Syntheses of Bile Pigments. Part 18. Synthesis and Conformational Studies of Oxa- and Thia-deaza-biliverdin Analogues

Article abstract of DOI:10.1002/hlca.19940770715

Following the conventional methodology used for the synthesis of bile pigments, some oxa- and thia-deaza-biliverdin analogues were synthetized for the first time.Both UV/VIS spectroscopic and 1H<1H>-NOE difference studies reveal that the oxa-deaza-biliverdin analogue 8a occurs in apolar solvents in a partly 'stretched' conformation, whereas the corresponding thia derivative 8b behaves rather like a genuine bile pigment.Unexpectedly, the helical-shaped conformation is also preponderant in a trioxa-trideaza-biliverdin analogue, which could be only characterized in its protonated form 14.