Synthesis of Guaipyridine Alkaloids Rupestine M and L by Cycloaddition/Cycloreversion of an Intermediate
Jonathan R Scheerer1, Ella B Leeth1, Jennifer A Sprow1
1Department of Chemistry, William & Mary, P.O. Box 8795, Williamsburg, VA 23187, USA.
Abstract:
A new method to prepare 1,4-oxazinone intermediates was developed based on aza-conjugate addition of β-amino alcohols to electron-deficient alkyne precursors. A tandem intramolecular cycloaddition/cycloreversion reaction sequence was evaluated, leading to the synthesis of the guaipyridine alkaloid natural products rupestine M and L. Starting from (-)-citronellal and thus a known configuration of the C5 stereocenter, a revised absolute configuration of natural rupestine L is suggested based on optical rotation.
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