Targeted Isolation of Saalfelduracin B-D from Using LC-MS/MS-Based Molecular Networking.

High-resolution tandem mass spectrometry (HR-MS)-based metabolomic studies of , isolated from the "Saalfelder Feengrotten" caves in Germany, led to the isolation of three ribosomally synthesized and post-translationally modified type II thiopeptides, saalfelduracin B-D (-) and the known saalfelduracin A (). The structures of all four compounds were determined by comparative two-dimensional NMR analysis and high-resolution tandem mass spectrometry.