Anthracene Bisureas as Powerful and Accessible Anion Carriers

Article abstract of DOI:10.1002/chem.201800508

Synthetic anion carriers (anionophores) have potential as biomedical research tools and as treatments for conditions arising from defective natural transport systems (notably cystic fibrosis). Highly active anionophores that are readily accessible and eas

Full text of DOI:10.1002/chem.201800508

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Title: Anthracene Bisureas as Powerful and Accessible Anion Carriers
Authors: Anthony Peter Davis, Christopher Dias, and Hennie Valkenier
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Anthracene Bisureas as Powerful and Accessible Anion Carriers
Christopher M. Dias,[a] Hennie Valkenier,*[b] and Anthony P. Davis*[a]
Abstract: Synthetic anion carriers (anionophores) have potential as
biomedical research tools and as treatments for conditions arising
from defective natural transport systems (notably cystic fibrosis).
Highly active anionophores which are readily accessible and easily
deliverable are especially valuable. Previous work has resulted in
steroid and trans-decalin based anionophores with exceptional
activity for chloride/nitrate exchange in vesicles, but poor accessibility
and deliverability. Here we show that anthracene 1,8-bisureas can
fulfil all three criteria. In particular, a bis-nitrophenyl derivative is
prepared in two steps from commercial starting materials, yet shows
comparable transport activity to the best currently known. Moreover,
unlike earlier highly active systems, it does not need to be
preincorporated in test vesicles but can be introduced subsequent to
vesicle formation. This transporter also shows the ability to transfer
between vesicles, and is therefore uniquely effective for anion
transport at low transporter loadings. The results suggest that
anthracene bisureas are promising candidates for application in
biological research and medicine.
Introduction
The transport of anions across biological membranes is essential
for the proper functioning of a cell.[1,2] Anion concentration
Figure 1. Scaffolds upon which powerful anionophores have previously been
developed.
gradients play an important role in helping to regulate cell pH,
maintaining cell volume and electrical signaling.[1-3] These
gradients are maintained and controlled through the action of
membrane-bound proteins which provide pathways through the
apolar phospholipid bilayer.[1,3-5] Dysfunction of these proteins is
known to give rise to a number of diseases including Bartter
syndrome,[6,7] Dent’s disease[8] and cystic fibrosis.[9,10] Synthetic
anion transporters (anionophores) which can mimic the function
of endogenous ion transport proteins could potentially be used to
treat these conditions and their development has become an
active area of supramolecular chemistry.[4,11,12]
ureas and thioureas in the cholapod (1)[13-19] and trans-decalin
(2)[15,17,20-22] series (Figure 1) can serve as highly effective chloride
transporters in large unilamellar vesicles (LUVs). The most
powerful, such as bisthioureas 1b and 2b (Figure 2), can promote
-
significant Cl-/NO3 exchange when present as single molecules
in LUV membranes.[15] Trans-decalin 2b, the most active reported
to date, transports 850 Cl- ions per second and is comparable to
a protein channel after allowing for molecular weight.[15] However,
while these carriers show high intrinsic activities, both families
require quite lengthy syntheses. Moreover the most active
variants tend to be highly lipophilic, and do not transfer well to a
preformed membrane. To express their activity, it is generally
necessary to incorporate them in the bilayer during membrane
An important goal in this area is the development of anion
carriers which are (a) highly active, (b) easily synthesised, and (c)
readily delivered to bilayer membranes. We have shown that
production.
Meanwhile other, simpler scaffolds also yield
powerful anionophores (e.g. 3-6,[23-28, 50] Figure 1), but none seem
able to match the activities of the cholapod and trans-decalin
families.
A key feature of transporters 1 and 2 is the 1,5-diaxial
arrangement of (thio)urea binding units. Parallel bonds between
scaffold and (thio)urea position the latter so that all four NH can
bind to Cl- simultaneously. Restricted rotation about these C-N
bonds ensures that intramolecular hydrogen bonding cannot
occur. Considering alternative structures which might be easier
to synthesise, we realised that the 1,8-disubstituted anthracenes
[a]
[b]
C. M. Dias, Prof. Dr. A. P. Davis
School of Chemistry, University of Bristol, Cantock's Close, Bristol,
BS8 1TS, UK.
