Mass spectroscopy of natural products. II—allogibberic acid—A model for the skeletal fragmentation of the molecular ions of GA3 type gibberellins
Dieter Voigt, Gabriela Violeta Adam, Jurgen G. Schmidt, P. Franke · Organic Mass Spectrometry · 1978
Abstract The positive ion mass spectrum of allogibberic acid was examined and fragmentation routes involving the carbon skeleton are proposed on the basis of mass measurements and metastable ion observations. The results are compared with the mass spectra of 3‐hydroxy‐epiallogibberic acid, as well as gibberellin A3 (GA3), 3‐epi‐GA3, 3‐dehydro‐GA3 and iso‐GA3, the latter compounds all being capable of undergoing aromatization of ring A giving a key ion corresponding to the molecular ions of the allogibberic acid and 3‐hydroxy‐epiallogibberic acid models, respectively. All the gibberellin derivatives investigated show the same fragmentation of the skeleton. Thus, the behaviour under electron impact of the GA3 type gibberellins follows a general pattern.