Total synthesis of optically active integerrimine, a twelve-membered dilactonic pyrrolizidine alkaloid of retronecine type. I. Enantioselective synthesis of the protected (+)-integerrinecic acid
For the total synthesis of optically active integerrimine, the twelve-membered dilactonic pyrrolizidinealkaloid, the necic acid component (+)-integerrinecic acid has been enantioselectively synthesized in the protected form.
A total synthesis of the natural enantiomer of integerrimine (1), a twelve-membered dilactonic pyrrolizidinealkaloid of retronecine type has been achieved through the enantioselective synthesis and regioselective coupling of (+)-retronecine (4) and (+)-integerrinecic acid (methylthio)methyl ether (6).