A modular synthetic route to dimeric calixarenes: A new family of DNA major groove binders

Article abstract of DOI:10.1055/s-0030-1259980

We describe here a general strategy for the synthesis of dimeric anilinium/guanidinium calix[4]arenes with aliphatic and heteroaromatic bridges. These compounds display a remarkably high affinity towards double-stranded (ds) DNA and act by a rare mechanism, i.e., insertion into the wide major groove of the nucleic acids. Georg Thieme Verlag Stuttgart New York.

Full text of DOI:10.1055/s-0030-1259980

FEATURE ARTICLE
1193
A Modular Synthetic Route to Dimeric Calixarenes: A New Family of DNA
Major Groove Binders
A
M
odula
r
Synth
.
etic Route to
J
D
imeric
.C
alixarenes Blecking,a W. Hu,a R. Zadmard,b A. Dasgupta,a T. Schrader*a
a
Department of Chemistry, University of Duisburg-Essen, Universitätsstr. 5, 45117 Essen, Germany
Fax +49(201)1834252; E-mail: thomas.schrader@uni-due.de
b
Chemistry and Chemical Engineering Research Center of Iran, P.O. Box 14335-186, Tehran, Iran
Received 24 December 2010; revised 18 February 2011
sembled in such a way that it ends with a carboxylic acid
group at both termini. Finally, both ends of the bridge are
simultaneously coupled to the calixarene heads and all
protecting groups are cleaved (Figure 1). More specifical-
Abstract: We describe here a general strategy for the synthesis of
dimeric anilinium/guanidinium calix[4]arenes with aliphatic and
heteroaromatic bridges. These compounds display a remarkably
high affinity towards double-stranded (ds) DNA and act by a rare
mechanism, i.e., insertion into the wide major groove of the nucleic ly, this is achieved here by triple tert-butoxycarbonyl
acids.
(Boc) protection of the parent tetraaniline/benzylamine
calixarene monomers,4 followed by double amide cou-
Key words: DNA, major groove, sequence selectivity, binding af-
finity, calixarenes, oligopyrroles
pling with the dicarboxylic acid linker. In the final step,
the resulting dimeric protected precursors are converted
into the cationic DNA binders by mild cleavage of all six
Boc groups with trifluoroacetic acid or hydrochloric acid
at ambient temperature. Figure 1 shows an overview of all
new dimeric calixarenes described in this survey.
Introduction
DNA binders represent the majority of all antitumor
agents.1 Most of these recognize the phosphodiester back-
bone, intercalate into the stacked base pairs, or intrude
into the minor groove. To date, however, only very few
artificial major groove binders have been developed, al-
though proteins favor this recognition site, because here
the sequence information of the base pairs is readily ac-
cessible. By serendipity we recently discovered that
dimeric aniliniumcalix[4]arenes display a high affinity to-
wards double-stranded (ds) DNA and were able to eluci-
date their mechanism of binding; inside the spacious
major groove.2 Several other calixarene derivatives have
already been reported, which bind to DNA; some of these
are transfection agents, but they all display different bind-
ing mechanisms, mostly related to the phosphodiester
backbone.3 In the course of this investigation, it became
necessary to develop a versatile, convergent synthetic ac-
cess to this new family of DNA binding agents. Our
present goal is the preparation of derivatives with an ex-
changeable functional bridge which can read the base se-
quence of the complexed DNA fragment, and ultimately
allow the external control of gene expression. We disclose
here our general synthetic strategy and the first hybrid
molecules with oligoheterocyclic bridges.
It is well known that major groove recognition by zinc fin-
ger or lysine zipper proteins employs lysines and argin-
ines for ion-pair-reinforced hydrogen bonds to phosphates
as well as nucleic base heteroatoms.5 We therefore decid-
ed to synthesize calixarene moieties with ammonium as
well as guanidinium functionalities both directly attached
to the benzene ring (aniline series D1–D10) and also sep-
arated by a methylene group (benzylamine series D11,
D12). The respective calix[4]arene monomers can be
readily trifold protected as Boc derivatives or as tetrafold
2-methylisothioureas, if exactly three or four equivalents
of the respective reagents are employed and a careful
chromatographic separation procedure is followed.
Monomers
Schemes 1 and 2 summarize the synthetic pathways to all
monomeric building blocks M1–M5.
Calixarene monomers with ammonium functionalities
M1–M3 are required to prepare all dimers D1–D10 of the
anilino series, interconnected by a broad range of spacers.
M1 is the key monomer; it can be prepared from p-tert-
butyl phenol (1) in five steps; careful control of the reac-
tion conditions allows selective consecutive condensation
and cyclization of p-tert-butylphenol (1) and formalde-
hyde to the calix[4]arene skeleton (Gutsche protocol,6,7
later improved by Biali8). The tetraphenol 2 already re-
sides in the cone conformation and is fourfold O-alkylated
at its lower rim with butyl bromide to give 3.9 At the upper
rim, ipso-nitration yields tetranitro derivative 4, which is
subsequently converted into tetraaniline 5 by catalytic hy-
drogenation.10
Various dimeric cationic calixarenes are accessible by the
same general synthetic avenue: it begins with the synthe-
sis of calix[4]arene monomers carrying four butoxy
groups at their lower rims and three masked cationic func-
tionalities at their upper rims. The fourth aromatic ring
carries a free amine/benzylamine. Next the bridge is as-
SYNTHESIS 2011, No. 8, pp 1193–1204
x
x
.
x
x
.2
0
1
1
Advanced online publication: 31.03.2011
DOI: 10.1055/s-0030-1259980; Art ID: E56410SS
© Georg Thieme Verlag Stuttgart · New York

1194
C. J. Blecking et al.
FEATURE ARTICLE
Biographical Sketches
Caroline Julia Blecking 2005, for a research trainee T. Schrader, where she de-
studied chemistry at the period at the University of veloped major groove bind-
University of Duisburg- Wisconsin, Madison/USA, ers for nucleic acids.
Essen from 2001–2006, and then conducted her
with a short interruption in Ph.D. work in the group of
Wenbin Hu was first en- where he received his M.Sc. group of T. Schrader and is
rolled for pharmacy at degree in chemistry. For his currently synthesizing high-
Beijing University/China doctoral work, he moved to affinity binders for DNA.
(1999–2003), then moved to the University of Duisburg-
Uppsala University/Sweden Essen, where he joined the
Reza Zadmard studied Engineering Research Cen- (2000–2003). During his
chemistry at the Sharif ter of Iran (also Tehran, subsequent postdoctorate,
University of Technology 1995–2000). For his doctor- he discovered the remark-
Tehran/Iran (1987–1995), al studies, he was on leave able affinity of cationic
where he received his M.Sc. and joined the Schrader dimeric calixarenes towards
degree in chemistry, and team at Marburg, to develop nucleic acids. He is current-
was later employed at the self-assembled ionic molec- ly working as a group leader
Chemistry and Chemical ular capsules in water for CCERCI.
Antara Dasgupta began tion for the Cultivation of Amherst, USA, and subse-
her career at Kalyani Uni- Science, Jadavpur, for her quently added a second
versity, India, where she re- doctorate and learned more postdoctoral research stay in
ceived her M.Sc. degree in about processes at mem- the group of T. Schrader,
chemistry in 2001. After an brane interfaces. In 2007, where she developed an en-
interim period as a Project she worked as a postdoctor- tirely artificial signal trans-
Assistant at the Indian Insti- al fellow on drug delivery duction system in liposomes
tute of Chemical Biology, systems in S. Thayumana- (2008–2009).
Kolkata, she joined, in van’s group at the Universi-
2003, the Indian Associa- ty
of
Massachusetts,
Thomas Schrader studied moved to Düsseldorf Uni- served as Associate Profes-
chemistry at Bonn Universi- versity to begin his own re- sor; there he developed new
ty and received his Ph.D. in search associated to the artificial receptors for small
1988 (new synthetic ave- group of G. Wulff. His Ha- biomolecules. In 2006 he
nues towards aminophos- bilitation and venia legendi moved to Essen, where he
phonic acids, W. Steglich). in organic chemistry were now holds a chair in organic
After a postdoctorate at achieved in 1998 on a topic chemistry. His research
Princeton University (USA) that combined asymmetric aims at gaining control over
with E. C. Taylor (total syn- synthesis with supramolec- biological functions by ra-
thesis of antitumor agents ular chemistry. He was sub- tionally designed receptor
based on C-analogues of tet- sequently called to Marburg molecules.
rahydrofolic
acid),
he University (2000), where he
Synthesis 2011, No. 8, 1193–1204 © Thieme Stuttgart · New York

FEATURE ARTICLE
A Modular Synthetic Route to Dimeric Calixarenes
1195
O
O
O
O
H2
N
NH3
HN
NH
NH3
OBu
NH3
OBu
HN
NH
NH3
OBu
n
2
3
3
3
3
OBu
OBu
6 CF3COO
D1: n = 2 D2: n = 4 D3: n = 6 D4: n = 8
OBu
OBu
OBu
8 CF3COO
D5
Cl
Cl
NH2
O
O
NH2
O
O
H2N
NH
HN
NH
HN
NH2
NH
NH3
OBu
NH3
OBu
HN
2
NH3
H3N
3
3
3
3
OBu
OBu
OBu
O
OBu
OBu
OBu
8 CF3COO
D7
D6
O
O
CF3COO
NH3
OBu
HN
NH3
HN
NH
CF3COO
H3N
N
3
NH
3
OBu
OBu
OBu
O
OBu
D8
OBu
O
N
O
HN
O
O
N
N
Cl
H
HN
NH
N
O
NH3
Cl
NH3
2
. CF3COO
NH3
NH
O
O
. CF3COO
NH3
HN
HN
3
3
D9
OBu
OBu
OBu
OBu
3
D11
OBu
OBu
OBu
OBu
O
N
O
N
Cl
Cl
NH2
N
H
HN
N
O
O
O
H2N
H2N
NH2
O
. CF3COO
NH3
NH
. CF3COO
HN
NH
O
NH
NH
2
HN
NH3
HN
D10
3
3
3
OBu
OBu
OBu
OBu
OBu
OBu
OBu
OBu
D12
Figure 1 Structure of different calixarene dimers D1–D12. Note the structural convention underlying all formulas and drawn in square
brackets (the dotted red line indicates a covalent bond).
Titration of 5 with four equivalents of hydrochloric acid resulting mixture of fourfold, threefold, and twofold-Boc-
furnished monomer M3,11 while base-catalyzed treatment protected anilinocalix[4]arenes the desired pure monomer
with 1,3-bis(tert-butoxycarbonyl)-2-methylisothiourea M1 was isolated in good yield after chromatographic sep-
lead to precursor M1a,12 whose hydrolysis (HCl, dioxane) aration (Scheme 1).
afforded tetraguanidine M2. To achieve triple Boc protec-
For the benzylamino series (D11, D12) monomer M4 rep-
tion, tetraaniline 5 was treated with exactly three equiva-
resents the key intermediate. It can be prepared from 26 by
lents of di-tert-butyl dicarbonate (Boc2O).13,14 From the
dealkylation (AlCl3),15a chloromethylation (HCl/HCHO),15b
Synthesis 2011, No. 8, 1193–1204 © Thieme Stuttgart · New York