E-mail: Anthony.Davis@bristol.ac.uk
Dr. H. Valkenier
Université Libre de Bruxelles, Avenue F.D. Roosevelt 50, CP165/64,
B-1050 Brussels, Belgium.
E-mail: Hennie.Valkenier@ulb.ac.be
Supporting information for this article is given via a link at the end of
the document, and includes all the data underlying this study.
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Results and Discussion
Design and Synthesis
Previous work has shown that electron-withdrawing terminal
groups favour binding and transport in (thio)urea-based
anionophores. 4-Nitrophenyl N, 4-trifluoromethylphenyl F and
3,5-bis(trifluoromethyl)phenyl (F2) (Figure 3) are especially well-
known and effective.[14-17,20,23-25,27,28,34,35] We therefore targeted
anthracene-based bisureas bearing these substituents (7ON,
7OF and 7OF2; Figure 3), with unsubstituted bisurea 7OP and the
bisthiourea 7SF2 included for comparison purposes. Molecular
modelling on 7ON confirmed the potential for chloride binding and
transport. The calculated ground state structure, shown in Figure
4a, features roughly antiparallel urea groups. Although not
preorganised for binding, they do not hydrogen bond to each other
and are therefore free to rotate. On addition of chloride, the ureas
adopt a convergent conformation to form a 1:1 complex, with
H··Cl distances of 2.3-2.5 Å (Figure 4b). These distances are
slightly shorter than the hydrogen bonds observed in a crystal
structure of a decalin 2 with Cl-.[17] The anthracenyl C(9)–H atom
is also positioned close to the chloride (H··Cl = 2.7 Å), potentially
contributing to binding.[29]
Figure 2. Structures of previously reported anionophores based on cholapod
(1) and trans-decalin (2) scaffolds.
a)
b)
Figure 3 a) General structure 7 of anthracene-1,8-bis(thio)ureas which have
previously been applied as receptors. b) Terminal groups R used in this work.
Molecules are labelled according to scaffold (7), X (O/S) and aromatic
substituent (P/N/F/F2). For example, 7ON refers to the bis-N-nitrophenylurea
based on scaffold 7.
7 (Figure 3) bear a close geometric resemblance to the 1,5-diaxial
systems. Compounds 7 have previously been shown to function
as receptors for anions[29-32] and neutral guests,[33] but
anionophore activity has not been investigated. Here we report
that anthracene bisureas 7 (X=O) can serve as outstandingly
effective anionophores, competitive with the best of the 1,5-diaxial
systems and superior in some respects. Given its accessibility,
this system could be considered the method of choice for inducing
rapid chloride transport in bilayer membranes.
Figure 4 a) Calculated ground state structure of 7ON (Monte Carlo Molecular
Mechanics, followed by Hartree-Fock 6-31G** optimisation in Jaguar). b)
Calculated structure of 7ON.Cl-, employing similar methodology.[39]
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bulk of the thiourea
S
might disfavour the near-planar
conformation required for strong binding.[39]
A
similar
phenomenon has previously been observed in receptors based
on scaffold 6, which are structurally related.[43]
Anion Transport
Anion transport by 7 was assessed using the previously reported
-
lucigenin assay for Cl-/NO3 exchange.[44] Briefly, LUVs (∼200 nm
diameter) containing aqueous NaNO3 (225 mM) and the halide-
sensitive dye lucigenin were prepared from 1-palmitoyl-2-oleoyl-
sn-glycero-3-phosphocholine (POPC) and cholesterol (7:3 ratio)
with the test anionophore preincorporated in the membrane. The
LUVs were suspended in aqueous NaNO3 (225 mM) and placed
Scheme 1. Synthesis of anthracene bis(thio)ureas: (i) Na2S∙9H2O, EtOH/H2O,
reflux, 65 h, 98%; (ii) NaBH4, NaOH, i-PrOH, reflux, 16 h, 60%; (iii) NaBH4, i-
PrOH, reflux, 43 h, 31%; (iv) 7O(P/N/F/F2): ArNCO, DCM, reflux, 4-16 h, 50-
90%, 7SF2: 3,5-(CF3)2C6H3NCS, pyridine, rt, 21 h, 61%.
inside a fluorescence spectrometer.
