2H-Pyran-2-carboxylic acid, 5-ethylidenetetrahydro-2-(hydroxymethyl)-3-methyl-6-oxo-, (E)-(2S,3R)- 34081-95-3 4-18-00-06282 (Beilstein Handbook Reference) BRN 0015065 Retronecic acid lactone Retronecic lactone