The synthesis of (−)-Ambrox® starting from labdanolic acid

Iododecarboxylation of labdanolic acid (1), followed by dehydrohalogenation led to alkenes 4 and 12. Both compounds were converted into (1R,2R,4aS,8aS)-1-(2-hydroxyethyl)-2,5,5,8a-tetramethyldecahydro-2-naphthalenol (8), which was transformed via cyclization into (−)-Ambrox® (9).