The molecule is the beta configuration has been determined in Fiecchi et al (1981) J. Org. Chem. DOI:10.1021/jo00320a061. for kermesic acid
7-carboxy-6-hydroxy-8-methyl-9,10-dioxo-2-[(2S,3R,4R,5S,6R)-3,4,5-trihydroxy-6-(hydroxymethyl)oxan-2-yl]anthracene-1,3-diolate