Novel and efficient stereoselective synthesis of (±)-orobanchol, a representative canonical strigolactone, based on acid-mediated cascade cyclization

[Display omitted] •(±)-Orobanchol, a representative canonical strigolactone, was successfully synthesized.•The key acid-mediated cascade cyclization proceeded with almost perfect diastereoselectivity.•The overall efficiency is far superior to the best previously reported synthesis.•This cascade cyclization must be based on 4π-electrocyclic reaction and analogous to that in planta. Strigolactones are a class of apocarotenoids known as rhizosphere semiochemicals and plant hormones that can be classified as either canonical or noncanonical. Although orobanchol has long been known as a representative canonical strigolactone, only two synthetic methods have been reported so far, and both have room for improvement in selectivity and overall efficiency. We report a novel and efficient stereoselective synthesis of (±)-orobanchol using acid-mediated cascade cyclization as a key step. This cascade cyclization is analogous to that occurring in planta and is understood to involve a conrotatory 4π-electrocyclic reaction.