Program - CCROS – Catalysts and Catalytic Reactions for Organic

7th
Annual PhD Workshop
of the
International Research
Training Group GRK1038
Program
July 25th to 25th, 2013
University of Freiburg
Großer Hörsaal Chemie
Welcome
Welcome to our 7th annual PhD Workshop here in Freiburg!
In this Guide you will nd the important information about and around the
following next two days including the scientic program and the get together.
Content
Program
General Informations
Maps
List of Participants
Abstracts
Notes
We thank Syngenta for their kind supply of note pads and pens.
1
2
Program
Program
Wednesday, 24th of July 2013
1230-1300
Registration and Get together
Foyer in front of lecture hall
1300-1305
Welcome and Opening Remarks
Großer Hörsaal Chemie
1305-1315
Welcome speach
by Prof. Dr. Bernhard Breit
1315-1445
Lectures - Session 1
13 -13
Max Hofferberth
ALU Freiburg, Prof. Dr. Reinhard Brückner
Total Synthesis of α- and β-Lipomycin: Application of a Highly Convergent and
adaptable Double Stille-Coupling
15
45
1345-1415
Ingo Schnapperelle
TU München, Prof. Dr. Thorsten Bach
C4 Selective Arylation of Thiophenes by Oxidative C-H Activation
1415-1445
Sarah Fernandez
LMU München, Prof. Dr. Paul Knochel
Chromonium-Catalyzed sp2-sp2 Cross-Coupling Reactions
1445-1515
Coffee Break
Foyer in front of lecture hall
1515-1615
Lectures - Session 2
1515-1545
Urs Gellrich
ALU Freiburg, Prof. Dr. Bernhard Breit
Mechanistical Studies of the Rhodium Catalyzed Hydroformylation with SelfAssembling Ligands
1545-1615
Robert Kastl
ETH Zürich, Prof. Dr. Helma Wennemers
Peptide-catalyzed Stereoselective Conjugate Addition Reactions Generating AllCarbon Quaterny Stereogenic Centers
1615-1645
Coffee Break
Foyer in front of lecture hall
1645-1745
Lectures - Session 3
1645-1715
Plamen Bichovski
ALU Freiburg, Dr. Jan Streuff
Titanium Catalyzed Redox-Umpolung Reactions
1715-1745
Richard Brimioulle
TU München, Prof. Dr. Thorsten Bach
Enantioselective [2+2] Photocycloadditions Catalyzed by Chiral Oxazaborolidine
Based Lewis Acids
1745-1800
Short Break (sorry no coffee)
Foyer in front of lecture hall / outside
3
1800-1920
Evening Lecture
1800-1920
Evening Lecture
Prof. Dr. Peter Hofmann
University of Heidelberg
Bulky, Electron-Rich, Small Bite-Angle Ligands: Organometallic Chemistry for
Homogeneous Catalysis
1930- open
end
Dinner
Restaurant „Harmonie“,
more information see page xy
Thursday, 25th of July 2013
0900-0915
Get together
0915-0945
Lectures - Session 4
0915-0945
Nico Santchi
ETH Zürich, Prof. Dr. Antonio Togni
Mechanistic Insights into Generation of CF 3-Radicals from Hypervalent Iodine
Reagents
0945-1015
Annette Frischmuth
LMU München, Prof. Dr. Paul Knochel
The Copper-mediated Intramolecular Carbomagnesiation - A new Approach to
Indoles and Azaindoles
1015-1045
Laetitia Souillart
EPF Lausanne, Prof. Dr. Nicolai Cramer
Exploiting Rh(I)-Rh(III) Cycles in Enantioselective Strain-promoted C-C Bond Cleavages
1045-1115
Coffee Break
Foyer in front of lecture hall
1115-1315
Lectures - Session 5
1115-1145
Marc-André Müller
University of Basel, Prof. Dr. Andreas Pfaltz
Asymmetric Hydrogenation of α, β-Unsaturated Nitriles Using Chiral Iridium N,P Ligand
Complexes
1145-1215
Uwe Jakob
ALU Freiburg, Prof. Dr. Willi Bannwarth
An Orthogonal Protection Scheme for Carboxylic Acids Based On the Metal Ion
Induced Cleavage of Chelating Amides
1215-1220
Closing Remarks and Goodbye
1225-1230
Group picture
1230
Lunch
„Mensa Institutsviertel“, more information see page xy
4
General Information
General Information
Scientic Sessions
Hotels
The talks will be given in English. The oral presentation of the PhD presentations will last
20 minutes followed by the discussion. The evening lecture will be given by Prof. Dr. Peter
Hofmann from the University of Heidelberg.
