Synthesis and Characterization of Folic Acid-Conjugated Terbium Complexes as Luminescent Probes for Targeting Folate Receptor-Expressing Cells.

Several conjugates between folic acid and a series of kinetically stable lanthanide complexes have been synthesized, using amide coupling and azide-alkyne cycloaddition methodologies to link the metal-binding domain to folate through a variety of spacer groups. While all these complexes exhibit affinity for the folate receptor, it is clear that the point of attachment to folate is essential, with linkage through the γ-carboxylic acid giving rise to significantly enhanced receptor affinity. All the conjugates studied show affinities consistent with displacing biological circulating folate derivatives, 5-methyltetrahydrofolate, from folate receptors.

Boronic ester functionalised 1,8-diboryl-naphthalene scaffolds: fluoride oxide chelation.

1,8-Bis(boronic ester) derivatives of naphthalene, 1,8-CH{B(OR)}, present an attractive target as receptors for the fluoride ion B-F-B chelation, but are synthetically challenging to access due to the competing formation of a very stable anhydride containing a B-O-B motif. By contrast, unsymmetrical systems of the type 1,8-CH{B(OR)}(BR') can be synthesized for (OR) = 1,2-OCH ( Cat) and R' = Mes. This system is shown to be competent for the uptake of F, making use of a chelating mode of action and the formation of a bridging B-F-B motif between the two boron centres.