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

Abstract
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[3.3.1]nonane ring system of halichonic acid along with the lactonized form of halichonic acid B in an 8:1 ratio. Optical rotation measurements confirmed that these synthetic compounds were in fact the enantiomers of the natural products, establishing both the relative and absolute configurations of the halichonic acids.

Beilstein J. Org. Chem. 2022, 18, 1629–1635. doi:10.3762/bjoc.18.174

Source: Beilstein Journal of Organic Chemistry - December 1, 2022 Category: Chemistry Authors: Beilstein Journal of Organic Chemistry - Syndicated Feeds Tags: alkaloid amino acid aza-Prins reaction cascade reaction natural product Full Research Paper Source Type: research