rel-(1R,6S,7S,8R,9S)-9-Methyl-8-phenyl-6-[(1S,2R)-(2-phenylcyclohexyl)oxy]-4-aza-3,5-dioxatricyclo[5.2.1.0^4,9]decane

The structure of the title compound, C₂₆H₃₁N₁O₃, was determined by X-ray crystallography. It was found to be a unique, bridged tricyclic nitroso acetal. Notable features include a chair conformation of the tetrahydro-1,2-oxazine ring and a highly pyramidalized N atom [Σ_angles = 314.2 (6)°]. The configurations of the five contiguous stereogenic centers in the nitroso acetal establish that the tandem cycloaddition sequence proceeded by an exo-[4 + 2]/endo-[3 + 2] pathway.

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