Highly stereoselective peptide modifications through Pd-catalyzed allylic alkylations of chelated peptide enolates |
| |
Authors: | Deska Jan Kazmaier Uli |
| |
Institution: | Institut für Organische Chemie, Universit?t des Saarlandes, Im Stadtwald, Geb. C4.2, 66041 Saarbrücken, Germany, Fax: (+49)?681‐302‐2409 |
| |
Abstract: | Deprotonation of peptides in the presence of zinc chloride gives rise to highly reactive nucleophiles that can be subjected to palladium-catalyzed allylic alkylation reactions. Excellent diastereoselectivities are obtained that are nearly independent of the allylic substrate used. By using this protocol, highly functionalized side chains can also be incorporated in excellent yields and selectivities. The stereochemical outcome of the reaction is exclusively controlled by the peptide chain as long as terminal pi-allyl-palladium complexes are involved. Probably, there is a threefold coordination, at least, of the deprotonated peptide chain to the chelating zinc ion. In such metal peptide complexes, one face of the generated enolate is shielded by the side chain of the adjacent amino acid, thus directing the electrophilic attack onto the opposite face. This behavior explains why an S amino acid always generates an R amino acid (and the other way round). |
| |
Keywords: | allylic alkylation asymmetric synthesis chelates palladium peptide modification peptides |
本文献已被 PubMed 等数据库收录! |
|