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.