Synthesis and photochemical reactivity of bilirubin model compounds

Abstract
The bilirubin model compounds 1, 2 and 3 were prepared in good yield. The photochemistry of 1, 2 and 3, which all have the 4Z,15Z form, was investigated; they show a Z‐E isomerisation to the 4Z,15E and the 4E,15E isomers. Unlike the isomers of 1, those of the compounds 2 and 3, could be isolated in a pure form.