A prototype calix[4]arene-based receptor for carbohydrate recognition containing peptide and phosphate binding groups

Article abstract of DOI:10.1021/jo034471q

A novel class of macrobicyclic receptors for carbohydrate recognition based on upper rim, peptide-bridged calix[4]arenes has been designed and synthesized. Receptor 12, in which a charged phosphate group cooperates with peptide hydrogen-bonding donor and

Full text of DOI:10.1021/jo034471q

A P r ototyp e Ca lix[4]a r en e-Ba sed Recep tor for Ca r boh yd r a te
Recogn ition Con ta in in g P ep tid e a n d P h osp h a te Bin d in g Gr ou p s
Margarita Segura,†,‡ Barbara Bricoli,† Alessandro Casnati,† Eva Maria Mun˜oz,§
Francesco Sansone,† Rocco Ungaro,*,† and Cristina Vicent§
Dipartimento di Chimica Organica e Industriale, Universita` degli Studi, Parco Area delle Scienze 17/ A,
I-43100 Parma, Italy, and Instituto de Qu´ımica Orga´nica General, CSIC, Dp.to Qu´ımica Orga´nica
Biolo´gica, C/ J uan de la Cierva 3, E-28006 Madrid, Spain
rocco.ungaro@unipr.it
Received April 14, 2003
A novel class of macrobicyclic receptors for carbohydrate recognition based on upper rim, peptide-
bridged calix[4]arenes has been designed and synthesized. Receptor 12, in which a charged
phosphate group cooperates with peptide hydrogen-bonding donor and acceptor groups in the binding
process, is the most efficient and selective in the complexation of simple carbohydrate derivatives.
The selectivity observed is toward â-glucoside 13a , which is better bound (∆G° ) 19.6 kJ mol-1
)
compared to the corresponding R anomer 13b (∆G° ) 17.0 kJ mol-1) and to the â-galactoside 13c
(∆G° ) 17.7 kJ mol-1) in CDCl3. A substantial drop in the stability constant is observed by
esterification of the phosphate group in the host 12 or by alkylation of the OH groups in the 2 and
3 positions in the â-glucoside and â-galactoside derivatives. On the basis of a careful analysis of
1
the H NMR data available, a binding mode of the â-octylglucoside 13a to receptor 12 is proposed.
In tr od u ction
organic media and only few in water solution,8 where
hydrophobic interactions could strengthen the sugar
binding. Calixarenes are a versatile class of cavity
containing macrocycles used in several areas of supramo-
lecular chemistry.9 In the past few years, we have been
interested to extend the use of calixarenes in bio-organic
chemistry10 by synthesizing several hydrogen bonding
macrocyclic receptors for anions,11 amino acids,12 and
small peptides.13 Few of these receptors are water
soluble,12b and others show interesting antibacterial
Carbohydrates are involved in numerous, very impor-
tant, biological molecular recognition processes ranging
from cell adhesion and migration to infection by bacteria
and viruses, toxins, or vaccine action, etc. The need of
understanding the biological role of carbohydrates in
molecular terms has stimulated the birth of chemical
glycobiology,1 a field mainly devoted to the study of
multivalent glycoclusters,2 and the flowering of the
biomimetic3 and supramolecular4 approaches to carbo-
hydrate recognition. Several synthetic receptors for car-
bohydrate recognition and sensing have been designed
and synthesized in recent years, some exploiting the
formation of covalent adducts with boronic acids,5 others
employing charged phosphate and phosphonate groups6
or a variety of hydrogen-bonding acceptor and donor
groups7 on several molecular scaffolds. Most of these
artificial receptors are able to complex carbohydrates in
(6) (a) Das, G.; Hamilton, A. D. J . Am. Chem. Soc. 1994, 116, 11139-
11140. (b) Das, G.; Hamilton, A. D. Tetrahedron Lett. 1997, 38, 3675-
3678. (c) Droz, A. S.; Neidlein, U.; Anderson, S.; Seiler, P.; Diederich,
F. Helv. Chim. Acta 2001, 84, 2243-2289. (d) Rusin, O.; Lang, K.; Kra´l,
V. Chem. Eur. J . 2002, 8, 655-663.
(7) (a) Davis, A. P.; Wareham, R. S. Angew. Chem., Int. Ed. Engl.
1998, 37, 2270-2273. (b) Smith, D. K.; Diederich, F. Chem. Commun.
1998, 2501-2502. (c) Inouye, M.; Chiba, J .; Nakazumi, H. J . Org.
Chem. 1999, 64, 8170-8176. (d) Lo¨wik, D. W. P. M.; Lowe, C. R. Eur.
J . Org. Chem. 2001, 2825-2839. (e) Mazik, M.; Sicking, W. Chem. Eur.
J . 2001, 7, 664-670. (f) Ryan, T. J .; Lecollinet, G.; Velasco, T.; Davis,
A. P. Proc. Natl. Acad. Sci. U.S.A. 2002, 99, 4863-4866. (g) Tamaru,
S.; Shinkai, S.; Khasanov, A. B.; Bell, T. W. Proc. Natl. Acad. Sci.
U.S.A. 2002, 99, 4972-4976.
(8) (a) Cote´ron, J . M.; Vicent, C.; Bosso, C.; Penade´s, S. J . Am. Chem.
Soc. 1993, 115, 10066-10076. (b) J ime´nez-Barbero, J .; J unquera, E.;
Mart´ın-Pastor, M.; Sharma, S.; Vicent, C.; Penade´s, S. J . Am. Chem.
Soc. 1995, 117, 11198-11204. (c) Morales, J . C.; Penade´s, S. Angew.
Chem., Int. Ed. Engl. 1998, 37, 654-657. (d) Sugimoto, N.; Miyoshi,
D.; Zou, J . Chem. Commun. 2000, 2295-2296.
(9) (a) Calixarenes in Action; Mandolini, L., Ungaro, R., Eds.;
Imperial College Press: London, 2000. (b) Calixarenes 2001; Asfari,
Z., Bo¨hmer, V., Harrowfield, J ., Vicens, J ., Eds.; Kluwer Academic
Publishers: Dordrecht, 2001.
* To whom correspondence should be addressed. Tel:
+39.0521.905555. Fax: +39.0521.905472.
† Universita` degli Studi.
‡ Current address: Dp.to de Qu´ımica Orga´nica, Facultad de Cien-
cias, Universidad Auto´noma de Madrid, Cantoblanco, E-28049, Madrid,
Spain.
§ Instituto de Qu´ımica Orga´nica General.
(1) Bertozzi, C. R.; Kiessling, L. K. Science 2001, 291, 2357-2364.
(2) (a) Mammen, M.; Choi, S.-K.; Whitesides, G. M. Angew. Chem.,
Int. Ed. Engl. 1998, 37, 2755-2794. (b) Lundquist, J . J .; Toone, E. J .
Chem. Rev. 2002, 102, 555-578.
(3) Rojo, J .; Morales, J . C.; Penade´s, S. Top. Curr. Chem. 2002, 218,
45-92.
(4) Davis, A. P.; Wareham, R. S. Angew. Chem., Int. Ed. Engl. 1999,
38, 2978-2996.
(5) (a) Morin, G. T.; Hughes, M. P.; Paugam, M.-F.; Smith, B. D. J .
