A Simple Biomimetic Synthesis of dl-Chamaejasmine, a Unique 3,3‘-Biflavanone

The first chemical synthesis of dl-chamaejasmine (1), a structurally unique 3,3‘-biflavanone natural product, was achieved as shown above, by a two-step sequence starting from trimethyl ether derivatives of 3-iodonaringenin (cis + trans) involving (i) metallic lanthanum-mediated reductive dimerization in refluxing THF and (ii) global demethylation with BBr₃ in CH₂Cl₂. This synthesis represents a generally applicable biomimetic (reductive) radical dimerization approach to the 3,3‘-biflavonoids.