Synthesis of (-)-halichonic acid and (-)-halichonic acid B.

The first syntheses of the amino acids (-)-halichonic acid and (-)-halichonic acid B have been achieved in ten steps starting from commercially available (-)-α-bisabolol. The optimized synthetic route includes a new purification method for isolating (-)-7-amino-7,8-dihydrobisabolene in enantiomerically pure form via recrystallization of its benzamide derivative. The key intramolecular aza-Prins reaction forms the characteristic 3-azabicyclo[3.