Nuovi approcci sintetici per strigolattoni non-canonici: verso l'eliolattone

Strigolactones (SLs) are a subject of increased scientific interest since 2008. Originally identified as allelochemicals involved in plant¿parasite interactions, more recently SLs have been shown to play multiple key roles as signalling molecules, plant hormones and anticancer agents. For these reasons they have become a cutting-edge topic in plant biology and agronomy, and have great potential in modern agriculture for regulation of plant development and interactions.1 Classic SLs feature a common structural framework including a tricyclic ring system (ABC-ring) linked to a butenolide ring (D-ring) via an enol ether bond. Recently, a novel subclass of strigolactones (non-canonical) lacking the canonical ABC-ring moiety has been identified: an open-chain unit links structurally diverse A-ring moieties to the D-ring, however the low natural abundance paired with the intrinsic instability of non-canonical SLs has so far hampered the investigation of these natural products. Among them, Heliolactone is the most abundant SL in sunflower and a germination stimulant for seeds of root parasitic weeds. We envisaged the first racemic total synthesis of Heliolactone starting from natural terpene citral and other renewable chemicals. Our strategy is focused on a convergent synthetic approach where the ¿non-canonical¿ SL's skeleton is assembled by means of a cross metathesis reaction between two terminal olefins ( A and B ) as the key synthetic step.