| Leptospermone | |
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2,2,4,4-Tetramethyl-6-(3-methylbutanoyl)cyclohexane-1,3,5-trione |
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Other names
Isovaleroylsyncarpic acid; 6-Isovaleryl-2,2,4,4-tetramethyl-1,3,5-cyclohexanetrione |
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| Identifiers | |
| CAS number | 567-75-9 |
| PubChem | 3083632 |
| ChemSpider | 2340805 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | C15H22O4 |
| Molar mass | 266.33 g mol−1 |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Leptospermone is a chemical produced by Callistemon citrinus (Lemon Bottlebrush), a shrub native to Australia. Allelopathic studies have led to the commercialization of the analogous herbicidal compound mesotrione. Leptospermone is also studied as an antibacterial.
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Leptospermone was first identified in 1927 and was extracted from a variety of plants in 1965, 1966 and 1968. It was first identified as a chemical in Callistemon citrinus in California in 1977. A biologist at the Western Research Centre of Stauffer Chemical Company noticed that very few plants grew under Callistemon citrinus bushes. After taking soil samples and creating an array of extracts, one was identified as an herbicide. While it did have herbicidal effects, the rate required for sufficient coverage was too high to be of practical use.
Leptospermone was optimized into thousands of compounds. Several were extremely effective but were too toxic, environmentally persistent or not selective enough. The final compound, mesotrione, is a triketone herbicide used as a selective herbicide for corn crops.[1]
Leptospermone is the common name for 1-hydroxy-2-isovaloryl-4,4,6,6-tetramethyl cyclohexen-3,5-dione. Leptospermone can be synthesized from phloroglucinol by a reaction with isovaleroylnitrile in the presence of a zinc chloride catalyst. Phluroisovalerone imine is produced and alkylated with iodomethane using sodium ethoxide to produce an intermediate which is treated with aqueous hydrochloric acid resulting in isovaleroylsyncarpic acid (leptospermone).[2]
Leptospermone was the blueprint for the compound mesotrione which has the trade name Callisto, a Syngenta herbicide.[1] This herbicide was deemed “not likely to be carcinogenic to humans” by the EPA.[3] Mesotrione has been proven to be an effective preemergent herbicidal treatment for velvetleaf. This is beneficial because atrazine is effective on many broadleaf weed species but does not effectively control velvetleaf. Surprisingly, using atrazine and mesotrione together produced greater weed control than just the summed effect. These two chemicals had synergistic effect on common ragweed and common lambsquarters.[4] Atrazine has been considered by the EPA for stronger regulation, encouraging the development of replacement or additive herbicides. The cost of phasing out atrazine and replacing it with mesotione is estimated at $9.2 million.[5]
Leptospermone also has antibacterial potential. Studies have shown that it has strong inhibitive effects on Clostridium difficile and Clostridium perfringens.[6]