Zweikernige Titan-(IV)-komplexe als Enzymmimikry

Enzymes are natural molcular machines, which control chemical reactions in biological systems. Although they consist of only about 20 aminoacids, they are highly complex and show great variety. Two-centered metalloenzymes are an important class of enzymes, which contain two metal-ions as active center. Most prominent examples are Proteinphosphatases, Catecholoxidases and Peroxiddismutases. The distance between the metal-ions of these enzymes is about 3-5 A. Using methods of Supramolecular Chemistry, it is possible to build model compounds via self-organisation, which imitate the structure of these active centers.To accomplish this, first it is necessary to find a sure way to synthesize aminoacid-bridged biscatechol-ligands, which may be used to create two-centered titanium(IV)-complexes in later complexion studies.In a first step biscatechol-ligands with functionalized sidechains are synthesized. Optimized reaction-parameters allow access to a stereokonservative synthesis which provides the aminoacid-bridged ligands in excellent yields. Via HBTU-cuppling it is now possible to insert any aminoacid as a spacer into the ligands. In complexion-studies with titanium(IV)ions two-centered, doublestranded conplexes are formed. Under thermodynamic reaction-control and in presence of lithiumions, in most cases, only a single isomer shows up. But under kinetic control up to seven isomers are formed. If sodium- or pottassiumions are present, it is almost impossible to gain access to a single isomer. Furthermore, these larger ions promote the occurrence of two-centered triplestranded complexes.It is possible to insert alcohols with linear carbonchains of any lengh as bridging coligands. However, alcohols which are branched at C1 do not fit in the substrate-pockets of these titaniumcompounds. The solubility of these compounds is limited to alcohols, DMF and DMSO.In a further step, the alkaline counterions are exchanged for tetra-n-butylammonia-ions. This allowed access to two-centered complexes which are soluble in organic solvences like acetone, acetonitrile, dichloromethane and THF and which occur as a single isomere, even under kinetic reaction-control. This is a first systematic access to isomeric pure two-centered doublestranded compounds and a successful method to avoid triplestranded complexes.Functionalised alcohols may now easily be inserted into the binding-pocket of these coordination compounds and transformed by chemical reactions in the ligandsphere. Examples are [2+4]-cycloaddition, hydroboration and Finkelstein-reaction.This thesis succeeded in showing the possibility of creating enzymemimikry which imitate the structure of the active side of two-centered metalloenzymes. These soluble, as a single isomer accessible coordination compounds may in further studies grant insight in the functions and reactionmechanism of enzymes and help along to imitate them. By optimizing the only rudimentary present proteinesphere it should be possible to accomplish functional enzymemimetics, which may prove as a basis for a new generation of chiral auxilliaries and catalysts.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2006

Author dc:creator

• Nolting, Rainer

Contributors dc:contributor

• Albrecht, Markus

• info:eu-repo/classification/ddc/540
• Chemie
• Titankomplexe
• Supramolekulare Chemie
• Metalloenzym
• Brenzcatechinderivate
• Enzymmimikry
• Zweikernige Metalloenzyme

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-122652%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:60967