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Total Synthesis of (±)-Luciduline
A Total Synthesis of d,l-Luciduline by a Regioselective Intramolecular Addition of an N-Alkenylnitrone.
J. Am. Chem. Soc. 1976;
In 1976, Oppolzer and Petrzilka reported the total synthesis of luciduline, an alkaloid isolated from Lycopodium lucidulum. The route featured a highly regioselective [3+2]-nitrone cycloaddition, which in this strategic setting can be interpreted as an equivalent of a Mannich reaction. In addition, the authors reported a highly concise route consisting of only seven linear steps. Of note, no protecting groups were required to furnish the natural product in 27% overall yield.
Ketone B is generated by a Diels–Alder reaction between cyclohexenone A and butadiene. B is converted to oxime C at which stage the diastereomers are separated by crystallization. After reduction, nitrone E is generated in situ from hydroxylamine D by condensation with formaldehyde. The nitrone undergoes an intramolecular [3+2] cycloaddition to furnish isoxazolidine F. Methylation, reduction of the N–O bond, and subsequent Jones oxidation finish the total synthesis of (±)-luciduline hydrochloride.
20 April 2021 (online)
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