Am. Chem. Soc. 1994, 116, 8895-8901. (b) Linnane, P.; J ames, T. D.;
Shinkai, S. J . Chem. Soc., Chem. Commun. 1995, 1997-1998. (c)
J ames, T. D.; Shinkai, S. Top. Curr. Chem. 2002, 218, 159-200.
(10) Sansone, F.; Segura, M.; Ungaro, R. In ref 9b, pp 496-512.
(11) Sansone, F.; Baldini, L.; Casnati, A.; Lazzarotto, M.; Ugozzoli,
F.; Ungaro, R. Proc. Natl. Acad. Sci. U.S.A. 2002, 99, 4842-4847.
(12) (a) Sansone, F.; Barboso, S.; Casnati, A.; Fabbi, M.; Pochini,
A.; Ugozzoli, F.; Ungaro, R. Eur. J . Org. Chem. 1998, 897, 7-905. (b)
Sansone, F.; Barboso, S.; Casnati, A.; Sciotto, D.; Ungaro, R. Tetrahe-
dron Lett. 1999, 40, 4741-4744.
10.1021/jo034471q CCC: $25.00 © 2003 American Chemical Society
Published on Web 07/10/2003
6296
J . Org. Chem. 2003, 68, 6296-6303

Calix[4]arene-Based Receptor for Carbohydrate Recognition
SCHEME 1. Syn th esis of P seu d op ep tid es 4a ,b
close proximity to a hydrophobic pocket by a pseudopep-
tide bridge, is already predisposed for water solubility
due to the hydrolyzable ester substituents at the lower
rim.
To obtain the final receptor, the convergent approach
consisted of the preparation of the phosphate-containing
pseudopeptides, the parallel synthesis of the calix[4]arene
platform, and the condensation of the two subunits. Two
different pseudopeptide chains were prepared (Scheme
1), one having two L-alanine and two L-phenylalanine
units and the other made up of two L-alanine and two
L-tryptophan moieties. The methyl ester group of the
dipeptides 1a ,b, synthesized according to literature
procedures,15 was reduced to the corresponding alcohol
using NaBH4, which gave 2a ,b. These were first treated
with methyl dichlorophosphite in the presence of 2,4,6-
collidine and then with iodine to afford the phosphates
3a ,b, which were finally deprotected from Boc group by
using 4 M HCl in dioxane, yielding the bisammonium
salts 4a ,b.
To form a macrocyclic loop with the pseudopeptides 4,
we chose the calix[4]arene derivative 9, blocked in the
cone conformation through the lower rim functionaliza-
tion with four ethyl acetate groups, which could be
eventually hydrolyzed to ensure water solubility to the
receptors. To this end, calix[4]arene was first dialkylated
in the diametral position to give the 25,27-bis(ethoxy-
carbonylmethoxy)-26,28-dihydroxycalix[4]arene16 (5) which
was reacted with Cl2CHOCH3 and TiCl4 to afford the
bisaldehyde derivative 6 (Scheme 2).
F IGURE 1. Basic design feature of a calixarene-based mac-
robicyclic carbohydrate receptor.
activity behaving as vancomycin mimics.13,14 The aim of
this work was to explore the potential of functionalized
calix[4]arenes in carbohydrate recognition.
Resu lts a n d Discu ssion
We completed the functionalization at the lower rim
by refluxing an acetonitrile solution of 6 in the presence
of ethyl bromoacetate and sodium carbonate in order to
obtain the tetraester 7 in the cone conformation. Oxida-
tion of the aldehyde to carboxylic acid groups, with
NaClO2, afforded compound 8. This was subsequently
transformed into the corresponding diacyl chloride 9,
which can be isolated and characterized or, alternatively,
reacted in situ with the pseudopeptides 4a ,b (Scheme 2),
Design a n d Syn th esis of th e Recep tor s. We de-
signed a general host architecture (Figure 1) on a calix-
[4]arene platform which is able to organize several
binding motives, differently from the other receptors
reported so far which exploit only one or two types of
supramolecular interactions to bind carbohydrates.5-8
Moreover, the minimized prototype of the novel host
family reported in this paper, which combines a phos-
phate negative charge and four amino acid units held in
(15) (a) Bodanszky, M.; Bodanszky A. In The Practice of Peptide
Synthesis; Springer-Verlag: New York, 1984. (b) Cardillo, G.; Genti-
lucci, L.; Tomasini, C.; Tomasoni L. Tetrahedron: Asymmetry 1995,
6, 1947-1955.
(16) Arena, G.; Casnati, A.; Mirone, L.; Sciotto, D.; Ungaro, R.
Tetrahedron Lett. 1997, 38, 1999-2002.
(13) Frish, L.; Sansone, F.; Casnati, A.; Ungaro, R.; Cohen, Y. J .
Org. Chem. 2000, 65, 5026-5030.
(14) Casnati, A.; Fabbi, M.; Pelizzi, N.; Pochini, A.; Sansone, F.;
Ungaro, R.; Di Modugno, E.; Tarzia, G. Bioorg. Med. Chem. Lett. 1996,
6, 2699-2704.
J . Org. Chem, Vol. 68, No. 16, 2003 6297

Segura et al.
SCHEME 2. Syn th esis of th e Ca lixa r en e Sca ffold 9 a n d of th e Ma cr obicyclic Recep tor s 10 a n d 11
after removal of the excess of oxalyl chloride. The cycli-
zation reactions were performed under high dilution con-
ditions, by the slow addition of the two reagent solutions,
to minimize the formation of oligomers. The macrobicyclic
compounds 10a ,b were isolated in 42-50% yield and
subsequently transformed into the phosphoric acid de-
rivatives 11a ,b by treatment with NaI in acetone, which
allowed the selective hydrolysis of the phosphoric methyl
ester in the presence of the lower rim carboxylic ethyl
ester groups. The compound 11a was titrated with Bu4-
NOH in MeOH to give the anionic receptor 12 (Chart 1).
Con for m a tion a l P r op er ties of th e Recep tor s. The
1H NMR spectra of the methyl ester derivatives 10a ,b
and the negatively charged macrocycle 12 are sharp and
well resolved in CDCl3, whereas those of acids 11a ,b are
quite broad. However, when the temperature is increased
(373 K) or a more polar solvent like DMSO-d6 is used
the spectra of 11a ,b become sharp. Dilution experiments
(range 10-2-10-4 M) performed with compound 11a in
group and the neighbor amide carboxy groups, which
determines a slow exchange (on the NMR time scale)
among different conformers at the level of the pseudopep-
tide bridge in equilibrium. Aside from this peculiarity,
1
the basic features of the H NMR spectra of all macro-
bicyclic compounds 10-12 are quite similar, indicating
that the calix[4]arene scaffold imposes a severe confor-
mational constrain to the entire macrocyclic pseudopep-
tide loop. The calix[4]arene backbone is not regular but
adopts a flattened cone conformation17 with the two
unsubstituted aromatic rings pointing outside and the
substituted ones being almost parallel each to the other.
This structure is clearly indicated by the high-field
resonance (6.50-6.60 ppm) of the protons belonging to
these latter rings which experience the shielding effect
of the π systems of the other two unsubstituted aromatic
nuclei, whose protons resonate at lower field (7.11-7.29
ppm).
1
(17) (a) Yamada, A.; Murase, T.; Kikukawa, K.; Matsuda, T.;
Shinkai, S. Chem. Lett. 1990, 455-458. (b) Arduini, A.; Fabbi, M.;
Mantovani, M.; Mirone, L.; Pochini, A.; Secchi, A.; Ungaro, R. J . Org.