The experiment was
commenced by the addition of NaCl (25 mM) and the influx of
chloride monitored by the decay in lucigenin fluorescence.[39]
The bis(thio)ureas were prepared via
a
short and
Table 1. Binding and transport data for bis(thio)ureas in the cholapod (1),
trans-decalin (2) and anthracene (7) series.
straightforward process from the commercially available (and
inexpensive) 1,8-dinitroanthraquinone (8) (Scheme 1). Following
literature procedures, 8 could be converted to diamine 10 via a
Compound
clogP[a]
Binding to Bu4N+Cl-
in DMSO-d6/0.5%
H2O[b]
Chloride transport in
LUVs
[33]
single-step reduction with NaBH4 (31 % yield) or in two steps
via diaminoquinone 9 (59% overall yield).[29,30,32] One further step
is then required to generate the bis(thio)ureas, through treatment
of 10 with the appropriate iso(thio)cyanate. Full synthetic
procedures and characterisation data are given in the ESI.
Ka, 1:1
(M-1)
Ka, 2:1
(M-1)
t
[I]
(s-1)[f]
D[i]
½
(s)[e]
1a[15,17]
1b[15,17]
2a[15]
12.0
10.2
11.3
11.6
7.3
n.d.
-
64
15
88
9
450
1800
340
0.12
0.37
n.d.
0.03
1
Binding Studies
17000[c]
880[c,j]
2600[c]
2000[d]
2600[d]
2200[d]
3000[d]
130[g]
-
To underpin transport studies, the binding of 7 to chloride was
characterised through titrations against Bu4N+Cl- in DMSO-
d6/0.5% H2O. Significant downfield shifts were observed for the
(thio)urea NH and C(9)–H anthracenyl signals upon the addition
of guest, which corroborates the computational prediction. To
determine the stoichiometry of the host-guest complex(es)
formed, we followed the approach outlined by Jurczak[36] and
Thordarson[37,38], whereby titration data is fitted to all reasonable
binding models (1:1, 1:2 and 2:1) and the residual distribution
plots compared. The model which yields the lowest and most
random distribution of residuals is the most likely to be valid.[39]
For bisureas 7OP, 7ON, 7OF and 7OF2, a 1:1+2:1 (host:guest)
binding stoichiometry was inferred and titration data were fitted to
this model. Association constants calculated for the 1:1 complex
were ≥2000 M-1, significantly higher than that for decalin bisurea
2a (Table 1). This is remarkable when one compares the
accessibility of the anthracene system with that of the decalins.
The affinities are also higher than receptors based upon other
simple scaffolds, e.g. 3–6, where binding constants measured
under the same conditions do not typically exceed 103 M-1.[23-28, 50]
The affinities are only modestly influenced by the electronic
effects exerted by the terminal aryl groups, although
unsubstituted bisurea 7OP was found to be the weakest chloride
receptor as anticipated. In the case of bisthiourea 7SF2, analysis
indicated much weaker binding, with Ka,1:1 = 130 M-1. This finding
runs counter to normal expectation, given that thioureas are more
-
[15,45]
2b
-
3800
90
7OP
7ON
7OF
240[d]
210[d]
250[d]
277
22
45
6.9
2100
1200
0.82
0.62
0.45
n.d.
9.3
7OF2
7SF2
11.4
11.7
390[d]
30
1900
[g]
[h]
[h]
n.d. = not determined. [a] Calculated logP, an estimate of lipophilicity.
Values were calculated using TorchLite (available as freeware from
www.cresset-group.com). [b] Obtained through 1H NMR titrations at 298 K.
