Atmospheric pressure chemical ionization multi-stage mass spectrometry in the characterization of stereoisomeric synthons of cyclopropane amino acids

Abstract

The mass spectrometric behaviour of (1S,2R)‐, (1R,2R)‐, (1R,2S)‐ and (1S,2S)‐2‐[(S)‐2,2‐dimethyl‐1,3‐dioxolan‐4‐yl]‐1‐spiro‐{4′[2′‐phenyl‐5′(4′H)‐oxazolone]} cyclopropane (2) and (1S,2R)‐, (1R,2R)‐, (1R,2S)‐ and (1S,2S)‐methyl‐1‐benzamido‐2‐[(S)‐2,2‐dimethyl‐1,3‐dioxolan‐4‐yl]cyclopropanecarboxylate (3) was studied under atmospheric pression ionization conditions and by multi‐stage mass spectrometric (MSn) experiments performed with an ion trap. Interestingly, by using methanol as solvent, compounds 2 lead to [M + H + CH3OH]+ ions which, as proved by collisional experiments, exhibit the same structure of the corresponding compound 3. MS/MS of [MH]+ ions allows a clear characterization of the different stereoisomers, which give rise to specific fragmentation pathways, rationalized with respect to the structure of the neutral molecules. Copyright © 2000 John Wiley & Sons, Ltd.

Natural Occurrence, Syntheses, and Applications of Cyclopropyl-Group-Containing α-Amino Acids. 1. 1-Aminocyclopropanecarboxylic Acid and Other 2,3-Methanoamino Acids

“…350 All of these products were extensively analyzed by mass spectrometry. 351 Under optimized conditions, the cyclopropanation of 236 occurred with reasonably high (E/Z) and (R/S) diastereoselectivities to give (R,S,S)-237 as the major stereoisomer in 73% isolated yield (Scheme 28). 350,352 The analogous transformation of the corresponding (R,E)-236 has also been investigated, and the origin of the high diastereofacial selectivities in the (Z)-as well as (E)-series was discussed on the basis of computational results.…”