Novel Water-Soluble β-Cyclodextrin-Calix[4]arene Couples as Fluorescent Sensor Molecules for the Detection of Neutral Analytes

Article abstract of DOI:10.1021/jo9723321

The synthesis and the host-guest chemistry of two novel fluorescent β-cyclodextrin-calix[4]arene couples 1 and 2 is described. The compounds were prepared by coupling a β-cyclodextrin linked with an aminoxylyl spacer with two different calix[4]arene building blocks each bearing a fluorophore. The fluorophores attached to 1 and 2 are the 2-naphthylamine and the dansyl moiety, respectively. The unsymmetric calix[4]arene functionalization was achieved by monoprotection of the 1,3-diformylcalix[4]arene. The host molecules 1 and 2 were used as fluorescent probes for several organic analytes in aqueous solution. 1 shows sensitivity for a series of neutral organic guest species, such as steroids, terpenes, and other natural products. In contrast, compound 2 does not show sensitivity for organic analytes in aqueous solution. The different behavior of the two fluorescent probes 1 and 2 is explained by the different strength of self-inclusion of each fluorphoric group into the β-cyclodextrin cavity.

Full text of DOI:10.1021/jo9723321

J . Org. Chem. 1998, 63, 5339-5344
5339
Novel Wa ter -Solu ble â-Cyclod extr in -Ca lix[4]a r en e Cou p les a s
F lu or escen t Sen sor Molecu les for th e Detection of Neu tr a l
An a lytes
,
†
,†
J u¨ rgen B u¨ gler, J ohan F. J . Engbersen,* and David N. Reinhoudt*
Laboratory of Supramolecular Chemistry and Technology, University of Twente, P.O. Box 217,
NL-7500 AE Enschede, The Netherlands
Received December 31, 1997
The synthesis and the host-guest chemistry of two novel fluorescent â-cyclodextrin-calix[4]arene
couples 1 and 2 is described. The compounds were prepared by coupling a â-cyclodextrin linked
with an aminoxylyl spacer with two different calix[4]arene building blocks each bearing a
fluorophore. The fluorophores attached to 1 and 2 are the 2-naphthylamine and the dansyl moiety,
respectively. The unsymmetric calix[4]arene functionalization was achieved by monoprotection of
the 1,3-diformylcalix[4]arene. The host molecules 1 and 2 were used as fluorescent probes for several
organic analytes in aqueous solution. 1 shows sensitivity for a series of neutral organic guest species,
such as steroids, terpenes, and other natural products. In contrast, compound 2 does not show
sensitivity for organic analytes in aqueous solution. The different behavior of the two fluorescent
probes 1 and 2 is explained by the different strength of self-inclusion of each fluorphoric group
into the â-cyclodextrin cavity.
In tr od u ction
â- and γ-cyclodextrins.5
-9
Sensing is based on the
competition for the hydrophobic cavity between a guest
molecule and the covalently linked fluorophore resulting
in a change in optical properties. Without appropriate
guest species present, the fluorophore is partially residing
in the hydrophobic cavity of the cyclodextrin, whereas
the presence of organic analytes leads to decomplexation
of the fluorophore and a concomitant decrease of its
Host-guest complexation is one of the basic principles
in the development of new devices for sensing of ions or
neutral molecules. In the field of ion sensing, high
sensitivity and selectivity have been achieved with a
variety of ion receptor molecules applied in ion selective
electrodes or field effect transistors.1-3 However, for
neutral molecules both selective recognition and its
transduction are much more difficult and detection of
13
fluorescence quantum yield.
The most important selectivity parameter for function-
alized cyclodextrins is the size fit between host and guest.
For the development of sensors for specific molecules, it
is necessary to introduce further selectivity to the host-
guest complexation characteristics of cyclodextrins by
attaching further functional groups or building blocks.
We have followed this approach by attaching function-
alized calix[4]arenes to the cyclodextrin moiety. Calix-
neutral organic species is mainly based on mass sensitive
or spectroscopic measurements.4
-10
A class of natural
host compounds for organic molecules is the cyclodex-
trins, which are cyclic oligosaccharides consisting of 6,
1
1,12
7
, or 8 glucose moieties.
They are water soluble and
have the shape of a truncated cone with a hydrophobic
cavity, which renders them capable of complexation of
organic molecules. To transduce the complexation of
cyclodextrins with guests into a physical signal, Ueno and
others have prepared fluorescent cyclodextrins by ap-
pending a fluorophore to one of the hydroxyl groups of
[4]arenes are a class of well-known and frequently used
building blocks in supramolecular chemistry that can
serve as a molecular platform and offer eight positions
for substitution, four each at the upper and the lower
rims.1
4,15
Their chemistry is rather well explored, and
†
To whom correspondence should be addressed. Fax: +31-53-
1
6,17
4
894645. Email: smct@ct.utwente.nl.
they are relatively easy to modify selectively.
Calix-
(
1) Cobben, P. L. H. M.; Egberink, R. J . M.; Bomer, J . G.; Bergveld,
P.; Verboom, W.; Reinhoudt, D. N. J . Am. Chem. Soc. 1992, 114, 10573.
