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

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 41[-electrocyclic reaction.(c) 2023 Elsevier Ltd. All rights reserved.