Azachlorins: Synthesis of a novel type of hydroporphyrins from the bile pigment bilirubin

Abstract

Abstract Azachlorins rac ‐ 10a,b , rac ‐ 11 , and rac ‐ 16 , a novel type of hydroporphinoid compounds, were synthesized from azaporphyrins 8 and 13 by regioselective cycloaddition of singlet oxygen and further transformation by amide acetal Claisen rearrangement. The azaporphyrins are readily accessible from the naturally occurring bile pigment bilirubin ( 5 ). The photophysical properties of the azachlorins recommend these chlorin derivatives as potential photosensitizers for Photodynamic Therapy (PDT).