[c] Obtained by fitting all data points to a 1:1 binding model using a least-
square fitting procedure. [d] Obtained by fitting all data points to a 1:1+2:1
(receptor:chloride) binding model (Nelder-Mead method) using the Bindfit
v0.5 applet (available as freeware from app.supramolecular.org). [e]
Obtained by fitting F0/F versus time (0-500 s) to a single exponential decay
function when transporter:lipid = 1:25k. [f] Specific initial rate: initial slope
for F0/F versus time, divided by transporter/lipid ratio and averaged for a
range of experiments at different loadings. [g] Obtained by fitting all data
points to a 1:1+1:2 binding model (method as for [d] above); Ka, 1:2 = 14 M-1.
[h] Transport was observed (see Figure 5a) but not quantified, due to the
instability of 7SF2 in the medium.[39] [i] D = deliverability. Calculated by
dividing I for the external addition experiment by that observed when the
anionophore was preincorporated. [j] Measured for the ethyl ester analogue
of 2a. The ester side-chain is not expected to affect affinities.[15]
acidic than ureas.[40 42] However, calculations suggest that the
-
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1 or 0 transporter molecules, thus the activity observed
corresponds to 7ON acting as a single molecule.[15]
Comparing 7ON to earlier systems, the anthracene does not
quite match decalin 2b, the current record-holder at [I] = 3800 s-1.
However, the examination of fluorescence decay traces shows
that in some respects the new system is more effective. We have
previously found that powerful transporters such as 2b and 1b
produce rapid initial drops in emission at the low loadings, but that
traces tend to plateau at relatively high levels. This is illustrated
in Figure 7 for transporter:lipid = 1:250k. We believe this is due
to the absence of transporter molecules from many vesicles (see
above), which therefore act as bystanders. By contrast, the traces
for 7ON tend towards lower emission values at all loadings
(Figures 6a, 7). Thus as the experiment progresses, the overall
effect of 7ON becomes greater than any of the earlier systems.
The reason for the difference is thought to be the ability of 7ON to
transfer between vesicles, unlike 2b which is trapped in its original
location. Experiments supporting this hypothesis are described
in the next section.
Considering their accessibility, the effectiveness of the
anthracene bisureas is remarkable. In contrast to decalin 2b,
which requires a nine step synthesis,[15] the anthracenes are
available in just two steps. Moreover, it is notable that 7ON and
7OF2 are ureas, while 2b possesses the more favourable
Figure 5. Chloride transport mediated by anthracene-based bis(thio)ureas in
200 nm POPC/cholesterol (7:3) LUVs as measured using the lucigenin method.
The anionophore was preincorporated in the membrane at a transporter to lipid
loading of a) 1:25k or b) 1:250k.
Transport rates were quantified by fitting the inverse of the
normalised fluorescence traces (F0/F) to single exponential
function to obtain approximate half-lives (t ) and a double
½
exponential function to obtain initial rates (I). Dividing I by the
transporter/lipid ratio and averaging for a range of experiments at
different loadings gives the specific initial rate, [I]. As described in
previous work,[15] [I] is independent of the transporter to lipid
loading and thus allows the performance of anionophores with
widely different activities to be compared directly.
b)
Results from these experiments are summarised in Table 1
and Figure 5. All the anthracene bisureas were found to mediate
chloride transport, with activities measurable at transporter to lipid
loadings as low as 1:250k (1.6 nM overall in the aqueous
suspension) (Figure 5b).
Consistent with previous
observations,[15,16,20,25,28,34,35] the electron-deficient aryl termini N,
F and F2 promoted faster transport than unsubstituted P. The
most powerful variant was the nitrophenyl bisurea 7ON, for which
[I] was measured as 2100 s-1. A dose-response study employing
six different loadings of 7ON (Figure 6a) revealed that this
compound was significantly active even at the lowest transporter
to lipid ratio of 1:1,000k. At this loading most LUVs contain either
Figure 6. Chloride transport mediated by 7ON in 200 nm POPC/cholesterol
(7:3) LUVs when preincorporated at various transporter to lipid loadings. (a)
Traces for F/F0 versus time. (b) Plot of the initial rate of transport induced by
7ON as a function of its concentration inside LUVs.
