Anonamine, C19H27NO7, neosenkirkine, C19H27NO6, and hydroxysenkirkine, C19H27NO7.CH3OH. Macrocyclic secopyrrolizidine alkaloids from Senecio anonymus Wood.

lambda(Mo K alpha) = 0.71069 A, T = 298 K. Anonamine (I) (12,21-dihydroxy-4-methyl-4,8-secosenecionan-8,11,16-trione): C19H27NO7, Mr = 381.2, monoclinic, C2, a = 24.247 (7), b = 8.766 (2), c = 9.072 (1) A, beta = 99.21 (2) degrees, U = 1903.3 (8) A3, Z = 4, Dm = 1.32 (1), D chi = 1.330 g cm-3, mu(Mo K alpha) = 1.09 cm-1, F(000) = 816. Neosenkirkine (II) (12-hydroxy-4-methyl-4,8-secosenecionan-8,11,16-trione): C19H27NO6, Mr = 365.2, monoclinic, C2, a = 24.45 (1), b = 8.781 (2), c = 9.029 (2) A, beta = 98.99 (3) degrees, U = 1915 (1) A3, Z = 4, Dm = 1.27 (1), D chi = 1.267 g cm-3, mu(Mo K alpha) = 1.01 cm-1, F(000) = 784. Hydroxysenkirkine (III) [12,18-dihydroxy-4-methyl-4,8-secosenecionan-8, 11,16-trione-methanol (1/1)]: C19H27NO7.CH3OH, Mr = 413.2, orthorhombic, P2(1)2(1)2(1), a = 9.052 (3), b = 13.150 (4), c = 17.404 (8) A, U = 2071 (1) A3, Z = 4, Dm = 1.33 (1), D chi = 1.325 g cm-3, mu(Mo K alpha) = 1.10 cm-1, F(000) = 888. Full-matrix least squares refinement converged at R values of 0.042, 0.043 and 0.051 for 3163, 2894 and 2896 reflections for (I), (II), (III), respectively. All three crystals exhibit hydrogen bonds, including intramolecular O11...HO12 and intermolecular O8...HO12. In addition, intermolecular hydrogen bonds appear in (I) between O21...HO21' and in (III) between O8...HOCH3. The observed N...C8 distances across the eight-membered otonecine rings were 2.200, 2.245 and 1.712 A in (I), (II) and (III) respectively.