Cinnamoyl shikonin.

The title compound, 1-(5,8-dihydro-1,4-dihydroxy-5,8-dioxo-2-naphthyl)-4-methylpent-3-en-1-yl cinnamate, C(25)H(22)O(6), crystallizes in space group P2(1). The phenyl ring of the cinnamate is anti to the carbonyl group of the same moiety [C-C-C-C = -175.6 (2) degrees] and is nearly parallel to the naphthyl ring system. Two six-membered rings formed by intramolecular hydrogen bonds, with O-H...O distances of 2.587 (2) and 2.589 (2) A, occur on either side of the fused ring system, creating a tetracyclic pyrene-shaped system. The phenyl ring forms an intermolecular stack with the benzoquinone ring, as a result of aromatic pi-pi interactions.