The mechanism of alkyl radical elimination from ionised γγ-disubstituted alkenyl methyl ethers

Abstract

The mechanism of alkyl radical loss from ionised alkenyl methyl ethers containing two γ-alkyl substituents, R 1 R 2 C=CHCH 2 OCH 3 +• • , has been studied by investigating the collision-induced dissociation spectra of the resultant C n H 2n-1 O + oxonium ions (n = 5-7). Comparison of these spectra with one another and those of reference ions generated by dissociative ionisation of secondary allylic alkenyl methyl ethers indicates that expulsion of a γ-alkyl group occurs without isomerisation of the heavy atom skeleton via an allylic rearrangement.

Screening and Identification of Glyceollins and Their Metabolites by Electrospray Ionization Tandem Mass Spectrometry with Precursor Ion Scanning

“…Indeed, fragmentation to form this product constitutes a violation of the even-electron rule, (i.e., normally formation of a radical product ion plus a radical neutral is forbidden from decompositions of an even-electron precursor). However, homolytic cleavage of even-electron ions has been documented to occur, especially in cases where exceptional stability is acquired by the formed radical ion and radical neutral. − Because the m / z 148 product ion is formed from the portion of the molecule that is conserved in all of the glyceollin isomers, we propose to use the appearance of this unique radical ion in MS/MS spectra as a product-ion diagnostic of all glyceollins . Thus, the presence of this product ion can be used as a signature to identify glyceollins and their related metabolites.…”