Synthesis and membrane activity of a bis(metacyclophane)bolaamphiphile

Article abstract of DOI:10.1021/jo0160930

The synthesis of macrocyclic tetraesters from 5-substituted isophthalic acids and 1,8-octane diol gave macrocylic metacyclophanes with the axially symmetric positions differentially protected. Dimer bis(metacyclophane)bolaamphiphiles proved to be extremely insoluble, but one derivative was shown to have significant membrane activity. Very high continuous conductance and the formation of discrete single-ion channels were both observed, depending on how the compound was incorporated into the bilayer membrane.

Full text of DOI:10.1021/jo0160930

1548
J . Org. Chem. 2002, 67, 1548-1553
Syn th esis a n d Mem br a n e Activity of a
Bis(m eta cyclop h a n e)bola a m p h ip h ile
Lynn M. Cameron, Thomas M. Fyles,* and Chi-wei Hu
Department of Chemistry, University of Victoria, Victoria, British Columbia, Canada V8W 3P6
tmf@uvic.ca
Received September 5, 2001
The synthesis of macrocyclic tetraesters from 5-substituted isophthalic acids and 1,8-octane diol
gave macrocylic metacyclophanes with the axially symmetric positions differentially protected.
Dimer bis(metacyclophane)bolaamphiphiles proved to be extremely insoluble, but one derivative
was shown to have significant membrane activity. Very high continuous conductance and the
formation of discrete single-ion channels were both observed, depending on how the compound
was incorporated into the bilayer membrane.
In tr od u ction
The synthesis of new channel-forming compounds
typically starts from the selection of molecular building
blocks bearing suitable functionality that are assembled
using a few well-optimized reactions.17 The main focus
in this property-directed synthesis18 is on the initial
choice of building blocks, as these define the structural
variations possible. Synthetic efficiency is often a second-
ary consideration. The reactions need to work well
enough to produce the material, but a few micromoles of
product is sufficient to assay the function of a putative
channel-forming compound. Nonetheless, wasteful and
inelegant syntheses eventually inhibit the optimization
of the desired channel function. An example is given by
our own work with bis(macrocyclic)bolaamphiphile pore-
formers. The parent compound 1 was initially prepared
as a structural control for a series of crown ether-based
unimolecular channels.19 The modest activity found for
1 was considerably enhanced through iterative optimiza-
tion to give compounds such as 2a b that form well-
defined ion-selective channels.20 The working hypothesis
is that channels formed by 2a b are membrane-spanning
aggregates of a few molecules. This reasoning leads to
3, which is capable of forming rectified ion channels.21
At each stage of this evolution of structure, the activity
and functional sophistication of the compounds increased.
However, it is not their functional strengths but their
synthetic weaknesses that are the issue here: despite
its highly desirable properties as a voltage-gated channel,
3 will remain a laboratory curiosity as a result of its
exceedingly tedious synthesis.
Synthetic compounds that insert into bilayer mem-
branes and open channels for the transport of ionic
species provide insights into the functional characteristics
of natural channels and may lead to new technologies in
sensors, separations, and signal propagation. Reports
over the past decade1-11 describe a wide range of com-
pounds that are functionally similar in their ability to
form ion channels, yet they are structurally disparate.
Despite the broad range of active structural types, many
of the classes of channel-forming compounds reported
show clear indications that channel-formation within the
class is closely controlled by structure.12,13 The apparent
dichotomy of structural disparity between classes of
compounds and structural specificity within those classes
is rationalized by an emerging view that mem-
brane-spanning chains or pools of water form the
channels.14-16 In this view, each class of compound
provides a general framework for water stabilization that
can be further optimized through structural variations.
* Corresponding author. Tel: 250 721 7184. Fax: 250 721 7184.
(1) Fyles, T. M.; van Straaten-Nijenhuis, W. F. In Comprehensive
Supramolecular Chemistry; Reinhoudt, D. N., Ed.; Elsevier Science:
New York, 1996; Vol. 10, pp 53-77.
(2) Kobuke, Y. In Advances in Supramolecular Chemistry; Gokel,
G. W., Ed.; J AI Press: Greenwich, CT, 1997; Vol. 4, pp 163-210.
(3) Gokel, G. W. Chem. Commun. 2000, 1-9.
(4) Merritt, M.; Lanier, M.; Deng, G.; Regen, S. L. J . Am. Chem.
Soc. 1998, 120, 8494-8501.
(5) Clark, T. D.; Buehler, L. K.; Ghadiri, M. R. J . Am. Chem. Soc.
1998, 120, 651-656.
(6) Otto, S.; Osifchin, M.; Regen, S. L. J . Am. Chem. Soc. 1999, 121,
7276-7277.
(7) Otto, S.; Osifchen, M.; Regen, S. L. J . Am. Chem. Soc. 1999, 121,
10440-10441.
(8) Tedesco, M. M.; Ghebremariam, B.; Sakai, N.; Matile, S. Angew.
Chem., Int. Ed. 1999, 38, 540-543.
