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The Evolution of Stereochemistry.

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Meeting Reviews
The Evolution of Stereochemistry**
Hans-Dieter Arndt
S
cientists from academia and industry
once again convened at Brgenstock,
above Lake Lucerne (Switzerland), for
the 41st EUCHEM Conference on Stereochemistry, chaired by Bernhard
Kr'utler (University of Innsbruck,
Austria). According to a long tradition
the program of the conference was not
disclosed beforehand, and so an element
of surprise lay in store for the 125 participants of this year.s meeting.
The President and his organizational
committee (Hans-Beat Brgi, University of Bern; Fran3ois Diederich, ETH
Zrich; E. Peter Kndig, University of
Geneva; Klaus Mller, HoffmannLa Roche; Philippe Renaud, University
of Bern; Jay Siegel, University of
Zrich) organized a series of lectures
that covered the breadth of current
research in organic chemistry and
encompassed aspects of structure, synthesis, and reactivity, as well as materials
science and nanotechnology, functional
biological oligomers, chemical biology,
and even molecular evolution. Two
poster sessions over four afternoons
provided the opportunity for additional
presentations and comprehensive discussions alike.
[*] Dr. H.-D. Arndt
Universitt Dortmund
Fachbereich Chemie
Otto-Hahn-Strasse 6
D-44221 Dortmund (Germany)
and
Max-Planck-Institut f-r molekulare
Physiologie
Otto-Hahn-Strasse 11
D-44227 Dortmund (Germany)
E-mail: hans-dieter.arndt@mpi-dortmund.mpg.de
[**] 41st EUCHEM Conference on Stereochemistry, April 22–28, 2006, B-rgenstock
(Switzerland)
4542
The scientific program was opened
by Peter Seeberger (ETH Zrich, CH),
who presented an insightful analysis of
the structural space of oligosaccharides,
the scalable syntheses of monosaccharide building blocks, and the scope as
well as some limitations of automated
oligosaccharide synthesis. He demonstrated, furthermore, how to prepare
and utilize microarrays of surfaceimmobilized oligosaccharides (e.g. heparin sulfates) and how potent synthetic
vaccines based on oligosaccharides can
be in the prophylaxis against malaria.
Thereafter, Antonio Echavarren
(ICIQ Tarragona, Spain) devoted his
presentation to noble-metal catalysis.
He showed what kind of complex cycloisomerizations and reaction cascades of
enynes can be induced by Pt and Au
catalysts. Fine tuning of the ligands
allowed the reactivities of Au catalysts
to be adjusted, and unforeseen reaction
pathways could be explained by the
intermediacy of Au–carbene complexes.
In the first evening lecture, Rainer
Herges (University of Kiel, Germany)
drew the participants into the world of
M=bius objects. He presented the first
synthesis of an isolable M=bius-aromatic compound from tetradehydrodianthracene and the cyclobutadiene
dimer, as well as studies about the
C17H17+ cation, for which he also expects
a M=bius-type ground state. The evening was crowned by a performance of
the Crab Canon from the musical offering (J.-S. Bach), whose score can be
deliberately projected onto a M=bius
strip to deliver a version that plays
continuously by two strings!
The next day was dedicated to the
materials sciences. Chad Mirkin (Northwestern University, Evanston, USA)
introduced a parallelized concept for
dip-pen lithography, which allows the
many thousandfold reproduction of
micrometer-scaled structures by AFM
manipulations. By optimizing the synthesis of DNA-functionalized nanoparticles, his group was able to develop
sensitive assay formats for bioanalytical
applications. Additionally he reported
that such DNA–nanoparticle conjugates
2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
surprisingly penetrate the wall of living
cells without transfection reagents and
as such can elicit antisense effects.
Collin Nuckolls (Columbia University, New York, USA) then turned to
molecular electronics and introduced
the investigation of conducting organic
single molecules, which had been
attached in nanometer-sized “gaps”
between conducting electrodes or the
ends of carbon nanotubes, both covalently as well as noncovalently. Furthermore, he presented a study on the
characterization of carbenes bound on
Ru metal surfaces (stable up to 1608C)
which enabled the stable cross-linking of
Ru nanoparticles by ring-opening metathesis polymerization (ROMP).
In the evening, Hermann Gaub
(LMU Mnchen, Germany) opened
the toolbox of force microscopy, which
his group uses to characterize the
unfolding of proteins and association
of molecules. He reported how DNA
oligonucleotides can be used to achieve
a higher sensitivity and perform measurements in parallel, and demonstrated
with force-coupled azobenzene molecules the principle of a molecular, lightdriven motor (a “photo-Otto-cycle”).
On the third day, Donald Hilvert
(ETH Zrich, Switzerland) gave an
account on catalytic antibodies and
their specific optimization and selection
by yeast cell surface display techniques.
