未知化合核の構造を微量でいかに速く決定するか 天然物構造決定におけるタンデム質量分折法の役割

Abstract

Unlike NMR, mass spectrometry seems to be used as a supplementary method in general, rather than a critical tool in the structural analysis of “truly unknown” compounds, such as newly isolated biologically active natural products. One of the reasons is that instruments designed for structural analysis tend to be relatively expensive and hard to maintain and/or operate by natural product chemists, until recently. However, another, and more essential reason is underlying the nature of mass spectrometric structural analysis, i.e., the process of analysis relies on non-quantitative, highly empirical, and hard-to-generalize fragmentation rules, and is difficult to explain deductively to non-experts. It may also be believed to be difficult to extract structural information from high-energy collision induced dissociation (CID) mass spectra generated by sector-based tandem mass spectrometers, which are basically rich in structural information but hard to interpret. In this situation, we have learned that, at least in some cases, tandem mass spectrometry (MS/MS) can be used as an aid to extract vital structural information unambiguously and can be used for building unknown structures rationally, without using inspiration of an expert. In this paper, examples from our experiences in structural elucidation of natural products are shown and following points, (1) how MS/MS can help extracting crucial structural information from complex structures and (2) how MS/MS can be used for rational building of a new structure, are focused. (3) A possible role of high-energy-CID MS3 in structural elucidation of natural products is also discussed.