Helical supramolecular aggregates based on ureidopyrimidinone quadruple hydrogen bonding

Article abstract of DOI:10.1002/chem.200204495

A series of mono- and bi-functional compounds 2-7, based on the ureido pyrimidinone quadruple hydrogen bonding unit, was prepared to study the mode of aggregation of these compounds in the bulk and in solution. Compounds 2-7 exhibit thermotropic liquid crystalline properties, as evidenced by differential scanning calorimetry and optical polarization microscopy. The presence of an ordered hexagonal discotic (D_ho) phase of 2a was confirmed by X-ray diffraction on an aligned sample. In chloroform, the bi-functional compounds form cyclic dimers at millimolar concentrations, and these dimers exist in equilibrium with linear species above a critical concentration, which may be from 6 mM to greater than 260 mM, depending on the structure of the spacer. Circular dichroism measurements in chloroform did not show a Cotton effect. Dodecane solutions of compounds 3, 4b, and 7b display a Cotton effect at the absorption band of the phenyl-pyrimidinone unit. Amplification of chirality was observed in mixtures of 7a and 7b, but not in mixtures of 4a and 4b, indicating that 7a and 7b form mixed polymeric aggregates with a helical architecture in dodecane solution, whereas 4a and 4b do not. The Cotton effect is lost upon increasing the temperature. Half of the helicity is lost at 25°C for 3 and at 60°C for 4b, suggesting that 3, bearing the shorter spacer, forms less stable columns than 4b. Compound 7b loses half of its helicity at 45°C. Compounds 2b, 5, and 6 do not exhibit helical organization, as evidenced by the absence of Cotton effects.

Full text of DOI:10.1002/chem.200204495

FULL PAPER
Helical Supramolecular Aggregates Based on Ureidopyrimidinone Quadruple
Hydrogen Bonding
[a]
J. H. K. Ky Hirschberg, Rolf A. Koevoets, Rint P. Sijbesma,* and E. W. Meijer*
Abstract: A series of mono- and bifunc-
tional compounds 2 7, based on the
ureido pyrimidinone quadruple hydro-
gen bonding unit, was prepared to study
the mode of aggregation of these com-
pounds in the bulk and in solution.
Compounds 2 7 exhibit thermotropic
liquid crystalline properties, as evi-
denced by differential scanning calorim-
etry and optical polarization microsco-
py. The presence of an ordered hexago-
nal discotic (Dho) phase of 2a was
confirmed by X-ray diffraction on an
aligned sample. In chloroform, the bi-
functional compounds form cyclic dim-
ers at millimolar concentrations, and
these dimers exist in equilibrium with
linear species above a critical concen-
tration, which may be from 6 mm to
greater than 260 mm, depending on the
structure of the spacer. Circular dichro-
ism measurements in chloroform did not
show a Cotton effect. Dodecane solu-
tions of compounds 3, 4b, and 7b display
a Cotton effect at the absorption band of
the phenyl-pyrimidinone unit. Amplifi-
cation of chirality was observed in
mixtures of 7a and 7b, but not in
mixtures of 4a and 4b, indicating that
7a and 7b form mixed polymeric aggre-
gates with a helical architecture in
dodecane solution, whereas 4a and 4b
do not. The Cotton effect is lost upon
increasing the temperature. Half of the
helicity is lost at 258C for 3 and at 608C
for 4b, suggesting that 3, bearing the
shorter spacer, forms less stable columns
than 4b. Compound 7b loses half of its
helicity at 458C. Compounds 2b, 5, and 6
do not exhibit helical organization, as
evidenced by the absence of Cotton
effects.
Keywords: aggregation
¥ helical
structures ¥ hydrogen bonds ¥ supra-
molecular chemistry
pyrimidinone
¥
ureido
polymers with high degrees of polymerization both in bulk
and in solution from monomers containing two of these
units.[14] The directionality and the selectivity of multiple
hydrogen bonds allow a high degree of control over polymer
architecture with respect to chain length–which can be
adjusted by mixing monofunctional and bifunctional com-
pounds–and with respect to the degree of cross-linking in
reversible networks–which can be controlled by addition of
trifunctional compounds. Even greater control over polymer
architectures can in principle be achieved by employing
additional noncovalent interactions between monomeric units
that favor a specific conformation of the polymeric chain.
Conformational control is the basis of the functionality of
biomacromolecules such as DNA and proteins, and has
become a fruitful area of research in synthetic covalent
polymers. Here, the conformational preferences of mono-
meric units in combination with inter-residue hydrogen bonds
or stacking interactions have been used to obtain macro-
Introduction
[2]
Supramolecular polymers[1]
,
are a fascinating class of
materials, formed by the association of monomers through
reversible, noncovalent interactions such as hydrogen bond-
ing, metal coordination, or p p stacking. Linear hydrogen-
bonded supramolecular polymers were first introduced by
Lehn and co-workers, who used triple hydrogen bonds
[4]
between monomers.[3]
,
Monomers with tartaric acid back-
bones were shown to form liquid-crystalline materials in
which the molecules are packed in helical columns,[5] which
form helically twisted fibers.[6] Stronger interactions have
been obtained with single hydrogen bonds between carboxylic
acids and pyridines,[7] or by use of arrays of more than three
hydrogen bonds.[8 11] We have employed the high strengths of
the ureidotriazine[12] and ureidopyrimidinone[13] quadruple
hydrogen bonding units to obtain linear supramolecular
[a] Dr. R. P. Sijbesma, Prof. Dr. E. W. Meijer, Dr. J. H. K. K. Hirschberg,
Ir. R. A. Koevoets
molecules that are folded into a well-defined secondary
17]
structure (™foldamers∫).[15
Recently we have applied this
Laboratory of Macromolecular and Organic Chemistry
Eindhoven University of Technology, P.O. Box 513
5600 MB, Eindhoven (The Netherlands)
Fax : (‡40)2451036
concept to supramolecular polymers, by using solvophobic
interactions between ureido-s-triazine (UTr) units connected
by a spacer and provided with solubilizing trialkoxyphenyl
groups to obtain supramolecular polymers with a helical
columnar architecture in dodecane (Figure 1).[18] The struc-
ture of the columns was shown to be biased towards a single
E-mail: R.P.Sijbesma@tue.nl, E.W.Meijer@tue.nl
Supporting information for this article is available on the WWW under
http://www.chemeuj.org or from the author. Simple model for ampli-
fication of chirality in n-mers.
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Chem. Eur. J. 2003, 9, 4222 4231

4222 4231
trialkoxyphenyl groups to pro-
mote a columnar architecture.
