Synthesis and germination activity study of novel strigolactam/strigolactone analogues

Herein, we report an efficient and practical synthetic route to assemble novel highly-tens [5,5] trans-fused B/C strigolactam/strigolactone analogues along with cis-fused strigolactams. The key feature of our synthetic strategy includes palladium-catalyzed carboxylate-directed olefination of commercially available N-Boc phenylalanines followed by direct photocatalytic decarboxylative Giese cyclization. The SAR studies were conducted for the newly synthesized scaffolds to stimulate seed germination of Orobanche cumana. The trans-fused compounds showed better activity then the cis-fused compounds. However, the strigolactones 35/36 and 39/40 showed superior bioactivity than the GR245DS and GR244DO.