13C NMR studies of isomeric piperidine derivatives with opiate properties and related compounds

The 13C NMR spectra of a series of methyl substituted 3‐arylpiperidines and 4‐aryl‐4‐piperidinols and related compounds are reported, and chemical shift data analysed in terms of the configuration and conformation of isomeric pairs. Special attention is given to the γ chemical shift parameter of axial methyl, and the effects of a nitrogen lone pair orbital and hydroxyl or acyloxy group on the chemical shifts of ring and methyl carbons.