Synthesis of Bis-γ-lactones from "Diacetone Glucose". 5. Optically Active Canadensolide

Article abstract of DOI:10.1021/jo00224a026

Details are given for the synthesis of optically active canadensolide.Use of "diacetone glucose" as the precursor affords the naturally occurring levorotatory enantiomer in 16 steps.The absolute configuration has been determined to be 2S,3R,4R.The investigation has revealed that the readily obtainable bis-lactone 10b is not a suitable intermediate for α-methylenation, since deprotonation with kinetic bases occurs preferentially at the methine position (C-2), which results in β-elimination.In the successful synthesis, the lactonic hemiacetal 10a emerges as the precursor of choice.