Synthesis and binding properties of hybrid cyclophane - Azamacrocyclic receptors

Article abstract of DOI:10.1021/jo048621o

(Chemical Equation Presented). Three new azamacrocyclic-cyclophane hybrid receptors L₁, L₂, and L₃ have been synthesized that incorporate either 1,4,7,10-tetraazacyclododecane (cyclen) or 1,4,7-triazacyclononane (tacn) uni

Full text of DOI:10.1021/jo048621o

Synthesis and Binding Properties of Hybrid
Cyclophane-Azamacrocyclic Receptors
Andrew C. Benniston,*,† Patrick Gunning,‡ and Robert D. Peacock*,‡
Molecular Photonics Laboratory, School of Natural Sciences (Chemistry), Bedson Building,
University of Newcastle, Newcastle upon Tyne NE1 7RU, U.K., and Chemistry Department,
Joseph Black Building, University of Glasgow, Glasgow G12 8QQ, U.K.
A.C.Benniston@ncl.ac.uk
Received August 9, 2004 (Revised Manuscript Received October 18, 2004)
Three new azamacrocyclic-cyclophane hybrid receptors L1, L2, and L3 have been synthesized that
incorporate either 1,4,7,10-tetraazacyclododecane (cyclen) or 1,4,7-triazacyclononane (tacn) unit-
(s) tethered via a short amidic spacer to an electron donor and a H-bonding crown ether polycycle.
The crown ether is designed to act as a host toward biologically relevant guests, whereas the
macrocycle can coordinate a zinc(II) or a copper(II) ion. The pKa of this bound water in the zinc(II)
complex of L1 and L2 is ∼7.5. Isothermal calorimetry experiments carried out on [ZnL1(OH2)](CF3-
SO3)2 and [Zn2L2(OH2)2](CF3SO3)4 in buffered water (pH 7.4) at 25 °C show that the host strongly
binds a series of phosphate derivatives. In comparison, the complex [CuL3(OH2)2](CF3SO3)2 is a
poor receptor toward phosphate substrates.
Introduction
using artificial systems has been the impetus for many
research groups4-15 over the past 20 years or so. Kimura
and co-workers16 have shown that zinc(II) complexes of
the azamacrocycles 1,5,9-triazacyclodecane and 1,4,7,10-
It has long since been recognized that Nature holds
the upper hand in the biological catalysis arena, espe-
cially with metal-based enzymes that perform varied and
critical organic transformations.1 Bovine carboxypepti-
dase A, for example, is a natural enzyme that efficiently
hydrolyzes C-terminal phenylalanine amino acids from
peptide substrates.2 Within the enzyme, the phenyl group
resides in a hydrophobic pocket with amino acid residues
Arg-145 and Tyr-248, providing secondary H-bonding
sites. The active center is a zinc(II) ion containing a
bound hydroxyl ion that acts as a nucleophilic center in
the hydrolysis of the amide bond.3 Mimicking this enzyme
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* To whom correspondence should be addressed. (A.C.B.) phone:
+44 (0)191 222 5706. Fax: +44 (0)191 222 6929. (R.D.P.) phone:
+44 (0)141 330 4375.
† University of Newcastle.
‡ University of Glasgow.
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10.1021/jo048621o CCC: $30.25 © 2005 American Chemical Society
Published on Web 11/25/2004
J. Org. Chem. 2005, 70, 115-123
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Benniston et al.
tetrazacyclododecane (cyclen) bind a water molecule with
a pKa value that is dramatically reduced when compared
to that of the bulk water molecule. Owing to the genera-
tion of the nucleophilic center, these complexes catalyti-
cally hydrolyze ester groups of simple substrates.17 The
next stage of development of artificial enzymes has
witnessed the inclusion of secondary structures such as
cyclodextrins,18 calixarenes,19 dendrimers,20 cavitands,21
and polymer supports.22 These groups tend to mimic the
second-coordination sphere and beyond and serve to
protect reactants, bind substrates, and promote reactions.
However, these secondary host sites generally do not
possess multiple specific groups capable of promoting
simultaneous H-bonding, π-π-stacking, and dipole-
dipole interactions that are found in the protein structure
of enzymes. This task requires the design of more
multifunctional second-coordination sphere assemblies.
For some time, it has been recognized that specific crown
ether polycycles such as DBC823 have the ability to play
host to molecules using multiple noncovalent interac-
tions, including π-π stacking of electron-deficient aro-
matics24 and H-bonding via the oxygen atoms.25 Thus,
we rationalized that grafting a crown cyclophane to a
macrocycle core would mimic the binding and active site
of enzymes. Our initial synthetic efforts toward this goal
are described in this paper along with binding of the
receptors in HEPES-buffered water (pH 7.4).
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Results and Discussion
Synthetic Procedures. A common theme of artificial
enzyme mimics is that they generally require the use of
macrocyclic metal complexes that contain a single metal
ion or use compartmentalized ligands that bind two or
more metal centers (see later). Our program of work has
focused on cyclic polyethers as the host site since the ring
size is readily controlled by synthetic means and thus
are easily functionalized with other groups. We also
considered that many systems have been developed for
anion recognition and the design features of our own
system are comparable to previously reported examples.26
The synthetic protocols used in the preparation of the
hybrid model enzyme receptor L1 are illustrated in
Scheme 1. One of our initial design themes was to
prepare a crown polycycle containing an aldehyde func-
tional group and use reductive amination to graft the
azamacrocycle directly onto the superstructure. This
method, however, was abandoned because of very poor
yields, but the aldehyde group was left in place since it
is readily converted to other functional groups. To
prepare the crown polycycle, it was decided to construct
it in a stepwise manner and use well-established syn-
thetic procedures.27 Compound 1 was thus prepared from
the commercial material 2,4-dihdroxybenzaldeyde with
good yield (∼80%) using a previously reported method.28
The terminal alcohol group of 1 was converted to a
leaving group via two standard steps to afford diiodide
derivative 2 in an overall 40% yield. Cyclization of 2
with 1,3-dihydroxybenzene using mildly basic conditions
(K2CO3) afforded the aldehyde-functionalized crown 3 in
25% yield. Our first effort at this stage of the procedure
was to convert the aldehyde to a leaving group and
directly attach the macrocycle. Although 3 could be easily
reduced to the benzyl alcohol, all attempts in our hands
to convert the alcohol into either bromide, OTs, OMs, or
OTf groups failed to afford pure materials. We therefore
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116 J. Org. Chem., Vol. 70, No. 1, 2005

Properties of Cyclophane-Azamacrocyclic Receptors
SCHEME 1. Synthetic Procedures Used in the
Preparation of the Hybrid Ligand L1
SCHEME 2. Synthetic Procedures Used in the
Preparation of the Multitopic Ligand L2
boxymethylamino)acetic acid 9 produced compound 10
in 82% yield. Deprotection of 10 was first undertaken
using 1,4-cyclohexadiene with Pd/C in ethanol, but this
failed to give the desired product. However, H2 gas using
Pd/C catalyst in methanol removed the CBZ protecting
group to afford 11 in 79% yield. Once again simple
coupling of 11 with 4 afforded the Boc-protected deriva-
tive 12 in a 45% yield. Deprotection of 12 under acidic
conditions yielded the functionalized ligand L2 in an
unoptimized 75% yield. Reaction of L2 with Zn(CF3SO3)2
in methanol gave the corresponding bimetallic complex
Zn2L2(OH2)2(CF3SO3)4.
In addition to working with zinc-based systems, we
were also interested in seeing if the outlined methodology
in Scheme 1 could be used to attach a triazamacrocycle
for complexation with biologically relevant copper(II).31
The monofunctionalization of 1,4,7-triazacyclononane
(tacn) is well documented and can follow a number of
approaches.32 Illustrated in Scheme 3 is the procedure
to create a hybrid tacn-cyclophane starting from the
Boc-protected derivative 13. Conversion of 13 to the
CBZ-protected aminoacetic acid 14 worked in 78% yield.
Deprotection of 14 again worked best under reductive
conditions to afford 15 as a colorless oil in 73% yield.
Using standard peptide coupling conditions, 15 was
coupled to 4 to give 16 in 61% yield. Final removal of
the Boc groups under standard conditions produced the
ligand L3, which was complexed with copper(II) to give
a dark-blue solid.
decided to oxidize the aldehyde to a carboxylate and
attach the macrocycle to the crown superstructure using
standard peptide-coupling methods.29 Oxidation of 3
was carried out using KMnO4 in water/acetone to afford
4 in 63% yield. The reaction of 4 with 5 using coupling
agents (e.g., DCC) gave materials that were problematic
due to their instability and was thus abandoned. Instead,
the alternative strategy of attaching a short spacer to
the azamacrocycle and coupling this to the crown poly-
cycle was attempted. Hence, reaction of 5 with the
CBZ-protected aminoacetic acid gave 6 in 95% yield.
