Compound Y (C8H4O3) dissolves slowly when warmed with aqueous sodium bicarbonate. The IR spectrum of Y has strong peaks at 1779 and at 1854 cm-1. The broadband proton-decoupled 13C spectrum of Y exhibits signals at d 125 (CH), 130 (C), 136 (CH), and 162 (C). Acidification of the bicarbonate solution of Y gave compound Z. The proton-decoupled 13C NMR spectrum of Z showed four signals. When Y was warmed in ethanol, compound AA was produced. The 13C NMR spectrum of AA displayed 10 signals. Propose structures for Y, Z, and AA.