About a Practical Synthesis of Ambrox® from Sclareol: a New Preparation of a Ketone Key Intermediate and a Close Look at its Baeyer–Villiger Oxidation

The latest route to Ambrox® (1) starting from sclareol (2) proceeds through an oxy ketone 4 (Scheme 1). A new practical synthesis of the key intermediate 4 is described; it is equivalent to a partial oxidative degradation of sclareol (2) with peracetic and periodic acids (Scheme 2). The final product of the BaeyerVilliger oxidation of the oxy ketone 4 with commercial peracetic acid is decisively dependent on the reaction conditions because the expected acetate 9 reacts with any nucleophile, especially the peracid (Scheme 3). Furthermore, this acetate 9 is very prone to eliminative coupling (Scheme 4).