Chemo and diastereoselective conjugate addition of Grignard reagents on parthenin, a bioactive natural sesquiterpene lactone

The conjugate addition on a natural bioactive pseudoguaianolide sesquiterpene lactone parthenin with various Grignard reagents leads to 13-C alkylated products chemo and diastereoselectively in fair overall yields. Compared with other Grignard reagents vinyl and smaller straight chain alkyl Grignard reagents gave better yields.