Solid phase synthesis of oligoethylene glycol-functionalized quinolinecarboxamide foldamers with enhanced solubility properties

Article abstract of DOI:10.1016/j.crci.2015.06.007

A series of octameric quinoline oligoamide foldamers has been synthesized consisting exclusively of monomers which display mono-, di-, tri- or tetra-ethylene glycol side-chains. These oligomers adopt stable helical conformations. New Fmoc-acid monomer precursors were first developed. The microwave assisted solid-phase synthesis (SPS) methodology for oligomer preparation is described, and it is demonstrated that small adjustments in side-chain length translate into large differences in the solubility profile of the oligomers. The impact of such modifications on foldamer preparation, handedness inversion kinetics and potential applications is also discussed.

Full text of DOI:10.1016/j.crci.2015.06.007

C. R. Chimie 19 (2016) 132e142
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Full paper/M eꢀ moire
Solid phase synthesis of oligoethylene glycol-functionalized
quinolinecarboxamide foldamers with enhanced solubility
properties
Synth ꢁe se en phase solide de foldam ꢁe res quinolinecarboxamide munis de
chaînes oligo ꢀe thyl ꢁe ne glycol augmentant leur solubilit ꢀe
Christos Tsiamantas b, Simon J. Dawson a b, Ivan Huc a
a
,
,
, b, *
a
Universit ꢀe de Bordeaux, CBMN (UMR 5248), Institut Europ ꢀe en de Chimie et Biologie, 2, rue Robert-Escarpit, 33607 Pessac, France
CNRS, CBMN (UMR 5248), Pessac, France
b
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of octameric quinoline oligoamide foldamers has been synthesized consisting
exclusively of monomers which display mono-, di-, tri- or tetra-ethylene glycol side-
chains. These oligomers adopt stable helical conformations. New Fmoc-acid monomer
precursors were first developed. The microwave assisted solid-phase synthesis (SPS)
methodology for oligomer preparation is described, and it is demonstrated that small
adjustments in side-chain length translate into large differences in the solubility profile of
the oligomers. The impact of such modifications on foldamer preparation, handedness
inversion kinetics and potential applications is also discussed.
Received 15 April 2015
Accepted 8 June 2015
Available online 28 January 2016
Keywords:
Foldamers
Solid phase synthesis
Aromatic amides
Helical structures
© 2015 Acad eꢀ mie des sciences. Published by Elsevier Masson SAS. This is an open access
article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
r é s u m é
Mots-cl ꢀe s:
Foldam eꢁ res
Synth eꢁ se en phase solide
Amides aromatiques
Une s eꢀ rie de foldam eꢁ res octam eꢀ riques de quinolinecarboxamide compos eꢀ s de monom eꢁ res
portant des chaînes laterales mono-, di-, tri- ou tetraethylene glycol a ete synthetisee. Ces
compos eꢀ s adoptent des conformations repli eꢀ es en h eꢀ lice stables. De nouveaux pr eꢀ curseurs
Fmoc-acide ont eꢀ t eꢀ d eꢀ velopp eꢀ s au pr eꢀ alable. La synth eꢁ se des pr eꢀ cuseurs ainsi que la
pr eꢀ paration des s eꢀ quences par synth eꢁ se en phase solide (SPS) sont d eꢀ crites. Il est
eꢀ galement d eꢀ montr eꢀ que des modifications mineures des chaînes lat eꢀ rales peuvent se
traduire par de grandes diff eꢀ rences dans les profils de solubilit eꢀ des oligom eꢁ res. L'effet des
modifications des chaînes lat eꢀ rales sur la pr eꢀ paration des foldam eꢀ res, sur la cin eꢀ tique
d'inversion du sens d'h eꢀ licit eꢀ et sur les applications pratiques est aussi discut eꢀ .
ꢀ
ꢀ
ꢀ
ꢁ
ꢀ ꢀ
ꢀ
ꢀ
Structures h eꢀ licoïdales
©
2015 Acad eꢀ mie des sciences. Published by Elsevier Masson SAS. This is an open access
article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
1. Introduction
*
Corresponding author. Universit eꢀ de Bordeaux, CBMN (UMR 5248),
Institut Europ eꢀ en de Chimie et Biologie, 2, rue Robert-Escarpit, 33607
Pessac, France.
The propensity of foldamers to fold and the properties
of their folded conformations directly express features
E-mail address: i.huc@iecb.u-bordeaux.fr (I. Huc).
http://dx.doi.org/10.1016/j.crci.2015.06.007
1
631-0748/© 2015 Acad eꢀ mie des sciences. Published by Elsevier Masson SAS. This is an open access article under the CC BY-NC-ND license (http://
creativecommons.org/licenses/by-nc-nd/4.0/).

C. Tsiamantas et al. / C. R. Chimie 19 (2016) 132e142
133
encoded in the structure of their building blocks [1]. As
such, foldamer research critically depends on the devel-
opment of new desirable monomers and their easy incor-
poration into sequences. Thus, synthetic foldamers do not
face the same limitations as biopolymers which are based
on small ensembles of units (e.g. twenty amino acids for
proteins and four nucleobases for nucleic acids). In this
manuscript, we present the synthesis of quinoline amino
acids bearing oligoethylene glycol side-chains of various
lengths, their incorporation into oligomers via solid-phase
synthesis (SPS), and the determination of solubility prop-
erties endowed by these side-chains.
Aromatic amide foldamers are a growing class of olig-
omers that combine relatively easy synthetic access and
stable and predictable conformations [2]. The folding of
aromatic oligoamide foldamers arises from backbone ri-
gidity due to local electrostatic repulsions and hydrogen
bonds between amide function and adjacent units. The size
and orientation of substituents on each monomer deter-
mine the strand curvature, leading to linear [3], zig-zag [4],
or bent shapes [5], which eventually give rise to macro-
cycles [6], hydrogen-bonded duplexes [7], single [8] and
aromatic amino acids bearing a wide range of side-chains
[14,16], and of microwave-assisted SPS methods to conve-
niently assemble them into varied sequences [18]. This al-
lows the rapid synthesis of oligomers where any position in
the sequence can be substituted for another, without the
laborious preparation and purification of intermediates
required by a solution-phase strategy.
In this manuscript, we focus on oligoamide foldamers
derived from 8-amino-2-quinolinecarboxylic acid having
side-chains in position 4 (Fig. 1) [8,11,14,15,17,18(a)]. These
oligomers adopt very robust helical conformations that
have been used to construct organic soluble, isobutoxy-
substituted structures, of the size of small proteins [13].
The installation of an aminopropyl (i.e. ornithine-like) side-
chain endows oligomers with good water solubility, with
cell penetration properties [14(a),19], and with high affinity
for G-quadruplex DNA [17]. Upon combining various pro-
teinogenic side-chains, interactions with protein surfaces
have been evidenced [14(b)]. In this context, we have been
interested in introducing oligoethylene glycol functional-
ized monomers. Such side-chains would ensure the solu-
bility of the same molecules in a wide range of solvents
allowing, for example, the locking of helix handedness in
water after inducing it in an organic solvent [15]; they may
also potentially reduce toxicity [20]; and avoid non-specific
interactions between foldamer surfaces and biomolecules
[21], discouraging any interference with interactions
involving designed recognition spots.
In a previous study [11(b)], we successfully incorporated
a triethylene glycol side-chain on a monomer and prepared
oligomers up to the octamer in solution (Fig. 1). These
oligomers were shown to be soluble in solvents ranging
from diethyl ether to methanol/water mixtures. However, it
was noted that the arylealkyl ether linkage connecting the
side-chain to the quinoline position 4 was somewhat acid-
labile, most likely via a beta-elimination process, and that it
would not be compatible with the acidic conditions
required to cleave oligomers from the Wang resin after SPS
[18]. Here we present a strategy for the synthesis of Fmoc
protected quinoline monomers possessing oligoethylene
glycol (OEG) side-chains ranging from mono- to tetra-
ethylene glycol attached at the quinoline position 4 via an
acid-resistant thioether linkage. These monomers were
subsequently assembled in the SPS of four octameric se-
quences each consisting exclusively of one monomer type.
