1,2-Dihydr-oxy-2-(3-methyl-but-2-en-yl)-3-oxo-2,3-dihydro-1H-indene-1-carboxylic acid monohydrate.

The title compound, C(15)H(16)O(5)·H(2)O, is an inter-mediate of the Hooker oxidation reaction, used for the synthesis of 2-hydr-oxy-3-(2-methyl-prop-1-en-yl)naphthalene-1,4-dione (nor-lapachol). The packing in the crystal structure is arranged by an O-H⋯O hydrogen-bonded network along the [100] and [010] directions. Each organic mol-ecule is linked to four other mol-ecules via the hydr-oxy groups. The water solvent mol-ecule is connected to carboxylic acid groups by three hydrogen bonds.