[4]arenes can be attached to surfaces via spacers on their
lower rim which offers the opportunity for immobilization
(
2) Engbersen, J . F. J .; Reinhoudt, D. N. Analysis 1994, 22, M16.
of sensing molecules.1
8-20
In previous experiments, we
(3) Antonisse, M. M. G.; Lugtenberg, R. J . W.; Egberink, R. J . M.;
Engbersen, J . F. J .; Reinhoudt D. N. In Chemosensors of Ion and
Molecule Recognition; Desvergne, J . P., Czarnik, A. W., Eds.; Kluwer
Academic Publ.; The Netherlands, 1997; p 23.
(13) Corradini, R.; Dossena, A.; Marchelli, R.; Panagia, A.; Sartor,
G.; Saviano, M.; Lombardi, A.; Pavone, V. Chem. Eur. J . 1996, 2, 373.
(14) Gutsche, C. D. Calixarenes, Monographs in Supramolecular
Chemistry; Stoddart, J . F., Ed.; Royal Society of Chemistry: Cam-
bridge, 1989; Vol. 1.
(15) B o¨ hmer,V. Calixarenes: A versatile Class of Macrocyclic Com-
pounds; Vicens, J ., B o¨ hmer, V., Eds.; Kluwer Academic Publishers:
Dordrecht, 1991.
(16) B o¨ hmer, V. Angew. Chem., Int. Ed. Engl. 1995, 34, 713.
(17) Takeshita, M.; Shinkai, S. Bull. Chem. Soc. J pn. 1995, 68, 1088.
(18) Thoden van Velzen, E. U.; Engbersen, J . F. J .; de Lange, P. J .;
Mahy, J . W.; Reinhoudt, D. N. J . Am. Chem. Soc. 1995, 117, 6853.
(19) Schierbaum, K.-D.; Weiss, T.; Thoden van Velzen, E. U.;
Engbersen, J . F. J .; Reinhoudt, D. N.; G o¨ pel, W. Science 1994, 265,
1413.
(4) Diamond, D.; McKervey, M. H. Chem. Soc. Rev. 1996, 15.
(5) Ueno, A. Supramol. Sci. 1996, 3, 31 and references cited herein.
(6) Ikeda, H.; Nakamura, M.; Ise, N.; Oguma, N.; Nakamura, A.;
Ikeda, T.; Toda, F.; Ueno,A. J . Am. Chem. Soc. 1996, 118, 10980.
7) Liu, Y.; Zhang, Y.-M.; Qi, A.-D.; Chen, R.-T.; Yamamoto, K.;
Wada, T.; Inoue, Y. J . Org. Chem. 1997, 62, 1826.
8) Hamasaki, K.; Usui, S.; Ikeda, H.; Ueno, A. Supramol. Chem.
997, 8, 125.
9) Corradini, R.; Dossena, A.; Galaverna, G.; Marchelli, R.; Panagia,
A.; Sartor, G. J . Org. Chem. 1997, 62, 6283.
(
(
1
(
(10) Dickert, F. L.; Bauer, P. A. Adv. Mater. 1991, 3, 436.
(11) Wenz, G. Angew. Chem., Int. Ed. Engl. 1994, 33, 803.
(12) Szejtli, J . Cyclodextrin Technology, Kluwer Academic Publish-
ers: Dordrecht, 1988.
S0022-3263(97)02332-3 CCC: $15.00 © 1998 American Chemical Society
Published on Web 07/17/1998

5
340 J . Org. Chem., Vol. 63, No. 16, 1998
B u¨ gler et al.
Sch em e 1
Ch a r t 1
have coupled â-cyclodextrin to calix[4]arene via a p- and
an o-xylyl spacer.21 Fluorescence titrations with these
â-cyclodextrin-calix[4]arene couples gave up to 400-fold
increased binding constants for the fluorescent probes
1
-anilino-8-naphthalenesulfonate (ANS) and 2-p-tolui-
dino-6-naphthalenesulfonate (TNS) in aqueous solution
compared with native â-cyclodextrin.22 This increased
binding was attributed to an extension of the hydrophobic
cavity of the cyclodextrin by the calix[4]arene moiety.
That is, the calix[4]arene does not only offer positions
for further modification but also improves the complex-
ation characteristics. A two-component sensor system,
consisting of an independent fluorophore as reporter
group and the â-cyclodextrin-calix[4]arene couple as host
molecule, was successfully tested in aqueous solution for
its ability to respond on the addition of organic analytes.22
The next step toward a realistic sensing system is to
combine the optical reporter and the cyclodextrin-calix-
[4]arene host covalently in one molecule.
In this paper we report the synthesis and the host-
guest chemistry of such novel cyclodextrin-calix[4]arene
couples 1 and 2 (Chart 1) which have fluorophores
covalently attached at the calix[4]arene moiety as a
reporter group for guest inclusion.
alized cyclodextrin derivative 7 were synthesized and
coupled in one of the last reactions. The key step in the
synthesis of the unsymmetrically substituted calix[4]-
arenes 5 and 6 is the monoprotection of bisaldehyde 3
(
Scheme 1).
