A molecular formula, C₃₈H₃₈O₁₁, has been given for pillaromycin A. Acid hydrolysis of pillaromycin A afforded an aglycone, pillaromycinone, C₂₀H₁₈O₇ and a new sugar, pillarose, C₈H₁₂O₅. From the results of spectrometrical and chemical studies on pillaromycinone and its derivatives the presence of the following functional groups was elucidated in pillaromycinone ; two sec-hydroxyls, a tert-hydroxyl, two phenolic hydroxyls, a chelated carbonyl and an acetyl conjugated with α, β-unsaturated double bond.