Anion complexation by glycocluster thioureamethyl cavitands: Novel ESI-MS-based methods for the determination of Ka values

Article abstract of DOI:10.1002/chem.200305612

A series of saccharide-thiourea functionalized cavitands was prepared in good yields (72-86 %) by reaction of a tetrakis(aminomethyl) cavitand with the thiocyanate derivatives of acetylated glucose, galactose, and cellobiose. The anion complexation behavior of the acetylated and deacetylated glycocluster thioureamethyl cavitands was studied with electrospray ionization mass spectrometry (ESI-MS) in acetonitrile and in a 1:1 acetonitrile/water mixture, respectively. All compounds show a preference for Cl^-. A linear relationship was found between the square root of the intensity and the concentration of the formed host-guest complex. Based on this relationship, novel methods have been developed to determine K_a values, by means of direct titration and competition experiments.

Full text of DOI:10.1002/chem.200305612

FULL PAPER
Anion Complexation by Glycocluster Thioureamethyl Cavitands: Novel ESI-
MS-Based Methods for the Determination of Ka Values
Gennady V. Oshovsky, Willem Verboom,* Roel H. Fokkens, and David N. Reinhoudt*[a]
Abstract: A series of saccharide-thiour-
ea functionalized cavitands was pre-
pared in good yields (72 86%) by reac-
tion of a tetrakis(aminomethyl) cavi-
tand with the thiocyanate derivatives
of acetylated glucose, galactose, and
cellobiose. The anion complexation be-
havior of the acetylated and deacetylat-
ed glycocluster thioureamethyl cavi-
tands was studied with electrospray
ionization mass spectrometry (ESI-MS)
in acetonitrile and in a 1:1 acetonitrile/
water mixture, respectively. All com-
pounds show a preference for Clꢀ. A
linear relationship was found between
the square root of the intensity and the
concentration of the formed host guest
complex. Based on this relationship,
novel methods have been developed to
determine Ka values, by means of
direct titration and competition experi-
ments.
Keywords: anions
¥
cavitands
¥
mass spectrometry
¥ molecular
recognition ¥ receptors
Introduction
Resorcinarene-based cavitands with proper ligating sites
give rise to different types of receptors.[6] Previously, we
have demonstrated that thiourea functionalized cavitands
are good receptors for halides in chloroform with a prefer-
ence for chloride.[7] With the ultimate objective of mimick-
ing nature, the study of supramolecular interactions in aque-
ous media is very challenging. Several groups have reported
the synthesis of cavitands with an enhanced solubility in
water. This requires the introduction of either charged moi-
eties, such as quaternary ammonium,[8] amidinium,[9] pyridi-
nium,[10] carboxylate,[11] phosphoric acid salt,[12] phenoxide,[13]
etc., or neutral substituents, such as peptides,[14] diethanola-
mine,[15] dendritic wedges,[16] Pd-organometallic centers.[17]
Saccharides have been used as water-solubilizing moieties in
the cases of calix[4]arenes[18] and resorcinols,[19] and there is
one example of a cavitand.[20]
Molecular recognition is the most important phenomenon in
supramolecular chemistry.[1] A number of established analyt-
ical methods are being used to study the strength of the
host guest interactions. The most commonly used methods
include NMR and UVspectroscopy, calorimetry, and elec-
trochemical techniques.[2]
Electrospray ionization mass spectrometry (ESI-MS) has
been applied to directly determine binding constants of
large biological complexes.[3] From titration experiments, the
intensities of both the free and the bound guest (or the free
and bound host) are used to derive a Scatchard plot. The
prerequisite is that the host or the guest and the host guest
complex are ionic; however, this approach is not applicable
when the guest is a small ion. Recently, ESI-MS has been
used to determine the binding constants of crown-ether
alkali-metal cation complexes by means of competition ex-
periments.[4] Very recently, Russell et al. reported a qualita-
tive study of the anion complexation by polydentate Lewis
acids by the use of nanoelectrospray MS.[5] However, to the
best of our knowledge, ESI-MS has not been used to study
anion complexation quantitatively.
Herein we report the synthesis of cavitands containing
both saccharide[21] and thiourea moieties and their complex-
ation with anions[22] in polar solvents. We describe novel
methods for the determination of the binding constants of
the anion complexation by means of ESI-MS.
Results and Discussion
[a] Dr. G. V. Oshovsky, Dr. W. Verboom, Dr. R. H. Fokkens,
Prof. Dr. Ir. D. N. Reinhoudt
Synthesis: The synthesis of the saccharide-thiourea function-
alized cavitands 11 14 is summarized in Scheme 1.
Tetrakis(aminomethyl) cavitand 5 was prepared starting
from the corresponding bromomethyl cavitand[23] 1 by reac-
tion with potassium phthalimide followed by deprotection of
phthalimido cavitand 2 with hydrazine hydrate, analogously
Laboratory of Supramolecular Chemistry and Technology
MESA+ Research Institute, University of Twente
P.O. Box 217, 7500 AE Enschede (The Netherlands)
Fax : (+31)53-489-4645
E-mail: W.Verboom@utwente.nl
D.N.Reinhoudt@utwente.nl
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DOI: 10.1002/chem.200305612
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FULL PAPER
linkers
(Scheme 2). Reaction of tetra-
kis(bromomethyl) cavitand
was
prepared
1
with 2,3,4,5-tetra-O-acetyl-b-d-
glucopyranosylthiol in dichloro-
methane gave gluco-thiamethyl
cavitand 15 in 88% yield. Sub-
sequent deacetylation with
a
catalytic amount of sodium
methoxide afforded cavitand 16
in 91% yield.
The formation of both the
acetylated (7 10) and deacety-
lated cavitands (11 14) clearly
followed from the MALDI
mass spectra and satisfactory el-
emental analyses. Their 1H
NMR spectra in CDCl3 and
CD3CN only exhibit broad sig-
nals. However, spectra with
sharp signals were obtained in
[D6]DMSO solutions. Charac-
teristic is the signal at d = 5.8
and 5.2 ppm of the anomeric
CH of the sugars in the acety-
lated and deacetylated com-
pounds, respectively.
In acetonitrile, the solubility
of the acetylated glycocluster
thiourea cavitands 7 10 is twice
as high as that of the propylth-
iourea cavitand 20 (ꢁ5 versus
2.2 mmLꢀ1). The solubility of
the corresponding propylurea
cavitand 19 in acetonitrile is
0.4 mmLꢀ1. The solubilities of
Scheme 1. Synthesis of glycocluster thioureamethyl cavitands. a) Potassium phthalimide, MeCN. b) Hydrazine
hydrate, MeOH).
to the synthesis of the previously reported pentyl derivative
6.
glycocluster thiourea cavitands 11 14 in water are 0.5, 0.6,
0.8, and >300 mmLꢀ1, respectively, while that of compound
15 is 1 mmLꢀ1. The much higher solubility of cavitand 14 in
water clearly shows the influence of four disaccharide moi-
eties. The solubility of 14 in water is even higher than that
of a cavitand containing dendritic wedges with a total of
45 tetraethylene glycol chains (221 mmLꢀ1).[16]
Reaction of tetrakis(aminomethyl) cavitand 5 with the
thiocyanate derivatives of acetylated glucose, galactose, and
cellobiose in pyridine at room temperature afforded the
acetyl-protected saccharide-thiourea functionalized cavi-
tands 7, 8, and 10 in 80, 85, and 86% yield, respectively. In
an analogous manner, cavitand
9 was prepared in 72% yield by
reaction of pentyl derivative 6
with acetylated glucosyl isothio-
cyanate. Subsequent deacetyla-
tion of compounds 7, 8, 9, and
10 with sodium methoxide in a
4:1 mixture of methanol and di-
chloromethane gave saccharide-
thiourea functionalized cavi-
tands 11 14 in 96, 95, 90, and
92% yield, respectively.
