Biomimetic Total Synthesis of Gambogin and Rate Acceleration of Pericyclic Reactions in Aqueous Media

A significant rate acceleration of a Claisen rearrangement and of a Claisen/Diels–Alder reaction cascade sequence was observed in the presence of water. This reaction sequence was used in a total synthesis of gambogin (1) from a tricyclic dialkene 3 via 2.