Structure of capnoidine, a phthalide isoquinoline alkaloid

Abstract

I n t r o d u c t i o n . In the course of our studies of natural products we investigated the crystal and molecular structure of capnoidine isolated from Corydalis cava collected from Vojvodinas Danube region. Extraction, isolation, separation and identification of capnoidine were performed as described by Slavik & Slavikova (1961), Preininger, gimanek, GaSi6 & gantavy (1973) and Ga~i6, Popovi6 & Dragutinovi6 (1985). The interest in this work lies in the accurate determination of molecular conformation of the compound which might assist in a better understanding of its biological action, studies of which are in progress. 0108-2701/91 / 102191-03503.00 Experimental. A crystal 0.22 × 0.35 × 0.15 mm was mounted on a CAD-4 diffractometer (University of Berne) using graphite-monochromated Mo Ka radiation. Cell constants were refined by a leastsquares fit for 22 centered reflections with 0 range from 4.2 to 8.5 ° . Intensity data were collected with w-20 scan in the range 20 3.5tr(/) were considered as observed. Data were corrected for Lorentz and polarization effects. The structure was solved using SHELXS86 (Sheldrick, 1986) with all non-H atoms obtained from the E map (R = 0-173). Full-matrix least-squares (on F) isotropic (R = 0.096) and anisotropic refinement with program SHELX76 (Sheldrick, 1976) minimized ~'.w(AF) 2 for 245 parameters with unit weights. Final R=0 .038 , wR=0.038, (A/tr)max = 0007. Positions of H atoms were generated from assumed geometries and their positions were taken into account without refinement in structure-factor calculations with common isotropic temperature factor U = 0.072 (4)/~2. A final © 1991 International Union of Crystallography 2192 C 2 o H I T N O 6 Table 1. Fractional atomic coordinates (× 104) and equivalent isotropic temperature factors ( x 10 3) I U v~= ~( , , + u~+ v~).