Mechanisms of the Aqueous Solvolysis of the Ring-opening of the Lactone Ring of Goniodomin A

The phycotoxin Goniodomin A is a Dinoflagellate of the Alexandrium genus and is a macrocyclic lactone. It is found widely in sea water and is known to open slowly the lactone in water. The cleavage of the lactone is sensitive to the pH of the water. As one changes the pH from ~6 to 8 its solvolytic rate dramatically increases. Treatment of kinetic data previously published indicates that there are two competing first-order reactions, an SN­1 and an intramolecular SN2, which is a pseudo first-order reaction.