Location
Großer Hörsaal Chemie
Faculty for Chemistry and Pharmacy
University of Freiburg
Albertstraße 21 | 79104 Freiburg
Description
A When entering the chemistry building from the main entrance continue
straight through the foyer, climb the stairs and turn to the left. You should
now pass our library with hart working students. Follow the corridor and step
down the stairs. Here you should nd us standing in the hall, welcoming you
with your name badge.
B When entering from the west side, you are standing directly in the mentioned hall.
Hotel Atlanta
Rheinstraße 29
79104 Freiburg
+49 (0)761 296970
www.atlantahotel.de/de/
about 5 min walk to Institute
Gästehaus Jacoby
Rieselfeldallee 23
79111 Freiburg
+49 (0)761 47 64 389 or +49 (0)178 13 30 856
www.gaestehausjacoby.de/
Coffee Breaks
Hotel Am Rathaus
Rathausgasse 4,
79098 Freiburg im Breisgau
+49 (0)761 296160
www.am-rathaus.de/
about 10 min walk to Institute
Coffee, tea and cold drinks will be waiting for us outside the lecture hall as well as some
cookies for the small hunger.
Location
Hall in front of Großer Hörsaal Chemie
Dinner on Wednesday Evening
The event is meant to stimulate the exchange between the participating universities.
After a day of scientic input, we will meet for dinner and enjoy the more informal get-together.
Location
Restaurant „Harmonie“ in the centre of Freiburg
http://www.harmonie-restaurant.de/
Grünwälderstr. 16-18 | 79098 Freiburg | 0761 / 202 56 76
Menu
We will have a three-course dinner with starter, main dish and dessert. Four
different main dishes (3x meat and 1x vegetarian) will be available.
One non-alcoholic drink will be for free. Further drinks (alcoholic or non-alcoholic) have to be paid individually (in €).
Parking
If you are coming by car, you need a ticket from the university
to be allowed to park on the faculty ground. It is 1,50€ per day.
Lunch on Thursday
Each participant of our conference will receive a food voucher for lunch in Mensa
Institutsviertel. This voucher is valid for one soft-drink and “Essen 1”, “Essen 2” or “Schneller
Teller”. It is not valid for the buffet.
Location
Mensa Institutsviertel
Stefan-Meier-Str. 28 | 79104 Freiburg
Description
Leaving the building on the west side, you will nd the Mensa when turning
to the right and following the ow of students.
Menu
Can be found online at:
http://www.swfr.de/essen-trinken/speiseplaene/mensa-institutsviertel/
5
6
Maps
List of Participants
University of Basel
Chemie
Atlanta
am Rathaus
Münster
Name
Group
Email
Johanna Auth
Pfaltz
johanna.auth@unibas.ch
Stefan Gruber
Pfaltz
stefan.gruber@unibas.ch
Patrick Isenegger
Pfaltz
patrick.isenegger@unibas.ch
Marc Müller
Pfaltz
marc-andre.mueller@unibas.ch
Larissa Pauli
Pfaltz
larissa.pauli@unibas.ch
Andreas Pfaltz, Prof. Dr.
Pfaltz
andreas.pfaltz@unibas.ch
Robin Scheil
Pfaltz
robin.scheil@unibas.ch
York Schramm
Pfaltz
york.schramm@unibas.ch
Chatterjee Anamitra
Ward
anamitra.chatterjee@unibas.ch
Maxime Barnet
Ward
maxime.barnet@unibas.ch
Name
Group
Email
Anika Ahrens
Bannwarth
anika.ahrens@ocbc.uni-freiburg.de
Uwe Jakob
Bannwarth
uwe-jakob@gmx.net
Swetlana Scherbakow
Bannwarth
swetlana.scherbakow@gmx.net
Markus Sterk
Bannwarth
markus-sterk@gmx.de
Simon Allmendinger
Breit
Simon.Allmendinger@ocbc.uni-freiburg.de
ThorstenBeck
Breit
thorsten.beck@ocbc.uni-freiburg.de
Bernhard Breit, Prof. Dr.