We demonstrate that these side-chains are compatible
with helix handedness separation by HPLC on a chiral
stationary phase, and also investigate the effect of OEG
side-chain length on the solubility profile of each octameric
sequence.
multiple [9] helices, and aromatic b-sheets [10]. In sheets
and helices, aromatic stacking, which may include elec-
trostatic and solvophobic components, brings about addi-
tional stabilization [11]. Thus aromatic oligoamide folding
depends primarily on main chain features, regardless of
side-chains which, with a few exceptions [9(a)] and unlike
in peptides and nucleotides, have little effect on the folded
conformations. Monomer development for aromatic amide
foldamers thus allows the consideration of main chain and
side-chain attributes in an orthogonal manner. Over the
years, a great variety of benzenic and heterocyclic building
blocks have been introduced that can be combined at will
[2,12].
For their part, side-chains determine the solubility. This
is not as trivial a question as it may appear as aromatic
oligoamides are inherently very poorly soluble molecules.
Nevertheless, appropriate substitution with groups
diverging from the folded structures allows solubility in all
kinds of media. Some side-chains like isobutoxy groups
provide high solubility in organic media and also favor
crystallogenesis [8,9,10,13]. Interest in controlling the sol-
ubility of aromatic oligoamides in a wide range of solvents
stems from the fact that folding has been shown to occur in
solvents as diverse as chloroform, toluene, dimethyl sulf-
oxide, methanol or water [11(b),14]. While folded confor-
mations do not depend much on the solvent, their stability
may be greatly influenced as illustrated by considerable
variations of the rate of helix handedness inversion in he-
lical foldamers [11(b)]. These variations may have practical
applications. For example, helix handedness induction by a
chiral residue may be effective in a solvent in which
handedness inversion is fast. Once handedness induction is
complete, the same molecule may be transferred into
another solvent in which the conformation is kinetically
inert [15].
Side-chains also determine the ability of the folded
structures to interact with other molecules, in particular
protein surfaces [14(b),16] and nucleic acids [17]. This
essential property has motivated the development of
Fig. 1. Isobutoxy, 3-aminopropoxy and triethylene glycol monomethyl ether
side-chains at position 4 of 8-amino-2-quinolinecarboxamide monomers.

134
C. Tsiamantas et al. / C. R. Chimie 19 (2016) 132e142
2
. Results and discussion
.1. Synthesis
Our strategy was to design a generic synthesis for Fmoc-
2
acid quinoline monomers ready for SPS which would allow
the attachment of potentially any length of OEG side-
chains. Thus, side-chains were introduced by the forma-
tion of the thioether linkage via aromatic nucleophilic
substitution of a 4-bromoquinoline intermediate [14(b)] by
the corresponding thiol (Scheme 1). Only the shortest side-
chain precursor (2-methoxyethanethiol) is commercially
available. Other precursors were prepared in three steps
from OEG monomethyl ethers which are commercially
available for a wide range of oligo- and poly-ethylene gly-
cols. Following previously reported methods [22], these
precursors were tosylated, subsequently substituted by
thiourea and hydrolyzed to yield the desired thiol products
in 24e64% yields over the three steps.
Fig. 2. Crystal structure of monomer 4. Hydrogen atoms have been omitted
for clarity.
Aromatic nucleophilic substitution of methyl 8-nitro-4-
bromo-2-quinolinecarboxylate [14(b)] afforded 8-nitro 2-
ester monomer intermediates in good yields (54e78%).
These could be obtained with excellent purity due to their
high crystallinity, even for the tri- and tetra-ethylene glycol
chains. From there, the desired monomers (1e4) could be
obtained through saponification of the methyl ester,
reduction of the nitro group by catalytic hydrogenation and
Fmoc protection of the amine.
Of these three steps, only the reduction step required
2
some optimization; H /PdeC was found to be somewhat
sluggish, presumably due to gradual poisoning of the cata-
lyst by traces of thiol intermediates. This problem was easily
overcome by using the more rapid NH HCO /PdeC system.
4 2
Fmoc monomers were therefore afforded in 30e50% overall
yields on 1 g scale syntheses from the bromoquinoline in-
termediate. Interestingly all the Fmoc monomers were
found to be amenable to crystallization. It was possible to
use this as an extra purification step for achieving mono-
mers of high purity. Fig. 2 shows the crystal structure of the
tetraethylene glycol-functionalized monomer 4.
SPS of quinoline carboxamide oligomers is commonly
carried out on Wang resin and affords a free C-terminal
carboxylic acid function after resin cleavage [18]. However,
in order to afford oligomers which would be amenable to
purification by both normal and reverse-phase HPLC,
recycling gel permeation chromatography (GPC), or even
flash chromatography, we decided to avoid the carboxylic
acid function and to follow a strategy which would provide
a primary amide at the C-terminus. This was anticipated to
significantly reduce oligomer polarity without causing
problems with solubility. Our initial attempts with SPS on
Rink amide resin [23] were unsuccessful due to an unex-
pected resistance to the normal acidic cleavage conditions
(95% TFA). We therefore utilized Sieber amide resin [24]
which has a higher degree of acid lability. The first mono-
mer could be loaded onto the resin either using HBTU/HOBt
in DMF, or via the acid chloride, pre-formed by treatment of
monomer acid with the Ghosez reagent (1-chloro-N,N,2-
trimethyl-1-propenylamine)
[25],
in
THF
under
Scheme 1. Synthesis of Fmoc quinoline building blocks with OEG side-chains.

C. Tsiamantas et al. / C. R. Chimie 19 (2016) 132e142
135
microwave heating (Scheme 2). Fmoc deprotection was
carried out at room temperature using 20% v/v piperidine
in DMF and SPS continued in this fashion by coupling of the
pre-formed monomer acid chlorides using the microwave-
assisted methodology [18]. The sequence was terminated
by coupling the nitro acid intermediate of each monomer in
the same manner.
solvents at concentrations sufficient to allow the mea-
surement of circular dichroism [11(b)]. However, while
methanol/water mixtures containing up to 50% v/v water
were tolerated, this octamer was not soluble in pure water.
By increasing the side-chain length by one ethylene glycol
unit, we hoped to access this property with compound 8. In
addition, we aimed to investigate the solubility behavior of
octamers 5 and 6, which during their purification had
shown themselves to be more compatible with low polarity
organic solvents.
Thus, homomeric octamers 5e8 were prepared from the
corresponding monomers 1e4 on a 16e32 mmol scale with
crude purities ranging from 80 to 86%. Each oligomer could
be purified by RP-HPLC, except for the monoethylene
glycol-functionalized compound 5, due to poor solubility in
water/acetonitrile mixtures. Instead, this was purified by
recycling GPC in chloroform (see Experimental section). The
tetraethylene glycol-functionalized octamer 8 was first
purified by RP-HPLC, however it was clear by NMR and MS
analysis that even after chromatographic treatment, the
material also contained a nonameric sequence which could
not be separated from the desired octamer due to very
similar retention times on the C18 reverse-phase prepara-
tive column. Fortunately this nonameric by-product was
sufficiently different in size from the desired octamer that it
could be removed by recycling GPC. The insertion of an
additional monomer presumably reflects slightly too harsh
coupling conditions during one of the steps that may result
in partial Fmoc cleavage while some activated acid is still
present. To avoid this kind of side reaction and the subse-
quent difficult purification, it is recommended not to exceed
the reported heating temperature and coupling duration.
