Amino acid bioconjugation via iClick reaction of an oxanorbornadiene-masked alkyne with a Mn-I(bpy)(CO)(3)-coordinated azide

The catalyst-free room temperature iClick reaction of an unsymmetrically 2,3-disubstituted oxanorbornadiene (OND) as a `` masked'' alkyne equivalent with [Mn(N-3)(bpy(CH3,CH3))(CO)(3)] leads to isolation of a phenylalanine ester bioconjugate, in which the model amino acid is linked to themetal moiety via a N-2-coordinated triazolate formed in a cycloaddition-retro-Diels-Alder (crDA) reaction sequence, in a novel approach to bioorthogonal coupling reactions based on metalcentered reactivity.