Protosappanin A, a polyphenolic natural product bearing a unique 6H-dibenzo[b,d]oxocin-7(8H)-one moiety, is an important and novel monomer component of Caesalpinia sappan L. that exerts a variety of promising biological activities. Herein, we report a formal synthetic route to protosappanin A. The key feature of our synthetic strategy involves a Suzuki coupling reaction, a ring-closing metathesis (RCM) reaction, a dihydroxylation reaction, and a hydrochloric acid-catalysed pinacol rearrangement for the construction of the core 6H-dibenzo[b,d]oxocin-7(8H)-one scaffold.
Keywords: 6H-dibenzo[b,d]oxocin-7(8H)-one; Protosappanin A; formal synthesis; pinacol rearrangement; ring-closing metathesis.