A quantitative assessment of the solubility of 5e8 in
eight typical solvents was carried out via UV absorbance
measurement. A saturated solution of the studied oligomer
was produced by adding excess solid material to a partic-
ular solvent, stirring and allowing a mixing time of 15 min
ꢀ
at 20 C. The mixture was then centrifuged at 6000 rpm for
5 min, or until a clear supernatant had been achieved as
assessed by light microscopy. An accurately measured
volume of the supernatant was then removed and evapo-
rated to dryness. The residue was dissolved in DMSO, a
solvent in which all foldamers were well soluble, and
diluted to a concentration appropriate for UV absorbance
measurement. This was subsequently carried out at
375 nm, corresponding to a local maximum of the quino-
line oligoamide foldamer absorbance. The extinction coef-
ficient at this wavelength had previously been calculated
by measuring the absorbance of serial dilutions of an NMR
sample of 8, for which the concentration had been assessed
by comparison with an internal calibrant (see Supporting
information). From this, the original concentration of fol-
damer in each solvent could be extrapolated, serving as an
accurate measure of solubility. As shown in Table 1, there
are significant differences in the solubility profile imparted
by the adjustment of side-chain length. As we had antici-
pated, the tetraethylene glycol side-chain permitted a
reasonable (mM) solubility of 8 in pure water. In contrast,
the other octamers showed negligible aqueous solubility.
2
.2. Solubility studies
We anticipated that one critical difference between the
four octamers synthesized would be their solubility
profile. Previous experience with a triethylene glycol-
functionalized octamer similar to 7 had demonstrated
that this side-chain afforded solubility in a wide range of
Scheme 2. SPS of OEG functionalized octamers.

136
C. Tsiamantas et al. / C. R. Chimie 19 (2016) 132e142
The octamer 8 also possessed excellent solubility in most of
the other solvents apart from n-hexane and isopropanol,
similarly to the remaining compounds.
successfully used a standard Chiralpak-IA chiral analytical
HPLC column to separate the P and M helix forms of
compound 8 at low temperature (Fig. 3a, b) in organic
solvents. In-line circular dichroism demonstrated elution
of the M-helix as the first peak, followed by the P-helix;
these could be isolated with ee values of >99% and 93%
respectively (Fig. 3c, d). Conveniently, handedness inver-
The behavior of the triethylene glycol-functionalized
octamer 7 matched well with our previous experiment,
which demonstrated similar properties to 8, with the
difference that solubility in protic solvents was dimin-
ished by at least one order of magnitude. Decreasing the
side-chain length further to diethylene glycol (6)
decreased the solubility of the octamer to sub-millimolar
levels in both toluene and methanol, with limited effects
on other solvents. Finally, as anticipated, the mono-
sion kinetics in the solvent mixture and temperature used
ꢀ
for chiral HPLC (MeOH/CHCl
3
, 75:25, ꢁ5 C) appeared to
be extremely slow: the isolated M helix was subsequently
incubated for up to eight hours under these conditions,
with no visible racemization (see Supporting information).
We could also use the same column to separate one-
handed forms of the monoethylene glycol-functionalized
octamer 5 at room temperature, and this also demon-
strated the same order of elution as compound 8 (see
Supporting information).
ethylene glycol-functionalized octamer
5 showed a
marked reduction in solubility in all polar solvents,
although this was also accompanied by a near doubling of
solubility in chloroform compared to 7, the next most
soluble oligomer in this solvent. These results show that
the solubility properties of the quinoline-based foldamers
can be effectively tailored by altering the length of OEG-
based side-chains, allowing access to highly soluble
oligomers compatible with both water and a range of
organic solvents.
In summary, the tetraethylene glycol side-chains allow
facile separation of P and M helices by using chiral HPLC in
organic solvents, yet also permit solubility under aqueous
conditions where helix handedness inversion kinetics are
essentially frozen. For oligomers bearing these side-chains,
this could conceivably be a convenient method to isolate
usable quantities of separate handedness forms without
requiring the installation of chiral groups for handedness
induction, or separation of diastereoisomers.
2
.3. Chiral HPLC
During studies of the tetraethylene glycol-
functionalized octamer 8, it became clear to us that its
highly soluble nature could be taken as an advantage, with
respect to the separation of helix handedness forms. We
have previously demonstrated that the handedness
inversion kinetics of the quinoline oligoamide foldamers
are highly solvent dependent, with an octameric sequence
similar to that of 7 demonstrating half lives varying from
minutes in aprotic solvents to days in protic solvents
3
. Conclusions
Four Fmoc-acid quinoline monomers have been syn-
thesized with OEG side-chains installed at position four
through an acid-stable thioether linkage. The general
methodology for their preparation is compatible with the
production of monomers possessing longer OEG units;
indeed probably the main limiting factor is the commer-
cial availability of the OEG monomethyl ether starting
material. From these monomers four octameric sequences,
each consisting exclusively of one monomer type, were
synthesized by a microwave-assisted SPS methodology.
Their solubility profiles were investigated and it was
shown that elongation of the side-chain unit to tetra-
ethylene glycol permitted excellent solubility of the cor-
responding octameric sequence (8) in the majority of
organic solvents studied. More importantly, this com-
pound was also found to possess modest solubility in pure
water, which has not been demonstrated before in quin-
oline oligoamide foldamers without the presence of mul-
tiple charged side-chains. The P and M helix handedness
forms of octamer 8 were separated using a standard chiral
HPLC stationary phase, providing for the first time a
method to isolate water-soluble helices as their separate
enantiomers, without requiring chiral groups for
handedness induction, or separation of the respective
diastereoisomers.
[11(b)]. In water, kinetics are essentially frozen: aqueous
solutions of separated P and M helices of octamers have
been left at room temperature for months and demon-
strated no evidence of handedness inversion [15]. Sepa-
ration of P and M helices of water-soluble oligomers was
previously carried out using a phenylalanine unit installed
at the C-terminus to permit RP-HPLC separation of the two
helix forms as diastereoisomers. In contrast, we envisaged
that the good solubility of 8 in both organic and aqueous
solvents would permit the use of chiral HPLC to separate
the two helix handedness forms as enantiomers. If left in
the solid state, or if dissolved in water handedness would
remain ‘locked’. This strategy proved to be valid as we
Table 1
Estimated solubility (mM) of foldamers 5e8 in each solvent.
Solvent
Estimated solubility (mM)
5
6
7
8
Hexane
Toluene
Chloroform
THF
<0.01
0.20
158
13
21
<0.01
0.28
39
70
73
<0.01
55
86
64
105
<0.01
69
59
85
88
Future work will investigate the use of OEG function-
alized monomer units in sequences designed to interact
with biomolecules. While providing foldamers with the
necessary aqueous solubility, we foresee that monomers
such as 8 can also have a potential role in eliminating un-
desired non-specific interactions of the foldamer backbone
with a biological target.
