Enantioselection in bilirubin analogs with only one propionic acid group

Article abstract of DOI:10.1016/S0957-4166(97)00481-3

Enantiopure synthetic bilirubin analogs (1 and 2) with only a single β- methyl propionic acid group adopt a folded, ridge-tile conformation stabilized by intramolecular hydrogen bonding. The β-methyl group forces the pigment to adopt a left-handed (M) helical conformation, as evidenced by exciton circular dichroism spectra and indicating that one propionic acid group is sufficient to control the pigment's conformation.