available, and synthetic carvone correspondingly inexpensively prepared. The biosynthesis of carvone is by oxidation of limonene. Chemical properties Reduction There are three double bonds in carvone capable of reduction; the product of reduction depends on the reagents and conditions used. Catalytic hydrogenation of carvone (1) can give either carvomenthol (2) or carvomenthone (3). Zinc and acetic acid reduce carvone to give dihydrocarvone (4). MPV reduction using propan-2-ol and aluminium isopropoxide effects reduction of the carbonyl group only to provide carveol (5); a combination of sodium borohydride and CeCl3 (Luche reduction) is also effective. Hydrazine and potassium hydroxide give limonene (6) via a Wolff–Kishner reduction. Oxidation Oxidation of carvone can also lead to a variety of products. In the presence of an alkali such as Ba(OH)2, carvone is oxidised by air or oxygen to give the diketone 7. With hydrogen peroxide the epoxide 8 is formed. Carvone may be cleaved using ozone followed by steam, giving dilactone 9, while KMnO4 gives 10. Conjugate additions As an α,β;-unsaturated ketone, carvone undergoes conjugate additions of nucleophiles. For example, carvone reacts with lithium dimethylcuprate to place a methyl group trans to the isopropenyl group with good stereoselectivity. The resulting enolate can then be allylated using allyl bromide to give ketone 11. Metabolism In the body, in vivo studies indicate that both enantiomers of carvone are mainly metabolized into dihydrocarvonic acid, carvonic acid and uroterpenolone. (–)-Carveol is also formed as a minor product via reduction by NADPH. (+)-Carvone is likewise converted to (+)-carveol. This mainly occurs in the liver and involves cytochrome P450 oxidase and (+)-trans-carveol dehydrogenase. References External links Carvone at The Periodic Table of Videos'' (University of Nottingham) Flavors Enones Monoterpenes Cyclohexenes Isopropenyl compounds