellow solid. tR(6S,15S)-10 =16.7 min (Dionex Acclaim 120-C18,
0.46ꢃ25 cm, 1.0 mLminÀ1, acetonitrile/50 mm AcONH4, pH 6.8, gradient
from 0:100 to 100:0 in 30 min); 1H NMR (300 MHz, CD3OD, 208C,
TMS): d=9.04 (brs, 2H; H5,14), 8.38 (brs, 2H; H9,18), 8.20–8.10 (m,
2H; H4,13), 7.97–7.81 (m, 4H; H1,7,10,16), 7.77–7.69 (m, 2H; H8,17),
7.50–7.35 (m, 6H; H2,3,11,12, 2ꢃNH), 6.79 (s, 2H; H6,15), 3.85–3.50 (m,
14H; 2ꢃNHCH2, 2ꢃNCH, 2ꢃNACHTNUTRGNE(UNG CH2)2), 1.90–1.10 ppm (m, 12H; 2ꢃ
NHCH2CH2CH2CH2); 13C NMR (50 MHz, CD3OD, 208C, TMS): d=
175.8 (2ꢃCO2H), 175.1 (4ꢃCO2H), 168.7 (2ꢃCON), 150.5 (2ꢃCCON),
145.2 (C5b,6a,14b,15a), 133.5 (C4a,13a), 132.6 (C5a,14a), 131.6 (C8a,17a),
129.5 (C4,13), 129.2 (C9a,18a), 129.0 (C1,10), 128.2 (C9,18), 126.8, 126.5,
126.4 (C8,17), 123.9 (C7,16), 121.3 (C5,14), 66.9 (2ꢃNCH), 55.3 (2ꢃN-
ACHTUNGTRENNUNG
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Chem. Eur. J. 2009, 15, 11187 – 11196
ꢂ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
11195

S. Meunier et al.
[18] To date, and as underlined by N. Komatsu (ref. [8]), CD measure-
ments do not allow the discrimination of optical activity due to
SWNTs and induced optical activity of racemic SWNTs (as ob-
served, for example, by adsorbing DNA on a racemic mixture of
SWNTs; G. Dukovic, M. Balaz, P. Doak, N. D. Berova, M. Zheng,
R. S. Mclean, L. E. Brus, J. Am. Chem. Soc. 2006, 128, 9004–9005).
For this reason, and because of the very high optical activity of com-
pounds 1, extensive washings were required for its complete remov-
al from the SWNT samples in order to unequivocally measure the
optical enrichment due to the chiral SWNTs. In this process, we in-
curred a dramatic loss in material, which prevented us from record-
ing CD signals strong enough to be conclusive.
Received: June 7, 2009
Published online: September 16, 2009
11196
www.chemeurj.org
ꢂ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 11187 – 11196