1196
C. J. Blecking et al.
FEATURE ARTICLE
O
NO2
H
H
HNO3, AcOH
NaH, BuBr
NaOH, 120 °C, 2 h
CH2Cl2
0 °C to r.t., 2.5 h
66%
4
4
4
DMF, 70 °C, 19 h
73%
Ph2O, r.t., 1 h
reflux, 4 h
56%
OBu
OH
OBu
OH
4
1
3
2
NHBoc
OBu
NH2
NH2
Boc2O
H2, Pd/C
(3 equiv)
CH2Cl2
r.t., 18 h
56%
4
MeOH
r.t., 24 h
quant.
3
OBu
OBu
5
M1
NH2
NBoc
Cl
SMe
H2N
BocHN
NH
NH
(4 equiv)
NHBoc
BocN
Et3N, AgNO3
HCl, dioxane
CH2Cl2, r.t., 48 h
91%
4
4
r.t., 24 h
93%
OBu
OBu
NH2
M1a
M2
4
NH3
Cl
OBu
HCl
5
CH2Cl2, r.t., 24 h
86%
4
OBu
M3
Scheme 1 Synthesis of the monomers M1–M3 (anilino series)
and conversion into the amine (NaN3, H2, Pd/C).12 In anal-
ogy to 5, monomer M4 could be tetraguanidinylated to
Bridges
yield tetraguanidine monomer M4a. Selective trifunction- In order to connect two calixarene monoamines, all bridg-
alization was again problematic and led to mixtures, from es are assembled in such a way, that they ended in two
which the desired protected trisguanidine monomer M5 a,w-terminal carboxylic acid groups. Simple alkyl bridges
was isolated in moderate yield (Scheme 2).
were synthesized from a,w-dicarboxylic acids by conver-
sion into their respective diacid dichlorides (D1–D4, D7,
Cl
N3
O
H
H
AlCl3
61%
NaH, BuBr
52%
NaN3
99%
NaOH, 120 °C, 2 h
HCHO, HCl
83%
Ph2O, r.t., 1 h
reflux, 4 h
56%
4
4
4
4
4
OH
OH
OBu
OBu
2c
OH
OBu
2d
1
2
2a
2b
Cl
H2N
NH2
SMe
Cl
NH3
NH
N3
(4 equiv)
1)
BocN
NHBoc
36%
H2, Pd/C
HCl, r.t., 12 h
2) HCl, r.t., 12 h, 72%
4
4
99%
4
OBu
M4
OBu
M4a
OBu
2d
NBoc
NH
BocHN
SMe
NH2
BocN
NHBoc
(3 equiv)
12%
3
OBu
OBu
M5
Scheme 2 Synthesis of the monomers M4–M5 (benzylamine series)
Synthesis 2011, No. 8, 1193–1204 © Thieme Stuttgart · New York

FEATURE ARTICLE
A Modular Synthetic Route to Dimeric Calixarenes
1197
D11, D12).16–17 In order to introduce additional positive For the longer bridges, tripyrrole amino acid P6 was ob-
charges into the bridge, two new free a,w-dicarboxylic tained as the key intermediate from the two monomers P1
acids were prepared in short routes, which carry an N- and P1a following a modified published four-step syn-
Boc-protected secondary amine in their chain (L5) or a thetic route:25 It consists of two iterative rounds of EDCl
primary amino group in the a-position (L6).19,20 These coupling, followed by Boc removal (HCl). P6 was then
were coupled to the triprotected tetraanilino calix[4]arene equipped with an isophthalate or malonate spacer in a
M1 with HCTU/Cl-HOBt; the additional Boc groups similar way as P1. Final base hydrolysis gave the tripyr-
were later removed during the final acidic deprotection role bridges P8 and P10 as a,w-dicarboxylic acids
step (D5, D6, D8–D10).
(Scheme 3).
At a more advanced stage, the bridging unit was equipped
with sequence-selective DNA minor groove binders used
by the Dervan group. Oligomeric five-membered hetero-
cyclic amino acids adopt a crescent shape which is fully
complementary to the curvature of DNA’s minor, and also
major, groove.21–26 As a prototype we therefore synthe-
sized a model unit which is selective for ATATAT in the
minor groove, and added on one end a short spacer which
ends again in a carboxylic acid. Specifically, three pyrrole
bridges: one monopyrrole P3, and two tripyrroles P8 and
P10 were synthesized (Scheme 3).
Dimers
The two final steps of each modular synthesis require dou-
ble peptide bond formation between the triBoc-protected
calixarene’s free anilino or benzylamino group and the
bridge’s two terminal carboxylic acids and final removal
of all protecting groups. This was realized in two ways: ei-
ther diacid dichlorides were directly used to acylate the
free amines under DMAP catalysis (D1–D4, D11, D12),
or free dicarboxylic acids were activated by peptide cou-
pling reagents, the best being Cl-HOBt/HCTU (D5 and
D6) and EDCI/DMAP (D8–D10). Guanidinylated dimer
D7 was an exception: its six guanidine functions were all
The monopyrrole bridge was obtained directly from
methyl 3-aminopyrrolecarboxylate P1 by coupling with
monomethyl glutarate monochloride and base hydrolysis.
⋅HCl
H2N
O
O
Cl
OMe
i-Pr2NEt, DMAP
H
H
OH
O
OMe
O
HO
N
MeO
N
OMe
NaOH, MeOH
60 °C, 48 h
89%
N
CH2Cl2–DMF (2:1), r.t., 24 h
78%
O
O
O
O
N
O
N
Me
P3
P2
P1
Me
Me
⋅HCl
H2N
⋅HCl
H2N
BocHN
BocHN
OMe
O
OMe
EDCl, DMAP
H
H
4 M HCl
N
OH
OMe
N
+
DMF, r.t., 24 h
76%
O
EtOAc, r.t., 24 h
97%
N
N
N
N
Me
N
N
O
O
O
O
Me
Me
Me
Me
P1
Me
P1a
P4
P4a
⋅HCl
H2N
BocHN
MeO
MeO
N
P1a (1 equiv)
EDCl, DMAP
H
O
H
O
4 M HCl
N
N
N
N
HN
HN
N
DMF, r.t., 24 h
80%
EtOAc, r.t., 24 h
quant.
Me
Me
Me
Me
O
O
N
N
O
O
Me
Me
P5
P6
MeO
HO
O
O
O
O
MeO
N
HO
N
HO
OMe
O
O
NH
NH
EDCl, DMAP
NaOH, MeOH
O
HN
O
HN
H
Me
H
Me
60 °C, 48 h
95%
DMF, r.t., 24 h
64%
N
N
N
N
.HCl
H2N
O
O
N
N
O
Me
O
Me
MeO
N
Me
Me
P7
P8
O
H
N
HN
O
N
Me
Me
O
N
MeO
HO
O
MeO
N
HO
N
O
O
Me
O
O
P6
O
NH
NH
Cl
OMe
i-Pr2NEt, DMAP
O
HN
O
HN
H
H
NaOH, MeOH
Me
Me
N
N
CH2Cl2–DMF, r.t., 24 h
54%
60 °C, 48 h
66%
N
N
O
O
N
N
Me
O
Me
O
Me
Me
P9
P10
Scheme 3 Synthesis of the mono- and tripyrrole spacers P3, P8, and P10
Synthesis 2011, No. 8, 1193–1204 © Thieme Stuttgart · New York

1198
C. J. Blecking et al.
FEATURE ARTICLE
introduced at the dimer stage due to massive side reac-
tions in the attempted bridging step.
OH
OH
O
H
O
A problem of intramolecular fragmentation was encoun-
tered during the attempted coupling between the linkers
carrying a dicarboxylic spacer on their one end with more
than one CH2 group and the calixarene monoamines,
which resulted in side reactions. The proposed mechanism
of the side-chain reactions is shown in Scheme 4; a poten-
tial solution lies in replacement by the succinylsarcosyl
linker.27
N
Pyr
N
Calix
N
H
– H2O, Pyr—NH2
Calix
n
O
O
H
N
O
Calix
O
n
OH
O
N
H
O
Calix
N
Pyr
O
– H2O, Pyr—NH2
Calix
n
N
H
O
O
OH
The last reaction in each dimer synthesis consisted in mild
trifluoroacetic acid or hydrochloric acid treatment at am-
bient temperature, which resulted in complete cleavage of
all protecting groups and released the final products as
their ammonium or guanidinium trifluoroacetates and ha-
lides, respectively (Scheme 5).
O
O
H
O
N
n = 1, 2
Calix
O
n
– Calix NH2
O
O
The two types of bridged calix[4]arene dimers were found
to differ in their physical properties to a great extent.
While monomers and dimers in the anilino series are only
soluble in a 1:1 mixture of methanol and aqueous buffer,
all compounds of the benzylamine series display high sol-
Calix = calix[4]arene
Pyr = pyrrole
Scheme 4 Side-chain reactions during amide coupling, leading to
intramolecular fragmentation
O
O
O
O
CF3COO
NH3
CF3COO
NH3
Cl
Cl
1)
n
NHBoc
NH2
HN
NH
n
i-Pr2NEt, DMAP, r.t., 24 h
95%
2) TFA, r.t., 24 h
98%
3
3
3
OBu
OBu
OBu
OBu
O
OBu
OBu
M1
D1–D4
NH2
Cl
Cl
O
O
O
NH2
CF3COO
NH3
CF3COO
SMe
HN
NH
NH3
H2N
NH
HN
NH
HN
NH2
(6 equiv)
NHBoc
BocN
Et3N, AgNO3
2
2
HCl
CH2Cl2–DMF, r.t., 48 h
71%
dioxane
r.t., 24 h
99%
3
3
3
3
OBu
OBu
OBu
OBu
OBu
OBu
OBu
OBu
D7
D1
1) P3, P8 or P10
NHBoc
OBu
NH2
OBu
1) L5 or L6
EDCl, DMAP
Cl-HOBt, HCTU, i-Pr2NEt
CH2Cl2–DMF, r.t., 24 h
CH2Cl2–DMF, r.t., 48 h
20–64%
77–80%
D8–D10
D5, D6
2) TFA, CH2Cl2, r.t., 24 h
99%
2) TFA, CH2Cl2, r.t., 24 h
96%
3
M1
O
O
O
O
Cl
HN
NH
NH3
Cl
NHBoc
NH2
NH3
2
1)
Cl
Cl
2
Et3N, r.t., 1 h
64%
2) HCl, r.t., 16 h
85%
3
3
3
OBu
OBu
OBu
OBu
OBu
OBu
D11
M4b
Cl
Cl
O
O
H2N
H2N
NH2
NBoc
NH2
BocHN
O
O
HN
NH
NH
NH
2
NH
NH2
Cl
Cl
1)
2
Et3N, r.t., 1 h
66%
2) HCl, r.t., 16 h
85%
3
3
3
OBu
OBu
OBu
OBu
OBu
OBu
D12
M5
Scheme 5 Synthesis of the dimers D1–D12
Synthesis 2011, No. 8, 1193–1204 © Thieme Stuttgart · New York

