Concise syntheses of natural diarylheptanoids containing a 1,4-pentadiene unit

Two concise and efficient synthetic routes were developed for the synthesis of three 1,7-diarylheptanoids (1-3) containing a 1,4-pentadiene unit, which were originally isolated from Ottelia acuminata var. acuminata. The first approach focused on the construction of linear diarylheptanoids 1 and 3 featuring a (1E,4E)-pentadiene moiety, via a Suzuki coupling reaction. The second strategy enabled the synthesis of sixteen-membered macrocyclic ether 2 with a (1Z,4E)-pentadiene unit. The challenging macrocyclization was successfully accomplished through an Ullmann coupling. Notably, the formation of the Z-olefin within the macrocyclic framework was promoted by the inherent ring strain of diarylether-type heptane system, which preferentially stabilizes this particular configuration.