Über die Biosynthese von γ‐Dodecanolacton in reifenden Früchten: Aroma‐Komponenten der Erdbeere (Fragaria ananassa) und des Pfirsichs (Prunus persica)

On the Biosynthesis of γ‐Dodecanolactone in Ripening Fruits: Flavor Constituents from Strawberries (Fragaria ananassa) and Peaches (Prunus persica) Administration of deuterium‐labelled 9,10‐expoxy[8,8‐2H2]heptadecanoic acid 8a/b and 9,10‐dihydroxy‐[8,8‐2H2]methylheptadecanoate 9 as lower analogues of oleic acid 1 to ripening fruits of strawberries (Fragaria ananassa) and peaches (Prunus persica) results in the emission of labelled γ‐undecanolactone (5) as the lower analog of γ‐dodecanolactone (2). The transformation proceeds with loss of a single D‐atom from C(8) of the precursors. Early precursors, like the C17‐epoxy‐acids 8a/b yield (4R)‐γ‐undecanolactone (5) of high enantiomeric purity, while later intermediates results in (4R)‐γ‐undecanolactone (5) of low purity. The data support a biosynthetic sequence involving the consecutive action of an epoxide hydrolase and β‐oxidation to generate the correct chain length of the lactone percursor. The final steps proceed via cyclization of the 3,4‐dihydroxyundecanoic acid 13 to the 3‐hydroxy‐γ‐undecanolactone 14. Elimination of H2O and reduction of the intermediate γ‐undec‐2‐enolactone 15 terminate the biosynthesis of 5. The sequence is representative for the biosynthesis of naturally occurring γ‐dodecanolactone (2).