Removal of the CBZ group and coupling of the amino
group with 4 gave the derivative 8 in 79% yield. Final
BOC deprotection of 8 using acid conditions gave the
desired hybrid ligand L1. The zinc(II) complex was
prepared by reacting L1 with Zn(CF3SO3)2 in methanol.
The complex [ZnL1(OH2)](CF3SO3)2 was readily soluble
in water as well as protic solvents.
Many enzyme systems such as superoxide dismutase,
ribonucleotide reductase, and alcohol dehydrogenase
contain bimetallic reactive sites for the activation and
reaction of substrates.30 Since functionalization of 5 is
readily carried out, we envisaged that a receptor could
be produced containing two azamacrocycle sites for the
synthesis of a bimetallic enzyme mimic. Thus, shown in
Scheme 2 is the procedure used in preparation of the
tritopic ligand L2. Coupling of 5 to the protected (car-
Binding of Metals toward L1-L3. The transition
metal ion Zn2+ has a high affinity for donors such a
nitrogen and sulfur, and less affinity for the hard oxygen
donor.33 Even so, the hybrid ligand L1 has potentially two
binding sites for a metal ion, namely, the azamacrocycle
and the crown polycycle. A 1H NMR titration experiment
was carried out to ascertain the site of binding of the Zn2+
(29) (a) Kurzer, F.; Douraghi-Zadeh, K. Chem. Rev. 1967, 67, 107.
(b) Finn, F. M.; Hofmann, K. Proteins, 3rd ed.; 1976; Vol. 2, p 105.
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Bra¨nden, C.-I. In Zinc Enzymes; Spiro, T. G., Ed.; John Wiley & Sons:
New York, 1983; pp 125-152. (c) Daly, R. I.; Martin L. L. Inorg. Chem.
Commun. 2002, 5, 777.
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Tyeklar, Z.; Karlin, K. D. Acc. Chem. Res. 1989, 22, 241. (c) Karlin, K.
D.; Tyeklar, Z. Bioinorganic Chemistry of Copper; Kluwer: Dordrecht,
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8717.
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J. Org. Chem, Vol. 70, No. 1, 2005 117

Benniston et al.
crown polycycle, whereas the region 2.5-3.0 ppm is
assigned to methylene signals of the azamacrocycle. Upon
addition of 0.25 equiv of Zn2+ ions, there is a clear shift
in the signals associated with the azamacrocycle and only
minor changes to the signals associated with the crown
ether. Upon addition of successive portions of Zn2+ ions
to a solution of the ligand, there is a considerable
broadening of the azamacrocycle methylene signals and,
to a lesser extent, the resonances associated with the
crown ether. A control 1H NMR titration experiment
using the BOC-protected derivative 8 did not show any
significant chemical shift alterations for the crown poly-
cycle methylene signals. In view of these findings, it is
clear that the Zn2+ ion is coordinated preferentially to
the azamacrocycle.
A similar titration of Zn2+ into L2 as outlined above
gave similar results, but because of the presence of two
azamacrocycle sites, a bimetallic complex was formed.
The binding of copper(II) toward L3 was confirmed by
titration experiments and monitoring the absorbance
change with added copper(II). A plot of absorbance
change versus molar ratio of copper (II) leveled off at ∼1,
indicating formation of a 1:1 complex. The strong blue
color of the complex associated with the d-d transition
is very much in line with copper(II) bound to the nitrogen
donor groups rather than the oxygen atoms of the crown
polycycle.34
Properties of ligands L1, L2, and L3. Natural
enzymes contain within short distances domains that are
hydrophilic and hydrophobic in nature. This unique blend
of functionality for binding and reactivity is what makes
enzymes such powerful catalysts. Artificial systems to
work at the same level need somehow to mimic this
diversity in physicochemical properties. The partition
coefficient of L1, L2, and L3 were calculated to ascertain
the lipophilic/hydrophobic nature of the ligands. The logP
values for L1, L2, and L3 are 0.23, -1.16, and 0.97,
respectively.35 This indicates that L1 and L3 are am-
phiphilic, whereas L2 is slightly more hydrophilic due to
the increased number of amines.
1
FIGURE 1. Partial 400 MHz H NMR spectrum of L1 in d4-
methanol in the absence (a) and presence of 0.25 equiv of Zn2+
(b), 0.5 equiv of Zn2+ (c), 0.75 equiv of Zn2+ (d) and 1 equiv of
Zn2+
.
SCHEME 3. Synthetic Procedures Used in the
Preparation of Derivative L3
Binding of Complexes toward Phosphate Sub-
strates. Clearly, natural enzymes work in an aqueous
environment, and so one important criterion for an
artificial system is to work under similar conditions.
Thus, the binding behavior of [ZnL1(OH2)](CF3SO3)2,
[Zn2L2(OH2)2](CF3SO3)2, and [CuL3(OH2)2](CF3SO3)2 to-
ward various phosphate substrates was measured in
buffered H2O at 25 °C using isothermal calorimetry.36 In
a previous communication, we described the binding
behavior of [ZnL1(OH2)](CF3SO3)2 toward phosphate and
concluded that it behaves as an ion-pair binder using
both the crown polycycle and zinc(II)-hydroxyl sites.37 It
is believed that the zinc(II) center binds the phosphate
anion with crown polycycle, acting cooperatively to bind
ion in the hybrid ligand L1. Figure 1 shows the partial
1H NMR of L1 upon the addition of aliquots of Zn-
(CF3SO3)2 in d4-methanol. The region 3.4-4.2 ppm is
characteristic of methylene signals associated with the
(34) Cotton, F. A.; Wilkinson, G. Advanced Inorganic Chemistry: A
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(35) We are confident that the calculated values of log P are reliable
since the measured value for L1 (0.18) is in very good agreement.
(36) Attempts to confirm binding of phosphate derivatives by
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Commun. 2004, 19, 2226.
118 J. Org. Chem., Vol. 70, No. 1, 2005

Properties of Cyclophane-Azamacrocyclic Receptors
TABLE 1. Binding Constants and Thermodynamic Parameters Obtained by Isothermal Calorimetry for [ZnL1(H2O)]2+
,
[Zn2L2(OH2)2]2+, and [CuL3(OH2)2]2+ at 25 °C in the Presence of Various Substrates
ligand:
∆G°/kcal
∆H°/kcal
-T∆S°/kcal
ligand
substratea
substrate
K/104b
mol-1
mol-1
mol-1
[ZnL1(H2O)]2+
[ZnL1(H2O)]2+
[ZnL1(H2O)]2+
[ZnL1(H2O)]2+
[Zn2L2(H2O)2]4+
[Zn2L2 (H2O)2]4+
[Zn2L2 (H2O)2]4+
[Zn2L2 (H2O)2]4+
[ZnL3(H2O)]2+
[ZnL3(H2O)]2+
2:1
2:1
1:1
1:1
1:2d
1:2d
1:1
1:1
1:1
1:1
Na[H2PO4]
K[H2PO4]
sodium glycerophosphate
disodium 4-nitrophenyl phosphate
Na[H2PO4]
4.93 ( 0.69c
9.32 ( 1.60c
0.48 ( 0.06
0.39 ( 0.04
e
-6.39 ( 0.90
-6.78 ( 0.17
-5.02 ( 0.63
-4.90 ( 0.50
na
3.47 ( 0.16
2.44 ( 0.09
0.48 ( 0.02
0.58 ( 0.04
na
9.86f
9.22f
5.50f
5.48f
na
K[H2PO4]
e
na
na
na
sodium glycerophosphate
disodium 4-nitrophenyl phosphate
Na[H2PO4]
1.78 ( 0.21
1.23 ( 0.34
<0.05h
-5.79 ( 0.68
-5.57 ( 1.54
3.89 ( 0.38
0.63 ( 0.11
9.68g
6.21g
K[H2PO4]
<0.05h
a Ratio obtained from least-squares fit to isothermal calorimetry data. b mol-1 dm3. c mol-2 dm6. d Binding stoichiometry obtained from
Job plot from UV-vis spectroscopy data and confirmed by ES-MS. e Unable to calculate from isothermal calorimetry data (see text), na,
not available. f Data taken from ref 37. g This work. h Confirmed by UV-vis titrations. Note: Reported errors are from the least-squares
ITC fitted data and are as reported from the output file (see Supporting Information).
the cation (i.e., Na+, K+). Thermodynamic data also
reveal a large entropic driving force for complexation that
is assigned to water expulsion from the crown ether.