To study the influence of the
thiourea linker between the
cavitand and the saccharide
Scheme 2. Synthesis of cavitand glycoclusters containing sulfide linkers. a) 2,3,4,6-Tetraacetyl-1-thiaglucose,
moieties, cavitand 16 with SCH2 Na2CO3. b) MeONa, MeOH, CH2Cl2.
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Glycocluster Thioureamethyl Cavitands
2739 2748
and 4) the settings of the mass
spectrometer, such as applied
voltage, temperature, gas flow,
etc. However, all these parame-
ters remain constant during a
set of experiments. We investi-
gated whether there is a rela-
tionship between the intensity
of the signal of the 1:1 complex
and the concentration of the
complex in the solution.
As a model experiment, the
chloride complexation of acety-
Scheme 3. Reference compounds.
lated glucose functionalized thi-
ourea cavitand 7 was studied in
MeCN. Two different kinds of
Simpler analogues of cavitand glycoclusters, used for com-
petitive experiments, are shown in Scheme 3.
titrations were carried out: titration of Bu4NCl with 7 (keep-
ing the total concentration of the chloride constant), and ti-
tration of host 7 with Bu4NCl (with a constant total host
concentration). For both titrations the relationship between
the intensity of the signal of the host guest complex 7@Clꢀ
and its concentration is depicted in Figure 1a and 1b, re-
spectively. In Figure 1a, the peak intensity increases para-
bolically, which is very clear compared to Figure 1c, which
depicts the square root of the peak intensity vs the concen-
tration of the host guest complex.[25] The relationship fits
with Equation (1), where I is the peak intensity and A is a
constant that includes the properties of the complex, the set-
tings of the mass spectrometer, etc. (vide supra).
Anion complexation behavior studied by ESI-MS:
General: The anion complexing ability of both the acetylat-
ed (7 10, 15) and deacylated glycocluster thiourea cavitands
11 14, 16 clearly followed from the signal of the 1:1 com-
plexes in the ESI-MS negative ion mode spectra. Since in
1
1
the H NMR spectra rather broad signals were obtained, H
NMR spectroscopy was not suitable to determine Ka values
of the complexes. Therefore we investigated whether ESI-
MS can be used to determine Ka values.
In ESI-MS, charged host guest complexes are transferred
from small droplets of solution into the gas phase under rel-
atively mild conditions.[24] In general, this does not give rise
to fragmentation. Some parameters involve: 1) properties of
the species measured, for example, ionization potential and
volatility, 2) the properties of the solvent used, for example,
conductivity and surface tension, 3) the co-solutes present,
2
ð1Þ
I ¼ A  ½HGŠ
In the case of Figure 1b, the increase of the peak intensity
of the host guest complex is followed by a decrease. This
so-called suppression[24c] is caused by a co-solute (in our case
the titrant) that is present in the measuring solution. A co-
Figure 1. a) Titration of Bu4NCl with 7, intensity versus concentration of 7@Clꢀ. b) Titration of 7 with Bu4NCl, intensity versus concentration of 7@Clꢀ.
p
p
c) Titration of Bu4NCl with 7, intensity versus concentration of 7@Clꢀ. d) Titration of 7 with Bu4NCl, intensity versus concentration of 7@Clꢀ.
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W. Verboom, D. N. Reinhoudt et al.
FULL PAPER
solute can prevent the formation of droplets of the required
small size as well as decrease the volatization efficiency of
the measured ions from the formed droplets, since they
occupy its surface. In general, electrolytes cause a higher
suppression than non-electrolytes. Figure 1d shows that the
same quadratic relationship as Equation (1) is obeyed until
suppression starts to play a role.
in MeCN; the Ka values are summarized in Table 1. In the
case of lower binding constants, the larger amount of host
necessary to give a sufficient amount of host guest complex
Table 1. ESI-MS and ITC data of the complexation of Clꢀ by compounds
7 9 in MeCN.
Compound ESI-MS
Isothermal microcalorimetry data
Ka
Ka
DG
DH
DS
[mꢀ1
]
[mꢀ1
]
[kcalmolꢀ1
]
[kcalmolꢀ1
]
[kcalmolꢀ1
]
Direct method for Ka value determination by ESI-MS titra-
tion: The relationship found [Eq. (1)] can be used to deter-
mine association constants. When the concentration of the
anion ([G]) is maintained constant, the concentration of the
host guest complex ([HG]) can be calculated at each
moment from the intensity I of the signal of the complex
with Equation (2).
7
8
9
15100
15000
14500
15000 ꢀ5.694
14700 ꢀ5.685
14600 ꢀ5.657
ꢀ4.685
ꢀ4.271
ꢀ4.283
1.009
1.414
1.374
may also give rise to suppression (vide supra) of the peak
intensity. Nevertheless, the Ka values can be calculated by
taking into account only the non-suppression area of the
ESI-MS titration curve (compare Figure 1d). In this way, a
Ka value of 720mꢀ1 (with ITC Ka = 680mꢀ1) was obtained
for the complexation of compound 7 with Bu4NBr in MeCN.
In all cases, the Ka values found are in excellent agree-
ment with those obtained with isothermal microcalorimetry
(ITC) (Table 1), confirming the validity of the described
ESI-MS titration method.
pffiffi
I
ð2Þ
max pffiffiffiffiffiffiffiffi
½HGŠ ¼ ½HGŠ
Imax
pffiffi
I
ð3Þ
tot pffiffiffiffiffiffiffiffi
½HGŠ ¼ ½GŠ
Imax
In Equation (2), Imax is the intensity when [HG]
=
[HG]max. Since the maximum concentration of the host
guest complex [HG]max is equal to the total concentration of
the anionic guest [G]tot, substitution gives a relationship be-
tween the intensity of the signal and the concentration of
the host guest complex [HG] and [G]tot [Eq. (3)].
Calibrated competitive method: Some years ago Kempen
and Brodbelt[4a] reported a method for the determination of
binding constants of crown ethers with cations by means of
ESI-MS. The peak intensity of a reference host guest com-
plex with a known Ka value was monitored before and after
addition of a second host or guest. The Ka value of the new
complex is calculated on the basis of the change in intensity
of the reference complex and extrapolation from a calibra-
tion curve ([HG] versus IHG).[26] To obtain reliable results,
the difference in the Ka values involved should be within
two orders of magnitude.[27]
We have used this methodology to study anion complexa-
tion by addition of a new host to an existing host guest
complex. The determination of the Ka value of 19@Clꢀ was
studied in more detail. A set of solutions with different con-
centrations of propylthiourea cavitand 19 in MeCN solution
containing constant initial total concentration of acetylated
Nonlinear fitting of the experimental data Iexp, [G]tot, and
[H]tot with the calculated value of the intensity Icalcd by vary-
p
ing Imax and Ka ultimately gives the calculated association
constant Ka. An example of the calculated and the experi-
mental ESI-MS data of a titration of acetylated galactose
functionalized thiourea cavitand 8 with Bu4NCl is presented
in Figure 2.
