= Solution
\b[Each isomer has one favourable anomeric interaction.] A has the favourable axial exocyclic <oxygen> in the upper-ring chair; B has it in the lower-ring chair. The NMR-constrained conformations therefore do not provide a doubly anomeric versus non-anomeric comparison.
Both can keep important <carbon> <substituents> equatorial and each obtains one anomeric stabilization. \b[Appreciable amounts of both are therefore a reasonable prediction], rather than a strong preference based solely on counting anomeric interactions. The environments of the two ring <oxygens> are not identical, so this argument does not determine an exact one-to-one equilibrium ratio; quantitative preference would require further energetic information.
Back to article page
