Ti(III)-promoted cyclizations. Application to the synthesis of (E)-endo-bergamoten-12-oic acids. Moth oviposition stimulants isolated from Lycopersicon hirsutum

The Ti(III)-promoted radical cyclization of epoxyenone 8 is described as the key step to access the diol 10 as a convenient starting material of the target molecules. The synthesis of β-(E)-endo-bergamoten-12-oic acid 2a from (+)-8,9-epoxycarvone 8 was successfully achieved by Suzuki-Miyaura coupling of the terminal alkene 20 with β-iodomethacrylate 21c, followed by deprotection and dehydration processes. Moreover, synthesis of the α-(E)-endo-1-hydroxy-bergamoten-12-oic acid derivative 34 was achieved by iterative elongation processes of the diol 10 lateral chain.