Here we present the results of a
study of compounds 2 7 in bulk
and in solution, by differential
scanning calorimetry (DSC) and
X-ray crystallography in the
bulk, and by 1H NMR and
circular dichroism in solution.
Figure 1. Ureido-s-triazine derivative C6-(UTr) , and schematic representations of helical supramolecular
2
polymers (observed in dodecane) and random coil polymers (observed in chloroform).
helicity by the use of homochiral
side chains. In CHCl3, a solvent
in which solvophobic interac-
tions between aromatic groups
are much weaker, but the hydro-
gen bonding between ureidotria-
zine groups is still relatively
strong (Kdim ˆ 2  104 mÀ1), the
compounds form random coil
polymers.[12] This approach was
extended to defined architec-
tures in water through the use
of chiral penta(ethylene oxide)
derivatives.[19]
Ureidopyrimidinones (UPy)
have a much higher dimerization
constant[20] (Kdim ˆ 6  107 mÀ1 in
CHCl3) and bifunctional com-
pounds containing this unit
should in principle allow the
construction of polymers with a
higher degree of polymerization
in either dodecane or chloro-
form. Previously, we have shown
that bifunctional UPy derivative
1, which is strongly preorganized
by its a,a'-tetramethyl xylylene
spacer, exclusively forms cyclic
dimers in CHCl3 and in the
crystal (Figure 2). In solution,
the cyclic dimers of 1 exist as a
slowly interconverting mixture
of syn and anti isomers, with
UPy units present in either the
keto or the enol tautomeric
form.[21]
To achieve highly preorgan-
ized supramolecular polymers
with a columnar architecture,
we studied the mode of aggre-
gation (cyclic versus polymeric)
of bifunctional ureidopyrimidi-
nones, with less preorganized
spacer units than 1, and we
Figure 2. a) Structural formula of bifunctional UPy derivative 1. b) Three isomeric cyclic dimers observed for this
compound. c) Crystal structure of the syn dimer.[21]
provided these molecules with
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R. P. Sijbesma, E. W. Meijer et al.
FULL PAPER
(Scheme 2). All compounds
were purified by column chro-
matography and were fully char-
acterized by 1H NMR, 13C NMR,
IR spectroscopy, MALDI-TOF
mass spectrometry, and elemen-
tal analysis.
Liquid crystallinity: Upon dime-
rization, the UPy derivatives 2a
and 2b form disk-shaped dim-
ers, with a rigid, planar core,
surrounded by flexible alkyl
groups. This architecture is con-
ducive to the formation of a
columnar discotic mesophase in
bulk.[25] In bifunctional deriva-
tives 3 7, similar columns of
UPy dimers may be formed
when each spacer moiety con-
nects two stacked disks. De-
pending on the arrangement of
the spacers, the columns are
either polymeric, or they consist
of stacks of cyclic dimers of the
bifunctional molecules (Figure 3).
Results
To investigate the presence of (columnar discotic) meso-
phases, the thermal behavior of the compounds was studied by
polarization microscopy and DSC. All compounds feature
strong birefringent textures, which are liquid-like at room
temperature. Monofunctional compound 2a and bifunctional
compound 3 feature fan-like textures upon slowly cooling
from the isotropic phase. These focal conic textures are typical
for discotic hexagonal phases. For compounds 2b and 4 7,
only tiny homeotropic monodomains were present in the
liquid crystalline state, probably due to the highly viscous
isotropic melt. Upon heating, the DSC traces of the com-
pounds each show a transition from the mesophase to the
isotropic state at temperatures between 98 and 2428C. The
transition was also observed upon cooling, except in the case
of chiral compound 3. Sharp melting points were observed for
achiral compounds 2a (Figure 4), 4a, and 7a, while the chiral
compounds only showed broad transitions, below À508C,
presumably due to a glass transition. The phase transition
temperatures are summarized in Table 1.
Synthesis: Monofunctional ureidopyrimidinone 2a and 2b and
bifunctional derivatives 3 7 were synthesized either by acyla-
tion of isocytosines 11a or 11b with butyl isocyanate or the
appropriate diisocyanate, when commercially available, or they
were prepared by the action of di-tert-butyl tricarbonate on the
corresponding diamine (Scheme 1). In the reported synthesis of
isocytosine 2a,[22] ethyl 3,4,5-trialkoxybenzoylacetate 9a was
obtained from the corresponding benzoyl chloride by treatment
with ethyl acetoacetate 8, followed by decarboxylation.[23] In
this work a more efficient method was used for the synthesis of
9b, in which the acid chloride was allowed to react with
potassium ethyl malonate (10) under the action of anhydrous
magnesium chloride/triethylamine as a base system.[24] By this
method, b-keto ester 9b was obtained in 86% yield. Con-
densation of the b-keto esters (used without further purifica-
tion) with guanidinium carbonate in ethanol afforded isocyto-
sines 11a and 11b in 39% and 45% yields, respectively
To confirm the presence of a columnar discotic arrange-
ment of dimers, as inferred from the textures in optical
polarized microscopy, the structures of the mesophases of 2a
and 3 were investigated by X-ray diffraction (Figure 5 and
Table 2). The diffraction pattern of 2a features a perpendic-
ular orientation of the low-angle and the wide-angle reflec-
tions, indicating an orthogonal phase. The low-angle reflec-
tions at spacings of 28.9, 15.4, and 14.1 allow indexation as the
200, 120, and 400 reflections in an orthogonal lattice with
lattice constants of a ˆ 56.4 ä and b ˆ 32.6 ä. The sharp wide-
angle reflections feature a perpendicular orientation with
respect to the small-angle reflections, which indicates that the
phase is ordered, and the disks are stacked with an interdisc
distance of 3.5 ä. For compound 3 a sharp reflection with a
Scheme 1. Synthesis of mono- and bifunctional ureidopyrimidinones 2 7.
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Helical Supramolecular Aggregator
4222 4231
tautomer in an 87:13 ratio. From
the position of the NH protons
(between d ˆ 10 and 14 ppm for
both tautomers) it can be con-
cluded that hydrogen bonds are
present.
1H NMR spectra of dilute
solutions of bifunctional com-
pounds 3 7 in CDCl3 are much
more complex. As examples,
spectra of solutions of 3 and 4b
are shown in Figure 7. Upon
addition of small amounts of
Scheme 2. Synthesis of isocytosine 11a, b.