Collected in Table 1 is a summary of these data along
with that for the other two complexes. A noticeable result
is the lack of any tangible substrate binding by the copper
complex of ligand L3. It is well-known that copper(II)
forms distorted five-coordinate complexes with triaz-
amacrocyclic ligands similar to L3.38 The lack of strong
phosphate binding could be due to a geometry mismatch
of phosphate interaction at the copper.
The design of the bimetallic system [Zn2L2(OH2)2](CF3-
SO3)2 was specific to promote phosphate binding between
the two zinc(II) centers and use the crown polycycle to
shield the bound substrate. A molar ratio plot obtained
by a UV-vis titration confirmed a 1:2 ([Zn2L2(OH2)2]4+
/
HPO42-) binding stoichiometry. The ITC binding iso-
therm (Figure 2), however, reveals a more complicated
process in fact takes place. The first segment of the ITC
trace reveals an exothermic process takes place that is
followed by an endothermic reaction. It should be noted
that the binding of [Zn2L2(OH2)2]4+ toward sodium gly-
cerophosphate and disodium 4-nitrophenyl phosphate is
endothermic and does not follow this behavior. One
possible argument to account for the data is that, at high
ligand/substrate ratios (i.e., beginning of the titration),
the phosphate anion acts as a template for cluster
formation of two [Zn2L2(OH2)2]4+ moieties. Indeed, there
is literature precedent for the templating action of anions,
especially in helicate formation around a spherical
chloride ion.39 As the ligand:substrate ratio increases, the
cluster is broken up, leading to 1:2 complex formation.
Unfortunately, electrospray mass (ES-MS) spectrometry
experiments carried out on solutions of varying [Zn2L2-
(OH2)2]4+/HPO42- ratios all displayed similar features. All
ES-MS results revealed an intense cluster of peaks
centered at m/z ) 701, corresponding to [Zn2L2(HPO4)2-
Na2]2+. This ratio of zinc complex to phosphate is in
agreement with the UV/vis titration results (i.e., 1:2
(ligand/substrate) complexation).
FIGURE 2. Isothermal calorimetry graphs showing the
binding of [Zn2L2(OH2)4]4+ toward NaH2PO4 in buffered water
(pH ) 7.4) at 25 °C.
Conclusions
We have shown that hybrid azamacrocycle-crown
ether receptors can be readily produced using well-
established synthetic procedures. The methodology used
is modular since all three parts can be readily changed,
and thus gives the opportunity for future systems of
designer engineering each segment for a particular
function. Our initial efforts at binding phosphate at
physiological pH using the hybrid derivatives have been
successful, and binding constants are comparable with
those for previously reported supramolecular receptors.8
Experiments are currently underway to see if hydrolysis
of the P-O bond can be carried out, and these results
will be reported at a later date.
(38) (a) Viara, M. D.; Mani, F.; Stoppiono, P. Inorg. Chim. Acta 2000,
303, 61. (b) Benniston, A. C.; Ellis, D.; Farrugia, L. J.; Kennedy, R.;
Peacock, R. D.; Walker, S. Polyhedron 2002, 21, 333.
(39) Vilar, R. Angew. Chem., Int. Ed. 2003, 42, 1460.
J. Org. Chem, Vol. 70, No. 1, 2005 119

Benniston et al.
71.3 (CH2), 72.3 (2 × CH2), 100.0 (CH), 107.0 (CH), 119.7 (C),
Experimental Section
130.7 (CH), 163.2 (C), 165.6 (C), 188.6 (CHO).
Preparation of 2,4-Bis{2-[2-(2-hydroxyethoxy)ethoxy]-
ethoxy}benzaldehyde (1). Solid 2,4-dihydroxybenzaldehyde
(10.00 g, 72 mmol) was added to a stirred mixture of K2CO3
(29.85 g, 216 mmol) in dry DMF (60 mL) at 90 °C under N2.
The mixture was stirred at this temperature for 1 h before
addition of 2-[2-(2-chloroethoxy)ethoxy]ethanol (24.28 g, 144
mmol) and KI (22.63 g, 158 mmol). The reaction mixture was
refluxed for 48 h and cooled to room temperature. The DMF
was removed by azeotropic distillation with toluene (3 × 250
mL) to leave a red oil, which was dissolved in CH2Cl2 (200
mL) and filtered to remove potassium salts. The organics were
dried over MgSO4 and concentrated under reduced pressure
to yield a viscous red oil (23.14 g, 79.9%): 1H NMR (CDCl3) δ
2.56 (1H, t, J ) 6 Hz, OH), 2.68 (1H, t, J ) 6 Hz, OH), 3.60-
3.63 (4H, m, CH2), 3.68-3.75 (12H, m, CH2), 3.86-3.92 (4H,
m, CH2), 4.21 (2H, t, J ) 5 Hz, CH2), 4.24 (2H, t, J ) 5 Hz,
CH2), 6.53-6.58 (2H, m, Ar-H), 7.80 (1H, d, J ) 8 Hz, Ar-
H), 10.35 (1H, s, CHO); 13C NMR (CDCl3) δ 68.2 (CH2), 68.8
(CH2), 69.75 (CH2), 69.78 (CH2), 70.1 (CH2), 70.4 (CH2), 70.5
(CH2), 71.0 (CH2), 71.1 (CH2), 72.5 (CH2), 72.7 (CH2), 72.8
(CH2), 100.3 (CH), 107.4 (CH), 119.6 (C), 131.5 (CH), 163.1
(C), 165.5 (C), 189.1 (CHO). Note: the crude compound was
carried through to the next stage as a result of purification
difficulties.
Preparation of 2,4-Bis{2-[2-(2-iodoethoxy)ethoxy]-
ethoxy}benzaldehyde (2). To a stirred solution of 1 (22.0 g,
54 mmol) and Et3N (17.3 mL, 162 mmol) in dry CH2Cl2 (50
mL) cooled to 0 °C under an Ar atmosphere were slowly added
portions of p-toluenesulfonyl chloride (27.31 g, 162 mmol). The
mixture was allowed to warm to room temperature and the
reaction monitored by TLC (silica gel, 5:1 ethyl acetate/petrol).
After disappearance of the starting material, water (150 mL)
was added to the reaction mixture. The product was extracted
with CH2Cl2 (200 mL) and washed with brine (3 × 100 mL).
The separated organic layer was dried over MgSO4 and the
solvent removed to afford a viscous brown oil, which was
purified using flash chromatography (silica gel 5:1 ethyl
acetate/petrol) to yield a yellow oil (20.06 g, 28.2 mmol, 52.3%).
Elemental analysis calcd for C33H42O13S2: C, 55.76; H, 5.95;
found C, 55.75; H, 5.81. νmax (neat)/cm-1 2861, 1731 (CdO),
1671, 1596, 1575, 1500 (Ar), 993, 933, 873, 815; 1H NMR
(CDCl3) δ 2.36 (6H, s, CH3), 3.51-3.56 (4H, m, CH2), 3.58-
3.63 (8H, m, CH2), 3.77 (2H, t, J ) 5 Hz, CH2), 3.80 (2H, t, J
) 5 Hz, CH2), 4.10 (8H, m, CH2), 6.42 (1H, d, J ) 2 Hz, Ar-
H), 6.47 (1H, dd, J ) 8, and 1.4 Hz, Ar-H), 7.25 (4H, d, J )
8 Hz, Ar-H), 7.71 (5H, d, J ) 8 Hz, Ar-H), 10.27 (1H, s, CHO);
13C NMR (CDCl3) δ 22.0 (2xCH3), 68.1 (CH2), 68.6 (CH2), 69.1
(CH2), 69.6(CH2), 69.8 (CH2), 70.6 (CH2), 71.1 (CH2), 71.17
(CH2), 71.2 (CH2), 72.3 (CH2), 99.9 (CH), 107.1 (CH), 119.6 (C),
128.3 (CH), 130.2 (CH), 130.6 (CH), 133.3 (C), 145.23 (C),
145.26 (C), 163.3 (C), 165.6 (C), 188.6 (CHO).
