NMR Spectra and Stereochemistry of some 7‐Substituted 6,14‐Bridged Thebaine Derivatives

The NMR spectra of eighteen 7α‐ and 7β‐substituted 6,14‐bridged thebaine derivatives are reported and the steric and other effects of the 7‐substituent on the C‐5‐H atoms examined. Although the H‐5 proton shift enabled compounds epimeric at C‐7 to be distinguished in the examples studied (values falling between δ 4.75‐4.40 ppm in the 7α series and δ 5.21‐4.97 ppm in the 7β series), the C‐5 shift values proved less useful owing to overlapping ranges.