Converting 9-methyldipyrrinones to 9-H and 9-CHO dipyrrinones

Abstract

Yellow 9-methyldipyrrinones can be converted readily and in high yields to symmetric linear tetrapyrroles, blue biliverdinoids, which are cleaved in half, smoothly at room temperature to afford yellow 9-H dipyrrinones, and 9-CHO dipyrrinones as their violet to orange colored adducts with the carbon acid used for the scission: thiobarbituric acid (TBA), N,N′-diethylthiobarbituric acid, barbituric acid, N,N′-dimethylbarbituric acid and Meldrum's acid. The adducts, usually only of passing interest, are formally Knövenagel condensation products of a 9-CHO dipyrrinone with TBA and other carbon acids of this work, and a reverse Knövenagel reaction of such adducts leads to 9-CHO dipyrrinones. Under a set of improved reaction conditions the sequence thus efficiently converts 9-CH 3 dipyrrinones to 9-H and 9-CHO dipyrrinones.

Expanding the eggshell colour gamut: uroerythrin and bilirubin from tinamou (Tinamidae) eggshells

“…Furthermore, this analysis also shed more light on the nature of the minor pigments present, one of which could be identified as a uroerythrin isomer 33 (Supplementary Fig. S7) and one to be likely a formyldipyrrinone 34 (Supplementary Fig. S13).…”