Investigating Bicyclobutane-Triazolinedione Cycloadditions as a Tool for Peptide Modification.

Acyl bicyclobutanes are shown to engage in strain-promoted cycloaddition reactions with a diverse array of triazolinedione reagents. The synthesis of an orthogonally protected urazole building block enabled the facile preparation of amino acid- and peptide-derived triazolinediones that undergo cycloaddition reactions to afford novel peptide conjugates. The additive-free and fully atom-economical nature of the transformation is a promising starting point for the generalization of this cycloaddition reaction for the functionalization of biomolecules.