Radical‐Induced Ring Opening of Epoxysilane in the Synthesis of (±)‐Supinidine and (±)‐Trachelanthamidine

An α‐(2‐silyloxiranyl)carbinyl radical fused to a pyrrolizidine skeleton was generated from the corresponding bromide 4 . This radical underwent rearrangements followed by hydrogen abstraction to give silyl allyl ether 8 and silyl enol ether 9 . The mixture was converted to (±)‐supinidine 1 and (±)‐trachelanthamidine 3. When triethylborane/oxygen was used to initiate the radical reaction, an α,β‐unsaturated aldehyde 15 was obtained, thus to accomplish a formal synthesis of (±)‐ 1 .