(9) Sakai, N.; Majumdar, N.; Matile, S. J . Am. Chem. Soc. 1999,
121, 4294-4295.
(10) Baumeister, B.; Sakai, N.; Matile, S. Angew. Chem., Int. Ed.
2000, 39, 1955-1958.
(11) Bandyopadhyay, P.; J anout, V.; Zhang, L.; Sawko, J . A.; Regen,
S. L. J . Am. Chem. Soc. 2000, 122, 12888-12889.
(12) Fyles, T. M.; J ames, T. D.; Kaye, K. C. J . Am. Chem. Soc. 1993,
115, 12315-12321.
(13) Gokel, G. W.; Murillo, O. Acc. Chem. Res. 1996, 29, 425-432.
(14) Fyles, T. M. Curr. Opin. Chem. Biol. 1997, 1, 497-505.
(15) Yoshino, N.; Satake, A.; Kobuke, Y. Angew. Chem., Int. Ed.
2001, 40, 457-459.
(16) Gokel, G. W.; Ferdani, R.; Liu, J .; Pajewski, R.; Shabany, H.;
Uetrecht, P. Chem.sEur. J . 2001, 7, 33-39.
The synthesis of 3 begins with maleic anhydride, 1,8-
octanediol, and triethylene glycol to give, in 6% yield, a
10.1021/jo0160930 CCC: $22.00 © 2002 American Chemical Society
Published on Web 02/05/2002

Bis(metacyclophane)bolaamphiphile
J . Org. Chem., Vol. 67, No. 5, 2002 1549
Sch em e 1: Syn th esis of Tetr a ester m eta cyclop h a n esa
a
Reagents: (i) Et3N, THF, 0 °C, 2 h, 80%; (ii) (1) H2/PtO2, EtOH, 1 equiv HCl, 25 psi, 2 h; (2) Boc2O, THF, rt, 16 h, 88% (iii) HCl,
MeOH, rt, 1 h, 70%; (iv) THF, rt, 16 h, 10-16%; (v) TFA, CH2Cl2, rt, 16 h, 93%; (iv) Et3N, THF, rt, 50-90%.
tetraester diene macrocycle with equivalent alkenes.
Monofunctionalization with mercaptopropanol, coupling
in a second monofunctionalization process, followed by
addition of the final headgroup completes the synthesis
in an abysmal yield after several months’ work.20 The
weaknesses of this synthetic plan are apparent: both the
macrocyclization yield and the two monofunctionalization
yields are low, and the regio- and stereoselectivity of the
thiol addition reactions are completely random, leading
to mixtures of isomers. These mixtures cannot be sepa-
rated but behave as single compounds.17 Some of the
intermediates are contaminated as a competing retro-
Michael reaction scrambles the thioacetate headgroups,
leading to extensive chromatography at all stages.17,19,20
Many of these synthetic problems might be resolved
through a redesign of the macrocyclic subunit. A simple
alkyl strand is unlikely to be sufficient, as long-chain
bolaamphiphiles are effective membrane-disrupting
agents.22 The macrocycle is expected to provide some
rigidity and to provide a framework for functional-group
substitutions that would influence channel properties.23
If macrocycles are required, then the focus must be on
high-yielding macrocyclization methods. To avoid dia-
steromeric mixtures, achiral or chirally pure macrocycles
are required. To avoid regioisomers, axial symmetry will
be required. To avoid the poor yields of monofunctional-
ization reactions, the “ends” of the macrocycle must be
different or differentially protected. All these require-
ments lead to metacyclophanes as candidates. Tetra-
esters such as 4 would be available from high-dilution
macrocyclization of a suitable diol with a diacid chloride
to ensure end-to-end discrimination. Starting from com-
mercially available 5-nitroisophthalic acid would give the
X and Y groups via nitro reduction and amine protection.
4 could be converted to head-to-head (5) or head-to-tail
(6) bis(macrocycles) through judicious choice of reaction
sequence. This contribution reports synthetic explora-
tions in this area and the eventual production of a new
active channel-forming compound of type 5.
Resu lts a n d Discu ssion
Syn th eses of Tetr a ester Cyclop h a n es. The synthe-
sis proceeds as in Scheme 1, using the monotetrahydro-
pyranyl derivative of 1,8-octanediol (8) coupled with the
acid chloride of 5-nitroisophthalic acid (7) to give 9 in
good yield. Reduction of the nitro group by hydrogenation
over Adams’ catalyst under neutral conditions gave an
amine that was directly protected as the Boc derivative
10 in 88% yield. Selective removal of the Thp group gave
diol 11. The macrocyclization of 11 and 7 was achieved
under high-dilution conditions in THF with excess Et3N
(final concentration < 3 × 10-4 M). The isolated yield of
macrocycle 12 was only 16%, which appears to be
fundamental, as the same coupling at a 10-fold higher
final concentration still gave a 10% yield of 12. Although
7 is a reactive acid chloride, 11 is likely to be relatively
unreactive, hence a poor partner for high-dilution mac-
rocyclization. Another feature of 12 that would prove
problematic was its restricted solubility in many solvents.