He also reported on the molecular
evolution of a chorismate mutase
dimer and its “halved” constructs. The
monomers thus obtained displayed
many properties of a molten globule,
with a high level of catalytic activity
retained.
The lecture by Morten Meldal
(Carlsberg Laboratory, Copenhagen,
Denmark) was directed towards combinatorial chemistry. With carefully optimized solid-phase synthesis of smallcompound libraries, cell-based assays on
beads could be developed. He then
described the combinatorial generation
of non-natural receptors and metallopeptides as catalysts, and then introduced a novel technique to encode and
automatically identify single polymer
Angew. Chem. Int. Ed. 2006, 45, 4542 – 4543
Angewandte
Chemie
beads by using a “fingerprint” of copolymerized fluorescent particles.
The focus of the fourth day was on
synthetic chemistry. Shengming Ma
(Institute of Organic Chemistry, Shanghai, China) illustrated how allenes can
be utilized for selective transformations.
He presented metal-induced reaction
cascades that lead to interesting polycyclic skeletons as well as detailed
investigations on steroselective electrophilic additions to allenes. He also
showed how allenyl thioethers and sulfoxides can be used as bifunctional
building blocks for synthesis.
Ilan Marek (Technion, Haifa, Israel)
continued in this direction with chiral
3,3-disubstituted allyl organometallics
for the generation of quaternary sterocenters. He described the development
of chiral sulfoxide directing groups to
suppress metallotropic shifts and allow
for good stereoinduction. The corresponding reagents could even be
sequentially formed and reacted in a
one-pot organometallic multicomponent reaction (alkenylsulfoxide, organocopper, diethylzinc, diiodomethane,
aldehyde).
In the evening, Donna Blackmond
(Imperial College, London, UK) gave a
provocative yet stimulating account of
her kinetic studies of catalytic reaction
systems. She reported detailed studies of
autocatalytic reactions (Soai reaction,
organocatalytic a-hydroxyamination of
aldehydes) and the intricate influence of
the solubility of single intermediates. A
systematic study of the phase diagrams
of stereoisomers of amino acids corro-
Angew. Chem. Int. Ed. 2006, 45, 4542 – 4543
borated the frequent enrichment of one
isomer in the supernatant (eutectic for
serine: 99 % ee in solution), which could
be of relevance for prebiotic organocatalytic reaction networks.
The final day was devoted to biomolecules and especially their molecular evolution. Ronald Breaker (Yale
University, New Haven, USA) demonstrated the successful in vitro evolution
of functional riboswitches on the basis of
coupled
aptamer
and
ribozyme
domains, respectively, which could
even be fused to realize molecular
logical gates. He then discussed how
biologically important riboswitches can
be successfully found and characterized,
opening up new aspects of gene regulation with small molecules.
Gerald Joyce (Scripps Research
Institute, La Jolla, USA) described
thereafter the in vitro evolution of
RNA-templated RNA polymerases
from oligonucleotides, which could
even be performed with a reduced set
of bases (three or even two) as well as
with DNA or RNA. He then presented
how up to 280 evolutionary cycles per
day can be carried out in a miniaturized
microfluidic device, which suggests that
“molecular evolution on a chip” may
become feasible in the near future.
The scientific program was concluded by Robert Stroud (UC San
Francisco, USA), who clarified the
transport of water and ammonia molecules by high-resolution crystal structure
analyses of membrane-bound transport
proteins. The surprising selectivity of
aquaporines for water molecule trans-
port versus the intrinsically much more
mobile protons could be traced to a
pseudo-centrosymmetrically
bound
water molecule at the center of the
channel. On the basis of a high-resolution structure of the ammonia channel
AmtB (1.34 N), Stroud suggested a
model to describe the permeation of
neutral NH3 molecules (instead of the
charged NH4+ ions) through the selectivity filter of this channel and thus
explain its extraordinary selectivity.
In his closing talk, Klaus Mller
(Hoffmann-La Roche) gave a humoristic review in the style of “Dr. Seuss” of
the scientific aspects of the meeting and
set the scene for lighthearted reflections.
The 41st EUCHEM Conference on
Stereochemistry displayed all facets of
organic chemistry and served as a crossdisciplinary platform for all participants.
Unfortunately, the venerable Brgenstock Hotel complex will close next year
for reconstruction. Nevertheless, the
president of next year.s meeting, Samir
Zard (Ecole Polytechnique, Paliseau,
France), and the organizing committee
have found an alternative nearby, still at
Brgenstock and not far from the traditional location. The 42nd EUCHEM
Conference on Stereochemistry will
take place on April 14–20, 2007 (http://
www.stereochemistry-buergenstock.ch).
We await with great anticipation to learn
what lies in store for the participants at
the next “Brgenstock Conference”.
DOI: 10.1002/anie.200602300
2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
4543
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