MASS-SPECTRAL STUDY OF DIASTEREOMERS ON ELECTRON-IMPACT, III - 2-BROMO-3-ACETOXYSUCCINATES AND TARTRATE DIACETATES

The interaction between two carboalkoxy groups (COOR) and a bromine at om in stereoselective fragmentation is reflected in the mass spectra o f dimethyl 2-bromo-3-acetosysuccinates as has already been reported in the case of 2,3-dibromosuccinates. These results could be explained b ased on the expected most favourable conformations in the gas phase. I n the case of dialkyl tartrate diacetates, the interaction between the two COOR groups is stereoselective, leading to different ions, and ca n be explained based on the preferred conformations as reported in the case of dialkyl tartrates, The mechanisms of formation of characteris tic ions were confirmed using deuterium labelled compounds. Collision- induced dissociation spectra of [M-OR](+) ions from L-isomers of diace tates are different from those of the corresponding meso-isomers, show ing a structural effect based on stereospecific interaction between th e two COOR groups.