Head-to-head coupling to give bis(cyclophanes) of type
5 is most easily achieved from an amine with a bis(acid
chloride). Thus, 12 was deprotected with TFA in CH2Cl2
(17) Cross, G. G.; Fyles, T. M.; J ames, T. D.; Zojaji, M. Synlett 1993,
449-460.
(18) Gokel, G. W.; Medina, J . C.; Li, C. Synlett 1991, 667-683.
(19) Fyles, T. M.; Kaye, K. C.; Pryhitka, A.; Tweddel, J .; Zojaji, M.
Supramol. Chem. 1994, 3, 197-209.
(20) Fyles, T. M.; Loock, D.; van Straaten-Nijenhuis, W. F.; Zhou,
X. J . Org. Chem. 1996, 61, 8866-8874.
(21) Fyles, T. M.; Loock, D.; Zhou, X. J . Am. Chem. Soc. 1998, 120,
2997-3003.
(22) J ayasuriya, N.; Bosak, S.; Regen, S. L. J . Am. Chem. Soc. 1990,
112, 5844-5850.
(23) Fyles, T. M.; Hu, C.; Knoy, R. Org. Lett. 2001, 3, 1335-1337.

1550 J . Org. Chem., Vol. 67, No. 5, 2002
Sch em e 2: Syn th esis of Bis(m eta cyclop h a n e) 19a
Cameron et al.
a
Reagents: (i) H2/PtO2, EtOH, 1 equiv HCl, 25 psi, 2 h, 45%; (ii) Et3N, THF, 0 °C, 2 h, 92%; (iii) TFA, CH2Cl2, rt, 16 h, 77%.
to give the nitro amine 13 and subsequently coupled with
the diacid chlorides of glutaric, pimelic, and terephthalic
acids. The glutaric acid system produced exclusively the
imide 16, indicating that cyclization competes efficiently
with intermolecular dimer formation. The rigid tereph-
thalic acid did give the expected diamide 15 as a very
insoluble powder; the mass spectrum and elemental
analysis were consistent with the structure, and the
NMR spectrum was eventually obtained in DMSO at 150
°C. The product from pimelic acid 14 was similarly
difficult to handle. Both 14 and 15 are well-characterized,
but their very poor solubility effectively precludes further
reactions.
Mem br a n e Activity of 19. The transport activity of
19 was initially assessed in vesicle bilayer experiments
of two types. The first method uses vesicle-entrapped
carboxyfluorescein at a high concentration: any mem-
brane disruption leading to large pores will release
entrapped carboxyfluorescein and will result in an en-
hancement of fluorescence.22,23 Vesicles were prepared in
0.1 M carboxyfluorescein sodium salt using a mixed-lipid
system of phosphatidyl choline (PC), phosphatidic acid
(PA), and cholesterol (Cho) (8:1:1 mole ratio). By this
assay, 19 is a remarkably ineffective membrane-disrupt-
ing agent, with 50% release achieved only at millimolar
concentration. Thus, large defects are formed only under
conditions where the concentration of 19 exceeds the lipid
concentration. The second assay method uses the titra-
tion of protons released from a vesicle-entrapped buffer
(pH 6.6) into an unbuffered electrolyte held at pH 7.6
using a pH-stat titrimeter. Vesicles were prepared from
PC/PA/Cho (8:1:1) by sonication and sized by extrusion
through a 0.4 µm Nucleopore filter. This method has been
used with other active transporters to determine trans-
port rates, cation selectivities, and the apparent kinetic
order of the transport process.19,20 Addition of 19 as a
DMSO solution always provokes an immediate consump-
tion of basic titrant to maintain the set pH, which is
proportional to the amount of 19 added. The release of
protons occurs within 5 s of the addition of compound,
but there is no further release during the following
500-1000 s. Addition of a detergent (Triton) results in
the release of the expected amount of entrapped buf-
fer. As little as a nanomole of 19 (less than 0.01 mol %
with respect to the total lipid concentration) will provoke
the initial response. The pH-stat technique measures the
rate that new channels are initiated. Because 19 is
virtually insoluble in water, injection of a DMSO solution
probably results in the precipitation of the compound
within the bulk solution and onto the surface of some of
the vesicles. Presumably, some fraction of the vesicles
will not have sufficient compound to form channels, so
they are not detected until after the addition of Triton.
The very low solubility of 19 would inhibit migration
between vesicles, so no new channels would be initiated
after the initial burst. Vesicle techniques, although
suggestive, do not provide clear evidence of membrane
activity.
