Structure of malagashanine,a new alkaloid with chloroquine-potentiating action

The molecular structure of malagashanine (C₂₃H₃₀N₂O₄), a new alkaloid occurring in MadagascanStrychnos species and showing chloroquine-potentiating action, has been determined by single crystal X-ray diffraction. The crystals, in the form of a 11 acetone solvate, are monoclinic, space group P2₁, witha=10.328(2),b=10.554(6),c=11.490(5)Å, =96.67(2)⁰,Z=2. Refinement based on 3650 reflections measured at 294K yieldedR=0.045. The X-ray analysis shows that the ring system in malagashanine differs from that in alkaloids of the strychnobrasiline type in containing only five-and six-membered rings. Thermal analysis of the solvate indicates that the acetone molecules are firmly held in the crystal and the X-ray analysis reveals that they are trapped in crystal voids. Only van der Waals forces and C–H...O hydrogen bonds stabilize the crystal structure.