8. Kishi and co-worker’s121 developed an NMR database of various molecules
in chiral solvents, for the assignment of relative and absolute stereochemistry
without derivatization or degradation. Kishi referred to this database as a
‘‘universal NMR database.’’122 The diagram provided for diols 45 illustrates
the method. The graph presents the difference in carbon chemical shifts
between the average and the values for 45 (100 MHz) in DMBA (N,adimethylbenzylamine).
Spectra were recorded in both enantiomers of the
solvent, where the solid bar was recorded in (R)-DMBA and the shaded bar in
(S)-DMBA. The X- and Y-axes represent carbon number and d (d45a-h – dave
in ppm), respectively. The graphs are taken from ‘‘the 13C NMR database in
(R)- and (S)-DMBA as a deviation in chemical shift for each carbon of a
given diastereomer from the average chemical shift of the carbon in question.
Each diastereomer exhibits an almost identical NMR profile for (R)- and
(S)-DMBA but shows an NMR profile distinct and differing from the other
diastereomers, demonstrating that the database in (R)- and/or (S)-DMBA can