Resu lts a n d Discu ssion
Compound 3 was obtained by Gross formylation of
F lu or escen t
â-Cyclod ext r in -Ca lix[4]a r en e
tetra(2-ethoxyethyl)calix[4]arene following a literature
procedure.23 Monoprotection of the bisaldehyde was
achieved by reacting 3 with 1 equiv of 2,2-dimethyl-1,3-
Cou p les. The â-cyclodextrin-calix[4]arene couples 1
and 2 were synthesized in a convergent way. The calix-
4]arene building blocks 5 and 6 as well as the function-
2
4
[
propanediol in refluxing toluene and TsOH as catalyst.
The yield of 56% for monoaldehyde-mono-1,3-dioxolane
4 was slightly higher than statistical, and 25% of the
(
20) Huisman, B.-H.; Thoden van Velzen, E. U.; van Veggel, F. C.
J . M.; Engbersen, J . F. J .; Reinhoudt, D. N. Tetrahedron Lett. 1995,
6, 3273.
21) van Dienst, E.; Snellink, B. H. M.; von Piekartz, I.; Grote
3
(
(23) Arduini, A.; Fanni, S.; Manfredi, G.; Pochini, A.; Ungaro, R.;
Sicuri, A. R.; Ugozzoli, F. J . Org. Chem. 1995, 60, 1448.
(24) In our hands, reacting 3 simply with 1,3-propanediol as a
protecting agent led to a redox reaction which did not result in the
desired monoprotected product.
Gansey, M. H. B.; Venema, F.; Feiters, M. C.; Nolte, R. J . M.;
Engbersen, J . F. J .; Reinhoudt, D. N. J . Org. Chem. 1995, 60, 6537.
(
22) van Dienst, E.; Snellink, B. H. M.; von Piekartz, I.; Engbersen,
J . F. J .; Reinhoudt, D. N. J . Chem. Soc., Chem. Commun. 1995, 1151.

â-Cyclodextrin-Calix[4]arene Couples as Fluorescent Sensors
J . Org. Chem., Vol. 63, No. 16, 1998 5341
Ch a r t 2
starting compound 3 could be recovered. For the chro-
matographic workup, the silica column was pretreated
with the eluent and 2 v/v% of triethylamine, as the 1,3-
dioxolane unit of 4 is partly cleaved on acidic silica. The
F igu r e 1. Fluorescence spectra of 1 in aqueous solution upon
addition of guest ) ethinyl-nortestosterone ([1] ) 1.45 µM, λex
2
-naphthylamine moiety was attached onto 4 by forma-
tion of the Schiff base from 4 and 2-naphthylamine in
dry methanol. Reduction with sodium cyanoborohydride
and cleavage of the dioxolane protective group by addition
of hydrochloric acid gave the fluorophore-appended calix-
)
350 nm, λem ) 408 nm).
reference compounds 8 and 9, which resemble the two
fluorophores that are appended at 1 and 2, respectively,
show maximum fluorescence emissions at 418 and 572
nm in aqueous solution. The blue shift of 10 and 34 nm
for the attached fluorophores in 1 and 2 respectively,
indicates that these are located in a less polar environ-
ment than the native fluorophores in water. The higher
blue shift for the dansyl fluorophore compared to the
naphthyl group is due to its higher sensitivity toward
changes in the polarity of its environment.27 The above
observations support the idea that the fluorophores of
compounds 1 and 2 are shielded from the aqueous
environment and most probably are located intramolecu-
larly in the cyclodextrin cavities.
Competition experiments provide further evidence for
this assumption. The fluorescence intensity of an aque-
ous solution of 1 decreased upon addition of various guest
species. In Figure 1, the changes in relative fluorescence
intensity of 1 (1.45 µM) upon the addition of ethinyl-
nortestosterone is shown. The excitation maximum in
the absorption spectra does not shift, which excludes that
a change in absorption is the reason for the decrease in
fluorescence intensity. As water is known to quench
fluorescence emission by radiationless decay, this implies
that the 2-aminonaphthyl fluorophore in 1 becomes more
exposed to water after addition of a guest.
[
(
4]arene 5 in a yield of 34%. For connecting the dansyl
) 1-dimethylaminonaphthalene-5-sulfonyl) fluorophore
to aldehyde 4, a reductive amination with methylamine
was performed. The resulting methylamine-dioxolane-
calix[4]arene was used without further purification for
the esterification with dansyl chloride. After in situ
hydrolysis of the dioxolane protective group and flash
chromatography, 6 was obtained in 40% yield. The
cyclodextrin building block 7 (Chart 2) was prepared as
previously reported from heptakis(6-O-TBDMS)-â-cyclo-
dextrin and p-bromomethylbenzonitrile.21 The overall
yield for 7 starting from â-cyclodextrin was 26%. This
lipophilic â-cyclodextrin building block with seven TB-
DMS groups allows an easy workup of the coupled
products by standard silica gel chromatography. The
combination of the building block 7 with the calixarenes
5
or 6, respectively, was achieved by a reductive amina-
tion using sodium cyanoborohydride in methanol. After
purification by column chromatography, 1a and 2a were
obtained in 66% and 67% yields, respectively. The
coupled products 1a and 2a were deprotected at the
primary hydroxyls with silicium tetrafluoride in aceto-
nitrile.25 The final purification of 1 and 2 was achieved
by dialysis in perbenzoylated cellulose tubes, resulting
in 1 and 2 as colorless powders after freeze-drying in
yields of 60% and 65%, respectively. The lack of sym-
metry both of the calix[4]arene and of the cyclodextrin
moiety of the novel compounds renders their NMR
spectra rather complicated. The signals for the protons
of the cyclodextrin moiety coincide with the signals for
the protons of the ethylethoxy chains and the methylene
bridges in the calixarene parts of the molecules. Com-
pounds 1 and 2 are soluble both in water and in polar
An additional indication for this mechanism is the
selectivity pattern of 1 for organic analytes. The selectiv-
ity of host molecules toward different analytes is gener-
0
ally expressed in terms of ∆I/I values for each guest
species, where ∆I is the difference in the fluorescence
intensity of the solution before and after addition of a
guest species.28 These values reflect binding constants
K and intrinsic fluorescence I at the saturation point
∞
and are concentration dependent. To obtain comparable
results, they are measured at saturation of complexation.
