Total synthesis of hyacinthacines B3, B4, and B 5 and purported hyacinthacine B7, 7-epi-hyacinthacine B7, and 7a-epi-hyacinthacine B3 from a common precursor

The total synthesis of hyacinthacines B3, B4, and B5 and purported hyacinthacine B7, 7-epi-hyacinthacine B7, and 7a-epi-hyacinthacine B3 from a common anti-1,2-amino alcohol precursor is described. These syntheses confirmed that the proposed structures and absolute configurations of hyacinthacines B3, B4, and B5 were correct and disclosed that the proposed structure of hyacinthacine B7 was incorrect. Our synthetic and spectroscopic studies suggest that the natural hyacinthacines B5 and B7 are the same compounds; however, without access to authentic samples this cannot be unequivocally proven.