Table 1. Thermotropic properties of compounds 2 7b determined by
DSC.[a]
Compound
K
T [8C] DH [kJmolÀ1
]
M
T8C DH [kJmolÀ1
]
I
2a
2b
3
4a
4b
5
6
7a
7b
¥
45
50
¥
¥
¥
¥
¥
¥
¥
¥
¥
131
98
2
1.5
2.2
3.7
¥
¥
¥
¥
¥
¥
¥
¥
173
164
160[c]
147
207
242
239
¥
¥
À 11
14
[b]
2.2
12.3
7.1
À 17
18
7.5
[a] ¥ The phase is observed; Kˆ crystalline phase; M ˆ mesophase; I ˆ
isotropic phase. [b] Only observed after precipitation in methanol. [c] This
value is obtained from the first heating curve.
Figure 3. Schematic representation of columns of bifunctional compounds
3
7, which are either polymeric (a), or consist of stacks of cyclic dimers (b).
Figure 4. DSC thermogram of compound 2a. First and second heating and
cooling scans are shown.
Figure 5. X-ray diffraction pattern of the mesophase of compound 2a.
spacing of 31.6 ä was found, but no higher order peaks were
observed. In combination with a fan-like texture observed by
polarization microscopy, this suggests the presence of a
columnar mesophase for 3.
trifluoroacetic acid, which disrupts the hydrogen bonds
between ureidopyrimidinone units, the spectra simplify dra-
matically (Figure 7d and 7h). Similar complex spectra have
been observed for bifunctional compound 1, which exists in
Aggregation in chloroform: Ureidopyrimidinones have been
shown[13] to exist in solution as mixtures of strongly dimerizing
tautomers, a [1H]-pyrimidin-4-one (keto) tautomer and a
pyrimidin-4-ol (enol) tautomer (Figure 6, inset). The position
Table 2. Diffraction spacings [ä] for the Dho mesophase of 2a.
Interdisc distance
200/110
120
400/220
Alkyl halo
3.5
1
of the keto enol equilibrium has been studied by H NMR
observed
spectroscopy, and is substituent- and solvent-dependent. The
1H NMR spectrum of monofunctional compound 2b in CDCl3
is shown in Figure 6 and shows signals of the keto and the enol
a ˆ 56.4; b ˆ 32.6
28.9
28.2
15.4
15.6
14.1
14.1
4.4
calculated
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R. P. Sijbesma, E. W. Meijer et al.
FULL PAPER
Table 3. Diffusion constants relative to solvent molecule of compound 3
and 4b.
3
4b
D/DCHCl cyclic aggregates
0.095 (Æ0.006)
0.129 (Æ0.013)
0.0312 (Æ0.003)
3
D/DCHCl polymeric aggregates
3
in keto and enol tautomeric forms. Upon increasing the
concentration to 260 mm, no signals originating from poly-
meric aggregates were observed.
Compound 4b, however, displays different behavior. In the
1H NMR spectrum of this compound, multiple sets of signals
are observed at low concentrations, with diffusion constants
similar to those to the cyclic dimers of 3, while above 10 mm,
an additional set of peaks from polymeric aggregates is
observed, showing a much lower diffusion constant (Table 3).
It has been predicted that equilibria between cyclic and
polymeric species consisting of strongly associating bifunc-
tional monomers should display
Figure 6. 1H NMR spectrum of monofunctional ureidopyrimidinone 2b in
CDCl3.
critical concentrations, below
which no polymer is present,
and above which the concentra-
tion of cycles remains con-
[27]
stant.[26]
,
Such behavior has
indeed been observed by us in
bifunctional UPy derivatives.[28]
The lowest concentrations at
which polymeric species could
be observed in the 1H NMR
spectra were determined for
compounds 3, 4b, 5, and 6. These
critical concentrations are sum-
marized in Table 4. The results
show that there is a large influ-
ence of spacer structure on the
critical concentration. Unfortu-
nately, due to the extremely
complex spectrum of 7b, it was
not possible to establish a critical
concentration for the most pre-
organized compound in the ser-
ies of molecules we have studied.
We have investigated the chi-
Figure 7. 1H NMR spectra of bifunctional compounds 3 and 4b in CDCl3 at different concentrations (spectra a
and e g, respectively), and spectra after addition of small amounts of TFA (d and h).
c
roptical properties of the chiral bifunctional compounds 3, 4b,
5, 6, and 7b by circular dichroism (CD) spectroscopy in
chloroform, at concentrations of 1 mm, at which polymeric
aggregates were shown by NMR spectroscopy to be absent.
None of the compounds showed a Cotton effect, indicating
that the cyclic dimers are not highly ordered in this solvent.
solution as a mixture of isomeric cyclic dimers I, II, and III,
interconverting slowly on the NMR time scale, and giving rise
to a set of four signals for each proton in the molecule.[21]
1
Concentration-dependent H NMR studies were performed
on compounds 3, 4b, 5, 6, and 7b in order to study the
equilibrium between cycles and polymer in chloroform.
Spectra of solutions of 3 show four sets of signals. To establish
the relative size of the aggregates giving rise to the different
sets of signals, NMR diffusion experiments were performed
on a 100 mm chloroform solution of 3. The diffusion constants
relative to solvent molecules are similar for all sets of signals
(Table 3) and are relatively high, indicating that at this
concentration 3 is present as small, cyclic aggregates. From the
similarity of the spectrum with that of 1, we conclude that
these cycles are mixtures of isomeric dimers with UPy groups
Aggregation in dodecane: 1H NMR spectra of 2 and of
bifunctional compounds 3 7 in deuterated dodecane showed
Table 4. Critical polymerization concentrations of compounds 3, 4b, 5,
and 6.
3
4b
5
6
> 260 mm
10 mm
7 mm
30 mm
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Helical Supramolecular Aggregator
4222 4231
broad unresolved signals for the alkyl chains and broad signals
for the phenyl-pyrimidinone cores of the molecules, indicating
the formation of large aggregates in this solvent. When the
temperature was increased from 208C to 1258C, the inten-
sities of the signals for the aromatic cores increased and the
peaks became sharper.
achiral molecules at a constant total concentration of
chromophores. The results of these measurements are plotted
in Figure 9b as the Cotton effect normalized to the concen-
tration of chiral chromophores. In this way chirality induced in
achiral molecules shows up as an amplification larger than 1.
