Readily Accessible Bicyclononynes for Bioorthogonal Labeling and Three‐Dimensional Imaging of Living Cells

I can see clearly now: Bicyclo[6.1.0]non-4-yne, an easily prepared, symmetrical cycloalkyne, displays excellent reaction kinetics in strain-promoted cycloaddition reactions with azides and nitrones (see scheme). Highly specific protein modifications are demonstrated in vitro and subcellular-resolved imaging of glycan expression was achieved in metastatic melanoma cells during invasive migration into three-dimensional collagen lattices.