Preparation of 2,5,8,11,17,20,23,26-Octaoxatricyclo-
[25.3.1.112,16]dotriaconta-1(30),12(32),
13,15,27(31),28-
hexaene-13-carbaldehyde (3). To a stirred suspension of
K2CO3 (10.71 g, 77 mmol) in dry DMF (30 mL) under N2 were
added simultaneously over a 28 h period separate solutions
of 2,4-bis [2-{2-(2-iodo-oxyethoxy)ethoxy}ethoxy]benzaldehyde
2 (6.08 g, 9.7 mmol) in dry DMF (40 mL) and 1,3-dihydroxy-
benzene (1.07 g, 9.7 mmol) in dry DMF (40 mL). The mixture
was heated at 90 °C for 5 days before being cooled to room
temperature. The residue was dissolved in distilled water (100
mL) and the solution extracted with CH2Cl2 (3 × 50 mL). The
organic washings were combined and washed with 2 M HCl
(100 mL) and distilled water (2 L). Sodium chloride was added
to break up the emulsion that formed during the partitioning
process. The organic phase was isolated, dried over MgSO4,
and concentrated under reduced pressure to yield a crude
product, which was chromatographed on silica gel (5:1 ethyl
acetate/petrol) to give the target compound as a pale-yellow
viscous oil (1.03 g, 22.5%). Elemental analysis calcd for
C25H32O9: C, 63.01; H, 6.76; found C, 62.60; H, 6.78; HRMS
(EI+) calcd for C25H32O9 [M+], m/z ) 476.2046, found 476.2046;
νmax (neat)/cm-1 2867, 1671 (CdO), 1594 and 1490, (Ar), 840,
815 (meta-disubstituted Ar); 1H NMR (CDCl3) δ 3.61-3.67 (8H,
m, CH2), 3.72-3.83 (8H, m, CH2), 3.99 (2H, t, J ) 5 Hz, CH2),
3.99 (2H, t, J ) 5 Hz, CH2), 4.06-4.10 (4H, m, CH2), 6.38-
6.47 (5H, m, Ar-H), 7.05 (1H, t, J ) 8 Hz, Ar-H), 7.68 (1H,
d, J ) 8 Hz, Ar-H), 10.34 (1H, s, CHO); 13C NMR (CDCl3) δ
67.6 (CH2), 67.8 (CH2), 68.0 (CH2), 68.5 (CH2), 69.7 (CH2), 69.8
(CH2), 70.0 (CH2), 70.1 (CH2), 71.0 (CH2), 71.2 (CH2), 71.4
(CH2), 71.6 (CH2), 100.0 (CH), 102.4 (CH), 106.9 (CH), 107.0
(CH), 107.7 (CH), 119.6 (C), 130.1 (CH), 130.5 (CH), 160.3 (C),
160.36 (C), 163.4 (C), 165.7 (C), 188.7 (CHO).
Preparation of 2,5,8,11,17,20,23,26-Octaoxatricyclo
[25.3.1.112,16]dotriaconta-1(30),12(32), 13,15,27(31),28-hex-
aene-13-carboxylic Acid (4). The macrocyclic aldehyde 3
(0.050 g, 1.0 mmol) was dissolved in acetone (2 mL) and treated
with a solution of KMnO4 (0.033 g, 2.1 mmol) in acetone/H2O
(1:1) (2 mL). The solution was stirred at room temperature
for 6 h. The insoluble inorganic salts were removed by filtration
through a short silica plug (10 g) and elution with ethyl acetate
(100 mL). The filtrate was concentrated, redissolved in CH2-
Cl2 (20 mL) that was washed with brine (2 × 30 mL),
separated, and dried over MgSO4. Removal of the CH2Cl2
afforded a crude product, which was purified by silica gel
chromatography using ethyl acetate/petrol (5:1) as eluent to
yield the pure product as a colorless oil (0.032 g, 62%): HRMS
(EI+) calcd for C25H32O10 [M+], m/z ) 492.1995, found 492.1997;
νmax(neat)/cm-1 3272, 2869, 2360, 1720 (CdO), 1604, 1490,
1438, 1361, 1284, 1255, 1182, 1120, 1056, 987, 943, 836, 763,
1
682, 634; H NMR (CDCl3) δ 3.62-3.66 (8H, m, CH2), 3.67-
3.71 (2H, m, CH2), 3.72 (2H, t, J ) 4 Hz, CH2), 3.77 (2H, t, J
) 4 Hz, CH2), 3.83 (2H, t, J ) 4 Hz, CH2), 3.88 (2H, t, J ) 4
Hz, CH2), 4.08 (2H, t, J ) 4 Hz, CH2), 4.12 (2H, t, J ) 4 Hz,
CH2), 4.27 (2H, t, J ) 4 Hz, CH2), 6.29 (1H, t, J ) 2 Hz, Ar-
H), 6.36 (1H, t, J ) 2 Hz, Ar-H), 6.38 (1H, t, J ) 2 Hz), 6.45
(1H, d, J ) 2 Hz, Ar-H), 6.55 (1H, dd, J ) 10 and 2 Hz, Ar-
H), 6.99 (1H, t, J ) 8 Hz, Ar-H), 7.92 (1H, d, J ) 8 Hz, Ar-
H); 13C NMR (CDCl3) δ 67.3 (CH2), 67.7 (CH2), 68.2 (CH2), 69.1
(CH2), 69.6 (CH2), 69.8 (CH2), 70.0 (CH2), 70.1 (CH2), 70.7
(CH2), 71.2 (CH2), 71.4 (CH2), 71.8 (CH2), 101.0 (CH), 102.3
(CH), 106.4 (CH), 107.6 (CH), 108.0 (CH), 111.5 (C), 130.2
(CH), 135.5 (CH), 159.1 (C), 160.2 (C), 160.3 (C), 164.5 (C),
165.8 (C).
Preparation of 1,4,7,10-Tetraazacyclododecane-1,4,7-
tricarboxylic Acid Tri-tert-butyl Ester (5). Under an N2
atmosphere at room temperature, a solution of di-tert-butyl
dicarbonate (3.42 g, 15.6 mmol) in CHCl3 (10 mL) was added
slowly over 3 h to a solution of cyclen (1 g, 6 mmol) and Et3N
(1.76 g, 16.1 mmol) in CHCl3. The reaction mixture was stirred
for a further 24 h, and the solvent was removed under vacuum
To a solution of the above compound 4-bis [2-{2-(2-
tosyloxyethoxy)ethoxy}ethoxy] benzaldehyde (20.06 g, 28 mmol)
in dry acetone (350 mL), at reflux, was added NaI (16.93 g,
113 mmol) over a 30 min period. The mixture was further
refluxed for 14 h under an N2 atmosphere. The solution was
cooled to room temperature and the solvent removed under
reduced pressure. To the mixture was added CH2Cl2 (150 mL)
and the resultant solid residue filtered. Removal of the solvent
afforded a yellow oil, which was further purified by silica gel
column chromatography (5:1 ethyl acetate/petrol) to give pure
product as a colorless oil 3 (13.77 g, 22 mmol, 77.7%).
Elemental analysis calcd for C19H28O7I2: C, 36.65; H, 4.50; I,
40.84; found C, 36.65; H, 4.61; I, 40.89; HRMS (EI+) calcd for
C19H28O7I2 [M+] m/z ) 621.9925, found 621.9926; 1H NMR
(CDCl3) δ 3.19 (4H, dt, J ) 7 and 2 Hz, CH2), 3.60-3.72 (12H,
m, CH2), 3.82 (2H, t, J ) 5 Hz, CH2), 3.86 (2H, t, J ) 5 Hz,
CH2), 4.11-4.16 (4H, m, CH2), 6.43 (1H, d, J ) 2 Hz, Ar-H),
6.50 (1H, dd, J ) 8 and 2 Hz, Ar-H), 7.73 (1H, d, J ) 8 Hz,
Ar-H), 10.28, (1H, s, CHO); 13C NMR (CDCl3) δ 68.1 (2 × CH2),
68.6 (2 × CH2), 69.9 (2 × CH2), 70.6 (2 × CH2), 71.2 (CH2),
120 J. Org. Chem., Vol. 70, No. 1, 2005

Properties of Cyclophane-Azamacrocyclic Receptors
to give crude product, which was purified by column chroma-
tography on silica gel (5:1 ethyl acetate/petrol) to afford the
pure product as a white solid (2.25 g, 82%): mp 54-55 °C;
HRMS (EI+) calcd for C23H45N4O6 [MH+] m/z ) 473.3339, found
473.3338; νmax(neat)/cm-1 3313, 2975, 2802, 1666 (CdO), 1463,
1413, 1386, 1363, 1319, 1288, 1247, 1149, 1116, 1087, 1058,
983, 943, 892, 858, 821, 773; 1H NMR (CDCl3) δ 1.37 (18H, s,
CH3), 1.39 (9H, s, CH3), 2.77 (4H, s (broad), CH2), 3.21-3.31
(8H, m, CH2), 3.54 (4H, s (broad), CH2); 13C NMR (CDCl3) δ
27.5 (9 × CH3), 43.9 (CH2), 44.9 (CH2), 47.8 (CH2), 48.4 (2 ×
CH2), 48.8 (CH2), 49.9 (2 × CH2), 78.1 (2 × C), 78.4 (C), 154.4
(CdO), 154.6 (2 × CdO).