CD spectra of the chiral compounds 2b, 3, 4b, 5, 6, and 7b
were recorded in dodecane in order to examine the degree of
order in aggregates of these compounds. A 1 mm solution of
monofunctional compound 2b in dodecane gave no Cotton
effect. In the series of bifunctional compounds, Cotton effects
at the p p* transition of the phenyl-pyrimidinone moiety
were observed in dodecane for compounds 3, 4b, and 7b,
while compounds 5 and 6–with C-7 and C-8 spacers,
respectively–each showed no CD signal. Although the CD
effects observed are relatively small (see Figure 8a), they are
Figure 8. a) CD spectrum of a 1 mm dodecane solution of compound 7b at
À68C. b) ™Sergeants and soldiers∫ experiment on mixtures of chiral and
achiral compounds at fixed total concentrations of 1 mm in dodecane at
Figure 9. Temperature dependence of the CD effect in spectra of 1 mm
solutions of compounds 3 (A), 4b (B), and 7b (C) in dodecane. The
fraction of the maximum ellipticity remaining is plotted against temper-
ature.
~
&
À68C: ( ) 4a and 4b; ( ) 7a and 7b. The amplification is defined as the
normalized CD effect per chiral molecule versus fraction of chiral
compound.
reproducible. The cooperativity of the CD effect in mixed
solutions of chiral and achiral bifunctional compounds 4a,b
and 7a,b was studied in a ™sergeants and soldiers∫ type of
experiment[29] by varying the relative amounts of chiral and
For mixtures of compounds 4, no amplification of chirality
was observed, even when the samples were annealed at 808C,
or when the mixtures were prepared in CHCl3, followed by
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R. P. Sijbesma, E. W. Meijer et al.
FULL PAPER
removal of this solvent and redissolution in dodecane. There-
fore, only the chiral molecules 4b contribute to the CD effect
in dodecane solution. For compounds 7, however, strong
amplification of chirality was observed. At a fraction of 0.1 of
chiral compound 7b, the CD effect is amplified by a factor of
6. Since a simple model suggests that in cyclic dimers the
amplification should not exceed 2 (see Supporting Informa-
tion), this suggests that polymeric aggregates with helical
order are present.
Temperature-dependent CD measurements were per-
formed on 1 mm dodecane solutions of 3, 4b, and 7b in order
to establish the thermal stabilities of the aggregates (Fig-
ure 9). A plot of the molar ellipticities at l ˆ 325 nm
(normalized against the values at À68C) versus temperature
shows that the chiral order gradually disappears for all three
compounds. The temperatures at which half of the CD effect
has been lost are different for these compounds, and vary
between 258C for 3, 608C for 4b, and 458C for compound 7b.
dodecane, Cotton effects are absent for compound 5 and 6,
which have longer spacers and are therefore less preorganized
to form ordered helical polymers. The Cotton effects observed
for compounds 3, 4b, and 7b, however, show that highly
ordered aggregates with supramolecular chirality are formed.
The observed strength of the ™sergeants and soldiers∫ effect in
mixtures of 7a and 7b demonstrates that in this solvent,
chirality may be transferred from 7b to a large number of
achiral molecules 7a. This makes it improbable that 7 forms
stacks of cyclic dimers in dodecane, and we conclude that
helical polymeric aggregates are formed instead. A sergeants
and soldiers effect is completely absent in dodecane solutions
of compounds 4. As even transfer of chirality in a cyclic dimer
would lead to amplification by a factor of 2, it is probable that
the formation of mixed aggregates of 4a and 4b is thermo-
dynamically unfavorable. Melting experiments, analogous to
thermal denaturation experiments performed on double-
helical DNA, show that the stabilities of the helical arrange-
ment of 4b and its direct ureidotriazine analogue are quite
similar (60 versus 708C).
The reason why 7 forms polymers in dodecane, whereas it
forms cyclic dimers in chloroform, is not fully understood by
us at the moment. A possible explanation would need to take
account of entropic effects, which strongly disfavor polymer-
ization in chloroform, whereas the entropic cost of polymer-
ization in dodecane would be much smaller, because cyclic
dimers would already be aggregated into columns by solvo-
phobic interactions. Further study of the structures of the
aggregates of 7 in dodecane would of great interest, because a
transition from a stack of cyclic dimers to a helical polymer is
analogous to the transition between a stack of disks and a
polymeric helix in the self-assembly of tobacco mosaic virus
(TMV),[30] which is brought about by subtle changes in
conditions such as ionic strength or pH.
Discussion and Conclusions
Like its ureido-s-triazine analogues[18], ureidopyrimidinone
2b, provided with a trialkoxyphenyl group, forms liquid-
crystalline mesophases in which dimeric units are stacked in
columns with hexagonal order. This arrangement of UPy units
is compatible with the presence of polymeric chains of
bifunctional molecules in the mesophases of bifunctional
compounds 3 7, although the possibility that the columns
consist of stacks of cyclic dimers in the thermotropic
mesophase cannot be ruled out with the knowledge available
at present. 1H NMR and CD spectroscopy in CDCl3 and
dodecane give valuable information that sheds additional
1
light on the mode of aggregation in solution. The H NMR
spectra of the UPy derivatives in CDCl3 are much more
complex than those of the corresponding triazine derivatives,
due to keto enol tautomerism. However, study of the
concentration dependence of the spectra show that com-
pounds 2 7 are present as small cyclic aggregates in the
millimolar concentration range. A more detailed study of
compounds 3 and 4b, including measurement of the diffusion
constants of the different species, shows that 3 is present as
cyclic dimer even at 260 mm, while for 4b, a critical concen-
tration of approximately 10 mm is observed, above which
polymeric aggregates are formed.
It is of interest to compare the aggregation behavior of the
UPy derivatives with that of the triazine derivative (C6-
Utr)2.[9] The latter compound forms columnar aggregates by
stacking of dimerized units induced by solvophobic interac-
tions. Preorganization by spacer moieties is required for a
helical stacked arrangement of dimerized UTr units, as no CD
effect is observed for the monofunctional triazine. In the
chiral monofunctional UPy derivative 2b, the absence of a
Cotton effect both in chloroform and in dodecane shows that
the same requirements hold for ureidopyrimidinones. The
absence of Cotton effects in cyclic dimers of bifunctional UPy
derivatives 3 7 in chloroform shows that even when the
spacers connecting the two layers enforce a stacked arrange-
ment, there is no bias in the supramolecular chirality. In
Experimental Section
General methods: All starting materials were obtained from commercial
suppliers and were used as received. All moisture-sensitive reactions were
performed under an atmosphere of dry argon. Dry and ethanol-free
dichloromethane was obtained by distillation from P2O5; dry tetrahydro-
furan (THF) was obtained by distillation from Na/K/benzophenone;
dimethylformamide was dried over BaO; pyridine was dried by standing
over 4 ä molecular sieves; dry toluene was obtained by distillation from
Na/K/benzophenone, and triethylamine was dried over potassium hydrox-
ide. Methyl 3,4,5-tridodecyloxybenzoate, methyl 3,4,5-tris((S)-3,7-dimethy-
loctyloxy)benzoate, 3,4,5-tri(dodecyloxy)benzoyl chloride, 3,4,5-tris((S)-
3,7-dimethyloctyloxy)benzoyl chloride, and ethyl 3,4,5-tri(dodecyloxy)ben-
zoylacetate (9a)[13] were synthesized by previously described procedures.
