Electrospray tandem mass spectrometry of epipolythiodioxopiperazines

✍ Scribed by Zhi-Jun Wu; Guo-You Li; Dong-Mei Fang; Hua-Yi Qi; Wei-Jian Ren; Guo-Lin Zhang

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 713 KB
• Volume: 42
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/jms.1209

✦ Synopsis

Abstract

Low‐energy collision‐induced electrospray ionization tandem mass spectrometry ESI‐CID‐MS/MS (in the positive ion mode) was used for the structural characterization of a series of five representative epioplythiodioxopipreazines: dethiotetra(methylthio)chemotin, chaetocochins A, B and C, and chemotin isolated from the fungus Chaetomium cochliodes. The fragmentation pathways were elucidated by ESI‐IT‐MS^n^. The elemental compositions of most of the product ions were confirmed by low‐energy ESI‐CID‐QTOF‐MS/MS analyses. The loss of the S~2~ molecule seems always to be the first when the SS bond is present. The loss of 77 Da corresponding to the loss of the [CH~3~SCH~2~O]' radical was diagnostic for chaetocochins A and B, in which the two piperazines rings are linked by an acetal group. It was found that a McLafferty rearrangement plays a significant role in the skeleton fragmentation of theses series of studied complex multicyclic piperazine compounds. This MacLafferty rearrangement affords the product ions at m/z 416 and 400, containing the two piperazine rings belonging to the epipolythiodioxopipreazines. In addition, the pentacyclic rearrangement involving the loss of the SMe^·^ radical seems to occur in the presence of the unfused ring. Finally the product ions at m/z 635 and 591 seem to be the characteristic ions for chaetocochin A. Copyright © 2007 John Wiley & Sons, Ltd.