Ethyl 2-[4-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]propanoate-d3 is labelled Ethyl 2-[4-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]propanoate (E926400) which is a reagent used to prepare substituted imidazopyridazines and benzimidazoles as inhibitors of FGFR3.