Analytical thin layer chromatography was performed on Kieselgel F-254
precoated silica plates. Visualization was accomplished with UV light.
Column chromatography was carried out on Merck silica gel 60 (70 230
mesh) or on Merck aluminium oxide 90 (70 230 mesh, activity II III).
1H NMR and 13C NMR spectra were recorded on a 400 MHz 4-nucleus
NMR (Varian Mercury Vx) (400.13 MHz for 1H NMR and 100.62 MHz for
13C NMR). Proton chemical shifts are reported in ppm downfield from
tetramethylsilane (TMS), and carbon chemical shifts in ppm downfield of
TMS, with the resonance of the deuterated solvent as internal standard.
Electrospray ionization mass spectrometry (ESI-MS) was carried out on a
Perkin Elmer API 300 MS/MS mass spectrometer. Matrix-assisted laser
desorption/ionization mass-time of flight spectra (Maldi-TOF) were
obtained by use of indole acrylic acid as the matrix on a PerSeptive
4228
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
Chem. Eur. J. 2003, 9, 4222 4231

Helical Supramolecular Aggregator
4222 4231
Biosystems Voyager-DE PRO spectrometer. IR spectra were measured on
a Perkin Elmer Spectrum One instrument. Optical properties and melting
points were determined with a Jeneval polarization microscope equipped
with a Linkam THMS 600 heating device with crossed polarizers. DSC
spectra were obtained on a Perkin Elmer Pyris 1 DSC. X-ray diffraction
patterns were recorded with a multiwire area X-1000 coupled with a
graphite monochromator.
solid, which was further purified by column chromatography (eluent: ethyl
acetate/hexane 1:3, and then 8% methanol in dichloromethane) (1.68 g,
1
ˆ À À ˆ
45%). H NMR (CDCl3) d ˆ 12.35 (br, 1H; C C NH C N), 7.13 (s, 2H;
À
À ˆ À
ˆ À
Ph H), 6.18(s, 1H; H C C N), 5.82(br, 2H; N C NH2) 4.07m, 6H;
À
À
À
O CH2), 1.7 1.9 (m, 6H; O CH2 CH2), 1.7 0.8 (multiple peaks,
51H) ppm; 13C NMR (CDCl3) d ˆ 159.8, 135.9, 153.5, 151.4, 142.7, 123.6,
105.7, 100.3, 71.9, 67.7, 39.6, 37.8, 37.6, 36.6, 30.1, 28.2, 24.9, 22.9, 22.8,
19.8 ppm; IR(UATR): nÄ ˆ 3148, 1649, 1120 cmÀ1; elemental analysis calcd
(%) for C40H69O4N3 (656.01): C 73.37, H 10.60, N 6.41; found: C 73.02, H
10.30, N 6.09.
Wide-angle X-ray diffraction: The X-ray diffraction pattern of an oriented
sample of 2a was recorded with a multiwire area detector X-1000 coupled
with a graphite monochromator. The oriented fibers were obtained by
shearing on a warm beryllium plate, and were measured by hanging in the
beam at the correct focus point. Samples were screened to find suitably
large monodomains. Diffraction of 3 was measured on a Bruker AXS D8
Discover, with a GADDS 2D counter.
N-Butylaminocarbonyl-6-[3,4,5-tri(dodecyloxy)phenyl]isocytosine (2a): A
solution of 6-[3,4,5-tri(dodecyloxy)phenyl]isocytosine (11a, 1 g, 1.35 mmol)
and n-butyl isocyanate (0.77 mL, 6.76 mmol) in dry pyridine (7 mL) was
boiled and stirred overnight at reflux temperature. The solution was
evaporated to dryness and the residue was co-distilled twice with toluene
(5 mL). The brown residue was dissolved in chloroform and precipitated in
ethanol. Thin layer chromatography showed that the product contained
two minor contaminants. These were removed by precipitation from ethyl
Ethyl 3,4,5-tris((S)-3,7-dimethyloctyloxy)benzoylacetate (9b): Potassium
ethyl malonate (10, 1.6 g, 9.4 mmol) and ethyl acetate (15 mL) were placed
in a 25 mL flask. The mixture was stirred and cooled to 08C. Et3N (2.56 g,
3.5 mL) was added to this mixture, followed by dry MgCl2 (1.17 g,
12.3 mmol). The mixture was heated to 358C over 30 min and was then
maintained at 358C for 6 h. The mixture was cooled to 08C, and 3,4,5-
tris((S)-3,7-dimethyloctyloxy)benzoyl chloride (4.2 g, 6.9 mmol) was added
dropwise over 15 min. The mixture was allowed to stir overnight at room
temperature and was then cooled to 08C before the cautious addition of
hydrochloric acid (13%, 20 mL), while the temperature was kept below
258C. The aqueous layer was separated and then back-extracted with
toluene. The combined organic layers were washed with hydrochloric acid
(12%, 2 Â 10 mL) followed by H2O (2 Â 10 mL) and NaHCO3 solution
(5%, 20 mL), and were then concentrated under vacuum to give the
1
acetate, resulting in pure 2a (0.85 g, 75%). H NMR (CDCl3): for 4[1H]-
pyrimidinone tautomer d ˆ 13.90 (s, 1H; NH), 12.06 (s, 1H; NH), 10.24 (s,
À
1H; NH), 6.83 (s, 2H; Ar H), 6.29 (s, 1H; alkylidene H), 4.05 (m, 6H;
À
À
À
À
O CH2), 3.29 (m, 2H; NH CH2), 1.86 (m, 6H; O CH2 CH2), 1.77 (m, 2H;
À
À
NH CH2 CH2), 1.65 (m, 2H; NH-CH2-CH2-CH2) 1.50 (m, 6H; O-CH2-
CH2-CH2), 1.29 (br, 48H; CH2), 0.890 (t, 12H; CH3) ppm; for pyrimidin-4-
ol tautomer d ˆ 13.58 (s, 1H; NH), 11.32 (s, 1H; NH), 10.02 (s, 1H; NH),
À
7.04 (s, 2H; Ar H), 6.65 (s, 1H; alkylidene H), 3.43 (m, 2H) ppm, rest of
the peaks overlap with peaks of the main tautomer; 13C NMR (CDCl3): d ˆ
4[1H]-pyrimidinone tautomer 173.6, 156.8, 155.1, 153.8, 149.1, 141.1, 126.0,
104.3, 103.7, 73.7, 69.4, 39.9, 32.0, 31.6, 30.4, 29.8, 29.9 29.4, 26.2, 22.8, 20.3,
14.2, 13.8 ppm; IR(UATR): nÄ ˆ 3226, 1694, 1120 cmÀ1; elemental analysis
calcd (%) for C51H90N4O5 (839.29): C 72.99, H 9.50, N 6.70; found: C 72.9;
H 9.6; N 6.7.
