The structural elucidation of polyene macrolide antibiotics by mass spectrometry. Nystatin, amphotericin B and pimaricin
✍ Scribed by Klaus D. Haegele; Dominic M. Desiderio Jr
- Publisher
- John Wiley and Sons
- Year
- 1974
- Tongue
- English
- Weight
- 645 KB
- Volume
- 1
- Category
- Article
- ISSN
- 1076-5174
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✦ Synopsis
Complete mass spectra of the pertrimethylsilylated derivatives of three high molecular weight polyene macrolide antibiotics are reported for the first time. The fragmentation pathways which are proposed have been corroborated by the stable isotope derivatives d,-TMS and d,-acetyl. Accurate mass measurements and metastable transitions confirm the proposed fragmentation mechanisms in the low mass range. Nystatin-the macrolide of highest molecular weight in this study --expels several TMSOH molecules and a TMS radical. Amphotericin B underwent extensive rearrangements preliminary to eliminating a series of TMSOH molecules. An apparent equilibrium between the keto and ketal forms of amphotericin B facilitated the rearrangements. Pimaricin fragmented in a manner parallel to that of the other two macrolides. The sugar portion of the molecules dominated the fragmentation in the low mass region in the spectra of all compounds. The transfer of a TMS group from the sugar amine to the glycosidic oxygen was observed when the amino sugar was eliminated from the intact molecule. The resulting sugar ion then expelled ammonia.