Breit
bernhard.breit@chemie.uni-freiburg.de
Lucie Colas
Breit
lucie.colas@hotmail.fr
Stephanie Ganss
Breit
stephanie.ganss@ocbc.uni-freiburg.de
Urs Gellrich
Breit
ursgellrich@gmx.de
Amelie Gutmann
Breit
amelie.gutmann@ocbc.uni-freiburg.de
Matthias Kähny
Breit
m.kaehny@web.de
Alexander Köpfer
Breit
alexanderkoepfer@gmx.de
Philipp Koschker
Breit
philipp.koschker@web.de
Adrian Pritzius
Breit
pritzius_adrian@web.de
Alexander Straub
Breit
alexander.straub@saturn.uni-freiburg.de
Adrian Pritzius
Breit
pritzius_adrian@web.de
Alexander Straub
Breit
alexander.straub@saturn.uni-freiburg.de
Johannes Ullrich
Breit
johannes.ullrich@ocbc.uni-freiburg.de
Sebastian Wünsch
Breit
wuensch-sebastian@web.de
Kun Xu
Breit
xukunchem@gmail.com
Harmonie
University of Freiburg
Mensa
Chemie
Atlanta
7
8
List of Participants
Abstracts
Name
Group
Email
Thomas Baumann
Brueckner
thomas.baumann@neptun.uni-freiburg.de
Johannes Beiche
Brueckner
j_beiche@gmx.de
Reinhard Brückner, Prof. Dr.
Brueckner
reinhard.brueckner@organik.chemie.uni-freiburg.de
Julian Diehl
Brueckner
Juliandiehl@googlemail.com
Tobias Engesser
Brueckner
tobiasengesser@gmx.net
Thomas Hampel
Brueckner
thomas.hampel@ocbc.uni-freiburg.de
Max Hofferberth
Brueckner
lemax80@googlemail.com
Michael Kreibich
Brueckner
michael.kreibich@cl.uni-freiburg.de
Markus Neumeyer
Brueckner
markusneumeyer85@googlemail.com
David Peter
Brueckner
david.peter@ocbc.uni-freiburg.de
Simon Ruppenthal
Brueckner
simon.ruppenthal@gmail.com
Frank Sartorius
Brueckner
mail@frank-sartorius.de
Marc Trebing
Brueckner
marctrebing@gmx.de
Huiji Zhu
Brueckner
huiji.zhu@ocbc.uni-freiburg.de
Hannes Boehrer
Krossing
hannes.boehrer@ac.uni-freiburg.de
Thies Olaf Petersen
Krossing
olaf.petersen@ac.uni-freiburg.de
Miriam Schwab
Krossing
miriam.schwab@ac.uni-freiburg.de
Sabrina Loschonsky
Mueller
sabrina.loschonsky@pharmazie.uni-freiburg.de
Name
Group
Email
Ingo Schnapperelle
Bach
ingo.schnapperelle@tum.de
Richard Brimiouelle
Bach
richard.brimioulle@mytum.de
Laetitia Souillart
Cramer
laetitia.souillart@ep.ch
Sarah Fernandez
Knochel
sarah.fernandez@cup.uni-muenchen.de
Annette Frischmuth
Knochel
afrch@cup.uni-muenchen.de
Nico Santschi
Togni
santschi@inorg.chem.ethz.ch
Robert Kastl
Wennemers
robert.kastl@org.chem.ethz.ch
Annette Bahlinger
Wennemers
annette.bahlinger@stud.unibas.ch
External
9
Max Hofferberth
ALU Freiburg, Prof. Dr. Reinhard Brückner
Total Synthesis of α- and β-Lipomycin: Application of a Highly Convergent
and adaptable Double Stille-Coupling
page 11
Ingo Schnapperelle
TU München, Prof. Dr. Thorsten Bach
C4 Selective Arylation of Thiophenes by Oxidative C-H Activation
page 12
Sarah Fernandez
LMU München, Prof. Dr. Paul Knochel
Chromonium-Catalyzed sp2-sp2 Cross-Coupling Reactions
page 13
Urs Gellrich
ALU Freiburg, Prof. Dr. Bernhard Breit
Mechanistical Studies of the Rhodium Catalyzed Hydroformylation with SelfAssembling Ligands
page 14
Robert Kastl
ETH Zürich, Prof. Dr. Helma Wennemers
Peptide-catalyzed Stereoselective Conjugate Addition Reactions
Generating All-Carbon Quaterny Stereogenic Centers
page 15
Plamen Bichovski
ALU Freiburg, Dr. Jan Streuff
Titanium Catalyzed Redox-Umpolung Reactions
page 16
Richard Brimioulle
TU München, Prof. Dr. Thorsten Bach
Enantioselective [2+2] Photocycloadditions Catalyzed by Chiral
Oxazaborolidine Based Lewis Acids
page 17
Nico Santchi
ETH Zürich, Prof. Dr. Antonio Togni
Mechanistic Insights into Generation of CF 3-Radicals from Hypervalent
Iodine Reagents
page 18
