Asymmetric synthesis of orobanchol, a representative canonical strigolactone, based on enzymatic kinetic resolution and its conversion to naturally occurring orobanchol derivatives

Strigolactones are apocarotenoids known as phytohormones and rhizosphere semiochemicals. Orobanchol, originally isolated from red clover, is recognized as one of the representative canonical strigolactones. A considerable number of naturally occurring orobanchol derivatives have been identified so far, and alectrol (orobanchyl acetate), fabacyl acetate, 7-oxoorobanchol, and 7-hydroxyorobanchol are known as orobanchol derivatives that retain its entire carbon skeleton. By combining our original synthetic method for (±)-orobanchol with enzymatic kinetic resolution, we successfully achieved the synthesis of the natural enantiomer of orobanchol and its conversion to naturally occurring orobanchol derivatives such as alectrol and fabacyl acetate.