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Koert Group
 

Bilder des Ehemaligentreffens

                      
 


Research Areas:


Synthesis of Biologically Active Compounds
Synthetically Modified Ion Channels
Organic Molecules for Internal Interfaces

Synthesis of target structures and their associated target functions is a main goal of organic chemistry. We design and carry out multistep organic synthesis. Part of the work is the structural and functional analysis of the synthetic products. Selectivity is the key factor for synthetic efficiency. Therefore questions of chemo-, regio- and stereo-selectivity are always central to our research projects. One group of synthetic targets includes natural products of medicinal interest and enzyme inhibitors.

Fulicineroside

Crotylboration

Ion channels perform key tasks in biological systems such as neuronal signaling, muscular control, and sensing. Malfunctions cause serveral serve or common diseases. We synthesize new membrane-bound ion channels for studying their function (charge transport) to understand the functionality. A derivatization leads to the control of key characteristics like selectivity, dwell times and gating.

 

Gramicidin crown ether
OmpF crown ether

Internal interfaces between two solids play an important role in modern materials science and their technological applications like novel solar cells, OFETs, OLEDs and biosensors.

We synthesize functionalized pentacene for studies of internal interfaces.

Surface modification

 

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Latest NEWS:

Apr 2017

  • "A new procyanidin B from Campylospermum zenkeri (Ochnaceae) and antiplasmodial activity of two derivatives of (±)-serotobenine", Nat. Prod. Res. 2017, in print.
 







Norbert TOC klein




Phytochemical investigation of the stem bark of Campylospermum zenkeri led to the isolation of five known compounds: (Z,Z)-9,12-octadecadienoic acid (1), serotobenine (2), agathisflavone (3), lophirone A (4) and lophirone F (5), together with a new derivative of procyanidin B, a catechin dimer named zenkerinol (6). Serotobenine (2) is structurally related to decursivine which shows moderate activity against D6 and W2 strains of Plasmodium falciparum. For a better understanding of structure-activity relationships, three new semi-synthetic derivatives of serotobenine (2) have been prepared. These are: serotobenine monopropionate (2a), serotobenine monopivalate (2b) and serotobenine cyclohexyl ether (2c) respectively. Two of them (2a) and (2b), were evaluated for their antiplasmodial activity against P. falciparum 3D7 strain in a parasite lactate-dehydrogenase (pLDH) assay. Compound 2b was more active than compound 2a based on their IC50 values (36.6 and 123 μM, respectively).

Mrz 2017

 
Paul TOC real

   The metal catalyzed cycloaddition of silyl nitronates and        nitriles leading to 1,2,4 oxadiazoles is described. AgOTf        and Yb(OTf)3 are suitable catalysts. A variety of functional    groups is tolerated in the nitrile. The reaction works well        for alkenyl and aryl silyl nitronates while the use of alkyl      silyl nitronates is less efficient.

 

Jan 2017

 
 
 
Tricarbonyl Lars
 

Methods for the regioselective alkylation, arylation and alkenylation of α,β-diketoesters using organozinc reagents are reported. Alkylation and arylation in α-position is possible using diorgano zinc compounds. Alkenylation can be achieved using mixed alkenyl-dineopentyl zincates.

 

 

Review Tricarbonyl

Due to their high density of functional groups vicinal tricarbonyl compounds are versatile building blocks for the synthesis of complex target molecules. Methods for their preparation and their use in stereoselective C C bond formations as well as for the synthesis of heteroaromatics are summarized for the period 2006-2016. Several examples for their applications in natural product synthesis are given (awajanomycin, cladoniamide, wailupemycin). 

 

Molecular

Most commonly studied bacteria grow symmetrically and divide by binary fission, generating two siblings of equal morphology. An exception to this rule are budding bacteria, in which new offspring emerges de novo from a morphologically invariant mother cell. Although this mode of proliferation is widespread in diverse bacterial lineages, the underlying mechanisms are still incompletely understood. Here, we perform the first molecular-level analysis of growth and morphogenesis in the stalked budding alphaproteobacterium Hyphomonas neptunium. Peptidoglycan labeling shows that, in this species, buds originate from a stalk-like extension of the mother cell whose terminal segment is gradually remodeled into a new cell compartment. As a first step toward identifying the machinery mediating the budding process, we performed comprehensive mutational and localization studies of predicted peptidoglycan biosynthetic proteins in H. neptunium. These analyses identify factors that localize to distinct zones of dispersed and zonal growth, and they suggest a critical role of the MreB-controlled elongasome in cell morphogenesis. Collectively, our work shows that the mechanism of growth in H. neptunium is distinct from that in related, polarly growing members of the order Rhizobiales, setting the stage for in-depth analyses of the molecular principles regulating the fascinating developmental cycle of this species.


