Chiral bipyridine and terpyridine ligands grafted with L-tyrosine fragments

The synthesis of stable terpyridine and bipyridine frames substituted with L-tyrosine fragments is reported. These highly functionalized compounds hav e been prepared from the corresponding iodo, and ethynyl substituted analog s by a reaction catalyzed by low valent palladium(0), itself generated in s itu from palladium(II) and Cal. A tertiary amine is required to quench the nascent acid. Complexation of the chelating part of the molecule with ruthe nium(II) metal afforded redox and photoactive complexes. With the terpy-Ru complex carrying a genuine tyrosine fragment an efficient quenching reactio n (k(q) = 2.2 x 10(9) s(-1)) due to electron transfer is observed in DMF an d in the presence of K2CO3 The blank experiment performed under the same co nditions with the tyrosine-protected benzoyl ester proved that this process is inhibited. The synthetic methods reported herein provide a practical me thodology to the rational design of transition metal complexes bearing diff erent kinds of bioactive functionalities.