product as a solid (3.9 g, 86%), which was used in the following step
1
À
without further purification. H NMR (CDCl3): d ˆ 7.21 (s, 2H; Ar H),
À
À
À
4.24 (q, 2H; O CH2 CH3), 4.06 (m, 6H; O CH2), 1.75 1.93 (m, 6H;
O CH2 CH2), 1.75 0.9 (multiple peaks, 54H; CH, CH2, CH3) ppm.
À
À
N-Butylaminocarbonyl-6-[3,4,5-tris((S)-3,7-dimethyloctyloxy)phenyl]-iso-
cytosine (2b): The title compound was synthesized by the same procedure
as used for compound 2a (Yˆ 43%). 1H NMR (CDCl3): for 4[1H]-
pyrimidinone tautomer d ˆ 13.93 (s, 1H; NH), 12.06 (s, 1H; NH), 10.17 (s,
Potassium monoethyl malonate (10): Diethyl malonate (50 g, 0.312 mol)
was dissolved in ethanol (200 mL). A solution of potassium hydroxide
(17.5 g, 0.312 mol) in ethanol (200 mL) was added dropwise over one hour.
A white precipitate was formed during the addition, and stirring was
continued for another 12 h at room temperature after addition of all the
hydroxide. The solution was evaporated to dryness, and the sticky residue
was then taken up in ether. The salt was collected by suction filtration,
washed with ether, and dried under reduced pressure at room temperature,
resulting in pure 10 (45.6 g, 86%). 1H NMR (CDCl3): d ˆ 4.06 (q, 2H;
À
1H; NH), 6.84 (s, 2H; Ar H), 6.28 (s, 1H; alkylidene H), 4.05 (m, 6H;
À
À
O CH2), 3.30 (m, 2H; NH CH2), 1.88 0.95 (m, CH2), 0.890 (t, 12H;
CH3) ppm; for pyrimidin-4-ol tautomer d ˆ 13.57 (s, 1H; OH), 11.30 (s, 1H;
À
NH), 10.0 (s, 1H; NH), 7.07 (s, 2H; Ar H), 6.64 (s, 1H; alkylidene H), 3.43
(m, 2H) ppm, rest of the peaks overlap with peaks of the main tautomer;
13C NMR (CDCl3): d ˆ 4[1H]-pyrimidinone tautomer 173.4, 156.7, 155.0,
153.8, 149.2, 141.9, 126.0, 104.1, 71.8, 67.7, 39.7 13.8 ppm; IR: nÄ ˆ 3226,
1694, 1120 cmÀ1; elemental analysis calcd (%) for C45H78N4O5 (755.13): C
71.58, H 10.41, N 7.42; found: C 71.6, H 10.5, N 7.4.
ˆ
OCH2), 3.15 (s, 2H; CH2C O), 1.12 (t, 3H; CH3) ppm.
6-[3,4,5-Tri(dodecyloxy)phenyl]isocytosine (11a): A solution of ethyl 3,4,5-
tri(dodecyloxy)benzoylacetate (9a, 17.6 g, 21.0 mmol) and guanidinium
carbonate (4.7 g, 26.25 mmol) in absolute ethanol (200 mL) was boiled and
stirred overnight at reflux temperature. The solution was then evaporated
to dryness and the residue was dissolved in chloroform (400 mL). The
solution was washed with water (300 mL) and the aqueous layer was back-
extracted with chloroform (150 mL). The combined organic layers were
washed with a saturated sodium chloride solution, dried over sodium
sulfate, and filtered. Evaporation gave a white solid that was further
purified by column chromatography (eluent: dichloromethane, then 2%
ethanol in dichloromethane, and finally 5% ethanol in dichloromethane)
(6.04 g, 39%). 1H NMR (CDCl3): d ˆ 12.35 (br, 1H; NH), 7.13 (s, 2H;
N,N'-(1,5-Pentamethylene)-bis(2-ureido-6-[3,4,5-tris((S)-3,7-dimethyloctyl-
oxy)phenyl]-4-pyrimidinone (3): Di-tert-butyl tricarbonate (0.20 g,
0.77 mmol) was added to
a solution of 1,5-pentanediamine (38 mL,
0.32 mmol) in dichloromethane. The solution was allowed to stir for 1 h
at room temperature to afford 1,5-pentane diisocyanate. The solution was
evaporated to dryness and the residue was dissolved in pyridine (3 mL).
6-[3,4,5-Tris((S)-3,7-dimethyloctyloxy)phenyl]isocytosine
(11b,
0.5 g,
0.76 mmol) was added to this solution, which was stirred at 908C for
12 h. The solution was evaporated to dryness and the residue was co-
evaporated twice with toluene (2 mL). The orange/white residue was
dissolved in chloroform and precipitated in ethyl acetate. The impure
product was further purified by column chromatography (eluent: 2%
tetrahydrofuran in chloroform, then hexane/chloroform 1:1) and precip-
itation in methanol, resulting in pure 3 (0.14 g, 30%). 1H NMR (CDCl3 ‡
À
Ar H), 6.19 (s, 1H; alkylidene H), 5.84 (br, 2H; NH2) 4.02 (m, 6H;
À
À
À
O CH2), 1.7 1.9 (m, 6H; O CH2 CH2), 1.49 (m, 6H; O-CH2-CH2-CH2),
1.28 (br, 48H; CH2), 0.89 (t, 9H; CH3) ppm; 13C NMR (CDCl3): d ˆ 159.7,
154.1, 153.5, 151.7, 142.4, 123.6, 106.0, 100.4, 72.0, 67.9, 32.0, 30.6, 29.7 29.3,
26.2, 26.0, 22.4, 13.9 ppm; IR: nÄ ˆ 3155, 1652, 1467, 1120 cmÀ1; elemental
analysis calcd (%) for C46H81N3O4 (740.35): C 74.63, H 11.03, N 5.70; found:
C 74.6, H 10.7, N 5.7.
