Synthesis of Ambrox® from labdanolic acid

A synthesis of the valuable amber-type odorant Ambrox® from labdanolic acid (main diterpenoid of the acid fraction of non-polar extracts of Cistus ladaniferus L.) is reported. The conversion is based on (a) the α,β-dehydrogenation of methyl labdanolate using an organoselenium reagent, (b) subsequent oxidative degradations of the side chain, and (c) final acid-promoted cyclization of the resulting tetranorlabdan-8α,12-diol. The influence of the...