Reaction mechanism of non-enzymatic stereoselective formation of wine lactone

The reaction mechanism of the non-enzymatic stereoselective formation of the (3S, 3aS, 7aR) configuration of the wine lactone from the (6R) form of (E)-8-carboxylinalool in acidic aqueous solution was analyzed by quantum chemistry calculations. The transition states for the cyclization and hydride shift of the carbocation intermediates were obtained (< 55 kJ/mol). As the wine lactone has three chiral centers and eight possible configurations, we compared the reaction barriers which would generate the different configurations. It was revealed that the formation of the (3S, 3aS, 7aR) configuration would be preferred than all the other forms among the present reaction paths.