Chem. 1995, 60, 1454-1457. (c) Scheerder, J .; Vreekamp, R. H.;
Engbersen, J . F. J .; Verboom, W.; van Duynhoven, J . P. M.; Reinhoudt,
D. N. J . Org. Chem. 1996, 61, 3476-3481. (d) Krebs, F. C.; Larsen,
M.; J orgensen, M.; J ensen, P. R.; Bielecki, M.; Schaumburg, K. J . Org.
Chem. 1998, 63, 9872-9878.
CDCl3 cause no change in the H NMR spectrum, thus
ruling out the presence of extensive intermolecular
aggregation. All together, these data suggest that the
observed broadening of the NMR signals of 11a ,b in
nonpolar solvents can be ascribed to the presence of an
intramolecular hydrogen bond between the acidic P-OH
6298 J . Org. Chem., Vol. 68, No. 16, 2003

Calix[4]arene-Based Receptor for Carbohydrate Recognition
CHART 1
The presence of the chiral centers in the pseudopeptide
loop is felt by several protons of all the macrobicyclic
derivatives. For instance, the four pseudoequatorial
protons of the calix[4]arene methylene bridge in 10a give
two doublets (δ ) 3.26 and 3.24 ppm) and the same
happens with the lower rim methylene groups CH2COOR
(δ ) 5.01 and 4.93 ppm) and the aromatic protons in
ortho to the upper rim substituents (δ ) 6.50 and 6.40
ppm). In addition, because of the phosphoric methyl ester
group determining for this compound the loss of all
symmetry elements, the amide NH protons give rise to
four distinct doublets (δ ) 7.46, 7.34, 6.63, and 6.60 ppm).
COSY NMR experiments (see the Supporting Informa-
tion) with compounds 10a , 10b, and 12 allowed, in
particular, the distinction between the NH and CH
protons of the different amino acid units. In all cases,
the amide protons of the alanine units, directly linked
to the calixarene scaffold, resonate at significantly higher
fields (δ ) 6.84 and 6.78 ppm in 10b, δ ) 6.63 and 6.60
ppm in 10a , and δ ) 6.52 ppm in 12a ) with respect to
those of tryptophan (δ ) 7.26 ppm in 10b) or phenyla-
lanine (7.46 and 7.34 ppm in 10a and 7.91 ppm in 12). It
is to be noted that, in the case of anionic receptor 12,
the phenylalanine NH protons are ca. 0.5 ppm downfield
shifted with respect to the corresponding signals in the
methyl ester derivative 10a , suggesting the presence of
a weak intramolecular H-bonding interaction with the
neighboring negatively charged phosphate group.
its complexes with both â and R anomers of octylglucoside
(13a and 13b) was also established by ESI-MS experi-
ments.
1
The H NMR spectra of the charged receptor 12 and
its complexes were analyzed in more details. Surpris-
ingly, the phenylalanine NH protons (NHphe) experience
a significant upfield shift upon guest addition (∆δ ) 0.3
ppm in the case of â-glucoside 13a with the concentra-
tions of host and guest being 2.5 × 10-3 and 2.2 × 10-2
M, respectively). This can be explained assuming that
complexation breaks a possible intramolecular hydrogen
bond between the NHphe and the phosphate anion, now
engaged in guest binding, or that the NHphe move under
the shielding zone of the phenylalanine aromatic nuclei,
as observed in other systems.7a The involvement of the
phosphate group of host 12 in the complexation was also
proved by the downfield shift (∆δ∞ ) 0.8 ppm) shown by
the phosphorus nucleus in the 31P NMR spectrum of the
complex with 13a compared with the free ligand. On the
other hand, the conformational changes induced in host
12 by the glycoside binding are quite modest as indicated
by the very small shifts experienced by the host protons
not directly involved in the binding. Moreover, the
NOESY maps (see the Supporting Information) of the
free host 12 and its complex with 13a show a very similar
pattern of NOE peaks. Unfortunately, no intermolecular
NOE correlation peak was detectable in this complex as
well as in others. Interestingly, the signals of the dias-
tereotopic phenylalanine benzylic protons, which are
partially overlapped in the free ligand 12, split into two
signals upon complexation with 13a , probably as a
consequence of the freezing of the pseudopeptide bridge.
All the OH groups of the â-glucoside derivative 13a
undergo substantial downfield shifts (g1 ppm) by inter-
acting with 12, which proves their involvement in com-
plexation.
Ca r boh yd r a te Recogn ition . To evaluate the binding
properties of this novel class of macrobicyclic receptors,
we used only the phenylalanine-containing derivatives,
since those functionalized with tryptophan show poor
solubility in most of the organic solvents examined. The
1 H NMR titration experiments were performed by adding
increasing amounts of the glycosides 13a -e (Chart 1) to
a CDCl3 solution of the host. The titration of 10a and 12
1
causes several changes in the H NMR spectra both of
Table 1 reports the stability constants obtained for the
complexes of hosts 10a and 12 with a selection of
lipophilic carbohydrates, including two derivatives 13d
and 13e whose OH groups in 2 and 3 position are
selectively alkylated. As expected, the best efficiency was
obtained with the negatively charged receptor 12 which
shows, in all cases, a better binding toward carbohydrates
hosts and guests, which were analyzed by nonlinear
regression methods showing a 1:1 stoichiometry for the
1
complexes in all cases. On the other hand, the H NMR
spectrum of the phosphoric acid derivative 11a shows
very little changes upon guests addition, indicating low
binding. In the case of host 12, the 1:1 stoichiometry of
J . Org. Chem, Vol. 68, No. 16, 2003 6299

Segura et al.
TABLE 1. Associa tion Con sta n ts (298 K, Er r or s e 10%) a n d , in P a r en th eses, ∆G° (k J m ol-1) Va lu es for th e In ter a ction
betw een th e Ca r boh yd r a te Der iva tives 13a -d a n d Recep tor s 12, 10a , a n d 11a in CDCl3
guest
host
13a â-Glu
13b R-Glu
13c â-Gal
13d â-Glu(4,6-OH)
13e â-Gal(4,6-OH)
<5 (<4.0)
12
10a
11a
2700 (19.6)
460 (15.2)
<5 (<4.0)
950 (17.0)
510 (15.5)
<5 (<4.0)
1260 (17.7)
<5 (<4.0)
320 (14.3)
F IGURE 2. Proposed mode of binding of â-octylglucoside 13a
to receptor 12.
compared to the ester 10a . Interestingly, a good selectiv-
ity is observed for the â anomer 13a of octylglucoside with
respect both to its R anomer 13b and to the â-galactoside
derivative 13c.