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Figure 7. Chloride transport mediated by compounds 1b, 2b and 7ON in 200
nm POPC/cholesterol (7:3) LUVs as measured using the lucigenin method. The
anionophore was preincorporated in the membrane at a transporter to lipid
loading of 1:250k in all cases.
thiourea units. Decalin bisurea 2a is considerably less active than
the anthracene bisureas, suggesting that the anthracene scaffold
is more effective than the decalin. It is more difficult to compare
the transporters with systems from other groups, but the dose-
response data for 7ON (Figure 6) allows the estimation of an EC50,
,
[46] a measure which is widely used by other laboratories. The
270 s
EC50, 270 s value calculated for 7ON is 0.0003 mol%, the lowest
reported to date for chloride–nitrate exchange, and even lower
than that of the natural anionophore prodigiosin.[28]
In contrast to the ureas, and counter to trends observed
previously,[15] the bisthiourea 7SF2 proved relatively ineffective
(Figure 5a). While its modest chloride affinity may be a factor, it
also showed limited stability under the conditions of the transport
experiment.[39] The anthracene bisthiourea design was therefore
not pursued further.
Figure 8. Chloride transport mediated by anthracene bisureas when the
anionophore was either preincorporated in the membrane (solid lines) or added
externally as solution in DMF to vesicles without anionophore (dashed lines).
The notional transporter to lipid loading was 1:25k for 7OP and 1:250k for 7ON,
7OF and 7OF2.
Mechanistic Studies
decay traces implied that the transporter was transferred rapidly
to the receiver vesicles, equilibration occurring in ≤ 5 min.[39] In
contrast, the same experiments with the more lipophilic 7OF2
showed negligible transfer on the same timescale. Despite the
ability of 7ON to exchange between vesicles, experiments
designed to detect leaching from the membranes gave negative
results, implying that the equilibrium concentration in water is very
low.[39]
Although the anthracene bisureas were designed as anion
carriers, it is also possible that they could act through formation of
self-assembled channels. The linear relationship between initial
transport rates and transporter:lipid ratios for 7ON (Figure 6b)
provides one line of evidence for the carrier mechanism; if more
than one transporter molecule is required to form the active
complex, one would normally expect reduced effectiveness at
lower concentrations.[47] To support this conclusion, transport
was also studied in vesicles composed of 1,2-dipalmitoyl-sn-
glycero-3-phosphocholine (DPPC), which undergoes a transition
between gel and liquid phases at 41 °C.[48] The transition is
expected to affect transport rates for mobile carriers, but much
less so for channels. As anticipated, 7ON proved inactive at 25 °C
(gel phase), but active at 45 °C (liquid phase), consistent with the
carrier mechanism.[39,49]
Deliverability
An important requirement for practical applications of
anionophores is that they must be readily deliverable to target
membranes. The most active cholapod and trans-decalin carriers
do not fulfil this criterion well. Decalin 2b, in particular, is almost
inactive when added to preformed LUVs and is only effective
when incorporated in the vesicles as they are prepared.[15,45] To
Studies were also undertaken to test the ability of the
transporters to move between vesicles, as implied for 7ON by the
results discussed earlier. “Delivery vesicles” containing 7ON but
not lucigenin were mixed with “receiver vesicles” containing
lucigenin but not 7ON, before addition of chloride. Fluorescence
provide
a quantitative estimate of deliverability, we have
developed a variant of the lucigenin assay in which the vesicles
are formed without transporter, and the latter is then added using
a standardised procedure, before the introduction of chloride.[17]
The decay of F0/F is followed, and the initial rate I is measured.
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Rodriguez-Soriano, J. M. Morales, S. A. Sanjad, C. M. Taylor, D. Pilz, A.
Brem, H. Trachtman, W. Griswold, G. A. Richard, E. John and R. P.
Lifton, Nat. Genet. 1997, 17, 171-178.
Deliverability (D) is quantified by dividing I for this experiment by
that observed when the anionophore was preincorporated.