DMF
Isopropanol
Methanol
Water
0.02
0.04
<0.01
0.03
0.13
<0.01
0.03
1.5
<0.01
0.27
20
2.5

C. Tsiamantas et al. / C. R. Chimie 19 (2016) 132e142
137
MilliQ water were used for RP-HPLC analyses and purifi-
cation. Reactions requiring anhydrous conditions were
performed under nitrogen. SPS was carried out manually
using a CEM Discover microwave and vacuum station, and
1
in proprietary reactor vessels. H NMR spectra were
13
measured at 300 MHz and C NMR spectra were measured
at 75 MHz. Chemical shifts are reported in ppm and are
calibrated against residual solvent signals of CDCl
3
(d 7.26,
7
7.2), or DMSO-d 2.50, 39.4). All coupling constants are
6
(d
reported in hertz (Hz). Signals were abbreviated as s,
singlet; br s, broad singlet; d, doublet; t, triplet; q, quartet;
m, multiplet, dd, doublet of doublets. Silica gel chroma-
tography was performed using a Merck Kieselgel Si 60. Thin
layer chromatography was performed using Merck Kie-
selgel Si 60 F254 plates. Recycling gel permeation chro-
ꢀ
matography was performed at 37 C on a JAI LC-9130G
NEXT using a JAIGEL 2.5H or a JAIGEL 3H column
(
20 ꢂ 600 mm) with chloroform (HPLC grade, ethanol
ꢁ
1
stabilized) as the eluent running at 3.5 mL min . Chiral
analytical HPLC was performed using a Daicel Chiralpak IA
column with either isocratic ethyl acetate/chloroform
(
50:50) or methanol/chloroform (75:25) as the eluent
-
1
running at 0.5 mL min at room temperature (compound
5
lyses were performed at 1.5 mL min using a Macherey-
Nagel Nucleodur C18 or C
3
ꢁ
1
ꢀ
) or 1.0 mL min at ꢁ5 C (compound 8). RP-HPLC ana-
ꢁ
1
8
Gravity column (4.6 ꢂ 100 mm,
m). The mobile phase was composed of 0.1% (v/v) TFA-
O (Solvent A) and 0.1% TFA-CH CN (Solvent B) running
m
H
2
3
the following gradients: 50e100% B over 15 min (System
A), 40e90% B over 20 min (System B), or 50e100% B over
20 min (System C). Monitoring by UV detection was carried
out at 214 nm, 254 nm and 300 nm using a diode array
detector. Semi-preparative purifications of oligomers were
ꢁ1
performed at 4 mL min on a semipreparative HPLC using
Macherey-Nagel Nucleodur HTEC column
21 mm ꢂ 125 mm, 5 m). The mobile phase was the same
a
C
18
(
m
as that for the analytical system, running the following
gradients: 50e100% B over 20 min (System D), 40e90% B
over 15 min (System E), or 10e100% B over 25 min (System
F). Monitoring by UV detection was carried out at 254 nm
and 300 nm using a diode array detector. High resolution
electrospray ionization time of flight (ESI-TOF) mass
spectra were measured in the positive ion mode on a Wa-
ters/Micromass Q-Tof Ultima. X-ray diffraction experiments
were carried out on a high flux RIGAKU FRX rotating anode
ꢀ
Fig. 3. Chiral HPLC separation of P and M helices of compound 8 at ꢁ5 C in
3
MeOH/CHCl (75:25). Expansion of: (a) UV detector trace (254 nm); (b) CD
detector trace (385 nm). Overlaid expansions of isolated P-8 (gray) and M-8
black); (c) UV detector traces (254 nm); (d) CD detector traces (385 nm).
at the Cu Ka wavelength.
(
CCDC-1056802 for monomer 4 contains the supple-
mentary crystallographic data for this paper. These data can
be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/
cif.
4
. Experimental
4
.1. General methods
4.2. Monomer synthesis
Sieber amide resin was purchased from Novabiochem.
Ghosez
reagent
(1-chloro-N,N,2-trimethyl-1-
2-Methoxyethanethiol was commercially available
propenylamine) was purchased from SigmaeAldrich. N,N-
diisopropylethylamine was distilled over calcium hydride.
Analytical grade organic solvents were used for solid phase
while the other 3 thiols [2-(2-methoxyethoxy)ethanethiol,
2-(2-(2-methoxyethoxy)ethoxy)ethanethiol, 2,5,8,11-
tetraoxatridecane-13-thiol] were synthesized according to
literature procedures [22]. Methyl 4-bromo-8-
2 2
synthesis. Anhydrous THF and CH Cl for solution and solid
phase synthesis were dispensed from an MBRAUN SPS-800
nitroquinoline-2-carboxylate was prepared as previously
solvent purification system. HPLC grade acetonitrile and
reported [14(b)]. Fmoc-monomers 1e4 were produced

138
C. Tsiamantas et al. / C. R. Chimie 19 (2016) 132e142
using the same general methodology. This is exemplified
below by the synthesis of compound 1 and its corre-
sponding intermediates:
(1H, dd, J ¼ 7.5, 1.3), 7.69 (1H, dd, J ¼ 8.5, 7.5), 4.04 (3H, s),
3.90 (2H, t, J ¼ 6.2), 3.73e3.61 (10H, m), 3.56e3.51 (2H, m),
13
3.45 (2H, t, J ¼ 6.2), 3.37 (3H, s). C NMR (CDCl
3
): d 165.73,
150.91, 149.46,149.02,128.30, 127.79, 126.99, 124.86, 117.20,
4
.2.1. General procedure for nucleophilic aromatic substitution
72.22, 71.04, 70.94, 70.90, 70.88,70.82, 68.92, 59.32, 53.67,
þ
S [MþH]þ
and 31.88. HRMS (ES ): m/z calcd for C10
H
26
N
2
O
8
4
.2.1.1. Methyl 4-(2-methoxyethylthio)-8-nitroquinoline-2-car-
455.1483 found 455.1493
boxylate. Methyl 4-bromo-8-nitroquinoline-2-carboxylate
2.5 g, 8.0 mmol) and Cs CO (3.9 g, 12.0 mmol, 1.5 equiv)
(
2
3
4.2.2. General procedure for saponification of methyl ester
were suspended in 75 mL anhydrous DMF. 2-
Methoxyethanethiol (815 mg, 8.8 mmol, 1.1 equiv) was
added and the resulting slurry stirred at room temperature
4.2.2.1. 4-(2-Methoxyethylthio)-8-nitroquinoline-2-carboxylic
acid. 4-(2-methoxyethylthio)-8-nitroquinoline-2-carboxy-
for 48 h under N
with brine, extracted with EtOAc and the combined organic
phases were dried over Na SO , filtered, and evaporated.
Recrystallization in DCM/MeOH afforded the title com-
2
. The reaction mixture was then diluted
late (1.8 g, 5.6 mmol) was dissolved in 280 mL THF/H
2
O
(4:1). LiOH$H O (470 mg, 11.2 mmol, 2 equiv) was added
2
2
4
and the reaction was stirred for 45 min at room tempera-
ture. 5% w/v citric acid solution was then added to reach pH
4, THF was evaporated under reduced pressure and the
resulting aqueous mixture was extracted with DCM. The
1
pound as an orange solid (1.8 g, 71%). H NMR (CDCl
8.39 (1H, dd, J ¼ 8.6, 1.3), 8.12 (1H, s), 8.08 (1H, dd, J ¼ 7.5,
.2), 7.69 (1H, dd, J ¼ 8.6, 7.4), 4.04 (3H, s), 3.81 (2H, t,
3
):
d
1
combined organic phases were washed with H
dried over Na SO , filtered and evaporated to yield the title
compound as a yellow solid (1.7 g, 97%). H NMR (CDCl
8.47 (1H, dd, J ¼ 8.6,1.2), 8.21 (1H, dd, J ¼ 7.6,1.1), 8.21 (1H,
s), 7.77 (1H, dd, J ¼ 8.3, 7.6), 3.83 (2H, t, J ¼ 5.9), 3.49 (2H, t,
2
O and brine,
1
3
J ¼ 6.0), 3.44 (2H, t, J ¼ 5.9), 3.44 (3H, s). C NMR (CDCl
3
):
2
4
1
d
128.17, 127.67, 126.92, 124.79, 117.02, 69.91, 59.26, 53.59,
3
):
þ
S [MþH]þ
31.76. HRMS (ES ): m/z calcd for C14
H
15
N
2
O
5
d
3
23.0696 found 323.0702.
1
3
J ¼ 5.9), 3.44 (3H, s). C NMR (CDCl
3
): d 163.53, 153.81,
4
.2.1.2. Methyl 4-(2-(2-methoxyethoxy)ethylthio)-8-nitroquin
148.03,146.48,136.91,128.43,128.25,127.44,126.00,114.76,
þ
oline-2-carboxylate. Synthesized using the general meth-
odology mentioned above. Purification by silica gel chro-
matography (cyclohexane/EtOAc (6:4) to cyclohexane/
EtOAc (4:6)) followed by precipitation in DCM/MeOH
69.70, 59.27, 31.95. HRMS (ES ): m/z calcd for C13
13 2 5
H N O S
[MþH]þ 309.0540 found 309.0551.
