Comparison of the room- and low-temperature
1H NMR spectra of the bis-(
R)- or bis-(
S)-MPA esterderivative of an open chain
sec,sec-1,2-diol allows the easy determination of its relative stereochemistryand in some cases absolute configuration. If the diol is anti, its absolute configuration can be directlydeduced from the signs of
![](/images/gifchars/Delta.gif)
T1T2 for substituents R
1/R
2, but if the relative stereochemistry of the diol issyn, the assignment of its absolute configuration requires the preparation of two derivatives (both thebis-(
R)- and bis-(
S)-MPA esters), comparison of their room-temperature
1H NMR spectra, and calculationof the
![](/images/gifchars/Delta.gif)
RS signs for the methines H
![](/images/gifchars/alpha.gif)
(R
1) and H
![](/images/gifchars/alpha.gif)
(R
2) and R
1/R
2 protons. The reliability of thesecorrelations is validated with 17 diols of known absolute configuration used as model compounds.