Total synthesis of the proposed structures of hyacinthacines C2, C3, and their C5-epimers

Synthesis and structural confirmation of highly oxygenated pyrrolizidine alkaloids, hyacinthacines C2 [(1S,2R,3R,5R,7S,7aR)-3,5-hydroxymethyl-1,2,7-trihydroxypyrrolizidine], C3[(1S,2R,3R,5S,7R,7aR)-3,5-hydroxymethyl-1,2,7-trihydroxypyrrolizidine], and their C5-epimers were achieved on the basis of the highly divergent method employing (S)-(−)-2-pyrrolidone-5-carboxylic acid as the starting material.