An alternative pathway to the same target was com-
pleted as shown in Scheme 2. Reduction of the nitro
group of 12 gave the monoprotected diamine 17. This
amine coupled with terephthaloyl chloride to produce the
insoluble dimer 18. Although only sparingly soluble in
hot DMSO and apparently insoluble in methylene chlo-
ride, the Boc protecting groups could be removed by
treatment with TFA in methylene chloride. This solid-
to-solid transformation produced a material assigned as
19 on the basis of the expected molecular ion in the mass
spectrum and on the 1H NMR spectrum that showed only
the expected resonances for the deprotected diamine. No
1
tert-butyl signal was found in the H NMR spectrum of
the product. Like the other bis(macrocyclic) products, this
material proved to be difficult to handle because of its
poor solubility in anything but hot DMSO. A satisfactory
13C NMR spectrum could not be obtained because of poor
solubility, and the elemental analysis suggested that a
small proportion of trifluoroacetic acid remained in the
solid product (∼0.25 equiv). Given that 18 was well-char-
acterized and that the deprotection is apparently com-
plete and preserves the core of the molecule the isolated
material is assigned as 19 in a partly protonated form.
The synthesis of bis(metacyclophane) 19 of type 5 from
1,8-octanediol is formally complete in an overall yield of
ca. 2% over eight steps. This synthesis is closely similar
to that of 1, a compound having the same centrosymme-
try as cyclophanes of type 5, which are produced in ∼2%
yield from the same starting diol. Although the interme-
diate 12 could give end-discriminated cyclophanes of type
6 more easily than was possible in the series that
produced 2a b and 3, the poor macrocyclization yield and
the poor solubility of the bis(cyclophanes) promise to
plague any further exploration of this avenue.
The voltage-clamp technique21,23 indicates that 19
shows significant activity in planar bilayers, but the type

Bis(metacyclophane)bolaamphiphile
J . Org. Chem., Vol. 67, No. 5, 2002 1551
F igu r e 2. Single-channel conductance records of 19 at an
applied potential of (150 mV (PC/PA/Ch 8:1:1). The compound
was incorporated as described in the text.
higher bulk concentration than that of the highest levels
explored with 19.
Discrete single channels can also be observed for 19.
Incorporation to produce single-channel events requires
a mechanical transfer of material to a preformed bilayer
held under a positive transmembrane potential. A 1-5
µL aliquot of a millimolar solution of 19 in hot DMSO
(1-5 nmol) was added to a clean fine-camel-hair brush.
The brush was then used to break and reform a bilayer.
This method was successful in about half the attempts;
failure resulted in no membrane activity rather than in
the general increase in conductance illustrated in Figure
1. Examples of the type of single-channel openings
observed are given in Figure 2: a main-step conductance
change of about 2 pA dominates the population of
openings at both potentials. At positive potentials, there
is a smaller opening as well, and occasional double
openings are seen at both potentials. The specific con-
ductance of the major opening is 13.7 ( 1.7 pS for the
experiment that included Figure 2 (1 M KCl electrolyte;
pH 4.7). Independent experiments on different days gave
the same specific conductance within experimental error.
Single channels were observed only at pH 4.7 in mem-
branes from mixed lipids (PC/PA/Ch).
F igu r e 1. Persistent bilayer membrane conductance induced
by 19 at various applied potentials (diphytanoyl phosphatid-
ylcholine, 1 M KCl, pH 4.7). The individual records are
consecutive 5 s snapshots separated by 15 s intervals in which
the potential was adjusted and stabilized. Bottom: a current-
voltage relationship constructed from the mean currents of the
data shown ((40 and (20 mV not shown).
of activity observed depends on the way the compound
is introduced to the bilayer. Direct injection of DMSO
solutions into the experimental system in the presence
of a preformed bilayer results in visible precipitation of
material in the electrolyte and no trace of membrane
activity. However, injection of the DMSO solution such
that the emerging drop contacts a preformed bilayer
results in very significant membrane conductivity of the
type shown in Figure 1. Incorporation by this method is
haphazard at best, and usually 3-5 cycles of injection,
sometimes resulting in membrane breakage, are required
to generate activity. Incorporation by this technique has
been achieved in diphytanoyl phosphatidylcholine mem-
branes and in a PC/PA/Cho (8:1:1) mixed-lipid mem-
brane. Incorporation by this method is apparently more
efficient at slightly acidic pH (4.7) than at neutral pH.
As seen in Figure 1, discrete channel openings are not
observed, but the current varies irregularly within a
range of 1-2 pA up to 50 pA above the baseline. Although
the general increase in bilayer conductance persists for
hours, the current-voltage characteristics vary over a
period of minutes. The current-voltage plot from the
data of Figure 1 corresponds to a specific conductance of
310 ( 10 pS. Two minutes later, the specific conductance
had shifted to 270 ( 10 pS (i-V plot not shown). An
example of how the shift occurs is given in the trace at
-80 mV applied potential in Figure 1: over 1 s, the
current at this potential decreases by 5 pA in a relatively
smooth fashion. The enhanced conductance of the bilayer
persists, following breakage and reformation of the
bilayer. Throughout the experiment, the bilayer capaci-
tance remains in the normal range for high-quality
bilayers (200 pF in our system). Control experiments
establish that DMSO alone is inactive up to a 10-fold
The available data support the qualitative conclusion
that 19 can insert into bilayer membranes and thereby
enhance ion conduction. The discrete channels of Fig-
ure 2 are similar in specific conductance to channels
formed by 2a b , another bis(macrocyclic) bolaamphi-
phile. In the case of 2a b, the active structure is postu-
lated to be a membrane-spanning dimer or trimer on the
basis of a combination of vesicle and planar bilayer
results. The same type of structure may be responsible
for the single channels shown in Figure 2. A systematic
study as was done with 2a b is precluded by the very low
solubility of 19: the mechanical transfer of material to
the bilayer is simply too ineffective to allow a broad
analysis. The high conductive states related to the
behavior shown in Figure 1 are even harder to study, as
the specific conductance is variable within an experiment
and from day to day. It is possible that the Figure 1 data
arises from domains of 19 incorporated in the bilayer.
