Leptospermone
Encyclopedia
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.
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.
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).
herbicide. This herbicide was deemed “not likely to be carcinogenic to humans” by the EPA. 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. 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.
Leptospermone also has antibacterial potential. Studies have shown that it has strong inhibitive effects on Clostridium difficile
and Clostridium perfringens
.
Callistemon citrinus
Callistemon citrinus, also known as Crimson Bottlebrush is a shrub in the family Myrtaceae. It is native to the states of Queensland, New South Wales and Victoria in Australia, occurring in the vicinity of rocky streams and near-coastal swamps....
(Lemon Bottlebrush), a shrub native to Australia. Allelopathic
Allelopathy
Allelopathy is a biological phenomenon by which an organism produces one or more biochemicals that influence the growth, survival, and reproduction of other organisms. These biochemicals are known as allelochemicals and can have beneficial or detrimental effects on the target organisms...
studies have led to the commercialization of the analogous herbicidal compound mesotrione
Mesotrione
Mesotrione is an herbicide sold under the brand names Callisto and Tenacity. It is a synthetic analog of leptospermone developed to mimic the effects of this natural herbicide. Mesotrione works by inhibiting the plant enzyme 4-hydroxyphenylpyruvate dioxygenase which is necessary for carotenoid...
. Leptospermone is also studied as an antibacterial.
History
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.
Chemistry
Leptospermone is the common name for 1-hydroxy-2-isovaloryl-4,4,6,6-tetramethyl cyclohexen-3,5-dione. Leptospermone can be synthesized from phloroglucinolPhloroglucinol
Phloroglucinol is a benzenetriol. It is an organic compound that is used in the synthesis of pharmaceuticals and explosives. This molecule exists in two forms, or tautomers, 1,3,5-trihydroxybenzene, which has phenol-like, and 1,3,5-cyclohexanetrione , which has ketone-like character. These two...
by a reaction with isovaleroylnitrile in the presence of a zinc chloride
Zinc chloride
Zinc chloride is the name of chemical compound with the formula ZnCl2 and its hydrates. Zinc chlorides, of which nine crystalline forms are known, are colorless or white, and are highly soluble in water. ZnCl2 itself is hygroscopic and even deliquescent. Samples should therefore be protected from...
catalyst. Phluroisovalerone imine is produced and alkylated
Alkylation
Alkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion or a carbene . Alkylating agents are widely used in chemistry because the alkyl group is probably the most common group encountered in...
with iodomethane
Iodomethane
Methyl iodide, also called iodomethane, and commonly abbreviated "MeI", is the chemical compound with the formula CH3I. It is a dense, colorless, volatile liquid. In terms of chemical structure, it is related to methane by replacement of one hydrogen atom by an atom of iodine. It is naturally...
using sodium ethoxide
Sodium ethoxide
Sodium ethoxide is an alkoxide salt with the chemical formula C2H5ONa.-Preparation:It is commercially available as a white solid, or as a solution in ethanol. It is easily prepared in the laboratory by reacting sodium metal with ethanol:...
to produce an intermediate which is treated with aqueous hydrochloric acid resulting in isovaleroylsyncarpic acid (leptospermone).
Uses
Leptospermone was the blueprint for the compound mesotrione which has the trade name Callisto, a SyngentaSyngenta
Syngenta AG is a large global Swiss agribusiness company which notably markets seeds and pesticides. Syngenta is involved in biotechnology and genomic research. The company is a leader in crop protection, and ranks third in total sales in the commercial agricultural seeds market. Sales in 2010 were...
herbicide. This herbicide was deemed “not likely to be carcinogenic to humans” by the EPA. 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. 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.
Leptospermone also has antibacterial potential. Studies have shown that it has strong inhibitive effects on Clostridium difficile
Clostridium difficile
Clostridium difficile , also known as "CDF/cdf", or "C...
and Clostridium perfringens
Clostridium perfringens
Clostridium perfringens is a Gram-positive, rod-shaped, anaerobic, spore-forming bacterium of the genus Clostridium. C. perfringens is ever present in nature and can be found as a normal component of decaying vegetation, marine sediment, the intestinal tract of humans and other vertebrates,...
.