4.2.2.2. 4-(2-(2-Methoxyethoxy)ethylthio)-8-nitroquinoline-2-
afforded the title compound as a yellow solid (2.3 g, 78%).
carboxylic acid. Synthesized using the general methodology
1
H NMR (CDCl
.07 (1H, dd, J ¼ 7.4, 1.3), 7.69 (1H, dd, J ¼ 8.5, 7.5), 4.03 (3H,
s), 3.90 (2H, t, J ¼ 6.2), 3.71e3.66 (2H, m), 3.58e3.54 (2H,
3
):
d
8.38 (1H, dd, J ¼ 8.5, 1.3), 8.12 (1H, s),
mentioned above to afford the title compound as a yellow
1
8
solid (1.8 g, 96%). H NMR (CDCl
3
):
d
8.44 (1H, dd, J ¼ 8.6,
1.2), 8.20 (1H, s), 8.19 (1H, dd, J ¼ 7.0, 1.3), 7.75 (1H, dd,
J ¼ 8.6, 7.6), 3.92 (2H, t, J ¼ 5.9), 3.71e3.66 (2H, m),
1
3
m), 3.46 (2H, t, J ¼ 6.3), and 3.38 (3H, s). C NMR (CDCl
3
):
13
d
165.60, 150.74, 149.34, 148.91, 138.73, 128.19, 127.69,
3.59e3.54 (2H, m), 3.49 (2H, t, J ¼ 6.1), 3.37 (3H, s). C NMR
1
26.88, 124.77, 117.10, 72.06, 70.85, 68.85, 59.30, 53.56,
3
(CDCl ): d 163.51, 153.83, 148.02, 146.50, 136.90, 128.45,
þ
S [MþH]þ
31.69. HRMS (ES ): m/z calcd for C16
H
19
N
2
O
6
128.28, 127.39, 125.96, 114.92, 72.03, 70.85, 68.71, 59.26.
þ
S [MþH]þ 353.0802
3
67.0958 found 367.0968.
HRMS (ES ): m/z calcd for C15
H
17
N
2
O
6
found 353.0812.
4
.2.1.3. Methyl 4-(2-(2-(2-methoxyethoxy)ethoxy)ethylthio)-8-
nitroquinoline-2-carboxylate. Synthesized using the general
methodology mentioned above. Purification by silica gel
chromatography (cyclohexane/EtOAc (8:2) to cyclohexane/
4.2.2.3. 4-(2-(2-(2-Methoxyethoxy)ethoxy)ethylthio)-8-nitroquino-
line-2-carboxylic acid. Synthesized using the general meth-
odology mentioned above to afford the title compound as a
1
EtOAc (1:1)) afforded the title compound as a yellow solid
yellow solid (1.9 g, 98%). H NMR (CDCl
3
):
d
8.46 (1H, dd,
1
(
(
4
3
2.3 g, 71%). H NMR (CDCl
3
):
d
8.36 (1H, dd, J ¼ 8.6,1.3), 8.11
J ¼ 8.6, 1.2), 8.24 (1H, s), 8.20 (1H, dd, J ¼ 7.6, 1.2), 7.76 (1H, dd,
1H, s), 8.06 (1H, dd, J ¼ 7.5, 1.3), 7.68 (1H, dd, J ¼ 8.4, 7.5),
J ¼ 8.5, 7.7), 3.93 (2H, t, J ¼ 6.0), 3.74e3.62 (6H, m), 3.55e3.51
1
3
.02 (3H, s), 3.89 (2H, t, J ¼ 6.2), 3.72e3.60 (6H, m),
(2H, m), 3.49 (2H, t, J ¼ 6.0), 3.36 (3H, s). C NMR (CDCl
3
):
13
.54e3.49 (2H, m), 3.44 (2H, t, J ¼ 6.2), 3.35 (3H, s). C NMR
): 165.64, 150.86, 149.38, 148.94, 138.75, 128.21,
d 163.50, 153.95, 148.10, 146.53, 136.96, 128.53, 128.31, 127.40,
(
CDCl
3
d
125.98, 114.98, 72.11, 71.00, 70.81, 68.80, 59.22, 32.02. HRMS
þ
S [MþH]þ 397.1069 found
1
5
27.71, 126.95, 124.81, 117.14, 72.15, 70.98, 70.85, 68.89,
(ES ): m/z calcd for C17
H
21
N
2
O
7
þ
9.27, 53.60, 31.82. HRMS (ES ): m/z calcd for C18
23
H N
2
O
7
S
397.1073.
þ
[MþH] 411.1226 found 411.1226.
4.2.2.4. 4-(2,5,8,11-Tetraoxatridecan-13-ylthio)-8-nitroquino-
4
.2.1.4. Methyl 4-(2,5,8,11-tetraoxatridecan-13-ylthio)-8-nitro-
line-2-carboxylic acid. Synthesized using the general
quinoline-2-carboxylate. Synthesized using the general
methodology mentioned above. Purification by silica gel
methodology mentioned above to afford the title com-
1
pound as a yellow solid (1.6 g, 93%). H NMR (CDCl
3
):
chromatography (cyclohexane/EtOAc (8:2) to cyclohexane/
d
8.43 (1H, d, J ¼ 8.5), 8.20 (1H, s), 8.19 (1H, d, J ¼ 7.3), 7.76
ꢀ
EtOAc (1:1)) followed by crystallization from Et
afforded the title compound as a white solid (2.0 g, 54%). H
NMR (CDCl ):
8.39 (1H, dd, J ¼ 8.6, 1.3), 8.13 (1H, s), 8.07
2
O at 4 C
(1H, t, J ¼ 8.0), 3.94 (2H, t, J ¼ 6.0), 3.75e3.60 (10H, m),
1
13
3.58e3.52 (2H, m), 3.49 (2H, t, J ¼ 6.0), 3.37 (3H, s).
C
3
d
NMR (CDCl ): 163.72, 153.53, 147.99, 146.76, 136.93,
3
d

C. Tsiamantas et al. / C. R. Chimie 19 (2016) 132e142
139
1
7
28.28, 128.15, 127.26, 125.80, 115.05, 71.99, 70.85, 70.71,
2 4
over Na SO filtered and evaporated under reduced pres-
sure. Purification by silica gel chromatography (100% DCM
þ
0.66, 70.55, 68.64, 59.09, 53.58, 31.89. HRMS (ES ): m/z
calcd for C19
H
25
N
2
O
8
S [MþH]þ 441.1326 found 441.1331.
to DCM/MeOH 9:1), followed by crystallization in DCM
1
afforded the title compound as a white solid (1.1 g, 43%). H
4
.2.3. General procedure for reduction of nitro group
NMR (DMSO-d
.93 (2H, d, J ¼ 7.4), 7.80e7.72 (3H, m), 7.67 (1H, t, J ¼ 8.3),
7.47e7.33 (4H, m), 4.62 (2H, d, J ¼ 6.7), 4.45 (1H, t, J ¼ 6.8),
6
): d 13.59 (1H, s), 10.44 (1H, s), 8.06 (1H, s),
7
4
.2.3.1. 8-Amino-4-(2-methoxyethylthio)quinoline-2-carboxylic
13
acid. 4-(2-methoxyethylthio)-8-nitroquinoline-2-carboxy-
lic acid (1.6 g, 5.2 mmol) was dissolved in 375 mL EtOAc/
3.72 (2H, t, J ¼ 6.0), 3.51 (2H, t, J ¼ 6.0), 3.31 (3H, s). C NMR
(DMSO-d ): 165.40, 153.52, 149.98, 144.30, 143.78, 140.89,
6
d
EtOH (4:1), 10% Pd/C (0.16 g, 10% by mass) and NH
VO
4 3
136.42, 135.62, 129.33, 127.85, 127.28, 126.65, 125.23,
(
124 mg, 1.1 mmol, 0.2 equiv) were added and the mixture
120.29, 116.50, 116.05, 114.75, 69.41, 66.54, 58.13, 46.68,
þ
S [MþH]þ
ꢀ
was heated to reflux (bath temperature 95 C). A solution of
NH HCO (15.7 g, 248 mmol, 48 equiv) in 12 mL H O was
30.38. HRMS (ES ): m/z calcd for C28
H
25
N
2
O
5
501.1479 found 501.1478.