FEATURE ARTICLE
A Modular Synthetic Route to Dimeric Calixarenes
1199
HRMS (ESI): m/z [M + H]+ calcd for C88H133N12O20: 1667.9754;
found: 1677.9792; m/z [M + Na]+ calcd for C88H132N12NaO20:
1699.9573; found: 1699.9569.
ubility of more than 1 mM in pure aqueous buffer, even at
physiological salt load (150 mM). Consequently, the re-
spective dimers D11 and D12 of the benzylamine series
display a superior affinity towards nucleic acids over all
anilino-type dimers D1–D10.
25,26,27,28-Tetrabutoxy-5,11,17,23-tetraguanidinium-
calix[4]arene Tetrachloride Salt (M2)
To a soln of M1a (168 mg, 0.10 mmol) in 1,4-dioxane (10 mL),
concd HCl (5 mL) was added dropwise. The mixture was stirred at
r.t. for 24 h. The solvent was removed under reduced pressure. The
crude product was dissolved in MeOH (1 mL) and EtOAc (5 mL)
and filtered. The solvents were removed under reduced pressure to
give M2 (102 mg, 0.1 mmol, 93%) as an off-white solid; mp >300
°C.
1H NMR (500 MHz, CD3OD): d = 1.05 (t, J = 7.4 Hz, 12 H, CH3),
1.52 [sext, J = 7.6 Hz, 8 H, O(CH2)2CH2CH3], 1.98 (quint, J = 7.5
Hz, 8 H, OCH2CH2CH2CH3), 3.31 (m, 4 H, aryl-CH2), 3.99 (t,
J = 7.4 Hz, 8 H, OCH2), 4.52 (d, J = 13.2 Hz, 4 H, aryl-CH2), 6.69
(s, 8 H, Haryl).
Outlook
In conclusion, we have described a modular general pro-
tocol for the synthesis of new monomeric and dimeric
calixarene derivatives with ammonium and guanidinium
groups at the upper rims. Their flexible architecture al-
lows them to specifically insert into the wide major
groove of DNA, where they bind to the nucleic bases by
means of multiple hydrogen bonds, reinforced by ion pair
formation with the phosphate backbone. Numerous bind-
ing studies demonstrate their high affinity and conforma-
tional preference for B-DNA, rendering them well-suited
drug candidates for a potential interference with gene ex-
pression. Preliminary antiproliferative studies with tumor
13C NMR (125.7 MHz, CD3OD): d = 14.6, 20.6, 31.8, 33.7, 76.7,
126.7, 130.0, 137.8, 157.2, 157.9.
HRMS (ESI): m/z [M + H]+ calcd for C48H69N12O4: 877.5559;
found: 877.5570.
cell lines already produced IG50 values in the low micro- N,N¢-Bis{11,17,23-tris[2,3-bis(tert-butoxycarbonyl)guanidino]-
25,26,27,28-tetrabutoxycalix[4]aren-5-yl}hexanediamide (D7a)
A soln of N,N¢-bis{11,17,23-triamino-25,26,27,28-tetrabutoxy-
calix[4]aren-5-yl}hexanediamide hexakis(trifluoroacetate) (D1,
261 mg, 0.118 mmol) in anhyd CH2Cl2–DMF (1:1, 40 mL) was
treated with Et3N (330 mL), AgNO3 (127 mg, 0.755 mmol), and 1,3-
bis(tert-butoxycarbonyl)-2-methylisothiourea (206 mg, 0.708 mmol)
and stirred at r.t. for 48 h. The resulting suspension was filtered off
and the filtrate was concentrated in vacuo. The residue was purified
by flash column chromatography (silica gel, EtOAc–cyclohexane,
3:1) to give D7a (250 mg, 0.084 mmol, 71%) as a pale-yellow solid;
mp 393 °C; Rf = 0.98 (EtOAc–cyclohexane, 3:1).
1H NMR (500 MHz, CDCl3): d = 0.97 (m, 24 H, CH3), 1.25 [m, 16
H, O(CH2)2CH2CH3], 1.50 [m, 112 H, C(CH3)3, NHC(O)CH2CH2],
1.82 [m, 20 H, OCH2CH2CH2CH3, NHC(O)CH2], 3.09 (m, 8 H,
aryl-CH2), 3.64 (m, 8 H, OCH2), 4.01 (m, 8 H, OCH2), 4.37 (m, 8
H, aryl-CH2), 6.14 (s, 2 H, Haryl), 6.39 (s, 2 H, Haryl), 7.20 (s, 4 H,
Haryl), 7.32 (s, 4 H, Haryl), 7.52 (s, 2 H, Haryl), 7.71 (s, 2 H, Haryl), 9.50
(s, 2 H, NH), 10.22 (s, 6 H, NH), 11.70 (s, 6 H, NH).
molar range. We are currently synthesizing a whole fami-
ly of oligoheterocycle-bridged new calixarene dimers,
along the synthetic path outlined above (D8–D10). These
will be thoroughly examined in studies directed at specific
binding to DNA strands of a predictable base sequence.
All reagents were purchased at highest commercial grade and used
as supplied. All solvents were freshly distilled. Anhydrous solvents
were distilled from the following drying agents: MeCN (CaH2),
CH2Cl2 (CaH2), and MeOH (Mg). Reactions were monitored by
TLC with Merck silica gel 60 F254 plates. Silica gel 60 for flash
chromatography (particle size 230–400 mesh) was supplied by
Merck. Yields refer to chromatographically and spectroscopically
pure compounds unless otherwise noted. Melting points were deter-
mined on a Melting Point B-540 from Büchi and are uncorrected.
1H and 13C NMR spectra were recorded at 300 K on a Bruker DMX
300 or DRX 500 spectrometer. Chemical shifts are reported as d
values relative to internal TMS. 13C NMR spectra are broadband de-
coupled and calibrated on the particular solvent signal. LR-MS and
HRMS (ESI) were recorded on a Bruker BioTOF III spectrometer.
13C NMR (125.6 MHz, CDCl3): d = 14.1, 14.3, 14.3, 14.6, 19.2,
19.7, 26.9, 28.2, 28.3, 28.4, 31.4, 31.5, 31.9, 32.1, 32.6, 36.1, 74.9,
83.5, 122.2, 122.4, 123.0, 129.0, 130.7, 131.1, 133.4, 133.7, 136.2,
153.3, 153.5, 155.0, 163.8, 167.9, 171.6.
HRMS (ESI): m/z [M + Na]+ calcd for C95H194N10NaO26:
1594.9895; found: 1593.4728.
5,11,17,23-Tetrakis[2,3-bis(tert-butoxycarbonyl)guanidino]-
25,26,27,28-tetrabutoxycalix[4]arene (M1a)
A
soln of 5,11,17,23-tetraamino-25,26,27,28-tetrabutoxy-
calix[4]arene (5, 200 mg, 0.28 mmol), AgNO3 (202 mg,
1.19 mmol), 1,3-bis(tert-butoxycarbonyl)-2-methylisothiourea
N,N¢-Bis{25,26,27,28-tetrabutoxy-11,17,23-triguanidinium-
calix[4]aren-5-yl}hexanediamide Hexachloride (D7)
(325 mg, 1.12 mmol), and Et3N (0.17 mL) in anhyd CH2Cl2 (25
mL) was stirred at r.t. for 48 h. The formed precipitate was filtered
off. The filtrate was concentrated in vacuo. The residue was purified
by flash column chromatography (silica gel, EtOAc–cyclohexane,
3:1) to give M1a (429 mg, 0.26 mmol, 91%) as a light orange solid;
mp 395 °C; Rf = 0.9 (EtOAc–cyclohexane, 3:1).
1H NMR (500 MHz, CDCl3): d = 0.98 (t, J = 7.7 Hz, 12 H, CH3),
1.44–1.47 [m, 80 H, O(CH2)2CH2CH3, C(CH3)3], 1.89 (quint,
J = 7.6 Hz, 8 H, OCH2CH2CH2CH3), 3.13 (d, J = 13.1 Hz, 4 H, aryl-
CH2), 3.84 (t, J = 7.5 Hz, 8 H, OCH2), 4.39 (d, J = 13.1 Hz, 4 H,
aryl-CH2), 6.90 (s, 8 H, Haryl), 9.81 (s, 4 H, NH), 11.59 (s, 4 H, NH).
To a soln of D7a (61 mg, 0.02 mmol) in 1,4-dioxane (10 mL), con-
cd HCl (6 mL) was added dropwise. After stirring at r.t. for 24 h, the
solvent was removed under reduced pressure. The resulting residue
was treated with EtOAc (5 mL) and the solvent was removed once
again. Compound D7 (40 mg, 0.02 mmol, 99%) was obtained as a
pale-brown solid; mp >350 °C.
1H NMR (500 MHz, CD3OD): d = 1.05 (m, 24 H, CH3), 1.49 [m, 8
H, O(CH2)2CH2CH3], 1.54 [m, 8 H, O(CH2)2CH2CH3], 1.72 [m, 4
H, NHC(O)CH2CH2], 1.97 (m, 16 H, OCH2CH2CH2CH3), 2.41 [m,
4 H, NHC(O)CH2], 3.23 (d, J = 14.3 Hz, 4 H, aryl-CH2), 3.29 (d,
J = 14.3 Hz, 4 H, aryl-CH2), 3.94 (m, 12 H, OCH2), 4.02 (t, J = 7.1
Hz, 4 H, OCH2), 4.49 (dd, J = 14.2 Hz, 8 H, aryl-CH2), 6.60 (br,
4 H, Haryl), 6.61 (br, 4 H, Haryl), 6.74 (s, 4 H, Haryl), 7.04 (s, 4 H,
Haryl).
13C NMR (125.7 MHz, CDCl3): d = 14.5, 19.4, 28.1, 31.5, 32.2,
75.2, 79.2, 83.1, 123.1, 130.8, 134.8, 154.1, 163.7, 171.2, 171.6.
Synthesis 2011, No. 8, 1193–1204 © Thieme Stuttgart · New York

