Photochemistry of α,β‐epoxy‐eucarvone.On π,π*‐excitation (λ = 254 nm)4isomerizes to the bicyclic ketoaldehyde5; on n,π*‐excitation (λ ⩾ 280 nm)4gives5, the β,γ‐unsaturated ketone6, the enone7and the cyclobutanone8. Scission of the (C—C)‐bond of the oxirane4would give the dihydrofuranee, which could isomerize to the ketoaldehyde5. On the other hand,4is assumed to isomerize to the β,γ‐unsaturated aldehydec, which could yield6and7by photodecarbonylation. The cyclo‐butanone8is shown to be a photoisomer of the ketone6.Furthermore, eucarvol (18) rearranges by a thermal [1,5]‐H‐shift to dihydro‐eucarvone (20); on UV.‐irradiat