4
2
2
then added drop-wise to the reaction mixture over 10 min
and the mixture stirred for 4 h under reflux. The reaction
mixture was cooled to room temperature, EtOAc added and
the resulting solution filtered on Celite. The organic phase
4.2.4.2. 8-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-4-(2-
(2-methoxyethoxy)ethylthio)quinoline-2-carboxylic acid (2).
Synthesized using the general methodology mentioned
was washed with water and brine, dried over Na
filtered, and solvents were evaporated under reduced
pressure to yield the title compound as an orange-red oil,
2
SO
4
,
above to afford the title compound as a white solid (0.96 g,
1
68%). H NMR (DMSO-d
6
):
d
7.99 (1H, s), 7.92 (2H, d, J ¼ 7.2),
7.74 (2H, d, J ¼ 7.3), 7.66 (1H, d, J ¼ 8.1), 7.53 (1H, t, J ¼ 7.8),
7.47e7.32 (4H, m), 4.64 (2H, d, J ¼ 6.1), 4.43 (1H, t, J ¼ 6.2),
3.76 (2H, t, J ¼ 6.2), 3.60e3.55 (2H, m), 3.47e3.42 (2H, m),
which was used directly in the next step without further
1
purification. H NMR (DMSO-d
6
):
d
12.83 (1H, s), 7.90 (1H, s),
1
3
7
.42 (1H, t, J ¼ 8.0), 7.12 (1H, dd, J ¼ 8.2, 1.0), 6.89 (1H, dd,
3.40 (2H, t, J ¼ 6.1), 3.23 (3H, s). C NMR (DMSO-d
6
):
J ¼ 7.8, 1.0), 6.63 (2H, br s), 3.70 (2H, t, J ¼ 6.0), 3.43 (2H, t,
J ¼ 6.0), 3.31 (3H, s).
d
167.67, 152.85, 150.73, 147.84, 143.59, 140.70, 135.79,
135.34, 128.87, 127.63, 127.12, 125.70, 124.96, 121.32, 119.97,
1
16.27, 115.89, 115.05, 69.24, 66.33, 57.85, 54.89, 46.49,
þ
S [MþH]þ
4
.2.3.2. 8-Amino-4-(2-(2-methoxyethoxy)ethylthio)quinoline-2-
30.22. HRMS (ES ): m/z calcd for C30
545.1741 found 545.1750.
H
29
N
2
O
6
1
carboxylic acid. H NMR (DMSO-d
6
):
d
12.83 (1H, s), 7.92 (1H,
s), 7.42 (1H, t, J ¼ 8.0), 7.12 (1H, dd, J ¼ 8.3, 1.1), 6.89 (1H, dd,
J ¼ 7.7,1.1), 6.63 (2H, br s), 3.77 (2H, t, J ¼ 6.1), 3.61e3.56 (2H,
m), 3.48e3.39 (4H, m), 3.23 (3H, s).
4.2.4.3. 8-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-4-(2-
(2-(2-methoxyethoxy)ethoxy)ethylthio)quinoline-2-carboxylic
acid (3). Synthesized using the general methodology
mentioned above. Purification by silica gel chromatography
(100% DCM to DCM/MeOH 92:8) followed by precipitation
4
.2.3.3. 8-Amino-4-(2-(2-(2-methoxyethoxy)ethoxy)ethylthio)
1
quinoline-2-carboxylic acid. H NMR (DMSO-d
6
):
d
7.91 (1H,
s), 7.37 (1H, t, J ¼ 7.9), 7.11 (1H, d, J ¼ 8.0), 6.87 (1H, d,
J ¼ 7.5), 6.45 (2H, br s), 3.77 (2H, t, J ¼ 6.1), 3.62e3.46 (6H,
m), 3.44e3.35 (4H, m), 3.21 (3H, s).
in DCM afforded the title compound as a white solid (1.2 g,
1
67%). H NMR (DMSO-d
6
):
d
13.60 (1H, s), 10.47 (1H, s), 8.38
(1H, br s), 8.08 (1H, s), 7.93 (2H, d, J ¼ 7.2), 7.81e7.72 (3H,
m), 7.67 (1H, t, J ¼ 8.1), 7.47e7.31 (4H, m), 4.62 (2H, d,
J ¼ 6.8), 4.45 (1H, t, J ¼ 6.6), 3.80 (2H, t, J ¼ 6.1), 3.62e3.45
4
.2.3.4. 4-(2,5,8,11-Tetraoxatridecan-13-ylthio)-8-aminoquino-
13
1
(8H, m), 3.40e3.35 (2H, m), 3.31 (2H, br s), 3.20 (2H, s).
C
line-2-carboxylic acid. H NMR (CD
3
OD):
d
8.13 (1H, s),
NMR (DMSO-d
40.79, 136.31, 135.56, 129.20, 127.74, 127.18, 126.58, 125.12,
20.19, 116.35, 115.97, 114.83, 71.22, 69.81, 69.74, 69.59,
6
): d 165.35, 153.41, 149.86, 144.36, 143.67,
7
.43e7.30 (2H, m), 6.98 (1H, dd, J ¼ 7.1, 1.3), 3.88 (2H, t,
1
J ¼ 6.4), 3.72e3.56 (10H, m), 3.54e3.48 (2H, m), 3.43 (2H, t,
J ¼ 6.4).
1
6
þ
8.05, 66.44, 64.89, 57.99, 46.57, 30.47, 15.13. HRMS (ES ):
m/z calcd for
89.2017.
C
H N
32 33 2
O
7
S
[MþH]þ 589.2003 found
4
.2.4. General procedure for Fmoc installation
5
4
.2.4.1. 8-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-4-((2-
4
.2.4.4. 8-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-4-
methoxyethyl)thio)quinoline-2-carboxylic acid (1). 8-Amino-
4
4
(
2,5,8,11-tetraoxatridecan-13-ylthio)-8-aminoquinoline-2-
-(2-methoxyethylthio)quinoline-2-carboxylic acid (1.2 g,
.1 mmol) was dissolved in 22 mL 1,4-dioxane, 73 mL of a
carboxylic acid (4). Synthesized using the general
methodology mentioned above. Purification by silica gel
chromatography (100% DCM to DCM/MeOH 9:1) affor-
ded the title compound as a white solid (1.1 g, 73%). H
NMR (DMSO-d
1
0% w/v aqueous solution of NaHCO
3
was added, and the
mixture was stirred at 0 C (ice-bath) under N . 1.2 g of
Fmoc-Cl (1.2 g, 4.5 mmol, 1.1 equiv) was dissolved in 63 mL
.4-dioxane, and added dropwise via a dropping funnel
ꢀ
2
1
6
): d 10.01 (1H, s), 8.31 (1H, s), 8.25 (1H, s),
.05 (1H, s), 7.89 (2H, d, J ¼ 7.4), 7.74e7.64 (3H, m), 7.58
1
8
under N
2
over approximately 1 h. The mixture was then
ꢀ
(1H, t, J ¼ 7.8), 7.40 (2H, t, J ¼ 7.3), 7.31 (2H, t, J ¼ 7.2), 4.55
stirred at 0 C for a further 1 h and then at rt for 20 h.
