Structure of 18'-epivinblastine.

Methyl (3aR-[3a alpha,4 beta,5 beta,5a beta,9(3R*,5S*,7R*,9R*), 10bR,13a alpha])-4-(acetyloxy)-3a-ethyl-9-[5-ethyl-1,4,5,6,7,8,9, 10-octahydro-5-hydroxy-9-(methoxycarbonyl)-2H-3,7- methanoazacycloundecino[5,4-b]indol-9-yl]-3a,4,5,5a,6,11,12, 13a-octahydro-5-hydroxy-8-methoxy-6-methyl-1H-indolizino-[8,1-c,d] carbazole- 5-carboxylate methanol solvate, C46H58N4O9. 2CH3OH (1), Mr = 875.07, monoclinic, P2(1), a = 10.2759 (12), b = 22.353 (3), c = 10.4051 (12) A, beta = 106.502 (9) degrees, V = 2291.6 (5) A3, Z = 2, Dx = 1.27 g cm-3, Mo K alpha radiation, lambda = 0.7107 A, mu = 0.8397 cm-1, F(000) = 940, T = 198 K, R = 0.0470 for 2751 reflections, Fo greater than or equal to 4 sigma(Fo). The C ring of the vindoline moiety is in the boat conformation with the hydroxy group and the tertiary N in the bowsprit positions resulting in a fairly short intramolecular hydrogen-bonding interaction. The relevant parameters for O3--H3...N9 are O...N 2.651 (6), H...N 1.94 (5) A and O--H...N 147 (5) degrees. The D and E rings are in the sofa and envelope conformations, respectively. The piperidine ring of the catharanthine portion of the molecule assumes the chair conformation while the conformation of the azacyclononene ring is a boat-chair. An intramolecular hydrogen bond between the indolino NH of the catharanthine moiety and methoxy O (O25) of the vindoline moiety is also observed. The relevant parameters for N16'--H16'...O25 are N...O 2.827 (6), H...N2.14 (6) A and O--H...N 136 (5) degrees.