Fast-atom bombardment mass spectrometry of brassinosteroid analogs

Positive ion fast-atom bombardment mass spectra of brassinosteroid analogs have been systematically obtained for the first time. The spectra of six brassinosteroid analogs and their corresponding 22S,23S isomers included the protonated molecule in medium to high relative intensity. The fragmentation pattern is dominated by side chain cleavage. There is a marked preferential loss of acetic acid from the [M + H]+ ion of 5α-hydrogen-3β-acetylated derivatives compared to the 5α-hydroxy-3β-acetylated analogs