À
TFA): d ˆ 6.87 (s, 4H; Ar H), 6.64 (s, 2H; alkylidene H), 4.19 (m, 4H;
À
À
À
O CH2), 4.09 (m, 8H; O CH2), 3.37 (m, 4H; NH CH2), 1.87 (m, 12H;
À
À
À
À
O CH2 CH2), 1.67 (m, 4H; NH CH2 CH2), 1.66 0.86 (multiple peaks,
104H; CH2, CH3) ppm; 13C NMR (CDCl3): d ˆ 173.2, 157.5, 155.3, 153.8,
148.6, 140.9, 132.12, 126.3, 103.9, 71.9, 67.8, 39.6, 39.5, 37.8, 37.5, 36.5, 30.2,
6-[3,4,5-Tris((S)-3,7-dimethyloctyloxy)phenyl]isocytosine (11b): A solu-
tion of ethyl 3,4,5-tris((S)-3,7-dimethyloctyloxy)benzoylacetate, (9b,
3.77 g, 5.71 mmol) and guanidinium carbonate (1.44 g, 8 mmol) in absolute
ethanol (100 mL) was boiled and stirred overnight at reflux temperature.
The solution was evaporated to dryness and the residue was dissolved in
dichloromethane (50 mL). The solution was extracted with water (50 mL)
and the water layer was extracted with dichloromethane (40 mL). The
combined organic layers were washed with a saturated sodium chloride
solution, dried over sodium sulfate, and filtered. Evaporation gave a white
29.9, 28.2, 25.0, 23.0, 22.0, 19.7 ppm; IR(UATR): nÄ ˆ 3222, 1694, 1114 cmÀ1
;
‡
‡
MALDI-TOF-MS: (1465.13) m/z: 1466 [M] , 1489.16 [M‡Na] ; elemental
analysis calcd (%) for C87H148N8O10 (1466.17): C 71.27, H 10.17, N 7.64;
found: C 71.58; H 9.80; N 7.39.
N,N'-(1,6-Hexamethylene)-bis(2-ureido-6-[3,4,5-tri(dodecyloxy)phenyl]-
4-pyrimidinone (4a): A suspension of 6-[3,4,5-tri(dodecyloxy)phenyl]iso-
cytosine 11b (4 g, 5.4 mmol) in dry pyridine (12 mL) and toluene (2 mL)
Chem. Eur. J. 2003, 9, 4222 4231
www.chemeurj.org
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4229

R. P. Sijbesma, E. W. Meijer et al.
FULL PAPER
À
À
was heated to reflux temperature. A clear solution was obtained and some
solvent was distilled off to remove traces of water. After the mixture had
cooled down to room temperature, 1,6-hexane diisocyanate (0.36 mL,
2.16 mmol) was added by syringe and the solution was stirred overnight at
reflux. The solution was evaporated to dryness and the residue was co-
distilled twice with toluene (5 mL). The brown residue was dissolved in
chloroform and precipitated in ethanol. Minor contamination was removed
by precipitation in ethyl acetate resulting in pure 4a (2.11 g, 59%). 1H NMR
(CDCl3 ‡ TFA): d ˆ 7.30 (s, 2H; m-Ph H), 7.10, 6.89 (s, 4H; Ar H), 6.61
À
(s, 2H; alkylidene H), 4.52 (d, 4H; NH CH2), 4.15 (t, 4H; OCH2), 4.06 (t,
À
À
À
8H; OCH2), 1.81 (m, 12H; OCH2 CH2), 1.49 (m, 12H; OCH2 CH2 CH2),
1.29 (br, 96H; CH2, CH3), 0.90 (t, 18H; CH3) ppm; IR(UATR): nÄ ˆ 3226,
1695, 1117 cmÀ1; elemental analysis calcd (%) for C102H170N8O10 (1668.51):
C 73.43, H 10.27, N 6.72; found: C 72.54, H 9.87, N 6.71.
Nw,Nw'-m-Xylylene-bis(2-ureido-6-[3,4,5-tris((S)-3,7-dimethyloctyloxy)-
phenyl]-4-pyrimidinone (7b): For the synthesis of the title compound see
the procedure for compound 3. Tetrahydrofuran in chloroform (2%) was
used as an eluent for column chromatography, and precipitation in
methanol gave pure 7b (Yˆ 14%). 1H NMR (CDCl3 ‡ TFA): d ˆ 7.34
À
(CDCl3 ‡ TFA) d ˆ 6.91 (s, 4H; Ar H), 6.37 (s, 2H; alkylidene H), 4.04
À
À
(m, 12H; O CH2), 3.32 (m, 4H; NH CH2), 3.17, 1.81 (m, 12H;
À
À
À
À
O CH2 CH2, 1.75 (m, 4H; NH CH2 CH2), 1.60 (m, 4H; NH-CH2-CH2-
CH2), 1.47 (m, 12H; O-CH2-CH2-CH2), 1.26 (br, 96H; CH2), 0.88 (t, 18H;
CH3) ppm; 13C NMR (CDCl3): d ˆ 173.3, 156.9, 155.3, 153.8, 149.5, 140.9,
126.0, 104.5, 103.8, 73.4, 69.3, 40.1, 32.1, 31.6, 30.5, 30.0, 29.9 29.4, 26.4,
22.5, 20.4, 14.2, 13.8 ppm; IR(UATR): nÄ ˆ 3226, 1693, 1117 cmÀ1; elemental
analysis calcd (%) for C100H174N8O10 (1648.52): C 72.86, H 10.64, N 6.80;
found: C 72.54, H 9.98, N 6.71.
À
À
(s, 2H; m-Ph H), 7.10, 6.87 (s, 4H; Ar H), 6.62 (s, 2H; alkylidene H), 4.50
À
À
À
(m, 4H; NH CH2), 4.13 (m, 4H; O CH2 intra), 4.08 (m, 8H; O CH2), 1.86
À
À
(m, 12H; O CH2 CH2, 1.68 0.86 (multiple peaks, 102H; CH2, CH3) ppm;
13C NMR (CDCl3): d ˆ 173.2, 157.6, 155.1, 153.8, 153.5, 148.6, 139.1, 125.4,
125.1, 124.6, 105.0, 103.6, 71.9, 67.6, 39.6, 38.4, 37.8, 37.7, 36.5, 31.5, 30.1, 29.9,
28.2. 25.0, 22.9, 19.7 ppm; IR(UATR): nÄ ˆ 3226, 1692, 1115 cmÀ1; MALDI-
‡
‡
TOF-MS: (MWˆ 1499.11) m/z: 1500.15 [M] , 1523.13 [M‡Na] ; elemen-
tal analysis calcd (%) for C90H146N8O10 (1500.19): C 72.06, H 9.81, N 7.47;
found: C 71.65, H 9.97, N 7.17.
