Fig. 2.
From: What are karrikins and how were they ‘discovered’ by plants?
The karrikin family. The first karrikin discovered was KAR1, also known as karrikinolide. Since karrikins can be produced by burning sugars such as xylose, the pyran ring of karrikins is probably derived from such pyranose sugars. Both karrikins and strigolactone hormones such as strigol have a butenolide ring