Fluorescence decay traces for both types of experiment, applied
to the four anthracene bisureas, are shown in Figure 8. Values of
D for the anthracene bisureas, as well as 1a, 1b and 2b, are listed
in Table 1. The results show that deliverability for 7OF and 7OF2
is only moderate, but that 7OP and 7ON are transferred quite
efficiently to the vesicles. In particular, the deliverability of 7ON,
at D = 0.82, contrasts starkly with that of 2b (D = 0.03). The good
deliverability of 7ON probably relates to its moderate lipophilicity
(clogP = 6.9, see Table 1). We suspect that highly lipophilic
agents such as 2b (clogP = 11.6) form intractable aggregates
after addition to the aqueous phase, and these interact poorly with
the membranes. While 7ON presumably also aggregates, the
individual molecules are less lipophilic and this could lead to
improved availability.
[7]
[8]
D. B. Simon, F. E. Karet, J. M. Hamdan, A. D. Pietro, S. A. Sanjad and
R. P. Lifton, Nat. Genet. 1996, 13, 183-188.
S. E. Lloyd, S. H. S. Pearce, S. E. Fisher, K. Steinmeyer, B. Schwappach,
S. J. Scheinman, B. Harding, A. Bolino, M. Devoto, P. Goodyer, S. P. A.
Rigden, O. Wrong, T. J. Jentsch, I. W. Craig and R. V. Thakker, Nature
1996, 379, 445-449.
[9]
M. J. Welsh and A. E. Smith, Cell 1993, 73, 1251-1254.
[10] D. N. Sheppard, D. P. Rich, L. S. Ostedgaard, R. J. Gregory, A. E. Smith
and M. J. Welsh, Nature 1993, 362, 160-164.
[11] a) P. A. Gale, J. T. Davis and R. Quesada, Chem. Soc. Rev. 2017, 46,
2497-2519. b) P. A. Gale, E. N. W. Howe and X. Wu, Chem 2016, 1, 351-
422. c) A. Vargas Jentzsch, A. Hennig, J. Mareda, S. Matile, Acc. Chem.
Res. 2013, 46, 2791-2800. d) S. Matile, A. Vargas Jentzsch, J.
Montenegro, A. Fin, Chem. Soc. Rev. 2011, 40, 2453-2474.
[12] H. Valkenier, A. P. Davis, Acc. Chem. Res. 2013, 46, 2898-2909.
[13] A. V. Koulov, T. N. Lambert, R. Shukla, M. Jain, J. M. Boon, B. D. Smith,
H. Li, D. N. Sheppard, J.-B. Joos, J. P. Clare and A. P. Davis, Angew.
Chem., Int. Ed. 2003, 42, 4931-4933; Angew. Chem. 2003, 115, 5081-
5083.
Conclusions
[14] B. A. McNally, A. V. Koulov, T. N. Lambert, B. D. Smith, J.-B. Joos, A. L.
Sisson, J. P. Clare, V. Sgarlata, L. W. Judd, G. Magro and A. P. Davis,
Chem. Eur. J. 2008, 14, 9599-9606.
In conclusion, we have shown that anthracene 1,8-bisureas are
exceptionally effective and practical anion transporters. The most
powerful promote chloride/nitrate exchange at rates comparable
to the highest previously observed, while being far more
accessible than the earlier systems. Dinitro variant 7ON
combines high activity with good deliverability in a manner
unmatched by previous systems. Taking into account its ability to
transfer between vesicles, it is arguably the most effective agent
currently available for transporting chloride across vesicle
membranes at low dosages. The anthracene scaffold has
potential for further modification to control binding affinities,
lipophilicities etc. We believe the design has promise for
application in tools for biomedical research, and perhaps in the
treatment of channelopathies such as cystic fibrosis.
[15] H. Valkenier, L. W. Judd, H. Li, S. Hussain, D. N. Sheppard and A. P.
Davis, J. Am. Chem. Soc. 2014, 136, 12507-12512.
[16] S. J. Edwards, H. Valkenier, N. Busschaert, P. A. Gale and A. P. Davis,
Angew. Chem., Int. Ed. 2015, 54, 4592-4596; Angew. Chem. 2015, 127,
4675–4679.
