Efficient Routes to ω-Chloroalkyl Bilirubins and C12-N22 Bridged Biliverdins

Summary.

 ω-Chloroalkyl biliverdins, prepared in three steps from 8-unsubstituted dipyrrinones in 70–80% overall yields, were reduced by sodium borohydride to provide the corresponding ω-chloroalkyl bilirubins in high yields. Upon treatment of the ω-chloroalkyl biliverdins with sodium hydroxide in ethanol, C12-N22 bridged biliverdins were obtained in high yields.