Studies Directed toward the Total Synthesis of Azaspiracid:  Stereoselective Construction of C1−C12, C13−C19, and C21−C25 Fragments

2000-11-07T00:00:00Z (GMT) by Rich G. Carter David J. Weldon
The efficient entry to the C1−C12, C13−C19, and C21−C25 fragments of azaspiracid is outlined. The C1−C12 portion is constructed using a key asymmetric allenyl borane addition to the corresponding α,β-unsaturated aldehyde. The synthesis of the C13−C19 portion utilizes an Evans asymmetric alkylation followed by Sharpless asymmetric dihydroxylation. In addition, a novel solution to the mismatched effects of a neighboring chiral oxazolidinone during a Sharpless dihydroxylation is detailed.