Leptospermone is a chemical compound (a β-triketone) produced by some members of the myrtle family (Myrtaceae), such as Callistemon citrinus (Lemon Bottlebrush), a shrub native to Australia, and Leptospermum scoparium (Manuka), a New Zealand tree from which it gets its name.

[1] Modification of this allelopathic chemical to produce mesotrione led to the commercialization of derivative compounds as HPPD inhibitor herbicides.

A biologist at the Western Research Centre of Stauffer Chemical Company noticed that very few plants grew under Callistemon citrinus bushes.

[3][4] Leptospermone can be synthesized from phloroglucinol by a reaction with 3-methylbutanenitrile (isovaleronitrile) in the presence of a zinc chloride catalyst.

Phloroglucinol is biosynthesized in a single step from malonyl-CoA[6] and could be the intermediate, but other routes of biosynthesis may be possible, such as via isobutyryl-CoA, the result of the decarboxylative condensation of ketoisovalerate (ketone form of valine) (cf.