Organometallics
Kevin Burgess Texas A&M University, US
Metallopeptide-based dirhodium catalysts
In a series of papers, the latest of which is J. Am. Chem. Soc., 2010, 132, 9289, Ball has made it possible to complex dirhodium complexes with carboxylic acid side-chains on peptides, for example, those from aspartic acid residues (D). They are able to complex these to peptides in which the two Asp residues are separated by three amino acids. Conditions for this complexation might be too harsh for the peptide when [Rh.sub.2][(OAc).sub.4] was the precursor, but it was a practical transformation when starting with [Rh.sub.2][([O.sub.2][CCF.sub.3]).sub.4]. Two isomers result from this reaction, one with the peptide chains aligned in the same direction, and the other with them opposed. These complexes give different enantioselectivities for the insertion (Reaction 1).
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A library of 22 peptides was prepared, complexed individually, the two isomers of each complex were separated by HPLC, then tested in Reaction 1. Thus the best …
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