Annette Frischmuth
LMU München, Prof. Dr. Paul Knochel
The Copper-mediated Intramolecular Carbomagnesiation - A new
Approach to Indoles and Azaindoles
page 19
Laetitia Souillart
EPF Lausanne, Prof. Dr. Nicolai Cramer
Exploiting Rh(I)-Rh(III) Cycles in Enantioselective Strain-promoted C-C Bond
Cleavages
page 20
Marc-André Müller
University of Basel, Prof. Dr. Andreas Pfaltz
Asymmetric Hydrogenation of α, β-Unsaturated Nitriles Using Chiral Iridium
N,P Ligand Complexes
page 21
Uwe Jakob
ALU Freiburg, Prof. Dr. Willi Bannwarth
An Orthogonal Protection Scheme for Carboxylic Acids Based On the Metal Ion Induced Cleavage of Chelating Amides
page 22
10
C4-Selective Arylation of Thiophenes by Oxidative C-H-Activation
Total Synthesis of - and -Lipomycin:
Application of a Highly Convergent and Adaptable Double STILLECoupling Strategy for the Synthesis of 3-(Polyenoyl)tetramic Acids
Ingo Schnapperelle and Thorsten Bach*
Lehrstuhl für Organische Chemie I and Catalysis Research Center (CRC), Technische Universität München, Lichtenbergstr. 4,
Garching, D-85747, Germany
Max Hofferberth and Reinhard Brückner*
Email: thorsten.bach@ch.tum.de - web page: http://www.oc1.ch.tum.de/home_en/
Institut für Organische Chemie, Albert-Ludwigs-Universität, Albertstraße 21,
79104 Freiburg, Germany; e-mail: max_hofferberth@web.de
3-( -Hydroxymethylidene)pyrrolidine-2,4-diones constitute the major tautomer of structures
Compounds in which
define
a class of natural products, which continues to evoke interest both in the synthetic[1] and biosynthetic
community[2].
For the synthesis of biaryl compounds, transition metal-catalyzed cross-couplings of aryl(pseudo)-halides are usually
the method of choice. Nevertheless, tremendous efforts have been made during the last decade in the field of
palladium-catalyzed C-H activation, no longer requiring prefunctionalization of at least one reaction partner. [1] More
recently this concept has been applied for the functionalization of heteroaromatics. [2] In this respect an additional
challenge has to be considered as regioselctivity becomes important, which is in many cases determined by the
inherent reactivity of the heterocycle.[3]
Under optimized conditions, monosubstituted as well as disubstituted thiophenes undergo a facile and regio selective
oxidative coupling reaction at carbon atom C4. [4] This uncommon selectivity was observed with various aryl boronic
acids as nucleophiles in the presence of silver oxide (2.0 equiv.), cesium trifluoracetate (tfa) (1.0 equiv.),
benzoquinone (BQ) (0.5 equiv.) and catalytic amounts of Pd(tfa)2 (10 mol%) employing mixtures of trifluoroacetic
acid (TFA) and acetic acid (AcOH) as the solvent.
Recently other groups[5,6] carried out mechanistic investigations based on computational calculations aiming towards
the elucidation of the catalytic cycle for the C4-selective arylation of thiophene derivatives. Unfortunately, previously
reported reaction conditions differ substantially from those shown above. Therefore we decided to carry out
mechanistic experiments to obtain mechanistic insights and an explanation for the observed selectivity.
We have synthesized a prototypical (polyenoyl)tetramic acids, namely -lipomycin,[3]
employing a novel approach, which is variable and convergent. In this approach a very useful
Distannane-buildingblock was utilized.[4] Furthermore, we have proven the, previously unknown,
-lipomycin by chiral chromatography of its degradation
products.