This methodology was used to study the chloride com-
plexation of acetylated glycocluster thiourea cavitands 7 9
glucose functionalized thiourea cavitand 7 and Bu4NCl were
pffiffiffiffiffiffiffiffi
prepared. From a calibration curve ([H1G] vs
IH G) the
1
changes in the intensities of 7@Clꢀ were transformed to its
concentration and used for the calculation of the Ka value of
19@Clꢀ (Table 2). The averaged Ka value of entries 2 4 in
Table 2. Ka values of 19@Clꢀ with the ESI-MS calibrated competitive
method with 7@Clꢀ as the reference complex.
Entry
Concentration[a] [mm]
[7@Clꢀ]
Ka (19@Clꢀ)
[mꢀ1
19
]
1
2
3
4
5
0
0.11
0.09
0.074
0.062
0.047
0.1
0.2
0.3
0.4
17200
17100
17000
22400
Figure 2. Nonlinear curve fitting of data of ESI-MS titration of 8 with
Bu4NCl. The titration data are within the Weber concentration range of
20 80% complex formation.
[a] Initial concentrations of Bu4NCl and 7 were 0.2 mm and 0.191 mm, re-
spectively.
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Glycocluster Thioureamethyl Cavitands
2739 2748
Table 2 is 17100Æ100mꢀ1, in agreement with the Ka value of
17300mꢀ1 determined with ITC. However, the Ka value in
entry 5 in Table 2 is much too high, originating from sup-
pression caused by the higher competitor concentration.
This also illustrates the disadvantage of this method. Several
experiments must always be carried out with different com-
petitor concentrations. When at least two of the initial Ka
values were within the experimental error, much higher Ka
values caused by suppression were excluded.
knowns in the equations can be solved to give the Ka2 value.
½HG1Š þ ½HG2Š þ ½HŠ ¼ ½HŠ
ð5Þ
ð6Þ
ð7Þ
tot
½HG1Š þ ½G1Š ¼ ½G1Š
tot
½HG2Š þ ½G2Š ¼ ½G2Š
tot
½HG1Š
ð8Þ
ð9Þ
Ka1
Ka2
¼
¼
½HŠ  ½G1Š
Complex 7@Clꢀ was used as the reference to study the
Clꢀ complexation of compounds 9, 10, 15, 17, and 20 in
MeCN; the Ka values are summarized in Table 3. The choice
½HG2Š
½HŠ  ½G2Š
This approach was used to study the complexation behav-
Table 3. Ka values of Clꢀ complexation by different hosts in MeCN ob-
tained with the ESI-MS calibrated competitive method with 7@Clꢀ as the
reference complex.
ꢀ
ior of compounds 7 and 8 toward Brꢀ, Iꢀ, ClO4ꢀ, HSO4
,
ꢀ
and NO3 (in all cases Bu4N+ salts) in MeCN; the Ka values
Entry
Host
Ka [mꢀ1
]
are summarized in Table 4 and typical examples of the spec-
1
2
3
4
5
9
14900
4600
5200
10
15
17
20
Table 4. Ka values in MeCN of different complexes of compounds 7 and
8 obtained with the ESI-MS competitive method.
450 (440[a], 430[b]
15400
)
Complexes[a]
Ka[b] [mꢀ1
]
Complexes[a]
Ka[b] [mꢀ1
]
7@Brꢀ[c]
680 (680)
170 (175)
39 (37)
1700
8@Brꢀ[c]
680 (670)
180 (173)
40 (35)
1680
[a] 8@Clꢀ as the reference complex. [b] ITC data.
7@Iꢀ
8@Iꢀ
ꢀ
ꢀ
7@ClO4
8@ClO4
ꢀ
ꢀ
7@HSO4
8@HSO4
ꢀ
ꢀ
7@NO3
870
8@NO3
880
of the reference complex has hardly any effect. Competition
experiments of compounds 7@Clꢀ or 8@Clꢀ with 17 in
MeCN gave Ka values of 450 and 440mꢀ1, respectively. The
Ka values are very close to that obtained with ITC, namely,
430mꢀ1. These experiments show the possibility to determine
relatively low Ka values using this methodology.
[a] 7@Brꢀ and 8@Brꢀ were used as the reference complexes. [b] ITC data
are in parentheses. [c] The corresponding Clꢀ complexes were used as
reference complexes.
tra are shown in Figure 3. The Ka values for the complexa-
ꢀ
Competition experiments of the reference complexes 7@
Clꢀ and 8@Clꢀ with Brꢀ, as an anionic guest, showed consid-
erable suppression of the signal. Upon titration with Brꢀ,
the intensity of the reference complex dropped much more
than expected, even if only small amounts of Brꢀ were
added. Suppression was even observed upon addition of
tion of Brꢀ, Iꢀ, and ClO4 were also determined with ITC
ꢀ
and are in excellent agreement. The data for ClO4 com-
plexation clearly demonstrate the validity of this method,
even for very low Ka values.
The possible influence of a change of the settings of the
mass spectrometer on the ratio of the peak intensities of the
complexes 7@Clꢀ and 7@Brꢀ (and consequently on the Ka
value) was studied. Varying the capillary voltage from
110 eVto 50 eVcaused significant changes in the intensities
of the complexes; however, the ratio remained the same
(only a variation of 5%). This means that the influence on
the Ka value is negligible.
This method has also been validated by studying the influ-
ence of variations in the concentrations of the competing
anions. The results in triplicate are summarized in Table 5
for the competitive titration of 8@Iꢀ with different concen-
trations of Bu4NBr. Table 5 clearly shows the reproducibility
within one set of experiments, but it also makes clear that
changing the concentration hardly influences the Ka value.
The absolute values of the intensities in 8@Brꢀ in entries 2
and 3 in Table 5 are almost the same, despite the larger Brꢀ
concentration in entry 3. This is caused by suppression (vide
supra); however, because the intensity of 8@Iꢀ also drops,
the ultimate Ka value is unaffected.
small amounts of the anions PF6 and BPh4ꢀ. Since anionic
species cause significant suppression, this methodology
cannot be used to study the complexation behavior of a host
toward a variety of anions.
ꢀ
Competition method: On account of the above-mentioned
problems, a novel, relatively simple competitive method was
developed.[28] For this approach, the Ka value of one host
guest complex has to be known, determined by the direct
ESI-MS titration (vide supra) or another method. Since we
are dealing with rather large hosts and relatively small
guests, we assumed that the volatility of the different com-
plexes is (almost) equal. This means that Equation (4) can
be derived from Equation (1). Equation (4) describes the
ratio of the concentration of the two HG complexes as the
ratio of the square roots of the respective intensities.
pffiffiffiffi
½HG1Š
½HG2Š
I
pffiffi1ffiffi
I2
ð4Þ
¼
The ESI-MS competitive method has also been successful-
ly applied to determine the Ka values of the anion complex-
ation behavior of the glucose- and galactose-functionalized
thiourea cavitands 11 and 12 toward Brꢀ, Iꢀ, HSO4ꢀ, and
Together with the mass balance Equations (5) (7) and the
binding constants Equations (8) and (9), the different un-
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W. Verboom, D. N. Reinhoudt et al.
FULL PAPER
same order: Clꢀ >HSO4ꢀ >Brꢀ >NO3ꢀ >Iꢀ (Table 6). For
the Clꢀ complexation of compounds 7, 8, and 9, thermody-
Table 6. Ka values of different complexes of compounds 11 and 12 in
MeCN/water = 1:1 obtained with the ESI-MS competitive method.
