A series of 4-aza-podophyllotoxin derivatives have been synthesized regioselectively via the three-component
reaction of aldehydes, aromatic amines, and tetronic acid catalyzed by L-proline. This method has the
advantages of high yield, high regioselectivity, extensive adaptability, easy operation, and environmental
friendliness. These compounds were also investigated in vitro, and some were found to have good anticancer
activity.