Abstract Upon treatment with dilute mineral acid, α-ylangene afforded two alcohols with amorphane carbon skeletons, 10β-hydroxyamorpha-4-ene (16) and 10α-hydroxyamorpha-4-ene (17). The carbonic acid-induced isomerization of α-ylangene epoxide yielded 3α-hydroxy-α-amorphene (19), 3α-hydroxy-δ-amorphene (20), and 3α, 10α-dihydroxyamorpha-4-ene (21). The structures of these compounds were strictly determined, and the revised structure 16 of δ-cadinol proposed by Lin was shown to conflict with the results of the isomerization of α-ylangene and with the previously-reported conversion of α-copaene into δ-cadinol (10) and T-muurolol (11) under similar conditions.