The ∆I/I values for 1 and several organic guest molecules
0
are shown in Figure 2. Sensing molecule 1 shows
sensitivity for steroids, terpenes, and some of the other
2
6
organic solvents.
F lu or escen ce Mea su r em en ts. The maximum emis-
sion wavelength of an aqueous solution of the fluorescent
probe 1 is at 408 nm, and for 2 it is at 538 nm. The
(
(
25) Corey, E. J .; Yi, K. Y. Tetrahedron Lett. 1992, 33, 2289.
26) Compounds 1 and 2 dissolve in water up to approximately 2
(27) Lakowicz, J . R., Ed. Principles of Fluorescence Spectroscopy;
Plenum Publishing: New York, 1983.
(28) Ueno, A.; Minato, S.; Suzuki, J .; Fukushima, M.; Ohkubo, M.;
Osa, T.; Hamada, F.; Murai, K. Chem. Lett. 1990, 605.
mg/mL. They also form aggregates in aqueous solution, as was
concluded from the soap-like appearance and line broadening in
NMR. This phenomenon is under investigation at the moment.
1
H

5
342 J . Org. Chem., Vol. 63, No. 16, 1998
B u¨ gler et al.
modifications but also changes the complexation proper-
ties of the novel sensing molecule compared to native
â-cylodextrin by expanding the available hydrophobic
cavity. More specifically, for steroid complexation it can
provide an additional surface to enhance the hydrophobic
interactions.32
In contrast to the behavior of compound 1, aqueous
solutions of compound 2, having a dansyl group as a
fluorophore, do not show a change in their fluorescence
intensity upon the addition of guests. CPK models
suggest a very strong, intramolecular inclusion of the
dansyl group into the cyclodextrin cavity. Similar to the
naphthyl group, the dansyl moiety can penetrate deeply
into the cyclodextrin cavity, but the latter can also form
strong hydrogen bonds between its sulfonamide group
and the secondary hydroxyl groups of the cyclodextrin.
Further evidence for the strong inclusion of the dansyl
group is the large blue shift of the maximum fluorescence
emission. Such a strongly included fluorophore can then
hardly be expelled upon addition of organic guest species,
explaining the insensitivity of 2 toward organic analytes.
A similar behavior for a fluorophore appended to the
secondary side of the natural â-cyclodextrin has been
reported recently.33
0
F igu r e 2. ∆I/I values for several organic analytes and host
compound 1 ([1] ) 1.45 µM): 1, Atropine; 2, p-tert-butylbenzoic
acid; 3, dl-menthol; 4, skatol; 5, dl-carvone; 6, 1-adamantanol;
7
, prednisolone; 8, cholic acid; 9, cholesterol; 10, corticosterone-
acetate; 11, ethinyl-nortestosterone; 12, 1-adamantylbenzoate.
tested organic analytes. The sensitivity for steroids is
approximately 10 times higher than that for terpenes.
This selectivity within this series of analytes suggests
Su m m a r y
that the cyclodextrin cavity is involved in the complex-
ation process.6
In summary, we have shown that by a convergent
approach different â-cyclodextrin-calix[4]arene host mol-
ecules with a fluorescent probe can be synthesized. The
novel fluorescent sensing molecule 1 shows sensitivity
for analytes such as steroids and terpenes. Its complex-
ation properties are different compared to those of native
â-cyclodextrin. This effect is attributed to the appended
calixarene moiety which represents an enlargement of
the cyclodextrin cavity. The similar compound 2 does not
show sensitivity which is attributed to the strong inclu-
sion of its fluorophore into the cyclodextrin cavity where
it can hardly be expelled by external guest species. The
difference in host-guest chemistry between compounds
Further quantification of the host-guest chemistry of
was achieved by fitting the data from fluorescence
1
titrations of 1 to a Benesi-Hildebrandt type equation for
:1 host-guest complexation (eq 1).29 In this equation,
1
∆
I denotes the change in fluorescence intensity of 1 upon
addition of guest species, I and I are the fluorescence
0
∞
intensities in the absence of guest and at the saturation
point, respectively, and [G] refers to the total concentra-
tion of added analyte. The assumption implied in this
equation, that the host concentration is much smaller
than the concentration of added analyte, is valid under
the conditions employed. In the case of a 1:1 host/guest
stoichiometry, a plot of 1/∆I against 1/[G] should give a
straight line from which the association constant Kass is
obtained by dividing the intercept with the ascent. For
1
and 2 demonstrates the importance of the right choice
of the attached fluorophore. In our current synthetic
efforts, we further use the possibilities for functionaliza-
tion of the calix[4]arene moiety in order to optimize the
binding properties of 1 and to enable attachment to
surfaces.
