Scheme 1.
The synthesis of the tetrazine‐fluorophore conjugates 6–11 and 19–20. A) Synthesis of BODIPY‐FL and AF488‐tetrazines through late stage fluorophore introduction: a) Boc2O, NaOH, H2O. b) (1) NH2NH2, Zn(OTf)2, acetonitrile/2‐cyanopyridine or formamidine acetate. (2) NaNO2 in DCM/AcOH (1 : 1, v:v). c) (1) 4 m HCl, dioxane/DCM (1 : 1, v/v) (2) AF488‐NHS or BODIPY‐FL NHS, DIPEA, DCM. B) Synthesis of BODIPY‐Tetrazines 19–20, through fluorophore formation on a tetrazine scaffold: d) DMP, DCM e) (1) 2,4‐Dimethylpyrrole, TFA. (2) DDQ. (3) TEA, BF3⋅OEt2.