High resolution mass spectrometry. Bufadienolides—II.

Complete low resolution mass spectra and high resolution data for selected important peaks are presented and discussed for a series of naturally occurring 14β, 15β‐epoxybufadienolides (toad poisons) and their derivatives. The compounds examined were resibufogenin, marinobufagin, cinobufagin, desacetylcinobufagin, cinobufotalin, desacetylcinobufotalin and resibufagin, and the derivatives were 11α‐hydroxyresibufogenin, 3β‐acetoxymarinobufagin, 3‐ketocinobufagin, 3β‐acetoxy‐16β‐desacetylcinobufagin, 3β‐acetoxy‐16‐ketocinobufagin, resibufaginol, 14α‐artebufogenin and 3β‐suberyloxyresibufogenin methyl ester. The relatively unsaturated 2‐pyrone group of C‐17β has been used as an integral label to distinguish (from elemental composition data) ions containing it from those arising in other parts of the molecule that do not, and the spectra are interpreted in terms of structural ‘ion types’.