2,3-Epoxyhelenalin 4-19-00-02749 (Beilstein Handbook Reference) 41945-41-9 BRN 0035774 Oxireno(1,2)azuleno(6,5-b)furan-5,8-dione, decahydro-7-hydroxy-2,7a-dimethyl-6-methylene-