Ka[a] [mꢀ1
]
Complexes
Ka[b] [mꢀ1
]
1
Complexes
11@Brꢀ
162
83
173
114
12@Brꢀ
157
78
176
109
11@Iꢀ
12@Iꢀ
ꢀ
ꢀ
11@HSO4
11@NO3
12@HSO4
12@NO3
ꢀ
ꢀ
[a] Reference complex 11@Clꢀ (Ka
=
260mꢀ1, determined by ITC).
[b] Reference complex 12@Clꢀ (Ka = 250mꢀ1, determined by ITC).
namic data have been determined with ITC (Table 1). The
complexation is enthalpically driven, but the entropy factor
also favors complexation. In the cases of compounds 7 and
8, there is a Clꢀ/Brꢀ selectivity of ꢁ22. Surprisingly, this se-
lectivity is much more pronounced than that found for the
corresponding thioureamethyl cavitands that do not contain
sugar moieties, such as 20 in CDCl3. The preference for Clꢀ
has also been found in other studies.[7c,29] The Brꢀ and Iꢀ
ions are more weakly complexed because of their ™softer∫
nature, despite their increased size. Presumably, the spheri-
cal Clꢀ has a better fit within the thiourea binding pocket
ꢀ
ꢀ
than the trigonal NO3 and tetrahedral HSO4
.
The presence of a glucose or a galactose moiety hardly in-
fluences the Ka value for the Clꢀ complexation (in MeCN).
The Ka value of propylthioureamethyl cavitand 20 is
15400mꢀ1, compared to 14900mꢀ1 for the corresponding
pentyl chain-containing acetylated glucose thioureamethyl
cavitand 9 (Table 3). However, probably for steric reasons,
the cellobiose unit has a negative effect on the complexa-
tion. Comparing the values for
Figure 3. ESI-MS spectra in MeCN of mixtures of the complexes: 7@Brꢀ
with a) 7@NO3
(0.2 mm), Bu4NBr (0.4 mm), Bu4NNO3 (0.4 mm), Bu4NI (0.4 mm),
Bu4NHSO4 (0.4 mm).
ꢀ
ꢀ
, . Initial concentrations: 7
b) 7@Iꢀ, c) 7@HSO4
the Clꢀ complexation of acety-
Table 5. Competitive titration of 8@Iꢀ with Bu4NBr.
lated 7 and 10 and deacetylated
pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
11 and 14, the Ka values drop
from 15100 to 4600mꢀ1 (in
MeCN) and from 250 to 100mꢀ1
Entry
Concentration[mm]
Run
Intensity
Ið8@ BrꢀÞ
pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
Ið8@ IꢀÞ
Ka(8@Iꢀ)[mꢀ1
]
Bu4NBr
Bu4NI
8@Brꢀ
8@Iꢀ
1
0.2
0.4
0.6
0.4
a
b
c
a
b
c
a
b
c
60322
60977
61231
81919
81435
80289
80458
81313
80425
18287
18653
18562
6111
6093
6132
2807
2803
2819
1.8162
1.8080
1.8166
3.6613
3.6558
3.6185
5.3538
5.3860
5.3413
172.9
173.7
172.8
172.7
173.0
174.8
178.4
177.3
178.8
(in MeCN/water
spectively.
= 1:1), re-
2
3
0.4
0.4
Our study clearly shows the
positive effect of bringing to-
gether ligating sites on a molec-
ular platform. For instance,
compound
7
binds Clꢀ in
MeCN about 33 times better
than the acyclic analogue 17
ꢀ
NO3 in a 1:1 mixture of MeCN and water. The results are
summarized in Table 6.
(Ka = 440mꢀ1). The corresponding deacetylated compounds
11 and 18 give Ka values of 250 and ꢁ5mꢀ1 for Clꢀ com-
plexation in MeCN/water (1:1).
Evaluation ofthe Ka values: The complexation behavior of
the acetylated cavitands 7 and 8 and their deacetylated ana-
logues 11 and 12 toward different anions was studied. There
is a selectivity for Clꢀ in all cases. For compounds 7 and 8
(in MeCN), the binding affinities follow the order: Clꢀ >
Despite the absence of a thiourea moiety, the thiamethyl-
linked glucose-containing cavitands 15 and 16 exhibit a rea-
sonable complexation of Clꢀ, namely, Ka values of 5200
(MeCN) and ꢁ60mꢀ1 (MeCN/water = 1:1), respectively. In
the former case, the Ka value is only three times lower than
that of the corresponding thiourea cavitand 7. Apparently,
the combination of a cavitand cavity and glucose units facili-
tates Clꢀ complexation.
ꢀ
HSO4ꢀ >NO3ꢀ >Brꢀ >Iꢀ >ClO4 (Table 4). As expected, in
a 1:1 MeCN/water mixture, the Ka values are much lower.
For compounds 11 and 12, the Ka values follow almost the
2744
¹ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
Chem. Eur. J. 2004, 10, 2739 2748

Glycocluster Thioureamethyl Cavitands
2739 2748
of the signal of the complex was calculated as the sum of the intensities
of all the components of the isotopic pattern.
Conclusion
ITC: The calorimetric titration experiments were performed in a Micro-
cal VP-ITC microcalorimeter with a cell volume of 1.4115 mL. The final
curves were modeled by means of a nonlinear regression analysis. The fit-
tings were calculated with Microcal Origin software.
In this study we have demonstrated the value of ESI-MS for
the determination of Ka values for anion complexation with
(acetylated) glycocluster thioureamethyl cavitands. The
linear relationship found between the square root of the in-
tensity and the concentration of the formed host guest com-
plex, allows direct determination of the Ka value by means
of a titration experiment. However, this linearity is only ob-
served when the suppression, the competitive influence of
the titrant, is negligible. To avoid the possible influence of
suppression, competitive methods were elaborated, namely,
the ™calibrated curve competitive method∫ and the ™com-
petitive method∫. The latter method is not sensitive to sup-
pression and does not require a calibration curve. It is based
on the comparison of the square roots of intensities of dif-
ferent related host guest complexes. It is an excellent
method for the rapid quantitative determination of the com-
plexation behavior of a host toward a variety of guests.
The (acetylated) glycocluster thioureamethyl cavitands
show a high affinity for chloride in MeCN. The Ka values for
compounds 7 9 is ꢁ1.5î104 mꢀ1, which is more than
20 times higher than the corresponding values for the com-
plexation of bromide. In general, the affinity of cavitand-
based anion receptors for anions is 30 times higher than that
of the simple analogues 17 and 18 in both MeCN and
MeCN/water (1:1).
Solubility measurements: A suspension of the relevant compound in
water (or acetonitrile) was sonicated for 20 min at 258C. The solid was
filtered off and the resulting solution (1 5 mL) was evaporated to dryness
(a freeze dryer was used in the case of water). The experiments were re-
peated twice.
Calculations: The system of Equations (4) (9) was numerically solved
with the Maple8 program (Waterloo Maple Inc.). Calibration curve data
were also treated with the Maple8 program based on the system of
Equations (10) (14) that include binding constant Equations (10) and
(11) and mass balance Equations (12) (14) (known parameters: Ka,ref
binding constant of the reference host guest complex; [Gref tot, [H]tot
[Gnew = total concentration of the reference guest, host, and the new
=
]
,
]
tot
guest added, respectively; [HGref] = concentration of the reference host
guest complex derived from the calibration curve; unknowns: Ka,new
=
binding constant of the host with new guest; [Gref], [Gnew], [H], [HGnew
]
= concentrations of the reference guest, new guest, host, and the com-
plex of the host with the new guest, respectively):
½HGref
Š
ð10Þ
ð11Þ
Ka; ref
¼
½HŠ½Gref
Š
½HGnew
Š
Ka; new
¼
½HŠ½Gnew
Š
½Gref
Š
¼ ½HGrefŠ þ ½Gref
Š
ð12Þ
ð13Þ
ð14Þ
tot
½Gnew
Š
tot
¼ ½HGnewŠ þ ½GnewŠ
We feel that the described ESI-MS-based methods are
very valuable, new tools for Ka value determinations. They
are a useful alternative when other methods of determina-
tion fail.
