DOI: 10.1002/chem.201404024
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Dendrimers
Dendrimer-Type Peptoid-Decorated Hexaphenylxylenes and
Tetraphenylmethanes: Synthesis and Structure in Solution and in
the Gas Phase
Katharina Peschko,[a] Alexandra Schade,[a] Sidonie B. L. Vollrath,[a] Ulrike Schwarz,[b]
Burkhard Luy,[a, c] Claudia Muhle-Goll,[a] Patrick Weis,[b] and Stefan Brꢀse*[a, d]
Abstract: Branched organic nanostructures are useful scaf-
folds that find multiple applications in a variety of fields.
Here, we present a novel approach to dendrimer-like struc-
tures. Our design contains a rigid hydrocarbon-based core
(hexaphenylxylylene/tetraethynylphenylmethane) combined
with a library of N-substituted oligoglycines (so-called pep-
toids) providing a flexible shell. The use of click chemistry
allows rapid assembly of the nanostructures. The possibility
of tuning the size and the solubility of this new type of
nanostructure will be advantageous for future applications
such as heterogeneous catalysis.
Introduction
erate highly symmetrical nanostructures having both a rigid
core and a soft, flexible shell. This type of well-defined struc-
ture could be applied in catalysis and drug-delivery, because
Nowadays, dendrimers are a common class of organic nano-
structures. Their branched topology offers a broad variety of
applications ranging from sensors[1] and catalysis[2] to tissue en-
gineering[3] and drug delivery.[4] Several syntheses have been
reported that have led to highly functionalized systems with
complete control of the total structure. In particular, through
modular synthesis using click chemistry, rapid assembly of the
nanostructures is enabled.[5] Herewith, we present a short,
straightforward strategy that can be used to synthesize new
dendrimer-like structures. Our design is based on a rigid core
containing multiple anchoring sites. Recently, we presented
hexaphenylxylylene (HPX) as an easily accessible pseudo-octa-
hedral core for covalent organic frameworks.[8] We combined
this core with N-substituted oligoglycines (so-called peptoids),
which are readily accessible by solid-phase synthesis,[9] to gen-
the potential of peptoids in these fields is well known.[9,10]
A
disadvantage is that these flexible compounds are seldom
crystalline[6] and therefore there are only a few examples avail-
able with a high-resolution X-ray structures.[7] Hence, other
techniques such as NMR or mass spectrometric characteriza-
tion have to be applied.
Results and Discussion
For the assembly of the new dendrimeric structures, two differ-
ent building blocks were synthesized. First, rigid cores were
constructed that were suitably functionalized for the click reac-
tion, then the peptoids were added to provide a flexible,
active shell.
HPX structure 2 was synthesized from the corresponding
bromide as previously described and shown in Scheme 1.[11]
With the HPX core in hand, we had a bulky and rigid scaffold
with six functional side chains. The tetraphenylmethane (TPM)
cores 4 and 6 are smaller alternatives to the HPX core, with
four functional groups, but they nevertheless provide a bulky
and rigid framework for the final dendrimer structure. The syn-
thesis of the TPM core started from tetraphenylmethane, and
involved nitration, reduction, diazotization, and subsequent ad-
dition of sodium azide, to generate the tetraazide core 4 in
good yields. Tetraphenylmethane-alkyne core 6 was synthe-
sized from TPM via the tetrabromide.
[a] K. Peschko, A. Schade, S. B. L. Vollrath, Prof. Dr. B. Luy, Dr. C. Muhle-Goll,
Prof. S. Brꢀse
Karlsruhe Institute of Technology (KIT), Institute of Organic Chemistry
Fritz-Haber-Weg 6, 76131 Karlsruhe (Germany)
[b] U. Schwarz, Dr. P. Weis
Karlsruhe Institute of Technology (KIT), Institute of Physical Chemistry
Fritz-Haber-Weg 2, 76131 Karlsruhe (Germany)
[c] Prof. Dr. B. Luy
Karlsruhe Institute of Technology (KIT), Institute of Biological Interfaces
Hermann-von-Helmholtz-Platz 1
76344 Eggenstein-Leopoldshafen (Germany)
[d] Prof. S. Brꢀse
The required peptoids were assembled on solid supports by
using standard conditions (see the Supporting Information).
For this purpose, the peptoids combined methoxyethyl side-
chains and hydrophobic residues in different amounts, to tune
the solubility of the final products. The solid support used was
Karlsruhe Institute of Technology (KIT), Institute of Toxicology and Genetics
Hermann-von-Helmholtz-Platz 1
76344 Eggenstein-Leopoldshafen (Germany)
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201404024.
Chem. Eur. J. 2014, 20, 1 – 7
1
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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