Fig. 7 Characteristic 13 C NMR chemical shifts and O - O bond length of some cyclic peroxide derivatives

(Scheme 29) [167]. The stereoisomers could be isolated by fractional recrys-tallization from ethanol. The major methyl ether was MeO-equatorial dioxane and the minor MeO-axial based on the X-ray crystallography.

In CDCl3 solution of the minor dioxane, NMR analysis showed that it existed as an equilibrium mixture of twisted boat conformers. Adding shift reagent, Eu(FOD)3, resulted in the MeO-axial chair conformer (Scheme 30).

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