(CH2), 71.2 (CH2), 71.3 (CH2), 71.4 (CH2), 80.7 (C), 80.8 (C),
80.9 (C), 100.7 (CH), 102.4 (CH), 106.4 (CH), 107.1 (CH), 107.6
(CH), 114.8 (C), 130.1 (CH), 133.8 (CH), 156.0 (C), 157.1 (C),
158.9 (C), 160.3 (C), 162.9 (C), 165.2 (C).
Preparation of 2,5,8,11,18,21,24,27-Octaoxatricyclo-
[26.3.1.012,17]dotriaconta-1(31),12(17),13,15,28(32),29-
hexaene-29-carboxylic Acid [2-Oxo-2-(1,4,7,10-tetraaza-
cyclododec-1-yl)-ethyl]-amide (L1). To a stirred solution of
8 (0.26 g, 0.25 mmol) in CH2Cl2 (3 mL) at room temperature
under an N2 atmosphere was added dropwise TFA (1 mL). The
solution was stirred for 3 h then quenched by addition of 3 M
NaOH (10 mL). The organic layer was washed with brine (3
× 20 mL), separated, and dried over Na2SO4. Removal of the
solvent afforded the pure product as a colorless oil (0.13 g,
72%): HRMS (FAB+) calcd for C35H54N5O10 [MH+] m/z )
704.3871, found 704.3866; νmax(neat)/cm-1 3361, 2867, 1631
(CdO tertiary amide), 1600 (CdO) secondary amide), 1521,
Preparation of 10-(2-Phenoxycarbonylaminoacetyl)-
1,4,7,10-tetraazacyclododecane-1,4,7-tert-butylcarbam-
ate (6). To a stirred solution of CBZ-Gly (0.27 g, 1.3 mmol) in
CH2Cl2 (2 mL) under an N2 atmosphere was added dropwise
neat DCC (0.26 g, 1.3 mmol), followed by slow addition of
1,4,7,10-tetraazacyclododecane-1,4,7-tricarboxylic acid tri-tert-
butyl ester (0.61 g, 1.3 mmol) and DMAP (0.16 g, 1.3 mmol).
The solution was left to stir overnight at room temperature
and then filtered to remove the urea side product. The solvent
was removed under reduced pressure to give a crude material,
which was purified by silica gel column chromatography (5:1
ethyl acetate/petrol) to yield the pure product as a white solid
(0.64 g, 75%): mp 66-67 °C; νmax (neat)/cm-1 2973, 1685
(amide), 1465, 1409, 1363, 1245, 1157, 1106, 1043, 971, 856,
775. Elemental analysis calcd for C33H53N5O9: C, 59.71; H,
8.05; N, 10.55; found C, 59.80; H, 8.24; N, 10.49; HRMS (EI+)
calcd for C33H53N5O9 [M+] m/z ) 663.3843, found 663.3841;
1H NMR (CDCl3) δ 1.31-1.45 (27H, m, CH3), 3.10-3.60 (16H,
m, CH2), 3.95 (2H, d, J ) 4 Hz, CH2), 5.05 (2H, s, CH2), 5.65
(1H, s (broad), NH), 7.20-7.30 (5H, m, Ar-H).
1
1452, 1353, 1257, 1184, 1106, 1056, 941, 800, 767; H NMR
(CDCl3) δ 2.55-2.90 (12H, m, CH2), 3.45-3.48 (2H, m, CH2),
3.52-3.55 (2H, m, CH2), 3.61-3.69 (8H, m, CH2), 3.72 (2H, t,
J ) 5 Hz, CH2), 3.78 (4H, t, J ) 5 Hz, CH2), 3.95 (2H, t, J )
5 Hz, CH2), 3.99-4.03 (4H, m, CH2), 4.07 (2H, t, J ) 5 Hz,
CH2), 4.13 (2H, t, J ) 5 Hz, CH2), 4.30 (2H, d, J ) 4.0 Hz,
CH2), 6.39 (5H, m, Ar-H), 7.05 (1H, t, J ) 8 Hz, Ar-H), 8.02
(1H, d, J ) 8 Hz, Ar-H), 8.78 (1H, s, NH); 13C NMR (CDCl3)
δ 43.1 (CH2), 45.3 (CH2), 46.8 (CH2), 47.8 (CH2), 48.5 (CH2),
48.6 (CH2), 49.0 (CH2), 49.8 (CH2), 67.5 (CH2), 67.8 (CH2), 67.87
(CH2), 68.9 (CH2), 69.4 (CH2), 69.8 (CH2), 69.9 (CH2), 70.1
(CH2), 70.9 (CH2), 71.1 (CH2), 71.3(CH2), 71.4 (CH2), 100.6
(CH), 102.3 (CH), 106.3 (CH), 107.0 (CH), 107.7 (CH), 114.8
(C), 130.1 (CH), 133.9 (CH), 158.9 (C), 160.3 (2 × C), 162.9
(C), 165.2 (C), 170.6 (C).
Preparation of 10-(2-Aminoacetyl)-1,4,7,10-tetraaza-
cyclododecane-1,4,7-tricarboxylic Acid Tri-tert-butyl
Ester (7). To a stirred solution of 6 (0.34 g, 51 mmol) in
absolute EtOH (5 mL) at room temperature, was slowly added
10% Pd/C (0.34 g, 1 equiv), followed by 1,4-cyclohexadiene (0.41
g, 5.1 mmol). The solution was stirred for 2 h and filtered
through a Celite pad, and the solvents were removed under
reduced pressure to yield pure product as a white solid that
required no further purification (0.25 g, 91%): mp 96-97 °C;
HRMS (EI+) calcd for C25H47N5O7 [M+] m/z ) 529.3475, found
529.3473; νmax (neat)/cm-1 2975, 1683 (CdO), 1467, 1409, 1363,
1247, 1159, 1106, 970, 856, 777; 1H NMR (CDCl3) δ 1.39-1.41
(27H, m, CH3), 3.20-3.65 (18H, m, CH2).
Preparation of [ZnL1(OH2)](CF3SO3)2. To a stirred solu-
tion of L1 (0.06 g, 0.08 mmol) in MeOH (1 mL) at room
temperature under an N2 atmosphere was added zinc(II)
triflate (0.034 g, 0.080 mmol). The mixture was stirred for 2 h
and filtered through glass fiber paper. The solution was
concentrated under reduced pressure to yield the product as
a white solid (0.062 g, 78%): mp 76-77 °C; HRMS (FAB) calcd
for [ZnL(CF3SO3)]+ m/z ) 916.2557, found 916.2492; νmax
(neat)/cm-1 3397, 2009, 1957, 1598 (CdO amide), 1452, 1222,
1
1166, 1025, 831, 761; H NMR (MeOD) δ 2.76-3.28 (16H, m,
CH2), 3.68-3.84 (12H, m, CH2), 3.90 (4H, t, J ) 4 Hz, CH2),
3.93 (t, 2H, J ) 4 Hz, CH2), 4.13 (2H, t, J ) 4 Hz,CH2), 4.19
(2H, t, J ) 4 Hz, CH2), 4.25 (2H, t, J ) 4 Hz, CH2), 4.32 (2H,
s, CH2(Gly)), 6.31-6.41 (1H, d, J ) 11 Hz, Ar-H), 6.44 (2H, t,
J ) 5 Hz, Ar-H), 6.56 (1H, t, J ) 8 Hz, Ar-H), 7.86 (1H, dd,
J ) 16 and 8 Hz, Ar-H); 13C NMR (MeOH-d4) δ 45.1 (CH2),
45.3 (CH2), 45.5 (CH2), 46.8 (2 × CH2), 47.8 (3 × CH2), 68.8
(CH2), 69.0 (CH2), 69.4 (CH2), 70.4(CH2), 70.6 (CH2), 70.9 (CH2),
71.2 (CH2), 71.8 (CH2), 72.1 (CH2), 72.2 (2xCH2), 72.3(CH2),
102.1 (CH), 103.6 (CH), 108.0 (CH), 108.4 (CH), 108.5 (CH),
117.5 (C), 120.5 (C), 123.7 (C), 127.1 (C), 131.3 (CH), 134.7
(CH), 161.0 (C), 161.83 (C), 161.85 (C).