[1] R. Schobert, A. Schlenk, Bioorg. Med. Chem. 2008, 16, 4203-4221 and literature cited therein.
[2] E. g.: C. Bihlmaier, E. Welle, C. Hofmann, K. Welzel, A. Vente, E. Breitling, M. Müller, S. Glaser, A. Bechthold,
Antimicrob. Agents Chemother. 2006, 50, 2113-2121.
[3] B. Kunze, K. Schabacher, H. Zähner, A. Zeeck, Arch. Mikobiol. 1972, 86, 147-174.
[4] First synthesis and applications A. Sorg, R. Brückner, Angew. Chem. 2004, 116, 4623-4626; Angew. Chem. Int. Ed.
2004, 43, 4523-4526; J. Burghart, R. Brückner, Eur. J. Org. Chem. 2011, 150-165; J. Burghart, A. Sorg, R. Brückner,
Chem. Eur. J. 2011, 17, 6469-6483.
11
1
X. Chen, K. M. Engle, D.-H. Wang, J.-Q. Yu, Angew. Chem. 2009, 121, 5196-5217; Angew. Chem. Int. Ed. 2009, 48, 5094-5115.
2
J. Roger, A. L. Gottumukkala, H. Doucet, ChemCatChem 2010, 2, 20-40.
3
L.-C. Campeau, M. Bertrand-Laperl, J.-P. Leclerc, E. Villemure, S. Gorelsky, K. Fagnou, J. Am. Chem. Soc. 2008, 130, 3276-3277.
4
I. Schnapperelle, S. Breitenlechner, T. Bach, Org. Lett. 2011, 13, 3640-3643.
5
M. Steinmetz, K. Ueda, S. Grimme, J. Yamaguchi, S. Kirchberg, K. Itami, A. Studer, Chem. Asian. J. 2012, 7, 1256-1260.
6
S.-Y. Tang, Q.-X. Guo, Y. Fu, Chem. Eur. J. 2011, 17, 13866-13876.
12
Mechanistical studies of the Rhodium Catalyzed Hydroformylation
with Self Assembling Ligands
Urs Gellrich, Bernhard Breit*
Institut für Organische Chemie und Biochemie,
Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104 Freiburg, Germany
E-mail:
Webpage:
bernhard.breit@chemie.uni-freiburg.de
http://www.breit-group.uni-freiburg.de/
Selectivity control in homogeneous metal complex catalysis is most frequently
achieved by crafting the microenvironment of the catalytically active metal center
upon binding of appropriate ligand architectures to the metal center. Among the
many ligands used, bidentate ligands occupy an important position. During the last
years our group was able to successfully develop self-assembling ligands, interacting
via hydrogen bonds.[1] In order to improve catalytic reactions and ligands it is by all
means necessary to completely understand the nature of the catalytically active
species. Hence, online monitoring of progressing catalytic transformations, supported
by quantum mechanical calculations, can deliver valuable informations on the
intermediates involved in catalysis. We herein report on our insights into
hydroformylation reactions with the 6-DPPon ligand using online ReactIRTM and
NMR-spectroscopy together with QM-calculations.[2,3]
Figure 1: Direct observation of the formation of an intermediate of the catalytic cycle
and the corresponding DFT calculated structures.
13
(1)
W. Seiche, B. Breit, J. Am. Chem. Soc. 2003, 125, 6608.
(2)
U. Gellrich, J. Huang, W. Seiche, M. Keller, M. Meuwly, B. Breit J. Am. Chem.
Soc. 2011, 133, 964.
(3)
U. Gellrich, W. Seiche, M. Keller, B. Breit, Angew. Chem. 2012, 124, 11195;
Angew. Chem. Int. Ed. 2012, 51, 11038.
14
15
16
17
18
The copper-mediated intramolecular carbomagnesiation – A new approach to indoles
and azaindoles
A mild and general intramolecular copper-mediated carbomagnesiation procedure for the synthesis of
functionalized indoles as well as 4-, 5-, 6-, and 7-azaindoles starting from the readily available ynamides.
Subsequent reaction with various electrophiles (acid chlorides, allylic bromides) provides polyfunctional Nheterocycles in good yields.
