Stereoselective syntheses of the glycosidase inhibitors hyacinthacine A2, hyacinthacine A3 and 5-epi-hyacinthacine A3

Stereoselective syntheses of the naturally occurring glycosidase inhibitors hyacinthacines A2 and A3 are reported. In the case of hyacinthacine A2, the pyrrolizidine system was created from an acyclic precursor via a double cyclization procedure with a one-pot formation of two C-N bonds. In the case of hyacinthacine A3, the two C-N bonds were created in separate steps. In addition, the non-natural epimer at C-5 of hyacinthacine A3 was obtained.