Diastereomeric 5,6-dimethyl-4H-1,3-dioxin-4-ones from (−)-(1R,4S)-menthone: Synthesis and NMR analysis

The two diastereomers of spirocyclic 5,6-dimethyl-4H-1,3-dioxin-4-one (5,6) have been synthesized by acetalization of tert-butyl 2-methyl-3-oxobutanoate (2) with (-)-menthone (4). Their structures have been determined by NMR analysis.