Features of this method:
Practical synthesis of the ring closing precursors:
Straightforward access to highly functional indoles starting from readily available ynamides:
Expeditive synthesis of 7-azaindoles:
Expeditive synthesis of 5-azaindoles:
Selective synthesis of 4- or 6-azaindoles from the same precursor:
19
20
Asymmetric Hydrogenation of
An Orthogonal Protection Scheme for Carboxylic Acids Based On the Metal Ion
Induced Cleavage of Chelating Amides
-Unsaturated Nitriles Using
Chiral Iridium N,P Ligand Complexes
Uwe Jakob, Stephan Mundinger and Willi Bannwarth
Marc-André Müller,1 and Andreas Pfaltz1*
Institut für Organische Chemie und Biochemie, Albert-Ludwigs-Universität Freiburg
Albertstraße 21, 79104 Freiburg, Germany
1
Department of Chemistry, University of Basel
St. Johanns-Ring 19, CH-4056 Basel, Switzerland
*Corresponding author; e-mail: andreas.pfaltz@unibas.ch
Asymmetric hydrogenation is one of the most commonly applied reactions to generate
enantiomerically enriched molecules from prochiral starting materials.1 In particular, iridiumbased catalysts showed high applicability in the hydrogenation of substrates bearing no or
only weakly coordinating groups attached to the double bond. 2 On the other hand, strongly
coordinating functional groups, such as nitriles, are frequently observed as inhibitors of
iridium-based catalysts.3
In most cases, the preparation of complex organic molecules entails the need to apply
protecting groups. When such groups are applied to multistep synthesis basic requirements are
straightforward insertion, robustness to different reaction conditions and selective cleavage,
preferably with high yields and under mild conditions. In addition, a cleavage step orthogonal
to that used for common protecting groups would also be desirable [1].
O
MeOH
O
R1
OH
O
N
1.) protection
N
2.) modification
R2
NH
N
R2
MX2
N
N
M
X
X
N
O
Ba(OH)2
x 8 H2O
MeOH
4a-c
The fact that nitriles are important functional groups in different research areas highlights
the demand for easily accessible enantiomerically enriched molecules containing this group.
By modifications of “standard reaction conditions” we were able to find an easy applicable
protocol for the asymmetric hydrogenation of this kind of substrates. Herein, we give an
overview on this transformation, providing a detailed insight into the substrate scope and
discussing important parameters of this reaction.
REFERENCES:
1.
2.
3.
4.
R. Noyori, Angew. Chem. Int. Ed. 2013, 52, 79.
D. H. Woodmansee, A. Pfaltz, Chem. Commun. 2011, 47, 7912.
D. H. Woodmansee, M.-A. Müller, M. Neuburger, A. Pfaltz Chem. Sci. 2010, 1, 72.
a) R. A. Michelin, M. Mozzon, R. Bertanix Coord. Chem. Rev. 1996, 147, 229; b) F. F. Fleming, Nat. Prod.
Rep. 1999, 16, 597; c) V. L. Rao, A. Saxena, K. N. Ninan, J. Macromol. Sci. C:Polym. Rev. 2002, C42, 513.
OMe
N
O
3.) deprotection
N
R2
R2
Our new protection scheme for carboxylic acids fulfills all these criteria. The carboxylic acids
can be protected as very stable chelating amides. The cleavage reaction can be achieved under
mild conditions in the presence of metal ions. Their complexation involves the amide nitrogen
which then allows for an attack by weak nucleophiles such as MeOH forming the
corresponding methyl esters. Alternatively, the carboxylic acid can be obtained in the
presence of Ba(OH)2 x 8 H2O after acidic work up [2, 3].
The cleavage rate depends both on the chelator and on the metal source. This fact makes it
possible to develop an orthogonal protection scheme for carboxylic acids based on the
attachment of different chelators to the carboxyl functions of a molecule. Since this
orthogonal protection scheme has the advantage of mild and selective cleavage reactions it
should find widespread application in synthetic organic chemistry.
O
N
O
N
N
O
N
N
N
N
N
N
CH3
N
CH3
References
[1]
P. Kocienski, Protecting Groups, 3rd Ed., Thieme, 2003.
[2]
M. C. Broehmer, S. Mundinger, S. Bräse, W. Bannwarth, Angew. Chem. Int. Ed. 2011, 50, 6175 – 6177.
[3]
S. Mundinger, U. Jakob, P. Bichovski, manuscript in preparation.
21
OH
22