Structure of an antitumour drug: 9-hydroxy-2,5,11-trimethyl-6H-pyridol[4,3-b]-carbazolium acetate (9-hydroxy-2-methylellipticinium acetate; Celiptium) dihydrate.

C18H17N2O. C2H3O2. 2H3O, Mr = 336.2, monoclinic, C2/c, alpha = 21.789 (2), b = 12.853 (1), c = 14.004 (2) A, beta = 114.80 (1) degree, V = 3560.2 A3, Z = 8, Dm = 1.24, Dx = 1.255 Mg m3, lambda (Cu K alpha) = 1.54178 A, mu = 0.754 mm-1, F(000) = 1584, T = 298 K, R = 0.052 for 2236 observed reflections. Antitumor drug. The crystal structure involves the packing of resonant rings held together by a network of hydrogen bonds involving hydroxyl groups, acetate ions and water molecules. The main feature is the two stacking patterns found together in the crystal structure; this feature appears to differ from other derivatives.

Nucleic acid intercalating drug. The structure of 9-hydroxy-2,5,11- tetramethylpyrido[4,3-b]carbazolium (9-hydroxy-2,6- dimethylellipticinium) chloride monohydrate.

C19H19N2O.Cl. H2O, Mr = 344.6, triclinic, P1, alpha = 12.980 (1), b = 9.454 (2), c = 7.148 (1) A, alpha = 75.23 (2), beta = 99.73 (3), gamma = 91.83 (2) degree, V = 835.9 A3, Z = 2, Dm = 1.35 (2), Dx = 1.369 Mg m-3, lambda (Cu Ka) = 1.54178 A, mu = 2.11 mm-1, F(000) = 364, T 298 k, R 0.059 for 2767 observed reflections. Antitumour drug that displays one of the highest DNA affinities (4 x 10(6) M 1) among ellipticine derivatives. The structure analysis confirms the intercalation hypothesis. There is stacking of centrosymmetrically related parallel molecules along c, alternately spaced by 3.43 and 3.48 A. The crystal structure confirms the desolvation effect of the sixth nitrogen position.