1200
C. J. Blecking et al.
FEATURE ARTICLE
13C NMR (125.6 MHz, CD3OD): d = 14.6, 20.6, 20.8, 26.6, 31.8,
32.1, 33.6, 33.8, 37.7, 76.5, 76.8, 122.3, 126.5, 126.7, 129.8, 133.7,
134.3, 136.4, 137.6, 138.1, 154.6, 157.2, 157.5, 157.9, 158.1, 174.3.
HRMS (ESI): m/z [M + Na]+ calcd for C100H138N20NaO10:
1803.0827; found: 1803.7475.
1H NMR (300 MHz, DMSO-d6): d = 8.39 (br s, 18 H, Benzal-
NH3Cl), 7.18 (s, 4 H, HAryl), 7.08 (s, 4 H, HAryl), 7.01 (s, 4 H, HAryl),
6.75 (s, 4 H, HAryl), 4.40 (d, J = 12.25 Hz, 4 H, ArCH2Ar), 4.37 (d,
J = 12.27 Hz, 4 H, ArCH2Ar), 3.96 (br s, 4 H, ArCH2N), 3.87 (br s,
16 H, ArOCH2), 3.78 (m, 12 H, ArCH2N), 3.24 (d, 4 H, ArCH2Ar),
3.19 (d, 4 H, ArCH2Ar), 2.21 (m, 4 H, NCOCH2), 1.92 (m, 16 H,
ArOCH2CH2), 1.47 (m, 20 H, NCOCH2CH2, ArOCH2CH2CH2),
1.02 (t, 24 H, ArOCH2CH2CH2CH3).
13C NMR (75 MHz, DMSO-d6): d = 172.11, 155.98, 155.71,
154.43, 134.80, 134.64, 134.19, 133.68, 133.05, 129.40, 129.22,
127.88, 127.76, 127.31, 74.86, 74.70, 41.72, 35.09, 31.86, 31.79,
29.94, 25.16, 18.82, 18.76, 13.91,
5-(Aminomethyl)-25,26,27,28-tetrabutoxy-11,17,23-tris{[(tert-
butoxycarbonyl)amino]methyl}calix[4]arene (M4b)
5,11,17,23-Tetrakis(aminomethyl)-25,26,27,28-tetrabutoxy-
calix[4]arene tetrahydrochloride (M4, 1.0 g, 1.10 mmol) was dis-
solved in a mixture of anhyd MeOH (10 mL) and Et3N (1 mL).
Boc2O (0.72 g, 3.30 mmol) was added to the soln. The mixture was
stirred at r.t. for 18 h. Subsequently, MeOH was removed in vacuo,
and the residue was purified by flash column chromatography (sili-
ca gel, CH2Cl2–MeOH, 100:1); yield: 0.25 g (21%).
HRMS (ESI): m/z [M + H]+ calcd for C102H143N8O10: 1641.0954;
found: 1641.1108.
1H NMR (300 MHz, CDCl3): d = 6.60 (s, 2 H, HAryl), 6.55 (s, 2 H,
HAryl), 6.50 (s, 2 H, HAryl), 6.48 (s, 2 H, HAryl), 4.39 (d, J = 13.09 Hz,
2 H, ArCH2Ar), 4.38 (d, J = 13.07 Hz, 2 H, ArCH2Ar), 4.01 (br s, 4
H, ArCH2N), 3.92 (br s, 2 H, ArCH2N), 3.87 (m, J = 7.37 Hz, 4 H,
ArOCH2), 3.82 (m, 4 H, ArOCH2), 3.72 (t, J = 4.79 Hz, 2 H,
ArCH2N), 3.09 (d, 2 H, ArCH2Ar), 3.08 (d, 2 H, ArCH2Ar), 1.87
(m, 8 H, ArOCH2CH2), 1.43–1.45 [m, 35 H, ArOCH2CH2CH2,
C(CH3)3], 0.98 (t, 12 H, ArOCH2CH2CH2CH3).
13C NMR (75 MHz, CDCl3): d = 156.18, 156.01, 155.85, 155.44,
135.39, 135.24, 134.91, 134.80, 132.15, 132.10, 127.43, 127.41,
126.90, 126.87, 75.09, 75.05, 75.00, 72.32, 32.37, 32.32, 32.25,
31.09, 28.57, 28.49, 19.45, 19.38, 14.16, 14.14.
5-(Aminomethyl)-11,17,23-tris{[2,3-bis(tert-butoxycarbon-
yl)guanidino]methyl}-25,26,27,28-tetrabutoxycalix[4]arene
(M5)
5,11,17,23-Tetrakis(aminomethyl)-25,26,27,28-tetrabutoxy-
calix[4]arene tetrahydrochloride (M4, 0.091 g, 0.1 mmol) was dis-
solved in the mixture of anhyd MeOH (10 mL) and Et3N (1 mL).
1,3-Bis(tert-butoxycarbonyl)-2-methylisothiourea
(0.087 g,
0.3 mmol) was added to the soln followed by AgNO3 (0.11 g,
0.65 mmol). The mixture was stirred at r.t. for 24 h. The catalyst
was filtered off over Celite and the soln was evaporated to dryness.
The residue was purified by flash column chromatography (silica
gel, CH2Cl2–cyclohexane, 80:20); yield: 0.018 g (12%); mp >300
°C.
1H NMR (300 MHz, CDCl3): d = 11.52 (s, 2 H, BocNH), 11.48 (s,
1 H, BocNH), 11.44 (s, 1 H, BocNH), 8.76 (s, 1 H, Benzal-NH),
8.47 (s, 2 H, Benzal-NH), 8.05 (s, 1 H, Benzal-NH), 6.87 (s, 2 H,
HAryl), 6.84 (s, 2 H, HAryl), 6.30 (s, 2 H, HAryl), 6.26 (s, 2 H, HAryl),
4.45 (d, J = 13.08 Hz, 4 H, ArCH2Ar), 4.01 (m, 2 H, ArCH2N), 3.73
(m, 6 H, ArCH2N, ArOCH2), 3.62 (m, 8 H, ArCH2N, ArOCH2),
3.10 (d, 4 H, ArCH2Ar), 1.89 (m, 8 H, ArOCH2CH2), 1.46–1.51 [m,
62 H, ArOCH2CH2CH2, C(CH3)3], 0.98 (m, 12 H,
ArOCH2CH2CH2CH3).
13C NMR (75 MHz, CDCl3): d = 163.77, 163.62, 156.24, 155.92,
155.53, 153.47, 153.26, 153.08, 137.02, 136.48, 136.18, 134.18,
133.68, 130.51, 130.05, 83.54, 83.02, 82.86, 79.49, 79.25, 79.14,
75.20, 75.17, 75.02, 72.51, 69.12, 61.98, 53.55, 45.05, 40.46, 29.14,
28.89, 28.54, 28.45, 28.20, 27.74, 27.69, 27.48, 19.66, 19.26, 14.75,
14.65, 13.65.
HRMS (ESI): m/z [M + Na]+ calcd for C81H122N10NaO16:
1513.8932; found: 1513.8998; [M + H]+ calcd for C81H123N10O16:
1491.9113; found: 1491.9163.
HRMS (ESI): m/z [M + Na]+ calcd for C63H92N4NaO10: 1087.6706;
found: 1087.6785; [M + H]+ calcd for C63H93N4O10: 1065.6886;
found: 1065.6972.
N,N¢-Bis[(25,26,27,28-tetrabutoxy-11,17,23-tris{[(tert-butoxy-
carbonyl)amino]methyl]}calix[4]aren-5-yl)methyl]hexane-
diamide (D11a)
Calix[4]arene M4b (250 mg, 0.235 mmol) was dissolved in the
mixture of anhyd CH2Cl2 (10 mL) and Et3N (1 mL). Adipic acid
dichloride (21.5 mg, 0.117 mmol) was added to the soln. The mix-
ture was stirred at r.t. for 1 h and subsequently evaporated to dry-
ness. The resulting residue was purified by flash column
chromatography (silica gel, CH2Cl2–MeOH, 100:1); yield: 0.17 g
(64%).
1H NMR (300 MHz, CDCl3): d = 6.49–6.53 (m, 16 H, HAryl), 4.38
(d, J = 13.20 Hz, 8 H, ArCH2Ar), 4.37 (d, J = 12.96 Hz, 8 H,
ArCH2Ar), 4.11 (br s, 4 H, ArCH2N), 3.96 (br s, 12 H, ArCH2N),
3.84 (m, 16 H, ArOCH2), 3.08 (d, 16 H, ArCH2Ar), 2.27 (m, 4 H,
NCOCH2), 1.86 (m, 16 H, ArOCH2CH2), 1.73 (m, 4 H,
NCOCH2CH2), 1.44–1.46 [m, 70 H, ArOCH2CH2CH2, C(CH3)3],
0.98 (t, 12 H, ArOCH2CH2CH2CH3).
13C NMR (75 MHz, CDCl3): d = 172.91, 156.09, 156.02, 155.93,
135.12, 132.13, 127.28, 79.30, 79.25, 75.04, 70.30, 68.78, 64.28,
54.83, 53.53, 50.83, 44.33, 42.84, 36.25, 32.33, 31.12, 31.07, 29.80,
28.58, 27.44, 25.55, 19.44, 14.17.
N,N¢-Bis(11,17,23-Tris{[2,3-bis(tert-butoxycarbonyl)guanidi-
no]methyl}-25,26,27,28-tetrabutoxycalix[4]aren-5-ylmeth-
yl}hexanediamide (D12a)
Calix[4]arene M5 (0.018 g, 0.012 mmol) was dissolved in a mix-
ture of anhyd CH2Cl2 (10 mL) and Et3N (1 mL). Adipic acid dichlo-
ride (1.1 mg, 0.006 mmol) was added to the soln. The mixture was
stirred at r.t. for 1 h and subsequently evaporated to dryness. The re-
sulting residue was purified by flash column chromatography (silica
gel, CH2Cl2–cyclohexane, 20:80); yield: 0.012 g (66%).
HRMS (ESI): m/z [M + Na]+ calcd for C132H190N8NaO22:
2263.3920; found: 2263.3994; [M + H]+ calcd for C132H191N8O22:
2241.4100; found: 2241.4260.
1H NMR (300 MHz, CDCl3): d = 11.48 (s, 4 H, BocNH), 11.46 (s,
2 H, BocNH), 8.44 (s, 2 H, Benzal-NH), 8.35 (s, 2 H, Benzal-NH),
8.29 (s, 2 H, Benzal-NH), 8.20 (s, 2 H, Benzal-NH), 6.64 (s, 8 H,
N,N¢-Bis{[11,17,23-tris(aminomethyl)-25,26,27,28-tetrabutoxy-
calix[4]aren-5-yl]methyl}hexanediamide Hexahydrochloride
(D11)
Diamide D11a (0.17 g, 0.07 mmol) was dissolved in anhyd MeOH
(10 mL). To this soln was added 1 M HCl (1 mL). The resulting
soln was stirred at r.t. for 16 h and subsequently evaporated to dry-
ness. The solid was washed with acetone; yield: 0.12 g (85%).
HAryl), 6.49 (s, 4 H, HAryl), 6.42 (s, 4 H, HAryl), 4.38 (m, J = 12.50
Hz, 8 H, ArCH2Ar), 4.11 (m, 4 H, ArCH2N), 3.90 (m, 8 H,
ArCH2N), 3.85 (m, 8 H, ArOCH2), 3.76 (m, 8 H, ArOCH2), 3.62 (m,
4 H, ArCH2N), 3.09 (m, 8 H, ArCH2Ar), 2.20 (m, 4 H, NCOCH2),
1.86 (m, 16 H, ArOCH2CH2), 1.65 (m, 4 H, NCOCH2CH2), 1.45–
Synthesis 2011, No. 8, 1193–1204 © Thieme Stuttgart · New York