The dramatic drop in the association constant of the
â-galactoside 13c, going from the charged receptor 12 to
the neutral derivative 10a , indicates that this carbohy-
drate derivative is mainly interacting with the anionic
center of receptor 12. On the other hand, the â-glucoside
13a takes advantage of both the negative charge and
additional H-bonding interactions with the pseudopeptide
backbone of receptor 12. In fact, this monosaccharide is
also complexed, although to a minor extent, by the
neutral receptor 10a . Compared to 13a and 13c, a
reduction in the stability constants is observed with 12
and sugars 13d and 13e where the 2 and 3 OH are
alkylated. This, together with the observation that a
similar drop is obtained with substrates 13a and 13c
going from 12 to the neutral receptor 10a , suggests that
the the OH-2 and OH-3 groups of 13a and 13c are
involved in hydrogen bonding with the phosphate anion
of the host. All the experimental data obtained are in
agreement with the proposed structure shown in Figure
2 for the complex between the anionic receptor 12 and
the â-octylglucoside 13a , which explains the observed
selectivity. In this structure, all OH groups of the guest
converge toward the H-bonding acceptor groups of the
host (either (O)PO- or amide carbonyl groups) and can
form hydrogen bonds with them as also suggested by the
1H NMR titration experiments (vide supra). Assuming
an equivalent mode of binding for the â-galactoside
derivative 13c, with OH-2 and OH-3 positioned toward
the phosphate anion, the axial OH-4 group is pointing
toward the outside and is not H-bonded to the pseudopep-
tide loop, thus explaining the glucose/galactose selectiv-
ity. On the other hand, the R-glucoside complex is
destabilized by a noncorrect orientation of the anomeric
OR group which, ideally, should be oriented toward the
F IGURE 3. Mode of binding of carbohydrates 14a -c toward
phosphate anion.
exterior of the binding region as in fact occurs in the â
anomers. The change in configuration of the anomeric
position not only changes the accessibility of the sugar
to the binding pocket, but also reduces the donor nature
of OH-2 in the R derivative due to the presence of an
intramolecular hydrogen bond OH-2‚‚‚O-1 which is less
efficient in the â anomer.7g,18
In addition to the classical and more studied carbohy-
drates 13a -e, we have also investigated the binding
properties of hosts 10a and 12 toward diols and amido
alcohols 14a -c19 (see in Figure 3) which are activated
as hydrogen bonding donors by intramolecular interac-
tions and have previously been shown to interact with a
phosphate salt (tetrabutylammonium bis(3,5-di-tert-bu-
tyl) phenyl phosphate, P h os) through the binding mode
depicted in Figure 3.20 The 1,2-trans-diaxial diol 14a and
the 1,2-trans-diaxial amido alcohol 14c present a coop-
erative D/D H-bonding motif that is very efficient for
phosphate binding (Figure 3).
The results with hosts 12 and 10a are reported in
Table 2 and were obtained following the changes of the
(18) (a) Amanokura, N.; Yoza, K.; Shinmori, H.; Shinkai, S.; Rein-
houdt, D. N. J . Chem. Soc., Perkin Trans. 2 1998, 2585-2591. (b) Yoza,
K.; Amanokura, N.; Ono, Y.; Akao, T.; Shinmori, H.; Takeuchi, M.;
Shinkai, S.; Reinhoudt, D. N. Chem. Eur. J . 1999, 5, 2722-2729.
(19) Lo´pez de la Paz, M.; Ellis, G.; Pe´rez, M.; Perkins, J .; J ime´nez-
Barbero, J .; Vicent, C. Eur. J . Org. Chem. 2002, 840-855.
(20) Mun˜oz, E. M.; Lo´pez de la Paz, M.; J ime´nez-Barbero, J .; Ellis,
G.; Pe´rez, M.; Vicent, C. Chem. Eur. J . 2002, 8, 1908-1914.
6300 J . Org. Chem., Vol. 68, No. 16, 2003

Calix[4]arene-Based Receptor for Carbohydrate Recognition
TABLE 2. Associa tion Con sta n ts (298 K, Er r or s e 10%)
a n d , in P a r en th eses, ∆G° (k J m ol-1) Va lu es for th e
In ter a ction betw een th e Ca r boh yd r a te Der iva tives 14a -c
a n d Recep tor s 12, 10a , a n d th e P h osp h a te Sa lt
(Tetr a bu tyla m m on iu m Bis(3,5-d i-ter t-bu tyl)p h en yl
P h osp h a te, P h os) in CDCl3
solvent was removed at reduced pressure, the residue was
dissolved in CH2Cl2 (15 mL), washed with brine, and dried
over Na2SO4, and the solvent was removed at reduced pres-
sure. The residue was purified by precipitation with cold Et2O,
yielding 2a as a white solid: yield 94%; TLC eluent hexane/
ethyl acetate 1:1; mp 114-115 °C; [R]20 ) -49.5 (c ) 1.0 in
D
EtOH); 1H NMR (300 MHz, DMSO-d6) δ 7.49 (d, J ) 8.4 Hz,
3
guest
3
3
1H), 7.28-7.16 (m, 5H), 6.76 (d, J ) 7.0 Hz, 1H), 4.74 (t, J
) 5.2 Hz,1H), 3.89-3.85 (m, 2H), 3.37-3.25 (m, 2H), 2.82 (dd,
host
12
14a
14b
14c
3J ) 5.8 Hz, 2J ) 13.6 Hz, 1 H), 2.65 (dd, J ) 7.8 Hz, 2J )
3
1530 (18.2)
520 (15.5)
840 (16.7)
540 (15.6)
4160 (20.7)
13.6 Hz, 1 H), 1.37 (s, 9 H), 1.09 (d, 3J ) 7.1 Hz, 3 H); 13C
NMR (75 MHz, DMSO-d6) δ 172.1, 154.8, 138.9, 129.1, 128.0,
125.8, 78.0, 62.1, 52.1, 49.8, 36.3, 28.1, 18.3; CI-MS m/z 323
(4, [M + H]+), 292 (4, [M + H - CH2OH]+), 267 (53, [M + H
- ((CH3)2CdCH2)]+), 223 (100, [(M + H - Boc)]+). Anal. Calcd
for C17H26O4N2 (322.2): C, 63.33; H, 8.13; N, 8.69. Found: C,
63.23; H, 8.10; N, 8.63.
10a
P h os20
1796 (18.6)
554 (15.7)
guest signals upon addition of increasing amounts of
the host solutions, in the same conditions previously
employed with P h os.20
N-ter t-Bu tyloxyca r bon yl-L-a la n yl-L-tr yp top h a n ol (2b).
Compound 2b was prepared from 1b15 with the same proce-
dure used for 2a . The product was purified by flash column
chromatography (hexane/ethyl acetate 1:1 f ethyl acetate):
yield 91%; 1H NMR (300 MHz, CDCl3) δ 8.14 (bs, 1H), 7.64 (d,
Compared to P h os, receptor 12 shows a lower effici-
ency and an inverse selectivity since it binds the diol 14a
better than the amide alcohol 14c, whereas the reverse
is true for P h os. The very similar association constants
found for 12 and P h os in the case of diols 14a and 14b
indicate that these guests mainly interact with the
phosphate anionic center of receptor 12. On the other
hand, the substantial decrease in the association constant
of the 1,2-trans-diaxial amido alcohol 14c with receptor
12 in comparison to P h os, suggests a different host-
guest binding mode. Probably the presence of a bulky
n-C15H31CO substituent on the nitrogen atom hinders the
formation of an efficient hydrogen bond with the phos-
phate anion of receptor 12 and the observed weak binding
is due to the guest interaction with other donor centers
of the pseudopeptide bridge. In line with this interpreta-
tion is the quite similar value of the association constant
observed for 14c and the neutral macrobicyclic receptor
10a .