Variable conductance might then be related to variable
domain size.
In conclusion, the successful synthesis and novel
membrane activity seen with 19 confirm the design
suggestions leading to structures of types 5 and 6. At the
same time, the compounds prepared are very intractable
and are produced in yields that are no improvement over
those leading to compounds 2a b. As with the previous
bis(macrocycle) systems, poor synthetic efficiency, coupled
in this case with undesirable physical properties, ef-
fectively truncates further development of the very
interesting membrane activity of the compounds.

1552 J . Org. Chem., Vol. 67, No. 5, 2002
Cameron et al.
28.5, 28.9, 65.4, 66.3, 81.2, 123.4, 124.5, 128.2, 131.5, 132.7,
135.3, 139.3, 148.5, 152.4, 163.7, 165.6; MS (-LSIMS,
mNBA): 712.2 (M-); exact mass (-LSIMS, mNBA) calculated
for C37H48N2O12: 712.3208; found: 712.3183.
Exp er im en ta l Section
Vesicle and planar bilayer procedures have been described
previously.20,21
B i s (8 -t e t r a h y d r o p y r a n y l o x y o c t y l )-5 -n i t r o i s o -
p h th a la te (9). The mono Thp ether of 1,8-octanediol (8, 4.81
g, 20.9 mmol) was dissolved in freshly distilled ice-cold THF
(200 mL), and 5-nitroisophthaloyl chloride (7, 9.95 mmol) in
THF (50 mL) was added dropwise simultaneously with tri-
ethylamine (2.11 g, 20.9 mmol). The reaction was stirred on
ice for 2 h. Triethylamine hydrochloride was removed by
filtration, and the filtrate was evaporated to a yellow oil that
was chromatographed on silica using 3:1 hexanes/Et2O as the
15-Am in o-33-n it r o-2,11,20,29-t et r a oxa -1,12,19,30-t et -
r a oxo-[122]-m eta cyclop h a n e (13). 12 (0.47 g, 0.66 mmol)
and 5.88 mL of TFA (trifloroacetic acid) were stirred at reflux
in 95 mL of methylene chloride overnight. After cooling,
saturated NaHCO3(aq) was slowly added to the reaction
mixture to neutralize TFA until the pH of the solution was
above 7. The organic layer was washed twice with water and
dried over Na2SO4. The methylene chloride was removed under
reduced pressure, and the resulting off-white solid was soni-
cated in CHCl3 (30 mL) for 20 min. This precipitate was
collected by filtration and was identified as 13. The CHCl3 was
removed under reduced pressure, and the residue was sepa-
rated by centrifugal chromatography using THF/CH2Cl2 (1:3)
as the eluent. The product from filtration was combined with
the product from chromatography to give a total of 0.40 g (93%)
1
eluent to give 9 as a clear oil (5.18 g, 82%). H NMR (CDCl3,
δ): 1.25-1.77 (m, 36H), 3.26-3.82 (m, 8 H), 4.33 (t, 4 H), 4.47-
4.49 (m, 2 H), 8.89 (s, 1 H), 8.92 (d, 2 H, J ) 1.5 Hz); 13C NMR
(CDCl3, δ): 19.6, 25.4, 25.8, 26.1, 28.5, 29.1, 29.3, 29.6, 30.7,
62.3, 66.3, 67.5, 98.7, 127.9, 132.7, 135.7, 148.4, 163.7; MS
(+LSIMS, mNBA): 634.4 (M - 1).
1
N-ter t-Bu toxyca r bon yl-bis(8-tetr a h yd r op yr a n yloxyoc-
tyl)-5-a m in oisop h th a la te (10). The nitro compound 9 (1.65
g, 2.6 mmol) was placed in a Parr hydrogenator with 95%
EtOH (∼100 mL/0.5 g of nitro compound), PtO2 (20 mol %),
HCl (1 equiv) and hydrogenated at 25 psi for 2 h with shaking.
When the hydrogenation was complete, the solution was clear
except for the catalyst. This black particulate was gravity-
filtered, and the solution was evaporated to yield the crude
ammonium salt that was used without further purification.