FEATURE ARTICLE
A Modular Synthetic Route to Dimeric Calixarenes
1201
1.50 [m, 124 H, ArOCH2CH2CH2, C(CH3)3], 0.98 (m, 24 H,
ArOCH2CH2CH2CH3).
13C NMR (75 MHz, CDCl3): d = 163.69, 155.75, 153.18, 135.47,
135.09, 134.51, 130.41, 130.03, 130.00, 129.09, 129.05, 129.01,
128.94, 128.90, 128.84, 128.34, 82.96, 79.16, 29.15, 28.91, 28.48,
28.20, 27.73, 27.48, 14.73, 14.65, 13.68, 13.62.
1H NMR (300 MHz, DMSO-d6): d = 7.90 (t, J = 5.41 Hz, 4 H, Ben-
zal-NH), 7.02–7.36 (br s, 16 H, CNH2Cl), 6.69 (s, 8 H, HAryl), 4.32
(d, J = 12.91 Hz, 4 H, ArCH2Ar), 4.08 (d, 4 H, ArCH2N), 3.80 (t,
J = 7.22 Hz, 8 H, ArOCH2), 3.15 (d, 4 H, ArCH2Ar), 1.85 (quint, 8
H, ArOCH2CH2), 1.41 (sextet, 8 H, ArOCH2CH2CH2), 0.96 (t, 12
H, ArOCH2CH2CH2CH3).
13C NMR (75 MHz, DMSO-d6): d = 156.66, 155.50, 134.50,
130.17, 127.58, 74.54, 44.03, 31.77, 30.12, 18.81, 13.87,
HRMS (ESI): m/z [M + H]+ calcd for C52H77N12O4: 933.6185;
HRMS (ESI): m/z [M + 2 Na]2+ calcd for C168H250N20Na2O34:
1569.4132; found: 1569.4113; [M
C168H252N20O34: 1547.4313; found: 1547.4319.
+ 2
H]2+ calcd for
found: 933.6296.
N,N¢-Bis({25,26,27,28-Tetrabutoxy 11,17,23-tris[(guanidini-
um)methyl]calix[4]arene-5-yl}methyl)hexanediamide
Hexachloride (D12)
Diamide D12a (0.012 g, 0.00 4mmol) was dissolved in anhyd
MeOH (10 mL). To this soln was added 1 M HCl (1 mL). The re-
sulting soln was stirred at r.t. for 16 h and subsequently evaporated
to dryness. The solid was washed with acetone; yield: 0.007 g
(85%).
1H NMR (300 MHz, DMSO-d6): d = 7.84 (br s, 2 H, CNH2Cl),
7.00–7.50 (br s, 8 H, Benzal-NH), 6.71 (s, 4 H, HAryl), 6.70 (s, 4 H,
HAryl), 6.66 (s, 4 H, HAryl), 6.60 (s, 4 H, HAryl), 4.31 (m, 8 H,
ArCH2Ar), 4.05 (m, 16 H, ArCH2N), 3.80 (m, 16 H, ArOCH2), 3.10
(m, 8 H, ArCH2Ar), 2.13 (m, 4 H, NCOCH2), 1.86 (m, 16 H,
Methyl 4-(5-Methoxy-5-oxopentanamido)-1-methyl-1H-pyr-
role-2-carboxylate (P2)
A soln of methyl 4-amino-1-methyl-1H-pyrrole-2-carboxylate hy-
drochloride (P1, 150 mg, 0.79 mmol) in anhyd CH2Cl2–DMF (2:1,
30 mL) was treated with methyl 5-chloro-5-oxopentanoate (110 mL,
0.79 mmol), i-Pr2NEt (200 mL, 1.19 mmol) and DMAP (cat.), and
was stirred at r.t. for 24 h. CH2Cl2 (20 mL) was added to the soln,
and the resulting mixture was washed with 0.5 M HCl (2 × 50 mL)
and H2O (3 × 50 mL). The organic phase was dried (Na2SO4) and
the solvent was removed in vacuo; P2 (175 mg, 0.62 mmol, 78%)
was obtained as a pale-brown solid; mp 130 °C.
1H NMR (500 MHz, DMSO-d6): d = 1.80 [quint, J = 7.4 Hz, 2 H,
NHC(O)CH2CH2], 2.25 [t, J = 7.4 Hz, 2 H, NHC(O)CH2], 2.23 [t,
J = 7.4 Hz, 2 H, (H3C)O2CCH2], 3.58 (s, 3 H, CO2CH3), 3.71 (s, 3
H, CO2CH3), 3.80 (s, 3 H, NCH3), 6.69 (d, J = 2.0 Hz, 1 H, Hpyrrole),
7.32 (d, J = 2.0 Hz, 1 H, Hpyrrole), 9.83 (s, 1 H, NH).
13C NMR (125.6 MHz, DMSO-d6): d = 20.6, 32.7, 34.5, 36.2, 51.0,
51.3, 107.7, 118.6, 120.5, 122.7, 160.8, 169.0, 173.1.
HRMS (ESI): m/z [M + H]+ calcd for C13H19N2O5: 283.1288; found:
283.1296; m/z [M + Na]+ calcd for C13H18N2NaO5: 305.1108;
found: 305.1121; m/z [M – H]– calcd for C13H17N2O5: 281.1143;
found: 281.1142.
ArOCH2CH2),
1.36–1.52
(m,
20
H,
NCOCH2CH2,
ArOCH2CH2CH2), 0.95 (m, 24 H, ArOCH2CH2CH2CH3).
13C NMR (125.6 MHz, CD3OD): d = 159.32, 158.55, 158.50,
157.81, 157.51, 156.81, 137.08, 136.91, 136.42, 135.90, 133.34,
130.88, 129.14, 129.07, 128.95, 128.70, 76.27, 73.78, 70.62, 46.13,
43.90, 43.05, 36.89, 33.71, 33.67, 33.61, 32.04, 31.97, 28.38, 26.75,
20.74, 20.69, 20.62, 14.65, 14.63, 14.60.
HRMS (ESI): m/z [M + 3 H]3+ calcd for C108H157N20O10: 631.4125;
found: 631.4155.
5,11,17,23-Tetrakis{[2,3-bis(tert-butoxycarbonyl)guanidi-
no]methyl}-25,26,27,28-tetrabutoxycalix[4]arene (M4c)
5,11,17,23-Tetrakis(aminomethyl)-25,26,27,28-tetrabutoxy-
calix[4]arene tetrahydrochloride (M4, 0.091 g, 0.1 mmol) was dis-
solved in a mixture of anhyd MeOH (10 mL) and Et3N (1 mL). 1,3-
bis(tert-butoxycarbonyl)-2-methylisothiourea (0.17 g, 0.59 mmol)
was added to the soln followed by AgNO3 (0.11 g, 0.65 mmol). The
mixture was stirred at r.t. for 24 h. The catalyst was filtered off over
Celite and the soln was evaporated to dryness. The residue was pu-
rified by flash column chromatography (silica gel, CH2Cl2–cyclo-
hexane, 70:30); yield: 0.062 g (36%); mp 107.3 °C.
1H NMR (300 MHz, CDCl3): d = 11.45 (s, 4 H, BocNH), 8.26 (t,
J = 4.62 Hz, 4 H, Benzal-NH), 6.59 (s, 8 H, HAryl), 4.38 (d,
J = 12.99 Hz, 4 H, ArCH2Ar), 4.27 (d, 4 H, ArCH2N), 3.85 (t,
J = 7.55 Hz, 8 H, ArOCH2), 3.10 (d, 4 H, ArCH2Ar), 1.89 (quint, 8
H, ArOCH2CH2), 1.45–1.48 [m, 80 H, ArOCH2CH2CH2, C(CH3)3],
0.98 (t, 12 H, ArOCH2CH2CH2CH3).
4-(4-Carboxybutanamido)-1-methyl-1H-pyrrole-2-carboxylic
Acid (P3)
Pyrrole-2-carboxylate P2 (148 mg, 0.52 mmol) was dissolved in
MeOH (15 mL). 2 M NaOH (2.0 mL) was added and the soln was
stirred at 60 °C for 48 h. The mixture was cooled down to r.t. and
diluted with H2O (30 mL). The soln was washed with Et2O
(3 × 30 mL) and the pH of the aqueous layer was reduced to 3 with
10% H2SO4. The mixture was extracted with EtOAc (3 × 30 mL)
and the combined organic phases were dried (Na2SO4), and concd
in vacuo; P3 (118 mg, 0.46 mmol, 89%) was obtained as a pale-
brown solid; mp 159 °C.
1H NMR (500 MHz, DMSO-d6): d = 1.77 [quint, J = 7.4 Hz, 2 H,
NHC(O)CH2CH2], 2.24 [m, 4 H, NHC(O)CH2, HO2CCH2], 3.79 (s,
3 H, NCH3), 6.64 (d, J = 2.0 Hz, 1 H, Hpyrrole), 7.28 (d, J = 2.0 Hz, 1
H, Hpyrrole), 9.78 (s, 1 H, NH), 12.10 (br, 2 H, CO2H).
13C NMR (125.6 MHz, DMSO-d6): d = 20.6, 33.0, 34.6, 36.1,
107.7, 119.6, 120.0, 122.5, 161.9, 169.0, 174.2.
HRMS (ESI): m/z [M + Na]+ calcd for C11H14N2NaO5: 277.0795;
found: 277.0797; m/z [M – H]– calcd for C11H13N2O5: 253.0830;
found: 253.0821.
13C NMR (75 MHz, CDCl3): d = 163.68, 156.00, 155.66, 153.10,
135.01, 130.56, 127.88, 82.78, 81.96, 75.07, 44.96, 32.31, 28.41,
28.15, 26.96, 19.40, 14.14.
HRMS (ESI): m/z [M + Na]+ calcd for C92H140N12NaO20:
1756.0199; found: 1756.0345; [M + H]+ calcd for C92H141N12O20:
1734.0380; found: 1734.0510.
4-(4-Carboxybutanamido)-1-methyl-1H-pyrrole-2-carboxylic
Acid N,N¢-Bis[25,26,27,28-tetrabutoxy-11,17,23-tris[(tert-bu-
toxycarbonyl)amino]calix[4]aren-5-yl] Diamide (D8a)
5-Amino-25,26,27,28-tetrabutoxy-11,17,23-tris[(tert-butoxycarbo-
nyl)amino]calix[4]arene (M1, 158 mg, 0.158 mmol) was dissolved
in anhyd DMF–CH2Cl2 (2:1, 15 mL) and treated with EDCl (61 mg,
0.316 mmol), DMAP (48 mg, 0.395 mmol), and P3 (20 mg,
0.079 mmol). The mixture was stirred at r.t. for 48 h. The soln was
diluted with CH2Cl2 (20 mL) and was washed with H2O
25,26,27,28-Tetrabutoxy-5,11,17,23-tetrakis[(guanidini-
um)methyl]calix[4]arene Tetrachloride (M4a)
Calix[4]arene M4c (0.062 g, 0.036 mmol) was dissolved in anhyd
MeOH (10 mL). To this soln was added 1 M HCl (1 mL). The re-
sulting soln was stirred at r.t. for 16 h and subsequently evaporated
to dryness. The solid was washed with acetone; yield: 0.028 g
(72%).
Synthesis 2011, No. 8, 1193–1204 © Thieme Stuttgart · New York