Oct 2016

 
Elevenol

Total syntheses: An efficient stereoselective synthetic approach to 7–20 oxa-bridged abietane type natural products is reported. Key steps are an asymmetric Mukaiyama aldol addition to construct the C3 stereocenter and an intramolecular organocatalyzed Stetter-type Michael addition followed by a Tishchenko reaction. An intramolecular lactone–enolate arylation delivers the tetracyclic skeleton. This synthetic strategy was applied for the first total synthesis of (+)-elevenol, an antihepatitis C active compound from Fluegga virosa, and the first total synthesis of (+)-przewalskin.

 

Sep2016

 
asd

Selectivity by strain: Cyclooctyne derivatives with different functional groups are shown to react on Si(001) selectively via the strained cyclooctyne triple bond. This selectivity originates from the distinctly different adsorption dynamics of the separate functional groups: The cyclooctyne triple bond exhibits a direct adsorption pathway as opposed to the majority of other organic functional groups, which generally react on Si(001) via a metastable intermediate.

 

Aug 2016


NPCyclooctine

Ethynylcyclooctynes and diazides were synthesized and applied for a chemoselective sequence of copper(I)-catalyzed azide–alkyne cycloadditions and strain-promoted azide–alkyne cycloadditions. Chemoselectivity within the reaction sequence was achieved by balancing three factors: Cu-catalysis/ring strain/steric shielding. A cholic acid derived triazide was subjected to the cycloaddition sequence as a model system for a layer-by-layer synthesis on surfaces.

 

 

 

Nov 2015

Hauser-heck

γ-Aryl-β-ketoesters can be prepared in one step from aryl bromides and bis(trimethylsilyl) enol ethers using catalytic amounts of Pd(dba)2/t-Bu3P and stoichiometric amounts of Bu3SnF. The wide range of γ-(hetero)aryl-β-ketoesters that can be obtained illustrate the scope and limitations of this novel Hauser-Heck combination. γ-Aryl-β-ketoesters with a 1,3-dioxane acetal in the ortho position can easily be transformed into the hydroxy naphthoate in very good yield. Aqueous formic acid at 65 °C provides optimal conditions for this deprotective aromatization.


Oct 2015

 
bromsulf

 

α-Bromosulfones have been synthesized diastereoselectively by reaction of β-hydroxy-gem-dibromides with aromatic sulfinates. More sterical demanding groups in the β-position lead to increased stereoselectivity in these SN2-reactions. The lithiated α‑bromosulfones react diastereoselectively with alkylating agents, aldehydes and ketones. No configurational stability of the lithiated α‑bromosulfones was observed, but a fast equilibration towards a chelate-stabilized intermediate. Treatment of the α-bromosulfone with methylcuprate resulted in the substitution of the bromine by a methyl group.


Jul 2015

toc3

Distinct dipoles: New non-symmetrical fluoro-substituted pentacene derivatives are synthesized which feature distinct molecular dipoles. All compounds are analyzed regarding their optoelectronic and structural properties as isolated molecules and in thin solid films. A precise comparison between the moelcular and solid-state properties allows detailed insights into the exciton binding energies.

Jun 2015

ketol rearrangement


The stereospecific BF3-mediated α-ketol rearrangement of β-hydroxy-α-ketoamides yields isolable difluoroboranyloxy-3-keto-amides. The air-stable boron complexes exhibit novel reactivity in bromination and dipolar cycloaddition reactions.


Feb 2015

 

Et2O auf Si

The adsorption of diethyl ether (Et2O) on Si(001) was studied by means of scanning tunneling  microscopy (STM) and photoelectron spectroscopy. Et2O reacts on Si(001) via a datively bonded intermediate, which was isolated at surface temperatures below 100 K. At higher surface temperature, Et2O converts dissociatively into the final state by  cleaving one O−C bond; the resulting −O−C2H5 and −C2H5 fragments are found to attach on two Si dimers of neighboring dimer rows. Tipinduced hopping of the −C2H5 fragment on one dimer was observed at positive sample bias.