The free amines were generated by CH2Cl2-extraction of a
basic solution of the ammonium salt, dried over MgSO4, and
used immediately upon solvent removal. 13C NMR (CDCl3, δ):
19.7, 25.5, 25.9, 26.2, 28.6, 29.2, 29.3, 29.7, 30.8, 62.4, 65.3,
67.6, 98.9, 119.6, 120.6, 131.8, 146.6, 166.1; MS (+LSIMS,
mNBA) 606.4 (M + 1)). The amine was protected as the Boc
derivative by overnight stirring with di-tert-butyl carbonate
(1 equiv based on starting nitro) in 10 mL of freshly distilled
THF. Solvent removal and purification by centrifugal chro-
matography on silica (10% MeOH in ether as eluent) gave the
Boc-protected product 10 in 88% overall yield. 1H NMR (CDCl3,
δ): 1.27-1.82 (m, 45H), 3.31-3.87 (m, 8H), 4.29 (t, 4H), 4.55
(t, 2H), 6.82 (s, 1H, N-H), 8.20 (d, 2H, J ) 1.5 Hz), 8.31 (t,
1H, J ) 1.5 Hz); 13C NMR (CDCl3, δ): 19.7, 25.5, 25.9, 26.1,
28.3, 28.6, 29.2, 29.3, 29.7, 30.8, 62.3, 65.5, 67.6, 81.1, 98.8,
123.4, 125.0, 131.7, 138.6, 139.0, 152.4, 165.7.
N -t e r t -B u t o x y c a r b o n y l -b i s (8 -h y d r o x y o c t y l )-5 -
a m in oisop h th a la te (11). The protected diol 10 (1.33 g, 1.9
mmol) was dissolved in MeOH (40 mL) and HCl (1 M, 20 mL),
and the mixture was stirred for 1 h at rt. The acid was
neutralized with 1 M NaOH, and the MeOH was allowed to
evaporate. The residue was taken up in CH2Cl2 and washed
with H2O twice, and the organic layer was dried over MgSO4
and evaporated. Centrifugal chromatography using Et2O as
the eluent afforded 11 as a white solid (0.71 g, 70%): mp 54
°C; 1H NMR (CDCl3, δ): 1.34-1.45 (m, 16H), 1.50 (s, 9H), 1.58
(m, 4H), 1.74 (dt, 4H), 3.61 (t, 4H, J ) 6.6 Hz), 4.30 (t, 4H, J
) 6.6 Hz), 7.01 (s, 1H), 8.21 (d, 2H, J ) 1.5 Hz), 8.30 (t, 1H, J
) 1.5 Hz); 13C NMR (CDCl3, δ): 25.6, 25.8, 28.3, 28.6, 29.1,
29.2, 32.7, 63.0, 65.5, 123.4, 124.7, 131.7, 139.6, 152.8, 165.9;
MS (mNBA, +LSIMS): 538.3 (M + 1); exact mass calculated
for C29H48NO8: 538.3380; found: 538.3394.
of 13 as an off-white solid. H NMR (360 MHz, DMSO-d6, δ):
1.40-1.62 (m, 16H), 1.78 (m, 8H), 4.2 (t, 4H), 4.35 (t, 4H), 5.4
(d, 2H), 7.3 (s, 2H), 7.5 (s, 1H), 8.7 (m, 3H); 13C NMR (90 MHz,
DMSO-d6, δ): 24.7, 24.8, 27.3, 27.5, 27.7, 64.1, 65.4, 116.3,
117.8, 117.8, 126.6, 130.7, 132.0, 133.8, 162.8, 165.0. Anal.
Calcd for C32H40N2O10: C, 62.73; H, 6.58; N, 4.57. Found: C,
62.39; H, 6.52; N, 4.41; MS: 613.2 (M + H)+.
N,N′-bis[33-n itr o-2,11,20,29-tetr aoxa-1,12,19,30-tetr aoxo-
[122]-m eta cyclop h a n e-15-yl]- octa d ioa m id e (14). To a
solution of 13 (0.15 g, 0.21 mmol) and Et3N (0.025 g) in 25 mL
THF was added pimeloyl chloride (0.0247 g, 0.21 mmol) as a
solid. The reaction mixture was refluxed under a nitrogen
atmosphere overnight. After cooling, the precipitate was
collected by filtration and washed extensively with CHCl3 to
give 14 as a white solid (0.153 g, 90%). 1H NMR (360 MHz,
DMSO-d6, 150 °C, δ): 1.48 (m, 34H), 1.78 (m, 20H), 4.3 (t, 8H),
4.4 (t, 8H), 8.1 (m, 2H), 8.37 (m, 4H), 8.74 (m, 6H); 13C NMR
(90 MHz, DMSO-d6, 150 °C, δ): 23.8, 24.5, 27.1, 27.2, 27.4,
27.6, 35.6, 64.2, 65.2, 122.9, 123.1, 126.4, 130.5, 132.2, 133.5,
139.5, 149.0, 162.5, 164.2, 170.9. Anal. Calcd for C71H88N4O22
:
C, 63.19; H, 6.57; N, 4.15. Found: C, 62.80; H, 6.54; N, 4.20.
