Synthetic Access to Noncanonical Strigolactones: Syntheses of Carlactonic Acid and Methyl Carlactonoate.

Strigolactones are plant hormones regulating essential stages of a plant's development. Their low natural abundance combined with a low chemical stability significantly hampered the detailed investigation of their biological activity. Noncanonical strigolactones lack the fused tricyclic ABC-ring system commonly present in canonical-type strigolactones but feature an open-chain unit linking structurally diverse A-ring moieties to the butenolide D-ring. We herein present an efficient synthetic access to enantiomerically pure noncanonical strigolactones by a Stille cross-coupling approach to forge the central diene moiety and demonstrate this strategy by syntheses of natural products methyl carlactonoate and carlactonic acid. Furthermore, a synthetic access to deuterium-labeled analogues of these natural products has been developed.