Firstly, the double bond in ring D is hydrogenated, followed by Oppenauer oxidation of the hydroxyl group and the concurrent migration of the remaining olefin from ring B to ring A so that it is in conjugation with the ketone carbonyl group at position 3.
12.
The A value is a thermodynamic parameter and was originally measured along with other methods using the Gibbs free energy equation and, for example, the Meerwein Ponndorf Verley reduction / Oppenauer oxidation equilibrium for the measurement of axial versus equatorial values of cyclohexanone / cyclohexanol ( 0.7kcal / mol ).
