On the sign of the anisochrony of diastereotopic groups

Abstract
The NMR anisochrony which characterizes the diastereotopism of the CH3 groups in an isopropyl group attached to a chiral residue is defined not only in magnitude but also in sign. The absolute signs of the anisochronies were determined for two series of derivatives of the type XYZC‐CH(CH3)2. Sign inversions were observed for a number of compounds belonging to the same homologous series when compared by 1H or 13C NMR spectroscopy.