sirenin noun1 •A sexual attraction pheromone in some fungi of the genus Allomyces.Aldrichimica Acta Volume 30 No 4 (pdf) from Sigma-Aldrich One notable early example was reported by Corey and involved an intramolecular cyclopropanation that was used in the synthesis of sirenin and has since been achieved asymmetrically using a chiral copper catalyst.