Synthesis of (±)-zeapyranolactone, a noncanonical strigolactone isolated from maize, and determination of its overall relative configuration

Abstract

Strigolactones are a class of apocarotenoids known as rhizosphere semiochemicals and plant hormones. They are classified as either canonical, with a tricyclic lactone (ABC ring) and a butenolide (D ring) comprising their basic skeleton, or noncanonical, deviating from the basic skeleton. Here, zeapyranolactone, a noncanonical strigolactone isolated from maize, was synthesized for the first time as a racemic and diastereomeric mixture, and its relative stereochemistry was determined by three-dimensional electron diffraction crystallography as 4S*,4aS*,2′R*. The synthetic route developed is straightforward and does not rely on the use of typical protective groups.