Phenols and lactones in Italo-Mitcham peppermint oil Mentha x piperita L

In the acidic fractions of Italo-Mitcham black peppermint oil (Mentha x piperita L.), some uncommon phenols, carboxylic acids and lactones have been identified, mostly related to menthone. The cis/trans isomers of 2,6-dimethyl-heptan-5-olide (19 and 20) and the (6R)-5,6-dihydro-3,6-dimethyl-benzol[b]furan-7(4H)-one (27) are new compounds, their structures have been proved by syntheses; the three diastereoisomers of perhydro-3,6-dimethyl-benzo[b]furan-2-one, 16, 17 and 18 as well as 2-isopropenyl-5-methylphenol (1), have not yet been identified in a natural raw material.