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Free, publicly-accessible full text available July 1, 2024
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Abstract Described herein are the first total syntheses of (±)‐dracocephalone A (
1 ) and (±)‐dracocequinones A (4 ) and B (5 ). The synthesis was initially envisioned as proceeding through an intramolecular isobenzofuran Diels–Alder reaction, a strategy that eventually evolved into a Lewis acid‐promoted spirocyclization. This highly diastereoselective transformation set the stage fortrans ‐decalin formation and a late‐stage Suárez oxidation that produced a [3.2.1] oxabicycle suited for conversion to1 . Brønsted acid‐mediated aromatization, followed by a series of carefully choreographed oxidations, allowed for rearrangement to a [2.2.2] oxabicycle poised for conversion to4 and5 . -
more » « less
Abstract Described herein are the first total syntheses of (±)‐dracocephalone A (
1 ) and (±)‐dracocequinones A (4 ) and B (5 ). The synthesis was initially envisioned as proceeding through an intramolecular isobenzofuran Diels–Alder reaction, a strategy that eventually evolved into a Lewis acid‐promoted spirocyclization. This highly diastereoselective transformation set the stage fortrans ‐decalin formation and a late‐stage Suárez oxidation that produced a [3.2.1] oxabicycle suited for conversion to1 . Brønsted acid‐mediated aromatization, followed by a series of carefully choreographed oxidations, allowed for rearrangement to a [2.2.2] oxabicycle poised for conversion to4 and5 .