MS: 1348.4 (M - H)-.
N,N′-bis[33-n itr o-2,11,20,29-tetr aoxa-1,12,19,30-tetr aoxo-
[122]-m eta cyclop h a n e-15-yl]- ter ep h th a la m id e (15). To a
solution of 13 (0.194 g, 0.27 mmol) and Et3N (0.032 g) in 25
mL THF was added terephthaloyl dichloride (0.032 g, 0.27
mmol) as a solid. The reaction mixture was refluxed under a
nitrogen atmosphere overnight and then cooled, and the
precipitate was collected by filtration. This residue was washed
extensively with CHCl3 to give 15 as a white solid (0.193 g,
90%). 1H NMR (360 MHz, DMSO-d6, 150 °C, δ): 1.43-1.59
(m, 32H), 1.75-1.85 (m, 16H), 4.35-4.45 (m, 16H), 8.13 (s,
4H), 8.23 (m, 2H), 8.65 (m, 4H), 8.7 (m, 6H), 10.3 (s, 2H); 13C
NMR (90 MHz, DMSO-d6, 150 °C, δ): 24.5, 24.5, 27.1, 27.3,
27.4, 64.4, 65.2, 123.8, 124.3, 126.4, 127.0, 130.6, 132.0, 133.5,
136.6, 139.3, 148.0, 162.5, 164.2, 164.4. Anal. Calcd for
C
72H82N4O22: C, 63.80; H, 6.10; N, 4.13. Found: C, 63.53; H,
6.08; N, 4.06. MS: 1354.4 (M - H)-.
15-(2,6-Dioxo-1-piper idin yl)-33-n itr o-2,11,20,29-tetr aoxa-
1,12,19,30-tetr a oxo-[122]- m eta cyclop h a n e (16). Glutaryl
dichloride (8 µL, 0.062 mmol) was added to 13 (0.077 g, 0.13
mmol) in THF (25 mL) containing Et3N (0.5 mL). The mixture
was refluxed overnight and cooled to room temperature, a
white precipitate was removed by filtration, and the filtrate
was concentrated under reduced pressure. The crude product
was purified by centrifugal chromatography using CHCl3 as
N-ter t-Bu t oxyca r b on yl-15-a m in o-33-n it r o-2,11,20,29-
tetr a oxa -1,12,19,30-tetr a oxo-[122]-m eta cyclop h a n e (12).
5-Nitroisophthaloyl dichloride 7 (0.20 g, 0.78 mmol) and the
diol 11 (0.42 g, 0.78 mmol) were separately dissolved in THF
(50 mL) and added dropwise overnight via a dual syringe pump
into vigorously stirred, freshly distilled THF (3 L) and tri-
ethylamine (0.16 g, 1.56 mmol). The triethylammonium hy-
drochloride was removed by filtration, and the filtrate was
evaporated to an off-white solid that was purified by centrifu-
gal chromatography using Et2O as the eluent to give 12 (0.09
g, 16% yield). An alternative reaction on the same scale using
1
the eluent to give 16 (0.022 g, 52%) as a white solid. H NMR
(300 MHz, CDCl3, δ): 1.3-1.62 (m, 16H), 1.64-1.82 (m, 8H),
2.0-2.2 (m, 2H), 2.75-2.82 (t, 4H), 4.2-4.5 (m, 8H), 7.9 (s,
2H), 8.6 (s, 1H), 8.8 (s, 1H), 9.0 (s, 2H); 13C NMR (75 MHz,
CDCl3, δ): 17.2, 25.9, 28.5, 28.6, 29.0, 32.9, 65.6, 66.3, 128.2,
130.3, 132.1, 132.8, 134.1, 135.3, 135.8, 148.6, 163.8, 164.9,
172.2; MS: 708.3 (M)-. The structure of 16 was confrimed by
reduction to the amine: 16 (0.141 g, 0.2 mmol) in THF (120
mL) was reduced over PtO2 (0.1 g) under 30 psi of H2.
Following an overnight reaction, the catalyst was removed by
1
only 200 mL of THF gave the same product in 10% yield. H
NMR (CDCl3, δ): 1.38-1.52 (m, 25H), 1.73-1.88 (m, 8H), 4.33
(t, 4H), 4.42 (t, 4H), 6.68 (s, 1H, N-H), 8.18 (2H), 8.25 (1H),
8.83 (1H), 8.89 (2H); 13C NMR (CDCl3, δ): 25.8, 28.3, 28.4,

Bis(metacyclophane)bolaamphiphile
J . Org. Chem., Vol. 67, No. 5, 2002 1553
gravity filtration, and the filtrate was evaporated. The crude
product was purified by a centrifugal chromatography plate
using THF/CH2Cl2 (1:4) as the eluent. The major band was
collected, and the solvent was evaporated to give an off-white
solid. This solid was washed with ether (5 mL) to give 16 (0.081
reaction mixture was refluxed under a nitrogen atmosphere
overnight and cooled, and the precipitate was collected by
filtration. The precipitate was washed with CHCl3 to give 22d
1
as a white solid (0.12 g, 92%). H NMR (360 MHz, DMSO-d6,
120 °C, δ): 1.33-1.61 (m, 50H), 3.53-3.72 (m, 16H), 4.16-
4.47 (m, 16H), 8.06-8.20 (d, 6H), 8.20-8.38 (d, 6H), 8.57-
8.75 (d, 4H), 9.26-9.40 (s, 2H), 10.39-10.5 (s, 2H). Anal. Calcd
for C82H102N4O22: C, 65.85; H, 6.87; N, 3.75. Found: 65.61; H,
6.94; N, 3.63. MS: 1493.7 (M - H)-.
