Left Panel: The co-crystal structure of analogue 81 bound to catalytic site of PI3Kδ (PDB 6G6W, 2.72 Å). Right Panel: The co-crystal structure of analogue 82 bound to catalytic site of PI3Kδ (PDB 5M6U, 2.85 Å). The protein is depicted as yellow ribbons, and the hydrogen bonds are illustrated with blue dashed lines; Analogue 81 and 82 atoms are colored as follows: carbon, red-orange; nitrogen, blue; oxygen, red; chlorine, green; fluorine, jade; hydrogen, white; the chiral carbon is highlighted in violet.