Is Methyl Dihydrojasmonate natural?

Cyclopentanone (from petrochemical adipic acid) is condensed with pentanal (from butene) to give 2-pentylcyclopent-2-enone; dimethyl malonate then adds to the ring and one ester group is removed. Cyclopentanone made from furfural, a biomass chemical, would make about a third of the molecule natural origin.

Methyl dihydrojasmonate, best known by the trade name Hedione, is built in three stages. Cyclopentanone and pentanal are first joined by an aldol condensation, and the product is isomerised so that its C=C bond sits inside the ring, giving 2-pentylcyclopent-2-en-1-one.

Dimethyl malonate is then added across that C=C bond in a Michael addition catalysed by sodium methoxide: the malonate carbon bonds to the ring carbon next to the one carrying the pentyl chain, and the resulting enolate is protonated.

Finally one of the two ester groups is removed by heating with water and a salt (a Krapcho-type decarbomethoxylation), which releases carbon dioxide and methanol and leaves the single methyl acetate arm. The product, a mixture of cis and trans isomers, is purified by vacuum distillation.

A fragrance ingredient, best known as Hedione, with a fresh, airy jasmine note used in a huge range of perfumes. It was modelled on a jasmine scent molecule but is built entirely from petrochemicals.