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.

(+)-Dimericbiscognienyne A: Total Synthesis and Mechanistic Investigations of the Key Heterodimerization.

The first total synthesis of (+)-dimericbiscognienyne A is described. Key to the successful access to (+)-dimericbiscognienyne A was a biosynthetically inspired Diels-Alder reaction between two differential epoxyquinoid monomers and the subsequent intramolecular hemiacetal formation. The selective formation of the natural product among other possible diastereomers during the late-stage [4+2] cycloaddition reaction was investigated by DFT calculations and experimental control studies.