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Bisphosphine‐Functionalized Cyclic Decapeptides Based on the Natural Product Gramicidin S: A Potential Scaffold for Transition‐Metal Coordination
Author(s) -
Burck Sebastian,
van Assema Sander G. A.,
Lastdrager Bas,
Slootweg J. Chris,
Ehlers Andreas W.,
Otero José M.,
DacunhaMarinho Bruno,
LlamasSaiz Antonio L.,
Overhand Mark,
van Raaij Mark J.,
Lammertsma Koop
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200901127
Subject(s) - phosphine , chemistry , alkyl , stereochemistry , natural product , chelation , combinatorial chemistry , cyclic peptide , peptide , organic chemistry , catalysis , biochemistry
The natural product Gramicidin S is a promising scaffold for novel oligopeptide‐based bisphosphine ligands, combining the advantageous rigid chiral backbone with the close proximity of phosphine substituents. The required unnatural, phosphine‐containing, amino acid building blocks were synthesized by means of a novel protocol that involves the enantioselective alkylation of a chiral nickel Schiff base template. Three Ni complexes were prepared with different alkyl chains between the phosphine group and the α‐carbon atom of the incorporated glycine; the absolute stereochemistry of two of them was determined by single‐crystal X‐ray structure analysis. By detaching the template, enantiopure L ‐phosphine amino acids resulted enabling the solid‐phase, stepwise construction of a linear sequence of the phosphine‐modified oligopeptides. On cyclization three bisphosphine‐substituted Gramicidin S analogues resulted, differing only in the size and shape of the linkage between the phosphine groups and the oligopeptides backbone. Their crystal structures suggest these species to have potential as chelating ligands.