Stereospecific 1,3 and 1,4 dehydration reactions in the mass spectra of podocarpan‐12‐ and ‐14‐OLS^†

Abstract

Specific deuterium labelling revealed that podocarpan-12%-and -14%-01, representing conformationally well defined cyclohexanols, eliminate water mainly by stereospecific 1,3 reactions involving cis tertiary hydrogens on electron-impact. Dehydration of podocarpan-I2~-ol, which also involves a cis tertiary hydrogen, occurs almost exclusively by a 1,4 reaction. Subsequent decomposition of the various [M -18]+-ions was found to lead to different products, thus explaining some of the intensity differences encountered in the lower parts of the spectra of the epimeric podocarpan-12-01s and -14-01s.

Elimination reactions of ions in the gas phase

“…-zHz-2-Adamantanol 26 83 % d,,16 % d,, 1 % do Values in parentheses resulting, when non-labelled equivalent positions are taken into account. b X[M -H02H]+ = overall sum of deuterowater elimination observed, when all positions in the skeleton are considered to be labelled.…”