Question

Suggest another way the stereochemistry of the acetonide could be experimentally determined.

Answer 1

Empirical Chemical Shift Correlations
This is the NMR version of the functional group concept. The
idea is that similar functional groups have similar conformations
and magnetic shieldings, so they have reliable chemical shifts.
If the relative configuration of a few test compounds can be
determined with other, more sophisticated or time-consuming
methods, then correlations can be made to related compounds.

The idea is pretty simple: syn-1,3-diol acetnoides exist in chair
conformations and have different methyl group chemical shifts,
while anti-1,3-diol acetonides exist in twist boat conformations
(due to 1,3-diaxial strain) and have pseudo C2-symmetry and
similar methyl group chemical shifts. Note that we are looking
at the 13C chemical shifts here. Therefore, it is useful to use 2D
NMR data to assign the acetonides properly:

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