A biomimetic total synthesis of (+)-ainsliadimer A.

A protecting group free and biomimetic total synthesis of (+)-ainsliadimer A has been accomplished in 14 steps from α-santonin. The synthesis relies on a hydrogen bonding promoted [4 + 2]-hetero-Diels-Alder dimerization to afford the key homodimer intermediate, which demonstrates the feasibility of using nonenzymatic conditions to achieve the proposed biosynthesis.