Biosynthetically Inspired Syntheses of Secu′amamine A and Fluvirosaones A and B

Presented here is a concise synthesis of secu′amamine A, and fluvirosaones A and B from readily available allosecurinine and viroallosecurinine. The key C2‐enamine derivative of (viro)allosecurinine, the presumed biosynthetic precursors of these natural products, was accessed, for the first time, by a VO(acac)2‐mediated regioselective Polonovski reaction. Formal hydration and 1,2‐amine shift of this pluripotent enamine compound afforded secu′amamine A. Formal oxidative [3+2] cycloaddition reaction between this enamine and TMS‐substituted methallyl iodide reagent paved the way to the precursors of fluvirosaones A and B. The relative stereochemistry at the C2 position of these advanced intermediates governs the fate of 1,2‐amine shift leading to fluvirosaones A and B. The syntheses of potential biosynthetic precursors and investigations of their chemical reactivities have provided insights regarding the biogenesis of these natural products. Biosynthetically inspiring: A vanadium‐mediated regioselective Polonovski reaction of (viro)allosecurinine N‐oxides afforded the key pluripotent enamine precursors that were further transformed into secu′amamine A and fluvirosaones A and B. The key steps of the transformations were biomimetic 1,2‐amine shifts and/or formal [3+2] cycloadditions of the enamine.