½HŠ ¼ ½HGrefŠ þ ½HGnewŠ þ ½HŠ
tot
Equation (15) represents the analytical solution of the system of Equa-
tions (10) (14), which is more convenient for the analysis of an array of
data. The calculations were performed with Microsoft Excel [Eq. (15)].
Ka;refð½Gref
Ka;refð½Gref totꢀ½HGrefŠÞð½Gnew
Ka; refð½Gref totꢀ½HGrefŠÞ
½HGref
Š
totꢀ½HGrefŠÞð½HŠtotꢀ½HGrefŠÞꢀ½HGref
Š
Experimental Section
Ka; new
¼
Š
Š
totꢀ½HŠ þ ½HGrefŠÞ þ ½HGrefŠ
tot
ð15Þ
Š
General: The reagents used were purchased from Aldrich or Acros Chi-
mica and used without further purification. All the reactions were per-
formed under a dry argon atmosphere. All solvents were freshly distilled
before use. Dry pyridine was obtained by distillation over calcium hy-
dride. Melting points were measured on a Sanyo Gellenkamp Melting
Point Apparatus and are uncorrected. Proton and carbon NMR spectra
were recorded on a Varian Unity Inova (300 MHz) spectrometer. Residu-
al solvent protons were used as an internal standard and chemical shifts
are given relative to tetramethylsilane (TMS). Chromatography was per-
formed with silica gel (SiO2, Merck, 0.063 0.2 mm). MALDI spectra
were recorded on a Voyager-DERP Biospectrometry Workstation by
PerSeptive Biosystems, Inc. (accelerating voltage 20000 V, mode of oper-
ation: reflector, polarity: positive, matrixes: dithranol and DHB). Com-
pounds 1,[23] 2,[30a] 4,[30a] 6,[30a] 17,[30b] 18,[30b] and 19[30c] were prepared fol-
lowing literature procedures.
Â
Š
Tetrakis(phthalimidomethyl)tetramethyl cavitand (3): A mixture of tetra-
kis(bromomethyl)tetramethyl cavitand 1 (0.96 g, 1 mmol) and potassium
phthalimide (1.11 g, 6 mmol) in MeCN (50 mL) was refluxed for five
days. The reaction mixture was evaporated to dryness, whereupon
CH2Cl2 (50 mL) and 1n NaOH (25 mL) were added to the residue. After
the mixture had been stirred for 10 min, the organic layer was separated
and washed with 1n NaOH (2î25 mL) and water (25 mL), dried over
MgSO4, and evaporated to dryness. The resulting solid was purified by
column chromatography (CH2Cl2 containing 2.5% MeOH). Yield: 65%;
m.p.>3508C (CH2Cl2/EtOAc); 1H NMR (CDCl3): d
= 7.93 7.78 (m,
8H; Phth), 7.78 7.63 (m, 8H; Phth), 7.20 (s, 4H; ArH), 5.81 (d, J =
7.3 Hz, 4H; O2CH), 4.92 (q, J = 7.3 Hz, 4H; Ar2CH), 4.43 (d, J =
7.3 Hz, 4H; O2CH), 4.66 (s, 8H; ArCH2N), 1.68 ppm (d, J = 7.3 Hz,
12H; CH3C); 13C NMR ([D6]DMSO): d = 168.0, 153.5, 138.8, 134.0,
123.4, 132.1, 121.1, 119.7, 99.6, 32.7, 31.1, 16.1 ppm; MS (MALDI): m/z
(%): 1228.9 (100) [M]+ ; elemental analysis calcd (%) for C72H52N4O16
(1229.2): C 70.35, H 4.26, N 4.56; found: C 70.07, H 4.18, N 4.83.
ESI-MS: The ESI-MS experiments were carried out with a Micromass
LST ESI-TOF instrument. The solutions were introduced at a flow rate
of 20 mLminꢀ1 for 2 min (120 scans). The standard spray conditions,
unless otherwise specified, were: capillary voltage 2500 V, sample cone
voltage 30 110 V(optimal conditions for compounds 7 10 80 V, and for
11 14 30 V), desolvation gas flow 250 Lhꢀ1, source temperature 1008C,
desolvation temperature 1008C, extraction cone voltage ~0 Vand flow
cone gas is maintained at about 0 Lhꢀ1. During a set of measurements,
the distance between the capillary and the cone is kept constant. Every
solution was injected five times. The values of the three intensities that
are the closest to one another were used for the calculations. To check
the stability of the signal, one of the solutions was used as a reference; it
was injected in between the five injections of each solution. The intensity
Tetrakis(aminomethyl)tetramethyl cavitand (5): A mixture of tetrakis-
(phthalimidomethyl)tetramethyl cavitand 3 (2.9 g, 2.36 mmol) and hydra-
zine hydrate (2.95 g) in MeOH/CH2Cl2 (1:3, 200 mL) was refluxed for
26 h. The solid was filtered off, the solution was evaporated to dryness,
and the crude product was triturated with diethyl ether (3î30 mL).
Double recrystallization from EtOH/iPrOH gave pure 5 as a white
powder. Yield: 60%; m.p.>3508C (EtOH/iPrOH); 1H NMR
([D6]DMSO): d = 7.61 (s, 4H; ArH), 5.89 (d, J = 7.3 Hz, 4H; O2CH),
2745
Chem. Eur. J. 2004, 10, 2739 2748
www.chemeurj.org
¹ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

W. Verboom, D. N. Reinhoudt et al.
FULL PAPER
4.80 (q, J = 7.7 Hz, 4H; Ar2CH), 4.41 (d, J = 7.7 Hz, 4H; O2CH), 3.46
(s, 8H; ArCH2N), 1.79 ppm (d, J
([D6]DMSO): d = 152.1, 138.7, 129.3, 119.6, 99.4, 35.2, 31.2, 16.1 ppm;
MS (MALDI): m/z (%): 708.5 (100) [M]+, 731.5 (50) [M+Na]+); ele-
mental analysis calcd (%) for C40H44N4O8 (708.8): C 67.78, H 6.26, N
7.90; found: C 67.94, H 6.50, N 7.71.
15.9 ppm; MS (MALDI): m/z (%): 3438.5 (100) [M+Na]+ ; elemental
analysis calcd (%) for C149H186N8O75S4 (3417.4): C 52.37, H 5.49, N 3.28, S
3.75; found: C 52.31, H 5.53, N 3.16, S 3.79.
=
7.7 Hz, 12H; CH3C); 13C NMR
General procedure for the preparation of the glycoclusters 11, 12, 13, 14,
16: A catalytic amount of MeONa (ꢁ5% with respect to each AcO-sub-
stituent in the precursor) was added to a solution of the acetylated glyco-
clusters 7, 8, 9, 10, 15 (0.088 mmol) in MeOH/CH2Cl2 (1:4, 50 mL). The
reaction mixture was stirred overnight at room temperature. Water
(5 mL) was added and the reaction mixture was stirred for an additional
20 min. Subsequently, Amberlite IR-120 H+ (washed before with metha-
nol) was added and stirring was continued for an additional 15 min. The
Amberlite was filtered off and the organic solvents were evaporated at
reduced pressure (t<308C); the water was removed by freeze-drying.