N,N′-b is[33-a m in o-2,11,20,29-t et r a oxa -1,12,19,30-t et -
r aoxo-[122]-m etacycloph an e-15-yl]- ter eph th alam ide (19).
A mixture of 18 (0.075 g, 50 µmol) and TFA (0.9 mL) in CH2-
Cl2 (25 mL) was stirred at reflux overnight. After cooling, the
white residue was collected by filtration and extensively
washed with CH2Cl2 to give 19 as a white solid (0.050 g, 77%).
1H NMR (360 MHz, DMSO-d6, 120 °C, δ): 1.16-1.61 (m, 32H),
1.61-1.87 (m, 16H), 4.10-4.49 (m, 16H), 7.35-7.46 (d, 4H),
7.67-7.74 (t, 2H), 8.07-8.18 (s, 4H), 8.21-8.29 (t, 2H), 8.60-
8.72 (d, 4H), 10.42-10.54 (s, 2H). Anal. Calcd for C72H86N4O18
+ 0.25CF3CO2H: C, 65.78; H, 6.55; N, 4.23. Found: 65.66; H,
6.54; N, 4.24. MS: 1293.5 (M - H)-.
1
g, 60%) as an off-white solid. H NMR (300 MHz, CD2Cl2, δ):
1.25-1.9 (m, 24H), 2.0-2.2 (m, 2H), 2.8 (t, 4H), 4.1 (b, 2H),
4.4 (m, 8H), 7.5 (s, 2H), 8.0 (m, 3H), 8.7 (s, 1H); 13C NMR (75
MHz, CD2Cl2, δ): 17.5, 26.4, 26.5, 28.9, 28.9, 29.4, 33.2, 65.6,
66.0, 119.7, 120.0, 130.1, 132.2, 132.5, 134.4, 136.6, 138.5,
147.7, 165.2, 166.3, 172.7. Anal. Calcd for C37H46N2O10: C,
65.47; H, 6.83; N, 4.13. Found: C, 65.28; H, 6.89; N, 3.98. MS:
679.2 (M + H)+.
ter t-Bu tyl 33-a m in o-2,11,20,29-tetr a oxa -1,12,19,30-tet-
r a oxo-[122]-m eta cyclop h a n e-15- ylca r ba m a te (17). Pt2O
(0.15 g) was added to a solution of 12 (0.23 g) in 400 mL of
THF/EtOH (1:1) and shaken under 35 psi of H2 overnight. The
catalyst was removed by filtration, the solvent was removed
under reduced pressure, and the crude product was purified
by centrifugal chromatography using CHCl3 as the eluent. The
major band was 17 (0.10 g, 45%). 1H NMR (300 MHz, THF-
d8, δ): 1.37 (m, 21H), 1.65 (m, 12H), 4.2 (m, 8H), 7.31 (s, 2H),
7.74 (s, 1H), 8.12 (s, 1H), 8.24 (s, 2H), 8.74 (s, 1H); 13C NMR
(300 MHz, THF-d8, δ): 27.0, 28.5, 29.5, 30.1, 65.4, 65.7, 80.4,
118.8, 119.5, 123.5, 124.1, 132.4, 141.7, 153.5, 165.8, 166.4.
Ack n ow led gm en t. The ongoing support of the
Natural Sciences and Engineering Research Council of
Canada is gratefully acknowledged.
Anal. Calcd for C37H50N2O10
: C, 65.08; H, 7.38; N, 4.10.
Found: C, 65.12; H, 7.35; N, 3.90. MS: 683.3 (M + H)+.
N ,N ′-b is [33-(t er t -b u t y lo x y c a r b a m o y l)-2,11,20,29-
tetr a oxa -1,12,19,30-tetr a oxo-[122]- m eta cyclop h a n e-15-
yl]-ter ep h th a la m id e (18). To a solution of 17 (0.13 g, 0.19
mmol) and Et3N (0.022 g) in THF (25 mL) was added
terephthaloyl dichloride (0.019 g, 0.19 mmol) as a solid. The
Su p p or t in g In for m a t ion Ava ila b le: 1H and 13C NMR
data of cyclophanes.This material is available free of charge
via the Internet at http://pubs.acs.org.
J O0160930