Abstract
The structures of two isomeric diterpenes, pterokaurene L2, [I], and pteroatisene P2, [III], isolated from Pteris longipes and Pteris purpureorachis, respectively, were elucidated by X-ray crystallographic analysis. The crystal structures were determined by the direct method. The crystal data are : I ; tetragonal, space group P4322, a=12.510 (5), b=12.510 (5), c=22.923 (10) Å, V=3587.5 Å3, z=8, Dx=1.239 g cm-3, III ; orthorhombic, space group P212121, a=14.370 (7), b=20.205 (10), c=12.808 (6) Å, V=3718.8 Å3, z=8, Dx=1.227 g cm-3. The structures of I and III were established to be ent-9, 15α-dihydroxykaur-16-en-19-oic acid and ent-9, 15α-dihydroxyatis-16-en-19-oic acid, respectively.