N,N'-(1,6-Hexamethylene)-bis(2-ureido-6-[3,4,5-tris((S)-3,7-dimethyl-
octyloxy)phenyl]-4-pyrimidinone (4b): A suspension of 6-[3,4,5-tris((S)-
3,7-dimethyloctyloxy)phenyl]isocytosine (11b, 0.5 g, 0.76 mmol) in dry
pyridine (4 mL) and toluene (1 mL) was heated to reflux temperature. A
clear solution was obtained, and some solvent was distilled of to remove
traces of water. After the mixture had cooled, 1,6-hexane diisocyanate
(0.05 mL, 0.3 mmol) was added by syringe. A trace of DMAP was also
added. The solution was stirred at 908C for 12 h. The reaction mixture was
evaporated to dryness and the residue was co-evaporated twice with
toluene (2 mL). The red residue was dissolved in chloroform and
precipitated in methanol, ethanol, and ethyl acetate. Further purification
by column chromatography (eluent: 6% tetrahydrofuran in chloroform)
and precipitation in methanol resulted in pure 4b (0.12 g, 27%). 1H NMR
Acknowledgement
We thank Dr. H. Fischer and Ing. M. Hendrix for measuring the X-ray
diffraction of 2a and 3.
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U. Hommel, H. Widmer, Helv. Chim. Acta 1996, 79, 913 941.
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4982.
À
(CDCl3 ‡ TFA): d ˆ 6.91 (s, 4H; Ar H), 6.48 (s, 2H; alkylidene H), 4.09
À
À
À
À
(m, 12H; O CH2), 3.33 (m, 4H; NH CH2), 1.87 (m, 12H; O CH2 CH2),
À
À
1.71 (m, 4H; NH CH2 CH2), 1.66 0.86 (multiple peaks, 106H; CH2,
CH3) ppm; 13C NMR (CDCl3): d ˆ 173.1, 157.0, 155.2, 153.4, 148.2, 140.9,
126.3, 103.7, 71.5, 67.8, 39.6, 39.5, 37.8, 37.5, 36.5, 30.2, 29.9, 28.2, 25.0, 23.0,
22.0, 19.7 ppm; IR(UATR): nÄ ˆ 3226, 1692, 1115 cmÀ1; MALDI-TOF-MS:
‡
‡
(1479.14) m/z: 1480.04 [M] , 1503.01 [M‡Na] ; elemental analysis calcd
(%) for C88H150N8O10 (1480.20): C 71.41, H 10.21, N 7.57; found: C 71.05, H
9.92, N 7.52.
N,N'-(1,7-Heptamethylene)-bis(2-ureido-6-[3,4,5-tris((S)-3,7-dimethyl-
octyloxy)phenyl]-4-pyrimidinone (5): The title compound was synthesized
from 1,7-diisocyanatoheptane in the same way as compound 4. Purification
was performed by column chromatography (eluent: 2% tetrahydrofuran in
chloroform) and precipitation in methanol, resulting in pure 5 (Yˆ 29%).
1
À
H NMR (CDCl3 ‡ TFA): d ˆ 6.88 (s, 4H; Ar H), 6.62 (s, 2H; alkylidene
À
À
À
H), 4.19 (m, 4H; O CH2), 4.09 (m, 8H; O CH2), 3.33 (m, 4H; NH CH2),
À
À
À
À
1.87 (m, 12H; O CH2 CH2), 1.68 (m, 4H; NH CH2 CH2), 1.66 0.86
(multiple peaks, 108H; CH2, CH3) ppm; 13C NMR (CDCl3): d ˆ 171.6,
157.5, 155.3, 153.8, 148.6, 140.9, 132.1, 126.3, 103.9, 71.8, 67.8, 39.5, 37.6, 37.4,
36.5, 36.4, 30.0, 28.1, 24.8, 22.8, 22.6, 19.6 ppm; IR(UATR): nÄ ˆ 3222, 1694,
‡
1114 cmÀ1
;
MALDI-TOF-MS: (1493.16) m/z: 1494.22 [M] , 1517.19
‡
[M‡Na] ; elemental analysis calcd (%) for C89H152N8O10 (1494.23): C
71.50, H 10.25, N 7.50; found: C 71.35, H 10.00, N 7.42.
N,N'-(1,8-Octamethylene)-bis(2-ureido-6-[3,4,5-tris((S)-3,7-dimethyl-
octyloxy)phenyl]-4-pyrimidinone (6): This compound was synthesized from
1,8-diisocyanatooctane by the procedure used for compound 3. Purification
was carried out by column chromatography (eluent: 2% tetrahydrofuran in
chloroform) and precipitation in methanol, resulting in pure 6 (Yˆ 28%).
1
À
H NMR (CDCl3 ‡ TFA): d ˆ 6.88 (s, 4H; Ar H), 6.57 (s, 2H; alkylidene
À
À
H), 4.08 (m, 12H; O CH2), 3.32 (m, 4H; NH CH2), 1.87 (m, 12H;
À
À
À
À
O CH2 CH2), 1.69 (m, 4H; NH CH2 CH2), 1.66 0.86 (multiple peaks,
110H; CH2, CH3) ppm; 13C NMR (CDCl3): d ˆ 173.0, 157.8, 155.2, 153.8,
149.0, 141.5, 132.1, 126.3, 104.5, 72.3, 69.5, 39.4, 39.3, 37.4, 37.1, 36.3, 29.8,
29.7, 28.0, 24.8, 22.7, 22.6, 19.5 ppm; IR(UATR): nÄ ˆ 3226, 1692, 1115 cmÀ1
;
‡
‡
MALDI-TOF-MS: (1507.18) m/z: 1508.18 [M] , 1530.16 [M‡Na] ; ele-
mental analysis calcd (%) for C90H154N8O10 (1508.25): C 71.67, H 10.29, N
7.43; found: C 71.71, H 10.09, N 7.35.
Nw,Nw'-m-Xylylene-bis(2-ureido-6-[3,4,5-tri(dodecyloxy)phenyl]-4-pyrimi-
dinone (7a): The title compound was obtained from m-xylylene diisocya-
nate in the same way as 3. Column chromatography (flash silica, methanol/
tetrahydrofuran/chloroform 2:4:94) gave pure 7a (Yˆ 36%). 1H NMR
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4230
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Helical Supramolecular Aggregator
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Received: October 10, 2002
Revised: May 7, 2003 [F4495]
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Chem. Eur. J. 2003, 9, 4222 4231
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¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4231