The mass spectra of some triterpenoid dehydration products

The mass spectra of ten dehydration and solvolysis products obtained from β-amyrin and glycyrrhetic acid were studied. With the exception of those resulting from ‘backbone’ rearrangement, they exhibited conventional fragmentation due to the ring C chromophore, like the parent alcohols. Only those products with a contracted ring A suffered loss of an isopropyl radical. In the latter type, special fragmentation features were exhibited by the isopropylcyclopentene and by the isopropylidene products. These differences enabled the assignment of probable structures for two unknown derivatives.