1202
C. J. Blecking et al.
FEATURE ARTICLE
(3 × 15 mL). The organic layer was dried (Na2SO4) and the solvent
was removed under reduced pressure. The resulting residue was pu-
rified by flash column chromatography (silica gel, CH2Cl2–EtOAc,
1:1) to give D8a (113 mg, 0.051 mmol, 64%) as a pale-brown solid;
mp 165 °C; Rf = 0.85 (CH2Cl2–EtOAc, 1:1).
1H NMR (500 MHz, DMSO-d6): d = 0.97 (m, 24 H, CH3), 1.37 [s,
18 H, C(CH3)3], 1.39 [m, 16 H, O(CH2)2CH2CH3], 1.43 [s, 36 H,
C(CH3)3], 1.86 [m, 18 H, OCH2CH2CH2CH3, NHC(O)CH2CH2),
2.20 (m, 4 H, NHC(O)CH2), 3.01 (m, 8 H, aryl-CH2), 3.70 (m, 8 H,
OCH2), 3.78 (s, 3 H, NCH3), 3.82 (m, 8 H, OCH2), 4.30 (m, 8 H,
aryl-CH2), 6.54 (br, 2 H, Haryl), 6.69 (br, 3 H, Haryl), 6.77 (s, 3 H, Har-
yl), 6.85 (s, 1 H, Hpyrrole), 6.95 (br, 6 H, Haryl), 7.13 (s, 2 H, Haryl), 7.15
(s, 1 H, Hpyrrole), 8.51 (br, 1 H, NH), 8.71 (br, 1 H, NH), 8.78 (br, 1
H, NH), 8.90 (br, 2 H, NH), 9.25 (br, 1 H, NH), 9.28 (s, 1 H, NH),
9.49 (s, 1 H, NH), 9.72 (s, 1 H, NH).
1H NMR (500 MHz, DMSO-d6): d = 3.74 (s, 3 H, pyrrole-
CO2CH3), 3.84 (s, 3 H, NCH3), 3.86 (s, 3 H, NCH3), 3.89 (s, 3 H,
NCH3), 3.91 (s, 3 H, aryl-CO2CH3), 6.92 (d, J = 1.7 Hz, 1 H,
Hpyrrole), 7.08 (d, J = 1.6 Hz, 1 H, Hpyrrole), 7.13 (d, J = 1.5 Hz, 1 H,
H
pyrrole), 7.26 (d, J = 1.5 Hz, 1 H, Hpyrrole), 7.36 (d, J = 1.5 Hz, 1 H,
Hpyrrole), 7.48 (d, J = 1.6 Hz, 1 H, Hpyrrole), 7.69 (t, J = 7.8 Hz, 1 H,
aryl), 8.13 (d, J = 7.7 Hz, 1 H, Haryl), 8.22 (d, J = 7.9 Hz, 1 H, Haryl),
H
8.54 (s, 1 H, Haryl), 9.95 (s, 1 H, NH), 10.01 (s, 1 H, NH), 10.57 (s,
1 H, NH).
13C NMR (125.6 MHz, DMSO-d6): d = 36.1, 36.2, 50.9, 52.4,
104.8, 104.9, 108.4, 118.5, 118.7, 119.0, 120.8, 121.9, 122.2, 122.6,
123.0, 123.1, 128.1, 129.1, 129.9, 131.7, 132.1, 135.2, 158.5, 160.8,
162.7, 165.9.
HRMS (ESI): m/z [M + Na]+ calcd for C28H28N6NaO7: 583.1912;
found: 583.1923.
13C NMR (125.6 MHz, DMSO-d6): d = 13.9, 18.8, 18.9, 21.2, 28.1,
28.2, 30.8, 31.5, 31.7, 31.8, 34.9, 35.3, 36.1, 74.3, 74.6, 78.2, 78.4,
104.5, 118.4, 118.8, 119.2, 119.6, 120.9, 121.9, 122.8, 132.9, 133.1,
133.2, 133.3, 133.4, 133.9, 134.0, 134.2, 134.7, 151.1, 151.2, 151.5,
151.6, 152.0, 152.8, 152.9, 159.4, 169.0, 169.9.
Methyl 4-{4-[4-(3-Methoxy-3-oxopropanamido)-1-methyl-1H-
pyrrole-2-carboxamido]-1-methyl-1H-pyrrole-2-carboxami-
do}-1-methyl-1H-pyrrole-2-carboxylate (P9)
A soln of methyl 4-[4-(4-amino-1-methyl-1H-pyrrole-2-carboxam-
ido)-1-methyl-1H-pyrrole-2-carboxamido]-1-methyl-1H-pyrrole-
2-carboxylate hydrochloride (P6, 140 mg, 0.32 mmol) in anhyd
CH2Cl2–DMF (2:1, 30 mL) was treated with methyl 3-chloro-3-
oxopropanoate (35 mL, 0.32 mmol), i-Pr2NEt (266 mL, 1.61 mmol),
and DMAP (cat.) and the resulting mixture was stirred at r.t. for
24 h. The soln was diluted with CH2Cl2 (40 mL) and washed with
0.5 M HCl (3 × 40 mL) and H2O (3 × 40 mL). The organic phase
was dried (Na2SO4) and the solvent was removed under reduced
pressure to give P9 (86 mg, 0.17 mmol, 54%) as a pale-brown oil.
1H NMR (500 MHz, DMSO-d6): d = 3.40 [s, 2 H, NHC(O)CH2],
3.64 (s, 3 H, CO2CH3), 3.74 (s, 3 H, CO2CH3), 3.84 (s, 9 H, NCH3),
6.90 (d, J = 1.9 Hz, 1 H, Hpyrrole), 6.91 (d, J = 1.9 Hz, 1 H, Hpyrrole),
7.05 (d, J = 1.9 Hz, 1 H, Hpyrrole), 7.17 (d, J = 1.7 Hz, 1 H, Hpyrrole),
7.24 (d, J = 1.9 Hz, 1 H, Hpyrrole), 7.47 (d, J = 1.9 Hz, 1 H, Hpyrrole),
9.92 (s, 1 H, NH), 9.93 (s, 1 H, NH), 10.10 (s, 1 H, NH).
13C NMR (125.76 MHz, DMSO-d6): d = 36.2, 42.7, 51.0, 51.9,
104.0, 104.8, 108.4, 118.3, 118.5, 118.6, 120.8, 121.5, 122.2,
122.5, 122.9, 123.0, 158.4, 158.5, 160.8, 162.2, 168.4.
HRMS (ESI): m/z [M + H]+ calcd for C23H27N6O7: 499.1936; found:
499.1951; m/z [M + Na]+ calcd for C23H26N6NaO7: 521.1755;
found: 521.1763.
HRMS
(ESI):
m/z
[M
+
Na]+
calcd
for
C129H178N10NaO23: 2259.2991; found: 2259.2970.
4-(4-Carboxybutanamido)-1-methyl-1H-pyrrole-2-carboxylic
Acid N,N¢-Bis[11,17,23-triamino-25,26,27,28-tetrabutoxy-
calix[4]aren-5-yl Diamide Hexakis(trifluoroacetate) (D8)
To a soln of D8a (30 mg, 13.4 mmol) in CH2Cl2 (5.0 mL), TFA
(5.0 mL) was added, and the mixture was stirred at r.t. for 24 h. The
solvent was removed under reduced pressure to give D8 (31 mg,
13.3 mmol, 99%) as a pale-yellow solid; mp 208 °C.
1H NMR (500 MHz, CD3OD): d = 1.03 (m, 24 H, CH3), 1.42 [m, 8
H, O(CH2)2CH2CH3], 1.58 [m, 8 H, O(CH2)2CH2CH3], 1.93 [m, 18
H, OCH2CH2CH2CH3, NHC(O)CH2CH2], 2.42 [br, 4 H,
NHC(O)CH2], 3.28 (m, 8 H, aryl-CH2), 3.88 (br, 11 H, OCH2,
NCH3), 3.99 (m, 4 H, OCH2), 4.08 (m, 4 H, OCH2), 4.51 (m, 8 H,
aryl-CH2), 6.53 (br, 2 H, Haryl), 6.57 (br, 2 H, Haryl), 6.63 (br, 4 H,
Haryl), 6.77 (s, 1 H, Haryl), 6.90 (br, 1 H, Haryl), 6.95 (s, 2 H, Haryl),
6.98 (s, 2 H, Haryl), 7.08 (s, 1 H, Haryl), 7.19 (s, 2 H, Haryl), 7.23 (br,
1 H, Haryl).
13C NMR (125.6 MHz, CD3OD): d = 14.5, 14.6, 14.7, 20.4, 20.5,
20.6, 20.7, 20.8, 23.2, 31.9, 32.0, 33.4, 33.5, 33.6, 33.7, 33.8, 36.6,
37.0, 37.2, 76.7, 76.9, 106.9, 115.1, 116.8, 117.3, 119.1, 123.0,
123.3, 123.4, 123.8, 123.9, 124.1, 124.4, 124.5, 124.6, 126.3, 126.4,
134.3, 136.5, 136.6, 137.1, 137.9, 138.0, 138.1, 138.6, 138.8, 154.9,
155.0, 157.5, 157.6, 158.1, 158.5, 158.6, 158.9, 159.3, 162.1, 162.4,
162.7, 163.0, 172.8, 173.9.
4-{4-[4-(3-Carboxybenzamido)-1-methyl-1H-pyrrole-2-carbox-
amido]-1-methyl-1H-pyrrole-2-carboxamido}-1-methyl-1H-
pyrrole-2-carboxylic Acid (P8)
To a suspension of P7 (164 mg, 0.29 mmol) in MeOH (45 mL), 2 M
NaOH (2.5 mL) was added and the mixture was stirred at 60 °C for
48 h. The resulting soln was cooled down, diluted with H2O
(30 mL) and washed with Et2O (3 × 30 mL). The aqueous layer
was adjusted to pH 3 with 10% H2SO4 and extracted with EtOAc
(3 × 30 mL). The combined organic phases were dried (Na2SO4)
and the solvent was removed under reduced pressure to give P8
(146 mg, 0.27 mmol, 95%) as a brown viscous oil.
HRMS (ESI): m/z [M + H]+ calcd for C99H131N10O11: 1637.0025;
found:
1637.0121;
m/z
[M
+
Na]+
calcd
for
C99H130N10NaO11: 1658.9845; found: 1658.9977.
Methyl 4-(4-{4-[3-(Methoxycarbonyl)benzamido]-1-methyl-
1H-pyrrole-2-carboxamido}-1-methyl-1H-pyrrole-2-carbox-
amido)-1-methyl-1H-pyrrole-2-carboxylate (P7)
A soln of methyl 4-[4-(4-amino-1-methyl-1H-pyrrole-2-carboxam-
ido)-1-methyl-1H-pyrrole-2-carboxamido]-1-methyl-1H-pyrrole-
2-carboxylate hydrochloride (P6, 200 mg, 0.46 mmol) in anhyd
DMF (30 mL), was treated with 3-(methoxycarbonyl)benzoic acid
(83 mg, 0.46 mmol), EDCl (176 mg, 0.92 mmol), and DMAP
(140 mg, 1.15 mmol) and the mixture was stirred at r.t. for 24 h. Af-
ter addition of EtOAc (40 mL), the soln was washed with 10% HCl
(3 × 40 mL) and sat. NaHCO3 (3 × 40 mL). The organic phase was
dried (Na2SO4) and the solvent was removed under reduced pres-
sure; P7 (165 mg, 0.29 mmol, 64%) was obtained as a brown solid;
mp 238 °C.
1H NMR (500 MHz, DMSO-d6): d = 3.83 (s, 3 H, NCH3), 3.86 (s, 3
H, NCH3), 3.89 (s, 3 H, NCH3), 6.86 (d, J = 2.0 Hz, 1 H, Hpyrrole),
7.08 (d, J = 1.8 Hz, 1 H, Hpyrrole), 7.13 (d, J = 1.9 Hz, 1 H, Hpyrrole),
7.26 (d, J = 1.7 Hz, 1 H, Hpyrrole), 7.36 (d, J = 1.8 Hz, 1 H, Hpyrrole),
7.43 (d, J = 1.9 Hz, 1 H, Hpyrrole), 7.66 (t, J = 7.8 Hz, 1 H, Haryl), 8.11
(dt, J = 7.8 Hz, J = 1.5 Hz, 1 H, Haryl), 8.19 (dt, J = 8.0 Hz, 4J = 1.5
Hz, 1 H, Haryl), 8.54 (t, J = 1.6 Hz, 1 H, Haryl), 9.91 (s, 1 H, NH),
10.00 (s, 1 H, NH), 10.55 (s, 1 H, NH), 12.72 (br, 2 H, CO2H).
13C NMR (125.6 MHz, DMSO-d6): d = 36.1, 36.2, 104.8, 104.9,
108.4, 118.6, 118.9, 119.5, 120.3, 122.0, 122.2, 122.6, 122.7, 123.0,
128.2, 128.8, 131.0, 131.8, 131.9, 135.0, 158.5, 162.0, 162.9, 166.9.
Synthesis 2011, No. 8, 1193–1204 © Thieme Stuttgart · New York

