Ketyl Radical Cyclization of β‑Disubstituted Acrylates: Formal Syntheses of (+)-Secosyrin 1 and Longianone and the Total Synthesis of (+)-4-epi-Secosyrin 1

A novel approach to the synthesis of a series of 1,7-dioxaspirononanes that applies a ketyl radical cyclization strategy is described. Radical cyclization of the β-disubstituted acrylate 23, prepared in five steps from (R)-1,2-isopropylideneglycerol, gives both 2,3-syn- and 2,3-anti-furan products. The densely functionalized furan heterocycles are used to complete a concise formal synthesis of secosyrin 1, a metabolite of Pseudomonas syringae, and the total synthesis of 4-epi-secosyrin 1.