[1] The name is also used for the class of compounds formally derived from bilane proper by replacement of some additional hydrogen atoms by various functional groups.

Natural bilanes usually have side chains substituted on the two carbons in each pyrrole ring that are not adjacent to the nitrogens.

[2] The parent (unsubstituted) bilane is difficult to prepare and unstable,[3] but substituted derivatives are synthesized by most living organisms as intermediates in the synthesis of natural porphyrins.

[2][3] Upon treatment with aldehydes, bilanes may cyclize to give porphyrinogens and various open or closed oligomers and polymers.

Also, the catabolism of hemoglobin in humans produces bilirubin, another linear tetrapyrrole that is a partially oxidized bilane.