The yield of glycoclusters is almost quantitative. An additional purifica-
tion by sonication with diisopropyl ether and washing with isopropanol is
also possible.
General procedure for the preparation of the acetylated glycoclusters 7
10: A solution of a pyranosylisothiocyanate[31] (1.06 mmol) and tetrakis-
(aminomethyl) cavitand 5 or 6 (0.21 mmol) in pyridine (20 mL) was stir-
red at room temperature for 3 d. After evaporation of the solvent, the re-
sulting solid was triturated with diethyl ether (2î20 mL) and subsequent-
ly recrystallized from 2-propanol. The pyranosylisothiocyanates used for
this synthesis (tetra-O-acetyl-b-d-glucopyranosylisothiocyanate,[31a] tetra-
O-acetyl-b-d-galacto-pyranosylisothiocyanate[31b] and hepta-O-acetyl-b-d-
cellobiosyl-isothiocyanate[31c]) were prepared by a slightly modified pro-
cedure used for the synthesis of the glucose derivative[31a] (refluxing the
corresponding a-bromopyranoside with Pb(NCS)2 in toluene for 4 6 h).
Tetrakis(1-glucosylthioureidomethyl)tetramethyl cavitand (11): Yield:
96%; m.p.>3508C; 1H NMR ([D6]DMSO): d = 7.73 (s, 4H; ArH), 7.67
(s, 4H; NH), 7.49 (s, 4H; NH), 5.95 (d, J = 6.6 Hz, 4H; O2CH), 5.16
(brs, 4H; H(1)-glu), 4.81 (q, J = 7.3 Hz, 4H; Ar2CH), 4.43 (brs, 8H;
ArCH2), 4.30 (d, J = 6.6 Hz, 4H; O2CH), 3.97 (brs, 16H; OH), 3.59
(brd, J2 = 11.3 Hz, 4H, H(6a)-glu), 3.42 (brd, J2 = 10.0 Hz, 4H; H(6b)-
glu), 3.22 2.85 (m, 16H; H(2), H(3), H(4), H(5)-glu), 1.81 ppm (d, J =
7.3 Hz, 12H; CH3C); 13C NMR ([D6]DMSO): d = 183.1, 152.5, 139.0,
123.8, 121.1, 99.1, 83.6, 78.0, 77.5, 72.8, 69.7, 60.5, 37.8, 31.3, 15.9 ppm;
MS (MALDI): m/z (%): 1615.8 (100) [M+Na]+ ; elemental analysis calcd
(%) for C68H88N8O28S4 (1593.7): C 51.25, H 5.57, S 8.05; found: C 50.98,
H 5.61, S 8.00.
Tetrakis(1-tetraacetylglucosylthioureidomethyl)tetramethyl cavitand (7):
Yield: 80%; m.p. 230 2318C (2-propanol); 1H NMR ([D6]DMSO): d =
7.73 (brs, 12H; ArH, NH), 5.91 (d, J = 7.0 Hz, 4H; O2CH), 5.78 (brs,
4H; H(1)-glu), 5.33 (t, J
= 9.3 Hz, 4H; H(3)-glu), 5.0 4.7 (m, 12H;
H(2), H(4)-glu, Ar2CH), 4.43 (brs, 8H; ArCH2), 4.25 (brs, 4H; O2CH),
4.15 (dd, J(6a,6b) = 12.0 Hz, J(6a,5) = 4.0 Hz, 4H; H(6a)-glu), 3.95 and
3.92 (brs + s, 8H; H(6b), H(5)-glu), 1.97 (brs, 36H; CH3CO), 1.93 (s,
12H; CH3CO), 1.81 ppm (d,
J =
7.0 Hz, 12H; CH3C); 13C NMR
([D6]DMSO): d = 183.1, 169.9, 169.4, 169.2, 152.5, 139.0, 123.3, 121.3,
99.2, 81.4, 72.7, 71.9, 70.4, 67.9, 61.6, 38.1, 31.3, 20.2, 20.2, 15.9 ppm; MS
(MALDI): m/z (%): 2265.1 (100) [M]+, 2288.1 (80) [M+Na]+ ; elemental
analysis calcd (%) for C100H120N8O44S4 (2266.4): C 53.00, H 5.34, N 4.94, S
5.66; found: C 52.73, H 5.59, N 4.86, S 5.62.
Tetrakis(1-galactosylthioureidomethyl)tetramethyl cavitand (12): Yield:
95%, m.p.>3508C; 1H NMR ([D6]DMSO): d = 7.23 (s, 4H; ArH), 7.67
(s, 4H; NH), 7.49 (s, 4H; NH), 5.95 (d, J = 6.6 Hz, 4H; O2CH), 5.15
(brs, 4H; H(1)-gal), 4.98 (brs, 8H; OH), 4.81 (brd, J = 7.3 Hz, 8H;
Ar2CH, OH), 4.42 (brs, 12H; ArCH2, OH), 4.29 (d, J = 6.6 Hz, 4H;
O2CH), 3.58 (d, J2 = 11.3 Hz, 4H; H(6a)-gal), 3.5 2.8 (m, 20H; H(2),
H(3), H(4), H(5), H(6b)-gal), 1.81 ppm (d, J = 7.3 Hz, 12H; CH3C); 13C
NMR ([D6]DMSO): d = 183.0, 152.5, 139.0, 123.8, 121.1, 99.1, 83.5, 78.0,
69.7, 72.8, 77.5, 60.5, 37.8, 31.3, 15.9 ppm; MS (MALDI): m/z (%): 1615.6
(100) [M+Na]+ ; elemental analysis calcd (%) for C68H88N8O28S4 (1593.7):
C 51.25, H 5.57, S 8.05; found: C 50.95, H 5.67, S 7.98.
Tetrakis(1-tetraacetylgalactosylthioureidomethyl)tetramethyl
cavitand
(8): Yield: 85%; m.p. 2338C (2-propanol); 1H NMR ([D6]DMSO): d =
7.73 (brs, 12H; ArH, NH), 5.91 (d, J = 7.5 Hz, 4H; O2CH), 5.78 (t, J =
9.5 Hz, 4H; H(1)-gal), 5.38 5.18 (m, 8H; H(4), H(3)-gal), 4.93 (t, J =
9.2 Hz, 4H; H(2)-gal), 4.81 (d, J = 7.5 Hz, 4H; Ar2CH), 4.44 (brs, 8H;
ArCH2), 4.22 (t + brs, J = 6.2 Hz, 8H; O2CH, H(5)-gal), 3.98 and 3.97
(s, 8H; H(6a), H(6b)-gal), 2.09 (s, 12H; CH3CO), 1.99 (s, 12H; CH3CO),
1.90 (s, 24H; CH3CO), 1.82 ppm (d, J = 7.3 Hz, 12H; CH3C); 13C NMR
([D6]DMSO): d = 183.2, 169.9, 169.4, 169.3, 152.5, 139.0, 123.1, 121.8,
99.1, 81.4, 72.7, 71.9, 70.4, 67.9, 61.6, 37.8, 31.3, 20.2, 20.3, 15.9 ppm; MS
(MALDI): m/z (%): 2265.0 (100) [M]+, 2288.0 (80) [M+Na]+ ; elemental
analysis calcd (%) for C100H120N8O44S4 (2266.4): C 53.00, H 5.34, N 4.94, S
5.66; found: C 52.80, H 5.50, N 4.83, S 5.60.