Preparation of 10-{2-[(2,5,8,11,18,21,24,27-Octaoxa-
tricyclo[26.3.1.012,17]dotriaconta-1(31),12(17),13,15,28(32),-
29-hexaene-29-carbonyl)-amino]-acetyl}-1,4,7,10-tetraaza-
cyclododecane-1,4,7-tricarboxylic Acid Tri-tert-butyl
Ester (8). To a stirred solution of 4 (60 mg, 0.13 mmol) in
CH2Cl2 (2 mL) under N2 atmosphere was added dropwise DCC
(0.25 g, 0.13 mmol), followed by the addition of 10-(2-ami-
noacetyl)-1,4,7,10-tetraazacyclododecane-1,4,7-tricarboxylic acid
tri-tert-butyl ester 7 (0.064 g, 0.13 mmol) and DMAP (0.014 g,
0.13 mmol). The solution was left to stir overnight at room
temperature and filtered to remove the urea side product. The
solvent was removed under reduced pressure to give a crude
material, which was purified by silica gel column chromatog-
raphy (5:1 ethyl acetetate/petrol) to yield pure product as a
white solid (0.74 g, 61%): HRMS (EI+) calcd for C50H78N5O16
[MH]+ m/z ) 1004.5444, found 1004.5446; νmax (neat)/cm-1
2931, 1685, 1641, 1604, 1465, 1409, 1365, 1249, 1159, 1106,
Preparation of [(2-Hydroxy-acetyl)phenoxycarbony-
lamino]acetic Acid (9). To a solution of aminodiacetic acid
(0.30 g, 2.2 mmol) in 2 M NaOH (10 mL) was added dropwise
benzyl chloroformate (0.35 mL, 2.4 mmol) and a further 2 M
NaOH (5 mL) at 5 °C. The mixture was stirred at room
temperature for 2 h, washed with diethyl ether (2 × 10 mL),
acidified to pH 2 with 1 M HCl, and extracted with ether (3 ×
10 mL). The combined organic layers were dried over MgSO4,
and the solvent was removed under reduced pressure to yield
pure product as a colorless oil (0.42 g, 70%). Elemental analysis
calcd for C12H13N5O6: C, 53.93; H, 4.87; N, 5.24, found C, 53.78;
H, 4.90; N, 5.27; HRMS (CI+) calcd for C12H14N3O6 [MH+] m/z
) 268.0821, found 268.0820; νmax (neat)/cm-1 3570, 2565, 1708,
1
973, 848, 775; H NMR (CDCl3) δ 1.40-1.60 (27H, m, CH3),
3.40-3.65 (16H, m, CH2), 3.70-3.75 (8H, m, CH2), 3.81 (2H,
t, J ) 2 Hz, CH2), 3.87 (4H, t, J ) 4 Hz, CH2), 4.03 (2H, t, J
) 5 Hz, CH2), 4.07 (2H, t, J ) 5 Hz, CH2), 4.10 (2H, t, J ) 4
Hz, CH2), 4.16 (2H, t, J ) 4 Hz, CH2), 4.21 (2H, t, J ) 4 Hz,
CH2), 4.28 (2H, d, J ) 4 Hz, CH2), 6.47-6.58 (5H, m, Ar-H),
7.12 (1H, t, J ) 8 Hz, Ar-H), 8.12 (1H, d, J ) 8 Hz, Ar-H),
8.80 (1H, s (broad), NH); 13C NMR (CDCl3) δ 28.8 (9 × CH3),
49.9-51.5 (m, 8 × CH2), 67.5 (CH2), 67.8 (CH2), 67.9 (CH2),
68.8 (CH2), 69.4 (CH2), 69.8 (CH2), 69.9 (CH2), 70.1 (CH2), 70.9
1
1687, 1474, 1406, 1303, 1194 1081; H NMR (CDCl3) δ 4.04
(s, 2H, CH2), 4.10 (s, 2H, CH2), 5.08 (s, 2H, CH2), 7.18-7.32
(m, 5H, Ar-H); 13C NMR (CDCl3) δ 50.2 (CH2), 50.4 (CH2),
69.0 (CH2), 128.3 (2 × CH), 128.8 (CH), 129.0 (2 × CH), 135.9
(C), 156.5 (C), 174.1 (C), 174.8 (C).
J. Org. Chem, Vol. 70, No. 1, 2005 121

Benniston et al.
Preparation of 10. To a solution of 9 (0.20 g, 0.7 mmol) in
CH2Cl2 (5 mL) was added dropwise DCC (0.32 g, 1.5 mmol),
followed by 5 (0.92 g, 1.9 mmol) in CH2Cl2 (10 mL) and DMAP
(0.19 g, 1.5 mmol) at room temperature under an N2 atmo-
sphere. The reaction solution was stirred for 24 h before being
filtered through glass fiber paper under suction to remove the
urea side product. The solvent was removed under reduced
pressure and purified by silica gel column chromatography (5:
1, ethyl acetate/petrol) to yield pure product as a white solid
(1.85 g, 82%): mp 97-98 °C. Elemental analysis calcd for
C58H97N9O16: C, 59.21; H, 8.31; N, 10.72, found C, 59.27; H,
8.41; N, 10.60; HRMS (FAB+) calcd for C58H98N9O16 [MH]+ m/z
)1175.7053, found 1175.7050; νmax (neat)/cm-1 3054, 2986,
2305, 1686, 1421, 1265, 1160, 896, 746, 705, 585, 429; 1H NMR
(CDCl3) δ 1.30-1.50 (m, 54H, CH3), 3.10-3.60 (m, 32H, CH2),
4.31 (s, 4H, CH2), 5.07 (s, 2H, CH2), 7.20-7.30 (m, 5H, Ar-
H).
Preparation of 11. To solution of 10 (0.34 g, 0.28 mmol)
in MeOH (4 mL) was added slowly Pd/C 10% (0.34 g) under
an N2 atmosphere at room temperature. The vessel was
evacuated, filled with H2, and left to stir overnight. After this
period, the H2 was expelled, the solution filtered through a
Celite pad, and the solvent removed under reduced pressure
to yield pure product as a colorless oil (0.24 g, 79%): mp 92-
93 °C. Elemental analysis calcd for C50H91N9O14‚0.5H2O: C,
57.12; H, 8.82; N, 11.99, found C, 57.15; H, 8.75; N, 11.84; νmax
(neat)/cm-1 3054, 2985, 1690, 1466, 1420, 1367, 1265, 1162,
896, 748, 705, 584, 435; 1H NMR (CDCl3) δ 1.41 (54H, s, CH3),
3.10-4.00 (37H, m, CH2); 13C NMR (CDCl3) δ 28.45 (6 × CH3),
28.48 (6 × CH3), 28.6 (6 × CH3), 49.4-52.0 (broad multiplet,
34 × CH2), 80.1 (2 × C), 80.2 (2 × C), 80.3 (2 × C), 155-158
(8 × C).
for C45H73N9O11: C, 59.00; H, 8.03; N, 13.76, found C, 58.79;
H, 8.25; N, 13.67; HRMS (FAB+), calcd for C45H74N9O11 [MH+]
m/z )916.5463, found 916.5457; νmax (neat)/cm-1 3741, 2927,
1974, 1646, 1542, 1461, 1361, 114, 817; 1H NMR (CDCl3) δ
2.40-3.54 (38H, m, NHs and CH2), 3.58 (4H, s, CH2), 3.62 (4H,
s, CH2), 3.71 (4H, t, J ) 5 Hz, CH2), 3.74 (4H, t, J ) 5 Hz,
CH2), 3.99 (4H, t, J ) 5 Hz, CH2), 4.02 (4H, t, J ) 5 Hz, CH2),
4.22 (2H, d, J ) 14 Hz, CH2), 4.40 (1H, s (broad), CH2), 4.46
(1H, s (broad), CH2), 6.35-6.50 (5H, m, Ar-H), 7.04 (1H, t, J
) 8 Hz, Ar-H), 7.12 (1H, d, J ) 8 Hz, Ar-H); 13C NMR
(CDCl3) δ 45.2 (CH2), 45.4 (CH2), 45.8 (CH2), 46.4 (CH2), 47.1
(CH2), 47.2 (CH2), 47.5 (CH2), 47.7 (CH2), 48.1 (2 × CH2), 48.2
(CH2), 48.3 (CH2), 48.7 (CH2), 48.7 (CH2), 49.0 (CH2), 49.4
(CH2), 49.8 (CH2), 51.4 (2 × CH2), 67.3 (CH2), 67.5 (CH2), 67.59
(CH2), 68.7 (CH2), 69.3 (CH2), 69.5 (CH2), 69.7 (CH2), 70.5
(CH2), 70.8 (CH2), 70.91 (CH2), 70.92 (CH2), 101.2 (CH), 102.3
(CH), 106.6 (CH), 106.9 (CH), 107.21 (CH), 118.4 (C), 129.8
(CH), 129.88 (CH), 155.9 (C), 160.01 (C), 160.02 (C), 160.9 (C),
169.9 (C), 170.2 (C), 170.25 (C).
