The phthalideisoquinoline system has been synthesized from substituted 2-phenyl-1,3-indandiones as starting materials. The key step in the synthesis is the rearrangement of the spirobenzylisoquinoline ring system to the phthalideisoquinoline system. The diastereomeric cordrastines, I and II, have been synthesized by this method and their relative configurations have been established by comparison of their p.m.r. spectra with those of phthalideisoquinoline alkaloids of known configuration.