FEATURE ARTICLE
A Modular Synthetic Route to Dimeric Calixarenes
1203
HRMS (ESI): m/z [M – H]– calcd for C26H23N6O7: 531.1634; found:
HRMS
(ESI):
m/z
[M
+
2
Na]2+
calcd
for
531.1639.
C144H188N14Na2O25: 1280.1843; found: 1280.1878.
4-{4-[4-(2-Carboxyacetamido)-1-methyl-1H-pyrrole-2-carbox-
amido]-1-methyl-1H-pyrrole-2-carboxamido}-1-methyl-1H-
pyrrole-2-carboxylic Acid (P10)
4-{4-[4-(2-Carboxyacetamido)-1-methyl-1H-pyrrole-2-carbox-
amido]-1-methyl-1H-pyrrole-2-carboxamido}-1-methyl-1H-
pyrrole-2-carboxylic Acid N,N¢-Bis{25,26,27,28-tetrabutoxy-
11,17,23-tris[(tert-butoxycarbonyl)amino]calix[4]aren-5-yl}
Diamide (D10a)
To a soln of 5-amino-25,26,27,28-tetrabutoxy-11,17,23-tris[(tert-
butoxycarbonyl)amino]calix[4]arene (M1, 335 mg, 0.332 mmol) in
anhyd CH2Cl2–DMF (1:1, 30 mL), EDCl (127 mg, 0.663 mmol),
DMAP (101 mg, 0.829 mmol), and P10 (78 mg, 0.166 mmol) were
added and the mixture was stirred at r.t. for 48 h. The soln was di-
luted with CH2Cl2 (20 mL) and washed with H2O (2 × 20 mL). The
organic phase was dried (Na2SO4) and concentrated to dryness in
vacuo. The resulting residue was purified by flash column chroma-
tography (silica gel, first cyclohexane–EtOAc, 3:1, then EtOAc–
CH2Cl2, 1:1) to give D10a (138 mg, 0.056 mmol, 34%) as a pale-
brown solid; mp 94–98 °C; Rf = 0.0 (cyclohexane–EtOAc, 3:1), 0.8
(EtOAc–CH2Cl2, 1:1).
1H NMR (500 MHz, DMSO-d6): d = 0.98 (m, 24 H, CH3), 1.34 [m,
8 H, O(CH2)2CH2CH3], 1.36 [s, 9 H, C(CH3)3], 1.37 [s, 9 H,
C(CH3)3], 1.39 [s, 18 H, C(CH3)3], 1.44 [s, 18 H, C(CH3)3], 1.49 [m,
8 H, O(CH2)2CH2CH3], 1.88 (m, 16 H, OCH2CH2CH2CH3), 3.03
(m, 8 H, aryl-CH2), 3.24 [br, 2 H, NHC(O)CH2], 3.69 (m, 4 H,
OCH2), 3.80 (m, 8 H, OCH2), 3.82, 3.83, 3.85 (3 s, 9 H, NCH3), 3.88
(m, 4 H, OCH2), 4.31 (m, 8 H, aryl-CH2), 6.45 (br, 2 H, Haryl), 6.58
(br, 2 H, Haryl), 6.79–6.84 (br, 6 H, Haryl), 6.89 (s, 1 H, Haryl), 7.01–
7.07 (br, 6 H, Haryl), 7.15 (br, 3 H, Haryl), 7.22 (br, 2 H, Haryl), 8.53
(br, 1 H, NH), 8.73 (br, 3 H, NH), 8.99 (br, 2 H, NH), 9.46 (s, 1 H,
NH), 9.53 (s, 1 H, NH), 9.89 (s, 2 H, NH), 10.01 (s, 1 H, NH).
13C NMR (125.6 MHz, DMSO-d6): d = 13.9, 18.7, 18.9, 19.0, 28.1,
28.2, 30.8, 31.5, 31.7, 31.9, 36.1, 36.2, 45.1, 74.2, 74.5, 74.6, 78.2,
78.4, 104.0, 104.7, 105.4, 118.1, 118.4, 118.6, 118.7, 119.0, 119.2,
119.7, 120.8, 121.7, 122.1, 122.8, 122.9, 126.2, 127.4, 129.3, 130.1,
132.3, 132.8, 133.2, 133.4, 134.0, 134.2, 135.0, 151.0, 151.3, 151.7,
152.0, 152.8, 152.9, 158.4, 158.5, 159.5, 163.8, 164.8, 172.0.
To a soln of P9 (140 mg, 0.281 mmol) in MeOH (40 mL), 2 M
NaOH (4 mL) was added and the mixture was stirred at 60 °C for
48 h. The soln was cooled down, diluted with H2O (50 mL) and
washed with Et2O (3 × 30 mL). The aqueous layer was adjusted to
pH 3 with 10% H2SO4 and extracted with EtOAc (3 × 30 mL). The
combined organic phases were dried (Na2SO4) and the solvent was
removed under reduced pressure to give P10 (87 mg, 0.185 mmol,
66%) as a brown solid; mp 178 °C.
1H NMR (500 MHz, DMSO-d6): d = 3.28 [s, 2 H, NHC(O)CH2],
3.82 (s, 3 H, NCH3), 3.83 (s, 3 H, NCH3), 3.84 (s, 3 H, NCH3), 6.85
(d, J = 2.0 Hz, 1 H, Hpyrrole), 6.89 (d, J = 1.9 Hz, 1 H, Hpyrrole), 7.05
(d, J = 1.9 Hz, 1 H, Hpyrrole), 7.17 (d, J = 2.0 Hz, 1 H, Hpyrrole), 7.24
(d, J = 2.0 Hz, 1 H, Hpyrrole), 7.42 (d, J = 2.0 Hz, 1 H, Hpyrrole), 9.90
(s, 1 H, NH), 9.91 (s, 1 H, NH), 10.04 (s, 1 H, NH), 12.39 (br, 2 H,
CO2H).
13C NMR (125.6 MHz, DMSO-d6): d = 36.1, 43.1, 103.9, 104.7,
108.4, 118.3, 118.6, 119.5, 120.3, 121.7, 122.2, 122.6, 122.7, 122.8,
158.4, 162.0, 162.8, 169.5.
HRMS (ESI): m/z [M + Na]+ calcd for C21H22N6NaO7: 493.1442;
found: 493.1404.
4-{4-[4-(3-Carboxybenzamido)-1-methyl-1H-pyrrole-2-carbox-
amido]-1-methyl-1H-pyrrole-2-carboxamido}-1-methyl-1H-
pyrrole-2-carboxylic Acid N,N¢-Bis[25,26,27,28-tetrabutoxy-
11,17,23-tris[(tert-butoxycarbonyl)amino]calix[4]aren-5-yl]
Diamide (D9a)
5-Amino-25,26,27,28-tetrabutoxy-11,17,23-tris[(tert-butoxycarbo-
nyl)amino]calix[4]arene (M1, 0.155 g, 0.154 mmol) was dissolved
in anhyd CH2Cl2–DMF (1:1, 30 mL). EDCl (0.059 g, 0.308 mmol),
DMAP (0.047 g, 0.385 mmol), and P8 (0.041 g, 0.077 mmol) were
added and the mixture was stirred at r.t. for 48 h. The solvent was
removed under reduced pressure and the resulting residue was dis-
solved in CH2Cl2 (20 mL). The organic phase was washed with H2O
(3 × 20 mL), dried (Na2SO4), and concentrated to dryness in vacuo.
The remaining crude product was purified by flash column chroma-
tography (silica gel, cyclohexane–EtOAc, 3:1, then EtOAc–
CH2Cl2, 1:1) to give D9a (0.039 g, 0.016 mmol, 20%) as a pale-
brown solid; mp 248 °C; Rf = 0.0 (cyclohexane–EtOAc, 3:1), 0.9
(EtOAc–CH2Cl2, 1:1).
HRMS
(ESI):
m/z
[M
+
Na]+
calcd
for
C139H186N14NaO25: 2475.3638; found: 2475.3682.
4-{4-[4-(3-Carboxybenzamido)-1-methyl-1H-pyrrole-2-carbox-
amido]-1-methyl-1H-pyrrole-2-carboxamido}-1-methyl-1H-
pyrrole-2-carboxylic Acid N,N¢-Bis[11,17,23-triamino-
25,26,27,28-tetrabutoxycalix[4]aren-5-yl] Diamide Hexakis(tri-
fluoroacetate) (D9)
To a soln of D9a (32 mg, 12.7 mmol) in CH2Cl2 (5 mL), TFA
(5 mL) was added and the mixture was stirred at r.t. for 24 h. The
solvent was removed under reduced pressure to give D9 (33 mg,
12.7 mmol, 99%) as a pale-brown solid; mp 235 °C.
1H NMR (500 MHz, CD3OD): d = 1.05 (m, 24 H, CH3), 1.46 [m,
8 H, O(CH2)2CH2CH3], 1.58 [m, 8 H, O(CH2)2CH2CH3], 1.95 (m,
16 H, OCH2CH2CH2CH3), 3.30 (m, 8 H, aryl-CH2), 3.91 (m, 8 H,
OCH2), 3.92 (s, 3 H, NCH3), 3.93 (s, 3 H, NCH3), 3.95 (s, 3 H,
NCH3), 4.02 (m, 4 H, OCH2), 4.09 (m, 4 H, OCH2), 4.54 (m, 8 H,
aryl-CH2), 6.56 (d, J = 2.1 Hz, 2 H, Haryl), 6.59 (d, J = 2.1 Hz, 2 H,
1H NMR (500 MHz, DMSO-d6): d = 0.98 (m, 24 H, CH3), 1.37 [s,
9 H, C(CH3)3], 1.39 [m, 16 H, O(CH2)2CH2CH3], 1.41 [s, 45 H,
C(CH3)3], 1.89 (m, 16 H, OCH2CH2CH2CH3), 3.05 (m, 8 H, aryl-
CH2), 3.74 (m, 4 H, OCH2), 3.80 (m, 4 H, OCH2), 3.82 (s, 3 H,
NCH3), 3.85 (m, 8 H, OCH2), 3.86 (s, 3 H, NCH3), 3.89 (s, 3 H,
NCH3), 4.35 (m, 8 H, aryl-CH2), 6.66 (s, 2 H Haryl), 6.80 (s, 4 H,
H
aryl), 6.84 (s, 2 H, Haryl), 6.93 (s, 4 H, Haryl), 7.05 (s, 2 H, Haryl), 7.08
(s, 2 H, Haryl), 7.12 (s, 1 H, Haryl), 7.15 (s, 2 H, Haryl), 7.23 (s, 1 H,
aryl), 7.24 (s, 1 H, Haryl), 7.34 (s, 1 H, Haryl), 7.60 (t, J = 7.6 Hz, 1
H, Haryl), 8.03 (d, J = 7.5 Hz, 1 H, Haryl), 8.07 (d, J = 7.6 Hz, 1 H,
aryl), 8.44 (s, 1 H, Haryl), 8.58 (br, 1 H, NH), 8.74 (br, 4 H, NH),
H
H
Haryl), 6.67 (d, J = 2.0 Hz, 2 H, Haryl), 6.69 (d, J = 2.0 Hz, 2 H, Haryl),
8.84 (br, 1 H, NH), 9.53 (s, 1 H, NH), 9.90 (s, 1 H, NH), 9.98 (s,
1 H, NH), 10.00 (s, 1 H, NH), 10.44 (s, 1 H, NH).
6.76 (s, 1 H, Hpyrrole), 6.94 (d, J = 2.2 Hz, 4 H, Haryl), 7.00 (d, J = 1.6
Hz, 1 H, Hpyrrole), 7.04 (d, J = 1.6 Hz, 1 H, Hpyrrole), 7.06 (d, J = 1.7
Hz, 1 H, Hpyrrole), 7.17 (s, 2 H, Haryl), 7.20 (d, J = 1.6 Hz, 1 H,
Hpyrrole), 7.24 (s, 2 H, Haryl), 7.34 (d, J = 1.8 Hz, 1 H, Hpyrrole), 7.66
(t, J = 7.6 Hz, 1 H, Haryl), 8.11 (m, 2 H, Haryl), 8.48 (br, 1 H, Haryl).
13C NMR (125.6 MHz, CD3OD): d = 14.6, 14.7, 20.5, 20.6, 20.8,
31.9, 32.1, 33.4, 33.5, 33.6, 33.7, 36.9, 76.7, 76.9, 106.7, 106.8,
107.7, 119.1, 121.3, 123.3, 123.4, 123.5, 123.7, 123.8, 123.9, 124.0,
124.4, 124.7, 124.8, 125.1, 126.3, 126.8, 128.2, 130.2, 131.6, 134.1,
13C NMR (125.6 MHz, DMSO-d6): d = 13.9, 18.9, 19.0, 28.0, 28.1,
28.2, 30.8, 31.6, 31.7, 31.8, 36.1, 74.4, 74.5, 78.2, 78.3, 104.7,
104.9, 105.4, 118.4, 118.7, 118.8, 119.0, 119.2, 120.8, 120.9, 122.0,
122.1, 122.2, 122.8, 122.9, 123.1, 126.8, 128.3, 130.0, 132.7, 133.1,
133.2, 133.3, 133.7, 134.0, 134.2, 134.4, 134.5, 134.7, 135.3, 151.2,
151.5, 152.0, 152.3, 152.8, 152.9, 158.4, 158.5, 159.5, 163.2, 164.5.
Synthesis 2011, No. 8, 1193–1204 © Thieme Stuttgart · New York