3
3
3J ) 7.7 Hz, 1H), 7.35 (d, J ) 7.9 Hz, 1H), 7.19 (dt, J ) 1.2
3
3
Hz, J ) 7.0 Hz, 1H), 7.12 (dt, J ) 0.7 Hz, 7.1 Hz, 1H), 7.06
3
(s, 1H), 6.43 (d, J ) 7.4 Hz, 1H), 4.88 (bs, 1H), 4.27-4.22 (m,
3
2
1H), 4.08-4.04 (m, 1H), 3.70 (dd, J ) 3.8 Hz, J ) 11.1 Hz,
1H), 3.60 (dd, 3J ) 5.2 Hz, 2J ) 11.2 Hz, 1H), 3.01 (d, 3J ) 6.9
Hz, 2H), 1.41 (s, 9H), 1.27 (d, J ) 7.0 Hz, 3H); 13C NMR (75
3
MHz, CDCl3) δ 173.0, 154.4, 136.3, 127.6, 122.6, 122.3, 119.7,
118.7, 111.6, 111.2, 80.4, 64.3, 52.2, 28.3, 26.5, 18.2; CI-MS
m/z 361 (11, [M]+), 306 (18, [M + H - ((CH3)2CdCH2)]+), 262
(49, [M + H - Boc]+). Anal. Calcd for C19H27O4N3 (361.2): C,
63.14; H, 7.53; N, 11.63. Found: C, 63.03; H, 7.46; N, 11.55.
Meth yl bis(N-ter t-bu tyloxyca r bon yl-L-a la n yl-L-p h en yl-
a la n in olyl)p h osp h a te (3a ). To a solution of dry 2,4,6-
collidine (0.18 mL, 1.36 mmol) in dry THF (1 mL) was added
methyl dichlorophosphite (0.031 mL, 0.33 mmol) under N2. The
suspension was vigorously stirred at room temperature for 15
min, and then a solution of 2a (0.20 g, 0.62 mmol) in dry THF
(2 mL) was added dropwise. The resulting white suspension
was stirred at room temperature for 4 h (TLC monitoring:
hexane/ethyl acetate 3:7). A solution of iodine (0.085 g, 1.08
mmol) in a mixture of THF (1 mL) and water (0.25 mL) was
added and the mixture stirred at room temperature for 45 min.
After concentration to dryness, the residue was dissolved in
CH2Cl2 (10 mL) and washed with Na2S2O3 (10%) until decol-
oration. The organic layer was dried over Na2SO4 and the
solvent removed at reduced pressure to give a residue that
was purified by flash column chromatography (dichloromethane/
methanol 20:1), yielding 3a as a white solid: yield 51%; TLC
Con clu sion
In summary, we have synthesized the first members
of a new family of macrobicyclic carbohydrate receptors
by bridging the upper rim of a calix[4]arene tetraester,
blocked in the cone conformation, with a pseudopeptide
chain bearing a phosphate anionic group in the center.
Detailed binding studies in CDCl3, using lipophilic
derivatives of simple carbohydrates as guests, revealed
a good selectivity for â-glucosides which are able to take
advantage, in the binding, of both hydrogen bonding and
anion-sugar interactions, thanks to a better host-guest
complementarity compared to other sugars.
The modular and convergent synthetic approach
adopted should lead to a broad range of carbohydrate
receptors having peptide bonds and anionic centers as
binding units. An attractive feature of these receptors is
the presence of four ester groups at the lower rim of the
calix[4]arene scaffold, which can eventually be hydrolyzed
to give water soluble carbohydrate receptors.
eluent hexane/ethyl acetate 3:7; mp 107-108 °C; [R]20
)
D
-22.3 (c ) 1.11 in EtOH); 1H NMR (300 MHz, DMSO-d6) δ
3
3
7.81 (d, J ) 8.2 Hz, 1H), 7.79 (d, J ) 8.2 Hz, 1H), 7.27-7.15
3
(m, 10H), 6.71 (d, J ) 6.9 Hz, 2H), 4.13-4.09 (m, 2H), 3.84-
3.80 (m, 2H), 3.87 (t, J ) 5.8 Hz, 4H), 3.64 (d, J (H,P) ) 11.2
Hz, 3H), 2.73 (dd, 3J ) 5.8 Hz, 2J ) 8.0 Hz, 2H), 2.81 (dd,
3
3
2
3
3J (H,P) ) 5.7 Hz, J ) 8.1 Hz, 2H), 1.42 (s, 18H), 1.08 (d, J
) 7.0 Hz, 6H); 13C NMR (75 MHz, CDCl3) δ 172.7, 155.5, 136.9,
129.2, 128.6, 126.8, 80.0, 67.7, 54.6, 50.7, 50.5, 36.9, 36.8, 28.3,
18.3; ESI-MS m/z 743.2 (55, [M + Na]+), 360.9 (90, [M +
2H]2+). Anal. Calcd for C35H53O10N4P (720.4): C, 58.33; H, 7.41;
N, 7.77. Found: C, 58.26; H, 7.39; N, 7.69.
Met h yl b is(N-ter t-b u t yloxyca r b on yl-L-a la n yl-L-t r yp -
top h a n olyl)p h osp h a te (3b). Compound 3b was prepared
from 2b with the same procedure used for 3a . The product
was purified by flash column chromatography (hexane/ethyl
Exp er im en ta l Section
N-ter t-Bu tyloxycar bon yl-L-alan yl-L-ph en ylalan in ol (2a).
A solution of 1a 15 (0.39 g, 1.14 mmol) in dry THF (7 mL) was
stirred under N2. Then NaBH4 (0.086 g, 2.27 mmol) was added,
and the suspension was heated at 60 °C. Dry MeOH (1.5 mL)
was added dropwise, and the mixture was heated at that
temperature for 50 min. The solution was cooled to room
temperature, and water (2 mL) was carefully added. The
1
acetate 1:1 f ethyl acetate): yield 33%; H NMR (300 MHz,
3
DMSO-d6) δ 10.81 (bs, 2H), 7.84 (d, J ) 6.9 Hz, 1H), 7.82 (d,
3
3
3J ) 6.9 Hz, 1H), 7.55 (d, J ) 7.6 Hz, 2H), 7.32 (d, J ) 8.1
3
3
Hz, 2H), 7.14 (bs, 2H), 7.05 (t, J ) 7.6 Hz, 2H), 6.95 (t, J )
7.4 Hz, 2H), 6.76 (d, 3J ) 8.6 Hz, 2H), 4.21-4.17 (m, 2H), 4.04-
3
3.99 (m, 2H), 3.91-3.88 (m, 4H), 3.61 (d, J (H,P) ) 11.0 Hz,
J . Org. Chem, Vol. 68, No. 16, 2003 6301

Segura et al.
3H), 2.87-2.85 (m, 4H), 1.36 (s, 18H), 1.14 (d, 3J ) 6.2 Hz,
6H); 13C NMR (75 MHz, CDCl3) δ 172.8, 154.2, 136.3, 127.5,
123.4, 123.1, 122.2, 119.7, 118.8, 111.3, 110.5, 82.8, 67.3, 54.7,
54.6, 49.6, 28.3, 26.2, 18.6, 18.4; ESI-MS m/z 821.4 (60, [M +
Na]+), 399.2 (90, [M + 2H]2+). Anal. Calcd for C39H55O10N6P
(798.9): C, 58.64; H, 6.94; N, 10.52. Found: C, 58.58; H, 6.90;
N, 6.89.
