Alkynyl β-sheet peptidomimetics retain their anti-parallel sheet conformation when coordinated to tungsten

Abstract

Peptide derivatives (8 and 9) of 2-amino-2′-carboxydiphenylacetylene (1) were prepared using the Sonogashira reaction and standard peptide chemistry. As reported earlier by Kemp and Li (Ref. [1]), 8 and 9 adopt anti-parallel β-sheet conformations in solution. Reaction of 8 and 9 with W(CO)3(dmtc)2 produced the tungsten mono-alkyne complexes 10 and 11 as a mixture of two inseparable diastereomers (10a and 10b, and 11a and 11b) resulting from two different spatial arrangements of the dmtc ligands. The respective mixtures of the two diastereomers were characterized by ES-MS and 1H NMR spectroscopy. The solution conformations of the diastereomers were probed using NOESY and DMSO titration experiments. The data from these experiments show that the peptide portions of 10 and 11 maintain their anti-parallel β-sheet conformations following coordination to tungsten.