1204
C. J. Blecking et al.
FEATURE ARTICLE
Casnati, A.; Ungaro, R. Org. Lett. 2008, 10, 3953.
(e) Galindo, M. A.; Olea, D.; Romero, M. A.; Gomez, J.;
del Castillo, P.; Hannon, M. J.; Rodger, A.; Zamora, F.;
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Commun. 2007, 4907. (g) Shahgaldian, P.; Sciotti, M. A.;
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134.2, 136.6, 136.8, 137.2, 137.3, 138.0, 138.1, 138.6, 138.8, 155.1,
155.4, 157.5, 157.6, 158.5, 158.6, 161.7, 161.8, 162.3, 162.5, 162.8,
166.7, 168.2.
HRMS (ESI): m/z [M + 2 H]2+ calcd for C114H142N14O13: 958.0451;
found: 958.0519.
4-{4-[4-(2-Carboxyacetamido)-1-methyl-1H-pyrrole-2-carbox-
amido]-1-methyl-1H-pyrrole-2-carboxamido}-1-methyl-1H-
pyrrole-2-carboxylic Acid N,N¢-Bis[11,17,23-triamino-
25,26,27,28-tetrabutoxycalix[4]aren-5-yl] Diamide Hexakis(tri-
fluoroacetate) (D10)
To a soln of D10a (78 mg, 0.032 mmol) in CH2Cl2 (5 mL), TFA
(5 mL) was added and the resulting mixture was stirred at r.t. for
24 h. The solvent was removed under reduced pressure to give D10
(82 mg, 0.032 mmol, 99%) as a light-brown solid; mp 180 °C.
1H NMR (500 MHz, CD3OD): d = 1.04 (m, 24 H, CH3), 1.47 [m, 8
H, O(CH2)2CH2CH3], 1.57 [m, 8 H, O(CH2)2CH2CH3], 1.94 (m, 16
H, OCH2CH2CH2CH3), 3.26 (m, 4 H, aryl-CH2), 3.30 [m, 6 H, aryl-
CH2, NHC(O)CH2], 3.90–3.93 (m, 17 H, OCH2, NCH3), 4.01 (m,
6 H, OCH2), 4.09 (t, J = 7.8 Hz, 2 H, OCH2), 4.53 (m, 8 H, aryl-
CH2), 6.60 (d, J = 2.5 Hz, 2 H, Haryl), 6.60–6.70 (br, 2 H, Haryl), 6.67
(s, 2 H, Haryl), 6.71 (d, J = 2.6 Hz, 2 H, Haryl), 6.77 (s, 1 H, Haryl),
6.78 (s, 2 H, Haryl), 6.82 (s, 1 H, Haryl), 6.87 (br, 2 H, Haryl), 6.90 (br,
2 H, Haryl), 6.93 (s, 2 H, Haryl), 6.98 (s, 1 H, Haryl), 7.04 (s, 1 H, Haryl),
7.15 (s, 2 H, Haryl).
13C NMR (125.6 MHz, CD3OD): d = 14.4, 14.5, 20.3, 20.4, 20.5,
20.6, 31.7, 31.8, 31.9, 33.3, 33.4, 33.6, 36.8, 37.0, 50.0, 76.5, 76.7,
76.8, 105.6, 106.6, 107.6, 112.7, 114.92, 116.3, 117.2, 118.6, 119.4,
122.4, 123.3, 123.8, 124.0, 124.2, 126.0, 126.1, 126.2, 126.3, 134.1,
135.5, 136.4, 137.1, 137.6, 138.0, 138.6, 138.9, 154.9, 157.5, 157.9,
158.2, 158.4, 158.5, 158.8, 159.1, 161.5, 161.8, 167.9.
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HRMS (ESI): m/z [M + H]+ calcd for C109H144N14O13: 1858.1071;
found: 1858.0999; m/z [M]2+ calcd for C109H145N14O13: 929.0536;
found: 929.0529.
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Acknowledgment
A.D. thanks the Alexander-von-Humboldt foundation for a research
stipend. Support from the Deutsche Forschungsgemeinschaft is
gratefully acknowledged.
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Synthesis 2011, No. 8, 1193–1204 © Thieme Stuttgart · New York