Base-Catalysed Reactions of Highly Hindered Phenols Used as

Base-Catalysed Reactions of Highly Hindered Phenols Used as Antioxidants 

Deduce the structure of A and give a mechanistic explanation for its formation. 

Oxonine 1, a derivative of the diterpene alkaloid aconitine, undergoes smooth oxidation when treated with exactly one equivalent of periodic acid. The product thus obtained, which shows no aldehyde or ketone absorption in the ir spectrum, is converted into 2 when heated in dilute aqueous base with air passing through the solution. 

Suggest a mechanism for the formation of 2 under these conditions. 

---