[17] H. Li, H. Valkenier, L. W. Judd, P. R. Brotherhood, S. Hussain, J. A.
Cooper, O. Jurček, H. A. Sparkes, D. N. Sheppard and A. P. Davis, Nat.
Chem. 2016, 8, 24-32.
[18] L. W. Judd and A. P. Davis, Chem. Commun. 2010, 46, 2227-2229.
[19] X. Wu, L. W. Judd, E. N. W. Howe, A. M. Withecombe, V. Soto-Cerrato,
H. Li, N. Busschaert, H. Valkenier, R. Pérez-Tomás, D. N. Sheppard, Y.-
B. Jiang, A. P. Davis and P. A. Gale, Chem 2016, 1, 127-146.
[20] S. Hussain, P. R. Brotherhood, L. W. Judd and A. P. Davis, J. Am. Chem.
Soc. 2011, 133, 1614-1617.
[21] S. J. Edwards, I. Marques, C. M. Dias, R. A. Tromans, N. R. Lees, V.
Félix, H. Valkenier and A. P. Davis, Chem. Eur. J. 2016, 22, 2004-2011.
[22] H. Valkenier, C. M. Dias, C. P. Butts and A. P. Davis, Tetrahedron 2017,
73, 4955-4962.
Acknowledgements
[23] H. Valkenier, C. M. Dias, K. L. Porter Goff, O. Jurček, R. Puttreddy, K.
Rissanen and A. P. Davis, Chem. Commun. 2015, 51, 14235-14238.
[24] C. Lang, X. Zhang, Q. Luo, Z. Dong, J. Xu and J. Liu, Eur. J. Org. Chem.
2015, 2015, 6458-6465.
This work was supported by the EPSRC through the Bristol
Chemical Synthesis Centre for Doctoral Training (EP/G036764/1)
and research grant number EP/J00961X/1 and by the F.R.S.-
FNRS through a Chargée de Recherche grant to HV.
[25] N. Busschaert, M. Wenzel, M. E. Light, P. Iglesias-Hernández, R. Pérez-
Tomás and P. A. Gale, J. Am. Chem. Soc. 2011, 133, 14136-14148.
[26] N. Busschaert, P. A. Gale, C. J. E. Haynes, M. E. Light, S. J. Moore, C.
C. Tong, J. T. Davis and J. W. A. Harrell, Chem. Commun. 2010, 46,
6252-6254.
Keywords: Supramolecular chemistry • Receptors • Anion
transport • Membranes • Ureas
[27] S. J. Moore, C. J. E. Haynes, J. Gonzalez, J. L. Sutton, S. J. Brooks, M.
E. Light, J. Herniman, G. J. Langley, V. Soto-Cerrato, R. Perez-Tomas,
I. Marques, P. J. Costa, V. Felix and P. A. Gale, Chem. Sci. 2013, 4, 103-
117.
[1]
J. T. Davis, O. Okunola and R. Quesada, Chem. Soc. Rev. 2010, 39,
3843-3862.
[2]
[3]
D. C. Gadsby, Nat. Rev. Mol. Cell Biol. 2009, 10, 344-352.
A. P. Davis, D. N. Sheppard and B. D. Smith, Chem. Soc. Rev. 2007, 36,
348-357.
[28] L. E. Karagiannidis, C. J. E. Haynes, K. J. Holder, I. L. Kirby, S. J. Moore,
N. J. Wells and P. A. Gale, Chem. Commun. 2014, 50, 12050-12053.
[29] J. Y. Kwon, Y. J. Jang, S. K. Kim, K.-H. Lee, J. S. Kim and J. Yoon, J.
Org. Chem. 2004, 69, 5155-5157.
[4]
N. Busschaert, C. Caltagirone, W. Van Rossom and P. A. Gale, Chem.
Rev. 2015, 115, 8038-8155.
