Mass spectrometric study of six cyclic esters

Abstract

A series of cyclic esters, which are optically active as a consequence of their helical structures, were synthesized to investigate the relationships between their structures and their optical activities. This paper reports the electron impact fragmentation mechanisms of these six cyclic esters. Accurate mass measurements and mass analyzed ion kinetic energy spectrometry confirmed fragmentation patterns. The stability of the fragment ions has a great influence on the fragmentation pathways, but no correlation with the optical activity was found.

Ring contraction reactions of 2,3‐dihydro‐4H‐1,3‐oxazin‐4‐ones under electrospray ionization conditions

“…One was retro‐Diels‐Alder (RDA) reaction to produce a pair of complementary ions, protonated imine fragments a and protonated α ‐carbonylketene fragments b , and ions a were the base peaks in the MS/MS of protonated compounds 1 – 4 and 8 – 10 . The RDA reaction of 4 H ‐1,3‐oxazin‐4‐one derivatives, such as 1,3‐oxazino[3,2‐ a ][1,5]benzodiazepin‐1‐ones and 1,3‐oxazino[3,2‐ d ][1,5]benzothiazepin‐1‐ones, has also been found under both FAB and CI conditions previously 24,25. Another one was a novel ring contraction reaction accompanied by elimination of isocyanates to produce protonated ions c ( c 1 – c 4 ).…”

Fragmentation mechanism of novel compounds: 3,3‐dichloro‐1‐[2‐(2,2‐dichloro‐1‐oxoethylthio)phenyl]‐4‐(4‐methoxyphenyl)‐4‐(1‐phenylvinyl)‐2‐azetidinone and its derivatives

“…Ion 2c ( m/z 424) was formed by loss of a neutral molecule (Cl 2 C=C=O), rationalized in terms of radical site initiation on the carbonyl oxygen of the four‐membered ring of ion 2a ( m/z 534) with two α‐cleavages 7,. 8 Close attention should be paid to the ion at m/z 424 which consisted of a contribution with a monoisotopic composition (C 23 H 16 NO 35 Cl 2 S) of ion 2c , plus a contribution from the [M + 2] + ion (C 23 H 14 NO 35 Cl 37 ClS) of 2d ; the calculated accurate mass for the former is 424.03247, and for the latter 424.01437.…”