Approximately 100 mL H O was then added, and the
2
resulting mixture acidified to pH 6 by portion-wise addi-
tion of 1 M HCl. The mixture was then extracted with DCM
and the combined organic phases washed with brine, dried
(
2H, d, J ¼ 6.4), 4.36 (1H, t, J ¼ 6.6), 3.74 (2H, t, J ¼ 5.8),
13
3
d
1
6
.58e3.54 (14H, m), 3.20 (3H, s). C NMR (DMSO-d ):
153.06, 148.55, 143.61, 140.72, 135.73, 128.87, 128.25,
27.68, 127.15, 126.06, 125.02, 121.33, 120.16, 119.97,

140
C. Tsiamantas et al. / C. R. Chimie 19 (2016) 132e142
1
6
15.97, 115.70, 115.53, 79.16, 71.21, 69.77, 69.73, 69.70,
d
11.43 (1H, s), 11.13 (1H, s), 11.03 (1H, s), 10.99 (3H, s),
þ
9.51, 67.98, 66.38, 57.98, 46.48, 30.40. HRMS (ES ): m/z
10.91 (1H, s), 8.23 (1H, dd, J ¼ 7.0, 2.6), 8.17e8.11 (3H, m),
8.03 (1H, dd, J ¼ 7.8, 1.1), 8.00 (1H, dd, J ¼ 8.4, 1.2), 7.95
(1H, dd, J ¼ 8.5, 1.1), 7.82e7.74 (3H, m), 7.67e7.57 (3H, m),
calcd for
33.2259.
C
34
H
37
N
2
O
8
S
[MþH]þ 633.2265 found
6
7
.56e7.47 (3H, m), 7.47e7.28 (9H, m), 7.22 (1H, d, J ¼ 7.8),
4
.3. General procedure for SPS of octamers
7.11 (1H, d, J ¼ 8.1), 7.07 (1H, s), 7.01 (1H, s), 6.96 (1H, s),
6
.91 (1H, s), 6.88 (1H, s), 6.57 (1H, s), 6.40 (1H, d, J ¼ 4.0),
Octamers 5e8 were produced using the same general
4.18 (1H, d, J ¼ 4.0), 4.08e3.96 (4H, m), 3.93e3.73 (10H,
m), 3.68 (3H, s), 3.66 (3H, s), 3.61 (3H, s), 3.56 (3H,s), 3.55
(3H, s), 3.52 (3H, s), 3.49 (3H, s), and 3.47e3.07 (21H, m).
methodology, exemplified here by the synthesis of com-
pound 5:
1
3
C NMR (CDCl
160.03, 159.96, 159.33, 58.89, 158.82, 154.92, 152.28,
51.34, 150.86, 150.78, 150.63, 150.52, 150.14, 149.89,
149.73, 149.63, 149.36, 147.17, 146.31, 146.20, 146.12, 145.97,
45.56, 145.47, 144.67, 144.51, 137.37, 136.28, 136.10, 136.02,
135.97, 135.64, 135.48, 134.73, 134.20, 133.53, 133.41,
33.32, 133.00, 132.89, 129.15, 128.44, 128.34, 128.22,
127.66, 127.63, 127.56, 127.45, 127.41, 127.35, 127.23, 127.12,
27.02, 126.98, 126.91, 126.86, 126.68, 125.88, 125.82,
25.15, 125.12, 118.86, 118.70, 118.40, 118.22, 117.94, 117.24,
17.09, 116.73, 116.03, 115.63, 114.47, 113.99, 113.23, 112.83,
12.41, 112.25, 112.13, 111.95, 70.71, 70.44, 70.11, 59.47,
3
): d 164.74, 163.72, 163.12, 160.61, 160.51,
4
.3.1. Monomer activation
1
4
.3.1.1. Compound 1-Cl. Compound 1 (49 mg, 0.098 mmol,
1
6
equiv relative to resin loading) was suspended in anhy-
drous CH Cl (2 mL) under N . Ghosez reagent was added
26 L, 0.195 mmol, 2 equiv) and the reaction was stirred for
h at rt under N . Solvents were evaporated under reduced
pressure on a vacuum line (approximately 2 h).
2
2
2
1
(
1
m
2
1
1
1
1
4
.3.1.2. 4-(2-Methoxyethylthio)-8-nitroquinoline-2-carbonyl
chloride. 4-(2-Methoxyethylthio)-8-nitroquinoline-2-carbo-
xylic acid (30.2 mg, 0.098 mmol, 6 equiv) was activated in the
same manner as described above.
5
3
9.45, 59.42, 59.40, 59.34, 59.31, 59.24, 31.70, 31.48, 31.38,
þ
1.27, 31.23. HRMS (ES ): m/z calcd for C104
H
98
N
17
O
18
S
8
þ
[MþH] 2128.5042 found 2128.5109.
4
.3.2. SPS
4
.3.2.2. Compound 6. Synthesized on a 32.5
mmol scale
(
0
50 mg Sieber amide resin with manufacturer's loading:
.65 mmol g ) using the general methodology mentioned
4
.3.2.1. Compound 5. Synthesized on a 16.3
mmol scale
ꢁ
1
(
25 mg Sieber amide resin with manufacturer's loading:
ꢁ
1
above. The crude product was purified by preparative RP-
HPLC (System D) to afford the title compound as a yellow
0
.65 mmol g ). The resin was initially swollen for 1 h in
DMF. Fmoc deprotection: the resin was stirred in a 20% v/v
solution of piperidine in DMF at rt for 10 min, reagents
were removed under vacuum, the resin was washed with
DMF briefly, and treatment was repeated twice. The resin
was then washed thoroughly with DMF. Coupling of
monomer acid chlorides (also the loading method for com-
pounds 5e7): The resin was washed thoroughly with
anhydrous THF, then suspended in 1.3 mL anhydrous THF,
to which anhydrous DIEA (34 mL, 0.196 mmol, 6 equiv) was
added. Compound 1-Cl (assuming complete conversion to
acid chloride, 0.098 mmol, 6 equiv) was dissolved in
2
1
solid (22 mg, 28%). RP-HPLC (System A): R
NMR (CDCl ):
1H, s), 10.99 (1H, s), 10.97 (1H, s), 10.90 (1H, s), 8.27e8.20
t
¼ 18.17 min H
3
d 11.42 (1H, s),11.13 (1H, s),11.03 (1H, s),11.00
(
(
(
(
1H, m), 8.19e8.11 (3H, m), 8.06e8.92 (3H, m), 7.82e7.74
3H, m), 7.68e7.56 (3H, m), 7.55e7.47 (3H, m), 7.46e7.28
8H, m), 7.20 (1H, d, J ¼ 7.2), 7.15e7.05 (3H, m), 7.04 (1H, s),
6
.96 (1H, s), 6.93 (1H, s), 6.88 (1H, s), 6.56 (1H, s) 6.38 (1H,
br s), 4.59 (1H, br s) 4.20e3.97 (14H, m), 3.90e3.60 (m,
5
0H), 3.57 (3H, s), 3.56 (3H, s), 3.55 (3H, s), 3.49 (3H, s), 3.46
þ
(3H, s), 3.44 (3H, s), 3.43 (3H, s), 3.40 (3H, s). HRMS (ES ):
m/z calcd for C120
2
H
130
N
17
O
26
S
8
[MþH]þ 2480.7139 found
2
.6 mL anhydrous THF under N , and 1.3 mL of this solu-
480.7204.
tion (i.e. 3 equiv of acid chloride) was added to the resin
which was then treated with microwaves (50 W, 50 C,
5
ꢀ
min). The resin was washed briefly with anhydrous THF
4.3.2.3. Compound 7. Synthesized on a 32.5
(
0.65 mmol
mentioned above. The crude product was purified by
preparative RP-HPLC (System E) to afford the title com-
pound as a yellow solid (14 mg, 15%). RP-HPLC (System B):
R
s), 11.03 (1H, s), 10.98 (3H, s), 10.89 (1H, s), 8.26e8.19 (1H,
m), 8.18e8.10 (3H, m), 8.07e7.92 (3H, m), 7.82e7.73 (3H,
m), 7.69e7.56 (3H, m), 7.55e7.47 (3H, m), 7.47e7.29 (8H,
m), 7.22e7.18 (1H, m), 7.12 (1H, s), 7.10e7.05 (1H, m), 7.04
(1H, s), 6.96 (1H, s), 6.93 (1H, s), 6.88 (1H, s), 6.56 (1H, s),
6.35 (1H, s), 4.67 (1H, s), 4.19e4.05 (4H, m), 4.00e3.52
(92H, m), 3.48 (6H, s), 3.45 (3H, s), 3.42 (3H, s), 3.41 (3H,
m
mol scale
50 mg Sieber amide resin with manufacturer's loading:
and the process was repeated with the remaining acid
chloride solution. The resin was then thoroughly washed
with anhydrous THF, then DMF. Coupling of the N-termi-
nal nitro-functionalized quinoline monomer 4-(2-
methoxyethylthio)-8-nitroquinoline-2-carbonyl chloride
was carried out in the same manner. Resin cleavage: the
resin was washed thoroughly with DMF, DCM and DCM/
MeOH (1:1), dried and desiccated. It was then suspended
in 2 mL of TFA/DCM (1:1 v/v) and stirred at rt for 1 h. The
resin was removed by filtration and solvents were evap-
orated under reduced pressure to yield the crude product.
