Crystal structure of vinblastine

Abstract

Vinblastine sulfate has been successfully crystallized by the hanging-drop vapor diffusion method against polyethylene glycol and lithium sulfate, and its structure determined by X-ray crystallography. The molecular geometry is rather similar to that of vincristine, with the most notable difference being that the key COOCH₃ group in the C18′ position is oriented in an opposite direction from that in vincristine. Half of the 9-membered azacyclononane ring in the catharanthine portion of the molecule is remarkably flat and coplanar with the indole ring, while the other half is in a boat conformation and fused with the piperidine ring in a chair conformation. The title compound crystallizes with an unusually large number of water molecules (nineteen), which form intriguing patterns of interconnected 5-membered rings (and some 6-membered rings) over substantial portions of the unit cell.