A Synthetic Route to the Saxitoxin Skeleton: Synthesis of Decarbamoyl α‐Saxitoxinol, an Analogue of Saxitoxin Produced by the Cyanobacterium Lyngbya wollei

Pick your poison: Salient features of a concise synthetic route for the saxitoxin skeleton are a bromonium-ion-initiated cascade cyclization of readily prepared 1 to give tricyclic intermediate 2 and the transformation of the gem-dibromomethylene group into an enol acetate unit. This new route enabled the preparation of 3, a naturally occurring analogue of saxitoxin. Cbz=benzyloxycarbonyl, Ms=methanesulfonyl, Py=pyridine.