Tetrakis(1-glucosylthioureidomethyl)tetraamyl cavitand (13): Yield:
90%; m.p.>3508C; 1H NMR ([D6]DMSO): d = 7.72 (s, 4H; NH), 7.58
(s, 4H; ArH), 7.48 (s, 4H; NH), 5.95 (d, J = 6.6 Hz, 4H; O2CH), 5.19
(brs, 4H; H(1)-glu), 4.96 (brs, 8H; OH), 4.82 (brs, 4H; OH), 4.62 (q,
J = 7.3 Hz, 4H; Ar2CH), 4.43 (brs, 8H; ArCH2), 4.30 (d, J = 6.6 Hz,
4H; O2CH), 3.60 (d, J2 = 11.0 Hz, 4H; H(6a)-glu), 3.46 (d, J2 = 10 Hz,
4H; H(6b)-glu), 3.4 2.9 (m, 20H; OH, H(2), H(3), H(4), H(5)-glu), 2.37
(q, J = 7.2 Hz, 8H; CH2CH), 1.52 1.15 (m, 24H; (CH2)3), 0.89 ppm (t,
J = 7.2 Hz, 12H; CH3); 13C NMR ([D6]DMSO): d = 183.1, 152.8, 138.0,
123.8, 121.5, 99.2, 83.6, 78.0, 77.5, 72.8, 69.7, 60.5, 37.8, 36.9, 31.4, 29.2,
Tetrakis(1-tetraacetylglucosylthioureidomethyl)tetraamyl cavitand (9):
Yield: 72%; m.p. 179 1808C (2-propanol); 1H NMR ([D6]DMSO): d =
7.77 (brs, 8H; NH), 7.58 (s, 4H; ArH), 5.91 (d, J = 7.3 Hz, 4H; O2CH),
5.82 (brs, 4H; H(1)-glu), 5.34 (t, J = 9.4 Hz, 4H; H(3)-glu), 4.95 4.7 (m,
8H; H(2), H(4)-glu), 4.60 (t, J = 7.9 Hz, 4H; Ar2CH), 4.43 (brs, 8H;
ArCH2), 4.28 (brd, 4H; O2CH), 4.15 (dd, J(6a,6b) = 12.4 Hz, J(6a,5) =
4.4 Hz, 4H; H(6a)-glu), 4.1 3.7 (brs + s, 8H; H(6b), H(5)-glu), 2.35
(brs, 8H; CH2CH), 1.98 and 1.97 (s, 36H; CH3CO), 1.93 (s, 12H;
CH3CO), 1.45 1.2 (brm, 24H; (CH2)3), 0.88 ppm (d, J = 7.0 Hz, 12H;
CH3C); 13C NMR ([D6]DMSO): d = 183.2, 169.9, 169.4, 169.2, 152.9,
138.0, 123.4, 121.7, 99.1, 81.4, 72.7, 71.9, 70.5, 68.0, 61.6, 38.1, 36.9, 31.4,
29.2, 27.4, 22.1, 20.2, 20.3, 13.9 ppm; MS (MALDI): m/z (%): 2489.1 (70)
27.4, 22.2, 13.9 ppm; MS (MALDI): m/z (%): 1840.0 (100) [M+Na]+
;
elemental analysis calcd (%) for C84H120N8O28S4 (1818.2): C 55.49, H
6.65, S 7.05; found: C 55.28, H 6.75, S 6.95.
Tetrakis(1-cellobiosylthioureidomethyl)tetramethyl cavitand (14): Yield:
1
92%; m.p.>3508C; H NMR ([D6]DMSO): d = 7.73 (s, 8H; ArH, NH),
7.51 (s, 4H; NH), 5.96 (brs, 4H; O2CH), 5.21 (brs, 4H; H(1)-cel), 4.81
(d, J = 6.9 Hz, 8H; Ar2CH, OH), 4.6 2.9 (brs + m, 88 H + water;
ArCH2, O2CH, OH, H(2,6b), H(1’’,6b’’)-cel), 1.81 ppm (d, J = 6.3 Hz,
12H; CH3C); 13C NMR ([D6]DMSO): d = 180.9, 152.5, 139.0, 123.8,
121.1, 103.0, 83.3, 79.7, 76.7, 76.4, 76.2, 75.7, 74.8, 73.3, 72.5, 70.0, 61.0,
60.2, 37.8, 31.3, 15.9 ppm; MS (MALDI): m/z (%): 2263.9 (100)
[M]+, 2512.1 (100) [M+Na]+
; elemental analysis calcd (%) for
C116H152N8O44S4 (2490.8): C 55.94, H 6.15, N 4.50, S 5.15; found: C 56.07,
H 6.25, N 4.26, S 5.07.
Tetrakis(1-tetracellobiosylthioureidomethyl)tetramethyl cavitand (10):
Yield: 86%; m.p. 248 2508C (2-propanol); 1H NMR ([D6]DMSO): d =
7.74 (brs, 12H; ArH, NH), 5.91 (brs, 4H; O2CH), 5.78 (t, J = 8.4 Hz,
4H; H(1)-cel), 5.35 5.1 (m, 8H; H1’’, H(3)-cel), 5.0 4.7 (m, 16H;
Ar2CH, H(2), H(2)’’, H(3)’’-cel), 4.65 (t, J = 9.0 Hz, 4H; H(4)’’-cel), 4.42
(brs, 8H; ArCH2), 4.25 (t + brs, J = 10.8 Hz, 8H, O2CH, H(4)-cel),
4.14 3.9 (m, 16H; H(6a), H(6a)’’, H(6b), H(6b)’’-cel), 3.7 3.9 (m, 8H;
H5, H5’’-cel), 2.05 (s, 12H; CH3CO), 2.02 (s, 12H; CH3CO), 2.0 1.94 (m,
48H; CH3CO), 1.92 (s, 12H; CH3CO), 1.82 ppm (d, J = 6.6 Hz, 12H;
CH3C); 13C NMR ([D6]DMSO): d = 183.2, 170.2, 169.9, 169.5, 169.4,
169.3, 169.1, 168.9, 152.5, 139.0, 123.3, 121.3, 99.2, 81.2, 76.2, 73.1, 72.6,
72.2, 71.0, 70.6, 70.4, 67.7, 62.2, 61.5, 38.0, 31.3, 20.6, 20.4, 20.3, 20.1,
[M+Na]+
; elemental analysis calcd (%) for C92H128N8O48S4¥10H2O
(2422.5): C 45.62, H 6.16, N 4.63, S 5.29; found: C 45.82, H 6.04, N 4.43,
S 5.18.
Tetrakis(1-glucosylthiomethyl)tetramethyl cavitand (16): Yield: 91%;
m.p.>3508C; 1H NMR ([D6]DMSO): d = 7.63 (s, 4H; ArH), 6.02 (d,
J = 7.3 Hz, 4H; O2CH), 5.04 (brs, 8H; OH), 4.79 (q, J = 7.3 Hz, 4H;
Ar2CH), 4.70 (brs, 4H; OH), 4.40 4.20 (m, 8H; O2CH, H(1)-glu), 3.85
3.67 (m, 8H; H(6a)-glu, OH), 3.5 3.25 (m, 12H; H(6b)-glu, ArCH2S),
3.25 3.0 (m, 12H; H(3), H(4), H(5)-glu), 2.93 (t, J = 9.0 Hz, 4H; H(2)-
glu) 1.82 ppm (d, J = 7.3 Hz, 12H; CH3C); 13C NMR ([D6]DMSO): d =
2746
¹ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Chem. Eur. J. 2004, 10, 2739 2748

Glycocluster Thioureamethyl Cavitands
2739 2748
152.1, 138.8, 125.9, 120.0, 99.2, 84.3, 81.0, 78.2, 73.0, 70.2, 31.2, 21.9,
16.0 ppm; MS (MALDI): m/z (%): 1447.6 (100) [M+Na]+ ; elemental
analysis calcd (%) for C64H80O28S4 (1425.6): C 53.92, H 5.66, S 9.00;
found: C 53.63, H 5.77, S 8.89.
