Compound (-)-19

Dimethyl (2R,5S,5'S,10aS,10'aS)-1,1',5,5'-tetrahydroxy-8,8'-dimethoxy-3,3'-dimethyl-9,9'-dioxo-5,5',6,6',7,7',9,9'-octahydro-10aH,10'aH-[2,2'-bixanthene]-10a,10'a-dicarboxylate

From: Atropselective syntheses of (−) and (+) rugulotrosin A utilizing point-to-axial chirality transfer