Synthetic studies on lignans and related compounds. VIII. Synthesis of justicidin B and diphyllin and of taiwanin C and E from 2,3-dibenzylidenebutyrolactones via .BETA.-apolignans: A chemical model for natural co-occurrence of 4-hydrogen- and 4-hydroxy-1-phenyl-2,3-naphthalides in plants.

The concurrent synthesis of justicidin B (3) and diphyllin (4) coexistent in Justicia procumbens var. leucantha and of taiwanin C (1) and E (2) in Taiwania cryptomerioides was achieved by combination of the photocyclization of 2, 3-dibenzylidenebutyrolactones (7 and 9) and subsequent air oxidation of the resulting β-apolignans (8a and 10a).