1
1
1
1
)
+
(1)
∆
I
(I - I )K [G] (I - I )
0 ∞ Ass 0 ∞
Exp er im en ta l Section
ethinyl-nortestosterone (norethindrone) and 1-adaman-
tanol, a fluorescence titration was performed and the
data were evaluated using eq 1. Straight lines were
found for the plots of 1/∆I against 1/[G] indicating 1:1
complex stoichiometries. The resulting apparent associa-
tion constant for the complex [1 + norethindrone] (K )
Ma ter ia ls a n d Meth od s. â-Cyclodextrin was kindly do-
nated by Wacker-Chemie, M u¨ nchen. All other chemicals were
used as received, unless otherwise stated. Solvents were
3
4
purified according to standard laboratory methods. Solvents
for fluorescence spectroscopy were of analytical grade. All
reactions were carried out in an inert atmosphere. TLC was
performed on aluminum sheets precoated with silica gel 60
F254 (E. Merck). The cyclodextrin spots were visualized by
dipping the sheets in 5% sulfuric acid in ethanol followed by
heating. Chromatographic separations were performed on
silica gel 60 (E. Merck, 0.040-0.063 mm, 230-240 mesh).
-
1
1
0300 ( 1100 M ) was larger than the one for [1 +
1
-
adamantanol] (K ) 1240 ( 120 M ). This is a remark-
able difference compared to the association behavior of
native â-cyclodextrin, which complexes 1-adamantanol
-
1 30
(
M
5900 M
)
more strongly than norethindrone (940
-
1 31
). This result suggests that the calix[4]arene moiety
Compounds 3 and 7 were prepared according to literature
procedures.2
1,23
The reference fluorophore 8 was prepared from
in 1 not only acts as a useful building block for future
(
29) Connors, K. A. Binding Constants; Wiley & Sons: New York,
(32) Higler, I.; Timmerman, P.; Verboom, W.; Reinhoudt, D. N. J .
Org. Chem. 1996, 61, 5920.
(33) Nelissen, H. F. M.; Venema, F.; Nolte, R. J . M. J . Chem. Soc.,
Perkin Trans. 2 1997, 2045.
(34) Perrin, D. D.; Armarego, W. F. L. Purification of Laboratory
Chemicals, 3rd ed.; Pergamon Press: Oxford, 1989.
1
3
1
987.
(30) Wang, Y.; Ikeda, T.; Ueno, A.; Toda, F. Tetrahedron Lett. 1993,
1, 4971.
(
997, 27, 31.
31) Sadlej-Sosnowska, N. J . Incl. Phenom. Mol. Recogn. Chem.

â-Cyclodextrin-Calix[4]arene Couples as Fluorescent Sensors
-naphthylamine by monomethylation;35 fluorophore 9 was
J . Org. Chem., Vol. 63, No. 16, 1998 5343
2
0.70 mmol), 1 mL of a MeNH
2
solution in EtOH (8 M), and 60
3
6
prepared from dansyl chloride and dimethylamine. Their
analytical data were in accordance with literature data. For
reasons of clarity, the name calix[4]arene was used instead of
mg of Pd/C (10%) were stirred in 50 mL of EtOH under an H
2
atmosphere for 24 h at room temperature. The solution was
then filtered over Celite (E. Merck), and the solvent was
removed in vacuo to give the intermediate monomethyl-
aminomonoformylcalix[4]arene as a colorless oil. This crude
intermediate product was reacted with 5-dimethylaminonaph-
thylsulfonyl chloride (dansyl chloride) (0.27 g, 1 mmol) in
3
,7 9,13 15,19
the official IUPAC name: pentacyclo[19.3.1.1 .1 .1
]-
octacosa-1(25),3,5,7(28),9,11,13(27),15,17,19(26),21,23-dode-
cane. Melting points are uncorrected. For mass spectra
recorded in the FAB mode, m-nitrobenzyl alcohol was used as
a matrix; for MALDI-TOF, mass spectroscopy dihydroxyben-
3 3
CHCl /NEt (50 mL, 5:1) at room temperature for 1 d. For
1
13
zoic acid was used. H NMR and C NMR spectra were
recorded at 250 and 63 MHz, respectively, and 297 K, unless
otherwise stated. Residual solvent protons were used as
internal standard. The preparation of the solutions for
fluorescence spectroscopy was done using pure water (Millipore
Q2) and a phosphate buffer (pH 7, I ) 0.02). Fluorescence
titrations were performed by adding aliquots (typically 10 µL)
of the methanolic stock solution of the guest species to the
aqueous host solution (3 mL). After each addition the fluo-
rescence spectrum was recorded. The observed reduction in
fluorescence intensity was corrected for the effect of pure
methanol (∆I < 3%/100 µL of methanol).