Mass Spectrom. 2002, 216, 1 27; g) B. Ganem, J. D. Henion, Bioorg.
Med. Chem. 2003, 11, 311 314.
[4] a) E. S. Kempen, J. S. Brodbelt, Anal. Chem. 2000, 72, 5411 5416;
b) M. Nakamura, T. Fujioka, H. Sakamoto, K. Kimura, New. J.
Chem. 2002, 554 559.
Tetrakis(1-tetraacetylglucosylthiomethyl)tetramethyl cavitand (15):
A
solution of 2,3,4,6-tetra-O-acetyl-b-glucopyranosylthiol[32] (530 mg,
1.45 mmol) in CH2Cl2 (5 mL) was added to a suspension of K2CO3
(0.95 g, 2.9 mmol) in a solution of tetrakis(bromomethyl)tetramethyl cav-
itand (1, 289 mg, 0.29 mmol) in CH2Cl2 (15 mL). The reaction mixture
was stirred at room temperature for 75 h, whereupon the salts were fil-
tered off. The solution was evaporated to dryness at reduced pressure
(T<408C). The solid was triturated with diethyl ether and recrystallized
from MeOH. Yield: 88%; m.p. 176 1778C (MeOH); 1H NMR (CDCl3):
d = 7.20 (s, 4H; ArH), 5.91 (d, J = 7.3 Hz, 4H; O2CH), 5.19 (t, J =
9.2 Hz, 4H; H(3)-glu), 5.09 (t, J = 9.5 Hz, 4H; H(4)-glu), 5.00 (t, J =
9.9 Hz, 4H; H(2)-glu), 4.98 (q, J = 7.3 Hz, 4H, Ar2CH), 4.55 (d, J =
[5] J. M. Koomen, J. E. Lucas, M. R. Haneline, J. D. Beckwith King, F.
Gabbai, D. H. Russell, Int. J. Mass Spectrom. 2003, 225, 225 231.
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52, 2663 2704; b) A. Jasat, J. C. Sherman, Chem. Rev. 1999, 99,
931 968; c) W. Verboom in: Calixarenes 2001 (Eds.: Z. Asfari, V.
Bˆhmer, J. Harrowfield, J. Vicens) Kluwer Academic Publishers,
Dordrecht, 2001, pp. 181 198; d) J. Sherman, Chem. Commun.
2003, 1617 1623.
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J. H. van der Maas, J. Chem. Soc. Perkin Trans. 2 1998, 2541 2546;
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J. H. van der Maas, J. Chem. Soc. Perkin Trans. 2 1998, 2623 2630;
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2000, 6, 999 1006; b) O. D. Fox, J. F.-Y. Leung, J. M. Hunter, N. K.
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[12] X. Gui, J. C. Sherman, Chem. Commun. 2001, 2680 2681.
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1995, 60, 1207 1213.
9.9 Hz, 4H; H(1)-glu), 4.36 (d, J
= 7.3 Hz, 4H; O2CH), 4.24 (dd,
J(6a,6b) = 12.5 Hz, J(5,6b) = 4.4 Hz, 4H; H(6b)-glu), 4.10 (dd, J(6b,6a)
= 12.5 Hz, J(5,6a) = 2.4 Hz, 4H; H(6a)-glu), 3.6 3.9 (m, 12H; ArCH2,
H(5)-glu), 2.07 (s, 12H; CH3CO), 2.04 (s, 12H; CH3CO), 2.00 (s, 12H;
CH3CO), 1.81 (s, 12H; CH3CO), 1.76 ppm (d, J = 7.3 Hz, 12H; CH3C);
13C NMR ([D6]DMSO): d = 169.9, 169.4, 169.2, 168.9, 152.2, 138.6, 124.2,
120.5, 99.5, 82.5, 74.3, 72.9, 69.6, 68.1, 61.9, 31.2, 23.5, 20.3, 20.2, 19.6,
15.9 ppm; MS (MALDI): m/z (%): 2119.7 (80) [M+Na]+ ; elemental
analysis calcd (%) for C96H112O44S4 (2098.2): C 54.96, H 5.38, S 6.11;
found: C 54.80, H 5.38, S 6.06.
Tetrakis(propylthioureidomethyl)tetraamyl cavitand (20): A solution of
propylisothiocyanate (242 mg, 0.25 mL, 1.8 mmol) and tetrakis(amino-
methyl) cavitand 6 (278 mg, 0.3 mmol) in MeOH:CH2Cl2 (1/3; 20 mL)
was stirred at room temperature for two days. The solvent was evaporat-
ed to dryness. The resulting solid was triturated with hexane (2î20 mL)
and then purified by column chromatography (CH2Cl2 containing 5%
MeOH, Rf = 0.17) followed by trituration with MeCN (2î5 mL). Yield:
83%; m.p. 214 2158C; 1H NMR (CDCl3): d = 7.12 (s, 4H; ArH), 6.30
(brs, 4H; NH), 6.13 (brs, 4H; NH), 5.99 (d, J = 7.2 Hz, 4H; O2CH),
4.73 (t, J = 8.0 Hz, 4H; Ar2CH), 4.41 (d, J = 7.2 Hz, 4H; O2CH), 4.35
(brs, 8H; ArCH2N), 3.42 (brs, 8H; AlkCH2N), 2.20 (q, J = 7.2 Hz, 8H;
CH2CH), 1.76 1.60 (m, 8H; MeCH2CH2N), 1.48 1.28 (m, 24H; (CH2)3),
[14] a) A. R. Mezo, J. C. Sherman, J. Org. Chem. 1998, 63, 6824 6829;
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1.02 0.86 ppm (m, 24H; CH3); 13C NMR (CDCl3): d
= 181.0, 153.1,
138.5, 122.8, 120.4, 99.9, 36.9, 32.0, 30.0, 27.6, 22.6, 22.2, 14.1, 11.5 ppm;
MS (MALDI): m/z (%): 1336.7 (100) [M]+ ; elemental analysis calcd (%)
for C72H104N8O8S4 (1337.9): C 64.64, H 7.83, N 8.38, S 9.59; found: C
64.67, H 7.82, N 8.29, S 9.64.
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Acknowledgement
We are grateful to the Council for Chemical Sciences of the Netherlands
Organization for Scientific Research (CW-NWO) for financial support.
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tric field gradient between the ESI needle and the counterelectrode.
Charged droplets, formed at the tip of the Taylor cone, move to-
wards the entrance of the mass spectrometer to produce free, charg-
ed analyte molecules by mechanisms that involve dividing large
droplets into smaller and smaller ones (coulomb fission mechanism)
and a release of ions from the droplet surface (ion evaporation
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¹ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

W. Verboom, D. N. Reinhoudt et al.
FULL PAPER
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Received: October 10, 2003
Revised: January 29, 2004
[28] For evaluations of relative binding affinities of different host guest
complexes based on relative intensities of signals in mass spectrome-
Published online: April 16, 2004
2748
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Chem. Eur. J. 2004, 10, 2739 2748