Preparation of [Zn2L2(OH2)2](CF3SO3)4. To a stirred
solution of L2 (0.012 g, 0.011 mmol) in anhydrous MeOH (0.5
mL) under an Ar atmosphere was added zinc triflate (0.010 g,
0.024 mmol). The reaction was stirred for 4 h at room
temperature before the excess zinc triflate was filtered off
through glass fiber paper and the solvent removed to yield pure
product as a white solid (0.020 g, 91% yield): mp 82-83 °C.
Elemental analysis calcd for C49H73F12N9O23S4Zn2: C, 35.82;
H, 4.48; N, 7.67, found C, 36.01; H, 4.59; N, 7.90; HRMS
(FAB+) calcd for C49H74N9O11Zn2 [M+] m/z ) 1045.3981, found
1045.3976; νmax (neat)/cm-1 3752, 3397, 2927, 1977, 1716, 1691,
1658, 1495, 1365, 121, 830, 764.
Preparation of [1,4,7]Triazecane-1,7-dicarboxylic Acid
Di-tert-butyl Ester (13). To a solution of tacn (0.16 g, 1.3
mmol) and TEA (0.23 mL, 1.8 mmol) in CHCl3 (10 mL) was
added (Boc)2 (0.50 g, 2.3 mmol) in CHCl3 (5 mL) via a syringe
pump over a 4 h period and left to stir overnight at room
temperature under an N2 atmosphere. The solvent was
removed under reduced pressure to yield a white solid, which
was purified by silica gel chromatography (10:1, ethyl acetate/
methanol) to give pure product as a colorless oil (0.27 g, 62%):
HRMS (FAB+) calcd for C16H31N3O4 [M+] m/z ) 329.2315,
found 329.2315; 1H NMR (CDCl3) δ 1.41 (18H, s, CH3), 2.85-
2.87 (4H, m, CH2), 3.15-3.22 (4H, m, CH2) 3.35-3.42 (4H, m,
CH2); 13C NMR (CDCl3) (rotamers) δ 28.9 (6 × CH3), 47.7
(CH2), 48.1 (CH2), 48.5 (CH2), 48.6 (CH2), 49.9 (CH2), 50.2
(CH2), 50.8 (2 × CH2), 52.0 (CH2), 52.7 (CH2), 52.8 (CH2), 53.4
(CH2), 80.0 (C), 80.1 (C), 156.1 (C), 156.4 (C).
Preparation of 12. To a solution of 4 (0.060 g, 0.13 mmol)
in CH2Cl2 (2 mL) was added dropwise DCC (0.30 g, 1.3 mmol),
followed by the addition of 11 (0.14 g, 0.13 mmol) in CH2Cl2
(3 mL) and DMAP (0.16 g, 0.13 mmol) at room temperature
under an N2 atmosphere. The reaction solution was stirred
for 24 h before being filtered through glass fiber paper under
suction to remove the urea side product. The reaction solution
was then washed with 1 M NaOH (20 mL) and brine (50 mL)
before the solvent was removed under reduced pressure and
purified by silica gel column chromatography (10:1, ethyl
acetate/methanol) to yield pure product as a white solid (0.090
g, 45%): mp 72-73 °C; HRMS (FAB) calcd for C75H122N9O23
[MH+] m/z )1516.8643, found 1516.8654; νmax (neat)/cm-1
2984, 1751, 1465, 1447, 1374, 1240, 1097, 1047, 938, 847, 634,
1
608, 443, 434, 410, 405; H NMR (CDCl3) δ 1.35-1.50 (54H,
m, CH2), 2.95-3.55 (32H, m, CH2), 3.58-3.65 (8H, m, CH2),
3.71-3.81 (8H, m, CH2), 3.98-4.07 (8H, m, CH2), 4.19 (2H, s,
CH2), 4.51 (2H, s, CH2), 6.39-6.44 (3H, m, Ar-H), 6.45 (1H,
d, J ) 2 Hz, Ar-H), 6.48 (1H, t, J ) 2 Hz, Ar-H), 7.04 (1H,
t, J ) 8 Hz, Ar-H), 7.11 (1H, d, J ) 8 Hz, Ar-H); 13C NMR
(CDCl3) δ 28.3 (6 × CH3), 28.4 (6 × CH3), 28.5 (6 × CH3), 48.5-
50.11 (16 × CH2), 51.2 (CH2), 53.4 (CH2), 60.3 (CH2), 67.3
(CH2), 67.5 (CH2), 67. 6 (CH2), 68.8 (CH2), 69.2 (CH2), 69.5
(CH2), 69.6 (CH2), 69.7 (CH2), 70.73 (CH2), 70.76 (CH2), 70.9
(CH2), 80.2 (2 × C), 80.3 (2 × C), 80.4 (2 × C), 101.6 (CH),
102.1 (2 × CH), 107.0 (CH), 107.2 (2 × CH), 118.47 (C), 129.7
(CH), 155.4 (C), 155.7 (C), 156.3 (2 × C), 156.7 (C), 157.1 (C),
159.9 (2 × C), 160.0 (2 × C), 161.0 (2 × C), 169.7 (C).
Preparation of 4-(2-Benzyloxycarbonylaminoacetyl)-
[1,4,7]triazecane-1,7-dicarboxylic Acid Di-tert-butyl
Ester (14). To a solution of CBZ-GLY (0.13 g, 0.63 mmol) in
CH2Cl2 (3 mL) were added sequentially DCC (0.14 g, 0.69
mmol), 13 (0.21 g, 0.63 mmol) in CH2Cl2 (3 mL), and DMAP
(0.076 g, 0.63 mmol) under an N2 atmosphere at room
temperature and stirred overnight. The reaction solution was
filtered to remove excess urea and solvent removed under
reduced pressure before purification by silica gel chromatog-
raphy (5:1, ethyl acetate/petrol) to give pure product as a white
solid (0.26 g, 78%): mp 85-87 °C; HRMS (EI+) calcd for
C26H40N4O7 [M+] m/z ) 520.2896, found 520.2897; νmax (neat)/
cm-1 3050, 2360, 2341, 1739, 1364, 1265, 1156, 1109, 901, 759;
1H NMR (CDCl3) δ 1.30-1.50 (18H, m, CH3), 3.10-3.60 (12H,
m, CH2), 3.95 (2H, s, CH2), 5.04 (2H, s, CH2), 5.57-5.73 (1H,
m, NH), 7.25 (5H, m, Ar-H); 13C NMR (CDCl3) (rotamers) δ
28.8 (6 × CH3), 43.1 (CH2), 43.3 (CH2), 47.3 (CH2), 47.6 (CH2),
48.7 (CH2), 49.0 (CH2), 49.4 (CH2), 49.8 (CH2), 50.1 (CH2), 50.4
(CH2), 50.7 (CH2), 52.2 (CH2), 52.9(CH2), 67.1 (CH2), 80.5 (C),
80.7 (C), 80.8 (C), 128.3 (2 × CH), 128.4 (2 × CH), 128.8 (CH),
155.7 (C), 156.1 (C), 156.4 (2 × C).
Preparation of 2,5,8,11,17,20,23,26-Octaoxatricyclo-
[25.3.1.112,16]dotriaconta-1(30),12,14,16(32),27(31),28-
hexaene-13-carboxylic Acid ({Bis-[2-oxo-2-(1,4,7,10-tet-
raazacyclododec-1-yl)-ethyl]carbamoyl}methyl)amide
(L2). To a stirred solution of 12 (0.059 g, 0.038 mmol) in CH2-
Cl2 (2 mL) under N2 at room temperature was slowly added
TFA (1 mL), and the solution stirred for 4 h. The reaction was
quenched with 3 M NaOH (10 mL), and the organics were
extracted with CH2Cl2 (3 × 10 mL) and further washed with
brine (30 mL) before being dried over Na2SO4. The solvent was
removed under reduced pressure to yield pure product as white
solid (0.025 g, 70%): mp 83-84 °C. Elemental analysis calcd
Preparation of 4-(2-Amino-acetyl)-[1,4,7]triazecane-
1,7-dicarboxylic Acid Di-tert-butyl Ester (15). To solution
of 14 (0.25 g, 0.49 mmol) in MeOH (3 mL) was added slowly
Pd/C 10% (0.20 g) under an N2 atmosphere. The vessel was
122 J. Org. Chem., Vol. 70, No. 1, 2005

Properties of Cyclophane-Azamacrocyclic Receptors
then evacuated and filled with H2 and left to stir overnight.