the deprotection of the acetal, the solvent was removed, the
residue was dissolved in MeOH (50 mL), and 1 N HCl (1 mL)
was added. After 1 h of stirring, the solvent was exchanged
for CH
(30 mL) and dried over Na
(eluent: hexanes/ethyl acetate 2:1), 6 was obtained as a
greenish powder in 40% yield: mp 68-69 °C; TLC R ) 0.39
) δ 9.61 (s, 1 H),
2
Cl
2
and the solution was washed with Na
2 3
CO solution
2
CO After chromatography
3
.
f
1
(hexanes/ethyl acetate 1:1); H NMR (CDCl
3
8.49 (d, 1 H, J ) 8.5 Hz), 8.34 (d, 1 H, J ) 7 Hz), 8.14 (d, 1 H,
J ) 6.8 Hz), 7.49 (q, 2 H), 7.20 (s, 2 H), 7.12 (d, 1 H, J ) 7.5
Hz), 6.44-6.33 (m, 8 H), 4.48 (ABq, 2 H, J ) 12.5 Hz), 4.35
(ABq, 2 H, J ) 13.3 Hz), 4.18-4.14 (m, 2 H), 4.05-3.95, 3.77-
3.71, 3.47-3.41 (m, 24 H), 3.15 (ABq, 2 H, J ) 13.5 Hz), 2.95
(ABq, 2 H, J ) 13.0 Hz), 2.82 (s, 6 H), 2.35 (s, 3 H), 1.16-1.06
5
-(5,5-Dim eth yl-1,3-dioxolan e-2-yl)-17-for m yl-25,26,27,28-
t et r a (2-et h oxyet h oxy)ca lix[4]a r en e (4). A solution of
diformylcalix[4]arene 3 (2.0 g, 2.51 mmol), 2,2-dimethyl-1,3-
propanediol (0.26 g, 2.51 mmol), and 10 mg of TsOH in 200
mL of toluene was refluxed for 24 h (Ott apparatus, molecular
(m, 12 H); 13C NMR (CDCl
) δ 191.6, 155.7, 136.5, 135.4, 134.5,
133.7, 130.9, 130.2, 128.4, 128.0, 122.7, 115.2, 73.3, 69.6, 66.4,
45.5, 33.2, 30.8, 15.3; MS (FAB) m/z calcd for C59
1016.49, found 1016.3. Anal. Calcd for C59
3
72 2 11
H N O S
H N O11S: C,
72 2
sieves (3 Å)). Subsequently, the solution was filtered over Na
2
-
CO and the solvent was evaporated. The crude reaction
3
69.66; H, 7.13; N, 2.75. Found: C, 69.17; H, 7.13; N, 2.63.
Com p ou n d 1a . A solution of 7 (225 mg, 105 µmol) and 5
(90 mg, 100 µmol) in MeOH (10 mL) and THF (1 mL, for initial
dissolving of 5) was stirred for 6 h at room temperature. Then
mixture was purified by chromatography (eluent: hexanes/
ethyl acetate 2:1, column pretreated with hexanes/ethyl ace-
tate 2:1 + triethylamine 2 v/v%) to give 4 as a thick, colorless
oil in 56% yield (1.20 g, 1.40 mmol). A total of 25% of the
3
Na(CN)BH (30 mg) and 1 drop of AcOH were added and the
starting material 3 could be recovered (0.50 g, 0.62 mmol):
solution was stirred for another 24 h at room temperature.
The solvent was removed in vacuo, and the residue was
1
TLC R
f
) 0.60 (hexanes/ethyl acetate 1:1); H NMR (CDCl
3
) δ
9
5
3
1
1
1
3
8
.58 (s, 1 H), 7.18 (s, 2 H), 6.78 (s, 2 H), 6.42-6.46 (m, 6 H),
dissolved in CHCl
N HCl and a Na
Na CO . After evaporation of the solvent, the crude product
was purified by chromatography (eluent: CH Cl /methanol 20:
1) to give 1a as a yellowish powder in 66% yield: mp 163-
3
(50 mL). The solution was washed with 2
.00 (s, 1 H), 4.51-4.37 (ABq, 4 H), 4.17-4.23 (m, 2 H), 4.02-
.97 (m, 6 H), 3.79-3.39 (m, 20 H), 3.18-3.07 (m, 4 H), 1.18-
2
CO solution (each 30 mL) and dried over
3
2
3
.06 (m, 15 H), 0.69 (s, 3H); 13C NMR (CDCl
57.1, 155.8, 136.6, 135.2, 134.6, 133.7, 132.4, 130.9, 130.2,
28.7, 128.0, 126.0, 122.6, 101.7, 73.5, 72.9, 69.6, 66.3, 30.8,
0.1, 23.1, 22.0, 15.3; HRMS (EI) m/z calcd for C51
54.4605, found 854.4636.
