Structure of elsinochrome A: a perylenequinone metabolite.

trans-1,2-Diacetyl-1,2-dihydro-5,10-dihydroxy-3,7,8,12- tetramethoxybenzo[ghi]perylene-4,11-dione, C30H24O10, Mr = 544.51, orthorhombic, P2(1)2(1)2(1), Z = 4, a = 12.428 (3), b = 13.048 (3), c = 14.933 (3) A, V = 2421.5 (9) A3, Dx = 1.494, Dm (by flotation) = 1.48 g cm-3, lambda(Mo K alpha) = 0.71069 A, mu = 1.057 cm-1, F(000) = 1136, T = 293 K, R = 0.046 (2065 observed reflections). Elsinochrome A is shown to exist in the solid state as a nonplanar quinone tautomer; the pigment adopts a helical conformation, in analogy with the related cercosporin, but the perylenequinone moiety in elsinochrome A appears to be significantly less skewed.