825 (100, [M + H]+). Anal. Calcd for C46H48O14 (824.9): C,
66.98; H, 5.87. Found: C, 66.89; H, 5.82.
5,17-Dica r boxyl-25,26,27,28-tetr a k is(eth oxyca r bon yl-
m eth oxy)ca lix[4]a r en e (8). Compound 7 (0.85 g, 1.03 mmol)
dissolved in a mixture of acetone/CHCl3 (1:1, 20 mL) was cooled
at 0 °C, and a solution of H2NSO3H (0.40 g, 4.12 mmol) in 4
mL of water was added followed by NaClO2 (0.33 g, 3.6 mmol).
The mixture was stirred at room temperature overnight. The
solvent was removed, the residue was partitioned between
ethyl acetate (35 mL) and HCl (10%, 35 mL), and the organic
layer was separated, dried over MgSO4, and evaporated to
dryness under vacuum. The residue was precipitated with cold
MeOH to give product 8 as a white solid: yield 45%; mp >
200 °C; TLC eluent hexane/ethyl acetate 1:1; 1H NMR (300
Met h yl b is(L-a la n yl-L-p h en yla la n in olyl)p h osp h a t e,
d ih yd r och lor id e (4a ). Compound 3a (0.10 g, 0.13 mmol) was
dissolved in a solution of HCl in dioxane (4 M, 2 mL), and the
mixture was stirred at room temperature for 30-40 min. The
solvent was removed at reduced pressure, and the residue was
dried under vacuum to give product 4a as a white foam in
quantitative yield: mp 63-64 °C; 1H NMR (300 MHz, DMSO-
d6) δ 8.77-8.75 (m, 2H), 8.16 (bs, 6H), 7.32-7.19 (m, 10H),
4.19-4.16 (m, 2H), 3.97-3.90 (m, 4H), 3.81-3.79 (m, 2H), 3.68
(d, 3J (H,P) ) 11.1 Hz, 3H), 2.85-2.81 (m, 4H), 1.36 (d, 3J )
6.9 Hz, 6H); 13C NMR (75 MHz, CD3OD) δ 170.9, 138.6, 130.2,
129.7, 127.9, 69.5, 55.6, 52.7, 52.6, 37.3, 17.9; ESI-MS m/z 543
(100, [M - 2HCl + Na]+). Anal. Calcd for C25H39O6N4PCl2
(593.5): C, 50.59; H, 6.62; N, 9.44. Found: C, 50.51; H, 6.68;
N, 9.38.
3
3
MHz, CDCl3) δ 7.16 (d, J ) 7.2 Hz, 4H), 7.05 (t, J ) 7.2 Hz,
2
2H), 6.80 (s, 4H), 4.88 (d, J ) 14.1 Hz, 4H), 4.81 (s, 4H), 4.51
(s, 4H), 4.23 (q, 3J ) 7.2 Hz, 4H), 4.16 (q, 3J ) 7.2 Hz, 4H),
3.25 (d, 2J ) 14.1 Hz, 4H), 1.29 (t, 3J ) 7.2 Hz, 6H), 1.26 (t, 3J
) 7.2 Hz, 6H); 13C NMR (75 MHz, CDCl3) δ 171.7, 170.5, 169.0,
159.2, 156.9, 135.9, 133.3, 130.1, 129.8, 124.1, 123.7, 71.5, 71.0,
60.9, 60.3, 31.4, 14.1; CI-MS m/z 857 (100, [M + H]+). Anal.
Calcd for C46H48O16 (856.9): C, 64.48; H, 5.65. Found: C, 64.40;
H, 5.59.
Met h yl
b is(L-a la n yl-L-t r ip t op h a n olyl)p h osp h a t e,
5,17-Di(ch lor oca r b on yl)-25,26,27,28-t et r a k is(et h oxy-
ca r bon ylm eth oxy)ca lix[4]a r en e (9). Compound 8 (0.25 g,
0.29 mmol) was dissolved in dry CH2Cl2 (10 mL), oxalyl
chloride (0.5 mL, 5.84 mmol) was added, and the mixture was
stirred at room temperature for 6 h. The solvent was removed
at reduced pressure, and the residue was dried under vacuum
to give the product 9 as a white solid in quantitative yield:
d ih yd r och lor id e (4b). Compound 4b was prepared from 3b
in quantitative yield, with the same procedure used for 4a :
3
1H NMR (300 MHz, DMSO-d6) δ 10.89 (bs, 2H), 8.68 (d, J )
3
7.6 Hz, 2H), 8.14 (bs, 6H), 7.58 (d, J ) 7.9 Hz, 2H), 7.35 (d,
3
3J ) 8.2 Hz, 2H), 7.20 (s, 2H), 7.07 (t, J ) 7.4 Hz, 2H), 6.97
(t, 3J ) 7.3 Hz, 2H), 4.26-4.22 (m, 2H), 3.99-3.96 (m, 4H),
3.85-3.81 (m, 2H), 3.64 (d, 3J (H,P) ) 11.2 Hz, 3H), 2.94-2.90
(m, 4H), 1.36 (d, 3J ) 6.9 Hz, 6H); ESI-MS m/z 623.2 (100, [M
- 2Cl + Na]+). Anal. Calcd for C29H41O6N6PCl2 (671.5): C,
51.87; H, 6.15; N, 12.51. Found: C, 51.79; H, 6.11; N, 12.46.
1
mp 78-79 °C; IR (liquid film) νmax 1754 cm-1 (CO); H NMR
(300 MHz, CDCl3) δ 7.65 (s, 4H), 6.60-6.45 (m, 6H), 4.90 (d,
3
2J ) 14.3 Hz, 4H), 4.60 (s, 8H), 4.23 (q, J ) 7.1 Hz, 4H), 4.22
3
2
3
(q, J ) 7.1 Hz, 4H), 3.35 (d, J ) 14.3 Hz, 4H), 1.30 (t, J )
7.1 Hz, 6H), 1.29 (t, 3J ) 7.1 Hz, 6H); 13C NMR (75 MHz,
CDCl3) δ 169.5, 167.3, 162.5, 155.1, 136.3, 132.3, 132.3, 128.7,
127.6, 123.6, 71.2, 60.8, 60.7, 31.2, 14.0, 14.1; CI-MS m/z 895
(50, [M + H]+).
5,17-Difor m yl-25,27-b is(e t h oxyca r b on ylm e t h oxy)-
26,28-d ih yd r oxyca lix[4]a r en e (6). A solution of 516 (0.10 g,
1.23 mmol) in dry chloroform (30 mL) was stirred at room
temperature under N2 atmosphere. Then, Cl2CHOCH3 (2.3 mL,
25.42 mmol) was added, followed by TiCl4 (5.4 mL, 49.24
mmol), and the reaction was stirred at room temperature for
19 h. The solution was carefully poured into cold HCl (5%, 20
mL), and the black residue was extracted with chloroform (2
× 30 mL). The combined organic layers were washed with
water and dried over MgSO4, and the solvent removed under
reduced pressure. The residue was purified by flash column
chromatography (hexane/ethyl acetate 6:4) to give a yellow
solid which was re-crystallized from ethyl acetate yielding the
product 6 as a white solid: yield 70%; mp 180-181 °C; 1H
NMR (300 MHz, CDCl3) δ 9.77 (s, 2H), 8.68 (s, 2H), 7.62 (s,
Com p ou n d 10a . A solution of 9 (0.161 g, 0.18 mmol) in
dry CH2Cl2, (1.5 mL) and a dry CH2Cl2 solution (1.5 mL)
containing 4a (0.11 g, 0.18 mmol) and Et3N (0.10 mL, 0.72
mmol) were simultaneously perfused into a solution of Et3N
(0.051 mL, 0.365 mmol) in dry CH2Cl2 (170 mL) over 2.5 h.