) δ 191.7, 162.7,
3
2
2
1
164 °C; TLC R
f
2 2 3
) 0.61 (CH Cl /methanol 9:1); H NMR (CDCl )
H
66
O
11
δ 7.64-7.51 (m, 3 H), 7.33-7.11 (m, 6 H), 6.82-6.44 (m, 12
H), 5.25-4.65 (m, 15 H), 4.46 (d, 4 H, J ) 12.5 Hz), 4.11-
4.02, 3.82-3.80, 3.63-3.47 (m, 85 H), 3.16-3.06 (m, 10 H),
1.71 (s(br), 2 H), 1.20-1.13 (m, 12 H), 0.84 (s, 63 H), 0.00 (s,
5
-F or m yl-17-(2′-n a p h t h yla m in om et h yl)-25,26,27,28-
tetr a(2-eth oxyeth oxy)calix[4]ar en e (5). A solution of mono-
protected monoformylcalix[4]arene 4 (0.80 g, 0.94 mmol) and
42 H); 13C NMR (CDCl
) δ 155.8, 145.9, 135.6, 135.1, 134.4,
3
2
-naphthylamine (0.14 g, 1.0 mmol) in MeOH (50 mL) was
stirred for 24 h at room temperature. Subsequently, Na(CN)-
BH (80 mg) was added and the solution was stirred for
another 24 h at room temperature. Then 1 N HCl was added
1 mL) and stirring was continued for 30 min. The solvent
was removed in vacuo, and the residue was dissolved in CH
Cl (100 mL). The solution was washed with 2 N HCl and
Na CO solution (each 30 mL) and dried over Na CO . After
128.7, 128.0, 127.7, 127.4, 126.2, 125.9, 122.4, 121.9, 118.1,
101.5, 82.2, 77.2, 73.2, 71.7, 70.0, 66.4, 61.6, 60.1, 30.9, 25.9,
3
254 2 7
18.3, 15.3; MS (FAB) m/z calcd for C154H N O43Si 3017.6,
+
found 3040.4 ([M + Na] ). Anal. Calcd for C154
254 2 7
H N O43Si :
(
C, 61.28; H, 8.48; N, 0.93. Found: C, 61.81; H, 8.49; N, 1.05.
Com p ou n d 2a . Compound 2a was prepared by following
the procedure as described for 1a from compound 7 (212 mg,
99 µmol) and 6 (160 mg, 157 µmol). The crude product was
2
-
2
2
3
2
3
evaporation of the solvent, the crude product was purified by
purified by chromatography (eluent: CH
2 2
Cl /methanol 20:1)
chromatography (eluent: hexanes/ethyl acetate 2:1) to give 5
to give 2a as a slightly greenish powder in 67% yield: mp 162
1
as a yellowish oil in 34% yield: TLC R
f
) 0.58 (hexanes/ethyl
) δ 9.64 (s, 1 H), 7.59-7.50 (m, 3
H), 7.29-7.22 (m, 1 H), 7.18 (s, 2 H), 7.13-7.07 (m, 1 H), 6.81-
°C; TLC R
f
2 2 3
) 0.58 (CH Cl /methanol 9:1); H NMR (CDCl ) δ
1
acetate 1:1); H NMR (CDCl
3
8.54 (d, 1 H, J ) 8.5 Hz), 8.40 (d, 1 H, J ) 8.5 Hz), 8.18 (d, 1
H, J ) 7.3 Hz), 7.57-7.46, 7.36-7.14 (m, 7 H), 6.75-6.21 (m,
10 H), 5.32-4.76 (m, 15 H), 4.44-4.35 (m, 4 H), 4.13-3.46
(m, 85 H), 3.16-3.13 (m, 10 H), 2.85 (s, 6 H), 2.48 (s, 3 H),
6
4
4
3
.77 (m, 1 H), 6.69 (s, 1 H), 6.58 (s, 2 H), 6.52-6.42 (m, 6 H),
.49 (ABq, 2 H, J ) 13.5 Hz), 4.39 (ABq, 2 H, J ) 13.4 Hz),
.18-4.14 (m, 2 H), 4.04-4.02 (m, 6 H), 3.92 (s, 2 H), 3.76-
.73 (m, 8 H), 3.51-3.41 (m, 8 H), 3.16 (ABq, 2 H, J ) 13.5
1
3
1.21-1.10 (m, 12 H), 0.84 (s, 63 H), 0.00 (s, 42 H); C NMR
(CDCl
3
) δ 151.7, 135.7, 135.5, 134.2, 134.1, 130.3, 130.1, 128.6,
Hz), 3.05 (ABq, 2 H, J ) 13.7 Hz), 1.64 (s(br), 1 H), 1.15-1.07
128.0, 127.7, 122.3, 120.0, 82.2, 77.3, 73.4, 73.1, 71.7, 69.6, 66.4,
1
3
(m, 12 H); C NMR (CDCl
3
) δ 191.8, 162.6, 156.0, 155.8, 145.8,
36.5, 135.4, 134.8, 134.0, 132.5, 130.9, 130.2, 128.8, 128.1,
27.6, 126.1, 122.6, 121.8, 118.1, 104.9, 77.3, 73.6, 73.2, 69.7,
6.4, 48.1, 30.8, 15.3; MS (FAB) m/z calcd for C56 895.5,
61.6, 60.1, 45.4, 30.7, 25.9, 18.3, 15.3; MS (FAB) m/z calcd for
+
1
1
6
C
157
H
259
N
3
O
45SSi
7
3136.6, found 3160.6 ([M + Na] ). Anal.
Calcd for C157
H
259
N
3 7
O45SSi : C, 60.10; H, 8.26; N, 1.34; S, 1.02.
