Dendritic tethers

Design and Synthesis of Dendritic Tethers for the Immobilization of Antibodies for the Detection of Class A Bioterror Pathogens, Chapter 10... 

Davis et al. synthesized dendritic tethers, which were linked to a protein to mimic glycoproteins. The protein scaffold that was nsed was a protease that had part of... 

Chemio-, regio-, and streospecific cross metathesis of terminal double bonds of dendritic tethers... 

The amidoferrocenyl or silylferrocenyl monomers do not show any effect, however. Therefore, the dendrimer topology is important for recognition of oxo-anions. The appropriate encapsulation of the anionic host between the dendritic tethers is a key factor that very much increases the interaction between the functional ferrocenyl termini and the guest (Scheme 8.6). 

To investigate this dendritic effect, a dimeric model compound was synthesized which mimics the tethered relationship of two catalytic units within one branch of the PAMAM dendrimer. All dendritic catalysts were more active in the HKR than the parent complex. Furthermore, the dendritic catalysts also displayed significantly higher activity than the dimeric model compound. The authors proposed that this positive dendritic effect arises from restricted conformation imposed by the dendrimer structure, thereby creating a bigger effective molarity of [Co(salen)] units. Alternatively, the multimeric nature of the dendrimer, may lead to higher order in productive cooperative interactions between the catalytic units. 

Branched phenylacetylene monomers can be used to construct dendrimers on supports. This was accomplished using a triazene tether as a focal point, the reaction triad outlined above, and an AB2 monomer, as seen in Scheme 7.16 As in similar solution-phase convergent dendrimer syntheses, the first step was to prime the periphery of the dendrimer with t-butyl groups by di-coupling of a triazene-tethered dibromoaryl monomer with (di-f-butyl-phenyl)acetylene. In this and all subsequent coupling steps, an excess amount of the monodendron acetylene was used to drive the reaction to completion. The reagents and catalysts were washed away and the excess monodendron was recovered. At the end of the first step, the tri-aryl dendron I-M3-(t-Bu)4 was cleaved from the support (M represents the dendritic monomer unit). Two equivalents of this product were then coupled with the triazene-tethered di-acetylene ary] monomer to produce the heptaaryl dendron I-M7-(r-Bu)8. 

Ar = polystyrene supported dendritic TADDOL with aromatic tether Ref. 25 ... 

Because observed environmental effects on the redox potential, such as heme solvation, polarity of the heme microenvironment, and nature of the surrounding protein shell are not well understood, it is important to design model systems with a unique local microenvironment around the electroactive core. Recently, dendritic iron porphyrins with tethered axial hgands were designed in which the dendritic branches guarantee a controlled microenvironment around the heme core." The complexes are soluble in solvents of widely differing polarities, and the redox potential of the complexes was found to be solvent-independent. 

Weyermann. P. Diederich. F. Gisselbrecht. J.-P. Boudon. C. Gross. M. Dendritic iron porphyrins with tethered axial... 

The vast range of supramolecular polymeric materials also extends from the use of small molecules (e.g., double-sided discotics or multifunctional monomers with a discrete tether) to very large molecules (polymeric or dendritic). Another important characteristic of SPs is the timescale upon which the chains exist, which is defined by the rate of association/ dissociation of the monomers. Tme dynamic SPs must be reversible (breaking and recombining) on experimental time-scales (e.g., NMR timescale). A physical model developed by Cates and co-workers predias many viscoelastic properties of SPs as a funaion of the strength of the noncovalent interactions existing between monomers.Although initial studies focused on wormlike micelles, the model has been demonstrated to successfully describe the viscosity behavior of reversible, self-complementary UPy-based SPs. ... 

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