The mixture was stirred at room temperature overnight. The
organic solution was washed with HCl (5%, 10 mL) and water
(140 mL) and dried over MgSO4 and the solvent removed at
reduced pressure to give a residue that was purified by flash
column chromatography (dichloromethane/methanol 10:1),
yielding 10a as a white solid: yield 50%; TLC eluent dichlo-
3
3
4H), 6.96 (d, J ) 12.0 Hz, 4H), 6.80 (t, J ) 8.1 Hz, 2H), 4.72
romethane/methanol 11:1; mp 170-171 °C; [R]20 ) -22.7 (c
D
2
3
(s, 4H), 4.40 (d, J ) 13.3 Hz, 4H), 4.35 (q, J ) 7.2 Hz, 4H),
1
3
) 1.11, in EtOH); H NMR (300 MHz, CDCl3) δ 7.46 (d, J )
6.8 Hz, 1H), 7.34 (d, 3J ) 7.4 Hz, 1H), 7.28-7.25 (m, 10H),
7.13-7.11 (m, 4H), 6.93-6.86 (m, 2H), 6.63 (d, 3J ) 6.9 Hz,
3.50 (d, J ) 13.3 Hz, 4H), 1.33 (t, J ) 7.2 Hz, 6H); 13C NMR
(75 MHz, CDCl3) δ 191.4, 166.9, 153.0, 152.4, 133.2, 129.2,
128.6, 128.4, 128.2, 125.6, 118.1, 72.5, 61.4, 31.5, 14.7; CI-MS
m/z 653 (100, [M + H]+). Anal. Calcd for C38H38O10 (654.7):
C, 69.71; H, 5.85. Found: C, 64.63; H, 5.80.
2
3
3
3
1H), 6.60 (d, J ) 6.9 Hz, 1H), 6.50 (d, J ) 1.7 Hz, 2H), 6.40
3
2
2
(d, J ) 1.7 Hz, 2H), 5.01 (d, J ) 16.6 Hz, 2H), 4.93 (d, J )
16.6 Hz, 2H), 4.90 (d, 2J ) 13.4 Hz, 4H), 4.48 (bs, 6H), 4.24 (q,
3J ) 7.1 Hz, 4H), 4.20-4.18 (m, 2H), 4.14 (q, 3J ) 7.1 Hz, 4H),
3.96-3.85 (m, 4H), 3.73 (d, 3J (H,P) ) 11.2 Hz, 3H), 3.26 (d, 2J
) 13.4 Hz, 2H), 3.24 (d, 2J ) 14.3 Hz, 2H), 3.01-2.99 (m, 2H),
5,17-Difor m yl-25,26,27,28-t e t r a k is(e t h oxyca r b on yl-
m eth oxy)ca lix[4]a r en e (7). Compound 6 (1.07 g, 1.64 mmol)
was refluxed with ethyl bromoacetate (2.75 mL, 24.57 mmol)
and anhydrous sodium carbonate (4.86 g, 45.85 mmol) in dry
acetonitrile (80 mL) for 19 h. The solvent was evaporated, and
the residue was dissolved in CH2Cl2, washed with HCl (5%)
and water, dried over MgSO4, and concentrated to dryness. A
small amount of cold Et2O was added to precipitate out the
product 7 as a white solid: yield 78%; TLC eluent hexane/
ethyl acetate 1:1; mp125-126 °C; 1H NMR (300 MHz, CDCl3)
δ 9.53 (s, 2H), 7.11 (s, 4H), 6.68 (s, 6H), 6.64-6.63 (m, 4H),
3
2
3
2.84 (dd, J ) 7.9 Hz, J ) 13.6 Hz, 2H), 1.33 (d, J ) 6.5 Hz,
6H), 1.30 (t, 3J ) 7.2 Hz, 6H), 1.25 (t, 3J ) 7.2 Hz, 6H); 13C
NMR (75 MHz, CDCl3) δ 172.9, 172.8, 170.6, 169.6, 167.0,
157.1, 156.8, 136.7, 135.9, 135.6, 133.7, 132.9, 130.9, 129.6,
128.7, 127.6, 126.8, 125.9, 123.3, 71.7, 70.9, 66.5, 60.9, 60.3,
55.2, 50.6, 49.8, 36.6, 36.1, 31.2, 17.6, 17.3, 14.1; ESI-MS m/z
1363.8 (100, [M + Na]+), 1341.8 (20, [M + H]+). Anal. Calcd
for C71H81O20N4P (1341.4): C, 63.57; H, 6.09; N, 4.18. Found:
C, 63.51; H, 5.98; N, 4.10.
Com p ou n d 10b. Compound 10b was prepared with the
same procedure reported for compound 10a . The product was
purified by flash column chromatography (dichloromethane/
methanol 7:1): yield 42%; TLC eluent dichloromethane/
2
4.80 (d, J ) 13.7 Hz, 4H), 4.80 (s, 4H), 4.68 (s, 4H), 4.20 (q,
2
3
3J ) 7.2 Hz, 8H), 3.32 (d, J ) 13.7 Hz, 4H), 1.27 (t, J ) 7.2
Hz, 12H); 13C NMR (75 MHz, CDCl3) δ 191.4, 169.8, 169.5,
161.2, 155.8, 136.0, 135.8, 135.3, 134.0, 133.8, 130.8, 130.2,
129.0, 128.5, 123.5, 123.3, 71.3, 60.7, 31.4, 14.2; CI-MS m/z
6302 J . Org. Chem., Vol. 68, No. 16, 2003

Calix[4]arene-Based Receptor for Carbohydrate Recognition
methanol 7:1; 1H NMR (400 MHz, CDCl3) δ 8.55 (s, 1H), 8.51
(s, 1H), 7.73 (t, 3J ) 7.7 Hz, 2H), 7.37 (d, 3J ) 7.6 Hz, 2H),
3J ) 7.4 Hz, 2H), 7.23-7.03 (m, 16H), 6.98 (t, 3J ) 7.2 Hz,
3 2
2H), 6.86 (t, J ) 7.2 Hz, 2H), 5.07 (bs, 4H), 4.79 (d, J ) 12.8
3
3
2
7.26 (bs, 2H), 7.17 (d, J ) 7.4 Hz, 2H), 7.13 (d, J ) 7.3 Hz,
Hz, 2H), 4.75 (d, J ) 15.3 Hz, 2H), 4.47 (bs, 4H), 4.21-4.08
3
3
2H), 7.12 (t, J ) 7.2 Hz, 2H), 7.05 (d, J ) 7.3 Hz, 2H), 7.03
(s, 1H), 6.99 (s, 1H), 6.86 (t, 3J ) 7.0 Hz, 2H), 6.84 (d, 3J ) 6.2
Hz, 1H), 6.78 (d, 3J ) 6.2 Hz, 1H), 6.63 (bs, 2H), 6.44 (bs, 2H),
4.99-4.89 (m, 4H), 4.52 (d, 2J ) 16.7 Hz, 2H), 4.48 (d, 2J )
16.7 Hz, 2H), 4.42-4.40 (m, 2H), 4.26 (q, 3J ) 7.1 Hz, 2H),
(m, 10H), 3.92-3.90 (m, 2H), 3.61-3.59 (m, 4H), 3.35-2.20
(m, 4H), 2.86-2.84 (m, 4H), 1.25 (t, 3J ) 7.2 Hz, 12H), 1.18
3
(d, J ) 6.7 Hz, 6H); ESI-MS m/z 1403 (80, [M - H]-). Anal.
