EPOXIDE CONFIGURATION IN PALMARIN JATEORIN AND CHASMANTHIN . X-RAY ANALYSIS OF A P-BROMOPHENACYL ESTER OF A PALMARIN DERIVATIVE

The epoxide ring in palmarin, jateorin, and chasmanthin is shown to be in the β-configuration by an X-ray analysis of a p-bromophenacyl ester of a palmarin derivative. The crystals are orthorhombic, space group P2 12121, with four molecules of C 23H23O7Br in a unit cell of dimensions a = 10.76, b = 8.95, and c = 21.79 Å. The structure was solved by the heavy-atom method and refined by least-squares calculations. R is 0.078 for 1907 independent reflexions. The molecular framework of the derivative is highly distorted because of intramolecular overcrowding effects. A δ-lactone ring in the system is constrained to adopt a conformation with five of the ring atoms coplanar.