Asymmetric total synthesis of natural pyrrolizidine alkaloid, (+)-alexine

The total synthesis of the potent glycosidase inhibitor (+)-alexine with five contiguous stereogenic centres [(1R,2R,3R,7S,7aS)-3-hydroxymethyl-1,2,7-trihydroxypyrrolizidine alkaloid] is described featuring the efficient and stereodefined novel elaboration of the functionalized homochiral lactam derived from 2,3,5-tri-O-benzyl-β-d-arabinofuranose.