Synthesis under reversible conditions of cyclic porphyrin dimers using palladium-catalysed allyl transesterification

Kaiser, Guido; Sanders, Jeremy K. M.

doi:10.1039/b006151o

Cited by 34 publications

(28 citation statements)

References 6 publications

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“…The equilibrium of allyl ester palladium complexes can be reached within hours in the presence of a mild base, palladium catalyst, and moderate heating [37,38] . These conditions are compatible with the binding between a zinc Related exchange processes that could be alternatives to the transesterifi cation reaction to produce similar DCLs of receptors under different reactions conditions are the exchange of thioesters and the exchange of amides.…”

Section: Esters and Related Connectionsmentioning

confidence: 99%

Development of Synthetic Receptors using Dynamic Combinatorial Chemistry

Escalante

Furlán

2010

Dynamic Combinatorial Chemistry

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In order to bind a given guest, a receptor must be complementary -it must have recognition groups which are of the appropriate electronic character to complement the binding sites of the guest. Those recognition groups must be positioned on the receptor in a way that they can interact with recognition groups from the guest when both receptor and guest are in the binding conformation. Upon binding, the receptor and guest reorganize their interactions with solvent molecules (disrupting some and probably creating new ones), and change their conformation to achieve a suitable binding conformation. In the process, noncovalent interactions within each molecule may be broken or formed.The requirement to balance all the variables involved in this recognition process makes the design of successful synthetic receptors a signifi cant challenge.A frequently explored shortcut that facilitates receptor design is to incorporate rigidity in order to avoid as much as possible changes in conformation that are diffi cult to predict. In addition, a rigid preorganized receptor will decrease the cost of unfavorable reorganization energy. However, high -affi nity perfectly rigid receptors are not easy to achieve in practice since minor errors in design that demand readjustment from the receptor can be energetically very expensive [1] . Indeed, nature does not use rigidity to improve affi nity, but it still produces receptors with affi nities that are on average much better than the best synthetic receptors prepared to date. A recent survey of the binding effi ciency of synthetic and biological hosts by Houk et al. indicates that synthetic systems are typically several orders of magnitude less effi cient in binding small molecules than their biological counterparts [2] .Guest binding by natural receptors such as proteins is reinforced by intrareceptor interactions, which require conformational rearrangements of parts of the receptor that are very similar to the conformational rearrangement necessary to interact with the guest. Consequently the interactions that contribute to guest binding extend beyond the immediate binding site well into the protein structure [3] . Synthetic receptors that operate by the same principle will need to be able to Dynamic Combinatorial Chemistry. Edited by Joost N. H. Reek and Sijbren Otto

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Section: Esters and Related Connectionsmentioning

confidence: 99%

Development of Synthetic Receptors using Dynamic Combinatorial Chemistry

Escalante

Furlán

2010

Dynamic Combinatorial Chemistry

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“…10c). We demonstrated that this could be used for the synthe- 16 Templated capping of a porphyrin dimer using Pd-catalyzed chemistry [23]. Fig.…”

Section: The Selection Approachmentioning

confidence: 99%

“…The reaction we have chosen for exploring this possibility is Pd-catalyzed allyl transesterification (Fig. 10d) [23]. Indeed, it has been possible to isolate capped dimers as shown in Fig.…”

Section: The Selection Approachmentioning

confidence: 99%

Adventures in molecular recognition. The ins and outs of templating

Sanders

2000

Pure and Applied Chemistry

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Two different approaches are described for the creation of supramolecular systems potentially capable of recognition and catalysis. Using the design approach, we have been able to accelerate and influence two different Diels-Alder reactions within the cavities of porphyrin dimers and trimers; this is templating from the outside inwards. The selection approach is a synthetic chemical attempt to capture some of the key evolutionary features of biological systems: dynamic combinatorial chemistry is used to create equilibrating mixtures of potential receptors, and then a template is used to select and amplify the desired system. Five potential reactions for such dynamic chemistry are discussed: base-catalyzed transesterification, hydrazone exchange, disulfide exchange, alkene metathesis, and Pd-catalyzed allyl exchange, and preliminary templating results (inside outwards) are presented.

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“…Unfortunately, this reaction generally requires harsh conditions that are likely to inter- fere with the weak interactions underlying recognition by a template (6,7). In the special case of allyl esters, Pd-catalyzed transesterification proceeds under mild conditions (8).…”

Section: Reversible Covalent Chemistrymentioning

confidence: 99%

“…Reversible reactions that feature unsymmetrical linkages include amide exchange (5), transesterification (6)(7)(8), as well as exchange of imines (9, 10) and derivatives thereof. Only one example of amide exchange has been reported (5), making use of enzymes to cleave and reform the amide bonds.…”

Section: Reversible Covalent Chemistrymentioning

confidence: 99%