Synthesis of isoxazoline-linked chlorins and their in vitro cell viabilities

A concise synthesis of isoxazoline-linked chlorins is described. This approach is carried out from methyl pyropheophorbide-a as the starting material via 1,3-dipolar cycloaddition of a vinyl group on the periphery with nitrile oxide to give regioselective products with excellent yields. This method represents an extensive and efficient entry into the functionalization of chlorins with a chlorophyll-a skeleton. Moreover, we have examined a preliminary in vitro effect of these new derivatives on mouse sarcoma S-180 cell line in photodynamic therapy.