Calcd for C74H81O20N6P (1405.4): C, 63.24; H, 5.81; N, 5.98.
Found: C, 63.50; H, 5.88; N, 5.71.
3
3
4.25 (q, J ) 7.1 Hz, 4H), 4.15 (q, J ) 7.1 Hz, 2H), 4.08-4.04
Com p ou n d 12. A solution in methanol of compound 11a
was titrated with a solution of Bu4NOH (0.001 M) in methanol
to obtain, after evaporation of the solvent, the anionic receptor
3
(m, 2H), 3.93-3.80 (m, 4H), 3.71 (d, J (H,P) ) 11.2 Hz, 3H),
2
2
3.27 (d, J ) 12.5 Hz, 2H), 3.24 (d, J ) 12.5 Hz, 2H), 2.99-
2.95 (m, 4H), 1.33-1.23 (m, 18H); ESI-MS m/z 1441.5 (100,
[M + Na]+), 1419.7 (20, [M + H]+). Anal. Calcd for C75H83O20N6P
(1419.5): C, 63.46; H, 5.89; N, 5.92. Found: C, 63.58; H, 5.98;
N, 5.96.
12 in quantitative yield as a solid: mp 133-134 °C; [R]20
)
D
1
+1.3 (c ) 0.15 in CHCl3); H NMR (400 MHz, CDCl3) δ 7.91
3
3
3
(bs, J ) 6.8 Hz, 2H), 7.29 (d, J ) 5.3 Hz, 2H), 7.23 (t, J )
4.8 Hz, 4H), 7.19-7.13 (m, 6H), 6.94 (t, 3J ) 5.6 Hz, 2H), 6.61
(bs, 2H), 6.53 (bs, 2H), 6.52 (bs, 2H), 5.04-5.00 (m, 4H), 4.89
Com p ou n d 11a . A mixture of 10a (0.05 g, 0.037 mmol) and
NaI (0.06 g, 0.373 mmol) in dry acetone (5 mL) was stirred
and heated at 60 °C in a Schlenk tube for 4 days. The solution
was concentrated to dryness, the residue was dissolved in CH2-
Cl2 (5 mL), washed with water (5 mL), dried over MgSO4, and
the solvent was removed at reduced pressure to give a residue
which was purified by precipitation with cold Et2O, yielding
the product 11a as a yellowish solid: yield: 73%; TLC eluent
dichloromethane/methanol 11:1; mp > 160 °C dec; 1H NMR
(400 MHz, DMSO-d6) δ 8.02 (d, 3J ) 7.0 Hz, 2H), 7.67 (bs,
2H), 7.26-7.13 (m, 14H), 7.07 (s, 4H), 6.90 (t, 3J ) 7.2 Hz,
2H), 5.09 (bs, 4H), 4.80 (d, 2J ) 13.4 Hz, 2H), 4.74 (d, 2J )
2
(d, J ) 13.4 Hz, 4H), 4.48 (bs, 4H), 4.36-4.34 (m, 2H), 4.25
3
3
(q, J ) 7.1 Hz, 4H), 4.15 (q, J ) 7.1 Hz, 4H), 4.06-4.03 (m,
2
2H), 3.86-3.83 (m, 4H), 3.28-3.23 (m, 8H), 3.25 (d, J ) 13.4
2
3
2
Hz, 2H), 3.24 (d, J ) 14.3 Hz, 2H), 3.00 (dd, J ) 5.7 Hz, J
) 13.4 Hz, 2H), 2.94-2.92 (m, 2H), 1.65-1.62 (m, 8H), 1.45-
1.39 (m, 8H), 1.33-1.25 (m, 18H), 0.98 (t, 3J ) 10.8 Hz, 12H);
13C NMR (75 MHz, CDCl3) δ 173.1, 171.5, 170.0, 157.2, 137.0,
136.1, 136.0, 129.9, 128.9, 127.3, 126.9, 124.0, 71.9, 71.2, 65.6,
59.8, 59.7, 59.6, 51.8, 49.7, 36.7, 31.8, 30.1, 24.6, 20.2, 18.1,
14.1, 14.0; ESI-MS m/z 1326 (80, [M - NBu4]-). Anal. Calcd
for C86H114O20N5P (1568.8): C, 65.84; H, 7.32; N, 4.46. Found:
C, 65.79; H, 7.90; N, 4.37.
3
13.4 Hz, 2H), 4.47 (bs, 4H), 4.20 (q, J ) 6.9 Hz, 4H), 4.13-
4.07 (m, 6H), 3.79-3.77 (m, 2H), 3.52-3.49 (m, 4H), 3.30-
3
2
3.27 (m, 4H), 2.80 (dd, J ) 5.8 Hz, J ) 13.6 Hz, 2H), 2.71-
Ack n ow led gm en t. This work was partially sup-
ported by MURST (“Supramolecular Devices” Project)
and EU (TMR Grant No. FMRX-CT98-0231). We thank
C.I.M.(CentroInterdipartimentaleMisure)dell’Universita`
di Parma for the NMR and Mass facilities. We thank
Dr. M. Tegoni for the helpful discussions on the associa-
tion constant determination.
3
3
2.69 (m, 2H), 1.25 (d, J ) 7.0 Hz, 6H), 1.18 (t, J ) 7.2 Hz,
6H), 1.12 (d, 3J ) 7.1 Hz, 6H); 13C NMR (75 MHz, CDCl3) δ
172.7, 170.6, 169.0, 157.4, 156.8, 137.0, 135.7, 135.6, 133.6,
133.3, 129.6, 129.4, 128.6, 127.4, 126.7, 126.2, 123.4, 71.7, 70.9,
66.6, 60.9, 60.3, 51.1, 49.7, 36.2, 31.5, 17.9, 14.2, 14.1; ESI-
MS m/z 1349.7 (100, [M + Na]+). Anal. Calcd for C70H79O20N4P
(1327.4): C, 63.34; H, 6.00; N, 4.22. Found: C, 63.29; H, 5.99;
N, 4.15.
Com p ou n d 11b. Compound 11b was prepared with the
same procedure reported for compound 11a . The product was
purified by flash column chromatography (dichloromethane/
methanol 9:1): yield 35%; TLC eluent dichloromethane/
Su p p or tin g In for m a tion Ava ila ble: General experimen-
tal methods and 1D and 2D 1H NMR spectra of pseudopeptides
and receptors are reported. This material is available free of
charge via the Internet at http://pubs.acs.org.
1
methanol 7:1; H NMR (300 MHz, DMSO-d6) δ 10.79 (s, 2H),
3
8.13 (bs, 1H), 7.74 (bs, 1H), 7.64 (d, J ) 7.2 Hz, 2H), 7.33 (d,
J O034471Q
J . Org. Chem, Vol. 68, No. 16, 2003 6303