Crystal and molecular structure of isovoacangine: An alkaloid from Stemmadenia Donnell-Smithii

C₂₂H₂₈N₂O₃ is monoclinic,P2₁. Unit-cell dimensions at 293 K area=10.023(5),b=6.615(3),c=14.749(6) Å,=91.41(4)°,V=978(1) ų,D _c =1.25 g cm^–3, andZ=2. The structure has been determined from single-crystal data collected with a four-circle diffractometer and refined from 1421 reflections toR=0.057. The structural features determined from chemical and spectroscopic studies are confirmed and extended. The stereochemistry at C(4) and C(18) is 4S and 18S. The indole ring is not planar and the seven-membered nitrogen-containing ring adopts a distorted-chair conformation. The angle between the normals to the planes of the indole and sevenmembered rings is 15.2(1)°, while the C(5)-N(6)-C(19)-C(2) atoms of the central axis of the iso-quinuclidine tricyclic structure is 69.1(1)°. The molecules in the crystal are held together by a hydrogen bond, a C-HO contact, and van der Waals interactions.