This was purified by recycling GPC (due to the limited
solubility under RP-HPLC conditions) and followed by an
ꢁ1
g
)
using the general methodology
1
t
¼ 8.98 min H NMR (CDCl
3
): d 11.42 (1H, s), 11.12 (1H,
þ
additional crystallization in DCM/MeOH to afford the title
compound as a yellow solid (8 mg, 20%). H NMR (CDCl
s), 3.39 (3H, s), 3.37 (3H, s), 3.31 (3H, s). HRMS (ES ): m/z
1
3
):

C. Tsiamantas et al. / C. R. Chimie 19 (2016) 132e142
141
calcd for C136
832.9309.
H
162
N
17
O
34
S
8
[MþH]þ 2832.9236 found
(c) C. Dolain, V. Maurizot, I. Huc, Angew. Chem. Int. Ed. 42 (2003)
737.
5] (a) J. Zhu, R.D. Parra, H. Zeng, E. Skrzypczac-Jankun, X.C. Zeng,
B. Gong, J. Am. Chem. Soc. 122 (2000) 4219;
2
2
[
(
b) B. Gong, Chem. Eur. J. 7 (2001) 4336.
6] (a) B. Gong, Acc. Chem. Res. 41 (2008) 1376;
b) M. Kline, X. Wei, I.J. Horner, R. Liu, S. Chen, S. Chen, K. Yung,
4
.3.2.4. Compound 8. Synthesized on a 16.3
mmol scale
[
(
25 mg Sieber amide resin with manufacturer's loading:
(
ꢁ1
0
.65 mmol g ) using the general methodology mentioned
K. Yamato, Z. Cai, F.V. Bright, X.C. Zeng, B. Gong, Chem. Sci. 6 (2015)
152;
above, with the exception that loading of the first monomer
was carried out using HBTU (18.5 mg, 0.049 mmol, 3 equiv),
and HOBt (7.5 mg, 0.049 mmol, 3 equiv) in the presence of
(
c) T. Hjelmgaard, O. Roy, L. Nauton, M. El-Ghozzi, D. Avignant,
C. Didierjean, C. Taillefumier, S. Faure, Chem. Commun. 50 (2014)
564.
3
DIEA (17
m
L, 0.098 mmol, 6 equiv) with 1 mL DMF as the
[7] (a) H. Zeng, R.S. Miller, R.A. Flowers, B. Gong, J. Am. Chem. Soc. 122
(2000) 2635;
ꢀ
solvent and treated with microwaves (25 W, 70 C, 10 min).
Loading was repeated once. The crude product was purified
by preparative RP-HPLC (System F) and then by recycling
(b) J. Zhu, J.-B. Lin, Y.-X. Xu, X.-B. Shao, X.-K. Jiang, Z.-T. Li, J. Am.
Chem. Soc. 128 (2006) 12307.
[8] H. Jiang, J.-M. L eꢀ ger, I. Huc, J. Am. Chem. Soc. 125 (2003) 3448.
[
9] (a) D. Haldar, H. Jiang, J.-M. L eꢀ ger, I. Huc, Angew. Chem. Int. Ed. 45
GPC to afford the title compound as a yellow solid (7 mg,
(
(
2006) 5483;
1
14%). RP-HPLC (System C): R
t
¼ 11.33 min H NMR (CDCl
3
):
b) Q. Gan, C. Bao, B. Kauffmann, A. Gr eꢀ land, J. Xiang, S. Liu, I. Huc,
d
11.45 (1H, s), 11.14 (1H, s), 11.06 (1H, s), 11.01 (2H, s), 11.00
H. Jiang, Angew. Chem. Int. Ed. 47 (2008) 1715;
c) Y. Ferrand, A.M. Kendhale, J. Garric, B. Kauffmann, I. Huc, Angew.
Chem. Int. Ed. 49 (2010) 1778;
d) J. Shang, Q. Gan, S.J. Dawson, F. Rosu, H. Jiang, Y. Ferrand, I. Huc,
Org. Lett. 16 (2014) 4992.
(
(
(
(
1H, s), 10.91 (1H, s), 8.27 (1H, m), 8.20 (3H, m), 8.11e7.98
3H, m), 7.82 (3H, m), 7.71e7.35 (15H, m), 7.23 (1H, m), 7.19
1H, s), 7.12 (1H, m), 7.08 (1H, s), 7.00 (1H, s), 6.97 (1H, s),
(
[
10] (a) L. Sebaoun, V. Maurizot, T. Granier, B. Kauffmann, I. Huc, J. Am.
6
4
3
C
.92 (1H, s), 6.60 (1H, s), 6.43 (1H, d, J ¼ 3.0), 4.65 (1H, m),
Chem. Soc. 136 (2014) 2168;
.16 (4H, m), 3.98e3.55 (108H, m), 3.47e3.40 (32H, m),
(b) L. Sebaoun, B. Kauffmann, T. Delclos, V. Maurizot, I. Huc, Org.
þ
.30e3.26 (6H, m), 3.17 (2H, m). HRMS (ES ): m/z calcd for
H N O S
152 193 17 42 8
Lett. 16 (2014) 2326.
[MþH]þ 3187.1410 found 3187.1431.
[11] (a) N. Delsuc, T. Kawanami, J. Lefeuvre, A. Shundo, H. Ihara,
M. Takafuji, I. Huc, ChemPhysChem 9 (2008) 1882;
(
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Acknowledgments
M. Takafuji, H. Ihara, I. Huc, Chem. Commun. 48 (2012) 6337.
12] M.L. Singleton, N. Castellucci, S. Massip, B. Kauffmann, Y. Ferrand,
I. Huc, J. Org. Chem. 79 (2014) 2115.
[
[
The authors would like to thank Dr P. Prabhakaran and
Dr. B. Kauffmann for the crystallization and diffraction
measurements of monomer 4, respectively. We would also
like to thank the Servier Research Institute of Medicinal
Chemistry for their assistance in developing monomer
synthesis protocols. This work was supported by the Eu-
ropean Union's Seventh Framework Programme through
Marie Curie actions (FP7-PEOPLE-2010-ITN-264645
DYNAMOL, pre-doctoral fellowship to C.T.) and through the
European Research Council (Grant Agreement Number
ERC-2012-AdG-320892, postdoctoral fellowship to S. D.).
13] (a) N. Delsuc, S. Massip, J.-M. L eꢀ ger, B. Kauffmann, I. Huc, J. Am.
Chem. Soc. 133 (2011) 3165;
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[
(b) J. Buratto, C. Colombo, M. Stupfel, S.J. Dawson, C. Dolain,
B. Langlois d'Estaintot, L. Fischer, T. Granier, M. Laguerre, B. Gallois,
I. Huc, Angew. Chem. Int. Ed. 53 (2014) 883.
ꢀ
ꢀ
ꢀ
ꢀ
[
15] S.J. Dawson, A. Meszaros, L. Petho, C. Colombo, M. Csekei, A. Kotschy,
I. Huc, Eur. J. Org. Chem. (2014) 4265.
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Appendix A. Supporting information
(
S.L. Warriner, A.J. Wilson, ChemBioChem 15 (2014) 1083;
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(f) A. Barnard, J.A. Miles, G.M. Burslem, A.M. Barker, A.J. Wilson,
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