[30] A. Dahan, T. Ashkenazi, V. Kuznetsov, S. Makievski, E. Drug, L. Fadeev,
M. Bramson, S. Schokoroy, E. Rozenshine-Kemelmakher and M. Gozin,
J. Org. Chem. 2007, 72, 2289-2296.
[5]
[6]
F. M. Ashcroft, Nature 2006, 440, 440-447.
D. B. Simon, R. S. Bindra, T. A. Mansfield, C. Nelson-Williams, E.
Mendonca, R. Stone, S. Schurman, A. Nayir, H. Alpay, A. Bakkaloglu, J.
This article is protected by copyright. All rights reserved.

10.1002/chem.201800508
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[31] P. Hamankiewicz, J. M. Granda and J. Jurczak, Tetrahedron Lett. 2013,
54, 5608-5611.
[42] E. Fan, S. A. Van Arman, S. Kincaid and A. D. Hamilton, J. Am. Chem.
Soc. 1993, 115, 369-370.
[32] F. Ulatowski and J. Jurczak, J. Org. Chem. 2015, 80, 4235-4243.
[33] K. Kellett, J. H. Broome, M. Zloh, S. B. Kirton, S. Fergus, U. Gerhard, J.
L. Stair and K. J. Wallace, Chem. Commun. 2016, 52, 7474-7477.
[34] J. A. Cooper, S. T. G. Street and A. P. Davis, Angew. Chem., Int. Ed.
2014, 53, 5609-5613; Angew. Chem. 2014, 126, 5715–5719.
[35] N. Busschaert, I. L. Kirby, S. Young, S. J. Coles, P. N. Horton, M. E. Light
and P. A. Gale, Angew. Chem., Int. Ed. 2012, 51, 4426-4430; Angew.
Chem. 2012, 124, 4502–4506.
[43] S. J. Brooks, P. R. Edwards, P. A. Gale and M. E. Light, New J. Chem.
2006, 30, 65-70.
[44] B. A. McNally, A. V. Koulov, B. D. Smith, J.-B. Joos and A. P. Davis,
Chem. Commun. 2005, 0, 1087-1089.
[45] N. López Mora, A. Bahreman, H. Valkenier, H. Li, T. H. Sharp, D. N.
Sheppard, A. P. Davis and A. Kros, Chem. Sci. 2016, 7, 1768-1772.
[46] Defined as the effective concentration of transporter required to induce
50% of maximum chloride influx at t = 270 s (see ESI for further details)
[47] The Hill coefficient (n) calculated from these data is 1.05, consistent with
a single molecule of 7ON in the active complex. See ESI for further
details.
[36] F. Ulatowski, K. Dąbrowa, T. Bałakier and J. Jurczak, J. Org. Chem.
2016, 81, 1746-1756.
[37] P. Thordarson, Chem. Soc. Rev. 2011, 40, 1305-1323.
[38] D. Brynn Hibbert and P. Thordarson, Chem. Commun. 2016, 52, 12792-
12805.
[48] M. J. Pregel, L. Jullien, J. Canceill, L. Lacombe and J.-M. Lehn, J. Chem.
Soc., Perkin Trans. 2 1995, 0, 417-426.
[39] For further details see Supporting Information.
[40] D. E. Gomez, L. Fabbrizzi, M. Licchelli and E. Monzani, Org. Biomol.
Chem. 2005, 3, 1495-1500.
[49] G. Deng, T. Dewa and S. L. Regen, J. Am. Chem. Soc. 1996, 118, 8975-
8976.
[50] C. M. Dias, H. Li, H. Valkenier, L. E. Karagiannidis, P. A. Gale, D. N.
Sheppard, A. P. Davis, Org. Biomol. Chem. 2018, DOI:
10.1039/c7ob02787g.
[41] S. Nishizawa, P. Bühlmann, M. Iwao and Y. Umezawa, Tetrahedron Lett.
1995, 36, 6483-6486.
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Anthracene 1,8-bisureas are among
the most powerful known anion
Christopher M. Dias, Dr. Hennie
Valkenier* and Prof. Dr. Anthony P.
Davis*
carriers, yet available in just two steps
from commercial starting materials.
The most active variant (see figure) is
highly deliverable and readily transfers
between vesicle membranes.
Page No. – Page No.
Anthracene Bisureas as Powerful and
Accessible Anion Carriers
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