After this period, the H2 was expelled, the solution filtered
through a Celite pad, and the solvent removed under reduced
pressure to yield pure product as a colorless oil (0.14 g, 73%):
mp 93-94 °C; HRMS (FAB+) calcd for C18H34N4O5 [M+] m/z )
386.2529, found 386.2534; νmax (neat)/cm-1 3366, 2924, 2855,
2363, 2340, 1693, 1515, 1461, 1409, 1364, 1320, 1246, 1032,
extracted with CH2Cl2 (3 × 10 mL) and further washed with
brine (30 mL) before being dried over NaSO4. The solvent was
removed under reduced pressure to yield pure product as white
solid (0.033 g, 75%): mp 76-77 °C; HRMS (FAB) calcd for
C33H49N4O10 [MH+] m/z ) 661.3449, found 661.3455; νmax
(neat)/cm-1 3741, 2927, 1708, 1646, 1538, 1457, 1365, 1226,
1
1087, 821; H NMR (CDCl3) δ 2.10 (2H, s, NH), 2.65 (4H, m,
1
987, 821; H NMR (CDCl3) δ 1.30-1.50 (18H, m, CH3), 1.59
CH2), 3.01 (4H, m, CH2), 3.36 (2H, t, J ) 5 Hz, CH2), 3.46 (2H,
t, J ) 5 Hz, CH2), 3.62-3.69 (8H, m, CH2), 3.72 (2H, t, J ) 5
Hz, CH2), 3.78 (4H, t, J ) 5 Hz, CH2), 3.96-4.06 (6H, m, CH2),
4.07 (2H, dd, J ) 8 and 4 Hz, CH2), 4.14 (2H, t, J ) 4 Hz,
CH2), 4.22 (2H, d, J ) 4 Hz, CH2) 6.39-6.50 (5H, m, Ar-H),
7.04 (1H, t, J ) 8 Hz, Ar-H), 8.05 (1H, d, J ) 8 Hz, Ar-H),
8.84 (1H, s (broad), NH); 13C NMR (CDCl3) δ 42.7 (CH2), 47.1
(CH2), 48.0 (CH2), 49.6 (CH2), 49.7 (CH2), 53.0 (CH2), 53.6
(CH2), 67.2 (CH2), 67.5 (CH2), 67.57 (CH2), 68.6 (CH2), 69.1
(CH2), 69.54 (CH2), 69.59 (CH2), 69.7 (CH2), 70.6 (CH2),70.8
(CH2), 71.0 (CH2), 71.1 (CH2), 100.3 (CH), 102.0 (CH), 106.0
(CH), 106.7 (CH), 107.3 (CH), 114.5 (C), 129.7 (CH), 133.5
(CH), 158.7 (C), 160.0 (2xC), 162.6 (C), 164.9 (C), 169.2 (C).
Preparation of [Cu(L3)(OH2)2](CF3SO3)2. To a solution
of Cu(CF3SO3)2 (0.03 g, 0.8 mmol) in MeOH (1.0 mL) was added
L3 (0.05 g, 0.8 mmol) in MeOH (0.5 mL) at room temperature
under an N2 atmosphere. The reaction solution was stirred
for 1 h before an insoluble blue solid precipitated out of
solution. The solid was filtered off and washed with MeOH
before being slowly recrystallized from nitromethane over 24
h to form pure product as a blue solid (0.061 g, 92%): mp 110-
111 °C. Elemental analysis calcd for C35H48N4O16F6S2Cu: C,
41.11; H, 4.73 N, 5.48, found C, 40.95; H, 4.81; N, 5.41; νmax
(neat)/cm-1 3569 (OH stretch), 3476 (N-H stretch), 2927, 1654,
1604, 1492, 1458, 1260, 1162, 1124, 1031, 639, 575; HRMS
(FAB+) calcd for C33H48N4O10Cu [M+] m/z ) 723.2666, found
723.2621.
(2H, s, NH2), 3.10-3.60 (14H, m, CH2); 13C NMR, because of
different rotamers, it was not possible to interpret the spec-
trum.
Preparationof4-{2-[(2,5,8,11,17,20,23,26-Octaoxatricyclo-
[25.3.1.112,16]dotriaconta-1(30),12,14,16(32),27(31),28-
hexaene-13-carbonyl)amino]acetyl}-[1,4,7]triazecane-
1,7-dicarboxylic Acid Di-tert-butyl Ester (16). To a solution
of 4 (0.070 g, 0.15 mmol) in CH2Cl2 (2 mL) was added dropwise
DCC (0.030 g, 0.15 mmol), followed by the addition of 15 (0.060
g, 0.15 mmol) in CH2Cl2 (2 mL) and DMAP (0.02 g, 0.3 mmol)
at room temperature under an N2 atmosphere. The reaction
solution was stirred for 24 h before being filtered through glass
fiber paper under suction to remove the urea side product. The
reaction solution was then washed with 1 M NaOH (20 mL)
and brine (50 mL) before the solvent was removed under
reduced pressure and purified by silica gel column chroma-
tography (10:1 ethyl acetate/methanol) to yield pure product
16 as a colorless oil (0.080 g, 61%): HRMS (FAB+) calcd for
C43H64N4O14Na [M + Na] m/z )883.4333, found 883.4317; νmax
(neat)/cm-1 3753, 2935, 1711, 1651, 1535, 1461, 1365, 1226,
1
1087, 821, 653, 543; H NMR (CDCl3) δ 1.30-1.50 (18H, m,
CH3), 3.10-3.57 (12H, m, CH2), 3.61 (2H, d, J ) 6 Hz, CH2),
3.66 (6H, s (broad), CH2), 3.72 (2H, t, J ) 4 Hz, CH2), 3.77
(4H, dd, J ) 4 and 2 Hz, CH2), 3.96-4.04 (6H, m, CH2), 4.07
(2H, t, J ) 5 Hz, CH2), 4.13 (2H, t, J ) 5 Hz, CH2), 4.19 (2H,
s (broad), CH2), 6.39-6.50 (5H, m, Ar-H), 7.04 (1H,t, J ) 8
Hz, Ar-H), 8.02 (1H, t, J ) 8 Hz, Ar-H), 8.68-8.82 (1H, m,
NH); 13C NMR (CDCl3) δ 28.4 (6 × CH3), 42.4-51.1 (12 × CH2
isomers of tacn), 67.2 (CH2), 67.5 (CH2), 68.5 (CH2), 68.6 (CH2),
69.1 (CH2), 69.52 (CH2), 69.58 (CH2), 69.6 (CH2), 69.7 (CH2),
70.4 (CH2), 70.6 (CH2), 70.8 (CH2), 71.0 (CH2), 80.0 (C), 80.3
(C), 100.3 (CH), 102.0 (CH), 106.0 (CH), 106.8 (CH), 107.3
(CH), 129.7 (2 × CH), 133.5 (CH), 155.5 (C), 155.7 (C), 158.5
(C), 160.0 (2 × C), 162.5 (C), 164.8 (C), 169.4 (C).
Acknowledgment. This work was supported by the
Universities of Glasgow and Newcastle and the EPSRC
(P.G.). We would like to thank Dr. S. K. Armstrong for
advice, Prof. A. Cooper and Margaret Nutley for the ITC
measurements, and Dr. A. Pitt and Dr. C. Evans for ES-
MS experiments and analysis.
Preparation of 2,5,8,11,17,20,23,26-Octaoxatricyclo-
[25.3.1.112,16]dotriaconta-1(30),12,14,16(32),27(31),28-
hexaene-13-carboxylic Acid (2-Oxo-2-[1,4,7]triazecan-4-
yl-ethyl)amide (L3). To a solution of 16 (0.059 g, 0.066 mmol)
in CH2Cl2 (2 mL) under N2 at room temperature was slowly
added TFA (1 mL) and the solution stirred for 4 h. The reaction
was quenched with 3 M NaOH (10 mL), and the organics were
Supporting Information Available: General experimen-
tal methods, 1H NMR and 13C NMR spectra of all new
compounds, as well as isothermal calorimetry traces, UV-vis
titrations, and ES-MS results. This material is available free
of charge via the Internet at http://pubs.acs.org.
JO048621O
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