H
65NO
9
Found: C, 60.02; H, 8.41; N, 1.41; S, 0.92.
found 895.7.
5,26,27,28-Tetr a(2-eth oxyeth oxy)-5-for m yl-17-[(N-m eth -
yl)-5-d im eth yla m in on a p h th ylsu lfon a m id om eth yl]ca lix-
4]a r en e (6). Monoprotected diformylcalix[4]arene 4 (0.60 g,
Com p ou n d 1. A solution of 1a (100 mg, 33 µmol) in CH
3
-
4
2
CN/CH
2
Cl
2
(each 20 mL) was stirred in an atmosphere of SiF
for 24 h. Then the solvents were removed in vacuo, and the
residue was dissolved in water (50 mL). The pH of the solution
[
was adjusted to 7 by adding a concentrated solution of Na
2
-
CO After two washings with hexanes (each 10 mL), the
solution was filled into a dialysis tube (benzoylated cellulose
tubing, Sigma) and was subjected to dialysis for 5 d. After
3
.
(
35) Wessely, F.; Svoboda, W. Monatsh. 1951, 82, 621.
(36) Seiler, N.; Schmidt-Glenewinkel, T.; Schneider, H. H. J . Chro-
matogr. 1973, 84, 95.

5
344 J . Org. Chem., Vol. 63, No. 16, 1998
B u¨ gler et al.
freeze-drying of the dialyzed aqueous solution, 1 was obtained
as a colorless powder in 60% yield: mp 205 °C (dec); TLC R
12.5 Hz), 7.68-7.60, 7.38-7.18 (m, 7 H), 6.78-6.75, 6.56-6.50,
6.45-6.40, 6.36-6.33 (m, 10 H), 5.11-4.98, 4.96-4.81, 4.77-
4.71, 4.17-3.92, 3.86-3.32 (m, 85 H), 3.19-3.13 (m, 6 H), 3.10
(d, 4 H, 13 Hz), 2.96 (d, 4 H, J ) 13 Hz), 2.82 (s, 6 H), 2.54 (s,
f
1
)
2 3 3
0.16 (EtOAc/MeOH/H O 25:2:1); H NMR (CD SOCD ) δ
7
.61-7.54 (m, 2 H), 7.45 (d, 1 H, J ) 8.4 Hz), 7.36-7.22 (m, 6
H), 7.08-7.00 (m, 2 H), 6.92-6.89 (m, 2 H), 6.65-6.61 (m, 2
H), 6.38-6.23 (m, 6 H), 4.99-4.33 (m, 19 H), 3.91-2.96 (m,
3 H), 1.84-1.43 (m, 12 H); MS (MALDI-TOF) m/z calcd for
+
C
115
H
161
+
N
3
O
45S 2337.9, found 2361.9 ([M + Na] ), 2377.9 ([M
1
1
7
2
2
04 H), 1.15-1.07 (m, 12 H); 13C NMR (CD
3
SOCD
3
, 303 K) δ
+ K] ). Anal. Calcd for C115
H
161
N
3
O
2
45S‚5H O: C, 56.90; H,
7.10; N, 1.73. Found: C, 56.97; H, 7.05; N, 1.74.
27.1, 124.4, 120.9, 118.1, 102.4, 98.6, 95.3, 81.1, 78.2, 75.0,
2.7, 71.6, 68.1, 64.6, 59.2, 58.5, 56.1, 50.9, 45.8, 39.3, 29.5,
7.8, 12.0; MS (MALDI-TOF) m/z calcd for C112
218.4, found 2241.1 ([M + Na] ), 2256.7 ([M + K] ). Anal.
H
156
N
2
O
43
Ack n ow led gm en t. We are grateful to R. Fokkens
University of Amsterdam) for recording the MALDI-
+
+
(
Calcd for C112
H
156
N
2
O
43‚8H
2
O: C, 56.94; H, 7.34; N, 1.19.
TOF mass spectra and to B. Perly (DECRAM/Saclay,
France) for recording the 500 MHz NMR spectrum. This
work was supported by a FAIR Program of the EU
3
7
Found: C, 56.87; H, 7.02; N, 1.15.
Com p ou n d 2. Compound 2 was prepared according to the
procedure described for 1 from compound 2a (90 mg, 29 µmol).
Dialysis and freeze-drying yielded 2 as a colorless powder in
(Project No. PL 95 0300).
6
H
5% yield: mp 233 °C (dec); TLC R
f
) 0.30 (EtOAc/MeOH/
J O9723321
1
38
2
O 25:2:1); H NMR (DMSO, 500 MHz, 303 K) δ 8.53 (d, 1
H, J ) 13 Hz), 8.26 (d, 1 H, J ) 12.5 Hz), 8.08 (d, 1 H, J )
1
(38) The signal at 2.54 ppm in the H NMR spectrum overlaps with
the solvent signal. Its exact position was deduced from a ROESY
1
3
(
37) In general, elemental analysis of cyclodextrin derivatives
experiment. We were not able to obtain a C NMR spectrum of
sufficient intensity of compound 2 due to the low amount of compound
available.
reveals the presence of several equivalents of water, even when the
compounds are dried vigourously.