(1e)-7-[(8e)-1,6-dihydroxy-3-methyl-7-oxo-8-[(pentylamino)methylidene]-5-propan-2-ylnaphthalen-2-yl]-3,8-dihydroxy-6-methyl-1-[(pentylamino)methylidene]-4-propan-2-ylnaphthalen-2-one