 

Sep 2014


thfsi001



The adsorption of diethyl ether (Et2O) on Si(001) was studied by means of scanning tunneling  microscopy (STM) and photoelectron spectroscopy. Et2O reacts on Si(001) via a datively bonded intermediate, which was isolated at surface temperatures below 100 K. At higher surface temperature, Et2O converts dissociatively into the final state by cleaving one O−C bond; the resulting −O−C2H5 and −C2H5 fragments are found to attach on two Si dimers of neighboring dimer rows. Tipinduced hopping of the −C2H5 fragment on one dimer was observed at positive sample bias.

Jun 2014


isochinocycline


An efficient total synthesis of isoquinocyclinone was achieved using a pentacyclic lactone as key intermediate. The pyrrolo-pyrrole substructure was elaborated by acetylide acylation, conversion of an O,O-acetal into an N,O-acetal and intramolecular amidine alkylation.

May 2014


clado



The enantioselective addition of indoles to mesoxalic ester amides is investigated. The feasibility of these vic-tricarbonyl compounds as building blocks in natural product synthesis is shown in the syntheses of cladoniamide G and F. They involve the arylation of mesoxalic ester amide, a Suzuki cross-coupling to a 2,2'-biindole and an intramolecular lactam formation as key steps.

Feb 2014


wailu

A synthesis of the 9-epimer of the marine natural product wailupemycin A is reported. The key reaction sequence consists of a diastereoselective enamine addition to a tricarbonyl monohydrate, the formation of an enol silyl acetal, and finally the stereocontrolled addition of the α-pyrone substructure.

Oct 2013

TricarbonylPasserini3

vic-Diketoamides react with a variety of isonitriles and carboxylic acids in a regioselective Passerini three-component reaction to give good to excellent yields of α-Acyloxy-β-keto-carboxamides. In case of Passerini reactions with electron withdrawing group-substituted acetic acids, a one pot Passerini-Knoevenagel reaction was accomplished by addition of triethylamine to produce 5-oxofuran-2,2(5H)-dicarboxamides in good to very good yields.

Aug 2013

  • Start of the Collaborative Research Centre "Structure and Dynamics of Internal Interfaces" (SFB 1083).

gren

The Collaborative Research Centre SFB 1083 of the German DFG has been established at Philipps-Universität Marburg in collaboration with the Donostia International Physics Center (DIPC), San Sebastián, Spain. The aim is to achieve a detailed microscopic understanding of the chemical bonding, the electronic coupling, and the dynamics of energy transfer for model systems of different classes of hetero-interfaces.

Our group synthesize pentacene derivatives and functionalized cyclooctynes as molecular building blocks for organic interfaces.

                                                                                                                                                                          

Mar 2013

Fulicinerosid

A total synthesis of the proposed structures of fulicineroside and its aglycone fulicinerine is reported. Comparison with the reported data for the natural product and the aglycone suggests a misassignment of the natural product's structure.

 

 


Jan 2013

cyclooctyne

Adsorption of cyclooctyne on Si(001) was investigated by means of scanning tunneling microscopy. Two different adsorption configurations were identified for the chemisorbed molecules which exhibit a tendency for clustering along the dimer rows. Our results suggest a direct adsorption pathway for cyclooctyne on Si(001) most likely governed by the molecule’s triple bond in combination with its high ringstrain.

 

 


pen

 

 

 

 

 

6,13‑Disubstituted pentacenes were synthesized. Their electrochemical and optical properties and their solid-state packing motif were determined. 6,13‑Bis(trifluoromethyl)pentacene and 6,13‑dimethoxypentacene exhibit slipped face to face pi-stacking in the solid state while 6,13‑diethoxypentacene forms pairs of pi-stacking molecules in the solid state.

 

 


Crotylboration

Crotylboration of vic-diketoamides and vic-diketo esters was achieved with high diastereoselectivity and complementary regioselectivity. Whereas (E)-crotylboration of α,β-diketoamides resulted in high yields (91–99%) of β-crotylated products obtained as a single diastereomer (anti), Lewis acid promoted crotylboration of α,β-diketo esters yielded the α-crotylated species with the anti product as main diastereomer.

 

Zuletzt aktualisiert: 10.04.2017 · schwabe4

 
 
Fb. 15 - Chemie

Arbeitsgruppe Koert, Hans-Meerwein-Straße 4, 35032 Marburg
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